JP5240611B2 - Exhaust gas denitration treatment system - Google Patents

Description

  The present invention relates to a technology for denitrating exhaust gas flowing through an exhaust system of a combustion device such as an engine, a gas turbine, a furnace, or a boiler.

For example, nitrogen oxide (NOx) contained in the exhaust gas of combustion equipment such as gas engines, gas turbines, furnaces, and boilers is a kind of air pollutant. The demand for reduction is increasing.
For example, in the past, regulations regarding NOx in exhaust gas from combustion equipment have been mainly "no average value of NOx exceeds the threshold value". In some cases, there is a new standard of “not exceeding the threshold”.
Thus, efforts to reduce NOx in the exhaust gas of combustion equipment have become even more severe in recent years.

FIG. 19 shows a schematic configuration of an exhaust gas denitration processing system 200 that reduces the NOx concentration in the exhaust gas of a combustion device according to the prior art.
In FIG. 19, an exhaust gas denitration treatment system 200 includes a combustion device (for example, a gas engine) 1, an exhaust system 2, a denitration catalyst 3, a combustion device output sensor 5, a tank 6 such as a urea water tank, and an input pump 7 such as urea water. , An injection nozzle 9 for urea water or the like, a NOx concentration measuring device 42J, and a control device 10J.

The denitration catalyst 3 is interposed in the exhaust system 2 of the combustion device 1, and an injection nozzle 9 such as urea water is interposed in a region between the combustion device 1 and the denitration catalyst 3 in the exhaust system 2. Then, the urea water or the like in the storage tank 6 such as urea water is boosted by a charging pump 7 such as urea water, and enters the exhaust system 2 from an injection nozzle 9 for urea water or the like via a supply line Ln for urea water or the like. It is comprised so that it may be injected.
The urea water or the like injected into the exhaust system 2 acts as a reducing agent, reacts with NOx contained in the exhaust gas, and decomposes NOx by a chemical reaction with the denitration catalyst 3, thereby purifying the exhaust gas.

An exhaust gas sampling pipe 41J is inserted on the outlet side of the denitration catalyst 3 in the exhaust system 2.
The exhaust gas collected by the sampling tube 41J is sent to the NOx concentration measuring device 42J, and the NOx concentration (in the exhaust gas at the outlet side of the denitration catalyst 3 in the exhaust system 2) is obtained by the NOx concentration measuring device 42J.
The NOx concentration obtained by the NOx concentration measuring device 42J is sent to the control device 10J. Then, the feedback control unit 50J of the control device 10J calculates the optimal input amount of the reducing agent such as urea water into the exhaust system 2 based on the NOx concentration on the outlet side of the denitration catalyst 3, and the calculated input amount Based on the above, a control signal is output to the charging pump 7 for urea water or the like so that the optimum urea water or the like is input to the exhaust system.

When calculating the input amount of urea water or the like by the feedback control unit 50J, it is necessary to estimate the nitrogen oxide emission amount from the combustion device 1. As a physical quantity that can estimate this nitrogen oxide emission amount, There are output, exhaust bypass valve opening, and supply pressure. In the following description, in order to facilitate understanding, the “output of the combustion equipment” will be described as an example, but the “output of the combustion equipment” is set to “exhaust bypass valve opening” and “supply pressure”. Can be substituted.
Since there exists a relationship (characteristic: P-Qg line) as shown in FIG. 3 between the exhaust gas amount Qg and the output P of the combustion device 1, a characteristic diagram (map α) as shown in FIG. 3 is prepared in advance. . If the map α shown in FIG. 3 is used, the exhaust gas amount Qg can be estimated from the measurement value (combustion equipment output P) by the output sensor 5.
Next, since there is a certain relationship (characteristic) between the output P of the combustion device 1 and the NOx concentration δ at that time, as shown in FIG. 20, a characteristic diagram (map β: combustion) as shown in FIG. A device output P-NOx concentration δ characteristic diagram) is prepared in advance, and the NOx concentration δ is obtained from the measured value (combustion device output P) by the output sensor 5.
If the exhaust gas amount Qg obtained using the map α in FIG. 3 is multiplied by the NOx concentration δ obtained using the map β in FIG. 20, the NOx amount contained in the exhaust gas of the combustion device 1 can be obtained.

If the amount of NOx contained in the exhaust gas of the combustion device 1 is obtained, the NOx removal rate (μ), which is the ratio with the amount of NOx to be deleted, corresponding to various standards is obtained. here,
“NOx amount to be deleted” = “NOx amount contained in exhaust gas of combustion equipment 1” − “target NOx amount (NOx amount capable of clearing reference)”
And
“NOx removal rate μ” = “NOx amount to be deleted” ÷ “NOx amount contained in exhaust gas of combustion device 1”
It is.
Between the equivalent ratio of urea water or the like to be introduced into the exhaust system (γ: equivalent of urea water as a reducing agent with respect to the NOx unit amount) and the denitration rate μ, the characteristics as shown in FIG. 4 (μ-γ characteristics) : Map γ) exists. If the μ-γ characteristic (map γ) as shown in FIG. 4 is prepared in advance, if the denitration rate μ is obtained, the equivalent ratio γ of urea water or the like can be obtained, and the urea water or the like to be introduced into the exhaust system can be obtained. The amount is determined.

Here, in the map α in FIG. 3, the exhaust gas of the combustion device 1 is caused by a change in the performance of the combustion device 1 or due to a change in air temperature or the like due to a change in season, an air ratio or the like. When the amount changes, it must be corrected.
For example, when the intake air temperature changes due to seasonal variations, correction in the direction of the arrow Yv in FIG. 3 is necessary.
However, when the exhaust gas amount Qg is obtained in the above-described manner, the map α is stored as a characteristic fixed in advance on the control side, and no such correction is performed. Therefore, in the conventional control described above, an error occurs every time the exhaust gas amount Qg is obtained using the map α in FIG.

Similarly, in the map β (P-δ characteristic diagram) in FIG. 20, correction (for example, correction as indicated by an arrow Yv in FIG. 20) is required due to a change in intake air temperature depending on the season. When the NOx concentration is obtained in the above-described manner, the map β is stored in advance as a fixed characteristic on the control side, and thus such correction is not performed. Therefore, an error occurs every time the NOx concentration is obtained by the conventional control described above.
Further, the map γ of FIG. 4 also needs to be corrected by the exhaust gas temperature or the like, but is stored as a fixed characteristic in the above-described conventional control, so the equivalent ratio γ of urea water or the like is obtained. An error occurs every time.

As a result, in the conventional control described above, characteristics used in the control (combustion device output P-exhaust gas amount Qg characteristic in FIG. 3, combustion device output P-NOx concentration characteristic δ characteristic in FIG. 20, and denitration rate μ- in FIG. 4). Since all of the equivalence ratio γ characteristics (such as urea water) are stored as a fixed map or characteristic diagram, the errors of each map are accumulated, resulting in a very large error.
Even if the amount of reducing agent input such as urea water is obtained by control including such a large error, it is difficult to always reduce the NOx concentration in the exhaust gas.

As a conventional technique other than the above, by obtaining an appropriate ammonia injection amount, the NOx concentration at the NOx removal outlet can always be kept below a predetermined value, the amount of leaked ammonia can be made almost zero, and the technically advanced Since knowledge is not required, an ammonia injection amount control method for a denitration apparatus excellent in maintenance has been proposed (see, for example, Patent Document 1).
However, the related art (Patent Document 1) can suppress the amount of leaked ammonia, but cannot solve the above-mentioned problem.

JP 2001-198438 A

  The present invention has been proposed in view of the above-described problems of the prior art, and always reduces the NOx concentration in the exhaust gas in the combustion equipment, and also responds to fluctuations in the NOx concentration in the exhaust gas at the exhaust gas outlet. The object is to provide an exhaust gas denitration treatment system with good performance.

