JP4301740B2 - Hybrid catalytic combustion apparatus and fan heater provided with the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a combustion catalyst part that allows catalytic mixture oxidation of a part of the fuel by passing an air-fuel mixture of combustion air and fuel, and provided downstream of the combustion catalyst part in the flow direction of the air-fuel mixture. A gas phase combustion part for burning the remainder of the fuel in a gas phase,
The inner cylinder provided with the combustion catalyst part inside one end part, and the inner cylinder and the combustion catalyst part between the one end part side of the inner cylinder and the outer side of the inner cylinder The present invention relates to a hybrid catalytic combustion apparatus including an outer member that forms a gas phase combustion section, and a fan heater including the same.
[0002]
[Prior art]
Equipment that operates at high air ratios, such as indoor open-air hot air heaters for home use, cogeneration, and gas turbine combustors for power generation, can achieve significantly lower NOx by improving combustion stability at high air ratios. May be achieved. On the other hand, in these devices, there is a demand for further NOx reduction. Among them, indoor open-air hot air heaters for home use emit exhaust directly into the living space, and therefore NOx reduction to the limit of NOx 1 ppm (oxygen 0%) or less is desired.
A combustion catalyst section filled with a combustion catalyst and a gas phase combustion section following the combustion catalyst are provided in the combustion flow path, and fuel and combustion air are mixed at a theoretical adiabatic combustion temperature of 1500 ° C. or lower (air ratio of about 1.6 or higher). Proposed as a means to achieve ultra-low NOx is a method that causes partial combustion by catalytic oxidation combustion in the combustion catalyst part and induces gas-phase oxidation in the downstream to complete combustion (called hybrid catalytic combustion method). (Japanese Patent Publication No. 6-506290).
[0003]
A hybrid catalytic combustion apparatus that employs such a combustion system is a means of partially combusting in the combustion catalyst section. Consisting of palladium as a main component, and using a metal honeycomb as a catalyst substrate, a catalyst coated layer (cell) and an uncoated layer (cell) are adjacent to each other, and heat generated by catalytic contact oxidation passes through a continuous non-catalytic layer. The catalyst layer in the combustion catalyst section is 20-70% catalytically oxidized and the catalyst temperature is set to 600-950 ° C. by means such as heat exchange with gas and physically preventing overheating.
[0004]
Such a hybrid catalytic combustion device is used for combustion so as to predetermine a temperature at the outlet of the combustion catalyst unit that can reliably achieve good combustion in the gas phase combustion unit according to each combustion amount, and always maintain that temperature. In some cases, the combustion air fan for supplying air is controlled to control the amount of air blown so that the combustion state in the gas phase combustion section is maintained in a good state. In this hybrid catalytic combustion apparatus, during operation, the outlet temperature of the combustion catalyst section becomes a predetermined temperature value that is higher than the temperature at which incomplete combustion or the like occurs in the gas phase combustion section. In addition, since there is a possibility that abnormal combustion such as incomplete combustion may occur, safety control such as stopping operation is performed to achieve safety.
[0005]
[Problems to be solved by the invention]
However, in practical use, if there is an abnormality in one system, it is preferable to have a double safety structure that can be complemented by another system. In the abnormal combustion detection by measuring the outlet temperature of the combustion catalyst section, the outlet temperature of the combustion catalyst section where about 50% of the air-fuel mixture burns in contact with the catalyst is constantly monitored. About the gas phase combustion part which carries out a gas phase combustion, the combustion state is not monitored.
Therefore, in the double safety structure, it is desirable to monitor the combustion state of the gas phase combustion section, that is, to monitor the presence of the flame in the gas phase combustion section.
[0006]
As a method for monitoring the presence of the flame, there are a method using the heat generated from the flame, a method using the electrical characteristics of the flame, a method using the light emission of the flame, etc. A thermocouple temperature detection method using heat generation and a frame rod method using electric characteristics of a flame have been put into practical use.
A flame rod that can detect the presence of a flame more directly in a wider area than the thermocouple temperature detection method, which is a local measurement, in order to detect a flame spread in the space of the gas phase combustion part as in this case. It is desirable to apply the law.
[0007]
It has already been proposed to apply flame detection by the flame rod method to a hybrid catalytic combustion apparatus (Japanese Patent Laid-Open No. 10-160159). In this hybrid catalytic combustion apparatus, a pair of frame rods close to the gas phase combustion part near the outlet of the combustion catalyst part are provided, and a flame generated at a position separated from the combustion catalyst part of the gas phase combustion part is The flame current peak generated by approaching the flame rod is detected, and the ignition in the gas phase combustion section is confirmed.
