DE102007041801B4 - Process for heating a solid bed and a corresponding device thereto - Google Patents

Abstract

A method for heating a solid bed (11), the solid bed (11) having at least one inflow area for a carrier gas to flow into the solid bed (11) and at least one downstream area for the carrier gas to flow out of the solid bed (11), with the following method steps: of electromagnetic radiation in the solid bed (11), - introduction of a transfer medium into the inflow area or another area of the solid bed (11) and simultaneous flow through the solid bed (11) with a carrier gas, - the solid bed (11) at least one adsorbing the transfer medium Contains component and the transfer medium is at least partially adsorbed on the solid bed (11), and - at least part of the electromagnetic radiation is absorbed by the transfer medium, - lingering of the transfer medium in the solid bed (11), the transfer medium increasing the energy absorption of the solid ffbettes (11) initiated, which leads to a heating of the solids bed (11), - heating of the solids bed (11) due to the increased energy absorption of the solids bed (11), - desorption ...

Description

The invention relates to a method and apparatus for the selective and selective heating of solid beds and to initiate a coupled material and energy flow using modified with ionic substances solids having the features mentioned in claims 1 and 31. Advantageous embodiments of the invention are contained in the subclaims.

The heating of solids, in combination with numerous physical, chemical and biological processes, is a widespread technical problem. While a variety of efficient methods are available for the heating of gaseous and liquid media, the heating of solids is still considered to be a major development, since bulk beds usually have a low effective thermal conductivity and are usually not mixed during the process can. In addition to the established methods based on indirect heating via interfaces with contact to the packed bed or via a carrier gas flow, the dielectric heating methods are characterized by the fact that the heat is generated directly in the volume of the material and therefore heat conduction processes have less importance. For direct dielectric heating usually microwaves (MW) or radio waves (RW) are used, which typically have frequencies in the GHz or MHz range. In contrast to MW, RW have greater penetration depths in most materials, so that the latter can be used to heat larger volumes. In the RW application, moreover, an electronic matching network can ensure energy transfer in media having different or varying dielectric properties during heating without major losses.

A special feature of dielectric heating methods compared to conventional methods, which are based on the heat conduction into the medium or within the material, is that specifically temperature differences can be established within a packed bed. This can be achieved, for example, by providing substances with different dielectric properties and thus different energy absorption. The establishment of internal temperature gradients has considerable application potential for a number of technical processes, for example in bifunctional catalysis.

The technical processes in connection with fixed beds are usually associated with material flows through the fixed bed, which take place via the carrier gas flow. The transported substances interact with the bed, so that processes such as adsorption and desorption, chemical reactions or separation processes can take place.

When conventional heating methods are used, the temperatures are over a longer period of time, since the heating rates and the heat removal are limited, and spatially constant. Consequently, the temperature can only be used to a limited extent as a process parameter. In order to overcome this limitation, according to the invention, when using a suitable transfer medium, dielectric energy can be used to initiate coupled energy and material stream pulses passing through the fixed bed, so-called thermochromatographic pulses ( DE 10 2006 062 651 A1 and DE 10 2006 062 652 A1

However, this method is practically limited to certain combinations of solid and transfer medium. For the process of a thermochromatographic pulse, in particular the dielectric properties of the fixed bed material and above all the dielectric loss factor are of importance. If these parameters are not in a corresponding range, it is not possible to initiate a stable pulse passing through the fixed bed by the parallel application of a transmission medium and an external high-frequency electric field. The consequence of this is that a number of materials which are particularly suitable for the respective technical process are not available for heating with a thermochromatographic pulse. This is the case, for example, for hydrophobic zeolites, which have particularly good sorption properties with respect to organic pollutants and are thus predestined for adsorptive purification of exhaust air streams and thermal regeneration by means of dielectric heating.

An object of the present invention beyond the optimization of the heating process is to provide a way of modifying solids with which materials are to be changed so that they become accessible to heating with a thermochromatographic pulse and, moreover, a method using such to describe modified solids that include optimized dielectric heating. This is intended to overcome the limitations of the prior art and to significantly expand the material basis for the specific heating process. It should be made available a range of materials that are optimized both for the respective processes optimized properties such. B. adsorption capacity or catalytic activity and can be heated by means of a thermo-chromatographic pulse.

This object is achieved by the features in the characterizing part of claim 1 (method claim) and claim 31 (device claim) in cooperation with the features in the preamble. Advantageous embodiments of the invention are contained in the subclaims.

