WO2016120395A1 - Electrode sealing arrangement for a plasma reactor - Google Patents

Abstract

Continuous, trouble-free operation is achieved by a plasma reactor that comprises the following: a reactor chamber; a reactor housing, which surrounds the reactor chamber and has at least one electrode opening by way of which a rod-shaped electrode can be introduced into the reactor chamber; an electrode sealing arrangement, with a first sealing ring provided at the electrode opening and suitable for leading through a rod-shaped electrode, and with a closure cap, which can be secured in a detachable and gastight manner to the reactor housing from outside in such a way that it covers the electrode opening and at the same time a receiving space for part of the rod-shaped electrode forms outside the reactor chamber. An operating method comprises the following steps: detaching and removing the closure cap; using an electrode segment to lengthen the rod-shaped electrode; and securing and sealing the closure cap. A small amount of the hydrogen will escape through the sealing ring or rings, but can be sucked away. In order to reduce the amount of escaping hydrogen still further, an operating pressure prevailing in the reactor chamber is optionally lowered. The lowering of the operating pressure is preferably performed before or during the detachment and removal of the closure cap.

Description

 Electrode sealing arrangement for a plasma reactor

The present invention relates to a plasma reactor, an electrode seal assembly, and a plasma reactor operating method.

background

From WO / 2013/091879 a process for the production of synthetic hydrocarbons is known in which one step comprises splitting a hydrocarbon-containing fluid into a H ₂ / C aerosol of carbon C and hydrogen H ₂ in a plasma reactor. Such a plasma reactor generates high temperatures during operation and may, for example, comprise metal electrodes or graphite electrodes. Depending on the level of operating temperatures, metal electrodes must be cooled, while graphite electrodes are insensitive to high temperatures. However, it has been found that graphite electrodes, at least in the above-mentioned technical field, are subject to severe wear and erode over time. This makes the operation of the plasma reactor consuming, and it breaks are necessary. In a remote technical field, metallurgy (iron, aluminum, silicon), trackable graphite electrodes are used. This allows continuous operation of the system. In metallurgy, the graphite of the electrode is usually used as a reducing agent and eroded then wanted. These metallurgical processes are usually operated under atmospheric pressure and the tightness of the reactor is not a problem, since any leaks can be controlled by discharge and exhaust devices. In particular, in the electrical melting furnaces of the steel industry, a type of graphite electrode has thus been established in which segments can be screwed on at the rear end. For example, DE 43 42 51 1 A1 discloses an electro-reduction furnace with a vessel for receiving a slag bath and a lid which closes the vessel from above. A rod-shaped electrode is suspended from a stage above the lid and trackable by means of regulating cylinders relative to the stage and to the slag bath. The electrode is freely accessible from the stage and is sealed from the lid by an electrode sealing unit made of an elastically deformable material. These trackable graphite electrodes, in which segments are screwed on the rear end, but can not be easily used in the above-mentioned plasma reactor, since there hydrogen is produced at 1600 ° C and a pressure of up to 20 bar. Because of its small molecular diameter, the hydrogen itself makes high demands on the tightness of the material. At 1600 ° C, hydrogen also has a high deflagration risk on contact with oxygen or air. Since the trackable electrodes must necessarily pass through the reactor housing, so as to be extended at its outer end, a movable parting line is necessary, which under the given conditions (pressure, temperature, etc.) can be very difficult or impossible to be sealed , The mechanical properties of graphite do not facilitate this task. Graphite is brittle and not very tensile, so it can break relatively easily, especially if it is tilted. Moreover, there are only a few materials that do not react with graphite in the corresponding temperature range (in the tip up to 3000 ° C) (carbide formation in metal seals) and have a suitable small expansion coefficient. Summary of the invention

The rate of erosion, according to the inventors, depends on the temperature of the electrode, the current density, the effectiveness of the cooling (e.g., plasma gas) and stabilizing factors.

To solve the above-mentioned problems, there is proposed a plasma reactor comprising: a reactor space; a reactor housing surrounding the reactor space and having at least one electrode opening through which a rod-shaped electrode can be introduced into the reactor space; an electrode packing arrangement with a first sealing ring at the electrode opening, which is suitable for passing a rod-shaped electrode, and with an end cap, which can be detachably and gas-tightly fastened to the outside of the reactor housing in such a way that it covers the electrode opening and thereby forms a receptacle outside the reactor space. meraum forms part of the rod-shaped electrode. In summary, it can be said that the trackable electrode is connected by a flange. leads and is sealed in this guide with a sealing ring. The seal through the sealing ring is not 100% tight under the prevailing conditions (hydrogen, 1600 ° C, 20 bar). Some hydrogen comes through. However, the passing hydrogen is trapped in a receiving space which is at least partially enclosed by the end cap.

