Current situation and development prospects of metallurgical by-product gas utilization in China's steel industry

China's annual metallurgical by-product gas production exceeds 1400 billion Nm³, the calorific equivalent of ∼266 million tonnes of coal. The widely-studied blast furnace gas used in hydrogen-enriched carbonic oxide recycling oxygenate furnaces ensures carbon-reduction. Converter gas contains abundant heat resources, equivalent to ∼6.5 million tonnes of coal. Using high-temperature by-product gas online reforming methods to convert thermal energy into chemical energy and combining it with power generation and other industries imparts physical heat recovery exceeding 60%. China's annual coke oven gas (COG) production could support more than 100 million tonnes of direct reduced iron production, thus reducing CO₂ emissions by more than 150 million tonnes (nearly 10% of China's steel industry CO₂ emissions). We summarise the characteristics, availability, and steel-chemical co-production utilisation of three by-product gases, and discuss the application of COG in direct reduced iron production and development of metallurgical by-product gas utilisation for carbon reduction in China.     

Biomass gasification coupled with producer gas cleaning,bottling and HTS catalyst treatment for H2-rich gas production

The aim of the present study is to demonstrate the production of hydrogen-rich fuel gas from J. curcas residue cake. A comprehensive experimental study for the production of hydrogen rich fuel gas from J. curcas residue cake via downdraft gasification followed by high temperature water gas shift catalytic treatment has been carried out. The gasification experiments are performed at different equivalence ratios and performance of the process is reported in terms of producer gas composition & its calorific value, gas production rate and cold gas efficiency. The producer gas is cleaned of tar and particulate matters by passing it through venturi scrubber followed by sand bed filter. The clean producer gas is then compressed at 0.6 MPa and bottled into a gas cylinder. The bottled producer gas and a simulated mixture of producer gas are then subjected to high temperature shift (HTS) catalytic treatment for hydrogen enriched gas production. The effect of three different operating parameters GHSV, steam to CO ratio and reactor temperature on the product gas composition and CO conversion is reported. From the experimental study it is found that, the presence of oxygen in the bottled producer gas has affected the catalyst activity. Moreover, higher concentration of oxygen concentration in the bottled producer gas leads to the instantaneous deactivation of the HTS catalyst.     

A strategy of mid-temperature natural gas based chemical looping reforming for hydrogen production

Steam methane reforming (SMR) needs the reaction heat at a temperature above 800 °C provided by the combustion of natural gas and suffers from adverse environmental impact and the hydrogen separated from other chemicals needs extra energy penalty. In order to avoid the expensive cost and high power consumption caused by capturing CO₂ after combustion in SMR, natural gas Chemical Looping Reforming (CLR) is proposed, where the chemical looping combustion of metal oxides replaced the direct combustion of NG to convert natural gas to hydrogen and carbon dioxide. Although CO₂ can be separated with less energy penalty when combustion, CLR still require higher temperature heat for the hydrogen production and cause the poor sintering of oxygen carriers (OC). Here, we report a high-rate hydrogen production and low-energy penalty of strategy by natural gas chemical-looping process with both metallic oxide reduction and metal oxidation coupled with steam. Fe₃O₄ is employed as an oxygen carrier. Different from the common chemical looping reforming, the double side reactions of both the reduction and oxidization enable to provide the hydrogen in the range of 500–600 °C under the atmospheric pressure. Furthermore, the CO₂ is absorbed and captured with reduction reaction simultaneously.Through the thermodynamic analysis and irreversibility analysis of hydrogen production by natural gas via chemical looping reforming at atmospheric pressure, we provide a possibility of hydrogen production from methane at moderate temperature. The reported results in this paper should be viewed as optimistic due to several idealized assumptions: Considering that the chemical looping reaction is carried out at the equilibrium temperature of 500 °C, and complete CO₂ capture can be achieved. It is assumed that the unreacted methane and hydrogen are completely separated by physical adsorption. This paper may have the potential of saving the natural gas consumption required to produce 1 m³ H₂ and reducing the cost of hydrogen production.     

