高压CO2管道放空及安全泄放的数值模拟

1.中海油研究总院有限责任公司;2.中海油(天津)管道工程技术有限公司·天津市海底管道企业重点实验室·海油发展海底管道安全服役保障技术重点实验室;3.中国石油大学(华东)储运与建筑工程学院·山东省油气储运安全重点实验室

CO2管道;碳捕集、利用与封存;放空模拟;安全泄放

Numerical simulation of high-pressure CO2 pipeline venting and safe release
LIU Xin1,WANG Haifeng2,YANG Teng3,HU Qihui3,YIN Buze3,LI Yuxing3,ZHU Jianlu3,ZHU Zhenyu1

1.CNOOC Research Institute Co. Ltd.; 2.CNOOC (Tianjin) Pipeline Engineering Technology Co. Ltd.//Tianjin Enterprise-based Key Laboratory for Submarine Pipeline//Key Laboratory of Submarine Pipeline Service Safety Guarantee Technologies, CNOOC Enertech Equipment Technology Co Ltd.; 3.College of Pipeline and Civil Engineering, China University of Petroleum (East China)//Shandong Key Laboratory of Oil & Gas Storage and Transportation Safety

CO2 pipeline, CCUS, venting simulation, safety relief

DOI: 10.6047/j.issn.1000-8241.2024.04.003

备注

【目的】碳捕集、利用与封存是实现碳中和不可缺少的关键技术,CO2管道输送是碳捕集、利用与封存技术的重要一环。超临界CO2管道输送过程中,当管道发生泄漏或进行放空作业时,因CO2强节流效应,主管及放空管内可能出现局部低温,生成干冰堵塞管道,并使钢管变脆。【方法】利用OLGA软件建立高压CO2管道泄放模型,并将模拟结果与国外实验数据进行对比,发现OLGA软件在计算压降方面较准确,在计算温降方面相对保守,可用于CO2管道设计计算。在此基础上,建立了长距离高压CO2管道放空模型,模拟分析了不同的阀门开度、初始温度及初始压力对CO2管道放空过程中管内低温、相态变化及放空时间的影响。【结果】减小放空阀阀门开度可以防止放空过程中管内温度过低,在选定的放空模拟条件下,不生成干冰的阀门开度应在13.5%,管内温度不低于-30℃时的阀门开度应在4.5%以下;高压CO2管道放空过程中,距离泄放口较远处,对流换热强度小、温降幅度较大;初始温度对于放空过程管内温度影响较大,初始温度越低,放空过程中管内温度越低,生成干冰的可能性也越大。【结论】在实际工程中应重点关注主管道上距离泄放端较远处管内流体温度,并在放空过程中根据管内温降情况自动控制放空阀阀门开度,减缓放空过程温降速率,对低温密相CO2管道放空需重点关注与防护。(图9表3,参[25]
[Objective] Carbon capture, utilization and storage (CCUS) is an indispensable technology for achieving carbon neutrality, and CO2 pipeline transmission is a significant component of this technology. In the process of supercritical CO2 pipeline transmission, unintentional pipeline leakage or venting operations may cause localized low temperatures in the trunk pipelines and vent piping due to the strong throttling effect caused by CO2, resulting in dry ice that blocks the pipeline and makes it brittle. [Methods] In the study, the OLGA software was utilized to develop a high-pressure CO2 pipeline relief model. The simulation results obtained from the model were then compared against foreign experimental data. The comparative analysis indicated that the OLGA software provided relatively accurate calculations for pressure drop and tended to be more conservative in calculating temperature drop. These findings supported the software’s suitability for performing calculations related to the design of CO2 pipelines. Building upon this foundation, a long-distance high-pressure CO2 pipeline venting model was established to simulate and analyze the effects of different valve openings, initial temperatures, and initial pressures on temperature decrease, phase state changes, and venting duration during the CO2 pipeline venting process. [Results] It was revealed that reducing the vent valve opening effectively prevented excessively low temperatures within the pipeline during venting. Under the venting simulation conditions selected for this study, 13.5% valve opening effectively prevented dry ice formation, and the valve opening below 4.5% could maintain the pipeline temperature at higher than -30 °C. The venting process of the high-pressure CO2 pipeline exhibited low convective heat transfer intensity and significant temperature drops, predominantly observed away from the relief port. The initial temperature had a substantial impact on the temperature in the pipeline during venting. More specifically, a lower initial temperature resulted in a decrease in the temperature in the pipeline during venting, increasing the likelihood of dry ice formation. [Conclusion] Therefore, in engineering practice, it is crucial to focus on fluid temperature in sections far from the relief port along the trunk pipelines and automatically reduce the vent valve opening in response to temperature drops, aiming to slow down the temperature drop rate during the venting process. Special attention should be paid to protecting CO2 pipelines, especially when operating under low-temperature dense phase conditions. (9 Figures, 3 Tables, 25 References)
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