| Show FRICTION PROCESS of ORE DRESSING OTTO WITT IN MINING MAGAZINE wi the question of the treatment of refractory ores is of much importance and has received considerable attention within late years A great deal of progress has been made in the methods of dealing with ores of that character the author in a pamphlet recently issued by craz and gerlach freiberg in saxony describes a method which has been elaborated by him and tested on a semi practical scale he claims that when the ores are crushed in which the mineral proper is softer than the gangue the mineral sticks to the grains of the gangue in the form of points the greater the difference is between the hardness of the mineral and that of the gangue the better this phenomenon will appear if for instance galena which is associated with or other spars is pulverized and in another case galena associated socia ted with hard quartz the points appear much better with the ore than with the spar ore in each case it is the soft galena which sticks as points on or to the harder quarts and never vice versa the method proposed by the author comprises three main operations namely 1 preliminary crushing of the material to suitable size or grain avoiding as much as possible the formation of dust or slimes 2 friction of the material thus obtained carefully avoiding the further diminution of i the harder material for the purpose of the gera test possible formation of slimes from the softer minerals 3 separation of the slimes from the materials of larger size briefly stated the method is carried out in such a manner that the comminuted com mass of ore is mixed evenly and a fine div division islon with a material the hardness of which is between that of the ore and the gangue and which have to have a suitable for this purpose iron is used the mixture is then thell subjected to a gentle rotating motion so that all the small parts of the mass rub against each other if this procedure is carried on long enough the softer material is ground down to very finely divided flour while the harder material retains its size clr 5 lR the finely divided iron which has b been eini mila ed with the mass is then taken out b by a mat ma 1 betic separator and is again used in III taj process the material obtained is separated in spitz kasten from which the coarser pa pap tides nicles are drawn off directly while the slina ore 1 is S collected in ponds sumps bumps or tanks n s the circumferential speed of the rota ing cylinder is very small and varies aa ac cording to the nature of the ore for copper coppe pyrites and quartz a speed of 03 to to 05 me ine should be suitable the length of taj thel cylinder also depends upon the nature 0 of the ore as does the diameter it is of th utmost importance that the interior surface surface of the cylinder should not be smooth and anil on that account the sheet iron walls of the cylinder are covered with cement into which sharp angular pieces of quartz aeme cement clinker and similar hard material are inserted the inner surface of the cylinder must mus have great hardness as well as a certain roughness the author gives a table of the mariom barlou degrees of hardness and the specific gra gravity of the most commonly occurring oreg oreas and minerals from which it appears that the following ores could be treated with advantage by a method similar to th that proposed by him copper pyrites and quartz which differ in hardness from 35 15 to 3 galena and quartz 45 copper pyrites and iron pyrites 3 to 25 zinc blende an and iron pyrites 27 to 23 galena and 35 to 3 9 galena and iron pyrites 4 galena and blende 17 to 13 and quartz 4 and quartz 6 to 65 on the contrary ores composed ot of copper pyrites and blende with a difference of hardness of 03 to 0 areno pyrite and quartz to 1 iron pyrites and quartz 05 and iron pyrites I 1 to 05 galena and cla espar 05 zinc blende and cal espar 08 could not be treated to advantage by this method in the last part of the pamphlet the author gives the r results of a series of experiments on various ores which shows the application of th thai process I 1 |
