JP2013194951A - Fluidized bed incinerator, combustion control device and operating method for fluidized bed incinerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluidized bed incinerator etc. capable of effectively reducing the amount of nitrous oxide to be generated, without increasing facility cost, while reducing the amount of carbon dioxide to be generated when fossil fuel is burned.SOLUTION: A fluidized bed incinerator includes: a first fuel supply part 15 disposed in an upper layer of a sand layer part 1A; a second fuel supply part 16 disposed in a lower layer of the sand layer part; and a combustion control device 20 controlling the amount of fuel to be supplied to the first fuel supply part and the second fuel supply part. The combustion control device includes: a first control part 21 controlling the amount of fuel F1 to be supplied to the first fuel supply part so that a lower combustion temperature of a free board part 1B becomes a first target temperature or higher that suppresses discharge of nitrous oxide; and a second control part 22 controlling the amount of fuel F2 to be supplied to the second fuel supply part so that a temperature of the sand layer part becomes a second target temperature or higher that pyrolyzes organic sludge. The second control part controls the amount of fuel F2 to be supplied so as to satisfy the following constraint condition: F2≤0.5F1.

Description

  The present invention relates to a fluidized bed incinerator, a combustion control device, and a method for operating a fluidized bed incinerator that incinerate organic sludge in a sand layer portion and a free board portion formed in the furnace.

  A fluidized bed incinerator is suitably used to incinerate sewage sludge. In Patent Document 1, two upper and lower burners composed of a sand layer upper burner and a sand layer lower burner are provided in the sand layer part, and a sand layer temperature sensor and a free board temperature sensor are provided in each of the sand layer part and the free board part. An in-furnace temperature controller for a fluidized bed incinerator has been proposed in which the lower sand layer burner and the upper sand layer burner are independently controlled using the sensor output as an index.

  According to the in-furnace temperature control device, by controlling the amount of fuel supplied to the sand layer upper burner and maintaining the freeboard temperature at a high temperature of about 850 ° C., the generation of harmful substances such as dioxins is suppressed. Independently of the above control, the amount of fuel supplied to the lower sand layer burner can be controlled to suppress changes in the sand layer temperature due to fluctuations in properties such as moisture content of the sludge, and the sludge can be stably pyrolyzed and burned. .

By the way, since organic sludge such as sewage sludge contains a large amount of nitrogen components, when nitrogen is incinerated, various nitrogen oxides are generated and released into the atmosphere. Of these nitrogen oxides, nitrous oxide (N ₂ O) is known to have a warming effect about 310 times that of carbon dioxide (CO ₂ ), which is known as a global warming gas. Reduction is a major issue.

As shown in FIG. 5, when the temperature of the free board portion is increased from 850 ° C. to 900 ° C., the conversion rate of nitrogen (N) in sludge to nitrous oxide (N ₂ O) is reduced to 5%. It is disclosed in Non-Patent Document 1.

Therefore, in Patent Document 2, the amount of air supplied to the sand layer portion is reduced to reduce the amount of nitrous oxide (N ₂ O) generated, and the secondary air supplied to the lower portion of the free board space is burned at a high temperature. Multi-layer combustion fluidized bed incinerators have been proposed that promote the decomposition of nitrous oxide (N ₂ O) and achieve complete combustion with air supplied to the top of the freeboard space.

  However, the fluidized bed incinerator described in Patent Document 2 is a long-distance air supply duct for supplying air heated to a high temperature of several hundred degrees to each of the sand layer portion, the freeboard space lower portion, and the freeboard space upper portion. There is a problem in that the equipment cost increases because it is necessary to arrange the cables in multiple stages.

JP 2001-74222 A Japanese Patent No. 4413275

Journal of Sewerage Association, Vol.42, No.508,2005 / 2, pp97-110

From the viewpoint of reducing the equipment cost, if the temperature of the freeboard portion is increased from 850 ° C. to 900 ° C. by controlling the sand layer upper burner using a fluidized bed incinerator as described in Patent Document 1, The amount of nitrogen oxide (N ₂ O) generated can be reduced.

However, this causes a problem that the amount of auxiliary fuel that is a fossil fuel increases, and the generation amount of carbon dioxide (CO ₂ ) increases accordingly. In addition, the sludge itself is biomass, and carbon dioxide (CO ₂ ) generated by the combustion is not subject to the regulation of greenhouse gases.

