KR101781100B1 - Heat medium boiler - Google Patents

Abstract

Provided is a fired boiler which can accurately control the supply amount of combustion air according to the variation of the combustion amount, thereby maintaining good combustion performance and stabilizing the combustion.
The blower 28 supplies combustion air to the burner 24. The heat exchanger 32 preheats the combustion air pushed in from the blower 28 by the exhaust gas generated by the combustion of the fuel by the burner 24. [ The second temperature sensor 36 detects the preheating temperature T of the combustion air preheated by the heat exchanger 32. The control device 44 controls the damper 42 so as to be opened according to the set amount of combustion. The control device 44 adjusts the number of revolutions of the blower 28 so that the air ratio becomes the predetermined target air ratio from the preheating temperature T detected by the second temperature sensor 36 in accordance with the set amount of combustion. The adjustment of the number of revolutions is performed so as not to exceed the upper limit temperature Th of the preheating temperature T preset for each gas fuel having a different heating value.

Description

HEAT MEDIUM BOILER

The present invention relates to a heat medium boiler. The present application is based on a patent application application number 2011-091783 filed on April 18, 2011 and a patent application application number 2011-186884 filed on August 30, 2011, and in Japan on September 21, 2011 Priority is claimed based on the filed patent application No. 2011-205860, the contents of which are hereby incorporated by reference.

BACKGROUND ART Heretofore, a fired boiler has been known in which a heating oil is heated to a desired temperature and supplied to a load in order to utilize heat at a high temperature (250 ° C to 300 ° C).

Generally, the fired boiler is controlled so as to maintain the temperature of the fuel oil circulating between the load side and the fired boiler at a substantially predetermined temperature by performing heat exchange of the combustion gas by the combustion of the fossil fuel. However, since the temperature of the fruit oil is high and the temperature of the heated fruit oil is near 300 ° C, the exhaust gas temperature after heating in the fruit boiler is as high as about 350 ° C, For example, the boiler efficiency of the small-flow type steam boiler is about 92%, while the boiler efficiency is about 80% in the boiler of the fired boiler and the thermal efficiency is low.

In order to increase the boiler efficiency, it is necessary to lower the exhaust gas temperature. However, in the case of the boiler of the boiler, it is impossible to preheat the water supply and the effect of preheating the oil during normal operation can not be expected. As shown in Patent Document 1, a recuperator (heat exchanger) is used in the discharge portion to perform heat exchange with the combustion exhaust gas while pushing the combustion air into the recuperator with a blower, Preheating the air has been done.

Japanese Patent Application Laid-Open No. 08-312944

When the combustion air is heated, there is the following problem.

When the amount of combustion (fuel) is increased in proportion to the decrease in temperature of the fuel oil circulating and returning to the fired boiler, it is necessary to increase the combustion air according to the increase of the combustion amount. However, the combustion air preheated by the heat exchange with the exhaust gas has a volume Therefore, if the number of revolutions of the blower is constant, the speed of the air passing through the damper portion increases, the pressure loss in the damper portion increases, the amount of air pushed by the blower decreases, do.

That is, there is a shortage of air for combustion (oxygen concentration is lowered), resulting in deterioration of combustibility.

Further, since the exhaust gas temperature changes, the amount of heat exchange with the exhaust gas changes and the temperature of the combustion air changes, resulting in excessive air or shortage of air. As a result, There is a problem that the combustion is not stable such as increase, flame, and blow off.

Therefore, in the case of preheating the combustion air, it is necessary to grasp the temperature change of the combustion air according to the change of the combustion amount, and to control so that the required air amount is sent to the combustion region.

Therefore, in the technique of Patent Document 1, in order to prevent the ignition from becoming unstable due to the increase of the flow velocity of the burner portion due to the expansion of the air due to the temperature rise, an air flow rate adjusting valve for supplying air preheated by the recuperator to the burner The air flow rate regulating valve is maintained at a predetermined initial opening degree for a predetermined time after the burner ignition and the initial opening degree of the air flow rate regulating valve is changed according to the detection result of the temperature of the preheated air, So that the combustion is performed.

However, in the technique of Patent Document 1, it is expected that the temperature of the combustion air preheated greatly varies until the load fluctuation is large and the combustion amount after the burner ignition stabilizes, and there is a fear that the air ratio greatly changes and the combustion becomes unstable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a fired boiler which can control the supply amount of combustion air appropriately in accordance with the variation of the combustion amount, .

According to a first aspect of the present invention, there is provided a burner comprising: a burner; fuel supply means for supplying gaseous fuel to the burner in accordance with a set amount of combustion; a blower for supplying combustion air to the burner; A heat exchanger disposed between the burner for preheating the combustion air by the exhaust gas generated by the combustion of the gaseous fuel by the burner and a burner for detecting the preheating temperature of the combustion air preheated by the heat exchanger An opening degree control means for controlling the opening degree of the damper in accordance with the set amount of combustion, and a control means for controlling the opening degree of the combustion air The rotation speed of the blower is controlled so that the air ratio becomes a predetermined target air ratio by the preheating temperature detected by the temperature detecting means. And a rotation number control means for controlling the number of revolutions.

According to the first aspect of the present invention, the opening degree of the damper is controlled in accordance with the set combustion amount, and the rotation speed of the blower is controlled so that the air ratio becomes the predetermined target air ratio from the preheating temperature of the combustion air detected by the combustion air temperature detecting means. The number was adjusted.

Therefore, it is possible to control the supply amount of the combustion air appropriately according to the change of the combustion amount, so that the air ratio can be controlled to be the target air ratio, and combustion stability can be maintained by satisfactorily maintaining the combustion performance.

The second aspect of the present invention is the fuel boiler according to the first aspect, wherein the rotation speed of the blower by the rotation speed control means is adjusted by adjusting the rotation speed of the blower so that the combustion air amount sufficient to maintain the air ratio at the target air ratio And a preheating temperature of the blower to supply the preheating temperature to the burner.

According to the second aspect of the invention, since the processing required for adjusting the rotational speed of the blower is performed using the relational expression, the rotational speed of the blower can be adjusted precisely.

In a third aspect of the present invention, in the first or second aspect of the present invention, the upper limit temperature of the preheat temperature is set in advance for each gaseous fuel having a different calorific value, and the rotational speed control means controls the rotational speed of the blower Is performed such that the preheating temperature detected by the combustion air temperature detecting means does not exceed the set upper limit temperature.

According to the third aspect of the present invention, since the upper limit temperature of the preheating temperature of the combustion air is set and the number of revolutions of the blower is adjusted so as not to exceed the temperature, the combustion efficiency close to the target air ratio is maintained, It is possible to suppress the rise of the combustion gas temperature caused by the NOx removal, and to suppress the emission of NOx (nitrogen oxide).

A fourth aspect of the present invention is the fuel boiler according to the first or second aspect, wherein the upper limit temperature of the preheat temperature is set in advance for every gaseous fuel having a different calorific value, and the heat exchanger is set to the upper limit temperature And a heat exchanger which has a heat transfer area changed for each of the gaseous fuels so as to become the upper limit temperature of the preheating temperature in accordance with the type of the gaseous fuel is selected.

According to the fourth aspect of the present invention, since the heat exchanger having the heat transfer area determined according to the upper limit temperature is used, the combustion efficiency is improved while the efficiency of the heat boiler is increased and the rise of the combustion gas temperature due to the preheating is suppressed, The discharge of NOx can be suppressed.

A fifth aspect of the present invention resides in the fourth aspect of the present invention, wherein the upper limit temperature corresponding to the heat exchanger selected in accordance with the type of the gaseous fuel is referred to as a first upper limit temperature Th1 and the first upper limit temperature Th1, Is a second upper limit temperature (Th2), the heat exchanger is configured to be able to preheat the combustion air to the second upper limit temperature (Th2), and the control means And adjusting the rotational speed of the blower so that the preheating temperature is equal to or less than the first upper limit temperature Th1.

