| 摘要 |
A process for the fractional desublimation of pyromellitic acid dianhydride in the form of free-flowing crystals which comprises reducing a reaction gas containing pyromellitic acid dianhydride produced by a chemical reaction which also produces by-products, to a temperature above the thaw point of the by-products but below the desublimation point of pyromellitic acid dianhydride by means of a smooth thermostaticized cooling surface, directing the reaction gases at maximal flow velocities of 3 m/sec parallelly to the cooling surface and separating the fraction of crystals not adhering to the surface. |
