Apparatus equipped with a reaction vessel for solid-phase reactions

Abstract

The present invention relates to an apparatus comprising at least one reaction vessel for receiving a powdered reaction product, the reaction vessel having a frame and a screen fabric removably connected to the frame, and its use in gas / solid phase reactions.

Description

[Technical Field]

[0001] The present invention relates to an apparatus having at least one reaction vessel for receiving a powdered reactant, the reaction vessel having a frame and a mesh fabric removably connected to the frame, and its use in gas / solid phase reactions. [Background technology]

[0002] The importance of metals to humanity can be seen, inter alia, from the fact that entire stages of human development are named after the materials used, such as the Bronze Age and the Iron Age. However, because very few metals exist in pure form in nature, the production of metals and their selected compounds plays an even more important role. Metals and their compounds, such as carbides, are typically obtained by reducing their corresponding oxides using solid-state reactions. Solid-state reactions are chemical reactions in which at least one reactant is in the solid state. Metals are typically produced by reducing their corresponding oxides with a reducing agent, such as hydrogen, in a gas-solid reaction, in which a gaseous reducing agent flows through the powdered solid. Therefore, the outcome of the reaction depends, on the one hand, on how effectively the powder used is contacted with the gas, and, on the other hand, on how quickly the by-products produced during the reaction are removed.

[0003] Gas-solid reactions are characterized by the contact of solids, primarily powders, with gaseous reactants. Gas transport through powdered solids can occur by diffusion, i.e., concentration gradient-based, and / or pressure gradient-based convection processes. Therefore, solid-state reactions are typically carried out in so-called boats, in which the solids are placed as a powder bed and subsequently exposed to a gas flow. However, these conventional boats have the disadvantage that removal of gaseous reaction products by diffusion processes occurs only upward, i.e., against gravity. Insufficient removal of these gaseous components usually has a negative effect on the progress of the reaction.

[0004] DE 2126843 describes a method for producing metal carbides in which a boat with a gas-permeable bottom is used.

[0005] GB 672,423 relates to a continuous method for producing metal powders in which material is spread over a sieve-like surface arranged so that all surfaces of the material are exposed to a reducing atmosphere.

[0006] DE 2120598 discloses a method for reducing powdered metal oxides supported in layers on perforated trays, in which boats are conveyed vertically downwards and a reducing gas stream flows upwards in the opposite direction through the boats. Summary of the Invention [Problem to be solved by the invention]

[0007] While the use of boats with gas-permeable bottoms is known in the art, there continues to be a need for improved methods for producing metal powders. Furthermore, it is desirable to achieve improved flexibility within the normal reaction range. [Means for solving the problem]

[0008] In this regard, the invention provides an apparatus with at least one reaction vessel in which the mesh fabric can be exchanged in a simple manner, so that, for example, powders with different particle sizes can be used or the removal of gaseous reaction products can be controlled. [Brief explanation of the drawings]

[0009] [Figure 1] The reaction progress up to 650°C is shown in the reduction process of tungsten oxide. [Figure 2] In the course of the reduction of tungsten oxide, the complete time course of the reaction is shown. [Figure 3] 1 shows a schematic cross-sectional view of an apparatus according to the invention comprising a clamping frame for clamping a mesh fabric supported by a support structure. [Figure 4] 4 shows a schematic top view of the device according to the invention shown in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] Accordingly, the present invention first relates to an apparatus having at least one reaction vessel for receiving a powdered reactant, the reaction vessel having a frame and a mesh fabric removably connected to the frame, the reaction vessel further having a support structure for supporting the mesh fabric.

[0011] The device according to the invention offers the advantage that the removal of gas components formed during the reaction is affected not only by diffusion processes but also by convective material transport processes caused by gravity, which allows additional material transport mechanisms and, inter alia, significantly shortens the reaction time and therefore increases the throughput.The detachable connection between the frame and the mesh fabric allows the mesh fabric to be exchanged in a simple manner, e.g., to be adapted in a simple manner to different particle sizes of the powders used.

[0012] The apparatus of the present invention is further characterized by the size of the reaction vessel, which is designed to allow for industrial-scale reactions. In a preferred embodiment, the reaction vessel has a width of at least 3 cm, preferably at least 10 cm, and more preferably at least 15 cm. The length of the reaction vessel is preferably at least 8 cm, more preferably at least 25 cm, and even more preferably at least 40 cm. These dimensions allow such an apparatus to be used beyond laboratory or small-scale pilot plant applications.

