US3239331A - Method for blast furnace operation - Google Patents

Description

March 8, 1966 Filed April 27, 1965 L5. OXYGEN/LB. FUEL J. H. MENK ETAL 3,239,331

METHOD FOR BLAST FURNACE OPERATION 2 Sheets-Sheet 1 RELATIONSHIP BETWEEN HYDROCARBON FUELS AND OXYGEN 4 LOG Y .O32 X .76

4 6 B IO [2 l4 l6 I8 20 22 24 CARBON HYDROGEN RATIO INVENTORS JAMES H. MENK JOHN B.POWERS A TTORNEV March 8, 1966 J. H. MENK ETAL METHOD FOR BLAST FURNACE OPERATION 2 Sheets-Sheet 2 Filed April 27, 1965 RELATIONSHIP BETWEEN HYDROCARBON FUELS AND BLAST TEMPERATURE LOG Z xv X A LOG Z .O33X L3 CARBON- HYDROGEN RATTO INVENTORS JAM ES H. M EN K JOHN B. POWERS By mur A77'ORNEV United States Patent 3,239,331 METHOD FOR BLAST FURNACE OPERATION James H. Menk, Mountainside, N.J., and John B. Powers,

Westport, Comm, assignors to Union Carbide Corporation, a corporation of New York Filed Apr. 27, 1965, Ser. No. 453,557 17 Claims. (Cl. 75-42) This application is a continuation-in-part of copending application Serial No. 264,863, filed March 13, 1963, in the name of J. H. Menk and J. B. Powers.

This invention relates to a method for operating blast furnaces and, more particularly, to an improved method for operating blast furnaces wherein greater economics are achieved over a wide range of production levels.

In the production of iron from iron ores in the blast furnace, the conventional practice is to charge iron ore, coke and limestone into the furnace. The coke is combusted by blast air preheated in the furnace stoves and then forced into the furnace through tuyeres to provide the heat and reducing gases required to smelt the iron oxides to iron. The amount of coke needed is quite large, generally about 1400 or 1500 pounds of coke for each ton of pig iron produced, and represents a large part of the cost of the iron making operation.

The state of the art has advanced considerably through experience in regard to more economical operating practices. The operating region of a blast furnace is determined by physical and thermochemical laws that govern the transfer of heat and chemical energy required for the smelting of the charge in the shaft and hearth of the furnace. With other blast variables held constant, it has been found that the rate of smelting of a given ore, and hence the iron production rate, is directly proportional to the rate at which coke and other fuels are oxidized in the furnace, which in turn is a function of the rate at which blast air is supplied through the tuyeres. In the interest of securing greater production from a furnace, and thereby securing a more economical rate of production by virtue of the proportionally larger base for distribution of fixed capital and operating expenses, it has been common practice to achieve maximum production by driving the furnace with the maximum amount of blast air allowable within the limits of proper furnace operation.

The maximum blast rate is generally determined by the limits of blower head pressure, lifting of the charge in the stack, or entrainment of fines in the top-gas exhausts. At the maximum blast rate permissible within these restrictions, there is a maximum blast temperature limit determined by the capability of the furnaces blast stove system. In many instances, this temperature limit is imposed by the total heat transfer capacity of the stove rather than by allowable operating temperatures of the blast air conveying system, meaning that the pipes, bustles and tuyeres could handle blast air at a higher temperature if the stoves could supply it. To supply blast air at such higher temperatures, it would be necessary to operate at wind rates lower than the maximum blower capaicty.

While increased production rates resulting from driving the furnace with maximum blast rates are beneficial, the high blast temperatures resulting from reduced wind rates will also greatly improve smelting efficiency and economy of furnace operation. Generally, the higher the blast temperature which can be utilized, the lower the quantity of coke required per ton of iron produced. Since the cost of the metallurgical coke consumed normally represents 25 to 40 percent of the cost of a ton of iron, it is obviously desirable to reduce the coke requirements as much as possible for lowest cost operation. It can Patented Mar. 8, 1966 be demonstrated theoretically and corroborated in practice that as the blast volume rate of a furnace is decreased, that the coke rate also decreases. This method of operation is termed slack wind blowing. The unfortunate feature of a slack wind operating technique is that as the blast volume rate is reduced to affect coke savings, the furnace production decreases proportionally, thus nullifying, and even wiping out the cost savings accruing from the lower coke fate. It has not generally been possible to combine the advantages of better thermal efficiency from slack wind blowing with the inherent cost savings which result from operating a facility at or greater than its maximum rated production.

Another area in which blast furnace operating economies are sought is in regard to the substitution of cheaper hydrocarbon fuels such as natural gas, fuel oil, and pulverized coal, for part of the normal coke requirement of the furnace. Typically, coke reductions of to 300 pounds per ton of iron have been achieved by such auxiliary fuel additions. The further substitution of hydrocarbon fuel for coke has been limited, however, by the inability to maintain proper furnace operation and efiiciency at the higher levels of fuel injection compared to results obtained at lower levels, thus restricting coke savings to the aforementioned 100 to 300 pounds per ton of iron.

It is the object of this invention to provide a more economical method for operating a blast furnace which method applies over a wide range of production levels.

It is also an object of this invention to provide a method for operating blast furnaces wherein the cost saving advantages of controlled blast volume rates as well as savings resulting from use of hydrocarbon fuel additions are achieved at all levels of furnace production, i.e., at normal capacity, at less than normal capacity, and in great excess of normal capacity.

