Introduction to Process Integration

Introduction to Process Integration
MODULE III Introduction to Process Integration

Outline 1. Introduction 2. Foundation Elements 3. Case Study
4. Open Ended Problem 5. Acknowledgments 6. References

TIER I

1. Introduction

1. Introduction “Do your best; then treat the rest”
Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

1. Introduction Pollution is an ongoing concern that has been addressed in many different ways, from no pollution control, end-of the-pipe treatment (1970’s), Implementation of Reuse/Recycle (1980’s) up to Process Integration. The focus of this module is to expose PI tools for pollution reduction/elimination

What is Process Integration?
1. Introduction What is Process Integration? “It is a holistic approach to process design, retrofitting and operation which emphasizes the unity of the process” Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

1. Introduction The use of PI methods started as early as 1970’s with Pinch Technology (Heat Integration) in order to optimize heat exchanger networks (HEN). The moving force for mass integration was initially pollution control; El-Halwagi and Manousiouthakis (1989) proposed the use of mass exchange networks (MEN) in analogy to the previously studied HEN. PI tools can be used in a variety of industries and with approaches as wide as those involving product distribution, life cycle assessment etc (research in these an other areas is currently on their way)

2. Foundation Elements

2. Foundation Elements 2.1. Holistic approach of process integration
2.2. Relationship of process integration to process analysis 2.3. Overview of energy, mass and property integration

2. Foundation Elements 2.1 Holistic Approach of Process Integration Holistic: Emphasizing the importance of the whole and the interdependence of its parts. Concerned with wholes rather than analysis or separation into parts Heuristic: Of or constituting an educational method in which learning takes place through discoveries that result from investigations made by the student Source :

2. Foundation Elements 2.1 Holistic Approach of Process Integration Process Integration can address a wide set of design issues such as: Efficient use of resources and raw materials Process debottlenecking Efficient use of energy Cost reduction Other process operation issues Pollution reduction

2. Foundation Elements 2.1 Holistic Approach of Process Integration Traditional process design has been addressed by heuristic methods, based on experience or corporate preferences, in which unit operations equipment have been design individually. However little attention has been placed on the relationships with other parts of the process Process Integration as a holistic approach, looks at the Big Picture and the relationships among the different operations and equipment alternatives

2. Foundation Elements 2.1 Holistic Approach of Process Integration In order to illustrate how Process Integration (PI) can aid in the design process an illustrative example is given we have 3 options for a chemical reactor in order to produce a chemical product, the options to choose from are: Source : July 2001

2. Foundation Elements 2.1 Holistic Approach of Process Integration
Using a heuristic approach the “best” option will be a mechanically agitated vessel that produces a yield of 73.9% with a volume of 12m3; however is there any other way to improve the process?

Two designs based on the same solution
2. Foundation Elements 2.1 Holistic Approach of Process Integration Two designs based on the same solution Source : July 2001

2. Foundation Elements 2.1 Holistic Approach of Process Integration
Using PI tools the following solution was found, 96.9% yield and 9.93m3 of volume. Two designs based on this solution are shown next; the benefits of using PI tools are evident. However a thorough analysis of the answer to the problem must be carried out in order to find a feasible design based on the findings obtained using a PI approach Source : July 2001

2. Foundation Elements 2.2. Relationship of Process Integration to Process Analysis In order to find solutions that include the relationship effects among the different options for a given design task, the engineer must use PI in order to find optimum answer to the problems at hand, therefore PI tools should be included in the process design structure. Seider, Seader and Lewin illustrate it as shown in the next slides, for a complete description of the design steps, referred to the above mentioned authors Process design is a dynamic process, always making sure that the solutions will agree with the constraints set by the stakeholders (management, governmental agencies, environmentalist groups, general public etc) and the process itself

2. Foundation Elements Process Analysis
2.2. Relationship of Process Integration to Process Analysis Process Analysis “Analysis of the process elements for individual study of performance, by using mathematical models and computer simulators” Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Part I
2.2. Relationship of Process Integration to Process Analysis Asses Primitive Problem (Define the objective of the design task based on the identified opportunity) Survey Literature (Identify all sources of useful information for the process design, e.g. Handbooks etc) Current Situation/Opportunity (e.g. a new technology is developed etc) Equipment Selection (Assess different options for the given process using process simulators, spreadsheets, in house software etc) Preliminary Process Synthesis, reactions, Separation, T-P Change Operations, Task Integration Preliminary Data Base Creation (Thermodynamic data, kinetics, toxicity etc) Part I Source : Product and Process Design Principles : Synthesis, Analysis, and Evaluation W D. Seider J. D. Seader, D.R. Lewin

Is the Gross Profit Favorable?
2. Foundation Elements 2.2. Relationship of Process Integration to Process Analysis Is the Gross Profit Favorable? No Equipment Selection (Assess different options for the given process using process simulators, spreadsheets, in house software etc) Reject Yes Part I a Part II Part IV Source : Product and Process Design Principles : Synthesis, Analysis, and Evaluation W D. Seider J. D. Seader, D.R. Lewin

2. Foundation Elements Part I a Part II Part VI
Create Process Flow Sheet Separation Train Synthesis Process Integration Qualitative Synthesis Second Law Analysis Create Detailed Data Base Pilot Plant Testing Modify Flow Sheet Prepare Simulation Model Flow Sheet Controllability Analysis Heat and Power Integration Part I a Dynamic Simulation Part II No Yes Part VI Go to I or I a Is the Process still Promising? Part III Source : Product and Process Design Principles : Synthesis, Analysis, and Evaluation W D. Seider J. D. Seader, D.R. Lewin

2. Foundation Elements Part IV Part III Operation Startup Part IV
2.2. Relationship of Process Integration to Process Analysis Part I or I a Detail Design, Equipment Sizing, Capital Cost Estimation, Profitability Analysis, Optimization Part IV Yes Is the Process still Promising? Startup Assessment (Additional Equipment, Dynamic Simulation) No Part III Reject Reliability and Safety Analysis (HAZOP, Pilot Plant Testing etc) No Is the Process still Feasible? Yes Operation Written Report, Presentation Final Design (P&ID, Bids etc) Part IV Construction Startup Source : Product and Process Design Principles : Synthesis, Analysis, and Evaluation W D. Seider J. D. Seader, D.R. Lewin

2. Foundation Elements 2.2. Relationship of Process Integration to Process Analysis Designing a new plant, retrofitting a existing one, has several operations and for each operation different equipment options and configurations to choose from. The main problem is that the number of alternatives can be unmanageable. If only heuristics are use for the design, the engineer will risk to miss the true optimal solution to the design problem. Moreover, a design solution for a given problem cannot be use for a different one, since the initial findings are tailored for a specific problem. Using a PI approach, one can avoid this issue, due to the fact that its methodology can be applied to any problem. The PI methodology is composed of three key components

2. Foundation Elements Process Synthesis Process Integration
2.2. Relationship of Process Integration to Process Analysis It defines what process units and how they should be interconnected Process Synthesis Analysis of the process elements for individual study of performance Process Integration Process Analysis Minimizing or maximizing a desired function, to find the best option Process Optimization

Preliminary equipment selection Equipment required during design
2. Foundation Elements 2.2. Relationship of Process Integration to Process Analysis As it has seen, process analysis is a step within the PI methodology. It is important to emphasize that PI will look at the generalities rather than into the details, and then the designer can analyze the performance of the solutions in order to optimize his/her findings. The following chart illustrate the impact of the process design steps over the budget $ Impact Preliminary equipment selection Spent Committed Equipment required during design Process Conceptual Detailed Plant Detail Construction Startup & Develop Design Design Layout Mech Commission.

