Volume Fraction Of H2 Research Articles

Effect of low volume fraction of H2 on explosion characteristics and mechanism of AlH3 dust via connected container

During the storage and use of AlH3, a small amount of H2 is easily decomposed, forming a multiphase composite system that increases explosive hazard. This article discussed the AlH3 dust inducing low concentration H2 explosion and venting characteristics by a connected vessel. The results show that when the concentration of H2 was 1 % and 3 %, which was lower than the lower explosive limit of H2 (4 %), H2 was non-flammable, and the explosion was dust-driven explosion. At H2 volume fraction of 5 %, a dual-fuel-driven explosion dominated, culminating in the maximum explosion pressure, reduced pressure, venting flame length, and velocity. The microscopic reaction mechanism of AlH3 with H2 was explored using molecular dynamics simulations. Meanwhile, for the security strategy of AlH3 dust explosion venting with low H2 atmosphere, the NFPA 68 and EN 14491 standards predicted the venting flame length effectively, offering critical insights for the application and safety design of AlH3.

Effect of cathode ink formulation on the hydrogen crossover and cell performance of proton exchange membrane water electrolyzers

The permeation of H2 through the membranes of proton exchange membrane water electrolyzers (PEMWEs) is a critical safety concern because of the risk of explosion when H2 mixes with O2 at the anode and increases in concentration. In this study, we investigated the modification of the cathode catalyst layer in the membrane electrode assembly as a strategy for achieving the safe operation of PEMWEs. The effects of the polytetrafluoroethylene (PTFE) content and type of ionomer in the cathode catalyst layer on the dissolved H2 concentration, H2 crossover, and electrochemical performance were investigated. The lowest dissolved H2 concentration and H2 permeation rate were achieved when 8 wt% PTFE was used. Consequently, the H2 volume fraction in O2 at the anode was less than 0.88 %. Additionally, using the Nafion ionomer (D520, ion exchange capacity: 1 mmol g−1), H2 volume fractions of 1.27 % and 1.34 % were obtained at 0.08 and 5 A cm−2, respectively. These values are below the lower explosion limit of H2 in O2 (4 %), implying that the PEMWE can be safely operated in the low-to-high current density range under ambient pressure. These results provide key guidelines for the design of high-safety cathode catalyst layers for PEMWEs.

Numerical simulation study on hydrogen ammonia mixed combustion in a swirl combustion chamber

Abstract The NO x emissions and combustion performance of pure ammonia and hydrogen-doped combustion (90% NH3 volume fraction and 10% H2 volume fraction) in the cyclone combustion chamber were comprehensively analyzed through numerical simulations under varying thermal operating conditions. The findings reveal that the flame characteristic length in hydrogen-doped combustion surpasses that in pure ammonia combustion, indicating an extended migration of the high-temperature zone after hydrogen doping. Furthermore, the addition of hydrogen results in an elevated exhaust temperature within the combustion chamber, while the Outlet Temperature Distribution Function (OTDF) decreases, signifies an enhancement in the uniformity of temperature distribution at the outlet. Moreover, the reflux zone experiences less impact, and the mixed gas velocity increases following hydrogen doping. Notably, NO x emissions demonstrate a significant decrease after the addition of hydrogen. The average NO emission concentration in pure ammonia combustion, under various operating conditions, is measured at 212.47 mg/m3, representing a 3.51-fold increase compared to hydrogen-doped combustion.

