Characteristics Of Hydrogen Production Research Articles

HYDROGEN POWER AND NOT ONLY: "PRO" AND "CONTRA"

The increase in global temperature caused by global climate warming is considered. Open data on Ukraine’s energy strategy until 2050, in particular on the production and use of natural gas and hydrogen, are provided. The results of the energy efficiency of the production of primary energy resources are presented, including main renewable energy sources. The relevance of the problem of production and use of hydrogen as a significant renewable source of reducing greenhouse emissions and increasing energy security is presented. The indicators and their critical indicators for the stability and stability of the terrestrial system of the socio-ecological state of the planet Earth are presented — the so-called planetary boundaries of sustainability, it is emphasized that not only climate change, but also the extinction of biodiversity is critical for life. In response to the latter, the main points of the Kunming-Montreal UN Global Framework Program until 2030 in the field of biodiversity are outlined, the main goal of which is to return the biosphere to recovery. Based on this year’s materials of the International Energy Agency, we will generally consider the global state of hydrogen issues from the point of view of the strategy for the development of production, distribution and final use of renewable hydrogen. Some environmental and energy characteristics of electrolytic hydrogen production are presented. Recommendations for the prospects of hydrogen use are given. Bibl. 34, Fig. 7, Tab. 2.

Pilot composite tubular bioreactor for outdoor photo-fermentation hydrogen production: From batch to continuous operation

A novel 70 L composite tubular photo-bioreactor was constructed, and its photo-fermentation hydrogen production characteristics of batch and continuous modes were investigated with glucose as the substrate in an outdoor environment. In the batch fermentation stage, the hydrogen production rate peaked at 37.6 mL H2/(L·h) accompanied by a high hydrogen yield of 7 mol H2/mol glucose. The daytime light conversion efficiency is 4 %, with 37 % of light energy from the sun. An optimal hydraulic retention time of 5 d was identified during continuous photo-fermentation. Under this condition, the stability of the cell concentration is maintained and more electrons can be driven to the hydrogen generation pathway while attaining a hydrogen production rate of 20.7 ± 0.9 mL H2/(L·h). The changes of biomass, volatile fatty acids concentration and ion concentration during fermentation were analyzed. Continuous hydrogen production by composite tubular photo-bioreactor offers new ideas for the large-scale deployment of photobiological hydrogen production.

Research on the Production of Turquoise Hydrogen from Methane (CH4) through Plasma Reaction

Turquoise hydrogen is produced through a process of separating carbon into solid carbon based on fossil fuels and refers to hydrogen that does not produce carbon dioxide. In this study, the characteristics of turquoise hydrogen production through a methane thermal cracking reaction using an arc plasma torch were investigated. The plasma torch operated stably under high voltage and transport gas flow conditions. The composition of the gas generated from the methane plasma reaction was analyzed using an online IR gas analyzer and GC-FID. The experimental results show that the hydrogen yield decreased to 16.4% as the methane feed rate increased but increased to 58.8% as the plasma power increased. Under these conditions, the yield of solid carbon, a valuable byproduct, was also shown to increase to 62.9%. In addition, solid carbon showed high-temperature heat-treated characteristics based on its generation location. Carbon oxides such as CO and CO2 are rarely generated under any experimental conditions. Consequently, it can be considered that plasma thermal cracking is a promising technology for CO2-free hydrogen production and a valuable solid carbon.

