Cryogenic CO2 Research Articles

Moving packed beds for cryogenic CO2 capture: analysis of packing material and bed precooling

This work expands upon previous work on a moving bed cryogenic carbon capture (CCC). Cryogenic carbon capture using a fixed packed bed captures CO2 frost deposited on the surface of the bed material; this build-up of frost fouls the heat transfer of the capture column and requires periodic shut down of the process to regenerate the bed material and collect CO2 for further storage. Using a moving bed continuously removes frosted bed material from the capture column preventing the excessive build-up of frost and eliminating the need for a regeneration step within the capture column. This paper sets out two objectives in evaluating an experimental moving bed system with a fixed volume of bed material; i) compare two different types of bed material within the capture column, a high-density ceramic and a steel bed material of similar particle sizes, and ii) combine the precooling step and capture step within the cryogenic capture column to allow the cooling of bed material and CO2 frost formation simultaneously. Frost front velocity results for the two different bed materials show 0.78 mm/s for steel bed material and 1.81 mm/s for ceramic bed material. Introducing a vertical gas injector into the capture column for additional cooling during the capture step allowed the capture step to be extended to approximately 5 minutes of continuous CO2 capture.

Cryogenic Removal of CO2 by Frost Formation from Biogas

Removal of carbon dioxide to upgrading biogas is possible by cryogenics and frost formation. In this work, it is targeted removing carbon dioxide by frost deposition (physical transition from gas to solid state) at low pressure and temperature from biogas, as well as assessing the impact of mass flow rate, temperature and the initial CO2 content in biogas on the carbon dioxide removal process. The Solid-Gas phase equilibrium between CH4 and CO2 is presented. It is followed by a sensitivity study of CO2 deposition on a flat plate and the assessment of different geometries of the heat exchanger generating frost. The global process including CO2 removal and biomethane liquefaction is simulated in AspenTech tools that are linked to a specific module modelling frost formation phenomenon. This module is coded in Dymola (Modelica language). Different operating modes of the heat exchanger are compared: thermal inertia or by direct cooling by nitrogen gas obtained after liquefaction of the biomethane. The temperature of the heat exchanger increases as CO2 deposits. Results show that cryogenic CO2 frost formation can be used for simultaneous liquefaction and upgrading of methane at 97% vol. minimum of purity and a reduction of cooling cycles on site by cold recovery from frost. This implies a reduction of energy intensity to remove carbon dioxide compared to conventional cryogenic technologies.

A reliable clean process for five-axis milling of knee prostheses

Prosthesis production for hips, knees, and other human body elements, including dental implants and spine screws, requires eliminating any risk of material damage or contamination. Five-axis milling is the most suitable technique to manufacture tailor-made prostheses for different personalized sizes with affordable costs. Human life expectancy is growing, so the demand of a higher prosthesis lifecycle and manufacturing optimization is a current necessity. In this work, a robust five-axis milling process using cryogenic CO2 as coolant fluid is presented and applied to a Ti6Al4V knee implant. Ti6Al4V (grade 5 and grade 23) alloys are very difficult to cut without lubri-cooling using oil emulsion coolant; however, this emulsion implies risks from introducing little oil drops entrapped in surface roughness valleys, hampering the cleaning process before patient’s surgery. CO2 reduces this risk uncertainty, making machining operations more feasible and suitable regarding environmental sustainability. In terms of feasibility, the surface finishing, roughness, and residual stresses was analysed, obtaining a standard of IT4-IT5, N4 and compressive stresses, respectively. Virtual simulation of machining is also a key in five-axis to make a more robust industrial process.

