脱硫废水烟道蒸发技术蒸发特性实验研究

采用PDA实验系统和燃煤热态实验系统,分别研究了不同双流体喷嘴的雾化特性及烟气温度、烟气湿度、氯离子质量浓度和脱硫废水温度等参数对脱硫废水蒸发特性的影响。结果表明:不同喷嘴雾化特性存在一定差异,加工精度更高的喷嘴雾化效果相对较好,大粒径液滴较少,蒸发时间较短;烟气温度对脱硫废水蒸发的影响最大,烟气温度升高可促进液滴蒸发,但粗液滴蒸发时间仍较长,要使脱硫废水进入电除尘器前基本蒸发完毕(停留时间≤0.75 s),则进口烟气温度需在130℃以上;烟气湿度增加,对脱硫废水蒸发有一定抑制作用;氯离子质量浓度和脱硫废水温度对脱硫废水的蒸发基本没有影响;脱硫废水蒸发后,约90%～95%氯离子以无机盐颗粒形式蒸发析出并被除尘器捕捉。     

中高温烟气干燥脱硫废水过程研究

脱硫废水零排放(ZLD)已成为现阶段环境治理的趋势,传统的治理方法具有高成本、难维护等缺点,因此提出一种利用中高温烟气干燥电厂脱硫废水的新技术。通过将选择性催化还原(SCR)脱硝后的热烟气引入喷雾干燥器,雾化废水使其与烟气充分接触,经干燥进入空气预热器后的原烟道。结果表明:抽取锅炉烟气量的7%左右可干燥脱硫废水2.5 t,使锅炉热效率降低0.68%左右,影响较小。干燥后烟气酸露点温度从93.20℃提高到96.72℃,不会腐蚀空气预热器等后续工艺设备,同时该技术有利于静电除尘器(ESP)、湿法烟气脱硫(WFGD)系统的运行,利用中高温烟气干燥脱硫废水是可行且有效的技术方法。     

半干法脱硫中应用蒸汽相变促进细颗粒脱除

在喷雾干燥烟气脱硫系统中进行了应用蒸汽相变促进细颗粒脱除的试验研究:通过向脱硫反应后的湿烟气中添加适量蒸汽,形成细颗粒凝结长大所需的过饱和水汽环境,进而由高效除雾器脱除凝结长大的含尘液滴。细颗粒数量浓度及粒径分布采用电称低压冲击器(ELPI)实时测量。考察了喷雾干燥烟气脱硫操作条件(如Ca/S、浆液量)及蒸汽添加量对细颗粒脱除效率的影响,结果表明:部分浆液滴和脱硫反应产物可随烟气排出脱硫反应塔,导致细颗粒数量浓度增加;在半干法脱硫工艺中应用蒸汽相变可促进细颗粒脱除,脱除效率随蒸汽添加量增加而提高,如蒸汽添加量为0.08kg/m3时,细颗粒数量浓度脱除效率可提高到55%以上;脱硫操作条件对蒸汽相变效果有较大影响。     

燃煤电站脱硫废水零排放烟道喷雾蒸发特性的试验研究

为了实现电厂脱硫废水真正零排放,将脱硫废水经机械蒸汽压缩蒸发技术(MVR)蒸发结晶后排出来的母液进行烟道喷雾蒸发试验,喷射点选在SCR之前,研究了脱硫废水母液喷入烟道后的蒸发特性,分析了不同体积流量脱硫废水母液喷入烟道后对SCR出口烟气烟尘质量浓度、烟气主要成分、飞灰粒径分布、SO3质量浓度、飞灰比电阻及烟尘化学成分的影响,并探讨了加碱后的脱硫废水喷入烟道后对烟气主要成分和飞灰比电阻等的影响。结果表明:在SCR前烟道喷入脱硫废水,对烟气烟尘浓度的影响不大,但会增加烟气中HCl和HF的质量浓度;加碱后,腐蚀气体的质量浓度会减少;喷入脱硫废水后SCR出口烟气中SO3质量浓度减少;与脱硫废水相比,加碱的脱硫废水喷入SCR前烟道后,相同温度下的飞灰比电阻降低,有利于提高除尘效率。     

