EP0478481A1 - Method for improving the combustion of a burner with air fan and device for carrying out the method - Google Patents

Abstract

Process for improving combustion, characterised in that the combustion is corrected continuously by injecting into the flow of the oxidising air a variable, metered and controlled flow rate of a catalytic, neutralising and corrosion-inhibiting gaseous complex, by making the flow rate of the oxidising air vary by varying the speed of the burner fan on the basis of the values of the main combustion parameters measured in the gases and combustion fumes and on the basis of the boiler and burner parameters. This invention is of interest to the manufacturers of burners and boilers and to users thereof. <IMAGE>

Description

The present invention relates to a combustion improvement method for a supply air burner.

More particularly, the invention relates to an improved combustion process both in terms of energy and in terms of pollution by a catalytic gas supply using a programmable computer or any other intelligent system.

It applies to all types of supply air burners for power boilers applied to collective or industrial domestic heating and to various fuels: fuel oil, gas or others used by such burners.

First of all, the present invention aims at improved combustion which consists in placing oneself in optimal combustion conditions.

This involves correcting the combustion in order to increase its energy efficiency by the continuous addition, suitably dosed and controlled, of a variable quantity of a complex fluid with an exothermic reaction responsible for continuously restoring the conditions for optimal combustion. as complete as possible and thus reduce the amount of unburnt volatile matter to a low value.

The present invention also relates to clean combustion.

To guarantee respect for the environment, the best possible combustion in the industrial sense must be accompanied by continuous monitoring of the quantity and nature of the discharges. This control must also serve to continuously correct the general combustion conditions for the necessary reduction of harmful waste to a low level or their neutralization or transformation.

The present invention simultaneously aims at the two previously mentioned objectives of improvement energy and establishing conditions for clean combustion.

It also aims to maintain, during operation and over long periods, optimal combustion conditions by continuous monitoring and correction thereof.

To this end, the clean optimal combustion method according to the invention is characterized in that the combustion is continuously corrected by injecting into the flow of the combustion air a variable, metered and controlled flow rate of a gaseous complex. catalytic and corrector and in that the flow rate of the combustion air is varied by varying the speed of the burner fan from the values of the main combustion parameters noted in the combustion gases and fumes and in operation of the boiler.

According to another characteristic, provision is made for monitoring the fouling of the boiler and the addition to the catalytic gaseous and corrective fluid of a fouling product.

According to yet another characteristic, the temperatures of flow and return of the heat transfer fluid are also monitored.

• . diminution sensible de l'encrassement de la chaudière et des cheminées ;
• . réduction importante de la production de matières volatiles imbrûlées ;
• . fréquence plus faible pour l'entretien du brûleur et le ramonage de la cheminée : fumées plus légères et moins grasses ;
• . économie de combustible ;
• . combustion propre : les suies se transforment en poudre grise ;
• . moins de corrosion et longévité augmentée des chaudières ;
• . diminution notable des rejets polluants ;
• . appareillage et dispositifs pouvant s'adapter à la régulation existante.

In addition to the main advantages of gaining in energy efficiency and of harmless or in any case less harmful discharges to the environment, the invention has many additional advantages justifying its interest even more:

• . significant reduction in fouling of the boiler and chimneys;
• . significant reduction in the production of unburnt volatile matter;
• . lower frequency for burner maintenance and chimney sweeping: lighter and less oily fumes;
• . saving fuel;
• . clean combustion: soot turns into gray powder;
• . less corrosion and increased longevity of boilers;
• . significant reduction in pollutant releases;
• . switchgear and devices that can be adapted to existing regulations.

Furthermore, the rejection to the atmosphere of combustion gases and fumes containing significantly less harmful volatile materials or less harmful transformants for the environment as in the process according to the invention does not yet constitute, in our modern world, a industrial advantage. However, it must be considered as one of the most important current values.

• . la figure 1 est le schéma général d'ensemble de l'installation montrant les liaisons entre les différentes parties composantes ;
• . la figure 2 est une vue schématique de détail du raccordement au brûleur ;
• . la figure 3 est une vue schématique illustrant la composition générale du générateur de complexe gazeux de correction.

