JP2009257731A - Temperature control method for circulating fluidized bed type incinerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature control method for a circulating fluidized bed type incinerator preventing equipment trouble and operation trouble caused by a local temperature rise by restraining a change of temperature distribution in the incinerator caused by various fuel changes and variation and incineration load changes in the circulating fluidized bed type incinerator. <P>SOLUTION: The temperature control method for the circulating fluidized bed type incinerator is carried out by performing automatic online setting of a target value or a restriction value of the temperature of each part in the incinerator according to an incineration load and the composition and properties of fuel used in the incinerator, and adjusting a primary combustion air amount and a secondary combustion air amount supplied to the incinerator based on at least one of the set target value and restriction value of the temperature of each part in the incinerator. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a temperature control method for a circulating fluidized bed incinerator (circulating fluidized bed boiler).

  As shown in FIG. 1, a circulating fluidized bed incinerator (circulating fluidized bed type boiler), as shown in FIG. 1, is a combustion furnace 1 for burning or gasifying a processing object (fuel), and collecting and burning a fluidized medium. The cyclone 2 is mainly composed of a cyclone 2 that returns to the furnace 1. A primary combustion air blowing port 3 for blowing primary combustion air into the combustion furnace 1 and an air flow rate from the blower fan 4 are formed in the lower part of the combustion furnace 1. Is provided with a primary combustion air damper (valve) 4a. Further, on the side wall of the combustion furnace 1, a secondary combustion air blowing port 5 for blowing the secondary combustion air into the combustion furnace 1 and a secondary combustion air damper (valve) for controlling the air flow rate from the blower fan 4. ) 4b and a charging port 6 for charging the processing object into the combustion furnace 1.

  Such a circulating fluidized bed incinerator has been developed as an incinerator suitable for pulverized coal combustion, but has recently been developed as an oil substitute boiler for burning various fuels. For example, biomass, RPF, waste tires, sludge, and dewatered sludge can be used as the fuel to be used.

  However, when fuels become diverse in this way, differences in drying, dry distillation, and combustion speed occur due to differences in the components, structure, and amount of stored heat for each fuel. The combustion position (position where fuel is mainly burned) and burnout position (position where combustion of gas and fixed carbon is completed) fluctuate, and the furnace temperature balance (furnace temperature distribution) changes. Further, depending on the type of fuel, the combustion load (total input fuel calorie) may have to be changed depending on the arrival status, and in that case, the furnace temperature balance changes as described above. As a result, there is a risk that the location in the furnace, which was not initially anticipated, will become hot and lead to equipment troubles.

Therefore, in Patent Document 1, an attempt is made to prevent equipment troubles due to the high temperature of the exhaust gas processing unit located further downstream by controlling the temperature of the cyclone outlet temperature near the burnout point position of gas combustion.
JP 2000-18542 A

  However, as controlled by the cyclone outlet temperature only as in Patent Document 1, depending on the fuel properties, the state where the heat balance of the entire furnace is biased to the rear of the furnace gas flow continues, and when the boiler is installed, Heat cannot be collected with good balance in the furnace body.

  Also, if only the cyclone outlet temperature is taken into consideration, when high calorie and high combustion speed fuel enters, it is not possible to cope with the local high temperature at the main combustion position of the incinerator near the fuel inlet in front of the gas flow If the time of high temperature (for example, thermometer measured value> 950 ° C.) continues, the probability that clinker is generated due to ash adhering is high. When the clinker generated in this way falls to the bottom of the furnace, the operation must be stopped and removed.

  In addition, when various / multiple fuels are used, the furnace temperature and temperature balance vary greatly depending on the blending / property of the fuel. When fuel with a high calorie and a high combustion rate is introduced due to a change in the composition, fluctuations in the properties of the fuel, etc., the boiler middle temperature close to the fuel injection part rises and rises to near 950 ° C. as described above There is. Considering the uneven temperature distribution in the furnace, there is a possibility that the temperature is locally close to 1000 ° C. or more, and there is a risk of clinker generation.

  In conventional circulating fluidized bed incinerators, pulverized coal, sludge, etc. are used as a single type of fuel, or a fuel having a small property distribution such as moisture content, for example, pulverized coal or plastic RPF is mixed and used. . For this reason, heating due to fluctuations in the main combustion position of the fuel and the equipment load due to the sticking matter are small, and the above-mentioned problems have not become apparent. For this reason, the conventional control system does not perform the control in consideration of the temperature distribution of each part in the furnace. Moreover, in the control system of the above-mentioned patent document 1, since the set values such as the cyclone outlet temperature are upper limit constraint values, constant values are used regardless of the incineration load, the fuel composition, and the in-furnace temperature balance state.

