【作者】 钟毅；

【导师】 骆仲泱； 高翔； 倪明江；

【作者基本信息】 浙江大学 ， 工程热物理， 2008， 博士

【摘要】 SO₂污染对环境、人类健康以及经济发展都具有非常大的影响。近年来随着电力行业的迅猛发展,SO₂、NO和Hg的污染有加重的趋势。针对电站锅炉的SO₂污染,我国开展了大规模的电站锅炉湿法烟气脱硫（WFGD）系统的建设。针对NO污染,目前比较常见的有炉内控制技术如低NOx燃烧器与选择性非催化还原（SNCR）技术,烟气脱硝技术如选择性催化还原（SCR）技术。今后排放标准如果提高,炉内控制技术可能无法保证烟气达标排放,而SCR技术因场地限制而使应用是受到一定制约。根据我国的环境现状以及国家节能减排的政策,正在对更多的其它污染物排放进行控制。如何利用已有的污染物控制设备实现多种污染物协同脱除具有非常重要的研究意义。目前我国石灰石/石膏WFGD工艺应用非常广泛,利用已有的WFGD系统进行污染物协同脱除具有非常良好的经济性,对于场地紧张的电站而言尤其具有吸引力。在对国内外污染物协同脱除的研究进展进行综述的基础上,对复合添加剂同时脱硫脱硝的反应动力学研究。采用平面传质搅拌反应器进行了SO₂和NO的吸收特性研究,确定了不同因素如气体分压、添加剂浓度对于SO₂和NO的吸收速率的影响,并根据实验结果确定了该反应的反应级数、反应速率常数、活化能等动力学参数;在反应动力学研究的基础上,对复合添加剂同时脱硫脱硝的影响因素进行了研究。采用不同反应器对复合添加剂进行了同时脱硫脱硝的实验,确定了各种因素如pH值、烟气流量、添加剂浓度、添加剂与污染物摩尔比、液气比对于脱硫脱硝效率的影响。采用洗瓶反应器进行了复合添加剂吸收零价汞的实验,确定了上述因素对于零价汞吸收的影响。针对实际工程,开展了WFGD系统喷淋塔多种污染物协同脱除性能优化的数值模拟研究。本文基于计算流体力学（CFD）技术,应用混合网格技术,采用标准κ-ε湍流模型描述塔内烟气湍流运动,颗粒轨道模型描述液滴运动,随机漫步模型描述湍流对液滴运动的影响,Rosin-Rammler模型描述液滴的粒径分布,采用SIMPLE算法进行计算。根据塔内实际情况,对脱硫过程采用非稳态传质理论建立了脱硫脱硝数学模型,从而实现对喷淋塔内污染物浓度分布的计算。对某300 MW机组WFGD吸收塔内不同设计和运行条件下脱硫脱硝效率的变化进行了数值计算。脱硫效率的计算结果与实测结果两者吻合较好。基于数值模拟结果对喷淋塔内污染物协同脱除性能优化提供了建议。依据数值模拟结果,提出了基于WFGD系统的脱硫脱硝除汞一体化的应用方案,并对该方案的经济性进行了比较。石灰石/石膏WFGD工艺因其优点已成为最广泛采用的工艺。该技术主要以国外引进技术为主,因国内外机组运行模式差异导致运行过程出现了故障与停运问题,研究与开发具有自主知识产权的脱硫技术势在必行。物料平衡计算是WFGD技术设计优化的基础与关键。基于物料衡算基本理论,结合系统设计流程,对WFGD系统的能量平衡、水平衡、固平衡、气平衡、氯平衡、镁平衡等进行了详尽分析,形成了系统物料平衡计算软件。采用该计算软件对具体工程项目进行了计算,并与实际工程设计运行结果进行比较。结果表明该软件可应用于实际工程的物料平衡计算。更多还原

【Abstract】 The pollution of SO₂ has many great influences on environment,human health and economic development.The pollution of SO₂,NO and mercury is becoming worse and worse with the rapid development of power industry in recent days.More and more large-scale wet flue gas desulfurizaiton（WFGD） systems were constructed to control the pollution of SO₂.In order to control the pollution of NO,the in-furnance control technologies such as low NOx burner（LNB） and selective non-catalytic reduction（SNCR） and flue gas deNOx technologies such as selective catalytic reduction（SCR） were taken.If the NO emission standard improves in future,the in-furnance control technologies can not gurantee the NO emission below the emission standard.The application of SCR technology is confined because of its space need.Control of emission of more pollutant is required to protect the environment and satisfy the policy of energy conservation and emission reduction in China.Therefore,it is meaningful to realize the multi-pollutants control in existed pollutant control system.Limestone/gypsum WFGD technique is applied widely for control the SO₂ emission in China.The technique to control multi-pollutants in the WFGD system is economical and attractive,especially for those power plants with limited space to take great construction.Based on the review of advance of multi pollutant removal technology,kinetics of DeSO₂ and DeNOx in the compound solutions was studied.Effects of partial pressure and concentration of reagents to the absorption rate of SO₂ and NO were determined in the experiments of absorption characteristic in stirred reactor with plate mass transfer surface. The kinetics parameters such as reaction order,rate constant,activated energy were determined according to experimental data.After the study of kinetics,effects to efficiency of removal of SO₂,NOx and Hg in the compound solutions were studied.The effects such as pH value,flow of flue gas,reagents concentration,and molar rate reagents to pollutants and liquid to gas rate to the efficiency of removal of SO₂,NOx were determined in the experiments with different reators.The absorptions of Hg⁰ in the compound solutions with washing bottle were taken.Effects of parameters mentioned above to the efficiency of Hg removal were determined.Aimming at the application of the WFGD systems in power plants,the numerical simulation of performance optimization for multi-pollutant removal in spray scrubber of WFGD system was studied.Based on computational fluid dynamics（CFD） technology and structuralized-non-structuralized hybrid grid technology,the standardκ-εturbulent model which describe the flue gas turbulent motion in the tower,the Discrete Phase Models which trace the movement of droplets,Discrete Random Walk model which describe the turbulent motion influence to the movement of droplets,the Rosin-Rammler model which describe droplets distribution,the gas-liquid fluid flow field in spraying tower was simulated with the SIMPLE calculation method.The pollutants concentration fields in the scrubber were determined by desulfurization and deNOx mathematical model which build up non-steady state mass transfer theory.The numerical calculation of the scrubber of a 300 MW power unit was taken in different design and operation conditions. The calculation results of desulfurization are in good agreement with the results measured in the performance test.Based on the numerical simulation results,some advices were proposed for the optimization of multi-pollutants removal in the spray scrubber.Based on the results of numerical simulation,the programme of removal of SO₂,NOx and Hg in WFGD system was proposed and the economy of the programme was analyzed.Limestone/gypsum WFGD technique is the most popular technique used in the desulfurization because of its advantages.Nearly all the limestone/gypsum WFGD techniques are from foreign corperation and lots of WFGD systems are in malfunction or out of service because the operation modes of utility boilers in China are different to those of foreign utility boilers.It is necessary to develop WFGD technique with independent intellectual property rights.Material balance is the key and base for the WFGD design and optimization.Based on the basic theory of material balance and system design,the system of sod energy balance,water balance,solid balance,gas balance,chlorine balance and magnesium balance of WFGD system are analyzed detailedly to form a material balance calculation software package.The calculation results of several WFGD systems by the software package are in good agreement with design and operation results in the large scale WFGD systems in power plants.The software package can be applied to the material balance calculations of WFGD system.更多还原