Carbon-Coated Nanopowder as Sintering Aid for Water-Atomized Iron Powder

The influence of carbon coating on the nanopowder when used as a sintering aid for water-atomized iron powder is explored. Iron nanopowder without such a coating was used as a reference sintering aid to isolate and depict the influence of the carbon coating. Both nanopowder variants were characterized using XPS and HRTEM, and the results showed a core-shell structure for both nanopowder variants. Iron nanopowder is covered by a 3-4 nm thick iron oxide layer, while the carbon-coated nanopowder is encapsulated with a number of nanometric carbon layers. Thermogravimetry carried out in a pure hydrogen environment shows a multipeak behaviour for carbon-coated nanopowder, while a single peak behaviour is observed for the iron nanopowder. This difference was correlated with chemical analysis. Two types of micro/nanobimodal powders were obtained by mixing the nanopowder with water-atomized iron powder. An improved linear shrinkage was observed when carbon-coated iron nanopowder was added. This can be explained by the reduced surface diffusion in the nanopowder due to the carbon coating, which allows the nanopowder to sinter at higher temperatures and improves densification.

Coupling Oil Increase by Coal Liquefaction Residue Pyrolysis and Coal Pyrolysis Depolymerization Based on Big Data

With the continuous improvement of big data technology, my country’s coal liquefaction technology has also continued to mature, maintaining a stable industrial development. Traditional coal pyrolysis technology for tar production with the purpose of increasing tar production, such as coal hydropyrolysis, has problems such as high cost of pure hydrogen atmosphere and complex process and equipment operations, which severely restrict its industrial operation process. Based on this, this paper proposes a new technology of coal pyrolysis and depolymerization coupled with oil increase by using hydrogen precipitated by the condensation polymerization reaction at relatively high temperature under big data technology to study the effect of this process on coal pyrolysis for oil production. Experiments show that at 700°C, the tar yield reaches 21.5wt.%, which is 6% and 7% higher than the pyrolysis tar yield under the same conditions under hydrogen and nitrogen atmospheres. At 600°C, the methane aromatization reaction is relatively weak, and it can be seen that the tar yield is only slightly higher than that under hydrogen and nitrogen atmospheres. As the temperature of the methane anaerobic aromatization reaction increases, the equilibrium conversion rate increases accordingly. Therefore, as the reaction temperature increases, the tar yield also begins to increase.

The effect of plastic type on the yield and quality of lignite and plastic waste pyrolysis products

Lignite is a low rank coal which has great potential in South Kalimantan. However, it has not been used optimally due to its low quality. One of the ways to improve it is pyrolysis. Pyrolysis is the thermal decomposition of organic material in the absence of oxygen which will produce three products (char, tar and gas). Pyrolysis can make lignite into liquid fuel (pyrolysis liquid), but it still requires improvement due to the need for pure hydrogen donors. Plastic waste has a higher hydrogen/carbon ratio than coal. This material can be used as an additive in the pyrolysis process because it is rich in hydrogen. The samples of plastic waste used were ppolyethylene (PE), ppolypropylene (PP), and polystyrene (PS). Samples of lignite and plastic (plastic composition was 25 wt%) were used for every experiment, and pyrolysis was carried out with a holding time of 60 minutes at 500°C. The pyrolysis liquid obtained is then analyzed for its yields and properties (density, kinematic viscosity, heating value). The most feasible result for fuel alternative was obtained with the addition of PE.

Simulation and Techno-Economic Analysis of a Power-to-Hydrogen Process for Oxyfuel Glass Melting

