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摘要：為提(ti)高電(dian)力(li)系(xi)統(tong)靈活性(xing)電(dian)源(yuan)占比，解決新能(neng)(neng)源(yuan)消納問題，本研究(jiu)提(ti)出百(bai)兆瓦級熔(rong)(rong)鹽(yan)儲(chu)(chu)能(neng)(neng)技(ji)術(shu)(shu)，在火(huo)電(dian)機組熱力(li)系(xi)統(tong)中的“鍋(guo)爐-汽(qi)機”之間，嵌入大容量高溫熔(rong)(rong)鹽(yan)儲(chu)(chu)熱系(xi)統(tong)，實(shi)現熱電(dian)解耦(ou)。研究(jiu)表明(ming)，百(bai)兆瓦級熔(rong)(rong)鹽(yan)儲(chu)(chu)能(neng)(neng)技(ji)術(shu)(shu)，可使汽(qi)機按(an)照最低出力(li)運(yun)行，同時(shi)保證鍋(guo)爐安全運(yun)行且不停爐，大幅度增加火(huo)電(dian)機組深度調峰(feng)能(neng)(neng)力(li)。

在保證鍋爐安全性和鹽水換熱器制造能力條件下，儲熱系統設計較高的主蒸汽壓力和較高的過冷高壓水溫度，能有效提高熔鹽儲熱過程熱熔鹽溫度和減少熔鹽使用量，達到降低熔鹽儲能初投資的目的。對百兆瓦級熔鹽儲能技術各模塊進行理論計算，結果表明，系統綜合效率高達77.8%，在大規模儲能領域具有廣泛的應用前景。

關鍵詞：儲能(neng)；高溫儲熱；深度調峰；熔鹽(yan)

“十三(san)五”期間，新(xin)能(neng)源(yuan)風光發(fa)(fa)電(dian)(dian)(dian)(dian)裝機(ji)規模迅猛(meng)發(fa)(fa)展，同(tong)時電(dian)(dian)(dian)(dian)力(li)負荷中居民用(yong)電(dian)(dian)(dian)(dian)和(he)第三(san)產業(ye)用(yong)電(dian)(dian)(dian)(dian)比(bi)重持(chi)續(xu)快速(su)增長。不(bu)論是新(xin)能(neng)源(yuan)發(fa)(fa)電(dian)(dian)(dian)(dian)出力(li)，還是居民和(he)第三(san)產業(ye)的(de)用(yong)電(dian)(dian)(dian)(dian)負荷，都(dou)具有很強的(de)日內(nei)波動性(xing)(xing)，這些都(dou)對電(dian)(dian)(dian)(dian)力(li)系(xi)統的(de)靈(ling)活(huo)(huo)性(xing)(xing)運行(xing)造(zao)成很大挑戰。在碳達峰(feng)、碳中和(he)“3060”目標的(de)背景下，以(yi)新(xin)能(neng)源(yuan)為主體的(de)新(xin)型電(dian)(dian)(dian)(dian)力(li)系(xi)統的(de)提出對電(dian)(dian)(dian)(dian)力(li)系(xi)統的(de)靈(ling)活(huo)(huo)性(xing)(xing)提出了更(geng)高的(de)要求。而(er)據中國電(dian)(dian)(dian)(dian)力(li)企(qi)業(ye)聯合會統計，我國發(fa)(fa)電(dian)(dian)(dian)(dian)裝機(ji)以(yi)煤電(dian)(dian)(dian)(dian)為主，抽水蓄能(neng)、燃氣發(fa)(fa)電(dian)(dian)(dian)(dian)等靈(ling)活(huo)(huo)調(diao)節電(dian)(dian)(dian)(dian)源(yuan)裝機(ji)占比(bi)不(bu)到(dao)6%，比(bi)較而(er)言，歐美等國靈(ling)活(huo)(huo)電(dian)(dian)(dian)(dian)源(yuan)比(bi)重較高，西班(ban)牙、德國、美國占比(bi)分別為34%、18%、49%[3]。電(dian)(dian)(dian)(dian)力(li)系(xi)統急需大比(bi)例靈(ling)活(huo)(huo)電(dian)(dian)(dian)(dian)源(yuan)改(gai)善電(dian)(dian)(dian)(dian)源(yuan)結構(gou)，緩(huan)解系(xi)統調(diao)峰(feng)壓力(li)，解決新(xin)能(neng)源(yuan)電(dian)(dian)(dian)(dian)力(li)消納問題，在現階段，對系(xi)統中容量占比(bi)最大的(de)火電(dian)(dian)(dian)(dian)機(ji)組(zu)進行(xing)靈(ling)活(huo)(huo)性(xing)(xing)改(gai)造(zao)是改(gai)善這一問題的(de)重要手段。

2018年3月，《國家(jia)發展改革(ge)委國家(jia)能(neng)(neng)(neng)(neng)源局關于提升(sheng)電(dian)(dian)力系統調節(jie)能(neng)(neng)(neng)(neng)力的(de)指(zhi)導意見》(發改能(neng)(neng)(neng)(neng)源〔2018〕364號)在關于加快推(tui)進電(dian)(dian)源側調節(jie)能(neng)(neng)(neng)(neng)力提升(sheng)的(de)要(yao)求中，明確提出實(shi)施火(huo)電(dian)(dian)靈(ling)活性(xing)提升(sheng)工程(cheng)和推(tui)動新型儲(chu)(chu)能(neng)(neng)(neng)(neng)技術發展及應用(yong)。但是(shi)，現有的(de)火(huo)電(dian)(dian)機組靈(ling)活性(xing)改造主要(yao)受(shou)限(xian)(xian)于鍋(guo)爐(lu)調峰深度(du)有限(xian)(xian)、機組經濟(ji)性(xing)和安全性(xing)不足的(de)問題。頻(pin)繁、大幅(fu)度(du)地調節(jie)會降低(di)(di)火(huo)電(dian)(dian)機組使(shi)用(yong)壽命，并(bing)導致收益較低(di)(di)。儲(chu)(chu)熱(re)技術可(ke)以實(shi)現能(neng)(neng)(neng)(neng)源整合(he)，提高(gao)能(neng)(neng)(neng)(neng)源系統調峰能(neng)(neng)(neng)(neng)力，但目前(qian)火(huo)電(dian)(dian)機組儲(chu)(chu)熱(re)技術均為汽機側民用(yong)供(gong)暖蓄熱(re)，容(rong)量有限(xian)(xian)，非供(gong)暖期不能(neng)(neng)(neng)(neng)發揮調峰作用(yong)。

熔鹽儲(chu)熱(re)(re)目前(qian)主要用(yong)(yong)于太陽能(neng)熱(re)(re)發電的(de)(de)大規模儲(chu)熱(re)(re)系統中，具有較好的(de)(de)經濟性。范慶偉等(deng)提出基于儲(chu)熱(re)(re)過程(cheng)的(de)(de)工(gong)(gong)業供汽(qi)(qi)機組熱(re)(re)電解耦方案(an)，在(zai)火(huo)電機組正常運行時(shi)(shi)抽取(qu)主蒸汽(qi)(qi)/高溫(wen)(wen)(wen)再(zai)熱(re)(re)蒸汽(qi)(qi)儲(chu)熱(re)(re)，在(zai)供汽(qi)(qi)高負荷(he)時(shi)(shi)熔鹽放熱(re)(re)，實現(xian)熱(re)(re)電解耦。鹿院衛等(deng)公開(kai)(kai)一(yi)種(zhong)火(huo)電廠深度調峰(feng)(feng)裝置(zhi)專利，分別抽取(qu)鍋(guo)(guo)爐主蒸汽(qi)(qi)、鍋(guo)(guo)爐高溫(wen)(wen)(wen)再(zai)熱(re)(re)蒸汽(qi)(qi)、汽(qi)(qi)輪機級間再(zai)熱(re)(re)蒸汽(qi)(qi)進行儲(chu)熱(re)(re)，實現(xian)火(huo)電機組靈活(huo)調峰(feng)(feng)。時(shi)(shi)正海等(deng)公開(kai)(kai)一(yi)種(zhong)鍋(guo)(guo)爐高溫(wen)(wen)(wen)煙氣熔鹽儲(chu)熱(re)(re)裝置(zhi)及其工(gong)(gong)作方法專利，利用(yong)(yong)鍋(guo)(guo)爐高溫(wen)(wen)(wen)煙氣加(jia)熱(re)(re)熔鹽儲(chu)熱(re)(re)，實現(xian)火(huo)電機組靈活(huo)調峰(feng)(feng)。當前(qian)熔鹽儲(chu)熱(re)(re)技術受限(xian)于鍋(guo)(guo)爐再(zai)熱(re)(re)器(qi)超溫(wen)(wen)(wen)問題，只能(neng)在(zai)火(huo)電機組正常運行時(shi)(shi)儲(chu)熱(re)(re)，不能(neng)在(zai)深度調峰(feng)(feng)低負荷(he)工(gong)(gong)況(kuang)下(xia)儲(chu)熱(re)(re)，調峰(feng)(feng)能(neng)力有限(xian)。

