Show PRESENT STATUS OF differential FLOTATION by A W fahrenwald the rate of progress in the last three years in the development elop ment of differential flotation has been rapid beyond the realization of most people differential flotation is no longer a delicate and unreliable process but is now in wide use its safety is due to the wide use of chemicals which either depress or enhance flot notability ability by definite modification t fi of surfaces the extent of the development and reliability of differential flotation methods may be emphasized by pointing out that there are now several custom all flotation plants in this country treating complex lead zinc iron ores from widely separated mines while these ores differ in chemical composition and apparently in physical nature the various ores treated in such a plant are passed through the same crushing and grinding equipment and through the same flotation machines and flow sheet with only slight changes if any in quantity and kind of chemicals and oils added some of the development in differential flotation is due to intelligent research on the part of well trained chemists and metallurgists much of it must be attributed to empirical testing much aluch of the success in differential flotation is due to more cart care being given to constant conditions with regard to such factors as 1 fineness of grinding 2 density of pulp entering flotation machines 3 quantity and constancy of oils and chemicals added to the pulp and 4 place of addition of reagents and time of conditioning treatment of pulp with reagents 16 type of flotation machine it is not intended here to discuss flotation machines suffice to say that flotation equipment is better now than a few years back flotation engineers b generally have come to lo realize that the type of machine is not the controlling factor in differential flotation there are however efficient and inefficient flotation machines the most efficient machines are those that give intense aeration with finely disseminated bubbles and effective positive circulation of the pulp fineness of grinding that high recoveries and good grades of products were riot not obtained in much of the earlier flotation testing is to attributed to insufficient grinding the microscope crosco p e is largely responsible for showing us the li liht light b ht it 1 this regard some of the complex lead zinc iron ores are so intimately inter crystallized that no amount of grinding nill 11 completely liberate one mineral from the other many of i these complex ores now bein being C treated are ground so fine that 65 to 90 per cent will pass through a mesh im screen the he fineness of grinding required in milling some ores 15 w well 1 e 11 ll illustrated by a novel departure in differential flotation suggested and in use by the operators of a large mill 11 ll the lead zinc iron ore treated by an all flotation scheme heme carried about 10 per cent lead and 10 per cent zinc d the mineral to be di carded as tailing was chiefly heavy iron fon sulphides sulp hides unusually good grades of lead and zinc concentrate len cen were being made the tailings assayed between 15 and 20 per cent lead and about 25 per cent zinc the grind was about 70 per cent through gla mesh the company wished to reduce the loss of metal in the tailing screen T ore dressing engineer U S bureau of mines annes moscow idaho mr his article is a companion or follow up treatise on ore dressing dressing by Pah as printed in the last issue of the mining minim review brider uni the caption of present trend in flotation flow alow sheets and classification of flotation reed feed analyses of the flotation tailing over a long period of time showed that the bulk of the metal in the tailing was in the mesh sands the problem was to recover the mesh sands as free from other sizes as possible experiments using a CD C D type of classifier showed that a product amounting roughly to 30 per cent of the flotation tailing could be recovered assaying between 3 and 4 per cent lead and 4 and 5 per cent zinc this product was a true middling consisting of galena and iron pyrite and this middling well justified further grinding and treatment density and temperature of pulp differential flotation is carried out at dilutions ranging from 17 to as high as 40 per cent of solids 25 to 30 per cent of solids being the common dilution in best practice considerable sid erable emphasis is placed on the control of this factor in a number of mills pulp density indicators are in use and the operators are required to watch these closely such indicators are simple reliable and easy to install in most mills differential flotation is carried out at normal temperatures and slight variations apparently have very little influence on results however in in one mill handling bandling large tonnages ton nages and doing exceptional work temperature control is necessary the pulp is floated at temperatures of 28 to 30 C recording indicators are in use heating of the pulp for differential flotation is expensive and the company has been trying to find a suitable substitute for heating constancy of addition of oils and chemicals in differential flotation the best results are obtained when the proper reagents are fed to the ore pulp at a uniform rate per ton of water and ore treated much