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Within hydrogen liquefaction cycles, refrigerant mixtures reach highly critical conditions, with temperatures approaching the solidification temperatures of the pure components. To ensure the feasibility of the hydrogen liquefaction process, it is necessary to verify that such mixtures do not solidify under specified temperature and pressure conditions. This verification is carried out through the minimization of Gibbs free energy by simulating a RGibbs reactor in Aspen Plus® V11. For a given refrigerant mixture, comprising light hydrocarbons, hydrogen and nitrogen, the solidification temperature is determined as a function of pressure. The solidification curve is plotted for four mixed refrigerants that have been utilized in the literature for the precooling section of the hydrogen liquefaction process. The composition of the mixed refrigerant greatly affects the minimum temperature at which a refrigerant can be safely used without incurring solid precipitation, which varies between 60 K and 100 K. This work provides a guide for selecting the appropriate mixed refrigerant composition and operating conditions, with the aim to enhance the efficiency, reliability, and safety of hydrogen liquefaction technologies. [ABSTRACT FROM AUTHOR]

The state parameter allows the evaluation of the in situ state of soils, which can be particularly useful in tailings impoundments where flow liquefaction is the most common failure model. Positive state parameter values characterize a contractive response during shearing and, for non-plastic soils, can indicate flow liquefaction susceptibility. This paper presents a methodology to classify and estimate the state parameter (Ψ) for non-plastic silty soils based on seismic cone penetration measurements. The method expands on a previous methodology developed for sands that use the ratio of the small strain shear modulus and the cone tip resistance G0/qt for classification and Ψ assessment. For non-plastic silty soils, drainage conditions during cone penetration must be accounted for and are used to allow soil classification and correct the cone tip resistance. An empirical formulation is proposed to correct qt for partial drainage measurements and predict Ψ for non-plastic silty soils. Mining tailings results of in situ and laboratory tests were used to validate the proposed methodology producing promising responses. The Ψ value estimated through the proposed methodology are in the range of those obtained from laboratory tests, indicating an adequate prediction of behavior for non-plastic silty soils. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering & Architectural Faculty of Eskisehir Osmangazi University / Eskişehir Osmangazi Üniversitesi Mühendislik ve Mimarlık Fakültesi Dergisi is the property of Eskisehir Osmangazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the 2000s, some projects were defined to export Liquefied Natural Gas (LNG) in order to increase Iran’s presence in gas export markets. However, despite the initial planning until 2020, when this research was conducted, none led to a result, and Iran could not play a role in this market. Delay in executing these plans will lead to losing the opportunity to use the joint South Pars field and billions of dollars of foreign exchange earnings. The purpose of this study, which was conducted 2019 to 2020, is to identify the factors leading to the failure of Iran’s LNG projects. In order to identify and prioritize these factors, the opinion of experts and the Fuzzy Delphi technique is employed . Investigating the condition at the national and international level indicates that some factors have prevented all of these projects from being successful, including political issues, international sanctions on Iran, lack of domestic capital, lack of appropriate foundation for attracting foreign investors, constraints of domestic rules and regulations, especially in the upstream sector for choosing the contract format, not having access to the liquefaction technology, and the issues pertinent to marketing, and the most important one, lack of suitable commercial structural design. Identifying these factors and planning for tackling them is the key to escaping this current situation and a guide for prospering in future projects of the country. [ABSTRACT FROM AUTHOR]

The present study is an analysis of the processes in the components of the LPG (propane/butane) reliquefaction plant under the conditions of co-mingling in tanks when transporting by sea. For the analysis, the monitoring data of an LPG cargo operation have been used. An energy analysis of the mixture-based reliquefaction plant has been performed. The characteristics of the mixture in the tanks, the operating conditions of the reliquefaction plant, and the performance of the system have been considered. The method of equivalence has been applied for thermodynamic analysis. The result of the substitution of actual processes with equivalent ones allows for the accomplishment of the parameters control of each working fluid within the mixture as a pure working fluid. It is shown that the low-boiling component determines the operating parameters of the entire reliquefaction plant. The method of equivalence and visualization of the processes within the LPG as a mixture using the thermodynamic diagrams of pure working fluids is recommended to shorten the path to set up the appropriate reliquefaction plant management strategy. The energy analysis performed using the method of equivalent cycles has been validated with the existing reliquefaction plant characteristics. The inaccuracies are in the limit of 4%. [ABSTRACT FROM AUTHOR]

