JP3602204B2 - Device for reducing particulates in exhaust gas - Google Patents

Description

[0001]
[Industrial applications]
TECHNICAL FIELD The present invention relates to a device for reducing particulates in exhaust gas, which can efficiently burn combustible particulates among particulates discharged from a diesel engine or a boiler of an automobile or a ship, thereby reducing particulates in exhaust gas.
[0002]
[Prior art]
In recent years, fine particles discharged from diesel engines and boilers have become a problem as a cause of environmental degradation. As a countermeasure, a particulate reduction device that captures fine particles with a filter and burns the captured fine particles has been studied.
[0003]
By the way, as a method of burning the captured fine particles, Journal of the M.D. E. FIG. S. J. , Vol. 27, no. 8, pp. As disclosed in 570 to 575, a system using an electric heater has been proposed.
[0004]
[Problems to be solved by the invention]
However, the heating and burning by the electric heater has not been put into practical use due to problems in durability and reliability of the heater. In the field of fuel vaporization, a heating device has been proposed in which a porous magnetic material such as a wire mesh, scrap iron, or foam metal is disposed in a portion where fuel passes, and the porous magnetic material is heated by electromagnetic induction. Have been. (See JP-A-55-82210, JP-A-61-38318, and JP-A-64-58906). It is not surprising that exhaust gas can be passed through such a porous magnetic material instead of fuel, but the pressure loss when passing through the porous magnetic material is large, and the temperature in the cross-sectional direction of the porous magnetic material is high. The unevenness is too large to be practical.
[0005]
The present invention has been made to solve this problem, and it is an object of the present invention to provide an apparatus for reducing fine particles in exhaust gas, which can heat a metal filter by electromagnetic induction and efficiently burn combustible fine particles in exhaust gas. With the goal.
[0006]
[Means for Solving the Problems]
The apparatus for reducing particulates in exhaust gas of the present invention that solves the above-mentioned problem is a pipe made of a nonmagnetic material through which exhaust gas passes, a coil wound around the pipe, and heated by electromagnetic induction caused by the coil housed in the pipe. A metal filter comprising a plurality of members regularly arranged along a gas passage direction, the members being electrically connected to each other, and an eddy current is generated over the entire cross section of the filter. The combustible fine particles in the exhaust gas are brought into contact with the heated filter and burned. It is preferable that the member of the filter is formed of a plate or a small-diameter pipe extending in the axial direction of the pipe, and the electrical connection of the member of the filter is performed by welding or brazing the members. Are preferred.
[0007]
Further, a system in which a metal removing device for removing trace metal particles in exhaust gas or a condenser for removing condensed components in exhaust gas may be provided downstream of the particle reducing device.
[0008]
[Action]
Since a large number of members are regularly arranged along the gas passage direction, the chance of the fine particles in the exhaust gas coming into contact with the wall of the member can be increased while the pressure loss is small. Since the plurality of members are electrically connected to each other and the entire cross section is heated, the combustible fine particles can be burned at a predetermined temperature without unevenness in the cross section direction.
[0009]
When the exhaust gas after burning the combustible fine particles is passed through a metal removing device, trace metal particles are removed. When the exhaust gas after burning the combustible fine particles is passed through a condenser, the condensed components in the exhaust gas are also removed.
[0010]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a device configuration diagram of a particle reduction device, and FIG. 2 is a cross-sectional view of a metal filter.
[0011]
In FIG. 1, a particulate reduction device 1 is attached to a chimney portion 3 of an exhaust gas generator 2 such as an engine. When the particulate reduction device 1 is attached to a portion close to the high-temperature and high-pressure exhaust gas from the exhaust gas generator 2, energy efficiency is increased, and a special blower or the like is not required, which is convenient.
[0012]
The particulate reduction device 1 includes a pipe 11, a coil 12, a metal filter 13, and an inverter 14.
[0013]
The pipe 11 is a non-magnetic material such as ceramic and is formed of a material having excellent heat resistance and corrosion resistance. It is usually round, but may be an elliptical or square pipe. The metal filter 13 is housed in the pipe 11, and the coil 12 is wound around the outer periphery of the pipe 11 where the metal filter 13 is housed.
[0014]
The coil 12 is formed by twisting litz wires. An inverter 14 for supplying a high-frequency current to the coil 12 is connected.
[0015]
The material of the metal filter 13 has a magnetic permeability such that electromagnetic induction easily occurs, and also has corrosion resistance to exhaust gas. Such materials include martensitic stainless steel, nickel alloys, chromium alloys and the like.
