US2690333A - Apparatus for smelting oxide ores - Google Patents

Description

p 28, 1954 E. s. POMYKALA 2,690,333

APPARATUS FOR SMELTING OXIDE ORES Filed April 15, 1951 5 Sheets-Sheet l Fig.1

INVENTOR p 28, 1954 E. s. POMYKALA 2,690,333

APPARATUS FOR SMELTING OXIDE ORES Filed April 13, 1951 3 Sheets-Sheet 2 L5 5p9 5,03 INVENTOR E. s. POMYKALA 2,690,333

APPARATUS FOR SMELTING OXIDE ORES Sept. 28, 1954 3 sheets sheet 3 Filed April 13, 1951 6 I 3 S2 IEVENTQR Patented Sept. 28, 1954 UNITED STATES ATENT OFFICE 4 Claims.

This invention relates to method and apparatus for smelting iron and other metals and converting the blast furnace exhaust gases after suitable treatment into ammonia and other useful chemicals. It is primarily devised for smelting iron particularly for localities where suitable coking coal is not readily available but where other fuels such as natural gas or oil are plentiful. However, it is not limited to smelting, it may be used to advantage as a step in the manufacture of ammonia, methyl alcohol, and other chemicals.

At the present time smelting of iron is done almost exclusively by means of coke. The process consists in blowing highly preheated air through blast pipes called tuyeres into the lower part of a high furnace or stack (about 100 feet high) filled with ore, coke, and a flux, generally of limestone. In the lower part of the furnace opposite the tuyres, the combustion is intense and temperatures are very high, about 2000 C. and the burden of the furnace at this point is mostly glowing coke, and a little slag and iron in liquid form precolating down. The ore in general is reduced at a point above this level. The ore is reduced mostly by carbon monoxide gas which is formed by combustion or chemical union of hot glowing coke and a blast of air. In the lower part of the stack the temperatures are so high that carbon dioxide (CO2) usually formed in combustion of coke can exist only momentarily and is immediately reduced by glowing carbon to carbon monoxide (CO). This may be expressed chemically as follows:

The reduction of iron ore is automatically carried out in stages.

(1) takes place in the upper part of the stack and (3) takes place in the hotter part of the stack, lower down approximately at one half the height of the stack above the tuyres. Below this point the reduction is accomplished mostly by carbon alone. All this is somewhat simplified as some of the equtaions are reversible depending on temperature conditions and there is some slight temporary oxidation taking place as the ore burden works down.

In the smelting of iron coke has a multiple function.

(1) Coke, by its combustion furnishes heat for the process.

(2) By its combustion, or chemical union with air it forms carbon monoxide (CO) gas, which is the main agent used in reduction of ore. Coke or carbon together with carbon monoxide also protect the reduced iron from oxidation by the blast air.

Finally coke has the important function as a load carrying medium supporting the overburden of ore and fluxing stone in the furnace.

All these functions are important, but it is felt they may be advantageously separated to a considerable extent and some of these powers of coke be assigned to other fuels such as hot gasified petroleum derivatives like ethane, CzI-Is; propane, CaHs; butane, C4H10; pentane, C5H12; etc., or natural gas which is mostly methane, CH4, and the unsaturated hydrocarbons like ethylene, propylene, butylene or various combinations of these fuels.

It is the main object of this invention to show how this may be done.

It is well known that in the production of industrial gases such as producer gas or water gas, hot steam may be reduced by glowing carbon to hydrogen and carbon monoxide the reaction being:

Both hydrogen and carbon monoxide incidentally are excellent reducing agents. However, to secure them it is proposed to blow not hot steam upon glowing coke, but hot hydrocarbons such as gasified petroleum fractions or even hot natural gas. This of course, cannot be done in a haphazard manner, as such gases are very explosive if not properly handled, and one of the principal objects of this invention is to show how this process may be carried out with safety.

Since in the operation of this new process for smelting iron and other ores, considerable carbon monoxide and hydrogen will flow out of the furnace with the exhaust gases which will still consist mainly of nitrogen. It is the further purpose of this invention to utilize these exhaust gases in the manufacture of ammonia, methyl alcohol, and other chemicals resulting therefrom.

In the operation of this new process coke will still be required, but in considerably smaller amount than at present, only about 40% of the present requirements will be necessary. Smaller amount of fluxing stone will also be required since the amount of impurities needing fiuxing will be less.

Another object of this invention is to improve the quality of the product manufactured namely, to reduce the carbon content in the smelted iron.

