Show J vi THE SMELTING OF LOW GRADE ORES i IV to AW W orb ia j 1 l S E bretherton in E and M journal j v 1 ITH a present and prospective capacity of 2100 tons per day of raw ores smelling smelting sm elting a in this state is a topic of large present interest and the inquiry is often heard what is smelting smelling sm elting and which chich classes of colorado ores are suitable to that process mr S E bretherton in a special article answers this question clearly the following extracts are from his article NATURE OF SMELTING smelting smelling sm elting is the utilization of sul aphides as both flux and fuel the metallic bases excepting copper uniting with the silica to form a slag ID and the copper acting as a collecting agent to gather the precious metals into a copper matte the sulphur uniting with the oxygen of the blast to generate heat just as the carbon from fuel does some of the first questions asked by parties contemplating the erection of a matting furnace for the reduction ion of a great variety of ore especially if it is to be a custom plant are first can as high a percentage of the values gold and silver be saved with copper as with lead second can the ore be smelted smelter as cheaply as with lead third can as many tons of 0 ore re be put into one ton of shipping product as in lead fourth can copper matte be sold as readily as lead bullion fifth can as factory re ore be smelted smelter as in lead smelting sm elting eltina sixth can as cheap a slag 0 be made seventh will the ore require more preliminary li crushing and roasting eighth will a plant of the same capacity cost more than if the ore is to be smelted smelter L in a lead furnace ninth Is the matting process as ble able for as many different characters of ore tenth will the copper coppe r matting process cost more or less than smelting smelling sm elting ore with lead for a saving agent question no 1 can be answered positively by stating that the writer who has been in the lead smelling smelting sm elting business twelve years and the copper amel smelling smelting sm elting birg business five years as superintendent and metallurgist in both cases found that after introducing his large heated m matte atte settling arrangement there was no loss of gold slightly over one percent loss of silver and an immense gain in copper coppe over rover the dry assay and only a slight loss from the wet assay this was done at a custom plant which is astill still running where the ore was all purchased sampled by the regular combing and abd quartering methods an and d assayed the concentration was from eight to fifteen tons into one ton of 50 to GO 60 per cent copper matte first operation SULPHUR AS FUEL second if the ore contains sufficient sulphur ul to act as fuel and hot blast is used the ore can be smelted smelter for less than half the regular secrular cost of lead smelling smelting in fact for about what the preliminary rolling and roasting alone costs in lead smelting smelling sm elting third As 1 13 0 per cent lead is about the minimum amount which can be used in lead smelting smelling sm elting and do good work eight tons fons into one is about the best concentration but in co copper smelting smelling sm elting one or two per cent copper in in the ore can be the minimum amount and do good work and the concentration is that much greater accordingly fourth there is a greater demand at the present time for copper than for lead fifth on account of the more rapid smelting smelling sm elting of the charges in the blast furnace greater heat and more slag as a rule much more zinc can be smelted smelter without trouble when matting than in lead smelt ing i n g sixth on account of being able to force more silica and zinc in the slag Z it costs costa less for flux seventh As there igno preliminary roasting required if hot blast is used nothing but an ordinary coarse crusher is required for the largest lumps eighth A ton plant where all the ore would have to be roasted unless roasted in in heaps and then there is the capital tied up for months in tha ore if hot blast is used so as to dispense with fine crushing and roasting can be built for about one third the regular cost ninth on account of being 1 able to make a greater variety of slag without danger of serious losses when co copper matting it is suitable a ble for a greater variety of ore excepting ore rich in lead which auld should go a regular regula r lead furnace tenth on account of the advantages just enumerated for smelting smelling sm elting it does not dost cost more inore than one third to one half the ordinary cost of lead smelting smelling sm elting of course if cold blast is used and ordinary matting resorted to the system has but little advantage over ordinary lead smelting smelling sm elting excepting that it requires less copper to save values than it does lead and a more slag can be made when matting CLASSES OF ORE NEEDED the question comes up what ore is suitable