JP2015148377A - Combustion control method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion control method and device capable of effectively using inexpensive auxiliary fuel without using expansive main fuel in a case where steam demand is satisfied only with auxiliary fuel in combustion control of a boiler or the like.SOLUTION: A combustion control method controls the combustion state of a combustion device activated by combusting main fuel and installed in a boiler 50 combusting main fuel and auxiliary fuel. The combustion control method changes over at least three combustion modes, which are single firing of main fuel (first mode), mixed firing of main fuel and auxiliary fuel (second mode) and single firing of auxiliary fuel (third mode), with a mode changeover switch 68 of a control panel 66, to thereby perform combustion control.

Description

  The present invention relates to a combustion control method and apparatus for burning fuel in a combustion apparatus installed in a boiler, a furnace, or the like.

  There is a growing demand for effective use of by-product fuel (by-product fuel) generated as a by-product from the production process of chemical products and the like. However, the amount of secondary fuel generated is not stable. For this reason, for example, when it is intended to secure the required amount of steam in a boiler, a method is adopted in which the shortage is supplemented with fossil fuel, which is the main fuel, and the main fuel and the sub fuel are co-fired (mixed combustion). .

  Conventionally, as a combustion control in this case, a boiler is used as an example by switching between two combustion modes, a main combustion of the main fuel (first mode) and a mixed combustion of the main fuel and the sub fuel (second mode). The steam (steam) demand was met.

  Conventionally, what is shown in FIG. 3 is known as an example of a combustion control apparatus. In FIG. 3, the start-up (combustion start) of the boiler 10 is performed by “main combustion of main fuel” (first mode). The main fuel cutoff valve 12 is opened and ignited according to the automatic control procedure. When the boiler 10 reaches a predetermined pressure (normal pressure), the main fuel flow control valve 14 is opened and closed so that the pressure of the boiler 10 becomes constant. The combustion air damper 18 is opened and closed via the combustion air operation device 16 so that the amount of air necessary for burning the fuel is reached, and an appropriate amount of air is sent to the burner 20. 22 is a boiler pressure transmitter, and 24 is a boiler pressure controller.

  Thereafter, when the secondary fuel is supplied, the secondary fuel flow rate command meter 30 sets the secondary fuel amount manually or automatically. Then, the mode changeover switch 28 of the control panel 26 is switched from “primary fuel mono-combustion” to “main fuel and sub-fuel co-firing”, and “main fuel and sub-fuel co-firing” (second mode) is set. In accordance with the automatic control procedure, the sub fuel cutoff valve 32 is opened, and the mixed combustion combustion is started while continuing the combustion. It is automatically controlled so that the drum pressure (boiler pressure) becomes constant by calculating and controlling the sub fuel flow rate controller 34 and the main fuel flow rate controller 36. 38 is a sub fuel flow control valve, 40 is a main fuel flow meter, and 42 is a sub fuel flow meter. When the main fuel is exclusively burned while continuing combustion, this is performed in the reverse procedure.

  FIG. 4 shows an example of a control flow in the conventional combustion control method. In FIG. 4, switching of the combustion mode between the primary combustion of the main fuel (first mode) and the combined combustion of the main fuel and the auxiliary fuel (second mode) is performed as follows, for example. That is, when there is a secondary fuel, the mode is switched to mixed combustion (second mode), and when there is no secondary fuel, the mode is switched to exclusive combustion (first mode). The presence of the secondary fuel is detected by, for example, the liquid level and pressure of the tank in which the secondary fuel is stored, and the combustion mode is switched manually or automatically.

  Patent Document 1 below discloses a standard fuel (main fuel) and biogas (sub fuel) mixed fuel or standard fuel (main fuel) in order to ensure stable combustion in a combustion apparatus using a biogas mixed fuel. ) Is controlled in accordance with a multi-stage combustion mode. In the technology of Patent Document 1 below, there is no exclusive combustion mode of biogas which is a secondary fuel.

