JPH0523545A - Waste gas denitrification method and its apparatus - Google Patents

Abstract

PURPOSE:To supply ammonia in proper quantity and carry out efficient and stable denitrification by computing the ammonia supply quantity to be injected to a waste gas based on the amount of discharged nitrogen oxides due to the load of an internal combustion engine and the amount of nitrogen oxides in the regulated concentration in the case that conversion as a constant oxygen concentration is carried out and then injecting ammonia. CONSTITUTION:The amount of nitrogen oxides discharged due to the load 11 of an internal combustion engine and an allowable nitrogen oxides' amount in the regulated concentration in the case that conversion as a constant oxygen concentration is carried out are calculated as a first degree function of each load. Based on the difference between the nitrogen oxide amount and the allowable nitrogen oxide amount, the ammonia supply amount until the nitrogen oxide concentration in a waste gas becomes below the regulated concentration is calculated 5 using the first degree function of the load. Based on the calculated amount the opening degree of an ammonia flow control valve 7 is controlled by a controller 4, thus the proper amount of ammonia is supplied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a denitration device for removing nitrogen oxides from exhaust gas of an internal combustion engine, and more particularly to an exhaust gas denitration device suitable for diesel engines.

[0002]

2. Description of the Related Art Conventionally, in the ammonia injection control of an exhaust gas denitration device, an engine start signal is received from a start / stop signal transmitter to open a valve, ammonia injection is started, and a stop signal is received to close the valve. Is supposed to end.

Further, in Japanese Patent Laid-Open No. 1-168318, a bypass duct that bypasses the denitration device provided in the exhaust duct of a diesel engine is provided, and a thermometer for measuring the exhaust gas temperature is provided in the exhaust duct downstream of this bypass duct. Is provided to compare the gas temperature signal of the thermometer, the engine operating signal, and the denitration device operating temperature set temperature signal to control the opening and closing of the ammonia valve.

Further, Japanese Laid-Open Patent Publication No. 2-223623 discloses a NOx device for generating diesel engine exhaust gas in which a ammonia supply amount is learned in advance by a sequencer and a required amount of ammonia is supplied based on the learned amount.

[0005]

However, in the case where ammonia is supplied by opening and closing only the above-mentioned conventional valve,
Since the ammonia flow rate cannot be delicately controlled according to the amount of generated nitrogen oxides, the amount of discharged nitrogen oxides cannot be controlled, and the amount of leaked ammonia increases.

Conventionally, control is performed to adjust the ammonia flow rate in response to changes in the amount of generated nitrogen oxides. In this method, however, the concentration of nitrogen oxides, the exhaust gas air volume, etc. are constantly measured, There is a problem that it is necessary to calculate the amount of ammonia supplied, and maintenance costs such as adjustment of the NOx meter and cleaning of the gas sampling pipe become high.

In Japanese Patent Laid-Open No. 2-223623, the sequence of the amount of ammonia supplied is learned in advance by a sequencer, and the required amount of ammonia is supplied based on the learned sequence. However, the device configuration and control method are complicated and the operation and There is a problem that adjustment is difficult. The present invention has been made in view of the above points, and eliminates the above problems, has a simple configuration, and is capable of supplying an appropriate flow rate of ammonia into exhaust gas by following changes in the load of an internal combustion engine. To provide a device.

[0008]

In order to solve the above problems, the present invention is directed to injecting ammonia into exhaust gas of an internal combustion engine,
In the exhaust gas denitration method of removing the nitrogen oxides in the exhaust gas by passing the exhaust gas into which the ammonia has been injected through a nitrogen oxide catalytic reaction tower, the amount of nitrogen oxides discharged to the load of the internal combustion engine and a constant oxygen concentration are converted. The allowable amount of nitrogen oxides at the regulated concentration in each case was determined as a linear function of the load, and the amount of ammonia supplied until the concentration of nitrogen oxides in the exhaust gas fell below the regulated concentration from the difference between this amount of nitrogen oxides and the allowable amount of nitrogen oxides. Is calculated by a linear function formula with respect to the load,
It is characterized in that the calculated amount of ammonia is supplied according to a change in load.

