JP2006132483A - Exhaust emission control device, exhaust emission control method and control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small and simple exhaust emission control device capable of highly efficiently and inexpensively performing simultaneous removal of NOx, soot and hydrocarbon in exhaust gas from an internal combustion engine etc. including oxygen at low temperature, even when the exhaust emission control device is a dry type and uses no ammonia, urea and a catalyst, and an exhaust emission control method and a manufacturing method of the exhaust emission control device. <P>SOLUTION: The exhaust emission control device 1 is provided with an oxygen sensor 10 or an air fuel ratio sensor 10' arranged on an exhaust passage 5 of the internal combustion engine 11, having an adsorbing filter 7 and a plasma reactor 6 arranged on the exhaust passage 5 or outside the exhaust passage 5, and detecting oxygen concentration in exhaust gas; and an electronic control part 9 making the adsorbing filter 7 perform emission control when the oxygen concentration detected by the oxygen sensor 10 or the air fuel ratio sensor 10' exceeds a predetermined value, and reducing the oxygen concentration in exhaust gas and operating the plasma reactor 6 when adsorption amount of the adsorbing filter 7 exceeds a predetermined value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention suppresses the total power consumption as much as possible by intermittently applying plasma to exhaust gas from an internal combustion engine such as a diesel engine. In principle, it is non-catalytic, and includes wet processing, ammonia injection, dust collection processing, etc. The present invention relates to an exhaust gas purification apparatus, an exhaust gas purification method, and a control method thereof for performing dry, high efficiency and energy saving without performing a typical process.

  In recent years, regulations on exhaust gas when exhausting combustion gas generated in a combustion apparatus such as an internal combustion engine, a boiler, a gas turbine, or a diesel engine of an automobile via an exhaust system are being strengthened. Along with this, improvements on the combustion device side such as improvement of fuel composition, emulsification or recirculation of exhaust gas to the combustion device, improvement of combustion itself, etc. are made, while in the exhaust gas discharged from the combustion device Hazardous components, especially nitrogen oxides (NOx), dry selective catalytic reduction (SCR method, Selective Catalytic Reduction) by blowing ammonia or urea into a high temperature catalyst, fine particles (PM, Particulate Matter) such as soot are DPF (Diesel) A continuous regeneration trap (CRT method, Continuous Regeneration Trap) is performed in which the particulate collection is performed using a Particulate Filter (diesel particulate filter) and burned and removed using an oxidation catalyst.

In addition, as another PM and NOx simultaneous purification system, a DPNR method (Diesel Particulate-NOx Reduction), which combines DPF (Diesel Particulate Filter) and NOx storage reduction catalyst, has been proposed. (Non-patent document 1, Patent document 1). This system has a structure in which a ceramic honeycomb DPF is supported with a three-way catalyst and a NOx storage material (such as alkali or alkaline earth metal). In the normal operation mode, the exhaust gas contains a large amount of oxygen (O ₂ ), and nitric oxide (NO) occupying most of NOx is oxidized and stored as nitrogen dioxide (NO ₂ ) in the storage material. In this system, when NO ₂ is occluded to some extent, the engine operation mode is switched, the fuel injection amount is excessive, O ₂ does not remain in the exhaust gas, and nitric oxide (CO) and hydrocarbons (HC) exist. Like that. The stored NO ₂ is reduced to N ₂ by the CO and HC, and at the same time, the CO, HC and PM are oxidized and converted into carbon dioxide (CO ₂ ) and water (H ₂ O) for purification.

  On the other hand, as one method for treating NOx in exhaust gas, research using non-thermal plasma, in which the electron temperature is extremely high and the gas temperature is low, is being advanced. Typical examples of this plasma include pulse corona plasma, AC barrier plasma, and DC corona plasma formed at high atmospheric pressure by high voltage discharge.

  For example, a PPCP system in which exhaust gas is passed through a non-thermal plasma reactor, and NO, which occupies most of the nitrogen oxides contained therein, reacts with ammonia gas to convert into ammonium nitrate fine particles and is recovered by an electrostatic precipitator ( (Pulse Corona Induced Plasma Chemical Process) (Non-patent Document 2).

