DE3439190A1 - LOW-ENERGY ELECTRONIC EMITTER WITH HIGH PERFORMANCE FOR DESULFURATION AND / OR DENITRATION OF SMOKE GASES - Google Patents

Description

DR. JOACHIM STEFFENS

DIPLOMA CHEMIST AND PATENT ADVOCATE

STEUBSTRASSE

D-8032 GRXFELFING-MONCHEN

TELEPHONE (089) 85 23 TELEXi 529 830steffd

YOUR SIGN i

MY CHARACTER i Physics-20

October 25, 1984

Polymer-Physik GmbH & Co. KG Lemförde

Low-energy electron gun with high power for desulfurization and / or denitration of

Smoke gases

Professional Representative before the European Patent Office

Pottscrwckkonto Munich no. 199520-805 (bank code 700 100 80) ■ Bayerische Vereinsbank Munich no. 905 200 (bank code 700 202 70)

The present invention relates to low-energy, high-power electron guns for desulfurization and / or denitration of flue gases.

In the German Offenlegungsschrift 34 03 726 is detailed the desulphurization and denitration of flue gases by irradiation with so-called low-energy Electrons described. The disadvantage of this method and the device used for it is that so that only relatively small amounts of flue gas can be treated, since the electron guns used there are only equipped with a point cathode and electron beam deflection (scanning principle) and due to the limited electron emission from the point cathode can not provide the required high performance.

It is true that US Pat. No. 3,863,163 already discloses an electron gun known with a large area cathode system which is used for irradiating web-shaped material is, but the performance of such an electron gun is not yet sufficient for large-scale The standard for desulphurising and / or denitrating flue gases.

The object of the invention is therefore to provide a simple, single-stage electron gun with the highest possible acceleration voltage and about 10 times the electron current compared to that in German Offenlegungsschrift 34 03 to create described electron gun, with the large-scale, with the flow velocities 15 to 25 m / s prevail in the exhaust air duct, taking into account the penetration depth and the distribution of the Electrons make certain cross-sections of the flue gas ducts necessary, flue gases desulphurized and / or denied

can be trated. Furthermore, when irradiating of the flue gases long service lives of cathodes and electron exit windows can be achieved, whereby surface loads of about 0.15 niA / cm of the beam generating arrangement and the electron exit window must not be exceeded.

This object is achieved according to the present invention by the use of low-energy electron guns, which thereby obtain the desired high performance that at least two large-area cathode systems in a vacuum housing are arranged in parallel to each other and each large area cathode system has its own Electron exit window is assigned that has the same width and length as the large area cathode system having.

The invention therefore relates to a low-energy electron gun with high performance for desulfurization and / or denitration of flue gases, which is characterized in that at least two in a vacuum housing Large area cathode systems are arranged in parallel with each other and each large area cathode system its own electron exit window is assigned, which is the same width and length as the large area cathode system having.

The upper limit of the single-stage electron acceleration is currently approx. 300 kV. It is conditioned by the maximum achievable breakdown field strength for high voltages in a vacuum, which essentially depends on the material and Surface quality of the electrode materials is dependent.

In the case of flue gas irradiation, the efficiency of the electron accelerators used for irradiation plays a role

significant role. The total beam power used is very high. Therefore, the losses in the generation of the electrons and in the passage of the electrons should be are kept as small as possible by the electron exit window. About the losses when the electrons pass through There are two possible solutions:

1. A window supported over a large area and cooled by water from the vacuum side, as in the German one Patent 26 06 169 is described.

2. A quasi cantilevered window that only occasionally has supporting webs transversely to the longitudinal direction of the window Contains copper without water cooling. These support bars carry the titanium foil and form for the electron beam only a slight "shadow". The design of these support webs is analogous to the double-comb type Support grids formed from German Patent 26 06 169, but the combs are missing. The support bars are not soldered into the window frame, but screwed into place. A water cooling of the support bars is not necessary. The window frame is water-cooled. The heat absorbed by the support webs is via the window flange discharged. The window film itself is caused by the flue gas to be irradiated, which is turbulent Flow is guided past the window film, cooled.

Another embodiment of window cooling is that Smoke-independent blowing of the window film with cold air or cooled flue gas via a fan or a Side channel blower.

The calculation bases for the penetration depth of the electrons and the radiation dose introduced into the material to be irradiated are in German Offenlegungsschrift 34 03

! changes

already presented in detail by the applicant.

