JPH094839A - Controller for pulverized coal boiler - Google Patents

Abstract

PURPOSE: To more acceptably conduct the operation of a boiler by correctly calculating the moisture ratio in coal even when the coal amount to be treated by a pulverized coal manufacturing facility, conveying air flow rate to be introduced into the facility and the outlet temperature of the facility are varied every moment. CONSTITUTION: Signals 62, 63, 64, 65 and vectors xk-1 , Uk-1 of previously calculated values stored in a memory 82 are input to a coal moisture estimating unit 81, the calculation is repeated until the converging condition of dynamic characteristic simulation model is satisfied. At the stage of completing the convergence, the vector xk is regarded as being a true value coincident with the behavior in an actual plant, and stored in the memory 82 together with the vector u1 , calculated from the signals 62, 63, 64, 65. Further, at the time point of the lapse of Δt, the memory 82 again applies the previously input value to the unit 81 as the vectors xk-1 , uk-1 . Similarly, the calculation and the storage are repeated at each time Δt.

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 pulverized coal boiler, and more particularly to a control device for maintaining good boiler operating characteristics regardless of the amount of water content during combustion.

[0002]

2. Description of the Related Art FIG. 2 shows a conventionally known pulverized coal boiler and its control device. The pulverized coal boiler of this example is
Pulverized coal production equipment 1 and raw coal 2 in the pulverized coal production equipment 1
A coal feeder 3 for supplying the pulverized coal, a furnace 4 for burning the pulverized coal produced in the pulverized coal manufacturing facility 1, a water wall 5 constituting a furnace wall of the furnace 4, and a water supply pump 6 for supplying water to the water wall 5. And a economizer 9 which is disposed in the flue 7 and preheats the water supply 8 of the water supply pump 6.
A horizontal superheater 10 provided in the flue 7, a suspension superheater 13 that superheats with the combustion gas 11 of the furnace 4 to generate main steam 12, and a part of the exhaust 14 It is mainly configured by a recirculation path 15 for recirculating in the furnace 4.

In the pulverized coal production facility 1, there is a carrier air 21.
Of the introduction pipe 22 is communicated, and in the introduction pipe 22,
A carrier air fan 23 that pressure-feeds the carrier air 21, a carrier air damper 24 that regulates the flow rate of the carrier air 21, and a throttle 27 that measures the carrier air flow rate are installed.
A flow rate detector 28 is set in the throttle 27, and a first temperature detector 29 is provided near the outlet of the introduction pipe 22.
Is set. Further, a second temperature detector 31 is set in a pipe line 30 for guiding the pulverized coal produced in the pulverized coal manufacturing facility 1 into the furnace 4 together with the carrier air 21. Further, the coal feeder 3 is provided with a coal feed amount estimator 32 for estimating the feed amount of the raw material coal 2. An introduction pipe 42 of combustion air 41 is communicated with the furnace 4,
A combustion air fan 43 that pumps the combustion air 41 and a combustion air damper 44 that regulates the flow rate of the combustion air 41 are installed inside the introduction pipe 42. A gas recirculation fan 46 for pumping a recirculation gas 45 is provided in the recirculation passage 15.
And a gas recirculation damper 47 that regulates the flow rate of the recirculation gas 45.

On the other hand, the control device of the present example is a control device for maintaining good boiler operation characteristics regardless of the amount of water during combustion, and mainly comprises a coal water estimator 51 and a correction operation amount calculation. And a container 52. The coal moisture estimator 51 has an outlet temperature signal 61 of the pulverized coal manufacturing facility 1 detected by the second temperature detector 31, and a coal feed amount signal 62 obtained by the coal feed amount estimator 32. , An inlet temperature signal 63 of the pulverized coal production equipment 1 obtained by the first temperature detector 29, an inlet air flow rate signal 64 of the pulverized coal production equipment 1 obtained by the flow rate detector 28, and The ambient temperature signal 65 of the pulverized coal manufacturing facility 1 obtained by the temperature detector 48 of No. 3 is input, and the coal moisture amount estimation signal 66 is output. The correction operation amount calculator 52 obtains the coal water content estimation signal 66, and supplies a coal feeder operation signal 71 for controlling the coal feeder 3 and a combustion air damper 44 provided in the combustion air introducing pipe 42. Combustion air operating signal 72 for controlling
And a gas recirculation operation signal 73 for controlling the gas recirculation damper 47 provided in the recirculation path 12.

