Liquefaction Plant Research Articles

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.

Molecular composition of direct coal liquefaction products obtained from the Shenhua industrial plant

The China Shenhua company has built and operated the only large industrial direct coal liquefaction (DCL) plant in the world for 15 years, with an oil product capacity of one million tons per year. However, there is insufficient information on the chemical composition of its products. In this study, the liquefaction product, including the distillate oil and the vacuum residue, as well as the circulating solvent were characterized by gas chromatography – mass spectrometry (GC–MS) and high-resolution mass spectrometry. The liquefaction oil has lower H/C ratio and higher oxygen and nitrogen contents compared to hydrogenation products derived from petroleum. The major component of the liquefaction oil is middle-temperature distillate, which is approximately 70 wt% concentrated in the range of 200–350 °C. Pyrene and perhydropyrene are the most abundant compounds in the liquefaction oil. Hydrocarbons with 1–4 aromatic rings were detected in the liquefaction oil, with skeletons of benzene, biphenyl, naphthalene, fluorene, phenanthrene, pyrene, etc.. Various partially hydrogenated and perhydrogenated aromatic compounds were identified in the oils and they even constitute the major component of the circulating solvent. 2,3-Dihydro-1H-phenalene was also found in high-relative abundance in the oils and has potential to be used as a marker for coal liquefaction produced through hydrogenation processes. Partially hydrogenated polycyclic aromatics exhibit higher dehydrogenation activity compared to tetralin. The organic component in the vacuum residue account for around 60 wt%, with toluene insoluble matter accounting for more than one third. The toluene soluble fraction has an H/C ratio of 0.82 and is mainly composed of aromatic with 4–8 rings. The molecular size and condensation degree of the residue are much higher than those of other fossil fuel-derived aromatic-rich substances. Further studies are necessary to evaluate whether aromatic hydrocarbons with such a high condensation degree are suitable for producing high-performance carbon materials.

Development and assessment of an offshore-based integrated hydrogen production and liquefaction system

The conventional hydrogen production methods depending on fossil fuels raise sustainability concerns. Therefore, there is a crucial need to develop sustainable and energetically self-sufficient hydrogen production processes. In this paper, an integrated hydrogen production and liquefaction system is developed to meet the hydrogen energy needs of communities. For this purpose, the present integrated system is considered and applied to the Hornsea Wind Farm, being developed off the east coast of the East Coast in the North Sea. The system aims to produce gaseous hydrogen by an electrolyzer and liquefy it by utilizing the energy input coming from a wind farm. The thermodynamic analysis is performed for the overall system and its components using energy and exergy methods through balance equations. Furthermore, the parametric evaluations are implemented to investigate the effects of varying operational conditions and design parameters on some key energy and exergy performance indicators. Under the specified conditions, the current study obtains the following results: an overall energy efficiency of 70.45 %, an overall exergy efficiency of 57.32 %, and a specific energy consumption of liquefaction plant (SEC) of 62.24 kWh/kg-LH2. Moreover, the levelized cost of H2 for the plant is found to be $7.28/kg. This research also reveals the primary sources of exergy losses by providing valuable insights to enhance the system's exergetic performance with some potential optimization opportunities. Furthermore, this study is expected to help achieve a more sustainable and decarbonized energy future with green hydrogen production and liquefaction for use.

H2-powered aviation – Design and economics of green LH2 supply for airports

The economic competitiveness of hydrogen-powered aviation highly depends on the supply costs of green liquid hydrogen to enable true-zero CO2 flying. This study uses non-linear energy system optimization to analyze three main liquid hydrogen (LH2) supply pathways for five locations.Final liquid hydrogen costs at the dispenser could reach 2.04USD/kgLH2 in a 2050 base case scenario for locations with strong renewable energy source conditions. This could lead to cost-competitive flying with hydrogen.Reflecting techno-economic uncertainties in two additional scenarios, the liquid hydrogen cost span at all five airport locations ranges between 1.37 and 3.48USD/kgLH2, if hydrogen import options from larger hydrogen markets are also available. Import setups are of special importance for airports with a weaker renewable energy source situation, e.g., selected Central European airports. There, on-site supply might not only be too expensive, but space requirements for renewable energy sources could be too large for feasible implementation in densely populated regions.Furthermore, main costs for liquid hydrogen are caused by renewable energy sources, electrolysis systems, and liquefaction plants. Seven detailed design rules are derived for optimized energy systems for these and the storage components. This and the cost results should help infrastructure planners and general industry and policy players prioritize research and development needs.