脱硫废水常规处理及零排放技术综述

针对目前火力发电厂对全厂废水零排放的要求,结合烟气脱硫系统外排废水的技术特点,采用较成熟的脱硫废水预处理方法,并根据电厂实际运行情况和自身特点,深入探讨、研究选取适宜的脱硫废水零排放及深度处理方案。     

600 MW火电机组单侧烟气脱硫废水零排放处理系统的应用

文中选用600 MW发电机组电厂第一套旋转雾化计划方案的高温烟气旁路蒸发对完成全厂废水零排放起着至关重要的作用,对类似电厂有较好的引领示范。旋转雾化器广泛应用于发电厂半干法脱硫装置中,将过饱和石灰浆液经旋转雾化器雾化时与加锅炉出口烟气接触反应,完成烟气烟气脱硫。该电厂作为西北地区第一家完成全厂废水零排放更新改造的电力企业,成功将旋转雾化装置用于600 MW发电机组脱硫废水烟气蒸发装置中,完成了设备创新实践,在这个环保科技行业具有重要示范性价值意义行业引领功效。     

燃煤电厂脱硫废水回用技术研究

针对燃煤电厂脱硫废水问题,通过采用烟道喷射处理技术来实现电厂废水的最终零排放问题。结合某电厂300 MW机组进行了相关技术方案的试验研究。结果表明:喷射时加入碱性吸附剂,烟气中的HCl最大可脱除68.21%;HF最大可脱除65.79%,SO_3最大可脱除19.20%。脱硫废水的烟道喷射方法可实现电厂脱硫废水的回用处理,同时还可实现脱除烟气中HF、HCl以及SO_3,减少了对尾部烟道的腐蚀。     

燃煤注汽锅炉脱硫废水零排放设想

燃煤注汽锅炉在生产过程中会产生大量含SO_2的烟气,注汽锅炉一般采用湿法脱硫技术。湿法脱硫废水为高含盐、高浓度重金属、高浓度悬浮物,对环境污染危害极大,对其进行深度处理,实现脱硫废水"零排放"对保护生态环境和水污染治理意义重大。传统的反渗透工艺对进水盐度适应性较差,产水率较低,存在较大弊端。针对脱硫废水蒸发工艺进行研究,提出"震动膜+烟道蒸发"脱硫废水零排放工艺,为我国今后脱硫废水零排放处理工艺提供参考。     

基于实测的循环流化床锅炉空气预热器及烟气处理设施对SO3脱除作用的研究

为了研究循环流化床锅炉(circulating fluidized bed boiler, CFB)的空气预热器和烟气处理设施对SO_3的脱除作用,利用控制冷凝法分别对装机容量在150～330 MW之间的10台循环流化床锅炉进行了实测。结果表明:空气预热器对SO_3的脱除率受空气预热器烟气出口温度的影响,在6.7%～36.5%之间,回转式空气预热器的SO_3脱除率高于管式空气预热器;布袋除尘器和电袋除尘器对SO_3的脱除率在40%以上;静电除尘器的SO_3脱除率在6.1%～10.8%之间;湿法脱硫的SO_3脱除率在41.7%～73.4%之间,其中双塔双循环的SO_3脱除率最高;炉外CFB半干法脱硫的SO_3脱除率达89.7%～97.9%,测试条件下炉内干法+炉外CFB半干法的工艺能使脱硫出口SO_3降至0.3 mg/m~3以下。     

烧结脱硫废水零排放并协同减排SO3技术分析

石灰石-石膏湿法脱硫废水含有大量Ca2+、Mg2+、S042-、Cl-与重金属等离子.脱硫废水中加入Ca(OH)2干粉制成吸收剂浆液,经雾化器雾化喷射而出的浆液粒径约10～60μm的细雾滴,在雾化干燥吸收塔内与高温烟气充分接触,烟气中的酸性成份(HCl、HF、SO2、SO3)被反应吸收,同时反应产物水份被蒸发,水蒸汽进入烟气中,干燥后反应产物部分落入干燥塔底端被收集外排,其余干燥产物随烟气中的飞灰一起被除尘器收集外排,实现脱硫废水零排放和对烟气中酸性气体的协同减排治理目的 .     

