US3602487A - Blast furnace stove control - Google Patents

Blast furnace stove control Download PDF

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US3602487A
US3602487A US875346A US3602487DA US3602487A US 3602487 A US3602487 A US 3602487A US 875346 A US875346 A US 875346A US 3602487D A US3602487D A US 3602487DA US 3602487 A US3602487 A US 3602487A
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stove
established
gas flow
blast furnace
burner
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Donald W Johnson
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Jones and Laughlin Steel Corp
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Jones and Laughlin Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B9/00—Stoves for heating the blast in blast furnaces
    • C21B9/10—Other details, e.g. blast mains
    • C21B9/12—Hot-blast valves or slides for blast furnaces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N1/00—Regulating fuel supply
    • F23N1/005—Regulating fuel supply using electrical or electromechanical means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/003—Systems for controlling combustion using detectors sensitive to combustion gas properties
    • F23N5/006—Systems for controlling combustion using detectors sensitive to combustion gas properties the detector being sensitive to oxygen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2221/00—Pretreatment or prehandling
    • F23N2221/10—Analysing fuel properties, e.g. density, calorific
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2225/00—Measuring
    • F23N2225/02—Measuring filling height in burners
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2225/00—Measuring
    • F23N2225/08—Measuring temperature
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/10—Reduction of greenhouse gas [GHG] emissions
    • Y02P10/143—Reduction of greenhouse gas [GHG] emissions of methane [CH4]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/32—Technologies related to metal processing using renewable energy sources

Definitions

  • This invention relates generally to blast furnace stoves and particularly to means for controlling the operation and enrichment of the combustion fuels of such stoves during their on-gas or firing cycle.
  • a blast furnace stove is essentially a large heat sink composed of large quantities of refractory brickwork or checkers. initially, such a stove is operated on an on-gas or firing cycle, during which a gaseous fuel is burned at the stove burner located near the bottom of the stove and the hot combustion gages circulated through the stove and out the stove stack.
  • Blast furnace gas typically has a low B.t.u. content, ranging from about 70 to 95 B.t.u./cubic foot, depending on furnace operating conditions.
  • the normal heating or firing cycle of a stove comprises a first period during which the stove dome temperature reaches a predetermined maximum, e.g., 2,300 F. and a second period during which the dome is held at that temperature to allow the stove checkerwork to absorb and store heat by soaking.
  • a predetermined maximum e.g. 2,300 F.
  • the fuel ignited at the stove burner have an average B.t.u. content of about 85 B.t.u./cubic foot. Since blast furnace gas cannot be relied upon for such a heat content at all times, enrichment of the blast furnace gas, typically with natural gas, is necessary.
  • the quantity of natural gas required to enrich the blast furnace gas is a function of the heat content of the blast furnace gas and it is desirable to provide a control scheme which will regulate the amount of natural gas used to achieve the desired on-gassoak-on-wind cycle time. This is necessary to achieve smooth furnace operation and keep natural gas purchases at a minimum.
  • the control system of the present invention utilizes stove dome temperature to control stove operation during the firing cycle. Control is generally initiated some short time after stove firing is started, after sufficient time has expired to allow burner combustion to stabilize. Control is accomplished by comparing the measured dome temperature against a profile of desired dome temperature as a function of time as generated by a function generator. Any error is referenced to a natural gas flow control loop. If the measured dome temperature is greater than or equal to the reference profile, the
  • the control system will regulate the flow of natural gas so as to keep the dome temperature from exceeding its set point (e.g. 2.300 F.) until zero natural gas flow or shutoff.
  • the blast furnace top gas When circumstances are such that the natural gas flow is zero and the measured dome temperature is at the predetermined maximum temperature, the blast furnace top gas will generally have more than enough of a heat content to hold the dome temperature at that maximum temperature. Therefore, the dome temperature will tend to exceed the predetermined maximum. To prevent this from occurring, excess air is added to the blast furnace gas to maintain the dome temperature at the desired level.
  • the control operation continues until the stove stack temperature reaches a predetermined limit (approximately 750 F.) indicating that the checkers have absorbed as much heat as design allows and, consequently, that the stove is ready to be put on blast
  • the system of the present invention also includes an oxygen loop.
