1. University of Texas at AustinMichigan Technological University 1 Module 6: Flowsheet Environmental Impact Assessment Chapter 11 David R. Shonnard Hui Chen Department of Chemical Engineering Michigan Technological University

2. University of Texas at AustinMichigan Technological University 2 Module 6: Outline l Educational goals and topics covered in the module l Potential uses of the module in chemical engineering courses l Review of environmental impact assessment methods l Application of Tier 3 environmental impact assessment to a detailed flowsheet - Chapter 11 After the flowsheet input output structure, unit operation designations, and mass/heat integration have been completed, the last step in the process to improve the environmental performance of a chemical process design is to perform a detailed environmental impact assessment

3. University of Texas at AustinMichigan Technological University 3 Module 6: Educational goals and topics covered in the module Students will: l learn to apply a systematic risk assessment methodology to the evaluation of chemical process designs l integrate emission estimation, environmental fate and transport calculation, and relative risk assessment to rank process design alternatives

4. University of Texas at AustinMichigan Technological University 4 Module 6: Potential uses of the module in chemical engineering courses Process Design course: develop and use environmental objective functions to rank process design alternatives rank process designs quantitatively based on environmental criteria Transport phenomena course: Module on interphase mass transfer in the environment

5. University of Texas at AustinMichigan Technological University 5 Module 6: Essential features of environmental impact assessment for chemical process design Computationally efficient  Environmental performance metrics quickly calculated using output from commercial process simulators Link waste generation and release to environmental impacts  Environmental metrics linked to process parameters Impacts based on a systematic risk assessment methodology  Release estimates  fate and transport  exposure  risk

6. University of Texas at AustinMichigan Technological University 6 Module 6: Systematic risk assessment methodology National Academy of Sciences, 1983 1. Hazard Identification (which chemicals are important?) 2. Exposure assessment (release estimation, fate and transport, dose assessment) 3. Toxicity assessment (chemical dose - response relationships) 4. Risk Characterization (magnitude and uncertainty of risk) Result: Quantitative risk assessment (e.g. excess cancers) Atmospheric dispersion Model, C a Thibodeaux, L.J. 1996, Environmental Chemodynamics, John Wiley & Sons

7. University of Texas at AustinMichigan Technological University 7 Carcinogenic Risk Example (inhalation route) Module 6: Quantitative risk calculation Exposure Dose Dose - Response Relationship, Slope Factor Result: # excess cancers per 10 6 cases in the population; 10 -4 to 10 -6 acceptable Disadvantage: Only a single compartment is modeled / Computationally inefficient Highly uncertain prediction of risk

8. University of Texas at AustinMichigan Technological University 8 Carcinogenic Risk Example (inhalation route) Module 6: Relative risk calculation Result: Risk of a chemical relative to a well-studied benchmark compound Advantage: If C is calculated for all compartments using a multimedia compartment model, computationally efficient

9. University of Texas at AustinMichigan Technological University 9 Module 6: Tier 3 Relative risk index formulation Exposure PotentialInherent Impact Parameter Chemical “i”Benchmark Compound Emission Rate of Chemical, i Chemical Specific Process

10. University of Texas at AustinMichigan Technological University 10 Module 6: Airborne emissions estimation o o Unit Specific EPA Emission Factors n n Distillation/stripping column vents n Reactor vents n Fugitive sources o o Correlation (AP- 42, EPA) n Storage tanks, wastewater treatment n Fugitive sources (pumps, valves, fittings) o Criteria Pollutants from Utility Consumption n Factors for CO 2, CO, SO 2, NOx, n AP- 42 (EPA) factors o Process Simulators (e.g. HYSYS  )

11. University of Texas at AustinMichigan Technological University 11 Waste stream summaries based on past experience 1. Hedley, W.H. et al. 1975, “Potential Pollutants from Petrochemical Processes”, Technomics, Westport, CT 2. AP-42 Document, Chapters 5 and 6 on petroleum and chemical industries, Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm 3. Other sources i. Kirk-Othmer Encyclopedia of Chemical Technology, 1991- ii. Hydrocarbon Processing, “Petrochemical Processes ‘99”, March 1999. Module 6: Release estimates based on surrogate processes

12. University of Texas at AustinMichigan Technological University 12 Model Domain Parameters surface area - 10 4 -10 5 km 2 90% land area, 10% water height of atmosphere - 1 km soil depth - 10 cm depth of sediment layer - 1 cm multiphase compartments Multimedia compartment model Processes modeled emission inputs, E advection in and out, D A intercompartment mass transfer, D i,j reaction loss, D R Module 6: Multimedia compartment model formulation Mackay, D. 1991, ”Multimedia Environmental Models", 1 st edition,, Lewis Publishers, Chelsea, MI

13. University of Texas at AustinMichigan Technological University 13 Module 6: Multimedia compartment model input data

14. University of Texas at AustinMichigan Technological University 14 Module 6: Multimedia compartment model typical results

