JPH109548A - Incineration of sludge by fluidized-bed incinerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To incinerate sludge in a stabilized state even where it differs in nature so as to suppress evolution of harmful gases in the exhaust gas and enable cutting down the use of supplementary fuel fed to the fluidized bed. SOLUTION: As regards oxygen concentration in the exhaust gas, of a maximum temperature, median temperature, and minimum temperature detected by a furnace-top thermometer 5, a median combustion chamber thermometer 6, and a lower part combustion chamber thermowameter 7 respectively the median temperatwuris selected as a representative combustion chamber temperature by use of a selector 11 and on the basis of this selected representative combustion chamber temperatirand in a manner of obtaining an oxygen concentration as set by an oxygen-concentration regulator 14 the amount of the supply of fluidized combustion air fed to a wind ox 1a is controlled in quantity. At the same time the amount of control obtainable on the basis of the combustion chamber temperature and the fluidized-bed temperature detected by a fluidized- bed thermometer 8 is added by an adder 17 and supplementary fuel so controlled in quantity as to make the representative combustion chamber temperature become a set furnace temperature and make the fluidized-bed temperature become a set fluidized-bed temperature is supplied to the fluidized bed 1b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a sludge incineration method using a fluidized bed incinerator, and more particularly, to a harmful gas in exhaust gas generated by sludge incineration, for example, N ₂ O, C.
The present invention belongs to the technical field of a sludge incineration method using a fluidized bed incinerator in which the amounts of O, NO _X , HCN, NH _{3 and the} like are reduced and auxiliary fuel can be reduced.

[0002]

2. Description of the Related Art As a combustion apparatus for efficiently and surely and completely burning incinerated substances such as sewage sludge in a short time, air for flow / combustion is blown from a wind box through a nozzle into a fluidized bed. A fluidized bed incinerator that fluidizes sand consisting of silica sand, etc., which forms the bed, breaks and gasifies incinerated materials using the sand flow and the excellent heat transfer characteristics of the sand, and burns the generated gas. Are often adopted. Various harmful gases are contained in the exhaust gas discharged from such a fluidized bed incinerator,
For example, since it contains N ₂ O gas, CO gas, NO _{X and the} like, various measures have been taken to reduce the emission of these harmful gases as much as possible. Examples of a fluidized bed incinerator for incinerating such incineration materials such as sewage sludge include, for example, JP-A-58-153016 (conventional example 1) and JP-A-7-17-1.
Japanese Patent No. 60125 (Conventional Example 2) is known. In addition, incinerated materials having a water content of 78 to 80 wt%, such as polymer-based sewage sludge, have low calories and are unlikely to raise the temperature in the combustion chamber. In some cases, HCN and the like are also generated. The fuel is supplied to increase the temperature in the combustion chamber.

First, an outline of a fluidized bed incinerator (fluidized bed incinerator) according to Conventional Example 1 is described in the same specification with reference to FIG. 7 which is an explanatory diagram of a method of operating a system around an incinerator. The reference numeral 1 shown in the figure is a fluidized bed of a fluidized bed incinerator, and a combustion chamber 2 is formed above the fluidized bed 1. A hot blast stove 5 for blowing hot air is provided in a wind box provided below the fluidized bed 1.
The combustion chamber 2 is provided with an auxiliary burner 3 and the combustion chamber 2 is provided with an ignition burner 4. An auxiliary fuel 8 is supplied to the hot blast stove 5, the auxiliary burner 3 and the ignition burner 4, and a combustion air 9 is supplied to the auxiliary burner 3 and the ignition burner 4. The auxiliary fuel 8 is supplied to the auxiliary burner 3 from two systems of fuel supply pipes branched on the way, and the auxiliary fuel 8 supplied from one of the fuel supply pipes reaches the temperature of the combustion chamber 2. The supply amount is controlled based on the supply amount.

Accordingly, when the temperature in the combustion chamber 2 decreases, a large amount of auxiliary fuel is supplied to the auxiliary combustion burner 3 to increase the temperature of the fluidized bed 1, and when the temperature increases, the auxiliary fuel supplied to the auxiliary combustion burner 3 Is controlled so that the temperature rise of the fluidized bed 1 is suppressed. Reference numeral 14 attached to the auxiliary burner 3 and the ignition burner 4 is a flame monitoring device. When a flame is detected by the flame monitoring device 14, in order to shorten the life and reduce the amount of power consumption, Burner burner 3
And an ignition device (not shown) provided in the ignition burner 4 is stopped.

