JP6347100B2 - Mill outlet temperature control method, apparatus and program for exhaust gas recirculation system crushing plant - Google Patents

Description

  The present invention relates to a technique for controlling a mill outlet temperature of an exhaust gas circulation system pulverization plant.

Conventionally, what was disclosed by patent document 1, for example is known as a pulverization plant for manufacturing pulverized coal, cement, etc.
First, fuel gas and combustion air are supplied to a hot gas generator, and hot air is generated as exhaust gas in the hot gas generator. The exhaust gas is supplied to the inside of a pulverizer that pulverizes the raw material. The raw material pulverized by the pulverizer is supplied to the bag filter together with the exhaust gas, and is collected by the bag filter. Thereafter, the exhaust gas is pressurized by a circulation fan and supplied again to the hot gas generator as a circulation gas. The exhaust gas (hot air) generated by the hot gas generator in this way is circulated from the hot gas generator to the hot gas generator via a pulverizer and a bag filter. In the following description, such a “pulverization plant” is referred to as an “exhaust gas circulation system pulverization plant”.

  In such an exhaust gas circulation system pulverization plant, in order to stably dry the raw material during pulverization, the fuel gas is set so that the outlet temperature of the pulverizer (referred to as the mill outlet temperature) becomes the target temperature of the raw material after pulverization. It is conceivable to perform feedback control for manipulating the flow rate.

JP 2011-219599 A

  Various environmental variables such as gases and raw materials used in the exhaust gas circulation crushing plant always fluctuate, and the mill outlet temperature fluctuates due to the fluctuation. When the mill outlet temperature fluctuates, the output of the hot gas generator also fluctuates due to the feedback control that tries to compensate for the fluctuation. When the output of the hot gas generator fluctuates, the pulverizer inlet temperature (referred to as the mill inlet temperature) fluctuates accordingly. Further, the average value of the mill inlet temperature increases as the amount of raw material to be input increases. However, the mill inlet temperature has an upper temperature limit for reasons such as the heat resistance temperature and the ignition temperature of the raw material, and if the operation is continued beyond this upper limit, the life of the equipment is shortened. For this reason, the operator cannot increase the amount of raw material to be charged in fear of exceeding the upper temperature limit due to fluctuations in the mill inlet temperature.

  If fluctuations in the mill outlet temperature can be reduced, fluctuations in the mill inlet temperature can also be reduced. As a result, more raw materials can be introduced than in the past. As means for reducing fluctuations in the mill outlet temperature, there is an improvement in control performance of mill outlet temperature control.

  As a technology relating to this, the applicant of the present application disclosed in Japanese Patent Application No. 2012-268513 a steady load of a hot gas generator before and after a change in the amount of raw material input from a steady state heat balance / mass balance model of an exhaust gas circulation system pulverization plant. It is proposed that the control output corresponding to the steady load is added to the calculation result of the mill outlet temperature control. Hereinafter, this is referred to as feedforward control. However, the feedforward control is a method that reduces only temperature fluctuations accompanying changes in the amount of raw material to be input, and is not a control method that can cope with other disturbance factors.

  The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to control the mill outlet temperature in the exhaust gas circulation system pulverization plant with high accuracy.