A novel small-scale biomethane liquefaction process: Assessment through a detailed theoretical analysis

The use of biomethane as fuel in the transport and power generation sectors is widely considered an effective tool to pursue the goals of carbon neutrality and energy security. Therefore, it is very important to promote not only the production and upgrading processes of biomethane from carbon neutral biomass, but also biomethane liquefaction processes, which can allow effective transportation of biomethane, thanks to the fact that the density of the liquid is higher than that of the compressed gas. Biomethane liquefaction plants can benefit from the technologies already used for the liquefaction of natural gas, but the size of biomethane liquefaction plants must be significantly smaller because of the limited quantities of biomethane generated by production and upgrading plants. Biomethane liquefaction plants have still limited diffusion; the most used technologies for the biomethane liquefaction are the Reverse Brayton cycle, the Lynde cycle, and the heat exchange with liquid Nitrogen. Single mixed refrigerant (SMR) processes, which are very effective for the liquefaction of natural gas, have a high potential for the biomethane liquefaction too, but the high specific energy consumption and high plant costs (mainly caused by typical multi-flow heat exchangers employed) are the major issues associated with SMR processes when applied to the very small size of biomethane liquefaction plants, characterised by very low biomethane flow rates. The aim of this paper is to propose a novel SMR process for biomethane liquefaction, which can overcome the above-mentioned issues, contributing towards the implementation of SMR processes for the liquefaction of biomethane and providing a valid alternative to currently used biomethane liquefaction plants; the proposed solution consists in using simple pipe-in-pipe heat exchangers in place of the more complex multi-flow heat exchangers. The validity of this solution is theoretically assessed using a detailed thermodynamic model based on well-stablished equations. Using this tool, it is shown that, by adjusting crucial parameters, such as the molar composition of the refrigerant, the heat exchange is satisfied with an affordable length of the heat exchangers, negligible pressure drops and good levels of the coefficient of performance with reference to such a small-scale application. The predicted specific energy consumption (accounting also for the biomethane compression and pre-cooling) for a biomethane flow rate of 0.03 kg/s is of the order of 0.8 kWh/kgCH4, which is a very good performance level compared to current commercial biomethane liquefaction processes.

Consideration of liquefied natural gas as an alternative source of gas supply to Ukraine

The object of research is the energy sector of Ukraine, specifically the gas supply system of the national economy. One of the most problematic places is the dependence of the Ukrainian economy on the import of natural gas (NG). Ukraine is rich in various natural resources, in particular, in natural and associated gas. However, own wells for NG extraction are not enough for gas supply to industrial enterprises and the population. Therefore, part of the necessary gas is imported. In the course of the study, methods of alternative supplies were analyzed, namely, liquefied natural gas (LNG), options for its supply with subsequent regasification were analyzed. The global market for liquefied natural gas (LNG) was studied and it was shown that the production and consumption of LNG is constantly increasing. Since Ukraine is part of Europe, and the main suppliers of LNG for European countries are the USA and Norway, one of the options for gas supply for Ukraine considered the supply of LNG to the territory of Poland by sea transport, its regasification and subsequent transportation to consumers through existing pipelines. The second option is the supply of LNG to the Ukrainian coast of the Black Sea. To do this, it is necessary to study prospective transportation routes, build logistics and terminals for receiving and regasifying LNG. Since the depth of the channels from the Mediterranean to the Black Sea is small, the option of supplying natural gas from Central Asia by pipeline to the Black Sea coast of Georgia, its liquefaction, transportation by sea and regasification is proposed. This option requires significant capital expenditures for the construction of a natural gas liquefaction plant on the territory of Georgia and a regasification complex on the Ukrainian coast or a floating terminal. In the course of the work, LNG quality criteria used in the world were studied, and it was noted that for the purchase and use of LNG in Ukraine, it is necessary to develop own standards for controlling its composition. Because the technology of providing the consumer with natural gas using LNG is more flexible than pipeline transport. Its implementation will make it possible to provide Ukraine with natural gas in the required quantities and, if necessary, to promptly change the volume of deliveries.

THE PROBLEM OF LIQUEFACTION OF NATURAL GAS CONTAINING NITROGEN IN SMALL-SCALE PLANTS

One of the problems in the implementation of natural gas liquefaction technology in a closed high-pressure cycle is the accumulation of low-boiling components, in particular, nitrogen in the circulating gas stream, as a result of which the throttle effect decreases and, accordingly, the specific energy consumption of the liquefaction plant increases. The nitrogen concentration influence on the liquefaction plant operation in the throttle cycle of high-pressure natural gas with a nitrogen content of 0 to 6 % was studied using the GazCondNafta software system for computer simulation of technological processes. To solve the problem of liquefaction of nitrogen-containing gases, a liquefaction scheme with two stages of throttling and intermediate separation with nitrogen vapor stripping is proposed. The effect of gas pressure in the nitrogen separator was determined from the point of view of minimizing losses of the main component of natural gas — methane — with stripping gas with a relatively small decrease in energy efficiency. Bibl. 14, Fig. 6, Tab. 4.

