JP2597733B2 - Combustion control method and apparatus for incinerator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for controlling combustion in an incinerator of municipal solid waste, sewage sludge, industrial waste and the like.

[Conventional technology]

2. Description of the Related Art Conventionally, as a method of controlling a combustion state by adjusting a combustion air amount in an incinerator, a method of automatically controlling a charge amount of a combustion substance and a combustion air amount using a ratio setting device is generally known.

In recent years, a method has been known in which residual oxygen in flue gas in an incinerator is analyzed, and the amount of combustion air is feedback-controlled based on the amount of oxygen.

[Problems to be solved by the invention]

Since the municipal solid waste, sewage sludge, industrial waste, etc. that are put into the incinerator contain various combustible components and non-combustible components, the calorific value per unit weight or unit volume of the input combustibles Is not constant. Therefore, in the method of adjusting the amount of combustion air based on the input amount of the combustibles, if the calorific value of the input combustibles is larger than expected, air shortage occurs, and carbon monoxide or black smoke (unburned carbon )
Inconveniences such as generation of unburned components occur.

On the other hand, in the method of controlling combustion by analyzing the oxygen in the flue gas, the time to flow from the flue gas furnace to the flue, the time to sample the flue gas to the analysis system, the analysis time of the analyzer itself, etc. It takes several minutes, and there is difficulty in response. Therefore, this method is effective when the change in the heat generation amount is small, but has a disadvantage that the change cannot be followed when the change in the heat generation amount is large. In addition, since the oxygen concentration generated by carbon monoxide or black smoke varies depending on combustibles such as styrofoam, plastic, paper, etc., it is difficult to set the replenishment amount of combustion air corresponding to this oxygen concentration to a constant value. Actually, it is necessary to set a larger air amount than the required air amount with a margin.

The present invention has been made in view of the above circumstances, and in response to a rapid increase in the amount of heat generated by combustion in an incinerator, the combustion of an incinerator capable of effectively suppressing the generation of carbon monoxide and black smoke immediately in response to the rapid increase. It is an object to provide a control method and device.

[Means for solving the problem]

The present inventors have analyzed and studied the combustion state of the incinerator in detail, and found that carbon monoxide and black smoke were generated even though the combustion air was constant. Increase or increase in the amount of heat generated, and in this case, the flame rapidly increases in the incinerator, and the radiant heat from this flame increases. I found it.

The present invention has been made as a result thereof. The combustion control of an incinerator in which combustion of combustion products is performed while fluid combustion air is supplied to the bottom of the combustion chamber and secondary air is supplied to a space above the combustion chamber. In the method, radiant heat generated from the flame in the upper combustion chamber space is detected, and only when the time change rate of the detected radiant heat is equal to or more than a certain value, the radiant heat is completely discharged to the gas discharge passage downstream of the secondary air supply space. It supplies combustion air.

The present invention also provides a combustion control device for an incinerator in which combustion of combustion products is performed while flowing combustion air is supplied to the bottom of the combustion chamber, and secondary air is supplied to a space above the combustion chamber. Flame radiant heat detecting means for detecting radiant heat generated from the flame in the indoor space, adjusting means for adjusting the supply amount of complete combustion air to a gas exhaust passage downstream of the secondary air supply space, and the flame radiant heat Control means for calculating the time change rate of the radiant heat detected by the detection means and controlling the operation of the adjustment means so as to supply complete combustion air to the gas discharge path only when the time change rate is equal to or more than a certain value; It is provided with.

(Operation)

According to the above method and apparatus, even if a large amount of combustion material or a high calorific substance is suddenly introduced into the incinerator, a rapid increase in radiant heat from the flame accompanying this is detected, and an immediate response to the increase in calorific value is detected. Complete combustion air to the flue gas in the gas exhaust passage downstream of the secondary air supply space to burn unburned components in the flue gas and generate carbon monoxide and black smoke. It can be suppressed effectively.

〔Example〕

FIG. 1 shows the overall configuration of an incinerator in which the method of the present invention is performed. Here, a fluidized bed municipal solid waste incinerator is shown as an example.

The incinerator includes a duster 10 for crushing municipal waste and a burner 12 for warming-up or auxiliary combustion, both of which are connected to a combustion chamber 14.

At the bottom of the combustion chamber 14, a fluidized bed 16 of a sand layer is provided, and the fluidized bed 16 is supplied with combustion products from the duster 10. At the bottom of the fluidized bed 16, a number of dispersion nozzles are provided.
18 is provided, and the sand flows due to the jet of the flowing combustion air from the dispersion nozzle 18. This sand has a large heat capacity and contributes to stable combustion of municipal solid waste.

