Patent Application
20240175577
The invention relates to a burner unit for a furnace, in particular a continuous furnace, a tunnel furnace, a chamber furnace, a bogie hearth furnace or the like, to a furnace and to a method for its operation, the burner unit having at least two burners which are configured for burning a combustion gas, the burner unit having a gas pipe and an air pipe for supplying the burners with combustion gas, the burner unit having at least one gas metering valve in the gas pipe and at least one air metering valve in the air pipe, the gas metering valve and the air metering valve being controllable by means of a shared control device, the gas metering valve being a magnet valve.
From the state of the art, burner units of this kind or rather furnaces having burner units of this kind are sufficiently known. In continuous furnaces or tunnel furnaces, a good to be treated, such as a ceramic product, is moved through the furnace continuously or periodically in time intervals; in chamber furnaces or bogie hearth furnaces, a burner performance can be adapted. For this purpose, the good to be treated is exposed to a predefined temperature profile, e.g., in predestined zones of the furnace for heating and cooling, or the temperature profile is realized solely in one zone of the furnace. What is known as a gas burner is used as a burner. The burners represent combustible-material metering devices which self-ignite above a flammability limit temperature in permanently prevailing temperatures.
Since furnaces for the mass production of goods are comparatively large, a plurality of burners is required at all times to generate a temperature required within the furnace. In a burner unit, the burners are disposed at a designated position in the furnace, while the burner unit having the burner remains solidly at the furnace, as the good is moved in relation to the burners. A furnace can be designed having a plurality of burner units having, in turn, a plurality of burners. Each of the burner units has a gas pipe and an air pipe for supplying the respective burner with a combustion gas. Since a material composition of air within the furnace is indeterminate, gas is always introduced together with air into the furnace via the corresponding burner. This prevents an incomplete combustion of the gas within the furnace due to a lack of oxygen, which could have an adverse effect on the good to be produced, and a risk of explosion.
For metering the gas or the combustion gas in the furnace via the burner, a gas metering valve can be provided at the gas pipe, the gas metering valve being controlled by means of a control device. The gas metering valve can be a magnetic valve. Magnetic valves of this kind are known from EP 2 192 336, for example, and are designed having a displaceable piston which is disposed in a valve casing, blocks two chambers from each other and is actuatable by means of an electromagnet. By actuating the piston, the gas can be metered to the burner. In the air pipe, an air metering valve can be provided which is also controllable by means of the control device. The air metering valve can be formed by an actuatable flap, e.g., by means of a servomotor or be pneumatically driven. Depending on the amount of required combustion gas, the control device can open or close or bring the flap in the air pipe in a partially open position such that a sufficient amount of air required for complete combustion can be supplied to the burner when combustion gas is introduced into the furnace for combustion. A disadvantage of the furnaces described above, however, is that their operation is cost-intensive due to regularly rising procurement costs for gas.
The object of the invention at hand is therefore to propose a burner unit, a furnace and a method for operating a furnace, all of which allow inexpensive operation.
This object is attained by a burner unit having the features of claim 1; a furnace having the features of claim 9; and a method having the features of claim 10.
The burner unit according to the invention for a furnace, in particular a continuous furnace, a tunnel furnace, a chamber furnace, a bogie hearth furnace or the like, has at least two burners which are configured for burning a combustion gas, the burner unit having a gas pipe and an air pipe for supplying the burners with combustion gas, the burner unit having at least one gas metering valve in the gas pipe and at least one air metering valve in the air pipe, the gas metering valve and the air metering valve being controllable by means of a shared control device, the gas metering valve being a magnet valve, and the air metering valve also being a magnet valve.
According to the invention, the gas metering valve and the air metering valve are controllable by means of the control device, meaning the gas metering valve and the air metering valve can be opened and closed via the control device. The fact that the air metering valve and the gas metering valve are both magnetic valves is what even makes it possible for an opening and a closing of the gas metering valve and the air metering valve to be coordinated relatively precisely. This allows the opening and the closing to take place essentially synchronously.
