Patent GB-715384-A (GB)
Title: Process of and apparatus for condensing vaporised phthalic anhydride
Inventor: BARTON EDMUND
IPC: B01D5/00
Filed: 1951-04-23
Abstract: Phthalic anhydride is separated from the hot gases produced in the catalytic oxidation of naphthalene by passing the gases through the tubes of a tubular condenser, the rate of flow of gases being such that the gas stream is in turbulent flow therein, and the rate of cooling being such that the hot gases are cooled below 130 DEG  C. and the effluent gases from the condenser have a temperature of not less than 50 DEG  C., whereby the phthalic anhydride condenses to the solid state in the tubes but water vapours are not condensed therein. When the flow of gases in the tubes becomes impeded by the solidified cake of phthalic anhydride therein, the hot gas stream is diverted to another condenser, and a heating medium is passed through the shell of the first condenser so that the phthalic anhydride melts and may be readily collected in a receiver.  The gases from the oxidation-converter are preferably precooled to a temperature of about 140 DEG  to 160 DEG  C. before being introduced into the condenser.ALSO:<PICT:0715384/III/1> Phthalic anhydride is separated from the hot gases produced in the catalytic oxidation of naphthalene by passing the gases through the tubes of a tubular condenser, the rate of flow of the gases being such that the gas stream is in turbulent flow therein, and the rate of cooling being such that the hot gases are cooled below 130 DEG C. and the effluent gases from the condenser have a temperature of not less than 50 DEG C., whereby the phthalic anhydride condenses to the solid state in the tubes but water vapours are not condensed therein.  When the flow of gases in the tubes becomes impeded by the solidified cake of phthalic anhydride therein, the hot gas stream is diverted to another condenser and a heating medium is passed through the shell of the first condenser so that the phthalic anhydride melts and may be readily collected in a receiver.  The gases from the oxidation-converter are preferably precooled to a temperature of about 140 DEG  to 160 DEG  C. before being introduced into the condenser.  For a gas flow of 300 to 650 pounds per hour, the tubes of the condenser may have an inside diameter of 2 inches and a length of 60 to 80 feet.  In the Fig., effluent gases from a converter (not shown) are precooled and then introduced through pipe a into the condensing system, which comprises two condensers 1, 2 connected to pipe a via valves b.  It is assumed that the upper valve b is open, and the lower one is closed.  The gas stream then enters the tubes d of condenser 2, the shell e of which is supplied with water through t in order to maintain it at 30 DEG  to 40 DEG  C.  The cooling water overflows from pipe s.  Most of the phthalic anhydride is condensed in the form of a cake on the insides of the tubes; but some is condensed as snow in the moving gas, and is carried along in the gas leaving the condenser through pipe h.  This gas passes by inlet j into chamber k where it filters through a wire gauze cylinder m mounted on the inner rim of an annular partition l. Finally the exit gas passes to a chimney via pipe r.  Phthalic annydride snow, filtered off by the gauze, is removed from the gauze by rotating scrapers q, and drops into the base of chamber k.  When, after about 30 minutes, the cake of solid phthalic anhydride formed in the tubes d of condenser 2 impedes the flow of gas, the latter is diverted to condenser 1 by adjustment of valves b.  The water in condenser 2 is then withdrawn, and steam at 165 DEG  C. is admitted through pipe s (with outflow of condensed steam through pipe t) in order to melt the phthalic anhydride, which flows out of the condenser through pipe g. Condenser 1 is connected to a filtering chamber (not shown) similar to that connected to condenser 2.  The alternatewise operation of the two condensers may be rendered automatic.