废弃物湿法烟气脱硫研究

湿法烟气脱硫以其高效获得了广泛的应用，但国外成熟技术的造价难以为我国接受。本文利用几种常见废弃物在填料吸收塔上对湿法烟气硫脱及其阻力特性和湿降问题进行了大量的试验研究，开发出了一种具有较高脱硫效率，较低投资和运行费用的湿法烟气脱硫技术，提出了较低温度下锅炉烟气排放的解决办法。     

静电除尘器和湿法烟气脱硫装置对烟气汞形态的影响与控制

利用安大略标准方法和在线汞监测技术对6套典型燃煤电站锅炉静电除尘器(ESP)和湿法烟气脱硫(WFGD)装置前后烟气汞的浓度及形态进行了测试,并研究了2种装置对烟气汞形态转化的影响及其汞控制能力.结果表明:ESP对飞灰的捕获直接降低了烟气中颗粒汞的比例,从已测试的典型燃煤锅炉来看,ESP前的燃煤烟气中颗粒汞的平均比例在30%左右,经ESP后颗粒汞所占比例降至5%左右;经WFGD装置洗涤后,烟气中汞的形态发生了较大的改变,二价汞基本被捕获,进入WFGD装置的烟气中二价汞的比例越高,WFGD装置对烟气汞的脱除效率也越高.配置有选择性催化还原(SCR)脱硝装置+ESP+WFGD尾部烟气处理装置的燃煤电厂,能够很好地控制燃煤烟气汞的排放.     

高硫煤机组低低温电除尘技术研究及工程应用

低低温电除尘器得到了广泛应用，但国内外鲜有高硫煤机组应用低低温电除尘器的案例。搭建了高硫煤机组低低温电除尘器试验台，测试了五种不同烟气温度下飞灰样本的比电阻、成分和粒径，提出了飞灰平均粒径与烟气温度的拟合公式；完成了国内首台高硫煤机组低低温电除尘器工程应用，并对低低温电除尘器进行了性能测试和运行优化。试验结果表明：烟气温度越低，飞灰比电阻越低，飞灰粒径越大；飞灰成分随着烟气温度变化较小；除尘效率随着烟气温度的降低明显提高；采用运行模式三和模式四相对日常运行模式可分别降低电除尘器电耗28%和35%。     

Mercury emission and adsorption characteristics of fly ash in PC and CFB boilers

The mercury emission was obtained by measuring the mercury contents in flue gas and solid samples in pulverized coal (PC) and circulating fluidized bed (CFB) utility boilers. The relationship was obtained between the mercury emission and adsorption characteristics of fly ash. The parameters included unburned carbon content, particle size, and pore structure of fly ash. The results showed that the majority of mercury released to the atmosphere with the flue gas in PC boiler, while the mercury was enriched in fly ash and captured by the precipitator in CFB boiler. The coal factor was proposed to characterize the impact of coal property on mercury emissions in this paper. As the coal factor increased, the mercury emission to the atmosphere decreased. It was also found that the mercury content of fly ash in the CFB boiler was ten times higher than that in the PC boiler. As the unburned carbon content increased, the mercury adsorbed increased. The capacity of adsorbing mercury by fly ash was directly related to the particle size. The particle size corresponding to the highest content of mercury, which was about 560 ng/g, appeared in the range from 77.5 to 106 µm. The content of mesoporous (4–6 nm) of the fly ash in the particle size of 77.5–106 µm was the highest, which was beneficial to adsorbing the mercury. The specific surface area played a more significant role than specific pore volume in the mercury adsorption process.     

A review on mercury in coal combustion process: Content and occurrence forms in coal,transformation, sampling methods,emission and control technologies