Simulation and optimization of hydrogen production by steam reforming of natural gas for refining and petrochemical demands in Lebanon

Steam reforming of natural gas produces the majority of the world's hydrogen (H₂) and it is considered as a cost-effective method from a product yield and energy consumption point of view. In this work, we present a simulation and an optimization study of an industrial natural gas steam reforming process by using Aspen HYSYS and MATLAB software. All the parameters were optimized to successfully run a complete process including the hydrogen production zone units (reformer reactor, high temperature gas shift reactor HTS and low temperature gas shift reactor LTS) and the purification zone units (absorber and methanator). Optimum production of hydrogen (87,404 MT/year) was obtained by fixing the temperatures in the reformer and the gas shift reactors (HTS & LTS) at 900 °C, 500 °C and 200 °C respectively while maintaining a pressure of 7 atm, and a steam to carbon ratio (S/C) of 4. Moreover, ~99% of the undesired CO₂ and CO gases were removed in the purification zone and a reduction of energy consumption of 77.5% was reached in the heating and cooling units of the process.     

Improving inter-plant integration of syngas production technologies by the recycling of CO2 and by-product of the Fischer-Tropsch process

This paper deals with the emission reduction in synthesis-gas production by better integration and increasing the energy efficiency of a high-temperature co-electrolysis unit combined with the Fischer-Tropsch process. The investigated process utilises the by-product of Fischer-Tropsch, as an energy source and carbon dioxide as a feedstock for synthesis gas production. The proposed approach is based on adjusting process streams temperatures with the further synthesis of a new heat exchangers network and optimisation of the utility system. The potential of secondary energy resources was determined using plus/minus principles and simulation of a high-temperature co-electrolysis unit. The proposed technique maximises the economic and environmental benefits of inter-unit integration. Two scenarios were considered for sharing the high-temperature co-electrolysis and the Fischer-Tropsch process. In the first scenario, by-products from the Fischer-Tropsch process were used as fuel for a high-temperature co-electrolysis. Optimisation of secondary energy sources and the synthesis of a new heat exchanger network reduce fuel consumption by 47% and electricity by 11%. An additional environmental benefit is reflected in emission reduction by 25,145 tCO₂/y. The second scenario uses fossil fuel as a primary energy source. The new exchanger network for the high-temperature co-electrolysis was built for different energy sources. The use of natural gas resulted in total annual costs of the heat exchanger network to 1,388,034 USD/y, which is 1%, 14%, 116% less than for coal, fuel oil and LPG, respectively. The use of natural gas as a fuel has the lowest carbon footprint of 7288 tCO₂/y. On the other hand, coal as an energy source has commensurable economic indicators that produce 2 times more CO₂, which can be used as a feedstock for a high-temperature co-electrolysis. This work shows how in-depth preliminary analysis can optimise the use of primary and secondary energy resources during inter-plant integration.     

Hydrogen production from phototrophic microorganisms: Reality and perspectives

Hydrogen is a promising alternative to fossil fuel for a source of clean energy due to its high energy content. Some strains of phototrophic microorganisms are known as important object of scientific research and they are being explored to raise biohydrogen (BioH₂) yield. BioH₂ is still not commonly used in industrial area because of the low biomass yield and valuable down streaming process. This article deals with the methods of the hydrogen production with the help of two large groups of phototrophic microorganisms – microalgae and cyanobacteria. Microalgal hydrogen is environmentally friendly alternative to conventional fossil fuels. Algal biomass has been considered as an attractive raw source for hydrogen production. Genetic modified strains of cyanobacteria are used as a perspective object for obtaining hydrogen. The modern photobioreactors and outdoor air systems have been used to obtain the biomass used for hydrogen production. At present time a variety of immobilization matrices and methods are being examined for their suitability to make immobilized H₂ producers.     

Assessment of ammonia as energy carrier in the use with reversible solid oxide cells

Ammonia represents one of the most promising potential solutions as energy vector and hydrogen carrier, having a higher potential to transport energy than hydrogen itself in a pressurized form. Furthermore, solid oxide fuel cells (SOFCs) can directly be fed with ammonia, thus allowing for immediate electrical power and heat generation. This paper deals with the analysis of the dynamic behavior of commercial SOFCs when fueled with ammonia. Several measurements at different temperatures have been performed and performances are compared with hydrogen and a stoichiometrically equivalent mixture of H₂ and N₂ (3:1 M ratio). Higher temperature led to smaller drops in voltage for both fuels, thus providing higher efficiencies. Ammonia resulted slightly more performant (48% at 760 °C) than hydrogen (45% at 760 °C), in short stack tests. Moreover, different ammonia-to-air ratios have been investigated and the stack area-specific resistance has been studied in detail by comparing numerical modeling predictions and experimental values.     