2. Foundation Elements Mass Integration
2.3. Overview of Mass, Energy and Property Integration Mass Integration “Systematic methodology that provides a fundamental understanding of the global flow of mass within the process and employs this holistic understanding in identifying performance targets and optimizing the generation and routing of species throughout the process” Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Mass Exchanger Mass Exchangers:
2.3. Overview of Mass, Energy and Property Integration 2.3.1 Mass Exchangers Lean Stream (MSA) Flow rate: Lj Inlet Composition xjin Outlet Composition yiout Mass Exchangers: A mass exchanger is any direct-contact mass transfer unit that employs a MSA (Mass Separation Agent), to remove selectively certain component (e.g. pollutant) from a rich phase (e.g. waste stream). The MSA should be partially or totally immiscible in the rich phase Mass Exchanger Rich (Waste) Stream, Flow rate: Gi Inlet Composition yiin Outlet Composition xjout Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration 2.3.1 Mass Exchangers Solute Transferred to lean phase Lean Phase When the two phases are in intimate contact the solutes are distributed between the two phases which leads to a depletion of solute in the rich phase and enrichment of the lean phase until equilibrium is reached. The difference in chemical potential for the solute is the moving force for mass transfer (Temperature difference for heat transfer, Pressure difference for fluid movement etc) Rich Phase

2. Foundation Elements Stripping Adsorption Leaching Absorption
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Mass Exchange involve the following operations: Only counter current operations will be consider because of their higher efficiency Adsorption Stripping Leaching Absorption Extraction Ion Exchange

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Adsorption: Separation of a solute from a liquid or gaseous stream by contacting the carrying phase with a small porous solid particles (adsorbent), usually arranged in a packed bed. The adsorbent can be regenerated by desorption using inert gas, steam etc Source : Université d’Ottawa / University of Ottawa - Jules Thibault

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers In order to select an adsorption column the designer must select a suitable adsorbent for the given solute by looking at the appropriate isotherm data as shown in the plot for a given set of process operation Source : Université d’Ottawa / University of Ottawa - Jules Thibault

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Absorption: A liquid solvent is place in contact with a gas containing a solute to be remove by taking advantage of the preferential solubility of the liquid. Reverse absorption is also know as stripping (separation of a solute using a gas stream from a liquid phase) Source : Université d’Ottawa / University of Ottawa - Jules Thibault

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Liquid Extraction: It employs a liquid solvent to remove a solute from another liquid by using the preferential solubility of the solvent to the solute in the MSA Source : Université d’Ottawa / University of Ottawa - Jules Thibault

2. Foundation Elements Leaching:
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Leaching: Selective separation of some constituents within a solid by contact with a liquid solvent Solvent Solid Mixing Slurry Overflow Solution Source : University of Ottawa - Jules Thibault

Cause of scale forming impurities
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Ion Exchange: Cation/anion resins are used to replace undesirable anions from a liquid phase by non hazardous ions Cause of scale forming impurities Water softeners Source : Université d’Ottawa / University of Ottawa - Jules Thibault

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers The mass exchanger is used to provide appropriate contact of the lean and rich phase; there are two principal categories of mass exchange units: Multistage (e.g. tray columns, mixer settlers etc), they provide intimate contact follow by phase separation Differential (e.g. packed columns, spray towers and mechanically agitated units), continuous contact between phases without intermediate separation and re-contacting

Multiple Mixers / Settlers Multistage Contactors
2. Foundation Elements Multiple Mixers / Settlers MSA Out Light Phase Out Tray Column Heavy Phase In Shell MSA In Waste In Perforated Tray Light Phase In Multistage Contactors Heavy Phase Out Waste Out

Differential / Continuous Contactors Mechanically Agitated Mixer
2. Foundation Elements Spray Column Light Phase Out Light Phase Out Mixer Heavy Phase In Heavy Phase In Differential / Continuous Contactors Heavy Phase Out Light Phase In Light Phase In Heavy Phase Out Mechanically Agitated Mixer

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Solute in the rich phase Equilibrium: When a rich phase in a solute is put in contact with a lean phase transfer of the solute to the lean phase occurs, also part of the solute In the lean phase also back transfer to the rich phase. At first the rate of solute being transfer from the rich phase is bigger than the rate of solute back transfer from the lean phase. However when the concentration of solute in the lean phase increases, the back transfer rate also increases. Eventually the mass transfer rate and the back transfer rates become equal and an equilibrium is reached (1) Equilibrium distribution function Maximum attainable composition in the lean phase Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Mol fraction of solute in liquid
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers In environmental applications the engineer will find very often, diluted systems which can be linearized over the operating range to yield: (2) Special cases, Raoult’s Law for absorption Partial pressure at T (3) Mol fraction of solute in liquid Mol fraction of solute in gas Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Henry’s Law for stripping
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Mol Fraction of solute in stripping gas Henry’s Law for stripping (4) Mole fraction of solute in gas Liquid phase solubility of pollutant at temperature T (5) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements For solvent extraction
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Composition of the solvent For solvent extraction (6) Composition of pollutant in liquid waste Distribution Coefficient Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements The following relationships are used to size multistage mass transfer exchangers: yi,N+1= yiin Gi yi,1= yiout yi,2 yi,3 yi,N-1 yi,N 1 2 N N-1 XJ,0= Xjin Lj XJ,1 XJ,2 XJ,N-2 XJ,N-1 XJ,N= XJout Overall Mass Balance: (7) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Rearranging (7): (9) (8) Eq. (8) represents the operating line in a McCabe-Thiele diagram: yiin LJ / Gi 1 Theoretical stages Operating Line 2 yiout Equilibrium Line xJin xJout

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers (10) The number of stages for a multistage unit can also be calculated with the following equations, with NTP being the number of theoretical plates (11) (12) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements (13) When the contact time for each stage is not enough to reach equilibrium, the number of actual plates (NAP) can be calculated using contacting efficiency (14) Stage efficiency can be define on the rich or lean phase, for the rich phase we have: Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements (15) For differential (continuous) mass exchangers, the height is calculated using: (16) (17) Based on rich phase Based on lean phase Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements For mass exchangers with linear equilibrium:
(18) (19) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements For mass exchangers with linear equilibrium (cont): (20) (21)

2. Foundation Elements (22) In order to calculate the diameter of the column (m) we have: (23) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements In order to calculate the diameter of the column we need volumetric flow rate of air (VFRA), maximum allowable superficial velocity of air (MASVA): (24) To complete the design of a mass exchange unit, the designer has to look into the costs that the unit will have. The total annual cost (TAC) is given by: (25) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Lean End of Exchanger
Where AOC is the annual operating cost and AFC is the annual fixed cost of the unit. Recall equation (8) Operating Line Lean End of Exchanger yiin eJ Equilibrium Line yiout Driving Force xJin,max xJin* xJout The number of mass exchange units will be higher for a small e, a vanishing driving force. Therefore, it is necessary to assign a minimum driving force between the two lines

2. Foundation Elements We have:
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers We have: (26) By using a minimum allowable composition difference, eJ the designer can identify the minimum practically feasible outlet composition of the waste stream Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Rich End of Exchanger
The number of mass exchange units will be higher for a small e, a vanishing driving force. Therefore, it is necessary to assign a minimum driving force between the two lines Operating Line Rich End of Exchanger eJ yiin Equilibrium Line yiout Remainder : An outlet composition on the equilibrium line = infinite number of stages Driving Force xJin xJout,max xJout* Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements We have:
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers (27) We have: Where, eJ is the “minimum allowable composition difference” and xJout,max is the maximum practically feasible outlet composition of the MSA which satisfies the eJ driving force As can be seen from (16 to 19) and (27), there is a trade off between the driving force and the cost/size of the equipment to be use for the separation. To illustrate the use of the previous equations a example is given Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Example 1
Air stripping is used to remove 95% of the rich trichloroethylene (TCE, molecular weight = 131.4) dissolved in a 200kg/s (3180gpm) waste water stream. The inlet composition of TCE in the waste water is 100ppm. Air (free of TCE) is compressed to kPa (2at) and diffused through a packed stripper. The TCE-laden air exiting the stripper is fed to the plant boiler which burns almost all the TCE. Physical Data: The stripping operation takes place isothermally at 293K and follows Henry's law. The equilibrium relation for stripping TCE from water is theoretically predicted using: Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

HTUy = Superficial Velocity of waste water/Kya
2. Foundation Elements (28) Where yi is the mass fraction of TCE in waste water and xJ is the mass fraction of TCE in air. The air-to-water ratio is recommended by the packing manufacturer to be: 24 m3Air / m3water Stripper Sizing Criteria: The maximum allowable superficial velocity of waste water in the column is taken as 0.02m/s (approximately 30 gpm/ft2).The overall height of transfer unit based on the liquid phase is given by: HTUy = Superficial Velocity of waste water/Kya Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Where ky is the water-phase overall mass transfer coefficient and a is the surface area per unit volume of packing. The value of Kya is provided by the manufacturer to be 0.002s-1 Cost Information: The operation cost for air compression is basically the electricity utility needed for the isentropic compression. Electric energy needed to compress air may be calculated using: Compression Energy (CE) (29) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Fixed cost of column = 4700HD0.9
2. Foundation Elements The isentropic efficiency of the compressor is 60% and the electric energy cost is $0.06/kWhr. The system is operated for 8000hr/y. The fixed cost, $, of the stripper (including installation and auxiliaries, but excluding packing) is given by: Fixed cost of column = 4700HD0.9 Where H is the height of the column (m) and D is the diameter (m). The cost of packing is $700/m3. The fix cost of the blower, $, is 12000LJ0.6, where LJ is the flow rate of air (kg/s). Assume negligible salvage value and a five year linear depreciation. (a) estimate the column size, fixed cost and annual operating cost. (b) Due to the potential error in the theoretically predicted value of Henry’s coefficient, it is necessary to asses the sensitivity of your results to variation Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