[0013] In a preferred embodiment, the reaction vessel may be provided with detachable side sections to ensure the stability of the powder bed within the reaction vessel. For example, this allows for larger amounts of powder to be reacted. The height of the side sections is preferably adapted to the height of the powder bed. Preferably, the upper end of the side section is at least 1 mm above the upper end of the powder bed. In this way, overflow of the reaction vessel can be prevented in reactions involving an increased volume of powder without adversely affecting the reaction rate. Powder beds with a height of at least 2 mm have proven particularly useful for converting economically relevant amounts of solids. Therefore, embodiments in which the powder bed height is at least 2 mm are preferred.

[0014] According to a preferred embodiment, the reactor has a rectangular layout, which allows for easy charging and discharging of the device comprising the reactor, and for this purpose the device and the reactor preferably further have guide rails that fit together, which guide rails are preferably provided on the longitudinal sides of the reactor.

[0015] Within the scope of the present invention, it has surprisingly been found that significantly larger amounts of reactants can be used than with conventional boats without adversely affecting the progress of the reaction or the quality of the product. In fact, a reduction in reaction time has been observed. To ensure the stability of the device according to the present invention under larger loads, the mesh fabric on which the reactants are supported can be stabilized. Therefore, the reaction vessel has a support structure for supporting the mesh fabric. Preferably, the support structure is designed so as not to impede the removal of gas components formed during the reaction. For example, the support structure can be formed as a perforated metal sheet or grid or from a porous material.

[0016] According to the present invention, the mesh fabric is detachably connected to the frame of the reaction vessel, which allows for easy replacement of the mesh fabric. Clamping means have proven particularly useful for this purpose. Therefore, in a preferred embodiment, the mesh fabric is connected to the frame by clamping means. Therefore, it is preferable that a clamp with a clamp bolt capable of clamping the mesh fabric within the frame is provided on at least one of the front faces of the reaction vessel.

[0017] The device according to the present invention is further advantageous in that several reaction vessels can be used simultaneously, thereby significantly increasing the reaction throughput, which is particularly interesting in industrial-scale production. Therefore, preferred embodiments are those in which the device comprises at least two, preferably at least three, reaction vessels. While there is no per se limit to the number of reaction vessels, in order for the reaction to proceed uniformly, too many reaction vessels should not be used. Therefore, preferred embodiments are those in which the device comprises no more than 10, preferably no more than 6, reaction vessels. The reaction vessels are advantageously arranged one on top of the other. Therefore, preferred embodiments are those in which the reaction vessels can be stacked.

[0018] The device according to the present invention allows the mesh fabric to be easily replaced and adapted to the respective reaction requirements, for example, by adapting the mesh size of the mesh fabric accordingly. Preferably, the mesh size of the mesh fabric is in the range of 25 μm to 5 mm, more preferably in the range of 40 μm to 5 mm.

[0019] The device according to the invention is particularly used in high temperature processes, and therefore preferred embodiments are those in which the frame and / or mesh fabric are made of alloys based on iron, nickel or cobalt, which have proven to be particularly suitable materials for high temperature processes within the scope of the invention. Alternatively, ceramic materials can also be used.

[0020] The structure according to the invention provides a particular stability to the reaction vessel and is therefore particularly suitable for use in continuous processes, which allow continuous production as opposed to batch processes. Preferred are therefore embodiments in which the device according to the invention is a continuously operated device, preferably a continuously operated furnace, in particular a forced furnace or a rotary kiln.

[0021] When a reaction vessel with a gas-permeable bottom is used, in contrast to conventional reactions in which gas is passed through the powder bed from below under pressure, the apparatus according to the present invention is preferably arranged so that the gas flows parallel to the apparatus according to the present invention, i.e., longitudinally relative to the reaction vessel. Among other advantages, this prevents powder from being discharged from the vessel during the reaction. It also prevents the formation of a concentration gradient of the reactant powder decreasing from bottom to top through the powder bed. Furthermore, in this way, a homogeneous gas flow can be established, which eliminates the need for a pressure gradient.

