妈湾发电总厂烟气海水脱硫工艺及运行分析

妈湾发电总厂烟气海水脱硫工艺及运行分析焦显峰(妈湾发电总厂,广东深圳　518052)[摘　要]　介绍了深圳妈湾发电总厂4号机组烟气海水脱硫系统的组成、工艺特点及投产以来的运行情况和出现的问题。

[关键词]　烟气脱硫;海水脱硫工艺;吸收塔;烟气-烟气换热器[中图分类号]X511 [文献标识码]B [文章编号]1002-3364(2002)01-0014-03 深圳妈湾发电总厂烟气海水脱硫工程引进挪威ABB环境公司的技术和关键设备,与4号机组300MW 锅炉相配套。

1999年7月,完成了性能考核试验。

结果表明,该脱硫系统的各项性能指标均达到了设计要求,符合该区域海水环保标准。

烟气海水脱硫系统主要包括:烟气系统、S O2吸收系统(吸收塔)、海水供排水系统、海水水质恢复系统、电气及仪表控制系统等。

该系统的设计寿命为30年。

当燃用煤的含硫量S ar小于0.63%时,能够保证S O2总脱除效率不低于90%;当燃用煤的含硫量S ar不大于0.75%时,能够保证S O2总脱除效率不低于70%。

从烟气-烟气(烟-烟)换热器排入烟囱的烟气温度高于70℃。

1　工艺原理天然海水含有大量的可溶性盐,其中主要成分是NaCl和硫酸盐以及一定量的可溶性碳酸盐。

海水通常呈碱性,自然碱度约为1.2～2.5mm ol/L,这使得海水具有天然的酸碱缓冲能力及吸收S O2的能力。

烟气海水脱硫技术就是利用海水的这种特性,不添加任何化学试剂,吸收烟气中的S O2。

当海水吸收S O2后,经氧化处理为无害时流回海洋。

烟气中的S O2在吸收塔内被海水吸收后,形成亚硫酸盐和H+(S O2+H20→S O32-+2H+),吸收S O2后的酸性海水流入曝气池的前段与来自汽轮机侧虹吸井的偏碱性海水充分混合,水溶性气体S O2和偏碱性海水相遇,发生中和反应。

在曝气池后段,通过曝气风机向混合后的海水中送入足够的空气,使有害的亚硫酸盐氧化成无害的硫酸盐(2S O32-+O2→2S O42-)。

同时,海水中的HC O3-与H+反应(HC O3-+H+→C O2+ H2O),生成C O2并从海水中释放出来,使从曝气池排出的海水pH值大于6.5,满足三类海水水质标准。

利用系统净化烟气再热装置,即烟-烟换热器,对净化后的烟气加热,以保证从吸收塔排出的烟气有足够的温升,防止烟气在烟囱内壁结露,产生腐蚀。

2　烟气海水脱硫系统设备概况及运行工艺流程 4号机组启动且电除尘器投入正常运行后才能将烟气海水脱硫系统投入运行。

启动2台海水升压泵、2台曝气风机,烟-烟换热器,然后将增压风机的出、入口挡板门打开,启动增压风机并调节其出力,使其与锅炉运行负荷相匹配,关闭旁路挡板使烟气进入脱硫系 λψ　热力发电・2002(1)统。

热烟气在烟-烟换热器中与冷烟气换热,降温后进入吸收塔底部,在吸收塔内与海水逆向混合,脱除其中的S O 2,脱硫后的冷烟气经过烟-烟换热器换热升温后排入烟囱。

该系统的海水取自4号机组循环冷却系统的虹吸井,部分海水经海水升压泵升压后,引入吸收塔顶部,在吸收塔内经海水分配装置均匀配水,在通过填料层时与自下而上的烟气均匀混合,吸收烟气中S O 2。

吸收S O 2的海水由吸收塔底部自流进入曝气池前段,在曝气池前段内与由虹吸井引入的其余部分大量海水混合,再经过曝气风机送入大量空气进行曝气氧化,使脱硫海水在水质恢复并满足排放标准后排入海洋(图1)。

