JP4486858B2 - Exhaust gas treatment apparatus and treatment method for diesel internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas processing device and a processing method for a diesel internal combustion engine, and more particularly to an exhaust gas processing device and a processing method for a diesel internal combustion engine for a moving body such as a ship, an automobile, and a vehicle.

  In the case of fixed (stationary) diesel internal combustion engines used in power plant and plant boilers, as a method to remove NOX contained in exhaust gas, vanadium oxide / titanium oxide catalyst and reducing agent (ammonia) The selective catalytic reduction method using SCR (SCR method) is widely used (see, for example, Patent Documents 1 to 3). As shown in FIG. 6, an example of an exhaust gas treatment device 60 using this method is provided with a denitration reactor 62 using a denitration catalyst (vanadium oxide / titanium oxide catalyst) at the subsequent stage of the diesel internal combustion engine 61. A supply means 63 for supplying a reducing agent (ammonia) 64 is provided facing the gas introduction part 62 a of the reactor 62. Further, an oxidation catalyst reactor 65 for oxidizing CO and hydrocarbon (HC) in the exhaust gas and removing particulate matter (PM) is provided at the subsequent stage of the denitration reactor 62. Furthermore, a control means 66 for controlling the supply amount of the reducing agent 64 from the supply means 63 according to the operating state of the diesel internal combustion engine 61 is provided.

  In Europe and the United States, this exhaust gas treatment device 60 is applied to a diesel engine for a moving body such as a ship, an automobile, or a vehicle, and ammonia gas is loaded on the moving body such as an automobile.

JP 05-031327 A Japanese Patent Application Laid-Open No. 08-215544 Japanese Patent Laid-Open No. 10-033947

  By the way, in a diesel engine such as a truck or a bus, an abrupt load fluctuation occurs because an operation state suddenly changes such as acceleration / deceleration, stop, and restart. For this reason, since the NOx concentration in the exhaust gas of the diesel engine also fluctuates rapidly, there is a concern that the excessively introduced ammonia gas is released into the atmosphere as it is due to ammonia slip. Since ammonia gas is a combustible gas and has an odor, it is not preferable to load ammonia gas on a moving body equipped with a diesel engine.

  In addition, in the case of a moving body equipped with a gasoline engine, it is possible to remove unburned components and NOX components from the exhaust gas by using a three-way catalyst. However, the exhaust gas of a diesel engine contains a large amount of oxygen gas, and particularly the exhaust gas during high-power operation is as high as 500 to 600 ° C. If a three-way catalyst is used in an excess oxygen, high-temperature atmosphere such as exhaust gas from a diesel engine, the catalytic metal will deteriorate quickly due to the oxidation reaction, so apply the three-way catalyst to a moving body equipped with a diesel engine. It is difficult.

  The object of the present invention, which was created in view of the above circumstances, is to provide an exhaust gas treatment apparatus and treatment method for a diesel internal combustion engine that efficiently removes NOX contained in high-temperature exhaust gas containing a large amount of oxygen. There is to do.

In order to achieve the above object, an exhaust gas treatment device for a diesel internal combustion engine according to the present invention comprises:
In the exhaust gas treatment device connected to the latter stage of the diesel internal combustion engine and denitrating NOX contained in the exhaust gas,
A non-catalytic denitration reactor connected downstream of the diesel internal combustion engine;
A denitration reactor with a denitration catalyst connected to the latter stage of the non-catalytic denitration reactor,
A spraying means for spraying a reducing agent provided facing each gas introduction part of the non-catalytic denitration reactor and the denitration reactor;
Gas analysis means for analyzing the gas discharged from the diesel internal combustion engine, the gas passed through the non-catalytic denitration reactor, and the gas passed through the denitration reactor;
It is equipped with.

Here, it is preferable that an oxidation catalyst reactor is provided after the denitration reactor. Furthermore, it is preferable to provide a gas analysis means for analyzing the gas that has passed through the oxidation catalyst reactor .

Further, an exhaust gas treatment device for a diesel internal combustion engine according to the present invention includes:
In the exhaust gas treatment device connected to the latter stage of the diesel internal combustion engine and denitrating NOX contained in the exhaust gas,
An oxidation catalyst reactor connected downstream of the diesel internal combustion engine;
A non-catalytic denitration reactor connected downstream of the oxidation catalyst reactor;
A denitration reactor with a denitration catalyst connected to the latter stage of the non-catalytic denitration reactor,
A spraying means for spraying a reducing agent provided facing each gas introduction part of the non-catalytic denitration reactor and the denitration reactor;
Gas analysis means for analyzing the gas discharged from the diesel internal combustion engine, the gas that has passed through the oxidation catalyst reactor, the gas that has passed through the non-catalytic denitration reactor, and the gas that has passed through the denitration reactor;
It is equipped with.

