US3689041A - Method of heating steel ingots soaking pits and combustion system for performing said method - Google Patents

Method of heating steel ingots soaking pits and combustion system for performing said method Download PDF

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Publication number
US3689041A
US3689041A US88281A US3689041DA US3689041A US 3689041 A US3689041 A US 3689041A US 88281 A US88281 A US 88281A US 3689041D A US3689041D A US 3689041DA US 3689041 A US3689041 A US 3689041A
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air
fuel
burner
burners
furnace
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US88281A
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English (en)
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Carlo Pere
Fulvio Tornich
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/70—Furnaces for ingots, i.e. soaking pits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • F23D14/46—Details, e.g. noise reduction means
    • F23D14/60—Devices for simultaneous control of gas and combustion air

Definitions

  • the burner includes two con; centric parts connected separately to commonfuel air manifolds so that one part may be switched off thereby causing higher rate of flow to the other burner part p 10 wipf lfi PAIENTED ms? 5 m2 SHEET t [If 4 VEN Toes.
  • the invention relates to a method of heating metal parts, particularly steel ingots or the like in soaking furnaces, particularly pit type furnaces, in which the furnace space is heated with the aid of a burner arrangement by the supply of fuel and air for combustion in suitably regulated proportions.
  • the most uniform possible temperature distribution in the furnace space may be achieved through intensive turbulence of the combustion gases, and the heating operation may consist of a heating-up period, in which the burner arrangement works at high heating rate and of a soaking period which follows and in which the burner arrangement works at reduced heating rate throughthe reduction of the total amount of fuel and air'for combustion supplied, while retaining the same fuel to air ratio.
  • the invention also relates to burner arrangements for carrying out such methods.
  • the problem underlying the invention consists in developing a method of this kind which reduces the total heating time, permits economical operation of the soaking or pit type furnace, and in conjunction with a general increase in output of the furnace plant provides uniform soaking of the furnace charge to the desired final temperature, for example rolling temperature, with the greatest possible accuracy.
  • this problem is solved by heating the furnace space walls during the heating-up period to a temperature which is higher than the highest permissible surface temperature of the furnace charge, while at least in the starting portion of the following soaking period the speed of admission of the fuel and air for combustion into the furnace chamber is increased to such an extent that the turbulence and uniformity of distribution of the combustion gases in the furnace space at least remain unchanged or are increased.
  • the furnace walls are thus first, that is to say in the heating-up period with the burner arrangement working at high or full power, heated to a temperature which is higher than the maximum permissible surface temperature of the furnace charge, that is to say than the temperature at which for example the surfaces of the steel ingots begin to melt.
  • Heat at high temperature is thus stored in the furnace space walls, while at the same time the still relatively cold furnace charge is heated rapidly and effectively by the hot combustion gases.
  • the burner arrangement is so constructed and designed, or is operated in such a manner, that in the entire furnace space the most uniform possible temperature distribution is achieved, particularly through intensive turbulence of the combustion gases.
  • the ratio of fuel to combustion air has a determined favorable value adapted to requirements in each particular case.
  • the power of the burner arrangement is reduced by throttling the total amount of fuel and air for combustion supplied, while retaining the same ratio of fuel to air for combustion.
  • the heat supplied by the burner arrangement and on the other hand the volume of combustion gases produced are correspondingly reduced. Consequently the furnace space walls, which were superheated during the heating-up period to a higher temperature than the maximum permissible surface temperature of the furnace charge, now give up their stored heat to the furnace charge and thereby provide the heat still required for the soaking of the furnace charge even though the power of the burner arrangement is now throttled.
  • Any desired gaseous fuel for example generator gas, blast furnace gas, coke oven gas, and the like, or any desired liquid or solid fuel, which however must be capable of being brought into a gaseous or gas-like condition, for example an atomized or gasified liquid fuel or a mixture of pulverized coal and air, or the like, may be used as fuel for carrying out the method according to the invention.
  • a gaseous or gas-like condition for example an atomized or gasified liquid fuel or a mixture of pulverized coal and air, or the like, may be used as fuel for carrying out the method according to the invention.
  • the speed of admission of the fuel and air for combustion into the furnace space may have any desired absolute value both during the heating-up period and in the soaking period.
