Method for treating flowable inorganic particles and a rotary tube suitable for carrying out the method

Abstract

To provide a method capable of performing the purification of SiO2 particles by heat chlorine treatment with reliability and reproducibility at the minimum treatment gas amount.SOLUTION: A method for treating fluidizable inorganic particles uses a heating rotary pipe rotating around a rotary axis and surrounding a treatment chamber divided into a plurality of treatment zones by a plurality of separation elements. Particles are fed from a particle inlet side to the treatment chamber, are carried to a particle outlet side in a particle carrying direction, and are exposed to a treatment gas in the process. Successively, for enabling the heat treatment of fluidizable inorganic particles, particularly, SiO2 particles in a rotary kiln with reliability and reproducibility, low in the consumption of the treatment gas and effective, the treatment gas after use is sucked out from a reaction zone of the treatment chamber by a gas manifold rotating around its longitudinal axis.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for treating flowable inorganic particles in a heated rotary tube surrounding a processing chamber that rotates around a rotation axis and is divided into a plurality of processing zones including at least one reaction zone by separation elements, wherein the particles are supplied from a particle inlet side to the processing chamber, transported in a particle transport direction to a particle outlet side, and exposed to a processing gas in the process.

[0002] The present invention further relates to a rotary tube for treating flowable inorganic particles, the tube being rotatable around a rotation axis inclined with respect to the horizontal, the tube surrounding a processing chamber for accommodating the particles, the chamber being divided into a plurality of processing zones including at least one reaction zone by separation elements, a particle inlet side for introducing the particles into the processing chamber, a particle outlet side for discharging the particles from the processing chamber, a gas introduction part for introducing a processing gas into the reaction zone, and a gas discharge part for removing the used processing gas from the processing chamber.

[0003] Such a processing method using a rotary kiln is used, for example, to purify amorphous or crystalline particles, particularly those composed of SiO 2 and the like.

Background Art

[0004] SiO 2 particles are used as raw materials for producing quartz glass. In many cases where quartz glass is applied, for example, for parts for semiconductor manufacturing and optical parts, high requirements are placed on purity, and this requirement can only be achieved with a considerable amount of time, materials, and costs.

[0005] Impurities such as iron, titanium, alkali, and alkaline earth metals are removed by treatment at high temperature in a chlorine atmosphere (thermal chlorine treatment). A continuous purification method of quartz powder by such thermal chlorine treatment in a rotary kiln is described in US5,637,284A. The quartz powder to be purified is continuously supplied to the inlet side of a rotating tube made of quartz glass, which is obliquely arranged and electrically heated, and passes through a preheating chamber, a reaction chamber, and a gas desorption chamber in succession. Each chamber is separated from each other by a non-closed separating element that is also used to mix the quartz powder. The quartz powder is heated to about 800 °C in the preheating chamber and then treated with a mixed gas of chlorine and hydrogen chloride at a temperature of about 1300 °C in the reaction chamber. The mixed gas is introduced into the reaction chamber from the outlet side by a gas lance extending along the longitudinal axis of the rotating tube. The mixed gas reacts with the impurities of the quartz powder to produce a metal chloride gas. The used mixed gas and the gaseous reaction products are sucked out in the desorption chamber. For this purpose, an additional gas lance is used, which protrudes into the desorption chamber from the outlet side.

[0006] The fixed lance for supplying the treatment gas is deformed at high temperature, for example, 1200 °C. As a result, the treatment gas touches the SiO 2 particles at various points, and the reproducibility of the purification result deteriorates. Due to the large cross-sectional area of the rotating tube and the openings at both ends on the end faces, the kiln releases a large amount of heat at both end faces. Due to this high temperature, a rotary joint sealed at the hot ends of the rotating tube cannot be used.

[0007] In the continuous purification method of SiO 2 particles in a rotary kiln disclosed in WO2010 / 037473A1, inserts such as blades and studs are installed inside the rotating tube, and the inserts are used to transport and mix the particles to be purified.

[0008] US 7,837,955 B2 describes a method for continuously purifying silica sand in a rotary kiln, where a vertical separation plate is placed in the rotary kiln and the silica sand passes between the outer edge of the separation wall and the inner wall of the rotating tube. In this case, the silica sand is introduced into the rotating tube from one end, and the processing gas is introduced into the tube from the other end. The internal pressure in the rotating tube may be higher than the external pressure (atmospheric pressure).

[0009] WO 88 / 03914 A1 teaches reducing the BET surface area of amorphous and porous SiO 2 powder in a helium and / or hydrogen-containing atmosphere using a rotary kiln. In one approach, fine SiO 2 soot dust is mixed with water so that wet, brittle lumps are obtained. These lumps are transferred to a rotary kiln, compressed at a temperature of 600 °C, and turned into powder with a particle size of 0.1 - 3 mm.

