Energy Recovery By Vapor Recompression

In the past vapor recompression ("heat pumps") has often been considered for distillation of materials boiling at low temperatures. The incentive in many instances was to be able to use water-cooled condensers, thus avoiding the expense of refrigeration. Another factor favoring vapor recompression is a small temperature difference between the top and bottom of the column.

Today the main interest is in getting the column vapor compressed to the point where its temperature is high enough to permit using the vapor as a heat source for the reboiler.4'5 An auxiliary, steam-heated reboiler and/or auxiliary water-cooled condenser may be necessary for startup (see Figure 8.6). A review of compression equipment and methods of estimating operating costs has been presented by Beesley and Rhinesmith.6 Mosler7 discusses the control of a number of vapor recompression schemes. Null9 presents investment equations and data. Fahmi and Mostafa10 indicate that the optimum location at which to use the compressed vapor may not be in a reboiler at the column base, but rather at an intermediate site.

Other papers on energy integration for distillation columns include those by O'Brien11 and by Rathore et al.12

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