Method for spinning and washing aramid fiber and recovering sulfuric acid

摘要

A method for spinning and washing aramid fiber and for recovering sulfuric acid by (a) spinning an aramid polymer from a sulfuric acid spin dope to a yarn and coagulating the yarn in a coagulation bath having an inlet for water or diluted sulfuric acid and an outlet for sulfuric acid enriched water; (b) washing the yarn with water to obtain a washed yarn and a washing water containing sulfuric acid; (c) recycling the sulfuric acid enriched water and optionally the washing water to a sulfuric acid recovery unit; (d) increasing the sulfuric acid content of the recycled sulfuric acid enriched water, and optionally the washing water, by evaporation to obtain 20 to 98% sulfuric acid and water; (e) mixing the 20 to 98% sulfuric acid with oleum to obtain 98-105% sulfuric acid; and (f) recycling the 98-105% sulfuric acid to the spinning unit for use as sulfuric acid spin dope.