本研究(jiu)在火(huo)電機(ji)(ji)組熱(re)(re)力系(xi)統中(zhong)的(de)“鍋(guo)爐(lu)-汽(qi)機(ji)(ji)”之間，嵌入(ru)大容量高(gao)溫熔鹽(yan)儲熱(re)(re)系(xi)統，削弱原(yuan)本剛性聯系(xi)的(de)“爐(lu)機(ji)(ji)耦合”。深度(du)調峰時，保(bao)持鍋(guo)爐(lu)正(zheng)常運(yun)(yun)行(xing)負荷(he)，汽(qi)機(ji)(ji)運(yun)(yun)行(xing)在低負荷(he)調峰工況，鍋(guo)爐(lu)側多余高(gao)參數蒸汽(qi)熱(re)(re)量被儲熱(re)(re)系(xi)統存儲，保(bao)證大規模儲熱(re)(re)和深度(du)調峰運(yun)(yun)行(xing)。

1、百兆瓦級熔鹽儲能工藝設計

1.1儲熱介質

大(da)型火電(dian)機組(zu)用(yong)于(yu)推動汽輪機做功的蒸汽溫(wen)度(du)在540～600℃，屬于(yu)高溫(wen)領域(yu)。在高溫(wen)儲(chu)熱(re)(re)(re)技(ji)術(shu)中，二元熔鹽(yan)(solar salt)儲(chu)熱(re)(re)(re)既能很好(hao)匹配這一溫(wen)度(du)參數，又能實現大(da)規模儲(chu)熱(re)(re)(re)和(he)放熱(re)(re)(re)，非常適(shi)合應用(yong)于(yu)火電(dian)機組(zu)儲(chu)熱(re)(re)(re)。二元熔鹽(yan)由KNO3(質量分(fen)數40%)和(he)NaNO3(60%)組(zu)成，熔點(dian)約為220℃，常壓條件下可在600℃時保持化學穩定性(xing)，熔化狀態下的流動性(xing)和(he)換熱(re)(re)(re)性(xing)能較好(hao)。二元熔鹽(yan)儲(chu)熱(re)(re)(re)是太陽能熱(re)(re)(re)發電(dian)項目中廣泛采用(yong)的儲(chu)能介質，已經(jing)投(tou)入商業示范運行，使用(yong)溫(wen)度(du)范圍280～565℃，具備技(ji)術(shu)可靠性(xing)、安全性(xing)和(he)經(jing)濟性(xing)。

1.2儲熱工藝

大(da)(da)型火電機組中的高(gao)溫介質包含煙氣(qi)、高(gao)壓主(zhu)蒸(zheng)汽(qi)(qi)和高(gao)溫再熱(re)(re)蒸(zheng)汽(qi)(qi)，均可通(tong)過換(huan)(huan)(huan)(huan)熱(re)(re)器與(yu)熔(rong)鹽(yan)換(huan)(huan)(huan)(huan)熱(re)(re)儲(chu)(chu)熱(re)(re)。其中煙氣(qi)的溫度(du)品位(wei)最高(gao)，爐膛出(chu)口煙溫在低(di)負荷時(shi)(shi)仍然高(gao)達(da)700～800℃，然而大(da)(da)量抽(chou)(chou)取爐膛出(chu)口煙氣(qi)用于(yu)儲(chu)(chu)熱(re)(re)時(shi)(shi)，將(jiang)導致尾部煙道換(huan)(huan)(huan)(huan)熱(re)(re)器受(shou)(shou)熱(re)(re)比例(li)失衡，造成蒸(zheng)汽(qi)(qi)參數(shu)不(bu)達(da)標問題(ti)。高(gao)壓主(zhu)蒸(zheng)汽(qi)(qi)與(yu)熔(rong)鹽(yan)換(huan)(huan)(huan)(huan)熱(re)(re)儲(chu)(chu)熱(re)(re)時(shi)(shi)，受(shou)(shou)限于(yu)鍋爐再熱(re)(re)器安全(quan)性問題(ti)，只能(neng)少量抽(chou)(chou)汽(qi)(qi)儲(chu)(chu)能(neng)，無(wu)法滿(man)(man)足(zu)深(shen)(shen)度(du)調峰要求。高(gao)溫再熱(re)(re)蒸(zheng)汽(qi)(qi)的主(zhu)要問題(ti)是，因蒸(zheng)汽(qi)(qi)壓力對應(ying)的飽和溫度(du)低(di)于(yu)熔(rong)鹽(yan)凝固風險(xian)溫度(du)，只能(neng)將(jiang)部分顯熱(re)(re)與(yu)熔(rong)鹽(yan)換(huan)(huan)(huan)(huan)熱(re)(re)儲(chu)(chu)熱(re)(re)，無(wu)法滿(man)(man)足(zu)深(shen)(shen)度(du)調峰要求。

本(ben)研究提出(chu)的火(huo)電機組百兆瓦級熔鹽儲(chu)能(neng)工(gong)藝(yi)，同時(shi)抽取高(gao)壓主蒸汽和高(gao)溫再熱(re)(re)(re)蒸汽與熔鹽換熱(re)(re)(re)，實現百兆瓦級儲(chu)熱(re)(re)(re)和深度調(diao)峰(feng)。詳細工(gong)藝(yi)方案如圖1所示，該(gai)工(gong)藝(yi)方案包含充熱(re)(re)(re)過(guo)程(cheng)、儲(chu)熱(re)(re)(re)過(guo)程(cheng)和放(fang)熱(re)(re)(re)過(guo)程(cheng)。

