腾冲火山区温泉甲烷气体现场富集取样效果研究

Enrichment Effect of Methane Escaped from Hot Springs in the Tengchong Volcanic Area

对具有甲烷富集功能的温泉逸出气体取样装置在腾冲火山区部分泉点采集样品的现场富集效果进行了分析,发现CO2含量和温度对甲烷富集效果的影响较大。在CO2含量很高(90%)的情况下,温度相对较高(>50℃)的泉点富集效果好,而低温泉点(<50℃)富集效果差,原因是:温度越高化学反应速率越大,反应越充分;高CO2的低温泉水中饱和的HCO3-与NaOH反应,消耗掉了大量的NaOH,导致NaOH浓度降低,从而大大降低了对CO2的吸收。据此,通过改用其他干净清洁的泉水(或纯净水)配制NaOH溶液和手动控制气体吸入流量等措施,对低温泉点的现场富集取样方法进行了改进,改进后的取样方法可以显著地提高温泉自由气体的CH4富集效果。

We sampled methane escaped from the hot spring in the Tengchong volcanic area,and analyzed the effect of enriching methane of sampling equipment.We find that the enrichment effect is constrained by both content of CO2 in spring and temperature of spring water.When the content of CO2 is high(>90%),the enrichment effect of methane from high-temperature spring(>50℃)is better than that from low-temperature ones(<50℃).This is because that the temperature impacts chemistry reaction speed or the ability for CO2 to dissolve into spring water.In the condition of high temperature,the content of HCO-3 in spring water is low and the reaction velocity between CO2 and NaOH solution is quick.In the condition of low temperature,because the content of HCO-3 in spring water is saturated or supersaturated,it makes NaOH depleted and the absorption of CO2 weaken.We improve sampling method for low temperature springs by two measures,using more clear water(purified water)to compound CO2 absorption solution(NaOH solution)and employing manually-controlling the flow of gas which enters the sample-collecting installation.These measures increase the effect of CH4 enrichment significantly.