JPH09273732A - Control method of combustion in incinerating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize combustion and obtain a given generating amount of steam by a method wherein the amount of drying air and the speed of a drying grating are controlled in accordance with the fluctuation of the quality of wastes. SOLUTION: The temperature in a furnace at the upstream side of a combustion grating 3b is measured and the opening degree of air damper 12a below a drying grating and the like is corrected or the speed of a drying grating 3a is corrected employing a function, using the measured value as a parameter, whereby even humid wastes can be burnt under sufficiently dried condition. Fuzzy control is employed for the control of the amount of air and the speed of drying grating except linear control. According to this method, drying is enhanced immediately so as to be compatible even when the supplied wastes are changed to humid wastes whereby the condition of combustion is stabilized and a given generating amount of steam can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control method for a grate type refuse incinerator, and more particularly to a control method for stabilizing the steam generation amount in a boiler by keeping the combustion state constant. .

[0002]

2. Description of the Related Art Municipal solid waste incinerators play an important role in treating various wastes discharged in social life. In recent years, interest in recovering the enormous amount of heat energy generated by incineration of waste, which is waste, has increased, and the number of boilers equipped with a power generation facility has increased.

In the refuse incinerator, the refuse is intermittently thrown into the hopper by a crane at intervals of several tens of minutes, and there is a drying grate under the hopper, and the drying grate feeds the refuse into the furnace. The grate in the furnace consists of several stages,
The waste is dried by the first-stage dry grate, then flows to the next combustion grate, and further flows to the post-combustion grate to be discharged as ash.

In order to maintain a good combustion state, air for drying or burning dust is blown from under each grate, and the air amount is adjusted by each air damper. The air blown under the dry grate is called dry air to distinguish it from the air blown under other grate, but when these airs are collectively referred to as combustion air, the furnace wall It is distinguished from the cooling air blown from another blowing port to prevent overheating of the.

Combustion gas generated by the combustion of refuse is
Boiler water is heated by a heat exchanger provided at the furnace outlet and then discharged. The temperature inside the furnace is measured upstream of the combustion grate, and in addition, the temperature at the furnace outlet is measured at the exit of the furnace, i.e. before the heat exchanger. In such a refuse incinerator, automatic combustion control is performed in order to keep the furnace outlet temperature constant and stably supply steam, and the combustion air amount, cooling air amount, grate velocity, etc. are controlled.

In order to stabilize the amount of steam generated in the boiler (hereinafter referred to as the amount of evaporation), it is necessary to control the amount of dust, which is a heat source, and to control the combustion state of the dust to keep the calorific value constant. There is. The properties and components of waste are not constant, and the amount of heat supplied is not constant only by controlling the amount of waste. In particular, when dust with a high water content is supplied, even if dust that has not been sufficiently dried on the dry grate is carried into the combustion grate, it will not burn immediately and the furnace outlet temperature and evaporation amount will decrease.

Conventionally, in order to prevent the above-mentioned decrease in the evaporation amount,
A method has been proposed in which waste having a large bulk specific gravity containing water and dry waste having a small bulk specific gravity are burned by changing the amount of dry air. For example, in Japanese Unexamined Patent Application Publication No. 2-106610, the weight of dust caught in a grab bucket of a crane is measured, and the bulk specific gravity is calculated by dividing the weight by the grip volume of the grab bucket. Corresponding to this bulk specific gravity , A control method for adjusting the amount of air under a dry grate is described.

[0008]

However, in reality, it is difficult to know exactly where in the furnace the dust thrown in the past is at present, so the amount of dry air is given at the wrong timing. There was an occasion. For example, when the bulk specific gravity is large, even if the amount of dry air is increased at the same time as the charging by the grab bucket, at that time, there is often dust that has been injected two times before on the dry grate.

Therefore, although it is necessary to increase the amount of dry air a short time after the charging, the timing may be wrong. In addition, the garbage component in the grab bucket is not constant, some of the garbage contains a large amount of water, and other garbage may be normal. Therefore, it may be judged that the garbage has a large amount of water only because it has a large bulk specific gravity. Can not. For this reason, the above method has a problem in that sufficiently accurate control cannot be performed.

