WO2025156835A1 - Microwave heating system and method, and microwave heating apparatus - Google Patents

Abstract

A microwave heating system, comprising a container body (1). The container body (1) comprises at least one heating cavity (11); a microwave shielding element (15) is provided in the heating cavity (11); the microwave shielding element (15) divides the heating cavity (11) into a plurality of sub heating cavities; a microwave heating apparatus (3) and a heated carrier (2) capable of absorbing microwaves to generate heat are provided in each sub heating cavity; the microwave heating apparatus (3) is arranged on the side wall of the sub heating cavity; the microwave heating apparatus (3) comprises a dielectric radiator (33) made of a dielectric material; and the dielectric radiator (33) has a radiation section (331) located in the sub heating cavity and used for radiating the microwaves into the sub heating cavity so as to heat the heated carrier (2). The microwave heating system can effectively improve the uniformity of the microwaves heating a large-size heated carrier (2) and the microwave incident efficiency.

Description

Microwave heating system, method and microwave heating device Technical Field

The present disclosure relates to the technical field of microwave heating, and in particular to a microwave heating system, method and microwave heating device.

Background Art

Volatile organic compound (VOC) control and near-zero emissions are gaining increasing public attention. Current VOC control methods are primarily divided into destruction and recovery. Destruction offers irreplaceable advantages over recovery in that it can completely and instantly convert VOCs into _CO₂ and _H₂O . It can also convert methane into _CO₂ , achieving the complete incineration of small-molecule hydrocarbons.

Microwave catalytic oxidation is a promising development among existing destruction methods. Figure 1 shows an example of catalytic oxidation using microwave technology in the prior art. A catalytic oxidation vessel 100 comprises a catalyst bed 101, an inlet 102, an outlet 103, and a waveguide 104. The catalyst bed 101 contains a substance (i.e., a catalyst) that promotes chemical reactions in VOCs. As VOCs pass through the heated catalyst bed, the catalyst promotes their decomposition, converting them into harmless gases such as carbon dioxide and water vapor. As shown in the figure, microwaves are introduced into the vessel 100 via the waveguide 104 and absorbed by the catalyst bed 101, heating the catalyst bed 101 to a sufficient temperature to trigger the decomposition reaction of the VOCs. VOCs, which may originate from exhaust gases from various industrial processes, enter the vessel 100 through the inlet 102. The VOCs react in the catalyst bed 101, converting them into harmless carbon dioxide and water vapor. These carbon dioxide and water vapor are then discharged through the outlet 103.

Microwave catalytic oxidation technology offers significant advantages, including fast heating response, high heating efficiency, and energy savings. However, existing microwave catalytic oxidation technologies still suffer from numerous drawbacks. For example, as the catalyst bed size increases to the meter level, microwaves struggle to uniformly heat the large bed, potentially causing localized overheating of the catalyst material, impacting the overall efficiency and safety of the catalyst bed.

Furthermore, existing technologies lack the technology to heat the entire catalytic bed through penetration. The skin depth of the material limits microwave penetration, and microwaves typically penetrate less than 5 cm into absorbing catalysts. This makes three-dimensional penetration heating of meter-scale beds difficult, making industrial applications impossible.

In addition, microwaves are introduced into the catalytic oxidation container through a waveguide, where the absorbing material (such as the catalyst bed) absorbs the microwaves, and the microwaves that are not absorbed are reflected and returned through the waveguide, thereby affecting energy utilization.

Furthermore, most waveguides used to guide and transmit microwaves are metal leakage waveguides. There is current on the metal surface, and the electric field strength at the leakage gap is high, even higher than the breakdown electric field strength under humid air conditions, which poses certain safety hazards for handling flammable and explosive VOCs.

Summary of the Invention

The purpose of the present disclosure is to solve at least one of the defects of the above-mentioned microwave catalytic oxidation method and to provide a microwave heating system, method and microwave heating device.

To achieve the above-mentioned object, the present disclosure provides a microwave heating system in a first aspect, comprising a container body, wherein the container body comprises at least one heating cavity;

A microwave shielding element is provided in the heating cavity, which divides the heating cavity into a plurality of sub-heating cavities, each of which is provided with a microwave heating device and a heating carrier capable of absorbing microwaves to generate heat.

The microwave heating device is arranged on the side wall of the sub-heating cavity, and includes a dielectric radiator made of dielectric material. The dielectric radiator has a radiation section located in the sub-heating cavity, which is used to radiate microwaves into the sub-heating cavity to heat the heated carrier.

According to the microwave heating system described in the first aspect of the present disclosure, the microwave shielding element extends the entire length of the heating cavity, so that each sub-heating cavity is arranged in parallel, and dielectric radiators are installed oppositely on the side walls at both ends of each sub-heating cavity.

According to the microwave heating system described in the first aspect of the present disclosure, each sub-heating cavity includes an even number of dielectric radiators, and the even number of dielectric radiators are divided into two groups and symmetrically installed on the side walls at both ends of the sub-heating cavity.

According to the microwave heating system described in the first aspect of the present disclosure, the container body includes multiple heating cavities, the multiple heating cavities are stacked up and down, the heat carrier is arranged into a heat carrier layer in the upper part and/or lower part of the sub-heating cavity, and the temperature of the stacked multiple heating cavities is independently controlled or forms a temperature gradient from top to bottom.

According to the microwave heating system described in the first aspect of the present disclosure, the microwave shielding element is called a second microwave shielding element, and a first microwave shielding element is arranged between two upper and lower adjacent heating cavities for shielding microwaves.

According to the microwave heating system described in the first aspect of the present disclosure, the second microwave shielding element is a steel plate for shielding microwaves and blocking gas, and the first microwave shielding element is a steel mesh for shielding microwaves and allowing gas to pass through.

According to the microwave heating system of the first aspect of the present disclosure, the radiation section has a multi-faceted structure, and the multi-faceted structure includes a radiation surface facing the heated carrier and emitting microwaves to the heated carrier.

According to the microwave heating system of the first aspect of the present disclosure, the radiation section has a tapered multi-faceted structure, and the radiation surface has a tapered shape.

According to the microwave heating system described in the first aspect of the present disclosure, the tapered multi-faceted structure of the radiation section is a truncated pyramid structure, the radiation surface is two opposite surfaces of the truncated pyramid structure, and the radiation section also includes side surfaces adjacent to the two radiation surfaces respectively, and the area of the radiation surface is larger than the area of the side surfaces.

