US3218155A - Method of operating metallurgical furnaces - Google Patents

Method of operating metallurgical furnaces Download PDF

Info

Publication number
US3218155A
US3218155A US77507A US7750760A US3218155A US 3218155 A US3218155 A US 3218155A US 77507 A US77507 A US 77507A US 7750760 A US7750760 A US 7750760A US 3218155 A US3218155 A US 3218155A
Authority
US
United States
Prior art keywords
blast
furnace
blast gas
gas
moisture
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US77507A
Inventor
Julius H Strassburger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
National Steel Corp
Original Assignee
National Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by National Steel Corp filed Critical National Steel Corp
Priority to US77507A priority Critical patent/US3218155A/en
Application granted granted Critical
Publication of US3218155A publication Critical patent/US3218155A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B5/00—Making pig-iron in the blast furnace

Definitions

  • This invention relates to blast furnaces and more particularly to improvements in the method of operating blast furnaces.
  • Conventional blast furnaces comprise a hearth, a stack and bosh between the hearth and the stack.
  • the blast comprising essentially compressed air, is blown through tuyeres mounted in the bosh into the upper portion of the hearth, and the burden, including specific proportions of limestone, ferrous bearing material and carbonaceous material is charged into the furnace at the top of the stack.
  • the ferrous bearing material is usually iron ore and may include some scrap metal, sinter or other material and the carbonaceous material is usually coke.
  • the charge moves down the shaft of the furnace and when it reaches a zone adjacent the tuyeres the coke is burned by the incoming blast to melt the iron ore producing molten pig iron and the hot gaseous products of combustion flow up through the stack, preheating the descending charge and reducing the iron ore as it approaches the combustion zone, and out through the top of the furnace.
  • the quantity and physical character of material discharged into the top of the furnace as burden and the volume of blast gas blown into the furnace are calculated and controlled to maintain the highest possible rate of pig iron production with minimum coke consumption and with minimum flue dust production.
  • the volume of blast gas required depends upon the physical characteristics of the furnace and the components of the burden and must be carefully controlled in order to maintain a smooth operating furnace. It is known that an insufiicient volume of blast gas results in low pig iron production and high coke rates, while excessive blast gas increases flue dust production without a corresponding rise in iron production.
  • the driving rate of a blast furnace is a measure of the quantity of carbon gasified at the tuyeres by combustion of coke. Since coke combustion is influenced by the oxygen available and by the existing temperature it has been proposed in the past to increase the production of blast furnaces without substantially increasing the volume of blast gas by either enriching the blast gas with oxygen or by blowing the blast gas to the furnace at an elevated temperature. It was found however that the mere enrichment of the blast gas with oxygen or the mere increase in temperature of the blast gas did not produce the expected results as the furnace either ran cold due to resulting high velocity of upwardly flowing bosh gas or that the movement of the burden slowed down and became intermittent or at times actually stopped and caused the furnace to hang which was followed by violent slips.
  • blast furnaces may be operated to produce, within limits, products of specified characteristics and it is desirable to obtain smooth operations in blast furnaces producing pig iron of different chemical compositions, temperatures, etc. Accordingly, the obtaining of a smooth operating furnace by means of moisture additions to the blast gas includes the feature of controlling the characteristics of the product by such moisture additions.
  • Another object is to provide a novel method of operating a blast furnace by which combustion of coke is intensified without correspondingly increasing the volume of blast gas in such a manner as to require minimum moisture additions to the blast gas.
  • predetermined quantities of moisture are required to be added to oxygen enrichedv blast gas or to blast gas at an elevated temperature in order to obtain smooth operating furnaces.
  • the quantity of moisture required may be considered as depending for the most part upon the percentage of oxygen enrichment or upon the blast temperature although the moisture actually required may be influenced by the physical characteristics of the furnace or by the constituents of the burden.
  • the in blast gas at about 1100 oxygen enrichment is shown in Table I.
  • Example A Example B
  • Example 0 Example D
  • Example E Example F
  • Example G Iron Prod. Net Tons Per Day 1, 499 1, 958 2, 236 1 963 2 301 1, 501 1, 613 Iron Piotr: Net Tons Per Day S.F 1, 499 1,870 2,122 11963 21181 1, 489 1, 606 goke Raige, 112211? Net Ton SJ 1, 602 1, 250 1, 270 1, 3 1, 270 1,163?
  • 1,263 X en 11110 en Wi Blown, 0.1.111 78,460 92,149 97,169 105, 521 101, 080 75,100 74,900 ll d l 6 Ft 11 8 17 3 187; 14 172 ib i5 gg 1: ins e u. 015 m r 31. 6 58.9 61.4 59.9 52.2 16. g 24. g 6. 9 13. 38 2' 33. 2 39 4 1 0 11.
  • Example H Example I Example I Example K Example L Example M Example N Iron Prod. Net Tons Per Day 1 596 1 582 1 820 1,601 1,685 1 720 1 822 Iron Prod Net Tons Per Day S.F 1: 596 1: 582 11 812 1, 597 1, 685 1: 720 1: 822 Coke Rate, Lbs. Per Net Ton S.F 1, 574 1, 642 1, 342 1, 652 1, 619 1, 591 1, 505 Oxygen Enrichment 3. 03 3. 54 1. 49 3.01 4.0 4.00 r) 4.
  • Table XIII is a comparison of moisture content of the blast gas in Examples A through N with the moisture content that would be expected to be required according to Table I for oxygen enrichment and in accordance with general rule of adding 1 grain of moisture for each F. increase in blast gas temperature- From Table XIII, it is seen that with blast gas temperatures at and below 1375 F. the total moisture actually used in the blast gas in order to maintain a smoothly operating furnace falls roughly within the range of Moisture expected to be required, while with blast gas temperatures of about 1400 to 1500" F., and above, the moisture actually needed for maintaining a smoothly operating furnace is about four grains or more of moisture per cubic foot ofblast gas less than the minimum moisture content expected to be required.
  • blast furnace performance depends upon physical characteristics of the blast furnace and upon variable factors including composition of the burden and physical characteristics of constituents of the burden it is believed the critical temperature for average blast furnace installations falls within the range of about 1400 F. to 1500 F., that is, with blast gas heated to a temperature above about 1400 F. to 1500 F. unexpected savings in required moisture can be realized.
  • blast gas temperatures above the critical temperature have some effect upon the combustion zones in front of the tuyeres to reduce the size of the core of substantially solid material in the region of the center of the hearth thus permitting combustion gases to flow more easily upwardly into the stack.
  • the use of oxygen enrichment which increases the oxygen contact per cubic foot of blast gas while actually decreasing the volume of the blast gas, may have some effect to compensate for the disadvantages resulting from expansion of blast gas with increasing temperature when theblast gas temperature is above the critical temperature of about 1400 F.
  • Tables 11 through XI include the range of moisture required according to the principles of the present invention for various ox gen enrichment percentages at blast gas temperatures. It will be noted that with blast gas temperatures below 1400 F., the moisture required according to the present invention is similar to the moisture expected to be required, while at blast gas temperatures above 1500 F. the range of moisture required according to the present invention is about four grains per cubic foot less than the moisture expected to be required for similar percentages of oxygen enrichment and blast gas temperatures.
  • Table XII show moisture savings greater than four grains per cubic foot of blast gas can be obtained with some furnaces at high blast gas temperatures and although moisture savings should increase with increasing blast gas temperatures, for the sake of clarity, the ranges of required moisture according to the present invention as set forth in Tables 11 through XI are based on minimum savings of four grains of moisture per cubic foot of blast gas.
  • blast gas temperatures in existence today are generally capable of operation with blast gas temperatures as high as about 2000 F. providing sufiicient stove capacity is available. For operation with blast gas temperatures above 2000 5., it will be necessary to utilize high temperature materials in the construction of certain components of the furnace. Although operation'with blast gas temperatures above 2000 F. is planned and high temperature materials necessary forsuch operation are either in existence or under development, the practical range of blast gas temperatures according to the present invention is from about 1400 F. to 1500 F. and up to about 2000 F. Inasmuch as the.
  • Table XV is a composite of data on moisture required in accordance with the invention taken from earlier in view of the present lack of As will be described in more detail in It is seen from Table XIV that furnace efiiciency tion the practical range of oxygen enrichment is The teachings of the present invention are applicable,
  • auxiliary fuels have many of the same elfects thermodynamically as aqueous additions and for many purposes can be considered control equivalents.
  • the teachings of the invention include methgrains Although this table TABLE XIV .5% TO 10% OXYGEN ENRICHMEN'I Table XIV discloses calculated av r S b .m mm Mm mm m m m m i m F 01 V1 3 t r moaebe t a f .lh C H O 0 1 r.
  • blast gas having an oxygen enrichment between 5% and 10% at temperatures from 1100 F. to 2500 F.
  • auxiliary fuel additions fuel introduced through the tuyeres or other than through the top of the furnace.
  • limestone, ferrous bearing material, and carbonaceous material such as coke are charged into the top of the furnace. The charge moves down the shaft of the fur nace and the coke, constituting the fuel of the mixture, is burned by the incoming blast to melt the iron producing molten pig iron.
  • Auxiliary fuels are not introduced at the top of the furnace but near the bottom of the furnace, preferably, in accordance with the invention, through the main tuyeres of the furnace and may include fuels such as natural gas, coke oven gas, fuel oil, powdered carbonaceous materials such as coal, chat or coke, or the products of combustion of these fuels.
  • fuels such as natural gas, coke oven gas, fuel oil, powdered carbonaceous materials such as coal, chat or coke, or the products of combustion of these fuels.
  • auxiliary fuel is burned before entering the furnace or added at the tuyeres a reduction in moisture additions is required in proportion to the products of combustion of auxiliary fuel when a like amount of auxiliary fuel is burned in a surplusage of oxygen.
  • teachings of the invention emphasize the advantages of introducing the auxiliary fuel at the tuyeres, such as the avoidance of plant heat losses.
  • Example Example 1 2 3 4 FURNACE PERFORMANCE Iron ProcL, Net Tons Per Day 18. 74 18.91 20.82 18. 31 Coke Rate, Lbs. Per Net 'Ion 1, 322 1, 006 1, 104 1, 105 Slag Volume, Lbs. Per Net Ton 085 993 957 1, 005
  • blast gas temperature should be increased approximately 120. From this data it can be seen that, as far as blast furnace control is concerned, one percent of natural gas is approximately equivalent, considering smooth operations, to four grains of moisture. In other words, when making auxiliary fuel additions of natural gas, for each percent of natural gas added to the blast, the aqueous additions should be reduced approximately four grains.
  • aqueous additions should not be eliminated entirely.
  • the furnace cannot be readily controlled by adjusting the rate of auxiliary fuel injections, but excellent control can be obtained by maintaining some aqueous additions to the furnace.
  • auxiliary fuel is not effective in instantaneous control, even though it serves as an equivalent in many other respects to aqueous addition, are multiple and speculative. Usually, the explanations hinge on the change in the amount of carbon available in the furnaces with changes in the auxiliary fuel injection rate.
  • aqueous additions or the moisture additions effect of adding auxiliary fuel would serve to cool this area and lengthen the combustion zone in the furnace and thereby reestablish smooth descent of the burden. In general, cooling of the hot zone takes place with either additive.
  • the amount of aqueous additions maintained should be sufficient to exercise furnace control. If dehumidifying equipment is not used, aqueous additions of about 7 grains are suflicient to allow for normal variations in the ambient atmospheric humidity and leave a margin for varying the aqueous addition to effect instantaneous control. If dehumidifying equipment is used on the blast, the aqueous additions to the furnace helpful in instantaneous control can be maintained by regulating the humidity of the air used in the blast.
  • the blast gas temperature should be increased and the aqueous additions reduced in accordance with the endothermic requirements of the auxiliary fuel.
  • the coke rate should be reduced in accordance with the carbon and reducing agents added by the auxiliary fuel. If oxygen enrichment is used the production rate will be increased since the consumption of the oxygen of the blast by the auxiliary fuel will be reduced and will be available for burning additional coke in the burden and increasing the driving rate.