In one embodiment of the plasma reactor, the reactor housing has an outer reactor housing part and an inner reactor housing part, and the first seal ring is formed by a part of the inner reactor housing part. In this case, the inner reactor housing part is preferably made of graphite and serves as insulation between the reactor space and the outer reactor housing part. Between the outer reactor housing part and the inner reactor housing part may also be arranged a damping layer, for example, fine bulk material or granules of heat-resistant material. The outer reactor housing part form a jacket around the inner reactor housing part and supports it against pressure in the reactor chamber. If the inner reactor housing part is made of brittle graphite, the outer reactor housing part is made of a tensile material, for example of metal or fiber-reinforced material.

Preferably, the first sealing ring is secured by a holder to the reactor housing. Thus, the sealing ring can be made of a different material than the inner reactor housing part, and it can be easily replaced by wear or abrasion by the electrode pushed forward. The holder can also stabilize the sealing ring. In this embodiment, the end cap may be directly connected to the reactor housing, but preferably the end cap is connected to the holder and fixed by means of the bracket to the reactor housing.

In an advantageous embodiment of the plasma reactor, the receiving space has an inlet and / or an outlet for a gas. For example, argon or any other non-toxic and sub- stances can be introduced via an inlet for gas In the given conditions inert gas will be directed into the receiving space. Via an outlet, air entering during the lengthening of the electrode or a part of the introduced gas can be omitted. Preferably, the electrode sealing arrangement has a second sealing ring which is suitable for passing through a rod-shaped electrode and which is spaced in the direction of the end cap from the first sealing ring in the longitudinal direction of the rod-shaped electrode. The electrode seal assembly in this case has a seal space; at least partially bounded by the first and second sealing rings and having an inlet and / or an outlet for a gas. For example, argon or any other suitable inert gas may be directed into the seal space via such an inlet for gas. Hydrogen leaking from the reactor space enters the seal space and can be vented through the outlet (and optionally purged with the argon or inert gas). In this embodiment, the receiving space preferably has only one outlet for a gas.

In all embodiments, the sealing ring is advantageously a heat-resistant sliding seal ring. The sealing ring is made of heat-resistant material, such as graphite or ceramic (each possibly fiber-reinforced).

A continuous and trouble-free operation of a plasma reactor according to one of the preceding embodiments is achieved by a method comprising the following steps: detaching and removing the end cap; Extending the rod-shaped electrode with an electrode segment; and attaching and sealing the end cap. A small amount of hydrogen will escape through the seal ring (s), but can be sucked off. In order to further reduce the amount of escaping hydrogen, an operating pressure prevailing in the reactor chamber is optionally reduced. The reduction of the operating pressure is preferably carried out before or during the loosening and removal of the end cap. When the plasma reactor has an electrode seal assembly having at least two seal rings and a seal space therebetween; which is at least partially bounded by the sealing rings and has an inlet and / or outlet for a gas, the method may alternatively or additionally comprise the step of increasing the pressure of the gas in the sealing space between the loosening and the sealing of the end cap , Thereby, the leakage of hydrogen from the reactor space during the lengthening of the electrodes is further reduced or avoided.

The invention as well as further details and advantages thereof will be explained below with reference to preferred embodiments with reference to the figures. Brief description of the drawings

FIG. 1 is an illustration of a plasma reactor having an electrode seal assembly according to a first embodiment; FIG.

 FIG. 2 is an illustration of a plasma reactor having an electrode sealing arrangement according to a second embodiment; FIG.

 Fig. 3 is an illustration of a plasma reactor having an electrode seal assembly according to a third embodiment; and

 4 is an illustration of a plasma reactor having an electrode sealing structure according to a fourth embodiment.

Detailed description

In the following description, the terms top, bottom, right and left as well as similar statements refer to the orientations and arrangements shown in the figures and are only used to describe the embodiments. These terms may indicate preferred arrangements, but are not to be construed in a limiting sense. By the term "releasably attached" is meant here that a connection can be detached non-destructively is, for example, a threaded or screw connection, a bayonet closure or tension lock.