  • the oxygen loop is used to trim the combustion airflow according to the measurement of oxygen in the stove exhaust stack. This loop has an inherent time delay in it since air is mixed with the fuel at the burner while oxygen content is measured at the stack, and it may take as long as 30 seconds for changes made at the burner to be manifested at the stack,
  • An object of the present invention is to provide a system for controlling the operation of a blast furnace stove during its ongas or firing cycle. Another object is to control the enrichment of the gases burned during the on-gas cycle. Another object of the invention is to provide such control by controlling blast furnace gas flow, natural gas flow and airflow. Yet another object of the present invention is to achieve such control by providing a profile for desired stove dome temperature from the start of the firing cycle through achievement of dome temperature and through the time the dome is held at temperature while the checkers are reaching an even heat and comparing the profile temperature to the measured dome temperature. Still another object of the invention is to provide an oxygen analyzer loop to control airflow in response to the oxygen content of the stove exhaust gases, while compensating for transport delay.
  • the control system of the present invention regulates the blast furnace gas flow, the natural gas flow, and the airflow to the stove burner.
  • Blast furnace gas flow regulation is achieved by a blast furnace gas flow control loop which continuously measures the blast furnace gas flow rate in the blast furnace gasline and controls that flow rate to substantially maintain the blast furnace gas flow to the stove burner at a preselected level.
  • This control loop includes first differential pressure to current transducer means 10 for sensing the differential pressure across the orifice plate 11 in the blast furnace gasline 12 leading to the stove burner and converting it to an electrical output signal of a magnitude depending on the magnitude of that differential pressure.
  • This line provides the conduit through which cleaned and scrubbed blast furnace top gas passes to the burner.
  • the output of the transducer means 10 which because it is a function of the differential pressure in line 12 is a function of the blast furnace flow rate squared, is fed to first square root extractor means 13 which develops an output signal which is the square root of the output signal of the transducer means 10.
  • Orifice plate 11, transducer means and square root extractor means 13 thus comprise means for measuring and providing an indication of the blast furnace gas flow rate in the blast furnace gasline 12.
  • a single blast furnace has associated with it two or more blast furnace stoves which are operated so that while one or more stoves are onwind, one or more stoves are ongas. From operating experience it is possible to determine generally the blast furnace gas flow which must be substantially maintained to a stove during its on-gas period so that at the time it is put on-wind, it is approximately at the requisite temperature.
  • This preselected blast furnace gas flow level is incorporated into the control system of the invention as a reference level by firing rate set point means 14.
  • the set point means comprises a linear potentiometer for developing an output signal measurably responsive to the preselected level of blast furnace gas flow in the same manner as the output of square root extractor means 13.
  • blast furnace gas loop controller means 15 which is a conventional proportional and reset controller.
  • the controller means develops an output signal measurably responsive to the difference between the output signals of the set point means 14 and extractor means 13 and the time the difference has existed and is thus related both to the magnitude of the difference between the measured blast furnace flow rate and the preselected level of blast furnace gas flow to be established or if established to be maintained to the stove and the period of the time the difference has existed.
  • Means for controlling the action of a valve in the gasline 12 in response to the difference between the measured blast furnace gas flow rate and the blast furnace gas flow rate to be established or if established to be maintained comprises first current-to-pressure transducer means 16 which converts the signal developed by controllermeans 15 to a pneumatic pressure measurably responsive thereto. That pneumatic pressure acts to control the action of the valve 17 in the gas line 12 to regulate the blast furnace gas flow to the burner,
  • Blast furnace top gas after it has been cleaned and scrubbed, typically has a composition of about 1.5 percent to 4.5 percent hydrogen, about 22 percent to 25 percent carbon monoxide, about 14 percent to 15 percent carbon dioxide, and remainder nitrogen.
  • oxygen in the form of air, is mixed with it.
  • a suitable mixture comprises about 1.4 parts blast furnace gas to one part air.
  • the system of the invention operates on the basis of such a suitable fuel-to-air ratio. This is accomplished by means including fuel-to-air ratio means 18 for calling for a combustion airflow rate which is a preselected constant multiple of the measured blast furnace gas flow rate.
  • Ratio means 18 has as its input the output of extractor means 13, representing the measured blast furnace flow rate. in response to that input, ratio means 18 develops an output signal which is representative of an airflow rate which is a constant multiple of the measured blast furnace gas flow rate, e.g., 0.7 of the blast furnace gas flow rate. This output is delivered to proportional and reset controller means 20.
  • the airflow rate is controlled not only in response to the blast furnace gas flow rate but also in response to the additional variables of the oxygen content of the gases issuing from the stove stack and the stove dome temperature. Changes in the oxygen content of the gases issuing from the stove stack affect airflow rate through an oxygen loop means and the stove dome temperature affects airflow rate through a means for calling for a greater combustion airflow rate than that called for by the ratio means and the oxygen loop means when the natural gas flow is zero and the measured dome temperature is greater than a predetermined maximum temperature.
