US3847593A - Process for refining metals, in particular liquid pig iron, in oxygen converters with continuous control of the operative procedure - Google Patents

Process for refining metals, in particular liquid pig iron, in oxygen converters with continuous control of the operative procedure Download PDF

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Publication number
US3847593A
US3847593A US00267694A US26769472A US3847593A US 3847593 A US3847593 A US 3847593A US 00267694 A US00267694 A US 00267694A US 26769472 A US26769472 A US 26769472A US 3847593 A US3847593 A US 3847593A
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Prior art keywords
refining
curve
bath
blowing
oxygen
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US00267694A
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English (en)
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A Ramacciotti
G Eminian
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Centro Sperimentale Metallurgico SpA
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Centro Sperimentale Metallurgico SpA
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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
    • C21C5/30—Regulating or controlling the blowing

Definitions

  • the present invention covers a process for refining metals, in particular liquid pig iron, in oxygen converters with continuous control of the operative procedure.
  • the invention relates to a liquid pig iron refining process, where an instantaneous determination of the refining pattern is performed as well as a continuous bringing back to a pattern preestablished as a standard model to be attained for the type of heat, by monitoring the oxygen instantaneous balance, for the purpose of keeping all the heats with temperature percentage of the final C and iron yield, within the allowance limits preestablished for each type of heat.
  • both the distance lance-metal bath and the flow of the oxygen jet are preestablished before the beginning of the refining, on the basis of considerations suggested by the experience and modified, during the refining itself, on the basis of the variation of some values, such as for example the intensity of some frequencies of the noise of the converter, or on account of the subjective impressions of the operating staff.
  • This kind of operation which requires a great deal of attention and of skill from the staff, turns into an actual uncertainty as far as the obtainable results are concerned; in fact, the variation of the operational values considered, affects in various ways the trend of the refining, depending on the conditions existing in the converter, such as the temperature and composition of the bath and of the slag, the amount of slag, etc.
  • the amount of oxygen to be blown, c in order to reach the required final value of carbon in the bath, is calculated a at a certain instant approaching the end point.
  • the amount of oxygen 0 still to be blown, in order to reach the final required temperature is calculated. If 0, 0 everything is proceeding normally; if instead O 0, one must intervene either adding coolants or modifying the distance between the lance and the bath.
  • the analysis of the flue gases at the stack supplies data affected by errors and it is not possible to determine, with sufficient precision, the various values and especially the constant k.
  • the model takes practically into account the decarburization reaction, while the oxygen supplied through the lance, besides reacting with the carbon of the bath, reacts also with the other present slag-forming elements, as well as with the carbon monoxide.
  • control of the refining pattern is performed by means of an analysis of the fumes at some location of the fume collecting and depuration system, far away from the converter and generally downstream of the waste heat boilers, and from these data a determination of the fumes analysis at the converter mouth is effected.
  • Thesemethods are made questionable both by the large amounts of nitrogen present in the analyzed gases, coming from the air drawn into the hood and by the uncertainty inherent to the determination of the extent of the combustion reactions of CO into CO which occur outside of the converter.
  • the object of the present invention is a refining process for metals, particularly for molten pig iron, in stationary or rotating oxygen converters, which allows to obviate the afore mentioned limitations, by continuously monitoring the refining process.
  • the process which is the object of the present invention, is characterized by an uninterrupted control'technique of the refining, in which recourse is made to a dynamic model based on the instantaneous balance of the oxygen blown through the lance, calculated by means of the analysis of the discharge gases at the hood and at the stack, taking into account that the said oxygen reacts not only with the carbon of the bath, to form carbon monoxide, but also with other elements present in the bath, to form slag, and also, in the region above the bath, with the carbon monoxide obtained in the initial reaction, to form carbon dioxide.
  • reaction (a) indicates how the decarburization is proceeding; reaction (b) allows to know how the thermal yield of the conversion itself is varying in the course of the refining; reaction (c) gives a measure of the amount of slag which is forming and this is of a great interest as far as the regularity of the refining and the control of the metallic yield are concerned.
  • a metallurgical reference parameter is determined, as a function of the reactions occurring inside the converter during the refining, and of the amount of oxygen blown.
  • the said reference parameter is defined by the following instantaneous experimental relationship:
  • the type of the charge and the characteristics required for the steel at the end point are preestablished.
