DE102009059016B4 - Process for the treatment of a quartz sand or quartz glass grain - Google Patents

Abstract

Method for treating a quartz sand or quartz glass grain (11) with a specific angle of repose (β) in the range of 25 to 36 degrees, in which the grain (11) is fed continuously via a grain inlet (7) to a heated treatment space (2), heated and gravity transported to a Körnungsauslass (8) and continuously discharged from the treatment chamber (2), wherein the grain (11) over at least a portion between Grannungseinlass (7) and Körnungsauslass (8) as a grain layer (18; 45) on a within the treatment chamber (2) arranged first chute (3; 43) which ends at a transfer opening (6) above the Körnungsauslasses (8), wherein the grain (11) one between a gas inlet (9) and a gas outlet (10) is subjected to flowing treatment gas, wherein the granulation layer (18; 45) has a minimum thickness of less than 5 cm and the first chute (3; Sliding surface which includes a cascade angle (α) with the horizontal, which is greater than 5 degrees greater than the specific angle of repose (β) of the grain (11).

Description

The present invention relates to a method for treating a grain of quartz sand or quartz glass.

State of the art

Mineral raw materials can be freed from impurities such as iron, titanium, alkali metals and alkaline earth metals by treatment under a chlorine-containing atmosphere at high temperature (thermochlorination). For the thermochlorination different methods and reactors are used, which are essentially fluidized bed, rotary kiln and shaft furnaces.

Fluidized bed ovens are used in particular for ore processing and are suitable for high material conversions. In the EP 1 098 846 B1 Such a cleaning method is also proposed for the purification of a quartz grain raw material. In this case, a bed of grain is flowed through in a reactor from bottom to top of chlorine-containing treatment gas, which is introduced via a plurality of nozzle openings, which are distributed over a large area. The bed is slightly raised by the flow of the treatment gas to form a so-called "fluidized bed". Reactor and gas shower are made of quartz glass.

By this procedure, a largely uniform treatment of the grain is ensured; However, it may come to a segregation of fine dust due to an air view effect. The known method is also suitable only for discontinuous operation.

This disadvantage avoids the continuous purification of crystalline quartz powder by thermochlorination in a rotary kiln, such as in the EP 0 737 653 A1 described. It is proposed to supply the quartz powder to be cleaned to an electrically heated rotary kiln in which it successively passes through a preheating chamber, a reaction chamber and a gas desorption chamber. In this case, metallic impurities of the quartz powder react with the chlorine-containing treatment gas to form volatile metal chlorides. The treatment gas and the gaseous reaction products are sucked off.

The thermochlorination in a rotary kiln also leads to a uniform treatment intensity of the grain and high grain fineness can be achieved. However, the cleaning of ultrafine powders and dusts is not readily possible because they are easily discharged with the gas stream. The rotary kiln has a large space requirement and the rotating components of the furnace are subject to considerable wear. In addition, it comes through frontally open ends of the rotary kiln to a considerable heat radiation.

The two last-mentioned disadvantages avoids the shaft furnace method for continuous cleaning of free-flowing quartz sand, as for example from the DD 144 868 A1 is known. The quartz sand to be cleaned is fed continuously from above to the vertically oriented shaft furnace. Due to its own weight, the silo-like quartz sand bed gradually passes through the furnace from top to bottom, passing through a warm-up zone, a thermochlorination zone and a cooling zone. These zones are designed as filling funnel-like, closed containers, which are arranged one above the other and connected to each other via an inlet or an outlet for the quartz sand. The treatment gas is introduced via a line in the center of the bed in the lower part of the container, which forms the Thermochlorierzone. In order to prevent the penetration of oxygen into the Thermochlorierzone and thus prevent the regression of the resulting during chlorination of volatile chlorides in solid metal oxides, a gas curtain of inert gas is generated at the entrance and exit area.

