PDD_34_Retrofit - Process Design Decisions(PDD Prof B V Babu Process Design Decisions Copyright © 2008-2009 B V Babu BITS-Pilani LECTURE 34

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Unformatted text preview: Process Design Decisions (PDD) Prof B V Babu Process Design Decisions Copyright © 2008-2009 B V Babu, BITS-Pilani LECTURE - 34 Process Design Decisions (PDD) Prof B V Babu Process Retrofits • What ? • When? • How? • Systematic procedure – Hierarchy of decisions Copyright © 2008-2009 B V Babu, BITS-Pilani – Identification of significant variables – Rank order parameters – Equipment constraints – Proximity parameter – Removing equipment constraints Process Design Decisions (PDD) Prof B V Babu Process Retrofits • Till now discussions have been for designing a new process • Same techniques are useful for retrofitting a process • Retrofitting – making minor changes in the interconnections between process quipment Copyright © 2008-2009 B V Babu, BITS-Pilani equipment • involves structural modifications of the flow sheet – replacement of one or more pieces of equipment by some other equipment – change in the sizes of one or more pieces of equipment in an existing process • flow sheet remains same Process Design Decisions (PDD) Prof B V Babu Where to retrofit? • Some examples for retrofitting a process – To increase the production capacity • debottleneck a process – Efficiently process new raw material feed stocks when they are cheaper – Utilize new process technologies Copyright © 2008-2009 B V Babu, BITS-Pilani • because the optimum operating conditions have changed since the plant was originally built – Reduce operating cost • this changing economic environment is the reason that most companies did not usually attempt to optimize processes in the past • The last goals are valid for a very large number of existing plants – and then therefore there is a great interest in retrofit procedures Process Design Decisions (PDD) Prof B V Babu A Systematic Procedure for Process Retrofits • Developed by Fisher, Doherty, and Douglas • The analysis is limited to single product & continuous processes • Hierarchy of decisions for process retrofits – Estimate an upper bound on the incentive for retrofitting stimate the economic incentive for replacing the existing plant Copyright © 2008-2009 B V Babu, BITS-Pilani – Estimate the economic incentive for replacing the existing plant by using the same process flow sheet – Estimate the economic incentive for replacing the existing plant with a better process alternative – Estimate the incremental investment costs and savings in operating costs associated with changing the existing process – Refine the retrofit calculations Process Design Decisions (PDD) Prof B V Babu Upper bound of incentive • Highest possible incentive – Prepare an operating cost diagram • do not include any of the capital costs – from cost diagram, see total cost of the raw materials lost in the form of by products (or) lost in waste streams – similarly see all the energy costs that are supplied to the process Copyright © 2008-2009 B V Babu, BITS-Pilani • For large number of processes such as HDA process...
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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_34_Retrofit - Process Design Decisions(PDD Prof B V Babu Process Design Decisions Copyright © 2008-2009 B V Babu BITS-Pilani LECTURE 34

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