US3193378A - Process for reduction of iron ore - Google Patents

Description

July 6, 1965 N. P. PEET PROCESS FOR REDUCTION OF IRON ORE Original Filed April 2;, 1959 COMPRESSOR 42 Y 40 3 39 28 x 1 F r=| 8 x E as 37 29 9 V 3s 25 16 33 FE2O3L on:

5EPARATOR/ 32 nenucnou 34 2 4 zone STEAM nsroemne 26 l4 :2 WATER l mom 5 I A A A 20 HYDROGARBON J v v v V II 1 I? v- SEPARATOR M3 m"? 44 40 WATER 58 I 52 ORE 57 59 6O REDUCTION FIG 2 F5203? HEATING 25 zone 2 4 6| 52" ,-5 26 mow STEAM cougg sz slon 57:1 53- 5o '64 HYDROCARBON 82 63 AIR 5O i AND FUEL FLUE 53 GAS FE o 73 2 3 80 Z? 1's FIG. 3 DRE REDUCTIGN zone 8| 7&- CYCLONE 82 SEPARATORS I 24 2s STE AM IN VEN TOR.

74 NICK P. PEET,

77 BY uyonocaaaou 7,0 AND FUEL A ATTOR ZE; f

United States Patent 3,193,378 PRGCESS FOR REDUCTION OF FRQN ORE Nick P. ieet, Houston, Tex., assignor, by mesne assignments, to Esso Research and Engineering Company,

Elizabeth, N.J., a corporation oi Delaware Continuation of application Ser. No. 803,749, Apr. 2,

1959. This application Mar. 16, 1964, Ser. No. 352,727 14 Claims. (@i. 7535) This is a continuation of copending application Serial No. 803,749 filed April 2, 1959 and now abandoned.

The present invention is directed to the reduction of iron ore. More specifically, the invention is concerned with reducing iron ore using a suitable reducing gas. In its more specific aspects, the invention is concerned with reducing iron ore in which the fuel gas employed to provide the reducing gas is substantially reduced in quantity.

The present invention may be briefly described as a method for reducing iron ore which comprises the steps of forming a mixture of hydrocarbon and a gas-containing hydrogen, carbon monoxide, water, and carbon dioxide. This mixture is subjected to conversion operations under suitable conditions to form a second mixture of approximately 2 to 3 parts of hydrogen to 1 part of carbon monoxide. Iron ore is then contacted with this second mixture under reducing conditions suitable to form sponge iron.

The hydrocarbons employed in the practice of the present invention suitably include natural gas and its component parts. For example, methane, ethane, propane, and the butanes may be used in the practice of the present invention, and under some circumstances the corresponding olefins may also be used. Normally, liquid hydrocarbons may be used and examples thereof are gasoline, kerosene, gas oil, and even heavier residual oils. The components of the gasoline and kerosene hydrocarbons may also be used. However, it will be preferred to use natural gas hydrocarbons, and methane is preferred of the natural gas hydrocarbons.

The conversion operation may be either thermal or catalytic and may be conducted in a suitable reforming zone.

The temperatures employed in the reforming zone may range from about 1300 F. to 1600 F.

Pressures may range from about 0 to about 200 p.s.i.g.

In the ore reduction operation, temperatures may range from about 900 F. to about 2500 F., while pressures may range from about 0 to about 200 p.s.i.g.

Suitable catalysts may be employed in the conversion zone, and as examples of such catalysts may be mentioned cobalt molybdate or nickel on silica or alumina, or mixtures thereof.

The present invention will be further illustrated by reference to the drawing in which:

FIG. 1 is a flow diagram of a preferred mode;

FIG. 2 illustrates the present invention using a fluidized solids technique; and

- FIG. 3 is a further modification of the mode of FIG. 2.