JP 2011-247554 A

  In the conventional combustion control, in the combustion of the main fuel and the secondary fuel, only the control in the two combustion modes of the primary combustion of the main fuel (first mode) and the mixed combustion of the primary fuel and the secondary fuel (second mode) is performed. I couldn't. For this reason, for example, when a boiler is used, the main fuel, which is a fossil fuel, is used even when the steam demand can be met with only the secondary fuel. Further, even when the number of sub fuels is not one but plural, only combustion control by co-firing of the main fuel and the plurality of sub fuels can be performed.

  The problem to be solved by the present invention is that, for example, when a boiler is used, even when the steam demand can be met with only the secondary fuel, the primary combustion of the primary fuel (first mode) and the primary combustion of the primary fuel and the secondary fuel are mixed. Since the control can only be performed in the two combustion modes (second mode), an expensive fossil fuel that is the main fuel must be used, and an inexpensive secondary fuel can be used effectively. It is a point that cannot be done.

  As an example, in the combustion control of a boiler, the present invention provides a combustion control method capable of effectively using an inexpensive secondary fuel without using an expensive primary fuel when the steam demand can be met with only the secondary fuel. And in order to provide the apparatus, in the combustion of the main fuel and the secondary fuel, in addition to the primary combustion of the primary fuel (first mode) and the combined combustion of the primary fuel and the secondary fuel (second mode), the secondary combustion of the secondary fuel The most important feature is to perform control in at least three combustion modes by adding (third mode) or the like.

  The combustion control method of the present invention is a method for controlling the combustion state of a combustion apparatus that starts by burning main fuel and burns main fuel and sub fuel, in which primary combustion of the main fuel (first mode), main fuel, and It is characterized in that combustion control is performed by switching at least three combustion modes of co-firing of secondary fuel (second mode) and exclusive combustion of secondary fuel (third mode).

  In the above method, when switching from the first mode to the second mode, when the secondary fuel is present, the secondary fuel is supplied and switched to the co-firing with the main fuel while continuing the combustion. When switching to the first mode, when the sub fuel is no longer present, it is possible to switch to the main combustion of the main fuel while continuing combustion. In the above method, when switching from the second mode to the third mode, when the control becomes possible with only the secondary fuel, the main fuel is shut off and the combustion is continued to exclusively burn the secondary fuel. However, when switching from the third mode to the second mode, if the control becomes impossible with only the secondary fuel, the main fuel is supplied and combustion is continued to co-firing with the secondary fuel. It can be switched while.

  In these methods, when the combustion mode is switched, the change in heat quantity is continuously increased by gradually decreasing the sub fuel while gradually increasing the main fuel, or gradually increasing the sub fuel while gradually decreasing the main fuel. It is preferable that If the control for changing the fuel gradually and gradually is not performed, the amount of heat changes intermittently when the mode is switched between exclusive combustion and mixed combustion. On the other hand, in any combustion mode, it is preferable that the required amount of heat changes continuously by automatic control. For example, when switching from the primary combustion of the main fuel (first mode) to the mixed combustion of the main fuel and the secondary fuel (second mode), when the switching signal is input, the secondary fuel is gradually increased while gradually decreasing the primary fuel, Ensure that the change in heat is continuous.

  Further, in these methods, when there are n (n ≧ 2) types of secondary fuels, the primary combustion of the primary fuel (first mode), the primary combustion of the primary fuel and a plurality of secondary fuels (second mode), and the secondary fuel Combustion control can be performed by switching the multi-mode of exclusive combustion (third to n + 2 mode) of each fuel. By-products such as hydrogen generated as a by-product from the production process of a factory, COG (coke oven gas), by-product gas such as gas generated by biomass, and by-products such as vegetable oil, animal oil, solvent, etc. Oil or the like can be used.

  The combustion control device according to the present invention is a device for controlling the combustion state of a combustion device that starts by burning main fuel and burns main fuel and sub fuel. Main fuel supply / cutoff for supplying main fuel to the combustion device And a main fuel supply line having a main fuel flow rate control means for adjusting the supply amount of the main fuel, a secondary fuel supply / shutoff means for supplying the secondary fuel to the combustion device, and a secondary fuel supply line for adjusting the supply amount of the secondary fuel A secondary fuel supply line having a primary fuel flow control means, a primary fuel supply / shutoff means, a primary fuel flow control means, a secondary fuel supply / shutoff means, and a secondary fuel flow control means. At least three combustion modes: a first mode), a co-firing of a main fuel and a sub fuel (second mode), and a co-firing of a sub fuel (third mode). A combustion mode switching control means for performing combustion control Te Rikae, it is characterized by comprising a.