According to the fifth aspect of the present invention, the second upper limit temperature (Th2), which is the upper limit value of the preheat temperature obtained by adding the predetermined temperature to the first upper limit temperature (Th1) which is the upper limit value of the preheat temperature according to the fuel species of the gaseous fuel, Performance, and when the preheating temperature exceeds the first upper limit temperature Th1, the number of revolutions of the blower is adjusted so that the preheating temperature is lowered to the first upper limit temperature Th1 or lower. Therefore, since the preheating temperature of the combustion air can be maintained at a temperature close to the upper limit temperature (first upper limit temperature (T1)) or the upper limit temperature, high efficiency can be maintained as a boiler for heat treatment and NOx emission can be suppressed .

A sixth aspect of the present invention is the fuel boiler according to the first aspect, further comprising exhaust gas oxygen concentration detecting means for detecting an oxygen concentration in the exhaust gas, wherein the rotation speed control means comprises: And a control unit for controlling the air-fuel ratio based on the first rotation number to set the rotation number of the blower whose air ratio becomes a predetermined target air ratio by the preheating temperature detected by the air- And feedback control means for feedback-controlling the rotational speed of the blower so that the air ratio becomes the target air ratio in accordance with the oxygen concentration detected by the concentration detecting means.

According to the sixth aspect of the present invention, the opening degree of the damper is controlled in accordance with the set amount of combustion, and the temperature of the combustion air detected by the combustion air temperature detecting means is controlled such that the air ratio becomes the predetermined target air ratio, The number of revolutions per 1 minute was set.

Therefore, it is possible to control the supply amount of the combustion air appropriately according to the change of the combustion amount, so that the air ratio can be controlled to be the target air ratio, and combustion stability can be maintained by satisfactorily maintaining the combustion performance.

Further, the number of revolutions of the blower is feedback-controlled so that the air ratio becomes the target air ratio according to the oxygen concentration in the exhaust gas.

Accordingly, it is possible to suppress the fluctuation of the air ratio while improving the responsiveness of the control of the number of revolutions of the blower, to maintain the combustion property more favorably, and to newly stabilize the combustion.

A seventh aspect of the present invention resides in the fact that in the boiler of the sixth aspect, the feedback control of the number of rotations of the blower by the feedback control means includes a fine adjustment factor and a rough correction And the feedback control means adjusts the fine adjustment factor in accordance with the detected oxygen concentration and controls the fine adjustment factor Adjusts the rough correction coefficient so that the fine adjustment coefficient is within the adjustment range, and stores the rough correction coefficient when the fine adjustment coefficient exceeds the predetermined adjustment range.

According to the seventh aspect of the present invention, when the combustion is stopped and restarted (restarted), the rotation number of the blower is controlled using the new correction formula obtained by the stored rough correction coefficient, so that the adjustment range of the fine adjustment coefficient So that the adjustment to the target air ratio can be realized in a short time, so that the stabilization of the combustion can be realized even more quickly.

According to an eighth aspect of the invention, in the boil-boiler according to the seventh aspect, the adjustment of the rough correction coefficient by the feedback control unit is performed when the fine adjustment coefficient exceeds the adjustment range, To a predetermined correction amount per hour.

According to the eighth aspect of the present invention, since the rough correction coefficient can be adjusted by a simple control of changing the predetermined correction amount, the feedback control of the number of revolutions of the blower according to the oxygen concentration in the exhaust gas can be simplified .

A ninth aspect of the present invention resides in the fact that in the boiler according to any one of the sixth to eighth aspects, the setting of the first rotational speed of the blower by the rotational speed setting means is such that, even if the preheating temperature changes, The relationship between the number of revolutions of the blower and the preheating temperature is used in order to supply the burner with a sufficient amount of combustion air for maintaining the target air ratio.

According to the ninth aspect of the present invention, since the processing required for setting the number of revolutions of the blower is performed using the relational expression, the number of revolutions of the blower can be precisely adjusted.

According to the present invention, the supply amount of the combustion air is controlled appropriately in accordance with the variation of the combustion amount, so that the combustion performance can be kept favorable, combustion can be stabilized, and NOx emission can be suppressed.

Fig. 1 is a configuration diagram showing the configuration of a boiler 100 according to the first embodiment.
2 is a perspective view showing the structure of the cylinder 10, the window box 22, the burner 24, and the damper 42 in the boiler 100 according to the first embodiment.
3 (A), 3 (B) and 3 (C) are explanatory views of the operation of the damper 42 in the boiler 100 according to the first embodiment.
4 is a functional block diagram of the boiler 100 according to the first embodiment.
5 is a line diagram of a function showing the correlation between the preheating temperature T of the combustion air and the number of rotations N of the blower 28. In Fig.
6 is a flowchart showing the operation of the boiler 100 according to the first embodiment.
7 is an explanatory diagram of a table associating the temperature difference DELTA T with the correction coefficient alpha.
8 is a flowchart showing the operation of the boiler 100 according to the second embodiment.
Fig. 9 is a configuration diagram showing the configuration of the boiler 100 according to the fourth embodiment.
10 is a functional block diagram of the boiler 100 according to the fourth embodiment.
11 is a flowchart for explaining the first rotation speed N1, the rough correction coefficient K1, and the fine adjustment coefficient K2.
12 is an explanatory diagram of a case where the rough correction coefficient K1 is adjusted such that the fine adjustment coefficient K2 falls within the adjustment range.
13 is a flowchart showing the operation of the boiler 100 according to the fourth embodiment.
14 is a function diagram showing a correlation between the temperature (T) of the combustion air and the number of revolutions (N) when the outside air temperature, the humidity, and the like are set to any condition.
Fig. 15 is a diagram for explaining the correction of the number of revolutions by the fine adjustment coefficient K2.
Fig. 16 is a diagram for explaining the correction of the correlation formula by the rough correction coefficient K1.
Fig. 17 is a diagram for explaining the adjustment of the rough correction coefficient K1.

 (First Embodiment)

Hereinafter, an embodiment of the present invention will be described.

Fig. 1 is a configuration diagram showing a configuration of a fired boiler 100. Fig.

The boiler (100) comprises a cylinder (10).

As shown in Fig. 2, the tubular body 10 is provided with a heating tube 12 wound in a coil shape.

As shown in Fig. 1, the upstream end of the heating pipe 12 is a heating medium return line 14, which is a line in which the heating oil whose temperature is lowered by releasing heat from the load side returns to the boiler 100. The downstream end of the heating tube 12 is a heating medium supply line 16 for supplying a heat to the load side.

The heating oil is circulated through the heating medium return line 14 and the heating medium supply line 16 between the heating tube 12 and the load by a circulation pump (not shown).

A combustion chamber 18 is formed inside the heating tube 12 wound in a coil shape and the gas fuel (gaseous fuel) is burned by the burner 24 described later in this combustion chamber 18, ) Is heated.

1, the frit boiler 100 includes a window box 22, a burner 24, a fuel supply unit 26, a blower 28, an inverter 30, a heat exchanger (not shown) Second, third and fourth temperature sensors 34, 36, 38, 40, a damper 42, and a control device 44. The first, second, third,

In this example, the window box 22 is provided at the upper portion of the cylinder 10 as shown in Fig. 2, and the burner 24 is accommodated and held.

The window box 22 is a box for uniformly sending the combustion air supplied from the air blower 28 to the burner 24. [ The combustion air supplied from the window box 22 is mixed with the fuel (gas fuel in this embodiment) supplied from the fuel supply means 26 to the burner 24 and the burner 24.

As shown in Fig. 2, the burner 24 mixes and combusts the gaseous fuel supplied from the fuel supply means 26 with combustion air. The gaseous fuel mixed with the combustion air is burned in the combustion chamber 18 inside the heating tube 12 of the cylinder 10 by the burner 24.

The fuel supply means 26 supplies the fuel to the burner 24 in accordance with the set amount of combustion.