As an energy-intensive industry sector, the glass industry is strongly affected by the increasingly stringent climate protection targets. As established combustion-based production systems ensure high process stability and glass quality, an immediate switch to low greenhouse gas emission processes is difficult. To approach these challenges, this work investigates a step-by-step integration of a Power-to-Hydrogen concept into established oxyfuel glass melting processes using a simulation approach. This is complemented by a case study for economic analysis on a selected German glass industry site by simulating the power production of a nearby renewable energy park and subsequent optimization of the power-to-hydrogen plant performance and capacities. The results of this study indicate, that the proposed system can reduce specific carbon dioxide emissions by up to 60 %, while increasing specific energy demand by a maximum of 25 %. Investigations of the impact of altered combustion and furnace properties like adiabatic flame temperature (+25 °C), temperature efficiency (Δξ = −0.003) and heat capacity flow ratio (ΔzHL = −0.009) indicate that pure hydrogen-oxygen combustion has less impact on melting properties than assumed so far. Within the case study, high CO2 abatement costs of 295 €/t CO2-eq. were determined. This is mainly due to the insufficient performance of renewable energy sources. The correlations between process scaling and economic parameters presented in this study show promising potential for further economic optimization of the proposed energy system in the future.

Reduction of New Zealand Titanomagnetite Ironsand by Hydrogen Gas in a Fluidised Bed System

<p>Titanomagnetite (TTM) ironsand has been used to produce steel in New Zealand (NZ) for about 40 years. However, the current steelmaking process in NZ produces high emissions of CO2 because it uses coal as a primary reducing agent. The fluidised bed (FB) process allows the use of pure hydrogen gas to reduce ironsand, and as a result, does not produce CO2 gas. However, for conventional hematite ores, reduction in a FB system is usually limited by the onset of particle sticking at temperatures ≳ 800°C. This thesis investigates the reduction of NZ TTM ironsand by hydrogen gas in the FB system with a key focus on ore sticking behaviour. Initially, this thesis reports preliminary fluidisation tests by nitrogen and helium gases at room temperature, carried out to determine key fluidisation parameters for ironsand powder. From these results, a laboratory-scale experimental FB reactor has been designed and built for the hydrogen reduction study at high temperatures. A key feature of the reactor is a novel in-situ sampling system, which enables extraction of multiple samples during a single experimental run without interrupting operation of the FB. Quantitative X-ray diffraction (q-XRD) has been used to determine the metallisation degree of partially reduced samples. Phase evolution during the reaction has also been analysed using q-XRD alongside scanning electron microscopy/energy dispersed spectroscopy (SEM/EDS). Additionally, the water vapour compositions in the exhaust gas were calculated from the q-XRD data and also measured in real-time using a high-temperature humidity sensor. The effect of various parameters has been investigated within the FB reduction experiments: hydrogen gas concentrations, hydrogen gas flow rate, bed mass, particle size, and temperature. The results indicate that across the entire range of controlled studied, the FB reduction rate of TTM ironsand is simply controlled by the rate of hydrogen gas supply. Interestingly, there were no occurrences of the sticking phenomenon at any point during the reduction by hydrogen gas at high temperatures of up to 1000°C. Sticking appears to be prevented by the formation of a protective titanium-rich oxide shell around each particle during the initial reduction stage. Importantly, this shell remains present throughout the reduction process, and as a result, the reduction reaction proceeds rapidly to completion with a metallisation degree of ~93%. The influence of temperature on the reaction progress has also been investigated. The reduction pathway appears to vary within different temperature regimes. At low temperatures (750°C-800°C), TTM is directly reduced to metallic iron and ilmenite without any evidence of wüstite phase. At ‘intermediate temperatures’ (850°C-900°C) small amount of short-lived wüstite is observed. Some of the amount of TTM appears to be reduced to wüstite, and some is directly reduced to metallic iron. At high temperatures (≥ 950°C), approximately half of the initial TTM phase is quickly reduced to wüstite. After that point, wüstite is then reduced to metallic iron whilst the reduction of TTM stops. This is due to the enrichment of Ti species in TTM phase, which stabilises TTM crystal. Once wüstite has been fully reduced, the reduction of TTM then resumes. Throughout the entire experimental program for this thesis, particle sticking was observed to occur only under two specific sets of experimental conditions. These were: reduction by 100% H2 gas at 1050°C (case A) and reduction by 7.5 mol.% H2O – 92.5 mol.% H2 at 950°C (case B). In both cases, sticking occurred as a sinter which nucleated at the reactor wall surface, while most particles remained fluidised as loose powder. The mechanism of these sticking cases has been analysed by XRD and SEM. The results suggest that silica from the quartz reactor wall reacted and bonded with Fe from particles to nucleate the initial sinter. In summary, the findings in this thesis show that the hydrogen-FB process is highly effective in reducing NZ ironsand to a direct reduced iron (DRI) product. These findings open up the possibility of developing a new industrial FB technology for the direct reduction of NZ TTM ironsand, with extremely low CO2 emissions.</p>