Alternatively, ammonia is not used, but NO is almost completely oxidized to NO ₂ by a plasma reactor installed inside or outside the exhaust passage, and nitrogen (N ₂ ) is harmless with a wet chemical process equipment installed separately. A hybrid system (Patent Document 2 and Patent Document 3) that reduces to an aqueous solution is performed.

Further, as one of methods for treating soot in exhaust gas, a method using plasma has been proposed. For example, soot is collected using a ceramic filter, and the collected soot is burned and removed at a low temperature by a plasma reactor installed inside or outside an exhaust passage. (Patent Document 4, Patent Document 5)
In addition, for NOx treatment, a technique has been devised that is once adsorbed on an adsorbent, desorbed by plasma, and concentrated (Patent Document 6).
JP 2002-256853 JP 2000-51653 A JP 2000-117049 JP2004-68684 Special table 2003-535255 JP-A-11-114351 Miyoshi, Tanaka, Matsumoto, “Development of NOx storage reduction catalyst”, TOYOTA Technical Review, 50, 2, pp.28-33, 2000. Masakata Sadakata, Chemical Engineering for Clean Air, Baifukan, p.76, 1999.

  However, when the conventional exhaust gas treatment device is applied to a stationary combustion device such as a boiler or a gas turbine or a mobile combustion device such as a diesel vehicle, the efficiency of the conventional technology is relatively low, and the cost is large. Need water. For reasons such as increasing the size of the apparatus, it is desirable to use a dry processing apparatus as much as possible.

  In addition, treatment methods using catalysts such as SCR, CRT, and DPNR require a high temperature of 300 ° C or higher, the catalyst itself contains noble metals or harmful heavy metals, the price is relatively expensive, and the reserves of noble metals are also high. It is limited and has a relatively short life, and there are problems such as poisoning due to sulfur in the fuel and a decrease in combustor performance due to increased back pressure due to clogging. It is desirable to eliminate the catalyst if possible.

  In addition, in the SCR method and PPCP method, etc., ammonia or the like is usually used for NOx treatment in combination with a catalyst or plasma, but it is difficult to handle and harmful to the human body. There is a problem that ammonia may be released into the atmosphere.

  In general, exhaust gas from an internal combustion engine that uses diffusion combustion, such as a diesel engine, usually contains oxygen at a volume concentration of about several to several tens of percent. For such exhaust gas, it is difficult to use a so-called three-way catalyst.

Further, in the exhaust gas purification method using plasma, which has been actively studied in recent years, NO contained in the combustion gas is NO by simply flowing an exhaust gas containing this type of oxygen into the plasma reactor and applying the plasma. _By being oxidized to ₂ , NOx (= NO + NO ₂ ) itself is hardly reduced and does not treat pollution. In order to remove the generated NO ₂ , there is a problem that additional processing such as a hybrid method and a PPCP method is always required.

  Furthermore, in the PPCP method, a large amount of combustible ammonium sulfate fine particles are generated. Therefore, when applied to a mobile combustion device such as a diesel vehicle, there are many restrictions such as a problem of a recovery processing infrastructure.

  On the other hand, the CRT method, which collects soot in exhaust gas using a ceramic filter and burns and removes soot collected by an oxidation catalyst at a low temperature, is a powerful method, but noble metals are used for the oxidation catalyst. The efficiency is often about 50%. In addition, the method of burning and removing soot collected using plasma at a low temperature is non-catalytic and high in efficiency, and these problems can be avoided, but soot combustion generates new NO, and then There was a problem that the processing apparatus had to be installed separately.

  In addition, for NOx treatment, the technology of once adsorbing to an adsorbent, desorbing with plasma, and concentrating treatment is low in efficiency when trying to perform desorption directly with plasma of exhaust gas containing oxygen. In order to process the desorbed NOx, there is a problem that additional processing such as a hybrid method and a PPCP method is always required.

  The present invention has been made to solve the above-described conventional problems, and is capable of simultaneously removing NOx and soot and hydrocarbons in exhaust gas from an internal combustion engine or the like containing oxygen with high efficiency, low cost, and dry ammonia and urea. It is an object of the present invention to provide a small and simple exhaust purification device, an exhaust purification method and a manufacturing method thereof that can be performed at a low temperature even without using a catalyst.

  The present invention realizes the simultaneous purification effect of NOx and fine particles in exhaust gas realized by catalyst and fuel injection in the DPNR method by applying plasma at a low temperature close to room temperature by applying plasma.

