Combined fluidizing and vacuum pump

A method of simultaneously pumping and degassing a suspension having a solids content between about 6-15% utilizing a fluidizing impeller in a main housing rotatable by a shaft, and a vacuum impeller mounted on the same shaft as the fluidizing impeller, for rotation therewith about the axis of rotation, comprising the steps of:

• feeding the suspension having a consistency between about 6-15% into operative association with the fluidizing impeller;
• rotating the fluidizing impeller continuously at high speed, the impeller effective pumping of the suspension and removing gas from the suspension, the gas tending to collect adjacent the shaft;
• withdrawing the gas from its collecting volume with the vacuum pump, the gas being pulled from the collecting volume generally parallel to the axis of rotation, through the vacuum pump past the vacuum pump impeller, and expelled from the opposite side of the vacuum pump as the fluidizing impeller;
• and
• supplying atmosphere make-up gas to the flow of gas drawn into the vacuum pump in response to the vacuum pump pulling a vacuum greater than predetermined amount.

A pump including a fluidizing impeller housing having a first inlet and first outlet, and second outlet;

• a vacuum impeller housing having a gas inlet, gas outlet, and liquid inlet;
• a shaft mounted for rotation about an axis;
• a fluidizing impeller mounted to said shaft for rotation therewith, and disposed in said fluidizing impeller housing;
• a vacuum pump impeller mounted to said shaft for rotation therewith and disposed in said vacuum pump housing;
• means defining gas passageways between said second outlet and said gas inlet, said second outlet being disposed adjacent, and extending generally parallel to, said axis of rotation and said gas passageway defining means defines a gas passageway in a common wall between said fluidizing impeller housing and said vacuum pump impeller housing;
• said gas outlet extending from the opposite said of said vacuum pump impeller from said second outlet;
• and means for supplying make-up atmospheric gas to an open annular volume in said common wall in response to the vacuum being pulled by the vacuum pump impeller being more than a predetermined amount.