[0010] DE 102010021693 A1 describes continuously vitrifying porous granular SiO 2 to form transparent synthetic quartz glass particles. In this case, the granular filler is heated by a laser beam in a rotary kiln comprising a rotating tube that rotates around its central axis and an inner wall made of quartz glass. By generating relative movement between the filler and the laser beam, uniform vitrification of the granular particles can be achieved without agglomeration.

[0011] WO 2017 / 062949 A1 describes a system for degassing granular polysilicon in a rotary kiln comprising a rotating tube that rotates around a rotation axis and surrounds a processing chamber containing a plurality of series of processing zones. The division into processing zones is made by stirring elements fixed to a shaft protruding into the rotating tube and extending close to the inner wall of the rotating tube. The polysilicon particles to be processed reach the particle outlet through the transport openings of the stirring elements from the particle inlet and are exposed to a purge gas in the process.

[0012] WO2018 / 084134A1 describes a method of dehydrating lithium hydroxide hydrate microparticles in a rotary kiln. The lithium hydroxide hydrate particles are introduced from one end of a rotating tube, fed into a heating zone, where they are exposed to an inert drying gas preheated to a temperature below 100 °C. The drying gas is introduced through a gas inlet tube, and the dried lithium hydroxide anhydride is withdrawn from the other end of the rotating tube. From that side, a gas suction tube protrudes into the reaction zone, and the hot used drying gas is withdrawn from the heating zone by this tube. By introducing the heated drying gas directly into the heating zone, condensation is prevented because the water vapor-containing gas also does not flow backward. In this way, it is possible to prevent lithium hydroxide from adhering and remaining in the rotating tube.

[0013] CN109269294 describes an airtight rotary kiln that feeds in and discharges from the same side. This rotary kiln consists of a stove pipe, three covers arranged on the outer wall of the stove pipe, and a support bearing. The material to be processed is indirectly heated through a bundle of tubes distributed axially along the kiln. The exhaust gas is discharged outside the kiln through a gas channel.

Summary of the Invention

Problems to be Solved by the Invention

[0014] The degree to which the processing gas acts on the particles in the rotary kiln depends on the action time and temperature. In particular, the purification effect of thermal chlorine treatment depends, for example, on the reaction time and reaction temperature between the SiO 2 particles and the chlorine-containing mixed gas.

[0015] At higher temperatures, chlorine reacts faster with metal impurities, so a better purification effect is expected at higher temperatures. However, the possibility of increasing the temperature is limited for several reasons. In particular, at high temperatures, due to the softening of the SiO 2 particles, aggregates are formed, which inhibits further access of the processing gas to the surface of the individual particles. As a result, the purification effect of the processing gas, which mainly acts on the surface of the particles, decreases.

[0016] The average residence time of the particles depends on the filling amount of the rotary tube. The larger the filling amount, the longer the contact time with the reaction gas, and thus the better the purification result. Conversely, at the same residence time, a relatively large filling amount results in a higher throughput. A longer residence time can also be obtained by reducing the rotation speed of the tube. However, as a result, the circulation of the contents also decreases, and the contact with the reaction gas also decreases.

[0017] If the proportion of outside air in the process gas is high, it may cause uncontrolled and undesirable side reactions. If the flow path is uncertain and ineffective, most of the process gas remains unused and must be discarded by complex means through neutralization.

[0018] The dissolved impurities condense in the cold region of the rotary tube and deposit as solids over time. The SiO to be processed 2 When deposits fall into the particles, it causes defects and scraps in the next processing steps, such as when melting the particles to produce quartz glass.

[0019] Therefore, an object of the present invention is to identify a method that enables reliable and reproducible purification of inorganic flowable particles, particularly SiO, with a minimum and effective amount of process gas used. 2 Particularly, it is to identify a method that enables heat treatment of the particles in a rotary kiln, especially purification by hot chlorine treatment.

[0020] Furthermore, an object of the present invention is to provide a rotary tube that is suitable for performing the above method, is as reliable as possible, and is intended for use in a rotary kiln.

Means for Solving the Problems

[0021] Regarding the above method, following the method described at the beginning, this object is achieved by the present invention in that the process gas after use is sucked out of the reaction zone by a gas manifold that rotates around its longitudinal axis.

[0022] The processing chamber defined by the internal bore of the rotary tube is divided into a plurality of zones (also referred to as "chambers") by a separating element such as a quartz glass plate. The plurality of zones are designed for various functions, such as preheating or cooling the particles, before and after the actual high-temperature treatment mainly carried out in the reaction zone.

