凝結(jié)水過冷度產(chǎn)生的原因分析

/凝結(jié)水過冷度產(chǎn)生的原因分析摘要:本文從各個方面分析了凝結(jié)水過冷度產(chǎn)生的原因及其對機組運行經(jīng)濟性、安全性的影響,從凝汽器的設(shè)計、改造、檢修以及運行維護幾個方面,提出了減小凝結(jié)水過冷度的對策,從而提高機組運行的經(jīng)濟性和安全性。Abstract: this paper analyzed from various aspects the causes of the condensate supercooling degree and its impact on unit operation efficiency, safety, from the design of the condenser, modification, overhaul and operation maintenance aspects, and puts forward the measures to reduce the condensate supercooling degree, so as to improve the economic benefit of unit operation and safety.關(guān)鍵詞:凝汽器;過冷度;經(jīng)濟性;安全性Key words: the condenser; Supercooling degree; Economy; security1、引言1, the introduction凝汽器是凝汽式汽輪機的主要輔助設(shè)備,是汽輪機組系統(tǒng)的重要組成部分,它工作性能的好壞直接影響著整個機組的熱經(jīng)濟性和安全性。而凝汽器運行狀態(tài)的優(yōu)劣集中表現(xiàn)在以下三個方面:是否保持在最佳真空、凝結(jié)水的過冷度是否最小以及凝結(jié)水的品質(zhì)是否合格。其中凝結(jié)水的過冷度越大,說明被冷卻水帶走損失的熱量越多,而這部分熱損失要靠鍋爐多燃燒燃料來彌補,從而導(dǎo)致整個熱力系統(tǒng)熱經(jīng)濟性降低。而且過冷度越大,凝結(jié)水中的含氧量也越多,從而加速了相關(guān)管道、設(shè)備的腐蝕速度。因此需從各個方面對凝汽水過冷度加以重視并采取措施使其減到最小,以此來提高機組運行的經(jīng)濟性和安全性。Condenser is a main auxiliary equipment of condensing steam turbine, steam turbine unit system is an important part of its work performance is good or bad directly affects the thermal efficiency of the entire unit, and security. And advantages and disadvantages of the condenser running status in the following three aspects: whether to maintain the best vacuum, minimum of condensate supercooling degree and water quality is qualified. Of condensate supercooling degree, the greater the instructions was taken away by cooling water the more heat loss, and this part of the heat loss will depend on the boiler burning more fuel to make up for, resulting in reduced the whole thermal system thermal efficiency. And the greater the degree of supercooling, is, the more oxygen in condensate, which accelerated the corrosion rate of related piping and equipment. Therefore need from all aspects on the soda supercooling degree of attention and take measures to minimize the make it, in order to improve the economic benefit of unit operation and safety.2、凝結(jié)水過冷度的定義和表示方法2, the definition of condensate supercooling degree and the said method2.1 定義2.1 definitions凝結(jié)水過冷度表征了凝汽器熱水井中凝結(jié)水的過度冷卻程度,凝汽器熱水井出口凝結(jié)水溫度與凝汽器在排汽壓力下對應(yīng)的飽和溫度之差即稱為過冷度。Condensate supercooling degree of characterization of the overcooling of the condensate in the condenser hot well, the condenser hot well export water temperature and the condenser in the exhaust steam pressure corresponding to the saturation temperature difference that is called the degree of supercooling.2.2 表示方法2.2 representation method溫度形式:Temperature of the form:tn=ts-tc tn = ts - tc式中:tn凝結(jié)水過冷度;Type: tn - condensate supercooling degree;ts凝汽器絕對壓力下的飽和溫度;Ts of the condenser under the absolute pressure of saturated temperature;tc凝汽器熱井中凝結(jié)水溫度。Tc - the condensate temperature in the condenser hot well.3、過冷度產(chǎn)生的原因3, the cause of supercooling degree凝汽器運行中產(chǎn)生凝結(jié)水過冷卻現(xiàn)象可能是凝汽器設(shè)計中的問題,也可能是運行不當(dāng)而產(chǎn)生的,一般主要原因有以下幾個。