The shaft furnace is relatively simple in construction and has no moving parts. However, due to its heat-insulating effect, the heating of the granulation pad from the outside to the inside takes a long time and forces a relatively slow throughput. The procedure also does not lead to a sufficiently reproducible purity of the grain, which can be attributed to different treatment intensities within the silo-like granulation in the thermochlorination zone, which results from uneven distribution of the treatment gas and by a pronounced silo flow in the bulk due to flow edge effects.

One of these standard methods fundamentally different method for the purification of SiO ₂ grain by thermochlorination is from the DE 198 13 971 A1 known. Therein it is proposed to disperse the SiO ₂ grain to be cleaned in a fuel gas flame containing a chlorine-containing fuel gas component. The purified SiO ₂ granules and the gaseous reaction products are introduced directly into a cyclone and separated from each other.

Out DE 10 2007 025 099 A1 Furthermore, a method and an apparatus for puffing a free-flowing mineral granules is known, which heated via a granulation inlet Treatment room continuously supplied, heated therein and exposed to a suspension. Due to its gravity, the granules pass through an angled radiation channel up to a grain outlet, where it is continuously discharged. The suspension is injected from below into the radiation channel. The granules initially move slidably on the sliding surface of the upper, obliquely extending radiation channel section and fall downwards when passing into the first angled channel section. At the same time it is whirled up and continues its erratic, staggering course.

US 3,330,046 A describes the thermal treatment of granules of inorganic material, such as calcium carbonate or aluminum hydroxide, in a shaft furnace. The shaft furnace has internals in the form of oppositely extending chutes which run obliquely from one furnace side wall to close to the other side wall, and on which the grain to be treated is gradually transported under its own weight down and taken there from time to time. At the same time a hot treatment gas is introduced in the lower furnace area, which flows around the grain in countercurrent and leaves the shaft furnace above again. The strength of the treatment gas stream and the arrangement of the chutes are designed to ensure turbulent turbulence of the grain in each section of the shaft furnace.

Similarly, in US 2 717 458 A describes a method and apparatus for thermal treatment of inorganic material grain in a shaft furnace. This has two parallel rows of slides arranged in zigzag. The grain to be treated is transported as a continuous graining layer under its own weight on the slides down and taken out via a valve. The stream of grain is controlled so that it does not break off. At the same time hot air is introduced in the lower furnace area, which flows around the grain in countercurrent and leaves the shaft furnace via an upper gas outlet again.

In CH 250 363 A Finally, it is about the sugar production from plant granules in a treatment device. This comprises an optionally heatable reactor of rectangular cross-section, in which a plurality of perforated, gas-permeable ramps in zigzag form one above the other. The granules are fed to the reactor at the top end and migrate as a granular layer through the ramps to the lower end, where it is continuously withdrawn by means of a discharge screw. Via the connections at the bottom and at the upper end of the reactor gaseous or liquid treatment media are supplied.

Technical task

The invention has for its object to provide a method that allows reliable and reproducible treatment of a quartz sand or quartz glass grain with low consumption of treatment gas.

This object is achieved according to the invention by a method for treating a quartz sand or quartz glass grain with a specific angle of repose β in the range of 25 to 36 degrees, in which the grain is fed via a granulation inlet a heated treatment room continuously, heated therein and by gravity to a Grain outlet is transported and continuously discharged from the treatment chamber, wherein the grain is transported over at least a portion of Körnungseinlass and Körnungsauslass as a grain layer on a disposed within the treatment room first chute, which ends at a transfer opening above the Körnungsauslasses, the grain one between a gas inlet and a gas outlet is exposed to the treatment gas flowing, wherein the granulation layer has a minimum thickness of less than 5 cm and the first chute has a sliding surface which is horizontal n includes a cascade angle α, which is greater than 5 degrees greater than the specific angle of repose β of the grain.

