Show progress 1 in n cyana catl on duri during ng 1914 BY A B while the year just passed presents no developments of a radical nature in either the art or application of still there has been a tendency toward growth along lines of previous practice and a review of the year is not without features of possible interest A number of new 1 plants in rhodesia the transvaal and australia 7 were completed and put in operation during the year but as usual the design followed closely the so called standard practice in their localities nissen stamps I 1 were used in one plant in rhodesia in mexico of course construction work was at a standstill so that the progress was confined largely to the united states and canada in spite of the apparently well founded view that the average ore from a breaker can call be crushed more economically with rolls providing they are properly handled 1 builders of new cyanide plants seem con tent to rely largely on the old gravity p stamp it is ig true that rolls have been lail adopted opted in some instances as have also chilean mills and ball mills but by far the bority seem stubbornly to persist in the idea that stamps are an essential feature in milling gold and silver ores screens with 4 mining engineer and metallurgist salt L ake ke city larger openings are being used three mesh being quite common and in at least one case two mesh screens is being employed this admittedly tends to increase the efficiency fici ency as a crusher the tendency seems to be toward stamps weighing around 1550 pounds compromising between the 1050 of a decade ago and the heavier stamp of the rand tube mills As all climers tube mills under the usual modern conditions of all sliming are of course practically indispensable but the dimensions seem to be almost as numerous as the number of installations it is generally recognized that in a mill of the old proportions or maximum efficiency is not even approached on account of the inability of a large proportion of the sufficiently reduced particles to escape from the tube the present idea is to get material through the mill rapidly classify the finished slime and regrind the oversize with this end in view mills have been installed w with 1 th unquestioned economy of power and still shorter lengths and greater diameters approaching pro aching the dimensions of the cylindrical section of the conical mill have been tried there ther e is of course a critical length somewhere beyond which it will not pay to shorten tile the tube varying no doubt with the character of the ore and conditions of feed in particular cases the proponents of the conical mill make the significant claim that no matter how this critical length may be improvement may he be had by supplementing the cylindrical portion with cones at each end chalmers and williams adjustable quick discharge is designed to the removal of finished particles and seems to have helped matters in some instances at one point in mexico experiment with a tube resulted in a remarkable reduction in per ton cost by simply crowding more than five times what had previously been normal feed through tile the mill the conclusion was that power consumption is independent of the feed while up to a certain point ultimate efficiency fici ency is proportional to the feed in several recent plants both conical and cylindrical mills have been installed the former as an intermediate crusher the latter as a grinder mechanical classifiers mechanical classifiers are as popular as ever and are used almost universally while there are a number of installations in this country where both the mechanical and diaphragm cone types are used side by side there is scarcely an instance where the cones are used exclusively on the other hand mechanical classifiers are gain ing ground 6 edine cacti a I 1 bacr aich which I 1 0 o or nver cla claims ims has a fine showing in thel their 65 foot shaft assays essays from which showed 39 per cent copper and 15 to 45 in gold at the property of the black rock copper mining alining 11 milling illing company of which walter james is the manager the tunnel is now in over feet with feet to drive in order to encounter the ledge of high grade ore that is exposed on the surface this property should be one of the big producers of the county lessees lessels on the 0 K mine of the majestic thines mines company were on the market with a car of ore last spring and another car is now ready for shipment the copper mountain property also shipped a car of ore in may the success mine belonging to I 1 cline has developed some good shipping ore map of beaver county 4 nor y tf Q t aj pi i acy u S t i i bew i mi i ri 1 s L based primarily on J V N dorrs simple contrivance the continuous thickener As a matter of fact the simplicity of the whole thing in theory as well as operation is responsible for its great success if a tank can be fed continuously at reasonable capacity with eight tons of solution to one of dry pulp and deliver a 30 or 40 per cent slime and a clear overflow which is being accomplished in a dozen instances it is easy to see how gold bearing solution can be replaced by a few repetitions of the process the problem of displacing solution with water is complicated by the necessity of caf limiting the amount of fresh water introduced trod into the system it is this last point largely which in some cases has made it advisable to include a filter in the process although there are several in atances where expensive filter plants previously installed have been forced into disuse the pulp from the final thickener is often discharged with moisture as low as 30 per cent and even with 50 per cent the loss may not be excessive when the diminished value of the contained moisture is considered i while the primary purpose of decantation is to displace valuable solution the extraction also benefits from the incidental ci agitation and application of fresh solutions it is possible to arrange any number of vari variations actions by which agitators and thickeners are put in series to best take advantage of conditions the solution to be precipitated can b be 1 e taken from any and it is possible sources of one of a variety small quantity comparatively to obtain a of high grade pregnant solution with an appreciable saving of zinc transferring solution experience seems to indicate that in