JPS6046336B2 - Boiler combustion control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device that controls a boiler that burns a plurality of types of fuel according to a boiler master signal.

In a boiler combustion control device, both the fuel flow rate and the air flow rate are controlled according to a boiler master signal.

In boilers that burn multiple types of fuel (such as boilers in steel plants), the amount of air required for each fuel is different.
Normally, a large amount of air is injected to ensure complete combustion.

However, such a method is inefficient and is also undesirable from the standpoint of preventing pollution. Therefore, it is necessary to devise a way to make the flow rate of air controlled according to the boiler master signal appropriate according to the composition of the fuel.

An object of the present invention is to provide a combustion control device for a boiler that burns multiple types of fuel, which operates the boiler with low excess air while controlling both the fuel flow rate and the air flow rate based on a boiler master signal. be.

In the present invention, a boiler master signal is given as a setting signal, an output signal of a first adder to be described later is given as an input signal,
A fuel flow controller that outputs a fuel flow control signal based on the difference between these two signals, a boiler master signal is given as a setting signal, an output signal of a multiplier to be described later is given as an input signal, and the difference between these two signals is given as a setting signal. An air flow controller that outputs an air flow rate control signal based on the flow rate of each of the plurality of types of fuel supplied to the boiler i, and the unit evaporation amount Ci of that fuel and the boiler master signal of 100
A first adder that weights and adds the product with the reciprocal of the amount of heat Z when expressed as a percentage, substantially calculates the flow rate Vi of each of the plurality of types of fuel supplied to the boiler by the unit theoretical air for that fuel. Quantity Ai and unit evaporation amount d of one fuel
The output of the second adder and the first adder weights and adds the product of the reciprocal of the unit theoretical air amount a1 of one fuel and the reciprocal of the heat amount Z when the boiler master signal is 100%. A divider that adds the signal with the output signal of the second adder, and a signal obtained by multiplying the flow rate signal of the air supplied to the boiler by the reciprocal of the excess air ratio η when the above one fuel is exclusively burned in the boiler. The function generator that generates, and the output signal of this function generator and the output of the divider! The above object has been achieved by a boiler combustion control device equipped with a multiplier for calculating the product of the signal and the signal.

The present invention will be explained below with reference to the drawings. The figure is a conceptual configuration diagram of an embodiment of the present invention. In the figure, this CTLl and CT! are a fuel flow controller and an air flow controller, respectively. The flow rate of each fuel quantity is detected by flow rate detectors F1 to F, respectively, weighted and added by an adder S1, and the result is given as an input signal to the fuel flow rate controller CTL1. The air flow rate is detected by a flow rate detector A, corrected by a function generator FX and a multiplier M, and then provided as an input signal to the air flow rate controller 5CTL2. Both controllers are commonly given the boiler master signal BMS as a setting signal. Both controllers produce a fuel flow control signal FCS and an air flow control signal ACS, respectively, based on the difference between the boiler master signal BMS and their respective four input signals. The function generator FX is given input/output characteristics as described below, and the air flow signal AF
An output signal E4 having a predetermined relationship with S is generated.

The divider D is given El, E2 as a result of weighted addition of the flow rate signals of each fuel amount by the adders Sl, S2.
Divider D divides signal E1 by E2 and provides the result E3 to multiplier M. Now, in order to maintain combustion with low excess air, the air flow signal AF'S is appropriately converted into a signal equivalent to the boiler master signal BMS, and the air flow controller CTL
2 must be entered.

The boiler master signal BMS is a signal based on the amount of heat and is expressed by the following equation. However, Z...The amount of heat when BMS=100% (Cae/H)
Qi...Measurement range of fuel flow meter Fi (Nm3/H)
C pi...Unit evaporation amount (Ca'/Nm3) f of fuel 1
Pi...Flow rate (%) of fuel 1 The required amount of air for this is expressed by the following formula.

However, η...Excess air rate Y...Air flow rate when AFS=100% (Nm3/
H) a pi... Unit theoretical air amount for 1 fuel (Nm3/
Nm3) Therefore, since the coefficient for converting the air flow signal AFS into a signal equivalent to the boiler master signal BMS is given by the following equation, by multiplying the air flow signal AF'S by the coefficient of equation (3), the air flow rate can be adjusted. A proper signal input to signal CTI-2 is obtained as follows.

That is, this equation becomes a function for converting the air flow rate signal AF'S into a signal equivalent to the boiler master signal.

