EP0479378B1 - Lit fluidisé avec combustion interne de gaz - Google Patents

Lit fluidisé avec combustion interne de gaz Download PDF

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Publication number
EP0479378B1
EP0479378B1 EP19910202512 EP91202512A EP0479378B1 EP 0479378 B1 EP0479378 B1 EP 0479378B1 EP 19910202512 EP19910202512 EP 19910202512 EP 91202512 A EP91202512 A EP 91202512A EP 0479378 B1 EP0479378 B1 EP 0479378B1
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EP
European Patent Office
Prior art keywords
fluidized bed
flow rate
gas
fuel gas
reference value
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EP19910202512
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German (de)
English (en)
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EP0479378A1 (fr
Inventor
Jozef Weedaeghe
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Bekaert NV SA
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Bekaert NV SA
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    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C21D1/53—Heating in fluidised beds
    • 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
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/567—Continuous furnaces for strip or wire with heating in fluidised beds
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B15/00—Fluidised-bed furnaces; Other furnaces using or treating finely-divided materials in dispersion
    • F27B15/02—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B15/18—Arrangements of controlling devices

Definitions

  • a fluidized bed furnace for internal gas combustion.
  • a fluidized bed furnace comprises a container that is filled to a certain height with granules that form the fluidized bed.
  • the granules are inert to high temperatures of 1500°C and more.
  • At the bottom of the granule bed there is an inlet adapted for blowing a carrying gas upwards into the bed, with an input flow that is as equally as possible distributed over the bottom surface of the bed.
  • the granules come to whirl up and down and the bed swells up so as to behave like a fluid in which a body can easily be immersed or which can easily be traversed continuously by a body such as by metal wires or wire mesh.
  • This fluid then has a high heat exchange coefficient with such bodies, which already comes near to the coefficient for liquids, as in lead or salt baths, and owing to the great mobility of the granules, the heat is very rapidly distributed over the bed.
  • a fluidized bed is consequently very adapted for heat treatment of such bodies.
  • Typical granule materials are silica-, alumina- or zirconiasand, silicon carbide or ferrosilicon, and typical granule dimensions lie in the range between 0.03 and 0.5 millimeter, preferably between 0.1 and 0.3 millimeter.
  • the blowing speed into the bed depends on the chosen type of granule, and typical speeds lie in the range between 0.06 and 0.15 meter per second. At a too low blowing speed, the fluidized bed collapses, and gas bubbles, bubbling up from the bed are only obtained. At a too high blowing speed, the granules are blown out of the bed, so that in both cases there is no fluidization.
  • a fluidized bed is often used for the warming up of bodies in the fluidized bed, in cases where the heat delivery has to be distributed as equally as possible over the surface of the body that has to be warmed up.
  • the heat source can be located outside said container. In that case, the heat has first to pass, by conduction, through the container wall before it can be delivered to the bed (external heating). But the heat source can also be located inside the container, in which case the heat is directly delivered to the whirling granules (internal heating). In the latter case, the heat source can be an electrical resistance, but it can also be a gas flame, when a fuel gas is blown in the bed together with oxygen, and burns in the bed.
  • An application for such fluidized bed furnace lies in the field of heat treatment of metallic products, especially where a fluidized bed temperature is necessary above the self ignition temperature of conventional fuel gas (i.e. above about 750°C), so that accidentally extinguished flame parts immediately come to inflame again, whereby a stable flame can be maintained.
  • a fluidized bed temperature is necessary above the self ignition temperature of conventional fuel gas (i.e. above about 750°C), so that accidentally extinguished flame parts immediately come to inflame again, whereby a stable flame can be maintained.
  • a fluidized bed furnace with internal gas combustion comprises a gas supply arrangement that comprises the necessary means to send a given flow of carrying gas, with a given composition, towards the inlet for the carrying gas at the bottom of the fluidized bed.
  • the outlet of that gas supply arrangement is consequently connected with the inlet for the carrying gas.
  • a mixture is used of the fuel gas that has to be burnt, and of an insufficient quantity of primary air, i.e. a quantity below the necessary proportion for ignition.
