Abstract:

The venting system is an important component of the supercritical CO₂ long-distance pipeline, but there has been little research on the impact of venting point location on the venting characteristics of CO₂ pipelines. The determination of venting points is very important for the venting system and the design of multi-segment planned venting schemes. Based on the venting calculation model established by the OLGA software, a simulation study was conducted on the multi-segment multi-point venting of a supercritical CO₂ long-distance pipeline planned in Xinjiang. The results showed that the downstream pressure drop rate of the venting far-end point can indirectly reflect the overall venting rate of the pipeline. The venting scheme with intermediate valve chambers for multiple segments, the fluid at the venting point of the intermediate valve chamber came from both upstream and downstream sections of the pipeline, and the pressure and temperature at this point can be supplemented by high-temperature and high-pressure fluid from both directions, so the pressure drop and temperature drop rate at this point was slower than that of the end-point venting point. As the number of venting points increased in the multi-pipe venting, the pressure drop and temperature drop rate at the same venting point gradually increased. The temperature at the lowest point of the pipeline in the dual-pipe single-point venting scheme dropped to -20℃ in 0.51h, the total venting time was 4.29h, and it had the advantages of short venting time and slow temperature and pressure drop at the venting point. Therefore, when implementing multi-pipe venting for supercritical CO₂ long-distance pipelines, it was recommended to prioritize the dual-pipe single-point venting scheme, also known as the intermediate valve chamber venting scheme, to achieve rapid release of CO₂ while ensuring temperature control. The study determined the principles for determining venting points in multi-segment venting operations of supercritical CO₂ long-distance pipelines, which can provide reference for venting system design and planned venting scheme design.

Key words: supercritical CO₂, CO₂ long-distance pipeline, venting, numerical simulation, scheme design

摘要：

放空系统是超临界CO₂长输管道的重要组成部分，已有的研究关于放空点位对CO₂管道放空特性的影响鲜有提及，而放空点位的确定对于放空系统及多管段计划放空方案设计非常重要。基于OLGA软件所建立的放空计算模型，对新疆已规划的某超临界CO₂长输管道多管段多点放空进行模拟研究。结果表明，放空远端点压降速率可间接反映出管道整体的放空速率；含中间阀室放空的多管段放空方案，中间阀室放空点的流体同时来源于上下游两段管道，该点的压力温度可由两个方向的高温高压流体进行补充，其压降及温降速率较端点放空点有所减缓；多管段放空时，随着放空点数的增加，相同放空点位置处压降及温降速率逐渐增大；双管单点放空方案管线最低点温度降至-20℃的时间为0.51h，总放空时长为4.29h，具有放空时长短，放空点温降、压降缓的优点。因此，超临界CO₂长输管道实施多管段放空时，推荐优先采用双管单点放空，即中间阀室放空方案，在保证温度可控的同时，实现二氧化碳的快速泄放。通过研究得到了超临界CO₂长输管道多管段放空作业时放空点的确定原则，可为放空系统以及计划放空方案设计提供参考。

关键词: 超临界CO₂, CO₂长输管道, 放空, 数值模拟, 方案设计