Mixed Gas Research Articles

Immediate cardiopulmonary responses to consecutive pulmonary embolism: a randomized, controlled, experimental study

BackgroundAcute pulmonary embolism (PE) induces ventilation-perfusion mismatch and hypoxia and increases pulmonary pressure and right ventricular (RV) afterload, entailing potentially fatal RV failure within a short timeframe. Cardiopulmonary factors may respond differently to increased clot burden. We aimed to elucidate immediate cardiopulmonary responses during successive PE episodes in a porcine model.MethodsThis was a randomized, controlled, blinded study of repeated measurements. Twelve pigs were randomly assigned to receive sham procedures or consecutive PEs every 15 min until doubling of mean pulmonary pressure. Cardiopulmonary assessments were conducted at 1, 2, 5, and 13 min after each PE using pressure-volume loops, invasive pressures, and arterial and mixed venous blood gas analyses. ANOVA and mixed-model statistical analyses were applied.ResultsPulmonary pressures increased after the initial PE administration (p < 0.0001), with a higher pulmonary pressure change compared to pressure change observed after the following PEs. Conversely, RV arterial elastance and pulmonary vascular resistance was not increased after the first PE, but after three PEs an increase was observed (p = 0.0103 and p = 0.0015, respectively). RV dilatation occurred following initial PEs, while RV ejection fraction declined after the third PE (p = 0.004). RV coupling exhibited a decreasing trend from the first PE (p = 0.095), despite increased mechanical work (p = 0.003). Ventilatory variables displayed more incremental changes with successive PEs.ConclusionIn an experimental model of consecutive PE, RV afterload elevation and dysfunction manifested after the third PE, in contrast to pulmonary pressure that increased after the first PE. Ventilatory variables exhibited a more direct association with clot burden.

Characteristics of Carbon Monoxide and Ethylene Generation in Mine’s Closed Fire Zone and Their Influence on Methane Explosion Limits

Methane explosions often occur during the closure process of mine fire zones, during which the concentration of combustible gases such as monoxide and ethylene produced by coal combustion dynamically changes, which changes the risk of methane explosion. Therefore, studying the gas concentration distribution and methane explosion limits during the process of mine closure is of great significance for disaster prevention and control. In this paper, a three-dimensional physical model of gob was built, and the distribution of monoxide and ethylene in the process of fire zone closure was investigated. Further, the explosion limits of methane enriched with CO and C2H4 in the closed fire zone of gob were analyzed. The results indicate that CO and C2H4 would form a small-scale accumulation phenomenon near the fire zone after the closure of the fire zone, and when the fire zone is closed for more than 15 min, the mixed combustible gases in the environment lose their explosiveness.

Adsorption characteristics of Ni cluster Modified-InN monolayer for indoor noxious gases (CH2O, C6H6, and NH3)

With the continuous enhancement of people's health awareness and the pursuit of high-quality life, the noxious gases generated after the renovation of new houses are receiving more attention. The gas sensing properties of InN monolayer modified with Ni clusters (1–3 Ni atoms) on CH2O, C6H6, and NH3 were analyzed based on DFT calculations, including the adsorption energy, charge transfer, density of states, bandgap structure, molecular orbitals, electrostatic potential, and desorption time investigation of gas adsorption systems. Moreover, different numbers of Ni atoms were introduced and their adsorption energies were analyzed. The results showed that the intrinsic InN and Ni–InN were suitable materials for gas sensors, while Ni2–InN and Ni3–InN were more suitable as adsorbents for clearing these three gases. The change in conductivity upon gas adsorption provides a theoretical basis for identifying the concentration of mixed gases of CH2O, C6H6, and NH3.