The invention comprises a method for operating blast furnaces wherein the furnace is charged with iron bearing materials, coke, and slagging materials such as limestone, comprising determining a minimum flame temperature in the smelting zone for maximum smelting efiiciency, substituting for part of the coke auxiliary hydrocarbon fuels while adding oxygen and blast heat in an amount sufficient to maintain the flame temperature at about its minimum level while increasing the rate of smelting, reducing the coke rate through the addition of the auxiliary fuels while the value of the resulting coke reduction is equal to or greater than the cost of supplying said auxiliary fuels and oxygen, and regulating the blast volume to give a desired iron production rate.

In the drawings:

FIG. 1 is a graphical representation of the equations showing the proper relationships of oxygen and fuel additions to a blast furnace;

FIG. 2 is a similar representation of the proper relationships of fuel and blast temperature additions to a blast furnace.

As previously stated, the substitution of cheaper hydrocarbon fuels for more expensive coke has already resulted in savings of up to 100 to 300 pounds of coke per ton of iron. The further substitution of larger amounts of such fuels as natural gas, fuel oil, or pulverized coal has been restricted, however, by an inability to maintain proper furnace conditions at the higher levels of fuel injection. One limitation on the amount of auxiliary fuels which can be substituted for coke is due to the fact that these fuels do not supply as much heat on combustion in the blast furnace as an equal weight of hot coke. When hydrocarbon fuels are injected into the smelting zone of the furnace, they require added themochemical energy for their dissociation and so their combustion does not liberate enough heat to maintain the normal smelting zone temperature. It is, therefore, necessary to make additional heat available in the blast furnace. This can be done by increased blast volume or temperature, decreasing the blast moisture, or by oxygen enrichment of the blast air. Fuel injections into blast furnaces have been made along with one or more of the above listed heat providing means to compensate for the heat load put on the furnace by the hydrocarbon fuel. These processes have resulted in some coke savings. The coke reductions were not as great as could be expected and were generally linked to operation at higher production levels.

The amount of hydrocarbon fuel additions, and hence the amount of coke savings, could be increased if better methods were available to compensate for the reduced flame temperature caused by the fuel additions. Blast temperature control is limited by the stove capacity of the furnace which means that to obtain substantially increased blast temperatures, blast volume must be reduced, and thus production rate is sacrificed. Moisture control is of course limited. Oxygen enrichment, as Well as each of the above heat supplying means, can cause either undercompensation or excessive overcompensation of the flame temperatures. Improper use of any of these can cause such a deficit of heat in the smelting zone as to ultimately result in freezing, or, on the other hand, release such great amounts of heat as to cause excessive smelting zone temperatures which lead to extremely rough stock descent and furnace hanging. The inability to cope with these factors and still produce cost savings at the higher levels of fuel injection has kept the amount of coke savings at the lower levels indicated before.

The operating limits of a blast furnace are dictated by physical and thermochemical laws that govern the transfer of heat and chemical energy required for the smelting of the charge. These laws establish a balance among the furnace charge ingredients, auxiliary fuels, enthalpy, oxidation capacity of the blast gas, etc. This balance must be maintained within prescribed bounds to provide suitable smelting conditions. Within these bounds there exist a number of operable combinations that satisfy the physical constraints without regard to economics of raw materials supplied.

It has been found that to achieve the most eflicient operation of a blast furnace when injecting auxiliary fuels, the blast furnace should be operated about the lower range of flame temperatures within the broader operable flame temperature limits. Therefore, in order to derive maximum benefits from the use of oxygen enrichment, blast temperature increase and hydrocarbon fuel injection, it is first desirable to establish this range pf maximum smelting efliciency and minimum flame temperatures for the particular blast furnace and raw materials involved. Maximum efiiciency in the economic sense results from operation in the lower range of flame temperature because it is cheaper to replace. as much coke as possible with lower cost hydrocarbon fuel, auxiliary hydrocarbon fuels tending to decrease flame temperature as discussed previously.

On a furnace without fuel injection, the normally considered optimum flame temperature can be approximated by a trial and error manipulation of the blast variables, volume, temperature, moisture content, etc., to achieve the lowest posible coke rate for a given burden and desired level of iron production. This optimum flame temperature and minimum coke rate will usually be found at the highest blast temperature consistent with smooth furnace operation. From this starting point a method for approaching the minimum flame temperature more closely comprises the following: Hydrocarbon fuels are added to the smelting zone of the furnace in increments of say to pounds per ton of iron, and concurrently the coke charged to the top of the furnace is reduced an equal amount. It is recognized that the amount of coke which can be removed per unit hydrocarbon fuel atoms in the fuel.

addition is dependent on many factors, among them the type of hydrocarbon fuel added, the amount of increased blast temperature available, etc. However, for the purpose of establishing a starting point, replacement of coke can be initially made on a 1 for 1 weight basis. The operator, by judging the temperature and quality of the iron can then decide whether even greater replacement of fuel for coke can be tolerated. For example, for a natural gas fuel with relatively high hydrogen content it may be possible to replace as much as two pounds of coke for each pound of gas added. For fuel oil or coal perhaps as much as 1.5 pounds of coke can be removed per pound of fuel. The operator starting from the suggested 1 to 1 replacement of fuel for coke, and modifying this according to iron quality and temperature, can then proceed to add fuel and substract coke in increments,-

until the incremental coke reduction per unit incrementalfuel addition falls off appreciably, to say or 50 percent of the initial ratio. The smelting conditions then existing represent approximately the minimum flame tem-- perature at which the furnace will operate properly at the available blast temperature.

