JPS61278334A - Method and apparatus for irradiating electron beam to exhaust gas - Google Patents

Abstract

PURPOSE:To perform the continuous dry treatment of an exhaust gas due to the irradiation of an electron beam without the loss of energy by irradiating the electron beam which is irradiated through a small hole provided to a pipe wall of a duct for transporting the exhaust gas to the exhaust gas while scanning it in the inside of the duct. CONSTITUTION:In a purifying apparatus for an exhaust gas generated by the combustion of fuel in a power plant or the like, after the electron beam irradiated from an electron beam accelerator 1' is irradiated in the specified direction through a small hole 6 provided to a duct 3' of the exhaust gas, it is scanned within a range of necessary scanning angle theta with a scanner 7 provided to the inside of the duct and irradiated to the exhaust gas. SO2 and NOX incorporated in the exhaust gas are made to dust or a mist with the irradiation of the electron beam and recovered with a dust collector or the like. Still more the inner pressure may be regulated with a suction pipe 9. Since a window foil is not necessarily stretched on an incident window by irradiating the electron beam through the small hole, the loss of energy is not caused and this apparatus is favorable in the industrial practice.

Description

DETAILED DESCRIPTION OF THE INVENTION It has been a long time since environmental pollution, especially air pollution, became a serious social problem worldwide. Through the efforts of many people concerned, various new exhaust purification techniques have been developed and attempted, but to date, no completely satisfactory solution has been obtained. However, research continues unabated and results are steadily being produced. The present invention was achieved as a result of research that is part of such efforts.

Sources of air pollutants are classified into fixed sources such as industry and mobile sources such as automobiles and airplanes, and sources of pollutants include fuel combustion, processing of raw materials, chemical reactions, etc. . The present invention is primarily aimed at purifying exhaust gas generated by combustion of fuel in factories and power plants. The pollutants contained in exhaust gas are sulfur oxides (SO
2, SO3 Human dust, nitrogen oxides (NOx), harmful substances (C: a, Pb, (J2HCl, F HF,
S iF , i and others), dung, etc. are 2+, but in the present invention, in particular, S02 and NOx are removed. The main focus is These are contained in relatively large amounts as toxic gas components in almost all combustion exhaust gas, and each
It is one of the most difficult pollutants to remove. Although many relatively good methods have been developed for removing SO2,
Many wet methods use large amounts of water and specific chemicals, which generate a large amount of wastewater and large amounts of byproducts, making their treatment difficult7, so the emergence of a better method is eagerly awaited. There is. It is thought that the cause of acid rain, which has become a serious social problem in European countries especially in recent years due to the heatwave in West Germany, is the large amount of SO□ released into the atmosphere. Removal of NOx is even more difficult than removal of SO2, and no advantageous industrial method for its removal has yet been established.

The present inventors have discovered that electron beams with high dose rates can be used with SO2 and N0.
By irradiating the exhaust gas containing xyl, SO□ and NOxY contained in the exhaust gas as toxic gas components
At the same time, after changing the form to solid dust or mist, this dust or mist is removed using a dust collector, etc.
We have developed a method for purifying exhaust gas to be recovered, and have already obtained numerous patents, including basic patents for the technology.This method is dry and produces only a small amount of by-products, so it is mainly used to remove waste gas from stationary sources. This is the most promising method for purifying the combustion exhaust gas that is generated, and has the potential to be widely disseminated throughout the world in the future.Our purpose is to improve this method to a higher level and disseminate it worldwide. Inventions also play a role.