Mercury, as a global pollutant, has raised worldwide concern due to its high toxicity, long-distance transport, persistence, and bioaccumulation in the environment. Coal-fired power plants (CFPPs) are considered as the major anthropogenic mercury emission source to the atmosphere, especially for China, India, and the US. Studies on mercury in coal combustion process have been carried out for decades, which include content and occurrence forms of mercury in coal, mercury transformation during coal combustion, sampling, co-removal and emission of mercury in CFPPs, mercury removal technologies for CFPPs. This current review summarizes the knowledge and research developments concerning these mercury-related issues, and hopes to provide a comprehensive understanding of mercury in coal combustion process and guidance for future mercury research directions.The average mercury content in the coal from China, the US, and South Africa is 0.20, 0.17, and 0.20 mg/kg, respectively, which is higher than the world's coal average value of 0.1 mg/kg. In general, mercury in coal is in the forms of sulfide-bound mercury (mainly pyritic mercury, dominant), clay-bound mercury, and organic matter-bound mercury, which are influenced by diagenetic, coalification, and post-diagenetic conditions, etc. Mercury transformation in coal combustion includes homogeneous (without fly ash) and heterogeneous (with fly ash) reaction. The transformation is affected by the coal types, flue gas components, flue gas temperature, combustion atmosphere, coal ash properties, etc. The effects of chlorine, NOx, SO₂, H₂O, O₂ NH₃ on elemental mercury (Hg⁰) homogeneous oxidation and the influence of physical structure properties, unburned carbon, and metal oxides in fly ash as well as flue gas components on Hg⁰ heterogeneous transformation are systematically reviewed in detail. For the mercury transformation in oxy-coal combustion, O₂ promotes Hg⁰ oxidation with Cl₂ while NO and CO₂ inhibit or do not favor that reaction. CO₂ increases Hg⁰ oxidation in the atmosphere of NO and N₂. SO₂ will limit Hg⁰ oxidation, while HCl has a higher oxidation effect on Hg⁰ than that in air-coal combustion atmosphere. Fly ash plays an important role in Hg⁰ oxidation. SO₃ inhibits mercury retention by fly ash while H₂O promotes the oxidation.The sampling or analysis principle, sampling requirements, and advantages and disadvantages of the commonly used on-site mercury sampling methods, namely, Ontarion Hydro Method (OHM), US EPA Method 30B, and Hg-CEMS, are compared. The air pollution control devices (APCDs) in CFPPs also have the mercury co-removal ability besides the conventional pollutants, such as NO_x, particulate matter (PM), SO₂, and fine PM. Selective catalytic reduction (SCR) equipment, electrostatic precipitator (ESP) or fabric filter (FF), and wet flue gas desulfurization (WFGD) device are good at Hg⁰ oxidation, particulate mercury (Hg^p) removal, and oxidized mercury (Hg²⁺) capture, respectively. The Hg⁰ oxidation rate for SCR equipment, and the total mercury (Hg^t, Hg^t = Hg⁰ + Hg²⁺ + Hg^p) removal rate for ESP, FF, and WFGD device is 6.5–79.9%, 11.5–90.4%, 28.5–90%, and 3.9–72%, respectively. Wet electrostatic precipitator (WESP) can capture Hg⁰, Hg²⁺, and Hg^p simultaneously. The mercury transformation process in SCR, ESP, FF, WFGD, and WESP is also discussed. Hg^t removal in ESP+WFGD, SCR+ESP+WFGD, SCR+ESP+FF+WFGD, and SCR+ESP+WFGD+WESP is 35.5–84%, 43.8–94.9%, 58.78–73.32%, and 56.59–89.07%, respectively. The mercury emission concentration in the reviewed CFPPs of China, South Korea, Poland, the Netherlands, and the US is 0.29–16.3 µg/m³. Mercury in some fly ash and gypsum, and in most WFGD and WESP wastewater, is higher than the relevant limits, which needs to be paid attention to during their processing.Mercury removal technologies for CFPPs can be divided into pre-combustion (including coal washing technology and mild pyrolysis method), in-combustion (including low-NO_x combustion technology, circulating fluidized bed combustion technology, and halogens addition into coal), and post-combustion (including existing commercial SCR catalyst improvement, inhibiting Hg⁰ re-emission in WFGD, mercury oxidizing catalysts, injecting oxidizing chemicals, carbon-based adsorbents, fly ash, calcium-based adsorbents, and mineral adsorbents) based on the mercury removal position. The mercury removal effects, mercury removal mechanism, and/or influencing factors are summarized in detail. One of the regenerable mercury removal adsorbents, the magnetic adsorbent modified by metal oxides or the metal halides, is the most promising sorbent for mercury removal from CFPPs. It has advantages of high mercury removal efficiency, low investment, easy separation from fly ash, and mercury recovery, etc. Lastly, further works about mercury transformation in coal combustion atmosphere, mercury co-removal by APCDs, the emission in CFPPs, and mercury removal technologies for CFPPs are noted.     

