Performance of an updraft rice husk gasifier system for powering village rice mills in the Philippines

In the Philippines, the tremendous quantity of rice husks (RH) produced by rice millers poses a variety of potentially harmful consequences to humans and the environment. We evaluated the burning of RH in updraft gasification systems to ameliorate the problem of RH disposal and reduce the use of other sources of energy that are usually purchased. In 2008, to assess the handling of rice by Philippine millers, we conducted a survey to determine the number and characteristics of rice milling factories in Central Luzon, specifically in Nueva Ecija, which is among the top rice-producing provinces. In this study, we focus on the most prevalent size of factory, which uses a single-pass mill with an average capacity of 1 t h^-1 and requires roughly 30 kW of electric power, as the type of operation that would benefit by employing was targeted to be powered by a rice husk (RH) gasification system as a source of power. We evaluated the performance of such a system that is installed at the Philippine Rice Research Institute (PhilRice). This system comprises a gasifier reactor (internal volume, 1.44 m³), scrubber, condensers, filter, gas storage unit, and an internal combustion engine coupled to an electric generator. The gasification temperature ranged from 703 to 837°C, and the average temperature of the gas entering the engine was 39°C. The conversion rate from raw RH to carbonized rice husk was 18% by weight. On average, the system generated 10-18 kW at 173-240 V, based on a RH consumption rate of 78 kg h^-1. Our results show that the generated power is insufficient to operate a rice mill processing 1 t h^-1, but assessment of the operation indicates that this type of gasification system may be technically feasible if modified. The current size of the reactor and rate of RH consumption could produce 30 kW, if the efficiency of the engine and electric generator was improved. Given these improvements, RH updraft gasification systems might provide the electricity needed for local milling factories, using 40% of the RH material produced during milling operations.