1, the fuel supply means 26 includes a gas fuel supply passage 2602, a shutoff valve 2604, a governor 2606, a proportional valve 2608, And a control device 44, which will be described later.

The gas fuel supply path 2602 has its upstream end connected to a gas supply source (not shown), and its downstream end connected to the burner 24.

The shutoff valve 2604 is provided in the gas fuel supply passage 2602 and is opened or closed by a control signal supplied from the control device 44.

The governor 2606 is provided on the downstream side of the shutoff valve 2604 in the gas fuel supply path 2602 and adjusts the pressure of the gaseous fuel flowing through the gas fuel supply path 2602 to a constant pressure.

The proportional valve 2608 is provided on the downstream side of the governor 2606 in the gas fuel supply path 2602 and the opening degree is adjusted by the motor 27. The motor 27 is constituted by a stepping motor (pulse motor) and the rotation amount of the motor 27 (rotation stop position) is controlled by the control device 44 so that the opening degree of the proportional valve 2608 is adjusted.

Therefore, the opening and closing of the shutoff valve 2604 is controlled by the control device 44, thereby controlling the supply and the stop of the gaseous fuel to the burner 24, and the opening degree of the proportional valve 2608 is controlled by the control device 44 The amount of gas fuel supplied to the burner 24, that is, the amount of combustion is controlled.

The blower 28 supplies combustion air to the burner 24.

The blower 28 is provided with a motor 2802 and a fan (not shown) rotated by the motor 2802. By rotating the fan by the motor 2802, air at room temperature is sucked from the suction port, And discharges combustion air.

The inverter 30 adjusts the number of revolutions of the motor of the blower 28 by a control signal supplied from the control device 44. [

The control device 44 adjusts the rotation speed of the motor of the blower 28 via the inverter 30 so that the supply amount of the combustion air is adjusted according to the temperature of the combustion air.

The heat exchanger 32 (recuperator) has a primary side 3202 and a secondary side 3204.

The primary side 3202 of the heat exchanger 32 is connected in the middle of an exhaust gas supply path 46 for guiding the combustion exhaust gas to the outside.

The secondary side 3204 of the heat exchanger 32 is connected in the middle of the air supply path 33 connecting the discharge port of the blower 28 and the window box 22.

That is, the heat exchanger 32 is provided with the combustion air that is pushed from the blower 28 by the combustion exhaust gas after the heat exchange of the circulating heat oil is performed with the combustion gas obtained by the combustion of the fuel by the burner 24 It is to preheat.

Hereinafter, the temperature of the combustion air preheated by the heat exchanger 32 is referred to as the preheat temperature.

When heat exchange is performed between the combustion exhaust gas and the combustion air by the heat exchanger 32, the combustion temperature rises as the preheating temperature of the combustion air is increased. It is known that as the combustion temperature becomes higher, the NOx concentration contained in the combustion exhaust gas becomes higher. And, the combustion temperature differs depending on the difference of the gas fuel species.

According to the experiment of the inventors, the upper limit temperature of the preheating temperature necessary for suppressing the concentration of NOx contained in the combustion exhaust gas to a predetermined concentration or lower is, for example, about 300 DEG C for the city gas 13A, ) Was found to be about 200 ° C. The reason why there is a difference in the upper limit temperature of the preheating temperature is that there is a difference in the amount of heat generation depending on the type of the gaseous fuel.

Therefore, in the present embodiment, in order to suppress the emission of NOx, the preheating temperature is set not to exceed the upper limit temperature as described later.

The first temperature sensor 34 is provided in the vicinity of the discharge port of the blower 28 and detects the temperature of the combustion air pushed into the air supply path 33 from the discharge port and outputs the detection result to the control device 44 . The first temperature sensor 34 may be provided at the inlet of the blower 28.

The second temperature sensor 36 detects the temperature of the combustion air preheated by the heat exchanger 32, that is, the preheating temperature, and supplies the detection result to the control device 44, Of the heat exchanger 32 and the window box 22, as shown in Fig. The second temperature sensor 36 constitutes the combustion air temperature detecting means in the claims.

The third temperature sensor 38 is provided in a part of the exhaust gas supply path 46 connected to the downstream end of the primary side 3202 of the heat exchanger 32 and detects the temperature of the exhaust gas discharged to the outside And supplies the detection result to the control device 44. [

The fourth temperature sensor 40 is provided in the vicinity of the outlet of the cylinder 10 (the heating tube 12) in the heating medium supply line 16 and detects the temperature of the oil supplied to the load from the cylinder 10 , And supplies the detection result to the control device (44).

The damper 42 includes a plate body 4202 as shown in Fig.

The plate body 4202 is rotatably installed in a portion of the air supply path 33 that connects the downstream end of the secondary side 3204 of the heat exchanger 32 and the window box 22, And is rotated in synchronization with the proportional valve 2608. [

3 (A), (B), and (C), the damper 42 is rotated by the rotation of the motor 27 by the control signal supplied from the control device 44, The opening degree of the damper 42 is adjusted in synchronization with the opening degree of the proportional valve 2608. [

That is, as the motor 27 rotates, the opening degree of the damper 42 is controlled, the supply amount of the combustion air flowing through the air supply path 33 is controlled, and the opening degree of the proportional valve 2608 is controlled, do.

The control device 44 accepts a command of the amount of combustion required from the outside and the detection signals from the first to fourth temperature sensors 34, 36, 38 and 40 and outputs the detection signal from the fuel supply means 26, (28) and the damper (42).

The control device 44 can be constituted by a microcomputer.

That is, the microcomputer includes a CPU, a ROM, a RAM, an interface, and the like connected via a bus line. The ROM stores the control program of the boiler of the boiler which the CPU executes, and the RAM provides the working area.

4, the control device 44 functions as the opening control means 48 and the rotation number control means 50 by the CPU executing the control program.

Based on the detected temperature of the fourth temperature sensor 40, the opening degree control means 48 determines the amount of combustion so as to keep the temperature of the circulating heat oil at a predetermined temperature, opens the shutoff valve 2604, The opening of the damper 42 is controlled such that the proportional valve 2608 is opened so as to be opened and the air ratio in the predetermined range. The setting of the combustion amount by the control device 44 is made proportional to the temperature difference between the detection temperature of the fourth temperature sensor 40 and the predetermined temperature (it is made by proportional control).

More specifically, on the assumption that the preheating temperature of the combustion air is maintained at a predetermined constant temperature (for example, 250 DEG C), the opening degree of the damper 42, which becomes the air ratio within a predetermined range for each combustion amount, is experimentally determined.

When the amount of combustion (opening degree of the proportional valve 2608) is set by the rotation of the motor 27, the opening amount of the damper 42, which is the air ratio in the predetermined range, is obtained. In other words, The proportional valve 2608 and the damper 42 are configured so that the opening degree of the proportional valve 2608 and the opening degree of the damper 42 are adjusted in synchronization with each other.

More specifically, the rotation stop position of the motor 27 is determined for each combustion amount, and the combustion amount and the rotation stop position are stored in the ROM as a data table.

When the combustion amount is determined, the control device 44 controls the motor 27 so as to obtain the rotation stop position read from the data table based on the determined combustion amount. Thus, the opening degree of the damper 42, which becomes the air ratio in the predetermined range corresponding to the amount of combustion, is adjusted.

Here, the air ratio will be described.

The air contains 20.9% oxygen (O ₂ ) at atmospheric pressure.

The air ratio is a value obtained by dividing the oxygen concentration (20.9%) of the combustion air by the value obtained by subtracting the oxygen concentration of the exhaust gas from the oxygen concentration, and is defined by equation (1).

Air ratio = 20.9 / (20.9-oxygen concentration in exhaust gas) ... ... (One)

Therefore, when air is supplied to the supplied fuel in such a manner that theoretically the complete combustion is performed, the air ratio becomes 1 (the theoretical air amount). In view of heat efficiency, air ratio = 1 is ideal, but it is difficult to achieve such theoretical combustion in an industrial boiler, so that the amount of air larger than the theoretical air amount, that is, (1) 1, the air ratio> 1 is satisfied.