[0005] Next, an outline of a suppressed fluidized-bed furnace (fluidized-bed incinerator) according to Conventional Example 2 will be described with reference to FIG. This will be described. That is, the suppression fluidized-bed furnace 1 and the temperature measuring device 4 for measuring the temperature in the combustion chamber of the suppression fluidized-bed furnace 1
When the atmosphere in the furnace is in the reduction region, the oxygen concentration signal is used as the oxygen deficiency signal. When the atmosphere in the furnace is in the oxidation region, the oxygen concentration signal is used. It comprises an oxygen analyzer 6 for measurement, a control valve 2 for adjusting the amount of combustion air supplied into the suppression fluidized-bed furnace 1, and a control device 10 for controlling the opening degree of the control valve 2. The opening of the control valve 2 is controlled in accordance with predetermined conditions based on the temperature in the combustion chamber measured in 4 and the oxygen concentration measured in the oxygen analyzer 6.

That is, the temperature of the combustion chamber or exhaust gas of the suppression fluidized-bed furnace 1 and the oxygen concentration in the exhaust gas are detected, and if the temperature of the combustion chamber of the suppression fluidized-bed furnace 1 or the temperature of the exhaust gas falls, it is determined that the amount of combustion air is too large. On the contrary, if the temperature rises, it is determined that the combustion air amount is too small, and the air supply amount is increased. If the oxygen concentration is too low, unburned gas is generated, so that the amount of combustion air is increased. If the oxygen concentration is high, it is determined that the amount of combustion air is large, and the amount of combustion air is reduced.

[0007]

By the way, in a fluidized bed incinerator, when burning air is supplied only to a wind box to incinerate an incinerated material, combustion is performed when the oxygen concentration is 4 to 6% (dry basis). Increasing the amount of air for use increases the rate of combustion in the fluidized bed (the ratio of sludge burning in the fluidized bed), so that the temperature of the fluidized bed rises while the oxygen concentration is 7 to 9% (dry basis). When the amount of combustion air is increased, the combustion rate in the fluidized bed further increases, and both the fluidized bed temperature and the combustion chamber temperature decrease due to an increase in the sensible heat of the exhaust gas due to an increase in the amount of exhaust gas. That is, the sensible heat of exhaust gas is reduced by reducing the amount of combustion air, and the temperature in the combustion chamber can be increased by decreasing the combustion rate in the fluidized bed and increasing the combustion ratio in the combustion chamber. However, when the oxygen concentration is lower than 6% (dry basis), there arises a problem that unburned gases such as CO and NH ₃ increase.

According to the fluidized bed incinerator according to Conventional Example 1,
Since the amount of auxiliary fuel supplied to the fluidized bed is controlled based only on the temperature in the combustion chamber, for example, a situation where the temperature of the fluidized bed and the temperature in the combustion chamber are 800 ° C. However, since the auxiliary fuel is always supplied to the fluidized bed, there is a disadvantage that the temperature of the fluidized bed becomes too high. This means that more auxiliary fuel is consumed than necessary.

That is, since the sensible heat of the exhaust gas increases with an increase in the amount of the exhaust gas, the heat output is increased by increasing the heat input by the auxiliary fuel to maintain the temperature. Further, if the properties of the sludge change or the supply amount of the sludge changes, the situation may result in a situation in which the amount of combustion air is too large, and the temperature in the combustion chamber also decreases. Of course, the supply amount of the auxiliary fuel is increased due to the decrease in the temperature of the combustion chamber, so that the fluidized bed temperature and the temperature of the combustion chamber are increased.
C. or higher, and various harmful gases such as HCN may be generated.

Next, in the suppressed fluidized-bed furnace according to Conventional Example 2, as described above, the oxygen concentration control and the combustion chamber temperature control are performed only by adjusting the air amount. It is difficult to satisfy the room temperature. Also,
In the case of a wide-area disposal site where sludge generated from several sewage treatment plants is collected and incinerated, it becomes more and more difficult due to changes in the properties of the sludge. That is, usually, the oxygen concentration in the exhaust gas is about 6% on a dry basis (air ratio: about 1.3 to 1.5).
However, if the properties of the sludge change, the temperature in the combustion chamber changes even if the oxygen concentration is kept constant. Therefore, regardless of the properties of the sludge, the temperature in the combustion chamber is set to N
_In order to decompose harmful gases such as ₂ O, CO, NO _X , HCN, and NH ₃ , the temperature must be 850 ° C. or higher (preferably closer to 900 ° C.). Oxygen concentration in exhaust gas is 6% on a dry basis to prevent
This is because it is necessary to keep the above.

