超临界供热机组主蒸汽氢电导率超标原因分析

Analysis on Causes of Hydrogen Conductivity Exceedance in Main Steam of Supercritical Heating Units

针对某超临界供热机组在运行中突然出现主蒸汽氢电导率超标问题,通过联合运用离子色谱仪、TOC仪、痕量TOCi分析仪,从有机物和无机阴离子含量等方面检测,用摩尔电导率与离子含量计算出不同离子产生的氢电导率贡献值,分析出主要杂质影响,通过排查制水设备、水源、药剂投加、供热等运行条件改变时氢电导率增量,研究得出多个运行影响因素。结果表明:给水中CH_(3)COO-和HCOO-对氢电导率贡献值为0.024μS/cm和0.018μS/cm,总占比为46.7%;主蒸汽中CH_(3)COO-和HCOO-离子含量继续升高,对氢电导率贡献值分别为0.056μS/cm和0.048μS/cm,总占比为76.5%。得出结论,在高温高压下锅炉补给水中的有机物会分解为低分子有机酸,主蒸汽中有机酸根升高是氢电导率超标的主要原因。长江水中有机物总量突增46.8%,超出目前水处理系统处理能力,该厂一级反渗透工艺对于原水突增有机物污染因子去除率为76%左右,远低于同类型设备,造成了补充水TOC超标。另外,有机溴非氧化性杀菌剂和阴树脂溶出物也会增加除盐水中有机物含量。建议对于供热机组,原水、补充水TOCi的监督控制应更严格,TOCi与离子色谱应作为必备的水质监督手段。

Aiming at the problem of hydrogen conductivity exceeding the standard in the main steam of a supercritical heating unit,the hydrogen conductivity contribution of different ions was calculated by the combination of ion chromatograph,TOC instrument and trace TOCi analyzer from the aspects of organic matter and inorganic anion content.The contribution of hydrogen conductivity generated by different ions was calculated by the molar conductivity and ion content,and the main impurity impact was analyzed.By investigating the hydrogen conductivity increment when the operating conditions such as water making equipment,water source,pharmaceutical dosage and heating were changed,multiple operation factors were studied.The results showed that the contribution ofCH_(3)COO-and HCO0-to the hydrogen conductivity in feed water was 0.024μS/cm and 0.018μS/cm,accounting for 46.7%.The content of CH_(3)COO-and HCOO-ions in main steam continued to increase,and the contribution to the hydrogen conductivity was 0.056μS/cm and 0.048μS/cm,accounting for 76.5%.It is concluded that the organic matter in the boiler feed water will decompose into low molecular organic acids at high temperature and high pressure.The increase of organic acids in main steam is the main reason for the hydrogen conductivity exceeding the standard.The total amount of organic matter in the Yangtze River water suddenly increased by 46.8%,exceeding the current capacity of the water treatment system.The removal rate of organic pollution factors in raw water by the first-stage reverse osmosis process of the plant is about 76%,far lower than that of the same type of equipment,resulting in the TOC of supplementary water exceeding the standard.In addition,organic bromo non-oxidizing bactericide and anion resin dissolved substance will also increase the content of organic matter in the desalination water.It is suggested that supervision and control of TOCi in raw water and supplementary water should be more strict for heating units,and TOCi and ion chromatography should be used as necessary water quality supervision means.