圖1火電機組(zu)百兆(zhao)瓦(wa)級熔(rong)鹽儲(chu)能工(gong)藝流(liu)程

如圖(tu)1所示，充熱(re)過(guo)程涉及主(zhu)機模(mo)(mo)(mo)塊和(he)(he)充熱(re)功率模(mo)(mo)(mo)塊，包括高(gao)(gao)(gao)壓主(zhu)蒸(zheng)汽(qi)(qi)(qi)換(huan)熱(re)和(he)(he)高(gao)(gao)(gao)溫(wen)再(zai)熱(re)蒸(zheng)汽(qi)(qi)(qi)換(huan)熱(re)過(guo)程。其中(zhong)(zhong)，鍋(guo)爐產(chan)生(sheng)的(de)(de)主(zhu)蒸(zheng)汽(qi)(qi)(qi)除滿足主(zhu)機模(mo)(mo)(mo)塊中(zhong)(zhong)的(de)(de)汽(qi)(qi)(qi)輪(lun)發電機組(zu)深度調峰所需蒸(zheng)汽(qi)(qi)(qi)流量(liang)外，剩余(yu)高(gao)(gao)(gao)壓主(zhu)蒸(zheng)汽(qi)(qi)(qi)進(jin)入(ru)充熱(re)功率模(mo)(mo)(mo)塊中(zhong)(zhong)，依(yi)次與(yu)過(guo)熱(re)加(jia)(jia)熱(re)器、相(xiang)變加(jia)(jia)熱(re)器和(he)(he)預熱(re)加(jia)(jia)熱(re)器內熔鹽換(huan)熱(re)，放(fang)熱(re)后(hou)變成(cheng)高(gao)(gao)(gao)壓凝結水回(hui)水，該(gai)回(hui)水經高(gao)(gao)(gao)壓給(gei)水泵升(sheng)壓后(hou)送回(hui)主(zhu)機模(mo)(mo)(mo)塊高(gao)(gao)(gao)壓加(jia)(jia)熱(re)器的(de)(de)出口給(gei)水管(guan)道，與(yu)高(gao)(gao)(gao)壓給(gei)水混合后(hou)送入(ru)鍋(guo)爐省煤器。進(jin)一步在鍋(guo)爐本體吸熱(re)后(hou)，再(zai)次產(chan)生(sheng)高(gao)(gao)(gao)壓主(zhu)蒸(zheng)汽(qi)(qi)(qi)，實現(xian)高(gao)(gao)(gao)壓主(zhu)蒸(zheng)汽(qi)(qi)(qi)在主(zhu)機模(mo)(mo)(mo)塊和(he)(he)充熱(re)功率模(mo)(mo)(mo)塊之(zhi)間的(de)(de)吸熱(re)-放(fang)熱(re)循環。

另外，鍋爐產生的(de)(de)高溫再熱(re)蒸(zheng)(zheng)(zheng)(zheng)汽(qi)(qi)(qi)(qi)除(chu)滿(man)足(zu)主機(ji)模塊(kuai)中的(de)(de)汽(qi)(qi)(qi)(qi)輪發電機(ji)組深度(du)調峰所需蒸(zheng)(zheng)(zheng)(zheng)汽(qi)(qi)(qi)(qi)流量外，剩余(yu)高溫再熱(re)蒸(zheng)(zheng)(zheng)(zheng)汽(qi)(qi)(qi)(qi)進入(ru)充(chong)熱(re)功(gong)(gong)率(lv)模塊(kuai)與再熱(re)加熱(re)器(qi)內熔鹽(yan)換熱(re)，放熱(re)后變成低溫低壓蒸(zheng)(zheng)(zheng)(zheng)汽(qi)(qi)(qi)(qi)，再被升壓設備提(ti)高壓力后送回主機(ji)模塊(kuai)中的(de)(de)低溫再熱(re)蒸(zheng)(zheng)(zheng)(zheng)汽(qi)(qi)(qi)(qi)管道，與高壓缸出口低溫再熱(re)蒸(zheng)(zheng)(zheng)(zheng)汽(qi)(qi)(qi)(qi)混(hun)合后送入(ru)鍋爐再熱(re)器(qi)。進一步在鍋爐中吸熱(re)后，再次產生高溫再熱(re)蒸(zheng)(zheng)(zheng)(zheng)汽(qi)(qi)(qi)(qi)，實現(xian)高溫再熱(re)蒸(zheng)(zheng)(zheng)(zheng)汽(qi)(qi)(qi)(qi)在主機(ji)模塊(kuai)和充(chong)熱(re)功(gong)(gong)率(lv)模塊(kuai)之(zhi)間的(de)(de)吸熱(re)-放熱(re)循環。

儲熱(re)(re)(re)(re)(re)(re)(re)過程(cheng)涉及充熱(re)(re)(re)(re)(re)(re)(re)功率模(mo)塊(kuai)和儲熱(re)(re)(re)(re)(re)(re)(re)能量模(mo)塊(kuai)。儲熱(re)(re)(re)(re)(re)(re)(re)能量模(mo)塊(kuai)中(zhong)的冷鹽(yan)(yan)罐內(nei)低(di)溫(wen)熔鹽(yan)(yan)由低(di)溫(wen)熔鹽(yan)(yan)泵加(jia)(jia)(jia)壓(ya)，首先送入(ru)(ru)(ru)(ru)充熱(re)(re)(re)(re)(re)(re)(re)功率模(mo)塊(kuai)中(zhong)的預(yu)熱(re)(re)(re)(re)(re)(re)(re)加(jia)(jia)(jia)熱(re)(re)(re)(re)(re)(re)(re)器，被加(jia)(jia)(jia)熱(re)(re)(re)(re)(re)(re)(re)后(hou)再進(jin)入(ru)(ru)(ru)(ru)相變加(jia)(jia)(jia)熱(re)(re)(re)(re)(re)(re)(re)器，加(jia)(jia)(jia)熱(re)(re)(re)(re)(re)(re)(re)后(hou)分成兩路(lu)熔鹽(yan)(yan)，一路(lu)進(jin)入(ru)(ru)(ru)(ru)過熱(re)(re)(re)(re)(re)(re)(re)加(jia)(jia)(jia)熱(re)(re)(re)(re)(re)(re)(re)器被加(jia)(jia)(jia)熱(re)(re)(re)(re)(re)(re)(re)，另一路(lu)進(jin)入(ru)(ru)(ru)(ru)再熱(re)(re)(re)(re)(re)(re)(re)加(jia)(jia)(jia)熱(re)(re)(re)(re)(re)(re)(re)器被加(jia)(jia)(jia)熱(re)(re)(re)(re)(re)(re)(re)，兩路(lu)熔鹽(yan)(yan)混合后(hou)進(jin)入(ru)(ru)(ru)(ru)熱(re)(re)(re)(re)(re)(re)(re)鹽(yan)(yan)罐儲存起來，實現熔鹽(yan)(yan)回路(lu)的流動和儲熱(re)(re)(re)(re)(re)(re)(re)。儲熱(re)(re)(re)(re)(re)(re)(re)過程(cheng)中(zhong)，冷鹽(yan)(yan)罐內(nei)熔鹽(yan)(yan)逐漸變少，熱(re)(re)(re)(re)(re)(re)(re)鹽(yan)(yan)罐內(nei)熔鹽(yan)(yan)逐漸增多。

放(fang)熱(re)過(guo)程涉(she)及儲(chu)熱(re)能(neng)量(liang)(liang)模塊、放(fang)熱(re)功率模塊和主(zhu)機(ji)模塊。熔(rong)鹽(yan)(yan)儲(chu)熱(re)為高(gao)溫(wen)儲(chu)熱(re)，放(fang)熱(re)過(guo)程可產(chan)生較高(gao)參數(shu)的蒸(zheng)汽。主(zhu)機(ji)模塊中(zhong)的除氧器(qi)水經(jing)加壓(ya)后送(song)入放(fang)熱(re)功率模塊，在(zai)熔(rong)鹽(yan)(yan)蒸(zheng)汽發生系統(tong)內與來自儲(chu)熱(re)能(neng)量(liang)(liang)模塊熱(re)鹽(yan)(yan)罐的高(gao)溫(wen)熔(rong)鹽(yan)(yan)換熱(re)，依次經(jing)過(guo)預熱(re)器(qi)、蒸(zheng)發器(qi)和過(guo)熱(re)器(qi)后變(bian)成(cheng)設定參數(shu)蒸(zheng)汽。放(fang)熱(re)產(chan)生的高(gao)參數(shu)蒸(zheng)汽可以返回主(zhu)機(ji)模塊，替代高(gao)壓(ya)加熱(re)器(qi)抽汽間接(jie)做功。放(fang)熱(re)過(guo)程中(zhong)，冷鹽(yan)(yan)罐內熔(rong)鹽(yan)(yan)逐漸增多，熱(re)鹽(yan)(yan)罐內熔(rong)鹽(yan)(yan)逐漸變(bian)少。

