CN111203164A - Gas phase reaction buffer chamber based on atmospheric pressure microwave plasma torch - Google Patents
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- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
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- B01J19/126—Microwaves
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Abstract
A gas phase reaction buffer chamber based on an atmospheric pressure microwave plasma torch belongs to the field of plasma technology and environmental chemistry application. The gas injection device comprises a gas injection component, a buffer chamber, a barometer and an exhaust pump, wherein the buffer chamber is arranged above the gas injection component, and the top of the buffer chamber is connected with the barometer and the exhaust pump. The gas injection component comprises a rectangular waveguide, a movable metal baffle, a buffer chamber flange and a discharge tube, working gas is introduced into the discharge tube to form a vortex gas flow field, and the working gas in the discharge tube is ionized under the induction of a microwave electric field to form microwave plasma discharge. And a certain working air pressure is kept in the buffer chamber, so that the plasma torch keeps a stable discharge state. The invention can increase the plasma density and the electron temperature in the interaction region of the plasma and the gas, is beneficial to further improving the chemical reaction rate of the gas phase reaction of the plasma, and simultaneously leads the gas introduced into the discharge tube to be capable of fully participating in the plasma chemical reaction.
Description
Technical Field
The invention relates to a gas phase reaction buffer chamber based on an atmospheric pressure microwave plasma torch, belonging to the field of plasma technology and environmental chemistry application.
Background
The gas temperature of the electrodeless pollution plasma generated by the atmospheric pressure microwave plasma torch is usually in the range of 3000-6000K, and the electron density is 1014cm-3The high-activity plasma atmosphere obtained by the method is very suitable for chemical gas phase reaction, and the high energy density also ensures large gas flux (>100m3The plasma can maintain a stable discharge state under/h). In addition, considering the advantages of high energy utilization rate (up to 60% or more) of microwave plasma and no need of vacuum system for operation under normal pressure, the gas modification, such as removal of perfluorinated greenhouse gas, CO, etc., can be realized not only in view of practical efficiency and economy2The gas is converted into synthesis gas, and hydrocarbon is used for hydrogen production, and the like, and the method has wide application prospect in the fields of plasma-assisted combustion, chemical vapor deposition synthesis of advanced materials and the like. A double-cavity excited microwave plasma torch as proposed in patent CN207070436U discloses a technical means for generating plasma by using a combination of compressed waveguide section, single-mode standing wave excitation, vortex gas flow field control, and double-cavity coupling, and has experimentally realized a stable atmospheric pressure microwave plasma torch having a post-discharge afterglow extension space of more than 40 cm long obtained in a discharge tube having a diameter of 3 cm.
In scientific research and industrial production, gas phase reactions in the plasma atmosphere generated by an atmospheric pressure microwave plasma torch are often utilized to carry out some practical applications, such as removal of perfluorinated greenhouse gases, CO2Conversion of the gas into synthesis gas, and production of hydrogen from hydrocarbons, etc. According to the characteristics of the atmospheric pressure microwave plasma torch, the introduction of the reaction precursor is usually completed in the plasma excitation area and the plasma afterglow area, for example, patent CN207307576U discloses an application of mixing industrial tail gas in the afterglow area of the atmospheric pressure microwave plasma torch to realize degradation and reduce emission, and in comparison, the premixing of the reactant precursor into the carrier gas in the plasma excitation area to be ionized, excited and decomposed can be more helpful for chemical gas phase reactionThe main reason for this is that the number density of active species and energetic particles with high energy in the plasma excitation region is higher than that in the plasma afterglow region, so in some gas phase chemical reactions, the precursor is often mixed into the carrier gas in advance to generate plasma by the microwave coupling excitation region discharge rather than being added in the plasma afterglow region. At the same time, the requirements for controlling the discharge stability of the plasma torch are greatly increased, because the discharge stability is often greatly affected when the active precursor reactant gas is mixed into the carrier gas under atmospheric pressure. The atmospheric pressure microwave plasma torch stabilizes plasma discharge through a vortex airflow field, working gas forms a gas insulation layer to isolate a high-temperature region of plasma in the center of the discharge tube from the wall of the discharge tube when being injected into the discharge tube, so that a space region without plasma filling is naturally formed in the discharge tube, and a part of mixed gas injected into the discharge tube passes through the region without participating in plasma gas-phase chemical reaction and is directly discharged out of the discharge tube, thereby limiting the improvement of reaction efficiency. One solution proposed in this regard solves this technical problem currently faced. The scheme is that a reaction buffer chamber is added at the outlet of an atmospheric pressure microwave plasma torch, so that a plasma expansion area is formed at the outlet of a discharge tube extending into the reaction buffer chamber and completely covers the outlet of the discharge tube, and gas flowing out of the discharge tube can be fully mixed with plasma in the area to generate a physicochemical reaction; in addition, the outer wall of the reaction buffer chamber adopts a cylindrical metal cylinder with certain wall thickness to form a waveguide structure, so that the electric field intensity of an excited electromagnetic mode is enhanced in the axial direction of a discharge tube extending into the buffer chamber, the electron density and the electron temperature in a mixing area are increased, the chemical reaction rate is greatly improved, and technical indexes such as degradation rate or conversion rate and the like corresponding to the chemical reaction rate in some applications are improved. Although in many practical applications plasma technology is employedThe application has a reaction buffer chamber, but the buffer chamber in the disclosed invention only plays a role of isolating the mixed gas for carrying out gas-phase chemical reaction from the outside, and does not show the role and application function of improving the reaction efficiency in the invention.
