JPH03121190A - Method for controlling combustion in coke oven - Google Patents

Abstract

PURPOSE:To always attain a target net coking time and to realize a stable operation and a reduction in heat consumption even when the operating efficiency of a coke oven is changed by establishing specified means for controlling combustion in a coke oven. CONSTITUTION:For controlling combustion in a coke oven, the following means are established: (1) a first means which comprises converting a deviation from a target value of net coking time, a change in coking time, and a change in the moisture contact of coal charge into at least two decision functions based on fuzzy logic in advance to determine control inputs respectively corresponding to these decision functions, selecting pertinent control inputs based on measured data, composing those control inputs depending on the degree to which fine measured data conform to the decision functions to determine composite control inputs, and changing the set value of the oven temperature based on the composite control inputs. (2) A second means which comprises changing the control range for fuel gas by a method based on fuzzy logic from a difference between a set value of the oven temperature and an actual value thereof, a change is the oven temperature, and time during which the fuel gas flow rate is held within upper and lower limits.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method of controlling combustion in a coke oven, and a method for controlling the combustion of a coke oven by setting the oven temperature setting value and the upper and lower limit values of fuel gas based on a good theory. Concerning how to operate economically.

[Prior art 1] In general, a coke oven has a structure in which a heat storage chamber 3 is located at the bottom of the furnace body, and combustion chambers 1 and carbonization chambers 2 are arranged alternately above the heat storage chamber 3, as shown in Fig. 2. The coal charged in chamber 2 becomes coke after dry distillation for 15 to 20 hours.

In coke oven operation, it is important to control the furnace temperature so that the carbonization of the coal charged into each furnace is completed within a predetermined time.

As shown in the flowchart in Figure 3, recent coke oven combustion control technology detects gaps at the end of carbonization based on temperature changes in the gas generated in each kiln, and calculates the average gap time for several kilns and the target value. The method used is to determine an appropriate furnace temperature setting value according to the deviation, compare it with the actual measurement value of the combustion chamber, and control the fuel gas flow rate so that the deviation becomes zero, thereby controlling the furnace temperature to the appropriate value. ing.

[Problem to be solved by the invention]

As mentioned above, the conventional combustion control method for coke ovens is to install thermometers, dust meters, etc. in the riser pipe of each oven of the coke oven to detect defects due to changes in the temperature of the generated gas and changes in the concentration of dust. A common method is to detect the missing time, process the data in units of several kilns, and change the furnace temperature according to the deviation between the representative missing time of the furnace group and the target value.

However, there is usually a response delay of 6 to 8 hours before a change in coke oven oven temperature affects the missing time. Making changes will result in overaction and increase the fluctuation of missed time.

For example, in JP-A-62-109887, a method is proposed in which the predicted future missing time is calculated from the actual missing time for each control cycle based on a multiple regression equation, and the furnace temperature setting is changed according to the deviation between this and the target value. is proposed.

This method can largely avoid the negative effects of response delays due to missing times, but the response delays due to missing times vary greatly depending on factors such as the pitch (operating rate) of the coke oven, and it is not easy to formulate dynamic characteristics. However, there were expectations for a method with a greater control effect, as the prediction accuracy was rather low because multiple regression was used to predict missing time.

Furthermore, the above control method allows the operating rate of the coke oven to be constant (
In other words, it is desirable to apply it during operation when the target missing time is constant), and when a large change in furnace temperature is involved, such as when changing the operating rate, there is a large fluctuation in the fuel gas flow rate, which may cause hunting in the furnace temperature. In some cases, it became difficult to automatically control the furnace temperature.

The present invention provides a combustion control method for a coke oven that always controls the missing time to match the target missing time even when the operating rate is constant or changes.

[Means for Solving the Problems 1] The present invention provides a method for controlling the furnace temperature when the operating rate of a coke oven is constant and when changing.
This was completed through detailed analysis of dynamic characteristics such as dropout time.

