JP2014001737A - Exhaust gas purifying method and exhaust gas purifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas purifying method with which, even when exhaust gas temperature is a low temperature equal to or lower than 200°C, nitrogen oxide in exhaust gas can be removed efficiently.SOLUTION: As a reduction catalyst for reducing and removing nitrogen oxide in exhaust gas, a catalyst having perovskite type complex oxide represented by a general formula La(FeNb)PdO(wherein 0.30≤y≤0.95 and 0.01≤z≤0.10 are satisfied) is used for adjusting the exhaust gas in such a manner that an oxygen gas concentration in the exhaust gas is made less than a predetermined value. Hydrogen is added to the exhaust gas in such a manner that the amount of reaction with the nitrogen oxide becomes more than the amount of reaction with oxygen gas correspondingly to the quantity of nitrogen oxide absorbed by the reduction catalyst and temperature of the exhaust gas, and the exhaust gas is brought into contact with the reduction catalyst, thereby reducing and removing the nitrogen oxide in the exhaust gas.

Description

  The present invention relates to an exhaust gas purification method and an exhaust gas purification device, and in particular, an exhaust gas purification method effective for use in removing nitrogen oxides, hydrocarbons, and carbon monoxide in exhaust gas discharged from diesel engines, combustion equipment, and the like. The present invention relates to an exhaust gas purification device.

  As an exhaust gas treatment catalyst for removing nitrogen oxides in exhaust gas discharged from a diesel engine or the like, for example, a honeycomb substrate is coated with a carrier on which a noble metal and a storage material that stores NOx are supported Is mentioned. Examples of the carrier include alumina, ceria, zirconia, and titania. Moreover, platinum, rhodium, and palladium are mentioned as said noble metal. Examples of the occlusion material include alkali metals such as potassium and alkaline earth metals such as barium.

  By installing such an exhaust gas treatment catalyst in an exhaust pipe of a diesel engine or the like, nitrogen oxides in the exhaust gas are removed. That is, when the exhaust gas is in a lean state (oxygen concentration is high (3% or more)), NO and oxygen react on the noble metal to generate NOx, and this NOx is occluded in the occlusion material.

  Also, create a reducing atmosphere in which exhaust gas is rich (oxygen concentration is low) by spraying organic compounds and fuels that serve as reducing agents on the exhaust gas treatment catalyst, or by increasing the amount of fuel injected by the engine. Thus, the NOx stored in the storage material moves onto the noble metal, and this NOx reacts with hydrocarbons and CO to produce water, nitrogen and carbon dioxide, which are discharged. Therefore, in the exhaust gas treatment catalyst, occlusion of nitrogen oxides and discharge of the occluded nitrogen oxides as nitrogen (catalyst regeneration treatment) are repeatedly performed.

  However, the basic metal (alkali metal, alkaline earth metal) of the above-described occlusion material is poisoned by sulfur contained in the fuel, and the occlusion performance of the nitrogen oxide is lowered. Sulfur is desorbed and removed by exposing the sulfur-poisoned occlusion material to a reducing atmosphere at a high temperature. The reducing atmosphere can be created by, for example, fuel injection or exhaust gas temperature increase, but the fuel consumption is deteriorated by such operation. Moreover, since the catalyst is exposed to a high temperature, thermal degradation occurs. Furthermore, the active metal is sintered and the performance of the exhaust gas treatment catalyst is degraded. Furthermore, when a diesel particulate filter (DPF) that removes particulate matter (PM) contained in the exhaust gas is installed in the exhaust pipe, the PM collected by the DPF is removed by combustion, and the exhaust gas treatment catalyst is hot. The chance of being exposed to increases.

  By the way, as a catalyst having high sulfur resistance and heat resistance in a denitration catalyst such as a NOx storage catalyst, various exhaust gas treatment catalysts containing a perovskite catalyst, so-called composite oxide, have been developed (see, for example, Patent Document 1). .

JP 2006-346602 A

  Although the exhaust gas treatment catalyst containing the composite oxide can remove nitrogen oxides contained in the exhaust gas at a high temperature where the exhaust gas temperature exceeds 200 ° C., even if the exhaust gas temperature is a low temperature of 200 ° C. or less. It has been desired to further improve the efficiency of removing nitrogen oxides in exhaust gas.

  From the above, the present invention has been made to solve the above-described problems, and can efficiently remove nitrogen oxides in exhaust gas even when the exhaust gas temperature is as low as 200 ° C. or lower. An object of the present invention is to provide an exhaust gas purification method and an exhaust gas purification device that can be used.