The process according to the invention involves the use of a starting material treated with ion-containing substances, which has the desired properties according to the process or obtains these properties by the treatment, and, if required, an aftertreatment which realizes the desired dielectric properties with respect to the thermochromatographic pulse. It is desirable that the material substantially or completely retains the initial process-adequate properties, such as sorption capacity or catalytic activity, and additionally obtains the dielectric properties through treatment with an ion-containing material. The inventive method for heating a solid bed, which has at least one Anstrombereich for influx of a carrier gas into the solid bed and at least one Abstrombereich for discharging the carrier gas from the solid bed, thus has the following overall process steps: 1) introduction of electromagnetic radiation in the solid bed 2) introduction a transfer medium into a region of the solid bed, the transfer medium absorbing at least a portion of the electromagnetic radiation; 3) flow through the solid bed with a carrier gas; 4) interaction of the transfer medium with the solid bed, wherein the transfer medium initiates increased energy absorption in the corresponding region of the solid bed; 5) heating of the solid bed due to increased energy absorption; 6) Mobilization of the transfer medium due to the heating of the solid bed and transport of the released transfer medium with the carrier gas stream, wherein the solid bed includes a treated with ionic materials material or treated prior to introduction of the transfer medium with at least one ion-containing material. The coupled, pulsed mass and energy propagation in the solid bed is referred to as a thermo-chromatographic pulse (or simplifying as a temperature pulse).

The materials forming the solid bed are preferably pourable and have particle sizes in the mm range, it being possible to use different geometries adapted to the respective use, such as, for example, spheres, rods or rings. For a variety of applications in the field of adsorption and catalysis are porous materials such as zeolites of different structure, porous metal oxides or activated carbon. Among these, zeolites, porous alumina or silica gel are used in particularly preferred use variants.

In order to modify these materials in order to make them useful for the initiation of a selective dielectric heating with a continuous temperature pulse, preferably salts are used, which are introduced into the material by impregnation with an aqueous solution. For the choice of the type of salt, the change in the dielectric properties and the binding ability of the cations or anions to the material to be treated are of great importance.

Preferably, water-soluble salts are used to modify the materials. For the same or comparable physical-chemical properties of the prepared materials, price and possible toxicity play a role in the selection of the salts used. Preferred ionic substances are sodium, potassium, calcium or magnesium salts. Chloride, sulfate, sulfite, nitrate or carbonate ions are preferably used as anions.

The mass content of the salt to be adjusted in the impregnated samples in turn depends on the specific material properties. In particular, the specific surface of the material to be impregnated, the water solubility of the salt and the pore diameter in porous materials play a role. Preference is given to mass contents below 5%, since otherwise constipation of the pore system or crystallization of the salts is likely. Another aspect to consider is that porosity may be important to the process to be supported. For example, for the regeneration of adsorbent beds by a thermo-chromatographic pulse, it must be taken into account that the impregnation must not impair the access of the molecules to be adsorbed to the pore system. Salt contents of between 2 and 5% by mass are particularly preferred, since salt contents that are too low can often not achieve the desired effect.

The interaction of the aqueous salt solution with the material to be impregnated should preferably be more than 30 minutes, more preferably several hours.

The method according to the invention for heating a solid bed comprises the following method steps: 1) introduction of electromagnetic radiation into the solid bed containing a material treated with ion-containing substances, 2) introduction of a transfer medium into the paint area or another area of the Solid bed and simultaneous flow through the solid bed with a carrier gas, wherein the solid bed contains at least one component adsorbing the transfer medium and the transfer medium is at least partially adsorbed on the solid bed, wherein the transmission medium absorbs at least a portion of the electromagnetic radiation, 3) residence of the transfer medium in the solid bed such, 4) heating of the solid bed due to increased energy absorption of the solid bed, 5) desorption of the transfer medium due to heating of the solid bed, and 6) transport of the desorbed transfer medium through the transfer medium Solid bed by means of the carrier gas stream, wherein the solid bed according to the invention prior to introduction of the transfer medium with at least one ion-containing substance treated elt becomes.

The treatment of the starting material involves the impregnation of a solid with an ion-containing compound, which is preferably present as an aqueous solution. Particularly preferred is the use of aqueous salt solutions. The impregnation is preferably carried out so that the ions are distributed homogeneously over the material to be impregnated. In a further sub-step, this material can be post-treated. Particularly preferred is the drying of the material. This process can take place, for example, in a dry gas stream or in a vacuum. Preferably, this process can be supported by increasing the temperature.

The material thus treated is preferably used in a fixed bed in particulate form as a bed. By the simultaneous application of a transmission medium and an external electromagnetic field, a selective heating is achieved, which leads to the initiation of a fixed bed passing through the coupled temperature and substance pulse.