Influences of cryogenic CO2 and LN2 on surface integrity of inconel 625 during face milling

ABSTRACT Inconel 625 is a nickel-based super alloy especially used in aeronautical industries, due to its high mechanical strength, exceptional weldability and good corrosion resistance properties. However, machinability of Inconel 625 is quite challenging because of high-level heat generation in the cutting zone. In this work, to improve sustainable machining of Inconel 625; cryogenic CO2 and LN2 have been used as lubricants. Face milling was performed at two feed rates (f) of 0.2 and 0.6 mm/rev and spindle speeds (n) of 509 and 764 rpm with cryogenic (CO2 and LN2) cooling environments. The resulting surface characteristics, such as morphology, topography, micro-hardness and residual stress, along with chip morphology and tool wear, were investigated. Both cryogenic lubricants offered relatively better results at lower feed rate (f) and spindle speed (n). While cryogenic CO2 provided better surface morphology and topography, LN2 provided lower residual stress and higher surface micro-hardness.

Microstructure and Microhardness Alterations of Inconel 718 under Cryogenic Cutting

This paper presents the experimental investigations to identify the effect of different machining parameters on the microstructure and microhardness alterations beneath the machined surface of Inconel 718. The high-speed milling experiments were conducted using PVD multi-coated ball nose carbide inserts, under cryogenic CO2 condition at controlled cutting speed of 120-140 m/min, feed rate of 0.15-0.25 mm/tooth, depth of cut of 0.3–0.7 mm and a fixed width of cut at 0.4 mm. The experimental results discovered that the formation of plastic deformation could only be observed when cutting with the highest value of feed rate and depth of cut, deepened until 8.87 µm from the machined surface. At the same time, those factors also significantly increased machined surface hardness, made the workpiece harder than its bulk hardness. However, the hardness values were found reduced towards the sub-surface and back to its bulk hardness approximately 250 - 300 µm from the top surface. This study suggests that the finishing milling process of Inconel 718 under cryogenic CO2 conditions and at predetermined parameters can be performed at a depth of cut less than 0.3 mm as its machined sub-surface microhardness and microstructure alteration were observed to be inconsequential. Thus, a more economical machining process can be performed.

Investigations on milling SKT4 steel by using cryogenic carbon-dioxide

ABSTRACT Machinability of cryogenic carbon-dioxide (CO2) coolant was compared with conventional wet coolant during end milling SKT4 die steel with TiAlN-coated cutting tools in this study. The cutting temperature values were reduced by about 3% to 51% by using CO2 compared to wet cooling. During end milling, CO2 cooling decreased by around 54% feed, 45% normal, and 32% thrust forces compared to wet condition. The die steel surface had a better surface morphology with cryogenic CO2 cooling compared to wet cooling. In particular, chips with smooth surfaces were obtained under cryogenic cooling conditions. The absence of tool edge chipping and minimum cutting tool wear were observed with cryogenic coolant.

Performance analysis and comparison of cryogenic CO2 capture system

ABSTRACT Excessive energy requirement for the cryogenic condition is still the challenge for the current cryogenic CO2 capture system. In this work, the capture performance is investigated for the aim of energy savings on different cryogenic CO2 capture system, based on the combination of pressure recovery and cold energy utilization on the process residual gas. Based on this, two novel energy saving CO2 capture processes are proposed, which are defined as the post-expansion and the pre-cooled processes, respectively. The study presents a detailed comparison of the proposed process with conventional one regarding CO2 recovery and energy consumption. Also, the energy saving potential of two proposed processes is analyzed by varying the operating parameters, including process temperature, compression pressure, and inlet gas CO2 concentration. The simulation results show that the specific energy consumption can be decreased by 3.9% and 7.4% in the proposed post-expansion and pre-cooled process due to the effect of less cooling energy and compression work consumption, respectively.

