Mercury speciation and removal across full-scale wet FGD systems at coal-fired power plants

The Ontario Hydro Method （OHM） recommended by the United States Environmental Protection Agency （EPA） was used to determine mercury speciation in the combustion flue gas across wet FGD systems. Four coal-fired units with wet FGD systems were chosen to evaluate mercury speciation and mercury removal efficiencies through these wet FGD systems. Chlorine content in coal had been suggested as a main factor that affects mercury speciation in flue gas. It is shown that the higher the chlorine concentration in coal is, the higher the percentage of oxidized mercury （Hg2＋） is removed in wet FGD systems, which can increase overall mercury removal efficiencies through wet FGD systems. The selective catalyst reduction （SCR） system has a function of oxidizing ele- mental mercury （Hg0） to oxidized mercury. A higher percentage of oxidized mercury in the total vapor mercury at the FGD inlet is observed when SCR is in service. Therefore, higher overall mercury removal efficiencies through wet FGD are attained. Because of different wet FGD operating conditions, there are different mercury removal efficiencies in different units. Elemental mercury reemission took place when a fraction of oxidized mercury absorbed in the slurry is reduced to elemental mercury, and Hg2＋ is reemitted from stack, which results in decreases in mercury removal efficiencies through wet FGD systems.

Study and Solutions to the Issue of Heavy Metals from Wet FGD Wastewater

The conventional wet FGD process has been applied in more than 85% units for SO2 removal in China. There are a great number of pollution components in the wastewater from wet FGD process,and the removal process of these components is very complicated and difficult,especially the removal of heavy metals in the wastewater. Even if a foreign advanced technology was applied,it is still difficult to meet the discharge requirements of heavy metals in spite of its much higher investment,operation and maintenance cost than that from the domestic widely-used and simple wastewater treatment process. Under the background of increasingly stringent environmental requirements,to improve the existing wastewater treatment process or to change the existing wet FGD process has become extremely urgent.

Treatment of Wet FGD Wastewater by a Modified Chemical Precipitation Method Using a Solid Powder Reagent

This research focused on developing a modified chemical precipitation (MCP) method for treating wet flue gas desulfurization (FGD) waste water by adding a solid powder reagent directly. Simulated wet FGD wastewater was treated by MCP method in simulation experiments. Optimization experiments were carried out with the help of response surface methodology (RSM) and central composite design (CCD) to evaluate the effects and the interactions of experimental variables, including reagent dosage, temperature and pH value. The optimal reagent dosage, temperature and pH value were 3018.0 mg/L, 40.5 °C and 5.7, respectively. The RSM was demonstrated as an appropriate approach for the optimization of wet FGD wastewater treatment with the MCP method. A comparative study between the MCP method and the traditional chemical precipitation (TCP) method on raw wet FGD wastewater treatment was conducted. Results indicate that the MCP had less reagent dosage and variety than the TCP method had. Thus, the MCP method had a lower cost. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

A pilot-scale jet bubbling reactor for wet flue gas desulfurization with pyrolusite

MnO2 in pyrolusite can react with SO2 in flue gas and obtain by-product MnSO4· H2O. A pilot scale jet bubbling reactor was applied in this work. Different factors affecting both SO2 absorption efficiency and Mn2^＋ extraction rate have been investigated, these factors include temperature of inlet gas flue, ration of liquid/solid mass flow rate（ L/S）, pyrolusite grade, and SO2 concentration in the inlet flue gas. In the meantime, the procedure of purification of absorption liquid was also discussed. Experiment results indicated that the increase of temperature from 30 to 70 K caused the increase of SO2 absorption efficiency from 81.4% to 91.2%. And when SO2 concentration in the inlet flue gas increased from 500 to 3000 ppm, SO2 absorption efficiency and Mn2^＋ extraction rate decreased from 98.1% to 82.2% and from 82.8% to 61.7%, respectively. The content of MnO2 in pyrolusite had a neglectable effect on SO2, absorption efficiency. Low L/S was good for both removal of SO2 and Mn2^＋ extraction. The absorption liquid was filtrated and purified to remove Si, Mg, Ca, Fe, Al and heavy metals, last product MnSO4· H2O was obtained which quality could reach China GB1622-86, the industry grade standards.