carelessness has been observed in the past in this regard at present well designed automatically controlled equipment is used to perform this duty there is little standardization of equipment for this work but in all of the mills doing differential ferent ial flotation the equipment is reliable place of addition of reagents the reagents employed in flotation work are of two types one being known as flotation controlling agents sn ana l the other as flotation agents flotation controlling agents are those substances or chern chemicals icalas of the inorganic c lass class that are added to the ground ore water pulp to add vigor to the of a particular mineral or to decrease the of a particular mineral flotation agents are those substances invariably of organic nature that cover the mineral particles with a film that permits them to be caught by the bubbles infected into the pulp another pio property perty of such substances is to lower the surface tension of the water thus permitting the formation of small bubbles and froth generally speaking the controlling agents should be and are added to the pulp at some point in the mill prior to the addition of the oils sometimes chemicals such as it is dumped into the mill feed litile lime are added to the ore as bins but as a rule the controlling agents are added to the fine grinding ball mills the oils if they are heavy and difficult to incorporate may be add added edwith with the controlling agents to the same grinding mill this would not seem to be good practice but it is often done again in many plants the reagents are mixed with the ore pulp in separate agitators the time of reaction required for contro controlling ailing agents to impart th the e desired change in sur surface face properties to th uie eq respective minerals present depends upon the ore being treated and the controlling agent found suitable for its treatment with avith most reagents and most products a conditioning period of one to five minutes generally is sufficient in the treatment of a collective float concentrate of two minerals A and B to be separated into A and B concentrates cen where say A is to be floated and B is to be suppressed a conditioning period of several minutes to a half hour may be necessary where sodium or potassium is the reagent it is fed direct into the first cell of the flotation machine and a conditioning period of any consequence does docs not seem to be required rougher concentrate the art of retreating the roughed off concentrate has improved greatly some plants practicing differential flotation are retreating as many as three times the rough froth concentrate which carries chiefly one mineral A and appreciable quantities of another mineral B this results in a concentrate high in mineral A but assaying low in mineral B and insoluble flotation controlling agents and flotation oils in flow sheets discussed in a previous paper on present trend in flotation flow sheets and classification of flotation feed published in the aug 30 issue of the salt lake mining review the letter A B C etc were lif used ed to represent the various minerals coni composing posing the ore to be treated we may now let these letters represent specific minerals and discuss the flotation controlling agents and the flotation a agents 6 ants that are conspicuously successful in present flotation practice such a list of controlling agents includes 1 soda ash asb sodium carbonate or sodium bicarbonate nacco NaH COa CO or trona a crude soda ash 2 copper sulphate CUS cosoi Cu SOi 04 3 sodium m or potassium cyanide naan or 4 sodium 5 or CS 2 6 lime cao 7 sodium sulphide naas 8 sulphuric acid fh HS 04 9 zinc sulphate 10 sodium sulo hite naasson NaaS NaS sOa 11 sodium hydroxide naoh 12 sodium silicate 13 potassium dl chromate K COT 14 sodium acid phosphate NasH POi 15 cement A list of flotation agents in general use includes 16 pine oils and pine tars 17 hardwood creosotes creo 18 19 coal tars and water pas gas tar oils 19 X C oke ice e NH 60 dissolved in 40 20 T T mixture or technically dichen t dissolved in nc 21 reconstructed oils for example one company uses a reconstructed oil made by heating in a still at a of 7 to 8 pounds for 8 hours a mixture of 1050 pounds blast furnace oil pounds pine oil and 60 pounds sulphur 22 solvent naptha typical examples of differential flotation the use of some of the above list of chemicals in differential flotation may be best illustrated by a few examples of their applications to various complex ores and the results obtained differential flotation of complex lead zinc iron ores the progress made in the last few years in the flotation treatment of the complex lead zinc iron ores of the country is one of the outstanding developments in metallurgy the selective flotation of galena is effected by the use of one of the following chemicals or combinations 1 soda asli ash 1 to 6 lb ib per ton of ore treated 2 sodium cyanide 01 to 02 lb ib per ton used in conjunction with soda ash dibasic sodium phosphate or lime about 2 to 4 lb ib per ton of ore 3 dibasic sodium phosphate 1 I 1 to 4 lb ib per ton of ore 4 sodium sulphite 1 I 1 to 6 lb ib per ton 5 sodium sulphide 01 to 10 lb ib per ton of ore 6 sodium or potassium lb ib per ton of ore the most common combination at present is the soda ash cyanide combination