JP2000229221A - Denitration apparatus and control method thereof - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To enable optimal control of a reducing agent injection amount. SOLUTION: When an operation of a generator 20 is started, an exhaust gas G from a diesel engine 12 causes a reactor 11 to be operated.
The temperature of the denitration catalyst 14 inside gradually increases. DeNOx catalyst 1
The temperature of 4 is measured by a thermocouple 34 provided in the reactor 11, and the temperature signal in the vaporizer 13 is measured by the thermocouple 31. When the temperature of the denitration catalyst 14 is raised to a temperature slightly lower than the reaction temperature, the thermocouple 3 is set so that the temperature in the vaporizer 13 is in a temperature range in which the thermal decomposition of urea is favorably performed.
The solenoid valve SV3 is opened based on the signal from the
3 is injected into the cooling water. When the temperature of the denitration catalyst 14 rises and reaches the reaction temperature of the catalyst, the urea water pump 3
5, the solenoid valve SV1 is opened, and the injection of urea water into the vaporizer 13 is started. The urea injection amount here is an initial injection amount set in advance based on the load of the generator 20, and is adjusted by the pump 35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a denitration apparatus and a control method thereof for removing NO _X from the nitrogen oxides such as flue gas of an internal combustion engine (NO _X) containing gas.

[0002]

Conventionally the NO _X processing techniques are required in various fields, as a general treatment method, it has been put into practical use as a flue gas denitrification technique. This flue gas denitration technology is roughly classified into a dry method and a wet method. At present, the selective catalytic reduction method, which is one of the dry methods, is technically advanced, and attracts attention as an effective denitration method. The main reaction of the selective catalytic reduction method is represented by the following equation.

4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O (1) In the reaction of the formula (1), ammonia, hydrocarbon, and carbon monoxide are used as a reducing agent. In particular, ammonia coexists with oxygen. also to remove selectively NO _X and is effective when used to remove of the NO _X contained in the exhaust gas such as a diesel engine. This reaction is performed using a noble metal such as platinum as a denitration agent, alumina, titanium oxide (TiO 2).
₂ ) The main component is a catalyst containing an oxide such as vanadium (V), molybdenum (Mo), tungsten (W) or a double salt as an additive.

[0004] The selective catalytic reduction method is able to handle the NO _X with a simple system, a high denitration ratio can be obtained. Moreover NO _X to harmless nitrogen gas (N ₂₎ and water (H ₂ O) This has the advantage that waste liquid treatment is unnecessary. Ammonia gas or aqueous ammonia is used as a reducing agent, but urea water is being used from the viewpoint of cost because ammonia is expensive.

[0005]

In the above-described denitration apparatus using ammonia, the injection amount of urea and ammonia must be controlled so that the denitration reaction occurs at a rate close to the theoretical reaction as shown in the above equation (1). Must. This is because if the injection amount is small, the denitration rate is reduced, and if it is too large, ammonia may leak and emit an odor.

[0006] Conventional injection amount control methods include a method of controlling the injection of ammonia (urea) in proportion to the output of a generator driven by a diesel engine, and a method of controlling the injection of exhaust gas discharged from an internal combustion engine. by measuring the NO _X concentration, and a method of injecting controlling ammonia (urea) is employed.

However, a diesel internal combustion engine, the amount of exhaust gas, since the NO _X concentration is greatly changed by the ambient conditions or the like, wherein (1) NO amount of expression is changed significantly. N
The O amount can be obtained from the NO concentration and the exhaust gas amount, but since the gas amount measurement cannot be performed automatically, the N amount is actually
It was impossible to control the injection amount of ammonia (urea) by measuring the amount of O generated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a denitration apparatus and a control method therefor, which enable optimal control of a reducing agent injection amount.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, a first aspect of the present invention is to provide a denitration catalyst by adding a reducing agent to exhaust gas discharged from an internal combustion engine and flowing through a pipe. In the denitration device that removes NO _X in the exhaust gas, the device has means for measuring the temperature of the denitration catalyst, and when the measurement temperature of the denitration catalyst reaches the reaction temperature of the denitration catalyst, The injection of the reducing agent is started.

According to a second aspect of the present invention, a vaporizer is provided in an exhaust gas pipe through which exhaust gas discharged from an internal combustion engine flows, and a reducing agent is added from the vaporizer to the exhaust gas flowing through the pipe to form a denitration catalyst. contact is in denitration apparatus for removing NO _X in the exhaust gas has a temperature measuring means within means and the evaporator to measure the temperature of the denitration catalyst, the vaporizer at a reaction temperature below the denitration catalyst Cooling water is injected and 9
The temperature is adjusted to a range of 0 to 162 ° C., and when the measured temperature of the denitration catalyst reaches the reaction temperature of the denitration catalyst, injection of urea water as a reducing agent into the vaporizer is started. It is assumed that.