  In the above apparatus, when there are n (n ≧ 2) types of sub fuels, n sub fuel supply lines are provided, and the main fuel mono-combustion (first mode), the main fuel, and a plurality of sub fuels are provided. The combustion mode switching control means for switching the multi-mode combustion modes of the mixed combustion (second mode) and the exclusive combustion of each sub fuel (third to n + 2 modes) can be provided. In these apparatuses, a combustion apparatus installed in a boiler can be used as the combustion apparatus, but other combustion apparatuses in other furnaces can of course be used.

  In the combustion control method and apparatus of the present invention, when the control is possible only with the secondary fuel, it is not necessary to use the expensive main fuel, so that the inexpensive secondary fuel can be used effectively. For example, in boiler combustion control, when the demand for steam (steam) can be met with only the secondary fuel, it is possible to effectively use the inexpensive secondary fuel without using the expensive primary fuel at all. Can be reduced.

  In the combustion system of the present invention, the main fuel is usually a fossil fuel purchased from the outside, and the secondary fuel is a by-product fuel generated by production activities at the installation site (hereinafter referred to as “by-product fuel”). It is. By-product fuel can be sold externally, but it is cheaper than fossil fuel. For this reason, when the steam demand can be met by the by-product fuel, the production cost can be reduced without using any fossil fuel.

  In addition, when switching the combustion mode, if the fuel is controlled so as to gradually increase / decrease, the amount of heat does not change intermittently, and the change in the amount of heat becomes continuous. can do.

FIG. 1 is an explanatory diagram showing an example of the configuration of the combustion control device of the present invention. FIG. 2 is an explanatory diagram showing an example of a control flow in the combustion control method of the present invention. FIG. 3 is an explanatory diagram showing an example of the configuration of a conventional combustion control device. FIG. 4 is an explanatory diagram showing an example of a control flow in a conventional combustion control method.

  In combustion control such as boilers that burn main fuel and sub fuel, when sub-fuel alone can meet the demand for steam, it is possible to effectively use inexpensive sub fuel without using expensive main fuel. In order to provide a combustion control method and apparatus, in addition to the primary combustion of the primary fuel (first mode) and the primary combustion of the primary and secondary fuels (second mode), the secondary combustion of the secondary fuel (third mode), etc. This was realized by performing control in at least three combustion modes by adding the above.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications. For example, in the following embodiment, a combustion apparatus installed in a boiler is described, but the present invention is also applied to a combustion apparatus installed in equipment other than a boiler, such as an incinerator, a combustion furnace, an absorption refrigerator, and the like. It goes without saying that can be applied.

  FIG. 1 shows a combustion control apparatus according to a first embodiment of the present invention. In the present embodiment, as an example, combustion control is performed by switching between the following three modes. The main fuel supply line 44 includes a main fuel shutoff valve 52 connected to the control panel 66 and the like as main fuel supply / cutoff means, and a main fuel flow rate control connected to the main fuel flow rate controller 76 and the like as main fuel flow rate control means. A valve 54 is provided. Further, the secondary fuel supply line 46 is connected to a secondary fuel cutoff valve 72 connected to the control panel 66 and the like as secondary fuel supply / shut-off means, and to a secondary fuel flow rate controller 74 as secondary fuel flow control means. A connected secondary fuel flow control valve 78 is provided. Combustion control is performed by switching between three combustion modes: primary combustion of the main fuel (first mode), mixed combustion of the main fuel and the secondary fuel (second mode), and secondary combustion of the secondary fuel (third mode). As a mode switching control means, a control panel 66 provided with a mode switching switch 68, a secondary fuel flow rate command meter 70, a secondary fuel flow rate controller 74, a main fuel flow rate controller 76, a two-input contact switch 84, and the like is provided. ing.

