| The disposing of sewage sludge is an important part of water pollution control and water environmental protection,and an important issue facing sewage treatment plants and urban sanitation.The goal of sludge treatment and disposal is to achieve reduction,stabilization,and harmlessness effects of sludge.Compared with landfill and incineration,gasification is one of the most potential technologies to realize the resource utilization of sludge.CaO is a chemical agent widely used in sludge drying.It is also proved to have excellent catalytic activity for biomass gasification with hydrogen production.By analyzing the synthesis gas gasified under the conditions of different CaO addition ratios,temperature and steam flow rate,the optimal conditions for preparing hydrogen-rich gas were obtained,and the solid phase product FTIR,XRD,and other analysis were supplemented to reveal the catalytic gasification mechanism.In addition,the sludge was subjected to different stages of hydrolytic acidification treatment.Then the treated sludge was gasified,the gasification characteristics of the sludge at different stages were studied,and the optimal gas production conditions and the influence of the hydrolysis acidification process on hydrogen production were explored.The results showed that CaO greatly improved the efficiency of sludge drying.With the addition of 20%CaO,and the moisture content quickly dropped from 80.11%to 48.28%after naturally dried for 1.5 hours.At the same time,research on steam gasification of dried sludge showed that the addition of CaO improved the performance of hydrogen production.The highest H2 composition in the synthesis gas was 63.28%at 750℃with 20%CaO adding,which was increased by 40.90%compared with the addition of 0%CaO.As the increasing of temperature,the production of H2 increased.At 900℃,the H2 yield was as high as 17.59 g/kg.When the steam flow rate was raised to 1.0 g/min,the purity and yield of H2 increased by 15.7%and 32.18%.It was due to the promoted decomposition of the oxygen-function groups with the increasing of CaO addition ratios.And the capture of CO2 by CaO could drive the water-gas shift reaction to improve the yield of H2.The study also found that CaO would reduce the release rate of N and S elements during the gasification process.When 20%CaO was added,the release rate of N-containing substances during the gasification process was 31.22%.After the sludge was hydrolyzed and acidified in different stages,the content of cellulose and hemicellulose decreased,and the relative content of lignin increased.At this time,gas production performance of sludge steam gasification has been improved.The purity and yield of H2 were the highest after 10 days of hydrolysis and acidification.The purity was 70.27%and the yield was 16.92 g/kg.Therefore,steam gasification of sludge after CaO drying and hydrolysis acidification treatment can improve the performance of gasification synthesis gas and obtain hydrogen-rich gas.It is conducive to promoting the advancement of sewage treatment plant sludge treatment and disposal technology,effectively avoiding secondary pollution,protecting and improving the ecological environment,and promoting energy saving,emission reduction,and sludge resource utilization. |
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