US3884677A

US3884677A - Blast furnace operating methods

Info

Publication number: US3884677A
Application number: US417622A
Authority: US
Inventors: Werner Wenzel; Heinrich Wilhelm Gudenau; Tsutomu Fukushima
Original assignee: Nippon Kokan Ltd
Current assignee: JFE Engineering Corp
Priority date: 1972-11-25
Filing date: 1973-11-20
Publication date: 1975-05-20
Anticipated expiration: 1992-05-20
Also published as: GB1438999A; IT1001934B; FR2207990A1; AT338306B; JPS4979910A; BR7309161D0; AU6251873A; ATA986773A; FR2207990B1; CA1009455A

Abstract

A blast furnace operating method according to which blast furnace gas is regenerated into a condition where it is enriched with carbon monoxide and hydrogen. The thus-regenerated blast furnace gas is then introduced into the hearth of the blast furnace as part of the blast.

Description

United States Patent [191 Wenzel et al.

[451 May 20, 1975 BLAST FURNACE OPERATING METHODS [56] References Cited [75] Inventors: Werner Wenzel; Heinrich Wilhelm UNITED STATES PATENTS Gudenau; Tsummu Fukushima, all 1790.711 4/1957 Sellers et a1. 75/42 of Aachen, Germany 3,15l,974 10/1964 Rheinlander 75/42 Assigneez pp n Kokan Kabushiki Kaisha, $594,154 7/1971 Kanokogi 75/41 Japan Primary ExaminerL. Dewayne Rutledge [22] Filed: Nov. 20, 1973 Assistant Examiner-M. J. Andrews [21] Appl NO: 417,622 Attorney, Agent, or FtrmStemberg & Blake [57] ABSTRACT [30] Forelgn Apphcatlon Pnorlty Data A blast furnace operating method according to which Nov. 25, 1972 Germany 2257922 blast furnace gas is regenerated into a condition where Mar. 8, 1973 Germany 2311466 it is enriched with carbon monoxide and hydrogen The thus-regenerated blast furnace gas is then intro- [52] U.S. Cl 75/42; 75/91 duced into the hearth of the blast furnace as part of [51] Int. Cl C21b 5/06 the blast [58] Field of Search 75/41, 42, 91

- 15 Claims, 2 Drawing Figures BLAST FURNACE OPERATING METHODS BACKGROUND OF THE INVENTION The present invention relates to blast furnace operation.

There are known methods for operating blast furnaces according to which part of the blast furnace gas is regenerated into a condition where it forms a reducing gas containing only a small amount of water and carbon dioxide, this regeneration generally being carried out by reacting the blast furnace gas with liquid or gaseous carbon-containing materials. This reaction, for example of methane with the carbon dioxide and water content of the blast furnace gas, is intensely endother mic. The heat which is required for this regeneration of the blast furnace gas is also in a known manner provided by burning a part of the blast furnace gas which is not regenerated.

It is also already known to blow such regenerated blast furnace gas directly after it has been produced, without any intermediate cooling, into the stack of a blast furnace at a temperature of approximately lOO-l200C. This introduction of the regenerated blast furnace gas takes place at a location along the stack where normally approximately the same temperatures prevail.

The above measures are provided in order to reduce the extent of coke which is consumed as well as to increase the output of the blast furnace. However, these procedures result in particular difficulties, as experience has demonstrated. Thus, the extent to which the regenerated blast furnace gas penetrates into the interior of the stack is limited, while on the other hand the gas in the hearth resulting from the blast flows upwardly along the interior central region of the blast furnace. The result is that the desired extent of high preliminary reduction of the ore is achieved only at the outer region of the blast furnace which receives the reducing gas blown into the stack, while the central vertically extending portion of the blast furnace does not receive any of this reducing gas. Therefore, any advantageous action resulting from blowing the regenerated reducing gas into the stack is limited as a result of the non-uniform distribution of the regenerated gas in the blast furnace.

It is also known to reduce the extend of coke consumedin the blast furncace by blowing together with the blast into the hearth of the blast furnace carboncontaining materials such as natural gas, oil, or coal. These carbon-containing materials customarily serve also as hydrogen-containing materials. This possibility of conserving coke has its limits in that the heating of this additional fuel and its decomposition in the hearth requires large amounts of heat which in general must be provided by way of preheating the blast. Inasmuch as the heat required for such preheating is limited to l300C or very little more, it is possible in this way to achieve only a relatively small reduction in the amount of coke which is required.

