玉米秸秆与油页岩混烧的热重试验

为了充分燃烧利用农业生物质与油页岩,采用热重-差示扫描量热(TG-DSC,thermogravimetric-differential scanning calorimetry)技术对玉米秸秆与油页岩混合燃料进行了热重试验,对其各燃烧特性与燃烧机理进行了分析并计算了燃烧动力学参数。结果表明,混烧试样的微分热重(DTG,differential thermogravimetric)曲线出现4个峰值,主要分别是半纤维素热解、纤维素热解、木质素和油页岩热解,以及油页岩焦炭燃烧和油页岩无机盐热解。在DTG曲线第1至第3峰之间出现DSC曲线放热峰,在DTG曲线第3峰至第4峰之间出现DSC曲线吸热峰,需要强化混合燃料的前期燃烧;玉米秸秆与油页岩的质量比例为4∶1时的混合燃料S2,其混烧的可燃特性、着火特性及综合燃烧特性指数均最大,燃尽时间最短,燃尽特性指数较大;在前3个温度区段,混合试样的活化能及频率因子均随温度区段的升高而降低,体现了活化能与频率因子变化的一致性;低温阶段与高温阶段反应级数分别约为1.5及0.7。研究结果可为生物质和油页岩的混烧利用提供参考。

Co-combustion thermogravimetry experiment of corn stalks and oil shale

Abstract: In order to efficiently burning utilize the agricultural biomass and oil shale, the thermogravimetry experimentation of corn stalks and oil shale mixed fuels was performed by using the TG-DSC (thermogravimetric-differential scanning calorimetry) thermal analysis technology. All of its combustion characteristics and combustion mechanisms were investigated and calculated using combustion kinetics parameters. The results showed that the DTG (differential thermogravimetric) curves of co-combustion samples have four peaks, the semicellulose volatile pyrolysis of corn straw, cellulose volatiles pyrolysis, combustion and ignition coke of lignin pyrolysis and oil shale volatiles pyrolysis, combustion and ignition of coke oil shale pyrolysis, and a small amount of oil shale inorganic salt pyrolysis, respectively. Each DTG peak becomes more obvious with the increasing of the oil shale content. The DSC curves showed that the mixed burning period is the main heat release process, but with the increasing of the oil shale content, the DSC curves of endothermic peak of combustion late were more obvious. Between the first and third peak of DTG curves, the DSC (differential scanning calorimetry) curve appears as the exothermic peak. Between the third and fourth peak of DTG curves, the DSC curve appears as the endothermic peak. It is needed to strengthen the pre-combustion of mixed fuels. The index of combustible characteristics, ignition characteristics, and synthetic combustion characteristics of the corn stalk and oil shale mass ratio of 4:1 of mixed fuel S2 are all the largest. The burnout time of S2 is the shortest, and the burnout characteristics index of S2 is the second in the mixed sample values, which shows the excellent comprehensive combustion performance. At the low temperature stage of the first three temperature sections of mixed samples, the corn straw pyrolysis of hemicellulose, cellulose, and lignin in the mixed sample absorb more heat. At the same time, the oil shale volatile pyrolysis also needs to absorb heat to increase the reaction activity of samples molecular, accelerating the samples pyrolysis. Then it needs the higher activation energy at the low temperature stage. At the higher temperature stage of the first three temperature sections of mixed samples, it is mainly the combustion process of lignin pyrolysis coke, and it requires less heat so the activation energy is lower. At the previous three temperature sections, the mixed samples of activation energy and frequency factor were reduced with the increasing of the temperature zone, reflecting of the activation energy, and frequency factor change consistency. The reaction order at the low temperature and the high temperature phase is about 1.5 and 0.7, respectively. The study results can provide the reference for large-scale co-combustion and utilization of agricultural biomass and oil shale.