The present invention has been made in order to solve such a problem, and it is possible to estimate the dry and wet state of refuse which has begun to be burned in consideration of the time delay until the thrown refuse is burned. Based on the measured value of the temperature in the furnace, the air damper control is performed, or at the same time, the control of the dry grate velocity is also used to stabilize the evaporation amount.

[0011]

A first aspect of the present invention is a combustion method for a refuse incinerator, in which air is fed from below the grate and burned in the furnace while moving the garbage on the grate, and a combustion grate upstream part. The upper furnace temperature is measured, and when this temperature is higher than the reference value, the air damper opening under the dry grate is reduced, and when it is lower than the reference value, the air damper control under the dry grate is increased. This is a combustion control method for a waste incinerator.

The temperature inside the furnace above the upstream part of the combustion grate reflects the combustion state of dust from the dry grate to the combustion grate. When the amount of water in the dust moving from the dry grate to the combustion grate is large, the internal temperature of the furnace decreases because of the latent heat of vaporization and poor ignition of the dust. About 30 minutes to 1 hour has passed, and this poorly-dried waste does not burn immediately when it reaches the main combustion part of the combustion grate, so the furnace outlet temperature decreases and a constant amount of evaporation can be maintained. Disappear.

When the temperature inside the furnace above the combustion grate is measured, when the measured value begins to fall below the reference value, the combustion state of dust from the dry grate to the combustion grate begins to deteriorate. You can judge that At this time, increase the damper opening of the air under the dry grate to increase the amount of dry air and accelerate the drying of the waste, so that the water vaporizes before the waste moves to the main combustion part of the combustion grate. Can be made.

Further, if the dust is dried, combustion becomes active, and the temperature inside the furnace above the upstream part of the combustion grate becomes higher than the reference value. When the temperature starts to exceed the reference value, the damper opening of the air under the dry grate is reduced to prevent excessive dry air blowing.

A second aspect of the present invention is a refuse incinerator for performing air damper control by correcting the air damper opening below the combustion grate in synchronization with the correction of the air opening below the dry grate in the air damper control. It is a combustion control method.

The main combustion takes place on the combustion grate, with the combustion grate being the longest. Therefore, air is blown into the combustion grate from two places. There are two locations, below the combustion grate upstream near the dry grate and below the combustion grate downstream near the post-combustion grate. Adjusted by damper.

Not only is the damper opening of the air below the dry grate corrected, but the damper opening of the air below the combustion grate is also corrected in synchronization with this correction. That is, when the furnace temperature above the combustion grate upstream is higher than the reference value, the dry grate lower air damper opening and the combustion grate upstream lower air damper opening are decreased, and when it is lower than the reference value, the dry grate is lower. Increase the lower air damper opening and the lower air damper opening upstream of the combustion grate.

These corrections further enhance the control effect. For waste that contains a large amount of water and is particularly difficult to dry, it may still be insufficient to dry even if it passes over the dry grate, but the dryness is enhanced by synchronizing the damper opening of the air under the combustion grate. , It can be turned into good quality waste and maintain stable combustion.

A third invention is a combustion control method for a refuse incinerator according to the first invention or the second invention, wherein fuzzy control is used for the air damper control.

As described above, the temperature in the furnace above the upstream part of the combustion grate is measured, and the amount of air is controlled using this as a parameter. However, as described above, the property of dust is indefinite, and the amount of combustion heat is constant. Not. For this reason, the change in temperature may be finely detected and the air amount may be linearly changed one by one, but there is a tendency to cope with a slight change in temperature too much. Is the temperature high?
It is more realistic to grasp whether it is normal or low and to relate it to the air volume in a non-linear manner. Fuzzy control is suitable as the air amount damper control for the furnace temperature.

A fourth aspect of the present invention performs the air damper control of the first aspect of the present invention, and increases the dry grate speed to a reference value when the temperature inside the furnace above the upstream portion of the combustion grate is higher than the reference value. It is a combustion control method for a refuse incinerator that performs grate speed control to reduce the dry grate speed when the temperature is lower than the above.

