Hot Model Experiment And Numerical Simulation Study On Two-stage Combined Coal Gasifier

The two-stage combined coal gasifier with the heat recovery via chemical energy was mainly researched in the thesis. The hot model experiment research of two-stage gasification process was carried out. At the same time, a three-dimensional numerical simulation was performed to study pressure distribution, flow field, temperature distribution and gas concentration distribution in the bed region of the second stage.The heat transfer process of porcelain balls was studied in the hot model experiment device. The results show that with the increase of bed height, the heat rate of the second stage will be slow down and thermal storage effect of bed region will be more significant. When the bed height is150mm and200mm, the effect of shift reaction on gases of the second stage outlet will be increased. In addition, the influences of the adding of KNO3and Ca(NO3)2on two-stage gasification process were researched when the reactant was Inner Mongolia lignite. The results show that the adding of KNO3and Ca(NO3)2can accelerate two-stage gasification reactions. The catalytic effect of KNO3is better than that of Ca(NO3)2. Ca(NO3)2can maintain excellent catalytic effect for60minutes throughout the two-stage gasification process, whereas KNO3can keep it for a long time. With the increase of Ca(NO3)2adding weight to the second stage, the gasification reactivity will become better. It can improve reaction rate when the adding of Ca is more than5%.Numerical simulations of two-stage combined gasifier were carried out by non-premixed combustion and porous media model. The results indicate that there is an obvious pressure drop in the bed area, which varied linearly with bed height. The high-temperature gas from the first stage passes through the fixed bed in plug flow. In the second stage, gas flows smoothly, but gas stream lines distort near the wall, which is similar to wall effect phenomenon of the actual packed bed. The temperature falls more quickly near the wall above the bed layer than that in the bed region. Gas flow and temperature distribution become more even in the bed region of the second stage. When the high-temperature gas from the first stage passes over bed region, water gas shift reaction will proceed towards the direction of forward reaction, and the gas concentration of CO2and H2will increase in some degree.