  In view of the above-described problems, the object of the present invention is to effectively reduce the generation amount of nitrous oxide without increasing the equipment cost while suppressing the generation amount of carbon dioxide due to the combustion of fossil fuel. The present invention provides a fluidized bed incinerator, a combustion control device, and a fluidized bed incinerator operating method.

  In order to achieve the above-mentioned object, the first characteristic configuration of the fluidized bed incinerator according to the present invention is an organic material comprising a sand layer portion and a freeboard portion formed in the furnace as described in claim 1 of the claims. A fluidized bed incinerator for incinerating sludge, wherein a first fuel supply unit disposed in an upper layer of the sand layer portion, a second fuel supply unit disposed in a lower layer of the sand layer portion, and a bottom portion of the sand layer portion An air supply unit disposed; a sludge input unit for supplying organic sludge from the upper part of the sand layer; and a combustion control device for controlling a fuel supply amount to the first fuel supply unit and the second fuel supply unit, The combustion control device controls a fuel supply amount F1 to the first fuel supply unit so that a lower combustion temperature of the free board unit becomes equal to or higher than a first target temperature for suppressing discharge of nitrous oxide. And the temperature of the sand layer part is capable of thermally decomposing organic sludge. And a second control unit that controls a fuel supply amount F2 to the second fuel supply unit so that the temperature is equal to or higher than a target temperature, and the second control unit is configured to satisfy the constraint condition F2 ≦ 0.5F1. This is in controlling the supply amount F2.

When the present inventors conducted earnest test research, the first controller supplies the first fuel supply unit so that the lower combustion temperature of the freeboard unit becomes equal to or higher than the first target temperature that suppresses the emission of nitrous oxide. The fuel supply amount F1 is controlled, and the second control unit controls the fuel supply amount F2 to the second fuel supply unit so that the temperature of the sand layer portion becomes equal to or higher than the second target temperature at which organic sludge can be pyrolyzed. In addition, the second controller controls the fuel supply amount F2 so as to satisfy the constraint condition F2 ≦ 0.5F1, thereby effectively reducing the amount of nitrous oxide (N ₂ O) generated, It was possible to find a balanced temperature control condition capable of suppressing the total fuel supply amount F1 + F2. As a result, the amount of carbon dioxide (CO ₂ ) generated by the fossil fuel can be suppressed.

  In the second feature configuration, as described in claim 2, in addition to the first feature configuration described above, the second control unit is configured such that the temperature of the sand layer portion is changed from the second target temperature to the first target configuration. The fuel supply amount F2 is controlled such that the fuel supply amount F2 is maintained within the range from the target temperature to the third target temperature lower than the second target temperature.

  If the second control unit controls the temperature of the sand layer portion to fall within the range of the second target temperature to the third target temperature, the water content of the sludge that is input while stably satisfying the constraint condition F2 ≦ 0.5F1 Corresponding to the change in properties such as the rate, a control range for maintaining the sand layer temperature above the second target temperature at which the organic sludge can be thermally decomposed can be secured.

  In the third characteristic configuration, as described in claim 3, in addition to the first or second characteristic configuration described above, the second control unit is configured such that the temperature of the sand layer portion is higher than the second target temperature. When it decreases, the fuel supply amount F2 is controlled so as to rise to a temperature higher than the second target temperature without being restricted by the constraint condition.

  If the temperature of the sand layer portion is lower than the second target temperature, the organic sludge does not proceed with thermal decomposition, and there is a risk of poor combustion. In such a case, the sand layer temperature can be quickly recovered to an appropriate temperature by controlling the fuel supply amount F2 without being restricted by the constraint conditions.

  In the fourth feature configuration, as described in claim 4, in addition to any of the first to third feature configurations described above, the first fuel supply unit is provided when the sand layer portion is stationary. The second fuel supply unit is disposed in a range lower than the sand layer height ½.

  Since the lower combustion temperature of the freeboard section is stably controlled to be higher than the first target temperature, and the sand layer temperature is stably controlled to be higher than the second target temperature while satisfying the constraint condition F2 ≦ 0.5F1, It is preferable that the first fuel supply unit is disposed in the range of the sand layer height ½ from the upper surface of the sand layer unit, and the second fuel supply unit is disposed in the range lower than the sand layer height ½.