[0008]
However, it is difficult to apply such flame detection to a hybrid combustion apparatus in which the position and movement of the flame in the gas phase combustion unit are different from those described above.
In particular, a gas phase combustion part extending from one end side of the inner cylinder to the outside of the inner cylinder is provided between the inner cylinder provided with the combustion catalyst part inside one end and the inner cylinder and the combustion catalyst part. In a hybrid catalytic combustion apparatus having a shape in which the shape of the gas phase combustion part is folded from the upper side of the combustion catalyst part to the outside of the inner cylinder, the catalyst combustion part is Since a flame is formed in the upper gas phase combustion section and the flame moves to the outside of the downstream inner cylinder, it is difficult to apply the flame rod method as it is.
[0009]
Therefore, in view of the circumstances as described above, the present invention realizes a technique for detecting a flame in a gas phase combustion section and monitoring abnormal combustion in the gas phase combustion section in such a hybrid catalytic combustion apparatus. The purpose is to do.
[0010]
[Means for Solving the Problems]
[Configuration 1]
  As described in claim 1, the hybrid catalytic combustion apparatus according to the present invention includes a combustion catalyst unit that allows a mixture of combustion air and fuel to pass through and catalytically oxidizes a part of the fuel, and the combustion catalyst unit. A gas phase combustion section provided on the downstream side in the flow direction of the air-fuel mixture and gas phase combustion of the remaining portion of the fuel,
  The inner cylinder provided with the combustion catalyst part inside one end part, and the inner cylinder and the combustion catalyst part between the one end part side of the inner cylinder and the outer side of the inner cylinder A hybrid catalytic combustion apparatus comprising an outer member forming a gas phase combustion section,
  At least three frame rods are disposed along the flow direction of the air-fuel mixture in the gas phase combustion section, and
  The at least three frame rods;As a frame rod of them,It includes a frame rod provided in a corner portion that is above the one end of the inner cylinder of the gas phase combustion section and outside the inner cylinder,
  A frame current detecting means for detecting a frame current flowing between the frame rods by applying a voltage between the frame rods is provided.
[0011]
  [Configuration 2]
  In the hybrid catalytic combustion apparatus according to the present invention, as described in claim 2, in addition to the configuration of the hybrid catalytic combustion apparatus having the configuration 1, the at least three frame rods are provided as one pole at the corner portion. Frame rod, upper part of the catalyst upstream of the corner part of the gas phase combustion part, and the corner of the gas phase combustion part-Each frame rod provided as the other pole on the side part downstream of the part,
  The frame current detection means is means for applying a voltage to each of the poles of the frame rod and detecting a frame current flowing between the poles.
[0012]
[Configuration 3]
According to the hybrid catalytic combustion apparatus of the present invention, as described in claim 3, in addition to the configuration of the hybrid catalytic combustion apparatus having the above configuration 1 or 2, the temperature of the combustion catalyst unit or the outlet of the combustion catalyst unit is detected. Possible temperature detection means,
When the temperature detected by the temperature detection means becomes a predetermined temperature or less, or when the frame current detected by the frame current detection means becomes a predetermined current value or less, a predetermined safety control is performed. A safety control means is provided for execution.
[0013]
[Configuration 4]
According to a fourth aspect of the present invention, in addition to the configuration of the hybrid catalytic combustion device having the first to third configurations, the hybrid catalytic combustion device according to the present invention is based on the temperature detected by the temperature detecting means. Control means for controlling the power of the air supply means for supplying the working air is provided.
[0014]
[Configuration 5]
According to a fifth aspect of the present invention, a fan heater includes the hybrid catalytic combustion device according to any one of the first to fourth aspects described above, and the combustion exhaust gas discharged from the gas phase combustion section is diluted with air to the outside. It is characterized by being discharged as warm air.
[0015]
[Function and effect]
In the hybrid combustion apparatus of the present invention, the combustion catalyst part is provided inside one end of the inner cylinder, and the gas phase combustion part is provided between the inner cylinder and the combustion catalyst part and the outer member. Thus, the air-fuel mixture in which a part of the fuel is burned in the combustion catalyst part is discharged from the end part of the inner cylinder and introduced into the gas phase combustion part formed around the inner cylinder, and the remaining part of the fuel is vaporized. It can be made to burn, the outer surface of an inner cylinder and a combustion catalyst part can be heated directly by the gas phase combustion, and the heat loss to the exterior can be controlled.
