Gas Liquefaction Research Articles

Comparative analysis of cryogenic distillation and chemical absorption for carbon capture in integrated natural gas liquefaction processes

Compared with the widely used chemical absorption, cryogenic distillation has a lower thermal energy consumption and smaller footprint of the carbon capture unit. However, the power consumption of cryogenic distillation is higher. This study aims to use the azeotropic properties of ethane-CO2 mixtures to achieve CO2 capture by cryogenic distillation for cleaner LNG production. A single mixed refrigerant LNG process integrated with cryogenic distillation (CD-LNG) or chemical absorption (CA-LNG) is proposed. These technologies are comprehensively compared with respect to energy, economy and environment. The results show that when the feed gas contains 1.8–17 mol% CO2, the power consumption of the CA-LNG process is 0.37–0.40 kWh/Nm3 NG with an exergy destruction of 0.20–0.23 kWh/Nm3 NG. The power consumption of the CD-LNG process is 0.41–0.42 kWh/Nm3 NG with an exergy destruction of 0.18–0.22 kWh/Nm3 NG. Due to the much higher heat load for chemical solvent regeneration, the overall exergy efficiency of the CA-LNG process (49.0–53.8%) is lower than that of the CD-LNG process (50.6–56.0%). In addition, the total annualized cost (TAC) in a 20-years lifespan of the CD-LNG and the CA-LNG for a case study with a process scale of 179,800 t/a and a specified feed gas composition (79 mol% CH4, 10 mol% C2H6 and 11 mol% CO2) are 8,441,117 $ and 9,860,792 $ respectively. The GWP analysis shows that the CO2-eq of the CA-LNG process is 37–67% higher than that of the CD-LNG process.

A displacer coupled thermoacoustic cooler driven by heat and electricity

A small-scale, heat-driven cooling system is required for the on-site liquefaction of unconventional natural gas in a distributed station. The thermoacoustic cooler has been considered a promising candidate for meeting such demands due to its high reliability and environmental friendliness. However, conventional thermoacoustic systems use a resonance tube to couple the thermoacoustic engine and cooler, which degrades cooling performancedue to poor phase-shifting capability and significant power dissipation of the resonance tube. To overcome the limitation, this paper introduces a novel driven by heat and electricity thermoacoustic cooler using displacers to replace the resonance tube, which enables better phase-shifting capability and less power dissipation, thus allowing better cooling performance. Numerical investigation and experimental study are performed on the displacer-coupled thermoacoustic cooler driven by heat and electricity. Firstly, the design method of the displacers is presented based on the acoustic impedance matching principle. Numerical investigations are then conducted to understand the operational characteristics better to explore the axial distribution of critical parameters. The effects of the displacer damping coefficient, operating frequency, and mean pressure are further studied. Experimental investigations are then carried out to understand the impact of operating temperatures on system performance. Experimental results show that the system achieves a record thermal-to-cooling exergy efficiency of 13.4 % and cooling power of 117 W at heating and cooling temperatures of 773 K and 110 K. This represents an over 34 % improvement in efficiency when compared to the previous record-holder thermoacoustic cooler.

A thermoacoustic cooler with a bypass expansion for distributed-temperature heat loads

In the context of the current energy crisis, a compact, simple, and reliable cooler is required at small-scale natural gas liquefaction stations. In this paper, a thermoacoustic cooler with a bypass expansion cooling for distributed-temperature heat loads is proposed. The bypass expansion configuration is used to carry out multiple refrigeration processes to achieve distributed cooling temperatures, thus realizing the cascade processes of natural gas liquefaction and improving the liquefaction efficiency. Simulations were carried out to investigate the effect of cooling-stage numbers on relative power consumption efficiency, exergy losses of components as well as axial distributions of key parameters. A proof-of-concept porotype of a two-stage thermoacoustic cooler was built, and the feasibility of the distributed heat loads was experimentally tested. Comparisons with a conventional single-stage thermoacoustic cooler without bypass expansion indicate that the proposed bypass expansion system improves the liquefaction cooling efficiency by a factor of 3.28 at 120 K. Experiments were also carried out to investigate the effect of the bypass expansion, an important factor, by verifying the total number of bypass orifices. Results show that increasing the number of bypass orifices with a more uniform gas distribution can improve the cooling performance of the system. The findings demonstrate the promising prospects of the proposed thermoacoustic cooler in the field of natural gas liquefaction.