This so-called thermochromatographic pulse can be used for a variety of processes such as zone heating of fixed beds, targeted separation of streams, influencing chemical reactions by preferential mobilization of one or more reaction products, temporary heating of fixed beds or targeted desorption of substances be used. The drying of a fixed bed, which can also be realized with this method, can be regarded as a special case of a desorption process (water desorption). Characteristic for the thermo-chromatographic pulse is the resulting temperature difference between the peak temperature in the bed and the bed temperature, which usually corresponds to the starting temperature. This temperature difference is in addition to the process parameters specific power input or amount of the transmission medium mainly on the type of salt, the charge and size of the introduced cations and anions and their concentration dependent. The salt concentration and thus the resulting ion concentration has an optimum for many materials, in which the selective increase in temperature for the material system is maximum. On the other hand, treatment of the solid should not result in impermissibly restricting properties relevant to the process, such as specific surface area or sorption capacity. Accordingly, the previous discussion applies not only to salts, but to ion-containing substances as well.

The initiation of a thermochromatographic pulse (temperature pulse) is bound to certain dielectric and other physical properties of the solid. According to the method, substances are used which are not suitable for the initiation of a thermo-chromatographic pulse without modification or in which the quality of the pulse with regard to the established temperature gradients and heating rates are not sufficient for the respective method. The modified substances, which have additional ions compared to the untreated starting material, however, allow the establishment of a thermo-chromatographic pulse under the relevant process conditions. Preferably, zeolites of different structure (dealuminated Y zeolites and others), γ-alumina, silica gel and / or activated carbon having certain properties may be used as matrices. The solid materials may also consist of mixtures or doped materials. In a preferred application, it is supported noble metal catalysts. The modification of the materials is preferably carried out by impregnation with a salt solution and subsequent drying.

Preferably, the heating of the solid bed by means of radio waves or microwaves.

Preferred fields of application of the invention are the coupling of adsorption with reaction processes, the focussing of chromatographic pulses associated with a concentration of selected substances, the discharge of thermally sensitive reaction products, the short-time activation of reactive zones in the fixed bed and the establishment of high heating rates with low thermal inertia.

The fixed bed is preferably flowed through continuously by the carrier gas, while the transfer medium is introduced discontinuously into the solid bed. Preferably, the transmission medium is at defined intervals in the Solid bed introduced, the corresponding time periods are process-dependent and are typically in the range between a few minutes and hours. Preferably, the transfer medium is metered every 5 to 60 minutes. The time for introducing the transmission medium is short compared to the interval. Preferably, the time for the dosage of the transmission medium is less than 60 s, which duration in turn depends on the specific technical process.

Preferably, transfer media are used whose dielectric loss factor, i. H. the imaginary part of the relative dielectric constant at the frequency used is large compared to the dielectric loss factor of the solid bed. Particularly preferred is the use of water as the transmission medium. For particularly preferred transfer media, the dielectric loss factor is more than three times the dielectric loss factor of the fixed bed material without transfer medium. Preferably, the transfer medium is introduced via the inflowing carrier gas or by direct injection into the solid bed. The injection is preferably carried out in the Anstrombereich the solid bed.

Preferably, the amount of transfer medium to be introduced is selected such that an interaction, for example by adsorption, of at least 50% (more preferably 80% and more preferably at least 99%) of the incorporated transfer medium is in a range less than 50% (more preferably 30%). and more preferably 15%) corresponds to the length of the solid bed. The length of the solid bed is understood here to be the distance of a representative carrier gas molecule, which covers this on average from the initial flow point to the outflow boundary surface. In a tubular reactor, this is the bed length, in a U-tube, the central axis of the bent glass tube.

The initiation of a thermochromatographic pulse (temperature pulse) is bound to certain dielectric and other physical properties of the solid. Preferably, zeolites of different structure (faujasites such as NaY zeolite, ZSM-5 and others), γ-alumina, silica gel and / or activated carbon can be used as matrices, which, however, are pretreated according to the invention. The solid materials may also consist of mixtures or doped materials. In a preferred application, it is supported noble metal catalysts.

Preferably, the heating of the solid bed by means of radio waves or microwaves. Since the heating of the solid bed is to be initiated by the energy absorption of the transfer medium, the use of porous solids with a correspondingly large adsorption capacity as a fixed bed material is preferred. Preference is given to using porous zeolites, metal oxides or activated carbons with mean pore sizes in the nanometer range.

In order to initiate a thermochromatographic pulse, the amount of the transfer medium to be introduced and the intensity of the electromagnetic radiation coupled into the fixed bed are preferably selected such that the solid bed is heated to a temperature in the region in which the transfer medium is adsorbed at least 60% (more preferably 80% and more preferably over 90%) of the adsorbed transfer medium are desorbed. Preferably, the solid bed is heated prior to introduction of a transfer medium such that adsorption of at least 90% of the introduced transfer medium takes place in a range which corresponds to less than 30% of the length of the solid bed.

