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

Thesis (M.Eng.) - Asian Institute of Technology, 1995

This study looks at the feasibility of using energy efficient systems in the Indian sugar industry. The study looks into the major energy consuming areas in a typical Indian sugar mill and examines opportunities to conserve energy or to optimize its use. The study has focused on the areas of the boiling house, condenser and cooling system, the turbo-alternator and steam generating systems. Energy models of these areas have been developed for a plant with a capacity of 2500 tonnes of cane crushing per day (TCD) using the sizes of equipment specified as standard by the Government of India. The optimization process looks at both the alternatives of bagasse maximization and power maximization. Nine different scenarios have been examined for the boiling house, covering different bleeding schemes and sources of heating for the juice heaters and for pan boiling. The nine scenarios incorporate the schemes and features used in some of the Indian factories. Two optimized models for the boiling house based on the above scenarios have been developed, using the pressure evaporation and with a mechanical vapour recompression system. The steam consumption figures for the optimized models have been estimated at 38.2 % (with MVR) and 40.2 % (without MVR) per tonne of cane crushed. Two schemes are also suggested for implementation in existing mills in India of either single effect pre-evaporator or double effect pre-evaporator system followed by a quadruple effect evaporator. Different configurations of high pressure systems (turbo-alternator and boiler unit) have been examined keeping the process steam demand in view and the type of mill drive used (Steam turbine system or electric I hydraulic motor drive system). The capacity of the mill to export electricity increases by approximately 20 % as the system pressure is changed from 42 bar to 64 bar and by 32 % as the system pressure is changed from 42 bar to 84 bar (with process steam demand at 50 % on cane in a mill with electrified drives). Financial analysis has been carried out for the systems proposed. The investments made in the boiling house to reduce the process steam demand are recovered in a short period especially for the power maximization alternative. The choice of 64 bar pressure for the turbo-alternator system seems very attractive from amongst the choices examined in the studied. The barriers which hamper the use of high energy efficient systems in the Indian sugar industry have been studied. The measures already taken or necessary for the improvement of energy efficiency in the Indian sugar industry and to overcome some of these barriers have been elaborated.