The technical characteristics and other advantages of the invention are set out in the description which follows, given by way of nonlimiting example on an embodiment with reference to the accompanying drawings in which:

• . Figure 1 is the general diagram of the installation showing the connections between the different component parts;
• . Figure 2 is a schematic detail view of the connection to the burner;
• . Figure 3 is a schematic view illustrating the general composition of the gas correction complex generator.

The combustion improvement method according to the present invention proceeds from the general inventive idea which consists in maintaining, during the entire operation of the burner, conditions of optimal combustion by varying the flow of combustion air and by adding, by addition to the flow of combustion air, a variable, metered and controlled flow rate of a gaseous catalytic complex, the variation of this flow rate being controlled by a central unit from the values of the main combustion parameters recorded in the combustion gases and fumes and from the general operating variables of a boiler.

According to another characteristic, the speed of the burner fan is varied to modify the flow of combustion air, that is to say the excess air, and thus correct and adapt the combustion and the catalytic gas supply. with a view to reducing the formation of polluting and corrosive products which are suitably neutralized elsewhere.

To do this, the optimal central combustion unit includes the various analyzers and circuits for determining the values of the physical quantities measured using the various sensors and probes.

• . le débit du combustible
• . le capteur de débit d'air comburant
• . la température de l'air comburant à l'entrée
• . les températures aller et retour du fluide caloporteur
• . les caractéristiques des gaz de combustion :
  • température des fumées
  • opacité des fumées
  • teneur en oxygène,
  • teneur en oxyde de carbone,
  • teneur en oxyde d'azote,
  • teneur en oxyde de soufre

Non-exhaustively, we can cite:

• . fuel flow
• . the combustion air flow sensor
• . the combustion air temperature at the inlet
• . the return and return temperatures of the heat transfer fluid
• . the characteristics of the combustion gases:
  • smoke temperature
  • smoke opacity
  • oxygen content,
  • carbon monoxide content,
  • nitrogen oxide content,
  • sulfur oxide content

In order to coordinate, manage and control the overall operation, a programmable calculator-regulator or any other intelligent system receives the various necessary information and acts on the burner fan taking into account the heating stages of the burner.

The method according to the invention applies more particularly to an existing boiler regulation having the particularity of controlling the commissioning and the heating stages of burners called "monoblock". These are burners whose air flap is mechanically controlled by the position of the fuel inlet valve or valve by means of adjustable cams, linkages or other mechanical means. In this type of burner, the air / fuel ratio is constant at the value set at the time of initial adjustment. The excess air does not follow the variations of atmospheric conditions and everything happens as if the burner remained adjusted for only one atmospheric condition.

This type of burner achieves powers of the order of 10,000 therms.

The technical characteristics of the invention and of the installation in which the boiler is chosen for liquid fuel, for example fuel known under the name fuel oil, will now be described in detail below.

Of course, the process works just as well with a gas fuel burner.

The method according to the invention is implemented in and around a boiler 1 equipped with a blast air burner 2 using fuel oil as liquid fuel, mentioned however by way of example. The boiler is connected to a flue 3 making the connection of its outlet nozzle 4 to a chimney 5 with connection section 6 to the chimney.

The burner conventionally comprises a pump 7 connected through a filter 8 to the fuel reserve, an adjustable air inlet 9 in front of a suction chamber 10, a fan 11 and a barrel 12 for forming a flame 13 in a blown air flow with deflector and flame catch.

According to the invention, the adjustable air inlet 9 of the burner 2 is connected by one or more conduits such as 14, 15, 16 to a gaseous generator 17 for correcting multi-channel combustion generating a composite gas flow correcting for combustion, whose injection or supply to the burner is controlled by an optimal central combustion unit 18.