The exhaust gas purification method according to the first invention for solving the above-described problem is as follows.
As a reduction catalyst for reducing and removing nitrogen oxides in exhaust gas, a general formula: La (Fe _y Nb _1-yz ) Pd _z O ₃ (where 0.30 ≦ y ≦ 0.95, 0.01 ≦ z ≦ 0.10.) Using a catalyst having a perovskite-type composite oxide represented by
The exhaust gas is adjusted so that the oxygen gas concentration in the exhaust gas is less than a predetermined value, and the reaction with the oxygen gas corresponds to the storage amount of nitrogen oxides stored in the reduction catalyst and the temperature of the exhaust gas. Hydrogen is added to the exhaust gas so that the amount of reaction with the nitrogen oxide is larger than the amount, and the nitrogen oxide in the exhaust gas is reduced and removed by bringing the exhaust gas into contact with the reduction catalyst.

The exhaust gas purification method according to the second invention for solving the above-described problem is as follows.
An exhaust gas purification method according to a first invention,
In the general formula, 1-yz is 0.05 or more and 0.69 or less.

An exhaust gas purification method according to the third invention for solving the above-described problem is as follows.
An exhaust gas purification method according to the first or second invention,
The hydrogen addition time is set to 9 seconds to 15 seconds.

An exhaust gas purification method according to the fourth invention for solving the above-described problem is as follows.
An exhaust gas purification method according to any one of the first to third inventions,
The hydrogen concentration is 4%.

An exhaust gas purification apparatus according to the fifth invention for solving the above-described problem is
An exhaust gas purification device that reduces and purifies nitrogen oxides in exhaust gas,
A collecting means for collecting particulate matter in the exhaust gas;
An exhaust gas treatment catalyst disposed downstream of the collecting means in the flow direction of the exhaust gas;
Hydrogen supply means for supplying hydrogen to the exhaust gas treatment catalyst upstream of the exhaust gas flow direction,
The exhaust gas treatment catalyst, the general _{formula: La (Fe y Nb 1-} yz) Pd z O 3 ( where a 0.30 ≦ y ≦ 0.95, is 0.01 ≦ z ≦ 0.10.) It is a catalyst which has the perovskite type complex oxide represented by these.

An exhaust gas purifying apparatus according to a sixth invention for solving the above-described problem is
An exhaust gas purifying apparatus according to a fifth invention,
In the general formula, 1-yz is 0.05 or more and 0.69 or less.

The exhaust gas purifying apparatus according to the seventh invention for solving the above-described problem is
An exhaust gas purification apparatus according to the fifth or sixth invention,
It further comprises an oxidation catalyst disposed upstream of the collecting means in the flow direction of the exhaust gas.

According to the exhaust gas purification method of the first invention, as a reduction catalyst for reducing and removing nitrogen oxides in exhaust gas, the general formula: La (Fe _y Nb _1-yz ) Pd _z O ₃ (provided that 0.30 ≦ y ≦ 0.95 and 0.01 ≦ z ≦ 0.10), and the oxygen gas concentration in the exhaust gas becomes less than a predetermined value using a catalyst having a perovskite type composite oxide represented by The amount of reaction with the nitrogen oxide is greater than the amount of reaction with the oxygen gas corresponding to the amount of nitrogen oxide stored in the reduction catalyst and the temperature of the exhaust gas. Hydrogen is added to the exhaust gas so as to increase, and nitrogen oxides in the exhaust gas are reduced and removed by contacting with the reduction catalyst, so even if the exhaust gas temperature is as low as 200 ° C. or less, the reduction catalyst Balances the denitration reaction and combustion reaction of It can act efficiently reducing agent under catalyst.

  According to the exhaust gas purification methods according to the third and fourth inventions, as in the exhaust gas purification method according to the first invention, even if the exhaust gas temperature is a low temperature of 200 ° C. or less, the denitration reaction and the combustion reaction with the reduction catalyst. Thus, the reducing agent can be made to act efficiently with the reduction catalyst.

According to the exhaust gas purification apparatus of the fifth aspect of the present invention, there is provided an exhaust gas purification apparatus that reduces and purifies nitrogen oxides in the exhaust gas, the collecting means for collecting the particulate matter in the exhaust gas, and the capture unit An exhaust gas treatment catalyst disposed downstream of the exhaust gas in the flow direction of the exhaust gas; and hydrogen supply means for supplying hydrogen upstream of the exhaust gas treatment catalyst in the flow direction of the exhaust gas, the exhaust gas treatment catalyst comprising: The general formula: La (Fe _y Nb _1-yz ) Pd _z O ₃ (where 0.30 ≦ y ≦ 0.95 and 0.01 ≦ z ≦ 0.10). By being a catalyst having a perovskite-type composite oxide, the collecting means can collect and remove particulate matter in the exhaust gas upstream of the exhaust gas treatment catalyst in the exhaust gas flow direction. Exhaust gas treatment catalyst by substance adhesion It is possible to suppress the aged deterioration, it is possible to suppress an increase in operating costs.