Produced in the operation of the condenser condensate supercooled phenomenon in condenser design might be the problem, also may be improper operation, generally has the following several main reasons.3.1 凝汽器內(nèi)管束排列不好3.1 within the condenser tube bundle arrangement is not good在舊式結(jié)構(gòu)的凝汽器上,凝結(jié)水過冷度可能很大。這些凝汽器通常均為非回?zé)崾降?凝汽器內(nèi)由于冷卻水管束布置過密和排列不當(dāng),使汽氣混合物在通往凝汽器的管束中心和下部時存在很大的汽阻,引起凝汽器內(nèi)部絕對壓力從凝汽器入口到抽氣口逐漸降低,使得凝汽器大部分區(qū)域的蒸汽實際凝結(jié)溫度要低于凝汽器入口處的飽和溫度,形成了過冷度。這同時造成了蒸汽負(fù)荷大部分集中在上部冷卻管束處,蒸汽所凝結(jié)的水通過密集的管束,又在冷卻水管外側(cè)形成一層水膜,又起到再冷卻凝結(jié)水的作用,加之排汽不能回?zé)釤崴心Y(jié)水,進一步加劇了凝結(jié)水的過冷卻。In the old structure of the condenser, the condensate supercooling degree could be large. These condenser are often a regenerative, condenser tube bundle arrangement due to the cooling water inside too close and improper arrangement, make the steam gas mixture in the center of the tube bundle to the condenser steam and lower when there is a big resistance, absolute pressure inside a condenser from condenser inlet to gradually reduce bleeding point, makes much of the condenser of the steam condenses temperature is lower than actual saturation temperature at the entrance of the condenser, formed the degree of supercooling. This caused a steam load at the same time mostly in the upper cooling tube bundle, steam condensation water through dense bundles, and form a layer of water film on the outside of the cooling water pipe, and have the effect of cooling the condensate again, combined with the exhaust steam cant back to hot Wells in the condensate, further exacerbating the overcooling of the condensate.3.2 空氣漏入凝汽器或抽氣器工作不正常3.2 air leakage into the condenser or ejector doesnt work properly機組運行過程中,處于真空狀態(tài)下的汽輪機的排汽缸、凝汽器以及低壓給水加熱系統(tǒng)等部分,若有不嚴(yán)密處,則會造成空氣漏入;另一方面,抽氣器工作不正常,不能及時地把凝汽器內(nèi)漏入的空氣抽走。這兩方面使得凝汽器內(nèi)積存的空氣等不凝結(jié)氣體增加,這不僅會在冷卻水管的表面形成傳熱不良的空氣膜,降低傳熱效果,增加傳熱端差;同時還使得凝汽器內(nèi)的汽氣混合物中空氣成分的增高,造成空氣分壓提高、蒸汽分壓降低,而凝結(jié)水是在對應(yīng)蒸汽分壓的飽和溫度下冷凝,所以此時凝結(jié)水溫度必然低于凝汽器壓力下的飽和溫度,因而產(chǎn)生了凝結(jié)水的過冷卻。Unit operation in the process, under a vacuum of steam turbine exhaust cylinder, condenser and low pressure feed water heating system, if there are not tight, it will cause air leakage into the; Ejector work, on the other hand, is not normal, not in a timely manner to the condenser leakage into the air. Within these two aspects makes the condenser stockpile dont condense gas such as air increases, this will not only on the surface of cooling water pipe form bad air heat transfer film, reduce the heat transfer effect, increase the heat transfer end difference; Also make the steam condenser in the higher air composition in the gas mixture, increase caused by air pressure, steam partial pressure is reduced, and the condensate is in condensing steam partial pressure of saturated temperature, so at this point the condensate temperature must be lower than the saturation temperature of condenser pressure, thus produced the overcooling of the condensate.3.3 凝結(jié)水水位過高3.3 the condensate water level is too high運行過程中,由于凝結(jié)水泵真空部分漏入空氣或其它故障,使凝汽器熱井中凝結(jié)水水位過高,淹沒了下部的冷卻水管,這樣冷卻水又帶走一部分凝結(jié)水的熱量,使凝結(jié)水再次被冷卻,過冷度必然增大。