复合型洗涤冷却室内多相流动及数值模拟研究

发布时间：2018-03-09 20:42

本文选题：洗涤冷却室　切入点：雾化　出处：《华东理工大学》2015年博士论文　论文类型：学位论文

【摘要】：本文以多喷嘴气流床气化的关键设备洗涤冷却室为研究背景,对复合型洗涤冷却室内的流体流动特性及温度分布进行了研究。考察了气速、液体流速、雾化器数量等参数对床层内压降、液滴夹带、雾化液滴粒径及液滴浓度的影响。采用数值模拟方法建立了洗涤冷却室内部流场及温度场数学模型,分析了复合型洗涤冷却室的工程应用可行性。(1)依据工业数据,对洗涤冷却管内高温合成气的温度分布进行数值模拟研究。模拟结果表明在洗涤冷却管入口处0-2m段降温最快,3-6m段降温较平缓,说明气液间热交换接近平衡。根据模拟结果,提出缩短洗涤冷却管长度及增加喷雾冷却雾化器的改进方案,以避免洗涤冷却管出现堵塞等工程问题。并搭建了冷态实验装置,研究了气速,液体流速等对床层内压降影响。研究结果表明：干塔状态下,由于床层阻力影响较小,整个床层内部的压力分布较为均匀；湿塔状态下,雾化液滴与气体的错流对床层压降起到扰动作用,压降比干塔时提高约50%。(2)对复合型洗涤冷却室气体出口处的气相液滴夹带过程进行了研究。考察了气体速度、液体流速、降膜冷却水流量、雾化器空间位置等因素对液滴夹带分率的影响。研究表明：液滴夹带分率随床层表观气速、液体流速的增加均呈上升趋势,而其在径向上的分布相对较为均匀；液体流速增大能降低雾化液滴粒径梯度,粒径较小的液滴易被气流夹带,导致出口液滴夹带分率有一定提高,但液滴在随气流运动过程中,小液滴会出现聚并,形成较大粒径液滴而脱离气流,因此液滴夹带分率增量较小。雾化器数量增加加剧雾化液滴聚并,沉降液滴数量增多。雾化器数量从对称两个设置变为同向对称四个时,液滴夹带量降低约40%。液滴夹带量受表观气速及液体流速影响较大,通过实验数据获得了液滴夹带分率与条件参数的经验关联式：(3)利用Malvern Spraytec测试仪对洗涤冷却室内雾化液滴的粒径分布进行了测定。结果表明：液体流速增大促使液滴粒径减小；气流速度增加促使洗涤冷却室气体出口液滴粒径增大。雾化器数量越多,液滴间剧烈作用导致液滴粒径梯度变大。靠近雾化器径向r/R=0.3位置雾化液滴粒径较大,洗涤冷却室中心位置处较小。液滴在洗涤冷却室轴向位置的分散主要依靠气流的携带,随着轴向距离的增大,气体能携带的液滴粒径逐渐变小,在洗涤冷却室气体出口处液滴能被气流携带的临界粒径约为80～150μm。(4)采用等速取样法,研究了洗涤冷却室内气液两相掺混过程中,雾化液滴浓度在床层内分布。获得了在不同雾化器数量及气液流速条件下,洗涤冷却室内的雾化液滴浓度分布图。研究发现液体流速的增大使流体错流诱导效应增强,促进液滴向床层空间的快速扩散；而床层气速的增大,则能增大气液相所形成漩涡的能量,从而促进液滴向轴向扩散运动。四雾化器条件下同一空间位置的液滴浓度较两雾化器增大将近一倍,但雾化液滴在洗涤冷却室内的分布更加均匀,即增加雾化器数量能消除床层内死区。依据实验结果获得了洗涤冷却室径向位置雾化液滴浓度经验式：(5)采用数值模拟方法建立了复合型洗涤冷却室内传质传热三维数值模型,研究了洗涤冷却室内的多相流动、传质和传热等行为。模拟结果表明,单雾化器喷雾范围有限,洗涤冷却室温度分布不均匀,降温效果不佳。液体流速的增加使得雾化液滴粒径减小,有利于热量传递。在相同热交换量下,随着液体流速增大,气体温度降幅相应提高。对置喷雾冷却,洗涤冷却室上部空间内雾化液滴的数量较多,保证了冷却效果。靠近雾化器轴向h/H=0.72处合成气温度最低。洗涤冷却室底部,液相分率增高,雾化液滴换热冷却效果降低。流场内气液两相错流作用,提高了液相的蒸发效率,强化了传热和传质的效果。
[Abstract]:In this paper the key device of scrubbing cooling chamber of multi nozzle entrained flow gasification as the research background, the characteristics of fluid flow and temperature distribution of the composite quench chamber is studied. The influences of the gas flow rate, liquid flow rate, the pressure drop of the bed number parameters of atomizer, droplet entrainment, effect of atomization droplet size and liquid droplet concentration. By using the method of scrubbing cooling chamber internal flow field and temperature field mathematical model numerical simulation, analyzed the feasibility of engineering application of composite scrubbing cooling chamber. (1) based on industrial data, numerical simulation of the temperature distribution of the scrubbing cooling tube in high temperature synthesis gas. The simulation results show that in the scrubbing cooling tube at the entrance 0-2m cooling is the fastest, 3-6M cooling slowly, the gas-liquid heat exchange near equilibrium. According to the simulation results, put forward to shorten the scrubbing cooling pipe length and increase improvement of spray cooling atomizer The case, in order to avoid scrubbing cooling pipe blockage and other engineering problems. And built a cold state experimental device, the influence of gas velocity, liquid flow rate on the bed pressure drop. The results show that under the condition of the tower, due to the small effect of bed resistance, the whole bed internal pressure distribution is uniform in the wet tower; under the condition of liquid droplets and gas flow on the bed pressure drop to disturbance, increased by about 50%. when the pressure drop Biganta (2) drop entrainment process exports to composite scrubbing cooling chamber gas gas liquid was studied. The effects of the gas velocity, liquid flow velocity, cooling water flow. Radial position factors on the rate of droplet entrainment. Research shows that the droplet entrainment rate increases with the superficial gas velocity, liquid flow rate increased, but the distribution is relatively uniform in the radial direction; the liquid flow rate increase can reduce the fog The droplet size of the gradient, the