Natural Gas Liquefaction Research Articles

Assessment of conventional and enhanced exergy analysis of the natural gas liquefaction plant

Assessment of conventional and enhanced exergy analysis of the natural gas liquefaction plant

Assessment of Conventional and Enhanced Exergy Analysis of the Natural Gas Liquefaction Plant

Assessment of Conventional and Enhanced Exergy Analysis of the Natural Gas Liquefaction Plant

Review of Reliquefication Plant System for Liquified Natural and Petroleum Gas Carriers

Abstract: The effectiveness of the liquefaction process for natural and petroleum gas is crucial to the supply chains overall production capacity, energy use, economics, and safety. Many academics have developed several traditional methods and undertaken a lot of research on various LNG/LPG processes. The optimization and design of petroleum and natural gas liquefaction processes during the last few years are summarized and discussed in this study. Comparing and contrasting the benefits and drawbacks of various liquefaction methods. Furthermore, highlighted are the recent fast advancements in pressurized liquefaction technology and its anticipated applications.

SIMPLIFIED HYDRAULIC CALCULATION OF THE CRYOGENIC PIPELINE OF EXTERNAL FACILITIES FOR FILLING LIQUEFIED NATURAL GAS

Natural gas is a mineral that is the most environmentally friendly energy fossil raw material. In recent decades, proven natural gas reserves have equaled oil reserves in terms of their indicators and, moreover, continue to grow actively. In this regard, the issue of transportation and storage of natural gas becomes relevant. One actively developing area has become the industry of natural gas liquefaction, transportation and distribution.The paper discusses the issues of shipment of liquefied natural gas (LNG) to gas tankers during its large-tonnage production. The authors propose the use of remote filling systems (VSN) for LNG in a similar way to similar devices for filling oil into tankers. However, the main feature of the VSN LNG is the cryogenic pipeline from the onshore facilities to the VSN. In this regard, it is necessary to make a simplified mathematical model of a cryogenic pipeline taking into account heat exchange with the environment and heat release during energy dissipation due to viscous friction forces.In the course of numerical simulation, the dependence of the maximum pumping distance was obtained for a given difference between the temperature of LNG on shore facilities and the maximum required temperature of LNG loading into a gas carrier. The influence of each component of the heat flow equation — heat exchange with the environment and LNG heating due to viscous friction forces was also evaluated.As an example, a section with a length of 10 km was selected and a simulation of the temperature distribution, as well as the required pressure on shore structures necessary to ensure a given loading speed of the gas carrier and the temperature of the supplied LNG was carried out.

Integrated ethane recovery and cryogenic carbon capture in a dual mixed refrigerant natural gas liquefaction process

Carbon capture by direct cryogenic distillation in conventional natural gas liquefaction plants is quite difficult due to the easy sublimation characteristics of CO2. The freeze–out temperature of CH4–CO2–C2H6 ternary mixtures is analyzed in this study, and the results show that with the azeotropic properties of ethane-CO2 mixtures, CO2 in natural gas can be reduced to below 50 ppm by cryogenic distillation. Based on thermodynamic analysis, a novel dual mixed refrigerant (DMR) liquefaction process integrated with ethane recovery and carbon capture is proposed for natural gas that is rich in ethane. CO2 is first captured from natural gas along with ethane by cryogenic distillation, and then further separated from the CO2–C2H6 mixture by extractive distillation to obtain ethane. The proposed process is simulated in HYSYS and optimized by a method combining a genetic algorithm (GA) and stepwise search. Energy analysis results show that when the ethane content is 2–20 mol%, the specific power consumption corresponding to the maximum allowable CO2 content with ethane recovery rate and purity both reaching 99.5 % is around 0.40 kWh/Nm3 (NG). In addition, the comparative analysis results show that the proposed process has better performance than chemical absorption in both energy consumption and cleaner production aspects.

