凝结水过冷度产生的原因分析.docx

1、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

2、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

3、, 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

4、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 th

5、ree 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 bur

6、ning 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 supercooli

7、ng 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

8、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 degre

9、e 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 con

10、denser 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 severa

11、l 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

12、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

13、 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

14、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 cool

15、ing 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

16、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 fe

17、ed 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

18、 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 reduc

19、ed, 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 h

20、igh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, c

21、ooling 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 wat

22、er 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

23、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 b

24、e 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 an

25、d 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

26、,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 impr

27、ovement 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 w

28、ill 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 re

29、asons 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 c

30、ondenser 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

31、 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 economic

32、al 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 calc