This mixer description is missing much of the practical information necessary to make an accurate recommendation, so several assumptions have been made in arriving at a reasonable answer. For a 2.9 m diameter x 2.5 m tall alum reactor, a 4-blade, 45-degree, pitched-blade impeller is recommended. The tank needs to have 4 vertical baffles, 0.24 m wide, to prevent uncontrolled swirling and provide good mixing from the top to the bottom of the reactor. The impeller should rotate at 68 rpm, which will require a 15 KW motor.