  The first characteristic configuration of the combustion control apparatus according to the present invention is the first fuel supply unit disposed in the upper layer of the sand layer portion and the second fuel disposed in the lower layer of the sand layer portion as described in claim 5. An organic sludge is provided in the sand layer portion and free board portion formed in the furnace, comprising a supply portion, an air supply portion disposed at the bottom of the sand layer portion, and a sludge inlet portion for introducing organic sludge from the upper portion of the sand layer. A combustion control apparatus for a fluidized bed incinerator for incinerating fuel, wherein the fuel to the first fuel supply unit is set so that the lower combustion temperature of the freeboard unit is equal to or higher than a first target temperature for suppressing nitrous oxide emission. A first control unit that controls the supply amount F1 and a fuel supply amount F2 to the second fuel supply unit such that the temperature of the sand layer portion is equal to or higher than a second target temperature at which organic sludge can be pyrolyzed. A second control unit, and the second control unit includes a constraint condition F2. To meet 0.5F1, it lies in controlling the fuel supply amount F2.

  As described in claim 6, the second characteristic configuration is that, in addition to the first characteristic configuration described above, at least the control executed by the second control unit is fuzzy control.

  When controlling the temperature of the sand layer, if linear control such as general-purpose PID control is used, stable control is difficult due to property fluctuations of organic sludge, etc. By using fuzzy control using fuzzy inference that takes into account, the temperature of the sand layer portion can be stably controlled to be equal to or higher than the second target temperature. In particular, this is suitable for maintaining the temperature of the sand layer portion between the second target temperature and the third target temperature.

  The characteristic configuration of the operation method of the fluidized bed incinerator according to the present invention includes a first fuel supply unit disposed in the upper layer of the sand layer portion and a second fuel layer disposed in the lower layer of the sand layer portion as described in claim 7. A fuel supply unit; an air supply unit disposed at the bottom of the sand layer unit; and a sludge input unit that inputs organic sludge from the top of the sand layer, and fuel to the first fuel supply unit and the second fuel supply unit An operation method of a fluidized bed incinerator in which organic sludge is incinerated in a sand layer part and a free board part formed in the furnace by controlling a supply amount, wherein a lower combustion temperature of the free board part is nitrous oxide A first control step of controlling the fuel supply amount F1 to the first fuel supply unit so as to be equal to or higher than a first target temperature that suppresses the discharge of water, and a temperature at which the temperature of the sand layer portion can thermally decompose organic sludge. 2 To the second fuel supply unit so that the target temperature is higher than Includes a second control step of controlling the fuel supply amount F2, and wherein in the second control step, so as to satisfy the constraint condition F2 ≦ 0.5F1, fuel supply amount F2 is in that it is controlled.

  As described above, according to the present invention, it is possible to effectively reduce the generation amount of nitrous oxide without increasing the equipment cost while suppressing the generation amount of carbon dioxide due to the combustion of fossil fuel. It is now possible to provide a fluidized bed incinerator, a combustion control device, and a fluidized bed incinerator operation method.

Configuration diagram of organic sludge incineration facility according to the present invention Illustration of fluidized bed incinerator according to the present invention Functional block diagram of combustion control device Explanatory drawing of the control table data of a 2nd control part Characteristic diagram showing the relationship between nitrous oxide gas and furnace combustion temperature Characteristic chart showing the difference in the amount of nitrous oxide generated with respect to the temperature at the bottom of the freeboard and the furnace outlet due to the difference in operation method Illustration of membership function

  FIG. 1 shows an incineration facility A for organic sludge (hereinafter simply referred to as “sludge”). Sludge generated in the sewage treatment facility is dehydrated by a dehydrator such as a screw press system, stored in the dehydrated cake storage silo S, and then put into the fluidized bed incinerator 1 for incineration. The fluidized bed incinerator 1 is provided with a combustion control device 20 having a plurality of control units for controlling the amount of sludge input, the flow air supply amount, the auxiliary fuel supply amount, and the like.

  In order to effectively use waste heat from the exhaust gas generated in the fluidized bed incinerator 1, a combustion air preheater 3 and a white smoke prevention air preheater 4 are disposed along the flue of the fluidized bed incinerator 1. By these, the retained heat of the combustion exhaust gas is recovered.

  Further, the gas cooling tower 5 and the dust collector 6 are arranged on the downstream side, and the exhaust gas removed by the dust collector 6 is alkali-treated in the smoke treatment tower 7 to remove SOx and HCl, and heated with air for preventing white smoke. Is exhausted from the chimney 8.

