Show concentration by CHAS FRYBERGER ME the subject of the concentration of base ores from their gangues gangnes has been gone over and has been threshed out so much that most people are of the opinion that nothing new can be said on the subject in writing this article I 1 do so for the benefit of the millman the man who has charge of the actual operation of the plant and who has to master the details of mill practice he is the man behind the machine and who gives the results that either swells the dividends or operates at a loss to the owner to these men I 1 say there is something new to be learned in up to date and improved machinery over the old methods that a great many of you are using but appreciating the fact that the majority of fillmen are tied to their work days in the year and have not the opportunity to see and study what other people are doing I 1 take pleasure in submitting the following for their consideration there is a certain amount of originality in every individual and that in going through the many reduction plants in the different mining districts fillmen will see these original ideas and by adopting these and applying them to their own particular cases will be able to raise the efficiency and saving of their respective plants from one to twenty per cent the main points of successful concentration are divided into three factors first proper crushing second perfect sizing and third stratifying there seems to be a tendency among mill men to think that almost anything will do to crush the ore which idea is absolutely wrong what is first needed is to positively know the ore and then crush to the size that will liberate five per cent or more of the mineral then concentrate at that size let it be whatever it may by using a progressive system of concentration where five per cent or more of the mineral is liberated using rolls to give a granular product which can be done successfully to forty mesh it will be found that excessive sliming of the mineral will be almost entirely eliminated then by using a system of sizing not classifying but sizing to an absolute size where the particle of mineral is as near the same size of the gangue as is possible to get it the diff difference arence in the gravities makes it an easy matter to separate w classifiers depend almost entirely upon the density of the particle regardless of its size and when these get to the concentrator there is no difference in their respective weights and the only reason they can be separated at all is the fact that the particles of gangue present larger surfaces to the current of wash water which washes a percentage off in most instances taking along too much of the mineral with it while I 1 appreciate the fact that to try to size with a screen finer than twenty mesh is not satisfactory there has been improvement along the screen line which makes its possible to screen ore to mesh without the screen becoming blind or giving any trouble whatever after the ore has been properly crushed making a granular product which can only be done successfully cess fully with rolls running at different speeds coarse rolls slow and graduating them to the different sizes to be crushed which would have to be determined by a thorough test of the ore to find how many sizes would be required and necessary to liberate not less than five per cent of the mineral then by screening to that particular size the ore is ready for the concentrators centra tors the coarser to the jiggs provided that it be coarser than eight mesh and the finer to the tables of which there are several different makes each manufacturer as a rule claiming for his table a superiority over all others but a thorough investigation should be made and a table selected having the largest capacity and giving the best results I 1 find that good mill practice is to return the head water and use it as feed water by doing this there will be a certain per cent of the mineral that is in suspension that can be settled in the sand bed of the table in the operation of any concentrator it should be borne in mind that the amount of water used should be only sufficient to keep the mineral alive and that an excess of water is very detrimental in making a close saving while above all keep the mill clean and tidy A conscientious hardworking hard working nan will more than save his salary by looking after the small details and by systematizing his work |