  The exhaust gas denitration treatment system of the present invention includes a denitration catalyst (3) interposed in an exhaust system (2) of a combustion device (1), and a physical quantity that can estimate a nitrogen oxide emission amount of the combustion device (1) ( A physical quantity measuring device for estimation (for example, output sensor 5) for measuring the output of the combustion device 1) and a reducing agent (for example, urea water, ammonia water, etc.) are supplied to the exhaust gas flowing through the exhaust system (2). The relationship between the measurement result (for example, the output of the combustion device 1) of the reducing agent supply device (urea injection pump 7) to be (injected) and the estimation physical quantity measuring device (for example, the output sensor 5) and the amount of exhaust gas (FIG. 3). Denitration rate / equivalence ratio characteristic data and target summarizing the relationship between the exhaust gas quantity characteristic data summarized on map α) and the denitration rate and equivalent ratio of the denitration catalyst (equivalent of reducing agent to NOx unit quantity) (Fig. 4: map γ) Stores oxide content data In the exhaust gas denitration processing system having a control device (control unit), the nitrogen oxide measuring device (for example, zirconia NOx sensor 4) having heat resistance against the exhaust gas temperature of the combustor gas (1) is provided. Provided in a region upstream of the denitration catalyst (3) of the exhaust system (2) (catalyst inlet 3i side) and downstream of the denitration catalyst (3) of the exhaust system (2) (side separated from the combustion device 1) The nitrogen oxide measuring device (catalyst outlet NOx sensor 42) interposed in the region (the catalyst outlet 3o side) is provided, and the control device (control unit) is more than the denitration catalyst (3) of the exhaust system (2). Based on the nitrogen oxide concentration (catalyst outlet side NOx concentration) in the downstream region (average value thereof), the characteristics of the output of the combustion device (1) and the exhaust gas (see FIG. 3: map α) and the denitration catalyst (3 ) A unit (60) for correcting (feedback correction: FIG. 5) the characteristic (see FIG. 4: map γ) of the rate and equivalent ratio (equivalent of reducing agent with respect to the NOx unit amount). The control unit) is a nitrogen oxide measuring device (catalyst inlet NOx sensor) interposed in a region upstream of the denitration catalyst (3) of the exhaust system (2) (on the combustion equipment 1 side) (catalyst inlet 3i side). For example, a unit (64) for determining whether or not the zirconia NOx sensor 4) is calibrated, and the nitrogen immediately before the calibration as the nitrogen oxide concentration in the region upstream of the denitration catalyst when calibrated. A unit (65) for setting a numerical value obtained by multiplying the numerical value of the oxide concentration by a predetermined coefficient, and the relationship between the physical quantity for estimation and the exhaust gas amount when calibration is performed (the output of the combustion device 1 and the exhaust gas) A characteristic that is not corrected (feedback correction) with respect to the characteristics (see map γ in FIG. 3) and the characteristics (see FIG. 4: map γ) between the denitration rate of the denitration catalyst and the equivalent ratio (equivalent of the reducing agent with respect to the NOx unit amount). (66).

  In the present invention, an exhaust gas temperature measuring device (exhaust gas temperature sensor 8) for measuring the exhaust gas temperature upstream of the denitration catalyst (3) of the exhaust system (2) is provided, and the control device (control unit) includes: The characteristics (FIG. 4, FIG. 11: μ-γ characteristics: map γ) between the NOx removal rate and the equivalent ratio (equivalent of the reducing agent with respect to the NOx unit amount) of the NOx removal catalyst (3) are corrected based on the exhaust gas temperature ( (Or modified) (FIG. 11: μ-γ2 characteristic: map γ2) It is preferable to include a unit (63).

Furthermore, in the present invention, the control device (control unit) varies the nitrogen oxide concentration (catalyst inlet side NOx concentration) in the upstream side (combustion equipment side) region (catalyst inlet 3i side) of the denitration catalyst (3). It is preferable to include units (57, 59) that increase or decrease the amount of reducing agent (for example, urea water or the like) input based on the amount.
Here, the fluctuation amount of the nitrogen oxide concentration (catalyst inlet side NOx concentration) in the region upstream of the denitration catalyst (3) (combustion equipment 1 side) (catalyst inlet 3i side) is denitration of the exhaust system (2). It is determined based on the measurement result of the nitrogen oxide measuring device (4) interposed in the region upstream of the catalyst (3) and measuring the temperature of the exhaust gas.
Moreover, the said control apparatus (control unit) can also be comprised so that it may have a function which determines whether to increase / decrease the charging amount of reducing agents (for example, urea water etc.) based on the output of a combustion apparatus.
Alternatively, if the combustion device is, for example, a gas engine, the control device (control unit) determines the amount of reducing agent (for example, urea water) input based on the throttle valve opening of the gas engine or the turbo bypass valve opening. It can also be configured to have a function of determining whether to increase or decrease.

  In the present invention, an exhaust gas temperature measuring device (exhaust gas temperature sensor 8) for measuring the exhaust gas temperature upstream of the denitration catalyst (3) of the exhaust system (2) is provided, and the control device (control unit) includes: The characteristics (FIG. 4, FIG. 11: μ-γ characteristics: map γ) between the NOx removal rate and the equivalent ratio (equivalent of the reducing agent with respect to the NOx unit amount) of the NOx removal catalyst (3) are corrected based on the exhaust gas temperature ( (Or modified) (FIG. 11: μ-γ2 characteristic: map γ2) includes a unit (63), and further, the control device (control unit) is upstream (combustion equipment side) from the denitration catalyst (3). Including a unit (57, 59) for increasing / decreasing the amount of reducing agent (for example, urea water) input based on the fluctuation amount of the nitrogen oxide concentration (catalyst inlet side NOx concentration) in the region (catalyst inlet 3i side) It is preferable.

In the present invention, the physical quantity capable of estimating the nitrogen oxide emission amount means the output of the combustion equipment, the exhaust bypass valve opening degree, and the supply air pressure. Further, the target nitrogen oxide amount (target NOx amount) refers to a target value of nitrogen oxide contained in exhaust gas released to the atmosphere.
Further, “the output of the combustion equipment (1), the characteristics of the output of the combustion equipment and the exhaust gas (see FIG. 3: map α), and the denitration rate and equivalent ratio of the denitration catalyst (3) (equivalent of the reducing agent to the NOx unit amount) The correction of the characteristic (see FIG. 4: map γ) is preferably performed for each predetermined range (range) rather than correcting the entire characteristic at once.

  Here, as a method of controlling the exhaust gas denitration treatment system (101), from the step (S1) of measuring a physical quantity (such as the output of the combustion device 1) that can estimate the nitrogen oxide emission amount, and the denitration catalyst (3) The step (S3) of measuring the nitrogen oxide concentration (catalyst inlet side NOx concentration) in the upstream (combustion equipment 1 side) region (catalyst inlet 3i side) and the physical quantity capable of estimating the measured nitrogen oxide emission amount A process of calculating the exhaust gas flow rate using the characteristics of the exhaust gas (see Fig. 3: map α) and the physical quantity (output of the combustion device 1 etc.) and the exhaust gas characteristics (e.g. From the denitration catalyst (3) based on the calculated exhaust gas flow rate and the nitrogen oxide concentration (catalyst inlet side NOx concentration) in the upstream region (catalyst inlet 3i side) of the denitration catalyst (3). Also upstream area A step (S5) of calculating a nitrogen oxide amount (catalyst inlet side NOx amount) at the catalyst inlet 3i side, and a nitrogen oxide amount in a region (catalyst inlet 3i side) closer to the combustion equipment (1) than the denitration catalyst (3) A step (S6) of calculating a nitrogen oxide amount (= catalyst inlet side NOx amount−target NOx amount) to be denitrated from (a catalyst inlet side NOx amount) and a target nitrogen oxide amount (target NOx amount), and the calculated denitration. The amount of the reducing agent (for example, urea water, etc.) input from the characteristics of the nitrogen oxide amount and the denitration rate of the denitration catalyst (3) and the equivalent ratio (equivalent of the reducing agent to the NOx unit amount) (see FIG. 4: map γ) It is preferable to have the process (S7) to determine.

Further, a nitrogen oxide measuring device (catalyst outlet NOx sensor 42) interposed in a region (catalyst outlet 3o side) downstream (side away from the combustion device 1) of the exhaust system (2) from the denitration catalyst (3). ) To measure the nitrogen oxide concentration (catalyst outlet side NOx value) in the region downstream of the denitration catalyst (3) of the exhaust system (2) (S11), and the measured nitrogen oxide concentration (catalyst outlet) Side NOx value) (average value thereof), characteristics of the output of the combustion device (1) and exhaust gas (see FIG. 3: map α) and the denitration rate and equivalent ratio of the denitration catalyst (3) (with respect to the NOx unit amount) It is preferable to include a step (S13) of correcting (feedback correction) the characteristic (see FIG. 4: map γ) with the equivalent of the reducing agent.
In this case, the output of the combustion device (1), the characteristics of the output of the combustion device (1) and the exhaust gas (see FIG. 3: map α) and the denitration rate and equivalent ratio of the denitration catalyst (3) (reducing agent with respect to the NOx unit amount) The characteristic (see Fig. 4: map γ) is preferably corrected for each predetermined range (range), rather than correcting the entire characteristic at once.

  Further, a step (S21) of measuring the exhaust gas temperature in the region upstream of the denitration catalyst (3) of the exhaust system (2) by the exhaust gas temperature measuring device (exhaust gas temperature sensor 8), and the measured exhaust gas The characteristics (see FIG. 4: map γ) between the NOx removal rate and the equivalent ratio (equivalent of the reducing agent with respect to the NOx unit amount) are corrected (or changed) based on the temperature of the catalyst (see FIG. 5: map γ2). ) Is preferably included (S22).

