Interactive Effect And Process Optimization Of Pyrolysis And Gasification Of Combustible Solid Waste

As the improvement of social economy and people living standard,the production of municipal solid waste increase gradually year by year.People appeal to stricter harmless municipal solid waste disposal technology.The new generation municipal solid waste(MSW)"controlled atmosphere" thermal disposal technologies such as pyrolysis,gasification,and gasification and melting will be a trend in the future,owing to its low pollution,energy conversation,and volume reduction.Pyrolysis and gasification are not only important thermal disposal methods of municipal solid waste,but also key steps of controlled atmosphere combustion technology.For development of clean,high efficiency energy conversation technology of Chinese municipal solid waste,it is important to further strengthen the study of pyrolysis and gasification reaction mechanism of multi-component combustible solid waste,and optimize pyrolysis and gasification process of practical Chinese municipal solid waste,which main characteristics are high moisture and low heat value.Based on above analysis,the main researches in this paper are as follows:(1)It showed that there are interactive effect during co-pyrolysis process of some components of municipal combustible solid waste,i.e.the co-pyrolysis results can't be described by weighted pyrolysis results of relative single components.The mechanism of interactive effect and influence of interactive effect degree on pyrolysis of solid waste in practice was investigated.The interactive effect of co-pyrolysis of different components(hemicellulose,cellulose,and lignin)in biomass waste and different plasties were studied by thermogravimetric method.The mass fraction of different components(hemicellulose,cellulose,and lignin)in biomass waste was determined by "Bigass" function fitting of weight loss rate curve from thermogravimetric experiments.Quantitative analysis of interactive effect degree was determined by variance analysis of regression fitting.It is showed that the interactive effect on co-pyrolysis of different component in biomass waste and plastics are of great difference.Compared to weighted experimental results,deviation degrees of co-pyrolysis of cellulose/PVC is most obvious,as high as 58.4%.Cellulose increase PP and PS pyrolysis temperature,and the deviation degree of PP is more than PS.Lignin lower PE pyrolysis temperature.The interactive effect of the rest co-pyrolysis of component in biomass and plastic can be neglected.Compared to weighted experimental results,deviation degrees of co-pyrolysis of paper/PP,paper/PS,and cabbage/PP decrease with heating rates.However,cabbage/PE is opposite.In practice co-pyrolysis progress,only the interactive effect on co-pyrolysis of lignin in biomass and PE can not be neglected.(2)The aim of this part is to analysis heat consumption of pyrolysis of raw combustible waste with high moisture,and obtain relative thermal equilibrium operation parameters of self-pyrolysis.Heat consumption measurement of pyrolysis of single waste component was carried on Differential Scanning Calorimeter(DSC).Combined with characteristics of raw waste and relative pyrolysis experimental results,thermal performance of pyrolysis of raw combustible waste was calculated and analyzed.It shows that heat consumption during pyrolysis process of each waste is small,no more than 10%of itself heating value.Drying heat takes most fraction of heat consumption during pyrolysis process of real combustible waste.The pyrolysis thermal performance of plastic waste in much more better than that of biomass waste.To improve the pyrolysis thermal performance,moisture controlling is the most important.if pyrolysis is the intermediate process of "controlled atmosphere" thermal disposal system,temperature should be controlled at about 500 ?.Besides,the energy balance of self-heating pyrolysis that coke is token as heat resource was calculated.The effect of moisture on operational parameter was obtained.The calculated results provide references for design and operation of solid waste pyrolysis technology.(3)Self-gasification is not only one of important thermal disposal technologies of municipal solid waste,but also a key step of controlled atmosphere combustion process.However,self-gasification of Chinese municipal solid waste is impossible,because of its high moisture and low heat value.Limitation of moisture and ash for optimal air gasification of Chinese MSW has been simulated based on the carbon boundary gasification(CBG)and Gibbs free energy theory.The relative optimal gasification operation parameters such as excess air ratio;gasification temperature,and preheating air temperature were analyzed.The results shows that there exist a critical moisture content for optimal gasification of waste with given combustible and ash content.Solid waste can access to optimal gasification if moisture content less the the critical point.Otherwise,gasification efficiency and heating value of syngas will decrease sharply with moisture content.To access optimal gasification,waste properties should be:moisture 15.5?27.8%,ash 10?30%,lower heating value 10.?17.3MJ/kg.Corresponding operating parameters are:equivalence ratio 0.20?0.26,preheating air temperature 300?400?.Corresponding gasification results:gasification temperature 600?650? heating value of syngas 6.0-6.8MJ/Nm3.(4)The operation parameter of municipal solid waste disposal technology should be adjusted timely according to fuel heat value.However,the component of municipal solid waste is very heterogeneous.The heat value of feed solid waste in reactor varies from time to time.But,the measurement of municipal solid waste is time and labor consuming.Therefore it is necessary to develop a simple and rapid municipal solid waste heat value predictive method based on wet physical component,which can provide reference for design and operation of different thermal disposal technology.The predictive error should be allowable in practice.Based on the measurement of heating value of more 20 kinds of clean solid wastes and moisture of each major real combustible,a rapid and cost-effective prediction method based on wet physical composition has been developed to determine the lower heating value(LHV)of municipal solid waste(MSW)for practical applications in China.The prediction equation is:Qnet,w,MS = 219Pl + 109(Ppa +PWo + PTe).To assess the prediction performance,information was collected on 103 MSW samples from 31 major cities in China from 1994 to 2012.Compared with five predictive models based on the wet physical composition from different regions in the world,the predictive result of the developed model is the most accurate.The prediction mean absolute error 18.21%,within the accepted error range in practice application.The prediction model is of practical application value for design and operation of relative thermal disposal system of MSW.