Investigation On Pyrolysis Of Agricultural Straws For Gas Products By Molten Salt

Biomass is a kind of clean and renewable energy sources and its utilization has great significance. Biomass pyrolysis is one of the high-efficiency energy conversion technologies and molten salt is an excellent heat carrier, has the advantage of high heat capacity and heat thermal conductivity which make it possible to heat biomass particles quickly and uniformly. In this paper, the rice straw(RS)was selected as biomass raw material, and the pyrolysis process of RS mixed with molten salts ZnCl2-KCl(ZK) and Li2CO3-Na2CO3-K2CO3(LNK) were investigated to study the apparent kinetics and evolution characteristic of products. The experimental research of pyrolysis was carried out in molten salts LNK to produce gas products.To explore the behavior of RS pyrolysis in exist of molten salt, pyrolysis process of RS mixed with ZK and LNK which were selected as basic molten salt system, loaded metal chlorides or sulfates were investigated by Thermogravimetry and Fourier Transform Infrared Spectroscopy(TG-FTIR), respectively. Coats-Redfern method was adopted to calculate the apparent kinetic parameters of RS pyrolysis process. The results showed that ZK changed the characteristic pyrolysis temperature and mass loss rate, the activation energy of pyrolysis decreased under the role of ZK. FTIR analysis indicated that the concentration of constituents of samples(CO2, CO, CH4, phenol, toluene, formic acid, H2O) in ZK decreased compared with that of RS. The activation energy of RS mixed with chlorides-ZK further decreased. Sulfates-ZK promoted the escape of volatiles, and the effect of NiSO4 was remarkable. The characteristic temperature, characteristic mass loss rate and activation energy of pyrolysis decreased under the role of LNK. FTIR analysis indicated that the concentration of constituents of samples(CO, CH4, toluene, phenol, formic acid and H2O) in LNK decreased compared with that of RS, while that of CO2 increased. The activation energy of RS mixed with chlorides-LNK further decreased. Sulfates-LNK and chlorides-LNK promoted the escape of volatiles. Particularly, LNK promoted Boudouard reaction(C+CO2â†'2CO) after 550 oC, and the LNK loaded sulfates and chlorides were capable of facilitating this reaction. NiCl2 and CoCl2 had better effectiveness on the conversion of RS.The experimental research of RS pyrolysis was carried out in mixed molten salts 31.1wt%Li2CO3-32.2wt%Na2CO3-36.7wt% K2CO3 which loaded with sulfates and chlorides. The results showed that the yield and the volume concentration of gas products increased under the role of LNK. Sulfates-LNK and chlorides-LNK promoted the escape of gas, and the component distribution changed. The gas yield of RS mixed with LNK increased by 41.3%, and the volume concentration of H2 increased from 41.21% to 77.08%. The yield of H2 increased to 366 mL/g under the role of CuSO4-LNK, and the volume concentration of H2 increased to 86.21% under the role of CoCl2-LNK. With the reduce of salt mass ratio, the yield of gas increased firstly and then decreased, the volume concentration of H2 and CO decreased, while the the volume concentration of CH4 and CO2 increased. The experiment provided the theoretical reference to study energy utilization of biomass resources.