According to the microwave heating system described in the first aspect of the present disclosure, the truncated pyramid structure is a truncated quadrangular pyramid structure, and there are two radiation surfaces and two side surfaces.

According to the microwave heating system described in the first aspect of the present disclosure, the heating cavity has a rectangular cross-section, and the dielectric radiators on the two adjacent heating cavities are arranged on adjacent sides or non-adjacent sides. When the dielectric radiators are arranged on non-adjacent sides, the extension directions of the upper and lower dielectric radiators are perpendicular to each other.

According to the microwave heating system described in the first aspect of the present disclosure, the heated carrier includes a catalyst, and the container body is provided with a reactant inlet and a product outlet to allow the fluid reactant introduced through the reactant inlet to flow through the heated carrier to undergo a chemical reaction under the action of the catalyst.

According to the microwave heating system of the first aspect of the present disclosure, the length of the heating cavity in the length extension direction of the dielectric radiator is 2-4 times the extension length of the radiation section extending into the heating cavity.

According to the microwave heating system described in the first aspect of the present disclosure, the microwave heating device includes a microwave generating unit, the dielectric radiator extending into the sub-heating cavity through the side wall of the container body, and a waveguide for guiding the microwaves generated by the microwave generating unit to the dielectric radiator.

According to the microwave heating system of the first aspect of the present disclosure, the dielectric radiator further includes a coupling section extending in the waveguide and a transmission section extending between the coupling section and the radiation section, the coupling section having a tapered multi-faceted pointed structure.

According to the microwave heating system described in the first aspect of the present disclosure, the length of the coupling section is 0.75-1 times the microwave wavelength; the length of the radiation section is more than 0.8 times the microwave wavelength.

According to the microwave heating system of the first aspect of the present disclosure, the dielectric constant of the material of the dielectric radiator is greater than 9, and the dielectric loss is less than 0.02.

A second aspect of the present disclosure relates to a microwave heating device for use in the microwave heating system described in the first aspect of the present disclosure. The microwave heating device comprises a microwave generating unit, a dielectric radiator for radiating microwaves generated by the microwave generating unit to a heated carrier, and a waveguide for guiding the microwaves generated by the microwave generating unit to the dielectric radiator. The dielectric radiator comprises a radiating section located within the heating cavity, the radiating section having a tapered multi-faceted structure including a radiating surface facing the heated carrier and uniformly emitting microwaves thereto. The dielectric radiator is made of ceramic or polystyrene.

A third aspect of the present disclosure relates to an exhaust gas treatment method performed on the microwave heating system described in the first aspect of the present disclosure, wherein the microwave heating system includes a controller and a temperature sensor disposed on a heated carrier or in a heating cavity for real-time monitoring of the temperature of each heated carrier. The method includes:

receiving a measured temperature from the temperature sensor;

comparing the measured temperature to the target temperature;

outputting a control signal to a microwave generating unit in the microwave heating device based on a difference between the measured temperature and the target temperature, thereby controlling the microwave generating unit to generate microwaves to heat a heated carrier in the heating cavity; and

In response to the measured temperature being greater than or equal to the target temperature, the reactant inlet is opened to inject the exhaust gas containing volatile organic compounds.

A fourth aspect of the present disclosure relates to a controller, comprising:

processor, and

A computer-readable storage medium comprises a computer program stored thereon, wherein the computer program comprises executable instructions, and when the executable instructions are executed by the processor, the method according to the third aspect of the present disclosure is implemented.

A fifth aspect of the present disclosure relates to a computer-readable storage medium, comprising a computer program stored thereon, the computer program comprising executable instructions, which, when executed by the processor, implement the method according to the third aspect of the present disclosure.

A sixth aspect of the present disclosure relates to a computer program product, comprising executable instructions, which, when executed by a processor, implement the method according to the third aspect of the present disclosure.

Through the above technical solution, the microwave heating equipment and exhaust gas treatment system disclosed in the present invention can use microwaves to achieve uniform heating of the bed on a larger scale, the microwaves are distributed more evenly in the heating cavity (also called the reaction cavity or free space), and the bed heating is more uniform.

In the microwave heating equipment and microwave heating device disclosed in the present invention, the dielectric radiator itself does not generate current and does not generate heat, and is inherently safe when in contact with flammable and explosive gases.

In summary, the use of the microwave heating device described in the present disclosure to heat a large-scale catalyst bed has the beneficial effects of being inherently safe, having high microwave energy utilization, uniform microwave radiation, uniform heating of the bed, and having relatively low cost.

Compared with the existing technology, the technical solution disclosed in the present invention has more advantages in large-scale heating, and can achieve larger-scale heating of catalyst beds, which is convenient for realizing large-scale microwave reaction devices; moreover, heating is safer, the maximum electric field intensity in the reactor is much smaller than the electric field breakdown intensity in humid air, and there is no current on the radiator surface; furthermore, the technical solution disclosed in the present invention can be used in flammable and explosive places, especially when processing flammable and explosive gases, and the reactor can be intrinsically safe both inside and outside. In addition, by adding dielectric radiators and shielding elements, the overall heating of the catalyst bed by microwaves can be made more uniform, avoiding local high temperatures, causing safety problems or reducing the service life of the catalyst.

The technical solution disclosed in the present invention can be applied to microwave heating of large-scale solids, such as heating of microwave-absorbing solids such as microwave-absorbing catalysts or microwave-absorbing adsorbents, to achieve rapid heating of microwave-absorbing solids; heating of microwave-absorbing catalysts to participate in chemical reactions of gases or liquids to achieve efficient and rapid heating of catalysts; heating of microwave-absorbing adsorbents to be used in the field of environmental protection management of thermal desorption of adsorbents.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various examples of various aspects of the present disclosure, and together with the description, they serve to explain the principles of the present disclosure. Those skilled in the art will appreciate that the particular embodiments shown in the drawings are exemplary only and are not intended to limit the scope of the present disclosure. It should be appreciated that in some examples, one element may be designed as multiple elements, or multiple elements may be designed as one element. In some examples, an element shown as an internal component of another element may also be implemented as an external component of the other element, and vice versa. In the drawings:

FIG1 is an example of catalytic oxidation using microwave technology in the prior art;

FIG2 is a schematic cross-sectional view of a microwave heating system according to a preferred embodiment of the present disclosure;

FIG3 is a front view of a dielectric radiator of a microwave heating device used in the microwave heating system of FIG2 ;

FIG4 is a different projection view of the dielectric radiator in FIG3;

FIG5 is a front view of a variant embodiment of the dielectric radiator according to the present disclosure;

FIG6 is a schematic structural diagram of a microwave heating system according to another preferred embodiment of the present disclosure;

FIG7 is a cross-sectional view showing an arrangement of multiple microwave heating devices of the microwave heating system in FIG6 ;

FIG8 shows a top view of an arrangement of multiple microwave heating devices of the microwave heating system in FIG6 ;

FIG9 is a schematic structural diagram of a microwave heating system according to another preferred embodiment of the present disclosure;

FIG10 is a cross-sectional view showing an arrangement of multiple microwave heating devices of the microwave heating system in FIG9 ;

FIG11 shows a top view of an arrangement of multiple microwave heating devices of the microwave heating system in FIG9 ;

FIG12 is a schematic structural diagram of a microwave heating system according to another preferred embodiment of the present disclosure;

FIG13 is a schematic structural diagram of a microwave heating system according to another preferred embodiment of the present disclosure;

FIG14 is a surface temperature distribution diagram of heating using a microwave heating device without a dielectric radiator;

FIG15 is a diagram showing a surface temperature distribution of a microwave heating system using multiple dielectric radiators but without a first microwave shielding element;

FIG16 is a diagram showing a surface temperature distribution of a microwave heating system using a plurality of dielectric radiators and provided with a first microwave shielding element;

17 is a diagram showing a surface temperature distribution of a microwave heating system using a plurality of dielectric radiators and provided with a first microwave shielding element and a second microwave shielding element;

FIG18 is a temperature distribution diagram corresponding to heating performed by a microwave heating system in which microwave heating devices of adjacent heating cavities are installed on the same side wall;

FIG19 is a temperature distribution diagram corresponding to the microwave heating system in which microwave heating devices of adjacent heating cavities are installed on adjacent side walls;

FIG20 shows the electric field distribution cloud diagram of Example 6;

FIG21 shows the electric field distribution cloud diagram of Example 7;

FIG22 shows the electric field distribution cloud diagram of Example 8;

FIG23 shows the electric field distribution cloud diagram of Example 9;

FIG24 shows a cloud diagram of the electric field distribution of Example 10;

FIG25 shows a cloud diagram of the electric field distribution of Example 11;

FIG26 shows a cloud diagram of the electric field distribution of Example 12;

FIG27 shows a cloud diagram of the electric field distribution of Example 13;

FIG28 illustrates a method for treating exhaust gas using the microwave heating system of the present disclosure; and

FIG. 29 shows a controller according to an embodiment of the present disclosure.

Description of Reference Numerals
1-container body; 11-heating cavity; 12-reactant inlet; 13-product outlet; 14-first microwave shielding element; 15-second microwave shielding element;
2-heating carrier;
3-microwave heating device; 31-microwave generating unit; 32-waveguide; 32a-pin; 33-dielectric radiator; 331-radiation section; 331a-radiation surface; 331b-side surface; 34-explosion-proof excitation cavity; 332-transmission section; 332a-flange portion; 333-coupling section; 35-dielectric sealing window.

DETAILED DESCRIPTION

In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate relative importance or implicitly specify the quantity of the technical features indicated. Therefore, unless otherwise specified, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features; "plurality" means two or more. The term "comprising" and any variations thereof are intended to be non-exclusive inclusion, and one or more other features, integers, steps, operations, units, components, and/or combinations thereof may be present or added.

In addition, terms indicating orientation or positional relationships such as “up,” “down,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inside,” and “outside” are described based on the orientation or relative positional relationships shown in the accompanying drawings. They are merely simplified descriptions for the convenience of describing this application, and do not indicate that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on this application.

Furthermore, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly, and may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; or internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on specific circumstances.

The following describes in detail the specific implementations of the embodiments of the present disclosure in conjunction with the accompanying drawings. It should be understood that the specific implementations described herein are only intended to illustrate and explain the embodiments of the present disclosure and are not intended to limit the present disclosure. Moreover, for the sake of brevity, only the components closely related to the embodiments of the present application are described in detail below.

Referring to FIG. 2 , a microwave heating system according to an embodiment of the present disclosure is shown. The microwave heating system includes at least a container body 1, which includes at least one heating cavity 11. A heating carrier 2 and a microwave heating device 3 mounted on the side wall of the heating cavity 11 are provided in the heating cavity 11. The heating carrier 2 can absorb microwaves and heat up. The heating carrier 2 is arranged flat to form a layer, which can be called a heating carrier layer. As shown in FIG. 2 , the microwave heating device 3 is mounted on the side wall of the heating cavity 11 to emit microwaves into the heating cavity 11.

When used for treating exhaust gases (e.g., VOCs), a catalyst is disposed within the heated carrier 2 within the heating chamber 11. The heated carrier absorbs microwaves, raising its temperature and heating the catalyst, thereby causing a decomposition reaction in the exhaust gases flowing through the catalyst. Alternatively, the heated carrier 2 itself may be a microwave-absorbing catalyst, in which case the heated carrier layer becomes a microwave-absorbing catalyst bed.

2 , the microwave heating device 3 includes a microwave generating unit 31 , a dielectric radiator 33 extending through the container body 1 or the side wall of the heating cavity 11 into the heating cavity 11 , and a waveguide 32 for guiding the microwaves generated by the microwave generating unit 31 to the dielectric radiator 33 .

Dielectric radiator 33 is a dielectric rod antenna, a typical traveling wave antenna made of a low-loss, high-frequency dielectric material. The dielectric material is either a dielectric or insulating material (e.g., polystyrene or ceramic). Dielectric rod antennas guide microwave propagation. Compared to metal waveguides, considerable power overflows from dielectric boundaries into free space (e.g., heating cavity 11).