FIG. 1 shows a plasma reactor 1 comprising: a reactor space 2; a reactor housing 4, which surrounds the reactor space 2 and has an electrode opening 6, via which a rod-shaped electrode 8 can be introduced into the reactor space 2. An electrode seal assembly has a seal ring 10 at the electrode opening 6 suitable for passing a rod-shaped electrode 8. An end cap 12 is detachably and gas-tight fastened to the outside of the reactor housing 4 such that it covers the electrode opening 6 and thereby forms a receiving space 14 for part of the rod-shaped electrode 8 outside the reactor space 2. The end cap 12 has the shape of a half-open tube, the open end of which is attached to the reactor housing 4 and sealed. The tubular end cap 12 completely surrounds a part of the trackable electrode 8 protruding beyond the reactor housing 4. In the embodiment of Fig. 1 of the plasma reactor 1, the reactor housing 4 has an outer reactor housing part 4a and an inner reactor housing part 4b, and the first seal ring 10 is formed by a part of the inner reactor housing part 4b.

Figures 2, 3 and 4 show embodiments in which the first sealing ring 10 is secured by a bracket 16 to the reactor housing. The holder 16 can stabilize the sealing ring 10 and simplifies the assembly of the plasma reactor 1.

In the embodiments of FIGS. 1 and 4, the end cap 12 is connected directly to the reactor housing 4. In the embodiments of FIGS. 2 and 3, the end cap 12 is connected to the holder 16 and attached to the reactor housing 4 by means of the holder 16.

In all embodiments of the plasma reactor 1, the receiving space 14 may have an inlet 18 and / or an outlet 20 for a gas (for better Clarity shown only in Fig. 2). For example, argon or any other non-toxic and inert gas under the given conditions may be directed into the receiving space 14 via an inlet 18 for gas. Through an outlet 20 air can be omitted, which occurs during the extension of the electrode 8.

2 and 3 show ESektrodendichtungsanordnungen with a first 10a and a second sealing ring 10b. The second sealing ring 10b is also suitable for passing a rod-shaped electrode 8 and spaced in the longitudinal direction of the rod-shaped electrode 8 in the direction of the end cap 12 from the first sealing ring 10a. The electrode seal assembly in this case has a seal space 22; 3 and 4). The seal chamber 22 may have an inlet 18 and / or an outlet 20 for a gas in all embodiments (for better clarity) only shown in Fig. 3). For example, argon or any other suitable inert gas may be directed into the seal space 22 via such an inlet 18 for gas. Hydrogen leaking from the reactor space enters the seal space 22 and may be diverted through the outlet 20 (optionally together with the argon or inert gas). When the seal space 22 is filled with inert gas, the receiving space 14 preferably has only one outlet 20 for a gas.

Fig. 4 shows an embodiment in which the reactor housing 4 has a tubular extension into which the holder 16 is inserted. The bracket 16 may include one or more seal rings 10, 10a, 10b.

The following features are possible with all versions:

The sealing rings 10 mentioned here can also have an arrangement of a plurality of sealing rings 10 arranged one behind the other, for example a seal packing of two or more sealing disks. The sealing ring 10 is advantageously a heat-resistant sliding seal ring. The sealing ring 10 is made of heat resistant material, such as graphite or ceramic (each possibly fiber reinforced).

The reactor housing 4 has an outer reactor housing part 4a and an inner reactor housing part 4b, and the inner reactor housing part 4b is preferably made of graphite and serves as insulation between the reactor chamber 2 and the outer reactor housing part 4b. Between the outer reactor housing part 4a and the inner reactor housing part 4b may also be arranged a damping layer, for example, fine bulk material or granules of heat-resistant material.

 Depending on the shape of the electrode 8 and the shape of the reactor housing 4, the end cap 12 may be elongate (Figures 1 to 3) or flat (Figure 4).

 - The electrode 8 may have a round or square cross-section.

Extension segments 8 'for lengthening the electrode 8 are screwed or glued, for example.

In operation, in the reactor space 2, hydrogen (mixed with carbon in the form of C particles) is at a temperature of 1000 to 1800 ° C. and a pressure of 5 to 25 bar. In these operating conditions, the electrode 8 is eroded by erosion and nachgeschoben by a tracking device, not shown in the figures, according to the erosion rate. The rod-shaped electrode 8 is easily displaced relative to the sealing ring 10, but does not have much play, so that a good seal is provided. The tracking device is arranged at a location where it is shielded from the operating conditions in the reactor space 2. The tracking device can be arranged, for example, in the seal chamber 22 or in the receiving space 14 and is cooled and protected there by inert gas introduced. If no gas is introduced, the sealing space 22 and / or the receiving space 14 can be cooled from the outside by gas or liquid. While the electrode 8 is passed through the sealing ring 10, the seal is not completely sealed by the sealing ring 10 at the above conditions. Some hydrogen passes through, but the passing hydrogen is trapped in the receiving space 14.

