Washing apparatus in chlorine dioxide production

An apparatus consisting of:

• an elongate generally cylindrical upright tower having a cross-sectional dimension corresponding to a unit area value of about 0.07 to about 0.11 ft..sup.2 /ton solids/day,
• a plurality of superimposed compartments within said tower extending from an upper-most compartment to a lower-most compartment, each separated from the next-lower compartment by a downwardly-sloping frusto-conical bottom wall,
• each said bottom wall having a central opening and being joined to a short axially downwardly-directed unobstructed pipe having an inlet coinciding with the central opening in said bottom wall, said short pipe establishing a fluid relationship between adjacent superimposed compartments and having a cross-sectional dimension corresponding to a unit area value of about 0.005 to about 0.015 ft..sup.2 /ton solids/day,
• slurry inlet means communicating with an upper region of the upper-most of said superimposed compartments for feeding thereto a slurry of solid materials to be treated in the apparatus,
• slurry outlet means communicating with a lower region of the lower-most compartment for removing therefrom a slurry of solid materials treated in the apparatus,
• treatment liquid inlet means communicating directly with the short pipe extending between the lower-most compartment and the next-higher compartment for feeding treatment liquid to said apparatus,
• spent treatment liquid outlet means communicating directly with an upper region of the upper-most compartment for removing spent treatment liquid for said apparatus,
• first liquid transfer means extending directly between an upper region of each said compartment in said column, with the exception of the two upper-most compartments, and said short pipe entering the next-higher compartment for transfer of liquid therethrough from one compartment to the next-higher compartment, and
• second liquid transfer means extending directly between an upper region of the next-lower than said upper-most compartment and an upper region of said upper-most compartment for transfer of liquid therethrough to said upper-most compartment.