JP2012180981A - Combustion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion device capable of improving the stability of combustion when shifting from the combustion by a small capacity burner to the combustion by a large capacity burner.SOLUTION: In the combustion device 2, the large capacity burner 5 and the small capacity burner 6 are alternately operated and overlapping combustion is carried out temporarily carried out only when shifting combustion, the rotational frequency of a blower and the flow channel area of a blowing channel 7 are set to a position where they becomes smallest during the combustion only by the small capacity burner 6, the rotational frequency of the blower is set larger and the flowing channel area of the blowing channel becomes smaller and the combustion is carried out with the static pressure of the blower increased compared to when minimum combustion by the large capacity burner 5 when shifting from the small capacity burner 6 to the large capacity burner 5, the flow channel area of the blowing channel is enlarged while reducing the rotational frequency of the blower and the minimum combustion by the large capacity burner is carried out after the completion of the overlapping combustion.

Description

  The present invention relates to a combustion apparatus that burns by installing a small-capacity burner and a large-capacity burner in parallel, such as a pilot burner and a main burner.

As described in Japanese Patent No. 4176686, a combustion apparatus that has a large-capacity main burner and a small-capacity pilot burner and uses a flame of a small-capacity burner to ignite the large-capacity burner is widely used. In addition to the pilot burner, there is a type that has a large-capacity burner and a small-capacity burner, and switches the burner to burn according to the required amount of combustion. When switching the burning burner from a small-capacity burner to a large-capacity burner, supply fuel to the large-capacity burner while the small-capacity burner is burning, and start combustion in the large-capacity burner before moving to the small-capacity burner. Stop the fuel supply. Also, when stopping the large-capacity burner, fuel is supplied to the small-capacity burner while burning with the large-capacity burner, and the fuel supply to the large-capacity burner is stopped after starting combustion with the small-capacity burner. To do. When burning a plurality of burners at the same time, depending on the combustion structure of the burner, the flame may become unstable due to overlapping combustion, and good combustion may not be ensured. In addition, in burners that continue overlapping combustion, in order to prevent that one burner flame disappears and only fuel continues to be injected, a device that can detect that each burner can form a flame normally is provided. It may be necessary to take such actions.
Even in the alternating combustion method, there are times when overlapping combustion is performed at the time of switching the combustion burner, so that combustion becomes temporarily unstable and problems such as vibration combustion may occur.

  In the invention described in Japanese Patent No. 4176686, the combustion amount by the pilot burner is switched between pilot combustion that burns with a relatively large thermal power and standby combustion that burns with a smaller thermal power than the pilot combustion. . When the combustion by the main burner is not required, the combustion by the pilot burner is the standby combustion with a small combustion amount, and when the combustion by the main burner is started, the pilot combustion with the larger combustion amount is performed, so that the combustion of the main burner is started. It is possible to achieve both improved ignitability and reduced fuel consumption during main standby. Although the ignitability of the main burner was improved by increasing the amount of combustion by the pilot burner during the transition to the main burner, even in this case, when the combustion by the pilot burner and the combustion by the main burner overlap, the combustion becomes unstable Thus, an increase in combustion noise and vibration combustion may occur.

Japanese Patent No. 4176686

  The problem to be solved by the present invention is to provide a combustion apparatus capable of improving the stability of combustion when switching from combustion by a small capacity burner to combustion by a large capacity burner.

  The invention according to claim 1 has a large-capacity burner and a small-capacity burner that can increase and decrease the amount of combustion, respectively, and when the large-capacity burner is burned, the combustion by the small-capacity burner is stopped and the combustion of the large-capacity burner is stopped. In some cases, alternating combustion is performed so that combustion is performed with a small-capacity burner, and combustion is performed only temporarily when switching combustion, and the small-capacity burner burns only the small-capacity burner. Burns with a small thermal power with a reduced amount of combustion.When switching from a small-capacity burner to a large-capacity burner, the combustion amount is increased and the combustion is performed with a large thermal power. After the combustion is switched from the small-capacity burner, the combustion power is changed by increasing / decreasing the combustion amount according to the load, and the combustion air is supplied from one path, and the rotation speed of the blower In the combustion apparatus in which the air flow rate is changed by the adjusting device and the adjusting device for the flow passage area of the air passage, when only the small-capacity burner is burned, the blower rotation speed and the flow passage area of the air passage are at the smallest position. When switching from a small-capacity burner to a large-capacity burner, the fan rotational speed is increased compared to the minimum combustion amount in the large-capacity burner, and the flow passage area of the air passage is reduced. After the overlap combustion is finished, change the movement to increase the flow area of the air passage while reducing the blower rotation speed, and make it the minimum combustion position in the large capacity burner Characterize.

