JP2567992B2 - Catalytic combustion device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a catalytic combustion apparatus which is used for heating, drying, etc. by applying an oxidation catalyst excellent in far infrared radiation efficiency.

[Conventional technology]

A catalytic combustion device in which a gaseous fuel and a vaporized liquid fuel are mixed with air and then sent to a catalyst layer to be in contact with a catalyst and flamelessly burned on the surface thereof does not emit nitrogen oxides,
Since it has excellent features such as realizing mild radiant heating by the effect of far infrared rays radiated from the catalyst layer, various proposals have been conventionally made and some of them have been put to practical use.

FIG. 3 (a) proposed by the applicant of the present invention has been proposed as an example of a conventional catalytic combustion apparatus that utilizes radiant heat generated from a catalyst layer by using a heat-resistant inorganic material for a carrier.
There is a catalytic combustion device having a structure as shown in FIG. Referring to FIGS. 3 (a) and 3 (b), 1 is a catalyst layer, 10 is a primary air adjusting hole, 11 is a preheating burner, 12 is a carburetor, 13 is a secondary air hole, 15 is a blower, 23 Is an ignition heater, and 25 is a temperature sensor. Thus, the catalyst layer 1 having a relatively large area
The single plate is erected vertically so that the premixed gas passes from the rear side to the front side of the catalyst layer, and the blower 15 is operated, and at the same time, the preheating burner 11 is ignited by the ignition heater 23 from the back side of the catalyst layer and the flame is emitted. Combustion is performed, the catalyst layer 1 is heated by this combustion heat, and when the catalyst layer reaches the flame temperature (activation temperature) or higher, the flame of the preheating burner is extinguished, and immediately vaporized kerosene and the primary air adjusting hole Primary air from 10 and 2 from secondary air holes 13
The structure is such that a premixed gas obtained by mixing the following air is supplied to the catalyst layer 1 to start catalytic combustion. At this time, the wide exit surface of the catalyst layer is used for radiation.

[Problems to be Solved by the Invention]

The above-mentioned conventional catalytic combustion apparatus has the following drawbacks.

Normally, for a catalyst layer having the same volume, if the combustion amount is reduced while maintaining a constant air ratio and the surface load, which is the combustion load per unit area of the catalyst, is reduced, the combustion temperature of the catalyst layer decreases. Further, if only the combustion amount is reduced while keeping the combustion air amount constant, the combustion temperature of the catalyst layer will drastically decrease. That is,
At the time of the maximum combustion amount, the catalyst layer burns in a red-hot state, whereas at the time of the minimum combustion amount, the catalyst layer does not reach the red-hot state and burns with the same appearance as that of a normal temperature state. At such a minimum combustion amount, since it is difficult for the user to easily visually recognize whether or not the combustion state is present, it is easy to cause anxiety and the visual effect is poor.

In order to bring the catalyst layer into a red heat state even at the minimum combustion amount, it has been necessary to reduce the load area of the catalyst layer and at the same time increase the thickness of the premixed gas in the flow direction to increase the surface load. However, in the case of such a method, there is an adverse effect that the amount of radiant heat becomes small because the negative stomach area of the exit surface, which is the radiation utilization surface, is small.

Further, in the case of the conventional structure, it is difficult to uniformly heat the catalyst layer during the preheating operation because the load area of the catalyst layer is large, and when the premixed gas is sent to start the catalytic combustion, the unburned gas is discharged from the low temperature portion. It's easy to do.

[Means for solving the problem]

The catalytic combustion apparatus according to the present invention is made to solve the above problems, and heat-treats a plurality of catalyst pellets having a small volume, such as a columnar shape or a prismatic shape, having a cross-sectional shape with excellent breathability such as a hole cam. Of the resistance heat-generating inorganic material, such as a honeycomb, which is molded into a shape having excellent air permeability, is inserted into the lowermost part of the catalyst pellet together with the electrode to form a catalytic combustion cylinder. A flow path is formed so that the premixed gas is supplied from the bottom by standing up one or more pieces, and a reflective plate for reflecting the infrared rays emitted from the catalyst pellets through the heat-resistant glass to the front side behind the catalyst combustion cylinder. It is arranged.