= Value of Henry’s Coeffcient/0.0063
2. Foundation Elements of the value of Henry’s coefficient. Plot the column height, annualized fixed cost and annual operating cost versus a the relative deviation from the nominal value, for 0.5 £ a £2.0. The parameter a is define by: = Value of Henry’s Coeffcient/0.0063 (c) Your company is planning to undertake extensive experimentation to obtain accurate values of Henry’s coefficient that can be used in designing and evaluating the cost of this stripper. Based on your results, what would you recommend regarding the undertaking of these experiments? Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Stripping of TCE from Wastewater
2. Foundation Elements Exhaust Gas 2.3. Overview of Mass, Energy and Property Integration xJout = ? Waste Water Gi = 200kg/s yiin = 10-4 Boiler Stripper Stripping of TCE from Wastewater Air, LJ = ? xJin = 0 yiout = 5*10-6 Blower Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Solution: (a)
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Solution: (a) 1. We will first have to calculate the flow and concentrations of the different streams as follows: Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Solution: Continuation
2.3. Overview of Mass, Energy and Property Integration Solution: Continuation Using the overall mass balance equation we have: 2. We now will calculate the height and diameter of the column, superficial velocity of waste water (SVWW) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Solution: Continuation Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Solution: Continuation 3. With the equipment dimension we can proceed to calculate the operating and fixed costs Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Solution: Continuation Annual Operating Cost (AOC): Equipment Cost (EC): Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Solution: Continuation Fixed Cost (FC):
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Solution: Continuation Fixed Cost (FC): Solution: (b) (c) Henry’s Law coefficient will affect the FC through the change in the size of the system. By changing a one can find different values of Henry’s Law coefficient and use them to calculate the size of the column and then the FC; we will use Excel for this procedure. Since we have a linear 5 year depreciation the FC will be divided by 5 Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Solution: Continuation As the plot and Table 1 show, there is a small change in the TAC and AFC with changing Alfa, meaning that we don’t have appreciable savings by changing the height of the column with more accurate values of Henry’s Law coefficient. Therefore the project is not required; we just saved our company a lot of money!!!! Alfa Henry H AFC TAC 0.5 0.75 1 0.0063 1.25 1.5 1.75 646865 2 0.0126

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Very slight change

2. Foundation Elements Mass Exchange Networks
2.3. Overview of Mass, Energy and Property Integration Mass Exchange Networks Mass Exchange Networks Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements MSA can be: Process MSA, NSP
2.3. Overview of Mass, Energy and Property Integration MSA can be: Mass Exchange Networks They are Lean Streams (Ns), LJ, j = 1, 2…Ns Process MSA, NSP Low cost or almost free “In plant” Mass Separation Agents (MSA) External MSA, NSE Must be bought externally Use to remove pollutants from rich streams, NR Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Ns = NSP + NSE
2.3. Overview of Mass, Energy and Property Integration Mass Exchange Networks Ns = NSP + NSE (28) Flow rates, stream concentration and target concentration of rich streams are known, Gi, ySS, yit Inlet compositions of lean streams are also known, xJS flow rate of lean streams, LJ, is to be determine to minimize network cost LJ £ LJC J = 1, 2…NSP LJC is the flow rate of the Jth MSA available in the plant (29) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Disposed Waste streams can be Comply with
2.3. Overview of Mass, Energy and Property Integration Mass Exchange Networks Disposed Comply with Environmental Regulations Waste streams can be Target composition is the constraint imposed by process Sink Forwarded to process Sinks (equipment) For recycle/reuse Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Solubility of pollutant
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchange Networks Target composition are assigned by designer based on the following constraints: Physical (e.g. maximum Solubility of pollutant In MSA) Technical (e.g. avoid corrosion, Viscosity) Environmental (e.g. EPA, OSHA Regulations) Safety (e.g. stay away of Flammability limits) Economic (e.g. optimize cost Of MSA regeneration) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Which MSA should be selected? Which ME operation should we use?
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchange Networks The following questions will arise: What is the optimum configuration? How to match MSAs to the waste streams? Which MSA should be selected? Which ME operation should we use?

2. Foundation Elements “Targeting Approach”
2.3. Overview of Mass, Energy and Property Integration Mass Exchange Networks The previous questions will result in a unmanageable number of combinations A systematic approach is required “Targeting Approach” Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Targeting Approach
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Targeting Approach “It is based on the identification of performance targets ahead of design and without prior commitment to the final network configuration” Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Minimum cost of MSA: By combining thermodynamic aspects of the problem with cost data of the MSA, the designer can identify the minimum cost of the separation, without designing the network GENERALLY INCOMPATIBLE Minimum number of mass exchange units: This objective is aim at minimizing fixed cost of the system, by doing so, one can reduce pipe work, foundations, maintenance and instrumentation Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements U = NR + Ni U = Number of units
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers U = NR + Ni U = Number of units Ni = Number of independent synthesis sub-problems in which original synthesis problem can be subdivided (30) In most cases there will be only one independent synthesis problem. In order to avoid the incompatibility of the two targets, one have to use techniques that will identify the MOC solution and then minimize the number of exchangers that satisfy the MOC (Minimum Operating Cost)

2. Foundation Elements eJ Feasibility area
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers eJ yiin yiout Feasibility area xJin xJout,max xJout* In order for the separation to be feasible one have to work in the feasibility area To relate the different concentrations in one scale, we need to use Equation (27)

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Mass Exchanged In order to minimize the cost of external MSA one must maximize the use of in plant MSA Pinch Point The pinch diagram is a graphical representation that considers the thermodynamic constraints of the system, calculate MR with: (31) y x1 x2 Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements How to construct the pinch diagram? MRi R2 R1
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers How to construct the pinch diagram? MRi Represent each stream with an arrow R2 2. Plot mass exchanged versus its composition 3. Tail of the arrow is the supply composition and head is target composition 4. The slope is the flow rate of the stream R1 5. The vertical distance between the tail and the head represent the amount of pollutant transferred ( MRi ) from the rich stream ( yi ) to the lean stream y1t y2t y1s y2s 6. Stack the arrows on top of one another starting with the one with the one having the lower composition yi

2. Foundation Elements How to construct the pinch diagram? MRi MR2 MR1
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers How to construct the pinch diagram? MRi MR2 MR1 7. Obtain the composite diagram by using the “diagonal rule” R2 8. The vertical axis is a relative scale, one can move up and down the curves while maintaining constant the vertical distance 9. Apply the same procedure for the lean streams R1 10. Plot both composite curves in one graph, slid the lean composite until it touches the rich (waste) composite stream y1t y2t y1s y2s yi Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements MSiMS2 MS1 S2 S1 yi x1s x1t x2s x2t
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers MSiMS2 MS1 How to construct the pinch diagram? S2 (32) S1 11. Use the above equation to obtain the horizontal scale and Equation 33 to calculate MS yi x1s x1t x2s x2t Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Excess Capacity of Process MSA’s Load to be removed by external MSA’s
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Mass Exchanged How to construct the pinch diagram? Lean Composite Stream Excess Capacity of Process MSA’s (33) Rich Composite Stream Load to be removed by external MSA’s yi x1 x2 Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Integrated mass exchange:
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Mass Exchanged How to construct the pinch diagram? Integrated mass exchange: Maximum amount of pollutant that can be transfer Lean Composite Stream Rich Composite Stream The Pinch point is the minimum feasible concentration, it is also a bottleneck, slid up or down the composite curves until they touch, keeping the vertical distance and the concentrations Pinch Point yi x1 x2 Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Load of pollutant above the pinch to be removed
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers In order to reduce the excess capacity of process MSA one can either reduce flow rate, or composition. Care must be given when choosing e, since it will cause the lean composite curve to move to the right, increasing the load to be removed by external MSAs (34) In the case that 2 or more MSAs are overlapped, one have to calculate the composition that will suit the requirements of the plant and compare the costs in order to identify the MSA that will be use in the separation Load of pollutant above the pinch to be removed Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers To calculate cost of recirculation MSA (Cj) and cost of removed pollutant (cjr) use: (35) Cost of Regeneration Cost of Make up (36) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements MR
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers MR There are cases when there are no process MSAs, therefore a different approach is required in order to construct the pinch diagram Draw the rich composite as before Draw the external MSA as Sj arrows with the tail as the supply composition and the head its target composition Calculate the cj If arrow S2 lies completely to the left of S1 and c2r < c1r then eliminate S1 Rich Composite Stream yi S1 x1 S2 S3 x2 Source : Pollution Prevention through Process Integration, M. M. El-Halwagi x3

2. Foundation Elements MR Rich Composite Stream
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers MR If arrow S3 lies completely to the left of S2 but c3r is > c2r then retain both MSAs In order to minimize the operating cost of the network one should use the cheapest MSA where it is feasible In this case S2 should be used to remove all the rich load to the left and the remaining load is removed by S3 Calculate flow rates of S2 and S3 by diving the rich load remove by the composition difference for the MSAs Construct the pinch diagram as shown Rich Composite Stream yi S1 x1 S2 S3 x2 Source : Pollution Prevention through Process Integration, M. M. El-Halwagi x3