The present invention is based on the fuzzy theory to set the furnace temperature set value and set value so that the actual missing time always matches the set target missing time, not only in steady operation with a constant operating rate, but also in unsteady operation when the operating rate changes. This is to determine the control range of fuel gas flow rate and control combustion.

The present invention provides a method for controlling combustion by increasing/decreasing the fuel gas flow rate based on the deviation between the measured furnace temperature and the set furnace temperature in a coke oven combustion chamber. It is characterized by seeking.

(1) Convert the deviation of the missing time from the target value, the change in the missing time, and the change in the charged coal moisture value into two or more judgment functions based on the vague theory, and calculate the respective manipulated variables corresponding to each judgment function. Based on the measured data, select the corresponding manipulated variable, combine them according to the proportion of the measured data that corresponds to the judgment function, determine the composite manipulated variable, and set the furnace temperature set value based on this composite manipulated variable. To change.

(2) Change the fuel gas control range using a method based on vague theory based on the deviation between the set value and actual value of the furnace temperature, changes in the furnace temperature, and the time the fuel gas flow rate is held at the upper and lower limits. thing.

According to the present invention, it is possible to always achieve the target missing time not only when the operating rate of the coke oven is constant (even when the operating rate is changed), it is possible not only to stabilize the operation, but also to reduce the amount of heat consumed. The above losses are also significantly reduced.

[Effect]

Hereinafter, the structure of the present invention will be explained in detail together with its operation.

(1) First, how to determine the set furnace temperature will be explained.

(a) Converting the missing time into a decision function Figure 4 shows an example of changes in the missing time, furnace temperature, and charged coal moisture value, which are the objects of control when the operating rate is constant. The missing time is affected by the furnace temperature and the moisture content of the charged coal, and varies over a large time cycle. For example, if the furnace temperature rises, the missing time becomes shorter, but there is a time lag.

Therefore, for example, when looking at time t, even though the missing time exceeds the target value, if the furnace temperature is increased even though the moisture content of the charged coal is decreasing, the missing time will rapidly decrease. This may cause the dropout time to fluctuate excessively.

In other words, in order to control the missing time to an appropriate value, simply
Is the missing time “shorter” or “longer” than the target value?
Based on information such as ``Has it become shorter?'' or ``Has it become longer?'' and ``Is there a factor causing it to become shorter?'' or ``Is there a factor causing it to lengthen?'', take action to change the furnace temperature setting. There is a need.

Therefore, in determining these missing times, the deviation of the actual missing time from the target value: 80Ti (minutes) Change in missing time: △CTi-Δc'rt-1 (minutes) Change in charged coal moisture value: TMi -TMi-, (%) Here, the subscript i is used to calculate two or more judgment functions using control timing, as shown in FIG.

In Figure 5, the vertical axis is what is called the fuzzy value,
1,0 is the maximum value. 1.0 means that everyone makes the same decision, indicating that everyone agrees.

The fuzzy value indicates the proportion corresponding to the judgment function.

A judgment function is a grouping of abstract judgments that humans make, such as ``just right'' and ``short gaps.'' Fifth
In the example shown in the figure, for example, the missing time deviation ΔC at the control timing
If Tj is 15 minutes, all the people judge that "the gap is long", and if Tj is 3 minutes, it is "just right". This shows that if it is 8 minutes, half of the people think that the gap is ``long'' and half of the people think that it is ``just right''.

The decision function for the missing time is created as described above, but in the future, the factors that determine whether the missing time will become shorter or longer will be determined not only by changes in the moisture content of the charged coal but also by the particle size of the charged coal,
For other indicators such as charging weight, a judgment function may be created as illustrated in FIG. 7, for example.

(b) Ruleization of manipulated variables Table 1 is a manipulated variable rule table in which the missing time deviation and missing time change tendency are each configured as three judgment functions, and Figure 6 shows the manipulated variables (furnace temperature change amount). show.

