JPH0694226A - Combustion apparatus - Google Patents

Abstract

PURPOSE:To prevent generation of drain due to exhaust gas by heating an exhaust gas circulation passage by heating means and forming an air intake port near an exhaust gas extraction port. CONSTITUTION:An upper part of an exhaust gas circulation passage 3 is disposed along a heat exchanger 12 to be heated by combustion flame. Thus, exhaust gas H in the passage receives heat to maintain at a high temperature thereby to prevent condensation of steam in the exhaust gas. Further, an air intake port 31 for intaking the air is formed near an exhaust gas extraction port 132 of the passage 3, and an air inlet tube 133 is connected to the port 31. Thus, since the gas H extracted from the port 132 and combustion air intaken from the port 31 are mixed in the passage 3, a ratio of steam in the exhaust gas can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus of a type in which a part of exhaust gas is returned to a combustion air passage of a burner in order to reduce NOx.

[0002]

2. Description of the Related Art Conventionally, the exhaust gas generated by combustion is mixed with the combustion air of a gas burner and the flame temperature is lowered (because the oxygen concentration in the combustion air is lowered) to reduce the NOx of the exhaust gas. Known combustion devices are known.

[0003]

However, such a combustion apparatus is apt to cause drainage in the exhaust gas recirculation passage, the fan casing, the mixing pipe, etc. due to the condensation of water vapor in the exhaust gas, especially when the combustion amount is small. Since the exhaust gas temperature is not so high, when the exhaust gas passes through the exhaust gas recirculation path, if the temperature of the exhaust gas decreases, drainage will occur. As a result, there is a drawback that the drain causes water leakage and corrosion. An object of the present invention is to prevent generation of drain due to exhaust gas in a combustion device in which a part of exhaust gas is recirculated to reduce NOx.

[0004]

[Means for Solving the Problems] In order to solve the above problems,
The present invention has the following configurations. (1) A burner, a combustion housing having a heat exchanger that is heated by a combustion flame, an exhaust stack that collects and discharges exhaust gas generated by combustion, and a portion of the exhaust gas in the exhaust stack is burned by the burner. In a combustion device having an exhaust gas recirculation path that recirculates to a commercial air path, a heating unit that heats the exhaust gas recirculation path is provided. (2) In addition to the configuration of (1) above, an air intake port for taking in air to the exhaust gas recirculation passage is formed near the exhaust gas recirculation passage in the exhaust gas recirculation passage. (3) In addition to the configuration of (1) or (2) above, the exhaust gas recirculation path is provided along the heat exchanger, and the heat exchanger serves as the heating means.

[0005]

[Action]

[Claim 1] Since the exhaust gas recirculation passage is heated by the heating means, the exhaust gas passing through the exhaust gas recirculation passage receives heat and the exhaust gas temperature does not decrease. Therefore, the condensation of water vapor in the exhaust gas can be prevented.

[Claim 2] Since the air intake port for taking in air is formed in the vicinity of the exhaust gas collection port of the exhaust gas recirculation passage, the ratio of water vapor in the exhaust gas in the exhaust gas recirculation passage is changed by the air taken in from the air intake port. Can be reduced. Further, the diluted exhaust gas is heated and the temperature of the diluted exhaust gas rises.

[Claim 3] Since the exhaust gas recirculation passage is provided along the heat exchanger, the heat exchanger serves as a heating means for heating the exhaust gas recirculation passage.

[0008]

【The invention's effect】

[Claim 1] Since the exhaust gas is heated, the condensation of water vapor in the exhaust gas does not occur, and the generation of drain due to the exhaust gas can be prevented.

[Claim 2] The intake air can reduce the proportion of water vapor in the exhaust gas, and the diluted exhaust gas can be heated to maintain the exhaust gas temperature at a high temperature. You can do it.

