HEAT EXCHANGER NETWORK DESIGN AND OPERABILITY EVALUATION (OPTIMIZATION)

The previous studies of heat exchanger network design have assumed that the process flows and temperatures are fixed and have focused on generating new networks. It was found that optimization of the flows and temperatures has a much greater impact on the profitability of a process than generating networks does. A generalized-network model was developed and computer coded which enables optimization prior to and completely separate from the network generation. A new network design method was developed which enables one to visualize the number of exchangers, the exchanger matches, the utilities usage, the exchanger duties, and the temperature driving forces all in one diagram. It was also found that sometimes pressure shifting columns saves energy but may not save money. Since heat exchanger network design leads to more coupling in the process flowsheet, an operability analysis is required. It was found that heat exchanger networks are operable when each heat exchanger has a by-pass and physically realistic disturbances are used. An approximate criterion was developed which indicates when heat exchangers will not be operable and stream splitting should be used