凝结水过冷度产生的原因分析

/凝结水过冷度产生的原因分析摘要:本文从各个方面分析了凝结水过冷度产生的原因及其对机组运行经济性、安全性的影响,从凝汽器的设计、改造、检修以及运行维护几个方面,提出了减小凝结水过冷度的对策,从而提高机组运行的经济性和安全性。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.关键词:凝汽器;过冷度;经济性;安全性Key words: the condenser; Supercooling degree; Economy; security1、引言1, the introduction凝汽器是凝汽式汽轮机的主要辅助设备,是汽轮机组系统的重要组成部分,它工作性能的好坏直接影响着整个机组的热经济性和安全性。而凝汽器运行状态的优劣集中表现在以下三个方面:是否保持在最佳真空、凝结水的过冷度是否最小以及凝结水的品质是否合格。其中凝结水的过冷度越大,说明被冷却水带走损失的热量越多,而这部分热损失要靠锅炉多燃烧燃料来弥补,从而导致整个热力系统热经济性降低。而且过冷度越大,凝结水中的含氧量也越多,从而加速了相关管道、设备的腐蚀速度。因此需从各个方面对凝汽水过冷度加以重视并采取措施使其减到最小,以此来提高机组运行的经济性和安全性。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、凝结水过冷度的定义和表示方法2, the definition of condensate supercooling degree and the said method2.1 定义2.1 definitions凝结水过冷度表征了凝汽器热水井中凝结水的过度冷却程度,凝汽器热水井出口凝结水温度与凝汽器在排汽压力下对应的饱和温度之差即称为过冷度。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温度形式:Temperature of the form:tn=ts-tc tn = ts - tc式中:tn凝结水过冷度;Type: tn - condensate supercooling degree;ts凝汽器绝对压力下的饱和温度;Ts of the condenser under the absolute pressure of saturated temperature;tc凝汽器热井中凝结水温度。Tc - the condensate temperature in the condenser hot well.3、过冷度产生的原因3, the cause of supercooling degree凝汽器运行中产生凝结水过冷却现象可能是凝汽器设计中的问题,也可能是运行不当而产生的,一般主要原因有以下几个。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 凝汽器内管束排列不好3.1 within the condenser tube bundle arrangement is not good在旧式结构的凝汽器上,凝结水过冷度可能很大。这些凝汽器通常均为非回热式的,凝汽器内由于冷却水管束布置过密和排列不当,使汽气混合物在通往凝汽器的管束中心和下部时存在很大的汽阻,引起凝汽器内部绝对压力从凝汽器入口到抽气口逐渐降低,使得凝汽器大部分区域的蒸汽实际凝结温度要低于凝汽器入口处的饱和温度,形成了过冷度。这同时造成了蒸汽负荷大部分集中在上部冷却管束处,蒸汽所凝结的水通过密集的管束,又在冷却水管外侧形成一层水膜,又起到再冷却凝结水的作用,加之排汽不能回热热水井中凝结水,进一步加剧了凝结水的过冷却。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 空气漏入凝汽器或抽气器工作不正常3.2 air leakage into the condenser or ejector doesnt work properly机组运行过程中,处于真空状态下的汽轮机的排汽缸、凝汽器以及低压给水加热系统等部分,若有不严密处,则会造成空气漏入;另一方面,抽气器工作不正常,不能及时地把凝汽器内漏入的空气抽走。这两方面使得凝汽器内积存的空气等不凝结气体增加,这不仅会在冷却水管的表面形成传热不良的空气膜,降低传热效果,增加传热端差;同时还使得凝汽器内的汽气混合物中空气成分的增高,造成空气分压提高、蒸汽分压降低,而凝结水是在对应蒸汽分压的饱和温度下冷凝,所以此时凝结水温度必然低于凝汽器压力下的饱和温度,因而产生了凝结水的过冷却。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 凝结水水位过高3.3 the condensate water level is too high运行过程中,由于凝结水泵真空部分漏入空气或其它故障,使凝汽器热井中凝结水水位过高,淹没了下部的冷却水管,这样冷却水又带走一部分凝结水的热量,使凝结水再次被冷却,过冷度必然增大。