Referring now to the drawing, numeral 11 designates acharge line by way of which a hydrocarbon such as methane is introduced into the system from a, source not shown into a reforming zone 12.. Reforming zone 12 may be either thermal or catalytic and may be provided with tubes or coils such as 13 which may contain a suitable catalyst as may be desired. In reforming zone 12, temperature and pressure conditions are suitably adjusted to provide conversion of the hydrocarbon charged to the system to produce a suitable reducing gas as will be described more fully hereinafter. In order to produce the'suitable reducing gas, there is. added to the hydrocarbon in line 11 an amount of steam introduced by line 14 controlled by valve 15 and a recycle gas introduced by line 16 from a source which will be described more fully hereinafter. The gas introduced by line 16 suitably contains hydrogen, water, carbon monoxide and carbon dioxide and supplies the necessary steam and oxygen for conversion of the hydrocarbon such as methane introduced by line 11. The hydrocarbon is employed in stoichiometric amounts relative to the carbon dioxide and water in the recycle stream introduced through line 16. The products from the conversion operation are discharged from reforming zone 12 by line 17 and are discharged into a condenser-cooler 18 into which a cooling medium is introduced by line 19. By cooling the products, water contained in the products in line 17 is condensed, and the cooled products are then discharged by line 20 into a separator 21. Since the hydrocarbon is in stoichiometric balance with the CO and H 0 of the recycle stream, an amount of water equivalent to the amount of steam introduced by line 14 is separated from the products and discharged from the separator by line 22 and may be recycled to line 14 via a boiler. The gaseous reducing product or gas is then withdrawn by line 23. This gas is approximately three parts of hydrogen and one part of carbon monoxide. The reducing gas discharges by line 23 into an ore reduction zone 24 where it is contacted under suitable temperature and pressure conditions with the iron ore introduced by line 25. Under the conditions obtaining in zone 25, reduced iron is formed which is withdrawn by line 26 for further processing.

The reduction operation obtaining in zone 24 results in a gaseous product or recycle gas being formed which is discharged by line 27. It is this recycle gas which forms the gas introduced into line 11 by line 16 and to achieve this desireble end, a portion of the gas in line 27 is withdrawn by line 28 and may be discharged directly into line 16. If desired, the recycle gas from line 28 may be passed through a condenser-cooler 29 by line 31) controlled by valve 31, condenser-cooler 29 being provided with a line 32 for introduction of a cooling medium. The recycle gas is discharged from condensercooler 29 by line 33 into a suitable separator 34 for withdrawal of any water which separates from the cooled recycle gas, the Water being removed by line 35. The separated gas is then discharged back into line 28 by line 36 controlled by valve 37 and the gas is then compressed using compressor 38 for return to line 11 by line 16, as has been described. In such operations as have been described employing condenser-cooler 29 and separator 34, valve 39 in line 31 will be closed.

It will be desirable under some circumstances not to employ condenser-cooler 29 and to discharge the hot recycle gases directly by lines 28 and 16 into line 11. Under these conditions, the condenser-cooler 29 would not be used and valves 31 and 37 would be closed and valve 39 opened.

In the practice of the present invention, it is also possible to use the remaining portion of the recycle gas as a fuel for reforming zone 12, and to this end branch line 40 controlled by valve 41 is provided which allows a second portion of the recycle gas to be discharged into the reforming zone 12 to supply heat thereto by combustion. When the portion of gas in line 4b is not recycled, then this portion of gas would be discharged from the system by opening valve 42 in line 27.

When the recycle gas is not employed as fuel, a portion of the hydrocarbon in line 11 may be introduced into the reforming zone 12 to supply heat thereto by combustion by opening valve 4-3 in line 44 which communicates with line 46*.

invention in which a fluidized solids technique is used with reference to FIG. 2, hydrocarbon is introduced into thesystem by line 50 and is mixed with steam. introduced by line 51 and recycle gas introduced by line 52 as will be described further. Alsointroduced into line 50 will be heated solids introduced by line 53 from heating zone 54. These solids may be either catalytic solids or catalytically inert solids. ticle diameters in the range from about to about 400 microns. The hydrocarbons, steam, and recycle gas with the solids in suspension are then discharged by line 50 into a conversion'zone 55 where a suitable residence time is provided to allow the hydrocarbons to be converted to forma reducing gas mixture of approximately 2 to 3 parts of hydrogen to 1 part of carbon monoxide. The reducing gas is then discharged by line 56 into a reducing zone 24, which is identical to reducing zone 24 of FIG. 1. In reducing zone 24 of FIG. 2 conditions prevail therein to cause reduction of the iron ore introduced by line 25, the reduced iron being withdrawn by line 26. The recycle gas is thus formed and withdrawn by line 57 and may be recycled to zone 55 by line 52. The other stoichiomctric balance between the hydrocarbon and the- CO and water in the recycle gas is' also employed. Also, it is contemplated to bein the purview of the present invention, as illustrated in the mode of FIG. 2, to condense and cool the recycle gas introduced into lineSO for separation of water. Also, it is within the purview of the present invention to separate from the conversion products water in order to make a more efficient operation, as has been described with respect to FIG. 1. a