[0016]
  When starting the operation of such a hybrid catalytic combustion apparatus, first, an air-fuel mixture with an air ratio capable of gas phase ignition is ignited by spark discharge or the like in the gas phase combustion section. Since this flame has a high adiabatic theoretical combustion temperature, the corner above the one end of the inner cylinder of the gas phase combustion section is-It is formed in the upper part of the catalyst upstream of the part. Therefore, at the time of such ignition, a positively charged particle (for example, H, for example) is considered that the combustion reaction is most actively performed at a high temperature in the vicinity of the frame rod provided in the upper part of the catalyst and contributes to the rectifying action._ThreeO⁺, C_ThreeH_Three ⁺Etc.) exist. On the other hand, in the vicinity of the frame rod provided at the corner portion, the combustion reaction is almost finished, and the concentration of positively charged particles is reduced. Due to the concentration difference of the positively charged particles, when a constant AC voltage is applied between the two frame rods, that is, between the two poles, the positively charged particles are captured only when the frame rod in the upper part of the catalyst has a negative potential. The frame current in a pulsating state flows in one direction. Therefore, the flame current detecting means for detecting the flame current can obtain the flame current signal together with the ignition, and can detect that the flame is normally formed and a flame is formed in the upper part of the catalyst.
[0017]
Further, after ignition, the temperature of the air-fuel mixture flowing in the inner cylinder or in the upstream side thereof rises due to heat transfer from the gas phase combustion section, and catalytic contact oxidation in the combustion catalyst section is started. It shifts to hybrid combustion which performs both combustion and gas phase combustion. And the flame formed in the catalyst upper part moves to the side part which is the downstream of the corner part of the gas phase combustion part. This is because about 50% of the fuel is burned by catalytic oxidation, and as a result, the fuel concentration of the air-fuel mixture supplied to the gas phase combustion section decreases, so that the gas phase oxidation rate becomes slow and a flame is formed. This is because the period of time becomes longer.
[0018]
As a result, the number of positively charged particles is the largest in the vicinity of the frame rod in the side portion on the downstream side of the gas phase combustion section, and the vicinity of the frame rod in the upper portion of the catalyst and the corner portion is reduced. In this state, due to the difference in the concentration of positively charged particles between the side part and the corner part, a frame current in a pulsating state flows in one direction between the two frame rods, that is, between the two poles. . Therefore, the flame current detection means for detecting the flame current can obtain the flame current signal even after the start of the hybrid combustion, and detects that a flame is normally formed in the side part of the gas phase combustion part. Can do.
[0019]
Thus, in the hybrid catalytic combustion apparatus of the present invention, for example, the frame current is detected using the frame rod at the corner portion as one pole and the two frame rods sandwiching the frame rod as the other pole. The presence of flame can always be detected over a wide range from the upper part of the catalyst to the side part in the combustion section.
Of course, there may be a plurality of each frame rod, and at the time of ignition and hybrid combustion, within the range where the electric field reaches effectively, one frame rod is always away from the flame, and the other two are flames with the same pole. It may be located near the center and capture positively charged particles.
[0020]
In the hybrid catalytic combustion apparatus of the present invention, the reduction of the flame current detected by the flame current detection means reflects that the flame is not present at a predetermined position, and the combustion catalyst part or its outlet part Combining the detection result of the temperature detection means for detecting the temperature and the detection result of the flame current detection means, when the outlet temperature of the combustion catalyst part becomes a predetermined temperature or less, or the flame current is a predetermined current value or less By providing safety control means for executing predetermined safety control that stops the operation of the hybrid catalytic combustion device or reduces the amount of combustion air and fuel to be supplied, etc. High double safety structure.
Therefore, the fan heater provided with such a hybrid catalytic combustion device has high reliability of safety control when abnormal combustion occurs, and can suppress indoor air contamination due to incomplete combustion or the like.
[0021]
The temperature detecting means detects the start of catalytic combustion when the control means controls the power of the air supply means to switch the supply amount of combustion air before and after the start of catalytic combustion. It can also be used as a temperature detection means.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
As an embodiment of the present invention, a combustion apparatus 50 (an example of a hybrid catalytic combustion apparatus) that uses natural gas city gas as fuel gas G and a fan heater 100 including the combustion apparatus 50 will be described with reference to the drawings.
