US1776826A - Refining of copper - Google Patents

Description

Patented Sept. 30, 1930 UNITED STATES, PATENT 1 OFFICE HARRY H. ALEXANDER, OF WESTFIELD, NEW JERSEY nnrmme or corrEa No Drawing.

impurities. In the furnace refining of cop-- per as heretofore more generally practiced, the metal and its impurities are melted. The molten material is suitably aerated to oxidize the impurities, some of which pass OK as vapors and gases, While others pass into the slag forming on the top, of the molten copper. In the case of sulfur and/or its compounds, the sulfur is in part volatilized and in part converted to sulfur dioxide which passes off as a gas.

The aeration of the molten material is effected in various ways. The older method is to flap the top surface of the molten material with a rabble, while admitting air into the refining furnace, in order to subject the impurities to the oxidizing effect of the air. A latermethod is to pass air, under pressure, into the body of molten material. The removal of sulfur and/or its compounds is accomplished with considerable difficulty, and a large excess of air must therefore be employed in the refining operation. Both methods have the desirable effect of oxidizing impurities, but the very undesirable eflect of also oxidizing appreciable amounts of the copperfrequently as much as 6%. I

The oxidized copper must then be subjected to a deoxidizing or reducing operation to obtain a relatively pure copper product. This latter refining or reducing operation is conducted in various ways, generally by the introduction into the body of molten copper of a suitable reducing agent, such as Wooden poles or carbonaceous materials. I

In the case of the usual copper to be refined, the removable impurities other than sulfur will pass out of the aerated copper Application filed July 5, 1928. Serial No. 290,703.

bath in about two hours. The'end'of this stage of the refining operation may be determined by noting when the formation of slag appears to cease. About two hours more aeration are required to drive out the sulfur.

As a result of my investigations I have determined that the aeration or scorification action may advantageously be terminated before the conversion of appreciable amounts of copper to copper oxide has taken place. he removable impurities present in the molten copper not oxidized or removed by the air treatment may be suitably removed in accordance Withthe practice of my invention.

In the practice ofthepresent invention, copper contaminated with sulfur and/or its compounds and the like maybe'refined without oxidizing the copper, and the customary deoxidizing or reducing step may therefore be avoided. Or, the invention may be practiced in such a way as to desulfurize the copper while oxidizingsome of the copper, but at a material saving in time over what the prior practice requires.

According to my invention, a body of molten copper contaminated with sulfur and/or itscompounds, hereafter to be referred to as sulfur, and the like is subjected to the action of steam, preferably dry steam under pressure, whereby the copper is desulfurized.

Steam at thetemperatures employed has the advantage of not oxidizing the molten copper, while at the same time oxidizing the sulfur to form sulfur dioxide gas. Steam, moreover, tends to drive out residual sulfur, as well as other removable impurities present in the copper bath. The steam is preferably superheated in order to dry the same.

When the contaminating sulfur is present as copper sulfide, the reaction results in the formation of copper and sulfur dioxide gas, in accordance with the reaction:

This reaction, moreover, has the advantage of forming free hydrogen which has the capacity for taking up free oxygen that may be present above the copper to be refined. So

long as the reaction takes place and hydrogen is being evolved, this free oxygen present above the copper cannot exercise an oxidizing effect on the copper. Hence, the formation of copper oxide is prevented. The prevention of the formation of copper oxide can be conducted in this manner, however, only i so long as there is sufiicient sulfur to keep on generating hydrogen until all of the free oxygen has been taken up. In case the above re action goes to completion, any free oxygen that has not been taken up bythe hydrogen becomes available as an oxidizing agent for the copper. Copper oxide then results,

This situation applies with equal force to' the gaseous condition maintained above the copper bath. Even though the formation'of copperbxide should be prevented within the copper bath, the maintenance of oxidizing conditions above the bath will result in the formation of copper oxide. This may or may not be avoided, as desired.

The invention may be practiced in various ways. Thus, the molten copper within the refining furnace may first be subjected to the usual air blast or rabbling o 'eration in order to oxidize substantially al of the impurities. That is to say, the aeration or scorification treatment may be conducted until all of the removable impurities, except some sulfur, have been taken out of the copper bath.

The introduction of air is terminated at that oint, which may be determined by observmg when the formation of slag begins'to cease. The copper bath will still contain ap- 1 the copper bath.

. Anot er procedure is to subject themolten material in the refining furnace to the steam treatment of the invention'in order to take out all such impurities as are removable by steam at the temperatures employed. Moreover, the steam treatment may be conducted until the sulfur has been removed. The desulfurized copper bath may then be subjected, if necessary, to the usual air blast in order to remove any remaining impurities. In this manner,the'oxidation of copper may be kept down to a minimum, particularly if a nonoxldizing atmosphere is again maintained a above the copper bath.

