Scrubber Flue gas from which Solids emoval Ground limestone VacuuM belt Blower Slurry recirculation pumps FIGURE 11 Flow diagram for forced- oxidation limestone wet scrubbing. The scrubber module is shown in detail in Fig. I1.6. The process is described in the text designs. In the tower the SOz dissolves in the slurry and reacts with limestone(and the other dissolved and suspended calcium salts) producing COz, which enters the gas stream, and solid CaSO3. The latter is almost entirely oxidized to CaSo4, partly by the excess oxygen in the flue gases in the tower, mostly in the bottom of the scrubber module. In earlier designs the oxidation took place in a separate vessel, but most current devices use the bottom of the scrubber as a liquid oxidation reactor The slurry of water and solid particles(CaCO3, CasO4 2H20, and CasO30 5H20is pumped from the sump Clean the module to th sprays, where it forms drops that fall through the ing flue nozzles Absorption actual SO removal slurry spray Finely ground limestone is sump. A small stream Recirculation s Oxidation E/pumps by the solid removal pump Oxidation Patented allo air supply perforated tray mixes slurry hydroclone (much like a multiclone, tre which FIGURE 11.6 termal details of the scrubber module which has one sieve tray without downcomers, several levels of spray the underflow ozzie, two levels of e ent separators, and a large sump that serves as a forced oxidation reactor For large installations there will often be several such inoxduies operating in parallel. Courtesy of The Babcock and wilcox Company, Barberton, Ohio.)11－8 designs. In the tower the SO2 dissolves in the slurry and reacts with limestone (and the other dissolved and suspended calcium salts) producing CO2, which enters the gas stream, and solid CaSO3. The latter is almost entirely oxidized to CaSO4, partly by the excess oxygen in the flue gases in the tower, mostly in the bottom of the scrubber module. In earlier designs the oxidation took place in a separate vessel, but most current devices use the bottom of the scrubber as a liquid oxidation reactor. The slurry of water and solid particles (CaCO3, CaSO4 .2H2O, and CaSO3 .0.5H20) is pumped from the sump at the bottom of the module to the sprays, where it forms drops that fall through the rising flue gas and do the actual SO2 removal. Finely ground limestone is added to the sump. A small stream of slurry is sent by the solid removal pump to a hydroclone (much like a multiclone,) from which the underflow passes to a