JP2012211741A - Dynamic characteristic identification method for sludge incinerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate dynamic characteristics of a sludge incinerator in a short time while the sludge incinerator is stabilized.SOLUTION: In a circulating fluidized incinerator 1, manipulated variables of a plurality of operation ends are changed according to operation patterns of the plurality of operation ends from which changes of response amounts of the circulating fluidized incinerator according to change of a manipulated variable of one target operation end among the plurality of operation ends can be extracted, the response amounts of the circulating fluidized incinerator in respective operation patterns are detected, and the response amount of the circulating fluidized incinerator with respect to the change of the manipulated variable of the target operation end is extracted using the detected response amounts of the circulating fluidized incinerator. Thereby, the dynamic characteristics of the circulating fluidized incinerator 1 can be formed in a short time while the circulating fluidized incinerator 1 is stabilized.

Description

  The present invention relates to a method for identifying the dynamic characteristics of a sludge incinerator for identifying the dynamic characteristics of a sludge incinerator such as a circulating fluidized incinerator or a bubble fluidized incinerator.

  As disclosed in Patent Document 1, the circulating fluidized incinerator is a flow in which a fluid medium composed of dredged sand or the like filled in the furnace body is caused to flow by flowing air and is discharged from the furnace body accompanied by combustion gas. It is a furnace that incinerates waste while collecting the medium with a cyclone and circulating it to the lower part of the furnace body, and decomposes the combustion gas in the post-combustion furnace. This circulating fluidized incinerator is used for incineration of waste such as sewage sludge because it can stably incinerate a wide variety of wastes having different moisture contents and calorific values.

JP 2001-263634 A

In recent years, in order to cope with environmental problems, there is a demand for reducing greenhouse gases such as N ₂ O discharged from a sludge incinerator. In order to reduce the temperature effect gas, it is effective to increase the temperature of the post-combustion furnace and increase the degree of complete combustion. For example, raising the temperature of the post-combustion furnace from 800 ° C. to 850 ° C. reduces the greenhouse gas by about 70%. On the other hand, the temperature of the furnace body needs to be maintained at a certain temperature or higher so that combustion can be maintained, and therefore the fuel needs to be increased.

  In conventional PID (Proportional Integral Differential) control, a control value can be controlled only for a single target value. For this reason, when there are a plurality of target values for maintaining the temperature of the post-combustion furnace at a high temperature while maintaining the temperature of the furnace body at a constant temperature, the temperature control is performed by cascade control. However, when temperature control is performed by cascade control, the fuel flow rate and the flow rate of flowing air interfere with each other, resulting in an excessive supply of fuel due to an excessive supply of flowing air, or a combustion stop due to a decrease in the temperature of the furnace body. In some cases, stable combustion control cannot be performed.

  Against this background, the patent applicant has proposed a temperature control device for a circulating fluidized incinerator and a temperature control method therefor, to which the multilayer combustion control (model predictive control) theory is applied. According to this temperature control device and temperature control method, temperature control for maintaining the temperature of the post-combustion furnace at the target temperature can be stably performed while maintaining the temperature of the furnace body at the target constant temperature.

  By the way, in order to apply the multilayer combustion control theory, it is necessary to identify the dynamic characteristics of the circulating fluidized incinerator. A step response method is generally known as a method for identifying the dynamic characteristics of a system. In this step response method, the operation amount at the operation end is changed one by one to detect the change in the response amount of the system with respect to the change in the operation amount at the operation end. However, according to such a step response method, since the operation amount of the operation end is changed one by one, the number of steps to be executed increases as the number of operation ends increases, which determines the dynamic characteristics of the system. It takes a lot of time to do.

  In addition, since the sludge properties of the circulating fluidized incinerator are not constant and change, the same behavior may not be obtained even if the step response test is executed under the same conditions. Further, in the circulating fluidized incinerator, it is necessary to stabilize the furnace in order to form the step start condition, and it takes a lot of time. Depending on the step condition, the furnace may be in a dangerous state. A similar problem occurs in a bubble fluidized incinerator. From such a background, it has been expected to provide a method for identifying the dynamic characteristics of a sludge incinerator that can identify the dynamic characteristics of the sludge incinerator in a short time with the sludge incinerator stabilized.

  The present invention has been made in view of the above problems, and its object is to identify the dynamic characteristics of a sludge incinerator capable of identifying the dynamic characteristics of a sludge incinerator in a short time with the sludge incinerator stabilized. Is to provide.

