JPS61238325A - Desulfurization and densitration apparatus of exhaust gas byelectron irradiation - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an apparatus consisting essentially of an exhaust gas path and at least one low-energy electron beam source with an electron beam potential in the vicinity of 250 keV, the device comprising: ammonia doping prior to irradiation; The present invention relates to a device that desulfurizes and denitrates exhaust gas by irradiating the exhaust gas with electrons.

Desulfurization and denitrification of exhaust gases from large-scale furnaces plays an important role in the waste management of our environment today.

In addition to catalytic dry methods and many wet methods used simultaneously or selectively, in recent years in Japan a physical method has been developed for the conversion of SO□ and NOx by irradiation with accelerated electrons in the presence of ammonia. It's here. This process produces ammonium sulfate and ammonium nitrate, which are removed in an air filtration system. Examples of this method are Radiat and Fiss.

(Rcidiat, Phys, Chem,) Volume 18, No. 1-2, Pages 389-398 (1981
), in which the exhaust gas is irradiated and simultaneously mixed by two opposing relatively high voltage electron beam sources (750 keV) in a spherical continuous flow reactor.

However, the use of these high voltage electron beams has proven disadvantageous for various reasons.

For these reasons, the present applicant proposed desulfurization and denitration of exhaust gas by irradiation with low-energy electrons (Japanese Patent Laid-Open No. 179123/1983).

This method and the equipment used in this method can only process relatively small amounts of exhaust gas, because the electron beam used is equipped with a one-point cathode and an electron beam deflector (which is the principle of scanning). This is because the electron emission from the swan point cathode is limited, making it impossible to obtain the required high performance.

To overcome this problem, it is possible to use low energy electron beam devices that achieve the required high performance. In this device, at least two wide area cathode systems are arranged in parallel in a vacuum vessel, each wide area cathode system having an electron emitting aperture having the same length and width as the wide area cathode system. High performance is achieved due to the fact that it has In this device, the optimum irradiation conditions for electron beam potential, electron flow, electron emission aperture load, electron transmittance, and cross section of the exhaust gas path are achieved with the two electron beam devices facing each other. It has been adjusted so that it can be done. However, two completely independent electron beam devices are required for the irradiation, and the electron beams are irradiated into the exhaust gas path from the outside. This is considered to be somewhat of a disadvantage. Furthermore, the exhaust gas path and the electron beam must be shielded by a lead plate.

Shielding the irradiated electron beam and the exhaust gas path requires considerable expense. This is because the electron beam device must be removed when performing maintenance work on the exhaust gas path. (See Japanese Patent Application No. 60-237776.) Therefore, it is an object of the present invention to provide an apparatus for desulfurizing and denitrating exhaust gas by electron beam irradiation, which requires the use of only one low-energy electron beam source.

Therefore, according to the present invention, in an apparatus for desulfurizing and denitrating exhaust gas by performing electron irradiation on exhaust gas to which ammonia has been added prior to electron irradiation, the apparatus has an exhaust gas path and an electron beam potential of 150 to 300
at least one low-energy electron beam source of keV, the electron beam source being arranged concentrically and coaxially in the exhaust gas path and having at least two electron emitting openings; There is provided an exhaust gas desulfurization and denitrification device using electron irradiation, which is characterized by the following.

Next, embodiments of the present invention will be described with reference to the drawings.

The invention provides significant savings in the cost of electron beam equipment and shielding equipment. The reason is that instead of a surface electron beam device, we use only a unidirectionally oriented electron beam source, a so-called emitting surface beam device, which is placed on the central axis of the tube-shaped exhaust gas path and the electron beam This is because the gases are arranged to radiate toward the outer wall of the exhaust gas passage in at least two directions. The radial surface beam device E (FIGS. 1 and 2) is arranged coaxially in the exhaust gas path in a cylindrical device and has at least two, preferably four or more electron emitting openings 6. have. Although this arrangement of the electron beam source E results in a non-uniform dose distribution in the exhaust gas path, this is not critical. This is because the turbulence of the exhaust gas is also used during the external to internal irradiation with two mutually facing electron beams.

