Gasification Characteristics Of Cotton Rod Pellets In Circulating Fluidized Bed

Biomass is a very important renewable energy.Using biomass energy will greatly reduce carbon dioxide emissions.Fluidized bed gasification is a very flexible means of biomass utilization,which has wide fuel adaptability and is suitable for large scale applications.Therefore.biomass gasification coupled coal-fired boiler is a very promising way to use biomass energy.The purpose of this paper is to test the circulating fluidized bed gasification characteristics of a shaped cotton rod pellets and provide reference for the subsequent biomass gasification coupled coal-fired boiler designing.A series of forming characteristics of cotton rod pellets are tested,such as feeding rate,bed velocity and the minimum fluidization speed of the material and the mixed distribution of the bed material and the biomass material.The circulating fluidized bed air gasification and air-vapour gasification tests were conducted in a small circulating fluidized bed.The results showed that:the increase in temperature has a significant effect on the gasification effect of the cotton rod pellets.As a result of the improvement,the total combustible components in the syngas increase with increasing temperature.As the combustible components increase,the calorific value of the syngas increases from 4016 kJ/m3 to 5842 kJ/m3,and the gas yield increases from 1.39 m3/kg increased to 1.52m3/kg.The equivalence ratio ER has a more comprehensive effect on the effect of gasification.There is a better equivalence ratio range on the test rig.Under the condition of the external heat source,the best ER is in the range of 0.20-0.22.Besides,introduce water vapor into the gasification medium,as S/B increases,the proportion of water vapor in the gasification medium increases,from 0 to 1.2,which promotes water gas reaction,water vapor shift reaction,and tar reforming reaction.As a result,the content of H2 increases rapidly and the CO content decreases.At the same time,the hydrocarbons in the synthesis gas,including CH4 and CnHm,tend to decrease.When the S/B ratio reaches 1.2 to 1.4,the reaction rate tends to decrease due to the limited power of the external heating source.The composition of various types of syngas tends to be flat,and the content of H2 instead falls from 7.63%to 7.02%.In a 1 MW circulating fluidized bed test,the gasification characteristics of the cotton rod pellets were studied at 7000?,7500?,and 8000?,and the synthesis gas composition characteristics and bottom slag analysis of the biomass were obtained.And,the tar content was analyzed.The results showed that the circulating fluidized bed gasification process of the cotton rod pellets was in good condition under all experimental conditions.After the end of the test,the internal circulation line of the furnace was smooth and no large-scale coking and plugging occurred.The gas yield of syngas is about 1.7 Nm3/kg.With the increase of temperature,the combustible components H2 and CO in the synthesis gas increase,the content of CH4 is basically the same,the total combustible components increase,and the heat value of gas production increases.The calorific value of syngas increased from 4295 kJ/Nm3 to 4913 kJ/Nm3.The amount of tar produced in the syngas is very low,only about 1g/m3.In the gasification process,more than 40%of the alkali metal in the cotton rod pellets enters the tail flue with the fly ash.