JPH09968A - Method and apparatus for controlling mill for pulverized coal combustion boiler - Google Patents

Abstract

(57) [Summary] [Object] To provide a control device having a good load followability, which can accurately predict a mill warm-up time in a method for controlling a pulverized coal combustion boiler mill that is automatically controlled according to a target load. [Configuration] A load input unit 1 for inputting a target load schedule at each time, a coal supply time calculation unit for calculating a coal supply start time to the mill according to the input load schedule, a mill state before the start of warming up of the mill, Mill process data input section 3 for inputting mill process data such as primary air supplied to the mill during warming and time lapse of ambient temperature, and a mill for calculating the required warming time of the mill based on the input mill process data. A simulation model 4, a warming time calculation unit 5 that calculates a warming start time from a coal supply start time and a mill warming time, and a control unit 6 that controls a mill based on the coal supply start time and the mill warming start time. A control device for a mill for a pulverized coal combustion boiler equipped with.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a power plant equipped with a pulverized coal combustion boiler using a coal pulverizing mill, and particularly to a fine powder suitable for operating according to a predetermined load schedule. TECHNICAL FIELD The present invention relates to a method and an apparatus for controlling a mill for a charcoal-fired boiler.

[0002]

2. Description of the Related Art First, warming of a mill for a pulverized coal combustion boiler will be described. In order to secure the mill crushing ability, it is important to secure the drying rate in the mill. Therefore, balance the hot air and the cold air with respect to the coal feed rate and set the mill outlet air temperature to the set value (usually The temperature is controlled to be 80 ° C. Even when the mill is started, warm-up operation is performed before the coal is fed so that the mill outlet air temperature reaches the set value, then coal feeding is started, and this warm-up operation is called mill warming.

Next, the mill warming time will be described. The time it takes for the mill outlet air temperature to rise to the set value after the start of mill warming is called the mill warming time. This time was significantly changed (on the order of several minutes to several tens of minutes) depending on the mill stop time, the outside air temperature, and the primary air flow rate, and it was difficult to predict.

Next, the determination of the mil warming time will be described. As shown in Fig. 1, when the boiler load is changed, the number of mills required is determined by the boiler load. Therefore, the required coal feeding start time (a in Fig. 1) for the mill to be charged is determined according to the load change. Come on. In contrast, mil warming time (Fig. 1b) = coal feeding start time (Fig. 1
a) -Mill warming time, it is necessary to determine the mill warming time and issue a mill warming command, but it is difficult to predict the mill warming time. I was expecting warming time.

Method 1) Schedule the maximum required time as the mil warming time. Method 2) Scheduling with the required mill warming time for the mill exit temperature as a function (Fig. 2).

[0006]

In the above-mentioned prior art, since the time required for mill warming cannot be known,
The following problems frequently occurred. (1) When the warming time is set (assumed) to be shorter than the actual value, the schedule is delayed because the warming is not completed even at the coal feeding start time. (2) If the warming time is set longer than it actually is,
Not only will unnecessary power (mill power and primary blower power) be consumed unnecessarily by the mill warming, which will increase the in-house rate, but when a high load changes, multiple mill warming will be carried out simultaneously. Normally, simultaneous warming is not possible, so it is impossible to operate according to schedule. (3) In the method 1) as well as in the method 1), the mill warming time has a large correlation with the time taken to warm up the mill metal temperature, but the error is large because only the mill outlet air temperature is observed. , These issues have not been resolved.

An object of the present invention is to provide a method and apparatus for controlling a mill for a pulverized coal combustion boiler, which enables operation of a mill according to a load schedule.

[0008]

The invention claimed in this application to achieve the above object is as follows. (1) In a method of controlling a mill for a pulverized coal combustion boiler according to a load schedule, a step of inputting a target load schedule at each time, and a step of calculating a coal feeding start time to the mill according to the input load schedule And the energy balance in the mill based on the amount of residual coal in the mill before the start of mill warming, the mill casing temperature, the temperature in the mill, and the primary air amount and temperature to the mill during mill warming and the ambient temperature over time. For
A step of obtaining a warming time as the completion of warming in a state where the time response of the temperature in the mill is stable within a predetermined range; a step of calculating a warming start time based on the coal feeding start time and the warming time; A method for controlling a mill for a pulverized coal combustion boiler, comprising: a step of controlling the mill based on a coal feeding start time and a warming start time.

