| Show commercial evolution in the treatment of lead zinc ores As worked out at the big international plant tooele thoele utah the following article by IV W C page E 31 superintendent of construction international smelting smelling Sm elting company tooele thoele utah was prepared early in the year tor for submission at the i annual miners convention in denver it is so full of information of value to the mine operator and complex lead sil ver ore producer as well as the metallurgist and mill man that its reproduction here Is considered pertinently worth while ed at the introduction of this paper I 1 wish to call your attention to what will certainly and most noticeably be evident throughout this discussion and that is the following while I 1 will attempt to point out and emphasize the general economic benefits resulting from the partial solving of this complex lead zinc ore problem which I 1 am certain will be self evident before I 1 am through it will appear that I 1 am limiting my remarks to the practice as followed at the tooele thoele lead zinc concentrator of the international smelting smelling Sm elting company I 1 am more or less forced to do this for two reasons first that I 1 have been intimately connected with this operation since its inception and consequently am more familiar with its practice than any other and second that the tooele thoele concentrator is the one and only plant operating operant op entirely on mixed lead zinc ores on a strictly custom basis which naturally furnishes an extremely wide field of study and observation it is requested that in those instances where the thoele tooele ic concentrator or the international smelting smelling Sm elting company jr r to go farther the anaconda copper mining company is brought into too much evidence that those remarks which seem to be too personal will be considered and taken merely as an example of what ma may y be and is successfully being 6 accomplished trusting that this preamble pre ample will be taken in this spirit we will proceed basic reasons for tackling problem basically there were two main reasons for our starting riff work on the problem of working out a successful operation operatic ope ratio 0 n for the separation and concentration of the values contained in the rather widespread deposits of those so called lead zinc ores 1st ast that the time was ripe and demanded some method of curtailing the eco economic homic waste resulting from the costs of the past and present practice of smelting smelling sm elting ores of this character or rather those ores which could stand the charges inherent with smelting smelling sm elting them and secondarily but rather emphatically primarily with us the belief that such a solution would greatly increase in general production of lead in the district tributary to the salt halt lake valley As most of you probably know there were three relatively large lead smelting smelling sm elting plants in the salt lake valley and the decreasing production of relatively clean lead ores was not sufficient to justify the existence of these three plants we ae could not hope for better lead smelting smelling sm elting metallurgy nor more efficient business management than was being practiced so the only outlook was to attempt to work out some way to increase the primary production and widen the scope of operations Wasteful Cost of old methods to give you some idea of the waste due to smelting smelling sm elting these zinc bearing ores direct it is conservatively estimated that at least tons of metallic zinc per year were being carried off in the slag at the three plants in the salt lake valley without even considering the colorado smelling smelting sm elting g operations it is safe to say that in addition to the loss of th this Is zinc it was costing approximately three fourths of a in mil il lion dollars to buy fluxes to carry this zinc over and above what it would have cost had the zinc not been present but the meat of this last statement is that this money came directly or indirectly out of the producers settlements due to the nonpayment non payment for zinc and in addition the penalties incident to the cost of handling the ores being treated in this way it might be well to briefly explain the reason for these zinc penalties it has been found through long years of experience that the addition of zinc to a lead blast furnace charge introduces metallurgical difficulties and economic losses which must be compensated for in the purchase of the ores which carry appreciable amounts of zinc As the zinc in the charge increases the type of slag made must be altered to accommodate the zinc which will become bedonie a constituent of it this change in type of slag must include a lowering of both its silica and lime content and an increase in its iron content this necessitates in a district where the ore supply contains an axce excess ss of silica over iron the purchase of barren barre niron iron flux of some kind this iron flux is considerably more expensive than the lime flux it replaces and in replacing silica it crowds profitable metal bearing material off the charge also the higher iron lower lime and silica slag made necessary by the high zinc will carry more copper and silver values th anthe lighter flags which can be made with lower zinc metallurgical