This paper investigates the steps of indirect liquefaction, specifically on the Fischer-Tropsch process. In particular, the essence of Fischer-Tropsch is elaborated, including its history and prerequisites. In the Fischer-Tropsch process, the catalytic conversion of synthetic gas produced from carbon feedstocks to synthetic fuels, works in specific conditions of temperature and pressure. This paper investigates the benefits of the diesel fuels derived from Fischer-Tropsch processes to the automotive industry, including the relatively low cost, the low greenhouse gas emission rates, and the facilitated process of gas conversion to synthetic fuel. In this paper, current and past investigations and experiments have been examined. As a result, several advantages of synthetic fuel over conventional crude oil were determined. [ABSTRACT FROM AUTHOR]

Joule-Thomson liquefiers are the commonest machines to liquefy gases. Over the years, countless number of articles have been published on the subject. Dozens of 1st and 2nd law analyses were carried out on Joule-Thomson liquefaction cycles. And yet an aspect of purely theoretical interest seems to have passed unnoticed, namely: for a given volume of gas, what conditions should be fulfilled to achieve maximum liquefaction without considering engineering details of design equipment and the highly irreversible character of work-consuming devices, heat exchangers, heat leaks and the throttling process. This work addressed this issue by applying the 1st law analysis and elementary calculus prescriptions to a simple Linde-Hampson liquefying process. The same approach could be applied to other liquefying cycles. As is well-known, for a given mass flow rate of a gas, maximum fraction liquefied occurs when the pre-cooling temperature, Ti, and initial pressure, Pi, lie on the inversion curve. It has been proved that this is only true if an additional condition is fulfilled. Expressions for it were derived for the van der Waals, RKS and PR equations of state. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering & Architectural Faculty of Eskisehir Osmangazi University / Eskişehir Osmangazi Üniversitesi Mühendislik ve Mimarlık Fakültesi Dergisi is the property of Eskisehir Osmangazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The adoption of hydrogen has been largely indicated as a feasible solution to support society in achieving its ambitious targets for a low-carbon future. The increased knowledge in liquefaction techniques has encouraged the study of technological solutions based on liquid hydrogen (LH2). Moreover, handling and distribution under cryogenic conditions represent attractive options due to the elevated energy density of LH2. Despite these advantages, the bottleneck for its widespread adoption is represented by safety aspects. Considering that an LH2 tank truck has a probability of suffering a car accident like all other road vehicles, an emergency autothermal burner has been designed in this work. This safety system has the purpose to dispose of the content of a tank truck to avoid the loss of containment. The disposal process includes the vaporization and pre-heating of the LH2, the mixing with ambient air, and its combustion. This device is completely self-supporting since the heat required to vaporize the LH2 is entirely provided by the combustion of the fuel itself. Firstly, the equation of energy balance around the burner was numerically solved to estimate the temperature of flue gases. Then, inner and outer heat transfer coefficients were determined for each section of the coiled-tube heat exchanger. Finally, the heat transfer surface was calculated. The spontaneous conversion between two spin isomers of hydrogen was considered. From the perspective of the heating process, the enthalpy of conversion represents an additional energy request. If the decrease of para-hydrogen fraction was neglected, the length of the heat exchanger would be significantly underestimated. Based on the obtained results, it is possible to conclude that the designed device can be transported on-site and started up easily, making it suitable for emergency response. [ABSTRACT FROM AUTHOR]

We consider an inventory routing problem (IRP) in the liquefied natural gas (LNG) supply chain, called the LNG-IRP. Here, an actor is responsible for the LNG production and inventory management at the liquefaction plants, the routing and scheduling of a heterogeneous fleet of LNG ships, as well as the inventories and sales at the regasification terminals. Furthermore, all ports have a limited number of berths available for loading and unloading. The LNG-IRP is more complicated than many other maritime inventory routing problems because a constant rate of the cargo evaporates in the tanks each day and is used as fuel during transportation. In addition, a variable number of tanks are unloaded at the regasification terminals. We introduce a new path flow formulation for this problem arising from a novel decomposition scheme based on parts of a ship schedule, called duties. A ship schedule for the entire planning horizon can be divided into duties consisting of a visit to a liquefaction plant, then one or two visits to a regasification terminal before ending in a liquefaction plant. The solution method suggested is based on a priori generation of duties, and the formulation is strengthened by valid inequalities. The same problem was previously solved by a branch-price-and-cut algorithm for a schedule-based formulation. Computational results show that the new formulation provides tighter bounds than the previous schedule-based formulation. Furthermore, on a set of 27 benchmark instances, the proposed algorithm clearly outperforms the previous branch-price-and-cut algorithm both with regard to computational time and the number of problems solved within a 10-h time limit. [ABSTRACT FROM AUTHOR]

