Show FT THE metallurgical laboratory STATE SCHOOL of minest MINES 0 U of U ROASTING AND SMELTING FOR COPPER MATTE by robert H bradford ph D prof of metallurgy supplementary to the lectures and textbook text book study on the principles of metallurgy the mining students are required during their senior year to familiarize themselves with the practical side of smelting smelling sm elting by a series of furnace runs the work with the large furnaces is led up to by tests on smaller amounts of ore in muffles and oven furnaces wherein the conditions necessary to bring about the desired results are accurately determined the exact temperature required is measured by pyrometers and the importance of oxidizing and reducing atmospheres especially noted when they have demonstrated that they silica with 2 to 33 per cent copper the carbonates ran much higher in copper and silica but lower in iron and sulphur the sulphide ore was roasted in the hand verber atory and bruckner roasters asters ro two lots in the former and one in the latter furnace the composition of the roasted sulphides sulp hides as well as the carbonate ore is given below ORE feo cu S bios cao pct act pct act pct act pct act pct act roast no I 1 rev 30 87 roast no 2 rev 55 6 30 89 roast no 3 bruck 30 carbonate 1285 71 it was desired to smelt the above ores 4 ak ja V 4 71 T kag understand the principles involved and the conditions necessary to bring about the required results the students proceed with the furnace run in the smelting smelling sm elting plant much of the ore used in the roasting and smelting smelling sm elting operations is prepared by mechanical ch anical concentration in the excellently equipped ore dressing laboratories adjoining the smelting smelling sm elting room in the school of mines laboratory the furnace run above referred to was carried out by the class of 1906 on copper sulphide ores from bingham and carbonate ores from tintic gintic and dixie the sulphides sulp hides carried 35 to 45 per cent sulphur 40 per cent fe and 28 per cent so as to produce a matte running 45 per cent copper and a slag containing 45 per cent feo and 40 per cent by calculation the students determined that in order to produce the above matte and slag the ores should be taken in the following amounts one hundred pounds of mixed roast and fifty pounds of carbonate As this was about the proportion in which the ores were on hand they were taken in these proportions this being the initial run of the furnace we had no matte or slag on hand to fuse down in the furnace in starting the smelting smelling sm elting proc process ess it was seen that it was necessary to obtain an intense heat in order to start the fusion and to accomplish this a strong blast was employed under the grate the mixture was spread over the hearth in a layer three inches thick and the heating forced until the materials reacted on each other and the desired fusion was accomplished then small quantities of the ore mixture were added at intervals through the opening in the roof until the furnace was full to its capacity the smelting smelling sm elting was continued with careful firing to maintain the desired temperature until the reactions between the constituents were completed as indicated by quiet fusion the contents of the furnace were run into slag pots and allowed to stand for the separation of the matte and slag by gravity when cold the material was dumped out and the matte was found to form a well defined layer on the bottom with a distinct line of separation between matte and slag the accompanying photograph of a cone after breaking in half illustrates the distinct layer of matte that settled to the bottom of the pot the analyses of the slag and matte is given in the following table sample cu act pct feo PM matte slag the samples of slag were taken from the top and interior of the cone care being taken not to select samples from the outer shell that had solidified next to the pot without giving time for the matte to separate the results were quite satisfactory indicating a high grade matte and a very low percentage of copper in the slag when it is considered that the time of separation by gravity was necessarily short because of the small amount of liquid material in the pot the matte ran slightly higher in copper than the calculation indicated this no doubt resulted from a more extended roasting off of sulphur during fusion than was allowed for in the calculation |