difficulties arise when high zinc flags are made due to the fact that the ill effects of other undesirable elements such as arsenic magnesium etc are greatly magnified when they accompany high zinc these metallurgical lurg ical difficulties cause economic loss through their effect on furnace operations causing a decrease in tonnages ton nages smelted smelter and an increase in slag losses and production ot of furnace also the presence of large amounts of zinc sulphide in an ore require additional roasting over ores high in in the other sulphides sulp hides only as it is absolutely necessary that almost all of the zinc be oxidized before it is put into the blast furnace or very serious metallurgical difficulties will te de encountered when considering these many factors which make zinc so undesirable to a lead smelter it is not to be wondered at that the miner is penalized for excessive zinc in leadore lead ore ores and that the smelter as well as the miner welcomes avith open arms a new metallurgy which will turn his tornie fornier troubles into future profits 1 these facts mentioned besides others not mentioned menti oneo are all reflected in the treatment rates and penalties quoted for lead zinc ores in one way or the other but they event I 1 ally come home to the producer in his settle settlement ment sheets might mention a great many other features in this conne tion but this is supposed to be a paper on new and I 1 will gelback get back to that beginning of research work j our concentration was dished testing department i ie the e in march 1922 and the preliminary work was started ia first difficulty experienced was in obtaining representative P samples of the class of ore which we wished to work wor j the character of the ore as mined for shipment to lead i smelting smelling sm elting plans differ differed cd so widely in ill physical prope arties it more or less irrespective of their chemical analyses that tn was difficult to form a definite opinion as to the possie pos pa sib good y ties of working this out on a custom basis illis co operation cooperation from the producers eventually corrected correct ed trouble however and was evidence of their good willand will and hopes the next apparent grief was the iron content of the ores under consideration compared to more or less successful operations carried on at that time in those few cases where lead zinc mines had a mill treating their ores by selective notation flotation and gravity methods while the ores of sun and simon silver lead assayed from three to five per cent iron the ores which must be treated in our district averaged from eight to twelve to eighteen per cent iron as pyrite iron As pyrite had always been the main of zinc in a zinc concentrate as to grade and oftentimes a penalty in a zinc smelter schedule it was evident that this was to be the outstanding stumbling block of the entire problem after getting the lead zinc separation fairly well worked out in the laboratory by the more or less hit and miss method of reagent combinations it was not until august 1923 that consistent results could be obtained on the lead zinc iron separation the next year was spent in checking and rechecking our laboratory test work and by july 1924 we had gotten results that justified operation on a commercial scale our initial installation was a unit having a daily capacity of five hundred tons of lead zinc ore operation of this started on november 1st ast 1924 before this was in operation it was evident that additional capacity would be necessary if the laboratory work wash was upheld it is not necessary e to go further into this than th an to state that a second unit of tons per day was put in operation on february ath 1925 following this an additional ton section was wag started in operation on may 1st ast 1925 this brought the plant up to 1000 tons lead zinc ore capacity at which it has hag been maintained most of the time methods of purchasing ore explained before I 1 get too far I 1 wish to explain the method we follow in the purchase of ores for this lead zinc operation it is evident that the treatment of 1000 tons a day by selective flotation of lead zinc ores of widely different origin analysis and physical characteristics calls for a different practice an attitude in ore purchasing that has been practiced to quite an extent in the past in the case of smelting smelling sm elting ores in the buying or selling of ores on a smelter schedule the only thing taken into consideration is the actual assay value of the ore based entirely on its analysis however irl in the purchase of ores for custom lead zinc selective flotation the actual assay of the ore might be said as being merely an indicator of its apparent value the vital feature upon which rests the decision as to the purchase of an ore is its amenability to selective flotation two ores can be of practically identical analysis and upon testing one will be found to be readily amendable to flotation treatment while the other will show no tendency to respond to the same identical treatment for this reason all new ore purchased for our lead zinc operation is based entirely upon laboratory tests with some slight deviation or interpretation of the results as gained by experience the structure of the schedules upon which the ores