  Specifically, the following apparatus or method is mainly provided to provide a means for solving the above-described problems, to perform exhaust gas purification of the internal combustion engine with high efficiency and energy saving, and to contribute to the preservation of the global environment. is there.

  The exhaust emission control device according to claim 1 is provided on the exhaust path of the combustion device, and includes a purification means including a NOx adsorbent and / or a particulate filter, and a plasma application means provided on the exhaust path. An exhaust purification device that detects an oxygen concentration in exhaust gas and, when the oxygen concentration detected by the oxygen concentration detection means is equal to or greater than a predetermined value, causes the purification means to perform exhaust purification. In addition, there is provided control means for lowering the oxygen concentration in the exhaust gas and operating the plasma application means when the amount of adsorption by the purification means exceeds a predetermined value.

  The exhaust emission control device according to claim 2 is characterized in that the oxygen concentration control by the oxygen concentration control means is performed by controlling the air-fuel ratio of the combustion device.

  The exhaust emission control device according to claim 3 is characterized in that the oxygen concentration control by the oxygen concentration control means is performed by injecting hydrocarbons into the exhaust passage.

  The exhaust emission control device according to claim 4 is characterized in that the oxygen concentration control by the oxygen concentration control means is performed by blowing nitrogen gas into the exhaust passage.

  In the exhaust emission control device according to claim 5, the oxygen concentration control by the oxygen concentration control means is performed by at least one filter selected from the group consisting of an oxygen adsorbent, an oxygen separation membrane, a nitrogen adsorbent, and a nitrogen separation membrane. It is characterized by being.

  The exhaust emission control device according to claim 6 further includes a catalyst for assisting purification of exhaust gas.

  The exhaust emission control device according to claim 7 is characterized in that the combustion device is a diesel engine, and a limit value of operation switching of the oxygen concentration is 2 vol% or less.

  In the exhaust gas purification method according to claim 8, the plasma application means is disposed outside the exhaust passage, and NOx is purified and collected by separately sucking air or gas and injecting the plasma into the exhaust passage after applying the plasma. It is characterized by burning and removing fine particles.

  The exhaust purification method of claim 9 further uses any of carbon monoxide, hydrocarbons, active oxygen, nitrogen dioxide or a combination thereof in the exhaust gas to assist the purification of the exhaust gas, and at the same time purifies itself. It is characterized by doing.

The control method according to claim 10 relates to the control of the generation time of the plasma, wherein the power consumption of the plasma is P, the total operation time of the internal combustion engine is DT, and the operation state of the internal combustion engine is equal to or higher than the limit value of the oxygen concentration in the exhaust gas. the operating time when not applied plasma DT _1, the operating time in the case of applying the plasma with decreasing below the limit value of the oxygen concentration in the exhaust when the DT _2, a DT ₂ to DT ₁ and DT It is characterized by being controlled to be smaller than the power consumption P × DT ₂ when the plasma power consumption P × DT ₂ is continuously applied.

  When the present invention is applied to a stationary combustion apparatus such as a boiler or a gas turbine or a mobile combustion apparatus such as a diesel vehicle, it does not require electric power at all times compared to the conventional plasma method. This makes it possible to simultaneously remove NOx and soot with high efficiency.

  In addition, since the dry method is used, water is not required, and the apparatus is small and low in cost. In addition, in principle, this method does not require the use of precious metals or heavy metal catalysts, is friendly to the global environment, and there is no problem of poisoning due to sulfur in the fuel. The exhaust gas temperature during the treatment may be a low temperature of 300 ° C. or lower. Therefore, when applied to a diesel vehicle or the like, NOx, soot, and hydrocarbons can be purified by applying plasma when the exhaust gas is at a low temperature, such as when idling or going down a slope.

  Furthermore, no harmful gas such as ammonia is used, and no flammable fine particles such as ammonium sulfate are generated. Further, when the collected soot is controlled to have a high oxygen concentration, the collected soot is collected and part of the soot is removed by oxygen combustion. When oxygen concentration is periodically lowered and plasma is applied, soot is burned and removed by active oxygen generated when NOx is reduced, so that new NO is generated by soot combustion There is no point. Furthermore, no additional wet processing such as a hybrid method is required.