In recent years, attention has been paid to environmental issues on a worldwide scale. In addition to incineration of municipal solid waste, incineration of sludge as well as fluidized bed incineration with an awareness of environmental conservation. Emphasis is placed on furnace design and operation. In particular, in the incineration of sludge, as described above, although various measures have been taken,
In addition to unburned gas such as CO, N that affects global warming
It has been reported that hundreds of ppm of ₂ O are emitted, and the necessity of countermeasures is emphasized. In addition, in the sludge incineration treatment using a fluidized bed incinerator, as described above, auxiliary fuel is indispensable because sludge has a high water content and low calorie, so reducing fuel consumption also improves the performance of the fluidized bed incinerator. It is an indispensable matter.

Accordingly, it is an object of the present invention is to stably incinerated in the sludge of any nature, N ₂ O gas in the exhaust gas generated in the sludge incineration, CO gas, harmful gas amount of such NO _X gas Another object of the present invention is to provide a method for incinerating sludge using a fluidized bed incinerator, which makes it possible to reduce fuel consumption and to reduce auxiliary fuel.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and therefore, the gist of the method for incinerating sludge by a fluidized bed incinerator according to claim 1 of the present invention is as follows.
The fluidized bed incinerator comprises a wind box, a fluidized bed above the wind box, a combustion chamber formed above the fluidized bed, and a flue gas outlet for discharging flue gas on the upper side. In the sludge incineration method using a fluidized bed incinerator for supplying and incinerating sludge to a bed, the oxygen concentration in the exhaust gas discharged from the exhaust gas outlet is a representative combustion chamber temperature selected from a combustion chamber temperature and a furnace top temperature. Control the supply amount of air for flow / combustion to be supplied to the wind box so that the concentration is set based on the temperature in the furnace, and the representative combustion chamber temperature is equal to or higher than the set temperature in the furnace, and the fluidized bed temperature is The auxiliary fuel is supplied to the fluidized bed in a controlled amount based on the representative combustion chamber temperature and the fluidized bed temperature.

The gist of the sludge incineration method using a fluidized bed incinerator according to claim 2 of the present invention is to provide a wind box, a fluidized bed above the wind box, and a combustion chamber above the fluidized bed. A sludge incineration method by a fluidized bed incinerator, which is formed and supplies sludge to the fluidized bed of the fluidized bed incinerator comprising an exhaust gas outlet for discharging exhaust gas on the upper side, and incinerates,
The oxygen concentration in the exhaust gas discharged from the exhaust gas outlet,
The supply amount of the flow / combustion air supplied to the wind box is controlled so that the concentration is set based on the representative combustion chamber temperature selected from the combustion chamber temperature and the furnace top temperature. When the temperature is lower than the preset furnace temperature, the auxiliary fuel is supplied to the fluidized bed in an amount corresponding to the temperature difference so that the representative combustion chamber temperature becomes equal to or higher than the furnace preset temperature. When the temperature is lower than the preset fluidized bed set temperature, the auxiliary fuel is supplied to the fluidized bed in an amount corresponding to the temperature difference so that the fluidized bed temperature becomes the fluidized bed set temperature. When the temperature in the furnace is lower than the set temperature and the fluidized bed temperature is lower than the set temperature in the fluidized bed, the representative combustion chamber temperature is higher than the set temperature in the furnace and the fluidized bed temperature is higher than the set temperature in the fluidized bed. Them An auxiliary fuel is controlled to an amount corresponding to degrees difference and supplying the fluidized bed.

The gist of the sludge incineration method using a fluidized bed incinerator according to claim 3 of the present invention is to provide a wind box, a fluidized bed above the wind box, and a combustion chamber above the fluidized bed. A sludge incineration method by a fluidized bed incinerator, which is formed and supplies sludge to the fluidized bed of the fluidized bed incinerator comprising an exhaust gas outlet for discharging exhaust gas on the upper side, and incinerates,
The oxygen concentration in the exhaust gas discharged from the exhaust gas outlet,
The supply amount of the flow / combustion air supplied to the wind box is controlled so that the concentration is set based on the representative combustion chamber temperature selected from the combustion chamber temperature and the furnace top temperature. When the temperature is lower than the preset furnace set temperature, an auxiliary fuel controlled to an amount corresponding to the temperature difference is supplied to the upper side of the fluidized bed so that the representative combustion chamber temperature becomes equal to or higher than the furnace set temperature, When the fluidized bed temperature is lower than the preset fluidized bed set temperature, auxiliary fuel controlled to an amount corresponding to the temperature difference between the fluidized bed temperature and the fluidized bed set temperature is set to the lower side of the fluidized bed so that the fluidized bed temperature becomes higher than the fluidized bed set temperature. It is characterized by supplying.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, a sludge incineration test is carried out by a fluidized bed incinerator, and N ₂ O, CO, NO
_This was done by seeking operating conditions for simultaneously reducing the harmful gases of _X. Hereinafter, such N ₂ O, CO,
The events that led to obtain simultaneously reduced to operating conditions harmful gases NO _X, the relationship explanation graph of oxygen concentration and N ₂ O, CO concentration of the oxygen concentration and temperature in the combustion chamber and in the exhaust gas in the exhaust gas 4 When, as in FIG. 5 of the relationships described graph of the combustion chamber temperature and the NO _X concentration, combustion chamber temperature and N ₂ O, CO,
Successively it will be described with reference to the Figure 6 Relationship Description graph of NO _X.

