Refrigerant Composition Research Articles

The increasing global demand for natural gas as a cleaner energy alternative has intensified the need for more energy-efficient liquefaction technologies. One of the key components in natural gas liquefaction is the refrigeration cycle, where the choice of refrigerant significantly influences system performance. Propane is widely used due to its favorable thermodynamic properties. However, there is growing interest in optimizing its performance through refrigerant blending. This study investigates the impact of different propane-based refrigerant mixtures, namely propane-NH₃, Propane-SO₂, and propane-CO₂ on the coefficient of performance (COP) in a natural gas liquefaction cooling cycle. Simulation results at two operating temperatures (-15.11°C and -20°C) demonstrate that refrigerant composition plays a crucial role in determining system efficiency. At -15.11°C, pure propane exhibited a COP of 2.79, while mixtures with NH₃ and SO₂ significantly improved performance, achieving peak COPs of 6.25 and 6.42, respectively, at a 1:9 mixing ratio. Similar trends were observed at -20°C, where the highest COP values for propane-NH₃ and propane-SO₂ mixtures were 5.79 and 5.96, respectively. In contrast, the propane-CO₂ mixture consistently yielded the lowest COP values, indicating inferior energy efficiency. These findings suggest that incorporating NH₃ or SO₂ into propane-based refrigeration cycles can substantially enhance the energy performance of natural gas liquefaction processes, whereas propane-CO₂ blends may increase energy consumption and operational costs.

Machine learning-driven optimization of refrigerant compositions for hydrogen liquefaction pre-cooling: A hybrid approach combining entropy prioritization, k-means clustering, and GMM refinement

Advanced dual mixed refrigerant (DMR) natural gas liquefaction plant with liquid air: Focus on configuration and optimization

Combined effect of refrigerant amount reduction and composition change on heat pump system performance during refrigerant mixture leakage

Performance improvement and multi-objective optimization of a two-stage and dual-temperature ejector auto-cascade refrigeration cycle driven by the waste heat

Innovative approaches to optimizing Li-Ion battery cooling performance using gas mixtures

Liquefied natural gas (LNG) technology, particularly the propane precooled mixed refrigerant (C3MR) process, has demonstrated efficiency and emerged as a distinctive dual-refrigerant technology widely used in LNG production. However, the liquefaction process is the highest energy-intensive stage within its supply chain as it consumes about 8 % of the LNG energy content. Thus, for the first time, this study proposes systematic knowledge-based and constrained Bayesian optimization approaches to identify the optimal operation of the C3MR process. These approaches optimize both the operational parameters (pressures and flow rates) and the composition of the mixed refrigerant with practical equipment specifications and rigorous constraints. The results show that the specific energy consumption (SEC) is reduced to 0.264 kWh/kgLNG, which is 14.6 %, and 26 % lower than the basic C3MR process (unoptimized case) and typical industrial C3MR processes, respectively. In addition, the optimized SEC in this study is 14.5 % to 38.6 % lower than those reported in the literature. At large-scale LNG production (10,000 tons per day), the reduction in the SEC is translated into an 18 MW decrease in compression power, saving approximately 4.7 million $ per year for each C3MR train. Moreover, the coefficient of performance (COP) of the C3MR process was improved by about 15 %, and the CO2 emissions were reduced by 17 % (7 tons per year) compared to the basic C3MR process, indicating potential advancements in large-scale LNG liquefaction processes.

Experimental study on performance characteristics of a −70 °C ultra-low temperature medical freezer with mixed hydrocarbon refrigerant

Abstract Joule–Thomson (J–T) refrigerators or J–T cryocoolers are extensively used in many low-temperature applications. J–T refrigerators operating with nitrogen–hydrocarbon (N2-HC) refrigerant mixtures offer several advantages, such as low operating pressures (<20 bar), high exergy efficiency, no moving parts in the cold section, and low cost. The cooling power or cooling capacity of the J–T refrigerator depends on the hardware used as well as the refrigerant composition. The proposed work focuses on estimating the cooling capacity of a mixed refrigerant J–T (MRJ–T) refrigerator of the given hardware and specified refrigerant. An iterative steady-state full-cycle simulation procedure has been presented in this work to simulate the complete system and estimate the cooling capacity, taking into account the possibility of choking of the expansion capillary. Some of the results have been validated against experimental results of an MRJ–T refrigerator available in the open literature. Details of the simulation model and the results of our studies on the prediction of stable operating range, maximum cooling capacity, the effect of heat exchanger geometry, expansion capillary geometry, mixture composition, and choking of the refrigerant mixture on the performance of an MRJ–T refrigerator are presented in this article.

Condensation heat transfer of zeotropic refrigerant mixtures R407C and R448A in a horizontal smooth tube

Mixed-refrigerant Joule-Thomson refrigeration (MJTR) is an important cooling method at temperatures from 80 to 230 K. It can be used in cryosurgery, high-temperature superconductivity and sensor cooling etc. However, most of the studies are on nitrogen-hydrocarbon refrigerants, which are not allowed in applications where there is a special need to avoid flammability risks. Therefore, non-flammable mixed refrigerants were investigated in this study.The composition of the mixed refrigerant is a key factor in the system performance (refrigeration temperature, refrigeration capacity, etc). However, the purely mathematical optimization methods lack system knowledge in the optimization of the process, and may have the disadvantages of being a time-consuming process. In this study, the isothermal throttling effect of mixed refrigerants is optimized, and the optimization process is based on the partial molar enthalpy difference of each component. The method is based on thermodynamic properties and is time-saving relative to purely mathematical optimization techniques.Non-flammable mixed refrigerants (NFMR) with refrigeration temperatures from 100 K to 140 K were designed in this study. The results show that the designed mixed refrigerant has a higher COP compared to the reference. Argon has an advantage at refrigeration temperatures from 120 K to 140 K, while nitrogen has an advantage from 100 K to 120 K. In addition, mixed refrigerants for systems with pre-cooling stage were optimized and the results showed that the highest exergy efficiency is achieved at a pre-cooling temperature of 250 K. The exergy efficiencies with pre-cooling stage are nearly twice as high as those without that. Therefore, a pre-cooling stage for nonflammable mixed refrigerants is necessary where there is no requirement for system size.

Study on a novel hydrogen liquification process applying mixed-refrigerant for pre-cooling and cryogenics

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

Performance comparison of pure, binary and ternary refrigerants considering different systems

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