The portion of the dielectric radiator 33 used to emit microwaves toward the heated carrier within the heating cavity is called the radiation section. The inventors have discovered that by adjusting the shape of the radiation section of the dielectric radiator 33, the impedance of the dielectric rod antenna can be adjusted, thereby achieving a good match between the dielectric rod antenna and the air impedance and improving radiation efficiency. Moreover, by adjusting the shape of the radiation section of the dielectric radiator 33, the microwaves emitted by the radiation section can be distributed more evenly on the heated carrier, thereby achieving uniform heating of the heated carrier layer. Specifically, in the present disclosure, the radiation section of the dielectric radiator 33 adopts a multi-faceted shape, such as a gradually tapering multi-faceted shape or a multi-faceted tapered structure, such as a pyramid shape or a truncated pyramid shape, preferably a quadrangular pyramid shape or a truncated quadrangular pyramid shape. This multi-faceted structure can achieve a good match between the dielectric rod antenna and the air impedance, reduce surface wave reflections, improve radiation efficiency, and allow most microwaves to be radiated or emitted into the heating cavity 11. Furthermore, the multi-faceted structure can adjust the microwave radiation direction so that the microwaves are evenly radiated onto the heated carrier 2, resulting in uniform heating of the heated carrier 2 and the entire heated carrier layer. The multi-faceted structure of the dielectric radiator 33 will be described in further detail below with reference to FIGS. 3-5 .

Continuing with FIG2 , two or more heating carrier layers may be included, each located around the dielectric radiator 33, for example, above and below the dielectric radiator 33. The dielectric radiator 33 is configured so as to be located between two opposing heating carrier layers. In order to ensure that each portion of the heating carrier layer receives microwave radiation uniformly, the microwave heating device 3 may be symmetrically installed on both sides of the heating cavity 11 (left and right sides in the figure), so that the dielectric radiators 33 in the microwave heating devices 3 arranged on both sides are opposite to each other, and the opposing dielectric radiators 33 are located on the same straight line in the longitudinal extension direction.

3-5 , which illustrate the multi-faceted structure of dielectric radiator 33. As shown, dielectric radiator 33 may include a coupling section 333, a transmission section 332, and a radiating section 331. The coupling section 333 and the radiating section 331 are disposed on opposite sides of the transmission section 332, and each may be formed in the shape of a truncated quadrangular pyramid.

The dielectric radiator 33 is generally formed into a structure that is thin at both ends and thick in the middle. The truncated quadrangular pyramid shape of the coupling section 333 and the radiating section 331, for example, includes four side surfaces, each of which is trapezoidal. The truncated portion of the truncated quadrangular pyramid forms end faces, each of which is a quadrilateral, preferably a rectangle or square. As shown in FIG4 , the four side surfaces of the truncated quadrangular pyramid are two upper and lower opposing side surfaces 331a and two front and rear opposing side surfaces 331b. Preferably, the width (or area) of the upper and lower side surfaces 331a of the coupling section 333 and the radiating section 331 is greater than the width (or area) of the front and rear opposing side surfaces 331b. The upper and lower side surfaces 331a face the heat receiving carrier layer. In other words, the side of the truncated quadrangular pyramid with the larger area faces the heat receiving carrier layer. Accordingly, the side facing the heat receiving carrier layer can be referred to as the radiation surface. In summary, as shown in FIG2 , the radiation section 331 is located in the heating cavity 11 and is formed with a pair of radiation surfaces 331a facing the corresponding heat carrier layer and a pair of side surfaces 331b adjacent to the radiation surfaces 331a. The width (or area) of the radiation surface 331a can be greater than the width (or area) of the side surface 331b. In the direction toward the interior of the heating cavity 11, the radiation surfaces 331a of the two oppositely arranged dielectric radiators 33 extend close to each other, and the side surfaces 331b also extend close to each other, so that the radiation section 331 has a tapered multi-faceted structure. Through this arrangement, the microwaves generated by the microwave generating unit 31 can be uniformly radiated into the heating cavity 11 by the radiation section 331, especially by the radiation surface 331a to the heat carrier layer it faces efficiently and uniformly, thereby being able to uniformly heat the heat carrier layer over a large scale range.

In the dielectric radiator 33, the length of the coupling section 333 is preferably 0.75 to 1 times the microwave wavelength; the length of the radiating section 331 is preferably at least 0.8 times the microwave wavelength, more preferably 0.8 to 2.5 times the microwave wavelength. The microwave can be, for example, a 2450 MHz or 915 MHz microwave. When the microwave is a 2450 MHz microwave, the wavelength is approximately 122.4 mm.

In the dielectric radiator 33, the multi-faceted tapering angle of the coupling section 333 (i.e., the angle between the center line and the side surface in the length direction of the dielectric radiator) is preferably 5-85°, and the multi-faceted tapering angle of the radiating section 331 is preferably 5-85°.

In the microwave heating system, preferably, the size of the heating cavity 11 along the length extension direction of the dielectric radiator 33 is 2-4 times the length of the radiation section 331 extending into the heating cavity 11 .

In the present disclosure, preferably, the dielectric constant of the material of the dielectric radiator is greater than 9, and the dielectric loss is less than 0.02. Further preferably, the material of the dielectric radiator is ceramic or polystyrene.

As shown in FIG5 , the transmission section 332 of the dielectric radiator 33 may have a flange portion 332a. When mounted to the container body 1 or the heating cavity 11, the transmission section 332 passes through the side wall of the container body 1 or the heating cavity 11, and the flange portion 332 is in contact with the wall surface (outer wall surface or inner wall surface) of the container body 1 or the heating cavity 11, and the flange portion can be pressed and fixed to the side wall of the heating cavity 11 via a waveguide flange. This contact and fastening structure is used to prevent VOCs in the container body 1 or the heating cavity 11 from leaking into the microwave heating device 3 or into the external environment, causing explosion or pollution.

2 , the microwave heating device 3 described herein may include an explosion-proof excitation cavity 34. The microwave generating unit 31 may be a magnetron disposed within the explosion-proof excitation cavity 34. The explosion-proof excitation cavity 34 is connected to one end of the waveguide 32, and the other end of the waveguide 32 is connected to a dielectric radiator 33. The coupling section 333 of the dielectric radiator 33 extends into the waveguide 32.

In a preferred embodiment, the explosion-proof excitation cavity 34 is physically isolated from the waveguide 32 by a dielectric sealing window 35, and the microwaves generated by the magnetron can enter the waveguide 32 through the dielectric sealing window 35. In a specific embodiment, the dielectric sealing window 35 is a sealed quartz window. The dielectric sealing window 35 is used to prevent VOCs in the container body 1 and/or the heating cavity 11 from leaking into the explosion-proof excitation cavity 34 and causing explosion or contamination.