  • an additional quantity of secondary air is blown in, so that the flame begins at the height at which the mixture reaches said necessary proportion for ignition.
  • This gas supply arrangement for making up the gas mixture consequently comprises a first inlet that has to be connected with a source of fuel gas, e.g. a gas pipe under pressure, or a chamber in which the fuel gas is produced. That supply arrangement also comprises a second inlet that has to be connected with an air source, e.g. an air duct where the air is blown, by means of a ventilator, towards the gas supply arrangement.
  • a source of fuel gas e.g. a gas pipe under pressure, or a chamber in which the fuel gas is produced.
  • That supply arrangement also comprises a second inlet that has to be connected with an air source, e.g. an air duct where the air is blown, by means of a ventilator, towards the gas supply arrangement.
  • the temperature in the fluidized bed is regulated from a sensor of the temperature, and correction is given by means of a control device which, in dependence on the deviation of the measured temperature from the desired reference temperature, makes that more or less fuel gas is supplied.
  • the invention consequently relates to a fluidized bed furnace for internal gas combustion, having a fluidized bed container of which the inlet for the carrying gas is connected with a gas supply arrangement that comprises a first and second inlet for fuel gas, respectively air, and that comprises a sensor of the temperature in the fluidized bed, said sensor being connected with the input of a control device.
  • a first important parameter of operation is the temperature T in the fluidized bed.
  • This temperature has to be regulated in order to be maintained at a desired reference value. Otherwise, and without any control, the temperature can deviate too far from the desired temperature, for instance when the production line speeds up or slows down, or when there is a switch-over towards another product, so that the heat that has to be taken up by the product is considerably changed, or when there is a switch-over towards another fuel gas with more or less combustion heat, or when fuel gas is received with largely fluctuating combustion heat. For that reason, it is necessary that the control device would be able to vary the supply of the fuel gas between very large limits, and even towards zero, in order to be able to react very strongly on the temperature variations.
  • a second important parameter of operation is the degree of oxydation/reduction of the combustion gas athmosphere above the flame.
  • a slight oxydation is desired at the surface of the steel wire, but in that case always to the same degree, or a slight reduction (e.g. decarbonization of steel), but then also always to the same degree.
  • a neutral athmosphere is desired, where the combustion gas athmosphere is the product of a complete combustion without excess of oxygen, and has to be maintained as such.
  • a third important parameter of operation is the condition of fluidization of the fluidized bed. It is not sufficient that the upward speed of the blown-in carrying gas would not come below the fluidization limit. It is also necessary that the pattern of the gas stream in het fluidized bed should be stable, so that a constant flame pattern can be maintained. It must also be avoided as much as possible that the flame would go up and down in dependence on the content of fuel gas in the carrying gas, or on the inlet speed of the latter. And it must especially be avoided that the flame would come down to the bottom of the fluidized bed container, which would then be damaged by heat, and further penetrate upstream into the supply arrangement.
  • the flow rate of startery air shall have to be strongly reduced by the control system, in order to keep the total quantity of air, primary and propely, in the same proportion with respect to the reduced quantity of fuel gas.
  • the inverse occurs when the temperature falls down.
  • the three fluidized bed operation parameters cannot simultaneously be regulated in order to be maintained each at a desired reference value.
  • the temperature is regulated by means of steering the fuel gas flow rate, then the total flow rate of the primary and secondary air has to be adjusted in proportion, and then no constant gas stream pattern can be maintained.
  • the proportion varies between the primary air and the fuel gas, so that the flame goes up and down under such variations, and can penetrate inside the supply arrangement when the proportion comes below the ignition limit.
  • this method does not allow very broad limits between which the fuel gas flow rate can be steered. Always a minimum flow rate of fuel gas is needed in order to deliver, together with the primary air, the necessary constant flow rate of carrying gas.
  • the carrying gas has to be blown in at a sufficient speed and in a sufficient concentration of fuel gas in order not to be inflammable and not to penetrate upstream into the gas supply arrangement.
  • the fuel gas has also a maximum flow rate, above which so much secondairy air has to be supplied, which is then insufficiently mixed with the carrying gas, in such a way that locally varying oxydation problems arise. In this way, it is not possible to simultaneously regulate the three fluidized bed operation parameters to a desired level each, without having to abandon the control of one of these, or to concede something with respect to two or all three of them.