Design and performance of asymmetric supported membranes for oxygen and hydrogen separation

Producing syngas and hydrogen from biofuels is a promising technology in the modern energy. In this work results of authors’ research aimed at design of supported membranes for oxygen and hydrogen separation are reviewed. Nanocomposites were deposited as thin layers on Ni–Al foam substrates. Oxygen separation membranes were tested in CH₄ selective oxidation/oxi-dry reforming. The hydrogen separation membranes were tested in C₂H₅OH steam reforming. High oxygen/hydrogen fluxes were demonstrated. For oxygen separation membranes syngas yield and methane conversion increase with temperature and contact time. For reactor with hydrogen separation membrane a good performance in ethanol steam reforming was obtained. Hydrogen permeation increases with ethanol inlet concentration, then a slight decrease is observed. The results of tests demonstrated the oxygen/hydrogen permeability promising for the practical application, high catalytic performance and a good thermochemical stability.     

Consumer acceptance under hydrogen energy promotion policy: Evidence from Yangtze River Delta

Hydrogen fuel cell vehicle (HFCV) as an emerging industry with great potential have received great attention in the Yangtze River Delta, China. Under government's promotion of hydrogen energy, whether HFCV can be accepted by consumers is an important topic for future policymaking. Therefore, this study takes consumers' willingness to consume HFCV as the dependent variable and collects questionnaires from 21 cities in the Yangtze River Delta from 2020 to 2021. Based on Ordinary Least Squares (OLS) and Logit Regression, the evaluation was conducted from four perspectives: personal and family situation, environmental awareness, energy attitude and local product confidence. The results show that gender, age and income differences are not necessarily determinants of HFCV purchase, but educational level is a significant factor. Consistent with social-psychological studies, personal awareness of environmental protection and energy attitudes are the key factors that are significant affect HFCV purchase. Lastly, it is found that in the Yangtze River Delta, consumers' confidence in Chinese local hydrogen products is also a significant factor. This paper confirms that HFCV consumers have commonalities with other new energy consumers. However, due to the expectation of greater local production and development, enhancing the social recognition and confidence of local hydrogen technology may be one of the promotion approaches neglected.     

Hydrogen production using chemical looping technology: A review with emphasis on H2 yield of various oxygen carriers

Natural H₂ in useful quantities is negligible, which makes hydrogen unsuitable as an energy resource compared to other fuels. H₂ production by solar, biological, or electrical sources needs more energy than obtained by combusting it. Lower generation of pollutants and better energy efficiency makes hydrogen a potential energy carrier. Hydrogen finds potential applications in automobile and energy production. However, the cost of producing hydrogen is extremely high. Chemical-looping technology for H₂ generation has caught widespread attention in recent years. This work, presents some recent findings and provides a comprehensive overview of different chemical looping techniques such as chemical looping reforming, syngas chemical looping, coal direct chemical looping, and chemical looping hydrogen generation method for H₂ generation. The above processes are discussed in terms of the relevant chemical reactions and the associated heat of reactions to ascertain the overall endothermicity or exothermicity of the H₂ production. We have compared the H₂ yield data of different Fe/Ni, spinel and perovskites-based oxygen carriers (OC) reported in previous literature. This review is the first comprehensive study to compare the H₂ yield data of all the previously reported oxygen carriers as a function of temperature and redox cycles. In addition, the article summarizes the characteristics and reaction mechanisms of various oxygen carrier materials used for H₂ generation. Lastly, we have reviewed the application of Density Function Theory (DFT) to study the effect of various dopant addition on the efficiency of H₂ production of the oxygen carriers and discussed ASPEN simulations of different chemical looping techniques.     