According to a third aspect of the present invention, a carburetor is provided in an exhaust gas pipe through which exhaust gas discharged from an internal combustion engine flows, and urea water is injected into the vaporizer through a urea water injection pipe to reduce exhaust gas. after addition by thermal decomposition of urea in the vaporizer to the exhaust gas by heat, by contact with a denitration catalyst, method of controlling a denitration apparatus for removing NO _X in the exhaust gas, stop of the internal combustion engine, Alternatively, the injection of urea water is stopped at any point in time when the temperature of the denitration catalyst is lower than the reaction temperature of the denitration catalyst. The cleaning is performed.

According to a fourth aspect of the present invention, a vaporizer is provided in an exhaust gas pipe through which exhaust gas discharged from an internal combustion engine flows, and a reducing agent is added from the vaporizer to the exhaust gas flowing through the pipe, and then a denitration catalyst is provided. By contact with N 2 in the exhaust gas.
In the control method of the denitration apparatus for removing O _X , NO _X
Set the NO _X concentration target value after removal, estimates the NO _X in the exhaust gas discharged from the operation state of the internal combustion engine, the required reduction to remove NO _X of the estimated amount to the target value After calculating the amount of the agent as an initial addition amount, measuring the temperature of the denitration catalyst and the temperature in the vaporizer, injecting cooling water into the vaporizer at a time equal to or lower than the reaction temperature of the denitration catalyst, and then vaporizing. The inside of the vessel was adjusted to the range of 90 to 162 ° C., and when the measured temperature of the denitration catalyst reached the reaction temperature of the denitration catalyst, the injection of urea water as a reducing agent into the vaporizer was started to contact the denitration catalyst. After the removal of NO _X by carrying out, the NO _X concentration in the exhaust gas from which NO _X has been removed is measured, the measured NO _X concentration is compared with the NO _X concentration target value, and based on the difference, Repeat the process of adding and reducing the amount of reducing agent added It is characterized by doing so.

A fifth aspect of the present invention relates to a denitration apparatus which removes NO _{X in} exhaust gas by adding a reducing agent to exhaust gas discharged from an internal combustion engine and flowing through a pipe and then bringing the exhaust gas into contact with a denitration catalyst. the control method, pre NO _X set NO _X concentration target value after removal, estimates the NO _X in the exhaust gas discharged from the operating state of the internal combustion engine, the estimated amount of N
The amount of reducing agent required to the O _X is removed to a target value to calculate an initial amount, the temperature of the denitration catalyst is measured and when the measurement temperature reaches the reaction temperature of the denitration catalyst , starting the injection of the reducing agent after carrying out the removal of the NO _X by contacting with denitration catalyst, NO _X
Measuring the concentration of NO _X exhaust gas to remove, makes a comparison between the measured NO _X concentration and the NO _X density target value, repeating the step of adding by increasing or decreasing adjusts the reducing agent adding amount based on the difference It is characterized by doing so.

[0014] The sixth invention, the step of the NO _X concentration was measured, to compare the measured NO _X concentration and the NO _X density target value is added by increasing or decreasing adjusts the reducing agent adding amount based on the difference Is characterized in that it is repeated after a time required for this step.

In the present invention, the vaporizer container may be filled with any of stainless steel wire, metal mesh, zeolite powder, and zeolite honeycomb.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment,
An example in which a denitration device is used in a diesel engine of a diesel engine generator as an internal combustion engine will be described.

FIG. 1 is a schematic diagram showing the structure of a denitration apparatus according to the present embodiment. Reference numeral 11 denotes a closed type denitration reactor (hereinafter abbreviated as “reactor”), and reference numeral 12 denotes an internal combustion engine (hereinafter a diesel engine) driving a generator 20. Is abbreviated). 11a is an introduction part for introducing the exhaust gas G from the internal combustion engine into the reactor 11 through the pipe 21, and 11b is an exhaust gas G from the reactor 11.
This is the discharge section that discharges. In the middle of the pipe 21, a vaporizer 13 is disposed as a means for adding a reducing agent to the exhaust gas G.

Inside the reactor 11, a denitration catalyst 14 formed in a honeycomb shape is laminated. DeNOx catalyst 1
As No. 4, a zeolite (ZSM-5) was used as a main raw material, which was formed into a honeycomb shape, fired to prepare a catalyst carrier, and cobalt supported by ion exchange on the catalyst carrier was used. 24 is an introduction part 11 in the reactor 11
It is a shielding plate arranged at a position facing a. Reference numeral 17 denotes a denitration control device (hereinafter abbreviated as a control device) for controlling a denitration device such as adjustment of the amount of a reducing agent added, and 19 denotes a program contra roller (hereinafter abbreviated as a controller) for performing various settings and operations. is there.

