Separation with heat integration

Synthesis is the step in design where one conjectures the building blocks and their interconnection to create a structure which can meet stated design requirements. This review paper first defines chemical process synthesis and indicates the nature of the research problems—to find representations, evaluation functions and search strategies for a potentially nearly infinite problem. It then discusses synthesis research and the most significant results in each of six areas—heat exchanger networks, separation systems, separation systems with heat integration, reaction paths, total flowsheets and control systems. 

Figure 5.19 Flowsheet with recycles, separation and heat integration.

Figure 7.10 Simplified PFD of the EDC cracking/VCM separation section with heat-integration scheme (after Lurgi Company). (1) EDC preheater, (2) Feed effluent heat exchanger (FEHE), (3) EDC quencher condenser,...

Whether heat integration is restricted to the separation system or allowed with the rest of the process, integration always benefits from colder reboiler streams and hotter condenser streams. This point is dealt with in more general terms in Chap. 12. In addition, when column pressures are allowed to vary, columns with smaller temperature differences are easier to integrate, since smaller changes in pressure are required to achieve suitable integration. This second point is explained in more detail in Chap. 14. 

Distillation is by far the most commonly used method for the separation of homogeneous fluid mixtures. No attempt should be made to optimize pressure, reflux ratio, or feed condition of distillation in the early stages of design. The optimal values will almost certainly change later once heat integration with the overall process is considered. 

Consider now the consequences of placing simple distillation columns (i.e. one feed, two products, one reboiler and one condenser) in different locations relative to the heat recovery pinch. The separator takes heat Qreb into the reboiler at temperature Treb and rejects heat Qcond at a lower temperature Tcond There are two possible ways in which the column can be heat integrated with the rest of the process. The reboiler and condenser can be integrated either across, or not across, the heat recovery pinch. 

Monoliths exhibit a large flexibility in operation. They are well suited for optimal semibatch, batch, continuous, and transient processing. Catalytic conversion can be combined with in situ separation, catalytic reactions can be combined, heat integration is possible, and all lead to process intensification. In the short term, catalytic monoliths will be applied to replace trickle-bed reactor and slurry-phase... 

A 8] The separation layer consists of platinum coated on a silicon substrate. Owing to the low heat capacity, quick temperature cycles can be executed and a resolution down to 7 ppm can be achieved with the integrated thermal conductivity detector. The standard length of the capillary is 860 mm with a channel width of 60 pm. A measurement cycle takes less than 60 s. 

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