Direct ink writing of hierarchical porous SiC ceramics as catalyst support for hydrogen production

Due to the tunable porosity at multiple scales, hierarchical porous ceramics feature large specific surface area and excellent heat and mass transfer performance, which can effectively improve the catalytic reaction performance. This paper presents a method to fabricate SiC scaffolds with regular and hierarchical pore structures by direct ink writing (DIW) combined with sacrificial template technology, which can be used as methanol steam reforming (MSR) microreactor catalyst supports. Through printing along a defined path, primary pores with a regular pore structure were created. After sintering, the sacrificial template was removed and secondary pores appeared. Four different types of hierarchical porous SiC scaffolds were successfully prepared and the pore structure, total porosity, linear shrinkage and compressive strength of these scaffolds were investigated. The catalyst coating was then loaded onto the scaffold, and the microstructure characterization showed that the pore structure would not be damaged and blocked. Finally, the hydrogen production experiments were carried out on the MSR microreactor, and the results showed that the support with larger and denser secondary pores had the best fluid flow and hydrogen production characteristics. At the temperature of 280 °C and the gas hourly space velocity (GHSV) of 30000 ml g−1 h−1, the methanol conversion and hydrogen production of the best support can reach 90.95 % and 44.96 ml/min, respectively.

A non-isolated DC power supply without circulating current for load characteristics testing of electrolytic hydrogen production

The circulating current in the non-isolated power supply composed of an AC current converter and a DC current converter affects the normal operation of the power supply for electrolytic hydrogen production characteristics testing. This paper proposes a novel topology without circulating current by using half bridge circuit. First, the circulating current in the traditional non-isolated circuit with a full bridge circuit is analyzed, and the loop of the circulating current is obtained. The influence of the DC side voltage of AC current converter on the circulating current is analyzed. Then, through the equivalent circuit, the circulating current loop has been removed and a novel topology is presented. The circulating current in the proposed topology can be eliminated. The proposed analysis results and topology have been verified through simulation and experimental results.

Enhanced hydrogen production from cracking of liquid toluene by applying liquid plasma and perovskite catalysts

In this study, a process for producing hydrogen from liquid hydrocarbons by applying plasma is proposed. Toluene was decomposed by discharging a pulse-type plasma into liquid toluene directly. The changes in the rate of hydrogen production and reaction characteristics owing to injecting a perovskite catalyst were also investigated. A high hydrogen production rate of approximately 130 NL/h·g was obtained from the liquid–phase plasma reaction of toluene using the BiFeO3 catalyst. The investigation into the reaction characteristics based on the plasma generation conditions indicated that the reaction was mainly affected by the plasma voltage. When titanium dioxide and perovskite (SrTiO3, BiFeO3) photocatalysts were applied to this reaction, the reaction activities also varied depending on the light-absorption capacity of the catalysts. The highest hydrogen evolution rate was obtained using the BiFeO3 catalyst, which absorbs visible light as well as UV light, compared with the TiO2 photocatalyst, which absorbs only UV light. Because the plasma emission from toluene is predominantly in the visible region, the reaction activity was also determined to be the highest for the BiFeO3 catalyst. The BiFeO3 absorbs visible light up to about 550 nm, and it has a small bandgap energy of about 2.15 eV. This led to high photocatalytic degradation activity in visible light generated by plasma discharge in toluene. The carbon obtained had a particle size of less than 20 nm and purity of approximately 99%.

Hydrogen production and pollutants emission characteristics by co-gasified of paper-mill sludge and automobile shredder residues in a commercial scale fluidized bed gasifier

This research investigated the hydrogen production and energy conversion from automobile shredder residues (ASRs) and paper mill sludge (PMS) co-gasified in a full-scale fluidized bed gasification plant. The results obtained from full-scale tests provided important information on the feasible assessment of ASRs-to-energy and the selection of alternative technologies for ASRs. Based on the analysis results of produced gas composition, H2, CO, and CH4 composition produced from paper-mill sludge gasified were 4.17%–6.01%, 3.08%–4.32%, 1.71%–2.4%, respectively. Another C2 gas composition ranged from 2.9% to 3.59%. The heating value of produced gas ranged between 1.64 MJ/Nm3 and 2.18 MJ/Nm3. In the case of 10% ASR addition, the heating value of produced gas was slightly increased to 1.84 MJ/Nm3-2.34 MJ/Nm3. The dioxin emission concentration of flue gas was approximately 0.064 ng I-TEQ/Nm3. It can comply with Taiwan regulation thresholds. The dioxin leaching concentrations of residues derived from gasification were also in compliance with regulation limits by the TCLP test. Meanwhile, in the case of 10% ASRs addition, the dioxin equivalence concentration of gasified residue was nearly 0.002 ng I-TEQ/Nm3. It was far below the current regulation standard limit. In summary, the results of this research have proved the performance of ASRs-to-energy by co-gasified with paper mill sludge using a full-scale gasification plant. The results obtained from this research also provided the information for selecting ASRs alternative technologies and operating full-scale gasifiers in the future.