  According to the exhaust gas purification apparatus of the seventh aspect of the present invention, the exhaust gas purification apparatus further includes an oxidation catalyst arranged on the upstream side of the collection means in the flow direction of the exhaust gas. In addition to having an advantageous effect, the oxidation catalyst can oxidize unburned hydrocarbons, carbon monoxide, nitrogen oxides and graphite carbon components in the exhaust gas upstream of the exhaust gas distribution direction of the exhaust gas treatment catalyst. Thus, the reducing agent can be made to act efficiently.

It is a graph which shows the relationship between the denitration rate of the exhaust gas treatment catalyst which concerns on one reference form of this invention, and exhaust gas temperature. It is a schematic block diagram of the exhaust gas purification apparatus which concerns on 1st embodiment of this invention. It is a schematic block diagram of the exhaust gas purification apparatus which concerns on 2nd embodiment of this invention.

  Hereinafter, an exhaust gas purification method and an exhaust gas purification device according to the present invention will be specifically described in each embodiment.

  The exhaust gas treatment catalyst according to one reference form of the present invention has a catalytic ability to purify the exhaust gas by storing nitrogen oxide in the exhaust gas and reducing the nitrogen oxide stored by contact with the reducing agent to nitrogen. It is a catalyst containing a perovskite-type composite oxide, specifically, a composite oxide represented by the following general formula (1).

A (B _y B ′ _(1-yz) ) (PM) _z O ₃ (1)
However, the A component is lanthanum (La), the B component is iron (Fe), the B ′ component is niobium (Nb), and the PM (noble metal) is palladium.

In the general formula (1) described above, y is in the range of 0.30 to 0.95, and z is in the range of 0.01 to 0.10. Preferably, y is in the range of 0.63 to 0.88, and z is in the range of 0.02 to 0.04. More preferably, y is 0.776 and z is 0.03. In other words, the niobium content is in the range from 0.05 mol to 0.69 mol, and preferably in the range from 0.09 mol to 0.35 mol. When the niobium content is less than 0.05 mol, the reaction between NOx occluded by acting on palladium and H ₂ gas (reducing agent) is not promoted. On the other hand, when the palladium content is less than 0.01 mol, the effect of containing the noble metal cannot be expressed. On the other hand, if the palladium content exceeds 0.10, the cost merit is reduced.

  By contacting the exhaust gas containing nitrogen oxides with the exhaust gas treatment catalyst containing the composite oxide represented by the general formula (1) described above, even if the exhaust gas temperature is 200 ° C. or lower, It is possible to balance the denitration reaction and the combustion reaction so that the reducing agent acts more reliably with the catalyst (specific examples will be described later). Examples of a method for preparing such an exhaust gas treatment catalyst include the following two types (liquid phase method and solid phase method), but are not particularly limited thereto.

<Liquid phase method>
In this method, as a starting material, a metal salt solution containing La, Fe, and Pd, and an organic acid aqueous solution (acetic acid, oxalic acid, amino acid, niobium dioxide aqueous solution of hydrogen peroxide or niobium hydrogen oxalate) containing the Nb component described above. Aqueous solution). However, the above-mentioned starting materials are prepared in an aqueous solution having an arbitrary concentration before the following preparation process.

[Preparation of niobium hydrogen oxalate aqueous solution]
The above-described niobium hydrogen oxalate aqueous solution is prepared, for example, as follows.
Distilled water was added to niobium hydrogen oxalate n hydrate (10.7 wt% in terms of Nb ₂ O ₅ ), sealed, and then stirred at room temperature for 48 hours to dissolve. Next, distilled water was added so that it might become 0.04 mol / L in Nb conversion, and the solution after concentration adjustment was stored in a sealed glass bottle.

<Preparation procedure>
(1) First, each of the above-mentioned metal salt aqueous solutions and organic compounds such as an organic acid aqueous solution are weighed so as to have a predetermined element ratio.
(2) Subsequently, each weighed aqueous metal salt solution is added to the reactor and mixed. This liquid is hereinafter referred to as a mixed liquid.
(3) Subsequently, the organic acid aqueous solution described above is gradually added while stirring the mixed solution, and stirred until the entire amount is dissolved.
(4) Subsequently, the water is evaporated and concentrated by an evaporator.
(5) Subsequently, it is put in a dryer, and the atmosphere in the vessel is dried at 250 ° C. to make a powder.
(6) Subsequently, this powder is pulverized in a mortar, and then mixed with a binder as necessary to be molded, and calcined at 600 to 1200 ° C. for 5 hours to obtain an exhaust gas treatment catalyst.

<Solid phase method>
In this method, an oxide or carbonate containing La, Fe, Nb, and Pd, a dispersant, and various solvents (H ₂ O, ethanol, methanol, etc.) are used as starting materials. However, the above-described starting materials are sufficiently dried by placing them in a dryer having an internal atmosphere of 120 ° C. before the following preparation steps.

