Effect of process parameters on the efficiency of the cogeneration system at Kinyara and Bwendero sugar factories
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Cogeneration is also referred to as combined heat and power (CHP) and it is defined as the sequential generation of two different forms of useful energy from a single primary energy source, typically mechanical energy and thermal energy (A. Tesfai, 2012). Mechanical energy may be used to drive an alternator for producing electricity, or rotating equipment such as motor, compressor, pump or fan for delivering various services. Thermal energy can be used either for direct process applications or for indirectly producing steam, hot water, hot air for dryer or chilled water for process cooling (study on cogeneration, 2014). The Indian sugar industry by its inherent nature can generate surplus power, in contrast to the other industries, which are not only consumers as well as producer of energy. This is mainly due to the 30% of fiber content in the sugar cane used by the sugar mills. This fiber referred to as bagasse, has good fuel value and is used for generation of the energy required for the operation of sugar mill (P.S Sankarnaraynan, et al 2000). The bagasse is fired in the boiler for producing steam at high pressure, which is extracted through various backpressure turbines and used in the process. The simultaneous generation of steam and power is commonly referred to as co-generation. Conventionally, the co-generation system was designed to cater to the in house requirements of the sugar mill only. The excess bagasse generated was sold to the outside market (A. Ataei 2009). In the recent years, with the increasing power ‘Demand Supply’ gap the generation of power from excess bagasse was found to be attractive. This also offers an excellent opportunity for the sugar mills to generate additional revenue (Idehara, 2004). Cogeneration option has been adopted in many of the sugar mills, which is substantially additional revenue for the mills. This also contributes to serve the national cause in a small way, by bridging the ‘Demand supply’ gap (V. Kirubakaran, et al; 2009). The electricity usage is constantly increasing worldwide and it is therefore of high importance to improve the utilization of renewable energy sources (Niels I. Meyer, et al, 2011). In the cogeneration unit of sugar factory electricity is generated in turbines from the steam produced in boilers by burning bagasse, a residue or byproduct from sugar production and a renewable energy resource. Since the electricity in Uganda is mainly generated from fossil fuels that contribute to high carbon dioxide emissions and they are the major components of greenhouse gases which bring about the greenhouse effect that comes with adverse effects on the environment for example climate changes in the form of global warming, use of renewable energy resources is the best option. Biomass e.g. bagasse has the potential to be used for electricity generation on a greater scale since emissions are low (C. Damodaran, et al; 2008).