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Green Engineering

Green Engineering. Process Integration: Three key components: - Synthesis - Analysis - Optimization. Green Engineering. Process Integration: Synthesis. Chemical Process Components Interconnectivity of components Tackle numerous design alternatives

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Green Engineering

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  1. Green Engineering • Process Integration: • Three key components: • - Synthesis • - Analysis • - Optimization

  2. Green Engineering Process Integration: Synthesis • Chemical Process Components • Interconnectivity of components • Tackle numerous design alternatives • Screen technologies, configurations and operating conditions • Process alternatives should be explored systematically.

  3. Green Engineering Process Integration: Synthesis • Targeting: provides the optimal solution without having to analyzed all possible alternatives. • Advantages: Disadvantages: • faster – no flowsheet • easier

  4. Green Engineering Process Integration: Synthesis • State Space Representations and Superstructures: provide optimal solution and realizing network. • Disadvantages: • Usually involves solving MINLP problems where there is no guarantee of global optimality.

  5. State Space Representation Product Treated Waste Pollutant Operator Raw Materials Physical Separation Operator Reactor Operator MEN HEN

  6. Heat Exchanger Network • Energy Integration is based on Pinch Technology. It provides with • Understanding of the energy utilization • Targets maximum stream-stream heat recovery • Targets minimum heating and cooling utility

  7. Mass Exchange Technology Polluted Streams Clean Streams MEN Mass Separating Agents

  8. Mass Exchange Technology • Advantages • Can screen different MSA without the need to build a flow-sheet. • Can guarantee minimum clean-up cost • Similar to Heat Pinch Technology • Disadvantages • Cannot operate at different temperatures.

  9. Scrubber 1 Scrubber 2 Perva- poration. Reactor Reactor Example 1: Production of Ethyl Chloride Ethyl Chloride FW FW Ethanol HCl CE- Wastewater Ethylene Dist. Wastewater to biotreatment Water

  10. Example 1: Production of Ethyl Chloride Problem Statement: Because of the toxicity of chloroethanol (CE), it is desired to reduce its amount in terminal wastewater to 1/6 of its current discharge. What would be the minimum-cost solution for this waste-reduction task?

  11. Example 1: Production of Ethyl Chloride • Several Strategies to reduce the load of CE: • From aqueous streams • Adsorption on a polymeric resin • Adsorption using activated carbon • Extraction using oil • From gaseous streams • Zeolite adsorption • Air stripping • Steam stripping

  12. Example 1: Production of Ethyl Chloride • To identify the optimum solution one should be able to answer the following questions: • Which phase(s) (gas,liquid) should be intercepted with a separation system to remove CE? • Which process streams should be intercepted? • To what extent should CE be removed from each process stream to render our reduction goal?

  13. Example 1: Production of Ethyl Chloride • Which separation operations should be used? • Adsorption, extraction, stripping? • Which MSA should be selected? • Resin, activated carbon, zeolite, air, steam? • Which units should be manipulated for source reduction? • Which streams should be recycled/reused?

  14. Scrubber 1 Scrubber 2 Perva- poration. Reactor Reactor Example 1: Production of Ethyl Chloride Ethyl Chloride FW Waste water Adsorption with activated carbon Ethanol HCl Ethylene Dist. Water

  15. Example 1: Production of Ethyl Chloride • The optimal solution can be obtained using the State Space Representation with a MEN Operator and minimizing the operating cost. • The optimal solution features: • Fresh water reduction by wastewater recycle and reuse. • CE is reduced by adsorption from a gaseous stream. • A 44 % lower operating cost than separating CE from the terminal wastewater.

  16. Example 2: Acrylonitrile Plant Debottlenecking Bottleneck: Biotreatment is at full capacity

  17. Example 2: Acrylonitrile Plant Debottlenecking Adsorption Column

  18. Example 2: Acrylonitrile Plant Debottlenecking • The optimal solution features: • Fresh water usage and influent to biotreatment was decreased by 7.2 kg/sec. • Influent in biotreatment is reduced 40 %. Plant production can be expanded to 2.5 times the current capacity.

  19. Example 2: Acrylonitrile Plant Debottlenecking • The optimal solution features: • Acrylonitrile production was increased from 3.9 kg/s to 4.6 kg/s. This production increase is a result of better allocation of process streams. • For a selling value of $0.6/kg of AN,the additional production can provide an annual revenue of $13.3 million/yr.

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