<Preparation procedure>
(1) First, various starting materials (dried at 120 ° C.), a dispersant, and a solvent are weighed (the amount of the dispersant is 5 wt% of the powder weight, and the solvent is the same amount as the raw material powder).
(2) Subsequently, various starting materials weighed, a dispersant, a solvent, and a ball for grinding are placed in a container.
(3) Subsequently, pulverization, stirring, and mixing are performed in a ball mill.
(4) Subsequently, the water is evaporated and concentrated by an evaporator.
(5) Subsequently, it is put in a dryer, and the atmosphere in the vessel is dried at 120 ° C. to make a powder.
(6) Subsequently, this powder is pulverized in a mortar, then mixed with a binder as necessary, and then shaped and calcined at 800 to 1200 ° C. for 5 hours to obtain an exhaust gas treatment catalyst.

  As the binder used in the above-described method for preparing an exhaust gas treatment catalyst, a binder containing cerium oxide as a main component is particularly effective.

  Since the exhaust gas treatment catalyst is composed of the composite oxide represented by the general formula (1) described above, the denitration reaction and the combustion reaction at the exhaust gas treatment catalyst can be performed even when the exhaust gas temperature is a low temperature of 200 ° C. or less. The reducing agent (hydrogen) can be made to act efficiently with the exhaust gas treatment catalyst (a specific example will be described later).

[Reference example]
Although the confirmation test performed in order to confirm the effect of the exhaust gas treatment catalyst according to the above-described reference embodiment will be described below, this reference example is not limited only to the confirmation test described below.

[Preparation of Specimen 1]
Lanthanum nitrate hexahydrate, iron nitrate nonahydrate, the above-mentioned niobium hydrogen oxalate aqueous solution and palladium nitrate solution (Pd = 50 g / L) were respectively added with water at 1 mol / L, 0.5 mol / L, Prepare solutions with concentrations of 0.04 mol / L and 0.05 mol / L.

  Subsequently, a predetermined amount of the solution prepared to a predetermined concentration is taken. Specifically, the amount of lanthanum nitrate aqueous solution is 100 ml, the amount of iron nitrate aqueous solution is 155 ml, the amount of niobium hydrogen oxalate aqueous solution is 485 ml, the amount of palladium nitrate aqueous solution is 60 ml, and the molar ratio of each metal ion (La: Fe: : Nb: Pd) is 1: 0.776: 0.194: 0.03.

  First, an aqueous lanthanum nitrate solution and an aqueous iron nitrate solution are mixed and sealed, and then the mixture is heated to 50 ° C. with stirring. After reaching 50 ° C., 120 g of glycine is added and dissolved. Further, an aqueous solution of palladium nitrate and an aqueous solution of niobium hydrogen oxalate are sequentially added, and then heated to 60 ° C. After reaching 60 ° C., the mixture is stirred at 60 ° C. for 2 hours while being sealed.

Furthermore, the mixed solution was concentrated by a rotary evaporator to be gelled. The gelled sample is put in a dryer, heat-treated at 220 ° C., pulverized, and then baked in air at 400 ° C. for 5 hours. After further pulverizing the obtained powder, the sample was calcined at 700 ° C. for 5 hours to obtain 20 g of an exhaust gas treatment catalyst having a composite oxide (LaFe _0.776 Nb _0.194 Pd _0.03 O ₃ ). The obtained exhaust gas treatment catalyst was designated as test body 1.

[Preparation of Specimen 2]
A nitrogen oxide storage catalyst (test body 2) was obtained by applying or supporting a noble metal containing at least one of barium carbonate and platinum, palladium, and rhodium on a base material made of ceria, zirconia, or alumina. .

[Confirmation test]
[Denitration performance evaluation test]
In this test, the denitration performance of the test bodies 1 and 2 was evaluated.

  Exhaust gas was circulated under the evaluation condition 1 shown in Table 1 below with respect to the test body 1, and the denitration performance was measured. The exhaust gas was circulated through the test body 1 under the evaluation condition 2 shown in Table 1 below, and the denitration performance was measured. Exhaust gas was circulated through the test body 1 under the evaluation condition 3 shown in Table 1 below, and the denitration performance was measured.

  Further, exhaust gas was circulated through the test body 2 under the evaluation condition 1 shown in Table 1 below, and the denitration performance was measured.

  In Table 1, space velocity indicates fluid flow rate / catalyst volume.

The test results 1, 2, 3, and 4 described above are shown in FIG.
In FIG. 1, the denitration rate is an average of the denitration rate when the exhaust gas (processing gas) is in a lean state and the denitration rate when the exhaust gas (processing gas) is in a rich state.