2. Foundation Elements Example 2
2.3. Overview of Mass, Energy and Property Integration Example 2 A process facility converts scrap tires into fuel via pyrolisis. The discarded tires are fed to a high temperature reactor where heat breaks down the hydrocarbon content of the tires into oils and gaseous fuels. The oils are further processed and separated to yield transportation fuels. The reactor off gasses are cooled to condense light oils. The condensate is decanted into two layers: organic and aqueous. The organic layer is mixed with the liquid products of the reactor The aqueous layer is a waste water stream whose organic content must be reduce prior to discharge. The primary pollutant in the waste water is a heavy hydrocarbon. The data for the waste water stream is given in the next slide. A process lean stream is a flare gas (a gaseous stream fed to the flare) which can be used as a process stripping agent. To prevent back propagation of fire from the flare, a seal pot is used. Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Target Composition (ppmw) Aqueous layer from decanter
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Stream Description Flowrate Gi kg/s Supply Composition (ppmw) yis Target Composition (ppmw) yit R1 Aqueous layer from decanter 0.2 500 50 Table 1 Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements yi = mjxj Example 2, Continuation
2.3. Overview of Mass, Energy and Property Integration Example 2, Continuation An aqueous stream is passed though the seal pot to form a buffer zone between the fire and the source of the flare gas. Therefore, the seal pot can be used as a stripping column in which the flare gas strips the organic pollutant off the waste water while the waste water stream constitutes a buffer solution preventing back propagation of fire. Three external MSAs are considered: a solvent extract S2, an adsorbent S3 and a stripping agent S4. The equilibrium data for the jth MSA and the process MSA are given in the next slide, the equilibrium data is given by yi = mjxj Where yi and xj are the mass fractions of the organic pollutant in the waste water and the jth MSA, respectively. Use the pinch diagram to determine the minimum operating cost of the MEN Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Upper Bound on flow rate Target Composition (ppmw)
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Example 2, Continuation Stream Upper Bound on flow rate Ljc kg/s Supply composition (ppmw) xsJ Target Composition (ppmw) xJt mJ eJ CJ $/kg MSA S1 0.15 200 900 0.5 - S2 300 1000 1.0 100 0.004 S3 10 0.8 50 0.030 S4 20 600 0.2 0.050 Table 2 Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Example 2, Continuation Pyrolisis Reactor
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers To atmosphere Example 2, Continuation Gaseous Fuel Flare Condenser Reactor Off Gases Water To waste water Decanter Seal Pot Waste water R1 Light oil Flare Gas S1 Separation Pyrolisis Reactor Finishing Shredded Tires Liquid Fuel Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements MEN Solution Pyrolisis Reactor
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers To atmosphere Solution Flare Gaseous Fuel Condenser S2 S3 S4 Waste water R1 Reactor Off Gases MEN To waste water Decanter Light oil Flare Gas, S1 Separation Pyrolisis Reactor Finishing Shredded Tires Liquid Fuel Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements S1 R1
2.3. Overview of Mass, Energy and Property Integration Mass Exchangers Solution, Continuation Calculate and plot the pinch diagram, using Equations 31,32,33 and Tables 1 and 2 MR y R1 50 90 500 S1 200 105 550 Mass Exchanged10-6 S1 MR y R1 50 90 500 S1 200 195 550 R1 y. ppmw

2. Foundation Elements Pinch Point Solution, Continuation
Mass Exchanged 10-6 Pinch Point Excess Capacity of Process MSA Integrated Mass Exchanged New S1 Target Composition Mass to be Removed by External MSA y. ppmw

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Solution, Continuation From the pinch diagram the load to be removed by the process MSA is 64 x 10-6 kg/s, the excess capacity is 45 x 10-6 kg/s; we have to use the whole flare gas flow rate to remove pollutant from the waste water, due to the fire hazard that it represents (we cannot by pass part of it directly to the flare, in order to reduce the excess capacity) from a mass balance or the pinch diagram we find the outlet composition of S1 to be: 400 ppmw We now have to evaluate the different external MSAs. The load to be removed by external MSA is approximately 31 x 10-6 kg/s, we need to check the thermodynamic feasibility of each external MSA Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Solution, Continuation

2. Foundation Elements S3 S2 S4 Solution, Continuation 48 10 200 300
Mass Exchanged 10-6 48 y. ppmw 10 S3 S2 200 300 1000 S4 20 600

2. Foundation Elements Solution, Continuation Calculating the costs of each separation agent, using Equation 36: c2r = $/kg c3r = $/kg c4r = $/kg Analysis: S2 is not a feasible MSA since its target concentration is higher that the target concentration of the rich stream therefore mass transfer is not possible. S4 is the selected MSA, flow is 31x10-6kg/s annual operating cost is 31x10-6x86.2x3600x24x365 = $84,270.5/yr Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Process (37)
2.3. Overview of Mass, Energy and Property Integration Targeting rules Energy In Process integration is conformed of mass and energy integration Process Mass In Mass Out In order to achieve a good mass integration, one has to set targeting goals; from an overall mass balance: Energy Out (37) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Targeting rules In order to reduce intake of fresh resources and reduce the discharge of waste streams one need to consider recycle, mixing, segregation and/or interception. In order to identify the recycle (direct or after segregation/interception) strategy that will have a net effect on the system the following procedure follows Fresh Load Terminal Load FLk,1 1 4 TLk,1 FLk,2 2 TLk,2 FLk,1 TLk,3 3 5 TLk,4 No Recycle

No Net effect = Poor Recycle
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Targeting rules Identify where recycle of streams will have the biggest net effect Fresh Load Terminal Load 1 4 TLk,1 + Rk,2 – Rk,1 FLk,1 FLk,2 2 TLk,2 - Rk,2 TLk,3 FLk,1 3 5 + Rk,1 TLk,4 No Net effect = Poor Recycle Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Effective Recycle from Terminal Streams
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Targeting rules Fresh Load Terminal Load 1 4 TLk,1 – Rk,1 FLk,1 – Rk,2 FLk,2 – Rk,1 2 TLk,2 – Rk,2 TLk,3 FLk,1 3 5 TLk,4 Effective Recycle from Terminal Streams Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Effective Recycle from Terminal and Intermediate Streams
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Targeting rules Fresh Load Terminal Load 1 4 TLk,1 – Rk,1 FLk,1 – Rk,2 FLk,2 – Rk,1 2 TLk,2 – Rk,2 TLk,3 FLk,1 3 5 TLk,4 Effective Recycle from Terminal and Intermediate Streams Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Acceptable Composition Range Pollutant Composition
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Targeting rules Recycle of streams must comply with sink constraints; such as composition and flow rate which a sink can take. In order to take advantage of direct recycle opportunities within a plant one has to identify them by using a graphical technique know and the source/sink mapping diagram Effective recycle should connect fresh intake and out streams Sink Source Acceptable Flow Range Flow Rate Load, kg/s Acceptable Composition Range Pollutant Composition

Pollutant Composition
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Targeting rules The interception of the two constraints is the area where any source within it can be recycled directly to the sink The maximum amount to be recycle is the minimum between the fresh inlet and outlet load. In order to recycle b and c use the mixing arm rule Direct recycling does not require new equipment Define equipment constraint from, technical data, operation conditions, physical and chemical properties etc Sink a Source S Flow Rate Load, kg/s b c Pollutant Composition Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Arm rule: (38) Fs (39) Fb b Fc c
2.3. Overview of Mass, Energy and Property Integration Targeting rules Arm rule: Flow Rate Load, kg/s (38) Resulting Mixture Fs Arm c (39) Arm b Fb b Sources Fc c If a fresh source is mixed with a polluted one, in order to minimize the use of fresh one has to minimize fresh arm yb ys yc Pollutant Composition

2. Foundation Elements Note:
2.3. Overview of Mass, Energy and Property Integration Targeting rules Note: The previous method can be simplified for a complex plant since no all equipment will required fresh utilities or discharge waste streams. We will identify those that do and apply the previous method Identifying equipment constraints can reduce fresh and waste streams with little process modifications, by working with minimum requirements

2. Foundation Elements The Composition-Interval Diagram (CID) (40)
2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach The pinch diagram is a very useful tool, however it has accuracy limitations common to any graphical method, therefore an algebraic approach that will overcome these limitations is presented The Composition-Interval Diagram (CID) This diagram shows the mass exchanged between the different streams, thermodynamically feasibility and the location of the pinch point The number of scales is equal to Nsp + 1, where Nsp is the number of lean streams. Each process is represented by a vertical arrow with supply and target compositions as the tail and head respectively. The horizontal lines are the composition intervals whose number is define as: (40) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements

Wj,kS = Ljc(xj,k-1 – xj,k) (42)
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach Within each interval it is possible to transfer mass from the rich stream to the lean stream and it is possible to transfer mass from the interval to any MSA that is in an interval below it Table of Exchangeable Loads (TEL) The TEL is used to determine the load of mass exchanged within each interval; for the waste stream the load is: Wi,kR = Gi(yk-1 – yk) (41) And the exchangeable load for the lean streams is: Wj,kS = Ljc(xj,k-1 – xj,k) (42)