Operation process, because of the condensate pump vacuum part leak into the air or other fault, the condensate in the condenser hot well water level is too high, covered the bottom of the cooling water pipe, cooling water and take away part of the heat of the frozen water, make water is cooled again, super-cooling degree will increase.3.4 冷卻水漏入凝結(jié)水內(nèi)3.4 cooling water leakage into the water凝汽器內(nèi)冷卻水管破裂,造成冷卻水漏入凝結(jié)水內(nèi),使凝結(jié)水溫度降低,過冷度增加,此時還伴有凝結(jié)水硬度增大的現(xiàn)象發(fā)生。Inside the condenser cooling water pipe burst, resulting in water leakage into the water, make water temperature is reduced, the supercooling degree, all peer originator.) Increased, accompanied by the phenomenon of water hardness increase occurred at this time.3.5 凝汽器冷卻水入口溫度和流量的影響3.5 condenser cooling water inlet temperature and flow rate現(xiàn)代電站凝汽器通常為回?zé)崾降?具有合理設(shè)計的管束結(jié)構(gòu),汽阻極小,在額定的設(shè)計工況下運行時,凝結(jié)水過冷度實際可為零。在這種情況下,凝結(jié)水過冷度主要受凝汽設(shè)備運行工況因素的影響,其中最重要的因素是凝汽器冷卻水的入口溫度和流量。Modern power plant condenser for regenerative, usually have a bundle structure of reasonable design, steam resistance small, under the design conditions of rated running, the condensate supercooling degree can be zero. In this case, the condensate supercooling degree is mainly influenced by condensing equipment operation condition factors, one of the most important factor is the condenser cooling water inlet temperature and flow rate.試驗與運行經(jīng)驗表明,在一定的蒸汽負(fù)荷下,當(dāng)冷卻水入口溫度降低或流量增加時,凝汽器壓力降低,真空增加,進入熱井的凝結(jié)水的過冷度將增大。Test and operation experience show that under certain steam load, when the cooling water inlet temperature decrease or increase traffic, condenser pressure, vacuum, in hot well of the condensate super-cooling degree will increase.3.6 蒸汽負(fù)荷的影響3.6 the influence of steam load凝汽器蒸汽負(fù)荷的大小對凝結(jié)水過冷度也有一定的影響。根據(jù)前蘇聯(lián)的試驗結(jié)果,對于汽流向心式凝汽器,隨著蒸汽負(fù)荷的提高,過冷度增大;而對于汽流向側(cè)式凝汽器,蒸汽負(fù)荷升高時,過冷度減小。對于舊式非回?zé)崾侥?蒸汽負(fù)荷減小時,不可避免地會引起過冷度增加。The size of the condenser steam load also have certain influence to the condensate supercooling degree. According to the former Soviet union test results, for steam flow to the heart type condenser, with the improvement of the steam load, super-cooling degree increased; For the steam flow to the lateral type condenser, steam load increases, the degree of supercooling. For old non regenerative condenser, steam load reduced, will inevitably cause super-cooling degree increase.3.7 將溫度較低的補充水直接補入凝汽器的熱水井Add 3.7 will be added cooler water directly into the condenser hot well機組在運行過程中,由于鍋爐排污等原因,導(dǎo)致工質(zhì)在循環(huán)過程中產(chǎn)生了汽水損失,因此為了滿足汽輪機進汽量的需要,必須及時補入到汽水工質(zhì)循環(huán)系統(tǒng)中。補充水補入的位置有除氧器和凝汽器兩種方案,如果采用補入凝汽器方案,冬天時補充水溫度一般低于設(shè)計工況時凝汽器中凝結(jié)水溫度可達十幾攝氏度。這樣將溫度較低的補充水直接補入凝汽器的熱水井,并且在補充水流量較大時,勢必會造成凝結(jié)水溫度的降低,致使過冷度增加。