  The exhaust gas temperature and denitration rate in test result 1 (test body 1, evaluation condition 1) are 29.8% at 150 ° C, 28.5% at 200 ° C, 51.6% at 250 ° C, and 50.7 at 300 ° C. %, 350 ° C. and 55.4%.

  The exhaust gas temperature and denitration rate in test result 2 (test body 1, evaluation condition 2) are 41.8% at 150 ° C, 31.2% at 200 ° C, 54.9% at 250 ° C, and 60.4 at 300 ° C. % At 350 ° C. and 62.4%.

  The exhaust gas temperature and denitration rate in test result 3 (test body 1, evaluation condition 3) are 41.3% at 150 ° C., 37.2% at 200 ° C., 61.2% at 250 ° C., and 71.5 at 300 ° C. %, 350 ° C. and 75.4%.

  The exhaust gas temperature and denitration rate in test result 4 (test body 2, evaluation condition 1) are 0% at 150 ° C, 23% at 200 ° C, 81% at 250 ° C, 85% at 300 ° C, and 88% at 350 ° C. there were.

When the test results 1 to 3 were compared with the test result 4, it was found that the denitration rate in the test results 1 to 3 was higher than the denitration rate in the test result 4 when the exhaust gas temperature was 150 ° C. and 200 ° C. In other words, when the exhaust gas temperature is in the range of 150 ° C. or higher and 200 ° C. or lower, the denitration rate when hydrogen is brought into contact with the composite oxide represented by La (Fe _y Nb _(1-yz) ) Pd _z O _3. However, it turned out that it becomes higher than the denitration rate when hydrogen is made to contact the conventional nitrogen oxide storage catalyst.

Therefore, according to the exhaust gas treatment catalyst according to the present embodiment, La (Fe _y Nb _(1-yz) ) Pd _z O ₃ (where 0.30 ≦ y ≦ 0.95 and 0.01 ≦ z ≦ 0.10)), by using hydrogen as a reducing agent, even if the exhaust gas temperature is a low temperature of 200 ° C. or less, the denitration reaction and combustion in the exhaust gas treatment catalyst The reaction is balanced and the reducing agent can be made to act efficiently with the exhaust gas treatment catalyst. As a result, compared with a conventional nitrogen oxide storage catalyst in which a noble metal containing at least one of barium carbonate and platinum, palladium, and rhodium is applied or supported on a base material made of ceria, zirconia, or alumina. The denitration rate can be improved. Furthermore, as a result, even when the exhaust gas temperature is high, such as when the engine is operating at high speed and high load, it can have a higher NOx removal rate compared to conventional catalysts, and the exhaust pressure increases and the exhaust gas temperature increases. As a result, the catalyst substrate having a high specific surface area that increases the temperature can be used, and the denitration apparatus can be made compact. Furthermore, since palladium is used as a noble metal element, it can be produced at a significantly lower cost than a catalyst containing platinum and is excellent in heat resistance at high temperatures. Therefore, when performing the sulfur removal process (regeneration process) required at the time of catalyst performance deterioration, there is little catalyst deterioration.

  In the above description, the exhaust gas treatment catalyst prepared by the liquid phase method has been described. However, an exhaust gas treatment catalyst prepared by the solid phase method may be used. Even the exhaust gas treatment catalyst prepared by such a technique has the same effects as the above-described exhaust gas treatment catalyst.

[First embodiment]
Below, 1st embodiment of the exhaust gas purification apparatus using the exhaust gas treatment catalyst mentioned above is described.

  As shown in FIG. 2, the exhaust gas purification apparatus 10 according to the present embodiment is used for a purification process of exhaust gas 30 discharged from a diesel engine. This exhaust gas contains nitrogen oxides, sulfur oxides, and particulate matter (particulate matter, hereinafter referred to as PM).

  The exhaust gas purification device 10 includes a diesel particulate filter (hereinafter referred to as DPF) 11, an exhaust gas treatment catalyst (reduction catalyst) 12, a hydrogen supply device 13, and an electronic control device (hereinafter referred to as ECU) 20.

  In the exhaust gas purification apparatus 10, the exhaust gas 30 is introduced into the DPF 11 through the exhaust gas circulation pipe 1, and particulate matter (PM) in the exhaust gas 30 is collected by the DPF 11 and PM is removed from the exhaust gas 30. The exhaust gas 31 from which PM has been removed is introduced into the exhaust gas treatment catalyst 12 through the communication pipe 2. A hydrogen supply device 13 is provided so that hydrogen 32 can be supplied into the communication pipe 2. Thus, hydrogen 32 is supplied to the exhaust gas treatment catalyst 12 together with the exhaust gas 31 from which PM has been removed, and the nitrogen oxides in the exhaust gas are purified by the exhaust gas treatment catalyst 12. The exhaust gas 33 from which nitrogen oxides have been purified is discharged out of the system through the exhaust gas discharge pipe 3. That is, in the exhaust gas purification apparatus 10, the DPF 11 and the exhaust gas treatment catalyst 12 are arranged in this order from the upstream side in the exhaust gas distribution direction.

