JP2005147472A - Combustion control method of combustion chamber of waste melting treatment facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustion control method of a combustion chamber of a waste melting treatment facility capable of supplying an adequate amount of air to a rapid combustion of char without delay, and corresponding to the rapid combustion of the char by taking an amount of a combustion state of the combustion chamber as an absolute amount. <P>SOLUTION: The combustion control method of the combustion chamber is provided with an exhaust gas oxygen concentration controller 4, a secondary air flow meter 17, and an air flow control valve 19 for detecting an oxygen concentration in exhaust gas from the combustion chamber 1 and controlling a flow rate of air blown to the combustion chamber 1. A radiation thermometer 5 for detecting a temperature in the combustion chamber by light is provided in the combustion chamber 1 for combusting flammable gas containing flammable dust generated in a waste melting furnace by combustion air. A change rate of an output of a temperature detection sensor is operated by a change rate computing unit 6, and the air flow blown in the combustion chamber 1 is continuously changed corresponding to an absolute value of an amount of change. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a waste melting treatment facility for combusting combustible gas and combustible dust (hereinafter referred to as “char”) generated when waste such as general waste and industrial waste is processed in a waste melting furnace. The present invention relates to a combustion control method for a combustion chamber.

  Conventionally, combustible gas containing char generated in a waste melting furnace is collected by a dust remover, supplied to the combustion chamber together with combustible gas, and burned with combustion air.

  FIG. 3 is a control system diagram of conventional combustion of combustible gas.

  An exhaust gas oxygen sensor 3 is disposed at a combustion chamber 1 or a boiler outlet provided after the combustion chamber or an exhaust gas outlet 2 at the outlet of the induction fan, and an oxygen concentration detection signal from the oxygen sensor 3 is sent to the exhaust gas oxygen concentration controller 4. The exhaust gas oxygen concentration controller 4 sends a signal to the secondary air flow controller 17 and the secondary air flow controller 17 measures the flow rate with the secondary air flow meter 18 while the oxygen concentration at the exhaust gas outlet 2 is constant. The opening degree of the secondary air flow rate adjustment valve 19 is adjusted so as to be.

  Normally, combustible gas components and char discharged from a waste melting furnace are not constant and change from moment to moment. For this reason, an excessive supply of secondary combustion air is supplied to suppress the generation of unburned CO. ing.

Further, as a combustion control method for keeping the oxygen concentration in the exhaust gas constant, Patent Document 1 discloses in a combustion chamber having an exhaust gas oximeter 3 after the outlet of the combustion chamber 1 as shown in a combustion control system diagram shown in FIG. A brightness detection sensor 5 is provided to detect the relative change in the combustion state in the furnace due to the change in brightness. When the combustion load increases, the air flow rate adjustment valve 19 of the secondary air is opened for combustion control. There is described a control that stabilizes the combustion control by increasing the degree for a certain time and increasing the amount of air. Reference numeral 6 denotes a calculator that calculates the rate of change of the signal from the brightness sensor 5. Reference numerals 12 and 13 denote signal adders.
JP-A-11-125414

  However, in the conventional combustion in the combustion chamber, if there is a large amount of excess air, dioxins are likely to be generated due to a decrease in the temperature of the combustion exhaust gas. The dioxin generation suppression guideline stipulates that the combustion chamber is 850 ° C. and 2 seconds or longer. Further, the increase in the amount of exhaust gas due to excess air is uneconomical because it increases the capacity of facilities such as an induction fan and exhaust gas dust collector at the rear stage of the combustion chamber.

  Furthermore, the amount of char generated may increase rapidly depending on the furnace conditions of the waste melting furnace, and the exhaust gas oxygen concentration does not meet the specified value due to the rapid combustion of char in the combustion chamber, but unburned CO is generated. The correction by the oxygen sensor and the exhaust gas oxygen concentration controller is not in time because of the measurement delay or the exhaust gas oxygen concentration measurement after combustion.

  Further, in the combustion control method using the brightness detection sensor, it is possible to determine a relative increase / decrease with respect to an increase in the load in the combustion chamber, but it is possible to capture the change amount of the load as an absolute change amount. I can't. For this reason, the change in the amount of secondary combustion air does not match the actual amount of change, and there are cases where unburned CO is generated or the temperature is lowered due to excess or deficiency in the amount of air.