FIG. 4 shows the relationship between the oxygen concentration in the exhaust gas and the furnace top temperature by open circles and solid lines, the relationship between the oxygen concentration in the exhaust gas and the temperature in the combustion chamber by black circles and solid lines, and FIG. The relationship between the concentration and the fluidized bed temperature is indicated by a black triangle and a solid line, the relationship between the oxygen concentration in the exhaust gas and the N ₂ O concentration is indicated by a black circle and a solid line, and the relationship between the oxygen concentration and the CO concentration in the exhaust gas is indicated by a white circle and a solid line. Each is shown. Further, the oxygen concentration (%) in the exhaust gas is shown on a dry basis, that is, the oxygen concentration in the exhaust gas after removing the water vapor.

The emission characteristics of N ₂ O and CO will be described with reference to FIG. First, the N ₂ O emission concentration is more affected by the temperature in the combustion chamber than by the temperature of the fluidized bed. That is, as can be clearly understood from the figure, the generation amount decreases with an increase in the temperature of the combustion chamber, and raising the temperature of the combustion chamber is effective for reducing N ₂ O. In addition, the following two cases can be considered as the CO emission concentration. Case 1: O ₂ deficiency Case 2: O ₂ is sufficient but C is low due to low temperature
Insufficient oxidation of O In other words, to reduce CO, it is necessary to raise the temperature of the combustion chamber and control the oxygen concentration.

Next, the discharge characteristics of the NO _X, will be described with reference to FIG. 5, NO _X is gradually increasing number generation amount with a rise in temperature in the combustion chamber, the absolute amount of N ₂ O Ya C
It is much smaller than O.

N ₂ O, C with respect to oxygen concentration in exhaust gas
O, it is shown in FIG. 6 when merging NO _X concentration and the combustion chamber temperature. Therefore, when incinerating sludge,
As can be clearly understood from the figure, when the fluidized bed incinerator is operated in a region where the oxygen concentration in the exhaust gas is indicated by oblique lines, the emission of these N ₂ O, CO and NO _X is reduced. It becomes possible to do.

Hereinafter, a fluidized bed incinerator (N ₂ O, C in exhaust gas) according to Embodiment 1 for realizing the sludge incineration method of the present invention will be described.
O, and also used to determine the operating conditions for the same time reducing harmful gases NO _X. ) Will be described with reference to FIG. 1 of a schematic structural explanatory view. Reference numeral 1 shown in the figure is a fluidized bed incinerator, and the fluidized bed incinerator 1 is a primary air to be described later for supplying air for fluidizing / combustion. A wind box 1a communicating with the supply pipe 2; a fluid bed 1b provided on the wind box 1a and communicating with an auxiliary fuel supply pipe 3 for supplying auxiliary fuel; formed above the fluid bed 1b; No secondary air supply pipe (However, when incinerating polymer sludge, unburned gas combustion air is not supplied from the secondary air supply pipe,
Only the air for flow and combustion through the primary air supply pipe 2 is supplied. ) Communicates with each other, and an exhaust gas outlet 1d for discharging exhaust gas that opens at an upper position of the combustion chamber 1c.

An exhaust gas duct 4 communicates with the exhaust gas outlet 1d, and the exhaust gas discharged from the exhaust gas duct 4 is supplied to the wind box 1a via, for example, a waste heat boiler (not shown) or a primary air supply pipe 2. The air is discharged from the chimney to the atmosphere via an air heater, a dust collector, etc., for heating the flowing air for combustion. The primary air supply pipe 2 communicating with the wind box 1a is provided with a primary air supply blower 2a and a primary air flow control valve 2b in order from the wind box 1a side. Thereby, sand made of silica sand or the like constituting the fluidized bed 1b is fluidized, and incineration of sludge is performed.

