GB2211860A

GB2211860A - Producing reformed gas for direct reduction of metal oxides to iron

Info

Publication number: GB2211860A
Application number: GB8808853A
Authority: GB
Inventors: Oscar G Dam; Henry R Bueno
Original assignee: ORINOCO SIDERURGICA; C V G Siderurgica del Orinoco CA
Current assignee: ORINOCO SIDERURGICA; C V G Siderurgica del Orinoco CA
Priority date: 1987-11-02
Filing date: 1988-04-14
Publication date: 1989-07-12
Anticipated expiration: 2008-04-14
Also published as: DE3811654A1; DE3811654C2; AR246986A1; GB8808853D0; MX167965B; GB2211860B; CA1336359C; BR8804025A

Description

METHOD AND APPARATUS FOR THE DIRECT REDUCTION OF IRON The present

invention is drawn to a process for producinq reformed gas for use in the direct reduction of metal. oxiaes containing iron to a metallized iron product and a method for and apparatus for the direct reduction of the metal oxides with the reformed gas.

The direct reduction of iron oxide, in forms such as pellets or lump ore, to metallic iron in the solid state has become a commercial reality throughout the 3-0 world in recent years. The combined annual capacity of direct reduction plants currently in operation or under construction is in excess of 15 million metric tons of direct reduced iron product, which is used primarily for feedstock in electric arc steelmaking furnaces. The world demand for additional direct reduced iron is projected to increase at a substantial rate for many years to satisfy a growing world need for such feedstock, as additional electric arc furnace steelmaking plants are constructed.

Known processes for the direct reduction of iron oxide to metallic iron utilizes a reformed gas as the reducing agent. Natural gas is used as a source for generating the reformed gas. The reformed gas for use in the direct reduction process is generated in a unit called a reformer by contacting the natural gas with an oxygen containing material in the presence of a catalyst, usually a nickel catalyst, which activates the reformation reaction of the natural gas so as to yield a.reformed gas which is rich in H 2 and CO. The reformed gas which is collected from the reformer is thereafter fed to a reduction reactor containing the iron oxide material wherein the direct reduction reaction is carried out. Thus, direct reduction processes heretofore known require two distinct reaction zones for carrying out the process; namely, a first zone for producing a reformed gas using a nickel catalyst and a second zone for carrying out the actual direct reduction process. In these conventional processes it is required that the reformed gas product in the first zone be treated prior to entering the reduction zone in order to remove CO 2 and/or water vapor.

Naturally, it would be highly desirable to provide a method for the direct reduction of iron oxide materials to metallic iron which would eliminate the necessity of separate reaction zones and thebse of nickel catalysts.

Accordingly, it is the principal object of the present invention to provide an improved method for the direct reduction of metal oxides containing iron to a metallized iron product.

- 2 It is a particular object of the present invention to provide a method as set forth above which is carried out in the single reaction zone of a direct reduction reactor.

It is a further object of the present invention to provide a method as set forth above wherein DRI material is used as a catalyst to produce a reformed qas directly in the reaction zone of a direct reduction reactor.

It is a still further object of the present invention to provide an apparatus for carrying out the method of the present invention.

Further objects and advantages of the present invention will appear hereinbelow.

SUMMARY OF THE INVENTION is In accordance with the present invention the foregoing objects and advantages are readily obtained.

The present invention is drawn to a process for producing reformed gas for use in the direct reduction of metal oxides containing iron to a metallized iron product and a method for and apparatus for the direct reduction of the metal. oxides with the reformed gas.

The method for the direct reduction of metal oxides containing iron to a metallized iron product in accordance with the present invention comprises providing a reduction reactor, positioning a first layer of DRI material in the reduction reactor, introducing a metal oxide material layer into the reactor above the DRI material, preheating the reactor to reduction temperature and thereafter feeding natural gas in the presence of an oxygen containing material to the DRI material.

In accordance with the present invention, the reformed gas is produced in the reduction zone of a direct reduction reactor wherein it immediately contacts the iron oxide material to be reduced. In accordance with the present invention, an apparatus is provided for the direct reduction of the metal oxides containing iron to a metallized iron product wherein a feeder gas is first contacted with the DRI maf-erial so as to form a reformed gas which thereafter contacts the metal oxides for the direct reduction thereof.

The method of the present invention allows for a single reaction zone of a direct reduction reactor to be employed for both the production of the reformed gas for use in the reduction process and for the actual direct reduction of the iron oxide material.

4 BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic illustration showing a reduction reactor in accordance with the present invention.

Figs. 2a, 2b and 2c are schematic illustrations of the test equipment used in the comparative examples of the instant disclosure.

Fig. 3 is a graph comparing the results of direct reduction in accordance with the present invention and that of-known processes.