Magnetic and magnetocaloric properties of Tb1.4Dy0.6In compound

This work summarizes the magnetic, thermal, magnetocaloric, and electrical transport properties of Tb1.4Dy0.6In and its critical behavior. First, we find that 60% Dy at the 2d (1/3, 2/3, 3/4) lattice sites of Tb2In (hexagonal Ni2In -type (space group- P63/mmc (No. 194))) leads to the formation of Tb1.4Dy0.6In, which undergoes a ferromagnetic transition at 155 K (T1) followed by an antiferromagnetic transition around 75 K (T2). Successive second-order magnetic transitions at T1 and T2 demonstrate a table-like hysteresis-free magnetocaloric effect around natural gas's liquefaction temperature (55–196 K). To understand the efficiency of Tb1.4Dy0.6In as a coolant, various cooling figures of merits such as isothermal entropy change, adiabatic temperature change, relative cooling power, the temperature averaged entropy change, and coefficient of refrigerant performance were determined. Along with the studies of magnetic properties, the critical exponent analysis endorses mean–field model that concord with the indirect long-range RKKY interaction between the rare-earth atoms in Tb1.4Dy0.6In. Furthermore, first-principle calculations indicate that the most hybridized dp states lie below the Fermi energy level and support the second-order magnetic nature of the transition. Overall, this study provides insights into the magnetocaloric properties of Dy-doped Tb2In and highlights its potential as an efficient coolant.

Numerical simulation of heat transfer performance of spiral wound heat exchanger under sloshing condition

LNG floating production storage and offloading (FPSO) unit is a new type of floating production unit developed for offshore natural gas fields. It performs the functions of natural gas extraction, pretreatment, liquefaction, and storage. In this study, the heat transfer characteristics of a spiral-wound heat exchanger were studied using numerical simulations, which provides a basis for equipment selection and structural optimization of spiral-wound heat exchangers. The main research contents and conclusions are as follows. Under land-based simulation conditions, the heat transfer coefficient of the shell side of the spiral-wound heat exchanger decreases with an increase in the winding angle of the heat exchange tube, decreases with an increase in the spacing of the heat exchange tube, and increases with an increase in the outer diameter of the heat exchange tube. When the winding angle increased from 5° to 8°, the heat transfer coefficient decreased by 6.70%. The heat transfer coefficient of the shell side decreased by 13.21% when the heat exchange tube spacing increased from 14 to 17 mm. The heat transfer coefficient of the shell side increased by 22.89% when the outer diameter of the heat exchange tube increased from 9 to 12 mm. When the sloshing angle is constant, the heat transfer coefficient of the spiral-wound heat exchanger decreases with an increase in the winding angle and spacing of the heat exchange tubes, and increases with an increase in the outer diameter of the heat exchange tubes. When the structural parameters of the heat exchanger are constant, the heat transfer coefficient decreases as the sloshing angle increases. When the sloshing angle was less than 3°, the sloshing promoted heat transfer on the shell side. When the sloshing angle was higher than 7°, the heat transfer effect of the shell side deteriorated considerably, which weakened the heat transfer performance of the heat exchanger. When the sloshing period is constant, the heat transfer coefficient of the wound heat exchanger decreases with an increase in the winding angle and spacing of the heat exchange tubes, and increases with an increase in the outer diameter of the heat exchange tubes. When the structural parameters of the heat exchanger are constant, the heat transfer coefficient increases with sloshing period. When the sloshing period was greater than 15 s, the influence of sloshing on the heat transfer on the shell side of the heat exchanger was relatively weak.

ALTERNATIVE METHODS OF USING OF BOIL OFF GAS

This work is devoted to the search and analysis of methods to improve the efficiency of using cold steam gases. The article raises the issue of one of the important problems of storage of liquefied natural gas – the formation of boil off gases. The main ways of using steam gas are given. New alternative methods of using of boil off gas are presented, such as the use of boil off gas as an additional cooling of natural gas in the propane cooling stage and propane in the propane refrigeration cycle. A three-flow tubular twisted heat exchanger is modeled to calculate the interaction of gas flows. Calculations were carried out, an analysis of the options for the useful use of the cold of the boil off gases was performed and a conclusion was made about the positive effect of the application of the considered methods of using boil off gases on increasing the efficiency of the natural gas liquefaction process.

