Separate Recovery of Liquid and Solids from Ferromanganese Sludge

摘要

The sludge that results from the scrubbing of the exit gases at a ferromanganese plant was tested to show whether the liquid could be recovered and recycled to the scrubbers and the solids could be submitted to further treatment by pelletizing or briquetting before being recycled to the furnace. The particulate matter in the sludge consists of a fine condensate of metalliferous fumes with some particles of coal tar. These particles account, on average, for approximately 1 per cent of the sludge. Two methods were investigated for the separation of the liquid and solid phases: thickening followed by filtration, and centrifuging. Both methods showed that the sludge can be thickened satisfactorily to over 30 per cent solids. A comparison is made between the capital and operating costs of several alternative methods for the dewatering and recovery of solids. Centrifuging has the lowest operating costs, but the initial capital costs are high. A procedure in which the slurry is thickened by being recycled prior to centrifuging is recommended as having the lowest capital costs. The use of binders, such as lime-molasses mixtures, pitch, and cement improved the green strength, but, when the briquettes were fired at 400 C, the compressive strength was found to be about half that of standard chromite briquettes with a lime-molasses addition of 20 per cent. A 2 per cent addition of cement gave similar results.