Preferably, a desired speed of the transfer medium in accordance with the process characteristics through the solid bed due to repeated adsorption, heating, desorption and further transport by carrier gas by the choice of the material of the solid bed and the transmission medium and the choice of the parameters dosage amount and metering rate of the transmission medium and intensity of the electromagnetic radiation , This speed, the speed of the thermochromatographic pulse as it moves through the fixed bed, is, for example, between 0.1 and 10 mm / min in preferred applications in the field of reaction technology.

The device according to the invention for the selective selective heating of a flow-through solid bed, which is connected to a means for dielectric heating of the solid bed, according to the invention comprises means for introducing a transfer medium for the purpose of initiating a heat and Stoffstrompulses passing through the solid bed. The fixed bed reactor has at least one upstream and at least one downstream opening.

Preferred solid bed materials are zeolites, γ-alumina, silica gel and / or activated carbon. Preferably, the means for introducing a transmission medium to a metering device for a liquid.

Preferably, the means for heating the solid bed by at least two electrodes suitable for dielectric heating characterized. Preferably, according to the invention, the means for heating the solid bed is characterized by at least two electrodes suitable for dielectric heating. Preferably, at least one electrode for generating an electromagnetic field in the solid is fed by means of a high-frequency generator (HF generator). The dielectric heating of the solid can be realized with different electrode geometries or with axial dipoles (antennas). Preferably, the solids bed is disposed between at least two electrodes suitable for dielectric heating and at least one of the electrodes suitable for dielectric heating is connected to a high frequency generator and at least one further of the electrodes suitable for dielectric heating is connected to the ground. Preferably, parallel, plate-shaped electrodes are used in pairs in order to realize the most homogeneous possible field distribution in the solid bed. Preferably, the solid bed and the at least two electrodes suitable for dielectric heating are arranged inside a shielding housing. The at least one electrode suitable for dielectric heating is preferably connected to the HF generator via an electronic matching network.

In a further preferred variant of the arrangement, the solid-bed reactor is connected to a device for producing microwaves in such a manner that the solid bed can be heated by means of microwaves.

Preferably, the means for flowing a gas mixture to a metering device and / or a gas analyzer and / or a gas humidity sensor. The means for discharging the gas mixture preferably has a flow meter and / or a gas analyzer and / or a gas moisture sensor.

Preferably, the device has at least one temperature sensor for measuring the temperature of the solid bed. In particularly preferred variants, the temperature sensors are arranged in the paint area and / or in the outflow area. In particularly preferred arrangements, fiber-optic temperature sensors are used which measure interference-free in electromagnetic fields.

Preferably, the device has a means for determining the loading of the solid bed with respect to the adsorption of a pollutant and / or a reactant. Preferably, the means for determining the loading of the solid bed is connected to a data processing / control unit, which in turn is connected to the RF generator and / or the at least one temperature sensor and / or the gas analyzers and / or the gas humidity sensors.

According to the invention, a targeted and selective heating of fixed beds by initiating a coupled material and energy flow can be realized. In this case, the coupling of energy into the fixed bed takes place in such a way that the desired spatial and temporal temperature and concentration profiles are achieved by the initiation of a thermo-chromatographic pulse.

The principle is that by a suitable medium electromagnetic energy is coupled into the fixed bed and thus a dielectric heating takes place. Through a thermally initiated continuous sequence of adsorption and desorption processes, a focused pulse of the coupling medium traverses the fixed bed in the same manner as a chromatographic column. Coupled with this is a continuous with the carrier gas flow temperature pulse, which in turn may be coupled with a mass transfer of different media.

The thermo-chromatographic heating of fixed beds can be used, for example, for the zone-wise heating of fixed bed reactors, for the targeted separation of streams, for influencing chemical reactions by mobilizing a reaction product or for the temporary heating of fixed beds.

Preferred fields of application of the invention are the coupling of adsorption with reaction processes, the focusing of chromatographic pulses associated with a concentration of selected substances, the discharge of thermally sensitive reaction products, the short-time activation of reactive zones in the fixed bed and the establishment of high heating rates with negligible thermal inertia.

The inventive method is based on the dielectric heating of a fixed bed, preferably by means of radio waves or microwaves (in a preferred frequency range between 100 kHz and 50 GHz) and thus a conversion of electromagnetic energy into heat directly in the volume of the material. The heating is thus not limited by heat transport processes over surfaces and interfaces. If the effects to be realized by the method according to the invention are not to be caused, the fixed bed is normally kept at a process-specific base temperature by introducing a basic power. This can also be the ambient temperature. In this case, no external heating is necessary during the respective periods. in principle it is also possible to maintain the base temperature by means of classical (non-dielectric) heating methods.