  • Method of operating a blast furnace in which iron bearing material is smelted and in which coke is burned comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 1400 F. to 1500 F., and blowing blast gas into the furnace, the oxygen enrichment being in the range of 1%-l0%, and the quantity of aqueous fluid in the blast gas being from about 12.2 to about 82.2 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 12.2 to about 82.2
  • Method of operating a blast furnace in which iron bearing material is smelted and in which coke is burned comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temr perature above about 1400 F. to 1500 F., and blowing blast gas into the furnace, the oxygen enrichment being in the range of 1%-5% and the quantity of aqueous fluid in the blast gas being from about 12.2 to about 70.2 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 12.2 to about 70.2 grains of moisture per cubic foot of blast gas as the oxygen enrichment increases from about 1% to about 5% l 3.
  • Method of operating a blast furnace in which iron bearing material is smelted and in which coke is burned comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 1400 F. to about 1500 F., and blowing blast gas into the furnace, the oxygen enrichment being within the range of 5 and the quantity of aqueous fluid in the blast gas being from about 26.2 to about 82.2 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 26.2 to about 82.2 grains of moisture per cubic foot of blast gas as the oxygen enrichment increases from about 5% to about 10%.
  • Method of operating a blast furnace in which iron bearing material is smelted and in which coke is burned comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 1400 F, to 1500 F. and up to 2000 F., and blowing blast gas into the furnace, the oxygen enrichment being in the range of 1% to 10% and the quantity of aqueous fluid in the blast gas being from about 12.2 to about 65.7 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 12.2 to about 65.7 grains of moisture per cubir foot of blast gas as the oxygen enrichment increases from about 1% to about 10%.
  • Method of operating a blast furnace in which iron bearing material is smelted and in which cokeis burned comprising the steps'of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 1400 F. to 1500 F. and up to about 2000 F., and blowing blast gas into the furnace, the oxygen enrichment in the blast gas being in the range of 1%5%, and the quantity of aqueous fluid in the blast gas being from about 12.2 to about 53.7 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 12.2 to about 53.7 grains of moisture per cubic foot of blast gas as the oxygen enrichment increases from about 1% to about 5%.
  • Method of'operating a blast furnace in which iron bearing material is smelted and in which coke is burned comprising the steps of forming blast gas including atmospheric air, enriching the blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 1400 F. to 1500 F.
  • the aqueous fluid bearing material is smelted and in which coke is burned, comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 2000 F.
  • the oxygen enrichment in the blast gas being in the range of l%l0%
  • the quantity of aqueous fluid in the blast gas being from about 28.7 to about 82.2 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 28.7 to about 82.2 grains of moisture per cubic foot of blast gas as the oxygen enrichment increases from about 1% to about 10%.
  • blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 2000 F. and up to about 2500 F., and blowing blast gas into the furnace, the oxygen enrichment in the blast gas being in the range of 1%5%, and the quantity of aqueous fluid in the blast gas being from about 28.7 to about 70.2 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 28.7 to about 70.2 grains of moisture per cubic foot of blast gas as the oxygen enrich ment increases from about 1% to about 5%.
  • Method of operating a blast furnace in which iron bearing material is smelted and in which coke is burned comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 2000 F. and up to about 2500 F., and blowing blast gas into the'furnace, the oxygen enrichment being within the range of 5%l0%, and the quantity of aqueous fluid in the blast gas being from about 42.7 to about 82.2 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 42.7 to about 82.2 grains of moisture per cubic foot of blast gas as the oxygen enrichment increases from about 5% to about 10%.
  • Method of operating a blast furnace in which iron bearing and carbonaceous material are charged into the top of the furnace and a blast gas is introduced into the bottom of the furnace comprising the steps of preheating the blast gas to a temperature above about 1400 F., and adding aqueous fluid to the blast gas in accordance with the temperature of the blast gas, the quantity of aqueous fluid added being about nine grains of aqueous fluid per cubic foot of blast furnace gas at a temperature of about 1400 F. with about three grains of moisture per cubic foot of blast gas required'to be added with each F. increase in blast gas temperature above 11.
  • Method of operating a blast furnace in'which iron hearing and carbonaceous materials are charged into the top of the furnace and a blast gas is introduced into the bottom of the furnace comprising the steps of preheating the blast gas to temperatures above 1400 5., adding aqueous fluid to the blast gas with about 9 grains of aqueous fluid per cubic foot of blast gas being added at 1400 F., adding auxiliary fuel to the blast gas in the range of about 1% to about 8% by volume of the blast gas, and controlling the blast gas temperature in accordance with the formula, blast gas temperature: 1400+(M)33 F.+(F) F, wherein M is equal to the grains of aqueous fluid above 9 grains per cubic foot of blast gas added and F is equal to the percentage of the blast gas by volume auxiliary fuel added to the blast gas.
  • a process of heating and humidifying the'blast for a metallurgical blast furnace which comprises: blowing cold blast air for the blast of the furnace through a preheating medium therefor and thereby preheating the blast for the furnace, thereafter augmenting the heat of the blast from said medium by burning combustible fuel with part of the total air of the blast directly in the preheated blast, and thereafter delivering the heat augmented hot blast into the hearth in the blast furnace While charged with Water vapor to a predetermined constancy of humidity
  • the improvement comprising the steps of; effecting said augmenting of the heat of the blast by burning a hydrogen containing fuel as the combustible fuel directly in the blast and thereby charging the blast with a substantial part of the water vapor for said predetermined constancy of humidity as a product of said combustion, and adding the remainder of the total amount of vapor to form said predetermined constancy of humidity in the form of aqueous fluid to the blast before the heat of the blast is augmented.
  • Method of operating a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and blast gas is introduced at the bottom of the furnace comprising the steps of preheating the blast gas to a predetermined temperature, adding auxiliary fuel to the blast gas, and adding aqueous fluid to the blast gas in accordance with the temperature of the blast gas and the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid being substantially equal to the aqueous fluid required at the predetermined temperature without auxiliary fuel being introduced into the furnace and a quantity of aqueous fluid equivalent to the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid required to be added to the blast gas at the predetermined temperature being from about 9 grains per cubic foot of blast gas at a temperature of about 1400 F. with about 3 grains of aqueous fluid per cubic foot of blast gas required to be added for each 100 F. increase in blast gas temperature above 1400 F.
  • the method of operating a blast furnace as defined in claim 15 including the step of controlling the quantity of carbonaceous material charged into the top of the blast furnace based on the exothermic equivalent of the auxiliary fuel added to the blast gas.
  • auxiliary fuel comprises natural gas added in the range of about 1 percent to about 8 percent by volume of the blast gas.
  • Method of operating a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and blast gas is introduced through blast furnace tuyeres at the bottom of the furnace comprising the steps of preheating the blast gas to a predetermined temperature, adding aqueous fluid to the blast gas, adding auxiliary fuel at the blast furnace tuyeres, and controlling the aqueous fluid additions to the blast gas in accordance with the temperature of the blast gas and the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid additions being substantially equal to the aqueous fluid required at the predetermined blast gas temperature offset by equivalent aqueous fluid substantially equal to the endothermic requirements of the added auxiliary fuel, the quantity of aqueous fluid required at the predetermined blast gas temperature being approximately 9 grains per cubic foot of blast gas at a temperature of about 1400 F. with 3 grains of aqueous additions per cubic foot of blast gas being added for each 100 F. increase in blast gas temperature above 1400 F.
  • Method of operating a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and blast gas is introduced into the bottom of the furnace comprising the steps of preheating the blast gas to a predetermined temperature, adding auxiliary fuel to the blast gas, and adding aqueous fluid to the blast gas in accordance with the temperature of the blast gas and the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid added to the blast gas being substantially equal to the difference between the quantity of aqueous fluid required to be added to blast gas at the predetermined temperature without auxiliary fuel being introduced into the furnace and a quantity of aqueous fluid equivalent to the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid required to be added to the blast gas without auxiliary fuel introduced into the furnace varying between about 9 grains of aqueous fluid per cubic foot of blast gas at 1400 F. and about 45 grains of aqueous fluid per cubic foot of blast gas at 2500 F.
  • Method of operating a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and blast gas is introduced into the bottom of the furnace comprising the steps of preheating the blast gas to a predetermined temperature, enriching the blast gas with a predetermined percentage of oxygen, in the range of about 1% to about 10% of the blast gas, adding auxiliary fuel to the blast gas, and adding aqueous fluid to the blast gas in accordance with the temperature of the blast gas, the percent of oxygen enrichment and the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid added to the blast gas being substantially equal to the difference between the quantity of aqueous fluid required to be added to blast gas at the predetermined temperature and the predetermined percentage of oxygen enrichment without auxiliary fuel introduced into the furnace and the quantity of aqueous fluid equivalent to the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid required to be added to the blast gas without auxiliary fuel introduced into the furnace varying between about 12 grains of aqueous fluid per cubic foot of blast gas
  • Method of operating a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and blast gas is introduced into the bottom of the furnace comprising the steps of preheating the blast gas to a predetermined temperature, adding natural gas to the blast gas in the range of about 1 percent to about 6 percent by volume of the blast gas, and adding aqueous fluid to the blast gas in accordance with the temperature of the blast gas and the endothermic requirements of the auxiliary fuel, the quantity of the aqueous fluid additions being equal to the aqueous fluid additions required at the predetermined blast gas temperature offset by equivalent aqueous fluid substantially equal to the endothermic requirements of the added natural gas, the quantity of aqueous fluid additions required by the blast gas temperature being equal to approximately 9 grains per cubic foot of blast gas at a temperature of about 1400 F.
  • a method for increasing the production rate of the furnace comprising the steps of adding natural gas to the blast gas in the range of about 1 percent to about 8 percent by volume of the blast gas, and controlling the blast gas temperature in accordance 19 with the endothermic requirements of the added natural gas, the endothermic requirements being an increase in blast gas temperature of about 120 F. for each percent by volume of natural gas added to the blast gas.
  • Method of operating a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and a blast gas is introduced at the bottom of the furnace comprising the steps of preheating the blast gas to a predetermined temperature, introducing material into the bottom of the'furnace as auxiliary fuel, and adding aqueous fluid to the blast gas in accordance with the temperature of the blast gas and the endothermic requirements of the introduced material, the quantity of aqueous fluid added to the blast gas being substantially equal to the difference between the quantity of aqueous fluid required to be added to the blast gas at the predetermined temperature
  • the predetermined temperature of the blast gas being from about 1400 F.
  • the quantity of aqueous fluid required to be added to the blast gas at the predetermined temperature being from about 9 grains of moisture up to about 45 grains of moisture per cubic foot of blast gas, and the quantity of aqueous fiuid equivalent to the endothermic requirements of the introduced material being approximately 4 grains of aqueous fluid per cubic foot of blast gas per endothermic requirement N, the endothermic requirement N being equal to the endothermic requirement of a quantity of natural gas equal to 1% of the blast gas.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Iron (AREA)

