CO_2管道泄压过程流动特性及参数影响

Flow characteristics during CO_2 pipeline venting and its influential parameters

针对CO_2管道放空过程管内参数变化的研究较少,且相关规范对放空无明确要求的问题,分析了CO_2管道泄压过程的特殊性,通过建立管内瞬变过程的数学模型,计算了不同输送压力和泄放速率对放空特性的影响。研究表明:管存量随时间的变化规律呈幂函数形式;高压低温会延长放空时间;各相态CO_2在放空过程中存在共同的"相态汇聚区域";密相CO_2的放空规律与液态CO_2相似;超临界放空将生成干冰;同时,放空速率对管内温降影响不大,但更小的放空速率导致更小的温降速率。因此,建议采用减缓放空阀开启速率、放空管局部加热等措施,实现对设备的保护和防止冰堵的发生。研究成果可为CO_2管道的放空方案以及相关规范的制定提供指导。

There is little research on how the flow parameters of CO2 pipeline vary during its venting, and the related codes have no definite requirements on venting. In this paper, the particularity of CO2 pipeline venting was analyzed, and the effect of delivery pressure and discharge rate on the venting characteristics was calculated after the mathematical model was established for the transient process inside pipelines. It is indicated that the remaining CO2 in the pipeline is the power function of time. The venting time becomes longer in high pressure and low temperature. The joint ＂convergence zone＂ of all phases of CO2 appears during the venting. The venting characteristics of dense phase CO2 are similar to that of liquid CO2. Dry ice may generate in the process of supereritical venting. And the venting rate has less influence on the temperature drop inside the pipeline, however, the lower discharge rate can cause slower temperature drop. Therefore, it is recommended to slow down the opening rate of vent valve and heat the vent pipe locally so as to protect the equipment and prevent dry ice blockage. The research results provide references for designing CO2 pipeline venting plan and drawing up the related codes.