PRESSURE STABILISATION SYSTEM―THE NEED OF THE SUGAR INDUSTRY

摘要

Overall stabilisation of sugar factory operations is achieved with various automatic control systems for the continuous operation of the sugar plant. Because batch type pans are used for crystallisation, process steam demand always fluctuates, thus disturbing the overall process stability. This poster paper outlines a system that has been successfully implemented to control and stabilise steam pressures around the evaporator and pan stations. Pan stage steam requirement is supplied from the evaporator station by adopting extensive vapour bleeding techniques for achieving better steam economy. Hence, fluctuation of the pan steam demand is transferred to the evaporator station, thus affecting evaporator performance, with fluctuation in syrup brix and exhaust steam pressure. A pressure reducing valve and overflow surplus valves are introduced to meet the fluctuating pan demand by bleeding steam from the boiler directly with a cascading effect. Proper controls of the valves are provided to maintain the boiler steam pressure within permissible limits. The cascading effect ensures stabilised conditions of the exhaust steam and pan vapour pressures. Hence, the evaporator performance is stabilised, resulting in uniform evaporation rates and constant syrup brix. This resulted in an increase in crushing capacity of the plant. Fluctuation in boiler steam pressure due to fluctuating process demand is eliminated. Hence, performance of boiler automation is further improved. In addition to other stabilisation measures, the steam pressure stabilisation system is essential for stabilised evaporator performance. This will lead to an increase in overall plant capacity and achieve better steam economy.