Special Case Dilute Waste Streams

3 Dradlng Off Fixed Cost versus Operating Cost 

Once the minimum utility cost has been identified, tradeoffs between operating and fixed costs must be established. This step is undertaken iteratively. For given values of minimum approach temperatures, the pinch diagram is used to obtain minimum cooling cost and outlet gas temperature. By ccmducting enthalpy balance around each unit, intermediate temperatures and exchanger sizing can be determined. Hence, one can evaluate the fixed cost of the system. Next, the minimum approach temperatures are altered, until the minimum TAC is identified. 

As can be seen from Fig. 10.4, the minimum cooling utility requirement is 

CHAPTER TEN Synthesis of heat-tnduced separation network 

then refrigerant u is preferred over u. This rationale can be employed to compare ail refrigerants below T with the result of identifying the one that yields the lowest cooling cost. 

6 Case Study Removal of Methjl Ethyl Ketone 

The cost of condensers/heat exchangers ( ) is taken as l,500 (heat transfer area in m ) . The overall heat-transfer coefficients for the dehumidification, the 

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