FIG. 1 is an overall schematic view of a fan heater 100 provided with a combustion apparatus 50 according to the present invention, and FIG. 2 is a schematic side sectional view of the combustion apparatus 50 shown in FIG.
[0023]
With reference to FIGS. 1 and 2, the combustion apparatus 50 includes a combustion catalyst unit 11 that catalytically oxidizes a part of the fuel gas G, and a gas phase combustion unit 12 that vapor-combusts the remaining part of the fuel gas G. This is a hybrid catalytic combustion type combustion apparatus.
The combustion device 50 mixes the combustion air A supplied by the combustion fan 1a with the fuel gas G supplied from the dispersion nozzle 17 via the fuel shut-off valve 3 and the proportional control valve 2 to provide premixed gas. An inner cylinder 20 provided with an air-fuel mixture channel 4 to be formed, a preheating unit 18 for preheating the pre-air mixture sent from the air-fuel mixture channel 4, and the combustion catalyst unit 11, and an entire outer periphery of the inner cylinder 20, Between the inner cylinder 20 and the combustion catalyst part 11, an outer member 22 that forms a gas phase combustion part 12 extending from one end side of the inner cylinder 20 to the outside of the inner cylinder 20 is provided, and the gas phase combustion part 12 is configured so that the heat generated by the combustion at 12 can be regenerated to the upstream side.
[0024]
The preheating portion 18 is provided with a plurality of heat exchange fins 19 that are in contact with the inner wall of the inner cylinder 20 and have plate surfaces in a direction perpendicular to the flow direction of the air-fuel mixture. As shown in FIG. 3, the heat exchange fin 19 is configured by alternately arranging two kinds of SUS punching metals 19 a and 19 b each having a different opening state of the opening 19 c. The air-fuel mixture flowing through the preheating section 18 passes through the openings 19 c of the heat exchange fins 19 and heats the inner cylinder 20 heated by the gas phase combustion of the gas phase combustion section 12 through the heat exchange fins 19. It receives heat and is heated to a preferred state.
The combustion catalyst portion 11 is attached to the tip portion of the inner cylinder 20 and has a square shape having an effective dimension, a width of 85 mm, a depth of 20 mm, and a layer height of 20 mm.
[0025]
The combustion catalyst unit 11 is formed with a carrier layer having a high specific surface area on one side of a support made of a corrugated metal sheet, and the carrier layer is composed of palladium or a platinum-based catalyst, or silver, gold, platinum as a main component. After applying and calcining a catalyst containing one or more auxiliary catalysts selected from palladium, ruthenium, iridium or rhodium, the support layer side coated with the catalyst is stacked in the same direction to form a communication cell. In this way, the pairs are further stacked and formed into a honeycomb shape.
The combustion catalyst portion 11 formed in this way is formed as an assembly of communication cells in which the catalyst is coated only on one side, so that the heat generated by catalytic combustion on the catalyst coated surface is coated with the catalyst on the opposite surface. Heat is transferred to the air-fuel mixture by heat conduction to the other surface. Thus, even when the catalyst temperature burns an air-fuel mixture having an adiabatic theoretical combustion temperature of 1500 ° C., the combustion rate is suppressed to 50% or less, the catalyst temperature is also suppressed to 950 ° C. or less, and deterioration of the catalyst is suppressed.
[0026]
The outer surface of the inner cylinder 20 is provided with a heat retaining mold having a thickness of 6 mm in order to stabilize the combustion by suppressing the heat protection of the metal and excessive heat transfer. This heat retaining mold is obtained by bonding a ceramic fiber as a material and molding it by dividing it into two vertically in the short axis direction.
[0027]
The outer member 22 is formed by a heat insulation mold having a thickness of 18 mm and is coated with a metal thin film. The outer member 22 has an upper surface of the combustion catalyst portion 11 provided on one end side of the inner tube 10 and a side surface of the inner tube 10. The inner cylinder 20 is surrounded by a gap of about 20 mm from each of the lower wall surfaces of the air-fuel mixture flow path 4, and the gap portion between the inner cylinder 20 and the outer member 22 is the gas phase combustion section 12. . The heat retaining mold of the outer member 22 is obtained by gas-sealing a mold formed by dividing the mold vertically into two in the short axis direction using ceramic fiber as a material.
