Numerical Simulation of Spray Shock Chilling Process of High Temperature Syngas in the Pipeline
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摘要: 采用数值模拟方法对管道内高温合成气的喷雾激冷过程进行了研究，考察了喷嘴直径、喷嘴雾化半角和冷却水流量对管内合成气流动与降温过程的影响。结果表明：减小喷嘴直径、增大喷嘴雾化半角和冷却水流量有利于管内合成气降温。为使废热锅炉进口合成气(7472.99 m3/h)从1523.31 K降温至1273.15 K，采用冷却水流量为1.41 kg/s，喷嘴直径为6 mm，喷嘴雾化半角为70°的压力旋流喷嘴能达到预期的降温效果。Abstract: Spray cooling is a technology of increasing interest for the high heat flux application, featuring high heat transfer, rapid cooling, and less cooling water consumption. In this work, a numerical study was carried out on the process of cooling water spray shock chilled syngas in the pipeline. To determine the influences of different initial conditions on velocity field and temperature field in the pipeline, numerical studies were performed by varying the nozzle diameter, nozzle spray half angle, and the cooling water mass flow rate. Based on the Euler method, the gas phase flow field in the pipeline was calculated using realizable k-ε turbulence model. Based on the Lagrange method, the droplet trajectory was calculated using the stochastic trajectory model. And the interphase mass and heat transfer between the gas phase and the droplet were solved by the bidirectional coupling method. Simulation results showed that reducing the nozzle diameter, increasing the nozzle spray half angle, or increasing the cooling water flow could reduce the syngas temperature. By using a pressure swirling atomizing nozzle with the diameter of 6 mm and the spray half angle of 70°, the syngas(7472.99 m3/h) temperature could be reduced from 1523.31 K to 1273.15 K when the cooling water flow rate was 1.41 kg/s. Effective cooling of the syngas before the fire tube waste heat boiler is achievable and can be used for the optimization of the operation environment of waste boiler.
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图 3 液滴索特平均直径随喷射压差的变化
Figure 3. Sauter mean diameter variation of droplet with injection pressure difference
图 7 流场参数Vz_max和Rz随喷嘴直径d0的变化
Figure 7. Variation of flow field parameters Vz_max and Rz with nozzle diameter d0
图 8 不同喷嘴直径d0下X=850 mm平面速度场
Figure 8. Velocity field on X=850 mm plane of different nozzle diameter d0
图 9 流场参数Vz_max和Rz随喷雾半角θ的变化
Figure 9. Variation of flow field parameters Vz_max and Rz with spray half angle θ
图 10 管道内温度场和X=850 mm截面上的温度分布曲线
Figure 10. Temperature field in the pipeline and temperature distribution curve on X=850 mm plane
图 11 不同喷嘴直径d0下管道内温度场
Figure 11. Temperature field in the pipeline of different nozzle diameter d0
图 13 不同喷雾半角θ下管道内温度场
Figure 13. Temperature field in the pipeline with different spray half angle θ
表 1 合成气和冷却水物性参数
Table 1. Physical properties of syngas and cooling water
Materials Temperature / K Flow rate / (m3·h−1) Pressure / MPa Density / (kg·m−3) Relative molecular weight Viscosity / (mPa·s) Thermal conductivity / (W·m−1·K−1) Syngas 1 523.31 7 472.99 3.50 3.68 13.56 0.04 0.26 Cooling water 448.6 804.58 18.02 0.11 0.62 
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表 2 不同降温要求下冷却水消耗量
Table 2. Cooling water consumption of different cooling requirements
Target temperature / K Water consumption / (kg·s−1) 1373.15 0.80 1323.15 1.10 1273.15 1.41 1223.15 1.74 1173.15 2.10
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表 3 合成气各组分摩尔分数
Table 3. Mole fraction of different syngas components
Syngas component Mole fraction / % CO 25.53 CO2 3.57 H2 50.05 H2O 19.76 N2 0.68 CH4 0.41
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