METHOD FOR SPINNING AND WASHING ARAMID FIBER AND RECOVERING SULFURIC ACID

摘要

The invention pertains to a method for spinning and washing aramid fiber and for recovering sulfuric acid, using a spinning unit and a sulfuric acid recovery unit, comprising the steps: 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 washed yarn and washing water containing 0.5-20 wt.% sulfuric acid; c) recycling the sulfuric acid enriched water and optionally the washing water to the 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; f) recycling the 98-105% sulfuric acid to the spinning unit for use as sulfuric acid spin dope.