Further, a nitrogen oxide catalytic reaction tower is connected to an exhaust gas duct for discharging the exhaust gas of the internal combustion engine, and ammonia is used as a nitrogen oxide reducing agent in the exhaust gas duct between the internal combustion engine and the nitrogen oxide catalytic reaction tower. In an exhaust gas denitration device connected to an ammonia supply device for supplying oxygen, the nitrogen oxide amount discharged with respect to the load of the internal combustion engine and the allowable nitrogen oxide amount at the regulated concentration when converted to a constant oxygen concentration are respectively linear functions of the load. As a result, the coefficient of the linear function equation for calculating the load as a linear function of the ammonia supply amount that makes the nitrogen oxide concentration in the exhaust gas equal to or lower than the regulation concentration from the difference between the amount of nitrogen oxide and the allowable amount of nitrogen oxide is stored, A calculation means for calculating the ammonia supply amount according to a change in load using a coefficient value, and the ammonia output by the calculation output of the calculation means. Characterized by a control nitrogen oxide concentration of ammonia supply from the charging device provided with a control means for the following regulation value.

[0010]

The exhaust gas discharged from the internal combustion engine is mixed with the supplied ammonia and flows into the nitrogen oxide catalyst reaction tower, where the nitrogen oxide is removed, that is, denitration is performed by the action of the catalyst.

The supply amount of ammonia injected into the exhaust gas depends on the difference between the amount of nitrogen oxides discharged with respect to the load of the internal combustion engine and the amount of nitrogen oxides at the regulated concentration when converted to a constant oxygen concentration. , Since it is calculated as a linear function with respect to the load, and ammonia is injected into the exhaust gas based on the calculation result, the ammonia is always supplied in an appropriate amount corresponding to the amount of nitrogen oxides in the exhaust gas. Stable denitration will be performed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration example of an exhaust gas denitration device of the present invention. The exhaust gas denitration device of FIG. 1 shows the configuration of the exhaust gas denitration device of the diesel engine 1 that drives the generator 11.

The exhaust port of the diesel engine 1 is connected to a nitrogen oxide catalytic reaction tower, that is, a denitration tower 2 by an exhaust gas duct 9. An ammonia injector 8 is installed in the exhaust gas duct 9 and upstream of the denitration tower. The load signal line 6 of the generator 11 directly connected to the diesel engine 1 is connected to the ammonia supply amount calculator 5, and the ammonia supply amount calculator is connected to the ammonia flow rate adjusting valve controller 4.

The ammonia injector 8 is connected to the ammonia storage cylinder 3 through the ammonia flow rate adjusting valve 7. The ammonia flow rate adjusting valve 7 is connected to the ammonia flow rate adjusting valve controller 4.

The outlet of the denitration tower 2 is the exhaust gas discharge duct 1
The exhaust gas, which is denitrated by the denitration tower 2, is connected to a not-illustrated chimney or the like through 0 and is released to the atmosphere. The operation of the exhaust gas denitration device having the above configuration will be described below.

In an apparatus in which ammonia is injected and mixed as a reducing agent for reducing nitrogen oxides into exhaust gas of an internal combustion engine (diesel engine 1) as described above, and denitration is performed by a nitrogen oxide catalytic reaction tower, As a result of measuring values with respect to the load of the internal combustion engine for various items of the internal combustion engine in which the device is provided, the results are shown in FIGS. 2 and 3.

FIG. 2A is a diagram showing the nitrogen oxide concentration NOx with respect to the load, and FIG. 2B is a diagram showing the exhaust gas flow rate with respect to the load. The amount of nitrogen oxides is calculated by the following equation (1). (Nitrogen oxide) = (Nitrogen oxide concentration) × (Exhaust gas air flow rate) (1) Therefore, the amount of nitrogen oxide is represented by a substantially linear function as shown in FIG. 2 (c).

The allowable nitrogen oxide amount when the regulated value (reduction target value) is expressed by the nitrogen oxide concentration expressed by converting it to a specific oxygen concentration is expressed by the following equation (2). (Allowable nitrogen oxide amount) = (Allowable oxide concentration) × (Exhaust gas air flow rate) × (21−O ₂ ) / (21−O ₂ O) (2) where O ₂ O is A specific oxygen concentration [%] is shown, O ₂ shows an arbitrary oxygen concentration, and 21 shows an oxygen concentration in the air. The emission standard for nitrogen oxides in the exhaust gas of diesel engines is set to 13% in terms of oxygen concentration (O ₂ O).

FIG. 3 (a) is a diagram showing the oxygen concentration with respect to the load, and FIG. 3 (b) is (allowable oxide concentration, that is, the regulation value) × (21-O ₂ ) / (21-O ₂ ) with respect to the load. It is a figure which shows O).