Optimization of Condensate Transfer Pump in the Hydrocarbon Condensate Stabilization Unit of Natural Gas Liquefaction Plant – An Industrial Case

PT. Badak NGL is a commercial LNG producer located in Bontang, Indonesia. In recent years, the decline in LNG production of PT. Badak NGL results in a lower hydrocarbon condensate flow rate. To prevent power losses since its pump operated at below rating, a new operation scheme was proposed. This new scheme adjusts the way of pump is operated without any alteration in terms of pump characteristics. Three pumps operated intermittently for 8 hours per day at a maximum flow rate. The pump power consumption was calculated based on electric current data monitored relay panel. The results show that the pump energy saved by 60% with the absolute value of annual energy efficiency of 957.7 MWh. This study contributes to reducing the greenhouse effect by 412 tons eq CO and the annual production cost of around USD 130,000. The new scheme reliability examines by evaluating pump vibration, pump performance, hydrocarbon condensate quality, and condensate tank liquid level. The result shows that the pump’s vibration in the range of 0.21 in/sec with a steady winding temperature.

Drop-in and hydrogen-based biofuels for maritime transport: Country-based assessment of climate change impacts in Europe up to 2050

Alternative fuels are crucial to decarbonize the European maritime transport, but their net climate benefits vary with the type of fuel and production country. In this study, we assess the energy potential and climate change mitigation benefits of using agricultural and forest residues in different European countries for drop-in (Fast Pyrolysis, Hydrothermal Liquefaction, and Gasification to Fischer-Tropsch fuels or Bio-Synthetic Natural Gas) and hydrogen-based biofuels (hydrogen, ammonia, and methanol) with or without carbon capture and storage (CCS). Our results show the combinations of countries and biofuel options that successfully achieve the decarbonization targets set by the FuelEU Maritime initiative for the next years, including a prospective analysis that include technological changes projected for the biofuel supply chains until 2050. With the current technologies, the largest greenhouse gas (GHG) mitigation potential per year at a European scale is obtained with bio-synthetic natural gas and hydrothermal liquefaction. Among carbon-free biofuels, ammonia currently has higher mitigation, but hydrogen can achieve a lower GHG intensity per unit of energy with the projected decarbonization of the electricity mixes until 2050. The full deployment of CCS can further accelerate the decarbonization of the maritime sector. Choosing the most suitable renewable fuels requires a regional perspective and a transition roadmap where countries coordinate actions to meet ambitious climate targets.

Surface crystallization mechanism of n-hexane droplets

Revealing the crystallization mechanism of alkane molecules is of great significance to promote the development of the natural gas liquefaction industry. Although many efforts have been made on the crystallization of chain molecules, the surface crystallization mechanism of short-chain alkanes has not yet been solved. In this paper, molecular dynamics simulations were employed to investigate the surface crystallization process of n-hexane nanodroplets and elucidate the surface crystallization mechanism. The results show that the crystallization process of supercooled heavy hydrocarbon droplets can be divided into two stages. The reduction of torsion energy and Lennard‒Jones energy makes important contributions to the droplet crystallization process. The molecules at the vapor-liquid interface tend to be arranged in an orderly manner, and the molecular principal axes are perpendicular to the interface. The molecules at the vapor-solid interface fluctuate strongly along their molecular axes. In addition, the entropy change value for the overall crystalline layer of n-hexane is approximately 1.4 times higher than that of the surface crystalline layer. It is proven that there is a significant energy gain in the surface crystalline layer, which is an important driving force for n-hexane crystallization.