Investigation of differential diffusion in lean, premixed, hydrogen-enriched swirl flames

Hydrogen combustion is a promising alternative to fossil fuel combustion in an effort to reduce our carbon footprint. However, hydrogen combustion is prone to thermodiffusive instabilities largely dependent on differential diffusion, a phenomenon that can lead to higher probabilities of flashback in industrial burners, given hydrogen’s high reactivity and diffusivity. This paper evaluates low-swirl flames of methane and air enriched with hydrogen to highlight the onset of differential diffusion. Testing was conducted in a fully controllable swirl burner, where bulk velocity Uav = 13 m/s and swirl number S = 0.6 were kept constant for each hydrogen–methane blend to isolate increases in flame surface area from increases in turbulence intensity. Furthermore, each fuel blend of hydrogen and methane is evaluated at the same laminar flame speed of SLo = 0.267 m/s to isolate flame stretch effects on the turbulent burning rate. Combined hydroxyl (OH) PLIF and stereoscopic PIV at the National Research Council of Canada were used to analyze the OH fluorescence in a 2D-3C velocity field for each flame condition. High-speed PIV at McGill University was used to resolve local flame phenomena, such as local flame displacement velocity and flame stretch rate. Using these techniques, it can be observed that the flame displaces axially in response to turbulent flame speed while exhibiting increases in flamefront wrinkling. This increased corrugation due to flame stretch is highlighted in the PDFs of local curvature and κSf and is further evidenced by a shift towards positive curvatures (κ> 0) for increasing H2 volume fraction. This trend suggests that there is a strong correlation with increases in turbulent burning rate and positive curvature as a result of differential diffusion, but it is not necessarily a control mechanism of the most forward propagating points proposed by the theory of leading points.

In-situ plasma assisted lithium-ion battery cathodes to catalytically pyrolyze lignin for H2-rich syngas production

In-situ plasma assisted lithium-ion battery cathodes catalysis was investigated to pyrolyze lignin to H2-rich syngas, oil and char. The effects of temperature, cathode to lignin ratio and plasma current on syngas production were investigated by using the typical ternary cathode NCM111 (LiNi1/3Co1/3Mn1/3O2) as catalyst and adopting dielectric barrier discharge mode. Response surface methodology based on BOX-BEHNKEN design was used to analyze the significance and interactions of process factors on the syngas yield. The conditions of 837℃, 10.4 %, and 185 mA for obtaining high-yield syngas (22.58 %) were more stringent; thereinto, from high to low, the intensity of factors on the yield was temperature, plasma current, and cathode ratio. Furthermore, different cathodes (non-cathode, NCM811 (LiNi4/5Co1/10Mn1/10O2), LCO (LiCoO2), and LMO (LiMn2O4)) were applied to decouple the catalytic effects of three metals in the NCM111. NCM111 enhanced both lignin gasification and carbonization by reducing condensable components, and NCM811 further improved gasification, but LCO and LMO had weaker gasification ability. NCM111 increased H2 volume fraction from 22.35 % to 67.31 %, NCM811 elevated the micro-discharge performance, promoting the hydrogasification reactions between energetic H species and char to produce more CH4, while LCO and LMO tended to produce the CO-rich syngas. Besides, in-situ plasma and its synergy with cathodes inhibited the formation of heavy aromatics and produced some high-value bio-oils rich in light aromatics, in which NCM111 achieved 92.30 % selectivity towards MAHs. High Ni ratio was beneficial for improving the char porosity, and the chars obtained by using NCM811 had a surface area of 409.29 m2/g, and a pore volume of 0.401 cm3/g. Comparably, the degree of catalytic lignin gasification for preparing H2-rich syngas could be ranked as Ni > Co > Mn in the ternary cathode.

Evaluation on thermal pyrolysis of biomass straw waste: Focusing aspects of products yields, syngas emissions and solid products characterization