FIG. 3C is a diagram showing the calculation result of the allowable amount of nitrogen oxides with respect to the load. As shown in FIG. 3C, the nitrogen oxide amount with respect to the regulation value of the nitrogen oxide concentration converted into the specific oxide concentration is represented by a linear function with respect to the load.

In the selective denitration action by ammonia, the reaction between ammonia and nitrogen oxide is carried out at a molar ratio of 1: 1. Therefore, the amount of ammonia required to satisfy the above nitrogen oxide concentration is expressed by the following equation (3). (Required ammonia amount) = (nitrogen oxide amount) − (allowable nitrogen oxide amount) · (3)

The above equation (3) for calculating the above ammonia amount
Since the (nitrogen oxide amount) and the (allowable nitrogen oxide amount) on the right side of are both approximated by a linear expression, the subtraction result can also be approximated by a linear expression. That is, the ammonia supply amount required to keep the nitrogen oxide concentration in the exhaust gas below the regulation value can be approximated by a linear expression with respect to the load.

As described above, with respect to the load of the internal combustion engine,
It can be seen that the amount of discharged nitrogen oxides and the amount of nitrogen oxides at the regulated (target) concentration when converted to the specific oxygen concentration are each represented by a substantially linear function. Therefore, the ammonia supply amount required for denitration may be set and supplied as a linear function of the load of the internal combustion engine.

In the exhaust gas denitration apparatus having the structure shown in FIG. 1, the NOx concentration with respect to the load of the diesel engine 1 in which the exhaust gas denitration apparatus is installed {see FIG. 2 (a)} and the exhaust gas flow rate with respect to the load are referred to with {see FIG. 2 (b). } Is actually measured and calculated. From the NOx concentration and the exhaust gas flow rate for this load, the amount of nitrogen oxides expressed as a linear function with respect to the load is obtained using the equation (1) {see FIG. 2 (c)}.

Further, the oxygen concentration with respect to the load of the diesel engine 1 is measured and obtained {see FIG. 3 (a)}. From the oxygen concentration for this load, the (allowable oxide concentration) × (21−O ₂ ) / (21−) for the load as shown in FIG.
O ₂ O). Then, the allowable amount of nitrogen oxides expressed as a linear function with respect to the load is obtained using the equation (2) {see FIG. 3 (c)}.

From the difference between the above amount of nitrogen oxides and the allowable amount of nitrogen oxides, the amount of supplied ammonia is calculated as shown in equation (3). In this case, since both the amount of nitrogen oxides and the amount of nitrogen oxides are expressed as a linear function of the load as described above, the formula for calculating the supply ammonia amount from the difference between the two is a linear function formula for the load. The coefficient of the linear function equation for calculating the supply ammonia amount from this load is stored in the internal memory of the ammonia supply amount calculator 5.

As described above, by storing the coefficient of the equation for calculating the supply amount of ammonia in the internal memory of the ammonia supply amount calculator 5, the load value from the load signal line 6 is supplied to the ammonia supply amount calculator 5 from the load signal line 6. When input, the ammonia supply amount required for this load value is calculated, and the result is output to the ammonia flow rate adjustment valve controller 4.

The ammonia flow rate adjustment valve controller 4 adjusts the opening degree of the ammonia flow rate adjustment valve 7, and the ammonia supply amount calculator from the ammonia storage cylinder 3 into the exhaust gas duct 9 via the ammonia flow rate adjustment valve 7 and the ammonia injector 8. The amount of supply ammonia calculated in 5 is injected.

As a result, the ammonia injected into the exhaust gas duct 9 is mixed with the exhaust gas and flows into the denitration tower 2. Then, the nitrogen oxides in the exhaust gas react with ammonia by the catalyst in the denitration tower 2, and are decomposed into water and nitrogen, that is, denitrated. The denitrated exhaust gas is released into the atmosphere through the chimney tower.

In the above embodiment, the load of the internal combustion engine (diesel engine) is used, but instead of this load, the fuel consumption amount or the load of the machine connected to the internal combustion engine, that is, the generated power in the power generator. Quantity, current, etc., and torque, etc. can be used in machines such as pumps.

Further, the supply of ammonia may be carried out when the internal temperature of the catalyst of the denitration tower is within a preset temperature range.

