WO2017148562A1

WO2017148562A1 - Device and method for thermal material treatment

Info

Publication number: WO2017148562A1
Application number: PCT/EP2017/000096
Authority: WO
Inventors: Horst BÜCHNER
Original assignee: Büchner Horst
Priority date: 2016-03-04
Filing date: 2017-01-27
Publication date: 2017-09-08
Also published as: DE102016002566B4; DE102016002566A1

Abstract

The invention relates to a method and to a device for the thermal treatment of a raw material (10), having a combustion chamber (5) in which a periodically transient, oscillating flame (1) burns for the purposes of generating a pulsating exhaust-gas stream (9), which exhaust-gas stream flows through a reaction chamber (7) which adjoins the combustion chamber (5). To achieve that the raw material is treated in an effective manner, it is proposed that an insert (13) be provided in the reaction chamber (7), which insert is flowed through by the exhaust-gas stream and is of reduced cross-sectional area (14) in relation to the reaction chamber (7) and has a length (15) shorter than a total length of the reaction chamber (7). In particular, the length (15) of the insert (13) and the geometry of the combustion chamber (5) are variable, such that two resonators are available which can be coordinated with one another.

Description

Apparatus and method for thermal material treatment

The invention relates to a device for the thermal treatment of a raw material, with a combustion chamber in which burns at least one burner at least one periodic-unsteady, oscillating flame to produce a pulsating oscillating exhaust gas stream which flows through a subsequent reaction chamber to the combustion chamber, and a corresponding Method.

Under a thermal treatment is understood in particular a thermal material treatment or a thermal material synthesis, wherein it may also be a raw material mixture in the raw material. The raw material or the raw material mixture can be present both in solid and in liquid or in gaseous or vaporous form.

By far the largest number of all technical or industrial combustion plants and combustion systems are designed and operated so that the combustion process is constant on average with the exception of small turbulent fluctuations whose size is at least one order of magnitude smaller than the average sizes of the combustion process (such as average flow velocity , mean temperature of the flame or the exhaust gas flow, average static pressure in the combustion chamber, etc.). This means that the conversion of the fuel used is continuous over time and, as a consequence, also the heat release from the combustion process and the mass flow of exhaust gas arising (combustion).

CONFIRMATION COPY Products) for a fixed burner setting have constant values over time.

Deviating from this, phenomena or "abnormalities" are sometimes referred to, which are referred to in the literature as combustion chamber oscillations, self-excited combustion instabilities or thermoacoustic oscillations, which are characterized by the fact that the initially steady (ie temporally constant) combustion process suddenly reaches a stability limit Along with this change, the heat release rate (s) of the flame (s) and thus the thermal firing performance of the incinerator as well as the exhaust gas flow will also go into and out of time-periodic oscillatory combustion process, the time function of which is close to sinusoidal the combustion chamber and the static pressure in the combustion chamber itself periodic-unsteady, ie swinging / l, 2 /.

The occurrence of these combustion instabilities often causes a changed compared to the stationary operation of the combustion pollutant emission behavior and causes not only increased noise pollution of the plant environment but also a significantly increased mechanical and / or thermal stress on the plant structure, e.g. the combustion chamber walls, the combustion chamber lining etc. These loads can lead to destruction of the furnace or of individual components. It is therefore easy to see that the undesired occurrence of the phenomena described above in furnaces which are designed for a time-constant combustion process in which the static pressure in the combustion chamber or in upstream or downstream plant components should also have constant values (constant pressure). Combustion), must be avoided.

Quite different, however, is the situation with a small number of very specific firing systems, which are assumed in the present invention and in which the phenomenon of self-excited, periodic incineration Instabilities deliberately induced and used to produce a periodic combustion process with periodic heat release rate of the flame and periodic oscillating exhaust gas flow (pulsating hot gas flow) in the combustion chamber and in downstream plant components (eg heat exchangers, chemical reactors, etc.).

For more than forty years, the relevant literature has reported chemical reactors in which thermal treatment of a raw material feedstock or thermally controlled material synthesis is from one or more raw materials, typically as vibrating-fire reactors, pulse dryer, pulse combustor or pulsation reactors be designated / 3, 4, 5, 6 /.

All of these reactors have in common that the thermal material treatment in a pulsating, oscillating hot gas flow - ie temporally-instationary - takes place, both the heat required for the thermal material treatment or material synthesis heat and the mechanical vibration energy of the pulsating hot gas flow of a transient, oscillatory Combustion process of a fuel originate. Natural gas, hydrogen, liquid fuels, etc. can be used as fuels.

The advantage of these systems compared to conventional, stationary combustion systems consists in the periodic average-transient and turbulent exhaust gas flow in the combustion chamber and in downstream components, eg heat ^¬ exchangers, reaction chambers, resonance tubes, etc.

