FR2732751A1 - FEEDING DEVICE AND METHOD FOR OPERATING A GAS BURNER - Google Patents

Abstract

The feeder consists of a main gas feed circuit (8), an oxidant gas feeder (10), a fuel gas enrichment line, a mixing chamber (16) for the fuel and oxidant gases, connected to the burner (14a,b) before the fuel and oxidant feeds, and a control valve (4) which allows the fuel gas to pass along the enrichment line during the burner ignition stage only. The gas enrichment line (6) branches from the main fuel gas feed line (8) in a control box (10) which regulates the delivery of the fuel gas to the main (8) and enrichment (6) lines, each of which is divided into two or more branches (8a,b,6a,b) before they reach the mixing chamber. The mixing chamber is in the form of two curved ducts connected by a crosspiece (17) to which the branches lines are connected at right angles to one another.

Description

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  The invention relates to a feed device for gas burners and aims more particularly to ensure a good ignition, that is to say instantaneous, safe and reliable of these burners while maintaining optimal operation out

ignition period.

  A device for supplying a burner with a mixture of combustible gas and oxidizing gas, comprising: a main supply duct for fuel gas, a means for supplying oxidizing gas, a mixing chamber, is already known. fuel gas and oxidizing gas, adapted to communicate with said burner, downstream part in the direction of circulation of the fuel gas, and to which are connected, in the upstream part, the main fuel gas supply pipe and the d food

  oxidizing gas. Such a device is described in patent FR-A-2 195 776.

  But, the feed device of this patent enriches only part of the mixture, in the immediate vicinity of the igniter device, which does not allow to have a good homogeneity of the mixture of fuel gas / oxidant gas throughout the area of combustion. The mixture that is likely to be too rich in fuel gas around the igniter device and too poor in areas that are far away may have trouble igniting. If, in order to overcome this difficulty of ignition, the mixture is further enriched with fuel gas, the combustion characteristics, and therefore the efficiency of the burner, may be disrupted once the transient ignition regime has been completed, without, however, obtaining a

really reliable ignition.

  The object of the present invention is to improve the supply of gas burners, in particular radiant burners with ceramic plates, or even torch burners, in order to ensure a fast and reliable ignition of the gas mixture, as well as a good operating efficiency. out of the ignition period, this in

  economically satisfactory conditions.

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  According to the invention, the feed device proposed to solve this problem is characterized in that it comprises, in addition to the aforementioned basic structure of FR-A-2 195 776: a gas mixture enrichment duct; fuel, connected bypass to the fuel gas supply pipe and connected downstream to said mixing chamber, and - a valve to allow the passage of fuel gas also

  in the enrichment duct during a period of ignition of the burner.

  To solve the same general problem as that already mentioned with regard to FR-A-2 195 776, the invention also proposes a method of operating a burner in which, as in FR-A-2 195 776 the burner, including an ignition zone thereof, is supplied with a mixture of combustible and oxidant gases in a given proportion, and during a period of ignition of the burner, the mixture is ignited; place of the ignition zone; but, in the invention unlike the patent FR-A-2 195 776: - during the ignition period of the burner, the mixture will be enriched fuel gas with respect to said determined proportion, and - at the end of the ignition period, we will delete this

  temporary enrichment of combustible gas.

  Thus, in the context of the device as in the context of the process, the problems already mentioned are solved by enriching at the appropriate moment the gas mixture supplied to the burner, that is to say that the richness of the gaseous mixture can be regulated. in order to obtain a good yield in normal operation, and modify this wealth only during a determined phase

  corresponding to the ignition of the burner, for a good ignition.

  It will be noted that in the context of the device, it is further enriched in the right place, that is to say upstream of the mixing chamber so as to obtain a mixture of homogeneous richness of fuel gas and oxidizer before

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  to feed the burner, unlike patent FR-A-2 195 776 which enriches

  punctually at the ignition zone.

  In order to avoid any ambiguity, the "ignition period" is defined in the invention as the period, corresponding at least to the spark or flame-out time for an igniter device, prior to the rated speed.

stable combustion.

  Another problem solved by the invention consists in being able on the one hand to cut off the general gas supply and on the other hand to easily obtain a richness of the gas mixture which is adapted to the ignition conditions while regulating the richness in normal operation for optimal performance. As part of the process, the solution of the invention is to independently adjust the richness of the mixture of oxidant gas / fuel gas during the ignition phase and the ignition phase. The advantage of this solution is to obtain good flame stability and excellent performance by enriching in each phase, ignition or normal operation, neither too much nor too little and whatever the fuel gas used (manufactured gases,

petroleum gas, natural gas, ...).