(2) In a device for controlling a mill for a pulverized coal combustion boiler according to a load schedule, a load input section for inputting a load schedule at each time and a start time for feeding coal to the mill are calculated based on the load schedule. Inputting data into the mill simulation model, such as the coal feeding time calculation unit, the temperature of the mill casing before starting the mill warming, the temperature inside the mill, and the amount of primary air to the mill during mill warming and the temperature and ambient temperature over time. The mill process input section, the mill simulation model section that calculates the mill warming time until the temperature inside the mill reaches the predetermined range based on the above input data, and the warming start based on the coal feeding start time and the mill warming time A warming time calculation unit for calculating the time, the coal feeding start time and the mill time. Control device for mill pulverized coal combustion boiler, characterized in that a control unit for controlling the mill on the basis of timing start time.

[0010]

OPERATION The prediction of the mill warming time will be performed as follows. 1. The mill casing temperature and the temperature inside the mill before the start of mill warming are set as initial conditions. 2. It is assumed that the primary air amount to the mill during warming and the time variation of the same temperature are the boundary conditions (assuming according to the mill warming operation method). 3. The differential equations for mass balance and energy balance in the mill are shown in 1.2. Solve using the initial and boundary conditions given in (determine time response). 4. 3 above. When the time response of the temperature inside the mill obtained in step 2 exceeds a predetermined value and the warming is completed at a stable stage, the time is obtained.

[0011]

EXAMPLE An example of the present invention will be described with reference to FIG. FIG.
In the above, 1, 2, 5, 6, and 7 are components of the conventional control device. An input unit 1 is an input display device through which an operator inputs a load schedule (load for each time). 2 is a coal feeding time calculation unit, which calculates a mill coal feeding start time. A warming time calculation unit 5 calculates a mil warming start time. A mill control unit 6 receives commands from the coal feeding time calculation unit 2 and the warming time calculation unit 5 and controls a mill-related damper, a coal feeding machine, and the like. Reference numeral 7 is a coal crushing mill, which includes electric contacts of the mill body such as a mill motor contactor and a coal feeder contactor. A mill process input unit 3 is an input device of mill process data necessary for calculation of the mill model 4. Reference numeral 4 denotes a mill model, which is a unit for calculating a mill warming time.

Predicting the warming time of the mill will be described below. Assuming that the temperature of the metal constituting the mill outlet pipe as the pulverized coal production equipment is T _m [° C.], the metal is transferred from the solid-gas two-phase flow from the pulverized coal production equipment 1 to the heat transfer coefficient α
_i [kcal / m ² s ° C.] and a heat transfer area A _i [m ² ] are heated, and a heat quantity Q ₁ [kcal / s] is received.

[0013]

[Equation 1]

Similarly, the amount of heat Q _e around the temperature T _e [° C.]
When heat dissipation of [kcal / s] is performed, the heat transfer coefficient at this time is α _e [kcal / m ² ° C], and the heat transfer area is A _e

[0015]

[Equation 2]

When the mass of the metal is W _m [kg] and the specific heat is C _m [kcal / kg ° C.], the following heat balance is established.

[0017]

(Equation 3)

The heat balance in the mill for pulverized coal production equipment is as follows.

[0019]

[Equation 4]

Here, the above equations (1), (2),
Considering the equation (3), the dynamic characteristic model of this example can be reduced to the following equation.

[0021]

(Equation 5)

[0022]

(Equation 6)

[0023]

(Equation 7)

[0024]

(Equation 8)

For the sake of simplification, the equation (5) will be discussed below.
Advance the argument. Equation (5) is a vectorial differential equation of continuous system
There are various methods to solve this with a computer, but the most
The simplest is the forward Euler method. This is time t_k-1
Where the vector x_k-1= X (t_k-1), Vector u
_k-1= U (t_k-1) Is known, t_k≒ t
_k-1The state of + Δt (after Δt [seconds]) is given by the following equation. What
Since the input u (t) can be measured, before the time of consideration,
The vector x, while all are known_k-1, Θ_k-1Is one
Generally, not all components can be measured, but the repeated
The assumption can be justified by calculation.