Further, based on the variation amount of the nitrogen oxide concentration (catalyst inlet side NOx concentration) in the upstream side (combustion equipment 1 side) region (catalyst inlet 3i side) of the denitration catalyst (3), the reducing agent (for example, urea) It is preferable to have a step (S34 to S36) of increasing or decreasing the input amount of water or the like.
Here, the fluctuation amount of the nitrogen oxide concentration (catalyst inlet side NOx concentration) in the region upstream of the denitration catalyst (3) (combustion equipment 1 side) (catalyst inlet 3i side) is denitration of the exhaust system (2). It is determined based on the measurement result of the nitrogen oxide concentration measuring device (4) interposed in the region upstream of the catalyst (3).
Further, based on the output of the combustion device (1), it can be determined whether to increase or decrease the input amount of the reducing agent (for example, urea water).
Alternatively, if the combustion device (1) is, for example, a gas engine, whether or not the amount of reducing agent (for example, urea water) input is increased or decreased based on the throttle valve opening of the gas engine or the turbo bypass valve opening. Can also be determined.

  In addition, a nitrogen oxide measuring device (catalyst inlet NOx sensor) interposed in a region upstream of the denitration catalyst (3) of the exhaust system (2) (on the combustion equipment 1 side) (catalyst inlet 3i side). For example, a step (S51) for determining whether or not the zirconia NOx sensor 4) is calibrated, and, if calibrated, the characteristics of the output of the combustion device (1) and the exhaust gas (FIG. 3: Nitrogen immediately before calibration without correcting (feedback correction) the characteristics (see map γ) of the denitration rate and equivalent ratio (equivalent of reducing agent to NOx unit amount) of denitration catalyst (3) (see map α) Nitrogen oxide concentration in the region upstream of the NOx removal catalyst (combustion equipment side) (catalyst inlet 3i side) by multiplying the value of oxide concentration (NOx concentration) by a predetermined coefficient (for example, 1.2) Step of setting the catalyst inlet side NOx concentration) (S53).

According to the present invention having the above-described configuration, the measurement of nitrogen oxides interposed in the region upstream of the denitration catalyst (3) of the exhaust system (2) (combustion equipment 1 side) (the catalyst inlet 3i side). Since the apparatus (catalyst inlet NOx sensor 4: zirconia NOx sensor, for example) directly measures the NOx concentration in the exhaust gas, the characteristics of the combustion equipment output and the exhaust gas NOx concentration used in the conventional control (for example, FIG. 20). There is no need to use the map β).
For this reason, errors (instantaneous fluctuations, performance changes, seasonal differences, etc.) due to the use of the characteristics of the combustion equipment output and the exhaust gas NOx concentration (map β in FIG. 20) used in the conventional control are used. NOx amount (catalyst inlet side NOx amount) in a region upstream of the denitration catalyst (3) (catalyst inlet side NOx amount) and NOx amount to be denitrated (= catalyst inlet side NOx amount− (Target NOx amount) can be calculated, so that an error is not included and high-precision control is possible.
However, in the present invention, a characteristic (for example, P-δ characteristic of FIG. 20: map β) of the exhaust gas NOx concentration and a physical quantity (for example, the output of the combustion device 1) that can estimate the nitrogen oxide emission amount is separately prepared. When the nitrogen oxide measuring device (catalyst inlet NOx sensor 4: for example, zirconia NOx sensor) fails, the NOx concentration of the exhaust gas can be estimated using the characteristics. In such a case, based on the urea water input amount (see the control described in the flowchart of FIG. 5) determined using the output of the nitrogen oxide measuring device (catalyst inlet NOx sensor 4: for example, zirconia NOx sensor), nitrogen It is possible to correct the characteristic (for example, P-δ characteristic: map β in FIG. 20) between the physical quantity (for example, the output of the combustion device 1 and the like) that can estimate the oxide emission amount and the NOx concentration of the exhaust gas.

Further, the nitrogen oxide measuring device (catalyst inlet NOx sensor 4) for measuring the NOx amount (catalyst inlet side NOx amount) in the upstream region (catalyst inlet 3i side) of the denitration catalyst (3) has heat resistance. In addition, since a sensor (for example, zirconia NOx sensor 4) having a high reaction speed is selected, the sensor (4) is deteriorated or measured even in the basin (catalyst inlet 3i side) close to the combustion device (1). Inconveniences such as an increase in error are prevented.
Here, for example, when a zirconia NOx sensor (4) is employed, since it has heat resistance, the zirconia NOx sensor (4) can be disposed inside the exhaust system (2). Therefore, it is not necessary to sample the exhaust gas from the exhaust system (2) and send it to the sensitive part, and the so-called “sampling time” can be set to 0, so that control with very good response can be achieved.

Here, if the error in the determined amount of reducing agent (for example, urea water) is corrected by the NOx concentration (catalyst outlet side NOx value) in the downstream side of the denitration catalyst (3), the NOx concentration ( The NOx value on the catalyst outlet side) is a result of the previous control (for example, control performed about 60 seconds before). Even if control is performed based on the result of such previous control, the accuracy of the control It is difficult to improve. In some cases, control hunting may be caused.
On the other hand, in the present invention, based on the measured NOx concentration (catalyst outlet side NOx concentration) (average value thereof), the characteristics of the output of the combustion device (1) and the exhaust gas (see FIG. 3: map α) Further, if the denitration rate of the denitration catalyst (3) and the characteristic of the equivalent ratio (equivalent of the reducing agent with respect to the NOx unit amount) (see FIG. 4: map γ) are corrected (feedback correction) (claim 2). By such correction or feedback control, control of the amount of reducing agent (for example, urea water or the like) input is shifted from control that instantaneously reflects the error to control that is relatively gradual, so that control hunting is prevented.
At the same time, since the control is performed based on the measured NOx concentration (NOx value on the catalyst outlet side) (average value thereof), the NOx concentration on the NOx removal catalyst outlet (3o) side can be reliably brought close to the control target.

In the prior art, the relationship between the temperature of the exhaust gas and the characteristics (see FIG. 4: map γ) of the denitration rate of the denitration catalyst (3) and the equivalent ratio (equivalent of the reducing agent to the NOx unit amount) is controlled. At that time, no consideration was given.
On the other hand, in the present invention, the characteristics (see FIG. 4: map γ) of the denitration rate and the equivalent ratio (equivalent of the reducing agent with respect to the NOx unit amount) of the denitration catalyst (3) are corrected based on the exhaust gas temperature. (Or change) (FIG. 5: Refer to map γ2) (Claim 3) (Claim 3) Considering the exhaust gas temperature, the denitration rate and equivalent ratio (reduction of NOx unit amount) of the denitration catalyst (3) The control accuracy can be improved by adjusting the characteristics (see map γ).

Here, if a change in the amount of reducing agent (for example, urea water or the like) input is made early with respect to a change in NOx amount or NOx concentration (in other words, reduction with respect to a change in NOx amount or NOx concentration). If the responsiveness of the dose of the agent is good), the control accuracy is further improved.
In the present invention, a reducing agent (for example, urea) is based on the amount of fluctuation of the NOx concentration (catalyst inlet side NOx concentration) in the region upstream of the denitration catalyst (3) (combustion equipment 1 side) (catalyst inlet 3i side). If configured so as to increase or decrease the input amount of water (Claim 4), the variation of the input amount of the reducing agent (for example, urea water) is delayed when the NOx amount or NOx concentration fluctuates. Therefore, the fluctuation rate or responsiveness of the amount of reducing agent (for example, urea water) input to the change in the NOx amount or NOx concentration is improved, and the controllability is improved.

  In addition to this, in the present invention, a nitrogen oxide measuring device (catalyst inlet NOx sensor: zirconia, for example) interposed in a region (catalyst inlet 3i side) upstream (combustion equipment 1 side) from the denitration catalyst (3). It is determined whether or not the NOx sensor 4) is calibrated. If calibration is performed, a numerical value obtained by multiplying the numerical value of the NOx concentration immediately before the calibration by a predetermined coefficient (for example, 1.2) is obtained. If the NOx concentration (catalyst inlet side NOx concentration) in the region upstream of the denitration catalyst (combustion equipment side) (catalyst inlet 3i side) is set (Claim inlet side NOx concentration), the actual denitration catalyst (3) Also, the NOx concentration (catalyst inlet side NOx concentration) in the upstream side (combustion device 1 side) region (catalyst inlet 3i side) is obtained by multiplying the numerical value of the NOx concentration immediately before calibration by a predetermined coefficient (for example, 1.2). Reducing agent because it is lower than the numerical value (For example, urea water etc.) Even if the input amount becomes excessive, avoid the situation where the NOx emission concentration exceeds the regulation value for a long time due to the shortage of the reducing agent (eg urea water etc.) input amount I can do it.