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach Since one or more streams will pass through one or more intervals we can express the total load of the stream that passes through that interval k; for the waste and lean streams we have (43) (44) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach Note that mass can be transferred within each interval from a waste stream to a lean stream, as a result it is possible to transfer mass from a waste stream in a interval to a lean stream in a lower interval, the resulting mass balance is: (45) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements The graphical representation is: K
2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach The graphical representation is: Residual Mass from Preceding Interval K Waste Recovered from Waste Streams Mass Transferred to MSA’s Residual Mass to Next Interval

2. Foundation Elements Note: Initial residual mass for k = 0 is zero
2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach Note: Initial residual mass for k = 0 is zero The most negative value of the residual mass load indicates the excess capacity of MSA’s, in order to reduce it, one can either reduce the flow rate, or the composition of the MSA’s, one this is done one needs to recalculate and apply the previous procedure. The pinch will be represented at the location when the residual mass is zero. This result will be equal to the one given by the pinch diagram After reducing flow rate or concentration, the remaining load is the load to be removed but external MSA’s

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach Example 3 A lean MSA will be used to reduce the composition of a rich stream, the data is give in the table Calculate the number of intervals Calculate the compositions of each stream for the y and x scales Prepare de CID diagram Calculate a TEL table, using 41, 42 Calculate the cascade diagram, by 43,44

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach Composition Table

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach CID Table

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach TEL Table

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Cascade Diagram

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach The excess capacity of the MSA is kg/s of pollutant and the actual flow required for the separation is: (45)

2. Foundation Elements Recalculating the TEL and cascade diagram Pinch
2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach Recalculating the TEL and cascade diagram Pinch

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach The concentrations at which the pinch point is located are: y = x = The quantity leaving the bottom of the cascade diagram is the amount to be removed by external MSA’s, kg/s

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, with Minimum Number of Exchangers In order to minimize the number of mass exchangers to obtain a MOC solution, we will decompose the design problem in to two sub-problems one above and one below the pinch (46) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Feasibility Criteria By starting the synthesis of mass exchangers at the pinch point one can ensure that the options will not be compromised at later steps, due to the fact that the pinch point the all streams match at the minimum driving force e. The matching of streams will be done in two sections, above and below the pinch, two criteria must be applied to ensure feasibility (47) Stream Population (48) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Thermodynamic Feasibility
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Feasibility Criteria If the previous inequalities do not hold with the rich and lean streams/branches then splitting of one or more of them is required, as before stream splitting might be required to comply with the following inequalities (48) Thermodynamic Feasibility (49) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Network Synthesis Example 4 The following example will illustrate the procedure for network synthesis; given a process with two waste streams and two process MSA’s

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Network Synthesis The composition for waste and lean streams are shown in the table Number of Intervals = 7 Calculate the CID Calculate TEL Revise TEL

2. Foundation Elements CID
2.3. Overview of Mass, Energy and Property Integration Network Synthesis CID

2. Foundation Elements TEL
2.3. Overview of Mass, Energy and Property Integration Network Synthesis TEL

2. Foundation Elements Cascade Diagram

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Network Synthesis The excess load of the MSA’s is kg/s; using Equation 45 and reducing the excess capacity of S2 we have an actual flow of kg/s and a revise TEL and cascade diagram can be calculated, with its pinch point at interval 4 and compositions y, x1, x2 = , , 0.01, respectively

2. Foundation Elements TEL, revised

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Network Synthesis We will now define the number of mass exchangers Define feasibility criteria Match streams

2. Foundation Elements Cascade Diagram, revised Pinch Point

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Network Synthesis The following figure will aid during checking of the feasibility criteria R1 S2 S1 R2 Pinch Point G1 = 2.5 kg/s G2 = 1 kg/s L1/m1 = 2.5 kg/s L2/m2 = 1.95 kg/s

2. Foundation Elements Match: R1 – S1 R2 – S2
2.3. Overview of Mass, Energy and Property Integration Network Synthesis Match: R1 – S1 R2 – S2

2. Foundation Elements Mass Exchanged Loads R1 = 0.08375 kg/s
2.3. Overview of Mass, Energy and Property Integration Network Synthesis Mass Exchanged Loads R1 = kg/s S1 = kg/s Mass exchanged = kg/s R2 = kg/s S2 = kg/s Mass exchanged = kg/s

2. Foundation Elements Remaining load from R1 = 0.045 kg/s
2.3. Overview of Mass, Energy and Property Integration Network Synthesis Remaining load from R1 = kg/s Excess capacity of S2 = kg/s Note that these values are equal, due to the fact that there is no mass transferred trough the pinch. Now we proceed to match exchangers represented by circles with streams; the mass exchanged appears within the circles and composition in arrows. Load to be removed by external MSA is kg/s

R1 capacity not removed by S1 R2 transfers all its load
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Network Synthesis S2 R1 R2 5 kg/s 0.015 S1 2.5 kg/s 0.05 0.045 0.045 1 kg/s 0.03 x2 ** S2 can remove load x1 * R1 capacity not removed by S1 0.0135 0.0135 0.0165 0.0165 0.01 R2 transfers all its load S1 is depleted

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Network Synthesis In order to calculate the intermediate compositions leaving exchanger R2 – S2 use a material balance using Equation 37: x2 ** = /3 = x1* = /2.5 = 0.032

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Network Synthesis After completing the network design above the pinch we will proceed to do the same below the pinch R1 R2 S1 S3 External MSA Pinch Point L1/m1 = 2.5 kg/s G1 = 2.5 kg/s G2 = 1 kg/s

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Network Synthesis Checking feasibility (Eq. 49) determines that S1 has to be split in two since L1/m > Gi. There are many different combinations in order to achieve it, for this case we will split them arbitrarily and match the streams R1 R2 S1 S3 External MSA Pinch Point L11/m1 = kg/s L12/m1 = kg/s G1 = 2.5 kg/s G2 = 1 kg/s L1= 5 kg/s

2. Foundation Elements Match: R1 – S11 R2 – S12 Mass Exchanged Loads
2.3. Overview of Mass, Energy and Property Integration Network Synthesis Match: R1 – S11 R2 – S12 Mass Exchanged Loads R1 = kg/s S11 = kg/s Mass exchanged = kg/s R2 = kg/s S12 = kg/s Mass exchanged = kg/s

2. Foundation Elements Remaining load from R1 = 0.0082625 kg/s
2.3. Overview of Mass, Energy and Property Integration Network Synthesis Remaining load from R1 = kg/s Remaining load from R2 = kg/s In order to remove the remaining load from waste streams it is required to use external MSA’s (S3)

2. Foundation Elements S3 External MSA R1 R2 S1 Pinch Point
G1 = 2.5 kg/s G2 = 1 kg/s S3 External MSA R1 R2 S1 Pinch Point Calculate the Intermediate Compositions Can you Suggest another Configuration for S3? L1= 5 kg/s

Complete Network Pinch Point R1 R2 1 kg/s 0.03 S2 5 kg/s 0.015
0.045 0.045 S1 x2 ** x1 * 0.0135 0.0135 0.01 0.0165 0.0165 Pinch Point L1= 5 kg/s Complete Network S3

2. Foundation Elements Heat Exchange Networks
2.3. Overview of Mass, Energy and Property Integration Heat Integration Heat Exchange Networks Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements Heat Exchange Network
2.3. Overview of Mass, Energy and Property Integration Cold Streams In Hot Streams Out Heat Exchange Network Every plant requires energy to be transfer from a hot stream to a cold one; hence the importance a proper heat exchange network in order to have a positive impact in the economics and operation of any process Hot Streams In Cold Streams Out Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Heat Integration To define the HEN (Heat Exchange Network) problem first we need to define the following: A number of hot process streams that need to be cooled NH and a number of cold process streams that need to be heated NC, we need to synthesize a network that will achieve the transfer of heat at minimum cost For hot streams the heat capacity can be expressed as: (50) For u = 1,2,…NH

2. Foundation Elements In addition for the cold streams we have:
2.3. Overview of Mass, Energy and Property Integration Heat Integration In addition for the cold streams we have: (51) For v = 1,2,…NC A number of cold and hot streams is available whose supply and target temperatures are known but not their flow rates. In order to design a HEN the following questions need to be answered:

2. Foundation Elements What is the Optimal configuration
2.3. Overview of Mass, Energy and Property Integration Heat Integration What is the Optimal configuration How should the hot and Cold streams be matched? What is the optimal heat load to be removed/added by each utility? Which heating/cooling utilities should be used Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Heat Integration In order to have heat transfer between two streams the following relationship will established a correspondence between the hot and cold streams temperature: (52)

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Heat Integration A special case of mass exchanged is the one that compares the heat exchanged problem corresponding T, t, DTmin with yi,xj and ej respectively, and having mj, bj equal to zero