  In the context of the device, the solution of the invention consists of a control means allowing the simultaneous arrival of gas in the main ducts and enriching fuel gas, and also to regulate the pressure. The advantage of this solution is, in addition to that presented previously in the context of the process of being able to easily control the general gas supply. It has been found that the general solution of the invention also makes it possible to feed several burners from a single feed device. To do this, the main and enrichment ducts are each divided into several branches upstream of the mixing chamber, which comprises a box

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  multiple comprising at least two bent lanes joined together upstream by a transverse section on which is connected the oxidizing gas supply means, each lane connecting downstream to a burner and each branch of said main fuel gas ducts and enrichment connecting to the mixing chamber substantially in the general plane of the corresponding channel. This solution makes it possible to feed several burners with a homogeneous and correctly dosed mixture, while having only a feeding device, in order to reduce the cost, in particular of manufacturing the assembly and

the burner adjustment time.

  Moreover, it has proved important to seek to optimize the homogeneity of the fuel gas / oxidant gas mixture. According to a characteristic of the invention, the main fuel gas and enrichment ducts are advantageously connected for this purpose to the mixing chamber substantially perpendicularly to one another and close to each other and the gas The oxidizer emerges, in one place, into a mixing chamber in the immediate vicinity of the location of the connection of said main fuel gas and enrichment conduits and substantially perpendicular to each of these conduits. This solution creates a beneficial diet

  turbulent flow of these gases, conducive to their mixture.

  Other features and advantages of the invention will appear from the

  description which follows, made with reference to the accompanying drawings in which:

  FIG. 1 is a diagram of the device of the invention, FIG. 2 is a diagram of an embodiment of an embodiment.

  preferred means for controlling the arrival of fuel gas.

  A mixture of oxidizing gas and fuel gas, here a mixing chamber 16, is supplied with combustion gas by a fan 10,

  and fuel gas via a main duct 8 and an enrichment duct 6.

  This mixing chamber feeds gas mixture at least one burner.

  In the illustrated case, the device supplies two burners 14a, 14b. The mixing chamber 16 comprises a multiple box comprising two lanes

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  cubits (a and b). A transverse section 17 on which is connected in substantially central position the fan 10 joins upstream these two channels. The main ducts and fuel gas enrichment are divided into two branches before introduction of the gas into the mixing means. For each of the branches, the two ducts open substantially perpendicular to each other and close to each other, in the general plane of the corresponding channel, in the mixing chamber (towards the upstream end 18 of channels a and b ) while each being disposed substantially perpendicularly and in the immediate vicinity of the combustion air inlet. Indeed, the combustion air, blown by the fan 10, is divided in the central section 17 in two flows flowing to each of the channels of the mixing chamber. These perpendicular arrivals are intended to achieve an optimal mixing of the fuel and combustion gases by creating from the upstream part of the chamber, a turbulent flow regime of these gases completed in

  this by the bent shape of the mixing chamber.

  A valve 4 placed on the enrichment duct 6 makes it possible to interrupt the flow of fuel gas flowing in this duct, while a control means 2 allows or prevents the arrival of combustible gas in the main ducts 8 and 8. enrichment 6 with combustible gas. Here, this means is constituted by a solenoid valve also allowing the adjustment of the pressure, therefore the flow, in the main ducts and enriching fuel gas in addition to the injectors 12a and 12b. The injectors 12a and 12b thus regulate the flow, alone or in addition to the control means 2 according to whether or not its control system is used. Arrow 1 shows the gas supply direction of

the main solenoid valve.

  According to a preferred embodiment, the control means 2 has a gas inlet channel and two main output channels and nightlight on which is connected respectively the main supply duct 8 and the enrichment duct 6 of combustible gas. For example, it will be possible to use a solenoid valve "SIT 822 NOVA", a simplified operating diagram is given in Figure 2. In this figure, the mark 30 represents the arrival

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  general fuel gas, the marks 32 and 34 respectively the main supply duct 8 and the enrichment duct 6 of fuel gas, the marks 36 and 38 two valves and the mark 40 a pressure regulator. In the case of the invention, the valve 38 is not used (left open) while the valve 36 controls the simultaneous arrival of fuel gas in the two ducts 6 and 8. Finally, the pressure regulator 40 regulates the pressure, so the flow, in the

  main conduit for supplying oxidizing gas.