The increase in energy demand and the need for lower CO2 emissions have increased the importance of natural gas as the cleanest fossil fuel in the energy market. Natural gas is mainly transported using pipelines or as liquefied natural gas (LNG). LNG is stored and transported in cryogenic storage tankers, where a part of the LNG evaporates, generating boil-off gas (BOG). The BOG is used normally as fuel for propulsion engines, but at low navigation speed, it is more than the engines’ fuel needs, and the excess quantity is either burnt or reliquefied. Existing technologies for on-board reliquefaction consume a large amount of energy and are costly, which arises the need for new concepts of reliquefaction technologies. The new proposed system operates on two modes; the first is the charging mode in which cold energy is stored when the LNG is evaporated to supply the LNG carrier propulsion system at high speed. The second is the discharging mode, in which the stored cold energy is used to condense the excess BOG at low navigation speed. The novel reliquefaction system utilizes latent or sensible heat storage materials that haven’t been examined before for cryogenic applications. A preliminary energetic assessment for the system is carried out using Aspen HYSYS, Excel and VBA, to study the impact of the variation of the operating conditions on the choice of suitable storage material and its performance. Results showed that low LNG evaporation and high BOG liquefaction pressures offer higher energy storage capacity for all types of thermal energy materials, with better performance for the latent ones. Further investigation on this technology helps in providing a suitable replacement for the costly available reliquefaction systems and avoids the burning of BOG with its consequent high CO2 emissions. [ABSTRACT FROM AUTHOR]

Stress controlled cyclic triaxial tests have been done on coastal sand of Digha, West Bengal, India, at different frequencies, confining pressures, and relative densities and cyclic stress ratios. Number of cycles for initial liquefaction (NL) has been determined for that number of cycle when excess pore pressure ratio has become equal to 1. Significant influences of density of sand, confining pressure and number of cycles for initial liquefaction on coastal Digha sand have been found. The test results have shown that increasing density of sand increases liquefaction potential, whereas cyclic strength of sand decreases with increase of confining pressure. An empirical correlation has been developed on cyclic strength of sand based on these parameters and this correlation fits quite well with the observed experimental results. Bender Element tests have been performed to determine maximum shear modulus (Gmax) of Digha sand at different densities and confining pressures. A high correlation coefficient between cyclic strength and Gmax of Digha sand at any NL has been found. A new pore water pressure generation model has been introduced for this sand along with upper bound and lower bound curves to predict excess pore water pressure build up due to seismic loads. [ABSTRACT FROM AUTHOR]

One of the significant achievements in Polish science was the liquefaction of oxygen, air, and other gases in 1883 by the Jagiellonian University professors -- Zygmunt Wróblewski and Karol Olszewski. Over the next few years, Krakow became one of the leading units in researching the physicochemical properties of gases. The mechanical workshop of the Jagiellonian University, which produced custom-made laboratory devices for liquefying gases, also gained recognition. The devices were designed by Karol Olszewski, a professor of chemistry at the Jagiellonian University, who modelled them on the countercurrent condenser by William Hampson. The apparatuses were made by the university mechanic, Władysław Grodzicki (1864--1927), who held this post in the years 1897--1927. He offered three types of apparatuses: a cased apparatus, a demonstration apparatus for air liquefaction, and a universal apparatus for liquefaction of air and hydrogen. In order to test how they functioned, a complete gas liquefaction apparatus was installed in the laboratory (including purifiers, a compressor, etc.). These devices were bought by European research institutions, universities, and schools. Grodzicki's activity contributed to the popularisation of research on low temperatures conducted at the Jagiellonian University. At the same time, it was one of the few Polish companies offering high-class scientific instruments. [ABSTRACT FROM AUTHOR]