The method for controlling the outlet temperature of the exhaust gas circulation system pulverization plant according to the present invention includes a hot gas generator that generates hot air as exhaust gas, and a raw material that is pulverized and the pulverized raw material flows into the exhaust gas generated by the hot gas generator. A pulverizer that is put on and discharged to the outside, a collector that collects the raw material after pulverization released from the pulverizer along the flow of the exhaust gas, and the exhaust gas that has passed through the collector is the hot gas generator. A circulation fan for sending to the exhaust gas, a path through which the exhaust gas circulates through the hot gas generator, the pulverizer, the collector, and the circulation fan, and a mill outlet temperature that is an outlet temperature of the pulverizer and a thermometer, in the exhaust gas circulation grinding plant with a mill outlet is feedback controlled so as to approach the measurement of the amount of by operating the mill outlet temperature of the fuel gas supplied to the heat gas generator to the target value A time control method,
The entire exhaust gas circulation system crushing plant as having a specific heat capacity as a single regenerator, a difference between the heat quantity consumed and the amount of heat applied to said exhaust gas circulation crushing plant, is divided by the heat capacity, based on heat balance equation to a mill outlet temperature change amount per unit time, enter the fuel gas flow rate, the amount of change in the mill outlet temperature to obtain a transfer function that outputs the mill outlet temperature indicator and response delay A derivation step of deriving a dynamic characteristic as an index and deriving a control parameter for the feedback control based on the derived dynamic characteristic of the mill outlet temperature ;
The heat balance equation is
The amount of heat obtained by the combustion of the fuel gas represented using the fuel gas flow rate that is a variable, and the power heat in the circulation fan are the given amount of heat,
The amount of heat required for heating the raw material represented by using the amount of heat that changes due to the injection of the gas containing the fuel gas, the measured value of the mill outlet temperature, and the amount of raw material input per unit time given according to the operation; The amount of heat necessary for heating and evaporation of water and the amount of heat lost by heat exchange between the exhaust gas circulation system pulverization plant and outside air are used as the amount of heat consumed.
The amount of heat lost due to heat exchange between the exhaust gas circulation system pulverization plant and the outside air is equal to the difference between the mill outlet temperature and the temperature of the atmosphere expressed by a single value multiplied by the heat dissipation coefficient.
The heat dissipation coefficient is determined by stopping the hot gas generator in a state in which raw materials are not charged into the pulverizer, maintaining the operation state of the circulation fan, and the heat balance equation while the mill outlet temperature has shifted to a steady state. Using the value previously identified from
The heat capacity is determined by the heat balance equation in a heat-up process in which a region including the inside of the pulverizer is preheated by exhaust gas generated from the hot gas generator with the heat dissipation coefficient identified. Comparing the time until the temperature reaches the target temperature, or the rate of decrease in the mill outlet temperature when the hot gas generator is stopped after the heat-up, and their actual data , It is characterized by using a value identified in advance while changing the heat capacity .
Another feature of the method for controlling the mill outlet temperature of the exhaust gas circulation system pulverization plant of the present invention is that the feedback control is performed by performing PID control so that the measured value of the mill outlet temperature is close to a target value, and the derivation. In the step, a PID control parameter is derived as the control parameter.
The mill outlet temperature control device of the exhaust gas circulation system pulverization plant of the present invention includes a hot gas generator that generates hot air as exhaust gas, a raw material that is pulverized, and the pulverized raw material is converted into a flow of exhaust gas generated by the hot gas generator. A pulverizer that is put on and discharged to the outside, a collector that collects the raw material after pulverization released from the pulverizer along the flow of the exhaust gas, and the exhaust gas that has passed through the collector is the hot gas generator. A circulation fan for sending to the exhaust gas, a path through which the exhaust gas circulates through the hot gas generator, the pulverizer, the collector, and the circulation fan, and a mill outlet temperature that is an outlet temperature of the pulverizer and a thermometer, in the exhaust gas circulation grinding plant with a mill outlet is feedback controlled so as to approach the measurement of the amount of by operating the mill outlet temperature of the fuel gas supplied to the heat gas generator to the target value A time control device,
The entire exhaust gas circulation system crushing plant as having a specific heat capacity as a single regenerator, a difference between the heat quantity consumed and the amount of heat applied to said exhaust gas circulation crushing plant, is divided by the heat capacity, based on heat balance equation to a mill outlet temperature change amount per unit time, enter the fuel gas flow rate, the amount of change in the mill outlet temperature to obtain a transfer function that outputs the mill outlet temperature indicator and response delay Deriving means for deriving a dynamic characteristic as an index and deriving a control parameter for the feedback control based on the derived dynamic characteristic of the mill outlet temperature ,
The heat balance equation is
The amount of heat obtained by the combustion of the fuel gas represented using the fuel gas flow rate that is a variable, and the power heat in the circulation fan are the given amount of heat,
The amount of heat required for heating the raw material represented by using the amount of heat that changes due to the injection of the gas containing the fuel gas, the measured value of the mill outlet temperature, and the amount of raw material input per unit time given according to the operation; The amount of heat necessary for heating and evaporation of water and the amount of heat lost by heat exchange between the exhaust gas circulation system pulverization plant and outside air are used as the amount of heat consumed.
The amount of heat lost due to heat exchange between the exhaust gas circulation system pulverization plant and the outside air is equal to the difference between the mill outlet temperature and the temperature of the atmosphere expressed by a single value multiplied by the heat dissipation coefficient.
The heat dissipation coefficient is determined by stopping the hot gas generator in a state in which raw materials are not charged into the pulverizer, maintaining the operation state of the circulation fan, and the heat balance equation while the mill outlet temperature has shifted to a steady state. Using the value previously identified from
The heat capacity is determined by the heat balance equation in a heat-up process in which a region including the inside of the pulverizer is preheated by exhaust gas generated from the hot gas generator with the heat dissipation coefficient identified. Comparing the time until the temperature reaches the target temperature, or the rate of decrease in the mill outlet temperature when the hot gas generator is stopped after the heat-up, and their actual data , It is characterized by using a value identified in advance while changing the heat capacity .
The program of the present invention includes a hot gas generator that generates hot air as exhaust gas, a pulverizer that pulverizes the raw material, and discharges the pulverized raw material to the outside on the flow of the exhaust gas generated by the hot gas generator; A collector that collects the pulverized raw material released from the pulverizer along with the flow of exhaust gas, a circulation fan for sending the exhaust gas that has passed through the collector to the hot gas generator, and the heat Exhaust gas circulation system pulverization comprising a gas generator, the pulverizer, the collector, a path through which the exhaust gas circulates through the circulation fan, and a thermometer that measures a mill outlet temperature that is an outlet temperature of the pulverizer In the plant , a program for performing feedback control so that the measured value of the mill outlet temperature approaches the target value by operating the amount of fuel gas supplied to the hot gas generator ,
The entire exhaust gas circulation system crushing plant as having a specific heat capacity as a single regenerator, a difference between the heat quantity consumed and the amount of heat applied to said exhaust gas circulation crushing plant, is divided by the heat capacity, based on heat balance equation to a mill outlet temperature change amount per unit time, enter the fuel gas flow rate, the amount of change in the mill outlet temperature to obtain a transfer function that outputs the mill outlet temperature indicator and response delay Deriving a dynamic characteristic as an index, causing a computer to execute a process for deriving a control parameter for the feedback control based on the derived dynamic characteristic of the mill outlet temperature ,
The heat balance equation is
The amount of heat obtained by the combustion of the fuel gas represented using the fuel gas flow rate that is a variable, and the power heat in the circulation fan are the given amount of heat,
The amount of heat required for heating the raw material represented by using the amount of heat that changes due to the injection of the gas containing the fuel gas, the measured value of the mill outlet temperature, and the amount of raw material input per unit time given according to the operation; The amount of heat necessary for heating and evaporation of water and the amount of heat lost by heat exchange between the exhaust gas circulation system pulverization plant and outside air are used as the amount of heat consumed.
The amount of heat lost due to heat exchange between the exhaust gas circulation system pulverization plant and the outside air is equal to the difference between the mill outlet temperature and the temperature of the atmosphere expressed by a single value multiplied by the heat dissipation coefficient.
The heat dissipation coefficient is determined by stopping the hot gas generator in a state in which raw materials are not charged into the pulverizer, maintaining the operation state of the circulation fan, and the heat balance equation while the mill outlet temperature has shifted to a steady state. Using the value previously identified from
The heat capacity is determined by the heat balance equation in a heat-up process in which a region including the inside of the pulverizer is preheated by exhaust gas generated from the hot gas generator with the heat dissipation coefficient identified. Comparing the time until the temperature reaches the target temperature, or the rate of decrease in the mill outlet temperature when the hot gas generator is stopped after the heat-up, and their actual data , It is characterized by using a value identified in advance while changing the heat capacity .

  According to the present invention, the mill outlet temperature in the exhaust gas circulation system pulverization plant can be controlled with high accuracy.

