The Ajax is the first mill to install the Moore-Clancy process. A. W. Warwick estimates that the chemical consumption will be 12c.; the total cost $1.20; and the gold in tailings, less than $1 per ton.
Last week the Ajax mill, at Victor, Colo., started operations. This mill, financed by E. A. Colburn, president of the Ajax Gold Mining Company, was built at the mine to treat the ores of the Ajax company and its lessees. It was concluded that treatment on the ground would be a profitable venture, because it not only would eliminate many handlings, but would make it economically possible to mine ore of a much lower grade.
First Use of Moore-Clancy Process
The Ajax or Colburn mill is unique as being the first mill to install the Moore-Clancy process, by which it is proposed to treat the highly refractory sulpho-telluride ores by a direct chemical method; the other mills of the Cripple Creek district depend upon concentration to remove the bulk of the refractory minerals for shipment to mills or smeltery at Colorado City or Pueblo, the tailings only being cyanided in the district.
The Moore-Clancy process, so far as has been made public, consists in using a complex solution composed of calcium cyanamide, potassium cyanide, potassium sulphocyanide and potassium iodide and electrolyzing the mixture, thereby generating among other compounds the halogen cyanide necessary to break up the telluride minerals. After a year's experimentation on Cripple Creek ores, A. W. Warwick, chief metallurgist of the Moore Filter Company, determined that a current density of from 5 to 7 amp. per sq.ft. and from 5 to 7 volts would do the work, 15 to 20 amp. per ton of ore treated or from 105 to 140 watts being all that was necessary. He also found that by keeping the solutions rather alkaline, the desired reactions were obtained and the difficult problem of keeping the solution neutral, originally proposed, was avoided.
Crushing and Cyanide Departments Separate
The mill, designed by S. A. Worcester, of Victor, Colo., has a capacity of 200 tons, but is so arranged as to permit of enlargement to 460 tons daily capacity when conditions warrant it. The only available site for the mill was not ideal and much ingenuity was necessary to provide a building and arrangement adequate for the requirements.
Essentially the mill consists of two parts: The crushing and sampling mill and the chemical-treatment plant proper. The ore is brought to the mill in a 6-ton, third-rail crane-motor car; dumped directly into a 5C Symons crusher and broken to about 1¼ in. From the crusher the ore is elevated and delivered to two conical sheet-iron ore bins. One of these bins is provided with a Fairbanks scale with a capacity of 35 tons, for weighing lessee ore.
Grinding by Rolls and Tube Mills
From the ore bins the material is passed through a magnet and is elevated to a set of Colorado Iron Works impact screens. After screening, the ore is delivered to three sets of Allis-Chalmers rolls 16x36 in. The screens used are 5/8, 1/4 and 10 mesh. All the material that passes a 1/4-mesh screen is passed over a 27-in. Snyder sampler, a cut of 5 per cent, taken and delivered to the sampling plant.
The finely crushed material is delivered to a 16-in. rubber conveyer belt, 250 ft. long, and is carried up a 20-deg. slope to a vertical elevator which delivers the crushed ore to three cylindrical steel ore bins, situated at the head of the chemical-treatment plant. The combined capacity of these ore bins amounts to 600 tons. Each bin will store a different character of material, and they are arranged so that each will feed a separate screw classifier.
The slime overflow from the classifiers is delivered by air lift immediately to the agitator system, and the oversize, which is diluted to a proper degree of thickness, feeds a Stearns-Rogers spiral-fed trunnion tube mill 16 ft. long and 5 ft. in diameter. There are three tube mills, each with its own closed cycle and each crushing to a different degree of fineness, according to the character of the ore which each tube mill is receiving. The ore is crushed in solution.
Slime Agitated and Electrolyzed
The slime goes to five specially designed agitators, each with a capacity of from 80 to 100 tons of dry slime. The pulp will have a ratio of one ton of ore to 1.5 tons of solution. In the agitators there are 20 electric baskets for the purpose of electrolyzing the solution. Each electrode basket has an anode surface of about 4 sq.ft., and with a capacity of 35 amp. each. The electrodes are carried on heavy steel-rail busbars. The current is furnished by a General Electric 15-kw. generator, arranged to deliver 3000 amp. at 5 volts, or 1500 amp. at 10 volts. By means of field resistances the voltage of the generator can be regulated at anything between 5 and 10 with corresponding amperages. The delivery of the current is regulated to each agitator by means of a Westinghouse switchboard.
The ore, crushed to approximately 150 mesh, is agitated for 24 hours with low-pressure air delivered by the mill compressor, although the air system is connected with the mine compressor giving air at 100 lb. in case of emergencies. After agitation the pulp is delivered directly to the loading tank of the Moore filter plant with a filtering area of about 9500 sq.ft. and a capacity of about 200 tons of dry slime daily.
The Moore filter plant offers some novelty in that the crane is entirely operated by hydraulic power both for lateral and vertical motion. The use of the equalized load furnished by a hydraulic pump compares favorably with electrical cranes both for economy and ease of operation.
The clear gold solution delivered by the filter system is precipitated by zinc dust fed intermittently by a tripping arrangement operated by the flow of gold solution. The precipitated gold is collected by two Stearns-Rogers special filter presses with 24x30-in. plates. Each press contains from 24 to 30 plates.
Aerial Tram to Tailing Dump
The slime delivery from the Moore filter plant will be made by a screw conveyer working in the bottom of the discharge tank. The slime will be conveyed from the mill to a large bucket carried on a cableway and moved by a small electric hoist. On the cableway, trips are provided so that, automatically, the bucket will dump in a different place at every trip. By this arrangement it is hoped that the material will have a chance to spread and dry before another bucketful is dumped upon it. This is of importance to prevent large slides in the slime piles.
Estimated Operating Cost
In the chemical-treatment part of the mill is situated the laboratory from which the metallurgical operations are controlled. It is, of course, too early to give exact figures as to cost, chemical consumption and extraction; but, based on results of several hundred tests, the Moore Filter Company expects that after adjustments are made and the mill has settled down to regular work less than $1 will be left in the tailings, with a chemical consumption of 12c. per ton and a total operating cost of $1.20 per ton. The plant is in charge of E. A. Coleman, Jr., as local manager; W. A. Kunkle, mill superintendent; J. A. Hitchcock, electrician; W. A. Gilbert, chemist; A. C. McKeehan, master mechanic.