IMPROVING THE ENERGY EFFICIENCY OF SUGAR FACTORIES: CASE STUDY FOR PIONEER MILL

SRI has undertaken a comprehensive study for prioritising low pressure (LP) steam reductions at a sugar factory and has applied the study to the cogeneration project at Pioneer Mill. This paper reviews the methodology for improving steam efficiency and relates this to the development at Pioneer Mill. The LP steam consumption for Pioneer Mill will decrease from about 51.6 steam%cane to about 39.2 steam%cane and estimated electricity export will increase from about 0.14 MWe to 44.0 MWe. The LP steam savings will accrue from several measures, including: installation of two new 5 000 m2 evaporators in a sextuple arrangement (one of the new vessels will be used as a pre-evaporator and the other as the first effect); repositioning of the existing final vessel as the second effect; vapour bleeding of: (i) pre-evaporator vapour to pan stage; (ii) vapour #1 to clarified juice heater; (iii) vapour #2 to secondary juice heater; (iv) vapours #3 and #4 to two stages of primary juice heating; flashing condensate to next effect (with noted exception of LP steam condensate); substitution of process water with clarified juice (where appropriate); reduced vapour consumption on the pan stage; and throttling of vapour #2 to #3 effect for rate control. The shredder, mills and the boiler drives will be electrified and the existing No. 1 boiler will be replaced with a new high efficiency No. 3 boiler operating at 65 bar(g). The existing No. 2 boiler will be upgraded from 17 bar(g) to 30 bar(g). The factory demand for electrical power in the new configuration will be about 17.0 MWe. The cogeneration capacity will expand to 61.0 MWe which will be cogenerated in (i) a 35 MWe condensing turbine alternator (dedicated to the new No. 3 boiler) and (ii) a 26 MWe turbine alternator exhausting steam at 150 kPa(g) to the evaporator station. The upgrade is sized for a crushing rate of 565 TCH.