摘要(yao)：本(ben)文對華能荊(jing)門熱(re)電2×350MW超臨(lin)界機組(zu)脫硝(xiao)(xiao)系(xi)統低負荷運(yun)行(xing)時存在脫硝(xiao)(xiao)入口煙溫(wen)偏(pian)低、兩(liang)側煙溫(wen)偏(pian)差大,脫硝(xiao)(xiao)入口NOx偏(pian)高、噴(pen)氨(an)量過(guo)大、局部(bu)氨(an)逃逸率大等問題(ti)進行(xing)分析,通過(guo)優化(hua)運(yun)行(xing)方(fang)式,采取相(xiang)關技(ji)術措施(shi),逐步(bu)改善了低負荷脫硝(xiao)(xiao)系(xi)統安(an)全(quan)運(yun)行(xing)相(xiang)關問題(ti),保證脫硝(xiao)(xiao)系(xi)統安(an)全(quan)運(yun)行(xing),機組(zu)排(pai)放合格。

1 機組概況(kuang)

華能荊門熱電(dian)1、2 號鍋(guo)(guo)(guo)爐(lu)(lu)采(cai)(cai)用(yong)(yong)(yong)(yong)(yong)東方(fang)鍋(guo)(guo)(guo)爐(lu)(lu)廠生產的(de)(de)350MW 超臨界直流鍋(guo)(guo)(guo)爐(lu)(lu)， 鍋(guo)(guo)(guo)爐(lu)(lu)型(xing)號為(wei)(wei)DG1131/25.4-Ⅱ2，為(wei)(wei)超臨界壓(ya)力、一(yi)次中(zhong)間(jian)再熱、變壓(ya)運(yun)行、單(dan)爐(lu)(lu)膛(tang)、平衡通風、采(cai)(cai)用(yong)(yong)(yong)(yong)(yong)低(di)NOx 旋流式、前(qian)(qian)后(hou)(hou)墻對沖布(bu)(bu)置(zhi)燃(ran)燒器(qi)(qi)(qi)。20 只HT-NR3 型(xing)燃(ran)燒器(qi)(qi)(qi)分(fen)(fen)前(qian)(qian)三(san)層(ceng)（A、B、C）、后(hou)(hou)兩(liang)層(ceng)（D、E）布(bu)(bu)置(zhi)在爐(lu)(lu)膛(tang)前(qian)(qian)、后(hou)(hou)墻上(shang)，制粉(fen)(fen)系(xi)統(tong)(tong)(tong)(tong)采(cai)(cai)用(yong)(yong)(yong)(yong)(yong)冷一(yi)次風機正壓(ya)中(zhong)速(su)磨直吹(chui)系(xi)統(tong)(tong)(tong)(tong)，每(mei)臺爐(lu)(lu)配五臺制粉(fen)(fen)系(xi)統(tong)(tong)(tong)(tong)。鍋(guo)(guo)(guo)爐(lu)(lu)前(qian)(qian)墻A 層(ceng)燃(ran)燒器(qi)(qi)(qi)中(zhong)布(bu)(bu)置(zhi)了等離(li)子點(dian)(dian)火(huo)裝置(zhi)，其他(ta)各層(ceng)燃(ran)燒器(qi)(qi)(qi)裝有(you)1 支簡(jian)單(dan)機械霧(wu)化(hua)點(dian)(dian)火(huo)油(you)槍。每(mei)臺機組配置(zhi)一(yi)臺100%B-MCR 汽(qi)動(dong)(dong)(dong)給水(shui)泵(beng)和(he)(he)兩(liang)臺機組共用(yong)(yong)(yong)(yong)(yong)一(yi)臺30%B-MCR 容量(liang)的(de)(de)定(ding)速(su)電(dian)動(dong)(dong)(dong)給水(shui)泵(beng)。機組旁路系(xi)統(tong)(tong)(tong)(tong)采(cai)(cai)用(yong)(yong)(yong)(yong)(yong)一(yi)級高(gao)壓(ya)旁路系(xi)統(tong)(tong)(tong)(tong)裝置(zhi)，容量(liang)為(wei)(wei)35%BMCR。機組啟動(dong)(dong)(dong)方(fang)式采(cai)(cai)用(yong)(yong)(yong)(yong)(yong)高(gao)壓(ya)缸啟動(dong)(dong)(dong)。