FGD系统不宜取消旁路的分析

从FGD系统的安全性出发,研究了影响石灰石-石膏湿法FGD系统安全性的7类主要因素。结果表明目前我国的FGD系统安全性较低,不宜取消旁路烟道。同时提出了要取消FGD旁路烟道需在设计、运行等各方面采取的对策和建议。

石灰石/石膏湿法FGD装置除尘效率和SO_3脱除率探讨

对石灰石—石膏湿法FGD装置除尘效率和SO3脱除率检测数据进行了对比分析,并探讨了净烟气中SO3的来源问题。

利用湿式FGD系统吸收汞

介绍巴布科克与威尔克斯(B&W)公司利用电厂现有的污染控制设备削减汞排放的技术。示范项目表明,在仅增加较低投资成本的情况下,利用湿式FGD(烟气脱硫)系统可脱除烟气中95%以上的氧化汞,同时对系统运行或SO_2去除性能影响很小甚至没有影响。

中小型锅炉烟气脱硫(FGD)的技术路线

概述了我国当前SO2减排控制的紧迫性和重要性,以及中小型锅炉烟气脱硫的特点和脱硫技术现状。对几种适用的FGD工艺和主要装置形式进行了分析介绍;对中小型锅炉烟气净化处理的各种技术路线进行了讨论比较,并对它们的发展方向及脱硫工艺中存在的问题提出了建议。

石灰石浆液制备系统运行中存在问题的探讨

石灰石-石膏湿法烟气脱硫装置FGD系统被证明是一种脱硫率高、可靠性高、性价比高的先进脱硫工艺,目前我国300 MW及以上的火力发电厂90%均采用了该技术,而石灰石浆液制备系统是脱硫系统稳定运行的基础,结合系统实际运行情况,探讨了过滤水坑搅拌器轴杆断裂、磨机再循环泵出口电动阀阀杆断裂、磨机再循环箱搅拌器液位低联锁停运后无法启动、球磨机停运时出口甩料严重、球磨机主电机运行过程中因润滑油系统油脂检测开关故障停运、石灰石旋流器旋流子堵塞几种常见故障及故障产生的原因,并提出了相应的解决办法。

FGD控制系统控制策略的优化与改进

介绍了杭州华电半山发电有限公司原FGD工艺流程及控制系统TXP存在的问题,将TXP改造为新型的NET-WORK-6000系统,并在控制策略上进行改进、优化,改造效果良好。

湿法FGD湿烟囱工艺的问题及对策

介绍了湿法FGD湿烟囱工艺的可行性和选择该工艺时应考虑的问题,并提出了湿烟道、湿烟囱设计的基本要求。

介绍2种湿式FGD强制氧化方法

介绍了 2种用于湿式石灰石烟气脱硫工艺的强制氧化方法 。

宝钢FGD工艺抉择之我见

论述了国外ＦＧＤ（烟气脱硫）的发展和国内的进展以及ＦＧＤ工艺选择原则。较详细地介绍了湿式氨法、干式氨法以及钢渣法的ＦＧＤ流程。同时就宝钢实施ＦＧＤ的可能性作了分析。

关于恒益电厂600MW机组湿法FGD是否设置GGH的探讨

湿法烟气脱硫系统是否设置GGH,是目前国内争议较大的问题,其对脱硫系统的投资和经济运行有重大影响。针对三水恒益电厂600 MW机组安装脱硝系统(SCR)之后,石灰石—石膏湿法烟气脱硫系统是否安装GGH进行了探讨,为工程初步技术设计提供参考。