  An example at this time is shown in FIG. FIG. 5A shows a case where the correction control is properly applied. FIG. 5B shows a state in which the duration of the combustion load is shorter than expected and the amount of air is excessive because the amount of stoppage is too large, and the combustion temperature is lowered. C in FIG. 5 is a temporary decrease in the temperature instruction value caused by a factor other than the change in the combustion load, and shows a state in which the combustion temperature is lowered similarly to B by applying correction unnecessarily. FIG. 5D shows a state where the oxygen concentration in the exhaust gas is lowered because the change rate of the combustion load is small and the correction control does not work.

  In addition, by applying a fixed time correction to the temporal change in brightness, the temporal integration amount of the combustion load can be calculated, and both the speed of change and the duration of change can be corrected comprehensively. There wasn't.

  On the other hand, a laser oximeter that measures the oxygen concentration in the combustion chamber without delay has been developed. However, the device itself is expensive, and expensive nitrogen is required as a measure for removing dust from the device. Therefore, it is uneconomical for implementation.

  The present invention is capable of supplying an appropriate amount of air without delay with respect to the rapid combustion of char, and considering the amount of combustion state in the combustion chamber as an absolute amount, which can cope with rapid combustion of char. A combustion control method for a combustion chamber of a material melting treatment facility is provided.

  The present invention relates to combustion in a combustion chamber provided with an exhaust gas oxygen concentration controller, a secondary air flow meter and an air flow control valve for detecting the oxygen concentration in the exhaust gas from the combustion chamber and adjusting the flow rate of the air blown into the combustion chamber. In the control method, a radiation thermometer that detects the temperature in the combustion chamber with light is installed in the combustion chamber that burns the combustible gas containing the combustible dust generated in the waste melting furnace with the combustion air, and the output of the temperature detection sensor The change rate is calculated by a change rate calculator, and the flow rate of air blown into the combustion chamber is continuously changed in accordance with the absolute value of the change amount.

  During normal operation, the oxygen concentration set value is set higher than the theoretical combustion air amount so that excessive air is always supplied into the combustion chamber. When the rate of change of the output of the temperature detection sensor exceeds the specified value, the air necessary for the initial combustion is allocated the excess air of the secondary combustion air, and the increased amount of air catches up until this air becomes insufficient. Thus, in order to compensate for the delay in correction by the exhaust gas oxygen concentration controller, an increase in the amount of combustion air is maintained for a time commensurate with the delay time of the exhaust gas oxygen concentration controller.

  The amount of change by the temperature sensor is continuously measured, the amount of change is regarded as the combustion load, the amount of increase in the amount of air blown is continuously changed, and the magnitude of the change and the change duration are short and long. It is characterized by the ability to continuously correct the appropriate amount of air. This is characterized in that the temporal integration value of the temperature change amount and the integration value of the correction amount of the blown air can be controlled with correlation (hereinafter referred to as “continuous correction control”). This control is used when importance is attached to the accuracy of the correction amount. A specific example of this control is shown in FIG. FIG. 6A shows a case where the correction control is properly applied. In FIG. 6B, although the duration of the combustion load is shorter than expected, an appropriate correction amount can be obtained by shortening the duration due to deviation from the moving average value, so that the air temperature is excessive and the combustion temperature does not decrease. Proper control can be continued. C in FIG. 6 is a temporary decrease in the temperature indication value caused by a factor other than the change in the combustion load, and causing the decrease in the combustion temperature as generated in C in FIG. 5 by not operating the correction control. Control can be continued in an appropriate state. In FIG. 6D, the change rate of the combustion load is small, but the deviation of the temperature from the average value becomes large, and the correction control works properly. Therefore, the decrease in the oxygen concentration in the exhaust gas as occurred in D of FIG. The state which can be prevented is shown.

  Using the instantaneous value of the amount of change by the temperature detection sensor and using the correction amount calculated from the amount of change, the valve opening of the air blowing control valve is corrected by opening it for a certain period of time. It is calculated as an amount, and the correction amount can be determined one-to-one with respect to the temperature change amount (hereinafter referred to as “step correction control”). This control is used when importance is attached to the speed followability of the correction amount.

