JPS6029515A - Combustion controller - Google Patents

Abstract

PURPOSE:To automatically switch fuel without disorder of air-fuel ratio by swtiching the set value and controlling the calculation of a feed forward when two or more types of fuels are used. CONSTITUTION:An air flow rate regulating meter 39 compares the output of an excess air ratio conversion factor (mu) with the root conversion value of an air flow rate to obtain a signal for reducing a deviation, and applies the calculated value through a feed forward calculation controller 40 to an air flow rate control valve 31 as an air flow rate operation signal. The controller 40 directly adds feed forward amounts DELTAMV1, DELTAMV2 to the output of the meter 39 to control the operation of the flow rate control valve 31. Thus, the fuel can be automatically switched without disorder of air-fuel ratio.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to combustion control devices for combustion furnaces, boilers, kilns, etc. that switch between two or more types of fuel, and in particular, to control devices that do not cause disturbances in the air-fuel ratio. The present invention relates to a combustion control device that switches fuel to a pan press.

[Technical background of the invention and its problems]

Combustion furnaces that use heavy oil, gas, coal, etc. as fuel, burners, kilns, and other combustion control systems, and from the perspective of energy conservation such as waste gas utilization, are increasingly switching between two or more types of fuel. . Conventionally, in an example in which one type of fuel is used, combustion control is performed while keeping the air-fuel ratio constant by the double cross limit method as shown in FIG. Specifically, a thermocouple 2 and a combustion burner 3 are attached to the furnace wall 1 that is subject to combustion control, the signal obtained by the thermocouple 2 is converted into a temperature signal by a temperature converter 4, and this signal is converted into a temperature signal. The control signal SV is supplied to the controller 5, where the operating signal SV which should bring the inside of the furnace to the optimum temperature is output.

On the other hand, a fuel supply pipe 8 in which a flow meter 6 and a fuel flow control valve 7 are inserted is introduced into the burner 3, and an air supply pipe 11 in which a flow meter 9 and an air flow control valve 10 are inserted as a separate pipe. has been introduced. Furthermore, the temperature control needle 5, the flow meter 6, and the fuel flow rate controller 7f? An arithmetic control unit 12 and a fuel flow rate controller 13 that adopt the double cross limit method and are configured using software such as a microcomputer are interposed between the temperature controller 5, the flow meter 9, and the air flow rate controller. The arithmetic control section 12 and the air flow rate adjustment needle 14 are interposed between the total 10 and the airflow control section 12 .

By the way, when performing optimal combustion using the above-mentioned combustion control means, the flow rate ratio between the air flow rate and the fuel flow rate (hereinafter referred to as
It is essential to keep the air-fuel ratio (commonly referred to as the air-fuel ratio) constant, and for this reason, the arithmetic and control unit 12 uses the double cross limit method. In other words, in this double cross limit method, the air flow rate detected by the flow meter 9 is set to (β is the stoichiometric air-fuel ratio, μ is the excess air ratio), and this converted value is converted into the fuel flow rate.
The upper limit level setting section 121a and the lower limit level setting section 121b of the signal limiting section 121O are limited by 3 and 10 Ks, and the high level selection section 121c and the low level selection section 121d select the operation signal Sv. The fuel flow control valve 7 is controlled by comparing and selecting the optimum fuel flow rate signal for the air flow rate.

Similarly, the air flow rate conversion control for the fuel flow rate is performed by converting the fuel flow cap signal pv detected by the flow rate needle 6 into the second signal restriction unit 1.
22 are supplied to a low level selection section 122C and a low level selection section 122d via a lower limit level setting section 122a and an upper limit level setting section 122b, respectively, and compared with the operation signal Sv.

The signal output through 122d is converted into an air flow rate using the stoichiometric air-fuel ratio β and the excess air ratio μ, and the air flow control valve 1o is controlled based on this converted value. In this case as well, the lower limit level setting section 122a and the upper limit level setting section 122b limit the parameter to 4ts1- to 2s.