Furthermore it is known to attempt to conserve coke' by enriching the blast with oxygen. However in this case also narrow limits are encountered because, as set forth above, nitrogen is required as a temperaturelimiting and heat-transfer agent, and since with high oxygen content a high degree of preheating is not possible for technical reasons, the extremely important possibility of conserving coke cannot be achieved.

Furthermore, it is known that steel mill installation costs reach a certain optimum value at given blast furance capacities. Thus, it does not follow that the greatest economies are achieved with respect to installation costs with increasing blast furnace diameters. Thus, the best installation costs are achieved for given blast furnace diameters, but with blast furnaces of this given size it is not always possible to achieve the largest output at the minimum cost.

Thus, it is highly desirable to achieve the maximum output at the minimum cost by reducing the amount of coke, oxygen, and fossil fuel consumed per ton of pig iron, but at the present'time there is an unavoidable creation of waste energy which results in added costs which do not contribute to the output.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide a blast furnace operating method which will avoid the above drawbacks.

In particular, it is one of the primary objects of the present invention to provide a blast furnace operating method which will enable the advantages to be derived from the regenerated blast furnace gas to be distributed throughout the entire blast furnace instead of being limited only to the outer wall region of the blast furnace.

Furthermore, it is an object of the present invention to provide a method of operating a blast furnace in such a way that for a given output a minimum amount of coke is required.

Also, it is an object of the present invention to operate a blast furnace in such a way that not only is the amount of coke consumed reduced to a minimum, for a given output, but in addition a minimum amount of total heat is required for a given output and a minimum amount of oxygen is also utilized.

A further important object of the present invention is to operate a blast furnace in such a way that all of the blast furnace gas is utilized without any excess blast furnace gas being present to be wasted.

In accordance with one of the features of the present invention blast furnace gas is regenerated into a condition where it is enriched with carbon monoxide and hydrogen. This regenerated blast furnace gas iis then introduced into the hearth of the blast furnace as part of the blast, and the components of the blast are such that the blast is substantially free of nitrogen while being made up at least in part of the regenerated blast furnace gas.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way of example in the accompanying drawings which form part of this application and in which:

FIG. 1 is a schematic illustration of one method according to the present invention; and

FIG. 2 is a schematic illustration of a further embodiment of a method according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS It has been found, in accordance with the present invention, that considerable improvement in the operation of a blast furnace can be achieved if the blast furnace gas which is regenerated outside of the blast furnace so as to form a suitable reducing gas is introduced entirely or partly into the hearth through the tuyeres, as part of the blast, instead of into the stack.

This method of operation is carried out while excluding nitrogen, as encountered, for example, in normal air, from the blast. The role which is performed by the nitrogen as a temperature limiting agent during burning of oxygen in the hearth and as a heat-transfer agent for transferring heat from the hearth up into the stack is taken over by the carbon monoxide and hydrogen. Together with the hot reducing gas, whose temperature, in the same way as the reducing gas which is blown into the stack, can be lO0-l200C or higher, there is blown into the hearth a highly concentrated oxygen, in a concentration of, for example, 95%, so that this oxygen together with the regenerated blast furnace gas is introduced through the tuyeres into the hearth. Initially combustion takes place with the reducing gas to form carbon dioxide and water, while as a result of the large excess of carbon monoxide and hydrogen only a part of the latter is burned by the oxygen blown in with the blast, and the remainder of the carbon monoxide and hydrogen acts in a manner similar to the nitrogen ballast which would normally be introduced with the blast to be heated up to the hearth temperature which at a maximum is approximately 18002000C.

If all of the regenerated blast furnace gas is introduced through the tuyeres, then a nitrogen-free reducing gas flows uniformly up through the blast furnace across the entire cross section thereof. As a result corresponding extents of preliminary reduction occur in the stack of the blast furnace, this extent of preliminary reduction being in the range of 100% and the extent to which coke is consumed is sharply reduced as a result of the exclusion of direct reduction in the hearth of the blast furnace.

With the method of the present invention, the conservation of coke resulting from blowing the regenerated blast furnace gas through the tuyeres into the hearth provides important advantages because it is possible to blow the blast furnace gas at higher temperatures, for example at temperatures of l400C and more in the same way as the remainder of the blast, because decomposition heat for the blast is not required and because the selected large excess of gas is blown with concentrated oxygen which requires only a small amount of preheating can be used, as contrasted with combustion oxygen, without requiring the amount of heat for raising the temperature of the oxygen to the hearth temperature, this latter amount of heat normally representing a loss at the hearth.