  By using a light temperature sensor with high responsiveness, it is possible to determine the transient state of the combustion state, and to control the temperature rise appropriately by returning from a low load, and to instantaneously change the temperature due to fluctuations in the furnace pressure. It is characterized in that it is possible to prevent an excessive state of the air correction amount due to erroneous detection without considering that the combustion load increases.

  Usually, the air blown into the combustion chamber may use agitation air for the purpose of improving the mixing property of the combustible gas, char and air in the combustion chamber separately from the primary and secondary air for the main purpose of combustion. In the above control method, the air to be increased may be air used for agitation installed separately from primary and secondary air. Moreover, a high effect is acquired by setting the flow rate of secondary air high and giving a stirring effect.

  In the present invention, the temperature change in the furnace is detected as light, and the oxygen concentration control and the secondary air flow rate are corrected using the temperature change as a feedforward element of the secondary air flow rate. Further, since the temperature change amount can be regarded as the combustion load amount, and the absolute amount of the air correction amount can be determined with respect to the absolute amount of the temperature change, combustion control with high accuracy is possible. In addition, by applying the correction continuously, it is possible to give an appropriate correction amount even to the temporal integration value of the change amount, which has been difficult to perform conventionally.

  FIG. 1 is a control system diagram of combustion of combustible gas according to the present invention.

  An exhaust gas oxygen sensor 3 for detecting the oxygen concentration in the exhaust gas is disposed at the exhaust gas outlet 2 of the combustion chamber 1, and an oxygen concentration detection signal of the exhaust gas oxygen sensor 3 is sent to the exhaust gas oxygen concentration controller 4.

  The combustion chamber is provided with a temperature detection sensor 5 comprising a photo sensor for measuring the state in the furnace, and a signal from the temperature detection sensor 5 is sent to a change rate calculator 6 and a moving average calculator 7.

  The change rate calculator 8 calculates the amount of change from the steady state of the combustion load from the output of the temperature detection sensor 5 and the output of the moving average calculator 7 and inputs it to the combustion load correction table 9.

  The combustion load correction table 9 calculates a necessary air amount for the change amount of the combustion load and outputs a corrected air amount.

  The primary and secondary air flow controllers 14 and 17 receive flow rate measurement signals from the primary and secondary air flow meters 15 and 18, and the air amount command from the oxygen concentration controller 4 and the combustion load correction table 9 The output value is input to the adder 11, and the signal of the adder 11 is input to the primary and secondary air flow controllers 14 and 17, and the primary and secondary air so that an appropriate amount of air is blown into the furnace. The flow control valves 16 and 19 are adjusted.

  It is possible to prevent the exhaust gas oxygen concentration from fluctuating by blowing in advance the air corresponding to the fluctuation of the combustion load into the combustion air (continuous correction control).

  The secondary air flow controller 17 receives a flow rate measurement signal from the secondary air flow meter 18. The signal of the change rate calculator 6 is input to the combustion load correction table 10.

  The combustion load correction table 10 calculates a change amount of the combustion load detected as a temperature change based on the input temperature change rate, outputs a necessary air amount as a valve opening degree, and outputs a secondary air flow rate adjustment valve. 17 is input.

  The signal of the secondary air flow rate controller 17 is input to the adder 13 together with the signal of the combustion load correction table 10, and the signal of the adder 13 is sent to the secondary air flow rate adjustment valve 19, where the secondary air flow rate adjustment valve is sent. Adjust the opening of 19.

  Next, the control method of the present invention will be described.

  FIG. 2 is a control flow chart of combustion of combustible gas according to the present invention.

  In the continuous correction control, the output of the temperature detection sensor 5, the temperature change amount is calculated from the moving average calculator 7 by the change rate calculator 8, and the calculation result is compared with the change amount of the combustion load by the combustion load correction table 9. In this way, it is output as an air amount correction value ΔMV. The correction value is added as a correction amount to the oxygen concentration control system. The correction amount ΔMV is output as the required air amount to the combustion air amount adjustment system as MV + ΔMV from the output value MV of the control system at the normal oxygen concentration. The oxygen concentration control system continues to control using PV detected as a result of the air volume controlled as MV + ΔMV.