The operation of the fluidized bed incinerator having such a configuration is performed by an operation control system described later. That is, the exhaust gas outlet 1d at the furnace top of the fluidized bed incinerator 1
In the vicinity, there is a furnace top thermometer 5 for detecting the temperature of the furnace top, and in the center of the fluidized bed incinerator 1, there is a combustion chamber middle part thermometer 6 for detecting the temperature of the middle part of the combustion chamber 1c. 1, a lower combustion chamber thermometer 7 for detecting the temperature of the lower part of the combustion chamber 1c is attached to each of the thermometers 5.
The detected temperatures detected in 6 and 7 are input to a selector 11 for selecting an intermediate temperature between the highest temperature and the lowest temperature as a representative combustion chamber temperature.

As described above, the temperature of the representative combustion chamber is detected by the three thermometers 5, 6, 7 because the maximum temperature, the intermediate temperature, and the minimum temperature depend on the combustion state of sludge and the combustion state of unburned gas. Is changed, but even if it changes, the intermediate temperature is selected as the representative combustion chamber temperature,
If the selected representative room temperature is controlled to be 850 ° C., the maximum temperature in the combustion chamber can always be maintained at 850 ° C. or higher, and the temperature in the combustion chamber can be prevented from rising excessively. .

The representative combustion chamber temperature output from the selector 11 is lower than the representative combustion chamber temperature output from the selector 11 (usually set to 850 ° C. or higher). When the oxygen concentration in the exhaust gas is lowered and the representative combustion chamber temperature is higher than the furnace set temperature, the oxygen concentration set value is obtained by a function signal from the function generator 13 which outputs a function to increase the oxygen concentration in the exhaust gas as a signal. Is input to an oxygen concentration controller 14 that compares this oxygen concentration set value with an oxygen concentration detection value from an oxygen concentration meter 9 provided in the exhaust gas duct 4. The oxygen concentration controller 14 compares the oxygen concentration set value with the oxygen concentration detection value, and sends the oxygen concentration detection value to the primary air flow control valve 2 b provided in the primary air supply pipe 2. When the oxygen concentration detection value is higher than the oxygen concentration set value, the opening degree control signal is controlled to decrease the flow / combustion air amount when the oxygen concentration detection value is higher than the oxygen concentration set value. , Primary air flow detector 1
This is input via the primary air flow controller 15 to which the detected value of the flow / combustion air amount is input from 0.

The representative combustion chamber temperature output from the selector 11 is input to the furnace temperature controller 12 in parallel with the function generator 13. The in-furnace temperature controller 12 compares a preset in-furnace set temperature with a representative combustion chamber temperature input from the selector 11, and when the representative combustion chamber temperature is lower than the in-furnace set temperature, A control signal for supplying an amount of auxiliary fuel according to the degree of the temperature difference is input to the adder 17. On the other hand, the adder 17 includes a preset fluidized bed set temperature (normally set to 700 ° C. or higher) and a fluidized bed temperature detection value from the fluidized bed thermometer 8 for detecting the fluidized bed temperature. When the detected value of the fluidized bed temperature is lower than the set temperature of the fluidized bed, a control signal is supplied from the fluidized bed temperature controller 16 to supply an auxiliary fuel in an amount corresponding to the degree of the temperature difference. You.

That is, when the representative combustion chamber temperature is higher than the furnace set temperature and the fluidized bed temperature is higher than the fluidized bed set temperature, the adder 17 detects one of the detected temperatures so as not to supply auxiliary fuel. Is lower than the set temperature, the auxiliary fuel is supplied in an amount corresponding to the temperature difference, and if any of the detected temperatures is lower than the set temperature, the added amount of auxiliary fuel is supplied. This is for controlling the auxiliary fuel control valve 3a interposed in the pipe 3.

Therefore, if the representative combustion chamber temperature does not rise to the furnace set temperature by adjusting the amount of flow / combustion air supplied to the wind box 1a, the fluidized bed 1b will be switched between the representative combustion chamber temperature and the furnace set temperature. Since the amount of auxiliary fuel is supplied according to the temperature difference, the temperature of the representative combustion chamber is increased until the temperature in the furnace reaches the set temperature in the furnace. Conversely, if the representative combustion chamber temperature becomes equal to or higher than the furnace set temperature by adjusting the flow / combustion air supply to the wind box 1a, no auxiliary fuel is supplied. Also,
When the properties of the sludge change and the temperature of the fluidized bed 1b decreases,
Regardless of the representative combustion chamber temperature, the auxiliary fuel is immediately supplied to the fluidized bed 1b, and the temperature rise of the fluidized bed 1b prevents the combustion chamber temperature from lowering, so that the generation amount of various harmful gases such as HCN is reduced. can do.