The distance between the electron emission opening 6 and the outer wall 10 of the exhaust gas channel depends on the maximum potential of the electron beam. It must be ensured that the maximum range of the electron beam does not in any case exceed the distance between the opening and the outer wall. Otherwise, the tube wall will overheat and the efficiency of the irradiation device will be reduced.

The blocking of the X-rays in the radial plane beam is of a very simple type in the present invention. The following methods are possible.

(a) With the radial plane beam device placed in the horizontal exhaust gas path (FIG. 3), the exhaust gas path is directly covered with a lead plate. In order to weaken the X-rays diffused into the exhaust gas path, the exhaust gas path is bent twice before and after the irradiation area. These bends are also coated with lead, which is simple since flat surfaces are included.

Electrical power or power is supplied to the electron beam device via one opposite end of the tortuous exhaust gas passage. This opposite end also serves as a security outlet for the radial beam device. The radial plane beam device is installed from the exhaust gas path through this part for maintenance purposes.

You can take it out.

(b) When a radial plane beam device is placed in a vertical exhaust gas path (Figure 4), there is a possibility of installing the exhaust gas path underground, and the earth may act as an X-ray blocker. can. For maintenance purposes, the radial beam device is removed from the exhaust gas duct via its upper end.

The radial plane beam device consists of components known in electron beam engineering, without any particular restrictions on their construction, the plane beam device having a long useful life and the electron-emitting aperture facing the cathode system, e.g. , Japanese Patent Application Laid-Open No. 179123/1983 and Japanese Patent Application No. 1983, which are the earlier applications of the applicant mentioned above.
It can also be designed similarly to that described in No. 0-237776.

The physical basis for optimizing the radial plane beam device and exhaust gas path is described below.

The one-stage electron accelerator has an odd beam potential of 150k.
Types from V to 300kV are manufactured. The beam potential is limited by the energy loss in the electron beam emission aperture at the lower limit and by the distance of one step of acceleration at the upper limit.
Limited by high potential strength.

The calculations shown below are for a theoretical beam potential of 600 kV. In today's industry, beam potentials of up to 300 kV have been reached.

The operational safety of the irradiation device is increased if the beam potential remains below the value of 300 kV.

When irradiating exhaust gas, the flow in the exhaust gas path is 15 m.
/s to 20 m/s, in special cases 30 m/s.

The calculation is based on a power plant of 500 MW, , and the exhaust gas generation of such a power plant is 1,500,000 OO
It corresponds to N♂/h (cubic meters per hour at standard pressure and temperature). Exhaust gas temperature approximately 80-10
At 0°C, the exhaust gas is then 2,000,000
m3/h, that is, 555+n'/s. Exhaust gas 1m
' has a weight of 1 kg.

Dose formula: IMrd=10kGy=10kJ/kg
:l0kll・s/kg Therefore, the dose of IMrcj is 50
When decontaminating a power plant of 0MIN, 1, 5,
An effective irradiation of 500 KWeff is required.

Industrially manufactured electron beam devices include the following main mechanical components: cathode, preacceleration path A section, postacceleration path section, and electron emitting aperture.

The electron emission aperture is 200cm long and has an operating width of 22cr.
II.

The opening load is 0.15 mA/c+n2.

The transmittance η of the backed electron emission aperture is 50%.

The electron current in the aperture is therefore 660 mA, which is 3
This corresponds to 30 mA f.

Next, two electron plane beam devices, each with two electron emitting openings, are placed in the tube-shaped exhaust gas path and irradiate opposite each other in the right-angled exhaust gas path (Figure 5). Compare with one radial surface beam device with four electron emitting apertures.

The purpose of this comparison is to reach the optimum conditions in both cases with respect to the number of electron beam devices, beam potential and number of exhaust gas channels.