This causes the heat transfer from the hot gas increases, both on the solid walls (combustion chamber wall, wall of a heat exchanger, steam generator, etc.) and on the material which is introduced for treatment in the hot gas flow with a defined treatment temperature. This increase is very clear and is two to five times higher than a steady-state, turbulent flow same average flow velocity and same temperature. Due to these relationships, the material to be treated experiences high heating gradients in pulsating hot gas flows ("thermal shock treatment" / 6 /).

Due to the analogy between convective heat transfer and mass transfer, the above statement also applies to the mass transfer: In the case of periodic-transient, oscillating flow, the transition rate of gaseous or vaporous substances from the hot gas to the material to be treated or from the material to the hot gas flow increases similar values. This is due to the almost complete absence of boundary layers, which are known to arise in stationary flows and represent diffusion or contact resistance.

The reactors / 6, 7, 8, 9 / described in the prior art typically consist of a combustion chamber in which the reaction conversion of the fuel used to release the chemically bound therein heat in a flame or flames, and then in the flow direction thereafter a reaction space It is known to add the raw material to be treated into this reaction space so that thermal treatment of the material takes place in the reaction space In some special embodiments, the raw material is already introduced into the combustion chamber.

However, the prior art vibrating fire reactors have significant disadvantages and technical problems:

Since the oscillation comprises the entire flowing hot gas column in the reactor, ie the exhaust gas in the combustion chamber as well as the hot gas in the reaction space up to the final filter, the mass of hot gases to be displaced by the periodic-transient combustion process, ie in periodic motion, is very high large. Because at the same time, however, only a very small part of the thermal energy from the combustion process is converted into mechanical vibration energy of the (entire) hot gas flow, the occurring amplitudes of the hot gas oscillation in the large volumes of the combustion chamber and the reaction chamber are extremely low and are further attenuated by the addition of the (vibrational energy) raw material stream.

Thus, in the limiting case, it is even possible to completely dampen the usually self-excited oscillations of the hot gas flow by sufficiently high raw material feed rates, with the consequence that the thermal material treatment then takes place in a now no longer oscillating but instead stationary hot gas flow. This no longer has the advantages of increased heat and mass transfer rates. For this reason in particular, today's vibrating-fire reactors are severely limited in several respects: the possible raw material application rates and thus also the producible product quantities per time are very severely limited by the described decrease in the oscillation amplitudes of the hot gas flow, so that also the plant capacities are relatively small.

In principle, a significant increase in the educt feed rates would first of all make it necessary to increase the firing rate required for their treatment, which would, however, be accompanied by a corresponding increase in the resulting exhaust gas volume flow. This would also require a large increase in the volume of the reaction space in which the material treatment takes place so as to ensure a consistent material treatment time. As a result, the gas mass to be vibrated would increase again and the recoverable amplitudes of the oscillation of the hot gas flow for material treatment would decrease again with the consequence of a decreasing product quality.

The object of the present invention is to overcome these limitations. This object is achieved in that in the reaction space a flowed through by the exhaust gas flow, in the cross-sectional area opposite the reaction space reduced use is provided, which has a length in the flow or axial direction, which is shorter than a total length of the reaction space.

A device according to the invention thus has a periodically unsteady, oscillating flame in the combustion chamber in front in the flow direction, which generates a pulsating, likewise oscillating, hot gas or exhaust gas flow. The used in the reaction space, reduced in cross-section can now with appropriate tuning of its length, the volume and the temperature of the introduced into the reaction chamber hot gas and the raw material to be treated in this by the vibration of the static pressure and the exhaust gas flow and by radiated sound waves of the periodic -instationary combustion process in the combustion chamber at the hot gas flowing therethrough stimulate a resonance-enhanced vibration, so that the abandoned raw material (educt) is here subjected to the desired thermal material treatment.

Thus, the hot gas, which contains the exhaust gas flow and oscillates, only resonantly excited in the section of the insert. The invention is based on the following finding:

In reality, there is no resonance phenomenon whatsoever in the vibrating resonators described in the prior art, since there is no periodic excitation source which sets the gas in periodic oscillations or stimulates resonance, in particular in the reaction space, which is often referred to as resonance tube. Rather, this is a system instability that affects the entire reactor and for their vibration frequency, the coupled vibration behavior of all system components, (ie burner, combustion chamber, Reaction space ("resonance tube"), separating devices (filters, cyclone) etc.) is responsible / 10 /.