Next, in the suppressed fluidized-bed furnace according to the conventional example 2, the oxygen concentration control and the temperature control are performed only by adjusting the air amount, and it is difficult to satisfy both the oxygen concentration condition and the temperature condition at the same time. According to the first embodiment, as described above, a controlled amount of auxiliary fuel is supplied to the fluidized bed based on the representative combustion chamber temperature and the fluidized bed temperature, and the fluidized bed 1b is controlled to follow the temperature decrease. Since the temperature is immediately increased, it is possible to reliably cope with incineration of sludge having different properties. Then, since the temperature in the combustion chamber can be prevented from lowering due to the increase in the temperature of the fluidized bed 1b, the temperature of 850 ° C. or higher required for decomposing harmful gases such as NH ₃ and HCN can be maintained. Further, since a necessary amount of the air for flow / combustion is supplied to the wind box 1a under the control of the oxygen concentration controller 14, the generation of unburned gas such as CO is suppressed.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
With reference to (a), (b), and (c), the oxygen concentration in the exhaust gas is 3% on a wet basis (6.7 on a dry basis) using the fluidized bed incinerator according to the first embodiment of the present invention. %.)
(See FIG. 2C). In addition, an example in which sludge (polymer sludge) is incinerated while controlling the representative combustion chamber temperature to be 850 ° C. or higher will be described. The representative combustion chamber temperature is shown in FIG. As described above, the temperature is 850 ° C. or higher without supplying the auxiliary fuel to the fluidized bed, and the N ₂ O and CO concentrations in the exhaust gas are stably low as shown in FIG. Level.

The operation results of the fluidized bed incinerator are as shown in Table 1.

[Table 1] According to Table 1, the average concentrations of N ₂ O, CO, and NO _{x in} the exhaust gas are 17 ppm, 29 ppm, and 6 pp, respectively.
m is extremely low, for example, several hundred pp in N ₂ O.
It is significantly below the reported value of m. Note that FIG.
As shown in (b), since the representative combustion chamber temperature is maintained at 850 ° C. or higher, HCN is not decomposed and generated.

The case where the present control is performed (hereinafter referred to as “after execution”) and the case where typical control for performing constant control of the flow / combustion air and the fluidized bed temperature are not performed (hereinafter referred to as “before execution”). The differences in the consumption of the auxiliary fuel (heavy oil) and the differences in the power consumption between the primary air supply blower 2a and the inducing fan (not shown) were examined. The results are as shown in Table 2.

[Table 2] According to Table 2 above, heavy oil consumption is reduced by about 70%. This is because, by performing the constant control of the oxygen concentration in the exhaust gas, no wasteful combustion air is supplied, and the amount of the exhaust gas is reduced. As a result, the ratio of the sensible heat carried out of the exhaust gas is reduced. Further, the power consumption of the primary air supply blower 2a and the inducing fan is reduced by 6.5%, suggesting that the amount of exhaust gas has been reduced.

Next, Table 3 shows the heat balance of the fluidized bed incinerator before and after the control. Table 3 shows the case where the polymer sludge is incinerated, and the calorific value of the polymer sludge is set to 100, and all other values are indicated by the ratio.

[Table 3] According to Table 3 above, the ratio of the retained heat, latent heat of vaporization, and heat release of the air for flow / combustion to the amount of heat of the sludge has not changed much, but the ratio of the sensible heat of the exhaust gas is 69.4% before the implementation. On the other hand, it decreased to 59.8% after the implementation, which clearly indicates that the calorific value of the sludge was effectively used.

In the above, the case where the oxygen concentration in the exhaust gas is controlled to be constant at 3% on a wet basis has been described as an example. By the way, it is known that the water content varies considerably depending on the type of sludge. For example, the water content of polymer sludge is 78 to 80 wt%, and the water content of lime sludge is 60 to 70% wt. Therefore, when the oxygen concentration in the exhaust gas is controlled on a wet basis, the moisture content in the exhaust gas is targeted at 6.7% on a dry basis depending on the moisture content of the sludge to be incinerated because the proportion of water vapor in the exhaust gas is different. It is preferable to change the value of the oxygen concentration at the base.