  The sludge incineration facility A is attached to a sewage treatment facility that employs a method such as an activated sludge method that biologically treats sewage sludge or a membrane separation activated sludge method that performs biological treatment and membrane filtration. The sludge incineration facility A according to the present invention is not limited to incineration of sewage sludge, but is also used for incineration of organic sludge having a high water content such as sludge generated by purifying sludge generated in a food factory or the like. It is possible.

  FIG. 2 shows the configuration of the fluidized bed incinerator 1. The fluidized bed incinerator 1 includes a furnace body in which heat-resistant and wear-resistant special bricks and casters are lined and a heat insulating material is arranged on the outside thereof. In the interior space of the furnace body, a sand layer portion 1A and a free board portion 1B, which are sludge combustion regions, are configured.

  A plurality of dispersion pipes serving as a flow air supply unit 14 are arranged at the bottom of the sand layer portion 1A, and the sand staying in the lower region of the furnace body is floated by the flow air supplied through the header pipe 14H. A fluidized bed is formed. The air supplied from the fluid blower B is preheated to about 550 to 650 ° C. by the combustion air preheater 3 and then supplied to the header pipe 14H. Normally, the secondary combustion air supply unit 17 is not provided, but when the secondary combustion air supply unit 17 is provided above the sand layer 1A, a part of the preheated air is used as the secondary combustion air. You may supply from the supply part 17 to the free board part 1B.

  Sand guns that serve as a plurality of first fuel supply sections 15 are arranged on the circumference around the upper layer of the sand layer section 1A, and sand guns that serve as a plurality of second fuel supply sections 16 around the lower layer of the sand layer section 1A. Are arranged on the circumference. The amount of fuel supplied to the sand guns 15 and 16 is adjusted by electromagnetic valves V1 and V2. Further, a temperature sensor S2 for detecting the temperature of the fluidized bed is installed in the sand layer portion 1A, and the temperature sensor S1 is also installed in the lower portion of the free board portion 1B. Furthermore, a sludge input part 10 is provided at the upper part of the sand layer part 1A.

  The first fuel supply unit 15 is disposed in a range L1 that is ½ of the sand layer height L from the upper surface when the sand layer unit 1A is stationary with respect to the installation height of the dispersion pipe 14, and the second fuel supply unit 16 is arranged in a range L2 lower than 1/2 of the sand layer height L. Note that the height of the sand layer portion 1A that has shifted to the fluidized state is approximately 1.2 to 1.5 times the height of the stationary state. The hatched area in FIG. 2 represents the fluidized bed.

  A tapered sand discharge portion 11 is provided at the lower end of the furnace body, and the fluid sand transported by the sand conveyor 18 provided below the sand discharge portion 11 is put into the sand after the foreign matter is removed by the sorting mechanism 19. The unit 12 is re-entered.

  When the furnace is started up, the starter burner 13 provided on the upper part of the sand layer 1A is ignited, air for flow is supplied, and auxiliary fuel is supplied to the first fuel supply unit 16 and the second fuel supply unit 15. The The temperature of the fluidized bed is adjusted to 700 to 800 ° C. by the auxiliary fuel supplied to the second fuel supply unit 15, and the lower temperature of the free board unit 1 B is 850 ° C. or more by the auxiliary fuel supplied to the first fuel supply unit 16. Adjusted to Heavy oil is used as auxiliary fuel, but other fossil fuels and digestion gas can be used.

  When the furnace rises, sludge having a water content of about 80% is introduced from the sludge introduction unit 10. The introduced sludge is thermally decomposed into organic gas in the fluidized bed, and the organic gas is combusted at a high temperature of about 850 ° C. or higher, specifically 850 to 900 ° C., in the free board portion 1B.

As shown in FIG. 5, when the temperature of the free board portion 1B is about 850 ° C. or higher, the amount of nitrogen-derived nitrous oxide (N ₂ O) contained in the sludge becomes extremely low.

The combustion control device 20 controls the fluidized bed incinerator 1 in order to reduce the amount of nitrogen-derived nitrous oxide (N ₂ O) contained in the sludge while suppressing the amount of carbon dioxide generated by fossil fuel combustion. To control.

