Numberical Models And Optimization Of Fixed-bed Coal Gasification

Coal is rich in our country which is far more than oil and natural gas. Coal gasification has become an intensive research topic in recent years,for it’s a highly efficient and clean way in the utilization of coal.In our country, we make most use of technology is the Fixed-bed coal gasification.The construction techniques of it is quite mature, but the optimal operation need further developing. Mathematical model is the most simple, convenient and low cost method in the study of fixed-bed coal gasification operation conditions.This article proposed a steady mathematical model which base on the physical changes and chemical reaction occur in a two-stage fixed-bed. The summary of its works as follows:(1)The mechanism of the pyrolysis and coal gasification in the fixed-bed has been discussed.The existed pyrolysis and gasification models are classified, consolidated and evalued. In the end,a steady gasification model is proposed to forecast the coal gasification of Shenhua coal in this fixed-bed.(2) Analysis the gasifier sensitivity by changing operation condition.The results as follows:when the amount of water vapor increase, it not only can absorb heat, but can prevent the ash particle caking;when the amount of vapor increase, water gas equilibrium constant will change which lead to improve the H2and CO2percentage content, and reduce the percentage content of CO;When the amount of air increase, the amount of oxygen increase, so the highest temperature and CO gasifier of content increased; When the pressure increases, the gas calorific value and gas production increase. But the amount of CH4only grow a little. Although pressure has less effect on the gasifier, increased pressure can improve the amount of coal gasification in unite time. The optimal operating conditions of the gasifier:Steam/coal ratio10.8～1.2; Air/coal ratio:2～3.