FR2507289A1 - Simultaneous regulation of burner and gas supply operation - has dual control system with hearth transducer regulating gas prodn. which in turn regulates combustion air flow - Google Patents

Abstract

The installation has a gas supply (1) feeding burners (13) which are also supplied by air from a fan (15). The associated air conduit is controlled by a diaphragm controlled by a servo-motor and controller which compares measured flow with a reference value. The gas supply is simultaneously regulated by a separate servo-motor which regulates the flow in terms of either sensed temp. or pressure of the evolved hot gases, by comparison with a reference. A switch (21) receives signals delivered from a sensor (20) which detects when the burner (13) should be stopped. The switch (21) output is connected to the reference input of the gas flow regulator (5c). The arrangement thus takes the calorific value of the gas into consideration and allows it to be changed rapidly.

Description

 Method and device for simultaneously regulating the operating speed of a burner and of a gasifier feeding this burner.

 The subject of the invention is a method and devices for simultaneously regulating the operating speed of a burner and of a gasifier feeding this burner.

 The technical sector of the invention is that of the construction of installations comprising one or more gas burners supplied by a gasifier.

 It is specified that the gasifier of an installation according to the invention can be a gasifier of any known type (fixed bed, fluidized bed, cyclonic suspension, etc.), which transforms a solid vegetable fuel into combustible gas or mineral. The oxidizing gas entering the gasifier can be air, oxygen, or a mixture of air and oxygen with or without water vapor.

 An objective of the invention is to ensure the automatic modulation of the running speed of a gas burner according to the needs of the hearth or of the calorie generator on which the burner is mounted and the simultaneous modulation of the flow rate of combustible gas supplied by the gasifier.

 Another objective of the invention is to ensure at the same time the safety of the installation and the setting in minimum operating mode of the gasifier in the event of safety shutdown of the burner.

 A third objective is to allow the use, as combustion air of the burner, of hot air, which has been used for cooling the gasifier or the combustible gases leaving it, in order to recover part of the calories contained in these gases.

 These objectives are achieved by means of a method for simultaneously regulating the running speed of a burner equipping a hearth and of a gasifier which supplies said burner with combustible gas, which gasifier comprises a supply of oxidizing gas, according to which regulates the rate of operation of the gasifier by regulating the flow of oxidant gas by means of a regulation loop which includes a first regulator which compares the flow of oxidant gas with a variable set value as a function of the rate of operation of the hearth, and the flow of combustion air supplying said burner is simultaneously regulated by means of a regulation loop which includes a regulator which compares the air flow with a variable reference value as a function of the flow of oxidizing gas entering the gasifier.

 In the case of a gas burner which operates alone to heat a fireplace, comprising a sensor with a variable parameter and a third regulator which emits a signal proportional to the difference between the value measured by this sensor and a set value , the output of this third regulator is connected to the setpoint of the first regulator, so that the flow of oxidizing gas entering the gasifier is modulated according to variations in the operating parameter of the fireplace.

 In the case where the gas burner operates simultaneously with a second burner which is supplied with rich fuel and whose stage is automatically modulated, the operating stage of the second burner is detected, this stage is compared with maximum and minimum thresholds and a set value of the first maximum regulator, minimum or equal to the oxidizing gas flow rate, is set, depending on whether the burner operating rate is respectively greater than the maximum threshold, less than the minimum threshold or between the two maximum and minimum thresholds .

 A device according to the invention is of the type comprising a hearth which is equipped with a gas burner which is supplied with combustible gas by a gasifier through a fuel gas treatment installation, which gasifier comprises means for supplying it with oxidizing gases which are equipped with a flow regulation loop comprising a first flow sensor and flow regulation means which comprise a first regulator which compares the flow measured by said sensor with an adjustable set point and the gas burner comprises a combustion air supply circuit equipped with a flow regulation loop comprising a second flow sensor associated with flow regulation means comprising a second regulator which compares the flow measured by the second sensor with a variable setpoint.

 The objectives of the invention are achieved by means of devices of this type, in which the output of the first flow sensor which measures the flow rate of the oxidizing gas, is connected to the variable setpoint of the second flow regulator of the combustion air. of the burner.

