Structure and Synthesis of the Process Flow Diagram

Slides:



Advertisements
Similar presentations
Hierarchy of decisions
Advertisements

Methanol Project Design a plant to make methanol from synthesis gas to supply a future market in direct methanol fuel cells.
Reactor-Separator-Recycle Networks Chapter 8 Terry Ring.
Hierarchy of Decisions LEVEL 3 : reactorseparator products purge feeds Liquid ? Liquid / Vapor ? Vapor ?
Kinetics Class #4 OB: reactions that are in dynamic equilibrium and how to “push” them forward, or reverse using LeChatelier's Principle.
Self-Optimizing Control of the HDA Process Outline of the presentation –Process description. –Self-optimizing control procedure. –Self-optimizing control.
R Pharmaceuticals Waste Incineration & Heat Recovery at Roche Ireland Ltd. Andrew Carden.
Chapter 19 Green Chemistry.
Fuel Cell Design Chemical Engineering Senior Design Spring 2005 UTC.
CHEN 4460 – Process Synthesis, Simulation and Optimization Dr. Mario Richard Eden Department of Chemical Engineering Auburn University Lecture No. 3 –
Group 6: Jacob Hebert, Michael McCutchen, Eric Powell, Jacob Reinhart
Structure and Synthesis of Process Flow Diagrams ENCH 430 July 16, 2015 By: Michael Hickey.
PROJECT AND STUDY DRAWINGS & DIAGRAMS
Chapter 1 - Chemical Process Diagrams
Chemical Engineering Plant Design
Proprietary work product, not for reproduction 1 BIOMASS GASIFIER 20 MW POWERPLANT Energy & Environmental Integrators Note! This system can be scaled from.
Chemical Engineering Plant Design
Hierarchy of Decisions
Chapter 6 Pollution Prevention for Unit Operations – Part 2.
Heuristics for Process Design
Chemical Engineering Plant Design Lek Wantha Lecture 05 Input-Output Structure of the Flowsheet.
THE CHEMICAL INDUSTRY Revised from:
INPUT-OUTPUT STRUCTURE OF THE FLOWSHEET
Production of Syngas and Ethanol Group II. Definition of Syngas Syngas is the abbreviated name for synthesis gas. It is a gas mixture that comprises of.
Combustion Analysis Compounds containing C, H and O are routinely analyzed through combustion in a chamber like this C is determined from the mass of.
Coal industry. Let my fuhrer Daniel give us some information about coal that we have already learned.
Plot Summary Petroleum coke is a major byproduct that historically has been used as a substitute for coal in power production or as a fuel in cement manufacture.
Chapter 8 Part 0 – Hierarchical Design Procedures.
Overview of Methanol Model
Lecture 22 Fuels. Reaction Rate. Electrolysis. Liquid, Solid, and Gaseous Fuels Reaction Rates Oxidation and Reduction Chapter 11.6 
Prentice Hall © 2003Chapter 15 Chapter 15 Chemical Equilibrium CHEMISTRY The Central Science 9th Edition David P. White.
Example of Process with Recycle: TOLUENE HYDRODEALKYLATION
 Fuel cells transform chemical energy from fuels such as hydrogen and methanol into electrical energy  The fuel is oxidised by oxygen from the air.
Plot Summary Petroleum coke is a major byproduct that historically has been used as a substitute for coal in power production or as a fuel in cement manufacture.
GREEN CHEMISTRY 2010/2011. background… Taken in large part from Paul L. Bishop’s Pollution Prevention – Fundamentals & Practice, Chapter 9.
CHEMICAL PROCESS DIAGRAM
Learning objective: To show the importance of ethanol as a chemical To find out about three routes to making ethanol To evaluate the alternative routes.
Prentice Hall © 2003Chapter 15 Chapter 15 Chemical Equilibrium CHEMISTRY The Central Science 9th Edition David P. White.
CHE Combustion Reactions Fuels –Gaseous –Liquid –Solid Oxidants Elementary combustion reactions Theoretical and excess air.
Gas Turbine Power Plant
Yousif Alqatari, Michael Seas, Christian Jones and Eric Fabrizius
Hierarchy of Decisions
Team Echo Leader: Matt Levy
ChE 402: Chemical Reaction Engineering
Natural Gas Processing I Chapter 2 In-feed System
5.7 - Green chemistry In industry
Objectives Understand how a fuel cell makes electricity
Energy, Chemistry, and Society
Engineering Chemistry
Crude oil Treatment process
THERMOCHEMISTRY OF COMBUSTION
Chemical Process Diagrams
LQ: How are pollutants formed?
Production of Sesame Oil
The most effective way of communicating information about a process is through the use of flow diagrams. Block Flow Diagram (BFD) Process Flow Diagram.
carbon capture and storage (CCS)
Heuristics for Process Design
Crude oil Treatment process
CHPE308 Engineering Economy
Unit 4: Chemical Equilibrium
CHPE404 Engineering Economy Estimation of Manufacturing Costs
Green Chemistry.
Chemical Process Industries
Lesson # 3 Le Chatelier’s Principle
Chapter 15 Chemical Equilibrium
CHAPTER 2 Description of Chemical Processes
Hierarchy of Decisions
Reactor-Separator-Recycle Networks
2.3 Optimizing Production Chemical Industry
Synthesis of the PFD from the Generic BFD
Presentation transcript:

