Liquid CO2 Research Articles

Selective Fmoc and Cbz protection of aromatic amino group in the presence of similar aliphatic function in liquid CO2

The selective protection of an aromatic amino group in the presence of aliphatic amino group in diamines by the action of FmocCl or CbzCl using liquid CO2 as the solvent has been proposed. The developed method is preparative, does not require complex purification of the product, and meets the principles of green chemistry.

Особенности роста пленок газового гидрата на границе жидкого углекислого газа с водой и раствором додецилсульфата натрия в тефлоновой и стальной кюветах

This work studied the features of a hydrate film growth at the interface between liquid CO2 and pure water or 0.1 mass% sodium dodecyl sulfate solution. In Teflon cell, a hydrate film in all cases is formed on the contact surface of the liquid phases, after whichno visible changes occur for an indefinitely long time. In the case of pure water in a steel cell, the hydrate layer formed at the water-CO2 interface slowly deforms due to its growth along the contact line between the hydrate and the cell wall. In experiments with a solutionof sodium dodecyl sulfate, the deformation of the hydrate film is much more pronounced, and the degree of water-to-hydrate conversion increases significantly. In our opinion, a previously undiscussed mechanism of hydrate capillary growth has been revealed,in which a capillary system is formed at the contact of a previously grown hydrate film with the reactor wall.

Numerical Investigation of Storage Behaviors of A Liquid CO2 Tank

The dynamic behavior of heat transfer induced by flow of the storage tank during the storage process was investigated using the computational fluid dynamics (CFD) approach, with the target of the liquid CO2 storage tank in a CO2 injection station in an oilfield. The flow field distribution outside the tank was simulated, exhibiting the patterns of air flow near the tank wall. The effect of progressive cooling leakage in the tank under various conditions was determined through simulation of the dynamic of flow heat transfer under various storage settings, with the result indicating that tank pressure has a beneficial effect on cooling capacity. The medium level, on the other hand, had a negative impact on cooling capacity. Finally, the impact of environmental variables on fluid loss was evaluated. This finding supports the safety and cost-benefit analysis of liquid CO2 storage systems.

Numerical-Experimental Analysis of the Coal Fracture Formation Mechanism Induced by Liquid CO2 Explosion

Numerical-Experimental Analysis of the Coal Fracture Formation Mechanism Induced by Liquid CO2 Explosion

Transient multiphase CO2 release from high‐pressure tanks: Influence of phase changes, viscous heating, and Joule–Thomson effect

AbstractIn this study, CO2 free expansion from high‐pressure tanks is studied in a transient state while considering the influence of different phenomena—that is, viscous heating, phase transition (solid/liquid/vapour phase), and the Joule–Thomson effect—in an initially supersonic flow. This investigation is performed using computational fluid dynamics (CFD) techniques, comparing the obtained results with some experimental data of the literature with a maximum discrepancy of around 8.5%. In particular, for the first time from the literature, it is observed that, according to the velocity evolution at the outlet, the discharge process is conveniently divided into three here‐defined stages: (1) shocking flow, where pressure abruptly decreases with time and flow becomes supersonic, this leading to the condensation of part of CO2; (2) transition flow, characterized by a sort of constant pressure time trend; and (3) flashing flow, where pressure decreases less abruptly following an asymptotic pattern up to the atmospheric one and flow becomes subsonic. Furthermore, non‐equilibrium condensation occurring in the tank, tube, and outlet is observed, finding that the minimum temperature reached by the fluid is around 235 K (−38°C). As well, the non‐equilibrium condensation is taken into account in order to give an indication of the amount of liquid CO2 leaving the outlet in the form of high‐speed jet, which can be a serious danger for personnel and surrounding installations. Moreover, we observe an important effect of viscous heating in the early‐stage expansion for a relatively short time range, within which the temperature in the tube experiences an abrupt increase of around 210 K (from 170 to 380 K). The same effect in the external room creates a convection flow, pushing CO2 towards the top. The results of the present work can be used for health, safety, and environment (HSE) management purposes and for a more precise process design related to CO2 storage and sequestration.

