JPH01114614A - System for controlling coal heating boiler - Google Patents

Abstract

PURPOSE:To reduce an energization time and prevent deterioration of performance of combustion during energization of a fine coal powder mill by a method wherein a required time until a fine powder coal mill outlet air temperature is made stable at a predetermined value and a required mill warming time are calculated and it is subtracted from a predetermined full load reaching time. CONSTITUTION:Gas of high temperature, air for example is guided to a fine powder coal mill 16 to perform a heating operation. After a fine powder coal mill outlet air temperature is increased more than a predetermined value, coal is fed and the fine powder coal mill 16 is energized. At this time, a full load reaching time is set in advance in a full load reaching time setting unit 15. A required time in which a mill outlet air temperature after feeding coal is made stable at a predetermined value and a required mill warming time is calculated under a fine powder coal mill simulation model 14. These required times are subtracted from the predetermined full load reaching time by a subtractor 19. An optimum mill warming starting time signal 22 being obtained is inputted to an energization sequence control device 14 and then an energization without any delay in the full load reaching time is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a boiler device that uses coal as fuel, and particularly to a control method for a boiler device that is suitable for starting up in a short time.

[Conventional technology]

An example of the configuration of a pulverized coal mill system according to the prior art is shown in FIG.
It is configured to pass through a hot air system consisting of a hot air system and a cold air system in which a cold air damper 3 is installed. The mixed cold and hot air adjusted by the cold air damper 3 and the hot air damper 4 is taken into the pulverized coal mill 6 via the secondary air fan 5. This secondary air is also used as pulverized coal mill warm-up air for starting the pulverized coal mill 6.

On the other hand, the coal stored in the coal bunker 8 is fed into the pulverized coal mill 6 by the coal feeder 7 and pulverized. The crushed pulverized coal is transported to the burner through the pulverized coal transport pipe 9 by primary air taken into the pulverized coal mill 6,
It burns together with the secondary air sent out from the forced fan l.

Startup control of such a pulverized coal mill system is performed using control signals (burner ignition signals 13 .
Coal feeder control signal 12. Hot air damper control signal 11. It was controlled by a cold air damper control signal 10).

FIG. 6 shows a conventional control method of the startup sequence control device 214. First, the secondary air fan 5 is started and warming of the pulverized coal mill 6 is started.

In this warming, the pulverized coal mill outlet air temperature is warmed up to a preset temperature or higher, that is, after it is confirmed that the warming is completed, the pulverized coal mill 6 and the coal feeder 7 are started. A series of steps from this warming to starting the coal feeder 7 are performed in sequence for the number of pulverized coal mills 6. In this way, the conventional startup control of a pulverized coal mill system is a control method (event feedback sequence control) that measures whether a certain state (event) such as a completion signal has been established and inputs the signal to the control device. It is carried out in

[Problem that the invention seeks to solve]

Fuel to coal-fired boilers is supplied by pulverized coal mills, but the properties of the coal fed into the pulverized coal mills vary depending on the production area, and the moisture content in particular is large, so the primary air used to transport the coal need to be dried.

For this purpose, it is necessary to warm up the inside of the pulverized coal mill to a specified value or higher in advance. Also, when warming up a pulverized coal mill,
The time required for warming up is affected by the season, weather, etc. and outside temperature. Therefore, if these are to be dealt with by the standard warming completion temperature, it is necessary to take these factors into consideration and set the temperature high in advance with a considerable margin.

In addition, the air temperature at the outlet of the pulverized coal mill after coal input must be maintained at a set value in order to send the pulverized coal crushed in the pulverized coal mill into the furnace at a predetermined transport speed. Due to the large drop in the air temperature at the outlet of the pulverized coal mill during the coal feeding process at startup, the moisture contained in the coal is insufficiently dried, deteriorating the combustion performance of the pulverized coal, and resulting in an increase in unburned content. At the same time, it also reduces the velocity of the primary air, which reduces the amount of pulverized coal supplied to the furnace.
Since combustion becomes unstable, it is necessary to confirm that the pulverized coal mill outlet air temperature after coal input is maintained stably at the set value.

In this way, the above-mentioned conventional technology does not take into account the setting of the required warming time for the pulverized coal mill.
There was the problem of extending the start-up time of coal-fired boilers, which necessitated allocating warm-up time with a margin. In addition, in conventional startup control, after the full load arrival time is set,
Since the startup sequence is started based on the operator's experience, it is important to maintain stable startup performance due to the above factors, but at the same time, the burden on the operator is large and the delay in reaching full load is a problem. there were.

The purpose of the present invention is to estimate the optimal startup control start time based on the full load arrival time and pulverized coal mill outlet air temperature setting, shorten the startup time, and prevent deterioration of combustion performance when starting the pulverized coal mill. It's about doing.

