US2132149A

US2132149A - Producing metals

Info

Publication number: US2132149A
Application number: US144727A
Authority: US
Inventors: Edwin Emil
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-06-13
Filing date: 1937-05-25
Publication date: 1938-10-04
Anticipated expiration: 1955-10-04

Description

E. EDWlN PRODUCING METALS @cit, 4, 1938.

Filed May 25, 1957 Wastegas Caa/ dust L imes [on 6 Hot gas M'x/hg vasse/ vesse/ /Pea ch'on Ca C03 Ma ne/Ia separaior' mw E Y E. Edwin prvpme/or Patented Oct. 4, 1938 UNITED STATES PATENT QFFICE In Norway June 17 Claims.

My invention relates to recovery of metals by direct reduction of their ores.

As is well known the question of direct reduction of oxydic and also of sulphidic ores at low temperatures for recovery of the metal content thereof has been studied for years, and much extensive research work has been made in connection therewith.

In spite of this fact no method has hitherto been developed, which has proved successful on a commercial scale. The main reasons for this failure are the following:

(1) It is extremely difflcult to supply the reaction energy necessary for the reduction in such manner that no overheating with bad attending phenomena occurs.

(2) Most ores have during the reduction process, irrespectively of whether the same .is effected by means of solid carbon or by means of gas, a strong tendency to undergo structural changes, which are frequently accompanied by a caking of the charge, which renders the accomplishment of the process very difllcult.

For solving these difilculties it has hitherto been necessary to make use of so complicated apparatus, that a common introduction thereof in the industry has not been ventured, although several methods on an experimental scale have given promising results.

It is the object of my present invention to provide a process by which the above mentioned drawbacks are avoided.

My invention is based upon an entirely new principle and a reaction hitherto unknown, and it provides a very simple method needing apparatus so plain as have previously been considered unattainable.

My invention is based upon the very simple reaction formulae:

(A) 2MeO+C+CaO- 2Me+CaCO:+Q1 or (using gas as reducing agent) In Equation (B) the relation HzZCO is to be so chosen, that the heat liberated Q2 is sufliciently high to compensate for all heat losses to the exterior and. to keep the reaction temperature at the necessary value. In some cases (by combination of Equations (A) and (13)) :c or y may theoretically take zero value, which means that either only CO or only H2 is used. The water vapour formed may, at the partial pressures prevailing, easily be condensed on the walls of the reaction vessel. It is directly possible to combine the Equations (A) and (B). Thus, if the reaction according to (A) is not sufflciently exothermal, small quantities of CO may be supplied to the reaction space in order to increase the positive heat value, since the reaction according to (B) is exceedingly exothermal for all oxides which can be reduced by gas.

Further, in order to increase the exothermicity of my process, it is in many cases possible to obtain still better results by supplying to the reaction vessel a little free oxygen, which will then react according to the equation (C) C+Oz+Ca0- CaCOa+l38000 In the case of iron ores, for the reduction of which the present invention is especially suitable,

As will be seen, the exothermity of this reaction is, indeed, sufilcient for the efiectuation of the reduction, but not excessively high. However, by a consumption of only 8% more of lime and coal in accordance with Reaction (C) the development of heat may be increased by more than quite small quantities of free oxygen being supplied to the reaction chamber.

However, the reaction in question will in general not take the course indicated by the equations cited above, or, more correctly stated, no reaction at all will take place under normal conditions.

At this place the novel conception of my in- .vention comes in. Below I will explain this fully,

considering. by way of example the reduction of iron ores.

If a mixture of iron ore, lime and coal is heated in an open vessel to an initial temperature of, say, 800 C., and is then left alone, without further energy being supplied thereto, some small reaction will, indeed, at first occur between ore and coal. After a short period of time however such reaction will stop by itself, even if no losses of heat to the exterior occur, as the charge very soon becomes so much cooled, that the temperature thereof goes below any usable reaction temperature.

Entirely different the result will be, if the above mentioned mixture is placed in a closed, well insulated pressure vessel and is then heated to the same initial temperature. Very soon a gas atmosphere, chiefly consisting of carbon monoxide (CO) "and carbon dioxide (CO2) having a subteht1ally raised pressure will then occur in the said closed vessel, and under these conditions the reactions really take the course indicated by the Equations (A), (B) and (C) cited above, such reactions running quantitatively or substantially quantitatively from left to right in the sense of said equations. If an iron ore of normal reductibllity is treated in this manner, a pressure of 25-30 atmospheres very soon is obtained, and the reaction then proceeds, the carbon dioxide formed being absorbed by the lime present. The energy hereby disengaged is by radiation and conduction transferred to the reaction between coal and ore, and said reaction on its side develops further quantities of carbon dioxide and carbon monoxide, in a mutual relation determined by the reaction. To each temperature corresponds a predetermined pressure, and by artificially keeping the pressure at a predetermined value, a reaction temperature suitable for each charge in question may be maintained most exactly. If the heat losses to the exterior are higher than the exothermicity of reaction (A) this may at any time easily be compensated for by the reactions (B) or (C), as described above.

In the drawing I have by way of example diagrammatically and flow sheet-like illustrated an arrangement for carrying out my method in the case of iron ore being reduced by means of solid carbon as reducing agent.