In a preferred embodiment, the waveguide may be further provided with a pin 32a, by which the microwave reflection power can be adjusted, thereby further reducing the microwave reflection power.

According to the microwave heating device described in the present disclosure, the microwave output power is adjusted by adjusting the microwave power supply of the microwave generating unit 31, thereby adjusting the temperature of the heated carrier layer composed of the heated carrier 2 (such as an absorbing catalyst), and the overall heating, uniform heating and safe heating of the large-sized catalyst bed can be achieved through the dielectric radiator.

According to the microwave heating device disclosed herein, the coupling section 333 of the dielectric radiator 33 is located within the waveguide 32, and the radiating section 331 is located within the heating cavity 11. The upper and lower sides of the heating cavity 11 are provided with a heating medium 2 (e.g., a catalyst bed) with excellent microwave absorption and thermal conductivity. The microwave generating unit 31 generates microwaves, which are transmitted through the waveguide 32. The microwaves are coupled to the coupling section 333 of the dielectric radiator 33, further transmitted by the transmission section 332, and uniformly radiated by the radiating section 331. The microwaves are ultimately absorbed by the heating medium 2, achieving the purpose of heating the heating medium.

In the microwave heating system of the present disclosure, a temperature sensor (not shown) is provided on the heated carrier 2 or in the heating cavity 11 to monitor the temperature of each heated carrier or heated carrier layer in real time. A controller (not shown) provided in the microwave heating system is configured to receive the measured temperature from the temperature sensor, compare the measured temperature with the target temperature, and output a control signal to the microwave generating unit 31 in the microwave heating device based on the difference between the measured temperature and the target temperature, thereby being able to control the output power of the microwave generating unit 31.

After the temperature reaches the target temperature, the reactant inlet is opened to inject the reaction medium (such as VOCs) through the heated carrier 2, and an efficient decomposition reaction occurs under the assistance of the heated carrier 2.

6-13 show microwave heating systems according to different preferred embodiments, wherein a plurality of microwave heating devices are arranged in different ways on the sidewalls of the heating cavity 11 , wherein the radiating sections 331 of the dielectric radiators 33 in the microwave heating devices extend into the heating cavity 11 .

Referring to Figures 6-8, a schematic structure of a microwave heating system is shown. Figure 6 shows an overall schematic diagram of the microwave heating system. As shown in the right half of Figure 6, a plurality of heating cavities 11 are provided in the container body 1. These are stacked up and down (can be referred to as stacked along a first direction) to form a microwave heating system. Two upper and lower heating carrier layers (can be referred to as arranged along a first direction) facing each other are arranged in each heating cavity 11. The microwave heating devices 3 are symmetrically arranged in pairs on opposite sides of the space formed between the upper and lower heating carrier layers. Referring to the left half of Figure 6, the dielectric radiators 33 of each pair of microwave heating devices 3 are located on the same straight line along their length extension direction. Referring to Figure 7, a cross-sectional view of the arrangement of the plurality of microwave heating devices in the microwave heating system of Figure 6 is shown. It can be seen that the arrangement is equivalent to a heating system formed by stacking the plurality of heating cavities 11 in Figure 2 up and down. The multiple layers of heating cavities 11 (or adjacent layers of heating carriers) can optionally be separated by a first microwave shielding element 14 (e.g., a shielding steel mesh). The first microwave shielding element 14 allows for independent control of the heating of each heating cavity 11, preventing interaction between adjacent heating cavities 11. Furthermore, the first microwave shielding element 14 does not block the passage of VOCs or other related gases. For example, the first microwave shielding element 14 may be a perforated stainless steel plate or a shielded steel mesh. Figure 8 shows a top view of the arrangement of multiple microwave heating devices in the microwave heating system of Figure 6. As can be seen from Figure 8, the container body 1 has a rectangular cross-section in the horizontal direction. In a preferred embodiment, within a heating cavity, microwave heating devices 3 or dielectric radiators 33 are arranged in pairs on the sidewalls in only one relative direction (e.g., left-right), and not in other directions (e.g., front-to-back). This arrangement is intended to achieve uniform electric field strength and prevent microwaves emitted by multiple microwave heating devices 3 from overlapping and converging in the center of the heating cavity. This strong electric field could potentially break down the air, posing a safety hazard for processing flammable and explosive VOCs.

The container body 1 may be provided with a reactant inlet 12 and a product outlet 13 to allow the fluid reactant introduced through the reactant inlet 12 to flow through the heated carrier 2 in the heated carrier layer in a first direction and be discharged through the product outlet 13. In the case of multiple superimposed or stacked heating cavities 11, the reactant flow entering the container body 1 is processed by the multiple heated carriers in sequence from bottom to top (first direction).

Through the microwave heating system including multiple heating cavities shown in Figures 6-8, each heating cavity 11 controls the heating temperature through its own dielectric radiator 33, and the temperature of each heated carrier is monitored in real time by arranging a temperature sensor on the heated carrier or in the heating cavity 11, and the temperature is fed back to the controller. The controller outputs a control signal to the microwave generating unit 31 based on the comparison between the monitored temperature and the target temperature, thereby controlling the output power of the microwave generating unit 31 and further controlling the temperature of the heated carrier.

By stacking multiple heating cavities 11 one above the other, multiple layers of heat carriers are stacked one above the other, and the total thickness of the heat carriers is heated in layers. This eliminates the need for the heat carrier layer in each heating cavity to be too thick, allowing microwaves to fully penetrate and heat the cavity, thus resolving the problem of insufficient microwave penetration depth.

Furthermore, the temperature in each heating chamber 11 can be individually controlled, thereby enabling more efficient treatment of different VOC components. Preferably, gradient temperature control can be implemented between multiple stacked heating chambers 11, so that a temperature gradient is achieved from bottom to top or from top to bottom in the container body 1.