With reference now to FIG. 3, another mode of the present invention will be described, and in these operations a hydrocarbon is introduced into the system by line 70, which forms a transfer line conversion zone. Solids which may be either catalytic or inert are introduced into zone 70 by line 71 from a separator zone 72. A conversion operation under conversion conditions takes place byvirtue of admixture with the solids which have particle diameters in the range from about 5 to 400 microns. The separated solids aredischarged by way of line 76 into. a transfer line heating zone 77 into which air is introduced. By virtue of the air introduced into zone 77 the fuel which may desirably be introduced thereto, and solids are suitably heated and introduced by transfer line heating zone 77 into cyclone separator 72 for separation of the gases from the heated solids which are then in:

troduced into transfer line conversion zone by line 71.

The gases separated from the solids in separation zone 72 are withdrawn therefrom by line 78 and introduced thereby into a'preheater 79, into which iron oxide is introduced by line '80. The preheated iron oxide is then discharged by line 81 into reduction zone 24 for admixture with the reducing gases withdrawn from cyclone separation zone 75 by line 8-2. Flue gas is Withdrawn from zone 79' by line 83 and may suitably be used for additional preheating of the iron ore introduced by line-80.

In the three modes of the present invention described relative tothe several figures of the drawing, it will be cellar that a new andi-rnproved operation has been provided in which improved hydrocarbon utilization is ob-. tained in a recycle operation in which a portion of the spent reducing gas containing combustion products is used in stoichiometric balance with the hydrocarbon to supply the oxygen required to reform the hydrocarbon. The

In any event, the solids will have par- 4i stoichiometry is obtainedby reference to the reaction (using methane as an example):

2CH +CO +H O 3C0 5H I The'relative proportions will change with the ratio in the recycle gas of 'CO :H O, which is a function of the reducing conditions. By virtue of an operation of the nature described herein, substantially improved and unexpected results are obtained, as will be brought out more fully hereinafter'by reference to the several examples In an operation such as has been described with referonce to FIG. 1, without employing condenser-cooler 29 and the separation zone, 34, 33.3 million cubic feet per day of methane are charged to a zone 12 and reformed under catalytic steam-reforming conditions, 50.0 million cubic feet of steam being employed and introduced by line 14. Introduced by line 16 are 100.0 million cubic feet of recycle gas, the composition of which will be given more fully hereinafter. In reforming zone 12, a

temperature in the range from about 1300" F. to about 1600 F. and pressure from about 0 to 200 p.s.i.g. are employed. The products are'introduced into a separator such as 21 and the water equivalent to the 50.0 million cubic feet of steam is withdrawn, leaving 200 million cubic feet of reducinggas having a composition of 2. parts of hydrogen to 1 part of carbon monoxide. This gas is introduced into a zone such as 24, operated at atemperature betwen 900 .F. and 2500 F. and a pressure of 0 to 200 p.s.i.g., and is employed to reduceiron oxide..

Under these conditions, 3270 tons per day of reduced iron are recovered. The spent gas amounts to 200 million cubic feet comprised of 44.5% of hydrogen, 22.2% of with the present invention, by employing 100.0 million 7 cubic feet of recycle gas, the amount of steam is reduced by 75.0 million cubic feet. Likewise, when using only steam for the conversion operation, 50 million cubic feet of methane per day are required, as contrasted to 33.3 million cubic feet in accordance with the present invention. It will be clear, therefore, that approximately 33% reduction in the amount of methane required results from the practice of this invention.

