Increasing H2 Concentration Research Articles

Configuration optimization of a biomass chemical looping gasification (CLG) system combined with CO2 absorption

Biomass chemical looping gasification (CLG) combined with CO2 absorption in a dual circulating fluidized bed (DCFB) has emerged as an advanced technology for clean and efficient biomass utilization, yet the reactor design for achieving higher gasification performance and the in-depth understanding of physical-thermal-chemical characteristics is still lacking. This study presents an optimized design aimed at enhancing hydrogen production and carbon reduction in the biomass CLG process with a DCFB reactor by employing the multiphase particle-in-cell (MP-PIC) method integrated with thermochemical sub-models. The proposed reactor is comprehensively compared with the original reactor from the experimental setup in terms of particle mixing, heat transfer, and gasification behaviors. The results indicate that compared to the original setups, the proposed CLG system demonstrates: (i) an improved gas-solid mixing, as evidenced by the particle mixing index rising from 0.23 to 0.34; (ii) an enhanced particle heat transfer coefficient, which boosts heat and mass transfer process; (iii) a 10.11 % increase in H2 concentration alongside a 23.71 % decrease in CO2 concentration; (iv) a particle distribution characterized by higher concentration at the bottom and lower concentration at the top, along with intensified particle back-mixing. The pressure drop inside the combustor is higher than that in the gasifier. A smaller absorbent mean particle diameter and lower-positioned biomass feeding port contribute to the improvement of the CLG performance.

Process Modeling and Simulation of Sugarcane Bagasse Gasification using different Oxidizing Medium: A Universal Gasification Model

Biomass gasification is gaining significant interests among the researchers as the syngas/producer gas obtained from gasification of biomass can be versatile in usage. However, the outcome of gasification (gas composition/LHV/CGE) varies with the gasification medium employed. This article presents the process modeling of sugarcane bagasse gasification for three different gasifying media, namely air, steam and air-steam, using cycle tempo software to identify the best among different gasification processes for the considered response variables. A process model has been developed, and the gas composition predicted by the proposed model is validated with published experimental results for different biomass feeds. The influence of important operational parameters such as SBR, ER and gasification temperature on gas composition, LHV, and CGE were analyzed and compared for all three gasifying media. SBR, ER and gasification temperature have a very strong impact on the gas composition, LHV, and CGE. With the increase in SBR value, H2 concentration increases, whereas the concentration of CO decreases. The maximum concentration of H2 was observed to be 57.81 % at an SBR of 2 and at a gasification temperature of 750ºC for steam gasification. For air-steam gasification, optimum values of SBR and ER are observed to be 0.5 and 0.2, respectively, at a gasification temperature of 750ºC, where LHV (9.91 MJ/kg) and CGE (84.14%) were found to be maximum.

Long-term carrier lifetime instabilities in n-type FZ- and Cz-silicon under illumination at elevated temperature

Even though n-type Si wafers show a lower extent of light-induced degradation, similar degradation and regeneration behavior as in p-type Si materials has been observed for various n-type Si monocrystalline materials. In this work, the long-term behavior of minority charge carrier lifetime in non-diffused n-type FZ-Si and Cz-Si wafers during illumination at elevated temperatures is investigated. Thereby, various influencing factors such as peak firing temperature and treatment temperature are considered. Degradation and a very strong regeneration effect, which exceeds the initial effective lifetime value, can be observed in the samples. Since surface-related saturation current density remains almost constant during degradation and regeneration, the effect seems to be bulk related. The extent of degradation and regeneration could be shown to be firing temperature-dependent. It could also be shown for n-type FZ-Si wafers that higher firing temperatures result in an increased H2 content within the silicon bulk. Investigations of the injection-dependent defect density revealed that the defect formed during degradation is not a deep level Shockley-Read-Hall defect. Observations at different treatment temperatures and constant illumination of 0.9(1) sun photon flux equivalent have shown that a higher treatment temperature leads to faster degradation and regeneration kinetics. Similarly, higher injection rates also speed up regeneration kinetics. Since degradation also occurs in darkness, the bulk related degradation effect in n-type FZ-Si is charge carrier-induced and not necessarily light-induced.

