US3321302A - Method of utilizing the heat content of a combustible gas during refining pig iron - Google Patents

Method of utilizing the heat content of a combustible gas during refining pig iron Download PDF

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US3321302A
US3321302A US419449A US41944964A US3321302A US 3321302 A US3321302 A US 3321302A US 419449 A US419449 A US 419449A US 41944964 A US41944964 A US 41944964A US 3321302 A US3321302 A US 3321302A
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minute
oxygen
heat
during
waste gases
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US419449A
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English (en)
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Rieder Karl
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Voestalpine AG
Voest AG
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Voestalpine AG
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C21C5/38—Removal of waste gases or dust
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
    • F22B1/18—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines
    • F22B1/183—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines in combination with metallurgical converter installations

Definitions

  • This invention relates to a method of utilizing the heat content of a combustible gas during refining pig iron with pure oxygen, the oxygen being blown onto the pig iron bath from above.
  • the disadvantage of the first method is seen in the fact that the escaping waste gases having a temperature of 1600 to 1800 C. are increased in temperature due to the combustion heat, for which reason the installations in the lower part of the chimney have to be made of a highly refractory and wear-resistant material.
  • the amount of heat accumulating in the waste heat boiler and, accordingly, the steam output are increased and decreased by bounds in the same rate as carbon oxide is produced, and it is a known fact that, e.g., between the 6th and 12th minutes the amount of heat obtained is doubled and from the 13th to the 18th minute is reduced by half.
  • the advantage of the first method is obvious, namely, a high operational safety, explosions being eliminated.
  • the disadvantage of the second method may be seen in that the sensitive (physical) heat of the hot waste gases is not or may not sufiiciently be utilized, that complicated control means are necessary to exclude the air, that also in periods in which there is no trapping, a certain minimum amount of an inert gas has to be circulated through the exhausting system in order to keep the control means in operation.
  • the oxygen content of the gas to be added to the waste gases is controlled in dependence on the progress of the refining reaction: From the 2nd to the 11th minute the oxygen content may be gradually decreased from 100% to 7%, and from the 16th to the 20th minute it may be increased again from 7% to 100%.
  • the exact content and time is, of course, dependent on the size or capacity of the crucible or converter. The mentioned data apply exactly to a 50 ton crucible. With a reduction or extension of the blowing periods they are varied accordingly.
  • the amount of gas added may be varied in the first phase of the refining process, for instance from the 2nd to the 10th minute, the amount may be increased, and in the subsequent phase, i.e. from the 10th to the 20th minute, it may be continuously decreased again.
  • the formation of the gas having a varying content of oxygen is preferably effected by pre-mixing oxygen and nitrogen.
  • an amount of nitrogen which is increased minute by minute until the middle of the refining process (12th minute), e.g. from to 100 standard cubic metres per minute, may be added to an amount of oxygen which is kept approximately constant at, e.g., 8 to 10 standard cubic metres per minute, and from this maximum a decreasing amount of nitrogen, decreasing from 100 standard cubic metres to 0 standard cubic metres per minute, may be added.
  • the method according to the invention has the advantage that the sensible heat of the converter waste gases produced is fully utilized in the waste heat boiler and that, moreover, an adjustable amount of heat of combustion is utilized, sudden loads on the waste heat boiler and excessive heating being avoided.
  • the calorific value of the gas collected may be adjusted, e.g., to a value of 1100 kcal./standard cubic metre, 1700 kcal./standard cubic metre or 2000 kcaL/ standard cubic metre.
  • the risk of explosion is substantially avoided by the method of the invention, because at any time in which the gas is in the chimney, the ignition temperature is exceeded and the carbon oxide has fully reacted with the oxygen in the addition gas. Behind the chimney the gas to be trapped is in any case free of oxygen so that explosive mixtures can be no longer be formed. Also the control in the exhaustion system is much simpler behind the chimney than in the known apparatus in which the valves had to be arranged in and behind the water-cooled hood. This advantage is due to the fact that the gas to be trapped behind the chimney already has a very low temperature of approximately 200 to 300 C., so that the valves and the control system are not exposed to such high stresses as when they have to operate at temperatures ranging at 800 or 1000 C.
  • FIG. 1 is a graph illustrating the amount of flue gases produced during a top blowing process in dependence on time, its calorific value which is constantly kept at 2000 kcaL/standard cubic metre during a definite period of the refining process, the amount and composition of the addition gas in dependence on time, and the amount of heat supplied by the flue gas to the boiler system in the chimney.
  • FIG. 2 is a graph illustrating the control of the amount and composition of the addition gas added to the converter waste gases, in dependence on time.
  • FIGS. 3 and 4 and FIGS. 5 and 6 are graphs applying to the production of flue gases having a calorific value constantly maintained at 1700 kcal./ standard cubic metre and 1100 kcaL/standard cubic metre, respectively, during a definite period of the refining process.
  • the refining period is 21 minutes.
  • the blowing time in minutes is plotted on the abscissa.
  • the ordinate of the graph contains three scales, viz: the amount of heat sup plied to the boiler system in the chimney in thermal units (kcal.) per minute, the amounts of gases added and recovered, respectively, per unit of time in standard cubic metres per minute, and the calorific value of the fiue gas and of the collected gas in thermal units (kcaL) per standard cubic metre.
  • Curve 1 represents the calorific value which the flue gas produced during refining under the mentioned conditions would have, if no additional measures were taken. As is evident, the curve rises considerably until the 12th minute and then strongly declines, which means that, if this gas were trapped, the calorific value thereof would vary considerably; similarly the heat supplied to the boiler system would correspond to the rise and fall, respectively, of the curve.
  • the embodiment of the method according to the invention as illustrated in FIG. 1 is based on the assumption that from the 1st to the 19th minute a constant amount of heat of 145,000 kcal./min. is supplied to the boiler. This area corresponding to the amount of heat delivered is bordered by curve 2.
  • the addition according to the invention of an oxygen-containing addition gas is shown by curves 3 and 4, curve 3 illustrating the amount of oxygen in standard cubic metres per minute and curve 4 illustrating the amount of nitrogen added in standard cubic metres per minute.
  • the amount of flue gas obtained under these conditions is indicated by curve 5.
  • Curve 6 defines an area which corresponds to the calorific value of the flue gas collected. As is shown, the calorific value of the flue gas is continuously increased until the 3rd minute and reaches the desired value of 2000 kcal./ standard cubic metre between the 3rd and 4th minute. This value is maintained constant until the 17th minute.
  • the varying composition of the addition gas from oxygen and nitrogen is controlled, according to the invention, as is indicated by curves 3 and 4.
  • This control is illustrated more clearly by FIG. 2.
  • numeral 3 again denotes the amount of the oxygen added
  • 7 designates the total of oxygen and nitrogen.
  • Curve 3 of FIG. 2 exactly corresponds in behaviour to the trend of curve 3 in FIG. 1, and curve 7 represents the sum of curves 3 and 4 of FIG. 1. Accordingly, the behaviour of curve 7 in those phases in which pure oxygen is added, i.e. from the 1st to the 3rd minute and from the 18th to the 21st minute, is exactly the same as that of the oxygen graph in FIG. 1.
  • Curve 8 indicates the percentage of oxygen in the addition gas.
  • the total addition gas (FIG. 2) is, for instance, at the end of the 12th minute standard cubic metre/minute.
  • composition of the addition gas exhibits, until the end of the 3rd minute, an oxygen content of 100%, at the end of the 4th minute 50%, at the end of the 12th minute 9%, at the end of the 16th minute 7%; then the oxygen content increases again and at the end of the 17th minute amounts to 14%, and at the end of the 18th, 19th, 20th and 21st minute to 100%.
  • FIGS. 3 and 4 and 5 and 6 corresponding curves are shown for the production of flue gases having a calorific value of 1700 kcaL/standard cubic metre, and 1100 kcaL/standard cubic metre, respectively assuming again that the flue gases, before being trapped, have supplied from the 2nd to the 19th minute a constant amount of heat of 145,000 kcal./min. to the boiler.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
US419449A 1963-12-23 1964-12-18 Method of utilizing the heat content of a combustible gas during refining pig iron Expired - Lifetime US3321302A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AT1037663A AT245595B (de) 1963-12-23 1963-12-23 Verfahren zur Ausnutzung des Wärmeinhaltes eines brennbaren Gases beim Frischen von Roheisen