[0028]
The outer member 22 surrounds the inner cylinder 20 with a gap of about 20 mm from the upper part of the inner cylinder 20, the peripheral part, and the lower part of the air-fuel mixture flow path 4. It is a gas phase combustion chamber 12.
In order to return the heat to the upstream side by radiant heat to the lower side of the external material 22, a discharge part heat transfer converter 14 having a width of 25 mm, a length of 130 mm and a thickness of 12 mm is incorporated, and the upstream surface is mixed with the inner cylinder 20 An exhaust port 15 is provided so as to face the air flow path 4, and this exhaust heat transfer converter 14 converts sensible heat of the combustion exhaust gas discharged from the gas phase combustion unit 12 to the radiant heat and converts it upstream. It can radiate to the side, that is, the outer wall surface provided with the gas mixture combustion section 12 and the air-fuel mixture flow path 4 of the inner cylinder 20.
Further, the upper portion of the inner cylinder 20 within the range from the position of the gas phase combustion section 12 corresponding to the inlet portion of the combustion catalyst section 11 of the inner cylinder 20 to the position of the gas phase combustion section 12 corresponding to the air-fuel mixture flow path 4. A gas phase combustion section heat transfer converter 16 having a thickness of 12 mm is set over the entire flow path cross section of the gas phase combustion section 12 at a position 50 mm from the edge. This gas phase combustion section heat transfer converter 16 converts the sensible heat of the combustion exhaust gas into radiant heat in the gas phase combustion section 12 and radiates it to the upstream side. By converting the heat into radiant heat and feeding it back to the space upstream of the combustion section heat transfer converter 16, high-temperature convective heat loss can be suppressed, and stable gas phase combustion can be performed.
The heat transfer converters 14 and 16 are silicon carbide ceramic foams having 6 cells / 25 mm cells, an apparent specific gravity of 0.43, and a thickness of 12 mm.
[0029]
Further, a temperature sensor 21 (an example of a temperature detection unit) that detects a temperature immediately after the outlet of the combustion catalyst unit 11 is provided, and an output value thereof is sent to the control device 30.
The temperature sensor 21 includes a strand of 0.6 mm in diameter called Nicrosil made of Ni, Cr, Si (on the positive side of the thermoelectromotive force) and a strand of 0.6 mm in diameter called Nisil made of Ni, Si. This is a thermocouple in which the tip (which becomes the negative side of the thermoelectromotive force) is welded and heat-treated at about 900 ° C. to form an oxide film on the surface and insulation treatment. The tip of the temperature sensor 21 is arranged before the combustion catalyst unit 11 so that it is immediately after the outlet of the combustion catalyst unit 11, and the temperature sensor 21 is fixed by the combustion catalyst unit 11. The wire on the inlet side of the combustion catalyst unit 11, that is, the inner side of the inner cylinder 20, reaches the gas mixture channel 4, is inserted into a two-hole ceramic tube, and is opposite to the dispersion nozzle 17 in the gas mixture channel 4. It is taken out from the wall portion, and the take-out portion and the ceramic tube are gas-sealed with an organic sealing material.
As such a temperature sensor 21, a sensor having the maximum wire diameter can be used in a trade-off relationship between durability and responsiveness.
[0030]
The gas phase combustion section 12 is a space that secures a residence time necessary for the unburned fuel partially heated by catalytic combustion and heated to be completely burned by the gas phase radical reaction. A heat insulating member is installed inside the external member 22, and the gas phase combustion unit 12 has a folded structure. An igniter 23 for spark-igniting the air-fuel mixture and starting combustion is provided at the folded portion of the gas phase combustion unit 12.
[0031]
Further, the gas phase combustion unit 12 is provided with three frame rods 24a, 24b, and 24c for detecting the flame of the gas phase combustion unit 12. The frame rod 24a is provided at an intermediate height position above the one end of the inner cylinder 20 and inside the upper part of the catalyst, which is inside the inner cylinder 20, and has a length of 80 mm. The frame rod 24b is provided at the same height as the frame rod 24a at the corner portion on the upper side of one end of the inner cylinder 20 and outside the inner cylinder 20, and has a length of 120 mm. . Further, the frame rod 24c is provided at a position 15 mm below the frame rod 24b on the side portion outside the inner cylinder and below one end of the inner cylinder, and has a length of 120 mm.
[0032]
The igniter 23 and the frame rods 24a, 24b, and 24c were made of YSS-SYTT (trade name), which is a heat-resistant alloy containing yttrium, and used for general combustors.