Investigation of Zr,Gd/Zr,and Pr/Zr – doped ceria for the redox splitting of water

There is a renewed interest in CeO₂ for use in solar-driven, two-step thermochemical cycles for water splitting. However, despite fast reduction/oxidation kinetics and high thermal stability of ceria, the cycle capacity of CeO₂ is low due to thermodynamic limitations. In an effort to increase cycle capacity and reduce thermal reduction temperature, we have studied binary zirconium-substituted ceria (Zr_xCe_1-xO₂, x = 0.1, 0.15, 0.25) and ternary praseodymium/gadolinium-doped Zr-ceria (M_0.1Zr_0.25Ce_0.65O₂, M = Pr, Gd). We evaluate the oxygen cycle capacity and water splitting performance of crystallographically and morphologically stable powders that are thermally reduced by laser irradiation in a stagnation flow reactor. The addition of zirconium dopant into the ceria lattice improves O₂ cycle capacity and H₂ production by approximately 30% and 11%, respectively. This improvement is independent of the Zr dopant level, up to 25%, suggesting that above 10% Zr dopant level, Zr might be displaced during the high temperature annealing process. The addition of Pr and Gd to the binary Zr-ceria mixed oxide, on the other hand, is detrimental to H₂ production. A kinetic analysis is performed using a model-based analytical approach to account for effects of mixing and dispersion, and to identify the rate controlling mechanism of the water splitting process. We find that the water splitting reaction at 1000 °C and with 30 vol% H₂O, for all doped ceria samples, is surface limited and best described by a deceleratory power law model (F-model), similar to undoped CeO₂. Additionally, we used density functional theory (DFT) calculations to examine the role of Zr, Pr, and Gd. We find that the addition of Pr and Gd induce non-redox active sites and, therefore, are detrimental to H₂ production, in agreement with experimental work. The calculated surface H₂ formation step was found to be rate limiting, having activation barriers greater than bulk O diffusion, for all materials. This agrees with and further explains experimental findings.     

Expected impacts on greenhouse gas and air pollutant emissions due to a possible transition towards a hydrogen economy in German road transport

Transitioning German road transport partially to hydrogen energy is among the possibilities being discussed to help meet national climate targets. This study investigates impacts of a hypothetical, complete transition from conventionally-fueled to hydrogen-powered German transport through representative scenarios. Our results show that German emissions change between ?179 and +95 MtCO₂eq annually, depending on the scenario, with renewable-powered electrolysis leading to the greatest emissions reduction, while electrolysis using the fossil-intense current electricity mix leads to the greatest increase. German energy emissions of regulated pollutants decrease significantly, indicating the potential for simultaneous air quality improvements. Vehicular hydrogen demand is 1000 PJ annually, requiring 446–525 TWh for electrolysis, hydrogen transport and storage, which could be supplied by future German renewable generation, supporting the potential for CO₂-free hydrogen traffic and increased energy security. Thus hydrogen-powered transport could contribute significantly to climate and air quality goals, warranting further research and political discussion about this possibility.     

Performance analysis of a novel solar PTC integrated system for multi-generation with hydrogen production

The performance analysis of a novel multi-generation (MG) system that is developed for electricity, cooling, hot water and hydrogen production is presented in this study. MG systems in literature are predominantly built on a gas cycle, integrated with other thermodynamic cycles. The aim of this study is to achieve better thermodynamic (energy and exergy) performance using a MG system (without a gas cycle) that produces hydrogen. A proton exchange membrane (PEM) utilizes some of the electricity generated by the MG system to produce hydrogen. Two Rankine cycles with regeneration and reheat principles are used in the MG configuration. Double effect and single effect absorption cycles are also used to produce cooling. The electricity, hot water, cooling effect, and hydrogen production from the multi-generation are 1027 kW, 188.5 kW, 11.23 kg/s and 0.9785 kg/h respectively. An overall energy and exergy efficiency of 71.6% and 24.5% respectively is achieved considering the solar parabolic trough collector (PTC) input and this can increase to 93.3% and 31.9% if the input source is 100% efficient. The greenhouse gas emission reduction of this MG system is also analyzed.     