[0019] 21 NO in _X analyzer, reactor 11 sensor 23 disposed in the connected flue 22 to the discharge unit 11b of the
In a, which measures the concentration of NO _X in the exhaust gas G after being denitration. Reference numeral 34 denotes a temperature sensor provided in the reactor 11 for measuring the temperature of the denitration catalyst 14, and a thermocouple is used in the present embodiment.
The temperature sensor 34 is not limited to the inside of the denitration reactor 11 but may be arranged in the vicinity of the discharge section 11 b in the flue 22 as long as the temperature can be measured on the exhaust gas G discharge side of the denitration catalyst 14.

Reference numeral 15 denotes a water pipe connected to a water pipe or a tank storing cooling water, and 16 denotes a tank for storing a reducing agent. As the reducing agent, ammonia gas, aqueous ammonia, urea, or the like can be used. In the present embodiment, aqueous urea is used. When urea water is used as the reducing agent, a method is employed in which urea water is heated and evaporated to decompose as shown in the following formula (2), and the generated ammonia is added to the exhaust gas. (NH ₂ ) ₂ CO + H ₂ O → NH ₃ + CO ₂ (2) However, depending on the decomposition conditions, urea does not decompose to ammonia but changes to other high-melting substances (cyanuric acid, melamine, isocyanic acid, etc.). As a result, decomposition efficiency may be reduced and harmful substances may be generated.

Then, when the decomposition characteristics of urea were examined, the results shown in FIGS. 2 and 3 were obtained. FIG. 2 is a graph showing the decomposition characteristics when urea was rapidly heated at 50 ° C./min using a parallax thermobalance, wherein line A shows the thermogravimetric change (TG,%) of urea, and line B Indicates a change in the reaction heat (DTA, converted from the measurement value μv of the thermocouple). The melting point of urea is 135 ° C., and the change of line B from 136 ° C. indicates urea evaporation. Similarly, the change at 263 ° C. in line B represents the melting point of melamine. 344 ° C of line A
The change from represents the degradation of cyanuric acid. The temperature range C indicates a region where a high melting point substance is generated, and generation of a high melting point substance was confirmed at a temperature exceeding 162 ° C. In addition, the temperature range D shows the decomposition region of the high melting point substance. And from line A, about 71.5% of the urea is directly vaporized by heat,
It can be seen that about 28.5% is converted to melamine and cyanuric acid which are high melting point substances.

That is, since the decomposition of urea starts at 90 ° C., the thermal decomposition of urea is preferably performed at a temperature in the range from 90 ° C. to 162 ° C. where no high-melting-point substance is found, which is confirmed from the results shown in FIG.

Further, when the temperature and the thermogravimetric change (TG) when the zeolite powder and urea were mixed were examined, the results were as shown in the graph of FIG. Zeolite is a substance mainly composed of an oxide of aluminum and silicon, and has pores of 5 to 10 ° (angstrom). A line E in FIG. 3 is a graph showing a decomposition characteristic when only urea water is rapidly heated at 50 ° C./min. A line F is obtained by adding zeolite powder to urea water and slowly raising the temperature at 2 ° C./min. It is a graph which shows the decomposition characteristic at the time of heating, and the line G is a graph which shows the decomposition characteristic at the time of adding a zeolite powder to urea water, and rapidly raising a temperature at 50 degreeC per minute.

From the results shown in FIG. 3, it can be seen that the coexistence of the zeolite powder reduces the generation rate of the high-melting substance to 16% even when the temperature of the urea water is rapidly increased at 50 ° C. per minute, and the zeolite has the heat of the urea. It was confirmed that it had an effect of promoting decomposition. It is considered that this is because urea is a strongly polar substance and is adsorbed on the surface of zeolite and decomposed on the surface into ammonia and carbon dioxide gas. When only urea water was rapidly heated at 50 ° C./min, the generation ratio of the high melting point substance was 28.5%.

In place of zeolite powder, various metal materials such as stainless steel, copper, iron, aluminum, etc. may be used in the form of a wire (ribbon, wire, chip, etc.), mesh, small sphere such as a bearing ball, etc. When the same experiment was attempted using various shapes of urea, it was confirmed that the urea had the effect of accelerating the thermal decomposition of urea in the same manner as zeolite powder. , A thermal decomposition accelerator).