These exhaust gas treatment devices preferably further comprise a control means for controlling the spray amount from the spray means based on the gas analysis value obtained by the gas analysis means.

  Moreover, it is preferable that a reducing agent is ammonium carbonate aqueous solution.

On the other hand, the exhaust gas treatment method for a diesel internal combustion engine according to the present invention is:
In an exhaust gas treatment method for denitrating NOX contained in exhaust gas discharged from a diesel internal combustion engine,
Exhaust gas discharged from the diesel internal combustion engine is introduced into a non -catalytic denitration reactor and sprayed with a first reducing agent under a non-catalytic condition to perform a first denitration treatment,
The exhaust gas after the first denitration treatment by spraying the second reducing agent is introduced into the denitration reactor according to the denitration catalyst, and facilities the second denitration treatment in contact with the denitration catalyst,
In addition, the gas before and after the first denitration treatment and the gas before and after the second denitration treatment are analyzed, and the spray amounts of the first and second reducing agents are controlled based on the gas analysis values .

Here, when the NOX concentration before the first denitration treatment is higher than the first reference NOX concentration, a predetermined amount of the first reducing agent is sprayed, and when the NOX concentration before the first denitration treatment is less than the first reference NOX concentration, the first reduction is performed. When the NOX concentration after the first denitration treatment is higher than the first reference NOX concentration without spraying the agent, the spray amount of the above-mentioned constant amount of the first reducing agent is increased, and the NOX concentration after the first denitration treatment is the first reference It is preferable to perform feedback control to reduce the spray amount of the first reducing agent when the concentration is lower than the NOX concentration . Further, when the NOX concentration before the second denitration treatment is larger than the second reference NOX concentration, a certain amount of the second reducing agent is sprayed, and when the NOX concentration before the second denitration treatment is less than the second reference NOX concentration, the second reducing agent is sprayed. When the NOx concentration after the second denitration treatment is higher than the second reference NOX concentration, the spray amount of the predetermined amount of the second reducing agent is increased, and the NOx concentration after the second denitration treatment is increased to the second reference NOX concentration. When the concentration is lower than the concentration, it is preferable to perform feedback control to reduce the spray amount of the second reducing agent .

  Moreover, it is preferable that a 1st reducing agent and a 2nd reducing agent are ammonium carbonate aqueous solution.

  According to the present invention, it is possible to effectively remove NOX from high-temperature exhaust gas containing a large amount of oxygen.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of the invention will be described with reference to the accompanying drawings.

  As shown in FIG. 5, the reaction temperature dependence of the denitration catalyst is indicated by a line 51 (indicated by a line marked with ◇ in FIG. 5). The normal denitration catalyst has a maximum denitration rate when the reaction temperature is about 320 ° C. 90%). On the other hand, the intermediate temperature denitration catalyst indicated by the line 52 (the line connected with the ■ mark in FIG. 5) has the maximum denitration rate (less than 80%) when the reaction temperature is about 400 ° C. Further, the high-temperature denitration catalyst indicated by the line 53 (line marked with ▲ in FIG. 5) has the maximum denitration rate (over 60%) when the reaction temperature is about 450 ° C.

  Here, the exhaust gas of the diesel internal combustion engine during high output operation is as high as 500 to 600 ° C. In this temperature range, a normal denitration catalyst can only obtain a denitration rate of about 40% or less, and even when a high-temperature denitration catalyst is used, a denitration rate of only about 55% or less can be obtained. A decline was inevitable.

  Therefore, as a result of intensive research by the present inventors, the denitration process is divided into two stages, the denitration is performed without using the denitration catalyst in the former stage, and the denitration is performed using the denitration catalyst in the latter stage, so that the temperature of the exhaust gas can be reduced. It has been found that a high denitration rate can be obtained even at a high temperature of 500 to 600 ° C.

  FIG. 1 shows a schematic diagram of an exhaust gas treatment device for a diesel internal combustion engine according to a preferred embodiment of the present invention.

  As shown in FIG. 1, an exhaust gas treatment device 10 according to the present embodiment is provided at the rear stage of a diesel internal combustion engine 11, and is a tubular first reaction located on the front stage side (left side in FIG. 1). The part 12a and the tubular second reaction part 12b positioned on the rear side (right side in FIG. 1) are configured. The first reaction part 12a and the second reaction part 12b shown in FIG. 1 have cone-shaped taper connection parts at both ends in the longitudinal direction (left and right direction in FIG. 1), and the central part and its vicinity expand. Although it is a diameter part, it is not limited to this in particular, A straight tube may be sufficient.