In another operation where the condenser-cooler 29 I and the separator 34 are employed, 100 mols of methane are admixed with 150 mols of steam and 500 mols of cold recycle gas introduced by way of line 16. This mixture is introduced into the reforming zone such as 12 operated at a temperaturepf about-1550 F. and about 75 p.s.i.g. Water is withdrawn from separator 21 in the equivalent of 150 mols perday. The reducing gas is in the amount of about 400 mols of hydrogen and 400 mols of carbon monoxide and is employed to reduced the iron oxide inj reduction zone 24 operated at a temperature 0151500 F. and 30 p.s.i.g. As a result, the spent gas totals 800 mols made of 266% mols, of hydrogen, 133 /3 mols of water,-

266% mols of carbon monoxide, and 133 /3 mols of carbon monoxide. Six hundred mols of this gas are then condensed and cooled in condenser-cooler 29 and water separates in the amount of 100 mols, leaving 500 mols of a cold recycle gas having a composition of 200 mols of hydrogen, 200 mols carbon monoxide, and mols of carbon dioxide.. Note that the 100 mols of CO are in by 75%, thereby saving about 50% of the natural gas employed and leaving the fuel equivalent of 200 mols of reducing gas to provide heat in conversion zone 12 amounting to about 15 million B.t.u.s per day. The amount of heat required for the reforming operation is approximately 22 million B.t.u.s per day, leaving only 7 million B.t.u.s to be supplied by burning methane introduced by line 44.

In another mode of practicing the present invention, referring again to FIG. 1, 100 mols of methane are admixed with 150 mols of steam and introduced into a conversion zone such as 12 along with 300 mols of a reducing gas. The conversion zone such as 12 is operated at a temperature of about 1550 F. at about 75 p.s.i.g. under catalytic steam-reforming conditions. The water separated from separation zone 21 by line 22 balances the amount of steam introduced by line 14 and amounts to 150 mols. As a result, there is charged by line 23 to reduction zone 24 a gas container 400 mols of hydrogen and 200 mols of carbon monoxide for a total of 600 mols. Iron oxide is reduced in ore reduction zone 24 at a temperature of 1500 F. and 30 p.s.i.g. to obtain reduced iron by line 26. The gas withdrawn from zone 24 by line 27 amounts to a total of 600 mols, of which 300 mols are charged directly to line 11 without cooling and without separation of water. This gas, amounting to 300 mols, has a composition of 133% mols of hydrogen, 66 /3 mols of water, 66% mols of carbon monoxide, and 33 /3 mols of carbon dioxide. The remaining gas having this composition is recycled by line 40 and is employed to provide the heat conversion zone 12, which is required for the operation. The savings in methane employed in this operation are about 33 /3 over that which would be necessary if the recycle is not employed, while the amount of heat required in zone 12 is supplied by the amount of gas recycled by line 40, it being found that the fuel requirement for catalytic steam reforming is 22 million B.t.u.s per day, while the fuel equivalent of the spent reducing gas is approximately 22 million B.t.u.'s per day. In other words, in the practice of the present invention, the only not feedstock in accordance with this mode of operation is hydrocarbon, since the amount of steam is balanced oil? by the amount of water withdrawn. In other words, it is the iron oxide itself which provides the amount of oxygen needed for the reforming operation, and it is the hydrocarbon charged which provides the heat required to convert the hydrocarbon.

It will be clear from the several modes of operation describing the present invention that a new, useful, and advantageous method has been provided.

The nature and objects of the present invention having been fully described and illustrated, what I wish to claim as new and useful and secure by Letters Patent is:

1. In the endothermic reduction of iron ore in a reduction zone at a temperature from 900 F. to 2500 F., wherein is utilized a reducing gas comprising hydrogen and carbon monoxide, and wherein is produced a combustible efiiuent gaseous stream, which has contacted all of the iron ore in said reducing zone, the improvement which comprises passing a first portion of said efliuent gaseous stream in contact with externally supplied steam and a hydrocarbon in a reforming zone whereby said reducing gas is produced substantially free of unreacted hydrocarbon, removing from said reducing gas an amount of water equivalent to said externally supplied steam, and passing the dewatered reducing gas through said reducing zone in contact with said iron ore, whereby reduced iron and said efiiuent gaseous stream are produced, and whereby the only net reactants in said reducing system are said hydrocarbon and said iron ore.

2. A method in accordance with claim 1 wherein the hydrocarbon is normally gaseous.

3. A method in accordance with claim 1 wherein the hydrocarbon is normally liquid.

4. A method in accordance with claim 1 further com prising the step of burning a second portion of said eiiluent gaseous stream to provide heat for said reforming reaction.