AbstractIn this study, a systematic and quantitative investigation of the pyrolysis characteristics of biomass was conducted in a fixed‐bed tubular reactor, and the influence of pyrolysis temperature on product yields, gas emission characteristics, and syngas compositions as well as physicochemical characterization of resulting solids (i.e., char/ash morphologies, mineral transformations, and elemental compositions) was explored in detail. The pyrolysis experiments were performed under N2, and the resulting solid characterization was detected by XRD, SEM, and EDX. The results indicated that with increasing the pyrolysis temperature from 400 to 800°C, the gaseous product yields increased from 54.9% to 66.7%, while the solid product yield showed a reverse trend, varying within 27.7%–40.5%. Meanwhile, the volume fraction of H2 in syngas increased from 7% to 33%, while the CO2 presented an opposite trend, suggesting that high temperature favored H2 formation and inhibited CO2 formation. On the whole, the CO and CO2 emissions were prior to CH4, H2, and CnHm in sequence. A large amount of sylvite (KCl), quartz (SiO2), dolomite (CaMg(CO3)2), and pyroxene (CaMgSi2O6) in the resulting solids were identified in crystal phases. Higher pyrolysis temperature had a significant influence on solid microstructures, resulting in a relatively higher slagging tendency due to low melting eutectics containing K‐rich and Ca‐rich minerals.

A NUMERICAL STUDY ON THE REDUCTION OF GREENHOUSE GASEOUS COMPONENT (CO2) DUE TO THE ADDITION OF H2 IN THE FUEL STREAM OF THE COUNTERFLOW CH4/AIR DIFFUSION FLAME

In this study, a series of 1-D and steady-state numerical simulations have been performed for the prediction of the effect of the addition of H2 on the characteristics of a non-sooting counterflow CH4/Air diffusion flame using detailed chemical reaction model, which is composed of 325 elementary chemical reactions and 53 chemical species. Under the steady-state assumption, a set of one-dimensional transport equations of mass, momentum, species, and energy along with the equation of state has been solved numerically at the atmospheric conditions over the counterflow configuration by exploiting an efficient numerical code, OPPDIF (a Fortran Program for Computing Opposed-Flow Diffusion Flames). The grid adaption technique has been used to achieve better convergence as well as to ensure the maximum accuracy of the simulated results. It is found that the flame temperature is increased due to the addition of H2 with CH4, which is injected into the fuel stream. The elevation in the temperature is caused by the augmentation of the integrated heat release rate of the elementary reactions supported by the active radicals (H, O, and OH), which are generated by the higher reactivity of H2. Besides, it is found that the mole fractions of H2O are increased as the percentage of H2 in the loading fuel (CH4) is increased and also, it is identified that the chain propagating reaction, OH + H2 => H2O + H is dominating one which produces highest amount of H2O. Furthermore, it is noticed that the indirect greenhouse gas or precursor, CO is reduced when H2 is added to CH4. Consequently, the mole fraction of the principle greenhouse gas, CO2 is decreased significantly when the fuel, CH4 percentage is modified by the higher percentage of H2. The sensitivity analysis of elementary reactions reveals the fact that the chemical reaction: OH + CO => H + CO2 is a dominating reaction in producing a lower amount of CO2 when the volume fraction of H2 is increased in the fuel (CH4) stream. In the presence of 75 % H2 in CH4, the pressure-dependent reaction, O + CO (+M) => CO2 (+M) appears as another chemical route that also generates greenhouse gas, CO2 but its contribution is negligibly small.

Experimental and computational studies of concentration and flow field variation of syngas released

AbstractSyngas is an important chemical energy source with broad application prospects. The main problem with using syngas is its hazards, such as high storage pressure, high dispersion, low mass density, explosive, and toxic. The aim of this article is to find the key factors for the diffusion of syngas leakage and analyze the distribution of the dangerous concentration range from the diffusion behavior and hazard range characteristics of syngas leakage under complex working conditions. Therefore, a syngas leakage experimental bench is established, and a three‐dimensional simulation of syngas leakage was modeled. The results show that the initial pressure is the most critical factor, and the concentration distribution under different initial pressures is significantly different. The time required for carbon monoxide (CO) and hydrogen (H2) to reach their maximum concentration increased as the initial pressure or temperature decreased. The volume ratio had little effect on the time when CO and H2 reached the maximum concentration. In the horizontal direction, CO diffused further than H2 in the buoyant jet. The max volume fraction of H2 and CO did not exceed 1% and 2.5%, respectively. The research results are expected to give guidelines for the safety protection and standard improvement of syngas leakage.