Furthermore, when a stainless steel packing (trade name: Pa11 Ring) shown in FIG. 4 which is commercially available from Iwao Porcelain Industry was used as a packing for a tower such as a distillation tower, similarly good results were obtained. Can be confirmed, and this can also be used as a thermal decomposition accelerator. And the heating rate is 2
It can be seen that when the temperature was set to ℃, the generation ratio of the high melting point substance was further reduced to 6%. This is considered to be because the reaction time until the decomposition of urea was completed was secured, and the urea was decomposed before reaching the temperature at which a high melting point substance was generated.

From the above results, when urea water is used as the reducing agent, the thermal decomposition of urea water in an environment in which any of the above-mentioned thermal decomposition accelerators coexists in the temperature range of 90 ° C. to 162 ° C. It has been found that it is preferable to add the generated ammonia to the exhaust gas. Therefore, in the present embodiment, a vaporizer whose schematic configuration diagram is shown in FIG. 5 is employed as a reducing agent adding means that satisfies these circumstances and adds a reducing agent. In FIG. 5, reference numeral 25 denotes a pot serving as a vaporizer container, and an opening 26 is formed in a side wall of the pot 25. The pot 25 is filled with a metal wire, for example, a stainless steel ribbon (hereinafter referred to as SUS ribbon) 27 having a width of 2 mm and a thickness of 0.05 mm as a thermal decomposition accelerator. Reference numeral 30 denotes a lid of the pot 25. The lid 30 has a hole 26 formed in the pot 25 facing the downstream side.
To the flange 32 formed in the opening 21a of the pipe 21
, The vaporizer is arranged in the pipe 21.

Reference numeral 28 denotes a liquid feed pipe for injecting urea water into the pot 25, and reference numeral 29 denotes a water pipe for supplying cooling water into the pot 25. The liquid supply pipe 28 and the water pipe 29
In addition to using independent pipes as shown in FIG. 1, the urea is solidified in the pipes by heat by forming a double pipe structure in which the outer circumference of the liquid feed pipe 28 is covered with a water pipe 29 as shown in FIG. However, it is also possible to prevent the piping from being clogged. Numeral 31 denotes a thermocouple which penetrates the lid 30 and is inserted into the pot 25 as temperature measuring means for measuring the temperature inside the pot 25.

It is to be noted that reference numeral 35 denotes the vaporizer 1 from the urea tank 16.
3 is a urea water pump for introducing urea water into
V1, SV2, and SV3 are solenoid valves that are opened and closed by signals from the controller 19, respectively.

In such a configuration, when urea water is supplied into the pot 25 from the liquid feed pipe 28, the urea water is thermally decomposed in the pot 25 by the heat supplied from the exhaust gas G, and the vaporized ammonia gas is opened. The reducing agent is added to the exhaust gas G by being discharged from the hole 26 into the pipe 21. At this time, the temperature inside the pot 25 is measured by the thermocouple 31, and cooling water is supplied from the water pipe 29 based on the measured temperature, and the temperature inside the pot 25 is adjusted to be in a range of 90 ° C to 162 ° C. I do.

FIG. 6 is a sectional view of a main part of the reactor 11. 2
Reference numeral 4 denotes a disc-shaped shielding plate which is a space between the introduction part 11a and the denitration catalyst 14 in the reactor 11, and is disposed at a position facing the introduction part 11a. By arranging the shielding plate 24, the reactor 11 can pass through the duct 33 of the pipe 21.
The exhaust gas G fed into the inside collides with the shielding plate 24 and generates a downstream swirl A on the downstream side of the exhaust gas G to rectify the exhaust gas G. After that, the exhaust gas G and the reducing agent are satisfactorily formed by the swirl A. As well as being mixed, the gas density can be averaged by the rectification effect and can be passed through the denitration catalyst 14.

Further, since the exhaust gas G and the reducing agent are mixed well by providing the shielding plate 24, the exhaust gas G
It is not necessary to provide a pipe 21 having a sufficient length for satisfactorily mixing the gas and the reducing agent, so that the size of the entire apparatus can be reduced. When the exhaust gas G is introduced through the duct 33 having the curved portion as shown in FIG. 6, the gas flow is concentrated on the outer portion in the bending direction, and the stagnation portion C is generated on the inner portion in the bending direction. The exhaust gas G may flow into the reactor 11 as a drift. When the exhaust gas G is introduced into the reactor 11 in a deflected flow as described above, the center O of the shielding plate 24 is positioned so as to coincide with the wind pressure center of the flowing exhaust gas G as shown in FIG. By adjusting and arranging, effects such as good mixing of the exhaust gas G with the reducing agent and averaging of the exhaust gas G can be obtained.