Compared with conventional dielectric heating, however, the novel process is characterized in that an increased energy absorption in the solid body is initiated by a suitable medium (transmission medium). Such a medium can be, for example, water, the effect of the increased energy input on the one hand based on the direct effect of water as a dipole molecule and on the other hand on the interaction of water with the fixed bed material. The latter mode of action has been demonstrated, for example, for the dielectric heating of zeolites. It has been shown that the increased dielectric loss in wet zeolites is due less to the dipole effect of the water itself than to the influence of the dielectric losses on cation movement by water adsorption.

By introducing the transfer medium into the fixed bed, a rapid dielectric heating, starting from the base temperature, is produced in the corresponding area. The external electromagnetic field must be switched on in any case. In general, the transmission medium is adsorbed at the base temperature on a fixed bed. Due to the increase in temperature, desorption and release of the transfer medium into the gas stream occur. This is associated with a Tran port through the solid bed and a repeated adsorption in the colder part of the solid bed. Due to the continuous coupling of electromagnetic energy, heating and desorption takes place a thermally initiated transport of the transfer medium through the fixed bed comparable to a chromatographic pulse. In addition to the transfer medium itself, other sorbable substances can be transported through the fixed bed (thermo-chromatographic effect).

The method is characterized in that under certain conditions, such as corresponding dielectric properties of the transmission medium and matrix, the time course of the injection of the transmission medium and gas flow very large temperature differences between base temperature and temperature in the pulse can be achieved. The transit time of the pulse through the packed column can be described very well by a process whose characteristic activation energy is closely correlated with the adsorption enthalpy of the transfer medium on the fixed bed matrix. For this reason, the duration of the thermo-chromatographic pulse generally decreases with increasing base temperature and rising peak temperature. This basic principle can be coupled with a number of technically relevant phenomena. So it is possible to release an already adsorbed substance and to transport with the pulse through the fixed bed. This transport can be linked to a chemical reaction that is thermally activated. Due to the strong temperature gradients in the vicinity of the pulse, a focusing of pulses, that is, an increase in the local concentration of the sorbed substances can be achieved. It is characteristic that the desorbed substances are generally only briefly in the range of high temperature, since the pulse transforms the fixed bed comparatively fast. Due to this fact, unwanted substance conversions, for example, in thermally sensitive substances can be avoided. Fields of application arise, for example, in the adsorptive removal of such substances from the gas stream and the subsequent regeneration of the adsorber bed or in the discharge of thermally sensitive reaction products in chemical conversions. In this context, the realizable fast heating and cooling processes can be very beneficial.

In general, the process according to the invention offers the advantage of far greater energy efficiency than conventional techniques, since heating processes in the solid bed can take place very effectively both spatially and in terms of time. The concentration of substances offers the option to remove them from the gas stream much cheaper and to recycle them after the regeneration of the adsorber.

The invention will be explained in more detail below with reference to embodiments.

Show it:

1 : a schematic representation of a device according to the invention for heating a solid bed and for initiating a thermo-chromatographic pulse (temperature pulse),

2 : with the in 1 shown device obtained measurement results (temperatures and mass flow of the transfer medium) during a complete passage of the transfer medium through the solid bed (due to repeated adsorption, desorption and transport by the carrier gas) according to a first exemplary embodiment of the method according to the invention,

3 the temperatures detected during the passage of the thermochromatographic pulse within the U-tube-shaped solid bed and the associated detection of the temperature pulse,

4 : with the in 1 shown device obtained for desorption of a hydrocarbon from the solid bed (temperatures, mass flow of the transfer medium and gas concentrations of the hydrocarbon toluene) during a complete passage of the transfer medium through the solid bed (due to repeated adsorption, desorption, transport of the transfer medium through the solid bed), which previously was loaded with hydrocarbon, according to a second exemplary embodiment of the method according to the invention, and

5 and 6 the with the in 1 shown device obtained measurement results (temperatures and mass flow of the transfer medium) during a complete passage of the transfer medium through the solid bed (due to repeated adsorption, desorption and transport by the carrier gas), was used as starting material for the packed bed γ-Al ₂ O ₃ , the was treated with saline solutions of different concentrations.