1 is a block diagram of an exhaust gas denitration processing system according to an embodiment of the present invention. The block diagram of the control apparatus in 1st Embodiment of this invention. The map which shows the characteristic of the output of the combustion apparatus and exhaust gas in embodiment. The map which shows the characteristic of the denitration rate and equivalent ratio of the denitration catalyst in embodiment. The map which shows that the characteristic shown in FIG. 4 changes with exhaust temperature. The flowchart which shows the control of 1st Embodiment. The block diagram of the exhaust-gas denitration processing system which concerns on 2nd Embodiment of this invention. The block diagram of the control apparatus in 2nd Embodiment of this invention. The flowchart which shows the control of 2nd Embodiment. The block diagram of the exhaust-gas denitration processing system which concerns on 3rd Embodiment of this invention. The block diagram of the control apparatus in 3rd Embodiment of this invention. The flowchart which shows the control of 3rd Embodiment. The block diagram of the control apparatus in 4th Embodiment of this invention. The flowchart which shows the control of 4th Embodiment. The block diagram of the control apparatus in the modification of 4th Embodiment. The flowchart which shows the control in the modification of 4th Embodiment. The block diagram of the control apparatus in 5th Embodiment of this invention. The flowchart which shows the control of 5th Embodiment. The block diagram which showed the structure of the exhaust-gas denitration processing system in a prior art. The map which shows the characteristic of the combustion equipment output and exhaust-gas NOx density | concentration used by the prior art.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Here, as described above, various reducing agents such as urea water and ammonia water can be applied. However, in the illustrated embodiment, urea water is exemplified as the reducing agent.
First, a first embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, the exhaust gas denitration processing system according to the first embodiment is denoted by reference numeral 101 as a whole.
The exhaust gas denitration treatment system 101 includes a combustion device (gas engine) 1, an exhaust system 2, a denitration catalyst 3, a NOx concentration sensor 4, a combustion device output sensor 5, a urea water tank 6, a urea water injection pump 7, and urea water injection. A nozzle 9 and a control device (control unit) 10 are provided.
Here, a sensor (for example, a zirconia NOx sensor) 4 having heat resistance and a fast reaction speed is used as the NOx concentration sensor 4.

The denitration catalyst 3 is interposed in the exhaust system 2 of the gas engine 1.
In the exhaust system 2, a NOx concentration sensor (zirconia NOx sensor) 4 is interposed in the vicinity of the gas engine 1 on the denitration catalyst inlet 3 i side (or upstream side of the denitration catalyst 3). A urea water injection nozzle 9 is interposed in a region between 4 and the denitration catalyst 3.
In FIG. 1, reference numeral 3 o indicates an outlet of the denitration catalyst 3.

The NOx concentration sensor (zirconia NOx sensor) 4 is connected to the FF controller 50 of the controller 10 via the input signal line Si1. The output sensor 5 is connected to the FF control unit 50 of the controller 10 via the input signal line Si2.
The urea water charging pump 7 is connected to the FF control unit 50 of the control unit 10 via the control signal line So.

The urea water stored in the urea water storage tank 6 is boosted by the urea water injection pump 7 and is injected into the exhaust system 2 from the urea water injection nozzle 9 via the urea water supply line Ln, and is injected into the exhaust gas. (Input).
The urea water injected into the exhaust system 2 is decomposed into ammonia and carbon dioxide in the exhaust system 2. Then, ammonia chemically reacts with the nitrogen compound inside the denitration catalyst 3 to be decomposed into water and nitrogen. That is, the urea water injected into the exhaust system 2 acts as a reducing agent and decomposes NOx.

The control unit 10 includes a feedforward control unit (FF control unit) 50.
FIG. 2 mainly shows the configuration of the FF control unit 50 in the control unit 10.
In FIG. 2, the control unit 10 operates as a conversion block 51, an exhaust gas flow rate conversion block 52, a denitration catalyst inlet side NOx amount calculation block 53, a NOx amount calculation block 54 to be denitrated, a urea water input amount calculation block 55, and a storage device. A database 56, a urea water supply pump control signal generation block 57, and interfaces IF1 and IF2.

The conversion block 51 includes a dry environment conversion block 511 and a NOx amount conversion block 512. A normal NOx concentration sensor (used in the prior art) is used for measurement in a dry environment (an environment with a low water content).
On the other hand, the NOx concentration sensor (zirconia NOx sensor) 4 used in the exhaust gas denitration processing system 101 according to the first embodiment is installed in an environment (so-called wet environment) where the water vapor partial pressure directly under the gas engine 1 is high. The NOx concentration of exhaust gas in a wet environment is measured.
For this reason, in the exhaust gas denitration processing system 101 according to the first embodiment, a conversion block 511 in a dry environment is provided, and the NOx concentration measured in the wet environment is converted into the NOx concentration in the dry environment. Calculation is made by dividing back the amount of water vapor contained in the exhaust gas flowing through the exhaust system 2.

Explaining the conversion in the dry environment conversion block 511, for example, if the water vapor contained in the exhaust gas flowing through the exhaust system 2 is 10%, the NOx concentration measured by the zirconia NOx sensor 4 (NOx measured in a wet environment). (Concentration) is denoted by “NOx (Wet)”, and the converted NOx concentration in the dry environment is denoted by “NOx (Dry)”.
NOx (Dry) = NOx (Wet) / (1-0.1)
It becomes.

Further, NOx concentration sensor (zirconia NOx sensor) 4, NOx (NO, NO ₂ etc.) in the exhaust gas flowing through the exhaust system 2 not all can be measured, for example, NO is able to measure 100%, NO ₂ has properties such that only 60% can be measured.
In view of the nature of such a NOx concentration sensor (zirconia NOx sensor) 4, the exhaust gas denitration processing system 101 according to the first embodiment is provided with a NOx amount conversion block 512, and component ratios of various NOx (NO and NO ₂ etc.). by preliminarily grasped accurately determine the content of such NO and NO _2, and is configured to be able to calculate the total NOx amount (all total NO and NO _2, etc.).

The conversion in the NOx amount conversion block 512 will be described. For example, the zirconia NOx sensor 4 has a property that NO can be measured 100%, but NO ₂ can be measured only 60%. If the NOx in the exhaust gas is composition only NO and NO _2, reference numerals the NOx concentration measured by the zirconia NOx sensor 4 "NOx (sensor)", the total NOx amount after conversion (in this case the, The sum of NO and NO ₂ is indicated by the symbol “NOx (after conversion)”.
NOx (after conversion) = NOx (sensor) / {2/3 + (1/3) × (60/100)}
It becomes.

  The conversion block 51 receives information on the NOx concentration δ from the NOx concentration sensor 4 via the input signal line Si1 interface IF1. Then, the measured value is converted into a dry environment by the dry environment conversion block 511, the total NOx amount in the exhaust gas is obtained by the NOx amount conversion block 512, and the NOx removal catalyst inlet side NOx concentration δ is calculated.

The exhaust gas flow rate calculation block 52 receives information related to the gas engine output from the output sensor 5 via the input signal line Si2 and the interface IF2. Then, based on the output information, a map showing the relationship between the output stored in the database 56 and the amount of exhaust gas (“Map α” in FIG. 3: gas engine output P-exhaust gas flow rate Qg characteristic), the exhaust gas flow rate Qg is calculated. It is configured to ask for.
In the map α shown in FIG. 3, the vertical axis represents the exhaust gas amount Qg, the horizontal axis represents the output P of the gas engine, and the gas engine output P-exhaust gas flow rate Qg characteristic (characteristic curve indicated by “P-Qg” in FIG. 3). ). If the output P of the gas engine is obtained by the output sensor 5, the exhaust gas amount (exhaust gas flow rate) Qg can be obtained from the P-Qg characteristic curve of FIG.

In FIG. 2, the NOx removal catalyst inlet side NOx amount calculation block 53 receives the NOx removal catalyst inlet side NOx concentration δ obtained in the conversion block 51 via the line L1, and the exhaust gas flow rate Qg calculated in the exhaust gas flow rate calculation block 52 is obtained. Received via line L2. The NOx removal inlet side NOx amount calculation block 53 is configured to calculate the NOx removal catalyst inlet side NOx amount (= Qg × δ) by multiplying the exhaust gas flow rate Qg by the NOx removal catalyst inlet side NOx concentration δ. Yes.
In the NOx amount calculation block 54 to be denitrated, the NOx removal inlet side NOx amount calculated in the NOx removal catalyst inlet side NOx amount calculation block 53 is received via the line L3 and stored in the database 56 on the outlet side of the NOx removal catalyst 3. A target NOx amount is received via line L4. Then, the NOx amount calculation block 54 to denitrate subtracts the target NOx amount on the NOx removal catalyst 3 outlet side from the NOx removal side NOx amount to obtain the NOx amount to be denitrated (= NOx removal catalyst inlet side NOx amount−NOx removal catalyst 3 outlet). Side target NOx amount).

The urea water input amount calculation block 55 receives the information of the map γ of FIG. 4 stored in the database 56 via the line L6, and stores the NOx amount to be denitrated calculated by the NOx amount calculation block 54 to be denitrated. Received via L5.
In the urea water input amount calculation block 55, the denitration rate μ is obtained by the following equation.
“NOx removal rate μ” = “NOx amount to be deleted” ÷ “NOx amount contained in exhaust gas of gas engine 1”
Then, in the urea water input amount calculation block 55, the equivalent ratio γ of urea water is obtained from the denitration rate μ using the map γ shown in FIG. 4, and the amount of urea water to be input to the exhaust system 2 is determined.