In this case, the air ratio in the predetermined range is in the range of about 1.15 to 1.45, in which the combustion property is such that carbon monoxide is not rapidly increased due to incomplete combustion or flaming does not occur during the flame.

The rotational speed control means 50 controls the blower 28 so as to obtain the target air ratio based on the detected value of the second temperature sensor 36 for detecting the preheating temperature in the damper opening degree set by the opening degree control means 48. [ And adjusts the blower 28 via the inverter 30 based on the set number of rotations.

Here, the target air ratio will be described.

Although the air ratio in the predetermined range or the vicinity thereof can be adjusted by setting the opening degree of the damper 42, the preheating temperature varies depending on the atmospheric temperature, the amount of combustion, the load, and the like.

As a result, only the adjustment of the opening of the damper 42 by the amount of combustion may increase the fluctuation of the amount of air, deviating from the air ratio in a predetermined range, or lowering the air ratio and deteriorating the combustibility.

Therefore, it is necessary to adjust the number of revolutions of the blower 28 so as to obtain the target air ratio.

The amount of air to be supplied is ideally close to the theoretical air ratio = 1 as much as possible, but in the case of the boiler 100 of the present embodiment, the target air ratio is about 1.201 to 1.237. This excess amount of air changes depending on the boiler of the fruit.

The rotation speed control means 50 adjusts the rotation speed of the blower 28 so that the amount of combustion air sufficient to maintain the air ratio at the target air ratio is supplied to the burner 24 even if the preheating temperature T of the combustion air changes (N) of the blower and the preheating temperature (T) in order to make the preheating temperature (T) constant.

That is, the rotation speed control means 50 sets the rotation speed N of the blower 28 on the basis of the following relational expression from the preheating temperature T detected by the second temperature sensor 36, do.

5 is a graph showing a correlation between the preheating temperature T and the number of rotations N. The horizontal axis indicates the preheating temperature T and the vertical axis indicates the number of rotations N of the blower 28. [

In the figure, the line indicated by N = f (T) represents a correlation, and f (T) is a value obtained by obtaining the number of revolutions N corresponding to the preheating temperature T for setting the air ratio to the target air ratio (Relational expression).

That is, a curve showing the correlation between the preheating temperature T at the outlet of the heat exchanger 32 and the number of rotations N of the blower 28 is obtained by calculation so that the air ratio becomes the target air ratio, And inserts the correlation expression into the control program of the control device 44. [

Various methods known in the art can be used for creating such a relational expression.

The setting of the rotation speed N of the blower 28 by the rotation speed control means 50 may be performed using the data table instead of using the correlation as described above.

That is, the relationship between the temperature of the combustion air detected by the second temperature sensor 36 and the number of revolutions of the blower 28 is calculated by calculation so that the air ratio becomes the target air ratio, The number of revolutions of the blower 28 necessary for every 5 DEG C is obtained and stored as a data table in the storage means such as the above ROM.

The rotation speed control means 50 obtains the rotation speed N of the blower 28 from the data table showing the above correlation from the temperature of the combustion air detected by the second temperature sensor 36 and sets it.

Since the temperature of the combustion air in the data table and the number of revolutions of the blower 28 are discrete values, values not in the data table can be obtained by using conventionally known methods, such as pre- .

The gas fuel (gas type) used in the boiler 100 is determined by the user using the boiler 100.

Further, as described above, since the calorific value is changed for each gaseous fuel present in a plurality of types, the upper limit temperature of the combustion air is set in advance for the gaseous fuel used in the boiler 100. In the following description, the upper limit temperature of the preheating temperature T preset for the gaseous fuel in the boiler 100 is assumed to be Th.

Therefore, the rotation speed control means 50 controls the rotation speed of the combustion air to be adjusted by the rotation speed control means 50 based on the preheating temperature T so that the preheating temperature T of the combustion air does not exceed the upper limit temperature Th The rotation speed N of the blower 28 is adjusted. In other words, the rotational speed control means 50 adjusts the rotational speed N of the blower 28 so that the air ratio becomes the target air ratio in the normal case, while the preheating temperature T of the combustion air is equal to the upper limit temperature Th , The rotational speed N of the blower 28 is further raised to further increase the air ratio so that the preheating temperature T of the combustion air does not exceed the upper limit temperature Th.

Next, the operation of the boiler 100 will be described with reference to the flowchart of Fig.

The boiler 100 is assumed to be in a stopped state in advance.

When the boiler 100 is started, the circulation pump starts circulation of the heat oil between the cylinder 10 and the load. At the same time, the control device 44 is activated to execute the process shown in Fig.

The control device 44 sets the amount of combustion (amount of fuel) based on the temperature of the fruit oil detected by the fourth temperature sensor 40 and the temperature difference between the target temperature of the fruit oil set in advance (steps S10 and S12) ).

The controller 44 then controls the fuel supply means 26 to supply the gaseous fuel to the burner 24 on the basis of the set amount of combustion to set the opening degree of the damper 42 in accordance with the set amount of combustion, The motor 4204 of the damper 42 is controlled to set the damper 42 to the open degree (step S14).

Next, the control device 44 receives the detection result of the preheating temperature T detected by the second temperature sensor 36 and determines whether or not the preheating temperature T is equal to or less than the upper limit temperature Th (Steps S16 and S18).

The control device 44 calculates the number of revolutions N of the blower 28 from the above relational expression on the basis of the preheating temperature T when the preheating temperature T is equal to or less than the upper limit temperature Th )).

Next, the control device 44 controls the rotation speed of the blower 28 to be the rotation speed N through the inverter 30 (step S22), returns to step S10, and repeats the same processing .

On the other hand, if the preheating temperature T exceeds the upper limit temperature Th in step S18, the control unit 44 determines the number of revolutions of the blower 28 from the above relational expression on the basis of the preheating temperature T (Step S24), and calculates a correction coefficient? Described later on the basis of the temperature difference? T = T-Th between the preheating temperature T and the upper temperature Th (step S26) , And the rotation number N obtained by multiplying the rotation number N by the correction coefficient alpha is calculated (step S28).

Here, the correction coefficient? Is described.

Fig. 7 is an explanatory diagram of a table relating the temperature difference DELTA T and the correction coefficient alpha. The control device 44 stores this table in advance.

As shown in Fig. 7, the correction coefficient? Is determined such that the larger the value of the temperature difference? T, the larger the correction coefficient?.

For example, when the preheating temperature T detected by the second temperature sensor 36 is smaller than the upper limit temperature Th in a certain amount of combustion, the rotation of the blower 28 is controlled so as to become the target air ratio in accordance with the preheating temperature T The number N is determined and controlled (correction coefficient? = 1).

The correction coefficient alpha is set to be equal to the rotational speed N of the blower 28 rotating at? = 1 when the preheating temperature T detected by the second temperature sensor 36 is greater than the upper limit temperature Th It is a value multiplied by the temperature difference? T.

In this manner, the correction coefficient? May be determined experimentally according to the temperature difference? T.

Alternatively, while detecting the preheating temperature T at the second temperature sensor 36, the rotation number N may be determined while increasing the correction coefficient alpha at a predetermined rate, for example, at a rate of 0.01 / minute .

Next, the control device 44 controls the rotation speed of the blower 28 to become the rotation speed? N via the inverter 30 (step S30), returns to step S18, and repeats the same process .

By performing such a process, the preheating temperature T of the combustion air is controlled to be equal to or less than the upper limit temperature Th.

As described above, according to the present embodiment, the opening degree of the damper 42 is controlled in accordance with the set combustion amount, and the air ratio is set to the predetermined target air temperature T from the preheating temperature T detected by the second temperature sensor 36 The rotation speed N of the blower 28 is adjusted so that the ratio becomes the ratio.

