Show description 0 of of the daly west mi mill 0 11 park city cit y BY LEROY A PALMER talk to the average mill man about a concentrator that makes an extraction of per cent of the metal for which it is treating and he will laugh at yoa you but at the daly west mill at park city utah it is down in black and white that the saving of lead is per cent and of silver 80 to 85 per cent the latter in itself an excellent showing the mill which is situated under the same roof as me shaft house at the mine is the design of its superintendent erin mr F W sherman it contains much machinery which is his own design and it is due to his constant watchfulness and study of conditions that its high state of efficiency haz hae been reached the p plant 1 a n t or rather plants for as will be seen there are three of them are located on a hillside where gravity assists as much as possible in the flow of the ore through the mill the rated capacity is tons per day but this can and frequently picked from the belt by hand this belt discharges over a grizzly to a no 4 gates gyratory crusher whose product goes to an eleva elevator torto to be raised to the crushed ore bins the elevator dumps to an automatic scale which registers every 1000 pounds and thus shows the exact amount of ore run into the bins beside the m T J view of daly west mills Cour fety of parl city record has been increased the cars as hoisted from the mine are dumped into the storage bins which have a capacity of 1800 tons from which plunger feeders feed the ore to a heavy thirty inch rubber conveyor alongside of this conveyor are a number of small bins for receiving the larger pieces of waste which are gates crusher is a blake jaw crusher to which the larger pieces of ore are fed by hand if there is too much of this class for the gates to handle from the crushed ore bin the ore is fed by a plunger to a set of rolls which in turn discharge it to a which cuts out all pieces above 3 16 inch and sends them to a second set of rolls for furth further er crushing these rolls discharge to the first in the screen line proper and the pro cess of sizing the ore previous to concentration is begun in the arrangement of the rolls and there is a marked decature depa ture from the customary method in most mills one finds the ore sent into the screen lines before going to the rolls which are usually beneath the oversize which it is necessary to regrind is dropped to the rolls passes them and is elevated to the screen line a lift frequently of sixty to seventy five feet of both oversize and undersize at the daly west the ore passes two sets of rolls before entering the screen line proper the first in the main screen line has a free opening of 3 16 inch lit di discharges 1 I harges its oversize over size to a conical placed beneath and crosswise of the main screen line this has a free opening of 5 16 inch it discharges its undersize to a double bull jig with both side and hutch discharge and its oversize to an elevator to the second set of rolls by this arrangement only the ore which must actually be reground is hoisted and by placing the rolls just above the screens the lift is materially shortened being not over twenty five or thirty feet in the main screen line there are four the first as stated having a free opening of 3 16 inch and the succeeding ones of 18 1 8 inch 1 16 inch and 1 32 inch each of these latter sends its oversize to a double two compartment hartz jig the undersize from the 1 32 inch goes to a settling tub whose settlings go to a double two compartment hartz jig and whose overflow goes to a centrifugal pump to be raised to the classifying tanks the jigs make finished concentrates through all of the hutches and the two coarser sizes work also through a side discharge all are discharged over the tailboards tail boards those of the first two sizes go to an elevator which raises them to a conical watering de the 0 9 G V uit 41 11 1 7 T I 1 A AWL 77 4 Q 0 9 view of chincy cuincy and daly west courtesy of pari city record oversize from this goes to the middling bins and the undersize which is very little the being of fine mesh mash goes to the classifying tanks the from the next two sizes those receiving the oversize of the 1 16 inch and 1 32 inch are sent to a settling tub the overflow of this tub is pumped to the classifying tanks and the settlings treated in one of two ways it if the ore is rich they are treated on a filfly table on the middling floor and the table tails sent to mill no 2 for further treatment but if the ore is low in grade these settlings are sent direct to mill no 2 the tailings from the fine jigs go to the pump which receives the overflow from the settling tub which feeds these jigs and are pumped to the classifying tanks the de watered tailings from the two coarser sizes of jigs are fed from their bins to three five foot sherman centrifugal roller mills the sherman mill is merely a huntington with the spindles of the extending upward two feet feel above the yokes the opposite spindles are tied together by stout rubber springs which can be tightened by buck stays thus giving additional pressure between the muller and the ring these mills grind to 1 8 inch and send their product to the sherman classifying tanks there are four of these in mill no 1 increasing in diameter from six to twelve feet each tank is twelve feet deep with a cone bottom and a suspended drum whose depth is six feet and cro ss sectional area one half that of the tank the feed discharges into this drum and settles through it the coarser particles going to the bottom while the lighter rise to the top and overflow the rim into