Reduction of New Zealand Titanomagnetite Ironsand by Hydrogen Gas in a Fluidised Bed System

<p>Titanomagnetite (TTM) ironsand has been used to produce steel in New Zealand (NZ) for about 40 years. However, the current steelmaking process in NZ produces high emissions of CO2 because it uses coal as a primary reducing agent. The fluidised bed (FB) process allows the use of pure hydrogen gas to reduce ironsand, and as a result, does not produce CO2 gas. However, for conventional hematite ores, reduction in a FB system is usually limited by the onset of particle sticking at temperatures ≳ 800°C. This thesis investigates the reduction of NZ TTM ironsand by hydrogen gas in the FB system with a key focus on ore sticking behaviour. Initially, this thesis reports preliminary fluidisation tests by nitrogen and helium gases at room temperature, carried out to determine key fluidisation parameters for ironsand powder. From these results, a laboratory-scale experimental FB reactor has been designed and built for the hydrogen reduction study at high temperatures. A key feature of the reactor is a novel in-situ sampling system, which enables extraction of multiple samples during a single experimental run without interrupting operation of the FB. Quantitative X-ray diffraction (q-XRD) has been used to determine the metallisation degree of partially reduced samples. Phase evolution during the reaction has also been analysed using q-XRD alongside scanning electron microscopy/energy dispersed spectroscopy (SEM/EDS). Additionally, the water vapour compositions in the exhaust gas were calculated from the q-XRD data and also measured in real-time using a high-temperature humidity sensor. The effect of various parameters has been investigated within the FB reduction experiments: hydrogen gas concentrations, hydrogen gas flow rate, bed mass, particle size, and temperature. The results indicate that across the entire range of controlled studied, the FB reduction rate of TTM ironsand is simply controlled by the rate of hydrogen gas supply. Interestingly, there were no occurrences of the sticking phenomenon at any point during the reduction by hydrogen gas at high temperatures of up to 1000°C. Sticking appears to be prevented by the formation of a protective titanium-rich oxide shell around each particle during the initial reduction stage. Importantly, this shell remains present throughout the reduction process, and as a result, the reduction reaction proceeds rapidly to completion with a metallisation degree of ~93%. The influence of temperature on the reaction progress has also been investigated. The reduction pathway appears to vary within different temperature regimes. At low temperatures (750°C-800°C), TTM is directly reduced to metallic iron and ilmenite without any evidence of wüstite phase. At ‘intermediate temperatures’ (850°C-900°C) small amount of short-lived wüstite is observed. Some of the amount of TTM appears to be reduced to wüstite, and some is directly reduced to metallic iron. At high temperatures (≥ 950°C), approximately half of the initial TTM phase is quickly reduced to wüstite. After that point, wüstite is then reduced to metallic iron whilst the reduction of TTM stops. This is due to the enrichment of Ti species in TTM phase, which stabilises TTM crystal. Once wüstite has been fully reduced, the reduction of TTM then resumes. Throughout the entire experimental program for this thesis, particle sticking was observed to occur only under two specific sets of experimental conditions. These were: reduction by 100% H2 gas at 1050°C (case A) and reduction by 7.5 mol.% H2O – 92.5 mol.% H2 at 950°C (case B). In both cases, sticking occurred as a sinter which nucleated at the reactor wall surface, while most particles remained fluidised as loose powder. The mechanism of these sticking cases has been analysed by XRD and SEM. The results suggest that silica from the quartz reactor wall reacted and bonded with Fe from particles to nucleate the initial sinter. In summary, the findings in this thesis show that the hydrogen-FB process is highly effective in reducing NZ ironsand to a direct reduced iron (DRI) product. These findings open up the possibility of developing a new industrial FB technology for the direct reduction of NZ TTM ironsand, with extremely low CO2 emissions.</p>