[0033]
Each of the frame rods 24a, 24b, and 24c is connected to a frame current detection means 25 that applies a voltage between the frame rods and detects a frame current flowing between the frame rods.
As shown in FIG. 2, the frame current detecting means 25 uses the frame rod 24b provided at the corner portion as one pole and the other frame rods 24a and 24c provided at the other catalyst upper portion and side portions as the other. The control device 30 side by measuring a power source 28 that applies a 200-V AC voltage of 60 Hz between the two electrodes, a resistor 26 that provides a resistance of 2 MΩ between the two electrodes, and a minute current that flows between the power source 28 and the resistor 26. It consists of the circuit which connected the current measuring device 27 which outputs to serially.
[0034]
The fan device 1 provided in the fan heater 100 dilutes the combustion exhaust gas E discharged from the exhaust port 15 with the combustion fan 1a for supplying the combustion air A to the mixing portion of the combustion device 50 with the air A. Then, a convection fan 1b for discharging to the outside as warm air H for heating is provided in parallel on the same rotating shaft 1c, and the rotating shaft 1c is rotated by the motor 1d to rotate both fans 1a and 1b. It is configured as follows.
[0035]
The fuel cutoff valve 3, the igniter 23, and the high-voltage power supply thereof were the same as those provided in a commercially available fan heater.
[0036]
Next, a result of a combustion test performed on the fan heater 100 will be described.
Combustion test with methane as the main component, calorific value 46MJ / m^Three(Normal) (11000 kcal / m^Three(Normal)) city-supplied natural gas city gas. The exhaust gas was sampled at the outlet of the convection fan 1b and analyzed for total hydrocarbons, CO, CO2, and NOx.
In addition, automatic control of combustion and data recording were performed using an externally installed personal computer as the control device 30. Further, as the frame current detected by the frame current detection unit 25, the voltage detected from both ends of the resistor 26 of the frame current detection unit 25 was continuously recorded.
In the combustion test, the combustion fan 1a and the convection fan 1b are configured to be driven by different motors. Furthermore, the motor drive voltage for the convection fan 1b and the adjustment for combustion by the proportional control valve 2 are manual, and the combustion start operation and the combustion control at the same combustion amount are automatic control.
[0037]
In the automatic combustion control, the controller 30 first drives the direct current motor drive voltage Va for the combustion fan 1a as 10V, the igniter 23 is turned on, the gas shut-off valve 3 is opened, and the proportional control valve 2 is turned on. For convenience, initial power corresponding to a combustion amount of 3 kW (2600 kcal / h) is applied. As a result, a homogeneous vapor combustion flame is formed in the upper portion of the catalyst of the gas phase combustion section 12.
[0038]
Then, combustion is performed based on the detection result of the temperature sensor 21 until the outlet temperature T11 of the combustion catalyst unit 11 detected by the temperature sensor 21 reaches 350 ° C. at which it can be recognized that the catalyst catalytic oxidation has started in the combustion catalyst unit 11. The motor drive voltage Va for the fan 1a is increased according to the following equation.
[0039]
[Expression 1]
Va [V] = 0.0045 × T11 [° C.] + 9.91
[0040]
Next, the combustion fan 1a is based on the detection result of the temperature sensor 21 until the outlet temperature T11 reaches 350 ° C. and reaches 760 ° C. where it can be recognized that the combustion in the combustion catalyst unit 11 and the gas phase combustion unit 12 is stable. Motor drive voltage Va is increased according to the following equation.
[0041]
[Expression 2]
Va [V] = 0.01 × T11 [° C.] + 8.0
[0042]
In such a combustion start operation, the motor drive voltage for the convection fan 1b is initially 49 V, and is increased so as to obtain appropriate warm air as the combustion progresses.
[0043]
After reaching the hybrid combustion, the combustion amount is changed on the basis of the initial value table of the outlet temperature T11 of the combustion catalyst unit 11 and the motor drive voltage Va of the combustion fan 1a, which is determined in advance according to each set combustion amount. The results of measurement of combustion performance, composition change of combustion exhaust gas including NOx, flame current detected by the flame current detection means 25, and the like will be described.
[0044]
FIG. 4 is a graph plotting the combustion aspect in the high combustion region from the start of combustion. After the start of combustion by homogeneous gas phase combustion in the gas phase combustion section 12, the catalyst is preheated by heat regeneration, catalytic oxidation is started after about 6 minutes, transition to hybrid catalytic combustion, and ultra-low NOx steady hybrid within 10 minutes It resulted in catalytic combustion.