Conceptual design, exergoeconomic analysis and multi-objective optimization for a novel integration of biomass-fueled power plant with MCFC-cryogenic CO2 separation unit for low-carbon power production

In the present study, the low-Carbon power production concept is proposed to introduce a novel integration. In the Bio-Energy Carbon Capture and Storage framework, Municipal Solid Waste is regarded as the main fuel for the system. To administer the analysis, a combination of a downdraft gasifier, a directly fired-gas turbine, Molten Carbonate Fuel Cell, Organic Rankine Cycle, and cryogenic CO2 separation unit is considered. The proposed integration is investigated from themodynamic, exergoeconomic, and environmental points of view. The multi-objective optimization is also conducted to minimize the CO2 emission and cost of electricity besides maximizing the overall exergy efficiency. By applying the optimum values for decision parameters, exergetic and economic results indicate that the combustion chamber and downdraft gasifier are identified as the component with maximum exergy destruction rate (17.44% and 14.59% of the total, respectively) due to high combustion and chemical reactions inefficiencies. Also, the net energy and exergy efficiency, cost of electricity, and specific CO2 emission result as 51.65%, 45.98%, 80.59 USD/MWh, and 101.20 kgCO2/kWh for the proposed system, respectively. The optimization results reveal that the CO2 emission was reduced by 33%. However, the exergy efficiency and cost of electricity will increase by 3% and 1.6%, respectively.

Experimental and simulation study on high-pressure V-L-S cryogenic hybrid network for CO2 capture from highly sour natural gas

Cryogenic carbon dioxide (CO2) capture technologies showed promising results for the purification of highly sour natural gas reserves. However, quantitative experimental data for solid and liquid CO2 formation during cryogenic separation is not adequately examined in the previous studies. Moreover, an economical and efficient cryogenic CO2 capture technology with reduced energy and hydrocarbon losses is necessary to make it attractive for commercial use. A high-pressure cryogenic hybrid network comprised of the packed bed and the cryogenic separator was developed for the cryogenic experimental study on CO2 capture from binary CO2−CH4 mixture to focus these areas. Feed containing 30, 50 and 70 % CO2 content were used and the separation study was conducted in vapor-solid (V-S), vapor-liquid (V-L), and vapor-liquid-solid (V-L–S) regions of phase equilibria. The packed bed was used in the V-S operational domain to quantify CO2 solid up to 20 bar because of the operational limitations. Separation characteristics and V-L isothermal flash measurements at 20, 30, and 40 bar pressure and temperature ranges from -20 to −60 °C were carried out in the cryogenic separator. The operation in the setups was carried out at different compositions of the CH4−CO2 binary mixture to define the boundaries of the hybrid cryogenic network. Liquid formation at 40 bar for 70 % CO2 feed was 0.15 kg at -55 °C as compared to 0.03 kg for 30 % CO2 feed. The simulation study was carried out using Aspen Plus along with the Peng Robinson Equation of State (EoS), and the results were compared with the experimental data, which showed good agreement. The hybrid cryogenic network showed an energy reduction of 37 % compared to the conventional cryogenic distillation network with 90.6–97.3 % CH4 purity and 2.65–12.39 % methane losses with different arrangements of the hybrid cryogenic network.

Experimental investigation of frost heave force on tubing and casing

Currently, CO2 injection is mainly used to rejuvenate oil reservoirs as a tertiary oil recovery technology. During the cryogenic CO2 injection process, when the temperature drops below the freezing point of water, the volume expansion caused by the freezing of the water in the tubing and casing annulus generates a frost heave force. This additional force increases the risk of tubing fracture and shortens the life of the well. Therefore, in this paper, a laboratory experiment is carried out to analyse the characteristics of tubing and casing stress under the effect of a frost heave force. The results show that the frost heave force in the annulus squeezes the tubing and casing into an ellipse during the freezing process and that the strength of the frost heave force is approximately equivalent to the internal pressure of 104 MPa in a thin-walled cylinder pressure vessel of the same size. The experimental results explain the tubing and casing failure mechanism with the effect of frost heave force and provide a theoretical basis for providing a solution to improve the service life of tubing and casing in a cryogenic CO2 injection well.

Sustainable functionalized metal-organic framework NH2-MIL-101(Al) for CO2 separation under cryogenic conditions.