This article provides an overview of the key areas of the legal landscape downstream of liquefaction terminals in the context of Canadian LNG projects. This will be of particular interest to those involved in Canada's nascent LNG industry, including project proponents, buyers and sellers of LNG, and owners and operators of LNG carriers and other vessels intending to load LNG, either as cargo or bunker fuel, from a terminal in Canada. Canada's LNG industry has had a rocky start in some respects, with many projects having been shelved and a number of the remaining projects facing an uncertain future due to market conditions, regulatory obstacles, and other challenges. However, there continue to be many factors supporting the development of LNG liquefaction capacity in Canada, including the desire to supply the world with responsibly sourced, cost-effective, and relatively clean fuel, and it is expected that a number of projects will ultimately proceed. The supply and transportation of LNG from such projects once they become operational will engage the body of maritime laws governing the operation of ships in Canadian waters and, where relevant, Canada's export laws. Other requirements may additionally apply by virtue of the contractual arrangements typically entered into in connection with such activities. Such regulatory and other requirements, and their place within the broader LNG value chain, are the subject of this article. [ABSTRACT FROM AUTHOR]

Cone pyrolysis liquefaction reactor is the key core device of biomass energy production equipment. The study of the dynamics of the cone is of great significance to the bioenergy conversion technology. Proper control of the movement time of the heat carrier in the cone can prevent it. Biomass superheated carbonisation can increase the ratio of gas and liquid formation. It is a difficult and key technology in the design of the cone pyrolysis liquefaction reactor. The kinetic differential equation of the relative motion of heat carrier particles can be obtained by kinetic analysis and calculation. It can play a key role in the in-depth study of the structural size design of the cone and the optimisation of the structural size parameters. This study conducts a dynamic simulation of the physical simplification model of biomass energy production equipment. The computer simulation software was used to simulate the running process of the simplified cone mechanism model. A reasonable physical prototype that meets the process parameters is designed. In view of the above complex dynamic phenomena, it is necessary to comprehensively analyse various methods of dynamics, and use appropriate numerical analysis and computer-aided design methods to carry out system equipment research and design. [ABSTRACT FROM AUTHOR]

The two water gas OH stretch vibrations that absorb in the infrared (IR) near 3700 cm-1 are redshifted to near 3300 cm-1 upon liquefaction. The bathochromic shift is due to the formation of four H-bonds: two are from the labile hydrogen atoms to neighbors and two are received from neighbors by the oxygen free electron pairs. Therefore, the water oxygen atom is surrounded by four hydrogen atoms, two of these make covalent bonds that make H-bonds and two are oxygen H-bonded. However, these permute at rate in the ps range. When the water molecules are isolated in acetonitrile (MeCN) or acetone (Me2CO), only the labile hydrogen atoms make H-bonds with the solvent. The bathochromic shift of the OH stretch bands is then almost 130 cm-1 with, however, the asymmetric (ν3) and symmetric (ν1) stretch bands maintained. When more water is added to the solutions, the oxygen lone doublets make H-bonds with the available labile hydrogen atoms from neighboring water molecules. With one bond accepted, the bathochromic shift is further displaced by almost 170 cm-1. When the second oxygen doublet is filled, another bathochromic shift by almost 100 cm-1 is observed. The total bathochromic shift is near 400 cm-1 with a full width at half height of near 400 cm1. This is the case of pure liquid water. Notwithstanding the shift and the band broadness, the ν3 and ν1 band individualities are maintained with, however, added satellite companions that come from the far IR (FIR) absorption. These added to the fundamental bands are responsible for the band broadness and almost featureless shape of the massive OH stretch absorption of liquid water. Comparison of light and heavy water mixture spectra indicates that the OH and OD stretch regions show five different configurations: OH4; OH3D; OH2D2; OHD3; and OD4 [J. Chem. Phys. 116, 4626 (2002)]. The comparison of the OH bands of OH4 with that of OHD3 indicates that the main component in OHD3 is νOH, whereas in OH4 two main components are present: ν3 and ν1. Similar results are obtained for the OD bands of OD4 and ODH3. These results indicate that the C2v symmetry of H2O and D2O is preserved in the liquid and aqueous solutions whereas Cs is that of HDO. [ABSTRACT FROM AUTHOR]

The evolution of temperature and velocity fields during direct metal deposition with coaxial powder injection was simulated using a self-consistent three-dimensional model based on the solution of the equations of mass, momentum, energy conservation, and solute transport in the liquid pool. The basic physical phenomena, including heat transfer, phase changes, mass addition, fluid flow, and interactions between the laser beam and the coaxial powder flow, were considered in the model. The level-set method was implemented to track the evolution of the liquid/gas interface. The temperature and velocity fields, liquid/gas interface, and energy distribution at liquid/gas interface at different times were simulated. For verification purposes, the cladding depth and height were compared with experimental results. [ABSTRACT FROM AUTHOR]