 In the case where the hearth is heated by a gas burner operating alone and has a third sensor, which measures an operating parameter of the hearth and which is associated with a third regulator which emits a signal proportional to the difference between the measured value by the third sensor and a setpoint, the output of this third regulator is connected to the variable setpoint of the first regulator which modulates the flow of oxidizing gas entering the gasifier.

 In the case where the fireplace is equipped with both a gasifier gas burner and a second rich fuel burner, which operate simultaneously, the rich fuel burner includes a running speed detector which is connected to a fourth multi-threshold regulator whose output is connected to the variable setpoint of the first regulator.

 The invention results in new installations comprising both a gasifier and a hearth which is heated by a burner supplied with gas by said gasifier, which burner can operate alone to heat the hearth, or can operate simultaneously with a second burner traditional, rich fuel, whose gait is automatically modulated.

 In both cases, the flow rate of oxidizing gas entering the gasifier is modulated, which modulates the calorific power of the gasifier and the air flow supplying the gasifier gas burner is simultaneously modulated.

 This control chain which simultaneously varies the flow of oxidizing gas entering the gasifier (hence a variation in the flow of combustible gas produced by the gasifier and arriving at the burner) and the combustion air flow from the burner has several advantages. .

 The operation of the burner and of the gasifier are controlled so that there is no accumulation of gas between the outlet of the gasifier and the burner which may lead to overpressures in the installation or in the gasifier.

 The regulation is done by two regulation loops; one placed on the oxidizing gas entering the gasifier and the other on the combustion air supplying the burner, i.e. on two clean gas circuits . No measurement is made of the flow rate of the combustible gas produced by the gasifier whose density, temperature and calorific value are variable.

 In the case where the hearth is heated both by a gasifier gas burner and by a second traditional burner supplied with rich fuel, which operate simultaneously, the regulating device according to the invention makes it possible to automatically modulate the gait of the traditional burner using the usual regulating devices, so that the modulation of the traditional burner makes it possible to cope with rapid variations in pace and to precisely modulate the gait. At the same time, the associated multi-threshold regulator a traditional burner speed detector; makes it possible to vary the gasifier's walking speed according to the walking speed of the traditional burner and to cause a cascade modulation of the gasifier gas burner, so that the speed can be maintained of the traditional burner in a range where it operates with optimum efficiency while saving the maximum fuel of the traditional burner.

 The following description refers to the appended drawings which represent, without any limiting character, several examples of devices according to the invention.

 Figure 1 is a general diagram of an installation comprising a hearth which is heated by burners which are supplied with combustible gas by a gasifier and which operate alone to heat the hearth.

 FIG. 2 is a general diagram of an installation comprising a hearth which is heated both by a burner supplied with combustible gas by a gasifier and by a second rich fuel burner, the shape of which is modulated automatically.

 Figures 3 and 4 are diagrams of devices for supplying the gasifier gas burner with hot combustion air.

 The devices according to the invention comprise, on the one hand, a fireplace equipped with one or more burners and, on the other hand, a generator of combustible gas of the gas-generating type which supplies the burners.

 It is specified that the gasifier or gasifier can be of any known type (fixed bed, fluidized bed, cyclonic suspension, etc.) and that it transforms any solid, mineral or vegetable fuel into combustible gas.

 The oxidizing gas which supplies the oxygen which combines with the carbon of the fuel to give combustible gases, may be air, oxygen, a mixture of air and oxygen or any mixture of air, d and water vapor.

 The fireplace can be a boiler producing hot water, superheated water or steam, or a generator of hot gases, an oven or any other calorie generator.

 The fireplace can be fitted with a single gas burner or with several non-independent gas burners which operate simultaneously.

 In certain installations, hot combustible gas can be used without having to cool it to ambient temperature, which makes it possible to recover all or part of the sensible heat of the combustible gas. To simplify the presentation, when we speak of a burner, it may be several burners equipping the same hearth and operating simultaneously while being supplied in parallel.

 The object of the invention is to ensure, in a reliable manner, the operating safety of the installation and the modulation of the flow rate of gas produced by the gasifier as a function of the calorific power requested by the burner, which automatically varies according to the needs of the calorie generator, on which the burner is mounted.

 Two cases of application may arise, in which the problems of regulation are very similar.