A further parameter is the number of electron beam devices for a dose of 0.5 Mrd plus the number of electron beam devices for a dose of IMrd.

New information obtained from experimental work shows that 0.3 Mrd.
It was shown that it is possible even with low electron beam doses. Such a low irradiation dose is of course extremely important in terms of the efficiency of the method.

Figure 6 [Copy by Bailey].

R, Bayley (D, R, Ba1lay), A, Wright (A, -Wright), "Print Technology (Print Technology)" (19
71) Volumes 9-12 are useful for calculating the maximum range of an electron beam as a function of beam potential.

The lower curve takes into account the passage of electrons through a 15 μm titanium plate corresponding to a surface weight of 6.75 mg/cm”.

(1) First comparison of ideal exhaust gas path and ideal electron beam device.

Two electron plane beam devices were placed opposite each other in a right-angled exhaust gas path.

In Table 1 below: kv: electron beam potential [unit: k
V], kWf5: total effective electron beam output of the four electron emission apertures, nl: ideal number of electron beam devices required when the dose is IMrd, n: ,: required when the dose is IMrd, Ideal number of electron beam devices, ro [unit: mg/cm2]: maximum range of the electron beam in exhaust gas with a density of 1 kg/m3, d, 0. C unit: ml: Overlapping portion of the depth of the exhaust gas path irradiated from two directions and the bell-shaped ionization curve (Figure 7); do, is twice r, 0.7 (: F04.4) and takes into account the degree of overlap.

do, s [Unit: ml: Same as doj, but when the overlap factor is small as ro・1.6, Fz, J Unit: m2E: dg, Exhaust gas path in case of 7) Area of cross section, FX, -[Unit: In"l++ d61g, same as F2.4, l113・S; [4: Depth of exhaust gas path is 1.4 (
r, sl, 4) throughput per cross-sectional area of the exhaust gas path [unit: m3・s゛1], N1.1.4: Exhaust gas velocity 15 m/s, depth of the exhaust gas path 1. Number of exhaust gas paths for decontamination of 500M Lipe power plant for case 4(ra・1-4).

It is.

These calculations are based on exhaust gas speeds of 15 m/s and 20 m/s.
and 30 m/s, and the exhaust gas path depth factor 0.7
and 0.8 (r, 1.4 and ro 1°6). The results of the calculation are shown in FIG.

The ideal number of electron beam devices and exhaust gas paths is
Curve n1 for an ideal electron beam with Mr d or curve no for an ideal electron beam with a dose of 0.5 Mrd,
s and the ideal number of exhaust gas channels n1. /1.4-
It is found at the point where n3°71.6 intersects.

It should be noted that the ideal number of electron beams always consists of two electron plane beams facing each other.

(2) Number of ideal electron beam devices and second ideal exhaust gas path
Second comparison.

The radial plane beam device is arranged concentrically in the circular exhaust gas path.

In each column of Table 2 described later: kv: Electron beam potential [unit: kV
], kυetr: total effective electron beam output of a radial surface beam device with a total of four electron emission apertures, n□
: Ideal number of electron beam devices required for decontamination at dose IMrd, no, H: Ideal number of electron beam devices required for decontamination at dose 0, 5-4rd, ra [unit: mg/am” Coni Maximum range of electron beam in exhaust gas with density 1 kg/m3.

d□ [Unit: 2m]: Diameter of the nearly circular radial surface beam, dZ [Unit: m]: Maximum range of the electron beam r0
Diameter of the exhaust gas duct taking into account, Fir unit 2 m2 Area of the cross section of the radial plane beam device, F2 [unit: m2]: Area of the cross section of the exhaust gas duct including the radial plane beam device, ΔF [Unit: m'']: The difference between F and F, and therefore the area of the resulting cross-sectional area of the exhaust gas path, I゛・S-′: Exhaust gas velocity for various exhaust gas velocities. Processing amount of gas path light [unit 213・S-'], n15
: 5008 li at exhaust gas velocity 15m/s
', the number of exhaust gas paths for one power plant decontamination, is .