• . catalytique et inhibiteur de corrosion
• . de neutralisation
• . de décrassage.

dont les rôles et les fonctions sont indiqués ci-après.According to the present combustion improvement method, a gaseous correction complex is generated and then supplied to the burner on its air inlet or in the vicinity thereof, or in the blast-air projection barrel. combustion from at least three separate elementary sources corresponding to three separate gaseous products, supplied by the combustion correction generator 17 and having different properties:

• . catalytic and corrosion inhibitor
• . neutralization
• . cleaning.

whose roles and functions are indicated below.

The catalytic complex is also a corrosion inhibitor. It causes a main exothermic reaction intended to increase the temperature of the flame, the heat transfer and to perfect the combustion. It is associated with surfactants, dispersants and peptizers giving it dispersing, detergency, anticorrosion and peptizing properties which make it possible to prolong the dispersion within the oil droplets and to cause the inflammation of the normally unburnt constituents and to difficult combustion.

The neutralization complex partly transforms the oxides of nitrogen and sulfur into neutral compounds which are harmless to the component parts of the boiler and the installation and which are not harmful to the environment. It also helps reduce carbon monoxide emissions. It forms a protective film on the walls of the combustion chamber and of exchanger elements which ensures their protection against all aggressive products generated by or resulting from combustion.

The scouring complex is sent in sequences, upon detection of fouling or a drop in performance. It makes it possible to disintegrate the soot layer, to avoid hard deposits with an encrusting character and to keep the exchange surfaces clean and all their qualities and properties.

• 1. Flux catalytique et inhibiteur de corrosion.
  On adoptera une solution aqueuse peroxydée complexe de sels organo-métalliques associés à des produits tensio-actifs tels que sels de fer, cuivre, manganèse, cobalt, chrome.
  Cette solution est traversée par barbotage d'un flux d'air contrôlé.
• 2. Flux gazeux neutralisant.
  On adoptera une solution aqueuse peroxydée de sels alcalino-terreux tels que des sels de baryum, de cérium, de lithium, de potassium, d'ammonium ou équivalents.
  Cette solution est traversée par barbotage d'un flux d'air contrôlé.
• 3. Flux gazeux de décrassage.
  Il s'agit d'un flux gazeux obtenu à partir de produits permettant de diminuer la température de fusion des matières volatiles imbrûlées.
  On adoptera une solution aqueuse peroxydée et légèrement chlorée obtenue à base de sodium, de potassium ou d'ammonium. Ces sels peuvent être remplacés par des nitrates.

Some possible products for the production of the correcting gas flow will be mentioned below.

• 1. Catalytic flux and corrosion inhibitor.
  A complex peroxidized aqueous solution of organo-metallic salts associated with surface-active products such as iron, copper, manganese, cobalt, chromium salts will be adopted.
  This solution is crossed by bubbling a controlled air flow.
• 2. Neutralizing gas flow.
  A peroxidized aqueous solution of alkaline earth salts such as barium, cerium, lithium, potassium, ammonium or equivalent salts will be adopted.
  This solution is crossed by bubbling a controlled air flow.
• 3. Gas cleaning flow.
  It is a gas flow obtained from products allowing the melting point of unburnt volatile matter to be reduced.
  We will adopt a peroxidized and slightly chlorinated aqueous solution obtained based on sodium, potassium or ammonium. These salts can be replaced by nitrates.

As regards the quantitative aspect, a gaseous complex is brought to the burner in an amount of the order of a thousandth of the amount of oxidizing air and more particularly as indicated below, a ratio of between 10 and 50 ppm by mass between gas flow and fuel.

The combustion correction generator 17 is responsible for delivering to the burner, suitably dosed, the gaseous combustion correction complex from one or more commands from the optimal central combustion unit 18 which is designed to reset the boiler and the burner in an autonomous situation, that is to say the correction system disconnected, in the event of a malfunction of one of the devices of the combustion correction installation.

It comprises a control interface in the form of a programmable controller 19 acting in a grouped or individual manner on the channels of the gaseous generator 17 multichannel combustion correction each corresponding to a specific combustion correction product which will be supplied individually or simultaneously to the burner with one and / or the other of the different corrective products.

