Ball mill slakers are best suited to applications where the lime quality is poor, water chemistry is poor, grit handling is costly or when the processing rate exceeds that achievable in a conventional slaker. Ball mill slakers operate on the same principle as detention slakers, with the added ability to grind inert materials (grit) contained in the quicklime and in general, require no grit removal or disposal facilities. Horizontal grinding mill slakers are, however, the most expensive of the slaker types, have limited capacity for turndown, and consume the most energy. They can also be difficult to tune as the temperature can only be measured at slaker discharge.
Horizontal ball mill slakers are similar to grinding mills commonly used in the mineral processing industry modified to withstand the temperature of lime slaking. They have the advantage of being relatively simple and rugged. A typical ball mill slaker (horizontal type) consists of a rotating drum supported by external rollers. The mill contains a grinding media (typically steel balls) agitated by means of horizontal lifting bars attached to the interior of the drum assembly. Slaked lime product discharges from the drum and is pumped to a hydrocyclone, which classifies the slurry to recirculate oversized particles to the mill inlet.
Ball mill slakers are made to order in quicklime slaking capacities up to 50,000 kg/hr. As with conventional detention slakers, horizontal ball mills operate at water to lime ratios (in the slaking compartment) between 3.5:1 to 6.0:1. The water to lime ratio in the mill is adjusted automatically to maintain a constant slaking temperature based on a temperature probe at the discharge of the mill. Horizontal ball mill slakers typically operate between 75 oC and 85oC. Because the temperature is not measured in the slaking zone it is difficult to maximize the operating temperature to minimize chemical consumption.
An alternate version of the horizontal ball mill slaker is vertical ball mill slaker which is a vertical stirred ball mill. This type is useful when very fine grinding is desired.