The effect of alkalized biomass on pulverized coal molding and carbonization of bio-briquette

The briquetting and carbonization technique is a comprehensive way to realize the clean and effective utilization of low pulverized coal. The bio-briquette was prepared by mixing pulverized coal with biomass binder, and the formed coke was obtained by carbonizing bio-briquette. Both the modification effects of alkalized biomass on the structure and carbonization characteristics of bio-briquette were revealed by the analysis of the characteristic of alkalized biomass binder, bio-briquette and formed coke. The results show that alkaline treatment alters the chemical structures and thus morphological features of the biomass. The alkalized sunflower seed shell (ASSS) and alkalized peanut shell (APS) exhibit larger average pore diameter with 34.55 nm and 13.54 nm, and pore volume with 0.0033 cm3/g and 0.0235 cm3/g respectively in comparison to original biomass. Highly ordered network structure composed of crystalline cellulose is formed in the alkalized biomass, which bonds the loose pulverized coal together to generate bio-briquette. The ASSS-briquette and APS-briquette possess higher bomb calorific value with 30.14 MJ/kg and 30.29 MJ/kg respectively that can release more heat during combustion. The weight loss percentage of ASSS-briquette (78.04 %) and APS-briquette (62.78 %), and the maximum weight loss temperature at 370 degrees C and 346 degrees C for ASSS-briquette and APS-briquette locate in the middle of coal and biomass, indicating a synergistic effect between the components which also promotes the briquette carbonization. Both superior carbonization characteristics and structure change of bio-briquette during carbonization are conducive to thermal molding thus facilitates the formation of formed coke with satisfactory mechanical strength. The drop shatter resistance, compressive strength and crushing strength can reach 98 %, 4000 N and 83 % respectively. This study can provide theoretical guidance for development of briquetting carbonization technique to realize industrialized fabrication of bio-briquette and formed coke.