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US3321302A true US3321302A (en) 1967-05-23

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US (1) US3321302A (de)
AT (1) AT245595B (de)
BE (1) BE657489A (de)
DE (1) DE1433675A1 (de)
GB (1) GB1085710A (de)
NL (1) NL6414934A (de)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2831467A (en) * 1953-02-12 1958-04-22 Waagner Biro Ag Apparatus for cooling and utilizing the heat of waste gases
GB1005590A (en) * 1961-06-09 1965-09-22 Waagner Biro Ag Improvements relating to waste heat boiler arrangements
US3222045A (en) * 1961-01-10 1965-12-07 Huettenwerk Oberhausen Ag Method and apparatus for waste heat economy in rotary converter plants

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2831467A (en) * 1953-02-12 1958-04-22 Waagner Biro Ag Apparatus for cooling and utilizing the heat of waste gases
US3222045A (en) * 1961-01-10 1965-12-07 Huettenwerk Oberhausen Ag Method and apparatus for waste heat economy in rotary converter plants
GB1005590A (en) * 1961-06-09 1965-09-22 Waagner Biro Ag Improvements relating to waste heat boiler arrangements

Also Published As

Publication number Publication date
BE657489A (de) 1965-04-16
GB1085710A (en) 1967-10-04
AT245595B (de) 1966-03-10
NL6414934A (de) 1965-06-24
DE1433675A1 (de) 1968-10-31

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