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 冷却水漏入凝结水内3.4 cooling water leakage into the water凝汽器内冷却水管破裂,造成冷却水漏入凝结水内,使凝结水温度降低,过冷度增加,此时还伴有凝结水硬度增大的现象发生。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 凝汽器冷却水入口温度和流量的影响3.5 condenser cooling water inlet temperature and flow rate现代电站凝汽器通常为回热式的,具有合理设计的管束结构,汽阻极小,在额定的设计工况下运行时,凝结水过冷度实际可为零。在这种情况下,凝结水过冷度主要受凝汽设备运行工况因素的影响,其中最重要的因素是凝汽器冷却水的入口温度和流量。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.试验与运行经验表明,在一定的蒸汽负荷下,当冷却水入口温度降低或流量增加时,凝汽器压力降低,真空增加,进入热井的凝结水的过冷度将增大。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 蒸汽负荷的影响3.6 the influence of steam load凝汽器蒸汽负荷的大小对凝结水过冷度也有一定的影响。根据前苏联的试验结果,对于汽流向心式凝汽器,随着蒸汽负荷的提高,过冷度增大;而对于汽流向侧式凝汽器,蒸汽负荷升高时,过冷度减小。对于旧式非回热式凝汽器,蒸汽负荷减小时,不可避免地会引起过冷度增加。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 将温度较低的补充水直接补入凝汽器的热水井Add 3.7 will be added cooler water directly into the condenser hot well机组在运行过程中,由于锅炉排污等原因,导致工质在循环过程中产生了汽水损失,因此为了满足汽轮机进汽量的需要,必须及时补入到汽水工质循环系统中。补充水补入的位置有除氧器和凝汽器两种方案,如果采用补入凝汽器方案,冬天时补充水温度一般低于设计工况时凝汽器中凝结水温度可达十几摄氏度。这样将温度较低的补充水直接补入凝汽器的热水井,并且在补充水流量较大时,势必会造成凝结水温度的降低,致使过冷度增加。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、过冷度对机组运行经济性和安全性的影响4, the supercooling degree of the impact on the unit operation economy and security4.1 对机组运行经济性的影响4.1 impact on unit operation economical efficiency凝汽器过冷度会增加冷源损失,引起作功能力的损失,降低系统的热经济性。Condenser supercooling degree can increase the cold source loss, cause the loss of work ability, reduce the thermal efficiency of the system.通过对N15一4.9/470型汽轮机实例计算结果表明,当凝结水过冷却度增加2时,新蒸汽等效焓降减少0.457kJ/kg,机组效率相对降低0.051%,电厂标准煤耗增加0.198g/kW.h。假设该机组年运行小时数为7500h,那么,一台该型号机组每年多耗标煤为147.6t,相当于每年多支出燃料成本3.1万元。可见,凝结水过冷度对机组的经济运行有明显的影响,是一项不可忽视的指标,因此采取各种措施降低凝结水过冷度是十分必要和有意义的。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 对机组运行安全性的影响4.2 impact on unit operation safety凝结水过冷度的存在会威胁机组运行的安全性和可靠性。凝结水温度过低,即凝结水水面上的蒸汽分压力的降低,气体分压力的增高,使得溶解于水中的气体含量增加,因为溶于凝结水的气体量和热井水面上气体的分压力成正比。因此若凝结水出现过冷度,则其含氧量增加,这将导致凝汽器内换热管、低加及相关管道阀门腐蚀加剧,以致降低设备的使用寿命,不利于机组的安全运行。这同时也加重了除氧器的工作负担,使除氧器的除氧效果变差,严重时会腐蚀处于高温工作环境下的给水管道和锅炉省煤器管,引起泄漏和爆管。据统计,2003年某电厂凝汽器冷却水管腐蚀造成的泄漏,使凝结水硬度超标,迫使机组降低出力带负荷查漏次数多达5次。可见,凝结水过冷度的存在对机组运行安全性极为不利。