Rotordynamic Analysis and Operating Test of an Externally Pressurized Gas Bearing Turbo Expander for Cryogenic Applications

This study designed an externally pressurized bearing and analyzed the rotordynamics of a turbo expander for a hydrogen liquefaction plant. The turbo expander, comprising a turbine and compressor wheel assembled to a shaft, lowered the temperature of the helium refrigerant. Its rated speed was 75,000 rpm, and an externally pressurized gas bearing was selected to support the rotor. Pressurized helium was used as the lubricant for the bearing operation. To design the rotor–bearing system, we conducted a bearing performance analysis and rotordynamic characteristic prediction using the developed numerical model. We calculated the bearing stiffness and flow rate of the bearing gas for various feed parameters and selected the appropriate orifice diameter for maximum stiffness. The predicted Campbell diagram showed that the system had a sufficient separation margin with the critical speed, and the predicted critical speed correlated well with the nonlinear orbit simulation. A successful operation was achieved with the manufactured turbo expander within the rated speed. The shaft vibration was monitored during the operation test, and the test results revealed two critical speeds below the rated speed, as predicted by the analytical model. In addition, the shaft vibration was maintained at <3 μm.

Raman spectroscopy for ortho-para hydrogen catalyst studies

For the design of efficient hydrogen liquefaction plants and for the production of accurate ortho-para hydrogen samples, precise knowledge about the kinetics of ortho-para catalysts and accurate ortho-para monitoring is mandatory. Raman spectroscopy as a direct measurement of the ortho-para ratio is independent of other gas parameters, such as temperature, pressure, and flow rate and also undisturbed by impurities, such as nitrogen and oxygen in the gas. Therefore, Raman spectroscopy is a superior technique for ortho-para monitoring, com-pared to methods based on thermodynamic properties like heat conductivity. Within this work, an experimental proof of concept of a Raman based system to study ortho-para catalyst kinetics is shown.

Optimisation de la traçabilité en endoscopie

For the design of efficient hydrogen liquefaction plants and for the production of accurate ortho-para hydrogen samples, precise knowledge about the kinetics of ortho-para catalysts and accurate ortho-para monitoring is mandatory. Raman spectroscopy as a direct measurement of the ortho-para ratio is independent of other gas parameters, such as temperature, pressure, and flow rate and also undisturbed by impurities, such as nitrogen and oxygen in the gas. Therefore, Raman spectroscopy is a superior technique for ortho-para monitoring, com-pared to methods based on thermodynamic properties like heat conductivity. Within this work, an experimental proof of concept of a Raman based system to study ortho-para catalyst kinetics is shown.

Novel dual-mixed refrigerant precooling process for high capacity hydrogen liquefaction plants with superior performance

Liquid hydrogen is a superior alternative for the current energy storage methods and energy carriers as it has higher energy density and cleanliness. However, hydrogen liquefaction is an energy-intensive process. In particular, the precooling process of hydrogen consumes a tremendous portion of about 30 % of the total compression power of the plant. Several previous studies introduced various pure-refrigerant and single mixed refrigerant (SMR) precooling processes, however, their specific energy consumption (SEC) still very high especially at large-scale capacities. Therefore, this study presents a novel, efficient, and large-scale dual-mixed refrigerant (DMR) process to precool the hydrogen from 25 °C to -192 °C at a pressure of 21 bar. New heavyweight-based mixed refrigerant MR1 and lightweight-based mixed refrigerant MR2 are developed for the DMR process using a new-proposed systematic approach. The proposed DMR process is capable of handling a wide range of hydrogen flow from 100 TPD to 1000 TPD with SEC of 0.862 kWh/kgH2Feed, which is 20.33 % lower than the most competitive SMR process available in the literature. Based on the sensitivity analysis, further optimization of the DMR operating parameters reduced the SEC to 0.833 kWh/kgH2Feed at an optimal capacity of 500 TPD. Furthermore, the COP of the new process is improved by 14.47 % and the total annualized cost is reduced by 12.24 %. Compared to five other technologies that use the pure-refrigerant and other SMR precooling processes, the DMR reduces the SEC by 39.0 % to 63.0 %. The novel precooling process presented herein has the potential to drive the development of large-scale hydrogen liquefaction processes.