[0023] During the heat treatment, it is desirable that the action of the processing gas on the particles is as uniform as possible. This treatment is used, for example, to purify inorganic particles, especially SiO 2 particles, and in this case, the processing gas may contain a halogen-containing substance.

[0024] The aim of the method according to the present invention is to prevent the exhaust gas, i.e., the impure processing gas after use, from coming into contact with the particles to be processed as much as possible. For this purpose, the used processing gas rotates around its own tube longitudinal axis and is sucked out of the reaction zone by a gas manifold that ends at the "suction end" of the rotary tube. As a result, there are a plurality of advantages.

[0025] · The used processing gas is guided inside the gas manifold and separated from the particles. In this regard, the gas manifold provides a mass transport path for the used processing gas separated from the particles to be processed.

[0026] · Due to the cross-section of the gas manifold being smaller than the inner diameter of the rotary tube, at least a part of the used processing gas can be effectively sucked out of the reaction zone.

[0027] By effectively removing the used processing gas containing a large amount of impurities from the processing chamber, condensation, deposition, and thus particle destruction and impurities at cold spots in the processing chamber are suppressed.

[0028] · In the simplest and most preferred case, the rotation axis of the rotary tube and the longitudinal axis of the gas manifold extend coaxially. Since the gas manifold preferably rotates about the rotation axis of the rotary tube, deformation due to high temperature is prevented. Therefore, the effectiveness of sucking the treated gas after use from the reaction zone is reproducible and, for example, is generally constant over time.

[0029] The treated gas after use is preferably sucked out from the gas manifold by a suction tube fixed with respect to rotation.

[0030] The suction tube is not connected to the gas manifold. This tube, for example, projects into the gas manifold or is adjacent to the gas manifold as closely as possible without touching it. The exhaust gas of the rotary kiln can be very hot, and it becomes difficult to realize a sealed rotary joint at this point to remove the hot treated gas. Since the suction tube is not mechanically rigidly connected to the rotating gas manifold, a fixed suction tube can be used and the rotary joint can be omitted. The suction tube is located at the end of the mass transport path of the treated gas. This tube can be further cooled by sucking in outside air from outside the gas manifold as well. The treated gas being sucked out and the outside air sucked out in the process will not come into contact with the particles to be treated.

[0031] In a particularly preferred procedure, a suction tube penetrating into the gas manifold is used.

[0032] The temperature inside the rotary tube and of the treated gas decreases as it approaches the "suction end". The end of the suction tube protruding into the gas manifold can be moved to a position inside the rotary tube where the temperature is still higher than the condensation temperature. Since the temperature at the effective suction position is higher than the condensation temperature, condensation occurs in the suction tube when the treated gas after use cools down. The deposits formed there cannot enter the particles. The suction tube is replaced from time to time due to the deposits.

[0033] The processing gas is introduced into the gas manifold from the particle outlet side and is conveyed in a direction opposite to the particle transport direction from one chamber to the next. The gas preferably exits the gas manifold through at least one gas outlet opening into the reaction zone, and the used processing gas re-enters the gas manifold from the reaction zone through at least one gas inlet opening.

[0034] By introducing the processing gas into the processing chamber in a countercurrent flow with respect to the particle transport direction, most of the processed, for example, most purified SiO 2 The particles can be made to contact only with fresh, more impurity-free processing gas.

[0035] This gas manifold enables the introduction of the processing gas into the reaction zone with little inclusion of outside air, being defined and precisely targeted. Uncertain and ineffective flow paths are mostly prevented. The introduction of outside air and the impurities brought in with it or generated by the reaction are reduced. The effective use of the processing gas reduces the costs of materials and disposal.

[0036] By rotating the gas manifold around its longitudinal axis, preferably around the axis of rotation of the rotating tube, deformation of the processing gas in the introduction region into the processing chamber is also prevented, whereby the introduction position of the gas into the reaction zone and the action of the processing gas on the particles are constant over time, ensuring a reproducible interaction between the processing gas and the particles.

[0037] In this case, when viewed in the direction of flow of the processing gas, at least one gas outlet opening is located as close as possible to the beginning of the reaction zone, and at least one gas inlet opening is located as close as possible to the end of the reaction zone.

[0038] The gas outlet opening can be designed as an opening in the front wall of the gas manifold, and the gas inlet opening can be designed as an opening in the rear wall of the gas manifold. In this case, the gas manifold is at least partially, preferably completely closed on the gas manifold between the openings of the front and rear walls. In this case, a gas manifold having a longitudinal axis extending coaxially with the rotary tube axis and extending throughout the processing chamber can be used.

