MXPA05006825A - Treatment of granular solids in an annular fluidized bed with microwaves - Google Patents

Abstract

This invention relates to a method for the thermal treatment of granular solids in a fluidized-bed reactor (1), in which microwave radiation from a microwave source (2) is fed into the reactor (1), and to a corresponding plant. To improve the utilization of energy and the introduction of the microwave radiation, a first gas or gas mixture is introduced from below through a preferably central gas supply tube (3) into a mixing chamber (7) of the reactor, the gas supply tube (3) being at least partly surrounded by a stationary annular fluidized bed (8) which is fluidized by supplying fluidizing gas. The microwave radiation is supplied to the mixing chamber (7) through the same gas supply tube (3).

Description

PROCESS AND EQUIPMENT FOR THERMAL TREATMENT GRANULATED SOLIDS Field of the Invention The invention relates to a process for the thermal treatment of granulated solids in a fluidized bed reactor in which microwave radiation is introduced from a microwave source.

Background of the Invention A process of this type is known from US Patent 5,972,302 in which sulphide minerals are subjected to microwave assisted oxidation. In this case, it is especially about the roasting of pyrite in a fluidized bed where the microwaves directed towards the interior of the fluidized bed help the formation of hematite and elemental sulfur, and suppress the formation of SO. It is worked there in a stationary fluidized bed that is irradiated by a microwave source that is directly above it. With that the microwave source or the microwave entry site necessarily comes into contact with the gases, vapors, and powders that emerge from the fluidized bed. Examples for the coupling of the microwaves to the fluidized bed chamber are: open tubular waveguides, slot antennas, with coupling ducts, deflection partitions, coaxial antenna filled with gas or some other dielectric material with a tubular waveguide closed by a substance transparent to microwaves. European Patent EPO 403 820 Bl describes a process for drying substances in a fluidized bed in which the microwave source is located outside the fluidized bed and the microwaves are introduced by tubular waveguides in the fluidized bed. In open tubular waveguides there is a problem that the microwave source is fouled over time by dust or gases and is thus damaged. This can be avoided by windows that are transparent to the microwaves that close the tubular waveguide between the reactor and the microwave source. However in this case deposits on the windows lead to reductions in microwave radiation.

OBJECTIVE AND SUMMARY OF THE INVENTION The invention is directed to the creation of a fluidized bed reactor under conditions of heat exchange and especially effective matter, where the microwave source is protected against the gases, vapors, and dust that are formed. This task is solved according to the invention by a process of the type described above, in which a gas or primary gas mixture is introduced from below by a preferably central gas duct (central tube / central valve) into the interior of a chamber of the fluidized-bed reactor, in which the gas-conducting tube is at least partially surrounded by a stationary annular fluidization layer which is fluidized by the supply of fluidizing gas, and in which the microwave radiation is introduced to the fluidized-gas reactor. the fluidized bed chamber by the same gas introduction tube. Surprisingly it is possible to join in the heat treatment according to the invention, the advantages of a stationary fluidized bed, such as a residence time of extended solid and a good exchange of matter and heat, typical of a circular fluidized bed, avoiding the disadvantages of both systems. When passing the upper space of the central tube the first gas or mixture of gases entrains solids of the stationary annular fluidization bed, which is called annular fluidized bed, and draws it towards the interior of the fluidized bed chamber, where due to the great difference of speed between the solid and the first gas, an intensively mixed suspension is generated and an exchange of heat and optimum material between both phases. For the heat generation of the required process, microwave radiation is used according to the invention. Since the microwaves are also introduced to the reactor through the central tube there is the maximum microwave power density in the fluidized bed chamber above the outlet of the central tube, where the solids contained in the suspension absorb microwaves with especially good intensity. Due to that, the energy efficiency of the microwaves is especially effective in the process according to the invention. Due to the emerging gas stream from the central tube, it is also avoided with maximum efficiency that dust or gases from the process enter the central tube, expand to the microwave source and damage it. Due to that one can forget in the process according to the invention of transparent windows to the microwaves to protect the tubular waveguide, as is customary in the normal techniques. In these there is the problem, that Deposits of dust and other solids on the window reduce the microwave irradiation and can absorb it in part. It has been observed that good process properties result when the gas velocity (flow rate) of the first gas or mixture of gases and the fluidization gas for the annular fluidized bed is adjusted such that the number of particles in the line gas admission is between 1 and 100, in the annular fluidized bed between 0.02 and 2 and in the fluidized bed chamber between 0.3 and 30. By corresponding adjustment of the gas velocity of the first gas or gas mixture and of the fluidizing gas, as well as the level of the annular fluidized bed chamber, can vary the solids load of the suspension above the area of the outlet of the central tube, varying in a wide range and / or increased up to 40 Kg of solid per Kg. of gas, where the change in pressure of the first gas between the outlet area of the central tube and the upper outlet of the fluidized mixing chamber can be between 1 mbar and 100 mbar. In case of a high solid density of the suspension in the interior of the fluidized bed chamber, a large part of the solid is separated