燃气-蒸汽联合循环发电厂在线化学仪表测量准确性研究

Study on measurement accuracy of on-line chemical instruments in combined-cycle power plants

国内不少燃气-蒸汽联合循环发电厂水汽品质监测合格率很高,但水汽系统热力设备仍然出现明显腐蚀、结垢和积盐现象。依据《发电厂在线化学仪表检验规程》(DL/T677-2018)对某大型发电集团下属的11家燃气-蒸汽联合循环发电厂共35台机组的6类在线化学仪表(包括电导率表、氢电导率表、pH表、溶解氧表、钠表、硅表)开展在线化学仪表检验。对检验结果进行统计,发现该类电厂在线化学仪表目前普遍存在准确性差的问题,总体合格率仅为54.4%,且6类在线化学仪表的合格率参差不齐。研究分析各类仪表的误差来源,并采取有效措施进行误差消除,在线化学仪表准确率由54.5%提高到93.0%,检验校准效果十分明显,但准确率总体仍未达到不低于96%的化学监督要求,主要原因为部分仪表的电极损坏。最后对在线化学仪表日常维护中存在的问题提出了改进建议,指出电厂应不断加强人员培训、制度建设、日常维护及定期检验等工作,这样才能最大程度上保证在线化学仪表的准确性和可靠性。

The qualified rate of water vapor quality monitoring in many gas-steam combined cycle power plants was very high,but the thermal equipment of water vapor system still appears obvious corrosion,scaling and salt accumulation.On-line chemical instruments(including conductivity meter,hydrogen conductivity meter,pH meter,dissolved oxygen meter,sodium meter,silicon meter)of 35 units in 11 gas-steam combined cycle power plants of a large power generation group were inspected according to DL/T677-2018《Inspection code of on-line chemical instruments for power plants》.According to the statistics of the test results,it is found that the accuracy of the on-line chemical instruments in this kind of power plant was poor at present,the overall qualified rate was only 54.4%,and the qualified rate of 6 kinds of on-line chemical instruments was uneven.The error source of all kinds of instruments was studied and analyzed,and effective measures were taken to eliminate the error.The accuracy of on-line chemical instruments was increased from 54.5%to 93.0%,and the calibration effect was very obvious.But the accuracy still did not no less than 96%.The main reason was the electrode damage of some instruments.Finally,some suggestions were put forward to improve the problems existing in the daily maintenance of on-line chemical instruments.It was pointed out that the power plant should constantly strengthen the work of personnel training,institutional construction,daily maintenance and regular inspection,so as to ensure the accuracy and reliability of on-line chemical instruments to the greatest extent.