JP2646526B2 - Catalytic combustor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a catalytic combustor used for heating, heating, drying and the like.

2. Description of the Related Art Catalytic combustion is a combustion method that has the advantages of having a wide A / F (air-to-fuel ratio) stable combustion area, extremely low nitrogen oxide generation, and a wide range of combustion control. However, the safety control technology was not completed, so it was only used for some special purposes. In particular, when the function of the catalyst is deteriorated over its life, incomplete combustion leads to emission of a large amount of toxic gas such as carbon monoxide, which may result in serious damage to humans and livestock. Although such catalyst life degradation necessarily occurs at some time, it is difficult to predict when it will occur, and there has been no effective safety control method.

In addition, in an actual catalytic combustor, it is inevitable that adverse conditions that can cause incomplete combustion, such as a decrease in oxygen concentration of air and a change in A / F, alone or in combination with the deterioration of the catalyst, In addition, under conditions in which changes in the combustion amount of the combustor itself, such as temperature adjustment, safety control that can reliably avoid the risk of incomplete combustion has been considered to be impractical.

For example, Japanese Patent Application Laid-Open No. 60-175919 discloses an invention that enables ignition detection, flashback and blow-off detection, and oxygen deficiency detection. It does not discuss safety controls relating to safety conditions that occur when adverse conditions are combined and when catalyst preheating is insufficient.

Problems to be Solved by the Invention The present invention seeks to provide a catalytic combustor that can be controlled to a safe state, including an unsafe state at the time of deterioration of catalytic ability, which has been difficult in the past, and other unsafe states. Is what you do.

Means for Solving the Problems The technical means of the present invention for solving the above problems is to install a temperature detector at each of an upstream point and a downstream point of the catalyst body and detect a temperature difference between the two points. This solves the conventional problem.

Operation The operation of the above means will be described below.

(1) At the time of preheating immediately before ignition, the upstream point temperature detector exceeds a preset temperature, so that the completion of preheating is detected, and then the ignition sequence is started.
This prevents incomplete combustion due to insufficient preheating,
A safe state can be maintained.

(2) At the time of ignition, ignition can be detected when the upstream point temperature detector exceeds a temperature higher than the preset temperature set in (1) above. If ignition cannot be detected within the specified time, the supply of fuel is forcibly stopped to return to a safe state.

(3) In the event of flashback, a temperature detector (flashback sensor) installed in the flashback area separately from the two-point temperature detector detects abnormal temperature, and forcibly supplies fuel. Stop and return to safety.

(4) If a blow-off occurs, the upstream point temperature detector can detect the abnormally low temperature in spite of the sequence during the combustion, thereby detecting the abnormally low temperature, forcibly stopping the fuel supply, and returning to the safe state.

(5) During normal combustion, the upstream point temperature detector detects a higher temperature than the downstream point temperature detector, but if the oxygen concentration in the air supplied to the equipment decreases, the A / F changes, and If the actual combustion situation approaches imperfect combustion due to reasons such as when the catalytic ability has deteriorated, or when the above situations have been combined, the upstream point temperature detector and the downstream point temperature detector , The difference in the detected temperatures is reduced, and the difference becomes extremely negative. When the temperature difference is out of the predetermined range, the fuel supply is forcibly stopped and the system returns to the safe state.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 is a combustion part case made of a metal, 2 is a heat insulating and cushioning material made of a heat-resistant porous material, 3 is a catalyst body in which a catalyst such as platinum or palladium is supported on a honeycomb-shaped ceramic base material, and is partially used for preheating. The heater is embedded.
Reference numeral 4 denotes a current plate, reference numeral 5 denotes an air-fuel mixture inlet, and reference numeral 6 denotes an exhaust port.

Reference numeral 7 denotes a vaporizer case, 8 denotes a vaporizer in which a heater 9 is embedded, and 10 denotes an air supply pipe communicating with a blower (not shown). A fuel supply pipe 11 communicates with a fuel pump and a fuel tank (not shown). The assembling section 7 to 11 is referred to as a vaporizing section B.

