JP2006214310A - Nox removing device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a NOx removing device for a vehicle using a fuel reforming means for lowering hydro carbon contained in fuel such as light gas oil with little input energy in a simple process. <P>SOLUTION: The NOx removing device has the fuel reforming means 10 equipped with a reforming tank 107 for holding light gas oil and with fine bubble introducing means 101-106 for introducing fine bubbles into the reforming tank 107 and generating a NOx reducing agent, a fuel delivering means 20, and a NOx reducing agent adding means 30 for adding the NOx reducing agent into exhaust gas. If fine bubbles of micro to nano sizes in diameter are mixed with fuel, when minute bubbles vanish, the fuel becomes high temperature and high pressure instantaneously and shock waves are generated. Hydro carbon in the fuel can be dissolved by the shock waves and lower hydro carbon of an objective molecular weight is generated. Fine bubbles are introduced in the fuel reforming means separate from the fuel tank and therefore a treating condition can be chosen without affecting fuel in a fuel tank. A cost and input energy of the device can be reduced remarkably. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an in-vehicle NOx purification device that reduces and purifies NOx contained in exhaust gas of an internal combustion engine.

  Exhaust gas discharged from an internal combustion engine such as an automobile contains a lot of harmful substances. One of the harmful substances generated is NOx (nitrogen oxide), and reducing this substance is currently one of the challenges. For example, one cause of NOx generation in a diesel vehicle is the coexistence of oxygen at a high temperature during combustion in the engine cylinder. Here, as a method for reducing the generation of NOx, combustion in the engine cylinder is performed in a short time. As a result, PM (particulate matter), which is one of other harmful substances, increases. It will be. Further, it is conceivable to reduce NOx generation by lowering the temperature at the time of combustion, but there is a risk that the output will be reduced this time.

As a method of avoiding these disadvantages, there is a method of reducing NOx in exhaust gas generated in the engine by post-processing. As an example, there is a method of purifying by injecting light oil, which is a fuel of a diesel engine, into exhaust gas and reacting with NOx. That is, NOx is reduced to N ₂ by reacting light oil (hydrocarbon). In that case, it is desirable to employ a lower component than the hydrocarbon contained in the light oil as the hydrocarbon to be added. Lower hydrocarbons are easy to evaporate and bind to oxygen, so that the reaction of scavenging oxygen from NOx tends to proceed. In particular, hydrocarbons having 12 or less carbon atoms are desirable. Therefore, it is desired that the hydrocarbon added to the exhaust gas is not directly employed as light oil but is added as a lower hydrocarbon.

As a conventional technique, a method of cracking by heating a hydrocarbon in light oil at 700 ° C. to obtain a lower hydrocarbon is disclosed (Patent Document 1). In addition, a method of adding ozone for the purpose of improving the NOx reducibility instead of producing lower hydrocarbons is disclosed (Patent Document 2).
JP 2001-132433 A JP 2001-73744 A JP 2002-143885 A JP 2003-181259 A JP 2003-205228 A

  However, the method described in Patent Document 1 is not practical because a large amount of energy is required to thermally decompose light oil. In addition, the method described in Patent Document 2 requires an expensive ozone supply device such as an ozone generator, which is difficult to adopt from the viewpoint of cost.

  The present invention has been made in view of the above circumstances, and provides an in-vehicle NOx purification device employing fuel reforming means capable of lowering hydrocarbons contained in fuel such as light oil with a small input energy and a simple method. This is a problem to be solved.

A vehicle-mounted NOx purification device of the present invention that solves the above problems includes a reforming tank that holds fuel for an internal combustion engine inside, and microbubbles are introduced into the reforming tank so that a NOx reducing agent is supplied from the fuel for the internal combustion engine. A fuel reforming means comprising a microbubble introducing means for generating;
Fuel delivery means for delivering the internal combustion engine fuel in the fuel tank to the reformer tank of the fuel reforming means;
And a NOx reducing agent adding means for adding the generated NOx reducing agent to the exhaust gas from the internal combustion engine. Here, it is desirable that the microbubbles to be introduced have a diameter of 10 nm or more and 20 μm or less.

  When micro-sized or nano-sized micro-bubbles are mixed in the fuel, when the micro-bubbles disappear due to dissolution of gas components, instantaneously high pressure and high pressure of several thousand atmospheres and several thousand degrees Celsius are generated, generating shock waves. To do. The generated shock wave can decompose (crack) hydrocarbons in the fuel, and obtain lower hydrocarbons of the desired molecular weight.