  Hereinafter, the combustion control device 20 will be described in detail. The combustion control device 20 includes a CPU and a memory in which an operation program for the CPU is stored. A specific configuration mode is not particularly limited, and may be a mode in which an application program for combustion control is installed in a general-purpose personal computer, or a mode in which a control program is incorporated in a dedicated control CPU. It may be.

  As shown in FIG. 3, the combustion control device 20 includes a drive unit that receives the value of the temperature sensor S1 installed in the lower portion of the free board unit 1B and drives the electromagnetic valve V1 of the first fuel supply unit 15. A first control unit 21 and a second control unit 22 including a drive unit that receives the value of the temperature sensor S2 installed in the sand layer unit 1A and drives the electromagnetic valve V2 of the second fuel supply unit 16 are provided. .

Further, although not shown in the figure, the combustion control device 20 includes a sludge charging control unit that controls the amount of sludge charged into the furnace from the sludge charging unit 10 based on the values of the temperature sensors S1, S2, etc. I have. If you have a secondary combustion air supply unit 17, based on the value or the like of the NO _X concentration sensor disposed in the flue, the air amount for the secondary combustion supplied from the secondary combustion air supply portion 17 There is a case where a secondary combustion air supply control unit for controlling the combustion is provided.

  The first control unit 21 is a control temperature storage unit in which a temperature target value below the free board unit 1B, in this case, a value of 850 ° C. is stored (this value can be appropriately changed and set by the operator via the input unit) And a PID calculation unit and a control target value storage unit.

  The PID calculation unit performs PID calculation based on a difference value, a differential value, and an integral value between the value of the temperature sensor S1 input at a predetermined cycle and the target value 850 ° C., and corresponds to the fuel supply control amount obtained as a result. The target opening of the electromagnetic valve V1 to be stored is stored in the control target value storage unit. The drive unit drives the electromagnetic valve V1 of the first fuel supply unit 15 based on the target opening degree stored in the control target value storage unit. With this control, the value of the fuel flow rate F1 supplied from the first fuel supply unit 15 is determined.

  The second control unit 22 includes a control table storage unit that stores control table data for the temperature of the sand layer unit 1A, a step control calculation unit, and a control target value storage unit, and the temperature of the sand layer unit is 700 to 700. Control to be in the range of 800 ° C.

  The step control calculation unit calculates a target opening degree of the electromagnetic valve V2 corresponding to the fuel supply control amount based on the value of the temperature sensor S2 input at a predetermined cycle and the control table data stored in the control table storage unit. The value is stored in the control target value storage unit.

  FIG. 4 shows an example of the control table data. If the current fuel flow rate F2 supplied to the second fuel supply unit 16 satisfies the constraint condition F2 ≦ 0.5F1, the current state is as long as the sand layer temperature input from the temperature sensor S2 is in the range of 730 to 780 ° C. Is maintained, and the target opening of the electromagnetic valve V2 is calculated so as to reduce the fuel flow rate F2 stepwise within a range of 780 to 800 ° C. If the sand layer temperature is in the range of 700 to 730 ° C., the target opening of the electromagnetic valve V2 is calculated so as to increase the fuel flow rate F2 stepwise.

  The up and down arrows shown in the control table data change the fuel flow rate F2 by one step (indicating a preset fuel flow rate) in the case of one, two steps in the case of two, and three steps in the case of three. Means that the up arrow increases, the down arrow decreases, and the more arrows, the greater the amount. An increase or decrease amount of the fuel flow rate F2 corresponding to one step can be appropriately changed and set by the operator via the input unit.

  If the current fuel flow F2 supplied to the second fuel supply unit 16 does not satisfy the constraint condition F2 ≦ 0.5F1, the current state is maintained if the sand layer temperature input from the temperature sensor S2 is 720 to 730 ° C. If the temperature is in the range of 730 to 800 ° C., the target opening degree of the electromagnetic valve V2 is calculated so as to decrease the fuel flow rate F2 stepwise. Moreover, if the sand layer temperature is in the range of 700 to 720 ° C., the target opening of the electromagnetic valve V2 is calculated so as to increase the fuel flow rate F2 stepwise.

  The drive unit drives the electromagnetic valve V2 of the second fuel supply unit 16 based on the target opening degree stored in the control target value storage unit. With this control, the value of the fuel flow rate F2 supplied from the second fuel supply unit 16 is determined.

