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快速悬浮床烟气脱硫的试验研究快速悬浮床烟气脱硫的试验研究 张小平，王乃华著，徐云贵译1文摘对快速悬浮床（FSB）烟气脱硫特性进行了实验研究。对脱硫运行时参数的影响进行了研究。得到接近饱和温度和摩尔比对脱硫的影响最强烈,还得到了最佳运行参数。最佳的参数接近饱和温度大约是10 ，最适摩尔比为1.5 。2011年在责任进展能源工程（ ICAEE ）第二届国际会议上 , 根据组委会同行评议并由Elsevier公司发布。关键词：烟气脱硫，去除效率;悬浮床快;最优参数。2介绍烟气脱硫（ FGD ）的方法可分为三种不同的类型：湿式洗涤器，半干燥过程和干燥过程。湿式除尘器已广泛运用商业行业，超过95的脱硫行业实现商业化。然而，这种技术会产生大量的湿固体废物，需要废水处理。它还涉及复杂的配置而和代价高昂。湿式烟气脱硫系统相比有吸引力洗涤器在成本方面，它们不需要水和再加热的能量。尽管如此，由于吸附剂成本高和低SO2的去除效率，这种类型的技术尚未被广泛使用。因此，已经开发了各种半干燥过程，以避免湿式洗涤器的缺点。即便如此，半干洗涤脱硫效率低于湿式洗涤器，这可能导致在一些场合不符合环保法规。喷雾机和循环流化床（ CFB ）烟气脱硫工序是两个传统的半干法工艺。喷雾机已经得到了广泛的测试。然而，这种方法的缺点是它的大空间消耗， 为了保持长久烟气脱硫反应居留和泥浆液滴蒸发，以及复杂的淤浆系统，以满足要求。循环流化床还广泛用于烟气脱硫，然而，窒息现象广泛的发生是由于非定常流动床。在本文中,一个快速悬浮床(FSB)烟气脱硫洗涤器开发旨在有效去除效率与湿式涤气器上高成本。这份FSB洗涤器可以同时提高气液和气 - 固反应的一个新型的烟气分配装置。同时,这种洗涤器可以防止石灰浆液撞击到涤气器内表面上。操作参数的影响包括Ca / S比值,接近饱和温度、烟气流速和泥浆颗粒直径。并且对脱硫效率分布进行了调查，脱硫机理反应进行了分析。3实验实验系统由模拟烟道气系统，钙水化系统， SO2洗涤器，织物过滤器和数据采集系统组成（如图1）。吸附剂的化学和物理特性如表1 所示。石灰存储在水合后的淤浆罐。石灰浆液的索泰直径为50 70微米。二氧化硫流量计以满足浓度后，加入到混合罐中。二氧化硫MSI -2000烟气分析仪浓度测定。型温度的测定K型热电偶通HP34970A资料记录器。测定贴边球温度的烟道气洗涤器的出口处。石灰浆液和水流速测量转子流量计和调整调速电机。图1 实验装置4 结果与讨论参考条件： Ca/S比为1.5，洗涤器入口温度150 ，烟气流量2000立方米/小时，入口SO2浓度为3000毫克标准立方米，接近饱和温度10 。研究一个参数对脱硫效率的影响，其他参数保持不变。4.1选择吸附剂两种类型的石灰被选为吸附剂,一个来自阜阳和另一个从萧山。化学成分和物理特性如表1所示。结果表明, 萧山石灰的脱硫效率是67% ,而阜阳石灰是80%。参考一下。所以阜阳石灰在这项研究被选为二氧化硫吸附剂。表1 石灰的化学成分和物理特性 萧山阜阳成分CaO MgOFe2O3SiO2Al2O3其他CaOMgOFe2O3SiO2Al2O3其他直径(m)85.31.50.80.200.5911.9187.60.720.60.250.818.46百分比(%)105090105090真实密度(g/cm3)22表观密度(g/cm3)0.78810.7502颗粒内部孔隙率(%)10.618颗粒之间孔隙率（%）3429.2比表面积(m2/g) 6.636610.4934.2运行参数对脱硫效率的影响在半干法脱硫工艺，操作参数对脱硫反应的影响主要是通过反应速度，反应时间和反应表面。在干燥期间，反应速率通过气相的传质阻力，液相的传质阻力和石灰溶于电阻控制。反应时间依赖于石灰浆液颗粒蒸发。4.2.1 Ca/S从图中可以看出。当Ca / S比小于1时，洗涤器的脱硫效率几乎呈线性增加，之后，变得光滑。二氧化硫去除效率织物过滤约10 20。石灰浆质量浓度的钙离子增加所以Ca / S比增加从而降低了液相的传质阻力和增加液膜传质系数。所以脱硫效率增加。 Ca / S比对脱硫效率的面料过滤有很大的影响。气相和固相密切联系的织物滤料表面上。二氧化硫颗粒的表面浓度是一样的，在烟道气中的SO2和气相的传质阻力不显著。 4.2.2接近饱和温度在FSB洗涤器的热力学过程可以被认为是由于其绝热加湿细绝缘。接近饱和温度来表示烟气接近饱和的程度。它从图3中可以看出。脱硫效率显着增加与减少的方法，以饱和温度为例。当接近饱和温度降低时，烟道气体的相对湿度增加，蒸发率降低 石灰浆液颗粒和液体颗粒存活时间延长。 SO2与Ca （OH）2在液相中的离子反应是非常快的，所以SO2去除率显著增加。另一方面，较低的接近饱和温度意味着更多的水注入洗涤器增加反应表面，增强在洗涤器中的反应。当接近饱和温度增加，烟气的相对湿度和吸附剂的水分含量增加，所以织物过滤的二氧化硫去除效率增加。对于气体固体脱硫反应，通过灰层是固相扩散速率控制阶段。在固体表面上吸附的水分减少扩散阻力，提高SO2扩散，使织物过滤器的脱硫效率增大。 图2 摩尔比对脱硫效率的影响 图3 接近饱和温度的影响 即使降低到接近饱和温度可以增加脱硫效率是显著的，太小的接近饱和温度，会带来一系列的经济和安全的问题。较低接近饱和温度，需要较长的干燥时间，较高的洗涤器。如果洗涤高度保持不变，水不能完全蒸发，由于石灰浆液粘合洗涤器和织物过滤的差异从而导致腐蚀。另一方面，脱硫产品，特别是硫酸钙形成水泥状时，将形成结合阻止纤维过滤水。通常情况下，接近饱和温度约10才考虑上述问题。4.2.3烟气流速烟气速度和残留时间在不同流速下如表2所示表2 烟气流率，速度和残留时间参数 值流速(m3/h) 1500 200025000速度(m/s)3.44.55.6停留时间（s） 5.243.2对于洗涤器的流量与烟气速度和残留时间变化。从图4中可以看出。在洗涤器中，残留时间减小时，洗涤器中的脱硫率略降低，但是二氧化硫去除效率在织物过滤器几乎是不变的。随着烟道气体速度增加，动荡增加混合将加剧，有利于SO2在气相中的扩散脱硫。但是，气相中烟气速度增加，蒸汽扩散将加快水分蒸发。此外以恒定的洗涤高度，烟道残留时间在洗涤器中的气体将减少，从而降低SO2脱除。在洗涤器中，反应主要是气体前浆料液体干燥。气液相反应时间很短，所以烟道气体残留时间对气体在洗涤器中的液体反应的影响不大。烟气剩余时间效应主要是不强的气 - 固反应期。即使气固反应周期短，脱硫效率不会改变多。4.2.4烟气在洗涤器入口温度 图4 流速对脱硫效率的影响 图5 入口温度对脱硫效率的影响从图5中可以看出。烟气脱硫效率随洗涤入口温度增加。泥浆温度升高时洗涤器入口烟气温度由于热转移增加。一方面，气相和液相的温度上升，将降低二氧化硫的溶解度，并吸收。另一方面，淤浆的温度升高会增加离子的扩散和二氧化硫吸收。