  • the gas supply arrangement comprises, in addition to the two inlets for air and fuel gas, a further third inlet for flue gas, and each of said three inlets comprises a supply device adapted for steering the corresponding inlet flow rate and having a steering signal input, connected with the output of said control device, said control device being arranged for steering the flow rate of said three inlets in a way as to maintain the carrying gas flow rate, the ratio air flow rate to fuel gas flow rate, and the temperature of the fluidized bed each at a respective reference value.
  • a control device is added to the system, in which these three flow rates are used as independently steerable variables in order to control three other variables that depend thereon: temperature of the bed, air to fuel gas proportion, and flow rate of carrying gas, by which the operating conditions of the fluidized bed are the determined.
  • the three inlets are consequently provided each with a supply device of which the flow rate can be steered.
  • these will be supply valves with steerable opening and having a steering signal input for receiving the signal for steering the opening.
  • the control device shall have to take into account that the flow rate is determined not only by the opening, but also by the pressure drop over the valve.
  • the manner in which the flow rate Qc of the carrying gas will be regulated to a reference value will similarly also depend on the design of the control device, as well the way for measuring the actual value that has to be regulated, as the way for readjusting that value.
  • the device When the total flow rate deviates from the reference value, then this can be observed by the device, either via addition of the three measured flow rates, or by measurement of the total flow.
  • the latter measurement can be made, either by measuring the pressure drop over a narrowing of the flow duct, or by measuring the overpressure, above athmospheric, of the gas on its transition from the supply arrangement towards the inlet for the carrying gas in the fluidized bed, because this overpressure is a function of the flow rate of the carrying gas.
  • the correction can be given, either to the flow rate of one of the components, or to two of them, or to all three in the desired proportion.
  • the ratio air flow rate to fuel gas flow rate can be regulated in different ways, depending on the design of the control device.
  • the device may measure the actual proportion (e.g. by division of the two measured inlet flow rates), and compare this to a reference value, in order to produce a signal for readjustment. But the device may for instance also multiply one measured inlet flow rate with the reference-ratio, and use the result as a reference value for steering the other inlet flow rate.
  • the reference values for the three magnitudes are desired values towards which the actual values are regulated by the control device.
  • Each reference value can be a constant value, determined by the internal parameters of the device, but shall preferably be an externally adjustable value, that is adjusted when switching over from one product or production manner to another. It can however also be a steerable value, that is steered by an input signal that is transmitted towards the control device from another control device, that continuously adjusts the reference value in function of, for instance, continuous measurements of the exit properties of the product.
  • the regulation towards the reference value can be done, as is known in control engineering, either by the proportional, or the proportional-integral, or the proportional-integral-differential principle.
  • the control device can be carried out either in an analog or in a digital manner, for instance, by a computer, in which the functions are not performed by separate components, but by programmes.
  • the measurements, signals and corrections can be continuous or intermitting.
  • the invention also relates to a process for steering a fluidized bed furnace with internal gas combustion, in which a carrying gas is blown into the fluidized bed and has, as a first and second component, a quantity of fuel gas and of air respectively, and in which the temperature of the fluidized bed is regulated on a reference value.
  • the process according to the invention is here characterized by the fact that said carrying gas comprises, as a third component, a quantity of flue gas, and that said carrying gas is supplied from three sources of said three components respectively, the flow rate of each of which being steered so as to regulate, simultaneously with the temperature, also the carrying flow ratio and the ratio of air flow rate to fuel gas flow rate, on a respective reference value.
  • the combustion gases of the fluidized bed itself are used as a source for said third component.
  • the flue gas that is blown in must not necessarily be neutral as to its oxydation/reduction decree, i.e. to be the procuct of a complete combustion without excess of oxygen.
  • the reference value for the air to fuel gas ratio can be adapted and continuously regulated, so that the desired oxydation/reduction degree is obtained after combustion.
  • the regulation is however very simple when the combustion athmosphere of the fluidized bed has to be neutral, and the flue gas is also derived from above the same fluidized bed.
