Experimental study on the safety of dry ice freeze plugging by throttling effect during pressure relief of industrial CO2 pipeline

Abstract

In the pipeline transportation of Carbon Capture Utilization and Storage (CCUS) technology, the manual pressure relief method is a key mean in pipeline maintenance work. However, dry ice will be generated in the pipeline during the large-scale pressure relief process, so it is necessary to assess the risk of dry ice freezing and plugging, and then to develop a reasonable and safe pressure relief scheme. In this study, three types of manual pressure relief experiments with different schemes were carried out based on an industrial-grade pipeline experimental platform. The influence of throttling effect was considered in the experimental study, and the generation and change of dry ice in the pipeline during the pressure relief process were investigated. On this basis, additional throttling levels were added, and then discussed the region of dry ice distribution in the pipeline under multi-stage throttling and the resulting evolution of the pipeline's low temperature characteristics. The results show that throttling prevents dry ice particles from flowing out of the pipeline and increases the dry ice accumulation at the outlet end of the pipeline, leading to a more severe temperature drop. When the throttling level was increased, the dry ice buildup was further severe, causing a high probability of freezing and plugging of the valve position. The specification of the experimental pipeline is the actual industrial grade, so the results of the study have a realistic guiding value for the development of safety relief programs for industrial CO₂ transportation pipelines, and also provide a reliable theoretical basis for the assessment of the dry ice risk.