Determining the reasonable volume required to inject liquid CO2 into a single hole and displace CH4 within the coal seam in bedding boreholes: case study of SangShuPing coal mine

Previously, determining the injection volume of liquid CO2 used to displace CH4 in coal seam boreholes has lacked scientific input, and has mostly been based on engineering experience and analogy. Here, one scientific method combining theoretical analysis, physical experimentation, and underground measurements was used to determine the reasonable injection volume for a single borehole along a coal seam when injecting liquid CO2 to displace CH4 within the coal seam. Therefore, the amount of CH4, ΔXCH4 , that needs to be displaced by injecting liquid CO2 in a single borehole was obtained by theoretical calculation, and the displacement ratio, β , of CH4 displaced by injecting liquid CO2 under different pressures was analyzed. An in-situ test was designed to obtain the relationship between the injection volume and the distribution of the CO2 content in coal seams located at different distances from the injection hole and the other two key parameters in the equation, such as the influence coefficient, η, of the distribution of the CO2 content in the coal seam and the effective diffusion radius, l0. Based on the relationship between ΔXCH4 , β , η and l0, the empirical equation for the reasonable injection volume of single hole is obtained, and the correction equation is obtained after considering the influence coefficient ξ of CO2 flow non-uniformity. The results showed that to displace CH4, 6.1–7.7 m3 is a reasonable liquid CO2 injection volume range within a single borehole along the bed in 3303 working face when ΔXCH4 is 0.75 m3 t−1, β is 0.0088–0.01, η is 0.275, l0 is 16 m and ξ is 0.155. This method provides a theoretical basis and scientific guidance for applying liquid CO2 injection technology to displace CH4 in coal seams.

Research on the Fracture Properties and Mechanism of Carbon Dioxide Blasting Based on Rock-like Materials

Liquid carbon dioxide blasting technology has a wide range of applications and is characterized by sound fracturing effects, low vibration hazards, and high safety. In order to investigate the characteristics and mechanism of CO2 phase change rock breaking, liquid CO2 blasting tests on rock-like specimens were carried out in this paper. The results show that 130 MPa is the threshold value at which a CO2 blasting system moves from dynamic tensile stress damage to dynamic pressure stress damage. When blasting pressures of 100 MPa and 70 MPa are used, the lumpiness ratio of the fragments does not change much as the strength of the rock changes, so a suitable blasting pressure should be chosen to improve the blasting effect. Under the impact of blast stress and high-pressure gas flow, cracks develop to form a rough failure surface.

Life cycle cost and environmental assessment of CO2 utilization in the beverage industry: A natural gas-fired power plant equipped with post-combustion CO2 capture

Besat is a natural gas-fired steam-turbine power plant in Tehran, Iran’s only power station equipped with a monoethanolamine-based post-combustion CO2 capture unit (PCCU). The PCCU operates at a low recovery rate of 4.7% and produces 58 t-CO2/day. Captured CO2 is encapsulated and sold to beverage companies for carbonated soft drink production. Before developing this CO2 capture and utilization (CCU) route, a beverage company like ZamZam produced CO2 on-site, capturing CO2 from flue gas of diesel-fired boilers using a 95%-efficient absorption-refrigeration unit. This paper conducts an attributional, comparative life-cycle assessment/costing of applying the CCU technology to supply the beverage industry with CO2. ReCiPe, cumulative energy demand, and AWARE impact assessment methods are adopted to assess changes in the life-cycle economic, energy, and environmental impacts of electricity, liquid CO2, and carbonated water supply chains with the CCU route. As per findings, the CCU route significantly improves the sustainability profile of liquid CO2 supply for carbonated water production. Compared to on-site production, the CCU route reduces the average economic, energy, and environmental impacts of liquid CO2 supply by 55, 44, and 62%, respectively. However, the figures for carbonated-water production are reduced by only 10.1, 0.85, and 0.77%, respectively, since associated impacts primarily result from citric acid and polyethylene terephthalate value chains rather than liquid CO2. The CCU route, in comparison, increases most environmental burdens of electricity generation. With an efficiency of 4.7%, the PCCU reduces the global warming potential of electricity generation by 6.22% while increasing average toxicity- and eutrophication-related impacts by 55 and 30%, respectively, and production costs by 8%.