When the dust is dried, combustion becomes active, and the temperature inside the furnace above the upstream part of the combustion grate becomes higher than the reference value. At this time, the damper opening of the air under the dry grate is reduced to suppress excessive blowing of the dry air, and the dry grate speed is increased to allow the dry dust to pass faster.

On the contrary, if the dust contains a large amount of water, the combustion becomes inactive, and the temperature in the furnace above the combustion grate upstream becomes lower than the reference value. At this time, the damper opening of the air under the dry grate is increased to increase the amount of the dry air blown in, and the speed of the dry grate is decelerated to lengthen the drying time so that there is a margin for drying.

By using the control of the air damper under the dry grate and the control of the dry grate speed together, the combustion in the furnace as a whole can be further stabilized and the steam generation amount of the boiler can be kept constant.

A fifth aspect of the present invention performs the air damper control of the second aspect of the present invention, and increases the dry grate speed to a reference value when the furnace temperature above the upstream part of the combustion grate is higher than the reference value. It is a combustion control method for a refuse incinerator that performs grate speed control to reduce the dry grate speed when the temperature is lower than the above.

When the dust is dried, combustion becomes active and the temperature inside the furnace above the upstream part of the combustion grate becomes higher than the reference value. At this time, the damper opening of the air under the dry grate and the damper opening of the air under the combustion grate upstream are reduced to further suppress the excessive blowing of the dry air and the blowing of the combustion air in the first half of the furnace, and the drying fire. The grid speed is increased to allow dry debris to pass faster.

On the contrary, if the dust contains a large amount of water, the combustion becomes inactive, and the temperature inside the furnace above the upstream part of the combustion grate becomes lower than the reference value. At this time, the damper opening of the air below the dry grate and the damper opening of the air below the combustion grate upstream are increased to increase the amount of dry air blown in, and the drying grate speed is reduced to lengthen the drying time. Allow some time to dry.

By combining the control of the air damper under the dry grate and the air damper under the combustion grate upstream and the dry grate velocity control together, the overall combustion in the furnace is further stabilized,
The amount of steam generated by the boiler can be kept constant.

A sixth invention is a combustion control method for a refuse incinerator according to the fourth invention or the fifth invention, wherein fuzzy control is used for the dry grate velocity control.

In the dry grate speed control as well as in the air damper control, a method in which the temperature and the amount of supplied dust are nonlinearly related to each other rather than linearly changing the air amount by finely grasping the temperature change. Conforms to reality. like this,
Fuzzy control is suitable as an air amount damper control for the furnace temperature.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION An example in which the air amount control method according to the present invention is applied will be described with reference to the drawings. FIG. 1 is a diagram showing the concept of a refuse incinerator and control means. In Figure 1,
Reference numeral 1 denotes a furnace, which has a dust inlet 2, a dry grate 3a, a combustion grate 3b, a post-combustion grate 3c, and an ash drop port 4. The dust introduced from the dust inlet is dried or burned by the air supplied from the combustion air blower 5.

The air from the combustion air blower 5 is distributed by a dry grate lower air damper 13a, a combustion grate upstream lower air damper 13b, a combustion grate downstream lower air damper 13c, and a post combustion grate lower air damper 13d. The dry grate air amount, the combustion grate upstream air amount, the combustion grate downstream air amount, and the post-combustion grate air amount are adjusted respectively.

The waste is mainly dried in the dry grate 3a, the waste is burned in the combustion grate 3b, and the post-combustion grate 3 is used.
In c, the dust is completely burned out and becomes ash. After burning,
The ash drops from the ash drop port 4 and is discharged to the outside of the furnace, and the exhaust gas generated by combustion is guided from the furnace outlet 6 to the chimney 7 and discharged to the outside of the furnace. A steam generator boiler 8b equipped with a heat exchanger 8a is installed at the exit of the furnace where the exhaust gas is discharged. Further, cooling air 10 is blown from the cooling air blowing port 9 so that the temperature in the furnace does not rise excessively.