from the suspension and precipitates back to the annular fluidization layer. This recoil movement is called "Solid Recirculation" where the current of solids circulating in this internal circular current is usually considerably greater than the amount of solid that is added to the reactor, by a unit of size. The (minor) part of solid not precipitated is entrained with the first gas or mixture of gases from the fluidization chamber. The residence time of the solid in the reactor can be changed to wide limits by the selection of the height and the section of the annular fluidization layer, and be adjusted to the desired heating. Due to the large solids loading on the one hand and the good suspension of the solid in the gas stream on the other side, excellent conditions for a good exchange of matter and heat are generated on the outlet area of the central tube. microwave radiations that act in this area. The part of solid that is entrained by the gas stream from the reactor is completely or at least partially recycled to the reactor, where recycling occurs conveniently in the stationary fluidization layer. The mass stream of solid recycled in this form to the annular fluidization layer is normally in the same size range as the mass stream of solid added from outside to the reactor. In addition to the excellent energy efficiency, an additional advantage of the process carried out according to the invention consists in the possibility of adjusting the energy transfer and the mass flow of the process in a fast, simple and reliable way by means of the change of the current velocity of the first gas or mixture of gases and fluidizing gas. In order to ensure an especially effective heat exchange in the fluidized bed chamber and a sufficient residence time in the reactor, the gas velocity of the first gas mixture and the fluidization gas for the bed is preferably adjusted in such a way that the Numberless particle number Froude in the central tube is 1.15 to 20, in the annular fluidization layer between 0.115 to 1.15 and / or in the entrainment mixing chamber between 0.37 to 3.7. For this the Froude number of particles is defined by the following equation: With u = effective velocity of the gas stream in m / s ps = density of solid particles in Kg / m3. Pf = effective density of the fluidization gas in Kg / m3 dp = average diameter of the particles present inside the reactor during the operation of the reactor (or of the particles that are formed) in meters. g = gravitational constant in m / s. In the application of this equation, it should be considered that dp does not represent the average diameter (d50) of the initial material, but represents the average diameter of the reactor content that is generated during the operation of the reactor, which can be significantly differentiated in both directions from the average diameter of the initially grouped material (primary particles). Also very fine materials with an average diameter of for example 3 to 10 μm can be formed during the heat treatment, particles (secondary particles) with an average diameter of 20 to 30 μm. On the other hand many materials, for example minerals, disintegrate during the heat treatment.

Following the development of the idea of the invention, it is recommended to adjust the volume of the solid in the reactor in such a way that the annular agitation layer is for example at least partly a few centimeters above the upper mouth of the central tube with which it continuously adds solids to the first gas or gas mixture and is thus carried by the gas stream to the agitation chamber above the solids of the central tube. In this way a high solids content is achieved in the suspension above the solids of the central tube. According to the invention it is recommended that the central tube be formed as a tubular waveguide so that the microwave radiation is fed directly by the central tube, acting as a microwave guide, to the mixing chamber by agitation of the reactor. This arrangement is especially interesting when the gas or gas mixture (test gas) that is conducted through the central tube is not heavily contaminated by dust or when the powder only adheres marginally to the microwave guide through the path of the central tube. However, when the powder contained in the process gas adheres intensely, the microwave guide can be fed into the stirring chamber by a separating guide of the central tube as an alternative or complement, which can be located inside the central tube and conveniently ends at the outlet of the central tube. With this, the microwave radiation can also be coupled in an equally directed manner to the area of the reactor mixing chamber, without the powder contained in the first gas mixture having previously absorbed a part of the capacity of the microwave radiation. In both cases, according to the invention, such a high gas velocity is used that a return of the powder from the reactor into the central tube and into the tubular waveguide is avoided. An improvement of the process is achieved when the microwave radiation is fed through several tubular waveguides where each tubular waveguide is provided by its own microwave source. For this, it is possible to use, instead of a central tube, of large diameter, which serves as a tubular waveguide, several central tubes that serve as tubular waveguides to which the microwave sources themselves are coupled. Alternatively, the invention also makes it possible to introduce one or more small-section tubular waveguides through a large central tube into the reactor, in which the tubular waveguides are sealed against the flow of gases from the tube. central and each tubular waveguide is provided with its own microwave source. By means of the central tube in this case, as before, powder-loaded process gas is fed to the stirring chamber as an alternative. A modular construction of this type also makes possible a greater use of these facilities. According to the invention, a washing gas is also conducted through the reactor, which can be treated, for example, by a waste gas filtered or otherwise cleaned from the reactor or from a parallel process. Due to the continuous stream of wash gas through the tubular waveguide, the deposition of solids in the tubular waveguide is prevented, which would undesirably change the