  • this speed of admission in conjunction with the construction or design of the burner arrangement, should ensure the greatest possible turbulence and the most uniform distribution of the combustion gases in the furnace space during the heating-up period with the burner arrangement operating at full power, and that in the following soaking period, with the burner operation operating at reduced power, this speed should be increased to such an extent that in consequence of the correspondingly higher turbulence of the combustion gases, at least the same uniform distribution of the combustion gases is maintained.
  • the invention provides a burner arrangement which is characterized by at least two burners, each with a fuel supply pipe and an air supply pipe, and also by control means, controlled automatically in dependence on the temperature in the furnace space, for throttling the fuel and air supply pipes of one burner and simultaneously correspondingly increasing the pressure in the fuel and air supply pipes of the other burner, at least in the initial portion of the soaking period, while the ratio of the fuel to air for combustion remains constant for both burners.
  • both burners may work practically with full power, the total amount of fuel and air for combustion supplied to the two burners corresponding to heat requirements for heating the furnace space walls to a predetermined maximum temperature which is higher than the maximum permissible surface temperature of the furnace charge.
  • the pressure in the fuel and air supply pipes for both burners, and consequently also the speed of admission of the fuel and air for combustion into the furnace space, which is dependent thereon, are so high that the turbulence of the combustion gases in the furnace space ensures the desired uniform temperature distribution.
  • the fuel and air supply pipes of one burner are automatically throttled progressively by the control means responding to the furnace space temperature, until the burner in question is completely disconnected or stopped. The entire amount of fuel and air for combustion introduced into the furnace space, and consequently both the heat supplied and the volume of the combustion gases produced, are thereby reduced.
  • the two burners are combined in a common burner head and disposed coaxially relative to each other, with concentric annular outlet nozzles for fuel and air.
  • the increase in pressure in the fuel and air supply pipes of one burner in dependence on the throttling of the fuel and supply pipes of the other burner can be achieved in a particularly simple manner by connecting on the one hand the fuel supply pipes and on the other hand the air supply pipes of both burners through respective fuel and air manifolds to common fuel and air blowers, while the fuel and air supply pipes of one burner are provided with simultaneously operable throttle elements.
  • the throttle elements in the fuel and air supply pipes of one burner need be closed simultaneously, whereby the pressure in the fuel and air supply pipes of the other burner is automatically increased while the fuel and air blowers continue to run unchanged.
  • FIG. 1 shows a burner arrangement for carrying out the method according to the invention, illustrated diagrammatically,
  • FIG. 2 is a longitudinal section of the burner head with two coaxial burners
  • FIG. 3 is an elevation of the burner head, viewed from the right-hand side in FIG. 2, and
  • FIG. 4 shows some characteristic curves of the method according to the invention during the heatingup and soaking periods.
  • FIG. 1 illustrates diagrammatically a pit type furnace 1 with a cover plate 101 and waste gas offtake 3 leading into a chimney 2.
  • the pit type furnace l is heated with the aid of a burner arrangement which is illustrated diagrammatically in FIG. 1 and of which a preferred form of construction is shown in FIGS. 2 and 3.
  • This burner arrangement consists of at least one burner head 4 provided in the side wall of the pit type furnace l and associated with two burners disposed coaxially one around the other and operated with a mixture of gaseous fuel, for example, coke oven gas and air for combustion.
  • the two burners consist of an air chamber 5 and three tubes 6, 7, and 8 disposed in said air chamber coaxially around one another and spaced radially apart.
  • the air chamber 5 is connected on the one hand to an air supply pipe 9 and on the other hand to a ring of air outlet nozzles 10 disposed in the burner head.
  • the air outlet nozzles 10 are inclined convergingly in relation to the longitudinal axis of the burner (as shown in FIG. 2) and at the same time are also directed obliquely to the respective radial planes, so that the axes of the nozzles do not pass through the axis of the burner as can be seen in particular from FIG. 3.
  • the outer tube 6 is joined to a fuel supply pipe 11 and leads into a central outlet aperture 12 in the burner head 4.
  • the other two coaxial pipes 7 and 8 likewise lead into the central outlet aperture 12 of the burner head 4, the intermediate tube 7 being connected by an elbow 13 to an air supply pipe 14 and the innermost tube 8 to a fuel supply pipe 15.
  • the air chamber 5, with the air outlet nozzles 10, and the outer fuel tube form a first, outer burner associated with the air and fuel supply pipes 9 and 1 1.