  The inside of the first reaction unit 12 a is a non-catalytic denitration reactor 13. The non-catalytic denitration reactor 13 may be a simple space, or may be one in which a metal honeycomb body is loaded in the internal space of the first reaction section 12a. By loading the metal honeycomb body, the exhaust gas G1 from the diesel internal combustion engine 11 and the reducing agent R described later are mixed more uniformly, and the temperature distribution of the mixed gas (exhaust gas G1 + reducing agent R) becomes more uniform. In addition, the denitration reaction in the non-catalytic denitration reactor 13 becomes easier to proceed.

  Inside the second reaction section 12b, a denitration reactor 14 is provided on the front side, and an oxidation catalyst reactor 15 is provided on the rear side.

  The denitration reactor 14 is a device in which a carrier carrying a denitration catalyst is loaded in the internal space of the second reaction unit 12b, and includes a reducing agent decomposition unit 14b on the front side and a denitration catalyst body 14a on the rear side. Composed. The reducing agent decomposition unit 14b prevents the reducing agent R sprayed from a supply line 16b, which will be described later, from coming into direct contact with the denitration catalyst main body 14a, and also generates a region by decomposing the reducing agent R and generating ammonia. Become. The reducing agent decomposing portion 14b may be a simple space, or may be one in which a metal honeycomb body is loaded in the internal space of the second reaction portion 12b. By loading the metal honeycomb body, the exhaust gas G2 after the first denitration treatment and the reducing agent R are more uniformly mixed, the temperature distribution of the mixed gas (exhaust gas G2 + reducing agent R) becomes more uniform, and the denitration is performed. The denitration reaction in the reactor 14 becomes easier to proceed.

  Examples of the oxidation catalyst reactor 15 include a reactor in which a honeycomb body carrying an oxidation catalyst is loaded in the internal space of the second reaction section 12b, or a DPF (Diesel Particulate Filter) having an oxidation catalyst.

  Further, the exhaust gas treatment device 10 includes a spraying means 16 for spraying the reducing agent R facing the gas introduction part 13 a of the non-catalytic denitration reactor 13 and the gas introduction part 14 c of the denitration reactor 14. The spraying means 16 is connected to the tank 16c for storing the reducing agent R, and a supply line that is connected to the tank 16c and sprays the reducing agent R to the gas introduction portions 13a and 14c of the non-catalytic denitration reactor 13 and the denitration reactor 14. 16a and 16b. Here, the spray ports of the supply line 16a for spraying the reducing agent R to the gas introduction part 13a of the non-catalytic denitration reactor 13 are multistage over the longitudinal direction of the non-catalytic denitration reactor 13 (left and right direction in FIG. 1). You may arrange in. By adjusting the spray amount of the reducing agent R from each spray port, the mixing condition of the exhaust gas G1 and the reducing agent R and the temperature of the exhaust gas G2 after the first denitration treatment can be adjusted more finely.

  Further, the exhaust gas treatment device 10 passes through the gas G1 discharged from the diesel internal combustion engine 11, the gas G2 that has passed through the non-catalytic denitration reactor 13, the gas G3 that has passed through the denitration reactor 14, and the oxidation catalyst reactor 15. The gas analysis means 17 for analyzing the gas G4 is provided. The gas analysis means 17 includes a gas sensor, is connected to gas analysis systems 17a to 17d for collecting data of the gases G1 to G4, and the gas analysis systems 17a to 17d, and gas is based on the obtained gas data. It is comprised with the main-body part 17e which performs an analysis.

  Further, the exhaust gas treatment device 10 includes a control means 18 that is electrically connected to the diesel internal combustion engine 11 and controls the gas analysis means 17 and the spray means 16. The control unit 18 controls the spray amount of the reducing agent R from the supply lines 16 a and 16 b of the spray unit 16 based on the gas analysis value obtained by the gas analysis unit 17 and / or the operation state of the diesel internal combustion engine 11. To do. The control means 18 controls the operating conditions of the diesel internal combustion engine 11 based on the gas analysis value.

  Examples of the denitration catalyst of the denitration reactor 14 include those containing V, Mo, or W as a main component, or a mixture thereof. The denitration catalyst may be any conventionally used normal denitration catalyst, intermediate temperature denitration catalyst, or high temperature denitration catalyst, but a normal denitration catalyst having a low preferred reaction temperature is desirable. The preferable reaction temperature here refers to the temperature at which the denitration rate is maximized.

  As the carrier constituent material of the denitration reactor 14, any material conventionally used as a carrier for a denitration catalyst can be applied, and it is particularly limited as long as it has excellent heat resistance, oxidation resistance, and corrosion resistance. For example, titanium oxide is used.

