Apparatus for purifying a suspension of fibrous material

In apparatus for removing impurities entrapped in a liquid suspension of fibrous material including a generally horizontal fluidized bed chamber having spaced opposite ends, an imperforate top wall, and a perforated bottom wall, first means for introducing said suspension to said fluidized bed chamber through one end thereof for flow across said bottom wall toward the other end, the space between said bottom and top walls being filled with said liquid suspension from said one and to said other end of said fluidized bed chamber, a pressure chamber below said fluidized bed chamber and communicating with said bottom wall, and second means for introducing a fluidizing agent under pressure to said pressure chamber for upward flow through the perforations in said bottom wall and through the suspension in said fluidized bed chamber thereby to separate impurities from said suspension by flotation, the improvement comprising:

• a separation chamber having a forward end communicating with the other end of said fluidized bed chamber for receiving said suspension therefrom and having top and bottom walls and a rear wall, said separation chamber having at least one withdrawal opening in the forward region of said top wall for removing separated impurities from said suspension which have relatively low specific gravity and thus float to the top thereof, said separation chamber having at least one discharge opening in its rear lower region for removing separated impurities from said suspension which have relatively high specific gravity and thus settle to the bottom wall thereof, said last-named bottom wall being imperforate apart from said discharge opening, said separation chamber having at least one outlet opening therein in its rear upper region rearwardly of said one opening for removing the purified fibrous suspension therefrom.