The Basic Study On Co-pyrolysis Of Municipal Sewage Sludge And Waste Biomass

The resource utilization of waste biomass and municipal sewage sludge(referredto as: sludge) is an essential treatment trend. In order to maximize the potentialenergy using of both agricultural/forestry waste and sludge, the resource utilizationprocess of co-pyrolysis of biomass and sludge have been investaged. On the basis ofthermogravimetric analysis, the characterization and distribution analysis of theproducts from fixed-bed co-pyrolysis were studied by GC, GC-MS, SEM, BET andother instruments. The synergies laws and mechanism from the co-pyrolysis ofbiomass and sludge provide the key technic and theoretical informations for theefficient conversion and product optimizationAccording to the results of TGA experiments, we could find that the pyrolysis ofsludge at the suitable heating rate (20°C/min) can be divided into three stages; thepyrolysis characteristics of biomass are closely relate to the content of its cellulose,hemicellulose and lignin; the blending ratio of biomass and types of biomass havesignificantly effect on co-pyrolysis. Some synergy existes in co-pyrolysis processwhen the biomass concent in mixtures is more than60wt%and it is beneficial for theco-pyrolysis process based on the value of R(the weight-loss rate addition in finaltemperture)>0.The kinetics results show that the C-R method has a better simulation effect thanthe F-C one; types of biomass and determining of DTG peak have a significantimpact on the reaction order (n) of both biomass and sludge pyrolysis; the highcellulose content biomass is helpful to reduce the activation energy (E) ofco-pyrolysis in290-370oC, but the high lignin content biomass can reduce theactivation energy (E) of co-pyrolysis in330-390oC; blending ratio of biomass havestrong effects on the activation energy (E) of co-pyrolysis and the E of experimentless than the E of linear summation. It illustrates that there are synergies inco-pyrolysis of the sludge and biomass; the apparent activation energy of theco-pyrolysis process was reduced and the pyrolysis process was improved.The optimized process parameters of co-pyrolysis have been obtained as: carrier gas flow rate:250mL/min, thickness of fixed-bed:10mm, holding time:10min, theheating rate:30oC/min, the pyrolysis final temperature:650oC; the suitable sludgeblending ratio dependented on bimass types. Generally, the certain synergy whichstimulated the process of co-pyrolysis exists in the high biomass content (≥60wt%)；the more lignin the biomass contained, the better synergy happened in co-pyrolysis,and its mechanism of synergy can be attributed to the catalysis of porous structure ofthe char (pre-product of lignin pyrolysis).The composition analysis and distribution characteristics of the gas, liquid andsolid products have been investigated. The results show that the components ofpyrolysis gas from both sludge and biomass contain H2，CH4，CO，CO2and C2-3alkanes. The GC/MS analysis results of bio-oils show that the liquid product(bio-oil)is a complex mixture, the bio-oil from the high lignin biomass contains more phenolsand alcohols than others, the bio-oil from the high cellulose biomass has lots ofcarboxylic acids, ketones and esters, the co-pyrolysis process has a good effect onincreasing carboxylic acids and esters of its bio-oil; the calorific value of bio-oilclosedly related with the types of biomass and the sludge blending ratio; withincreasing of the final pyrolysis temperature and the sludge blending ratio，the changeof viscosity bio-oil presents a first decreasing and then increasing trend. The analysisof SEM and BET of the solid product (char) indicated that a large specific surfacearea and mesoporous or macroporous structure existed in char, and an excellentadsorption characteristics were found in the iodine adsorption experiments of char,and the highest iodine adsorption value is910.082mg/g.The results of this study might provide basic research data for the developmentof resource utilization technology for sewage sludge, tannery sludge, printing/dyeingsludge and waste biomass resource utilization technology.