上(shang)述熔(rong)鹽(yan)儲熱工(gong)藝(yi)流程建立之后，鍋(guo)爐和汽(qi)(qi)輪(lun)(lun)機(ji)之間的剛性聯系被打(da)斷(duan)，鍋(guo)爐可保(bao)持在正常負荷運(yun)(yun)行(xing)，產生的主蒸(zheng)汽(qi)(qi)和高溫再熱蒸(zheng)汽(qi)(qi)一(yi)部分進(jin)(jin)入汽(qi)(qi)輪(lun)(lun)機(ji)，按照電(dian)力調(diao)度需求進(jin)(jin)行(xing)汽(qi)(qi)輪(lun)(lun)機(ji)低負荷透平發(fa)電(dian)，而另外(wai)一(yi)部分高參數(shu)蒸(zheng)汽(qi)(qi)進(jin)(jin)入熔(rong)鹽(yan)儲能(neng)換(huan)熱系統。如此(ci)，汽(qi)(qi)機(ji)能(neng)夠按照最低出力運(yun)(yun)行(xing)，同(tong)時保(bao)證鍋(guo)爐安(an)全運(yun)(yun)行(xing)且不(bu)停爐，解決傳(chuan)統靈活性改造方案存在的鍋(guo)爐低負荷脫硝和穩(wen)燃問題。

2、百兆瓦級熔鹽儲能工藝設計

2.1熱質平衡理論

如圖2所示(shi)，百兆瓦級熔(rong)(rong)鹽(yan)(yan)儲能工藝包含4個換熱(re)(re)過(guo)(guo)程。一是高(gao)(gao)(gao)壓(ya)主(zhu)(zhu)蒸汽(qi)(qi)(qi)過(guo)(guo)熱(re)(re)放熱(re)(re)過(guo)(guo)程，從(cong)過(guo)(guo)熱(re)(re)蒸汽(qi)(qi)(qi)(Qm、pm1、Tm1)變(bian)為接近飽(bao)和蒸汽(qi)(qi)(qi)(Qm、pm2、Tm2)，將(jiang)熔(rong)(rong)鹽(yan)(yan)從(cong)(Qs1、ps2、Ts2)升溫(wen)至(Qs1、ps3、Ts3)；二是高(gao)(gao)(gao)壓(ya)主(zhu)(zhu)蒸汽(qi)(qi)(qi)凝結放熱(re)(re)過(guo)(guo)程，從(cong)接近飽(bao)和蒸汽(qi)(qi)(qi)(Qm、pm2、Tm2)變(bian)為飽(bao)和高(gao)(gao)(gao)壓(ya)水(Qm、pm3、Tm3)，將(jiang)熔(rong)(rong)鹽(yan)(yan)從(cong)(Qs0、ps1、Ts1)升溫(wen)至(Qs0、ps2、Ts2)；三(san)是高(gao)(gao)(gao)壓(ya)主(zhu)(zhu)蒸汽(qi)(qi)(qi)過(guo)(guo)冷放熱(re)(re)過(guo)(guo)程，從(cong)飽(bao)和高(gao)(gao)(gao)壓(ya)水(Qm、pm3、Tm3)變(bian)為過(guo)(guo)冷高(gao)(gao)(gao)壓(ya)水(Qm、pm4、Tm4)，將(jiang)熔(rong)(rong)鹽(yan)(yan)從(cong)(Qs0、ps0、Ts0)升溫(wen)至(Qs0、ps1、Ts1)；四(si)是高(gao)(gao)(gao)溫(wen)再(zai)熱(re)(re)蒸汽(qi)(qi)(qi)的放熱(re)(re)過(guo)(guo)程，從(cong)高(gao)(gao)(gao)溫(wen)再(zai)熱(re)(re)蒸汽(qi)(qi)(qi)(Qr、pr1、Tr1)變(bian)為低溫(wen)再(zai)熱(re)(re)蒸汽(qi)(qi)(qi)(Qr、pr2、Tr2)，將(jiang)熔(rong)(rong)鹽(yan)(yan)從(cong)(Qs2、ps2’、Ts2)升溫(wen)至(Qs2、ps3’、Ts3)。

圖2熔鹽(yan)儲熱工藝熱質平衡

其(qi)中，Q為(wei)流量，kg/s；p為(wei)壓力，MPa；T為(wei)溫度，℃；下標m表(biao)示主蒸(zheng)汽；r表(biao)示再熱蒸(zheng)汽；s表(biao)示熔鹽。主要熱質平衡(heng)計算式如下

式(shi)中，H為焓值，kJ/kg；cp為熔(rong)鹽比(bi)熱容，kJ/(kg·℃)；Ts為熔(rong)鹽溫度(du)，℃。熔(rong)鹽比(bi)熱容與溫度(du)關系如下

由(you)圖2和熱質平衡方程可知，儲(chu)熱換(huan)熱過程中，受限于(yu)熔鹽(yan)(yan)凝(ning)固溫度(du)(du)，主(zhu)(zhu)(zhu)蒸(zheng)汽(qi)(qi)(qi)和再熱蒸(zheng)汽(qi)(qi)(qi)換(huan)熱后的溫度(du)(du)(Tm4、Tr2)不能低于(yu)凝(ning)固風險(xian)溫度(du)(du)，主(zhu)(zhu)(zhu)蒸(zheng)汽(qi)(qi)(qi)和熔鹽(yan)(yan)換(huan)熱夾點溫差的上端溫度(du)(du)(Tm2)取(qu)決于(yu)主(zhu)(zhu)(zhu)蒸(zheng)汽(qi)(qi)(qi)壓力(pm2)，熔鹽(yan)(yan)儲(chu)熱過程的熱熔鹽(yan)(yan)溫度(du)(du)(Ts3)取(qu)決于(yu)主(zhu)(zhu)(zhu)蒸(zheng)汽(qi)(qi)(qi)和再熱蒸(zheng)汽(qi)(qi)(qi)的最(zui)高(gao)溫度(du)(du)(Tm1、Tr1)和熔鹽(yan)(yan)流量(Qs1、Qs2)。

2.2儲熱過程優化

為(wei)進一步(bu)闡述熱質平衡方(fang)程(cheng)中不(bu)同變量(liang)之間的(de)邏輯關系，分析自變量(liang)變化對因變量(liang)的(de)影響，并論證最優熔鹽儲(chu)能(neng)(neng)方(fang)案。本研究以電功率350 MW超臨界火電機(ji)組(zu)(zu)百兆瓦(wa)級熔鹽儲(chu)能(neng)(neng)為(wei)例，汽(qi)輪發電機(ji)組(zu)(zu)維持深度(du)調峰30%負(fu)荷出力，鍋爐保持在70%負(fu)荷高(gao)出力，則火電機(ji)組(zu)(zu)減(jian)少的(de)40%負(fu)荷用于(yu)熔鹽儲(chu)能(neng)(neng)，故熔鹽儲(chu)能(neng)(neng)等效電功率為(wei)140 MW。此時用于(yu)熔鹽儲(chu)熱的(de)高(gao)壓(ya)主蒸汽(qi)517.8 t/h，高(gao)溫(wen)再(zai)熱蒸汽(qi)237.8 t/h，兩者溫(wen)度(du)分別為(wei)566℃和528℃。

熔鹽儲(chu)熱(re)成本主要(yao)受(shou)熔鹽使(shi)用量的(de)影響，在西班(ban)牙Andasol 1槽(cao)式光熱(re)電站中，熔鹽和儲(chu)熱(re)罐(guan)分(fen)別占(zhan)其儲(chu)熱(re)系(xi)(xi)統(tong)50%和20%的(de)成本。因此，有必要(yao)優(you)化儲(chu)熱(re)系(xi)(xi)統(tong)方案，達(da)到(dao)減少熔鹽使(shi)用量、降低(di)儲(chu)熱(re)系(xi)(xi)統(tong)初(chu)投(tou)資的(de)目的(de)。