This is not the case in the state of the art, in particular when a different type of valve, e.g., flap having a servomotor or a pneumatic drive, is used as an air metering valve. In this case, the operational costs are comparatively high and an actuation of the corresponding valve is comparatively slow, meaning a synchronization of the gas metering valve and the air metering valve is not readily possible. Owing to the fact that the gas metering valve and the air metering valve can now be opened and closed synchronously, it becomes possible to save energy. This is yielded from an air volume required for combustion now being able to be metered out relatively precisely to the furnace. When using a different type of valve for the air metering valve, an air volume larger than required commonly enters the furnace to ensure that complete combustion of the gas is possible. For this reason, according to the state of the art, air is continuously supplied to the furnace while quickly opening and closing the gas metering valve, as an air flap actuated using a servomotor, for example, and used as an air metering valve can only be actuated comparatively slowly. Since, however, the air suctioned from the surroundings of a furnace has a significantly lower temperature than an atmosphere in a furnace interior, the air supplied to the furnace must be heated, whereby energy and thus gas is consumed. If more air is supplied to the furnace than necessary, this air must also be heated correspondingly, for which, in turn, a larger volume of gas is required. Owing to the fact that the air in the furnace can be adjusted more precisely to an amount of gas supplied to the furnace via the magnet valve, the amount of used gas can be reduced in total, whereby large cost savings can be achieved when continuously operating the furnace.
The burner unit can comprise a regulating apparatus of the control device, the regulating apparatus being able to be configured for synchronizing a corresponding operating state of the gas metering valve and the air metering valve. The regulating apparatus and the control device can, for example, be formed in a shared structural unit, e.g., via a programmable logic controller, a computer, having a software executed thereon, or the like. Alternatively, however, the regulating apparatus and the control device can also be formed via two structurally separate units, e.g., as a computer each. In this instance, an operating state of the gas metering valve and the air metering valve is understood to be a position of the corresponding valve, i.e., open or closed. The regulating apparatus can now synchronize the gas metering valve and the air metering valve in such a manner that they are either open or closed at essentially the same time. In this context, a slight prematurity and/or slag of one of the two valves can be possible, e.g., in a range of <3 seconds to 0.05 seconds. Thus, it can be ensured that no more than the amount of air required for complete combustion of the gas is supplied to the furnace.
The gas pipe and the air pipe can be branched toward the corresponding burners, the burners being able to be switched in series at the gas pipe and the air pipe. At the gas pipe and the air pipe, branches from the gas pipe and the air pipe, respectively, to the corresponding burners, can be formed. Consequently, it can be ensured that the burners are supplied consistently with gas and air. Generally, however, burners can also be connected in series at the gas pipe and/or the air pipe. A pressure in the corresponding pipes can be 1 bar to 3 bar.
The burner unit can have a gas metering valve and an air metering valve assigned to the gas metering valve per burner. If each burner is supplied with combustion gas via a gas metering valve and an air metering valve intended therefor, a performance of the burners can be adjusted individually. Thus, a particularly even temperature distribution can be established within the furnace. Likewise, a particularly precise dose of combustion gas becomes possible.
The burner unit can have a check valve in the gas pipe and/or the air pipe per burner and/or for the entire burner unit. For instance, a check valve can be provided in a branch of the gas pipe and/or the air pipe, respectively, toward the burner. The check valve can be a manually acuatable valve. This makes it possible to easily exchange an individual burner should it be defective, without having to block the entire gas pipe and the air pipe for all burners. Nevertheless, the burner unit can centrally have a check valve, with which the burner unit can be switched off entirely, in the gas pipe and/or the air pipe for the entire burner unit.