15. University of Texas at AustinMichigan Technological University 15 1. The percentages in each environmental compartment depend upon the emission scenario a) the highest air concentrations result from emission into the air b) the highest water concentrations are from emission into water c) the highest soil concentrations are from emission into soil d) highest sediment concentrations are from emission into water 2. Chemical properties dictate percentages and amounts a) high K H results in high air concentrations b) high K OW results in high soil concentrations c) high reactions half lives results in highest pollutant amounts Module 6: Multimedia compartment model typical results - interpretations

16. University of Texas at AustinMichigan Technological University 16 Module 6: Nine Environmental Impact / Health Indexes

17. University of Texas at AustinMichigan Technological University 17 Module 6: Nine Environmental Impact / Health Indexes

18. University of Texas at AustinMichigan Technological University 18 Multi-Criteria Decision Analysis..... Chemical I1I1 InIn I2I2 Emission Rate ABCn..... Report Process Simulator Output or Conceptual Design EFRAT..... MS Excel ® List of Chemicals, Equipment specifications, Utility consumption, Annual throughput Chemicals, Equipment specifications, annual throughput Chemicals, K H, K OW Chemicals, , LC 50, HV, MIR… Physical Properties, Toxicology, Weather, Geographical, and Emission Factors Databases Air Emission Calculator Chemical Partition Calculator Relative Risk Index Calculator

19. University of Texas at AustinMichigan Technological University 19 Environmental Fate and Risk Assessment Tool (EFRAT) links with HYSYS for automated assessments WAste Reduction Algorithm (WAR) reported to be linked with ChemCAD US EPA National Risk Management Research Laboratory Cincinnati, OH Dr. Heriberto Cabezas and Dr. Douglas Young US Environmental Protection Agency National Risk Management Research Laboratory 26 W. Martin Luther King Dr. Cincinnati, OH 45268 Module 6: Software tools for environmental impact assessment of process designs

20. University of Texas at AustinMichigan Technological University 20 Module 6: Absorption - distillation process: analysis of an existing separation sequence HYSYS  Flowsheet

21. University of Texas at AustinMichigan Technological University 21 Module 6: Unit-specific emission summary 100 kgmole/hr Oil Flow Rate; Oil Temperature = 82˚F;  T=180˚F Where are the centers for energy consumption and emissions?

22. University of Texas at AustinMichigan Technological University 22 Module 6: Risk index summary Which chemicals have the highest impact indexes?

23. University of Texas at AustinMichigan Technological University 23 Module 6: Process environmental summary 100 kgmole/hr Oil Flow Rate; Oil Temperature = 82˚F;  T=180˚F

24. University of Texas at AustinMichigan Technological University 24 Module 6: VOC recovery by absorption into tetradecane (C14)

25. University of Texas at AustinMichigan Technological University 25 Module 6: Environmental index profiles

26. University of Texas at AustinMichigan Technological University 26 Module 6: Interpretation of environmental assessment results Risk reductions at 50 kgmole/hr flow rate  Global Warming Index - 41% reduction  Smog Formation Index - 86 % reduction  Acid Rain Index - small increase  Inhalation Route Toxicity Index - 78 % reduction  Ingestion Route Toxicity Index - 18 % reduction  Ecotoxicity (Fish) Index - 19 % reduction Absorber oil choice is not an optimum  Oil selectively absorbs toluene, but ethyl acetate has a higher value Multiple indexes complicate the decision

27. University of Texas at AustinMichigan Technological University 27 l Use of EFRAT : evaluate the MA process l Basecase (Dibutyl phthalate absorber oil) with and without heat integration l Simulate 3 case studies using heat integrated flowsheet »Dibutyl phthalate absorber oil »Dibenzyl ether absorber oil »Diethylene glycol butyl ether acetate absorber oil Module 6: Maleic anhydride from n-butane process flowsheet evaluation

28. University of Texas at AustinMichigan Technological University 28 l Follow the tutorial instructions given in the notebook! l The SCENE file has been linked to a HYSYS case file l Add three additional emission sources l Complete the relative risk assessment calculations Module 6: Maleic anhydride from n-butane: Use of EFRAT on basecase flowsheet

29. University of Texas at AustinMichigan Technological University 29 Module 5: Heat integration of the MA flowsheet Without Heat Integration 9.70x10 7 Btu/hr -9.23x10 7 Btu/hr 2.40x10 7 Btu/hr -4.08x10 7 Btu/hr Reactor streams generate steam

30. University of Texas at AustinMichigan Technological University 30 Module 5: Maleic anhydride flowsheet with heat integration

31. University of Texas at AustinMichigan Technological University 31 Module 6: Maleic anhydride from n-butane: effect of heat integration on risk indexes 30.4% reduction 72.2% reduction Remaining Indexes are unchanged

32. University of Texas at AustinMichigan Technological University 32 Module 6: Maleic anhydride from n-butane: effects of absorber oil choice 16.3% reduction 85.1% reduction 81.7% reduction 42.1% reduction

33. University of Texas at AustinMichigan Technological University 33 Module 6: Summary / Conclusions l Educational goals and topics covered in the module l Potential uses of the module in chemical engineering courses l Review of environmental impact assessment methods l Application of Tier 3 environmental impact assessment to a detailed flowsheet - Chapter 11 »Heat integration of the Maleic Anhydride flowsheet »Effects of absorber oil choice for the MA flowsheet