湿法FGD系统石灰浆池射流搅拌动力学研究
发布时间：2018-08-02 19:22
【摘要】：在现阶段我国电力行业仍以燃煤为主燃料,随之而来的SO2污染问题不容小觑。在我国,燃煤电场对于SO2的吸收以湿法烟气脱硫为主,代表方式为石灰石/石膏脱硫法。为了实现对SO2的充分吸收,就需要混合搅拌设备运行良好,但是由于广泛使用的侧进式搅拌系统造价高、易泄露且存在安全隐患等问题,故将旋转射流系统引入湿法烟气脱硫吸收系统中以克服以上缺点。本文在前人基础上对旋转射流系统加以完善并将其引入石灰浆池搅拌系统,以蒲城600MW浆池建立几何模型,分别在气液及液固两相工况下研究了旋转射流器自转角速度与射流出口速度对浆池流场的影响,并将两相模拟结果与三相模拟结果加以比对,探究第三相的出现对流场所产生的影响。在气液两相工况中,氧化空气分布的优劣依赖于近壁面处的横向分布速度与Z向速度的综合作用。随着自转角速度的增加,氧化空气的分布呈现出先趋于良好后趋于恶化的状态；随着射流出口速度的改变,氧化空气分布趋于良好,但是当速度高于50m/s之后,持续优化现象并不十分明显。在液固两相工况中,随着自转角速度的增加,石灰石颗粒相浓度呈现出递减趋势,这是由于射流长度随自转角速度的增加而呈现出先增后减的趋势,从而导致在近壁处的横向分布速度呈现出先增后减的趋势,进而导致混合浆液与原纯液相混合不足。随着射流出口速度的增加,射流长度有所增加,从而使横向分布速度增加,且由于总体流量的增大,浆池内大循环加剧,从而使混合作用进一步增强,石灰石颗粒相浓度愈发接近射流出口处浓度。通过气液两相、液固两相与气液固三相工况进行对比,结果表明气液固三相工况中氧化空气VOF高于气液两相工况,这是由于固相的出现使三相工况中的横向分布速度趋于整体平缓,占优势体积的向下液流为氧化空气的横向分布提供了重要作用；液固两相中石灰石颗粒相VOF高于三相工况,这是由于在中部向下液流流速基本相同的情况下,三相工况中近壁处混合液流横向速度偏低而Z向速度偏高,导致未能与纯液相充分混合,而导致三相工况下石灰石颗粒相浓度偏低。
[Abstract]:At the present stage, the power industry of our country still uses coal as the main fuel, and the SO2 pollution problem should not be underestimated. In China, wet flue gas desulfurization (FGD) is the main absorption of SO2 in coal-fired electric field, and limestone / gypsum desulfurization is the representative method. In order to fully absorb SO2, it is necessary for mixing equipment to run well, but the widely used side-feed mixing system is easy to leak and has some problems, such as high cost, easy leakage and hidden danger of safety, etc. Therefore, the rotary jet system is introduced into the wet flue gas desulfurization absorption system to overcome the above shortcomings. In this paper, the rotating jet system is improved and introduced into the lime slurry mixing system on the basis of predecessors, and the geometric model of Pucheng 600MW slurry pool is established. The effects of rotation angle velocity and jet exit velocity on the flow field of slurry tank were studied under the condition of gas-liquid and liquid-solid two-phase operation, and the results of two-phase simulation and three-phase simulation were compared. Explore the impact of the third phase of the presence of convection sites. In gas-liquid two-phase operation, the distribution of oxidized air depends on the combination of transverse velocity and Z-direction velocity near the wall. With the increase of rotation angular velocity, the distribution of oxidized air tends to be good first and then tends to deteriorate. With the change of jet velocity, the distribution of oxidized air tends to be good, but when the velocity is higher than 50m/s, the distribution of oxidized air tends to be good. The phenomenon of continuous optimization is not very obvious. In liquid-solid two-phase operation, the phase concentration of limestone particles decreases with the increase of rotation angular velocity, which is due to the increase of jet length with the increase of rotation angular velocity. Therefore, the transverse distribution velocity at the near wall shows a tendency of increasing first and then decreasing, and then leading to the insufficient mixing of mixed slurry and pure liquid phase. With the increase of the velocity of jet outlet, the length of jet increases, which makes the velocity of transverse distribution increase, and because of the increase of overall flow rate, the large circulation in the slurry pool intensifies, thus the mixing effect is further enhanced. The concentration of limestone particle phase is closer to the concentration of jet outlet. Through the comparison of gas-liquid two-phase, liquid-solid and gas-liquid-solid three-phase working conditions, the results show that the oxidized air VOF in gas-liquid-solid three-phase operation is higher than that in gas-liquid two-phase operation. This is because the appearance of solid phase makes the velocity of transverse distribution in three-phase operation tend to be smooth, and the dominant downward flow of liquid provides an important role for the transverse distribution of oxidized air, and the VOF of limestone particle phase in liquid-solid phase is higher than that in three-phase condition. This is due to the fact that the transverse velocity of the mixed liquid flow near the wall is lower and the Z-direction velocity is higher in the three-phase working condition when the downward flow velocity in the middle part is basically the same, which results in the failure to be fully mixed with the pure liquid phase. The phase concentration of limestone particles is low under three-phase working conditions.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773