  • the means for calling for a greater combustion airflow rate, the oxygen loop means and the ratio means collectively comprise means for calling for a combustion airflow rate to be established or if established to be maintained to the burner.
  • the manner in which changes in airflow rate are made in response to changes in the oxygen content of the stove stack gases and the stove dome temperature is discussed in detail below. However, it is here noted that their influence is manifested as an electrical signal delivered to controller 20 through line 19.
  • a third input to controller 20 comprises the output of square root extractor means 21 which output is measurably responsive to the airflow rate in air line 24 leading to the stove burner.
  • Extractor means 21 is operatively connected to differential pressure-to-current transducer means 22 and its output signal is the square root of the output signal of transducer 22.
  • the output of transducer 22 is measurably responsive to the differential pressure which it senses across orifice plate 23 in air line 24.
  • Orifice plate 23, transducer 22 and square root extractor means 21 thus comprise means for measuring and providing an indication of the combustion airflow in the air line 24.
  • controller 20 In response to its three inputs, controller 20 develops a signal measurably responsive to the difference between the measured airflow rate and the airflow rate to be established or if established to be maintained to the stove and the length of time the difference has been existing.
  • Means for controlling the action ofa valve in air line 24 in response to the difference between the measured combustion airflow rate and the combustion airflow rate to be established or if established to be maintained comprises current-to-pressure transducer means 25 which converts the signal developed by controller 20 to a pneumatic pressure measurably responsive thereto. That pressure acts to control the action of valve 26in air line 24 to regulate the airflow to the stove burner.
  • the system of the invention controls stove heating during the on-gas period primarily by controlling natural gas flow to the burner. Natural gas flow is regulated by means of a natural gas flow control loop which functions in response to a temperature comparison circuit.
  • the temperature comparison circuit develops an output which is measurably responsive to the difference between the instantaneous measured stove dome temperature and a desired temperature, as indicated by a stove dome temperature-time schedule representing a desired heating-up program for the stove.
  • the circuit comprises temperature profile function generator 30, dome temperature sensor 31 and proportional controller means 32.
  • the basic reference for the control system is temperature profile function generator means 30 which provides a representation of the temperature desired to be established in the stove dome as a function of time during the on-gas cycle.
  • the output of function generator 30 is measurably responsive to the temperature at which it is desired the stove dome temperature be at any instant during the on-gas period.
  • the normal practice is to heat the stove so that the stove dome temperature rapidly reaches a desired maximum and is maintained there while the checkers continue to soak up heat until they have absorbed a quantity .of heat according to their design.
  • a desired heating-up schedule can be arrived at from a consideration of optimum past practices and the function generator programmed in accordance therewith so that its output with time represents a temperature profile which tracks the desired heating-up schedule.
  • the stove dome temperature is measured by a temperaturesensing means 31, such as a Ray-O-Tube, manufactured by Leeds and Northrup, mounted in the stove dome.
  • the sensor develops an output signal measurably responsive to the temperature of the the top checkerwork and that signal along with the output signal of the function generator 30 is delivered to natural gas flow proportional controller means 32.
  • the controller means 32 in response thereto develops an output signal measurably responsive to the difference between the measured stove dome temperature and the desired stove dome temperature. This signal is related to some natural gas flow rate, including zero, which should be established or if established should be maintained to the stove burner to effectuate or maintain the desired stove temperature.
  • controller 32 The output of controller 32 is delivered to the natural gas flow control loop. There, it sets natural gas flow set point means 33 which keeps the natural gas flow rate called for by controller means 32 from exceeding a predetermined maximum which is based on the blast furnace gas flow rate desired to be maintained to the burner.
  • Set point means 33 comprises a linear potentiometer for developing up to a preset maximum a signal measurably responsive to the output of controller 32. The preset maximum is a function of the preselected level of blast furnace gas flow substantially maintained to the burner as set by firing rate set point means 14.
  • the natural gas flow rate needed to rapidly bring the dome temperature to the desired level according to the programmed reference would be so great with relation to the level of blast furnace gas flow set in set point means 14 that the richness of the fuel delivered to the burner would result in excessive burner flame temperatures, resulting in accelerated destruction or weakening of the materials used in the construction of the stove.
  • the natural gas flow rate be no greater than about 2 percent of the blast furnace gas flow rate.