熔(rong)(rong)鹽(yan)(yan)儲熱(re)(re)為顯熱(re)(re)儲熱(re)(re)，在(zai)充熱(re)(re)功(gong)率和充熱(re)(re)時長確定的(de)條件下，熔(rong)(rong)鹽(yan)(yan)使用量取(qu)決于(yu)(yu)熔(rong)(rong)鹽(yan)(yan)流量(Qs0)和熔(rong)(rong)鹽(yan)(yan)儲熱(re)(re)過(guo)程(cheng)溫(wen)(wen)(wen)差(?T=Ts3-Ts1)。如前(qian)所述，受限(xian)于(yu)(yu)熔(rong)(rong)鹽(yan)(yan)安全(quan)使用溫(wen)(wen)(wen)度(du)(du)范圍，熔(rong)(rong)鹽(yan)(yan)儲熱(re)(re)過(guo)程(cheng)冷(leng)熔(rong)(rong)鹽(yan)(yan)溫(wen)(wen)(wen)度(du)(du)(Ts1)設(she)計為280℃，夾點(dian)溫(wen)(wen)(wen)差5℃，假定主(zhu)蒸汽(qi)換熱(re)(re)后(hou)(hou)的(de)溫(wen)(wen)(wen)度(du)(du)，即(ji)過(guo)冷(leng)高壓(ya)水溫(wen)(wen)(wen)度(du)(du)，和再熱(re)(re)蒸汽(qi)換熱(re)(re)后(hou)(hou)的(de)溫(wen)(wen)(wen)度(du)(du)相(xiang)同(tong)，即(ji)Tm4＝Tr2。則(ze)熔(rong)(rong)鹽(yan)(yan)儲熱(re)(re)過(guo)程(cheng)熱(re)(re)熔(rong)(rong)鹽(yan)(yan)溫(wen)(wen)(wen)度(du)(du)(Ts3)和熔(rong)(rong)鹽(yan)(yan)流量(Qs0)隨主(zhu)蒸汽(qi)壓(ya)力(pm2)的(de)變化關系分別如圖3和圖4所示(shi)。

圖(tu)3熱熔鹽溫度(Ts3)隨主(zhu)蒸汽壓(ya)力(li)(pm2)的變化關(guan)系

圖4熔鹽流量(Qs0)隨主蒸汽壓力(pm2)的變化關系

計算選(xuan)取的主(zhu)蒸汽壓力范圍是13.5 MPa≤p≤21.5 MPa，該壓力范圍對應的蒸汽飽和溫度(du)范圍是333.8～371.8℃，可保證主(zhu)蒸汽冷凝放出大量(liang)熱被冷熔鹽(yan)(280℃)吸收。由圖3可知，隨著(zhu)主(zhu)蒸汽壓力(pm2)的增大，熔鹽(yan)儲熱過程熱熔鹽(yan)溫度(du)(Ts3)也逐漸(jian)提高(gao)，且(qie)兩者(zhe)近似呈線(xian)型關系(xi)。以(yi)過冷高(gao)壓水溫度(du)(Tm4)290℃為(wei)例，兩者(zhe)關系(xi)為(wei)

由于(yu)主(zhu)蒸汽(qi)(qi)壓(ya)力(li)(li)(li)(pm2)的增(zeng)(zeng)大(da)，其對(dui)應凝(ning)(ning)(ning)結(jie)溫度(du)越高(gao)(gao)，在(zai)凝(ning)(ning)(ning)結(jie)放熱(re)(re)(re)段(duan)大(da)量釋放出更高(gao)(gao)溫度(du)的熱(re)(re)(re)量，有助于(yu)提(ti)(ti)(ti)高(gao)(gao)熔鹽(yan)(yan)在(zai)凝(ning)(ning)(ning)結(jie)放熱(re)(re)(re)段(duan)之后的溫度(du)(Ts2)。而凝(ning)(ning)(ning)結(jie)換熱(re)(re)(re)段(duan)換熱(re)(re)(re)量占(zhan)熔鹽(yan)(yan)換熱(re)(re)(re)量比例可(ke)達70%以上(shang)，所以，儲(chu)熱(re)(re)(re)系統設(she)計較高(gao)(gao)的主(zhu)蒸汽(qi)(qi)壓(ya)力(li)(li)(li)(pm2)，可(ke)提(ti)(ti)(ti)高(gao)(gao)熔鹽(yan)(yan)儲(chu)熱(re)(re)(re)過程熱(re)(re)(re)熔鹽(yan)(yan)溫度(du)(Ts3)。圖3中(zhong)，在(zai)主(zhu)蒸汽(qi)(qi)壓(ya)力(li)(li)(li)pm2=21.5 MPa時，熔鹽(yan)(yan)儲(chu)熱(re)(re)(re)溫度(du)(Ts3)最高(gao)(gao)可(ke)達485℃；但主(zhu)蒸汽(qi)(qi)壓(ya)力(li)(li)(li)降至pm2=15.5 MPa時，熔鹽(yan)(yan)儲(chu)熱(re)(re)(re)溫度(du)(Ts3)最高(gao)(gao)僅有395℃，儲(chu)能?損失大(da)幅增(zeng)(zeng)加(jia)。由此進一(yi)步推(tui)測，若將主(zhu)蒸汽(qi)(qi)壓(ya)力(li)(li)(li)提(ti)(ti)(ti)高(gao)(gao)到臨(lin)界(jie)(jie)點以上(shang)，還可(ke)繼續提(ti)(ti)(ti)高(gao)(gao)熔鹽(yan)(yan)儲(chu)熱(re)(re)(re)溫度(du)(Ts3)。但目前管殼(ke)式(shi)換熱(re)(re)(re)器(qi)受高(gao)(gao)溫高(gao)(gao)壓(ya)換熱(re)(re)(re)介(jie)質的限制(zhi)，要(yao)做到超臨(lin)界(jie)(jie)換熱(re)(re)(re)非常困(kun)難。故本方案(an)熔鹽(yan)(yan)儲(chu)熱(re)(re)(re)過程中(zhong)，主(zhu)蒸汽(qi)(qi)壓(ya)力(li)(li)(li)(pm2)宜取21.5 MPa，接(jie)近臨(lin)界(jie)(jie)壓(ya)力(li)(li)(li)。

在儲熱(re)量(liang)(liang)固(gu)定(ding)的(de)條件下，熔(rong)鹽(yan)(yan)(yan)儲熱(re)過程熱(re)熔(rong)鹽(yan)(yan)(yan)溫度(Ts3)的(de)提(ti)高有助于(yu)減少(shao)熔(rong)鹽(yan)(yan)(yan)使用(yong)量(liang)(liang)。如圖4所示，熔(rong)鹽(yan)(yan)(yan)流(liu)量(liang)(liang)(Qs0)隨(sui)主蒸汽壓(ya)(ya)力(li)(li)(pm2)的(de)增加均呈負相關(guan)(guan)關(guan)(guan)系。隨(sui)著(zhu)主蒸汽壓(ya)(ya)力(li)(li)(pm2)的(de)提(ti)高，熔(rong)鹽(yan)(yan)(yan)流(liu)量(liang)(liang)(Qs0)緩步減小(xiao)。在主蒸汽壓(ya)(ya)力(li)(li)pm2=21.5 MPa時(shi)，熔(rong)鹽(yan)(yan)(yan)流(liu)量(liang)(liang)(Qs0)最少(shao)只有3171 t/h；但主蒸汽壓(ya)(ya)力(li)(li)降至pm2=15.5 MPa時(shi)，熔(rong)鹽(yan)(yan)(yan)流(liu)量(liang)(liang)(Qs0)高達6371 t/h，導致儲能(neng)所需(xu)熔(rong)鹽(yan)(yan)(yan)量(liang)(liang)增加1倍。進一步分析(xi)圖4可(ke)知，當主蒸汽壓(ya)(ya)力(li)(li)接近pm2=21.5 MPa時(shi)，熔(rong)鹽(yan)(yan)(yan)流(liu)量(liang)(liang)(Qs0)的(de)變(bian)化(hua)已趨于(yu)平緩，這(zhe)表(biao)明繼續提(ti)高主蒸汽壓(ya)(ya)力(li)(li)(pm2)的(de)優(you)化(hua)作用(yong)有限，取主蒸汽壓(ya)(ya)力(li)(li)(pm2)為21.5 MPa較為合適。

