Mechanisms Of Sludge Pyrolysis Reaction And Its Energy Technology Life Cycle Assessment

With the rapid development of urbanization and the increase of the output of sewage sludge,how to realize the energy treatment of sewage sludge has become a difficult problem in the field.This paper aimed at understanding the reaction mechanism of sewage sludge pyrolysis and technological characteristics through the comprehensive analysis of the reaction types,product release patterns,energy balance,organic and inorganic components etc in the pyrolysis process;and put forward a new method of life cycle assessment,combined with the experimental results of pyrolysis mechanism of sewage sludge and related data information to carry out the environmental,energy and economic evaluation of the pyrolysis technology,and analyze the mechanism of the pyrolysis process,providing basic theoretical reference for sludge treatment and disposal in the future.Research shows: the pyrolysis of sludge existed stages of free radical formation,oxygen-containing functional group decomposition,aliphatic side chain breakage,cleavage and dehydrogenation etc,Which is closely related to the-OH bond of functional groups of alcohol,phenol and carboxylic acid,aliphatic-CH3,-CH2 alkyl chain structure,C=O bond,aromatic ester etc on the surface of sludge;the temperature affected most organic functional group of the char surface,but little on heteroatom group.Improving product value,less waste of energy and heat consumption can reduce energy consumption,slow heating,long retention time and high temperature conditions will increase the system's energy input and the heat loss.As the byproducts of heat treatment,the yield of pyrolysis gas increased linearly with the temperature,and the components at 350? were mainly CO and CO2,the content of the flammable gas components increased rapidly at 650?;the solid yield was little affected by temperature,and the calorific value gradually decreased with the increasing of temperature;the liquid yield reached the maximum at 450?,and the calorific value increased first and then decreased.Building the sludge energy utilization evaluation model and analyzing list,then based on the Simapro software,ecological index method,energy conservation law and LCC cost method,a new life cycle assessment method was proposed and the pyrolysis process of sludge under different working conditions was analyzed.The results show that: if the environmental impact is the primary target,as the temperature increases,the environmental damage relative load increases gradually,and the impact categories are mainly fossil fuels,atmospheric inorganic pollutants and climate change;if the energy recovery is the main consideration,the energy consumption of the system can be reduced with the increase of the temperature and the energy recovery rate will be decreased gradually,the yield of hydrogen and the total calorific value of the product reached the maximum at 750?,the bio-oil production was the highest at 450?,and the solid yield decreased gradually;according to the economic evaluation,the cost of sludge pyrolysis system increased with temperature and the maximum is at 750?,the total cost increased first and then decreased,and reached the maximum at 650?.