Next, a fluidized bed incinerator according to a second embodiment for realizing the sludge incineration method of the present invention will be described with reference to FIG. Only described below. That is, as is well understood from FIG. 3, the operation control system of the fluidized bed incinerator according to the second embodiment includes an upper auxiliary fuel control valve 3 on the upper side of the fluidized bed 1b.
a is connected to the upper auxiliary fuel supply pipe 3 in which the lower auxiliary fuel control valve 3 is connected to the lower side of the fluidized bed 1b.
a 'is connected to the lower auxiliary fuel supply pipe 3' in which the upper auxiliary fuel control valve 3a is directly controlled by the furnace temperature controller 12, and the lower auxiliary fuel control valve 3a 'is The configuration is directly controlled by the adjuster 16, and the other configuration is exactly the same as that of the first embodiment.

The operation of the fluidized bed incinerator according to the second embodiment will be described below. If the temperature of the fluidized bed is lower than 700 ° C., for example, the auxiliary fuel is supplied from the lower auxiliary fuel supply pipe 3 ′ to the lower side of the fluidized bed 1b. Is supplied and the combustion rate of the auxiliary fuel in the fluidized bed is high, so that the temperature of the fluidized bed rises. On the other hand, if the temperature in the combustion chamber is lower than 850 ° C., auxiliary fuel is supplied from the upper auxiliary fuel supply pipe 3 to the upper side of the fluidized bed 1b. In this case, the combustion rate of the auxiliary fuel in the fluidized bed is low. It does not contribute much to the rise, and most of the heat of combustion of the auxiliary fuel is spent on raising the temperature in the combustion chamber. Therefore, the fluidized bed temperature and the combustion chamber temperature can be appropriately maintained, and the fluidized bed temperature can be reliably prevented from rising excessively. Incidentally, when the auxiliary fuel is supplied from the lower auxiliary fuel supply pipe 3 'to the lower side of the fluidized bed 1b, the combustion rate of the auxiliary fuel in the fluidized bed is 80%. The combustion rate of auxiliary fuel in the fluidized bed when supplied to the upper side is 60%.

[0037]

As described above, according to the first and second aspects of the present invention,
According to the sludge incineration method using the fluidized bed incinerator according to 2 or 3, the auxiliary fuel is supplied to the fluidized bed in a controlled amount based on the representative combustion chamber temperature and the fluidized bed temperature. Even when the combustion chamber temperature is 800 ° C., the fluidized bed temperature does not become excessively high as in Conventional Example 1 in which auxiliary fuel is supplied to the fluidized bed.
The consumption of the auxiliary fuel and the supply of the combustion air are suppressed. Further, when the fluidized bed becomes cold due to a change in the properties of the sludge, auxiliary fuel is immediately supplied, and the temperature of the fluidized bed rises, preventing the temperature in the combustion chamber from dropping. Can be reduced. Furthermore, since the control is based on the representative combustion chamber temperature and the fluidized bed temperature as described above, instead of the method of performing the oxygen concentration control and the temperature control only by adjusting the air amount as in Conventional Example 2, the temperature decreases. The temperature of the fluidized bed is increased to follow the incineration of sludge with different properties, so that NH ₃
It can contribute to the reduction of the generation amount of harmful gases such as HCN and HCN.

[Brief description of the drawings]

FIG. 1 is a first embodiment for realizing a sludge incineration method of the present invention.
It is a schematic structure explanatory view of the fluidized-bed incinerator which concerns on.

FIGS. 2 (a), 2 (b), and 2 (c) are explanatory diagrams of the operating state of a fluidized bed incinerator according to Embodiment 1 for realizing the sludge incineration method of the present invention.

FIG. 3 is a second embodiment for realizing the sludge incineration method of the present invention.
It is a schematic structure explanatory view of the fluidized-bed incinerator which concerns on.

FIG. 4 is a graph illustrating the relationship between oxygen concentration in exhaust gas and representative combustion chamber temperature, and oxygen concentration in exhaust gas and N ₂ O and CO concentrations.

5 is a relation explanatory graph of a representative temperature in the combustion chamber and the NO _X concentration.

FIG. 6 is a graph illustrating the relationship between a representative combustion chamber temperature and N ₂ O, CO, and NO _X.

FIG. 7 is an explanatory diagram of an operation method of a system around an incinerator of a fluidized bed incinerator (fluidized bed incinerator) according to Conventional Example 1.

FIG. 8 is a diagram showing a configuration of a suppression fluidized-bed furnace (fluidized-bed incinerator) according to Conventional Example 2.