1 (a) and 1 (b) are explanatory views schematically showing the principle of a plasma activated diesel particulate-NOx reduction system used in an exhaust gas purification apparatus according to an embodiment of the present invention. As shown in the figure, the exhaust gas purification of this system is performed on a filter wall having a filter hole on the surface. It has a structure in which a NOx occlusion material (zeolite, also referred to as NOx adsorbent, alkali metal, etc.) is supported on the surface of ceramic or metal DPF, and non-thermal plasma can be applied to the DPF.

In the normal engine operation mode shown in (a), since there is a lot of O _{2 in the} exhaust gas (exhaust gas), NO is oxidized and stored as NO ₂ in the NOx storage material. In addition, a part of the soot PM collected by the filter is burned and removed in a state where O ₂ is abundant.

Next, when NOx is occluded to some extent, the engine operation mode is switched to an excessive fuel injection amount as shown in FIG. By using this mode, the oxygen concentration in the exhaust gas is lowered by changing the air-fuel ratio so that O ₂ does not remain in the exhaust gas and CO and HC exist. Here, when plasma is applied, the occluded NO ₂ is desorbed and reduced to N ₂ . At the same time, PM trapped in the filter hole and HC in the exhaust gas are oxidized by active oxygen O ^* and converted to CO ₂ and H ₂ O. That is, in this system, in order to assist the purification of exhaust gas, any one of carbon monoxide (CO), hydrocarbon (HC), active oxygen (O ^* ), nitrogen dioxide (NO ₂ ) in the exhaust gas, or a combination thereof. It is characterized by purifying these themselves at the same time.

  The plasma used in the present invention is preferably energy-saving and so-called non-thermal non-equilibrium low-temperature plasma formed by corona discharge, glow discharge, barrier discharge, pulse discharge or the like, but is not particularly limited.

  Examples of the plasma applying means used in the exhaust emission control device of the present invention include a configuration as shown in FIG. That is, this is a configuration in which non-thermal plasma is intermittently generated in the DPF internal flow path by applying a pulse high voltage between electrodes facing each other so as to sandwich a DPF having a NOx adsorbent layer on the surface. By using such a method, the process of FIG. 1 can be realized on the DPF wall surface.

FIG. 3 is an explanatory view showing a schematic configuration of another plasma applying means used in the exhaust purification apparatus of the present invention.
As shown in the figure, non-thermal plasma can be generated in the cylinder by applying a pulse high voltage between the discharge line of the concentric cylindrical barrier plasma reactor and the external electrode. Thereby, non-thermal plasma can be generated inside the ceramic NOx adsorbent filter, and the system shown in FIG. 1 can be realized inside the filter.

  FIG. 4 is a schematic diagram showing the overall configuration of the exhaust emission control device 1 provided in the internal combustion engine 11 according to the embodiment of the present invention. The internal combustion engine 11 is configured as, for example, a diesel engine or a lean burn gasoline engine. The internal combustion engine 11 includes an engine body 2 and a generator 3 connected to the engine body 2 and driven by the engine body 2. Electricity generated by the generator 3 is stored in the battery 4. For example, a plasma reactor 6 and an adsorbent filter 7 having the structure shown in FIG. 2 or 3 are arranged in the exhaust passage 5 extending from the engine body 2. Note that 6 and 7 can be integrated by installing the adsorbent filter 7 inside the plasma reactor 6. Electric power is supplied to the plasma reactor 6 from a plasma power source 8. The plasma power supply 8 boosts the DC voltage supplied from the battery 4 and adjusts the frequency and voltage value to change the input power to the plasma reactor 6.

Next, operation | movement of the exhaust gas purification apparatus 1 which concerns on this Embodiment is demonstrated.
The electronic control unit 9 (oxygen concentration control means) controls the operation of the engine body 2 and the plasma power source 8 and operates by receiving power supply from the battery 4. The electronic control unit 9 receives an output signal from an oxygen concentration sensor 10 or an air / fuel ratio sensor 10 ′ (oxygen concentration detection means) installed in the exhaust passage 5, detects an operating state such as an air / fuel ratio of the engine body 2, and controls the operation. To do.