Detailed performance analysis of a novel small-scale biomethane liquefaction plant

In the current global energy scenario, an important role is played by the increasing production of biomethane, which is carbon-neutral when burned. In addition to production processes, it is paramount to increase the construction of liquefaction plants, in order to simplify the transportation and use of biomethane. However, biomethane liquefaction plants have limited diffusion because of the complexity of current biomethane liquefaction technologies, which have been adapted from natural gas liquefaction plants. Therefore, novel biomethane liquefaction plants are needed to assist the increasing demand of biomethane in the global market. In previous papers, an innovative biomethane liquefaction plant was proposed and studied; compared to current liquefaction technologies, the main advantage is given by the use of simplified heat exchangers. In this paper, the plant performance is explored in more detail by changing some operating parameters to study the efficiency of the whole process by means of a parametric analysis. The results confirm a high potential of the proposed plant, in terms of coefficient of performance and compactness of the heat exchangers.

Tunable magnetocaloric effect towards cryogenic range by varying Mn:Ni ratio in all-d-metal Ni(Co)-Mn-Ti Heusler alloys

Cryogenic magnetic refrigeration is a highly efficient and environmentally friendly technique for gas liquefaction. However, refrigerant materials undergoing large magnetocaloric response at the interesting cryogenic range are dominated by critical elements (mainly rare-earth elements) which impedes practical applicability of such refrigeration systems. Therefore, there is a need for dedicated investigations on optimization of magnetocaloric response at cryogenic range by utilizing compositions that are rare-earth free. In this work, we synthesize the mechanically stable and rare-earth free, all-d-metal Ni35Co15Mn35Ti15 Heusler alloys and investigate the role of varying Mn:Ni ratio on the magnetostructural and magnetocaloric properties of the alloy system. The results of the microstructural characterization indicate homogenous composition for the investigated alloy series. As the Mn:Ni ratio increases from 1.01 to 1.10, the martensitic transition shifts from near-room temperature down to cryogenic region (120–140 K) while the magnetization of the austenitic phase remains unaltered. Isothermal entropy change as high as ∼ 13 J kg−1 K−1 at 1.5 T is achieved for the sample with the highest Mn:Ni ratio at the temperature region for natural gas liquefaction, which significantly surpasses the values previously reported in the literature for similar alloys. In addition to large magnetocaloric response, the martensitic transformation falls in an interesting temperature of the cryogenic region, paving the way for various low-temperature magnetocaloric applications.

Exergy and energy analysis of a hybrid natural Gas/Hydrogen liquefaction cycle combined with methanol production plant

This paper presents an innovative renewable multi-generation system designed to simultaneously produce various fuels, including biomass-based methanol, liquid hydrogen, and liquid natural gas. This system is part of a broader strategy aimed at streamlining different processes within a comprehensive plant, enabling the simultaneous production of multiple biomass-based fuels at a single location. The implementation of this system in regions where natural gas liquefaction plants coexist with abundant forest resources allows for the efficient production of all required fuels. In this process, a new configuration leverages to regenerate the waste heat of methanol synthesis process in the diffusion absorption refrigeration cycle integrated to the natural gas liquefaction process to maximize energy and exergy efficiencies. Additionally, three hydrogen liquefaction processes are evaluated to identify the most suitable option based on performance, efficiency, and power consumption. The investigations reveal that the combined mixed refrigerant cycle (CMRC) emerges as the ideal choice for hydrogen liquefaction process, characterized by lower power consumption and a higher coefficient of performance. The energy and exergy efficiencies of biomass gasification and methanol synthesis processes are 87.54% and 80.41%. The energetic coefficient of performance of the natural gas liquefaction process and CMRC is 0.9 and 0.2209. The specific power consumption of natural gas liquefaction process is 0.225 kWh/kgLNG, and the specific power consumption of CMRC is 5.462 kWh/kgLH2. The natural gas liquefaction process is responsible for the highest portion of the total exergy destruction, with 32%.

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

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

An Innovative Approach for Natural Gas Liquefaction Using a Mixed-Multi-Component-Refrigerant

The natural gas liquefaction is the most expensive and energy-intensive phase in the natural gas-to-liquefied natural gas-to-natural gas chain. In addition, this region has the biggest development potential. As a result, numerous LNG production methods have been developed and are deployed at export facilities around the world. The goal of this study is to describe and assess an innovative approach for mixed-refrigerant (MR) LNG method. The authors have dubbed this technique the MR-X approach. The MR-X process was developed based on the globally proven liquefaction technology C3MR and its large-scale successor AP-X™ (which offers many benefits and flexibility), but with a novel precooling phase construct. In pre-cooling and liquefaction phases, the refrigerant is a combination of methane, nitrogen, propane, ethane, butane, and isobutane. The paper investigates the creation of the MR-X technology, as well as its modelling, energy, and exergy investigations.