  On the other hand, in the step correction control, if the change rate does not exceed the specified value as a result of calculation by the change rate calculator 6 from the output of the temperature detection sensor 5, the secondary air flow rate is adjusted so as to become the normal secondary air flow rate SV. The valve is set to a normal opening MV. The specified value of the temperature change rate is set to 10 ° C to 30 ° C.

  When the rate of change exceeds a specified value, it is determined that char is suddenly burned, and the amount of combustion air is increased by changing the secondary air flow rate control valve from the normal opening MV to MV + ΔMV.

  When the temperature in the combustion chamber changes, the load in the combustion chamber has already increased, so that the air required for the initial combustion is used by applying the excess air content of the secondary combustion air until this air becomes insufficient. The amount of air increased by the above judgment is caught up. In order to compensate for the delay in correction by the exhaust gas oxygen concentration controller, the increase in the combustion air amount is maintained for a time corresponding to the delay time of the exhaust gas oxygen concentration controller. For example, when about 20 seconds elapse after a certain time has elapsed, the secondary air flow rate follows the correction by the exhaust gas oxygen concentration controller.

  When the moving average value is smaller than a specified value, correction is not performed, so that a normal temperature increase such as a recovery process from a low load state is determined, and a temperature decrease due to excess air is prevented.

The specified value is set to about 800 ° C to 900 ° C. In addition, by detecting the difference from the moving average value as a temperature change, the temperature change detection result due to instantaneous fluctuations in the furnace pressure is recognized as a change unrelated to the combustion load, and control is performed without any correction. To prevent instability.

  A waste melting treatment facility that can supply an appropriate amount of air without delay in response to the rapid combustion of char, and can treat the amount of combustion in the combustion chamber as an absolute amount, and can respond to sudden combustion of char. This is used to control the combustion of the combustion chamber.

It is a control system diagram of combustion of combustible gas by the present invention. It is a control flow figure of combustion of combustible gas by the present invention. It is a control system diagram of the combustion of the conventional combustible gas. It is a combustion control system diagram which keeps the oxygen concentration in the conventional exhaust gas constant. It is a figure which shows the state by the combustion control using the brightness detection sensor of FIG. It is a figure which shows the state by the combustion control of this invention.

Explanation of symbols

1: Combustion chamber, 2: Exhaust gas outlet, 3: Exhaust gas oxygen sensor, 4: Exhaust gas oxygen concentration controller, 5: Temperature detection sensor, 6: Change rate calculator, 7: Moving average calculator, 8: Change rate calculator 9: Combustion load correction table, 10: Combustion load correction table, 11: Adder, 12: Adder, 13: Adder, 14: 1 primary air flow controller, 15: 1 primary air flow meter, 16: 1 Secondary air flow control valve, 17: Secondary air flow controller, 18: Secondary air flow meter, 19: Secondary air flow control valve

Claims (3)

  When combustible gas containing combustible dust generated in a waste melting furnace is burned with combustion air in the combustion chamber, the oxygen concentration in the exhaust gas from the combustion chamber is detected and the flow rate of air blown into the combustion chamber is adjusted In the combustion chamber combustion control method comprising the exhaust gas oxygen concentration controller, the air flow meter, and the air flow control valve, a radiation thermometer that detects the temperature in the combustion chamber by light is provided in the combustion chamber, and the radiation thermometer The difference between the current value of the temperature detection sensor output and the moving average value is calculated by a deviation calculator, and when the deviation exceeds a specified value, a correction air amount corresponding to the temperature deviation is obtained, and the correction air amount The combustion control method for the combustion chamber of the waste melting treatment facility is characterized in that combustion is controlled so that the oxygen concentration in the exhaust gas on the exit side of the combustion chamber becomes constant by adding to the amount of blown air.   The rate of change of the output of the temperature detection sensor of the radiation thermometer is calculated by a rate of change calculator, and when the rate of change exceeds a specified value, a corrected air amount corresponding to the temperature change is obtained, and the corrected air amount is calculated. The combustion control method for a combustion chamber of a waste melting treatment facility according to claim 1, wherein the combustion air is added to the amount of blown air.   2. The corrected air amount corresponding to the temperature change is calculated from output calculation data indicating a relationship between a corrected air amount and a temperature difference obtained by subtracting a previously measured temperature from a measured temperature of a radiation thermometer. Control method for the combustion chamber of the waste melting treatment facility.

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