Optimal operational analysis of metamodel based single mixed refrigerant cryogenic process for floating liquefied natural gas plant technology

Since natural gas liquefaction operation is an energy-intensive technology. Research has been published for the optimization of the process by utilizing the first principal complex nonlinear SMR model. The process is computationally expensive and requires several hours or even days for optimization. To address this issue, this study proposes a metamodel for natural gas liquefaction featuring a single mixed refrigerant cryogenic cycle. The SMR model was modeled and simulated by utilizing Aspen Hysys software. However, the metamodel was developed by utilizing radial basis function methodology and optimization work using Matlab. The results summary comparison for specific compression duty for metamodel was 0.3863 kW/kg-NG. The first principle-based published study of this duty was 0.3625 (kW/kg-NG) which is approximately 6.5% lower than the current study. However, a huge reduction in computational time was obtained. The metamodel building and optimization time-lapse was 292.96 s while the same first principle-based model lapse 201.24 h using 300 iterations. In comparison, it can be inferred that metamodel could capture almost all-important characteristics of the firs-principle based model. Hence, the proposed study could be considered as an alternative to the first principle model for optimization purposes. This research may prove to be more vital especially in any abrupt changing or uncertain conditions or for real-time plant optimization.

Energy and economic comparison of five mixed-refrigerant natural gas liquefaction processes

The demand for liquified natural gas grows as it is an energy resource that has more flexible means of transport than non-liquefied natural gas, and is more eco-friendly than other fossil fuels. This paper focused on comparing five different mixed-refrigerant liquefaction processes to determine which one is the most efficient in energetic and economic terms for four different natural gas processing scales (20,000 kg/h and 2, 4, and 8 MTPA of natural gas feed). Simpler processes with one or two refrigerant cycles (single mixed refrigerant, propane pre-cooled mixed refrigerant, and dual mixed refrigerant) and more complex processes with three cycles (mixed fluid cascade and AP-X) were analyzed. All processes were simulated in Aspen HYSYS, and the energy consumption was optimized by a communication between the simulator and an optimization algorithm based on Particle Swarm Optimization coded in MATLAB. The economic analysis was performed using the CAPCOST technique and the rule of six-tenths for upscaling. In the best-optimized scenario, the results show that the most complex process, AP-X, consumes the lowest amount of energy (0.2367 kWh/kg-LNG) while the simplest one, the single mixed refrigerant, consumes the highest value (0.2561 kWh/kg-LNG). In the economic analysis, the results indicate that energetically better processes may not provide a higher economic return even on large scales.

The Design and Optimization of Natural Gas Liquefaction Processes: A Review

As the energy crisis intensifies, the global demand for natural gas is growing rapidly. Liquefied natural gas (LNG) technology is among the delivery solutions with flexible and reliable application prospects and is already a significant field of research in energy utilization. The performance of natural gas liquefaction process has a major influence on the production capacity, energy consumption, economics, and safety of the entire supply chain. Many scholars have conducted numerous studies on various LNG processes and designed many classical processes. This paper summarizes and discusses current research status and development level in the design and optimization of natural gas liquefaction processes in recent years, mainly focusing on cascade liquefaction process, expansion liquefaction process, and mixed refrigerant liquefaction process. The advantages and disadvantages of various liquefaction processes are compared and analyzed in terms of liquefaction capacity, energy consumption, economy, safety, and adaptability. In addition, the rapid development of pressurized liquefaction technology in recent years and its application outlooks are also introduced in detail. Finally, the present situation and industrial demand of LNG process are analyzed, and reasonable suggestions and future research prospects are put forward.

Multi-objective simulation–optimization via kriging surrogate models applied to natural gas liquefaction process design

A surrogate-based multi-objective optimization framework is employed in the design of natural gas liquefaction processes using reliable, black-box process simulation. The conflicting objectives are minimizing both power consumption and heat exchanger area utilization. The Pareto solutions of the single-mixed refrigerant (SMR) and propane-precooled mixed refrigerant (C3MR) processes are compared to determine the suitability of each process in terms of energy consumption and heat exchanger area. Kriging models and the ɛ-constraint methodology are used to sequentially provide simple surrogate optimization subproblems, whose minimizers are promising feasible and non-dominated solutions to the original black-box problem. The surrogate-based ɛ-constrained optimization subproblems are solved in GAMS using CONOPT. The Pareto Fronts achieved with the surrogate-based framework dominate the results from the NSGA-II, a well-established meta-heuristics of multi-objective optimization. The objective functions of non-dominated solutions go as low as 1045 and 980.3 kJ/kg-LNG and specific UA values of 212.2 and 266.9 kJ/(°C kg-LNG) for SMR and C3MR, respectively. The trade-off solutions that present the minimum sum of relative objectives are analyzed as well as the dominance of C3MR over SMR at low power consumption values and conversely at low heat exchanger area utilization.