  • firing rate set point means 14 and natural gas set point means 33 are appropriately interconnected so that when the firing rate set point means is set, the natural gas set point means is automatically set at a maximum representing a natural gas flow rate about 2 percent of the blast furnace gas-firing rate; in this manner, irrespective of the measured dome temperature, the output of set point means will not exceed the preset maximum.
  • the natural gas set point means 33 is automatically set at a maximum representing a natural gas flow rate of 600 c.f.m.; and regardless of the difference between the measured dome temperature and the desired stove temperature, the output of controller means 32, which is a measure of the temperature difference, is unable to drive set point means 33 beyond the point representing a natural gas flow rate of 600 c.f.m.
  • controller 32 and set point means 33 function as means for developing up to a preset maximum and in response to the measured stove temperature and the desired stove temperature, as represented by the output of function generator 30, an output signal which is measurably responsive to an increased natural gas flow rate when the desired stove temperature exceeds the measured stove temperature and a decreased natural gas flow rate when the measured stove temperature exceeds the desired stove temperature.
  • the blast furnace top gas flow would become so low that the firing rate set in means 14 could not be maintained.
  • the natural gas flow called for by set point means 33 while it might be less than about 2 percent of the firing rate set in means 14, could be greater than about 2 percent of the reduced blast furnace gas flow.
  • the blast furnace gas flow rate would fall below 30,000 c.f.m. to say, for example, 20,000 c.f.m. despite the fact that valve 17. would be full open.
  • the natural gas flow called for bycontroller 32 could be in excess of 400 c.f.m. (2 percent of 20,000 c.f.m.) although below 600 c.f.m.
  • the output of set point means 33 is delivered to modifier means 34 along with the output of extractor means 13.
  • the output of the extractor 13 is scaled to the same basis as the output of set point means 33 and the modifier means compares these two signals, determines which signal is smaller and applies that signal to conventional proportional and reset controller means 35.
  • Modifier 34 thus keeps the natural gas flow rate called for below a preselected percentage of the measured blast furnace gas flow rate to the burner. In this manner the system allows for natural gas enrichment as a function of actual blast furnace gas flow rates rather than the set point rate, if the actual blast furnace gas flow rate is below the blast furnace gas set point.
  • the natural gas flow control loop further includes differential pressure to current transducer means 36 for sensing the differential pressure across the orifice plate 37 in the natural gas line 38 leading to blast furnace gasline 12 and converting the pressure to an electrical output signal of a magnitude dependent thereon.
  • Second square root extractor means 39 is operatively connected to transducer means 36 for developing an output signal which is the square root of the output signal of transducer means 36.
  • orifice plate 37, transducer means 36and extractor means 39 comprise means for measuring and providing an indication of the natural gas flow rate in the natural gas line.
  • the output of extractor means 39 is fed to proportional and reset controller means 35 along with the output of modifier 34, and the controller in response thereto develops a signal measurably responsive to the difference between those outputs and the time the difference has existed.
  • This signal is thus related both to the magnitude of the difference between the measured natural gas flow rate and the natural gas flow rate to be established or if established to be maintained to the stove and the period of time the difference has existed.
  • Means for controlling the action of a valve in natural gas line 38 in response to the difference between the measured natural gas flow rate and the natural gas flow rate to be established or if established to be maintained comprises current to pressure transducer means 40 which converts the signal developed by controller means 35 to a pneumatic pressure measurably responsive thereto. That pressure acts to control the action of valve 41 in natural gas line 38 to regulate the natural gas flow to blast furnace gasline 12, the two gases mixing at intersection 42.
  • function generator 30 is not activated nor is natural gas enrichment initiated until the closing of relay 43 which occurs some little time after stove firing is initiated.
  • Relay 43 both resets and activates function generator 30. It first resets the generator to time scale zero at the completion of the on-wind cycle of the stove and initialization of stove burner combustion. A measured time later, e. g., 30 seconds, it activates the generator.
  • the system of the invention controls airflow to the stove burner by continuously measuring the airflow rate in the air line and controlling that flow rate so as to provide both an oxygen level at the burner in excess of that required to oxidize all the combustible gases thereat and a sufficient airflow to lower the stove temperature when the natural gas flow is zero and the measured stove temperature exceeds a preselected maximum temperature.
  • Airflow to the stove burner is thus controlled in response to three variables; the blast furnace gas flow rate, the oxygen content of the gases issuing from the stove stack and the stove dome temperature.
