Vol 61, No 5 (2018)

The influence of oxidation of long-flame coal pieces (at 100–250°C for 5–40 h) on the yield and composition of the pyrolytic products, the emission dynamics of volatiles, and the properties and porous structure of the semicoke is studied.

Currently, the most promising blast-furnace technology involves pulverized-coal injection, and the most promising blast-furnace technology for coke production involves ramming the coal batch before delivery to the coke ovens, so as to ensure high packing density. In classic bed coking, the packing density of the coal batch is also of great importance. In the absence of mechanical methods (such as ramming or partial briquetting), the packing density mainly depends on the ash and moisture content and the degree of crushing of the batch. It follows from industrial tests in the coke plant at PAO ArcelorMittal Krivoy Rog and analysis of the multifactorial correlation of the strength M₂₅ and wear resistance M₁₀ with the packing density of the batch that, with decrease in packing density, the coke strength and wear resistance decline. That increases coke consumption and considerably complicates blast-furnace operation. Since improvement in coke quality entails decreasing the moisture content of the coal batch, a method has been developed for decreasing the moisture content directly in the silo, on the basis of osmosis and vacuum, that permits decrease in the coal’s moisture content to the optimal value, thereby boosting coke quality and improving blast-furnace performance. For example, it has been established that, in the blast-furnace shops at PAO ArcelorMittal Krivoy Rog, 1% decrease in M₁₀ lowers the mean coke consumption by 5.5%. With increase in M₂₅ by 1%, the mean coke consumption falls by 2.1%, on average.

Attention focuses on the structure and electrical conductivity of carbon materials produced by the carbonization (at 900°C) of coal-tar pitch with the addition of 0.03–0.3% graphite foam and oxidized graphite foam. In these quantities, the additives do not change the X-ray diffraction characteristics but considerably increase the conductivity of the product over the whole temperature range. With increase in concentration of the additives, the conductivity of the carbon material increases. At room temperature, it is 14–20 S/cm, which is at least 2–3 times the value in the absence of the additives. The influence on the conductivity is greater for the oxidized graphite foam. This may be attributed to the smaller size of the crystallites and the greater distance between the planes, resulting in greater accessible surface area of the graphite layers orienting the pitch molecules on carbonization.

Research on the natural radioactivity of coal is analyzed. The safe use of coal containing radioactive nuclides is addressed. Systematic monitoring of radioactive coal and its combustion products must be organized.