  In the present embodiment, the internal combustion engine 11 is equipped with fuel injection means (not shown). The timing of the fuel injection means is changed according to a predetermined cycle to reduce the oxygen concentration in the exhaust gas. In synchronism with this, the plasma reactor 6 is intermittently operated to perform exhaust purification. The above operating conditions are incorporated into a program in the electronic control unit 9 to perform operation. The oxygen concentration in the exhaust gas when operating the plasma reactor is not particularly limited, but is preferably 0 to 20 vol%, more preferably 0 to 18 vol%, and most preferably 0 to 6 vol%.

  The control for changing the oxygen concentration in the exhaust gas can be performed by blowing hydrocarbons into the exhaust passage 5. Alternatively, nitrogen gas can be blown into the exhaust passage. In addition, if necessary, any one of an oxygen adsorbent, an oxygen separation membrane, a nitrogen adsorbent, a nitrogen separation membrane, or a combination of two or more of these may be installed in the exhaust passage.

  However, by placing the plasma reactor 6 outside the exhaust passage 5 and separately sucking air or gas and applying the plasma to the exhaust passage 5, NOx can be purified and the collected particulates can be removed by combustion. .

  Further, a catalyst for assisting the purification of exhaust gas can be further provided in the apparatus to improve the performance, but the installation of the catalyst is not essential.

  A diesel engine is a preferred example of the internal combustion engine that is the subject of the present invention. Further, it is desirable that the limit value of the operation switching of the oxygen concentration be a certain value of 2 vol% or less.

Furthermore, regarding the generation timing control of the plasma, P is the power consumption of the plasma, DT is the total operation time of the internal combustion engine, and the plasma is applied in the operation state of the internal combustion engine that is equal to or higher than the limit value of the oxygen concentration in the exhaust gas. the operating time of the absence DT _1, the operating time in the case of applying the plasma with decreasing below the limit value of the oxygen concentration in the exhaust when the DT _2, taken smaller than the DT ₂ to DT ₁ and DT, The plasma power consumption P × DT ₂ can be reduced as compared with the power consumption P × DT when the plasma is continuously applied.

  Hereinafter, embodiments of the exhaust emission control device of the present invention will be described in detail with reference to the drawings. However, the present invention is not construed as being limited thereto, and unless it departs from the scope of the present invention. Various changes, modifications, and improvements can be added based on the inventor's knowledge.

(Example 1)
The concentric circular plasma reactor shown in FIG. 5 was used as the plasma reactor (plasma application means), and NOx and PM (soot) in the exhaust gas were removed simultaneously by applying plasma. First, the NOx (= NO ₂ ), nitrogen (N ₂ ), and air (Air) cylinders were each adjusted in flow rate by a mass flow controller to form a NOx simulated exhaust gas with a constant oxygen concentration.

The concentric circular plasma reactor shown in FIG. 5 has a configuration in which a stainless steel discharge wire with a diameter of 2 mm is passed through the center of a quartz tube and an electrode is wound outside. The inner diameter is 20 mm, the outer diameter is 23 mm, and the outer electrode length is 60 mm. ) At a flow rate of 2.0 L / min (25 ° C). Inside the electrode, a ceramic NOx adsorbent filter (soot collector, material is BaTiO ₂ ) was placed, and 50 mg and 113 mg of diesel engine soot were collected in advance, respectively. By changing the oxygen concentration of the exhaust gas, the amount of NOx simultaneously purified by the plasma reactor was investigated. A pulse high voltage with a frequency of 530 Hz was applied to the plasma reactor by a pulse high voltage power source using SI thyristor switching. The voltage waveform, current waveform, and instantaneous power waveform to the plasma reactor were measured with a voltage probe (Sony Tektronix, P6015A), a current probe (Sony Tektronix, P6021), and an oscilloscope (Yokogawa, DL1740). The treated gas was measured for each gas concentration (NOx, CO, CO ₂ , dinitrogen monoxide N ₂ O, etc.) with a gas analyzer (PG-235, VIA-510 manufactured by Horiba, Ltd.). The amount of soot removed (combustion amount) was calculated from the amount of CO and CO ₂ increased by combustion.

  When the collected amount of soot collected by the NOx adsorbent filter is 50 mg and the oxygen concentration is 0%, 0% (a) is set, and when the collected amount of soot is 113 mg and the oxygen concentration is 0% 0% (b), 2%, 5%, 17% (soot trapping amount is 113mg), soot removal amount (combustion amount) when plasma is applied The gas concentration change was measured.