  • the basic variable on which the airflow control functions is in the blast furnace gas rate. The manner in which the other two variables influence airflow will now be described.
  • the ratio of air to fuel delivered to the burner is controlled primarily by controlling the flow of air as a proportion of fuel flow pipe on each side of the orifice plate.
  • This length of pipe is completely impracticable for a blast furnace stove because it requires too great a length of unimpeded pipe for a typical blast furnace installation. Consequently, the orifice plates will not provide precisely accurate readings over a large range of flows and in many instances too little air (reducing atmosphere) or too much air (oxidizing atmosphere) is present in the stove during firing.
  • a reducing atmosphere causes checker deterioration and creates the likelihood of an explosion due to incomplete combustion. Too much air reduces the flame temperature at the burner and lengthens the heating cycle. Accordingly, the present system trims combustion airflow according to the oxygen content of the'stove stack gases.
  • an oxygen loop means for calling for an increase in the combustion airflow rate over that called for by ratio means 18 when the oxygen gas content of the gases issuing from the stove exhaust stack is below a preselected level and a decrease in the combustion airflow rate below that called for by the ratio means when the oxygen gas content of the gases issuing from the stove exhaust stack is above said preselected level.
  • a stack gas sample line 46 is inserted in stove stack 47 whereby samples of the gas passing through the stack pass into line 46.
  • the gas samples then pass through a sample clean and pump station 48 where moisture and dirt particles are removed and from there the gas samples pass onto the oxygen analyzer 49.
  • the oxygen analyzer determines the oxygen content of the gas samples and develops a signal measurably responsive to that oxygen content. That output is then fed to the conventional combustion airflow proportional controller means 50.
  • Oxygen set point means 51 which comprise a linear potentiometer, is provided in the oxygen loop means for selecting a range of excess air percentage which is to be maintained, the output of the set point means 51 being measurably responsive to the excess air value selected.
  • This output is fed to summing amplifier 52 along with the output of controller means 61, in those instances where an an output is present at controller 61, and the sum of those two outputs delivered to controller 50.
  • the output of controller means 61 represents the influence of the dome temperature on airflow as is more fully described below.
  • Controller 50 develops an output signal measurably responsive to the difference between the signal developed by summing means 52 and the signal developed by oxygen analyzer means 49 thereby calling for an increase in the combustion airflow rate over that called for by ratio means 18 when the oxygen gas content of the gases issuing from the stove stack is below the preselected level of oxygen set point 51 and a decrease in the combustion airflow rate below that called for by ratio means 18 when the oxygen gas content of those gases is above that preselected level.
  • the output of controller 50 is then delivered to time lag compensator means 53. This occurs only after closing of relay 54 which is controlled by a timer set to activate the relay when burner combustion has stabilized.
  • the system of the present invention has an inherent time delay since the air is introduced at the burner while oxygen content is measured adjacent the stack and it may take as long as 30 seconds for a change at the burner to be manifested by a change at the stack and analyzer 49.
  • This time delay is referred to as transport time and if not properly compensated for can cause system instability.
  • the system of the present invention compensates for transport time by providing in the oxygen loop a sampling circuit in the form of time lag compensator means 53 which keeps the mag nitude of the increase or decrease in airflow rate called for out of controller 50 constant for intermittent time periods in order to compensate for the time which is required for changes made in the airflow rate to be manifested at analyzer 49.
  • Time lag compensator 53 examines the output of controller 50 for a short period of time referred to as on-time, this output being integrated at the compensator during that period at a slow rate. At the end of the on-time integrated signal is held constant for a much longer period of time referred to as off-time. The length of the off-time period is selected to be long enough to allow changes made in the air-fuel mixture to be manifested at the oxygen analyzer. At the end of the off-time the on-time is again initiated. One of three events may then occur: The integrated signal will increase in response to a positive signal from controller 50, indicating an oxygen analysis lower than that called for by summing amplifier 52.
  • the integrated signal will decrease in response to a negative signal from controller 50, indicating an oxygen analysis higher than that called for by summing amplifier S2.
  • the integrated signal will remain constant in response to a zero signal from controller 50, indicating an oxygen analysis the same as that called for by summing amplifier 52.
  • a new off-time begins with the signal developed by the compensator 53 at the end of that new on-time being maintained during the new offtime. This procedure continues throughout the on-time period. Suitable onand offtimes are l and 10 seconds respectively, with the off-time being adjusted as a function of blast furnace gas rate.
  • the system of the present invention acts to increase the airflow to the stove burner and the increased airflow acts to cool the combustion flame.
