Abstract: A plasma burner has an annular passage extending along an insulated tube defining the outer wall of the electrode lance and located between the electrode lance and the multi wall burner shell to deliver the auxiliary gas outwardly of the plasma gas. The nozzle forming end of the electrode lance has a coolant circulation as has the burner shell and the annular passage extends substantially to the coolant inlets and outlets of the burner. The construction avoids the formation of parasitic arcs.

Abstract: A method is disclosed for the biological aerobic purification of waste waters wherein a temperature from 30.degree. to 60.degree. C. is maintained in a first process stage and a temperature from 20.degree. to 40.degree. C. is maintained in a second process stage, with the temperature in the first process stage always being higher than the temperature in the second process stage and wherein a part of the activated sludge of the second process stage, after being seperated, is returned to the first process stage. The process provides a high decomposition output and produces an activated sludge which exhibits good sedimentation behavior.

Abstract: A method is provided for processing raw manganese nodules for the selective recovery of metal values of nickel, copper, cobalt and zinc contained therein by hydrometallurgical means. The raw nodules are suspended in water or dilute wash solution to form a suspension. The suspension and sulfuric acid are charged to a pressure vessel to provide a solid-liquid suspension of nodules and leach solution. The solid-liquid suspension of nodules and leach solution is heated in the pressure vessel to a temperature between about 150.degree. C and about 300.degree. C to cause the nickel, copper, cobalt and zinc to be selectively leached from the nodules into the leach solution to form a metal rich leach solution containing these metals and a residue, with the solid-liquid suspension having a sulfuric acid content of less than 35 g/l upon completion of the leaching. The metal rich leach solution containing nickel, copper, cobalt and zinc is separated from the residue.