Insights into the interaction of a shale with CO2

Abstract. Caprock formations, such as shales, play a key role in safe underground CO2 storage since they serve as a hydromechanical barrier that prevents migration of the injected CO2 to the surface. While their hydromechanical response is important to ensure their sealing capacity, interaction with the injected CO2 involves additional thermo–hydro–chemo–mechanical (THCM) phenomena that may threaten the long-term integrity of the caprock. The low-transport properties of shales make them a suitable caprock material, but at the same time challenging to study due to the very long timescales (months/years) that are required for the various THCM processes to manifest. In this work, the long-term multiphysical interaction of the Opalinus Clay shale with liquid and supercritical CO2 is studied in 3D with live X-ray tomography. Three-dimensional analysis reveals the localised response of the coupled THCM processes that is often indistinguishable with conventional lab testing protocols. To improve spatial and temporal resolution while applying field-representative pressure and temperature conditions, small-sized samples are studied. Long-term injection of liquid CO2 resulted in significant fissuring of calcite-rich zones that were for the first time visualised and quantified from the X-ray images. Additionally, a re-arrangement of the pre-existing micro-fissures in the clay matrix was observed. The volumetric response during direct exposure of an Opalinus Clay sample to supercritical CO2 revealed an initial swelling at pre-fissured zones and initiation of new micro-fissures at areas of direct contact with the anhydrous CO2 due to pore water evaporation. Advanced 3D image analysis showed an increasing CO2 uptake in the caprock material with time, suggesting potential CO2 trapping in the material.

Recent advances in biogas purifying technologies: Process design and economic considerations

Biogas is a promising renewable energy source that is produced from biowaste and can potentially replace conventional energy resources. The economic value of biogas, which is primarily comprised of CH4, CO2, and other impurities (e.g. H2S, and N2) can be increased by upgrading and purification. This study presents the techno-economic feasibility of the cryogenic biogas upgrading process (CBioUP) based on product purities, biomethane selling prices and different refrigeration systems over 25 years of lifetime. The proposed CBioUPs is comprised of compression, refrigeration, and separation sections. Compressed biogas was liquefied in two refrigeration systems (propane pre-cooled mixed refrigerants and optimized cascade technologies) followed by a distillation separation unit. CBioUP proved its flexibility in terms of the number of distillation columns to produce low-grade CH4 (≈94.58 mol%), high-grade CH4 (≈97.13 mol%), and liquid CO2 by-product. The process's robustness to varying biogas feed composition revealed higher CO2 content would necessitate additional duty and/or equipment to enhance separation efficiency, whereas a CH4 content of ≥70% generated biomethane with a purity >99.6 mol% even in a single distillation column. CBioUP demonstrated its suitability for producing different grades of CH4 with a promising net present value (NPV) of $28.3 and $30.9 billion for low/high-grade biomethane.

Throttle and expansion characteristics of supercritical carbon dioxide during its venting

Supercritical CO2 has important applications in the fields of power cycle generation systems and carbon capture, utilization and storage (CCUS). The venting equipment represents a fundamental pressure-relief method for the purpose of depressurizing sections of those systems for inspection, maintenance or repair. The extremely low temperatures, dry ice blockage and overpressurization will appear in the system due to the throttling and expansion effect during venting. Meanwhile, the released CO2 may cause the exposure for the high density gaseous CO2, solid CO2 particles and cryogenics to the people in the venting area. The study of flow characteristics during CO2 venting is absolutely essential for assessing the hazard probability of dry ice formation and the blockage of relief valves during emergency or routine operational venting. In this paper, the theoretical analysis and experimental tests were conducted to study the throttle and expansion characteristics through the elbow, valve and orifice during straight vertical venting of supercritical CO2 with a 258 m long, 233 mm inner diameter pipeline system. The pressures and temperatures inside the main pipe and vent pipe, and the temperatures near field region were recorded during venting. After the valve was opened, the pressure in the vent pipe rose rapidly, and the rising range decreased with the decrease of the distance from the orifice. The temperature drops of CO2 were obvious after supercritical CO2 passed through the bend, the valve and the orifice. The supercritical CO2 in the main pipe changed into gas-liquid two-phase, and the liquid CO2 were produced in the vent pipe due to the throttling expansion effect. The CO2 temperature near the orifice were in quasi steady state after reaching the lowest value due to the continuous vaporization of liquid-phase CO2 and sublimation of dry ice particles, accompanied by the air entrainment process.