Flammability limits of methanol/methacrolein mixed vapor under elevated temperatures and pressures

The one-step oxidative esterification of methanol and methacrolein to yield methyl methacrylate (MMA) at elevated temperatures and pressures is a crucial chemical procedure for producing MMA. However, the conditions under which fire and explosions may occur during this procedure must be determined. This study models gas mixing to predict concentration distribution. Simulation results indicate stability with increasing pressure but wider gradients with higher temperature. Experimental studies on the flammable limits of methanol and methanol/methacrolein vapor mixtures under high temperatures and pressures show that the initial pressure has a significant impact on expanding the explosive limit of flammable vapor, whereas temperature has a relatively minor effect. The combustible limit of the mixed vapor is predicted using the heat balance approach, and a comparison with experimental data shows that the anticipated and real values coincide well.

Polyvinyl Alcohol/Zr-based Metal Organic Framework Mixed-matrix Membranes Synthesis and Application for Hydrogen Separation

Membrane gas separation is an environmentally friendly and economical method used to separate valuable gases, industrial process gas wastes, and carbon dioxide from mixed gases. The most important part of this method is the membranes. Gas separation membranes are expected to have high separation and permeability performance, high mechanical strength, easy and fast production capability, and low prices. Polymer-based membranes are mostly preferred depending on the ease of modification capability. In this study, a zirconium-based metal organic framework (Zr-MOF, MIL-140 A) was synthesized and used as a filler within polyvinyl alcohol (PVA) matrix for the selective separation of hydrogen (H2) from carbon dioxide (CO2). The effect of MIL-140 A addition on the mechanical, structural, and morphological properties of PVA was evaluated. The MIL-140 A significantly improved the mechanical strength of the membrane. According to the gas separation results, the increasing concentration of MIL-140 A increased the selective separation performance of the nanocomposite membrane. The highest mechanical strength (43.1 MPa) and best film-forming ability were obtained with 3 wt% MIL-140 A loaded membrane. The ideal H2/CO2 selectivity and hydrogen permeability were obtained as 5.6 and 944 Barrer, respectively at 2 bar feed pressure and room temperature. The highest ideal H2/CO2 selectivity was obtained as 6.3 with the H2 permeability of 959 Barrer when the MIL-140 A ratio was 4 wt%.

Carbon capture, carbon storage and utilization

This aspect of Energy law prompts the Department of Energy to initiate a series of research and development endeavors aimed at assessing environmental suitability and safety, capacity. Additionally, it explores proposed geological storage sites. High-purity carbon dioxide finds primary application in the electronics sector, medical research, and clinical diagnostics. It serves as a calibration gas for carbon dioxide lasers, testing devices, and various mixed gases, besides being a regular component in polyethylene polymerization. The objective of this article is to shed light on theories that model the movement of stored carbon dioxide, aiding in the interpretation and anticipation of chemical alterations and the potential impact of increased pressure.

Estimation of mixed-gas selectivity of membranes using the linear friction-based model

The development of analytical models for predicting the transport properties of membranes in the separation of multicomponent mixtures is highly relevant because (1) measurements of permeability and sorption of gas mixtures in membrane materials are laborious and time-consuming, and (2) estimation of transport properties based on pure gas measurements is desirable, however, rather unreliable and can lead to serious errors. In this paper, within the framework of the well-known frictional-coefficient formalism, we present nonlinear equations for the fluxes of gas mixture components through the membrane, which take into account the diffusional coupling of the fluxes compared to independent gas transport. As a result, an analytical equation for the mixed-gas selectivity was obtained. This equation has an implicit form, which is not quite convenient for practical application, since it has to be solved numerically. A simple explicit expression for mixed gas selectivity was derived using the so-called linear transport model, which is a linearized version of the original nonlinear flux equations. It is important to emphasize that a comparison of the linear model with the formally more rigorous nonlinear model showed only minor quantitative differences. The input parameters for the model are the single gas transport parameters. Testing the linear model using experimental data for the separation of hydrocarbons (n-butane/methane, n-butane/i-butane, propylene/propane) revealed an acceptable fit. A comparison of the model with recent experimental data on the separation of CO2-containing mixtures using microporous polymers is also presented. It is found that the calculated CO2/N2 mixed gas selectivity is in good agreement with the experimental data, while only a semi-quantitative agreement is observed for the CO2/CH4 separation. Besides, it is shown that the model developed for binary gas separation can be extended to ternary gas mixtures.