2. Foundation Elements HE T T H NOTE:
2.3. Overview of Mass, Energy and Property Integration Heat Integration HE NOTE: The order of X and Y axis used here are different from what has been commonly used in the literature. The reason is that there is a strong interactions between mass and energy making the enthalpy expression non linear function of temperature therefore it is easier to have enthalpy in function of temperature, this specially important when combining mass and heat integration T v. H Approach T DT min T HE vs. T Approach H Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Heat Integration The procedure use to set up the pinch diagram is exactly the same as the one use for mass integration, by placing the hot and cold streams temperatures in the diagram, starting by their supply temperature as the tail of an arrow and the target temperature as the head of an arrow. The following equation can be used to calculate the vertical distance or heat loss by the hot stream (53) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Heat Integration And for the heat gained by the cold stream we have: To construct the pinch diagram we have: (53) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements HE HE HH2 HC2 HH1 HC1 C2 H2 C1 H1 T
2.3. Overview of Mass, Energy and Property Integration Heat Integration HE HH2 HH1 HE HC2 HC1 C2 H2 C1 H1 T1t T2t T1s T2s T T t1t t2t t1s t2s t = T - DTmin Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

Integrated Heat Exchange
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Heat Integration Heat Exchanged Minimum Heating Utility How to construct the pinch diagram? Cold Composite Stream Integrated Heat Exchange Hot Composite Stream Minimum Cooling Utility T Thermal Pinch Point t = T - DTmin Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Heat Integration The analysis of the thermal pinch diagram is as follows: The cold composite curve cannot be slid down any further otherwise there will not be thermal feasibility, if the cold composite is moved up less heat integration is possible therefore more utilities are required Above the pinch there is a surplus of cooling and below the pinch there is a surplus of heating utilities Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Heat Integration A similar analysis as the one used for mass integration can be done in order to apply an algebraic cascade diagram, the number z of intervals is: (54) To construct a Table of Exchangeable Heat Load TEHL we need: (55) (56) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Heat Integration The collective total load for the hot and cold process streams are: (57) (58) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Heat Integration As it was mentioned for mass exchanged, it is feasible to transfer heat from a hot process stream to a cold one within each temperature interval, a heat balance around a temperature interval yields: Residual Heat from Preceding Interval Z Heat Removed by Process Cold Stream Heat Added by Process Hot Stream Residual Heat to Next Interval

2. Foundation Elements The resulting heat balance is:
2.3. Overview of Mass, Energy and Property Integration Synthesis of MEN, Algebraic Approach The resulting heat balance is: (59) Source : Pollution Prevention through Process Integration, M. M. El-Halwagi

2. Foundation Elements The resulting TID is:
2.3. Overview of Mass, Energy and Property Integration Heat Integration The resulting TID is:

Property Integration:
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration Property Integration: “Functionality based holistic approach to the allocation and manipulation of streams and processing units which is based on tracking, adjustment, assignment and matching of functionalities throughout the process” Source : Property Integration: Componentless Design Technique and Visualization Tools

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration Component mass balances are an integral part of process design. There are several design problems in which the designer is interested in a group of properties such as viscosity, corrosion, density etc. Solvent selection is a clear example in which one is interested in its volatility, viscosity, equilibrium distribution, instead of its chemical constituents. Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration Property visualization tools are limited to 3 properties, an algebraic approach is used to deal with more complex cases. The advantage of visualization tools is based on the insides that give of the process, and how the design problem can be addressed. In order to apply this method to a set of properties we need to introduced the concept of cluster Properties are not conserved, as a result they cannot be tracked among units without using mass balances, the problem is that often is not possible to identify every single chemical species e.g. Gasoline, Dowtherm

2. Foundation Elements Cluster
2.3. Overview of Mass, Energy and Property Integration Property Integration Cluster “Defines as condensed surrogate properties which can be used to characterize the complex mixture and can be tracked my mapping the raw properties of infinite compounds onto finite domains” Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration The problem statement is: given a number of process streams Ns which contain the chemical species of interest, can be used in a number of sinks Nsinks (process units) in order to optimize a a desired objective e.g. minimize usage of fresh resources, maximize use of process resources, minimize cost of external streams etc. Each sink has a set of constraints defined as: Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration Each stream can be characterized by Nc raw properties with a mixing rule that characterized a given stream (60) Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements pi,s can be normalized as:
2.3. Overview of Mass, Energy and Property Integration Property Integration pi,s can be normalized as: (61) An augmented property index (AUP) for each stream s, is define as the summation of the dimensionless raw property operators: (62)

2. Foundation Elements Ci,s is the cluster for property i in stream s
2.3. Overview of Mass, Energy and Property Integration Property Integration Ci,s is the cluster for property i in stream s (63) For any stream s, the sum of clusters must be conserved adding up to a constant e.g. unity (64) (65)

Processed Sources (back to process)
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration The framework for allocation and interception for property integration is: Property Integration Network (PIN) u = 1 s =1 u = 2 . . Processed Sources (back to process) s =1 u = Nsinks Sources Segregated Sources Sinks

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration Consider a cluster of stream s to unit u, with three targeted properties i, j, k we have: (66) (67)

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration (68) In order to obtained an overestimation of the feasibility region we have: (69)

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration (70) (72) (71) (73) In order to allocate, mix or intercept streams one needs to identify a feasibility region for the sinks, by using the following relationships:

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration (74) These points will now need to be plotted in a ternary diagram will be shown next Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration

2. Foundation Elements Ci Cj,smin Ci,smax Cj,smax Cj,smin Cj Ck
2.3. Overview of Mass, Energy and Property Integration Ci Property Integration Overestimated Region We need to find the true estimation of the feasibility region (for a more detailed explanation of how to obtained these results, review the references at the end of the module) Cj,smin Ci,smax Cj,smax Cj,smin Cj Ck Ck,smin Ck,smax

2. Foundation Elements Ci Cj Ck True Region
2.3. Overview of Mass, Energy and Property Integration Ci Property Integration True Region Cj Ck

2. Foundation Elements Ci Y (0.866, 0.50) S Ys Ci,s (1, 0) (0, 0) Cj X
2.3. Overview of Mass, Energy and Property Integration Property Integration In order to plot these diagrams in a spread sheet, we need to related this ternary coordinates in a X vs. Y plane as follows: Ci Y (0.866, 0.50) S Ys Ci,s (1, 0) (0, 0) Cj X Ck Xs

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration The equations that relate X vs. Y with ternary coordinates are: (75) (76) Source : Component less design of recovery and allocation systems: a functionality based approach

