JPH04203802A - Method and apparatus for controlling secondary combustion chamber of combustion furnace - Google Patents

Abstract

PURPOSE:To eliminate a local presence of non-ignited gas such as CO in a combustion furnace and unify the presence of the non-ignited gas in the combustion furnace by a method wherein a secondary combustion spacing within the combustion furnace is divided into some control segments and a temperature of each of the segments and/or a gas concentration in each of the segments is independently controlled. CONSTITUTION:Dust 9 to be ignited is fed into a fluidized bed 3 at a feeding port 10, where it is fluidized and ignited together with a flowing medium under blowing of a primary air 5. Combustion discharging gas is passed through a secondary combustion chamber above the fluidized bed and an amount of supplying secondary air in each of supplying pipes is adjusted in such a way as measured values with a thermometer 13 and an oxygen concentration meter 11 disposed at a downstream side may become set values in addition to a dividing effect of a gas flow by the secondary air supplying pipe itself while the combustion discharging gas passes through a row of the first stage segment 39 arranged in a cross sectional direction of a flow passage, a pipe row 33 for dividing a gas flow and a row of the second stage segment 37, thereby an amount of air getting a predetermined temperature and a complete combustion of non-ignited fuel is supplied for every segment, so that carbon mono-oxide gas or the like are not locally present over an entire secondary combustion chamber and thus a complete combustion of these non-ignited fuel and a temperature control can be realized.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method and device for controlling the secondary combustion chamber of a combustion furnace, and more specifically, the present invention relates to a secondary combustion chamber control method and apparatus for a combustion furnace, and more specifically, in a furnace that generates a large amount of unburned gas, etc., complete combustion is performed. The present invention relates to a method and apparatus for controlling a secondary combustion chamber of a combustion furnace to improve efficiency.

[Prior Art] Conventionally, in an incinerator for waste, etc., for example, a fluidized bed incinerator, an oxygen concentration meter 11 and a thermometer 13 are installed at the outlet 2 of the fluidized bed furnace 1, as shown in FIG. 6A. The total amount of secondary air 11 supplied to the secondary combustion chamber 7 of the fluidized bed furnace 1 was controlled based on the measured data. In the figure, 9 indicates dust, 3 indicates a fluidized bed, and 5 indicates a primary air supply pipe. In such a fluidized bed furnace, the composition of the flue gas varies depending on the location within the furnace due to changes in the quality and quantity of input waste, and also changes over time.

In this way, in the exhaust gas passing through the secondary combustion chamber 7, a high carbon oxide (CO) gas portion is generated due to temporal fluctuations in waste quality, as shown in the shaded area in FIG. As shown in C, a phenomenon occurs in which gas with a high carbon monoxide concentration is unevenly distributed in the furnace due to the distribution of the input garbage. Furthermore, in such a furnace, the injection speed of secondary air, etc. is generally as low as 3 Om/sec or less, so mixing with the combustion exhaust gas is poor, and the gas temperature in the secondary combustion chamber 7 cannot be increased arbitrarily. - There was a limit to reducing the concentration of unburned gas such as carbon oxide.

[Problems to be Solved by the Invention] The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art, and to solve the problem in that the nature and amount of raw materials vary over time or from place to place within the furnace, such as in a waste incinerator, etc. For this reason, unburned gas such as carbon monoxide is unevenly distributed in the freeboard part of the furnace, and a secondary combustion chamber control method for a combustion furnace is provided to prevent highly concentrated harmful gases from being discharged outside the furnace. The goal is to provide equipment.

[Means for Solving the Problems] In order to achieve the above object, the present inventors created a combustion space into which the secondary air of the secondary combustion chamber is blown into a large number of virtual segments (without partition walls) consisting of small sections. partition) into
A secondary air supply means and a specific gas, for example, an oxygen concentration meter and/or thermometer are installed in each space of this small section, and a concentration meter and/or thermometer for a specific gas, such as oxygen, is installed on the downstream side of the secondary air supply means, and The amount of secondary air supplied is controlled so that the measured value of the gas concentration meter and/or thermometer becomes a predetermined value, thereby eliminating uneven distribution of unburned gas in the combustion gas space and achieving complete combustion. This is what I did.