Description

nited States Patent 3,218,155 METHOD OF OPERATING METALLURGICAL FURNACES Julius H. Strassburger, Coraopolis, Pa., assignor to National Steel Corporation, a corporation of Delaware No Drawing. Filed Dec. 22, 1960, Ser. No. 77,507 23 Claims. (Cl. 7542) This application is a continuation-in-part of Serial No. 54,366, filed September 7, 1960, and now abandoned.
This invention relates to blast furnaces and more particularly to improvements in the method of operating blast furnaces.
Conventional blast furnaces comprise a hearth, a stack and bosh between the hearth and the stack. The blast, comprising essentially compressed air, is blown through tuyeres mounted in the bosh into the upper portion of the hearth, and the burden, including specific proportions of limestone, ferrous bearing material and carbonaceous material is charged into the furnace at the top of the stack. The ferrous bearing material is usually iron ore and may include some scrap metal, sinter or other material and the carbonaceous material is usually coke. The charge moves down the shaft of the furnace and when it reaches a zone adjacent the tuyeres the coke is burned by the incoming blast to melt the iron ore producing molten pig iron and the hot gaseous products of combustion flow up through the stack, preheating the descending charge and reducing the iron ore as it approaches the combustion zone, and out through the top of the furnace.
The quantity and physical character of material discharged into the top of the furnace as burden and the volume of blast gas blown into the furnace are calculated and controlled to maintain the highest possible rate of pig iron production with minimum coke consumption and with minimum flue dust production. The volume of blast gas required depends upon the physical characteristics of the furnace and the components of the burden and must be carefully controlled in order to maintain a smooth operating furnace. It is known that an insufiicient volume of blast gas results in low pig iron production and high coke rates, while excessive blast gas increases flue dust production without a corresponding rise in iron production.
The driving rate of a blast furnace is a measure of the quantity of carbon gasified at the tuyeres by combustion of coke. Since coke combustion is influenced by the oxygen available and by the existing temperature it has been proposed in the past to increase the production of blast furnaces without substantially increasing the volume of blast gas by either enriching the blast gas with oxygen or by blowing the blast gas to the furnace at an elevated temperature. It was found however that the mere enrichment of the blast gas with oxygen or the mere increase in temperature of the blast gas did not produce the expected results as the furnace either ran cold due to resulting high velocity of upwardly flowing bosh gas or that the movement of the burden slowed down and became intermittent or at times actually stopped and caused the furnace to hang which was followed by violent slips. It was theorized that the inability to obtain a smooth operating furnace when enriching the blast gas with oxygen or by elevating the temperature of the blast gas results from the fact that oxygen enrichment of the blast gas or increase in blast gas temperature produces more intensified burning of the coke and thereby shortens the combustion zones in front of the tuyeres, and that reducing the size of the combustion zones enlarges the mass of burden centrally positioned with respect to the hearth and decreases the area available for upward flow of combustion gases. It was then discovered that the addition of moisture to the blast gas made it possible to obtain a smooth operating furnace when enriching the blast gas with oxygen or when blowing the blast gas at an elevated temperature. The addition of moisture or its equivalent to blast gas makes it possible to enrich the blast gas with oxygen or to blow the blast gas at a higher temperature and thereby improve furnace production. While added moisture comprises a cheap source of oxygen which is introduced into the furnace without nitrogen and also provides a source of hydrogen gas which is more eflicient than carbon monoxide in reducing iron ore, higher rates of iron production would be obtained if it were possible to reduce the quantity of moisture required since disassociation of water is an endothermic reaction absorbing heat from the combustion zone and since the coke rate is proportional to the temperature.
It is well known that blast furnaces may be operated to produce, within limits, products of specified characteristics and it is desirable to obtain smooth operations in blast furnaces producing pig iron of different chemical compositions, temperatures, etc. Accordingly, the obtaining of a smooth operating furnace by means of moisture additions to the blast gas includes the feature of controlling the characteristics of the product by such moisture additions.
It is, therefore, a principal object of the present invention to provide a novel method of operating a blast furnace by which maximum iron production is obtained with a minimum coke rate.
Another object is to provide a novel method of operating a blast furnace by which combustion of coke is intensified without correspondingly increasing the volume of blast gas in such a manner as to require minimum moisture additions to the blast gas.
It has been established that predetermined quantities of moisture are required to be added to oxygen enrichedv blast gas or to blast gas at an elevated temperature in order to obtain smooth operating furnaces. The quantity of moisture required may be considered as depending for the most part upon the percentage of oxygen enrichment or upon the blast temperature although the moisture actually required may be influenced by the physical characteristics of the furnace or by the constituents of the burden. In particular, the in blast gas at about 1100 oxygen enrichment is shown in Table I.
TABLE I quantity of moisture required Moisture in blast (grains Oxygen enrichment (percent): per cubic foot) It has also been established that under average conditions about 2.5 to 3.5 grains of moisture percubic footof blast gas is required to maintain a smooth operating furnace when blown with blast gas at a temperature of about 1100 F. Without oxygen enrichment, and that about 1 grain of moisture per cubic foot of blast gas is required to be added to the blast gas upon each 30 F. increase of the blast gas temperature. From the foregoing, it 'is possible to ascertain the quantity of moisture that would be expected to be necessary in blast gas at varying temperatures and at various percentages of oxygen enrichment in order to obtain a smooth operating furnace. Tables II through XI disclose the range of moisture required throughout a blast temperature range F. for varying percentages of TABLE X.4.5% OXYGEN ENRICHMENT It was believed in the past that the quantity of moisture required in blast gas for maintaining a smoothly op- Bl tT t Mgisgure expecged Moisturgrequjred crating furnace is a function of the percentage of oxygen as empera ure erequire accor ing to R 1 (grains per cubic foot) present invention enr1chment and of the blast gas temperature and that (grams per oubictoot) 5 the total molsture required is, for all practical purposes, a summation of the moisture necessary for the oxygen g :8 3 E8 3 enrichment and the moisture necessary for the blast gas 21, 21,51 0 311 temperature. Tables 11 through XI, under the heading 3;; 3 3%: 3 31332221 Moisture expected to be required, disclose ranges of gig i 3 g 23-; mo1sture requ1red for d1iferent percentages of oxygen O 38,1 to 48,1 341 to 44,1 enrichment and blast gas temperatures according to this i 2 2g 2;; 25-2 g3? prior understanding of blast furnace operation. gagto 28g 44I0to 5410 It has been determined from observing actual furnace 1. to 1. 47.3t0 57.3 6M we to m 6 15 operations that unexpected advantages are reahzed by 57-910 to utlhzing blast gas heated to a temperature above a critlcal 61. 2 to 71. 2 57. 2 to 67. 2
range. In particular 1t has been dlscovered that blast furnaces blown with blast gas heated to temperatures below TABLE OXYGEN ENRICHMENT 1400 F. require a moisture content that falls within the M t d d expected ranges, while with blast gas heated to temperaois ure expeete Moisture require c 6 Blast Temperature F0 be requiged accorqing tq tures above about 1400 1 .4500 F. the quant1ty of o ains per cu l f P e gu g moisture required to mamtain a smooth operating furnace grams per cu 1c 00 is substantially less than the minimum moisture that would 17 toy/8 17 to 28 be expected to be requ1red according to the prior underto to standing of blast furnace operations. 1 1 In Table XII, Examples A, B, C, D, and Bare a tabulagg'fl i -g gg-gz 2g? t1on of data obtained when operating 1dent1cal furnaces O 0 36.8to 47.8 32.8t0 43.8 having a hearth d1ameter of 28 feet and a height of 108 40.1 to 51.1 36.1 to 47.1 v 43L 4 to 54. 4 4 to 50. 4 30 feet without o ygen enrichment. Examples F through 46. 7 t 57.7 42.7 t 53.7 N are a tabulation of data obtamed when operatmg ldenggjggg 21 2 2321325 3 tical furnaces having a hearth diameter of 25 feet, 6 5&6, 526106315 inches, a height of 100 feet and a working volume stock 59. 9 to 70. 9 55. 9 to 66. 9 h 63.2t0 74.2 59.2to 70.2 lme to center lme of tuyeres of 37,872 cubic feet wit oxygen enrichment. The data given are averages of values obtained during the period of operation indicated.
TABLE XII Example A Example B Example 0 Example D Example E Example F Example G Iron Prod. Net Tons Per Day 1, 499 1, 958 2, 236 1 963 2 301 1, 501 1, 613 Iron Piotr: Net Tons Per Day S.F 1, 499 1,870 2,122 11963 21181 1, 489 1, 606 goke Raige, 112211? Net Ton SJ 1, 602 1, 250 1, 270 1, 3 1, 270 1,163? 1,263: X en 11110 en Wi Blown, 0.1.111 78,460 92,149 97,169 105, 521 101, 080 75,100 74,900 ll d l 6 Ft 11 8 17 3 187; 14 172 ib i5 gg 1: ins e u. 015 m r 31. 6 58.9 61.4 59.9 52.2 16. g 24. g 6. 9 13. 38 2' 33. 2 39 4 1 0 11.
52 5 Blast Tem erature 1 277 1,602 1 641 1 654 1 673 1 260 1 285 Top Temp rature, 271 304 301 264 278 30 295 Stone Rate, Lbs. Per Net 553 442 337 599 539 715 667 Dust Rate, Lbs. Per Net Ton S F 214 146 261 128 182 190 193 Burden, Lbs. Per Charge--- 28, 626 76, 493 80,102 75, 033 78, 072 25, 703 27, 093 Charges Per Day 188 92 95 103 206. 5 211. 9 Delays, Minutes Per Day- 54 44 91 38 26.3 29. 5 Days Operated 31 31 29 30 31 31 31 Slag Volume, Lbs. Per Net To 848 846 (JO/CO Ratio- 1. 83 1. 76
Example H Example I Example I Example K Example L Example M Example N Iron Prod. Net Tons Per Day 1 596 1 582 1 820 1,601 1,685 1 720 1 822 Iron Prod Net Tons Per Day S.F 1: 596 1: 582 11 812 1, 597 1, 685 1: 720 1: 822 Coke Rate, Lbs. Per Net Ton S.F 1, 574 1, 642 1, 342 1, 652 1, 619 1, 591 1, 505 Oxygen Enrichment 3. 03 3. 54 1. 49 3.01 4.0 4.00 r) 4. 0 Wind Blown, 0.1m 72,800 73,000 75,200 73,000 72, 900 72,900 7-,900 Equivalent Wind, e.f.m ,300 85, 300 80, 500 83, 500 86,900 86,900 86,900 Moisture, Grains Per Cu. Ft 16, 82 21.37 11. 92 20.01 23.88 23.96 24.15 Sinter, percent 36.3 36. 6 66. 6 24. 6 37. 5 40. 4 50.0 Lima in Sinter, percent- 8-10 8 8 8 8 9 8 8 Oversize, percent 12.8 12. 8 19. 9 10.8 12. 7 1-. 7 12. 7 Fe in Burden, percent. 54. 58 54.60 56. 08 54.19 54. 65 54. 84 55. 34 Blast; Temperature, F 1, 305 1, 375 1, 425 1, 540 1, 565 1, 570 1, 580 Top Temperature, F 265 260 305 260 235 240 261 Stone Rate, Lbs. Per Net Ton S.F 672 742 387 778 766 733 643 Dust Rate, Lbs. Per Net Ton S.F 127 112 104 139 111 104 84 Burden, Lbs. Per Charge 27,899 27,423 44,612 27,250 27,166 27,381 28, 000 Charges Per Day 196. 5 202. 2 134. 7 203. 5 216. 8 216. 2 214. 3 Delays, Minutes P Day 27.7 27.8 17. 5 30.3 28. 7 28.4 27. 5 Days OperatetL. 31 30 30 31 23 31 8 Slag Volume, Lb 900 939 762 920 950 933 872 CO/COZ Ratio 1.80 1.83 1.76 1.72 1. 72 1. 71
3,2 1 a, i 5 s 3 8 TAB LE X111 Blast E nric'ued Actual Moisture Tcmpera- O xygeu, Moisture Expected Moisture ture, F. Percent (grains per grains pct Saving cubic loot) cubic foot) Example A..- 1, 277 11.8 11. 8 0 Example B 1, 602 0 17. 3 22. ii 5. 3 Example C 1, 641 0 1S. 23. 9 5. 3 Example D 1, 654 0 14. 0 24. 4 10. 0 Example E 1, G73 0 1T. 2 25. 0 7. 8 Example F 1, 200 1t 65 10. 7 .3 3i 3 0 Example G 1, 235 2. 98 15. SS 2 l3 0 Example H 1, 305 3. 03 10. 82 t. 1 6 0 Example I..- 1, 37:3 3. 51 21. 37 1-28.1 0
1, 425 1. 49 11. 92 1 1S.4 2. 8 1, 5-10 3. 01 20. ()1 5 33. 53 52 1, 555 4. 0 23. 7. 3 4. 4S 1, 570 i. 0 23. 00 i7. 53 4. 57 l. 580 4. 0 2 15 1 3T. 85 4. T1
