JPS6021293B2 - Multi-fuel mixed combustion control device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a multi-fuel mixture combustion control device.

In combustion, demands for energy saving, pollution prevention, combustion safety, etc. are becoming particularly strong, and sophistication of control is required. In response to this, combustion control in dedicated combustion furnaces has become considerably more sophisticated, but there is still a strong feeling that the combustion of multiple types of fuels has been left behind, and efforts have been made to adapt to the demands. The current situation is that nothing is available.

In other words, when burning a mixture of multiple types of fuel, only one type of typical fuel system is made to follow the load, and other types of fuel are controlled in a dedicated combustion furnace with a constant flow rate. Excess rate control is more difficult than in a dedicated combustion furnace, so it is basic and low-oxygen combustion control cannot be expected. However, recently, when burning a mixture of multiple types of fuel, m wants to control all fuels in accordance with the load.

■I would like to improve the excess air ratio control function to enable low oxygen operation. These demands are gradually becoming stronger. The reason for this is to save energy by using fuel rationally,
This is to prevent pollution and ensure combustion safety. An object of the present invention is to provide a multi-fuel mixture combustion control device that can satisfy the above requirements.

The outline of achieving this objective is to control the air flow rate and the flow rate of multiple types of fuel using a signal proportional to the required heat amount, and for the fuel system, it is calculated from the required heat amount signal Co and the measured air flow rate signal F^. The lower one of the upper limit allowable heat amount signals obtained by adding an instantaneous value proportional bias of K to the allowable heat amount obtained by Regarding the system, K2 is added to the required heat amount signal Co and the measured total heat amount signal C^.
Subtracting the instantaneous value proportional bias, C^(1-&)
Select the higher signal from the lower limit allowable heat amount signal, calculate the theoretical air flow rate by multiplying the selected signal by the ratio of theoretical air amount/heat amount in the current mixed combustion state, and add the theoretical air flow rate to the The air flow rate is controlled by multiplying the excess rate by the set value of the air flow rate control system.

Such a multi-fuel mixture combustion control device is capable of determining an accurate allowable amount of heat that does not produce black smoke based on the accurate required theoretical air flow rate and the current air flow rate, regardless of the mixed combustion state of multiple types of fuel. Since the upper limit value of can be calculated, it is possible to achieve low-oxygen combustion control operation that is close to the limit without the risk of generating black smoke even when a sudden load increase occurs, making a great contribution to energy conservation and pollution prevention. .

An embodiment of the present invention in which two types of fuels A and B and air are supplied to a burner section of a boiler and mixed and combusted there will be described with reference to the drawings.

The amount of heat required for the furnace load is known from any one of the temperature inside the furnace, the steam pressure of the boiler, and the steam flow rate of the boiler.

In the figure, it is determined from the steam pressure of the boiler. boiler 11
A pressure transmitter 1 that is provided on the outlet side of the
2 outputs a signal proportional to the steam pressure to the pressure regulator 13. This pressure regulator 13 has a pressure set value and a pressure transmitter 12.
The required heat amount signal C is obtained by calculating the difference between the output of Calculate. The required heat quantity signal CD calculated here is applied to the input sides of the low selector 14 and the high selector 15, respectively.