[0039] In the reaction zone, considering the need to effectively and forcibly flow the fresh process gas through the inorganic particles as much as possible, it is effective that the openings in the front wall and the rear wall are at different circumferential angles on the side surface of the gas manifold, preferably on the side surfaces on the opposite outer circumferences.

[0040] However, discharging the process gas from the gas manifold as completely as possible can also be ensured by the gas manifold consisting of separate length portions of the tube, where the front length portion of the tube as seen in the direction of the process gas flow ends at the front separation element or at most extends slightly into the reaction zone from there, and the rear length portion of the tube ends at the rear separation element or at most extends slightly into the reaction zone from there. In this case, the gas outlet opening and the gas inlet opening can in principle be designed as end-face tube openings, but it is preferable that there are openings in the longitudinal tube wall to deflect the process gas from the central axis of the reaction chamber towards the particles.

[0041] The process gas is introduced from the gas manifold into the reaction chamber through the gas outlet opening, and at least a part of this process gas is sucked back into the gas manifold through the gas inlet opening and further transported within the gas manifold. This also contributes to the pressure gradient where the pressure is low in the gas phase of the inner hole of the rotary tube at the suction end of the rotary tube. By either sucking out the used process gas from one side, the "suction end", or from both sides of the rotary tube, but with a higher suction volume at the "suction end", the pressure gradient is automatically established, whereby the process gas and the used process gas are transported towards the suction end of the rotary tube.

[0042] The gas manifold is preferably fixed in rotation with respect to at least one separating element, each separating element including a conveying opening for the particles to pass from one zone to the next.

[0043] The separating elements are firmly fixed to the rotating tube and rotate with the tube. Since the gas manifold is firmly fixed to at least one, preferably all, of the separating elements, it rotates synchronously with the rotating tube and does not require separate power. The conveying openings each form a passage between two adjacent processing zones, ensuring a continuous transport path for the particles. Each separating element can include one or a plurality of conveying openings. The position of the conveying openings on the separating element and the position and distribution of a plurality of conveying openings on the separating element are not specified.

[0044] In this case, the separating element preferably comprises at least one particle baffle which is inserted into the particles by the rotation of the rotating tube and, in the process, conveys the particles thereon to the conveying opening.

[0045] The particle baffle is located on the side surface of the separating element facing the flowing particles. Due to the rotation of the rotating tube, the particle baffle scoops the particles through the conveying opening from one processing zone to the adjacent processing zone. This baffle is designed, for example, as a semi-split shape or an inclined table of a tube ending at the conveying opening.

[0046] The separating element provided with such a particle baffle is used not only to divide the processing chamber into a plurality of zones, but also to cause or facilitate the transport of particles from one processing zone to the next due to the rotation of the rotating tube about its own axis of rotation.

[0047] In a preferred embodiment of the method of the present invention, the separating element provided with such a particle baffle is also utilized to control the throughput of the particles. This is because when the rotating tube rotates in the reverse direction, the particle baffle is SiO 2This is because it does not have the function of scooping up particles. Instead, it pushes the particles out from the conveying opening, and further particle conveyance is stopped.

[0048] When viewed in the particle conveyance direction, the front separation element is arranged downstream of the particle inlet side, and the rear separation element is arranged upstream of the particle outlet side. It has been found that it is advantageous for these front and / or rear separation elements to be made of opaque quartz glass.

[0049] The opaque quartz glass protects the particle inlet and / or outlet sides from the heat of the reaction zone by reflecting the thermal radiation from the processing chamber. The rear opaque quartz glass separation element protects, for example, the particle outlet side (corresponding to the introduction side of the processing gas) from the heat of the hot zone, and it is possible to arrange the rotary joint for the rotating gas manifold outside the separation element.

[0050] From the viewpoint of effective heat shielding, a modification of the method is advantageous in that the rotating tube includes a non-heated end face end portion, and the front and rear separation elements are respectively arranged on the non-heated end face end portion.

[0051] In this connection, it has also been found that it is advantageous for the gas manifold to include a length portion that protrudes from the rotating tube on the particle outlet side, and at least this length portion is made of opaque quartz glass.

[0052] The length portion of the opaque quartz glass reflects the thermal radiation and reduces the conduction to the end face on the particle outlet side within the wall of the gas manifold. This contributes to the possibility of guiding the rotating gas manifold into the processing chamber via the rotary joint, thereby enabling the introduction of the processing gas into the processing chamber without external air.

[0053] Regarding the rotating tube, in addition to the rotating tube as described at the beginning, the above-specified object is achieved by the present invention in that the gas discharge portion includes a gas manifold that rotates around its longitudinal axis.