  • dome temperature set point means 60 comprises a linear potentiometer which develops a signal measurably responsive to a dome temperature set thereon.
  • the set point means 60 is set at the maximum temperature at which it is desired the stove dome attain. Delivery of the output of set point means 60 to controller 61 does not occur until the closing of relay 63 which occurs at the same time relay 54 closes.
  • the airflow is controlled in one of two ways.
  • the airflow rate to the burner is based on the fuel-to-air ratio to be maintained, as established by ratio means 18, modified by additions of air as called for by con troller 61 whenever the natural gas flow is zero and the measured stove temperature exceeds the profile temperature.
  • the airflow rate is additionally modified on the basis of the oxygen content of the stove stack gases. Selection of the method of operation is accomplished by means of relays 55 and 56 and OR gate 57. When operation 13.
  • the system of claim 12 including time-lag compensator means for alternately integrating the electrical error signal developed by the combustion airflow proportional controller means during a first period of time while developing an electrical output signal during that period of time as a function of the integration and maintaining the integrated signal developed at the end of the first period of time constant for a following second period of time whereby to allow for changes made in the combustion airflow rate to be manifested at the oxygen analyzer means.
  • the system of claim 13 including natural gas set point means for developing an electrical signal in response to the electrical signal developed by the natural gas flow proportional controller means and for keeping the electrical signal which it develops from exceeding a predetermined maximum which is representative of a predetermined maximum natural gas flow rate based on the blast furnace gas flow rate desired to be maintained to the burner.
  • modifier means for developing an electrical signal in response to the electrical signal developed by the natural gas set point means and for keeping the electrical signal which it develops below a value representative of a maximum preselected percentage of the measured blast furnace gas flow rate to the burner.
  • relay 56 is closed while relay 55 is opened and the output of controller 61 is delivered to controller 20.
  • Operation according to the second method occurs by closing relay 55 and opening relay 56 so that the output of compensator 53 is delivered to controller 20.
  • a system for controlling the operation of a blast furnace stove during its on-gas period said stove having a stove burner and associated blast furnace gas, natural gas and combustion air lines for conveying blast furnace gas, natural gas and combustion air respectively to the stove burner, said lines each including both means for measuring and providing an indication of the gas flow rate therein and means for controlling the action of a valve in the line in response to the difierence between the measured gas flow rate and a gas flow rate to be established or if established to be maintained in the line including a. means for providing a representation'of the temperature desired to be established in the stove dome as a function of time during the on-gas cycle,
  • the means for calling for a combustion airflow rate to be established or if established to be maintained to the burner further includes oxygen loop means for calling for an increase in the combustion airflow rate over that called for by the ratio means when the oxygen gas content of the gases issuing from the stove exhaust stack is below a preselected level and a decrease in the combustion airflow rate below that called for by the ratio means when the oxygen gas content of the gases issuing from the stove exhaust stack is above said preselected level.
  • the oxygen loop means includes means for keeping the magnitude of the increase or decrease in the airflow rate called for constant for intermittent time periods in order to compensate for the time which is required for changes made in the airflow rate to be manifested at a means for measuring the oxygen content of the gases issuing from the stove stack.
  • the system of claim 1 including means for keeping the natural gas flow rate called for from exceeding a predetermined maximum which is based on the blast furnace gas flow rate desired to be maintained to the burner.
  • the system of claim 5 including means for keeping the natural gas flow rate called for below a preselected percentage of the measured blast furnace gas flow rate to the burner.
  • the means for calling for a combustion airflow rate to be established or if established to be maintained to the burner further includes oxygen loop means for calling for a greater airflow rate than called for by the ratio means when the oxygen gas content of the gases issuing from the stove exhaust stack is below a preselected level and a lesser airflow rate than that called for by the ratio means when the oxygen gas content of the gas issuing from the stove exhaust stack is above said selected level.
  • the means for calling for a combustion airflow rate tobe established or if established to be maintained to the burner further includes means calling for a greater airflow rate than that called for by the ratio means and the oxygen loop means when the natural gas flow is zero and the measured dome temperature is greater than a predetermined maximum temperature.
  • the oxygen loop means includes means for keeping the greater or lesser flow rate called for constant for intermittent time periods in order to compensate for the time which is required for changes made in the airflow rate to be manifested at a means for measuring the oxygen content of the gases issuing from the stove stack.