Molecular Hydrogen Promotes Adipose-derived Stem Cell Myogenic Differentiation via Regulation of Mitochondria.

Acute skeletal muscle injuries are common physical or sports traumas. Cellular therapy has excellent potential for regeneration after skeletal muscle injury. Adipose-derived stem cells (ADSCs) are a more accessible type of stem cell. However, it has a low survival rate and differentiation efficiency in the oxidative stress-rich microenvironment after transplantation. Although molecular hydrogen (H2) possesses anti-inflammatory and antioxidant biological properties, its utility in mitochondrial and stem cell research has not been adequately explored. This study aimed to reveal the role of H2 on adipose-derived stem cells' myogenic differentiation. The protective effects of H2 in ADSCs were evaluated by MTT assay, live-dead cell staining, western blot analysis, immunofluorescence staining, confocal imaging, and transmission electron microscopy. An appropriate volume fraction of H2 significantly decreased mitochondrial reactive oxygen species (ROS) levels, increased the number of mitochondria, and promoted mitophagy, thus enhancing the survival and myogenic differentiation of ADSCs. This study reveals the application potential of H2 in skeletal muscle diseases or other pathologies related to mitochondrial dysfunction.

Comprehensive parametric study of fixed-bed co-gasification process through Multiple Thermally Thick Particle (MTTP) model

Co-gasification technology provides a promising solution for the energetic valorization of various biomass feedstocks, especially those not directly applicable for gasification owing to their low-calorific values or high ash content, but the complexity of co-gasification technology has put forward challenges to model formulation when using numerical methods to evaluate the performance of the gasifier. In the present work, the Multiple Thermally Thick Particle (MTTP) model is developed and validated for fixed-bed co-gasification process. The sub-phase treatment that extends the conventional Eulerian-Eulerian framework allows calculating the inhomogeneity in the solid phase, and the intra- and inter-particle heat and mass transfer sub-models enable quantitative evaluation of the conversion of different solid fuels with nonnegligible intraparticle gradients. Parametric analyses of moisture content and particle size were performed to evaluate how the degree of difference between each fuel would influence the reaction processes, gasification performances and steady-state operating conditions. Upon changing the moisture content of the fuel mixtures (biomass and MSW) from both 9.0 wt% to 9.0 wt% for MSW and 27.0 wt% for biomass, the maximum temperature difference between the solid particle surfaces of different fuels was nearly 150 K, and the regions of different conversion processes became highly overlapped. When increasing the moisture content of biomass from 9.0 wt% to 27.0 wt% under 1:1 mixing ratio, the cold gas efficiency, volume fraction of H2 and higher heating value of syngas increased from 65.26%, 12.03%, and 6.29 MJ/Nm3 to 68.39%, 15.62%, and 6.44 MJ/Nm3, respectively. Therefore, the quality and efficiency can be improved when increasing the moisture content in a certain range although the overall capacity of the gasifier will decrease. The intraparticle temperature profiles calculated by the MTTP model also revealed that decreasing the particle size from centimeter- to millimeter-level will significantly reduce the temperature difference between the surface and center of the fuel particles, thus accelerating the in-bed reaction rates and increasing the overall capacity of the gasifier. The MTTP model is flexible for various working conditions and solid fuel mixtures, which is a versatile and convenient tool to optimize the complicated co-gasification process.