Next, a method of controlling the amount of the reducing agent added according to the present embodiment will be described by taking the denitration apparatus shown in FIG. 1 as an example. The parameters taken into the control device 17 as control factors are the generator load (load factor of the generator) and the NOx concentration in the exhaust gas G at the outlet of the denitration device.

FIG. 7 is a process explanatory view for explaining the control method.
7, 41 is the amount of NO _X estimating step of schematic estimating the amount of NO _X discharged by the operation of the internal combustion engine. This N
In O _X amount estimation step 41, for example, the relationship characteristic diagram of the generator load and the exhaust gas amount in FIG. 8, and generator load and NO _X in FIG. 9
As shown example in relation characteristic diagram of the concentration, the generator was measured pre-load / exhaust gas amount Vkw the generator load / NO _X concentration V _NO
Each relationship is taken into the control device 17 shown in FIG.
The estimated NO _X amount is obtained from the product of the central value of the NO _X concentration and the central value of the exhaust gas amount according to the generator load in the operating state of the internal combustion engine taken as a parameter.

As can be seen from the relation characteristic diagrams shown in FIGS. 8 and 9, the estimated NO _X amount obtained here includes a considerable variation. In the target NO _X concentration (range) setting step, the estimated N obtained in the NO _X amount estimating step 41 is calculated.
The reduction target of NO _X with respect to the O _X amount is set as a target NO _X concentration (range). In the reducing agent an initial injection amount calculation step 43, to achieve a target NO _X concentration set by the target NO _X concentration (range) setting step 42 (range), denitration ratio (the outlet side N
The O _X concentration the amount of reducing agent required to obtain or to reduce) the percentage of the inlet side, is calculated as the reducing agent an initial injection rate.
In the reducing agent initial injection step 44, injection of the reducing agent is started with the amount calculated in the reducing agent initial injection amount calculating step 43.

The reducing agent is added to the exhaust gas G via a vaporizer, and the exhaust gas G to which the reducing agent has been added flows into the reactor to mix and average the gas density by the action of the shielding plate. after being made, NO _X in the exhaust gas G are removed in contact with the denitration catalyst by the reaction shown in the equation (1).

Next, in the NO _X concentration measuring step 45, the NO _X concentration of the exhaust gas G from which NO _X has been removed is measured at the outlet side of the reactor, and the measured NO _X concentration is compared with the NO _X concentration. in step 46, comparison between the target NO _X concentration (range) target NO _X concentration is set by the setting step 42 (range) are performed. The injection amount of the reducing agent is adjusted in the reducing agent injection amount adjusting step 47 based on the result of the comparison in the NO _X concentration comparing step 46,
Thereafter, the adjusted amount of the reducing agent is injected.

If there is no difference between the measured NO _X concentration and the target NO _X concentration (range), it means that the initial injection amount was appropriate, and the adjustment amount in the reducing agent injection amount adjustment step 47 is: At 0 (zero), the injection of the reducing agent with the initial injection amount is continued. And, thereafter by returning Kumiri the 45 to 47 steps, even if variations in the initially set estimated amount of NO _X, also, NO _X in the exhaust gas G due to changes in the operating state of the internal combustion engine even if the amount change has occurred, since the reducing agent can be adjusted to an amount necessary to target NOx concentration (range), it is possible to perform appropriate control in order to obtain the concentration of NO _X target.

The measurement of the NO _X concentration by the NO _X analyzer requires a time (usually about 1 minute) from the sampling by the sensor to the analysis. Therefore, the repetition time of each of the steps 45 to 47 is set as follows. It needs to be set long.

The target NO _X concentration may be set in a range. For example, when it is desired to set the average value of the target NO _X concentration to 100 ppm, the upper limit is set to 110 ppm and the lower limit is set to 80 ppm. concentration of NO _X reactor outlet side 110-8
The amount of the reducing agent may be adjusted when the amount falls outside the range of 0 ppm.

At this time, in order to carry out the reaction of the formula (1) without changing urea to a high melting point substance, the inside of the pot 25 is always kept in a proper temperature range (for example,
Since it is necessary to control the temperature from 90 ° C. at which the decomposition of urea starts to 162 ° C. or less at which no high-melting-point substance is generated), the temperature in the pot 25 is measured by a measuring means such as a thermocouple, and the temperature within the above-mentioned temperature range is measured. The cooling water is appropriately injected from the water pipe 15 into the pot 25 so as not to come off.