DETAILED DESCRIPTION

The method for the direct reduction of metal oxides containing iron to a metallized iron product comprises providing a reductioE'reactor, positioning a first layer of DRI material in the reduction reactor, introducing a metal oxide material layer into the reactor above the DRI material, preheating the reactor to reduction temperature and thereafter feeding natural gas in the presence of an oxygen containing material to the DRI material.

Fig. 1 is a schematic illustration of an apparatus for carrying out the method of the present invention.

The apparatus comprises a reduction reactor 10 having a first support surface 1.2 for supporting direct reduced iron (DRI) which acts as a catalyst in the method of the present invention for producing reformed gas rich in 5 H 2 and CO from natural cas. The direct reduced iron (DRI) is a product of the direct reduction process of the present invention. The first support surface 12 is provided with a plurality of apertures 14 through which gas is fed from an annular preheating zone 16 which defines a reaction zone 18. Inlet 20 is provided for feeding a feeder gas (to be described in detail hereinafter) to the annular preheating zone 16. The reactor includes a second support element 22 positioned above the first support surface 12 so as to define a space therebetween which is occupied by thle DRI material. The second support surface 22 supports the iron oxide particles 24 which are to be reduced to metallic iron in the direct reduction process of the present invention. The second support surface 22 is provided with a plurality of orifices 26 in the same manner as first support surface 12.

In accordance with the method of the present invention a feeder gas is fed to the annular preheating zone and from there up through the.DRI material wherein 6 the feeder gas is reformed to a gas rich in H 2 and CO. The feeder gas consists of natural gas mixed with an oxygen containing material.. The oxygen containing material may be air, CO H 0, pure oxygen or any 2# 2 1 other process gas having oxygen as a component thereof. In accordance with the present invention, the oxygen should be present in an amount with respect to the natural gas of about 0.75:1.0 to 1.0:1.0. In accordance with the further feature of the present invention, nitrogen can be fed to the reactor during the preheating thereof or with the natural gas in oxygen mixture. The purpose of.the nitrogen is to avoid reoxidation of the DRI material. In accordance with the method of the present invention, the feeder gas first contacts the DRI material in the reduction reactor and is reformed so as to form a reformed gas which is rich in H 2 and CO. The DRI material should be present in an amount with respect to said iron oxide material of from about 0.25:1.0 to 0.50:1.0 in order to assure enough reformed gas for the direct reduction process. The reactor is operated under the following conditions during the gas reforming-direct reduction process: Temperature: 850 to 950C; Pressure: 1.1 to 1.2 BAR7 GAS FLOW RATE: 5 to 20 LT/min. The reformed gas produced by contacting 7 the feeder gas with the DRI material flows up through the iron oxide particles and acts as the reducing agent for the direct reduction of the metal oxides to a metallized iron product. In order to have an effective reduction process, the reformed gas shoulrl be present in an amount of from about 800 to 1400 Nm 3 /ton, preferably from about 1000 to 1200 Nm 3 /ton with respect to the iron oxide material.

The method and apparatus of the present invention allows for an efficient direct reduction process which is superior to processes heretofore known.

Further advantages of the present invention will be obvious from the following exemplificative examples.

EXAMPLE 1 is In order to demonstrate the advantages of the method and apparatus of the present invention compared to prior art direct reduction processes, a three step program was conducted. Figs. 2a, 2b and 2c are schematic illustrations representing each of the three steps.

Fig. 2a represents the direct reduction processes heretofore known. In accordance with these known processes a reactor 100 defininq a reaction zone 102 contains a mineral sample 104 of a metal oxide containing iron. The reaction zone is selectively fed 8 - via line 106 with nitrogen from reservoir 108 and a reducing gas mixture comprising 72% H29 14% CO, 9% CO 5% CH from reservoir 110. The reduction 2 p 4 # process was carried out under standard direct.reduction conditions. After completion of the reduction process the weight loss of the material was measured continuously by means of a thermobalance and a reduction curve generated using the following formula:

%R = initial weight - final weight x 100 initial weight The reduction curve as shown in Fig. 3 indicates that 90% reduction was obtained for the iron oxide material employing the prior art direct reduction process.

EXAMPLE 2

In order to demonstrate the utility of DRI as a catalyst in the generation of a reformed gas, a reaction zone identical to that of Example 1 was employed. With reference to Fig. 2b the reaction zone contained a charge of DRI material. The reaction zone was selectively fed with nitrogen (solely for heating and cooling purposes), CO 2 and natural gas from reservoirs 112, 114, and 116 respectively at the following flow rates: 5 its/min., 4 its/min. and 6 lts/min. The reformatiod reaction was conducted under the following conditions: 200 gr. DRI material; Temperature of 900C with a feeder gas of 10 lts/min. (4 lts/min. CO 2 and 6 Its/min. CH 4). At different times during the reformation reaction exit gases were sampled in order to determine composition of same. Table 1 hereinbelow sets forth the time exposure in the reaction chamber and the reformed gas produced using DRI as a catalyst. As can be seen, the reformed gas is rich in H 2 and CO.