Reference numeral 11 is a thermometer for measuring the furnace outlet temperature in the exhaust gas, and 12 is a flow meter for measuring the evaporation amount. Reference numeral 14 denotes an in-furnace thermometer that measures the temperature in the furnace upstream of the combustion grate 3b, and is arranged above the front part of the combustion grate 3b. Reference numeral 15 is a control means, which receives a signal from the in-core thermometer as an input, and uses a dry grate lower air damper 13a and a combustion grate upstream lower air damper 13
b, and outputs signals to the dry grate drive 16.
A computer is used for the control means 15, for example.

A method of controlling the air damper under the dry grate will be described below. The control is performed according to the rules shown in Table 1.

[0036]

[Table 1]

The correction of the opening of the air damper under the dry grate is as follows.
When the conditions (1) to (3) are satisfied, the control indicated by the arrow (⇒) is executed. The determination of the conditions (1) to (3) is performed at regular intervals,
The correction amount for each cycle is calculated, the calculation result is used as the increase / decrease amount in that cycle, and this increase / decrease amount is added to the opening degree from normal combustion control to output the air damper opening under the dry grate this time. It becomes a value.

The calculation of the correction amount and the output value will be specifically described as follows. First, the case of linear control will be described. Assuming that the reference range upper limit value of the furnace temperature above the combustion grate upstream part is T ₁ , the lower limit value is T ₂ , the measured value is T, and the opening correction amount is Z ₁ , the following (1 Z ₁ is calculated from the equations (1), (2), and (3).

[0039]

[Equation 1]

[0040]

[Equation 2]

[0041]

(Equation 3)

However, k ₁ and k ₂ are control parameters. Then, the calculated Z ₁ is added to the damper opening Z ₀ determined by the normal combustion control by the equation (4) to calculate the damper opening output signal Z.

[0043]

(Equation 4)

Above, regarding the air damper under the dry grate,
Although the specific method of the correction has been described, the same applies to the air damper upstream of the combustion grate. That is, in the above description, the dry grate lower air damper is read as the combustion grate upstream lower air damper to control the combustion grate upstream lower air damper. When controlling the air damper opening below the dry grate as well as the air damper upstream of the combustion grate, both controls are performed in synchronization.

The choice between controlling only the air damper under the dry grate and controlling the air damper under the upstream part of the combustion grate in synchronization with the air damper under the dry grate is not limited at all. However, if, for example, only the air damper opening under the dry grate is corrected at all times and only the same conditions continue to appear, the air damper opening under the dry grate and the air damper opening under the combustion grate upstream part are opened together. Are selected in the same manner.

Next, a method in which fuzzy control is used for air damper control will be described with an example of the air damper opening under the dry grate.

The control is performed according to the rules shown in Table 2. Further, in order to calculate the control amount, the inputs and outputs are organized, and the control parameter Y is determined and shown in Table 3.

[0048]

[Table 2]

[0049]

[Table 3]

The operations of rules (1) to (3) are performed based on the membership function shown in FIG. The inference result of the consequent part of each rule obtained by the damper opening control means is integrated, and the inference result of the entire rule is output. A general method of fuzzy operation, such as a min-max centroid method or a singleton method, is used for integrating the consequent part inference results of each rule.

A practical singleton method with a short calculation time will be described with reference to FIG. First, the degree of conformity with the condition of the antecedent part of the rule of Table 3 is obtained. When the measured value of the furnace temperature is T, the conformity to the condition of rule (1) is shown in FIG.
(A) From the figure, it is X ₁ . Similarly, the goodnesses of fit for the conditions of rule (2) and rule (3) are X ₂ and X ₃ , respectively.

Next, in order to make an inference in the consequent part,
Opening change parameter Y₁, Y_Two, Y _ThreeIs determined. Y₁Is
Positive when increasing the opening, for example 1, and Y_TwoIs normally open
Zero when maintaining degrees, Y_ThreeIs negative when decreasing the opening,
For example, -1.

