Show I 1 selective flotation of lead carbonate ores successful ful at the shattuck denn property bisbee district arizona by I 1 H stanley the bisbee district is the largest producer of lead in the state of arizona most of the lead ore comes from the mines of the phelps dodge 6 corporation and the Sha shattuck denti denn mining alining corporation up to date most of the lead ore mined has been a ore carrying 6 native gold silver chloride and carbonates oxides and sulphates of lead the bulk of the lead produced has been from direct si sm elting ore the first concentration of lead carbonate ore in the bisbee or warren mining district cochise county arizona was begun in the concentrator of the shattuck arizona copper company in august 1918 under the supervision of glenn L allen alien who worked out the metallurgy and supervised the construction of a concentration plant it was july 1919 before satisfactory recoveries of lead and silver were obtained by tabling and notation flotation the concentrator was operated continuously from july 1919 to december 1 1920 when both the mine and mill were closed down A description of the flow sheet equipment then used and results obtained are given in an article by glenn L allen alien published in the engineering mining journal of of october 16 1920 during the year 1920 there was treated approximately wet tons per day in the shattuck concentrator from the shattuck mine and the average heads tails and recoveries for that period are shown by table no 1 gold oz silver oz lead to tails 2272 concentrates 2299 heads per cent recovery the ratio of concentration in 1920 was to one on the 1920 flow sheet the best recoveries were obtained when the lead content of the combined table and flotation concentrates were approximately 30 per cent while production of ores was resumed by the shattuck mine in february 1923 due to the early termination of the pittman act which ran out in june 1923 and the expected low price of silver to rule thereafter the concentrator was not operated until april 1925 experimental work begins As the decline in price of silver after the pittman act terminated more than offset the profit that had previously been een obtained from concentration concentrating ratin 9 lead ores experimental work was begun in the hope to i improve results sufficiently to overcome the reduction in price of silver the lh research work was done by the shattuck company the me minerals separation company and the southwestern eng meering gme ering corporation and by march 1925 it was be lieveld that more satisfactory results could be obtained by h had straight E flotation of the low grade lead carbonate ore than ad been obtained previously by tabling and flotation therefore operations under the supervision of I 1 H t stanley niamey mill superintendent were resumed at the concen balor 01 on april ril 14 1925 and a revised flow sheet was rn y 1 out by september 1925 and operate operations 0 ns have continued P up P to date ate on flotation only there has been eliminated tables the screening ahead of tabling the primary mi the re grinding the secondary tables the allen alien cones Purn of ping for r re e grinding the sand tables and the thickening the pulp ah ahead ead of flotation the changes resulted in se superintendent nten dent b shattuck denn mining corporation in a ning presented con at the meeting of the arizona chapter american contress iress bisbee arizona september 13 and 14 milling costs nearly one half as well as improvement in in gold and silver recoveries present milling methods no change has been made in the crushing and storage of the ore nor rearranging 6 of the mill equipment from the coarse ore bins the ore is conveyed and delivered to a no 5 Tel smith gyratory crusher which delivers to a 4 ft x 5 ft hummer screen the oversize of which is delivered to a set of 42 in x 16 in traylor rolls in closed circuit with the hummer screen equipped with a screen cloth havin having 6 one half inch openings the undersize is delivered to the mill storage bins from the fine ore bins the feed is delivered by disc feeders and conveyed dry direct to two 64 in marcy ball mills where it is ground in closed circuit with dorr type C drag classifiers to 95 per cent through mesh the pulp is delivered at around 26 per cent to 28 per cent solids direct from the classifiers to one 8 cell groch machine where a primary gold silver lead concentrate is taken and run to the dorr thickening thickening tanks for filtering about 45 per cent of the gold and silver and 20 per cent of the lead is obtained in this concentrate the tails from the groch machine are delivered to a single groch cell which is used as a mixer for the application of the sodium sulphide and oils ahead of final flota notation and the feed from the groch mixer passes by gravity direct to four sin single gle spitz K K 10 foot notation flotation machines where a high lead low gold silver concentrate is produced and nd sent to the dorr thickening tanks and the tails delivered by gravity to one double spitz K K 10 foot flotation machine A secondary concentrate is taken from the double spitz machine and delivered by pump to the head of the four K K machines the tail from the double spitz machine goes to waste when the lead content of the feed is low an alternate method is used to maintain the grade of lead silver concentrates A rou rougher her concentrate is taken from the four K K X single spitz machines and sent by pump to one single spitz KAS K K machine for cleaning the tails from the cleaner flowing by b gravity to the head of the four K K machines the concentrates are delivered by a 3 inch diaphragm pump to one 8 foot diameter by 6 foot face oliver continuous filter the cake from the filter falls into a concrete bin from which it is loaded by shoveling and mine cars into the railroad cars for shipment to the smelter at el paso texas