The electron guns according to the invention with high power, but low dose rate due to the large electron exit window can be ideally adapted to the flow conditions of the flue gas in power plants. Also can you can thus irradiate a large amount of smoke gas with as few electron emitters as possible.

Low dose rates mean relatively low current load on the cathode and the electron exit window per unit area and thus extremely long service lives for the wearing parts, which is the case with the electron guns according to the invention makes it extremely noticeable.

_If chemical reactions with a radiation dose requirement of more than 0.5 to 1 billion are necessary for the simultaneous supply of SO ₂ and Ν0 _χ due to new findings, the large-area cathode system can be expanded from two cathode arrangements to three or more parallel cathode arrangements. The lamp output increases accordingly.

In German Offenlegungsschrift 34 04 726, a flue gas duct is parallel or perpendicular to the longitudinal direction of the electron exit window. The "equalization" of the dose is done once by two-sided irradiation achieved in an approximately uniform dose field. On the other hand, one always becomes a turbulent one Strive for a gas flow which, through its movement, has the mean radiation intensity for each gas particle Dose transfers.

In another embodiment of the flue gas duct meets the gas flow is perpendicular to the electron exit window front and is blown off in a turbulent manner perpendicular to the direction of impact.

343919C

leads. Here, the electron exit window front can be rectangular or round. The variation of the round arrangement is interesting for flue gas irradiation systems with a smaller throughput. A scanning system is used here according to the German Offenlegungsschrift 34 03 726 with circular electron beam deflection directly placed on a round flue gas pipe. The irradiated flue gas is discharged perpendicular to its direction of flow.

The present invention is further explained below with reference to Figures 1 to 8 and Examples 1 and 2, but without restricting them to this.

In Figures 1 to 8 and the claims Reference symbol has the following meaning:

1 window frame
2a, 2b electron exit window

3a, 3b large area cathode systems, each assigned to the electron exit windows 2a, 2b

4 receiving box for the large area cathode systems

5 High voltage supply and supply for the large area cathode systems

6 vacuum housing

7 channels for water cooling the window frame

8 screwed-in bar elements

9 titanium foil

10 film frames

11 Electron exit window front

12 Round electron exit window

13 Angular electron exit window front

Fig. 1 shows in a schematic perspective view an insight into the electron gun according to the invention, However, without the two large-area cathode systems 3a, 3b, which extend over the Electron exit windows 2a, 2b are visible.

Fig. 2 shows a plan view of the electron exit window front 2a, 2b.

Fig. 3 shows a cross section through the electron gun along the section line A-A in Fig. 2. In this The two large-area cathode systems 3a, 3b in the common receiving box can be clearly seen in FIG 4, which is located in the vacuum housing 6.

4 shows a plan view of part of the electron exit window according to German patent specification 26 06 169, but with the modification that the double-comb-like Bar elements have no tooth teeth and no holes designed as cooling lines, but are solid and e.g. consist of copper.

FIG. 5 shows a section along the cutting line in FIG. 4. On the window frame 1, the one with the channels 7 is provided for water cooling, the web elements 8 are screwed. On the web elements 8 lies the titanium foil 9, which is held on the window frame 1 by means of the foil tensioning frame 10 and the vacuum housing 6 hermetically seals.

Fig. 6 shows a section through the electron exit window front 11, to which the smoke gases perpendicular impinge and forming turbulence, which leads to an increase in the efficiency of the irradiation contribute to be derived at right angles to it.

Pig. 7 shows a round design of the electron exit window front.

8 shows a rectangular configuration of the electron exit window front.

The following two examples show the use of inventive Electron guns in large-scale systems.

example 1

Electron emitters for large-scale flue gas desulfurization and / or denitration

250 kV acceleration voltage

1.5 iiiA window load at 10 cm width of the electron exit window s
Gas flow: 15 m / s or 20 m / s
Two-sided irradiation
Distance between the electron guns 750 mm, window length 2,000 mm

Cross section of the flue gas duct 1.5 m

Smoke gas volume

- at 15 m / s 22.5 m ³ / s = 81,000 m ³ / h

- at 20 m / s 30.0 m ³ / s = 108,000 m ³ / h

These are 22.5 kg / s or 30 kg / s of irradiated material.

Conversion formula

1 _billion = 10 ^ J ₌ 10 kW s
kg kg

This is 22.5 kg = ^ ~ -

or 30.0 kg = 300 kW s

§§§1ΐ§§ £ 1οη_νοη ^ 225 _] <^^ ζ ^ _Λ _300_] ζ ^ _Εΐβ] ζ ££ θη§η3 ^ £ § ^ 11§ί3 ^ \ ιη2 efficiency 50% with electron guns.

