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A submersible centrifugal pump for downhole pumping of methane-saturated water from wells drilled in coal formations, has an electric motor-driven vertical shaft having centrifugal impellers distributed therealong, each impeller being located in a stationary diffuser within the pump wall to form a m

A submersible centrifugal pump for downhole pumping of methane-saturated water from wells drilled in coal formations, has an electric motor-driven vertical shaft having centrifugal impellers distributed therealong, each impeller being located in a stationary diffuser within the pump wall to form a multi-stage pump. A concentric shroud is located at the lower portion of the pump wall. It is sealed with the pump wall such that all fluid to be pumped must enter holes near the top of the shroud and travel downward through an annulus to the pump inlet. A charge impeller and a solids grinder are located at the lower end of the pump central shaft. The multi-stage centrifugal pump is located above the solids grinder and includes multiple compression stages of diminishing volume as the methane and fluid mixture travels upward through the pump. Another charge impeller may be located at the upper end of the shaft at the outlet pipe. Pressure equalization vents allow fluid flow from the fourth centrifugal stage to the pump-shroud annulus to maintain pump prime. Centrifugal impellers, each having a hub extending upward and downward along the length of the driving shaft such as to rest upon each other in turn, while avoiding contact with the stationary diffusers.

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1. A centrifugal submersible pump comprising:a) a generally cylindrical pump casing of such diameter as to fit within a well borehole for insertion and removal of the pump; b) a pump intake in the vicinity of a base of said pump; c) an axial drive shaft extending substantially the length of said pum

1. A centrifugal submersible pump comprising:a) a generally cylindrical pump casing of such diameter as to fit within a well borehole for insertion and removal of the pump; b) a pump intake in the vicinity of a base of said pump; c) an axial drive shaft extending substantially the length of said pump and adapted to be driven by a submersible motor located below said pump; d) a plurality of centrifugal impellers spaced along said axial drive shaft, each of said centrifugal impellers having a central hub attached for rotation to said axial drive shaft and having an opening adjacent said drive shaft for fluid intake; e) a plurality of diffusers corresponding, each corresponding to one of said centrifugal impellers to form a series of pump stages; f) said diffusers being supported by inward compression of said pump housing so as to remain stationary relative to said centrifugal impellers, and having a central bore of such diameter as to allow fluid to travel upward through the annulus between said central bore and said axial drive shaft and into said impeller intake; g) a pump outlet located and attached for flow to a conduit for receiving pumped fluid in the vicinity of an upper end of said pump housing for connection to a conduit for carrying said fluid to the surface, or into the casing of another immersible pump; h) a cylindrical coaxial shroud located along the lower portion of said pump housing and having a plurality of fluid inlet holes located near the upper end of said shroud, said shroud being sealed at its upper end with said pump housing and at its lower end with said pump housing at a location below said pump inlet such that all intake fluid must enter said pump through said shroud.