The liquid-gas transition of an electroneutral mixture of oppositely charged colloids, studied by Monte Carlo simulations, is found in the low-temperature–low-density region. The critical temperature shows a nonmonotonous behavior as a function of the interaction range, κ-1, with a maximum at κσ≈10, implying an island of coexistence in the κ-ρ plane. The system is arranged in such a way that each particle is surrounded by shells of particles with alternating charge. In contrast with the electrolyte primitive model, both neutral and charged clusters are obtained in the vapor phase. [ABSTRACT FROM AUTHOR]

Natural gas is the fastest-growing fossil fuel and LNG is playing a growing role in the world's gas supply. The liquefaction process is also by far the most energy-consuming part of the LNG chain. It is thus a priority today for the gas industry to decrease the cost and improve the efficiency of the liquefaction process of a plant. In this way, a novel techno-economic evolution of an existing NGL plant with adding an appropriate LNG production part is presented. Concerning the availability of propane, use of existing equipments and conditions of no structural changes in the existing installation, C3MR is used as the refrigeration system. For full recognition of the process, a high-accuracy surrogate model based on D-optimal approach is developed. MR composition (nitrogen, methane, ethane, and propane), inlet gas pressure of the LNG production part, demethanizer pressure, and high and low pressure of MR as the eight manipulated variables of the surrogate model predict the earned profit of the integrated plant. To increase profit, a hybrid GA-SQP optimization method is used. The results show that the earned profit of the optimized proposed plant with the LNG production capacity of 3.33 MTPA is 60.2% more than the existing NGL plant. In addition to increased earned profit, the thermodynamic efficiency is improved in the liquefaction section, too. Furthermore, the SPC value of 0.347 kWh kg-1 LNG shows that the optimized plant has acceptable liquefaction efficiency. According to the optimization results, mixture variables are more effective than process variables on the earned profit. It is noticeable that increasing the ethane recovery not always increases profit in such integrated units. [ABSTRACT FROM AUTHOR]

In these years, risk mitigation measures against the cryogenic spill hazard become one of the critical factors to ensure the level of safety in cryogenic liquid handling process plant, such as LNG liquefaction facility. The cryogenic risk mitigation can be achieved by spill control, welding connection instead of flange connection, and cryogenic spill protection insulation on the structure and equipment, etc. In the LNG liquefaction facility, cryogenic spill protection insulation is commonly applied for the critical area in combination with other risk mitigation measures. On the other hand, there is no recognized standard approach to define the extent of area which cryogenic spill protection insulation applied even if the installation of cryogenic spill protection insulation is high cost and have difficulties in construction phase. This paper proposes the simplified method to define the extent of cryogenic spill hazard area supported by the experimental test and simulation. For the less congested area of the facility, point source approach is applied. Leak frequency is calculated per flange and credible leak hole size is defined. Then, the extent of brittle fracture hazard area due to cryogenic hydrocarbon spill is decided from each flange. For the congested area, generic source approach is applied. In these areas, all leak sources are counted around the equipment to define the leak frequency, and credible leak hole size is defined. Then, the extent of brittle fracture hazard area is defined from the equipment. The cryogenic spill hazard area is considered as the extent of the LNG liquid droplet travel distance because the cryogenic liquid contact on the structure will cause the brittle fracture hazard (Wet condition on the surface on the structure cause the significant temperature drop). Simulation and Experimental Test are conducted to determine the extent of hazard area against the leak hole size. [ABSTRACT FROM AUTHOR]

The present work proposes a methodology for optimization of a liquefied biomethane (LBM) production plant. The LBM production plant comprises amine-based absorption upgrading followed by a single expander refrigeration cycle. The processes were modeled using Aspen HYSYS® and optimized through a Sequential Quadratic Programming algorithm. Any changes in the operating conditions of the upgrading process will affect the cooling demand in the liquefaction, while the opposite is not true. Based on this, a sequential optimization approach starting with the upgrading process is proposed. In order to accommodate the connection between the processes, different objective functions were formulated for the sequential optimization approach. The results from the sequential approach were compared with an overall optimization approach, where the entire LBM plant was optimized simultaneously. The results indicate that the same solution was obtained both for the sequential approach and the simultaneous approach. For the sequential approach, however, the best result was observed when the interaction between the upgrading and liquefaction processes was accounted for by considering the effect of the upgrading process on the exergy requirement in the liquefaction process. [ABSTRACT FROM AUTHOR]