The amount of water in the fuel coal in the pulverized coal boiler is not only the lower calorific value of the fuel, that is, the calorific value that is usable by the boiler except for the calorific value carried away by the steam in the combustion gas is reduced, but also in the furnace. In the boiler having 4 and the superheaters 10 and 13 in the combustion gas flow path, the heat absorption distribution of the both must be changed, and therefore, must be properly treated. The change in the lower heating value can be compensated simply by the increase in the fuel, but the change in the heat absorption distribution is a phenomenon brought about by the change in the combustion temperature in the furnace and the change in the radiative heat transfer coefficient of the combustion air 41. Flow rate and recirculation gas 4
This is complicated because the flow rate of No. 5 must be adjusted by operating the calculated value of the corrected manipulated variable calculator 52. In any case, the amount of water in the fuel must be accurately grasped by the coal moisture estimator 51 for these compensations and adjustments.

The calculation of the amount of water in the fuel by the coal water estimator 51 can be performed very easily when the pulverized coal manufacturing facility 1 is in a steady state. That is, in an environment where the ambient temperature is T _c [° C.], coal having a total weight including water of w _c [kg / s] and a total water of θ [%] is transferred from the coal feeder 3 to the pulverized coal crushing equipment 1. Air 21 for supplying and supplying the pulverized coal pulverizing equipment 1 for drying and carrying the pulverized coal is flow rate w _a [kg / s] and temperature T _a [° C.].
It is supposed to be blown by. Assuming that the temperature of the solid-gas two-phase flow of the pulverized coal produced at this time is T _o [° C], the steam in the solid-gas two-phase flow in this state is saturated vapor enthalpy h ″ at T _o [° C]. (T _o ) [kcal / kg], and the enthalpy of the supplied water is T _c [° C.].
Enthalpy h ′ (T _c ) [kcal / k of saturated water at
g] does not cause a large error, so assuming that the system is stationary, the energy balance and the mass balance can be described by algebraic expressions, and the following equation is obtained.

[0007]

[Equation 1]

Since the specific heats of air and coal can be regarded as constant within the range of the consideration, C _c [k]
cal / kg ° C], C _a [kcal / kg ° C], the water content in coal can be calculated by the following formula (2).
It is obtained by the formula.

[0009]

[Equation 2]

Variables T _o , w _c , T _a , w in the equation (2)
_a and T _c are respectively the above-mentioned second temperature detector 31,
It is obtained by the coal feed rate estimator 32, the first temperature detector 29, the flow rate detector 28, and the third temperature detector 48, and h ″ and h ′ are the functional forms thereof issued by the Japan Society of Mechanical Engineers. The water content θ in the coal can be easily calculated from the equation (2) because it is obtained from the steam table and the values of C _a and C _c can be obtained by referring to the science chronology.

[0011]

The above-mentioned conventional method of calculating the amount of water is effective when the operating conditions of the boiler are in a steady state. However, in a plant that is subject to load changes, various amounts such as the coal feed amount w _c , the air amount w _a , and the outlet temperature T _o change from moment to moment, and these amounts maintain a constant value for many hours. Driving methods that do this are rather rare. Therefore, the water content calculation method according to the conventional technique cannot obtain a sufficient effect even when applied to such a plant.

The present invention has been made in view of such circumstances, and an object thereof is to estimate the water content in coal not only in a steady state but also in a non-steady state and maintain good boiler operating characteristics. It is to provide a control device.

