Study On Characteristic And Synergistic Effects Of Co-pyrolysis Behavior Of Sewage Sludge And Vinegar Residue

Sewage sludge pyrolysis is a heat treatment method with the advantages of reduction,harmlessness,and recycling.Due to the low volatile content,high ash content and low calorific value of sludge itself,which are not conducive to thermochemical treatment,it is often necessary to add another organic substance with higher energy density to achieve energy supplementation and improve sludge pyrolysis efficiency.Vinegar grains are abundant in output,low in ash and high in calorific value,and are considered as an ideal biomass fuel.However,there are few reports on the research on the pyrolysis of vinegar grains alone and the co-pyrolysis of sludge and vinegar grains.In this paper,the thermogravimetric analyzer and vacuum fixed bed reactor were used to study the co-pyrolysis characteristics,reaction kinetics,product yield distribution and product c haracteristics of sewage sludge and vinegar to explore the Synergy in the process of co-pyrolysis.TGA experiments show that,compared with the pyrolysis behavior of sludge alone,the addition of vinegar grains moves the completion temperature of thermal decomposition reaction of organic matter in sludge to a low temperature,and the devolatization index Di of the pyrolysis process is 3.75×10^-7;Compared with the theoretical calculation,the devolatilization index of the decomposition of the mixture is 0.35×10^-7 lower than the calculation.There is no overlap between the thermal weight loss process of the mixed sample measured by the experiment and the thermal weight loss process of the sample calculated by the theory.There is synergy in the process of co-pyrolysis of mud and vinegar,when the mixing ratio is 1:1,the synergy is most obvious;Coats-Redfern model shows that when the mixing ratio is 1:1,the required activation of the reaction reaches the lowest value;The model-free mechanism of FWO and KAS is used.Compared with theoretical calculations,the FWO method results show that the activation energy required for the decomposition of the mixture decreases by 44.80-33.49%,and the KAS calculation results decrease by 35.38-29.49%,indicating that the addition of vinegar Total pyrolysis activation energy.Vacuum fixed bed reaction shows that under the experimental conditions of high temperature and long reaction time,the gas-solid reaction and the secondary cracking of tar lead to the generation of non-condensable gas,which increases the gas yield and decreases the yield of tar and biochar.Gas chromatography analysis of the co-pyrolysis gas composition showed that the addition of vinegar resulted in a significant increase of hydrogen and carbon monoxide and a reduction of carbon dioxide in the mixed gas composition;infrared spectroscopy analysis showed that the-CH peak on the surface of the biochar disappeared compared with the raw material,Indicating that organic aliphatic hydrocarbons decompose into methane,carbon dioxide,and other gases or aromatic structures.With the addition of vinegar,Car-H in the blend carbon also decreases,indicating that co-pyrolysis promotes the cracking of aromatic hydrocarbons.Raman analysis showed that co-pyrolysis promoted the cracking of fused-ring aromatic hydrocarbons on the carbon surface;specific surface area analysis showed that co-pyrolysis promoted the precipitation of volatiles and promoted the formation of pore structures the specific surface area increases.GC-MS determined the composition of bio-oil,and it was found that the aliphatic hydrocarbons and nitriles in the co-pyrolysis oil decreased significa ntly,the phenols and esters increased significantly,and a certain amount of ketones appeared.With the increase of pyrolysis temperature,the precipitation rate of alkali metals in the blend biochar increased,and the precipitation rate of alkali metals in the total pyrolysis reached 79.19-86.73%.The alkali metals volatilized into the gas atmosphere,which played a catalytic role in the co-pyrolysis process.