Costmixture = xs (Costs – Costs+1) + Costs+1
2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration The next step is to set up optimization rules as follows: Relating cost to fractional contribution of sources Consider two sources s and s+1 that are mixed to satisfy sinks constraints, let xs and xs+1 denote the fraction contribution of sources s and s+1 to the total flow rate of the mixture. Let s be more expensive than s+1, as Costs>Costs+1, therefore we have: Costmixture = xs (Costs – Costs+1) + Costs+1 From the previous equation we can conclude that in order to minimize the cost of the mixture xs must be minimized (77) Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements Rule No. 1
2.3. Overview of Mass, Energy and Property Integration Property Integration Rule No. 1 “When two sources (s and s+1) are mixed to satisfy the property constraints of a sink with source s being more expensive than s+1, minimizing Costmixture is achieved by selecting the minimum feasible value of xs” Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration Derivation of relationships between minimum cluster arms (bs) and minimum fractional contribution xs xs cannot be visualized in a ternary diagram, the lever arm on the ternary cluster diagram represents another quantity defined as bs, to relate both quantities the AUP is described by equation 62 (78) (79) Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements Rearranging we have:
2.3. Overview of Mass, Energy and Property Integration Property Integration Rearranging we have: (80) Taking the first derivative: (81) Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements Rearranging and simplifying:
2.3. Overview of Mass, Energy and Property Integration Property Integration Rearranging and simplifying: (82) From the previous development rule 2 is obtained: Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements Rule No. 2
2.3. Overview of Mass, Energy and Property Integration Property Integration Rule No. 2 “On a ternary cluster diagram, minimization of the cluster arm of a source corresponds to minimization of the flow contribution of that source; minimum bs corresponds to minimum xs” Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration Consider the case of fresh external source F, the objective is to minimize its use. A process internal stream W that can be recycled or reused to reduce the use of F. It is desired to mixed them in order to obtain a minimum cost mixture that satisfy sink constraints, the feed to the sink is subject to a number of property constraints that can be mapped in a cluster diagram as follows Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements Ci W a Sink Optimum bF b c F Cj Ck
2.3. Overview of Mass, Energy and Property Integration Ci Property Integration Minimum distance, this is a necessary condition only. For sufficiency AUP and flow rate must be matched as well W a Sink Optimum bF b Multiple mixtures c F Cj Ck Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements Ci W2 W1 bF Sink F Cj Ck Multiple sources case:
2.3. Overview of Mass, Energy and Property Integration Ci Property Integration Multiple sources case: For multiple sources the line connecting W1 and W2 represents the possible mixtures, the optimal mixing point is the one that gives the minimum bs W2 W1 bF Sink Multiple mixtures F Cj Ck Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements Ci W Wintercepted Sink F Cj Ck
2.3. Overview of Mass, Energy and Property Integration Ci Property Integration Adjusting properties When the process stream W target cannot be met, the stream can be adjusted via an interception device e.g. separation, reaction etc W Wintercepted Sink Adjusting properties will change the cluster value F Cj Ck Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration For a selected mixing point and a desired bs, the fresh arm can be drawn to determine the desired location of the desired location of Wintercepted. Moreover, since the values of AUP are known for F and the mixing point of the sink, one can plug the targeted value of xF into Equation 78 to calculate the desired value of AUP for Wintercepted. Once Wintecepted and AUP are known, we can solve the cluster equations backwards to calculate the raw properties of Wintercepted Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration This is the minimum extent of interception to achieve maximum recycle of W or minimum usage of F since the additional interception will still lead to the same target or minimum usage but will result in a mixing point inside the sink and not just on the surrounding of the sink Once the task for interception is define, conventional process synthesis techniques can be apply to develop the design and operating parameters for the interception system. The same procedure can be repeated for multiple mixing points resulting in the task identification of the locus for minimum extend to interception Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements Ci W Sink F Cj Ck Locus Identification
2.3. Overview of Mass, Energy and Property Integration Ci Property Integration Locus Identification Locus for minimum extent of interception W Sink F Cj Ck Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements Multiplicity of Optimal values of AUP
2.3. Overview of Mass, Energy and Property Integration Property Integration Multiplicity of Optimal values of AUP A cluster point made of C1sink, C2sink, C3sink can correspond to multiple combinations of properties that can give the same cluster values. As a result one can have nMultiple, points within the feasible property domain giving a single cluster value. Three conditions must be satisfied in order to insure feasibility of the sources or mixture of sources going into a sink: 1. The cluster value of the source must be contain within the feasibility region of the sink on the cluster diagram 2. The values of AUP for the source and the sink must match 3. The flow rate of the source must lie within the acceptable feed flow rate range of the sink Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration From Rule No. 1 minimizing xs will minimize CostMixture, therefore we need to select an AUPm (given for the feasible properties p1,m, p2,m, p3,m) that will be minimized by the following relationship between AUPm and xs. (83) (84) Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration To minimize xs and as a result the cost we should select: (85) (86) If no mixture matches the AUP selected for the sink for the case given by Equation 84 then one has to decrease the value of the sink’s AUP starting with Argmax AUPm till getting the highest value of AUPm within the feasible range of AUP which matches that of the mixture; same procedure is used for Equation 85, by increasing the value of sink’s AUP starting with Argmin AUPm till getting the highest value contained within the feasible range of the sink which matches that of the mixture Source : Component less design of recovery and allocation systems: a functionality based approach

2. Foundation Elements 2.3. Overview of Mass, Energy and Property Integration Property Integration Currently research is being undertaken to design tools that will cover cases for 1, 2 and more than three properties. This is a very dynamic and changing field of research Source : Component less design of recovery and allocation systems: a functionality based approach

TIER II

3. Case Study 3.1. Tire to Fuel Processing Plant A tire to fuel processing plant flow sheet is shown in the next slide which is a more complete description for the one given in Example 2. Tire shredding is achieved by using high pressure water jets. The shredded tires are fed to the process while the spent water is filtered. The wet cake collected from the filtration system is forwarded to solid waste handling. The filtrate is mixed with 0.20 kg/s of fresh water makeup to compensate for water losses with the wet cake, 0.08 kg water/s and the shredded tires 0.12 kg water/s. The mixture of filtrate and water make up is fed to a high pressure compression station for recycling the shredding unit. Due to the pyrolisis reactions, 0.08kg water is generated

3. Case Study 3.1. Tire to Fuel Processing Plant The plant has two primary sources for waste water, the decanter (0.20 kg water/s and the seal pot 0.15 kg/s. The plant has been shipping the waste water for off-site treatment. The cost of wastewater transportation and treatment is $0.02/kg leading to a wastewater treatment cost of approximately $129,000/yr

Waste water to treatment 0.20 kg/s 500 ppmw
3. Case Study To Atmosphere Flare Tire to Fuel Plant Flow Sheet Gaseous Fuel Condenser Waste water to treatment 0.20 kg/s 500 ppmw Reactor Off-Gases Decanter Waste water to treatment, 0.15 kg/s 0 ppmw Seal Pot Tires Fresh water 0.15 kg/s 0 ppmw Light Oil Flare Gas, 0.15 kg/s 200 ppmw Shredded Tires Pyrolisis Reactor Water Jet Shredding Separation Finishing Liquid Fuel Wet Cake to Solid Handling 0.08 kg/s, 0 ppmw Filtration Fresh Water 0.20 kg/s ppmw Compression

3. Case Study 3.1. Tire to Fuel Processing Plant The plant wishes to stop off site treatment of wastewater to avoid the cost ($129,000/yr) and alleviate legal liability concerns in case of transportation accident or inadequate treatment of wastewater treatment. For capital budget authorization, the plant has the following economic criteria:

3. Case Study Economic Data
3.1. Tire to Fuel Processing Plant Economic Data Fixed cost of extraction system associated with S2. $ = 130,000 (flow rate of wastewater, kg/s)0.60 Fixed cost of adsorption system associated with S3, $ = 800,000 (flow rate of wastewater, kg/s)0.72 Fixed cost of stripping system associated with S4, $ = 280,000 (flow rate of wastewater, kg/s)0.66 A biotreatment facility that can handle 0.35kg/s waste water has a fixed cost of $260,000 and an annual operating cost of $72,000/yr Technical Data Water may be recycle to two sinks: the seal pot and the water-jet

3. Case Study 3.1. Tire to Fuel Processing Plant Compression station. The following constrains on flow rate and composition of the pollutant (heavy organic) should be satisfied: Seal Pot 0.10 £ Flow rate of feed water (kg/s) £ 0.20 0 £ Pollutant content of feed water (ppmw) £ 500 Make up to water-jet compression station 0.18 £ Flow rate of make up water (kg/s) £ 0.20 0 £ Pollutant content of make up water (ppmw) £ 50

3. Case Study 3.1. Tire to Fuel Processing Plant Solution We will start with an overall mass balance, note that 0.12 kg/s of water are lost in the process and cannot be re used 0.2 kg/s to Compression Station 0.08 kg/s from Wet Cake Water Generation 0.08kg/s 0.15 kg/s from Seal Pot 0.15 kg/s to Seal Pot 0.2 kg/s from Decanter

3. Case Study 3.1. Tire to Fuel Processing Plant Solution From the overall mass balance we can set the targets for fresh use and wastewater production 0.2 kg/s 0.08 kg/s Water Generation 0.08kg/s No Fresh Water 0.15 kg/s 0.08 kg/s Wastewater 0.35 kg/s The source diagram is shown in the next slide

3. Case Study WW from Decanter Compression Station WW from Seal Pot
WW from Wet Cake

3. Case Study 3.1. Tire to Fuel Processing Plant From the source/sink diagram we can see that wastewater from the decanter can be accepted by the seal pot only; the outlet composition of the wastewater coming from the seal pot is 400 ppmw (from the pinch diagram) as shown in Example 2

Composition from Seal Pot
3. Case Study 3.1. Tire to Fuel Processing Plant Mass Exchanged 10-6 Composition from Seal Pot

3. Case Study Seal Pot W W from Decanter W W from Seal Pot
Compression Station Seal Pot W W from Wet Cake

3. Case Study 3.1. Tire to Fuel Processing Plant Wastewater coming from the seal pot cannot be recycled directly to the compression station due to its high pollutant composition, therefore it is required to treat it using an external MSA as shown in Example 2; for this case S4 is the best stripping agent, which will bring down the composition to 50ppmw

3. Case Study 3.1. Tire to Fuel Processing Plant Seal Pot
WW from Stripper WW from Decanter WW from Seal Pot Compression Station Seal Pot WW from Wet Cake

3. Case Study Tire to Fuel Plant Flow Sheet (Revised) Tires Stripper
To Atmosphere Flare Tire to Fuel Plant Flow Sheet (Revised) Gaseous Fuel Condenser Reactor Off-Gases Decanter Stripper Seal Pot Tires Light Oil Shredded Tires Flare Gas Pyrolisis Reactor Water Jet Shredding Separation Finishing Liquid Fuel Filtration Wet Cake to Solid Handling Compression

3. Case Study 3.1. Tire to Fuel Processing Plant Now we will proceed to compare the different alternatives in order to make a decision. For the bio-treatment plant we have: Annualized Saving Cost = $129,000/yr - $72,000/yr = $57,000/yr Pay Back = $260,000 / $57,000/yr = 4.56 years For the recycling/stripping system: Annualized Saving Cost = $129,000/yr - $84,270.5/yr = $44,729.5/yr Fixed Cost of Stripping = $280,000(0.2)0.66 = $96,791.6 Pay Back = $96,791.6 / $44,729.5/yr = 2.16 years