That is, the method of the present invention divides the combustion chamber space in the combustion furnace into which secondary air is blown into a large number of virtual segments consisting of small sections, and for each space of the small sections, a secondary air supply means and its downstream are connected. A specific gas, a concentration meter, and/or a thermometer are installed, and the supply amount of secondary air is adjusted as necessary so that the measured value of the gas concentration meter and/or thermometer becomes a predetermined value for each segment. This is a method for controlling a secondary combustion chamber of a combustion furnace to control the amount of fuel.

Further, the device of the present invention includes a secondary air blowing nozzle, a concentration meter and/or a temperature meter for a specific gas component provided downstream of the combustion gas in the vicinity of the blowing nozzle, and a concentration meter and/or temperature meter of a specific gas component provided in the downstream of the combustion gas near the blowing nozzle. a secondary air blowing control unit group, which is arranged in each predetermined virtual segment space that divides the combustion exhaust gas flow path into a number of sections, and each of the control units described above; A secondary combustion chamber control device for a combustion furnace, comprising: control means for adjusting the amount of secondary air blown into each control unit so that the measured value becomes a set value based on the measured value of the gas concentration meter and/or thermometer. It is.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

[Embodiment] FIG. 1 is an explanatory diagram of a method and apparatus for controlling a secondary combustion chamber of a combustion furnace, showing an embodiment of the present invention. This combustion furnace is a fluidized bed furnace, which consists of a furnace body 1, a fluidized bed 3 formed by fluidizing a fluidized medium by air blown in from a primary air supply pipe 5 provided at the bottom, and a fluidized bed 3 formed by fluidizing the fluidized medium with the Garbage 9
, a supply pipe 17 for secondary air 15 provided above the fluidized bed 3, and detection units 29 and 31 provided in the combustion gas downstream of the secondary air supply pipe, respectively. 13 and an oxygen concentration meter 11, and a thermometer 13 having detection parts 29 and 31 provided at the furnace outlet 30, respectively.
and an oxygen concentration meter 11, a control line 23 that transmits these signals to a control device to be described later, and the secondary air 1.
A control valve 2LA for supplying the exhaust gas 15A to the air conditioner 5 to adjust its oxygen concentration, and a fuel 19 supply nozzle 27 provided immediately below the lowermost secondary air supply pipe 17,
Regulating valves 22, 21, 21A and control lines 24.2 are installed in the supply pipes of the fuel 19, secondary air 15, and exhaust gas 15A so that the temperature and oxygen concentration at each location are at predetermined values.
5 and 26 for providing a flow signal.

In this device, the secondary combustion chamber in the furnace has a small section (control unit 7) comprising a fuel supply nozzle 27, a secondary air supply pipe 17, a temperature detection section 25, and an oxygen concentration detection section 31. Segments 37 and 39 are provided in four rows in the cross-sectional direction of the flow path, spanning two stages above and below, and one pipe 33 for dividing the gas is provided between these rows.
It is arranged in rows. Note that the lower control segment 39 includes the fuel supply nozzle 27, but this may be provided as needed and is omitted in the upper control segment.

In addition, a thermometer 13 and an oxygen concentration meter 1 in each segment
1, both or either one may be provided depending on the desired control performance. As shown in detail in Part 2, the secondary air supply pipe 17 is directed downward at an angle θ (preferably 90 to 18
Nozzles 17A are provided so as to form an angle of 0 degrees), and these nozzles are provided at intervals of, for example, about 201 degrees in the axial direction of the tube, so that secondary air is ejected at a high velocity (2).

This secondary air is controlled by the control valve 21A to control the exhaust gas 1.
5A may be mixed as appropriate, and hereinafter, the term "secondary air" may include exhaust gas.

In such a configuration, the waste 9 to be incinerated is charged into the fluidized bed 3 from the input port 10, where it is fluidized and combusted together with a fluidized medium under the blowing of secondary air 5. The combustion exhaust gas passes through the secondary combustion chamber above the fluidized bed, during which a row of first-stage segments 39 provided in the cross-sectional direction of the flow path, a row of tubes 33 for dividing the gas flow, and a second-stage segment are used. 3
In addition to the splitting effect of the gas flow by the secondary air supply pipe itself while passing through the row No. 7, each supply pipe By adjusting the amount of secondary air supplied to each segment, the amount of air that achieves a predetermined temperature and complete combustion of unburned matter is supplied to each segment, so carbon monoxide gas etc. are unevenly distributed throughout the secondary combustion chamber. Complete combustion of these unburned substances and temperature control can be achieved without In this case, when the temperature of a predetermined segment does not reach a predetermined value, fuel is ejected from the fuel injection nozzle 27, and control can be performed so that the temperature reaches a predetermined temperature. In this embodiment, each segment row is provided in two stages, but this may be one stage or three stages.
Of course, more than one stage may be provided.