The bulk bed 11 was realized by filling a U-tube (inner diameter 8 mm) with a NaY zeolite in granular form (particle diameter about 1 mm) (bed length about 170 mm). The U-tube 11 was between two parallel plate electrodes 10 . 12 and thus formed the dielectric of a capacitor. The electrodes 10 . 12 were via an electronic matching network 13 using coaxial cables to a water-cooled HF generator 14 (Frequency 13.56 MHz, maximum power 1 kW) connected. In the solid bed 11 were fiber optic temperature sensors at various points 9 positioned, which allowed a continuous measurement in the electromagnetic field. Packed bed reactor 11 and Matchbox were from a shield case 16 surrounded by copper sheet to minimize the parasitic electromagnetic radiation into the environment. The carrier gas flow (dried air) through the solid bed was about 150 ml / min. In the inlet and outlet of the reactor 11 were humidity sensors 7 Installed. The overall arrangement is in 1 shown schematically.

The electrode 12 is via the electronic matching network 13 with the HF generator 14 connected. The latter are coupled with a control system PC. The other electrode 10 is grounded. The solid bed 11 has a paint area and a downflow area. The carrier gas is via a line 3 to which a metering device 5 , a gas analyzer 6 and a gas humidity sensor 7 are connected, over the Anstrombereich in the solid bed 11 directed. That from the solid bed 11 escaping carrier gas (air) is via the effluent area and a pipe 2 to which a flow meter 4 , a gas analyzer 6 and a gas humidity sensor 7 are connected, from the solid bed 11 directed. The solid bed 11 is formed in the present embodiment U-tube-shaped (see in particular 3 ), but the invention is not limited thereto. Rather, any type of solid bed with at least one Anstrombereich and at least one Abstrombereich is conceivable.

In a first trial phase the bulkbed became 11 heated with a power of 70 W to a base temperature of about 60 ° C. Due to the isotropic field and substance distribution, the temperatures achieved were within the fixed bed 11 almost constant. The transition to the second test phase was carried out by injecting a water pulse (about 50 μl, injection time <1 s) via direct water injection 8th in the Anstrombereich the solid bed 11 , This initiated a progressive temperature pulse, which passed through the solid bed in about 20 min. This was associated with a water pulse, which also left about 20 minutes after the solid bed with the carrier gas stream. Temperature and humidity curves are in 2 illustrated. In the 2 and 4 represents m. _{according to} the mass flow of the transfer medium (water) in the effluent, T _beginning represents the temperature of the solid bed 11 in the paint area, T _center represents the temperature in the middle of the U-tube; T _end represents the temperature of the solid bed 11 in the effluent and C _toluene represents the concentration of toluene in the effluent.

The maximum temperature reached in the pulse was about 220 ° C, the temperature difference to the base temperature thus about 160 K. The resulting strong temperature gradients within the solid bed 11 are also illustrated by means of an infrared image (through glass measurement) ( 3 ). It should be noted that approximately the same width of the water pulse was achieved in the effluent when the water was introduced as a transfer medium for a longer period at the base temperature in the reactor.

In a further embodiment (see 4 ), the above-described reactor ( 1 ) loaded with toluene via the gas stream at ambient temperature (concentration in the gas stream about 3000 ppmv, loading time 20 min). Subsequently, it was switched to pure, dried air as the carrier gas, the gas flow remained constant at 150 ml / min. After about 15 minutes, the desorption phase was initiated by the injection of a water pulse (40 μl) as the transfer medium. A coupled temperature and mass transfer pulse passing through the solid bed led to the in 4 shown concentration curves of water and toluene in the effluent of the packed bed reactor 11 , A subsequent analysis of the residual charge (<5% of the initial value) showed that the toluene was almost completely removed from the adsorbent bed by the thermochromatographic heating and a high temporary hydrocarbon concentration (maximum 1.1% by volume) was achieved. The latter aspect is relevant, for example, if the exhaust air is subsequently to be purified by a thermo-catalytic process or if reuse of the desorbate is intended.

With reference to the following embodiments ( 5 and 6 ), the use of materials treated with ionic substances will be explained in more detail.

In a first series of experiments, the starting material γ-Al ₂ O ₃ with a specific surface area of 280 m ² / g was treated with saline solutions of different saline concentrations. The resulting after drying NaCl content was between 0.1 and 20 wt .-%. The specific surface area of the material was not drastically reduced by the impregnation, for example, for a NaCl content of 5% by mass, it was 240 m ² / g after the treatment. The material with a mean particle diameter of about 2 mm was filled into a U-tube reactor (mass about 4.9 g) and then by a thermo-chromatographic pulse (water dosage 100 .mu.l, RF power 70 W, frequency 13 , 56 MHz) is dielectrically heated. The arrangement used is schematically in FIG 1 shown. The achieved temperature increase in the pulse is for the individual samples 5 refer to. If the same experiment was carried out with conventional temperature control to the same starting temperature, the water injection due to the heat of adsorption only led to a temperature increase of about 5 K. It is found that the dielectric heatability by means of thermo-chromatographic pulses on this system (NaCl / γ-Al ₂ O ₃ ) is optimal for medium salt contents.