Simulation of boil-off gas recovery and fuel gas optimization for increasing liquefied natural gas production

In a natural gas liquefaction plant, boil-off gas (BOG) is generated in both liquefaction and loading processes. During the holding mode (no loading operation), the fuel gas supply, including the BOG generated in the liquefaction process, is less than the fuel gas demand. Therefore, make-up gas is added to the fuel gas system. BOG recovery systems are designed to absorb the maximum amount of BOG during liquefied natural gas (LNG) loading to ships (loading mode). Additional BOG is generated during the loading process (loading mode). At this stage, the fuel gas supply is higher than the demand. To avoid fuel gas flaring, BOG from the liquefaction process is reduced by cooling the LNG from the main heat exchanger (MHE) to a lower temperature, which consequently reduces LNG production by more than 1%. This study aimed to optimize liquefaction, storage, loading, fuel gas and BOG recovery processes to increase LNG production. In this study, a natural gas liquefaction plant producing 8 mtpa (million tonnes/ year), where LNG production was limited by the capacity of the BOG recovery system and fuel gas demand, was modelled using UniSim software. In the model, the optimization of BOG recovery during the holding mode increased LNG production by 46,850 tonnes/ year. The volumetric flow rate of BOG generated during LNG loading was reduced by decreasing the temperature of the ship’s cargo tanks, decreasing the loading pumps’ discharge pressure, reducing the discharge pressure of the ship’s compressors, and reducing the loading rate. This study shows that BOG generated during loading can be significantly reduced by around 50% from the initial rate, which increases LNG production by around 36,576 tonnes/ year. In total, the potential production increase from BOG recovery and fuel gas optimization was around 90,260 tonnes/ year or equivalent to 1.4 cargo of LNG per year.

Effect of ethane on condensation characteristics of methane heterogeneous nucleation: A molecular dynamics study

Clarification on condensation characteristics of alkane gases plays a fundamental role in the development of natural gas liquefaction processes. However, the microscopic condensation characteristics of alkane gas on the heat exchanger wall are still not well understood, which holds significant practical implications for advancing liquefaction technologies. Therefore, this study investigates the microscopic condensation process of heterogeneous nucleation with methane gas through molecular dynamics (MD) simulations. By varying wall energy and ethane content, we analyzed the nucleation kinetic properties of methane heterogeneous condensation. The results demonstrate that high-energy walls enhance heat transfer by enhancing the interaction between wall and methane, thereby accelerating condensation core formation and increasing methane condensation rates. Additionally, increasing ethane content also shortens the time for the formation of condensation cores in methane gas. Ethane has a higher condensation temperature compared to methane, and its presence reduces the difficulty of forming condensation cores in alkane gases and shortens the time for liquid core formation, thus facilitating methane condensation. The above research results will provide new insight for natural gas liquefaction process.

Thermodynamic performance of a cryogenic energy storage system based on natural gas liquefaction

Cryogenic energy storage (CES) is a viable method for grid-scale electrical energy storage. Considering the high energy density and mature application of liquefied natural gas (LNG), we proposed an LNG cryogenic energy storage (LNGES) system. A steady-state process model of the LNGES system was established using Aspen HYSYS. The effects of the natural gas composition and key operating parameters such as the charging pressure, discharging pressure, throttling temperature, and liquid storage pressure on the system performance were investigated. A multi-parameter genetic algorithm model built using the MATLAB software was used to optimize the LNGES system to optimize the round-trip efficiency (RTE). Then, an exergy analysis of the optimal configuration was conducted. The results suggested that the LNGES system could achieve optimal RTE and exergy efficiency values of 60.14% and 71.64%, respectively. Exergy destruction mainly occurred during the compression, throttling, expansion, and heat exchange. The proposed LNGES system could be a promising candidate for the large-scale application of CES technology in power grids and gas networks.