When the minimum flame temperature has been established as outlined, hydrocarbon fuels are then added to the furnace and the coke rate is reduced, while oxygen enrichment of the blast, or increasing blast temperatures are made, in such amounts that the minimum flame temperature is maintained and not overcompensated for nor undercompensated.

It has been found that the proper amount of oxygen to be added or degree of blast temperature increase needed to accompany any hydrocarbon fuel addition may be expressed as a function of the carbon-hydrogen atomic weight ratio of the fuel. In the drawings, graphs are shown which can be used to determine the amount of oxygen or blast temperature increase needed to ac-- company any hydrocarbon fuel injection.

Based on the graph of FIG. 1, the minimum amount of oxygen (Y) needed per pound of fuel addition is log Y=.042X-i-0.61 or Y=antilog (0.042X+0.61)

where X is the carbon-hydrogen atomic weight ratio of the hydrocarbon fuel added. The carbon-hydrogen atomic weight ratio, as used herein, is the ratio of the weight of carbon atoms in the fuel to the weight of hydrogen For example, the gaseous fuel methane will have a carbon-hydrogen weight ratio of 12 to 4X1 equal to 3. Where the addition is of more than one fuel, or a slurry of several fuels, such as oil and pul verized coal, then X is the weighted ratio of the combined carbon to hydrogen atomic weights. The maximum amount of oxygen which should be added with the injection of a fuel having a carbon-hydrogen ratio X is log 10Y=-0.032X+0.76

On the semi-logarithmic chart of FIG. 1 the minimum oxygen addition needed is Y=antilog (-0.042X +0.61) and the maximum oxygen addition that should be is Y=antilog (0.032X+0.76). The vertical offset between these curves represents the range of proper oxygen additions for any given carbon-hydrogen ratio.

For any given furnace, the operator should select an oxygen-fuel addition ratio representing about the mid point of the indicated range for the particular fuel being injected, and then vary the oxygen-fuel addition ratio either higher or lower from this mid point, while staying within the range, as is found necessary to maintain proper iron temperature and quality.

In regard to the case where blast temperature is increased along With hydrocarbon fuel injections and diminishing coke rates, FIG. 2 shows a chart from which can be determined the number of pounds of hydrocarbon fuels of a given carbon-hydrogen ratio (X) that can be added to a furnace for each 100 F. increase over the normal blast temperature used in that furnace. For either a single fuel or a mixture of fuels having a combined carbon-hydrogen weighted ratio X, the maximum number of pounds of fuel (Z) per ton of iron which can be added for each 100 F. blast temperature increase is g10 OI' Z=antilog (0.033X-I-L3) and the minimum number of pounds of fuel (Z) per ton of iron which should be added for each 100 blast temperature increase is log Z= 0.032X+ 1.08

On the semi-logarithmic chart of FIG. 2 the maximum hydrocarbon fuel addition for each 100 F. blast temperature increase is Z=antilog (0.033X-|-1.3) and the minimum is Z=autilog (0.032X +1.08). The vertical offset between these curves represents the range of proper fuel additions for a fuel having the given carbon-hydrogen ratio for each 100 F. blast temperature increase.

For any given furnace, the operator should select a fuel addition per 100 increase in blast temperature which is about the mid point in the range indicated for that particular fuel, and then vary the amount of the fuel addition per 100 temperature increase either higher or lower from this mid point, while staying within the range, as is found necessary to maintain proper iron temperature and quality.

For common hydrocarbon fuels natural gas, oil, and pulverized coal the following figures, based on the abovedescribed equations and typical carbon-hydrogen ranges for such fuels, can be used: in the case of hydrocarbon fuel injection at constant blast temperature with oxygen enrichment, add 2.7 to 4.5 pounds of oxygen per pound of natural gas; for fuel oil, add 1.7 to 3.0 pounds of oxygen per pound of oil; for coal, add 0.64 to 1.4 pounds of oxygen per pound of coal; when more than one of these hydrocarbon fuels are to be simultaneously injected into the furnace, then the amount of oxygen to be added is the sum of the oxygen requirements for each individual fuel addition.

Similarly, when common hydrocarbon fuels are to be substituted for coke with an accompanying blast temperature increase, the amount of such fuels which may be added for each 100 F. blast temperature increase is as follows: for natural gas, 16 to 27 pounds of natural gas per ton of iron; for fuel oil, 20 to 40 pounds of oil per ton of iron; and for pulverized coal, 50 to 90 pounds of coal per ton of iron; when more than one of these hydrocarbon fuels are to be simultaneously injected into the furnace, then the amount of each fuel which may be added is proportioned according to the ranges given above, i.e., on the basis of the portion of the total blast temperature increase assigned to overcome the heat load on the furnace created by that fuel. Additionally, when oxygen enrichment and blast temperature increases are both utilized the proper fuel additions are determined by combining the amount of fuel which can be added because of the amount of oxygen enrichment with the amount of fuel that can be added because of the degree of blast temperature increase.

It is seen from the above discussions that cheaper hydrocarbon fuels may be substituted for part of the normal furnace coke requirement provided that either oxygen is added to the furnace or blast temperatures are increased. The greatest economies are achieved, however, with oxygen enrichment of the blast and blast temperature increases. When hydrocarbon fuels and oxygen are added to the furnace in the ratios taught herein, the hydrocarbon fuels will replace part of the furnace coke requirement, while the oxygen not only counteracts the chilling effect of the hydrocarbon fuel and maintains optimum smelting efliciency, but also increases the burning rate of the coke. While increased coke burning rates cause increased production, it is possible, because of the oxygen injections, to control production by regulating the blast volume or wind rate to the furnace, i.e., the blast volume rate can be adjusted to either maintain normal production or to operate at substantially below normal or above normal, with substantial coke savings at all levels. Additionally, as blast volumes are cut back, the resulting blast temperature increases allow the use of greater amounts of hydrocarbon fuels, thereby further reducing coke rates.