[Explanation of symbols]

1: Fluid bed incinerator, 1a: Wind box. 1b ... fluidized bed, 1c ...
Combustion chamber, 1d: exhaust gas outlet, 2: primary air supply pipe, 2a
... Primary air supply blower, 2b ... Primary air flow control valve 3
... Auxiliary fuel supply pipe or upper auxiliary fuel supply pipe, 3a ...
Auxiliary fuel control valve or upper auxiliary fuel control valve, 3 '... lower auxiliary fuel supply pipe, 3a' ... lower auxiliary fuel control valve, 4 ...
Exhaust gas duct, 5: Furnace top thermometer, 6: Combustion chamber middle thermometer, 7: Combustion chamber lower thermometer, 8: Fluidized bed thermometer, 9 ...
Oxygen concentration meter, 10 primary air flow detector, 11 selector, 12 furnace temperature controller, 13 function generator, 14
Oxygen concentration controller, 15: Primary air flow controller, 16: Fluidized bed temperature controller, 17: Adder.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location F23G 5/50 ZAB F23G 5/50 ZABH ZABJ F23N 5/00 F23N 5/00 J

Claims (3)

[Claims] An air box is provided, a fluidized bed is provided above the wind box, and a combustion chamber is formed above the fluidized bed.
In a sludge incineration method using a fluidized bed incinerator that supplies sludge to the fluidized bed and incinerates the fluidized bed of a fluidized bed incinerator having an exhaust gas outlet for discharging exhaust gas on the upper side, oxygen in exhaust gas discharged from the exhaust gas outlet is The flow / flow supplied to the wind box so that the concentration becomes a concentration set based on the representative combustion chamber temperature selected from the combustion chamber temperature and the furnace top temperature.
Amount controlled based on the representative combustion chamber temperature and the fluidized bed temperature such that the supply amount of combustion air is controlled and the representative combustion chamber temperature is equal to or higher than the furnace set temperature, and the fluidized bed temperature becomes the fluidized bed set temperature. A sludge incineration method using a fluidized bed incinerator, wherein the auxiliary fuel is supplied to a fluidized bed. 2. A wind box is provided, a fluidized bed is provided above the wind box, and a combustion chamber is formed above the fluidized bed.
In a sludge incineration method using a fluidized bed incinerator that supplies sludge to the fluidized bed and incinerates the fluidized bed of a fluidized bed incinerator having an exhaust gas outlet for discharging exhaust gas on the upper side, oxygen in exhaust gas discharged from the exhaust gas outlet is The flow / flow supplied to the wind box so that the concentration becomes a concentration set based on the representative combustion chamber temperature selected from the combustion chamber temperature and the furnace top temperature.
In addition to controlling the supply amount of combustion air, when the representative combustion chamber temperature is lower than a preset furnace preset temperature, an amount corresponding to the temperature difference is set so that the representative combustion chamber temperature becomes equal to or higher than the furnace preset temperature. Is supplied to the fluidized bed, and when the fluidized bed temperature is lower than the preset fluidized bed set temperature, the fluidized bed temperature is controlled to an amount corresponding to the temperature difference so that the fluidized bed temperature becomes the fluidized bed set temperature. When the representative combustion chamber temperature is lower than the furnace set temperature and the fluidized bed temperature is lower than the fluid bed set temperature, the representative combustion chamber temperature is higher than the furnace set temperature. A method for incinerating sludge by a fluidized bed incinerator, characterized in that an auxiliary fuel controlled to an amount corresponding to the temperature difference between the fluidized bed and the fluidized bed is set to a temperature equal to or higher than a set temperature of the fluidized bed to the fluidized bed. 3. A wind box, a fluidized bed is provided above the wind box, and a combustion chamber is formed above the fluidized bed.
In a sludge incineration method using a fluidized bed incinerator that supplies sludge to the fluidized bed and incinerates the fluidized bed of a fluidized bed incinerator having an exhaust gas outlet for discharging exhaust gas on the upper side, oxygen in exhaust gas discharged from the exhaust gas outlet is The flow / flow supplied to the wind box so that the concentration becomes a concentration set based on the representative combustion chamber temperature selected from the combustion chamber temperature and the furnace top temperature.
In addition to controlling the supply amount of combustion air, when the representative combustion chamber temperature is lower than a preset furnace preset temperature, an amount corresponding to the temperature difference is set so that the representative combustion chamber temperature becomes equal to or higher than the furnace preset temperature. Is supplied to the upper side of the fluidized bed, and when the fluidized bed temperature is lower than the preset fluidized bed set temperature, the temperature difference between them is adjusted so that the fluidized bed temperature becomes higher than the fluidized bed set temperature. A method for incinerating sludge by a fluidized bed incinerator, characterized in that an auxiliary fuel controlled to a corresponding amount is supplied to a lower side of a fluidized bed.