  In order to solve the above-mentioned problems and achieve the object, the sludge incinerator dynamic characteristic identification method according to the present invention is a sludge incinerator dynamic characteristic identification method that responds to the operation amounts of a plurality of operation ends. The amount of operation of the plurality of operation ends is determined according to the operation pattern of the plurality of operation ends that can extract the amount of change in the response amount of the sludge incinerator accompanying the change in the operation amount of one target operation end among the plurality of operation ends. And detecting the response amount of the sludge incinerator in each operation pattern, and using the response amount of the sludge incinerator detected in the detection step, the sludge incinerator And an extraction step for extracting a change amount of the response amount.

  According to the method for identifying the dynamic characteristics of a sludge incinerator according to the present invention, the dynamic characteristics of the sludge incinerator can be identified in a short time while the sludge incinerator is stabilized.

FIG. 1 is a diagram showing a configuration of a circulating fluidized incinerator to which a dynamic characteristic identification method for a circulating fluidized incinerator according to an embodiment of the present invention is applied. FIG. 2 is a diagram showing an outline of model prediction calculation processing in the control device shown in FIG. FIG. 3 is a diagram showing a determinant of the evaluation function based on the model prediction calculation. FIG. 4 is a conceptual diagram for explaining a method for identifying dynamic characteristics of a circulating fluidized incinerator according to an embodiment of the present invention. FIG. 5 is a conceptual diagram for explaining a modification of the dynamic characteristic identification method for a circulating fluidized incinerator according to an embodiment of the present invention.

  Hereinafter, a method for identifying the dynamic characteristics of a circulating fluidized incinerator according to an embodiment of the present invention will be described with reference to the drawings.

  First, a configuration of a circulating fluidized incinerator to which a dynamic characteristic identification method for a circulating fluidized incinerator according to an embodiment of the present invention is applied will be described with reference to FIG. FIG. 1 is a diagram showing a configuration of a circulating fluidized incinerator to which a dynamic characteristic identification method for a circulating fluidized incinerator according to an embodiment of the present invention is applied. As shown in FIG. 1, a circulating fluidized incinerator 1 to which a dynamic characteristic identification method for a circulating fluidized incinerator according to an embodiment of the present invention is applied includes a furnace body (riser) 10. The riser 10 is constituted by a substantially cylindrical member, and a particle retention of a fluid medium such as filled sand, which is called a dilute layer 11 and a rich layer 12, is formed inside.

  The fluid medium (average particle size 200 to 500 μm) filled in the lower part of the riser 10 is fluidized in the furnace by the fluid air, and the introduced sludge is combusted at 800 to 900 ° C. with vigorous stirring. The combustion gas is sent to the cyclone 20 together with the fluid medium and the incineration ash, separated into solid and gas, and incinerated sludge while being circulated to the lower part of the riser 10. The combustion gas is thermally decomposed in the post-combustion furnace 30 to reduce greenhouse gases. Sludge is supplied to the lower portion of the riser 10 via a sludge supply pump 60, and similarly, fuel 70 is supplied via a valve 51 and a fuel flow rate detector 71. The opening degree of the valve 51 is controlled by a fuel flow rate controller (FIC) 41 so that the fuel flow rate detected by the fuel flow rate detector 71 becomes a control amount instructed by the control device 100.

  Primary air supplied from the primary air blower 80 through the valve 52 is provided at the lower part of the riser 10, and secondary air supplied from the secondary air blower 90 is provided at the upper or middle part of the post-combustion furnace 30. Tertiary air generated by branching from the secondary air is supplied to the middle or lower part of the post-combustion furnace 30. The primary air temperature controller 42 is based on the detection result of a primary air flow rate detector (not shown) so as to supply the control air instructed by the control device 10 to the concentrated layer 12 below the riser 10. In addition, the opening degree of the valve 52 is controlled. The secondary air temperature controller 43 supplies the detection result of a secondary air flow rate detector (not shown) so as to supply the controlled air secondary air instructed from the control device 100 to the upper part or the middle part of the post-combustion furnace 30. Based on this, the opening degree of the valve 53 is controlled. The tertiary air temperature controller 44 also provides a detection result of a tertiary air flow rate detector (not shown) so as to supply a controlled amount of tertiary air instructed by the control device 100 to the middle or lower part of the post-combustion furnace 30. And the opening degree of the valve 54 is controlled.

