Abstract: An improvement in a method and apparatus is provided in extruding a powder material to form an article, in which the material is passed through an extruder and then through a die, wherein the material is provided in the form of a mixture which includes a vehicle, the improvement comprising having one or more gear pumps in succession between the extruder and the die, so that the powder material passes through the gear pump(s) after it leaves the extruder and before it enters the die. The gear pump(s) can have one or more pair of gears which are arranged sequentially with respect to the flow of the material.

Abstract: An improvement is provided in a gear pump comprising a pair of intermeshing gears enclosed in a housing, the improvement comprising having at least one additional pair of intermeshing gears, wherein the gear pairs are non-meshing with one another.

Abstract: Tungsten is recovered from tungsten ore concentrates in the form of sodium tungstate by a basic process in which ground ore is first digested in a sodium hydroxide solution followed by diluting the solution to dissolved sodium tungstate separating the solution from the caustic insoluble sludge and crystallizing soluble sodium tungstate, wherein the present invention permits improved recovery of tungsten from difficult to process ores by the process steps of comminuting said tungsten ore concentrate to a particle size less than about 200 mesh, adding the comminuted ore to an aqueous solution of sodium hydroxide at a temperature from about 10 to about 30 degrees centigrade, dispersing said comminuted ore in the aqueous solution of sodium hydroxide prior to digestion, digesting at a temperature of from about 75.degree. C. to about 150.degree. C.

Abstract: Tungsten is recovered from tungsten ore concentrates in the form of sodium tungstate by a basic process in which ground ore is first digested in a sodium hydroxide solution followed by diluting the solution to dissolve sodium tungstate separating the solution from the caustic insoluble sludge and crystallizing soluble sodium tungstate, wherein the present invention permits improved recovery of tungsten from difficult to process ores by the process steps of comminuting said tungsten ore concentrate to a particle size less than about 200 mesh, dispersing the comminuted ore to separate agglomerated particles, adding the dispersed ore to aqueous sodium hydroxide at a concentration of at least 10 molar and digesting at a temperature of from about 75.degree. C. to 150.degree. C. for a sufficient period of time to convert substantially all of the tungsten values to soluble sodium tungstate, and diluting the mixture to reduce the sodium hydroxide concentration to between about 4.5 and 5.

Abstract: Tungsten is recovered from tungsten ore concentrates in the form of sodium tungstate by a basic process in which ground ore is first digested in a sodium hydroxide solution followed by diluting the solution to dissolve sodium tungstate separating the solution from the caustic insoluble sludge and crystallizing soluble sodium tungstate, wherein the present invention permits improved recovery of tungsten from difficult to process ores by the process steps of comminuting said tungsten ore concentrate to a particle size less than 325 mesh, adding said comminuted ore to aqueous sodium hydroxide at a concentration of at least 10 molar and digesting at a temperature of from about 75.degree. C. to 150.degree. C. for a sufficient period of time to convert substantially all of the tungsten values to soluble sodium tungstate, and diluting the mixture to reduce the sodium hydroxide concentration to between about 4.5 and 5.5 molar at a temperature below about 90.degree. C.

Abstract: Tungsten is recovered from tungsten ore concentrates in the form of sodium tungstate by a basic process in which ground ore is first digested in a sodium hydroxide solution followed by diluting the solution to dissolve sodium tungstate separating the solution from the caustic insoluble sludge and crystallizing soluble sodium tungstate, wherein the present invention permits improved recovery of tungsten from difficult to process ores by the process steps of drying the insoluble sludge portion, comminuting the dried sludge to a particle size less than about 200 mesh, and dissolving said comminuted sludge in 4.5-5.5 molar NaOH to recover substantially all of the tungsten values.

Abstract: In a process for recovering tungsten from cemented tungsten carbide, the cemented tungsten carbide is oxidized to form an oxidized product which is digested in an aqueous solution of an alkali metal hydroxide to form a water soluble alkali metal tungstate portion and an insoluble portion. The improvement of the present invention provides for recovery of tungsten values from the above mentioned insoluble portion by digesting the insoluble portion in an aqueous alkali metal hydroxide solution with a suitable amount of titanium oxide to promote the formation of a soluble alkali metal tungstate.