  • the reference value for the air to fuel gas ratio is set at the stoechiometric ratio air/fuel gas, and must not further be adapted in function of the oxydation/reduction degree of the flue gas.
  • This reference value shall however possibly have to be set in function of the fuel gas in use, and have to be readapted when the composition of the fuel gas fluctuates.
  • Figure 1 shows a fluidized bed furnace according to the invention, adapted for continuously austenitizing steel wires in the patenting heat treatment operation, although the invention is not limited to this application.
  • the steel wires are firstly heated up to a temperature in the range from about 900 to about 1050°C, and directly thereafter quenched to a temperature in the range around about 550°C, e.g. in a quenching bath or in a fluidized bed.
  • This is in general a continuous operation, in which the wires that have to be treated are continuously guided side by side and in parallel in axial direction of the wire through the heating furnace and the quenching device.
  • the invention is applied to a heating furnace that is carried out as a fluidized bed furnace, that is consequently provided with the necessary access openings an wire guiding means (not shown), in order to guide the wire 33 in and out the fluidized bed.
  • a typical bed height ranges then around 40 to 60 centimeter.
  • the furnace comprises a container 1, made of refractory material. At the bottom of the container, there is a distribution chamber 2 that extends over the whole bottom surface of the container.
  • the distribution chamber has a horizontal upper wall. This wall is traversed by a multitude of small vertical gas pipes 3, that project for about 6 centimeter above that wall. They serve to blow the carrying gas vertically upward. They are equally distributed over the upper surface of the distribution chamber, so that the flow of carrying gas is about equally distributed over the horizontal cross-section of the container. These pipes are carried out as explained in European patent N° 181 653.
  • the function of the distribution chamber is to take care that the carrying gas would be blown in under the same pressure over the whole bottom surface of the fluidized bed, and this is obtained by the fact that the carrying gas comes from a common room 2 at the same pressure.
  • the carrying gas is not blown in through gas pipes, as in this example, but through a ceramic floor that separates the distribution chamber from the fluidized bed above, and that is porous or has a multitude of openings that are equally distributed over its surface.
  • Each sort of inlet to the fluidized bed is usable, even without distribution chamber, but where the carrying gas is blown in upwardly and with a flow that is equally distributed over the horizontal cross section of the bed.
  • the pressure for blowing in can approximately be made equal over the pipes, by supplying them from ducts that do not lie in series, but are connected in parallel.
  • Al2O3 alumina sand
  • the supply arrangement for the carrying gas also comprises a mixing chamber (5) with three entries 6, 7 and 8, respectively for air, fuel gas and flue gas.
  • a supply valve, respectively 9, 10 and 11, is associated to each of these entries, the inlet flow rate of each valve being steerable in response to a steering signal that is entered at a steering signal input 12, 13 and 14 respectively.
  • This signal can be a pneumatic, mechanical or electrical signal, either analog or digitally coded.
  • the steering signal input shall consequently be adapted to the sort of signal that it has to receive.
  • the supply valve for the air is connected at its inlet 22 to an air source 15 that is at sufficient overpressure with respect to the mixing chamber 5, e.g. 1500 mm above athmospheric pressure, so that the air can be blown towards that mixing chamber with the desired flow rate.
  • This pressure is obtained by sucking the air through ventilator 15, possibly preceded by a filter.
  • ventilator 17 is connected with an outlet 18 for the combustion gases of the fluidized bed itself, via a cyclone 19, a heat exchanger 20 for cooling the combustion gases towards a temperature that is no longer detrimental to the construction of the gas supply arrangement (e.g.
  • the supply valve for the fuel gas is connected at its inlet 23 to a fuel gas source under sufficient pressure (not shown), e.g. a gas pipe 16 supplying propane or natural gas.
  • the steering signal inputs 12, 13 and 14 for the supply valves are connected with the output 26 of a control device 25.
  • the nature of the steering signals can be mechanical as well as pneumatic or electrical, analog or digitally coded, said output has to be adapted to the nature of the signal that it has to send out.
  • the mixing of the three gases is carried out in one single mixing chamber 5.
  • two gases e.g. fuel gas with air
  • the third gas at a second location of confluence, together with the mixture of the first two gases.
