GB1220761A - Improvements relating to the pickling of metal - Google Patents

Abstract

1,220,761. Treatment of spent pickle liquors. CHEMICAL SEPARATIONS CORP. 25 June, 1969, No. 32099/69. Heading C1A. [Also in Division B1] In a process for pickling metal, the spent pickle liquor is continuously regenerated by (1) continuously withdrawing spent pickle liquor from a pickling process, (2) passing said liquor through a first section of an ion-exchange column loop having a movable ion exchange resin bed, whereby metal ions in the spent liquor are exchanged for hydrogen ions in the exchange resin (thus regenerating the pickle acid) whilst (3) simultaneously treating a second portion of said ion exchange resin loaded with metal ions from (2) with a regenerating agent in second section of said column loop; (4) substantially simultaneously stopping the flow of spent pickle liquor, and said regenerating agent; (5) moving the ion exchange resin bed from one section of the loop to another contiguous section therein, thereby replacing at least a part of said resin in said first section with regenerated resin from step (3) and moving a further part of used resin from step (2) to said second section for regeneration; (6) withdrawing from said second section a solution of the metal salt of the ion exchange regenerating agent, and obtaining the regenerating agent therefrom; (7) continuously recycling the regenerated regenerating agent to said second section of said column loop. The movement of the ion exchange bed and solutions in the column loop is controlled by conductivity probes which detect solution interfaces. The solution of the metal salt of the ion exchange regenerating agent is either (a) hydrolysed at elevated temperature and pressure to produce regenerated regenerating agent and the metal oxide, e.g. iron, by hydrolysis in the presence of an O 2 containing gas such as air or (b) treated in a fluidized bed reactor to produce the metal oxide and vapours which are scrubbed with water to produce the regenerating agent. The regenerating agent specified is nitric acid and resins specified are "Dowex", a sulphonated polystyrene resin, "Amberlite" and "Permutit" (Registered Trade Marks). Pickle acids specified are sulphuric, phosphoric, hydrochloric and citric, the pickle solution being controlled to contain acid of 5-20% strength and metal salt at a concentration of 1-10%. Apparatus is described (see Division B1, ion exchange).