Therefore, by appropriately controlling the supply amount of the combustion air according to the fluctuation of the combustion amount, the combustion air can be precisely preheated and the exhaust gas temperature can be lowered to increase the boiler efficiency (combustion efficiency) When the combustion amount (fuel) is increased, the amount of combustion air supplied due to the thermal expansion of the preheated combustion air is reduced while the combustion air is accurately increased, and the blower 28 is controlled Therefore, it is possible to keep combustion well and to stabilize the combustion.

Therefore, it is possible to control the supply amount of the combustion air appropriately according to the change of the combustion amount, so that the air ratio can be controlled to be the target air ratio, and combustion stability can be maintained by satisfactorily maintaining the combustion performance.

According to the present embodiment, the adjustment of the rotational speed N of the blower 28 is performed by adjusting the amount of combustion air sufficient to maintain the air ratio at the target air ratio even if the preheating temperature T of the combustion air changes, The relationship between the rotational speed N of the blower 28 and the preheating temperature T for supplying the air to the blower 28 is adjusted so that the rotation speed N of the blower 28 can be adjusted precisely .

According to the present embodiment, the upper limit temperature Th of the preheating temperature T of the combustion air is set in advance for each gaseous fuel having a different heating value, and the detected preheating temperature T is set to the upper limit temperature Th The rotation speed N of the blower 28 is adjusted so as not to exceed.

Therefore, since the preheating temperature T is controlled so as not to exceed the upper limit temperature Th, the combustion efficiency close to the target air ratio can be maintained, and the rise of the combustion gas temperature due to preheating can be suppressed, can do.

(Second Embodiment)

Next, the second embodiment will be described.

In the following embodiments, description of the same portions as those of the first embodiment will be omitted, and only different portions will be described.

In the first embodiment, the case where the control device 44 adjusts the number of rotations N of the blower 28 so that the preheating temperature T does not exceed the upper limit temperature Th has been described, In order to prevent the preheating temperature T from exceeding the upper limit temperature Th, a heat exchanger 32 is provided in which the heat transfer area is changed for each gaseous fuel in accordance with the type of the gaseous fuel used in the boiler 100 And the heat exchanger 32 whose temperature is below the upper limit temperature Th is selected.

The operation of the boiler 100 according to the second embodiment will be described with reference to the flowchart of Fig. The same processing steps as the processing steps in the flowchart of Fig. 6 are denoted by the same reference numerals.

The control device 44 sets the amount of combustion (amount of fuel) based on the temperature of the fruit oil detected by the fourth temperature sensor 40 and the temperature difference between the target temperature of the fruit oil set in advance (steps S10 and S12) ).

Next, the control device 44 controls the fuel supply means 26 based on the set amount of combustion, supplies the gaseous fuel to the burner 24, sets the opening degree of the damper 42 in accordance with the set amount of combustion, The motor 4204 of the damper 42 is controlled to set the damper 42 to the open degree (step S14).

Next, the control device 44 receives the detection result of the preheating temperature T detected by the second temperature sensor 36 (step S16).

The control device 44 calculates the number of revolutions N of the blower 28 from the relational expression based on the detected preheating temperature T (step S20).

Next, the control device 44 controls the rotation speed of the blower 28 to be the rotation speed N through the inverter 30 (step S22), returns to step S10, and repeats the same processing .

By performing such a process, the rotation number N of the blower 28 is adjusted so that the air ratio becomes an ideal air ratio. As described above, since the heat exchanger 32 is selected so as to be equal to or less than the upper limit temperature Th in accordance with the type of the gaseous fuel used in the boiler 100, the preheating temperature T of the combustion air is set at the upper limit Is controlled to be equal to or lower than the temperature Th.

According to the second embodiment, the supply amount of the combustion air can be controlled appropriately in accordance with the change of the combustion amount without exceeding the upper limit temperature Th according to the fuel type, so that the air ratio is controlled to be the target air ratio So that the combustion performance can be maintained favorably, so that the combustion stability can be achieved and the NOx emission can be suppressed.

(Third Embodiment)

Next, the third embodiment will be described.

In the description of the second embodiment, a heat exchanger 32 that changes the heat transfer area for each gaseous fuel is prepared, and a heat exchanger 32 (hereinafter, referred to as " ).

Actually, however, when the temperature of the combustion gas rises and falls due to a change in the atmospheric temperature or a change in humidity, the preheating temperature T exceeds the upper limit temperature Th, The temperature is lowered, and the efficiency of the boiler is lowered.

Therefore, in consideration of the effect of the change in the atmospheric temperature and the change in the humidity in advance, in the third embodiment, the maximum value of the preheat temperature in the heat exchange in the heat exchanger 32 does not exceed the preheat temperature set in accordance with the fuel species , It is possible to select a design with a margin above the preheating temperature set in accordance with the fuel species so that it can be selected according to the type of fuel and also the number of revolutions N of the blower 28 can be adjusted Thereby suppressing an increase in the temperature of the combustion gas.

That is, in the third embodiment, the upper limit temperature set for each gaseous fuel is referred to as a first upper limit temperature Th1, and a temperature obtained by adding a predetermined temperature to the first upper limit temperature Th1 is referred to as a second upper limit temperature Th2 , And the heat exchanger (32) is configured to be able to preheat the combustion air to the second upper limit temperature (Th2).

The control device 44 adjusts the rotation speed N of the blower 28 such that the preheating temperature T becomes equal to or less than the first upper limit temperature Th1.

The operation of the boiler 100 according to the third embodiment is the same as that of the first embodiment shown in Fig. 6, and the upper limit temperature Th in Fig. 6 is replaced with the first upper limit temperature Th1.

That is, the control device 44 adjusts the rotational speed N of the blower 28 so that the air ratio becomes the target air ratio in the normal state, while the preheating temperature T of the combustion air is higher than the first upper limit temperature Th , The control is performed so that the preheating temperature T becomes equal to or less than the first upper limit temperature Th1 by further increasing the rotational speed N of the blower 28 so that the air ratio is further increased.

In the third embodiment as described above, similarly to the first embodiment, the supply amount of the combustion air can be controlled accurately according to the change in the amount of combustion, so that the air ratio can be controlled to be the target air ratio, The stability of combustion can be achieved, and the following effects can be obtained.

That is, the second upper limit temperature Th2, which is the upper limit value of the preheating temperature T obtained by adding the predetermined temperature to the first upper limit temperature Th1 which is the upper limit value of the preheating temperature T according to the fuel species of the gaseous fuel, 32). Then, when the preheating temperature T exceeds the first upper limit temperature Th1, the rotational speed N of the blower 28 is adjusted so that the preheating temperature T is lowered to the first upper limit temperature Th1 or lower Respectively. Therefore, since the preheating temperature T of the combustion air can be maintained at a temperature close to the upper limit temperature (the first upper limit temperature T1) or the upper limit temperature, it is possible to maintain high efficiency as a boiler of the fuel, can do.

Next, the fourth embodiment will be described.

In the first to third embodiments, the number of revolutions of the blower is controlled so that the air ratio becomes the predetermined target air ratio based on the preheating temperature of the combustion air. In the fourth embodiment, however, according to the oxygen concentration in the exhaust gas, The present embodiment differs from the first to third embodiments in that the number of revolutions of the blower is feedback-controlled so that the ratio becomes the target air ratio.

Fig. 9 is a configuration diagram showing the configuration of the boiler 100 according to the fourth embodiment.

9, the oxygen concentration sensor 52 is added as shown in Fig.

The oxygen concentration sensor 52 constitutes exhaust gas oxygen concentration detecting means and detects the oxygen concentration in the combustion exhaust gas and supplies the detection result to the control device 44. [

In the fourth embodiment, the oxygen concentration sensor 52 is provided at a portion of the exhaust gas supply path 46 connected to the downstream side of the primary side 3202 of the heat exchanger 32.