Numerical Investigation of a Two-Phase Ejector Operation Taking into Account Steam Condensation with the Presence of CO2

The application of a two-phase ejector allows for the mixing of liquid and gas and provides effective heat transfer between phases. The aim of the study is a numerical investigation of the performance of a water-driven, condensing two-phase ejector. The research was performed using CFD methods, which can provide an opportunity to analyze this complex phenomenon in 2D or 3D. The 2D axisymmetric model was developed using CFD software Siemens StarCCM+ 2022.1.1. The Reynolds-Averaged Navier–Stokes (RANS) approach with the Realisable k-ε turbulence model was applied. The multiphase flow was calculated using the mixture model. The boiling/condensation model, where the condensation rate is limited by thermal diffusion, was applied to take into account direct contact condensation. Based on the mass balance calculations and developed pressure and steam volume fraction distributions, the ejector performance was analyzed for various boundary conditions. The influence of the suction pressure (range between 0.812 and 0.90) and the steam mass flow rate (range between 10 g/s and 25 g/s) is presented to investigate the steam condensation phenomenon inside the ejector condenser. The provided mixture of inert gas (CO2) with steam (H2O) in the ejector condenser was investigated also. The weakening of the steam condensation process by adding CO2 gas was observed, but it is still possible to achieve effective condensation despite the presence of inert gas.

Constructing 3D sandwich-like structured Ti foam/TiO2−x/SnO2-Sb composite electrodes for the degradation of PPCPs

The fabrication of Sb-doped SnO2 electrode with high catalytic activity and excellent durability for decomposition PPCPs (Pharmaceuticals and personal care products, PPCPs) is challenging. Herein, a Ti3+/Ovs-related TiO2−x is prepared by short-time annealing at low temperature in mixed gas with Zr as a cocatalyst. DFT calculations indicate that the introduction of Ti3+/Ovs defects could promote the formation of more ·OH. Then, the nanoflower rod-like SnO2-Sb catalytic layer supported on dual-defects TiO2−x is successfully synthesized by one-step pulse electrodeposition (PLED) combined with hydrothermal methods (H). This newly pulse electrodeposition technique solves the short lifetime problem of SnO2-Sb nanoflower electrodes current hydrothermal-based methods. 1O2 and ·OH are found to be the primary reactive oxygen species (ROSs) by radical quenching tests and electron paramagnetic resonance analysis. The optimized Ti foam/TiO2−x /SnO2-Sb electrode could degrade over 96.3 % of 20 mg L−1 amoxicillin (AMX) within 30 min, corresponding kinetic constant 0.10228 min−1. This will provide inspiration for the construction of defect engineering and new insights for the development of low-cost and high electrooxidation activity Sb-doped SnO2 electrode.

Theoretical simulation of steady flowing manifold in hybrid pneumatic power system

Improving the energy efficiency of existing power systems is part of energy conservation and carbon reduction efforts. Internal combustion engines (ICEs) are currently the most commonly used power source in transportation, and they can be combined with gas power sources to form hybrid power systems for enhanced energy efficiency and potential commercialization. This study introduces hybrid pneumatic systems that integrate energy from ICEs and exhaust gas through a manifold to reuse waste heat. However, the turbulence caused by compressed air in the manifold can prevent the smooth transfer and mixing of thermal energy, leading to reduced power at the final outlet. We use ANSYS Fluent software to conduct heat flow streamline analysis of the three-dimensional flow field in the manifold structure, with key parameters including throttle valve opening, manifold geometry, pressure, and temperature. Through this analysis, we explore the flow situation and heat transfer phenomenon inside the pipe, observe the flow field changes in the pipe, and adjust the diameter of the compressed air end channel for effective thermal energy. A backflow with velocity magnitude up to 72 m/s in high pressure case can be solved by compressing pipe and temperature increases from 349.9 K to 682.5 K with more efficient heat transfer and gas mixing. Thermal power, enthalpy, and mass flow rate of the hybrid power system are also investigated, enabling the ICE to operate at its optimal point. The waste heat from the ICE can also be recycled and converted into effective mechanical energy through flow work.

