JPH10141658A - Combustion control method for burner for asphalt plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the temperature of gravel at all times by a method wherein the amount of combustion of a burner is controlled correctly and promptly in accordance with the amount, moisture content and the like of the gravel, supplied to a dryer, even when the amount, moisture content and the like of the gravel are changed. SOLUTION: In heating gravel in a dryer 1, the supplied amount of gravel into the dryer 1, the temperature of heated and discharged gravel, and the set value of gravel temperature are detected at every predetermined times. Then, the amount of necessary combustion is operated at first based on a logical combustion formula from the detected supplied amount of gravel and the set value of the temperature of the gravel. The changing amount of temperature is operated from the temperature of the gravel, which is detected at the outlet port of the dryer successively, while the tendency of gravel temperature is estimated from the changed amount of temperature and, thereafter, the corrected amount of combustion for correcting the necessary amount of combustion is obtained from the estimated value. Then, an actual combustion amount is determined while adding the corrected amount of combustion to the necessary amount of combustion and the burner 6 is controlled so as to develop the determined amount of combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an asphalt plant for producing an asphalt mixture as a road paving material,
The present invention relates to a burner combustion control method used for a dryer that is an aggregate heating device for a recycling plant, a drum mixing plant, or the like.

[0002]

2. Description of the Related Art Burner combustion control when an aggregate is heated by a dryer is usually performed by detecting the temperature of the aggregate heated and discharged from the dryer outlet, and setting the aggregate temperature and a preset aggregate temperature set value. And the burner combustion amount is adjusted in accordance with the difference value, but the method of simply adjusting the burner combustion amount in proportion to the difference value is a uniform combustion amount control. For example, as disclosed in Japanese Patent Application Laid-Open No. Hei 4-7401, the applicant of the present application has proposed a method of exhaust gas that has a high speed of passing through the dryer and easily catches the temperature change in the dryer in addition to the amount of change in the aggregate temperature. We propose a burner combustion control method that takes into account the amount of temperature change, and realizes highly accurate combustion control.

[0003]

However, even with the above-described conventional burner combustion control method considering the exhaust gas temperature, the control method that simply feeds back these measured values to the combustion amount based on rules prepared in advance is not used. In the case of a dryer having a time lag of 3 to 5 minutes from the supply of the aggregate to the discharge thereof, when the properties such as the supply amount of the aggregate and the water content change, the discharge from the dryer outlet is performed. The temperature of the aggregate was not stable for a while, and it took some time to settle to the set temperature.

SUMMARY OF THE INVENTION In view of the above, the present invention controls the amount of aggregate supplied to the dryer and the water content, etc., in a corresponding manner, by controlling the burner combustion amount accurately and promptly, and thereby controlling the aggregate temperature. It is an object of the present invention to provide a burner combustion control method for an asphalt plant that can constantly stabilize the burner.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method in which the amount of aggregate supplied to a dryer, the temperature of aggregate heated and discharged, and the set value of aggregate temperature are determined at predetermined time intervals. To calculate the amount of combustion required for heating from the aggregate supply amount and the aggregate temperature set value, and calculate the temperature change from the sequentially detected aggregate temperature to calculate the trend of the aggregate temperature. The method is characterized in that a predicted combustion value is obtained from the predicted value, and the actual combustion amount of the burner is determined by adding the corrected combustion amount to a required combustion amount.

[0006]

According to the burner combustion control method of the present invention, when the aggregate is heated by the dryer, the amount of the aggregate supplied to the dryer, the temperature of the aggregate to be heated and discharged, and the aggregate temperature setting value Are detected at predetermined time intervals. First, a required combustion amount is calculated from the detected aggregate supply amount and the aggregate temperature set value based on a theoretical combustion equation.

Further, the amount of change in the temperature is calculated from the aggregate temperature sequentially detected at the dryer outlet, the trend of the aggregate temperature is predicted from the change in the aggregate temperature, and the required combustion amount is calculated from the predicted value. A corrected combustion amount to be corrected is obtained, and an appropriate combustion amount is determined by taking the corrected combustion amount into consideration with a required combustion amount to perform burner combustion control. For example, when it is expected that the aggregate temperature will exceed the set temperature in view of the aggregate temperature and the amount of temperature change, the corrected combustion amount is set to a negative value and the combustion amount is set to be smaller than the required combustion amount obtained from the theoretical combustion equation. When it is expected that the aggregate temperature will be lower than the set value in view of the aggregate temperature and its temperature change, the corrected combustion amount is set to a positive value and the combustion is performed at a larger combustion amount than the required combustion amount. is there.

