GB250824A - Improved process of treating waste liquors containing cyanogen compounds - Google Patents

Abstract

250,824. Denis, J. Sept. 18, 1925. Treating-materials; plant.-Waste waters containing cyanogen compounds such as waters from gas manufacture, coke ovens, blast furnaces and certain sugar refineries are treated to render them harmless by adding an alkali or alkaline earth hydrate and ferrous sulphate while passing in carbon dioxide to precipitate iron ferrocyanide which is allowed to settle and adding to the remaining liquor barium hydrate or other reagent capable of forming a carbonate precipitate to carry down any remaining iron ferrocyanide. When the liquor contains phenols and hydrocarbons, these are separated by drawing off the oily layer from the top before or after the addition of one or both of the reagents for precipitating the ferrocyanide in the first phase of the process. The waste liquor is raised from a tank 1 by a pump 2 and pipes 3 to treatment vessels A1, A2 which are worked alternately. Ferrous sulphate solution and milk of lime are prepared in vessels 4, 5 and are supplied to the vessels A1, A2. Carbon dioxide is supplied from a pipe 16. The oily upper layer is drawn off by a pipe 12 into a closed chamber 10 and the settled ferrocyanide sludge is led through a valve 17 to a tank 18 and thence to a filter 19, the filtrate passing through a pipe 20 to a decanting vessel B. The liquor in the vessel A1 after separation of the sludge is then discharged through a valve 24 to the vessel B. Barium hydrate solution from a tank 21 is led to the vessel B, the clarified liquor overflowing at 25 through a pipe 26 while the precipitate as drawn off by a pipe 28, to a pit 29. Hot air or other gas is delivered through a pipe 13 to the vessel 10 and escapes as carburetted air by a pipe 14 from which it may be led to a furnace and burnt. Any sediment in the tanks 4, 5 is discharged into the decanting vessel B. The whole apparatus, except the vessels A1, A2, may be worked continuously.