  • the flow rate of each gas is not only determined by the opening of the supply valves, but also by the pressure drop between the inlet of each valve and the mixing chamber. The steering of each of said flow rates shall consequently have to take this pressure drop into account.
  • the inlet pressure of each gas is measured at the inlet locations 22, 23 and 24, and also the pressure in the mixing chamber 5, and the measurement signals are transmitted towards an input 27 of the control device.
  • the nature of these signals can be mechanical, as well as pneumatic or electrical.
  • this control device everything is calculated and steered from a central control device 25 that treats these pressure signals together with the other input signals so as to create output signals that are then to be transmitted towards the steering signal inputs of the supply valves.
  • a more decentralized supply device can be designed, in which these pressure drops are taken into account in another way.
  • the control device further comprises a sensor 31 of the flow rate Qc of the carrying gas that is sent to the fluidized bed chamber, and the output of that sensor is connected with the input 28 of the control device.
  • This sensor can for instance be a meter of the pressure difference between both sides of a diaphragm, where this voltage difference is representative of the volumetric flow rate.
  • the overpressure above atmospheric can also be representative of this volumetric flow rate, and consequently, a sensor of this overpressure can also be used. In that case, the control device shall keep this overpressure at a constant value, e.g. at 800 mm.
  • the control device further comprises another sensor 32 of the temperature T in the fluidized bed, and of which the output is connected with the input 29 of the control device.
  • Such sensor can, for instance, be a thermocouple.
  • the input of the control device is further provided with an adjustment button 30, where the desired ratio of air to fuel gas (L/G) can be preset. In this case, the desired ratio is determined by the position of the button. But this desired ratio can also be introduced as a signal entering via a signal input, when this ratio has to vary frequently without any human intervention.
  • L/G desired ratio of air to fuel gas
  • the fluidized bed is traversed by steel wires 33, perpendicular to the plane of the figure, that continuously travel through the bed in their longitudinal direction.
  • the control device 25 is presented in this example as a black-box, because it can be designed in various ways, pneumatically, electrically, digital or analog, with continuous or intermitting signals, steered by a computer programme or not.
  • the important thing in this invention is not how the regulation is realized, but what the variables are that are regulated, and by means of what independently steerable variables.
  • the function of the control device lies herein, that the flow rate Qc (volumetric) of carrying gas, the fluidized bed temperature T, and the ratio air flow rate to fuel gas flow rate (L/G) are each regulated on a respective reference value, and this by means of three steering variables that have to achieve the reduction of the deviations from the reference values: the flow rates of fuel gas, of air, and of flue gas.
  • Different concepts are possible for the control device, where some types may aim at simplicity, others at accuracy or reaction speed, and still others at safety. In general, such design lies in the normal activity of the man, skilled in control engineering, although particularly ingenuous concepts may exist.
  • FIG 2 shows a very simple concept for the control device.
  • the fuel gas as delivered from gas pipe 16 and via duct 37, flows together first with the air, the latter being delivered via ventilator 15, and supplied via duct 36 to a first location of confluence.
  • the obtained mixture of fuel gas with air is then led to a second location of confluence, where the mixture flows together with the combustion gases of the fluidized bed chamber, as delivered by ventilator 17 and supplied via duct 38 to said second location of confluence.
  • the flue gas duct runs from ventilator 17 via a steerable control valve 51 towards duct 38.
  • This control valve 51 is steered from a sensor 61 of the gas pressure (overpressure above athmospheric) in the supply duct 40 that goes from said second location of confluence towards the distribution chamber 2.
  • the measuring signal of this gas pressure is supplied towards a control circuit 62, that generates a correction signal, according to the proportional, integral or differential principle or a mixture thereof, as known in control engineering.
  • This correction sinal is the led as a steering signal towards control valve 51, and the operation is such, that the gas pressure (overpressure) in supply duct 40 is maintained at a constant value.
  • the duct for the fuel gas runs from gas pipe 16, via differential control valve 48 and, in series and downstream therewith, via steerable control valve 50 towards duct 37.
  • the differential valve 48 serves to make the steering of the opening of control valve 50 independent from the overpressure at which the fuel gas is supplied from gas pipe 16.
