Mixed Refrigerant Composition Research Articles (Page 1)

A mathematical model based on energy and exergy methods is established to analyze the performance of an auto-cascade refrigeration system at varying compositions of the mixed refrigerants, condensation temperature, evaporation temperature, and vapor quality at the condenser outlet. Furthermore, grey correlation theory is employed to assess the correlation degrees between refrigerant mass fractions and system performance, enabling the identification of the state that has the greatest impact on the output parameters. It has been concluded that while maintaining a constant mass fraction of R600a, an increase in the mass fraction of R1150 (state 1) leads to a higher cooling capacity but a decrease in exergy efficiency. The performance decreases with the increase of the R600a mass fraction (state 2) as the R1150 mass fraction is unchanged. When the component of R14 is constant while the other two components R600a/R1150 vary (state 3), and the COP exists as the optimal value. The mixture of R600a/R1150/R14 with a mass fraction of 0.5:0.2:0.3 has better performance at COP of 0.5027 and exergy efficiency of 29.43 % under a condensation temperature of 30?. Based on the results of the grey correlation degree, the greatest factor in cooling capacity is state 1, while the COP and exergy efficiency are primarily controlled by state 3.

Numerical study of multicomponent mixed refrigerant composition regulation during natural gas liquefaction

Optimization method for mixed refrigerants in Joule–Thomson refrigerators with fixed-temperature heat loads

Liquefaction technologies of natural gas using a mixed refrigerant cycle provide a high liquefaction coefficient at low specific energy consumption, but are characterized by high requirements for the organization of production. There is no methodology for simultaneous optimization of the technical and economic parameters for the production process of liquefied natural gas and the composition of the refrigerant in publications, and therefore a combined optimization criterion is needed to achieve the minimum cost of liquefied natural gas. The aim of the work is to determine optimal pressure for natural gas inlet compression, taking into account the minimization of the complex criterion – the conditionally variable part of the cost of liquefied natural gas. The results were obtained using an applied calculation program, and the method of differential evolution was chosen as an optimization method. The optimization was carried out using the OCMR PEGAZ 1.0 program. The article considers the influence of the discharge pressure of the low-pressure natural gas inlet compressor on the technical characteristics of heat exchange equipment, the energy efficiency of the liquefaction process and the economic characteristics of a low-tonnage liquefied natural gas production plant under conditions of optimized composition and flow rate of mixed refrigerant. A method of optimizing process parameters taking into account economic indicators is proposed, regularities of changes in the optimal composition of mixed refrigerant depending on the discharge pressure of the natural gas inlet compressor are determined. It is determined that with an increase in the discharge pressure of the natural gas inlet compressor, the optimal content of components in the mixed refrigerant changes as follows: methane and n-pentane decrease, and ethane and isobutane increase. It is shown that the optimal discharge pressure range of the natural gas inlet compressor is 6,0±0,5 MPag, which leads to the best total energy efficiency of inlet compression and circulation of mixed refrigerant, equal to 0,25 kWh/kg of LNG, and its cost is minimal. The assessment of capital costs at this pressure will allow choosing the optimal technology of natural gas liquefaction at the FEED stage, which will reduce the cost of production of liquefied natural gas and reduce the payback period to 5 years.

A new strategy for mixed refrigerant composition optimisation in the propane precooled mixed refrigerant natural gas liquefaction process

Synthesis of N2-hydrocarbon refrigerant composition for maximum LNG production in PRICO processes

Process knowledge inspired opportunistic approach for thermodynamically feasible and efficient design of hydrogen liquefaction process

As the use of semiconductors in industrial site increases, research on ultra-low refrigerators is required to increase the life and quality of the semiconductors. While various types of refrigerators exist, Joule–Thomson refrigeration with the mixed refrigerant is preferred because of its compactness and stability. The performance of Joule–Thomson refrigeration with mixed refrigerants is based on the mixing ratio of the refrigerants. Therefore, in this study, three kinds of refrigerant groups, namely high boiling point (R-600a), middle boiling point (R-23), and low boiling point (R-14), are used to examine the change in the system’s performance according to the composition ratio of each refrigerant. The results indicate that as the ratio of the high boiling point refrigerant increases, the discharge, and suction temperature decrease. As the ratio of the middle boiling point refrigerant increases, the condensation pressure decreases, and thus, the inlet temperature of the expansion valve also decreases. As the ratio of the low boiling point refrigerant increases, the cooling capacity tends to increase.

