| The influence of different conditions on the pyrolysis products during the process of sludge pyrolysis has been extensively studied.In order to obtain more high-quality hydrogen-rich gas,the“mechanochemical pretreatment”was introduced in this study.The five aspects of the size of grinding ball,the milling time,the material ratio?mass ratio of CaO to sludge?,the material ratio?mass ratio of balls to sludge?and rotating speed were optimized using CaO as a catalyst during the rapid pyrolysis process of sewage sludge in the cause of achieving the purpose of increasing the gas production yield and the proportion of CH4,H2and CO gas components.The CaO/coke catalytic system was introduced to study the influence of catalyst on the quality of gas produced by rapid pyrolysis and the substitution effect of coke to CaO.The influence mechanism of sewage sludge pyrolysis was analyzed through determining the composition and structure of the mixture after mechanical milling by elemental analysis,FTIR and XRD.The main conclusions are as follows:?1?The results showed that the gas yield was the highest reached 30.35%under the material ratio?mass ratio of CaO to sludge?of 1:1,the material ratio?mass ratio of balls to sludge?of 18:1,all small balls?6mm in diameter?milling sludge of 3h at speed 425r/min.For this condition,the combined proportion of CH4,H2 and CO reached 87.42%.?2?The sewage sludge pyrolysis under the action of three different catalytic systems?CaO,Coke,CaO/Coke?,CaO contributed to increasing of H2,CH4 volume fraction and absorbing CO2 at the same time;As a catalyst,Coke mainly promoted the tar yield of sewage sludge pyrolysis.The tar of sewage sludge can be re-cracked to produce small molecule gas in the process of the sewage sludge pyrolysis.Therefore,it is possible to use coke instead of CaO as a catalyst to promote gas production of sewage sludge pyrolysis.?3?The H/C?element ratio?and H element in the mixture of sludge and catalyst after mechanical milling are high,which has a positive effect on the production of H2 and CH4.And high O/C?element ratio?and O element in the mixture after mechanical milling is beneficial to improve the production of CO.The element content is not positively related to the results of gas production because of the sludge complex composition,the content of other substances in the sludge may also affect the gas-producing.?4?The chemical bonds of the mixture after mechanical milling are mainly O-H,C=O,C-H,C-O-?H?.The different mechanochemical pretreatment conditions can cause the change of organic chemical bond content in the sludge.The increase of organic chemical bonds has a positive effect on the yield and gas composition distribution during the rapid pyrolysis process of sewage sludge to certain extent.Whether these chemical bonds can be broken during the rapid pyrolysis process and generate the target product is also related to the content of other substances in the sewage sludge.?5?The mineral structure in the mixture after mechanical milling is mainly SiO2 and Ca?OH?2.It has a positive effect on the yield and gas composition distribution by destroying the crystal structure of SiO2 and improving the crystallinity of Ca?OH?2. |
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