| Résumé : |
Waste waters from leather tanning operations contain sludge consisting of hair, lime, protein, calcium sulfate, chromium, salt, etc., derived from various stages of processing. Typically waste water and sludge run to an equilization tank where the sludge mixture settles and supernatant water overflows to a municipal sewer. Periodically, settled sludge is removed and taken to a landfill for disposal. In some plants in the United States, the hair is removed by screening at the dehairing step. Then the hair-free sludge in the equilization tank is dewatered (sometimes by a belt filter) to about 25 to 30 percent solids. The dewatered sludge is then taken to a landfill for disposal.
Disposal of chromium-bearing sludges to landfills is now unacceptable because of environmental concerns. It is also a waste of valuable chromium resource.
Gahagan Associates, Inc., have arranged for the installation of a novel system of dehydrating tannery waste sludge by pulse-jet driers. The prototype drier, located on a floating barge in Vancouver, B.C., is being used in an attempt to particulate and dry a variety of sludges by means of high intensity sound waves and hot combustion gases generated by valveless pulse-jet engines. Tests of the system were made : to determine if the sludge could be dried, to determine the nature and quality of the dried tannery wastes, to estimate the thermal energy required for evaporation of water; and to determine the quantity and composition of gaseous emissions and liquid discharges.
this report documents the results of performance runs made on September 27 and 28, 1979. |
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Performance of a pulse-jet dehydrating system for drying tannery waste sludge in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. LXXVI (Année 1981)
