纤维素快速热裂解试验研究及分析

Research on cellulose rapid pyrolysis

纤维素快速热裂解试验在石英管反应器内进行,试验发现辐射源低于400℃时纤维素由于受热不足导致不完全反应;400～450℃时以炭化为主;450℃后由于受热增强,生成生物油的反应加强,并在600℃左右得到78%的最高产率;气相挥发份的二次反应使生物油产量明显降低而轻质气体产量大大提高.二次反应主要以二次裂化为主,而环化重整生成焦炭的概率很小,这可以从二次焦炭生成相当之少来说明.随着氮气流量的增加,二次裂化反应受到部分抑制,生物油产量增大,不可凝气体产量降低,但其影响程度远不如温度剧烈.纤维素热解生成的气体主要为CO、CO2、CH4、C2H4以及少量的H2,各成分变化趋势与整体气体变化规律一致.通过GC-MS检测,生物油主要成分为一些含甲基、乙基、甲氧基、羟基等官能团的酮、苯酚及醛、醇类化合物.其中左旋葡聚糖质量分数在600℃左右达到生物油的72%,并随温度升高或氮气流量降低而降低,相应乙醛、甲醇等小分子组分含量则有增加趋势.

Experimental research on cellulose rapid pyrolysis was carried out on bench scale unit, which was made of quartz glass. Incomplete thermo-decomposition occurred for low heat supply when the temperature of the thermal radiation source (TRS) was below 400°C. Carbonization was the main process in the range of 400-450°C. When TRS temperature was beyond 450°C, more bio-oil was produced with TRS temperature increase and a maximum bio-oil production of 78% was obtained at 640°C. After that, bio-oil production decreased markedly while more incondensable gas was produced as TRS temperature rose. Volatile secondary reaction was mainly controlled by secondary crack reaction prior to carbonization according to less second-char formation. In the case of higher nitrogen flow, more bio-oil was produced while incondensable gas production decreased as the secondary crack reaction was restrained partly. The major gas consisted of CO, CO2, CH4, C2H4 and a little H2 which acted in same trend with the experimental condition. GC-MS analysis revealed some main components, such as phenol, aldehyde, ketone and ethanol components with methyl group, ethyl group methoxyl group and hydroxy group. Levoglucosan took up a big proportion of about 72% in bio-oil at 600°C, which became lower with TRS temperature increase and nitrogen flow decrease, at the same time, small molecule, such as aldehyde and methanol, took up larger proportion.