In the modification of the known shaft furnace method according to the invention, the grain is not exposed to the treatment gas in a silo-like, vertical bed within the reaction vessel, but it trickles due to their flowability along a slope to form a grain layer of comparatively small thickness through at least a portion of the treatment space. As a result of this movement and because of the comparatively small thickness of the graining layer on the chute, a comparatively large graining surface is available to the treatment gas, which enables a uniform and effective treatment of the grain and thus, for example, a high degree of purity. The movement of the grain occurs due to their flowability and their own weight. Moveable mechanical parts are not required.

In that regard, the invention combines the advantages of rotary kiln and shaft furnace method while avoiding their disadvantages.

The grain gradually flows in the form of the granulation layer from the granulation inlet via the transfer opening in the direction of the granulation outlet and is treated with the treatment gas. On the slide forms a bed with a grain-specific angle of repose. Depending on the "slope" of the chute, the thickness of the grain layer is substantially constant, or it decreases from top to bottom, or it increases from top to bottom. The grain-specific angle of repose depends, for example, on the grain size, grain size distribution, morphology and chemical composition of the grain. As a rule, the grain-specific angle of repose decreases with the mean grain size.

The chute extends between the grit inlet and the transfer opening. It is in the simplest case a plate inclined to the vertical; However, it may also be formed, for example, half-shell-shaped. Even with a horizontal orientation of the chute, a bed with the grain-specific angle of repose arises between the grain outlet and the transfer opening, but in this case, there are still or poor-moving grain areas within the grain layer. The chute can also run helically within the treatment room. All that is essential is that a granulation layer with the specific angle of repose forms on the chute and between the grain outlet and the transfer opening.

The treatment gas is, for example, a chlorine-containing gas, as is otherwise used in the prior art for the purification of mineral bulk material, a doping gas for doping the grain, or a flushing gas such as hydrogen or helium for exchange with another adsorbed on the graining surface gas. During the treatment with the treatment gas, the grain is heated to a high temperature within the treatment space, for example to a temperature above 800 ° C.

The granulation is quartz sand from naturally occurring raw material or synthetic quartz glass grain and the like.

The granulation passes through the transfer opening into a region of the treatment space arranged below the first slide. In this space may be arranged another slide for receiving the granulation layer, or it is a free space which opens into the granulation outlet and in which the granulation can be poured up and removed via the granulation outlet.

In the method according to the invention thus results in at least two granulation beds within the treatment chamber, of which a bed on the first slide and a further bed below the first slide are formed.

It has been found that, due to this procedure, with within the treatment chamber in a relatively small layer thickness of less than 5 cm trickling granulation, rapid heating of the grain and a uniform and effective treatment can be achieved. This contributes to the fact that the granulation layer can be heated from all sides, especially from below. The process is continuous and therefore also advantageous from a productivity point of view.

The thinner the granulation layer is formed on the chute, the higher the treatment effect, in particular a cleaning effect. Therefore, a procedure is preferred in which the granulation layer above the transfer opening has a minimum thickness of less than 3 cm.

From the transfer opening, the layer thickness either decreases or increases in the direction of the grain inlet in accordance with the grain-specific angle of repose. The minimum thickness of the granulation layer, due to the ratio of addition and removal of the granulation, will either be above the transfer orifice or below the granule inlet, depending on the slope of the first chute. Ideally, the removal of the grain is such that a minimum layer thickness approaches zero.

At the transfer opening there is a bridging between the bed on the first slide and the area below it.

In the method according to the invention is further provided that the first chute has a sliding surface which includes a cascade angle with the horizontal, which is greater than 5 degrees greater than the specific angle of repose of the grain.

In this procedure, the slope of at least the first chute is greater than the grain-specific angle of repose. This results in the formation of a graining layer which is thin in the region of the grain inlet and which increases downwards according to the grain-specific angle of repose, and is largest at the transfer port. The large cascade angle has the advantage that the grain on the chute can not rest stably, but trickles away. As a result, areas with little movement are avoided within the granulation layer, which contributes to a more uniform treatment. It is also particularly advantageous that the treatment room can be emptied completely of grain even without tilting.

