Synopsis :In recent years, the reduction of CO 2 emissions and the stable supply of raw materials are two major issues for the steel industry. Low reducing agent operation in the blast furnace is required to reduce CO 2 emissions in ironmaking. As a mean of realizing low reducing agent operation with using low-grade raw materials, ferro coke characterized by high coke reactivity is considered to be useful. Theoretical and experimental studies were carried out to verify the effect of the ferro coke usage on reaction behavior in blast furnace. Investigation of CO 2 reactivity at the simulated blast furnace condition revealed that the initial temperature of CO 2 reaction of ferro coke is lower than the temperature of conventional coke. At the temperature of over 1100°C, the deterioration of ferro coke strength after reaction was depressed because the reaction occurred preferentially at the surface of the ferro coke.The coke and ferro coke strength after reaction was estimated based on the experimental results with the two-dimensional mathematical model of the blast furnace. The average coke strength of ferro coke and conventional coke with charging of ferro coke (100 kg/t) was little less than the coke strength without ferro coke charging. It is predicted that the carbon saving with charging of ferro coke (100 kg/t) is about 6% in comparison to without ferro coke charging.

No abstract

and Pittston-MV coal samples were heated to temperatures between 200 and 550 °C at a rate of 3 °C/min in an autoclave under nitrogen and then cooled rapidly to room temperature. Heat-treated coals were extracted with a carbon disulfide-N-methyl-2-pyrrolidinone mixed solvent at room temperature; the extracts were fractionated further with pyridine and chloroform. Raw coals contained a significant fraction of solvent-soluble constituents (20-45 wt %). For high-caking coals, the amount of heavy solventsoluble constituent, i.e., the pyridine-insoluble and the mixed solvent-soluble fraction, greatly increased at the fluidity stage. There is a good linear relation between the maximum extraction yield and the Gieseler fluidity of the coals. This result suggests that heavy constituents are an important factor for the occurrence of fluidity in coals.

A novel measurement method for coal thermoplasticity was developed, where permeation distance of thermally plastic coal into glass beads layer placed on the coal sample was measured. The characteristic of this method is simulating the condition in a coke oven, especially void structure around the plastic layer by using glass beads and coking pressure by applying a load. In a standard condition, the coal sample is heated to 550°C, and coal sample softens and permeates into the glass beads layer, then the permeation distance is measured after cooling the sample. The maximum permeation distance measured is roughly correlated with Gieseler fluidity, however large deviation is observed especially for high fluidity coals. Moreover, the deterioration of coke strength is observed in case that long permeation distance coal is used in a coal blend for cokemaking. This new measurement method clearly shows the difference in coking property of high fluidity coal as well as solving the problems in Gieseler plastometer method for evaluating high fluidity coals. By employing the permeation distance method, contribution to the production of high strength coke and effective usage of caking coal will be expected.

No abstract