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、减少凝结水过冷度的对策5, to reduce the condensate supercooling degree of countermeasures通过上述对凝结水过冷度产生原因及其对机组运行经济性和安全性的影响的分析可以看到,凝结水过冷度的存在威胁着机组运行的安全性和可靠性,同时也会降低机组运行的经济性。因此须从设计、改造、检修以及运行维护等各个环节对其采取有效措施,以期降低凝结水过冷度,提高机组运行的经济性和安全性。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 设计中所采取的对策5.1 in the design of countermeasures(1)在冷却水管束设计中改进管束的布置,在管束结构中适当留有足够宽的蒸汽通道,这除了可以保证汽流均匀进入管束各区域外,还可保证部分排汽可直接通至凝汽器底部,以加热凝结水,减少凝结水过冷度;同时应使抽气口位置离开凝结水远一些,以减少凝结水过冷度;(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)从凝汽器入口至抽气口的路径应力求直接,且有足够的流通面积,蒸汽进入管束的流速不超过40m/s50m/s,蒸汽沿程阻力尽量小,以减少汽阻,降低凝结水的过冷度;(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)合理选择凝汽器内的淋水装置,优化设计循环冷却水量;(3) selection of condenser in the water spray device, to optimize the design of circulating cooling water;(4)汽轮机排汽口与凝汽器的连接采用柔性连接,以防止运行中膨胀不畅导致空气的漏入;(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)对于排入凝汽器的各种疏水、补充水、再循环水及其它附加流体,接至凝结器的位置一定要高于凝结水水位,最好接至凝结器上部蒸汽空间,并装折流档板,防止冲刷冷却水管,以除掉这些水源中的空气,减少对凝结水溶氧及对过冷度的影响;(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)利用锅炉连续排污对补充水进行加热,以减少补入凝汽器的补充水对凝结水的过冷却。一般凝汽器的补充水箱与除氧器、连续排污扩容器布置在同一平台处,因此可在补充水箱内加装一组管式换热器,由连续排污扩容器引出一管,将排污水送入换热器中作为热源,(下转76页)(上接75页)以加热补充水,然后再排入地沟。(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 改造中所采取的对策5.2 reform countermeasures taken in旧式凝汽器通常均为非回热式的,冷却管束通道很窄,汽阻很大,可达1.32.0 kPa,这本身就可使过冷度达到510。对于这些老式凝汽器,凝结水过冷度与工况因素几乎无关,消除这种过冷现象唯一有效的措施是改造凝汽器冷却管束结构。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)拆除一部分冷却水管(减少一部分冷却面积),让排汽可深入到冷却面中部,并留有足够的宽度,但不穿通,使蒸汽能沿着冷却面作均匀的分配,并使凝结水加热到排汽温度;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)在冷却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,使其尽可能不超过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 检修中所采取的对策5.3 maintenance of countermeasures(1)对真空系统进行灌水查漏,重点检查凝汽器喉部、低压抽汽管路、低压缸轴封蒸汽进出管道焊口、低压缸法兰接合面、热井焊接处、凝结水管道法兰连接处、凝汽器水位计接头处、疏水扩，版权归原作者所有。）容器焊接处、与热井连接的真空系统阀门等部位,并修补泄漏处;(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)检查凝汽器内的淋水装置;(2) check the tube in the condenser water device;(3)对凝汽器水位调节器和轴封压力调节器进行检修;(3) the regulator and shaft seal water level in the condenser pressure regulator for maintenance;(4)对抽真空系统进行检修,保证抽气设备的正常工作,以便运行时可及时抽出凝汽器内不凝结气体。(4)