The low selector 14 receives the requested thermal energy signal C. and the upper limit allowable heat amount signal A, select a low level signal, and output this as a signal for the fuel flow rate set value. The high selector 15 receives the required heat amount signal C. is compared with the lower limit allowable heat amount signal B, a high level signal is selected, and this is output as a signal for the air flow rate set value. The output of the low selector 14 is multiplied by the ratio Q of the ratio setter 16 for setting the mixture ratio of fuel A, and the coefficient of the coefficient unit 17 for converting heat quantity to flow rate, and is output to the fuel A flow meter 18. is given as the fuel flow rate target value of the fuel flow rate controller 19 with the process variable being . Further, the output of the low selector 14 is sent to the ratio setter 16 by a subtracter 20.
The value from which the output value of is subtracted (Co or A) (1-Q,)
is given as the fuel flow rate target value of the fuel flow rate controller 22 with the fuel B flow meter 21 as a process variable. The lower limit allowable heat amount signal B given to the high selector 15 is the fuel A
The total heat amount C^ is calculated by the total heat amount calculator 23 which receives the output of the flow meter 18 of the fuel B and the output of the flow meter 21 of the fuel B.
is calculated, and this signal C^ is given (1
-K2) times the value obtained. Upper limit allowable heat amount signal A
are the output of the fuel A flowmeter 18 and the fuel B flowmeter 21
The total required theoretical air flow rate calculation unit 25 which inputs the output of C^/ A square root calculator 2 calculates the amount of heat per unit air flow rate by using the AR calculation formula, and calculates the square root of this amount of heat per unit air flow rate and the output of the air flow rate detector 27.
A multiplier 29 multiplies the measured air flow rate signal F^, which is the output of 8, by the reciprocal of the excess air ratio mountain.
This is the upper limit allowable heat amount obtained by applying a bias of (10 K,) to the value obtained in step 9. The signal selected by the high selector 15 is used to calculate AR/C^ by inputting the output C^ of the total heat amount calculator 23 which calculates the total heat amount C^ and the output AR of the total required theoretical air flow rate calculator 25. The theoretical air amount per unit heat output from the divider 31 that calculates the formula is multiplied by the multiplier circuit 32 to become an air flow rate setting signal, which is input to the ratio setting device 33, where it is multiplied by the excess air ratio, The air flow rate is controlled by giving the output of the square root calculator 28 as a set value to an air flow rate controller 34 which uses the process variable.

Note that 35, 36, and 37 indicate control valves. 38 indicates a burner section.

Next, the operation of such a configuration will be explained.

A pressure transmitter 12 measures the steam pressure on the outlet side of the drum boiler 11.
The signal is converted into a signal proportional to the steam pressure and transmitted to the pressure regulator 13. In this pressure regulator 13, the amount of adjustment required to make the difference between the pressure setting value and the output of the pressure transmitter 12 zero is determined using an adjustment calculation formula, and a signal corresponding to the amount of adjustment is obtained. The magnitude of the output signal of the pressure regulator 13 increases or decreases as the load on the boiler 11 increases or decreases.

In other words, it becomes the required heat amount signal Co. The required heat amount signal Co of the pressure regulator 13 is basically given as a target value for the fuel control system and the air control system, and in the fuel system, the total amount of various fuel flow rates is determined and the fuel flow rate is controlled. However, in the air system, the set value of the air flow rate is determined and the air flow rate is controlled.

First, the fuel system will be explained.

The air flow rate is detected by the air flow rate detector 27, and the square root calculator 2
8, a signal F^ proportional to the air flow rate is obtained.

This air flow rate signal F^ is multiplied by the reciprocal 1/mount of the excess air ratio peak and is supplied to the input side of the multiplier 29.

This multiplier 29 inputs signals of the actual measured total heat amount C^ in the current mixed combustion state output from the divider 26 and the total required theoretical air amount AR, and multiplies these two inputs to obtain the bias ( 10K,) into the coefficient unit 30, and the upper limit allowable heat amount signal AA = FAX house X
Obtain Master X (1 mountain).

The low selector 14 inputting the required heat amount signal CD and the above-mentioned allowable heat amount signal A dynamically limits the required heat amount signal Co with the upper limit allowable heat amount signal by selecting the lower signal. Therefore, the required heat amount signal Co does not exceed the upper limit permissible amount, and this selected signal is multiplied by Q in the ratio setter 16 set to the mixed combustion rate of fuel A, and the output of the ratio setter 16 is The coefficient unit 17 converts the amount of heat into the flow rate of fuel A, which is then given as the target value of the fuel flow rate A of the fuel flow rate controller 19 for fuel A.

The selected signal is used in the subtracter 20 to calculate the amount of heat allocated to fuel B by subtracting the amount of heat allocated to fuel A from the required amount of heat signal Co, and further converts it into the flow rate of fuel B to adjust the fuel flow rate. It is given as a total of 22 setting values. The output of the fuel flow rate controller 19 is given to the control valve 35, and the flow rate of fuel A is controlled so as to reach a set value.