 In a first case, it is a burner which is supplied only with combustible gas produced by a gasifier or else a burner which has a double supply, one in traditional liquid or gaseous fuel and the other in gasifier gas and a switching device that automatically switches from one supply to another. In this first case, the device according to the invention relates to the operating phase of the burner when it is supplied with gas by the gasifier. The traditional fuel market is well known and the electrical switching of the supply from one fuel to another poses no particular problem.

 In a second case, it is a mixed burner, comprising a double simultaneous supply, part of the calorific power being provided by a supply of traditional rich fuel (fuel oil, natural gas, liquefied petroleum gas etc.). ..) and the complement by a lean gas produced by a gasifier.

 In this case, it is sought to ensure rapid and significant variations in the calorific power by modulating the flow rate of rich fuel, faster to modulate than the appearance of the gasifier.

Likewise, precise regulation of the generator parameter which must remain constant (pressure or temperature) is more surely ensured by varying the flow rate of rich fuel whose calorific value is more constant than that of the combustible gases produced by the gasifier whose quality can vary.

 However, even in this second case, it is necessary to gradually and automatically adapt the power of the gasifier to the needs of the home in order to limit as much as possible the consumption of traditional rich fuel, which is more expensive, the modulation of flow rate of the rich fuel only intervening. in short transient phases or for low amplitude power adjustments.

 The invention relates to installations very close to each other corresponding to the two cases which have just been described.

 Apart from the devices for simultaneously regulating the rate of operation of the burner and the gasifier, the installations according to the invention may advantageously include devices making it possible to use, as combustion air of the burner, hot air for cooling the gasifier. or hot air from the cooling of the hot gases leaving the gasifier if such cooling is provided, for any reason.

 The installations according to the invention then comprise a double combination between a burner and a gasifier which feeds it, a first combination at the level of the gait regulation and a second combination at the level of the use as combustion air of the burner, hot air used to cool the gas generator or combustible gases produced by the gas generator in order to recover calories contained in these gases.

 FIG. I represents the general diagram of an installation according to the invention which comprises a hearth or generator of calories 14 equipped with one or more burners 13. The installation comprises, in addition, a gasifier or gasifier 1 which produces gases fuels to supply the burner 13.

 The outlet of the gasifier is connected to the inlet of the burner by a gas treatment chain which includes a dust removal device 6, for example a cyclone, a multicyclone or a filter and which can also include devices for cooling and washing the The gas treatment chain can include a fan 7 associated with a gasifier pressure regulation chain which is composed of a gasifier pressure sensor, a flap 8a located on the discharge of the fan, of an actuator 8b which is for example a servomotor or a jack controlling the movements of the shutter 8a and of a regulator 8c of any known type, which makes it possible to display a set pressure and which acts automatically on the servomotor to correct the difference between the pressure measured by the sensor 9 and the set pressure.

 In order to simplify the installation, the fan 7 and the pressure regulation chain 8a, 8b, 8c, 9 can be omitted and, in this case, the pressure in the gasifier is variable.

 The pipe connecting ~ the outlet of the dust collector 6 to the burner comprises a motorized valve 11 mounted on a bypass vent and a motorized sectioning valve 10 mounted downstream of the bypass.

 As a safety measure, the shut-off valve 10 can be doubled with a second shut-off valve 12b, with venting through a second intermediate bypass fitted with a second vent valve 12a.

 In the event of burner 13 stopping by securing the installation, the shut-off valves 10 and 12b are closed automatically and the vent valves 11 and 12a are opened automatically.

 The burner or burners 13 are supplied with combustion air by a fan 15. The fan discharge duct (or the suction duct) is equipped with a flow regulation loop which comprises a flow sensor 16a, 16b, for example a diaphragm or a convergent-divergent 16a, associated with a differential pressure switch 16b.

 The flow regulation loop further comprises a flap 17a, which is controlled by an actuator or servomotor 17b and by a regulator 17c which compares the flow rate measured by the sensor 16b with a set value.

 As a variant, the flow sensor 16a, 16b. Can be constituted by a sensor for opening the shutter 17a or for the position of the actuator 17b.

 The gasifier 1 is equipped with means for supplying it with oxidizing gas. These means include a fan 2, the discharge line of which comprises a motorized shut-off valve 3, a flow sensor 4a, 4b and flow control members composed of a flap 5a, an actuator or servomotor 5b and a regulator 5c which compares the flow rate measured by the sensor 4b with a set value.

