Show REVIEW OF MODERN MILLING METHODS S H boylan salt lake city I 1 the benefits to be derived from the principle died by the flotation process as applied to ore dressing 6 r apparently unlimited two and possibly three vital acts have been established acas B first that the patent issued by our government patent abent office to the minerals separation company is valid the he validation of this valuable patent prove proved d the statement of one ne of the worlds I 1 greatest inventors to be true when he said receiving a letter patent from the united states patent office is is an introduction to the united states supreme court it is not known whether a desire to infringe b im prove or violate this patent was the motive the result is that reagents have been discovered which are claimed by the discoverers not to infringe the minerals separation company Ys s patents these reagents not only perform th the e same functions as oils they go farther and produce a selective action second the flotation process has made the recovery of fine particles of minerals of a known character possible the recovery of these fines is the first big step in that direction tion that has been made in years now that this step has been made it is up to our metallurgists not to abuse it by the excessive grinding of particles of mineral that tha t should be recovered by the well es established gravity methods third the recovery of these fine particles having za been established a method of producing them has p prompted the resurrection of a principle involved in the now obsolete stone drags or ar astras it is a serious question whether the metallurgy of the ores prompted the universal adoption of this new form of or the zealous inventor invent or and manufacturer I 1 the writer is inclined to belie believe ve that the latter latte r is is responsible to a large degree 6 this impression is is 9 gained and nd supported by the various various types on the mar market ket and the claims made by the advocates of these machines it is possible t that the zeal teal exercised by the advocates of this form of grinding has blinded the eyes of our rn metallurgists with capacities costs etc this can be easily accomplished dished by unceasingly riveting the thoughts on the grinding 7 machine and not allowing them to wander from it th this is is is a Z good principle from the manufacturers point of view the question arises can the same be said from a metallurgical and d plant cost viewpoint view point mineralogists inform us that in the major majority ity of ores there is is a point of s the mineral is freed from the gan galil 2 pt chis th this poin pons 11 Is naturally changed by the character common sense suggests sug ge ats that when the ore is is gj groua to that point brindi ag shourd cease and metallurgy finish binish the process the grinding binding rin ding of the ore is is one and jaci rea relegated gated to engineers following thaine tiny liine k trig separation ep 1 a ration of bf the mineral contents from the gangue angue is a metallurgical process and should be under the supervision of metallurgical engineers these eng engineers should dictate the grinding operations if our metallurgical engineers do not assert their rights the mechanical ch anical brothers are justified in grinding the mass toan to an impalpable pulp irrespective of the character of the mineral content old and new method of crushing it is not desired to convey the impression that fine grinding is not essential it is and combined with the flotation process can and should be adopted by the metallurgist me 6 or if some one does not defend our old grinding b b machines they will soon sink into oblivion th the e old reliable rolls whose efficiency has not been questioned have been assailed and their field invaded by the late machines and are threatened with annihilation the reputation of the old form of blake crusher has been impaired by the merciless advance of science and invention it is possible that all of these have been tried convicted and sentenced without a fair and impartial trial there is no doubt that if the grinding mills using screens screen s in their construction had received the support odthe I 1 manufacturers that was given the new type of mills the results from an operating cost viewpoint would be equal and the crushed product produce be far superior from a metallurgical view it is impossible to defend one without espos expos i ng the other to defend the old types it will be necessary to mention a few of the favors shown the new 1 the return circuit or circulating 6 load is an operation opera ion that is absolutely essential to the new form of brindi grinding ng this circuit is seldom below three and often as high as five times that of the original feed to the machine the equipment consisting of elevators elevator s classifiers and power to circulate from 1500 to 2500 tons of solids and an a n amount of bf water to accommodate a machine rated at tons of solids solids and its costs are not per day is a separate operation charged t against the grinder rinder where partial concentration is is used in the process rolls and screens are a re used to reduce the original feed to a concentration size this operation assists the fine grinding machine and the cost of ta this us operation is also not charged against the I 1 latter atter thus adding CI taits to its s efficiency the foregoing foregoing ore going b is a fair description of the processo ss 0 0 1 the fine grinding arin ding machines the effect on the mineral output can be surmised it is all ground around 6 to a degree of f me ness so that the coarsest particles are amenable to the f flo 1 0 tation process This being a fact fa ct it is reasonable to suppose that a