[Claim 3] Since the heat exchanger is used as the heating means for heating the exhaust gas, the exhaust gas can be heated without providing a separate heating means.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention (corresponding to claims 1 and 3) will be described with reference to FIGS. A forced combustion gas water heater A shown in FIGS. 1 and 2 includes a combustion housing 1 in which a gas burner 11 and a heat exchanger 12 heated by a combustion flame are installed, and a fan for supplying combustion air N to the gas burner 11. 2, an exhaust gas recirculation path 3 that recirculates a part of the exhaust gas H in the exhaust tube portion 13 to the fan 2, a recirculation solenoid valve 5 disposed in the exhaust gas recirculation path 3, and opening / closing of the recirculation solenoid valve 5. The controller 6 controls the combustion of the gas burner 11, the rotation speed of the fan 2, and the like.

The combustion housing 1 has a combustion air N at the bottom.
The supply port 14 is provided. Further, in the exhaust tube portion 13 that collects and discharges the exhaust gas H generated by combustion, an exhaust port 131 for discharging the exhaust gas H to the outside and an exhaust gas collection port 132 (perforated on the peripheral wall). Is provided.

The gas burner 11 has a large number of gas ejection ports 11
1 and a burner group 113 located above the nozzle pipe 112 and forming a combustion flame. In addition, from the upstream side to the nozzle pipe 112, the original solenoid valve 114, the main solenoid valve 1
Gas is supplied from a gas pipe 117 in which a proportional valve 15 and a proportional valve 116 are sequentially arranged.

The heat exchanger 12 disposed inside the combustion housing 1 is composed of a box-shaped body in which a meandering water pipe with fins is installed, and a water pipe connected to the upstream end of the meandering water pipe. Water is supplied from a water supply pipe 123 in which a water amount adjuster 121 and a water flow switch 122 are connected in series, and when the water passes, the water is heated by a combustion flame and becomes hot water and flows out from the hot water supply pipe 124. The water flow switch 122 is a switch whose electrical contacts conduct when it detects running water in the heat exchange channel.

The fan 2 has sirocco type blades and supplies the taken-in air as combustion air to the gas burner 11 through a combustion air supply passage 21 communicating with the supply port 14.

The exhaust gas recirculation passage 3 whose upper part is fixed to the combustion housing 1 along the body of the heat exchanger 12 has its lower end exposed to the inside of the fan 2 as an exhaust gas discharge port 32.

The recirculation solenoid valve 5 is a solenoid valve which is opened by energization, and maintains the electric output of the frame rod 71 at a predetermined value or more (stable combustion state) and while the gas burner 11 burns with a high input. Exhaust gas recirculation is performed by holding the valve open.

The controller 6 includes an operation control section 61 for controlling the combustion of the gas burner 11, a proportional valve drive circuit 62 for controlling a current supplied to the proportional valve 116, a fan drive circuit 63 for controlling the rotation speed of the fan 2, and a recirculation. It has a circulation solenoid valve drive circuit 64 for controlling the opening / closing of the solenoid valve 5.

The operation controller 61 includes a temperature setter 72 for setting the temperature of the hot water and the water supply pipe 1 near the inlet of the heat exchanger 12.
23 for supplying water temperature thermistor 125, heat exchanger 12
A water amount sensor 74 for detecting the amount of water flowing into the chamber, a frame rod 71 for transmitting an electric output according to the heat received by the combustion flame, and each electric output transmitted from a thermocouple 75 for detecting incomplete combustion are input. Further, the operation control unit 61, based on these electric outputs, the original solenoid valve 114 and the main solenoid valve 11
5, opening and closing, operation of the sparker 76, proportional valve drive circuit 62,
The drive signals are sent to the fan drive circuit 63 and the return solenoid valve drive circuit 64.

In the proportional valve drive circuit 62, the temperature of the hot water flowing out of the hot water supply pipe 124 is set by the temperature setter 72 based on the water supply amount detected by the water amount sensor 74 and the water supply temperature detected by the water supply temperature thermistor 125. This is a circuit for controlling the current flowing through the proportional valve 116 so that the set temperature becomes a set temperature.

The fan drive circuit 63 supplies a current corresponding to the magnitude of the proportional valve current to the fan 2 so that the combustion air corresponding to the combustion amount of the gas burner 11 is supplied to the gas burner 11.
It is a circuit that flows to.

