牛粪不同组分的热解特性研究

为研究牛粪不同组分的热裂解机理,根据范式洗涤原理对牛粪进行洗涤处理获得不同成分组合的洗涤纤维,利用扫描电镜观察牛粪及洗涤纤维的表观形貌,采用热重分析试验方法探讨牛粪中不同组分洗涤纤维的热解特性。电镜扫描结果表明:牛粪表面密实,没有裂缝和孔洞,随着洗涤的进行,表面结构破坏越来越严重,由出现凹陷条纹到最后呈蜂窝状结构,洗涤纤维的空隙结构有助于热解时传热和挥发分的析出。热重分析结果表明:以纤维素为主要成分的酸性洗涤纤维,热解速率最大,为14.310%/min,强酸洗涤纤维热解速率最小,为1.615%/min;不同组分的热解具有内在关联,并不是简单的叠加,纤维素的加入使木质素的热解速率和温度区间发生变化;半纤维素的存在对纤维素的热解挥发具有一定的抑制作用,使纤维素的热解速率由14.310%/min降低到7.617%/min。中性洗涤溶解物的存在,使得牛粪在较低温度开始热解,但半纤维素和纤维素的热解速率较低。

Pyrolysis Characteristics of Different Components of Cattle Manures

Cattle manure is a kind of complicated biomass mainly consisting of hemicellulose, cellulose, and lignin. In order to study the pyrolysis characteristics and interaction among these constituents, Van Soest method was adopted to effectively segregate hemicellulose, cellulose, lignin, extractives and ash. The obtained detergent fibers and cattle manure original samples were investigated by using scanning electron microscopy to analyze their microscopic structures. The results showed that the apparent morphology of cattle manure and detergent fibers was changed from surface compression without cracks and holes to a honeycomb structure with numerous cracks and holes along with the washing process. Furthermore, those samples were also addressed by dynamic thermogravimetry and derivate thermogravimetry (TG-DTG) method. Thermogravimetric experiments showed that the pyrolyis rate of acid detergent fiber mainly including cellulose had the largest value among the detergent fibers, e.g. 14.310%/min, and the strong acid detergent fiber at the smallest one with the value of 1.615%/min. The pyrolysis processes of the different components were intrinsically interacted with each other. Hemicellulose inhibited extremely the devolatilization of cellulose, resulting in the volatile rate of cellulose was decreased from 14.310%/min to 7.617%/min. For the presence of the neutral detergent dissolved matter, the starting temperature of pyrolysis of cattle manures was reduced, and the thermal degradation rates of hemicellulose and cellulose were also restrained.