NaOH处理炉水溶液温度系数测定

DETERMINATION OF SOLUTION TEMPERATURE COEFFICIENT FOR PH MEASUREMENT OF NAOH TREATED BOILER WATER

NaOH处理炉水的pH值测量受温度影响较大,当水样温度偏离25℃时,需要通过溶液温度系数(STC)将其补偿到25℃,对此提出了一种用于测定炉水STC值的试验方法,并给出了国内常见在线pH仪表STC值的设置。试验表明,NaOH处理炉水的STC值为-0.026～-0.028pH/℃,与弱电解质碱性溶液STC计算值相近,与纯水、普通水和强电解质溶液的STC值相差较大。应选用具备STC补偿设定功能的pH表并正确设置STC补偿值,确保炉水pH表测量的准确性。

The accuracy of pH measurement of boiler water with caustic treatment is badly influenced by temperature.Appropriate STC(Solution Temperature Coefficient)was needed in order to obtain accurate pH measurement when the sample temperature is much beyond 25 ℃(reference temperature).The theoretical derivation process of STC was complicated and the result uncertainty was great.Therefore,an efficient and reliable experimental method to determine the STC was presented,and the setting methods of STC value for common domestic online pH analyzers were introduced.Results showed that the STC of NaOH treated boiler water was between 0.026 pH/℃ and 0.028 pH/℃,which was close to that of weak electrolyte alkaline solution by calculation but quite different from that of pure water,common water and strong electrolyte solution.Proper selection of pH analyzer with STC compensation and setting function is important,and to ensure the accuracy of pH measurement for boiler water,the STC value should be rightly set.