放空管设计对超临界CO2管道放空影响研究

与天然气管道相比，超临界CO2管道放空时的降压可能导致管道内的低温，甚至形成干冰对管道及设备造成损伤，危害管道安全。针对超 临界CO2放空过程可能出现的潜在风险，建立了超临界CO2管道放空计算模型，借助OLGA软件对超临界CO2管道放空进行了稳态和动态模拟，并研 究放空管设计对管道放空的热力水力影响。研究表明:超临界CO2管道放空时管道沿线上各点之间的压力、温度变化差异不大；CO2首先由超临 界相变为气相，然后沿着气液相平衡线或气固相平衡线进行，管内温度降到一定值后逐步回升至管道埋地温度；放空管的直径对超临界CO2管道 放空过程的总时间、放空速率、最大温降以及是否生成干冰有直接影响；放空管高度对放空过程管内参数变化几乎无影响。

Study on influence of blow-down pipe design on blow-down of supercritical CO2 pipeline

Compared with natural gas pipeline, the decompression in the blow-down of CO2 pipeline may cause a low temperature in the pipeline, and even the formation of dry ice, which may damage the pipeline and equipments so as to endanger the pipeline safety. Against the potential risks that may arise in the blow-down process of super-critical CO2, a calculation model for blow-down of supercritical CO2 pipeline was established. By the OLGA soft-ware, the steady and dynamic simulation were conducted on the blow-down of supercritical CO2 pipeline, and the thermal and hydraulic effects of blow-down pipe design on pipeline blow-down were studied. It showed that during the blow-down process, the difference of pressure and temperature change at each node along the whole pipeline is insignificant. CO2 will transfer from supercritical phase into gas phase first, and continue along the vapor-liquid equilibrium line or gas-solid equilibrium line. The temperature in the pipeline will recover gradually to the buried temperature after reducing to a certain value. The diameter of blow-down pipe has a direct effect on the total blow-down time, the blow-down rate, maximum temperature drop and the formation of dry ice, while the height of blow-down pipe has almost no effect on the parameters change in the blow-down process of supercritical CO2 pipe-line.