A novel wide flow matching approach of hydrogen-powered F-class gas turbine based on multistage installation angle

To achieve excellent power performance of F-class gas turbine when using pure H2 or H2-rich fuel, this work develops a novel and flexible flow matching approach by modifying the turbine multistage installation angle, with obvious features of easy implementation and low cost. An accurate thermodynamic model of heavy-duty gas turbine considering turbine-stage cooling is established and verified by the actual operation data from Ban-Shan power plant, and to investigate variable condition property and emission characteristic of gas turbine with natural gas and H2-rich fuel. Faced with the inefficiency and narrow working area caused by the flow mismatch between 18-stage compressor and 3-stage turbine when natural gas is switched to H2-rich fuel, the scheme of modifying the installation angles of multistage rotary blade and static blade is proposed. By calculating the pressure and temperature at each turbine stage, the gas turbine power, efficiency, Mach number and NOx emission with different H2 concentration are predicted. Results show that, as the H2 concentration increases, the fuel volume flow required to reach the same turbine inlet temperature increases.When H2-rich fuel increases the turbine inlet volume flow by 3.23 %, the cooling effect significantly decreases, and the turbine outlet temperature rises by about 13.60 K, which deviates from the appropriate operating point. The most serious is the phenomenon of over Mach number and airflow blocking at the outlet of the 2-stage and 3-stage turbine static blades. The installation angle variation increases with the increase of H2, and the higher the stage, the bigger the angle change. The gas turbine can be realized the wide flow matching feature corresponding to the installation angle variation of 0.19°/-0.41°, 0.38°/-0.48°, and 0.53°/-0.94°, respectively for all stages static/rotary blades. After re-matching, the maximum fluctuation of rated power and efficiency are 1.5 % and 1.7 %, and the NOx emission will reach the maximum value of 14.3 ppm with 70 % H2. Research work will provide a novel and feasible retrofit scheme for the heavy-duty gas turbine using clean and low-carbon fuel to widen flow matching scenario.

Novel experimental method to simulate reduction behaviour of burden in blast furnace shaft

In order to evaluate the effects of CO and H2 for the gas–solid reaction behaviour of the ferrous burden and coke in blast furnace shaft, a near-steady-state simulation test method of the blast furnace shaft was designed. The reduction behaviour of the ferrous burden, carbon solution loss reaction under different temperatures and atmospheres, and the effect of hydrogen enrichment on the CO gas utilisation ratio were investigated. The results show that above 830 °C, the reduction degrees of different ferrous burden structures under H2 atmosphere are higher than that under CO atmosphere. Better reduction degradation behaviour could be obtained under the hydrogen-rich atmosphere. The H2O generated under H2 atmosphere could promote the carbon solution loss reaction. The solution loss ratio reaching the maximum at 950 °C. Under hydrogen-rich atmosphere, CO gas utilisation ratio increased with the increased H2 concentration due to the effects of the products H2O and CO2.

The influence of radiation modeling on flame characteristics and emissions prediction in microcombustors with Ammonia/Hydrogen blends

This study advances numerical methodologies for designing microcombustor-based thermophotovoltaic systems by incorporating comprehensive analyses of radiation models and absorption coefficients. It examines the impact of non-premixed hydrogen-ammonia-air fuel blends on the micro combustion process using three-dimensional CFD simulations on a Y-shaped microcombustor under atmospheric conditions.Key to this research is modeling radiative heat transfer from multiple species, including ammonia (NH3), nitric oxide (NO), and water vapor, ensuring accurate predictions and optimization of thermal behavior and efficiency. Three modeling approaches were compared: a multispecies Planck-mean approximation radiation model (PMAC), a narrowband model for water vapor, and a scenario excluding radiation effects.The PMAC model, incorporating the absorption coefficients of ammonia and its products, consistently produced lower errors in flame length compared to the NB method across all equivalence ratios, with errors ranging from 0 % to 7 % for PMAC and 10 % to 30 % for NB, with the lowest error observed at Φ = 1.0. Additionally, the prediction of laminar burning velocity (LBV) differed by approximately 4 % between the two models.Considering different fuel blends, two scenarios were compared: constant input thermal power and constant fuel flow rate. Efficiency in the constant input thermal power scenario maintained higher radiation efficiency, in the range of 32–38%. Additionally, radiation efficiency initially increased with increasing H2 content but subsequently decreased for high H2 values due to effects on flame area, flame position, and temperature.

