大规模埋地CO2管道泄漏过程中的温度场变化

Temperature field in the process of the buried CO2 pipeline release in large scale

化石燃料燃烧产生温室效应明显,为解决这一问题,提出碳捕集利用(CCS)技术。CO2管道运输在CCS技术链中占有重要地位,研究埋地管输安全是重中之重。基于大规模CO2埋地泄漏试验装置开展了高压CO2的泄漏试验。测量了CO2在泄漏口径为1 mm、3 mm时,泄漏过程中的埋地管道壁面温度、土壤温度分布、干冰球和冻土球的大小。分析了干冰球和冻土球体积增大的过程。结果表明,泄漏过程中泄漏口附近有椭球形的冻土球生成,冻土球内包裹着干冰球。泄漏口径增大,干冰球和冻土球的体积增大,体积增大的速率加快。在泄漏过程中管壁温度先上升后下降最后稳定。泄漏口附近的土壤温度经历了恒定、缓慢下降、温度快速下降和稳定4个阶段。越靠近泄漏口温度越低,泄漏口径越大低温区域越大。

Based on the industrial-scale experimental surface-below buried pipeline,we have done an experiment of the dense CO2 release by using the experimental device mainly comprising a principal pipe,a pneumatic valve,a connecting pipe,a buried pipe and a sandbox. The experimental data to be measured has been arranged in a form of T-type thermocouple around the release orifice. At the same time,the temperature of the buried pipeline surface and the soil in addition to the dry ice ball and frozen soil ball are supposed to be able to be measured during the CO2 release with 1 mm and 3 mm orifice. What is more,the increasing process of the volume of the dry ice hockey and the frozen soil balls have been laid out likely to be analyzed through the isotherm mapping. And,then,physical parameters of the initial sand in the sandbox have also been tested before doing the experiment so as to ensure the accuracy of the experiment. The results of the above experimental study show that the ellipsoid-like frozen soil balls formulated around the release orifice and the dry ice balls both exist inside the frozen soils. The dry ice accumulation may take place in all the directions of the pipeline. Nevertheless,in the leakage direction,the dry ice accumulation gap and the leakage time intends to show a logarithmic function relation. With the increase of the orifice size,the volume of the frozen soil and the dry ice tend to turn to bigger and bigger with the speed of the volume increase getting faster and faster. And,meanwhile,the temperature at the surface of the frozen soil may increase first and then decrease to get stable at last. In addition,the temperature on the soil may experience 4 stages: i. e. from being constant to get to decrease slowly,and,quick decrease to get stabilized. What is more,the closer to the release orifice,the lower the temperature would be getting to. And the greater the release orifice,the greater the low temperature area would appear. Besides,the temperature drop and the temperature drop rate in the leakage direction should be greater than that of the opposite direction to the leakage. Thus,correspondingly,the increase of the diameter of the soil may lead to the broadened drop rate in the temperature of the soil area due to the greater temperature change.