The controlled fuel A is sent to the burner 38. The control output of the fuel flow rate controller 22 is given to the control valve 36 to control the flow rate of fuel B, and the outputs of the flowmeters 18 and 21 which detect the flow rate of each fuel sent to the burner 38 are as follows.
It is given to a total heat amount calculator 23 and a total required theoretical air flow rate calculator 25. In this total calorific value calculator 23,
The total calorific value of fuels A and B, that is, the total calorific value C^, is calculated, and the total required theoretical air flow rate calculation unit 25 calculates the total required theoretical air flow rate AR of fuels A and B, and the calculated total required theoretical air flow rate is guided to dividers 26 and 31, respectively. I'm nervous.

The divider 26 calculates C^/AR, that is, the amount of heat per unit air flow rate in the current mixed combustion state, and the divider 31 calculates AR/C^, that is, the theoretical amount of air per unit amount of heat in the current mixed combustion state. Calculate.

The air system will be explained.

K2 is added to the required heat amount Co and the total heat amount C^ using the coefficient machine 24.
Lower limit allowable heat amount signal B = (1-K2
)×C^ is guided to the high selector 15.

After the higher signal is selected, it is multiplied by the multiplier 32 by the output signal AR/C of the divider 31, that is, the theoretical air amount per unit heat in the current trench firing state, to obtain the required heat amount Co.
The theoretical air amount corresponds to To this theoretical air amount signal,
The set value of the air flow rate is obtained by multiplying the excess air ratio mountain set in the ratio setting device 33, and is led to the air flow rate adjustment meter 34 for adjustment calculation, and then the output controls the control valve 37.

The controlled air is introduced into burner 38 and combusted.

With such a system, the accurate required air flow rate required for the current combustion state can be calculated in any mixed combustion state.

(2) From the current air flow rate, at any mixed combustion rate,
The upper limit of the allowable amount of heat that does not emit black smoke can be accurately calculated, and from this, the required amount of heat C.

Since there is an upper limit on the amount of oxygen, no matter how sudden a load increase occurs, there is no risk of black smoke being emitted, allowing operation at the lowest possible oxygen concentration. '3} In the event that the air system becomes abnormal and becomes roiling, no matter what the Y/required heat amount Co is,
The fuel flow rate setting is also zero, so there is no risk of excess fuel, making it a safe system.

There are other effects.

Although the above description is for a case where a single instrument is configured using an analog type, this can also be applied within the scope of the gist even when a digital controller is used to perform configuration calculation control using software.

[Brief explanation of drawings]

The figure is a block diagram showing an embodiment of the present invention. 11... Boiler, 12... Pressure transmitter, 1
3...Pressure regulator, 14...Low selector, 15...High selector, 16...Ratio setter, 18, 21... ...Flowmeter, 19,22...
...Fuel flow rate controller, 23... Total calorific value calculator, 25... Total required theoretical air flow rate calculator, 26, 31... Divider, 29.・・・・・・
Multiplier, 24, 30...Coefficient unit, 32...
... Multiplier, 33... Ratio setter.

Claims (1)

[Claims] 1. In a combustion furnace that mixes and burns two or more types of fuel in air, there is a device that detects the load on the combustion furnace and outputs a required heat amount signal C_D corresponding to this load, and a device that detects the measured air flow rate and outputs the an air flow rate detector that outputs a flow rate signal F_A; a device that calculates the measured total amount of heat from the total measured fuel flow rate of each fuel system and outputs a signal C_A corresponding to this total amount of heat; A device that calculates a theoretical air amount corresponding to the total amount of air and outputs a signal A_R corresponding to this air amount, a signal F_A, a signal C_A, a signal A_R, μ
, based on K_1, F_A×(C_A)/(A_R)×1
/μ(1+K_1) (where μ is excess air ratio and K_1 is a constant). A selection circuit, a ratio setter that sets the ratio α and outputs a signal of C_A×α as a target value of the fuel control system, and a signal C_A and the output signal of C_A×α of the ratio setter are input, and C_A(1 -α) as a target value for other fuel control systems, and a subtractor that outputs the signal of -α) as a target value for other fuel control systems, and a subtractor that outputs the signal of
1-K_2) (where K_2 is a constant), the high selection circuit selects and outputs the higher value, and the output of the high selection circuit is μ×(
A multi-fuel mixture combustion control device comprising: a second arithmetic circuit that calculates a required theoretical air flow rate by multiplying A_R)/(C_A) and uses this as a set value for air flow rate control.