FIELD: dehydration of magnesium chloride raw material. SUBSTANCE: apparatus includes housing with partitions dividing it into chambers. Partitions are provided with drain holes for flow of material from chamber to chamber. Chambers are provided with gas distributing grids which divide each chamber into above-grid portion and lined under-grid portion. First chamber is provided with loading device and last chamber is provided with overflow lip. Upper above-grid portion of each chamber is provided with hole for suction of dust-laden waste gases; under-grid portion is connected with remote furnace by means of lined gas duct. Remote furnace is provided with combustion chamber and mixing chamber. Air is fed to fuel burning jet and chlorine is fed to furnaces of some chambers. Connecting gas duct and side walls of furnace are provided with double casings to which cooling air is fed wherefrom it flows to combustion chamber and/or mixing chamber of furnace through openings in cavity between casings, thus cooling the flue gases. Chlorine supply branch pipes are connected in some chambers of apparatus to branch pipes feeding air to combustion chambers of furnaces or directly to burning devices. At least part of chambers of apparatus including chambers whose furnaces are supplied with chlorine have hollow casing of their under-grid portion which is fitted with branch pipes for feeding cooling air and passages for discharge of heated air from hollow casing into under-grid portion of chamber of apparatus and/or to connecting gas duct located between furnace and under-grid portion of chamber of apparatus. Furnace is also provided with hollow casing at its end which is brought in communication with hollow casing of its side walls. Hydrogen-containing (vapor) product supply branch pipes may be connected to branch pipes feeding air for burning in those furnaces where chlorine supply branch pipes are connected to primary air branch pipes or directly to burning devices. These branch pipes may be directly connected to burning devices. When furnaces work on liquid fuel (at vapor atomization), vapor pipe union of burning device may be connected with chlorine and hydrogen-containing product supply branch pipes. Gas-distributing grid and walls separating under-grid portions of chambers whose furnaces are supplied with chlorine are made from steel 1X18H9T or from any other steel resistant to hydrogen chloride. EFFECT: enhanced efficiency. 5 cl, 2 dwg