However, it can be seen from the use of the term "resonance" for the occurring physical effects, that there is a substantial, persistent error in connection with the causal phenomena underlying the generation of the oscillating hot gas flow: In the phenomenon of self-excited combustion instabilities described above namely, is it a system instability in which the system, when reaching a plant-specific stability limit of a stationary, vibration-free operating condition (stationary combustion process) abruptly in a periodic-transient, oscillatory operating state (periodic-transient combustion process) turns without a foreign excitation of the system is present.

The term "resonance", on the other hand, derives precisely from this, physically completely different phenomenon of an externally or force-excited oscillation: an oscillatory system is stimulated to "resonate" by an external, periodic excitation (for example periodic force by periodic imbalance etc.).

The resulting oscillation frequency of the prior art reactor with self-excited combustion instability thus does not correspond to such a resonant frequency of a component as e.g. Thus, with this procedure, it is also not possible to exploit a resonance-induced amplification of amplification, as is possible with the device according to the invention.

In other words, in the vibrating fire reactors for thermal material treatment according to the prior art, the entire, located in the reactor hot gas column (hot gas flow) must be set in vibration, even in places where no material treatment takes place at all or taking place at this point Process step of material handling does not benefit at all from any existing vibrations of the hot gas flow. This goes hand in hand with a low treatment amplitude. It can be seen that, with an embodiment according to the invention, the provision of an insert with a reduced cross-sectional area and suitable length can purposefully excite a resonance of the hot gas flow flowing through the insert, so that the portions of the reaction space upstream and downstream of the insert in the flow direction whose dimensions are of minor importance.

Another strong limitation in the applicability of prior art thermal material handling vibrating fire reactors is that for a successful thermal treatment of feedstock, a material-specific material treatment time, i. a dependent on the product to be produced and the desired product properties minimum residence time of the raw materials in the hot gas zone of the reactor, is absolutely necessary. If this minimum residence time is exceeded, the reaction sequence / reaction conversion is not completed and the desired product is not yet "finished" thermally treated.

In vibrating-fire reactors described in the patent literature, the material treatment is typically carried out in the reaction space, which is often referred to as "resonance tube." The achievable material treatment time in these prior art reactors therefore depends on the flow rate of the hot gas flow, which is determined by the firing capacity and the air ratio Increase of the material treatment time by an extension of the reaction space would simultaneously lower the oscillation frequency of the oscillation of the hot gas flow and also the recoverable amplitudes of the Hot gas oscillation by the increased total mass of the gas column now to be displaced in Schwin ^¬ tion further reduce in the reaction chamber.

One recognizes here easily the technical disadvantages of the reactors according to the current state of the art: oscillation frequency and amplitude and the material treatment time depend on each other coupled to the reactor geometry, in particular of the length of the reaction space in the flow direction. An extension of the residence time is thus in the prior art only at the expense of reduced frequencies and amplitudes of the hot gas oscillation and thus at the expense of reduced heat and mass transfer rates of the hot gas to the raw material to be treated and thus at the expense of the advantages of a thermal material treatment in the oscillating hot gas flow. These problems are also overcome with the inventive design of a vibration reactor.

In a development of the invention, the insert provided in the reaction space can be variable in its flow-through length.

It is also possible that alternatively or additionally, the combustion chamber is variable in its geometry.

While a reactor according to the invention as described so far shows the desired resonance in use only at a specific operating point of the reactor with very specific boundary conditions, such a further developed reactor thus has at least one, possibly also two frequency tunable resonators. This has the consequence that the reactor can be set to a large number of different operating states or operating points.

In this regard, it should be noted that, for example, the resonance within the insert depends on the speed of sound, which in turn is temperature-dependent. The temperature is among others by the Combustion temperature, the possible admixture of cooling air, the amount and the temperature of the raw material / educt, etc. affected.

In the case of a reactor which has been developed as described above, it is thus possible to carry out a coordination with respect to the boundary conditions at the first resonator in the flow direction, namely the combustion chamber, and at the second resonator in the flow direction, namely the insert reduced in cross-section. The first resonator thus has a burner with the associated supply connections for fuel and combustion air, a flame and a combustion chamber, which acts as a resonator, which in terms of their geometry and the resulting vibration behavior of the gas column contained in it (the exhaust gas of the combustion process the flame) in the frequency range between 50 and 1000 Hz frequency tunable. The device is suitable for the targeted generation of self-excited combustion instabilities in the reactor part burner-flame combustion chamber, ie in the first resonator. Connected by a preferably insulated pipe into which cooling air can be added if necessary to set a desired material treatment temperature, the oscillating, ie periodically unsteady hot gas from the oscillating combustion process of the flame in the combustion chamber, ie from the first resonator, the reaction chamber is supplied , In this then takes place the Eduktzugabe and thus also the thermal material treatment, the latter in particular in the integrated into the reaction chamber second resonator. By tuning the oscillation frequency of the periodic-transient combustion process in the first resonator (self-excited combustion instability with oscillating flame) at the combustion temperature there to the resonance behavior of the second resonator with the material treatment temperature present there, which is typically lower than that due to the addition of cooling air and Eduktzugabe Combustion temperature in the first resonator, there is a coordinated resonant excitation of the second resonator by the periodic excitation transmitted to it, which results from the combustion oscillation in the first resonator and which is characterized by periodic oscillations of the static pressure and the hot gas flow.