Techno-economic modeling of zero-emission marine transport with hydrogen fuel and superconducting propulsion system: Case study of a passenger ferry

This paper proposes a techno-economic model for a high-speed hydrogen ferry. The model can describe the system properties i.e. energy demand, weight, and daily operating expenses of the ferry. A novel aspect is the consideration of superconductivity as a measure for cost saving in the setting where liquid hydrogen (LH2) can be both coolant and fuel. We survey different scenarios for a high-speed ferry that could carry 300 passengers. The results show that, despite higher energy demand, compressed hydrogen gas is more economical compared with LH2 for now; however, constructing large-scale hydrogen liquefaction plants make it competitive in the future. Moreover, compressed hydrogen gas is restricted to a shorter distance while LH2 makes longer distances possible, and whenever LH2 is accessible, using a superconducting propulsion system has a beneficial impact on both energy and cost savings. These effects strengthen if the operational time or the weight of the ferry increases.

A novel integrated system of hydrogen liquefaction process and liquid air energy storage (LAES): Energy, exergy, and economic analysis

With the global positive response to environmental issues, cleaner energy will attract widespread attention. To improve the flexible consumption capacity of renewable energy and consider the urgent need to optimize the energy consumption and cost of the hydrogen liquefaction process, a novel system integrating the hydrogen liquefaction process and liquid air energy storage (HLP–LAES) is proposed. The operating strategy of the system ensures that it can produce liquid hydrogen and has the function of energy storage and power generation. A 3E study (energy, exergy, and economics) is carried out to evaluate the techno-economic performance of the proposed energy-intensive process. After optimization of key parameters, when the daily output of liquid hydrogen is 50 tons, the maximum daily power generation can reach 131.3 MWh, accounting for 1.21% of the daily electricity consumption of urban and rural residents in Qinghai Province, China. The round-trip efficiency of the proposed process is 58.9%, the specific energy consumption of liquid hydrogen is 7.25 kWh/kgLH2, and the total exergy efficiency is 53.2%. The payback period will be reduced to 1.7 years when the liquid hydrogen is sold at 7.0 $/kgLH2. If the proposed process is retrofitted from a stand-alone hydrogen liquefaction plant, the shortest retrofitting payback period is 9.2 years. The charging and discharging processes of the LAES are innovatively redesigned to better match the hydrogen liquefaction process, while achieving deep coupling and good synergy between the systems. This work aims to provide a reference for the efficient consumption of renewable energy, grid load balancing, and commercialization of the combination of liquid air energy storage and hydrogen liquefaction plants.

Nano-Enhanced Microbial Remediation of PAHs Contaminated Soil

The emergence of polycyclic aromatic hydrocarbons (PAHs) from a variety of natural and anthropogenic sources, such as coal gasification and liquefaction plants, coke and aluminum production, catalytic cracking towers, and motor vehicle exhaust, among others, results in significant soil pollution, and a threat to human health, igniting a surge of interest in advanced research. Even though the cleanup of PAHs-contaminated areas received a great consideration. In the last decade, nanotechnology has exploded in popularity as a result of several unique properties of nanomaterials, and remediation is no exception. Thus, nano-enhanced bioremediation reported to act as a viable and effective strategy for PAHs remediation. Further, the integration of nano-enabled materials with microorganisms emerged as a promising biodegradation approach for PAHs remediation. As a result, the focus of this mini review is on depicting the possible roles of various nanomaterials in decontaminating PAHs as a green strategy by boosting the efficacy of microbial functionality, and mechanism of nanoparticles-microbes interaction in PAHs degradation. The future perspective of nano-enhanced microbial remediation of PAHs in realistic environments are also discussed.

Thermodynamic Analysis and Optimization of the C3/MRC Liquefaction Process

In the natural gas liquefaction process, the mixed refrigerant natural gas liquefaction process is widely used in LNG liquefaction plants because of its advantages of low energy consumption. This paper focuses on the influences of important parameters in the C3/MRC liquefaction process, that is, the comparison between propane precooling temperature and the number of moles of methane in mixed refrigerant, power consumption and loss. In addition, the total process was optimized with the optimizer and manual adjustment in HYSYS software to minimize the total power consumption. The results show that with increasing propane precooling temperature, the propane flow rate is almost unchanged, while the mixed refrigerant flow rate decreases significantly, and the loss of the heat exchanger increases significantly. The power consumption of the propane precooling cycle and hybrid refrigeration cycle increases with increasing methane content in the refrigerant, so the power consumption of the whole process increases accordingly. The effect of the methane content in the mixed refrigerant on the process evaluation index is more significant than that of the propane precooling temperature.

