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1、碱性处理技术在发电机内冷水系统中的应用徐岚游喆刘文强王安宁（上海吴泾第二发电有限责任公司）摘要：介绍了碱性处理技术改善发电机内冷水水质的基本原理和该技术在上海吴泾第二发电有限责任公司2600MW机组上试验研究和成功应用情况，并提出了将氢型混床改为碱化混床运行时应考虑对系统改进和运行控制的若干建议。关键词：发电机；内冷水；pH值；碱性处理1引言大中型发电机组设备普遍采用水-氢-氢冷却方式，发电机内冷水选用除盐水或凝结水作为冷却介质。发电机内冷水是在高电场中作冷却介质，对内冷水的水质要求严格，除了清洁、透明、无机械杂质外，还必须要有足够的绝缘性（即极小的电导率），不结垢，并对发电机铜导线和系统无侵
2、蚀性等，冷却水的水质对保证发电机组设备的安全运行至关重要。近年来随着大容量、亚临界、超临界发电机组的投入运行，为了确保发电机组设备的安全运行，对发电机内冷水品质的要求越来越高，我国电力行业标准大型发电机内冷却水质及系统技术要求（1）（DL/T8012002）对发电机冷却水水质的要求为：电导率（25C） 7.09.0，Cu40g/L，溶氨量 300g/L。为了改善发电机内冷水水质，目前国内外普遍采取的防腐、净化处理方式主要有单纯补充除盐水或凝结水运行方式、内冷水加铜缓蚀剂法、小混床处理法等。1）添加铜缓蚀剂，其作用是与水中铜离子络合形成保护膜，覆盖在铜表面以减缓基体的腐蚀，但该方法可能引起电导率
3、升高或缓蚀剂析出沉积等问题；2）大机组已不推荐使用添加缓蚀剂的方法，一般采用大量补充纯水-二级除盐水或凝结水，前者使内冷水电导率、pH偏低，后者使内冷水电导率、氨量偏高，造成铜的氨蚀。采用排污换水方式维持铜含量处于标准范围内，未从根本上解决铜导线的腐蚀问题；3）小混床法一般采用H/OH型小混床旁路净化处理内冷水，采用这种运行方式内冷水pH一般处于6.57.0甚至更低，水化学工况的缓冲性弱。总之，上述方法普遍存在pH偏低、电导率偏高、铜含量超标等问题。国内外相关文献表明，内冷水pH、电导率、溶氧等水质指标是影响铜导线腐蚀的主要因素，其中pH是关键因素。内冷水碱性处理技术是近年发展的新技术，为协调
4、控制内冷水pH、电导率、铜含量找到简便易行的好方法。碱性处理技术采用碱化混床对内冷水进行旁路处理，基本原理在于当含微量杂质的内冷水通过碱化混床时，有微量NaOH释放，在净化水质同时流出液呈微碱性，通过合理控制碱化混床处理流量，在内冷水与碱化混床达到交换平衡时，使内冷水pH长期稳定维持在89（25）、电导率小于2S/cm（25），相应地使铜处于钝化区，从根本上减缓铜导线的腐蚀，维持较低的铜含量。2吴泾二发电内冷水系统运行状况上海吴泾第二发电有限责任公司（以下简称“吴泾二发电”）2台600MW发电机采用水-氢-氢冷却方式。内冷水系统采用闭式循环（见图1）。内冷水由水箱经定冷泵、冷却器、滤网，然后进
5、入发电机励端，流经空芯铜导线至机端，沿管路返回水箱，此为主回路；经冷却器后另引出一路通过H/OH型小混床处理返回水箱，此为旁路。设置二级除盐水和凝结水两路补水可供选择，补水全部经小混床处理后补入水箱。水箱装有通往大气的排气组件，原设计充氮密封，但未投运。设计内冷水额定循环流量105t/h，旁路流量为510%。该系统存在如下问题：1）系统监测手段不够完善，未安装pH值监测仪表；2）H/OH型小混床投运时，易降低内冷水pH而带来系统酸性腐蚀隐患；3）系统处于半密闭方式运行，内冷水溶氧在45mg/L，微酸性或中性条件下，溶氧将加剧铜导线的腐蚀。图1 发电机内冷水系统简图图2 2003年11月2号机组
6、内冷水pH、Cu含量曲线运行数据显示（以2号机组2003年11月份内冷水水质为例，见图2），存在内冷水pH偏低、时有铜含量超标、水质不稳定等问题，采用补充凝结水提高pH和大量排污换水的方式降低内冷水铜含量，未从根本上解决铜导线的腐蚀问题。为提高内冷水pH值，稳定内冷水水质，从根本上减缓铜线棒的腐蚀，吴泾二发电于2004年会同上海市电力试验研究所进行内冷水碱性处理技术研究。3试验内容及结果分析试验分实验室和工业性试验两部分进行，通过试验掌握了不同碱化剂调节pH对铜腐蚀的影响、稀氢氧化钠溶液pH与电导率关系。试验结果还表明：通过合理控制，内冷水碱性处理技术有效解决了吴泾二发电600MW发电机内冷水
7、水质pH偏低、电导率和铜含量偏高、水质不稳的问题。3.1不同碱化剂的腐蚀试验取定量除盐水分别置于具塞锥形瓶中，用不同碱化剂调节pH至所需条件，将紫铜腐蚀试片悬挂于溶液中进行静态试验。试验结果表明（图3）：采用不同碱化剂将纯水pH由微酸性（6.13）调节至微碱性（89），铜在水中的腐蚀速率降低，采用NaOH调节对铜的防腐效果明显优于氨水。图3 铜静态腐蚀试验结果3.2稀氢氧化钠溶液pH与电导率关系试验取一组除盐水置于具塞瓶中，采用氢氧化钠溶液调节水样至不同pH值，测定水样对应的电导率和pH值。理论值可从NaOH摩尔电导率、水样电导率（DD）和氢电导率（HD）推导出NaOH稀溶液的pH算式：pH=