  In other words, the combustion control device 20 supplies the fuel supply amount F1 to the first fuel supply unit 15 so that the lower combustion temperature of the free board unit 1B becomes equal to or higher than the first target temperature (850 ° C.) that suppresses the emission of nitrous oxide. The fuel supply amount F2 to the second fuel supply unit 16 is set so that the temperature of the first control unit 21 that controls the temperature and the temperature of the sand layer unit 1A is equal to or higher than the second target temperature (700 ° C.) at which organic sludge can be pyrolyzed. The second control unit 22 is configured to control the fuel supply amount F2 so as to satisfy the constraint condition F2 ≦ 0.5F1.

  Further, the second control unit 22 has a temperature of the sand layer portion 1A from the second target temperature (700 ° C.) to the third target temperature (800 ° C.) lower than the first target temperature (850 ° C.) and higher than the second target temperature. The fuel supply amount F2 is controlled so as to be maintained in the range.

  Furthermore, when the temperature of the sand layer portion 1B decreases from the second target temperature (700 ° C.), the second control unit 22 supplies fuel so as to rise to a temperature higher than the second target temperature without being restricted by the constraint condition. The amount F2 is configured to be controlled.

The constraint condition is a condition that the fuel flow rate F2 supplied to the second fuel supply unit 16 is limited to ½ or less of the fuel flow rate F1 supplied to the first fuel supply unit 15, while satisfying this condition. When the auxiliary fuel is supplied so as to be maintained at the above target temperature, the total fuel supply amount F1 + F2 can be suppressed while effectively reducing the amount of nitrous oxide (N ₂ O) generated. is there.

  And in order to make such control effective, the 1st fuel supply part 15 makes sand layer height L 1 from the upper surface when the sand layer part 1A is a stationary state on the basis of the installation height of a dispersion | distribution pipe. The second fuel supply unit 16 is preferably disposed in a range L2 lower than ½ of the sand layer height L.

  In the operation method of the fluidized bed incinerator according to the present invention, the fuel supply amount F1 to the first fuel supply unit 15 is set so that the lower combustion temperature of the free board unit 1B becomes equal to or higher than the first target temperature that suppresses the emission of nitrous oxide. And a second control for controlling the fuel supply amount F2 to the second fuel supply unit 16 so that the temperature of the sand layer portion 1A is equal to or higher than a second target temperature capable of thermally decomposing organic sludge. In the second control step, the fuel supply amount F2 is controlled so as to satisfy the constraint condition F2 ≦ 0.5F1.

  FIG. 6 (a) shows the operation method according to the present invention (satisfying the constraint condition) and the first control unit and the second control unit independently of each other without the above-described constraint condition. The characteristic diagram which compared the relationship between the free board part lower part temperature and the furnace exit temperature, and the discharge | emission amount of nitrous oxide by the method of performing PID control is shown. In both cases, the target of the sand layer temperature is set to about 750 ° C., and the target of the free board lower temperature is set to about 850 ° C.

Right edge of the gray scale represents the emissions of nitrous oxide _{(kg-N 2 O / t} ), the arrows indicate the reference values at 850 ° C. of MOE _{(0.645kg-N 2 O / t} ). In the graph on the left, the area surrounded by a solid circle is the lower limit area that satisfies the reference value, and in areas where the furnace outlet temperature decreases or the freeboard lower temperature decreases, nitrous oxide above the reference value is discharged. Has been shown to be.

  In the left graph, the region surrounded by the broken ellipse is the characteristic of the combustion control according to the present invention, and the region surrounded by the two-dot chain line ellipse is the first control unit and the second control unit without restriction conditions. It is the characteristic when the sand layer part temperature and the freeboard part lower part temperature are controlled independently.

  Comparing the characteristics of the lower temperature of the free board section with respect to the same furnace outlet temperature, it can be seen that the combustion control according to the present invention provides a higher temperature. In addition, when comparing the characteristics of the furnace outlet temperature with respect to the lower temperature of the same freeboard part, when the first control part and the second control part independently control the sand layer part temperature and the freeboard part lower part temperature without constraint conditions It can be seen that the furnace outlet temperature is higher. It can be seen that the amount of heat input is increased when the restraint conditions are not imposed, and the amount of auxiliary fuel used is increased.

  From this, it can be seen that the combustion control according to the present invention can reduce the amount of nitrous oxide generated while reducing the amount of auxiliary fuel used.