From the manipulated variable rules in Table 1, for example, if the missing time is long and the missing time is getting longer, select the manipulated variable 3. In this way, the amount of furnace temperature change can be determined based on the measured value of the missing time.

In the present invention, in addition to the rules shown in Table 1, the furnace temperature change amount is calculated from the manipulated variable shown in FIG. 6 using the rules shown in Table 2 regarding moisture changes.

Table 1 Table 2 (c) Synthesis of manipulated variables FIG. 7 shows the aforementioned missing time deviation, missing time change trend, and judgment function for moisture change.

For example, if the missing time deviation is 13 minutes from FIG. 7(a), and the missing time change is 18 minutes from FIG. 7(b), then the following ■～■
case is selected.

■ The percentage that determines that the missing time is long is 0.8 ■ The percentage that determines that the missing time is just right is 0.2 ■ The percentage that judges that the missing time is short (it has become) is 0.
．． 6 ■ The corresponding ratio for determining that the missing time does not change is 0.4. Compare this with the rules in Table 1 and select the amount of operation.

In the above example, i) the missing time is "long" and the missing change is "shortish", so the manipulated amount is 2°; ii) the missing time is "long" and "no change", so the manipulated amount is 3°; ii) the missing time is "just right" If the missing time is "just right" and "no change", select the manipulated variable 1゜ivl.

Also, if the change in the moisture content of the charged coal at this time is 1.0%, the judgment function will be 1.0 from Figure 7 (C), based on the rules in Table 2. vi) Select the manipulated variable 3 because the missing time is "just right" and the water content is "increase".

Next, a method of synthesizing each of these manipulated variables will be explained.

First, each manipulated variable is weighted according to the corresponding ratio of the judgment function. That is, when selecting the manipulated variable 2 in the example of i) above, the corresponding ratio corresponding to the "long" missing time is 0.8.
The lower of the applicable ratios of 0.6 and 0.6 corresponding to the "shorter tendency" is selected as the relevant ratio (weighting) of the manipulated variable. In this way, the corresponding proportion of each manipulated variable is determined. As a result, i)
In vil, i) Manipulated amount 2 Corresponding ratio 0.6 ii) Manipulated amount 3 Corresponding ratio 0.4 iii1 Manipulated amount l Corresponding ratio 0.2 iv) Manipulated amount 2 Corresponding ratio 0.2 ■) Manipulated amount 3 Corresponding ratio 0. 8 vi) Manipulated amount 3 corresponding ratio will be 0.2.

Figure 8 shows the distribution of the above manipulated variables, and each manipulated variable is
After cutting the peaks according to the fuzzy value (corresponding ratio), it is determined as a union. In other words, the shaded area in Fig. 8 is the missing time deviation of 1.
This is the distribution of the manipulated variable (furnace temperature change) when 3 minutes, missing time change -8 minutes, and charged coal moisture change 1.0%, and the center of gravity of this distribution is taken as the manipulated output. This center of gravity C is calculated using a method called the weighting method.

(d) Calculating the furnace temperature set value The furnace temperature set value Tsv is the furnace temperature change amount △Tsv (that is, the value of the center of gravity C mentioned above) obtained by the above method and the previous set value T.
It is determined by the following formula based on sv-t.

T SV" T 5V-1 + ΔTsv In this example, the current temperature setting value is increased by 2.25℃ (for example, if the current TSV-1 is 1100℃, the Tsv after the change is 1102. Set to 25°C.

(2) Next, how to determine the control range of the fuel gas flow rate will be explained.

In a system with a large heat capacity, such as a coke oven, the thermal response delay is large, as shown in FIG. 9(a).

When the set furnace temperature is changed significantly, the fuel gas flow rate fluctuates greatly, which deteriorates the controllability of the furnace temperature. Therefore, when the furnace temperature is significantly changed, it is necessary to define the control range of the fuel gas flow rate to an appropriate control range within the upper and lower limits, as shown in FIG. 9(b).

