JP5264301B2 - Sludge incineration method using fluidized bed incinerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique controlling &Delta;T by increasing or decreasing the number of used fuel supply guns while controlling the fuel supply amount to each fuel supply gun, and keeping the optimum combustion efficiency in a sand layer section while keeping a temperature of a free board section at a constant temperature necessary for complete decomposition of a dioxin component, in a fluidized bed type incinerator composed of the sand layer section and the free board section. <P>SOLUTION: In incinerating sludge in the fluidized bed type incinerator 1 comprising a number of fuel supply guns 13 on the sand layer section 2, the number of used fuel supply guns 13 is increased or decreased so that temperature difference &Delta;Tp (measured value) between a temperature (Ts) of the sand layer section and a temperature (Tf) of the free board becomes a target value &Delta;Ts, while controlling the total amount of the fuel supply amount to each fuel supply gun 13 so that the temperature of the free board section 3 becomes the constant temperature necessary for complete decomposition of the dioxin component. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a sludge incineration method using a fluidized bed incinerator.

  Conventionally, fluidized bed incinerators that hardly generate dioxins have been widely used for incineration of sewage sludge. Generally, incineration at about 800 degrees has been performed. When the sludge combustion state fluctuates due to changes in the moisture content of sludge to be incinerated or changes in organic components, temperature control in the combustion furnace is required. As shown in FIG. 1, the control switching device 16 selects either the sand layer part 2 temperature or the freeboard part 3 temperature as the control target, and the fuel flow rate is adjusted so that the control target temperature approaches the target temperature. The method of control was common. In particular, since the fuel supply gun 13 supplies fuel to the sand layer portion 2, a furnace temperature management method for controlling the temperature of the sand layer portion 2 by fuel control is generally used (Patent Documents 1 and 2). ).

  However, in recent years, in order to satisfy the emission standards based on the Dioxin Countermeasures Law, it has become necessary to keep the exhaust gas at 850 degrees or more for 2 seconds or more in the freeboard section 3 of the fluidized bed incinerator 1. Among them, the mainstream method is to detect the temperature of the freeboard unit 3 and feedback control the fuel flow rate by the auxiliary fuel control unit 7 so that the temperature of the freeboard unit 3 approaches the target temperature.

  As shown in FIG. 1, the auxiliary fuel control unit 7 includes a flow rate indicating controller (FIC) 9, a temperature indicating controller (TIC) 8, and an auxiliary fuel calculator 12. The temperature indicating controller (TIC) 8 sends a control output MV1 to the auxiliary fuel calculator 12 according to the deviation between the input set furnace top temperature SV1 and the furnace top temperature PV1 measured by the freeboard thermometer 6. Output. The auxiliary fuel calculator 12 performs a calculation for executing feedback control based on the received control output MV1 so that the furnace top temperature PV1 approaches the set furnace top temperature SV1.

  In the auxiliary fuel computing unit 12, a correlation equation (hereinafter referred to as “first correlation equation”) derived in advance by a heat balance calculation in a predetermined data storage area or modified based on actual operation data. And the required auxiliary fuel consumption is calculated using the first correlation equation. The calculated required auxiliary fuel consumption is input to the flow rate indicating controller (FIC) 9 as the auxiliary fuel consumption setting value SV2, and the flow rate indicating controller 9 is a measurement auxiliary value that is a measurement value of the auxiliary fuel flow meter 10. The control output MV2 is performed so that the fuel usage amount PV2 becomes the set auxiliary fuel usage amount SV2, the opening and closing of the auxiliary fuel supply valve is operated, and the flow rate is adjusted.

  However, the fuel flow rate control method shown in FIG. 1 is a method for detecting either the sand layer portion 2 temperature or the freeboard portion 3 temperature and controlling the fuel flow rate so as to approach the target temperature as described above. When the temperature of the free board part 3 is set as a control target, the temperature control in the sand layer part 2 is not performed, and the temperature of the sand layer part remains as a result of the temperature control of the free board part.

  The sludge combustion process in the fluidized incinerator 1 mainly comprises a sludge moisture evaporation process, a pyrolysis process, and a combustion process. An endothermic reaction occurs in the sludge moisture evaporation process and the pyrolysis process, and an exothermic reaction occurs in the combustion process. Yes. The progress of each process is controlled by conditions such as furnace temperature, sludge moisture content, air content, etc., and sludge moisture content, etc., so temperature control in the sand layer is not performed. If the incinerator is operated with only the freeboard part temperature as a control factor, there will be a problem that excessive air and fuel will be thrown in as a result, and on the contrary, the sand part part temperature will be too low and cause a misfire. It was happening.

