US3773495A - Process for the automatic control of the pig iron refining operation - Google Patents

Process for the automatic control of the pig iron refining operation Download PDF

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Publication number
US3773495A
US3773495A US00214209A US3773495DA US3773495A US 3773495 A US3773495 A US 3773495A US 00214209 A US00214209 A US 00214209A US 3773495D A US3773495D A US 3773495DA US 3773495 A US3773495 A US 3773495A
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Prior art keywords
oxygen
temperature
fume temperature
fume
amount
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Expired - Lifetime
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US00214209A
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English (en)
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P Nilles
Y Noel
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Centre de Recherches Metallurgiques CRM ASBL
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Centre de Recherches Metallurgiques CRM ASBL
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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 invention concerns an automatic control process in which the rate Foreign Application Priority Data June 26, 1968 Belgium......................... together
  • the lance height is regulated relative to the bath of molten 7 C21: metal accordmg to a predetermined program based on [58] Field of Search /60 the amount of oxygen blown in.
  • the blowing rate is regulated in such a manner that the temperature of the fumes follows a predetermined path.
  • the invention relates to processes for the automatic control of the pig iron refining operation in a converter using the top blowing method.
  • thermometers with very short response times are important factors pointing to the advantages of automatic control of the blow.
  • thermometers with very short response times are important factors pointing to the advantages of automatic control of the blow.
  • thermometers with very short response times are important factors pointing to the advantages of automatic control of the blow.
  • thermometers with very short response times are important factors pointing to the advantages of automatic control of the blow.
  • by measuring the temperature of the fumes it is possible to calculate with accuracy and at any moment during the blow, the decarburization rate and the degree of oxidation of the slag.
  • the invention is based on the discovery that better correlations exist between the oxygen flow and the metallurgical reactions (decarburization rate, degree of oxidation of the slag and so on) than between the latter and the lance height.
  • acting on the oxygen flow rate offers the advantage of making it possible to allow automatically for the oxygen supplied by the ore and contributing to decarburization.
  • the present invention provides a process for automatically controlling pig iron refining in an oxygen topblown converter wherein the oxygen is blown through a lance, comprising the steps of:
  • the oxygen flow rate will be increased in order that the predetermined decarburization rate be achieved, with out consequent increase in the rate of oxygen transferred to the slag.
  • the process for the control of refining may be adapted to a given analysis of pig iron or to obtaining a given steel.
  • the control provided by the invention enables inter alia wear on the lance to be compensated. It is moreover possible to operate with a lance height program in which the lance height at any instant is set at a mean value determined from oxygen flow rates normally found, so that the desired metallurgical conditions will be approximately realised.
  • FIG. 1 shows a program for controlling the lance height
  • FIG. 2 shows various relationships between the graph of fume temperature against time and the graph of blowing rate against time
  • FIG. 3 is a block diagram of an automatic control installation; and I FIG. 4 shows a graph of various values recorded during a blow, against time.
  • the process was carried out on the two metric ton converters of an LD steel plant; the automated blowing installation monitors four operations;
  • the principle on which the process is based is that of regulating the lance height in relation to the bath of molten metal in accordance with a predetermined program based on theamount of oxygen blown in, while regulating the flow of oxygen blown in, in such a manner that the temperature of the fumes follows a predetermined course.
  • FIG. 1 represents a program for controlling the lance height; it can be seen that the lance height program is a curve imposed as a function of the percentage Oxygen blown/total oxygen to be blown and not as a function of time.
  • the lance height program is a curve imposed as a function of the percentage Oxygen blown/total oxygen to be blown and not as a function of time.
  • Start the lance is lowered at maximum speed, then reduced progressively, down to the initial lance level HL imposed by an off-line computer and manually introduced by the operator.
  • the lance stays at this l-IL level until a volume of oxygen equal to x, percent of the total volume to be blown (x, VOS Nm has passed through.
  • the lance is lowered at a constant speed (corre sponding to the gradient p if the oxygen flow rate is constant) down to the l-IL AH, level. Supposing there is a steady oxygen flow and the adjustments are correct, this lance height must in principle be reached for x; VOS Nm 0, (line a in FIG. 1). If the I-IL, AI-I level is reached a little before the moment corresponding to x: VOS, the lance is kept at the I-IL AH line b. If x VOS is reached before the AH, step is totally performed, the lowering of the lance is immediately completed, line 0.
  • the lance is maintained at a steady level up to x;, VOS.
  • the lance is raised by a height equal to AI-l and is kept at the value HL, Al-l Al-I up to x VOS. This operation makes foaming easier.
  • the lance is lowered by AH and stays at the height I-IL AH, AH AI-I until the end of the blowing operation represented by x, VOS (x 100%).
  • the installation automatically gives the signal for upward movement of the lance to a top limit switch, and gives the oxygen valve the closing signal.
  • the automatic installation performs the following functions:
  • auxiliary functions such as resetting of the integrator after blowing, starting the integrator, and resetting of the slope p generator, must also be added to these functions.
  • the lance height order is constituted by means of potentiometers and servo-mechanisms.
  • the initial lance height I-IL, and the total volume of oxygen to be blown VOS must be introduced into the automatic installation by the operator, before blowing.
  • these values are determined by a computer on the basis of a program used for calculating the charge.
  • the variables can be adjusted over a very wide range and this results in a great flexibility in the choice of the lance height program.
