加压射流流化床煤催化气化制天然气的模拟研究

Simulation Study on Pressurized Jetting Fluidized Bed of Catalytic Coal Gasification to SNG

以煤催化气化制合成天然气技术为研究背景,内径0.2 m,高6 m,处理量为0.5 t/d的流化床气化炉为研究对象,建立了煤催化气化流化床气化炉的数学模型。将气化炉简化为3个区域:分布板区、气泡区和自由段区,基于稳态一维模型,考虑了加压下流体力学性质(最小流化速度、射流高度和直径、气泡直径和速度以及床层膨胀比),质量和热量传递,以及催化气化反应动力学(煤焦燃烧、水蒸气气化、变换和甲烷化)等因素对气化结果的影响。计算结果表明:当射流管引入氧气后,颗粒温度迅速达到最大值随后下降最后趋于平缓;氢气和二氧化碳浓度随着床高近似线性增加,但一氧化碳和甲烷随床高增加缓慢;3.1 MPa时最大气泡直径约为0.11 m,气化炉内不会发生节涌现象。计算床温和气体组成与实验结果有良好的一致性。

A mathematics model was established to simulate the pressurized jetting fluidized bed gasifier of catalytic coal gasification to synthesis natural gas. The gasifier is simply divided into three zones： grid zone, bubble zone and freeboard zone. It is based on a one-dimensional steady-state model which considers the effects of pressured hydrodynamics （minimum fluidizing velocity, jet height and diameter, bubble diameter and velocity and bed expansion）, mass and heat transfers, and catalytic reactions （char combustion, steam gasification, water-gas shift reaction and methanation） on the gasifier performances. The results show- that the temperature of particles in jet zone almost reaches the maximum value when the oxygen is introduced, then decreases sharply and levels off＇. The hydrogen and carbon dioxide concentrations almost increase monotonically with the bed height, however the methane and carbon monoxide concentrations grow- slowly. The maximal bubble size is about 0.11 m at 3.1 MPa, the slug phenomenon may not occur. The prediction bed temperature and gas compositions are in good agreement with experimental data.