DE1045986B - Fluidized bed device - Google Patents

Description

GERMAN

For many years the so-called fluidized bed processes have been used, in which more or less fine particles of a material to be treated or to be reacted in an ascending one Gas stream are kept suspended, the speed of which is sufficient to remove the particle layer get in one violent motion, but not enough to get something else out of that layer than to pull out the easiest particles.

These procedures may no longer work properly if as a result of high temperatures or from a any other reason caking of the particles colliding in the gas stream he follows.

Do you want to z. B. apply the fluidized bed process to gas generators, so you can only with one relatively work at low temperature. The ashes of the fine particles are indeed in dust form taken away, but the ashes of the coarser particles fall onto the grate at the bottom of the apparatus, where they are must be removed by a mechanical device. Every sintering of the ashes becomes the discharge device block quickly and must therefore * be avoided by keeping the temperature below the Start of sintering is held. However, the relatively low temperature of the gasification has to The result is that the gas generated is very far from the theoretical reduction equilibrium. It As a result, it contains a high proportion of carbon dioxide and water vapor, which are emitted by the fuel could not be reduced to carbon dioxide and hydrogen. Furthermore, the carbon grains are through their gasification becomes easier and easier, so that finally the finest grains are carried away by the gas stream from which they then have to be eliminated later. This dust is only partially burned but cannot be reinserted into the apparatus, otherwise it will be carried away again immediately would without noticeably reacting. This dust, which is still rich in fuel, must therefore be thrown away or used for other applications, e.g. B. coal dust heating.

From the Swiss patents 291 145 and 297 662 it is known to operate with fluidized bed processes working gas generators to improve the fact that on the one hand the coal and the Gasification agents (air, air and steam, oxygen and steam, oxygen and carbonic acid) through the The generated gas is preheated and thus the sensible heat contained in it is recovered and on the other hand uses a much higher gasification temperature. So you get a better efficiency, a lower consumption of gasifying agents and a gas that has less carbonic acid and water vapor Vertebral sealing device

Applicant:
Jean Marie Louis Longchambon, Paris

Representative: Dr.-Ing. H. Negendank, patent attorney,
Hamburg 36, Neuer Wall 41

Claimed priority:
France 19 January 1956

Leon Jean Roland Jequier, Geneva (Switzerland),

and Gerard van de Putte, Bully-les-Mines (France),

have been named as inventors

contains and is richer in carbon monoxide and hydrogen. As a result of the turbulence of the constantly with each other colliding particles, which are already partially burned and with a result of high Temperature melting layer of ash is coated, the particles stick to each other and bake together, so that they eventually fall in the lower part of the gasification zone. In the patent mentioned the gasification zone has the shape of a cone, the tip of which is directed downwards, and the gasification means exit through this tip. As soon as the granules of ash shaped into pellets are sufficient are large, they fall into the top of the cone, from which they are easily controlled by speed the flow of gasifying agents can be discharged.

Constructions have already become known with which one has tried to remove the heavy particles in a special vertical central channel to then discharge the gas to be introduced in the area to feed this vertical central channel via inclined tubular channels.

In this construction, however, there is the disadvantage that due to the low gas velocity In the vicinity of the central channel, agglutinations and adhesions occur at this point.

809 698/496

According to the invention it has now been found that considerably better results can be achieved, if the grate, which is slightly inclined towards the center and forms the bottom of the fluidization tank, is placed in the center merges into a strongly inclined cone through which the fluidizing gas is fed, and a second connection for gas supply is arranged under the grate outside the steeply inclined cone.

While the cone alone produces a very violent and irregular vortex, the inventive device a very good turbulence and a uniform distribution of fine particles in the process of gasification. The gas is so better divided between the fine particles, whose reducing effect is thus better distributed over the gas flow. You get one like that better reduction of the gasification agent and thus a gas of better quality and higher efficiency. The advantages of the cone for removing the ashes are also retained.

It was also possible to determine with the fluidized bed device according to the invention that the through Agglomerations of larger particles despite the aerodynamic drag they have the gas flow opposes, migrate to the base of the fluidization container without any danger, that they stick to the conical surfaces.

These improvements offer advantages not only for gasification, but also for other applications the fluidized bed process.

The invention is explained below by way of example with reference to the drawing.

Fig. 1 is a schematic vertical section of an embodiment of an apparatus according to the invention for gasification of solid fuels;

Fig. 2 is an enlarged section through the annular grate surrounding the central cone;

Fig. 3 is a smaller-scale plan view of this grate;

Fig. 4 shows a vertical section of a device for reintroducing the dust into the circuit.