Structure and Synthesis of the Process Flow Diagram Chemical Engineering Department West Virginia University Copyright - R. Turton and J. Shaeiwitz, 2008

Copyright - R. Turton and J. Shaeiwitz, 2008 Outline Generic Structure of Processes Process Design Hierarchy Batch vs. Continuous Processes Input – Output Structure Recycle Structure Copyright - R. Turton and J. Shaeiwitz, 2008

Generic Structure of Process Flow Diagrams Often the environmental controls are centralized (wastewater treatment, sour water stripper, incinerators, etc.) and do not show directly on a process PFD – but they are there. Also some pollution prevention devices are present on process equipment, e.g., NOx reduction on fired heaters, etc. Copyright - R. Turton and J. Shaeiwitz, 2008

Generic Structure of Process Flow Diagrams Generic PFD may have varying topology but always contains a subset of the 5 basic blocks. Copyright - R. Turton and J. Shaeiwitz, 2008

Generic Structure of Process Flow Diagrams Identify each equipment with one of the five blocks – Purple – recycle, grey – reactor prep, flesh – reaction, green – separator prep, and green-grey - separation C6H5CH3+H2  C6H6 + CH4 Copyright - R. Turton and J. Shaeiwitz, 2008

Environmental Control End of Pipe vs. Green Approach Most significant changes obtained by changing process chemistry within reactor – eliminate/minimize unwanted by-products End of Pipe vs. Common Units Fired Heaters - excess oxygen - low sulfur fuel - NOX control Wastewater - biological/sedimentation/ filtration Copyright - R. Turton and J. Shaeiwitz, 2008

Copyright - R. Turton and J. Shaeiwitz, 2008 Approach of Douglas1 Five step process to tackle a conceptual process design Batch vs. continuous Input-output structure Identify and define recycle structure of process Identify and design general structure of separation system Identify and design heat-exchanger network or process energy recovery system 1 – Douglas, J.M., Conceptual Design of Chemical Processes, McGraw-Hill, NY, 1988 Copyright - R. Turton and J. Shaeiwitz, 2008

Copyright - R. Turton and J. Shaeiwitz, 2008 Batch vs. Continuous Variables to Consider: Size Batch < 500 tonne/yr ~ 1.5 tonne/day (< 2 m3 of liquid or solid per day) Continuous > 5,000 tonne/yr Copyright - R. Turton and J. Shaeiwitz, 2008