[0016]
Next, the structure of the metal filter 13 will be described with reference to FIG. Although three types are shown in FIG. 2, each filter has a large number of plate members or small-diameter pipe members extending in the axial direction of the pipe 11 regularly arranged. The pipe members are joined by welding or metal brazing so as to enable electrical conduction.
[0017]
In FIG. 2A, the horizontal plate member 21 and the vertical plate member 22 are assembled in a lattice, and the respective plate members 21 and 22 are joined by welding or metal brazing. In FIG. 2B, the plate members 23 are arranged in parallel and at equal intervals, and each plate member 23 is penetrated by a bar 24 arranged at a key position, thereby maintaining shape and electrical conduction between the plate members. It was secured. FIG. 2C shows a small-diameter pipe 25 closely bundled and joined by welding or metal brazing, and the space in the small-diameter pipe 25 and the space between the small-diameter pipes 25 are used as exhaust gas passages. .
[0018]
In this way, if the cross section of the metal filter assembles a plate member or a small-diameter pipe member regularly, and these members are not electrically independent, and have a structure particularly easy to conduct in the radial direction, the generation of eddy current due to electromagnetic induction causes This occurs over substantially the entire area of the cross section of the filter, and heat generation unevenness in the cross section is reduced. Further, since the plate member or the small-diameter pipe member extends in the axial direction, the exhaust gas flows in the axial direction along small segments separated by the plate member or the small-diameter pipe member. As a result, although the pressure loss of the exhaust gas is small, there is a high possibility that the fine particles contained in the exhaust gas come into contact with the walls of the small and elongated segments separated by the plate member or the small-diameter pipe member.
[0019]
Next, a structural example of the inverter 14 will be described with reference to FIG. The inverter 14 shown in FIG. 3 sequentially switches the four main switches S1 to S4 to generate forward and reverse currents. As the main switches S1 to S4, self-extinguishing switches using semiconductor devices such as IGBTs, B-SITs, and MOSFETs are used.
[0020]
In particular, the circuit of FIG. 3 connects the diodes Dp1 and Dp2 in antiparallel to the main switches S1 and S2 so that soft switching is possible, and connects the small reactors L1 and L2 to the diodes Dp1 and Dp2, respectively. No anti-parallel diodes are connected to S3 and S4, and diodes Ds3 and Ds4 for reverse current prevention and reverse withstand voltage are connected in series, respectively. In addition, Ed is a power supply unit including a commercial power supply, a rectifying unit, a non-smoothing filter, and the like. The metal filter 13 connected between the main switches S1 and S4 and between the main switches S2 and S3 can be approximated to a transformer circuit model having a large leakage inductance, and is represented by a simple RL circuit composed of Lo and Ro. it can. When a compensation capacitor Co is connected in series to this RL circuit, a non-time-variable circuit system in which the electric circuit constant hardly changes is obtained.
[0021]
As shown by the waveforms i1 and i2 in the waveform diagrams of FIGS. 4A and 4B, when Dp1 and Dp2 are conducting (i1 = i2 <0), S3 and S4 are triggered to turn on. , Dp1 and Dp2 do not suddenly become zero due to the action of L1 and L2, but decrease with a certain slope. At the same time, the currents i3 and i4 due to the turn-on of S3 and S4 also increase with a certain slope from zero because the current i0 = i1-i4 flowing through Lo cannot be changed abruptly.
[0022]
That is, a ZCS operation when Dp1 and Dp2 are turned off and a ZCS (Zero, Current Switching) operation when S3 and S4 are turned on are realized. When i3 = i4 = 0 due to resonance, the turned-on currents of S3 and S4 naturally turn off by the ZCS operation. When S1 and S2 are triggered at t = 0, they rise from i1 = i2 = 0 and perform ZCS operation. As described above, all switches can realize the ZCS operation as soft switching without adding an extra active switch.
[0023]
Further, as shown in FIG. 4B with respect to FIG. 4A, when the time delay td (phase difference) at which S1, S2 and S3, S4 are triggered is changed, the current (regeneration current) flowing through Dp1, Dp2 is reduced. The magnitude can be controlled, so that the input current id and thus the input / output power can be adjusted. In other words, this means that the input and output power can be controlled at a constant frequency, as opposed to the method of controlling the input and output power by changing the output frequency. In addition, the surge voltage and switching loss peculiar to high frequency are solved by the ZCS operation. are doing.
[0024]
Not only the inverter capable of soft switching described above, but also a phase shift PWM method using a voltage-type series additional resonance full bridge, a current power supply control (PAM method) using an active PAM rectifier circuit or a high-frequency transistor chopper, and a variable frequency control (PFM) Method), pulse density modulation control (PDM method) by pulse cycle control, or any of these various methods provided with an auxiliary circuit for promoting soft switching.
