海上CCS长距离海管输送相态及关键参数研究

Research on Transportation Phase State and Key Parameters for the Offshore CCS Longdistance Subsea Pipeline

CO_(2)海底管道是目前海上CCS(Carbon Capture and Storage)实现CO_(2)从陆地转运至海上的重要方式。相比于CO_(2)陆地管道,CO_(2)海底管道投资成本高、检测监测难度大、维修维护费用高,对输送的安全性和经济性提出了更高的要求。基于东海自然环境条件,考虑CO_(2)封存量在1、5、10 Mt/a下,利用OLGA软件,采用PR气体状态方程,开展了CO_(2)在气态、液态、密相和超临界相四种相态下的长距离海底管道(300 km)仿真模拟研究,并对起输相态、起输温度和起输压力参数优选进行了分析研究。结果表明:针对CO_(2)长距离海底管道,采用密相输送具有较好的经济性与可行性,但需保证CO_(2)输送压力始终在临界压力之上;在海上封存潜力允许的情况下,增大CO_(2)输量能够有效降低CO_(2)输送成本;由于海底管道特殊性,起输相态采用密相更有利于输送;起输温度对CO_(2)流体管道沿程输送特性影响较小,而起输压力是影响管道输送特性及管径选择的一个重要敏感因素,对海底管道建设投资和操作成本影响显著,起输压力在9~12 MPa之间具有良好的综合经济效益。

It is an important way for current offshore CCS(Carbon Capture and Storage)projects to transport CO_(2)from onshore land to offshore site by CO_(2)subsea pipelines.Compared to CO_(2)onshore pipelines,CO_(2)subsea pipelines have high investment costs,difficulty in detection and monitoring,and high maintenance costs,thus proposing higher requirements for the safety and economy of transportation.Based on the natural environmental conditions of the East China Sea,considering the annual CO_(2)storage capacity at 1,5,and 10 Mt/a,OLGA software and PR gas state equation are used to simulate the four phase states(gas,liquid,dense,supercritical)of CO_(2)long-distance(300 km)subsea pipeline transportation.The optimization of parameters such as starting phase state,starting temperature,and starting pressure are analyzed and studied.The results indicate that dense phase transportation has good economy and feasibility for long-distance CO_(2)subsea pipelines,but it is necessary to ensure that the pressure of CO_(2)is always above the critical pressure.If the potential for offshore storage allows,increasing CO_(2)output can effectively reduce CO_(2)transportation costs.Due to the particularity for subsea pipelines,it is more suitable to use the dense phase as starting phase state,the starting temperature has a relatively small impact on the transportation characteristics of CO_(2)fluid along the route,while the starting pressure is a highly sensitive factor that affects the transportation characteristics and diameter selection of pipelines,and has a dramatic impact on the investment and operating costs of CO_(2)subsea pipeline construction.Generally,the starting pressure of 9-12 MPa has a good comprehensive economic benefit.