JPH06323510A - Combustion control method in fluidized bed type furnace - Google Patents

Abstract

PURPOSE:To enable a processed material having a high range of generating heat to be completely ignited within a fluidized bed type furnace by a method wherein an amount of circulating discharged gas is controlled in response to a temperature of a fluidized bed and a temperature within the fluidized bed is kept within a specified temperature range. CONSTITUTION:In a device having a fluidized bed 1, a part of discharged gas cooled and of which dust is removed is extracted through a discharged gas circulation line 20 and circulated to an air box 2 of the fluidized bed type furnace 1 together with primary air. Then, an amount of circulating discharged gas is controlled by a temperature indicating control 21. connected to a fluidized bed 3 through a flow rate control means 22 such as a damper, a valve and an inverter and the like. That is, as a temperature of the fluidized bed 1 is higher than the set value, the flow rate control means 22 is operated in such a direction as one in which the means 22 is opened, resulting in that an amount of discharged gas circulation is increased, a partial pressure of O2 is decreased to cause a temperature of the fluidized bed 1 to be lowered and in turn when a temperature of the fluidized bed 1 is lower than the set value, the flow rate control means 22 is operated in a closing direction, the amount of circulating discharged gas is reduced, the partial pressure of O2 is increased so as to increase the temperature of the fluidized bed 1. Accordingly, a stable combustion of low CO becomes possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to coal, waste, sludge,
The present invention relates to a combustion control method when burning an object to be treated such as municipal waste in a fluidized bed furnace.

[0002]

2. Description of the Related Art Conventionally, when a material to be processed is burned in a fluidized bed furnace, the temperature of the fluidized bed becomes high (for example, 700 ° C. or more) especially for the material to be processed having a high calorific value, and stable combustion is maintained. In addition, a method of cooling the fluidized bed by injecting water into the fluidized bed or providing a heat transfer surface such as a heat transfer tube in the bed was essential.

[0003] in JP-A-54-16731, the low NO _X fluidized bed combustion method of circulating a portion of the dust removal by exhaust gas into the fluidized bed of the fluidized bed combustion system is described. Also,
In Japanese Utility Model Publication No. 2-29371, a forced draft fan that circulates a portion of the exhaust gas that has been removed with a combustion air into a fluidized bed boiler and that supplies the combustion air and an exhaust gas mixing fan are on the same axis. There is described a fluidized bed boiler that is provided and can be driven by a single motor and that can reduce NO _X.

[0004]

In order to solve the above-mentioned problems in the prior art, it is conceivable to reduce the amount of primary air flowing into the wind box. However, in this method, the defective uniform flow of the fluid medium, or There is a drawback that it becomes difficult to discharge unsuitable substances (incombustible substances contained in the object to be treated) from the furnace. Further, the inventions described in the above two publications are both intended to circulate a part of the exhaust gas to reduce NO _X , and these publications are the features of the present invention.
Nothing is mentioned about controlling the amount of circulating exhaust gas by the temperature of the fluidized bed.

The present invention has been made in view of the above points, and an object of the present invention is to control the temperature in the bed in a fluidized bed furnace by controlling the amount of exhaust gas recirculation so that a material having a wide range of calorific values can be completely treated. It is to provide a combustion control method capable of burning.

[0006]

In order to achieve the above object, a combustion control method in a fluidized bed furnace of the present invention is a method for removing dust from exhaust gas from a fluidized bed furnace and then partially removing the exhaust gas from the primary In the method of circulating to the fluidized bed furnace together with air or separately, the circulating exhaust gas amount is controlled by the temperature of the fluidized bed to maintain the temperature in the fluidized bed within a constant temperature range.