As indicated, each path constitutes an elementary generator such as 20 for a specific gaseous product.

The present invention is aimed, without limitation, at three basic gaseous products.

Each channel is for example individually controlled by the programmable controller 19. A collective or individual air preparer 21 comprising a compartment such as 22 air dryer-dehumidifier is followed by a low flow pump 23 specific to each channel and several bubbling tanks or cans, for example two in number, 24 and 25, each filled for the same route with the same solution of one of the specific products indicated above. These bubbling cans are mounted in series by tubing or bubbling conduits and terminated by a buffer tank 26. Each production circuit continues, before the outlet, by a low flow alarm 27. Each outlet is connected to the burner by a leads separate individual, previously referenced 14, 15 and 16, as shown in the figures.

The dryer 21 controls the humidity of the air and stabilizes it at around 40%.

The controller 19 individually controls the flow rate of the gaseous product by establishing and varying the air flow rate at the inlet or outlet of the air preparer using the low-flow pump 23 or an equivalent specific to each way. An auxiliary supply pump (not shown) makes it possible to replenish each container with liquid from a reserve, for example by maintaining a constant level using an appropriate device.

Each gaseous product forming the gaseous correction complex is driven weakly, minimally, towards the burner by the effect of the internal pump 23 placed upstream on each of the paths of the generator 17 but also and above all by the depressogenic effect generated by the burner fan or turbine. To do this, the pipes connecting to the burner open into the suction chamber 9 of the burner or into the flow of air blown along the barrel 12, thus benefiting from the general aeraulic drive.

Thus, by means of an appropriate command coming from the central unit 18 through the programmable controller 19, it is possible to dose on each channel, at will and gradually, the flow rate of the product supplied to the burner and sucked in by it.

Due to the location upstream of the pump 23, the last tanks 25 and 26 are under negative pressure for reasons of safety and non-backflow into the other tanks of aqueous solutions and possibly even into the pump.

The tanks of the aqueous solutions are equipped with level detectors thus avoiding a unnecessary operation of air pumps due to lack of products

The tanks of the aqueous solutions are also equipped with pressure drop regulators ensuring by these devices the regular flow of the air pumps.

The correction gas circuit is also equipped with a device for stopping the pumps by overpressure in the conduits.

As indicated, in the context of the present invention, at least three separate paths are provided corresponding to the three basic products. However, this number is not limiting and it is possible to envisage adding other routes, such as routes in continuous or momentary production of oxygenation, vaporization or any other supply of product (s) whose properties come into play. the scope and spirit of the invention.

According to the invention, the speed of rotation of the fan is controlled by a speed controller 28 which acts on a given speed variation range of the burner drive motor which is also that of the fan without varying the pressure values. liquid fuel supply or without intervening on the heating rate.

This variable speed drive 28 is responsible for modifying the flow rate of the aspirated combustion air flow at any time in order to correct and adapt the excess combustion air to the optimal combustion conditions. The flow of the correcting gas complex supplied to the burner and drawn in by it is controlled separately by the central unit. The combustion air and corrector gas complex flow rates vary according to the values of the quantities and parameters monitored with a view to maintaining optimal combustion conditions during the total operating time of the burner.

According to a preferred variant, the variation in the speed of rotation of the motor is obtained by means of a speed variator with frequency variation, this variator being controlled by the central unit. The variation in the air flow rate extends over a range of 10% on either side of the preset value.

• . pallier les variations d'excès d'air pour l'obtention d'un meilleur rendement de combustion en se rapprochant au maximum de la courbe stoechiométrique ;
• . diminuer les surpressions lors de l'allumage et au démarrage ;
• . stabiliser les pressions intérieures du foyer qui sont modifiées par les variations de tirage naturel ;
• . pallier les variations atmosphériques qui modifient les caractéristiques physiques de l'air comburant ;

This variation in the air inlet flow makes it possible to:

• . compensate for variations in excess air to obtain a better combustion efficiency by getting as close as possible to the stoichiometric curve;
• . reduce overpressures during ignition and start-up;
• . stabilize the interior pressures of the fireplace which are modified by variations in natural draft;
• . alleviate atmospheric variations which modify the physical characteristics of the combustion air;

According to the invention, the combustion parameters are adjusted to lower the value of the soot and carbon monoxide formation point.

