DE7402846U - DEVICE FOR CARRYING OUT REACTIONS BETWEEN POWDER AND GAS MATERIALS - Google Patents

Description

KEG 1 DT G? - 'X> Ivolkhoin, dnn May 12, 1977

MP - K er / Ar;

VARTA Batterie Aktiengesellschaft 3000 Hannover 21, Am Leineufer 51

Device for carrying out reactions between powder and gaseous substances

The innovation relates to a device for carrying out reactions between powdery and gaseous substances that a Has a reaction vessel into which the powdery substances and a reaction gas can be introduced,

To carry out reactions between powder and gaseous substances, roasting ovens, Rotary kiln or fluidized bed arrangements and packed columns are used.

In the roasting oven, the powder to be converted is treated in a relatively thick layer on a grate in a discontinuous process. Because of the large layer thicknesses required to process sufficiently large batches, the The conduct of the reaction, in particular due to the poor diffusion, is inconsistent and the processes take a long time Time. For this reason, the resulting products are not uniform in terms of their structure and chemical properties.

Rotary kilns allow a higher throughput and continuous In and out, however, due to the uneven distribution of the powder to be converted on the wall of the reaction vessel produces a not completely homogeneous product. The possibility of the gas coming into contact with the powder is due to the inner surface and the speed of rotation

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capacity of the header is limited.

Implementations in fluidized beds are difficult on an industrial scale feasible, in particular when it is a powder with a small grain size or a powder with a wide range of grain sizes acts because the residence time of the grain size fractions is different and there is therefore the risk of inhomogeneous Products to receive.

When converting gases on solids, so-called packed columns are used. The bulk of powder is located is in a container through which gas generally flows from bottom to top. Such arrangements can only be operated discontinuously in cyclic operation and the powder must have certain grain sizes in order to achieve a To enable gas passage and on the other hand to keep the diffusion path small. Furthermore, can get in the debris easily form channels through which the gas breaks through.

The innovation is based on the task of continuously working device for carrying out reactions between powder and gaseous substances to develop ·. In, in which homogeneous and highly active products can be obtained in the shortest possible time.

This object is achieved in that the reaction vessel is a vibrating spiral conveyor with a gas-tight casing.

The vibratory spiral conveyor has reaction gas supply lines and reaction gas discharge lines and, below the spiral duct, a heating device, and in the V / end spiral duct Mixing devices arranged.

The device according to the innovation is particularly applicable in the production of active metal powders and catalysts, for example for the production of oxidation, reduction or hydrogenation catalysts and also during production active masses for galvanic elements on a large scale

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i'assstab.

The device according to the invention is explained in more detail below with reference to FIGS. 1 and 2.

In FIG. 1, the vibratory spiral conveyor is shown with the casing cut open, while in FIG. 2 the device indicated in various perspective representations for mixing the powdery starting material is.

In its lower area a vibration generator, for example a vibration magnet 7 or an unbalance motor having a spiral conveyor 1 has a gas-tight casing, which consists of two double half-shells 8, the spaces 2 of which are filled with diatomite for thermal insulation are. This coat can also be wrapped with a glass wool mat 9.

If air is not used as the reaction gas, the vibratory spiral conveyor and The rest of the apparatus must first be made air-free by passing a stream of nitrogen through it. Then then the nitrogen is displaced by flushing with the reaction gas. The required reaction gas pressure is then set and the reactor is brought to the reaction temperature. Afterward the powdery material is continuously fed into the filler neck 10 of the spiral conveyor from above via a metering chute given. The powdery material runs through the spiral thread 4, which runs through

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a heater mounted below its bottom, for example Heating rods, heated or cooled by cold rooms, and is arranged in a spiral with the help of several Mixing devices mixed. The thin layer of powdery material moving from top to bottom is with a countercurrent in excess passed through the spiral conveyor reaction gas, which via the supply lines is fed at different heights of the vibratory spiral conveyor, brought into contact and converted. The powdery material is continuously discharged in the lower part of the spiral conveyor via a discharge pipe 13. The gaseous reaction products are diverted with the flow of reaction gas and freed from the fine powder dust that has been entrained.