新型高效脱硫吸收剂提高火电厂FGD系统灵活性的试验研究

石灰石/石膏湿法脱硫工艺中吸收剂石灰石(主要成分为CaCO_(3))反应活性低,在机组深度调峰快速升负荷、燃煤含硫变化大时净烟气SO_(2)排放质量浓度经常存在超标问题。为此以某电厂600 MW机组为例,采用一种新型高效脱硫吸收剂进行试验,结果表明:新型高效脱硫吸收剂的加入可在3min内快速提高烟气脱硫(flue gas desulfurization,FGD)系统的脱硫效率,抑制SO_(2)排放质量浓度在快速升负荷的超标现象,同时可增加FGD系统最大出力,拓宽FGD系统对高硫分煤种的适应能力,提高电厂燃煤采购的灵活性。

加装湿法脱硫后烟囱防腐期间FGD运行及措施

由于环保要求,目前我国发电厂现有机组脱硫改造工程越来越多,其中大多数采用湿法脱硫工艺。湿法脱硫后烟气含水量大,湿度高,烟气各项性能指标发生了变化,致使烟气具有强腐蚀性,且200～300 MW机组一般是2台炉共1个烟囱,从而带来了如何在不停机情况下老烟囱的防腐问题。目前国内还缺乏经验;通过洛河发电厂一期烟囱防腐实例,推荐无旁路FGD的烟囱防腐改造工程实施方案,希望对燃煤发电厂旧烟囱防腐改造有所参考。

浅谈提升高硫煤机组FGD可靠性之措施

针对高硫煤机组FGD的技术特点,从设计源头介绍了如何提升高硫煤机组FGD可靠性的措施,并佐以工程实例。

高硫煤烟气湿法脱硫氧化空气风机设计技术经济分析

基于石灰石-石膏湿法烟气脱硫化学反应机理,提出了强制氧化工艺的氧化空气风机参数计算模型。对可用于氧化空气风机选型的罗茨风机、多级离心鼓风机、单级高速离心鼓风机、空气悬浮鼓风机、磁悬浮鼓风机特性进行了比较。阐述了高硫煤烟气脱硫氧化空气供给技术,并对不同型式的氧化空气风机选型设计进行了技术经济性分析。对石灰石湿法烟气脱硫氧化空气系统设计、氧化空气风机选型设计具有指导意义。

湿法烟气脱硫系统中折板式除雾器性能的数值模拟

采用CFD软件对湿法烟气脱硫系统中广泛使用的折板式除雾器的主要性能进行了数值模拟。建立了数学模型,对气体相采用基于雷诺时均方程的SSTk-ω湍流模型封闭N-S方程,对液滴相采用基于Eu ler-Lagrange的DPM方法。通过调节除雾器的结构参数和工作参数,揭示了气液两相流动的流场,分析了结构参数对除雾器分离效率和工作压力降的影响,可用于湿法烟气脱硫系统中折板式除雾器的设计和优化。

火电厂烟气潜热和凝结水回收的试验研究

介绍了使用氟塑料换热器回收大型火电厂烟气潜热和凝结水的试验研究.火电厂湿法脱硫系统出口温度为50~55℃的饱和或过饱和烟气,其烟气水蒸气浓度为12％~18％.烟气中的水蒸气携带大量潜热,降低了锅炉效率.拟在脱硫系统出口烟道中加装冷凝换热回水装置（换热器）,以实现高水分烟气的深度凝结,回收大量水分,同时回收气化潜热.为此,在某褐煤电厂搭建中试试验系统,抽取实际烟气进行试验.结果显示：当烟气温度降低9~10℃,将结果折算到全烟气量（2500000 m3/h,标准状态,下同）,可以回收凝结水92．25 t/h,回收热量226．97 GJ/h；该系统可实现褐煤机组湿法脱硫零耗水,这对干旱地区的水资源保护有重要意义.