Abstract:

Micro-scale discrete particle method (DPM) and meso-scale computational fluid dynamics (CFD) simulations, both based on the energy-minimization multi-scale (EMMS) model, were carried out on the complex gas-solid flow in the regenerators of fluid catalytic cracking (FCC), aiming to provide visualized quantitative analysis for the performance improvement of the newly designed systems with unprecedented 7 Mt·a^-1 throughput. For verification, a current 3.5 Mt·a^-1 regenerator was first successfully simulated. Then, a 7 Mt·a^-1 regenerator was simulated to investigate the performance of the air and solids distributors. The simulation results showed that increasing the gas ring number from 2 to 3 can improve the homogeneity of solids distribution significantly, while increasing the gas inlet number from 1 to 2 for the 3-gas-ring case made little improvement. For solid phase distributor, the injection of solids and their mixing with the internal material were simulated and analyzed. It was demonstrated that decreasing the hole fraction can effectively increase the resistance and improve the mixing performance. The necessity of understanding the detailed flow field around the nozzles for further improvements is demonstrated, and EMMS-DPM can be a powerful tool for this purpose.

Key words: EMMS model, EMMS-DPM, FCC regenerator, gas distributor, solids distributor, mixing

摘要：

大型催化裂化装置中再生器的规模庞大,其中的气固分布装置对整体性能有重要影响。与传统的冷模实验相比,对再生器整体和气固分布器局部的多尺度计算机模拟有利于更深入地了解其流动规律,高效便捷地考察不同结构设计与操作条件对气固分布的影响,辅助其优化设计。结合双流体模型和EMMS曳力模型,首先模拟了中石化现有3.5 Mt·a^-1大规模清洁汽油生产装置的再生反应器,进而模拟并分析了基于同一工艺设计的7 Mt·a^-1超大规模再生反应器内不同气体和固体分布器对流动与混合过程的影响。模拟结果表明:3环较2环分布器能有效改善气体分布的均匀性,但增加每个环上的气体入口数对其分布的改善有限;而对固体分布器,开孔率减小可增加其阻力,并在一定程度上改善混合性能。进一步讨论了研究分布环喷口处的气固流动与混合细节的必要性,初步展示了基于EMMS模型的离散颗粒模拟方法(EMMS-DPM)对其的有效性。

关键词: EMMS模型, EMMS-DPM, 催化裂化再生器, 气体分布器, 固体分布器, 混合