熔(rong)(rong)(rong)(rong)鹽(yan)(yan)儲(chu)(chu)熱(re)(re)(re)(re)(re)(re)過(guo)(guo)程熔(rong)(rong)(rong)(rong)鹽(yan)(yan)流量(Qs0)和(he)熱(re)(re)(re)(re)(re)(re)熔(rong)(rong)(rong)(rong)鹽(yan)(yan)溫(wen)度(du)(Ts3)隨過(guo)(guo)冷(leng)(leng)(leng)高(gao)(gao)壓(ya)水(shui)溫(wen)度(du)(Tm4)的(de)(de)(de)(de)變化(hua)關系分別(bie)如圖(tu)5和(he)圖(tu)6所示。由(you)圖(tu)知，在相同主蒸汽壓(ya)力(pm2)條件下(xia)，熔(rong)(rong)(rong)(rong)鹽(yan)(yan)流量(Qs0)隨過(guo)(guo)冷(leng)(leng)(leng)高(gao)(gao)壓(ya)水(shui)溫(wen)度(du)(Tm4)的(de)(de)(de)(de)增(zeng)(zeng)加近(jin)似呈線型減(jian)小的(de)(de)(de)(de)關系，熔(rong)(rong)(rong)(rong)鹽(yan)(yan)儲(chu)(chu)熱(re)(re)(re)(re)(re)(re)過(guo)(guo)程熱(re)(re)(re)(re)(re)(re)熔(rong)(rong)(rong)(rong)鹽(yan)(yan)溫(wen)度(du)(Ts3)隨過(guo)(guo)冷(leng)(leng)(leng)高(gao)(gao)壓(ya)水(shui)的(de)(de)(de)(de)溫(wen)度(du)(Tm4)增(zeng)(zeng)加呈加速增(zeng)(zeng)大(da)的(de)(de)(de)(de)關系。由(you)于(yu)過(guo)(guo)冷(leng)(leng)(leng)高(gao)(gao)壓(ya)水(shui)溫(wen)度(du)(Tm4)的(de)(de)(de)(de)增(zeng)(zeng)大(da)，其與(yu)凝結放熱(re)(re)(re)(re)(re)(re)溫(wen)差越(yue)小，在過(guo)(guo)冷(leng)(leng)(leng)換熱(re)(re)(re)(re)(re)(re)段(duan)釋放出(chu)更少(shao)的(de)(de)(de)(de)熱(re)(re)(re)(re)(re)(re)量，有助(zhu)于(yu)減(jian)少(shao)在過(guo)(guo)冷(leng)(leng)(leng)加熱(re)(re)(re)(re)(re)(re)段(duan)的(de)(de)(de)(de)熔(rong)(rong)(rong)(rong)鹽(yan)(yan)流量(Qs0)。與(yu)此同時(shi)，熔(rong)(rong)(rong)(rong)鹽(yan)(yan)充熱(re)(re)(re)(re)(re)(re)熱(re)(re)(re)(re)(re)(re)量將被更高(gao)(gao)溫(wen)度(du)的(de)(de)(de)(de)凝結換熱(re)(re)(re)(re)(re)(re)段(duan)和(he)過(guo)(guo)熱(re)(re)(re)(re)(re)(re)換熱(re)(re)(re)(re)(re)(re)段(duan)占據更高(gao)(gao)比(bi)例，故熔(rong)(rong)(rong)(rong)鹽(yan)(yan)儲(chu)(chu)熱(re)(re)(re)(re)(re)(re)過(guo)(guo)程熱(re)(re)(re)(re)(re)(re)熔(rong)(rong)(rong)(rong)鹽(yan)(yan)溫(wen)度(du)(Ts3)會逐(zhu)漸增(zeng)(zeng)大(da)。所以，儲(chu)(chu)熱(re)(re)(re)(re)(re)(re)系統設計較高(gao)(gao)的(de)(de)(de)(de)過(guo)(guo)冷(leng)(leng)(leng)高(gao)(gao)壓(ya)水(shui)溫(wen)度(du)(Tm4)，可提高(gao)(gao)熔(rong)(rong)(rong)(rong)鹽(yan)(yan)儲(chu)(chu)熱(re)(re)(re)(re)(re)(re)過(guo)(guo)程熱(re)(re)(re)(re)(re)(re)熔(rong)(rong)(rong)(rong)鹽(yan)(yan)溫(wen)度(du)(Ts3)和(he)減(jian)少(shao)熔(rong)(rong)(rong)(rong)鹽(yan)(yan)流量(Qs0)。

圖5熔鹽(yan)流量(Qs0)隨過冷高壓水溫度(Tm4)的變化關系

圖6熱熔鹽(yan)溫(wen)度(du)(du)(Ts3)隨(sui)過冷高壓水溫(wen)度(du)(du)(Tm4)的變化關系(xi)

進一步(bu)分(fen)析圖(tu)5和(he)圖(tu)6可知，最小熔鹽流量(Qs0)和(he)最大(da)熱(re)(re)熔鹽溫(wen)(wen)(wen)度(du)(du)(du)(du)(Ts3)均出(chu)現在過(guo)(guo)(guo)冷(leng)高(gao)壓(ya)水(shui)(shui)的溫(wen)(wen)(wen)度(du)(du)(du)(du)Tm4=360℃條件下，故儲熱(re)(re)過(guo)(guo)(guo)程理論(lun)上應盡量提(ti)高(gao)過(guo)(guo)(guo)冷(leng)高(gao)壓(ya)水(shui)(shui)的溫(wen)(wen)(wen)度(du)(du)(du)(du)(Tm4)才(cai)能(neng)(neng)降低儲熱(re)(re)成本，但實際(ji)上過(guo)(guo)(guo)冷(leng)高(gao)壓(ya)水(shui)(shui)的溫(wen)(wen)(wen)度(du)(du)(du)(du)過(guo)(guo)(guo)高(gao)(Tm4>360℃)會造(zao)成數(shu)(shu)個換(huan)熱(re)(re)器(qi)(qi)(qi)處于水(shui)(shui)的臨界點附近(jin)換(huan)熱(re)(re)，由于此時水(shui)(shui)的熱(re)(re)物(wu)性參數(shu)(shu)波動較大(da)，導(dao)致換(huan)熱(re)(re)器(qi)(qi)(qi)制(zhi)造(zao)困難或者成本增大(da)。此外，較高(gao)溫(wen)(wen)(wen)度(du)(du)(du)(du)的過(guo)(guo)(guo)冷(leng)高(gao)壓(ya)水(shui)(shui)(Tm4>360℃)與(yu)主機(ji)模塊高(gao)加加熱(re)(re)器(qi)(qi)(qi)出(chu)口(kou)給水(shui)(shui)混合后(hou)，可能(neng)(neng)導(dao)致鍋(guo)爐省煤器(qi)(qi)(qi)入口(kou)給水(shui)(shui)接近(jin)飽和(he)態(tai)，容易造(zao)成省煤器(qi)(qi)(qi)內給水(shui)(shui)汽化(hua)問題(ti)，影響鍋(guo)爐安全性。故本方案(an)熔鹽儲熱(re)(re)過(guo)(guo)(guo)程中，過(guo)(guo)(guo)冷(leng)高(gao)壓(ya)水(shui)(shui)溫(wen)(wen)(wen)度(du)(du)(du)(du)(Tm4)宜取360℃。