Slow pyrolysis experimental investigation of biomass tar formation and hydrogen production by tar reforming

The characteristics of pyrolysis tar and catalytic hydrogen production during tar reforming with catalysts were investigated. Through the pyrolysis experiment of wheat straw at 400–800 °C, the change of tar yield and tar composition with pyrolysis temperature was obtained. In order to remove tar, different nickel-based catalysts were prepared and catalytic experiments were carried out. The results showed that the pyrolysis tar yield first increased and then decreased with the increase of temperature, and the maximum tar yield was 32.82% at 700 °C. The generation of tar mainly comes from the thermal decomposition of biomass before 500 °C, the homogeneous reactions of tar compositions begin to occur after 500 °C. Through the characterization of the catalysts and their catalytic performance, it was found that due to the interaction of Ni and Ce on the support surface, Ni particles were more evenly distributed on the surface of the support. By adding Ce into Ni/HZSM-5, more oxygen vacancies are formed on the catalyst surface, which makes the catalyst have higher reducibility and more active sites. Compared with 9Ni/HZSM-5, 9Ni3Ce/HZSM-5 has a better catalytic performance with the tar conversion of 89.34% and H2 composition of 0.43.

Possibility Study in CO2 Free Hydrogen Production Using Dodecane (C12H26) from Plasma Reaction

Turquoise hydrogen refers to hydrogen produced through a fossil-fuel-based process in which carbon is separated into solid carbon and no carbon dioxide is produced. In this study, dodecane was selected as a simulated oil for waste plastic pyrolysis recovery oil, and the turquoise hydrogen production characteristics through the thermal cracking reaction using an arc plasma torch were investigated. The plasma was stably discharged at 2 to 4 kW. Hydrogen in the produced gas was analyzed through an online IR gas analyzer, and hydrocarbons from C1 to C5 were analyzed through GC-FID. As a result of the experiment, the hydrogen yield tended to increase as the plasma power increased, and a maximum of 11.5% based on mass was obtained. On the other hand, carbon oxides such as CO and CO2 were not generated. Along with hydrogen, the valuable by-products of this process are solid carbon and gaseous hydrocarbons. The solid carbon yields also increased up to 66% as the plasma power increased. On the other hand, the yield of gaseous hydrocarbons showed an opposite trend to that of hydrogen and carbon and consisted mainly of C2 series (average content of 77%) and olefins (average fraction of 0.67). Consequently, it can be considered that the plasma thermal cracking is a promising technology for the CO2-free hydrogen production, as well as solid carbon and C2-olefin.

Experimental study on hydrogen production characteristics of kaolin supported Ni catalyzed by steam gasification of citrus peel

This work aims to reveal the advantages of Ni/kaolin and to explore its influence on the gasification reaction characteristics in a fixed-bed reaction system. It was shown that 10 wt% was the optimum loading of Ni, when the carbon conversion efficiency was 84.54 % and the hydrogen yield was 36.79 mmol/gbiomass. According to the evolutionary behavior of gas products and kinetic analysis, it is known that when using 10 wt% Ni/kaolin, it accelerated the precipitation of volatiles and the reaction, greatly improved the carbon conversion efficiency of the reaction, and increased the instantaneous hydrogen yield from 4.26 mmol/(gbiomass·min) without catalyst to 5.12 mmol/(gbiomass·min) and the total yield of hydrogen was also increased to 60.70 mmol/gbiomass. The catalytic effect of 10 wt% Ni/kaolin was caused by the Ni(111) crystalline facets generation on the support surface, that could promote the cleavage of carbon–carbon and carbon-hydrogen bonds of tar.