The circulation solenoid valve drive circuit 64 stabilizes combustion, maintains the electric output of the flame rod 71 at a predetermined value or more (flame detection is performed), and while the gas burner 11 burns with high input, This is a circuit for energizing the return solenoid valve 5. The input amount is calculated from the proportional valve current, the fan rotation speed, the temperature inside the fan casing, and the like.

Next, the operation of the controller 6 of the forced combustion gas water heater A will be described with reference to the flowchart of FIG.
When the user adjusts the water amount adjuster 121 to flow the water into the heat exchange channel, the water flow switch 122 is turned on (Yes) in step s1 and the process proceeds to step s2. In step s2, the controller 6 starts energizing the fan 2 to energize the sparker 76 for a predetermined time, and energizes the original solenoid valve 114 and the main solenoid valve 115 to open the valve. In addition, energization of the proportional valve 116 is started, and the process proceeds to step s3. In step s3, the controller 6 determines whether or not the electric output of the flame rod 71 is a predetermined value or more (the gas burner 11 is in a stable combustion state), and if it is the predetermined value or more (Ye
s), the process proceeds to step s4, and if it is less than the predetermined value (N
o), the process proceeds to step s8. In step s4, the controller 6
Starts proportional valve control of the proportional valve 116 and rotation speed control of the fan 2, and proceeds to step s5. In step s5, the controller 6 determines whether or not the gas burner 11 is burning with a low input, and if the input is low (Yes), the process proceeds to step s6, and if the input is not low (No), the process proceeds to step s7. . In step s6, the controller 6 stops energization of the return solenoid valve 5 (maintains energization stop if already closed), and returns to step s5. Step s7
Then, the controller 6 energizes the return solenoid valve 5 (maintains energization when the valve is already open), and returns to step s5.
In step s8, it is determined whether or not a predetermined time has elapsed. If it has not elapsed (No), the process returns to step s3, and if it has elapsed (Yes), the process proceeds to step s9. In step s9, the controller 6 determines that an error has occurred, closes the original solenoid valve 114 and the main solenoid valve 115,
The operation of the forced combustion type gas water heater A is stopped.

Next, the advantages of this embodiment will be described. (A) Since the upper part of the exhaust gas recirculation path 3 is along the heat exchanger 12, the exhaust gas H in the exhaust gas recirculation path 3 receives heat and the exhaust gas temperature is maintained at a high temperature. Condensation can be prevented (because the temperature of the exhaust gas H does not fall below the dew point temperature). Therefore, the drain is extremely unlikely to occur in the fan casing, the exhaust gas recirculation path 3, and the like.

(Ii) When the gas burner 11 is in a stable combustion state (the electric output of the flame rod 71 is a predetermined value or more) and the input amount is large, the recirculation solenoid valve 5 is opened and the exhaust gas H is exhausted. The air is discharged into the fan 2 through the recirculation path 3, and the fan 2 is supplied to the gas burner 11 together with the combustion air sucked from the periphery 2a of the fan 2, and thus is discharged to the outside from the exhaust port 131 at the time of a large input. The proportion of NOx contained in the exhaust gas H can be reduced. When the input amount is small, the recirculation solenoid valve 5 is closed and exhaust gas recirculation is stopped (there is no problem because the amount of NOχ generated is small at low input), so a good combustion range is secured. it can.

(C) Even if the ignition operation of the gas burner 11 is performed, if the electric output of the frame rod 71 is less than the predetermined value, the recirculation solenoid valve 5 is not energized and the recirculation solenoid valve 5 is Keep the valve closed. Therefore, at the start of ignition,
Even if an ignition failure occurs and unburned gas is released from the gas burner 11 into the combustion housing 1, it does not recirculate and mix into the combustion air N, so that a large ignition noise does not occur.

(E) Since the heat exchanger 12 is used as a heating means for heating the exhaust gas H, the exhaust gas H can be heated without providing a separate heating means.

A second embodiment of the present invention (corresponding to claims 2 and 3) will be described with reference to FIGS. The forced combustion type gas water heater B shown in FIGS. 4 and 5 differs from the forced combustion type gas water heater A in the following configuration.