smaller size of droplets easily by air entrainment, leading to the export droplet entrainment rate increased, but with the droplets in the air flow process, droplet coalescence will appear, the formation of large size droplets from the air, so the droplet entrainment rate increment a small increase in the number of atomizer. Increasing droplet coalescence and sedimentation, droplets increased in number. The number from the atomizer two symmetric set to four symmetric, droplet entrainment decreased about 40%. droplet entrainment by the superficial gas velocity and liquid velocity is affected by the experimental data obtained experience association type droplet entrainment rate parameters and conditions: (3) the scrubbing cooling chamber of atomized droplet size distributions were determined using the Malvern Spraytec tester. The results showed that the liquid velocity increases the particle size decreases; flow velocity increase gas scrubbing cooling chamber The outlet of the body of the droplet size increases. The atomizer amount is more, interaction between droplets leads to the droplet size gradient becomes larger. Near the radial position of r/R=0.3 droplet in spray atomizer of large particle size at the center position of the washing cooling chamber is smaller. Droplet in the scrubbing cooling chamber axial position dispersion mainly depends on the airflow carrying, with the increase of the axial distance, can carry the gas droplet size becomes smaller, the scrubbing cooling chamber gas outlet of liquid droplet can be air carries the critical particle size is about 80~150 M. (4) by isokinetic sampling method of scrubbing cooling chamber of gas-liquid two-phase mixing process, droplet concentration in bed layer distribution. Obtained in different number of nozzles and liquid velocities under the condition of droplet concentration distribution in scrubbing cooling chamber. The study found that increasing liquid flow rate of the fluid cross flow induced effect enhancement, promote the drop to the empty bed Fast diffusion between the bed; and the gas velocity increases, can increase the gas-liquid phase form a vortex of energy, so as to promote the droplet axial diffusion motion. The droplet concentration four atomizer conditions the same spatial position compared to the two increase of atomizer nearly doubled, but the atomized droplets in the washing cooling indoor distribution uniform, increase the number of nozzles can eliminate the bed dead. According to the experimental results obtained the scrubbing cooling chamber radial position of the atomized droplet concentration formula: (5) using the method to establish the value model of the composite quench chamber of mass and heat transfer in 3D numerical simulation of scrubbing cooling chamber of multiphase flow, heat transfer and mass transfer such behavior. The simulation results show that the single sprayer limited, scrubbing cooling chamber temperature distribution is not uniform. The cooling effect is poor. The increase of liquid velocity makes the droplet size decreased, favorable for heat transfer Delivery. In the same amount of heat exchange, along with the liquid flow rate increases, the gas temperature drop increased. Opposite spray cooling, a large number of droplets in the upper space of scrubbing cooling chamber, the cooling effect is ensured. Near the axial h/H=0.72 synthesis gas atomizer. The lowest temperature washing cooling chamber bottom, liquid chromatography rate increased. The droplet heat cooling effect is reduced. The role of gas-liquid two-phase flow in the wrong, improve the evaporation efficiency of liquid phase, strengthen the effect of heat and mass transfer.

【学位授予单位】：华东理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ051.5

【引证文献】