FIG. 3 shows another embodiment of the present invention, which differs from the apparatus of embodiment 1 in that vertical partitions 41 and 45 are provided in the secondary combustion chamber of the combustion furnace, and a U-shape is formed in the vertical direction. A flow path having a bent portion of a mold is formed, and a control segment 57 consisting of a temperature detection section 29, an oxygen concentration detection section 31, and a secondary air supply nozzle 17B is provided in the flow path in two stages.

In addition, the pipe 33 for gas division in the embodiment shown in FIG.
The column is omitted, and instead, a supply port for exhaust gas 39 for gas mixing is provided below the supply section for fuel 19.

Further, in this embodiment, a heat exchanger 49 is provided in the flow path 47 closest to the outlet 30 of the gas flow path, and an ash 53 having a screw 53 connected to a motor 55 at the bottom of the heat exchanger 49 is provided.
Two extraction pipes 51 are provided.

In such a configuration, the combustion exhaust gas generated in the fluidized bed 3 flows through the vertical U-shaped bent passages 43 and 47 of the secondary combustion chamber.
The temperature detection section 29 and the oxygen concentration detection section 3
1 and the secondary air supply nozzle 17B, and the amount of secondary air supplied to each segment is controlled by the control device 35 so that the measured value of each segment matches the set value. The temperature is controlled at each location, the uneven distribution of unburned components is eliminated, and heat is recovered by the heat exchanger 49 while passing through the flow path 47, and the heat is discharged from the furnace outlet 30. . While passing through this final exhaust gas flow path, the ash falls downward,
The extraction pipe 53 is taken out to the outside by rotating the screw 51.

According to the above embodiment, the secondary combustion chamber is formed by a plurality of control segments, in the case of FIG. 1 a row of control segments 37 provided in two stages in the cross-sectional direction of the flow path, and in the case of FIG. By providing two rows of control segments 57 in the direction, the temperature and oxygen concentration of each segment can be independently controlled.
, N20, etc.) can create a space with optimal combustion temperature and oxygen concentration. For example, even if the quality and quantity of input waste fluctuates over a time span of 1 to 2 minutes, and this fluctuation directly affects the gas composition flowing from the fluidized bed into the secondary combustion space (for example, Fig. 6B), As the gas passes through each segment, it is homogenized and can reach the optimum temperature to achieve low NOx and the optimum oxygen concentration for complete combustion of CO. Similarly, Figure 6C
Even when the gas composition in the horizontal direction fluctuates due to fluctuations in the garbage input position as shown in FIG. 2, uniformity can be achieved by adjusting the temperature and oxygen concentration of each segment to predetermined values in the same way as described above. Furthermore, since the combustion space is finely divided and controlled, the excess oxygen concentration can be lowered, making it possible to improve the efficiency even if it is used as a heat recovery furnace.

In the above embodiments, the oxygen concentration meter may be replaced with another gas concentration meter such as a carbon dioxide concentration meter or a component analyzer using laser light. Further, as the thermometer, a thermocouple, a radiation thermometer, etc. are used.

The combustion conditions in the apparatus of the present invention are not particularly limited, but for low CO and NOx combustion, the combustion temperature of the fluidized bed is 650-700'C1 air ratio 0.7-0
．． 9. Secondary air temperature 200-300°C1 Secondary air temperature 200"C or more, secondary air blowing speed 10m/sec or more, secondary combustion chamber temperature 700-950"C1 furnace outlet oxygen concentration 5-6% The following conditions are preferable, and in order to maintain a low air ratio, it is desirable to include exhaust gas in the secondary air to ensure a sufficient amount of gas for mixing.