As described above, the amount of combustion required for combustion is theoretically calculated from the amount of aggregate supplied to the dryer, and the appropriate amount of combustion of the burner is determined in consideration of the change in the temperature of the heated aggregate. Therefore, even when the aggregate supply amount and the moisture content change, the burner combustion amount is controlled accurately and promptly when the aggregate is supplied to the dryer. Can always be stabilized.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall structure of a dryer to which the present invention is applied.

A dryer 1 rotatably supports a cylindrical drum 2 on a machine base 3 and rotates the drum 2 at a predetermined speed by a drum driving motor (not shown). A large number of scraping blades 4 are arranged inside the drum 2, and the aggregate fed by the aggregate supply bell-con 5 is scraped by the blades 4.
While rolling down the inside of the drum 2 while dropping it in a curtain shape, the aggregate is brought into contact with hot air sent from the burner 6 to heat the aggregate to a desired temperature.

The dryer 1 is provided with an aggregate temperature sensor 7 for detecting the temperature of the heated aggregate discharged from the drum 2, and an exhaust gas temperature sensor 8 for detecting the temperature of the exhaust gas.
Is arranged.

In addition, aggregate hoppers 9a, 9b and 9c for storing aggregates according to particle size are arranged at the end of the aggregate supply bell-con 5, and below the aggregate hoppers 9a, 9b and 9c. A cutout feeder 10a for cutting out an aggregate by a predetermined amount;
10b and 10c are provided. An aggregate detection sensor 11 for confirming supply to the drum 2 is provided near the aggregate supply port of the drum 2.

Signals from these sensors are input to the burner combustion control device 12. This burner combustion control device 1
2 is connected to a data input unit 13 for setting and inputting an aggregate cutout amount from each of the aggregate hoppers 9a, 9b, 9c, and further infers a combustion amount based on various signals and data as described later, A control signal is output via a driver 14 to a control motor 16 that drives a fuel valve 15 that controls the amount of combustion.

Reference numeral 17 denotes a combustion air damper which is linked to the control motor 16, and reference numeral 18 denotes a fuel meter for measuring a fuel flow rate.

Next, a burner combustion control method according to the present invention will be described.

The combustion control of the burner is performed as shown in FIG.
From the start of operation, through the process of burner ignition, low combustion, aggregate supply, aggregate detection, initial combustion wait, initial combustion,
The shift to high combustion control that heats the aggregate in earnest will be made. The combustion control method of the present invention is directed to the high combustion control section, and the embodiment employs an inference method applying fuzzy logic.

First, prior to operating the dryer, calibration is performed by driving the cutout feeders 10a, 10b, and 10c for the aggregate hoppers 9a, 9b, and 9c in advance.
The relationship between the number of rotations and the cutting speed is determined in advance.

Next, when various data such as the water content, the composition type, and the shipment amount of each aggregate are input through the data input unit 13 of the burner combustion control device 12, the burner combustion control device 12
In each of the aggregate hoppers 9 based on the compounding type, shipping amount and moisture content
The amount of aggregate to be cut out from the cutout feeders 10a, 10b, and 10c (t) is calculated.
on / h). At this time, the desired temperature of the heated aggregate at the dryer outlet is input and set as an aggregate temperature set value.

Then, by the operation start operation, the burner 6 is ignited to start low combustion. After a lapse of a predetermined time, the cutout feeders 10a, 10b, and 10c are driven, and the aggregate hoppers 9a and 9 are set based on the cutout speed set previously.
Various aggregates are cut out from b and 9c.

When the aggregate cut out from the aggregate hoppers 9a, 9b and 9c is transported to the aggregate supply port of the drum 2 by the aggregate supply bell-con 5, the aggregate arranged near the aggregate supply port of the drum 2 is transferred. The detection sensor 11 detects the aggregate. When the aggregate is detected by the aggregate detection sensor 11, the burner combustion control device 12 calculates the supply amount of the aggregate from the cutting speed from each of the aggregate hoppers 9a, 9b, 9c every predetermined time, for example, every 5 seconds. Then, it is stored in time series as the aggregate supply amount every 5 seconds.