[0054] The processing chamber defined by the internal hole of the rotating tube is divided into a plurality of zones (also referred to as "chambers") by a separating element such as a quartz glass plate. The plurality of zones are designed for various functions, such as preheating or cooling particles, before and after the actual high-temperature treatment mainly carried out in the reaction zone.

[0055] To suck the used processing gas from the reaction zone, the rotating tube according to the present invention is rotatable around its tube longitudinal axis and includes a gas manifold ending at the "suction end" of the rotating tube. As a result, there are a plurality of advantages.

[0056] · The used processing gas is guided through the gas manifold and separated from the particles. In this regard, the gas manifold provides a material path for the used processing gas separated from the particles to be processed.

[0057] · At least a part of the used processing gas can be effectively sucked out from the reaction zone by the cross-section of the gas manifold smaller than the inner diameter of the rotating tube.

[0058] By effectively removing the used processing gas containing a large amount of impurities from the processing chamber, condensation, deposition at cold points in the processing chamber, and thus particle destruction and impurities are suppressed.

[0059] · In the simplest and most preferred case, the rotation axis of the rotating tube and the tube longitudinal axis of the gas manifold extend coaxially. Since the gas manifold is preferably rotatable about the rotation axis of the rotating tube, deformation due to high temperature is prevented. Therefore, the effectiveness of sucking the used processing gas from the reaction zone is reproducible and, for example, is generally constant over time.

[0060] It is advantageous for the gas discharge part to include an intake tube that protrudes into the gas manifold so as not to come into contact, or is adjacent to the gas manifold without direct contact. The intake tube is used to suck the used processing gas from the gas manifold.

[0061] The suction pipe is not rigidly fixed to the gas manifold and, for example, projects into the gas manifold or is adjacent to the gas manifold as closely as possible without contacting it. Since the suction pipe does not mechanically contact the rotating gas manifold, a suction pipe fixed with respect to rotation can be used, and thus the rotary joint can be omitted.

[0062] The preferred embodiments of the rotating pipe according to the present invention described below correspond to the means of the method according to the present invention. For this reason, for each means of the method, refer to the above description.

[0063] The gas introduction part is preferably provided at the gas introduction end of the gas manifold located at the particle outlet end of the rotating pipe.

[0064] The gas manifold advantageously includes a gas outlet opening for moving the process gas from the gas manifold to the reaction zone and at least one gas inlet opening for introducing the process gas from the reaction zone to the gas manifold, and the internal holes of the gas manifold are preferably at least partially closed between the gas outlet opening and the gas inlet opening.

[0065] It has been found to be advantageous that the gas manifold is fixed with respect to rotation to at least one separation element, each separation element includes a transport opening for particles to pass through, the gas manifold extends through this opening, and the separation element is provided with a particle baffle designed to be inserted into the particles by the rotation of the rotating pipe and transport the particles riding on it to the transport opening in the process.

[0066] Also, when viewed in the particle transport direction, the front separation element is arranged downstream of the particle inlet side, the rear separation element is arranged upstream of the particle outlet side, and it has been found to be advantageous that the front and / or rear separation elements are made of opaque quartz glass.

[0067] In this connection, it has been found to be advantageous that the rotating pipe includes a non-heated end face end, and the front and rear separation elements are respectively arranged at the non-heated end face end.

[0068] In a preferred embodiment of the rotary tube, the gas manifold includes a length portion that protrudes from the rotary tube on the particle outlet side, and at least the length portion is made of opaque quartz glass.

[0069] Hereinafter, the present invention will be described in more detail with reference to preferred embodiments and the drawings. Specifically, the schematic diagrams are as follows.

Brief Description of the Drawings

[0070]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0071] The rotary kiln 1 schematically shown in FIG. 1 includes a rotary tube 2 made of quartz glass that can rotate around a rotation axis 21 that extends slightly obliquely (the inclination angle is about 4 degrees) with respect to the horizontal 3. The SiO 2 particles 5 are fed into the upper end 22 (particle inlet side) of the rotary tube through a filling device indicated by the block arrow 4. The direction arrow 51 is led out of the housing of the rotary kiln 1 by the pivot bearing 25 and continues to the lower end 23 of the rotary tube into the material removal device 13 for the processed SiO 2 particles. The direction in which the SiO 2 particles 5 move during the processing is shown.

[0072] The inner hole of the rotating tube 2 forms a processing chamber 7 that is divided by quartz glass plates 6a, 6b, and 6c into four channels, specifically, a material inflow chamber A, a preheating chamber B, a reaction chamber C, and a cooling or desorption chamber D. The quartz glass plates 6a, 6b, and 6c are welded to the inner wall of the rotating tube 2 and each have a through-hole that is concentric with the longitudinal axis of the rotating tube. A gas guide tube (gas manifold) 8 made of quartz glass is guided through the through-hole.