8、8.60+ log（DD-1/3HD）。试验结果表明（图4）：1）除盐水用氢氧化钠微碱化时，电导率随着pH增大而增大，当pH在88.8时，电导率可以保持小于2S/cm；2）受空气中二氧化碳影响，稀氢氧化钠溶液电导率实测值大于对应的理论值。图4稀氢氧化钠溶液pH与DD曲线3.3工业性试验吴泾二发电2号、1号发电机内冷水分别于2004年3月、2004年7月转为碱性处理，实施内冷水碱性处理过程中对系统、方法和控制方式进行了改进： 1）安装pH在线监测仪表（系统原有电导率表、小混床流量表）；2）内冷水补水改为直接补入定冷水箱，避免补水直接进入碱化混床影响交换平衡；3）补充水采用二级除盐水；4）将系统原
9、有的H/OH型小混床树脂更换为国产特制的碱化混合树脂，该树脂具有机械强度高、耐热性好、颗粒均匀等特点，树脂运行更换周期在1年以上；5）调整碱化混床流量在适当状态，即在长期不排污条件下，维持内冷水各指标稳定协调达标。吴泾二发电1、2号发电机内冷水转为碱性处理初期，据内冷水水质适当调整小混床流量和排污，待内冷水与碱化混床达到交换平衡且稳定运行后，控制一定的碱化混床流量可长期维持内冷水pH、电导率、铜含量协调达标，基本上无须排污和调整小混床流量，性能可靠、运行控制方便。发电机内冷水碱性处理前后一年水质状况统计见表1。表1 1、2号发电机内冷水碱性处理调整前后水质状况统计项目工况pH（25C）电导率(
10、S/cm, 25C)Cu（g/L）溶解氧（mg/L）Na（g/L）#1调整前6.588.910.062.182.25361451调整后8.358.881.051.751.7514.1950100#2调整前6.838.960.062.1720126.91调整后8.548.931.021.71010501002号机内冷水碱性处理调整过程中（投运初期）内冷水pH、电导率、Cu变化曲线如图57。 图5 内冷水碱性处理后pH、DD变化曲线图6 内冷水电导率与pH关系曲线图7 内冷水Cu含量与pH关系曲线工业性试验结果表明： 1）碱化混床能够在内冷水pH为中性情况下，经过几小时运行即可将pH调节到8.8左
11、右；2）通过合理控制碱化混床流量，随着运行时间的推移，pH值、电导率相对稳定地维持在8.08.8、0.52.0S/cm（图5）； 2）内冷水pH值与电导率的关系曲线表明（图6），内冷水pH值与电导率变化趋势一致，实测电导率值较理论值偏高，主要是受二氧化碳和铜、铁等杂质离子影响；3）碱性处理前后pH值与铜含量变化曲线（图7）显示，当内冷水pH值由7升到8以上，铜含量由原来的20g/L以上降到10g/L以下；当pH在8.58.8之间，铜含量最低。碱化混床能将发电机内冷水电导率稳定控制在0.52.0S/cm的原因，是利用离子交换技术的特殊情况，即在某种具体条件下（如补充水为电导率小于2.0S/cm、
12、中等密闭系统）离子交换能达到的极限状态，且当补充水水质不变、循环运行条件恒定时，内冷水电导率趋于某平衡值，但因系统存在杂质离子，如铁、铜、氯离子、硫酸根等，因此实际运行的电导率始终在平衡值附近。2号机组内冷水碱性处理前期，1号机组采用H/OH型混床旁路、补充凝结水方式运行。由图8可见，在相近pH范围内由于受氨蚀影响，1号机组内冷水的铜含量明显高于2号机组，与3.1试验结果一致。图8 1、2号机组内冷水相近pH范围Cu含量4 结论与建议4.1 内冷水采用碱性处理技术可从根本上减缓铜导线的腐蚀，有效解决内冷水长期以来pH偏低、电导率和铜含量偏高、水质不稳定的问题，使内冷水水质满足有关标准（DL/T
13、8012002）对发电机内冷水水质的要求；4.2 通过控制碱化混床运行流量和改进系统运行方式，可以实现内冷水碱性处理后长周期稳定运行及免维护功能；4.3 采用国产特制的碱化混合树脂，具有强度高、耐热性能好、颗粒均匀的特点，有效避免树脂破碎、泄漏对系统的影响，树脂运行更换周期在一年以上； 4.4 发电机内冷水采用碱性处理技术，系统必须设置内冷水pH、电导率在线监测仪表和小混床的流量表，以便运行监控；4.5 根据系统特性选择适当的碱化混合树脂比例，正常运行时为防止内冷水pH波动过大应控制较小的碱化混床流量，补充水应直接补入定冷水箱。参考文献：1 中华人民共和国电力行业标准，大型发电机内内冷水质及系
14、统技术要求，DL/T 801-2002,2002-09-01实施2 R.Dortwege, The Chemistry of Copper Restrctions in Water and Related Studies Planned at The Advanced Photon Source, proceeding of the 2001 Particle Accelerator Conference3 EPRI project opportunity, Preventing Flow Restriction in Water-Cooled Generations, July 20034
15、闻人勤等，发电机内冷水铜导线腐蚀的原因及影响因素分析，华北电力技术，2003（3）：1517Editors note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to h
16、uddle around a shortwave radio and through the crackling static from space hear the faint beeps of the worlds first satellite - Sputnik. I also missed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I wa