the next larger tanks where the process is repeated and in this way the feed is thoroughly classified A high pressure airline air line is connected to the discharge pipe of each tank to blow it out if it becomes choked up each of the first two tanks feeds three filfly tables which make concentrates tailings and slimes the are treated on the lower floor the tailings go to mill no 2 and the slimes to a centrifugal tri fugal pump which returns them to the classifying tanks the third tank feeds three and the fourth tank two wilfley tables these tables send their tailings to mill no 2 and their and slimes to the pump which returns them to the tanks the overflow from the last sherman tank goes to twelve rectangular settling tanks which thicken the pulp and discharges it through spigots in the bottom the overflow being pumped back as wash water the from the first first t two 0 groups of wilfley tables go 90 to a settling tub from which they are fed to five difley tables on the middling floor beside these tables are three sherman sl imers which treat the thickened slime from the rectangular tanks the sherman slimer consists of canvas covered panels on the same general principles as the wilfley slimer but the sherman is a smaller machine with a different head motion from the wilfley all rejections from the middling floor go t to 0 mill mill no 2 for further treatment mill no 2 the tailings from mill no I 1 are run in launders to mill no 2 where they are pass ed through a which cuts out the coarser sizes which are found to be barren and are consequently rejected the undersize from this is elevated to a con coni cal which sends its undersize to a sizing tank the overflow from this tank which is practically clear water is used to wash the rejected oversize from the first through its launder the settlings s from the sizing tank go to a double hartz jig whose tailings are further treated at mill no 3 the oversize from the conical is reground on a five foot sherman mill and sent to the first of a series of sherman classifying tanks the tailings from the medium jigs at no 1 are run to a sizing tank the settlings from this tank are elevated to fco the conical and re rewound round and the overflow goes to the first classifying bank tank at mill no 2 there are six sherman tanks which increase in diameter from three to fifteen feet each of the first three feeds an table and each of the second three a sherman slimer the overflow from the last sherman tank goes to a centrifugal pump which raises it to a series of nineteen sizing tanks round tanks four and one half feet in diameter and of the same depth the slime for such it is flows successively ces cea from one side to the other settling alln 0 a portion of the solid matter in each until by the time the last tank is reached the overflow is clear water which can be pumped back to no 1 and reused ahwash as wash water the settlings from these sizing tanks go to another tank of the same size which feeds a sherman slimer the overflow from the tank going to mill no 3 all rejections injections from the jig tables and climers of mill no ab 2 are further treated at mill no 3 mill no 3 mill no 3 is situated about feet from mill no 2 and somewhat down the afie hill hilf from it so that it may receive its feed from the latter by gravity the overflow from the last sizing tank runs to three square similar to those an mentioned I 1 in no 1 at the top of the mill these further settle the slime and fee feed d it to two tw sherman sl imers the overflow from the ese sizing tanks tank s is returned to mill no 2 from which it is pumped back to no 1 for reuse as a wash water the tailings from the concentrating machines in no 2 are run to a series of three rectangular whose overflow is pumped back for wash water the settlings from these go to a fourth which feeds a centrifugal pump the overflow of this sizer if any is wasted the pump mentioned raises the thickened pulp to a series of square sizing tanks of increasing size the first two of these feed two Wilf leys and each of the last two a sherman slimer the overflow of the last sizer is pumped back as wash water A horsepower hamilton corliss engine drives the two alternating current generators supplying the power for these mills mill no 1 has one 40 horsepower motor m c to the coarse crushing department and one horsepower motor to the remainder of the mill mill no 2 has one 40 horse power and one 15 horse power motor and mill no 3 one 15 horsepower motor general electric company induction motors wound for volts are used the assay of the final tailings shows that about per cent of the lead values have been extracted although this figure is partially an estimate as it hasteen has been found that with such insignificant values neither the wet nor fire assay is strictly reliable A point of interest to the practical mill man is ahe absence of all hydraulic classify ers all classifying simply being done by settling one naturally enquires also if the additional working pays an examination of the reports for a period of six months shows that a profit of per ton was made on every ton of ore run through mills two and three there is no crushing expense in connection with this treatment except for the five foot mill in no 2 and the machines are of such a nature and so arranged that the attendance required is small several factors contribute to the high efficiency of this plant the chief of these is the thorough working and reworking to which the ore is subjected with the attendant close classification needless to say careful design and close superintendence play an important part mining engineer salt lak |