Study on cold box lift of mixed refrigerant liquefaction process in LNG plant

In order to study the way of mixed refrigerant liquefaction situation and its adjustment in LNG plant, taking the actual production conditions of Hubei 5 million cubic meters/day LNG plant localization demonstration project (from 4 million cubic meters/day to 5 million cubic meters/day) as an example, the data about each measuring point temperature changes, mixed refrigerant components, differential pressure, and adjusting operation collected from the quantity improving were analyzed comprehensively. The results showed that: 5 million cubic meters/day LNG plant in Hubei combined traditional cascade refrigeration cycle with mixed refrigerant refrigeration cycle, which has advantages both on the system stability and adjustability. In the case of uneven heat transfer of cold box, the plant can still operate normally. However, before improving quantity the system occurs uneven cooling mixing and two phase flow in the cold box, etc. During improving quantity, although taking the measures of dropping amount and recovering heat, raising production by curves, and improving rotating speed of compressor and optimizing BOG for enhancing the system stability, the influence by uneven refrigerant mixing cannot be solved entirely. For this reason, we should made the feasible plans and the periodic verification at the each stage during improving quantity.