最重要的是，洗涤器入口烟道气体的温度升高时，水注射会增加。浆料颗粒和反应表面积也将增加，从而导致二氧化硫去除效率增加。为了进一步了解洗涤器入口烟气温度对脱硫效率的影响，轴向SO2浓度分布在洗涤器中150和200下进行了研究。结果是如图6所示。在洗涤塔下部，二氧化硫的浓度迅速下降，它对应于石灰浆液颗粒干燥阶段1.5秒。在洗涤部分高于6米液浆颗粒已经干燥，二氧化硫浓度下降是相当慢的，反应速度下降快。由于水喷射和干燥期间增加。在较高的洗涤器入口烟气温度，SO2脱除效率较高（ 81.6 83.3 ）。4.2.5石灰浆液粒子直径石灰浆液粒子直径对脱硫的影响示于图中7。当直径小于50m时， SO2去除率显着增加，料浆颗粒增加。当直径大于50m时， SO2的去除效率略有增加，然后浆颗粒的增加变得稳定。SO2去除率随浆织物过滤颗粒增加由于织物过滤器反应表面积降低。在恒速干燥阶段，生石灰化浆直径对脱硫效率的影响是通过两个方面浆直径增加，干燥时间增加，但反应的表面积和外部大容量传输速率下降。当直径小于50m时，干燥期间占SO2的去除效率主导地位。当直径为50 100微米之间这两种效果几乎相互抵消。当直径大于100m ，外部传质速率是在反应的控制阶段。因此，必须有一个最佳的浆液粒径介于50 100m的基于本研究的范围内 图6 沿喷雾塔二氧化硫分布 图7 初始浆液直径去除效率的影响5 结论快速悬浮床（ FSB ）烟气脱硫特性的实验。对脱硫运行参数的影响进行了研究接近饱和温度和Ca / S比对脱硫效率有显着的影响。 SO2脱除效率增加与减少的方法是接近饱和温度和Ca / S比。根据经济和安全方面的FSB烟气脱硫的最佳工作参数已经得到了。接近饱和温度大约是10 ，最佳的Ca / S比1.5和浆料的最佳直径为50m 。 FSB - FGD这种创新过程的脱硫高于90以上。它不仅适用于新建锅炉也在改造锅炉中使用。参考文献1 Xu GW, Guo QM, Kaneko T, Kato K. A new semi-dry desulfurization process usinga powder-particle spouted bed. Adv Environ Res 2000; 4: 9-18.2 Wang NH, Luo ZY, Gao X, Cen KF. Study of new semi-dry flue gas desulfurization. J Power Eng (Chinese) 2003; 23:2586-88.3 William. Characterization of NO2 and SO2 removal in a spray dryer/baghouse system. Ind. Eng. Chem. Res 1994; 33: 2749-56.4 Zhou Y, Zhu X, Peng j, Liu Y, Zhang D, Zhang M. The effect of hydrogen peroxide solution on SO2 removal in the semidry flue gas desulfurization process. J Hazard Mater 2009; 170: 436-42.5 Du B, Warsito W, Fan LS. ECT studies of the choking phenomenon in a gas-solid circulating fluidized bed. AICHE J 2004;50: 1386-1406.第 6页（共6页）Energy Procedia 14 (2012) 1665 16701876-6102 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the organizing committee of 2nd International Conference on Advances in Energy Engineering (ICAEE).doi:10.1016/j.egypro.2011.12.887Available online at Available online at Energy Procedia Energy Procedia 00 (2011) 000000 /locate/procedia ICAEE 2011 Experimental Study on Fast Suspension Bed Flue Gas Desulfurization Xiaoping Zhanga, Naihua Wangb, * aDepartment of Science, Shandong Jianzhu University, Fengming Road, Jinan 250101, China bInstitute of Thermal Science, Shandong University, Jingshi Road, Jinan 250061, China Abstract Characteristic of Fast Suspension Bed (FSB) flue gas desulfurization have been experimentally investigated. The influence of operation parameters on SO2 removal has been investigated. The approach to saturation temperature and the mole ratio influence SO2 removal strongly. The optimum operating parameters have been got. The optimum approach to saturation temperature is about 10, the optimum mole ratio 1.5. 