Therefore, in order to always maintain the control range of the fuel gas flow rate within the appropriate range, the judgment function manipulated variables and manipulated variable rules shown in FIGS. 1O, 11, and Table 3 are used.

Here, the hold time refers to the elapsed time θ during which the gas flow rate remains at the upper limit or lower limit of the control range of the fuel gas flow rate, as shown in FIG. 9(b).

Note that the rules in Table 3 apply only to cases where the hold time is long, 2 hours or more, because the control range of the fuel gas flow rate can be considered to be at an appropriate level when the hold time is short or normal.

Similarly to the method (1) above, the fuzzy value of each judgment function is calculated from the actual measurement data at each control timing, and the manipulated variable ΔGs
v (control range change amount of fuel gas flow rate) is calculated.

Table 3 For example, in Figure 10, if the furnace temperature deviation is 19°C, the furnace temperature change is 3.5°C, and the hold time is 3 hours, ■ The corresponding ratio that determines that the furnace temperature is low is 0.8■ Furnace temperature The corresponding percentage that determines that the furnace temperature is good is 0.2 ■ The applicable percentage that determines that the furnace temperature has increased is 0.5 ■ The applicable percentage that determines that the furnace temperature has not changed is 0.5 ■ The applicable percentage that determines that the hold time is long A ratio of 1.0 is selected.

Next, the operation amount is selected in comparison with the rules shown in Table 3 for the cases ① to ② above.

The manipulated variable is selected as follows.

i) The manipulated variable is 2° because the furnace temperature deviation is “low”, the furnace temperature is “increased”, and the hold time is “long” ii) The furnace temperature deviation is “low”, “no change”, and the hold time is “long” Manipulated amount 3゜1ii) The furnace temperature deviation is ``just right'' and the furnace temperature is ``increasing'' and ``long'', so the manipulated variable 2゜iv) The furnace temperature deviation is ``just right'' and ``no change'', so the manipulated variable 2 is set. select.

Next, each manipulated variable is weighted according to the corresponding ratio of the judgment function. As a result, for i) to ivl, i) Manipulated amount 2 Corresponding ratio 0.5 ii) Manipulated amount 3 Corresponding ratio 0.5 iii1 Manipulated amount 2 Corresponding ratio 0.2 iv) Manipulated amount 2 Corresponding ratio 0.2.

FIG. 12 shows the distribution of the above-mentioned manipulated variables, and similarly to the calculation of the furnace temperature change amount, the center of gravity of the distribution is weighted by a method called the modulus and used as the manipulated output.

=250 (Ngo/m) The fuel gas control range is determined from the previous control range and the manipulated variable using the following formula.

F (upper limit); F (upper limit) - 1 + △Gsv F (lower limit) 2 F (lower limit) - 1 + △Gsv Also, the judgment function in Figure 10 is: Deviation from furnace temperature set value: ΔT PVL ('C) Change in furnace temperature: Ti -T<-1 (''C) Hold time during which the fuel gas flow rate is held at the upper and lower limit values: θ (minutes) is used. Here, the hold time θ is the fuel gas flow rate. This is the elapsed time from the time when the temperature reaches the upper limit or lower limit of the allowable control range, and it is determined whether the control is in an appropriate state based on the length of this time and the deviation and change tendency of the furnace temperature.

For example, the case where θ is long and does not follow the furnace temperature set value as shown in FIG. 9(b) is clearly due to the low control range of the fuel gas flow rate, and at this time the control range is changed by ΔGsv.

With the above method, the furnace temperature change amount and the fuel gas flow rate control range change amount are calculated at each control timing i, and the respective set values are changed. Note that the control timing is every 2 to 4 hours.

[Example J FIG. 1 shows the configuration of an apparatus according to an embodiment of the present invention.