For this it is sufficient if the cascade angle is slightly larger than the grain-specific angle of repose. On the other hand results at cascade angles, which are much larger than the grain-specific angle of repose, an unnecessarily high bed and thus a comparatively poorer treatment and cleaning effect. Therefore, in the method according to the invention, the cascade angle is adapted to the grain-specific angle of repose, such that the cascade angle is greater by a maximum of 5 degrees than the specific angle of repose of the grain.

In a preferred variant of the method, it is provided that the granulation layer is transferred via the transfer opening to a second chute disposed within the treatment space, which extends opposite to the first chute within the treatment space.

In this embodiment, at least two slides are arranged within the treatment space, which form a cascade with one another, for example by running zigzag or meandering within the treatment space. At the transfer opening, the granulation layer passes from the first, upper chute to the second, lower chute. The respective granulation layers are connected via a granulation bridge which extends through the transfer opening. The second chute ends at the grain outlet or at another transfer opening, so that one or more further chutes can be arranged in cascade manner below the second chute.

Due to this spreading of the grain in the form of a cascade-like grain layer extending within the treatment space, a particularly high surface area and an effective treatment effect result, even at high throughputs.

This contributes to the fact that the graining layer has underside grains resting on the first chute and a free upper side, the graining layer being turned over from the first to the second chute in such a way that at least part of the undersize grains come to rest on the free upper side. The "turning" of the graining layer at the transition from the first, upper chute to the lower chute additionally contributes to the homogenization of the reaction with the treatment gas.

In order to ensure optimal trickling of the grain over the granulation layer, it has proven useful if the granulation inlet in an upper opening plane and the transfer opening lie in a lower opening plane, wherein the connecting line between Grazernseinlass and transfer opening with the horizontal includes a plant angle that is at least as large is like a specific angle of repose of the grain.

This ensures that a grain charge with the grain-specific angle of repose can form between the grain inlet and the transfer opening. Otherwise, it may slow down the trickle or backwater. The connecting line between the granulation inlet and the transfer opening results as a connection between the intersections of the respective opening plane and the opening center line.

A large installation angle has the advantage that one and the same treatment method can be used for a large number of different grain sizes of quartz sand or quartz glass with grain-specific angles of repose. On the other hand results in plant angles that are much larger than the grain-specific angle of repose, an unnecessarily high bed and thus a comparatively poorer treatment and cleaning effect.

Therefore, a procedure is preferred in which the installation angle is adapted to the grain-specific angle of repose, such that the contact angle is greater than the specific angle of repose of the grain by a maximum of 10 degrees, preferably a maximum of 5 degrees. In the case of quartz glass grains typical angle of repose in the range of 25 to 36 degrees, so that plant angles to a maximum of 46 degrees, preferably at most 41 degrees prove to be particularly favorable.

It has proven particularly useful if the treatment gas flows through the treatment space from bottom to top and through the transfer opening.

The treatment gas is guided over at least a partial section within the treatment chamber in countercurrent to the movement of the granulation layer. This results in a particularly effective treatment effect.

This applies in particular to the granulation layer in the region of the transfer opening. Because there, the treatment gas is forcibly passed simultaneously with the opposite grain through the transfer opening, so that it comes to a particularly intimate contact and thus to an effective treatment, in particular an effective cleaning. In this context, it has proved to be advantageous if the opening width of the transfer opening has a maximum of 20 mm. The maximum opening width determines the layer thickness of the granulation layer in the region of the transfer opening.

It has proven useful if the treatment gas is a chlorine-containing reaction gas and the grain in the treatment room undergoes a residence time of at least 30 minutes.

The throughput through the treatment room determines the mean residence time of the granulation. For different areas of the graining layer, however, different treatment periods result. The grain areas with minimal residence time can be easily determined empirically. The throughput is to be adjusted on the basis of this finding so that a minimum residence time of 30 minutes or longer results. In the case of cleaning the grain using a chlorine-containing reaction gas usually results in a sufficient cleaning effect.

The treatment room and the at least one slide can be made of quartz glass.