Below the combustion chamber 14, an incineration residue discharger 20 is installed,
By the operation of the incineration residue discharger 20, the incineration residue 22 is extracted from the central part of the bottom of the fluidized bed 16. This incineration residue 22 is passed through a vibrating sieve 24, and only the fluidized sand contained therein is returned to the combustion chamber.

Further, a secondary combustion air hole 25 for supplying secondary air for reducing NOx into the room is provided on a side portion of the combustion chamber.

Above the combustion chamber 14, an optical detector (flame radiation heat detection means) 26 for monitoring the combustion state inside the combustion chamber 14 is provided. The optical detector 26 measures the fluctuation of the radiant heat from the flame in the combustion chamber 14 above the fluidized bed 16, and specifically, measures only the radiant heat from the flame as an inexpensive one. Radiometers and the like are preferred. Since the convection heat generated in the combustion chamber 14 can always be regarded as substantially constant,
Even if a heat flow meter or the like that measures both the convection heat and the radiant heat is used, it is possible to detect a change in the radiant heat.
Although expensive, the above detection can be performed using an industrial color television, an image processing system, or the like.

The conical viewing angle θ of the optical detector 26 is an important factor, and it is ideal to cover most of the fluidized bed 16. Specifically, it is preferable to install the optical detector 26 on a furnace ceiling or the like. When it is desired to detect only rapid mass combustion, the optical detector 26 may be arranged on the furnace side wall so that the combustion chamber 14 above the fluidized bed 16 can be seen.

On the other hand, above the combustion chamber 14, a flue pipe 28 that forms a flue gas discharge passage is provided. The flue pipe 28 has a combustion air supply system for supplying complete combustion air to the flue gas. 30 is connected.

The combustion air supply system 30 includes a donut-shaped air annular pipe 32 disposed around the flue pipe 28, and a supply pipe 34 for supplying complete combustion air to the air annular pipe 32. Annular tube 32 is communicated within flue tube 28 by a number of radially extending branch tubes 36. A flow adjusting valve (adjusting means) 38 for adjusting the supply amount of the complete combustion air is provided in the middle of the supply pipe 34. When the flow control valve 38 is opened, the air is supplied through the supply pipe 34. Combustion air is supplied into the annular pipe 32, and complete combustion air is introduced into the flue pipe 28 from various directions through the branch pipe 36.

The combustion air supply system 30 preferably injects this air at high speed in the radial direction, or injects it with swirling so that the complete combustion air is quickly and uniformly mixed with the combustion gas. .

The detection signal of the optical detector 26 is input to a combustion control device (control means) 40 including a microcomputer or the like. The combustion control device 40 sets the supply flow rate of the complete combustion air in accordance with the variation of the radiant heat which is the detection result of the optical detector 26, and supplies the complete combustion air by the set flow rate. A signal is output to the flow control valve 38 to perform this open / close control.

In this embodiment, radiant heat B detected at the current time,
A ratio B / A with the radiant heat A detected at a time earlier than the predetermined time, that is, a time change rate of the radiant heat is calculated, and the setting based on this is performed. More specifically, when the ratio B / A is less than 1.2, the supply of complete combustion air is not performed as the fluctuation of radiant heat is moderate, and only when the ratio B / A is 1.2 or more, Assuming that there is a sudden change in the radiant heat, an air flow rate that matches the value is set.

In this combustion method and apparatus, the combustion state in the combustion chamber 14 (specifically, radiant heat generated from the flame in the combustion chamber 14) is directly monitored by the optical detector 26, so that the heat generation in the combustion chamber 14 Even if the amount increases rapidly, the optical detector 26 immediately detects this in the form of a sudden increase in radiant heat,
The combustion control device 40 receiving the output outputs a control signal to the flow control valve 36 to supply complete combustion air into the combustion exhaust gas through the combustion air supply system 30. The unburned components contained in the exhaust gas can be completely burned to prevent black smoke and the like from occurring. On the other hand, if there is no rapid increase in the calorific value, the supply of complete combustion air is not performed, so that the exhaust gas temperature is kept high in a normal state, sufficient heat recovery is possible, and the furnace temperature is also kept high. be able to.

Specifically, since the response time of the optical detector 26 is about 15 msec, which is almost equal to real time, it is possible to execute the combustion control according to the change of the actual combustion state.

FIG. 2 shows the changes over time in the radiometer output and the concentration of carbon monoxide in the exhaust gas when the amount of combustion air is controlled based on the oxygen concentration of the flue exhaust gas as in the prior art.
51 and a dashed line 52. In this graph, the actual radiation amount (kcal / m ²
The conversion rate to h) is 88,636 ((kcal / m ² · h) / mV), and the viewing angle θ of the optical detector 26 is 11.2 °. Also,
As for the detection of the concentration of carbon monoxide, a response time of about 2 minutes is required when the convection time in the combustion chamber 14 and the flue pipe 28, the sampling time of the gas, and the analysis time of the carbon monoxide concentration meter are summed up. The one corrected and synchronized by that amount is indicated by a chain line 52 in the graph.