It should be pointed out here that both alternatively and cumulatively, the second resonator can also be adapted to the frequency of the first resonator by altering its length throughflow - or rather to the frequency of the resonator emerging from the first resonator and exciting the second resonator as a sound wave Vibration. The open at its two ends insert, so the second resonator has as V2 wave resonator its fundamental frequency resonance at a given speed of sound (and thus at a given material treatment temperature) if and only half a wavelength of the sound wave or vibration in the use, ie fits the second resonator. This forms a standing half-wave in this ¹ /2-wave resonator, which is used for material treatment. The length of the second resonator discussed here thus correlates with the temperature which prevails in it for the material treatment, since this influences the speed of sound in use, which in turn is of relevance with respect to the oscillation desired in use.

In contrast to the vibrating fire reactors described in the literature, there is a genuine external or forced excitation with resonance in relation to the generation of vibrations in the second resonator, ie in the actual reaction space of the material treatment. Depending on the frequency tuning of the excitation frequency and the vibration damping, resonance-induced amplifications (amplification) of the excitation can be set up to a factor of ten in the second resonator. So here is actually an active ability to influence the vibration amplitudes in the reaction chamber in the thermal material treatment. Independently of the choice of the excitation frequency from the first resonator, the duration of the material treatment in the reaction space or in the second resonator is independent of the existing there oscillation frequency of the hot gas flow, as long as the middle Throughput or the average flow rate is kept constant, since the length of the second resonator (ie, the length of the "resonance tube") does not have to change so that there are different material treatment frequencies.

Thus, the frequency of the material treatment in the pulsating hot gas flow is physically decoupled from the duration of the material treatment in the reaction space or in the second resonator. Thus, both variables now represent independent process parameters of the thermal material treatment.

In addition, there is also the possibility of using this method also directly harmonics, i. to specifically excite higher harmonic resonance frequencies of the second resonator in the reaction space.

If this resonator is, for example, a ¹ / ^2- wave resonator with, for example, a fundamental frequency of 100 Hz for a given hot gas or material treatment temperature, then frequencies of 200 Hz, 300 Hz, 400 Hz, etc. would be targeted for the thermal treatment of material excitable.

Surprisingly, it has been shown that the material properties achieved of the treated products at the same material treatment temperature depend on the product of treatment frequency and treatment duration. That is, at a treatment frequency of 100 Hz and a material treatment time of 400 milliseconds, the same result is achieved in terms of product properties and product quality as at 400 Hz and 100 milliseconds. One reason for this is presumed to be that the particles of a raw material to be treated experience the same number of oscillation cycles in the reaction space during their treatment in both cases, especially during use.

So if you are in a device according to the invention in a position to increase the frequencies of the thermal material treatment by a targeted excitation of the second resonator in the reaction chamber significantly, for example, by a targeted resonant excitation of the harmonics of the second resonator, you can simultaneously for complete thermal treatment of the raw material necessary residence times and thus the size or the volume of the reaction space (or the length of the required resonance tube with a fixed cross-sectional area) significantly reduced.

At the same time, however, the necessary gas mass, which must be vibrated, is reduced in comparison with the devices and methods described in the patent literature, in which the hot gas column of the entire vibrating fire reactor must be vibrated with a significantly greater mass of gas. Thus, and with the previously described, resonance-induced elevation (amplification) of the oscillation amplitude in the second resonator can thus be treated at the same average firing capacity of the reactor there are thus considerably larger than the Rea ktoren enforced according to the prior art. Accordingly, the achievable reactor throughput increases significantly and improves the profitability of the thermal process.

Finally, the good order's sake it should be noted that the type of the resonator (Helmholtz resonator, ^1/4-wave resonator V2- wave resonator), which is used as the first resonator and / or as a second resonator 2, generally not is of importance, as long as it is ensured that associated with the generation of self-excited combustion instabilities in the first resonator (combustion chamber) vibration frequencies of the static pressure and the Flow rate of the resulting from the transient combustion process, oscillating hot gas flow are suitable to resonantly excite the second resonator in the reaction chamber for the thermal treatment of material.

In a further preferred embodiment of the invention, the insert proposed in the reaction space can be changed in its axial position within the reaction space and thus parallel to its axial extension.