The aggregate supply amount may be calculated from the cutting speed from each of the aggregate hoppers 9a, 9b and 9c as described above. The supply amount may be measured, or the amount of aggregate deposited on the aggregate supply bell-con may be calculated.

When the supply of the aggregate to the drum 2 is started in this way, the initial combustion is started after the initial combustion waiting time calculated according to the supplied amount of the aggregate. The aggregate heated to a predetermined temperature is discharged from the drum 2 while rolling down the inside of the drum 2, and the aggregate temperature sensor 7 sets the aggregate temperature set value input in advance. Plus minus 3
When 0 ° C. is detected and it is determined that the aggregate charged into the drum 2 has been heated and is discharged from the dryer in a stable state, the combustion control of the burner is switched from the initial combustion control to the high combustion control.

When the burner combustion control shifts to the high combustion control, the amount of aggregate supplied to the dryer, the temperature of the aggregate to be heated and discharged, and the set value of the aggregate temperature are detected at predetermined time intervals. . Then, the combustion amount required for heating the aggregate is calculated from the detected aggregate supply amount and the aggregate temperature set value.

The required amount of combustion is expressed, for example, by the following equation.

[0026]

(Equation 1)

This equation is obtained by multiplying the theoretical combustion amount by the dryer efficiency τ. The dryer efficiency τ is a value in consideration of the thermal efficiency of the dryer, and may be appropriately determined based on past measured data. However, here, the dryer efficiency τ is treated as a variable because it is considered from experience that it varies depending on the aggregate supply amount and the water content.

The dryer efficiency τ is determined by fuzzy inference from the aggregate temperature set value and the aggregate supply amount. The inference method will be described. FIG. 3 shows that the aggregate temperature set value Ts is qualitatively determined. This is a membership function for evaluation. In the figure, Ts (i) (i = 1 to 5) is a constant that defines the form of the membership function and is determined as appropriate. P
B, PM, PS, ZR, NS, NM, and NB are names given to the membership function for qualitatively evaluating the rank of the aggregate temperature set value Ts, and have the following meanings.

PB: Positive Big PM: Positive Medium PS: Positive Small ZR: Zero NS: Negative Small NM: Negative Medium NB: Negative Medium is a member of NB: Negative is a bone material and Tegative is a bone material. Is qualitatively evaluated.

FIG. 4 shows a membership function for qualitatively evaluating the aggregate supply amount M, and M (i) in the figure.
(I = 1 to 5) are constants that define the form of the membership function and are determined as appropriate. PB, PM, PS, ZR, N
S, NM, and NB are names given to the membership function for qualitatively evaluating the rank of the aggregate supply amount M and have the same meaning as described above, and the vertical axis in the figure is the membership value. is there.

FIG. 5 is a fuzzy inference rule for qualitatively determining the dryer efficiency τ from the qualitative relationship between the aggregate temperature set value Ts and the aggregate supply amount M.

For example, the inference rule in the upper right represents the meaning of IF (TsisNB and MisPB) THEN (τisNM).

This is "if the aggregate temperature set value Ts is very low and the aggregate supply amount M is very large" (the antecedent part), "set the dryer efficiency τ to a medium value" ( (Consequent part). The rule table does not rank the aggregate temperature set value.

FIG. 6 shows a membership function for converting the qualitatively determined dryer efficiency τ into a quantitative value. In the drawing, τ (i) (i = 1 to 5) is a constant that defines the form of the membership function and indicates the dryer efficiency τ, and is appropriately determined. PB, PM, PS, ZR, NS,
NM and NB are names given to a membership function for qualitatively expressing the dryer efficiency τ, and have the same meaning as described above. Here, membership functions named PO, PW, PF, NF, NW, and NO are provided between the membership functions so that the dryer efficiency τ can be finely ranked. The vertical axis in the figure is the membership value.

The membership function is used to qualitatively determine to which membership function the dryer efficiency τ previously inferred belongs. When the dryer efficiency τ is defined by a plurality of inference rules, a weighted average corresponding to each membership value is defined as the dryer efficiency τ.

In this way, with the start of the high combustion, the set value of the aggregate temperature and the aggregate supply amount are grasped, and the dryer efficiency τ of the above-mentioned combustion equation is inferred from them by fuzzy inference. The necessary amount of combustion U is determined.