It is an important aspect of this invention that substantial coke savings can be made essentially independent of the furnace production rate whereby the economies of reduced coke rates can be achieved at any desired production level. As an illustration, consider the case Where it is desired to maintain normal production rate on a blast furnace, but to achieve greater economies in use of raw materials. The blast furnace will have a certain production, coke rate, blast temperature and volume, and blast moisture content. Before making the supplementary fuel additions, it is generally desirable to start out with optimum flame temperature conditions in the smelting zone. Generally the furnace will be operating with the highest-blast temperature consistent with smooth operation which would result in optimum flame temperature for a furnace without fuel injection. The minimum flame temperature range can then be approached starting from this point by the incremental fuel addition procedure previously outlined.

Starting from this minimum flame temperature point, further auxiliary fuel additions are made. The graphs can be used for any hydrocarbon fuel or mixture of fuels by determining the carbon-hydrogen ratio of the fuel or of the mixture, and then adding the indicated amount of oxygen or blast temperature increase for each increment of fuel addition. As an example, for fuel oil with a C-H ratio of 8.8 to 1, from 1.7 to 3.0 pounds of oxygen per pound of oil should be injected to maintain the flame temperature and drive the smelting rate faster. When compensating with blast temperature increases, 24 to 40 pounds of oil per F. increase should be used. These relationships hold for constant blast moisture. It is recognized that blast moisture can be used to control flame temperature in both situations of increasing blast temperature or in increasing oxygen content. For example, it is known that a quantity of moisture can be added to the blast with an associated amount of oxygen enrichment. If hydrocarbon fuels were added to a furnace already having this moisture-oxygen injection, then additional oxygen would be added with the fuel according to the relationships set forth herein. In other words, the method of this invention relates oxygen enrichment and blast temperature enrichment to hydrocarbon fuel additions; if moisture control or other pertinent operating factors are varied, then any oxygen enrichment or blast temperature increases associated with these variables are not to be considered in regared to the hydrocarbon fuel addition.

The auxiliary fuel additions are then made along with the indicated oxygen additions and blast temperature increases, or both, while the coke rate is reduced. In actual practice the coke reductions may be made in the form of increasing the burden to coke ratio. As a starting point coke reductions can be made on the basis of the substitution of a unit weight of hydrocarbon fuel for a unit weight of coke. It is to be noted that variations from this one to one substitution are to be expected depending on the type of hydrocarbon fuel used. The actual substitution of hydrocarbon fuels for coke is to be made by the blast furnace operator according to the principles of proper furnace operation and the directions set forth above in regard to the incremental fuel injection method for determining the minimum flame temperature. The extent to which hydrocarbon fuels, oxygen and blast temperature can be profitably substituted for coke depends on the relative cost of these materials. Generally, the substitutions should be made as long as the value of the coke saving is equal to or greater than the cost of supplying the hydrocarbon fuel and oxygen necessary to produce that coke saving. The relative costs of coke, various hydrocarbon fuels and oxygen will vary from area to area, but it will be generally the case that the combination of hydrocarbon fuels and oxygen will allow savings with reduced coke rates of up to 40 to 60 percent of normal coke requirements.

Since the addition of oxygen has the effect of increasing the smelting rate and, hence the amount of iron produced, the wind rate should now be cutback to reduce the iron production rate from the level which would result from the use of the given amount of oxygen back to the normal production rate. The amount of wind rate cutback should be such as to supply to the furnace only about enough total oxygen as is needed to combust with the amount of coke and auxiliary fuels needed for the desired iron production rate. It is important to note that this wind rate reduction is not the same as slack wind blowing where production rates fall off sharply and the coke rate per ton of metal drops only slightly. Here much greater coke reductions are achieved, while the production rate may remain the same or be dropped drastically, to say, 50 percent of normal.

The wind rate reductions here are not the same as the reductions in blast volume made in conjunction with prior art oxygen enrichment methods. There the wind rate would be reduced by the amount of air equivalent in oxidizing power to the amount of pure oxygen supplied. In effect, this is a reduction in blast volume of the excess, unneeded nitrogen content of the air. This slight reduction in blast volume gave some increase in blast temperature, but the resulting coke reductions were not of the order involved in this process.

The substantial reductions in wind rate made possible by the use of oxygen additions according to the process of this invention allow the attainment of higher blast temperatures, which, in turn, allow the substitution of additional hydrocarbon fuels for the more expensive coke.

In the actual practice of the invention, oxygen and fuel are added while the coke rate is reduced. The oxygen-fuel proportioned additions will cause an increase in the production rate. The furnace operator will observe this increased production rate and cut back the wind rate to the furnace so as to reduce the production rate to the desired level.

If it were desired to operate the furnace with a lower than normal capacity, then the blast volume would be cut back still further so as to provide only enough total oxygen to combust the coke and auxiliary fuels needed to produce the desired lower iron production rate.

When a greater than normal iron production is required, the auxiliary fuels and oxygen are added as above, but the blast volume reductions are not so great as with normal production rates. Oxygen enrichment can produce much more iron at the same or even lower blast volumes. For example, furnaces can be made to produce 150 percent of their normal capacity with substantial coke reductions by following the teachings of this invention without exceeding the blower capacity of the furnace.

