JP2968709B2 - Control method of fluidized bed refuse incinerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a fluidized-bed refuse incinerator, and more particularly, to burning refuse in a sand bed fluidized by blowing primary air and generating steam generated by waste heat. The present invention relates to a method for controlling a fluidized-bed refuse incinerator that circulates and heats in the sand layer.

[0002]

2. Description of the Related Art In a refuse incinerator equipped with a waste heat boiler, in order to stably control the amount of generated steam to a target value, it is necessary to calculate a combustion phenomenon by a model and to perform control by predicting means. For this reason, a combustion control method has been proposed in which a combustion phenomenon is modeled for a stoker furnace and multivariable optimal control is performed (Japanese Patent Publication No. 3-1575). Here, in the internal circulation type energy recovery furnace, the system from the combustion of waste to the recovery of steam energy after internal circulation is complicated, and the combustion phenomena are considered in the next series in view of the strong nonlinearity and the large influence of disturbance. It is expressed by a model, and the amount of steam generated is controlled by multivariable control.

[0003]

However, in the conventional combustion control method as described above, the instantaneous combustion is characterized by a fluidized-bed refuse incinerator in a fluidized-bed refuse incinerator and a combustion by a waste heat boiler. Inability to cope with the dead time seen before steam generation. Further, it is not possible to sufficiently cope with a change in the control target value when the furnace is started up or shut down, or when the waste input plan is changed when the waste is exhausted. The present invention has been made in view of the above circumstances, and its purpose is to cope with the dead time seen from combustion to generation of steam, when starting up or shutting down a furnace, or when exhausting waste. An object of the present invention is to provide a control method of a fluidized bed refuse incinerator which can sufficiently follow a change of a control target value when a refuse input plan is changed and can stably control a steam generation amount to a target value.

[0004]

In order to achieve the above object, the present invention provides a method for burning waste in a sand layer fluidized by blowing primary air, and circulating steam generated by waste heat in the sand layer. In the control method of a fluidized-bed incinerator, which heats by heating, the measured value of the amount of primary air blown up to the immediately preceding point is expressed as the relationship between the amount of primary air blown and steam generated in advance. By substituting into the model, the current steam generation amount is calculated, and the error of the calculated value with respect to the actual measurement value of the current steam generation amount, the desired steam generation trajectory, and the past primary air total blowing amount Based on the above, a predictive control method is used to determine the amount of primary air blown at the present time, so as to control the fluidized bed incinerator. Furthermore, the above model is

(Equation 3) Here, k: time point y: steam generation amount u: primary air blowing amount g: weighting factor N: constant This is a method of controlling a fluidized bed incinerator.

Further, the above-mentioned predictive control method is

(Equation 4) Where: k: time point u: amount of primary air blown y _d : desired amount of steam generated y: actual measured value of steam generated y _M : calculated value of steam generated γ, δ: weighting factor N, P: constant τ: A control method for a fluidized bed refuse incinerator expressed by dead time.

[0006]

DETAILED DESCRIPTION OF THE INVENTION AND

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and examples of the present invention will be described below with reference to the accompanying drawings to facilitate understanding of the present invention.
The following embodiments and examples are examples embodying the present invention, and do not limit the technical scope of the present invention. Here, FIG. 1 is a block diagram showing a schematic configuration of a control method of a fluidized bed refuse incinerator according to an embodiment and an example of the present invention, and FIG. 2 is a fluidized bed refuse incinerator to which the above control method can be applied. FIG. 3 is a schematic diagram showing a schematic configuration of the surroundings, FIG. 3 is a flowchart showing an operation procedure of a fluidized bed incinerator, and FIG. 4 is an explanatory diagram showing a method for setting a desired steam generation trajectory.

