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Title: Distillation column integration and overall design of subambient plants.
Author: Dhole, Vikas Raghunath.
ISNI:       0000 0001 3423 3134
Awarding Body: University of Manchester, Institute of Science and Technology,
Current Institution: University of Manchester
Date of Award: 1991
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Distillation is the most widely used separation process in the chemical industry. It is also a highly energy intensive unit operation. Any thermal modifications in the distillation columns will normally affect the heat exchanger network (HEN) and the utility system. Pinch analysis offers a systematic approach for considering this effect ahead of column modifications i.e. integrating the columns with their background processes. However, the guidelines for column modifications mainly emerge from the analysis of the HEN and the utility system. The potentials for modifications in the columns are not fully exploited. The columns are largely treated as "black boxes". Within the thesis, a new approach to distillation column integration is proposed. It extends the current pinch analysis approach. Using insights from column thermodynamics, the potential for the various column modifications can be directly assessed ahead of design. This allows the designer to set heat load and temperature targets for the column modifications. A new set of thermal profiles for the column are developed. These provide insights into the effect of column modifications on the number of stages. Only a single converged simulation is sufficient to generate all the targeting information. These "column targets" when linked with the normal pinch analysis targets, provide an approach for column integration which directly identifies the modification potential in the distillation columns as well as the potentials in the HEN and the utility system, resulting in a more reliable approach in comparison to the conventional pinch analysis. A combined pinch and exergy approach is proposed for the overall design of subambient plants. Pinch analysis is mainly applicable for setting the most economic energy target ahead of design. These targets are mainly in the form of heat loads. The combined pinch and exergy analysis extends this application to heat and power targeting for subambient plants. Any subambient plant has three main components namely; the process, the HEN and the refrigeration system. All the three components are highly interlinked and a modification in anyone of the components affects the other two. The task of overall design becomes quite complex due to these interactions. The new approach allows the designer to resolve these interactions and set the most economic "shaftwork or power targets" ahead of deSign. It combines the three components into a single design task. The approach when linked with the column targets, identifies the potential column modifications and evaluates their benefits directly in terms of shaftwork, thus even by-passing the repeated column simulations. Thus the overall design procedure systematically modifies a given subambient plant considering its distillation system, the HEN, and the refrigeration system on a simultaneous basis. The procedure has been demonstrated on an ethylene cold end case study. Typically 15-20% shaftwork savings have been observed on flowsheets which have already undergone pinch analYSis. The approach can be extended for certain applications above ambient involving heat and power.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Chemical engineering