The advantage of this further development becomes apparent in the following consideration:

Typically, a thermal material treatment in a vibrating-fire reactor, for example when using a liquid raw material (for example raw material solution or aqueous suspension with solids content) consists of the following individual steps:

Atomization of the liquid raw material e.g. with the help of a spray nozzle

- Heating and evaporation of the raw material solution / drying of the solid

- Heating the raw material to material treatment temperature

- Thermal treatment e.g. Calcination, sequence of solid-state reactions, degassing

- Crystal growth / crystal transformations, etc.

It is very unlikely that all of these physically very different single cuts of thermal material treatment in a vibrating-fire reactor will be equally affected by oscillation of the hot gas flow around the droplets / particles to be treated benefit over a thermal treatment in a stationary flowing, non-oscillating hot gas flow.

In the reactors described in the prior art, however, the entire flowing hot gas column in the entire reactor space is vibrated with the consequence of a large and inert gas mass with significant vibration damping and resulting small vibration amplitudes and low vibration frequencies of the oscillating hot gas flow.

With the described here, particularly preferred embodiment of the invention, however, it is possible, in the outwardly gas and heat sealed reactor housing the actual reaction space of the material treatment, d. H. to position the second resonator or the use having an axial extension at exactly that point at which the product experiences the strongest change in its material properties that can be achieved in accordance with the individual step or physical sub-process of the thermal material treatment taking place there compared to a thermal treatment in a stationary one Hot gas flow without vibrations.

Such an optimizing position of the insert can easily be determined in preliminary tests by repeating the material treatment in differently positioned use within the reactor space on the basis of the measured material properties of product samples manufactured in this way.

It should be mentioned as a particular advantage that the material after passing through the thermal treatment in the second resonator with a reduced diameter over a certain length with increased flow rate resulting from mass constancy at accordingly high treatment frequencies and short residence time (typically below 200 milliseconds, preferably below 100 milliseconds) in the downstream reactor section with again increased reactor diameter and therefore markedly reduced flow speeds undergoes a thermal aftertreatment, which can be used for complete degradation of unwanted residual components of the raw material mixture / raw material solution.

For example, when processing a nitrate-containing raw material of the residual nitrate content in the product or organic components in the raw material, the residual carbon content in the product significantly reduced or completely avoided. To ensure this safely, after-treatment periods in the reaction space downstream of the second resonator are greater than 2 seconds, preferably greater than 3 seconds.

Finally, it should be pointed out that the insert or resonator displaceable in its axial position in the reaction space can also be designed such that it is adjustable in terms of its resonance frequency, in particular by the change or adjustment of its axial length, that is to say tuned in terms of frequency.

Typically, finely divided particles with an average particle size in the range from 5 nm to 100 μm can be produced with the device according to the invention and the associated method. By means of this process according to the invention, finely divided particles, for example in the form of carbides, nitrides, simple oxides, complex mixed oxides, doped oxides, mixtures of oxides or coated particles can be produced in a targeted manner.

For this purpose, a so-called precursor mixture is produced from educts, which contains at least all constituents of the solid particles to be formed.

For the special case that only one reactant is needed, the term precursor mixture will nevertheless be used below.

The precursor mixture formed from the raw material components can be used both as a solid, for example in the form of a finely divided Powder or powder mixture, in the form of a solution, a suspension, a dispersion or a gel, as a gas or vapor.

When using liquid mixtures of raw materials, such as solutions, dispersions or emulsions result in particularly spherical particles.

By means of a single-stage or multi-stage wet-chemical intermediate step, the precursor mixture can be conditioned so that a specific particle shape or size is established in the thermal process, for example a particularly narrow particle size distribution. Known methods such as co-precipitation or hydroxide precipitation can be used for the wet-chemical intermediate step.

The mentioned forms of the precursor mixture are introduced into the hot gas stream of the device according to the invention, for example by spraying, introduction or injection. The nature of the precursor task, such as the type, diameter and spray pattern of a multi-fluid nozzle used for this purpose, the direction of feed (e.g., direction of injection), and feed location, influence the process control and the resulting thermal treatment regime and are thus important control factors for the resulting particle properties.

The forming particles are transported with the hot gas stream through the reactor and thermally treated in this hot gas stream. The properties of the hot gas stream thus significantly influence the thermal treatment and thus the properties of the forming particles. The device according to the invention offers a multitude of possibilities for the targeted setting of process parameters for the inventive thermal production and / or treatment of these finely divided particles. For example, the temperature profile, the maximum process temperature, the residence time of the gas flow and the residence time of the particles in the gas flow can be adjusted in a manner known to the person skilled in the art. A special feature of the device according to the invention is that the hot gas stream can be set in vibration. In oscillating or pulsating hot gas flows results in a significantly increased heat transfer due to the high flow turbulence. The heat transfer significantly influences the reaction and phase-forming mechanisms during the transformation or phase formation. By choosing the frequency and amplitude of the pulsating gas flow, the reaction conditions can be adapted exactly to the requirements of the material to be produced.