As an example of the application of the invention to a particular furnace, take the case of a blast furnace having a normal, present day production rate of 800 tons per day. This furnace consumed coke at the rate of 1310 pounds per ton of iron and used 1140 cu. ft. of natural gas per ton of metal produced. The blast temperature was 1300 F. with volume of 45,000 c.f.m. The blast was air, i.e., contained 21 percent by volume oxygen, and had 3 grains per cubic foot moisture content.

To meet a hypothetical reduction in steel demand, the blast furnace production was ordered cut back to 500 tons per day. An economical method of operation comprised eliminating the natural gas injection and injecting 335 pounds per ton of pulverized coal with an accompanying oxygen addition. The blast volume was cut back to 25,000 c.f.m., and the percent oxygen in the blast was 22.5 percent by volume. The moisture content was the same, 3 grains per cubic foot. The blast temperature was raised to 1600 F. because of the blast volume reduction. The resulting coke rate was only 790 pounds per ton of metal produced.

When normal production Was required, the process of this invention provided the following method of operation: the production rate was still 800 tons per day, but the coke rate was reduced from 1310 pounds per ton to 900 pounds per ton by adding 290 pounds of pulverized coal per ton and 2380 cu. ft. of natural gas per ton along with oxygen. The blast temperature was 1600 F. with an oxygen content of 25.7 percent by volume in a 35,000 c.f.m. blast and the same moisture content, 3 grains per cu. ft.

When the desired furnace production rate was 1000 tons per day, 400 pounds of pulverized coal per ton and 1400 cu. ft. of natural gas per ton were added to the furnace. The blast volume was 46,500 c.f.m. at a blast temperature of 1,450 P. and a moisture content of 3 grains per cu. ft. The oxygen content of the blast was 25.3 percent by volume. The coke rate was only 900 pounds per ton of metal produced.

If such increases in blast temperature were not available, then by increasing the oxygen content according to the principles of this invention, then the desired increase in production could be achieved with the blast temperatures actually available.

It is clear from the above description and examples, that substantial cost reductions are attainable by substituting lower cost hydrocarbon fuels with oxygen and increased blast temperatures for part of the normal coke requirement according to the process of this invention. For any hydrocarbon fuel or mixture of fuels, oxygen and blast temperature increases can be added in the proper quantities to maintain maximum smelting efiiciency While realizing substantial savings in coke. Furthermore, maximum smelting efficiency and low coke rates can be achieved independent of furnace production rates.

What is claimed is:

1. A method for the operation of a blast furnace wherein iron-containing materials, coke, and slagging materials are charged, comprising substituting for part of the coke an auxiliary hydrocarbon fuel while adding oxygen to the blast furnace, the minimum oxygen addition being according to the equation Y=antilog (0.042X +0.61), and the maximum oxygen addition according to the equation Y=antilog (0.032X +0.76), where Y is oxygen addition in pounds per pound of fuel and X is the carbon-hydrogen ratio of the fuel, reducing the coke rate through the addition of the auxiliary fuels, and operating the blast furnace at a desired production rate by decreasing the wind rate from the normal wind rate for desired production rates equal to and less than the normal rate and increasing the wind rate for production rates substantially greater than the normal rate.

2. A method for the operation of a blast furnace wherein iron-containing materials, coke, and slagging materials .are charged, comprising substituting for part of the coke an auxiliary hydrocarbon fuel while adding blast heat to the furnace, the maximum number of pounds of fuel added being according to the equation Z=antilog (0.033X-1.3), and the minimum number of pounds of fuel according to the equation Z: antilog (0.032X+1.08), where Z is the number of pounds of fuel added per 100 F. blast temperature increase per ton of iron produced, and where X is the carbon-hydrogen ratio of the fuel, reducing the coke rate through the addition of the auxiliary fuels, and reducing the blast volume to the furnace to achieve blast temperature increases and to give a desired production rate.

3. A method for the operation of a blast furnace wherein iron-containing materials, coke, and slagging materials are charged, comprising substituting for part of the coke an auxiliary hydrocarbon fuel while adding oxygen and heat to the blast furnace, the minimum oxygen addition being according to the equation Y: antilog (0.042X+0.6 1)

the maximum oxygen addition according to the equation Y=antilog (0.032X +0.76), where Y is the oxygen addition in pounds per pound of fuel added with oxygen enrichment, and X is the carbon-hydrogen ratio of the fuel, the heat added to the furnace as increases in blast temperature accompanied by additional hydrocarbon fuel additions, the maximum number of pounds of additional fuel being according to the equation Z=antilog (0.033X+ 1.3)

and the minimum number of pounds of fuel according to the equation Z=antilog (0.032X +1.08), where Z is the number of pounds of fuel per 100 F. blast temperature increase per ton of iron produced, and X is the carbon- .hydrogen ratio of the fuel, reducing the coke rate through the addition of the auxiliary fuels, and operating the blast furnace at a desired production rate by decreasing the wind rate from theinormal wind rate for desired production rates equal to and less than the normal rate and increasing the wind rate for production rates substantially greater than the normal rate.

4. A method for the operation of a blast furnace Wherein ironcontaining materials, coke, and slagging materials are charged, comprising setting a minimum flame temperature in the furnace, and then substituting for part of the coke an auxiliary hydrocarbon fuel while adding oxygen to the blast furnace, the minimum oxygen adition being according to the equation Y antilog (-0.042X+O.6l)

and the maximum oxygen addition according to the equation Y antilog (-0.032X +0.76), where Y is oxygen addition in pounds per pound of fuel and X is the carbonhydrogen ratio of the fuel, reducing the coke rate through the addition of auxiliary fuels, and operating the blast furnace at a desired production rate by decreasing the wind rate from the normal wind rate for desired production rates equal to and less than the normal rate and increasing the wind rate for production rates substantially greater than the normal rate.

