Show THE metallurgy OF LEAD WRITTEN FOR THE MINING REVIEW BY H B accessories to the ore hearth in our consideration of the ore hearth w we have already tried to make it clear that the hearth by itself is quite incapable of rendering available a satisfactory amount of lead from even the richest galena while the hearth may be worked to recover from 50 to over 80 per cent of the lead in the ore as metallic lead this depending on local conditions ore requirements the remainder roa inder of the lead is either flagged slag ged or driven off as fume and is not then in as suitable condition as even the ore originally was for getting out the lead in fact the lead that has been flagged is quite beyond recovery in the hearth the devices which we find used to supplement the hearth in its recovery of lead are thus the cupola or small lead blast furnace the settling and cooling flues the bag house and in two instances the subliming furnace for white lead the ore hearth produces pig lead the products byproducts by resulting at the same time are slag and those materials which are carried r up into the hood that is dust and fume the slag is immediately ready for its further treatment in the cupola the dust settles fairly readily in the flues and has but to be cleaned from their floors or from the bases of the upright towers or pipes the fume will not settle of itself it has to be strained away from the gas by means ol of cloth bags in the bag house although cooling assists in the settling of dust its particular necessity arises from the fact that gases too hot will ruin the cotton or wool cloth used for the bags to collect the rume lume the fume which is collected in the bag ba house is extremely fine and would be easily blown from the cupola were it attempted to smelt it direct along with the slag and fluxes fortunately it is a combustible substance easily ignited when in mass SM smoldering ol 01 to a sintered and lumpy material this latter is fairly acceptable burden for charging into the cupola the cupola as at present used has developed from a much simpler furnace long used for smelting smelling sm elting the slag residues from the hearth this general type of furnace has also been extensively used to smelt oxidized or roasted lead ores and its development will be more carefully followed under the topic of blast furnaces at the time when percy wrote his metallurgy of lead that is more than forty years ago blast furnaces quite similar to the hearth were in common use in the north of england for smelting smelling sm elting the hearth flags the blast furnace thus used was operated intermittent antly had one no crucible internally and differed from the hearth bearth mostly in that the front or breast was closed the burden was not worked by hand and the slag was fully liquid lead blast furnaces have undergone enormous ev evolution alution since the time of percy their development has been most marked in the united states it is however not their highest type but a small and fairly simple type which has proved most suitable and generally used in connection with hearths heart hs the accompanying illustration is of a cupola as it appears when out of blast the front is out the pipes are down and the hand holes are open so that the water jacket may be cleaned out two openings appear one on either side of the opening in front while the pipe chich supplies water to the tap jacket is r MM V ra 7 J fl ali IA cupola for smelting smelling Sm elting hearth byproducts by products photo by H B seen to end in a coupling just over the opening A cupola of this sort is run contin continuously bously the charge consists of the slag from the hearths heart hs the binte sintered red dust and fume and any other materials low in lead for fuel coke is used flux consists of limestone flags rich in iron from iron foundries and any sort of scrap iron or tin cans that may be available the metallic iron is of particular value in that tha t it precipitates out lead from its it sulphide and replaces it if present as silicate the tin cans are of other value besides for the iron of which they chiefly consist of in that they are so bulky keeping the charge open and porous A typical analysis adapted from hofmans metallurgy of lead shows the composition ution of the hearth slag this being the chief constituent of the cupola charge per cent metallic lead 2145 silica lead sulphate ferric oxide 61 zinc oxide 1141 lime 0 magnesia 09 lead sulphide 1157 iron pyrites 7 53 zinc blende lead oxide this altogether making a total of slightly over per cent it will be noticed that the slag is very rich in lead it commonly runs well over 50 per cent metallic lead the gases from the cupola will go through the usual cooling flues and ba bag house the lead will be collected from the lead well and with that from the hearths melted pooled and cast into pigs for shipment the slag from the cupola should contain less than I 1 per cent of lead and is waste some lead may run with the slag and collect in the bottom of the slag pots as buttons of lead it is thus customary to away the still liquid slag from the center of the slag pot and leave a shell containing the of lead this to go back to the cupola the second illustration gives a good idea of the type of cooling flues commonly used in the southwest missouri lead fields doors are seen at the bottom of each upright steel flue the dust and fu fume in e being easily removed and allowed to sinter into a cake just outside the door before it is char charged ed into the cupola the large building in the background of the second illustration is the ba bag house the basement of the building consists of five separate e cellars brick walled concrete floored