Hydrogen production and energy efficiency optimization of exhaust reformer for marine NG engines: A view of surface reaction kinetics

In the present study, for an insight into the catalytic reforming process of the exhaust reformer and its optimization strategy, a one-dimensional inhomogeneous reforming model and a thermodynamic model were implemented in a Ni/Al2O3 catalytic packed-bed description of single reforming tube inside the reformer. The models were evaluated by comparison of numerical simulations with data derived from reforming experiments in a flow reactor over a columnar nickel-based catalyst. Meanwhile, the effects on reforming characteristics and energetics of the process of exhaust gas-methane reforming inside the reformer was investigated from a view of surface reaction kinetics under the variation of temperature and O2 concentration of the exhaust gas from the engines, as well as the supply of CH4 and H2O into reformer. The results showed that the hydrogen production characteristics of exhaust gas-methane reforming is mainly controlled by the exhaust temperature and various inlet feedstock of the reformer. There is a critical exhaust temperature of 610 K to activate the process of exhaust gas-methane reforming. For the efficient operation of the exhaust reformer, it is necessary to increase the O2 concentration of the exhaust gas via adjusting the excess air coefficient of the engine, because in this case the dehydrogenation process of CHi(s) is enhanced and more hydrogen production on the catalyst surface with an atmosphere of more H(s) through the desorption way. Compared with the thermodynamic values, the used catalyst still has some space for improvement in the catalytic properties to approach the thermodynamic hydrogen production characteristics of the reforming system at different initial exhaust temperatures and M/O values. Summarily, the optimal operation conditions for the exhaust reformer were determined: M/O = 0.8–1.5 and S/M = 0.5–1.5, which can achieve efficient hydrogen production (about 13–23 %) and maintain high reforming energy efficiency (≥60 %).

Furfural Influences Hydrogen Evolution and Energy Conversion in Photo-Fermentation by Rhodobacter capsulatus

Furfural, as a typical byproduct produced during the hydrolysis of lignocellulose biomass, is harmful to the photo fermentation hydrogen production. In this work, the effects of furfural on the photo fermentation hydrogen production by Rhodobacter capsulatus using glucose as substrate were investigated. The characteristics of cell growth, hydrogen production, and fermentation end-products with the addition of different concentrations of furfural (0–20 mM) were studied. The results showed that furfural negatively affected the maximum hydrogen production rate and total hydrogen yield. The maximum hydrogen yield of 2.59 ± 0.13 mol-H2/mol-glucose was obtained without furfural. However, 5 mM furfural showed a 40% increase in cell concentration. Furfural in high concentrations can favor the overproduction and accumulation of inhibitive end-products. Further analysis of energy conversion efficiency showed that most of the energy in the substrate was underused and unconverted when the furfural concentration was high. The maximum glucose consumption (93%) was achieved without furfural, while it dramatically declined to 7% with 20 mM furfural addition. The index of half-maximal inhibitory concentration was calculated as 13.40 mM. Moreover, the possible metabolic pathway of furfural and glucose was discussed.

Continuous hydrogen production characteristics and environmental analysis of a pilot-scale hydrogen production system by photocatalytic water splitting