5. A method in accordance with claim 4 wherein said first and said second portions are substantially equal, and wherein the sum of said first and said second portions comprises substantially all of said eflluent stream.

6. A method in accordance with claim 1 wherein said first portion is cooled and at least a portion of the water therewithin is withdrawn before introduction of said first portion into said reforming zone.

7. A method in accordance with claim 1 wherein the efiiuent gaseous stream comprises hydrogen, carbon monoxide, water and carbon dioxide in the approximate ratios of 4:222: 1.

8. In the endothermic reduction of iron ore in a reduction zone at a temperature from 900*" F. to 2500" F., wherein is utilized a reducing gas comprising hydrogen and carbon monoxide, and wherein is produced a combustible efiiuent gaseous stream, which has contacted all of the iron ore in said reducing zone and which contains at least one compound of the group consisting of carbon dioxide and water, the improvement which comprises passing a first portion of said effluent gaseous stream in contact with externally supplied steam and a hydrocar bon in a reforming zone whereby said reducing gas is produced substantially free of unreacted hydrocarbon, said hydrocarbon being in stoichiometric balance with the total of carbon dioxide and water in said first portion, removing from said reducing gas an amount of water equivalent to said externally supplied steam, and passing the dewatered reducing gas through said reducing zone in contact with said iron ore, whereby reduced iron and said eiliuent gaseous stream are produced, and whereby the only net reactants in said reducing system are said hydrdocarbon and said iron ore.

9. A method in accordance with claim 8 wherein the hydrocarbon is normally gaseous.

10. A method in accordance with claim 8 wherein the hydrocarbon is normally liquid.

11. A method in accordance with claim 8 further comprising the step of burning a second portion of said eflluent gaseous stream to provide heat for said reforming reaction.

12. A method in accordance with claim 11 wherein said first and said second portions are substantially equal, and wherein the sum of said first and said second portions comprises substantially all of said efliuent stream.

13. A method in accordance with claim 8 wherein said first portion is cooled and at least a portion of the water therewithin is withdrawn before introduction of said first portion into said reforming zone.

14. A method in accordance with claim 8 wherein the effluent gaseous stream comprises hydrogen, carbon monoxide, water and carbon dioxide in the approximate ratios of 4:2:2:1.

References Cited by the Examiner UNITED STATES PATENTS 1,849,561 3/32 Wiberg 35 2,048,112 7/36 Gahl 7535 2,057,554 10/36 Bradley 75-45 2,577,730 12/51 Benedict 7535 2,592,783 4/52 Aspegren 75-35 DAVID L. RECK, Primary Examiner.

Claims (1)

1. IN THE ENDOTHERMIC REDUCTION OF IRON ORE IN A REDUCTION ZONE AT A TEMPERATURE FROM 900*F. TO 2500*F., WHEREIN IS UTILIZED A REDUCING GAS COMPRISING HYDROGEN AND CARBON MONOXIDE, AND WHEREIN IS PRODUCED A COMBUSTIBLE EFFLUENT GASEOUS STREAM, WHICH HAS CONTACTED ALL OF THE IORN ORE IN SAID REDUCIG ZONE, THE IMPROVEMENT WHICH COMPRISES PASSING A FIRST PORTION OF SAID EFFLUENT GASEOUS STREAM IN CONTACT WITH EXTERNALLY SUPPLIED STEAM AND A HYDROCARBON IN A REFORMING ZONE WHEREBY SAID REDUCING GAS IS PRODUCED SUBSTANTIALLY FREE OF UNREACTED HYDROCARBON, REMOVING FROM SAID REDUCING GAS AN AMOUNT OF WATER EUQIVALENT TO SAID EXTERNALLY SUPPLIED STEAM, AND PASSING THE DEWATERED REDUCING GAS THRUGH SAID REDUCING ZONE IN CONTACT WITH SAID IRON ORE, WHEREBY REDUCED IRON AND SAID EFFLUENT GASEOUS STREAM ARE PRODUCED, AND WHEREBY THE ONLY NET REACTANTS IN SAID REDUCING SYSTEM ARE SAID HYDROCARBON AND SAID IRON ORE.

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