 The shut-off valve 3 closes automatically at the same time as the valves 10 and 12b in the event of a safety stop.

 The hearth 14 includes a sensor 18 which measures a parameter from which the operating speed of the burner 13 is modulated. This parameter is, depending on the case, the vapor pressure or the temperature of hot or superheated water, the temperature hot gases produced by the fireplace, etc. The sensor 18 is associated with a regulator 19 of any known type, which compares the value measured by the sensor 18 with a reference value displayed on the regulator and which generates a signal function of the difference between the value measured by the sensor 18 and the setpoint displayed on the regulator 19. In traditional homes powered by a rich fuel burner, the signal produced by the regulator 19 acts on a device which automatically modulates the fuel flow feeding the burner 13 to bring the signal emitted by the regulator 19 to zero.

 In the present case, it is not possible, as in the case of a usual gas network, to modulate the flow of combustible gas to ensure the variations in speed required of the burner 13, taking into account the inertia of the gasifier. which reacts with delay to changes in the demand for combustible gas.

 A fuel gas buffer storage tank can be interposed between the gas generator and the burner to cope with short-term increases in demand, but if it is to supply a burner that consumes a large flow of gas, the volume of the intermediate tank represents only a few tens of seconds of burner consumption unless it is of an enormous volume (gasometer), which would cost too much, and it cannot therefore be sufficient to compensate for the variations in speed required to the burner. In addition, if you can avoid cooling the gas to recover sensible heat, building a buffer tank to store the hot gas would be too complicated and expensive, so you need to develop another regulation and operational safety of the assembly formed by the burner and the gasifier and this is one of the objectives of the invention.

 The hearth 14 includes a second sensor 20 which controls the shutdown of the burner 13, for example in the event of a temperature or pressure threshold being exceeded. it includes a switch 21 which receives the signals delivered by the stop sensor 20 and by the regulator 19 and which gives priority to the signal supplied by the stop sensor 20 over the signal supplied by the regulator 19.

 According to the invention, the output of the switch 21 is connected to the variable setpoint of the regulator 5c which controls the flow of oxidizing gas from the gasifier, so that the deviation signal produced by the regulator 19 acts as the variable setpoint of the regulator 5c flow to adjust the flow of oxidant gas entering the gasifier. The method of regulation used results from the observation that the thermal flow rate of the gasifier, that is to say the calorific power of the gas which it produces, is approximately proportional to the flow rate of oxidizing gas which it receives in the range of normal modulation of the device. This regulation has the advantage of directly controlling the operation of the gas generator to the calorie requirements of the fireplace 14. It allows the calorific power of the gas generator to be varied as quickly as possible. In addition, it avoids measuring the flow of gas leaving the gasifier whose density, temperature and calorific value vary over time and according to the nature of the fuel, which would cause an unreliable measurement.

 According to another characteristic of the invention, the output of the flow sensor 4b is connected to the regulator 17c, so that the signal delivered by the oxidant gas flow sensor serves as a variable setpoint for the regulator 17c, and that the combustion air flow rate of the burner 13 varies in the same direction as the flow of oxidizing gas entering the gasifier and that the flow of combustible gas supplied by the gasifier to the burner.

 Advantageously, the actuator 17b is a cam device which is adjusted empirically during the commissioning of the installation to obtain that the combustion air flow rate varies as a function of the combustion air flow rate according to a determined and optimum law. .

 differences remain between the quantity of combustion air supplied and that which should theoretically be supplied in order to obtain perfect combustion of the gases. These differences result from the inertia of the device and from variations in the quality of the combustible gas. They are largely minimized by the regulation process used and they are easily absorbed by a variation of the excess combustion air at the burner without producing unburnt matter and without risk of extinction of the flame.

 The regulation devices according to the invention are simple and reliable. They are independent of the possible soiling of certain circuits by dust. They are also independent of variations in the pressure drop of the gasifier. The flow measurements are made on combustion air and on the oxidizing gas (which may also be air) which are both clean gases.

 In the case where the sensor 20 detects a threshold being exceeded, the switch 21 gives priority to the signal emitted by the sensor 20 over the signal from the regulator 19.