Table XIII is a comparison of moisture content of the blast gas in Examples A through N with the moisture content that would be expected to be required according to Table I for oxygen enrichment and in accordance with general rule of adding 1 grain of moisture for each F. increase in blast gas temperature- From Table XIII, it is seen that with blast gas temperatures at and below 1375 F. the total moisture actually used in the blast gas in order to maintain a smoothly operating furnace falls roughly within the range of Moisture expected to be required, while with blast gas temperatures of about 1400 to 1500" F., and above, the moisture actually needed for maintaining a smoothly operating furnace is about four grains or more of moisture per cubic foot ofblast gas less than the minimum moisture content expected to be required. Thus, according to the principles of the present invention by blowing blast gas heated to a temperature above 1400 F. and/ or enriched with oxygen it is possible to reduce the quantity of moisture in the blast gas by at least four grains per cubic foot of blast gas as compared to the total moisture believed to be necessary. A reduction of four grains of moisture in the blast gas blown to the furnace makes it possible to increase the blast gas temperature by at least 120 F. Without additional moisture, as a result the coke consumed per ton of iron produced decreases by the order of to pounds with a corresponding increase in pig iron production. From a comparison of Examples I, J, and K, for the particular blast furnace producing these operational examples, it appears that the critical blast gas temperatures above which the unexpected saving in required moisture is obtained is probably around 1425 F. to 1450 F. However, since blast furnace performance depends upon physical characteristics of the blast furnace and upon variable factors including composition of the burden and physical characteristics of constituents of the burden it is believed the critical temperature for average blast furnace installations falls within the range of about 1400 F. to 1500 F., that is, with blast gas heated to a temperature above about 1400 F. to 1500 F. unexpected savings in required moisture can be realized.
While it is not known precisely why the blowing to a blast furnace of blast gas heated to temperature above about 1400 F. to 1500 F. makes it possible to reduce the moisture required in order to obtain a smoothly operating furnace, it is believed that blast gas temperatures above the critical temperature have some effect upon the combustion zones in front of the tuyeres to reduce the size of the core of substantially solid material in the region of the center of the hearth thus permitting combustion gases to flow more easily upwardly into the stack. it is also possible, but not known as a matter of fact, that the use of oxygen enrichment, which increases the oxygen contact per cubic foot of blast gas while actually decreasing the volume of the blast gas, may have some effect to compensate for the disadvantages resulting from expansion of blast gas with increasing temperature when theblast gas temperature is above the critical temperature of about 1400 F. to 1500" F. Although it cannot be said definitely why the combination of oxygen enrichment and elevated blast gas temperatures above about 1400 F. to 1500 F. results in a reduction in the moisture required in order to obtain a smoothly operating furnace, observations of furnaces in actual operation demonstrate that the unexpected results are obtained.
Tables 11 through XI include the range of moisture required according to the principles of the present invention for various ox gen enrichment percentages at blast gas temperatures. It will be noted that with blast gas temperatures below 1400 F., the moisture required according to the present invention is similar to the moisture expected to be required, while at blast gas temperatures above 1500 F. the range of moisture required according to the present invention is about four grains per cubic foot less than the moisture expected to be required for similar percentages of oxygen enrichment and blast gas temperatures. Although the examples in Table XII show moisture savings greater than four grains per cubic foot of blast gas can be obtained with some furnaces at high blast gas temperatures and although moisture savings should increase with increasing blast gas temperatures, for the sake of clarity, the ranges of required moisture according to the present invention as set forth in Tables 11 through XI are based on minimum savings of four grains of moisture per cubic foot of blast gas.
Blast furnaces in existence today are generally capable of operation with blast gas temperatures as high as about 2000 F. providing sufiicient stove capacity is available. For operation with blast gas temperatures above 2000 5., it will be necessary to utilize high temperature materials in the construction of certain components of the furnace. Although operation'with blast gas temperatures above 2000 F. is planned and high temperature materials necessary forsuch operation are either in existence or under development, the practical range of blast gas temperatures according to the present invention is from about 1400 F. to 1500 F. and up to about 2000 F. Inasmuch as the. quantity of moisture saved by practicing the present invention is believed to increase with increasing blast gas temperatures, and since more efiicient overall operation will be obtained when it is possible to operate blast furnaces with higher blast gas temperatures, the operation range of blast gas temperatures extends also from about 2000 P. to 2500 F.
10 Table XV is a composite of data on moisture required in accordance with the invention taken from earlier in view of the present lack of As will be described in more detail in It is seen from Table XIV that furnace efiiciency tion the practical range of oxygen enrichment is The teachings of the present invention are applicable,
without oxygen enrichment and without moisture addition.
creases as the percentage of oxygen enrichment increases. However, at the present time it is not economical to operate furnaces with oxygen enrichment of the order of 10%, for example,
facilities of oxygen producing equipment of the necessary capacity. Accordingly, for practicing the present inven from about 1% to while the preferred range is from about 5% to with or without oxygen enrichment, no matter how moisture or its control equivalent is added to the furnace. For example, it has been discovered that the high blast temperatures taught by the invention permit, in fact, actually are required for, auxiliary fuel additions to the blast furnace.
subsequent paragraphs, these auxiliary fuels have many of the same elfects thermodynamically as aqueous additions and for many purposes can be considered control equivalents. The teachings of the invention include methgrains Although this table TABLE XIV .5% TO 10% OXYGEN ENRICHMEN'I Table XIV discloses calculated av r S b .m mm Mm mm m m m m i m F 01 V1 3 t r moaebe t a f .lh C H O 0 1 r. 0 C F m e 0 m m% S S H mm a H 1 1 t g0 n 1 e 1 n 6 O 6 1 h f fl g t T O n O I 0 a m 6 S ek .1 f m t 0 5 r r 6 S V S 0 G H O a .11 a D.H 3 .ud r eue d e mm md fln H I q 6 m :1 e I e m a S 6 O m 25814703692 m m nm mawpm t d d .1.Ho a C 7 00000000000 nenv. O f lO N O ttttttttttt a H 310 S P f. g 0 m 0 1 25814703692 u a M m fm n l e I m .aaaaaaaaasa S e m H O 0.1 0 6 f T 5 .22333444555 Ii d 6 e t e t eh N o u t S a a X m t m m w e I w t S a E u mm xbww m dv V m m m 0 3 gm 0 O S H a N 25814703692 a I m m w th w t e w yd a m T swcamammeam nmmu mwasvmww s L 5 w 0 Nud 8 S g N mmtwmmm twmtwtw 011123334455667 r. w m t e m m m g a t E 5 25814703692 11111111111111.1111 fb r W u w u t a S 6 zaa maala .w 9 0 MM 0 m S g q S S E 2 333 4455 M R Vw w. .mmuwm mmhm R RD u U l d 8 b P .1 .1 a .1 H m I m H M a 0 25814703692 620 I v t h p v P n o o u m T uu a m a a asr ewaemwamama at n H W m a S ..lb G 445567789901123 H a t e e e mi m M dd N mmmmmmmmmmm .mmm LLLLLLLLLLZZZZZ m d mm W n m m e I 4 25814703692 WI s d 0 e a a c a m D zssiasasara n .Ed wk .m O t. H a 0 m u R 22233344455 MGM a mm a T m mm m m k m o O n b .1 e t. e h 0. u a O C T H t 0 T O 8 t. W U C C C HM 25814703692 8 11%850000099999 & & r t 5 0 5 2333444555 NB HHE UHHfl 1 .l. m mmmmmmmmmwm SIC E0 3 m 1 25814703692 M W t m m mm maaaaanaua .1 of r. .1 n 36925814703692 m n ww flmw ww qge 0 m tfifiaaaaaammm m ......8.1....7.0.3.... M e r mmwmmwmmmmmwwmw Et %%%wu Q%% I amw te mw 36925814703692 R mmmm wmwmmmw W W H C a v v a v c J 4 p ma m maamammmeawmmm m 2 E o I P 4 047047 037 W D E 1 222333444 L g 0 m B I) 005000000000000 I eet r m p umaawmawmaaaaa W 25814703692 m d m aaaaaafiaasa .w. .m w f. m 11222333L44 3 wmm sssajsiaa fita A 1 mmwmwwwwwmm Magma OOOMMM O MMMMMM M M E zamomlraoma/Toocli 111115555500000 01H ttttttttttttttt T 11122233344. M 11111 W 225814703692 I m m 70360. so izzzswamaama m mm mff P 4703692500147 wfi m M mmwmaaaame w 0 000000000000 E C 0 tttttttttttt u 470369258147 "h u m m nmwaaaaaaau m m m m m m t m n w m m m m m m B r. E HF L PF 0 n n n r n h m 6o B m o T m 1 T t T t T ta u t n n w m w u n 1 00000 0 l 0 l B B B WW m. 1 1 1112 2 Although Tables II through XI show the expected moisture required and the moisture required according to the present invention for percentages of oxygen enrichment from 1 to 5, which range of oxygen enrichment percentages may be economically obtained with presently available equipment, it is known that greater increases in iron production may be obtained by increasing the percentage of oxygen enrichment up to about 10%, for example, and it is expected that blast furnaces will be operated in the future with such high percentages of oxygen enrichment.
ranges of moisture that would be expected to be required and that would be required according to the principles of the present invention for blast gas having an oxygen enrichment between 5% and 10% at temperatures from 1100 F. to 2500 F.
shows that operation in accordance with the principles of the present invention, that is, at blast gas temperatures about 1400 F. to 1500 F., makes it possible to obtain a reduction in required moisture of four per cubic foot of blast gas, it is to be expected, as mentioned above, that the actual moisture saving will be greater especially at higherblast gastemperatures.
l l ods for taking full advantage of such auxiliary fuel additions so that, in combination with reduced moisture additions, a smooth operating furnace is obtained, the coke-rate reduced, and the production rate increased at substantial economic savings over conventional practice.
By auxiliary fuel additions is meant fuel introduced through the tuyeres or other than through the top of the furnace. As pointed out earlier, conventionally, limestone, ferrous bearing material, and carbonaceous material such as coke are charged into the top of the furnace. The charge moves down the shaft of the fur nace and the coke, constituting the fuel of the mixture, is burned by the incoming blast to melt the iron producing molten pig iron. Auxiliary fuels, on the other hand, are not introduced at the top of the furnace but near the bottom of the furnace, preferably, in accordance with the invention, through the main tuyeres of the furnace and may include fuels such as natural gas, coke oven gas, fuel oil, powdered carbonaceous materials such as coal, chat or coke, or the products of combustion of these fuels.
The problems, economic and otherwise, of acquiring and using quality coke in blast furnace operations are Well known in the art. The economic supplanting of quality blast furnace coke with auxiliary fuels is a desirable object. By supplying such auxiliary fules through the sides of the furnace, for example with the blast, the heat supplied through the blast is increased and it would ordinarily be expected that moisture additions should be increased proportionally. However the complex reactions taking place within the furnace present problems of furnace control, solution loss, and economic use of auxiliary fuels which, it has been discovered dictate processes other than expected. In actualit a furnace being operated at high blast temperatures and reduced moisture additions in accordance with the invention, must have the mositure additions further reduced in order to economically use auxiliary fuel additions. That is, when a blast furnace is operated with blast gas temperature above about 1400-1500" F. and with auxiliary fuel additions, optimum results can only be obtained with aqueous additions less than the reduced additions set forth in Tables 11 to XI.
In explaining the invention, natural gas will be used as an example of the auxiliary fuel although the invention is not to be limited thereby. When adding natural gas to a blast furnace the following reactions are believed to have significance:
(1) CO -l-CQZCO C. 2C+O +2CO Consider the situation Where natural gas is added prior to the tuyeres, for example burned in the wind prior to the blast furnace stoves. In such case the formula B above is applicable because the natural gas is burned with a surplus of oxygen and it adds heat to the blast plus the products of combustion CO and H moisture or its control equivalent is being added to the furnace when fuel is added in this fashion. CO has the same thermodynamic effect as H O as it requires heat to dissociate (see Formula 13(1) As pointed out earlier it has been discovered that when making auxiliary fuel additions it is necessary to operate the furnace at higher blast temperatures in order to economically take advantage of the auxiliary fuel. When operating at higher blast temperatures the moisture additions are expected to increase and normally would be increased to obtain a smooth operating furnace. Since fuel additions add moisture, or its control equivalent, a surplus of moisture results and the furnace runs cold. However, it has been discovered that a blast furnace operated on moisture additions can be operated with a precise and predeterminable reduction in moisture additions to counteract the moisture and carbon dioxide produced by burning injectedfuel. By reducing the amount of moisture additions in an amount equivalent to the endothermic requirements of the products of combustion of injected fuel, it is possible to obtain the full economic benefits of the auxiliary fuel in improved blast furnace operations including reduction of the coke rate in accordance with the exothermic equivalents of the auxiliary fuel and the reducing agents added thereby.