Effect of reaction temperature and raw material particle size on the composition of corn straw pyrolysis biological oil

Quartz sand was used as bed material in a small fluidized bed reactor with 1 kg/h feed. Corn straw powder with particle size of 20–40 mesh, 40–60 mesh, 60–80 mesh and 80–120 mesh was used as raw material for rapid pyrolysis at reaction temperatures of 400 °C, 450 °C, 500 °C and 550 °C. The bio-oil obtained after liquefaction of pyrolysis gas was analyzed. The variation trend of bio-oil composition in pyrolysis of corn straw powder with different reaction temperatures and raw material sizes was compared. The results show that: (1) the content of 3-hydroxyl-2-phenyl-2-acrylic acid in bio-oil increases with the decrease of raw material particle size, but it is less at 450 °C; (2) with the increase of reaction temperature, the content of hydroxyacetaldehyde in bio-oil increases at first and then decreases: the content of hydroxyacetaldehyde in bio-oil is the highest at 500 °C when the particle size is 20–40 mesh, and the highest at 450 °C with the other three particle sizes. Compared with other particle sizes, raw material with the particle size of 60–80 mesh is not conducive to the formation of aldehyde compounds; (3) the reaction temperature of 500 °C and the particle size of 60–80 mesh of raw materials are more conducive to the formation of phenolic compounds in bio-oil; (4) the ester compounds with particle size of 20–40 mesh in bio-oil is 20% higher than that of other particle sizes; (5) the reaction temperature and the particle size of raw materials had no significant effect on the formation of ketones, alcohols and alkane compounds in bio-oils.

Investigation of novel passive methods of generation of swirl flow in supersonic separators by the computational fluid dynamics modeling

In this paper, three passive methods for the generation of swirl flow in the supersonic separator (3S) were investigated, and their structures were optimized by computational fluid dynamics (CFD) modeling. The influence of the structural and operational parameters on the dew point depression, phase envelope diagram, rate of natural gas liquid (NGL) recovery, and separation efficiency have also been evaluated. The collection efficiency was significantly improved for the nozzle equipped with the passive swirler compared with the simple nozzle. The selection of passive swirler type played a crucial role in the natural gas liquefaction and separation. The side injected swirler, and serpentine swirler showed the most significant improvement in separation efficiency than the U-turn swirler. For the side injected swirler at the optimum injection angle, the maximum collection efficiency was about 89% at the pressure loss ratio (PLR) of 0.2. Besides, the simulation results demonstrated that for the serpentine 3S, with the increase in serpentine twist number, the highest improvement on the collection efficiency of the investigated nozzle was obtained. In addition, it was observed that, when the convergent section profile was designed according to the Witoszynski line-type, a larger refrigeration zone was obtained than other considered profiles.

Review of Unconventional Natural Gas Liquefaction Processes

Liquefied natural gas (LNG) has become an important part in the energy industry on account of its high energy density, low carbon emission, and convenient transportation. In recent years, with the discovery of unconventional natural gas resources, the situation of the world’s natural gas liquefaction plants using conventional natural gas as feedstock is changing. Unlike traditional LNG plants, unconventional natural gas liquefaction processes require special considerations in design and manufacturing. This review summarizes and analyzes the characteristics and differences of several typical unconventional natural gas liquefaction processes compared to traditional natural gas liquefaction processes, including coalbed methane liquefaction, synthetic natural gas liquefaction, LNG-FPSO, and PLNG (pressurized liquefied natural gas). Moreover, a state-of-the-art review of the recent progress on design and optimization of unconventional natural gas liquefaction processes is presented.

Казус белли практической и теоретической оценок технологических процессов крупнотоннажного производства сжиженного природного газа

Almost always the results of theoretical research do not bring the desired result in practice. This is especially true if there is at least one alternative (competitive) option for applying the process. Production of the liquefied natural gas is a prime example of the need for an understanding of the choice of a single process option that will provide performance indicators with optimal energy efficiency and acceptable safety during the preliminary design stage of a project. One of the research steps may be a comparative analysis of the results of practical (operation of similar facilities) and theoretical (thermodynamic analysis) assessments of the choice of the natural gas liquefaction process at the stage of the feasibility study of the gas field development project (without considering the financial component). The task of the presented study was solved based on the indirect comparative analysis of the results of an expert evaluation of operation and theoretical results of a thermodynamic analysis of the liquefaction processes for a project in the territory of the Russian Federation. The following studies were conducted: choice of LNG technologies; expert evaluation of large-capacity projects for production of the liquefied natural gas in the climatic conditions close to the Arctic; thermodynamic analysis of the energy efficiency of the technological process of large-tonnage production of the liquefied natural gas in the territory of the Russian Federation. The result of the study is the integration of safety and efficiency for making a decision on the choice of the technological process of the natural gas liquefaction at the stage of the Safety Case of the gas field development project.