  The present invention has been made in view of the above-described problems, and suppresses changes in the temperature distribution in the furnace that occurs when various / various fuel changes / variations and incineration load changes are made in a circulating fluidized bed incinerator, and equipment by locally increasing the temperature It is intended to provide a temperature control method for a circulating fluidized bed incinerator that can prevent troubles and operational troubles.

  Originally, it is ideal that the temperature of each part follows a constant temperature regardless of the fuel composition, fuel properties, and incineration load, but it is not realistic in view of the internal shape and operation capability of the furnace. Forcibly changing the manipulated variable greatly disrupts the balance of combustion. For example, if the primary combustion air is significantly reduced, the flow of combustion / fluidized sand will decrease, resulting in a large residue and a reduction in the carbonization rate. If the secondary combustion air is significantly reduced, the gas stirring effect is reduced, leading to an increase in unburned gas, residue and NOx. Therefore, in order to reduce the equipment load and realize a stable operation, it is necessary to set a target temperature according to the fuel / incineration load.

  Based on such an idea, the present invention has the following features in order to solve the above problems.

  [1] In a circulating fluidized bed incinerator, the target value or constraint value of each temperature in the furnace is automatically set online according to the incineration load of the incinerator, the fuel composition used, and the properties. The circulating fluidized bed incineration is characterized in that the amount of primary combustion air and the amount of secondary combustion air supplied to the incinerator are adjusted based on at least one of the target value and constraint value of each temperature in the furnace. Furnace temperature control method.

  [2] The temperature of the circulating fluidized bed incinerator according to [1], wherein a target value or a constraint value of each temperature in the furnace is corrected online using a past actual temperature in the furnace. Control method.

  In addition, when the above [1] or [2] is applied to an actual plant, the upper and lower limit flow rates of the primary combustion air amount and the secondary combustion air amount are set and adjusted in preparation for the case where residual and unburned gas components are generated. Therefore, it also has the following characteristics.

  [3] The temperature control method for a circulating fluidized bed incinerator according to [1] or [2], wherein a restriction is imposed on an adjustment amount of the primary combustion air amount and the secondary combustion air amount.

  According to the present invention, the target temperature of each part in the furnace is automatically determined online and controlled so as to follow it, so that various / various fuel changes / variations and incineration load changes in the circulating fluidized bed incinerator It is possible to suppress changes in the furnace temperature distribution that occur and to prevent equipment troubles and operational troubles due to local high temperatures.

  An embodiment of the present invention will be described with reference to the drawings. In this embodiment, a case where a circulating fluidized bed incinerator using two types of fuel is targeted will be described. However, the following explanation is based on a circulating fluidized bed incinerator using three or more types of fuel. It is the same even if there is.

  First, the process of the circulating fluidized bed incinerator targeted in this embodiment will be described with reference to FIG.

  The circulating fluidized bed incinerator is mainly composed of a combustion furnace 1 for combusting or gasifying an object to be treated (fuel) and a cyclone 2 for collecting a fluid medium and returning it to the combustion furnace 1. In the lower part of the furnace 1, a primary combustion air blowing port 3 for blowing the primary combustion air into the combustion furnace 1 and a primary combustion air damper (valve) 4 a for controlling the flow rate from the blower fan 4 are provided. Further, on the side wall of the combustion furnace 1, a secondary combustion air blowing port 5 for blowing secondary combustion air into the combustion furnace 1 and a secondary combustion air damper (valve) for controlling the flow rate from the blower fan 4. 4b and an inlet 6 for introducing a processing object (fuel) into the combustion furnace 1 are provided. A fuel conveyance / calibration / injection amount control device 7 for controlling the input amount by conveying / calibrating by a conveyor provided for each fuel type is also provided as necessary.

  In the combustion furnace 1, by blowing air into the combustion furnace 1 from the primary combustion air blowing port 3 and the secondary combustion air blowing port 5, the object to be treated (fuel) charged into the furnace from the charging port 6 is burned into the combustion furnace 1. 1. Fluidize together with a fluid medium such as sand filled at the bottom. In the process, the object to be treated is dried to emit volatile matter and burned.

  And as above-mentioned, it is equipped with the collection part (cyclone) 2 which collects a fluid medium and unburned matter, and the return pipe 2a which returns the collected fluid medium etc. to the combustion furnace 1, In the cyclone 2, These are separated into exhaust gas and fluid medium or ash having a relatively large particle size. The exhaust gas separated by the collection unit 2 is sent to the exhaust gas treatment facility 2b accompanied with ash having a relatively small particle diameter, and is discharged from the chimney 2c to the outside after dust removal. Moreover, the fluid medium collected by the cyclone 2 or the ash having a relatively large particle size is returned to the lower part of the combustion furnace 1 through the return pipe 2a as the fluid medium, and the unburned portion is reburned.