In the above method, the primary air supply amount is
It is preferable to control by the total flow rate of the circulating exhaust gas amount and the primary air supply amount. Further, it is preferable to control the amount of secondary air supplied to the freeboard section by controlling the oxygen concentration in the exhaust gas. Further, it is preferable to control the amount of secondary air supplied to the freeboard section according to the exhaust gas temperature at the outlet of the fluidized bed furnace. In addition, it is preferable to control the amount of secondary air supplied to the freeboard unit according to the supply amount of the object to be processed. Further, in these methods, when the calorific value of the object to be treated is high, it is preferable that the circulating exhaust gas is further cooled and then circulated to the fluidized bed furnace.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. However, the shape of the constituent devices described in this embodiment, the relative arrangement thereof, and the like, unless otherwise specified, are not intended to limit the scope of the present invention only to them, but merely illustrative examples. Nothing more. Example 1 In FIG. 1, 1 is a fluidized bed furnace having a wind box 2, a fluidized bed 3, and a freeboard section 5. A fluidizing gas supply pipe 6 is connected to the wind box 2, and a combustion secondary air supply pipe 7 is connected to the freeboard portion 5. Reference numeral 8 is a gas dispersion plate, 10 is a processing object feeding device, 11 is a primary blower, and 12
Is a secondary blower, 13 is a primary air supply pipe, 15 is a gas cooling facility such as an air preheater, 16 is an exhaust gas treatment facility such as a dedusting / denitration / desulfurization device, 17 is an induction fan (IDF), 18
Is a chimney.

In the apparatus including the fluidized bed furnace configured as described above, part of the cooled and removed exhaust gas is extracted through the exhaust gas circulation line 20 and circulated in the wind box 2 of the fluidized bed furnace 1 together with the primary air. To do. The amount of circulating exhaust gas is controlled by the temperature indicator controller (TIC) connected to the fluidized bed 3.
It is controlled by the flow rate adjusting means 22 such as a damper, a valve, and an inverter. That is, when the temperature of the fluidized bed 1 becomes higher than the set value, the flow rate adjusting means 22 is operated in the opening direction to increase the exhaust gas circulation amount and lower the O ₂ partial pressure to lower the temperature of the fluidized bed 1. When the temperature of the fluidized bed 1 becomes lower than the set value, the flow rate adjusting means 22 is operated in the closing direction to reduce the exhaust gas circulation amount and raise the O ₂ partial pressure to raise the temperature of the fluidized bed 1.

The above operation will be described in more detail below. By using the exhaust gas after the exhaust gas treatment for part or all of the primary air for combustion, the amount of primary air required for fluidization is secured and the combustion rate in the bed is reduced (previously, 21
% O ₂ air was used, but in the present invention, the exhaust gas for recirculation (O ₂ ≈6 to 12%) is mixed, or the entire amount is used, so the partial pressure of O ₂ in the layer is reduced. Therefore, the combustion rate can be reduced by that much), so that it is possible to control the layer temperature without providing a transmission surface in the layer. Therefore, it is not necessary to recover the heat in the layer and cool it, so that the heat can be recovered in the downstream of the conventional waste heat boiler, so that the reliability of the entire device can be improved and the conventional device can be effectively used. can do.

Table 1 shows a conventional example in which only the fluidizing gas is air, the method of the present invention in which the exhaust gas is 40%, and the method of the present invention in which the exhaust gas is 100% (the whole amount is recycled exhaust gas). , The O ₂ amount, the N ₂ amount, and the primary air ratio λ ₁
Is shown.

[0012]

[Table 1]

As shown in Table 1, by exhaust gas recirculation,
The in-layer primary air ratio λ ₁ is 0.9 to 0.71 or 0.4
Can be lowered to 3. Since the flow rate of the fluidizing gas is the same, the fluidizing state is the same, and the O ₂ partial pressure in the bed is lowered, so that the combustion rate in the bed is lowered and the temperature in the bed can be lowered. The temperature in the bed is controlled within a certain temperature range by changing the exhaust gas recirculation amount and changing the O ₂ partial pressure in the bed.

Further, depending on the primary exhaust gas circulation amount, it is predicted that the O ₂ concentration at the furnace outlet becomes too low.
It is preferable that the oxygen concentration in the exhaust gas is detected by the oxygen concentration meter 23, and the amount of secondary air supplied to the freeboard unit 5 is controlled by this value. Reference numeral 24 is a secondary air amount adjusting means.
Also, the temperature of the exhaust gas at the outlet of the fluidized bed furnace 1 is adjusted by the temperature indicating controller 2
5, the secondary air amount supplied to the freeboard unit 5 may be controlled by this value. Further, the supply amount of the object to be processed may be detected by the object supply amount detecting means 26, and the amount of secondary air supplied to the freeboard portion 5 may be controlled by this value.