湿式电除尘器用于控制燃煤烟气污染物的测评

湿式电除尘器是一种对多污染物深度控制的环保设备。介绍了长兴岛第二发电厂将湿式电除尘器用于控制燃煤烟气污染物的工程特点以及湿式电除尘器投运后的性能试验。通过对燃煤烟气多种污染物的检测,分析与解读了测试烟尘、微细颗粒物与PM2.5、烟气三氧化硫、雾滴与石膏雨、烟气二氧化硫的方法、排污标准、检测数据和试验结果,并进行了综合评价。试验结果表明,国产除尘设备对多种污染物的控制效果与三菱、日立技术基本相当。分析认为,在绿色、环保的大环境下推广应用湿式电除尘技术时要注意:增加比集尘面积可以进一步提高燃煤烟气污染物的净化能力;采取间断冲洗工艺流程可以降低水力清灰水;消除烟气携带游离水分的关键是设计要优化。     

飞灰未燃尽碳对吸附烟气汞影响的试验研究

采用HYDRA AA全自动测汞仪对3个燃煤电厂的飞灰未燃尽碳进行测试,并利用垂直炉试验系统对电厂飞灰吸附烟气汞进行了试验研究.结果表明：不同燃煤电厂飞灰中的未燃尽碳含量不同是由于各电厂不同煤种、不同燃烧工况以及机组的不同参数造成的;同一电厂的飞灰在灼烧后与原灰相比,对烟气汞的吸附效率相差不大;除了飞灰中的未燃尽碳对汞有吸附外,尾矿对汞也有一定的吸附作用;未燃尽碳含量高的飞灰对汞的吸附效率也较高.     

复合相变换热器在锅炉烟气余热回收中的应用

为了降低锅炉排烟温度,回收锅炉尾部烟气热量,提高机组效率,降低机组发电煤耗,确保电除尘、引风机安全运行,采用复合相变换热器加热同机组的凝结水,在避免换热器结露积灰的前提下,能大幅度降低锅炉排烟温度,回收锅炉尾部烟气的余热,减少汽轮机的抽汽量,增加机组发电能力,可获得较好的经济效益。     

氯和灰分对大型燃煤锅炉烟气中汞形态的影响

采用安大略标准燃煤烟气汞采样分析方法,对大型燃煤锅炉出口烟气中汞形态的形成及分布机理进行了研究.分析了煤中Cl、灰分及采样位置对锅炉出口烟气中汞形态分布的影响.结果表明:烟气中的飞灰能够直接影响颗粒汞与气态汞之间的平衡比例;煤中灰分含量越多,锅炉出口烟气中颗粒汞所占比例越大;煤中Cl对气态汞中Hg0向Hg2 形态转变有促进作用;较高的烟气温度和较短的停留时间会严重阻碍飞灰对汞的吸附,影响颗粒汞的形成,同时也会阻碍Cl元素对Hg0的氧化作用.     

A review on the utilization of fly ash

Fly ash, generated during the combustion of coal for energy production, is an industrial by-product which is recognized as an environmental pollutant. Because of the environmental problems presented by the fly ash, considerable research has been undertaken on the subject worldwide. In this paper, the utilization of fly ash in construction, as a low-cost adsorbent for the removal of organic compounds, flue gas and metals, light weight aggregate, mine back fill, road sub-base, and zeolite synthesis is discussed. A considerable amount of research has been conducted using fly ash for adsorption of NO_x, SO_x, organic compounds, and mercury in air, dyes and other organic compounds in waters. It is found that fly ash is a promising adsorbent for the removal of various pollutants. The adsorption capacity of fly ash may be increased after chemical and physical activation. It was also found that fly ash has good potential for use in the construction industry. The conversion of fly ash into zeolites has many applications such as ion exchange, molecular sieves, and adsorbents. Converting fly ash into zeolites not only alleviates the disposal problem but also converts a waste material into a marketable commodity. Investigations also revealed that the unburned carbon component in fly ash plays an important role in its adsorption capacity. Future research in these areas is also discussed.