In this study, a sustainable NH2-MIL-101(Al) is synthesized and subjected to characterization for cryogenic CO2 adsorption, isotherms, and thermodynamic study. The morphology revealed a highly porous surface. The XRD showed that NH2-MIL-101(Al) was crystalline. The NH2-MIL-101(Al) decomposes at a temperature (>500°C) indicating excellent thermal stability. The BET investigation revealed the specific surface area of 2530m2/g and the pore volume of 1.32cm3/g. The CO2 adsorption capacity was found to be 9.55wt% to 2.31wt% within the investigated temperature range. The isotherms revealed the availability of adsorption sites with favorable adsorption at lower temperatures indicating the thermodynamically controlled process. The thermodynamics showed that the process is non-spontaneous, endothermic, with fewer disorders, chemisorption. Finally, the breakthrough time of NH2-MIL-101(Al) is 31.25% more than spherical glass beads. The CO2 captured by the particles was 2.29kgm-3. The CO2 capture using glass packing was 121% less than NH2-MIL-101(Al) under similar conditions of temperature and pressure.

Experimental analysis of CO2 frost front behaviour in moving packed beds for cryogenic CO2 capture

In this work, the feasibility of a novel method of cryogenic carbon capture based on carbon dioxide frost deposition onto a cold moving bed is explored. As a gas mixture including CO2 flows through a sufficiently cold packed bed, CO2 is deposited onto the bed material as a frost. As the bed is warmed by the gas stream the frost front advances through the bed. Experimental measurements of the rate of frost advance within a static packed bed are used to set up a moving bed to achieve continuous CO2 removal. Precooled and dry binary gas mixtures of CO2 and nitrogen are used to determine frost front velocity in a capture column. The frost front velocity measured in fixed bed experiments with varying CO2 concentrations and gas flow rates are in the range of 0.4–1 mm/s. The experimental results were used to design a moving bed system that would match this range of frost front velocities so that continuous capture would be possible. Experiments were conducted to investigate the behaviour of temperature profiles within the capture column under moving bed conditions. These show that frost accumulation does not occur and successfully demonstrates continuous cryogenic carbon capture.

Development of a novel switched packed bed process for cryogenic CO2 capture from natural gas

Desublimation-based Carbon dioxide (CO2) removal from the natural gas (NG) in a cryogenic packed bed becomes challenging due to the dry ice formation inside the packed bed. Therefore, the cryogenic packed bed has been used for NG purification only in batch processes. However, to fulfill the energy requirements, it is crucial to develop a continuous process for NG purification, which is difficult for a single cryogenic packed bed. In the current research, a novel cryogenic packed bed system is proposed for continuous capture of desublimation based CO2 capture from natural gas. The process feasibility of the switching concept was proved through dynamic simulation and experimental study on CO2 separation from multi-component NG. It was observed that increasing CO2 content decreases the switching and saturation time of the cryogenic packed bed. The total energy required per packed bed per cycle in the switching system is 133.35. The saturation time for pure CO2 feed, NG sample-1, and NG sample-2 were 300, 500, and 600 s, respectively. An excellent agreement was observed between the results obtained from the experimental results and that obtained through dynamic simulation. A switching time of 200 s was found for a CO2 recovery of more than 98 %. This research work offers scientific data and theoretical support for the industrial application of switched cryogenic packed bed setup in CO2 capture from natural gas in the future. Moreover, in the current research work, scale-up study, and automatic control system for the switched packed bed are recommended for the future.

Influence of different cooling strategies on the process temperatures and chip transport quality in one-shot drilling CFRP/Al-stacks

This study focusses on the influence of different cooling strategies on process temperatures and chip transport quality in one-shot drilling CFRP/Al-stacks. In addition to the maximum temperatures in both individual stack components, temperature changes in the CFRP material due to hot aluminium chip interactions are analysed. The following cooling strategies are compared: compressed air through the drilling tool, cryogenic CO2 cooling at the aluminium bore exit as well as the combination of both. It is shown that process temperatures and chip transport quality significantly differ for the tested cooling strategies. Whereas CO2-cooling of the Al-plate results in overall smaller chips, the use of compressed air mainly improves chip evacuation. The combination of both cooling strategies shows high potential to prevent clogging in the chip flute as well as its negative impacts on workpiece quality.