Bose-Einstein condensation of non-ground-state caesium atoms

Bose-Einstein condensates of ultracold atoms serve as low-entropy sources for a multitude of quantum-science applications, ranging from quantum simulation and quantum many-body physics to proof-of-principle experiments in quantum metrology and quantum computing. For stability reasons, in the majority of cases the energetically lowest-lying atomic spin state is used. Here, we report the Bose-Einstein condensation of caesium atoms in the Zeeman-excited mf = 2 state, realizing a non-ground-state Bose-Einstein condensate with tunable interactions and tunable loss. We identify two regions of magnetic field in which the two-body relaxation rate is low enough that condensation is possible. We characterize the phase transition and quantify the loss processes, finding unusually high three-body losses in one of the two regions. Our results open up new possibilities for the mixing of quantum-degenerate gases, for polaron and impurity physics, and in particular for the study of impurity transport in strongly correlated one-dimensional quantum wires.

Hyperlactataemia is a marker of reduced exercise capacity in heart failure with preserved ejection fraction.

Heart failure with preserved ejection fraction (HFpEF) is associated with an array of central and peripheral haemodynamic and metabolic changes. The exact pathogenesis of exercise limitation in HFpEF remains uncertain. Our aim was to compare lactate accumulation and central haemodynamic responses to exercise in patients with HFpEF, non-cardiac dyspnoea (NCD), and healthy volunteers. Right heart catheterization with mixed venous blood gas and lactate measurements was performed at rest and during symptom-limited supine exercise. Multivariable analyses were conducted to determine the relationship between haemodynamic and biochemical parameters and their association with exercise capacity. Of 362 subjects, 198 (55%) had HFpEF, 103 (28%) had NCD, and 61 (17%) were healthy volunteers. This included 139 (70%) females with HFpEF, 77 (75%) in NCD (P=0.41 HFpEF vs. NCD), and 31 (51%) in healthy volunteers (P<0.001 HFpEF vs. volunteers). The median age was 71 (65, 75) years in HFpEF, 66 (57, 72) years in NCD, and 49 (38, 65) years in healthy volunteers (HFpEF vs. NCD or volunteer, both P<0.001). Peak workload was lower in HFpEF compared with healthy volunteers [52W (interquartile range 31-73), 150W (125-175), P<0.001], but not NCD [53W (33, 75), P=0.85]. Exercise lactate indexed to workload was higher in HFpEF at 0.08mmol/L/W (0.05-0.11), 0.06mmol/L/W (0.05-0.08; P=0.016) in NCD, and 0.04mmol/L/W (0.03-0.05; P<0.001) in volunteers. Exercise cardiac index was 4.5L/min/m2 (3.7-5.5) in HFpEF, 5.2L/min/m2 (4.3-6.2; P<0.001) in NCD, and 9.1L/min/m2 (8.0-9.9; P<0.001) in volunteers. Oxygen delivery in HFpEF was lower at 1553mL/min (1175-1986) vs. 1758mL/min (1361-2282; P=0.024) in NCD and 3117mL/min (2667-3502; P<0.001) in the volunteer group during exercise. Predictors of higher exercise lactate levels in HFpEF following adjustment included female sex and chronic kidney disease (both P<0.001). HFpEF is associated with reduced exercise capacity secondary to both central and peripheral factors that alter oxygen utilization. This results in hyperlactataemia. In HFpEF, plasma lactate responses to exercise may be a marker of haemodynamic and cardiometabolic derangements and represent an important target for future potential therapies.

