JP3902737B2 - Ammonia injection control method for denitration catalyst device of waste treatment facility - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for controlling the amount of ammonia blown in 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]
[Prior art]
As treatment of waste such as municipal waste, incineration processing using an incinerator, melting processing using a melting furnace, and the like are known. These waste treatment facilities include an exhaust gas treatment facility in order to remove harmful substances in the exhaust gas discharged from the waste treatment furnace and make them harmless.
[0003]
FIG. 5 is a system diagram of exhaust gas treatment of a conventional waste melting treatment facility. Waste melting furnace 1, combustion chamber 2, waste heat boiler 3, exhaust gas temperature controller 4, dust collector 5, denitration catalyst device 6, 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 the 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, it is introduced into the dust collector 5 and collected.
[0004]
The exhaust gas discharged from the dust collector 5 is introduced into a denitration catalyst device (hereinafter referred to as “SCR”) in which a catalyst layer is formed, and nitrogen oxides (NO _X ) are reduced and decomposed by ammonia and released from the chimney 7. thereby reducing the concentration of NO _X exhaust gas to be. NO _X and ammonia (NH ₃ )
4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O
Thus, the optimum ammonia blowing amount is determined from this reaction formula so as not to emit leaked ammonia, and the NO _x concentration is kept below the regulation value.
[0005]
FIG. 4A is a diagram showing a conventional feedback control system for injecting ammonia into the SCR, and FIG. 4B is a diagram showing an example of a feedforward control system.
[0006]
The ideal method for controlling the ammonia injection amount is feedforward control as shown in FIG. 4B, but requires another NO _X measuring device 15 and there is a time delay in NO _X measurement. Feedback control as shown in FIG. 4 (a) is often adopted for such may not be sufficiently follow the actual of the nO _X concentration change.
[0007]
In FIG. 4A, the amount of ammonia blown into the SCR 11 is determined by measuring the exhaust gas flow rate at the outlet of the SCR 11 with the flow meter 12, measuring the NO _x concentration with the NO _x measuring device 13, and feeding the ammonia with the control valve 14. To control.
[0008]
In FIG. 4 (a), assuming a value in the concentration of NO _X inlet SCR11, this is a method of blowing calculates the ammonia supply amount required by applying the exhaust gas flow rate. Excess and deficiency of this time the reaction is carried out to correct the excess and deficiency of ammonia blowing amount by the outlet NO _X concentration.
[0009]
NO _X concentration (assumed value) × exhaust gas amount = NH ₃ injection amount FIG. 3A is a graph showing the relationship between the SCR 1 inlet NO _X concentration and the exhaust gas amount in the case of conventional feedback control, and FIG. 3B is ammonia injection. It is a graph which shows the relationship between quantity and waste gas quantity.
[0010]
For feedback control shown in FIG. 4 (a), FIG. 3 SCR inlet NO _X concentration regardless the amount of exhaust gas as shown in (a) were set to a constant, FIG relationship between the exhaust gas amount and the ammonia blown amount 3 ( as it will be proportional as shown in b), to control the ammonia blown quantity is performed to adjust the excess and deficiency in the measurement results of SCR11 outlet NO _X meter 13.
[0011]
[Problems to be solved by the invention]
However, in the case of 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, and as shown in FIG. 3 (b), the inlet of the SCR NO _{Since the X} concentration is set constant, control is performed to blow ammonia in proportion to the amount of exhaust gas. However, in practice, the amount and quality of waste due amount of exhaust gas and NO _X concentration is changed, it is difficult blowing ammonia proper amount to variations in concentration of NO _X SCR inlet.
[0012]
Therefore, 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, chimney concentration of NO _X 2 As shown in the conventional example of the graph showing the relationship between the processing time and the processing time, the deflection width is large.
[0013]
Therefore, what the present invention is the exhaust gas treatment system of the waste treatment furnace, which can stably control the chimney NO _X concentration, it is possible to reduce the leakage amount of ammonia, which provides ammonia blowing amount control method in the denitration catalyst device It is.
[0014]
[Means for Solving the Problems]
The present invention relates to an ammonia blowing control method of a denitration catalyst device for decomposing NOx by blowing 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. the exhaust gas amount determined by the exit side or flow meter installed on the entry side of the apparatus, NOx concentration at the inlet of the denitration catalyst device based on the amount of exhaust gas from the relationship of concentration of NO _X denitration catalyst device inlet is proportional to the amount of exhaust gas Is calculated, and the amount of ammonia injection necessary for the decomposition of the NOx concentration is controlled by a control valve from the inlet side of the denitration catalyst device to control the NOx concentration at the smoke outlet.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The present inventor has exhaust gas amount and the SCR inlet concentration of NO _X relationship, and the exhaust gas amount and the ammonia blown amount of results of experiments and study the relationship was found that the SCR inlet NO _X concentration varies with the amount of exhaust gas.
