Design And Experimental Study Of Biomass Burner For Chopped Agricultural And Forest Residue

Energy and environment are two major concerns in the world nowadays.Due to it’s limited resource reservoir and the environmental pollution caused by using it,fossil fuel energy will be gradually replaced by others,however more attention has been paid to biomass energy as a new clean and efficient energy source.China is rich in biomass resources,which are produced from a large amount of agricultural wastes,forest products processing wastes firewood,municipal solid waste,etc.every year.However,on-site burning of agricultural and forestry wastes will cause not only the waste of resources,but also environment pollution.At the same time,there is great demand for thermal energy during industrial production process in the field of light industry,building materials,metallurgy,chemical industry,medicine,textile,ceramic,glass and other industries.However,most of the currently used biomass boilers are mainly designed for producing hot water and steam,it can’t meet the demand of cheap heat source in these above industries.To solve these problems,a new type of agroforestry biomass burner is designed and manufactured.This has obvious social and economic significance for protecting environment and ecological balance,increasing farmers’income and promoting the adjustment of rural industrial structure.In this study,corn stalks and mixed wood chip fuels are selected as two kinds of raw materials,and the proximate analysis,elemental analysis,higher heating value,thermo-gravimetric analysis and physical and chemical properties of two materials are analyzed,and the biomass combustion characteristics such as compaction characteristics and combustion design calculation are also studied for providing a strong theoretical basis for subsequent burner design.Based on the proposed design principles and requirements,the overall structure,protection structure,the furnace wall,the furnace chamber,the ventilation system,the feeding system,the prevent tempering system and the control system of biomass burner for chopped agricultural and forest residue is designed and calculated.And the cold-state test was carried out in the designed feeding system.The effective area value of the fire grate is 1.55 m²,the furnace volume is 1.66 m³,the furnace height is 1.071 m and the effective area diameter of the fire grate is 1.405 m.Secondary air distribution and air distribution of wind cooling furnace wall are implemented.Three-stage design is used in tube feeding auger with the equal diameter and equal pitch auger in the first stage,the variable diameter and variable pitch auger in the second stage and a short bare shaft in the third stage.Finally,a series of thermal tests are carried out on biomass burner,which mainly including biomass burning hot air distribution test,temperature measurement test of biomass burner and the gas and ash composition tests.Four different combustion conditions of the burner were determined under the condition of excessive air coefficient being 1.2.The four working conditions of the first and secondary air distribution ratio of 0.8:0.2 and 0.7:0.3 were analyzed in detail.The experimental results show that the optimal condition of air distribution ratio being0.8:0.2 is suitable for the combustion of corn stalk and wood chip fuels.The combustion of wood chip fuels is better than that of corn stalk and the former is not easily lagging under the same combustion condition.In the meantime,the variation trend of oxygen content in the flue gas is opposite to carbon dioxide,while similar change was observed in the content of CO and CO₂.The results of smoke test has achieved the requirements of the national standard（GB13271-2014）,which is in accordance with environmental guidelines.