Show lead matte at thoele tooele ele in january and february of the current year at the tooele thoele plant of the international smelting smelling Sm elting co tooele thoele utah a modification fi of the usual method of converting for the treatment of copper lead matte from lead blast furnaces was developed and put into successful operation in brief the method consists in blowing molten matte direct from the blast furnaces in basle basic lined converters without the addition of siliceous ous fluxing flexing ores to the almost complete elimination of the lead contained and to the production of copper bullion the resulting lead fume being recovered by the filtration of the converter gases through woolen fume bags the process is carried out in conjunction with the converting of copper matte the heavy iron slag together with the copper precipitated being transferred to converters blowing copper matte the purpose of this transfer is to reduce the copper oxide formed due to the necessary of the lead matte charge and to utilize as far as possible the value of iron from the lead matte for the fluxing flexing of siliceous dry ores the final slag from the copper converters is then skimmed off and transferred molten to a smelting smelling sm elting furnace treating copper ores this variation from general converting practice was the outgrowth of results obtained during 1913 when it was endeavored to convert copper lead matte in the usual manner with the direct addition of siliceous fluxing flexing ores to make clear the reasons lying back of the process it is necessary to recount at some length the results of operations during that year in the design of the lead plant it was planned to treat the copper lead matte from the furnaces by direct converting without and thereby to recover the copper silver and gold as quickly as possible A converter plant of ample capacity treating copper matte already being in operation era tion it was only necessary to install a bag house a fan and the necessary flues to complete the equipment the bag house constructed has a bag cloth filtering area of square feet provided by fume bags eighteen inches inched in ill diameter by thirty feet in length A no 20 sirocco fan of cubic feet capacity delivers the gases from the converter plant to the bag house the converter plant consists of five stands of horizontal cylindrical type shells 96 by inches in size thoele tooele To oele utah paper read at salt lake meeting of the american institute of mining engineers reprinted from july bulletin of the institute by OSCAR M KUCHS A common flue received the gases from all stands the admission of outside air was mainly relied upon for cooling the bases gases to the desired temperature means were provided for bypassing by passing gases to the stack in case of excessive temperatures temperature pera ture control of gases was made possible by the installation of recording thermometers converting operations were beenu in february 1913 with the bag house equip ped with woolen fume bags of cross woven fabric twenty four threads to the inch warp and filling As regards the converting operation itself test runs had shown mat no nc difficulties attended the handling of this type of matte and operations were conducted in a manner parallel to the treatment of copper matte for a period of two months no difficulties were encountered the production of products byproducts by however appeared as a disadvantageous vant ageous feature the passage of 45 per cent of the lead contained in the matte to the slag necessitated its in the blast furnaces bag house difficulties began after several months of operation leakage developed first through perforations at the tops of the bags while leakage of water through a prepared roofing material that had become affected by the converter gases was partly responsible for this condition it soon became apparent that the destruction of the fabric was due to condensation of acid inside the bags this condensa condensation ion manifested itself in the form of spots first at the top and later at the bottom of the bags about five to six feet at each end being affected at the points where it appeared the fabric became weakened by acid corrosion and would eventually be blown out by fan pressure leaving enlarged perforations fo the nap of the cloth was also rapidly corroded away giving a screen like appearance to the bags and finally a general weakening of the whole fabric resulted in their being torn from the thimble floor frequent renewals of bags became necessary to prevent leakages and inability to correct causes made it necessary to discontinue operations pending a thorough investigation vesti gation of the problem A solution of all the difficulties required either the destruction of acid by the add addition of a neutralizing agent such as zno or cao or the production of a fume in itself sufficiently alkaline to preclude the formation of acid and the production of a converter slag sufficiently low in lead to permit of its disposal by pouring bac back k into ies As a result of considerable esperi mental work the process as outlined at the beginning of this paper was worked out tests carried out intermittently during the day shift in a converter set aside tor for the purpose showed a rapid formation of a uniform magnetite coating on the walls of the converter it was expected that difficulty would be encountered due to the gradual closing in and reduction in capacity of the converter this however under continuous operation did not develop the crusting under these conditions being confined to the wall opposite the being heaviest at the mouth due to spattering of the charge and thinning out toward the bottom the fume produced was more actively alkaline the percentage of zinc eliminated from the converter as zno approximating 50 per cent as against less than 10 per cent under the previous conditions it was not deemed necessary therefore to consider the addition of a neutralizing agent to the gases preparatory to putting the process into continuous operation changes were made in the flue system in order that gases from lead converters only would be filtered through the bag house three converter stands were consequently connected with a separate flue for lead matte work the remaining two stands being conducted directly to the stack of copper matte blowing the necessity for better temperature control was realized and flues were equipped with dampers to control the admission of outside aside cooling air an automatic alarm system was installed to record by gongs and colored lamps the passing of the allowable maximum and minimum temperatures the operating range of temperature of the gases entering the bag house is maintained at from degrees F to degrees F the bag house was equipped with bags from the la porte woolen mills pendleton woolen mills and knight woolen mills the former are cross woven and have twenty four threads to the inch warp and filling the latter is a twilled weave bag converting pPe operations rations were begun in february 1914 the formation of a monolithic magnetite lining as stated did not develop rather rapid building up of the converter mouth at first gave considerable trouble however enlargement of the mouth relieved this condition materially corrosion at the line proved to be somewhat more severe than results from the blowing of copper matte and more frequent patching is necessary the time required for the blowing of a charge of ten tons is about two hours the time depending on the care given to the tu yeres frequent punching is necessary A tendency on the part of the to blind when silica is absent is very marked fume is evolved in dense clouds as soon as blowing begins the volume of fume gradually diminishes after the blow is half over and finally if the blowing is continued long enough fades out the end of the blow is thus indicated by the character of the fume and flame discharged from the converter the flame becoming more and more visible as the fume diminishes the charge in the converter at this stage contains about 1 to 15 per cent lead and has been reduced in weight to approximately 65 to 70 per cent of the matte charged the fume produced under the new conditions does not seem to affect the bags materially conditions at the bag house being greatly improved after three months of operation only four bags had failed these failures were due to apparently defective material in that one failed through splitting at the seam and the remainder were torn shaking of the bags appearing to have gradually opened up and extended flaws in the fabric no acid spotting of the bags is noticeable the following are comparative figures of matte blown and products formed under the former practice as compared with the present practice 1913 converting lead matte with the addition of siliceous fluxing flexing ores ab cup cu ag sio 2 fe cao S an per per oz per per per per per cent cent ton cent cent cent cent cent matte 16 5 50 siliceous ore 34 03 60 51 07 converter slag 68 58 92 38 32 bag house fume 12 56 11 25 1914 converting lead matte without the addition of siliceous flu flexing fluxing xing ores to lead matte charge lead elimination blow ab cu ag sio fe cao S an per per oz per per per per per cent cent ton cent cent cent cent cent lead matte 54 transfer slag to copper converter 14 17 18 40 bag house I 1 fume 03 7 57 02 04 copper converter blow copper matte 2 2 siliceous ore 34 03 74 30 08 converter slag blag 23 16 15 12 29 As indicated by these analyses the converter slag from present practice can be disposed of through either ies les or blast furnaces depending on economic conditions the high active alkalinity of the fume as indicated by the percentage of zno present should afford simple protection ag against ainest acid corrosion for the fume filter bags the condition of the bag house after nearly four months of operation seeming to vindicate this view in conclusion I 1 desire to express my appreciation of assistance rendered by A austin J C welch and A C wandel in the preparation of this paper |