and covered with sheet steel this steel ceiling is pierced with the thimbles about which the cotton bags are tied at their base in each compartment are thimbles to fit the bags which are eighteen inches in diameter the bags are suspended from rods directly over the thimbles each ba bag 6 being twenty five feet long lo ng this is the common type of ba bag t house in missouri the bags are usually shaken by hand when enough fume has collected in a c ellar cellar it is ignited later on being removed and used on the cupola charge at the granby smelter there is no cupola and tile the dust an and d fume must be re smelted smelter in the hearth heart hs s apparently 0 good recovery is made but the slag from the heart hs has to be shipped to some other plant for the final recovery of its lead in any ally case the ba bag 0 house is an indispensable adjunct to the hearth it is interesting to remember that bags were first used in the united states for filtering lead fume at the old lone elm at joplin missouri they were installed at the by E 0 bartlett in ili 1878 and proved remarkably successful before this fume had been thrown in the streams buried or thrown to waste the bag house was later tried at smelt eries in edg and refining company also operates two furnaces for the production of the same material by equipment almost exactly similar il lar to that used at the plant of the pitcher lead company blue roasted white fume fume pal paint nt lead sulphide lead sulphate 6 52 3 lead oxide 2578 zinc oxide 50 27 Y 1 K 1 X 71 11 13 t 1 11 ue in A g iaac minina rk view in yard of new webb city mo P hoto by H B Pul the more western states and under underwent wenc great development in missouri however the original design has been pretty closely adhered to minor improvements improvement s only resulting sul ting the third illustration indicates how the gas from the cooling goose necks is divided as it passes into the bag house from the last down take the gas pases up to tb a larger transverse flue which has five branches passing on the other side each into one of the cellars of the bag house each branch will be seen to be provided with a sliding damper so that its cellar may be shut off lor for burning fume or cleaning out the subjoined sub joined table of chemical compositions S is one supplied by hofman in his metallurgy of lead it is old data but as there has been slight change in the method of smelting smelling sm elting during the last twenty years it is likely fairly representative ot of present compositions the first column is the average of four samples of the fume collected from different parts beneath a bag house the second column is the fume after it has smoldered into cake form and the third column is the composition of sublimed white lead as made by the process which we shall now describe this process was invented by bartlett and first put in operation in connection with the bag house at the lone elm in 1868 since that time the method has been successfully followed and is still in operation the company is now known as the pitcher lead company the st louis smelt ferric oxide and 07 37 03 calcium oxide 07 48 02 09 2 carbon dioxide 19 90 sulphur dioxide 55 02 moisture 37 72 silica 14 10 08 on combustion organic water carbon dioxide A most acceptable paper by J T blair on the manufacture of white lead by this process at these two plants appeared in the engineering and mining journal of november 5 1910 vol p the slag from the hearths and the fume from the hearth bag house is smelted smelter in a special ial small blast furnace which is run with a very hot top and a combustion chamber directly over the furnace in which C h the lead fume is burned to the basic lead sulphate A very recent article in the mining world of february 17 1912 by evans W buskett gives further details of the process calling attention to the fact that a large amount of raw galena is always added to the charge in the subliming furnace this table is given as representing the charge for an 8 hour run pounds Dry bone lead carbonate ore 1000 ashes from cooling towers 1500 blue fume from ore hearths 2000 galena 1 white fume off color pigment 1000 cuttings from beehive 1000 grey slag from ore hearths iron metallic I 1 goo limestone 1400 coke total 17 SOO the lead of the charge is largely vola utilized in the furnace in the combustion chamber the oxidation is completed the white fume is then collected in a special bag house and packed to be sold as white paint is the formula assigned to this basic lead sulphate the large amount of oxide is not there as which would give a pronounced color to the pigment but is combined as a part of the sulphate and gives no discoloration L F hughes had a short paper about this sublimed white lead in the journal of the society of chemical industry 1909 vol 28 1 p he says the composition of the pa pigment m ent is approximately lead sulphate 75 per cent combined oxide 20 per cent zinc oxide 5 per cent these two plants are the only ones which manufacture sublimed white lead collins in his IMe metallurgy of lead states that sublimed white lead is made by the bristol sublimed lead company I 1 have noticed no reference to this latter company the plants of the federal lead company granby mining and smelting smelling Sm elting 21 company and webb city smelting smelling Sm elting and manufacturing company have been described rather often iu in the current literature all these plants use ore hearths as does also the lead smelt 75 t tr 07 T el J bag house connections webb city mo photo by H B Pul Puls itier 1912 ery cry at galena kansas from whence our illustration odthe cupola was obtained H B armour institute of technology 0 chicago 0 |