An opening cross section of the air metering valve can be larger than an opening cross section of the gas metering valve. Thus, a significantly larger volumetric flow of air can be metered via the air metering valve than a volumetric flow of gas. This allows combustion in an essentially stoichiometric relationship. Consequently, a pipe cross section of the gas pipe can also be significantly smaller than a pipe cross section of the air pipe. Furthermore, a pressure in the gas pipe can be significantly larger than a pressure in the air pipe. Further, this allows using a fan for suctioning and conveying the air in the air pipe, whereby the use of compressed air, the provision of which would be connected to high costs, is no longer required.
The burner unit can have at least 3, 4, 5, 6, 7, 8 or more burners. Preferably, the burner unit can have an even or uneven number of burners. The burner unit can be symmetrical regarding the position of the burners at the furnace.
The burner unit can have a fan for conveying air into the air pipe or be connected to a central air circulation pipe of a furnace using the air pipe. The fan can be disposed at one end of the air pipe and suction air from the surroundings of the furnace and blow or convey it into the air pipe. A burner unit having a fan specifically intended therefor enables a flexible positioning of the burner unit at the furnace and its exchange, without other burner units of the furnace being impacted thereby. Alternatively, the air pipe can be connected to an air circulation pipe, to which, in turn, a fan of this kind is connected. Via the air circulation pipe, it becomes possible to convey air to the burners in a number of air pipes, which branch from the air circulation pipe.
The furnace according to the invention, in particular a continuous furnace, a tunnel furnace, a chamber furnace, a bogie hearth furnace or the like, comprises at least one burner unit according to the invention. However, the furnace can also comprise a plurality of burner units, in particular burner units according to the invention or burner units of different types. For instance, the furnace can have 5, 10, 15, 20 or more burner unit. In this context, the burner units can be disposed above a furnace interior, for instance on a furnace or its top or laterally on a furnace or a furnace interior.
In the method according to the invention for operating a furnace, in particular a continuous furnace, a tunnel furnace, a chamber furnace, a bogie hearth furnace or the like, a combustion gas is burned using at least two burners of a burner unit of the furnace, the burners being supplied with the combustion gas via a gas pipe and an air pipe, at least one gas metering valve in the gas pipe and at least one air metering valve in the air pipe being controlled by means of a shared control device, a regulating apparatus of the control device synchronously opening and closing the gas metering valve and the air metering valve. For this purpose, the burner unit comprises the gas pipe, the air pipe, the gas metering valve, the air metering valve and the control device. Regarding the advantages of the method according to the invention, reference is made to the description of advantages of the burner unit according to the invention.
An operating state of the air metering valve can be regulated as a reference variable according to the operating state of the gas metering valve, for example open or closed. This makes it possible to adjust an air demand relatively precisely to an amount of gas supplied to an interior of the furnace at all times. For regulation, the regulating apparatus can have a PID regulator. Alternatively, it would also be possible for the control device to operate the gas metering valve and the air metering valve parallel or synchronously, without the air metering valve being regulated according to the gas metering valve.
The regulating apparatus can regulate the combustion gas in a stoichiometric relationship. According to this, the precise amount of air required for a stoichiometric relationship can then be metered in relation to the gas via the air metering valve. Excess air which was introduced via the burners and would have to be unnecessarily heated in the interior of the furnace is not present. Burners at a spacious furnace are not always tasked with supplying a combustion gas or combustion gas mixture as stoichiometric as possible to a furnace space, as a sufficient amount of air is always available in the furnace space via the general operation type; however, it cannot always be used to its full extent for combustion. The task of the burner is therefore more akin to covering areas where oxygen has been exhausted, further to contribute to cooling the burner lances and to be available as a pre-mixture with the combustion gas.
The regulating apparatus can regulate the gas metering valve according to a requirement of a burner performance and/or a furnace temperature as a reference variable of the control device. Thus, the burner performance and/or the furnace temperature can be processed by the regulating apparatus via a specification of the control device. A controlled variable can be determined by means of a sensor, for example, in particular a temperature sensor, of the regulating apparatus. Besides this regulating circuit, the regulating apparatus can also comprise a plurality of regulating circuits, e.g., cascading regulating circuits and/or regulating circuits for the burner unit and individual burners of the burner unit.