在(zai)實際熔(rong)(rong)鹽儲熱(re)(re)(re)(re)(re)系統方案(an)設計中(zhong)，過冷(leng)高(gao)壓水溫(wen)(wen)度(du)(du)(du)(Tm4)和再(zai)(zai)熱(re)(re)(re)(re)(re)蒸汽(qi)換熱(re)(re)(re)(re)(re)后(hou)的(de)溫(wen)(wen)度(du)(du)(du)(Tr2)可(ke)設為不同值。在(zai)Tm4＝360℃時，若(ruo)再(zai)(zai)熱(re)(re)(re)(re)(re)蒸汽(qi)換熱(re)(re)(re)(re)(re)后(hou)的(de)溫(wen)(wen)度(du)(du)(du)(Tr2)取相同值，則會(hui)導致進入鍋(guo)爐再(zai)(zai)熱(re)(re)(re)(re)(re)器(qi)(qi)的(de)冷(leng)段蒸汽(qi)溫(wen)(wen)度(du)(du)(du)偏(pian)高(gao)，在(zai)保證鍋(guo)爐出(chu)口蒸汽(qi)溫(wen)(wen)度(du)(du)(du)一定條件下(xia)，可(ke)造成再(zai)(zai)熱(re)(re)(re)(re)(re)器(qi)(qi)一直處于(yu)事故(gu)噴水工況。故(gu)同時考慮鍋(guo)爐再(zai)(zai)熱(re)(re)(re)(re)(re)器(qi)(qi)安全性和冷(leng)熔(rong)(rong)鹽換熱(re)(re)(re)(re)(re)溫(wen)(wen)差，則本方案(an)熔(rong)(rong)鹽儲熱(re)(re)(re)(re)(re)過程中(zhong)，再(zai)(zai)熱(re)(re)(re)(re)(re)蒸汽(qi)換熱(re)(re)(re)(re)(re)后(hou)的(de)溫(wen)(wen)度(du)(du)(du)(Tr2)宜(yi)取320℃。

3、百兆瓦級熔鹽儲能工藝參數及綜合效率分析

3.1主要工藝參數

結(jie)合(he)工程實際(ji)和前述(shu)理論分析，百兆瓦級熔(rong)鹽儲(chu)(chu)能(neng)(neng)技(ji)術選定技(ji)術參(can)數見表(biao)1。儲(chu)(chu)熱(re)(re)容量(liang)指熔(rong)鹽儲(chu)(chu)能(neng)(neng)系統設計(ji)(ji)儲(chu)(chu)存熱(re)(re)量(liang)，由充(chong)熱(re)(re)功(gong)率和充(chong)熱(re)(re)時長決(jue)定。其中(zhong)，充(chong)熱(re)(re)時長取火(huo)電機(ji)組供熱(re)(re)季常見的調峰(feng)時長6 h。充(chong)熱(re)(re)功(gong)率為(wei)主(zhu)機(ji)模塊中(zhong)鍋爐(lu)熱(re)(re)功(gong)率與汽輪機(ji)所需(xu)蒸(zheng)汽熱(re)(re)功(gong)率差值(zhi)，則(ze)本例充(chong)熱(re)(re)功(gong)率為(wei)279.6 MW。故熔(rong)鹽儲(chu)(chu)能(neng)(neng)系統設計(ji)(ji)儲(chu)(chu)熱(re)(re)量(liang)為(wei)1677.5 MW·h。

表1百兆瓦級熔鹽儲能技術參(can)數

3.2百兆瓦級熔鹽儲能(neng)綜合效率(lv)分析

為進(jin)一(yi)步分析儲(chu)(chu)熱(re)系統(tong)工藝(yi)特點，有必要建立各模塊的理論(lun)計算模型(xing)，并論(lun)證其(qi)邊界條件和綜合(he)效(xiao)(xiao)率。本研究將熔鹽(yan)儲(chu)(chu)能綜合(he)效(xiao)(xiao)率定(ding)義(yi)為儲(chu)(chu)熱(re)效(xiao)(xiao)率和做功(gong)?效(xiao)(xiao)率之(zhi)積，表示熱(re)量(liang)經過熔鹽(yan)儲(chu)(chu)能系統(tong)充放過程，還剩余(yu)做功(gong)能力(li)的比(bi)例。其(qi)中，儲(chu)(chu)熱(re)效(xiao)(xiao)率為放熱(re)產生(sheng)蒸汽(qi)(qi)熱(re)量(liang)與(yu)充熱(re)所(suo)需蒸汽(qi)(qi)熱(re)量(liang)之(zhi)比(bi)，做功(gong)?效(xiao)(xiao)率為放熱(re)產生(sheng)蒸汽(qi)(qi)可轉(zhuan)(zhuan)化為有用功(gong)的最高(gao)(gao)份額與(yu)充熱(re)所(suo)需蒸汽(qi)(qi)可轉(zhuan)(zhuan)化為有用功(gong)的最高(gao)(gao)份額之(zhi)比(bi)。

充熱(re)功率(lv)模塊的主要(yao)功能是將鍋爐產(chan)生的高壓主蒸汽和高溫再(zai)熱(re)蒸汽的熱(re)量傳遞給熔鹽，并以溫度的形式儲(chu)存起(qi)來。充熱(re)功率(lv)是按照火電機組(zu)調峰深度進(jin)行配置(zhi)，具體計算模型如下

式中(zhong)，Pc為(wei)(wei)(wei)(wei)充熱(re)(re)(re)功率；Pe為(wei)(wei)(wei)(wei)火電機組額定(ding)功率；k0為(wei)(wei)(wei)(wei)基本調(diao)峰負(fu)荷率；k1為(wei)(wei)(wei)(wei)深度調(diao)峰負(fu)荷率；Qm為(wei)(wei)(wei)(wei)主(zhu)蒸(zheng)(zheng)(zheng)汽(qi)流(liu)量；Hm1為(wei)(wei)(wei)(wei)主(zhu)蒸(zheng)(zheng)(zheng)汽(qi)換(huan)熱(re)(re)(re)前(qian)焓值；Hm4為(wei)(wei)(wei)(wei)過冷高(gao)壓(ya)水焓值；Qr為(wei)(wei)(wei)(wei)高(gao)溫再熱(re)(re)(re)蒸(zheng)(zheng)(zheng)汽(qi)流(liu)量；Hr1為(wei)(wei)(wei)(wei)高(gao)溫再熱(re)(re)(re)蒸(zheng)(zheng)(zheng)汽(qi)換(huan)熱(re)(re)(re)前(qian)焓值；Hr2為(wei)(wei)(wei)(wei)高(gao)溫再熱(re)(re)(re)蒸(zheng)(zheng)(zheng)汽(qi)換(huan)熱(re)(re)(re)后(hou)(hou)焓值；Qs為(wei)(wei)(wei)(wei)儲(chu)熱(re)(re)(re)熔(rong)鹽流(liu)量；cp為(wei)(wei)(wei)(wei)儲(chu)熱(re)(re)(re)熔(rong)鹽比熱(re)(re)(re)容(rong)；Ts1為(wei)(wei)(wei)(wei)熔(rong)鹽儲(chu)熱(re)(re)(re)前(qian)的溫度；Ts3為(wei)(wei)(wei)(wei)熔(rong)鹽儲(chu)熱(re)(re)(re)后(hou)(hou)的溫度。

充(chong)熱(re)(re)功率(lv)模塊涉及管道和(he)(he)設備熱(re)(re)損失率(lv)η1和(he)(he)儲(chu)熱(re)(re)系統(tong)電(dian)(dian)耗率(lv)η2，取熱(re)(re)損失率(lv)η1=1%，增壓(ya)泵(beng)電(dian)(dian)耗率(lv)與再熱(re)(re)蒸汽(qi)流(liu)量(liang)相關，當再熱(re)(re)蒸汽(qi)流(liu)量(liang)約為主蒸汽(qi)流(liu)量(liang)0.8倍時，運行電(dian)(dian)耗率(lv)η2=12.84%(其中，增壓(ya)機(ji)電(dian)(dian)耗率(lv)8.75%，高低溫熔鹽泵(beng)電(dian)(dian)耗率(lv)共1.15%，高壓(ya)水泵(beng)電(dian)(dian)耗率(lv)1.93%，電(dian)(dian)伴熱(re)(re)等其他輔機(ji)電(dian)(dian)耗率(lv)計1%)。

儲熱(re)容量模塊的主要功能(neng)(neng)是保(bao)證當前充(chong)熱(re)功率條件下，鍋爐富余熱(re)量能(neng)(neng)夠(gou)在需求的調峰時(shi)長內全部儲存(cun)起來，儲熱(re)容量是按照火電機組深度調峰時(shi)長進(jin)行配置，具體計算模型如下