[Means for solving problems]

In short, the present invention estimates the optimal startup control start time based on the full load arrival time and the pulverized coal mill outlet air temperature setting value, shortens the startup time, and prevents deterioration of combustion performance when starting the pulverized coal mill. The purpose is to calculate the time required to warm up the pulverized coal mill to a set value or higher based on the coal properties and outside air temperature that affect the pulverizing performance of the pulverized coal mill, and to calculate the air temperature at the exit of the pulverized coal mill after coal is input. The part that calculates the time required for the pulverized coal mill to stabilize at the set value is constructed using a simulation model of the pulverized coal mill, and by subtracting the above required time from the preset full load arrival time, the pulverized coal mill This is achieved by calculating the optimal starting time to warm up the

[For production]

The present invention is capable of calculating the required warming time for the properties of coal to be charged into a pulverized coal mill and the outside air temperature at that time, and the time required for the pulverized coal mill outlet air temperature to stabilize at a set value after the coal is charged. . As a result, there is no need to set a warming time that takes into account factors that affect the grinding performance of the pulverized coal mill, so the time required to warm up the pulverized coal mill is shortened, and a stable pulverized coal mill outlet air temperature can be achieved. Since the amount of pulverized coal supplied to the furnace is stabilized, deterioration of fuel performance can be prevented.

Moreover, since the optimal startup start time can be set by subtracting the required time from the preset full load arrival time, the delay in the full load arrival time is eliminated.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention. The startup control system diagram in FIG. 1 shows an embodiment of the present invention. FIG. 2 is a startup control system diagram that performs optimal startup start control to shorten startup time and prevent delay in reaching full load.

In the figure, 15 is a start-up completion time setting device, 16 is a pulverized coal mill simulation model, 17 is a mill outlet air temperature stabilization time calculation unit, 18 is a mill warming time calculation unit, 1
9 is a subtracter, 20 is a start-up completion time signal, 21 is a feeder start-up time signal, 22 is a warming start time signal, 23
24 is a mill outlet air temperature stabilization time signal, and 24 is a mill warming required time signal.

The optimal warming start time is determined by setting the full load arrival time in the full load arrival time setting device 15 in advance, and waiting until the mill outlet air temperature after coal input, which is determined by the pulverized coal mill simulation model 16, stabilizes at the specified value. Subtractor 19 subtracts the time required for mill warming and the time required for mill warming.
By subtracting , the optimal warming start time signal 22 can be obtained.

Therefore, this mill warming start time signal 22 is the starting sequence 111? When inputted to II device 14, cold and hot air damper control signal 1 is generated by the activation control method shown in FIG.
0.11. Coal feeder control signal 12 and burner ignition signal 13
etc. are activated by event feedback, so
Start-up control of the pulverized coal mill is performed without delay in reaching full load.

The heat transfer process inside the pulverized coal mill using the pulverized coal mill simulation model 16, which is the basis of the present invention, will be explained on an internal energy basis.

This model takes into account changes in the state of water, that is, latent heat and sensible heat of water and steam, regarding the pulverized coal mill outlet air temperature, which is a factor that determines the completion of mill start-up.

First, the thermal energy balance inside the pulverized coal mill is shown below.

+w, cm'r+WeCeT) -FalCmTai+Fc1CcTcl+FwtHt-
(FaOC, T+FC, CeT+F*.h“tenF,.h
')-Q@, ・----
−−１−・−・−・−・・(1) Here, W w, Wc
, Wc, and Wc are the water mass, steam mass, and air mass 2 coal mass in the pulverized coal mill, respectively, and F a! ＋FC
1+F MA denotes the air mass flow rate, 2 coal mass flow rate, and water mass flow rate at the pulverized coal mill inlet, respectively, and Fl. +
FCO+pm. +Fw. are the air mass flow rate, pulverized coal mass flow rate, steam mass flow rate, and water mass flow rate at the outlet of the pulverized coal mill, respectively, and T, Tml + Tc1 are the average temperatures in the pulverized coal mill (air 1 coal, water, and (assuming that the water vapor temperatures are equal).

The air temperature and coal temperature at the pulverized coal mill inlet are shown.

C,, Cc are the specific heats of air and coal, and h'.

h#, v/, v'', p are the specific enthalpy, specific volume and pressure of saturated water and saturated steam, respectively.

Moreover, Q and f are the amounts of heat transfer between the solid air in the pulverized coal mill and the mill casing metal, and can be determined by simultaneously using the following equations.