are purchased ar are e also based upon the resu results its of ther the laboratory test work our first start on an ore is to obtain from 50 to pounds from the prospective customer which we hope will be representative of his shipping 1 grade in case this ore works out well in the test work a contract for 1000 tons is offered based upon a schedule which continues in in effect in case the resultant shipments live up to the sample this 1000 ton contract answers two purposes first it checks up on the grade as represented by the original sample sampie and second it gives us a chance to tx try it out under tinder operating conditions conditions so as to check our previous pre previous s test work jas as to its amenability also it enables the miner manerto to deter K mine fairly accurately what he may expect from froin his mine as to future production it is needless to say that such procedure in the purchase ot of lead zinc ores for custom treatment necessitates the clo closest s operation cooperation co between the ore purchasing department and the concentration department without that it is difficult to anticipate what the results would be the fact that the he metallurgical amenability of every new ore tested has to be passed on by the concentration department more or less puts that responsibility in the proper hands local ore handling all lead zinc ore coming into the plant goes through our automatic sampling plant for assay determination in this way all coarse crushing is done in the sample mill with the one exception which I 1 will note later from the sample mill the ore is conveyed to what we term our bedding bins here the ores are segregated and disposed of to these bedding bins more according to its concentrating properties than to its assay the ores as contained in these respective bins are then withdrawn on apron feeders and delivered on to the main bedding belt simultaneously resulting in a uniformly bedded mixture this bedding may be considered practically identical with the methods employed in bedding smelting smelling sm elting ores and fluxes especially as regards the desired object in order to take care of the current surges of receipts it is necessary that stockpiles stock piles be maintained an attempt is made to limit the multiplicity of stockpiles stock piles and we really depend upon one stockpile made up of a mixture of two or three ores this can then be picked up and sent to the mill and treated as the regular bedded custom mixture it might be well at this time to explain what is meant by custom mixture or custom milling as we practice it it has been the popular saying and general belief that every ore required its own and individual treatment process for its economic concentration especially when employing flotation this statement I 1 believe has been pretty much disproved as will be evident also a custom concentrator in the old sense of the word used to be in reality a batch concentrator cen that is I 1 mean one in which one lot of a particular when finished lot of different ore was run through and a ore was treated and so on each of these operations called generally for a change in conditions and no uniformity was maintained naturally there was some sacrifice of efficiency and recovery by this method due to the inability of the average operators to quickly adapt themselves or their visual judgment to such rapid changes or conditions now just for this reason mainly and also to take care of the wide range of shipments we were you might say forced to treat the ores as received as a uniform and homogeneous mixture of the various ores to point this out clearly I 1 will give you the tabulation from a few daily concentrator reports selected more or less at random which represents the tonnage of the re respective spec tive ores treated at the concentrator in one section in in one day 7 ores 3 01 potosi D W lynch park utah bin binham bingham C ham meta metals as aou utah apex falcon utah delaware J here is another 7 ores oies I 1 D W lynch 90 0 park utah t Q bingham metals Q utah apex e Q akron mines Continue djon dion page continued from page 1 15 5 bell leasing 2 7 1 utah delaware 0 here is another 6 ores and 1 middling akron mines leadville L mines 2600 park utah ontario utah apex U S mines 70 70 P C here is another 9 ores and 1 middling falcon potosi 11 1 ontario park utah 1790 0 atlantic cable parthenay Par parth thenan enan 90 akron con copper mines shamrock 40 1 11 I 1 P C middle I 1 will say however in this regard reg ard that wedo make a fairly definite segregation of some ores for separate section treatment this is due primarily to some peculiarity of some ores for separate section treatment this is due primarily to some peculiarity of some individual ores such as partial oxidation this is being done now and anticipated more so in the near future more for the purpose of admitting additional ore which may have been reject rejected ea previously on account of its characteristics this custom ore mixture as made up in the bedding bin bins s is then ready for the concentrator in some cases other concentrator cen feed in the shape of gravity zinc is loaded onto these cars of custom mixture with a locomotive crane before being sent to the concentrator in any event the loaded cars are delivered to the concentrator dumped and |