Comparative Analysis of the Liquid CO2 Washing with Conventional Wash on Firefighters’ Personal Protective Equipment (PPE)

Firefighters are exposed to several potentially carcinogenic fireground contaminants. The current NFPA 1851 washing procedures are less effective in cleaning due to the limited intensity of the washing conditions that are used. The 2020 edition of NFPA 1851 has added limited specialized cleaning for higher efficacy. The liquid carbon dioxide (CO2) laundering technique has gained popularity in recent years due to its availability to remove contaminants and its eco-friendliness. The primary aim of this study is to address the firefighter questions regarding the efficacy of cleaning with liquid CO2 and to compare it with the conventional washing technique. The unused turnout jackets were contaminated with a mixture of fireground contaminants. These turnout jackets were cleaned with conventional NFPA 1851-appoved aqueous washing and a commercially available liquid CO2 method. Post-cleaning samples were analyzed for contamination using pressurized solvent extraction and GC-MS. The liquid CO2 technique demonstrated considerable improvement in washing efficiency compared to the conventional washing.

Термодинамическая модель глубинного происхождения нефти и ее фазового «замерзания»

Based on the deep inorganic concept of the origin of oil and gas deposits, the evolution of these petrogenic reservoirs in the lithosphere is considered. The analysis of phase diagrams and experimental data made it possible to determine two trends in the evolution of non-methane hydrocarbons in the Earth's interior. In the upper mantle, the "metastability" of heavy (with a lower H/C ratio) hydrocarbons increases with depth. However, at temperatures and pressures corresponding to the surface mantle-crustal hydrothermal conditions, the “relative metastability” of heavy hydrocarbons increases with approach to the surface. When deep HCs fluids rise to the surface, petrogenic oil reservoirs are formed as a result of a drop in hydrogen fugacity and a gas → liquid oil phase transition. Under the physical and chemical conditions of an oil reservoir, metastable reversible phase equilibria are established between liquid oil, gas hydrocarbons and CO2 and solid (pseudocrystalline) "mature" and "immature" kerogens of "oil source" rocks. A decrease in hydrogen pressure and temperature leads to a stoichiometric phase transition (“freezing”) of liquid oil into solid kerogens. This occurs as a result of oil dehydrogenation in the processes of high-temperature CO2 fixation and low-temperature hydration of oil hydrocarbons, which are the main geochemical pathways for its transformation into kerogen. Thus, the formation of carbon matter in petrogenic reservoirs is the result of regressive metamorphism of deep hydrocarbon fluids, natural gas, liquid oil, and emerging accumulations of naphthides.

Exploitation of Liquid CO2 Based Greener Process for Valorization of Citronellal-Rich Essential Oils Into Flavor Grade (−)-Menthol Using Novel Sn/Al-B-NaYZE Composites

A two-step greener catalytic process has been developed for the semi-synthesis of (−)-menthol from citronellal-rich essential oils such as Cymbopogon winterianus and Corymbia citriodora by using novel bi-acidic composites. These novel composites (Al-B-NaYZE or Sn-B-NaYZE) were prepared by impregnation of Sn-B and Al-B over NaYZE framework to increase the Lewis and Bronsted acidic sites. These composites were thoroughly characterized using TDP, FT-IR, UV, XRD, SEM, HRTEM, SA, and TGA. The composite Sn-B-NaYZE cyclized 99% of citronellal to isopulegol isomers with 99% selectivity in 45 min under a liquid CO2 medium, while composite Al-B-NaYZE is showing 95% selectivity towards isopulegol isomers. Sn-B-NaYZE displayed enhanced selectivity due to its higher Lewis and Bronsted acidic characteristics. The chiral study indicated that the Sn-B-NaYZE composite is giving the highest selectivity (94%) towards (−)-isopulegol. (+)-Citronellal or citronella essential oil was found as an ideal substrate for (−)-menthol production. It observed that the Sn-B molar ratio over base material NaY-Zeolite played a major role in catalytic activity and selectivity towards (−)-isopulegol. Further, isopulegol isomers were reduced to 98% of menthol using 1%Pd/AC at 40 psi H2 pressure in 1 h. The reaction mixture was slowly frozen to -40 °C for trouble-free isolation of the crude menthol. Further, pharmaceutical and flavor grade (−)-menthol was purified from the crude menthol through an esterification process. This (−)-menthol was found to be 100% biobased on 14C-radiocarbon-dating to authenticate as nature-identical.