In this way, the detected fuel flow rate and the detected air flow rate mutually limit the flow rate of the other side. That is, in the double cross limit method fuel control shown in FIG.
s To~+Kt ts, the air flow rate is 4/10 ts~
Combustion is controlled so as not to exceed -Kg '16.

By the way, conventionally, when switching and using two or more types of fuel, one type of fuel is supplied using the same fuel supply pipe 8, and then that fuel is completely cut off and the other type of fuel is supplied. system and multiple fuel supply pipes 8 as shown in Figure 2.
1.82 is provided, and the fuel is switched by manually operating the switch 15.15. However, the former method has the drawback that the supply of one type of fuel must be stopped, and combustion cannot be controlled smoothly. The latter method requires an interrogation operator to switch fuels, and has drawbacks such as the air-fuel ratio being disturbed when switching between fuels 1 and 2.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and provides a combustion control device that can automatically switch fuel while maintaining an appropriate air-fuel ratio even during fuel switching in a combustion control system that uses two or more types of fuel. There is a particular thing.

[Summary of the invention]

When using two or more types of fuel, the present invention performs arithmetic control of double cross limit, set value switching, and feed forward using a hard sequence, an analog meter, or a micro combination. This is a combustion control device that automatically switches fuel without causing disturbances in the air-fuel ratio.

[Embodiments of the invention]

FIG. 3 is a diagram showing an example of a sixth embodiment of the combustion control device according to the present invention. That is, in this device, a thermocouple 22 and a combustion burner 23 are attached to a wall 21 to be controlled for combustion.
The signal obtained by the thermocouple 22 is converted into a temperature signal by the temperature converter 24 and then sent to the temperature controller 1125. This temperature controller 25 generates and outputs an operating signal MV that will bring the temperature inside the furnace to an optimum level.

First and second fuel supply pipes 261 and 262 for individually supplying fuel 1 and fuel 2 are introduced into the combustion burner 23, and the first fuel supply pipe 261 is equipped with a flow meter. 271 and a fuel flow control valve 281 that adjusts the flow rate of fuel 1 are inserted, and a flow meter 272 and a fuel flow control valve 282 that adjusts the flow rate of fuel 2 are similarly inserted in the second fuel supply pipe 262. ing. Also,
The combustion burner 23 has an air supply pipe 29 as a separate pipe, a flow meter 30, and an air flow control valve 3 for adjusting the air flow rate.
1 is inserted.

Furthermore, a temperature controller 25 and a fuel flow control valve 281.28
Fuel flow that controls 2! Between the controllers 321 and 322, an arithmetic and control unit 33 that employs the double cross limit method and configured using a microcomputer or the like is sandwiched between the first and second set value automatic switching type arithmetic and control units. 34.35 are provided.

The first set value automatic switching calculation control unit 34 receives the operation signal MY output from the temperature controller 25 and the fuel 1, respectively.
and i! to the input signals to the fuel flow rate controllers 322, 321 of the other systems. 2 to rameta
11 Subtract Klm from Jl signal with elements 341, 34
These subtracted outputs are supplied to the high level selection sections 331 and 332 of the double cross limit calculation control section 33.

The double cross limit calculation control unit 33 performs a route calculation on the air flow rate detected by the flow meter 30 so that the air-fuel ratio does not deviate from a certain range even in a transient state where the temperature fluctuates rapidly. After the sill calculation is performed by element 36, this calculated value is converted into a fuel flow rate by VC (where β1 and β3 are the stoichiometric air-fuel ratio 1μI for fuels 1 and 2, and Iμ2 is the excess air ratio for fuels 1 and 2). The converted value is
Upper limit L/Hell setting fm corresponding to fuel 1 and fuel 2 systems
331■, 5stxI and lower limit level setting section 333T
, , 334 L-shaped meter K11iKls K
11 r K21 and high level selection section 331.
332 and low level selection sections 338 and 334 respectively compare and select the set value with the output of the automatic switching calculation control section 34, and determine the optimum fuel flow rate of Fuel 1 and Fuel 2 for the air flow rate.