[0017]
That is, as shown in graph of the exhaust gas amount and the SCR inlet concentration of NO _X Figure 1 (a), SCR inlet NO _X concentration when the amount of exhaust gas increases also increases, proportionally quantity of exhaust gas and the SCR inlet NO _X concentration I found out that there is a relationship. This is a decrease of the quantity of exhaust gas from being synonymous with increase or decrease of the combustion load, NO _X concentration to become many high-temperature portion in the combustion chamber by the increase of the combustion load is high, conversely combustion load decreases combustion since the high-temperature portion is reduced in the indoor unit, it is believed to be that the NO _X concentration is low.
[0018]
The present invention, SCR inlet NO _X concentration predicts the SCR inlet NO _X concentration based on the amount of exhaust gas from the relationship that is proportional to the amount of exhaust gas, ammonia blowing amount calculated by the chimney outlet NO _X concentration required in the NO _X decomposition Can be controlled.
[0019]
The present invention can be implemented with a system configuration similar to the feedback control system shown in FIG. 4 (a), and is a flow meter provided on the outlet side of the denitration catalyst device for the amount of exhaust gas passing through the denitration catalyst device. Measure the SCR inlet NOx concentration (Fig. 1 (a)) determined by the exhaust gas amount, and control the ammonia injection amount (Fig. 1 (b)) required for NOx decomposition by the control valve 4 to supply ammonia to the denitration catalyst device. Blow in to control the NOx concentration at the smoke outlet. As a result, as shown in the embodiment of the graph showing the relationship between the chimney NOx concentration and the processing time in FIG. 2, the fluctuation width of the chimney outlet NOx concentration can be reduced and controlled to a stable chimney NOx concentration. In addition, ammonia required for NOx decomposition is injected into the SCR inlet NOx concentration predicted by the amount of exhaust gas, so that leakage of ammonia due to excessive ammonia injection is reduced, and deterioration of the function of the denitration catalyst due to excessive ammonia injection is prevented. Can be planned.
[0020]
Moreover, there is no need to install an SCR inlet NO _X meter is required to feed-forward control.
[0021]
Further, as shown in FIG. 4A, a NO _X concentration measuring device 13 may be provided at the SCR outlet, and feedback control for correcting the NH ₃ supply amount in accordance with the increase or decrease of the SCR outlet NO _X concentration may be applied.
[0022]
Further, if the catalyst is in a healthy state, SCR outlet NO _X concentration + (ammonia blown amount / quantity of exhaust gas) = since SCR is the inlet NO _X concentration, by relating the constantly updated in FIG. 1 (a), it is also possible more predictable high SCR inlet NO _X concentration precision.
[0023]
【The invention's effect】
Without installing a denitration catalyst inlet NO _X meter, it enables the proper amount of ammonia supplied to predict the inlet NO _X concentration, reduce the leakage amount of ammonia, and, to control the chimney NO _X concentration constant it can.
[Brief description of the drawings]
[1] the amount of exhaust gas and the SCR inlet NO _X concentration graph of the (a), (b) the relationship between the graph Figure 2 chimney NO _X concentration and the treatment time showing the relationship between the quantity of exhaust gas and ammonia blowing amount graph Figure 3 showing the (a) shows a graph, the relationship between (b) is NH ₃ blow amount and the exhaust gas amount indicating the relationship between the inlet NO _X concentration and the exhaust gas amount of SCR1 for a conventional feedback control Graph [FIG. 4] (a) is a diagram showing a feedback control system of NH ₃ blowing into the SCR, (b) is a diagram showing an example of a feedforward control system [FIG. 5] of a conventional waste melting treatment facility System diagram of exhaust gas treatment.
[Explanation of symbols]
1: Waste melting furnace 2: Combustion chamber 3: Waste heat boiler 4: Exhaust gas temperature controller 5: Dust collector 6: Denitration catalyst device 7: Chimney 11: SCR 12: Flow meter 13: NO _X concentration meter 14: Control valve 15: NO _X concentration measuring device

Claims (1)

In the ammonia blowing control method of the denitration catalyst device for decomposing NOx by blowing ammonia into the denitration catalyst device in the exhaust gas treatment facility for treating the exhaust gas discharged from the waste treatment furnace of the waste treatment facility,
The measured amount of exhaust gas by the exit side or flow meter installed on the entry side of the denitration catalyst device, the inlet of the NO _X concentration of the denitration catalyst device inlet based on the amount of exhaust gas from the relationship that is proportional to the amount of exhaust gas denitration catalyst device Waste treatment characterized in that NOx concentration of NOx concentration is calculated and the amount of ammonia injection required for decomposition of the NOx concentration is controlled by a control valve from the inlet side of the denitration catalyst device to control NOx concentration at the smoke outlet Ammonia injection control method for denitration catalyst equipment of equipment.

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