Although the diesel engine has been described in the above embodiment, the present invention is not limited to this and can be applied to all internal combustion engines.

[0033]

As described above, according to the present invention, the following excellent effects can be obtained. (1) Since an appropriate amount of ammonia is constantly supplied to the exhaust gas in accordance with the amount of nitrogen oxides in the exhaust gas, efficient and stable denitration can be performed, and the risk of ammonia leakage can be reduced. (2) Since the ammonia flow rate is controlled only by the load signal, NO for detecting nitrogen oxides in the exhaust gas for control
The x-meter is not required and the device is simplified. (3) Since the ammonia supply amount is expressed as a linear function, it is easy to change the coefficient set in the arithmetic unit, the constitution of the arithmetic unit is easy, and the control is reliable.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a denitration device of the present invention.

FIG. 2 is a diagram showing various values with respect to the load of an internal combustion engine,
2 (a) is the NOx concentration with respect to the load, FIG. 2 (b) is the exhaust gas flow rate with respect to the load, and FIG. 2 (c) is the NOx with respect to the load.
The amount relationships are shown below.

FIG. 3 is a diagram showing various values with respect to the load of the internal combustion engine,
FIG. 3A shows the relationship between the O ₂ concentration with respect to the load, FIG. 3B shows the regulation value with respect to the load × (21−O ₂ ) / (21−13), and the allowable nitrogen oxide load NOx amount with respect to the load. .

[Explanation of symbols]

1 diesel 2 Denitration tower 3 Ammonia storage cylinder 4 Ammonia flow rate adjustment valve controller 5 Ammonia supply amount calculator 6 load signal line 7 Ammonia flow control valve 8 Ammonia injector 9 Exhaust gas duct 10 Exhaust gas exhaust duct 11 generator

Claims (6)

[Claims] 1. An exhaust gas denitration method for injecting ammonia into exhaust gas of an internal combustion engine, and passing the exhaust gas into which the ammonia has been injected through a nitrogen oxide catalytic reaction tower to remove nitrogen oxides in the exhaust gas. The amount of nitrogen oxides discharged for each load and the allowable amount of nitrogen oxides at the regulated concentration when converted to a constant oxygen concentration were obtained as a linear function of the load, respectively, and the difference between this amount of nitrogen oxides and the allowable amount of nitrogen oxides was calculated. An exhaust gas denitration method characterized in that an ammonia supply amount for making a nitrogen oxide concentration in exhaust gas equal to or lower than a regulated concentration is calculated as a linear function with respect to a load, and the calculated ammonia amount is supplied according to a change in the load. 2. A nitrogen oxide catalytic reaction tower is connected to an exhaust gas duct for discharging exhaust gas of an internal combustion engine, and ammonia is used as a reducing agent of nitrogen oxide in an exhaust gas duct between the internal combustion engine and the nitrogen oxide catalytic reaction tower. In an exhaust gas denitration device connected to an ammonia supply device for supplying the amount of nitrogen oxides discharged to the load of the internal combustion engine and the allowable amount of nitrogen oxides at a regulated concentration when converted to a constant oxygen concentration As a function, the coefficient of the equation for calculating the ammonia supply amount as the linear function of the load to keep the nitrogen oxide concentration in the exhaust gas below the regulation concentration from the difference between this nitrogen oxide amount and the allowable nitrogen oxide amount is stored. A calculation means for calculating the ammonia supply amount according to the change of the load used, and an output from the ammonia supply device based on the calculation output of the calculation means. Exhaust gas denitration apparatus characterized by providing a control means for controlling the pneumoniae supply amount or less regulation value of nitrogen oxide concentration. 3. The exhaust gas denitration device according to claim 2, wherein the fuel consumption of the internal combustion engine is used instead of the load of the internal combustion engine. 4. The exhaust gas denitration device according to claim 2, wherein the load of the device connected to the internal combustion engine is used instead of the load of the internal combustion engine. 5. The proportional constant of the fuel consumption amount or load and the ammonia amount according to claim 2, 3 or 4, is arbitrarily set by the ammonia supply amount calculation means according to the type of the internal combustion engine or the nitrogen oxide reduction target value. An exhaust gas denitration device characterized by: 6. The method according to claim 2, 3 or 4 or 5,
The exhaust gas denitration apparatus, wherein the ammonia is supplied when the temperature of the catalyst of the nitrogen oxide catalytic reaction tower is within a set temperature range.