The burning of auxiliary fuel in the blast presents certain problems, however. For one thing, the refractories in the blast furnace stoves and the mains would have to be replaced in order to withstand the high temperatures of the burning auxiliary fuel. With the extremely high temperatures of the blast encountered heat losses are in reased before the blast reaches the furnace and yet the products of combustion of the auxiliary fuel would require additional heat once inside the furnace to be dissociated and made available as reducing agents. Therefore, practically speaking, it has been discovered that it is more economically feasible to add the natural gas, or other auxiliary fuel, at the tuyeres.
When adding the natural gas at the tuyeres the reaction set forth in A above can take place within the furnace. That is the auxiliary fuel burns in a shortage of oxygen and CO and H reducing agents, are formed directly. The question presented is what effect does this reaction have on the endothermic requirements of auxiliary fuel additions. heat losses, the endothermic requirements of auxiliary fuel additions are approximately the same whether added at the tuyeres or burned prior to introduction to the furnace. It is believed that the reason for this could be, quite simply, that the same reaction (B above) takes place regardless of where the auxiliary fuel is added.
' Another explanation behind the endothermic equivalency could be that when reaction A takes place with constant wind the addition of natural gas at the tuyeres reduces the 0 available for the C reaction. A reduction in the C reaction reduces the heat available in the furnace, as this reaction is more exothermic than the A reaction since the coke is already heated and inherently produces more heat in combustion. The natural gas, being gaseous, is more readily combustible and to some extent takes the place of coke combustion. Therefore even in the absence of the formation of H 0 and CO the introduction of natural gas into the tuyeres produces the same overall effect as adding moisture in spite of the fact that neither H O nor CO may be formed. Therefore whether the auxiliary fuel is burned before entering the furnace or added at the tuyeres a reduction in moisture additions is required in proportion to the products of combustion of auxiliary fuel when a like amount of auxiliary fuel is burned in a surplusage of oxygen. However, the teachings of the invention emphasize the advantages of introducing the auxiliary fuel at the tuyeres, such as the avoidance of plant heat losses.
Examples of blast furnace operations, using moisture additions for furnace control, with and without auxiliary fuel additions, are included in Table XVII to follow. The experimental data included therein are averages of values obtained during the operation periods indicated. The experimental blast furnace employed has a hearth diameter of four feet, a height of approximately 26 feet, and a working volume of approximately 305 cubic feet. Owing to the greater heat losses per unit of production in an experimental furnace of this size, as compared to a commercial furnace, higher blast temperatures are employed and must be converted for commercial furnace application based on established conversion tables recognized in the art as follows:
Experimental Furnace: Commercial Furnace, F.
1,600 P. 1,250 1,80() F. 1,425 2,100 P. 1,700 2,475 F. 2,000
It has been discovered that, disregarding plant.
TABLE XVII Example Example Example Example 1 2 3 4 FURNACE PERFORMANCE Iron ProcL, Net Tons Per Day 18. 74 18.91 20.82 18. 31 Coke Rate, Lbs. Per Net 'Ion 1, 322 1, 006 1, 104 1, 105 Slag Volume, Lbs. Per Net Ton 085 993 957 1, 005
OPERATING CONDITIONS Oxygen Enrichment Wind Rate, c.f.rn 800 800 800 800 Moisture, Grains Per Cu. Ft. 27 6. 8 5.6 4 Gas Iniec. Bate, c.f.1n 4O 40 Blast Temp, F 2, 475 2, 475 2, 475 2, 475 Top Temp, F 328 458 340 452 nor METAL DATA Silicon, Percent 0.88 0.77 0.88 0.74 Sulfur, Percent. 0. 039 0. 045 0. 031 0. 038 Temperature, F 2, 515 2, 490 2, 525 2, 499 Number of Oasts 24 12 28 16 Hours of Operation 72 122 27 i It can be seen from the above data that the use of auxiliary fuel and high blast temperatures brings about an increased metal production rate and a decreased coke rate. Additional coke savings are realized from the carbon of the auxiliary fuel which replaces carbon from the burden coke.
An important discovery of the invention is that fuel additions cannot be economically used without increasing the blast temperature. The production rate of a furnace will increase directly with auxiliary fuel additions if the cooling effect of the auxiliary fuel and aqueous additions are compensated for by increased blast temperatures and decreased aqueous additions. In practice, the necessary increase in temperature has amounted to about 120 F. for each percent of auxiliary fuel (natural gas) added. The necessary increase in blast temperature with auxiliary fuels would not be as high as 120 F. with each percent of auxiliary fuel addition if a more exothermic fuel than natural gas, such as powdered coal, were used. Within the practical limits of blast temperatures imposed at most blast furnace sites today the maximum percentage of natural gas which could be effectively used would be around 5 to 6% by volume of the blast. With more exothermic auxiliary fuels the percentage may be increased to 8% or beyond.
' As pointed out earlier about one grain of moisture per cubic foot of blast gas is added with each 30 increase in blast gas temperature. For each percent by volume natural gas added blast gas temperature should be increased approximately 120. From this data it can be seen that, as far as blast furnace control is concerned, one percent of natural gas is approximately equivalent, considering smooth operations, to four grains of moisture. In other words, when making auxiliary fuel additions of natural gas, for each percent of natural gas added to the blast, the aqueous additions should be reduced approximately four grains.
The reduction in aqueous additions is not without limitation, however. A significant discovery, forming part of the invention, is that aqueous additions should not be eliminated entirely. In practice, the furnace cannot be readily controlled by adjusting the rate of auxiliary fuel injections, but excellent control can be obtained by maintaining some aqueous additions to the furnace.
The reasons why the auxiliary fuel is not effective in instantaneous control, even though it serves as an equivalent in many other respects to aqueous addition, are multiple and speculative. Mostly, the explanations hinge on the change in the amount of carbon available in the furnaces with changes in the auxiliary fuel injection rate. Consider a furnace which is hanging and the area beneath abridge or scaffolding causing the furnace to hang is becoming increasingly hot. Ideally, aqueous additions or the moisture additions effect of adding auxiliary fuel would serve to cool this area and lengthen the combustion zone in the furnace and thereby reestablish smooth descent of the burden. In general, cooling of the hot zone takes place with either additive. However, due to the presence of carbon in the auxiliary fuel and the tendency of this carbon to combine with 0 more readily than the carbon in the coke, there is less coke burned. Descent of the burden will be sluggish because of the lowered demand for burden carbon. On the other hand, aqueous additions effect the necessary cooling and charge only 0 or H into the furnace so that the burden starts to move more readily. Also, maintaining limited aqueous additions to the furnace permits temperature control of the furnace affecting silicon and sulphur content of the melt without adding carbon to the furnace.
In actual practice, the amount of aqueous additions maintained should be sufficient to exercise furnace control. If dehumidifying equipment is not used, aqueous additions of about 7 grains are suflicient to allow for normal variations in the ambient atmospheric humidity and leave a margin for varying the aqueous addition to effect instantaneous control. If dehumidifying equipment is used on the blast, the aqueous additions to the furnace helpful in instantaneous control can be maintained by regulating the humidity of the air used in the blast.
In summary, when using auxiliary fuel, to obtain an increased production from a blast furnace, the blast gas temperature should be increased and the aqueous additions reduced in accordance with the endothermic requirements of the auxiliary fuel. The coke rate should be reduced in accordance with the carbon and reducing agents added by the auxiliary fuel. If oxygen enrichment is used the production rate will be increased since the consumption of the oxygen of the blast by the auxiliary fuel will be reduced and will be available for burning additional coke in the burden and increasing the driving rate.
It is to be expressly understood that various changes and substitutions may be made in the specific embodiments described herein without departing from the spirit of the invention as well understood by those skilled in the art. Therefore, reference will be had to the appended claims for a definition of the limits of the invention.
I claim:
1. Method of operating a blast furnace in which iron bearing material is smelted and in which coke is burned, comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 1400 F. to 1500 F., and blowing blast gas into the furnace, the oxygen enrichment being in the range of 1%-l0%, and the quantity of aqueous fluid in the blast gas being from about 12.2 to about 82.2 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 12.2 to about 82.2
'1 55 grains of moisture per cubic foot of blast gas as the oxygen enrichment increases from about 1% to about 10%.
2. Method of operating a blast furnace in which iron bearing material is smelted and in which coke is burned, comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temr perature above about 1400 F. to 1500 F., and blowing blast gas into the furnace, the oxygen enrichment being in the range of 1%-5% and the quantity of aqueous fluid in the blast gas being from about 12.2 to about 70.2 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 12.2 to about 70.2 grains of moisture per cubic foot of blast gas as the oxygen enrichment increases from about 1% to about 5% l 3. Method of operating a blast furnace in which iron bearing material is smelted and in which coke is burned, comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 1400 F. to about 1500 F., and blowing blast gas into the furnace, the oxygen enrichment being within the range of 5 and the quantity of aqueous fluid in the blast gas being from about 26.2 to about 82.2 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 26.2 to about 82.2 grains of moisture per cubic foot of blast gas as the oxygen enrichment increases from about 5% to about 10%.
4. Method of operating a blast furnace in which iron bearing material is smelted and in which coke is burned, comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 1400 F, to 1500 F. and up to 2000 F., and blowing blast gas into the furnace, the oxygen enrichment being in the range of 1% to 10% and the quantity of aqueous fluid in the blast gas being from about 12.2 to about 65.7 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 12.2 to about 65.7 grains of moisture per cubir foot of blast gas as the oxygen enrichment increases from about 1% to about 10%.
5. Method of operating a blast furnace in which iron bearing material is smelted and in which cokeis burned, comprising the steps'of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 1400 F. to 1500 F. and up to about 2000 F., and blowing blast gas into the furnace, the oxygen enrichment in the blast gas being in the range of 1%5%, and the quantity of aqueous fluid in the blast gas being from about 12.2 to about 53.7 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 12.2 to about 53.7 grains of moisture per cubic foot of blast gas as the oxygen enrichment increases from about 1% to about 5%.
6. Method of'operating a blast furnace in which iron bearing material is smelted and in which coke is burned, comprising the steps of forming blast gas including atmospheric air, enriching the blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 1400 F. to 1500 F. and up to about 2000 F., and blowing the blast gas into the furnace, the oxygen enrichment being within the range of about 5%l0%, and the quantity of aqueous fluid in the blast gas being from about 26.2 to 65.7 grains of moisture per cubic foot of blast gas, the aqueous fluid bearing material is smelted and in which coke is burned, comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 2000 F. and up to about 2500 F, and blowing blast gas into the furnace, the oxygen enrichment in the blast gas being in the range of l%l0%, and the quantity of aqueous fluid in the blast gas being from about 28.7 to about 82.2 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 28.7 to about 82.2 grains of moisture per cubic foot of blast gas as the oxygen enrichment increases from about 1% to about 10%.