  When the DPF 11 adsorbs PM in the exhaust gas and adsorbs a predetermined amount, the sub-injection after the main injection is performed by an electronically controlled combustion injection valve (not shown) arranged upstream of the DPF 11 in the exhaust gas flow direction. The post-injection can be performed, and the PM adsorbed on the DPF 13 can be burned and removed at a high exhaust gas temperature.

  As the exhaust gas treatment catalyst 12 described above, a catalyst having a catalytic ability for purifying the exhaust gas by storing nitrogen oxide in the exhaust gas and reducing the nitrogen oxide stored by contact with hydrogen as a reducing agent to nitrogen. And the catalyst containing the complex oxide represented by General formula (1) mentioned above is mentioned.

  Examples of the hydrogen supply device 13 described above include a device that produces and supplies hydrogen as it is, or stores the produced hydrogen or hydrogen supplied from outside the system in a tank or an adsorbent and supplies the hydrogen. Examples of the apparatus for producing hydrogen include a microreactor that generates hydrogen from water vapor and fuel and oxygen in exhaust gas, and a water electrolysis apparatus that generates hydrogen by electrolyzing water. These can be used alone or in combination. Examples of the hydrogen adsorbent (hydrogen storage means) include carbon materials or metal materials (hydrogen storage alloys) such as palladium. In the water electrolysis apparatus, water obtained by condensing moisture in exhaust gas or supplied from outside the system and stored in a tank or the like is used.

In the exhaust gas distribution pipe 1, the communication pipe 2, and the exhaust gas discharge pipe 3 described above, a sensor 21, which is an exhaust gas measuring means for constantly measuring the exhaust gas temperature and its components (NOx, O ₂ , H ₂ , NH ₃ ), 22 and 23 are provided. As each of the sensors 21, 22, and 23, there is a sensor using laser light such as a molecular laser light absorption type fast response gas component concentration sensor. By using such a sensor, the exhaust gas temperature and the gas component in the exhaust gas can be measured in real time.

  The above-described sensors 21, 22, 23 and the ECU 20 are connected by signal lines, respectively, and data measured by the sensors 21, 22, 23 is sent to the ECU 20. In addition, the ECU 20 is not shown in the figure, and a sensor (not shown) for measuring an engine (operation) state (not shown) (engine speed, torque, fuel amount with respect to intake air, etc.), the above-described electronically controlled fuel injection valve, and the like. Connected with a signal line for combustion control. While the engine state measured by the sensor is transmitted to the ECU 20, the ECU 20 controls the electronically controlled fuel injection valve and the like. Based on a predetermined control flow, the ECU 20 performs opening / closing control of an EGR valve (not shown) and post injection control by an electronic control fuel injection valve (not shown). The ECU 20 performs control of the hydrogen supply device 13 (specification of the hydrogen concentration of the reducing agent and identification of the hydrogen addition time) and the like.

  Here, the control flow in ECU20 mentioned above is demonstrated below.

  First, data obtained by measuring the state of the internal combustion engine (such as the engine speed, torque, fuel amount with respect to the intake air amount, and the temperature of the cooling water described above) is input to the ECU 20.

Subsequently, based on the map of the exhaust gas temperature distribution and the concentration distribution of nitric oxide in the exhaust gas, which are correlated with the obtained data on the state of the internal combustion engine, the exhaust gas temperature, the oxygen concentration C _O2 in the exhaust gas, And estimate the nitric oxide concentration _CNO . For example, in the case of the low rotation and low torque, the ECU 20 has a low exhaust gas temperature, and the exhaust gas contains a low concentration of nitric oxide. In the high rotation and high torque, the exhaust gas is hot and the exhaust gas The exhaust gas temperature T, the oxygen concentration C _O2 in the exhaust gas, and the nitrogen monoxide concentration C _NO are estimated, such as containing a high concentration of nitric oxide. Further, when the concentration of nitrogen oxides in the exhaust gas at the next moment during deceleration and acceleration cannot be predicted on a map in the high load range and at high speed rotation, the ECU 20 determines the state of the internal combustion engine and the amount of change. Based on the following prediction formula, the nitrogen oxide concentration D _NOX in the exhaust gas is predicted.

NOx prediction formula: D _NOX = f (n, P1,..., Px, T1,..., Tx,..., Δn,..., ΔX)
n: Current rotational speed of the internal combustion engine Px: Pressure at a specific part of the engine (for example, in-cylinder pressure)
Tx: the temperature of a specific part of the engine (for example, the temperature of the combustion gas in the cylinder)
Δn: Current speed change amount ΔX: Current engine specific part change amount (including accelerator depression amount, engine load (slope and slip), etc.)

