二氧化硫由于其对环境的破坏性和对人类健康的危害性，是当今人类面临的主要大气污染物之一。工业用能和电力行业中的燃煤是产生SO2的主要的人为来源。目前我国二氧化硫排放量居世界首位，SO2污染已成为我国经济可持续发展的一个重要制约因素。我国目前的湿法烟气脱硫技术基本由国外引进，昂贵的投资和运行费用尚不能被国内一般电厂和工业锅炉所接受。研究和开发具有自主知识产权的新型烟气脱硫技术是我国控制和解决SO2污染的重要手段。本文以此为目的在对典型湿法烟气脱硫设备喷淋塔研究的基础上，
Sulfur dioxide is one of the main air pollutants that human beings are facing today because of its damage to the environment and harm to human health. Industrial energy consumption and coal combustion in the power industry are the main anthropogenic sources of SO2 generation. At present, China's sulfur dioxide emissions rank first in the world, and SO2 pollution has become an important constraint factor for the sustainable development of China's economy. The current wet flue gas desulfurization technology in China is basically imported from abroad, and the expensive investment and operation costs cannot be accepted by the general domestic power plants and industrial boilers. Research and development of new flue gas desulfurization technology with independent intellectual property rights is an important means to control and solve SO2 pollution in China. Based on the comprehensive study of spray tower of typical wet flue gas desulfurization equipment,
提出的液幕式湿法烟气脱硫技术从试验研究、理论建模和数值模拟等方面进行了深入研究。，利用自行设计和搭建的喷嘴雾化测试系统对压力式喷嘴的雾化特性进行了详细的试验研究。采用高速动态摄像仪与扇形排状量筒结合计算机图像处理技术对液滴粒径分布、径向喷淋密度分布和雾化角等进行了测量和数据处理，得到喷嘴的雾化压力与雾化液滴粒径、径向喷淋密度分布及雾化角之间的关系。在此基础上，试验分析了气体动力学参数、喷淋密度等因素对喷淋式吸收塔阻力特性的影响；以及烟气流速、循环浆液量、液气比、浆液pH值、烟气入口SO2浓度和脱硫剂粒径等因素对脱硫效率的影响。运用两相流运动学理论，建立了吸收塔内单颗粒液滴的运动方程。
The proposed liquid curtain wet flue gas desulfurization technology has been deeply studied from experimental research, theoretical modeling and numerical simulation. First of all, the atomization characteristics of the pressure nozzle were studied in detail by using the self-designed and built nozzle atomization test system. The droplet size distribution, radial spray density distribution and atomization angle were measured and processed with high-speed dynamic camera and fan-shaped measuring cylinder combined with computer image processing technology. The relationship between atomization pressure of nozzle and droplet size, radial spray density distribution and atomization angle was obtained. On this basis, the effects of aerodynamic parameters, spray density and other factors on the resistance characteristics of spray absorption tower were analyzed experimentally; The effects of flue gas flow rate, circulating slurry volume, liquid-gas ratio, slurry pH value, SO2 concentration at flue gas inlet and particle size of desulfurizer on desulfurization efficiency are also discussed. Based on the kinematics theory of two-phase flow, the motion equation of a single droplet in the absorber is established.
通过理论分析和计算得到了临界雾化粒径与烟气流速的关系以及液滴在塔内停留时间与粒径、烟气流速的关系。建立了吸收塔气侧阻力计算模型，计算表明离散相阻力是吸收段气相阻力的主要阻力，计算与试验数据吻合较好。得到该装置的工况运行参数。其次，分别对顺流/逆流液幕塔内气液两相流动、传热和脱硫特性进行了试验研究和理论分析。得到液幕床层高度与液体喷射速度、烟气流速、喷嘴直径的关系，提出顺流/逆流吸收塔压降与液气比、烟气流速的关联式和液幕床床层高度的计算公式 。根据液幕床吸收塔内气液两相温度分布的规律，提出液幕塔内气液平均传热系数的计算公式和顺、逆流塔内气液两相传热传质的几何参数范围。
Through theoretical analysis and calculation, the relationship between critical atomization particle size and flue gas flow rate, and the relationship between droplet residence time in the tower and particle size and flue gas flow rate were obtained. The calculation model of the gas side resistance of the absorption tower is established. The calculation shows that the discrete phase resistance is the main resistance of the gas phase resistance in the absorption section, and the calculation is in good agreement with the test data. The operating parameters of the device are obtained. Secondly, the gas-liquid two-phase flow, heat transfer and desulfurization characteristics in the co-flow/counterflow liquid curtain tower were comprehensively studied and theoretically analyzed. The relationship between the height of liquid curtain bed and liquid injection velocity, flue gas velocity and nozzle diameter is obtained. The correlation formula between the pressure drop of downstream/countercurrent absorption tower and the liquid-gas ratio, flue gas velocity and the calculation formula for the height of liquid curtain bed are proposed. According to the law of gas-liquid two-phase temperature distribution in the liquid curtain absorption tower, the calculation formula of gas-liquid average heat transfer coefficient in the liquid curtain tower and the geometric parameter range of gas-liquid two-phase heat and mass transfer in the forward and reverse flow tower are proposed for the first time.
