JPH0360016B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improvement in means for setting a co-firing ratio in a co-firing boiler using a plurality of types of fuel.

<Prior Art> A typical example of a co-firing boiler control device will be explained with reference to FIG. 1 and 2 are the first fuel F ₁ and the second fuel F ₂
supply pipes, 3 and 4 are flow control valves inserted into these supply pipes, 5 and 6 are first and second flow controllers that supply operation signals MV ₁ and MV ₂ to these flow control valves, 7 , 8 are first and second flow rate sensors that measure the flow rates of the first fuel F ₁ and the second fuel F ₂ , and their measurement outputs
E _F1 and E _F2 are supplied as measured values to flow rate controllers 5 and 6, respectively.

9 is a boiler pressure regulator, 10 is a pressure sensor, and its measurement output E _P is supplied to the pressure regulator 9 as a measured value. S _P is the pressure set value, MV ₃ is the operation output, which is led to the adder 11 and outputs the output steam flow rate signal.
E _S is added as a feed forward signal and converted into the boiler master signal BM.

12 is a multiplier that multiplies the boiler master signal BM by the co-firing ratio R _S , and the multiplication output is supplied to the first fuel controller 5 as the flow rate set value S _F1 . 13 is a subtracter that subtracts the set value S _F1 of the first flow rate controller 5 from the boiler master signal BM, and the subtraction output is supplied to the second fuel controller 6 as the flow rate set value S _F1 .

With such a configuration, the boiler master signal
As BM increases/decreases, each fuel is controlled to increase/decrease at a set ratio.

Generally, when performing co-firing, for example, the first fuel
As _F1 , the response is fast, but expensive fuel (heavy oil, crude oil,
LNG, etc.) is often used as the second fuel _F2 , and a cheap but slow-response fuel (coal, wood waste) is often used as the second fuel F2. In such a case, it is natural to use the inexpensive second fuel _F2 as the base fuel, and use the fast-responsive first fuel _F1 for load absorption.

<Problems to be Solved by the Invention> However, in the configuration of the conventional device as shown in Fig. 4, in order to reduce F ₁ , it is necessary to reduce the co-firing ratio _R The amount of change in the installed value S _F1 with respect to the amount of time also decreases, and it may become difficult to absorb the load change. On the other hand, if the value of R _S is increased so as to increase the flow rate of F ₁ , a large amount of the expensive first fuel F ₁ will be consumed even when there is no load change, which is uneconomical.

The purpose of the present invention is to perform constant flow control for fast-responsive but expensive fuel, and to cover the load base with cheap but slow-responsive fuel, while at the same time allowing the fast-responsive fuel to follow the boiler master signal on a one-to-one basis when the load changes. The purpose of this invention is to improve the load following characteristics and realize a control device that solves the problems of the conventional technology.

<Means for Solving the Problems> The structural feature of the device of the present invention is that in a mixed combustion boiler control device that burns a first fuel that has a quick response but is expensive, and a second fuel that is cheap but has a slow response, 1. First and second flow rate sensors that measure the flow rate of the second fuel, and a second flow rate sensor that directly inputs the measured values from these sensors and sends an operation signal to the means that controls the flow rates of the first and second fuels. 1. The second flow rate controller determines the first flow rate by calculating the difference between the boiler master signal given based on the operational output of the boiler pressure adjustment and the signal related to the measured value of the second flow rate sensor. a first subtraction means for supplying a set value to the controller; and a second subtraction means for supplying a difference between the master signal and the first fuel requirement set value to the second flow rate controller as a set value. The point is that it is equipped with the following.

<Function> When the boiler master signal changes upward in a stepwise manner, since the response of the second fuel is slow, the output of the first subtraction means also responds in a stepwise manner to rapidly change the set value of the first fuel to follow it. . The output of the second subtraction means also increases in a stepwise manner, but the flow rate of the second fuel increases with a delay, and this increase causes the output of the first subtraction means to decrease and the flow rate of the first fuel to become smaller. That is, the first fuel increases and backs up during a transient period until the second fuel increases.