Supercritical water gasification mechanism of polymer-containing oily sludge

In the offshore petroleum industry, polymer-containing oily sludge (PCOS) hinders oil extraction and causes tremendous hazards to the marine ecological environment. In this paper, an effective pretreatment method is proposed to break the adhesive structure of PCOS, and the experiments of supercritical water gasification are carried out under the influencing factors including residence time (5–30 min) and temperature (400–750 °C) in batch reactors. The increase of time and temperature all show great promoting effects on gas production. Polycyclic aromatic hydrocarbons, including naphthalene and phenanthrene, are considered as the main obstacles for a complete gasification. Carbon gasification efficiency (CE) reaches maximum of 95.82% at 750 °C, 23 MPa for 30 min, while naphthalene makes up 70% of the organic compounds in residual liquid products. The highest hydrogen yield of 19.79 (mol H₂/kg of PCOS) is observed in 750 °C for 25 min. A simplified reaction pathway is presented to describe the gaseous products (H₂, CO, CO₂, CH₄). Two intermediates are defined for describing the reaction process bases on the exhaustive study on organic matters in residual liquid products. The results show that the calculated data and the experimental data have a high degree of fit and tar formation reaction is finished within 10 min.     

Exergetic analysis of hydrogen utilisation pathways – Part 1: Energy supply in buildings

This article analyses exergy losses along hydrogen utilisation pathways recently discussed in Germany and other countries. As a renewable fuel hydrogen will be an important part of sustainable future economies. Hydrogen can be used in all sectors, especially in buildings, for mobility and in industry, e.g. in steel production or ammonia synthesis. However, hydrogen has to be produced in a sustainable way. The most promising production is via water electrolysis using renewable electricity. In the first part of this work, exergy analysis is made for the complete hydrogen pathways from production until final utilisation for energy supply in buildings. The second part will focus on pathways for mobility. In the third part, the results are compared with available alternatives to hydrogen such as direct use of electricity in building supply or mobility. The results for building energy supply show that firstly transportation in pipelines (mixture with natural gas and pure hydrogen) is very efficient. Secondly, major exergy losses are caused by the electrolyser. Thirdly, combustion of renewable hydrogen for room heating in common boilers cause the highest exergy losses, but the use of combined heat and power (CHP) units or fuel cells can improve the exergy efficiency substantially.     

Review of hydrogen economy in Malaysia and its way forward

Heavy fossil fuels consumption has raised concerns over the energy security and climate change while hydrogen is regarded as the fuel of future to decarbonize global energy use. Hydrogen is commonly used as feedstocks in chemical industries and has a wide range of energy applications such as vehicle fuel, boiler fuel, and energy storage. However, the development of hydrogen energy in Malaysia is sluggish despite the predefined targets in hydrogen roadmap. This paper aims to study the future directions of hydrogen economy in Malaysia considering a variety of hydrogen applications. The potential approaches for hydrogen production, storage, distribution and application in Malaysia have been reviewed and the challenges of hydrogen economy are discussed. A conceptual framework for the accomplishment of hydrogen economy has been proposed where renewable hydrogen could penetrate Malaysia market in three phases. In the first phase, the market should aim to utilize the hydrogen as feedstock for chemical industries. Once the hydrogen production side is matured in the second phase, hydrogen should be used as fuel in internal combustion engines or burners. In the final phase hydrogen should be used as fuel for automobiles (using fuel cell), fuel-cell combined heat and power (CHP) and as energy storage.     

Preparation of hydrogen from metals and water without CO2 emissions

Considering the high calorific value and low-carbon characteristics of hydrogen energy, it will play an important role in replacing fossil energy sources. The production of hydrogen from renewable energy sources for electricity generation and electrolysis of water is an important process to obtain green hydrogen compared with classic low-carbon hydrogen production methods. However, the challenges in this process include the high cost of liquefied hydrogen and the difficulty of storing hydrogen on a large scale. In this paper, we propose a new route for hydrogen storage in metals, namely, electricity generation from renewable energy sources, electrolysis to obtain metals, and subsequent hydrogen production from metals and water. Metal monomers facilitate large-scale and long-term storage and transportation, and metals can be used as large-scale hydrogen storage carriers in the future. In this technical route, the reaction between metal and water for hydrogen production is an important link. In this paper, we systematically summarize the research progress, development trend, and challenges in the field of metal to hydrogen production. This study aim to aid in the development of this field.     