[0073] The gas guide tube 8 is used to supply new processing gas to the processing chamber 7 and to remove the used processing gas (exhaust gas) from the processing chamber 7. This guide tube extends through all of the chambers A - D of the processing chamber 7. Inside the processing chamber 7, the wall of the gas guide tube 8 has a plurality of wall openings that are divided into a gas outlet opening 82 through which the processing gas 11 passes when it exits the gas manifold 8 into chamber C, and a gas inlet opening 83 through which the used processing gas passes when it re-enters the gas manifold 8 from the processing chamber C. Between the gas outlet opening 82 and the gas inlet opening 83, the gas manifold 8 is closed (closure 81). Inside the processing chamber C, in order to better direct the flow of the new processing gas through the SiO 2 particles 5, the gas outlet opening 82 and the gas inlet opening 83 are located on opposite sides on the outer circumference of the gas guide tube 8 (different from that schematically shown in FIG. 1).

[0074] The gas manifold 8 is connected to the plurality of quartz glass plates 6 and is rotatable around the axis of rotation (the longitudinal axis 21 of the rotating tube) in the same manner as these quartz glass plates. The longitudinal axis of the gas manifold, the longitudinal axis 21 of the rotating tube, and the axis of rotation extend coaxially.

[0075] For each of the quartz glass plates 6a, 6b, 6c, the inflowing SiO 2The side facing the particle 5 is connected to the tube half shell 9. This is only shown in FIG. 1 and can be seen more clearly in FIG. 2. The free end of the tube half shell 9 ends at the conveying opening 61, and the other end ends near the edges of the quartz glass plates 6a, 6b, and 6c. When the rotating tube rotates in the rotation direction determined with reference to the direction arrow 29, the outer peripheral side end is filled with SiO 2 is inserted into the particle 5 and further rotated, and during this process, SiO that has ridden on it 2 lifts the particle 5 into the conveying opening 61, and SiO 2 The particle 5 reaches the chambers B, C, and D arranged downstream in the conveying direction 51 from there. For this purpose, the conveying opening 61 is designed to have an elliptical cross-section and extends asymmetrically with respect to the rotation axis 21.

[0076] Resistance heating means (not shown) is provided on the outer surface of the rotating tube 2. The quartz glass plates 6a and 6c are located outside the heated length portion of the rotating tube 2 and are made of opaque quartz glass that reflects heat radiation.

[0077] The lower end of the gas guide tube 8 is also made of opaque quartz glass that reflects heat radiation. This end is led out from the rotary kiln 1 through the rotary joint 24 and connected to a line (indicated by the block arrow 11) for supplying the processing gas. The processing gas 11 fed into the gas manifold 8 flows through the processing chamber 7 in the direction 11a opposite to the particle conveying direction 51.

[0078] At the upper end of the gas manifold 8, the used processing gas is sucked out from the gas manifold 8. For this purpose, the suction pipe 14 protrudes into the upper end of the gas manifold 8. The block arrow 15 indicates the connection to the suction outlet of the suction pipe 14. The suction pipe 14 does not rotate and has no mechanical contact with the inner wall of the gas manifold 8, or at most has only a slight mechanical contact. The end of the suction pipe 14 protruding into the gas manifold 8 ends at the position P2 in the processing chamber B, where the sucked-out used processing gas has a temperature higher than the condensation temperature (T K ) of the impurities in the processing gas.

[0079] The manufacture of the rotary tube 2, including the insert, involves the following steps.

[0080] · Prepare a rotary tube 2 made of quartz glass with a length of 2500 mm and an inner diameter of 210 mm.

[0081] · Prepare laser-cut discs 6a, 6c of opaque quartz glass with a thickness of 5 mm and an outer diameter of 208 mm. The plates 6a, 6c each include two openings, circular and concentric through-holes for passing the gas manifold 8, and an elliptical transport opening 61 offset from the center for SiO 2 particles. Prepare laser-cut discs 6b of the same dimensions as the plates 6a, 6c made of transparent quartz glass.

[0082] · Prepare a gas manifold 8 made of transparent quartz glass with an outer diameter of 40 mm and an inner diameter of 32 mm. Weld the end portion of a tube with a length of 50 mm made of quartz glass to the end face to form a gas manifold 8 with an overall length of 2700 mm.

[0083] · Divide the quartz glass tube to create the blades 9 and weld them to the quartz glass plates 6a, 6b, 6c.

[0084] · Laser-cut the gas inlet opening and the gas outlet openings (82, 83) in the wall of the gas manifold 8 and attach a plug 81 to close the internal hole of the gas manifold between the gas inlet opening and the gas outlet openings (82, 83).