Next, a description will be given of a method of controlling the burner burning amount by obtaining the actual burning amount from the required burning amount and the aggregate temperature at the dryer outlet.

The aggregate temperature at the dryer outlet is measured at predetermined time intervals, for example, every second while the required combustion amount U is obtained, and the measured aggregate temperature data is sequentially stored. For example, the change speed of the aggregate average value every 5 seconds),
The acceleration, change in acceleration, and the like are calculated and stored. Then, the trend of the aggregate temperature is predicted from the temperature change amount. For example, the predicted aggregate temperature is calculated based on the predicted aggregate temperature calculation rule as shown in FIG. The predicted aggregate temperature is not a temperature like what the predicted aggregate temperature is after a few seconds, but is calculated to find a point to be controlled.

For example, according to the rule at the upper right of FIG. 7, when the change in the acceleration of the aggregate temperature is minus (-) and the change in the speed is large (+), A in the figure is selected as the arithmetic expression, and the predicted aggregate temperature = The predicted aggregate temperature is calculated by the formula of average aggregate temperature for 5 seconds + (speed + acceleration / 3) × 5. It should be noted that the predicted aggregate temperature calculation rule and the predicted aggregate temperature formula are merely examples and are appropriately determined. Thus, it is possible to predict the trend of the aggregate temperature in association with the amount of change in the temperature of the aggregate. The prediction is made by appropriately employing a method. Note that this predicted aggregate temperature is calculated to find a point to be controlled as described above, and is a guide to how much the required combustion amount obtained by the above-mentioned theoretical formula is corrected from the trend of the aggregate temperature. It is determined by an appropriate calculation formula according to the required combustion accuracy.

Next, a corrected combustion amount for correcting the combustion amount is calculated from the calculated aggregate temperature trend prediction. One example of this will be described first. The aggregate temperature is compared with the aggregate temperature, and an aggregate temperature error with respect to the estimated aggregate temperature (predicted aggregate temperature−measured aggregate temperature) is obtained. From the aggregate temperature error and the required combustion amount, a corrected combustion amount is obtained by fuzzy inference.

FIG. 8 shows a membership function for qualitatively evaluating the required combustion amount U. In FIG. 8, U (i) (i =
1 to 5) are constants that define the form of the membership function, and are appropriately determined. PB, PS, ZR, NS, and NB are names given to the membership function for qualitatively evaluating the rank of the required combustion amount U, and have the following meanings.

PB: Positive Big PS: Positive Small ZR: Zero NS: Negative Small NB: Negative Big The vertical axis in the figure is a membership value and the set required combustion amount U is qualitatively evaluated.

FIG. 9 shows a membership function for qualitatively evaluating the aggregate temperature error Δta.
a (i) (i = 1 to 5) is a constant that defines the form of the membership function and is determined as appropriate. PB, PS, ZR,
NS and NB are names given to the membership function for qualitatively evaluating the rank of the aggregate temperature error Δta and have the above-described meaning, and the vertical axis is the membership value.

FIG. 10 shows the required combustion amount U and the aggregate temperature error △.
This is a fuzzy inference rule for qualitatively determining the corrected combustion amount Uf from a qualitative relationship with ta.

For example, the inference rule shown in the upper right is IF (Uis PB and Δtais NB
) Represents THEN (Ufis PB).

This is because if the required combustion amount U is very large,
And if the aggregate temperature error Δta is extremely large on the negative side ”(the antecedent part), and“ Let the correction combustion amount Uf be very large ”(the consequent part).

FIG. 11 shows a membership function for converting the qualitatively determined corrected combustion amount Uf into a quantitative value. Uf (i) (i = 1 to 5) in the figure is a constant that defines the form of the membership function and indicates the corrected combustion amount Uf, and is appropriately determined. PB, PM, PS,
ZR, NS, NM, and NB are names given to a membership function for qualitatively representing the corrected combustion amount Uf, and have the same meaning as described above. Also, here, PO, PF, N
Membership functions named F and NO are provided for fine ranking. The vertical axis in the figure is the membership value.

Using this membership function, it is determined qualitatively to which membership function the corrected combustion amount Uf inferred previously belongs. When the corrected combustion amount Uf is defined by a plurality of inference rules, a weighted average according to each membership value is set as the corrected combustion amount Uf.

