JPH03267611A - Fluidized-bed combustion method for waste - Google Patents

Abstract

PURPOSE:To allow wastes to completely burn, prevent CO gas etc., from being discharged from a furnace and improve recovery ratio of steam in the case of a boiler etc., by providing an air feed rate control means including a damper in each diffuser pipe and by opening and closing each of the dampers at specific intervals in such a manner that the ratio of air flow rate to minimum fluidization air rate falls within a specific range when the damper is opened or closed. CONSTITUTION:A damper is provided in each diffuser pipe 5 for feeding primary air for combustion. The dampers are opened and closed in such a manner that the ratio Uo/Umf, wherein flow rate of primary air is Uo and minimum air rate for fluidization Umf, falls in the range of 1.4-4 when the damper is opened and 0.5-2 when closed at intervals of 1-10 seconds and 10-100 seconds respectively. In the device, air flow rate is controlled in such a manner that at first a valve 13 is opened to feed minimum quantity of air required for combustion to each of the diffuser pipes from a line 9A, in which primary air corresponding to a ratio above the lower limit of Uo/Umf at the closing of damper is supplied and further damper control valve 7 for each diffuser pipe 5 is adjusted so that Uo/Umf comes in the range aboded by oblique lines when the damper is opened or closed. As a result, in the case of a boiler etc., steam is stably produced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for fluidized bed combustion of waste, and in particular, the present invention relates to a fluidized bed combustion method for waste, and in particular, a method for burning combustible materials such as municipal waste, which varies in quantity and quality over time, under the formation of a fluidized bed. This relates to a combustion method for burning.

[Prior art] One of the problems with conventional fluidized bed combustion furnaces for incinerating municipal waste, etc. is that unburned matter remains in the exhaust gas due to time fluctuations in the quantity and quality of the supplied waste, resulting in black smoke. Alternatively, there is a problem in that harmful gases such as carbon monoxide are generated. This becomes a bigger problem as the size of the furnace becomes smaller, as the influence of the size of the waste becomes greater.

In order to solve this problem, methods have been proposed in which the amount of air and other factors are controlled in advance according to the amount of waste to be supplied and the award, and methods in which the waste is crushed into small pieces and quantitatively fed into the furnace. , there were many design constraints (and it was difficult to put it into practical use).

The generation of unburned matter in the fluidized bed incineration is a problem that occurs because the combustion rate is extremely high in fluidized bed furnaces, and in mechanical furnaces such as stoker furnaces that have been used since ancient times. Since the waste was slowly fed into the furnace, the generation of unburned material was relatively small.

[Problem to be solved by the invention]

The purpose of the present invention is to solve the problems specific to the fluidized bed combustion apparatus described above, and to achieve slow combustion regardless of temporal fluctuations in the quantity and quality of waste input into the fluidized bed furnace. The purpose of the present invention is to provide a fluidized bed combustion method that can completely burn waste at a high speed, prevent CO gas, etc. from being discharged outside the furnace, and improve the steam recovery rate when used in a boiler, etc. .

[Means to solve the problem]

The present invention uses a fluidized bed furnace in which a large number of aeration tubes each having a large number of primary air supply nozzles are arranged in a fluidized bed section, supplies primary air from the aeration tubes to combust waste, and furthermore, the empty column section In the fluidized bed combustion method for waste in which unburned content in the combustion gas is combusted under the supply of secondary air, each diffuser pipe is provided with an air supply amount adjusting means including an opening/closing damper, and the air flow rate U0 and fluidization are adjusted. At intervals of 1 to 10 seconds and 10 to 100 seconds, respectively, so that the ratio U, /U, with the minimum air amount U + ef is in the range of 1°4 to 4 when the damper is open and 0.5 to 2 when the damper is closed. It is characterized by opening and closing the damper.

In the present invention, the combustible material to be burned is one whose quantity and quality change over time, such as municipal waste, and preferably one whose bulk density, moisture content, calorific value, etc. change over time. In addition to municipal waste, the present invention can be applied to any combustible material having different appearance and quality, examples of which include sludge, ore, and the like.

In the present invention, an opening/closing damper is provided in the diffuser pipe that supplies primary air for combustion, and the ratio Uo-/U+er between the flow rate U0 of the primary air and the minimum fluidizing air amount Umf is 1.0 when the damper is open.
4 to 4, so that it is in the range of 0.5 to 2 when the damper is closed.
The damper is opened and closed at intervals of 1 to 10 seconds and 10 to 100 seconds, respectively. However, if the damper is opened for less than 1 second, stirring by the fluidizing air is insufficient, and the damper is opened for less than 1 second. If it exceeds 10 seconds, there will be too much air contributing to combustion, and the CO reduction effect will no longer be obtained. Moreover, if UO/U when the damper is open exceeds 4, an excessive amount of fluidizing air will be supplied, increasing operating costs and making it easier for ash to be entrained in the combustion gas.

On the other hand, if u0/Umf when the damper is open is less than 1.4, the stirring effect of the fluidized bed will not be sufficient. Further, when the damper is closed, if the damper is closed for less than 10 seconds, the CO reduction effect will not be sufficient, and if it exceeds 100 seconds, temperature unevenness will occur in the fluidized bed, and local overheating will progress, resulting in clinker and the like.