per cent of the mineral often being I 1 subjected to this treatment bacon becomes ies so fine that it is beyond the pale of flotation and is relegated to the process for recovery no set method of ore dressing the there re are few set rules in ore dressing each ore is a problem in itself and it would be unwise unwise for one to attempt to even suo suggest gg est a set method we all agree agree 11 that it is good mill practice to remove the mineral ini from the gangue as soon as it is liberated taking this as a starting point stage grinding suggests itself then to car carry ry out the plan stage 6 follows when concentration is is concentration naturally natura ily used sizing and classification are absolu absolutely absolutes tel y essential this point is not open for discussion there are machines on are are claimed by their designers to products numerous atten attempt 1 an s have hake been mac alig this line I 1 venture to say thi th at an a n equal number of faiai leave been made I 1 will admix adath 1 ekit at installations of this charder cha raer er have been made and af aroen ol fi operation oper ope Arion ai d daill ai lai aimed ined t successful cess ful in the major majority ity of af cases eradication bation orsome of 61 soine some character has been resorted to on the tailings from these machines prior to the application of the flotation process this refinement was not essential the fine particles of ore were considered legitimate mill losses and no doubt the primary cause of the numerous monuments standing as silent reminders of a worthless mine and not the process used during this period the efforts of our mechanical engineers were directed towards grinding machines that would not produce fines the claim of one of these was the only way to save the fine ore is not to produce it pages could be written describing the success and failures encountered during this period at this time it was demonstrated that the shortest space of tinie time that the particles remained in the grinding zone the smaller the percent of fines produced it is needless to say that the old faithful rolls won all the laurels it does not appear consistent to grind the mineral fine simply because we have a method of savin saving it and emphatically not when it can be recovered in a coarse state at a much reduced cost and a superior marketable pro product duct produced the efficiency capacities and operation of rolls are too well known to devote space to them this also can be said of tro minel screens vibrating screens of various types have invaded their realm and possibly shown some improvement over them the standard types of circular internal feed revolving screens on the coarser sizes when water is is present are quite efficient down to 14 inch opening where the particles of mineral occur coarse the different products from a series of these screens can be treated successfully and economically on jigs 1 where the Mill mans grief comes in the undersize of the 14 inch screens is where the mill mans grief starts to successfully treat this mass efficient classification is absolutely necessary the binef inefficiency ficken cy of machines to effectively classify this product is the primary cause of lessening the popularity of gravity concentration machines and also increasing the demand for fine grinders this is the critical point in ore dressing at the present time the unsuccessful attempts to effectively effectively classify this product has prompted the mill operators to abolish all machines designed b to perform this function ind and relegate the entire mass to the merciless action of the fine grinding machines it is unnecessary to say that the successful operation of these mills is due to keeping the coarser and heavier particles confined to the action of the grinding b zone it is obvious that the mineral owin owing b to specific gr gravity amity is confined to this zone and not allowed allowe d to escape until it is reduced to such a degree of fineness that it loses a portion if not all of its it gravity and makes an ideal product for the flotation process pro cess should any coarse mineral escape the first treatment the classifiers used in the return circuit capture camtu re it and return it thus assuring a complete destruction of its gravity the present method of mining and transporting the ore to the mill produces an alarming percent of fines over which the mill operator has no control the reduction of the ore at the mill to a comparatively small size for concentration cent ration produces produce s fines under tinder the most favorable con editions dit ions adding the fines produced by fine grinding grindl ng those unavoidably produced has a tendency to overload load I 1 machines treating treatie b the fine products the results will t the efficiency of the fine machines will be lowered or r t mal mill tonnage reduced one authority on ore dressing has devoted years to 0 t t perfecting of machines which will successfully cover t isel el points in classification this article has pointed out I 1 ge e efforts and those of others along the same saine lines have i M been successful in retarding the increasing demand for fi afi dog oa grinding and flotation ina machines chines r admitting this to be true the question naturally aris what is the solution the answer is that an invest investing investigate ig gati will show that a large percent of the coarse minerals dd ai c barren sand now being Z treated in fine grinding machines ma chines c T be successfully treated otherwise in this manner the I 1 lo 10 I 1 of the fine grander will be lessened and the mineral rec ered at a lower cost it is an established fact that grav gra machines are highly efficient on products as fine as 60 mes me |