Units in the process of operation, due to reasons such as boiler blowdown, cause working substance produced soda loss in the circulation process, so in order to meet the needs of the steam turbine inlet steam quantity, must add into the soda medium circulation system in a timely manner. Supplement water add the location of the deaerator and condenser coagulation two plans, if add the condenser was used in this supplement in winter when the condenser water temperature is lower than the design conditions of the condensate temperature can be up to ten degrees Celsius. Such low temperature add supplementary water directly into the condenser hot well, and supplement the water flow is large, will inevitably cause the condensate temperature is reduced, the supercooling degree increase.4、過冷度對機組運行經(jīng)濟性和安全性的影響4, the supercooling degree of the impact on the unit operation economy and security4.1 對機組運行經(jīng)濟性的影響4.1 impact on unit operation economical efficiency凝汽器過冷度會增加冷源損失,引起作功能力的損失,降低系統(tǒng)的熱經(jīng)濟性。Condenser supercooling degree can increase the cold source loss, cause the loss of work ability, reduce the thermal efficiency of the system.通過對N15一4.9/470型汽輪機實例計算結(jié)果表明,當(dāng)凝結(jié)水過冷卻度增加2時,新蒸汽等效焓降減少0.457kJ/kg,機組效率相對降低0.051%,電廠標(biāo)準(zhǔn)煤耗增加0.198g/kW.h。假設(shè)該機組年運行小時數(shù)為7500h,那么,一臺該型號機組每年多耗標(biāo)煤為147.6t,相當(dāng)于每年多支出燃料成本3.1萬元?？梢?凝結(jié)水過冷度對機組的經(jīng)濟運行有明顯的影響,是一項不可忽視的指標(biāo),因此采取各種措施降低凝結(jié)水過冷度是十分必要和有意義的。A 4.9/470 type steam turbine of N15 calculation results show that when the condensate supercooled degree increase 2 , the new steam equivalent enthalpy drop by 0.457 kJ/kg, the unit efficiency is relatively lower 0.051%, the standard coal consumption of power plant by 0.198 g/kW. H. Assume the unit in operation hours for 7500 h, so, one the model units annually more BiaoMei consumption is 147.6 t, equivalent to more spending on fuel costs the city $31000 a year. Visible, the condensate supercooling degree has distinct effect on the economic operation of the unit, cannot be ignored is an indicator, so to take various measures to reduce the condensate supercooling degree is very necessary and meaningful.4.2 對機組運行安全性的影響4.2 impact on unit operation safety凝結(jié)水過冷度的存在會威脅機組運行的安全性和可靠性。凝結(jié)水溫度過低,即凝結(jié)水水面上的蒸汽分壓力的降低,氣體分壓力的增高,使得溶解于水中的氣體含量增加,因為溶于凝結(jié)水的氣體量和熱井水面上氣體的分壓力成正比。因此若凝結(jié)水出現(xiàn)過冷度,則其含氧量增加,這將導(dǎo)致凝汽器內(nèi)換熱管、低加及相關(guān)管道閥門腐蝕加劇,以致降低設(shè)備的使用壽命,不利于機組的安全運行。這同時也加重了除氧器的工作負(fù)擔(dān),使除氧器的除氧效果變差,嚴(yán)重時會腐蝕處于高溫工作環(huán)境下的給水管道和鍋爐省煤器管,引起泄漏和爆管。據(jù)統(tǒng)計,2003年某電廠凝汽器冷卻水管腐蝕造成的泄漏,使凝結(jié)水硬度超標(biāo),迫使機組降低出力帶負(fù)荷查漏次數(shù)多達5次。可見,凝結(jié)水過冷度的存在對機組運行安全性極為不利。The existence of condensate supercooling degree will threat the safety and reliability of the equipment operation. Condensation water temperature was low, namely the condensate water of steam partial pressure is reduced, the gas partial pressure increases, made the gas dissolved in the water content increases, because in the condensate gas amount and hot well water surface is directly proportional to the partial pressure of the gas. Therefore appears if the condensate supercooling degree and its oxygen content increases, this will lead to the condenser heat exchange tube, low corrosion intensifies and related pipeline valve, so as to lower the service life of equipment, is not conducive to the safe operation of unit. It also adds to the deaerators work burden, make the deaerating effect of deaerator, severe corrosion under high temperature working environment