GB916882A - Method and apparatus for the continuous separation of sublimed products from hot carrier gases - Google Patents

Abstract

<PICT:0916882/III/1> <PICT:0916882/III/2> Sublimable solid substances such as maleic anhydride, phthalic anhydride and naphthalene are condensed as solids from a stream of gas containing said substances in gaseous form by passing said stream into contact successively with a plurality of heat exchange elements and alternately heating and cooling each of said elements so that whilst sublimate is condensing on some elements it is melting off other elements for removal. In Fig. 4 in addition to the elements 2 for both heating and cooling, elements 18 are provided for cooling only, their temperature being such as to result in the condensation of the substance in liquid form. Heating and cooling are provided by means of oil respectively circulated through a steam energized heater 11 and a cooler 13 by means of pumps 10 and 12. The cooling oil for the elements 18 is circulated by a pump 19 through an oil/air cooler 20. The elements 2 comprise banks of horizontal finned tubes through which the oil flows in a series/parallel manner (Figs. 1 and 2, not shown). The tubes can alternatively be connected in serpentine fashion, and where smooth, unfinned tubes are employed, they may be arranged vertically. The elements may be mounted on guide rails so as to be retractable for cleaning. Troughs 3 are provided to collect molten sublimate, these and the outlet tubes therefrom being provided with heating jackets which are supplied with oil from the heating circuit. In Fig. 5 the heating circuit is eliminated by the inclusion in the cooling circuit of heat exchangers 26 which may employ steam as the heating medium or may be heated electrically. In a further embodiment (not illustrated) heat exchangers 26 may themselves be eliminated by including electrical heating elements within the tubes making up elements 2. The cooler 22 in these modifications must be capable of removing the additional heat imparted to the cooling medium. In the above embodiments valves 8, 9 and valves 28 are individually controllable either manually or automatically on a time basis or on a temperature basis, i.e. when the cooling becomes inefficient due to deposited condensate.ALSO:Maleic anhydride and phthalic anhydride are condensed as solids from a stream of gas containing said substances, which may be derived from the catalytic oxidation of benzene or naphthalene, by passing said stream into contact successively with a plurality of heat exchange elements and alternately heating and cooling each of said elements so that whilst sublimate is condensing on some elements, it is being melted off other elements for removal. Naphthalene may be similarly recovered from a stream of gas. Suitable apparatus is described (see Group III).