  The in-vehicle NOx purification device of the present invention decomposes hydrocarbons in the fuel by introducing microbubbles into the fuel for the internal combustion engine. The molecular weight of the hydrocarbon can be controlled by the amount of microbubbles introduced in the fuel reforming means and the time of exposure to the microbubbles. In addition, since the introduction of microbubbles is performed by the fuel reforming means independent of the fuel tank, the fuel in the fuel tank is not affected, so the processing conditions that are optimal only for the NOx reducing agent are selected. It is also possible to do. Here, the cost and input energy of the apparatus required for introducing microbubbles into the fuel can be made much smaller than those disclosed in Patent Documents 1 and 2.

(In-vehicle NOx purification device)
The in-vehicle NOx purification device of this embodiment is applied to a vehicle equipped with an internal combustion engine. In particular, the present invention is suitably applied to a vehicle equipped with a diesel engine that is an internal combustion engine for which PM suppression is desired. This in-vehicle NOx purification device is a device that reduces NOx in exhaust gas by reforming fuel for an internal combustion engine to generate a NOx reducing agent and adding the NOx reducing agent to the exhaust gas of the internal combustion engine. . The apparatus includes a fuel reforming unit, a fuel delivery unit, and a NOx reducing agent addition unit. Here, the “NOx reducing agent” is a compound produced from a fuel for an internal combustion engine (for example, light oil) used in the internal combustion engine, and is composed mainly of hydrocarbons lower than the fuel for the internal combustion engine. is there. That is, the hydrocarbon contained in the fuel for the internal combustion engine used in the applied internal combustion engine is decomposed, and the molecular weight distribution is on the lower molecular weight side.

  The fuel reforming means is a means for generating a NOx reducing agent by reducing the molecular weight of the fuel for the internal combustion engine. By adding microbubbles to the fuel for the internal combustion engine, the fuel reforming means reduces the molecular weight and generates the NOx reducing agent. The fuel reforming means includes a reforming tank and microbubble introduction means. By introducing microbubbles into the reforming tank by the microbubble introducing means, the fuel for the internal combustion engine in the reforming tank is reformed to generate a NOx reducing agent.

  The reformer tank holds fuel for the internal combustion engine inside. Since it is assumed that the preferred molecular weight (distribution) in the fuel for internal combustion engines does not match the preferred molecular weight (distribution) in the NOx reducing agent, a reformer tank separate from the fuel tank or the like as a place for introducing microbubbles Is provided. This reformer can also be provided in the fuel tank. When fuel reforming means is provided in the fuel tank, separation between the two prevents the generated NOx reducing agent from mixing with the fuel tank and adversely affecting the fuel for the internal combustion engine in the fuel tank. To do. Therefore, complete separation is not essential unless it has an adverse effect.

  The microbubble introduction means is a means for introducing microbubbles into the reforming tank. Here, the microbubble is a bubble having a diameter of nanometer order to micrometer order, and has a size called nanobubble or microbubble. Specifically, the diameter of the microbubbles is preferably about 10 nm to 20 μm under normal pressure, and more preferably 10 nm to 100 nm. When the diameter of the microbubbles is controlled to this level, the shock wave is generated by disappearing in the fuel for the internal combustion engine, and the chemical bond in the fuel for the internal combustion engine is cut to reduce the molecular weight. The gas constituting the microbubbles is not particularly limited, but it is preferable to use air unless particularly necessary.

  It does not specifically limit as a production method of microbubbles. For example, there are a rheological method, a water electrolysis method and an ultrasonic wave generation method. The water electrolysis method is a method of generating microbubbles by introducing water into an internal combustion engine fuel and electrolyzing the water. The ultrasonic generation method is a method of generating microbubbles by controlling ultrasonic irradiation conditions. Microbubbles can be generated by irradiating the fuel for the internal combustion engine held in the reforming tank as it is, or by irradiating the ultrasonic wave while introducing the gas. When the ultrasonic wave is irradiated while introducing the gas, the input energy can be reduced.

  As will be described below, the rheological method can reduce input energy and is the most suitable method for generating microbubbles. The microbubble introduction means for generating microbubbles by a rheological method includes a main body part that forms a conical space having an opening at the apex, and a tangential direction of a circle that opens into the conical space and constitutes the conical space A fuel inlet for an internal combustion engine that allows the fuel for the internal combustion engine to flow toward the bottom, and a gas inlet that opens near the center of the bottom surface of the conical space and allows gas to flow in the axial direction of the cone that constitutes the conical space. Have.