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of name organizer Keywords: Flue gas desulfurization; removal efficiency; fast suspension bed; optimal parameters 1. Introduction Various technologies for flue gas desulfurization (FGD) can be classified into three different types: wet scrubbers, semi-dry processes and dry processes 1. Wet scrubbers have been widely commercialized in industry achieving SO2 removal in excess of 95%. However, this kind of technology generates a large amount of wet solid waste and requires waste water treatment. It also involves complicated configuration and costly operation 2. Dry FGD systems are attractive compared to wet scrubbers in terms of cost because they do not require water and reheating energy. Nonetheless, this type of process has not yet been widely used due to high sorbent cost and low SO2 removal efficiency. Therefore, various semi-dry processes have been developed to avoid the disadvantages of wet scrubbers and dry FGD techniques. Even so, SO2 removal efficiency of semi-dry scrubber is lower than wet scrubber, which may lead to not meet environmental regulation in some occasion 3. * Corresponding author. Tel.: +86-531-8839-9596 ; fax: +86-531-8839-9598 . E-mail address: wnh . 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the organizing committee of 2nd International Conference on Advances in Energy Engineering (ICAEE).1666 Xiaoping Zhang and Naihua Wang / Energy Procedia 14 (2012) 1665 1670Spray-dryer and circulating fluidized bed (CFB) FGD processes are two traditional semidry processes. Spray-dryer process has been extensively tested. However, a great drawback of this method is its large space consumption in order to maintain long flue gas residence for desulfurization reaction and slurry droplet evaporation, as well as to meet the requirement for the complicated slurry system 4. Circulating fluidized bed is also widely used for flue gas desulfurization; however, the choking phenomenon widely occurs due to unsteady flow in the bed 5. In this paper, a fast suspension bed (FSB) FGD scrubber was developed aiming to removal efficiency as high as those of wet scrubber with effective cost. This FSB scrubber can enhance both gas-liquid and gas-solid reaction with an innovative flue gas distribution apparatus. Also, this scrubber can prevent choking due to lime slurry impinging onto the scrubber inner surface. Effect of operating parameters including Ca/S ratio, approach to saturation temperature, flue gas flow rate and slurry particles diameter and distribution on SO2 removal efficiency were investigated. Moreover, mechanism of desulfurization reaction was analyzed. 2. Experimental The experiment system consists of simulation flue gas system, lime hydration system, SO2 scrubber, fabric filter and data acquisition system (Fig. 1). Chemical and physical characteristics of sorbent are presented in Table 1. Lime was stored in the slurry tank after hydration. Sauter diameter of the lime slurry is 5070m. SO2 was added into the mixing tank after a flow meter to meet the concentration. SO2 concentrations were measured with MSI-2000 flue gas analyzer. Temperatures were measured with type K thermocouples through HP34970A Data Logger. Welt bulb temperature of the flue gas was measured at the outlet of the