there is no drying of concentrates after filtering principal factors governing recoveries the principal princia a I 1 factors that govern satisfactory recoveries are fine grinding water of the proper alkalinity proper pulp density to the flotation machines selective flotation reagents of certain proportions and skilled operators proper grinding 5 to 12 or 14 mesh would release about 60 per cent of the lead for tabling and to 60 mesh would release the lead sufficiently for flotation however g grinding binding to 95 cent through mesh which gives a product of 75 per per cent to is necessary to re release lease the gold and silver which is associated principally with the silica gangue therefore as it is necessary first to take off a gold silver concentrate one grinding is made of the total feed to approximately 95 cent through mesh per the character of the water used is is very important the best results are obtained when the total alkalinity is 13 grains per gallon an excess of iron in the water is detrimental to both lead and silver silver recovery if mine mine water is used containing copper in solution the silver recovery is poor the use of sodium sulphide or sodium silicate or both in the circuit leaves a certain amount of gangue and reagents in suspension in the tailing water while the water can be reclaimed claimed re and reused re used by settling with lime there is required an increasing amount of lime and eventually a stage is reached when the lime has no effect the only water now reclaimed is that obtained from the thickener tanks the amount of new water used is approximately gallons per ton ion of ore experiments seemed to indicate that th the e use of reclaimed water settled with ferrous sulphate improved the lead recoveries but lowered the silver recoveries eventually to where the loss in silver more than offset off set the gain in water saved and additional lead recovered reagents the reagents that give the most uniform results and the best recoveries of gold silver and lead are sodium sulphide sodium silicate lewis tar and no 70 frothing oil the quantity required of each reagent varies varies continually and the recoveries obtained depend upon the skill of the operators in applying the reagents the average quantity of the reagents used is shown by table no 2 per ton ore sodium sulphide 20 lbs sodium silicate 20 lbs 1 lbs lewis tar 10 lb lbs s no 70 75 lbs the sodium sulphide and silicate will vary a half pound either way from the average the lewis tar will vary a fifth of a pound the no 70 about one tenth of a pound the is practically uniform the use of seems to steady the results no marked improvement in recoveries is obtained by its use other than possibly in gold the podium sodium silicate and part of the tar and oil oils is put into the ball mills the sodium sulphide and remainder of tar and oil in the mixer following the groch flotation machine recoveries on revised flow sheet on the revised flow sheet adopted and using the reagents specified the results for the month of january 1926 are shown by table no 3 I 1 gold silver lead ratio heads tails 55 per cent recovery concentrates these results are according to mill assays essays which achl check eck reasonably close with results based on smelter returns the ratio of concentration depends on the lead content of the mill feed it is difficult to produce a combined concentrate cen higher than 45 per cent lead the recoveries of all metals are about the same on a concentrate up to 40 per cent lead regardless of the ratio of concentration A 40 per cent lead concentrate apparently cabbe can be made with as good recovery on a 4 per cent lead head as on an 8 per cent the gold tail is fairly constant up to a head content of one half ounce the silver tail is not constant even on a uniform head content however the silver tail rarely exceeds 25 ounces even on a 12 ounce head there is a gradual rise in the lead tail with the increase in lead content facts not previously known some of the matters that have been proven since operations were resumed i in n april 1925 using selective flotation instead of tabling and flotation are as follows 1 that equal recoveries can be obtained by strai straight notation flotation as by tabling and flotation 2 that better recoveries and a higher grade concen can be obtained by selective flotation 3 grinding 95 per cent through mesh is sufficient to release the gold and silver as well as the lead for flotation 4 that the recovery of the gold and silver does not depend upon finer grinding but upon proper reagents 5 that selective flotation is as cheap as tabling and flotation 6 that a delay after the application of sodium sulphide before flotation is not necessary 7 that thickening of pulp ahead of flotation is not necessary to good results 8 that violent agitation in flotation is not necessary to good lead recoveries but appears necessary to obtain satisfactory is gold and silver recoveries 9 that the use of sodium silicate reduces the amount of sodium sulphide required and makes a higher grade concentrate cen the flotation of lead carbonate ores seems to beas be as much a matter of experience and skill of operators as the type oi of flotation machines however it is believed that machines which de depend as much upon mechanical agitation as on air are the best for the flotation of lead carbonate ores the principal advantage in milling the low grade lead ore from the shattuck mine is the profit made from the direct smelting smelling sm elting ore of high grade lead copper and gold that is is found as the milling ore is mined the concentrator of the shattuck company treating a lead carbonate ore containing gold and silver by selective flotation is the only one of its kind the recoveries obtained are equal to or better than obtained elsewhere on lead carbonate ore using straight flotation or tabling arld and flotation |