when feed water pipeline and the economizer of boiler tubes, leakage and detonation tube. According to statistics, in 2003, a certain power plant condenser cooling water pipe leakage caused by corrosion, make the water hardness is high, forcing the crew to reduce output loading leak frequency up to 5 times. Visible, the existence of condensate supercooling degree of unit operation to the detriment of security.5、減少凝結(jié)水過冷度的對策5, to reduce the condensate supercooling degree of countermeasures通過上述對凝結(jié)水過冷度產(chǎn)生原因及其對機組運行經(jīng)濟性和安全性的影響的分析可以看到,凝結(jié)水過冷度的存在威脅著機組運行的安全性和可靠性,同時也會降低機組運行的經(jīng)濟性。因此須從設(shè)計、改造、檢修以及運行維護等各個環(huán)節(jié)對其采取有效措施,以期降低凝結(jié)水過冷度,提高機組運行的經(jīng)濟性和安全性。By the above reasons of condensate supercooling degree and its effect on the unit operation economy and security analysis of the as you can see, the condensate supercooling degree of the existence of the threat to the safety and reliability of the equipment operation, also can reduce the running efficiency. So must be from the design, modification, maintenance, and operation maintenance and so on each link to take effective measures, in order to reduce the condensate supercooling degree, improve the economic benefit of unit operation and safety.5.1 設(shè)計中所采取的對策5.1 in the design of countermeasures(1)在冷卻水管束設(shè)計中改進管束的布置,在管束結(jié)構(gòu)中適當(dāng)留有足夠?qū)挼恼羝ǖ?這除了可以保證汽流均勻進入管束各區(qū)域外,還可保證部分排汽可直接通至凝汽器底部,以加熱凝結(jié)水,減少凝結(jié)水過冷度;同時應(yīng)使抽氣口位置離開凝結(jié)水遠一些,以減少凝結(jié)水過冷度;(1) the improvement in the design of cooling water tube bundle tube bundle arrangement, proper in the vascular bundles have enough wide steam channel, in addition to this can ensure uniform steam flow into the tube bundle district outside, still can ensure some exhaust steam directly through condensing bottom, heating water, reduce the condensate supercooling degree; Should be at the same time make the bleeding point location away from the condensate far away, in order to reduce the condensate supercooling degree;(2)從凝汽器入口至抽氣口的路徑應(yīng)力求直接,且有足夠的流通面積,蒸汽進入管束的流速不超過40m/s50m/s,蒸汽沿程阻力盡量小,以減少汽阻,降低凝結(jié)水的過冷度;(2) from the condenser to the path of the entrance to the suction port directly. And there are enough circulation area, the flow rate of the steam into the tube bundle is not more than 40 m/s 50 m/s, steam on-way resistance small, as far as possible to reduce the steam resistance, reduce the condensate supercooling degree;(3)合理選擇凝汽器內(nèi)的淋水裝置,優(yōu)化設(shè)計循環(huán)冷卻水量;(3) selection of condenser in the water spray device, to optimize the design of circulating cooling water;(4)汽輪機排汽口與凝汽器的連接采用柔性連接,以防止運行中膨脹不暢導(dǎo)致空氣的漏入;(4) the exhaust mouth connected to the condenser of the steam turbine adopts flexible connection, in order to prevent confusing cause air leakage into the operation of inflation;(5)對于排入凝汽器的各種疏水、補充水、再循環(huán)水及其它附加流體,接至凝結(jié)器的位置一定要高于凝結(jié)水水位,最好接至凝結(jié)器上部蒸汽空間,并裝折流檔板,防止沖刷冷卻水管,以除掉這些水源中的空氣,減少對凝結(jié)水溶氧及對過冷度的影響;(5) for into the condenser of hydrophobic, replenish water and circulating water and other additional fluid, connect to the location of the condenser must be higher than that of the condensate water level, the best upper connected to the condenser steam space, and baffle plate, to prevent scour cooling water pipe, to get rid of the water in the air, to reduce across cold water dissolved oxygen and the degree of influence;(6)利用鍋爐連續(xù)排污對補充水進行加熱,以減少補入凝汽器的補充水對凝結(jié)水的過冷卻。