Технико-технологические решения проектов сжижения метана угольных пластов

The paper presents technological and cost studies aimed at substantiating selection of technical and technological solutions in the coal bed methane liquefaction projects on the example of Naryksko-Ostashkinskoye and Taldinskoye methane-coal deposits in Kuzbass. Required capacity of the coal bed methane liquefaction plant is substantiated taking into account phasing of the capacity commissioning. Results of technological calculation of the preferred cycles of the coal bed methane liquefaction, as well as estimate of the cost of the main technological equipment of the compared options, are presented. It is concluded that it is necessary to adapt the initial deposit development project to the schedule for commissioning capacities of the coal bed methane liquefaction, and that using the SMR cycle is preferable.

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.

Gravitational effects on liquefaction systems for Lunar and Mars exploration

There is interest at NASA, other space agencies, and industry, in the liquefaction of fluids produced through in-situ processes on the surfaces of the Moon and Mars. A multi-center team at NASA recently considered multiple different refrigeration cycles and refrigeration integration methodologies and how these might fit into early liquefaction plants for NASA's exploration initiatives and In-Situ Resource Utilization (ISRU). The rate of liquefaction for ISRU is quite slow in comparison to large scale terrestrial applications. These studies concluded that, for both structural and heat spreading reasons, integrating the refrigeration tubing on the surface of the storage tank wall is an attractive path to pursue in the near term. In order to develop a technology development path and inform investors, it was desired to investigate the sensitivity of gravity of the processes involved.An analysis of the condensation processes within the tank is performed. The objective is to determine the sensitivity of liquefaction to gravitational effects. The heat transfer mechanisms include forced convection heat removal to the refrigeration system (or cryocooler), conduction through the tank wall heat exchanger, and convection and condensation on the inner tank wall. Gravity affects the liquefaction process via condensate liquid drainage, natural convection in the ullage, and the shape of the liquid–vapor interface within the tank. Analysis of these mechanisms shows that while there is some sensitivity to gravitational level in general, within the bounds of current interest (rate of liquefaction appropriate to Lunar and Martian applications, and cooling capacity of the cryocooler), this sensitivity of liquefaction to gravity is quite small. Thus, system level testing on the Earth should suffice for the performance prediction and demonstration of liquefaction operations as applicable to Lunar and Martian applications.

43+T Grenoble Hybrid Magnet: From Final Assembly to Commissioning of the Superconducting Outsert

The Grenoble Hybrid magnet is a modular platform using resistive and superconducting technologies to produce various DC high magnetic field and flux configurations for the scientific community. They range from 43 T in 34 mm diameter with 24 MW electrical power to 9 T in 800 mm diameter when the superconducting coil is used alone. Thanks to the ongoing upgrade of the electrical power installation at LNCMI-Grenoble to 30 MW, and possibly to 36 MW, the opportunity to increase the total field well above 45 T in the near future is anticipated and studied in detail. The key design parameters will be recalled comprising the specifically developed Nb-Ti/Cu conductor, the large-bore outsert superconducting coil, the magnet cryostat with its structure including the eddy-current shield, the cryogenic line for the interconnection with the cryogenic satellite and the dedicated 150 l/h He liquefaction plant. All components of the superconducting part of the hybrid magnet platform have been built, tested and delivered to LNCMI-Grenoble, where integration and final assembly are continuing. The status of the project will be presented with the main problems encountered and solved. It includes the recent commissioning tests of the cryogenic satellite producing the pressurized superfluid He at 1.8 K as well as the successful powering tests of the specially developed current leads at ultimate current and under fully degraded cooling conditions simulating the worst-case accidental scenario.

An Application: A Multi-Mode Natural Gas and Liquefied Natural Gas Supply Chain Management Problem

Natural Gas (NG) and Liquefied Natural Gas (LNG) are environmentally friendly and price-competitive energy resources that can be used in every part of the world. In this study, we develop a mixed-integer programming model for the NG and LNG supply chain that includes the location of liquefaction plants, regasification units, storage facilities, and distribution hubs together with the routing of the vehicles for inland distribution of LNG and cryogenic vessels for sea transportation. Unlike other models in the literature, the location of the NG and LNG facilities and routing of vehicles of different modes are optimized by considering the minimization of costs by using the 𝜺 – Constraint method, and different transportation modes, like sea, road, and pipeline, are used together for better effectiveness and cost reduction. The developed model is applied to Turkey to check whether the model is viable for real-world systems