Reference numeral 12 denotes an upstream point temperature detector composed of a thermocouple, and a temperature measurement point is set in an intermediate zone on the gas flow of the catalyst 3. More desirably, it is desirably installed near the highest temperature position of the catalyst body 3 when the maximum combustion amount of the catalytic combustor is burned. Reference numeral 13 denotes a downstream point temperature detector composed of a thermocouple similar to the upstream point temperature detector 12, and the temperature measurement point is located near the most downstream point on the gas flow of the catalytic body of the catalytic combustor. Numeral 14 denotes a flashback sensor, which comprises a thermocouple whose temperature measurement point is installed upstream of the rectifier plate. 15 is a vaporizer temperature detector. Each of the temperature detectors 12 to 15 is connected to a control unit (not shown).

 Next, an operation state of the catalytic combustor of the embodiment will be described.

In the operation of the catalytic combustor, first, the catalytic converter 3 and the carburetor 8 are preheated by a start operation. The point temperature detector 12 detects the temperature of the catalyst body 3,
The vaporizer temperature detector 15 detects the temperature of the vaporizer 8 and sets a predetermined preheating set temperature (catalyst: about 450 ° C., respectively).
When the temperature exceeds the vaporizer (approximately 300 degrees C), the process automatically proceeds from the preheating mode to the combustion mode.

In the combustion mode, the fuel pump and the blower are driven to supply fuel and air to the vaporizing section B. At this time, the fuel supplied to the vaporization section B is heated and vaporized in the vaporizer 8 and mixed with air to be supplied to the catalyst body 3 as an air-fuel mixture.
The combustion exhaust gas is discharged from the exhaust port 6 to the outside.

The normal detection temperature of each detector of this combustor is as follows.

Vaporizer temperature detector; Approx. 280 ° C Flashback sensor; Approx. 190 ° C Upstream point temperature detector; Maximum combustion amount, 850 ° C Minimum combustion amount, approximately 832 ° C Downstream point temperature detector: Combustion amount At maximum, about 838 degrees C When combustion amount is minimum, about 800 degrees C In addition, the maximum combustion amount of this combustor is 3200 Kcal / h,
The minimum burning amount is 800kcal / h.

The first of the safety controls in the combustion mode is the abnormal low temperature monitoring monitor. If the upstream point temperature detector falls below the confirmed combustion temperature of 600 ° C within 30 seconds after entering the combustion mode, the fire is forcibly extinguished as an abnormal state. Move to mode. With this safety control, safety control can be performed in the event of poor ignition, blow-off, or running out of fuel.

The second type of safety control is a flashback monitoring monitor.
If it exceeds 0 degrees C, it is forcibly shifted to the fire extinguishing mode as a flashback.

The third type of safety control is the normal combustion monitoring monitor. The difference between the detected temperature of the downstream point temperature detector and the detected temperature of the upstream point temperature detector becomes smaller than the limit set value 30 seconds after entering the combustion mode. If this occurs, the system is forcibly shifted to the fire extinguishing mode as abnormal combustion.

That is, more specifically, if the value obtained by subtracting the temperature detected by the downstream point temperature detector from the temperature detected by the upstream point temperature detector during combustion is equal to or greater than a certain set value, combustion is continued, and the set value is not reached. In this case, the operation is to extinguish the fire.

How much the set value is depends on the margin of the catalytic ability or the design such as the heat radiation condition of the catalyst body. In this embodiment, zero degree C is set as the limit set value. With this control, it is possible to perform safety control when catalyst performance is degraded, oxygen deficiency, abnormal A / F, and a combination thereof.

When the fire is extinguished by the user's will, the mode is switched to the fire extinguishing mode manually or by a timer. In the fire extinguishing mode, the fuel supply is stopped and the blower is also stopped after the post-purge for about 10 seconds.

In the catalytic combustor of the present invention, an upstream point temperature detector and a downstream point temperature detector are provided on the catalyst body. FIGS. 3 and 4 show the relationship between the detected temperatures of these two temperature detectors and the catalytic ability. FIG. 3 shows the case of the maximum combustion amount of the combustor, and FIG. 4 shows the case of the minimum combustion amount. In each case, the solid line shows the case where the catalyst body which has not deteriorated at all is used. Shown is the use of a significantly degraded catalyst body corresponding to the turning point where carbon monoxide begins to increase. Arrow A indicates the change in the detected temperature of the upstream point temperature detector between the solid line and the broken line, and arrow B indicates the same change in the case of the detected temperature of the downstream point temperature detector.