To further reduce N20, the fluidized bed temperature should be set to 500-6
It is preferable to set the air ratio to about 014-0.5, set the temperature of the secondary combustion chamber as high as 700 to 1100°C, and uniformly supply secondary air for combustion.

In the present invention, the temperature and specific gas concentration of each segment space are set depending on the performance of the furnace and the target control conditions as described above.

The above has been explained using a fluidized bed furnace as an example, but the present invention
It is also applicable to other combustion furnaces that require a secondary combustion space.

Moreover, the combustible material can also be applied to combustible materials other than garbage.

〔Effect of the invention〕

According to the present invention, the secondary combustion space of the combustion furnace is divided into a large number of control segments, and the temperature and/or gas concentration of each segment is independently controlled. It is possible to eliminate local uneven distribution of gas, to make it uniform, to suppress the generation of CO, and to comply with regulations on the total amount of oxygen monoxide, which is considered as one of the countermeasures against dioxin. Furthermore, since temperature control can be performed at the same time, it is possible to prevent the generation of NOx and also to suppress the generation of N20 due to relatively low temperature combustion.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a secondary air control method and apparatus for a fluidized bed combustion furnace showing one embodiment of the present invention, and FIG. 2 is a secondary air supply pipe arranged in the combustion space of the combustion furnace. A cross-sectional view of
FIG. 3 is an explanatory diagram of a secondary air control method and apparatus for a combustion furnace showing another embodiment of the present invention, and FIG. 4 is a sectional view taken along the line ■-■ in FIG. 3 in the direction of the arrow. , Figure 5 shows the third
A cross-sectional view along the line V-V in the figure and FIG. 6A,
B and C are explanatory diagrams showing the combustion state of a conventional fluidized bed combustion furnace. DESCRIPTION OF SYMBOLS 1... Combustion furnace main body, 3... Fluidized bed, 5... Secondary air, 9... Garbage, 11... Oxygen concentration meter, 13...
Thermometer, 15...Secondary air, 15A...Exhaust gas, 1
7... Secondary air supply pipe, 19... Fuel, 21...
Secondary air control valve, 21A...exhaust gas control valve,
22...Fuel control valve, 23.24.25 and 2
6... Control line, 27... Fuel supply nozzle, 29
...Temperature detection section, 31...Oxygen concentration detection section, 30.
...Furnace outlet, 33...Gas division pipe, 35...
Control device (computer), 37... Control segment, 39... Exhaust gas, 41 and 45... Partition, 43... Combustion space section, 47... Gas flow path, 49
...Heat exchange section, 51...Ash extraction pipe, 52...
Ash, 53...Screw, 55...Motor, 57
...control segment.

Claims (4)

[Claims] (1) The combustion chamber space into which secondary air is blown in the combustion furnace is divided into a large number of virtual segments consisting of small sections, and each space of the small section has a secondary air supply means and a specific gas, concentration, etc. A meter and/or thermometer is installed, and the amount of secondary air supplied and, if necessary, the amount of fuel is controlled so that the measured value of the gas concentration meter and/or thermometer becomes a predetermined value for each segment. A method for controlling the secondary combustion chamber of a combustion furnace. (2) A secondary air blowing nozzle, a specific gas component concentration meter and/or thermometer installed in the downstream of the combustion gas near the blowing nozzle, and a necessary device in the upstream of the combustion exhaust gas near the blowing nozzle. a group of secondary air blowing control units arranged in each predetermined virtual segment space that divides the combustion exhaust gas flow path into multiple sections; and a group of secondary air blowing control units each consisting of a fuel supply nozzle provided according to A control device for controlling a secondary combustion chamber of a combustion furnace, comprising: control means for adjusting the amount of secondary air blown into each control unit based on the measured value of a thermometer and/or a thermometer so that the measured value becomes a set value. (3) The secondary combustion chamber control device for a combustion furnace according to claim 2, wherein the segment space that divides the flue gas flow path and the control unit provided in the space are formed in multiple rows and stages in a cross-sectional direction of the flow path. . (4) A partition is provided in the combustion space so that the combustion exhaust gas flows through the U-shaped bent part in the secondary combustion chamber space,
3. The secondary combustion chamber control device for a combustion furnace according to claim 2, wherein a plurality of said segment spaces and control units are formed at predetermined intervals in the flow path formed in this way.