scrubber. Lime slurry and water flow rates were measured with rotor flow meter and adjusted with speed-regulating motors. Fig. 1. Experimental setup 3. Results and discussion The reference condition were: Ca/S ratio 1.5, scrubber inlet temperature 150oC, flue gas flow rate 2000 m3/h, inlet SO2 concentration 3000 mg/Nm3, and approach to saturation temperature 10oC. When effect of one parameter on SO2 removal efficiency was studied, other parameters were kept constant. Xiaoping Zhang and Naihua Wang / Energy Procedia 14 (2012) 1665 167016673.1. Selection of sorbent Two types of lime were selected as sorbent, one from Fuyang and another from Xiaoshan. Chemical ingredients and physical characteristics of limes are shown in Table 1. It is found that SO2 removal efficiency was 67% with Xiaoshan lime, whereas 80% with Fuyang lime under reference condition. So Fuyang lime was selected as SO2 sorbent in this study. Table 1. Chemical ingredients and physical characteristic of limes Lime XiaoshanFuyang Ingredients CaO MgOFe2O3SiO2Al2O3others CaOMgOFe2O3 SiO2 Al2O3 others 85.3 00.5911.9187.60.720.60 0.25 0.81 8.46Diameter (m) 3.15 3.925.852.573.17 4.87 Percentage (%) 10 5090105090 Real density (g/cm3) 2 2Apparent density (g/cm3) 0.7881 0.7502Porosity rate inside the particles (%) 10.6 18Porosity rate between the particles (%) 34.0 29.2 Specific area (m2/g) 6.6366 10.8493 3.2. Effect of operating parameters on SO2 removal efficiency In semi-dry SO2 removal process, effect of operating parameters on desulfurization reaction is mainly through reaction rate, reaction time and reaction surface. During drying period, reaction rate is controlled by gas phase mass transfer resistance, liquid phase mass transfer resistance and lime dissolve resistance. Reaction time relies on the lime slurry particles evaporation. 3.2.1 Ca/S It can be seen from Fig. 2 that SO2 removal efficiency of the scrubber increases almost linearly with Ca/S ratio when it is less than 1, and become smooth after that. SO2 removal efficiency of fabric filter is about 10%20%. Mass concentration of calcium ion in the lime slurry increases as Ca/S ratio increases which reduces liquid phase mass transfer resistance and increases liquid film mass transfer coefficient. So that SO2 removal efficiency increases. Ca/S ratio has great effect on SO2 removal efficiency of the fabric filter. Gas and solid phases closely contact on the fabric filter surface. SO2 concentration on the particle surface is the same as that in the flue gas and the gas phase mass transfer resistance of SO2 is not significant. 