These calculations are based on exhaust gas speeds of 15 m/s and 20 m/s.
s and 30 m/s. The result of the calculation is the 9th
It is shown in the figure.

The ideal number of electron beam devices and exhaust gas paths is the dose IMrd
The curve ni for the ideal electron beam or the radiation dose 0.5
It is found at the point where the curve n0.5 for Mrd's ideal electron beam intersects the curve n, -n3° for the ideal number of exhaust gas paths.

Commentary on Comparative Experiments (1) and (2): (,) Radial plane beams require only high voltage equipment, vacuum mechanical elements, and control equipment, so the design is simple.

(b) Radial plane beams require beam potentials of up to 300 kV depending on exhaust gas velocity and dose requirements, but for higher exhaust gas velocities and lower irradiation doses, beam potentials may be smaller. , thereby increasing the safety of operation.

(c) Irradiation of the exhaust gas from one direction in the case of a radial plane beam should not be disadvantageous, since the exhaust gas flow is perturbed even when the electron plane beams face each other. .

(d) X-ray shielding is best resolved for radial plane beams.

(e) When using two mutually facing electron plane beam devices, i.e. irradiating from two directions, the ideal beam potential is between 300 kV and 600 kV, depending on the exhaust gas velocity and the required dose. .

Such a beam potential is not easily achieved.

(f) In the case of irradiation from two directions, two electron plane beam devices must always be used per exhaust gas path.

(g) The case of irradiation from two directions complicates the problem of possible X-ray shielding.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an exhaust gas path with an electron radial beam arrangement. FIG. 2 is a longitudinal sectional view of the radial beam device and the exhaust gas path. FIG. 3 shows a "horizontal" exhaust gas path with a radial plane beam arrangement and a lead shield. FIG. 4 shows a ``vertical'' exhaust gas path with a radial plane beam arrangement and a ground shield. FIG. 5 illustrates the arrangement of the electron plane beam and the shield when irradiating toward each other. FIG. 6 shows the maximum degree r of the electron beam as a function of the beam potential. This is a graph (by Bailey) showing
. FIG. 7 shows ionization curves for various beam potentials. FIG. 8 is a diagram comparing the number of electron beam devices arranged to face each other and the number of exhaust gas paths. FIG. 9 is a diagram comparing the number of radial beam devices and the number of exhaust gas passages. In each figure, reference numbers represent the following: E...Radial plane beam device as an electron beam source, 1
...Field cathode, 2.
... Cathode holder, 3... Extraction grid, 4... Acceleration grid, 5... Acceleration distance, 6... Electron emission opening, 7... Vacuum part, 8... Container wall, 9... Irradiation area in the exhaust gas path, 10... Outer wall of the exhaust gas path, 11.
...Shielding body, 12... Support body of the beam device, 13...
・Power supply line, 14... Vacuum transmission tube, 15...
Exhaust gas path, 16... Direction of exhaust gas flow, 17...
Vacuum pump, 18...factory, 19...concrete, 2o...earth, 21...electronic surface beam device. Patent Applicant: Bolimar-Physik GmbH und Zeor. Car game FIG, 1 FIG, 3 FIG. 4 FIo, 8 57.1 FIG. 9

Claims (2)

[Claims] (1) In a device that desulfurizes and denitrates exhaust gas by irradiating ammonia-added exhaust gas with electrons prior to electron irradiation, the device has a minimum at most one low-energy electron beam source, characterized in that the electron beam source is arranged concentrically and coaxially in the exhaust gas path and has at least two electron emitting openings. Exhaust gas desulfurization and denitration equipment using electron irradiation. (2) The apparatus according to claim 1, wherein the electron beam source has four or more electron emitting apertures.