A generated gas temperature sensor 4 installed in the riser pipe section of each kiln detects the temperature of the generated gas, and a lack determination device 5 measures the missing time of each kiln.

From this missing time measurement value, the charged coal moisture value determined by the moisture analyzer 6, and the target missing time, the fuzzy value of each judgment function is calculated by the judgment function calculator 7 at each control timing, and the fuzzy value of each judgment function is calculated by the manipulated variable calculator 8. The amount of change in the set furnace temperature is calculated based on.

Furthermore, the amount of change in the gas flow rate control range is similarly calculated based on the fuel gas flow rate and furnace temperature data.

The determined set furnace temperature and gas flow rate control range are set in the furnace temperature setting device 9 and gas flow rate control range setting device IO, respectively.
Appropriate automatic temperature control is performed by changing the gas flow rate.

Operational data when the present invention was implemented at a control cycle of every 4 hours are shown in FIG. 13 and Table 4 in comparison with the conventional method.

Table 4 In the conventional method, the set furnace temperature is changed in response to changes in the moisture content of the charged coal, but when the settings are changed significantly, the gas flow rate of Axilane becomes excessive to follow this change, and there is a tendency for the controllability of the furnace temperature to deteriorate. Also, due to this, there is a large variation in the dropout time. On the other hand, in the method of the present invention, since the control range of the gas flow rate is appropriately defined even with respect to moisture fluctuations, there is less hunting in the furnace temperature, and the controllability of the missing time is also good. As described above, according to the present invention, the controllability of the dropout time is greatly improved.

[Effects of the Invention] When controlling the combustion of a coke oven, the present invention can make judgments and actions similar to a human operation sense based on the change trend of missing time, increase/decrease of change factors, etc. Stable control can be maintained even for

Furthermore, since the controllability of the missing time is improved compared to the conventional method, it can greatly contribute to reducing the amount of heat consumed and stabilizing the quality of coke, and is an extremely effective means for controlling combustion in a coke oven.

[Brief explanation of drawings]

Fig. 1 is a flow sheet of an embodiment of the present invention, Fig. 2 is a cross-sectional view of a coke oven, Fig. 3 is a system diagram of coke oven combustion control, and Fig. 4 is a graph showing an example of changes in missing time and oven temperature. , 5th
The figure is a judgment function diagram for observed events, Figure 6 is a manipulated variable function diagram for furnace temperature changes, Figure 7 is a decision function diagram for furnace temperature changes, Figure 8 is a manipulated variable distribution diagram, and Figure 9 is a furnace temperature, Graphs showing examples of gas flow rate transitions; Figure 1O is a judgment function diagram for changing the gas flow rate control range; Figures 11 and 12 are manipulated variable function diagrams for changing the gas flow rate control range; Figure 13 is the present invention and conventional method. This is a control wholesale comparison chart. l... Combustion chamber, 2-... Carbonization chamber, 3... Heat storage chamber, 4
... Missing judgment sensor (generated gas thermometer), 5...- Missing judgment device, 6- Moisture analyzer, 7-... Judgment function calculator,
8.--Manipulated variable calculator, 9.--Furnace temperature setting device, 10..
・Gas flow control range setting device

Claims (1)

[Claims] 1. In the combustion control of a coke oven, the deviation of the missing time from the target value, the change in the missing time, and the change in the charged coal moisture value are converted in advance into two or more judgment functions based on an ambiguous theory. , determines each operation amount corresponding to each judgment function, selects the corresponding operation amount based on the actual measured data, and then synthesizes and synthesizes the operation amounts according to the proportion of the actual measurement data that corresponds to the judgment function. A first means of determining the manipulated variable and changing the furnace temperature set value based on this composite manipulated variable, and determining the deviation between the furnace temperature set value and the actual value, the change in the furnace temperature, and the fuel gas flow rate to the upper and lower limits. and a second means for changing the control range of fuel gas using a method based on an ambiguous theory.