The control device 44 receives commands of the amount of combustion required from the outside and detection signals from the first to fourth temperature sensors 40 and the oxygen concentration sensor 52 and controls the fuel supply means 26, (28) and the damper (42).

As shown in Fig. 10, the control device 44 functions as opening degree control means 48 and rotation speed control means 50 by the CPU executing the control program.

The opening degree control means 48 is configured in the same manner as in the first embodiment, and a description thereof will be omitted.

The rotational speed control means 50 includes a rotational speed setting means 54 and a feedback control means 56. [

The rotational speed setting means 54 sets the target air ratio described in the first embodiment on the basis of the detected value of the second temperature sensor 36 for detecting the preheat temperature in the damper opening degree set by the opening degree control means 48 The number of revolutions of the blower 28 necessary for obtaining the first rotational speed N1 is set as the first rotational speed N1.

The setting of the first rotation speed N1 by the rotation speed setting means 54 is the same as the adjustment of the rotation speed of the blower 28 by the rotation speed control means 50 in the first embodiment .

That is, the setting of the first rotational speed N1 by the rotational speed setting means 54 is performed so that the amount of combustion air sufficient to maintain the air ratio at the target air ratio is supplied to the burner 24 even if the preheating temperature T of the combustion air changes, And the preheating temperature (T) for supplying the air to the blower (1).

It is the same as in the first embodiment that the setting of the first rotation speed N1 by the rotation number setting means 54 may be performed using the data table.

That is, the relationship between the temperature of the combustion air detected by the second temperature sensor 36 and the number of revolutions of the blower 28 is calculated by calculation so that the air ratio becomes the target air ratio, The number of revolutions of the blower 28 necessary for every 5 DEG C is obtained and stored as a data table in the storage means such as the above ROM.

The rotation number setting means 54 obtains the first rotation number N1 of the blower 28 from the data table showing the above correlation from the temperature of the combustion air detected by the second temperature sensor 36 do.

The feedback control means 56 feedback-controls the number of revolutions of the blower 28 so that the air ratio becomes the target air ratio in accordance with the oxygen concentration detected by the oxygen concentration sensor 52 on the basis of the first rotation speed N1 will be.

Based on the second rotation number N2 obtained by multiplying the first rotation number N1 by the fine adjustment coefficient K2 and the rough correction coefficient K1 described later, the feedback control means 56 calculates the rotation speed N2 of the blower 28 And performs feedback control of the number of revolutions.

The feedback control means 56 adjusts the fine adjustment factor K2 in accordance with the detected oxygen concentration and when the fine adjustment factor K2 exceeds the predetermined adjustment range, the fine adjustment factor K2 The rough correction coefficient K1 is adjusted so as to be within the adjustment range, and the rough correction coefficient K1 is stored.

In the fourth embodiment, the feedback control means 56 includes a rough correction calculation circuit 58 and a fine adjustment calculation circuit 60. [

The fine adjustment computation circuit 60 controls the air flow rate of the combustion air with the revolution number (first revolution number N1) calculated on the basis of the correlation formula from the preheat temperature detected by the second temperature sensor 36 And changes the number of revolutions of the blower 28 so that the air ratio becomes the target air ratio according to the oxygen concentration in the exhaust gas detected by the oxygen concentration sensor 52.

The rough correction calculation circuit 58 obtains a new correlation between the preheating temperature and the number of revolutions of the blower when the correlation between the preheating temperature and the number of revolutions of the blower changes due to outside temperature or humidity.

The fine adjustment calculation circuit 60 finely adjusts the first rotation number N1 of the blower 28 obtained from the correlation (correlation formula) of the preheating temperature and the rotation number of the blower 28, Is performed by adjusting the number of revolutions of the blower 28 so that the target air ratio is obtained in accordance with the oxygen concentration detected by the oxygen concentration sensor 52. [

That is, the fine adjustment calculation means 60 calculates the difference (difference) between the oxygen concentration (target value) corresponding to the target air ratio and the detected oxygen concentration (present value) so that the deviation The fine adjustment coefficient K2 to be multiplied by the first rotation speed N1 is calculated.

In this case, if the variation per unit time of the calculated fine adjustment coefficient K2 is too large, it is disadvantageous to stabilize the target air ratio. Therefore, the variation per unit time of the fine adjustment coefficient K2 is, for example, 0.01 / Min.

When the frequency of the inverter 30 is 40 Hz, the amount of change per unit time of the fine adjustment factor K2 is 0.01 x 40 Hz / min = 0.4 Hz / min.

Since the amount of change per unit time of the fine adjustment coefficient K2 is determined in this manner, the larger the amount of change in the fine adjustment factor K2 between before fine adjustment and after fine adjustment is, the longer the actual air ratio reaches the target air ratio It takes time.

Therefore, in order to shorten the time required until the actual air ratio reaches the target air ratio, the fine adjustment coefficient K2 is set to fall within the predetermined adjustment range.

That is, when the fine adjustment factor K2 is adjusted so that the actual air ratio becomes the target air ratio using the fine adjustment factor K2, if the fine adjustment factor K2 exceeds the above adjustment range, the sum of the variation amounts of the fine adjustment factor K2 The rough correction coefficient K1, which will be described later, is adjusted so as to be within the adjustment range.

The adjustment range of the fine adjustment coefficient K2 is, for example, ± 2% with respect to the first rotation speed N1 determined from the correlation (correlation formula) based on the combustion air temperature.

The rough correction calculation circuit 58 performs fine adjustment of the number of revolutions so that the actual air ratio becomes the target air ratio using the fine adjustment coefficient K2 and when the fine adjustment coefficient K2 exceeds the adjustment range (Correlation formula) between the preheating temperature and the number of revolutions of the blower 28 is corrected.

Next, the operation procedure of the feedback control means 56 including the rough correction calculation circuit 58 and the fine adjustment calculation circuit 60 will be described.

First, the relationship between the pre-heating temperature and the number of rotations of the blower 28 is calculated so that the air ratio becomes the target air ratio, and this is stored in the ROM as equation (1) showing the correlation.

N = K1 x K2 x f (T) ... ... (One)

N: the number of revolutions of the blower 28

K1: Rough correction coefficient

K2: fine tuning coefficient

T: Preheating temperature

f: a function indicating the correlation between the preheating temperature (T) and the number of revolutions (N) (without considering the influence of outside temperature, humidity, etc.)

From the preheating temperature T detected by the second temperature sensor 36, the first rotation number N1 of the blower 28 is obtained using the equation (1) with K2 = K1 = 1, The control means 56 changes the rotational speed of the blower 28 to N1.

The fine adjustment calculation circuit 60 obtains the fine adjustment coefficient K2 by the method shown in Fig. 12 on the basis of the oxygen concentration detected by the oxygen concentration sensor 52 in the state of the number of revolutions N1, (1) to finely adjust the rotation speed (N). At this time, the state of the rough correction coefficient K1 = 1 is maintained.

That is, by changing the variation amount of the fine adjustment coefficient K2 per unit time to 0.01 / minute, the rotation number N is finely adjusted so that the air ratio becomes the target air ratio.

When the fine adjustment coefficient K2 exceeds the adjustment range as a result of the adjustment of the air ratio to the target air ratio, the rough adjustment coefficient K2 in the equation (1) is adjusted so that the fine adjustment coefficient K2 falls within the adjustment range K1) is changed (increased or decreased) at a constant ratio, thereby making a new correlation (correlation) between the combustion air and the number of revolutions of the blower 28. That is, the value of the rough correction coefficient K1 of the equation (1) is increased or decreased.

The feedback control means 56 controls the rotation speed of the blower 28 on the basis of the second rotation speed N2 of the blower 28 determined based on the new correlation (correlation formula).

Further, the rotation speed N2 of the blower is multiplied by the fine adjustment coefficient K2 so as to achieve the target air ratio in accordance with the oxygen concentration detected by the oxygen concentration sensor 52 to perform fine adjustment.

