Optimized Production of Syngas from Rice Hush Using Steam Explosion in Dual Fluidized Bed Gasifier
Authors:   Department of Chemical Engineering, University of WAH, WAH Engineering College, Pakistan, F Ahmad , N Ahmad ,   Department of Microbiology, PMAS Arid University, Pakistan, U Asghar ,   Department of Chemical Engineering, University of WAH, WAH Engineering College, Pakistan, A Ali ,   Department of Chemical Engineering, University of WAH, WAH Engineering College, Pakistan, A Masoom ,   Department of Chemical Engineering, University of WAH, WAH Engineering College, Pakistan
Published: May 2021

Converting rice husk into energy is a promising method of generating renewable energy and reducing greenhouse gas emissions. In this research rice hush is considered as biomass fuel. The characteristics of rice husk gasification were investigated at an Equivalence Ratio (ER) of 0.25–0.38 and a gasifier temperature of 750-870°C in 20 tons per day (TPD) using steam explosion process in fluidized bed gasifier system. Different operation conditions, temperatures and loads, are investigated for their effects on the compositions, calorific properties, gasification efficiencies of syngas. The effects of the critical parameters, namely, Steam-to-Biomass Ratio (S/B), Particle size variation and gasification temperature on the quality of the product gas as well as the gasifier cold gas efficiency were analyzed. This is the new finding in the research. The optimal conditions of the gasification operation were an ER of 0.20 and gasifier temperature of 800°C. The low heating value of the gas product and cold gas efficiency were 1390kcal/Nm³ and 75%, respectively. After passing the generated gas through the gas cleaning units, it was confirmed that the tar in the product gas was removed with an efficiency of 98%. The cleaned product gas was used for the operation of 420kW, gas engine. Pressure loss often occurred at the bottom of the gasifier during the gasification operation; we found that the agglomerates generated by the gasification process caused it. To prevent the pressure loss caused by the agglomerates, the stable control of temperature inside the gasifier is needed and an ash removal device remove agglomerates should be installed to maintain stable long-term operation. This paper leads towards the production of Syngas and further on the electricity from the rice husk, an eminent biomass, copiously available all around the world. Especially in Pakistan, the rice is used abundantly so the raw material is easily available. The gas is produced using the gasification process in dual fluidized gasifier. It is a wonderful alternative to the natural gas with high calorific value. The sulfur contents are quite less compared to natural gas. It also have a good correlation with environment as flue gases emission is negligible relative to other source like coal, wood, plastic, waste etc. Another benefit of this process is the waste management and pollution control. The results are developed by using the detailed analysis of the process values of plants which is generating electricity by rice husk gasification. We learned, all results revealed that the dual fluidized bed gasification is more economical and efficient method compared to all other methods for commercial scale production of syngas. Results are analyzed which imply that the biomass is more gigantic source which replace the fossil fuels and leads towards the green energy in a more economical way. This paper provides an overview of previous works on combustion and gasification of rice husk in atmospheric fluiuidized bed reactors and summarizes the state of the art knowledge. As the high ash content, low bulk density, p characteristics and low ash melting point makes the other types of reactors like grate furnaces and downdraft gasifers either inefficient or unsuitable for rice husk conversion to energy, the fluiuidized bed reactor seems to be the promising choice. The overview shows that the reported results are from only small bench or lab scale units. Although a combustion efficiency of about 80% can normally be attained; the reported values in the literature, which are more than 95%, seem to be in higher order. Combustion intensity of about 530kg/h/m² is reported. It is also technically feasible to gasify rice husk in a fluidized bed reactor to yield combustible producer gas, even with sufficient heating value for application in internal combustion engines.