Next, refer to Figures 9-11, which illustrate schematic structural diagrams of a microwave heating system according to another embodiment of the present disclosure. The microwave heating system illustrated in Figures 9-11 further improves upon the microwave heating system illustrated in Figures 6-8. Specifically, instead of the microwave heating device arrangement illustrated in Figures 6-8, as illustrated in Figures 9-11, the microwave heating devices, or the dielectric radiators included therein, are vertically staggered in two adjacent heating cavities 11. To simplify the description, only the differences from the structure illustrated in Figures 6-8 are described below.

Specifically, referring to Figure 9, the left half shows a left view of the microwave heating system, and the right half is a front view of the microwave heating system. As can be seen from the figure, between the two adjacent heating cavities 11, the extension directions of the dielectric radiators of the microwave heating devices are perpendicular to each other and staggered. The staggered configuration means that the two adjacent heating cavities 11 are provided with dielectric radiators on the non-adjacent sides. In other words, if the microwave heating device or dielectric radiator of a heating cavity is arranged relative to the left and right sides of the heating cavity, then the microwave heating device or dielectric radiator of the heating cavity adjacent to the heating cavity is arranged relative to the front and back sides of the heating cavity. According to this preferred arrangement, the heat carrier can be heated more evenly.

10 is a cross-sectional view showing an arrangement of multiple microwave heating devices in the microwave heating system of FIG. 9 ; and FIG. 11 is a top view showing an arrangement of multiple microwave heating devices in the microwave heating system of FIG. 9 .

Next, refer to Figure 12, which shows a schematic structural diagram of a microwave heating system according to another preferred embodiment of the present disclosure. This system further improves upon the microwave heating system shown in Figures 6-8 or the microwave heating system shown in Figures 9-11. In this embodiment, to further enhance the uniformity of heating of the heated carrier, in addition to the first microwave shielding element 14 disposed between the heating cavities 11, a second microwave shielding element 15 may be provided within at least a portion of the heating cavities 11. This second microwave shielding element 15 extends across the entire length of the heating cavities, thereby separating multiple pairs of opposing microwave heating devices 3 or the dielectric radiators included therein. Accordingly, the heating cavities 11 are divided into multiple sub-heating cavities distributed sequentially and in parallel. Each sub-heating cavity is located at either end of the heating cavity 11 and is provided with one or more pairs of opposing microwave heating devices 3 or the dielectric radiators included therein (see Figure 12). In a specific embodiment, the first microwave shielding element 14 and the second microwave shielding element 15 are made of metal. For example, the first microwave shielding element 14 may be a perforated steel plate or steel mesh, while the second microwave shielding element may be a steel plate. The division of the second microwave shielding element 15 makes the heating of the heated carrier in the single heating cavity 11 more uniform, and can prevent the microwaves emitted by adjacent microwave heating devices 3 from overlapping each other, thereby preventing the electric field strength from increasing beyond the air breakdown strength.

Next, refer to Figure 13, which shows another embodiment of a microwave heating system according to the present disclosure. Instead of stacking multiple heating cavities 11 in the vertical direction as described in previous sections 6-12, in Figure 13, multiple heating cavities are arranged side by side in the left-right direction within the container body. Accordingly, the individual heat carriers in the heating cavities are laid out in the vertical direction, forming a heat carrier layer located on the left and right sides of the heating cavity. Multiple microwave heating devices 3 are mounted on the sidewalls at the upper and lower ends of the container body 1, corresponding to each heating cavity 11. The dielectric radiators 33 of the microwave heating devices 3 extend vertically into the heating cavity 11. As shown in the figure, in this embodiment, the first microwave shielding element 14 is no longer provided between the heating cavities 11. The heat carrier layers in two adjacent heating cavities are combined to form a single body. Reactant inlets 12 and product outlets 13 are provided on the container body 1 corresponding to the combined heat carrier layer, allowing the fluid reactant introduced through the reactant inlet 12 to flow vertically through the heat carrier layer 2 and be discharged through the product outlet 13.

The present disclosure is further described below through examples.

Comparative Example 1

As shown in Figure 14, without a dielectric radiator, heating is achieved solely through an eight-port waveguide (each rectangular block at the upper and lower ends of the figure represents a port). The microwave radiation efficiency is 94.94%, resulting in a significant maximum temperature difference of 350°C across the catalyst bed. Furthermore, the temperature is primarily concentrated at the microwave radiation indentation, making uniform heating difficult to achieve away from the microwave feed port.

Example 1

As shown in Figure 15, employing the technical solution shown in Figure 2, with the use of dielectric radiators, the uniformity of the catalyst bed is significantly improved. The catalyst bed away from the microwave feed is heated effectively, with microwave injection efficiency increased to 96.11% and the maximum temperature difference reduced to 180°C. However, the temperature in the middle range away from the microwave feed is higher on both sides and slightly lower in the middle.

Example 2

As shown in Figure 16, using a dielectric radiator and the presence of a first microwave shielding element significantly improved the uniformity of the catalyst bed, reducing the maximum temperature difference to 180°C. The incident efficiency increased to 99.11. Although the maximum temperature difference did not significantly decrease, the temperature uniformity of the majority of the catalyst bed, away from the microwave feed port, was significantly improved.

Example 3

As shown in Figure 17, with a dielectric radiator and both a first and second microwave shielding element, the uniformity of the catalyst bed is significantly improved, with the maximum temperature difference reduced to 30°C. The first shielding element is preferably a steel mesh, which shields microwaves while allowing gas to pass through. The second microwave shielding element is a steel plate, which shields microwaves and isolates air. However, those skilled in the art will appreciate that the material of the first shielding element is not limited to steel mesh; any material that can shield microwaves and allow gas to pass through can be used. Similarly, the second microwave shielding element is not limited to steel plate; any material that can shield microwaves and block gas can be used.

Example 4

As shown in Figure 18, the dielectric radiators at different levels above and below adopt a co-directional radiation scheme. The maximum temperature difference of the middle catalyst bed is 60°C.

Example 5

As shown in Figure 18, the dielectric radiators at different levels above and below adopt a 90° intersecting (perpendicular) radiation scheme. The maximum temperature difference of the middle catalyst bed is 52°C.

It can be seen that in the microwave heating reaction system, both the heating method using multiple radiators and multiple layers arranged in parallel and the heating method using multiple radiators and multiple layers arranged in an interlaced manner can achieve better uniform heating effects; moreover, by setting metal partitions between multiple groups of radiators, the radiation efficiency and heating uniformity can be further improved.

