Electric dehydration of coal tar – a by-product of coke production for blast furnace smelting

Abstract

The aim of the study was to adapt the technology of electric dehydration of oil for use with coal tar (a by-product of coke production for blast furnace smelting) in order to remove ash (tar decanter sludge) and water. The research focuses on coal tar generated in coke ovens, which forms a colloidal system with water and ash. The method of electric dehydration was employed in the study, which is currently used to remove water from the oil–water colloidal system. The construction of the 2-EG-160-2 electric dehydrator was examined, along with the specifics of introducing coal tar into it in comparison to oil. It was demonstrated that, under the proposed operational conditions for the electric dehydrator, the coal tar and tar decanter sludge would settle at the bottom of the unit due to their higher density than that of water (the density of coal tar is approximately 1200 kg/m3 and higher). A scheme for integrating the electric dehydrator into the de-ashing process at a coke-chemical plant was proposed. The process of separating coal tar in the electric dehydrator was calculated. The results demonstrated that the efficiency of the equipment in the dehydration of coal tar, in comparison to oil, is considerably lower due to its higher density and viscosity (approximately 40 times higher at 80°C). Consequently, the performance of the electric dehydrator for coal tar would be approximately 40,000 tons, as opposed to approximately 1 million tons for oil. Nevertheless, the aforementioned performance per electric dehydrator is sufficient to meet the dehydration needs of AO “Ural Steel” for coal tar. Therefore, it is recommended that the electric dehydrator be integrated into the general coal tar dehydration scheme in order to ensure that the required quality standards for the tar are met, allowing it to be used and sold as a target product.