  • the intermediate air tube 7 and the innermost fuel tube 8 form a second, inner burner with the associated air and fuel supply pipes 14 and 15.
  • the air supply pipes 9, 14 of both the outer burners 5, 6 and the inner burner 7, 8 are connected through an air manifold 16 to a common air blower 17, as illustrated particularly in FIG. 1.
  • the fuel supply pipes 11 and 15 of the two burners 5, 6 and 7, 8 are likewise connected by a fuel manifold 18 to a common fuel blower l9.
  • Throttle elements 20 and 21 respectively are provided in the air supply pipe 9 and in the fuel supply pipe 1 1 of the outer burner 5, 6.
  • the air and fuel manifolds 16 and 18 respectively are likewise each provided with a throttle element 22 and 23 respectively.
  • the throttle elements 20, 21, 22, 23 are operated by electrical adjusting motors 120, 121, 122 and 123 respectively.
  • the adjusting motors and 122 of the throttle elements 20 and 22 in the air supply pipe 9 of the outer burner 5, 6 and in the air manifold 16 associated with the two burners 5, 6 and 7, 8 are controlled by a temperature sensor 25 responding to the temperature of the inner wall of the pit furnace 1, with the aid of a thermoelectric transducer 25 and a control device 26, which is known in itself.
  • the suction pipes 117 and 119 of the air and fuel blowers 17 and 19 respectively each contain a flow measuring device 27 and 29 respectively, these devices being known in themselves.
  • These measuring devices 27, 29 are each connected by a respective transducer 127 and 129 to a controller 28, which is likewise known in itself and which controls the adjusting motor 121 of the throttle element 21 in the fuel supply pipe 11 of the outer burner 5, 6 and the adjusting motor 123 of the throttle element 23 in the fuel manifold 18 associated with the two burners 5, 6 and 7, 8.
  • the controller 28 is constructed in a manner known in itself so that in the event of fluctuations of the flows in the suction pipes 1 17, l 19 of the air and fuel blowers l7, l9, and particularly in theevent of variations of the air flow in the suction pipe 117 of the air blower 17, it operates the throttle elements 21, 23 so as to maintain a predetermined, adjustable and readjustable fuel/air for combustion ratio in both the coaxial burners.
  • FIG. 4 shows the following characteristic curves plotted against time T:
  • Curve I-I Pressure of fuel and air for combustion in the outer burner 5, 6, in millimeters of water column.
  • Curve K Pressure of fuel and air for combustion in the inner burner 7, 8, in millimeters of water column.
  • Curve L Total inflow of fuel and air for combustion in both burners 5, 6 and 7, 8 as a percentage of the total fuel and air for combustion inflow with both burners at full power.
  • Curve M Temperature of combustion gases in the pit furnace space, in C.
  • Curve N Temperature of inner wall of pit furnace space, in C.
  • the heating-up period A extends to the point of time T1 and then the soaking period D commences.
  • S indicates the maximum permissible surface temperature of the steel ingots, that is to say the temperature at which the surfaces of the ingots begin to melt.
  • the throttle elements 20, 21 in the air and fuel supply pipes 9, ll of the outer burner 5, 6 are open. Both burners 5, 6 and 7, 8 work at full power.
  • the throttle elements 22 and 23 in the air and fuel manifolds 16, 18 are opened to such an extent that on the one hand the adjusted ratio of fuel to air for combustion and on the other hand the total inflow of fuel and air for combustion required for maximum power operation of both burners 5, 6 and 7, 8 are achieved.
  • the pressure in the air and fuel manifolds 16, 18 and in the air and fuel supply pipes 9, 11 and 14, branching off therefrom and feeding the two burners 5, 6 and 7, 8 respectively, is so high that the admission speed of the fuel and air for combustion entering the pit type furnace 1, which is pressure dependent, is correspondingly high and gives rise to great turbulence of the combustion gases and consequently uniform distribution of the combustion gases and of the temperature in the furnace space.
  • the still relatively cold steel ingots absorb heat from the hot combustion gases, while at the same time the walls of the pit type furnace l are heated.
  • the heating-up period A lasts until the walls of the pit type furnace reach a temperature N] which is higher than the maximum permissible surface temperature S of the steel ingots.
  • the temperature sensor 24 responds to this maximum temperature N1 of the furnace space walls and by means of the control device 26 and the adjusting motor 120 effects the gradual closing of the throttle element 20 in the air supply pipe 16 of the outer burner 5, 6.
  • the measuring instrument27 disposed in the suction pipe 117 of the air blower 17 responds to the reduction of air flow produced by the closing of the throttle element 20.
  • the controller 28 consequently closes the throttle element 21, by means of the adjusting motor 121.
  • This increased speed of the air for combustion and fuel feeding the inner burner 7, 8 is so great that even though the total volume of combustion gases produced in now smaller it produces approximately the same intensive turbulence of the combustion gases in the furnace l as in the heating-up period A, or even produces still greater turbulence and consequently, despite the reduced power of the burners, ensures uniform distribution of the combustion gases and of the temperature in the furnace space.