As shown in FIG. 1, a method for controlling a fluidized-bed refuse incinerator according to the present embodiment and an example involves burning refuse in a sand layer fluidized by blowing primary air.
This is a control method of an actual process A, which is a fluidized-bed incinerator for circulating and heating steam generated by the waste heat in the sand layer. By substituting into a model M representing the relationship between the amount of primary air blown and the amount of generated steam prepared in advance, the current amount of generated steam y _M (k) is calculated, and the actual measurement of the amount of currently generated steam is performed. The error Δy of the calculated value y _M (k) with respect to the value y (k) and the desired steam generation trajectory y _d (τ + k + L)
This is a method of determining the current primary air blowing amount u (k) by a predictive control method based on the past and the total primary air blowing amount Σu (k−j). Hereinafter, a specific structure of a fluidized bed incinerator to which this method can be applied will be described with reference to FIG. In FIG. 2, the refuse is thrown into the hopper 1 and falls into the sand layer 2. In the sand layer 2, the primary air 4 is sent by operating the valve 3, so that the sand flows and the injected dust burns in the sand layer 2. The gas generated in the furnace passes through the exhaust gas outlet 6 from the free board 5 and is sent to the waste heat boiler 7. In the waste heat boiler 7, the heat energy (heat amount) of the exhaust gas is converted into steam. This water vapor is further heated by passing through a pipe 8 circulating in the sand layer 2 and superheated steam 9
Will be collected as The steam amount is measured by the steam amount sensor 10.

The steam generation process here is generally expressed as an impulse response model by the following model.

(Equation 5) Here, k is the sampling time, y is the amount of generated steam, u is the operation input of the amount of primary air (corresponding to the amount of blowing of primary air), g is the weighting factor of the impulse response, and N is a constant representing the approximate order. is there. Here, a method of controlling the amount of steam generated by the predictive control method is described in the literature (Nishitani; Design of Process Control System, System and Control, vol. 30, No. 1, pp. 16-
25, 1986).

In this predictive control method, the above (1)
Based on the equation, the target trajectory ｛y _S (k +
L), L = 1,..., P} orbit of the desired steam generation amount (corresponding to the desired steam generation trajectory) {y _d (k + L),
L = 1,..., P}. Next, the trajectory ｛y (k + L | k) of the steam generation amount given by the above equation (1), L = 1,
, P} match the trajectory of the desired steam generation amount as much as possible so that the operation input sequence {u (k), u (k) of the primary air amount
+1),..., U (k + P-1)}. Such a problem is formulated as an optimization problem described below.

(Equation 6) Based on the above equations (2) and (3), a sequence {u} of operation inputs of the primary air amount that minimizes the evaluation function given by the following equation
(K), u (k + 1),..., U (k + P−1)}.

[0010]

(Equation 7) Where y (τ + k + L | k), d (τ + k + L | k)
Is the sample time (τ + k +
L) represents the predicted value of the steam generation amount and the predicted value of the disturbance.
Further, y _M (τ + k + L) and y _d (τ + k + L) represent the output value of the model M and the value of the desired steam generation amount at the sampling time (τ + k + L). α _L and β _L are weighting factors for the output error and the input, respectively. The above problem is solved as a least squares problem, and the manipulated variable u (k) of the primary air is derived as follows.

[0011]

(Equation 8) Here, gamma _j, [delta] _L is a coefficient that is calculated in deriving the least squares solution, that contains the values of the weighting factors g _i. Next, referring to FIG. 3 (and FIG. 2), the outline of the control system of the fluidized bed incinerator and the operation thereof will be described in steps S1, S2,.
It will be described in order. Prior to online control for each control cycle,
Alternatively, the setting of each parameter is calculated in the following procedure during online control. Step S1: The waste input planning function processing unit 11
Set up a treatment plan that includes a change in the waste input plan when starting up or shutting down the furnace or when the waste runs out.