Normalized sensitivity analysis of LNG processes - Case studies: Cascade and single mixed refrigerant systems

In this article, a precooling cycle was used to reduce the power consumption and improve the heat transfer efficiency of a mixed refrigerant cycle. Propane precooling and mixed refrigerant precooling are two common precooling methods. The cascade dual mixed refrigerant cycle, which involves mixed refrigerant precooling and has a specific power consumption 10.9% lower than that of propane precooling, has been widely used. In order to analyze the relationships among precooling temperature, mixed refrigerant composition, and specific power consumption, the specific power consumption of a cascade dual mixed refrigerant cycle was investigated. A mixed refrigerant cooling temperature of 223 K, a precooling mixed refrigerant comprising C2H6–C5H12, and a subcooling mixed refrigerant comprising N2 and CH4–C3H8 yielded optimal results. In addition, a mixed refrigerant component ratio optimization model was established for the dual mixed refrigerant cycle. The results indicated that the optimum mixed refrigerant component ratios corresponded with the lowest levels of specific power consumption. Furthermore, by studying the effects of the feed gas pressure and temperature on the mixed refrigerant component ratios, the optimal operating conditions of the cascade dual mixed refrigerant cycle were determined to be 5.0 MPa and 298 K.

Enhancement of single mixed refrigerant natural gas liquefaction process through process knowledge inspired optimization and modification

냉열을 이용한 랭킨 사이클 방식의 발전시스템에서 혼합냉매유체 조성비의 적용한계 분석

Design and comprehensive optimization of C3MR liquefaction natural gas cycle by considering operational constraints

Robustness analysis of the mixed refrigerant composition employed in the single mixed refrigerant (SMR) liquefied natural gas (LNG) process

Mixed refrigerant composition shift due to throttle valves opening in auto cascade refrigeration system

LNG plant requires a lot of energy for its production especially in liquefaction process. One of the reasons is due to inefficiency on some of its major equipments, particularly on Main Cryogenic Heat Exchanger (MCHE). The efficiency of this unit can be improved by the usage of Mixed Refrigerant (MR) which matches closely the heating curve between hot and cold stream. However, the study on this refrigerant is complex and tedious due to multi component refrigerant and phase changing process inside MCHE. In this study, effect of varying MR composition towards MCHE performance is analyzed, with focus on heat transfer coefficient in shell side of MCHE. The analysis was based on single and two phase flow conditions which are gas flow and liquid falling film flow. The adjustment of binary components in MR composition was studied for each flow regime. By doing this, the best composition adjustment that gives the highest value of heat transfer coefficient was determined. It was found that the adjustment of methane-propane (C1-C3) is the best arrangement for both cases. However, it needs to be tested by applying this to actual process condition, in this case by implementing it in simulated LNG process.

Optimization and analysis of mixed refrigerant composition for the PRICO natural gas liquefaction process

With the increased utilization of natural gas, there has been an increase in the research on peak-shaving natural gas liquefaction technologies. The NGE-MR natural gas liquefaction process, which precools natural gas with the cold energy generated by high pressure natural gas pipeline pressure energy recovery, is a promising technical candidate for peak-shaving LNG facilities. In this study, the effect of high pressure of the mixed refrigerant cycle (MRC) on the performance of the NGE-MR liquefaction process is analyzed under a fixed MRC pressure ratio. The result shows that for a certain mixed refrigerant composition, there is a corresponding optimal high pressure of the MRC, under which the minimum specific power of the liquefaction process could be obtained. The minimum specific power should be regarded as the evaluating indicator to represent the performance of the mixed refrigerant composition. Finally, the effect of mixed refrigerant composition on the performance of the NGE-MR liquefaction process is analyzed and the optimal operating conditions for the NGE-MR liquefaction process are obtained. As a result, the required specific power at the optimal operating conditions is less than 0.23 kW·h·kg-1 and is decreased by about 24% compared with the specific power of C3-MR natural gas liquefaction process.

The correlation between mixed refrigerant composition and ambient conditions in the PRICO LNG process

Development and analysis of a natural gas reliquefaction plant for small gas carriers