The iron and steel industry accounts for approximately 45% of the CO₂ emissions in the Japanese industrial sector, and therefore is investing in improvements to reduce the CO₂ emissions. Current projections are for the stock of scrap iron and steel products to increase in the future. Being already in the reduced state, such scrap can be regenerated to steel with lower CO₂ emissions than iron ore. The “Packed bed type Partial Smelting Reduction process” (PSR), which concurrently smelts scrap and reduces iron ore, is a promising method to utilize scrap iron. This work evaluates the feasibility of combining PSR with top gas recycling, a process commonly called the ‘SMART steelmaking system’. In the SMART system, CO₂ derived from the PSR gas is reduced into CO or CH₄ and recycled to the furnace as a reducing agent. The integrated whole process including shaft furnace, CO₂ electrolysis, pressure swing adsorption, and other conventional auxiliary systems was modelled in Aspen Plus, and CO₂ emissions reduction and exergy analysis of the system adaptive for flexible operating conditions was performed. Increasing the scrap ratio by 5% consistently lead to a 4% reduction in CO₂ emissions. Similarly, increasing the CO input rate by 100 kg/THM consistently resulted in a reduction of CO₂ emissions of approximately 3%. The maximum CO₂ emissions reduction of 22% was achieved at the condition of the operably highest scrap ratio and CO input rate.

The minimum carbon requirement for ironmaking under carbon and hydrogen co-existing condition was discussed. The reaction system consisted of the reductions of iron oxides by carbon monoxide, hydrogen and solid carbon, the partial combustion of solid carbon, and melting of metallic iron and slag. The analysis took into account the equilibrium constrains for the reductions of the iron oxides and thermal requirement to produce hot metal and molten slag. The carbon requirement was plotted against the contributions of solid carbon, carbon monoxide and hydrogen to the FeO reduction. A valley (minimum route) of carbon requirement appeared from the C–CO reduction to the CO–H₂ reduction condition on the ternary diagram, and the requirement got smaller with increase in H₂ contribution. The carbon requirement decreased with lowering the temperature of FeO reduction. The effect of the water gas shift reaction was also analyzed. The water gas shift reaction (direction to generate CO₂ and H₂) decreased the carbon requirement due to its exothermic reaction heat.

Preparation of metal supported La_0.9Sr_0.1Ga_0.8Mg_0.2O₃ (LSGM) thin film cell for CO₂ electrolysis was studied and by using selective reduction method of NiO–NiFe₂O₄, it was found that porous Ni–Fe(9:1) based substrate with ca.30% porosity was successfully prepared without large volume change resulting in the successful preparation of LaGaO₃ dense thin film on metal substrate. By using Ce_0.8Sm_0.2O₂ (SDC) thin film, Ni diffusion from Ni–Fe substrate was prevented. CO₂ electrolysis was performed on the prepared LSGM/SDC on Ni–Fe porous substrate. When Sm_0.5Sr_0.5CoO₃ (SSC) anode was prepared by screen print method using SSC powder, sintering of SSC powder was significantly occurred resulting in the large IR loss and overpotential. In contrast, when SSC anode layer was deposited by PLD (30 min) after LSGM/SDC layer deposition, tight contact between SSC anode and LSGM electrolyte film was obtained and the large CO₂ electrolysis current of 3 and 0.5 A/cm² were achieved at 973 and 773 K, respectively. Impedance analysis suggests that increased CO₂ electrolysis current was obtained by decreased IR loss and electrode overpotential.

Micro-tubular type solid oxide electrolysis cell was prepared by using Ni-YSZ anode support tube and La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ (LSGM) electrolyte film which was prepared by dip coating and co-sintering method. Application of the prepared tubular type solid oxide cells for CO₂ electrolysis was studied. It was found that CO₂ to CO was occurred selectively on tubular type solid oxide cells using LSGM thin film prepared by dip-coating method. However, comparing with the electrolysis current on planer type cells using LaGaO₃ based oxide electrolyte, that of tubular type cell was much smaller and this could be assigned to the low activity to CO₂ electrolysis and large IR loss of Ni-YSZ porous substrate which could be explained by re-oxidation of Ni.