It is a figure which shows the structure of the PCI plant of the exhaust gas circulation system in embodiment. It is a figure which shows an example of a function structure of the mill exit temperature control apparatus in embodiment. It is a characteristic view which shows the relationship between a mill exit temperature calculation value, a mill exit temperature track record, and a burner load track record. It is a characteristic view which shows the relationship between the mill exit temperature calculation value in 1st Example, the mill exit temperature track record, and the burner load track record. It is a characteristic view which shows the relationship between the amount of coal supply in a 2nd Example, and the water | moisture content contained in a raw material. It is a characteristic view which shows the relationship between the proportional band of the mill exit temperature PID control in 2nd Example, and integration time. It is a characteristic view which shows the mill exit temperature in the conventional PID control in a 2nd Example. It is a characteristic view which shows the mill exit temperature in PID control to which the present invention is applied in the second embodiment. It is a characteristic view which shows the deviation | shift amount from the target value of mill exit temperature when the amount of coal supply in a 2nd Example changes. It is a characteristic view which shows the deviation | shift amount from the target value of mill exit temperature when the moisture ratio of the raw material in a 2nd Example changes.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
In this embodiment, the case where the exhaust gas circulation system pulverization plant is an exhaust gas circulation system PCI plant that pulverizes coal to perform pulverized coal injection (PCI; Pulverized Coal Injection) into the blast furnace is taken as an example. explain.
FIG. 1 is a diagram illustrating a configuration example of an exhaust gas circulation PCI plant (hereinafter simply referred to as a PCI plant). In FIG. 1, a solid line connecting each component indicates piping, and a broken line indicates a signal transmission path. Moreover, an arrow line shows the advancing direction of the gas and coal in piping. Note that the configuration of the PCI plant can be realized by a known technology such as the technology described in Patent Document 1, for example, and therefore, each configuration will be briefly described here and a detailed description thereof will be omitted.

In FIG. 1, a hot gas generator 101 has one or a plurality of burners, uses fuel gas and combustion air (air) as inputs to the burner, controls the air-fuel ratio of the burner, and generates hot air as exhaust gas. The oxygen concentration of the exhaust gas is approximately 0 (zero)%. In the present embodiment, BFG (Blast Furnace Gas) is used as the fuel gas. In the air-fuel ratio control, the burner load transmitted from the mill outlet temperature control device 200 and the flow rates of the fuel gas and combustion air supplied to the burner are input as described later, and the air-fuel ratio is controlled (for example, feedback control). ) And adjusting the opening degree of the valve for adjusting the flow rate of the fuel gas and combustion air supplied to the burner. Here, the burner load indicates the ratio of the flow rate of the fuel gas supplied to the burner to the maximum value of the flow rate of the fuel gas that can be supplied to the burner. Further, the air-fuel ratio control can be realized by a known technique by using a programmable logic controller (PLC) or the like, and therefore detailed description thereof is omitted here.
The combustion air fan 102 sends combustion air into the hot gas generator 101.

The bunker 103 stores coal as a raw material.
The coal feeder 104 has a chain conveyor, cuts coal stored in the bunker 103 by the chain conveyor, and puts it into the mill 105.
The mill 105 is a pulverizer that pulverizes coal supplied from the coal feeder 104. The mill 105 includes, for example, a roll mill 105a and a crushing table 105b. Coal input from the upper part of the mill 105 is supplied between the roll mill 105a and the crushing table 105b. By rotating the pulverizing table 105b while pressing the roll mill 105a, the coal is crushed and pulverized. The pulverized coal is supplied to the upper part of the mill 105 along the flow of the exhaust gas supplied from the hot gas generator 101, classified by a classifier, and then discharged to the outside. In the following description, “pulverized coal discharged to the outside from the mill 105” is referred to as “pulverized coal” as necessary.

  The seal air fan 106 is supplied with the pulverized coal to be discharged to the outside from the gap by supplying the seal air into the gap inside the mill 105 (bearing portion of the crushing table 105b). Push back into the exhaust gas flow. The flow rate of the seal air is determined so that the pressure inside the mill 105 is less than the pressure of the seal air. In this way, the seal air fan 106 has pulverized coal entering the bearing portion of the pulverizing table 105b, resulting in poor lubrication of the bearing portion of the pulverizing table 105b and from the bearing portion of the pulverizing table 105b to the outside. To prevent being released.

  The mill outlet thermometer 110 measures the temperature at the predetermined position on the outlet side of the mill 105 (the temperature of the pulverized coal in the pipe). In the following description, “temperature at a predetermined position on the outlet side of the mill 105” is referred to as “mill outlet temperature” as necessary.

The bag filter 107 is a filtration type collector that collects pulverized coal discharged from the mill 105 using a filter cloth. Foreign matter other than pulverized coal may be collected by the bag filter 107.
The foreign matter removing device 108 removes the foreign matter collected by the bag filter 107.
The reserve tank 109 stores pulverized coal from which foreign matter has been removed by the foreign matter removing device 108. The pulverized coal stored in the reserve tank 109 is blown into the blast furnace from the tuyere of the blast furnace (pulverized coal is blown).

The Venturi tube 111 measures the flow rate of the exhaust gas that has passed through the bag filter 107.
The damper 112 adjusts the flow rate of the exhaust gas that has passed through the bag filter 107.
The circulation fan 113 boosts the exhaust gas so that the exhaust gas that has passed through the damper 112 can be circulated to the hot gas generator 101.
The chimney 114 releases a part of the exhaust gas (radiated gas) pressurized by the circulation fan 113 into the atmosphere.
The diffusion system pressure regulating valve 115 regulates the pressure of the exhaust gas discharged from the chimney 114 into the atmosphere.

  The circulation system pressure adjusting valve 116 adjusts the pressure of exhaust gas that is circulated to the hot gas generator 101 without being released into the atmosphere via the chimney 114 among the exhaust gas pressurized by the circulation fan 113. In this way, the exhaust gas generated in the hot gas generator 101 is supplied again to the hot gas generator 101 as a circulating gas, and the hot gas generator 101, the mill 105, the bag filter 107, the venturi 111, the damper 112, and the circulation. It circulates through the path of the fan 113, the circulation system pressure regulating valve 116, and the hot gas generator 101.

  In the present embodiment, air in the atmosphere (dilution air) is supplied to the PCI plant. The orifice flow meter 117 adjusts the flow rate of the dilution air. The air flow rate adjustment valve 118 adjusts the flow rate of air supplied to the PCI plant. The dilution air fan 119 pressurizes the dilution air whose flow rate is adjusted by the air flow rate adjustment valve 118 and pushes the dilution air into the piping on the inlet side of the hot gas generator 101. Thereby, the oxygen concentration of the circulating gas can be increased.