一般凝汽器的補充水箱與除氧器、連續(xù)排污擴容器布置在同一平臺處,因此可在補充水箱內(nèi)加裝一組管式換熱器,由連續(xù)排污擴容器引出一管,將排污水送入換熱器中作為熱源,(下轉(zhuǎn)76頁)(上接75頁)以加熱補充水,然后再排入地溝。(6) using the boiler continuous sewage for make-up water for heating, in order to reduce the added water add condenser overcooling of the condensate. General additional tank condenser and deaerator, continuous blowdown flash tank arranged on the same platform, thus can supplement the tank equipped with a set of pipe heat exchanger, the continuous blowdown flash tank leads to a tube, the domestic sewage as heat source, heat exchanger into in turn (page 76) (on page 75) supplemented by heating the water, and then into the gutter.5.2 改造中所采取的對策5.2 reform countermeasures taken in舊式凝汽器通常均為非回?zé)崾降?冷卻管束通道很窄,汽阻很大,可達1.32.0 kPa,這本身就可使過冷度達到510。對于這些老式凝汽器,凝結(jié)水過冷度與工況因素幾乎無關(guān),消除這種過冷現(xiàn)象唯一有效的措施是改造凝汽器冷卻管束結(jié)構(gòu)。如:Old condenser are usually non regenerative, cooling tube bundle channel is very narrow, steam resistance is very big, can reach 1.3 2.0 kPa, that in itself can make the supercooling degree reach 5 to 10 . For these old condenser, the condensate supercooling degree has little to do with working condition, eliminate the supercooling phenomenon is the only effective measures to reform the condenser cooling tube bundle structure. Such as:(1)拆除一部分冷卻水管(減少一部分冷卻面積),讓排汽可深入到冷卻面中部,并留有足夠的寬度,但不穿通,使蒸汽能沿著冷卻面作均勻的分配,并使凝結(jié)水加熱到排汽溫度;Part (1) the demolition of part of the cooling water pipe (reduce cooling area), and allow the exhaust steam into the central cooling surface, and had enough width, but not through, make the steam can make uniform distribution along the cooling surface, and makes the water heated to steam discharge temperature;(2)在冷卻管束中合理布置一些集水、排水元件;(2) in the cooling bundles reasonable decorate some catchment and drainage element;(3)限制管束中汽流流速,使其盡可能不超過40m/s50m/ s。(3) bundle ZhongQi flow velocity, to make it as far as possible, no more than 40 m/s 50 m/s.5.3 檢修中所采取的對策5.3 maintenance of countermeasures(1)對真空系統(tǒng)進行灌水查漏,重點檢查凝汽器喉部、低壓抽汽管路、低壓缸軸封蒸汽進出管道焊口、低壓缸法蘭接合面、熱井焊接處、凝結(jié)水管道法蘭連接處、凝汽器水位計接頭處、疏水?dāng)U，版權(quán)歸原作者所有。）容器焊接處、與熱井連接的真空系統(tǒng)閥門等部位,并修補泄漏處;(1) the vacuum system for water leak, check the condenser throat, low pressure extraction, low pressure cylinder shaft sealing steam pipeline in and out of the pipe joint, the low pressure cylinder flange joint surface, thermal Wells, condensate pipeline flange joint welds, condenser water level gauge, hydrophobic expansion joint Hot Wells with vessel welds, connecting the vacuum system of the valve and other parts, and repair the leak;(2)檢查凝汽器內(nèi)的淋水裝置;(2) check the tube in the condenser water device;(3)對凝汽器水位調(diào)節(jié)器和軸封壓力調(diào)節(jié)器進行檢修;(3) the regulator and shaft seal water level in the condenser pressure regulator for maintenance;(4)對抽真空系統(tǒng)進行檢修,保證抽氣設(shè)備的正常工作,以便運行時可及時抽出凝汽器內(nèi)不凝結(jié)氣體。(4)