  • This differential valve is in the form of a membrane valve, where at one side of the membrane the pressure is brought that exists in the supply duct 40 towards the distribution chamber, and at the other side, the pressure is brought that exists just before control valve 50.
  • the operation is such, that the valve, in function of the difference between both pressures, is set more or less open, so that this pressure difference is kept at a constant value.
  • control valve 50 As the pressure in supply duct 40 is regulated in order to keep a constant value, the pressure just before control valve 50 is also constant, and then, the pressure existing after that latter valve is then a value that is representative of the flow rate.
  • the control valve 50 is steered from a sensor 32 of the fluidized bed temperature, in a way that it closes more or less, according as the temperature comes above, respectively below, the reference value.
  • the air duct from ventilator 15 similarly runs via a differential control valve 47 and, in series and dowstream therewith, via steerable control valve 49 towards duct 36.
  • the differential control valve 47 serves to make the steering of the opening of control valve 49 independent from the pressure drop over that valve, so that a given opening corresponds to a given flow rate.
  • the operation is analog to the operation of differential control valve 48, and such that the pressure drop over control valve 49 remains constant.
  • This control valve 49 is steered from a sensor 46 of the pressure in the fuel gas duct 37 (this is a measure for the fuel gas flow rate als explained above), and in a manner that control valve closes more or less according as the pressure drops more or less, and in a way that the ratio air to fuel gas flow rate is maintained at a constant value.
  • this control device is as follows: when the temperature T in the fluidized bed exceeds the reference value, then this is announced by sensor 32 towards the control valve 50, that will close somewhat more, in order to reduce the combustion. But then the air to fuel gas ratio is too high. By the fact however that the control valve 50 closes somewhat more, the pressure, as measured by sensor 46, will drop, and this makes control valve 49 to close more, to that extent as to bring the ratio air to fuel gas back to the reference value. But, as to the flow rates of air and fuel gas have dropped, the total flow rate Qc of carrying gas has then dropped below the reference value. This is felt by sensor 61 in the supply duct 40, and this makes control valve 51 to open somewhat more for admitting more flue gases, whereby the total flow rate is brought back towards its reference value.
  • the regulation of the fuel gas supply can for instance be switched with the regulation of the air supply, where, upstream of differential control valves 47 and 48, are then not located respectively the air and fuel gas supply, but inversely, the fuel gas and air supply respectively.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
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  • General Engineering & Computer Science (AREA)
  • Fluidized-Bed Combustion And Resonant Combustion (AREA)

Claims (10)

  1. Four à lit fluidisé pour combustion interne de gaz, comportant un récipient à lit fluidisé (1) dont l'orifice d'entrée du gaz vecteur est relié à un dispositif d'alimentation en gaz, comprenant un premier (23) et un deuxième (22) orifice d'entrée, respectivement d'un gaz combustible et d'air, et comprenant un capteur (32) de la température T du lit fluidisé, ce capteur étant relié à l'entrée (29) d'un dispositif de régulation (25), caractérisé en ce que le dispositif d'alimentation en gaz comprend en outre un troisième (24) orifice d'entrée d'un gaz de combustion, et en ce que chacun des trois orifices d'entrée (22, 23, 24), comprend des moyens d'alimentation (9, 10, 11) adaptés pour régler le débit d'entrée correspondant et ayant une entrée de signal de réglage (12, 13, 14), reliée à la sortie (26) de ce dispositif de régulation, le dispositif de régulation étant agencé pour régler le débit de ces trois orifices d'entrée de façon à maintenir le débit de gaz vecteur Qc, le rapport du débit d'air au débit de gaz combustible (L/G), et la température T du lit fluidisé, à une valeur de référence respective.
  2. Four à lit fluidisé selon la revendication 1, caractérisé en ce que ce troisième orifice d'entrée (24) est relié à l'orifice de sortie de gaz de combustion (18) du lit fluidisé lui-même.
  3. Four à lit fluidisé selon la revendication 1 ou 2, caractérisé en ce qu'au moins une des valeurs de référence peut être prélablement ajustée ou réglée.