Examples 6-9

Define el1 as the coupling segment length, el2 as the radiation segment length, and el3 as the transmission segment length. Under simultaneous irradiation from eight 1kW microwave magnetrons, with a single catalyst bed measuring 700mm x 700mm and two opposing dielectric radiators in separate radiation cavities measuring 175mm, the corresponding electric field strengths and incident efficiencies for different el1/el2/el3 values are shown in Table 1 below.

Table 1

In Examples 6-9, the maximum electric field intensity in the container body does not exceed 3.87×10 ³ V/m, which is much lower than the electric field breakdown intensity in humid air.

The electric field distribution cloud maps of Examples 6-9 are shown in Figures 20-23, respectively. In the figures, the uniformity of the electric field intensity represented by each represents whether the temperature of the heated catalyst bed is uniform. As can be seen from the figures, the electric field intensity of Examples 6 and 7 is mainly concentrated near the wall of the container body, indicating that the electric field intensity distribution is uneven, the catalyst bed temperature distribution is uneven, and the microwave energy utilization rate is also low; Examples 8 and 9 have relatively more uniform electric fields, indicating that the heated catalyst bed temperature is more uniform and the incident efficiency is relatively high. Within a certain range, the length of the radiator represented by Examples 8 and 9 is more conducive to producing a uniform and efficient heating effect.

Examples 10-13

Except for the adjustments to the coupling section length, radiation section length, and transmission section length, the other conditions are the same as those in Examples 6-9. The electric field strength and incident efficiency corresponding to different el1/el2/el3 are shown in Table 2 below.

Table 2

The electric field distribution cloud diagrams for Examples 10-13 are shown in Figures 24-27, respectively. As can be seen from the figures, when the coupling segment lengths are the same or similar and within a reasonable range, the dielectric radiator achieves high utilization efficiency, exceeding 95%. When the radiating segment lengths are shorter (as in Examples 10 and 11), the microwave distribution within the container body becomes uneven. When the directed radiating segment lengths are within a reasonable range, the microwave electric field distribution and radiation efficiency are improved.

It can be seen from the above embodiments 6-13 that by adjusting the length of the coupling section, the length of the transmission section and the length of the radiation section, the distribution of the electric field can be further adjusted, thereby adjusting the bed heating uniformity and radiation efficiency.

Next, referring to Figure 28 , a method for treating waste gas (e.g., VOCs) using any of the aforementioned microwave heating systems is disclosed. As shown in Figure 28 , at step 2801, a controller (not shown) receives a temperature signal from a temperature sensor located on the heated carrier 2 or within the heating cavity 11. The method then proceeds to step 2802, where the controller compares the received temperature signal with a target temperature. Next, at step 2803, a determination is made as to whether the temperature signal has reached the target temperature. If so, the method proceeds to step 2805. At 2805, the reactant inlet is opened to allow the introduction of waste gas containing volatile organic compounds (e.g., VOCs). If, at step 2803, it is determined that the temperature signal has not yet reached the target temperature, the controller outputs a control signal based on the difference between the temperature signal and the target temperature. The control signal is used to control the microwave generating unit in the microwave heating apparatus 3 to continue generating microwaves to continue heating the heated carrier within the heating cavity 11. Additionally, the controller can also control the inlet airflow based on the composition of the product at the outlet of the container body 1. In the case where there are multiple heating chambers, the controller may control the temperature of each heating chamber separately.

Those skilled in the art will understand that the order of the method steps in Figure 28 does not necessarily have to be executed in the order shown in the figure, and some steps may even be executed simultaneously, or some steps may be removed, as long as they do not conflict with the technical problems to be solved by the technical solution of the present disclosure.

Now refer to Figure 29, which shows a controller 2900 according to an embodiment of the present disclosure, which may be the controller mentioned in the previous embodiment. The controller includes a processor 2901, a memory 2902, and an interface 2903. The processor 2901 implements the exhaust gas treatment operation by executing computer-executable instructions that define the method shown in Figure 28. A computer program product including computer-executable instructions can be stored in the memory 2902. The method described in Figure 29 can be defined by computer-executable instructions included in the computer program product stored in the memory 2902 and controlled by the processor 2901 that executes the computer-executable instructions. The interface 2903 may include a network interface for communicating with other devices via a network, and the interface may also include other input/output devices (e.g., a display, keyboard, mouse, speaker, button, touchpad, touch screen, etc.) that enable a user to interact with the controller 2900. Those skilled in the art will recognize that the implementation of the actual control system may also include other components, and Figure 29 is a high-level representation of some components of such a control system for illustrative purposes.

Memory 2902 includes tangible, non-transitory machine-readable storage media and may also include high-speed random access memory, such as dynamic random access memory (DRAM), static random access memory (SRAM), double data rate synchronous dynamic random access memory (DDRRAM), or other random access solid-state memory devices, and may include non-volatile memory, such as one or more magnetic disk storage devices (such as internal hard disks and removable disks), magneto-optical disk storage devices, optical disk storage devices, flash memory devices, semiconductor memory devices (such as erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)), compact disk read-only memory (CD-ROM), digital versatile disk read-only memory (DVD-ROM) disks, or other non-volatile solid-state storage devices.

While embodiments of the present disclosure have been described in detail above, it should be appreciated that certain features of the present disclosure described in the context of separate embodiments for clarity may also be provided in combination in a single embodiment. Conversely, various features of the present disclosure described in the context of a single embodiment for simplicity may also be provided individually or in any suitable subcombination or in any other described embodiment of the present disclosure as appropriate. Certain features described in the context of various embodiments should not be considered essential features of those embodiments unless the embodiment would be ineffective without those elements.

Although the present disclosure has been described in conjunction with the specific embodiments thereof, it is apparent that many substitutions, modifications and variations will be apparent to those skilled in the art. It is therefore intended to encompass all such substitutions, modifications and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents, and patent applications mentioned in this specification are incorporated herein by reference in their entirety to the same extent as if each individual publication, patent, or patent application was specifically and specifically indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this disclosure should not be construed as an admission that such reference is available as prior art to the present disclosure. Where section headings are used, they should not be construed as necessarily limiting.