  According to a second aspect of the present invention, in the above-described combustion apparatus, the air supply amount at the time of switching from the small-capacity burner to the large-capacity burner is larger than the air supply amount at the minimum combustion amount in the large-capacity burner. In addition, after the overlap combustion is finished, the air supply amount is reduced to the minimum combustion position when the flow passage area of the air passage is increased while reducing the rotational speed of the blower.

  When combustion is performed only with a small-capacity burner and switching to a large-capacity burner is not performed, the fuel consumption can be reduced by reducing the combustion amount of the small-capacity burner. When ignition is performed, the combustion stability at the time of switching can be improved by increasing the combustion amount of the small capacity burner. Therefore, it is possible to achieve both a reduction in fuel consumption and an improvement in ignitability of a large-capacity burner. And when switching to a large-capacity burner, the rotation speed of the blower and the air passage area are increased to increase the amount of blown air, whereas the rotation speed of the blower is larger than that during the minimum combustion in the large-capacity burner, By making the air passage area smaller than that at the time of minimum combustion in the large-capacity burner, the air blowing static pressure is maintained in a high state, and the occurrence of vibration combustion can be suppressed by suppressing the fluctuation of the flame with the high air blowing static pressure. In addition, the amount of combustion in the large-capacity burner + the amount of combustion in the small-capacity burner at the time of overlapping combustion is increased. By doing so, an appropriate combustion state can be maintained even at the time of switching, and generation of CO can be suppressed.

The flowchart of the combustion apparatus in one Example of this invention The time chart of the combustion condition in one Example of this invention

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart when a combustion apparatus embodying the present invention is installed in a boiler, and FIG. 2 is a time chart of the boiler embodying the present invention. In the boiler, vertical water pipes are arranged in a ring around the combustion chamber 3 provided in the center, and are connected to the header at the upper and lower parts of the water pipe. A combustion device 2 that generates a downward flame is provided above the combustion chamber 3, and the flame is burned in the combustion chamber 3 in the center of the boiler. The combustion apparatus 2 is provided with a large capacity main burner 5 and a small capacity pilot burner 6. The combustion air used in the combustion device 2 is supplied by the blower 10. Combustion air from the blower 10 is supplied through the air passage 7, and the combustion air is rectified by the wind box 8 and supplied to the main burner 5 and the pilot burner 6. An inverter device 17 that changes the power supply frequency of the blower is connected to the blower, and the amount of combustion air sent to the main burner 5 and the pilot burner 6 is adjusted by changing the rotational speed of the blower by the inverter device 17. Further, a damper 15 for changing the flow passage area of the air passage 7 is provided in the middle of the air passage 7, and the amount of combustion air sent to the main burner 5 and the pilot burner 6 is also adjusted by the damper 15. Yes.

  Fuel is supplied to the combustion device 2 through the fuel supply pipe 4. The fuel supply pipe 4 branches off in the middle and is connected to each of the main burner 5 and the pilot burner 6. The fuel supply pipe 4 connected to the main burner 5 is provided with a main fuel cutoff valve 13 and a main flow rate switching valve 14 as fuel supply amount adjusting means, and the fuel supply pipe 4 connected to the pilot burner 6 is piloted. A fuel cutoff valve 12 and a pilot flow rate switching valve 16 are provided. The fuel is supplied to the main burner 5 by opening the main fuel shut-off valve 13, and by switching the flow rate with the main flow rate switching valve 14, the fuel supply for high combustion with a large combustion amount and low combustion with a small combustion amount is provided. To be able to do. Here, since the combustion amount is controlled in two stages of high combustion and low combustion, low combustion is the minimum combustion amount of the large-capacity burner. Similarly, fuel is supplied to the pilot burner 6 by opening the pilot fuel shut-off valve 12, and by switching the flow rate with the pilot flow rate switching valve 16, combustion with a relatively large thermal power performed at the time of main switching, and pilot single combustion Be prepared to burn with small firepower at the time.