section of the tubular waveguide and absorb a part of the energy of the tubular waveguide. microwave, which was originally designed for solids in the reactor. Due to the absorption of energy in the tubular waveguide, it would also be intensely heated so that the material would be exposed to intensive thermal wear. Furthermore, the deposition of solids in the tubular waveguide would result in undesirable adhesions on the microwave source. As a source of electromagnetic waves (microwave sources) serve for example a magnetron or a klystron. In addition, high frequency generators with appropriate coils or power transistors can be used. The frequencies of micromagnetic waves, which come from the microwave source, are usually in the range of 300 MHz to 30 GHz. Preferably ISM frequencies of 435 MHz, 915 MHz and 2.45 GHz are used. The optimum frequencies are conveniently determined for each area of application in experimental test runs. Since the frequency of the microwave sources is fixed, so is the maximum drying capacity. The drying capacity can be adjusted optimally through the installation of a large number of small microwave sources of the agitation layer. In the invention it is also envisaged to adjust the section and the dimensions of the tubular waveguide to the frequency used in the microwave ranges, to allow a maximum of energy addition without losses. The temperatures in the fluidization bed (stationary annular fluidization layer) are usually from 150 ° C to 1500 ° C. For certain processes, indirect heat can additionally be added to the stirring bed. For the Temperature measurement in the stirring bed are particularly suitable isolated sensors, radiation pyrometers or fiber optic sensors. To adjust the average residence time in the reactor, it is provided according to the invention, at least partially recycle solids emerging from the reactor and that have been separated in a coupled separator are recycled at least partially to the annular agitation layer of the reactor. to this. The rest is then led to a next step of processing. In a desirable form, the reactor has for that coupled a cyclone for the separation of the solids where the cyclone contains a duct of solids that leads to the agitation layer of the reactor. A further improvement results when the gas that is fed through the tubular waveguide is also used for fluidization in a fluidization bed. A portion of the gas is therefore used to remove the powder from the tubular waveguide that had hitherto been introduced to the fluidization layer by other ducts. According to the invention, fine solid granules are used for the starting material, where the grain size of most of the solid is less than 1 mm. The granulated solids to be treated can be, for example, minerals and especially sulphurous minerals which, for example, are prepared for the production of gold, copper or zinc. In addition, recycled substances can be subjected to a thermal treatment in a fluidization bed such as, for example, oxide of the zinc-containing rollers or waste. If sulphurous minerals, such as arsenopyrite with gold, are subjected to the process, the sulfur is transformed into oxide and with that, by using an appropriate process of the process, elemental sulfur and only small amounts of SO2 are generated. The process according to the invention disaggregates the structure of the ore in a convenient manner, so that a subsequent leaching gives higher yields. The arsenious iron sulfide (FeAsS) thus formed by the heat treatment can be deposited without problems. A device for the invention which is particularly suitable for carrying out the process described above consists of a reactor in the form of a fluidization layer for the thermal treatment of finely granulated solids, and a microwave source. Connected to the reactor is a gas intake system, which can specifically be a gas addition tube which is shaped in such a way that the gas passing through this gas intake system draws solids from an annular fluidization layer. stationary that at least partially surrounds the gas addition system, to a reactor mixing chamber, and, that the microwave radiation generated by the microwave generator, is feedsable through the gas intake system. Conveniently this system of "addition" of gases extends to the mixing chamber of drag. According to the invention, the gas addition system (central tube) preferably consists of a gas intake pipe that runs essentially vertically upwards, preferably up to the reactor mixing chamber and which is at least partially surrounded by a chamber in which a stationary annular fluidization layer is formed. The outlet of the central tube may have the shape of a nozzle and / or may have one or more openings in its mantle, so that during the operation of the reactor solids continuously enter through this opening into the central tube and are carried with the first gas or gas mixture through the central tube to the entrainment mix chamber. Of course, the reactor can also be provided with two or more central tubes with the same or different dimensions and shapes. However, it is convenient that one of the side tubes be approximately half the section of the reactor. According to the invention, the microwave radiation is introduced into the reactor by a tubular waveguide. Microwave radiation can be conducted in electrically conductive tubular waveguides of different geometries, provided they do not exceed certain minimum dimensions. The tubular waveguide consists totally or mainly of electrically conductive material, such as copper. In a first form, the gas addition tube is designed as a tubular waveguide for feeding the microwaves. In addition to the simple construction of such a shaped reactor, the gaseous stream, which is additionally located in the tubular waveguide, prevents dust and other impurities from penetrating through the tubular waveguide to the microwave source, and damaging the microwave source. . It is also possible that the gas in the gas inlet pipe can be preheated by microwaves due to the absorption capacity of the gas or particles it contains. Alternatively or additionally, at least one additional tubular waveguide can be added in the gas addition tube according to the invention for the introduction of microwave radiation into the reactor, possibly in the form of a lance.

