Pyrolysis-gasification Technology Development And Process Simulation Analysis For MSW Treatment

For the treatment methods of Municipal Solid Waste(MSW), pyrolysis and gasification technology,which has obvious advantages in terms of environmental protection and pollution controlcompared with incineration and landfill, is regardedas one of the most promising treatments in the future.On the basis of fully understanding forMSW characteristic in our country, a pyrolysis-gasification process system was developed, and the modelforpyrolysis-gasification processwas built. This study also estimatedthe economy of pyrolysis-gasification process in order to provide the basis and reference for design and operation. The main research contents included in the following:(1) Based on sufficientliterature investigation, the characteristic of MSW including physicalcomposition, moisture content, heating value and proximate and ultimate analysisin China was summarized. Then prediction methods for heating value,and proximate and ultimateanalysis of MSW were discussed.(2)According to the characteristic of MSW in China, combining with the other system of the cooperator,a pyrolysis-gasification processsystemwas developed. This system reuses the self producedcombustible gas to supply energy.(3)Aiming at the developed system, forecast model was established by usingprinciple of material balanceenergy balance.At the same time, thermal efficiency, heat loss of pyrolysis-gasification furnace and reuse rate of gas obtained from pyrolysis-gasification was analyzed and predicted. On the basis of incineration triple diagram, thepyrolysis-gasificationtriple diagram was plottedfor the presented process to discriminate whether the feedstock is suitable to this system. Furthermore a method using thepyrolysis-gasificationtriple diagram was proposed to predict the reuse rate of gas when the physical composition of feedstock changed. This paper also analyzed the ash content of MSW, the exhaust gas temperature of pyrolysis-gasification furnace and the effect of excess air coefficient onpyrolysis-gasification.(4) Based on Aspen Plus platform, the equilibrium model of pyrolysis-gasification for MSW was built: RYieldand RGibbsmodels for pyrolysis section, RGibbsmodule for gasification section.When steam was used as gasification agent,the influence of gasification temperature and the amount of gasification agenton gas characteristics and carbon conversion ratewere simulated and analyzed. It showed that the best condition was temperature at 800℃, the gasification agent/ dry MSW ratio at 0.4. In the meantime, on the best condition, using four different gasification agents(steam, CO2, steam-CO2(0.45/0.55) and steam-flue gas(0.2/0.8)), through comparison and analysis of the obtained gas characteristic, steam-flue gas, it turned out that steam-flue gas(0.2/0.8) as gasification agents was a economic and high efficient method.(5) Taking Langfang city as an example,this paper preliminarily designed the process schemefor pyrolysis-gasification system. This design mainly included pre-treatment process, pyrolysis-gasification furnace, and relatedappurtenance. At the last, through economic analysis of this scheme in 10 years cost recovery period, this scheme needed government policy subsidy for MSW treatment.