According to a particularly advantageous method of the invention, the blowing of the regenerated blast furnace gas into the hearth through the tuyeres is combined with blowing the regenerated gas into the stack. This particularly favorable operating method involves deriving from the total regenerated gas a part thereof in the form of a reducing gas which primarily is made up of carbon monoxide and hydrogen, approximately 60% of the total regenerated gas having this latter characteristic and being introduced into the hearth of the blast furnace while the remaining 40% is blown into the stack. With this method of partially blowing the regenerated gas into the stack, the drawback of the known method according to which the regenerated gas is blown only into the stack is avoided with the result that the action of the regenerated gas is not limited only to the outer wall region of the furnace. With the method of the invention the part of the regenerated gas which is introduced into the stack is of course effective also only at the outer wall region of the furnace, but in addition the part of the regenerated gas which is introduced through the tuyeres flows upwardly from the hearth through the central region of the furnace and has the same nitrogen-free composition so that the reducing action takes place throughout the entire cross section of the blast furnace in a uniform manner.

This method of combining introduction of the reducing gas into the hearth and into the stack has with respect to coke consumption and total fuel consumption optimum conditions, with achievement also of the added advantage of requiring for combustion purposes in the hearth only a particularly small amount of concentrated oxygen.

The above features of the method of the invention and the combinations thereof can be combined with additional already known methods of operation of a blast furnace. Thus, in order to conserve coke it is pos sible to combine with the above features of the invention the feature of introducing with the blast, as part thereof, a fossil fuel such as oil, which is blown in through the tuyeres. In addition there is the possibility of deriving the reducing gas from sources other than regenerated blast furnace gas obtained outside of the blast furnace.

Referring to FIG. 1, there is schematically illustrated therein one possible method according to the invention. With the method illustrated in FIG. 1 the blast furnace gas which gas regenerated with the oil is blown only into the hearth of the blast furnace. Thus, FIG. 1 illustrates schematically the blast furnace l as well as the blast furnace gas cleaning unit 2 in which, as a result of cooling, the greatest part of the steam is separated from the blast furnace gas in the form of liquid water, and in addition the dust or foreign particle content-is reduced in the usual way by known measures. The blast furnace gas after passing through the cleaning unit 2 is received by the reactor or gas converter 3 in which the blast furnace gas is regenerated by means of a fossil fuel such as natural gas, oil or coal, so that the carbon dioxide of the blast furnace gas and 'the residual content of steam is converted by way of the carboncontaining material so as to form carbon monoxide and hydrogen. The top end or mouth of the blast furnace 1 receives the coke charge 4 as well as the charge 5 composed of ore and flux. The blast furnace gas 6 discharges from the top of the blast furnace and flows through the cleaning unit 2. The cleaned blast furnace gas 7 is divided into three

streams

8, 9 and 10. The stream 8 is directed to the regenerator 3 so as to form the regenerated blast furnace gas, the stream 9 is used as a source of heat for the regenerator 3, and the remaining stream 10 is excess blast furnace gas which is discharged to the exterior from the blast furnace installation.

The regenerator 3 receives not only the

streams

8 and 9 but also the fossil fuel 11 required for regenerating the blast furnace gas stream 8. This fossil fuel, may, for example, take the form of oil. In addition combustion air 12 is introducted to the regenerator 3. The regenerated blast furnace gas 13 discharges from the regenerator 3 and flue gas 14 also is discharged from the regenerator 3.

The regenerated blast furnace gas 13 is blown into the blast furnace l, to be received in the hearth thereof through the tuyeres. At the same time, the blast introduced through the tuyeres contains not only the regenerated blast furnace gas 13 but also the oxygen 15 and if desired a liquid fuel 16 such as, for example, oil. The pig iron 17 and the slag l8 flow out of the hearth at the bottom of the blast furnace. In the schematic illustration of the method of the invention shown in FIG. 1, additional auxiliary units such as blowers, controls, and the like are not illustrated.

