US2105574A - Process of smelting - Google Patents

Description

Patented Jan. 18, 1938 UNITED STATES orleE No Drawing. Application March 12, 1936, Serial No. 68,444

2 Claims.

My invention relates to the smelting of sulfide ores by the combustion of the oxidizable elements of the ores, thereby producing matte of a desired grade, or metallic copper.

Having in mind the defects of this special class of smelting processes in particular, and the ponderous and complicated character of modern sulfide ore smelting in general due to the use of roasters, blast furnaces and reverberatory furnaces and heavy and expensive machinery required in their operation, an object of my invention is to provide a process in which a furnace is operated continuously at a smelting heat thereby eliminating great changes in temperature which is detrimental to furnace linings.

Another object is to provide a process wherein the sulfide mineral and the silicious ores are intimately mixed in the charges so that silica is immediately available to flux iron oxides formed in the process.

Another object is to use to the fullest possible extent the heat producing elements of ores for ore smelting and concentration.

Another object is to avoid the use of masters, reverberatory furnaces, blast furnaces etc., thereby accomplishing a material economy in equipping the plant and enabling a small operator to smelt his own ores without too great an investment in the furnaces.

Another object is to avoid the loss of heat producing elements which are Wasted by roasting sulfide ores.

Another object is to avoid the use of great quantities of carbonaceous fuel, thereby effecting a great economy in operation.

A still further object of the invention is to provide a process of smelting which is more efficient, simple and economical as compared with other processes.

I attain the above and other objects by carrying out the following described process:

The sulfide ores, With other ores in mixture, are smelted in a battery of converter furnaces, maintaining a condition therein whereby a quantity of molten matte is always available in one furnace as a starter or nucleus for another furnace. This nucleus of molten matte is of sufficient quantity to cover the tuyres and is used for the purpose of providing a bath through which compressed air is forced and to which mixed ores are periodically added in small quantities, the ore being provided either naturally or artificially with the required amount of silica mixed or incorporated with it.

The term silicious ores as used in this specifi cation refers to such material as is commonly called silica in copper converter plants, which constitutes a flux in which silicon dioxide is the active agent and consists preferably of high silica quartzite ores of copper, gold, and silver. The term silica refers to silicon dioxide, SiOz as found in such minerals as quartz, flint, etc.

The above term small quantities is used to distinguish this process from any in which ores are added in mass to an empty furnace.

This is essentially a combined pyritic smelting and bessemerizing process and may be carried out in a battery of suitable basic lined converters; in fact this apparatus is the furnace in mind for the purpose, but any suitable tilting or stationary furnace may be used if built so as to fulfill the requirements of the process. Ordinarily a blast pressure of from 12 to 20 pounds to the square inch is used.

I have found that the use of a battery of converter furnaces in the manner herein described accomplishes a very material increase in production of. metal at a decreased cost as well as providing a convenient means of obtaining any desired molten product during the prosecution of the process.

It is preferred to use two or more converters or furnaces each of which will be operating at different stages of the process at the same time so that a nucleus of low grade molten matte may be obtained from one furnace for another furnace which has finished and poured its product, thereby providing a substantially continuous produc tion of matte or metal and yet permitting the shutting down of any of the converters for repair or other purposes.

The several furnaces may be of different size or shape. They may operate in a horizontal or vertical position. By furnaces of the converter type I mean the furnaces are provided with tuyres through which a blast of compressed air is injected into a molten bath of aforesaid quantity contained therein.

The process depends for its success largely upon rapidity of oxidation and the quick removal of the gaseous products of combustion, and therefore the gas outlets of the furnaces should not be restricted.

It is of course understood that I use air under controlled pressure to blow through the tuyresthrough the molten metal to provide the necessary oxygen to oxidize the sulfur and iron and thereby to produce the smelting heat and new compounds.

The process may be used to produce a copperfree iron sulfide matte from pyritic iron ores for the purpose of collecting gold, silver or metals other than copper. Y

The process may be used to produce a white metal consisting of a mixture of copper and nickel sulfides since nickel-copper alloys follow, in the matte blow, exactly the same laws as govern copper alone.

The process may be .used' to produce metallic copper .by blowing a copper sulfidewhite metal produced from copper matte, and further, the process may be used to smelt limited quantitiesof oxide, carbonate and other ores together with the sulfide ores. The fact that I use asiliciousfiux permits the use of silicious ores having considerable metallic value. I

For the production of an iron'sulfidematteithe following typical charge is suggested and-may be made up of the following elements inthe following approximate proportions. Silica 25%, alumina 5% ,jlI0I1 35%, sulfur'35%. The proportion of silica may be'somewhat'increased with free silica ores. For the production of copper sulfide matte the followingapproximate charge is suggestedrsilica 29%, alumina 5%, iron 35%, sulfur 35% and copper 5%. For the production of a copper-nickel matte'theichargeis similar to the copper-sulfide matte except thecharge of the copper and nickel together should approximate at least 5% for a close collectionofthe .gold and silver of the ores.

