A Novel Design for Plate Heat Exchangers in LNG Liquefaction Cycle

LNG production is an intense and complex process, in which the liquefaction accounts for more than 50% of costs. In recent years, design engineers have been made several attempts to optimize this process. The main objective was to increase the production yield and capacity, and minimize the costs. The most important process equipment in liquefaction stage is devoted to compact heat exchangers of Plate Fin or Spiral Wounded types. This article described the simulation of liquefaction cycle of Iran LNG project with triple mixed refrigerant to provide a new method for designing the plate heat exchanger used in this cycle; in addition, a simple method was introduced for selecting the best secondary surface based on the conceptual development of the volume performance index (VPI). The designed exchanger had the minimum surface area and volume. The reduction of required heat transfer surface area had a significant role in the reduction of investment capital cost in LNG production process. The liquefaction cycle of Iran LNG was fully investigated in this article as an industrial case. According to the simulation, the cold and hot surface areas of the plate heat exchanger, used in the given process, are as large as 3001m2 and 1933m2 with the overall heat transfer coefficient of 425 W/m2K°; whereas, designing this exchanger by developed rapid design algorithm (RDA) significantly can be reduced the required cold and hot surface areas by 5.2 and 3.3 times, respectively. The overall heat transfer coefficient was also increased by 2 times.