Q+++r=AtUt (T-Tll) --
−−−−−=−−−−−−−−(2) Q*v−−AOU
6 (Tll Tea) -==-=-=-=
=-(3) dTII Here, Q and lI are the amount of heat transfer between the mill casing metal and the outside air, and T and T are the mill casing metal temperature and the outside air temperature, respectively. A1. A indicates the heat transfer area,
Ul and U indicate the heat transfer coefficient, C1 is the specific heat of the mill casing metal, and W.

is the mass of the mill casing metal.

In addition, the mass balance in the pulverized coal mill is calculated using the following formula % formula % Here, F and v are the amounts of water evaporated.

Therefore, (5), (6), (7), (81 formulas (
By substituting into the equation 1) and rearranging the rate of change of the average temperature T in the pulverized coal mill, the following equation is obtained.

T t Further, the evaporation amounts F and v of water are determined as follows.

Therefore, by using equation (9) and 01, the pulverized coal mill outlet air temperature T can be predicted.

Figure 2 shows an example of the results of simulating the outlet air temperature (curve 2) of the pulverized coal mill.The input data for the simulation are the pulverized coal mill inlet air temperature (curve 1), the amount of coal fed (curve 4) .

- has the following air mass flow rate (curve 7), and also curve 3.5
．． 6 indicates the pulverized coal mill casing metal temperature, the amount of coal produced, and the amount of coal held in the mill, respectively.

From these simulation results, the time required for the pulverized coal mill outlet air temperature to stabilize at the specified value as shown in Figure 3,
And the required time for mill warming shown in FIG. 4 can be calculated.

The factors that determine the time required for the air temperature at the outlet of the pulverized coal mill to stabilize in Figure 3 are the amount of water contained in the coal fed into the pulverized coal mill, the salinity of the coal, and the amount of water contained in the coal.

- There are considerable differences in the required time depending on the air temperature and outside air temperature, and the amount of moisture contained in the coal.

Further, there are similar factors that determine the time required for mill warming as shown in FIG. 4, and as shown in the figure, the time required varies depending on the outside temperature (for example, season).

By predicting changes in the pulverized coal mill outlet air temperature using this pulverized coal mill simulation model, it is possible to optimize the mill outlet air without any margin even when coal properties, outside air temperature, secondary air temperature, etc. change. Since the time required for the temperature to stabilize at a specified value and the time required for mill warming can be calculated, the time required for warming up the pulverized coal mill can be shortened and the delay in reaching full load can be eliminated.

In addition, since the mill outlet air temperature is stable, good combustion can be obtained.

〔Effect of the invention〕

According to the present invention, the time required for the air temperature at the outlet of the pulverized coal mill to stabilize at a specified value and the time required for mill warming are calculated, and the calculated time is subtracted from the preset full load arrival time to start optimal mill warming. Since the time can be obtained, it is possible to shorten the time required for warming, eliminate the delay in reaching full load, reduce the burden on the operator, and achieve good combustion.

In addition, before starting the pulverized coal mill, the primary air is heated by combustion in a light oil burner, and light oil is used until stable combustion is achieved with the fuel supplied from the pulverized coal mill, reducing the time required for mill warming. For example, the amount of diesel oil consumed can be significantly reduced compared to the conventional method, resulting in cost savings.

[Brief explanation of the drawing]

FIG. 1 is a startup control system diagram according to an embodiment of the present invention, and FIG.
The figure is a characteristic diagram to explain the pulverized coal mill simulation model, Figure 3 is a mill outlet air temperature characteristic diagram, Figure 4 is a mill warming time characteristic diagram, Figure 5 is a conventional start-up control system diagram, and Figure 6 is a characteristic diagram for explaining the pulverized coal mill simulation model. The figure is a flowchart for starting the mill. 14... Startup sequence control device, 15... Startup completion time setter, 16... Pulverized coal mill simulation model, 17... Mill outlet air temperature stability time calculation unit,
18... Mill warming time calculation section, 19...
- Subtractor, 20... Start-up completion time signal, 21... Feeder start-up time signal, 22... Warming start time signal, 23... Mill outlet air temperature stabilization time signal, 24
... Mill warming time signal. Figure 1 Figure 2 TIME (Sec) Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) In a start-up control method for a coal-fired boiler that warms up the pulverized coal mill by introducing high-temperature gas, and after the pulverized coal mill outlet air temperature rises above a set value, coal is introduced and the pulverized coal mill is started. , having a part that calculates the time required to warm up the pulverized coal mill to a set value or higher, and a part that calculates the time required for the pulverized coal mill outlet air temperature to stabilize at the set value after coal is input. Characteristic coal-fired boiler startup control method. (2) In claim (1), the time required to warm up the pulverized coal mill and the time required for the air temperature at the pulverized coal mill outlet to stabilize after coal is input are set in advance. 1. A coal-fired boiler start-up control method, comprising: a calculation section that calculates a time to start warming up a pulverized coal mill by subtracting it from a time when a full load is reached.