FIG. 6 (b) shows the operation method according to the present invention (satisfying the constraint condition) and the first control unit and the second control unit independently without the constraint condition described above, the sand layer part temperature and the free board part bottom temperature. Is a characteristic diagram in which the furnace outlet temperature and the amount of nitrous oxide discharged are compared by the PID control method.

  It can be seen that, even at the same furnace outlet temperature, the operation method according to the present invention reduces the amount of nitrous oxide discharged more effectively.

  Hereinafter, another embodiment will be described. In the previous embodiment, the first control unit 21 monitors the temperature sensor S1 disposed at the lower part of the free board unit, and the lower combustion temperature of the free board unit 1B suppresses the emission of nitrous oxide. Although the structure controlled to become (850 degreeC) or more was demonstrated, the 1st control part 21 monitors the temperature sensor arrange | positioned at the furnace exit, and the lower combustion temperature of a free board part discharges | emits nitrous oxide. You may comprise so that it may control more than the 1st target temperature to suppress. As shown in FIGS. 6A and 6B, in the case of the present invention, there is a certain correlation between the lower combustion temperature of the free board portion and the furnace outlet temperature.

  In the above-described embodiment, the example in which the first target temperature is 850 ° C., the second target temperature is 700 ° C., and the third target temperature is 800 ° C. has been described, but specific numerical values of each target temperature are limited to these values. Instead, the first target temperature may be a temperature that can suppress the discharge amount of nitrous oxide below the reference value, and the second target temperature is 700 if the sludge can be thermally decomposed in the sand layer portion. The third target temperature may be any temperature as long as it is lower than the first target temperature, and can be set as appropriate.

  The first control unit controls the fuel supply amount F1 to the first fuel supply unit such that the lower combustion temperature of the freeboard unit is equal to or higher than the first target temperature that suppresses the emission of nitrous oxide, and is auxiliary Alternatively, the secondary combustion air amount may be controlled to be increased or decreased.

  Of the first and second control units, at least the second control unit is preferably a fuzzy control unit. The first control unit needs to control the lower temperature of the free board unit to at least 850 ° C. and can sufficiently achieve the purpose by feedback control using PID control, while the second control unit satisfies the constraint condition and the sand layer In order to control the part temperature, it is necessary to provide a range for the control temperature range. In such a control, the control characteristics are better when the control is roughly controlled by the above-described step control or the fuzzy control is added with ambiguity than the control target value is frequently changed by the PID control. .

  A fuzzy rule storage unit storing membership functions and fuzzy rules corresponding to the antecedent part and the consequent part, a fuzzy inference part adopting the Min-Max centroid method, and a control value obtained as a result of the fuzzy inference are stored. What is necessary is just to comprise a control value memory | storage part and to drive an electromagnetic valve based on the control value which the drive part mentioned above memorize | stored in the control value memory | storage part.

  FIG. 7 shows an example of the membership function of the antecedent part and the membership function of the consequent part when the constraint condition is satisfied and not satisfied.

  The fuzzy inference rules are illustrated below. 1. When the sand layer temperature is “too low”, the auxiliary fuel is “increased”. 2. When the sand layer temperature is “low”, the auxiliary fuel is “increased”. 3. When the sand layer temperature is “slightly low”, the auxiliary fuel is “slightly increased”. 4). When the sand layer temperature is “appropriate”, the auxiliary fuel is “maintained”. 5. When the sand layer temperature is “slightly high”, the auxiliary fuel is “slightly reduced”. 6). When the sand layer temperature is “high”, the auxiliary fuel is “decreased”. 7). If the sand layer temperature is “too high”, the auxiliary fuel will be “significantly reduced”. 7 rules.

  The above-described membership function and fuzzy inference rules are examples, and are not limited to these and can be set as appropriate. In this case, the membership function of the antecedent part in the case where the constraint condition is satisfied places importance on the lower temperature of the free board part, and is appropriate in a relatively wide range from the median value in the control range of 700 ° C. to 800 ° C. Configured to build the region. In addition, the membership function of the antecedent part in the case where the constraint condition is inadequate, the auxiliary fuel supply amount is set in the temperature range higher than 730 ° C. out of the control range of 700 ° C. to 800 ° C. so as to satisfy the constraint condition as quickly as possible. It is set to reduce.

  Needless to say, the first control unit can be controlled by the fuzzy control unit.

  Each of the above-described embodiments is an example of the present invention, and the present invention is not limited by the description. The specific configuration of each part can be appropriately changed and designed within the range where the effects of the present invention are exhibited. Needless to say.

