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朋友们，您不必再为双水机组水质控制问题而苦恼！
总结过去，阔步未来！
1引言
目前，在不频繁换水的前提下，利用传统的离子交换方法稳定的控制双水内冷发电机内冷水水质满足电导率DD≤2.0μS/cm（25℃）、pH值（25℃）≥7.8、铜≤40μg/L的成功案例未见报道。现在，我们可以郑重宣布：这个水质指标，我们达到了。
我们通过大量的实验室和实地现场试验，采用了具有创新的研发思路，成功的推出了一套全新的双水机组内冷水处理工艺，将国内双水机组内冷水水质调控水平进行了大幅度提升。该工艺的配套系统为HiTech-III型水质调控系统。
2双水机组处理为何如此之难——传统方法的弊端
目前最新的内冷水控制标准是中华人民共和国电力行业标准DL/T 1039-2007《发电机内冷水处理导则》2007-12-01实施。其前言中有如下两段文字：
该标准的适用范围如下：
该标准水质指标如下：
由上可见，该标准在总结过去经验的基础上，对内冷水处理方法进行了总结。这里，我们将对其列举的方法一一进行剖析，具体的细节问题篇幅所限，不予论述了，请见谅。
- 单床离子交换微碱化法：该方法现在在系统密闭性较好的水氢氢机组上已经成功应用，笔者也成功应用十多台。然而对于双水机组或是密闭性较差的水氢氢机组（如水箱开放），该方法的应用情况效果就相当糟糕。幸运的是，现在的水氢氢机组密闭性基本还可以。总而言之，单纯的应用该方法对于双水机组就是一个字——“死”。
- 离子交换——加碱碱化法：该方法说“白”了，就是单床离子交换微碱化法的加强版，加强在哪里呢？就是加了碱。从这里我们可以觉察出一些问题来，单床离子交换微碱化法提高pH值的能力非常有限，想通过树脂配比就能保证使得水氢氢机组的内冷水pH值提高到8.0以上稳定运行，估计谁都没这个把握。现在加碱了，问题就解决了，pH值想提多高就能多高，打打药就轻松搞定了pH值。说到双水机组，还是那句话：单纯的应用该方法对于双水机组就是一个字——“死”。
- 氢型混床一钠型混床处理法：这个国外机组和国内机组都有应用，其对密闭性较好的水氢氢机组也是OK的，笔者搞了多年的内冷水，大大小小机组研究了不少，能用这种方法的就能用“单床离子交换微碱化法”和“离子交换——加碱碱化法”。有些人曾经想过（估计也试过，这里就不详述了），这种方法装树脂多，再把水箱密封一下，用于双水机组可能会成功，还是那句话：单纯的应用该方法对于双水机组就是一个字“死”。你就算装1000L树脂，也就硬撑个50天，铜的指标没什么大问题，都过滤掉了，pH值和电导率只有天知道行不行了！^_^哈哈
- 凝结水与除盐水协调调节法：这个方法，调pH值没什么大问题，铜的控制只要有交换柱也能搞定。能把凝结水和除盐水两种水调到电导率≤2.0μS/cm（25℃）稳定运行的，笔者和几个技术人员亲自调过，无法搞定，笔者直到目前也从来没亲眼见过搞定的案例。不知道哪个电厂的现场工作人员和电厂化学主管或是哪位专家有这水平，笔者真想虚心请教。还是那句话：天知道行不行了！^_^哈哈
- 离子交换一充氮密封法：该方法说“白”了，就是单床离子交换微碱化法的另一种加强版，参照国内外资料，理论上讲，这种方法应该是最好的，因为没了“氧”，pH值又偏碱性，腐蚀最小。理论归理论，实践又是另一码事情了，除氧法，特别是低氧运行（溶解氧≤30μg/L），谈何容易，国外的运行导则中一大串注意事项。幸运的是，现在的水氢氢机组安装氧表的少之又少，笔者建议：最好也别装，国内现有的水平很难合格，装了，数据不合格，还要挨领导批，何苦呢，第一线干工作都不容易啊。^_^开个玩笑，千万别当真哦。针对这种方法，如果不考察溶解氧指标，对于水氢氢机组，相比单床离子交换微碱化法、离子交换——加碱碱化法，其优势也不是十分明显。既然如此，那又何苦弄个氮气瓶推来推去，除非想锻炼身体？^_^哈哈。说到双水机组，还是那句话：应用该方法对于双水机组就是一个字——“死”。
- 溢流换水法：如果该方法能搞定，笔者认为，大家就没有必要来讨论了，皆大欢喜，回去喝茶，^_^哈哈。
- 缓蚀剂法：郑重申明，该方法笔者是不推荐的。如果您一定要做，也没什么大关系。标准中对该方法有句话“采用本方法时，应密切监视其运行情况，防止络合物沉积。”话谁都可以这样说，第一线的兄弟姐妹们，做事情难呀，“密切监视”，笔者眼睛不好，监视不了，“防止络合物沉积”，难道要第一线的兄弟姐妹们，整天提心吊胆，总惦记着拆设备看看。干好工作不容易啊，还是别用这方法，历史上可是有过这方面的教训的。
- 催化除氧法：这是赶个时髦，说说玩玩而已。该方法需要氢，当然也只能应用于水氢氢机组了。哪位想在双水机组上试试，还要弄个氢气瓶，记得，开工的时候劳驾通知我一下，我真的想去瞧瞧。钯树脂太贵，国内的一个电子研究所弄这个，几百块一升哦。
- 其他新方法：导则原文如下：
这条写的好，引出了本文正题“一套全新的双水内冷发电机内冷水处理工艺——HiTech-III型水质调控系统”。该方法对于双水机组就是一个字——“活”。
2双水机组溶解氧无须进行特别控制
双水机组由于其结构的特殊性，转子冷却水始终不断地接触空气，使得其氧量处于2~4个ppm，可以按照高氧系统要求进行水系统处理，系统无须进行特别的溶解氧控制。
 
笔者听说有些方法，对双水机组的内冷水进行旁路脱气。脱气法存在一个问题，就是很可能使得内冷水的溶解氧处于100ppb~1000ppb，这在内冷水高氧运行工况下，容易造成腐蚀加速。
3 HiTech-III型水质调控系统介绍
该系统总结了国内外这方面研究的成功经验，针对双水机组的自身特点，确定了高氧系统运行工况（High-Oxygen System Operationg Conditon）做为出发点，研制了HiTech-III型水质调控系统。该系统具有“离子交换——加碱碱化法”调节pH值能力强的特点，同时克服了其调节电导率弱的缺点，因为树脂配比一旦确定，很难调整电导率了。 Generator Cooling System Operating Guidelines：Cooling System Maintenance and Performance Guidelines During Startup, Operation, and Shutdown 1004004，Final Report, December 2001
报告结论：
Generator stator water cooling systems have been designed to operate with dissolved oxygen
(DO) concentrations of either more than 2 parts per million (ppm) or less than 50 parts per
billion (ppb). If the system operates with the DO concentration in either design range, copper