Coupling amino acid injection and slow depressurization with hydrate swapping exploitation: An effective strategy to enhance in-situ CO2 storage in hydrate-bearing sediment

Natural gas (mainly methane, CH4) hydrates are a prospective energy resource. CH4-CO2 hydrate swapping has the advantages of producing CH4 gas for clean energy recovery and simultaneously storing CO2 in-situ for carbon emission reduction. Depressurization is the most feasible strategy to recover CH4 from hydrate-bearing sediments. The combination of these two methods has been proved feasible to produce CH4-rich gas and store CO2-rich hydrate. However, the efficiencies of CH4 recovery and CO2 storage decrease significantly when the reservoir is depressurized to the points below CH4/CO2 mixed hydrate equilibrium pressure causing unwanted CO2-rich hydrate dissociation. In this work, amino acid injection (AAI) (L-tryptophan or L-methionine) was employed for CH4/CO2 mixed hydrate formation with enhanced CO2 storage, followed by slow depressurization in various controlled manners, i.e., multistep depressurization, constant-pressure depressurization or multistep constant-pressure depressurization (MCPD) to recover CH4 from the mixed hydrates. In-situ Raman and gas chromatograph (GC) were employed to confirm the compositions of mixed hydrates formed and mixed gases produced. The results showed that AAI decreased CO2 fraction from 30 mol% to 3.1–8.4 mol% in the residual gas, indicating the technique helped regaining reservoir pressure and kinetically promoting further hydrate formation. The pressure recovered by AAI compensated the performance discrepancy caused by different solutions injected. Raman spectra and GC results confirmed CO2-rich hydrate formation, and up to 91.3% CO2 was stored in the sediments. During mixed hydrate dissociation, slow depressurization maintained high CH4-rich gas production (CH4 fraction over 87.5 mol%), with 9.7–30.6% CH4-rich gas recovered and 5.8–17.9% water produced among various trials. The best performance of CO2 storage and CH4 recovery was achieved by AAI of 1000 ppm L-tryptophan at 33.2 bar and MCPD to 20.9 bar, showing a final CO2 storage efficiency of 82.3%, gas recovery percentage of 30.6% and gas/water production ratio of 37.9 STP m3/m3. These findings provided guidance to enhance CO2-rich hydrate storage and CH4-rich gas production by multiple AAI and slow depressurization at controlled depletion pressures after hydrate swapping.

Gas mixing and double frequency operation of the permanent magnet quadrupole minimum-B electron cyclotron resonance ion source CUBE-ECRIS

CUBE-ECRIS is a recently commissioned permanent magnet electron cyclotron resonance (ECR) ion source developed at the university of Jyväskylä accelerator laboratory. The special features of the new ion source design include an unconventional quadrupole minimum-B magnetic field structure and a slit beam extraction system necessitated by the line-shaped plasma loss fluxes. Gas mixing and double frequency operation are widely used methods to optimize high charge state ion production of conventional ECR ion sources. The work presented here demonstrates the applicability of these methods for boosting the high charge state beam currents of argon, krypton and xenon extracted from CUBE-ECRIS. Oxygen and helium were used as mixing gases and microwave frequencies between 10 and 11 GHz were used for single and double frequency operation. Gas mixing has a strong impact on the high charge state beam currents. For example, the highest observed charge state increased from 15+ to 19+ for krypton and from 16+ to 23+ for xenon with oxygen gas mixing. Double frequency operation provides an additional performance improvement, for example the currents of argon 9+ and 11+ beams, produced with gas mixing, increased 30% and 100% in double frequency operation at the same total power.

Further experimental work in mixed gas Joule-Thomson cryocooling

Miniature Joule-Thomson (JT) cryocoolers are attractive for many applications due to their small size and resulting fast cool-down time. Finned-tube heat exchangers are one of the most widely used heat exchanger for miniature JT cryocoolers. The basic configuration, known as a Giauque-Hampson (GH) or coiled tube heat exchanger, involves the high-pressure stream flowing through a finned-tube that is helically coiled upon a cylindrical core while the low-pressure return stream flows over the fins in the annular space created by the core and the inner diameter of a shell. The experimental work in this study aimed to gain insight into thermal characteristics of the shell-side of a GH heat exchanger by developing a test facility capable of measuring the two-phase heat transfer coefficient (htc) for this flow at operating conditions of interest to mixed-gas JT (MGJT) cryocooling. The capabilities of the test facility were demonstrated and measurements of the two-phase htc of the mixed gas on the shell-side of the GH heat exchanger prototype revealed that the shell side is the dominant thermal resistance for these operating conditions, even though the fins provide a larger surface area.