  A thermocouple group 13 composed of a plurality of thermocouples is arranged on the upper part of the riser 10, and a plurality of thermocouples 33 are arranged in the post-combustion furnace 3 in a distributed manner so that the respective furnace temperatures can be measured. ing. In the circulating fluidized incinerator 1, the sludge supplied to the lower part is combusted by the fuel and the primary air supplied from the lower part in the riser 10, and the exhaust gas discharged from the riser 10 is sent to the upper part in the post-combustion furnace 30. Alternatively, it is burned by the secondary air supplied to the middle part, and in the lower part, the incompletely burned parts in the upper part or middle part of the riser 10 and the post-combustion furnace 30 are completely burned using the tertiary air.

The control device 100 includes a fuel flow rate detector 71, a sludge flow rate detector (not shown), a primary air flow rate detector, a secondary air flow rate detector, a tertiary air flow rate detector, and a flowing air detector, respectively. The sludge flow rate, the primary air flow rate, the secondary air flow rate, the tertiary air flow rate, and the flowing air flow rate are input, and the furnace temperature of the riser 10 and the furnace temperature of the post-combustion furnace 30 from the thermocouple groups 13 and 33, respectively. Is entered. An exhaust gas component value such as O ₂ or N ₂ O detected by the gas sensor 35 from the post-combustion furnace 30 is also input to the control device 100. After the model prediction calculation to be described later, the control device 100 supplies a fuel flow rate as a control amount to the fuel flow rate adjuster 41, the primary air flow rate adjuster 42, the secondary air flow rate adjuster 43, and the tertiary air flow rate adjuster 44, respectively. The primary air volume, the secondary air volume, and the tertiary air volume are output.

  The control device 100 maintains the input furnace temperature of the riser 10 and the furnace temperature of the post-combustion furnace 30 at the set temperatures, respectively, and the fuel flow rate, the primary air flow rate, the secondary air flow rate, and the tertiary air flow rate. Model predictive control is performed so that the For this reason, the control apparatus 100 outputs the control value of each flow volume and air volume to each of the fuel flow detector 71, a primary air air volume detector (not shown), a secondary air air volume detector, and a tertiary air volume detector. The fuel flow rate detector 71, a primary air flow rate detector (not shown), a secondary air flow rate detector, and a tertiary air flow rate detector perform hoodback control by PID control based on the input control values. Do it individually.

  As shown in FIG. 2, the control device 100 includes a model prediction calculation unit 100a, and the model prediction calculation unit 100a performs the model prediction control described above. Note that model predictive control is control that predicts future outputs and states based on a system model, solves an optimal control problem at fixed time intervals, and determines an input at that time. Moreover, the multi-input / multi-output control peculiar to the modern control is enabled, and the interference of the control amount does not occur. In particular, this model predictive control is attracting attention as a control method capable of handling the constraint conditions because the constraint conditions can be easily described.

  When the control of the circulating fluidized incinerator 1 is performed, the supply amounts of fuel and air are unknown control amounts that largely depend on the size of the furnace, and in this case, problems such as fuel stoppage do not occur. As a general constraint, the fuel and air supply amounts are applied, and the fuel 70 and air supply amounts are predicted while maintaining a plurality of temperature target values at the upper, middle, and lower portions of the post-combustion furnace 30 at a constant temperature. Can be controlled.

  The model prediction calculation unit 100a generates the dynamic characteristics of the sludge thermal firing system in advance. Since it is difficult to construct a precise physical model, a step response model is generated here. The step response model is expressed by time and value until the step response when the step input is saturated. In the present embodiment, a plurality of temperatures in the riser 10 detected by the thermocouple group 13, a plurality of temperatures of the post-combustion furnace 30 detected by the thermocouple group 33, an air volume of primary air, an air volume of secondary air, A step response model for the air volume of the tertiary air and the flow rate of the fuel 70 is generated. A method of generating the step response model will be described later.

  The model prediction calculation unit 100a describes the air ratio constraint condition in the step response model. As described above, the control amounts of fuel and air are unknown, and in controlling the heat charge and air, the constraint condition of the air ratio is described in the step response model. Here, the air ratio is a ratio between a minimum required theoretical air amount A for completely burning the fuel and an actually supplied air amount B. For example, the air ratio AFR is fair / (ηcake × fcake + ηfuel). Xffuel). ηcake is the sludge theoretical air ratio required for complete combustion of sludge, fcake is the sludge flow rate, ηfuel is the calorific value air ratio required for complete combustion of fuel, and fuel is the fuel flow rate. is there. In the air ratio AFR, a constraint condition that falls within the range between the upper limit air ratio rmax and the lower limit air ratio fmin is described.

