JPS5886322A - Controlling device for mechanical stokers of boiler - Google Patents

Abstract

PURPOSE:To calculate the rate of speed change of mechanical stokers in order to suppress the disturbance as low as possible by a method wherein the rate of change of combustion quantity in proportion to the rate of change of load accompanied by the increase and decrease of the number of the mechanical stokers under operation at the start and stop of the boiler in the controlling device of the mechanical stokers of the boiler used in a thermoelectric power plant. CONSTITUTION:An instruction 109 of the rate of change of load from a plant general- controlling device X, which controls both the combustion system of the boiler 2 and the steam of a turbine 6 in keeping co-operation with each other, is converted into a rate of change signal 112 of the speed of mechanical stoker. Said rate of change signal 112 of the speed of mechanical stoker, a speed setpoint signal 106 and speed signals from the respective mechanical stokers are inputted to a mechanical stoker controlling signal generator 64 in order to calculate speed controlling signals of mechanical stokers. Said speed controlling signals are sent to the respective mechanical stokers under operation at present out of a plurality of mechanical stokers, being selected by a signal selector switch 54' in order to control the speeds of the mechanical stokers at their start and stop based upon the change of rate of load at that time resulting in suppressing the disturbance as low as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of the Invention The present invention relates to a control device for a boiler coal feeder in a thermal power plant.

(b) Technical background 1 As is well known, a coal-fired power plant is shown in Figure 1. In other words, water is supplied to the boiler 2 by the water supply pump 1 F.
A system that supplies WF, superheats it with a coal burner 3 in a boiler 2, generates steam, rotates a turbine 6 through a steam pipe 4 and a steam control valve 5, and generates electric power MW from a generator 7. It is. The amount of generated power is increased or decreased by controlling the steam control valve 5 by the plant integrated control device 8. This plant general control device 8 calculates the amount of water supply and fuel required to obtain the target amount of generated electricity,
A command is issued to the water supply pump 1 and coal feeder A. Water supply FWF
This is why the steam pressure P and its temperature are also fed back to the turbine 6 to generate steam that meets the required conditions, and the amount of steam is controlled by the steam control valve 5. It is controlled to reach the target amount of electricity.

Here, each coal burner 3 in the boiler 2 is connected to a crusher (
Mill) Powdered fuel (fine coal powder) is sent to mill B. Coal feeder A supplies coal to this crusher B. In addition, in coal-fired power plants, coal is treated as fuel for boiler 2, so the total fuel F in the power plant is
When n coal feeders A and n crushers B are provided, F=ΣFn.

n=1 By the way, there is a limit to the range in which the plant integrated control device 8 can automatically perform feedback control to reach the target power amount as described above, and generally when the generated power MW becomes 25% or more of the rated maximum output It is stipulated that Therefore, until the plant integrated control device 8 is in a state where it can control the water supply FWF and the fuel amount F in automatic mode, various operations that the plant integrated control device 8 should originally control must be performed manually. Then, it is necessary to switch to automatic after that. In addition, even if the load is 25 cm or more, the startup, warming, and initial fuel injection of coal feeder A and crusher B are performed manually, and the coal supply to the coal burner 3 allows stable combustion. It is necessary to increase or decrease fuel.

However, this manual control of increase or decrease of fuel (in this case, manual means outside the automatic control by the plant integrated control device 8, and also includes control by another control device such as a computer) If this is done without considering the state, the balance between the load change and the total fuel flow rate (=total coal feeding amount) will be lost, and to compensate for this, the command for coal feeding mA in automatic mode of the plant integrated control device 8 will vary. It turns out.

For example, consider a case where one coal feeder Ai is additionally activated manually when m coal feeders out of n coal feeders are operating in automatic mode. In general, the commands for each coal feeder A in automatic mode have upper and lower limit values set in order to overload the crusher B and limit the lower limit of the coal feed amount. The blocking action blocks feeder speed control. In addition, the rate of change in load changes depending on the startup mode self-load zone, etc., but if the startup speed of the coal feeder Ai in manual mode is controlled at the 1 rate, depending on the rate of change in load at that time, the plant integrated control The command to the coal feeder A fluctuates in accordance with the variation in the amount of coal fed by the coal feeder Ai which is not under the control of the device 80. If this fluctuation causes the upper and lower limits of φ to be exceeded, a blocking operation will occur, which is not preferable.

Furthermore, if there is a deviation between the combustion amount command for the load and the total coal feed amount, the air flow rate command and the water supply flow rate command will also be affected, causing disturbance to the plant. Therefore, it is necessary to manually increase or decrease the amount of fuel so as not to change the coal feeder command of the plant general control device 8 as much as possible. Particularly in the case of coal feeders, when changing the number of coal feeders, the load is not controlled at a fixed value as in water supply control, so special care must be taken when controlling the load.

(C) Purpose of the Invention The purpose of the present invention is to determine the combustion amount change rate (=coal feed capital change 1) according to the load change rate when the number of coal feeders increases or decreases during normal coal combustion of the plant or during startup. From this, the speed change rate of the coal feeder is calculated and automatically excluded, and the speed control of the coal feeder is performed based on the main speed change rate, thereby obtaining a control device for a boiler coal feeder that can suppress disturbances as much as possible. It is in.