鍋(guo)(guo)(guo)爐(lu)(lu)的(de)(de)啟動(dong)(dong)(dong)系(xi)統(tong)(tong)(tong)(tong)為(wei)(wei)不帶再循環(huan)泵(beng)的(de)(de)大氣(qi)擴容式啟動(dong)(dong)(dong)系(xi)統(tong)(tong)(tong)(tong)。系(xi)統(tong)(tong)(tong)(tong)包(bao)含1 個汽(qi)水(shui)分(fen)(fen)離(li)器(qi)(qi)(qi)、1 個儲(chu)水(shui)罐、2 個儲(chu)水(shui)罐液位(wei)調節(jie)閥(fa)(fa)(361 閥(fa)(fa)）及1 個361 閥(fa)(fa)前(qian)(qian)電(dian)動(dong)(dong)(dong)隔離(li)閥(fa)(fa)。鍋(guo)(guo)(guo)爐(lu)(lu)脫硝(xiao)系(xi)統(tong)(tong)(tong)(tong)采(cai)(cai)用(yong)(yong)(yong)(yong)(yong)選擇性催化(hua)還原法（SCR）方(fang)式進行脫硝(xiao)處理(li)，脫硝(xiao)催化(hua)劑設計運(yun)行溫(wen)度為(wei)(wei)295~430℃。脫硝(xiao)設備布(bu)(bu)置(zhi)包(bao)括二部(bu)分(fen)(fen)。脫硝(xiao)設施本體布(bu)(bu)置(zhi)在鍋(guo)(guo)(guo)爐(lu)(lu)省煤(mei)器(qi)(qi)(qi)和(he)(he)空預(yu)器(qi)(qi)(qi)之間(jian)，空預(yu)器(qi)(qi)(qi)鍋(guo)(guo)(guo)爐(lu)(lu)鋼架上(shang)方(fang)的(de)(de)布(bu)(bu)置(zhi)。煙(yan)(yan)(yan)(yan)道分(fen)(fen)兩(liang)路從(cong)省煤(mei)器(qi)(qi)(qi)后(hou)(hou)接(jie)出(chu)，經過垂直上(shang)升后(hou)(hou)變為(wei)(wei)水(shui)平，接(jie)入SCR 反(fan)(fan)應(ying)器(qi)(qi)(qi)，SCR反(fan)(fan)應(ying)器(qi)(qi)(qi)內(nei)裝有(you)催化(hua)劑。反(fan)(fan)應(ying)器(qi)(qi)(qi)為(wei)(wei)垂直布(bu)(bu)置(zhi)，經過脫硝(xiao)以后(hou)(hou)的(de)(de)煙(yan)(yan)(yan)(yan)氣(qi)經垂直煙(yan)(yan)(yan)(yan)道接(jie)入空預(yu)器(qi)(qi)(qi)入口煙(yan)(yan)(yan)(yan)道。1、2 爐(lu)(lu)分(fen)(fen)別于2017 年(nian)5 月、2016 年(nian)12 月分(fen)(fen)別完成超低(di)排放改造(zao)，現階段執行的(de)(de)環(huan)保污染物控制標準為(wei)(wei)：NOx≤50mg/Nm3、SO2 濃(nong)度≤35mg/Nm3、粉(fen)(fen)塵(chen)濃(nong)度≤10mg/Nm3。鍋(guo)(guo)(guo)爐(lu)(lu)尾部(bu)煙(yan)(yan)(yan)(yan)道采(cai)(cai)用(yong)(yong)(yong)(yong)(yong)雙煙(yan)(yan)(yan)(yan)道結構，其中(zhong)低(di)溫(wen)再熱器(qi)(qi)(qi)布(bu)(bu)置(zhi)于前(qian)(qian)部(bu)煙(yan)(yan)(yan)(yan)道，低(di)溫(wen)過熱器(qi)(qi)(qi)、省煤(mei)器(qi)(qi)(qi)布(bu)(bu)置(zhi)于后(hou)(hou)部(bu)煙(yan)(yan)(yan)(yan)道。再熱汽(qi)溫(wen)度采(cai)(cai)用(yong)(yong)(yong)(yong)(yong)煙(yan)(yan)(yan)(yan)氣(qi)擋板(ban)輔以微量(liang)噴水(shui)作為(wei)(wei)調節(jie)手段。