If the tubular waveguide terminates approximately at the outlet of the central tube or a little lower, the gas stream entering the entrainment mixing chamber prevents the entry of impurities into the tubular waveguide. At the same time the microwave radiation can be introduced practically without losses to the reactor. According to the invention there may also be several gas addition tubes (center tubes) and several tubular waveguides, provided that each tubular waveguide is connected to its own microwave source. With this, the microwave intensity in the reactor can be varied by connecting and disconnecting one or the other microwave source, without having to change the intensity or frequency of a microwave source. This is especially convenient, because it is thus possible to maintain the optimum ratio of the microwave source and the tubular waveguides connected and at the same time change the total intensity in the reactor. The exact mathematical calculation of the resonance variables is quite complex since we have to solve the Maxwell equations (non-stationary and non-linear differential equations) with their respective boundary conditions. In the case of a rectangular or circular section, these equations can be simplified to such an extent that they can be solved analytically and thus show problems in the design of tubular waveguides, and solve them easily. For this reason and based on the ease of its manufacture in the industry, only tubular waveguides of rectangular and circular section are used, which are also used preferentially according to the invention. Rectangular tubular waveguides in most cases are normalized in English literature. These standardized measures were used in Germany, resulting in dimensions that are not standard in part. In general, all industrial microwave sources for the frequency of 2.45 GHz are provided with a rectangular tubular waveguide of type R26 having a section of 43 x 86 mm. In the tubular waveguides there are different states of vibration: in the transverse electric mode (TE mode) the electric component of the field is perpendicular to the direction of the tubular waveguide and the magnetic component in parallel to the direction of the guide tubular waves. In the transverse magnetic mode (TM Mode) the magnetic field component is perpendicular to the direction of the tubular waveguide and the electrical component in parallel to the direction of the tubular waveguide. Both states of vibration can be present in all directions with different mode numbers (eg, TE-1-1, TM-2-0). The length of a tubular waveguide is according to the invention in the range between 0.1 and 10 m. It has been found that tubular waveguides of these lengths can be handled especially well in practice. The tubular waveguide under these conditions can be straight or bent. According to the invention, it is possible to introduce equipment for redirecting the currents of solids and / or fluids to the annular fluidization layer and / or to the reactor mixing chamber. Thus it is possible to position in the ring fluidization layer a circular-shaped partition whose diameter is between that of the central tube and the reactor wall, so that the upper edge of the partition protrudes from the level of solids that is established during the operation, while that the lower edge is installed at a distance from the gas distributor or similarly. Solids that sediment in the vicinity of the reactor wall of the entrainment chamber must thus pass the septum first in its lower part, before they are dragged by the gas from the central tube back into the mixing chamber. drag. In this form an exchange of particulate matter in the annular fluidization layer is forced so that a uniform residence time of the solid is established in the annular fluidization layer. Continuation possibilities, advantages and applications of the invention are also given by the descriptions of design examples and drawings that follow. With this, all the features described and / or represented by themselves and in any combination form the subject matter of the invention, independently of what is established in the claims or the references thereof.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1. Shows a diagram of a process and an equipment according to the first embodiment of the present invention. Figure 2. Shows a reactor for carrying out the process according to a second embodiment experiment of the present invention. Figure 3. Shows a reactor for carrying out the process according to a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With the aid of FIG. 1, the equipment and the process for the thermal treatment of solids are first described in a general manner to explain the operation according to the invention. The installation contains for the thermal treatment of solids a possible cylindrical reactor 1 with a central tube 3 in an approximately coaxial form with the vertical axis of the reactor, which essentially extends from the bottom of the reactor 1 upwards