Next, an operation flowchart of the above embodiment is shown in FIG. In FIG. 10, S1 is a step of estimating the NO _X amount of the denitration apparatus.
When estimating the O _X amount, the estimation is performed by taking the generator load / exhaust gas amount V _KW and the generator load / NO _X concentration V _NO as parameters. From the result of the estimation of the NO _X amount, a target NO _X concentration range is set in step S2. After the setting in step S2, the initial injection amount of the reducing agent is calculated in step S3, and the calculation of the injection amount (l / hr) is obtained from the following equation (3). The initial injection of the reducing agent is performed in step S4 according to the injection amount calculated in this manner. Injection amount (l / hr) = A × V _KW + B (3) where A is a constant determined by the output of the engine, B
Is a constant for the operation of the engine other than the output such as warm-up operation (which does not affect the generator load).

The injection of the reducing agent in step S4 is performed by a pump (not shown). Here, assuming that the injection amount of the reducing agent by the pump is (P _V ), the injection amount is obtained by the following equation. P _V = correction coefficient (k) × reducing agent injection amount (4) where correction coefficient k = 1 (initial value).

[0044] When the reducing agent in step S4 is injected, the measurement of the NO _X concentration of the denitration apparatus is performed in step S5.
NO _X concentration measurement step S6 due to the step S5
Is determined to be within the target NO _X concentration range indicated by. If the NO _X concentration V _NO is in the range represented by the following equations (5) and (6), the process returns to step S4. _VNO > upper limit (ppm) ... correction coefficient k '= k + 2% (5) _VNO <lower limit (ppm) ... correction coefficient k' = k-2% (6) Also, the judgment in step S6 If it is out of the range, the reducing agent injection amount is adjusted by operating the pump in the process of step S7, and the process returns to step S4. At this time, the injection amount (P _V ′) of the reducing agent by the pump operation is obtained from P _V ′ = k ′ × P _V.

FIG. 11 shows the result of controlling the NO _X concentration of the denitration apparatus as described above. When changing the load of the generator from FIG. 11, although temporarily NO _X concentration may be higher than the upper limit, it is obvious the overall control is performed satisfactorily.

In the characteristic diagram showing the control result of FIG. 11, the injection amount of the reducing agent is dramatically increased in the time period before the initial injection of the reducing agent. This is when the denitration equipment is stopped
By automatically (or manually) flowing the cooling water to the liquid feed pipe, discharging the urea remaining in the pipe and cleaning the pipe,
This is because the pipe is prevented from being clogged by urea solidification. The water remaining in the pipe is discharged by the washing at the time of the stop.

Next, a method of operating the denitration apparatus will be described with reference to the operation flowcharts shown in FIGS.
Before starting operation, each of the solenoid valves SV1, SV2, SV
3 is a closed state. Further, in the present embodiment, the reaction temperature of the denitration catalyst 14 at which the denitration treatment is favorably performed is set to a temperature higher than 320 ° C.

First, after the power of the control device 17 is turned on, the operation of the diesel engine generator 20 is started.
When the operation of the diesel engine generator 20 is started, the temperature of the denitration catalyst 14 in the reactor 11 gradually increases due to the exhaust gas G from the diesel engine 12. The temperature of the denitration catalyst 14 is measured by a thermocouple 34 provided in the reactor 11 when the power of the control device 17 is turned on.
The temperature signal from 4 is constantly monitored by the program controller 19 of the control device 17. Further, the temperature inside the vaporizer 13 is also measured by the thermocouple 31, and the temperature signal from the thermocouple 31 is constantly monitored by the controller 19 of the control device 17.

When it has been confirmed that the temperature of the denitration catalyst 14 has been raised to a temperature slightly lower than the reaction temperature (for example, 300 ° C.), the temperature in the vaporizer 13 is set such that the thermal decomposition of urea is favorably performed. The solenoid valve S is controlled based on a signal from the thermocouple 31 so as to be in a temperature range (90 to 162 ° C.).
V3 is opened, and cooling water is injected into the vaporizer 13. If the temperature in the vaporizer 13 is 90 to 162 ° C., urea is decomposed satisfactorily, but the control is easier if the temperature range is narrower.
During the operation, the solenoid valve SV3 is controlled so that the inside temperature is always between 91 ° C. and 94 ° C. to adjust the cooling water injection amount.

Further, when the temperature of the denitration catalyst 14 rises and reaches the reaction temperature (320 ° C.) of the denitration catalyst 14, the urea water pump 35 is operated and the solenoid valve SV 1 is opened to put the urea water into the vaporizer 13. Start the infusion. The urea injection amount here is an initial injection amount set in advance based on the load of the generator 20, and is adjusted by the pump 35.

During the operation of the diesel engine generator 20, according to the measurement signals from the sensor 23 and the NO _x analyzer 21, the NO contained in the exhaust gas G after the denitration processing by the controller 19 according to the control method described above. monitoring _X concentration have always done, the sensor 2323 and NO _X analyzer 2
Based on signals from the 1, the concentration of NO _X after denitration so that the target NO _X concentration (range) and controls the pump 35 to adjust the urea injection amount is performed.