  Conventionally, the mill outlet temperature control of such a PCI plant has been performed by feedback control based on the mill outlet temperature measured by the mill outlet thermometer 110. In the embodiment to which the present invention is applied, the entire PCI plant is approximated as a single heat storage body, and the heat capacity of the entire PCI plant (heat storage body) and the coefficient (heat dissipation coefficient) related to the heat exchange amount between the PCI plant and the outside air are used. Thus, feedback control is performed in accordance with the state of the PCI plant.

  Next, a method for deriving the dynamic characteristics of the mill outlet temperature will be described. Here, the dynamic characteristic is composed of a process gain and a process time constant derived from the amount of raw material input per unit time, that is, the amount of coal supply.

[Assumptions for deriving dynamic characteristics of mill outlet temperature]
In the present embodiment, the following conditions are assumed when the dynamic characteristics of the mill outlet temperature are derived.
(A) The entire PCI plant is considered as a single heat storage body and has a specific heat capacity.
(B) It is assumed that the entire PCI plant and the atmosphere surrounding the entire PCI plant exchange heat, and the heat exchange amount is equal to the difference between the mill outlet temperature and the atmospheric temperature multiplied by the heat dissipation coefficient.
(C) The heat dissipation coefficient used for heat exchange between the heat capacity of the entire PCI plant and the atmosphere is always constant.
(D) Air temperature is expressed as a single value.
(E) Considering an unsteady balance in the heat balance, it is assumed that the difference between the heat given to the PCI plant and the consumed heat appears in the mill outlet temperature with a delay in the heat capacity of the entire PCI plant.
(F) The calorie | heat amount required for the phase change of the water | moisture content contained in a raw material (coal) is calculated by the latent heat required in order to produce | generate the amount of water vapor | steam generated from a raw material (coal).
(G) The flow rate of the exhaust gas generated by the combustion of the fuel gas is the sum of the flow rate of the fuel gas and the flow rate of the combustion air for simplicity.
(H) The power heat in the circulation fan 113 is simplified if it contributes only to the circulation gas.
(I) The temperature in the system of the PCI plant and the temperature of the emitted gas are assumed to be equal to the mill outlet temperature.
(J) Fuel gas shall burn completely, and excess combustion air shall remain as it is.

[Parameters for deriving dynamic characteristics of mill outlet temperature]
In the present embodiment, as the minimum necessary parameters for realizing the mill outlet temperature control, in addition to the mill outlet temperature and the fuel gas flow rate, a coal supply amount is given as an input value for deriving dynamic characteristics of the mill outlet temperature. The amount of coal supply is changed to an arbitrary value according to the operation.
The following parameters are given as fixed values.
・ The heat capacity of the entire PCI plant ・ The heat dissipation coefficient of the entire PCI plant The heat capacity and heat dissipation coefficient of the entire PCI plant are unique to each process and are single values, but they are difficult to determine physically, so they are identified as described later. Derived by experiment.

About other parameters, you may determine suitably according to the content of an installation or operation. Preferably, one or more of the following parameters are used.
The following parameters are given as fixed values:
・ Specific heat (water, gas, raw material (coal))
・ Latent heat of water ・ Theoretical air-fuel ratio of burner (theoretical air-fuel ratio in the combustion reaction of fuel gas and air)
・ Burner excess air ratio (excess air ratio in combustion reaction of fuel gas and air)

The following parameters are given as semi-fixed values as environmental conditions. These values preferably give measurements from sensors, but may give average values in a PCI plant. In this embodiment, an average value in the PCI plant is given.
-Moisture ratio in raw material (coal)-Moisture ratio in product (pulverized coal)-Temperature (raw material, injected gas, air)
-Calorie of fuel gas (per unit amount)-Flow rate of ingress air (per unit time)-Flow rate of seal air (per unit time)-Power heat (per unit time) in the circulation fan 113

The following parameters are also given as environmental conditions. These values are preferably given as measured values from sensors, but may be given values according to the amount of coal supplied in the PCI plant. In this embodiment, the measured value from the sensor is given.
-Flow rate of diluted air (per unit time)-Flow rate of diffused gas (per unit time) The water ratio and temperature can be obtained in advance by sampling, for example. Since the theoretical air amount of the burner varies depending on the composition of the fuel gas, it is set based on the composition of the fuel gas. If the value of the excess air amount of the burner is increased, poor combustion can be prevented, so the excess air amount of the burner is appropriately set from this viewpoint.

[Calculation method of heat amount given to PCI plant and heat amount consumed]
In the present embodiment, the difference between the amount of heat given to the PCI plant and the amount of heat consumed is divided by the heat capacity of the entire plant and formulated as a mill outlet temperature change amount. Below, the calculation method of the calorie | heat amount given to the PCI plant and the calorie | heat amount consumed is demonstrated.
<Formula of calorie required for heating raw materials>
The amount of heat ΔQ _COAL [kcal] required to heat the raw material to the mill outlet temperature is expressed by the following equation (1).
ΔQ _COAL = specific heat of raw material x amount of coal supply x 1000 x (T-temperature of raw material) (1)
The unit of the coal supply amount is [ton / hr], and the mill outlet temperature T [° C.] is measured by the mill outlet thermometer 110. As described above, the specific heat [kcal / kg · ° C.] of the raw material and the temperature [° C.] of the raw material are given as environmental conditions.

<Formula of calorie required for heating water>
The amount of heat ΔQ (sensible heat) [kcal] required to heat the water contained in the coal to the product temperature is expressed by the following equation (2).
ΔQ (sensible heat) = specific heat of water × WM × (T-temperature of raw material) (2)
As described above, the specific heat of water [kcal / kg · ° C.] is given as an environmental condition.
In the formula (2), WM is the weight [kg / hr] per unit time of water contained in coal, and is represented by the following formula (2a).
WM = coal feed amount × 1000 × moisture ratio contained in raw material / (100−moisture ratio contained in raw material) (2a)
As described above, the moisture ratio [% by mass] contained in the raw material is given as an environmental condition.