  The model prediction calculation unit 100a performs a model prediction calculation based on this model. In order to perform this model prediction calculation, first, as shown in FIG. A set temperature value 101 of a plurality of furnace temperatures of the furnace 30 is input. Further, a constraint condition 102 which is a condition value of the above-described constraint condition is also input. For example, the upper limit value and the lower limit value of the air ratio described above. The upper limit of the upper temperature of the riser 10 is very good as a constraint. Further, the calculation condition 103 is input. The calculation conditions are set scales and calculation parameters necessary for actual calculation, such as a calculation cycle (sampling cycle) and a prediction period.

The model prediction calculation unit 100a subjected to such setting processing acquires the current temperature 110 from the thermocouple groups 13 and 33, and the current temperature 110 is the temperature set value 101, O ₂ or N ₂ O which is an exhaust gas component. , And a current manipulated variable 120 of the fuel flow rate and the air flow rate are input, as well as a prediction calculation for maintaining the set value 104 (for example, 5% for O ₂ , 50-100 ppm for N ₂ O, etc.) Then, the next time manipulated variable 130 of the fuel flow rate and air flow rate is output within a range that satisfies the constraint conditions. The solid content of the sludge is obtained by solid content = sludge flow rate × (1−water content), and the combustion content can be known from the composition analysis result of the solid content. Since this combustion component is involved in the calculation of the “required combustion air volume from sludge” related to the air volume, a step response model of the sludge flow rate is generated and incorporated into the model predictive control. Can be suppressed.

  As shown in FIG. 3, the outline of the model prediction calculation is as follows. The known parameter 201 and the current input / output value 202 at the current time (time k) are set as initial values, and the set parameter 203 is used for every predetermined sampling time (k + 1, k + 2, .., K + N, where N is an integer), a state equation representing the predicted input value 204 is obtained, and an evaluation function J is generated using the predicted output value 204 of these, and an optimal solution for this evaluation function J, ie, a minimum Performs an optimal calculation to obtain a value. This optimum value calculation satisfies the constraint condition 102 such as the air ratio, finds the minimum value of each element including the distance of the control error between the temperature setting value 101 and the predicted temperature value, and calculates the predicted input value 200 at this time as Output as a time operation amount 130. As a result, control is performed so that temperature control values such as the furnace temperature of the riser 10 and the furnace temperature of the post-combustion furnace 30 are maintained at a plurality of target values, and the fuel flow rate and air flow rate are within a predetermined range. , Stable control can be performed.

  Next, a method for generating a step response model will be described with reference to FIGS. In the circulating fluidized incinerator 1 according to an embodiment of the present invention, the operating ends (fuel flow rate and primary to primary air flow rate) are simultaneously varied, and the response of the circulating fluidized incinerator 1 is obtained by canceling each step. By extracting only the influence of the target operation end on the quantity (riser temperature and post-combustion furnace temperature), the dynamic characteristics of the circulating fluidized incinerator 1 can be generated in a short time with the circulating fluidized incinerator 1 stabilized. To. That is, in this step response model generation method, as shown in FIG. 4, (1) the fuel flow rate is changed by + 10% from the previous step, and the air volumes of primary air, secondary air, and tertiary air are respectively changed to the previous step. (2) The fuel flow rate is changed by + 10% from the previous step, and the air volumes of primary air, secondary air, and tertiary air are each + 10% from the previous step, and + 10%, −10%, + 10%. + 10%, -10% change step, (3) The fuel flow rate is changed by + 10% from the previous step, and the air volume of primary air, secondary air, and tertiary air is -10%, + 10%, respectively, from the previous step. (4) Change the fuel flow rate by + 10% from the previous step, and change the primary air, secondary air, and tertiary air to -10% and -10% from the previous step, respectively. The step of varying -10% executed sequentially detects a change amount A~D riser temperatures or post combustion furnace temperature in each step. At this time, there is a relationship as shown in the determinant shown in FIG. 4 between the fuel flow rate and the primary air flow rate and the change amounts A to D of the riser temperature or the post-combustion furnace temperature. By using this, it is possible to extract the influence of the fuel flow rate and the primary to tertiary air flow rates on the rise amounts A to D of the riser temperature or the post-combustion furnace temperature. In addition, it is desirable to perform the same step using the value which reversed the value of the operation amount of each step after completion | finish of each step of said (1)-(4).