1: Fluidized bed incinerator 1A: Sand layer part 1B: Free board lower part 3: Combustion air preheater 4: White smoke prevention air preheater 5: Gas cooling tower 6: Dust collector 7: Smoke treatment tower 8: Chimney 15 : First fuel supply unit 16: Second fuel supply unit 20: Combustion control device 21: First control unit 22: Second control unit A: Incineration equipment S: Dehydrated cake storage silo S1: Free board lower temperature sensor S2: Sand layer Temperature sensor V1: Electromagnetic valve V2: Electromagnetic valve

Claims (7)

A fluidized bed incinerator that incinerates organic sludge in a sand layer part and a free board part formed in the furnace,
A first fuel supply unit disposed in an upper layer of the sand layer unit; a second fuel supply unit disposed in a lower layer of the sand layer unit; an air supply unit disposed in a bottom part of the sand layer unit; A sludge input unit for supplying activated sludge, and a combustion control device for controlling the amount of fuel supplied to the first fuel supply unit and the second fuel supply unit,
The combustion control device controls a fuel supply amount F1 to the first fuel supply unit such that a lower combustion temperature of the free board unit becomes equal to or higher than a first target temperature for suppressing discharge of nitrous oxide. And a second control unit that controls a fuel supply amount F2 to the second fuel supply unit such that the temperature of the sand layer unit is equal to or higher than a second target temperature at which organic sludge can be pyrolyzed, The second control unit is a fluidized bed incinerator that controls the fuel supply amount F2 so as to satisfy the constraint condition F2 ≦ 0.5F1.   The second control unit is configured to maintain a fuel supply amount so that the temperature of the sand layer portion is maintained in a range from the second target temperature to a third target temperature lower than the first target temperature and higher than the second target temperature. The fluidized-bed incinerator of Claim 1 which controls F2.   When the temperature of the sand layer portion falls below the second target temperature, the second control unit sets the fuel supply amount F2 so as to rise to a temperature higher than the second target temperature without being restricted by the constraint condition. The fluidized-bed incinerator of Claim 1 or 2 to control.   The first fuel supply unit is disposed in a range of 1/2 sand layer height from the upper surface when the sand layer unit is stationary, and the second fuel supply unit is disposed in a range lower than the sand layer height 1/2. The fluidized bed incinerator according to any one of claims 1 to 3. A first fuel supply unit disposed in the upper layer of the sand layer unit, a second fuel supply unit disposed in the lower layer of the sand layer unit, an air supply unit disposed in the bottom of the sand layer unit, and organic from the upper part of the sand layer A combustion control device for a fluidized bed incinerator comprising a sludge input portion for introducing sludge, and incinerating organic sludge in a sand layer portion and a freeboard portion formed in the furnace,
A first control unit that controls a fuel supply amount F1 to the first fuel supply unit such that a lower combustion temperature of the freeboard unit is equal to or higher than a first target temperature that suppresses discharge of nitrous oxide;
A second control unit that controls a fuel supply amount F2 to the second fuel supply unit such that the temperature of the sand layer unit is equal to or higher than a second target temperature capable of thermally decomposing organic sludge,
The second control unit is a combustion control device that controls the fuel supply amount F2 so as to satisfy the constraint condition F2 ≦ 0.5F1.   The combustion control device according to claim 5, wherein at least the control executed by the second control unit is fuzzy control. A first fuel supply unit disposed in the upper layer of the sand layer unit, a second fuel supply unit disposed in the lower layer of the sand layer unit, an air supply unit disposed in the bottom of the sand layer unit, and organic from the upper part of the sand layer An organic sludge in a sand layer portion and a free board portion formed in the furnace by controlling a fuel supply amount to the first fuel supply portion and the second fuel supply portion. A fluidized bed incinerator operating method for incinerating
A first control step of controlling a fuel supply amount F1 to the first fuel supply unit such that a lower combustion temperature of the free board unit is equal to or higher than a first target temperature for suppressing emission of nitrous oxide;
A second control step of controlling the fuel supply amount F2 to the second fuel supply unit such that the temperature of the sand layer part is equal to or higher than a second target temperature capable of thermally decomposing organic sludge,
In the second control step, the fluidized bed incinerator operating method in which the fuel supply amount F2 is controlled so as to satisfy the constraint condition F2 ≦ 0.5F1.