The gas generator shown in FIG. 1 has a gasification zone 1 surrounded by a refractory wall. The fine particles of solid fuel are introduced into this zone either directly from the outside by any suitable device or by preheating steps not shown here. A part of the preheated or not preheated gasification agent arrives through the pipe 2 in the central conical part 3 of the grate. This conical part 3 with a fairly strong conicity (angle at the tip e.g. between 10 and 50 °) has a full wall which connects to a Venturi tube 4, which gives the gasification agent an equal speed over the entire inlet cross-section of the cone so that ash globules of a very uniform size can be separated out, but prevent particles that are too small from falling down. The purpose of the venturi is to give the gas a velocity at the lower part of the cone 3 and, moreover, to maintain the same velocity over the entire constricted cross-section, which prevents the small particles from falling, while the velocity of the gas is lower within this venturi, so as not to prevent the downward movement of the coarser particles which have passed through the neck of the venturi tube. The diverging portion of the \ ^r enturirohres can be formed by the cone 3 or be connected to this if it has a taper greater than that of the diverging portion of the venturi tube with the best efficiency. It is expedient that the gasification means have a speed perpendicular to the smallest cross section of the Venturi tube and that they do not perform any helical movement at this point. In order to dampen any such movement, the line la between the tube 2 and the venturi 4 can either be made long enough or provided with internal longitudinal ribs; these ribs must of course leave a free path, the diameter of which is at least as large as that of the neck of the venturi tube. The other part of the gasification agent comes through the pipe 5 under the annular grate 6. This is formed by overlapping radiating or concentric parts. The gases can pass between these parts, but their overlaps prevent the fine particles from passing into the lower distribution chamber 7 into which the pipe 5 opens. 2 and 3 show, by way of example, the formation of the part 6 by metal rings 6 a, which are placed concentrically on radial holders 6 b which are fastened at their ends to the wall of the chamber 7 and to the wall of the cone 3, respectively. These rings form between them small spaces 6 c along a broken line, which are permeable to the gases coming from the chamber 7, but not to the solid particles. These spaces are kept at the correct value by approaches 6 d of the rings 6 α. Any other arrangement can also be used, e.g. B. the overlapping radiating parts. The parts of the grate 6 are arranged so that this has a uniform slight inclination of the order of 10 ° or less between the wall of the gas generator and the central section 3. A dense, uniform fluidized bed is thus obtained in the gasification chamber 8. In the lower part of this the reaction of the fine carbon particles with the oxygen of the gasifying agents takes place extremely quickly and violently, all the oxygen being converted into carbonic acid with a very strong development of heat. The carbonic acid formed in this way and the carbonic acid and water vapor introduced with the gasification agents are immediately brought to the high gasification temperature. Since these gases are also kept in intimate contact with the fine particles during their passage through the fluidized bed 8, they are quickly reduced to carbon oxide and hydrogen. These reductions take place under very favorable conditions, owing to the very high reaction temperature, which is about the same in the whole room, and owing to the intimate contact between the gas and the fine carbon particles, their large surface area and their rapid movement caused by the turbulence.

As already stated above, these cause very fast movements and the ones generated thereby numerous collisions result in the caking of the fine particles when partially melted ash hits its surface. The grains gradually thicker and fall to the bottom of the Apparatus. The grains, which fall on the somewhat inclined annular grate 6, are due to the effect of the gas flow continued until they fall into the cone 3. Once in this, they will

caught again by a rather violent stream of gas, which returns them to the fluidized bed, in which they come into contact again with other grains come and get fatter. This circulation takes place until the moment when the almost Completely spherical grains of ash are so heavy that they fall down and through the cone come off the venturi. The size of the balls thus discharged depends on the speed of the Gasifying agent in the throat of the venturi tube. This speed in turn depends on that Cross-section of the Venturi tube as well as the flow rate and the temperature of the gasifying agents at this point. This speed can be easily regulated, with the amount increasing the gasification agent flowing through the grate can change within wide limits without the fluidized bed to affect.

Experience has shown that these grains of ash accumulating in the center, their diameter depending on the operating conditions of the apparatus are between a few millimeters and a few centimeters can, are practically free of unburned coal, of which they contain less than 0.5%.

The gasification temperature must be close to the temperature at which the ash begins to melt so that the ash cakes together well. It is therefore very important to be able to regulate this temperature, which can easily be done by changing the proportion of steam or of CO ₂ and oxygen in the gasifying agents.

It can also be useful not to use the same proportions of air · - · steam, oxygen - steam or Oxygen - carbonic acid in the gasifying agent streams to have which enter through the grate 6 or through the cone 3. It is useful to to have more steam or more carbonic acid in the part of the gasifying agent which passes through the grate 6 enters in order to avoid that in the layer located directly on this grate a too violent exothermic reaction occurs, which increases the temperature too much at this point, so that there is a risk of the ashes actually melting, which could result in the ashes sticking to the Can cause rust.

In order to have a sufficient throughput per square meter of the cross section of the gas generator, must choose fairly high gas velocities above the fluidized bed. The gas generated decreases thus part of the fine particles which enter the gasification zone. These fine particles are partially retained in the upper, not shown stages of the apparatus, which are used for preheating which serve fine particles. However, a certain proportion of the coal dust is always carried away, which is useful in a centrifugal separator or any other separator is recovered.