  Further, by integrating the operation time, the predicted value, and the gas amount (which can be calculated from the engine speed and the exhaust amount per rotation) (NOx instantaneous predicted value × operation time × gas amount), NOx to the catalyst The amount of exposure is calculated.

  Subsequently, the amount of NOx stored is estimated from the temperature map of the NOx storage rate (denitration rate) with respect to the amount of exposure to the catalyst during normal operation. The ECU 20 controls the hydrogen supply device 13 to supply hydrogen 32 into the communication pipe 2 so that the desired NOx removal rate is obtained in accordance with the NOx amount and the exhaust gas temperature.

  Therefore, according to the exhaust gas purification apparatus 10 described above, the above-described configuration adjusts the exhaust gas so that the oxygen gas concentration in the exhaust gas is less than a predetermined value, and reduces and purifies nitrogen oxides in the exhaust gas. The exhaust gas so that the reaction amount with the nitrogen oxide is larger than the reaction amount with the oxygen gas corresponding to the storage amount of the nitrogen oxide stored in the exhaust gas treatment catalyst 12 and the temperature of the exhaust gas. By supplying (adding) hydrogen 32 to the exhaust gas treatment catalyst 12, nitrogen oxides in the exhaust gas can be reduced and removed. As a result, as in the above-described reference embodiment, even when the exhaust gas temperature is a low temperature of 200 ° C. or lower, the amount of hydrogen consumed by the reaction with nitrogen oxides increases compared with the reaction with oxygen gas, and the exhaust gas treatment catalyst Therefore, the denitration reaction and the combustion reaction at 12 are balanced, and the exhaust gas treatment catalyst 12 can efficiently act on the hydrogen 32.

In the above description, the exhaust gas temperature, the oxygen concentration C _O2 in the exhaust gas, and one of the exhaust gas temperature distribution and the concentration distribution of nitrogen monoxide in the exhaust gas, which are prepared in advance, are correlated with the data of the internal combustion engine. The exhaust gas purification device 10 that performs control for estimating the nitrogen oxide concentration _CNO , selecting the type of reducing agent, and specifying the concentration has been described, but is measured by the sensors 21, 22, and 23 and sent to the ECU 20. It is also possible to control the reflected exhaust gas temperature and its gas component data by reflecting them in the above-mentioned data map, and fine adjustment is directly performed by feedback control using the exhaust gas temperature and the gas component data sent to the ECU 20. It is also possible. According to the exhaust gas purifying apparatus controlled in this way, the same effect as the exhaust gas purifying apparatus 10 described above can be obtained, and the hydrogen concentration of the reducing agent and the hydrogen addition time can be specified with higher accuracy. It is possible to improve the denitration performance. Furthermore, it can be controlled according to the state of the engine and can cope with transients.

  By measuring the concentration of hydrogen downstream of the exhaust gas treatment catalyst 12 in the exhaust gas flow direction, the amount of hydrogen used as the reducing agent in the exhaust gas treatment catalyst 12 can be specified. Therefore, the amount of reducing agent added can be controlled, and the exhaust gas can be purified even more efficiently.

[Second Embodiment]
An exhaust gas purifying apparatus according to a second embodiment of the present invention will be described with reference to FIG.
In this embodiment, the same code | symbol is attached | subjected to the same apparatus as the apparatus which the exhaust gas purification apparatus 10 of 1st embodiment mentioned above comprises.

  In the exhaust gas purifying apparatus 50 of the present embodiment, as shown in FIG. 3, the oxidation catalyst 14 is connected to the exhaust gas circulation pipe 1, and the exhaust gas introduction pipe 4 is connected to the oxidation catalyst 14.

  In the exhaust gas purification device 50, the exhaust gas 40 discharged from the diesel engine is introduced into the oxidation catalyst 14 through the exhaust gas introduction pipe 4, and HC, CO, NO in the exhaust gas 40 is oxidized by the oxidation catalyst 14. The exhaust gas 41 in which HC, CO, and NO are oxidized is introduced into the DPF 11 through the exhaust gas circulation pipe 1. The exhaust gas 42 from which PM has been removed by the DPF 11 and the hydrogen 32 supplied from the hydrogen supply device 13 are supplied to the exhaust gas treatment catalyst 12 through the connection pipe 2. The exhaust gas treatment catalyst 12 purifies the nitrogen oxides in the exhaust gas, and the exhaust gas 43 from which the nitrogen oxides have been purified is discharged out of the system through the exhaust gas discharge pipe 3. That is, in the exhaust gas purification device 50, the oxidation catalyst 14, the DPF 11, and the exhaust gas treatment catalyst 12 are arranged in this order from the upstream side in the exhaust gas circulation direction.

