GB592551A - Improvements in a process of and means for continuously purifying and concentrating acid pickle liquors for the treatment of iron and steel - Google Patents

Abstract

In the continuous purification and concentration of spent hot sulphuric acid iron pickling liquors with the removal of copperas therefrom and the addition of fresh sulphuric acid thereto, the spent liquors are subjected to a first stage of cooling in open-topped tubes 1 to crystallise and precipitate copperas, and then to a second stage of cooling in a barometric tube 3 to further crystallise and precipitate copperas therefrom, the water vapour evaporated in vacuum head 9, in the second stage, being absorbed by concentrated sulphuric acid sprayed into condensing column 10 disposed between the vacuum head 9 and conduit 10a, and returned via container 38 and tube 39 to the spent liquors entering said first stage, the liquor purified and concentrated in the second stage being caused to flow successively through heat interchange jackets surrounding tube 3 and tubes 1 in a direction counter to that of the spent pickling liquor, to be finally discharged by siphon 28 into tank 12, and the copperas crystallised and <PICT:0592551/III/1> precipitated from said liquors being continuously or intermittently collected and removed therefrom. The spent liquors are agitated during the first coating stage by means of stirring mechanism 5a. The passages between the open-topped and barometric tubes and their respective jackets are forced to provide a helical passage for the liquor around said tubes. Axial heat flow may be prevented by employing tubes 1 and 3 formed as a series of metal rings separated by rings of adherent insulating and acid resistant material, e.g., rubber, ebonite or vulcanite, formed of helical metal strips the interstices of which are filled with the adhering insulating material, or formed with transverse slits which are in staggered relationship vertically and filled with the insulating material. The walls of the jackets enclosing the tubes may be lined internally with rubber or ebonite and lagged eternally. In a modification, the rate of flow of the regenerated liquor into tank 12 is automatically adjusted by a float, rigidly attached to a siphon vessel and counterbalanced by a system of pulleys and weights, which moves up and down with the liquor level in tubes 1, moving with it the siphon vessel and adjusting the head of liquor in the siphon pipe 28 and the rate of discharge from the siphon vessel into tank 12 according to atmospheric pressure variations.