图1　烟气海水脱硫系统示意2.1　烟气系统该系统的主要设备有烟气海水脱硫装置的进出口挡板、旁路挡板、增压风机、烟-烟换热器等。

出、入口挡板门为双层百叶窗型,设有压力密封装置。

旁路挡板门为单层百叶窗型,带自密封装置。

增压风机为动叶可调轴流式风机,采用液压调节叶片,布置在烟-烟换热器热端进口,与锅炉引风机串联运行。

烟-烟换热器为再生、二分仓式,具有较高的换热效率,良好的机械性能,高耐腐蚀性,可清洗,低压降,低漏风,可“在线”控制。

烟-烟换热器的清洗系统是一套多喷嘴、多组可收缩装置,允许分别执行,具体有:(1)压缩空气吹扫;(2)高压“在线”和“非在线”水清洗;(3)低压水冲洗和低压、高压水冲洗相结合。

在锅炉稳定运行时,烟气海水脱硫装置的启、停造成炉膛压力波动值在±50Pa 范围内。

当负荷发生变化时,此系统可使脱硫装置的负荷平稳地随机组负荷的变化而变化,对锅炉运行的影响很小。

锅炉负荷快速变化时(例如磨煤机跳闸、给水泵跳闸等),脱硫装置所造成的最大炉膛压力波动在±50Pa 的范围内。

增压风机在收到锅炉送风机或引风机的跳闸信号后,能迅速调整出力,以适应锅炉负荷的需要。

2.2　SO 2吸收系统吸收塔(脱硫岛)是该系统的主要设备,为填料塔型,塔体为钢筋混凝土结构。

吸收塔位于2号烟囱的后方,外形尺寸为13m ×13m ×12m 。

烟气自吸收塔底部进入,向上流经填料层,海水自吸收塔填料层上部引入,烟气与海水以逆流方式接触,可获得非常高的二氧化硫吸收率。

脱硫后的烟气通过设在吸收塔顶部出口的除雾器将所带的水滴捕集,之后干净的烟气进入烟-烟热交换器。

吸收塔在设计参数工况下能够保证S O 2脱除率大于90%,吸收塔的效率大于95%;在校核参数工况下,烟气海水脱硫系统S O 2的脱除率大于70%,吸收塔效率大于74%。

2.3　海水供排水系统该系统布置有2台卧式离心泵,每台泵容量为吸收塔供水量的50%,不设备用泵。

2台海水升压泵并联运行,向吸收塔配水管供水;海水升压泵的吸水管和出水管分别设置电动阀门,出口阀为缓闭阀,以防止水锤现象的发生。

热力发电・2002(1)λζ　该系统与4号机组循环水系统为一体,水源直接取自4号机组凝汽器排出口的虹吸井,然后海水被分配到海水升压泵吸水池和曝气池。

海水经升压泵升压后进入吸收塔,吸收S O2后的酸性海水以重力自流方式通过一根排水干管进入曝气池前段,与其余部分循环水在曝气池内经充分混合后,进行曝气处理。

处理合格的海水通过4号机组循环水排水管排入海洋。

2.4　海水恢复系统该系统设有曝气风机2台,每台曝气风机的容量为总曝气容量的50%,不设备用。

2台曝气风机并列运行。

曝气池占地面积为37m×70m,曝气池出口装设成套的pH、溶解氧和氧量监测装置。

来自凝汽器排出的偏碱性海水与吸收塔排出的酸性海水在曝气池中充分混合,并通过鼓风曝气系统向曝气池内送入大量的压缩空气,压缩空气在进入曝气池过程中所产生的大量细碎气泡使曝气池内海水中的溶解氧达到饱和,并最终将亚硫酸盐氧化成硫酸盐。