  Further, as shown in FIG. 5, (1) the fuel flow rate is changed by + 10% from the previous step, and the air volumes of primary air, secondary air, and tertiary air are + 10%, −10%, +10 from the previous step, respectively. (2) A step of changing the fuel flow rate by + 10% from the previous step and changing the air volume of primary air, secondary air, and tertiary air by + 10%, + 10%, and -10%, respectively, from the previous step. (3) The fuel flow rate is changed by -10% from the previous step, and the air volumes of primary air, secondary air, and tertiary air are changed by -10%, + 10%, + 10% from the previous step, respectively (4) ) Changing the fuel flow rate by + 10% from the previous step, changing primary air, secondary air, and tertiary air by -10%, -10%, -10% from the previous step, respectively, and (5) fuel flow Is changed by -20% from the previous step, and the steps without changing the primary air, secondary air, and tertiary air are executed in order, and the change amounts A to E of the riser temperature or the post-combustion furnace temperature in each step are detected. May be. At this time, since there is a relationship as shown in the determinant shown in FIG. 5 between the fuel flow rate and the air volume of the primary to tertiary air and the change amounts A to E of the riser temperature or the post-combustion furnace temperature, this determinant By using this, it is possible to extract the influence of the fuel flow rate and the primary to tertiary air flow rates on the rise amounts A to E of the riser temperature or the post-combustion furnace temperature. In addition, it is desirable to perform the same step using the value obtained by inverting the value of the manipulated value in each step after the end of each of the steps (1) to (5).

  Thus, in the circulating fluidized incinerator 1 which is one embodiment of the present invention, the amount of change in the response amount of the circulating fluidized incinerator accompanying the change in the manipulated variable at one target operating end among the plurality of operating ends. The operation amount of the plurality of operation ends is changed according to the operation pattern of the plurality of operation ends that can be extracted, the response amount of the circulating fluidized incinerator is detected in each operation pattern, and the detected response amount of the circulating fluidized incinerator is detected Is used to extract the amount of change in the response of the circulating fluidized incinerator with respect to the change in the manipulated variable at the target operating end, so that the circulating fluidized incinerator 1 is stabilized in a short time in a stable state. Dynamic characteristics can be generated.

[Experimental example]
Finally, an experimental example of the step response model generation method will be described. In this experimental example, a step response model of the circulating fluidized incinerator 1 was generated under the step conditions shown in Tables 1 and 2 below. Table 3 shows the response amounts of the post-combustion furnace temperature and the riser temperature with respect to the unit operation amount at the operation end obtained by this experiment. The response values of the post-combustion furnace temperature and the riser temperature with respect to the unit operation amount at the operation end obtained by this experiment were values close to the response amounts obtained by the conventional method in which step input is performed for each operation end. From this, it was confirmed that the dynamic characteristics of the circulating fluidized incinerator 1 can be generated in a short time in a state where the circulating fluidized incinerator 1 is stabilized according to the method for generating the step response model.

  Although the embodiment to which the invention made by the present inventor is applied has been described above, the present invention is not limited by the description and the drawings that form a part of the disclosure of the present invention according to this embodiment. For example, this embodiment identifies the dynamic characteristics of a circulating fluidized incinerator, but the present invention is not limited to this embodiment, and the operation amount of a plurality of operation ends such as a bubble fluidized incinerator. It can be applied to all sludge incinerators that respond to the above. That is, other embodiments, examples, operational techniques, and the like made by those skilled in the art based on the present embodiment are all included in the scope of the present invention.

1 Circulating fluidized incinerator 10 Main body (riser)
DESCRIPTION OF SYMBOLS 11 Dilute layer 12 Rich layer 13, 33 Thermocouple 20 Cyclone 30 Post combustion furnace 35 Gas sensor 41 Fuel flow regulator 42-44 Air temperature regulator 51-54 Valve 60 Sludge supply pump 70 Fuel 71 Fuel flow detector 80 Primary air blower 90 Secondary Air Blower 100 Controller 100a Model Prediction Calculation Unit

Claims (2)

A method for identifying the dynamic characteristics of a sludge incinerator that responds to the amount of operation at a plurality of operation ends,
The operation amount of the plurality of operation ends is changed according to the operation pattern of the plurality of operation ends capable of extracting the change amount of the response amount of the sludge incinerator accompanying the change of the operation amount of one target operation end among the plurality of operation ends. Detection step of detecting the response amount of the sludge incinerator in each operation pattern,
An extraction step for extracting the amount of change in the response amount of the sludge incinerator to the change in the operation amount of the target operation end using the response amount of the sludge incinerator detected in the detection step;
A method for identifying the dynamic characteristics of a sludge incinerator characterized by comprising The sludge incinerator is a circulating fluidized incinerator, and the plurality of operation ends include at least a fuel flow rate, a primary air flow rate, a secondary air flow rate, and a tertiary air flow rate, and the response amount of the sludge incinerator The method for identifying the dynamic characteristics of a sludge incinerator according to claim 1, wherein the temperature includes a riser temperature and a post-combustion furnace temperature.

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