  In FIG. 1, the boiler 50 is started (combustion start) in “main combustion of main fuel” (first mode). The main fuel shut-off valve 52 is opened and ignited according to the automatic control procedure. When the boiler 50 reaches a predetermined pressure (normal pressure), the main fuel flow control valve 54 is opened and closed so that the pressure of the boiler 50 becomes constant. The combustion air damper 58 is opened and closed via the combustion air operation device 56 so that the amount of air necessary for burning the fuel is reached, and an appropriate amount of air is sent to the burner 60. The pressure of the boiler 50 is kept constant by transmitting a pressure signal from the boiler pressure transmitter 62 to the boiler pressure controller 64 and transmitting from the boiler pressure controller 64 as a fuel flow rate signal or a damper opening / closing signal. Further, the main fuel flow rate is sent from the main fuel flow meter 80 to the main fuel flow rate controller 76 as a feedback signal, so that control is performed so that there is no deviation from the main fuel flow rate instruction. As the boiler, for example, a furnace tube fire tube boiler, a water tube boiler, a once-through boiler, or the like can be used.

  Thereafter, when the secondary fuel is supplied, the secondary fuel flow rate command meter 70 sets the secondary fuel amount manually or automatically. Then, the mode changeover switch 68 of the control panel 66 is switched from “main fuel mono-combustion” to “main fuel and sub-fuel co-firing” to be “main fuel and sub-fuel co-firing” (second mode). In accordance with the automatic control procedure, the secondary fuel cutoff valve 72 is opened to start the mixed combustion combustion while continuing the combustion. It is automatically controlled so that the drum pressure (boiler pressure) becomes constant by calculating and controlling the sub fuel flow controller 74 and the main fuel flow controller 76. As an example of the mixed combustion combustion control, the combustion by the main fuel is automatically controlled while the sub fuel is combusted. At this time, the sub fuel flow rate signal is transmitted from the sub fuel flow rate controller 74 to the main fuel flow rate controller 76, and the main fuel flow rate is controlled by subtracting the heat amount of the sub fuel flow rate. Further, by sending the main fuel flow rate from the main fuel flow meter 80 to the main fuel flow rate controller 76 as a feedback signal, control is performed so that there is no deviation from the main fuel flow rate instruction. By sending the secondary fuel flow rate as a feedback signal to the secondary fuel flow rate controller 74, control is performed so that there is no deviation from the secondary fuel flow rate instruction. As the main fuel, fossil fuels such as city gas can be used. For example, by-product hydrogen generated as a by-product from a production process of a chemical product or the like can be used as the by-product fuel.

  For example, when the demand for steam can be met with the secondary fuel, the mode changeover switch 68 of the control panel 66 is switched from “mixed combustion of the main fuel and secondary fuel” to “exclusive combustion of the secondary fuel”. In accordance with the automatic control procedure, the main fuel shut-off valve 52 is closed to stop the main fuel supply, and the combustion is continued and “sub-fuel exclusive combustion” (third mode) is set. Then, a sub fuel amount command is input from the sub fuel flow rate command meter 70 to the two-input contact switch 84, and the signal is switched to the “sub fuel flow signal” by the two-input contact switch 84, so that the sub fuel amount is changed. The flow rate controller 74 calculates and controls the secondary fuel flow rate control valve 78 to automatically open and close the drum pressure (boiler pressure). In this way, the automatic control using the main fuel is switched to the automatic control using the sub fuel.

  The above is an example of new three-mode control. As a result, when the vapor demand can be met with only the secondary fuel, the inexpensive secondary fuel can be effectively used without using the expensive primary fuel at all. When the main fuel is exclusively burned while continuing combustion, the procedures described in paragraphs [0026] and [0027] may be performed in reverse order. Further, in the case of the three-mode control as in the present embodiment, the boiler can be started (combustion start) even in the “sub-fuel exclusive combustion” (third mode).

