The steel industry will move toward more value additive products in the future. In order to support the value additive steel products, iron sources have to be secured with stable operation of furnaces and control of furnace have to be evolved. Environment consciousness including CO2 reduction leads more toward lower reducing agents ratio operation. It is common technical issue on both the more value additive products the environment consciousness to control the sulfur in the hot metal, slag and gas phase.In the present study, the amount of sulfur gasification was measured by combustion experiments with the attention on the simultaneous gasification of sulfur with carbon. By description of sulfurization from gas to burden materials based on the temperature distribution measured in actual furnace, the amount of sulfur transferred to gas was evaluated.
A swirl motion induced by gas injection through a bottom nozzle has high mixing ability and useful for the mixing of a molten steel bath in the refining processes. As one of the fundamental characteristics of the swirl motion, the period is mentioned in this study. A semi-empirical equation is proposed for the period of swirl motion by referring to the rotary sloshing appearing in a cylindrical vessel oscillated in the vertical or the horizontal direction.
Efficient agitation of molten steel and slag is requested in the steelmaking industry. The conventional agitation methods are mainly classified into Ar gas injection and electromagnetic stirring. These methods are very expensive and use much energy, and accordingly, we have proposed an alternative, cheap and effective mixing method using a swirl motion. This method does not need any driving devices in the reactor. In this study, low-density liquids and low-density particles are used as models for slag. The effects of the upper slag layer on the occurrence region and the amplitude of a swirl motion of a molten steel jet are investigated.
Dispersion behavior of inclusions is influenced by molten steel flow in a continuous casting mold. The analysis of molten steel flow in the mold has been performed by using techniques such as three-dimensional numerical simulation and cold model experiments. However, these techniques cannot reveal the cleanliness level of inclusions in the mold directly. Therefore we focus in this study on some parameters for characterizing the flow of molten steel in the mold and the cleanliness level of the steel. The molten steel flow in the mold can be inferred from the solidification structure and the cleanliness can be evaluated from the observation of the surface of the slab containing inclusions. An index is introduced on the basis of the mold width and casting speed for an understanding of the relationship between the molten steel flow in the mold and the properties of inclusions in the steel products. The main findings can be summarized as follows: (1) The inclusion distribution under the slab surface is affected by the fluctuation of molten steel at the meniscus. The fluctuation can be estimated from the oscillation mark pitch. (2) The velocity of molten steel flow at a solidification interface can be estimated from the inclination angle of dendrite structure. (3) The distribution of inclusions accumulated in the continuous casting curved zone can be evaluated by the above-mentioned index.
Automobile Shredder Residue (ASR) and Refuse derived fuels (not carbonized and carbonized: YRDF and RDF) as carbonaceous wastes were reacted isothermally with sub-supercritical water (600-695°C, 200 atm) together with a CO2 fixation reagent Ca(OH)2 inside a closed metallic tube reactor (7cm3). Product gas mainly consisted of hydrogen gas and a little methane gas except YRDF. As a whole, gas generated more in order ASR, YRDF, and RDF. Addition of catalysis NaOH or KOH made product gas increase more. KOH was more effective to product gas than NaOH. X-ray diffraction followed that Ca(OH)2 and CaCO3 existed mainly in residues after reaction tests with a CO2 fixation reagent Ca(OH)2 or CaO. Therefore, it was supposed that an overall chemical reaction took place as shown below. BOF steelmaking slag for CO2 fixation provided maximum gas generation 1.42 times as much as molar carbon in a RDF sample with KOH. C + H2O + Ca(OH)2 = CaCO3 + 2H2 Two kinds of wastes from integrated steel mills (sludge from mill scale and activated sludge) were each reacted with supercritical water (600-650°C, 200 atm). Both sludges were effective to generate hydrogenous gas. It was found that harmful cyan in the latter sludge mostly decomposed after reaction. Also, the crushing strength after curing the steelmaking slag bearing residue briquette was not as high as that from Portland cement.
A direct combustion method of automobile shredder residue at high temperature is considered to be an effective process, because the volume of residue can be reduced and many valuable metals can be recovered. However, the fly ash containing large amounts of heavy metals and fluorine are generated inevitably by this process. Therefore, the treatment for detoxification of this fly ash is significantly important. It is found in the present research that cement is effective on the immobilization of harmful elements in the fly ash. The hydrothermal treatment of the solidified mixture of fly ash, cement and water is also superior in the immobilization effect.
Experiments to inhibit the formation of hazardous substances such as benzenes and dioxins in a combustion furnace were carried out by the centrifugation and recombustion method of fly unburned matters (fly carbonaceous matters (C*)) in an exhaust gas at high temperatures. Total dioxin’s and Cl5 benzene’s concentrations in the exhaust gas have a good correlation with the number of the fly C* remaining in the exhaust gas, and their concentrations increase as the number of the fly C* rises. Total dioxin’s and Cl5 benzene’s concentrations after the centrifugation and recombustion with the present cyclone reduce to 10% and 20% of their initial concentrations in the exhaust gas from combustion furnace, respectively, in proportion to the decrease in the fly C*. On the other hand, in the case of low dioxin’s and benzene’s concentrations in the exhaust gas under the complete combustion conditions their reduction ratios become worse. The reason why their reduction ratios decrease is considered a decrease in the partial separation efficiency for fine particles in the present cyclone, which is attributed to the increase in the relative ratio of the fly C* with the sizes smaller than 2μm under the complete combustion conditions. The predictive equation of the partial separation efficiency at high temperatures obtained for the present cyclone of a small size indicates that the reduction ratios of dioxins and benzenes are much improved by using the cyclone of larger sizes and increasing in the inlet velocity of the exhaust gas to the cyclone. The present centrifugation and recombustion method of the exhaust gas at high temperatures is expected to be useful for the actual incineration plants.
Dissimilar smart joints are useful. In this research, welded quality of dissimilar aluminum alloys of 3 mm thickness by various welding processes and process parameters have been investigated by hardness and tensile tests, and observation of imperfection and microstructure. Base metals used in this study are A1050-H24, A2017-T3, A5083-O, A6061-T6 and A7075-T651. Welding processes used are YAG laser beam, electron beam, metal inert gas arc, tungsten inert gas arc and friction stir welding. The properties of weld zones are affected by welding processes, welding parameters and combination of base metals. Properties of high strength aluminum alloy joints are improved by friction stir welding.