The assembly is controlled by the central combustion unit 18 for optimal combustion connected to the gas generator 17 of the combustion correcting gas flow, to the variable speed drive 28 and to the adjustable air inlet 9 of the burner, but also to various sensors of the main physical quantities and combustion parameters.

Alternatively, one can also act on the opening of the adjustable air inlet 9 to the burner to modify the flow rate of the combustion air.

These sensors are placed in various locations outside the boiler.

• . les capteurs de brûleur, disposés dans ou à proximité du brûleur ;
• . les capteurs de chaudière ;
• . les capteurs de sortie placés dans le tronçon de raccordement 6 à une distance de la sortie de la chaudière égale à environ deux fois et demi le diamètre de ladite sortie.

They are divided into the following three groups:

• . the burner sensors, arranged in or near the burner;
• . boiler sensors;
• . the outlet sensors placed in the connection section 6 at a distance from the outlet of the boiler equal to approximately two and a half times the diameter of said outlet.

Among the burner sensors, there is a sensor 29 for fuel flow, a sensor 30 for the temperature of the combustion air, a sensor 31 for the flow of the combustion air or the position for opening the combustion air valve.

Among the boiler sensors, it is necessary to mention in a non-exhaustive manner, two heat-transfer fluid temperature sensors. These are inlet temperature 32 and outlet temperature sensors 33 for the heat transfer fluid, making it possible to measure the temperature difference between the inlet and the outlet of the heating fluid distribution circuit.

Among the smoke outlet sensors, mention is made of a smoke temperature sensor 34, an oxygen content sensor 35, a carbon oxide content sensor 36, a carbon dioxide content sensor 37, as well as another group 38 of sensors providing the content of polluting gases such as sulfur dioxide and its compounds, nitrogen oxide and its compounds. A last sensor 39 makes it possible to measure the opacity of the fumes.

The parameters monitored are those which condition the quality, efficiency and cleanliness of the combustion.

The central unit 18 for optimal combustion acts on the basis of a computer-regulator 40, for example with a microprocessor, on the one hand on the speed of rotation of the fan motor, that is to say on the flow rate of oxidizing air, allowing to dose the excess air which plays an important role in the formation of nitrogen oxides, but also, on the other hand, according to a variant, on the rate of mixing of the combustion air with the gaseous combustion-correcting complex from the values of the parameters monitored according to a law of regulation and correction allowing optimum combustion conditions to be maintained at all times during burner operation.

The proportion of mass evaluation of the catalysts relative to the mass of fuel is between 10 and 50 ppm.

• . la capacité d'enrichissement de l'air au taux d'humidité présent à la sortie du deshumidificateur à travers les solutions aqueuses que l'air doit traverser ;
• . la vitesse de passage du complexe gazeux correcteur qui est fonction de l'aspiration de l'air comburant engendrée par la turbine du brûleur.

The flow rate of the correcting gas complex is mainly determined by the following considerations:

• . the capacity for enriching the air at the humidity present at the outlet of the dehumidifier through the aqueous solutions which the air must pass through;
• . the speed of passage of the correcting gas complex which is a function of the suction of the combustion air generated by the burner turbine.

The total flow rate of the correcting gaseous complex required will determine the number of generating circuits of this gaseous complex to be commissioned on the basis of an average of 200 liters / hour per circuit for a fuel consumption equal to 30 KW / hour.

This process can be used in a simplified version, use in which the means include only the correction gas flow generator 17 which is managed by the programmable controller 19 operating from the fuel flow rate, the combustion air flow rate and the temperature of the fumes, the values of which are sensed by appropriate probes as indicated above.

According to this simplified process, the variation of the combustion air flow is controlled by the engine of the fan only from fuel flow rates and flue gas temperature.