Explosion dynamics of premixed LPG/H2 fuel in a confined space

To reveal the impact law of H2 on the kinetics of LPG explosion reaction, a list of explosion experiments were conducted in a 10 L duct with LPG/H2 as the research object. The influence of H2 volume fraction on the explosion characteristics of LPG was investigated, and analyzed the combustion mechanism of mixed-gas. Results indicate that the flame development of LPG/H2 mixed under different RH conditions is divided into four different development modes. The Pmax increase, and the explosion relief pressure decrease as the RH elevates. The effect of equivalence ratio on the Thermo-Diffusive instability and Darrieus-Landau instability of LPG/H2 mixture is large. Under the same conditions, there is a noticeable discrepancy in the flame duration and explosive pressure duration. The chain reaction (R2: H2 + OOH + H, R3: H2 + OHH2 + OH), which produces a significant amount of H, OH important radicals and boosts the reaction activity, is the principal way that hydrogenation affects the reaction of LPG/H2 gas combination. The impact of H2 on LPG in terms of reaction mechanism is explained and confirmed by the fact that hydrogenation encourages the rise of the sensitivity coefficient of the fundamental reactions of the LPG/H2 mixture explosion.

An experimental study of the characteristics of blended hydrogen-methane non-premixed jet flames

The addition of hydrogen to natural gas promotes the reactivity of fuel and thus increases the jet fire risk from pipeline leakage during the transport process of blended hydrogen-natural gas. Aiming to evaluating the potential jet fire risk, this paper experimentally studied the characteristics of H2/CH4 jet flames at varied heat release rates (HRRs) with H2 volume fraction (fv) ranging from 0% to 90% by two circular nozzles (diameters: 3 and 5 mm). The results show that with the increase of H2 volume fraction, two competing effects on flame height were observed, that is, the increase in mixture molecular diffusivity, radicals pool, and air entrainment decreases the flame height, while the increase in flame temperature and jet velocity of fuel flow with a small flow Reynold number increases the flame height. Comparisons of different previous correlations of flame height with current experiments were conducted to obtain the applicable flame height model for H2/CH4 flames. The ratio of flame width to flame height for two nozzle diameters increases with dimensionless HRR when HRR is small, and then becomes nearly constant (∼ 0.145). The flame width normalized by nozzle diameter has a power dependence on dimensionless HRR, i.e., 0.48 and 0.59 power for the 3 and 5 mm nozzle, respectively. Further theoretical analysis suggested the dimensionless correlations of lift-off height of H2/CH4 flames with fv ≤ 50%.

Reactivity and performance of steam gasification during biomass batch feeding

The steam gasification characteristics of poplar sawdust were investigated in a piston fed fixed-bed gasifier, reflecting the batch feeding process of fixed-bed gasifiers in industrial applications. The effects of operating conditions, including steam supply, the flow rate of inert gas, gasification temperature, and feeding rate, on gasification reactivity and performance were investigated online. The major gas product during pyrolysis was CO, followed by H2, CH4, and CO2, and the gasification was greatly facilitated by the injection of steam to generate H2. The gasification reactivity and performance were improved with increased steam supply and temperature. The maximum production rate of H2 by char gasification was tripled and doubled, respectively, with an increase in steam supply from 50 to 400 mL/min and a temperature rise from 800 to 900 °C, and the time required for complete gasification was also halved. Compared to pyrolysis, the volume fraction of H2 increased from 23% to 37%, and correspondingly, the H2/CO ratio increased from 0.42 to 0.95.

Study on catalytic gasification of pine wood with cerium loaded dolomite based clay ceramics

With dolomite as the main aggregate, a clay ceramic carrier was prepared by one-step powder sintering method. After being impregnated with Ce and calcined, a Ce loaded dolomite based (Ce-Dol) clay ceramic catalyst was prepared, which was used for the catalytic gasification of pine wood. The influence of the addition amount of Ce, steam flow rate, gasification temperature and other parameters on the catalytic gasification of pine wood was investigated using a self-developed two-stage gasifier, and the optimal operating conditions were determined. The results show that the dolomite based clay ceramics loaded with cerium can effectively improve the catalytic activity, reduce the stretching vibration peak absorbance of some functional groups in the gasification products, effectively promote the secondary cracking of tar, and improve the quality of gaseous product. When catalyzed by the Ce-Dol clay ceramic containing 6% cerium, the volume fraction of H2 peaks with 32.43%. With the rise in gasification temperature, aliphatic carboxylic acids and ketones in biomass tar are gradually decomposed into small molecular compounds such as CO, CO2. The content of H2 shows an ascending trend, and a maximum value is reached at 900 °C. Moreover, adding an appropriate amount of steam promotes the forward water-gas reaction, and a maximum volume fraction of H2 (37.37%) is achieved at a steam flow rate of 4 mL/min.