2低負(fu)荷脫硝(xiao)系(xi)統運行(xing)存(cun)在的問題及運行(xing)調整措施

2.1 低(di)負荷脫硝入口煙溫(wen)過低(di)、偏差大(da)。

隨著機組負(fu)荷降(jiang)低(di)(di)，鍋爐出口煙(yan)(yan)溫(wen)也隨之降(jiang)低(di)(di)，導致(zhi)尾(wei)部煙(yan)(yan)道煙(yan)(yan)溫(wen)都有(you)不(bu)(bu)同(tong)程度(du)的(de)下(xia)降(jiang)。而且(qie)低(di)(di)負(fu)荷時由于火焰充滿程度(du)較弱，導致(zhi)兩側煙(yan)(yan)溫(wen)也有(you)所不(bu)(bu)同(tong)。煙(yan)(yan)溫(wen)降(jiang)低(di)(di)對脫硝系統運行不(bu)(bu)利，煙(yan)(yan)溫(wen)過低(di)(di)，催化活(huo)性太低(di)(di)，導致(zhi)脫硝系統運行效(xiao)率(lv)(lv)下(xia)降(jiang)，氨(an)逃逸率(lv)(lv)上升。長(chang)時間運行會使空預器堵(du)塞(sai)。若脫硝入口煙(yan)(yan)溫(wen)低(di)(di)于低(di)(di)限(xian)值(zhi)295℃（三取二），保護動作關(guan)閉脫硝入口噴氨(an)快關(guan)閥(fa)，若不(bu)(bu)及(ji)時調整則會導致(zhi)凈煙(yan)(yan)氣NOx超(chao)排。

針對低(di)(di)(di)(di)負(fu)(fu)(fu)荷(he)(he)工況(kuang)下(xia)，主(zhu)要(yao)是煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)偏(pian)低(di)(di)(di)(di)及(ji)兩側(ce)煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)有偏(pian)差，降(jiang)(jiang)負(fu)(fu)(fu)荷(he)(he)過(guo)程(cheng)脫硝(xiao)(xiao)有退出(chu)運行的(de)可(ke)能性，因此(ci)在運行方式采取(qu)相關優(you)化措施：1）針對低(di)(di)(di)(di)負(fu)(fu)(fu)荷(he)(he)工況(kuang)運行方式，結合(he)(he)爐膛結渣情況(kuang)，對爐膛吹灰(hui)系統進行了(le)相關優(you)化，每天按(an)照(zhao)單(dan)雙號來進行爐膛吹灰(hui)。尾(wei)部(bu)煙(yan)(yan)(yan)(yan)(yan)(yan)道間隔(ge)一(yi)天來吹灰(hui)，空預器冷端(duan)采取(qu)2H 吹灰(hui)一(yi)次。采取(qu)此(ci)種方式后低(di)(di)(di)(di)負(fu)(fu)(fu)荷(he)(he)運行下(xia)脫硝(xiao)(xiao)入口煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)基(ji)本都能達(da)到要(yao)求。同時(shi)也減少汽(qi)(qi)水損耗(hao)。2）低(di)(di)(di)(di)負(fu)(fu)(fu)荷(he)(he)運行時(shi)加強監視，適(shi)(shi)當(dang)降(jiang)(jiang)低(di)(di)(di)(di)機組(zu)負(fu)(fu)(fu)荷(he)(he)率，避免(mian)煤量(liang)過(guo)減后導(dao)致(zhi)煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)下(xia)降(jiang)(jiang)，必要(yao)時(shi)解(jie)除協調(diao)(diao)方式手動(dong)(dong)調(diao)(diao)整(zheng)。3）低(di)(di)(di)(di)負(fu)(fu)(fu)荷(he)(he)運行下(xia)采用不同磨煤機組(zu)合(he)(he)，采用前(qian)墻ABD磨組(zu)合(he)(he)較后墻ADE 磨組(zu)合(he)(he)對提升煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)更有利。4）針對脫硝(xiao)(xiao)入口兩側(ce)煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)偏(pian)差，通過(guo)尾(wei)部(bu)煙(yan)(yan)(yan)(yan)(yan)(yan)氣(qi)擋板進行小(xiao)幅度偏(pian)差調(diao)(diao)節，對煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)調(diao)(diao)平有明顯(xian)效果。5）低(di)(di)(di)(di)負(fu)(fu)(fu)荷(he)(he)運行，尾(wei)部(bu)煙(yan)(yan)(yan)(yan)(yan)(yan)道煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)特點是前(qian)煙(yan)(yan)(yan)(yan)(yan)(yan)道布置(zhi)為低(di)(di)(di)(di)再，汽(qi)(qi)溫(wen)(wen)煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)均較高；后煙(yan)(yan)(yan)(yan)(yan)(yan)道中布置(zhi)低(di)(di)(di)(di)過(guo)和省煤器，由(you)于低(di)(di)(di)(di)負(fu)(fu)(fu)荷(he)(he)時(shi)給水溫(wen)(wen)度降(jiang)(jiang)低(di)(di)(di)(di)，導(dao)致(zhi)換熱溫(wen)(wen)差增大。從而導(dao)致(zhi)后煙(yan)(yan)(yan)(yan)(yan)(yan)道煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)降(jiang)(jiang)低(di)(di)(di)(di)較多，最終(zhong)的(de)結果是混合(he)(he)后的(de)煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)偏(pian)低(di)(di)(di)(di)，影響到了(le)脫硝(xiao)(xiao)入口的(de)煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)。所以(yi)低(di)(di)(di)(di)負(fu)(fu)(fu)荷(he)(he)運行，為保證(zheng)脫硝(xiao)(xiao)安全運行，盡量(liang)關小(xiao)過(guo)熱側(ce)的(de)煙(yan)(yan)(yan)(yan)(yan)(yan)氣(qi)擋板。調(diao)(diao)節煙(yan)(yan)(yan)(yan)(yan)(yan)氣(qi)擋板時(shi)幅度也要(yao)緩慢，避免(mian)大幅度波動(dong)(dong)后導(dao)致(zhi)煙(yan)(yan)(yan)(yan)(yan)(yan)溫(wen)(wen)下(xia)降(jiang)(jiang)。6）在保證(zheng)燃燒穩定的(de)前(qian)提下(xia)，可(ke)適(shi)(shi)當(dang)提

