Linde LNG terminal pre-cooling project
-CNOOC Tianjin Liquefied Natural Gas (LNG) Co., Ltd.
中海油天津液化天然气有限责任公司
秉承“奉献清洁能源、创造美好生活”的愿景,中海油天津液化天然气有限责任公司致力于液化天然气清洁能源的推广利用,是中国首个引入浮式LNG接收终端技术的企业。公司主导建设的天津LNG项目,不仅是国家试点清洁能源工程,天津市重点工程,也是中国海洋石油总公司的重点工程。
此次中海油天津液化天然气LNG卸料管预冷项目的要求,是LNG运输船舶进行液化天然气卸料前,林德根据降温曲线向卸料管内注入低温氮气,将管道温度由常温降低到-120℃,从而减少低温液化天然气在管道内遇热蒸发造成的浪费,同时减少向大气的废气排放。
项目难点
目前国内尚无针对LNG管道进行预冷的成熟方案,如果方案制定不周详或者操作失误,会在管道内形成温度分层,甚至造成管道底部液氮堆积过冷,进而损害设备安全。林德的项目方案确保在每个注氮点进入管道的氮气都能在规定时间内精准地将管道温度降低到设定温度,并防止管道积液和温度分层。
林德解决方案
林德团队基于LNG管道预冷时间,针对现场管道实际走向、长度及林德设备特点,进行设备配置和方案设计。方案的难点是防止管道积液和温度分层,因此整个方案必须严格按照设定的降温曲线进行降温。林德天津团队利用软件对各注氮点的注氮量和温度变化进行了详细的推算,反复和客户沟通并进行现场调研,对操作中各种可能发生的突发情况准备了全面的预案。LNG管道预冷项目于2014年11月完成,项目方案圆满达到客户预期。
此次项目中,林德帮助客户减少了低温液化天然气的浪费,为客户节省了宝贵的能源消耗,并减少了天然气向大气的污染排放。如果今后采取进一步优化方案,更多采用数字化仪表进行自动检测和控制,并使用液氮雾化技术,将可更精确地控制液氮使用量,并节省人工投入。
由于林德在中海油天津液化气LNG预冷项目的出色发挥和优质服务,建立了良好的信誉,中国海洋石油总公司已将林德列为LNG预冷项目的合格供应商,为林德今后和中海油的更多合作打下了扎实基础。
CNOOC Tianjin LNG Co., Ltd.
Aiming to "dedicate clean energy and create a better life", CNOOC Tianjin LNG Co., Ltd. is committed to promotion and use of clean energy of LNG. It is the first enterprise to introduce floating LNG receiving terminal technology in China. Tianjin LNG project led and constructed by CNOOC Tianjin LNG Co., Ltd. is not only a pilot clean energy project nationwide and key project in Tianjin, but also a key project launched by CNOOC.
In the light of Tianjin LNG discharge pipeline pre-cooling project of CNOOC, Linde is required to inject cryogenic nitrogen into the discharge pipeline pursuant to the cooling curve before discharge of LNG from carrier ship so as to cool the temperature of pipeline from room temperature to -120℃ and thereby minimize the waste caused by evaporation of low temperature LNG within the pipeline and the emissions to the atmosphere.
The challenges
At present, there is no sophisticated plan for pre-cooling of LNG pipelines in China. In the event of any negligence in planning or any error in operation, there will be temperature stratification within the pipeline, or even accumulation of liquid nitrogen at excessively low temperature at bottom of pipeline, thus causing damages to the equipment. Linde's project plan can ensure that the nitrogen injected into the pipeline at each injection point will accurately cool the pipeline to the set temperature within the time limit as required and prevent fluid accumulation or temperature stratification in pipeline.
Linde solutions
Based on the time spent on LNG pipeline pre-cooling, Linde team worked on device configuration and plan design in view of actual layout and length of pipeline on site and features of Linde equipment. The difficulties of the plan are how to prevent fluid accumulation and temperature stratification in the pipeline. So during the entire plan, it is imperative to cool the temperature in strict accordance with the set cooling curve. Linde Tianjin team employed software to make meticulous estimate for nitrogen injection amount at each injection point and the change in temperature, repeatedly communicated with customers and performed research on site to prepare a comprehensive plan on various potential emergencies likely to occur in the course of operation. LNG pipeline pre-cooling project was completed in November 2014 to the satisfaction of our customer.
In this project, Linde helped customer reduce waste of cryogenic LNG, to save valuable energy consumption and decrease gas emissions into the atmosphere. Should further optimization steps be taken in the future, the digital instrumentation will play an even greater role in automatic detection and control, with introduction of liquid nitrogen atomization technology, to control the amount of liquid nitrogen more precisely and save manpower cost.
Owing to the outstanding performance and excellent service in CNOOC Tianjin LNG pre-cooling project, Linde has established a good reputation, and ranked among CNOOC’s qualified suppliers for LNG pre-cooling project, which has laid a solid foundation for more cooperation between Linde and CNOOC in the future.