LNG加气站BOG再液化工艺

BOG reliquefaction process in LNG filling station

为了减少LNG加气站中BOG直接放空造成的环境污染与能源浪费,以加气能力为1×104 m3/d的LNG加气站为例,计算BOG的日蒸发量,并使用HYSYS软件模拟适用于该LNG加气站的BOG再液化工艺流程,逐步优化制冷网格,计算该加气站BOG再液化所需的LNG流量。对于加气能力为1×104 m3/d的LNG加气站,增设1套BOG再液化装置(1台BOG压缩机、1个BOG缓冲罐、1台再冷凝器及1个调压阀),即可实现BOG的再液化。调节流程中各节点参数后得出:当过冷LNG的流量达到90 kg/h时,BOG完全冷凝。该BOG再液化流程利用LNG自身冷量冷凝BOG,并回注于LNG储罐中,不仅可提高BOG回收率,使其在LNG加气站中循环利用,保证罐内温度、压力在一定范围内,同时可有效地减少LNG冷能浪费。(图4,表7,参10)

In order to reduce the environmental pollution and energy dissipation caused by direct BOG venting in LNG filling station, taking the 1×104 m3/d capacity of LNG filling station as an example, the BOG volume per day is calculated. BOG reliquefaction process applied in this LNG filling station is simulated by HYSYS, and refrigeration grid is optimized step by step. Then, the required LNG flowrate for BOG reliquefaction in this station is calculated. For the LNG filling station, the BOG reliquefaction can be realized with the addition of one set of BOG reliquefaction plant（including 1 BOG compressor, 1 BOG buffer tank, 1 recondenser and 1 pressure regulating valve）. After parameters at each node of the process are adjusted, when the LNG flowrate reaches 90 kg/h, BOG is condensated completely. The BOG is condensated in this process by using LNG cold quantity, and reinjected into the LNG tank. In this way, the BOG recovery is improved so as to realize its circulation in the LNG filling station and accordingly ensure the tank temperature and pressure within a certain range, and the LNG cold energy waste can be effectively reduced.