Experimental studies on cryogenic CO2 face milling of Inconel 625 superalloy

ABSTRACT In this study, face milling operation was carried out on an Inconel 625 superalloy. About 27 experiments (L27) were conducted using Design of Experiments (DOE), which comprised three levels of cutting speed (V c ) and feed rate (f z) with a constant cutting depth (ap ). The study included three coolant environmental conditions such as no coolant (dry), normal coolant (wet) and cryogenic CO2 coolant. The output responses such as cutting temperature (T s), cutting forces (Fx, Fy and Fz ) and surface roughness (R a) were observed during the experiments. The results were optimized using the TOPSIS technique with ANOVA tests. The optimization results of highest closeness coefficient (Ci ) value indicated the lowest level of cryogenic CO2 coolant environment and the input parameters were the cutting speed (V c) 80 m/min and feed rate (f z) 0.05 mm/tooth. The optimization results of the highest closeness coefficient (Ci ) value were at cutting speed (V c) 80 m/min, feed rate (f z) 0.05 mm/tooth in cryogenic CO2 coolant environment. The findings indicated that cryogenic CO2 was both environmentally harmless and the best choice in comparison with dry and wet coolant.

Drilling Process on CFRP: Multi-Criteria Decision-Making with Entropy Weight Using Grey-TOPSIS Method

Moisture strongly affects the quality and mechanical specificity of carbon fiber reinforced plastic (CFRP) when using lubrication fluids during machining, and the significant impact of the cutting tool geometry and cryogenic gas cooling on CFRP machining capabilities are observed. The main body of this paper aims at making decisions about the optimum parameter of the drilling process while machining on CFRP base on the grey relational coefficient embed to the technique for order of preference by similarity to an ideal solution (Grey-TOPSIS). The entropy method was used to determine the weight of decision-making for handling a multiple measure decision-making response. The twist angle of the tool drill, lubrication, and feed rate were used as the input variables, and were analyzed while taking into account several multi-response outputs, such as the surface roughness, uncut fiber, and delamination. The result showed that a feed rate of 228 mm/min, the high-helix twist angle, and cryogenic CO2 lubrication leads the calculated value to close the relative value, which minimizes the value of the surface roughness, the uncut fiber, and the delamination. Finally, verification of the valid effect of each parameter process was conducted using analysis of variance. The results indicated that the lubrication was the highest remarkable criterion on the uncut fiber, the delamination, and the surface roughness. By integrating the advantage of grey systems theory, and the technique for order preference by similarity to an ideal solution, to evaluate and optimize the machining parameter, the results indicate that the proposed model is useful to facilitate the multi-criteria decision-making problem under the environment of uncertainty and vagueness. This relatively advanced approach is very effectual in rejecting process variation and a great assistive strategy than other multi-criteria decision-making approaches.

Developing an Innovative biomass-based Power Plant for low-carbon Power production: Exergy and Exergoeconomic analyses