Step S2: Set target value of steam generation amount The target processing unit 12 sets the target trajectory y _S of the steam generation amount according to the above-mentioned waste input plan. Step S3: Desired steam generation amount setting function processing unit 13
Accordingly, setting the trajectory y _d of the steam generation amount of desired corresponding to the desired trajectory y _S. Here, the trajectory ｛y _d (k + L), L = 1, of the desired steam generation amount in the above step S3
, P} will be described with reference to FIG.
Based on the waste incineration plan, the target trajectory of steam generation ｛y _S
(K + L), L = 1,..., P}. On the other hand, the actual measured value y (k) of the steam generation amount at the time point k is obtained. Considering that the prediction is made from the time point k to the time point (k + P), the actual measured value y of the steam generation amount at the time point (k + q)
Consider that (k + q) reaches the target value y _S (k + q). However, it is necessary to satisfy 0 <q <P.

[0013] Therefore, as a track y _d of the steam generation amount desired, in the period from time k to time (k + q), connecting the measured value of the steam generation amount y (k) and a target trajectory y _S (k + q) a straight line L _1, in the period from time point (k + q) to time (k + P), using a portion of the target trajectory y _S L _2. Step S4: The control coefficient calculation function processing unit 14
Coefficients γ _j , δ composed of weight coefficients g _i in the above equation (1)
Calculate _L. Step S5: Primary air manipulated variable calculation function processing unit 15
Thus, the operation amount u (k) of the primary air is calculated for each control cycle, and the primary air control valve 3 is operated according to the calculated value.
Here, the processing procedure of the calculation function of the manipulated variable of the primary air in step S5 will be described in detail in the order of steps S11, S12,... With reference to FIG. 3 (and FIG. 1). The meaning is also explained.

Step S11: The actually measured value y (k) of the amount of steam generated at the present time k by the steam amount sensor 10 and the above (1)
Error Δ from output value y _M (k) of model M calculated by equation
Calculate y. This means that the error of the model M at the time point k has been estimated. Step S12: The difference between the value of the steam generation amount obtained from the trajectory y _d (τ + k + L) of the desired steam generation amount taking the dead time τ into consideration and the error Δy is obtained, and the difference is multiplied by the control coefficient δ _L to be superimposed. The trajectory y _d (τ + k + L) is corrected by the modeling error Δy at the time point k, and the manipulated variable u ₁ of the primary air that predicts the future up to the time point P is obtained. Step S13: On the other hand, by superposing by multiplying the control coefficients gamma _j past input u (k-j), obtains the operation amount u ₂ of primary air as seen from past input information. Step S14: By adding the operation amount u ₁ and -u _2, above (4) determine the optimum primary air of the manipulated variable u (k) in the sense of minimizing the evaluation function of the equation. Step S15: The loop of steps S11 to S14 is repeated for each control cycle, and the amount of generated steam is controlled by manipulating the amount of primary air.

The features of the control method are as follows. (1) Fluid-bed refuse incinerators are characterized by instantaneous combustion, which is a disturbance to the control of the amount of generated steam.
In this method, since the disturbance is considered in the above equation (2), the method is robust against the disturbance. (2) In the internal circulation type energy recovery furnace, a control dead time is generated due to a long moving distance of the heat flow from generation of steam to recovery of energy in the sand layer. In the present method, the dead time τ is taken into account, so that stable control of the amount of generated steam can be achieved. (3) In this method, when starting up or shutting down the furnace,
Alternatively, when the waste is exhausted, the target value y _S of the steam generation amount is changed at the time of changing the waste input plan. Since the change of the input amount plan is performed according to the scheduled schedule, the trajectory of the target value y _S ｛y _S (k + L),
L = 1..., P} can be set. In this method,
The trajectory {y _d (k + L), L = 1,..., P} of the desired steam generation amount is given after knowing the change in the trajectory y _S of the target value in advance. This allows stable control of the amount of generated steam even when the waste input plan is changed. In addition, by adjusting the setting of the trajectory, it is possible to adjust the responsiveness of controlling the amount of generated steam. That is, the time point q is defined as q <
If the value is set large in the range of P, the stability of control is emphasized. On the other hand, when the time point q is set small in the range of q <P, the responsiveness of the control is emphasized. In the control of the amount of generated steam, since the stability of the control is given more importance, it is effective to set the time point q to be large.

