Research On Anaerobic Digestion Process For High Temperature Thermal Hydrolysis Based On Energy Efficiency Improvement

Over the past few years,the municipal sludge has been increasing,as the most cost—effective way in disposing sludge,anaerobic digestion process can greatly perform amount reduction,stability,harmlessness and resource utilization of sludge.At present,the anaerobic digestion process of most sewage plants has exposed following issues,long digestion time,a huge pool,low productivity of gas and high energy consumption while sludge drying.To further uplift the operation performance of sewage plants,add high temperature thermal hydrolysis and frame dehydration.Gas produced by the sludge is 1.5 times the original after the high temperature thermal hydrolysis process.By gaining sludge fluidity,the solid-state rate of anaerobic fermented sludge increased more than double;volume of fermenter is reduced;the dehydration performance of sludge is improved;moisture content can be less than 50 percent by mechanical dehydration after fermentation,which saves quantity of heat required by sludge drying.Thermal hydrolysis makes sludge hygienic and harmless.By sampling from one sewage plant in Qingdao,conduct experiment of thermal hydrolysis with raw sludge,waste activated sludge and mixed sludge(30min under 170?),conduct biomethane potential experiment with pre-processed sludge,then analyze gas production upon different experiment temperature.As a result,high—temperature thermal hydrolysis does not have much effect on the raw sludge,whereas it has positive impact on waste activated sludge and mixed sludge,appropriately rise the anaerobic digestion temperature can distinctly boost gas productivity.Optimize the operation process of the sewage plant in Qingdao in reference to the experiment result,sludge processing system adopts pre-dehydration,high temperature thermal hydrolysis,40?medium temperature anaerobic digestion and frame dehydration process.By analyzing the difference between ordinary anaerobic digestion and thermal hydrolysis,it is proposed that the superiority of sludge reduction,resource utilization,harmlessness and hygiene is created by the improvement of sludge process system,also,analysis of the characteristics of thermal hydrolysis and relevant need-to-concern factors of its operation.Forming a simulation model of sludge process system on TRNSYS simulation platform,by leveraging the sewage plants' annual operation data,perform a full—year simulation analysis of the system,compare and analyze the improved system and the original one regarding the anaerobic fermentation process,the steam required for thermal hydrolysis provided by methane,analyze the cogeneration of remaining methane and waste heat recovery process.Propose measures for further energy efficiency improvement.The thermodynamic and economic analysis and evaluation of the system showed that the high temperature thermal hydrolysis system is ready to be popularized.