8. Method of operating a blast furnace in which iron.
bearing material is smelted and in which coke is burned, comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 2000 F. and up to about 2500 F., and blowing blast gas into the furnace, the oxygen enrichment in the blast gas being in the range of 1%5%, and the quantity of aqueous fluid in the blast gas being from about 28.7 to about 70.2 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 28.7 to about 70.2 grains of moisture per cubic foot of blast gas as the oxygen enrich ment increases from about 1% to about 5%.
9. Method of operating a blast furnace in which iron bearing material is smelted and in which coke is burned, comprising the steps of forming blast gas including atmospheric air, enriching blast gas with oxygen, adding aqueous fluid to the blast gas, heating the blast gas to a temperature above about 2000 F. and up to about 2500 F., and blowing blast gas into the'furnace, the oxygen enrichment being within the range of 5%l0%, and the quantity of aqueous fluid in the blast gas being from about 42.7 to about 82.2 grains of moisture per cubic foot of blast gas, the aqueous fluid in the blast gas increasing from about 42.7 to about 82.2 grains of moisture per cubic foot of blast gas as the oxygen enrichment increases from about 5% to about 10%.
10. Method of operating a blast furnace in which iron bearing and carbonaceous material are charged into the top of the furnace and a blast gas is introduced into the bottom of the furnace comprising the steps of preheating the blast gas to a temperature above about 1400 F., and adding aqueous fluid to the blast gas in accordance with the temperature of the blast gas, the quantity of aqueous fluid added being about nine grains of aqueous fluid per cubic foot of blast furnace gas at a temperature of about 1400 F. with about three grains of moisture per cubic foot of blast gas required'to be added with each F. increase in blast gas temperature above 11. Method of operating a blast furnace in'which iron hearing and carbonaceous materials are charged into the top of the furnace and a blast gas is introduced into the bottom of the furnace comprising the steps of preheating the blast gas to temperatures above 1400 5., adding aqueous fluid to the blast gas with about 9 grains of aqueous fluid per cubic foot of blast gas being added at 1400 F., adding auxiliary fuel to the blast gas in the range of about 1% to about 8% by volume of the blast gas, and controlling the blast gas temperature in accordance with the formula, blast gas temperature: 1400+(M)33 F.+(F) F, wherein M is equal to the grains of aqueous fluid above 9 grains per cubic foot of blast gas added and F is equal to the percentage of the blast gas by volume auxiliary fuel added to the blast gas.
12. In a process of heating and humidifying the'blast for a metallurgical blast furnace, which comprises: blowing cold blast air for the blast of the furnace through a preheating medium therefor and thereby preheating the blast for the furnace, thereafter augmenting the heat of the blast from said medium by burning combustible fuel with part of the total air of the blast directly in the preheated blast, and thereafter delivering the heat augmented hot blast into the hearth in the blast furnace While charged with Water vapor to a predetermined constancy of humidity, the improvement comprising the steps of; effecting said augmenting of the heat of the blast by burning a hydrogen containing fuel as the combustible fuel directly in the blast and thereby charging the blast with a substantial part of the water vapor for said predetermined constancy of humidity as a product of said combustion, and adding the remainder of the total amount of vapor to form said predetermined constancy of humidity in the form of aqueous fluid to the blast before the heat of the blast is augmented.
13. A process as claimed in claim 12, and in which the preheating by the aforesaid preheating medium is effected by regenerative heating of the blast by heat previously stored in heat storing material.
14. A method as claimed in claim 12, and in which the amounts of the hydrogen containing gas that is burned as aforesaid, and of the part of the total air of the blast that is burned with the gas, is controlled by, and in accordance with variations in the total amount of cold blast air blown in the first aforesaid blowing step for the blast.
15. Method of operating a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and blast gas is introduced at the bottom of the furnace, comprising the steps of preheating the blast gas to a predetermined temperature, adding auxiliary fuel to the blast gas, and adding aqueous fluid to the blast gas in accordance with the temperature of the blast gas and the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid being substantially equal to the aqueous fluid required at the predetermined temperature without auxiliary fuel being introduced into the furnace and a quantity of aqueous fluid equivalent to the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid required to be added to the blast gas at the predetermined temperature being from about 9 grains per cubic foot of blast gas at a temperature of about 1400 F. with about 3 grains of aqueous fluid per cubic foot of blast gas required to be added for each 100 F. increase in blast gas temperature above 1400 F.
16. The method of operating a blast furnace as defined in claim 15 including the step of controlling the quantity of carbonaceous material charged into the top of the blast furnace based on the exothermic equivalent of the auxiliary fuel added to the blast gas.
17. The method of operating a blast furnace as defined in claim 15 in which the auxiliary fuel comprises natural gas added in the range of about 1 percent to about 8 percent by volume of the blast gas.
18. Method of operating a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and blast gas is introduced through blast furnace tuyeres at the bottom of the furnace comprising the steps of preheating the blast gas to a predetermined temperature, adding aqueous fluid to the blast gas, adding auxiliary fuel at the blast furnace tuyeres, and controlling the aqueous fluid additions to the blast gas in accordance with the temperature of the blast gas and the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid additions being substantially equal to the aqueous fluid required at the predetermined blast gas temperature offset by equivalent aqueous fluid substantially equal to the endothermic requirements of the added auxiliary fuel, the quantity of aqueous fluid required at the predetermined blast gas temperature being approximately 9 grains per cubic foot of blast gas at a temperature of about 1400 F. with 3 grains of aqueous additions per cubic foot of blast gas being added for each 100 F. increase in blast gas temperature above 1400 F.
19. Method of operating a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and blast gas is introduced into the bottom of the furnace comprising the steps of preheating the blast gas to a predetermined temperature, adding auxiliary fuel to the blast gas, and adding aqueous fluid to the blast gas in accordance with the temperature of the blast gas and the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid added to the blast gas being substantially equal to the difference between the quantity of aqueous fluid required to be added to blast gas at the predetermined temperature without auxiliary fuel being introduced into the furnace and a quantity of aqueous fluid equivalent to the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid required to be added to the blast gas without auxiliary fuel introduced into the furnace varying between about 9 grains of aqueous fluid per cubic foot of blast gas at 1400 F. and about 45 grains of aqueous fluid per cubic foot of blast gas at 2500 F.
20. Method of operating a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and blast gas is introduced into the bottom of the furnace comprising the steps of preheating the blast gas to a predetermined temperature, enriching the blast gas with a predetermined percentage of oxygen, in the range of about 1% to about 10% of the blast gas, adding auxiliary fuel to the blast gas, and adding aqueous fluid to the blast gas in accordance with the temperature of the blast gas, the percent of oxygen enrichment and the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid added to the blast gas being substantially equal to the difference between the quantity of aqueous fluid required to be added to blast gas at the predetermined temperature and the predetermined percentage of oxygen enrichment without auxiliary fuel introduced into the furnace and the quantity of aqueous fluid equivalent to the endothermic requirements of the auxiliary fuel, the quantity of aqueous fluid required to be added to the blast gas without auxiliary fuel introduced into the furnace varying between about 12 grains of aqueous fluid per cubic foot of blast gas at 1500 F. and 1% oxygen enrichment and about 82 grains of aqueout fluid per cubic foot of blast gas at 2500 F. and about 10% oxygen enrichment.
21. Method of operating a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and blast gas is introduced into the bottom of the furnace comprising the steps of preheating the blast gas to a predetermined temperature, adding natural gas to the blast gas in the range of about 1 percent to about 6 percent by volume of the blast gas, and adding aqueous fluid to the blast gas in accordance with the temperature of the blast gas and the endothermic requirements of the auxiliary fuel, the quantity of the aqueous fluid additions being equal to the aqueous fluid additions required at the predetermined blast gas temperature offset by equivalent aqueous fluid substantially equal to the endothermic requirements of the added natural gas, the quantity of aqueous fluid additions required by the blast gas temperature being equal to approximately 9 grains per cubic foot of blast gas at a temperature of about 1400 F. with about 3 grains of aqueous additions per cubic foot of blast gas being added for each F. increase in blast temperature above 1400 F. and the equivalent aqueous fluid for the natural gas added being approximately 4 grains of aqueous fluid for each percent by volume of natural gas added to the blast gas.
22. In the operation of a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and blast gas is introduced at the bottom of the furnace, a method for increasing the production rate of the furnace comprising the steps of adding natural gas to the blast gas in the range of about 1 percent to about 8 percent by volume of the blast gas, and controlling the blast gas temperature in accordance 19 with the endothermic requirements of the added natural gas, the endothermic requirements being an increase in blast gas temperature of about 120 F. for each percent by volume of natural gas added to the blast gas.
23. Method of operating a blast furnace in which iron bearing material and carbonaceous material are charged into the top of the furnace and a blast gas is introduced at the bottom of the furnace, comprising the steps of preheating the blast gas to a predetermined temperature, introducing material into the bottom of the'furnace as auxiliary fuel, and adding aqueous fluid to the blast gas in accordance with the temperature of the blast gas and the endothermic requirements of the introduced material, the quantity of aqueous fluid added to the blast gas being substantially equal to the difference between the quantity of aqueous fluid required to be added to the blast gas at the predetermined temperature Without auxiliary fuel being introduced into the furnace and a quantity of aqueous fluid equivalent to the endothermic requirements of the introduced material, the predetermined temperature of the blast gas being from about 1400 F. and up to about 2500" F. and the quantity of aqueous fluid required to be added to the blast gas at the predetermined temperature being from about 9 grains of moisture up to about 45 grains of moisture per cubic foot of blast gas, and the quantity of aqueous fiuid equivalent to the endothermic requirements of the introduced material being approximately 4 grains of aqueous fluid per cubic foot of blast gas per endothermic requirement N, the endothermic requirement N being equal to the endothermic requirement of a quantity of natural gas equal to 1% of the blast gas.
References Eited by the Examiner UNITED STATES PATENTS 1,510,271 9/1924 Gottschalk 75--41 2,219,046 10/ 1940 Koller et al. 7542 2,715,575 8/1955 Coutant 75-41 2,719,083 9/1955 Pomykala 75-42 2,729,555 1/1956 Shipley 75-41 2,735,758 2/1956 Strassburger 7541 2,778,018 1/1957 Strassburger 75-41 X OTHER REFERENCES Blast Furnace Proceedings, 1958, vol. 17, pages 4-39.
Iron Age, vol. 184, July 16, 1959, "rages 104 and 105 relied on.
Journal of Metals, January 1961, pages 25-30 (also Blast Furnace Proceeding, vol. 19, 1960, pages 238-278).
Metal Progress, August 1949 (pp. 234 and 236 relied on). a
Steel, vol. 139, No. 22, Nov. 26, 1956, pages 98, 101, 104, 107, and 110 relied on.
Sweetser, Blast Furnace Practice, 1st Edition, 1938,
McGraw-Hill Book Co., Inc, New York (page 253 relied,
DAVID L. RECK, Primary Examiner.
RAY K. WlNDHAM, ROGER L. CAMPBELL,
Examiners.