Influence of Mine Environmental Factors on the Liquid CO2 Pipeline Transport System with Great Altitude Difference.

To prevent coal spontaneous combustion and store CO2 in the coal mine, it is necessary to establish a fire-prevention pipeline transport system which continuously injects a large amount of liquid CO2 from the ground to the underground area directly. At present, few studies are focused on the law of liquid CO2 transport with great altitude difference. Moreover, the complex transport environment in the coal mine affects the design and application of the pipeline transport system for ground direct injection of liquid CO2. This study explores the influence of environmental factors at different depths in the coal mine on the liquid CO2 transport. Excessive altitude difference, ambient temperature and airflow velocity may lead to the boiling of liquid CO2 during pipeline transport and a sudden drop in CO2 temperature and pressure, which may cause danger in the pipeline transport system. The critical insulation thickness is determined based on the occurrence of the boiling of CO2. In addition, the influence law of adding an insulating layer of different thicknesses to the CO2 pipeline system is obtained. This study is of great significance to the establishment of a pipeline system that safely transports liquid CO2 from the ground to the underground mine.

Deformation mechanism and displacement ability during CO2 displacing CH4 in coal seam under different temperatures

Liquid CO2 has the synergistic effect of low-temperature damage and displacing CH4 after injecting into the coal seam, which can effectively improve coalbed permeability and promptly promote the adsorbed CH4 to desorption state for preventing the coal and gas outburst disasters. The injected CO2 gets adsorbed at the surface of the coal pores, which causes the coal swelling. In this work, we developed a triaxial experimental platform to explore the features of CO2 displacing CH4 under different temperatures. The variation of coal swelling and segmentation features of the displacing concentration was elucidated. The seepage ability and mechanism of gas mitigation in the coal seam during LCO2-ECBM were revealed. The results showed that the coal samples displayed swelling deformation in the CH4 adsorption and CH4 displacement stages, and the strain curves can be divided into rapid and slow deformation phases. The strain in the CO2 displacing CH4 stage is notably larger than that in the CH4 adsorption stage. Three dominant results were obtained during the CH4 displacement: Free CH4 driving by CO2 injection, CH4 self-desorption, and CO2–CH4 competitive adsorption. The displacing flow rate increased swiftly in the initial stage, and then decreased to a stable tendency. The cumulative displacement volume of CH4 in different stages exhibited distinct functional relationships. The integrated contribution of the coal matrix shrinkage and thermal stress damage to gas seepage improvement was more prominent than that of the adsorption swelling to seepage inhibition in the coal seam.

Waterless Dyeing and In Vitro Toxicological Properties of Biocolorants from Cortinarius sanguineus.

As a part of an ongoing interest in identifying environmentally friendly alternatives to synthetic dyes and in using liquid CO2 as a waterless medium for applying the resulting colorants to textiles, our attention turned to yellow-to-red biocolorants produced by Cortinarius sanguineus fungus. The three principal target anthraquinone colorants (emodin, dermocybin, and dermorubin) were isolated from the fungal bodies using a liquid-liquid separation method and characterized using 700 MHz NMR and high-resolution mass spectral analyses. Following structure confirmations, the three colorants were examined for dyeing synthetic polyester (PET) textile fibers in supercritical CO2. We found that all three biocolorants were suitable for dyeing PET fibers using this technology, and our attention then turned to determining their toxicological properties. As emodin has shown mutagenic potential in previous studies, we concentrated our present toxicity studies on dermocybin and dermorubin. Both colorants were non-mutagenic, presented low cellular toxicity, and did not induce skin sensitization. Taken together, our results indicate that dermocybin and dermorubin possess the technical and toxicological properties needed for consideration as synthetic dye alternatives under conditions that are free of wastewater production.