Enhanced Production of Multicharged Ions by Mixing Low Z Gas and Emittance Measurement on Electron Cyclotron Resonance Ion Source

We have studied to enhance efficiency of producing multicharged ions in an electron cyclotron resonance ion source (ECRIS). The gas mixing method is known as an empirical method for highly efficient production of multicharged ions. This method is to mix low Z gas into the multicharged ions plasma. There are various explanations for the gas mixing effect. One of them is the ion cooling effect. It is necessary to obtain parameters related to the ion temperature in order to experimentally confirm the effect. We measured emittances for ion beams by using a wire probe and a multi-slit. He was mixed as a low Z gas into the operating Ar gas. Charged state distributions of ion beams was measured to confirm the gas mixing effect. We have also measured emittances for the multicharged Ar ion beams and compared root mean square emittances (ε rms) of those for pure Ar and Ar mixed by He. We confirmed that ε rms for Ar mixed by He was lower than that for pure Ar.

Spatially averaged global model of HBr/Cl2 inductively coupled plasma discharges

The utilization of HBr/Cl2 mixed gas discharge in semiconductor etching processes has been a subject of analysis both experimentally and through simulations to understand its discharge characteristics. In this study, we have developed a model that extends the previous global model of the HBr/Cl2 plasma. The electron temperature and densities are solved in a self-consistent manner, while previous global model uses the measured electron temperature and electron density. Additionally, we have included further data on electron collision reactions to enhance accuracy. This model was then compared with experimental results obtained from pure HBr, pure Cl2, and HBr/Cl2 plasmas. The calculated results align well with the experimental findings within the margin of error. One notable observation from our study is the occurrence of an unusual phenomenon: as the HBr partial concentration increased, the Br+ ion flux initially increased until the ratio reached 0.5, after which it decreased. This behavior can be attributed to Br+ ions being predominantly produced through collisions between Br atoms and electrons. The dominant mechanisms for Br atom generation involve dissociations by Cl radicals, such as Br2 + Cl → Br + BrCl. Consequently, there exists an optimal flow rate at which the Br+ ion flux is maximized.

Constructing ether-rich and carboxylate hydrogen bonding sites in protic ionic liquids for efficient and simultaneous membrane separation of H2S and CO2 from CH4

Removing H2S and CO2 is of great significance for natural gas purification. With excellent gas affinity and tunable structure, ionic liquids (ILs) have been regarded as nontrivial candidates for fabricating polymer-based membranes. Herein, we firstly reported the incorporation of protic ILs (PILs) having ether-rich and carboxylate sites (ECPILs) into poly(ether-block-amide) (Pebax) matrix for efficient separation H2S and CO2 from CH4. Notably, the optimal permeability of H2S reaches up to 4310 Barrer (40 °C, 0.50 bar) in Pebax/ECPIL membranes, along with H2S/CH4 and (H2S + CO2)/CH4 selectivity of 97.7 and 112.3, respectively. These values are increased by 1125%, 160.8% and 145.9% compared to those in neat Pebax membrane. Additionally, the solubility and diffusion coefficients of the gases were measured, demonstrating that ECPIL can simultaneously strengthen the dissolution and diffusion of H2S and CO2, thus elevating the permeability and permselectivity. By using quantum chemical calculations and FT-IR spectroscopy, the highly reversible multi-site hydrogen bonding interaction between ECPILs and H2S was revealed, which is responsible for the fast permeation of H2S and good selectivity. Furthermore, H2S/CO2/CH4 (3/3/94 mol%) ternary mixed gas can be efficiently and stably separated by Pebax/ECPIL membrane for at least 100 h. Overall, this work not only illustrates that PILs with ether-rich and carboxylate hydrogen bonding sites are outstanding materials for simultaneous removal of H2S and CO2, but may also provide a novel insight into the design of membrane materials for natural gas upgrading.