 The signal emitted by the sensor 20 is transmitted to the regulator 5c and it places the latter's set value. At the same time, it automatically controls the closing of the shut-off valves 10 and 12b and the opening of the vent valves 11 and 12a, so that the gasifier is kept in minimum operation, ready to refuel the burner as soon as the hearth 14 will have returned to a normal state. provision may be made to return the burner 13 to service after the excess signal has disappeared, either manually or automatically.

 FIG. 2 represents the general diagram of an installation of the second category, in which the hearth or generator of calories 14 comprises at the same time a gas burner 13, which is supplied with combustible gas by a gasifier 1 through a chain d purification of the combustible gas identical to that of FIG. 1 and a second burner 22 which is supplied with rich fuel (gaseous or liquid). The two burners operate simultaneously.

The parts homologous to those of FIG. 1 are represented by the same references and will not be described again.

 The traditional burner 22 can be mounted on the same burner as the gas burner or in any other arrangement. it is a complete burner which includes a heating regulation device 23, which receives signals modulating the heating rate, from the regulator 19 or from the excess sensor 20 through the switch 21.

The burner 22 includes a speed detector 24 which detects the running speed or the load of the burner 22. This detector 24 measures for example the angle of rotation of the shutter actuator controlling the flow of combustion air or any other actuator. it is constituted for example by a potentiometer for copying the position of a register or a valve or by any other means measuring the flow of light or of fuel arriving at the burner 22,
The output of the pace detector 24 can be connected, if necessary only, to a converter 25 which transforms the signal delivered by the detector 24.

 The output of the converter 25 (or the output of the detector 24 if there is no converter) is connected to a regulator 26 having several manually adjustable thresholds. For example, the regulator 26 may include an adjustable "maximum" and a "minimum" threshold.

 The output of regulator 26 is connected to regulator 5c which controls the flow of combustion air entering the gasifier. The output of the flow sensor 4b is connected to the regulator 26.

 The operation is then as follows. When the signal coming from the converter 25 (or from the detector 24) is greater than the selected maximum threshold, the regulator 26 sends to the regulator 5c a "maximum" setpoint value * with a speed of ramping up which may be adjustable. The working pace of the gas generator gradually increases, as does that of the gas burner 13.

When the signal delivered by the converter 25 (or by the sensor 24) is between the "maximum" and "minimum" thresholds, the regulator 26 sends to the regulator 5c a fixed instruction which is constantly equal to the value of the flow rate measured by the sensor 4b. The regulator 5c receiving a set value equal to the flow measurement, blocks the rate of the gasifier at a fixed value which is the rate reached when the burner 22 has passed below
e of the maximum position.

 When the signal coming from 25 (or 24) becomes lower than the minimum threshold, the regulator 26 sends to the regulator 5c a "minimum" set value with a rate of descent under load possibly adjustable.

 The regulator with adjustable thresholds 26 can be advantageously improved.

 The maximum threshold and the minimum threshold can have two different values depending on whether the signal from 25 (or 24) crosses the increasing or decreasing threshold.

 In addition, the regulator 26 may include an additional threshold below the minimum threshold. When the signal delivered by the converter 25 falls below this threshold, the regulator 26 causes a safety shutdown of the gas generator by putting it on the minimum running speed and by controlling the closing of the valves 10 and 12b and l opening of the vent valves 11 and 12a.

 One of the advantages of this regulating device is that it allows the "maximum" and "minimum" thresholds to be adjusted, so that the traditional burner provides fine adjustment and rapid variations in speed and that it most often works stable at a speed at which it has a good yield and a low consumption from where the realization of an important saving of traditional fuel cumulated with a very good regulation of the hearth.

 FIG. 3 represents an additional device which can be used on the installations according to FIGS. 1 and 2 and which makes it possible to recover the calories contained in the air for cooling the gasifier or the air for cooling the combustible gases leaving the gasifier.

 The tendency in the construction of gas generators is to build devices whose tank or gasification chamber is cooled by a current of air circulating in a coil or in a double envelope surrounding it in order to cool the walls and to be able to control the room temperature.

 The gasifiers operating in cyclonic suspension can comprise an intermediate cooling of the recycled gases.

 Combustible gases - leaving the gasifier often have to be cooled to allow passage through dedusting, filtering or washing facilities.

 The air leaving the cooling exchangers is at a temperature which can be between 50 and 200 and the sensible heat of this air can represent up to 10% of the calorific power of the fuel consumed.