高(gao)磨(mo)煤機的一次風速，風粉出口溫度降低(di)5℃左右(you)。通過以上優(you)化(hua)措施，基本(ben)能夠滿足低(di)負荷脫硝系統運行的安(an)全(quan)。

2.2 低負荷(he)運(yun)行，脫硝(xiao)入(ru)口(kou)NOx偏(pian)大。

低負(fu)荷(he)運(yun)(yun)行下(xia)往(wang)往(wang)氧(yang)(yang)量(liang)偏大(da)(da)(da)(da)，導(dao)(dao)致(zhi)脫硝(xiao)入(ru)口的NOX 折(zhe)算值(zhi)(zhi)過(guo)高。結果導(dao)(dao)致(zhi)噴(pen)氨(an)(an)量(liang)增大(da)(da)(da)(da)，存在局部氨(an)(an)逃逸(yi)過(guo)大(da)(da)(da)(da)現象。運(yun)(yun)行中采取以下(xia)措(cuo)施：1）控制總風量(liang)，嚴格按照氧(yang)(yang)量(liang)曲線來調(diao)整。避免氧(yang)(yang)量(liang)偏離目(mu)標(biao)值(zhi)(zhi)較(jiao)多。2）減少漏(lou)風，主要是(shi)爐膛(tang)漏(lou)風，檢查尾(wei)部煙道人孔門(men)全部關嚴。合理控制爐底(di)干排(pai)渣冷(leng)卻風門(men)，規(gui)定爐底(di)溫(wen)度低于100℃全關爐底(di)冷(leng)卻風門(men)。3）定期(qi)對脫硝(xiao)入(ru)口氧(yang)(yang)量(liang)顯示(shi)進行校驗。4）由(you)于脫硝(xiao)噴(pen)氨(an)(an)量(liang)過(guo)度開大(da)(da)(da)(da)后(hou)，導(dao)(dao)致(zhi)液(ye)(ye)氨(an)(an)消耗(hao)大(da)(da)(da)(da)不經濟(ji)且氨(an)(an)逃逸(yi)率增大(da)(da)(da)(da)。為規(gui)范(fan)運(yun)(yun)行人員操(cao)作，在經濟(ji)指標(biao)競賽中調(diao)整噴(pen)氨(an)(an)量(liang)權重(zhong)，用(yong)氨(an)(an)量(liang)越大(da)(da)(da)(da)得分越低，加(jia)強值(zhi)(zhi)班員對液(ye)(ye)氨(an)(an)調(diao)整的重(zhong)視，勤(qin)調(diao)整，減少液(ye)(ye)氨(an)(an)消耗(hao)量(liang)。低負(fu)荷(he)控制好鍋爐氧(yang)(yang)量(liang)對NOx 生成影響很大(da)(da)(da)(da)，所以低負(fu)荷(he)階段(duan)盡量(liang)降低鍋爐總風量(liang)及(ji)氧(yang)(yang)量(liang)，對鍋爐NOx 控制及(ji)低負(fu)荷(he)鍋爐穩燃均有利。

