Concentrate Storage In A Platform-Lift Thickener

At Balmat in northern New York State, the St. Joseph Lead Co.'s 2100-tpd zinc mining and milling operation is utilizing a unique thickener in conjunction with conventional crushing, grinding and flotation methods. From 1930 through 1962, zinc concentrates went directly from flotation to the filtering, drying and loading facilities, all of which had to operate 24 hr per day. Wide fluctuations in tonnage also had to be accommodated due to variations in the grade of ore. Many problems were thus encountered in filtering and drying, but the cost of installing a conventional, large diameter thickener could never be justified. In 1963, after thorough investigation, an unconventional thickener that is unusual in several respects was installed at Balmat. The tank depth is 16 ft instead of the normal 8 ft. The rakes are raised and lowered by having the main drive gear located on a movable platform. Automatic controls are programmed to raise the drive platform and rakes during one shift of storage. During the next two shifts of withdrawal, the controls are programmed to lower the drive platform and rakes.