式(shi)中，Qc為儲(chu)熱(re)(re)(re)容(rong)量；t為調峰時長。儲(chu)熱(re)(re)(re)容(rong)量模(mo)塊(kuai)涉(she)及管道和設備熱(re)(re)(re)損失(shi)率η3，取熱(re)(re)(re)損失(shi)率η3=1%。

放(fang)(fang)(fang)熱功(gong)(gong)率(lv)(lv)(lv)模塊(kuai)的主(zhu)要功(gong)(gong)能是將(jiang)儲(chu)存(cun)熱量(liang)釋放(fang)(fang)(fang)，產(chan)生高參數(shu)蒸汽，并返回汽輪機做功(gong)(gong)發電。放(fang)(fang)(fang)熱功(gong)(gong)率(lv)(lv)(lv)模塊(kuai)涉(she)及(ji)管道和設備熱損(sun)(sun)失(shi)率(lv)(lv)(lv)η4和做功(gong)(gong)?損(sun)(sun)失(shi)率(lv)(lv)(lv)η5。取熱損(sun)(sun)失(shi)率(lv)(lv)(lv)η4=1%，而(er)做功(gong)(gong)?損(sun)(sun)失(shi)與放(fang)(fang)(fang)熱溫度有關，假(jia)定主(zhu)蒸汽溫度566℃的?效率(lv)(lv)(lv)為(wei)100%，則在(zai)儲(chu)能過(guo)程熱熔鹽溫度480.1℃條件下，放(fang)(fang)(fang)熱過(guo)程產(chan)生蒸汽溫度進一步降(jiang)低到470℃以內，溫度降(jiang)低導致做功(gong)(gong)?損(sun)(sun)失(shi)率(lv)(lv)(lv)η5=8%。

系統(tong)綜合效(xiao)率η可以按(an)如下方(fang)式進行計算

經(jing)計算，系(xi)統(tong)綜合效率(lv)高達77.8%，在大規模儲能領域具有廣泛的(de)應用(yong)前景。

4、結論

本(ben)研(yan)究建(jian)立(li)了(le)百兆瓦(wa)級(ji)熔鹽儲(chu)能技(ji)術在火電機組深度(du)調峰的理論模型，通過(guo)技(ji)術研(yan)究分析，論證(zheng)了(le)儲(chu)熱工藝參(can)數及綜合(he)效率。主要結論如下。

（1）百兆瓦(wa)級(ji)熔鹽儲能(neng)技術用于火電機組深度(du)調(diao)峰可(ke)削弱原本剛性聯系的“爐(lu)機耦合”，實現(xian)儲熱(re)過程中汽機的低負荷深度(du)調(diao)峰和鍋爐(lu)的正常負荷運行。

（2）儲(chu)熱使(shi)火電(dian)(dian)機(ji)組具備大(da)規模熱電(dian)(dian)分離效果，可將機(ji)組在供(gong)電(dian)(dian)低負(fu)(fu)荷無法降(jiang)低出力的部分能(neng)量(liang)儲(chu)存(cun)，并轉(zhuan)移至(zhi)供(gong)電(dian)(dian)高(gao)負(fu)(fu)荷時釋放能(neng)量(liang)，做到(dao)“削(xue)峰填谷(gu)”。

（3）儲熱(re)系(xi)統(tong)設(she)計(ji)較高(gao)的(de)(de)(de)主蒸汽壓(ya)力(pm2)，可在凝結放熱(re)段(duan)大量釋放出(chu)更(geng)高(gao)溫(wen)度(du)的(de)(de)(de)熱(re)量，能有效提(ti)(ti)高(gao)熔(rong)(rong)鹽(yan)儲熱(re)過程熱(re)熔(rong)(rong)鹽(yan)溫(wen)度(du)(Ts3)。進一步地，熔(rong)(rong)鹽(yan)儲熱(re)過程熱(re)熔(rong)(rong)鹽(yan)溫(wen)度(du)(Ts3)的(de)(de)(de)提(ti)(ti)高(gao)有助于減(jian)少熔(rong)(rong)鹽(yan)使用(yong)量。例如(ru)，在主蒸汽壓(ya)力(pm2)分(fen)別(bie)為21.5 MPa和15.5 MPa時，前(qian)(qian)者熔(rong)(rong)鹽(yan)流量(Qs0)僅為后者的(de)(de)(de)1/2，前(qian)(qian)者熱(re)熔(rong)(rong)鹽(yan)溫(wen)度(du)(Ts3)比后者高(gao)出(chu)90℃。

（4）儲熱(re)(re)(re)(re)(re)系統設計(ji)較(jiao)高(gao)的過(guo)(guo)冷(leng)高(gao)壓水溫(wen)度(du)(du)(Tm4)時，熔(rong)鹽(yan)充(chong)熱(re)(re)(re)(re)(re)熱(re)(re)(re)(re)(re)量(liang)將被更高(gao)溫(wen)度(du)(du)的凝結換熱(re)(re)(re)(re)(re)段(duan)和過(guo)(guo)熱(re)(re)(re)(re)(re)換熱(re)(re)(re)(re)(re)段(duan)占(zhan)據更高(gao)比例，可提高(gao)熔(rong)鹽(yan)儲熱(re)(re)(re)(re)(re)過(guo)(guo)程熱(re)(re)(re)(re)(re)熔(rong)鹽(yan)溫(wen)度(du)(du)(Ts3)和減少(shao)熔(rong)鹽(yan)流量(liang)(Qs0)。

（5）本方(fang)案熔(rong)鹽儲(chu)熱(re)(re)過(guo)(guo)程中，熔(rong)鹽儲(chu)熱(re)(re)過(guo)(guo)程冷熔(rong)鹽溫(wen)(wen)度(du)(du)(Ts1)設計為280℃，夾點溫(wen)(wen)差5℃。經優化后(hou)的(de)主蒸(zheng)汽壓力(pm2)取(qu)21.5 MPa，過(guo)(guo)冷高壓水溫(wen)(wen)度(du)(du)(Tm4)取(qu)360℃，再(zai)熱(re)(re)蒸(zheng)汽換熱(re)(re)后(hou)的(de)溫(wen)(wen)度(du)(du)(Tr2)取(qu)320℃。分析(xi)可得(de)，儲(chu)熱(re)(re)過(guo)(guo)程熱(re)(re)熔(rong)鹽溫(wen)(wen)度(du)(du)480.1℃，儲(chu)熱(re)(re)容(rong)量1677.5 MW·h，熔(rong)鹽使用量23150 t。

（6）對百兆瓦級(ji)熔鹽(yan)儲能技術各(ge)模(mo)塊的進行(xing)理論計算，結果表明，系統綜合效率高(gao)達(da)77.8%，在大規(gui)模(mo)儲能領域具有廣泛的應用前景。

第一作(zuo)者(zhe)：王輝（1970—），男(nan)，教授級高工，從(cong)事電(dian)力工程設計咨詢工作(zuo)和熱能動力技術(shu)研究，E-mail：wanghui csepdi.com；

通(tong)訊作(zuo)者(zhe)：李(li)峻，教授(shou)級高(gao)工(gong)(gong)，從事電力工(gong)(gong)程設計咨詢(xun)工(gong)(gong)作(zuo)和新(xin)能源(yuan)發電技術(shu)研究，E-mail：lijun csepdi.com。

注(zhu)(zhu)：本文作者為王輝、李峻、祝培(pei)旺(wang)、王堅、張(zhang)春琳，工(gong)(gong)作單位：中國電(dian)力工(gong)(gong)程顧(gu)問集團中南電(dian)力設計院有(you)限公(gong)司。轉載(zai)此文是出于傳遞更多信息之目的，若有(you)來(lai)源標(biao)注(zhu)(zhu)錯誤或侵犯(fan)了您的合法(fa)權益(yi)，請作者與本網聯系。