<Equation for the amount of heat required for evaporation of water contained in the raw material>
The amount of heat ΔQ (latent heat) [kcal] required for the water contained in the raw material to evaporate is expressed by the following equation (3).
ΔQ (latent heat) = latent heat of water × WV (3)
As described above, the latent heat [kcal / kg] of water is given as an environmental condition.
In the formula (3), WV is the weight [kg / hr] of water existing as water vapor per unit time, and is represented by the following formula (3a).
WV = coal feed amount × 1000 × {water content contained in raw material / (100−water content contained in raw material) −water content contained in product / (100−water content contained in product)} (3a )

<Formula of the amount of heat obtained by combustion of fuel gas>
The amount of heat ΔQ _HGG [kcal] generated by the combustion of the fuel gas is expressed by the following equation (4).
ΔQ _HGG = fuel gas calorie x fuel gas flow rate (4)
As described above, the calorie [kcal / Nm ³ ] of the fuel gas is given as an environmental condition. The flow rate [Nm ³ / hr] of the fuel gas is a decision variable.

<Formula of Flow Rate of Combustion Air Consumed by Hot Gas Generator 101>
The flow rate [Nm ³ / hr] of combustion air consumed by combustion is expressed by the following equation (5).
Combustion air flow rate = fuel gas flow rate x theoretical air fuel ratio x excess air ratio (5)
As described above, the theoretical air-fuel ratio [-] and the excess air ratio [-] are given as environmental conditions. If the combustion gas flow rate can be measured by installing a sensor or the like, equation (5) is not necessary, and the measured value is preferably the flow rate of combustion air.

<Formula of flow rate of exhaust gas generated from hot gas generator 101>
The flow rate [Nm ³ / hr] of the exhaust gas generated by the combustion of the fuel gas is expressed by the following equation (6).
Exhaust gas flow rate = Fuel gas flow rate + Combustion air flow rate (6)
Actually, the flow rate of the exhaust gas is smaller than the sum of the flow rate of the fuel gas and the flow rate of the combustion air, but even if the flow rate of the exhaust gas is expressed as the sum of these, a large error does not occur.

<Power heat in circulation fan 113>
The power heat ΔQ _FAN in the circulation fan 113 is given as a fixed value as an environmental condition as described above.

<Heat exchange between PCI plant and atmosphere>
The amount of heat lost by the PCI plant due to heat exchange with the atmosphere is expressed by the following equation (7).
ΔQ _loss = heat dissipation coefficient x (T-outside temperature) (7)

[Heat balance formula of PCI plant]
From the above formulas (1) to (7), the following formula (8) is obtained as the heat balance formula of the PCI plant.
C × dT / dt = (ΔQ _HGG + ΔQ _FAN ) − (ΣΔQ _GAS (i) + ΔQ _COAL + ΔQ (sensible heat) + ΔQ (latent heat) + ΔQ _loss ) (8)
In the equation (8), C represents the heat capacity [kcal / ° C.] of the entire PCI plant, and dT / dt represents the amount of change in the mill outlet temperature per unit time [hr]. The right side is the difference between the total amount of heat given to the PCI plant and the total amount of heat consumed by the PCI plant, and the left side is the change in the mill outlet temperature with a delay in the heat capacity of the entire PCI plant. It represents the amount.
Further, ΣΔQ _GAS (i) is expressed by the following equation (8a).
ΣΔQ _GAS (i) = Σ {specific heat of gas (i) × flow rate of gas (i) × (T−temperature of injected gas (i))} (8a)
The gas (i) refers to all the gases injected into the system, and in this embodiment, the gas (i) is fuel gas, combustion air, dilution air, entry air, and seal air. Although nitrogen may be used, in this embodiment, nitrogen is excluded because it is used only for a short time and intermittently. The flow rate of nitrogen (per unit time) may be included in the parameter.
As described above, the specific heat of the gas [kcal / (Nm ³ × ° C.)], the temperature of the injection gas, the flow rate of dilution air [Nm ³ / hr], the flow rate of inlet air [Nm ³ / hr], and the seal air The flow rate [Nm ³ / hr] is given as an environmental condition.

[Identification method of heat dissipation coefficient]
Until the mill outlet temperature reaches a steady value, the coal feeder 104 and the hot gas generator 101 are stopped and the operation state of the circulation fan 113 is maintained. At this time, since the heat given to the PCI plant and the heat consumed are balanced, it can be regarded as dT / dt = 0 from the equation (8). Moreover, since the coal feeder 104 and the hot gas generator 101 are stopped, ΔQ _HGG , ΔQ _COAL , ΔQ (sensible heat), and ΔQ (latent heat) are zero. The heat balance of the PCI plant at this time is expressed by equation (9).
0 = ΔQ _FAN − ( ΣΔQ _GAS (i) + ΔQ _loss ) (9)

In equation (9), the only unknown coefficient is the heat dissipation coefficient, and therefore the heat dissipation coefficient can be identified by solving equation (9) as an equation. Since the expression (9) has no change in the mill outlet temperature, the influence of the heat capacity of the entire plant can be ignored, and since the coal feeder 104 is stopped, Variations in the water content of the raw material can be ignored. Therefore, this identification method can determine the heat dissipation coefficient uniquely and with high accuracy.
The amount of heat exchange between the PCI plant and the atmosphere is very small compared to ΔQ (latent heat), so it is not a big factor in the heat balance calculation when the raw material is being crushed. Since raw materials are not charged during the up, the amount of heat exchange between the PCI plant and the atmosphere can be a significant factor in the heat balance calculation. Therefore, it is necessary to identify the heat dissipation coefficient in advance and incorporate it into the heat balance calculation.
In this way, the hot gas generator 101 is stopped in a state where the raw material is not charged into the mill 105, and the heat dissipation calculation is identified from the heat balance calculation while the operation state of the circulation fan 113 is maintained and the state is shifted to the steady state.