Limestone is calcined in a lime kiln l, and a mixture of iron ore and coal is preheated in a preheater 2. Preferably the waste gases from the lime kiln are utilized for heating said preheater. The hot lime from the kiln I and the mixture from the preheater are then taken to a mixing vessel 3 of any suitable construction, in which the lime, ore and coal are mixed. From this mixer the reaction mixture is by means of a transfer vat 4 transferred to the reaction vessel 5, in which the reduction of the ore takes place in the manner already described. The mixture of iron and limestone hereby formed is then taken to a cooling drum 6, and after sufficient cooling the iron sponge is separated from the limestone on a magnetic separator I. The limestone hereby separated out is in part returned to the lime kiln.

If free oxygen is to be supplied to the reaction vessel, in order to act in accordance with Equation (C), such oxygen must be supplied at the necessary pressure, obtained by a compressor indicated at 8.

The reaction vessel may have any suitable shape, and is preferably provided with a gas inlet pipe and a gas blow off pipe (not shown). The latter also may be provided with a blow ofl' safety valve, in order that the pressure and temperature shall not be able to rise above the desired value.

In order that the charge shall in no way cake together during the reduction operation, 'it is preferable to keep the reaction vessel slowly moving, say rotating. Such movement also furthers the exchange of energy between the reaction components.

Principally my method has been developed for the treatment of oxydic ores; however in certain cases the method may as well be used for sulphidic ores, since the reactions proceed in accordance with laws which are entirely similar to those of the oxides.

What I claim is:

1. A method of producing metals from their ores, in which the ore is heated in the presence of a reducing agent containing the element carbon and of calcium oxide at such a pressure that carbon dioxide formed by the reaction taking place is substantially quantitatively taken up by the oxide of calcium under formation of carbonate of calcium.

2. A method according to claim 1, in which the reducing agent contains the element carbon in combined form.

3. A method according to claim 1, in which the element carbon is used in the form of carbon monoxide.

4. A method of producing metals from their ores, in which the ore is heated in the presence of a reducing agent containing the element carbon and a reducing agent containing the element hydrogen and of calcium oxide, at such a pressure that carbon dioxide formed by the reaction taking place is substantially quantitatively taken up by the oxide of calcium under formation of carbonate of calcium.

5. A method according to claim 1, in which oxydic iron ore, solid carbonaceous reducing agent and calcium oxide are caused to react at raised pressure in a closed vessel.

6. A method according to claim 4, in which oxydic iron ore, a mixture of carbon monoxide and hydrogen, and calcium oxide are caused to react at raised pressure in a closed vessel.

7. A method according to claim 1, in which a sulphidic ore, solid carbonaceous reducing agent and calcium oxide are caused to react at raised pressure in a closed vessel.

8. A method according to claim 4 in which a sulphidic ore, a mixture of carbon monoxide and hydrogen, and calcium oxide are caused to react at raised pressure in a closed vessel.

9. A- method of producing metals from their ores consisting in heating a mixture of ore, reducing agent containing the element carbon and calcium oxide to a temperature at which the reducing agent starts to reduce the ore, bringing the mixture thus heated into a reaction chamber, closing said reaction chamber pressure tight, and allowing the reduction process to proceed by itself.

10. A method according to claim 9, in which the pressure developed by the gases formed during the reaction is controlled by means of a valve on the reaction chamber.

11. A method of producing metals from their ores, in which the ore is heated in the presence of a reducing agent containing the element carbon and of calcium oxide at such pressure that carbon dioxide formed by the reaction taking place is substantially quantitatively taken up by the oxide of calcium under formation of carbonate of calcium, and where some free oxygen is supplied to the mixture in the pressure chamber.

12. A method of producing iron from its ores consisting in making a mixture of said ore with solid carbon, preheating said mixture, supplying hot calcium oxide thereto, transferring the mixture thus obtained to a pressure vessel, maintaining in said vessel 9. pressure sufllcient for the progress of the reduction of the ore, cooling the reaction mixture, and separating the iron from the other reaction products formed during the reduction.

13. A method of producing a magnetic metal from an ore thereof, consisting in heating the ore with calcium oxide and with reducing agent con- 75 taining the element carbon under such pressure, that magnetic metal and carbonate of calcium are substantially quantitatively formed, and separating the metal from said carbonate over a magnetic separator.

14. A method of producing a magnetic metal from an ore thereof, consisting in treating the ore under pressure and heat together with calcium oxide and with reducing agent containing the element carbon at such a pressure, that magnetic metal and carbonate of calcium is substantially quantitatively formed, and separating the metal from said carbonate over a magnetic separator, and calcining the calcium carbonate to calcium oxide, using the calcium oxide thus obtained for repeated operation of the method.

15. A method of producing a metal from an ore thereoi. consisting of heating the ore together with calcium oxide and with solid reducing agent containing the'element carbon and with a reducing gas, under such pressure that metal and carbonate of calcium are substantially quantitatively formed, and separating the metal out of the reaction product.

16. A method according to claim 15, in which the reducing gas is carbon monoxide.

17. A method according to claim 15, in which the reducing gas is a mixture of carbon monoxide and hydrogen.