Gas scrubbing tower

A gas scrubbing tower having a top region, a sump region and at least two washing stages therebetween which tower comprises

• (A) a gas entry means for introducing waste gas to be scrubbed into the tower, which entry means is located between the sump region and the first of said washing stages,
• (B) gas exit means in the top region of the tower for the discharge of purified gas therefrom,
• (C) the first washing stage, in the direction of upward gas flow from said entry means to said exit means, being constituted by at least one layer of packing elements, which layer extends in a horizontal plane across the cross-sectional area of the tower, and by supporting means for said packing elements,
• (D) a first circulating line for conducting wash liquid from said sump region to the first washing stage, said first line being connected to said sump region, passing through pump means and terminating in spray nozzles which are positioned in said first washing stage above said packing elements for irrigating said layer of packing elements therein,
• (E) a second, packing-free washing stage, located in said scrubbing tower above said first washing stage, and comprising a plurality of slot-defining gas baffling elements adapted for accelerating and then decelerating gas flow therethrough, and means for introducing a liquid into said elements, wherein each said element has a slot inlet thereto and a slot outlet therefrom and includes two coaxial guide surfaces defining an annular passage diverging from the slot inlet toward the slot outlet, the mean angle of divergence being in the range of 10.degree. to 90.degree., and the cross-sectional area of the annular passage decreasing in the direction of gas flow from the slot inlet and then increasing towards the slot outlet and the mean radius of the cross-sectional area increasing in the direction towards the slot outlet, the liquid introduction means including means to produce a rotationally symmetrical liquid jet substantially parallel to said guide surfaces and in the same direction as the flow of gas through each element and comprising a deflector disc centrally disposed on the gas inlet side of said element and an axial feed tube through which liquid is fed onto the deflector disc in a direction opposite to that of the gas flow and is then deflected by the deflector disc rotationally symmetrically into the direction of the gas flow;
• (F) a second circulating line for conducting wash liquid from the sump region to the second washing stage, said second line being connected between said sump region and said axial feed tube of said second washing stage;
• (G) a sludge separator, constituting the said sump region of the tower, and comprising a settling vessel having an upper portion, a central portion and a base portion, the upper portion comprising an upper inner partition wall which tapers conically inwardly and with its apex downwardly to define a central orifice;
• an inlet tube for sludge-carrying liquid from said first washing stage and extending via the central orifice into the central portion of the settling vessel and connected therebetween, a first outlet means for removal of liquid of reduced sludge content from the settling vessel and extending from the central portion of the settling vessel, above the lower end of the liquid inlet tube radially toward the outside as part of said first circulating line, and a second outlet means connected to the base portion of the settling vessel for the removal therefrom of liquid charged with sediment;
• and
• (H) conduit means for introducing water from outside the tower into said scrubbing tower.