As can be seen from this graph, in the conventional control method,
It is difficult to follow the rapid increase in the calorific value in the furnace, and it is difficult to prevent the rapid increase of carbon monoxide in the combustion exhaust gas. Further, in this graph, the current radiation amount B and the radiation amount A a predetermined time ago are shown.
It has been shown that the carbon monoxide concentration sharply increases to 400 to 500 ppm or more when the ratio B / A to 2 or more increases, which indicates that the amount of emission of carbon monoxide and the rapid change in radiation amount It shows that there is a significant correlation between them.

On the other hand, FIG. 3 shows the changes over time in the radiometer output and the carbon monoxide concentration when the method according to the present embodiment is carried out, as indicated by solid line 51 and dashed line 52, respectively. As shown in this graph, according to the method of the present embodiment, when the amount of radiation rapidly increases, the air for complete combustion is immediately sent to the flue tube 28, so that the concentration of carbon monoxide is constantly kept at a low level ( (In the figure, 100 ppm or less), no black smoke is generated. In addition, the generation of dioxin and the like can be suppressed with a decrease in the concentration of carbon monoxide, and low-pollution combustion can be realized.

Note that the present invention is not limited to such an embodiment, and the following embodiments can be taken as examples.

(1) In the present invention, means for supplying complete combustion air is not limited.

(2) In the method of the present invention, the supply amount of the combustion air may be adjusted manually according to the fluctuation of the radiation amount instead of the automatic control.

(3) The method and apparatus of the present invention can exhibit more excellent effects when combined with other conventional methods and apparatuses. That is, as described above, the present invention mainly supplies complete combustion air in response to a rapid change in the amount of generated heat. However, the control for a gradual change in the amount of generated heat over a relatively long time is other than that described above. May be supplemented by the conventional method described above.

〔The invention's effect〕

As described above, the present invention detects the radiant heat generated from the flame in the combustion chamber space in the incinerator, monitors the time variation thereof, and supplies complete combustion air to the gas discharge path only when the radiant heat increases rapidly. If the calorific value in the furnace rises sharply due to the introduction of a large amount of combustion products or high calorific substances, the complete combustion air is immediately mixed with the flue gas in the gas discharge path. By doing so, the generation of black smoke and the like can be suppressed more effectively than carbon monoxide,
While it is possible to achieve low-pollution and lean combustion, the supply of complete combustion air is stopped when it is not necessary, so that the exhaust gas temperature can be kept sufficiently high and the furnace temperature can be kept high.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an incinerator according to an embodiment of the present invention, FIG. 2 is a graph showing a change over time of a carbon monoxide concentration and a radiometer output when a conventional method is carried out, and FIG. It is a graph which shows a carbon monoxide density | concentration at the time of implementing a method, and the time change of a radiometer output. 14 combustion chamber, 26 optical detector (flame radiant heat detecting means), 28 flue pipe (forming gas discharge path), 30 combustion air supply system, 38 flow control valve (control means) ), 40
... Combustion control device (control means).

Continuation of the front page (56) References JP-A-3-122414 (JP, A) JP-A-62-29822 (JP, A) JP-A-59-86814 (JP, A) JP-A-63-123913 (JP) JP-A-51-138077 (JP, A) JP-A-64-49818 (JP, A) JP-A-60-132534 (JP, U)

Claims (2)

(57) [Claims] 1. A combustion control method for an incinerator wherein combustion of a combustion product is performed while flowing combustion air is supplied to a bottom portion of the combustion chamber, and secondary air is supplied to a space above the combustion chamber. Detecting radiant heat generated from the flame in the indoor space, and supplying complete combustion air to the gas exhaust passage downstream of the secondary air supply space only when the time change rate of the detected radiant heat is equal to or more than a certain value. A combustion control method for an incinerator. 2. A combustion control apparatus for an incinerator, wherein combustion of a combustion product is performed while flowing combustion air is supplied to a bottom portion of the combustion chamber, and secondary air is supplied to a space above the combustion chamber. Flame radiant heat detecting means for detecting radiant heat generated from the flame in the indoor space, adjusting means for adjusting the supply amount of complete combustion air to a gas exhaust passage downstream of the secondary air supply space, and the flame radiant heat Control means for calculating the time change rate of the radiant heat detected by the detection means and controlling the operation of the adjustment means so as to supply complete combustion air to the gas discharge path only when the time change rate is equal to or more than a certain value; And a combustion control device for an incinerator.