[0085] · On a glass lathe, weld the quartz glass plates 6a, 6b, 6c to the outer surface of the gas manifold 8.

[0086] · Connect the gas manifold 8 to the through-holes of the quartz glass plates 6a, 6b, 6c, and on a glass lathe, insert this group into the internal hole of the rotary tube 2 and weld the quartz glass plates to the inner wall of the rotary tube by local heating to reduce the diameter of the internal hole of the rotary tube.

[0087] Hereinafter, embodiments of the processing method according to the present invention will be described in more detail with reference to the apparatuses schematically shown in FIGS. 1 and 2.

[0088] To a rotary tube 2 rotating at 8 rpm around its own rotation axis 21, amorphous SiO to be purified 2 particles 5 are continuously supplied at a feed rate of 8 kg / h. Over the entire length of the rotary tube 2, the filled particles 5 continuously moving from the particle inlet 22 to the particle outlet 23 form an approximately uniform thickness of SiO 2 particles 5 at a specific angle of repose of the particles 5, and the rotary tube 2 is inclined in the longitudinal direction.

[0089] By a resistance heating device, the rotary kiln 1 is heated to a maximum temperature of about 1200° C. in the region of the reaction chamber C. A reactive processing gas 11, which is a mixed gas of HCl, chlorine, and nitrogen, rotates around the rotation axis 21 and is introduced at a volumetric flow rate of 200 l / h from the end of the gas manifold 8 protruding beyond the rotary joint 24 from the rotary kiln 1.

[0090] SiO 2 The processing gas 11 flowing in a countercurrent to the particles 5 is heated rapidly and is distributed particularly to the processing zones C and B, and is sucked out as the used processing gas 11 from the gas manifold 8 through the suction pipe 14 from the upper end.

[0091] In Figure 1, a graph of a typical temperature curve (T) and pressure curve (p) of the process gas 11 is shown above the rotary kiln 1. The position P2 indicates the point where the hot exhaust gas (used process gas) is removed from the gas manifold 8 by the suction pipe 14. Here, the hot exhaust gas is mixed with the outside air sucked in from the outside through the suction pipe 14 and passing through the gas guide pipe 8. As a result, both the temperature curve (T) and the pressure curve (p) of the process gas jump. The position P1 indicates the start of the preheating chamber B and the position of the front quartz glass plate 6a made of reflective quartz glass. The position P3 corresponds to the start of the reaction chamber C, and the position P4 corresponds to the end of the reaction chamber C and the position of the rear quartz glass plate 6c made of reflective quartz glass. The position P5 corresponds to the particle outlet. In the gas phase, there is a pressure gradient over the entire length of the rotary tube 2, and it can be seen that the gas is transported to the suction position P2 by this gradient. At position P rel = 0, the process gas has a gas pressure that coincides with the outside pressure (atmospheric pressure).

[0092] · When introducing the process gas through the rotating gas guide pipe 8 sealed by the rotary joint 24, since almost no outside air is supplied to the processing chamber 7, it contributes to a higher concentration of the reactive process gas 11 in the hot zone. As a result, the purification result is improved, the reactive process gas can be saved, and the disposal cost can be reduced.

[0093] · The fact that the still-hot process gas 11 is sucked out at position P2 means that this gas has a high concentration of dissolved foreign substances and must be removed from the processing chamber in the gas phase. Furthermore, by sucking out the exhaust gas at position P2 at a temperature exceeding the condensation point T K condensation at cooler points and deposition within the processing chamber 7 are prevented.

[0094] · The suction pipe 14 that does not rotate within the rotary kiln is cooled by the outside air sucked in from the outside, reducing the risk of thermal deformation.

[0095] · Reversing the rotation direction 29 causes SiO 2Further transportation of the particles is stopped, batch operation is possible, and particularly strong purification can be achieved at the expense of throughput.

[0096] · If the outer quartz glass plates 6a and 6c are formed of an opaque material, the radiation of the rotary kiln at the end face is reduced, and by using a sealed rotary joint, the sealing between the rotating rotary tube 2 and the rotating gas manifold 8 can be improved.

Claims

1. A method for treating flowable inorganic particles (5) in a heating rotary tube (2) surrounding a processing chamber (7) that rotates around a rotation axis (21) and is divided into a plurality of processing zones (A, B, C, D) including at least one reaction zone (C) by separation elements (6a, 6b, 6c), wherein the particles (5) are supplied from a particle inlet side (22) to the processing chamber (7), transported in a particle transport direction (51) to a particle outlet side (23), and exposed to a processing gas (11) in the process, and the used processing gas (11) is sucked out from the reaction zone (C) by a gas manifold (8) that rotates around its own longitudinal axis, and the used processing gas (11) is sucked out from the gas manifold (8) by a suction pipe (14) fixed with respect to rotation.