In this research, a novel integration of a downdraft gasifier, an externally fired gas turbine, a molten carbonate fuel cell (MCFC), an organic Rankine cycle (ORC), and a cryogenic CO2 separation unit is developed. The exhaust air flow from the gas turbine is completely recirculated to the combustion chamber to utilize the air's high-temperature potential as the oxidizer in the syngas combustion. Produced hot gasses flow into the hot temperature heat exchanger (HTHE) to raise the compressed air temperature up to the gas turbine inlet temperature. Besides this, the MCFC unit is utilized both for producing additional power for the retrofitting CO2 separation unit. Finally, a cryogenic separation unit has been utilized for liquid CO2 production and for recovering H2 and CO from the fuel cell anode exhausts. Detailed exergy and exergoeconomic analyses have performed on the developed thermodynamic model, including a parametric analysis on critical design parameters. The overall exergy efficiency of the system results as 40.76%, the LCOE results as 77.74 USD/MWh, and specific CO2 emission results as 133.3 kgCO2/kWh. Results of the exergoeconomic analysis indicate the gasifier and the combustion chamber are identified as the components with the highest exergy destruction rates (20.18% and 15.54% with respect to the total). Exergoeconomic analysis allows to identify strategies for improving the system, focusing on the heat recovery unit (HRU) and the MCFC as the components with lowest and highest values of the exergoeconomic factor (0.47% and 96.39%), respectively due to high thermodynamic inefficiencies and high investment cost.

Identification of Active Sites on High-Performance Pt/Al2O3 Catalyst for Cryogenic CO Oxidation

Exclusive Pt species supported on inert substrates have not achieved satisfactory performance for cryogenic CO oxidation because of the constraint of the competitive Langmuir–Hinshelwood process in...

Ice formation and growth in supercooled water–alcohol mixtures: Theory and experiments with dual fiber sensors

Increased knowledge on fluid-solid phase transitions is needed, both when they are undesired and can impair process operations, and when strict control is required in fields such as food technology, the pharmaceutical industry and cryogenic CO2 capture. We present experimental results and theoretical predictions for the solid-formation and melting temperatures of ice in four binary water–alcohol mixtures containing methanol, ethanol, 1-propanol and 1-butanol. A dual fiber sensor set-up with a fiber Bragg grating sensor and a thin-core interferometer is used to detect the solid-formation. The predictions of melting temperatures with the cubic plus association equation of state combined with an ice model are in good agreement with experiments, but deviations are observed at higher alcohol concentrations. The measured degree of supercooling displays a highly non-linear dependence on the alcohol concentration. A heterogeneous nucleation model is developed to predict the solid-formation temperatures of the binary alcohol–water mixtures. The predictions from this model are in reasonable agreement with the measurements, but follow a qualitatively different trend that results in systematic deviations. In particular, the predicted degree of supercooling is found to be an essentially colligative property that increases smoothly with alcohol concentration. Experimental results are also presented for the growth rate of ice crystals in water–ethanol mixtures. For pure water, the measured crystal growth rate is 10.2 cm/s at 16 K supercooling. This is in excellent agreement with previous results from the literature. The crystal growth rate observed in ethanol–water mixtures however, can be orders of magnitude lower, where a mixture with 2% mole fraction ethanol has a growth rate of 2 mm/s. Further work is required to explain the large reduction in crystal growth rate with increasing alcohol concentration and to reproduce the behavior of the solid-formation temperatures with heterogeneous nucleation theory.

Machining Investigation of Nimonic-80A Superalloy Under Cryogenic CO2 as Coolant Using PVD-TiAlN/TiN Coated Tool at 45° Nozzle Angle

Manufacturing sectors are observing for methods to mitigate the use of cutting fluids for economic and ecological causes. The approach of cryogenic cooling looks to be an effective solution to enrich the process sustainability, as it is non-toxic and substantially increases the life of the tool. In this present research, milling experiments were performed to examine the surface aspects in the machining of Nimonic-80A using PVD-TiAlN/TiN-coated tool under various speed–feed combinations and nozzle orientation of 45°. Cryogenic carbon dioxide in machining enhances the quality of the newly machined face, and the outcomes were correlated with minimum quantity lubrication (MQL) and wet condition. The usage of cryogenic coolant significantly lowers the surface roughness by 38–45% and 13–18% over wet and MQL conditions. The effectiveness of cryogenic cooling curtails the contact between tool and chip, which diminishes the flank wear and chip thickness. Furthermore, it exhibits improved compressive residual stress over the other cooling strategies.