Toward the realization of carbon neutrality in society, many industries have started to make very elaborate efforts. On the basis of COP (Conference of Parties) -FCCC (Framework Convention on Climate Change) indication, Japan is expected to reduce CO₂ emission by 46% until 2030 which target was declared by the prime minister Kishida in COP26. To attain this target, one of most effective ways is to reduce the CO₂ emission of ironmaking and steelmaking industries which are rather responsible due to the fact of their having 14% emission of total domestic CO₂ in all the industries, transportation, civil use and so on. The secondary iron resource, namely, steel scrap should like to be increasingly utilized since the reduction process of iron ore inevitably generating CO₂ can be avoided and only melting process of recycled steel should be managed. In this process, tramp elements such as copper are problematic, because copper induces surface cracks called copper embrittlement for instance. In this article, suppression of this drawback is extensively intended by the investigation of refinement of austenite grain size by cooling process and additional element as well as fine precipitation of copper sulfide. In addition, primary iron resource, namely, virgin steel is reconsidered toward realization of zero-carbon ironmaking process by smelting reduction by CO gas, which reducing gas is recovered from CO₂ produced in iron ore reduction process by zero-carbon energy such as renewable and nuclear power. Attempt by GXI project being implemented in the laboratory of zero-carbon energy in Tokyo Insite of Technology is also briefly introduced.

Chemical looping combustion poly generation technology for Biomass/coal is able to produce H₂, CO₂ and heat simultaneously with high efficiency. The oxygen carrier based on iron is a key component and has been studied for reactivity performance by a thermogravimetric (TG) experimental apparatus. The process under development consists of three fluidized bed reactors and oxygen carrier circulation equipment. A transparent cold model (CM) was built with a scale equivalent to 300 kW_th hot model for recognizing steady state conditions for oxygen carrier circulation and fluidization. The obtained data from TG and CM reported here will be used to design and operation of hot model for the next step.

Oxygen combustion is being considered as a carbon dioxide reduction technology for industrial furnaces, partly due to the impact of soaring fuel prices. In order to achieve carbon neutrality by 2050 as set by the government, the introduction of combustion technology using hydrogen and ammonia as substitutes for fossil fuels is expected. In this report, we will introduce the basic characteristics of oxy-fuel combustion, the oxy-combustion technology that we have been working on for about 50 years, and our approach to carbon neutrality using oxy-fuel combustion technology.

Since it is difficult to generate electricity in small to medium sized MSW treatment facilities less than 100 t/day from an economic point of view. Therefore, the perspective of recovering and utilizing energy by introducing MSW carbonization technology is considered to be effective. It is important for the widespread use of MSW carbonization facilities to ensure that there is a source of carbonized fuel for use. Since the use of carbonized fuel as a substitute for coal is limited, we focused on asphalt plants and MSW treatment facilities, which are distributed nationwide, and decided to develop a burner that can replace the liquid fuel used at these facilities with carbonized fuel. In this paper, based on the good results obtained at the test facility, we moved on to the demonstration test at the asphalt plant, and confirmed that it is applicable to the emission limits of the facility as well as to the pavement durability on the road constructed with the composite material produced here. It was also estimated that producing carbonized fuel in areas where wide-area expansion is difficult and using it at MSW treatment facilities can reduce CO₂ emissions by 30% compared to a waste incineration facility alone, thus expanding the number of sites where it can be used more than 10 times.

In this study, pool flame of iso-octane on a shallow dish under various furnace temperature conditions (25 - 700 ℃) was investigated as fundamental study of fuel film combustion. Flame appearance during from ignition to combustion end under various furnace temperature conditions was observed. Further, maximum flame length just after combustion end, flame formation period from ignition to extinction and duration of open flame tip were obtained. Moreover, total masses of CO₂, CO and PM emitted during flame formation period were measured. As the result, it was found that total mass of CO₂ emitted during flame formation period decreased with furnace temperature raise, and total masses of CO and PM increased with furnace temperature raise.

Development of high-performance hydrogen combustion technology is underway to expand the use of hydrogen toward building a decarbonized society. Hydrogen is characterized by a higher combustion temperature than conventional hydrocarbon fuels such as LNG or LPG, which causes formation of a large amount of thermal NOx. Focusing on the characteristics of hydrogen, which enables stable combustion even at low air ratios, it was demonstrated that NOx formation in boiler furnaces can be significantly reduced by appropriately mixing hydrogen with combustion air. In addition, numerical simulation has been conducted to elucidate the mechanism of low NOx combustion.

Understanding cool flame ignition phenomena under high-pressure conditions is crucial in terms of developing advanced internal combustion engines. In this study, ignition characteristics of the premixed cool flame have been investigated with the aid of the Tunable Diode Laser Absorption Spectroscopy (TDLAS) technique under the mildly elevated pressure condition of 1-3 atm. Two-dimensional wall-stabilized cool flames were established by impinging a premixed gas of DME and air on a heated wall. The wall temperature was ramped up in the range of 550-750 K to ignite the cool flame. Changes in the HCHO mole fraction, which is a key species of low-temperature oxidation, were measured by using the TDLAS. The results show that the initiation and progress of the low-temperature oxidation are inhibited by the increase in pressure. The DME reaction kinetics generally reproduces the effect of pressure, but still requires further modification to properly estimate the temperature not only of the cool flame ignition but also starting the negative temperature coefficient (NTC) phenomenon.

Flame propagation toward a leaner or richer zone in a compositionally stratified mixture leads to modification of the flame speed, which is known as the back-support phenomenon. A majority of previous studies have focused on the propagation of methane/air stratified flames under standard temperature and pressure. However, stratified combustion often occurs under elevated temperature and pressure in practical applications, which may influence the characteristics of the back support. This study performs numerical simulations of laminar counterflow flames propagating in a stratified methane/air mixture under an Atmospheric Temperature and Pressure (ATP) condition and an Elevated Temperature and Pressure (ETP) condition, respectively. In particular, the influence of elevated temperature and pressure on the back-support is examined. It is found that, when scaled by the stratification Damköhler number, the back-support on the rich-to-lean stratified flame is weaker under the ETP condition than the ATP condition in the stoichiometric to lean region. The influence of the increased pressure was identified in the chain-branching reactions. It is implied that the back-support may be negligible for modeling stratified turbulent combustion in practical combustors operating under high-pressure conditions.