Method and apparatus for blending and withdrawing solid particulate material from a vessel

An apparatus for blending and withdrawing solid particulate material, comprising:

• a vertically oriented vessel having an upper part, a lower part, an inlet for particulate material to be blended, an outlet for blended particulate material and a tubular extension at said lower part,
• a vertical lift column (i) centrally mounted in said vessel, (ii) having a lower part extending into said tubular extension, and (iii) including an inlet within said tubular extension and an outlet in the upper part of the vessel, means for supplying gaseous fluid under pressure to said tubular extension below said lift column for entraining material in the tubular extension into the inlet of the lift column and upwardly through the lift column whereby material is discharged from the outlet of said lift column in a geyser-like manner into the upper part of the vessel, said tubular extension and the lift column being dimensioned to define a seal leg to enable a major portion of said gaseous fluid to be directed upwardly through the lift column, and
• a first downcomer channel through which said material downwardly travels associated with said vessel and having an outlet at a bottom portion thereof, said first channel comprising n successive vertical sections and n flow ports through which said material enters said first downcomer channel respectively located at a top portion of said n sections, at least two of said n sections having flow areas different in size from one another, wherein material that travels downward through said first downcomer channel will pass through the flow area of any of said sections located beneath the section into which said material first entered said downcomer channel.