Four Ways to Store Large Quantities of Hydrogen

Hydrogen can be stored in underground caverns or geological structures in one of four ways. The easiest way to store hydrogen is in salt caverns. These are created by injecting fresh water or water with low salt content into a well down to a salt geological layer, with the extraction of salt-saturated brine. The caverns measure between 50 and 100 metres in diameter and up to several hundred meters tall where the salt formation is thick enough. Salt caverns are not lined, as the salt itself acts as a sealant. This type of storage is suitable for storing hydrogen at extremely high pressures where the salt layer is deep enough. The second way to store large quantities of hydrogen is to inject pure hydrogen or a hydrogen-methane mix into porous rock, in a depleted oil or gas field, or an aquifer. The hydrogen content may vary from a few per cent to 100 per cent. Reservoir and biochemical testing/modelling are to be performed accordingly. The hydrogen-methane mix can be withdrawn and injected into the network. Alternatively, hydrogen can be separated from methane at the well head, for example using pressure swing adsorption technology. Hydrogen can also be stored underground by converting it into a liquid carrier, such as ammonia, which can then be stored in a Lined Rock Cavern. A liner is required to prevent contact between ammonia and water. The pressure and temperature are adapted to optimise the entire supply chain. The advantage of using ammonia is that proper storage conditions can be fulfilled without the need for excessive pressure or temperature. Lastly, hydrogen can be stored underground by directly injecting it into a Lined Rock Cavern. This may take the form of compressed storage (gaseous hydrogen) or cryogenic storage (liquid hydrogen), the choice once again depending on the supply chain as a whole. A liner is required owing to extremely high pressures or extremely low temperatures. It should be noted that storing hydrogen in a Lined Rock Cavern involves a few technical difficulties that have yet to be resolved. These four underground hydrogen storage techniques differ in terms of their technology readiness level (TRL) and cost. All four will likely be required in the coming years to satisfy the needs of a booming market.

Separation of ferromanganese ore components by non-contact and contact carbothermic reduction

The possibility of joint selective solid-phase reduction of iron and phosphorus in ferromanganese ore has been experimentally confirmed. The experiments were carried out in a Tamman laboratory furnace at a temperature of 1000 °C and holding for two and five hours. The article presents results of the study of phase composition and phases' quantitative ratio of the reduction products, as well as chemical composition of the phases. It was established that reduction roasting in CO atmosphere provides a transition from oxide phase to metal phase only of iron and phosphorus. At the same time, the concentration of manganese oxide MnO increases in the ore oxide phase. The use of solid carbon as a reducing agent under the same conditions leads to transition to the metallic phase together with iron and phosphorus of a part of manganese. Based on the obtained data, it is proposed to selectively reduce iron and phosphorus at a temperature of 1000 °C with a reducing gas. Gas reduction will make it possible to use existing gas furnaces, in particular, multi-pod furnaces, for metallization of iron and phosphorus in ferromanganese ore, and natural gas, including hydrogen -enriched gas, and even pure hydrogen, as a reducing agent and energy carrier. Due to this, at the stage of ore metallization in production of manganese alloys, greenhouse gas CO2 emissions can be reduced. The results of the work can be used in the development of theoretical and technological bases for processing ferromanganese ores with a high content of phosphorus, which are not processed by existing technologies.

Effect of Hydrogen in Mixed Gases on the Mechanical Properties of Steels—Theoretical Background and Review of Test Results

This review summarizes the thermodynamics of hydrogen (H2) in mixed gases of nitrogen (N2), methane (CH4) and natural gas, with a special focus on hydrogen fugacity. A compilation and interpretation of literature results for mechanical properties of steels as a function of hydrogen fugacity implies that test results obtained in gas mixtures and in pure hydrogen, both at the same fugacity, are equivalent. However, this needs to be verified experimentally. Among the test methods reviewed here, fatigue crack growth testing is the most sensitive method to measure hydrogen effects in pipeline steels followed by fracture toughness testing and tensile testing.