Magnetocaloric performance of the three-component Ho1-xErxNi2 (x = 0.25, 0.5, 0.75) Laves phases as composite refrigerants

To date, significant efforts have been put into searching for materials with advanced magnetocaloric properties which show promise as refrigerants and permit realization of efficient cooling. The present study, by an example of Ho1−xErxNi2, develops the concept of magnetocaloric efficiency in the rare-earth Laves-phase compounds. Based on the magneto-thermodynamic properties, their potentiality as components of magnetocaloric composites is illustrated. The determined regularities in the behaviour of the heat capacity, magnetic entropy change, and adiabatic temperature change of the system substantiate reaching high magnetocaloric potentials in a desired temperature range. For the Ho1−xErxNi2 solid solutions, we simulate optimal molar ratios and construct the composites used in magnetic refrigerators performing an Ericsson cycle at low temperatures. The tailored magnetocaloric characteristics are designed and efficient procedures for their manufacturing are developed. Our calculations based on the real empirical data are very promising and open avenue to further experimental studies. Systems showing large magnetocaloric effect (MCE) at low temperatures are of importance due to their potential utilization in refrigeration for gas liquefaction.

Strategic approach to implementation of innovation in the Arctics on the example of “Arctic Cascade” natural gas liquefaction technology

The article examines the current situation in the world production and consumption of the liquefied natural gas (LNG). The main global trends as well as the reasons for significant growth in LNG consumption in most countries are analyzed. The authors also study the structure of global import of LNG and the opportunities for increasing supplies by the Russian energy companies. Russian companies are primarily supplying LNG to European countries. However, the results of the analysis show high export potential of the Asian market. Realizing the potential is the most important strategic task for domestic energy companies. The article also examines the history and the current process of developing LNG production on the Russian territory. The authors reveal various aspects of the current implementation of such projects as “Yamal LNG” and “Arctic LNG 2” within the Arctic area of the Russian Federation. Particularly, the authors describe development of transportation-logistics system as part of these projects. Moreover, the article contains the analysis of the problem of ensuring technological independence in the process of implementation of LNG projects. Russian energy companies should increase their technological independence and localization of production by consistent implementation of the import substitution strategy. One of the solutions in ensuring technological independence is innovation technology of natural gas liquefaction “Arctic Cascade”. The article presents the detailed technical and economical aspect of implementing this technology. Using this technology ensures 30 % reduction of the LNG production cost price. Besides, this innovation technology can ensure 100 % localization of production.

Transient Simulation of an Industrial Steam Boiler

The safety analysis of an industrial installation is extensively based on modeling and simulation. However, the analysis of simulation using realistic computer codes like RELAP5/Mod3.2 will help understand thermal-hydraulic behavior of an installation during normal and accidental conditions. In a steam boiler operation, it is very important to evaluate numerous accident scenarios under real plant conditions. One of the main accidental transients is tube rupture of steam boiler. The main objective of this study consists toinvestigate the behavior of an industrial steam boiler installed in the complex of natural gas liquefaction (LNG) at Skikda in Algeria during feed water line break accident. A RELAP5 model was set up to simulate the entire system, the model represents all steam boiler components to be suitable for the analysis of the several accidents. The control and regulation systems are also considered. The model was qualified against the steam boiler data at steady-state conditions. As seen from the results, a good agreement was obtained. The transient simulation results show that the thermal-hydraulic code correctly predicts the behavior of the main steam boiler parameters and how the control system, when required, can successfully mitigate the accident.