In the device according to the invention, it is possible to use the gas space of the thermal material treatment, i. to excite the second resonator by an external, periodic excitation for resonating. In the case of resonance, this results in an 8-10 times higher amplitude of the gas column oscillation in the thermal material treatment within the second resonator than in an excitation with frequencies outside this resonance band. The resulting higher amplitudes significantly increase the heat and mass transfer.

Even higher frequencies increase the heat and mass transfer significantly. Since the device according to the invention also high harmonic frequencies, ie very high frequencies, for example, in the range greater than 300 Hz can be generated, this results in a further adjustment parameters for a particularly high heat transfer.

The rate of heat transfer significantly defines the heating rate of the precursors or particles and thus the actual temperature profile. Higher amplitudes and higher frequencies of the pulsating gas stream accelerate the reaction and phase-forming mechanisms. Thus, for example, a higher degree of reaction conversion of the precursor mixture can be achieved with a comparable residence time, or the activity can be increased in, for example, catalytic materials. The inventive possibility for significantly higher amplitudes and higher frequencies than conventional Systems thus expands the possibilities for process control, expands the possible spectrum of substances to be treated, disseminates the adjustable particle properties and simplifies process control.

Depending on the material system, the frequency and amplitudes of the oscillating hot gas flow have different effects on partial reaction steps such as drying, heating, (time) different phase reactions, cooling, etc. and thus on the particle formation and / or the thermal particle treatment.

With the device according to the invention and the method according to the invention, the reaction section or the reaction sections in which, for example, the desired influence by high amplitudes and frequencies is particularly strong, can be selected specifically by the axial positioning of the second, a certain axial extent resonator within the reactor and the location of the precursor mixture is selected accordingly. In a particularly preferred embodiment, at least partial coating of particles takes place by means of a suitable precursor combination of a prepared precursor mixture in the form of a dispersion. In this case, for example, the solid phase in the case of suspensions or the inner phase in the emulsion at least includes all components which are necessary for the formation of the particles to be coated. The liquid phase in the suspension or the outer phase in the emulsion contain at least all coating components. By choosing a suitable thermal treatment regime, it is thus possible to form the solid particles and at least partially coat these particles.

The finely divided particles produced in the pulsating hot gas stream according to the invention are finally separated from the hot gas stream with a suitable separator. The hot gas is optionally before it enters the separator on a per cooled according to the type of separator required temperature. In a preferred embodiment, the separation of the particles formed from the hot gas stream at temperatures above 300 ° C, preferably above 500 ° C, more preferably above 600 ° C, for example by a cyclone or a hot gas reactor. This can be prevented, for example, that highly reactive particles hot gas components, such as water record. The hot gas can be cooled in this embodiment, if necessary after the filter.

Further advantages and features of the invention will become apparent from the following description of exemplary embodiments. Showing:

Figure 1 is a schematic diagram of a device for the thermal treatment of a raw material with a combustion chamber, a reaction space and an integrated in the reaction space insert, wherein the combustion chamber is variable in geometry;

2 shows the schematic diagram of a device according to FIG. 1 with a different variability of the combustion chamber geometry.

In Fig. 1 shows the schematic diagram of a reactor for the thermal treatment of a raw material within a periodically-unsteady oscillating hot gas stream. This hot gas stream is generated by a flame 1 on a burner 2, for which purpose this fuel 3 and combustion air 4 are supplied. The flame 1 burns in a combustion chamber. 5

Fuel is understood to be fuel gases such as natural gas, methane, hydrogen or liquid fuels such as alcohol, etc. For the purposes of this application, combustion air is generally understood to mean an oxidizing agent which provides the oxygen required for combustion. In addition to air, this includes, for example, pure oxygen or oxygen-enriched air, etc. In principle, it is possible to operate the flame in a foreign-controlled manner by means of a corresponding oscillating supply of the flame with a periodically modulated fuel / air mixture or with a temporally periodically modulated flow of combustion air. The variability of the mass flow of fuel / air mixture is particularly preferred in the case of premix combustion or a change in the mass flow of the combustion air, in particular in the case of a diffusion combustion. Incidentally, the combustion is operated so that it has a periodic-transient, oscillatory operating state. In this case, the frequency of the pulsating combustion is influenced, for example, by the geometry of the combustion chamber and by the process temperature. The pulsating hot gas flow ultimately generated with the pulsating flame flows through a coupling tube 6 into a reaction space 7 whose wall 8 is gas- and heat-proof. The heat-sealing can be ensured in particular by a separate insulation. In the effluent from the coupling tube 6 exhaust stream 9 is on the one hand to be treated raw material 10 abandoned as well as cooling air 11. This forms a hot gas stream 12 which flows through the reaction chamber 7 and passed at the end by a hot gas filter or cyclone, not shown here is, in which the raw material 10 thermally treated in the reaction chamber 7 is separated from the hot gas stream.