3. Case Study 3.1. Tire to Fuel Processing Plant From the results we can conclude that the recycling/stripping alternative is the best economical and technical option. We need to point out that the water contained in the wet cake will not be recovered or treated

3. Case Study 3.2. Pulp and Paper Process Plant Wood chips are chemically cooked in a Kraft digester using a white liquor (mainly NaOH and Na2S). Black liquor (spent white liquor) is converted back to white liquor by a recovery cycle. The digested pulp is then bleached to obtain bleached pulp (fiber I). The plant also buys pulp from another plant (fiber II), the pulp is then sent to two different paper machines (Sink I and Sink II). Paper machine I uses 200 tons/hr of fiber I. A mix of fiber I and II (20 ton/hr and 30 ton/hr, respectively) is fed to paper machine II. Due to interruptions and other disturbances, a certain amount of partly and completely manufactured paper is rejected

3. Case Study 3.2. Pulp and Paper Process Plant The rejected fiber is referred as broke, which is passed through a hydro-pulper and a hydro-sieve resulting in two streams, an underflow which is burnt and an overflow which goes to waste treatment. Part of the broke contains fiber which can be recycle for paper making. The properties that are important for the process are: Objectionable material (OM), undesirable material in the fiber Reflectivity (R), reflectance of an infinite thick material compared to a standard Absorption coefficient (k), measure of absorptivity of light into the fibers

3. Case Study 3.2. Pulp and Paper Process Plant The mixing rules are:

3. Case Study Wood Chips 200 t/hr Pulp Fiber I Paper I Kraft Digester
OM =0.0 k = R = 0.85 Wood Chips 200 t/hr Pulp Fiber I Paper I Kraft Digester Bleaching Paper Machine I White Liquor Black Liquor OM =0.085 k = R = 0.95 Broke (Overflow) Reject 20 t/hr Chemical Recovery Cycle Hydro- Sieve Hydro- Pulper Underflow Reject Fiber II Paper Machine II Paper II OM =0.0 k = R = 0.95 30 t/hr

3. Case Study 3.2. Pulp and Paper Process Plant

3. Case Study 3.2. Pulp and Paper Process Plant Determine the optimal allocation of the three sources, fiber I, II and broke for a direct recycle reuse without new equipment In order to maximize use of process resources and minimize wasteful discharge (broke) how should the designer change the properties of the broke as to achieve maximum recycle?

3. Case Study 3.2. Pulp and Paper Process Plant Solution In order to translate the data from property domain to cluster domain we will select arbitrarily reference values as:

3. Case Study 3.2. Pulp and Paper Process Plant We will proceed to calculate the cluster values for the sources as follows:

3. Case Study Similarly for Fiber I and II we obtain:
3.2. Pulp and Paper Process Plant Similarly for Fiber I and II we obtain:

3. Case Study 3.2. Pulp and Paper Process Plant Now we can proceed to transform the ternary points to X vs. Y plot

Broke Fiber I Fiber II COM Ck CR

3. Case Study 3.2. Pulp and Paper Process Plant Now we need to proceed to locate sinks in the diagram by using the point illustrated in slide 187 For Sink I:

3. Case Study For Sink I, continuation:
3.2. Pulp and Paper Process Plant For Sink I, continuation:

COM Broke Fiber II CR Ck Sink I Fiber I

3. Case Study Similarly for Sink II we have:
3.2. Pulp and Paper Process Plant Similarly for Sink II we have:

COM Broke Sink II Fiber I Fiber II CR Ck Sink I

COM CR Ck 3.2. Pulp and Paper Process Plant
Now we proceed to identify the minimum distance for Sink I, that will minimize the use of fresh sources 3.2. Pulp and Paper Process Plant COM Broke Fiber II CR Ck Sink I Fiber I

In order to get the length of the arm to obtain bs one can measure it from the graph or:
COM or By Equation 65 CR Ck (0.27, 0.85)

3. Case Study The distance between mixture and broke is:
3.2. Pulp and Paper Process Plant The distance between mixture and broke is: The Total distance is:

3. Case Study Therefore bs is: Using Equation 65:
3.2. Pulp and Paper Process Plant Therefore bs is: Using Equation 65:

3. Case Study From Equation 86, AUPmoptimum = 2.035 Therefore xs is:
3.2. Pulp and Paper Process Plant From Equation 86, AUPmoptimum = 2.035 Therefore xs is:

TIER III

4. Open Ended Problem An ethylene/ethyl benzene plant is shown in the next flow sheet. Gas oil is being cracked with steam in a pyrolysis furnace to form ethylene, low BTU gases, hexane, heptanes, and heavier hydrocarbons. The ethylene is then reacted with benzene to form ethyl benzene. Two waste water streams are formed one of the streams is the quench water recycle for the cooling tower and the second one is the waste water from the ethyl benzene portion of the plant. The primary pollutant present in the two waste water streams in benzene. Benzene must be removed from the waste water that will be use to quench the cooling tower, coming from the settling unit to a concentration of 180ppm before it can be recycled back to the cooling tower and the boiler water treatment process. Benzene must also be removed from the waste water stream coming from the lower separation unit down to a composition of 380ppm before the waste water stream can be sent to biotreatment

Recycle Quenched Water Hexane 0.8kg/s 10ppmw Gas Oil
FreshWater Low BTU gases Recycle Quenched Water Hexane 0.8kg/s 10ppmw Gas Oil Pyrolysis Furnace Cooling Tower Upper Separation Heptane 0.4kg/s 17ppmw Steam Heavy Hydrocarbons Benzene Ethyl benzene Reactor FreshWater Ethylbenzene Boiler Water Treatment Settling Refuse Vent Fuel Lower Separation Waste water 150kg/s 1100ppm Waste water 70kg/s 2100ppm To Biotreatment

4. Open Ended Problem The heptane and hexane streams will be used to recover part of the benzene, the desired final composition of them is unknown and has to be determined by the engineer, after which they are sent to finishing and storage. The mass transfer driving forces e1 and e2, should be at least 25,000 and 29,000ppmw respectively. The equilibrium data for benzene transfer from waste water to hexane (1) and heptane (2) are: y = 0.012x1 y = 0.009x2 Where y, x1 and x2 are in mass fractions. Two external MSA are being considered for removing of benzene; air and activated carbon. Air is compressed to 2 atmospheres before stripping. Following stripping, benzene is separated from air using condensation.

4. Open Ended Problem Henry’s law can be used to predict equilibrium for the stripping process. Activated carbon is regenerated using steam in a ratio of 2kg steam : 1 kg of benzene adsorbed on activated carbon. Make up at a rate of 1.2% of recirculating activated carbon is needed to compensate for losses due to regeneration and deactivation. Over the operating range, the equilibrium relation for the transfer of benzene from waste water onto activated carbon can be described by: y = 6.8x10-4x4

4. Open Ended Problem Label the rich and lean streams
Construct a pinch diagram, identify pinch location, minimum load of benzene to be removed by external and excess capacity of MSA’s Consider the four MSA’s to choose from and find the MOC needed to remove benzene. Use the cost data found in slide 97 Apply the algebraic approach Design the network for the plant and draw a modified flow sheet Comment on your results, what limitations do you think have the methods used in the calculations if any, what conclusions can you draw based on your results?

5. Acknowledgments I wish to thank for their cooperation and guidance:
Dr. Mahmoud M. El-Halwagi Professor Texas A&M Dr. Jules Thibault Professor University of Ottawa Dr John T. Baldwin Professor Texas A&M Dr. Dustin and Georgina Harrel Texas A&M Vasiliki Kazantzi PhD student Texas A&M Qin Xiaoyun Researcher Candidate Texas A&M Daniel Grooms PhD student Texas A&M William Acevedo, April 2004

References El-Halwagi M. Mahmoud, Pollution Prevention through Process Integration Systematic Design Tool, Academic Press, 1997 El-Halwagi M. Mahmoud, Glasgow M. Ian, Eden R. Mario, Qin Xiaoyun, Property Integration: Componentless Design Techniques and Visualization Tools, Texas A&M Kazantzi V., Harell D., Gabriel F., Qin X., El-Halwagi M.M., Property Based Integration For Sustainable Design, AIChE Annual Meeting, 2003 Seider D. Warren, Seader J.D., Lewin Daniel R., Product and Process Design Principles, Wiley International, 2004, 2d ed Shelley, M.D. and El-Halwagi M.M., Component-less Design of Recovery and Allocation Systems: A Functionality based Clustering Approach, Computers and Chemical Engineering, 24, , 2000 Qin X., Gabriel F., Harell D., El-Halwagi M.M., Algebraic Techniques for Property Integration Via Componentless Design, Texas A&M

Introduction to Process Integration

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