3.2.2 Approach to saturation temperature Thermodynamic process in the FSB scrubber can be considered as adiabatic humidification due to its fine insulation. Approach to saturation temperature indicates extent of flue gas approaching saturation. It can be seen from Fig. 3 that SO2 removal efficiency increases significantly with decrease of approach to saturation temperature. When the approach to saturation temperature decreases, relative humidity of flue gas increases, evaporation rate of lime slurry particles decreases and liquid particles survival time is extended. Ion reaction of SO2 with Ca(OH)2 in the liquid phase is very fast, so SO2 removal efficiency increases significantly. On the other hand, lower approach to saturation temperature implies more water injected into the scrubber which increases reaction surface and enhances reaction in the scrubber. When approach to saturation temperature increases, relative humidity of flue gas and water content of sorbent increase, so does SO2 removal efficiency of fabric filter. For gas solid desulfurization reaction, solid diffusion through ash layer is the rate control stage. Adsorbed moisture on the solid surface 1668 Xiaoping Zhang and Naihua Wang / Energy Procedia 14 (2012) 1665 1670decreases diffusion resistance and improve SO2 diffusion into the sorbent, so that SO2 removal efficiency of the fabric filter increases. Fig. 2. Influence of mole ratio on SO2 removal efficiency Fig. 3. Influence of approach to saturation temperature on SO2 removal efficiency Even though lower approach to saturation temperature can increases total SO2 removal efficiency significantly, too small approach to saturation temperature will bring a series of economy and safety problems. The lower approach to saturation temperature, the longer drying period, and the higher scrubber needed. If the scrubber height is kept constant, water cannot evaporate completely when it goes away from the scrubber which leads to corrosion due to lime slurry bonding to the scrubber and the fabric filter. On the other hand, desulfurization products, especially CaSO4 will form cement-like material when combining with water which will block the fabric filter. Normally, approach to saturation temperature is about 10oC considering issues above. 3.2.3 Flue gas flow rate Velocity and residue time of flue gas under different flow rate are shown in Table 2. Table 2. Flow rate, velocity and residue time of flue gas Parameters ValueFlow rate (m3/h)150020002500Velocity (m/s)Residence time (s)5.24.03.2Flue gas velocity and residue time in the scrubber change with the flow rate. It can be seen from Fig. 4 that when residue time in the scrubber decreases, SO2 removal efficiency in the scrubber decreases slightly and SO2 removal efficiency in the fabric filter is almost constant. With the increase of flue gas velocity, turbulence will increase and mixing will be intensified which benefit SO2 diffusion in gas phase and SO2 removal. But, with the increase of flue gas velocity, steam diffusion in the gas phase and evaporation of water will be accelerated. Moreover, with a constant scrubber height, residue time of flue gas in the scrubber will decrease which decreases SO2 removal. In the scrubber, reaction is mostly gas liquid before