It is now essential that an insert 13 is provided in the reaction space 7, which has a cross-sectional area 14 reduced in relation to the reaction space 7 over a certain length extending in the axial and flow directions.

In the example shown here, this insert 13 is formed as a single tube and has a flow-through axial length 15, which has only a fraction of the total length of the reaction chamber 7. In addition, the Insert 13 substantially gas-tightly connected to the wall 8 of the reaction space, so that the hot gas flow 12 flows completely through the radially inward internal free cross section of the insert 13, but not laterally past this.

The insert 13 is adjustable in its axial length 15, so that there is the possibility to adjust it in its length such that it is tuned to the oscillation frequency of the periodically unsteady combustion process in the combustion chamber 5 so that the excited by this periodically unsteady hot gas flow 12 is excited resonantly as it passes through the insert 13 and thus passes in the field of this insert 13 in a foreign or forced excitation vibration. The resonances of the excitations, which are caused by resonance, can go up to a factor of 10.

The resonant frequency within the insert 13 is dependent, in particular, on the temperature of the hot gas stream 12, since this temperature influences the speed of sound relevant for resonance production. Furthermore, the resonance frequency is also dependent on the axial length 15 of the insert 13.

The insert 13 is referred to below as the second resonator.

In the example shown here, the combustion chamber 5 is adjustable by the presence of a displaceable bottom 16. In the following, the assembly described so far is also referred to as the first resonator. With the adjustability of the first resonator, a further manipulated variable can be adjusted by way of which a true resonance within the second resonator, thus of the insert 13, in the reaction space 7 can be adjusted.

In order to illustrate and illustrate the meaning and operation of two frequency tunable resonators in the reactor described herein, an exemplary Calculation presented without, however, wanting to restrict the general validity by this concrete example calculation:

The first resonator with the combustion chamber 5 should be designed as a ¹ /4-wave resonator with a variable length between 0.5 m and 1.0 m. Due to the adjustable burner / flame parameters (fuel gas mass flow, air mass flow, air ratio, preheating temperature of the air, etc.), the flame 1 is stable oscillating burn in a temperature range of the flame 1 and the exhaust stream 9, which is generated by the flame 1, between 800 ° C and 1,800 ° C. Depending on the selected combustion temperature, sound velocities of between about 630 m / s and 830 m / s are established in the first resonator. (For simplicity, only air as the medium is used here and not with the complete exhaust gas composition.) According to the set length of the first resonator, oscillation frequencies occur when self-excited combustion oscillations occur in the first resonator between approx. 160 Hz and approx. 420 Hz. The lowest temperature of about 800 ° C and the maximum length of the first resonator of 1.0 m give, for example, the lowest frequency of the oscillating ^quarter-wave resonator of approximately 160 Hz. with this, the subsequent second resonator can be excited in the reaction chamber to resonance.

In the insert 13 as a second resonator, which is designed as a ¹ /2-wave resonator, a thermal material treatment in the temperature range between 200 ° C and 800 ° C is to be made possible under resonant excitation of the second resonator by means of the adjustable combustion oscillation in the first resonator , The sound velocities in the second resonator are in the temperature range desired for the material treatment 430 m / s to 630 m / s.

In the case of a selected through-flow length 15 of the second resonator of 2.0 m, the resonance fundamental frequency would be approximately 160 Hz at the highest material treatment temperature of 800 ° C. and would therefore be just at the lowest, adjustable oscillation frequency in the first resonator at 800 ° C. Flame / exhaust gas temperature resonantly excitable. If, however, a material treatment temperature in the second resonator of 200 ° C. is desired, then the resonant frequency of the second resonator would be approximately 105 Hz at this temperature and a through-flow length 15 of the second resonator. The second resonator would therefore no longer be through the first resonator with its minimum Oscillation frequency at 800 ° C of 160 Hz resonant to the fundamental vibration excitable.

In this desired case, the length 15 of the insert 13 as a second resonator would have to be reduced to approximately 1.34 m in order to achieve a resonant frequency as a fundamental of approximately 160 Hz in the second resonator at 200 ° C. material treatment temperature first resonator at its minimum frequency of 160 Hz could be excited resonantly.