Therefore, from the viewpoint of avoiding excessive air and fuel consumption input, reducing CO ₂ emissions in sewage treatment facilities, and preventing misfire of incinerators and realizing stable operation, There was a demand for controlling the combustion efficiency. The “combustion efficiency in the sand layer portion” in the present invention means that the sludge and fuel supplied to the sand layer portion react by φ% to generate heat, and as a result, the temperature of the sand layer portion becomes T. It is a value obtained by taking the heat balance between the calorific value at the inlet and the calorific value at the outlet of the sand layer, and the value obtained as the calorific value at the inlet of the sand layer = the calorific value at the outlet of the sand layer. Specifically, the sand layer combustion efficiency (φ) Solid heat of combustion xφ) + (fuel combustion heat x φ) + (retained heat amount of supplied air), and the sand layer outlet heat amount (retained heat amount of exhaust gas generated by combustion) + (combustion reaction) The residual heat of the sludge that was not present (solid combustion heat x (1-φ))) + (the retained heat of the water vapor generated by the reaction) was approximated to obtain φ as the sand layer inlet heat = sand layer outlet heat Value.

Patent Document 3 discloses a technique for controlling the fuel usage fee by feedforward control based on the temperature of the sand layer portion and the freeboard portion 3, but air and fuel are used from the viewpoint of reducing the CO ₂ emission amount. There is also a demand for a technology that optimally maintains the combustion efficiency in the entire furnace by controlling the combustion efficiency in the sand layer portion 2, not only in the control of the input amount of.
Japanese Patent No. 3235643 Japanese Patent No. 3235646 Japanese Patent No. 3946170

  An object of the present invention is to control ΔT by increasing or decreasing the number of fuel supply guns used in a fluidized bed incinerator composed of a sand layer part and a freeboard part, in addition to controlling the amount of fuel supplied to each fuel supply gun. It is to provide a technique for optimally maintaining the combustion efficiency in the sand layer part while keeping the temperature of the free board part at a constant temperature necessary for complete decomposition of the dioxin component.

The sludge incineration method using a fluidized bed incinerator according to the present invention, which has been made to solve the above problems, is a free board when incinerating sludge in a fluidized bed incinerator equipped with a number of fuel supply guns in the sand layer. While controlling the total amount of fuel supplied to each fuel supply gun so that the temperature of the part becomes a constant temperature necessary for complete decomposition of the dioxin component, the sand layer part temperature (Ts) and the free board part temperature (Tf) When the temperature difference ΔTp (actually measured value) is smaller than the target value ΔTs, the number of fuel supply guns used is decreased, and when ΔTp (actually measured value) is greater than the target value ΔTs, the use of the fuel supply gun is reduced. The number is increased .

The invention according to claim 2 is characterized in that in the sludge incineration method using the fluidized bed incinerator according to claim 1 , Ts is 580 to 850 ° C. and Tf is 850 to 950 ° C.

The invention described in claim 3 is characterized in that, in the sludge incineration method using the fluidized bed incinerator according to claim 2 , the number of fuel supply guns used is increased or decreased by opening / closing a shutoff valve for the fuel supply gun. is there.

The invention described in claim 4 is a sludge incineration method using a fluidized bed incinerator according to any one of claims 1 to 3, wherein a correlation equation between ΔT and the number of fuel supply guns used is derived in advance. Feedback control is performed according to the correlation equation.

  According to the present invention, while controlling the total amount of fuel supplied to each fuel supply gun so that the temperature of the free board is a constant temperature required for complete decomposition of the dioxin component, the sand layer temperature (Ts) The number of fuel supply guns used is increased or decreased so that the temperature difference ΔTp (actually measured value) with the freeboard portion temperature (Tf) becomes the target value ΔTs. It becomes possible to control the combustion efficiency.

When ΔTp (actually measured value) is smaller than the target value ΔTs, the number of fuel supply guns used is decreased. When ΔTp (actually measured value) is larger than the target value ΔTs, the number of fuel supply guns used is increased. According to the second aspect of the present invention, the ΔT control is performed. For example, when the sand layer temperature (Ts) rises excessively and ΔTp (actually measured value) decreases, the usage fee of the fuel supply gun is reduced. The combustion efficiency at the sand layer can be reduced, and the problem of excessive air volume and fuel consumption when the temperature of the sand layer has excessively increased can be solved. It is possible to reduce CO ₂ emissions at the treatment facility. On the other hand, when the sand layer temperature (Ts) decreases excessively and ΔTp (actually measured value) increases, the combustion efficiency in the sand layer can be increased by increasing the usage fee of the fuel supply gun. Sudden misfire is prevented, and the incinerator can be operated stably.

