管道输送二氧化碳泄漏模型研究进展及展望

Advances and prospects of the study of modeling CO_2 accidental releases from a pipeline

随着碳捕集和储存(Carbon Capture and Storage,CCS)项目的深入开展与大规模长输管线的大量应用,管道的破裂、泄漏将会造成重大事故。通过查阅国内外近几年的文献,提出了3种针对不同泄漏口径下CO2管道泄漏率的计算模型;阐述了CO2管道泄漏的3个阶段的物理过程;考虑到CO2特殊的相态特性,分析了其泄漏后形成干冰的可能性,并进一步讨论了泄漏方向和埋地管道对泄漏后形成干冰堆积的可能性的影响。现有的计算模型在模拟气固两相射流方面还不完善,也无法完整地模拟整个泄漏过程。未来CO2泄漏的研究一方面需要通过试验来验证水平方向泄漏及埋地管道泄漏是否会形成干冰堆积,另一方面要在结合实际情况的基础上完善和整合泄漏模型,并通过全尺寸试验和缩比试验对模型进行验证。

The paper is to present the research advances and prospects of modeling CO2 accidental releases from the pipeline. As a matter of fact, with the CCS projects moving forward, large-scale long-distance pipeline transmitting of CO2 has become more and more popular in China as well as in the world. However, if the pipeline breaks up or leads the gas-release through, unexpected disasters and even catastrophes would result in, from which comes the great need to study how to prevent such accidents and determine the underlying risks due to the use of CO2 pipelines. It is just due to the above reasons that push us to pick up such a research topic and establish our own model. As the first step, we have collected and studied the papers published in recent years and summarized three methods for the CO2 releasing rate from the pipelines in dependence of the different sizes of the holes or a complete break of a pipe. In the hole-type model, it is believed that only when the diameter of the cross-section of the pipe is approximately equal to no more than 20 mm, would it be easy to work out the likely leakage involved, though the scenarios of the likely release and leakage rate can be very limited. Since the hole-pipe generalized model is well accepted, in spite of its high cost for the calculation with iteration arithmetic. And, the next step is to discuss the three processes of release, that is, the jet expansion, the dense gas dispersion and the dry ice bank sublimation. Although it is similar to release CO2 from the pipeline and release other compressed or liquefied gas from other processes, it is known that CO2 can not be liquefied under the normal atmospheric pressure but only under the accumulation of dry ice bank. Therefore, according Joule-Thompson Effect, if CO2 is released from the pipeline under the liquid phase or supercritical phase, the temperature of CO2 release could be reduced significantly to make the temperature after volume expansion lower than its sublimation point. From what is said above, it can be seen that this paper has analyzed the possibility to form the dry ice, and discussed the influence of release direction and the condition of the pipelines buried. Since the present mathematical models for gas-liquid-solid phase transformation are not perfect, there is no model that can simulate the whole release process perfectly. Therefore, it would be necessary in future to determine through experiments whether an ice bank can form the condition of horizontal release or from the buried pipelines on one hand, and, on the other hand, it is needed to perfect and integrate the release models, so as to verify them with experiments in combination with the actual technical realities.