Energy Analysis in White Rice and Par-Boiled Rice Mills for Cogeneration in Thailand

Abstract

This research is a part of study entitled “Cogeneration Potential of Rice Mills in Thailand”. Three types of rice mills are studied: the white rice mills that use only electricity, the white rice mills that use electricity and steam engines, and the par-boiled rice mills that used electricity and steam in the par-boiled process. The white rice mills and par-boiled rice mills use steam in the heating process for paddy drying. Electrical energy consumption in the milling process of white rice mill and par-boiled mill are approximately 110MJ/ton paddy and 134 MJ/ton paddy, respectively. Electrical enrgy consumption of white rice mill spent in whitening and polishing process is 43%, 26% in screening and blowing process, 23 % in bucket and conveyor process, and 8% in husking process. Similarly, 43 % of electrical energy consumption in the milling process of par-boiled rice mill is spent in whitening and polishing process, 30% in screening bucket and conveyor process, 23%in blowing process, and 4% in husking process. The thermal energy consumption for par-boiled rice process is 2410 MJ/ton paddy, of which 8% is for soaking process, 6% for cooking process and 86% for paddy drying process.

            The result of the analysis show that the total electrical energy consumption – milling process, drying process, improving and packing process, office and boiler in the white rice mill—is approximately 190 MJ/ton paddy and for par boiled rice millit is 234 MJ/ton paddy. Assuming that steam turbine cogeneration is used, the electrical power generated from 312 rice mills is therefore 217 MW, of which 123MW is used within the rice mills and 94 MW is surplus. The thermal energy generated from the rice mills is 3.16×10¹⁰ MJ/year, of which 17% is used with in the rice mills and 83% is surplus. How ever, optimization of cogeneration system may help reduce the amount of surplus steam.