The double mixed refrigerant liquefaction process has high efficiency and large capacity, which has obvious advantages under the conditions of stable sea and large amount of gas. The research verified the accuracy of the double mixed refrigerant flow, the adaptability of the liquefaction technology and the performance of the coil wound heat exchanger under sloshing conditions using the floating DMR experimental device which belongs to CNOOC gas electric R & D Center.
There are abundant gas and oil located in remote offshore regions. A large quantity of oil and natural gas was found in the East China Sea and the South China. Given the complexity of offshore production conditions and the economy of transportation equipment, FLNG-FPSO (LNG Floating Production Storage and Offloading unit) is a new conceptual unit and an effective and realistic way for offshore oil/gas exploration.
The complex marine environment proposes the high requirements for the device and process of FLNG. There are several processes for offshore natural gas liquefaction, such as Mixed Refrigerant liquefaction process, Nitrogen expander liquefaction process and cascade liquefaction process. Based on the previous researches, Nitrogen expander liquefaction processes have relatively weak processing ability, while MR liquefaction processes have high efficiency, great capacity and small land occupation in skid-mounted package.Mixed Refrigerant liquefaction process should be applied under the conditions of stable sea and large amount of gas.
The present papers about Mixed Refrigerant liquefaction process in the open literature force mainly on simulation and optimization of liquefaction process. Finn (2002) selected technology in LNG-FPSO design is the double nitrogen expander cycle. A similar concept was proposed by Wood, Mokhatab and Economides (2007) for plant capacities up to 3 million tones per annum. It was also noted (Barclay and Denton, 2005; Festen and Leo, 2009) that for an LNG-FPSO, except for very large ones, the expander processes (including nitrogen expander and methane-nitrogen dual expander process) would be preferred. Barclay and Yang (2006) introduced single mixed refrigerant process fully utilizing two-phase expander which is suitable for medium-scale and offshore natural gas liquefaction. SBM and Linde have performed a thorough evaluation process through comparing a wide range of processes and selected the Linde Multistage Single Mixed Refrigerant process (Meek, Cariou and Schier, 2009). Zubin Zhang et al.(2016) investigated MR composition and optimized MR composition using stepwise regression. Jianlu Zhu et al.(2012)simulated and compared six different processes which are suited to offshore liquefaction, analyzed their adaptability on sea. Hongpeng Du et al.(2011) simulated and compared three different offshore natural gas liquefaction processes. Wensheng Cao et al.(2015) simulated carbon dioxide pre-cooling and air-expander liquefaction process as FLNG process and analyzed the power consumption and safety. However, it is also found that not enough has been done on the experimental studies of MR process, especially experiments and adaptability analysis of whole liquefaction process.