Batch vs. Continuous(cont.) Flexibility Batch can handle many different feeds and products – more flexible Continuous is better for smaller product slate and fewer feeds Copyright - R. Turton and J. Shaeiwitz, 2008

Batch vs. Continuous(cont.) Continuous allows the process to benefit from the “Economy of Scale,” but the price is less flexibility Batch – scale-up often consists of multiple parallel units Copyright - R. Turton and J. Shaeiwitz, 2008

Batch vs. Continuous(cont.) Other Issues Accountability and quality control – FDA requires batch accountability Safety – batch is more accident prone Scheduling of equipment – may be most important issue Seasonal demands – e.g., antifreeze, food products Pharma companies are often batch because of FDA (Food and Drug Administration) requirements for accountability and ease of recall of faulty products Scheduling of batch products is covered in Chapter 3 Copyright - R. Turton and J. Shaeiwitz, 2008

Input – Output Structure (Process Concept Diagram) This cloud diagram is even more primitive than the traditional block flow process diagram discussed in Chapter 1. Copyright - R. Turton and J. Shaeiwitz, 2008

Copyright - R. Turton and J. Shaeiwitz, 2008 Input-Output on PFD This is equivalent to the previous diagram Copyright - R. Turton and J. Shaeiwitz, 2008

Input-Output – Utility Streams Note that utilities are not considered in the input-output structure since they are not (usually) process streams. Utilities for pumps and compressors are usually electricity and are not shown on the PFD. Copyright - R. Turton and J. Shaeiwitz, 2008

Other Input – Output Issues Purify Feed ? Feed purity and trace components Small quantities and “inerts” – do not separate Example H2 in feed contains CH4 CH4 does not react so – do not remove Copyright - R. Turton and J. Shaeiwitz, 2008

Other Input – Output Issues (cont) If separation of impurities is difficult – Do not separate Azeotrope – (water and ethanol) Gases – (requires high P and low T) How would you remove CH4 from H2? Copyright - R. Turton and J. Shaeiwitz, 2008

Other Input – Output Issues (cont) If impurities foul or poison catalyst then separate Sulfur – Group VIII Metals (Pt, Pd, Ru, Rh) CO in platinum PEM fuel cells S and CO are big problems for PEM fuel cells (because of platinum) Note: S and CO may be present in very small amounts (ppm) Copyright - R. Turton and J. Shaeiwitz, 2008

Other Input – Output Issues (cont) If impurity reacts to form difficult-to-separate material or hazardous product then separate Phosgene Example CH4 + H2O CO + 3H2 CO + Cl2 COCl2 Any H2 HCl Note that phosgene is so dangerous that it is no longer transported within the US and is always made on site. In this example, phosgene is used in the the production of polyurethane precursors and any HCL in the phosgene causes problems downstream – therefore great efforts must be made to eliminate its production. Copyright - R. Turton and J. Shaeiwitz, 2008

Other Input – Output Issues (cont) Impurity in large quantities then purify – why? A notable exception is air By allowing large amounts of impurity to flow through the process (even if it is essentially inert) causes all the equipment to be larger and for the utility usages to increase proportionally. Usually cheaper to remove it prior to processing. Copyright - R. Turton and J. Shaeiwitz, 2008

Copyright - R. Turton and J. Shaeiwitz, 2008 Add Materials to Feed In order to Stabilize products Enable separation/minimize side reactions Anti-oxidants and scavengers Solvents and catalysts Copyright - R. Turton and J. Shaeiwitz, 2008

Copyright - R. Turton and J. Shaeiwitz, 2008 Inert Feeds Control exothermic reactions Steam controls oxidation reactions (and may eliminate or modify explosion limits) Reduces coke formation on catalyst Control equilibrium Adding inerts shifts equilibrium to the right e.g., styrene reaction C6H5CH2CH3 C6H5CHCH2 + H2 Copyright - R. Turton and J. Shaeiwitz, 2008