  As shown in the figure, the flow rate of the pilot fuel is switched by providing a parallel portion in the fuel supply pipe downstream of the pilot fuel cutoff valve 12, providing an orifice in one of the parallel portions, and a cutoff valve in the other. ing. When the fuel supply pipes are arranged in parallel and one orifice and one shut-off valve are provided, the fuel flows through the orifice portion even if the shut-off valve provided in the parallel portion is closed if the upstream pilot fuel shut-off valve 12 is opened. A relatively small amount of fuel will flow. When the shut-off valve in the parallel portion is opened, the fuel flows also to the shut-off valve portion, so that a relatively large amount of fuel flows.

  The boiler supplies water from the lower water supply pipe, takes out the steam from the upper steam pipe 9 and sends it to the steam-using device, and provides a pressure detection device 1 for detecting the steam pressure value in the steam section. An operation control device 11 connected to each of the pressure detection device 1, the pilot fuel cutoff valve 12, the pilot flow rate switching valve 16, the main fuel cutoff valve 13, the main flow rate switching valve 14, the damper 15, and the inverter device 17 is provided and operated. The control device 11 controls the operation of each device to control the operation of the boiler.

  In the operation control device 11, a necessary combustion amount is determined according to the steam pressure value. In this embodiment, the combustion amount is high combustion in which combustion is performed at the rated combustion amount of the main burner 5, low combustion in which combustion is performed with a smaller thermal power than high combustion, the main burner 5 is stopped, and combustion is performed in the pilot burner. Control is performed at the standby position. High combustion when the steam pressure value is lower than the low pressure set value, low combustion when the steam pressure value is between the low pressure set value and the high pressure set value, and when the steam pressure value is higher than the high pressure set value Set to perform main standby. The operation control device 11 adjusts the combustion air supply amount and the fuel supply amount in accordance with the combustion amount of the main burner 5 determined from the steam pressure value detected by the pressure detection device 1. For the damper that adjusts the combustion air supply amount, a high combustion position with a large combustion amount and a low combustion position with a small combustion amount are set so that a predetermined amount of combustion air can be supplied. deep. The combustion air supply amount is increased by increasing the opening of the damper 15 during high combustion, and the combustion air supply amount is decreased by reducing the opening of the damper 15 during low combustion. The inverter device 17 that controls the rotational speed of the blower 10 can also set a high combustion frequency with a large combustion amount and a low combustion frequency with a small combustion amount, and supply a predetermined amount of combustion air. Keep it like that. The combustion air supply amount is increased by increasing the rotation speed of the blower 10 during high combustion, and the combustion air supply amount is decreased by decreasing the rotation speed of the blower 10 during low combustion.

  Further, the operation control device 11 is also set for combustion by the pilot burner 6. The pilot burner 6 serves as a fire type for the main burner 5. The pilot burner 6 is burned before the combustion of the main burner 5 is started, and the combustion of the pilot burner 6 is stopped when the combustion by the main burner 5 is started. When the combustion of the main burner 5 is stopped, combustion by the pilot burner 6 is started immediately before the combustion is stopped, and alternate combustion is performed in which only the pilot burner 6 is burned until the start of combustion by the next main burner 5. Although the combustion amount of the pilot burner 6 is much smaller than that of the main burner 5, two large and small combustion amounts are determined for the pilot burner 6. When the main burner 5 is ignited, the combustion amount by the pilot burner 6 is combusted with a comparatively large amount of combustion power, and only the pilot burner 6 is combusted, not when the main burner 5 is ignited. In the case of setting, fine combustion is performed with a thermal power smaller than the rating of the pilot burner 6.