These charges may be varied to suit the conditions but it will be found that the process allows of higher silica slags and thus .a, good metal .I provide, .byany known process a quantity of molten sulfides as a nucleus for aseries of steps in smelting; for instance this nucleus may be originally provided by heating afurnace or converter until the brick or other. lining has become red,.or even white hot, then introducing a comparatively small amount of cokeorcth'er fuel, say about two hundred, pounds, then placing a certain tonnage of ,ore, say"-l5 tons, on top of the fuel and turning on. a slight blast of compressed air of about one or two pounds persquareflinchuntil aquantity of sulfidesis smelted out-of the ore and is.in sufficient quantity to cover the tuyres.

The blast is then gradually increaseduntil the charge has neared thepoint ofbeing entirely smelted when a'blast of from twelve to twenty pounds is used until thecharge is fully. fused, and may now be used as a nucleus for the production of matte. V

A nucleus of matte havingbeen obtained as above described/in sufiicient'quantityto cover the tuyres and provide a molten bath,.small quantities of a mixture of sulfide. mineral and silicious .ores area dded'from time to time to this bath and .are smelted by the heat produced by the oxidation of theiron and sulfur of the mattebath. "The smelted ores increase the volume of the matte. The silicious ores flux and slag the iron oxideand the resultant slag is poured periodically. The

.quantity of the'matte is'thus built upto the capacity of the furnace. The quality of the matte is enriched by the oxidation of the iron sulfide by the blast and the slagging of the iron oxidewith silica.

When. a sufiicientgquantity of matte has been accumulated a portion may be transferred to a smelting continued in the first furnaceby the addition of fresh ores. The nucleus should be transferred to the hot empty furnace in the earlier stages of the converting so as to provide a nucleus of low grade matte therefor, or a quantity of such low grade matte may be set aside in a suitable container until needed as a molten nucleus for any hot empty furnace.

The steps in the process are normally as follows:

l. The furnace having been in use is still hot,

or in the case of a first charge the furnace is suit ably heated.

2. A sufficient quantity of molten matte nucleus 'is placed in the furnace to cover the air inject- :ing means.

3. A mixture of sulfide and silicious ores is aiddedgin small quantity, until enough has been added for one blow for matte and slag production.

4. The chargingof the ores is discontinued and *sdfiiizient' blowing timeallowed to sufficiently fuse the ores so thata" fluid slag may be obtained and the temperatureof the furnace raised.

5. Slag is poured from the furnace.

' fig-The chargingof ore, blowing and slagging as in steps 3, 4-a-n'd 5 is repeated untila sufficient volume of matte is accumulated to transfer a part thereof asa nucleusand still -leave sufficient matte in the furnace for a-nucleus to repeat the aforesaidsteps.

"7.'-The abovequa-ntity of molten matte, as in step No; 2 is removed'to start operation in another furnace, or this portion may be'added' to 'another furnace already =in process of operation.

8. The steps 3,-4 and 5 of the process-are then continued as before andthe concentration of -'t-he=-matte-results from such continuation by the elimination'of theironsulfide-throug-h the oxidizinge'ffect of thejairblastpassing through the matte, and slagging iron oxide with the'silica ofthebharge until a concentrated iron matte, a copper sulfide white metalor a nickel-copper sulfide white metal is-obtained=as the case may 'be. In the case of -aconcentrated iron sulfide matte or a nickel-copper white metal, these are the ultimate products of the process. They are then poured and'the process repeated.

9.-In the case of having produced a copper sulfide white metal this White metal is finished to metallic copper byan oxidizing blow, the copper poured-and the process repeated.

Silica may be furnished by the gangue rock of the sulfide ore. Otherwise sulfide and silicio us' ores are charged, in intimate mixture so that silica may be immediately available, when the iron oxide isiformed, to'slag this oxide and to prevent '-the excessive formation of the higher oxides of iron as would be the case in the'absence of sufficient silica.

The amount of'the ore charged for any particular period of smelting and'blowing for slag depends upon-the character of-the ore; ordinarily five or six-repeated charging, blowing and skimmingperiods will be necessary for the accumulation of 'afull charge, the idea being to skim often enoughto relieve the furnace of burdensome quantities of slag whichis an inert mate rial. The ore. is charged through the stack while .the furnace istilted forward .and.the air partially shutoff, or..it is charged .by means of a Garragun orother contrivance while the furnace is blowing withfull' blast butnot in such quantities as to solidify the molten material therein. For instance, normallyv a .completeblow "for slag will require about an' hour. Ordinarily the charge of ore can be put in at one time at the earlier part of the blow, but it can readily be seen that in the case of having a small nucleus of molten material it may be advantageous to add the charge of ores in two or more separate and distinct parts, each charging requiring several minutes. But in any case the charging of all ore should be discontinued for say 20 minutes or more before the skimming of slag is attempted, during which time the air supply is continued in order to allow for the smelting of the ore and to allow the contents of the converter to heat up to a sufiicient degree, such that magnetic iron oxide may be reduced and a clear fluid slag formed.