An opening and a closing is executed at a stroke of at least 50 strokes/minute, preferably 100 strokes/minute, particularly preferably 200 strokes/minute, up to 400 strokes/minute. The opening and closing of the gas metering valve and the air metering valve accordingly can be executed comparatively quickly. This quick stroke does not become possible until magnet valves are used. A stroke can be at least 50 ms. Other types of valves, e.g., having an actuatable flap, would hardly be suitable for this purpose and become worn comparatively quickly compared to magnet valves, which would require cost-intensive corrective maintenance. Further, it has proven that a particularly strong whirling of the combustion gas within the furnace and thus an evening-out of the combustion are achieved with this stroke. The yielded, more even temperature distribution within the furnace leads to an improved quality of the good treated in the furnace. Consequently, a more even burn result can be attained with ceramics, for example.
The control device can initiate a sequence of strokes of an opening and closing when a lower furnace temperature is not met and can terminate the sequence of the strokes when an upper furnace temperature is exceeded, preferably the regulating apparatus being able to regulate a burner performance by varying stroke times and/or stroke durations. Thus, corrective maintenance of a corresponding burner can be caused by the execution of the sequence of strokes. A stroke duration can remain unaffected in this context. When switching off the corresponding burner, the sequence of strokes is terminated. The initial operation of the corresponding burner can take place when the control device detects the lower furnace temperature, and the switching-off can take place when the control device detects the higher furnace temperature. The lower furnace temperature and the higher furnace temperature consequently define a temperature range in which the furnace can be operated. By varying a stroke frequency as a function of a target temperature value, the target temperature values are exceeded or not met in only rare instances or for exceptional perturbations.
Air at a temperature of below 100° C., preferably below 70° C., can be metered via the air metering valve, a temperature of up to 400° C., preferably up to 700° C., particularly preferably 1,000° C. or higher, being generated in the furnace. Owing to the fact that comparatively cold air compared to the temperature in the furnace is metered via the air metering valve, it becomes possible to realize a volumetric flow which is as small as possible and air metered via the air metering valve. If, in contrast, hotter air were to be used, a difference in temperature between the air and an atmosphere in the furnace would be smaller, however, a significantly larger volumetric flow of air would have to be supplied to the furnace owing to the volumetric expansion of the hotter air. The required structural measures and the energy costs for the conveyance, for example for fans, would surpass possible savings for gas and/or costs. A furnace can therefore be operated particularly cost-efficiently in the indicated relationships of a temperature of the air and a temperature of an atmosphere of the furnace.
Other embodiments of the method are derived from the description of features of the dependent claims referring to device claim 1.
In the following, a preferred embodiment of the invention is described in more detail with reference to the enclosed drawings.
Burner unit 10 further comprises a fan 16, which is disposed at an end 17 of air pipe 15, and suctions air from surroundings 18 of furnace 13 and conveys it to air pipe 15. Air pipe 15 branches towards corresponding burner 14 via branches 19, meaning burners 14 can be supplied with air. In corresponding branches 19 of air pipe 15, check valves 20 are disposed, which are manually actuatable and allow a complete blocking of air pipe 15 at this location. Furthermore, an air metering valve 21 is provided, which is disposed essentially at end 17 of air pipe 15 downstream of fan 16 in a flow direction of the air. Air metering valve 21 has a servomotor 22 and a flap (not shown in this instance) within air pipe 15. Via air metering valve 21, a volumetric flow of air supplied to burners 14 can be set by air supplied to burners 14. By means of a control device (not shown in this instance) of burner unit 10, air metering valve 21 is set such that a sufficient amount of air is always available for a complete combustion of the gas within furnace 13.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 131 222.4 | Nov 2022 | DE | national |
