Optimal design of a rice mill utility system with rice husk logistic network

Abstract

Thermal energy for drying and electricity for milling operations typically comprise a significant 55% of a rice mill operating cost. Optimal design of rice mill utility system that efficiently utilizes rice husk biomass has potential to increase profitability of rice milling industry. This paper presents a mathematical approach for simultaneous optimal planning of rice husk logistic network as well as optimal design of a rice mill utility system that efficiently utilizes rice husk supplied from various locations in order to satisfy the electricity and drying requirements of the rice mill throughout the year. A mixed integer linear programming (MILP) problem was formulated to determine: (1) the optimal logistic network for the rice husk supply, (2) the economic scale of the rice husk cogeneration system, and (3) an optimal utility supply network for a series of dryers consisting of a combination of cyclonic husk furnace (CHF) and cogeneration systems. Solution to the MILP problem yields an optimal utility system configuration consisting of a specified network of rice husk logistic network, a 15 tons boiler for the cogeneration system and 8 units of CHFs to satisfy the rice mill heat and power requirements. Compared to the baseline, the optimal utility network manages to reduce 18.5% of the total rice mill annualized cost which include the costs of capital, fuel, and electricity.