Claims (22)

A microwave heating system comprises a container body (1), wherein the container body (1) comprises at least one heating cavity (11); A microwave shielding element (15) is provided in the heating cavity (11), and the microwave shielding element (15) divides the heating cavity (11) into a plurality of sub-heating cavities, each of which is provided with a microwave heating device (3) and a heating carrier (2) capable of absorbing microwaves to generate heat. The microwave heating device (3) is arranged on the side wall of the sub-heating cavity, and the microwave heating device (3) includes a dielectric radiator (33) made of dielectric material, and the dielectric radiator (33) has a radiation section (331) located in the sub-heating cavity, which is used to radiate microwaves into the sub-heating cavity to heat the heated carrier (2). The microwave heating system according to claim 1, wherein the microwave shielding element (15) extends the entire length of the heating cavity (11), so that each sub-heating cavity is arranged in parallel, and dielectric radiators (33) are installed oppositely on the side walls at both ends of each sub-heating cavity. According to the microwave heating system of claim 2, each sub-heating cavity comprises an even number of dielectric radiators (33), and the even number of dielectric radiators (33) are divided into two groups and symmetrically installed on the side walls at both ends of the sub-heating cavity. The microwave heating system according to any one of claims 1 to 3, wherein the container body (1) comprises a plurality of heating cavities (11), the plurality of heating cavities (11) are stacked up and down, the heat carrier (2) is arranged as a heat carrier layer at the upper part and/or the lower part of the sub-heating cavity, and the temperature of the stacked plurality of heating cavities (11) is independently controlled or forms a temperature gradient from top to bottom. The microwave heating system according to claim 4, wherein the microwave shielding element (15) is called a second microwave shielding element (15), and wherein a first microwave shielding element (14) is arranged between two upper and lower adjacent heating cavities (11). The microwave heating system according to claim 5, wherein the second microwave shielding element (15) is a steel plate for shielding microwaves and blocking gas, and the first microwave shielding element (14) is a steel mesh for shielding microwaves and allowing gas to pass through. The microwave heating system according to any one of claims 1 to 6, wherein the radiation section (331) has a multi-faceted structure, the multi-faceted structure including a radiation surface (331a) facing the heated carrier (2) and emitting microwaves toward the heated carrier (2). The microwave heating system according to claim 7, wherein the radiation section (331) has a tapered multi-faceted structure, and the shape of the radiation surface is a tapered shape. The microwave heating system according to claim 8, wherein the tapered multi-faceted structure of the radiation section (331) is a truncated pyramid structure, the radiation surface (331a) is two opposite surfaces of the truncated pyramid structure, and the radiation section (331) further includes side surfaces (331b) respectively adjacent to the two radiation surfaces (331a), and the area of the radiation surface (331a) is larger than the area of the side surface (331b). According to the microwave heating system of claim 9, the truncated pyramid structure is a truncated quadrangular pyramid structure, and there are two radiation surfaces (331a) and two side surfaces (331b). The microwave heating system according to any one of claims 1 to 10, wherein the heating cavity (11) has a rectangular cross-section, and the dielectric radiators (33) on the two upper and lower adjacent heating cavities (11) are arranged on upper and lower adjacent sides or on non-adjacent sides. When the dielectric radiators are arranged on upper and lower non-adjacent sides, the extension directions of the upper and lower dielectric radiators are perpendicular to each other. The microwave heating system according to any one of claims 1 to 10, wherein the heated carrier (2) includes a catalyst, and the container body (1) is provided with a reactant inlet (12) and a product outlet (13) to allow the fluid reactant introduced through the reactant inlet (12) to flow through the heated carrier (2) to undergo a chemical reaction under the action of the catalyst. The microwave heating system according to any one of claims 1 to 10, wherein the length of the heating cavity (11) in the length extension direction of the dielectric radiator is 2 to 4 times the extension length of the radiation section (331) extending into the heating cavity (11). The microwave heating system according to any one of claims 1 to 10, wherein the microwave heating device (3) comprises a microwave generating unit (31), the dielectric radiator (33) extending through the side wall of the container body (1) into the sub-heating cavity, and a waveguide (32) for guiding the microwaves generated by the microwave generating unit (31) to the dielectric radiator (33). The microwave heating system according to claim 14, wherein the dielectric radiator (33) further includes a coupling section (333) extending within the waveguide (32) and a transmission section (332) extending between the coupling section (333) and the radiation section (331), the coupling section having a tapered multi-faceted pointed structure. The microwave heating system according to claim 15, wherein the length of the coupling section (333) is 0.75-1 times the microwave wavelength; and the length of the radiation section (331) is more than 0.8 times the microwave wavelength. The microwave heating system according to any one of claims 1 to 10, wherein the dielectric constant of the material of the dielectric radiator (33) is greater than 9 and the dielectric loss is less than 0.02. A microwave heating device, used in the microwave heating system according to any one of claims 1 to 17, the microwave heating device comprising a microwave generating unit (31), a dielectric radiator (33) for radiating the microwaves generated by the microwave generating unit (31) to a heated carrier, and a waveguide (32) for guiding the microwaves generated by the microwave generating unit (31) to the dielectric radiator (33), the dielectric radiator (33) comprising a radiating section (331) located within the heating cavity (11), the radiating section (331) having a tapered multi-faceted structure, the multi-faceted structure comprising a radiating surface (331a) facing the heated carrier (2) and emitting microwaves toward the heated carrier (2). A method for treating exhaust gas performed on a microwave heating system according to any one of claims 1 to 17, wherein the microwave heating system comprises a controller and a temperature sensor disposed on a heated carrier or in a heating cavity for real-time monitoring of the temperature of each heated carrier, the method comprising: receiving a measured temperature from the temperature sensor; comparing the measured temperature to the target temperature; outputting a control signal to a microwave generating unit in the microwave heating device based on a difference between the measured temperature and the target temperature, thereby controlling the microwave generating unit to generate microwaves to heat a heated carrier in the heating cavity; and In response to the measured temperature being greater than or equal to the target temperature, the reactant inlet is opened to inject the exhaust gas containing volatile organic compounds. A controller comprising: processor, and A computer-readable storage medium comprising a computer program stored thereon, the computer program comprising executable instructions which, when executed by the processor, implement the method according to claim 19. A computer-readable storage medium comprising a computer program stored thereon, the computer program comprising executable instructions which, when executed by the processor, implement the method according to claim 19. A computer program product comprising executable instructions which, when executed by a processor, implement the method according to claim 19.