Further, the double cross-return calculation control section J3 performs each subtraction element 341. of the set value automatic switching calculation control section 34.
The air flow control valve 31 is controlled using the output from the air flow control valve 342, and the flow rate signal pv for the fuel 1 and the fuel 2 is used.

9- A lower limit level setting unit 335L individually sets Pv2.

336L and upper limit level setting section J, 97H.

338H No. 10, 104 and 2*K
The low level selection section 335, 3:16 and the high level selection section 337#338 compare and select the signal limited by l, and output the result. Then, the high level selection section 33'i, 3
After taking into account the stoichiometric air-fuel ratios βl and β3, the output of 3B is added by an addition element 37, and sent to an excess air ratio conversion element μ to be converted into an air flow rate. A correction signal for low combustion is supplied from a correction element 38 to this excess air ratio conversion element μ. A signal output from the excess air ratio conversion element μ is introduced into the air flow rate controller 39. This air flow controller 39 is
The output of the excess air ratio conversion element μ is compared with the route conversion value of the air flow rate, and after a signal that reduces the deviation is calculated, this calculated value is sent to the air flow rate via the feedforward calculation control unit 40. The signal is given to the control valve 31 as a signal for controlling the air flow rate. This feedforward calculation control unit 10-40 applies a feedforward amount ΔMVt to the output of the air flow rate controller 39 when switching between fuel #1 and fuel #2.
, ΔMV, are directly added to control the operation of the air flow control valve 31.

Further, the second set value automatic switching calculation control section 35 controls the fuel 1
and fuel 2 according to a predetermined program.
The main turn set value Sv is supplied to the fuel flow rate controllers 321 and 322.

In addition, on the input/output side of the fuel flow rate controller 321, there is a switching unit 411 for selecting the output of the double cross IJj but calculation control unit 33 and the output of the flow meter 271, and a switch unit 411 for selecting the output of the double cross IJj but calculation control unit 33 and the output of the flow meter 271, respectively.
A switching unit 421 is provided for supplying and canceling the operation signal supplied from the control valve 281 to the control valve 281. Similarly, a switching unit 412 is provided on the input/output side of the fuel flow rate controller 322.
．． 422 is provided. Furthermore, the second set value automatic switching calculation control 35 is also provided with switching units 351 and 352. These switching units 351, 352, 411,
412. CHI.

422 is manually or automatically switched at a required timing when fuel 1 and fuel 2 are selectively used.

In the case of automatic switching, it is assumed that the switching is performed while detecting the sequence program or combustion state.

Next, the operating state of the apparatus configured as described above, particularly when switching fuel, will be explained with reference to the time chart shown in FIG. 4. First, it is assumed that the temperature control needle 25 outputs an operation signal MY as shown in FIG. When combustion control is performed using one type of fuel in this state, by employing the arithmetic control section 33 using the double cross limit method, combustion control is performed while maintaining an appropriate air-fuel ratio as described in the conventional example.

By the way, combustion control is performed using the operating line fuel 1 shown in FIG. 2, but in this state, it is assumed that combustion control is performed by switching to fuel 2 at timing t1. In this case, a switching signal is manually or automatically applied to switch the switching sections ssi and ssx to the set value side, and the switching sections 412 and 422 are selectively closed.

(2) As a result, a pattern setting value such as 8V1 shown in FIG. 4 is inputted from the calculation control unit 35 of the second set value automatic switching method to the fuel flow rate controller 321 according to a predetermined program.

As a result, the set value Sv1 of fuel 1 gradually decreases to zero according to the program. According to this, the fuel flow controller 3
21 outputs an operation signal MVI as shown in FIG. 4, which is applied to the fuel flow control valve 28.

■ On the other hand, in the fuel 20 control system, the switching section 352,
412, 422, the calculation control unit 35 of the second set value automatic switching method is activated, and the pattern set value SVZ
Since the value increases slowly from zero, the calculation control section 34 of the first set value automatic switching method switches to the pan press. As a result, the set value SV2 of the fuel flow rate adjustment needle 322 is set to SV2.
=MVmK12-8V1mK1°. Kl is a conversion coefficient when switching fuel 1 to fuel 2.