Experiments have shown that the dust so separated from the gas stream does not contain a noticeably higher ash content than the original fine particles. It is thus possible to reintroduce this into the cycle and convert it into useful gas. The best way to do this is to reintroduce the dust into the apparatus with the help of a small amount of the gasifying agent. The reintroduction is preferably carried out below the Venturi tube 4, as shown in FIG. 4. In this figure, the dust is deposited e.g. B. in a centrifugal separator 50. The gas to be dedusted arrives in this separator through the pipe 21, while the clean gas exits through the pipe 22. The dust collected in the lower part of the separator is led downwards through a pipe 23 which is provided with gas feeds 24 which are intended to keep the dust in the column always in a slightly agitated state in order to avoid any clogging. This gas can be an inert gas or a part of the gas produced and cooled in the apparatus which is taken from the compressor 25. At the foot of the pipe 23, which guides the dust downwards, there is a valve 26 or a rotatable distributor. The dust falls into a chamber 27, where it is picked up again by a branched flow of gasifying agents arriving through the pipe 28. The dust suspended in this stream is passed through the pipe 29 into the vertical pipe 2 α , which feeds the gasification agent to the venturi 4 of FIG. This supply pipe 29 is preferably arranged obliquely in the vertical pipe and opens out in the vicinity of the wall of the same, so that the dust jet breaks on this wall and so that no caking of the dust occurs. The mouth of the pipe

as 29 is above that of the pipe 2 of Fig. 1. The cross section of the vertical pipe 2 a is chosen so that the speed in it is large enough to lead the introduced fine particles up into the gasification zone, but without the case of to slow down large ash particles that have crossed the venturi.

The dust reintroduced into the circuit comes into intimate contact with the gasification agents and is very quickly brought to the temperature prevailing in the apparatus. As a result of his large specific surface area and its introduction into the part of the apparatus in which the reaction takes place is most violent, he reacts immediately, and his ashes bake with that of those in the process of caking fine particles together. The reintroduced dust is therefore no longer out of the gasification zone torn out.

In a similar way, one or more reactants can also be introduced into the apparatus by using a gas stream which opens into the line 2 α upstream of the venturi 4 to carry them along.

The device according to the invention does not have any movable ones at a high temperature Split it up and have the following advantages:

a) The reaction zone is at a high temperature and the gasifying agents are instantaneous brought to this temperature, the specific surface area of the fine particles present in this zone is considerable and their movement in relation to the gas flow is very strong, which favors the reduction reactions.

b) The ash comes out with practically no unburned components.

c) The entrained dust is reintroduced into the cycle and fully utilized.

In the case of small and medium-sized apparatus, a single conical part 3 is used to remove the ashes. In the case of very large apparatus, it may be useful to have two or more conical parts connected in parallel to use to remove the ashes.

According to a variant embodiment, the uniform conical surface can be replaced by another widening area, e.g. B. be replaced by the area of a pyramid.

The device can also find uses other than the gasification of fuels. she can e.g. B. for the production of hydrogen from lean gas by reducing the water vapor with The help of iron or iron oxide are used, the latter in turn by the lean gas beforehand is reduced, the reduction takes place in a fluidized bed and the iron oxide used in powder form will. In such a manufacture, a gas ίο can be used to generate the lean gas from fine coal Generators are used with a fluidized bed zone, which at its lower part according to the invention is trained.

It can also be used for the continuous production of iron or steel by treatment and reduction of oxide, hydrate or metal salt are used, these substances being used in powder form and the whole treatment and reduction or parts of the various stages thereof The help of gas streams take place, of which certain reducing gas streams the powder in fluidized bed keep. Here, a fluidized bed device designed according to the invention is used, in particular in the step of reducing the Fe 0 for extraction of the caked iron particles as well as ores which require a fairly high reduction temperature, the iron particles through Bake together sintering.

The device according to the invention can also be used for the production of cement. The forming Clinker bricks, when they have reached a sufficient size, are made through the middle cone and that Venturi tube discharged.

In the production of zinc by reducing the ore with the help of coal in a fluidized bed working apparatus, the device according to the invention can also be used, with the excretion the caked particles formed by the coal ashes and the ore rock through the middle cone and the venturi.

Claims (6)

Patent claims: 1. Fluidized bed device with a fluidization tank, the bottom of which is partly of a grate slightly inclined towards the center is formed, characterized in that the In the middle of the grate (6) merges into a steeply inclined cone (3) through which the fluidizing gas is fed, and that under the grate (6) outside the steeply inclined cone (3) second connection (5) is arranged for gas supply. 2. Apparatus according to claim 1, characterized in that the grate (6) with covers or zigzag guides (Fig. 2) is provided. 3. Apparatus according to claim 1 and 2, characterized in that the gas supply in the strongly inclined cone (3) a Venturi tube (4) is provided, the narrowing of which the falling of the large particles allowed. 4. Apparatus according to claim 1 to 3, characterized by mutually independent pipelines (2, 5) for the gas supply to the steeply inclined cone (3) and the grate (6). 5. Apparatus according to claim 1 to 4, characterized in that the steeply inclined cone (3) has an inclination between 5 and 25 ° relative to the vertical. 6. Apparatus according to claim 3, characterized by an introduction line (29) for finely divided Solids in the gas stream that feeds the steeply inclined cone (3), this line opens below the narrowing of the venturi tube (4). Considered publications:
French patent specification No. 953 869,1 079 088. 1 sheet of drawings © 809 698/496 12.