同时,通过曝气过程使海水中的HC O3-中和释放出C O2,使排水的pH值得到恢复,达到排放标准pH≥6.5的要求。

3　运行状况及不足(1)该烟气海水脱硫系统脱除S O2的效率在90%以上(S ar<0.63%),吸附海水在恢复处理过程中,没有明显的S O2溢出情况,脱硫工艺排水中重金属含量低。

脱硫系统投运前后,附近区域海水环境质量类别没有变化,对海洋生物和表面沉积的影响也不明显。

(2)系统设计烟气处理量为1.1×106m3/h(标准状态),考虑设计裕度,最大可处理烟气量为1.22×106 m3/h(标准状态)。

实际运行中,在保证电负荷300MW 的情况下,锅炉实际的烟气总流量约为1.4×106m3/h (标准状态)。

此时,超过设计值的烟气量需要打开旁路调节挡板,直接排入烟囱。

同时,由于增压风机入口压力设定值偏低,致使该处的实际压力低于脱硫系统出口压力,造成烟气通过已打开的旁路挡板回流至增压风机入口,使增压风机的动叶继续开大,形成恶性循环,最后导致增压风机过负荷跳闸。

对此所采取的解决措施是:(1)提高增压风机入口压力设定值;(2)当增压风机动叶开度大于80%时,解列为手动控制。

通过这些措施,增压风机过负荷跳闸的现象已基本上得到了控制。

(3)烟-烟换热器吹扫用空压机不能自动启停,不符合设计要求,特别是该吹扫系统超压后不能自动卸载,导致油气分离器上的安全门起跳,大量的油喷出,威胁空压机的安全运行,也使得烟-烟换热器的吹灰效果变差。

(4)报警及有关跳闸信号不完善,如增压风机油站流量、压力等报警及跳闸信号未接入主控室;脱硫系统中没有一个信号上声光报警牌及进入事故追忆系统,应增加“烟气海水脱硫装置紧急停”、“增压风机跳闸”等声光报警牌并进入事故追忆系统。

主控与脱硫系统的硬接线虽完成但内部的组态尚未完成;增压风机跳闸且旁路挡板打不开使主燃料跳闸功能无法实现;两侧电除尘器跳闸使脱硫系统紧急停运功能无法实现。

(5)在对脱硫系统各处进行检查时发现,增压风机处的烟道内壁有腐蚀痕迹。

4　结　语(1)该烟气脱硫系统简单,在燃煤含硫量S ar小于0.63%时脱硫效率可达90%以上,环保效益好,投资和运行费用低,易于实现国产化及设备配套。

适合在燃煤含硫量小于0.75%的沿海电厂中逐步推广应用。

(2)应进一步强化设备的制造、安装、调试、维护、运行及检修管理,进一步优化完善设备的选型及系统的设计,使安全、经济、稳定运行的水平更上一层楼。

(3)该系统运行时间较短,其排水对海洋生态环境及表层沉积物的影响虽不明显,但应当予以足够的重视,可在排水口附近海域布置一定数量的水质监测点,以加强海洋生态环境的监测与管理工作,为该项工艺的推广应用提供科学的依据。

(4)从安全可靠性考虑,为了防止吸收塔填料层因出现电除尘器跳闸或除尘效率突然下降时被积灰所堵,在推广使用时,除将电除尘器跳闸、电除尘器出口飞灰浓度高等信号可靠接入该系统的紧急停运自动控制系统外,适当考虑在吸收塔底部增设除灰装置。