[Method for identifying the heat capacity of the entire PCI plant]
After identifying the heat dissipation coefficient, the heat capacity of the entire PCI plant is identified. The heat capacity C of the entire PCI plant is identified from data at the time of heat-up in which there is no disturbance due to coal supply and the outlet temperature varies. In the PCI plant, there is a process called preheating that preheats the mill outlet temperature to the target temperature before the start of grinding. In the heat-up, the coal feeder 104 is stopped and no coal is input. On the other hand, the hot gas generator 101 and the circulation fan 113 are operating.
The heat balance of the PCI plant at this time is expressed by equation (10).
C × dT / dt = (ΔQ _HGG + ΔQ _FAN ) − (ΣΔQ _GAS (i) + ΔQ _loss ) (10)

By identifying the heat dissipation coefficient, ΔQ _loss in equation (10) can be derived, so the unknown coefficient in equation (10) is only the heat capacity C of the entire PCI plant. Therefore, while changing the heat capacity of the entire PCI plant, by comparing between the calculated mill outlet temperature derived by equation (10) and the actual mill outlet temperature when actually heating up, The heat capacity of the entire PCI plant that matches can be identified. In this embodiment, as a method of obtaining the heat capacity of the entire PCI plant, the heat capacity of the entire PCI plant is calculated by convergence calculation so that the time until the mill outlet temperature actual reaches the target temperature at the time of heating up is closest to the actual data. Asked. As another method, the heat capacity of the entire PCI plant may be obtained from the decreasing rate of the mill outlet temperature when the hot gas generator 101 is stopped during the heat-up. In this identification method, the heat dissipation coefficient is identified in advance so that the unknown coefficient is limited only to the heat capacity of the entire plant, and the coal feeder 104 is stopped in the same manner as the heat dissipation coefficient identification method. Variations in the amount of coal supply that changes the outlet temperature and fluctuations in the moisture content of the raw material can be ignored. Therefore, this identification method can determine the heat capacity of the whole plant uniquely and with high accuracy.

  In FIG. 3, the result of having identified the heat capacity C of the whole PCI plant from the mill exit temperature at the time of heat-up using the heat radiation coefficient identified by the method mentioned above is shown. In FIG. 3, 301 shows the burner load performance, 302 shows the mill outlet temperature performance, and 303 shows the mill outlet temperature calculation value. The mill outlet temperature was calculated from the mill outlet temperature model based on the actual flow rate of the fuel gas. Then, evaluate the time until the mill outlet temperature reaches the target temperature and the decrease in the mill outlet temperature after the mill outlet temperature reaches the target temperature, and the calculated mill outlet temperature is the closest to the mill outlet temperature. The heat capacity C of the entire PCI plant was determined.

[Derivation of mill outlet temperature dynamics]
The process gain which is the mill outlet temperature dynamic characteristic in this embodiment is obtained by converting the equation (8) by Laplace conversion by the above-described identification method, and transforming it into a transfer function with the fuel gas flow rate as input and the mill outlet temperature as output. Deriving K and the process time constant τ. When both sides of the equation (8) are Laplace transformed, the equation (11) is obtained.
T = K / (τ × s + 1) × (fuel gas flow rate + u _st ) (11)
At this time, the process gain K, the process time constant τ, and the constant term u _st are expressed as (11a) to (11c). T _GAS (i) is the temperature of the injected gas (i).
K = calorie of fuel gas / {(ΣΔQ _GAS (i) / (T−T _GAS (i))) + (ΔQ _COAL + ΔQ (sensible heat)) / (T−raw material temperature) + heat dissipation coefficient)}.・ (11a)
τ = heat capacity of the entire PCI plant / (ΣΔQ _GAS (i) T _GAS (i) / (T−T _GAS (i)) + (ΔQ _COAL + ΔQ (sensible heat)) × raw material temperature / (T−raw material temperature ) + Heat dissipation coefficient (11b)
u _st = {(ΣΔQ _GAS (i) + (ΔQ _COAL + ΔQ (sensible heat)) × raw material temperature / (T−raw material temperature)) + ΔQ _FAN −ΔQ (latent heat) −heat radiation coefficient × atmospheric temperature} / fuel Calories of gas ... (11c)

Hereinafter, an example of the function of the mill outlet temperature control device 200 will be described in detail. The mill outlet temperature control device 200 inputs the mill outlet temperature measured by the mill outlet thermometer 110, and derives the deviation of the measured value of the mill outlet temperature from the target value. Then, P operation, I operation, and D operation are performed on the derived deviation (that is, PID control is performed), and a burner load is derived so that the derived deviation becomes 0 (zero) to generate hot gas. Output to the device 101.
In the conventional PID control, the PID control parameter is fixed, but in this embodiment, the mill outlet temperature dynamic characteristic is derived from the amount of input raw material (coal supply amount) and environmental conditions, and the PID parameter corresponding to the dynamic characteristic is determined. For setting, the PID control parameter is variable.

[Functional configuration of mill outlet temperature control device 200]
FIG. 2 is a diagram illustrating an example of a functional configuration of the mill outlet temperature control device 200. Each part shown in FIG. 2 is realizable by using a programmable logic controller (PLC), for example.

The mill outlet temperature target value storage unit 201 stores a target value of the mill outlet temperature. The target value of the mill outlet temperature is set by the operator.
The mill outlet temperature deviation deriving unit 202 reads the target value of the mill outlet temperature at the time of pulverization from the mill outlet temperature target value storage unit 201. Then, the mill outlet temperature deviation deriving unit 202 subtracts the target value of the mill outlet temperature during pulverization from the measured value of the mill outlet temperature, and derives the deviation of the measured value of the mill outlet temperature from the target value.
The mill outlet temperature dynamic characteristic deriving unit 203 derives the dynamic characteristic of the mill outlet temperature at the current time based on the coal supply amount at the current time and the environmental conditions. In this embodiment, there are two process gains: a process gain that is an indicator of the amount of change in the mill outlet temperature due to a change in the unit amount of fuel gas, and a process time constant that is an indicator that represents a delay in the response of the mill outlet temperature to the change in fuel gas. Was the dynamic characteristics of the mill outlet temperature.

The PID control parameter deriving unit 204 reads the dynamic characteristic of the mill outlet temperature at the current time from the mill outlet temperature dynamic characteristic deriving unit 203, and determines the PID control parameter based on the dynamic characteristic of the mill outlet temperature. In this embodiment, the process gain and the process time constant at the minimum coal supply amount are used as a reference, and the proportional band is increased when the process gain is larger than this, and the integration time is increased when the process time constant is increased. A rule was created and PID control parameters were determined based on this rule.
The PID control unit 205 reads the PID control parameter at the current time from the PID control parameter deriving unit 204 and sets the PID control parameter. When the burner load derivation command output from the mill outlet temperature deviation deriving unit 202 is input, the deviation from the target value of the measured value of the mill outlet temperature input together with the burner load derivation command is input, and a proportional operation, an integral operation, Then, a differential operation is performed, and a burner load is derived as an operation amount and repeatedly output to the burner load output unit 206, thereby performing control (PID control) to bring the measured value of the mill outlet temperature closer to the target value.
The burner load output unit 206 outputs the burner load to the hot gas generator 101.

