JP2003164725A - Ammonia blow-in control method for denitration catalyst device of waste treatment equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ammonia blow-in quantity control method in a denitration catalyst device capable of stably controlling the concentration of NOX in a flue and capable of reducing the amount of leaked ammonia in the exhaust gas treatment equipment of a waste treatment furnace. <P>SOLUTION: In the ammonia blow-in quantity control method for the denitration catalyst device for decomposing NOX by blowing ammonia in the denitration catalyst device in the exhaust gas treatment equipment for treating the exhaust gas discharged from the waste treatment furnace of the waste treatment equipment, the concentration of NOX at the inlet of the denitration catalyst device is proportional to the amount of the exhaust gas passing through the denitration catalyst device. Therefore, ammonia is blown in the denitration catalyst device in an amount necessary for decomposing NOX calculated on the basis of the amount of the exhaust gas to decompose NOX to control the concentration of NOX at the outlet of a flue. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the amount of ammonia blown into a denitration catalyst device in an exhaust gas treatment facility of a waste treatment furnace such as a melting furnace or an incinerator in a waste treatment facility.

[0002]

2. Description of the Related Art As the treatment of waste such as municipal waste, incineration treatment using an incinerator and melting treatment using a melting furnace are known. These waste treatment facilities are equipped with an exhaust gas treatment facility in order to remove harmful substances in the exhaust gas discharged from the waste treatment furnace to render them harmless.

FIG. 5 is a system diagram of exhaust gas treatment of a conventional waste melting treatment facility. The waste melting furnace 1, the combustion chamber 2, the waste heat boiler 3, the exhaust gas temperature controller 4, the dust collector 5, the denitration catalyst device. 6 and chimney 7 are sequentially connected. The combustible exhaust gas generated in the waste melting furnace 1 is sent to the combustion chamber 2 for combustion, and the exhaust gas generated by combustion is sent to the waste heat boiler 3 for heat recovery, and the exhaust gas temperature controller 4 adjusts the exhaust gas temperature. Then, the dust collector 5 is introduced to collect dust.

The exhaust gas discharged from the dust collector 5 is a catalyst.
A denitration catalyst device with a layer (hereinafter referred to as "SCR")
U ), Nitrogen oxides (NO_X) Is ammonia
Of the exhaust gas that is reduced and decomposed by the
NO_XThe concentration has been reduced. NO _XAnd ammonia (NH
_Three) Is 4NO + 4NH_Three+ O_Two→ 4N_Two+ 6H_TwoO Since it reacts according to the reaction formula of
Determines the amount of near-blowing and does not emit leak ammonia
And NO_XThe concentration is kept below the regulation value.

FIG. 4A is a diagram showing a conventional feedback control system for blowing ammonia into an SCR, and FIG. 4B is a diagram showing an example of a feedforward control system.

An ideal method of controlling the amount of injected ammonia
Is feedforward control as shown in FIG.
But no_XRequires another measuring device 15, and
NO _XActual NO due to measurement delay_XFor changes in concentration
As shown in Fig. 4 (a) due to insufficient tracking.
Feedback control is often adopted.

In FIG. 4A, the air blown into the SCR 11 is
The amount of ammonia blown is the exhaust gas flow rate at the exit of the SCR11.
Is measured by the flow meter 12 and NO_XWith the measuring device 13
NO _XMeasure the concentration and blow ammonia with the control valve 14.
Control the amount of inclusion.

In FIG. 4 (a), NO _X at the inlet of the SCR 11
This is a method in which the concentration is assumed to be a certain value, and the exhaust gas flow rate is applied to this to calculate the required ammonia supply amount and blow it. At this time, the excess or deficiency of the reaction is corrected by adjusting the outlet NO _X concentration.

NO _X concentration (assumed value) × exhaust gas amount = NH ₃ injection amount FIG. 3 (a) is an SCR in the case of conventional feedback control.
A graph showing the relationship between the inlet NO _X concentration of No. 1 and the amount of exhaust gas,
(B) is a graph showing the relationship between the amount of injected ammonia and the amount of exhaust gas.