  FIG. 2 shows an example of a control flow in the combustion control method of the present invention. In FIG. 2, the combustion mode switching between the primary combustion of the main fuel (first mode) and the combined combustion of the main fuel and the secondary fuel (second mode) is performed, for example, as follows. That is, when there is a secondary fuel, the mode is switched to mixed combustion (second mode), and when there is no secondary fuel, the mode is switched to exclusive combustion (first mode). The presence of the secondary fuel is detected by, for example, the liquid level and pressure of the tank in which the secondary fuel is stored, and the combustion mode is switched manually or automatically.

  Next, switching of the combustion mode between the co-firing of the main fuel and the sub fuel (second mode) and the co-firing of the sub fuel (third mode) is performed, for example, as follows. In other words, when it becomes possible to perform automatic control only by the presence of some secondary fuel (for example, when the vapor demand can be met only by secondary hydrogen, which is the secondary fuel), the main fuel is shut off and the secondary fuel is supplemented. Switch to exclusive combustion of fuel (third mode). If the secondary fuel alone cannot be controlled automatically (for example, if the by-product hydrogen, which is a secondary fuel, is not enough to meet the steam demand), the main fuel will be supplied and the secondary fuel will be secondary. Switch to mixed combustion with fuel (second mode). Whether or not automatic control is possible with only the secondary fuel is determined by, for example, boiler load, and the combustion mode is switched manually or automatically.

  Further, in the first embodiment of the present invention, when the combustion mode is switched by the mode change switch 68 of the control panel 66, it is desirable that the necessary heat amount is continuously changed by automatic control in any mode switching. Therefore, in the apparatus shown in FIG. 1, it is preferable that the amount of heat does not change intermittently, but the amount of heat gradually and gradually decreases. Specifically, the secondary fuel is gradually decreased while gradually increasing the main fuel, or the secondary fuel is gradually increased while gradually decreasing the main fuel.

  For example, when switching from the primary combustion of the main fuel (first mode) to the mixed combustion of the main fuel and the secondary fuel (second mode), the main fuel flow rate control connected to the main fuel flow rate controller 76 or the like when the switching signal is input. While the main fuel is gradually reduced by opening and closing the valve 54, the secondary fuel is gradually increased by opening and closing the secondary fuel flow rate control valve 78 connected to the secondary fuel flow rate controller 74 and the like, and the change in heat quantity becomes continuous. Like that. Similarly, when switching from the co-firing of the main fuel and the sub fuel (second mode) to the co-firing of the sub fuel (third mode), the main fuel connected to the main fuel flow controller 76 or the like when the switching signal is input. While the main fuel is gradually reduced by opening and closing the flow control valve 54, the sub fuel is gradually increased by opening and closing the sub fuel flow control valve 78 connected to the sub fuel flow controller 74 and the like, and the change in the heat quantity is continuous. To be.

  In the second embodiment of the present invention, in the apparatus as shown in FIG. 1, when there are a plurality of types of sub fuels instead of one type, for example, two types, for example, combustion control by switching of four modes as described below. Is to do. Needless to say, the present invention can also be applied to cases where there are three or more types of secondary fuels. The present embodiment can be applied, for example, in the case where the steam demand can be met only by each sub fuel in the combustion control of the boiler.

  Specifically, when there are two types of sub fuels, two sub fuel supply lines are provided, and the main fuel is exclusively burned (first mode), and the main fuel and a plurality of sub fuels are mixed (second mode). ), And as a combustion mode switching control means for performing combustion control by switching four combustion modes of the sub-fuel dedicated combustion (third mode, fourth mode), a mode switching switch, two sub fuel flow command meters A control panel having two sub fuel flow controllers, a main fuel flow controller and the like is provided. As two types of secondary fuels, for example, hydrogen generated as a by-product from a production process such as a factory and gas generated by biomass (two types of by-product gases) can be used. In addition, by-product gas such as COG (coke oven gas), and by-product oil such as vegetable oil, animal oil, and solvent can be used.

  By using the configuration as in the present embodiment, when the demand for steam can be met with only each secondary fuel, the inexpensive secondary fuel is effectively used without using the expensive primary fuel at all. Can do. Other configurations and operations are the same as those in the first embodiment.