Then, the correction amount U is deduced from the equation (5).

[0054]

(Equation 5)

Finally, the calculated correction amount is added to the normal opening Z ₀ by the equation (6) to calculate the output value Z.

[0056]

(Equation 6)

However, k is a control parameter. If the above method is applied to the air damper upstream of the combustion grate, the output value of the air damper opening upstream of the combustion grate can be obtained.
When controlling the air damper opening below the dry grate as well as the air damper upstream of the combustion grate, both controls are performed in synchronization.

The above is the method of controlling the air damper.
Next, the method of grate velocity control will be described. The control is performed according to the rules shown in Table 4.

[0059]

[Table 4]

The correction of the dry grate velocity is performed by executing the control shown by the arrow (⇒) when the conditions (1) to (3) are satisfied. The determination of the conditions (1) to (3) is performed for each constant cycle, the correction amount for each cycle is calculated, and the calculation result is used as the increase / decrease amount in that cycle. The output value of the dry grate velocity this time is added to the lattice velocity.

The calculation of the correction amount and output value will be described below.
Will be specifically described. First, the case of linear control will be described.
You. Upper limit of reference range of furnace temperature above combustion grate upstream
To T ₁, The lower limit is T_Two, The measured value is T, and the speed correction amount is S
₁Then, according to the rule of Table 4, the following expression (7),
From equation (8) and equation (9), S₁Is calculated.

[0062]

(Equation 7)

[0063]

(Equation 8)

[0064]

[Equation 9]

However, p ₁ and p ₂ are control parameters. Then, the calculated S ₁ is added to the grate velocity determined by the normal combustion control by the equation (10) to calculate the dry grate velocity output signal S.

[0066]

(Equation 10)

Next, the case where the dry grate speed control means is fuzzy control will be described.

Table 5 shows the rules for fuzzy control. Also,
Table 6 summarizes the inputs and outputs.

[0069]

[Table 5]

[0070]

[Table 6]

The operations of rules (1) to (3) are performed based on the membership function shown in FIG. The inference result of the consequent part of each rule obtained by the damper opening control means is integrated, and the inference result of the entire rule is output. A general method of fuzzy operation, such as a min-max centroid method or a singleton method, is used for integrating the consequent part inference results of each rule.

A practical singleton method with a short calculation time will be described with reference to FIG. First, the degree of conformity with the condition of the antecedent part of the rule of Table 3 is obtained. When the measured value of the furnace temperature is T, the conformity to the condition of rule (1) is shown in FIG.
(A) From the figure, it is X ₁ . Similarly, the goodnesses of fit for the conditions of rule (2) and rule (3) are X ₂ and X ₃ , respectively.

Next, in order to make an inference in the consequent part,
Speed change parameter V₁, V_Two, V _ThreeIs determined. V₁Is
Positive when accelerating, eg 1 and V_TwoIs normal burning
Zero when maintaining speed by control, V_ThreeIs the place to slow down
The sum is negative, for example, -1.

Then, the correction amount S ₁ is inferred from the equation (11).

[0075]

[Equation 11]

Finally, the calculated correction amount is added to the normal speed S ₀ by the equation (12) to calculate the output value S.

[0077]

(Equation 12)

However, k _s is a control parameter. Since the calculation time in fuzzy control is very short, if the temperature in the furnace is continuously measured and the calculation frequency is increased, it is possible to obtain 10 times in both air damper control and dry grate speed control.
It is also possible to correct at a frequency of 0 Hz or higher. However, it is usually sufficient to make corrections at intervals of several seconds.

[0079]

[Embodiment] Using the refuse incinerator shown in FIG. 1, the air damper opening under the dry grate is corrected by a fuzzy control system.
It was carried out every second, and the change in the evaporation amount of boiler water was examined and compared with the conventional example. The results of the investigation are shown in FIGS. 3 and 4.