vertically. In the area of the bottom of the reactor 1 is planned a gas distributor, not shown, into which the inlet ducts 19 open. In the vertically upper area of the reactor 1, which forms a mixing chamber 7, there is an outlet 13 which opens into a separator in the form of cyclone 14. If solids are introduced for example in the form of granular minerals from a container of solids 5 through a duct of solids 6 into reactor 1, a layer is formed on the gas distributor. ring-shaped central tube 3, which is called annular fluidization layer 8. Both the reactor 1, and the central tube 3 can naturally also have a different section than the preferred circular, provided that the annular fluidization layer 8, surrounds the Cenfral tube 3 at least in part. The fluidization gas introduced by the intake duct 19 through the gas distributor fluidizes the annular fluidization layer 8 so that a stationary fluidization bed is formed. Preferably the gas distributor for this is constituted by a grid of nozzles with a large number of individual nozzles, which are connected to the intake duct 19 in a simpler form; The gas distributor can also be a grid with a gas distribution chamber below it. The rate of gas admission to reactor 1 is adjusted for this in such a way that the particle number Froude of the annular fluidization layer 8 is between approximately 0.115 and 1.15. By adding more solid to the annular fluidization layer 8 the height of the solids level in the reactor 1 increases to such an extent that solids enter the outlet of the central tube 3. A gas or mixture of solids is introduced through the central tube 3. preferably hot gases with a temperature between 200 and 1000 ° C in the reactor 1. The velocity the gas added through the central tube 3 to the reactor 1 is conveniently adjusted in such a way that the number Froude of particles in the central tube 3 is approximately 1.15 and 20 and in the mixing chamber 7 approximately between 0.37 and 3.7. Due to the higher level of solids in the annular fluidization layer 8 with respect to the upper edge of the central tube 3, solid overflows this edge and enters the central tube 3. The upper edge of the central tube 3 can be formed in a straight or other form, for example toothed (as toothed crown) or have side openings. Due to the high velocity of the gas passing through the central tube 3, it drags, as it passes, the area of the upper outlet, solids of the ring fluidization layer 8, stationary, to the entrainment chamber 7, thereby an intensively mixed suspension is formed. At the end of the central tube 3 which is opposite the reactor 1 is located a microwave source 2. The microwave radiations generated therein are introduced through the central tube 3 which is shaped as a tubular waveguide 4 to the mixing chamber of drag 7, and participate at least in part in the heating of the reactor 1. The decoupling of the microwaves from the tubular waveguide 4 serving as the feeding guide can occur in several ways. Theoretically, microwave energy can be transported without losses in tubular waveguides. The section of the tubular waveguide is given as a logical development of a coil and capacitor oscillation circuit towards high frequencies. This type of oscillation circuit theoretically can also work without losses. By strongly increasing the resonance frequency the coil of the oscillation circuit is transformed into a coiled medium, which corresponds to one side of the section of the tubular waveguide. The capacitor becomes a plate capacitor, which also corresponds to two sides of the section of the tubular waveguide. In the real case an oscillation circuit loses energy by the ohmic resistance in the coil and the capacitor. The tubular waveguide loses energy by the ohmic resistance of the tubular waveguide wall. From an electric oscillation circuit, energy can be diverted by coupling a second oscillation circuit, which takes energy from the first. In an analogous way, energy can be extracted from a tubular waveguide by coupling a second tubular waveguide by means of flanges (transfer of tubular waveguides). If the first guide of Tubular waves are closed behind the coupling site by a septum / short circuit it is possible to divert even all the energy to the second tubular waveguide. The microwave energy is contained in the tubular waveguide by walls with electrical conductivity. On the walls there are currents of walls and in the section of the tubular waveguide there is an electromagnetic field whose intensity can be several times 10 KV / m. If an antenna is introduced that is able to conduct electricity to the tubular waveguide it can directly deflect the potential difference of the electromagnetic field and it can radiate it again at its end if it has the appropriate shape (disconnection of antenna or spike). An antenna that enters through an opening in the tubular waveguide and touches the tubular waveguide wall in another location can also absorb wall currents directly and also radiate them at its end. If the