  In the damper 15, as a setting position for burning only the pilot burner 6, a fine combustion position that is further closed than the low combustion position and a main ignition position that is an opening between the low combustion position and the fine combustion position are set. Keep it. The operation control device 11 sets the damper 15 to a minute combustion position where the amount of combustion air supplied is reduced during minute combustion, and then ignites the main burner 5 to the main ignition position while performing overlapping combustion.

  In the inverter device 17, in the minute combustion in which only the pilot burner 6 is combusted, the blower is operated at a rotation speed with a small set frequency. During the overlap combustion, the engine is operated at a rotational speed set to a value larger than the low combustion frequency, which is the minimum combustion amount of the main burner.

  Based on the time chart of FIG. 2, the state of operation control will be described. In the case of FIG. 2, a small combustion in which the pilot burner is burned with a small heating power, a switching combustion in which the combustion amount of the pilot burner is increased for main ignition, a main ignition in which the pilot burner flame is transferred to the main burner, and a relatively small main burner. The operating state is shifted in the order of low combustion that burns with the combustion amount and high combustion that burns with the rated combustion amount of the main burner. A plurality of setting frequencies of the inverter device for controlling the air supply amount and a set opening degree of the damper device are respectively set. In the figure, the air supply amount increases as the shaded portion becomes wider. The fuel is supplied by a control valve at two positions of opening and closing, and the time when the valve is open is indicated by a hatched portion. The portion of the total fuel supply amount indicates that the fuel supply amount increases as the shaded portion increases.

  In the minute combustion, since it is not necessary to burn the main burner 5, the fuel consumption is reduced by reducing the thermal power. For fuel supply, only the pilot fuel shut-off valve 12 is opened, and the other fuel valves are closed. When the pilot fuel shut-off valve 12 is opened, fuel is sent to the pilot burner 6 through the orifice portion even if the pilot flow rate switching valve 16 is closed, but the amount of fuel sent to the pilot burner 6 is limited by the orifice. Less. Since the inverter frequency and the damper are set to the smallest combustion position which is the smallest setting, the air supply amount is also reduced. Therefore, stable combustion can be performed while suppressing fuel consumption.

  When the steam pressure of the boiler decreases and the steam pressure value detected by the pressure detection device 1 decreases to a pressure value at which combustion of the boiler starts, the operation control device 11 burns the boiler and supplies steam. The operation control device 11 opens the pilot flow rate switching valve 16 to increase the fuel supply amount to the pilot burner 6 and increase the thermal power of the pilot burner 6. Then, the amount of air supplied to the combustion apparatus is increased by changing the inverter frequency to the main ignition frequency and changing the damper position to the main ignition position.

  Thereafter, ignition of main combustion is performed by opening the main fuel cutoff valve 13. The main flow rate switching valve 14 is such that a predetermined amount of fuel is sent even when the valve body is closed. When the main fuel cutoff valve 13 is opened and the main flow rate switching valve 14 is closed, a limited amount of fuel is sent. Fuel is sent to the main burner 5. The operation control device 11 opens the main fuel cutoff valve 13 in a state in which the damper 15 and the inverter device 17 supply air at the main ignition position. When the main fuel cutoff valve 13 is opened and fuel supply to the main burner 5 is started, the flame of the pilot burner 6 spreads to the main burner 5 and combustion in the main burner 5 is started. At this time, in the inverter device 17, the frequency is increased and the rotation speed is increased, and the damper 15 is squeezed to reduce the flow area, so that the static air pressure is high, and the high static air pressure is high. Therefore, it is possible to suppress a temporary increase in combustion noise and vibration combustion.

  In addition, since the fuel supply amount at this time overlaps the supply to the main burner 5 and the supply to the pilot burner 6, the total fuel supply amount becomes larger than that in the low combustion of the main alone. For this reason, in the main ignition process in which the fuel supply amount increases, the air supply amount corresponding to the amount of fuel supply amount added to the pilot burner 6 is set to be larger than in the case of low combustion. When overlapping combustion of the main burner 5 and the pilot burner 6 is performed for a predetermined time, the main ignition process is terminated, the pilot fuel cutoff valve 12 and the pilot flow rate switching valve 16 are closed, and combustion of the pilot burner 6 is stopped. Then, while reducing the frequency at the inverter device 17 to the low combustion frequency, the position of the damper 15 is increased to the low combustion position, so that the relationship between the fuel supply amount and the combustion air supply amount becomes appropriate.