Utilization of renewable energy has been proposed for solution of the Global Warming. Electroreduction of CO₂ into valuable chemicals using renewable electricity is a promising technology. Electroreduction of CO₂ to CO and CH₄ was studied using the polymer-electrolyte-membrane (PEM) gas cell. The electrocatalyst prepared by partial pyrolysis of Co-4,4’-dimethyl-2,2’-bipyridine supported on KEJENBLACK at 673 K (Co-dmbpy/KB(673K)) has been found for selective reduction of CO₂ to CO. Screening of co-catalysts to promote formation of CH₄ during the CO₂ reduction by the Co-dmbpy/KB(673K) cathode was conducted in this work. An effective Ni/KB co-catalyst prepared by H₂ reduction at 673 K was found. Suitable preparation conditions and methods of the cathode and effects of cathode potentials on the CO₂ reduction to CO and CH₄ were studied. The reaction path for the formation of CH₄ in the CO₂ reduction was studied and the successive reduction of CO₂ to CO on the Co-dmbpy/KB(673K) catalyst and CO to CH₄ on the Ni/KB(673K) co-catalyst was determined.

Using iACRES, which is an ironmaking system based on the Active Carbon Recycling Energy System concept, to reduce or recycle CO₂ emitted from ironmaking processes, we electrolyzed CO₂ with a metal-supported solid oxide electrolysis cell (MS-SOEC) capable of providing a large cell surface area for the processing of large amounts of CO₂. The MS-SOEC current-density–voltage (I-V) curves reveal a change in slope at around 0.8 V, which is the theoretical decomposition voltage of CO₂. The CO production rate was 0.88 µmol cm⁻² s⁻¹ when 2.0 V was applied between the cathode and the anode at 800°C, while that for O₂ was 0.44 µmol cm⁻² s⁻¹, which is consistent with the stoichiometry for CO₂ electrolysis. The Faraday efficiency was 48% at 900°C. Gas was observed to leak from the cell; this leakage will need to be overcome through improvements in the layer-production process in order to achieve an efficiency close to 100%. On the basis of the cell-based experimental results, the feasibility of a blast furnace based on iACRES and driven by an HTGR (high-temperature gas-cooled reactor) was evaluated. To reduce CO₂ emissions by 30.0%, the required MS-SOEC surface area was estimated to be 8.30×10⁴ and 3.98×10⁴ m² with 968 and 480 MWth of HTGR thermal output under Faraday efficiency of 48% and 100%, respectively. We confirmed that iACRES using MS-SOEC contributes to realizing low-carbon ironmaking by recycling CO₂ and reducing its emissions into the atmosphere.

CO–H₂ gas mixture is often used for gas-based DRI process where carbon deposition reaction and Fe₃C metal dusting play negative roles for a stable reduction operation. Fe₃C decomposition leads to the formation of iron particles which is a catalyst for carbon fiber deposition. Because of the parallel occurrence of these reactions, kinetic analysis of them would be complicated. In the present study, to simplify the kinetic analysis, quantitative analysis of carbon fiber deposition was conducted by using thermobalance. A powdery iron sample was prepared by reduction of Fe₂O₃ with 100vol%H₂ at 673 K. Carbon deposition on the iron sample was investigated under flowing 100%CO, 90vol%CO-10vol%H₂, 75vol%CO-25vol%H₂, 50vol%CO-50vol%H₂, 25vol%CO-75vol%H₂ and 10vol%CO-90vol%H₂ gas mixtures at 773 K, 873 K and 973 K. Results showed that amount of the deposited carbon in the CO–H₂ gas mixture are larger than that in the pure CO gas. The largest amount of deposited carbon was obtained in 75vol%CO-25vol%H₂ gas mixture at 873 K. According to SEM observations and weight change measurements, carbon was deposited in fiber shape on the iron surface and amount of it was increased linearly with an increase in sample’s weight change. The rate constant of carbon fiber deposition was calculated considering Rideal mechanism with focusing on elementary reaction steps. It was found that the rate constant of the hydrogen-oxygen reaction step was the largest indicating a significant effect of hydrogen on promoting carbon deposition 773 K and 873 K. This would be due to the removing oxygen from CO by hydrogen on the iron catalyst.

For the decrease of CO₂ emission from ironmaking field, it is important to clarify the behaviors of hydrogen in blast furnace (BF). However, when hydrogen content increased in BF, many reactions related to hydrogen occurred, and many complicated relationships among the reactions are generated. Especially, the behavior of water gas shift reaction (WGSR) is not understood correctly and the effects on the gasification reaction and the reduction reaction are not known at all.

In the present study, the interest was focused on the relationship between WGSR and coke gasification reaction. The WGSR was examined experimentally and kinetic analysis was performed with and without gasification reaction. The quantification of reaction rates was carried out by gas analysis method. Several kind of crucibles were developed for determining the respective reaction rates occurring in different position.

