Title : A study on the possibility and optimization of SMR cycle natural gas liquefaction process for LNG-FPSO using polar seawater temperature
Abstract:
Recently, as the demand for natural gas has increased, the global liquefied natural gas (LNG) market has also expanded significantly. Consequently, several new LNG production projects are currently under development worldwide. The Arctic region is believed to contain significant deposits of natural gas. According to estimates from the US Geological Survey, the Arctic region may hold up to 1,669 trillion cubic feet of technically recoverable natural gas resources, accounting for approximately 25% of the world's total. Nowadays, several LNG projects are being planned or developed in the Arctic region. However, accessing and developing most other potential natural gas deposits in the Arctic region is challenging due to the region's specific characteristics. Mining natural gas and employing LNG production methods using LNG-FPSO are expected to offer significant advantages in developing various small and medium-sized gas fields located in the sea and along the coast of the Arctic region. The LNG-FPSO is an innovative solution for offshore natural gas liquefaction, providing flexibility and cost-effectiveness in remote locations. However, compared to the existing Cascade method, the liquefaction of natural gas in LNG-FPSO requires a significant amount of power and refrigerant consumption. This is because LNG-FPSO aims to minimize the need for liquefaction facilities, and SMR (Single Mixed Refrigerant) refrigeration cycles with simple structures are generally utilized for natural gas liquefaction. Therefore, this study focuses on the following objectives to enhance the overall efficiency and sustainability of LNG-FPSO operations while reducing harmful emissions:
1. Reducing the total refrigerant usage required for the SMR refrigeration cycle.
2. Decreasing compressor power consumption, which is the primary contributor to power consumption in SMR refrigeration cycles.
3. Substituting environmentally harmful or expensive refrigerants with environmentally friendly and cost-effective alternatives.
To achieve these goals, this study presents the concept and feasibility of the SMR liquefaction process using polar seawater temperature and optimizes it using HYSYS, a process simulation program. In this study, natural gas liquefaction was conducted by mixing propane, ethylene-based (R-1150), methane, and nitrogen refrigerants. Taking Sakhalin-3, a representative medium-scale natural gas production project, as a reference, LNG production was assumed to be 6,741 kg/hour. Additionally, the average seawater temperature in the Arctic region, -2?, was utilized as the temperature of the polar seawater used for cooling. As a result, the total refrigerant flow rate used in the entire SMR refrigeration cycle was reduced by approximately 8.66%, from 37,114 kg/hour to 33,900 kg/hour. Among them, the flow rate of the hydrocarbon refrigerant, which was 12,434 kg/hour, was replaced by a more environmentally friendly and cost-effective nitrogen refrigerant with a flow rate of 7,038 kg/hour. Furthermore, the compressor power consumption of the SMR liquefaction process could be reduced from 4,335 kW to 2,182 kW, representing a decrease of about 49.67%. This study demonstrates the potential of utilizing polar seawater temperature in the SMR cycle of the natural gas liquefaction process for LNG-FPSO. Further research and development are needed to refine the optimization strategies and validate the feasibility on a larger scale.
Audience Take Away:
- The audience can gain knowledge about the design of the SMR cycle LNG liquefaction process and the natural gas cooling system that utilizes the ocean temperature difference. This information can be used to conduct in-depth research on the LNG industry in the polar region.
- The utilization of a natural gas cooling system that employs cold seawater in the polar region is expected to assist the audience in determining the power consumption and flow rate of propane, ethylene, and methane refrigerants required for the SMR natural gas liquefaction process facility in the polar region.
- The design of the SMR LNG liquefaction process can serve as a basis for lectures on its fundamental concepts. The process itself utilizes a cooling system that takes advantage of the temperature difference in the polar region, resulting in high efficiency through a design method that employs simple ideas and variables. This applied concept is beneficial for both lectures and research.
- The natural characteristics of the polar region can be utilized to increase the efficiency of natural gas liquefaction, as opposed to using power, without requiring complicated additional processes. This solution may simplify the designer's job, making the process more efficient.