本文编号：2160476
[Abstract]:At the present stage, the power industry of our country still uses coal as the main fuel, and the SO2 pollution problem should not be underestimated. In China, wet flue gas desulfurization (FGD) is the main absorption of SO2 in coal-fired electric field, and limestone / gypsum desulfurization is the representative method. In order to fully absorb SO2, it is necessary for mixing equipment to run well, but the widely used side-feed mixing system is easy to leak and has some problems, such as high cost, easy leakage and hidden danger of safety, etc. Therefore, the rotary jet system is introduced into the wet flue gas desulfurization absorption system to overcome the above shortcomings. In this paper, the rotating jet system is improved and introduced into the lime slurry mixing system on the basis of predecessors, and the geometric model of Pucheng 600MW slurry pool is established. The effects of rotation angle velocity and jet exit velocity on the flow field of slurry tank were studied under the condition of gas-liquid and liquid-solid two-phase operation, and the results of two-phase simulation and three-phase simulation were compared. Explore the impact of the third phase of the presence of convection sites. In gas-liquid two-phase operation, the distribution of oxidized air depends on the combination of transverse velocity and Z-direction velocity near the wall. With the increase of rotation angular velocity, the distribution of oxidized air tends to be good first and then tends to deteriorate. With the change of jet velocity, the distribution of oxidized air tends to be good, but when the velocity is higher than 50m/s, the distribution of oxidized air tends to be good. The phenomenon of continuous optimization is not very obvious. In liquid-solid two-phase operation, the phase concentration of limestone particles decreases with the increase of rotation angular velocity, which is due to the increase of jet length with the increase of rotation angular velocity. Therefore, the transverse distribution velocity at the near wall shows a tendency of increasing first and then decreasing, and then leading to the insufficient mixing of mixed slurry and pure liquid phase. With the increase of the velocity of jet outlet, the length of jet increases, which makes the velocity of transverse distribution increase, and because of the increase of overall flow rate, the large circulation in the slurry pool intensifies, thus the mixing effect is further enhanced. The concentration of limestone particle phase is closer to the concentration of jet outlet. Through the comparison of gas-liquid two-phase, liquid-solid and gas-liquid-solid three-phase working conditions, the results show that the oxidized air VOF in gas-liquid-solid three-phase operation is higher than that in gas-liquid two-phase operation. This is because the appearance of solid phase makes the velocity of transverse distribution in three-phase operation tend to be smooth, and the dominant downward flow of liquid provides an important role for the transverse distribution of oxidized air, and the VOF of limestone particle phase in liquid-solid phase is higher than that in three-phase condition. This is due to the fact that the transverse velocity of the mixed liquid flow near the wall is lower and the Z-direction velocity is higher in the three-phase working condition when the downward flow velocity in the middle part is basically the same, which results in the failure to be fully mixed with the pure liquid phase. The phase concentration of limestone particles is low under three-phase working conditions.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773
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