PTA装置雷达液位计假液位故障分析与控制

Fault analysis and control of false level indication of radar level gauge for PTA plant

介绍了雷达液位计的测量原理及特点,以及雷达液位计在精对二甲酸（PTA）装置对二甲苯（PX）储罐液位测量中的应用,分析了雷达液位计液位测量时产生假液位的原因,并提出了相应的改进措施。结果表明：PX储罐内蒸汽在竖直壁面上冷凝而形成17~26 mm的液滴,因液滴尺寸大于雷达液位计发射波波长（12 mm）,雷达发射波遇到液滴时产生反射回波,导致假液位的产生;选择频率为6 GHz,波长为50 mm的低频雷达液位计,将雷达天线由喇叭形改为直杆式,同时将PX储罐内温度由16~40℃提高至30~42℃,可有效避免PX储罐竖直壁面液滴产生的反射回波,控制雷达液位计假液位的产生;改进后的雷达液位计假液位故障明显减少,由改进前3次/d减少到改进后的（1~2）次/a,为PTA装置安全稳定运行提供了保障。

The measuring principle and characteristics of radar level gauge were introduced,as was the application of radar level gauge in the liquid level indication of p-xylene（ PX） tank of purified terephthalaic acid（ PTA） plant. The reasons for the false level indication of radar level gauge were analyzed,and the corresponding solution measures were put forward. The results showed that the false level indication occurred when the vapor in PX tank condensed into liquid droplets of 17- 26 mm on the vertical wall and the reflection echo returned from the liquid droplets due to their size higher than the emission wave length（ 12mm） of radar level gauge; the reflection echo and the false level indication could be efficiently avoided by choosing the low-frequency radar level gauge with the frequency of 6 GHz and wave length of 50 mm,transforming trumpet antenna into rod antenna,elevating PX tank temperature from 16- 40 ℃ to 30- 42 ℃; and the false level indication could be profoundly depressed from 3times a day to once or twice a year after the improvement,which guaranteed the safe steady operation of PTA plant.