Patent ID: 6368389
Filing Date: 2002-04-09
Classification: B01J,C07C

Abstract:
A method of recovering phthalic acid anhydride from a gas stream containing phthalic acid anhydride as a vapor, comprising the steps of:(a) continuously passing said gas stream containing phthalic acid anhydride as a vapor upwardly through a vertical tube having a discharge orifice at an upper end of said vertical tube; (b) fluidizing a bed of granules containing phthalic acid anhydride around said tube by passing a fluidizing gas upwardly through said bed and inducing granules from said bed to migrate above said discharge orifice and to mix with the gas stream containing phthalic acid anhydride an a vapor an said gas stream emerges from said orifice; (c) cooling said gas stream at least in part by expanding said gas stream into a space above said bed and said orifice wherein said gas stream mixes continuously with said granules, whereby phthalic acid anhydride deposits on said granules and said granules fall back from said space into said bed; (d) indirectly cooling said bed to a temperature in a range of 20Â° C. to 90Â° C. by passing a cooling fluid through cooling elements in contact therewith; (e) maintaining a suspension density of the granules in said bed of 300 to 700 kg/m3 and an interior of said tube free from said granules; (f) continuously withdrawing gas from said space above said bed and said orifice; and (g) withdrawing granules containing phthalic acid anhydride from said bed.