In FIG. 2, the urea water input pump control signal generation block 57 receives information about the urea water input amount calculated by the urea water input amount calculation block 55 via the signal transmission line L7.
A control signal for discharging the urea water charging amount from the urea water charging pump 7 is transmitted to the urea water charging pump 7 via the interface IF3 and the control signal line So. .

Next, mainly based on FIG. 5, the control of 1st Embodiment is demonstrated with reference also to FIGS. 1-4.
In step S <b> 1 of FIG. 5, the output of the gas engine 1 is measured by the output sensor 5 and transmitted to the exhaust gas flow rate calculation block 52 of the control unit 10.
The exhaust gas flow rate calculation block 52 calculates the exhaust gas flow rate Qg flowing through the exhaust system 2 using the measurement result of the output sensor 5 and the map α (FIG. 3) (step S2).

In step S <b> 3, the NOx concentration on the inlet side of the denitration catalyst 3 is measured by the zirconia NOx sensor 4. Then, the measurement result of the zirconia NOx sensor 4 is converted into the NOx concentration in the dry environment by the conversion block 511 in the dry environment, and the total of all types of NOx flowing through the exhaust system 2 in the NOx amount conversion block 512. (NOx amount) is calculated (step S4).
In FIG. 5, steps S3 and S4 are executed after steps S1 and S2, but steps S1 and S2 may be executed after steps S3 and S4. Moreover, you may perform step S1, S2 and step S3, S4 simultaneously.
In step S5, the denitration catalyst inlet side NOx amount calculation block 53 multiplies the exhaust gas flow rate Qg calculated by the exhaust gas flow rate calculation block 52 by the NOx removal catalyst inlet side NOx concentration δ converted by the conversion block 51 to obtain the denitration catalyst inlet side. The amount of NOx (= Qg × δ) is calculated. Then, the process proceeds to step S6.

  In step S 6, the NOx amount calculation block 54 to be denitrated is a target on the NOx removal catalyst 3 outlet side stored in the database 56 from the NOx removal inlet side NOx amount calculated by the NOx removal inlet side NOx amount calculation block 53. The NOx amount is subtracted to calculate the NOx amount to be denitrated (= NOx removal catalyst inlet side NOx amount−denitration catalyst 3 outlet side target NOx amount). Then, the process proceeds to step S7.

In step S7, the urea water input amount calculation block 55 first obtains the NOx removal rate μ (= NOx amount to be deleted / NOx amount contained in the exhaust gas of the gas engine 1), and is stored in the database 56. Based on the characteristics of 4 (map γ), the equivalent ratio γ of urea water (equivalent amount of urea water to the NOx unit amount) is obtained, and the amount of urea water to be introduced into the exhaust system 2 is calculated from the equivalent ratio γ.
In the next step S8, the urea water supply pump 7 is controlled in the urea water supply pump control signal block 57 so that the urea water input amount calculated in step S7 is discharged from the urea water input pump 7. Send a signal.
Then, the process returns to step S1.

According to the exhaust gas denitration processing system 101 according to the first embodiment having the above-described configuration, the NOx concentration on the inlet side of the denitration catalyst 3 is directly measured by the exhaust system 2 by the zirconia NOx sensor 4, so that the conventional control is performed. It is not necessary to use the characteristics of the gas engine output P and the NOx concentration δ in the exhaust gas (map β in FIG. 20).
Therefore, an error caused by using the gas engine output P-NOx concentration δ characteristic (map β in FIG. 20) in a fixed manner, that is, an error caused by instantaneous output fluctuation, performance change, seasonal difference, etc. is controlled. Is not superimposed on the error.
As a result, it is possible to perform control with less error and higher accuracy than the control in the conventional technique described above.

  Furthermore, according to the exhaust gas denitration treatment system 101 of the first embodiment, the catalyst inlet NOx sensor 4 that measures the NOx amount (catalyst inlet side NOx amount) in the upstream region of the denitration catalyst 3, that is, the catalyst inlet 3i side. Since a sensor having heat resistance and a high reaction speed, for example, a zirconia NOx sensor 4 is used, a NOx sensor (zirconia NOx sensor 4) is disposed in the basin close to the gas engine 1 (catalyst inlet 3i side). Even so, the NOx sensor does not deteriorate due to the high heat of the gas engine exhaust gas.

In the conventional system shown in FIG. 19, since the NOx concentration is measured behind (downstream side) the NOx removal catalyst 3, even if the output of the gas engine 1 fluctuates and the NOx concentration fluctuates, After such a change has occurred, it takes a relatively long time to detect that change with the NOx sensor.
On the other hand, according to the first embodiment of FIG. 1 to FIG. 5, in the exhaust system 2 of the gas engine 1, the zirconia NOx sensor 4 can be disposed at a position immediately downstream of the gas engine 1. It is possible to detect a change in the NOx concentration caused by the fluctuation of the output of 1 in real time.

In addition, in the NOx sensor used in the conventional system in FIG. 19, the portion exposed to the exhaust system 2 is an exhaust gas sampling device, and the exhaust gas collected by the sampling device is used as the NOx sensitive portion. It was impossible to measure the NOx concentration without moving to. Therefore, a time until the exhaust gas collected by the sampling device moves to the NOx sensitive portion, so-called “sampling time”, is required, and this is detected after the output of the gas engine 1 fluctuates. It was a factor that required a relatively long time.
On the other hand, when the zirconia NOx sensor 4 is employed, since it has heat resistance, the sensitive part in the zirconia NOx sensor 4 can be disposed inside the exhaust system 2. Therefore, it is not necessary to sample the exhaust gas from the exhaust system 2 and send it to the sensitive part, and the “sampling time” can be set to 0, so that the response is very good.

Next, a second embodiment of the present invention will be described with reference to FIGS.
In the second embodiment of FIGS. 6 to 8, the NOx concentration is measured on the outlet 3o side of the denitration catalyst 3 (the side away from the gas engine 1; the downstream side of the denitration catalyst 3), and the measured denitration catalyst outlet side NOx. 3 differs from the first embodiment of FIGS. 1 to 5 in that the map α in FIG. 3 and the map γ in FIG. 4 are corrected by feedback control based on the density.

The exhaust gas denitration processing system according to the second embodiment of FIGS. 6 to 8 is generally indicated by reference numeral 102 in FIG.
In the exhaust gas denitration processing system 102 of FIG. 6, a gas sampling device 41 is interposed on the outlet 3o side (downstream side of the denitration catalyst 3) of the denitration catalyst 3, and the gas sampling device 41 is connected to the catalyst outlet side NOx by a line Lg. It communicates with the sensor 42. The exhaust gas (a part) collected by the gas sampling device 41 is sent to the catalyst outlet side NOx sensor 42, and the NOx concentration (catalyst outlet side NOx concentration) is measured.
The measurement result (catalyst outlet side NOx concentration) in the catalyst outlet side NOx sensor 42 is sent to the feedback control unit (FB control unit) 60 of the control unit 10A via the input signal line Si3.

FIG. 7 shows details of the control unit 10A.
The control unit 10A shown in FIG. 7 has a configuration substantially common to the control unit 10 shown in FIG. 2, but is different from the control unit 10 shown in FIG. 2 in that an FB control unit 60 is provided. Yes.
The FB control unit 60 performs feedback control on the basis of the measured value of the catalyst outlet side NOx concentration measured by the catalyst outlet side NOx sensor 42, thereby providing the gas engine output P-exhaust gas flow rate Qg characteristic (map α) shown in FIG. It has a function of correcting the denitration rate μ-urea water equivalent ratio γ characteristic (map γ) shown in FIG.

In FIG. 7, the FB control unit 60 includes a moving average value calculation block 61, a map α correction block 62, a map γ correction block 63, and a database 56A.
The moving average value calculation block 61 receives the catalyst outlet side NOx concentration information from the catalyst outlet side NOx sensor 42 (see FIG. 6) via the input signal line Si3 and the catalyst outlet side NOx sensor interface IF4. Then, for example, the moving average value of the catalyst outlet side NOx concentration for the past 3 minutes is calculated, and the calculation result (moving average value of the catalyst outlet side NOx concentration for the past 3 minutes) is corrected by the map α via the line L8a. The data is transmitted to the block 62 and transmitted to the map γ correction block 63 via the line L8b.

The map α correction block 62 that has received the calculation result (the moving average value of the catalyst outlet side NOx concentration over the past three minutes) corrects the map α based on the calculation result, and the map α (showing the gas engine shown in FIG. (Output P-exhaust gas flow rate Qg characteristic) is stored in the database 56A via the line L9.
On the other hand, the map γ correction block 63 that has received the calculation result (the moving average value of the catalyst outlet side NOx concentration over the past three minutes) corrects the map γ based on the calculation result, and the map γ (denitration removal) that has been corrected. Ratio μ-urea water equivalent ratio γ characteristic) is stored in the database 56A via the line L10.
Here, for example, a conventionally known technique is applied to correct the map α and the map γ based on the moving average value of the catalyst outlet side NOx concentration over the past 3 minutes.

