{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,8]],"date-time":"2026-02-08T04:21:09Z","timestamp":1770524469815,"version":"3.49.0"},"reference-count":28,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2025,12,26]],"date-time":"2025-12-26T00:00:00Z","timestamp":1766707200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Natural Science Foundation of China for Regional Fund","award":["52562047"],"award-info":[{"award-number":["52562047"]}]},{"DOI":"10.13039\/100009110","name":"Natural Science Foundation of Xinjiang Uygur Autonomous Region","doi-asserted-by":"publisher","award":["2023D01A19"],"award-info":[{"award-number":["2023D01A19"]}],"id":[{"id":"10.13039\/100009110","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Xinjiang Uygur Autonomous Region \u201cTianchi talents\u201d introduction plan project","award":["TCYC12"],"award-info":[{"award-number":["TCYC12"]}]},{"name":"Xinjiang Tianshan Innovation Team for Research and Application of High-Efficiency Oil and Gas Pipeline Transportation Technology","award":["2022TSYCTD0002"],"award-info":[{"award-number":["2022TSYCTD0002"]}]},{"name":"Xinjiang Uygur Autonomous Region \u201cOne Case, One Policy\u201d Strategic Talent Introduction Project","award":["XQZX20240054"],"award-info":[{"award-number":["XQZX20240054"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Supercritical CO2 pipeline transportation is a crucial link in Carbon Capture, Utilization, and Storage (CCUS). Compared with traditional oil and gas pipelines, if a supercritical CO2 pipeline is shut down for an excessively long time, the phase state of CO2 may transform into a gas\u2013liquid two-phase state. It is urgently necessary to conduct research on the phase change mechanism and safety control during the restart process of gas\u2013liquid two-phase CO2 pipelines. Based on a certain planned supercritical carbon dioxide pipeline demonstration project, this paper proposes a new pipeline safety restart scheme that actively seeks the liquefaction of gaseous CO2 inside the pipeline by injecting liquid-phase CO2 at the initial station. Through numerical simulation and experimental methods, the co-variation laws of parameters such as temperature, pressure, density, and phase state during the pipeline restart process were revealed. It was found that the pipeline shutdown and restart process could be subdivided into four stages: shutdown stage, liquefaction stage, pressurization stage, and displacement stage. The phase transition line would form a closed curve that is approximately trapezoidal. It is suggested to optimize the restart scheme from aspects such as reducing the restart time, controlling the pressure rise rate, and saving CO2 consumption. It is proposed that the liquid holdup of CO2 fluid in the pipe at the initial moment of restart and the mass flow rate of CO2 injected at the initial station during the restart process are the main controlling factors affecting the evolution of the phase path of pipeline restart. For the demonstration project, the specific critical threshold values are given. The research results can provide a certain theoretical guidance and reference basis for the safe restart method of supercritical CO2 pipelines.<\/jats:p>","DOI":"10.3390\/molecules31010104","type":"journal-article","created":{"date-parts":[[2025,12,28]],"date-time":"2025-12-28T23:54:36Z","timestamp":1766966076000},"page":"104","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Phase Change Mechanism and Safety Control During the Shutdown and Restart Process of Supercritical Carbon Dioxide Pipelines"],"prefix":"10.3390","volume":"31","author":[{"given":"Xinze","family":"Li","sequence":"first","affiliation":[{"name":"School of Engineering, China University of Petroleum (Beijing) at Karamay, Karamay 834000, China"},{"name":"Xinjiang Key Laboratory of Multi-Medium Pipeline Safety Transportation, Urumqi 830011, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0009-0288-9898","authenticated-orcid":false,"given":"Dezhong","family":"Wang","sequence":"additional","affiliation":[{"name":"School of Engineering, China University of Petroleum (Beijing) at Karamay, Karamay 834000, China"},{"name":"Xinjiang Key Laboratory of Multi-Medium Pipeline Safety Transportation, Urumqi 830011, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Weijie","family":"Zou","sequence":"additional","affiliation":[{"name":"PipeChina West Pipeline Co., Ltd., Urumqi 830011, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jianye","family":"Li","sequence":"additional","affiliation":[{"name":"School of Engineering, China University of Petroleum (Beijing) at Karamay, Karamay 834000, China"},{"name":"Xinjiang Key Laboratory of Multi-Medium Pipeline Safety Transportation, Urumqi 830011, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xiaokai","family":"Xing","sequence":"additional","affiliation":[{"name":"School of Engineering, China University of Petroleum (Beijing) at Karamay, Karamay 834000, China"},{"name":"Xinjiang Key Laboratory of Multi-Medium Pipeline Safety Transportation, Urumqi 830011, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,12,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1038\/s41558-019-0659-6","article-title":"Carbon dioxide emissions continue to grow amidst slowly emerging climate policies","volume":"10","author":"Peters","year":"2020","journal-title":"Nat. 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