FIG. 6 shows the change of each gas concentration when the plasma is applied in the case of 0% (b). It can be seen that plasma is applied at an elapsed time> 0, but NOx decreases and CO and CO ₂ increase simultaneously with the application. Moreover, the mass of the collected black soot fell, and removal was observed visually.

FIG. 7 shows the amount of decrease in soot when the oxygen concentration is changed. The horizontal axis represents the plasma application time. From FIG. 7, the maximum soot removal rate (burning rate) was 38 mg / h. Converting this to a removable soot concentration gives 350 mg / Nm ^{3 under} standard conditions. As an example, the standard soot concentration of a commercially available diesel engine with a displacement of 10 liters is about 300 mg / Nm ³ , which is almost the same as this value. Therefore, continuous removal by plasma is possible by scaling up the equipment. FIG. 8 shows the relationship between the amount of NOx reduction and the plasma application time. NOx decreased at oxygen concentrations below 2% and was almost eliminated at 0% (a). In this case, NOx and soot can be removed simultaneously as can be seen from FIG.

FIG. 9 shows the voltage V, current I, and power waveform P in the case of 0% (b). The average power P _avg was calculated by integrating P for one period and multiplying the positive area by the magnification and frequency of the voltage probe and current probe, and P _avg = 17.2 W.

Although the complete details of the mechanism of the simultaneous removal of soot and NOx when the oxygen concentration is low are not clear, in this experiment, the lower the soot, the higher the CO and CO ₂ , and the lower the NOx. In other words, NOx and soot can be removed simultaneously mainly by the following reactions (1) and (2) if plasma is applied in a state where the exhaust gas oxygen concentration is reduced after a relatively small amount of soot is collected by the filter. It was shown that there is.

2NO ₂ + 2C → N ₂ + 2CO ₂ (1)
2NO ₂ + 4C → N ₂ + 4CO (2)

(Example 2)
Next, with the apparatus shown in FIG. 10, adsorption of NOx in exhaust gas when the oxygen concentration is high and simultaneous removal of adsorbed NOx and collected PM (soot) by applying plasma when the oxygen concentration is low went. A small diesel engine generator (Yanmar Diesel, YDG200SS-6E, direct-injection single-cylinder diesel engine, displacement 200 cc, maximum electrical output 2.0 kW) is sampled part of the exhaust gas, and some moisture and soot Part of it was removed, and an actual exhaust gas with a flow rate of 2.0 L / min (25 ° C) was prepared using a mass flow controller.

  This gas was passed through the concentric circular plasma reactor of FIG. This reactor is made by passing a stainless steel discharge wire with a diameter of 2 mm in the center of a quartz tube and winding an electrode on the outside. The inner diameter is 20 mm, the outer diameter is 23 mm, plasma reactor A (adsorbent part, electrode length 60 mm), and plasma. Two regions of reactor B (air core, electrode length 200 mm) are arranged in series. Inside the reactor A, a ceramic adsorbent (MS-13X, manufactured by Merck KGaA) was enclosed, and diesel engine soot was collected in advance.

  By applying plasma and changing the oxygen concentration of the exhaust gas, the simultaneous purification amount of soot and NOx was investigated. The oxygen concentration in the exhaust gas was measured by an oxygen concentration sensor, and the plasma power source was controlled via the power control device based on the information.

Each gas concentration (NOx, CO, CO ₂ , N ₂ O, etc.) of the plasma-treated gas was measured by a gas analyzer (PG-235, VIA-510 manufactured by Horiba, Ltd.). The voltage waveform, current waveform, and instantaneous power waveform to the plasma reactor were measured with a voltage probe (Sony Tektronix, P6015A), a current probe (Sony Tektronix, P6021), and an oscilloscope (Yokogawa, DL1740).

