Show F the ti U S smelter electrostatic separating plant A PALMER the problem of the treat ement of zinc when associated with other ores has always been a perplexing one to the metallurgist when it is associated with ores being treated for lead or silver it makes a pasty slag in which some of the values are carried off and drives off a certain amount of silver by volatilization when iron or lime is associated with it it is equally al hard to effect a successful separation of the zinc the shelters smelters sm elters exact a penalty for all zinc in excess of a certain per cent in lead silver ores and refuse absolutely to accept zinc ores containing in excess of a certain per cent of lime or iron the elimination of the lime by concentration is an easy matter as there is a wide difference in their specific gravities but it has been a hard matter t to 0 separate the iron and zinc as they usually occur in the form of sulphides sulp hides of of which the specific gravities are very nearly the same several attempts have been made to accomplish com this separation the process of the grasselli chemical co uses very close sizing followed by concentration the blake marscher process struck the right note i when it tried electrostatic separation but it was found that the blake machines would not do the work under certain conditions of climate or at Mo biosphere sphere the blake idea was improved upon by devising an apparatus 1 that would at all times produce the proper conditions of electrification at the separating machines and the company dev devising sing the latter apparatus took over the patents of the other process this process was called the huff process and the company the huff Y IV j 1 7 25 r united states zinc mill photo ly leroy 4 palmar electrostatic separator company in a former article we described the preparation of the concentrator of the united states smelting smelling Sm elting company and in this we S shall ha I 1 take up the process by which these are separated into two products a lead iron product in which the zinc has haa been eliminated to a point well within the limit set by lead smelters shelters sm elters and a zinc product in which iron and lead form so small a portion of the contents as to give no trouble in smelting smelling sm elting for the zinc it has been found that when brought under the influence of a current of v very ery high voltage most of the sulphide minerals such as pyrite galena chaleo pyrite etc becomes conductive while the gangue minerals such as quartz lime quartzite etc are no not t affected zinc blende although h a sulphide is n not ot aff affected acted unless it is chemically combined with iron or manganese a condition that does not exist in the ores of the united states company the process is very simple in its principle and is based on the well known principle of static electricity that bodies charged with electricity of like signs will repel each other and that those charged with electricity of unlike signs will attract this principle is exemplified by the laboratory experiment ent of the pith ball and also by the attraction and repulsion of the opposite ends of the compass needle if we a a mixture of good and poor conductors to some surface charged to a high potential we s shall hall f find nd that the goo good d conductors will receive a charge of electricity similar to that of the surface and will be repelled while the poor conductors will not be charged and will therefore simply drop off the zinc iron lead are tram med by hand from the concentrator and as it is essential that when fed to the electrostatic machines they be absolutely free from moisture the first process is that of drying they are taken on to a hoist and elevated and dropped into the ore bins from which they are fed to a bartlett snow dryer rion from the bin the feed drops into a horer hopper ind and an eccentric works a feeder bacic and forth pushing a portion of the into the dryer with each stroke the dryer consists of two brick chambers one of which contains a revolving cylinder the chambers have a common wall and the cylinder is three by twenty feet this cylinder receives the feed and is revolved by a chain and drive at the rate of eight revolutions per minute the gases pass from the firebox into this cylinder and the dried ore drops from it to the boot of the first elevator A suction fan draws the gases through the cylinder and the second chamber before they discharge through the stack this second chamber acts as a collector for the dust which is removed as necessary and fed to the boot of the ele elevator av slack coal is used for the firing so that t the he fuel bill is kept to a low point the elevator discharges the to a series of three impact screens the first screen is of twelve mesh the second twenty four mesh and the third sixty mesh the oversize from the first screen is not sub subjected acted to any further treatment as it is almost all iron the percentage of zinc being so low that further separation would not be profitable the oversize from the second screen is designated as the A size from the third screen as the B size and the undersize from the third screen as the C size each separate size is discharged into a pipe to the boot of an elevator for that size and is elevated to the top of the mill to go to the machines where the actual process of separation takes place reference has been made to the fact that special mac machinery chinery had been designed for the process of electrostatic separation and before we take up the separation proper it will be well to consider this machinery al electrical machinery is placed in a room at the end of the second floor of th the emill mill here is an induction motor which is used to drive an alternating current generator belted so as to make 1800 revolutions per minute and at this plant generating to volts this current goes to a transformer which steps the voltage up times delivering a current of to volts this current is transmitted through a circuit chichis chis so arranged that the machines receive a current with the proper electrical conditions and one that Is not only free from all dis disturbing influences of climate and atmosphere but uni form and constant at all times this current has a very high voltage but a very low amperage and a peculiar feature of it is that a shock from it is not fatal a fact that was proved when an employed of one of the plants received the full force of the current for ten minutes before he was discovered and released A machine consists of eight one and one half inch shafts arranged one above the other something in the manner of a sectional bookcase the uppermost shaft receives motion from a pulley which it transmits by belts to the other shafts A felt brush bears against the back of each shaft to keep it clean in front of each shaft shaf t 71 i t ak M ac 4 11 WA T W A A N photo bl 11 haimof electrostatic separator U S smelter is an insulated electrode which is connected to one side of the electrical circuit tha other side being connected to the shaft the machines are made of iron and are grounded so that there may be no danger of the employed emp loyes getting shocked which although as stated is not fatal is nevertheless decidedly unpleasant between the electrode and the shaft and a little lower than both is a wood divider with a sharp edge which is adjustable by means of a hand wheel by this means the minerals repelled from the shaft can be divided at any desired point from froin those not repelled when the current is passing through the machine a strong electrostatic field is set up between the electrode and the mill the dried are fed to the machine by a pipe from the elevator and fall over the rolls in a thin stream the lead and iron being conductive receive a charge sl similar Vallar to that of the shaft and are strongly repelled while the zinc being nonconductive conductive non is not acted on by the charge and simply falls off or is brushed off by the belt brush by careful adjustment of the dividers the iron and lead can be thrown over very high grade while the zinc falls from one shaft to the other until practically all of the iron and lead are removed the machines are operated in units of three each on the third floor of the plant are five machines known as the roughing machines one for the A size and two for each of the other two sizes the roughing machines make rough iron and lead and rough zinc these rough products go to the next lower floor where two machiels mac hiens treat the tha product of each roughing machine here the process is repeated exactly as on the floor above but each finishing machine makes finished iron and lead or finished zinc as the case may be and a small amount of pro product duct the go to the boot of the elevator for that parti particular cula r size and are passed again over the roughing machines the finished iron and lead is hauled to the smelter and sintered for use as flux the finished zinc is shipped to the plant of the american zinc lead and smelting smelling Sm elting company at caney kansas the plant is now past the experimental stage and is running night and day besides the motor in the electrical room two induction motors are used one for the hoist and one for the elevators machines etc when running at full fuli capacity 50 56 tons and with the lights on the consumption con sump of horsepower is only thirty horsepower this process is an important one as the zinc in the ores of many of the western mines h has as been a source of gre great at trouble and owing to the pe penalties naltie s exacted by the smelters shelters sm elters of loss as well the daly judge has had this same trouble and has employed one of the methods mentioned in the beginning of this article the honerine had it and the miners of pioche and the coeur dalene face it now the electrostatic ro process is still in its infancy and promises developments as interesting as those already revealed it would be hard to overestimate its possibilities and it may be that this very process will be the means of resurrecting some of the failures of thip the past and alaci placing ng them in the list of dividend paying mines salt lake city utah |