FIG. 2 schematically illustrates an embodiment of the invention according to which the regenerated blast furnace gas which is blown into the blast furnace is divided into a pair of streams. The larger of these pair of streams is blown in the manner described above into the hearth through the tuyeres while the smaller of the pair of streams is blown into the stack. Thus, in FIG. 2 the stream 13a illustrates that part of the regenerated blast furnace gas which is introduced through the tuyeres while the stream 13b illustrates that part of the regenerated blast furnace gas which is blown into the stack, primarily directly over the melting zone of the charge.

The method of the invention makes possible a series of further variations which are capable of providing optimum operating conditions. Thus, it is possible with the invention to achieve a benefit from the fact that the reducing gas which is blown into the hearth of the blast furnace has smaller requirements with respect to the residual content of carbon dioxide and water as well as with respect to cracking carbon, than reducing gas which is blown into the stack. This benefit results from the fact that the carbon dioxide and water is regenerated in the hearth itself into carbon monoxide and hydrogen at the high temperatures in the hearth resulting from the presence of coke or from the simultaneous blowing of liquid fuel into the hearth, while when the reducing gas is blown into the stack, as a result of the lower temperatures such a regeneration is normally not possible, so that the partial pressures of carbon dioxide and water detract from the extent to which use is made of the stack gas as a result of the thermodynamic operating conditions. Moreover, as a result of blowing the regenerated blast furnace gas into the hearth, the cracking carbon which results is burned with the oxygen which is simultaneously blown in with the blast, while the regenerated blast furnace gas which is blown into the stack does not meet the requirements essential for this purpose.

In accordance with the invention it is possible when forming the reducing gas in the gas regenerating installation 3 to divide the total amount of reducing gas into one type of gas which has a relatively large amount of cracking carbon and/or a high content of carbon monoxide and hydrogen while another type of reducing gas is provided which has a relatively small amount of these components. For example a division of the total regenerated blast furnace gas into these two types can be achieved in a relatively simple manner by converting the blast furnace gas in the regenerator 3 during an initial operating phase during which the regeneration is carried out at a conversion temperature which is higher than that which is present during a final operating phase of the regenerator 3. Normally there will be produced in this way during the initial operating phase a gas product which has relatively small carbon dioxide and water content, as compared with the gas product resulting from the final phase, so that in accordance with the present invention the type of gas which is achieved during the initial operating phase of the regenerator is delivered to the stack while the type of gas which is achieved during the final operating phase of the regenerator is delivered to the hearth.

. A further possibility of achieving two different types of regenerated blast furnace gas resides in directing the gas product from the regenerator to a cyclone separator. This gas product contains cracking carbon, and in the cyclone separator, as a result of the known cyclone action the particles of cracking carbon become situated at the outer wall region of the cyclone while at the central region thereof there is a regenerated blast furnace gas which is substantially free of the cracking carbon or has a much lower content thereof. Thus, in accordance with the invention when utilizing this method for achieving the different types of regenerated blast furnace gas, the gas fromthe central region of the cyclone is delivered to the stack while the gas product at the outer wall region of the cyclone with its high content of cracking carbon is delivered to the hearth.

Furthermore, an important feature of the invention resides in further elevating the preheating temperature for the reducing gas introduced into the hearth, such as up to l400l500C, while additionally preheating the other components of the blast which is introduced into the hearth, these other components being oxygen and oil or CH.,, the temperature of these latter components being raised to 400500C. Through these latter measures it is possible to completely eliminate any excess blast furnace gas. In this way it is possible with the present invention to achieve an optimum blast furnace operation with minimum consumption of coke, minimum comsumption of total heat, and minimum consumption of oxygen.

Thus, in accordance with the method of the invention nitrogen is eliminated from the hearth gas by introducing through the tuyeres together with oxygen the reducing gas derived from regenerating the blast furnace gas with a liquid fossil fuel, with the regenerated blast furnace gas also being advantageously blown into the stack.

Experience has shown that with the method of the invention it is possible to achieve an optimum blast furnace operating method, with respect to total fuel consumption as well as with respect to the output which can be achieved.

One of the most important objectives to be achieved in connection with blast furnace operation is the production of the pig iron with the smallest possible consumption of fuel. Initially it was considered satisfactory to reduce the coke consumption to a considerable extent, and in this connection an important auxiliary measure was the blowing of auxiliary fuel, particularly oil, into the hearth of the blast furnace through the tuyeres. With such known expedients, it is indeed possible to reduce the coke in the charge to approximately 350-450 kg, in accordance with the particular operating conditions, per ton of produced pig iron, while at the same time utilizing for this purpose oil in an amount of approximately 40 kgkg per ton of pig iron. However, with these measures the total heat requirement per ton of produced pig iron is not reduced, and in some cases is in fact increased. However, one of the most important objectives to be achieved in connection with the development of blast furnace operation is to provide special measures by which not only the coke consumption is reduced but also the total heatrequirement is maintained as low as possible.