[Work]

In the above structure, during the preheating operation of the catalyst layer, the resistance heating inorganic material under the catalyst combustion cylinder is energized to generate heat, so that the catalyst pellets disposed above the catalyst pellet are heated by heat conduction and natural convection heat transfer. Preheating can be done efficiently and preheating is completed quickly. In addition, since the load area of one catalyst combustion cylinder is small, soaking in the catalyst cross section is also good,
It is possible to reliably shift to steady combustion without discharging unburned gas. During steady combustion, the load area of the catalyst layer is smaller than that of the conventional structure, so even if the combustion amount is small, the catalyst pellet inlet can be kept in a red heat state. Therefore, the user can easily visually recognize the combustion state through the heat-resistant glass regardless of the amount of combustion. At the same time, infrared rays radiated from the side surfaces of the catalyst pellets that have become hot due to combustion pass through the heat-resistant glass tube and are reflected forward by the reflector, so that comfortable radiant heating with a large radiant area can be performed. Further, since it is composed of a small catalyst pellet and an aggregate of preheating resistance heating inorganic material, individual molding is easy and the cost is low.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In the catalytic combustion device according to the present invention, FIG.
As shown in the figure, 1A is a catalytic combustion cylinder, and one or more of them are vertically standing. Reference numeral 2A denotes a diffuser chamber, which is a box difficult chamber that firmly supports the catalytic combustion cylinder 1 from the lower portion and evenly supplies the premixed gas sent from the bottom opening to the ceiling opening that passes to the catalytic combustion cylinder. Reference numeral 3A denotes a mixing chamber, which mixes the fuel sent from an oil sending pump (not shown) through the oil sending pipe 4A with the combustion air sent under pressure from the blower 5A to generate a premixed gas. When the fuel is liquid fuel, a heater for vaporizing the fuel is installed in the mixing chamber 3A. Reference numeral 6A denotes a waste duct, which is a box difficulty chamber that firmly supports the catalytic combustion cylinder 1A at the upper portion and collects the combustion gas sent from the bottom opening passing through the catalytic combustion cylinder and discharges it into the atmosphere from the upper opening. The catalytic combustion cylinder 1A is mainly composed of a cylindrical heat-resistant glass cylinder 12A having excellent heat transmission rate and a heat resistance such as cordierite molded into a shape having a columnar or prismatic shape and a honeycomb structure or the like with excellent air permeability. A catalyst pellet 11A having an inorganic material as a carrier and carrying an oxidation catalyst such as a platinum group metal on its surface, and a preheating heater 13A formed by a resistance heating inorganic material such as silicon carbide in the same shape as the catalyst pellet. In the heat-resistant glass tube 12A, the preheating heater 13A is inserted in the most upstream side of the inlet side, and several catalyst pellets 11A are inserted in the upper downstream side.
Electrodes for applying a voltage are attached to two locations on the outer circumference of the preheating heater 13A, and the lower end portion of the connection portion with the diffuser chamber 2A is insulated and held by an insulating sealant. 16A is a temperature sensor and is attached to the top of each catalytic combustion cylinder. 7A is a guard net, which secures safety by entrusting the catalytic combustion cylinder 1 that becomes hot during operation. 8A is a reflector plate, and a catalytic combustion tube in cabinet 9A
It is arranged to surround the back of 1A. A hot air outlet 10A is located on the ceiling of the cabinet 9 and discharges hot air discharged from the exhaust duct 6A upward.

The operation of the catalytic combustion device having the above configuration includes a preheating operation of heating the catalyst layer to an ignition temperature or higher prior to catalytic combustion,
It consists of a steady combustion operation in which a fixed combustion amount of the premixed gas is sent to the catalyst layer that has reached the ignition temperature to start catalytic combustion, and an arbitrary combustion amount of the premixed gas is flamelessly burned in the catalyst layer.

In the preheating operation, first, the preheating heater 13A is energized. The preheating heater generates heat due to the energization, and heat transfer and natural convection gradually transfer from the catalyst pellet immediately above to the catalyst pellet above. In this way, if the control unit (not shown) determines based on the output of the temperature sensor 16A that the temperature of the catalyst pellets of all the temperature sensors 16A attached to the respective catalyst combustion tubes has reached the ignition temperature (for example, 300 ° C.), The energization of the preheating heater is stopped, at the same time weak air blowing is started by the blower 5A, and fuel supply is started from the fuel pipe to generate premixed gas in the mixing chamber 3A and send it to the diffuser chamber 2A. In the diffuser chamber 2A, the premixed gas is evenly spread over the flow path and sent to the catalytic combustion cylinder 1A to start catalytic combustion. That is, the preheating operation is terminated and the steady combustion operation is started.