Electron beam in exhaust gas? In the method of removing toxic gas components by irradiation, the conventionally adopted electron beam irradiation method is the second method.
The method was as shown in the figure. That is, an electron beam generator of an integrated structure in which an electron beam accelerator 1 and a scanning device 2 communicate with each other in the same vacuum is placed near the outside of a reaction chamber, and the electron beam is scanned from the irradiation window A of the generator. The exhaust gas inside the reactor was irradiated with the electron beam 5 through the entrance window 47 of the reactor. This is because the exhaust gas can only be irradiated with the electron beam 7 for a very short period of time when it passes near the entrance window, so it is necessary to irradiate the electron beam scanned with a constant spread. However, with this method, is there a certain amount of space? Since it is necessary to provide the entrance window 7 with the entrance window 7 open, it is difficult to continue operation for a long time with the entrance window open. That is, if the pressure inside the reactor is negative, a large amount of outside air will flow in through the entrance window, interfering with the gas treatment 7, and if the pressure is positive, the exhaust gas will blow out to the outside of the duct, causing problems 7. For this reason, in the conventional method, a thin metal foil was placed over the entrance window of the reactor, and the electron beam was irradiated through the entrance window foil.

However, when the electron beam passes through the window foil, the energy of the electron beam is greatly reduced, and this energy loss turns into heat and heats up the window foil, so appropriate cooling is required. In order to reduce this energy loss and reduce the need for cooling equipment, the window foil must be made as thin as possible, and typically a foil of 0.05 mm or less is used. On the other hand, due to the nature of exhaust gas, the window foil that comes into contact with the exhaust gas must be corrosion resistant, and for example, corrosion resistant alloy foil such as titanium alloy is used.

Corrosion of window foil is not only caused by gas components.

When foreign matter in the gas or solid or mist-like products generated by electron beam irradiation adheres to the window foil, this adhered area becomes
The window foil is locally heated by the passing electron beam, synergistically promoting corrosion and causing significant damage 7 to the window foil. in this way,
Window foil is used under harsh environmental conditions such as contact with corrosive gases and exposure to high temperatures, and for the reasons mentioned above, it has to be extremely thin (7), making it difficult to operate. This has traditionally been an important problem in operational management.Therefore, such a window foil for the entrance window should not be used (if the exhaust gas in the reactor is not exposed to the electron beam accelerator). If it were possible to do so, there would be no problems such as energy loss due to absorption of electron beams or cooling of heat generated thereby, and it is clear that this would be a major technical contribution in the field. The present invention provides a method and apparatus for performing such irradiation.

The present inventor completed the present invention by discovering that exhaust gas can be continuously irradiated with electron beams without using a window foil for the entrance window by performing irradiation using the following non-conventional method. did. That is, in the irradiation method of the present invention, a small hole is formed in a part of the pipe wall of the exhaust gas transport duct (conduit), and an electron beam is irradiated in a fixed direction from the outside to the inside of the duct through the small hole. It is characterized by irradiating the flowing exhaust gas with the electron beam while scanning the electron beam within a certain range of angles after passing through a small hole.

Hereinafter, the method of the present invention will be explained in more detail with reference to FIG.

FIG. 1 is a diagram which does not explain the principle of the electron beam irradiation method of the present invention, and also shows a cross-sectional structure of a specific example of a preferred apparatus that can be used to carry out the method.