An air intake port 31 for taking in air is formed near the exhaust gas collection port 132 of the exhaust gas recirculation path 3, and an air introduction pipe 133 is connected to the air intake port 31.
The exhaust gas recirculation fan 8 is arranged in the exhaust gas recirculation path 3 and when rotated, the air intake port 3 is introduced through the air introduction pipe 133.
The air taken in from No. 1 is mixed upstream of the exhaust gas recirculation passage 3, the mixed diluted exhaust gas H ′ is discharged into the combustion air supply passage 21 through the exhaust gas recirculation passage 3, and the released diluted exhaust gas H is discharged. 'Is mixed with the air sucked by the fan 2 and is supplied to the gas burner 11 as the combustion air N.
The combustion air N is also sucked from the periphery 2a of the fan 2.

When the electric output of the frame rod 71 becomes a predetermined value or more (the combustion state is stable) and the gas burner 11 enters the combustion state, the recirculation fan drive circuit 81 supplies a small current to the exhaust recirculation fan 8 for a predetermined time. And the exhaust gas recirculation fan 8 is rotated at a low speed. After the low speed rotation period of the exhaust gas recirculation fan 8 ends, when the gas burner 11 burns with a large input, the exhaust gas recirculation fan 8 rotates in proportion to the input amount (proportional valve current). When the number is increased and combustion is performed with a small input, power supply to the exhaust gas recirculation fan 8 is stopped.

Next, the operation of the controller 6 of the forced combustion type gas water heater B will be described with reference to the flowchart of FIG.
When the user adjusts the water amount adjuster 121 to flow the water into the heat exchange channel, the water flow switch 122 is turned on (Yes) in step S1 and the process proceeds to step S2. In step S2, the controller 6 starts energizing the fan 2 to energize the sparker 76 for a predetermined time, and energizes the original solenoid valve 114 and the main solenoid valve 115 to open them. Further, energization of the proportional valve 116 is started, and the process proceeds to step S3. In step S3, the controller 6 determines whether or not the electric output of the flame rod 71 is a predetermined value or more (the gas burner 11 is in a stable combustion state), and if it is the predetermined value or more (Ye
s), the process proceeds to step S4, and when it is less than the predetermined value (N
o), the process proceeds to step S9. In step S4, the controller 6
Starts proportional valve control of the proportional valve 116 and rotation speed control of the fan 2, and proceeds to step S5. In step S5, the controller 6 rotates the exhaust gas recirculation fan 8 at a low speed (for preventing the lift of the gas burner 11) for a predetermined time, and proceeds to step S6. In step S6, the operation control unit 61 of the controller 6 determines whether or not the gas burner 11 is burning with a low input, and if the input is low (Yes), the process proceeds to step S7, and if the input is not low (No). , Step S8
Proceed to. Although the input amount is calculated by the proportional valve current, it may be calculated by the combustion chamber pressure, the fan rotation speed, or the like. In step S7, the controller 6 controls the exhaust gas recirculation fan 8
Is stopped (the energization is stopped if it is already stopped), the exhaust gas recirculation is stopped, and the process returns to step S6. In step S8, the controller 6 energizes the exhaust gas recirculation fan 8 based on the input amount (maintains energization when already in operation), and returns to step S6. In step S9, it is determined whether or not a predetermined time has elapsed. If it has not elapsed (No), the process returns to step S3, and if it has elapsed (Yes), the process proceeds to step S10. In step S10, the controller 6 determines that an error has occurred,
The original solenoid valve 114 and the main solenoid valve 115 are closed, and the operation of the forced combustion type gas water heater B is stopped.

Next, the advantages of this embodiment will be described. (O) Exhaust gas H collected from the exhaust gas collection port 132,
Since the combustion air taken in from the air intake port 31 is mixed in the exhaust gas recirculation passage 3, the rate of water vapor in the exhaust gas can be reduced. Furthermore, since the upper part of the exhaust gas recirculation path 3 is along the heat exchanger 12, the diluted exhaust gas H'in the exhaust gas recirculation path 3 receives heat and the exhaust gas temperature is maintained at a high temperature. Of water vapor can be prevented (because the temperature of the diluted exhaust gas H'does not fall below the dew point temperature). For this reason, drain is extremely unlikely to occur in the exhaust gas recirculation fan 8, the exhaust gas recirculation path 3, and the like.