tubular waveguide is closed by a short-circuit partition behind the coupling of the antenna, it is also possible in this case to divert all the energy from the tubular waveguide to the antenna. If the field lines of the wall currents in tubular waveguides are interrupted by slots, microwave energy comes out through these slots in the tubular waveguide (slot uncoupling), since energy can no longer flow through the wall . The wall constants in a rectangular tubular waveguide run through the center of the wide wall on the side of the tubular waveguide parallel to the centreline and in the middle of the narrow side of the tubular waveguide perpendicular to the line cenfral Grooves crossed in the wide sides and longitudinal grooves in the narrow sides therefore uncouple microwave radiations from tubular waveguides. Microwave radiation decoupled, for example, by some of the described forms of the tubular waveguide 4 is absorbed by the suspension formed in the dragging chamber 7, specifically the solids contained therein, and contributes to its heating. In the entrainment chamber 7, the reaction of the granular solids with the process gas added by the central tube 3 then occurs. The temperature here is between 200 ° C and 1500 ° C. Granular material that has reacted returns due to the reduction of the flow rate of the first gas (process gas) expanded in the entrainment chamber 7 or due to collisions with the reactor wall back to the annular fluidization layer 8 and may be heated or maintained there at the desired temperature by the elements heaters 9. Too thick solids can be removed through the outlet duct 10. The gas containing the rest of the solids, which have not precipitated / settled, flows to the top of the reactor where the gases with dust are cooled by the elements 12. Through the exhaust pipe 13, the gases are directed towards the cyclone 14 which serves as a settler in which part "head" are extracted by the gas pipe 15 and cooled by the cooler 16. The gas is it removes the remainder of the solid powder by means of a second separator 17, for example a cyclone or filter and the gas without solids is conducted through the pipes 18, 19, again to the annular fluidization layer 8, for a continuous processing. An additional gas pipe 20 deflects clean gas to the central pipe 3 or to the tubular waveguide 4 and acts here as washing gas and / or process gas to keep the pipe 3, 4 free of dust. Additionally fresh process gas can be added on a pipe, not shown, to the central pipe 3. The separated solids in the separator, especially dust, are recirculated from the bottom of the cyclone 14 to the annular fluidization layer 8, where there is the possibility of removing fine solid as a product by means of the pipeline 11. In this form, the level of solids in the annular fluidization layer 8 of the reactor 1 can be simply adjusted. In order to adjust the recycling of the solids, good results have been obtained in this invention. measure the loss of pressure against the central tube 3 and the exhaust duct (exhaust! 3), which leads to the separator 14 of the reactor 1 and regulate it by varying the amount of recycled solid. For this it has been shown that it is convenient to use a fluidized intermediate container with a dosing device by coupling in series, for example a rotary vane valve with adjustable speed of rotation, with which the solid not required for recycling can be diverted by means of of a spill and led to another use. Solid recycling provides a simple way of maintaining the process conditions in the reactor 1 constant and / or adjusting the average residence time of the solid in reactor 1. In Figure 2 the lower part of reactor 1 is shown according to a second embodiment. Two microwave sources 2a, 2b are planned, where each microwave source is coupled with its own central tube 3 a, 3b to drive the microwaves to the mixing chamber 7. Also in this case the central tube is directly used 3a, 3b, as a tubular waveguide 4a, 4b. Both central tubes 3a, 3b are fed onto the gas pipe 20 with dust-free gas that also here it serves as washing gas. Instead of the two microwave sources 2a, 2b it is also possible to use a number of microwave sources with an equivalent number of tubular waveguides and central tubes. In FIG. 3, the lower part of the reactor 1 is also shown. Also in this embodiment of the reactor 1, two microwave sources 2 a, 2 b are provided, each carrying their own tubular waveguide 4 a, 4 b, microwaves to the drag mix chamber. The tubular waveguides 4a, 4b are introduced into the central tube 3 and are guided into it into the mixing chamber 7. To prevent fouling of the tubular waveguides 4a, 4b, they are provided with free gas powder from the duct 20, which here serves as a wash gas. In this case the central tube 3 is used for introducing, for example, process gas loaded with powder. For a subsequent reconstruction of an already existing reactor 1, only a change of a sector of the central tube 3 is required to enable a gas-proof introduction