Numerical Simulation And Experimental Study Of Biomass Gasification Process

At present,the international and domestic energy situation is becoming more and more severe,the oil and gas problem and its environmental issues have boosted the rapid growth of renewable sources of energy,of which bioenergy is a renewable energy source with wide distribution,total volume and quantity.Biomass gasification technology is a low-carbon economy,green and sustainable way of using biological energy,the aggressive pursuit of biomass gasification technology can efficiently tackle the worldwide energy deficit and is crucial to preserving China’s energy security and optimising and adjusting the composition of the energy industry.This article begins with the establishment of a three-dimensional prototype of a lowersuction fixed-bed biological reactor through Solidworks based on the actual application of the gasifier in engineering,and a numerical model of the biological reactor under simplified requirements through FLUENT software to simulate the internal gasification process and investigate the effects of the selected variable factors on the performance of the reactor.Finally,with reference to the chosen variable factors in the digital simulation,the effect weights of different variable factors on the assessment parameters of the gasification effect are investigated by designing orthogonal experiments and analyses,and an ideal set of gasification processes parameters is summarised,which is of certain importance to instruct the engineering practical application of biomass gasification technology.By using agricultural waste maize straw as the biomass material and adopt normal air as the gassing agent,the numerical model of biomass gasifier was constructed by FLUENT software,and the influence of air to biomass ratio(ER),gasifier/biomass mass ratio(S/B),gasifier temperature and biomass feedstock particle size on the main gasification performance indicators such as effective gas composition,gas output,gasification temperature,gas thermal value and gasification efficiency in a certain range was investigated,and the findings indicated that:(1)The increase in ER causes the percentage of active ingredients in the syngas to display different trends,with higher methane,lower carbon monoxide,higher hydrogen and then lower hydrogen reaching a peak at an ER of 0.3.The gas output increases dramatically and the gas heating index and gasification efficiency both show a declining trend;(2)An enlargement of S/B leads to a downward trend in nitrogen,carbon monoxide and methane content in the syngas,an adverse trend in hydrogen and carbon monoxide,a decrease in gasification temperature and gas heating value,and a slight increase in gas output and gasification capacity;(3)With the raising of the gasifier temperature in a certain range,the amount of nitrogen and methane in the syngas tends to reduce,carbon monoxide and hydrogen change in the contrary,the heating value of the gas first down and then up,and all other gasification indicators obviously improve;(4)As the diameter of the feedstock rises,the percentage of inert gas nitrogen content consequently rises,the combustible gas percentage tends to decline,and all other gasification targets show a descending tendency.The quality of the gas produced by the gasifier under different operating situations is investigated by designing orthogonal experiments to analyse the impact weights of airequivalent ratio,gas-solid ratio and gasifier temperature on the gasification index under different operating situations,and to determine the most optimal solution affecting the biomass gasification index within a certain range.The findings revealed that the weight sizes of the three variables affecting the gasification output and the thermal value of the gas were ER,S/B and the temperature of the gasifying agent,and the weight sizes influencing the gasification effectiveness were ER,temperature of gasifying agent and S/B.By comparing the experimental results,an appropriate methodology of gasification process parameters was analysed and summarised i.e.ER value of 0.2,S/B value of 0.3 and gasifying agent temperature of 600°C.This article has successfully confirmed the feasibility of the gasification concept of a downdraft type fixed bed biological fuel gasifier based on biomass through numerical simulations and experimental studies,and the extensive simulation and laboratory data and practical experience acquired can be used to instruct the design and running of the next gasification equipment.