  When the combustion amount is set to high combustion, the frequency at the inverter device 17 is set to the high combustion frequency, and the position of the damper 15 is set to the high combustion position, so that the fuel supply amount for high combustion and the air supply amount for combustion are To do. When the main flow rate switching valve 14 is opened, the amount of fuel passing through the main flow rate switching valve 14 increases, so that the combustion amount in the main burner 5 increases.

  When combustion in the main burner 5 is no longer necessary due to an increase in the steam pressure value, switching from combustion in the main burner 5 to combustion in the pilot burner 6 is performed. In this case, the combustion of the main burner 5 is stopped after the combustion of the pilot burner 6 is started. When combustion is performed only with the pilot burner 6, the pilot burner 6 burns with a smaller heating power and returns to the state of minute combustion.

  When the combustion of the main burner 5 is started, the amount of combustion by the pilot burner 6 is set to combustion with a relatively large heating power, and then the combustion of the main burner 5 is started, so that the main burner 5 can be ignited reliably. Further, the heating power in the pilot burner is increased immediately before the combustion of the main burner 5 is started, and it is not necessary to burn the main burner 5, and the combustion amount when only the pilot burner 6 is burned is the thermal power. Due to the small micro-combustion, the amount of fuel consumption during standby can be reduced. Furthermore, since the amount of air to be supplied is reduced, the amount of heat dissipated from the boiler can be reduced.

  Further, since the static pressure of the blown air is increased in the main ignition process, it is possible to prevent an increase in combustion noise and vibration combustion from occurring during the main ignition. And even at the time of overlapping combustion, an appropriate combustion state can be maintained by maintaining an appropriate ratio of fuel and air, and generation of CO can be suppressed.

1 Pressure detection device 2 Combustion device
DESCRIPTION OF SYMBOLS 3 Combustion chamber 4 Fuel supply piping 5 Main burner 6 Pilot burner 7 Air supply path 8 Wind box 9 Steam piping 10 Blower 11 Operation control device 12 Pilot fuel cutoff valve 13 Main fuel cutoff valve 14 Main flow rate switching valve 15 Damper 16 Pilot flow rate switching valve 17 Inverter device

Claims (2)

  It has a large-capacity burner and a small-capacity burner that can increase and decrease the amount of combustion, respectively. Is a combustion device that performs alternate combustion temporarily only when switching combustion, and a small-capacity burner is a small thermal power with a reduced combustion amount when only a small-capacity burner is burned When burning from a small-capacity burner to a large-capacity burner, the combustion amount is increased and combustion is performed with a large heating power, and the large-capacity burner is switched from the small-capacity burner to the minimum combustion amount position. After that, the heating power is changed by increasing / decreasing the combustion amount according to the load, and the combustion air is supplied from one path, the blower rotation speed adjusting device, In a combustion device in which the air volume is changed by the area adjustment device, when only the small-capacity burner is combusted, the blower rotation speed and the flow passage area of the air passage are set to the smallest position, and from the small-capacity burner to the large-capacity Switching to the burner is performed in a state where the fan rotational speed is increased and the flow passage area of the air passage is reduced compared to the minimum combustion amount in the large-capacity burner, and the static pressure of the blower is increased, and overlapping combustion is performed. A combustion apparatus characterized in that, after being finished, it is changed by a motion to increase the flow passage area of the air passage while reducing the rotational speed of the blower, and is set to the minimum combustion position in the large-capacity burner. The combustion apparatus according to claim 1, wherein the air supply amount at the time of switching from the small-capacity burner to the large-capacity burner is set to be larger than the air supply amount at the minimum combustion amount in the large-capacity burner, and overlap combustion is performed. A combustion apparatus characterized in that, after finishing, the air supply amount is reduced to the minimum combustion position when the flow passage area of the blower passage is increased while reducing the blower rotational speed.

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