(Or) When the low speed rotation period of the exhaust gas recirculation fan 9 (step S5) is completed and the input amount is large, the exhaust gas recirculation fan 8 rotates according to the input amount,
Since the diluted exhaust gas H ′ corresponding to the input amount is discharged into the combustion air supply passage 21 and supplied to the gas burner 11 as the combustion air N together with the indoor air sucked by the fan 2, it is discharged to the outside from the exhaust port 131. The content ratio of NOx in the exhaust gas H can be efficiently reduced. When the input amount is small, turn off the power to the exhaust gas recirculation fan 8,
Since the exhaust gas recirculation is stopped, a good combustion range can be ensured, and drain is unlikely to occur in the exhaust gas recirculation fan 8, the exhaust gas recirculation path 3, and the like.

(G) Even if the ignition operation of the gas burner 11 is performed, if the electric output of the frame rod 71 is less than the predetermined value, the exhaust gas recirculation fan 8 is not energized. Therefore, even if an ignition failure occurs and unburned gas is discharged from the gas burner 11 into the combustion housing 1 at the start of ignition,
Since there is no possibility that the air will be recirculated and mixed into the combustion air N, a large ignition noise will not occur.

(5) Since the low-speed rotation period of the exhaust gas recirculation fan 8 (step S5) is provided at the initial stage of ignition, the lift of the gas burner 11 can be prevented and NO at the initial stage of ignition.
It is effective in reducing the emission of χ.

(Vi) Since the heat exchanger 12 is used as the heating means for heating the diluted exhaust gas H ', the diluted exhaust gas H'can be heated without separately providing a heating means.

The present invention includes the following embodiments in addition to the above embodiments. a. In the first embodiment, in the vicinity of the exhaust gas collection port 132 of the exhaust gas recirculation path 3, the air intake port 31 is provided as in the second embodiment.
May be provided. In this case, all the combustion air may be taken in from the exhaust gas recirculation passage 3. b. In each of the above embodiments, the opening of the electromagnetic valve 5 for recirculation or the operation of the exhaust gas recirculation fan 8 is performed based on the output of the flame rod 71 for detecting the combustion state. However, a predetermined time has elapsed from the start of ignition. You may choose to do it later. Further, the exhaust gas may be recirculated from the time of ignition. In this case, the return solenoid valve 5 may be omitted in the first embodiment. c. The heating means may be an electric heater, for example, a heating wire may be wound around the outer periphery of the exhaust gas recirculation path 3.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a forced combustion type gas water heater according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a forced combustion type gas water heater according to the first embodiment.

FIG. 3 is a flowchart showing an operation of a controller of the forced combustion type gas water heater according to the first embodiment.

FIG. 4 is a structural explanatory view of a forced combustion type gas water heater according to a second embodiment of the present invention.

FIG. 5 is a block diagram of a forced combustion type gas water heater according to a second embodiment.

FIG. 6 is a flowchart showing an operation of a controller of the forced combustion type gas water heater according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion housing 3 Exhaust gas recirculation path 11 Gas burner (burner) 12 Heat exchanger 13 Exhaust tube part 21 Combustion air supply path (combustion air path) 31 Air intake port 132 Exhaust gas sampling port A, B Forced combustion gas water heater ( Combustor) H exhaust gas (exhaust gas)

Claims (3)

[Claims] 1. A burner, a combustion housing having a heat exchanger heated by combustion flames, an exhaust stack for collecting and discharging exhaust gas generated by combustion, and a part of the exhaust gas in the exhaust stack for the burner. In the combustion device having an exhaust gas recirculation path that recirculates to the combustion air path, the heating device that heats the exhaust gas recirculation path is provided. 2. The combustion apparatus according to claim 1, wherein an air intake port for taking in air to the exhaust gas recirculation passage is formed in the exhaust gas recirculation passage in the vicinity of the exhaust gas collection port. 3. The combustion apparatus according to claim 1, wherein the exhaust gas recirculation path is provided along the heat exchanger, and the heat exchanger serves as the heating means.