  • the second characteristic of the process is to regulate the flow of oxygen blown in, in such a manner that the temperature of the fumes will follow a predetermined curve. This latter measurement is carried out by means of a thermocouple arranged in the hood at the optimum level.
  • the blow is divided into four sections or phases:
  • Temperature level from a second given moment, the temperature of the fumes is kept constant and the oxygen flow regulator receives the command signal necessary for this. The temperature remains constant up to the moment when x,, VOS Nm of oxygen have been blown.
  • phase 1 when the normal rate of increase of fume temperature (phase 1) reaches a fixed threshold value of B C/min.
  • FIG. 3 is a block diagram of an automatic installation applying the lance height program and fume temperature-oxygen flow loop described above.
  • the analog circuit as illustrated is set up to apply the lance height program of FIG. 1 and the fume temperature program of FIG. 2 lb, but the elements necessary to follow the programs of FIG. 2 la, Ila, and IIb are also included.
  • the input variables to the converter 1 are the rate of oxygen blown in, Q, and the lance height, H,,; the only output variable considered here is the fume temperature, T].
  • the lance height H is controlled as follows: the measured oxygen blowing rate Q is transmitted to an integrator 2 whose output signal represents the total amount of oxygen blown in up to each moment of time,
  • This signal is transmitted to the first input of a comparator 3, which at a second input receives signals representing x x x x and x (see FIG. 1) from an ordinator 4, e.g., a series of potentiometers.
  • an ordinator 4 e.g., a series of potentiometers.
  • the comparator 3 emits a control signal to a program unit 5 in which the program of the pre-set values of H represented by FIG. 1 are set up.
  • the output of the unit 5 is transmitted to a controller 6 which adjusts the lance height [-1 accordingly.
  • the fume temperature program of FIG. 2 lb is controlled as follows: the output of the integrator 2 is trans mitted to the first input of a comparator 7, which at a second input receives signals representing x .x-,, x,,, and x,, from an ordinator 8, e.g., a series of potentiometers. As the oxygen amount coincides with x x x and x successively, the comparator 7 emits a control signal to a program unit 9 in which the program of the pre-set values of T, represented by FIG. 2 lb are set up. Each control signal initiates and terminates successive phases of the fume temperature curve, as indicated by the vertical broken lines in FIG. 2 lb. The unit 9 continuously transmits a signal, representing the instantaneous set value of fume temperature, to the first input of a comparator 1 0, which at a second input receives a signal representing T,. I
  • the resulting control signal representing any deviation of T, from the instantaneous set value, is fed to a controller 1 l which adjusts the oxygen blowing rate, Q, so as to reduce the: deviation.
  • the other units illustrated in FIG. 3 relate to the determination of the other two control factors, B, AT, shown in FIG. 2, which have been rendered inoperative by the opening of switches l2, l3, 14, 15.
  • 2 Ila or b is generated as follows: the measured fume temperature, T, is fed to a differentiator 16 whose output signal represents dl ,/dt. This signal is transmitted to the first input of a comparator 17, which at a second input receives a signal representing B from an ordinator l8, e.g., a potentiometer. When dl /dt becomes equal to B the comparator l7 emits a control signal which can be fed to the program unit 9 through the switch 15 to initiate the second phase of the fume temperature curve.
  • a control signal derived from T, used to control the unit 9 in the mode shown in FIG. 2 la or Ila, is generated as follows: the measured fume temperature, T, is fed to a memory unit 19 which, when supplied with a blocking signal, retains the last value T, of fume tem perature received.
  • the memory 19 is blocked at the end of the first phase of the fume temperature curve either by a blocking signal from the comparator 17 when dT ldt B, or by a blocking signal from a comparator 20, supplied at respective inputs by an ordinator 2! representing 1:, and the integrator 2, the blocking signal being emitted when the oxygen amount coincides with x,.
  • the particular blocking signal used is selected by the switches l2, 13.
  • the output of the memory 19 is fed to one input of a summator 22, which at a second input receives a signal representing AT (FIG. 2), the desired rise in fume temperature during the second phase, from an ordinator 23.
  • the output, T, AT, of the summator 22 is transmitted to the input of a comparator 24, which at a second input receives the measured fume temperature, T,.
  • T becomes equal to T
  • AT the comparator 24 emits a control signal which can be fed to the program unit 9 through the switch 14 to initiate the third phase of the fume temperature curve.
  • FIG. 4 shows the simultaneous recording of various values, carried out during a blow taking place in accordance with the automatic control process forming the subject of the invention.
  • the values shown as a function of time are:
  • A lance height (meters);
  • G the noise level emitted by the converter.
  • phase 2 was defined by means of the pair of parameters x AT (FIG. 2, la).
  • a process for automatically controlling pig iron refining in an oxygen top-blown converter wherein the oxygen is blown through a lance comprising the steps of:
  • a process as claimed in claim I further comprising, before the comparison of the fume temperature with the predetermined fume temperature curve of step (e), introducing said oxygen amount into an analog device which compares said amount with a pre-set value of the amount, and initiating said comparison of step (e) when said oxygen amount becomes equal to said pre-set value.
  • said predetermined fume temperature curve comprises two distinct contiguous sections, the process further comprising introducing said oxygen amount into an analog device which compares said amount with a pre-set value of said amount, adjusting said oxygen blowing rate so that the fume temperature follows the first of said sections until said oxygen amount becomes equal to said pre-set value, and then adjusting said oxygen blowing rate so that the fume temperature follows the second of said sections.
  • said pre determined fume temperature curve comprises two dis-- tinct contiguous sections
  • the process further comprising introducing said fume temperature into an analog device which compares the rise in temperature with a pre-set value, adjusting said oxygen blowing rate so that the fume temperature follows the first of said sections until said temperature rise becomes equal to said preset value, and then adjusting said oxygen blowing rate so that the fume temperature follows the second of said sections.