[0026]

[Equation 9]

Equation (9) is a recurrence equation. As described above, if the values at the time when it is easy to grasp each component of the vector x when the pulverized coal manufacturing facility 1 is stationary or stopped, By repeatedly using the equation (9) over time, the above-mentioned assumption that the vector x _k-1 is known can be justified. The other way to solve equation (5) is to use Runge =
There are various methods such as the Kutta method, the Paddy approximation method, the backward Euler method, and the trapezoid method, but these are positioned aiming at accuracy and stability of numerical calculation in exchange for complexity, and in terms of a recurrence formula ( It is essentially the same as equation (9).

The mill control is performed as shown in FIG. 3 by using the mill model 4 which performs the above-described calculation. From the input unit 1, the operator key-in (input) the time and target load,
The coal feeding time calculation unit 2 calculates the coal feeding start time from the keyed-in load schedule. From the mill process data input by the mill process input unit 3, the mill model 4
Calculates the mil warming time using the above-mentioned arithmetic expression. The warming time calculation unit 5 calculates the mill warming start time from the coal supply start time and the mill warming time. Based on the mill warming time and the coal feeding start time calculated as described above, the mill control unit 6 performs mill control of the necessary dampers, coal feeders, and the like.

[0029] Accordingly, the specific procedure for obtaining the warming time of the mill, as shown in FIG. 4, the mill at the time of stopping the mill outlet temperature T _oi, assuming a mill casing temperature T _mi, during warming operation Primary air flow rate W _a [kg /
s], while sequentially inputting the time change of the mill ambient temperature T _e ° C, it is possible to predict the time change of the mill outlet temperature T _o and the casing temperature T _m by repeatedly calculating the equation (9). Warming may be completed when the value stabilizes near a predetermined value.

[0030]

According to the present invention, since the mill warming time can be accurately calculated, the mill and the boiler can be operated without delay according to the load schedule of the boiler plant. Further, it is possible to prevent excessive energy consumption for mill warming.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a relationship between a coal feeding start time and a warming time in a boiler mill.

FIG. 2 is an explanatory diagram of a conventional technique.

FIG. 3 is an overall configuration diagram of the present invention.

FIG. 4 is a diagram showing a method of predicting a mill warming time.

[Explanation of symbols]

1 ... Load schedule input unit, 2 ... Coal supply time calculation unit, 3
... Mill process data input unit, 4 ... Mill simulation model, 5 ... Warming time calculation unit, 6 ... Mill control unit, 7 ... Mill.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nozomu Iyama 6-15-1 Ginza, Chuo-ku, Tokyo Power development company (72) Inventor Koji Yamamoto 6-9 Takaracho, Kure-shi, Hiroshima Babcock-Hitachi Stock Company Kure Factory (72) Inventor Koho Miyama 336 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Co., Ltd. Kure Laboratory (72) Inventor Shunichi Tsumura 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Kure Factory (72) Inventor Takayo Kawase 6-9 Takara-cho, Kure-shi, Hiroshima Babcock Hitachi Kure factory

Claims (2)

[Claims] 1. A method for controlling a mill for a pulverized coal combustion boiler according to a load schedule, the step of inputting a target load schedule at each time, and the time at which coal is fed to the mill is calculated according to the input load schedule. And the amount of residual coal in the mill before the start of mill warming, the temperature of the mill casing, the temperature inside the mill, and the primary air amount and temperature of the mill during mill warming and the ambient temperature over time, The step of calculating the energy balance and obtaining the warming time as the completion of warming in a state where the time response of the temperature inside the mill is stable within a predetermined range, and the warming start time based on the coal feeding start time and the warming time. A step of calculating and a step of controlling the mill based on the coal feeding start time and the warming start time are provided. A method for controlling a mill for a pulverized coal combustion boiler characterized by the above. 2. A device for controlling a mill for a pulverized coal combustion boiler according to a load schedule, and a load input section for inputting a load schedule at each time, and a time at which coal is supplied to the mill is calculated based on the load schedule. Inputting data into the mill simulation model, such as the coal feeding time calculation unit and the mill casing temperature before the start of mill warming, the temperature inside the mill, the primary air amount to the mill during mill warming, the temperature, and the ambient temperature over time. A mill process input section, a mill simulation model section that calculates a mill warming time until the temperature inside the mill reaches a predetermined range based on the above input data, and a warming start time based on the coal feeding start time and the mill warming time Warming time calculation unit for calculating A control unit for a mill for a pulverized coal combustion boiler, comprising: