Heat integration minimum utilities

Constraints (10.15) states that the amount of cold duty required by unit j at any point along the time horizon of interest is comprised of external cold utility and cold duty from heat integration with another unit j. Constraints (10.16) is similar to constraints (10.15) and applies to unit j requiring heating. Constraints (10.17) is a feasibility constraints, which ensures that in the absence of heat integration all the heat duty requirements of either unit j or j are satisfied by external utilities. The upper bound on the amount of heat exchanged between unit j and unit j will always be the minimum of the required cold and hot utilities as captured in Constraint (10.17 ). 

The portion of the hot composite curve and the cold composite curve shows the minimum cooling and heating utilities, respectively, that must be supplied. Increasing the minimum approach temperature will shift both curves farther apart, reducing the total heat integration... 

Steady-state minimum-cost designs utilize very small hold-ups and high levels of heat integration. Both of these factors reduce the dynamic operability and controllability of a process. 

The cogeneration potential is affected by the reduction of hot utility demand. As the minimum hot utility demand is reduced, the steam production in the CHP plant is reduced which consequently reduces the electricity production (which is estimated at 46 MW ). The electricity demand of the combined processes is estimated at 38 MW. Accordingly, material and heat integration of the two processes results in an excess electricity production of 8 MW j. 123 MW of excess solid residues is available after fuelling the cogeneration unit. 

Figure 13.3 shows a process represented simply as a heat sink and heat source divided hy the pinch. Figure 13.3a shows the process with an exothermic reactor integrated above the pinch. The minimum hot utility can be reduced by the heat released by reaction, Qreact-... 

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