  4. Four à lit fluidisé selon l'une quelconque des revendications 1 à 3, caractérisé en ce qu'il est doté de moyens d'accès et de guidage de fil métallique, afin de guider de manière continue de nombreux fils métalliques, côte à côte et parallèles entre eux à travers ce lit fluidisé.
  5. Four à lit fluidisé selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le dispositif de régulation est muni d'une première partie de dispositif (48-50), adaptée pour régler le débit du dispositif d'alimentation en gaz combustible ou en air, afin de réduire l'écart entre la température mesurée et la valeur de référence correspondante, et comprenant en outre une deuxième partie de dispositif (47-49) comportant un capteur (46) du débit de ce dispositif d'alimentation, adapté pour régler le débit du dispositif d'alimentation respectivement en air ou en gaz combustible, de façon à maintenir le rapport du débit d'air au débit de gaz combustible à sa valeur de référence correspondante, et comprenant en outre une troisième partie de dispositif (51) comportant un capteur (61) du débit de gaz vecteur, et disposé de façon à régler le débit du dispositif d'alimentation en le gaz de combustion, afin de réduire l'écart entre le débit de gaz vecteur mesuré, et sa valeur de référence correspondante.
  6. Procédé de réglage d'un four à lit fluidisé pour combustion interne de gaz, dans lequel on insuffle un gaz vecteur dans le lit fluidisé et comprenant, comme premier et deuxième composants, une quantité respectivement de gaz combustible et d'air, et dans lequel la température T du lit fluidisé est régulée par rapport à une valeur de référence, caractérisé en ce que le gaz vecteur comprend en tant que troisième composant, une quantité de gaz de combustion, et en ce que le gaz vecteur est fourni respectivement à partir de trois sources de ces trois composants. le débit de chacun de ceux-ci étant réglé de façon à réguler, en même temps que la température T, le débit de gaz vecteur Qc ainsi que le rapport de débit d'air au débit de gaz combustible (L/G), chacun par rapport à une valeur de référence respective.
  7. Procédé selon la revendication 6, caractérisé en ce que les gaz de combustion du lit fluidisé lui-même, sont employés comme source pour ce troisième composant.
  8. Procédé selon la revendication 6 ou 7, caractérisé en ce que le rapport stoechiométrique est pris comme la valeur de référence pour le rapport du débit d'air au débit de gaz combustible.
  9. Procédé selon l'une quelconque des revendications 6 à 8, caractérisé en ce que l'on choisit une température supérieure à 750 °C comme valeur de référence pour la température du lit fluidisé.
  10. Procédé d'austénitisation continue d'une rangée de fils d'acier guidés de manière continue, côte à côte, à travers un four à lit fluidisé, caractérisé en ce que ce four à lit fluidisé est réglé selon les revendications 7 et 8, une température de 900 °C à 1 050 °C étant choisie comme valeur de référence pour la température de lit fluidisé.
EP19910202512 1990-10-02 1991-09-27 Lit fluidisé avec combustion interne de gaz Expired - Lifetime EP0479378B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
BE9000934 1990-10-02
BE9000934 1990-10-02

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EP0479378A1 EP0479378A1 (fr) 1992-04-08
EP0479378B1 true EP0479378B1 (fr) 1995-07-12

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Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6270597B1 (en) * 1998-12-16 2001-08-07 Praxair Technology, Inc. Process for continuous heating and cleaning of wire and strip products in a stratified fluidized bed

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4242077A (en) * 1978-11-06 1980-12-30 Fennell Corporation Fluid bed furnace and fuel supply system for use therein
EP0049592B1 (fr) * 1980-10-06 1987-08-19 The Energy Equipment Company Limited Unités de combustion à lit fluidisé
GB8426455D0 (en) * 1984-10-19 1984-11-28 Bekaert Sa Nv Fluidised bed apparatus
DE3734168C1 (en) * 1987-10-09 1989-01-05 Ewald Schwing Process and installation for the heat treatment of metallic objects in a fluidised-bed retort

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EP0479378A1 (fr) 1992-04-08
DE69111173T2 (de) 1995-11-16
DE69111173D1 (de) 1995-08-17

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