[0022] The device according to the invention is provided in particular for gas / solid reactions such as those used in the production of metal or other powders. The invention therefore further relates to the use of the device according to the invention for gas / solid reactions, in particular reduction, carburization, oxidation, calcination and / or nitriding reactions.

[0023] The device according to the present invention is particularly suitable for reactions in which gaseous components are formed as by-products or waste products, allowing for their effective removal. Thus, for example, in a typical reduction reaction using hydrogen as a reducing agent, in addition to the reduced compound, water vapor, an oxidation product of hydrogen, is obtained. However, the presence of water vapor can adversely affect the progress of the reduction reaction, and in the worst case, can even stop the reduction reaction. This is prevented by the device according to the present invention, which allows for the rapid removal of the water vapor formed. Therefore, reactions in which the device according to the present invention can be used advantageously include water vapor, CO2, Ar, hydrocarbon gases, CO, Cl2, NO x or reactions in which SO2 is formed or used.

[0024] The present invention is further illustrated by the following examples, which should not be construed as limiting the scope of the present invention in any way. [Example]

[0025] Figures 1 and 2 show the progress of the reduction of tungsten oxide. Figure 1 shows the reaction progress up to 650°C, and Figure 2 shows the complete time course of the reaction. Thus, tungsten oxide was heated in a rotary kiln under a constant hydrogen flow at a constant heating rate to a temperature of 650°C, after which the temperature was held constant. The hydrogen dew point was measured at the gas outlet. The dew point is a measure of the amount of water produced during the reduction. The dew point can be determined using commercially available measurement methods, such as a chilled mirror dew point hygrometer, a capacitance probe, or a laser measurement device. As can be seen from the measurement curves, when using a conventional reaction vessel (boat, dashed line), the reaction proceeds significantly slower and may even stop. Furthermore, the residual hydrogen dew point indicates a significantly increased water content when using a conventional boat compared to when using the apparatus of the present invention (solid line). As Figure 2 shows, the reaction proceeds significantly faster in the reaction vessel of the present invention (solid line).

[0026] Figure 3 shows a schematic cross-sectional view of an apparatus according to the invention, comprising a clamping frame (1) for clamping a mesh fabric (2) supported by a support structure (3). The clamping frame (1) can be fixed by clamps (4) with clamping screws, thus forming together with the mesh fabric (2) a reaction vessel for receiving a powdered reactant (5).

[0027] FIG. 4 shows a schematic top view of the device according to the invention shown in FIG.

Claims

1. having at least one reaction vessel for receiving a powdered reactant; The reaction vessel comprises: The frame and a mesh fabric detachably connected to the frame, The apparatus, wherein the reaction vessel further comprises a support structure for supporting the mesh fabric.

2. 2. The apparatus of claim 1, wherein said mesh fabric is connected to said frame by clamping means.

3. 2. The apparatus according to claim 1, characterized in that the reaction vessel has a width of at least 3 cm, preferably at least 10 cm, more preferably at least 15 cm.

4. 2. Apparatus according to claim 1, characterized in that the reaction vessel has a length of at least 8 cm, preferably at least 25 cm, more preferably at least 40 cm.

5. 10. The apparatus of claim 1, wherein the reaction vessel has a rectangular shape.

6. 2. Apparatus according to claim 1, characterized in that the apparatus comprises at least two reaction vessels, preferably at least three reaction vessels.

7. The apparatus described in Claim 6, characterized in that the reaction vessels are arranged on top of each other.

8. 2. Apparatus according to claim 1, characterized in that the apparatus comprises not more than 10 reaction vessels, preferably not more than 6 reaction vessels.

9. 9. The apparatus according to claim 8, wherein the reaction vessels are arranged one above the other.

10. 10. The apparatus of claim 1, wherein the reaction vessels are stackable.

11. 2. The device according to claim 1, characterized in that the mesh fabric has a mesh size of 25 μm to 5 mm, preferably 40 μm to 5 mm.

12. 10. The apparatus of claim 1, wherein the apparatus is arranged so that the gas flow is longitudinal with respect to the reaction vessel.

13. 2. The device according to claim 1, characterized in that the frame and / or the mesh fabric are made of an alloy based on iron, nickel or cobalt.

14. Use of the device according to any one of claims 1 to 13 for gas / solid phase reactions, preferably reduction, carburization, oxidation, calcination and / or nitriding reactions.

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