slurry being dried. Gas liquid reaction time is very short, so flue gas residue time has little effect on gas liquid reaction in the scrubber. Flue gas residue time effect is mainly on gas solid reaction Xiaoping Zhang and Naihua Wang / Energy Procedia 14 (2012) 1665 16701669period which is not strong. Even gas solid reaction period is short, SO2 removal efficiency will not change much. 3.2.4 Flue gas temperature at scrubber inlet Fig. 4. Influence of flow rate on SO2 removal efficiency Fig. 5. Influence of inlet temperature on SO2 removal efficiency It can be seen from Fig. 5 that SO2 removal efficiency increases with increasing scrubber inlet flue gas temperature. Slurry temperature increases when increasing scrubber inlet flue gas temperature due to heat transfer. On one hand, temperature increase of gas and liquid phases will decrease SO2 solubility and absorption. On the other hand, temperature increase of slurry will increase ions diffusion and SO2 absorption. The most important is that when the scrubber inlet flue gas temperature increases, water injection will increase. Slurry particles and reaction surface area will also increase which leads to higher SO2 removal efficiency. In order to further understand impact of scrubber inlet flue gas temperature on SO2 removal efficiency, axial SO2 concentration distribution in the scrubber under 150oC and 200oC were studied. The results are shown in Fig. 6. SO2 concentration decreases quickly at the scrubber lower part, which corresponds to lime slurry particles drying stage of 1.5s. In the scrubber part higher than 6 m, SO2 concentration decrease is quite slow where liquid slurry particles have already dried and reaction rate is quick slow. SO2 removal efficiency is higher (81.6%83.3%) at higher scrubber inlet flue gas temperature due to water injection and drying period increasing. 3.2.5 Lime slurry particle diameter Impact of lime slurry particle diameters on SO2 removal is shown in Fig. 7. When the diameter is smaller than 50m, SO2 removal efficiency of scrubber increase significantly as slurry particle increase. When the diameter is larger than 50m, SO2 removal efficiency of scrubber increases slightly and then becomes stable as slurry particle increases. SO2 removal efficiency of fabric filter decreases with slurry particles increases due to reaction surface area decreases of in the fabric filter. Impacts of lime slurry diameter on SO2 removal efficiency in constant drying stage are through two aspects: as slurry diameter increases, drying period increases but reaction surface area and external mass transfer rate decrease. When the diameter is less than 50m, drying period dominates SO2 removal efficiency. When the diameter is between 50100m, both effects almost counteract with each other. When diameter is larger than 100m, external mass transfer rate is control stages of th
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