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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)
  • Treatment Of Steel In Its Molten State (AREA)
US00214209A 1968-06-26 1971-12-30 Process for the automatic control of the pig iron refining operation Expired - Lifetime US3773495A (en)

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Application Number Priority Date Filing Date Title
BE717199 1968-06-26

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US (1) US3773495A (de)
JP (1) JPS502366B1 (de)
BE (1) BE717199A (de)
DE (1) DE1931725B2 (de)
ES (1) ES368445A1 (de)
GB (1) GB1241242A (de)
LU (1) LU58814A1 (de)
NL (1) NL6909856A (de)

Cited By (3)

* 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
US5584909A (en) * 1995-01-19 1996-12-17 Ltv Steel Company, Inc. Controlled foamy slag process
US5885323A (en) * 1997-04-25 1999-03-23 Ltv Steel Company, Inc. Foamy slag process using multi-circuit lance

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113502400A (zh) * 2021-07-12 2021-10-15 上海环境工程设计研究院有限公司 一种富氧顶吹熔池熔炼炉系统及其控制方法

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB989993A (en) * 1961-07-13 1965-04-22 Stora Kopparbergs Bergslags Ab Method for the control of the refining by a stream of oxygen of carbon-containing metal melts
GB1008213A (en) * 1961-07-20 1965-10-27 Pompey Acieries Improvements in or relating to methods of and devices for controlling and monitoring the pneumatic refining of crude iron
US3372023A (en) * 1964-05-23 1968-03-05 Beteiligungs & Patentverw Gmbh Method of monitoring and controlling the oxygen blowing process
US3377158A (en) * 1965-04-28 1968-04-09 Jones & Laughlin Steel Corp Converter control systems and methods
US3432288A (en) * 1966-06-29 1969-03-11 Allegheny Ludlum Steel Process control of top-blown oxygen converter
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

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB989993A (en) * 1961-07-13 1965-04-22 Stora Kopparbergs Bergslags Ab Method for the control of the refining by a stream of oxygen of carbon-containing metal melts
GB1008213A (en) * 1961-07-20 1965-10-27 Pompey Acieries Improvements in or relating to methods of and devices for controlling and monitoring the pneumatic refining of crude iron
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
US3377158A (en) * 1965-04-28 1968-04-09 Jones & Laughlin Steel Corp Converter control systems and methods
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
US3432288A (en) * 1966-06-29 1969-03-11 Allegheny Ludlum Steel Process control of top-blown oxygen converter

Cited By (3)

* 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
US5584909A (en) * 1995-01-19 1996-12-17 Ltv Steel Company, Inc. Controlled foamy slag process
US5885323A (en) * 1997-04-25 1999-03-23 Ltv Steel Company, Inc. Foamy slag process using multi-circuit lance

Also Published As

Publication number Publication date
NL6909856A (de) 1969-12-30
DE1931725B2 (de) 1973-04-05
ES368445A1 (es) 1971-05-01
JPS502366B1 (de) 1975-01-25
LU58814A1 (de) 1969-10-28
GB1241242A (en) 1971-08-04
BE717199A (de) 1968-12-27
DE1931725A1 (de) 1970-05-27
DE1931725C3 (de) 1973-11-22

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