Title : A study on cascade cycle natural gas liquefaction process using polar sea temperature
Abstract:
Recently, in order to achieve the global objective of reducing greenhouse gas emissions, renewable energy technologies are growing rapidly. There are still several challenging challenges that need to be overcome, such as low energy efficiency, intermittency, grid infrastructure, cost, and more. Nowadays, demand for natural gas as an alternative energy source is growing at a time when it is unknown when renewable energy technologies will be able to fully replace fossil fuels. As demand for natural gas increased, the global liquefied natural gas (LNG) market also expanded significantly. Accordingly, several new LNG production projects are under development worldwide. Particularly in the Arctic region is believed to contain significant deposits of natural gas. According to estimates from the US Geological Survey, the Arctic region may contain up to 1,669 trillion cubic feet of technically recoverable natural gas resources, which accounts for approximately 25% of the world's total. There are several LNG (liquefied natural gas) projects being planned or developed in the Arctic region nowadays. There are notable examples such as the 'Yamal LNG' and 'Arctic LNG 2' projects in Russia. In addition to these projects, there are also plans for other LNG projects in the Arctic region, including Canada and Norway. Based on this background, the concept of a liquefaction process using seawater temperature in the polar region was established as a means of increasing productivity in LNG production facilities while reducing harmful emissions. Research was conducted using the Cascade cycle liquefaction process, which is a three-step liquefaction cycle utilizing propane, ethylene, and methane refrigerants in that order. The flow rate of natural gas flowing into the LNG production facility was arbitrarily set at 1000 kg/h. Since the seawater temperature can only be used in the first-stage liquefaction cycle using propane refrigerant, the power consumption of the compressor and condenser in this cycle and the flow rate of the propane refrigerant were measured. As a result, the study found that the power consumption of the compressor and condenser in the existing Cascade cycle, operated in an environment up to 40 degrees Celsius, was 35.3kW and 95.86kW, respectively, with a propane refrigerant flow rate required for cooling of 927.2kg/h. However, when the polar seawater temperature was used in the liquefaction process, the operating environment was -2 degrees Celsius, and the power consumption of the compressor and condenser was reduced to 6.321kW and 33.63kW, respectively, while the required propane refrigerant flow rate was 292.7kg/h. To summarize, the study found that utilizing polar seawater temperature in the first-stage liquefaction cycle using propane refrigerant reduced power consumption by 29.35% and propane refrigerant flow by 30.11% when compared to the existing Cascade cycle operated in an environment up to 40 degrees Celsius.
Audience Take Away:
- The audience can gain knowledge about the design of the Cascade 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 Cascade natural gas liquefaction process facility in the polar region.
- The design of the Cascade 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 efficiencythrough 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.