5. A method for the operation of a blast furnace wherein iron-containing materials, coke, and slagging materials are charged, comprising setting the minimum flame temperature in the furnace for maximum smelting efficiency by first operating the furnace under normal conditions and making supplemental incremental additions of hydrocarbon fuels while making incremental reductions in the coke rate until the incremental coke reduction per incremental hydrocarbon fuel addition falls off substantially, and thereupon substituting additional hydrocarbon fuel for part of the coke requirement while adding oxygen to the blast furnace, the minimum oxygen addition being according to the equation Y=antilog (-0.042X-|-0.61), and the maximum oxygen addition according to the equation Y=antilog (0.032X+0.76), where Y is oxygen addition in pounds per pound of fuel and X is the carbon-hydrogen ratio of the fuel, reducing the coke rate through the addition of auxiliary fuels, and operating the blast furnace at a desired production rate by decreasing the wind rate from the normal wind rate for desired production rates equal to and less than the normal rate and increasing the wind rate for production rates substantially greater than the normal rate.

6. A method for the operation of a blast furnace where- 1.0 in iron-containing materials, coke, and slagging materials are charged, comprising setting a minimum flame temperature in the furnace, and then substituting for part of the coke an auxiliary hydrocarbon fuel while adding oxygen and blast heat to the blast furnace, the minimum oxygen addition being according to the equation and the maximum oxygen addition according to the equation Y=antilog (0.032X+0.76), where Y is the oxygen addition in pounds per pound of fuel added with oxygen enrichment, and X is the carbon-hydrogen ratio of the fuel, the heat added to the furnace as increases in blast temperature over normal with additional hydrocarbon fuel addition, the maximum number of pounds of fuel being according to the equation Z =antilog (0.033X+ 1.3), and the minimum number of pounds of fuel according to the equation Z==antilog (0.032X+1.08), where Z is the number of pounds of fuel per F. blast temperature increase per ton of iron produced, and X is the carbon-hydrogen ratio of the fuel, reducing the coke rate through the addition of the auxiliary fuels, and reducing the blast volume to the furnace to give a desired production rate and blast temperature increase.

7. A method for the operation of a blast furnace wherein iron-containing materials, coke, and slagging materials are charged, comprising setting the minimum flame temperature in the furnace for maximum smelting efficiency by first operating the furnace under normal conditions and then making incremental additions of hydrocarbon fuels while making incremental reductions in the coke rate until the incremental coke rate per incremental fuel addition falls off substantially, and substituting additional hydrocarbon fuel for part of the coke fuel while adding oxygen and blast heat to the blast furnace, the minimum oxygen addition being according to the equation Y=antilog (0.042X+0.6 1)

and the maximum oxygen addition according to the equation Y=antilog (0.032X+0.76) where Y is the oxygen addition in pounds per pound of fuel added with oxygen enrichment, and X is the carbon-hydrogen ratio of the fuel, the heat added to the furnace as increases in blast temperature accompanied by additional hydrocarbon fuel addition, the maximum number of pounds of fuel being according to the equation Z=antilog (0.033X +1.3), and the minimum number of pounds of fuel according to the equation Z :antilog (0.032X +1.08), Where Z is the number of pounds of fuel per 100 F. blast temperature increase per ton of iron produced, and X is the carbonhydrogen ratio of the fuel, reducing the coke rate through the addition of the auxiliary fuels, and operating the blast furnace at a desired production rate and economy by decreasing the wind rate from the normal wind rate for desired production rates equal to and less than the normal production rate and increasing the wind rate for production rates substantially greater than the normal rate.

8. A method for the operation of a blast furnace wherein iron-containing materials, coke, and slagging materials are charged, comprising setting a minimum flame temperature in the furnace, and then substituting for part of the coke an auxiliary hydrocarbon fuel while adding oxygen to the blast furnace, the minimum oxygen addition being according to the equation Y antilog (0.032X+0.76), where Y is the oxygen addition in pounds per pound of fuel and X is the carbon-hydrogen ratio of the fuel, reducing the coke rate through the addition of the auxiliary fuels, while the value of the coke saved is at least equal to the cost of supplying the auxiliary fuels and oxygen, and reducing the Wind rate from the normal wind rate with air so that the total mass of oxygen entering in the blast is less than that of the normal Wind rate with air.

9. A method for the operation of a blast furnace wherein iron-containing materials, coke, and slagging materials are charged, comprising setting a minimum flame temperature in the furnace, and then substituting for part of the coke an auxiliary hydrocarbon fuel while adding oxygen and blast heat to the blast furnace, the minimum oxygen addition being according to the equation Y=antilog (0.042X +0.61), and the maximum oxygen addition according to the equation Y=antilog (-0.032X+0.76), where Y is the oxygen addition in pounds per pound of fuel added with oxygen enrichment, and X is the carbonhydrogen ratio of the fuel, the heat added to the furnace as increases in blast temperature over normal with additional hydrocarbon fuel addition, the maximum number of pounds of fuel added being according to the equation Z=antilog (0.033X+1.3), and the minimum number of pounds of fuel according to the equation Z=antilog (0.032X-|-l.08), where Z is the number of pounds of fuel per 100 F. blast temperature increase per ton of iron produced, and X is the carbon-hydrogen ratio of the fuel, reducing the coke rate through the addition of the auxiliary fuels, and reducing the wind rate from the normal wind rate with air so that the total mass of oxygen entering in the blast is less than that of the normal wind rate With air.

