Design of a Lab-Scale Two-Stage Rice Husk Gasifier

Abstract

Rice is a major product in Thailand and a large quantity of rice husk are generated annually in the rice milling industries, which can be used for energy exploitation. A commercial two-stage gasifier has been constructed in Lopburi province using rice husk as the fuel. It is necessary to perform a further development and study of the optimization conditions to achieve a desired operating of the plant. A design procedure was developed for a 50 kWth lab-scale gasifier, and the calculations were made based on the essential parameters such as volumetric flow rate, minimum fluidized velocity, residence time to find out the dimension parameters of the reactor. On the basis of the air supplied rate, the dimensions of the first stage was calculated to provide a sustaining condition of the fluidization. The calculated diameters and heights of the lower part and upper part of the first stage were found to be 0.09, 0.13, 0.50, and 0.50 m, respectively. The height of char reduction chamber in the second stage was estimated to be 1.40 m and the calculated diameter was 0.10 m, whereas, the height of the char bed was variable. This design can facilitate varying parameters such as equivalence ratio, superficial velocity, and temperature. The optimization design is obtained from the experiments and from the theoretical and experimental information available in the literature.