Since the catalyst pellet aggregate is designed to have a volume that gives a sufficient space velocity to completely burn any premixed gas of any combustion amount with a set combustion amount, discharge odorous gases such as CO and HC. Without ignition → temperature rise → transition to steady weak combustion, upstream catalyst pellets red heat (650 to 750 ℃)
The temperature reaches a stable state. Further, at the time of steady combustion, the fuel delivery amount and the air delivery amount of the blower 5A are controlled, and the volume ratio (ie, air ratio) of the combustion supply air amount to the theoretical air amount of the premixing gau is constantly set to about 2 to 4, and the fusing catalyst is used. Combustion is performed while preventing backfire and incomplete combustion of the premixed gas by constantly controlling the air flow rate appropriate for the combustion amount using the temperature sensor 16A so that the maximum temperature of the pellet 11A does not exceed 800 ° C. The amount can be increased or decreased. At this time, when the combustion amount of the catalyst pellet is low, only a part of the catalyst pellet near the upstream side is in a red heat state, whereas the red heat portion expands upward as the combustion amount increases. Exhaust gas that has been completely burned is the catalyst pellet 11
After being discharged from A, it passes through the exhaust duct 6A and is discharged as warm air from the warm air 10A. On the other hand, infrared rays are emitted from the catalyst pellets through the heat-resistant glass tube 12A. Therefore, the convection heating by the warm air and the radiant heating by the infrared rays are simultaneously performed.

At the time of fire extinguishing, the power supply to other devices except the blower 5A is cut off, only the blower 5A is operated for several tens of seconds to blow air, and the system mainly including the catalytic combustion cylinder is cooled. At this time, since the catalyst pellets have a relatively large heat capacity, even if the supply of premixed gas is suddenly cut off, odorous gases such as CO and HC will not be emitted for a while after extinguishing as in combustion with ordinary flames. , Is completely oxidized on the catalyst pellets.

〔The invention's effect〕

The catalytic combustion apparatus according to the present invention has a plurality of small-volume columnar or prismatic honeycomb cross-section catalyst pellets inserted into a heat-resistant glass tube, and further has excellent air permeability such as honeycomb at the bottom of the catalyst pellets. A resistive heating inorganic material molded into a shape is inserted together with an electrode to form a catalytic combustion cylinder, and one or more catalytic combustion cylinders are erected to form a flow path so as to supply a premixed gas from the lower part. A reflection plate for reflecting infrared rays emitted from the catalyst pellets through the heat-resistant glass to the front side is disposed behind the combustion cylinder. This produces the following effects.

(1) Since the red heat part of the catalyst pellet expands in the flow direction in proportion to the amount of combustion, the user can easily visually check the combustion state through the heat-resistant glass tube and do not feel uneasy during operation. . Further, a large amount of radiant heat for reflecting the radiant heat from the side surface of the catalyst pellet through the heat-resistant glass soot to the front by the reflecting plate can be obtained.

(2) During the preheating operation of the catalyst layer, the resistance heating inorganic material in the lower part of the catalyst combustion cylinder is energized to generate heat, so that the catalyst pellets arranged above the catalyst pellet are efficiently preheated by heat conduction and natural convection heat transfer. Can be preheated or completed quickly. Also, since the area of the catalyst layer to be preheated is small,
It is easy to equalize the temperature on the cross section of the catalyst pellet during preheating, and it is possible to reliably shift to steady combustion without discharging unburned gas.

(3) Since it is composed of an aggregate of small catalyst pellets and a resistance heating inorganic material for preheating, individual molding is easy and the cost is low.

[Brief description of drawings]

FIG. 1 is an overall view showing an embodiment of the present invention, and FIG. 2 is a sectional view of a catalytic combustion cylinder. 3 (a) and 3 (b) show a conventional example and are a plan view and a side view. 1A is a catalytic combustion tube, 3A is a mixing chamber, 5A is a blower, 10A is a hot air inlet, 11A is catalyst pellets, 12A is heat-resistant glass, 13A is a preheating heater, and 16A is a temperature sensor.

Claims (2)

(57) [Claims] 1. A catalytic combustion apparatus for mixing a gaseous fuel or a vaporized liquid fuel with combustion air to form a premixed gas, and sending the mixture to a catalyst layer for flameless combustion to oxidize a honeycomb or the like having excellent air permeability. A catalyst cylinder is formed by molding a catalyst layer into a small columnar shape or a prismatic shape, and one or more catalyst combustion cylinders are formed by inserting a plurality of catalyst pellets into a heat-resistant glass cylinder with excellent heat permeability. The flow path is configured so that the premixed gas passes through the lever from below, and a reflector for reflecting the radiant heat from the side surface of the catalyst pellet forward through the heat-resistant glass cylinder is arranged behind the catalyst combustion cylinder. Catalytic combustion device. 2. A resistance heating inorganic material formed into a cross-sectional shape having the same outer shape as that of the catalyst pellet, which is excellent in air permeability, is disposed as a preheating heater below the catalyst pellet in the catalyst combustion cylinder. The catalytic combustion device according to claim 1.