  Here, the fluidized medium filled in the floor portion of the combustion furnace 1 described above becomes a fluidized state by the primary combustion air blown from below, forms a concentrated layer by the fluidized medium, and has a high heat capacity and stirring effect possessed by the fluidized medium. Accelerate the drying and volatile emissions of the object to be treated. In addition, a thin layer is formed in the upper part of the combustion furnace 1 by a fluid medium that is blown up and fluidized by blowing primary combustion air and secondary combustion air, and is treated by the heat capacity and stirring effect of the fluid medium. The object is burned or gasified.

  In this embodiment, the temperature in the middle of the combustion furnace 1 (the temperature in the middle of the combustion furnace) and the temperature at the outlet of the cyclone 2 (the cyclone outlet temperature) are used as the representative temperatures in the combustion furnace 1, and the combustion furnace A combustion furnace middle thermometer 8 for measuring the middle temperature and a cyclone outlet meter 9 for measuring the cyclone outlet temperature are installed.

  Next, the configuration of the control device for calculating the in-furnace target temperature in this embodiment will be described.

  As shown in FIG. 2, the control device 10 receives the weight values of the two types of fuel to be input from the fuel transfer / calibration / input amount control device 7. Similarly, the measured value of the combustion furnace middle temperature and the measured value of the cyclone outlet temperature are received from the combustion furnace middle thermometer 8 and the cyclone outlet thermometer 9, respectively. These data, parameter values set by a human in the setting computer 11, and past reactor temperature actual values stored in the database 12 (here, past combustion furnace middle temperature actual values and cyclone outlet temperature actual values) Then, the target temperature of each part in the furnace (here, the middle part of the combustion furnace and the outlet of the cyclone) is determined by the control device 10 from the measured offline component values of each fuel. The amount of primary combustion air blown from the primary combustion air blow-in port 3 and the amount of secondary combustion air blown from the secondary combustion air blow-in port 5 are calculated so as to follow the determined target, and the respective combustion air blow-in ports 3 and 5 are calculated. The opening degree of the primary combustion air damper 4a and the secondary combustion air damper 4b is adjusted based on the measured value of an installed flow meter (not shown).

  Next, a specific method for calculating the target temperature of each part in the furnace (here, the middle part of the combustion furnace and the cyclone outlet) and a control method for following the target temperature will be described.

(A) Target temperature calculation As shown in FIGS. 3 and 4, the target temperature (FIG. 3) and the target temperature of the cyclone outlet temperature (FIG. 3) and the target temperature of the cyclone outlet temperature (in FIG. 3) are input in a matrix table format with the fuel blend ratio and incineration load as inputs. 4) is automatically determined. As for the set temperatures (B1 to B9, S1 to S9) on the matrices in FIGS. 3 and 4, humans set reasonable values based on simulations and operation results. At the time of setting, it should also be noted that when the incineration load is the same, the temperature inside the combustion furnace and the cyclone temperature are in a trade-off relationship, that is, when one is increased, the other is decreased. Further, the target temperature is calculated by automatically performing linear interpolation between the matrices in accordance with the input of the fuel blending ratio and the incineration load. In addition, the actual value of the fuel calibration device 7 for each fuel may be used as the fuel blending ratio, or a blending ratio value set by a human may be used. Similarly, the incineration load may be calculated based on the actual value of the fuel calibration device 7 and the calorie of each fuel measured offline, or an incineration load set by a human may be used.

  In this embodiment, the case where the target value of the furnace temperature is set has been described, but the same applies to the case where the constraint value of the furnace temperature is set.

  In addition, when three or more types of fuel are used, a plurality of patterns are provided for the matrix table according to the fuel blending ratio of the patterns normally used in operation so that the number of parameters does not increase (for example, FIG. 5). Calculate the target temperature. When the blending state deviates from the matrix table, the target temperature is calculated by interpolation / extrapolation using two blending parameter values close to the blending state.

(B) Correction based on current operation performance temperature The target temperatures (combustion furnace middle target temperature T1a, cyclone outlet temperature T2a) determined by the method shown in (a) above are the past results and operations. Although it was reasonably determined based on experience, there is a possibility that a deviation from the current operation will occur. In order to solve this problem, correction is performed using the average value T1s of the past actual temperature in the combustion furnace and the average value T2s of the past cyclone outlet temperature. A specific correction formula is as follows.

Combustion furnace middle target temperature correction value T1b
T1b = T1a × α + T1s × (1−α)
Here, α is an adjustment parameter, where 0 ≦ α ≦ 1.

Cyclone outlet target temperature correction value T2b
T2b = T2a × β + T2s × (1−β)
Here, β is an adjustment parameter, where 0 ≦ β ≦ 1.

  Note that the average actual temperature T1s and the average cyclotron outlet temperature T2s in the combustion furnace are not used, and the latest temperature results within 30 minutes (for example, within 5 minutes) at the latest are not used. The average value of the measured value of the combustion furnace middle thermometer 8 and the measured value of the cyclone outlet thermometer 9) is used. Thereby, a kind of feedback control is performed.