17、s fascinated with what goes on in the sky, and when NASA pulled the plug on the shuttle program I was heartbroken. Yet the privatized space race has renewed my childhood dreams to reach for the stars.As a meteorologist, Ive still seen many important weather and space events, but right now, if you we
18、re sitting next to me, youd hear my foot tapping rapidly under my desk. Im anxious for the next one: a space capsule hanging from a crane in the New Mexico desert.Its like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an
19、 unimaginable free fall from the edge of space - live.The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if the
20、y would just line up in a vertical straight line we would be go for launch.I feel this mission was created for me because I am also a journalist and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to
21、do this, Felix Baumgartner, must have that same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre bal
22、loon, with skin no thicker than a dry cleaning bag, scraped the ground I knew it was over.How claustrophobia almost grounded supersonic skydiverWith each twist, you could see the wrinkles of disappointment on the face of the current record holder and capcom (capsule communications), Col. Joe Kitting
23、er. He hung his head low in mission control as he told Baumgartner the disappointing news: Mission aborted.The supersonic descent could happen as early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with
24、 no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher th
25、an the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here,
26、Fearless Felix will unclip. He will roll back the door.Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so desp
27、ite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving into the shallow end.Skydiver preps for the big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he
28、will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to stop him completely.If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy h
29、is 270-square-foot (25-square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).In order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if eve
30、rything goes as planned, it wont. Baumgartner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