[0013]

In order to achieve the above object, the present invention provides a pulverized coal pulverizing equipment, a coal feeder for supplying raw coal to the pulverized coal pulverizing equipment, and the pulverized coal pulverizing equipment. Attached to a pulverized coal boiler having a boiler plant that burns the pulverized coal produced, at least an outlet temperature signal of the pulverized coal manufacturing facility, a coal feed amount signal supplied to the pulverized coal pulverizing facility, and the pulverized coal. Manufacturing facility inlet temperature signal,
The inlet air flow rate signal of the pulverized coal production facility and the ambient temperature signal of the pulverized coal boiler are input to calculate the amount of water in the coal supplied to the pulverized coal production facility, the coal feeder and the boiler. In a control device that outputs a signal that controls the flow rates of combustion air and recirculated gas that are introduced into the plant, each dynamic variable model of the pulverized coal boiler is given the same operation amount as the actual boiler, and a constant or variable cycle The amount of water in the coal supplied to the pulverized coal manufacturing equipment is calculated for each, and the calculated value is stored in the storage unit for each calculation, and the differential describing the dynamic characteristic model with reference to the previous calculated value. The equation was solved to find the calculated value this time.

[0014]

A dynamic characteristic model is a model described by a differential equation for analyzing a non-steady state, and a static characteristic of a steady state in which a set of solutions can be immediately obtained from input information at a certain point. Unlike the model, even if the input information is the same, the result is different depending on the past history. Therefore, even if the operating conditions of the pulverized coal boiler change from moment to moment, the amount of water in the coal at the present time can always be calculated by following it, and the coal feeding from the coal feeder to the pulverized coal manufacturing facility can be performed. The amount, the flow rate of the combustion air introduced into the boiler plant, and the flow rate of the recirculated gas can be controlled with good responsiveness. As long as it is premised that such a calculation is performed by digitizing the differential equation with respect to time and solving it with a computer, the model is executed with a constant or variable cycle, and the calculation results of the previous cycle are calculated. It can be realized by reflecting in the calculation of.

[0015]

EXAMPLE FIG. 1 shows the configuration of a pulverized coal boiler control apparatus according to an example. In this figure, reference numeral 81 indicates a coal moisture estimator, reference numeral 82 indicates a storage device, vectors x _k and u _k indicate calculated values, vectors x _k-1 and u _k-1 indicate previously calculated values, and other figures described above. In the portion corresponding to 2, the same reference numeral is displayed.

Next, the dynamic characteristic model of the pulverized coal boiler necessary for carrying out the present invention will be described. The supply amount of the raw coal 2 supplied from the coal feeder 3 to the pulverized coal manufacturing facility 1 is w _c [k
g / s], the amount of coal output from the pulverized coal manufacturing facility 1 is w _o [kg
/ S], the amount of coal pulverized coal production equipment 1's W _h
If there is [kg], there is the following relationship between them.

[0017]

(Equation 3)

The amount of coal produced W _o is proportional to the amount of stored coal W _h. Therefore, assuming a proportional constant ε [1 / s],

[0019]

(Equation 4)

Consider that Of course, the above equation is the simplest assumption, and for example, the dynamic characteristic model of the coal crusher using the cumulant statistic announced by the inventor (December 13, 1991, China Society of Instrument and Control Engineers) Academic lecture)
Can also be used to consider the effect of changes in the pulverized coal particle size distribution on the retained coal.

Next, assuming that the temperature of the metal forming the outlet pipe 30 of the pulverized coal manufacturing facility 1 is T _m [° C.], the metal is heated by the solid-gas two-phase flow conveyed from the pulverized coal manufacturing facility 1. It is heated at a transfer rate α _i [kcal / m ² s ° C.] and a heat transfer area A _i [m ² ] and receives a heat quantity Q _i [kcal / s] represented by the following formula.

[0022]

(Equation 5)

Further, from the metal, the ambient temperature is changed to T _c
[° C], the heat transfer coefficient is α _c [kcal / m ² ° C], and the heat transfer area is A _c , the heat quantity Q _c [kc
[al / s] of heat is diffused to the surroundings.

[0024]

(Equation 6)

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

[0026]

(Equation 7)

At this time, the heat balance inside the pulverized coal production facility 1 is as follows.

[0028]

(Equation 8)

In deriving the equation (8), the solid-gas two-phase flow is uniform, and the carrier air 21 is the pulverized coal manufacturing facility 1.
Not accumulated within the water in the coal is moved in association with the coal, and changes in the ratio x is to depend on the weather and coal lots, remarkably as compared with the change in Kyusumiryou w _c Is assumed to change slowly.

The left side of the equation (8) can be modified as follows in consideration of the above equations (3) and (4).