What can be said in common from FIGS. 3 and 4 is as follows. a The maximum temperature position of the catalyst body moves downstream due to catalyst deterioration. (b) When the maximum temperature position of the catalyst approaches the most downstream point, the turning point of exhaust gas deterioration approaches.
c If the safety control is invalidated and the combustion continues beyond the turning point and the cause of incomplete combustion continues to increase, the carbon monoxide in the exhaust gas continues to increase and the difference value becomes smaller. Show. d Even when the maximum combustion amount or the minimum combustion amount is burned, the difference between the detection temperature of the upstream point temperature detector and the detection temperature of the downstream point temperature detector is 12 degrees for the new combustion with the maximum combustion amount. C, 16 ° C. is shown at the minimum combustion amount. However, in the case of the deteriorated catalyst, any combustion amount shows minus 6 ° C. at the turning point. Incomplete combustion can be safely controlled only by the limit value in the reduction direction. That is, catalyst deterioration, oxygen deficiency, abnormal A /
When the completion position of the combustion reaction such as F, excess combustion amount, or a combination thereof moves downstream of the catalyst body (that is, when approaching incomplete combustion), the above difference decreases, and conversely, The difference increases when the position where the combustion reaction is completed moves upstream of the catalyst body (that is, when flashback approaches), such as when the combustion amount is excessively reduced. Therefore, in a state where these fluctuation factors are singly or in combination, by controlling the value of the difference between the two detected temperatures at the limit set value, it is possible to perform safety control against incomplete combustion.

The limit set value of the forced fire extinguishing in the embodiment is zero degree C. Therefore, safety control can be performed with sufficient margin against incomplete combustion at the turning point at minus 6 degrees C.

In addition, a method of performing safety control beforehand with a limit set value in the direction of enlargement of the difference value may be considered for flashback. In the present embodiment, a safety control that operates after a flashback is generated by the flashback sensor is employed.

In the embodiment shown in FIG. 1, a preheater is embedded in a part of the catalyst body, but another structure capable of preheating may be adopted. In addition, when using a plurality of catalyst bodies, when the gas flow direction of the catalyst body is vertical, when horizontal,
The present invention can be carried out in the same manner as in the above embodiment in any case, such as when the catalyst body temperature during combustion is different from that in the above embodiment, or when the fuel is gaseous fuel.

Effect of the Invention The risk of incomplete combustion can be avoided with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a catalytic combustor according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of an essential part of the catalytic combustor, and FIGS.
The figure is an explanatory diagram relating to the safety control of the catalytic combustor. 3 ... catalyst body, 4 ... rectifier plate, 8 ... vaporizer, 9 ... heater, 10 ... air supply pipe, 11 ... fuel supply pipe, 12 ...
Upstream point temperature detector, 13: Downstream point temperature detector, 14: Flashback sensor, 15: Vaporizer temperature detector.

Claims (2)

(57) [Claims] An air-fuel mixture obtained by mixing air and fuel supplied from a fuel supply section and an air supply section in a mixing chamber is burned in a combustion section provided with a catalyst body, and combustion exhaust gas is discharged from a discharge section to the outside. At least two temperature detectors are installed in the combustion part so that they are located at the upstream and downstream points in the gas flow direction during combustion, and the temperature detected by the upstream point temperature detector during combustion decreases from the downstream point temperature. A catalytic combustor characterized in that combustion is continued when the value obtained by subtracting the temperature detected by the detector is equal to or higher than a set value, and the fire is forcibly extinguished when the value is lower than the set value. 2. A method according to claim 1, wherein the downstream point temperature detector is installed at a position near the most downstream point of the catalyst body, and the upstream point temperature detector is installed at an intermediate zone in the gas flow of the catalyst body. The catalytic combustor according to claim 1, wherein