  According to the fifth aspect of the present invention, the correlation equation between ΔT and the number of fuel supply guns used is derived in advance, and the feedback control performed according to the correlation equation enables stable operation of the incinerator. Become.

  Hereinafter, the fluidized bed incinerator suitable for the sludge incineration method according to the present invention will be described with reference to FIG. 2, and the sludge incineration method according to the present invention will be described with reference to FIG. FIG. 2 is a block diagram schematically showing the in-furnace temperature control system of the fluidized bed incinerator of the present invention, and the incinerator structure (air supply pipe etc.) not subject to control of the present invention is shown in the figure. Omitted.

  In FIG. 2, 1 is a fluidized bed incinerator, 2 is a sand layer part, 3 is a free board part, 4 is an exhaust gas discharge port, 5 is a sand layer part thermometer, 6 is a free board part thermometer, 13 is a fuel supply gun, Reference numeral 7 denotes an auxiliary fuel control unit. A method of controlling the auxiliary fuel flow rate by the auxiliary fuel control unit 7 based on the free board temperature selected by the control switching device 16 is the same as the conventional method shown in FIG. The fluidized bed incinerator used in the sludge incineration method according to the present invention is provided with ΔT control means by the ΔT control section 15 in addition to the auxiliary fuel flow rate control means by the fuel control section 7. In FIG. 2, the plurality of fuel supply guns 13 are illustrated so as to be overlapped in the incinerator height direction for convenience of drawing, but in an actual incinerator, the incinerator sand layer of FIG. 4 is illustrated. As the partial sectional view shows, it is arranged in the circumferential direction of the incinerator sand layer.

  The ΔT control means includes a sand layer thermometer 5, a freeboard thermometer 6, a ΔT control unit 15, a plurality of fuel supply guns 13, and a fuel supply gun opening / closing valve 14 provided for each fuel supply gun 13. It consists of. The temperature (Ts) data value PV3 measured by the sand layer thermometer 5 and the temperature (Tf) data value PV1 measured by the free board thermometer 6 are input to the ΔT control unit 15. Further, in a predetermined data storage area of the ΔT control unit 15, a correlation value (hereinafter referred to as “second correlation equation”) indicating a correlation between ΔT and the target number (ΔTs) of the set ΔT and ΔT and the number of gas guns used. And the number of auxiliary fuel supply valves 13 used is calculated and determined using the stored data and the measurement data (PV1, PV3). The calculated required number of use is output as an opening / closing operation signal MV3 of the fuel supply gun opening / closing valve 14, and the number of auxiliary fuel supply guns 13 used is adjusted by opening / closing the fuel supply gun opening / closing valve 14. In order to increase the control range of ΔT control, it is preferable to set the number of fuel supply guns 13 installed in the fluidized bed incinerator 1 in advance to be greater than the necessary capacity. Here, the required capacity indicates that the incinerator has a fuel supply capacity necessary for continuously performing a supplementary combustion operation.

  As for the second correlation formula, it is preferable to obtain an optimal relation formula in accordance with fluctuations in the combustion reaction rate-limiting conditions such as sludge properties in each fluidized bed incinerator. The example which calculated | required the 2nd correlation equation below is shown.

  As shown in FIG. 2, a fluidized-bed incinerator (furnace diameter 6.9 m) having 12 fuel supply guns 13 each having a fuel supply gun opening / closing valve 14 is used to open and close the fuel supply gun opening / closing valve 14. Thus, the number of fuel supply guns 7 to be used was changed to 6, 8, and 12 to operate the incinerator, and the data shown in Table 1 below were obtained. The operating conditions were a sludge incineration amount of 7200 kg / h, a free board temperature target value of 850 degrees, and fuel control was automatic control. In Table 1 below, FB means a free board part, and SB means a sand layer part. A gas gun was used as the fuel supply gun 7, and city gas was used as the fuel.

FIG. 3 is a graph obtained by extracting the relationship between the number of gas guns used and ΔT and the relationship between the number of gas guns used and the sand layer combustion efficiency from Table 1 above. From FIG. 3, the following linear approximation formula can be derived.

