大气采样干燥技术除湿效果的测试与对比

高湿、云雾影响大气污染物的测量结果,甚至损坏测量设备,因此在大气采样中需采用干燥技术进行除湿。测试对比了旋风切割器、加热带、Nafion干燥管、硅胶干燥管4种干燥装置的除湿效果和影响因素。结果表明,旋风切割器能有效去除液态水,主要用于痕量气体和细颗粒物;加热带快速降低样品空气的相对湿度,但波动较大,平均除湿效率约为20%~40%,用于热稳定污染物;Nafion干燥管除湿效率通常小于20%,适用于各种痕量气体和颗粒物;硅胶干燥管除湿效率稳定,在50%左右,用于颗粒物。几种干燥装置的使用均会引起痕量气体的损失,其中加热带较大,约为10%,旋风切割器和Nafion干燥管不超过10%,甚至低于5%。不同干燥技术各有其适用性和优缺点,使用时应综合考虑。

Tests and comparison of the dehumidification effectiveness of drying techniques involving in atmospheric sampling

High humidity and fog water can affect the measurement results of atmospheric pollutants, or even damages the instruments. Therefore, it was necessary to dehumidify the sample air with specific drying techniques when sampling. This study tested and compared the dehumidification effectiveness and the influencing factors of four common drying devices, i.e., cyclone cutter, heating belt, Nafion drying tube, and silicone drying tube. The results showed that the cyclone cutter could effectively remove liquid water and it was suitable trace gases and fine particulate matters. The heating belt quickly reduced the relative humidity of the sample air; however, the relatively humidity exhibited large fluctuation. The average dehumidification efficiency was about 20%~40%. The heating belt was mainly suitable for the thermally stable pollutants. The dehumidification efficiency of Nafion drying tube was usually less than 20%, but it was suitable for all kinds of trace gases and particulate matters. The silica gel drying tube could quickly dry the sample air with stable and high efficiency of about 50% and it was mainly suitable for particulate matters. The use of the above drying techniques would cause a loss of trace gases in certain degree. Among them, the loss caused by heating was highest, about 10%. The loss caused by cyclone cutters and Nafion drying tubes was no more than 10% and even less than 5%. These drying devices had different applicability, advantages, and disadvantages, so it was necessary to take account into the measured component.