for smelting smelling sm elting or as I 1 w would call it semi smelt smelling smelting sm elting imi the ore should contain sufficient sulphur r to make the desired matte necessary for clean work in the first ope operation ratio n using fuel then as the sulphur is in excess oi of the amount required to form the matte the percentage of fuel can and should be reduced in the blast furnace so th that at the oxygen I 1 from the blast will unite with the sulphur and not carbon quite often in my experience after using b hot ot blat blast when n the matte got over 65 per cent copper copper too t rich for clean work the for foreman eman would add A either more coke or more sulphide ore to reduce the grade of the matte I 1 found mix m esthe tur tures the lime usually has to be added ol f 3 cent and over 20 per copper to 30 per percent cent iron 8 to 13 per cent lime up to 10 per cen cent zinc 30 to 36 per cent silica 10 to so 30 per cent sulphur the safest limits the n original ore may carry a very high per ce cent t of zinc or sulphur but the percent percent ages are reduced by the time the ore is fluxed that is the excess of bases properly neutralized with silica of course too much zinc is objectionable but it can be utilized to better bel ter advantage as a base in copper smelting than in lead smelting smelling sm elting in fact zinc blende seems to give less trouble in a blast furnace with hot blast than when roasting 1 in a ber atory furnace as it requires so much more heat to liberate its sulphur than when roasting C ordinary pyrites and it most mast be with hot blast that the oxygen not having to unite with fuel has a better chance to combine with the sulphur where such an intense heat exists as in the blast furnace of course at times when it is necessary copper as low as one per cent will answer to save the values some metallurgists claim that no copper is 13 necessary and an iron matte will save the values and mixtures containing muth much less iron and more silica can be melted to better advantage than those I 1 have named but it will make these notes too long to go into the question of the different combining powers of each base with silica and wh when en each should be added or reduced on account of the specific gravity of the proper slag to be made for matte settling purposes VALUE OF THE HOT BLAST the object of my researches has been to secure a hot blast which would furnish the air heated to a sufficient degree of heat to prevent chilling at the same time increasing the capacity of the furnace and minimizing the use of fuel and to accomplish this witt without out any additional cost for operation this I 1 have been able to do by what is known as the bretherton hot air apparatus in constructing this apparatus I 1 have kept in mind the principal features required for its successful operation doing away with the back pressure on the blower so that the volume of air would not be minimized taking the heat from the escaping heat of the hot slag by building r all oven around ar aund the fore hearth the oven having flues passing through r it for the es escaping capin fumes of the slag alao and augmenting the heat acquired in that manner somewhat by using usina 0 a set of air jackets above the water jackets around the furnace in this way I 1 have been able to keep the top of the furnace cool so 89 to prevent volatilization the first and most important item to consider when heating the air blast is that it w no way interferes with the re regular aular corking vor king of the blower as the blast passes through the tae the to blower cold all calculations as to amount of blast required aired ano and used I 1 cau call be based on the regular volume ilan aled by the bi blower ower the same as when using cold blast Itis tt is customary to calculate the amount of blast furnished by the tables sent out b by y the manufacturers to the different blowers in this way the amount of free oxygen sent into the blast furnace whether heated or cold can be calculated provided there is no ob st ruction to the free passage of air through the heating apparatus it is therefore necessary that the area of the heating box should be larger than the inlet where the cold blast enters so that no back pressure is created the outlet of this heating box should should be made with nearly double the capacity of the inlet by our latest arrangement at silverton colo we not only utilize what little heat theres there is to be saved practically above the feed floor but utilize the heat which would otherwise go to waste through a much needed large matte settling arrangement it is the same arrangement excepting that all the heat in that case was wa ob obtained from the slag and the wood burned on the settlers furnace as in one we first started with with that we reduced our fuel to one third and dispensed with all preliminary roasting where we had been roasting two thirds of the ore and concentrates smelted smelter smelt ed |