Next, control of the exhaust gas denitration processing system according to the second embodiment will be described mainly based on FIG. 8 and also with reference to FIGS. 6 and 7.
In step S11 of FIG. 8, the NOx removal catalyst side NOx concentration (NOx removal catalyst side NOx value) is measured by the catalyst outlet side NOx sensor 42 (FIG. 6). In step S12, the moving average value calculation block 61 (FIG. 7) uses the NOx removal outlet NOx concentration measured in step S11 to use the moving average value of the NOx removal outlet NOx concentration (the moving average value of the NOx value in S11). ) Is calculated.

Proceeding to step S13, the control unit 10A converts the map α in FIG. 3 and the map γ in FIG. 4 into the map α correction block based on the moving average value (moving average value of the NOx removal outlet NOx concentration) in step S12. 62 and the map γ correction block 63 correct each output range.
Here, the output range means a certain range on the vertical axis and / or the horizontal axis in the map α and the map γ.
After step S13 ends, the process returns to step S11.

  Here, the NOx concentration at the outlet side of the NOx removal catalyst in the region downstream of the NOx removal catalyst 3 is measured, and the measurement result is directly fed back as a change amount for correcting the error of the urea water input amount as the reducing agent. In other words, the NOx concentration on the outlet side of the NOx removal catalyst is the result of the urea water input control before that, for example, the urea water input control performed about 60 seconds before, and follows the output fluctuation of the gas engine 1 in real time. It is not a thing. And even if it controls based on the NOx removal catalyst exit side NOx density | concentration which is a control result after considerable time (for example, 60 second) passes after the output fluctuation | variation of the gas engine 1, the precision of control is not improved. In some cases, control hunting may be caused.

On the other hand, in the exhaust gas denitration processing system 102 according to the second embodiment, the output P-exhaust gas flow rate Qg characteristic of the gas engine 1 (see FIG. 5) based on the measured moving average value of the NOx removal outlet side NOx value. 3 and the denitration rate μ-urea water equivalent ratio γ characteristic of the denitration catalyst 3 (map γ in FIG. 4) are feedback-corrected. With such correction or feedback control, the control of the urea water input amount reflects the output fluctuation of the gas engine 1 instantaneously. Even if such output fluctuation occurs, the control parameter fluctuates relatively slowly based on that fluctuation. Therefore, control hunting is prevented.
At the same time, based on the measured average value of the NOx removal side NOx value, correction is performed by feedback control of characteristics (map α, map γ) necessary for controlling the amount of urea water used as the reducing agent. The NOx concentration on the denitration catalyst outlet 3o side can be reliably brought close to the control target.

  The configurations and operational effects of the second embodiment shown in FIGS. 6 to 8 other than those described above are the same as those of the first embodiment shown in FIGS.

9 to 12 show a third embodiment of the present invention.
9 to 12 corrects the denitration rate μ-urea water equivalent ratio γ characteristic (map γ) of the denitration catalyst 3 shown in FIG. 4 according to the exhaust gas temperature flowing through the exhaust system 2 (or FIG. 11 is different from the second embodiment of FIGS. 6 to 8 in that the map is changed to a map γ2 shown in FIG.

In FIG. 9, the exhaust gas denitration processing system according to the third embodiment is denoted by reference numeral 103 as a whole.
In the exhaust gas denitration processing system 103 shown in FIG. 9, an exhaust gas temperature sensor 8 that measures the exhaust gas temperature is provided upstream of the zirconia NOx sensor 4 in the exhaust system 2.
The exhaust gas temperature sensor 8 and the FF control unit 50 are connected by an input signal line Si4.

10, the control unit 10B of the exhaust gas denitration processing system 103 according to the third embodiment is different from the control unit 10A of FIG. 7 in that an exhaust gas temperature sensor interface IF5 is provided.
In the control unit 10B of FIG. 10, the exhaust gas temperature measured by the exhaust gas temperature sensor 8 (see FIG. 9) interposed in the exhaust system 2 is input to the map γ correction block 63 via the input signal line Si4. To do.

In the map γ correction block 63, in response to the input exhaust gas temperature, the denitration rate μ-urea water equivalent ratio γ characteristic (characteristic curve μ-γ) of the map γ shown in FIG. Denitration rate μ-new urea water equivalent ratio γ2 characteristic (characteristic curve μ-γ2 in FIG. 11: map γ2). In FIG. 11, the same characteristic curve as the map γ in FIG. 4 is indicated by a solid line (characteristic curve μ−γ), and the corrected map γ2 (characteristic curve μ−γ2) is indicated by a dotted line.
The corrected characteristic (μ-γ2 characteristic: map γ2 in FIG. 11) is stored in the database 56B via the line L10a.

Next, the control of the exhaust gas denitration processing system 103 according to the third embodiment will be described mainly based on FIG. 12 and also with reference to FIGS. 9 to 11.
In step S <b> 21 of FIG. 12, the exhaust gas temperature immediately after the gas engine 1 is measured by the exhaust gas temperature sensor 8 interposed in the exhaust system 2. Then, the process proceeds to step S22.
In step S22, the map γ correction block 63 corrects the characteristic curve μ-γ (FIG. 4) of the map γ to the characteristic curve μ-γ2 (FIG. 11) based on the measured exhaust gas temperature. Then, the corrected map γ2 (FIG. 11) is stored in the database 56B.
Then, the process returns to step S21.

In the prior art, the relationship between the exhaust gas temperature, the denitration rate of the denitration catalyst 3 and the equivalent ratio (equivalent of the reducing agent with respect to the NOx unit amount) (map γ in FIG. 4) is completely considered in the control. Was not.
On the other hand, according to the third embodiment described with reference to FIGS. 9 to 12, the denitration rate μ of the denitration catalyst 3 and the urea water equivalent ratio γ (the equivalent of urea water to the NOx unit amount) based on the temperature of the exhaust gas. ) And the map γ2 (μ−γ2 characteristic shown in FIG. 11) are corrected, and the denitration rate μ of the denitration catalyst 3 is taken into consideration in consideration of the exhaust gas temperature. Since the urea water equivalent ratio [gamma] (equivalent urea water to NOx unit amount) is adjusted with respect to the amount of urea water, the amount of urea water introduced into the exhaust gas is controlled with higher accuracy.

  Configurations and operational effects other than those described above in the third embodiment of FIGS. 9 to 12 are the same as those of the second embodiment of FIGS.

13 and 14 show a fourth embodiment of the present invention.
The fourth embodiment of FIGS. 13 and 14 is that the supply amount of urea water as a reducing agent is increased or decreased depending on the amount of fluctuation in the NOx concentration on the catalyst inlet side (upstream side of the denitration catalyst 3: gas engine 1 side). 9 to 12 are different from the third embodiment.
The exhaust gas denitration processing system according to the fourth embodiment has the same configuration as the system 103 shown in FIG. 9 except for the control unit 10C shown in FIG.

Hereinafter, with reference to FIG. 13, the control unit 10C used in the fifth embodiment will be described mainly with respect to differences from the control unit 10B shown in FIG.
In FIG. 13, the control unit 10 </ b> C is different from the control unit 10 </ b> B of FIG. 10 in that it includes a catalyst inlet side NOx concentration calculation block 58 and a comparison block 59.

In the control unit 10C of FIG. 13, the measurement result of the zirconia NOx sensor 4 provided on the catalyst inlet side (upstream side or gas engine 1 side) is converted into the catalyst inlet side NOx concentration calculation block via the conversion block 51 and the line L11. 58.
In the catalyst inlet side NOx concentration calculation block 58, the fluctuation amount of the catalyst inlet side NOx concentration is calculated, and this fluctuation amount (fluctuation amount of the catalyst inlet side NOx concentration) is input to the comparison block 59 via the line L12.

On the other hand, a threshold value (for example, ± 5 ppm) of the catalyst inlet side NOx concentration fluctuation amount is sent to the comparison block 59 from the database 56C via the line L13.
In the comparison block 59, the fluctuation amount of the catalyst inlet side NOx concentration sent from the catalyst inlet side NOx concentration calculation block 58 via the line L12 and the amount of fluctuation of the catalyst inlet side NOx concentration sent from the database 56C via the line L13 are calculated. The threshold value is compared, and it is determined whether to increase or decrease the urea water input amount based on the comparison result.
The comparison block 59 is configured to send a control signal corresponding to the determination of whether to increase or decrease the urea water input amount to the urea water input pump control signal generation block 57 via the line L14.

The control of the exhaust gas denitration processing system according to the fourth embodiment will be described mainly based on FIG. 14 and also with reference to FIG.
In step S31 of FIG. 14, the NOx concentration on the inlet side (upstream side or gas engine 1 side) of the denitration catalyst 3 is measured by the zirconia NOx sensor 4, and the catalyst inlet measured by the catalyst inlet side NOx concentration calculation block 58 is measured. A fluctuation amount of the catalyst inlet side NOx concentration is calculated based on the side NOx concentration (step S32). Then, the process proceeds to step S33.