As described above, according to the combustion control method for a refuse incinerator of the present invention, in a refuse incinerator having a function of recovering energy by circulating steam generated by a waste heat boiler inside a sand layer, The amount of steam generated is calculated using a model that takes the manipulated variable of the primary air as input and the amount of steam generated as output, calculates the error between the measured steam generation and the calculated value, the desired steam generation trajectory, and the past primary The primary air amount to the sand layer is determined by the predictive control method based on the total operation amount of air, and the air valve opening for primary air control is operated according to the value. This makes it possible to cope with the dead time from combustion to steam generation.
Alternatively, it is possible to sufficiently control the change in the control target value when the waste input plan is changed when the waste is exhausted, and to stably control the steam generation amount to the target value.

[0017]

As described above, the control method for a fluidized bed refuse incinerator according to the present invention, which is configured as described above, can cope with the dead time observed from combustion to generation of steam, and can start up and shut down the furnace. It is possible to sufficiently follow the change of the control target value at the time or when the waste input plan is changed when the waste is exhausted, and to stably control the steam generation amount to the target value.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a control method for a fluidized bed refuse incinerator according to an embodiment and an example of the present invention.

FIG. 2 is a schematic diagram showing a schematic configuration around a fluidized bed refuse incinerator to which the above control method can be applied.

FIG. 3 is a flowchart showing the operation procedure of a fluidized bed refuse incinerator.

FIG. 4 is an explanatory view showing a method for setting a desired steam generation trajectory.

[Explanation of symbols]

A: Actual process (corresponding to a fluidized bed refuse incinerator) M: Model u (k): Operated amount of primary air (corresponding to the blowing amount of primary air) y (k): Actual measured value of steam generation Δy Error y _M (k): Calculated value of steam generation amount y _d (τ + k + L): trajectory of desired steam generation amount (corresponding to desired trajectory of steam generation) u (k-j): Past operation amount of primary air ( (Equivalent to the amount of primary air blown in the past)

Continuation of the front page (72) Inventor Tomoyuki Maeda 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Kobe Steel, Ltd. Kobe Research Institute (72) Inventor Nobuyuki Tomochika 1 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo 5-5-5 Kobe Steel, Ltd. Kobe Research Institute (58) Field surveyed (Int.Cl. ⁶ , DB name) F23G 5/50 ZAB F23G 5/30 ZAB

Claims (3)

(57) [Claims] 1. A method of controlling a fluidized bed incinerator in which refuse is burned in a sand layer fluidized by blowing primary air, and steam generated by waste heat is circulated and heated in the sand layer. Calculate the current steam generation amount by substituting the measured value of the primary air blowing amount up to the immediately preceding time point into a model that represents the relationship between the primary air blowing amount and the steam generation amount prepared in advance. However, based on the error of the above calculated value with respect to the actual measurement value of the steam generation amount at the present time, the desired steam generation trajectory, and the total injection amount of the primary air in the past, the predictive control method is used to calculate the current primary air amount. A method for controlling a fluidized-bed refuse incinerator, characterized by determining a blowing amount. 2. The above model is expressed by the following equation: The control method for a fluidized bed incinerator according to claim 1, wherein k: time point y: steam generation amount u: primary air blowing amount g: weighting factor N: constant. 3. The prediction control method according to claim 2, wherein Where: k: time point u: amount of primary air blown y _d : desired amount of steam generated y: actual measured value of steam generated y _M : calculated value of steam generated γ, δ: weighting factor N, P: constant The control method for a fluidized bed refuse incinerator according to claim 1 or 2, wherein τ is represented by τ: dead time.