Claims (1)

1. METHOD OF OPERATING A BLAST FURNACE IN WHICH IRON BEARING MATERIAL IS SMELTED AND IN WHICH COKE IS BURNED, COMPRISING THE STEPS OF FORMING BLAST GAS INCLUDING ATMOSPHERIC AIR, ENRICHING BLAST GAS WITH OXYGEN, ADDING AQUEOUS FLUID T THE BLAST GAS, HEATING THE BLAST GAS TO A TEMPERATURE ABOVE ABOUT 1400*F. TO 1500*F., AND BLOWING BLAST GAS INTO THE FURNACE, THE OXYGEN ENRICHMENT BEING IN THE RANGE OF 1%-10%, AND THE QUANTITY OF AQUEOUS FLUID IN THE BLAST GAS BEING FROM ABOUT 12.2 TO ABOUT 82.2 GRAINS OF MOISTURE PER CUBIC FOOT OF BLAST GAS, THE AQUEOUS FLUID IN THE BLAST GAS INCREASING FROM ABUT 12.2 TO ABOUT 82.2 GRAINS OF MOISTURE PER CUBIC FOOT OF BLAST GAS AS THE OXYGEN ENRICHMENT INCREASES FROM ABOUT 1% TO ABOUT 10%.
US77507A 1960-12-22 1960-12-22 Method of operating metallurgical furnaces Expired - Lifetime US3218155A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US77507A US3218155A (en) 1960-12-22 1960-12-22 Method of operating metallurgical furnaces