corrosion rates are low and do not lead to reduced cooling capacity or adversely affect generator
availability. In the range between the extremes—when the DO levels are between 50 ppb and 1
ppm—cooling systems have lost at least some of their capacity as a result of clogging or
plugging, making it necessary to reduce the generator load or shut it down altogether. These
operating guidelines apply to systems with either high- or low-DO concentrations and are
intended to mitigate excursions into the detrimental range, or at least minimize the time spent
there.
Prevention of Flow Restrictions in Generator Stator Water Cooling Circuits
For an aerated system, it has been shown that DO concentration should certainly be greater
than 1 ppm, and 2 to 3 ppm is preferred. A goal of 2 to 3 ppm is realizable in a wellmaintained
system. Less than 1 ppm can cause increased copper cooling strand corrosion.
A pH in the 8 to 8.5 range has proven to be effective in reducing the release of corrosion
products in both aerated and deaerated systems. The rate of corrosion even at a DO in the
dangerous 200 to 500 ppb range is only about 1/7 of that at a pH of 7. However, operating at
an elevated pH is not recommended for stators susceptible to clip leakage due to crevice
corrosion.
Inhibitor Use
Although there is widespread use of inhibitors in many industrial processes using water as a
coolant, it is virtually non-existent in stator winding cooling circuits. Only one case was found in
the literature where hydrazine was injected periodically to control copper corrosion. There have
been several investigations to determine the potential for the use of benzotriazole (BTA) as an
inhibitor. It has been shown that BTA does not significantly raise the conductivity of water while
reducing the corrosion of copper in pure water by a factor of 10. Nevertheless, its use is not
currently recommended in high-DO units that are susceptible to crevice corrosion in the strandto-
clip connection because of the potential for accelerated crevice attack in the presence of BTA.
RECOMMENDATIONS
For aerated systems, corrective action should certainly be taken if the DO drops below 1 ppm
and, preferably, when the DO drops below 2 ppm.
5. A shut down should be scheduled for an aerated system if a DO less than 1 ppm persists.
Check stator windings for clip leaks
Clip leaks in aerated systems can allow excessive hydrogen ingress into the stator cooling
water and thereby deplete the DO content. This is further reason to repair any such leaks as
soon as practical.
Consider operating at elevated pH if clip leaks due to crevice corrosion are not a problem.
Use a 1-micron filter medium. Since the particulates released from the strands are in the 2 to
4 micron range, the filter should then be capable of trapping them before they can redeposit
in the strands.
12. Install a supplemental air supply to the storage tank if it is not possible to maintain an aerated
system above 1.5 ppm. |