 The device according to FIG. 3 makes it possible to recover a large part of these calories by using the air for cooling the gasifier or the gases as combustion air from the gas burner 13.

 FIG. 3 shows the fan 15, the device for measuring the combustion air flow rate 16a, 16b and the device for regulating the combustion air flow rate 17a, 17b, 17c. The regulator 17c compares the flow measurement delivered by the sensor 16b to a set value C which is delivered by the flow sensor 4b as shown in FIGS. 1 and 2.

 The fan suction duct 29 is connected to a hot air outlet from one or more coils or heat exchangers for cooling the gasifier 1 or the combustible gases leaving the gasifier 1. The pipe 29 is equipped with a shut-off valve 32 motorized. it includes a bypass 31, connected upstream of the valve 32 whose open end communicates with the atmosphere. This derivation comprises a diaphragm 29 pierced with an orifice or any other equivalent device such as a calibrated orifice, a valve, a tap, making it possible to create a pressure drop between the line 29 and the atmosphere.

 In addition, a temperature sensor 28 measures the air temperature and sends a signal depending on this temperature to the sensor 16b. The sensor 16b uses this signal to calculate the value of the mass air flow which is sent to the regulator 17c.

 The operation is as follows.

 If the flow of hot air arriving through line 29 is overabundant, that is to say if it is greater than the flow rate required by the burner, there is an overpressure in line 30 and the excess air is escapes to the atmosphere. If, on the contrary, the flow of hot air is insufficient, a vacuum tends to arise in the pipe 29 and cold air enters through the diaphragm 30 and mixes with the hot air.

 If the burner 13 is shut down for safety reasons, the motorized valve 32 is closed automatically and the cooling air escapes through the vent 31. In summary, the gasifier cooling air flow or combustible gas is maintained in all cases. A large part of the calories contained in the hot air used for cooling is recovered and the mass flow of combustion air is precisely regulated by virtue of the temperature correction effected by the sensor 16b.

 FIG. 4 represents an alternative embodiment of the device according to FIG. 3 in which the fan 15 is eliminated and the combustion air circulates under the effect of the pressure available in the duct 29 for the arrival of hot air coming from one or more devices for cooling the gasifier or combustible gas. This pressure results for example from the fact that the cooling air is pushed by a fan located upstream and operating in cold air, which is calculated to supply at 29 a sufficient pressure despite the pressure drops in the circuits.

 In this example the vent duct 31 comprises an air flap 30a, which is coupled to the flap 17a by a cam device 30b which is such that the sum of the air flow passing through the flap 17a and that which escapes towards the vent 31 going outwards is approximately constant and equal to the cooling air flow required.

 The shutter 30a is bypassed by a bypass comprising a motorized valve 33. In the event of a safety shutdown of the burner which can occur for any position of the shutter 30a, the valve 32 is closed automatically at the same time as the valve 33 is open, so as to keep the cooling air flow constant. The other parts of FIG. 4 are identical to those of FIG. 3.

 This last embodiment has the advantage of eliminating a fan conveying hot air by replacing it with a slight oversizing of the cooling fan which operates on cold air and which has better efficiency.

 Reference 34 represents a flow sensor which makes it possible to control the flow of air arriving through line 29.

 The latter device provides maximum thermal recovery with a constant cooling air flow by simplifying installation and reducing the electrical power consumed by the fans.

Claims (12)

