CONCEPTUAL DESIGN OF CONTINUOUS VACUUM PAN OPERATING ON LOW PRESSURE VAPOURS

摘要

In the present day scenario of Cogeneration plants (Comprising of high pressure boilers coupled with multi extraction cum condensing mode turbines), the heating medium @ 1st effect calendria (of Quintuple set of Evaporators), could be kept around 1.25 Kg/cm~2, g pressure @ 124 deg C saturation temperature, with the resulting 3rd effect vapour temperature in the range of 96-98 deg C & 4th effect vapour temperature in the range of 82-83deg C. Meanwhile the Indian Sugar Industry slowly & steadily used low pr. Vapours starting from 2nd effect vapours onwards. While carrying out pan boiling with 3rd/4th vapours for the sake of steam economy ,& because of prevailing low vapour temperatures, ways & means of incorporating mechanical circulators are being thought over. While considering horizontal configuration with short vertical tubes in case of Continuous pans, two designs could be thought of. First one, the heating surface corresponding to Boiling zone is accommodated in case of horizontal configuration of CVP i.e. with multi compartment module/ multiple heating medium entries & the tightening zone operation could be carried out in a regular batch pan with mechanical circulator & the heating surface corresponds to the tightening zone. The basic idea is to get desired Brixes, which results in better exhaustion. The second one is of integral design, the boiling zone is carried out in regular continuous pan with multi compartment design, subsequently the tightening zone is converted to a regular batch pan module with circulator in the same unit. The first design is tried in Northern India for B & C massecuites boiled with 2nd vapours. Thisconcept could be applied to 3rd vapour boiling also. In a sequel to above, surveying the past, FCB-Lille France has originated the concept (in late nineties) of introducing Mechanical agitation, in the later compartments (tightening zone) in the normal CVP with horizontal configuration of course with horizontal tubes. It has introduced, three designs normal (standard pan), Double pan & Ovoidal types. The results reported were quite encouraging.