Research On Reaction Mechanism And Pilot-scale Test Of Pulverized Coal And Biomass High-temperature Pyrolysis,partial Gasification Process

China is accelerating the pace of energy transformation,energy structure has been continuously optimized and upgraded.Coal still occupies an important strategic position in China's national economy,and it is crucial to select and develop technologies that can utilize coal in an integrated,efficient and clean way.The coal partial gasification polygeneration system has fully proved its advancement and is widely used in the coal chemical industry.However,there are still few studies on the reaction,regulation mechanism and pilot test of the high-temperature pyrolysis partial gasification technology of pulverized coal,and it is urgent to make up for the gaps in key core areas.and there is an urgent need to fill the gap in the key core areas.At the same time,renewable energy sources have achieved strong growth and replaced some coal that will definitely become one of the pillars of energy consumption in the near future.Northeast China has the most abundant biomass resources,but the kinetic mechanism and product conversion characteristics of typical biomass and coal co-utilization in Northeast China are not clear,and the synergistic effects and pollutant emission characteristics are not specific,which greatly restricts the efficient utilization of biomass resources.In response to the above problems,a systematic study was conducted in this paper to comprehensively investigate the kinetics and conversion characteristics of coal and biomass co-combustion and co-gasification,to deeply analyze the reaction mechanism of high-temperature pyrolysis partial gasification of pulverized coal,and to comprehensively test the reliability and stability of the system through pilot tests.First,the co-combustion characteristics of three typical biomasses and coal are studied on a thermogravimetric platform to obtain the variation patterns of kinetic parameters and synergistic mechanisms,followed by exploring the emission characteristics of pollutants during co-combustion by means of a tubular furnace platform.It is shown that biomass has lower ignition and burnout temperatures,is easier to ignite and burn,and the combustion performance of the mixture is significantly enhanced with the increase of biomass blending ratio.The mixture of corn straw and rice straw show promoted synergistic interactions,while the large amount of Si O₂ in rice husk ash would hinder the combustion of fixed carbon.The largest SO₂ and NO_x emission concentrations are found for single biomass,and with the increase of coal share in the mixture,both pollutants show a significant decreasing trend,indicating that co-combustion is conducive to controlling and reducing the emissions of both pollutants.Based on the above analysis,20%biomass blending ratio is considered to be an ideal mixing ratio.Then,corn straw and coal with better combustion performance are selected as the research objects,and the gas and solid product generation characteristics of coal and biomass co-gasification process under various reaction conditions(temperature,blending ratio,particle size)were systematically analyzed on the platform of the entrained-flow drop furnace.As the gasification reaction temperature increases,the addition of biomass to coal enhances the performance of co-gasification,and the syngas quality was significantly improved,with both CO and H₂ content peaking at 1000 ^oC.On the contrary,the volume content of CH₄ and CO₂continuously reduces.The substantial increase in the proportion of combustible gas increases the calorific value of the gas accordingly.There is a significant synergistic effect in the co-gasification process of coal and biomass,and the peak values of both CO and H₂ are obtained by the group blended with 80%biomass,which are 36.13%and 32.67%,respectively.The smaller the fuel particle size,the more effective the heat and mass transfer is,and the generation of CO and H₂ is supported,while the CO₂ content is higher due to incomplete reaction caused by increasing particle size.The volatile content in the gasified char is greatly reduced,the content of fixed carbon is significantly increased,and the calorific values are all above 20 MJ/kg.The oxygen-containing functional groups on the surface of the char reduces.Co-gasification has a certain quality improvement effect on the char of the mixed sample.Subsequently,based on the pilot platform of high-temperature pyrolysis partial gasification of pulverized coal at Zhejiang University,the effects of pure oxygen,oxygen-enriched and air on the output characteristics of gasification syngas at medium and high temperatures were systematically investigated,and the physicochemical and microscopic morphology characteristics of gasified char wre comprehensively analyzed.The study showed that with the increase of oxygen concentration in the gasification agent,the combustible component content in the gas increased significantly,and the carbon conversion rate,cold gas efficiency and syngas efficiency were all improved.The percentage of syngas exceeded 90%at 1200 ^oC for oxygen gasification,and the calorific value of gas achieved the maximum value of 11545.1 k J/m³.The apparent aromaticity of gasification char increased significantly,and it had high structural maturity;the pore structure of char surface is more developed,and the number of uniform macropores increases significantly.Finally,the steady-state experimental study of the pilot-scale platform was carried out to study the distribution and variation of temperature and composition in the steady-state operation furnace of pure oxygen gasification under wide equivalence ratio.The stable operation of the pilot-scale gasifier with high efficiency,long time and multiple working conditions under medium-high temperature and atmospheric pressure was realized.The results show that the temperature distribution in the gasifier is:Furnace 2>Furnace 3>Furnace 4,corresponding to different gasification reaction zones.When the gasification equivalent ratio increased from 0.16to 0.29,the furnace temperature increased from 957 ^oC to 1269 ^oC,the CO volume share increased from 50%to 60%,and the H₂ share showed a downward trend.The final carbon conversion rate was 76%,the peak value of gas production was 134.33 m³,and the effective gas volumes were all above 114 m³.The high calorific values of the gas was all over 11.5 MJ/m³.Considering the variation of parameters and feedstock consumption,the air equivalent ratio in the range of 0.2?0.24 is considered to be a reasonable range in this paper.Through comparison with other gasification processes,it is found that the ZJU gasifier has lower operational requirements and can be operated under atmospheric pressure and medium-high temperature reaction environment,and the gas composition are not significantly different from those of commercial gasifiers.ZJU gasifier has strong feasibility,economy,broad application and market prospect.It can be applied to the renovation of industrial boilers and the optimization design of coal polygeneration system in the future.