The exhaust gas introduction pipe 4 is provided with a sensor 24 as exhaust gas measuring means for constantly measuring the exhaust gas temperature and its components (NOx, O ₂ , H ₂ , NH ₃ ). Examples of the sensor 24 include a sensor using laser light, such as a molecular laser light absorption type high-speed gas component concentration sensor. By using such a sensor, the exhaust gas temperature and the gas component in the exhaust gas can be measured in real time.

  Examples of the oxidation catalyst 14 include noble metal catalysts such as platinum, palladium and iridium, and complex oxide catalysts such as perovskite. The oxidation catalyst 14 is a catalyst that is formed in a honeycomb shape and causes an oxidation reaction at 200 ° C. or higher. Since the oxidation catalyst 14 oxidizes HC, CO, and NO in the exhaust gas, the reduction rate of the exhaust gas treatment catalyst 12 disposed on the downstream side in the exhaust gas circulation direction is improved.

  Therefore, according to the exhaust gas purifying apparatus 50 described above, by adopting the above-described configuration, the exhaust gas is adjusted so that the oxygen gas concentration in the exhaust gas becomes less than a predetermined value, and the nitrogen oxides in the exhaust gas are reduced and purified. The exhaust gas so that the reaction amount with the nitrogen oxide is larger than the reaction amount with the oxygen gas corresponding to the storage amount of the nitrogen oxide stored in the exhaust gas treatment catalyst 12 and the temperature of the exhaust gas. By adding hydrogen 32 to the exhaust gas treatment catalyst 12, nitrogen oxides in the exhaust gas can be reduced and removed. As a result, as in the reference embodiment and the first embodiment described above, even when the exhaust gas temperature is a low temperature of 200 ° C. or less, the amount of hydrogen consumed in the reaction with nitrogen oxides compared with the reaction with oxygen gas. Therefore, the denitration reaction and the combustion reaction at the exhaust gas treatment catalyst 12 are balanced, and the hydrogen 32 can be efficiently operated by the exhaust gas treatment catalyst 12.

  According to the exhaust gas purification method and the exhaust gas purification apparatus according to the present invention, even when the exhaust gas temperature is a low temperature of 200 ° C. or lower, the reducing agent can be made to act efficiently with the catalyst for treating nitrogen oxides in the exhaust gas. It is useful for industries that treat exhaust gas emitted from diesel engines and combustion equipment.

10, 50 Exhaust gas purification device 11 DPF
12 Exhaust gas treatment catalyst 13 Hydrogen supply device 14 Oxidation catalyst 20 Electronic control unit (ECU)

Claims (7)

As a reduction catalyst for reducing and removing nitrogen oxides in exhaust gas, a general formula: La (Fe _y Nb _1-yz ) Pd _z O ₃ (where 0.30 ≦ y ≦ 0.95, 0.01 ≦ z ≦ 0.10.) Using a catalyst having a perovskite-type composite oxide represented by
The exhaust gas is adjusted so that the oxygen gas concentration in the exhaust gas is less than a predetermined value, and the reaction with the oxygen gas corresponds to the storage amount of nitrogen oxides stored in the reduction catalyst and the temperature of the exhaust gas. Exhaust gas, characterized in that hydrogen is added to the exhaust gas so that the amount of reaction with the nitrogen oxide is larger than the amount, and the nitrogen oxide in the exhaust gas is reduced and removed by contacting with the reduction catalyst Purification method. The exhaust gas purification method according to claim 1,
1-yz is 0.05-0.69 in the said general formula, The exhaust gas purification method characterized by the above-mentioned. An exhaust gas purification method according to claim 1 or claim 2, wherein
An exhaust gas purification method, wherein the hydrogen addition time is 9 seconds to 15 seconds. It is an exhaust gas purification method as described in any one of Claims 1 thru | or 3, Comprising:
An exhaust gas purification method, wherein the hydrogen concentration is 4%. An exhaust gas purification device that reduces and purifies nitrogen oxides in exhaust gas,
A collecting means for collecting particulate matter in the exhaust gas;
An exhaust gas treatment catalyst disposed downstream of the collecting means in the flow direction of the exhaust gas;
Hydrogen supply means for supplying hydrogen to the exhaust gas treatment catalyst upstream of the exhaust gas flow direction,
The exhaust gas treatment catalyst, the general _{formula: La (Fe y Nb 1-} yz) Pd z O 3 ( where a 0.30 ≦ y ≦ 0.95, is 0.01 ≦ z ≦ 0.10.) An exhaust gas purification apparatus comprising a perovskite-type composite oxide represented by An exhaust gas purification device according to claim 5,
The exhaust gas purifying apparatus according to the general formula, wherein 1-yz is 0.05 or more and 0.69 or less. The exhaust gas purifying apparatus according to claim 5 or 6,
An exhaust gas purifying apparatus, further comprising an oxidation catalyst disposed upstream of the collecting means in the flow direction of the exhaust gas.

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