Effects of drive pulse shape on graded metal pushered single shell capsule implosions on the National Ignition Facility

Graded metal pushered single shells (PSS) are a viable alternative to low-Z capsules (Z is the atomic number) for indirect drive inertial confinement fusion implosions due to enhanced core tamping and radiation trapping, but they can be compromised by the pusher mixing with the fuel. We compare 2-shock and 3-shock laser pulses for Be/Cr PSS capsules filled with deuterium–tritium gas fuel at 6 mg/cc density. 1D radiation-hydrodynamic simulations predict higher core compression and, hence, ∼2× higher fusion yield for the 3-shock drive than for 2-shock. Nevertheless, we observe similar core ion temperatures and fusion yields for both drives. The implosion burn duration is 25% shorter and the core volume is ∼2.5× smaller for the 3-shock drive than for 2-shock, consistent with a higher compression. 1D LASNEX mix simulations using a buoyancy-drag model matching the measured yields also agree with the observed core sizes and burn durations and suggest ∼40% and ∼70% yield degradations for 2-shock and 3-shock drives due to hydrodynamic instabilities and atomic mix at the pusher–fuel interface. At the same time, 2D HYDRA simulations show that mid-mode (2–250) instability degradations are negligible for the 2-shock implosion (9%) and significant (45%) for 3-shock. Subtracting these from the 1D mix simulations, we infer similar degradations from high-mode instabilities and atomic mix for both drives. Due to its robustness to mid-mode instabilities, future pusher–gas mix studies will use the 2-shock drive.

Onboard pre-combustion carbon capture with combined-cycle gas turbine power plant architectures for LNG-fuelled ship propulsion

This paper investigates the concept of pre-combustion carbon capture (Pre-CCS) with a combined cycle gas turbine (CCGT) propulsion system to achieve energy efficient carbon capture onboard a Liquid Natural Gas fuelled vessel. A basic CCGT model with energy efficiency of 51.6 % when using LNG as fuel was integrated with a Pre-CCS system composed of a steam methane reformer, water–gas shift reactors, pressure swing adsorption (SMR-PSA), and liquid CO2 storage. Various waste heat utilisation schemes integrated with the CCGT-reformer were modelled in Aspen HYSYS. The modelling of the waste heat recovery networks as energy streams integrating between various processes and unit of operations has facilitated a closed-loop simulation of various systems. It was concluded that a proper utilisation of the high-grade heat from the gas turbine (GT) exhaust and from the reformer is crucial to improve the overall energy efficiency and carbon capture rate, exemplified by a scheme where the heating needs for the SMR and the cooling needs from the water–gas-shift reactors are fully integrated. When optimised, the integrated system had an overall energy efficiency of 41.5 % and 43.2 % (i.e. an efficiency loss of 10.2–10.5 percentage points from the base CCGT system) accompanied with specific GHG emission reduction of 51.2 % and 52.3 % for operation of the GT at a turbine entry temperature of 1700 K and 1850 K, respectively. Intermediate levels of reforming, where the GT uses a mix of LNG and reformate gases, were also simulated, showing an almost linear evolution from the 100 % LNG feed to the GT to the 100 % reformate case. Such a strategy could be used for gradual evolution to meet the required CO2 reduction timeline. It was determined that the 100 % reformate case provides the highest CO2 capture rate. Estimates of other emissions from the GT assuming typical combustor residence times for the whole range of fuel blends were also carried out, showing that the overall greenhouse gas emission is dominated by CO2, given that the GT emits negligible N2O and unburnt methane. Some capital cost estimates were also made to determine the unit price of hydrogen fuel produced onboard, suggesting that the CAPEX was not prohibitive. These findings support the pre-combustion CCS − CCGT integrated system as a promising long-term decarbonisation and propulsion strategy to comply with emissions regulations, displaying good performance in terms of cost, energy consumption, and CO2 reduction. The scalability and adaptability of the proposed system for existing and new-built ships across the decarbonisation timeline is also discussed.