火力发电厂高效脱硫及除尘一体化超洁净技术研究及应用

[目的]文章主旨为满足国家对火力发电厂烟气污染物排放"超洁净"排放指标的要求。[方法]通过对广东某火力发电厂除尘和脱硫技术进行研究,提出了高效脱硫及除尘一体化超洁净技术,并在该电厂顺利应用。在常规烟尘和SO_2脱除方案上的基础上,通过对已有除尘和脱硫设备进行一体化设计和优化,并增加MGGH装置和电除尘除雾装置,协同对污染物包括烟尘和SO_2进行脱除,并提高烟囱出口烟气温度,减少烟气中液滴和烟尘浓度。[结果]机组投运后,实测烟囱出口烟尘和SO_2排放浓度为2.2 mg/Nm~3和16.7 mg/Nm~3,满足并优于火力发电厂"超洁净"排放的要求,且消除了烟囱出口的"石膏雨"现象。[结论]应用该项技术,可以在不设置湿式除尘器的条件下即可满足"超洁净"的排放要求,对新建或改造项目有很好的指导和借鉴意义。     

超低排放机组协同脱汞效益研究

采用安大略法对3台典型工艺路线的机组烟气汞浓度进行测试,研究超低排放机组汞排放水平和电除尘器、高效湿法脱硫装置、湿式电除尘器及烟气冷却器等污染物控制设备的协同脱汞效果.研究结果表明:超低排放改造后,燃用低汞煤的机组汞排放浓度为1.06～3.13μg/m3,总汞脱除效率为67.9％～88.7％;电除尘器的总汞脱除效率为2...     

燃煤工业锅炉超低排放改造后微细颗粒物排放特征研究

采用切割器+滤膜的取样系统,对超低排放改造后的循环流化床(CFB)锅炉、链条炉产生和排放的微细颗粒物(PM_(10)、PM_(2.5)和PM_1)进行了现场测试。结果表明,CFB锅炉炉膛出口的微细颗粒物浓度远大于链条炉。CFB锅炉布袋除尘器对微细颗粒物的脱除效率可达98.12%～99.56%,而对应链条炉只有90.0%～93.6%。脱硫塔和湿式电除尘对微细颗粒物联合脱除效率约为50%～60%,脱除效果较为明显。超低排放改造后PM_(10)、PM_(2.5)和PM_1排放因子分别为0.028～0.033kg·t~(-1)、0.025～0.028 kg·t~(-1)和0.014～0.017 kg·t~(-1)。最终排放的PM_(2.5)占PM_(10)的百分比为85.2%～88.6%。这些结果对修订《大气细颗粒物一次源排放清单编制技术指南》有参考意义。     

EPM电风拦截装置对湿法脱硫后烟气复合污染物协同治理探讨

介绍了EPM电风拦截除尘除雾一体化技术对湿法脱硫后烟气复合污染物处理工艺的路线、原理、优势等内容。以广东粤电大埔电厂2×660MW机组新建工程中配套EPM电风拦截装置为例,结合各项性能试验及试验数据,探讨了EPM电风拦截除尘除雾一体化装置的除尘效果以及对PM_(2.5)、SO_3和雾滴等烟气复合污染物的协同治理。研究表明,EPM电风拦截除尘除雾一体化装置不仅具有高效的除尘效率,而且对于湿法脱硫后烟气复合污染物也具有良好的脱除效果,其应用前景广阔。     

火电厂湿式静电除尘器的发展现状综述

通过对湿式静电除尘器技术的结构特点、国内外发展与应用情况进行综述分析,表明湿式静电除尘器通过改进传统除尘器的结构,可以对火电厂湿法脱硫系统产生的硫酸雾、细颗粒物、石膏雨等有显著脱除效果,是火电厂控制燃烧源产生的PM2.5等细颗粒物、实现多种污染物联合减排的重要手段,有着很好的发展前景。     

燃煤电厂脱硫系统的脱汞特性研究

作为未来潜在的多污染物排放控制装置,烟气脱硫系统对汞赋存价态和脱除效率的影响成为目前汞污染控制研究的热点.对2种具有代表性的脱硫系统[湿法脱硫(WFGD)和新型整体一体化脱硫(NID)]进行了汞测试.试验结果表明:WFGD系统对烟气中氧化态汞的脱除效率达到74.68%,但对烟气中单质汞的脱除效率很差,氧化态汞在全汞中所占的比例是决定WFGD全汞脱除效率的关键因素;NID系统对烟气中单质汞的脱除效率高达99.97%,对氧化汞的脱除效率为79.03%,对总汞的脱除效率是83.52%,这说明NID系统可以非常有效地控制燃煤电厂汞的排放.     