  • the com puter chooses the relevant type of optimal curve and, during the blowing, receives the data which allow it to calculate A and B and thence the ratio K (A B)/Q m. Then it compares the value of this ratio at eac instant of the blowing to the optimal value preestablished for this instant, and if necessary, modifies the flow rate Q in such a way that the actual value of m be the nearest possible to the optimal value, or at least, be comprised within the preestablished variability range.
  • the refining control is performed by means of a continuous series of samplings and analyses of the gases issuing from the converter, for the purpose of ascertainmg:
  • the analysis of the gases at the converter mouth is performed by an indirect measurement, by sampling of the gas with a sampler within the hood, at adistance from the converter mouth ranging from 0.3 to 2.5 meters.
  • the sampler which can be tilted from 0 to 90 in respect to the horizon, is thus introduced into the hood, in such way that its suction extremity is located approximately in the center of the hood itself, at a distance of 0 to 0.5 meters from the axis of the hood itself, and at a distance from the converter mouth ranging from 0.3 to 2.5 meters.
  • the present invention it is also possible to perform the sampling of the gases at a distance from the converter mouth, lesser than 0.3 meters or even inside the converter itself, by means of a sampler directly incorporated in the blowing lance or attached to it, or separated from it and introduced into the converter mouth; however the preselected technique (that is the sampling of the gases in the hood) is to be preferred as being the most practical, since no further lifting apparatus for the sampler is necessary, and the chance that a spray of slag or liquid metal plugging the sampler is less probable; besides, the composition differences between the gases sampled inside the converter and those sampled with the suggested method are not too important.
  • the gas sampled by the sampler is first depurated of dust and then conveyed to a continuous analyzer, of a conventional type, for CO and CO2 analysis and then to another continuous analyzer, also of a conventional type, for the analysis of oxygen.
  • the nitrogen percentage possibly present is calculated as a complement to one hundred of the total of the C0, C02 and 02 per centages.
  • the instantaneous values of the thus determined percentages, are recorded and simultaneously fed to an electronic computer.
  • the gases are practically cold and saturated with water vapor, because of the countercurrent water cooling and are already depurated of dust; they are sampled by a sampler and conveyed directly into an analytical system, similar to that installed in the hood, and the analysis data thus obtained are also recorded and simultaneously fed to an electronic computer.
  • thermoresistances In the stack, by means of a venturimeter-and a series of thermoresistances, measurements of the differential pressure AP, and of temperature T, are also performed. These data too are recorded and fed into the computer.
  • the computer be gins to read, with a proper frequency, the values corresponding to the single measurements mentioned above.
  • the computer elaborates the input data calculates the instantaneous value of m and compares it with the value preestablished for this particular type of refining at the corresponding instant.
  • the calculation procedure is the following where the data a e indicated with:
  • the computer compares continuously, during the blowing, the actual instantaneous value of m with that indicated by the preestablished curve, and gradually, by trials, prescribes the corrections to be possibly made to the distance between the lance and the bath and/or, preferably, to the flow rate of the oxygen delivered by said lance, in order to bring the instantaneous value of m back to the optimal value.
  • FIG. 1 shows an optimal curve 1 of the parameter m, as a function of the blowing time, with the relevant allowance band or strip preestablished for a certain type of charge and for a certain requested result and delimited by the dashed lines 2 and 3.
  • FIG. 2 shows the actual curve 4 of m, related to the heat indicated in Example I, superimposed over the curve of FIG. 1.
  • FIG. 3 shows the actual curve 5 of m, relative to the curve of the heat indicated in Example 2 and superimposed over the curve of FIG. 1;
  • FIG. 4 shows the actual curve 6 of m related to the heat indicated in the Example 3, superimposed over the curve of FIG. 1.
  • the lance position is kept constant, while the oxygen flow rates are permitted to vary within an interval ranging from 600 to 800 Nm /min.
  • the oxygen flow rate is 800 Nm /min
  • the lance distance from the bath is still 1.50 meters.
  • the automatic control is interrupted at about 2 minutes before the end point.
  • the iron yield, at the allowance limits, is due to a sparking period during the first 3 minutes of blowing.
  • the on-line computer on the basis of the previous data, indicated the charge composition as follows:
  • the lance distance from the bath I was brought to 1.50 meters.
  • the oxygen flow rate was maintained constant until the 17th minute, and thereafter was brought to 800 Nm /min.
  • the final data of the metal bath are:
  • a process for refining liquid pig iron into steel in a liquid bath comprising blowing a gas containing oxygen onto the bath, and analyzing the gas above the bath; the improvement comprising the steps of predetermining a desired graphical curve of m versus time on the basis of at least the actual initial and desired final physical characteristics of the bath, in which A being the instantaneous flow rate of the oxygen in said analyzed gas employed for the combustion of C into CO in Nm /min., B being the instantaneous flow rate of the oxygen in said analyzed gas used for the combustion of CO to CO in Nm /min., and Q being the instantaneous flow rate of the total oxygen in said blown gas in Nm /min., k being a constant; determining at a plurality of time intervals the actual instantaneous values of m on the basis of the physical characteristics of gas emitted from the bath; and varying the flow rate of said blown gas so as to decrease the difference between each said actual value of m and the predetermined value of m

