Spinning bath vapour condensing - uses the spinning bath to cool the recirculation sulphuric acid used for water condensation

摘要

To condense the vapours emerging from spinning baths, with recirculating H2SO4, a spinning bath is used to cool the H2SO4 and is then cooled in a vacuum. The spinning bath is recirculated for cooling and part of the concentrated cooled bath is taken to be mixed with an equal vol. of new spinning bath. The water vapours are drawn off during cooling, and condensed with cold water. The spinning bath is cooled in a number of successive stages. The vapours from each cooling stage are condensed in an acid mixt. condenser, and the H2SO4 is circulated and recooled by the spinning bath in a separate heat exchanger. The condensers, using H2SO4 are in series and part of the H2SO4 from each condenser is passed to the next condenser. At the final condenser, part of the H2SO4 is extracted and an equal vol. of fresh H2SO4 is added to the first condenser. The heat exchangers are in series, with the same spinning bath flowing through them for cooling. The H2SO4 concentration increases from the initial condenser to the highest level at the final condenser. USE/ADVANTAGE - The system is used in rayon spinning where, according to the compsn., the spinning bath is cooled from 35-40 deg.C to 0-15 deg.C with simultaneous steam evapn., and the sodium sulphate is crystallised out as mirabilite. The method increases the cost-effectiveness of vacuum cooling and crystallisation assemblies where the vapours are condensed by recirculating H2SO4 on cooling the spinning ba