transferring solution the air lift affords the best results while for slime the diaphragm pump appears to h have ave given most general satisfaction although air lifts and other used with varying i types of pumps have been success in the diaphragm pump power eon consumption is small a thick pulp can be handled and maintenance is principally confined to the replacement of rubber dia and if made these are inexpensive of the best material last for several months A simple scheme for regulating the duty of the pump is the placing of a small pet cock on the suction which can be adjusted to provide for any required amount of pulp new plants where agitation is conducted by the tc charge harge system have been rather conspicuous by their absence so that in the selection of agitators a very important consideration has been their performance when operated continuously in series in spite of all arguments to the contrary it is almost out of the question to prevent an accumulation in the bottom and along the sides of a pachuca tank with consequent reduction in capacity when operated continuously in one case a pachuca drained after more than a years operation was found with twenty feet of slime packed in the bottom with a two foot shaft through the mud leading to the bottom of the lift pipe still in spite of this and the other recognized drawbacks we find Pach being installed the hendryx agitator is subject to the same criticism only to a still greater degree the parral has been carefully developed and with a properly proportioned tank and a multiplicity of transfer pipes footing in an annular V shaped trough in the bottom sufficient current can be set up to keep the floor swept clean the parral also has the advantage of dimensions more easily adapted to a continuous countercurrent counter current system the trent seems to hold its own and users as a rule are with difficulty persuaded to the belief that any other agitator is its superior the machine however which seems to have been selected for the majority of recent installations is the dorr it has the great advantage of absolutely preventing any accumulation in the bottom and in addition is simple and affords satisfactory agitation the use of filters in new plants where filters have been deemed necessary preference has been all in favor of the continuous revolving types this is no doubt in a large measure due to the development of the decantation system where as a result of replacement with low grade solution in previous steps the washing of the cake is not so essential j a feature the function of the filter being beine I 1 largely the de watering of the pulp oper 1 acors of the oliver filters suggest a number f of essential conditions inattention to which s i may be the cause of indifferent results obtained by some users among other things the specific gravity of the pulp should be at least and preferably higher vacuum should be maintained at 25 inches there should be ample agitation in the filter tank J and the wash should be applied as an ail atom 5 zed spray the portland filter shares A favor with the oliver for similar reasons both are practically automatic in operation and with a system of continuous agitation and decantation the cyanide end of a large plant can be looked after by a single at i the kelly filter the kelly filter press has been installed in several new plants and the burt revolving pressure filter is receiving some at not a great deal has been heard of the butters and moore vacuum m types although each of course continues ts t handle immense tonnages ton nages of slime where thorough washing is essential proper clarification of pregnant solution previous to precipitation with shavings as well as with dust has been given closer at presses of various types leaf filters and filters and excelsior filters of dif ferent kinds are used one operator effects clarification by giving a bonus to his shift men for keeping slime out of the gold 1 tanks no matter how good his results this way it is probable that he could get better precipitation if he had a clarifier too de canted solution generally carries fine slime j no matter how clear it is to the eye A recent plant in canada has adopted a simple substitute for a press for collect ing zinc dust precipitate A long slender cotton bag of light material is incased encased in j a slightly smaller one of heavy duck A j series of such bags are fastened to small pipe nipples on the discharge line f from rom the precipitating pump the inner bag does the filtering and is burned with the precipitate the outer resists the pres sure and is reused until worn out the plan was first used some years ago in mexico lex but is novel and has manifest advant ages which might recommend for adoption elsewhere precipitation with aluminum dust has and a ne ile Z lived up to every expectation high grade mill at cobalt has been built along lines similar to the plant plan an in using aluminum as the precipitant of the tu te resting item here is the recovery by tran transferring S ferring 11 mercury from the residues to all a the washed cake on the filter leaves sol so additional vat and drawing a mercury then P vent through it the mercury is for reuse refining precipitate for refining precipitate either a ber atory or blast furnace followed in either case by is the method in vogue in most large plants A notable exception is the tonopah belmont where a large bulk of precipitate is smelted smelter at cost in a single operation by means of a direct fired monarch tilting furnace at a number of small plants it has been fig ared economical to ship the precipitate direct to the smelters shelters sm elters instead of refining at the mill A possibility which has been discussed and experimented upon to some extent is the recovery of zinc by distillation during or just preceding the process of melting elting m the precipitate A glance into the past reveals the time not long since when the presence of almost anything but free gold and sili clous ganke gange was thought to preclude the possibility of successful cyaniding cyan iding through rapid stages the process was developed to silver ores refractory tell urides heavy concentrates complex sulphides sulp hides of every description ores of cobalt and even silver bearing a product of blast furnace smelting smelling sm elting what will be next |