Zhi Xuting, Wang Haifeng, Liu Baijun, Song Xiaoping, Li Zhanyuan, Li Jia
China University of Petroleum-Beijing.
National Institute of Metrology of China.
Anal Sci. 2019 Jul 10;35(7):777-782. doi: 10.2116/analsci.18P575. Epub 2019 Mar 22.
Measuring the water content in natural gas is important for safety; however, complex matrixes make the results inaccurate. Natural gas contains hydrogen sulfide (HS), which react with iodine (I), causing Karl Fischer coulometric titration (KFCT) to give higher results. The KFCT method for the determination of water content of nitrogen containing HS was investigated. A chilled mirror hygrometer offered a reference water content to calibrate the KFCT. The interfering of HS was reduced by subtracting I consumed by HS according to the reaction mechanism of ISO 10101; however, the modified results remained higher. A possible reaction mechanism with a stoichiometry of HS to I of 1:2.5 was proposed. The improved KFCT method had an error of water content no more than (3 + 2%·x) mg/kg (x, water content in mg/kg) and had the potential of online monitoring of natural gas.
测量天然气中的含水量对安全至关重要；然而，复杂的基质会使测量结果不准确。天然气中含有硫化氢（HS），它会与碘（I）发生反应，导致卡尔费休库仑滴定法（KFCT）得出偏高的结果。对测定含HS氮气含水量的KFCT方法进行了研究。采用冷镜湿度计提供参考含水量来校准KFCT。根据ISO 10101的反应机理，通过减去HS消耗的I来减少HS的干扰；然而，修正后的结果仍然偏高。提出了一种HS与I化学计量比为1:2.5的可能反应机理。改进后的KFCT方法的含水量误差不超过（3 + 2%·x）mg/kg（x，以mg/kg为单位的含水量），并且具有在线监测天然气的潜力。