Experimental and numerical study on the influence of N2/H2 on the laminar combustion characteristics of syngas premixed flames

This paper primarily analyzes the influence of N2 and H2 content on the laminar combustion characteristics of low calorific value syngas, using a constant-volume combustion bomb to measure the laminar combustion velocity (SL) of the fuel and compare it with five commonly used mechanisms. The study reveals that higher N2 content significantly reduces the SL of CO/CH4/CO2 mixed fuels, primarily due to a general decrease in the mole fractions of key intermediates and net reaction rates. Increasing H2 content leads to an increase in the SL of CO/CH4/CO2/N2 mixed fuels. The thermal effect becomes increasingly prominent with the elevation of H2 content, while the proportion of thermal effect initially decreases and subsequently increases as the equivalence ratio rises. With the increase in N2 content, the mole fraction of NO experiences a significant decrease, and the rate of decline in thermal NO production is even faster. Conversely, with the increase in H2 content, the rate of rise in non-thermal NO generation is faster, and the mole fraction of NO tends to increase.

Advancing hydrogen generation: Kinetic insights and process refinement for sorption-enhanced steam gasification of biomass utilizing waste carbide slag

Sorption enhanced steam gasification of biomass (SESGB) presents a promising approach for producing high-purity H2 with potential for zero or negative carbon emissions. This study investigated the effects of gasification temperature, CaO to carbon in biomass molar ratio [CaO/C], and steam flow on the SESGB process, employing carbide slag (CS) and its modifications, CSSi2 (mass ratio of CS to SiO2 is 98:2) and CSCG5 (mass ratio of CS to coal gangue (CG) is 95:5), as CaO-based sorbents. The investigation included non-isothermal and isothermal gasification experiments and kinetic analyses using corn cob (CC) in a macro-weight thermogravimetric setup, alongside a fixed-bed pyrolysis-gasification system to assess operational parameter effects on gas product. The results suggested that CO2 capture by CaO reduced the mass loss during the main gasification as the [CaO/C] increased. The appropriate temperature for SESGB process should be selected between 550 and 700 °C at atmospheric pressure. The appropriate amount of sorbent or steam could facilitate the gasification reaction, but excessive addition led to adverse effects. Operational parameters influenced the apparent activation energy (Ea) by affecting various gasification reactions. For each test, Ea at the char gasification stage was significantly higher than that at the rapid pyrolysis stage. The addition of CS notably increased H2 concentration and yield, while sharply reducing CO2 levels. H2 concentration initially rose and then fell with greater steam flow, peaking at 76.11 vol% for a steam flow of 1.0 g/min. H2 yield peaked at 298 mL/g biomass with a steam flow of 1.5 g/min, a gasification temperature of 600 °C and a [CaO/C] of 1.0. Increasing gasification temperature remarkably boosted the H2 and CO2 yields. Optimal conditions for the SESGB using CS as a sorbent, determined via response surface methodology (RSM), include a gasification temperature of 666 °C, a [CaO/C] of 1.99, and a steam flow of 0.5 g/min, under which H2 and CO2 yields were 464 and 48 mL/g biomass, respectively. CSSi2 and CSCG5 demonstrated excellent cyclic H2 production stability, maintaining H2 yields around 440 mL/g biomass and low CO2 yields (∼60 mL/g biomass) across five cycles. The study results offer new insights for the high-value utilization of agroforestry biomass and the reduction and resource utilization of industrial waste.