  Although the linear approximation formulas (1) and (2) vary depending on the characteristics of the incinerator, a preliminary experiment similar to that described above is performed in each incinerator, so that the sand layer combustion efficiency, the number of fuel supply guns 13 used, and ΔT A linear approximation formula with the number of fuel supply guns 13 used can be obtained. Among these, a linear approximation expression between ΔT and the number of fuel supply guns 13 used is stored in the ΔT control unit 15 as a second correlation expression, and ΔT is controlled.

  More specifically, the control of ΔT means that when ΔTp (actual value) is smaller than the target value (ΔTs) of ΔT, the number of fuel supply guns 13 used is decreased and ΔTp (actual value) is the target value. When it is larger than ΔTs, the number of fuel supply guns 13 used is increased. The increase / decrease in the number of fuel supply guns 13 used is performed by opening / closing the auxiliary fuel supply valve 14 provided for each fuel supply gun 13 as described above. Here, the fuel supply gun open / close valve 14 is a cutoff valve. These functions can be used in combination. The shut-off valve is a valve provided in the fuel supply path in order to shut off the fuel supply when a pressure abnormality in the furnace or a sand layer misfire is detected.

  As shown in FIG. 3, when the total amount of fuel supply is constant, as the number of gas guns used increases, the combustion efficiency of the sand layer increases, and ΔT decreases (= sand layer temperature increases). Can be read. As shown in FIG. 4, when the total amount of fuel supply is constant, the decrease in ΔT decreases as the number of gas guns used increases and the amount of fuel supplied per gas gun decreases. The retention time in the sand layer is secured by reducing the gas flow rate, and the combustion zone in the sand layer increases as the number of gas guns used increases, so the reaction rate in the sand layer, that is, the sand layer combustion efficiency increases. It is thought to be caused by That is, in the present invention, the control of ΔT by increasing / decreasing the number of gas guns used means control of the combustion efficiency of the sand layer portion by increasing / decreasing the number of gas guns used, and the present invention indirectly controls the visible parameter of ΔT. In particular, the combustion efficiency of the sand layer can be controlled. From the viewpoint of combustion efficiency, as shown in FIG. 4, it is preferable to perform control using gas guns arranged symmetrically as a pair of control units.

It is a block diagram which shows typically the control system of the combustion control apparatus of the conventional fluidized bed incinerator. It is a block diagram which shows typically the control system of the combustion control apparatus of the fluidized bed incinerator of this invention. It is a figure which shows the relational expression of the number of gas gun use, (DELTA) T, a gas gun use number, and sand layer combustion efficiency. It is a model figure which shows the combustion zone fluctuation | variation of a sand layer part cross section. (When using the same amount of fuel and changing the number of gas guns used)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluidized bed incinerator 2 Sand layer part 3 Free board part 4 Outlet 5 Sand layer part thermometer 6 Free board part thermometer 7 Auxiliary fuel control part 8 Temperature indication controller (TIC)
9 Flow rate indicating controller (FIC)
10 Auxiliary fuel flow meter 10
11 Fuel Flow Control Valve 12 Auxiliary Fuel Calculator 13 Fuel Supply Gun 14 Fuel Supply Gun Open / Close Valve 15 ΔT Control Unit 16 Control Switching Device 17 Combustion Zone in Sand Layer

Claims (4)

When incinerating sludge in a fluidized bed incinerator equipped with a number of fuel supply guns in the sand layer,
While controlling the total amount of fuel supplied to each fuel supply gun so that the temperature of the free board part becomes a constant temperature necessary for complete decomposition of the dioxin component,
When the temperature difference ΔTp (measured value) between the sand layer temperature (Ts) and the freeboard temperature (Tf) is smaller than the target value ΔTs, the number of fuel supply guns used is decreased, and ΔTp (actual value) is A sludge incineration method using a fluidized bed incinerator characterized by increasing the number of fuel supply guns used when the target value ΔTs is greater . Ts is 580-850 degreeC and Tf is 850-950 degreeC, The sludge incineration method by the fluidized-bed incinerator of Claim 1 characterized by the above-mentioned. The method for sludge incineration using a fluidized bed incinerator according to claim 2, wherein the number of fuel supply guns used is increased or decreased by opening or closing a shutoff valve for the fuel supply gun. The fluidized bed incineration according to any one of claims 1 to 3 , wherein a correlation equation between ΔT and the number of fuel supply guns used is derived in advance, and feedback control is performed according to the correlation equation. Sludge incineration method using a furnace.

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