Numerical Simulation of Catalytic Coal Hydrogasification in a Lab-Scale Pressurized Fluidized Bed

Catalytic coal hydrogasification has been tested in a 36mm diameter pressurized fluidized bed at 3 MPa and 1123 K, and a 77.3 wt.% CH₄ yield in 30 mins is achieved with the Co-Ca catalyst. To help in the design and scale-up of an industrial pressurized bed gasifier, a thorough understanding of the bubble dynamics is needed.

In this presentation, we conducted a TFM-KTGF simulation of catalytic hydrogasification in the lab-scale bed operated at 3.7u_mf. The predicted bed expansion height is validated with the empirical correlation. The average bubble size is found to be much smaller than the Mori-Wen correlation. As a key parameter, the bubble size distribution (BSD) is detected and statistically analyzed using a novel post-processing MATLAB code. The BSDs at different heights (0.25H, 0.50H, 0.75H, 1.0H) are shown to have a similar bimodal distribution. Furthermore, the bubbles are divided into three groups: the small (1 mm-3 mm), middle (3 mm-6 mm), and large (6 mm-9 mm) sized bubbles. The number of small bubbles decreases along the bed height, but the number of large bubbles increases. It is noted that the number of the middle sized bubbles is almost unchanged along the bed height. This suggests that the bubble coalescence and breakup tend to approach a balance. A catalytic hydrogasification model is coupled with the gas-solid hydrodynamics, and distributions of temperature and CH₄ concentration were predicted and compared with the experimental results. Further work will be focused on the effects of bed height, bed diameter and particle size on the overall performance of the gasifier.