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Edition and Publication:
< Natural Gas and Oil > Editorial Department
Hosted by:
China Petroleum Engineering & Construction Corporation Southwest Company
Authorized by:
China Petroleum Engineering & Construction Corporation
Co-hosted by:
Overseas Research Center of Research Institute of Petroleum Exploration and Development
Editor in Chief:
Du Tonglin
Vice Editor in Chief:
Tang Xiaoyong,Pu Liming
Address:
No.6, Shenghua Road, High-tech District, Chengdu, Sichuan, China
Postal Code:
610041
Tel:
028-86014709
028-86014500
Email:
cnpc-ngo@cnpc.com.cn
Issue:ISSN 1006-5539
CN 51-1183/TE

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Online Sampling Technology Used for LNG Terminal Custody Transfer

Author of the article:Zhang Yi, Ai Shaoping, Wang Hao, An Na

Author's Workplace：PetroChina Jing-Tang LNG Co., Ltd.,

Key Words：LNG terminal; Metering; Online sampling; Fractionation; Super cooling; Probe; Vaporizer; Supercritical

Abstract：Accurate online sampling is necessary to obtain LNG heat value during its unloading at LNG terminal and it is the precondition of accurate custody transfer. Analyzed are technological processes of custody transfer metering and online sampling and online sampling system structure, studied is the key technology used in sampling process and proposed are control requirements of sampling system. Analysis and study results show that online sampling shall be completed during full speed unloading process when gas quality transition flow is smooth and unloading rate and pressure are stable so as to ensure the representative of samples. LNG samples shall be kept in super cooled state before being put into the vaporizer in order to prevent gasification and fractionation. All of LNG samples shall be gasified fully and not condensate in supercritical state when passing the vaporizer so as to keep the same components with those of original samples, which is the key controlling factor of sampling. The key parameters shall be closely monitored throughout the whole sampling process. Therefore, selection of sampling time is very important and sampling system shall have good property.