  As the reducing agent R, any conventionally used reducing agent for denitration can be applied, and is not particularly limited, and examples thereof include ammonia, urea, ammonium hydrogen carbonate, ammonium carbonate and the like. . If the reducing agent R is an aqueous solution or a solid material, it can be safely loaded on a moving body such as an automobile. In particular, when the reducing agent R is an aqueous solution, the supply amount is easy to control, and it is more preferable to supply it in the form of a mist because it can be easily mixed uniformly with the exhaust gas. Therefore, by using the reducing agent R in the aqueous solution, the denitration treatment reaction can be advanced more quickly than in the case of using the solid reducing agent R. Moreover, as the reducing agent R of an aqueous solution or a solid is decomposed into ammonia gas at a lower temperature, the activity as a reducing agent is higher and the denitration rate is higher. The difference in the denitration rate depending on the decomposition temperature of the reducing agent R is particularly remarkable in the non-catalytic denitration reactor 13.

Specifically, as the reducing agent R, urea (CO (NH ₂ ) ₂ ) and ammonium carbonate ((NH ₄ ) ₂ CO ₃ ) are taken as examples. The decomposition temperature of these reducing agents, non-catalytic denitration reactor Table 1 shows the denitration rate and solubility at room temperature.

  As shown in Table 1, the decomposition temperature of ammonium carbonate is 58 ° C., the decomposition temperature of urea is 160 ° C., and ammonium carbonate has a lower decomposition temperature. The lower the decomposition temperature, the higher the activity as the reducing agent R. Therefore, the denitration rate of ammonium carbonate is about 20 to 35%, the denitration rate of urea is 10 to 30%, and so on. It becomes good. Ammonium carbonate has a higher solubility, such as ammonium carbonate has a solubility of 400%, urea has a solubility of 52%. That is, the concentration of the ammonium carbonate aqueous solution can be further increased as compared with the urea aqueous solution.

  Therefore, when it is desired to obtain the same denitration rate as the urea aqueous solution by using the ammonium carbonate aqueous solution, the amount of the ammonium carbonate aqueous solution used may be smaller than the amount of the urea aqueous solution used if the same concentration aqueous solution is used. Further, when it is desired to obtain the same denitration rate as the urea aqueous solution by using the ammonium carbonate aqueous solution, the concentration of the ammonium carbonate aqueous solution may be lower than the concentration of the urea aqueous solution if the same amount of the aqueous solution is used. From the above, the reducing agent R is particularly preferably an aqueous ammonium carbonate solution.

  Next, an exhaust gas treatment method according to the present embodiment will be described with reference to the accompanying drawings.

  Since the exhaust gas of the diesel internal combustion engine 11 contains a large amount of oxygen and has a high temperature of about 500 to 600 ° C., NOx cannot be removed so much when a normal denitration catalyst is used. Therefore, a high-temperature denitration catalyst is used. It was. However, since the denitration catalyst for high temperature has a lower denitration rate than the normal denitration catalyst, NOX removal cannot be performed with high efficiency.

  The exhaust gas treatment apparatus 10 according to the present embodiment divides NOX removal into two or more stages, and performs NOX removal with an aqueous reducing agent R in the absence of a catalyst before performing NOX removal using a denitration catalyst. Has the features.

  First, as shown in FIG. 3, the high-temperature (about 500 to 600 ° C.) exhaust gas G1 discharged from the diesel internal combustion engine 11 is analyzed by a gas analysis system 17a and a main body portion 17e (NOX concentration, SOX concentration, PM). Concentration, CO concentration, HC concentration, etc.). When the NOx concentration CA of the exhaust gas G1 is larger than the first reference NOx concentration S1 (CA> S1), that is, when the branch instruction BI1 is yes, the supply is made so that CA ≦ S1 before the non-catalytic denitration reactor 13 A fixed amount (V1) of the aqueous reducing agent R (first reducing agent) is sprayed from the line 16a (step A). As a result, the exhaust gas G1 and the reducing agent R are mixed and contacted. When CA ≦ S1, that is, when the branch instruction BI1 is no, the reducing agent R is not sprayed from the supply line 16a, and the denitration process is not performed in the non-catalytic denitration reactor 13. Here, the first reference NOX concentration S1 is determined in advance based on the denitration capability of the non-catalytic denitration reactor 13. Further, the spray amount V1 is determined according to the NOX concentration CA.