Furthermore, if U, /U, when the damper is closed exceeds 2, the CO reduction effect will be lost, and if it is less than 0.5, it will not be possible to secure the amount of air necessary for combustion of waste. The above damper opening/closing time and Us /Umf17) The preferred range is U, /v
, t2. o ~3.0, damper open 3~7 seconds, U, /U,
, is 0.5 to 1°5 and the damper is closed for 30 to 60 seconds.

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

[Example] FIG. 1 is a plan sectional view showing an example of a fluidized bed combustion apparatus for carrying out the present invention, and FIG. 2 is a front sectional view thereof.

This device includes a furnace body 1 of a fluidized bed combustion apparatus, and a furnace body l.
A blower 15 for feeding primary air into the interior, and a pipe 8.9 and a valve 11 for the primary air fed by the blower 15.
and a bypass pipe 5 for introducing air into the furnace 1 through a valve 13 and a bypass pipe 9A branched from the pipe 8, respectively, for introducing air during off-time through a valve 13. is attached. The on-off control of the aeration pipe 5 is performed by repeatedly turning on and off according to a predetermined pattern using a valve 7 (control valve), while a constant amount of air is always supplied to the pipe 9A via a valve 13 regardless of the above-mentioned on-off operation. is supplied. Note that the air supply during the off-state is carried out in the same manner as in Fig. 1 by providing control valves 7A with low limiters in each pipe 9 as shown in Fig. 3, instead of using the bypass pipe 9A as shown in Fig. 1. May be controlled. In this case, when the control valve 7A is turned off, the low limiter works and a constant amount of air always flows.

The air amount control in the device shown in FIG. 1 is performed by first opening the valve 13 and sending the line 9A to each diffuser pipe 5 with the minimum amount of air required for combustion, that is, Un /U-r when the damper is closed as shown in FIG. 4.
The primary air corresponding to above the lower limit of is supplied, and the damper control valve 7 of each diffuser pipe 5 is adjusted so that Uo/Ut is as shown in Fig. 4 when the damper is open and when the damper is closed. Adjust so that it falls within the shaded range. Note that the black circle plot in FIG. 4 is an example of data obtained in this manner.

As for other conditions for the fluidized bed, it is preferable that the average diameter of the sand that is the fluidizing medium is small, but it is generally 1.5 to 0.3.
0.3 to 0.8, preferably 0.3 to 0.8.

Incidentally, the primary air for fluidization may be mixed with combustion exhaust gas in an appropriate proportion.

In the present invention, various means and methods used in fluidized bed combustion methods for waste can be used in combination. For example, means for promoting mixing with secondary air, such as grids or tube rows, may be provided in the cavity of a fluidized bed furnace, or the supply amount of primary air may be controlled by detecting the temperature of the fluidized bed, or Methods such as controlling the amount of waste supplied by detecting internal pressure, flame, and the amount of oxygen at the furnace outlet can be used in combination.

[Effects of the Invention] According to the present invention, waste can be mildly combusted using a fluidized bed furnace with a simple on-off control system. For this reason, even small-scale combustion furnaces can be operated under stable conditions with almost no unburned matter in the combustion gas and no black smoke, and in the case of boilers, etc., the amount of steam generated is small. Stabilize.

Additionally, since the air ratio can be set lower than in a normal fluidized bed combustion apparatus, the amount of exhaust gas is reduced. Furthermore, since stable combustion can be performed regardless of the amount of combustible material, a pretreatment device such as a crusher, which is normally installed in the case of fluidized bed incineration of municipal waste, becomes unnecessary. In addition, problems such as heat spots and welding that occur in mechanical furnaces can be easily avoided by selecting combustion conditions, and the permissible operating range is wide, so there is a wide range of combustion conditions to choose from for combustible materials. It has also been greatly expanded and can be applied to large, medium, and small scale fluidized bed combustion furnaces.

[Brief explanation of drawings]

FIG. 1 is a plan sectional view showing an example of a fluidized bed combustion apparatus for carrying out the present invention, FIG. 2 is a front sectional view thereof, and FIG.
This figure is a plan sectional view of a fluidized bed combustion apparatus showing another embodiment of the present invention, and FIG. 4 is a diagram showing numerical ranges in the combustion method of the present invention. 1... Furnace body, 2... Combustion chamber, 3... Fluidized bed, 4
... air diffuser plate, 5... air diffuser pipe, 6... wind box, 7...
・Valve (control valve), 7A...Control valve, 8.9.9A
... tube, 10 ... partition wall, 11.13 ... pulp,
15...Primary air blower. Figure 1

Claims (1)

[Claims] (1) Using a fluidized bed furnace in which a large number of diffuser tubes each having a large number of supply nozzles for primary air are arranged in the fluidized bed section, the primary air is supplied from the diffuser tubes to burn the waste, and then the waste is combusted in the empty tower section. In a waste fluidized bed combustion method in which unburned content in combustion gas is combusted under the supply of secondary air, each diffuser pipe is provided with an air supply amount adjusting means including an opening/closing damper to adjust the air flow rate U_o and the minimum fluidization. 1 to 10 seconds and 10 to 10 seconds, respectively, so that the ratio U_o/U_m_f with the air amount U_m_f is in the range of 1.4 to 4 when the damper is open and 0.5 to 2 when the damper is closed.
A fluidized bed combustion method for waste, characterized by opening and closing a damper at intervals of 0 seconds.