When the sum of the amounts of change of the fine adjustment coefficient K2 exceeds the adjustment range again as a result of adjusting the rotation speed based on the fine adjustment coefficient K2 and adjusting it to the target air ratio, the fine adjustment coefficient K2 is adjusted , The rough correction coefficient K1 is changed at a constant rate to create a new correlation (correlation formula), and the above-described operation is repeated.

Next, the operation of the feedback control means 56 including the rough correction calculation circuit 58 and the fine adjustment calculation circuit 60 will be described again with reference to the diagrams shown in Figs. 14, 15 and 16 do.

Fig. 14 is a diagram showing a function indicating the correlation between the preheating temperature T and the number of revolutions N when the outside temperature, the humidity, and the like are set to any condition.

Fig. 15 is a diagram for explaining the correction of the number of revolutions by the fine adjustment coefficient K2.

16 is a diagram for explaining the correction of the correlation formula by the rough correction coefficient K1.

14, 15, and 16, the horizontal axis represents the preheating temperature T and the vertical axis represents the rotational speed N of the blower 28. In FIG.

In Fig. 14, the lines indicated by N = f (T) = K1 x K2 x f (T) show a correlation, and in this case, K1 = K2 = 1.

f (T) is a correlation formula for obtaining the number of revolutions N corresponding to the preheating temperature T for setting the air ratio to the target air ratio.

The correlation f (T) becomes a curve. The equation of this curve is derived and the number of revolutions of the blower 28 necessary for the outlet temperature of the heat exchanger 32 is obtained based on this correlation formula.

Hereinafter, in order to simplify the explanation, a case is described in which the number of rotations of the blower 28 is controlled by using a linear equation (f (T) = a 占 + b) approximate to a curve as a correlation .

This correlation assumes that the correlation between the preheating temperature T and the number of revolutions N for obtaining the target air ratio does not change due to external factors.

However, if it is influenced by outside temperature, humidity, or the like, the above-described correlation is not maintained and the air ratio can not be controlled with the target air ratio. Therefore, it is necessary to correct the rotation number and correct the correlation do.

That is, it is necessary to determine the fine adjustment coefficient K2 for correcting (finely adjusting) the rotation number N obtained by N = f (T) and the rough correction coefficient K1 for correcting the correlation.

The expression for this is the above formula (1).

As shown in Fig. 15, the detected warm-up temperature is, if a change from T ₀ to _{T 1, N = f (T} ) = K1 × K2 × f (T) can be rotated by using a (where K1 = K2 = 1) (N) is changed from N ₀ to N ₁ .

Subsequently, the rotational speed N of the blower 28 is finely adjusted so as to become the target air ratio m ₀ on the basis of the oxygen concentration in the detected exhaust gas. That is, the roughness correction coefficient K1 is set to 1, and the fine adjustment factor K2 is multiplied by f (T) to finely adjust the number of rotations N of the blower 28. [ As a result, it is assumed that the number of revolutions N is changed from N ₁ to N ₂ .

As a result, when the finely adjusted fine adjustment coefficient K2 exceeds the adjustment range, it is determined that the initial correlation does not hold, and a new correlation is created.

So, changes the fine adjustment coefficient rough correction factor (K1) to (K2) is entered into the control area of the to as a target air ratio (m ₀₎ for the air ratio as shown in Fig.

That is, N '= K1 × K2 × f (T) (where K1 = 1 and K2 ≠ 1) are created as a new correlation.

The change of the rough correction coefficient K1 will be described.

17 is a diagram for explaining the adjustment of the rough correction coefficient K1.

The horizontal axis represents time (t), and the vertical axis represents air ratio (m).

And by changing the fine adjustment coefficient (K2), as described above, and the air ratio of the target air ratio (m _0), as the value of the fine adjustment coefficient (K2) at this time it is 1.03 (rough correction factor (K1) = 1).

Next, the operation is performed so that the fine adjustment coefficient K2 falls within the above adjustment range or the fine adjustment coefficient K2 is equal to one.

This is because the following operations are concerned. That is, when the fine adjustment coefficient K2 is outside the adjustment range, when the combustion is started again after the combustion is stopped, in order to perform the control in the state of the rough correction coefficient K = 1, It is feared that the control of the number of revolutions K2 takes a long time because the amount of change per unit time is fixed.

Hereinafter, it is assumed that the preheating temperature is constant.

As described above, it is assumed that the air ratio is the target air ratio m ₀ , with the rough correction coefficient K1 = 1 and the fine adjustment coefficient K2 = 1.03.

Here, the value of the rough correction coefficient K1 is changed so as not to be far from the target air ratio m ₀ so as not to affect the combustibility.

In Fig. 17, the rough correction coefficient K1 is increased by 0.01 from 1 to 1.01 (t2-t1).

At this time, since the fine adjustment coefficient K2 is maintained at 1.03, the air ratio exceeds the target air ratio m ₀ .

Then, when the rough correction coefficient K1 reaches 1.01, the fine adjustment coefficient K2 is decreased so that K1 x K2 = 1.03. In this case, the fine adjustment coefficient K2 is 1.02.

Thus, the air ratio drops to the target air ratio m ₀ .

In order to further reduce the fine adjustment coefficient K2, the rough correction coefficient K1 is increased by the above-described change amount and the above-mentioned time. That is, the rough correction coefficient K1 is increased from 0.01 to 1.02 by the same time (t3-t2) = (t2-t1) by 0.01. As a result, the rough correction coefficient K1 becomes 1.02.

That is, adjustment of the rough correction coefficient K1 is performed by changing the rough correction coefficient K1 to a predetermined correction amount per unit time when the fine adjustment coefficient K2 exceeds the adjustment range.

By repeating this operation, the fine adjustment coefficient K2 is adjusted to fall within the above adjustment range or the fine adjustment coefficient K2 is adjusted to be equal to one.

Then, the obtained rough correction coefficient K1 is stored in the blower 28 from the preheating temperature based on the correlation (correlation formula) using the stored rough correction coefficient K1 at the time of combustion after the combustion is stopped. The number of revolutions (N)

Next, the operation of the boiler 100 will be described with reference to the flowchart of Fig.

The boiler 100 is assumed to be in a stopped state in advance.

When the boiler 100 is started, the circulation pump starts circulation of the heat oil between the cylinder 10 and the load. At the same time, the controller 44 is started, and the processing of Fig. 13 is executed.

11, the feedback control means 56 (rough correction calculation circuit 58) controls the blower 28 by the first rotation speed N1 determined according to the temperature obtained in the correlation formula (S20).

Then, the rotation number is adjusted so that the air ratio becomes the target air ratio by using the fine adjustment coefficient K2 in accordance with the oxygen concentration detected by the oxygen concentration sensor 52 (S22, S24).

11, when the fine adjustment coefficient K2 exceeds the adjustment range, the feedback control means 56 (fine adjustment calculation circuit 60) sets the fine adjustment coefficient K2 to the adjustment The correlation is multiplied by the rough correction coefficient K1 at a predetermined ratio to create a new correlation (N 'in FIG. 16) to obtain the second rotation speed N2 (S26).

Control of the blower 28 is performed at the second rotation speed N2 and a fine adjustment coefficient K2 for multiplying the second rotation speed N2 by the air ratio to the target air ratio is calculated in accordance with the detected oxygen concentration, After repeating the steps S24 and S26 until the ratio becomes the target air ratio (S28), the process returns to the step S10 and the same process is repeatedly executed.

That is, the feedback control means 56 feedback-controls the number of revolutions of the blower 28 such that the air ratio becomes the target air ratio according to the oxygen concentration detected by the oxygen concentration sensor 52.

Thereafter, the fuel oil is heated by the boiler 100 by the combustion of the gaseous fuel, and the heated fuel oil is circulated between the load and the boiler 100.

When the combustion is stopped, the rough correction coefficient K1 immediately before the stop is stored. When the combustion is started, on the basis of the correlation formula using the rough correction coefficient K1, The number of revolutions is obtained, and the blower 28 is controlled by the number of revolutions.