FIG. 11 shows the results of NOx adsorption and desorption by plasma with an oxygen concentration of 0.01% on diesel engine exhaust gas. The horizontal axis is the elapsed time, and the vertical axis is the NOx concentration. Only the plasma reactor A filled with the adsorbent is operated (on). The experimental conditions are as follows. Adsorption: NO = 280 ppm, NOx = 330 ppm, moisture = 4.0 g / m ³ , soot = 18 mg / m ³ , O ₂ = 10.0%, CO = 480 ppm, CO ₂ = 4.5%, THC (Total hydrocarbon , Total hydrocarbons) = 160 ppm, Q = 2.0 L / min, adsorption time (cycle) DT _p = 60 min. During plasma desorption: O ₂ = 0.01%, flow rate Q = 1.0 L / min, pulsed plasma frequency f = 420 Hz, peak voltage V _peak = 36 kV. Adsorption and desorption were repeated three times. In the adsorption process, 85% or more of NOx is removed by adsorption. In the desorption process of FIG. 11, only the reactor A is operated, and the adsorbed NOx is desorbed and released as it is into the exhaust passage. Adequate NOx desorption of 2500 ppm or more exceeding the measurable range is obtained in each of the three desorptions.

FIG. 12 shows the result of simultaneous reduction and removal of NOx and soot of diesel engine exhaust gas with plasma having an oxygen concentration of 0.01% or less by simultaneously operating (on) reactor A and reactor B during desorption. The horizontal axis is the elapsed time, and the vertical axis is the NOx concentration. The exhaust gas conditions are the same as in FIG. Adsorption: NO = 260 ppm, NOx = 350 ppm, O ₂ = 10.0%, flow rate Q = 2.0 L / min, total adsorption time DT ₁ = 191 min (3 adsorption times). During plasma desorption: O ₂ = 0.01%, flow rate Q = 1.0 L / min, total desorption time DT ₂ = 9 min (3 adsorption times). Pulse plasma frequency f = 420 Hz, peak voltage V _peak = 31 kV.

In the case of FIG. 12, as can be seen from comparison with FIG. 11, NOx adsorbed by the reactor A is released at the time of plasma application, a part is reduced to N ₂ by low oxygen concentration plasma, and the generated active oxygen is burnt. Furthermore, the remaining NOx was successfully reduced and purified almost completely to N ₂ by the downstream reactor.

Here, it was confirmed with a gas analyzer or a gas detector tube that NOx was hardly oxidized to harmful by-products such as N ₂ O, HNO ₃ , and N ₂ O ₅ .

In addition, the concentration of CO ₂ generated by a CO ₂ meter was measured and it was confirmed that combustion occurred. Moreover, the combustion of the soot at the time of plasma application and the removal after the experiment of the collected soot were confirmed visually.

FIG. 13 shows voltage V, current I, and power waveform P when reactors A and B corresponding to the experimental results of FIG. 12 are operated in series. The average power P _avg was calculated by integrating P for one period and _multiplying the positive area by the magnification and frequency of the voltage probe and current probe, and P _avg = 83.9 W. When this value is converted into energy SED per unit exhaust gas volume, SED = 701 Wh / m ³ .

In FIG. 12, the total operating time of the internal combustion engine DT = 200 min, the operating time when plasma is not applied is DT ₁ = 191 min, the operating time when plasma is applied is DT ₂ = 9 min Exhaust gas can be purified. In other words, the plasma power consumption for 200 min can be reduced to DT ₂ / DT ´ 100 = 9/200 ´ 100 = 4.5% compared to the power consumption when plasma is continuously applied, and the effective SED _eff = 701 ´ 0.045 = 31.5 Wh / m ³ was achieved.

  As is clear from the above results, by using the exhaust gas purification apparatus of the present invention and controlling the oxygen concentration of the exhaust gas so as to be within a predetermined range and applying plasma, the soot that is efficiently trapped with NOx. Can be removed simultaneously.

  According to the present invention, the exhaust gas discharged from an internal combustion engine such as a diesel engine is processed by a combination of adsorption, desorption, and low oxygen plasma treatment, and in principle, no catalyst or additional treatment is performed with a simple apparatus. A dry process can be performed with high efficiency, and an apparatus and an operation method therefor can be provided.

