METHOD OF COLLECTING PYROMELLITIC ANHYDRIDE

摘要

A method of collecting pyromellitic anhydride, which comprises introducing a high-temperature gas containing pyromellitic anhydride together with an inert cooling gas into an empty column-type collecting device whose wall temperature is maintained at 150 DEG to 200 DEG C., effecting heat exchange between the high-temperature gas and the cooling gas in the collecting device to lower the temperature of the high-temperature gas to 150 DEG to 200 DEG C., thereafter passing the gaseous mixture through the collecting device at an average linear gas velocity of 0.05 to 0.5 m/sec with an average residence time to 5 to 60 seconds, and recovering needle-like crystals of pyromellitic anhydride from the bottom of the collecting device.