Quartz glass is characterized by high mechanical resistance and temperature resistance and contributes little to an additional contamination of the grain to be cleaned; this applies in particular when the grain to be cleaned is quartz glass grains. A particular advantage of this construction is also the transparency of the quartz glass components, in that the grain size can be effectively heated by thermal radiation. For example, transparent walls of the treatment space allow the rapid heating of the grain from the outside and transparent chutes the heating of the granulation layer from all sides, especially from below.

list of figures

• 1 eine erste Ausführungsform eines Reinigungsmoduls zur Durchführung des erfindungsgemäßen Verfahrens in einer Seitenansicht,
• 2 das Reinigungsmodul von 1 in einer Draufsicht (ohne Körnung),
• 3 eine zweite Ausführungsform eines Reinigungsmoduls zur Durchführung des erfindungsgemäßen Verfahrens, und
• 4 eine dritte Ausführungsform eines Reinigungsmoduls zur Durchführung des erfindungsgemäßen Verfahrens.

The invention will be explained in more detail with reference to an embodiment and a drawing. Specifically, shows in schematic and not to scale representation

• 1 A first embodiment of a cleaning module for carrying out the method according to the invention in a side view,
• 2 the cleaning module of 1 in a top view (without grain),
• 3 a second embodiment of a cleaning module for performing the method according to the invention, and
• 4 a third embodiment of a cleaning module for performing the method according to the invention.

This in 1 illustrated cleaning module 1 consists of a in plan view ( 2 ) round containers with an inner diameter of 30 cm made of quartz glass. The container 2 is completely sealed from the environment and from a heated oven chamber 16 surround.

Inside the container 2 are three slides 3 . 4 . 5 of quartz glass arranged in cascade to each other. At the slides 3 . 4 . 5 it is at an angle to the central axis 17 and oriented to the vertical quartz glass plates, with the inner wall of the reaction vessel 2 are welded. The angle of inclination of the plates is in 1 with α, it is for all plates 3 . 4 . 5 about 10 degrees.

The two upper slides 3 . 4 each end just before the opposite side wall of the container 2 leaving a circular segment-shaped transfer opening 6 with a maximum opening width of 5 cm. The lower slide 5 ends at a graining outlet 8th at the bottom of the container 2 that as a ball cut 19 is formed and to which a (not shown in the figure) cooling chamber is connected.

At the top of the container 2 is a grit inlet 7 intended. A gas inlet 9 is as in the opening of the grain outlet 8th protruding supply line formed of quartz glass, and as a gas outlet 10 is in the upper part of the container 2 a quartz glass tube passed through the container side wall gas-tight.

About the grit inlet 7 Quartz sand reaches the topmost chute 3 and forms on this a graining layer 18 with an angle of repose β (in 1 For reasons of a clearer representation, the corresponding vertex angle is drawn with the horizontal). The angle of repose β is specific to the particular quartz sand grain and in the exemplary embodiment is about 36 degrees.

The midline 12 the grain intake 7 intersects with the opening plane in one point P1 , and the midline 13 the transfer opening 6 cuts itself in its opening plane in one point P2 , The connecting line between P1 and P2 forms a plant angle with the horizontal γ , The plant angle γ is always greater than the grain-specific angle of repose β , And he is in the embodiment 40 degrees. The same plant angle γ is also between the upper transfer opening 6 and the lower transfer opening 15 , as well as between the lower transfer opening 15 and the upper opening plane of the grain outlet 8th realized. The thickness of the graining layer 18 above the respective transfer openings 6 . 15 is about 1 to 2 cm.

From the transfer opening 6 the grain gets 11 on the second slide 4 , The graining layer 18 It is turned in such a way that previously on the slide 3 overlying grain 11 on the slide 4 comes to rest on the surface. About the slide 4 the grain gets 11 to the transfer opening 15 and from there to the bottom slide 5 , wherein the granulation layer 18 is turned again.