Effect of hydrogen flow rate on the synthesis of carbon nanofiber using microwave-assisted chemical vapour deposition with ferrocene as a catalyst

Carbon nanostructure materials are becoming of considerable commercial importance, with interest growing rapidly over the decade since the discovery of carbon nanofibers. In this study, a new novel method is introduced to synthesize the carbon nanofibers by gas-phase, where a single-stage microwave-assisted chemical vapour deposition approach is used with ferrocene as a catalyst and acetylene and hydrogen as precursor gases. Hydrogen flow rate plays a significant role in the formation of carbon nanofibers, as being the carrier and reactant gas in the floating catalyst method. The effect of process parameters such as microwave power, radiation time and gas ratio of C₂H₂/H₂ was investigated statistically. The carbon nanofibers were characterized using scanning and transmission electron microscopy and thermogravimetric analysis. The analysis revealed that the optimized conditions for carbon nanofibers production were microwave power (1000 W), radiation time (35 min) and acetylene/hydrogen ratio (0.8). The field emission scanning electron microscope and transmission electron microscope analyses revealed that the vertical alignment of carbon nanofibers has tens of microns long with a uniform diameter ranging from 115 to 131 nm. High purity of 93% and a high yield of 12 g of CNFs were obtained. These outcomes indicate that identifying the optimal values for process parameters is important for synthesizing high quality and high CNF yield.     

Life Cycle Assessment (LCA) for use on renewable sourced hydrogen fuel cell buses vs diesel engines buses in the city of Rosario,Argentina

The purpose of this paper is to build the first Energy and Life Cycle Analysis (LCA) comparison between buses with internal combustion engine currently used in the city of Rosario, Province of Santa Fe, Argentina, and some technological alternatives and their variants focusing on buses with an electrical engine powered by compressed hydrogen that feet fuel cells of polymer electrolyte membrane (PEM). This LCA comprehend raw material extraction up to its consumption as fuel. Specifically, hydrogen production considering different production processes from renewable sources called “green hydrogen” (Velazquez Abad and Dodds, 2020) [1] and non-renewable sources called “grey hydrogen” (Velazquez Abad and Dodds, 2020) [1]. Renewable sources for hydrogen production are rapid cut densified poplar energy plantation, post-industrial wood residues such as chips pallets, and maize silage. For non-renewable hydrogen production sources are the local electrical power grid from water electrolysis and natural gas from the steam methane reforming process.Buses whose fuel would be renewable hydrogen, produced near the City of Rosario, Province of Santa Fe, Argentina, meet one of the main criteria of sustainability biofuels of the European Union (EU) taken into account Renewable Energy Directive (RED) 2009/28 [2] and EU RED Directive 2018/2001 [3] that need significant reduction on net greenhouse gases (GHG) from biomass origin row material respect fossil fuels. At least 70% of GHG would be avoided from its main fossil counterpart of the intern combustion engine (ICE), in the worst and current scenario of the emission factor of the electrical grid of Argentina in the point of use that is about 0.40 kg CO_2eq/kWh with energy and environmental load of 100% in the allocation factor in the hydrogen production stage of the LCA analysis.     

Evaluating influences of impurities on hydrogen production in the reaction of Si with water using Si sludge

Hydrogen has attracted much attention as a next-generation energy resource. Among various technologies, one of the promising approaches for hydrogen production is the use of the reaction between Si and water, which does not require any heat, electricity, and light energy as an input. Notwithstanding the usefulness of Si as a prospective raw material of hydrogen production, the manufacturing process of Si requires a significant amount of energy. Therefore, as an alternative to pure Si, this study used a wasted Si sludge, generated though the manufacturing process of Si wafer, for the direct reuse. Thus, the Si-water reaction for the hydrogen generation was investigated in comparison with pure Si and Si sludge by employing X-ray absorption near edge structure (XANES) to evaluate the feasibility of hydrogen production with the use of Si sludge and to identify the influence of impurities contained in Si sludge. As a result, hydrogen was not produced with the use of Si sludge because of containing Al compound as the impurity. Through the XANES analysis, the formation of SiO(OH)₂ was found as core-shell structure, which potentially would hinder the hydrogen generation.