With these and other objects and advantages in view, the details of construction and operation are further illustrated by having reference to the accompanying drawings wherein:

Figure 1 is a general schematic plan and arrangement of the apparatus.

Figure 2 is a sectional plan of the blast furnace or smelting stack taken on lines 2-2, in Fig. 3, approximately at the elevation of the tuyeres.

Figure 3 is a vertical section of the lower part of the blast furnace taken on lines 3-3, in Fig. 2.

Figure 4 is a horizontal section of a tuyere taken on lines d l in Fig. 5.

Figure 5 is a vertical sectional view of a tuyere taken on lines 55 of Fig. 4.

Figure 6 is a general sectional view of a blast furnace.

In all views similar numerals or numerals and letters designate similar parts.

Designations la, lb, and lo indicate retaining walls in the storage area.

2 is a general storage area for ore, coke and limestone.

3a, 3b, 3c are railroad tr czs used for general transportation of smelting burden.

d is a chain conveyor used for delivering sme1ting burden from the bins or storage into the fur nace.

Numeral 5 indicates the blast furnace.

Now starting at the oth r end, numeral 6 indicates main oil feed line; i is a valve in the line; 8 is an oil pump; 9 is another valve on the outlet side. H3 is heating coil or suitable heat exchanger, i2 is an outlet valve, it is a hot hydrocarbon gas receiver, Etc is a gas temperature indicator, E3?) is a gas pressure indicator, i is a gas relief valve, and it is suitable piping for gas relief purposes. Numeral it indicates main outlet valve for gas from the receiver is into main supply line 20. ll is a receiver or storage tank for nitrogen or other suitable inert gas. it is a valve in line is controlling the flow of nitrogen from receiver ll into main supply line Main supply line 253 feeds the hot hydrogen gas into suitable bustle pipe shown in Figures 3 and 6. From bustle pipe 570 the hot hydrogen gas is led through goose neck pipe 51 into tuyeres 5p whence it is dischargedinto the furnace on glowing coke of the furnace charge, through aperture The heated air comes from the air heating stoves through rnain feed line '28, into large bustle pipe whence it is directed through goose neck pipes 'Ein into combined tuyeres The hot air and hydrocarbon blast is discharged into the furnace on glowing carbon through apertures 5 95 and As in existing practice there are a multiple number of tuyeres, generally about twelve units for a standard size furnace.

The furnace 5 in general follows present standard practice, except for the double bustle pipe, special tuyeres, combined for leading hydrocarbon gas together with standard air blast, and a special construction for the bottom of the furnace at the crucible for giving a better support to the overburden than is the practice at present.

The blast furnace construction is shown in Figure 6, and the details are shown in Figures 2, 3, 4 and 5.

In the construction of the crucible a departure is made from the present practice, inasmuch as cross walls to are built in and a ledge ii? is provided around the periphery of the crucible. These are arranged in a honeycomb fashion but may follow other patterns. All cross walls are interconnected through holes for discharging molten ported partially on the converging walls of the bosh (which is that part of the furnace directly above the crucible) and partially on the bottom. The coke tends to dome over or arch over to the converging walls of the bosh but because of the large spans and also because a great deal of colic is consumed here there is a slippage and a considerable amount of coke below the lines of eouilibrium falls and is pressed down into the crucible. This is undesirable since in this manner coke comes in contact with, and saturates the -molten iron.

It has been found that iron freshly cruel-ted as it percolates down through the glowing coke has a carbon content of about 1 percent. After it is in contact with carbon in the crucible the percentage of carbon is raised to about e2 percent. This is not good since nearly all this carbon has to be burned out in making steel, either in the Bessemer converter or Siemens open hearth furnace. This processing is quite expensive. By placing these cross walls so, as shoen in Figure 2, 3 and 6 the spans of any domes of coke are greatly lessened. This is shown as E? in Figure 6. Lines of stability are more easily maintained and the little of the coke that falls below floats in the molten slag which is indicated by the boundary line x-az, between the slag and molten iron in Figures 3 and 6. By so doing, contact of coke with molten iron is minimized, and saturation of iron with carbon is avoided.

The remainder of the details of the furnace follow standard practice. In Fig. 2, 50 are walls of the furnace at the bosh, are structural bands at the bosh. Eie are structural bands at the crucible. 5g is outlet hole for molten metal, 5b is slag hole, 52' is a concrete slab foundation, 5; are wall cooling plates. {is (Fig. 6) are struc aural columns supporting the main walls of the furnace.

