玉米芯炭质燃料的理化性能及热解过程分析

Analysis on pyrolysis process and physicochemical properties of char fuels deprived from corn cobs

研究了农业生物质废弃物玉米芯热解产物炭质燃料的理化性能与裂解温度的关系及热解机理,用FT-IR,XRD,SEM对玉米芯炭进行表征,分析了化学组成、官能团分布、芳构化程度与温度的关系.结果表明,随热解温度升高,热解所得焦炭中固定碳和灰分增加,挥发分和水分减小,产率下降,热值先增加后减少,羰基和脂肪族官能团逐渐被破坏,结晶度和芳构化程度不断增强.500℃时,焦炭热值大于32 MJ/kg,产率大于24%,固定碳大于80%,灰分小于4%,且具有发达的孔洞结构,各项指标接近或优于市售燃料炭;233~533℃下玉米芯挥发最剧烈,具有1.5级反应的特征;热解温度从233~353℃上升至353~533℃时,表观活化能从68.15 k J/mol降至37.25 k J/mol.

The effect of pyrolysis temperature on the physicochemical properties of corn cob char fuel as well as the pyrolysis mechanism were investigated. Moreover, the bio-char fuels were characterized by FT-IR, XRD and SEM, thoroughly analyzing the effect of pyrolysis temperature on chemical components, functional groups＇ distribution and aromatization degree of corn cob chars. The results showed that the fixed carbon and ash contents increased, volatile matter, moisture content and char yield decreased with increasing pyrolysis temperature. Heat value increased firstly and tended to decline later with the increase of temperature. Carbonyl and aliphatic functional groups were gradually destroyed, crystallinity and aromatization degree of chars increased with increasing pyrolysis temperature. The characterization of chars were heat value above 32 MJ/kg, char yield above 24%, fixed carbon above 80% and ash content of chars below 4% corresponding to the pyrolysis temperature of 500℃. Furthermore, chars obtained under 500℃ were endowed with developed porous structures, each index parameter was close to or superior to those of market sold char fuels. 233~533℃ was the temperature range in which volatile matter released the most drastically, it was characterized by reaction order of 1.5 level. When pyrolysis temperature increased from 233~353℃ to 353~533℃, the apparent activation energy decreased from 68.15 k J/mol to 37.25 k J/mol, correspondingly.