The actual combustion amount Uw is determined by adding the corrected combustion amount Uf obtained in this way to the required combustion amount U obtained in advance, and the control motor 16 for driving the fuel valve 15 of the burner 6 based on the actual combustion amount Uw. Is operated to perform optimal combustion amount control.

As described above, in the burner combustion control method of the present invention, the amount of aggregate required for heating the aggregate to the set value is theoretically determined from the amount of aggregate supplied to the dryer and the set value of the aggregate temperature. Calculate and further calculate the temperature change amount from the sequentially detected aggregate temperature to predict the trend of the aggregate temperature, and correct the necessary combustion amount from the prediction to obtain an appropriate combustion amount. Therefore, even when the aggregate supply amount and the water content change, the burner combustion amount can be controlled accurately and quickly when the aggregate is supplied to the dryer. The temperature can be stabilized.

It should be noted that the present invention is not limited to the above-described embodiment. For example, the combustion control has been described using an example in which fuzzy theory is applied. However, the present invention is not limited to fuzzy theory at all, and various control theories are not limited to fuzzy theory. It goes without saying that various changes can be made without departing from the gist of the present invention, such as application.

[0052]

As described above, in the method for controlling burner combustion in an asphalt plant according to the present invention, the aggregate supply amount to the dryer, the temperature of the aggregate to be heated and discharged, and the aggregate temperature setting value Are detected at predetermined time intervals, the required combustion amount required for heating is calculated from the aggregate supply amount and the aggregate temperature set value, and the temperature change amount is calculated from the sequentially detected aggregate temperature to calculate the bone temperature. Since the trend of the aggregate temperature is predicted, the corrected combustion amount is calculated from the predicted value, and the corrected combustion amount is added to the required combustion amount to determine the actual combustion amount of the burner. Even when such changes occur, the burning amount of the burner is accurately and quickly controlled when the aggregate is supplied to the dryer, whereby the temperature of the heated aggregate can be constantly stabilized.

[Brief description of the drawings]

FIG. 1 is a diagram showing an entire configuration of a dryer applied to one embodiment of the present invention.

FIG. 2 is a diagram showing a combustion process.

FIG. 3 is a diagram showing a rank evaluation membership function of an aggregate temperature set value.

FIG. 4 is a diagram illustrating a rank evaluation membership function of aggregate supply amount.

FIG. 5 is a diagram illustrating an example of an inference rule for dryer efficiency.

FIG. 6 is a diagram showing a membership function for rank evaluation of dryer efficiency.

FIG. 7 is a diagram showing an example of a predicted aggregate temperature calculation rule.

FIG. 8 is a view showing a membership function for rank evaluation of a required combustion amount U.

FIG. 9 is a diagram showing a membership function for evaluating the aggregate temperature error.

FIG. 10 is a diagram illustrating an example of an inference rule of a corrected combustion amount.

FIG. 11 is a diagram showing a rank evaluation membership function of a corrected combustion amount.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Dryer 2 ... Drum 5 ... Belt supply for aggregate supply 6 ... Burner 7 ... Temperature sensor for aggregate 8 ... Temperature sensor for exhaust gas 9a, 9b, 9c ... Aggregate hopper 10a, 10b, 10c ... Cutting feeder 11 ... Aggregate Detection sensor 12 Burner combustion control device 13 Data input unit 15 Fuel valve 16 Control motor

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshio Fujiwara 1013 Eijima, Okubo-cho, Akashi-city, Hyogo Prefecture Inside Niko Corporation (72) Inventor Yasuaki Izumi 1013 Eijima, Okubo-cho, Akashi-shi, Hyogo 1 Niko Corporation (72) Inventor Daisuke Nakahara 1 Niko Corporation at 1013 Eijima, Okubocho, Akashi City, Hyogo Prefecture

Claims (1)

[Claims] An aggregate supply amount to a dryer, a temperature of an aggregate to be heated and discharged, and an aggregate temperature set value are detected at predetermined time intervals, and the aggregate supply amount and the aggregate temperature set value are detected. The required combustion amount required for heating is calculated, and the temperature change amount is calculated from the sequentially detected aggregate temperature to predict the trend of the aggregate temperature, and the corrected combustion amount is obtained from the predicted value to obtain the corrected combustion amount. A burner combustion control method for an asphalt plant, characterized in that an actual combustion amount of a burner is determined in consideration of a required combustion amount.