after the lead mineral galena has been floated the zinc mineral in one form or other is floated in nearly all instances by the addition of copper sulphate if iron minerals such as pyrite are present zinc sulphate is added ahead of the lead flotation cells in the tabulations that follow the quantities of reagents used are expressed in pounds per ton of ore treated example no 1 flotation treatment of miscellaneous complex lead zinc iron ores mixed results of assay of feed and products cu ag ansol fe an ab co oz elo ca co ve heads 24 42 43 80 34 I 1 cad flotation concentrate 22 39 zinc flotation concentrate 90 30 39 35 table flotation concentrate 34 98 26 tailings 12 38 06 4 kind and quantity of reagents used L lead cad flotation and zinc suppression zinc flotation sodium cyanide 03 lb ib sodium hydroxide 10 lb b sodium bicarbonate 30 ib copper sulphate 10 lb b zinc sulphate 05 ib barrett no oil 9 lb b barrett no 4 oil 3 ib pine oil 1 lb example no 2 complex lead zinc iron ore the following lowin 1 results are typical of the work being b done it t on one plant by use of the flow sheet no 3 in the paper 0 on n present trend in flotation F flow low sheets previously mentioned the reagents used are arc shown results result s of assay of feed and products cu ag ansol fe Z lb 0 0 oz elo co heads 41 27 1 0 13 j lead flotation concentrate 08 24 H 0 zinc flotation concentrate 58 29 56 5 18 1 table flotation concentrate 22 8 84 4 w bailin tailing 06 06 22 0 08 8 01 kind and quantity of reagents used treatment of coll collective active lead collective or bull bulk lead zinc zinc concentrate to 9 rive ive lead ua u a concentrate and zinc concentrates 2 lb lime 40 lb sodium cyanide I 1 ab sodium 01 lbs zinc sulphate 3 lb solvent naptha 03 lb sodium bicarbonate in ati example no 3 complex lead zinc iron ore other ore being treated by differential flotation the thema mineral to be rejected as tailing is chiefly siderite fhe flotation not flo zinc feed assays essays about 5 per cent lead and 5 per cent e per the lead concentrate carries 57 per cent lead and 1 cent zinc zinc and the zinc concentrate assays essays 4 41 1 per cent cen zinc and 80 per cent lead kind and quantity of reagents used lead flotation and zinc suppression zinc flotation lb sodium 01 lb sodium 0 35 lb I 1 sodium odium 01 lb copper sulphate 09 9 lb ab hardwood creosote rj pine oil 0 33 lb ab cleveland cliffs no 1 25 lb barrett no 4 oil hardwood tsara creosote rik cleveland cliffs no 0 o 1 example no 4 complex lead zinc iron ore in this ore as in example no 3 the mineral to be discharged as tailing is chiefly siderite the flotation feed assayed 44 per cent lead and 43 per cent zinc large scale flotation tests using 20 pounds of dibasic sodium phosphate and 03 pound of hardwood creosote cleveland cliffs no 1 gave a lead concentrate assaying per cent lead and per cent zinc without cleaning the concentrate in a second flotation machine example no 5 complex lead zinc iron ore assays essays of products and recoveries bb an ansol fe ag per cent clo oz recoveries head 45 1500 ag 90 lead concentrate 1000 ab 89 zinc concentrate an 70 to 75 iron concentrate tail reagents used lead flotation and zinc suppression sodium carbonate 1 10 to 90 lb and SS I 1 added to ball mill 10 to 02 ab sodium cyanide lb 11 ii head i i of flotation rougher zinc sulphate lb I 1 zinc flotation copper sulphate lb ib T 1 mixture 01 to 02 ib sodium carbonate 10 ib iron flotation sodium lb ib remarks the flotation is carried on at a pulp density of 20 percent solids and the grind is 1 per cent on 65 63 mesh and 70 per cent through mesh example no 6 complex lead zinc iron ore results of assay aib clo Z an n clo F fe e clo ansol oz ag head 1480 lead concentrate 1950 1537 zinc inc concentrate tail 1060 reagents used lead flotation and zinc suppression lb sodium sulphite 1 zinc sulphate lead rougher sodium J zinc sulphate 1001 1 sodium lead cleaner pine oil J zinc flotation lb copper sulphate 15 to 20 sodium zinc rougher pine oil copper sulphate lime zinc cleaner sodium pine oil example no 7 complex lead zinc iron ore results of assay clo ab clo an ansol 90 fe oz ag oz au head 68 f 7 lead ead concentrate 07 07 06 06 42 zinc inc concentrate 35 10 42 26 iron concentrate 20 16 94 19 tail 1 l 0 01 reagents used lead flotation and zinc Z inc suppression lb soda ash 05 coal tar and barrett no 4 oil 10 added to lead boughers rou ghers 4 to 1 mixture pine oil darmour Yar mour 05 05 barrett no 4 oil 02 sodium silicate 40 20 added to lead cleaners sodium 01 zinc flotation lb copper sulphate 10 sodium sulphide fused 20 j added to zinc c rougher calcin hydroxide 1 50 1 copper sulphate Z 05 0 5 added to zinc cleaner sodium 01 1 j iron flotation barrett no 4 oil 05 lb ib example no 8 complex lead zinc iron ore results of assay clo ab P b clo an Z n F fe e oz ag head 70 80 70 80 lead concentrate 10 zinc concentrate 60 tail 15 1525 25 10 reagents used lead flotation and zinc suppression lb sodium carbonate 40 1 sodium sulphide added to grinding mill J pine oil 1 added to lead circuit it sodium cyanide j zinc flotation copper sulphate 1 11 A T T mixtures 05 J added to zinc circuit example no 9 complex lead zinc iron copper ores in one plant treating complex ore the flotation feed assays essays as follows an ab 25 cu fe 30 S 84 sio 60 |