Next, an operation method when the diesel engine generator 20 is stopped will be described. At the same time as the generator 20 is stopped, the solenoid valve SV1 is closed based on the operation stop contact signal of the circuit breaker (not shown) on the generator 20 side to stop the injection of the urea water. Then, when the diesel engine 12 enters a warm-up operation before stopping, the solenoid valve SV2 is opened, a part of the cooling water is caused to flow to the liquid supply pipe 28 side, and urea remaining in the liquid supply pipe 28 is discharged. The cleaning of the liquid supply pipe 28 is performed. Thereby, it is possible to prevent the piping from being clogged due to the solidification of urea. With the end of warm-up operation,
The pump 35 is stopped, the solenoid valves SV2 and SV3 are closed, and the operation of the denitration apparatus is terminated.

During operation, if the temperature of the denitration catalyst 14 falls below the reaction temperature (320 ° C. in the case of the present embodiment) due to, for example, some abnormality or the like, the injection of urea stops the denitration catalyst 14 Is lower than the cooling water injection start temperature (300 ° C. in the present embodiment),
Injection of cooling water is stopped by a signal from the controller 19, respectively.

In addition to the stop of the diesel engine 12, when the injection of the urea water is stopped, for example, when the temperature of the denitration catalyst 14 falls below the reaction temperature of the denitration catalyst 14 due to some abnormality as described above, The solenoid valve SV2 is opened to allow a part of the cooling water to flow toward the liquid feed pipe 28, to discharge the urea water remaining in the liquid feed pipe 28, to prevent the pipe from being clogged by urea solidification, and to stand by in that state. Then, appropriate measures such as waiting for the solution of the abnormality or stopping the diesel generator 20 are taken.

Further, when cleaning any of the liquid feed pipes 28 described above, the solenoid valve SV3 may be controlled to close.

In the above embodiment, urea water is used as a reducing agent, urea water is injected into the pot 25 arranged in the pipe 21 from outside the pipe, and urea is supplied by heat supplied from the exhaust gas. After being decomposed into ammonia, the reducing agent may be added to the exhaust gas by discharging from the pot 25. In this embodiment, the pot 2
5 is measured, and the pot 2 is measured based on the measured temperature.
5 by supplying water from outside the pipe to the inside of the pot 2
The temperature in 5 may be adjusted so as to be 90 ° C. or more and 162 ° C. or less, and furthermore, any one of stainless steel wire, metal mesh, zeolite powder, and zeolite honeycomb is filled in pot 25 as a thermal decomposition accelerator. You may.

[0057]

As described above, according to the present invention,
As can reliably even concentration of NO _X removed by ambient conditions, there is an advantage that by controlling the injection start time of the reducing agent can be optimally controlled reductant injection quantity.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a denitration apparatus showing an embodiment.

FIG. 2 is a graph showing the decomposition characteristics of urea.

FIG. 3 shows the decomposition characteristics of urea (with or without zeolite).

FIG. 4 is a perspective view of a filling made of stainless steel.

FIG. 5 is a schematic configuration diagram of a vaporizer.

FIG. 6 is a sectional view of a main part of a reactor provided with a shielding plate.

FIG. 7 is a process explanatory view illustrating the embodiment of the present invention.

FIG. 8 is a characteristic diagram showing a relationship between a generator load and an exhaust gas amount.

FIG. 9 is a characteristic diagram showing a relationship between a generator load and a NO _X concentration.

FIG. 10 is a flowchart illustrating the operation of the embodiment.

FIG. 11 is a characteristic diagram showing a control result.

FIG. 12 is an operation flowchart for explaining a urea water injection operation method.

[Explanation of symbols]

11 ... denitration reactor 12 ... engine 13 ... vaporizer 14 ... denitration catalyst 15 ... water pipe 16 ... tank 17 ... denitration controller 19 ... program controller 20 ... generator 21 ... NO _X analyzer 22 ... flue 23 ... sensor 24 ... shield plate 31, 34 ... thermocouple 41 ... NO _X amount estimation step 42 ... target NO _X concentration (range) setting step 43 ... reducing agent an initial injection amount calculation step 44 ... reducing agent an initial implantation step 45 ... NO _X concentration measurement Step 46: NO _X concentration comparison step 47: Reducing agent injection amount adjustment step

Continued on the front page (72) Inventor Toshiharu Sato 2-1-117 Osaki, Shinagawa-ku, Tokyo Inside the company Meidensha Corporation (72) Inventor Yuji Ogawa 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Inside the company Meidensha F term (reference) 4D048 AA06 AB02 AC04 BA03Y BA11Y BA35Y BA36Y DA01 DA02 DA10 DA13