Abstract Magnetic refrigeration based on magnetocaloric effect (MCE) has become a promising alternative technique to the traditional gas-compression refrigeration due to its friendly environment and high energy efficiency. In addition to room temperature magnetic refrigeration, this novel technology can be applied at low temperature, especially for the potential applications in gas liquefaction. Therefore, attention has been paid to explore suitable materials with large MCE near the gas liquefaction temperature and develop low temperature magnetic refrigerators. Herein, the typical magnetocaloric materials and prototypes in the temperature range of nitrogen and hydrogen liquefaction are reviewed. Heavy rare earth intermetallic compounds are promising for low temperature magnetic refrigeration due to a low ordering temperature and large magnetic moments. For example, DyFeSi compound shows a large reversible MCE under a low field change of 1 T around T C = 70 K, which is near the liquefaction temperature of nitrogen (77 K). It has been proposed that a composite can be formed by a group of magnetic refrigeration materials with successive transition temperatures and nearly constant MCEs, therefore expanding the range of working temperature desirable for Ericsson-cycle magnetic refrigeration. Highlights • Magnetic refrigeration based on magnetocaloric effect (MCE). • Technology applications at low temperature. • Typical magnetocaloric materials and prototypes in the temperature range of nitrogen and hydrogen. • Issues that still impede the development of low temperature magnetic refrigeration. • Focus on the future research. [ABSTRACT FROM AUTHOR]

The present paper describes the composition, characteristics, properties and technological flow of liquefied petroleum gas operation for motor vehicles, an increasingly economical and environmentally friendly alternative to petrol and diesel. The technological flow of liquefied petroleum gas may involve phase transition. A computing relation is established on the basis of the correlation between pressure- temperature liquefaction and regasification, respectively, at constant pressure, in the case of propane, a relation that is easy to apply. [ABSTRACT FROM AUTHOR]

We have performed a comparative analysis of the bio-oil produced by thermal liquefaction of microalgae in different solvents using high-resolution Orbitrap mass spectrometry and GC-MS approach. Water, methanol, ethanol, butanol, isopropanol, acetonitrile, toluene, and hexane were used as solvents in which the liquefaction was performed. It was observed that all resulting oils demonstrate a considerable degree of similarity. For all samples, compounds containing 1 and 2 nitrogen atoms dominated in the positive ESI spectra, while a relative contribution of other compounds was small. In negative ESI mode, compounds having 2 to 7 oxygens were observed. Statistical analysis revealed that products can be combined in two groups depending on the solvent used for the liquefaction. To the first group, we can attribute the products obtained by using protic (alcohols) and to the second by using aprotic (acetonitrile, toluene) solvents. Nevertheless, based on our results, we concluded that solvent possesses a minor impact on molecular composition of bio-oil. We suggested that the driving force of the liquefaction reaction is the thermal dehydration of the carbohydrate in algae, resulting in water formation, which could be the trigger of the producing of bio-oil. To prove this hypothesis, we performed the reaction with the dry algae in the absence of the solvent and observed the formation of bio-oil. Graphical Abstract [ABSTRACT FROM AUTHOR]

The primary energy mix forecasted for the future shows that growth rates will be the highest for renewable energy sources but, in absolute terms, fossil fuels will remain dominant. Among them, natural gas is the most attractive due to the advantages it offers in terms of environmental impact. This has recently contributed to the increased demand for natural gas and to the interest in developing those reserves that were left undeveloped in the past because of their high acid gas (particularly CO2) content. This has driven the recent research towards novel technologies that are suitable for the production of these gas fields. These novel technologies are based on low-temperature/cryogenic separation methods, which produce a purified natural gas stream at a temperature much lower than that reached when conventional technologies are used for acid gas removal. In addition to the key role played by natural gas, it is important to also take into account the one played by liquefied natural gas, which represents a valuable alternative to the common method for natural gas transportation via pipelines to reach the utilization zones. Currently, all the natural gas liquefaction technologies are developed for a natural gas stream coming from a conventional purification process that produces a purified stream at about ambient temperature. Considering the recent development of lowtemperature/cryogenic natural gas purification technologies, it is important to study liquefaction cycles so that they can be applied to a purified natural gas stream at low/cryogenic temperatures. This work deals with this study and aims at adapting the Single Mixed Refrigerant (SMR) liquefaction process currently used to liquefy a natural gas stream at ambient temperature, so that it can be applied to a purified natural gas stream at low/cryogenic temperatures. Simulations have been carried out in Aspen Hysys® V9.0 in order to adjust the composition and flowrate of the mixed refrigerant depending on the conditions of the purified natural gas stream that undergoes the liquefaction process. [ABSTRACT FROM AUTHOR]