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)
US00267694A 1971-07-13 1972-06-29 Process for refining metals, in particular liquid pig iron, in oxygen converters with continuous control of the operative procedure Expired - Lifetime US3847593A (en)

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US (1) US3847593A (de)
AT (1) AT338845B (de)
DE (1) DE2234204B2 (de)
GB (1) GB1394240A (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4148629A (en) * 1976-08-04 1979-04-10 Vereinigte Osterreichische Eisen- Und Stahlwerk-Alpine Montan Aktiengesellschaft Process for controlling a steel refining process for steels having a carbon content within the range of 0.1 to 0.8 % by weight
RU2228370C1 (ru) * 2003-03-20 2004-05-10 ООО "Сорби стил" Способ управления электроприводом исполнительных механизмов металлургических машин и агрегатов

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10122922A1 (de) * 2001-05-11 2002-11-14 Mgp Instr Gmbh Verfahren und Filtereinrichtung zur Fluktuatiuonsunterdrückung bei Meßdaten

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3372023A (en) * 1964-05-23 1968-03-05 Beteiligungs & Patentverw Gmbh Method of monitoring and controlling the oxygen blowing process
US3475599A (en) * 1965-03-30 1969-10-28 Leeds & Northrup Co Process measurement system for basic oxygen refining of steel
US3485619A (en) * 1965-10-04 1969-12-23 Beteiligungs & Patentverw Gmbh Method of automatic control and adjustment of oxygen blowing processes
US3533778A (en) * 1966-04-20 1970-10-13 Centre Nat Rech Metall Automatic control of pig iron refining
US3594155A (en) * 1968-10-30 1971-07-20 Allegheny Ludlum Steel Method for dynamically controlling decarburization of steel
US3598386A (en) * 1967-10-09 1971-08-10 Crucible Steel Co America Apparatus for making steel
US3700429A (en) * 1970-01-05 1972-10-24 Allegheny Ludlum Steel Method of controlling vacuum decarburization
US3719469A (en) * 1970-07-22 1973-03-06 Allegheny Ludlum Ind Inc Control for basic oxygen steelmaking furnace
US3720404A (en) * 1967-06-27 1973-03-13 Westinghouse Electric Corp System for controlling carbon removal in a basic oxygen furnace
US3723099A (en) * 1970-01-28 1973-03-27 Sumitomo Metal Ind Method for static control of an oxygen blown converter

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3372023A (en) * 1964-05-23 1968-03-05 Beteiligungs & Patentverw Gmbh Method of monitoring and controlling the oxygen blowing process
US3475599A (en) * 1965-03-30 1969-10-28 Leeds & Northrup Co Process measurement system for basic oxygen refining of steel
US3485619A (en) * 1965-10-04 1969-12-23 Beteiligungs & Patentverw Gmbh Method of automatic control and adjustment of oxygen blowing processes
US3533778A (en) * 1966-04-20 1970-10-13 Centre Nat Rech Metall Automatic control of pig iron refining
US3720404A (en) * 1967-06-27 1973-03-13 Westinghouse Electric Corp System for controlling carbon removal in a basic oxygen furnace
US3598386A (en) * 1967-10-09 1971-08-10 Crucible Steel Co America Apparatus for making steel
US3594155A (en) * 1968-10-30 1971-07-20 Allegheny Ludlum Steel Method for dynamically controlling decarburization of steel
US3700429A (en) * 1970-01-05 1972-10-24 Allegheny Ludlum Steel Method of controlling vacuum decarburization
US3723099A (en) * 1970-01-28 1973-03-27 Sumitomo Metal Ind Method for static control of an oxygen blown converter
US3719469A (en) * 1970-07-22 1973-03-06 Allegheny Ludlum Ind Inc Control for basic oxygen steelmaking furnace

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4148629A (en) * 1976-08-04 1979-04-10 Vereinigte Osterreichische Eisen- Und Stahlwerk-Alpine Montan Aktiengesellschaft Process for controlling a steel refining process for steels having a carbon content within the range of 0.1 to 0.8 % by weight
RU2228370C1 (ru) * 2003-03-20 2004-05-10 ООО "Сорби стил" Способ управления электроприводом исполнительных механизмов металлургических машин и агрегатов

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GB1394240A (en) 1975-05-14
AT338845B (de) 1977-09-12
DE2234204A1 (de) 1973-02-01
ATA600472A (de) 1977-01-15
DE2234204B2 (de) 1975-11-13

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