In the case of the feedback control shown in FIG. 4 (a), as shown in FIG. 3 (a), the SCR
The inlet NO _X concentration is set to a constant value, and the ammonia injection amount is controlled so that the relationship between the exhaust gas amount and the ammonia injection amount is in a proportional relationship as shown in FIG.
11 Exhaust is adjusted based on the measurement result of the NO _X measuring device 13.

[0011]

[0006] However, the conventional feedback control, to set the inlet concentration of NO _X SCR from actual values, as shown in FIG. 3 (a) to a constant value, FIG. 3 (b) As shown in (1), since the inlet NO _X concentration of the SCR is set to be constant, control is performed to blow ammonia in a proportional relationship with the exhaust gas amount. However, in reality, the NO _X concentration changes depending on the amount and quality of waste, the amount of exhaust gas, etc., and it is difficult to inject an appropriate amount of ammonia with respect to fluctuations in the NO _X concentration at the SCR inlet.

[0012] Therefore, the ammonia excess blowing function of the denitration catalyst by the or increased SCR outlet NO _X concentration by insufficient amount blown ammonia reduction and or reverse, chimney NO _X concentration as a result of which, in FIG. 2 chimney NO
_As shown in the conventional example of the graph showing the relationship between the _X concentration and the processing time, the deflection width is large.

[0013] Therefore, the present invention is, in the exhaust gas treatment equipment of waste incinerator, chimney NO _X concentration can stably controlled, it is possible to reduce the leakage amount of ammonia, ammonia blowing amount control method in the denitration catalyst device It is provided.

[0014]

The present invention is directed to a waste treatment facility.
Exhaust gas that treats the exhaust gas emitted from the waste treatment furnace of Bibi
Ammonia is blown into the denitration catalyst device in the gas treatment facility
So no_XInjection of ammonia into the denitration catalyst device
In the amount control method, the denitration catalyst device inlet NO _XConcentration
Since it is proportional to the amount of exhaust gas passing through the denitration catalyst device,
NO calculated based on the exhaust gas amount_XThe amount of
Blow ammonia and NO_XTo disassemble the smoke outlet NO
_XIt is characterized by controlling the concentration.

[0015] In the arrangement, it controls the chimney outlet NO _X concentration by adding the correction by the chimney outlet NO _X concentration, or the outlet NO _X concentration, the amount of exhaust gas, the optimum calculates the NO _X concentration from the ammonia blown amount It is also possible to update the setting of the amount of injected ammonia.

[0016]

DETAILED DESCRIPTION OF THE INVENTION The present inventors have, exhaust gas amount and the SCR inlet concentration of NO _X relationship, and the exhaust gas amount and the ammonia blown quantity of the result of experiment and study about the relationship, that the SCR inlet NO _X concentration varies with the amount of exhaust gas I found out.

That is, the amount of exhaust gas and the SCR of FIG.
As shown in the graph of the relationship between the inlet NO _X concentration, it was found that the SCR inlet NO _X concentration increases as the exhaust gas amount increases, and the exhaust gas amount and the SCR inlet NO _X concentration have a proportional relationship. This is because the increase / decrease in the amount of exhaust gas is synonymous with the increase / decrease in the combustion load. Therefore, the increase in the combustion load increases the number of high-temperature parts in the combustion chamber, resulting in a higher NO _X concentration. It is conceivable that the NO _x concentration will be low because the high temperature part will be reduced in the indoor part.

According to the present invention, the SCR inlet NO _X concentration is proportional to the exhaust gas amount, and therefore the SCR based on the exhaust gas amount is used.
It is possible to predict the inlet NO _X concentration, calculate the amount of ammonia blown in for NO _X decomposition, and control the smoke outlet NO _X concentration.

The present invention can be carried out in a system configuration similar to the feedback control system shown in FIG. 4 (a), and the amount of exhaust gas passing through the denitration catalyst device can be adjusted to the outlet side (or inlet side) of the denitration catalyst device. ), The SCR inlet NO _X concentration (Fig. 1 (a)) determined by the amount of exhaust gas is measured, and the ammonia blowing amount (Fig. 1 (b)) required for NO _X decomposition is determined by the control valve 4. controlled and by controlling the chimney outlet NO _X concentration by blowing ammonia denitration catalyst device. As a result, as shown in the example of the graph of the relationship between the chimney NO _X concentration and the processing time in FIG. 2, the fluctuation range of the chimney outlet NO _X concentration is reduced, and a stable chimney NO _{X is obtained.}
The concentration can be controlled. Further, since ammonia required for NO _X decomposition is blown into the SCR inlet NO _X concentration predicted by the amount of exhaust gas, leak ammonia caused by excessive blowing of ammonia is reduced, and the function of the denitration catalyst is lowered due to excessive blowing of ammonia. It can be prevented.