By the gas-liquid contact between the exhaust gas G1 and the reducing agent R, the reducing agent R is evaporated and decomposed, and ammonia gas is generated as shown in the equation (1). At this time, by using an aqueous ammonium carbonate solution as the reducing agent R, ammonia gas can be generated with the highest reactivity (efficiency). Further, the temperature of the first mixed gas (exhaust gas G1 + ammonia gas) decreases due to the heat of vaporization when the reducing agent R evaporates. The degree of the temperature decrease can be freely adjusted within a certain range by controlling the spray amount of the reducing agent R.
(NH ₄ ) ₂ CO ₃ (or CO (NH ₂ ) ₂ ) + H ₂ O → NH ₃ (1)

The ammonia gas generated by the decomposition of the reducing agent R reacts with the exhaust gas G1 in the non-catalytic denitration reactor 13, and as shown in the formula (2), a part of NOx contained in the exhaust gas G1 is nitrogen gas. (The reduction ratio is about 10 to 30% of the total NOx amount). That is, in the non-catalytic denitration reactor 13, the exhaust gas G1 is subjected to the first denitration process to become the exhaust gas G2. The reduction ratio of NOX increases as the volume of the non-catalytic denitration reactor 13 increases, and can be freely controlled within a certain range by controlling the spray amount V1 of the reducing agent R and / or the aqueous solution concentration of the reducing agent R. Can be adjusted.
NOX + NH ₃ + O ₂ → N ₂ (2)

The exhaust gas G2 after the first denitration treatment is subjected to gas analysis by the gas analysis system 17b and the main body portion 17e. Here, when the NOX concentration CB of the exhaust gas G2 is larger than the first reference NOX concentration S1 (CB> S1), that is, when the branch instruction BI2 is yes, the spray amount V1 of the reducing agent R is increased ( stepB1), if CB ≦ S1, that is, if the branch instruction BI2 is no, feedback control is performed to reduce the spray amount V1 of the reducing agent R (step B2).

  Next, when the NOx concentration CB of the exhaust gas G2 is larger than the second reference NOx concentration S2 (CB> S2), that is, when the branch instruction BI3 is yes, CB ≦ S2 should be set before the denitration reactor 14 A fixed amount (V2) of the aqueous reducing agent R (second reducing agent) is sprayed from the supply line 16b (step C). Thereby, the exhaust gas G2 and the reducing agent R are mixed and contacted. In the case of CB ≦ S2, that is, when the branch instruction BI3 is no, the reducing agent R is not sprayed from the supply line 16b, and the exhaust gas G2 is introduced into the denitration reactor 14 as it is. Here, the second reference NOX concentration S2 is determined in advance based on the denitration capability of the denitration reactor 14. The spray amount V2 is determined according to the NOX concentration CB and / or the reaction temperature of the denitration catalyst.

  By the gas-liquid contact between the exhaust gas G2 and the reducing agent R, the reducing agent R is evaporated and decomposed, and ammonia gas is generated as shown in the equation (1). The generation of the ammonia gas is performed in the reducing agent decomposition unit 14b (ammonia generation region) provided in the front stage of the denitration reactor 14. By providing the reducing agent decomposition part 14b, the reducing agent R can be prevented from coming into direct contact with the denitration catalyst main body part 14a. In the reducing agent decomposing portion 14b, the exhaust gas G2 becomes the second mixed gas (exhaust gas G2 + ammonia gas), but the temperature is lowered again by the heat of vaporization when the reducing agent R evaporates. As a result, the temperature of the second mixed gas is sufficiently lowered to near the preferred reaction temperature of the denitration catalyst. Furthermore, since the reducing agent decomposition unit 14b can be regarded as a non-catalytic denitration reactor, a part of the exhaust gas G2 is also denitrated in the reducing agent decomposition unit 14b.

  Next, the ammonia gas generated in the reducing agent decomposition unit 14b is introduced into the denitration reactor 14 while being mixed with the exhaust gas G2. Under the denitration catalyst, the exhaust gas G2 reacts with ammonia gas, and as shown in the equation (2), most of the NOx contained in the exhaust gas G2 is reduced to nitrogen gas. That is, in the denitration reactor 14, the second denitration process is performed on the exhaust gas G2, and the exhaust gas G3 is obtained. The reduction rate of NOX increases as the denitration capacity of the denitration reactor 14 increases, and can be freely controlled within a certain range by controlling the spray amount V2 of the reducing agent R and / or the aqueous solution concentration of the reducing agent R. Can be adjusted.

The exhaust gas G3 after the second denitration treatment is subjected to gas analysis by the gas analysis system 17c and the main body portion 17e. Here, when the NOX concentration CC of the exhaust gas G3 is larger than the second reference NOX concentration S2 (CC> S2), that is, when the branch instruction BI4 is yes, the spray amount V2 of the reducing agent R is increased ( stepD1), when CC ≦ S2, that is, when the branch instruction BI4 is no, feedback control is performed to reduce the spray amount V2 of the reducing agent R (stepD2).