13- ■ During the switching operation, the operation signal MV2 output from the fuel flow rate controller 322 has ML as the lower limit, and is 8V lower than ML.
Double cross limit control is performed with pattern setting value 2.

■ On the other hand, in the air flow control system, in order to maintain the optimum air-fuel ratio during switching operations, the air flow control system is controlled to maintain the optimum air-fuel ratio. The feedforward amount ΔMV is added to the output of the controller 39 to obtain an operation signal MV3 for the air flow control valve 31. In this way, the air flow controller 3
The reason why the feedforward amount ΔMV is added to the output of 9 is to prevent the air-fuel ratio from being disturbed due to the delay of the air flow rate controller 31 and the flow rate of the fuel 2 becoming ML. In Figure 4, S
is a switching signal of the switching section.

■ The fuel 1 operation signal MVJ decreases, and MY 1 = M
When L is reached and the main turn setting value of fuel 1 becomes zero, a fuel 1 cutoff request signal Do is output. When the operator is not involved, a cutoff command signal DI is directly output to turn off the switching section 421, and the predetermined switching section is returned to its original state.

■ Note that when the 14-cut command DI is input from the outside by deisotal input, the operating amount of fuel 1 is set to OmA.
Then, the valve 281 is fully closed.

When switching from fuel 2 to fuel 1, the switching control is also performed according to the sequences ① to ① above.

In the above embodiment, the calculation control section 33 using the double cross limit method was used to keep the air-fuel ratio constant, but even if the air-fuel ratio is controlled using the single cross limit method or other methods, it will not be possible to control the air-fuel ratio using two types of fuel. It is possible to switch automatically.

〔Effect of the invention〕

As detailed above, according to the present invention, the microcombi,
- By using a software-configured arithmetic control unit, the air-fuel ratio is maintained at the time of fuel switching, and the setting values for each fuel are distributed to the pan press automatically, without operator intervention. Fuel switching can be performed at any time, and there is no need to temporarily stop combustion when switching fuels.

Further, since the air-fuel ratio can be maintained at a predetermined value even when switching fuels, it is possible to provide a combustion control device that is effective in terms of energy conservation and can avoid pollution problems caused by the generation of black smoke.

[Brief explanation of drawings]

1 and 2 are block diagrams showing a conventional combustion control device, FIG. 3 is a block diagram showing an embodiment of the combustion control device according to the present invention, and FIG. 4 is a block diagram of the device shown in FIG. FIG. 3 is a timing chart explaining the operation. 21... Wall part subject to combustion control, 22... Thermocouple, 23
... Combustion burner, 24... Temperature converter, 25...
・Temperature controller, 2#...Air supply piping, 33...Arithmetic control unit using double cross limit method, 34.35
...Set value automatic switching calculation control unit, 38...Correction element, 39...Air flow rate controller, 40...Feedforward calculation control unit, 261...First fuel supply pipe,
262...Second fuel supply pipe, :4!1, :I2
2...Fuel flow rate controller.

Claims (1)

[Claims] In a combustion control device that switches between two or more types of fuel, there is a temperature control system that detects the temperature of the combustion control target and outputs a signal to set the temperature to a predetermined temperature, and a temperature control system that supplies a signal to the combustor that is the combustion control target. The first thing to be done. an arithmetic control section that detects the fuel flow rate and the air flow rate of the second fuel and controls the air-fuel ratio of the air and the fuel to a constant level while comparing the parameter signal and the output of the temperature control system; Set value automatic switching means are provided at the input and output terminals of the control unit, and the set value automatic switching means distributes the set value of each fuel to the pump press when the fuel is switched, and the set value automatic switching means is provided at the input and output terminals of the control unit. It is characterized by comprising a fuel flow rate adjustment needle that controls the fuel flow rate based on a set value, and a feedforward calculation control means that controls the air flow rate by adding a feedforward signal to the air flow rate control signal when switching the fuel. Combustion control device.