Thermodynamic simulation of hydrogen production from the nano-CaO reactive sorption enhanced biomass steam reforming

Based on the principles of thermodynamic reaction equilibrium, a simulation method enhanced by the nano-CaO reactive sorption CO2 for hydrogen production from biomass steam reforming has been established. MATLAB R2022b software has been utilized to calculate the composition concentration of the product gas. Detailed simulations have been conducted to understand the changes in gas component concentration and yield under various reaction conditions, includes temperatures, steam to biomass (S/B) molar ratios, and CaO to carbon (CaO/C) molar ratios. The result demonstrated that temperature plays a significant role in both the concentration and yield of hydrogen. At an optimal reaction temperature of 650 °C, the concentration of H2 in the product reaches 77% (S/B = 2 and CaO/C = 0.5). S/B molar ratio over 2 is necessary to increase the H2 concentration. The study also reveals CaO/C molar ratio 0.5 enable successful removal of CO2 generated by reaction. The application of nano-CaO notably enhanced the efficiency of hydrogen production from biomass steam reforming, leading to a 25% increase in H2 concentration and a boost in H2 yield to 50 mL/gBiomass, and reaction temperature decrease 200 °C compared to the case without CaO.

The combination of hydrogen gas and hydrogen-rich solution does not protect against ischemic spinal cord injury in rabbits.

This study aimed to determine whether the combination of H2 gas inhalation and administration of hydrogen-rich acetated Ringer's solution (HS) could protect against ischemic spinal cord injury in rabbits. In Experiment 1, rabbits were randomly assigned to a 1.2% H2 gas group, HS group, 1.2% H2 gas + HS group (combination group), or control group (n = 6 per group). The H2 concentration of HS was 0.65mM. H2 was inhaled for 60min, starting 5min before reperfusion. HS (20mL/kg) was divided into six bolus injections at 10-min intervals, starting 5min before reperfusion. Spinal cord ischemia was produced by occluding the abdominal aorta for 15min. Neurologic and histopathologic evaluations were performed 7days after reperfusion. In Experiment 2, H2 concentrations in spinal cord tissue according to the administration of 1.2% H2 gas or HS were compared by measuring the electric current through a platinum needle electrode (n = 2). In Experiment 3, rabbits were assigned to a 2% H2 gas group or control group (n = 6 per group). Spinal cord ischemia was produced and neurologic and histopathologic evaluations were performed as in Experiment 1. There were no significant differences among the groups in the neurologic and histopathologic outcomes in Experiments 1 and 3. Bolus administration of HS (10mL) transiently increased the current to only 1/30th and 1/27th of the plateau current with 1.2% H2 gas inhalation in two animals. These results suggest that the combination of 1.2% H2 gas inhalation and administration of a hydrogen-rich solution does not protect against ischemic spinal cord injury and that the increase in H2 concentration in spinal cord tissue after administration of HS is very low compared to 1.2% H2 gas inhalation.

Temperature and Thermal Diffusivity Diagnostics in Laminar Methane Flames Using Infrared Four-Wave Mixing Techniques.

Four-wave mixing techniques, such as coherent anti-Stokes Raman spectroscopy (CARS), laser-induced grating spectroscopy (LIGS), and degenerate four-wave mixing (DFWM), have been widely used in combustion diagnostics due to their advantages of high signal-to-noise ratio (S/N), coherent signal, and spatial resolution. In this work, a nano-second pulsed laser is utilized to generate mid-infrared (near 3 µm) pump beams, exciting the rovibrational transitions of nascent water in flames. Combined LIGS and DFWM measurements are demonstrated in premixed laminar CH4/O2/N2 flames with equivalence ratios from 0.6 to 1.5, to achieve precise thermometry in a wide range of flame conditions. The flame temperatures were also measured by thermocouple as a reference, and the results from LIGS and DFWM align well with the trends shown in the thermocouple measurements. In fuel-lean flames, where the mass-to-specific-heat ratio variation is minimal, LIGS provides temperature data with a precision better than 16 K (0.8%). In fuel-rich flames, where the increased H2 concentration in the flame introduces uncertainty in gas constants thus affecting the accuracy of LIGS thermometry, DFWM is instead employed for temperature measurement since it is less sensitive to the gas composition within the measured volume. The high-precision LIGS temperatures in lean flames serve as temperature reference during the DFWM calibration of the degree of saturation, and a precision better than 90 K (4.5%) is achieved for DFWM thermometry. In addition to temperature, a theoretical model is employed to fit LIGS signal time waveforms, extracting the local speed of sound and thermal diffusivity with precisions better than 0.5% and 1.3%, respectively. These high-precision measurements contribute additional data for flame research and simulation calculations. This way, the combined use of DFWM and LIGS proves the potential for accurate thermometry and diagnostics of other thermodynamic parameters across a wide range of flame conditions.

Effects of type of substrate and dilution rate on fermentation in serial rumen mixed cultures.

Forages and concentrates have consistently distinct patterns of fermentation in the rumen, with forages producing more methane (CH4) per unit of digested organic matter (OM) and higher acetate to propionate ratio than concentrates. A mechanism based on the Monod function of microbial growth has been proposed to explain the distinct fermentation pattern of forages and concentrates, where greater dilution rates and lower pH associated with concentrate feeding increase dihydrogen (H2) concentration through increasing methanogens growth rate and decreasing methanogens theoretically maximal growth rate, respectively. Increased H2 concentration would in turn inhibit H2 production, decreasing methanogenesis, inhibit H2-producing pathways such as acetate production via pyruvate oxidative decarboxylation, and stimulate H2-incorporating pathways such as propionate production. We examined the hypothesis that equalizing dilution rates in serial rumen cultures would result in a similar fermentation profile of a high forage and a high concentrate substrate. Under a 2 × 3 factorial arrangement, a high forage and a high concentrate substrate were incubated at dilution rates of 0.14, 0.28, or 0.56 h-1 in eight transfers of serial rumen cultures. Each treatment was replicated thrice, and the experiment repeated in two different months. The high concentrate substrate accumulated considerably more H2 and formate and produced less CH4 than the high forage substrate. Methanogens were nearly washed-out with high concentrate and increased their initial numbers with high forage. The effect of dilution rate was minor in comparison to the effect of the type of substrate. Accumulation of H2 and formate with high concentrate inhibited acetate and probably H2 and formate production, and stimulated butyrate, rather than propionate, as an electron sink alternative to CH4. All three dilution rates are considered high and selected for rapidly growing bacteria. The archaeal community composition varied widely and inconsistently. Lactate accumulated with both substrates, likely favored by microbial growth kinetics rather than by H2 accumulation thermodynamically stimulating electron disposal from NADH into pyruvate reduction. In this study, the type of substrate had a major effect on rumen fermentation largely independent of dilution rate and pH.

Effects of H2, CO, and a gas mixture on the reduction process of raw and pre-oxidized ilmenite concentrate powders

Herein, we reduce raw and pre-oxidized ilmenite concentrates by H2, CO, and a gas mixture (H2/CO = 1) at different temperatures. The results show that the reduction rate of both concentrates increases with increasing H2 concentration. Furthermore, the reducing ability of the three types of reducing gases increases in the order of CO < H2 < gas mixture. Moreover, we elucidate the coupling effect of H2–CO on the reduction process and propose a comprehensive utilization index for hydrogen-rich reduction gas. The results indicate that H2–CO coupling plays a positive role in both the concentrate reduction processes, improving the reduction rate and gas utilization efficiency. The maximum reducing gas comprehensive utilization indices for the hydrogen-rich reduction of the raw and pre-oxidized ilmenite concentrates are observed at 1000 and 950 °C, respectively. Additionally, changing the reducing atmosphere and pre-oxidation treatment significantly affects the distribution of metallic iron in the product particles.

Reaction behavior of sulfides in blast furnace raw materials under hydrogen-rich reducing atmosphere

Understanding the transformation behavior of sulfides in the blast furnace raw materials during the ironmaking process is crucial for controlling the form and emission of gaseous sulfides in the blast furnace top gas. This study investigates the reactions of coke and sinter at different reducing atmosphere ranging from 200 °C to 1000 °C by using of thermogravimetry and mass spectrometry (TG-MS). Additionally, thermodynamic theoretical calculations were performed to enhance the understanding of the reaction behavior. The results showed that the mixed sinter and coke started to generate H2S at 100 °C under the mixed H2-CO atmosphere and reached the peak between 350 and 400 °C. With the increase of H2 concentration, the peak temperature of H2S generation initially decreased and then increased, with the lowest peak temperature observed under a 50% H2-50% CO atmosphere. Furthermore, COS generation started around 300 °C and reached its peak at approximately 800 °C. The peak content of COS generation increased as the CO concentration. Low temperatures favored the generation of H2S from the mixed sinter and coke, while high temperatures were conducive to the generation of COS.