2.3 氨(an)逃逸率過大，導致空預器堵(du)塞(sai)。

長期(qi)低負荷(he)運行(xing)，存在(zai)(zai)空預(yu)(yu)器堵塞(sai)的(de)情(qing)況。特別是(shi)在(zai)(zai)2017 年9 月(yue)-10 月(yue)份(fen)機組長期(qi)在(zai)(zai)低負荷(he)運行(xing)，環境(jing)溫度較往(wang)年偏(pian)低，且入爐(lu)摻燒煤硫份(fen)較大(da)，導致空預(yu)(yu)器差(cha)壓(ya)逐漸(jian)增(zeng)大(da)。空預(yu)(yu)器煙氣差(cha)壓(ya)最(zui)大(da)漲(zhang)至2.1KPA 左右。

根據(ju)相關數(shu)據(ju)統(tong)計，長期(qi)在低負荷(he)運行(xing)(xing)，受(shou)環(huan)境溫度(du)影響，空(kong)(kong)預器(qi)冷(leng)端(duan)綜合溫度(du)偏低，導致燃用高(gao)硫(liu)煤(mei)后，空(kong)(kong)預器(qi)差壓呈(cheng)逐漸上(shang)(shang)升(sheng)趨勢，引風機(ji)電(dian)流上(shang)(shang)漲(zhang)，導致電(dian)耗上(shang)(shang)升(sheng)。停機(ji)后檢查確定是空(kong)(kong)預器(qi)冷(leng)端(duan)的結垢(gou)較多(duo)，為硫(liu)酸氫銨垢(gou)樣。短時(shi)間也(ye)難清理。因此在運行(xing)(xing)需要(yao)加強監視(shi)，調整配煤(mei)摻燒策(ce)略(lve)，盡量減(jian)少(shao)入(ru)爐煤(mei)硫(liu)份(fen)，同(tong)時(shi)提(ti)升(sheng)負荷(he)率(lv)，盡量在高(gao)負荷(he)運行(xing)(xing)。嚴格控制噴(pen)氨量，根據(ju)環(huan)境溫度(du)變(bian)化(hua)及時(shi)投入(ru)熱風再(zai)循環(huan)，提(ti)升(sheng)空(kong)(kong)預器(qi)入(ru)口(kou)冷(leng)端(duan)風溫，加大吹(chui)灰(hui)頻率(lv)，提(ti)高(gao)蒸(zheng)汽吹(chui)灰(hui)溫度(du)等策(ce)略(lve)，減(jian)緩空(kong)(kong)預器(qi)上(shang)(shang)升(sheng)速(su)率(lv)。

3 總結

針對機組低負荷工況下脫硝運行存在相關問題，經過優化吹灰方式，磨煤機組合方式，氧量控制，提高吹灰頻率，規范運行人員操作減少噴氨量等措施。保證了脫硝系統在低負荷工況下能夠安全穩定經濟運行。
新(xin)澤煙氣(qi)(qi)在線(xian)監測系(xi)統是采用世界(jie)先(xian)進(jin)在線(xian)分析技術(shu)與中國(guo)環(huan)保(bao)(bao)監測技術(shu)相結合，通過多年在工業流程領域中積累(lei)的豐富(fu)經驗精心打(da)造(zao)而成(cheng)(cheng)。應用于煙氣(qi)(qi)中煙塵濃度和固態(tai)污染物以及溫(wen)度、壓(ya)力、流速(su)、濕度、大氣(qi)(qi)壓(ya)及氧氣(qi)(qi)的在線(xian)監測，并通過數(shu)據(ju)(ju)采集處理系(xi)統生成(cheng)(cheng)圖譜、環(huan)保(bao)(bao)報表，可(ke)將數(shu)據(ju)(ju)遠傳至各級環(huan)保(bao)(bao)部門。