In a second series of experiments, the starting material γ-Al ₂ O _{3 was} impregnated with different salts (NaCl, CaCl ₂ , Na ₂ SO ₄ ), the same mass content of about 4.7% by mass being set. As 6 clarified, the influence of different salts on the expression of thermo-chromatographic pulses under otherwise identical conditions (water dosage 100 .mu.l, RF power 70 W, frequency 13.56 MHz) was different. In the respective experiments was always the in 1 illustrated schematic arrangement used. The achieved temperature increases or temperature drops due to the thermo-chromatographic pulse are for the individual samples 6 refer to. If the same experiments were carried out with conventional temperature control at the same starting temperature, the water injection due to the heat of adsorption only led to a temperature increase of about 5 K.

LIST OF REFERENCE NUMBERS

1

diluent gas

2

exhaust

3

supply air

4

Flowmeter

5

metering

6

Gas analyzer

7

Sensor for gas humidity

8th

Water Direct

9

fiber optic temperature sensors

10

"Cold" electrode

11

Solid bed / packed bed

12

"Hot" electrode

13

Electronic adjustment network

14

RF generator

15

Control system PC with data recording

16

shield

Claims (37)

Process for heating a solid bed ( 11 ), wherein the solid bed ( 11 ) at least one Anstrombereich for flowing a carrier gas into the solid bed ( 11 ) and at least one outflow region for the outflow of the carrier gas from the solid bed ( 11 ), comprising the following method steps: introduction of electromagnetic radiation into the solid bed ( 11 ), - introduction of a transfer medium into the paint area or another area of the solid bed ( 11 ) and simultaneous flow through the solid bed ( 11 ) with a carrier gas, - wherein the solid bed ( 11 ) contains at least one component adsorbing the transfer medium and the transfer medium at least partially on the solid bed ( 11 ) is adsorbed, and - at least part of the electromagnetic radiation is absorbed by the transmission medium, - residence of the transmission medium in the solid bed ( 11 ), wherein the transmission medium increased energy absorption of the solid bed ( 11 ), which leads to a heating of the solid bed ( 11 ), - heating of the solid bed ( 11 ) due to the increased energy absorption of the solid bed ( 11 ), - desorption of the transfer medium due to heating of the solid bed ( 11 ), and - transport of the desorbed transfer medium through the solid bed by means of the carrier gas stream, characterized in that the solid bed ( 11 ) contains a material treated with an ionic substance or is treated with at least one ionic substance prior to introduction of the transfer medium. Process according to Claim 1, characterized in that the transfer medium in the solid bed ( 11 ) so long until the transmission medium increased energy absorption of the solid bed ( 11 ), which leads to a heating of the solid bed ( 11 ) leads by at least 10K. Process according to Claim 1, characterized in that the transfer medium in the solid bed ( 11 ) so long until the transmission medium increased energy absorption of the solid bed ( 11 ), which leads to a heating of the solid bed ( 11 ) leads by at least 50 K. Method according to one of the preceding claims, characterized in that as material for the solid bed ( 11 ) Solid particles with a size between 0.1 mm and 10 mm are used. Method according to one of the preceding claims, characterized in that the solid bed material ( 11 ) is treated with the at least one ion-containing substance for more than 30 minutes. Method according to one of the preceding claims, characterized in that a salt is used as the ion-containing substance. Method according to one of the preceding claims, characterized in that the solid bed ( 11 ) has a salt content of less than 20% by mass after treatment with the ion-containing substance. Method according to one of the preceding claims, characterized in that the solid bed ( 11 ) has a salt content of less than 5% by mass after treatment with the ion-containing substance. Method according to one of the preceding claims, characterized in that the solid bed ( 11 ) has a salt content of between 2 and 5% by weight after treatment with the ion-containing substance. Method according to one of the preceding claims, characterized in that the carrier gas continuously into the solid bed ( 11 ) is introduced. Method according to one of the preceding claims, characterized in that the transmission medium is not continuously in the solid bed ( 11 ) is introduced. Method according to one of the preceding claims, characterized in that the transfer medium at intervals in the solid bed ( 11 ) is introduced. A method according to claim 11, characterized in that the transmission medium is introduced periodically every 2 to 60 minutes. A method according to claim 11, characterized in that the transfer medium again in the solid bed ( 11 ) is introduced when the transfer medium the solid bed ( 11 ) has completely migrated due to repeated adsorption, heating, desorption and further transport by means of carrier gas. A method according to claim 12 or 13, characterized in that the introduction of the transmission medium takes place within a period of 90 s. Method according to one of the preceding claims, characterized in that the transmission medium via the inflowing