In the upper part of the furnace 573 is the chute for loading the burden of the furnace. This burden of coke, ore, and flux is lifted by means of a chain conveyor 6 (Fig. 1) and deposited in chute 5t, whence it is lowered by stages into the furnace by means of movable bells, 5a and the. to is a working platform.

In construction of the tuyeres 5p a departure is made from the existing practice. Where formerly it was one Water cooled blow pipe, it now has three apertures or nozzles, one for hot hydrocarbon gas and hot air mixture 5116, two for hot air blast 5175. Part of the preheated delivered to nozzles 5105 passes through apertures 51:19 and mixes with the hydrocarbon gases in nozzle 5106 and the resulting mixture then pinges on the glowing furnace charge. The zles are made from one casting or forging and surrounded with a continuous wall The whole is so built that it is water-tight, bctween 5134 and walls Epl. There is a water space 5102, for circulating cooling water. 5123 are space lugs. 5:01 is cooling water inlet and cps is water outlet.

The gases discharged from the furnace are handled in a standard manner. They are discharged to main exhaust pipe or downcorner 2i, and are led into dust catcher 22. From there they are led by pipe 23 into a battery of dust precipitators, 2d, thence through another duct 25 which leads a part of the hot gases into regenerative stoves 26a, 26b, 26c, 2601. Here the exhaust gases are burned, heating the walls of the stoves to a high temperature. After this heat extraction these gases are discharged, and a blast of air is circulated through the stoves by means of air fans or blowers 21a. and 2122. This air is preheated to a temperature of about 1200 F. (650 0.), and is then redirected to the furnace through main air feed line 28.

Since only a part of the exhaust gases are used for heating the stoves, the remainder of the gases can be put to other uses such as power or preferably making chemicals. This will be shown later.

Opcration.ln the operation of this process, the furnace is loaded with smelting burden as at present. The fires are started exactly the same, and the furnace is brought up to smelting on air blast alone, at about 12 lbs. per square inch gage pressure. As this is taking place the generation and heating of hydrocarbon gas is started. This in general follows existing practice in the petroleum industry for making gasoline. Gasoline in the modern practice is largely made from heavier stock like petroleum generally by one of several cracking processes. The base stock is heated either in the liquid state or injected into a heated chamber in the vapor state and in contact with a suitable catalyst whereby the heavier molecules are broken down into smaller units. The general approximate and typical equation being as follows: 700 C.

In my new process, great precision is not required and a greater variety of size of molecules can be used. What is required is a; hot hydrocarbon gas about 1200 F. (650 C.), and at approximately 12 pounds gage pressure. Small molecular size is desirable but not essential mainly since gas of smaller molecular structure causes less expansion in the products of combustion. This heating and cracking process can be performed in a hot coil I and a heated chamher is operating in the neighborhood of the temperature and pressure indicated above.

When the smelting furnace is well heated and operating on full blast, it may then be switched over to hydrocarbon gas fuel. This is done in the following manner: The lines 20 conducting the hot hydrocarbon gas from the receiver I3 have to be first flushed with inert gas preferably nitrogen, stored in tank ll. Nitrogen gas can be secured and purified from the exhaust gases issuing from the regenerative heating stoves 20a to 26d inclusive by a process shown in my U. S. patent application Serial No. 148,492.

After the lines are flushed, the hot hydrocarbon gas can be let in through valve it. As valve [6 is opened, the nitrogen valve I8 is closed. The hydrocarbon gas is forced in the lines at 12 pounds per square inch gage pressure. This hot gas drives out the nitrogen and is forced into the furnace through tuyres p. Just before issuing from the nozzle 5133 it is mixed partially with the air blast which is blown at slightly higher pressure than the hydrocarbon gas. This mixing is done by means of apertures 5p0 and the hydrocarbon gas is burned partially at the tip of the nozzle 5175. Because the mixing of the gases is incomplete in the nozzle and also because there is a shortage of oxygen at the tip of nozzle Epfi,

combustion is incomplete here. The generally accepted theory for combination of hydrocarbons is that they first burn to alcohol and by stages break down to aldehydes and carbon monoxide, Water vapor and finally carbon dioxide. However, as stated above due to the high temperatures existing in the furnace at this point and in the presence of glowing carbon, carbon dioxide and water vapor the usual end products of combustion of hydrocarbons cannot exist and if they do it is only momentarily for they are immediately reduced by glowing coke to carbon monoxide and hydrogen. The end average result that may be expected say for methane gas would be:

(a) CH4+ /2O2- 2H2+CO+ 6,620 cal. per gram mole with additional carbon of the coke bed.