The speed loss of the electrons in the window from 250 kV to 240 kV is determined by the permeability that is over 50% at this high acceleration voltage, compensated so that a total of 50% efficiency is achieved will.

The emitters must therefore have a total output of 450 kW or 600 kW.

§ ££ ahler concept

Electron exit window 2 25 cm χ 2 πι per emitter This window can be loaded with 2 χ 3.75 mA / cm electron radiation.
This results in a total radiated power of

2 χ 3.75 mA / cm χ 200 cm = 1.5 A or 375 kW / heater.

With two opposing electron emitters, this results in a beam power of 750 kW or 375 kW effective Beam power in the reaction channel.

You need £ 0jJh% * Ax * M \ -i

"f at 15 m / s 225 kW eff. ^ beam power ^ at 20 m / s 300 kW eff. Electron beam power.

This means that the electron guns in the 1st case are used to 60%, in the 2nd case to 80%.

Conversion to a large power plant

Since 81,000 m ³ / h = 63,000 Nm ³ / h and Nm ³ / h corresponds to 1/3000 = electrical output in MW, per flue gas duct

approx. 21 MW elj. . be disposed of.

For a 100 MW power plant there would be around 5 flue gas ducts necessary.

This calculation applies to a radiation dose of 1 billion.

Example 2

Another large-scale solution for flue gas irradiation can look like this:

- Electron acceleration voltage 300 kV

- Average speed of the electrons after passing through the electron exit window 280 kV

- Total current of the electron accelerator 1500 mA

- Max.electron current in the object with a water-cooled window 750 mA

-Max. Electron flow in the object with gas-cooled

Window 1162.5 mA

_- corresponding to an effective beam power of λμλ * £ \ nv € u. "ί <Χ ^ öa ²¹ ° ^{kw or} · ³²⁵ ' ^{5 kw} ^

jfcij <tieri

- Depth of the flue gas duct with 2-sided irradiation 1000 mm

- Area of the electron exit window 2000 χ 500 mm

- Cross section of the flue gas duct 2 m

- Flue gas throughput at 15 m / s or 25 m / s flue gas speed:

30 m ³ / s = 108,000 m ³ / h or 50 m ³ / s = 180,000 m ³ / h

These are 30 kg / s or 50 kg / s irradiated material.

_{- I Mrd = 10} kGy = iiLH = iS ^ JL applies to the absorbed radiation dose

At a radiation dose assumed for the smoke gas treatment of 1 billion can be achieved with the electron guns specified above in the first case 21 kg / s and in the second case Irradiate 32.5 kg / s flue gas.

At a dose of 0.5 billion, the corresponding values are 42 kg / s and 65 kg / s, respectively.

The flue gas flow runs transversely to the extent of the electron exit window .

Conversion to a large power plant:

This corresponds to 108,000 m / h or 180,000 m / h of flue gas

equal to 83,000 Nm ³ / h or 139,000 Nm ³ / h flue gas and it is an approximate value

Nm / h flue gas 1/3000 = electrical output of a power plant in MW.

This means that approx. 27 MW, and in the swaiton case approx. 46 MW, dispose of power

For a 100 MW power plant, therefore, i »ersJhpn FsI 1 £> 3-4 flue gas ducts and in ^ thi * - ^ ™ U '- \ 2-3 flue gas ^' - ^ T5 ducts, depending on the radiation dose required .

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Claims (3)

Claims Low-energy electron gun with high power for desulphurisation and / or denitration of Flue gases, characterized in that at least two large-area cathode systems in a vacuum housing (6) (3a, 3b) are arranged in parallel to one another and each large area cathode system (3a, 3b) has its own Electron exit window (2a, 2b) is assigned, which is the same width and length as the large area cathode system (3a / 3b). 2. Electron emitter according to claim 1, characterized in that it has electron exit window (2a, 2b), whose support grid consists of several double-comb-like web elements (8) that are detachably connected to the window frame are formed, which are connected to a bore as a cooling line. 3. Electron gun according to claim 1 and 2, characterized in that that it has electron exit windows (2a, 2b) which are quasi self-supporting and in which the Double-comb-like bar elements (8) are replaced by massive copper bar elements without comb teeth, which only are screwed into the water-cooled window frames.