  One method of realization advantageously consists in using an enrichment flow representing approximately 10 to 20% of the main flow. This relatively large quantity of enrichment gas makes it possible to obtain an easy, fast and reliable ignition of the burners by homogeneously enriching all the gas injected during this period, while allowing optimal operation under normal use conditions since the flow

  enrichment is only injected during the ignition cycle.

  The control box 20 makes it possible to coordinate the succession of operations of a preferred ignition cycle: - the fan is switched on, when the combustion gas reaches the desired pressure, the igniter 22 sends a high voltage to the electrodes 19 to create during the ignition a load likely to ignite the gas at the determined time, - it opens at the same time the valve 4, - a few fractions of seconds after (to prevent the accumulation of gaseous combustion mixture), opens the control means 2, allowing the fuel gas to arrive through the main and enrichment pipes, - after five seconds (time necessary to ensure a good ignition), the igniter ceases to deliver a voltage to the electrodes, - Concomitantly or at least fairly quickly (of the order of a few seconds to a few tens of seconds), the control means 4 is closed, the fuel gas no longer circulates in the conduit

enrichment.

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  the burner is then in operation at the rated speed.

  Provision can thus be made to temporarily enrich the useful mixture in operation at nominal speed, at each ignition cycle, and not

  only at first (at first use when the installation is cold).

  Of course, the invention is not limited to the embodiment described above. Thus, one could consider any other means controlling the arrival of gas by the fuel gas enrichment duct such as a simple tap or other igniter device such as a device

pyrophoric or piezoelectric.

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Claims (7)

claims   1. Device for supplying at least one burner with a mixture of combustible gas and oxidizing gas comprising: a main fuel gas supply pipe (8), an oxidizing gas supply means (10) - a mixing chamber (16) for the fuel gas and the oxidizing gas, adapted to communicate with said burner (14), downstream with respect to the direction of flow of the fuel gas and to which the main duct of the fuel is connected upstream; fuel gas supply (8) and the oxidizing gas supply means (10), characterized in that it further comprises: - an enrichment duct (6) of the combustible gas mixture, branched bypass on the fuel gas supply duct (8) and connected downstream to said mixing chamber, and - a valve (4) for allowing the fuel gas to pass through the enrichment duct (6) for a period ignition of the burner.   2. Device according to claim 1, characterized in that it also comprises a control means (2), placed upstream of the bypass duct to control and / or regulate the simultaneous arrival of fuel gas in the   main and enrichment ducts.   3. Device according to one of the preceding claims, characterized in   the main and enrichment ducts are each divided into several branches (6a, 6b, 8a, 8b) upstream of the mixing chamber, which comprises a multiple box comprising at least two bent tracks joined together upstream by a transverse section on which is connected the combustion gas supply means, each channel connecting downstream to a burner and each branch of said main fuel gas ducts and enrichment 9 2732751   connecting to the mixing chamber substantially in the general plane of the corresponding channel.   4. Device according to one of the preceding claims, characterized in   the main fuel gas and enrichment gas pipes are connected to an upstream zone (18) of the mixing chamber, substantially perpendicular to each other and in proximity to each other and the gas oxidant opens locally in the mixing chamber in the immediate vicinity of the location of the connection of said main fuel gas ducts and enrichment and substantially perpendicular to each of these ducts.   5. Device according to one of the preceding claims, characterized in   the control means (2) comprises a solenoid valve having a general inlet (30) and two main and pilot outlet channels on which the main supply duct (8) and the main duct are connected respectively.   enriching (6) fuel gas.   6. A method of operating a burner in which: - the burner, including an ignition zone thereof, is fed into a mixture of combustible and oxidant gases in a determined proportion, and, during a period of igniting the burner, igniting the mixture at the location of the ignition zone, characterized in that: - during the ignition period of the burner, the fuel mixture is enriched with respect to said determined proportion, and - at the end of the ignition period, this enrichment is eliminated temporary fuel gas.   7. Process according to claim 6, characterized in that the richness of the oxidant / fuel gas mixture is independently regulated.   during the ignition phase and out of the ignition phase.