It is easy to see from the illustrated example the advantages that arise when both resonators can be tuned in frequency to one another and to the desired temperatures via individual geometry settings.

Another aspect of the present invention is that the insert 13 can be positioned in its axial position within the reaction chamber 7 according to the arrows 17 as needed. In the hot gas flow 12 conveyed raw material particles are thus first applied in the area before the insert 13 with the hot gas flow 12 with the present in the reaction chamber 7 frequency and amplitude, then within the free cross section 14 over the length 15 of the insert 13 from there due to the constant mass at least flowing at elevated speed hot gas flow and then back in the again because of the mass constancy at a slower speed flowing hot gas flow in no longer limited in cross-section region of the reaction chamber. In this case, with a corresponding coordination of the vibration generated in the combustion chamber 1 and the length 15 of the insert 13, the flow through the insert 13 are brought into resonance not only with a fundamental but possibly also with a harmonic, which correspondingly increases the intensity of the thermal treatment effected in the region of the insert 13.

If the raw material consists of a mixture of raw materials, in which it makes sense to have different intensities of the thermal treatment in time, this can thus be adjusted accordingly by the appropriate axial position of the insert 13 is selected within the reaction chamber 7, if necessary.

In FIG. 2, a substantially same device as shown in Fig. 1 is shown. In this case, the combustion chamber 5 differs by the way it is tuned as a resonator to the flame 1 burning in it. Instead of changing the volume of the combustion chamber 5 via a displaceable bottom, as shown in FIG. 1, a tubular insert 18 surrounding the flame 2 on the burner 2 in the radial direction is provided in this embodiment, which is displaceable in the axial direction 19 of the combustion chamber 5 so as to be able to tune the vibration generated in the combustion chamber 5 accordingly on the insert 13 with its reduced cross section 14 and its axial length 15, so as to resonate with respect to the hot gas flow 12 flowing therethrough.

literature

III A.A. Putnam and W.R. Dennis: "Organ Pipe Oscillations in Flamed Tubes"; Proc. Comb. Inst. 4, p. 556 ff., 1952

III H. Büchner: "Experimental and theoretical investigations of the development mechanisms of self-excited pressure oscillations in technical premix combustion systems" Dissertation University of Karlsruhe, Shaker-Verlag Aachen, 1992

131 DD 114 454 Bl

141 DD 155 161 Bl

151 DD 245 648 AI

161 DE 10 2006 046 803 AI

171 DE 101 09 892 B4

181 DE 10 2006 046 880 B4

191 DE 10 2006 032 452 B4

/ 10 / Chr. Bender: "Measurement and Calculation of the Resonance Behavior-Coupled Helmholtz Resonators in Technical Combustion Systems" Dissertation Universität Karlsruhe KIT, 2010 LIST OF REFERENCE NUMBERS

1 flame

2 burners

3 fuel

4 combustion air

5 combustion chamber

6 coupling tube

7 reaction space

8 wall

9 exhaust gas flow

10 raw material

11 cooling air

12 hot gas flow

13 use

14 cross-sectional area

15 Axial length

16 Adjustable bottom

17 arrows

18 pipe insert

19 axial direction

Claims

claims

1. A device for the thermal treatment of a raw material (10), with a combustion chamber (5) in which a periodically unsteady, oscillating flame (1) burns to produce a pulsating exhaust gas stream (9) by a to the combustion chamber (5) subsequent Reaction space (7) flows,

characterized,

in that in the reaction space (7) there is provided an insert (13), which is flowed through by the exhaust gas flow and reduced in its cross-sectional area (14) with respect to the reaction space (7), having a length (15) which is shorter than an overall length of Reaction space (7).

2. Device according to claim 1,

characterized,

that the length (15) of the insert (13) is variable.

3. Apparatus according to claim 1 or 2,

characterized,

that the combustion chamber (5) is variable in its geometry.

4. Device according to one or more of the preceding claims,

characterized,

that the flame (1) is externally excitable to vibrations.

5. A method for the thermal treatment of a raw material in a periodically unsteady oscillating exhaust gas stream (9) which is generated by a periodically unsteady oscillating flame (1), wherein the exhaust gas stream is passed through a reaction space (7),

characterized, the exhaust gas stream is excited into a resonant oscillation in an insert (13) provided in the reaction space (7) with a reduced cross-sectional area compared to the reaction space (7) and a shorter length (15) than the total length of the reaction space (7).

A process for the production of finely divided particles in which the finely divided particles form from a precursor mixture which comprises at least all components for forming the finely divided particles, wherein the particle formation and / or a thermal particle treatment takes place in a vibrating exhaust gas stream and the particles subsequently formed from Exhaust stream are separated,

characterized,

that the oscillating exhaust gas flow in a section is excited resonantly.