Wonsub Lim

Optimization of mixed-refrigerant system in LNG liquefaction process

Abstract LNG liquefaction is an energy intensive process. For this reason, various liquefaction processes for saving energy exist. Searching optimal process condition is very difficult because of its high nonlinearity. Pressure level, refrigerant flowrate, and refrigerant composition are key operation variables to reduce energy consumption. These variables play an important role in affecting the overall performance. Compressor is a major energy-consumption unit in LNG plant and it spends much energy depending on operating conditions. In this paper, searching optimal condition is carried out by using simultaneous optimizations. NLP model is applied for the SMR process. The optimization result shows that refrigerant composition is a major key variable and half of energy consumption can be reduced by changing operating conditions and refrigerant composition only.

Integration of qualitative and quantitative risk assessment methods for gas refinery plants

This paper focuses on the development of an integrated risk assessment system to increase the safety of gas refinery plants. This integration is important in managing the design and the operation of chemical plants and it requires significant time, effort and specialized expertise. We propose a systematic procedure to apply quantitative and qualitative hazard identification methods before constructing the refinery plants. Advantages of this assessment procedure are 1) systematic method in identifying most of the important hazards, 2) complete and rigorous analysis, and 3) reducing budget and time. The qualitative and quantitative assessment method consists of two and three steps, respectively. After these five steps, the risk of the same plant was calculated and analyzed. This method can identify risk and potential hazards from local gas refinery plants effectively and systematically. We applied the integrated qualitative and quantitative risk assessment method to remove the risk of a local gas refinery plant with 160 P&ID sheets. The result of this work confirmed that no residential population existed within the bounds of the 1×10−6 per annum risk contour. Therefore, the risk to the public from the gas refinery plants should be considered acceptable.

Optimization of Pure-Refrigerant Cycle Compressing Ratio on C3-MR Process

Abstract The natural gas liquefaction process is an energy intensive process due to its low temperature. Compressor units are one of primary factors in minimizing energy consumption of natural gas liquefaction process. Among various natural gas liquefaction processes, C3-MR (Propane Pre-cooled Mixed-Refrigerant) process is the most commonly used in LNG market. C3-MR process uses two types of refrigerants such as mixed-refrigerant and pure-refrigerant. In this study, pure-refrigerant cycle is simulated, along with different compressing ratios and different pressure levels. The simulation of case studies shows that energy consumptions mainly depend on both compressing ratios and pressure levels.. This study has achieved the energy consumption savings by 27.7% through different case studies with an emphasis on compressing ratios and pressure levels.