As described above, according to the fourth embodiment, the opening degree of the damper 42 is controlled in accordance with the set amount of combustion, and the air ratio is adjusted to the predetermined target air ratio from the preheating temperature detected by the second temperature sensor 36 The first rotation speed N1 of the blower 28 is set.

Therefore, by appropriately controlling the supply amount of the combustion air according to the fluctuation of the combustion amount, the combustion air can be precisely preheated and the exhaust gas temperature can be lowered to increase the boiler efficiency (combustion efficiency) When the combustion amount (fuel) is increased, the amount of combustion air supplied due to the thermal expansion of the preheated combustion air is reduced while the combustion air is accurately increased, and the blower 28 is controlled Therefore, it is possible to keep combustion well and to stabilize the combustion.

In addition, simply by setting the first rotation speed N1 in accordance with the combustion air, the first rotation speed N1 is not sufficiently adjusted with respect to changes in ambient temperature, humidity, load temperature, etc., It is assumed that it deviates from the air ratio. That is, it is difficult to ensure the responsiveness of the control of the number of revolutions of the blower 28 only by setting the first rotation speed N1 in accordance with the combustion air.

Therefore, in the fourth embodiment, based on the first rotation speed N1, the number of rotations of the blower 28 is feedback-controlled so that the air ratio becomes the target air ratio according to the oxygen concentration in the exhaust gas.

Accordingly, the responsiveness of the control of the number of revolutions of the blower 28 can be enhanced, and the fluctuation of the air ratio of the burner 24 can be suppressed, so that the combustion performance can be kept better and the combustion can be further stabilized .

In the fourth embodiment, the above-described feedback control is performed based on the second rotation number obtained by multiplying the first rotation number by the fine adjustment coefficient K2 and the rough correction coefficient K1, The fine adjustment factor K2 is adjusted in accordance with the detected oxygen concentration and when the fine adjustment factor K2 has exceeded the predetermined adjustment range, the fine adjustment factor K2 is adjusted by the adjustment The rough correction coefficient K1 is adjusted so as to be within the range, and this value is stored.

Thereby, based on the temperature detected by the second temperature sensor 36, the necessary blower 28 (correlation) is obtained by using the new correction formula (correlation formula) obtained by the rough correction coefficient K1 corrected when the combustion is stopped and restarted Can be obtained. Therefore, since the adjustment range of the fine adjustment coefficient K2 can be set in a small range, the adjustment to the target air ratio can be realized in a short time, so that the stabilization of the combustion can be realized even earlier.

In the fourth embodiment, the adjustment of the rough correction coefficient K1 by the feedback control means 56 is performed when the fine adjustment coefficient K2 exceeds the adjustment range, And changing it to a predetermined correction amount.

Therefore, since the rough correction coefficient K1 can be adjusted by a simple control of changing the predetermined correction amount, the feedback control of the rotational speed of the blower 28 according to the oxygen concentration in the exhaust gas can be simplified.

In the fourth embodiment, the setting of the first rotational speed N1 of the blower 28 by the rotational speed setting means 54 is set so that the amount of combustion air sufficient to maintain the air ratio at the target air ratio even if the preheating temperature changes The relationship between the number of revolutions of the blower 28 and the preheating temperature is used to supply the air to the burner 24 so that the number of revolutions of the blower 28 can be adjusted precisely.

10: cylinder 12: heating tube
15: combustion chamber 14: heating medium return line
16: heating medium supply line 18: combustion chamber
22: window box 24: burner
26: fuel supply means 28: blower
30: inverter 32: heat exchanger
34: first temperature sensor
36: second temperature sensor (combustion air temperature detecting means)
38: third temperature sensor 40: fourth temperature sensor
42: damper 44: control means (control device)
48: opening degree control means 50: rotation speed control means
52: oxygen concentration sensor (exhaust gas oxygen concentration detection means)
54: rotational speed setting means 56: feedback control means
58: rough correction calculation circuit 60: fine adjustment calculation circuit
100: Fruit boiler

Claims (9)

The burner,
Fuel supply means for supplying the gaseous fuel to the burner in accordance with the set combustion amount,
A blower for supplying combustion air to the burner,
A heat exchanger provided between the blower and the burner for preheating the combustion air by an exhaust gas generated by combustion of the gaseous fuel by the burner;
A combustion air temperature detecting means for detecting a preheating temperature of the combustion air preheated by the heat exchanger,
A damper which is provided in an air supply passage connecting the heat exchanger and the burner and whose degree of opening is controlled,
An opening degree control means for controlling the opening degree of the damper in accordance with the set amount of combustion,
And rotation speed control means for adjusting the rotation speed of the blower so that the air ratio becomes a predetermined target air ratio based on the preheating temperature detected by the combustion air temperature detection means,
The upper limit temperature of the preheating temperature is preset for each gaseous fuel having a different heating value,
Wherein the rotational speed control means adjusts the rotational speed of the blower such that the preheating temperature detected by the combustion air temperature detecting means does not exceed the set upper limit temperature. The method according to claim 1,
Wherein the adjustment of the number of revolutions of the blower by the number-
Wherein the relationship between the number of revolutions of the blower and the preheating temperature is used to supply the burner with an amount of combustion air sufficient to maintain the air ratio at the target air ratio even if the preheating temperature changes. Boiler. delete 3. The method according to claim 1 or 2,
The upper limit temperature of the preheating temperature is preset for each gaseous fuel having a different heating value,
Wherein the heat exchanger is a heat exchanger that changes the heat transfer area for each gaseous fuel so that the temperature is equal to or less than the upper limit temperature set for each gaseous fuel and a heat exchanger having a temperature equal to or lower than the upper limit temperature of the preheat temperature is selected Wherein the boiler is a boiler. 5. The method of claim 4,
The upper limit temperature corresponding to the type of the gaseous fuel is referred to as a first upper limit temperature Th1 and a temperature obtained by adding a predetermined temperature to the first upper limit temperature Th1 is referred to as a second upper limit temperature Th2, The heat exchanger is configured to be able to preheat the combustion air to the second upper limit temperature Th2,
Wherein the rotational speed control means adjusts the rotational speed of the blower such that the preheating temperature is equal to or less than the first upper limit temperature Th1. The method according to claim 1,
Further comprising exhaust gas oxygen concentration detecting means for detecting an oxygen concentration in the exhaust gas,
The rotation speed control means,
A rotational speed setting means for setting the rotational speed of the blower whose air ratio becomes a predetermined target air ratio as a first rotational speed by the preheating temperature detected by the combustion air temperature detecting means,
And feedback control means for feedback-controlling the rotational speed of the blower so that the air ratio becomes the target air ratio in accordance with the oxygen concentration detected by the exhaust gas oxygen concentration detecting means on the basis of the first rotational speed Fruit boiler. The method according to claim 6,
Wherein feedback control of the number of rotations of the blower by the feedback control means is performed based on a rotation speed of the blower based on a second rotation number obtained by multiplying the first rotation number by a fine adjustment coefficient and a rough correction coefficient, By controlling the number,
Wherein the feedback control means adjusts the fine adjustment coefficient according to the detected oxygen concentration and when the fine adjustment coefficient exceeds a predetermined adjustment range, the fine adjustment coefficient is adjusted to be within the adjustment range, And stores the rough correction coefficient. 8. The method of claim 7,
Wherein the adjustment of the rough correction coefficient by the feedback control means is performed by changing the rough correction coefficient to a predetermined correction amount per unit time when the fine adjustment coefficient exceeds the adjustment range. 9. The method according to any one of claims 6 to 8,
Wherein the setting of the first number of rotations of the blower by the number-
Wherein the relationship between the number of revolutions of the blower and the preheating temperature is used to supply the burner with an amount of combustion air sufficient to maintain the air ratio at the target air ratio even if the preheating temperature changes. Boiler.

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