GB960891A - Improvements in and relating to coal tar products - Google Patents

Abstract

<PICT:0960891/C4-C5/1> The thermal treatment of coal tar binders to increase the material insoluble in benzene or toluene comprises heating the coal tar binder directly with a hot substantially inert gas, condensing the volatile material entrained with the gas, and returning said material to the binder. The inert gas is one which does not react with heated coal tar to any great extent, air being precluded, suitable gases include N2, CO2, and flue gas. The gas may be the combustion product of a gas burned with the theoretical amount of air, before its introduction into the binder or burnt below the surface of the molten pitch. The gas is preferably preheated to a temperature above 1000 DEG C. As shown, coal gas and air are burned in the combustion chamber C and the hot gases are distributed by E, a perforated pipe or a porous ceramic disc, through the coal tar binder in the vessel D. The coal tar pitch preferably has a residence time of 5 minutes. A soft pitch produced in an adjacent continuous tar still enters the vessel D by line F at 300 DEG to 350 DEG C., and the flow of coal gas and air into the combustion chamber is regulated to maintain a temperature of 370 DEG to 375 DEG C. in vessel D. The treated tar is continuously removed through run off H via a liquid seal through collar I where the temperature is reduced to 200 DEG to 250 DEG C. The off-gases pass through condenser L and cyclone M and the condensed volatiles collected in N are blended back with the cooled treated pitch in the amount required. The condensed volatiles may be returned to the thermal treatment vessel or may be blended with the treated product. A coal tar heavy oil may also be blended with the product.