10. A method for the operation at less than normal capacity of a blast furnace wherein iron-containing materials, coke, and slagging materials are charged, comprising setting a minimum flame temperature in the furnace, and then substituting for part of the coke an auxiliary hydrocarbon fuel While adding oxygen, and blast heat to the blast furnace, the minimum oxygen addition being according to the equation Y=antilog (0.042X+0.6l), and the maximum oxygen addition according to the equation Y=antilog (0.032X +0.76), where Y is the oxygen addition per pound of fuel added with oxygen enrichment, and X is the carbon-hydrocarbon ratio of the fuel, the heat being added to the furnace as increases in blast temperature over normal with additional hydrocarbon fuel addition, the maximum number of pounds of fuel added being according to the equation Z=antilog (0.033X +1.3), and the minimum number of pounds of fuel according to the equation Z=antilog (0.032X+ 1.08), where Z is the number of pounds of fuel per 100 F. blast temperature increase per ton of iron produced, and X is the carbon-hydrogen ratio of the fuel, reducing the coke rate through the addition of the auxiliary fuels, and reducing the wind rate from the normal Wind rate with air so that the total mass of oxygen entering in the blast is less than that of the normal wind rate with air and is only sufficient to supply the furnace requirements at the desired lower rate production.

11. A method for the more economical operation of a blast furnace at about its normal capacity, wherein ironcontaining materials, coke, and slagging materials are charged, comprising determining a minimum flame temperature in the furnace, and then substituting for part of the coke an auxiliary hydrocarbon fuel while adding oxygen and blast heat to the blast furnace, the minimum oxygen addition being according to the equation Y=antilog (-0.042X +0.61), and the maximum oxygen addition according to the equation Y=antilog (0.032X+0.76)

where Y is the oxygen addition in pounds per pound of fuel added with oxygen enrichment, and X is the carbonhydrocarbon ratio of the fuel, the heat being added to the furnace as increases in blast temperature over normal with additional hydrocrabon fuel addition, the maximum number of pounds of fuel added being according to the equation Z antilog (0.033X+1.3), and the minimum number of pounds of fuel according to the equation Z antilog (0.032X+l.08), where Z is the number of pounds of fuel per 100 F. blast temperature increased per ton of iron produced, and X is the carbon-hydrogen ratio of the fuel, reducing the coke rate through the addition of the auxiliary fuels, and reducing the wind rate from the normal wind rate with air so that the total mass 12 of oxygen entering in the blast is less than that of the normal wind rate with air and is only sufficient to supply the furnace requirements at the given normal production rate.

12. A method for the operation of a blast furnace at an increased rate of production wherein iron-containing materials, coke, and slagging materials are charged, comprising ilame temperature in the furnace, substituting for part of the coke an auxiliary hydrocrabon fuel while adding oxygen and blast heat to the blast furnace, the minimum oxygen addition being according to the equation Y=antilog (0.042X+0.6l), and the maximum oxygen addition according to the equation Y: antilog (-0.032X+0.76)

where Y is the oxygen addition in pounds per pound of fuel added with oxygen enrichment, and X is the carbonhydrocarbon ratio of the fuel, the heat being added to the furnace as increases in blast temperature over normal with additional hydrocarbon fuel addition, the maximum number of pounds of fuel added being according to the equation Z=antilog (0.033X+1.3), and the minimum number of pounds of fuel according to the equation Z=antilog (0.032X+1.08), where Z is the number of pounds of fuel per F. blast temperature increased per ton of iron produced, and X is the carbon-hydrogen ratio of the fuel, reducing the coke rate through the addition of the auxiliary fuels, and regulating the wind rate to the furnace so that the total mass of oxygen entering in the blast is only suflicient to supply the furnace requirements at the desired higher production rate.

13. A process for the operation of a blast furnace wherein iron-containing materials, coke in a normal amount of about 1400-1500 pounds of coke per ton of iron, and slagging materials are charged into the furnace, comprising substituting for part of the coke an auxiliary hydrocarbon fuel while adding oxygen and heat to the blast furnace, the minimum oxygen addition being according to the equation Y=antilog (0.042X+0.6l), and the maximum oxygen addition according to the equation Y=antilog (.032X+0.76), Where Y is the oxygen addition in pounds per pound of fuel added with oxygen enrichment, and X is the carbon-hydrogen ratio of the fuel, the heat added to the furnace as increases in blast temperature over normal with accompanying hydrocarbon fuel additions, the maximum number of pounds of fuel added being according to the equation Z=antilog (0.033X+1.3), and the minimum number of pounds of fuel according to the equation Z=antilog (0.032X+l.08), where Z is the number of pounds of fuel per 100 F. blast temperature increase per ton of iron produced, and X is the carbon-hydrogen ratio of the fuel, reducing the coke rate through the addition of the auxiliary fuels, and, as a lower limit, to a coke rate of 700 to 850 pounds of coke per ton of iron, and operating the blast furnace at a desired production rate and economy by decreasing the wind rate from the normal wind rate for desired production rates equal to and less than the normal production rate and increasing the wind rate for production rates substantially greater than the normal rate.