  • the temperature of the combustion gases consequently rises slightly further and is stabilized at the temperature value M2, which is still lower than the maximum permissible surface temperature S of the steel ingots.
  • the temperature of the furnace space walls retains its maximum value N1 for a relatively short time and then gradually declines.
  • the controller 28 which maintains unchanged the adjusted ratio of air for combustion to fuel, simultaneously closes by means of the adjusting motor 123 the throttle element 23 in the fuel manifold 18.
  • the inflow of fuel and air for combustion drops further from the value L2 corresponding to the full power of the inner burner 7, 8, while at the same time the pressure of the fuel and of the air for combustion in the inner burner 7, 8 drop from the maximum value L2 which it had attained.
  • the main advantage of the method according to the invention consists in that the furnace charge, for example the steel ingots disposed in the pit type furnace l, is heated uniformly throughout to the desired temperature in a substantially shorter time than by known methods, while the burner arrangement proposed according to the invention as being preferable for carrying out this method has a particularly simple, compact, operationally reliable, and economical construction.
  • the invention is naturally not restricted to the example of embodiment illustrated and described, but within the framework of the general principle of the invention various modifications are possible.
  • other burner arrangements may be used for carrying out the method according to the invention.
  • the burner arrangement proposed in accordance with the invention may also be modified in respect of its construction or operation.
  • the inner burner 7, 8 may be :throttled or put out of action and the outer burner 5, 6 kept in operation.
  • the throttle elements 20, 21 it is merely necessary for the throttle elements 20, 21 to be disposed in the air and fuel supply pipes 14 and respectively of the inner burner 7, 8 instead of in the supply pipes 9, 11 of the outer burner.
  • a soaking furnace including furnace walls enclosing a furnace space to contain an ingot to be treated and a burner arrangement connected thereto, comprising at least two burners, each of which is provided with a fuel supply pipe and an air supply pipe, and control means controlled automatically in dependence on the temperature in the furnace space for throttling the air and fuel supply pipes of one burner and causing simultaneous corresponding increaseof pressure in the air and fuel supply pipes of the other burner at least in the initial portion of the soaking period, the ratio of fuel to air for combustion remaining constant for both burners.
  • a burner arrangement according to claim 1 in which the two burners arecombined in a common burner head and are disposed coaxially around one another with concentric annular outlet nozzles for fuel and air.
  • a burner arrangement according to claim 2 in which on the one hand the air supply pipes and on the other hand the fuel supply pipes of the two burners are each connected by an air manifoldand a fuel manifold to common air and fuel blowers, and that the air and fuel supply pipes of one burner are provided with simultaneously operable throttle elements.
  • a burner arrangement in which the throttle element in the air supply pipe of one burner is controlled by a control device responding to the temperature in the furnace space and the throttle element in the fuel supply pipe of the same burner is controlled by a controller maintaining an adjusted ratio of fuel to air.
  • a burner arrangement according to claim 4 in which the air and fuel manifolds common to the two burners are each provided with a throttle element downstream of the respective air and fuel blowers, and these throttle elements can be operated simultaneously while retaining the same ratio of fuel to air.
  • a burner arrangement in which the throttle element in the air manifold is controlled by a control device responding to the temperature in the furnace space or to the temperature of the furnace charge, and the throttle element in the fuel manifold is controlled by a controller maintaining an adjusted ratio of fuel to air.
  • a method of heating metal ingots in a soaking furnace of the type including a pair of concentric burners having separate individual fuel and air supply systems, the steps of heating the soaking furnace walls to a temperature of the maximum permissible surface temperature of the metal ingot by initially operating both burners at their maximum capacity producing an intense turbulence of the combustion gases in the furnace space, reducing the total fuel and air supplied to the burners during a soaking period while simultaneously increasing the speed of admission of the fuel and air for combustion into the furnace space to an extent such that the turbulence of the combustion gases in the furnace space does not initially decrease.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Combustion & Propulsion (AREA)
  • General Engineering & Computer Science (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Furnace Details (AREA)
  • Regulation And Control Of Combustion (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
US88281A 1969-11-15 1970-11-10 Method of heating steel ingots soaking pits and combustion system for performing said method Expired - Lifetime US3689041A (en)