Hydrogen-rich gas as a fuel for the gas turbines: A pathway to lower CO2 emission

Hydrogen-rich fuel for the gas turbines can be considered as a transient way from hydrocarbon fuel to zero-carbon hydrogen fuel. In this paper, thermodynamic analysis of a combined cycle power plant (CCPP) fired with a hydrogen-rich fuel obtained via various ways is performed to understand the effect of a transient to this fuel on the CO2 emission as well as the efficiency of a power plant. Hydrogen-rich fuel with different content of hydrogen is analyzed. Two types of hydrogen-rich fuel are considered: fuel obtained via methane dilution with hydrogen (hydrogen from internal fuel supply infrastructure) — first case; fuel obtained via steam methane reforming (on-board hydrogen production technology) — second case. The first case showed that hydrogen addition to methane non-linearly leads to a decrease in CO2: hydrogen-rich fuel with 20% of H2 volume fraction gives a reduction in CO2 emission of 7.2%; 50% of H2 gives 23.5% reduction; 75% of H2 gives 51.1% reduction. The second case is considering hydrogen-rich fuel obtained via steam methane reforming using a renewable energy source. Hydrogen volume fraction up to 75% in hydrogen-rich fuel can be obtained after the reforming process. When 100% of methane is reformed, the reduction in CO2 emission up to 27% can be achieved. The minimum achievable level in CO2 emission is 75.17 gCO2/kW for an on-board hydrogen production technology via steam methane reforming which is corresponding to a hydrogen-rich fuel obtained via H2 dilution up to 53%.

The inhibition effects of helium gas on liquid hydrogen droplets group combustion

With the rising interest in safety of liquid hydrogen (LH) combustion, a numerical simulation was conducted to investigate the “group” combustion of LH droplet arrays. Point source method (PSM) was employed to characterize the inhibition effects of helium on three specific LH arrays “group” combustion (binary, equilateral triangular, and five-particle arrays). The present study aims to contribute to the future development of helium inhibitor for LH combustion, providing detailed characterization of helium inhibition effects. It was found that the burning rate and flame temperature of all the three LH arrays decreased after adding helium to the air. In addition, both the H2 volume fraction and temperature around the array surfaces decreased significantly. Moreover, flame location of arrays combustion became far away from droplet surfaces with helium dilution and it became more obvious as droplet numbers increasing. As a result, helium can be employed as a potential inhibitor for LH combustion.

Coupled Typical Coke Gasification and Sintering Ore Reduction in CO-N2-H2.

Through thermodynamic calculation and high-temperature simulation experiments, the coupling behavior between gasification of high- and low-reactivity cokes and reduction of sintering ore in CO–N2–H2 mixed gas with 25% H2 volume fraction was studied, and the evolution of the coke carbon structure and the pore structure was analyzed. The results show that the reaction rate of the two cokes increases with the increase in temperature after the coupling reaction, and the strength after drumming decreases with the increase in temperature. The strength of low-reactivity coke after the reaction is higher than that of high-reactivity coke, and the reduction degree of sintering ore after the coupling reaction with low-reactivity coke is higher than that with high-reactivity coke. At high temperatures and high hydrogen-rich atmospheres with φ(H2) of 25%, the strength of high-reactivity coke after drum rotation is greater than 60.4%. The graphitization degree and carbon structure order of low-reactivity coke are higher than those of high-reactivity coke.