[0031]

[Equation 9]

By applying this to the equation (8), the following equation is obtained.

[0033]

(Equation 10)

Here, the formula (10) correctly evaluates the influence of the retained coal amount Wh, but is a form which is eliminated from the formula. Similar processing can be performed for the equations (3) and (4), and at this time, the following equation is obtained.

[0035]

[Equation 11]

Here, the above equations (5), (6),
Considering the equation (7), the dynamic characteristic model of this example can be reduced to the following equation.

[0037]

(Equation 12)

[0038]

(Equation 13)

[0039]

[Equation 14]

For the sake of simplicity, the discussion will proceed in the form of equation (12). The equation (12) is a continuous vector fine powder equation, and there are various methods of solving it by a computer, but the simplest is the forward Euler method. This is at a time t _k-1, the vector _{x k-1 = x (t} k-1), if the vector _{u k-1 = u (t} k-1) is known, t
_{The state of k} = t _k−1 + Δt (after Δt [seconds]) is given by the following equation. Since the input u (t) can be measured, all of them are known before the time of consideration, whereas the vectors x _k−1 and θ _k−1 are known.
In general, it is not always possible to measure all components, but the assumption can be justified by the repeated calculation described later.

[0041]

(Equation 15)

Equation (15) is a recurrence equation, and as described above, given values at the time when it is easy to grasp each component of the vector x when the pulverized coal manufacturing facility 1 is in a steady state or stopped, After that, by repeatedly using the equation (15) with the passage of time, the above-mentioned assumption that the vector x _k−1 is known can be justified. In addition to this, there are various methods such as the Runge-Kutta method, the Paddy approximation method, the backward Euler method, and the trapezoidal method for solving the equation (12). It is positioned aiming at sex, and it is essentially the same as Eq. (15) in that it is a recurrence formula.

Here, the temperature T _{o, k} = T _o (t _k ) of the solid-gas two-phase flow of the pulverized coal production facility 1 which is the first component of the vector x _k .
Suppose that it was possible to measure without large measurement noise. At this time, at the time point k, the water content θk _-1 of the coal is obtained by the following Newton-Raphson method. That is, under the known vector x _k−1 and vector u _k−1 , the measured T _{o, k}
Unknown parameter θ such that is equal to the calculated value T _{o, k}
Search for k. this is,

[0044]

(Equation 16)

Toki,

[0046]

[Equation 17]

The following equation may be repeated until

[0048]

(Equation 18)

Here, the superscript (l) of the first term on the right side of the equation (18) represents the number of times of repetition, and when the convergence is completed at the (n + 1) th time, the value is used as the estimated value. The estimated value is

[0050]

[Equation 19]

Can be expressed as

The initial value of the repetition of the equation (18) is

[0053]

(Equation 20)

For the numerator of the second term on the right side of the equation (18), the numerical derivative of the following equation may be used.

[0055]

(Equation 21)

As described above, the above method does not give good results when the measurement noise of T _o is large. In this case, the most orthodox method is to apply the extended Kalman-filter theory including the unknown parameter θ to the equation (12). However, even in this case, the calculated value by the model T _o is measured value T _o + V (V: Observation noise) closest (least squares sense) to an estimation of θ was the norm and positioning Is the same as in the case of Expression (18). Fuzzy reasoning and application of neural networks are also considered for the purpose of changing the measured values so that the measured values match the measured values. However, in any case, the idea is the same in that the unknown parameter is searched so that the predicted value obtained by the dynamic characteristic model matches the measured value.

The operation of the control device shown in FIG. 1 will be described below.