It has proven to be particularly expedient to design the mixing device as reversing metal sheets 6 arranged in the spiral thread 4. Such a reversing plate 6 is shown in Figure 2 in various perspective representations and has two planes 62, 63 separated from one another by a web 61, of which the upper plane 62 is in the middle of the plane occupied by the powder Cross-section and the lower plane 63 from the spiral floor along the web 61 in the direction of movement of the mixing Increase powder. The upper level 62 has an upwardly bent spiral path 4 in the direction of movement of the powder separating edge 64 and between the web 61 and the wall of the walkway 4 a space is arranged.

By means of such a reversing plate 6, the cross-section of the layer of powdery material is divided horizontally into two halves, the powder layer half moved on the upper level 62 is deflected below the slightly rising lower level 63 and the layer half picked up by the lower level 63 falls at a breaking edge 65 onto the powder layer half arriving below this.

Examples 2 to 4 show the production of some catalysts as well as active masses for galvanic elements with

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Using the inventive method explained in more detail.

Furthermore, with the aid of the method according to the invention, other chemical reactions and exchange reactions can also be carried out continuously be performed. Such reactions are explained in more detail in Examples 5 and 6.

1. Manufacture of a copper chromite catalyst for selective Hydrogenations using air as the oxidizing gas

In ammoniacal solution, a double chromate is obtained by precipitation from copper nitrate with sodium chromate of the composition

fCu (NHv) oI (NH ,,) _o . (OrOj _{0 obtained} as a fine powder. J c. \ 4 <- 4 c-

The powder is washed thoroughly and largely dried by drying freed from water. Then the powder is countercurrent to a preheated air stream at 300-350 ° C and a layer thickness of 10-20 mm is continuously decomposed in the reaction spiral conveyor. The following plays out Reaction from:

air

. (NHj _0. (CrOj ₀ -
4 2 4 2 - _3C

+ NH, + 4

(CrOj _? - ■> CuO

^{4 ά} 300 - 35O ⁰ C

The gaseous reaction products are removed by condensation (HpO) and water washing (NH ^). The nitrogen will blown off with the air flow near the outside. The core size can 'can be varied within wide limits depending on the grain size of the double chromate. The catalyst prepared in this manner is particularly effective for selective hydrogenation of carbonyl groups: aldehydes and ketones become alcohols, esters and Carboxylic acids and amides reduced to amines.

2. Production of a nickel-Ti'ägerkatalysators for large-scale Fat hardening

The bulk of a supported Ni catalyst consists of basic Nickel carbonate precipitated on kieselguhr. It is continuously fed into the reaction spiral conveyor at one

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Reaction temperature between 350 - 50 ° C and a layer height between 1-10 mm. Hydrogen gas is fed in countercurrent in excess (approx. 10 times the stoichiometric amount). The hydrogen is preheated to the reaction temperature before it is fed into the reactor. At a dwell time between 5-20 minutes the basic carbonate is then completely reduced to very finely divided nickel. These endothermic reaction proceeds according to the following equations:

350 - 500 ° C _N1 . ο η ο Ni (OH) ₂ + H ₂ > Ni + 2 H ₂ O

350 - 500 ° C
Ni CO, + H ₀ . S * Ni + CO ₀ + H ₀ O

These reactions are through short diffusion paths of the gaseous Reactants and favored by the rapid removal of the water of reaction and the carbon dioxide. Also enables the continuous implementation of the reduction in a thin layer a very even heat supply, and thus becomes a consistent product is also guaranteed.

The gaseous reaction products (CO ₂ , H ₂ O vapor) carried along in the hydrogen stream are removed without difficulty in packed columns by absorption or condensation.

The catalysts prepared by the above process Compared to the catalysts prepared by conventional processes, they have 10-20 $ higher hydrogenation activities on.