(First embodiment)
In the embodiment shown in FIG. 4, the mill exit temperature during pulverization is simulated using the heat dissipation coefficient and the heat capacity of the entire PCI plant. In FIG. 4, 401 indicates the burner load record, 402 indicates the mill outlet temperature record, and 403 indicates the mill outlet temperature calculation value. As a result of calculating the mill outlet temperature from the mill outlet temperature model based on the actual flow rate of the fuel gas, the calculated mill outlet temperature 403 is almost the same as the actual mill outlet temperature 402 even when the raw coal is charged. The mill outlet temperature model has been shown to be valid.

(Second embodiment)
5 to 10 show a comparison between the conventional PID control in which the PID control parameter is fixed and the PID control to which the present invention is applied.
FIG. 5 shows a change in the coal supply amount 501 and the water ratio 502 contained in the raw material.
FIG. 6 shows changes in the proportional band 601 and the integration time 602 of the variable PID control in the same time series as FIG. Here, since the moisture contained in the raw material is an average value in the PCI plant at the time of deriving the dynamic characteristics of the mill outlet temperature, the PID control parameter does not change due to the change in the moisture ratio contained in the raw material.

FIG. 7 shows a change in the mill outlet temperature in the conventional PID control in the same time series as FIG. 5 and FIG.
FIG. 8 shows changes in the mill outlet temperature in the PID control to which the present invention is applied, in the same time series as FIG. 5 and FIG.
In a PCI plant, the process gain is low when operating at a high coal supply rate, so that stability is maintained even if the gain of PID control is set high. Therefore, by applying the present invention, the fluctuation of the mill outlet temperature can be reduced as compared with the conventional PID control when the amount of coal supply is high. FIG. 9 shows a comparison of the maximum deviation from the target value of the mill outlet temperature when the amount of coal supply is changed. FIG. 10 shows a comparison of the maximum deviation from the target value of the mill outlet temperature when the moisture content in the raw material changes. In either case, the application of the present invention is smaller.

In the embodiment described above, the present invention is applied to an exhaust gas circulation system PCI plant, but can also be applied to an exhaust gas circulation system grinding plant other than the exhaust gas circulation system PCI plant. For example, the present invention is also applicable to an exhaust gas circulation system pulverization plant for producing cement.
Further, while the set value of the coal supply amount is being changed, it is preferable to perform feedforward control based on the calculation of the material / heat balance model, but this control need not necessarily be performed.
In the above embodiment, PID control is applied as a method for controlling the mill outlet temperature. However, any other control may be used as long as the measured value of the mill outlet temperature is brought close to the target value.

The present invention can be realized by a computer executing a program. Further, a computer-readable recording medium in which the program is recorded and a computer program product such as the program can also be applied as an embodiment of the present invention. As the recording medium, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
In addition, all of the embodiments described above are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. . That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

  101: Hot gas generator, 103: Bunker, 104: Coal feeder, 105: Mill, 107: Bag filter, 110: Mill outlet thermometer, 200: Mill outlet temperature controller, 201: Mill outlet temperature target value storage unit 202: Mill outlet temperature deviation deriving section 203: Mill outlet temperature dynamic characteristic deriving section 204: PID control parameter deriving section 205: PID control section 206: Burner load output section

Claims (4)