Assuming that the main fuel 1 (normally, the rated boiler load can be operated only with this fuel) is in the exclusive combustion state as the single fuel, equation (4) becomes as follows.

Here, if a value that can ensure an appropriate excess air ratio for each load zone for a single fuel is used as η, then the conversion function should be as shown in the following equation. Therefore, it becomes.

Since η is the excess air ratio in the state of exclusive combustion of a single fuel, it can be easily determined, and therefore the conversion function AFS
/η can be easily set in the function generator FX.
Generally, main fuel 1 is selected as the single fuel, but even if other fuels 2 to 4 are selected, the relationship equivalent to equation (7) can be easily derived. For various fuels (
By inserting the relationship in equation (7) into equation (4), the following conversion function can be obtained.

Here, equation (8) can be written as follows.

It can be said that Ki in equation (9) is a coefficient that converts the flow rate Fi of fuel 1 into a flow rate calorie basis of fuel 1, and H in the [phase] equation is a coefficient that converts the flow rate Fi of fuel i into a theoretical air basis.

Here, since Qf, c,, a, and z are known constants, Ki, h, is also a constant.

Therefore, the adder S1 calculates ΣK,f in equation (11), and generates an output E1 obtained by weighting and adding the fuel flow signal F by a coefficient K.

Next, the adder calculates the coefficient H,fi in equation (9), and generates an output E2 obtained by weighting and adding the fuel flow rate F, with the coefficient Hi. D is a divider that calculates the quotient of these outputs and outputs E3=E1/E2, so E3=Tk
, flgi H, f. becomes. When this is multiplied by the output signal of the function generator lower X by the multiplier M, a signal according to equation (11) is obtained. Therefore, since an appropriate input signal is given to the air flow rate adjustment CTL2, the air flow rate adjustment CTL2 is given an appropriate input signal.
2, the air flow rate is controlled to an appropriately low excess state.

Note that the above embodiment is an example in which the output signals F, of the fuel flow rate detectors F1 to F4 are obtained as a percentage of the respective measurement ranges Q, but since Qifi is nothing but the absolute value flow rate, it can be expressed as ■. The conversion may be performed using the following equation.

A feature of the present invention is that, by focusing on one of the plurality of fuels, for example, the main fuel, other fuel flow rate signals are converted on either a calorific value basis or a theoretical air amount basis. In other words, since we use only the simple physical property values of the calorific value per unit fuel and the theoretical air amount, which are the most important factors for boiler fuel, the appropriate air flow rate can be calculated without being influenced by other fuel specific gravity or flow rate measurement methods. can do. As described above, according to the present invention, in a boiler that burns multiple types of fuel, the combustion control device operates the boiler with low excess air while controlling both the fuel flow rate and the air flow rate based on the boiler master signal. can be realized.

[Brief explanation of the drawing]

The figure is a conceptual configuration diagram of an embodiment of the present invention. CTLl...Fuel flow rate controller, CTL2...
...Air flow rate controller, F1-F4...Fuel flow rate detector, A...Air flow rate detector, Sl, S2...
... Adder, D ... Divider, M ...
・Multiplier, FX...Function generator.

Claims (1)

[Claims] 1 A boiler master signal is given as a setting signal, an output signal of a first adder to be described later is given as an input signal, and a fuel flow controller, a boiler master signal, which outputs a fuel flow control signal based on the difference between these two signals. A master signal is given as a setting signal, an output signal of a multiplier (described later) is given as an input signal, and an air flow rate control signal is output based on the difference between these two signals. The flow rate Vi of each fuel is substantially equal to the unit evaporation amount ci of the fuel and the boiler master signal 1.
The first adder adds the weighted amount by the product of the reciprocal of the amount of heat Z when the value is 00%, and the flow rate Vi of each of the plurality of types of fuel supplied to the boiler is substantially calculated based on the unit theory for that fuel. The air amount ai, the unit evaporation amount cl of one fuel, the reciprocal of the unit theoretical air amount al of one fuel, and the amount of heat Z when the boiler master signal is 100%
A second adder that weights and adds the product with the reciprocal of , a divider that divides the output signal of the first adder by the output signal of the second adder, and a flow rate of air supplied to the boiler. A function generator that generates a signal multiplied by the reciprocal of the excess air ratio η when the above one fuel is exclusively burned in the boiler, and the product of the output signal of this function generator and the output signal of the divider. A boiler combustion control device equipped with a multiplier that calculates .