Supercritical carbon dioxide extraction was utilized for the fractionation of a pinewood derived hydrothermal liquefaction bio-crude. The experiments were performed at temperature 120 °C and at pressure levels that correspond to CO2 density of 500, 615 and 730 kg/m³. Extraction yields of 34 to 49% were achieved, which increased with increasing solvent density. Density was reduced for all extracts (2-10%) while the H/C ratio increased when compared to the bio-crude. Low boiling point components such as ketones, 1-ring aromatic hydrocarbons and low molecular weight fatty acids were extracted preferentially (K-values up to 11). 1-ring phenols and benzenediols were enriched in the extracts as well (K-values 1-3). Heavy hydrocarbons and long chain fatty acids were extracted at the later stages of extraction when the lighter components were depleted. [ABSTRACT FROM AUTHOR]

A re-liquefaction plant is essential for a liquid ethylene gas (LEG) vessel to liquefy the boil-off gas (BOG) and return it to the cargo tank. In this study, three potential BOG re-liquefaction processes for LEG vessels have been compared in terms of coefficient of performance (COP) and exergy efficiency. The effects of the ethylene storage pressure, propane condensing temperature, propane evaporating pressure, intermediate pressures of refrigeration, and liquefaction cycles on the system performances were analysed. The parameters of the processes were optimised individually with the aim to minimise the system power consumption. The results showed that a cascade process denoted as Case-I is superior to other two processes. The optimal COP of Case-I is about 0.767 and the maximum exergy efficiency is 63.1%. This work could provide some reference for selection of the BOG re-liquefaction processes for LEG vessels. [ABSTRACT FROM AUTHOR]

The present research focuses on evaluating the kinetics for the liquefaction process and optimizing the process variable using Design expert software to maximize oil yield and by suppressing by‐products like gas and char. Optimum conditions for the maximum yield of oil (25.04%) was calculated as375°C, 45 min retention time, 3–5 mm particle size and at a constant heating rate of 15 °C min−1. Coats Redfern's approach showed maximum R2 of 0.9459 which requires less activation energy of 61.44 kJ kg−1 mol−1. The endothermic heat required for liquefaction was 20.91 MJ kg−1. The calorific value of oil was measured as 6.502 MJ kg−1. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 489–499, 2019 [ABSTRACT FROM AUTHOR]

Reports on experiments performed on iron particles with radii produced by pulsed evaporation from an electroplated tungsten filament in a cryogenic helium gas atmosphere. Description of the grids and collector used to control and detect charged particles; Features of waveforms designated and their causes; Equation for the average motion of particles of mobility in electric field in gas with flow velocity relative to the laboratory.

Abstract In this study, a conventional hydrogen liquefaction process is comprehensively analyzed. The studied hydrogen liquefaction process is consisted of two independent MR (Mixed Refrigerants) refrigeration cycles. In order to evaluate the liquefaction process and obtain valuable and noteworthy results, the process is examined through a comprehensive exergy based analyses. The exergy based analyses includes conventional exergy analysis to examine the performance of the liquefaction process, exergoeconomic analysis to obtain the effect of cost and economy on the performance, and exergoenvironmental analysis to provide beneficial information about the mutual effect of system's performance and environmental conditions. In addition, a sensitivity analysis is provided to assess and determine the mutual interaction among costs, environmental effects of each component, and the amount of exergy destruction. From the results, it is shown that the first refrigeration cycle exergy efficiency is obtained about 67.53% and the second refrigeration stage exergy efficiency is calculated about 52.24%. The whole hydrogen liquefaction process is exergy efficiency is 55.47%. The specific energy consumption (SEC) of this process is equal to 1.102 kWh/kg LH2. The total performance coefficient of the total process is 0.1797 which is higher than other reported articles. It is recommended from the Exergoeconomic and Exergoenvironmental analyses that the employed turbo-expanders and compressors are in priority for possible modification of the total process in the future. Highlights • A new hydrogen liquefaction process is investigated by exergy based analysis methods. • Two independent mixed refrigerant cycles are used for hydrogen liquefaction. • The process is evaluated by a 3E (exergy/exergoeconomic/exergoenvironmental) analysis. [ABSTRACT FROM AUTHOR]