总结归纳发现，在试验参数范围内，提高烟气流速或增大喷液量均能有效提高脱硫效率，喷液量对脱硫效率的影响较烟气流速的影响大。得到顺流/逆流塔的较佳运行工况点：在顺流塔烟气流速为6.44m/s，循环浆液量为27m3/h（液气比为14L/m3），氧化浆池pH值为5.6～5.8，脱硫效率为93.7%；逆流塔烟气流速为2.31m/s，循环浆液量为54m3/h（液气比为27.5L/m3），氧化浆池pH值5.6～5.8时可使脱硫效率达到96.8%。采用镜像分析和热重分析方法对脱硫产物的物理结构和成分分析结果表明，脱硫产物中石膏含量较高，但由于设备氧化工艺等问题，中间产物含量偏高，改进氧化系统增强氧化效果可得到满足工业和民用的石膏。针对液幕塔的气液传质特点，采用表面更新理论建立了塔内SO2吸收过程的物理和数学模型。
It is concluded that within the range of test parameters, increasing the flue gas flow rate or increasing the liquid injection volume can effectively improve the desulfurization efficiency, and the effect of liquid injection volume on the desulfurization efficiency is greater than that of the flue gas flow rate. The better operating conditions of the downstream/countercurrent tower are obtained: the flue gas flow rate of the downstream tower is 6.44m/s, the circulating slurry volume is 27m3/h (the liquid-gas ratio is 14L/m3), the pH value of the oxidation slurry tank is 5.6~5.8, and the desulfurization efficiency is 93.7%; The flue gas flow rate of the countercurrent tower is 2.31m/s, the circulating slurry volume is 54m3/h (liquid-gas ratio is 27.5L/m3), and the desulfurization efficiency can reach 96.8% when the pH value of the oxidation slurry tank is 5.6~5.8. The physical structure and composition of desulfurization products are analyzed by image analysis and thermogravimetric analysis. The results show that the content of gypsum in desulfurization products is high, but the content of intermediate products is high due to equipment oxidation process and other problems. Improving oxidation system to enhance oxidation effect can meet the requirements of industrial and civil gypsum. According to the characteristics of gas-liquid mass transfer in the liquid curtain tower, the physical and mathematical models of SO2 absorption process in the tower were established using the surface renewal theory.
该模型考虑了浆液中各种离子以及各种有限速率的反应，同时考虑了气相传质阻力、液相传质阻力和石灰石溶解阻力的影响。通过模型分析确定了湿法烟气脱硫工艺中吸收段和氧化段的反应机理。模型计算得到了逆流式液幕塔的脱硫效率与烟气流速和液气比的关系、烟气中SO2浓度随吸收塔高度的变化曲线和循环浆液pH值随高度的变化规律。对塔内各段SO2的吸收速率进行了分析，发现液柱上升段对SO2吸收较少，液滴下落阶段是SO2吸收的主要阶段。逆流式液幕床层底端SO2的吸收为液相传质阻力控制。计算结果与试验结果吻合较好，基本上反映了反应塔内的实际过程。
The model considers all kinds of ions in the slurry and all kinds of finite rate reactions, as well as the effects of gas phase mass transfer resistance, liquid phase mass transfer resistance and limestone dissolution resistance. The reaction mechanism of the absorption section and the oxidation section in the wet flue gas desulfurization process was determined by model analysis. The relationship between desulfurization efficiency of countercurrent liquid curtain tower and flue gas flow rate and liquid-gas ratio, the variation curve of SO2 concentration in flue gas with the height of absorption tower and the variation law of pH value of circulating slurry with the height were obtained by model calculation. The absorption rate of SO2 in each section of the tower was analyzed. It was found that the rising section of the liquid column absorbed less SO2, and the falling phase of the liquid drop was the main phase of SO2 absorption. The absorption of SO2 at the bottom of the countercurrent liquid curtain bed is controlled by the resistance of liquid phase mass transfer. The calculated results are in good agreement with the test results, and basically reflect the actual process in the reactor.
采用GAMBIT软件构造三维网格模型，运用Fluent 6.0软件对液幕塔内气液两相流动和传热过程进行了数值模拟。采用离散相模型，考虑两相间的相互作用，在欧拉坐标系下采用RNG k-ε模型来描述气相湍流，在拉格朗日坐标系下对液滴颗粒相进行描述，建立液幕塔内气液流动和传热的三维数学模型。
GAMBIT software was used to construct a three-dimensional mesh model, and fluent 6.0 software was used to simulate the gas-liquid two-phase flow and heat transfer process in the liquid curtain tower. The discrete phase model is adopted, and the interaction between two phases is considered. RNG k is adopted in Euler coordinate system- ε The model is used to describe the gas phase turbulence, describe the droplet particle phase in the Lagrange coordinate system, and establish a three-dimensional mathematical model of gas-liquid flow and heat transfer in the liquid curtain tower.
数值模拟了不同液气比时塔内气液流动和传热状况，计算与试验结果吻合较好。表明所建立的模型和采用的算法具有良好的预测性和可靠性。针对逆流塔内烟气偏流现象进行了流场优化设计，计算表明当烟气入口通道与塔体连接处夹角为圆角时，塔内气液流场分布均匀性较好。
The gas-liquid flow and heat transfer in the tower at different liquid-gas ratios were numerically simulated, and the calculated results were in good agreement with the experimental results. It shows that the model and the algorithm have good predictability and reliability. The flow field optimization design is carried out for the phenomenon of flue gas deflection in the countercurrent tower. The calculation shows that when the angle between the flue gas inlet channel and the tower body is a fillet, the gas-liquid flow field in the tower is well distributed.
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2023-01-18
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