Investigations On Agricultural And Forestry Residues For Bio-fuels By Pyrolysis

The efficient exploitation and utilization to bio-energy have great strategic significance on the high-value utilization of agricultural and forestry residues,the transformation of energy construction,the environmental protection and the construction of new countryside.As the core of thermo-chemical conversion technologies of bio-energy,pyrolysis can convert the biomass into bio-fuels including liquid,gaseous and solid.Molten salts are of high capacity and high heat transfer coefficient,so they have the potential to be used as heat carrier and and dispersant in biomass pyrolysis process.In this paper,the pyrolysis kinetics and reaction mechanism were analyzed and pyrolysis experiments were carried out with the agricultural and forestry residue.This investigation is sponsored by the National Natural Science Foundation of China(20876150),the Doctoral Foundation of Ministry of Education(20103317110001)and the Innovative Team Projects of Science and Technology Department of Zhejiang Province(2009R50012-10).The thermogravimetric analysis(TGA)method was adopted to investigate the pyrolysis characteristics of rice straw.The effects of operating conditions such as heating rate,different anions(Cl-,CO32-and SO42-)of sodium salt and different cations(Na+,K+)of chloride salt were examined,and the kinetic parameters were calculated,the pyrolysis mechanism functions were deduced with integration method of Satava.The results indicated that,the increasing of heating rate was beneficial to the release of volatile products,and the maximum lose weight temperature as well as the maximum lose weight rate raised with the increasing of heating rate.Pyrolysis started at a lower temperature region under the role of CO32-,and SO42-can promote the formation of residue carbon.Comparing with Na+,K+ was easier to the generation of solid carbon within the chloride salts.The results showed that the activation energy of rice straw changed lightly compared with the original sample under the role of NaCl,Na2SO4 and KCl,but the activation energy of sample increased with the addition of Na2CO3.The pyrolysis mechanism function of untreated rice straw was inferred with the method of Satava,and the pyrolysis of rice straw with NaCl,Na2SO4 and KC1 accorded with the ninth mechanism Zhuralev-Lesakin-Tempelman equation,which was a three-dimension diffusion mechanism function,its integrated form was[(1-a)-1/3-1]2.However the pyrolysis of the sample with the addition of Na2C03 greed with the eighteenth mechanism-Avrami-Erofeev equation,which was the random nucleation and growth process,and the integrated form of the kinetic equation was[-ln(1-a)]2.The pyrolysis product evolution characteristics of several kinds of forestry and agricultural residues,such as sawdust,rice straw and wheat straw were investigated by TG-FTIR technology.The effects of operating conditions,such as the sorts of biomass,heating rate and additive content of CoCl2 were studied.The results showed that the components of the volatiles were almost the same except for tiny distinctions in concentration.The products concentration changed with pyrolysis time.It was beneficial to generate gas products with the increasing of heating rate.The additives ZnCl2-KCl and CoCl2 promoted the decomposition and transformation of tars.Pyrolysis experiments were performed in the molten ZnCl2-KCl on the basis of pyrolysis kinetics and gas release characteristics investigations.The influences of biomass material,pyrolysis temperature,feeding rate,the flow rate of carrier gas,the species and contents of inorganic additives on the pyrolysis were investigated.The results showed that wood-based biomass had benefit to the production of liquid fuel.With the increasing of heating temperatures,the bio-oil yield increased firstly and then decreased,and reached the maximum yield of 19.4wt.%at 440 ?.The suitable increasing of feeding rate promoted the generation of bio-oil.When the flow rate of carrier gas was kept at 100L·h-1,the maximum yield of gas products was about 48.6 wt.%and a lowest solid product yield about 31.8 wt.%.The catalytic additive CoCl2,FeCl3 and NiCl2 had positive effects for the generation of bio-oil,and it was found that H2,CH4 and CO2 were the main compositions of gas products,and the oxygenated compounds such as ketones,esters,phenols and carboxylic acids were the main compositions of the liquid products.This research provided a certain theoretical reference for a further understanding of biomass pyrolysis mechanism,the release properties of the productions,the structural design of the equipment and the operating parameters selection of the pyrolysis.