  At that time, for the adjustment parameters α and β, the response time of the object to be controlled by changing the manipulated variable (here, after changing the primary combustion air injection amount and the secondary combustion air injection amount, The time until the cyclone outlet temperature changes may be set. If α and β are too large, the target temperature will be reached quickly, and the fluctuation of the combustion state in the combustion furnace 1 will increase. Conversely, if α and β are too small, it will take time to reach the target temperature. It takes too much. Therefore, α and β may be determined so as to obtain a desired response according to the response time of the control target.

(C) In-furnace temperature leveling control Current measured values of each temperature in the furnace (combustion furnace middle temperature measured value T1r, cyclone outlet temperature measured value T2r) and the above-mentioned furnace target temperature correction value (combustion furnace middle target temperature correction) Based on the difference between the value T1b and the cyclone outlet target temperature correction value T2b), the balance between the primary combustion air injection amount and the secondary combustion air injection amount is changed.

  To explain using a specific example, when the ratio of fuel with high calorie and high combustion speed increases, the temperature in the combustion furnace rises, so the amount of primary combustion air blown is increased and the main combustion position is set. The gas flow is shifted to the downstream side. What is changed at this time is only the balance of the combustion air, and the total amount of the primary combustion air and secondary combustion air is adjusted by the furnace outlet oxygen concentration. In other words, the in-furnace temperature leveling control is intended to burn the input heat quantity in the combustion furnace 1 as much as possible in a well-balanced manner.

  In addition, even when the above-described method is applied to an actual plant, there may be a case where residues and unburned gas are generated. For this reason, in order to prevent subsequent generation, the upper and lower limit flow rate constraints of the primary combustion air amount and the secondary combustion air amount can be set and adjusted.

  FIG. 6 shows the result of actual temperature control of the circulating fluidized bed incinerator based on the embodiment of the present invention.

  In FIG. 6, when the control is performed by providing an upper limit restriction (<980 ° C.) only for the cyclone outlet temperature as in Patent Document 1 (conventional example), the control is performed according to one embodiment of the present invention. (Case of the present invention).

  As shown in FIG. 6, in the conventional example, since only the cyclone outlet temperature is restricted, the temperature inside the combustion furnace is 950 ° C. or higher, and the risk of clinker generation is increased.

  On the other hand, in the present invention example, the combustion furnace middle target temperature T1a is set to 940 ° C., the cyclone outlet target temperature T2a is set to 930 ° C., and the measured cyclone outlet temperature T2r is gradually approaching the cyclone outlet target temperature T2a. The outlet target temperature was corrected, and the cyclone outlet target temperature correction value T2b was set to 993 ° C. As a result, the combustion furnace middle temperature measurement value T1r is controlled to 940 ° C., and the cyclone outlet temperature measurement value T2r is controlled to be around 993 ° C., which is a stable combustion state with low risk of equipment troubles and operation troubles.

It is a figure which shows the circulating fluidized bed type incinerator in one Embodiment of this invention. It is explanatory drawing of the control apparatus for furnace target temperature setting in one Embodiment of this invention. It is a figure which shows the matrix table for a combustion furnace middle target temperature setting. It is a figure which shows the matrix table for cyclone exit target temperature setting. It is a figure which shows the matrix table in the case of using 3 or more types of fuels. It is a figure which shows the temperature control result in Example 1 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Combustion furnace 2 Cyclone 2a Return pipe 2b Exhaust gas treatment equipment 2c Chimney 3 Primary combustion air blow-in port 4 Blower fan 4a Damper for primary combustion air 4b Damper for secondary combustion air 5 Secondary combustion air blow-in port 6 Fuel inlet 7 Fuel transfer / calibration / injection amount control device 8 Combustion furnace central thermometer 9 Cyclone outlet thermometer 10 Control device for setting the target temperature in the furnace 11 Setting computer 12 Database

Claims (3)

  In the circulating fluidized bed incinerator, according to the incineration load of the incinerator, the fuel composition to be used and the properties, the target value of each temperature in the furnace or the restriction value is automatically set online, and the set value The temperature of a circulating fluidized bed incinerator characterized by adjusting the amount of primary combustion air and the amount of secondary combustion air supplied to the incinerator based on at least one of a target value and a constraint value of each temperature in the furnace Control method.   2. The temperature control method for a circulating fluidized bed incinerator according to claim 1, wherein a target value or a constraint value of each temperature in the furnace is corrected online using a past actual temperature in the furnace.   The temperature control method for a circulating fluidized bed incinerator according to claim 1 or 2, wherein a restriction is provided on an adjustment amount of the primary combustion air amount and the secondary combustion air amount.

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