(12) C+ A2O2+CO+28,800 cal. per gram mole Adding Equations a and b the result is as follows:

CH4+C+O2=2H2+2CO+ 35,420 cal. per gram mole This indicates that the temperature at the tuyeres with this new process will be less than under existing process. However, the interior temperatures will be higher on account of the higher heat content per gram in the hydrocarbon over that in the coke.

CH4+2OL=CO2+2H20+13,200 cal.

C+O2=CO2+8100 cal.

There are other reasons why higher temperatures may be expected in the interior of the furnace above the tuyeres than at present. Considerable amount of ferrous oxide FeO will be re duced by hydrogen rather than carbon.

From the above it would appear that there would be some increase in temperature in the interior of the furnace with this new process. However, high specific heat of hydrogen works against this increase and a considerable part may be nullified. This use of hydrogen in smelting iron should have other useful benefits however, particularly it would tend to keep the carbon con tent in the iron lower than at present. Also it is possible that the process may lend itself to reducing other ores which are difiicult to smelt at present.

In the interest of safety it is necessary to consider the expansion of the gases in the furnace under the two methods. Under the existing method it may be assumed that coke in the vicinity of the tuyeres burns with oxygen of the air blast to carbon monoxide.

20- -02+snen-z=zoo+avsm Solid-P1 vol.+3.'76 vol.=5.70 volumes Volume increase=g =l.35

The temperature of the gas increased as before. Total volume expansion=1.35 2.46:3.3.

From this it is seen that expansion is not abnormal and well within control. Also in the interest of safety it may be mentioned that pipe lines from hydrocarbon receiver to the furnace should always be flushed with nitrogen whenever the furnace is being closed down, the operation being similar but in reverse to that when starting the furnace on hydrocarbon gas.

The gases as they issue from the top of the furnace will contain nitrogen as the main component, as well as carbon monoxide, carbon dioxide, hydrogen and Water vapor (steam) These can be treated by suitable processes some existing and some recently devised (like the process shown in my U. S. patent application Serial No. 148,492) whereby all the gases except nitrogen and hydrogen are eliminated and forming am monia from these two. Also by existing systems.

CO+H2O=CO2+H2 Catalyst CO2 can be eliminated by process shown in patent application Serial No. 148,492. The remaining gases, nitrogen and hydrogen in proper pro-- portion and under high temperature and pressure can be made to combine to form ammonia by various modern processes like Haber, Claude, etc.

From ammonia other important industrial chemicals may be made. The economic advantages using this method are: the vast supply of cheap raw materials and fairly low temperatures of the exhaust gases permit easy and eificient separation.

Methyl alcohol can also be made from these exhaust gases by processes now in existence.

The exhaust gases as noted above contain nitrogen, hydrogen, carbon monoxide, carbon dioxide, water vapor and small amount of various impurities. Carbon dioxide, Water vapor and other impurities may be easily washed out as noted above for ammonia. The remaining gases, namely, nitrogen, carbon monoxide, and hydrogen which are fairly insoluble in water remain. Ihese gases can be highly compressed and heated, and with the aid of a suitable catalyst carbon monforming methanol:

CO 21-12 =C'H3 .OH

Catalyst Having described the general features of the process and apparatus of this invention, it is felt others skilled in the art may make changes in arrangement of parts and details without departing from the spirit of this invention or the scope of the appended claims.

I claim:

1. An apparatus for smelting iron and other metal oxide ores with the simultaneous production of reducing gases, which comprises a blast furnace, a source of liquid hydrocarbons, means for cracking and gasifying said hydrocarbons, means for compressing and preheating air to high temperatures, tuyeres for introducing the cracked hydrocarbons and the preheated air into the furnace, each tuyere having a central hydrocarbon nozzle and a pair of air nozzles mounted in a common structure directly adjacent to and on either side of said hydrocarbon nozzle, said nozzles being provided with apertures positioned close to the exit of the tuyre which connect the air nozzles with the central hydrocarbon nozzle for mixing the cracked hydrocarbon gases with part of the air as the gases enter the furnace; said nozzles being so constructed and arranged that the bulk of the air passes through the air nozzles to impinge directly on the glowing furnace charge at either side of the hydrocarbonair mixture discharged from the central nozzle, a crucible at the bottom of said furnace provided with vertical interconnected cross walls forming a honeycomb structure with interconnecting passageways for supporting the overburden out of contact with the molten metal, means for charging the furnace, an external source of inert gas, conduit means connecting said source with the tuyeres for flushing an inert gas through the hydrocarbon nozzles of the tuyeres through the conduit means when the furnace is started and when it is shut down, means for recovering the reducing gases discharged from the furnace, and means for Withdrawing molten metal from the furnace.