of the tubular waveguides 4a, 4b to the central tube 3. Instead of the two microwave sources 2a, 2b is again possible a number of microwave sources that are located below the reactor 1 or around the reactor 1. A number of microwave sources makes it possible to vary the intensity of microwave radiation introduced to reactor 1 by igniting or by turning off individual microwave sources, without having to change the operating parameters of a microwave source for which the tubular waveguide is optimally adjusted. In the application of the process, the solids to be treated absorb at least part of the electromagnetic radiation used and thereby heat the fluidization bed. Surprisingly it has been seen that especially if the material has been treated with high intensity fields, these can be easily leached. Ofras also often offer technical advantages such as shortened residence times or reduction of the required process temperature. The reactor 1 with central tube 3 and annular fluidization layer 8 is especially suitable for the treatment of granular material since it is characterized by a combination of very good characteristics of heat and matter exchange with long periods of residence. According to the invention, most of the process gas is introduced through the center tube 3 into the dragging chamber 7 so that the solid is dragged from the fluidization layer to the entrainment chamber 7 which is located on the stationary fluidization layer. This leads to an especially well-mixed suspension. Choosing the section of the reactor 1 achieves that a low average velocity is generated in the dragging chamber 7. The result is that most of the solid reprecipitates from the suspension and is returned to the annular fluidization layer 8. The The circulation of solids that is generated in front of the annular fluidization layer and the entrainment mixing chamber is usually greater by an order of magnitude than the stream of solid added to the reactor from outside. This ensures that the solid present in the dragging chamber passes through several times the area of maximum density of the microwave power that is on the central tube, where the solids can absorb the microwave radiation coupled there through the tubular waveguide.

Example Gold Mineral Toasting An example of a concrete application for the process according to the invention is the roasting of gold ores which is carried out in an equipment according to Figure 3. For this case the Froude number of particles Frp of the Stationary annular fluidization layer 8 is 0.35, in the entrainment mixing chamber 7 it is 1.3 and in the center tube 3 it is 15. The microwave frequency used is 2.42 GHz. In the Table below shows the important parameters of the process. Feeding: Type Gold ore ground, dried and classified Gold content approx. 5 ppm = 5 gr / ton Gram fraction max μm 50 Composition% by weight C organic 1.05 CaCO3 19.3 Al2O3 12.44 FeS2 2.75 Inert, for example, SiO2 64.46 Solids flow, approx. T / h 100 Equipment Type of reactor: Reactor in annular fluidization layer, air preheating at 500 ° C, equipped with: Connected: In-line gas analyzer + exhaust gas cleaning Diameter of the upper part of the reactor mm 5000 Working method Continuous Installed microwave power KW 6 Tubular wave guide R26 (43 x 86 mm, Stainless steel) Flow rate air flow NmJ / h 9200 Working conditions Residence time of the solid min 5 Temperature ° C 550 to 650 Residue of O2 in exhaust Vol% 0,5 to 3,00 The organic carbon content in the product is less than 0.1% List of components of drawings: 1 Reactor 2, 2a, 2b Microwave sources 3 Central tube 4, 4a, 4b Tubular waveguide 5 Solids container 6 Solids pipe 7 Drag mix chamber 8 Ring fluidization layer 9 Elements of Heating 10 Exit Pipe 11 Duct Cooling element Exit, exhaust pipe Separator, cyclone Gas duct Cooler Separator Gas pipeline Intake duct Gas pipeline

Claims (23)

1. Claims 1. A process for the thermal treatment of granulated solids in a reactor (1) in which microwave radiation from a microwave source (2) is introduced to the reactor (1), CHARACTERIZED because a first gas or mixture of gases is introduced from below by at least one central gas inlet pipe (3) to a reactor mix chamber (7) where the gas inlet pipe (3) is at least partially surrounded by an annular fluidization layer (8) stationary fluidized by the fluidizing gas and because the microwave radiation is introduced to the entrainment mixing chamber (7) by the same gas intake pipe (3).
2. 2. A process according to claim 1, CHARACTERIZED in that the velocity factor of the first gas or mixture of gases and the fluidizing gas by the annular fluidization layer (8) is adjusted such that the particle number Froude in the gas inlet pipe (3) it is between 1 and 100, in the annular fluidization layer (8) it is cool 0.02 and 2, and in the drag mixing chamber (7) it is cooled 0.
3. 3 and 30. A process according to claims 1 and 2, CHARACTERIZED because the Froude number of particles in the gas inlet pipe (3) is cooled to 1.15 and 20.