If the electrode 8 has been tracked by a significant amount, the AbschSusskappe 12 is released and removed during operation of the plasma reactor 1. Thereafter, the rod-shaped electrode 8 is extended with an electrode segment 8 '. While the end cap 12 is released, a small amount of hydrogen will exit through the seal ring or seals 10, 10a 10b, but may be exhausted. In order to further reduce the amount of escaping hydrogen, the operating pressure prevailing in the reactor chamber 2 is optionally reduced, e.g. to 5 to 10 bar. The lowering of the operating pressure is preferably carried out before or during the loosening and detaching of the end cap 12. In the embodiments with a plurality of sealing rings 10 and an interposed seal chamber 22 is alternatively or additionally increased, the pressure of the gas, which is introduced into the seal chamber 22. The lengthening of the electrode 8 can be carried out, for example, by means of automatic handling devices. After extending the electrode 8, the end cap 12 is re-attached and sealed.

The purging with argon or inert gas preferably takes place with slight overpressure relative to the pressure in the reactor space 2. Argon is significantly heavier than hydrogen and air. This can be after the extension of the

Electrode 8 flush all the air from the receiving space 14 and / or sealing space 22. The absence of oxygen increases safety. The slight overpressure seals the seal by the movable parting line between electrode 8 and sealing ring 10, 10 a, 10 b. Any argon entering the reactor chamber 2 does not interfere in the plasma reactor 1.

The seal space 22 between the two seals 10 may be held under argon pressure, and when the end cap 12 is loosened to release the To prolong electrode 8, the plasma reactor 1 still remains tight due to the back pressure of argon or inert gas in the seal space 22. Then no hydrogen leaks to the outside, but only inert gas, which is dangerous neither to the environment nor to the operating personnel.

The invention has been described with reference to preferred embodiments, wherein the individual features of the described embodiments can be combined freely with each other and / or replaced, provided that they are compatible. Likewise, individual features of the described embodiments can be omitted, unless they are absolutely necessary. Numerous modifications and embodiments are possible and obvious to those skilled in the art without departing from the inventive idea.

Claims

claims A reactor (1) comprising: a reactor space (2); a reactor housing (4) surrounding the reactor space (2) and having at least one electrode opening (6) through which a rod-shaped electrode (8) can be introduced into the reactor space (2); an electrode sealing arrangement comprising a first sealing ring (10, 10a) on the electrode opening (6) suitable for passing a rod-shaped electrode (8) and an end cap (12) detachable from the outside of the reactor housing (4) gas-tight fastened bar is that it covers the electrode opening (6) and outside the reactor space (2) forms a receiving space (12) for a part of the rod-shaped electrode (8). A plasma reactor (1) according to claim 1, wherein the reactor housing (4) has an outer reactor housing part (4a) and an inner reactor housing part (4b), and the first seal ring (10, 10a) is formed by a part of the inner reactor housing part (4b). A plasma reactor (1) according to claim 1, wherein the first sealing ring (10, 10a) is fixed to the reactor housing (4) by a support (16). A plasma reactor (1) according to claim 3, wherein the end cap (12) is connected to the support and secured to the reactor housing by means of the support (16). Plasma reactor (1) according to one of the preceding claims, wherein the receiving space (14) has an inlet (18) and / or an outlet (20) for a gas. 6. Plasma reactor (1) according to one of the preceding claims, wherein the electrode sealing arrangement has a second sealing ring (10b) which is suitable for passing a rod-shaped electrode (8) and in the longitudinal direction of the rod-shaped electrode (8) in the direction of the end cap (12). from the first sealing ring (10 a) is spaced, and  the electrode seal assembly having a seal space (22); at least partially bounded by the first and second sealing rings (10a, 10b) and having an inlet (18) and / or an outlet (20) for a gas. 7. A plasma reactor (1) according to claim 6, wherein the receiving space (14) has only one outlet (20) for a gas. A plasma reactor (1) according to any one of the preceding claims, wherein the sealing ring (10, 10a, 10b) is a heat-resistant sliding seal ring. Method for operating a plasma reactor (1) according to one of the preceding claims, comprising the following steps:  Loosening and removing the end cap (12);  Extending the rod-shaped electrode (8) with an electrode segment (8th');  Attach and seal the end cap (12). The method of claim 9, including the step of reducing an operating pressure prevailing in the reactor space (2). The method of claim 9 or 10, wherein the plasma reactor (1) comprises an electrode seal assembly having at least two seal rings (10a, 10b) and a seal space (22) therebetween; which is at least partially bounded by the sealing rings (10a, 10b) and has an inlet (18) and / or an outlet (20) for a gas. , the method comprising the step of increasing the pressure of the gas in the seal space (22) between disengaging and sealing the end cap (12).