Experimental Studies On The Influence Of Moisture In MSW Pyrolysis/Gasification Process

The treatment of municipal solid waste (MSW) has become one of the important worldwide issues, which are related to the energy, environment and social development. MSW is considered as the main source of environmental pollution, as well as an important recycling resource. The design and development of waste treatment technologies have gained focused attention in the world, while the pyrolysis/gasification process is proved to be as an effective technology for the waste treatment, which can reduce the pollutant emission, such as dioxins and heavy metals, and realize the energy recycling.The characteristics of representative MSW components in the pyrolysis/ gasification process have very important guidance for design and operation of waste treatment. Due to high moisture and low heat value of MSW in China, the moisture in the waste has great influence on the distribution of pyrolysis/gasification products and gas quality. However, such characteristic has usually been ignored when considering the reaction mechanisms in the waste treatment. Therefore, it's necessary to study the effect of moisture on the MSW Pyrolysis/Gasification process.A large inventory iso-thermal TGA system has been setup to investigate the characteristics of six typical waste components under different operating conditions (with and without steam) at 600～800℃in the pyrolysis/gasification processes. The thermogravimetric process is analyzed by weight conversion rate and volatile loss rate.The produced gases are characterized on-line by gas analysis system. The effect and mechanism of the moisture on the waste components have been investigated through gas yield, gas composition and heat value of gas product.Based on the results from small-scale experiments, a comparative one between the polyethylene (PE) and PE with 20% moisture at 750℃has been carried out on a pilot-scale fluidized-bed gasification system. The results of syngas yield, heat value of syngas, tar yield and heat value of tar indicate that the steam plays a significant role in the reforming and cracking of gaseous products. It is also found that the existence of the steam decreases the heat value of tar, and increases the heat value of syngas, thus improving the syngas quality.