14. A method for the operation of a blast furnace wherein iron-containing materials, coke, and slagging material are charged, comprising substituting for part of the coke an auxiliary hydrocarbon fuel selected from the group consisting of natural gas, oil and coal while adding oxygen to the blast furnace, the amount of oxygen added to the furnace per pound of fuel added being from 2.7 to 4.5 pounds for natural gas, from 1.7 to 3.0 pounds for oil, from 0.64 to 1.4 pounds for coal, and in amounts proportional to these when more than one fuel is selected, reducing the coke rate through the addition of the auxiliary fuels, and operating the blast furnace at a desired production rate by decreasing the wind rate from the normal wind rate for desired production rates equal to and less than the normal production rate and increasing 13 the wind rate for production rates substantially greater than the normal rate.

15. A method for the operation of a blast furnace wherein iron-containing materials, coke, and slagging materials are charged, comprising substituting for part of the coke auxiliary hydrocarbon fuels selected from the group consisting of natural gas, oil, and pulverized coal While adding heat to the furnace through increases in the blast temperature, the amount of fuel added for each 100 F. increase in blast temperature per ton of iron being from 16 to 27 pounds of natural gas, from 20 to pounds of oil, from to pounds of coal, and in amounts proportional to these when more than one fuel is selected, reducing the coke rate through the addition of the auxiliary fuels, and reducing the blast volume to achieve blast temperature increases and give a desired level of production.

16. A method for operating a blass furnace wherein iron-containing materials, coke, and slagging materials are charged, comprising substituting for part or" the coke auxiliary hydrocarbon fuels selected from the group consisting of natural gas, oil, and pulverized coal while adding oxygen and heat to the furnace, the amount of oxygen added per pound of fuel being from 2.7 to 4.5 pounds for natural gas, from 1.7 to 3.0 pounds for oil, from 0.64 to 1.4 pounds for coal, and in amounts proportional to these when more than one fuel is selected, the heat added to the furnace being in the form of blast temperature increases accompanied by additional hydrocarbon fuel additions, the amount of additional fuel added for each F. increase in blast temperature per ton of iron being from 16 to 27 pounds of natural gas, from 20 to 40 pounds of oil, from 50 to 90 pounds of coal, and in amounts proportional to these when more than one additional fuel is selected, reducing the coke rate through the addition of the auxiliary hydrocarbon fuels, and operating the blast furnace at a desired production rate by decreasing the wind rate from the normal wind rate for desired production rates equal to and less than the normal production rate and increasing the Wind rate for production rates substantially greater than the normal rate.

17. A method for operating a blast furnace wherein iron-containing materials, coke, and slagging materials are charged, comprising determining a minimum flame temperature in the furnace, and then substituting for part of the coke auxiliary hydrocarbon fuels selected from the group consisting of natural gas, oil, and pulverized coal while adding oxygen and heat to the furnace, the amount of oxygen added per pound of fuel being from 2.7 to 4.5 pounds for natural gas, from 1.7 to 3.0 pound for oil, from 0.64 to 1.4 pounds for coal, and in amounts proportional to these when more than one fuel is selected, the heat added to the furnace being in the form of blast temperature increases accompanied by additional hydrocarbon fuel additions, the amount of additional fuel added for each 100 F. increase in blast temperature per ton of iron being from 16 to 27 pounds of natural gas, from 20 to 40 pounds of oil, from 50 to 90 pounds of coal, and in amounts proportional to these when more than one additional fuel is selected, reducing the coke rate through the addition of the auxiliary hydrocarbon fuels, and regulating the blast volume to the furnace to give a desired production level.

References Cited by the Examiner FOREIGN PATENTS 872,062 7/1961 Great Britain.

OTHER REFERENCES Blast Furnace, Coke Oven and Raw Materials Prooeedings, published by AIMME, vol. 19, 1960, pages 23 8- 253; vol. 21, 1962, pp. 15-41.

References Cited by the Applicant UNITED STATES PATENTS 2,727,816 12/1955 Raick. 2,735,758 2/1956 Strassburger. 3,062,640 11/1962 Agarwal et al.

OTHER REFERENCES Blast Furnace Performance With Injection at the Tuyeres, J. M. Ridgion, Journal of the Iron and Steel Institute, October 1961, pages to 143.

DAVID L. RECK, Primary Examiner.

Claims (1)

1. A METHOD FOR THE OPERATION OF A BLAST FURNACE WHEREIN IRON-CONTAINING MATERIALS, COKE, AND SLAGGING MATERIALS ARE CHARGED COMPRISING SUBSTITUTING FOR PART OF THE COKE AN AUXILIARY HYDROCARBON FUEL WHILE ADDING OXYGEN TO THE BLAST FURNACE, THE MINIMUM OXYGEN ADDITION BEING ACCORDING TO THE EQUATION Y=ANTILOG (-0.042X +0.61), AND THE MAXIMUM OXYGEN ADDITION ACCORDING TO THE EQUATION Y=ANTILOG (-0.032X+0.76), WHERE Y IS OXYGEN ADDITION IN POUNDS PER POUND OF FUEL AND X IS THE CARBON-HYUDROGEN RATIO OF THE FUEL, REDUCING THE COKE RATE THROUGH THE ADDITION OF THE AUXILIARY FUELS, AND OPERATING THE BLAST FURNACE AT A DESIRED PRODUCTION RATE BY DECREASING THE WIND RATE FROM THE NORMAL WIND RATE FOR DESIRED PRODUCTION RATES EQUAL TO AND LESS THAN THE NORMAL RATE AND INCREASING THE WIND RATE FOR PRODUCTION RATES SUBSTANTIALLY GREATER THAN THE NORMAL RATE.

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