The grain 11 when trickling through the container 2 along cascading grain layer 18 by means of the oven 16 heated to a temperature of about 1270 ° C. Because of the comparatively small thickness of the granulation layer 18 and the transparency of the container wall and the slides 3 . 4 . 5 is the graining layer 18 Heatable from all sides by heat radiation, so that the heating in a short time succeeds. Because of the encapsulation of the container 2 the heat losses by radiation compared to a rotary kiln are relatively low.

From below, via the gas inlet 9 , becomes countercurrent to the direction of movement of the granulation layer 18 , a chlorine-containing cleaning gas introduced into the container. This flows through the container 2 from bottom to top and reacts with impurities of the grain 11 with the formation of volatile chlorides. Due to the comparatively large spreading surface of the grain 11 over the cascaded slides 3 . 4 . 5 , the small thickness of the graining layer 18 and the intimate contact of grain 11 and cleaning gas in the area of the transfer openings 6 and 15 results in a particularly uniform and effective cleaning effect.

The throughput through the cleaning module 1 depends on the removal of the grain 11 over the grain outlet 8th (or via downstream facilities). If the removal is stopped, the grain inflow is also automatically stopped, as the beds on the slides 3 . 4 . 5 can not build up steeper. In that regard, the cleaning module shows 1 a certain self-control. With continuous removal, the throughput is typically 20 kg / h and the minimum residence time of the grain at 60 min.

In the in the 3 and 4 schematically shown embodiments of the cleaning module are the same or equivalent components and components of the device designated by the same reference numerals.

In the embodiment of the cleaning module 21 according to 3 are on the ground 22 of the container 2 two sampling nozzles 23 . 24 for the grain 11 provided by the respective cleaning gas via the supply lines 26 . 27 made of quartz glass in the container 2 is initiated. The lowest slide 25 ends here at the central axis 17 , Because of their shorter length, it turns on the slide 25 a smaller layer thickness of the granulation layer 18 a, so that in this embodiment allows a slightly larger throughput with the same cleaning effect.

This in 4 illustrated cleaning module 41 also consists of a round top container with an inner diameter of 30 cm made of quartz glass. The container 2 is completely sealed from the environment and from a heated oven chamber 16 surround.

Inside the container 2 are two slides 43 . 44 of quartz glass arranged in cascade to each other. At the slides 43 . 44 it is at an angle to the central axis 17 and oriented to the vertical quartz glass plates, with the inner wall of the reaction vessel 2 are welded. The angle of inclination of the plates is in 4 denoted by α and is 40 degrees. This angle is 4 degrees greater than the grain-specific angle of repose of the quartz sand grain to be cleaned.

The upper slide 43 ends just before the opposite side wall of the container 2 leaving a circular segment-shaped transfer opening 6 with a maximum opening width of 5 cm. The lower slide 44 ends at a graining outlet 8th at the bottom of the container 2 ,

At the top of the container 2 is a grit inlet 7 intended. A gas inlet 9 is as in the opening of the grain outlet 8th protruding supply line formed of quartz glass, and as a gas outlet 10 is in the upper part of the container 2 a quartz glass tube passed through the container side wall gas-tight.

About the grit inlet 7 Quartz sand reaches the topmost chute 43 and forms on this a graining layer 45 with a repose angle β (in 4 For reasons of a clearer representation, the corresponding vertex angle is drawn with the horizontal). The angle of repose β is specific to the particular quartz sand grain and in the exemplary embodiment is about 36 degrees.

The midline 12 the grain intake 7 intersects with the opening plane in one point P1 , and the midline 13 the transfer opening 6 cuts itself in its opening plane in one point P2 , The connecting line between P1 and P2 forms a plant angle with the horizontal γ , The plant angle γ is always greater than the grain-specific angle of repose β and also greater than the angle of inclination α of the plates 43 . 44 and it is 45 degrees in the embodiment. The same plant angle γ is also between the transfer opening 6 and the upper opening plane of the grain outlet 8th realized. The graining layer 45 has above the respective transfer openings or above the Körnungsauslasses 8th their largest thickness and each at the top of the slides 43 . 44 their smallest thickness, which is about 1 to 2 cm.

