Study On Ash Formation Characteristics Of Rice Husk By Rapid Heating Treatment Using Wire-Mesh Reactor

Rice husk is a kind of agricultural processing waste with a large output at home and abroad.Its combustion and utilization is of great significance to China to meet the challenges of "carbon peak" and "carbon neutralization".In particular,the main component of rice husk ash is amorphous silica,which accounts for more than 90%（in terms of SiO₂）,so that rice husk ash can be used as a silicon-based additive in many industrial fields.In the field of energy and power,silicon-based additive is one of the main additives to prevent and control the slagging and contamination of high alkali fuel such as Zhundong coal.The physical and chemical properties of rice husk ash determine its efficacy as an additive,which is closely related to the heating time and temperature.In order to understand the effect of rapid heating preparation conditions on the thermal reactivity of rice husk ash,rice husk ash under rapid heating conditions was prepared from Anhui and Neimeng rice husks by wire-mesh reactor,and compared with rice husk ash prepared by slow heating in muffle furnace.The microstructure characteristics of rice husk ash were analyzed by SEM,DSC and other analytical instruments to study the self-transformation characteristics of rice husk ash prepared under rapid heating conditions and the thermal reaction characteristics with calcium oxide.The influence of rapid heating treatment on rice husk ash as an additive for the prevention and control of slagging and contamination of Zhundong coal was studied by analyzing the DSC spectrum heat flow of the mixed samples of rapid heating rice husk ash and Zhundong coal high calcium fly ash.The results showed that with the increase of the maximum temperature in the wire-mesh reactor,the damage degree of the surface structure of rice husk ash increased.The internal structure of the ash particles changed from a complete original skeleton to a honeycomb shape with multiple holes,and the shape of the ash particles changed from an irregular state to a regular round shape.The maximum temperature in the fast heating experiment of wire-mesh reactor was 900℃,and the crystallization peak temperature of silica in the rice husk ash sample was higher than that in the ash sample prepared at 815℃.Although the inorganic elements of Anhui and Neimeng rice husks are similar,Neimeng rice husks are easier to burn into crystalline silicon oxide than Anhui rice husks under rapid heating treatment.When the maxmum temperature of wire-mesh reactor experiment was 815℃,amorphous silica in Neimeng rice husk ash began to transform to crystal,while Anhui rice husk ash transformed to crystal at 900℃.In DSC analysis,the crystallization peak temperature of silica in Anhui rice husk ash prepared at the same heating temperature was higher than that in Neimeng rice husk ash.The activity of rice husk ash prepared by slow heating at 815℃ is lower than that prepared by rapid heating.Neimeng rice husk ash prepared at 815℃ and 900℃ and Anhui rice husk ash prepared at 900℃ could further generate calcium silicate at 1160℃during the thermal reaction with calcium oxide,indicating that the reactivity of these samples was stronger than that of the other samples.In the DSC test of 1:1 mixing with Zhundong coal fly ash,the 1:1 mixing ratio of each rice husk ash can delay the formation temperature of ash melting substances,increase the ash melting point of fly ash by about 40℃,and alleviate the problem of Zhundong coal ash deposition.Rapid heating of rice husk ash with the 900℃ increased the bottom heat flux with the mixing sample by more than 0.4 mw/mg,and the bottom heat flux of Anhui rice husk ash blending sample was increased by 0.57 mw/mg,which could significantly reduce the formation of ash fusion material.When the highest temperature is 700℃,815℃ of rapid heating rice husk ash,the bottom heat flux of fly ash is reduced,and the formation of ash fusion material is intensified.In terms of reducing the effect of ash fusion material formation,the rice husk ash sample prepared by 900℃ rapid heating is better than that prepared by other heat treatment methods,and the effect of Anhui rice husk ash is better than that of Neimeng rice husk ash under 900℃rapid heating.