I have found that the proposal of previous inventors as to the continuous charging of ore through the whole blow is not desirable for the following reasons: In a strongly oxidizing operation, such as is carried on in a bessemer converter, the higher oxides of iron will easily be formed.

The formation of these higher oxides occurs most readily when the furnace is slightly cooled by the introduction of fresh ores, therefore such charge must have a plentiful supply of silica to reduce the quantity of such higher oxides thus formed. The temperature of the furnace is rapidly raised by the above described oxidizing reactions, thereby quickly reducing such higher oxides of iron as may have been formed.

The importance of preventing the formation if possible, of magnetic oxide of iron, or if formed to reduce it, may be understood from the following facts:

First, these oxides freeze at the tuyeres and colder parts of the converter thus making it exceedingly difiicult to keep the tuyres open so as to get the blast into the furnace.

Second, the slag does not readily separate.

Third, the slag has a mottled appearance on the skimming rabble indicating that metal is being carried into the slag and the flow of slag stops short in the pouring thus preventing a clean skim.

In a process of this special class using little, if any, carbonaceous fuel, the conditions recited above must especially be guarded against as a precaution to preserve the heat of the furnace and proper working conditions. However, with proper practice, i. e., that of using mixed ores and segregating the charging of the ores to the earlier part of the blow, the heat developed is suificient and the working conditions and the results are satisfactory.

The process may be carried out in a single furnace by setting aside a quantity of matte in a suitable container and reserving it in its molten condition until needed as a nucleus to repeat the process.

In the case that a withdrawal of matte is not needed from any particular charge the matte may be built up as to quantity and quality without separating any matte and the ultimate product obtained.

In the practice of the invention it may be found advantageous to operate for a time one furnace of the battery solely in the stage of smelting and matte accumulation, upon anucleus of molten matte; making transfers to other furnaces of the battery as a surplus, above the required nucleus, is accumulated. This furnace will continue in matte production, always retaining and building up from a nucleus of molten matte. Another furnace of the battery being used to accumulate a full charge of white metal and blow this to metallic copper.

In the above description it is not intended to imply that the several ores must be premixed before charging, though normally such would be preferred, but the required quantities of the several ores can be dumped either together or at practically the same time (without sufiicient interval to permit independent action,) into the converter where the actual mixing of the ores is caused by the agitation of the molten mass therein.

Having fully described the invention, what I claim as new and desire to secure by Letters Patent, is:

1. A process of producing matte, white metal and copper which comprises the steps of periodically charging small amounts of a mixture of sulfide ore and silicious fiux in amounts sufiicient to flux the iron oxide formed in converting the sulfide ore upon a nucleus of molten matte in a container provided with means for injecting air into the charge contained therein, the matte being sufiicient to cover the air injecting means; blowing air into the mass, whereby the mixture of sulfide ore and silicious flux is periodically smelted by the heat generated from the oxidation of the iron and sulphur by means of the air blast injected into the matte until a desired quantity of matte is obtained; separating a portion of this matte, as a nucleus, and maintaining it in its molten condition; and continuing the smelting process to restore the quantity of matte in the said container and simultaneously building up the grade of the matte, until the quality of the matte reaches the white metal stage; converting the white metal to copper by means of an air blast injected therein; pouring the copper; and introducing into the hot converter the previously separated portion of molten matte as a nucleus for a repetition of the process.

2. A process of smelting sulfide ore which comprises periodically introducing a charge consisting of small amounts of a mixture of sulfide ore and silicious flux, the fiux being sufiicient in amount to slag the iron oxide formed in converting the sulfide ore until enough has been introduced for one blow for matte and slag production; the charge being introduced upon a nucleus of molten matte in a container provided with means for injecting air into the charge con tained therein, the matte being sufiicient in amount to cover the air injecting means; periodically smelting the mixture of sulfide ore and silicious fiux by the heat generated from the oxidation of iron and sulfur by means of an air blast injected into the matte, without further additions of ore or flux during the smelting period in order to maintain the full heat of the blow throughout each smelting period; repeating the periodic charging and smelting of a mixture of sulfide ore and silicious flux until the desired quantity of matte is obtained; separating a portion of this matte, maintaining it in its molten condition; and using the same as a nucleus in repeating the above sequence of operations.

FORREST E. WING.