  In a state where the conical space is filled with the fuel for the internal combustion engine, the swirling flow is generated in the conical space by flowing the fuel for the internal combustion engine from the fuel introduction port for the internal combustion engine. As a result, negative pressure is generated near the bottom of the conical space, and gas flows in from the gas inlet. The inflowing gas swirls together with the fuel for the internal combustion engine and advances toward the top of the conical space, and the introduced gas is reduced in diameter and expanded as it advances toward the top, thereby forming microbubbles. Then, it is led out from the cylindrical space together with the fuel for the internal combustion engine from the opening provided at the top of the conical space. By controlling the shape of the conical space (cone diameter, cone angle size, cone length, etc.), the introduction speed of the fuel for the internal combustion engine, the opening diameters of the fuel inlet and the gas inlet for the internal combustion engine, etc. The diameter of microbubbles can be controlled. Note that methods and apparatuses for generating microbubbles based on this principle are partially disclosed in Patent Documents 3 to 5.

  The NOx reducing agent adding means is means for adding the NOx reducing agent generated in the exhaust gas of the internal combustion engine. The location of addition of the NOx reducing agent in the exhaust gas is not particularly limited, but it is common to add the NOx reducing agent to the exhaust gas before being introduced into the NOx reduction catalyst. As a result, NOx is efficiently reduced by the NOx reduction catalyst. The NOx reduction catalyst is not particularly limited, and a known catalyst can be employed. For example, a catalyst in which a catalytic metal (such as copper) is supported on zeolite can be used. The addition method of the NOx reducing agent is not particularly limited, and an appropriate amount is added by atomizing or vaporizing in advance.

  The NOx reducing agent addition means desirably includes a separation means for separating low molecular weight hydrocarbons in the reforming tank. As a separation means, a membrane whose molecular weight changes its permeability (molecular sieves, zeolite, etc., which can easily control the pore diameter and control the molecular weight to be separated) can be exemplified as a preferable one. By controlling the diameter of the pores of the membrane, it is possible to preferentially separate the NOx reducing agent whose main component is a hydrocarbon having a molecular weight or less.

  The in-vehicle NOx purification device of this embodiment is a device used for a vehicle equipped with a diesel engine as an internal combustion engine. FIG. 1 shows an outline of the vicinity of a fuel injection device and an exhaust gas purification device for a vehicle incorporating the present purification device. The purification apparatus includes a fuel reforming means 10, a fuel delivery means 20, and a NOx reducing agent addition means 30 in the apparatus (means) shown in FIG.

  The fuel reforming means 10 includes microbubble introducing means 101 to 106 and a reforming tank 107. As shown in FIG. 1 and FIG. 2A, the microbubble introducing means 101 to 106 include a main body 101 having an internal space 101c and a lead-out port 101d, a fuel supply path 104 and an air supply path that open to the internal space 101c. 106, a fuel suction path 103 that opens into the reforming tank 107, a pump 102 that supplies fuel sucked from the fuel suction path 103 to the fuel supply path 104, and a flow rate of air that flows into the air supply path 106 is measured. A flow meter 105.

  The space 101c of the main body 101 forms a conical space. A fuel supply path 104 from the pump 102 is connected to the space 101c. The fuel supply path 104 opens in a tangential direction of a circle forming a cone formed by the space 101 c, and a swirl flow is generated in the space 101 c by light oil introduced from the fuel supply path 104. One end of the air supply path 106 opens at the bottom center of the conical space 101c. A flow meter 105 is connected to the other end of the air supply path 106 and opens into the atmosphere via the flow meter 105.

  In the state where the conical space 101c is filled with light oil, the microbubble introducing means 101 to 106 generate a swirling flow in the conical space 101c by flowing fuel from one end of the fuel supply path 104. As a result, a negative pressure is generated near the bottom of the conical space 101c, and air flows from one end of the air supply path 106. The amount of air flowing in can be controlled and measured by the flow meter 105.

  The inflowing air swirls with the light oil in the conical space 101c, and then proceeds toward the top of the conical space 101c. As the air travels in the top direction, the introduced air is reduced in diameter and expanded to form microbubbles, which are led into the reforming tank 107 together with light oil as fuel from the outlet 101d provided at the top of the conical space 101c. To go. As a result, microbubbles are dispersed in the reforming tank 107. That is, by introducing light oil from the fuel supply path 104, air is sucked from the air supply path 106, and light oil containing microbubbles is discharged into the reforming tank 107 from the outlet 101d.

  The size of the generated microbubbles is controlled to have a diameter of 10 nm to 100 nm. When the dispersed microbubbles disappear, a shock wave is generated and acts on the hydrocarbons in the gas oil to decompose and reduce the molecular weight of the hydrocarbons. The microbubble introduction means 101 to 106 are operated until the hydrocarbons in the light oil are decomposed to a predetermined molecular weight (distribution). Here, it is desirable to adopt a value having 12 or less carbon atoms as the predetermined molecular weight. In particular, the number of carbon atoms is about 10, 12, or 10 to 12, preferably 12 or less, and more preferably 10 or less.