The rate equation of invers WGSR was decided aswhere the rate constant in the alumina crucible was obtained as

The single WGSR in alumina crucible is in an equilibrium state over 1573 K. Calculation of gasification reaction (K_B, Boudouard reaction) in Zone 1 and Zone 1+2+3 were in excellent agreement with the observation under CO–CO₂ system (without Hydrogen). When H₂ was added to the reaction gases, Water gas reaction I (K_W1) and II (K_W2) in addition to K_B were calculated separately and the total gasification reaction RCS_cal (=K_B+K_W1+K_W2) was in good agreement with the observation. The relationship between the separated gasification reactions (K_B, K_W1 and K_W2) and WGSR was discussed.

Scrap melting process is one of biggest energy required process in the ironmaking process with EAF. Carbon based scrap melting process has a potential problem about CO₂ emission. An aim of this study is finding an optimal surface texture of carbon source for scarp melting with reaction acceleration. Combinations between pure iron cylindrical block and several kinds of carbonaceous materials were evaluated with isothermal condition at 1673 K and keeping contact each other with loading condition. In order to avoid effect from object lower temperature range, rapid heating and quenching condition was applied to reach to 1673 K. As different surface texture carbonaceous material’s samples, coke, charcoal from eucalyptus and graphite were prepared. The coke needed obvious longer time to melt iron sample than other carbonaceous materials. It is indicated that coke ash has an obvious effect to prevent carbon transportation at reaction interface. Although charcoal has a better carbon structure for carburization reaction than graphite, the charcoal showed almost similar time for the melting as graphite. An effective contact area on interface of iron and carbon samples was estimated from surface observation by laser microscope and SEM-EDS. The effective area was decreased by existing of ash, porosity, and roughness. Decreasing of the effective contact area had obvious effect on carburization reaction as melting start temperature rising.

Cold agglomerated iron ore mini-pellets (diameter 3–8 mm) with high mechanical strength were prepared. The use of carbon-based nanomaterials (carbon nanotubes and graphite nanoplatelets) as additives to the binder (liquid sodium silicate) promoted the increase of the mechanical strength of the agglomerate to about 285%. The dispersion of the nanomaterials into the binder combined with the resting time of the dispersed material were considered key points on the formation of agglomerates with high mechanical strength. The results have shown that the solely use of ultrasonic processor is inefficient to disperse the nanomaterials into the binder. However, using a resting period of approximately fifteen days, the dispersion of the nanomaterials has improved considerably. Subsequently, the increase in the mechanical strength of the agglomerate (mini-pellet) was related to the dispersion capacity of the nanomaterials in the sodium silicate.

Molded coal charging process into coke oven has been used to improve coal charging density. Molded coal charging process can improve coke strength even if the rank of blended coal is low. However, the molded coal is quite expensive because the cost of coal tar binder is high. Thus, we developed a new process that could reduce the amount of tar binder by utilizing used plastics. In this new process, used plastics were charged into heavy tar and dissolved at 200°C. The resulting binder with plastics could improve the strength of the molded coal, thus, coke was prepared experimentally using molded coal with the new binder.

The drum strength of the molded coal with plastics binder was better than that of coke using conventional molded coke with heavy tar binder.

Used plastics for the binder could reduce CO₂ emissions from coke ovens. This new process is one of the suitable ways of recycling used plastics in steel works.

Carbothermic reduction of FeS in the presence of CaO was experimentally studied by employing a multi-mode microwave generator at 1050 W and 2.45 GHz as an external heat source to mitigate CO₂ and SO₂ emissions. According to XRD analysis, an ion exchange reaction between FeS and CaO was initiated at temperatures lower than 645°C and progressed by a further heating to 850°C without any evidence for the onset of a reduction reaction. Detection of Fe phase in the XRD pattern of sample heated to 920°C and existence of CO/CO₂ in the off-gas during microwave treatment demonstrated that the reduction reaction initiates at ca. 850°C. It was found that the onset of reduction reaction promotes the ion exchange reaction by FeO consumption via reduction to Fe. Moreover, optical microscope and SEM-EDX observations showed that carbon can be absorbed by metallic iron to make molten iron particles at 1290°C.