同时,对于增压风机超负荷运行、吹扫空气压缩机超压等故障保护及警示装置也应改进或增设。

(5)因该系统是将海水作为脱硫剂,因此对设备的腐蚀较为严重,应当加强设备防腐,扩大设备防腐范围,例如吸收泵本体、增压风机附近的烟道内壁等。

λ{　热力发电・2002(1)THERMAL POWER GENERATION2002.N o.1ContentsC A LC U LATI ON AND ANA LY SIS ON THERM A L EC ONOMIC ASPECT FOR ASSE M BLE D HE AT -E LECTRICITY -C OO L TRI -C OGERATI ON SY STE M C OMPOSE D OF H AT CY C LE ZH U Hua et al (2)…………………………………………T he assembled heat -electricity -cool tri -cogeneration system is an effective way for reas onable and full -scale utilization of energy s ource.E x perts are paying a great deal of attention to the hum id air turbine (H A T )cycle due to its g ood therm odynam ic and environmental performance.A com paris on between H A T cycle and STIGcycle has been made ,putting forward a new way of energy utilization ,i.e ,an assembled heat -electricity -cool tri -cogeneration system com posed of H A T cycle ,and com paring the form and specific property of the said system w ith th ose of conventional power -generation system ad opting tri -cogeneration.T he said assembled tri -cogeneration system com 2posed of sim ple H A T cycle on the basis of single -shaft com press or has been programmed and calculated ,and the regular in fluence pattern of main system operational param 2eters upon the specific property of H A T cycle and the said assembled system has been studied.A C OMPARIS ON BET WEE N C ORRESPONDI NG SY STE MS OF H OME -M ADE 300MW UNIT AND HIT ACHI M ADE UNIT WITH S AME C APACITY H AN Z i -jun (6)…………………………………………………………………………………T here are s ome differences in the start -up m ode ,the cooling water system ,the heating m ode of deaerator and the drain system of LP heater of title um its ,T hrough com pari 2s on ,the said differences are identified and analyzed.T he obtained results can be used as references in the design of thermal system for new um its or in retrofitting old ones.THE I NF LUE NCE OF BOI LER ’STRUCT URA L PARAMETERS UPON IT ’S NO X E MISSI ON C APACITY W ANG Chun -chang et al (11)……………………………………………………………………………………………………………Based on the results of measurement and test ,the difference of N o x em ission capacity between tw o W -shaped flame furnaces in Huaneng Y ueyang P ower Plant and Huaneng Lu ohuang P ower Plant has been discussed and analyzed from aspects of operation ,burned coal s orts ,and structure of equipment.T he in fluence of furnace structural parame 2ters upon the N o x em ission capacity has specially been em phasized.ANA LY SIS ON THE OPERA TI ON OF F LUE G AS DES U LFURIZ A TI ON PROCESS WITH E A -W A TER I N M A W AN GE NERA L POWER P LANT J I AO X ian -feng (14)……………………………………………………………………………………T he com position of flue gas desulfurization system w ith sea -water used on unit N o 4at M awan G eneral P ower Plant of Shenzhen C ity ,the process features ,as well as opera 2tion situation and troubles ome problems occurred from putting this system into service are presented.EXPERI ME NT A L ST UDY T O HY DRODY NAMIC PROPERTY OF VERTIC A L NA T URA L CIRC U LA TI ON UNDER THE I NF LU 2E NCE OF I MPU LSE HE A T LOAD ZH U Y u -qin et al (17)…………………………………………………………………In order to investigate the heat recovery b oiler of steel smelting converters ,a sim ple and reliable ex perimental system has been designed ,and the investigation of hydrodynam 2ic property for vertical natural circulation under im pulse heat load has been carried out.T he in fuence of im pulse heat load and under -enthalpy of w orking medium upon hy 2drodynam ic property concerning vertical natural circulation has been analyzed ,the general variational rule of hydrodynam ic property having been obtained ,and s ome recom 2mendations for im proving water circulation conditions of heat -recovery b oiler for steel smelting converters having been put forward.C ORRECTI ON T O THER M ODY NAMIC PERFOR M ANCE TEST FOR BOI LERS WITH I NF LUE NCE OF LIFAC DES U LFURIZ A 2TI ON XI AO J IE (20)………………………………………………………………………………………………………T he in fluence of LIFAC desulfurization to therm odynam ic performance