Graphical abstract Typical structures of supersonic separator. Highlights • Advances in supersonic separation technology are systematically reviewed. • Condensation models and mathematical methods are generally summed up. • Problems existed in the practical application of the technology are pointed out. • Further research topics and methods to promote future applications are clarified. Abstract Supersonic separation technology is a new approach to condense and separate water, heavy hydrocarbons and other impurities from natural gas. This paper reviews the research advances in condensation characteristics of the Laval nozzle and separation mechanism of the supersonic separator in detail from the perspectives of theoretical analysis, experiments and numerical simulation, and summarizes the new application of this technology including natural gas liquefaction and removal of the acid gases. This review points out that while several aspects of this technology have been well studied, there still exist several issues in the practice. The further research topics are clarified to promote future applications such as the model modification of gas spontaneous nucleation rate to improve the prediction accuracy, and the combination the molecular dynamics technology with interface mechanics theory to study the collision and coalescence of the droplets and the interaction between gas and droplets under supersonic conditions. [ABSTRACT FROM AUTHOR]

Abstract The real gas effect was not taken into account in the current nucleation models, which will cause relatively big errors in the simulation of condensation process, and the supersonic condensation characteristics in the nozzle are still not clear now. Therefore, the fugacity is introduced into the model to increase the calculation accuracy of nucleation rate. Based on the modified model, the supersonic condensation process of the methane-ethane binary mixture was studied to clarify the nucleation and droplet growth process. Then the condensation characteristics of natural gas with different operation parameters were analyzed. The results show that in the condensation process of methane-ethane binary mixture, the ethane vapor first reaches critical radius and breaks through the free energy barrier and serve as the condensation nuclei for methane and ethane gas. The latent heat of condensation plays a dominant role in the change of the droplet growth rate of the binary mixture. Higher pressure or lower temperature or higher ethane content will result in greater nucleation rate and humidity. Highlights • Models for binary mixture spontaneous nucleation are modified. • Condensation process of methane-ethane mixture is clarified. • Condensation process of the multi-component gas is speculated. • Effects of operation parameters on liquefaction characteristics are studied. [ABSTRACT FROM AUTHOR]

Highlights • The working mechanism of imposing a DC flow on the regenerator is investigated. • The real gas losses are reduced significantly with an optimized DC flow. • The coefficient of performance of the refrigeration cycle is improved exponentially. • The mechanism of improving the liquefaction rate is further revealed. • The entropy loss of this approach and reduction possibilities are analyzed. Abstract Improving efficiency is an enduring effort for all refrigeration cycles. Real gases cause "intrinsic" heat losses in the regenerator and degrade the coefficient of performance (COP) of the regenerator of the refrigeration cycle. Previous experimental and numerical studies found that the COP of the regenerative refrigerator can be improved by imposing a direct-current (DC) flow, and the liquefaction rate can be improved by several times when the gas is precooled by the regenerator that works down to the temperatures close to or below the critical point. However, the working mechanism of such improvements has not been fully explored. In this paper, the working mechanism of imposing a DC flow on the regenerator working with a real gas is revealed based on thermodynamic analyses. The theoretical value of the DC flow and its influence on the COP of the regenerator are analyzed. The results show that the COP of the regenerator can be improved by over 10 times with a DC flow. An even higher relative Carnot COP of around 80% is possible to obtain in some specific temperature ranges. The enthalpy loss and the entropy loss of this approach has been estimated. This approach provides a potential way to improve the refrigeration COP and the liquefaction rate significantly. Measured liquefaction results found in the relevant literature have been analyzed to demonstrate the effectiveness of this approach. [ABSTRACT FROM AUTHOR]

Highlights • Crude polysaccharide was extracted from Enteromorpha prolifera and characterized. • The crude polysaccharide was converted into liquid oil by deoxy-liquefaction. • The low nitrogen content in crude polysaccharide oil can be comparable to that in petroleum. • The crude polysaccharide oil had higher calorific value than Enteromorpha prolifera oil. Abstract The objective of this study is to extract crude polysaccharide from Enteromorpha prolifera , investigate its structure and convert it into high-quality liquid oil by deoxy-liquefaction. This liquid oil was compared with that directly obtained from Enteromorpha prolifera raw material via elemental, FTIR and GC–MS analyses. The relative nitrogen content of the crude polysaccharide oil (0.97%) was much lower than that of Enteromorpha prolifera oil (4.85%), which can be attributed to the deproteinization process during the extraction of crude polysaccharide. Meanwhile, the crude polysaccharide oil featured high quality such as low oxygen (4.35%) and high calorific value (44.26 MJ/kg). The deoxy-liquefaction technique may be an effective way to convert crude polysaccharide into high-quality liquid fuel. [ABSTRACT FROM AUTHOR]