Thereafter, the exhaust gas G3 is introduced into the oxidation catalyst reactor 15, and the CO, HC, etc. contained in the exhaust gas G3 are oxidized (step E) as shown in the equations (3) and (4). At this time, PM may be removed and removed using a filter, DPF, or the like.
CO + O ₂ → CO ₂ (3)
HC + O ₂ → CO ₂ (4)

  Finally, the oxidized exhaust gas G4 is discharged into the atmosphere (step F). At this time, the gas analysis of the exhaust gas G4 may be performed using the gas analysis system 17d and the main body 17e. Based on this gas analysis value, it is possible to know the degree of deterioration of the performance of the oxidation catalyst reactor 15.

  Further, feedback control of the combustion conditions of the diesel internal combustion engine 11 may be performed based on each gas analysis value obtained using the gas analysis systems 17a to 17d and the main body portion 17e.

  Furthermore, operation data is accumulated by operating the exhaust gas treatment device 10 for a long period of time based on the exhaust gas treatment method according to the present embodiment. The operation data may be obtained in advance, and the spray amounts V1 and V2 of the reducing agent R may be directly controlled in accordance with the operation state of the diesel internal combustion engine 11.

  Further, instead of controlling the spray amounts V1 and V2 while keeping the aqueous solution concentration of the reducing agent R constant, the aqueous solution concentration may be controlled while keeping the spray amounts V1 and V2 of the reducing agent R constant. .

  As described above, the exhaust gas treatment apparatus 10 according to the present embodiment divides NOX removal into two or more stages, and before performing NOX removal using the denitration catalyst, the reducing agent R in the form of an aqueous solution under no catalyst. By performing the NOx removal by the NOx removal, the NOx removal can be efficiently performed even with the high-temperature exhaust gas G1 containing a large amount of oxygen.

  In addition, the diesel engine mounted on the moving body undergoes a sudden load fluctuation due to a sudden change in the operating condition such as acceleration / deceleration, stop, and restart. However, according to the exhaust gas processing apparatus 10 according to the present embodiment, exhaust gas is analyzed by performing gas analysis in each part of the apparatus to measure the NOX concentration and supplying an appropriate amount of reducing agent R in each part of the apparatus. The NOX content contained therein can be efficiently reduced and removed.

  Furthermore, by using an aqueous solution as the reducing agent R, it is possible to quickly cope with sudden load fluctuations. In particular, by using an aqueous ammonium carbonate solution as the reducing agent R, it is possible to more efficiently reduce and remove the NOx content contained in the exhaust gas as compared with a conventionally used urea aqueous solution.

  The exhaust gas treatment apparatus 10 according to the present embodiment can be applied to a stationary or mobile diesel internal combustion engine, and is particularly mounted on a moving body (agricultural equipment such as a ship, an automobile, a tiller or a tractor). It is suitable as an exhaust gas treatment device for a diesel engine.

  Next, another embodiment of the present invention will be described with reference to the accompanying drawings.

  A schematic diagram of an exhaust gas treatment device for a diesel internal combustion engine according to another preferred embodiment of the present invention is shown in FIG. In addition, the same code | symbol is attached | subjected to the member similar to FIG. 1, and description is abbreviate | omitted about these members.

  The exhaust gas treatment apparatus 10 according to the previous embodiment shown in FIG. 1 has an oxidation catalyst reactor 15 at the rear stage of the denitration reactor 14.

  As shown in FIG. 2, the exhaust gas processing apparatus 20 according to the present embodiment has the same basic configuration as the exhaust gas processing apparatus 10 according to the previous embodiment. The difference between the exhaust gas treatment device 20 and the exhaust gas treatment device 10 is the position of the oxidation catalyst reactor. The exhaust gas treatment device 20 is provided between the diesel internal combustion engine 11 and the non-catalytic denitration reactor 13. It has a reactor 25.

  The exhaust gas treatment device 20 includes a gas G1 discharged from the diesel internal combustion engine 11, a gas G5 that has passed through the oxidation catalyst reactor 25, a gas G6 that has passed through the non-catalytic denitration reactor 13, and a gas that has passed through the denitration reactor 14. Gas analysis means 27 for performing G7 analysis is provided. The gas analysis means 27 includes a gas sensor, and is connected to the gas analysis systems 27d, 17a to 17c for collecting data of the gases G1, G5 to G7, and the gas analysis systems 27d, 17a to 17c. And a main body 17e that performs gas analysis based on the gas data.