 1. Method for simultaneously regulating the running speed of a burner (13) equipping a hearth (14) and of a gasifier (1) which supplies said burner with combustible gas, which gasifier (1) comprises a gas supply oxidizer, characterized in that the flow of oxidant gas is regulated by means of a regulating mouth comprising a first regulator (5c) which compares this flow to a variable reference value as a function of the pace of the hearth, and the flow of combustion air supplying the burner is simultaneously regulated by means of a regulation loop comprising a second regulator which compares the air flow with a variable reference value as a function of the flow of oxidizing gas entering the gasifier.  2. Method according to claim 1 for regulating the running speed of a burner (1) which operates alone to heat a hearth (14) comprising a sensor (18) of a variable parameter and a third regulator (19) which emits a signal proportional to the difference between the value measured by said sensor and a setpoint, characterized in that the output of said third regulator (19) is connected to the setpoint of said first regulator (5c).  3. Method according to claim 1 for regulating the running speed of a gas burner (1) which operates simultaneously with a second burner (22) with rich fuel whose pace is automatically modulated, characterized in that the the running speed of said second burner is detected, it is compared with maximum and minimum thresholds and a set value of said first maximum regulator is set if the running speed of the second burner is greater than the maximum threshold, minimum if l The pace is less than the minimum threshold and equal to the oxidant gas flow rate if the pace is between the maximum and minimum thresholds.  4. Device of the type comprising a hearth (14) equipped with a gas burner (13) which is supplied with combustible gas by a gasifier (1) through a fuel gas treatment installation, which gasifier comprises means for the '' supply oxidant gas equipped with a flow control loop comprising a first flow sensor (4a, 4b) and regulation means (Sa, 5b, 5c) which include a first regulator (5c) which compares the measured flow by said sensor to an adjustable setpoint, which gas burner (1) comprises a combustion air supply circuit equipped with a flow regulation loop comprising a second flow sensor (16a, 16b) associated with means for flow control (17a, 17b) comprising a second regulator (17c) which compares the flow measured by the second sensor with a variable setpoint, characterized in that the output of said first oxidant gas flow sensor is connected to the variable setpoint of said second regula combustion air flow rate.  5. Device according to claim 4 used with a hearth (14) which is heated by a gas burner operating alone and which comprises a third sensor (18) which measures an operating parameter of said hearth and which is associated with a third regulator ( 19) which emits a signal proportional to the difference between the value measured by said third sensor and a reference value, characterized in that the output of said third regulator (19) is connected to the variable reference of said first regulator (5c).  6. Device according to claim 5, characterized in that said hearth further comprises a detector (20) for exceeding the safety threshold and a switch (21) which is connected to the output of said detector for exceeding the threshold (21 ) and on the output of said third sensor (18) and the output of which is connected to the setpoint of said first regulator (5c), which switch (21) brings said setpoint to a minimum value when said detector (20) detects a threshold being exceeded and controls the closing of shut-off valves (10, 12b) located on the connection between the gasifier outlet (1) and the burner (13) and the opening of vent valves (11, 12a).  7. Device according to claim 4, used in combination with a fireplace equipped with a burner (22) of rich fuel and a gas burner (13) which operate simultaneously, characterized in that said rich fuel burner comprises a walking pace detector (24) which is connected to a fourth regulator (26) with multiple thresholds, the output of which is connected to the variable setpoint of said first regulator (5c).  8. Device according to claim 7, characterized in that said multiple threshold regulator comprises a maximum threshold and a minimum threshold and it is connected to the output of said flow sensor (4b) of the oxidizing gas and when said pace detector ( 24) detects a speed greater than the maximum threshold it transmits a maximum set value, when it detects an intermediate speed between the maximum threshold and 5 minimum threshold, it transmits a set value equal to the flow rate measured by said sensor (4b) oxidant gas flow rate, and when it detects a speed above the minimum threshold, it transmits a minimum setpoint.  9. Device according to any one of claims 4 to 8, characterized in that the combustion air supply circuit of said gas burner (13) is connected to a pipe (29) of hot air produced by cooling gasifier or combustible gas, which pipe comprises a bypass (31) open to the atmosphere and equipped with a narrowed passage (30).  10. Device according to claim 9, characterized in that said pipe (29) of hot air inlet is slightly overpressure, which avoids a suction fan of the hot combustion air, said bypass (31) comprises a movable flap (30a) which is connected to said flap (17a) placed on the combustion air duct by a cam device (30b) such that the sum of the flow of air leaving by said bypass and the flow of combustion air is constant and substantially equal to the flow of hot air.  11. Device according to claim 10, characterized in that the vent duct (31) comprises a bypass which bypasses said movable flap (30a), which is equipped with a motorized valve (33), that said inlet duct hot air (29) comprises a motorized shut-off valve (32) which is placed downstream of said vent and that the device includes means for automatically closing said shut-off valve (32) and for opening said bypass valve (33) in the event of a safety stop of said gas burner (13).  12. Device according to any one of claims 9 to 11, characterized in that said sensor (16b) of burner combustion air flow is associated with a temperature sensor (28) and comprises means for delivering to the regulator flow (17c) a measure of the mass flow taking into account the air temperature.