Copyright - R. Turton and J. Shaeiwitz, 2008 Profit Margin If $ Products - $ Raw Material < 0, then do not bother to pursue this process, but start looking for an alternate route Toluene HDA vs. Toluene Disproportionation C6H5CH3 + H2 C6H6 + CH4 Toluene benzene 2C6H5CH3 C6H6 +C6H4(CH3)2 Toluene benzene xylene The actual profitability of the benzene production process also depends on what the benzene is used for. IF it is an intermediate then adverse overall economics for this part of the process may not prohibit production. Nevertheless, the second route via disproportionation makes a lot more sense since all the toluene makes useful products and does not require a second reactant. Fuel gas is generally a low value byproduct. Toluene used more efficiently Copyright - R. Turton and J. Shaeiwitz, 2008

Copyright - R. Turton and J. Shaeiwitz, 2008 Recycle Since raw materials make up from 25 to 75% of total operating costs, should recover as much raw material as possible Exception is when raw materials are very cheap For example, Air Separation Copyright - R. Turton and J. Shaeiwitz, 2008

3 Basic Recycle Structures Separate and purify unreacted feed from products and then recycle, e.g., toluene Recycle feed and products together and use a purge stream, e.g., hydrogen with purge as fuel gas Recycle feed and products together but do not use a purge stream - must come to Equilibrium 2C6H6 C12H10 + H2 The diphenyl production is discussed as an example in Chapter 2. Copyright - R. Turton and J. Shaeiwitz, 2008

Recycle Structure in PFD The pink lines represent raw material recycles while the blue lines are recycles for process control purposes. Copyright - R. Turton and J. Shaeiwitz, 2008

Recycle without separation or purge Recycle increases and equip. and op. costs increase When using this option, the intermediate product (diphenyl) must react further – either to destruction or equilibrium. 2C6H6 C12H10 + H2 Copyright - R. Turton and J. Shaeiwitz, 2008

Recycle with Separation (and Purge) 2C6H6 C12H10 + H2 Extra tower with associated operating costs If the diphenyl is not recycled (this would be the case when it either did not react further or the equilibrium was such that the amount in the recycle loop became very large) then separation as a byproduct must be used. The choice of which option is best is purely economic. Note that if diphenyl is not a saleable product then it must be destroyed (possibly by incineration) and this cost should also be included. Copyright - R. Turton and J. Shaeiwitz, 2008

Other Issues on Recycle Number of recycle streams Does excess reactant affect structure Size of Recycle Loop H2 : Toluene = 5 : 1 Number of Reactors Separate and recycle to different reactors The reason for using such a high ratio of hydrogen to toluene in the reactor feed is to suppress coke formation on the catalyst. Otherwise, it would make economic sense to run the reactants at close to stoichiometric ratios. Copyright - R. Turton and J. Shaeiwitz, 2008

Other Issues on Recycle (cont.) Do we need to purify prior to recycling? Is recycling of inerts warranted? Can recycling an unwanted inert material push equilibrium to the right? Gasification of coal – CO2 recycle These questions must at least be addressed when considering process alternative. The recycling of CO2 to a gasifier will certainly suppress the shift reaction (CO + H2O  CO2 + H2) but it requires compression and increases the flow through the gasifier loop. Copyright - R. Turton and J. Shaeiwitz, 2008

Other Issues on Recycle (cont.) Can recycling an unwanted inert control reaction CO2 in Gasifier Phase of Recycle Stream? It is a lot easier and cheaper to recycle a liquid compared to a gas. Copyright - R. Turton and J. Shaeiwitz, 2008

Copyright - R. Turton and J. Shaeiwitz, 2008 Summary All processes are comprised of the same five basic steps – reactor feed prep, reactor, separation feed prep, separation, recycle, and environmental control blocks Hierarchy of process design looks at batch vs. continuous, feeds, recycles, and heat and mass integration. Copyright - R. Turton and J. Shaeiwitz, 2008