A further important objective of blast furnace development is to achieve as large an output as possible, with the specific output in general being achieved either with respect to the hearth area of the furnace or with respect to the useful volume thereof. Experience has shown that under optimum commerical operating conditions, steel mills require blast furnaces which have a daily output capacity for each individual blast furnace which is in the range of approximately 10,000 tons. In order to achieve such a large output capacity the required hearth diameter is approximately 13m 1 m, in accordance with, the specific charge requirements. However, opposed to this latter factor is the fact that the specific installation cost of a blast furnace, which is to say the amount of capital required per ton of produced pig iron, does not continuously decrease with an increase in the size of the furnace. Instead the optimum installation cost is achieved with a furnace which has a hearth diameter on the order of approximately llm. Therefore, it is important to attempt to achieve a maximum output from each individual blast furnace with each blast furnace having a hearth diameter which does not exceed in a substantial manner 1 lm.

Aside from these considerations with respect to the specific installation costs, there is a clear increase in output with cost reduction where a blast furnace of relatively small hearth diameter and thus of relatively small cost is capable of achieving the same output as would normally be achieved from a blast furnace which has a larger hearth diameter.

It has been found that these desirable or necessary optimum operating conditions with respect to total fuel consumption and output can be achieved if the excess blast furnace gas, which is to say the amount of blast furnace gas normally discharged in the outer atmosphere, and therefore not utilized in the steel mill operations, is reduced to a minimum or if possible is entirely eliminated. It has been found in accordance with the present invention that these optimum operating conditions can be achieved if on the basis of the present invention the following operating conditions are maintained, where the data which follows is given per ton of pig iron which is derived from the blast furnace:

The amount of coke which is included in the charge delivered to the top mouth of the blast furnace should be approximately between 225kg and 255kg.

The amount of oil which is delivered to the regenerator for the blast furnace gas should be between l30kg and l45kg.

The amount of oil which is blown into the tuyeres so as to be burned with oxygen in the hearth or immediately before reaching the hearth should be approximately 40kg-60kg.

The regenerated blast furnace gas derived at the regenerator from the oil and from the part of the blast furnace gas which is delivered to the regenerator is divided between the tuyeres and the stack. In the stack of the blast furnace, which is to say at the location thereof where the operating temperature is between approximately l00O and l200C, the amount of regenerated blast furnace gas which is blown inshould be approximately 37-45% of the total amount of regenerated blast furnace gas which is produced. The amount of regenerated blast furnace gas which is blown in through the tuyeres, is the remainder of the total 8 amount of regenerated blast furnace gas which is produced and should be between 63 and 55%.

The blast furnace gas which discharges from the top of the blast furnace is utilized in the following way in accordance with the operating method of the invention:

In order to be converted with oil into the regenerated blast furnace gas, the total amount of blast furnace gas flowing from the blast furnace to the regenerator 3 is approximately 4045% of the total blast furnace gas.

In order to serve as a source of heat in the gas regenerator approximately 42-52% of the blast furnace gas is delivered to the regenerator. For the purpose of preheating the components introduced into the tuyeres, the residual amount of blast furnace gas in a range of approximately 0l0% is utilized.

In this way all of the blast furnace gas issuing from the mouth of the blast furnace is utilized, either to be converted into the regenerated reducing gas, or to provide heat at the regenerator, or to preheat the components introduced with the blast.

Thus with the present invention experience has shown that it is possible to operate the blast furnace in such a way that there is no excess ,of blast furnace gas to be wasted.

One of the features utilized to achieve this operation is that the temperature of the regenerated blast furnace gas which is blown into the stack is approximately 1 C 1250C, while the temperature of the blast introduced into the hearth through the tuyeres has with respect to the components of the blast the following the charge by simultaneously increasing the amount of oil which is blown in with the blast. However, with this particular feature the total heat consumption of the method of the invention is not substantially changed.