4. 4. A process according to any of the previous claims, CHARACTERIZED because the Froude number of particles in the annular fluidization layer (8) is cooled to 0,115 and 1, 15.
5. 5. A process according to any of the preceding claims, CHARACTERIZED because the Froude number of particles in the dragging chamber (7) is cooled to 0.37 and 3.7.
6. 6. A process according to any of the preceding claims, CHARACTERIZED because the level of solids in the reactor (1) is adjusted in such a way that the annular fluidization layer (8) extends higher than the upper outlet of the tube. gas admission (3), and that the solid material is continuously introduced into the first gas or gas mixture and carried by the gas stream to the entrainment mixture chamber (7) which is on the exit area of the gas tube. gas admission (3).
7. 7. A process according to any of the preceding claims, CHARACTERIZED because the microwave radiation is fed by a tube of gas inlet (3, 3a, 3b) formed by a tubular waveguide (4, 4a, 4b) and / or by a tubular waveguide (4a, 4b) disposed inside the gas inlet pipe (3 ).
8. 8. A process according to any of the preceding claims, CHARACTERIZED because the microwave radiation is introduced by several tubular waveguides (4a, 4b) where each tubular waveguide (4a, 4b) is provided by a microwave source own (2a, 2b).
9. 9. A process according to any of the preceding claims, CHARACTERIZED because the washing gas is conducted by the tubular waveguide (4, 4a, 4b).
10. 10. A process according to any of the preceding claims, CHARACTERIZED because the frequency of a microwave source (2) is between 300 MHz and 30 GHz, preferably between 400 MHz and 3 GHz, specifically at the ISM frequencies 435 MHz, 915 MHz and 2.45 GHz.
11. 11. A process in accordance with Any of the previous claims, CHARACTERIZED because the section and dimension of the tubular waveguide (4) is adjusted to the frequency of the microwave radiation used.
12. 12. A process according to any of the preceding claims, CHARACTERIZED in that the temperature in the stationary annular fluidization layer (8) is between 150 ° C and 1500 ° C.
13. 13. A process according to any of the preceding claims, CHARACTERIZED because the solids coming from the reactor (1) and separated by the separator (14) are recycled at least in part to the annular fluidization layer (8) of the reactor.
14. 14. A process according to any of the preceding claims, CHARACTERIZED because the gas introduced in the tubular waveguide (4) is used for an additional fluidization of the stationary fluidization layer (8).
15. 15. A process according to any of the preceding claims, CHARACTERIZED because a fine granular solid with a granular size of less than 1 mm is added as a raw material.
16. 16. An apparatus for the treatment of granular solids, especially consisting of a reactor (1) constructed as a fluidization layer reactor and a microwave source (2) to perform a process according to claims 1 to 15, characterized in that the reactor (1) has a gas intake system configured in such a way that the gas flowing through the gas intake system entrains solids from a stationary annular fluidization layer (8) that at least partially surrounds the gas intake system to the entrainment mixing chamber (7), and because microwave radiation can be introduced through the intake system of gases
17. 17. An apparatus according to claim 16, CHARACTERIZED in that the gas intake system consists of a gas intake pipe (3) that starts up in the bottom part of the reactor (1) upwards in an essentially vertical manner until it reaches the drag mixing chamber (7) of the reactor (1), where the gas intake pipe (3) is surrounded by a chamber that at least partially surrounds the gas intake pipe (3) in which it is generated the ring fluidization layer (8) stationary.
18. 18. An apparatus according to claim 17, CHARACTERIZED in that the intake pipe (3) is located approximately in the center of the cross section of the reactor (1).
19. 19. An apparatus according to any of claims 16 to 18, characterized in that the gas inlet pipe (3) is configured as a tubular waveguide (4) for the introduction of microwave radiation.
20. 20. An apparatus according to any of claims 16 to 19, CHARACTERIZED because at least one tubular waveguide (4a, 4b) is located in the gas inlet tube (3) for feeding the microwave radiation.
21. 21. An apparatus according to any of claims 16 to 20, CHARACTERIZED because several gas inlet tubes (3a, 3b) and / or several tubular waveguides (4a, 4b) are considered where each tubular waveguide (4a, 4b) is connected to its own microwave source.
22. 22. An apparatus according to any of claims 19 to 21, CHARACTERIZED in that the tubular waveguide (4) has a rectangular or round section.
23. 23. An apparatus according to any of claims 19 to 22, CHARACTERIZED in that the tubular waveguide (4) has a length of 0.1 m to 10 m.