紫外_过氧化氢法同时脱硫脱硝的研究

介绍了UV/H_2O_2脱除废气中污染物的研究进展.分析了UV/H_2O_2体系的强氧化性对模拟烟气中SO_2和NO_x的脱除作用,在最佳实验条件下,应用UV/H_2O_2对S_2和NO_x的脱除效率可达到95%以上.对UV/H_2O_2体系脱除SO_2和NO_x的反应机理进行了分析,提出自由基反应是使污染物得以氧化脱除的基础.指出此方法可用于改造现有的湿式烟气脱硫塔,使之成为具有烟气多污染物控制能力的大气污染控制设备.     

百万千瓦燃煤机组烟气超低排放设计及应用

为实现燃煤机组烟气超低排放,对某电厂1 000 MW燃煤机组实施烟气超低排放的技术改造:脱硝采用低氮燃烧器调整技术和SCR反应器内加装催化剂技术,除尘采用低低温电除尘器和湿式电除尘器,脱硫采用交互式喷淋技术。改造后机组烟气排放按下述流程:低氮燃烧器的锅炉出口烟气依次流经省煤器、SCR、空预器、管式换热器降温段、低低温电除尘器后进入吸收塔,然后经过湿式静电除尘器和管式换热器升温段进入烟囱。改造后烟囱入口的主要烟气污染物NO_x、烟尘、SO_2排放浓度分别达到25.83、1.61和22.08mg/Nm~3,污染物排放浓度数值上低于天然气燃气轮机组排放标准。     

湿法脱硫参数对Hg~0脱除效率的影响

湿法脱硫系统在除去SO_2的同时也能脱除单质汞,但脱硫参数对单质汞脱除效率的影响较大。为了研究湿法脱硫的各个参数对于单质汞脱除效率的影响,在实验室条件下模拟湿法脱硫过程。主要考察了温度、O2浓度、SO_2体积分数、pH值、脱硫液浓度和卤素离子(Cl~-、Br~-、I~-)浓度对于单质汞脱除效率的影响。结果表明湿法脱硫对单质汞的最佳脱除温度在55℃左右。Hg~0的脱除效率随p H值、O2浓度和脱硫液浓度的增加而增加,而SO_2浓度的增加对Hg~0的脱除有抑制作用。Cl~-、Br~-、I~-都能促进Hg~0的氧化脱除,促进顺序为Br~-I~-Cl~-。     

湿法烟气脱硫系统的脱汞性能研究

通过测量湿法烟气脱硫(WFGD)系统进出口烟气中汞的浓度,考察了采用NH3·H2O、NaOH、Na2CO3、Ca(OH)2、CaCO3等5种脱硫荆时系统的脱汞性能,并在脱硫液中添加KMnO4,Fenton试荆、K2S2O8/CuSO4、Na2S进行试验.结果发现:燃煤烟气中气态总汞主要成分是单质汞,二价汞所占比例不超过40%;常规WFGD系统能高效脱除烟气中的气态二价汞(Hg2+),脱除效率高达81. %～92.60%,而对气态总汞的脱除效率仅为13.27%～18.26%,经WFGD系统后单质汞略有增加;脱硫剂种类对脱汞效果影响不明显,提高液气比有利于提高WFGD系统的脱汞效率;KMnO4、Fenton试剂、K2SzO8/CuSO4和Na2S等添加剂均可提高脱汞效率,但不同添加剂的效果有所不同,其中Na:S效果最为显著,脱汞效率最高可达67%.     

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.     

混燃石油焦CFB锅炉汞排放特性研究

为研究烟煤与石油焦混燃的循环流化床锅炉汞的迁移排放特性,采用安大略法(OHM)对机组布袋除尘器(FF)前后和湿法脱硫装置(WFGD)后的烟气进行取样,并同时对入炉燃料、飞灰、脱硫浆液、清洗水、石膏和脱硫废水进行了取样并分析。通过汞的质量平衡核算得到了汞在燃煤副产物中的分配比例以及汞的迁移排放特性。结果表明:飞灰中排放的汞占总汞排放的62.31%,大约30.38%的汞排放到大气中。FF可以高效地脱除颗粒态汞,对总汞的脱除率可达67.36%。WFGD对可溶性的二价汞脱除性能较好,对总汞的脱除率达24.24%。单质汞的排放因子远大于氧化汞,说明电厂大气汞的排放主要以单质汞为主。     

静电增强湿式除尘器捕集可吸入颗粒物的定量描述

湿式重力喷淋除尘器一般对可吸入颗粒物的除尘效率较差,而借助静电力,则有望改善湿式除尘器对细微颗粒的除尘效果.首先介绍了静电增强湿式除尘器的捕集机制,包括布朗扩散、拦截、惯性碰撞和静电捕集;然后利用事件驱动常体积法描述了典型火电厂中三峰分布的烟尘颗粒群的尺度分布函数的动力学演变过程,以此量化静电增强湿式除尘器的除尘过程.结果表明,典型的传统湿式重力喷淋除尘器对PM的分级除尘效率在5%以上;如果液滴荷电,有望使得该除尘器对PM的分级除尘效率达到70%以上;如果颗粒荷电,PM的分级除尘效率将在25%以上;在液滴和颗粒同时荷上相反电荷的静电增强湿式除尘器中,PM的分级除尘效率接近100%.     

