The influences of loose gas on gas-solid flows in a large-scale circulating fluidized bed (CFB) gasification reactor were investigated using full-loop numerical simulation. The two-fluid model was coupled with the QC-energy minimization in multi-scale theory (EMMS) gas-solid drag model to simulate the fluidization in the CFB reactor. Effects of the loose gas flow rate, Q, on the solid mass circulation rate and the cyclone separation efficiency were analyzed. The study found different effects depending on Q: First, the particles in the loop seal and the standpipe tended to become more densely packed with decreasing loose gas flow rate, leading to the reduction in the overall circulation rate. The minimum Q that can affect the solid mass circulation rate is about 2.5% of the fluidized gas flow rate. Second, the sealing gas capability of the particles is enhanced as the loose gas flow rate decreases, which reduces the gas leakage into the cyclones and improves their separation efficiency. The best loose gas flow rates are equal to 2.5% of the fluidized gas flow rate at the various supply positions. In addition, the cyclone separation efficiency is correlated with the gas leakage to predict the separation efficiency during industrial operation.

中文翻译：

---

全循环数值模拟研究松散气体对循环流化床反应器中气固流的影响

利用全循环数值模拟研究了疏松气体对大型循环流化床气化反应器中气固流的影响。将双流体模型与多尺度理论中的QC能量最小化（EMMS）气固阻力模型耦合，以模拟CFB反应器中的流化。分析了松散气体流量Q对固体物质循环速率和旋风分离效率的影响。研究发现，不同的影响取决于Q：首先，回路密封和竖管中的颗粒趋于变得更紧密地堆积，同时散逸的气体流速降低，从而导致整体循环速率降低。最小Q可以影响固体物质循环速度的大约是流化气体流速的2.5％。其次，随着松散气体流速的降低，颗粒的密封气体能力得到增强，这减少了气体进入旋风分离器的泄漏并提高了其分离效率。最佳松散气体流速等于各个供应位置的流化气体流速的2.5％。另外，旋风分离效率与气体泄漏相关，以预测工业操作期间的分离效率。