Intensified effect of K adhering to hematite involved in the sulfurous chemical looping gasification

When sulfur in petroleum coke (petcoke) converts to H2S instead of SO2, it is the resource which can be recovered by Claus process. Chemical looping gasification (CLG) is capable of achieving petcoke conversion and sulfur recovery. To simultaneously overcome the obstacles of low gasification reactivity and improve H2 and H2S production, hematite modified by K as oxygen carrier (OC) was involved in the high-sulfur system to investigate the effect on sulfur conversion via batch fluidized bed in petcoke CLG process. K enhanced H2 generation beyond expectation because K not only improved the petcoke gasification but also enhanced the steam oxidation of deep reductive OC. Especially when using 10 % KNO3-hematite, H2 yield increased by 3.9 times as compared to 0 % K, with the carbon conversion efficiency of 99.92 % in the 22nd minute. The different K sources had a different H2 selectivity. The sulfur fate had been originally studied using K-modified hematite OC. H2S was the main phase of sulfur release and the high H2 yield also assisted H2S production. Introducing K contributed to in-situ sulfur capture forming K-Fe-S compounds in the OCs due to the deep reduction of Fe. 10 % KNO3-hematite exhibited excellent cyclic stability with a H2 volume fraction of more than 65 % in 21 cycles. Furthermore, the mechanism of hematite modified by K involved in sulfur-containing system was summarized in petcoke CLG process.

Analysis of process parameters on energy utilization and environmental impact of hydrogen metallurgy

Based on the heat energy and mass balance, the gas demand and carbon emission of per ton of direct reduced iron were calculated using a hydrogen-metallurgy process with an H2 and CO mixture as the reducing gas in the reduction temperature range of 800–1300 °C. The effects of the reduction temperature and H2 volume fraction on the gas demand and carbon were analyzed. The direct reduction process was evaluated based on the recovery rate of the reducing gas, gas energy efficiency, and heat recovery rate. The of the study results indicated that when the temperature does not exceed 900 °C, the minimum gas demand and lowest recovery rate of the reducing gas increase with an increase in the H2 volume fraction. When the temperature increases, the minimum gas demand and the lowest recovery rate of the reducing gas first decreased and then increased. When the reduction temperature was 1000 °C and the H2 volume fraction was 22%, the energy consumption reached its lowest value of 3.00 GJ/t. Increasing the H2 volume fraction or increasing the temperature of the hydrogen metallurgy process can effectively reduce the carbon emissions. In the all-hydrogen state, the higher the temperature, the lower the energy efficiency of the reducing gas. The thermal energy recovery rate decreased with an increasing H2 volume fraction and reduction temperature. The selection and design of the physical parameters of hydrogen metallurgy to achieve different goals would be more convenient if these calculations are used during the actual operation.

Simulations of aluminum dosage and H2O-H2 flow in a pre-pilot twelve-cell electrocoagulation stack

This paper investigates the aluminum dosage generation and H2O-H2 flow simulations in a pre-pilot twelve-cell stack electrocoagulation (EC) reactor in continuous operation mode. Each cell contains two aluminum plate electrodes. The electrochemical reactor is open to the atmosphere at the top to facilitate the H2 release produced at the cathodes, while aluminum oxidation occurs at the anodes. The two-phase (H2O-H2) flow simulations were performed by solving the Navier-Stokes (NS) equations for the continuous (H2O) phase and the bubbly flow model for the dispersed (H2) phase. Since H2 formation is promoted at the cathode due to H2O reduction, the momentum and Laplace's equations were simultaneously solved. The aluminum dosage calculations were attained by solving the diffusion-convection equation. The influence of volumetric inflow rate (8.3 ≤ Q ≤ 33.3 cm3 s−1) and applied current density (4 ≤ j ≤ 8 mA cm−2) on the coagulant dosage, current distribution, and H2O-H2 flow dispersion was systematically examined. The H2 volume fraction showed a typical bubble curtain profile close to the cathode surface. Homogeneous current distribution along the electrodes was obtained due to the well-engineering cell design, guaranteeing even wear of the sacrificial electrodes. There was an excellent agreement between the experimental and theoretical data for residence time distribution (RTD) curves and aluminum dosage generation.