Optimized Production of Syngas from Rice Hush Using Steam Explosion in Dual Fluidized Bed Gasifier

Research Article

Austin Chem Eng. 2021; 8(1): 1085.

Optimized Production of Syngas from Rice Hush Using Steam Explosion in Dual Fluidized Bed Gasifier

Ahmad F¹*, Ahmad N², Asghar U¹, Ali A¹ and Masoom A¹

¹Department of Chemical Engineering, University of WAH, WAH Engineering College, Pakistan

²Department of Microbiology, PMAS Arid University, Pakistan

*Corresponding author: Fazeel Ahmad, Department of Chemical Engineering, University of WAH, WAH Engineering College, Pakistan

Received: March 04, 2021; Accepted: March 24, 2021; Published: March 31, 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.

Keywords: Rice Hush; Dual fluidized bed gasifier; Syngas Production; Combustion; Gasification; Optimization


The world is moving towards energy crisis due to continuous deployment of natural sources. It is the need of the hour to invent alternative and sustainable sources for energy production. Biomass is more flourishing, extended and sustainable source to produce energy and other chemical products. Keeping scarcity and environmental hazards of fossil fuels in mind, researchers are increasingly shifting their attention to renewable energy sources. Biomass is considered as one of the most favored forms of renewable sources [1]. Apparent carbon neutrality and worldwide availability are the most notable characteristic of biomass [2,3]. Major types of biomass are primary biomass, collected directly from plantation areas and waste biomass like municipal solid wastes.

Energy crops are mainly grown for use in energy conversion systems. In both large and small scale power generation, biomass can be utilized as a replacement of fossil fuels [4-6]. Biomass gasification is a process where biomass undergoes thermal conversion to produce a combustible gas mixture, which contains hydrogen, methane, carbon monoxide, carbon dioxide, and water vapor. In air gasification, solid biomass is combusted partially in the presence of air at substoichiometric ratio and the product gas contains substantial amount of N2. In steam gasification, steam is the primary gasifying agent and the product gas is rich in H2 while N2 content is minimal. Further, steam gasification produces minimal amounts of oxides of Sulphur and Nitrogen because of the oxygen-deficient condition and lower gasification temperature [7]. There are different gasifiers available in the market. Of them, Fluidized Bed Gasifiers (CFBs) are suitable for the gasification of agricultural residues such as rice husk, straw, stalk etc. utilizing steam as gasification agent. The parameters that affect the performance of gasification are the gasifying agent (air or steam), gasification temperature and the size of the biomass particle [8,9].

Higher gasification temperature and small particle size are favorable for the gasification process, as they help to increase in conversion of biomass while reducing the concentration of char. Advanced Simulation and Process Engineering (ASPEN) can be used to model gasification processes and to estimate the composition of syngas obtained after gasification. Li et al. [10] developed a novel trigeneration system taking biomass and solar energy as co-feeds, and they performed energy analysis on the system. The effects of Steam-to- Biomass Ratio (S/B) and equivalence ratio were investigated, and the highest destruction of exergy was found to be in the gasifier. Zhang et al. [11] modeled a biomass partial gasification process. The authors carried out the exergy and energy analyses of the gasification model. The performance of gasification model was investigated considering different parameters of the system and exponential increase in the product of exergy destruction and time was observed after carbon conversion ratio value of 0.7. Chen et al. [12] modeled a supercritical water coal gasification system and O2-H2O coal gasification system, and reported the comparative performances (Figure 1).