A hot gas generator that generates hot air as an exhaust gas, a pulverizer that pulverizes the raw material, puts the pulverized raw material on the flow of the exhaust gas generated by the hot gas generator, and releases the exhaust gas from the pulverizer. A collector that collects the pulverized raw material released on the flow, a circulation fan for sending the exhaust gas that has passed through the collector to the hot gas generator, the hot gas generator, and the pulverizer In the exhaust gas circulation system pulverization plant , the hot gas is provided with a passage through which the exhaust gas circulates through the circulator, the collector, and the circulation fan, and a thermometer that measures a mill outlet temperature that is an outlet temperature of the pulverizer. A mill outlet temperature control method that performs feedback control so that the measured value of the mill outlet temperature approaches a target value by manipulating the amount of fuel gas supplied to the generator ,
The entire exhaust gas circulation system crushing plant as having a specific heat capacity as a single regenerator, a difference between the heat quantity consumed and the amount of heat applied to said exhaust gas circulation crushing plant, is divided by the heat capacity, based on heat balance equation to a mill outlet temperature change amount per unit time, enter the fuel gas flow rate, the amount of change in the mill outlet temperature to obtain a transfer function that outputs the mill outlet temperature indicator and response delay A derivation step of deriving a dynamic characteristic as an index and deriving a control parameter for the feedback control based on the derived dynamic characteristic of the mill outlet temperature ;
The heat balance equation is
The amount of heat obtained by the combustion of the fuel gas represented using the fuel gas flow rate that is a variable, and the power heat in the circulation fan are the given amount of heat,
The amount of heat required for heating the raw material represented by using the amount of heat that changes due to the injection of the gas containing the fuel gas, the measured value of the mill outlet temperature, and the amount of raw material input per unit time given according to the operation; The amount of heat necessary for heating and evaporation of water and the amount of heat lost by heat exchange between the exhaust gas circulation system pulverization plant and outside air are used as the amount of heat consumed.
The amount of heat lost due to heat exchange between the exhaust gas circulation system pulverization plant and the outside air is equal to the difference between the mill outlet temperature and the temperature of the atmosphere expressed by a single value multiplied by the heat dissipation coefficient.
The heat dissipation coefficient is determined by stopping the hot gas generator in a state in which raw materials are not charged into the pulverizer, maintaining the operation state of the circulation fan, and the heat balance equation while the mill outlet temperature has shifted to a steady state. Using the value previously identified from
The heat capacity is determined by the heat balance equation in a heat-up process in which a region including the inside of the pulverizer is preheated by exhaust gas generated from the hot gas generator with the heat dissipation coefficient identified. Comparing the time until the temperature reaches the target temperature, or the rate of decrease in the mill outlet temperature when the hot gas generator is stopped after the heat-up, and their actual data , A method for controlling a mill outlet temperature of an exhaust gas circulation system pulverization plant, wherein the value identified in advance is used while changing the heat capacity . As the feedback control , PID control is performed so that the measured value of the mill outlet temperature approaches the target value,
And in the deriving step, the mill outlet temperature control method of the exhaust gas circulation system crushing plant according to claim 1, characterized in that to derive a PID control parameter as the control parameter. A hot gas generator that generates hot air as an exhaust gas, a pulverizer that pulverizes the raw material, puts the pulverized raw material on the flow of the exhaust gas generated by the hot gas generator, and releases the exhaust gas from the pulverizer. A collector that collects the pulverized raw material released on the flow, a circulation fan for sending the exhaust gas that has passed through the collector to the hot gas generator, the hot gas generator, and the pulverizer In the exhaust gas circulation system pulverization plant , the hot gas is provided with a passage through which the exhaust gas circulates through the circulator, the collector, and the circulation fan, and a thermometer that measures a mill outlet temperature that is an outlet temperature of the pulverizer. A mill outlet temperature control device that performs feedback control so that the measured value of the mill outlet temperature approaches a target value by manipulating the amount of fuel gas supplied to the generator ,
The entire exhaust gas circulation system crushing plant as having a specific heat capacity as a single regenerator, a difference between the heat quantity consumed and the amount of heat applied to said exhaust gas circulation crushing plant, is divided by the heat capacity, based on heat balance equation to a mill outlet temperature change amount per unit time, enter the fuel gas flow rate, the amount of change in the mill outlet temperature to obtain a transfer function that outputs the mill outlet temperature indicator and response delay Deriving means for deriving a dynamic characteristic as an index and deriving a control parameter for the feedback control based on the derived dynamic characteristic of the mill outlet temperature ,
The heat balance equation is
The amount of heat obtained by the combustion of the fuel gas represented using the fuel gas flow rate that is a variable, and the power heat in the circulation fan are the given amount of heat,
The amount of heat required for heating the raw material represented by using the amount of heat that changes due to the injection of the gas containing the fuel gas, the measured value of the mill outlet temperature, and the amount of raw material input per unit time given according to the operation; The amount of heat necessary for heating and evaporation of water and the amount of heat lost by heat exchange between the exhaust gas circulation system pulverization plant and outside air are used as the amount of heat consumed.
The amount of heat lost due to heat exchange between the exhaust gas circulation system pulverization plant and the outside air is equal to the difference between the mill outlet temperature and the temperature of the atmosphere expressed by a single value multiplied by the heat dissipation coefficient.
The heat dissipation coefficient is determined by stopping the hot gas generator in a state in which raw materials are not charged into the pulverizer, maintaining the operation state of the circulation fan, and the heat balance equation while the mill outlet temperature has shifted to a steady state. Using the value previously identified from
The heat capacity is determined by the heat balance equation in a heat-up process in which a region including the inside of the pulverizer is preheated by exhaust gas generated from the hot gas generator with the heat dissipation coefficient identified. Comparing the time until the temperature reaches the target temperature, or the rate of decrease in the mill outlet temperature when the hot gas generator is stopped after the heat-up, and their actual data , A mill outlet temperature control device for an exhaust gas circulation system pulverization plant, wherein the value identified in advance is used while changing the heat capacity . A hot gas generator that generates hot air as an exhaust gas, a pulverizer that pulverizes the raw material, puts the pulverized raw material on the flow of the exhaust gas generated by the hot gas generator, and releases the exhaust gas from the pulverizer. A collector that collects the pulverized raw material released on the flow, a circulation fan for sending the exhaust gas that has passed through the collector to the hot gas generator, the hot gas generator, and the pulverizer In the exhaust gas circulation system pulverization plant , the hot gas is provided with a passage through which the exhaust gas circulates through the circulator, the collector, and the circulation fan, and a thermometer that measures a mill outlet temperature that is an outlet temperature of the pulverizer. A program for controlling the amount of fuel gas supplied to the generator to perform feedback control so that the measured value of the mill outlet temperature approaches the target value ,
The entire exhaust gas circulation system crushing plant as having a specific heat capacity as a single regenerator, a difference between the heat quantity consumed and the amount of heat applied to said exhaust gas circulation crushing plant, is divided by the heat capacity, based on heat balance equation to a mill outlet temperature change amount per unit time, enter the fuel gas flow rate, the amount of change in the mill outlet temperature to obtain a transfer function that outputs the mill outlet temperature indicator and response delay Deriving a dynamic characteristic as an index, causing a computer to execute a process for deriving a control parameter for the feedback control based on the derived dynamic characteristic of the mill outlet temperature ,
The heat balance equation is
The amount of heat obtained by the combustion of the fuel gas represented using the fuel gas flow rate that is a variable, and the power heat in the circulation fan are the given amount of heat,
The amount of heat required for heating the raw material represented by using the amount of heat that changes due to the injection of the gas containing the fuel gas, the measured value of the mill outlet temperature, and the amount of raw material input per unit time given according to the operation; The amount of heat necessary for heating and evaporation of water and the amount of heat lost by heat exchange between the exhaust gas circulation system pulverization plant and outside air are used as the amount of heat consumed.
The amount of heat lost due to heat exchange between the exhaust gas circulation system pulverization plant and the outside air is equal to the difference between the mill outlet temperature and the temperature of the atmosphere expressed by a single value multiplied by the heat dissipation coefficient.
The heat dissipation coefficient is determined by stopping the hot gas generator in a state in which raw materials are not charged into the pulverizer, maintaining the operation state of the circulation fan, and the heat balance equation while the mill outlet temperature has shifted to a steady state. Using the value previously identified from
The heat capacity is determined by the heat balance equation in a heat-up process in which a region including the inside of the pulverizer is preheated by exhaust gas generated from the hot gas generator with the heat dissipation coefficient identified. Comparing the time until the temperature reaches the target temperature, or the rate of decrease in the mill outlet temperature when the hot gas generator is stopped after the heat-up, and their actual data , A program characterized by using a value identified in advance while changing the heat capacity .

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