2. The method according to claim 1, characterized in that a suction pipe (14) protruding into the gas manifold (8) is used.

3. The processing gas (11) is introduced from the particle outlet side (23) into the gas manifold (8), transported in a direction opposite to the particle transport direction (51) from one zone (A, B, C, D) to the next zone, and exits into the reaction zone (C) from the gas manifold (8) through at least one gas outlet opening (82), and the used processing gas (11) re-enters the gas manifold (8) from the reaction zone (C) through at least one gas inlet opening (83). The method according to claim 1 or claim 2, characterized in that.

4. The method according to claim 3, characterized in that the gas manifold (8) is at least partially closed (81) between the gas outlet opening (82) which is an opening in the front wall and the gas inlet opening (83) which is an opening in the rear wall.

5. The gas manifold (8) is fixed with respect to rotation to at least one separation element (6a, 6b, 6c), and each of the separation elements (6a, 6b, 6c) includes a transport opening (61) for the particles (5) to pass from one zone (A, B, C, D) to the next zone. The method according to any one of claims 1 to 4, characterized in that.

6. The separation elements (6a, 6b, 6c) are inserted into the particles (5) by the rotation (29) of the rotary tube, and in the process, a particle baffle (9) that conveys the particles thereon to the conveying opening (61) is provided. The method according to claim 5, characterized in that.

7. When viewed in the particle transport direction (51), the front separation element (6a) is arranged downstream of the particle inlet side (22), and the rear separation element (6c) is arranged upstream of the particle outlet side (23). The method according to claim 5 or claim 6, characterized in that the front separation element (6a) and / or the rear separation element (6c) is made of opaque quartz glass.

8. The rotary tube (2) includes a non-heated end face end portion, and the front separation element (6a) and the rear separation element (6c) are respectively arranged at the non-heated end face end portions. The method according to claim 7, characterized in that.

9. The gas manifold (8) includes a length portion protruding from the rotary tube (2) on the particle outlet side (23), and at least the length portion is made of opaque quartz glass. The method according to any one of claims 1 to 8, characterized in that.

10. A rotary tube (2) for treating flowable inorganic particles (5), the tube being rotatable around a rotation axis (21) inclined with respect to the horizontal (3), the tube surrounding a treatment chamber (7) for accommodating the particles (5), the chamber being divided by separation elements (6a, 6b, 6c) into a plurality of treatment zones (A, B, C, D) including at least one reaction zone (C), a particle inlet side (22) for introducing the particles (5) into the treatment chamber (7), a particle outlet side (23) for discharging the particles (5) from the treatment chamber (7), a gas introduction part for introducing a treatment gas (11) into the reaction zone (C), and a gas discharge part for removing the used treatment gas (11) from the treatment chamber (7), the gas discharge part including a gas manifold (8) that rotates around its own longitudinal axis, the gas discharge part including an inhalation tube (14) that protrudes into the gas manifold (8) or is adjacent to the gas manifold (8) without direct contact. A rotary tube characterized by that.

11. The gas manifold (8) includes a tube longitudinal axis extending coaxially with the rotation axis (21) of the rotary tube. The rotary tube according to claim 10, characterized in that.

12. The gas introduction part is provided at the gas introduction end of the gas manifold (8) located on the particle outlet side (23) of the rotary tube (2), and the rotary tube according to claim 10 or claim 11 is characterized in that.

13. The gas manifold (8) is fixed in rotation to at least one separation element (6a, 6b, 6c), and each of the separation elements (6a, 6b, 6c) includes a transport opening (61) for particles (5) to pass through, and the gas manifold (8) extends through the opening. The separation element (6a, 6b, 6c) is provided with a particle baffle (9) designed to be inserted into the particle (5) by the rotation (29) of the rotary tube and to transport the particles riding on it to the transport opening (61) in the process. The rotary tube according to any one of claims 10 to 12 is characterized in that.

14. When viewed in the particle transport direction (51), the front separation element (6a) is arranged downstream of the particle inlet side (22), and the rear separation element (6c) is arranged upstream of the particle outlet side (23). The front separation element (6a) and / or the rear separation element (6c) are made of opaque quartz glass. The rotary tube according to claim 12 or claim 13 is characterized in that.

15. The rotary tube (2) includes a non-heated end face end portion, and the front separation element (6a) and the rear separation element (6c) are respectively arranged at the non-heated end face end portion. The rotary tube according to claim 14 is characterized in that.

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