Финансово-экономическое обоснование проекта по строительству малотоннажного комплекса сжижения природного газа

In modern economic conditions, the increased demand for liquefied natural gas necessitates the engineering design of technological solutions for the production of liquefied natural gas and its financial and economic justification. The scientific article is devoted to the development of a financial and economic model and the evaluation of the effectiveness of the project for the construction of a small-scale natural gas liquefaction complex and the analysis of project risks. The proposed format of the financial and economic model is based on the calculation of key indicators of the project's operating and investment activities, including OPEX and CAPEX, as well as on the formation of financial plans that reflect the net profit and net cash flow. The presented financial models are used in calculating the performance indicators of the design solution and are the information basis for the analisis influence risk factors for net monetary income. The article examined the impact of macroeconomic drivers and deflator indices — liquefied natural gas prices, the dollar exchange rate against the ruble on the change in income from gas sales and on the formation of key project indicators. The authors of the article substantiate the expediency of applying the financial and economic model in practice for further use in project documentation as an economic part of the feasibility study.

Experimental and numerical approach for characterization and performance evaluation of cryogenic turboexpander under rotating condition

A small-scale radial expansion turbine is distinguished by its ease of production, higher efficiency, and reliability. Such turbines have been successfully used in cryogenic turboexpander systems for refrigeration and liquefaction of the process gas. This paper presents a methodology for design optimization, numerical, and experimental investigation of a radial turbine and nozzle (turboexpander), the most necessary and extortionate component of a nitrogen liquefaction system based on Claude cycle. The initial investigation starts with the preliminary design of a turboexpander using an in-house developed Matlab® code. Then, a Sobol method-based optimization approach has been proposed to determine the normalized sensitivity index and optimal range of major non-dimensional and geometrical variables for the better off-design performance of the turboexpander. After that, different losses of the turbine have been determined using an optimum set of loss correlations which is incorporated into the preliminary design process. This approach can overcome the optimization issues caused by the high sensitive design parameters, which may not be addressed through conventional methods, and ameliorates the off-design performance of the turboexpander (improves power output, total-to-static efficiency, and diminishing the turbine losses by 14.28%, 3.89%, and 9.61% respectively) as compared to the initial design. Based on this, three turboexpander systems are designed and a comparative numerical study has been conducted to study the flow field phenomenon and their thermodynamic performance at three operating pressure and cryogenic temperature (16 bar & 150 K, 8 bar & 120 K, and 4.5 bar & 95 K) using ANSYS CFX®. Finally, the Claude cycle-based experimental facility has been established to determine the thermal performance of the turboexpander at various operating pressure (16 and 8 bar), rotational speeds (120,612, 102,419, and 80,914 rpm), inlet temperatures (150 and 120 K), and mass flow rates (0.01–0.10 kg/s). The results illustrate that the predicted performance from the numerical simulation shows good agreement with the experimental results. Additionally, error analysis of experimental parameters has also been discussed.

Modeling of a Three-Stage Cascaded Refrigeration System Based on Standard Refrigeration Compressors in Cryogenic Applications above 110 K

More and more applications, such as natural gas liquefaction, LNG reliquefaction, whole body cryotherapy and cryopreservation, require cooling in the temperature range from 110 to 150 K. This can be achieved in systems using standard refrigeration compressors, which are reliable and cost-effective, but are subject to certain operating limits. This paper investigates the potential of a three-stage cascaded refrigeration system based on standard refrigeration compressors in this range of temperatures. The investigation takes into account the vital limitations of refrigeration compressors and aims to look for possible refrigerant configurations (taking into account PFCs, HFCs, HCs and HOs); performance limitations such as cooling power temperature and system COP; and the influences of system architecture (single-stage and two-stage compression). The paper investigates whether it is possible to design a three-stage cascaded refrigeration system using standard refrigeration compressors, and if so, at what cost? This investigation shows that the three-stage cascaded refrigeration system can reach the lowest temperature of 127 K with a COP of 0.179, which corresponds to a Carnot efficiency of 0.262. Moreover, systems based on natural refrigerants are found to be advantageous in terms of achieved temperatures compared to those that use synthetic refrigerants. Furthermore, only the application of R50 (methane) is shown to allow temperatures below 130 K to be achieved, and this is possible only in a two-stage compression cascade system. For most of the investigated configurations, the suction pressure must be below atmospheric pressure to thermally couple cascade stages.