3. Production of an electrochemically active: Ti (0H) ₂ powder (positive ground for alkaline batteries)

Powdered nickel (II) oxalate (NiC ₂ O.) (grain size> 50 / u) is now conveyed in a layer height of 10-15 in the reaction spiral conveyor at 150-200 ° C from top to bottom. Air saturated with water vapor at approx. 2 atm overpressure, which is preheated to approx. 300 ° C, is fed in countercurrent to the powder transport. A decomposition (hydrothermal decomposition) of the nickel oxalate occurs with the formation of finely divided nickel hy-

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ctroxid (Ni (OH) ₂ ) according to the following reaction equation: S.

Air _{t v}
NiC ₂ O ₄ + H ₂ O> Ni (OH) ₂ + CO ₂ + CO

_{• The gaseous reaction products CO 2} and CO discharged with the air as the carrier gas _{are discharged to the outside as CO 2} after the CO has been transferred by catalytic post-combustion.

The resulting nickel hydroxide powder with a grain size between 2 - 5 / u has proven particularly positive for use active mass in alkaline accumulators proven. It should be emphasized that because of the even, fine grain distribution of the resulting hydroxide the long formation times customary in practice for accumulators from approx. 60 h to 20 up to 25 h. Finally, the current yields, especially in the case of high-current discharges, because of the higher Surface and better accessibility of the powder for the electrochemical processes taking place in the electrode Operations can be increased considerably.

4. Production of negative, pre-charged cadmium masses with metallic Nickel conductive matrix for alkaline batteries

A one-part powder (grain size <10 / u), consisting of a mixed crystal of 10 $ nickel formate and 90 % cadmium formate, is continuously moved from top to bottom in a layer thickness of 15-25 mm at 270-290 ° C in the reaction spiral conveyor. Hydrogen gas, which has been preheated to the reaction temperature, is allowed to flow counter to the flow of powder. The processes taking place in the reactor in this temperature range can be represented by the following chemical conversion equations written as partial reactions:

Cd (HCO ₉ ) ₉ + H ₉ "-> Cd + 2 H ₉ O + CO

* ^d * 270 - 290 ° C *

Ni (HCO ₉ ) ₉ + H ₉ -> Ni + 2 H ₉ O + CO

^from 270 - 290 C.

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^: AA

Another example of the treatment of gases with powdered plague bodies is COg washing with molecular sieves. Molecular sieves are substances with a high adsorption capacity for gases and vapors. In the case of CO ₂ , this adsorption capacity is in some cases more than 15% by weight at room temperature. At higher temperatures, for example 150 ° C, most of the CO _{2 is released} again.

This fact can be used to remove COp from raw reformer gases. Such a gas consists of 25 % CO ₂ and 75 % H ₀ . This gas is fed from below to a spiral conveyor in an amount of 55 Nm / h. In the spiral aisle

ρ with a helical area of 1 m in total, it flows over a length of 13 m towards a bed of granules of the molecular sieve material. The amount of molecular sieve passed through per unit of time is around 180 l / h, corresponding to 275 kg / h, which corresponds to a dwell time of 6 minutes in the spiral conveyor with a layer thickness of 2 cm. The gas leaving the spiral conveyor at the top contains only a fraction of a percentage of CO ₂ , while the loaded molecular sieve removed from the spiral conveyor at the bottom contains _{more than 10% by weight of CO 2.} The Reak

tion temperature is 25 ° C; the heat generated during the reaction wii ^: d dissipated with the help of cooling tubes on the spiral base.

It has proven to be expedient to also carry out the regeneration of the molecular sieve in a Wendelföräerer. For this purpose, the granules are fed to above, is heated during the helical gear to 150 ° to 250 ⁰ C. Air flows into the spiral passage from below and is loaded with carbon dioxide on the way up. This process is particularly effective because it is a countercurrent process and the final loading of the molecular sieve is due to the low COp concentration in the air before it exits of the powder from the spiral path is kept very low.

The two spiral conveyor regulators for adsorption and. "De-

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sorption of the COp are to a system with a closed molecular sieve circuit combined, the expedient devices for the intermediate storage of a certain amount of surplus of the molecular sieve granules.