Plastic waste is recycled in a coke oven and a blast furnace. An alternative to these existing methods has been studied by infiltrating plastic into a lump ore with a high content of combined water. A plastic mixture containing plastic materials is used in this study instead of plastic waste. Pyrolysate recovered from a thermally decomposed gas of the plastic mixture is used for plastic infiltration. The lump ore is dehydrated at an elevated temperature, immersed in a plastic fluid of the pyrolysate, and cured for drying. Dehydration generates pores inside the ore and the plastic fluid infiltrates the ore through the pores by immersion. The plastic-infiltrated ore cured at 450°C and above contains carbon and hydrogen but generates no tar condensation from an outlet gas through a reduction test. This ore causes no problematic tar condensation at the upper shaft and exhaust gas treatment facilities of the blast furnace. The lump ore with a high content of combined water has a tendency toward reduction disintegration at a blast furnace shaft but the plastic-infiltrated ore has less reduction disintegration. The degree of reduction at the softening–melting temperature of the lump ore is lower than that of a sinter. However, the degree of reduction at the softening–melting temperature of the plastic-infiltrated ore becomes equivalent to or higher than that of a sinter.

A prediction of the nucleation lag time of iron and steelmaking melts solely from elemental composition and temperature was produced via deep neural networks trained on data available in the literature. To the best of our knowledge, this constitutes the first published instance of prediction of nucleation lag time that does not require composition specific empirical data. Control of the nucleation process is critical for the production of ground granulated blast furnace slag, control of slag properties for heat recovery or utilization, and the optimization of slag for CO₂ mineralization. The deep neural network achieved an average absolute scaled error (AASE) over a testing set of 947 points covering 7 orders of magnitude of 39.9%. Performance was further improved by bootstrapping with a prediction of liquidus temperature from a separate deep neural network (AASE = 33.4%). Bootstrapping using DNN-generated viscosity data did not increase prediction accuracy. The negligible calculation load of the trained deep neural networks allows for rapid design, analysis, and optimization of novel slag compositions and treatment methods. This ability was demonstrated by calculating the necessary continuous cooling rate to generate amorphous slag across all CaO–Al₂O₃–SiO₂ and CaO–FeO–SiO₂ compositions and the potential to use additives to alter said cooling rate.

Fundamental experiments were conducted with the aim of crude separation of the phosphorus contained in high-P iron ore prior to the ironmaking process. By reducing high-P iron ore with lime and graphite at an appropriate blending ratio and temperature, a reduction product was obtained consisting of a P-concentrated phase, metallic Fe with low P, and an Fe oxide-containing phase. The reduction product was pulverized by electrical pulse disintegration, and a magnetic separation experiment was performed for each particle group. As a result, 57.5% of the P contained in the reduction product was removed by removing particles of 250 µm or less. Samples simulating the constituent phases of the reduction products were synthesized and subjected to magnetization measurement. It was assumed that the Fe oxide-containing phase was paramagnetic and the P-concentrated phase was diamagnetic. We calculated the magnetic and drag forces acting on the paramagnetic particles in wet magnetic separation. When the magnetic field gradient was low, the magnetic forces acting on the fine particles were low, and attraction was difficult due to the drag force of water.

The ability of calcium to absorb copper and tin is investigated in order to know the possibility to remove such tramp elements in iron by calcium. In this work, molten iron is equilibrated with Ca–Pb alloy at 1823 K, and the distribution ratio of Cu and Sn between iron and Ca–Pb alloy is directly measured at 1823 K. The mass distribution ratio of M (M: Cu or Sn) between Fe and Ca–Pb alloy, L_M (mass), is defined by L_M (mass) = {mass%M}/[mass%M], where {mass%M} and [mass%M] denote the M contents of Ca–Pb alloy and of Fe, respectively. The mass distribution ratio of Cu between iron and Ca–Pb alloy is increased with an increase of calcium activity. The maximum value is 17 in the measured range of calcium activity in this work. The mass distribution ratio of Sn between iron and Ca–Pb alloy is increased with an increase of calcium activity. The maximum value is 440 in the measured range of calcium activity in this work. Calcium is considered to be effective to remove tin in iron, in particular. If pure calcium is equilibrated with iron directly at 1823 K, the higher distribution ratios of 3400 for Pb and 200 for Cu are expected.