It is explanatory drawing of the principle of the plasma application diesel particulate-NOx simultaneous removal system in this invention. It is the schematic which shows one Embodiment in this invention. It is the schematic which shows other one Embodiment in this invention. 1 is a schematic diagram showing an overall configuration of an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention. It is the schematic of the apparatus of the plasma application diesel particulate matter-NOx simultaneous removal system in Example 1 of this invention. It is a graph showing the relationship between the elapsed time in Example 1 of this invention, and each gas concentration at the time of plasma application. It is a graph showing the relationship between the elapsed time in Example 1 of this invention, and the decreasing amount of the soot mass by plasma application. It is a graph showing the relationship between the elapsed time in Example 1 of this invention, and the NOx density | concentration in exhaust_gas | exhaustion. It is a graph showing the measurement result of the voltage waveform of the plasma reactor in the apparatus in Example 1 of this invention, a current waveform, and a power waveform. It is the schematic of the apparatus of the plasma application diesel particulate matter-NOx simultaneous removal system in Example 2 of this invention. It is a graph showing the relationship between the elapsed time at the time of operating only the plasma reactor A in Example 2 of this invention, and NOx density | concentration in exhaust_gas | exhaustion. It is a graph showing the relationship between the elapsed time and the NOx concentration in the exhaust when the plasma reactors A and B in the embodiment of the present invention are operated simultaneously. It is a graph showing the measurement result of the voltage waveform of the plasma reactor in the apparatus in Example 2 of this invention, a current waveform, and a power waveform.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust purification device 2 Engine main body 3 Generator 4 Battery 5 Exhaust passage 6 Plasma reactor 7 Adsorbent filter 8 Plasma power supply 9 Electronic control part 10 Oxygen sensor 10 'Air-fuel ratio sensor 11 Internal combustion engine

Claims (10)

Disposed on the exhaust path of the combustion device,
Purification means comprising a NOx adsorbent and / or particulate filter;
An exhaust gas purification device having a plasma application means disposed on the exhaust path,
Oxygen concentration detection means for detecting oxygen concentration in the exhaust,
When the oxygen concentration detected by the oxygen concentration detection means is equal to or higher than a predetermined value, the purification means performs exhaust gas purification, and when the amount of adsorption by the purification means exceeds a predetermined value, oxygen in the exhaust gas Control means for reducing the concentration and operating the plasma application means;
An exhaust emission control device comprising: The exhaust emission control device according to claim 1, wherein the oxygen concentration control by the oxygen concentration control means is performed by controlling an air-fuel ratio of a combustion device. The exhaust emission control device according to claim 1, wherein the oxygen concentration control by the oxygen concentration control means is performed by injecting hydrocarbons into the exhaust passage. The exhaust gas purification apparatus according to claim 1, wherein the oxygen concentration control by the oxygen concentration control means is performed by blowing nitrogen gas into the exhaust passage. The oxygen concentration control by the oxygen concentration control means is performed by at least one filter selected from the group consisting of an oxygen adsorbent, an oxygen separation membrane, a nitrogen adsorbent, and a nitrogen separation membrane. Exhaust gas purification device described in 1. The exhaust emission control device according to any one of claims 1 to 5, further comprising a catalyst for assisting in purification of exhaust gas. The exhaust emission control device according to any one of claims 1 to 6, wherein the combustion device is a diesel engine, and a limit value of operation switching of the oxygen concentration is 2 vol% or less. The plasma applying means is disposed outside the exhaust passage, and separately purifies NOx and burns and removes the collected fine particles by sucking air or gas separately and injecting the plasma into the exhaust passage after applying the plasma. An exhaust gas purification method using the exhaust gas purification device according to any one of claims 1 to 7. 9. The carbon monoxide, hydrocarbon, active oxygen, nitrogen dioxide, or a combination thereof in the exhaust gas is further used to assist the purification of exhaust gas, and at the same time, these are also purified. The exhaust gas purification method described in 1. Regarding the generation timing control of the plasma, the plasma power consumption is P, the total operation time of the internal combustion engine is DT, and the plasma is not applied in the operation state of the internal combustion engine that is equal to or higher than the limit value of the oxygen concentration in the exhaust gas. the operation time DT _1, the operating time in the case of applying the plasma with decreasing below the limit value of the oxygen concentration in the exhaust when the DT _2, taken smaller than the DT ₂ to DT ₁ and DT, plasma consumption an exhaust emission control device as claimed in any one of claims 1 to 9 which is controlled so as to reduce as compared with the power consumption P × DT in the case of continuously applying a plasma power amount P × DT ₂ Control method.