Embodiment 2 In this embodiment, as shown in FIG. 2, primary air and circulating exhaust gas are separately supplied to a wind box 2 of a fluidized bed furnace 1. Two
Reference numeral 7 is a primary air blower, and 28 is a circulating exhaust gas blower.
Other configurations and operations are similar to those of the first embodiment.

Embodiment 3 In this embodiment, as shown in FIG. 3, the total flow rate of the circulating exhaust gas amount and the primary air supply amount is determined by a flow rate indicating controller (FIC).
It is detected by 30, and the primary air supply amount is controlled by this value. Reference numeral 31 is a primary air amount adjusting means. Other configurations and operations are similar to those of the first embodiment.

Embodiment 4 In this embodiment, as shown in FIG. 4, the exhaust gas circulation line 20
Further, a cooler 32 such as an economizer and an air preheater is provided to further cool the circulating exhaust gas, and then circulates it to the wind box 2 of the fluidized bed furnace 1. In this embodiment, the cooler 3
By providing 2, there is an advantage that the amount of gas in the exhaust gas circulation line is reduced, and an effect that the in-layer temperature can be appropriately controlled even with a higher calorie processed object is obtained. Other configurations and operations are similar to those of the first embodiment.

[0018]

Since the present invention is configured as described above, it has the following effects. (1) Since the temperature in the fluidized bed is controlled to a constant temperature by the exhaust gas circulation amount, stable combustion with low CO becomes possible. (2) Since it is not necessary to inject water for cooling the temperature in the fluidized bed and to install a transmission surface, the construction cost can be reduced. (3) The required power of the exhaust gas induction fan (IDF) can be reduced.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an example of an apparatus for carrying out a combustion control method in a fluidized bed furnace of the present invention.

FIG. 2 is a flow sheet showing another example of an apparatus for carrying out the method of the present invention.

FIG. 3 is a flow sheet showing another example of an apparatus for carrying out the method of the present invention.

FIG. 4 is a flow sheet showing still another example of an apparatus for carrying out the method of the present invention.

[Explanation of symbols]

 1 Fluidized Bed Furnace 3 Fluidized Bed 5 Freeboard 6 Gasification Pipe for Fluidization 7 Secondary Air Supply Pipe for Combustion 11 Primary Blower 12 Secondary Blower 13 Primary Air Supply Pipe 15 Gas Cooling Facility 16 Exhaust Gas Treatment Facility 20 Exhaust Gas Circulation Line 21 Temperature Indicator Controller 22 Flow Rate Controlling Means 23 Oxygen Concentrator 25 Temperature Indicator Controller 27 Primary Air Blower 28 Circulating Exhaust Gas Blower 30 Flow Rate Regulator 32 Cooler

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location F23G 5/50 M 8409-3K N 8409-3K (72) Inventor Masahiro Tsunai 2 Tenjinbashi, Kita-ku, Osaka 5-2-5 Kawasaki Heavy Industries, Ltd. Osaka Design Office (72) Inventor Tatsuyuki Shimokawa 2-5-25 Tenjinbashi, Kita-ku, Osaka City Kawasaki Heavy Industries Ltd. Osaka Design Office

Claims (6)

[Claims] 1. A method in which after exhaust gas from a fluidized bed furnace is treated to remove dust, a part of this exhaust gas is circulated to the fluidized bed furnace together with primary air or separately, A combustion control method in a fluidized bed furnace, characterized in that the temperature in a fluidized bed is maintained within a constant temperature range by controlling the temperature. 2. A combustion control method in a fluidized bed furnace according to claim 1, wherein the primary air supply amount is controlled by a total flow rate of the circulating exhaust gas amount and the primary air supply amount. 3. The combustion control method in a fluidized bed furnace according to claim 1, wherein the amount of secondary air supplied to the freeboard section is controlled by the oxygen concentration in the exhaust gas. 4. The combustion control method in a fluidized bed furnace according to claim 1, wherein the amount of secondary air supplied to the freeboard section is controlled by the temperature of the exhaust gas at the outlet of the fluidized bed furnace. 5. The combustion control method in a fluidized bed furnace according to claim 1 or 2, wherein the amount of secondary air supplied to the freeboard section is controlled by the supply amount of the object to be treated. 6. The method for controlling combustion in a fluidized bed furnace according to claim 1, wherein the circulating exhaust gas is cooled and then circulated to the fluidized bed furnace.