A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1994

The study on the export power options for Habeeb Sugar Mills in Pakistan was performed. In the present situation, their exists a 3.5 percent of cane crushing, surplus bagasse availability but no excess steam generation capacity to make utilization of the bagasse for power generation during milling season. Thus this quantity has a low value when sold to a paper and board factory. However in such situation power generation with the existing power plant will only be possible in non-milling season or with the higher investment it could be generated during milling season as well. For reliable supply of fuel, the potential of additional bagasse saving and the availability of cane tops and leaves were assessed. The boilers at the mill had a low efficiency of 55%. The causes of low efficiencies found were use of higher excess air (100-140% ), and 52% moisture content in bagasse. Minimizing the above losses could bring approximately 12% additional availability of bagasse. The cane trash availability and its costs favored their use as a boiler fuel. As these were under utilized in the mill's procurement region, mostly by burning in the fields. The specific collection cost found was about Rs 227 per ton. For power generation at the mill several alternatives were studied. These include the use of existing power plant, generating power in non-milling season only, incorporation of a new 50 ton/h boiler with 7.5 MW condensing turbogenerator, fueled with bagasse (surplus and that saved with bagasse dryers) during milling season and cane trash during non milling season; and partial or full replacement of the existing power plant with single or double extraction condensing turbine systems using bagasse and cane trash in milling and non-milling seasons respectively. Cogeneration application with absorption chillers with the existing power plant were also studied. Although under choice 1 the alternatives, except power generation only with bagasse saved with dryers, showed attractiveness, the optimum solution occurred in employing bagasse drying and cane trash system with 50 ton/h boiler and 7.5 MW condensing turbogenerator; as the other alternatives were found to be sensitive in variation of costs. The system gave a net benefit of 33.09 million rupees per year, with NPV 60.93 million rupees, IRR 44.27%, and pay-back of 3.19 years. With the choice 2 both, single and double extraction systems were unattractive at the existing buy back. However the double extraction system showed attractiveness at electricity buy back of Rs. 1.80 per kWh.