Poly:phosphoric acid prodn. from ortho:phosphoric acid - by polymerisation and concn. by passing AC through soln.

摘要

Prodn. of polyphosphoric acid (I) from thermal and/or extractive H3PO4 is effected by polymerisation and concn. in >=1 stage by passing a single or 3-phase a.c. current through the soln. at a current density of 100-1000 A/dm2 and a reaction temp. of 200-350 degrees C. If several concn. stages are used, the ppte. is sepd. after each stage. The yield per unit vol. is relatively high, and there is a considerable redn. in the amt. of equipment needed for absorbing or condensing vapours, since less gas and vapour is released. Energy control can be carried out in a very short time and raising of the energy is limited only by vigorous boiling of the acid or the formation of considerable amts. of deposit near the electrode contacts with acid contg. a high proportion of impurities. The possibility of sealing the equipment completely is esp. important for improving the working environment.