[0045]
The flame current (measured by converting to voltage as described above) is 3 μA in about 15 seconds after the start of the combustion of the hybrid catalyst, and the effectiveness as flame detection at the time of ignition can be demonstrated first. When shifting to hybrid combustion, it temporarily decreased but increased with the progress of combustion. After that, even if it changes from 3.5 kW (3000 kcal / h) to 4.1 kW (3500 kcal / h), a high level of flame current is maintained, and a flame is stably formed in the gas phase combustion section. I understand. The flame current temporarily decreases immediately after the start of catalytic combustion because the flame located in the upper part of the catalyst moves to the side part in the gas phase combustion part. This is because the charged particle concentration difference between the electrodes 24a, 24b, and 24c temporarily decreased.
[0046]
Next, when the combustion amount is 2.4 kW (2100 kcal / h), the outlet temperature T11 of the combustion catalyst unit 11 is decreased by 10 ° C., and the voltage as the flame current value and the incomplete combustion component CO, The state of UHC (unburned hydrocarbon) concentration change is shown in the graph of FIG.
If the catalyst outlet temperature T11 is set to 750 ° C., the CO concentration increases rapidly, indicating that incomplete combustion has occurred. At this time, the flame current is reduced to 0.5 μA, and the effectiveness as flame detection during incomplete combustion can be verified.
Next, when the catalyst outlet temperature T11 is increased to 800 ° C., the CO concentration is reduced to the original 5 ppm or less, and it can be seen that the combustion has returned to good combustion. Therefore, with this combustion amount, if the catalyst outlet temperature T11 is controlled around 800 ° C. and the lower limit value of the flame current is about 2 μA, a double combustion safety structure can be obtained. Then, when the catalyst outlet temperature T11 and the flame current are less than or equal to these values in this combustion amount, the operation of the combustion device 50 is stopped, the amount of combustion air supplied, the amount of fuel, etc. are reduced. It is preferable to execute predetermined safety control, and means for performing such safety control is referred to as safety control means.
[0047]
FIG. 6 shows the results when the same measurement as in FIG. 5 is performed at a combustion amount of 1.1 kW (1000 kcal / h).
In this case, it can be seen that incomplete combustion occurs when the catalyst outlet temperature T11 reaches 800 ° C. At this time, the frame current has decreased to 0.3 μA. However, if the catalyst outlet temperature T11 is 840 ° C., the flame current increases to 0.7 μA and returns to the original good combustion.
[0048]
As a result, the correlation between the catalyst outlet temperature T11 and the flame current is good in a wide range from the combustion start operation of the homogeneous gas phase combustion to the hybrid combustion 4.1 kW to 0.7 kW (3500 to 600 kcal / h) in the steady state. Each value can be monitored to realize a double safety structure of hybrid combustion.
[0049]
In these tests, the responsiveness of the temperature sensor 21 that measures the catalyst outlet temperature T11 as the control basic value is good, and the durability is not changed in the accelerated deterioration test 1000h conducted separately at 1015 ° C. There was nothing at all. Since the temperature sensor is used at 900 ° C. or lower in the combustion apparatus, it can be seen that the combustion apparatus has practical durability.
[0050]
[Comparative Example 1]
Next, as a first comparative example, except for the frame rod, the structure is the same as that of the combustion apparatus 50 of the above embodiment, and the frame rods 24b and 24c other than the frame rod 24a in the upper part of the catalyst are removed, and the counter electrode of the frame rod 24a is removed. The flame current was measured using a combustion apparatus having an inner cylinder 20 provided with the combustion catalyst unit 11. As a result, a large flame current was observed in the homogeneous gas phase combustion period in which a flame was formed in the upper part of the catalyst at the start of combustion, but almost no flame current was observed when shifting to hybrid combustion. Also, the noise level of the frame current was high.
[0051]
[Comparative Example 2]
Next, as a second comparative example, a combustion apparatus having a configuration similar to that of the combustion apparatus 50 of the above embodiment except for the frame rod, the frame rod 24a in the upper part of the catalyst is used as one pole, and the other frame rods 24b and 24c. Was the other pole and the frame current was measured. As a result, a large flame current was observed in the homogeneous gas phase combustion period in which a flame was formed in the upper part of the catalyst at the start of combustion, but almost no flame current was observed when shifting to hybrid combustion. Therefore, it can be seen that such a configuration cannot be used as flame detection.