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。     

高效脱硫复合添加剂配方筛选及增效试验研究

通过单组分有机酸添加剂的筛选、多组分有机酸添加剂组合优化和脱硫效率验证实验,最后优选出脱硫效果佳、对运行参数具有良好适应性和稳定性的高效复配脱硫添加剂。结果表明,当进口SO2浓度为4500mg/m3时,复配添加剂可使系统脱硫效率达99%以上,比相同条件下脱硫效果最好的单组分添加剂提高0.4%~0.7%,比无添加剂时提高5%~8%。     

脱硫废水荷电喷雾干燥对燃煤烟气特性影响

脱硫废水富含氯离子,是燃煤电厂难以处置的污染物之一。使用荷电喷雾干燥的方法,将富氯脱硫废水返喷除尘器前,研究了其干燥迁移规律和对烟气成分的影响,证实了将其有害成分固定到飞灰颗粒物中脱除实现零排放的可行性;同时研究了荷电喷雾过程对超细粉尘的凝并作用,可以有效的提高常规除尘器对超细粉尘的脱除效率。富含氯离子的脱硫废水对烟气中的元素态汞具有促进氧化脱除的作用,为脱硫废水零排放同时促进多种污染物联合脱除提出了一条新思路。     

喷钙脱硫成套技术

介绍炉内喷钙──炉后喷水增湿烟气脱硫成套技术以及国内研究开发的集除水滴、固硫和除尘于一体的湿颗粒层过饱和增湿高效脱硫除尘技术。     

EDV湿法烟气脱硫装置的优化措施

辽河石化0.8Mt/a重油催化裂化装置采用EDV湿法烟气洗涤脱硫技术,可以有效脱除装置排放的烟气中的SO2、催化剂颗粒等污染物。应用该技术,可将SO2含量从313.1mg/m3(标准)降到31.1mg/m3(标准),脱除率达到90.37%;催化剂固体颗粒从363.1mg/m3(标准)降到30.6mg/m3(标准),脱除率达到91.58%,均优于国家排放标准。为解决装置运行中存在的耗电量高、新鲜水用量大和装置排水中TSS含量高等问题,分别采取洗涤塔吸收区喷管分层可选洗涤功能、降低入塔烟气温度,以及废液处理单元选用絮凝剂-助凝剂组合加注方式,代替絮凝剂单一加注等优化措施。优化后,装置排放烟气中SO2、固体颗粒等污染物含量仍优于国家排放标准,装置每小时节电176kW·h,新鲜水用量从15t/h减少到12t/h,排水中TSS含量从101mg/L降到43mg/L。     

湿法脱硫协同蒸汽相变脱除燃煤PM_(2.5)的试验研究

对燃煤细颗粒在湿法烟气脱硫(WFGD)系统中的脱除效果进行了试验研究.通过向塔内添加蒸汽以促进细颗粒的凝结长大,实现脱硫过程协同脱除燃煤细颗粒,并分析了不同操作参数对细颗粒和SO2脱除效率的影响.结果表明:在常规湿法烟气脱硫过程中,PM10的质量浓度脱除效率较高,约为55%,而PM2.5质量和数量浓度脱除效率很低;通过在洗涤塔内添加蒸汽,可以有效提高PM10和PM2.5的脱除效率,脱除效率随液气比的增大而提高,特别是数量浓度的脱除效率;燃煤细颗粒的脱除效率随塔内烟气过饱和度的增大而提高,而脱硫效率几乎不受塔内过饱和度的影响,均能稳定在75%左右;随脱硫塔入口烟气温度的升高,细颗粒的脱除效率降低.     

220MW煤粉炉PM2.5浓度排放特性的试验研究

本文采用荷电低压撞击器(ELPI),通过对二级稀释系统采样对某电厂220 MW煤粉锅炉PM2.5的浓度排放特性进行了研究。研究结果显示,煤粉锅炉所产生烟气中PM2.5粒数浓度呈较明显的双峰分布,小颗粒峰值一般在0.12μm或0.07μm,较大颗粒峰值一般在0.76μm,PM2.5粒数浓度一般为几百万粒/cm3,主要取决于由气化凝结机理形成的细模态颗粒物PM0.38,PM2.5质量浓度呈单峰分布,一般为几百mg/m3,其质量浓度主要取决于由中间模态颗粒物PM0.38~2.5;采用覆膜滤料的布袋除尘器和电袋联合除尘器对PM2.5具有较好的除尘效果,二电场电袋复合除尘器出口烟气中PM2.5最小可达200μg/m3,粒数浓度在几万粒/cm3;当除尘效果较好时,湿法脱硫装置出口烟气中PM2.5粒数浓度和质量浓度可能会有所增加。