  Further, the exhaust gas processing device 20 includes a control means 28 that is electrically connected to the diesel internal combustion engine 11 and controls the gas analysis means 27 and the spray means 16. The control means 28 controls the spray amount of the reducing agent R from the supply lines 16 a and 16 b of the spray means 16 based on the gas analysis value obtained by the gas analysis means 27 and / or the operation status of the diesel internal combustion engine 11. To do. The control means 18 controls the operating conditions of the diesel internal combustion engine 11 based on the gas analysis value.

  Next, an exhaust gas treatment method according to the present embodiment will be described with reference to the accompanying drawings.

  First, as shown in FIG. 4, the high-temperature (about 500 to 600 ° C.) exhaust gas G1 discharged from the diesel internal combustion engine 11 is introduced into the oxidation catalyst reactor 25, and is expressed by Equations (3) and (4). As shown, CO and HC contained in the exhaust gas G1 are oxidized, and PM contained in the exhaust gas G1 is removed (step E).

  The exhaust gas G5 subjected to oxidation and dust removal is subjected to gas analysis by the gas analysis system 17a and the main body portion 17e. Thereafter, the exhaust gas is processed in the same procedure as the exhaust gas processing method according to the previous embodiment. The exhaust gas is processed in the order of exhaust gas G5 → exhaust gas G6 → exhaust gas G7, and then discharged into the atmosphere (step F).

  Here, in the front stage and the rear stage of the oxidation catalyst reactor 25, the gas analysis values of the exhaust gases G1 and G5 are obtained by performing the gas analysis of the exhaust gases G1 and G5 using the gas analysis systems 27d and 17a and the main body portion 17e. Based on this, it is possible to know the degree of deterioration of the performance of the oxidation catalyst reactor 25.

  Also in the exhaust gas processing apparatus 20 according to the present embodiment, the same effects as those of the exhaust gas processing apparatus 10 according to the previous embodiment shown in FIG. 1 can be obtained.

  In recent years, a dust removing means such as a filter is often provided immediately after the exhaust gas discharge part of the diesel internal combustion engine 11. For this reason, the exhaust gas treatment device 20 according to the present embodiment has an apparatus volume that is greater than that of the exhaust gas treatment device 10 by incorporating an oxidation catalyst into the dust removing means and integrating them into the oxidation catalyst reactor 25. Can be reduced.

  As described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various other things are assumed.

  Next, although this invention is demonstrated based on an Example, this invention is not limited to this Example.

  The exhaust gas treatment device 10 shown in FIG. 1 was connected to the diesel generator, and NOX removal of the exhaust gas was performed. NOX removal was performed in two cases, using an ammonium carbonate aqueous solution and a urea aqueous solution as the reducing agent R. The NOx concentration of the initial exhaust gas was 200 ppm, and the concentration of each aqueous solution was 10 wt%.

  Table 2 shows the difference in the denitration rate due to the difference in the reducing agent. The denitration rate was measured for the exhaust gas after the first denitration treatment (exhaust gas after passing through the non-catalytic denitration reactor) and the exhaust gas after the second denitration treatment (exhaust gas after passing through the denitration reactor).

  As shown in Table 2, the denitration rate of the exhaust gas after the first denitration treatment was 28% when the ammonium carbonate aqueous solution was used as the reducing agent, and 19% when the urea aqueous solution was used as the reducing agent. Further, the denitration rate of the exhaust gas after the second denitration treatment was 84% when the ammonium carbonate aqueous solution was used as the reducing agent, and 58% when the urea aqueous solution was used as the reducing agent.

  From the above, it was possible to remove about 20-30% of the total amount of NOx contained in the exhaust gas by performing denitration with a non-catalytic denitration reactor in the previous stage of the denitration reactor.

  It was also confirmed that the use of an aqueous ammonium carbonate solution as the reducing agent improved both the NOx removal rates of the first and second denitration treatments by 40% or more compared to the case of using an aqueous urea solution as the reducing agent. .

