METHOD OF MOULDING AND WASHING ARAMID FIBRE AND REGENERATING SULPHURIC ACID Russian patent published in 2013 - IPC D01F13/04 D01F6/60 

FIELD: chemistry.

SUBSTANCE: method employs a moulding apparatus and an apparatus for regenerating sulphuric acid. The method involves the following steps: a) moulding a (spinning) thread from aramid polymer from a spinning solution which contains sulphuric acid, and coagulating the thread in a coagulation bath having an inlet for water or diluted sulphuric acid and an outlet for water rich in sulphuric acid; b) washing the thread with water to obtain a washed thread and washing water containing 0.5-20.0 wt % sulphuric acid; c) reusing the water rich in sulphuric acid and, optionally, the washing water, which is fed into the apparatus for regenerating sulphuric acid; d) increasing content of sulphuric acid in the reused water which is rich in sulphuric acid and, optionally, in the washing water by evaporation to obtain sulphuric acid with concentration of 98% and water; e) mixing sulphuric acid with concentration of 98% with oleum to obtain sulphuric acid with concentration of 98-105%; f) reusing the sulphuric acid with concentration of 98-105% in the moulding apparatus as a spinning solution containing sulphuric acid.

EFFECT: invention enables restoration and reuse of sulphuric acid which can be carried out in a closed cycle.

14 cl, 4 dwg