  • a system for controlling the operation of a blast furnace stove during its ongas period said stove having a stove burner and associated blast furnace gas, natural gas and combustion air respectively to the stove burner, said lines each including both means for measuring and providing an indication of the gas flow rate therein and means for controlling the action of a valve in the line in response to the difference between the measured gas flow rate and a gas flow rate to be established or if established to be maintained in the line including a. temperature profile function generator means for providing an electrical output representative of the temperature desired to be established in thestove dome as a function of time during the on-gas cycle,
  • sensing means for measuring the stove dome temperature and developing an electrical signal measurably responsive thereto
  • natural gas flow proportional controller means for developing an output signal measurably responsive to the difference between the signals of the temperature profile function generator means and the sensing means, said signal being representative of a natural gas flow rate to be established or if established to be maintained to the burner as a function of the magnitude of the difference between the desired stove dome temperature and actual stove dome temperature,
  • means for developing an electrical signal representative of a combustion airflow rate to be established or if established to be maintained to the burner including ratio means for developing an electrical signal representative of a combustion airflow rate which is a preselected constant multiple of the measured blast furnace gas flow rate.
  • the means for developing an electrical signal representative of a combustion airflow rate to be established or if established to be maintained to the burner further includes oxygen analyzer means for developing an electrical signal representative of the oxygen gas content of the gases issuing from the stove stack and a combustion airflow proportional controller means for developing, in response to the electrical signal developed by the oxygen analyzer means and an electrical signal representative of an oxygen gas content desired to be maintained in the exhaust gases issuing from the stove stack, an electrical signal representative of an increase in the combustion airflow rate over that called for by the ratio means when the oxygen gas content of the gases issuing from the stove exhaust stack is below the desired level and a decrease in the combustion airflow rate below that called for by the ratio means when the oxygen gas content of the gases issuing from the stove exhaust stack is above said desired level.
  • the means for developing an electrical signal representative of a combustion airflow rate to be established or if established to be maintained to the burner further includes proportional controller means for developing, in response to the electrical signal developed by the temperature-sensing means and an electrical signal representative of a preselected maximum dome temperature, an electrical signal representative of an increase in the combustion airflow rate over that called for by the ratio means and the oxygen loop means when the natural gas flow is zero and the measured dome temperature is greater than the preselected maximum dome temperature.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Regulation And Control Of Combustion (AREA)
US875346A 1969-11-10 1969-11-10 Blast furnace stove control Expired - Lifetime US3602487A (en)

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US87534669A 1969-11-10 1969-11-10

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US (1) US3602487A (enrdf_load_stackoverflow)
DE (1) DE2054964A1 (enrdf_load_stackoverflow)
FR (1) FR2069721A5 (enrdf_load_stackoverflow)
GB (1) GB1283790A (enrdf_load_stackoverflow)
NL (1) NL7016341A (enrdf_load_stackoverflow)

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3768955A (en) * 1972-06-26 1973-10-30 Universal Oil Prod Co Reactant ratio control process
US3887326A (en) * 1971-02-08 1975-06-03 Ici Ltd Kilns and furnaces
US4033712A (en) * 1976-02-26 1977-07-05 Edmund D. Hollon Fuel supply systems
US4097218A (en) * 1976-11-09 1978-06-27 Mobil Oil Corporation Means and method for controlling excess air inflow
US4162889A (en) * 1976-12-14 1979-07-31 Measurex Corporation Method and apparatus for control of efficiency of combustion in a furnace
US4330261A (en) * 1979-09-17 1982-05-18 Atlantic Richfield Company Heater damper controller
US4360336A (en) * 1980-11-03 1982-11-23 Econics Corporation Combustion control system
US4369026A (en) * 1980-02-21 1983-01-18 Phillips Petroleum Company Control of the fuel/oxygen ratio for a combustion process
