| 摘要 |
<PICT:0449621/IV/1> Phthalic anhydride is recovered from gases or vapours containing it by passing the gases or vapours in a turbulent stream through a cooled tubular condenser. The process is particularly useful in recovering phthalic anhydride from the catalytic vapour-phase partial oxidation products of naphthalene or methylnaphthalene. As shown, air is passed through a pipe 3 into molten naphthalene in a vessel 1, and the mixture of air and naphthalene vapour is led into a catalytic apparatus 5 of known type; additional air may be supplied by a pipe 6. The reaction products are cooled in a cooler 8 to a temperature slightly above the dew point of phthalic anhydride and are then passed to a cooled tubular condenser 10 through which they flow as a turbulent stream. The condenser 10 is fitted with a screw conveyer 13 which scrapes the walls of the condenser and delivers the condensed phthalic anhydride through a valve 23 into a collecting vessel. To avoid clogging the condenser at the inlet end, the conveyer shaft 15 is abbeviated in the manner shown. The gases from the condenser pass to a two-part bag filter 18 of known type in which any phthalic anhydride dust entrained in the gases is separated; the bags are shaken periodically by mechanism 19<a>, and their contents are carried by a conveyer 22 through the valve 23 to the collecting vessel. |