TABLE I

Exposure Reactor Reformed Gas With DRI Time Feeder iTa-tural (mins) Gas H2 CO C02 gas 10 Mixture of C02 49.5 36 7.5 7.0 Natural Gas Mixture of C02 49.5 36 7.5 7.0 Natural Gas Mixture of C02 49.5 36 7.5 7.0 Natural Gas Mixture of C02 49.5 36 7.5 7.0 Natural Gas 1 - 1 1 - EXAMPLE 3

In order to determine the effectiveness of the direct reduction process of the present invention, iron oxide was reacted in the.reactor described in Fig. 1 in the following manner. The DRI material 200 grams was positioned in the reactor and the iron oxide material 500 grams was placed on top of the DRI material. The reaction zone was preheated to the reduction temperature of 9000C. Thereafter a mixture of CO 2 and natural qas 10.40% CO 2 and 60.% CH 4 was fed to the reaction zone at a rate of 10 Its/min. from the bottom of the reaction zone so as to insure contact with the DRI material prior to contact with the metal oxide. After completion of the reduction process weight loss was measured and a second reduction curve generated. As can be seen from Fig. 3, the grade of reduction obtained in accordance with the process of the present invention is virtually identical to that obtained in the known reduction process of Example 1 thereby demonstrating the effectiveness of the method of the present invention.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The 12 present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein. - m

Claims

CLAIMS:

1. A method for the direct reduction of metal oxides containing iron to a metallized iron product comprising feeding natural gas in the presence of an oxygen-containing material to a reactor preheated to reduction temperature and containing a first layer of direct reduced iron (DRI) material and a metal oxide material layer.

2. A method according to claim 1 including feeding said natural gas and oxygen material through said DRI material so as to generate a reformed gas rich in H 2 and CO which contacts said metal oxide containing iron.

3. A method according to claim 1 wherein the ratio of DRI material to metal oxide is between 0.25:1.00 to 0.50:1.00.

4. A method according to claim 1 including operating said reactor at a temperature of 850 to 9500C, at a natural gas pressure of about 1.1 to 1. 2 BAR in the presence of oxygen in an amount of 16 to 20% by volume.

14 - a

5. A method according to claim 1 wherein the ratio of oxygen to natural gas is from 0.75:1.0 to 1.0:1.0.

6. A process for producing reformed gas for use in the direct reduction of metal oxides containing iron to a metallized iron product comprising feeding natural gas in the presence of an oxygen containing material to a reaction zone preheated to reformation temperature for contacting direct reduced iron (DRI) material within the reaction zone.

7. A process according to claim 6 wherein said reformation temperature is between 850 to 9500C.

8. 'A process according to claim 6 including feeding said oxygen and natural gas containing material to said reaction zone wherein the ratio of oxygen to natural gas to oxygen is in an amount from about 0.75:1.00 to 1.00:1.00.

- 15

9. An apparatus for the direct reduction of metal oxides containing iron to a metallized iron product comprising a reactor defining a reaction zone, first support means for holding a catalyst material in said reaction zone at a first location, second support means for holding said metal oxides in said reaction zone at a second location-proximate to said first location and a feed-means for feeding a feeder gas to said reaction zone such that said feeder gas contacts said catalyst material and is reformed prior to contact with said metal oxides.

10. An apparatus according to claim 9 wherein said reaction zone is elongated and the location of said first support means is above said feed means and below the location of said second support means.

T i 16 - Amendments to the claims have been filed as follows

11. A process for the direct reduction of metal oxides containing iron to obtain a DRI metallized iron product by contacting said metal oxides with a reformed gas rich in H D- and CO in a reduction reaction, the improvement which comprises:

providing a reduction reactor having a single reaction zone; locating a layer of said DRI metallized iron product in said reaction zone, positioning a layer of said metal oxides proximate to said layer of DRI product; heating said reaction zone to a temperature of from 850 to 9500C so as to heat said DRI product and said metal oxides; feeding a feeder gas comprising natural gas and an oxygen containing material selected from air, CO p-, H J-0, pure oxygen, product gases containing oxygen and mixtures thereof to said reaction zone to covert the natural gas and oxygen-containing material to H.2 and CO so that said oxygen containing material and said natural gas pass through said heated DRI product in said reaction zone so as to produce the reformed gas used in the reduction process, said reformed gas being rich in H j 0 and C0; and contacting said metal oxides with said reformed gas so as to reduce said metal oxides to said DRI product wherein the ratio of DRI product to metal oxides is maintained between 0. 25: 1.00 to 0.50 1.00 throughout the process.

Published 1989 at The Patent Office, State House, 66 71 Fligh Holborn, London WC1R 4TP. Further copies maybe obtained from The Patent office. Sales Branch, St Mary Gray, Orpington, Kent BR5 3RD Printed by Multiplex techniques ltd, St Mary Gray, Kent, Con. 1187