US4449918A (en) * 1981-07-06 1984-05-22 Selas Corporation Of America Apparatus for regulating furnace combustion
WO1986001581A1 (en) * 1984-08-29 1986-03-13 West John S System and process for controlling the flow of air and fuel to a burner
US4576570A (en) * 1984-06-08 1986-03-18 Republic Steel Corporation Automatic combustion control apparatus and method
EP0213940B1 (en) * 1985-08-30 1990-06-06 British Steel plc Method and apparatus for individual control of burners in a multiple burner system
US5168200A (en) * 1989-12-18 1992-12-01 Payne Kenneth R Automatic powered flowmeter valves and control thereof
US5532925A (en) * 1994-08-12 1996-07-02 Fisher Controls International, Inc. Current-to-pressure transducer with selectable, adjustable input filter
US6213758B1 (en) 1999-11-09 2001-04-10 Megtec Systems, Inc. Burner air/fuel ratio regulation method and apparatus
US20080211148A1 (en) * 2007-01-16 2008-09-04 U.S. Steel Canada Inc. Apparatus and method for injection of fluid hydrocarbons into a blast furnace
US20090142717A1 (en) * 2007-12-04 2009-06-04 Preferred Utilities Manufacturing Corporation Metering combustion control
WO2011065907A1 (en) * 2009-11-26 2011-06-03 Linde Ag Method for heatng a blast furnace stove
US9151492B2 (en) 2011-02-22 2015-10-06 Linde Aktiengesellschaft Heating apparatus

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3037936A1 (de) * 1980-10-08 1982-05-27 Robert Bosch Gmbh, 7000 Stuttgart Temperatur-regeleinrichtung fuer gas- oder oelbeheizte wassererhitzer
EP0121437A3 (en) * 1983-03-31 1985-01-23 Monarflex Limited Control system for a boiler or furnace
FR2544744B1 (fr) * 1983-04-22 1989-11-17 Solmer Batterie de fours pour chauffer de l'air injecte dans un haut fourneau et procedes de conduite automatique

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3887326A (en) * 1971-02-08 1975-06-03 Ici Ltd Kilns and furnaces
US3768955A (en) * 1972-06-26 1973-10-30 Universal Oil Prod Co Reactant ratio control process
US4033712A (en) * 1976-02-26 1977-07-05 Edmund D. Hollon Fuel supply systems
US4097218A (en) * 1976-11-09 1978-06-27 Mobil Oil Corporation Means and method for controlling excess air inflow
US4162889A (en) * 1976-12-14 1979-07-31 Measurex Corporation Method and apparatus for control of efficiency of combustion in a furnace
US4330261A (en) * 1979-09-17 1982-05-18 Atlantic Richfield Company Heater damper controller
US4369026A (en) * 1980-02-21 1983-01-18 Phillips Petroleum Company Control of the fuel/oxygen ratio for a combustion process
US4360336A (en) * 1980-11-03 1982-11-23 Econics Corporation Combustion control system
US4449918A (en) * 1981-07-06 1984-05-22 Selas Corporation Of America Apparatus for regulating furnace combustion
US4576570A (en) * 1984-06-08 1986-03-18 Republic Steel Corporation Automatic combustion control apparatus and method
WO1986001581A1 (en) * 1984-08-29 1986-03-13 West John S System and process for controlling the flow of air and fuel to a burner
GB2177493A (en) * 1984-08-29 1987-01-21 John S West System and process for controlling the flow of air and fuel to a burner
US4645450A (en) * 1984-08-29 1987-02-24 Control Techtronics, Inc. System and process for controlling the flow of air and fuel to a burner
EP0213940B1 (en) * 1985-08-30 1990-06-06 British Steel plc Method and apparatus for individual control of burners in a multiple burner system
US5168200A (en) * 1989-12-18 1992-12-01 Payne Kenneth R Automatic powered flowmeter valves and control thereof
US5532925A (en) * 1994-08-12 1996-07-02 Fisher Controls International, Inc. Current-to-pressure transducer with selectable, adjustable input filter
US6213758B1 (en) 1999-11-09 2001-04-10 Megtec Systems, Inc. Burner air/fuel ratio regulation method and apparatus
US20080211148A1 (en) * 2007-01-16 2008-09-04 U.S. Steel Canada Inc. Apparatus and method for injection of fluid hydrocarbons into a blast furnace
US7837928B2 (en) 2007-01-16 2010-11-23 U.S. Steel Canada Inc. Apparatus and method for injection of fluid hydrocarbons into a blast furnace
US20090142717A1 (en) * 2007-12-04 2009-06-04 Preferred Utilities Manufacturing Corporation Metering combustion control
WO2011065907A1 (en) * 2009-11-26 2011-06-03 Linde Ag Method for heatng a blast furnace stove
US9896735B2 (en) 2009-11-26 2018-02-20 Linde Aktiengesellschaft Method for heating a blast furnace stove
US9151492B2 (en) 2011-02-22 2015-10-06 Linde Aktiengesellschaft Heating apparatus

Also Published As

Publication number Publication date
NL7016341A (enrdf_load_stackoverflow) 1971-05-12
DE2054964A1 (de) 1971-05-19
GB1283790A (en) 1972-08-02
FR2069721A5 (enrdf_load_stackoverflow) 1971-09-03

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