<Embodiment> The structure and operation of an embodiment of the device of the present invention will be explained based on FIGS. 1 and 2. Elements that are the same as those in FIG. 4 are given the same reference numerals and their explanations will be omitted. 14 is a first subtraction means that subtracts the measured output E _F2 of the second fuel flow rate sensor 8 from the boiler master signal BM and supplies a set value S _F1 to the first fuel F ₁ flow rate controller 5.
15 is a second subtraction means, which is a boiler master signal
Setting value from the first fuel requirement setting device 16 from BM
S _G is subtracted and a set value S _F2 is supplied to the flow rate controller 6 of the second fuel F ₂ .

Next, the operation will be explained with reference to FIG. 1st fuel
It is assumed that the response of F ₁ is fast and the response of the second fuel F ₂ is slow. A is the change in the boiler master signal BM, B is the measured value of the first fuel F ₁ with respect to the change in BM
Changes in E _F1 and set value S _F1 , and C also indicate changes in measured value E _F2 and set value S _F2 of the second fuel _F2 with respect to changes in BM, respectively.

When the boiler master signal BM rises in a stepwise manner at time _t1 , each of the set values S _F1 and S _F2 follows BM in a one-to-one manner and rises in a stepwise manner as shown by the dashed line. Since the response of the second fuel F ₂ is slow,
The set value S _F1 , which is the output of the first subtraction means, remains at a high level even after _t1 , and the flow rate of the first fuel increases rapidly to absorb the load change. When the flow rate of the second fuel F ₂ gradually increases at time t ₂ , the output S _F1 of the first subtraction means decreases as E _F2 increases, and settles to the original value at t ₃ . On the other hand, the flow rate of the second fuel _F2 gradually increases from _t2 and reaches the set value determined by the boiler master signal BM and the first fuel required amount set value _SG at time _t3.
The value is reached at , and thereafter it settles to a constant value.

When the boiler master signal BM falls stepwise at time _t4 , it exhibits a change of opposite polarity in the same way as above, and E _F1 and E _F2 stabilize at time _t6 .

FIG. 3 shows another embodiment of the invention. If it is difficult to measure the actual flow rate of the second fuel _F2 with a slow response due to coal, wood chips, etc., use the speed signal E _F2 of the fuel feeder 17 to the mill (pulverizer) in place of the actual fuel flow rate. will be carried out. In this case, since there is no delay in the feeder speed signal, if it is input as is to the first subtraction means 14, a difference will occur between it and the actual fuel flow rate of _F2 . 18 to compensate for this delay.
(dead time + first-order delay circuit) is inserted between E _F2 and the second subtraction means 14, and makes the actual flow rate of fuel _F2 substantially coincide with the feeder speed signal E _F1 .

<Effect> As explained above, according to the present invention, expensive fuel can be regulated to a constant low level regardless of the size of the boiler master signal, and It is possible to realize a control device with a simple configuration in which the fuel with a quick response can follow the boiler master signal on a one-to-one basis.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
3 is a block diagram showing another embodiment of the present invention, and FIG. 4 is a block diagram showing an example of a conventional control device. 1, 2...first and second fuel supply pipes, 5, 6...
...1st, 2nd flow controller, 7, 8...1st, 2nd
Flow rate sensor, 9... Pressure regulator, 10... Pressure sensor, 14, 15... First and second subtraction means, 1
6...First fuel requirement setting device, BM...Boiler master signal.

Claims (1)

[Claims] 1. A mixed combustion boiler control device that burns a fast-response but expensive first fuel and an inexpensive but slow-response second fuel, including first and second flow rate sensors that measure the flow rates of the first and second fuels; first and second flow rate controllers that directly input the measured value from the sensor and send operation signals to the means for controlling the flow rates of the first and second fuels, and based on the operation output of the boiler pressure adjustment. The given boiler master signal and the second
a first subtraction means that calculates a difference between a signal related to the measured value of the flow rate sensor and supplies the calculated value to the first flow rate controller as a set value; a second subtraction means for supplying the difference between the two as a set value to the second flow rate controller.