In step S33, in the comparison block 59, it is determined whether or not the fluctuation amount of the NOx concentration obtained in step S32 is within the threshold value range stored in the database 56C.
If the fluctuation amount of the NOx concentration is within the range of threshold values (for example, ± 5 ppm) stored in the database 56C (step S33 is YES), the process proceeds to step S34, as described in the first embodiment. Control (control shown in FIG. 5) is executed. Then, the process returns to step S31.

If the fluctuation amount of the NOx concentration falls below the threshold range (for example, falls below −5 ppm), the process proceeds to step S35, and if the fluctuation amount of the NOx concentration exceeds the threshold range (eg, exceeds +5 ppm). Proceed to step S36.
In step S <b> 35, the comparison block 59 generates a control signal for decreasing the urea water input amount, and transmits the control signal to the control signal generation block 57.
In step S <b> 36, the comparison block 59 generates a control signal for increasing the urea water input amount and transmits the control signal to the control signal generation block 57.
After steps S35 and S36, the process returns to step S31.

In the description of FIG. 13 and FIG. 14, ± 5 ppm is exemplified as the threshold value of the variation amount of the measured NOx concentration on the inlet side (upstream side or gas engine 1 side) of the denitration catalyst 3. It is just an example.
In other words, such numerical values should be determined on a case-by-case basis according to various specifications in the exhaust gas denitration processing system, the use conditions of the gas engine 1, and the like.

  According to the fourth embodiment shown in FIG. 13 and FIG. 14, the reducing agent is immediately based on the variation amount of the NOx concentration in the region upstream of the denitration catalyst 3 (gas engine 1 side: catalyst inlet 3 i side). Since the input amount of urea water is increased or decreased, it is possible to cover that the control for changing the input amount of urea water (adjustment of the input amount) is delayed when the NOx amount or NOx concentration changes. Therefore, the fluctuation speed or responsiveness of the urea water input amount with respect to the change in the NOx amount or NOx concentration is improved, the controllability is improved, and the NOx concentration at the outlet side (downstream side) of the denitration catalyst 3 can be reduced.

  In the fourth embodiment of FIGS. 13 and 14, the configuration and operational effects other than those described above are the same as those of the third embodiment of FIGS. 10 to 12.

Here, in FIG. 13 and FIG. 14, the fluctuation amount of the catalyst inlet side NOx concentration is used as a parameter for determining the increase / decrease of the urea water supply amount, but other parameters can also be adopted.
FIGS. 15 and 16 show a modification of the fourth embodiment, which is configured to determine the increase / decrease of the urea water supply amount using parameters other than the fluctuation amount of the catalyst inlet side NOx concentration.

Hereinafter, a modification of the fourth embodiment will be described with reference to FIGS. 15 and 16.
In the control unit 10D of FIG. 15, the comparison block 59 for comparing the catalyst inlet side NOx concentration and the threshold value of the catalyst inlet side NOx concentration fluctuation amount in the control unit 10C shown in FIG. 13 is not provided. The output fluctuation amount calculation block 72 and the comparison block 59A are provided.

The measurement result of the gas engine 1 output transmitted from the output sensor 5 (see FIG. 9) is received by the output fluctuation amount calculation block 72 via the input signal line Si2 and the output sensor interface IF2. Then, in the output fluctuation amount calculation block 72, the fluctuation amount of the gas engine output is calculated.
The fluctuation amount of the gas engine output is sent to the comparison block 59A via the line L15. On the other hand, the threshold value of the gas engine output fluctuation amount is sent from the database 56C to the comparison block 59A via the line L13.

In the comparison block 59A, the fluctuation amount of the gas engine output sent from the output fluctuation amount calculation block 72 is compared with the threshold value sent from the database 56C, and the urea water input amount is changed (increase / decrease) based on the comparison result. ) Is determined. Then, a control signal corresponding to the determination result of whether or not to change (increase / decrease) the urea water input amount is sent from the comparison block 59A to the urea water input pump control signal generation block 57.
Here, the threshold value of the fluctuation amount of the gas engine output should be determined on a case-by-case basis according to various specifications in the exhaust gas denitration processing system, the use conditions of the gas engine 1, and the like.

Mainly based on FIG. 16, the control in the modification of 4th Embodiment is demonstrated with reference also to FIG.
In step S41 of FIG. 16, the output of the gas engine 1 is measured by the output sensor 5, and the process proceeds to step S42.
In step S42, the comparison block 59A compares the absolute value of the fluctuation amount of the gas engine 1 output with the threshold value of the fluctuation amount absolute value.

If the absolute value of the fluctuation amount of the gas engine output exceeds the threshold value (YES in step S42), the urea water input amount is increased or decreased by a predetermined amount (step S43), the process returns to step S41 and step S41 is repeated again. Here, the “predetermined value”, which is the fluctuation amount of the urea water input amount, is also determined on a case-by-case basis according to various specifications in the exhaust gas denitration processing system, use conditions of the gas engine 1, and the like.
If the absolute value of the fluctuation amount of the gas engine output is equal to or less than the threshold value (NO in step S42), the control described in the first embodiment (see FIG. 5) is executed (step S44).
After executing Steps S43 and S44, the process returns to Step S41.

  According to the modification of the fourth embodiment described with reference to FIGS. 15 and 16, the amount of urea water serving as a reducing agent is increased or decreased based on the amount of fluctuation in the gas engine output. It is possible to reduce the NOx concentration on the outlet side (downstream side) of the denitration catalyst 3 by covering that the control for changing the input amount of urea water (adjustment of the input amount) is delayed when the engine output changes. I can do it. Therefore, the fluctuation speed or responsiveness of the urea water input amount with respect to the change in the gas engine output is improved, and the controllability is improved.

Although not shown in FIG. 15, instead of the output sensor 5 of the gas engine 1, for example, the throttle valve opening (of the gas engine) detected by a throttle valve opening sensor (not shown) of the gas engine 1, or not shown The turbo bypass valve opening (of the gas engine) detected by the turbo bypass valve opening sensor is selected as a control parameter, and the throttle valve opening and the turbo bypass valve opening are input to the urea water supply pump control signal generation block 57. It may be configured to send out and increase or decrease or maintain the urea water supply amount.
The throttle valve opening and the turbo bypass valve opening are numerical values that affect the intake pressure of the gas engine, and are numerical values that also affect the NOx concentration. Therefore, the NOx concentration on the outlet side (downstream side) of the denitration catalyst 3 can be reduced by selecting the valve opening as the control parameter.

  In the modification of the fourth embodiment of FIGS. 15 and 16, the configuration and operational effects other than those described above are the same as those of the fourth embodiment of FIGS. 13 and 14.

17 and 18 show a fifth embodiment of the present invention.
The control unit 10E according to the fifth embodiment shown in FIGS. 17 and 18 is different from the fourth embodiment shown in FIGS. 13 and 14 in that the processing at the time of calibration of the zirconia NOx concentration sensor 4 is taken into consideration.
The exhaust gas denitration processing system according to the fifth embodiment has the same configuration as the system 103 shown in FIG. 9 except for the control unit 10E shown in FIG.

Hereinafter, with reference to FIG. 17, the difference between the control unit 10E of the fifth embodiment and the control unit 10C of FIG. 13 will be mainly described.
In FIG. 17, the control unit 10E is configured to determine whether the zirconia NOx sensor is calibrated in the FB control block 60B, a zirconia NOx sensor calibration determination block 64, a catalyst inlet side NOx value fixing block 65, maps α, γ ( γ2) It differs from the control unit 10C of FIG. 13 in that a correction stop block 66 is provided.
Here, the map α, γ (γ2) correction stop block 66 has a function of stopping correction of the map α shown in FIG. 3 and the map γ shown in FIG. 4 (or the map γ2 shown in FIG. 11). .

In the control unit 10E of FIG. 17, the zirconia NOx sensor calibration determination block 64 is based on the value of the NOx concentration input from the zirconia NOx concentration sensor 4 via the interface IF1, or based on other evaluation criteria (for example, the period of use). Thus, it is configured to determine whether or not the zirconia NOx concentration sensor 4 is calibrated.
The determination result of the zirconia NOx sensor calibration determination block 64 (determination of whether or not the zirconia NOx concentration sensor 4 is calibrated) is transmitted to the catalyst inlet side NOx value fixing block 65 via the line L17, and the line L19 is transmitted through the line L19. Via the map α, γ (γ2) correction stop block 66.

If the calibration determination block 64 determines that “calibration is being performed”, the catalyst inlet side NOx value fixing block 65 sets a specific numerical value to the upstream side of the denitration catalyst 3 (catalyst inlet 3i side). NOx concentration (catalyst inlet side NOx concentration). Here, the specific numerical value is a numerical value obtained by multiplying a numerical value of NOx concentration measured by the zirconia NOx sensor 4 immediately before calibration by a predetermined coefficient, for example, 1.2.
The catalyst inlet side NOx value fixing block 65 is connected to the NOx removal catalyst inlet side NOx amount calculation block 53 by a line L18.

