摘要
为研究金属盐对水稻秸秆热裂解特性的影响,在Li2CO3-Na2CO3-K2CO3(LNK碳酸盐)中分别添加氯化盐和硫酸盐与水稻秸秆干混,采用热重分析与傅里叶变换红外光谱联用技术(thermogravimetric analyzer coupled with Fourier transform infrared spectrometry,TG-FTIR)研究了水稻秸秆的热裂解过程,并使用Coats-Redfern法计算了热裂解过程的动力学参数。结果表明:在LNK碳酸盐作用下,热裂解的活化能降低。与添加硫酸盐相比,氯化盐作用下热裂解活化能更低,热裂解反应更易进行。与纯水稻秸秆热裂解相比,LNK碳酸盐能使CO、CH4、苯酚、甲苯、甲酸和水等的浓度明显下降,而CO2浓度显著上升。在LNK碳酸盐基础上,氯化盐和硫酸盐均能促进水稻秸秆热裂解产物的生成和逸出。当温度高于550℃时,碳酸盐能催化Boudouard反应,氯化盐和硫酸盐均能促进该反应的进行。其中,Ni Cl2和Co Cl2对该反应的影响尤其明显。研究为生物质资源的高值化利用提供了一定的理论参考。
To explore the effects of mixed metal salts on rice straw （RS） pyrolysis behavior, pyrolysis process of RS mixed with basal additives, i.e. carbonates Li2CO3-Na2CO3-K2CO3（LNK）, added with metal chlorides or sulfates （MCS） were investigated by Thermogravimetry and Fourier Transform Infrared Spectroscopy （TG-FTIR）, respectively. Coats-Redfern method was adopted to calculate the kinetic parameters of pyrolysis process. The results showed that the activation energy of pyrolysis decreased under the action of carbonates, and further decreased as metal chlorides were added, which indicated that the reaction needed less energy to support the pyrolysis process. FTIR analysis indicated that the constituent concentrations （CO, CH4, toluene, phenol, formic acid, H2O） of RS samples decreased after LNK was added, while CO2 concentration increased. Compared to LNK-RS, the concentration increased when MCS were added to LNK-RS, which indicated MCS promoted the conversion of RS into light species. Particularly, LNK promoted Boudouard reaction when temperature was over 550℃, and the LNK added with MCS was capable of facilitating this reaction. Among these MCS, NiCl2andCoCl2 had better effectiveness on the conversion of RS. The research provided the theoretical reference for better utilization of biomass resources. The rice straws were obtained from the countryside of Hangzhou City, Zhejiang Province. The rice straws were dried under sunlight, with physical impurities separated, and ground in a rotary cutting mill and screened into fractions less than 100 mesh （particle size ＆lt;0.15 mm）. The spectrum scope was in the range of 650-4 000 cm-1 and the resolution factor was 4 cm-1. The sample was dried at 90℃ for 24 h prior to the experiments. Pyrolysis was conducted at the heating rate of 70 K/min from 30 to 650℃. According to the thermogravimetric/derivative thermogravimetric （TG/DTG） curves, RS pyrolysis in the temperature range of 30-650℃was characterized by three mass loss stage： 30-208, 208-376, 376-650℃. The results showed that the values of maximum mass-loss temperature and maximum mass-loss rate both decreased after adding additives. The kinetic analysis showed that the activation energy was lowered under catalyzed pyrolysis added with metal additives, compared to that without extra cations and anion, and metal chlorides had better catalytic effectiveness than metal sulphates. FTIR analysis showed that peaks of CO2 and H2O corresponding to RS added with CuSO4 and CuCl2 were stronger than that of RS in the first peak. It was known that the carboxylates in RS would undergo decomposition at relatively low temperatures. In this way, CuSO4 and CuCl2 were more likely to associate with the –COO group at the outer particle surface, resulting in the release of CO2 if the bond between the –COO group and the RS matrix was broken first. It should be pointed out here that the NiCl2-form sample behaved quite differently from other samples. The study here did not exclude the possibility that trivalent cations （Fe3＋） had more sites to connect with the–COO group. In fact, further studies are needed to make sure of the forms of cations during pyrolysis. With increasing temperature, not only the characteristic absorbance bands of CO2, but also the absorbance bands of H2O and CO emerged. However, the absorbance of C-Hυs, C=O, C=C, and C-O（H） apparently decreased in catalyzed pyrolysis. The reduced CO2 and tars （C-O（H）, C=C, C=O） were responsible for the decrease of mass loss.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2015年第2期246-252,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金(20876150)
教育部博士点基金(20103317110001)
浙江省科技创新团队项目(2009R50012-10
2011R09012-04)
浙江省科技厅计划项目(2009C31073)
关键词
秸秆
热裂解
金属盐
氯化盐
硫酸盐
TG-FTIR
Coats-Redfern
straw
pyrolysis
metallic compounds
TG-FTIR
coats-redfern
chlorides
sulfates
