GB312089A - Evaporating method and means therefor - Google Patents

Abstract

312,089. Industrikemiska Aktiebolaget, (Assignees of Oman, E.). May 18, 1928, [Convention date]. Heating arrangements.-Liquids are evaporated and solids are dried in a multiple-effect apparatus in which heat is supplied by a gasvapour mixture not in contact with the liquid or solid, and the vaporized liquid is removed by a current of non-condensable gas. In a quadruple-effect apparatus (Fig. 3) solution is sprayed in at a' - - a<4>, so as to flow in a thin film down heating surfaces; the temperature of the entering solution is lowest at a<1> and highest at a<4>. Air circulated by a pump A<1> flows through the first evaporating chamber c<1> and takes up vapour from the liquid film; it then passes by a pipe d' to the evaporating chamber c<2> of the second effect, and the temperature being higher, the air absorbs more vapour. The process is continued in the third and fourth effects, and the air-vapour mixture leaves by a pipe d<4> leading to a heater C' where it is completely saturated with vapour and raised to a temperature above that of the solution entering at a<4>. The hot air-vapour mixture passing by a pipe g<4> to the heating chamber e<4> gives up a portion of its heat to the evaporating film, and then passes at successively lower temperatures through the heating chambers e<3>, e<2>, e<1>, in each of which it gives up a further portion of its heat. Condensate is removed by pipes f<1> - - f<4>. The air issuing from the chamber e<1>, is finally freed from vapour in a condenser D, and is re-circulated through a pipe H to the evaporating chambers c<1> - - c<4>. Concentrated solution is drawn off by pipes b<1> - - b<4>, and may be returned, with or without preheating, to the corresponding inlets a<1>, a<4>, or to different inlets, as from the outlet b<2> to the inlet a<1>. The pressure in the whole apparatus is kept substantially atmospheric by liquid seals as at E, F, G. Intimate contact between the liquid film and the air current may be obtained by baffles and obstructions as in Figs. 8<a>, 8<b>, 9<a>, 9<b>, 9<c> Several heating or evaporating chambers may be worked in parallel. The method may be applied to the rotating drum type of evaporator.