[0052]
The fuel supplied to the hybrid catalytic combustion apparatus described so far is not limited to city gas and natural gas, but various fuels such as LPG and kerosene vaporized gas can be used.
[0053]
【The invention's effect】
The hybrid catalyst combustion apparatus of the present invention and a fan heater equipped with the hybrid catalyst combustion apparatus can always monitor the presence of a flame in the gas phase combustion section downstream of the combustion catalyst section from the start of combustion. Heavy combustion safety can be achieved, and safety can be greatly improved.
In addition, a commercially available fan heater is equipped with this hybrid catalytic combustion device, which enables high air ratio operation, suppresses the generation of NOx, a pollutant, to the limit, and makes the fan heater recognized as an environmentally friendly device. Can do.
[Brief description of the drawings]
FIG. 1 is an overall schematic diagram showing an embodiment of a hybrid catalytic combustion apparatus according to the present invention.
FIG. 2 is a schematic side sectional view of the combustion apparatus shown in FIG.
FIG. 3 is an enlarged perspective view of a heat exchange fin.
FIG. 4 is a graph showing a state of combustion start and a high combustion amount of the hybrid catalytic combustion device
FIG. 5 is a graph showing a change state of the flame current due to a change in the catalyst outlet temperature of the hybrid catalytic combustion apparatus.
FIG. 6 is a graph showing a change state of the flame current due to a change in the catalyst outlet temperature of the hybrid catalytic combustion apparatus.
[Explanation of symbols]
1 Fan device
1a Fan for combustion
4 Mixture flow path
11 Combustion catalyst section
12 Gas phase combustion section
14 Heat exchanger of discharge section
15 outlet
16 Gas phase combustion part heat transfer converter
19 Heat exchange fins
18 Preheating part
20 inner cylinder
21 Temperature sensor (temperature detection means)
22 External material
24a Frame rod
24b Frame rod
24c frame rod
25 Frame current detection means
50 Combustion device (hybrid catalytic combustion device)
100 fan heater
A Air
E Combustion exhaust gas
H Warm air for heating

Claims (5)

A combustion catalyst part that catalytically oxidizes a part of the fuel by passing a mixture of combustion air and fuel; and a remaining part of the fuel provided downstream of the combustion catalyst part in the flow direction of the mixture A gas phase combustion section for gas phase combustion,
The inner cylinder provided with the combustion catalyst part inside one end part, and the inner cylinder and the combustion catalyst part between the one end part side of the inner cylinder and the outer side of the inner cylinder A hybrid catalytic combustion apparatus comprising an outer member forming a gas phase combustion section,
At least three frame rods are disposed along the flow direction of the air-fuel mixture in the gas phase combustion section, and
Said at least three frames rod, as a frame rod of them, flame rod which is provided at a corner portion which is outside of the upper and the inner cylinder of the one end of the inner cylinder of the gas-phase combustion portion Between
A hybrid catalytic combustion apparatus comprising flame current detection means for applying a voltage between the flame rods and detecting flame current flowing between the flame rods. Said at least three frames rod, a flame rod which is provided as one pole in the corner portion, the Corner of the catalyst upper part and the gas phase combustion portion on the upstream side of the corner portion of the gas-phase combustion portion Each frame rod provided as the other pole on the side part downstream of the part,
2. The hybrid catalytic combustion apparatus according to claim 1, wherein the flame current detection means is means for applying a voltage to both of the poles of the flame rod and detecting a flame current flowing between the poles. Temperature detecting means capable of detecting the temperature of the combustion catalyst part or the outlet part of the combustion catalyst part,
When the temperature detected by the temperature detection means becomes a predetermined temperature or less, or when the frame current detected by the frame current detection means becomes a predetermined current value or less, a predetermined safety control is performed. The hybrid catalytic combustion apparatus according to claim 1, further comprising a safety control means to be executed. The hybrid catalytic combustion according to any one of claims 1 to 3, further comprising a control unit that controls power of an air supply unit that supplies the combustion air based on the temperature detected by the temperature detection unit. apparatus. A fan heater comprising the hybrid catalytic combustion device according to any one of claims 1 to 4, wherein the combustion exhaust gas discharged from the gas phase combustion section is diluted with air and discharged to the outside as hot air.

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