发电厂碱性水-蒸汽回路中胺的在线痕量分析
AN-PAN-1044
2021-02
zh
添加中和胺是为了调节发电厂水-蒸汽回路中的 pH 值，以避免出现诱发腐蚀的情况。这种预防性维护可以减少因腐蚀而造成的代价高昂的关键停机时间，但必须经常监测胺的化学成分，以确保保持最佳状态。采用 Metro瑞士万通智能部分循环技术 (MiPT) 选件的 2060 离子色谱过程分析仪是这一应用的理想之选，它能够通过自动化方法精确、可靠地测量痕量被分析物。使用 离子色谱仪的好处是可以同时监测多种被分析物，在这里，除了高浓度的铵或胺之外，还能测量钠的存在，这表明冷却水正在渗入回路，说明上游出现了问题。
Thermal power plants use the heat generated by combustion or nuclear fission to produce high pressure steam, which is fed into a turbine driving a generator that converts the mechanical energy into electrical energy. Downstream of the turbine, the steam condenses to water, forming a vacuum critical for the power plant efficiency. This water is returned to a feed tank from where it is pumped back into the steam boiler. Cooling water flows through the condenser in a separate circuit, removing the heat of condensation released by the steam via a heat exchanger.
Unplanned maintenance can lead to costly and critical downtimes and corrosion is often the cause. Exceptionally low pH values increase the corrosion potential, whereas excessively high pH values destroy the protective layer on the metals. Adjustment of the pH value is challenging because the requirement for minimum corrosion and maximum protective layer leaves very little flexibility. To keep corrosion low, the pH value of the watersteam should be in a slightly alkaline range, frequently achieved with All-Volatile Treatment. In this treatment procedure, neutralizing amines such as morpholine, methoxypropylamine, and ethanolamine among others are added to the demineralized feed water to raise pH, inhibiting corrosion in steam condensate systems.
Frequent monitoring of the chemistry ensures safe and efficient power plant operation. Ion chromatography with conductivity detection provides an effective means to control amine addition in alkaline water-steam circuits of thermal power plants. Precise, reliable trace analysis requires the method to be automated as much as possible. Metrohm Process Analytics offers a complete solution for this task: the 2060 Ion Chromatograph (IC) Process Analyzer featuring the Metrohm intelligent Partial Loop Technique (MiPT) option.
In a single analysis, the 2060 IC Process Analyzer is able to measure numerous ionic compounds in aqueous media from ng/L to % concentrations. Most important is the sensitive determination of sodium next to the high ammonium or amine concentrations, because an increase thereof indicates that cooling water is seeping into the circuit. The analysis system is fed directly and continuously with samples via a bypass in the process. The Metrohm Partial Loop Technique allows, in addition to the automatic calibration feature, a working calcium and magnesium determination. Automated calibration guarantees excellent detection limits, a high reproducibility, and excellent recovery rates. Additionally, sequential cation suppression reduces baseline noise, considerably lowering the detection limits.
The analysis is carried out fully automatically. Analyte detection is by conductivity.
The column oven should be used in this application to maintain analytical column stability above room temperature (up to 40 ºC).
- Inline eluent preparation ensures consistently stable baselines
- Safe working environment and automated sampling
- High precision analyses for a wide spectrum of analytes with multiple types of detectors
- Protect valuable company assets (e.g. pipes, PWR, and turbines, which are prone to corrosion)
Related application notes
AN-C-049 Trace cations in power plant feed water stabilized with 7 ppm monoethanolamine (MEA)
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