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IT744869 1969-11-15

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US (1) US3689041A (fr)
BE (1) BE758886A (fr)
CA (1) CA943761A (fr)
DE (1) DE2054608C3 (fr)
FR (1) FR2069232A5 (fr)
GB (1) GB1329578A (fr)
LU (1) LU62061A1 (fr)
NL (1) NL7016702A (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4083677A (en) * 1976-09-22 1978-04-11 Bloom Engineering Company, Inc. Method and apparatus for heating a furnace chamber
US4108594A (en) * 1976-12-06 1978-08-22 Venetta, Inc. Method for fuel/air feed pressure control by stack temperature
US4120642A (en) * 1976-05-25 1978-10-17 Nippon Kokan Kabushiki Kaisha Method for heating ingot in soaking pit
US20090214989A1 (en) * 2008-02-25 2009-08-27 Larry William Swanson Method and apparatus for staged combustion of air and fuel
US20150232770A1 (en) * 2012-08-14 2015-08-20 Thyssenkrupp Industrial Solutions Ag Device and method for introducing oxygen into a pressurized fluidized-bed gasification process
SE2250969A1 (en) * 2022-08-16 2024-02-17 Luossavaara Kiirunavaara Ab A gas heater assembly for a gas heating process and a system for a gas heating process

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2189591B (en) * 1986-04-18 1989-11-29 British Gas Plc Heating method and system

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2543388A (en) * 1946-12-20 1951-02-27 Steel Proc Company Method of furnace operation
US2776827A (en) * 1953-06-24 1957-01-08 Amsler Morton Corp Method of alternate low and high fuel firing of a soaking pit furnace

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2543388A (en) * 1946-12-20 1951-02-27 Steel Proc Company Method of furnace operation
US2776827A (en) * 1953-06-24 1957-01-08 Amsler Morton Corp Method of alternate low and high fuel firing of a soaking pit furnace

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4120642A (en) * 1976-05-25 1978-10-17 Nippon Kokan Kabushiki Kaisha Method for heating ingot in soaking pit
US4083677A (en) * 1976-09-22 1978-04-11 Bloom Engineering Company, Inc. Method and apparatus for heating a furnace chamber
US4108594A (en) * 1976-12-06 1978-08-22 Venetta, Inc. Method for fuel/air feed pressure control by stack temperature
US20090214989A1 (en) * 2008-02-25 2009-08-27 Larry William Swanson Method and apparatus for staged combustion of air and fuel
US7775791B2 (en) * 2008-02-25 2010-08-17 General Electric Company Method and apparatus for staged combustion of air and fuel
US20150232770A1 (en) * 2012-08-14 2015-08-20 Thyssenkrupp Industrial Solutions Ag Device and method for introducing oxygen into a pressurized fluidized-bed gasification process
US9862900B2 (en) * 2012-08-14 2018-01-09 Thyssenkrupp Industrial Solutions Ag Device and method for introducing oxygen into a pressurized fluidized-bed gasification process
SE2250969A1 (en) * 2022-08-16 2024-02-17 Luossavaara Kiirunavaara Ab A gas heater assembly for a gas heating process and a system for a gas heating process

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Publication number Publication date
LU62061A1 (fr) 1971-05-11
GB1329578A (en) 1973-09-12
BE758886A (fr) 1971-04-16
DE2054608A1 (de) 1971-05-27
DE2054608B2 (de) 1979-07-05
FR2069232A5 (fr) 1971-09-03
NL7016702A (fr) 1971-05-18
CA943761A (en) 1974-03-19
DE2054608C3 (de) 1980-03-06

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