  The light oil in the fuel tank 40 is sent into the reforming tank 107 by the fuel sending means 20. When the pressure in the reforming tank 107 becomes larger than a predetermined value for some reason, the regulator 108 is opened and the fuel in the reforming tank 107 is discharged into the fuel tank 40.

  The NOx reducing agent adding means 30 adds the NOx reducing agent generated in the reforming tank 107 to the exhaust gas. The NOx reducing agent is added after the oxidation catalyst 82 and before the NOx reduction catalyst 83. The amount of the NOx reducing agent to be added can be determined based on the temperature, NOx concentration, oxygen concentration, etc. detected by the sensors 71 to 74 such as the NOx concentration and temperature.

(Modification 1)
As the microbubble introduction means, an ultrasonic irradiation means 111 as shown in FIG. 2B may be adopted instead of the main body 101, the air supply path 106 and the flow meter 105 in FIGS. 1 and 2A. it can. The ultrasonic wave irradiation means 111 includes a flat rectangular parallelepiped internal space 111c, a fuel supply path 104 is connected to one end of the internal space 111c, and a lead-out port 111d (and others) having one end open on the opposite side of the internal space 111c. The end portion opens into the reforming tank 107). An ultrasonic transducer 112 is disposed in the internal space 111c.

  The light oil supplied from the fuel supply path 104 is irradiated with ultrasonic waves by the ultrasonic vibrator 112. When ultrasonic waves are irradiated, microbubbles are generated in the light oil. When the generated microbubbles disappear, a shock wave is generated to decompose and reduce the molecular weight of hydrocarbons in the gas oil.

(Modification 2)
In order to selectively add low molecular weight hydrocarbons into the exhaust gas, the NOx reducing agent addition means 30 can be provided with a separation means 31 (FIG. 3) for separating hydrocarbons in the reforming tank 107 according to molecular weight. The separation means 31 includes a separation membrane 311 that separates molecules by molecular weight (molecular size) such as a zeolite membrane, and internal spaces 31a and 31b divided into two by the separation membrane 311. In the internal space 31a, the fuel (NOx reducing agent) in the reforming tank 107 is introduced from one side. In the introduced NOx reducing agent, low molecular weight components permeate the separation membrane and move to the internal space 31b, and high molecular weight components remain in the internal space 31a. The NOx reducing agent adding means 30 for injecting the NOx reducing agent into the exhaust gas is connected to the opening c of the internal space 31b from which the low molecular weight component has been separated. The opening b of the internal space 31 a where the high molecular weight component remains opens again into the reforming tank 107. Therefore, the low molecular weight component is selectively extracted from the reforming tank 107, and the generated NOx reducing agent can be added more effectively.

It is a figure which shows the outline of the fuel-injection apparatus and exhaust-gas purification apparatus vicinity of the vehicle incorporating the vehicle-mounted NOx purification apparatus of an Example. It is sectional drawing of the microbubble generation means employ | adopted in the Example. It is sectional drawing of the isolation | separation means employ | adopted in the Example.

Explanation of symbols

10. Fuel reforming means (rheological method)
DESCRIPTION OF SYMBOLS 101 ... Main-body part 101c ... Internal space 101d ... Outlet 102 ... Pump 104 ... Fuel supply path 106 ... Air supply path 107 ... Reforming tank 11 ... Fuel reforming means (ultrasonic generation method)
DESCRIPTION OF SYMBOLS 111 ... Main-body part 111c ... Internal space 111d ... Outlet port 104 ... Fuel supply path 112 ... Ultrasonic vibrator 107 ... Reforming tank 20 ... Fuel delivery pump 30 ... NOx reducing agent addition means 31 ... Separation means 311 ... Separation membrane

Claims (3)

A fuel reforming means comprising: a reforming tank that holds internal combustion engine fuel; and a microbubble introduction means that introduces microbubbles into the reforming tank and generates NOx reducing agent from the internal combustion engine fuel;
Fuel delivery means for delivering the internal combustion engine fuel in the fuel tank to the reformer tank of the fuel reforming means;
NOx reducing agent addition means for adding the produced NOx reducing agent to exhaust gas from the internal combustion engine;
A vehicle-mounted NOx purification device characterized by comprising:   The in-vehicle NOx purification device according to claim 1, wherein the microbubbles have a diameter of 10 nm or more and 20 μm or less.   The in-vehicle NOx purification device according to claim 1 or 2, wherein the NOx reducing agent adding means includes separation means for preferentially separating the NOx reducing agent.

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