Numerical simulation of microscopic CO2 hydrate formation in sandy sediment with two-phase flow

This study provides a numerical simulation method of CO2 hydrate formation within microscopic porous media with the presence of two-phase flow of liquid CO2 and water. The influence of the hydrate formation rate and the two-phase flow speed on permeability reduction were studied numerically. The results showed that, when the hydrate saturation is small, say 0.2 or less, whatever the water shape is, grain-coating hydrate is dominant and the difference in flow speed hardly affect permeability reduction. When the hydrate saturation is about 0.3 or more, the larger the ratio of the flow speed to the hydrate formation rate, the larger the solid-phase surface area and the smaller the pore size are: that is, the smaller the permeability is. As the hydrate grows further, most of the water turns into hydrate and the difference in effective permeability due to the flow speed becomes noticeable as the water shape changes over time. It is thought that, at a high flow speeds, the flow purges more water from sand surfaces and places the purged water in the wake of sand grains, resulting in more pore-filling hydrate rather than the grain-coating type. However, such a difference is not so large and it seems that the existing mathematical models of permeability reduction due to hydrate formation can be applied even when there is two-phase flow.

Study on the Mechanism of Liquid Carbon Dioxide Fracturing and Permeability Enhancement Technology in Low Permeability Thick Coal Seam

For the urgent need of gas management in high gas and coal and gas herniated mines, liquid CO2 fracturing is used to increase the permeability and promote the pumping treatment of low permeability coal seams. In this paper, we construct the coal deformation and damage model, gas diffusion and seepage model, and coal seam permeability change model; simulate and solve the plastic zone and gas pressure of coal seam after fracturing with the COMSOL Multiphysics software; and set 4 different hole spacing groups of 2 m, 3 m, 4 m, and 5 m and 3 different hole layout methods of single hole, double hole, and net hole to get the best solution for liquid CO2 fracturing. At the same time, the specific effect of liquid CO2 on coal seam fracturing was verified by field experiments using coal seam No. 2 of the 12316 comprehensive mining working face of Wangjialing Coal Mine as the background of the study. The numerical simulation results show that the stress concentration area around the fracturing hole appears in single-hole fracturing, and the coal seam is prone to fatigue damage in this area, but the damage range is limited, and the reduction of gas pressure after fracturing is small; the fracturing effect of double-hole and net-hole fracturing is better than that of single-hole fracturing due to the existence of sufficient critical air surface. After negative pressure extraction, the coal seam gas pressure is positively correlated with the distance from extraction hole to fracturing hole, and the best extraction effect can be seen from the field experimental results with the netted hole layout at the hole distance of 3 m. The field test results show that the pure amount of gas extraction is improved about 4 times after liquid CO2 fracturing, which proves that liquid CO2 fracturing has a better enhancement effect on gas management in low permeability coal seams.

Enhancing Methane Recovery with Cryogenic Liquid CO2 Cyclic Injection: Determination of Cyclic Injection Parameters.

Carbon dioxide (CO2) is both a primary greenhouse gas and a readily available energy source. In this study, a new underground coal permeability enhancement technique utilizing cryogenic liquid CO2 (L-CO2) cyclic injection is proposed. The key parameters that determine the feasibility of this technique are cycle period and cycle number within a fixed working period. The optimal value of these two parameters mainly depends on the pore structure evolution law of coal cores before and after cryogenic L-CO2 cyclic freeze–thaw. Accordingly, nuclear magnetic resonance (NMR) was employed to study the evolution characteristics of the fracture networks and pore structures in coal cores subjected to different freeze–thaw cyclic modes. The results demonstrated that the amplitude and width of all peaks of the T2 spectra of the three coal cores (lignite, gas coal, and 1/3 coking coal) increased with an increase in the number of injection cycles. Additionally, as the number of freeze–thaw cycles (Nc) increased, the total porosity and effective porosity of the coal cores increased linearly before stabilizing, while the residual porosity first steadily diminished and afterwards became constant. Furthermore, the variation in the total porosity and residual porosity of the coal cores continuously diminished with an increase in the level of metamorphism. The NMR permeability of the coal cores showed a similar pattern to the porosity. Accordingly, the optimal parameters for cryogenic L-CO2 cyclic injection during a complete working time were determined to be Nc = 4 and Pc = 30 min. A field test demonstrated that after L-CO2 cyclic freeze–thaw treatment, the average gas drainage concentration of a single borehole in the test region increased by 1.93 times, while the pure flow of a single gas drainage borehole increased by 2.21 times. Finally, the gas attenuation coefficient decreased from 0.036 to 0.012. We concluded that the proposed permeability enhancement technique transformed coal seams from hard-to-drain to drainable.