Vanadium extracting BOF suffers serious corrosion from slag. Maintenance on MgO–C refractory based on slag splashing has not been applied because of high oxidizability, low CaO content and dispersed distribution crystalline phase of slag. The present study proposed MgO addition and iron oxides reduction for component modification. Crystallization behaviors were expectantly optimized on the premise of reducing corrosion and ensuring reasonable melting temperature. The results showed [FeO4]-tetrahedral increased from 0 to 19.1% in the slag structure with the increase of MgO content, and MgO played a role in motivating FeO change into Fe₂O₃. Pleonaste (MgO.Fe₂O₃) and solid solution (MgO–FeOss) with high melting temperature generated and FeO.V₂O₃ precipitation weakened. The melting temperature increased with the increase of MgO content and decreased with the decrease of TFe content. MgO addition reduced the polymerization degree of slag and TFe decrease reduced the precipitation of crystalline phases, which led to decreasing of crystallization activation energy. Vanadium slag with MgO=12 wt% and TFe=16% satisfied the demands on melting temperature and crystallization tendency for slag splashing. Microstructure changed from dispersed distribution to blocky crystals combined with banded solid solution which greatly promoted the corrosion resistance of slag splashing layer.

The reaction of sodium ferrite (NaFeO₂) with carbon dioxide shows great promise for use in new high temperature thermochemical energy storage (TcES) systems. Therefore, the chemical reaction between NaFeO₂ and CO₂ was investigated via thermogravimetric experiments. Analysis of x-ray diffraction patterns confirmed that a mixture of Na₂CO₃ and Fe₂O₃ was completely converted to NaFeO₂ after heating at 900°C. Under a CO₂ pressure of 100 kPa, decarbonation and carbonation of the sample proceeded at temperatures over 850°C and under 750°C, respectively. The starting temperatures of decarbonation and carbonation decreased with decreasing CO₂ pressure. A cyclic experiment was conducted using the pressure swing absorption method at temperatures of 700–900°C. The change in reacted mole fraction kept increasing gradually after the second cycle, and it reached 0.835 during the 15th cycle. According to surface observations, a porous structure formed after the 15th cycle. This improved CO₂ diffusivity through the sample and it appears to be the cause of the enhanced reactivity observed during the cyclic experiment with increasing cycle number. The volumetric and the gravimetric thermal energy densities of NaFeO₂ were estimated as 760 kJ L⁻¹ and 450 kJ kg⁻¹, respectively. These results indicate that NaFeO₂ has potential to be used as a TcES material at temperatures around 700–900°C for utilization of surplus heat in iron-making and other high-temperature processes.

Thermochemical energy storage (TcES) system using lithium orthosilicate/carbon dioxide (Li₄SiO₄/CO₂) reaction was developed for recovery and utilization of high temperature thermal energy generated from high temperature industrial process. Li₄SiO₄/CO₂ TcES packed bed reactor (LPR) and zeolite packed bed reactor (ZPR) were developed as thermal energy storage and CO₂ reservoir. Both reactors, LPR and ZPR, were connected by flexible tube and thermal driving operation of TcES system was demonstrated. For lithium orthosilicate packed bed reactor, tablet forms of Li₄SiO₄ named K-tablet was developed and used in this study.

Li₄SiO₄ carbonation (thermal energy output process) and lithium carbonate (Li₂CO₃) decarbonation (thermal energy storage process) were conducted sequentially with specific condition. All experimental results showed similar tendency; a middle temperature in the Li₄SiO₄ packed bed reactor rapidly increased and decreased at the initial time of carbonation and decarbonation respectively. From kinetic analysis, it was confirmed that the developed K-tablet reacted around 80% and a thermal energy output density of LPR was estimated 331–395 kJ/L-packed bed, 759–904 kJ/L-material. The thermal driving demonstration of Li₄SiO₄/CO₂/Zeolite TcES system shows high possibility to utilize surplus heats in low-carbon ironmaking system efficiently.

Through the support for reconstruction from the disaster of the great earthquake in the eastern Japan in 2011, The Iron Technology and History Forum” of the Iron and Steel Institute of Japan received a request to study the molten iron and steel production in low height furnace with iron-sand smelting, and started up “IMPRESSIVE”, the research workshop of the Iron Manufacturing Process Engineering and Scientific Study in Vetus Iron in 2013. The research workshop IMPRESSIVE has studied the process engineering of ironmaking with iron sand under dynamic states in a low height furnace. As results, in the iron-sand refining using a low-height furnace, the subjects of unit operations in the dynamic state are considered to be three couplings of reactivity of wood charcoal, basicity of iron sand and furnace structure with tuyere. Combining these unit operations, the metal discharge shows a variety including flow out like a serpent and its composition being converted into higher purity molten pig iron.