carrier gas or by direct injection into the solid bed ( 11 ) is introduced. Method according to one of the preceding claims, characterized in that for the solid bed ( 11 ) a zeolite-structured solid, a porous metal oxide, silica gel and / or activated carbon is used. Process according to claim 17, characterized in that for the solid bed ( 11 ) a solid is used which contains at least one of the zeolites of the types NaY and 3A. Method according to one of the preceding claims, characterized in that water is used as the transmission medium. Method according to one of the preceding claims, characterized in that the heating of the solid bed ( 11 ) by means of radio waves or microwaves. Method according to one of the preceding claims, characterized in that the amount of the transfer medium to be introduced in such a way it is chosen that an initial adsorption of at least 50% of the introduced transfer medium takes place in a range which is less than 80% of the length of the solid bed ( 11 ) along the flow area. Method according to one of the preceding claims, characterized in that the amount of the transfer medium to be introduced is selected such that an initial adsorption of at least 80% of the introduced transfer medium in a range which is less than 50% of the length of the solid bed ( 11 ) along the flow area. Method according to one of the preceding claims, characterized in that the amount of the transfer medium to be introduced is selected such that an initial adsorption of at least 90% of the introduced transfer medium takes place in a range which is less than 30% of the length of the solid bed ( 11 ) along the flow area. Method according to one of the preceding claims, characterized in that the amount of the transfer medium to be introduced is selected such that an initial adsorption of at least 99% of the introduced transfer medium in a range which is less than 15% of the length of the solid bed ( 11 ) along the flow area. Method according to one of the preceding claims, characterized in that in the solid bed ( 11 ) contains at least one porous material whose average pore size is less than one micrometer. Method according to one of the preceding claims, characterized in that the amount of the transfer medium to be introduced and the intensity of the in the fixed bed ( 11 ) coupled electromagnetic radiation can be selected such that the solid bed ( 11 ) is heated in the region in which the transfer medium is adsorbed to a temperature at which at least 60% of the adsorbed transfer medium is desorbed. Method according to one of the preceding claims, characterized in that the amount of the transfer medium to be introduced and the intensity of the in the fixed bed ( 11 ) coupled electromagnetic radiation can be selected such that the solid bed ( 11 ) is heated in the region where the transfer medium is adsorbed to a temperature at which at least 80% of the adsorbed transfer medium is desorbed. Method according to one of the preceding claims, characterized in that the solid bed ( 11 ) is heated prior to introducing a transmission medium by means of electromagnetic radiation such that an adsorption of at least 90% of the introduced transfer medium takes place in a range which is less than 30% of the length of the solid bed ( 11 ) along the flow area. Method according to one of the preceding claims, characterized in that in the solid bed ( 11 ) high local temperature gradients are generated. A method according to claim 29, characterized in that the temperature gradient generated is at least 1 K / cm. Device for heating a solid bed ( 11 ), comprising: a solid bed ( 11 ) with a heating means for dielectric heating of the solid bed ( 11 ), the solid bed ( 11 ) with an inflow means ( 3 ) for flowing a carrier gas into the solid bed ( 11 ) and an outflow means ( 2 ) for the outflow of the carrier gas from the solid bed ( 11 ), and the solid bed ( 11 ) additionally with a means for introducing a transfer medium to initiate a solid bed ( 11 ) continuous heat and Stoffstrompulses is connected, characterized in that the solid bed ( 11 ) has a porous base material of solid particles having a size between 0.1 mm and 10 mm and at least one ion-containing material and the heating means for heating the solid bed ( 11 ) by at least two electrodes suitable for dielectric heating ( 10 . 12 ) is trained. Apparatus according to claim 31, characterized in that the salt content of the solid bed ( 11 ) is less than 5% by mass. Apparatus according to claim 31, characterized in that the salt content of the solid bed ( 11 ) is between 2 and 5 mass%. Device according to one of claims 31-33, characterized in that the solid bed ( 11 ) has at least one adsorbent component. Device according to one of claims 31-34, characterized in that the solid bed ( 11 ) contains as base material at least partially a zeolite, γ-alumina, other porous metal oxides, silica gel and / or activated carbon. Device according to one of claims 31 to 35, characterized in that the means for introducing a transmission medium comprises an injection device for a liquid. Apparatus according to claim 36, characterized in that the means for introducing a transmission medium containing a metering device for adding the transfer medium in the carrier gas stream.

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