FIG. 3 shows the results of a control test by the method of controlling only the air damper opening under the dry grate according to the present invention. FIG. 3A is a furnace temperature, FIG. 3B is an air amount under the dry grate, and FIG.
The figure (c) shows the change in the evaporation amount of boiler water. Fig. 4 shows the results of a control test by a method of controlling the amount of air under a dry grate based on the bulk density of conventional waste. Fig. 4 (a) is the furnace temperature, and Fig. 4 (b) is the evaporation amount of boiler water. Shows the change of.

In the present invention, in FIG. 3 (a), the temperature in the furnace decreases about 0.3 hours after the start of measurement. At this time, as shown in FIG. The air volume under the grid is increasing. Therefore, as shown in FIG. 3 (c), the evaporation amount is prevented from dropping for a long time, and stable combustion is realized.

On the other hand, in the conventional control method, as shown in FIG.
In the figure (a), the temperature in the furnace has fallen about 0.5 hours after starting the measurement. However, since the control of the air damper opening under the dry grate is performed based on the specific gravity at the time of dumping dust into the hopper, this decrease in the temperature inside the furnace is overlooked and the amount of air under the dry grate is not corrected and The air volume is not compatible. Therefore, as shown in FIG. 4 (b), the state in which the evaporation amount continues to decrease for about 0.3 hours after the temperature inside the furnace has decreased.

[0083]

As described above, according to the present invention, the temperature in the furnace is measured, and the amount of air sent to the dry grate or the combustion grate is controlled by using the function with this as a parameter, Alternatively, the dryness of the refuse is improved by controlling the dry grate speed together with the air volume. For this reason, the generation of combustion heat is stabilized, and the amount of water evaporated in the boiler is kept constant. As described above, the effect of the present invention, which realizes effective use of the enormous amount of heat energy generated by incineration of waste as waste, is great.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a refuse incinerator and its control system for explaining an embodiment of the invention.

FIG. 2 is a diagram showing a membership function of an antecedent part.

FIG. 3 is a diagram showing a control test result by the combustion control method of the present invention, in which (a) is a temperature change in the furnace, (b) is a change in air amount under the dry grate, and (c) is an evaporation amount. Each is shown.

4A and 4B are diagrams showing a control test result by a conventional combustion control method, in which FIG. 4A shows a temperature change in a furnace, and FIG. 4B shows an evaporation amount.

[Explanation of symbols]

 1 Furnace 2 Waste Inlet 3a Dry Grate 3b Combustion Grate 3c Post Combustion Grate 4 Ash Drop Port 5 Combustion Air Blower 6 Furnace Outlet 8a Heat Exchanger 8b Boiler 12 Flowmeter 13a Dry Grate Under Air Damper 13b Combustion Grate Upstream lower damper 13c Combustion grate downstream lower air damper 14 Reactor thermometer 15 Control means.

Claims (6)

[Claims] 1. In a combustion method of a refuse incinerator, in which air is fed from below the grate and burned in the furnace while moving the garbage on the grate, the temperature inside the furnace above the combustion grate is measured, and When the temperature is higher than the reference value, the air damper opening under the dry grate is reduced, and when the temperature is lower than the reference value, the air damper opening under the dry grate is increased. Combustion control method. 2. The air damper control is carried out by correcting the air damper opening below the combustion grate in synchronization with the correction of the air damper opening below the dry grate in the air damper control according to claim 1. Combustion control method for rubbish incinerator. 3. The combustion control method for a refuse incinerator according to claim 1, wherein fuzzy control is used for the air damper control. 4. The air damper control according to claim 1 is performed, and when the temperature inside the furnace on the upstream side of the combustion grate is higher than the reference value, the drying grate speed is increased, and when it is lower than the reference value, the drying grate is dried. A combustion control method for a refuse incinerator, characterized by performing grate speed control for reducing the grate speed. 5. The air damper control according to claim 2 is performed, and when the furnace temperature on the upstream side of the combustion grate is higher than a reference value, the drying grate speed is increased, and when it is lower than the reference value, drying is performed. A combustion control method for a refuse incinerator, characterized by performing grate speed control for reducing the grate speed. 6. The combustion control method for a refuse incinerator according to claim 4, wherein fuzzy control is used for the grate velocity control.