The process described can be carried out at modified operating temperatures also to remove other impurities from gas equipment, e.g. HpS, NEW, benzene and methanol to name a few, use it. In such cases, active charcoal, powder or granules can also advantageously be used as molecular sieves can be used.

6. Supported nickel catalysts of the type described in Example 1 contain nickel in addition to their use in fat hardening other impurities. In the course of the environmental pollution problems makes the storage of such waste increasingly difficult because of the nickel content. That's why one looks for Process of nickel recovery from catalyst waste,

It has been shown that, after removing the _{amount of main} fat, the old catalyst can be freed from nickel by feeding the material in a spiral conveyor reactor at slightly below 100.degree. C. in countercurrent to a stream of CO gas. It forms nickel carbonyl as a volatile compound, which is carried out of the reactor with the circulating CO and decomposed at 180 ° C. into nickel powder and CO. In this way, the nickel is recovered as a valuable, high-purity material and the carrier mass that comes out of the bottom of the spiral conveyor can be put to a new use.

Another group of procedures in which the use of the helix Conveyor reactor is useful, are catalytic gas treatment processes, in which after a certain operating time Regeneration of the catalyst is required. An example is the catalytic treatment of natural gas or oil derivatives, which in many cases leads to the catalyst being poisoned by sulfur components. Here the continuous Throughput of the catalyst through the reactor whose regeneration

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ration outside the reactor with the most economical use within the reactor system. This makes the use of this mostly Expensive catalytic converters are minimized and capital commitment is reduced.

The series of examples of performing exchanges in the spiral conveyor reactor could be expanded at will; only mention should be made of the drying of crystalline powders, in which the movement in the spiral conveyor counteracts the tendency to cake ". Roasting of sulphidic materials is a Example for the treatment of powdery solids with Help of gases where changing the solids is't the purpose of the process.

The examples can be seen that with Hitfe of the invention Process, in particular, active metal powders with very good characteristics can be produced.

Because the powder grains are moved by vibration, is Prevents caking and by increasing the vibration amplitude Difficult free-flowing powder can also be processed. Since the gas is supplied in excess, the equilibrium is achieved the chemical reaction is shifted in favor of the end product and thus the residence time of the powder in the vibratory spiral conveyor scaled down. The diffusion inhibitions that occur in the previously known methods are eliminated by the method according to the invention Mixing with the help of reversing plates and by passing the reaction gas in countercurrent largely reduced, and as a result, the dwell times customary up to now can be reduced from a few hours to a few minutes.

Since according to the invention the heat supply through a below the floor of the spiral path arranged heating device both from below and from above (by radiation) and by convection as a result of the Reaction gas takes place, a very uniform heating of the powdery material is achieved, and this contributes significantly the uniform that can be achieved with the aid of the method according to the invention End product at.

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Claims (5)

Protection claims 1) Device for carrying out reactions between powdery and gaseous substances, which a reaction vessel has, into which the powdery substances and a reaction gas can be introduced, characterized in that the The reaction vessel is a vibrating spiral conveyor (1) with a gas-tight casing (8). 2) Device according to claim 1, characterized in that the vibrating spiral conveyor (1) with reaction gas supply lines and reaction gas discharge lines (11,12) is provided and that the powdery substances at his Upper side can be continuously fed in and continuously removed from its underside. 3) Device according to claims 1 and 2, characterized in that that the spiral flights (4) in the vibrating spiral conveyor (1) are assigned heating or cooling devices (5). 4) Device according to claims 1 to 3. » characterized, that mixing devices are arranged in the helical flights (4). 5) Device according to claim 4, characterized in that the mixing devices are arranged as in the spiral thread (4) Reversing plates (6) are designed so that each reversing plate (6) separates two from one another by a web (61) Levels (62,63) has that the upper level (62) in the middle of the cross section occupied by the powder and the lower level (63) from the spiral floor along the web (61) in the direction of movement of the powder to be mixed increase so that the upper level (62) has an upwardly bent spiral path (4) in the direction of movement of the powder separating edge (64) and that between the web (61) and the wall of the spiral path (4) there is an intermediate space is.