PDD_28_RS1 - Process Design Decisions (PDD) Process Design...

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Process Design Decisions (PDD) Prof B V Babu Process Design Decisions Copyright © 2008-2009 B V Babu, BITS-Pilani LECTURE - 28
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Process Design Decisions (PDD) Prof B V Babu Recycle Structure of the Flow Sheet Introduction Level-3 Decisions (determining the Recycle Structure) – Number of reactor systems – Number of recycle streams – Use of excess reactants equirement of Gas compressors Copyright © 2008-2009 B V Babu, BITS-Pilani – Requirement of Gas compressors – Reactor Heat effects – Requirement of Shift in equilibrium conversion – Effect of reactor cost on EP Summary
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Process Design Decisions (PDD) Prof B V Babu Introduction Recycle structure is the next level (L3) of decision making – after deciding the Input-output structure of the flow sheet (L2) Product distribution dominates the design – and so we add the details of the reactor system as compressors are the most expensive processing Copyright © 2008-2009 B V Babu, BITS-Pilani Gas compressors are the most expensive processing equipment – and hence we add the annualized capital and operating costs of the required compressors However, at this level of the synthesis and analysis procedure – we treat the separation system as just a black box – and we consider the details of the separation system later (in the next level)
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Process Design Decisions (PDD) Prof B V Babu Level-3 Decisions (to determine Recycle Structure) 1. Number of reactor systems required Is there any separation between the reactor systems? 2. Number of recycle streams required 3. Use of an excess of any one reactant at the reactor inlet 4. Gas compressors are required ? Copyright © 2008-2009 B V Babu, BITS-Pilani What are the costs? 5. Should the reactors be Operated adiabatically, or With direct heating or cooling, or Is a diluent or heat carrier required? 6. Is shift in equilibrium conversion required? If so how? 7. Effect of reactor cost on Economic Potential
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Process Design Decisions (PDD) Prof B V Babu L3 Decisions: 1. Number of reactor systems Consider HDA process: – Toluene + H 2 Benzene + CH 4 1150-1300 0 F, 500 psia – 2 Benzene ± Diphenyl + H 2 1150-1300 0 F, 500 psia – Both the above reactions take place at the same temperature and pressure without a catalyst – Hence, there is only one reactor required for this case Copyright © 2008-2009 B V Babu, BITS-Pilani Consider another process: – Acetone Ketene + CH 4 700 0 C, 1 atm – Ketene CO + ½ C 2 H 4 700 0 C, 1 atm – Ketene + Acetic Acid Acetic Anhydride 80 0 C, 1 atm – The first two reactions take place at a higher temperature, whereas the third reaction takes place at a lower temperature – Hence, two reactor systems would be required for this case
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Process Design Decisions (PDD) Prof B V Babu L3 Decisions: 1. Number of reactor systems If sets of reactions take place – at different temperatures – or pressures – or if they require different catalysts – then we use different reactor systems for these reaction sets Copyright © 2008-2009 B V Babu, BITS-Pilani
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This note was uploaded on 02/29/2012 for the course CHEMICAL 332 taught by Professor Profb.v.babu during the Spring '09 term at Birla Institute of Technology & Science.

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PDD_28_RS1 - Process Design Decisions (PDD) Process Design...

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