In the coal moisture estimator 81 of this embodiment, T _{o, k} , w _{c, k} , T _{a, k} , w _{a, k} and T _{c, k} are respectively detected by the second temperature detector 31. An outlet temperature signal 61 of the pulverized coal manufacturing equipment 1 detected, a coal feeding amount signal 62 obtained by the coal feeding amount estimator 32, an inlet of the pulverized coal manufacturing equipment 1 obtained by the first temperature detector 29 The temperature signal 63, the inlet air flow rate signal 64 of the pulverized coal production equipment 1 obtained by the flow rate detector 28, and the ambient temperature signal 65 of the pulverized coal production equipment 1 obtained by the third temperature detector 48 are input. . Further, the coal moisture estimator 81 inputs the vectors x _k-1 and u _k-1 which are the previously calculated values stored in the memory 82, as vector signals (to have a plurality of scalar signals as components). Then, the convergence condition (Equation (16)) described above for the operation of Equation (18)
Repeat until satisfied. When the convergence is completed,
The vector x _k in the equation (16) (calculated by the equation (15)) is regarded as the true value that matches the behavior in the actual plant, and the vector obtained from the signals 62, 63, 64, 65. It is sent to and stored in the storage device 13 together with u _k (see the equation (13)). At the time when the time further passes by Δt, the storage device 82 stores the previously input value in the vector x _k−1 ,
It is given to the coal moisture estimator 81 again as u _k-1 . Similarly, the above calculation and storage are repeated every time Δt.

In the above embodiment, the signals 62,
Although 63, 64, and 65 are temporarily stored in the storage device 82, they are read out and used by the coal moisture estimator 81, but the time when both the signal sampling and the coal moisture estimator 81 are processed on the computer. Since it is usual that a slight fluctuation occurs during the passage of one calculation cycle Δt, the signals 62, 6 input by the coal moisture estimator 81 depend on the degree of fluctuation.
In some cases, it may be better to consider 3, 64, 65 as the vector u _k-1 . In this case, the memory 82 stores the vector signal u
Since it is not necessary to handle _k and u _k−1 , the configuration is slightly simplified.

In the above embodiment, the constant period Δ
The calculation and the storage are repeated for each t, but when the operating condition of the pulverized coal boiler is in a steady state or an unsteady state to the extent that it can be regarded as a steady state, the coal feed amount W _c , the air amount W _a , the outlet temperature T _It is not necessary to repeat these calculations and storage in the same cycle as when the quantities such as _o change from moment to moment. Therefore, the cycle of calculation and storage can be made variable according to the operating conditions of the pulverized coal boiler.

[0061]

As described above, according to the present invention,
Conveying air flow w _a pulverized coal producing equipment is introduced into the coal weight w _c and powder coal production facility for processing, moisture correctly in the coal even if the outlet temperature T _o such pulverized coal producing equipment changes momentarily Since the ratio θ can be calculated,
A more qualified boiler operation becomes possible.

[Brief description of drawings]

FIG. 1 is an embodiment diagram of the present invention.

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

[Explanation of symbols]

 1 Pulverized coal crushing equipment 3 Coal feeder 4 Furnace (boiler plant) 61 Pulverized coal production equipment outlet temperature signal 62 Coal feed amount signal supplied to pulverized coal pulverization equipment 63 Pulverized coal production equipment inlet temperature signal 64 Pulverized coal production Equipment inlet air flow rate signal 65 Pulverized coal boiler ambient temperature signal 71 Coal feeder operation signal 72 Combustion air operation signal 73 Gas recirculation operation signal 81 Coal moisture estimator 82 Memory

Claims (1)

[Claims] 1. A pulverized coal boiler having a pulverized coal pulverizing equipment, a feeder for supplying raw coal to the pulverized coal pulverizing equipment, and a boiler plant for burning the pulverized coal produced in the pulverized coal pulverizing equipment. Attached to, at least the outlet temperature signal of the pulverized coal manufacturing equipment, a coal feed amount signal supplied to the pulverized coal pulverizing equipment, an inlet temperature signal of the pulverized coal manufacturing equipment,
The inlet air flow rate signal of the pulverized coal production facility and the ambient temperature signal of the pulverized coal boiler are input to calculate the amount of water in the coal supplied to the pulverized coal production facility, the coal feeder and the boiler. In a control device that outputs a signal that controls the flow rate of combustion air and recirculated gas introduced into the plant, a constant or variable cycle is given to each of the pulverized coal boiler dynamic characteristic models by giving the same operation amount as the actual boiler. To calculate the water content in the coal supplied to the pulverized coal manufacturing equipment, store the calculated value for each calculation in the storage unit, the differential equation describing the dynamic characteristic model with reference to the previous calculated value A control device for a pulverized coal boiler, which is characterized by solving and calculating the calculated value this time.