Hydrogen production by photocatalytic water splitting (HPPCWS) is a promising clean energy conversion technology. However, this technology lacks quantitative environmental impact information and comparison with other hydrogen production technologies. In the process of the technology scale-up, the environmental impact assessment of the whole life cycle is essential. Life cycle assessment (LCA) based on a pilot plant of HPPCWS constructed in China is conducted to evaluate the environmental performance using Simapro software. As the source of inventory, the continuous hydrogen production characteristics of the system are predicted by using local radiation data and reveal that the cumulative hydrogen production of the system is closely related to the local radiation data and the time intervals for replacing the reaction solution. The LCA results on environmental impact show that the construction stage of the system has a more significant impact. In contrast, the dismantling stage can offset part of the environmental impact due to partially recycling primary materials. Transportation and power consumption are the main factors affecting the environment during system operation. The value of the leading midpoint indicator, global warming potential (GWP), could be as low as 4.53 kg CO2 eq/kg H2 under suitable design conditions. Compared to other hydrogen production routes, this work has significant advantages on environmental impact, while there is no denying that the application of the system is facing opportunities and challenges. The results reflect the problems that should be paid attention to in the process of the technology scale-up from the aspects of material and energy utilization and environmental risk. This paper aims to provide credible data on the environmental impact of photocatalytic hydrogen production technology and supply a professional reference for industry decision-making on complete process control.

Kinetic studies for hydrogen and methane co-production from food wastes using multiple models

This study was designed to assess the applicability of various modeling tools for representing hydrogen and methane co-production kinetics from food waste using a three-stage bioprocess. Firstly, to elucidate the effect of substrate to inoculum ratio (S/X) on the kinetic characteristics of hydrogen and methane production, multiple kinetic models were applied under different S/X ratios. Secondly, a statistical comparison among different models was conducted to select the most appropriate one able to accurately describe the kinetic characteristics of each stage. The third major goal was to exemplify the linkage between kinetic parameters and hydrogen and methane potentials. Results argued that the Cone model fitted hydrogen curves better than others. The modified Logistic model was best fitted for hydrogen production using microbial electrolysis cell. Based on rigorous methane kinetic analysis, the modified Gompertz model was found to be the most suitable model able to simulate the methane production. Moreover, the kinetic study showed that S/X ratio influenced the lag phase and the hydrolysis constant. Taken together this research proved the fitness and the attractiveness of kinetic analysis providing a sound basis for future application of the hydrogen and methane co-generation processes.

The Effect of Anode Material on the Performance of a Hydrogen Producing Microbial Electrolysis Cell, Operating with Synthetic and Real Wastewaters

The aim of the study was to assess the effect of anode materials, namely a carbon nanotube (CNT)-buckypaper and a commercial carbon paper (CP) on the performance of a two-chamber microbial electrolysis cell (MEC), in terms of hydrogen production and main electrochemical characteristics. The experiments were performed using both acetate-based synthetic wastewater and real wastewater, specifically the effluent of a dark fermentative hydrogenogenic reactor (fermentation effluent), using cheese whey (CW) as substrate. The results showed that CP led to higher hydrogen production efficiency and current density compared to the CNT-buckypaper anode, which was attributed to the better colonization of the CP electrode with electroactive microorganisms, due to the negative effects of CNT-based materials on the bacteria metabolism. By using the fermentation effluent as substrate, a two-stage process is developed, where dark fermentation (DF) of CW for hydrogen production occurs in the first step, while the DF effluent is used as substrate in the MEC, in the second step, to further increase hydrogen production. By coupling DF-MEC, a dual environmental benefit is provided, combining sustainable bioenergy generation together with wastewater treatment, a fact that is also reinforced by the toxicity data of the current study.

Characteristics of hydrogen production from steam gasification of plant-originated lignocellulosic biomass and its prospects in Vietnam

Demands for the decline of CO2 emissions resulted in a significant transformation of the energy systems working on carbon sources towards more sustainable, clean, and renewable characteristics. Hydrogen is emerging as a secondary energy vector with ever-increasing importance in the decarbonisation progress. Indeed, hydrogen, a green and renewable energy source, could be produced from steam gasification of plant-originated lignocellulosic biomass. In this current review, key factors affect the hydrogen production yield from steam gasification of plant-originated lignocellulosic biomass, including the design of the gasifier, temperature, pressure, and steam-to-biomass ratio, steam flow rate, moisture and particle size of fed biomass, and catalysts were thoroughly analysed. Moreover, the effects of the abovementioned factors on the reduction of tar formation, which is also a key parameter towards ensuring the trouble-free operation of the reactor, were critically evaluated. More importantly, the separation of produced hydrogen from steam gasification of biomass and challenges over technological, environmental, and economic aspects of biomass gasification were also presented in detail. In addition, this paper is also profiling the prospect of Vietnam in fulfilling its hydrogen economy potential because Vietnam has vast biomass due to its tropical weather and availability of arable land, providing abundant lignocellulosic biomass with 45% of agricultural waste, 30% of firewood, and 25% of other sources. Besides, some primary factors hindering the broad application of biomass for hydrogen production were indicated. Finally, some solutions for implementing the hydrogenization strategy in Vietnam have also been discussed.

Status and development of hydrogen preparation, storageand transportation

<p indent=0mm>As a kind of important clean and renewable energy, hydrogen energy has received increasing attention. In the past, the majority of researchers from colleges and universities, Chinese Academy of Sciences and other institutions carrying out hydrogen energy related research were supported by the National Natural Science Foundation of China, Ministry of Science and Technology. Nowadays many enterprises are also involved, including both private enterprises and state owned enterprises. This is a significant shift in this research field that will further promote the development of hydrogen energy industry. Hydrogen industry includes hydrogen production, separation, storage and transportation, application and other links. Great strides have been made in these fields in recent years. Some of these fields are developing rapidly, while others are still facing many challenges. This paper makes a systematic analysis and induction of the status, issues and future development potential of the hydrogen industry chain. The paper is divided into seven parts, including hydrogen preparation, hydrogen storage, hydrogen transportation, hydrogen pipeline transportation, liquid hydrogen manufacturing, storage and transportation, hydrogen refueling station, conclusions and suggestions. In the part of hydrogen preparation, we introduce the methods of hydrogen preparation, separation and purification, the annual changes of world pure hydrogen and mixed hydrogen production, the relationship between hydrogen price of different hydrogen production methods and main raw material price, and the comparison of hydrogen production technologies and characteristics of different electrolytic water. In the part of hydrogen storage, four main methods: High-pressure gas hydrogen storage, low-temperature liquid hydrogen storage, solid hydrogen storage and organic liquid hydrogen storage are introduced, and the performances of these four methods are compared. In the part of hydrogen transportation, we introduce several common hydrogen transportation methods, the performance comparison of several common hydrogen transportation methods, and the price variance by distance of the three main hydrogen transportation methods. In the part of hydrogen pipeline transportation, the construction of two domestic hydrogen pipelines and the comparison of relevant parameters, as well as the situation of hydrogen transportation pipelines around the world are introduced. In the part of liquid hydrogen production, storage and transportation, the production methods of liquid hydrogen, the difference in calorific value between hydrogen fuel and other fuels, the preparation level of liquid hydrogen all over the world and the development direction in the future are introduced. In the part of hydrogenation stations, the construction, operation, cost and problems of hydrogenation refueling stations around the world are introduced. Finally, based on the contents above, we draw some conclusions and suggestions as follows: (1) In terms of hydrogen production, it is necessary to reduce the cost, develop hydrogen production from fossil raw materials to clean energy electrolytic water, focus on the development of proton exchange membrane green hydrogen preparation technology and enlarge its scale. (2) In terms of hydrogen storage, it is necessary to select appropriate hydrogen storage methods and improve their performance according to different applications. In the field of transportation, it is necessary to develop a hydrogen storage system with a weight density greater than 5wt% and a volume density greater than <sc>40 g/L,</sc> which is cost-effective and easy to control hydrogen absorption and desorption. In the non-transportation field, it is necessary to develop large-scale, low energy consumption and high safety hydrogen storage technology. (3) In terms of hydrogen transportation, it is necessary to strengthen the development of pipeline hydrogen transportation and liquid hydrogen transportation technology. (4) In terms of hydrogen refueling station, it is necessary to realize the localization of key equipment such as compressors and hydrogen injectors, improve the operation efficiency of hydrogen refueling stations and reduce the operational cost; Hydrogen production stations and liquid hydrogen refueling stations need to be developed.

Molecular dynamic investigation on sulfur migration during hydrogen production by benzothiophene gasification in supercritical water

Benzothiophene (BT) is a key sulfur-containing intermediate product in the thermal conversion process of coal and heavy oil. The migration process of the sulfur element may affect the thermal utilization design of BT. In this paper, BT was used as a model compound to simulate the supercritical water gasification (SCWG) process by molecular dynamics with a reactive force field (ReaxFF) method, and the laws of hydrogen production and sulfur migration mechanisms were obtained. Increasing the molecule number of supercritical water (SCW) and increasing the reaction temperature can enhance the generation of hydrogen and promote the conversion of organic sulfur to inorganic sulfur. Water was the main source of H2, and H2S was the main gaseous sulfur-containing product. SCW had a certain degree of oxidation due to a large number of hydroxyl radicals, which could increase the valence of sulfur. The conversion process of BT in SCW was mainly divided into four stages, including thiophene ring-opening; sulfur separation or carbon chain broke with sulfur retention; carbon chain cleaved, and gas generation. The lumped kinetic parameters of the conversion of sulfur in BT to inorganic sulfur were calculated, and the activation energy was 369.98 kJ/mol, which was much lower than those under pyrolysis conditions. This article aims to clarify the synergistic characteristics of hydrogen production and sulfur migration in the SCWG process of BT from the molecular perspective, which is expected to provide a theoretical basis for pollutant directional removal during hydrogen production by sulfur-containing organic matters in SCW.

Oyster shells improve anaerobic dark fermentation performances of food waste: Hydrogen production, acidification performances, and microbial community characteristics

Anaerobic dark fermentation (DF) performances of food waste (FW) were investigated using oyster shells. The different amount oyster shells(6%-12%(w/w)) were added to the DF system of FW. The result showed that the H2 production rate and cumulative H2 production improved after addition oyster shells. The highest H2 production rate and cumulative H2 production of 8% oyster shells addition group were 8.4 mL/(gVS·h) and 88.2 mL/gVS, which were 11.7%-30.6% and 17.4%-52.9% higher than those of the other test groups. TVFAs production, especially acetic and butyric acids improved after addition oyster shells. The highest TVFAs production was 19291.4 mg/L for 8% oyster shells added group, which was 90.24% higher than that of the unadded group. For 8% oyster shells added group, Lactobacillales, Gallicola, and Bacteroides were the dominant species at genus levels. Thus, the addition of an appropriate amount oyster shells could improve H2 production rate, cumulative H2 production, promote buffering capacity, enhance TVFAs production.

Study on Hydrogen Production of ZhunDong Coal Using Chemical Looping with Cu-Fe as Oxygen Carrier

ABSTRACT The main problem of coal direct chemical looping hydrogen generation (CLHG) is that coal ash and oxygen carrier (OC) cannot be effectively separated, which makes the OC activity is reduced after multiple cycles. In this study, a double plate-fixed bed reactor is adopted. The gasification of coal and the reduction reaction of oxygen carrier were integrated in the same furnace, and the hydrogen production characteristics of ZhunDong coal by chemical looping were studied. Cu-Fe composite oxygen carrier was prepared by chemical synthesis method. The results show that the higher the copper oxide content and the smaller the coal particle size, the better the effect of hydrogen yield. The potassium can promote the rate of coal gasification and increase oxygen carrier reduction rate, but faster reduction reaction rate will aggravate the formation of carbon deposition. The oxygen consumed in reduction of OC is preferentially from CuO, while Fe/FeO reacts with H2O prior to Cu/Cu2O in the hydrogen production stage. Compared with Cu-Fe OC, the implantation of MgAl2O3 plays an important role in stabilizing the redox ability and mechanical properties of OC.