During the ignition phase and temperature rise to steady state, the production circuits of the gas complex will be used, the aqueous solutions of which are composed of a support such as a light topping gas oil which will have dissolved a catalyst as in example of the cobalt or manganese or nickel or iron or chromium or cerium salts or mixtures or compositions of one or the other of these salts.

This regime is also that of operation at a low heating rate for which the addition of a combustion correcting gas in the combustion air makes it possible to significantly reduce the production of volatile materials and unburnt gases.

During the upper combustion phase or steady state, the circuits whose aqueous solutions are composed of mixtures of metal salts with chlorinated compounds such as ammonium or potassium chloride will be used.

It will be recalled here that the method according to the invention makes it possible to reduce the excess of air resulting in a correlative decrease in the production of nitrogen oxides which are, in part, by virtue of said method, transformed into nitrates while retaining optimal combustion .

It is also recalled here that the method according to the invention is applicable to any combustion from a solid, liquid or gaseous fuel.

Furthermore, it is conceivable to use the above method for odor treatment applications resulting from combustion, pyrolysis, cooking or other sources of gassing.

It is understood that beyond the means described, various obvious modifications and simple variants fall within the scope of the present invention.

Claims (12)

Optimal combustion process by adding a gaseous complex to the combustion air flow and maintaining optimal combustion conditions for a boiler equipped with a blast air burner, characterized in that the combustion air is enriched with gaseous combustion correction complex and the combustion air flow is varied to adapt the combustion by an excess of air just below the formation of soot and carbon monoxide, by speed variation of the burner fan based on the main parameters of combustion and boiler operation, the correcting gas complex to keep combustion optimal. Method according to claim 1, characterized in that the variation of the flow rate of the gas complex is obtained by the variation of the speed of rotation of the turbine of the burner. A method according to claims 1 and 2 characterized in that the combustion correction complex is a mixture of a catalytic gas flow and a corrosion inhibiting gas flow and sequentially of a gas scrub flow. Process according to Claims 1 and 2, characterized in that the combustion conditions are regulated just below the point of formation of the series and of the carbon monoxide Method according to the preceding claims, characterized in that the gaseous complex sequentially contains a gas flow of neutralization with respect to sulfurous and sulfuric anhydride. Method according to the preceding claims, characterized in that the catalytic gas flow and corrosion inhibitor is obtained by bubbling an air flow in an aqueous solution peroxidized organometallic salts associated with surface-active products. Method according to the preceding claims, characterized in that the neutralizing gas flow is obtained by bubbling an air flow in an aqueous peroxidized solution of alkaline earth salts. Process according to the preceding claims, characterized in that the gaseous cleaning flow is obtained by bubbling an air flow in a peroxidized and slightly chlorinated aqueous solution based on sodium, potassium or ammonium. Method according to one of the preceding claims, characterized in that during the ignition phase and the rise in temperature to the steady state, the production circuits of the gaseous complex will be used, the aqueous solutions of which are composed of a support such as a light topping gas oil which will have dissolved a catalyst such as, for example, cobalt or manganese or nickel or iron or chromium or cerium salts or mixtures or compositions of one or the other of these salts. Method according to any one of the preceding claims, characterized in that the variation of the air flow rate is controlled solely from the flow rate of the fuel and from the temperature of the fumes. Means for carrying out the above process, characterized in that it comprises, around a boiler equipped with a supply air burner, several groups of sensors including burner sensors, boiler sensors and smoke outlet sensors, a central unit controlling the speed controller of the fan motor to adapt the flow of combustion air to variations in combustion, in order to maintain the conditions for optimal combustion without formation of soot, and a generator of gaseous correction complex controlled by the central unit and connected by several conduits to the suction chamber of the burner. Means according to claim 11, characterized in that the generator of the gaseous combustion complex consists of several independent elementary generators supplied by an air preparer and each formed by an air pump at low flow rate, several bubbling cans crossed by the piping for transporting the gaseous product and a flow alarm located near the outlet, the assembly being controlled in flow by a programmable controller itself controlled by the central unit.

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