Eng. Kunio KATAOKA
Kansai Chemical Engineering Co. Ltd.
ABSTRACT: Recent heat integrated distillation technology developed as a Japanese governmental project of prevention against global warming is reported as to how to reduce energy consumption for distillation processes of petroleum refinery. One possible way for pumping up the thermal energy released in the overhead condenser to the reboiler is to raise the pressure of the rectifying section by a compressor so as to make the boiling point higher than that of the thermally-contacted stripping section. The internal reflux liquid of the stripping section is vaporized by gaining thermal energy discharged due to vapor condensation in the pressurized rectifying section. This is a basic configuration of the internal heat integrated distillation column (HIDiC) systems devised in order to reduce heat duties of the reboiler and condenser of a single column. Another possible way is to construct a heat integrated distillation system (HIDiS) without a compressor by thermally contacting two or more columns arbitrarily chosen from the existing multi-component distillation plant of petroleum refinery.This paper deals with both the HIDiC and HIDiS systems for the C-5 splitter distillation plant extracting cyclopentane from petroleum hydrocarbon mixtures selected as a subject of national project research. This plant consists of three columns in series. The first two columns are chosen as an example of energy-saving analysis. For the case of HIDiC system devised for energy saving of the first column, the compression ratio of the compressor, i.e. the pressure ratio of the rectifying to the stripping section, is the primary parameter of HIDiC condition controlling the energy-saving rate. It has been successfully demonstrated that the heat duty required for the reboiler can be reduced almost to zero, so that the target of energy-saving rate higher than 50 % of the energy consumption of the existing same plant can easily be attained.For the case of HIDiS system consisting of two thermally-contacted columns, the rectifying section of the second column is pressurized without a compressor to make the temperature higher than that of the stripping section of the first column. It has been demonstrated that the external reflux ratio of the second column reduced by heat integration can greatly reduce heat duty of the first column reboiler without any compressor. The energy-saving rate of this system has come to approximately 30% of the energy consumption of the existing same plant.As a successful result of national project, this paper finally introduces a packed column HIDiC pilot plant recently constructed in place of the first column of the same C-5 splitter. This pilot plant has actually achieved a great energy-saving rate higher than 50% of the energy consumption of the existing first column.