  In combustion control of a boiler or the like that burns main fuel and sub fuel, in addition to main fuel mono-combustion (first mode) and main fuel and sub-fuel co-firing (second mode), sub-fuel mono-combustion (second mode) By using at least three combustion modes with the addition of (3 mode), etc., it is possible to use cheap secondary fuel without using expensive main fuel at all when steam demand can be met with only secondary fuel. Can be used for

10, 50 Boiler 12, 52 Main fuel shut-off valve 14, 54 Main fuel flow control valve 16, 56 Combustion air operation unit 18, 58 Combustion air damper 20, 60 Burner 22, 62 Boiler pressure transmitter 24, 64 Boiler pressure Controllers 26, 66 Control panels 28, 68 Mode changeover switches 30, 70 Sub fuel flow command meters 32, 72 Sub fuel shut-off valves 34, 74 Sub fuel flow controllers 36, 76 Main fuel flow controllers 38, 78 Secondary fuel flow control valves 40, 80 Primary fuel flow meter 42, 82 Secondary fuel flow meter 44 Primary fuel supply line 46 Secondary fuel supply line 84 2-input contact switch

Claims (8)

  In a method for controlling a combustion state of a combustion apparatus that starts by burning main fuel and burns main fuel and sub fuel, the main fuel mono-combustion (first mode), main fuel and sub-fuel co-firing (second) Mode), and combustion control by switching at least three combustion modes, ie, fuel combustion (second mode) as a secondary fuel.   When switching from the first mode to the second mode, if there is a secondary fuel, the secondary fuel is supplied and switched to the co-firing with the main fuel while continuing combustion, and the second mode is switched to the first mode. In this case, the combustion control method according to claim 1, wherein, when the sub fuel is no longer present, the main fuel is exclusively switched to combustion while continuing combustion.   When switching from the second mode to the third mode, when the control becomes possible with only the secondary fuel, the main fuel is shut off and switching is performed while continuing combustion to exclusively burn the secondary fuel. 3. When switching from the second mode to the second mode, when the control becomes impossible with only the secondary fuel, the main fuel is supplied and the combustion is continuously switched to the co-firing with the secondary fuel while continuing the combustion. The combustion control method described.   When changing the combustion mode, the secondary fuel is gradually decreased while gradually increasing the primary fuel, or the secondary fuel is gradually increased while gradually decreasing the primary fuel, so that the change in heat quantity is continuous. The combustion control method according to 1, 2 or 3.   When there are n (n ≧ 2) types of sub fuels, the main fuel is exclusively burned (first mode), the main fuel and a plurality of sub fuels are mixed (second mode), and each of the sub fuels is exclusively burned (second) The combustion control method according to any one of claims 1 to 4, wherein combustion control is performed by switching between three modes (3 to (n + 2) modes). In an apparatus for controlling the combustion state of a combustion apparatus that starts by burning main fuel and burns main fuel and sub fuel,
A main fuel supply line having main fuel supply / shut-off means for supplying main fuel to the combustion apparatus and main fuel flow rate control means for adjusting the amount of main fuel supplied;
A secondary fuel supply line having secondary fuel supply / cutoff means for supplying secondary fuel to the combustion device and secondary fuel flow rate control means for adjusting the supply amount of secondary fuel;
Main fuel supply / cutoff means, main fuel flow control means, sub fuel supply / cutoff means and sub fuel flow control means are connected to the main fuel mono-combustion (first mode), main fuel and sub fuel co-firing ( A combustion mode switching control means for performing combustion control by switching at least three combustion modes of a second mode) and a special combustion of the sub fuel (third mode).   In the case where there are n (n ≧ 2) types of sub fuels, n sub fuel supply lines are provided, and main combustion of the main fuel (first mode), co-firing of the main fuel and a plurality of sub fuels (second) 7. A combustion control apparatus according to claim 6, further comprising combustion mode switching control means for switching a multi-mode combustion mode of a mode) and a dedicated combustion of each sub fuel (third to n + 2 modes).   The combustion control device according to claim 6 or 7, wherein the combustion device is a combustion device installed in a boiler.

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