Furthermore, it is possible to make different changes in the above operating conditions without departing from the basic concept of the invention. Thus, for example, instead of utilizing oil as an auxiliary fuel it is 2 possible to use other fossil fuels such as byproducts of other processes. For example, waste oil resulting from petroleum refining or hydrogenation installations or other waste gases or gaseous fuels such as natural gas, coke plant gas, or the like may be used as the additional fuel to be blown in with the oxygen and regenerated blast furnace gas, forming the blast which is-delivered to the hearth. v

The present invention also is fully effective in the case where for commercial reasons the surlfur-free blast furnace gas is partially withdrawn from the blast furnace to be utilized for other purposes and is replaced for the purposes of the present invention with a I more economical interchangeable fuel such as oil. In general this latter possibility is available for that part of the blast furnace gas which is utilized for heating purposes in accordance with the data presented above.

What is claimed is:

1. In a blast furnace operating method for producing metal comprising providing a blast furnace having an hearth, stack and top, charging said blast furnace with ore and coke, introducing a blast into the hearth of the blast furnace, introducing a reducing gas into the stack of the blast furnace, reducing the ore to form metal and simultaneously producing blast furnace gas, recovering the metal and discharging all of the blast furnace gas from the top of the blast furnace, the improvement in combination therewith comprising the steps of regenerating a first portion of blast furnace gas issuing from the top of a blast furnace by means of fossil fuel into a condition where it is enriched with carbon monoxide and hydrogen, utilizing a second portion of the blast furnace gas as at least part of a source of heat for regenerating the first portion of the blast furnace gas, introducing into the hearth of the blast furnace a blast which is substantially free of nitrogen and which is made up in part of a portion of the regenerated blast furnace gas, preheating that part of the blast which does not include the regenerated blast furnace gas at least partly with the residual portion, if any, of the blast furnace gas remaining after said first and second portions are taken therefrom, and simultaneously introducing the remainder of the regenerated blast furnace gas, which does not form part of the blast, into the stack.

2. In a method as recited in claim 1 and the improvement wherein the amount of regenerated blast furnace gas which is included in the blast is sufficient to provide in the hearth an amount of carbon monoxide and hydrogen adequate to provide a peak combustion temperature of approximately 2,000C while also providing a sufficient excess of carbon monoxide and hydrogen at the hearth to flow from the hearth up into the stack of the blast furnace for transferring into the stack by way of the excess carbon monoxide and hydrogen heat for carrying out the required reactions in the stack.

3. In a method as recited in claim 2 and the improvement wherein the blast introduced into the hearth also contains as a combustion medium oxygen in a concentration of approximately 95%.

4. In a method as recited in claim 2 and the improvement wherein the regenerated blast furnace gas which is introduced with the blast into the hearth of the blast furnace is preheated to an extent sufficient to provide the regenerated blast furnace gas at the blast with a temperature at least as high as from approximately 1,000C to approximately l ,40()C.

5. In a method as recited in claim 4 and the improvement wherein the temperature of the blast furnace gas introduced with the blast into the hearth of the blast furnace is achieved during regeneration of the blast furnace gas.

6. In a method as recited in claim 2 and the improvement wherein together with the regenerated blast furnace gas there is introduced with the blast into the hearth of the blast furnace a fossil fuel, and charging the blast furnace with a charge containing an amount of coke which is reduced to an extent which corresponds to the extent to which fossil fuel is introduced into the hearth with the blast.

7. In a method as recited in claim 1 and the improvement wherein the total regenerated blast furnace gas which is introduced both with the blast and into the stack having a proportion of regenerated blast furnace gas introduced with the blast which is approximately 45-70%, of said total.

8. In a method as recited in claim 7 and the improvement wherein the blast furnace gas is regnerated to provide two types of blast furnace gas, one of said types being rich in carbon and the other of said types having a lesser amount of carbon, and combining the regenerated blast furnace gas which is enriched with carbon with the blast while introducing the blast furnace gas which has the lesser amount of carbon into the stack.

9. In a method as recited in claim 8 and the improvement where the two types of regenerated blast furnace gas are achieved by regenerating the blast furnace gas at different temperatures.

10. In a method as recited in claim 8 and the improvement wherein the regenerated blast furnace gas has carbon particles suspended therein, and subjecting the regenerated blast furnace gas to a cyclone action producing a central region of blast furnace gas which has a reduced amount of carbon particles and an outer region of blast furnace gas surrounding the central region and having a relatively large amount of carbon particles, and directing the blast furnace gas from the central region to the stack and from the outer region to I the blast.

