It is important to maintain a certain amount of melt during sintering of iron ores to improve product yield and strength of sinter product. Spreading phenomena of the initial melt within adhering layer in pseudo-particles are essential to achieve efficient agglomeration. Penetration tests have been conducted to demonstrate the spreading behavior of the initial melt. Paired samples consisting of ore tablet and initial melt tablet were heated and penetration length was measured. Penetration behavior of melt during sintering was discussed on a base of capillarity. Determining factors of penetration were morphology of the ore surface before and after dehydration and chemical composition of ores. Product yield and the strength of sinter were reflected by the penetration length of blended ores in a sintering plant.

As an initial step of collaborative studies carried out by the SDD project, some series of sinter-pot tests were carried out to examine formation/decomposition behavior of dioxins in the sintering bed. Test method was first assessed from a view of accurate determination of dioxins discharged in the outlet gas. It was confirmed that the pot test is an effective way to measure dioxins emissions from the sintering process.Then, the effect of additives, i.e., PVC, NaCl, oil, mill scale, anthracite and dusts form steel works, was evaluated by the pot tests. They were chosen in terms of organic/inorganic chlorine sources, volatile matters convertible to "soot" during combustion and so forth. Based on the results, possibility of de novo synthesis of dioxins from the electrostatic precipitator (EP) dust and soot formed/trapped in the sintering bed was discussed. Further, accumulation behavior of dioxins in the raw materials due to the recycle use of dusts formed in the waste gas treatment process was examined using raw materials initially containing the dust from an electrostatic precipitator of a sintering process and 13 C-labeled reagents of O8CDF, 2378-T4CDF and 246-CP.

Understanding of the formation mechanism of dioxins in the sintering bed is of importance in developing countermeasures to reduce the emission of dioxins from sintering plants. This research has clarified the behavior and the possible mechanism of dioxin formation and the relation to Cl and Cu components in the sintering bed by conducting a series of quenching tests utilizing sintering pots.The progress of flame front was quenched by terminating the air supply, then introducing N 2 gas in the reverse direction when the sintering process progressed halfway through the test pots, specifically to the position of the thermocouples. The primary specimens were obtained from the raw mixture zone situated beneath the combustion interface for chemical analysis.Concentrations of dioxins, Cl and Cu were found at the depth of 10-20 mm beneath the combustion interface in raw mixture zone. This was considered to be the site of dioxin synthesis. Slight increase of dioxins in the wet zone was related to dioxin vaporizing from the site of the synthesis, then to be trapped in this zone. Significant amounts of dioxins escaping into the outlet gas at and after burn through point could be explained by both the releasing of trapped dioxins and the acceleration of the synthesizing process attributable to the increased concentration of Cl and Cu.KEY WORDS: agglomeration; copper; chlorine; dioxins; iron ore sintering; sintering bed.series of experiment, which was conducted to examine the influence of the use of Ore C containing a higher Cu content. The type and quantity of additives were varied according to the purpose of experiment. As the base condition of the experiment, 200 mg/kg NaCl was added to a raw mixture, so as to accelerate the dioxin formation during sintering to a detective extent. The chemical composition of the sintered product aimed for 5.1 mass% as SiO 2 , 9.5 mass% as CaO, and 1.9 mass% as Al 2 O 3 .The sintering pot was 300 mm in diameter and 600 mm in height. To quench the sintering at a specified position, a thermocouple was inserted into the bed at 400 mm from the top of the bed. Upward N 2 gas flow was applied to stop the combustion of coke and cool the bed when quenching (Fig. 1). Procedure of Sintering and QuenchingThe raw mixture was mixed for 60 s and granulated with adding water for 180 s in a drum-type mixer of 1 m in diameter. The moisture content was set at 6.5 mass%. The granulated mixture was charged into a pot to form a bed with 560 mm in thickness. The average mass of charges weighed 66 kg. After ignition at 1 100°C for 90 s, the sintering process was conducted under a constant suction pressure of 12 kPa.The quench technique applied in the present study was basically follows after Soma et al. 14) Quenching proceeded as follows: when the thermocouple gave the maximum bedtemperature, the main blower was stopped and simultaneously N 2 gas was introduced from the bottom of the pot. For experimental series 1 and 2, the flow rate of the N 2 gas was set at 0.3 Nm/s. It required 2 h to cool the bed. For se...

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