The grain 11 when trickling through the container 2 along cascading grain layer 45 by means of the oven 16 heated to a temperature of about 1270 ° C. Because of the comparatively small thickness of the granulation layer 45 and the transparency of the container wall and the slides 43 . 44 is the graining layer 45 Heatable from all sides by heat radiation, so that the heating in a short time succeeds. Because of the encapsulation of the container 2 the heat losses by radiation compared to a rotary kiln are relatively low.

From below, via the gas inlet 9 , becomes countercurrent to the direction of movement of the granulation layer 45 , a chlorine-containing cleaning gas in the container 2 initiated. This flows through the container 2 from bottom to top and reacts with impurities of the grain 11 with the formation of volatile chlorides. Due to the comparatively large spreading surface of the grain 11 over the cascaded slides 43 . 44 the small thickness of the graining layer 45 and the intimate contact of grain 11 and cleaning gas in the area of the transfer openings results in a particularly uniform and effective cleaning effect.

The throughput through the cleaning module 41 depends on the removal of the grain 11 over the grain outlet 8th (or via downstream facilities). If the removal is stopped, the grain inflow is also automatically stopped, as the beds on the slides 43 . 44 can not build up steeper. In that regard, the cleaning module shows 41 a certain self-control. With continuous removal, the throughput is typically 20 kg / h and the minimum residence time of the grain at 60 min.

At the with a ball cut 19 provided grit outlet 8th is a (not shown in the figure) identical desorption connected, in which the on the grain 11 adhering cleaning gas is removed. For this purpose, hydrogen is introduced into the container through the gas inlet of the desorption chamber, which substitutes the adhering chlorine-containing reaction gas.

Claims (8)

Method for treating a quartz sand or quartz glass grain (11) with a specific angle of repose (β) in the range of 25 to 36 degrees, in which the grain (11) is fed continuously via a grain inlet (7) to a heated treatment space (2), heated and gravity transported to a Körnungsauslass (8) and continuously discharged from the treatment chamber (2), wherein the grain (11) over at least a portion between Grannungseinlass (7) and Körnungsauslass (8) as a grain layer (18; 45) on a within the treatment chamber (2) arranged first chute (3; 43) which ends at a transfer opening (6) above the Körnungsauslasses (8), wherein the grain (11) one between a gas inlet (9) and a gas outlet (10) is subjected to flowing treatment gas, wherein the granulation layer (18; 45) has a minimum thickness of less than 5 cm and the first chute (3; Sliding surface which includes a cascade angle (α) with the horizontal, which is greater than 5 degrees greater than the specific angle of repose (β) of the grain (11). Method according to Claim 1 , characterized in that the granulation layer (18; 45) has a minimum thickness of less than 3 cm. Method according to Claim 1 or 2 characterized in that the granulation layer (18; 45) is transferred, via the transfer opening (6), to a second chute (4; 44) located within the treatment space (2) which is opposite to the first chute (3; Treatment room (2) extends. Method according to Claim 3 , characterized in that the grit inlet (7) in an upper opening plane (P1) and the transfer opening (6) lie in a lower opening plane (P2), and in that the connecting line between grit inlet (7) and transfer opening (6) with the horizontal one Plant angle (y) which is at least as large as the specific angle of repose (β) of the grain (11). Method according to Claim 4 , characterized in that the installation angle (y) by a maximum of 10 degrees greater than the specific angle of repose (β) of the grain (11). Method according to Claim 5 , characterized in that the installation angle (y) by a maximum of 5 degrees greater than the specific angle of repose (β) of the grain (11). Method according to one of the preceding claims, characterized in that the treatment gas flows through the treatment space (2) from bottom to top and through the transfer opening (6). Method according to one of the preceding claims, characterized in that the treatment gas is a chlorine-containing reaction gas and that the grain (11) in the treatment chamber (2) undergoes a residence time of at least 30 min.

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