Claims (6)

[Claims] 1. A reducing agent is added to exhaust gas discharged from an internal combustion engine and flowing through a pipe, and the exhaust gas is brought into contact with a denitration catalyst.
In denitration apparatus for removing NO _X in the exhaust gas, comprising means for measuring the temperature of the denitration catalyst, when the measured temperature of the denitration catalyst by the means has reached the reaction temperature of the denitration catalyst, the reducing agent A denitration apparatus characterized in that injection is started. 2. A carburetor is provided in an exhaust gas pipe through which exhaust gas discharged from the internal combustion engine flows, and a reducing agent is added from the carburetor to the exhaust gas flowing through the pipe, and the exhaust gas is brought into contact with a denitration catalyst. in denitration apparatus for removing NO _X in the exhaust gas has a temperature measuring means within means and the evaporator to measure the temperature of the denitration catalyst, the cooling water to the vaporizer at a reaction temperature below the denitration catalyst After the injection, the inside of the vaporizer is adjusted to a range of 90 to 162 ° C., and when the measured temperature of the denitration catalyst reaches the reaction temperature of the denitration catalyst, the injection of urea water as a reducing agent into the vaporizer is started. A denitration apparatus characterized in that the denitration is performed. 3. A carburetor is provided in an exhaust gas pipe through which exhaust gas discharged from the internal combustion engine flows, and urea water is injected into the vaporizer through a urea water injection pipe, and vaporized by heat of the exhaust gas. After the urea is thermally decomposed in the vessel and added to the exhaust gas, the urea is brought into contact with a denitration catalyst to reduce the N
A method of controlling a denitration apparatus for removing O _X, the stop of the internal combustion engine, or the temperature of the denitration catalyst is stopped either by injection of the urea water at the time of lower than the reaction temperature of the denitration catalyst, the urea water injection A method for controlling a denitration apparatus, characterized in that water is supplied to a urea water injection pipe to clean the pipe when the operation is stopped. 4. A carburetor is provided in an exhaust gas pipe through which exhaust gas discharged from the internal combustion engine flows, and a reducing agent is added from the carburetor to the exhaust gas flowing through the pipe, and then brought into contact with the denitration catalyst. it allows the control method of the NOx removal system for removing NO _X in the exhaust gas, previously set NO _X NO _X concentration target value after removal, the NO _X in the exhaust gas discharged from the operation state of the internal combustion engine Estimated, the amount of reducing agent required to remove the estimated amount of NO _X and set it as the target value was calculated as the initial addition amount, and the temperature of the denitration catalyst and the temperature in the vaporizer were measured. Then, after injecting cooling water into the vaporizer at a time point equal to or lower than the reaction temperature of the denitration catalyst, the inside of the vaporizer was adjusted to a range of 90 to 162 ° C., and the measured temperature of the denitration catalyst reached the reaction temperature of the denitration catalyst. At this point, as a reducing agent in the vaporizer To initiate the injection of Motomi, NO by contact with a denitration catalyst
_After the removal of _X , the N 2 in the exhaust gas from which NO _X was removed
The O _X concentration was measured, to compare the measured NO _X concentration and the NO _X concentration target value, and characterized in that so as to repeat the step of adding by increasing or decreasing adjusts the reducing agent adding amount based on the difference Control method of the denitration device to be performed. 5. A control method for a denitration apparatus for removing NO _{X in} exhaust gas by adding a reducing agent to exhaust gas discharged from an internal combustion engine and flowing through a pipe, and then bringing the exhaust gas into contact with a denitration catalyst. , previously set the NO _X removal NO _X concentration target value after estimates the NO _X in the exhaust gas discharged from the operation state of the internal combustion engine, to remove the NO _X of the estimated amount to the target value While calculating the amount of the reducing agent necessary for the initial addition amount, measuring the temperature of the denitration catalyst, when the measured temperature reaches the reaction temperature of the denitration catalyst, start the injection of the reducing agent, after performing removal of the NO _X by contacting with denitration catalyst, measured concentration of NO _X exhaust gas to remove NO _X, makes a comparison between the measured NO _X concentration and the NO _X density target value, the Increase or decrease the amount of reducing agent added based on the difference A method for controlling a denitration apparatus, wherein a step of adding a solution is repeated. 6. measure the NO _X concentration was measured NO _X
It makes a comparison between the concentration and the NO _X density target value, adding by increasing or decreasing adjusts the reducing agent adding amount based on the difference, according to claim 4, characterized in that repeated at the time required for this process, 6. The method for controlling a denitration apparatus according to claim 5.