Further, it is not necessary to install the SCR inlet NO _X measuring device necessary for the feedforward control.

Further, as shown in FIG. 4 (a), a NO _X concentration measuring instrument 13 is provided at the SCR outlet, and feedback control is performed so as to correct the NH ₃ supply amount as the NO _X concentration at the SCR outlet increases or decreases. Good.

Further, if the catalyst is in a healthy state, SC
Since the R outlet NO _X concentration + (ammonia injection amount / exhaust gas amount) = SCR inlet NO _X concentration, FIG.
By updating the relationship in (a) and updating at any time, S with higher accuracy can be obtained.
It is also possible to predict the CR inlet NO _X concentration.

[0023]

Without installing a denitration catalyst inlet NO _X meter according to the present invention, by predicting the inlet NO _X concentration enables ammonia supply an appropriate amount to reduce the leakage amount of ammonia, and constant chimney NO _X concentration Can be controlled.

[Brief description of drawings]

[1] the amount of exhaust gas and the SCR inlet NO _X concentration graph of the (a), (b) is a graph showing the relationship between the quantity of exhaust gas and ammonia blowing amount

FIG. 2 is a graph showing the relationship between the stack NO _X concentration and the processing time.

FIG. 3A shows S in the case of conventional feedback control.
A graph showing the relationship between the inlet NO _X concentration of CR1 and the exhaust gas amount, (b) is a graph showing the relationship between the NH ₃ blowing amount and the exhaust gas amount

FIG. 4A is a diagram showing a feedback control system for blowing NH ₃ into the SCR, and FIG. 4B is a diagram showing an example of a feedforward control system.

FIG. 5 is a system diagram of exhaust gas treatment of a conventional waste melting treatment facility.

[Explanation of symbols]

1: Waste melting furnace 2: Combustion chamber 3: Waste heat boiler 4:
Exhaust gas temperature controller 5: Dust collector 6: DeNOx catalyst device
7: Chimney 11: SCR 12: Flowmeter 13: NO _X
Concentration measuring instrument 14: Control valve 15: NO _X concentration measuring instrument

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Atsushi Kobayashi             46-59 Nakahara, Tobata-ku, Kitakyushu City Made in Japan             Engineering Co., Ltd. F-term (reference) 4D002 AA12 AC04 BA06 BA14 CA07                       DA07 EA02 GA02 GA03 GB01                       GB02 GB06                 4D048 AA06 AB02 AC04 CC38 CC61                       DA01 DA02 DA03 DA05 DA08                       DA10

Claims (3)

[Claims] 1. A method for controlling ammonia injection in a denitration catalyst device for decomposing NO _x by injecting ammonia into a denitration catalyst device in an exhaust gas treatment facility for treating exhaust gas discharged from a waste treatment furnace of a waste treatment facility. was bubbled ammonia blowing amount of ammonia necessary for the breakdown of the NO _X calculated based on the amount of exhaust gas from the catalytic converter inlet NO _X concentration is proportional to the amount of exhaust gas passing through the denitration catalyst device by decomposing NO _X chimney A method for controlling injection of ammonia in a denitration catalyst device of a waste treatment facility, which comprises controlling an outlet NO _X concentration. Wherein ammonia blowing control method of a denitration catalyst unit waste treatment facility according to claim 1, wherein the controlling the chimney outlet NO _X concentration by adding the correction by the chimney outlet NO _X concentration. 3. The disposal according to claim 1 or 2, wherein the NO _x concentration is calculated from the smoke outlet NO _x concentration, the exhaust gas amount, and the ammonia blowing amount to update the optimum ammonia blowing amount setting. A method for controlling ammonia injection in a denitration catalyst device of a material treatment facility.