1 is a schematic diagram of an exhaust gas treatment device for a diesel internal combustion engine according to a preferred embodiment of the present invention. It is a schematic diagram of the exhaust-gas processing apparatus of the diesel internal combustion engine which concerns on other preferable one Embodiment of this invention. It is a figure which shows the flow of the exhaust-gas processing method of the exhaust-gas processing apparatus of FIG. It is a figure which shows the flow of the exhaust-gas processing method of the exhaust-gas processing apparatus of FIG. It is a figure which shows the relationship between the reaction temperature of a denitration catalyst, and a denitration rate. It is a schematic diagram of the exhaust gas processing apparatus of the conventional diesel internal combustion engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Exhaust gas treatment apparatus 11 Diesel internal combustion engine 13 Non-catalytic denitration reactor 13a Gas introduction part 14 Denitration reactor 14a Gas introduction part 16 Spray means G1 Exhaust gas R Reducing agent

Claims (10)

In the exhaust gas treatment device connected to the latter stage of the diesel internal combustion engine and denitrating NOX contained in the exhaust gas,
A non-catalytic denitration reactor connected downstream of the diesel internal combustion engine;
A denitration reactor with a denitration catalyst connected to the latter stage of the non-catalytic denitration reactor,
A spraying means for spraying a reducing agent provided facing each gas introduction part of the non-catalytic denitration reactor and the denitration reactor;
Gas analysis means for analyzing the gas discharged from the diesel internal combustion engine, the gas passed through the non-catalytic denitration reactor, and the gas passed through the denitration reactor;
An exhaust gas treatment device for a diesel internal combustion engine, comprising:   The exhaust gas treatment apparatus for a diesel internal combustion engine according to claim 1, further comprising an oxidation catalyst reactor at a stage subsequent to the denitration reactor. Exhaust gas treatment apparatus for a diesel internal combustion engine according to claim 2, further comprising a gas analysis means for analyzing a gas that has passed through the upper hexane catalyst reactor. In the exhaust gas treatment device connected to the latter stage of the diesel internal combustion engine and denitrating NOX contained in the exhaust gas,
An oxidation catalyst reactor connected downstream of the diesel internal combustion engine;
A non-catalytic denitration reactor connected downstream of the oxidation catalyst reactor;
A denitration reactor with a denitration catalyst connected to the latter stage of the non-catalytic denitration reactor,
A spraying means for spraying a reducing agent provided facing each gas introduction part of the non-catalytic denitration reactor and the denitration reactor;
Gas discharged from the diesel engine, and the gas passing through the oxidation catalyst reactor, the gas passing through the non-catalytic denitration reactor, and a gas analysis means for analyzing a gas that has passed through the denitration reactor,
An exhaust gas treatment device for a diesel internal combustion engine, comprising: The exhaust gas treatment apparatus for a diesel internal combustion engine according to any one of claims 1 to 4, further comprising a control means for controlling a spray amount from the spray means based on a gas analysis value obtained by the gas analysis means. The exhaust gas treatment device for a diesel internal combustion engine according to any one of claims 1 to 5, wherein the reducing agent is an aqueous ammonium carbonate solution. In an exhaust gas treatment method for denitrating NOX contained in exhaust gas discharged from a diesel internal combustion engine,
The exhaust gas discharged from the diesel internal combustion engine is introduced into a non-catalytic denitration reactor and sprayed with a first reducing agent in the absence of a catalyst to perform a first denitration treatment,
The exhaust gas after the first denitration treatment is introduced into the denitration reactor using the denitration catalyst and sprayed with the second reducing agent, and is contacted with the denitration catalyst to perform the second denitration treatment.
In addition, the gas before and after the first denitration treatment and the gas before and after the second denitration treatment are analyzed, and the spray amounts of the first and second reducing agents are controlled based on the gas analysis values. An exhaust gas treatment method for a diesel internal combustion engine. When the NOX concentration before the first denitration treatment is larger than the first reference NOX concentration, a predetermined amount of the first reducing agent is sprayed, and when the NOX concentration before the first denitration treatment is less than or equal to the first reference NOX concentration, the first reducing agent is sprayed. Without spraying
When the NOx concentration after the first denitration treatment is greater than the first reference NOx concentration, the spray amount of the first reducing agent is increased, and when the NOx concentration after the first denitration treatment is less than the first reference NOx concentration, The exhaust gas treatment method for a diesel internal combustion engine according to claim 7, wherein feedback control for reducing the spray amount of 1 reducing agent is performed. When the NOX concentration before the second denitration treatment is higher than the second reference NOX concentration, a predetermined amount of the second reducing agent is sprayed. When the NOX concentration before the second denitration treatment is less than or equal to the second reference NOX concentration, the second reducing agent is sprayed. Without spraying
When the NOX concentration after the second denitration treatment is larger than the second reference NOX concentration, the spray amount of the predetermined amount of the second reducing agent is increased, and when the NOx concentration after the second denitration treatment is less than the second reference NOX concentration, The exhaust gas treatment method for a diesel internal combustion engine according to claim 7 or 8, wherein feedback control for reducing the spray amount of the reducing agent is performed. The exhaust gas treatment method for a diesel internal combustion engine according to any one of claims 7 to 9, wherein the first reducing agent and the second reducing agent are aqueous ammonium carbonate solutions.

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