OXYGEN MASS-TRANSFER IN AIR-AGITATED PACHUCA TANKS .1. LABORATORY-SCALE EXPERIMENTAL MEASUREMENTS

Pachuca tanks are extensively used for the cyanide leaching of gold an d the carbonate leaching of uranium, processes in which oxygen mass tr ansfer plays a very important role. Despite the fact that these tanks have been in use since the turn of the nineteenth century, very little attention has been paid to the subject of oxygen mass transfer in the m. Experiments were carried out with four laboratory-scale Pachuca tan ks to clarify the effect of design and operating parameters on oxygen mass transfer. The investigation provided some important results that are crucial to the design and scale-up of Pachuca tanks. Such paramete rs as the ratio of tank height to tank diameter, the ratio of draught- tube diameter to tank diameter and tank design should not influence ox ygen mass transfer in this type of tank. In addition, the results indi cate that equal superficial gas velocities may be used as a criterion for scaling up oxygen mass transfer in both full-centre-column and fre e-air-lift Pachuca tanks with clear water.