It will, of course, also be apparent that the use of steam and the use of air may be alternated, as seen fit in the refining operation. In some instances, the refining operation may also lend itself to the practice of subjecting both steam and air, separately but simultaneously, or a mixtureof steam and air, into the copper bath. Such a procedure may be particularly advanta eous if it is desired to materially decrease t e time for performing the refining operation, and where there is no particular concern as to the production of a final copper product that is relatively free of copper oxide. Various other modifications of the practice of the invention may, of course, be resorted to, but it is to be understood that the omission of a discussion of them is not to be regarded as otherwise restrictive of the scope of the invention.

The apparatus usually employed to inject air into copper refining furnaces may advantageously employed for the introduction of steam into the metal bath. In order that a 'thorough distribution of the steam may be effected throughout the body of the molten material, it is advisable to introduce steam into the molten bath at a plurality of points,

referably near the bottom of the refining urnace. Since it is preferred to use dry steam, the pipes leading from the source of steam to the refining furnace should be insulated to minimize condensation of steam. Special injectors may, of course, be provided for steam alone.

In case it is desiredto inhibit the formation of copper oxide, the openings leading into the furnace shouldbe tightly closed to prevent the ingress of air. In other words, a non-oxidizing atmosphere should be provided above the metal batli. Reducing gases may of course be maintained above the metal bath. A molten protecting cover, such as described and claimed in my copending application, Serial No. 123,886, filed July 21, 1926, of which this application is a continuation in part, may advantageously be employed to protect the molten, bath from oxidizing influences during the steaming treatment. According to said copending application a molten protective cover is contemplated that consists at least in part of soda glass having a melting point not higher, and preferably lower, than that of the copper.

In case it is not desired to inhibit the formation of copper oxide, an oxidizing atmosphere may, of course, be maintained above the metal bath. The highly heated molten copper at the top of the metal bath then con- .tacts with the oxygen of the airand copper oxide is formed. The use of steam instead of air, particularly at the end of the refining operation, is nevertheless advantageously resorted to in order to driveout the sulfur. Even though cop er oxide has been formed, the time of the refining operation will be materially reduced over that heretofore gener required.

all

Ifivenin the case ofdesulfurization with a1r, some of. the sulfur dioxide gases tend to be occluded in, or are retained by, the molten copper. When an excessive amount of air is made to rise through the body of molten copthe other hand, not only inhibits the formation of copper oxide, but also effectively drives out these sulfur dioxide gases.

It will thus be seen that in the practice of this invention, it is possible to effectively remove the chief impurity of copper, sulfur, Without oxidizing the copper, or at least oxidizing a. minimum of copper if that is desirable. The practice of-the invention, more-' over, has the advantage of removing otherimpurities. In the instances where it is not desired to inhibit the formation of copper oxide, the refining operation contemplated by the invention may be conducted in much less time, thereby effecting a very important economy.

I claim:

1. The method of refining copper which comprises maintaining a substantially nonoxidizing atmosphere above the copper in the form of a molten bath while subjecting the molten copper to the action of steam under pressure, said steam being introduced into the body of molten copper, whereby the copper is desulfurized and the formation of copper oxide is inhibited.

2. The method of refini g copper containinr an appreciable amoi nt of sulfur as at least one of the-contaminating impurities, which comprises aerating the copper while in a molten state,- said aerating operation being continued until the formation of slag ceases, and then introducing steam under pressure into the body of molten copper to complete the refining operation.

3. The method of refining copper which comprises maintaining a molten protective cover consisting at least inpart of soda glass having a melting pointnot higher than that of the copper over the copper bath, and introducing steam under pressure into the body of molten copper. a

4. The method of refining copper which comprises aerating the molten copper partially to remove nnpurities, maintaining a molten protective cover consisting at least in part of soda glass having a melting point not higher than that of the copper over the partially refined copper, and then introducing steam under pressure into the body of molten copper.

5. lhe method of refining copper which comprises aerating molten copper partially to remove impurities, then providing a substantially non-oxidizing atmosphere above the copper bath, and introducing steam under pressure into the body of molten copper.

6. The method of refining copper containing sulfur as at least one of the contaminants which comprises maintaining an oxidizing atmosphere over the copper bath, introducing steam under pressure into the body of molten copper until only a relativelysmall amount of sulfur remains, then providing a substantially non-oxidizing atmosphere over the copper bath, and introducing further amounts of steam under pressure into the body of partially refined copper to complete the refining operation.

7. The method of refining copper containing an appreciable amount-of sulfur as at least one of the contaminating impurities which comprises substantially sealing the furnace in which the refining operation is conducted against the seepage of outside air, and subjecting the copper in the form of a molten bath to the action of steam under pressure whereby the copper is desulphurized and the formation of copper oxide is inhibited.

8. The method of refining copper containing sulfur as at least one of the contaminants which comprises maintaining an oxidizing atmosphere over the copper bath by permitting the seepage of outside air into the furnace in which the refining operation is conducted, introducing steam under pressure into the body of molten copper until only a relatively small amount of sulfur remains, then providing a substantially non-oxidizing atmosphere over the copper ath by sealing the furnace against the entrance of outside air, and introducing further amounts of steam under pressure into the body of partially refined copper to complete the refining operation;

In testimony whereof I affix my signature.

HARRY H. ALEXANDER. I