Combustion Characteristics Of Municipal Solid Waste

With the development of economy and urbanization of China, the disposal ofMunicipal Solid Waste is becoming a serious problem for society which cannot beneglected. Incineration of MSW has the advantages of Reduce, Reuse, Recycle, and hasbecome one of the most important disposal methods. While, as for the reason that MSWcomposition is complicated and varies with locations and seasons, the fuel characteristics isvery complex. So in the thesis, studies have been carried for the combustion characteristicsof typical components in MSW.Kitchen waste is regarded as a typical component of MSW, and studied for thecombustion process and influence variables including heating rate, oxygen concentrationand moisture content. Increase of heating rate leads to the increase of maximum weight lossrate, moves DTG peaks to higher temperature, and also increases the amount of ash residue.The influence of oxygen concentration on combustion is mainly focus on thedecomposition of cellulose and lignin, while limited influence on the hemi-cellulose. Byreducing the resistance of boundary layers, higher oxygen concentration promotes thecombustion process. The existence of moisture makes the combustion more difficult, butthe influence is limited at high temperature.Influence Factor is introduced to weigh the importance of different variables duringthe combustion process. Oxygen concentration has the largest influence on ignition andsecond weight loss peak, while the first weight loss peak is mainly influenced by heatingrate. Besides, kinetic parameters including activation energy and frequency factors arecalculated for the combustion process. With higher heating rate, lower moisture content,and higher oxygen concentration, the activation energy can be decreased. Among the threevariables, oxygen concentration has the largest influence on kinetic parameters.Distributed Activation Energy Model (DAEM) was used to study the change of kineticparameters during combustion process. The activation energy increases with the devolatilization process at the initial stage, the heat released by combustion of char willlead to the decrease of activation energy, but activation energy has an increasing trend at theburnout stage. In the thesis, a new classification method is given for the MSW based onactivation energy. Different kinds of MSW components are classified into four groupsbased on the number of activation energy, which does help for the disposal of MSW withsimilar characteristic.A self-made fast heating thermogravimetric analyzer was used to study the interactionbetween different components, and also the reasons for the interaction. The results showthat, there are interactions for the combustion process, and the reaction rate for combustionof mixtures is higher than the linear adding of single components. The mixing of samplesdoesn’t have significant influence on decomposition rate of pyrolysis, but changes the charstructure. Compared to those of single component, the formation of pores and proportion ofamorphous carbon are promoted for chars of mixtures. Both the change of physicalmorphology and chemical structure of chars, promote the combustion process for themixtures.