Experimental and numerical studies on the interaction between two identical slot jet H2/CO diffusion flames

Hydrogen offers a unique opportunity in achieving a CO2-neutral future, but great challenges exist for the successful transition from conventional fossil fuels to H2, due to the great component variation and safety issues of H2 energy. The multiple-injection combustor concept effectively addresses these problems, with the merits of flexible nozzle distance satisfying the varying H2 content in the fuel and low flash-back risk comparable to diffusion flames. In such combustors, flame interaction plays an essential role in the performance of multiple-injection combustors. This work focused on the flame interaction behavior of two identical slot jet H2/CO diffusion flames. OH* chemiluminescence was captured by an intensified CCD camera and the flame temperature was measured using a type-B thermocouple. The combustion process was modeled using a Fortran flame code by incorporating the detailed thermal and transport properties as well as the chemical kinetic mechanism. With these experimental and numerical efforts, the effects of burner separating distance, fuel composition, and fuel velocity were parametrically studied. Results showed that flame interaction enables a more uniform temperature distribution. Increasing H2 content in the fuel decreases the flame length for the merged flames, but this effect is less distinguished for the merging and separated flames. In addition, flames with a higher H2 content merge more easily because of the enlarged flame radius, featured with a linear relationship between the merging distance and H2 content. When increasing the fuel flow rate, the twin flames contact and merge at farther separating distances, and this influence of fuel flow rate on flame interaction was observed to be fuel-composition-dependent. Increasing the burner separating distance lowers the flame length, which is attributed to the enhancement of CO oxidization rather than the H2 reactions. Moreover, burner separating distance plays a critical role in NO emissions, with a non-monotonical impact due to the combined effect of flame temperature and O2 concentration.

A modified two-stage sorption-enhanced steam gasification of biomass process for H2 production

A modified two-stage sorption-enhanced steam gasification of biomass (SESGB) process for H2 production is proposed and studied using a dual fixed-bed system. This process can be controlled independently for each stage, enabling the catalytic gasification and reforming processes to proceed at their respective optimal temperatures. In this process, CaO is alternately circulated, i.e., when the CaO sorbent in the second stage needs to be regenerated it is replaced by the CaO acting as a catalyst in the first stage, which reduces the regeneration frequency of CaO by half. In the first stage, tar can be almost completely removed by catalytic thermal cracking of CaO. In the resulting tar-free atmosphere, the CaO sorbent in the second stage can maintain a rapid carbonation rate. As a result, the concentration and yield of H2 can be as high as 70.5 vol% and 600.7 mL/g-SB, respectively, while the sorbent/carbon ratio is as low as 0.82. The conventional one-stage SESGB process, by contrast, requires sorbent/carbon ratio as high as 3.82 to obtain syngas with H2 concentration above 70 vol%. Compared with the one-stage process, this two-stage process is more effective in removing tar, increasing H2 concentration and yield as well as reducing CaO consumption.

Influence of reduction conditions on the structure-activity relationships of NaNO3-promoted Ni/MgO dual function materials for integrated CO2 capture and methanation