(d) Structure of the Invention The present invention will be described below with reference to an embodiment shown in FIGS. 2 and 3. FIG. 2 is a control block diagram of a plant integrated control device for a coal feeder system that completely incorporates the control device X of the present invention. Signal 100 indicates the total amount of coal fed, signal 101 indicates the total amount of fuel oil, and the adder 50 adds them together to obtain the total fuel flow.
It becomes 1k102. Normally, when the load exceeds 50 inches, the total fuel oil flow rate 101 becomes 0 and the signals 100 and 102 become equal. A signal 103 is a load command, and a combustion amount command 104 is generated through a function generator 5. Reference numeral 52 denotes a deviation calculator which calculates a fuel flow rate deviation 105 between the total fuel flow i: 102 and the combustion amount command 104. A gain corrector 53 corrects the combustion amount command to a command for each coal feeder depending on the number of coal feeders in the automatic mode. 54 is PID
It is corrected by a gain corrector 53 in a computing unit, and a coal feeder speed command 1 is calculated from the combustion amount command.

The signal 106 is commonly called a mill master and is the basic signal for controlling the flow rate of the coal system.
When 4 is set to manual, the target value set manually is 10.
At step 6, coal feeder speed control is performed. A signal 106 after the mill master changeover switch 54 is uniformly transmitted to all coal feeders. In the figure, the l- diagram is drawn for a plurality of coal feeders, but since the operation contents are the same, only the a system will be described below.

Reference numeral 55a is a switch for switching between automatic and manual mode for each coal feeder, and in this figure, the a system is in the manual mode, and the b to y systems are in the automatic mode. 56a is the coal feeding machine that is the controlled object, and the idle signal 1 is
This is the speed command for actual coal feeding in 2007a.

57a is a function generator that changes the coal feeder speed 107a to the coal feed amount 10
Convert to 8a. The adder 58 is connected to each coal feed i: 108a to 2.
A total coal feed amount signal of 100 is created by adding the following.

The above is an outline of the control of the coal feeder within the plant integrated control device 8, and in the present invention, the boiler feed control is performed by this coal feeder. In the figure, numeral 59 denotes a main calculation unit which calculates a coal feeder speed command signal 110 by inputting a load change rate signal 109, a coal feeder speed target signal 106, and a coal feeder actual speed signal 107a-z from the outside. The signal changeover switch for each of the 60 coal feeders is used to switch to the coal feeding amount that is currently operating outside of APC control, and the signal 110 is used to set the analog memo 1J61a. The load change rate signal 109 passes through the function generator 64 and is converted into a fuel gauge change rate signal 111, and further passes through the function generator 63 and is converted into a coal feeder speed change rate signal 112. 64 is a coal feeder control signal generator.

FIG. 3 is a flowchart showing the coal feeder control signal generator 640 function. First, the coal feeder speed target value 106 and speed change rate signal 112 necessary for control are read in at 5TEPI. 8TEP2 compares the target value with a certain constant value 1~ to determine whether a speed request or a speed increase request is required.

This is the minimum speed target value that allows this coal feeder to switch from manual to automatic, and the speed target value when starting the coal feeder is always above this value. On the other hand, when the coal feeder is stopped, the target value of pumping speed can be determined from the minimum load limit of the mill, such as a speed increase request at the value Ra>K, and a speed request at the target value <K. In 5TEP3, the output pulse signal is determined based on the speed change rate command signal, but due to constraints on the equipment side, there is a maximum of li < motion fj at one time, so the obtained output pulse signal is the maximum drive amount. If the maximum drive amount is exceeded, control is performed using this maximum drive amount.

In the next KSTEP4, a pulse is output, and a time delay is applied to the actual speed for a delay time required for a response.

In 5TEP5, the deviation between the target value and the actual speed is calculated, and if the deviation is within the specified value ε, it is assumed that the control has been completed, and if the control is not likely to end, 8TEP1 to 5 are repeated.

(e) Effects of the Invention By using the control device for a coal feeder according to the present invention, it is possible to control the coal feeder startup/stop filtration process according to the rate of load change, so that the coal feeder can be started or stopped during load changes. AP also by
The C mill master signal has the advantage that it can be kept at a high level and avoid giving a large disturbance.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a coal-fired power plant, FIG. 2 is a block diagram showing one embodiment 9(1) of the present invention, and FIG. 3 is a flowchart showing the operation of the main calculation section. X...Control device 59...Main calculation unit 60
... Signal changeover switch 62, 63 ... Function generator 64 ... Coal feeder control signal generator

Claims (1)

[Claims] In the boiler fuel supply system VC, which has a plurality of coal feeders for supplying coal as fuel to the boiler of the power generation unit and a pulverizer for pulverizing the supplied coal, the combustion system of the boiler and the steam of the turbine are a function generator that converts a load change rate command from a plant general control device that coordinately controls both yarn tonneaus into a coal feeder speed change rate signal; and this coal feeder speed change rate signal and the plant general control device. Input the speed target value signal from the coal feeder and the speed signal of each coal feeder [7] Input the speed target value signal from the coal feeder and the speed signal of each coal feeder. A boiler characterized in that the boiler is equipped with a signal changeover switch for selecting a coal feeder and sending a control signal to select a coal feeder, and performs speed control when starting and stopping the coal feeder based on the load change rate at that time. Control device for coal feeding.