11. In a method as recited in claim 1 and the improvement wherein together with the regenerated blast furnace gas, the blast introduced into the hearth of the blast furnace contains oxygen and a fossil fuel, with these components of the blast being delivered to the hearth in amounts and temperatures which substantially eliminate any excess blast furnace gas in the discharge from the blast furnace.

12. In a method as recited in claim 11 and the improvement wherein the regenerated blast furnace gas is introduced with the blast at a temperature of approximately l,400-l ,500C while the oxygen and fossil fuel are preheated so as to enter the hearth with the blast at a temperature of approximately 4005( )0C.

13. In a method as recited in claim 12 and the improvement wherein the regeneration of the blast furnace gas produces a flue gas at an elevated temperature, and utilizing the latter flue gas for preheating the oxygen and fossil fuel introduced with the blast.

14. In a method as recited in claim 11 and the improvement wherein the blast furnace is operated to produce pig iron and in a manner according to which for each ton of pig iron which is produced the following conditions are maintained:

approximately 230 kg-255 kg approximately I30 kg-l45 kg approximately 40 kg-60 kg approximately 37%45% approximately 63%55% approximately 40%45% Percentage of blast furnace approximately 42%-52% approximately 0%-l 0% Temperature of regenerated blast furnace gas delivered to the stack Temperature of regenerated gas in the blast Temperature of fossil fuel -Cntinued approximately l 150 C- l250 C approximately 1 150 C- I400 C 15. In a method as recited in claim 14 and the improvement wherein the fossil fuel is oil.

Claims

1. IN A BLAST FURNACE OPERATING METHOD FOR PRODUCING METAL COMPRISING PROVIDING A BLAST FURNACE HAVING AN HEARTH STACK AND TOP, CHARGING SAID BLAST FURNACE WITH ORE AND COKE, INTRODUCING A BLAST INTO THE HEARTH OF THE BLAST FURNACE, INTRODUCING A REDUCING GAS INTO THE STACK OF THE BLAST FURNACE, REDUCING THE ORE TO FORM METAL AMD SIMULTANEOUSLY PRODUCING BLAST FURNACE GAS, RECOVERING THE METAL AND DISCHARGING ALL OF THE BLAST FURNACE GAS FROM THE TOP OF THE BLAST FURNACE, THE IMPROVEMENT IN COMBINATION THEREWITH COMPRISING THE STEPS OF REGENERATING A FIRST PORTION OF BLAST FURNACE GAS ISSUING FROM THE TOP OF A BLAST FURNACE BY MEANS OF FOSSIL FUEL INTO A CONDITION WHERE IT IS ENRICHED WITH CARBON MONOXIDE AND HYDROGEN, UTILIZING A SECOND PORTION OF THE BLAST FURNACE GAS AT LEAST PART OF A SOURCE OF HEAT FOR GENERATING THE FIRST PORTION OF THE

2. In a method as recited in claim 1 and the improvement wherein the amount of regenerated blast furnace gas which is included in the blast is sufficient to provide in the hearth an amount of carbon monoxide and hydrogen adequate to provide a peak combustion temperature of approximately 2,000*C while also providing a sufficient excess of carbon monoxide and hydrogen at the hearth to flow from the hearth up into the stack of the blast furnace for transferring into the stack by way of the excess carbon monoxide and hydrogen heat for carrying out the required reactions in the stack.

4. In a method as recited in claim 2 and the improvement wherein the regenerated blast furnace gas which is introduced with the blast into the hearth of the blast furnace is preheated to an extent sufficient to provide the regenerated blast furnace gas at the blast with a temperature at least as high as from approximately 1,000*C to approximately 1,400*C.

10. In a method as recited in claim 8 and the improvement wherein the regenerated blast furnace gas has carbon particles suspended therein, and subjecting the regenerated blast furnace gas to a cyclone action producing a central region of blast furnace gas which has a reduced amount of carbon particles and an outer region of blast furnace gas surrounding the central region and having a relatively large amount of carbon particles, and directing the blast furnace gas from the central region to the stack and from the outer region to the blast.

12. In a method as recited in claim 11 and the improvement wherein the regenerated blast furnace gas is introduced with the blast at a temperature of approximately 1,400*-1,500*C while the oxygen and fossil fuel are preheated so as to enter the hearth with the blast at a temperature of approximately 400*-500*C.

15. In a method as recited in claim 14 and the improvement wherein the fossil fuel is oil.