According to the present invention, the electron beam 5 irradiated from the electron beam accelerator 1' is irradiated in a fixed direction through small holes 6 (two in series in the illustrated example) provided in a part of the exhaust gas duct 3'. Thereafter, the light is scanned by a scanner 7 provided in the duct 3', using the "S" point as a refraction point, within the range of the required scanning angle θ. In this method, the small hole 6 corresponds to the entrance window of the reactor, but unlike the conventional irradiation method, the small hole 6 corresponds to the electron beam entrance window before being scanned. - Since it is only necessary to pass the electron beam in a certain direction, the entrance window may be an extremely small hole having a diameter somewhat larger than the diameter of the cross section of the electron beam beam passing through. Therefore, even if the entrance window is not covered with window foil and operated in an open state, there will not be any major hindrance, but if necessary, the following structure may be adopted to avoid the anticipated inconveniences. ? It is possible to avoid it. In other words, if the exhaust gas pressure inside the duct 3' is higher than the outside pressure,
As shown in the figure, a low pressure chamber 8 is provided at the opening of the small hole 6, and suction is carried out from the chamber through an intake pipe 9, and the sucked exhaust gas is passed through a duct 3.
′. By setting it in this way, the pressure inside the low pressure chamber 8 can be set lower than the outside pressure, so leakage of exhaust gas to the outside air can be prevented.On the other hand,
If the exhaust gas pressure inside the duct 3' is lower than the outside pressure, c.
Although outside air enters the exhaust gas duct 3' through the small hole 6, the exhaust gas does not leak into the outside air. The area of the small hole should be small enough to allow the electron beam traveling in a certain direction to pass through, so in any of the above cases, the exhaust gas duct 3
The amount of outside air mixed in with ' is so small that its influence on the effectiveness of exhaust gas treatment can be ignored. The scanner 7 is preferably arranged so that the refraction point S occurs very close to the position where the electron beam passes through the small hole. Is the scanner placed outside the duct of the main part of the device, and only the parts that need to be brought close to the electron beam for electron beam scanning? , it can be covered with a corrosion-resistant member, inserted into the duct, and placed across the bending point SY as shown in the figure. The part of the duct that is irradiated with the electron beam at the scanning angle θ is a part corresponding to the reactor, and may be a part of the duct itself that is completely integrated with the duct,
As shown in the figure, it may have a partially protruding outer shape. As shown in the figure, it would be reasonable to assume that the outer wall of the protruding portion has a cross-sectional shape that is parallel to two fan-shaped linear portions with a central angle that is the apex of the refraction point Si.

According to the method of the present invention, it is possible to irradiate the exhaust gas with an electron beam in an open state without placing a window foil on the reactor entrance window, so there is no energy loss due to the window foil absorbing the electron beam sound. Of course, there is no need for a cooling device to cool down the generated heat.

The apparatus of the present invention enables industrial implementation of the method of the present invention by various means. It can be said that the method and apparatus of the present invention have brought practical use and widespread use of dry continuous large-scale treatment of exhaust gas by electron beam irradiation.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a preferable irradiation device that can be used to carry out the electron beam irradiation method of the present invention. FIG. 2 is a diagram showing a cross-sectional structure of an irradiation device commonly used in a conventional electron beam irradiation method. The symbols in the figure represent the following: Figure 1 Figure 2 1', 1...Electron beam accelerator 2...Scanning device 3...Exhaust gas duct 4...Window foil (incidence window) 5...Electron beam 6...Small Hole 7 ... Scanner Figure 1 Figure 2 8 ... Low pressure chamber 9 ... Intake pipe A ... Irradiation window Patent applicant Ebara Corporation (5 others)

Claims (4)

[Claims] (1) A small hole is provided in a part of the pipe wall of the exhaust gas transport duct,
An exhaust gas characterized in that an electron beam is irradiated in a certain direction from the outside to the inside of the duct through the small hole, and the exhaust gas is irradiated with the electron beam that has passed through the small hole while scanning it within a certain range of angles. A method of irradiating with electron beams. (2) A part of the tube wall has a small hole for passing the electron beam in a certain direction, and both open ends are connected to the exhaust gas transport duct and substantially constitute a part of the duct. An electron beam irradiation reaction chamber consisting of a tubular body, an electron beam placed outside and near the tubular body, and set so that the generated electron beam passes through the small hole and is irradiated in a fixed direction toward the inside of the duct. It is characterized by comprising an accelerator and a scanner for scanning the electron beam that has passed through the small hole within the required scanning angle θ with a point S near the tube wall inside the reaction chamber as a refraction point. A device that irradiates the exhaust gas with an electron beam. (3) The small hole portion of the reaction chamber is composed of a pair of small holes arranged concentrically with an interval in the direction of propagation of the electron beam, and the middle of the two opposing members each containing the two small holes is 3. The device according to claim 2, wherein the device is configured to form a low-pressure chamber that is a small space with reduced pressure. (4) An intake pipe connected to a part of the low pressure chamber, and a suction means for sucking gas in the low pressure chamber through the intake pipe, and the discharge end of the intake pipe is connected to a reaction chamber or a duct for transporting exhaust gas. 4. Device according to claim 3, characterized in that it is connected to a part of the wall of a tube.