CALCIUM-CARBONATE DEPOSIT FORMATION UNDER ISOTHERMAL CONDITIONS

Scale formation of calcium carbonate on tube walls is studied in a onc e-through flow system under isothermal conditions. The effects of supe rsaturation ratio, flow velocity and liquid temperature on the deposit ion rates are investigated. For relatively small supersaturation ratio s (in the range 3.5 to 8) the deposition rate tends to increase with i ncreasing supersaturation. For higher fluid supersaturations with resp ect to calcium carbonate, the deposition rates remain roughly constant but they are influenced strongly by the fluid velocity. This dependen ce of the deposition rate on fluid flow suggests a mass transfer-contr olled process.