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US77507A US3218155A (en) 1960-12-22 1960-12-22 Method of operating metallurgical furnaces

Publications (1)

Publication Number Publication Date
US3218155A true US3218155A (en) 1965-11-16

Family

ID=22138483

Family Applications (1)

Application Number Title Priority Date Filing Date
US77507A Expired - Lifetime US3218155A (en) 1960-12-22 1960-12-22 Method of operating metallurgical furnaces

Country Status (1)

Country Link
US (1) US3218155A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4248624A (en) * 1979-04-26 1981-02-03 Hylsa, S.A. Use of prereduced ore in a blast furnace
US6264723B1 (en) * 1998-06-10 2001-07-24 Sms Schloemann-Siemag Aktiengesellschaft Method for manufacturing steel

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1510271A (en) * 1921-08-03 1924-09-30 Firm Vulkan Werk Reinshagen & Blast of cupola furnaces and blast furnaces
US2219046A (en) * 1934-05-12 1940-10-22 Koller Karl Treatment of iron ores
US2715575A (en) * 1953-05-07 1955-08-16 Barium Steel Corp Method of treating iron ore blast furnaces
US2719083A (en) * 1954-08-02 1955-09-27 Edmund S Pomykala Smelting method
US2729555A (en) * 1952-06-05 1956-01-03 Earl H Shipley Method of operating blast furnaces
US2735758A (en) * 1956-02-21 strassburger
US2778018A (en) * 1952-10-03 1957-01-15 Nat Steel Corp Method of and apparatus for operating metallurgical furnaces

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2735758A (en) * 1956-02-21 strassburger
US1510271A (en) * 1921-08-03 1924-09-30 Firm Vulkan Werk Reinshagen & Blast of cupola furnaces and blast furnaces
US2219046A (en) * 1934-05-12 1940-10-22 Koller Karl Treatment of iron ores
US2729555A (en) * 1952-06-05 1956-01-03 Earl H Shipley Method of operating blast furnaces
US2778018A (en) * 1952-10-03 1957-01-15 Nat Steel Corp Method of and apparatus for operating metallurgical furnaces
US2715575A (en) * 1953-05-07 1955-08-16 Barium Steel Corp Method of treating iron ore blast furnaces
US2719083A (en) * 1954-08-02 1955-09-27 Edmund S Pomykala Smelting method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4248624A (en) * 1979-04-26 1981-02-03 Hylsa, S.A. Use of prereduced ore in a blast furnace
US6264723B1 (en) * 1998-06-10 2001-07-24 Sms Schloemann-Siemag Aktiengesellschaft Method for manufacturing steel

Similar Documents

Publication Publication Date Title
US4917727A (en) Method of operating a blast furnace
US4861369A (en) Process for gaining electric energy in addition to producing molten pig iron and an arrangement for carrying out the process
US4844737A (en) Method for operating a blast furnance by blowing pulverized coal
US5234490A (en) Operating a blast furnace using dried top gas
US2952533A (en) Method of operating a furnace in which the material treated is reduced
US5149363A (en) Process for smelting or melting ferrous or non-ferrous metal from self-reducing agglomerates or metal
US4248624A (en) Use of prereduced ore in a blast furnace
US5632953A (en) Process and device for melting iron metallurgical materials in a coke-fired cupola
US3218155A (en) Method of operating metallurgical furnaces
US2795497A (en) Method and apparatus for producing molten iron
US2650161A (en) Production of iron in a blast furnace
US2727816A (en) Method for reduction-smelting of ferrous materials in a modified blast furnace with a specific combination of gaseous injection at two levels
JPS62120413A (en) Operating method for blast furnace
US2219046A (en) Treatment of iron ores
US2715575A (en) Method of treating iron ore blast furnaces
EP0047314A1 (en) Carbonaceous fines in an oxygen-blown blast furnace
US3591364A (en) Reducing gas generation
US3231367A (en) Iron producing blast furnace operations
EP0027320B1 (en) Method for lower-rate operation of blast furnace
US2745732A (en) Method of reducing ores by a particular fuel combustion mixture
US2824793A (en) Process for producing steel by high temperature gaseous reduction of iron oxide
US3062640A (en) Method of operating a blast furnace
JP2001234213A (en) Blast furnace operation method
US1921212A (en) Operation of furnaces
US1360711A (en) Process for the manufacture of iron and steel directly from the ore and improved apparatus therefor