Comparative study of CO2-N2 and N2-N2 dual expansion in natural gas liquefaction process

The processes were modelled using the Aspen Hysys version 11. The paper compared two refrigeration systems with different refrigerants, CO2-N2 and N2-N2, and their expenders. The parameters compared are the liquefaction power, specific power, production capacity, and heat duty of the expander cycle. The liquefaction power of CO2-N2 (547.669kW) is lower than that of N2-N2 (815.85kW). The specific power consumption for CO2-N2 was 0.44096kW/kg, and for N2-N2 was 0.6569kW/kg. The production capacity N2-N2 gave a higher value of 6945.6MTPA than CO2-N2 4904.38MTPA.

Impact of liquefaction ratio and cold energy recovery on liquefied natural gas production

The partial liquefaction of natural gas (NG) is commonly conducted in the liquefied natural gas (LNG) industry toward facilitating the use of non-liquefied gas for power generation and utility systems, while simultaneously achieving the desired heating value of LNG. This study investigated the impact of the partial liquefaction of NG and the recovery of cold energy from non-liquefied gas on the efficiency of the liquefaction process, in terms of specific work. The optimal liquefaction ratio (LR) with no recovery was 64.2% (778.7 kJ/kg LNG), which is 21.7% reduction of specific work in relation to that achieved through full liquefaction (995.0 kJ/kg LNG). The result showed a trade-off relationship between a higher LR to compensate energy consumption for cooling NG to its dew-point temperature with no liquid production and produce flash gas at a cryogenic temperature and lower LR to avoid the liquefaction of light components, which are difficult to condense. However, this trade-off resolved upon cold energy recovery, because there was no energy consumption until an LR of 8.1% could be achieved through an expansion of high-pressure NG feed by the recovery. For practical reason, a case study was conducted with lower bounds of the LR at 85%, 90%, and 95%. The findings of this study can guide the decision-making of future LNG projects for an optimal LR.

Enhancing Energy Efficiency and Reliability in Floating LNG Operation: A Hydrofluoroolefin-Based SMR Cycle with Thermo-Economic Assessment and Uncertainty Analysis

Natural gas liquefaction is the most energy-intensive technique in floating liquefied natural gas (FLNG) operations. Hence, a hydrofluoroolefin-based single mixed refrigerant (SMR) technology was proposed to achieve energy-efficient and eco-friendly operations. The study was perfomed to enhance the SMR process by substituting expansion valves with hydraulic turbines to improve process reversibility and enhance energy efficiency. The proposed process was optimized using a sine–cosine concept-based algorithm that tuned the design variables which yielded an overall compression energy consumption of 0.2501 (kWh/kg-LNG), resulting in a 21.43% saving as compared to the conventionally used mixed refrigerant-based process. This resulted in a reduction of about 38.81% in overall exergy destruction. The economic analysis results draw curtains that the process saves about 26.02% of total annualized cost as compared to conventional study. Owing to the appropriate mixed refrigerant component mixture ratio and process design improvement. To determine the process reliability under uncertain conditions the optimal compression power and minimum approach temperature were determined. Further, uncertainty analysis reveals that the methane and butane refrigerant flow rates along with evaporation, and condensation pressure, were among the most influential parameters that influence the process most that may affect the whole operation in uncertain process inlet conditions. In summary, our approach presents immense promise for achieving energy efficiency, environmental responsibility, and economic viability in FLNG operations, offering a robust solution for the challenges of offshore plants.

Heterogeneous nucleation condensation of methane gas on the wall-A molecular dynamics study

Methane is condensed in a low-temperature heat exchanger, a critical step in the liquefaction of natural gas. Currently, the microscopic mechanism regarding the heterogeneous condensation of methane on the heat exchanger wall remains unclear. This lack of understanding is of scientific importance in advancing the development of natural gas liquefaction processes. Therefore, molecular dynamics simulation is used in this paper to study the process of methane heterogeneous nucleation and core growth during the early stage of condensation, and analyze the influence mechanism of wall energy and cold source temperature on nucleation kinetics. The results show that the high-energy wall can enhance the interaction between cold wall atoms and methane molecules, facilitate heat transfer, accrete methane molecules to condense and adsorb on the wall to form a core, thus increasing the condensation rate of methane. Whereas, the low-temperature cold source promotes the condensation nucleation and growth process by increasing the supersaturation of methane. This study investigates the process and kinetic characteristics of heterogeneous nucleation of methane from a microscale perspective, providing guidance for the development of natural gas liquefaction in low-temperature heat exchangers, with the aim of enhancing the diversity and reliability of energy supply.