  The map α, γ (γ2) correction stop block 66 is connected to the map α correction block 62 by a line L20, and is connected to the map γ correction block 63 by a line L21. If the calibration determination block 64 determines that “calibration is being performed”, the map α correction block 62 described with reference to FIG. 8 corrects the map α (FIG. 3) and the map γ correction block 63 maps. It has a function of stopping correction of γ (FIG. 4) (or map γ2 of FIG. 11).

Based on FIG. 18, the control of the exhaust gas denitration processing system according to the fifth embodiment will be described with reference also to FIG.
In step S51 of FIG. 18, the zirconia NOx sensor calibration determination block 64 determines whether the zirconia NOx sensor 4 is calibrated. If calibration has been performed (YES in step S51), the process proceeds to step S52. If calibration has not been performed (NO in step S51), the process proceeds to step S55.

In step S52, the zirconia NOx sensor calibration determination block 64 calls the measurement value (NOx concentration) immediately before calibration. In other words, the measurement of the zirconia NOx sensor 4 in the control cycle immediately before the control cycle in which it is detected that the zirconia NOx sensor 4 is calibrated, and in which the zirconia NOx sensor 4 is not calibrated. Call value. Then, the process proceeds to step S53.
In step S53, the value obtained by multiplying the measured value immediately before calibration (the measured value of the zirconia NOx sensor 4 in the control cycle in which the zirconia NOx sensor 4 immediately before calibration is not calibrated) by the constant “1.2” is obtained. And the NOx concentration on the inlet side. Then, the process proceeds to step S54.
Here, the constant of 1.2 is an example, and such a constant should be set on a case-by-case basis.

In step S54, the map α, γ (γ2) correction stop block 66 does not perform the control shown in FIG. 8 (control for correcting the map α, map γ by feedback control), and the gas engine output P-exhaust gas flow rate Qg characteristic. (Map α) and denitration rate μ-urea water equivalent ratio γ characteristics (map γ, γ-2) remain fixed. Then, the process returns to step S51.
That is, if the zirconia NOx sensor 4 has been calibrated (YES in step S51), the NOx concentration on the inlet side of the denitration catalyst 3 is fixed to a value obtained by multiplying the measured value immediately before calibration by the constant “1.2”. (Step S53), the control for determining the urea water input amount is performed in a state where the map α and the map γ (γ-2) are also fixed.

On the other hand, if the zirconia NOx sensor 4 is not calibrated (NO in step S51), the measured value of the zirconia NOx sensor 4 is used as the NOx concentration on the inlet side of the denitration catalyst 3 (step S55), and the control of FIG. (Control for correcting maps α and γ by feedback control) is executed (step S56).
Then, the process returns to step S51.

According to the fifth embodiment of FIGS. 17 and 18, is the calibration of the zirconia NOx sensor 4 interposed in the region on the combustion device 1 side upstream of the denitration catalyst 3 (catalyst inlet 3i side)? In the case where calibration is performed, a value obtained by multiplying the numerical value of the NOx concentration immediately before the calibration by a predetermined coefficient, for example, 1.2, is a region upstream of the denitration catalyst 3 (catalyst inlet). (3i side) NOx concentration (catalyst inlet side NOx concentration).
During calibration of the zirconia NOx sensor 4, the NOx concentration (catalyst inlet side NOx concentration) in the region upstream of the glass catalyst 3 (catalyst inlet 3i side) is a predetermined constant (for example, NOx concentration immediately before calibration). Actually lower than the value multiplied by 1.2). For this reason, during calibration of the zirconia NOx sensor 4, even if the amount of urea water input becomes excessive, the amount of urea water input is insufficient and the NOx emission concentration exceeds the regulation value for a long time. Can be avoided.

During calibration of the zirconia NOx sensor 4, the NOx concentration (catalyst inlet side NOx concentration) in the upstream region (catalyst inlet 3i side) of the glass catalyst 3 used in the control is a numerical value of the NOx concentration immediately before calibration. Is fixed to a value obtained by multiplying a predetermined constant (for example, 1.2), and control is performed based on a value different from the actual catalyst inlet side NOx concentration. That is, during calibration of the zirconia NOx sensor 4, the NOx concentration on the catalyst inlet side is inaccurate, and the maps α and γ are corrected by the feedback control described in FIG. 8 with reference to the inaccurate catalyst inlet side NOx concentration. If performed, the error may increase due to the correction by the feedback control.
Therefore, the control shown in FIG. 8 (control for correcting the map α and map γ by feedback control) is stopped by the map α, γ (γ2) correction stop block 66, so that the error increases. It is preventing.

Although not shown, the configuration and function of the fifth embodiment shown in FIGS. 17 and 18 can be added to the modification (of the fourth embodiment) shown in FIGS. 14 and 15.
In the fifth embodiment shown in FIGS. 17 and 18, configurations and operational effects other than those described above are the same as those in the fourth embodiment shown in FIGS. 13 and 14.

It should be noted that the illustrated embodiment is merely an example, and is not a description to limit the technical scope of the present invention.
For example, in the present invention, a characteristic (for example, P-δ characteristic: map β shown in FIG. 20) between a physical quantity (for example, the output of the combustion device 1 and the like) that can estimate nitrogen oxide emission and the NOx concentration of exhaust gas is prepared separately. When the catalyst inlet NOx sensor 4 (for example, a zirconia NOx sensor) fails, the NOx concentration of the exhaust gas can be estimated using the characteristics.
When the P-δ characteristic (map β) shown in FIG. 20 is prepared separately, it is determined by the control described in the flowchart of FIG. 5 using the output of the catalyst inlet NOx sensor 4 (for example, zirconia NOx sensor). Based on the input amount of urea water, the P-δ characteristic (map β) shown in FIG. 20 can be corrected.

DESCRIPTION OF SYMBOLS 1 ... Combustion apparatus / gas engine 2 ... Exhaust system 3 ... Denitration catalyst 4 ... NOx measuring device / Catalyst inlet NOx sensor / Zirconia NOx sensor 5 ... Output measuring device / Output sensor 6 ... · Urea water tank 7 ··· Reducing agent supply device / urea water charging pump 8 · · · exhaust gas temperature measuring device / exhaust gas temperature sensor 9 · · · urea water injection nozzle 10 · · · controller / control unit 51 .. Conversion block 52 ... Exhaust gas flow rate calculation block 53 ... NOx removal amount NOx amount calculation block 54 ... NOx amount calculation block 55 for denitration ... Urea water input amount calculation block 56 ... Database 57 ... Urea water charging pump control signal generation block

Claims (4)

A denitration catalyst interposed in the exhaust system of the combustion equipment, an estimation physical quantity measuring device for measuring a physical quantity capable of estimating the nitrogen oxide emission of the combustion equipment, and a reducing agent for the exhaust gas flowing through the exhaust system Exhaust gas amount characteristic data that summarizes the relationship between the reducing agent supply device to be supplied, the measurement results of the estimation physical quantity measuring device and the exhaust gas amount, and denitration rate / equivalent ratio characteristic data that summarizes the relationship between the denitration rate and equivalent ratio of the denitration catalyst And an exhaust gas denitration treatment system having a control device storing target nitrogen oxide amount data, a nitrogen oxide measuring device having heat resistance against the exhaust gas temperature of the combustion equipment is upstream of the denitration catalyst of the exhaust system. The nitrogen oxide measuring device is provided in a region downstream of the exhaust system denitration catalyst, and the control device is provided in a region downstream of the exhaust system denitration catalyst. And a unit that corrects the characteristics of the output of the combustion equipment and the exhaust gas and the characteristics of the denitration rate and the equivalent ratio of the denitration catalyst based on the nitrogen oxide concentration in the exhaust system. A unit for determining whether or not the nitrogen oxide measuring device interposed in the upstream region is calibrated, and in the region upstream of the denitration catalyst when the calibration is performed A unit for setting a numerical value of nitrogen oxide concentration immediately before calibration as a product concentration by a predetermined coefficient, a relationship between the estimated physical quantity and exhaust gas amount when calibration is performed, and a denitration rate of the denitration catalyst And a unit that does not correct the relationship between the equivalent ratio and the exhaust gas denitration processing system. An exhaust gas temperature measuring device that measures the exhaust gas temperature upstream of the denitration catalyst in the exhaust system is provided, and the control device corrects the characteristics of the denitration rate and equivalent ratio of the denitration catalyst based on the temperature of the exhaust gas. The exhaust gas denitration system according to claim 1 including a unit. 2. The exhaust gas denitration processing system according to claim 1, wherein the control device includes a unit that increases or decreases a reducing agent input amount based on a variation amount of a nitrogen oxide concentration in a region upstream of the denitration catalyst. An exhaust gas temperature measuring device that measures the exhaust gas temperature upstream of the denitration catalyst in the exhaust system is provided, and the control device corrects the characteristics of the denitration rate and equivalent ratio of the denitration catalyst based on the temperature of the exhaust gas. 2. The exhaust gas denitration according to claim 1, further comprising: a unit, wherein the control device further includes a unit for increasing or decreasing the amount of reducing agent input based on a variation amount of the nitrogen oxide concentration in a region upstream of the denitration catalyst. Processing system.

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