Experimental Study On Releasecharacteristics Of Alkali Metal And Cl During Biomass Pyrolysis

As a clean renewable energy source,biomass is becoming more and more concerned.China is a large agricultural country with a large number of agricultural straws,and the straw resources have been vigorously developed accordingly.Although the research on biomass has been going on for several years,the problems of ash accumulation,slagging and agglomeration caused by alkali metals and related elements have still not been solved,which has caused great obstacles to the utilization of biomass.In order to better understand the key to solving the problem,this paper studied corn stalk,sorghum straw,pine and distiller's grains as the research object,and studied the release characteristics of K and Cl in the pyrolysis process,combined with the microscopic macrophysics of the coke sample.The structure and the release of smoke have further studied the precipitation of alkali metals.Corn stover,sorghum straw,pine and distiller's grains were selected as the research objects in a horizontal tube furnace under nitrogen atmosphere.A single biomass pyrolysis experiment was carried out at a temperature of 300-900 °C,and corn stalks were also used.The base material and the other three biomass materials were auxiliary materials,and the mixed biomass pyrolysis experiments at 400 ° C and 800 ° C were carried out in a nitrogen atmosphere.The coke sample and acetone absorption solution were collected during the reaction.The AAEMs and Cl in the coke sample were detected by ICP-AES and ion chromatography,and the surface structure and chemical composition of the SEM-EDX were used for analysis.The gas analyzer measures the release characteristics of CO and CH4 during the reaction.First,a single biomass pyrolysis experiment was carried out.It was found that temperature was the most important factor in the pyrolysis process.At the same time,the higher the pyrolysis temperature,the higher the weight loss rate.The K content in biomass is much higher than that in Na.The precipitation of K can be mainly divided into the decomposition of organic potassium and the decomposition of inorganic potassium.The decomposition of potassium is affected by inorganic elements such as Cl and Si,which is related to the adsorption of coke.At about 50%;sodium is the most easily released of the four elements.The precipitation of sodium is similar to that of potassium,but the sodium content is much lower than the potassium content.At the same time,the chemical bonds of sodium and carbon are unstable,which is easy to break.The peak of the precipitation rate can reach more than 60%.Both calcium and magnesium are divalent in the compound,and the chemical properties are more stable than potassium and sodium.Therefore,the precipitation rate of calcium and magnesium is not high during the release process,and is lower than potassium and sodium,and is not easily precipitated.The release law of Cl is different from the alkali metal elements K and Na.It does not increase with the increase of temperature.In the reaction,a gaseous compound which is insoluble in water and insoluble in acetone is formed.The precipitation of Cl is also affected by the content of metal.Impact.During the entire pyrolysis process,Cl interacts with K and Na,affecting the release characteristics of the elements.Next,the pyrolysis products were analyzed by macroscopic and microscopic physical structure and the surface chemical elements were analyzed.With the increase of temperature,the pyrolysis of the pyrolysis showed a macroscopic state of carbonization,corn cob,sorghum straw and pine coke.The microstructure is similar.During the whole pyrolysis process,the stable layered fiber structure is gradually broken to form a molten state,and finally the entire fiber structure is completely broken,and the molten state is also smoothed,accompanied by potassium chloride in the process.The formation of crystals of silica forms a relatively stable coke product.The distiller's grains are easy to agglomerate in the macroscopic state,and the aggregation state of the distiller's grains can be clearly observed in the microstructure.The EDX spectrum determined that the main components of the biomass coke surface existed in C,O,K,Si and Cl.The distiller's grains contained a certain amount of S and P.No Si was detected,so the structure of the distiller's grains was not strong and it was easy to collapse.Both Mg and Ca elements exist as stable oxides on the focal surface.Finally,the mixed biomass experiment was carried out.The mixed biomass components were not affected by the interaction between the mixed components.The effect of the mixed components on the pyrolysis rate and pyrolysis efficiency was different at different temperatures.At 400 °C The pyrolysis rate of the mixed components is increased,and the pyrolysis efficiency is improved;at 800 ° C,there is no obvious reaction speed and efficiency improvement after mixing;in the mixed pyrolysis process,different mixed components have different release for K and Cl.The effect of the effect is that when the temperature is low,the precipitation of K is promoted,and the high temperature is inhibited.The precipitation rate of Cl of the mixed pyrolysis component is obviously higher than that of the corn straw alone,and the mixed pyrolysis is favorable for the precipitation of Cl in the biomass component.And the more precipitated Cl is released in the form of gas,and the binding ability of Cl and K in the mixed component is weakened,and the pyrolysis reaction is promoted as a whole.