test meth od of b oilers and data processing thereof has been studied ,a correction meth od for data pro 2cessing of efficiency test under condition of putting LIFAC system into operation has been proposed.W hen the said system was under operation ,the dust flow ,flue gas flow and the com position of flue gas were affected by the injection of limestone into the furnace.A part of heat was carried off by the h ot air being extracted for heating the flue gas ,and the sam pling meth od of fly ash in test was different from n ormal test due to ash -recirlculation.EXPERI ME NT A L ST UDY OF BURNI NG K AIY UAN BROW N C OA L I N CF B BOI LERS W ANG Zhi -wen et al (22)…………T he ex perimental results of burning K aiyuan brown coal in a CF B b oiler are presented.E x periments sh ow that the said coal has very high ability of self -desulfurization ,combustion efficiency being 99%and over .It is considered to burn said coal in CF B b oilers w ould be feasible ,and have g ood environmental benefits.ANA LY SIS OF THE NODA L DI AMETER VI BRA TI ON M ODE FOR BLADES I NDUCE D E NTIRE LOOP FOR M A TI ON BYUSI NG W A VE TRANS MISSI ON METH OD Z OU Xu -d ong et al (25)………………………………………………………………T he mathematical m odel to calculate the n odal diameter vibration m ode for blades induced entire -loop formation by using the wave transm ission meth od has been ex pounded ,the frequency values of a blade vibrating at different n odal diameters have been calculated ,and the m odes of 1st and 3rd n odal diameter vibration have been analyzed as well.ANA LY SIS OF STRUCT URE PROPERTY FOR AUSTE NITIC/BAI NITE DIFFERE NT STEE L WE LD JOI NT I N E AR LY-AND -ME DI UM ST AGE OF OPERA TI ON ZH ANG Y a -lin (28)……………………………………………………………………In view of the failure trend in early -stage operation of the title steel weld joints ,specimens were taken from the high -tem perature superheater of a 1025t/h b oiler after a practical operation of one overhaul period (ab out20000h ),and structure property analysis had been carried out thereafter.T hrough metallurgical structure analysis ,αphase observation ,intergranular corrosion test ,tensile test ,and bending test etc.,it was found that the mechanical property of S A213-TP347H +12Cr2M oW VT iB steel weld joint under n ormal tem perature hadn ’t n otable variation after 20000h operation ,but the austenitic granular b oundary had been in a remarkable sensitive condition ,being easily subjected to intergranular corrosion and stress corrosion ;At location near weld seam on the side of 12Cr2M oW VT iB ,there are n otable canals of oxidation ,form ing easily stress concentration ,and bringing out m icro root -cracks.Based on the test and analysis ,measures for ensuring safe operation of said differen steel weld joints have been put forward.ABOUT THE RE LA TI ONSHIP BET WEE N TECH NO LOGIC A L PROPERTY AND PHISIC O -CHE MIC A L PROPERTY OF 201×7STRONG BASE ANI ON EXCH ANGE RESI N C UI Huan -fang et al (31)…………………………………………………T he relevant test results for w orking out a standard for reporting 201×7strong base anion exchange resin as w orthless have been presented ,finding out the relationship be 2tween various factors and the w orking exchange capacity of the said resin.T hese factors include :(1)variation of strong -ty pe redical capacity ;(2)the rate of water con 2tent ;(3)the rate of small round spheres ;(4)the organic pollution ;(5)the ironic pollution.At last ,a standard for reporting the said anion exchange resin as w orthless is given.A STY DYON THE TECH NO LOGYOF DETECTI NG TRACE CH LORIC I ONS I N W A TER AND STE AM OF THER M A L POWER P LANT TI AN Li et al (34)…………………………………………………………………………………………………Ad opting ion -exchange resin to concentrate C l -in highly pure water ,and simultaneously using ion chromatography to m onitor the concentration of C l -in outlet water fromexchange column ,a meth od of detecting the trace am ount of C l -in water or steam has been developed.T he said meth od can concentrate water sam ple of 1μg/L ～10μg/L。