Integrated CO2 capture and utilization (ICCU) represents an innovative concept and technique for reducing industrial carbon emissions. Ni-MgO dual function materials (DFMs) promoted by alkali metal salt (AMS) for integrated CO2 capture and methanation (ICCU-M) is gaining increasing interest. The in-situ methanation performance depends heavily on the high-temperature NiO reduction process, while this might adversely affect CO2 adsorption due to loss of AMS. Herein, we investigated the effects of H2 concentration and reduction temperature on structure–activity relationships of AMS-promoted Ni-MgO DFMs for ICCU-M. The increase in H2 concentration and reduction temperature favors NiO reduction to metallic Ni0 and boosts oxygen vacancy concentration in the DFMs. Both CO2 uptakes and CH4 yield increase with the elevating H2 concentration, and CH4 yield also increases with the increasing reduction temperature, considering the increased metallic Ni0 content and oxygen vacancy concentration. CO2 uptakes of the DFMs decline with the increase in reduction temperature, due to the obvious loss in AMS. The bulk diffusion kinetics in CO2 adsorption stage will be improved under higher H2 concentration and reduction temperature, while the chemisorption kinetics will be weakened at elevating reduction temperature. The methanation kinetics will be enhanced when the DFMs are reduced under higher H2 concentration and temperature. The AMS-NM-100-450 DFMs reduced in 100 %H2 and 450 °C exhibit good ICCU-M performance with high CO2 adsorption capacity and CH4 yield of 6.46 mmol CO2/g and 0.85 mmol CH4/g. The results in this work enlighten that the ICCU-M performance of AMS promoted Ni-MgO DFMs can be tuned by regulating the operating parameters for catalyst reduction.

Thermophysical properties of the energy carrier methanol under the influence of dissolved hydrogen

The present experimental work focuses on revealing the influence of hydrogen (H2) on the interfacial tension, viscosity, density, and thermal diffusivity of the liquid phase of the energy carrier methanol under saturation conditions, which has been only fragmentarily investigated so far, and on providing corresponding H2 solubility and Fick diffusion coefficient data. For this, conventional methods, dynamic light scattering from the liquid bulk and from the liquid-gas interface as well as Raman spectroscopy were used at temperatures up to 393 K and pressures up to 8 MPa. The results show that with H2 under saturation conditions, the viscosity and density of liquid methanol are nearly pressure-independent, whereas the interfacial tension is reduced by about 6% at 8 MPa. The latter effect is temperature-independent despite the increasing H2 concentration with increasing temperature, which may be associated with a counteracting influence of temperature on a presumed surface enrichment of H2.

System analysis of a protonic ceramic fuel cell and gas turbine hybrid system with methanol reformer

The performance of a methanol-fed protonic ceramic fuel cell (PCFC)/gas turbine (GT) hybrid system is investigated in this work. To build the system, Thermolib software is employed with input parameters obtained from references. Effects of air stoichiometry on system performance are analyzed. Results show that, as air stoichiometry is increased, the reformer temperature and CO concentration decrease, while H2 concentration increases. High air stoichiometry decreases PCFC temperature and performance. GT output power increases with increasing air flow. But, the power consumption by compressor also increases. Overall, to achieve higher system efficiency for this hybrid system, the optimum values of air stoichiometry are from 2.7 to 2.9. An additional heat recovery steam generator can also improve the overall system efficiency from 66.5% to 71.7%. This work helps in understanding the modeling and optimum functioning parameters of high power generation systems.

Effect of hydrogen on microstructure and mechanical properties of plasma-nitrided pure titanium by cathodic cage plasma nitriding

Surface modification technologies have been applied for the improvement of surface properties, and low temperature nitriding in the mixed N2-H2 atmospheres by cathodic cage plasma nitriding (CCPN) is identified to be an effective way to enhance the mechanical properties of Ti and its alloys. However, little attention was paid on the absorbed H2 in the nitrided specimen under different H2 proportion and the consequent deleterious influence. In this paper, the influence of different H2/(N2 + H2) ratio on microstructure of the nitrided Ti specimens by CCPN were investigated by XRD, EDX, SEM, respectively. And the surface structure of the compound layer is consisted of an outer layer of δ-TiN over the inner layer of ε-Ti2N, formed on the top of diffusion layer consisting of mainly of α-Ti solid solution enriched with nitrogen. It is found that the thickness of compound layer on Ti increases with the introduction of H2. And the N-rich top layer of TiN layer with coarse grain structure is resulted by the combined effect of the introduction of H2 and the plasma action. The surface mechanical properties of nitrided layer were also measured by microhardness tester and tensile test. The results show an average surface hardness of 900 HV0.2–1100 HV0.2 of the nitride surface compared to that of Ti (200 HV0.2 in average). And the surface hardness of nitrided Ti samples increases with the increasing H2 concentration. However, the tensile properties are badly deteriorated independent of hydrogen concentration with the introduction of H2 due to the generation of titanium hydride during nitriding process.