[0025]
In the particle reduction device 1 of FIG. 1 provided with the above-described devices, when a high frequency (10 to 100 KHz) is applied to the coil 12 as the excitation coil by the inverter 14, the high frequency magnetic flux passes through the metal filter 13. Then, an electromotive force is generated on the surface of the member constituting the metal filter 13, and as a result, an eddy current flows. This eddy current is generated substantially uniformly or more in the center than in the peripheral portion over the entire cross section of the metal filter 13, and the surface of the member of the metal filter 13 is heated in a non-contact manner. become.
[0026]
An exhaust gas passage is formed along each member of the metal filter 13, and the exhaust gas passes through an axially elongated segment defined by each member. At that time, the combustible fine particles contained in the exhaust gas come into contact with the walls of the respective members and are burned instantaneously and reduced. The fine particles of the exhaust gas include not only flammable substances such as organic compounds but also non-combustible substances such as trace metals. It is not completely eliminated.
[0027]
Therefore, as shown in FIG. 5, a liquid tank 4 as a metal removing device is provided downstream of the particle reducing device 1 of the present invention to precipitate a trace amount of metal particles in exhaust gas, and almost all of the particles are removed. It can also be a particulate reduction device or a particulate reduction system for removal. When the components removed in the exhaust gas are composed of condensable components, as shown in FIG. 6, a condenser 5 is provided downstream of the particulate reduction device 1 of the present invention, and the components are concentrated. A particulate reduction device or a particulate reduction system for removing the component to be removed may be used. At this time, a removal cycle can be promoted by increasing the concentration of the removal component by setting a circulation cycle in which a part of the removal component is returned to the upstream of the particle reduction device 1.
[0028]
Further, when the material of the metal filter of the particulate reduction device 1 contains or is attached with a catalyst metal, it is possible to detoxify the characteristic components (for example, NOx) of the exhaust gas by a heating reaction.
[0029]
【The invention's effect】
The present invention configured as described above allows exhaust gas to pass through a metal filter that has been contactlessly heated to 600 ° C. or higher by electromagnetic induction. Therefore, the combustible fine particles in the exhaust gas come into contact with the members constituting the metal filter and are instantaneously burned and removed. The structure of the metal filter is composed of a large number of members arranged regularly along the gas passage direction, and the members are electrically coupled to each other, so that the entire cross section of the filter generates heat. The combustible fine particles can be efficiently burned without heating the metal filter more than necessary. In addition, if a metal removing device or a condenser is disposed downstream of the particle reduction device of the present invention, trace metal particles and condensed components in the exhaust gas are removed, and the cleanness of the exhaust gas is further improved.
[Brief description of the drawings]
FIG. 1 is a device configuration diagram of a particle reduction device.
FIG. 2 is a sectional view of a metal filter.
FIG. 3 is a circuit diagram of an inverter.
FIG. 4 is a waveform diagram of an inverter.
FIG. 5 is a system diagram of another particle reduction device.
FIG. 6 is a system diagram of still another particle reduction device.
[Explanation of symbols]
1 particle reduction device 2 exhaust gas generator 3 chimney 4 fluid tank (metal removal device)
5 Condenser 11 Pipe 12 Coil 13 Metal filter 14 Inverter

Claims (5)

A pipe made of a non-magnetic material through which exhaust gas passes, a coil wound around the pipe, and a metal filter housed in the pipe and heated by electromagnetic induction by the coil, the metal filter is arranged in a gas passing direction. It is composed of a large number of members regularly arranged along a line, and the members are electrically coupled to each other, so that an eddy current is generated and heated over the entire cross section of the filter, thereby heating the combustible fine particles in the exhaust gas. A device for reducing particulates in exhaust gas that is brought into contact with a burned filter and burned. The apparatus according to claim 1, wherein the member of the filter is a plate or a small-diameter pipe extending in an axial direction of the pipe. The particulate reduction device according to claim 1, wherein the electrical connection of the members of the filter is performed by welding or brazing the members. A particle reduction device provided with a metal removal device for removing trace metal particles in exhaust gas downstream of the particle reduction device according to claim 1. A particle reduction device provided with a condenser for removing a condensed component in exhaust gas downstream of the particle reduction device according to claim 1.

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