2. In a furnace for smelting iron and other metal oxide ores, tuyeres combining in one structure a central nozzle for introducing preheated hydrocarbon gases into the bosh of the furnace, a pair of air nozzles mounted directly adjacent said hydrocarbon nozzle for introducing preheated combustion air into the furnace, said nozzles being provided with apertures close to the exit of the tuyere connecting the air nozzles with the central hydrocarbon nozzle so constructed and arranged that part of the combustion air, insufficient to produce complete combustion, passes through said apertures to mix with the h drocarbon in the hydrocarbon nozzle while the remainder of the air passes directly through the air nozzles to impinge upon the furnace charge.

3. An apparatus for smelting iron and other metal oxide ores with the simultaneous generation of reducing gases, which comprises a blast furnace provided with a bosh and at the bottom with a crucible, means for supplying partially cracked hydrocarbon gases preheated to high temperatures to said furnace, and for supplying compressed air preheated to high temperatures to said furnace, said means comprising a plurality of tuyeres mounted around the bosh of the furnace each tuyre having in a single structure a central hydrocarbon nozzle and directly adjacent air nozzles mounted on either side of the hydrocarbon nozzle, said nozzles having interconnecting passageways so constructed and arranged as to cause a' portion of the air to mix with the hydrocarbon gases as they pass through the central nozzle in amount insufficient to pro duce complete combustion of the hydrocarbon gases while the bulk of the air passes directly from said air nozzles into the bosh of the furnace to impinge against the glowing furnace charge, vertical cross walls built in the crucible at the bottom of the furnace and arranged in honeycomb fashion for supporting the furnace charge out of contact With the molten metal in the cm cible and provided with interconnecting passageways for discharging molten metal, means for charging the furnace, means for withdrawing molten metal from the furnace and means for recovering reducing gases discharged from the furnace.

4. The apparatus of claim 3 including an external storage chamber for an inert gas and con- 9 duit means connecting said storage chamber with the tuyres for flushing the inert gas through the hydrocarbon nozzles of the tuyres and through said conduit means when the furnace is shut down and before it is placed in operation.

References Cited in the file of this patent UNITED STATES PATENTS Number Number 10 Name Date Weber Sept. 1, 1885 Perkins May 7, 1907 Kemp Oct. 12, 1909 Frick Dec. 5, 1911 Carstens Oct. 18, 1921 Ward Dec. 14, 1926 Valentine Aug. 4, 1941 Hansgirg Dec. 28, 1943 Williams May 8, 1945 Kinney May 13, 1947

Claims (1)

1. AN APPARATUS FOR SMELTING IRON AND OTHER METAL OXIDE ORES WITH THE SIMULTANEOUS PRODUCTION OF REDUCING GASES, WHICH COMPRISES A BLAST FURNACE, A SOUCE OF LIQUID HYDROCARBONS, MEANS FOR CRACKING AND GASIFYING SAID HYDROCARBONS, MEANS FOR COMPRESSING AND PREHEATING AIR TO HIGH TEMPERATURES, TUYERES FOR INTRODUCING THE CRACKED HYDROCARBONS AND THE PREHEATED AIR INTO THE FURNACE, EACH TUYERES FOR INTRODUCING THE CARBON NOZZLE AND A PAIR OF AIR NOZZLED MOUNTED IN A COMMON STRUCTURE DIRECTLY ADJACENT TO AND ON EITHER SIDE OF OF SAID HYDROCARBON NOZZLE, SAID NOZZLES BEING PROVIDED WITH APERTURES POSITIONED CLOSE TO THE EXIT OF THE TUYERE WHICH CONNECT THE AIR NOZZLES WITH THE CENTRAL HYDROCARBON NOZZLE FOR MIXING THE CRACKED HYDROCARBON GASES WITH PART OF THE AIR AS THE GASES ENTER THE FURNACE; SAID NOZZLES BEING SO CONSTRUCTED AND ARRANGED

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