The industrial tail gas treatment application by utilizing the atmospheric pressure microwave plasma torch is a typical example realized by plasma gas phase chemical reaction, the achieved degradation rate is a technical index which is considered first, and meanwhile, the energy efficiency is another index for measuring the technology. For example, in the aspect of removing perfluorinated compounds, in addition to reasonably setting the working conditions of the atmospheric pressure microwave plasma torch according to practical conditions, a gas buffer chamber which is butted with the atmospheric pressure plasma torch is introduced, and through reasonable design of the structure of the gas buffer chamber and optimization of specific parameters, the removal rate reaches 99% under the conditions of practical conditions. Experimental data obtained in specific applications are presented in specific examples of this specification.
Disclosure of Invention
The invention provides a solution method with improved performance for improving reaction efficiency based on the analysis and aiming at the technical problems of the existing atmospheric pressure microwave plasma torch in the practical application of chemical vapor phase reaction.
In order to achieve the purpose, the invention adopts the technical scheme that:
the utility model provides a gaseous phase reaction buffer chamber based on atmospheric pressure microwave plasma torch, gaseous phase reaction buffer chamber include that gas injection part 1, buffer chamber 2, barometer 3, exhaust pump 4, wherein, buffer chamber 2 locates gas injection part 1 top, and buffer chamber 2 top is connected with barometer 3, exhaust pump 4. The gas injection part 1 comprises a rectangular waveguide 11, a movable metal baffle 12, a buffer chamber flange 13 and a discharge tube 14. The buffer chamber 2 comprises an outer sleeve 21, a metal cylinder 22, a buffer chamber cover 23, an exhaust port 24, a gas pressure measuring port 25 and an extension tube 26.
The movable metal baffle 12 is arranged at one end of the rectangular waveguide 11, the microwave generated by the microwave generator is introduced into the rectangular waveguide 11 by the transmission device, and the microwave generates TE in the rectangular waveguide 11 under the reflection of the waveguide end face formed by the movable metal baffle 201Standing wave mode, the electric field within the waveguide is perpendicular to the broad face of the rectangular waveguide 11. A hole is formed in a pair of waveguide wide wall surfaces corresponding to the position of the maximum electric field intensity, a discharge tube 14 vertically penetrating through the rectangular waveguide 11 wide surfaces is installed, the discharge tube 14 is located in an atmospheric pressure microwave plasma torch waveguide excitation area, working gas is introduced into the discharge tube 14 through a gas injection component 1 to form a vortex gas flow field distributed in the radial direction, and the working gas introduced into the discharge tube 14 is ionized under the induction of a microwave electric field to form microwave plasma discharge under the atmospheric pressure.
One end face of the buffer chamber 2 is vertically butted with the wide wall face of the rectangular waveguide 11 through a buffer chamber flange 13, so that the discharge tube 14 vertical to the rectangular waveguide 11 extends into the buffer chamber 2 for a certain depth distance through a discharge tube mounting hole 132, and a microwave plasma torch generated in the discharge tube 14 is introduced into the gas buffer chamber 2; the extension tube 26, which is circumscribed by the length, can also be extended into the buffer chamber 2 by inserting an extension tube 26, which has an inner diameter slightly larger than the outer diameter of the discharge tube, into the end of the discharge vessel 14. The other end of the outer sleeve 21 of the gas buffer chamber is connected with the inlet of the exhaust pump 4 through an exhaust port 24 on a buffer chamber cover 23, and a gas pressure meter 3 is externally connected to a gas pressure measuring port 25 on the buffer chamber cover 23 and used for monitoring the gas pressure in the buffer chamber, so that the proper working gas pressure in the buffer chamber 2 is maintained by controlling the total gas flow on line, and the gas pressure in the buffer chamber 2 can be controlled by adjusting and setting the flow of input gas and the flow of exhaust gas.
The metal cylinder 22 forms the outermost layer of the buffer chamber 2 and is fixed between the buffer chamber flange 13 and the buffer chamber cover 23.
The total length of the outer sleeve 21 of the gas buffer chamber is 3 times longer than the extension length of the extension tube 26 or the discharge tube 14 in the gas buffer chamber, and the outer sleeveThe inner diameter D2 of 21 is more than 2 times larger than the outer diameter D1 of the discharge tube 14; the length of the discharge tube 14 extending into the gas buffer chamber is set to be 1-5 discharge tubes 14 with the diameter D1; the value of the outer diameter D1 of the discharge tube 14 is in the range of 0.05-0.38 times of the width of the rectangular waveguide 11; the diameter D3 of the metal cylinder 22 is larger than the outer diameter of the outer sleeve 21 of the gas buffer chamber and smaller than 22.98 x 109The calculated value of/f cm, where f is the microwave frequency, is, for example, 9.38 cm for microwaves having a frequency of 2.45GHz, the discharge vessel 14 has an outer diameter D1 of 0.5 to 3.4 cm, 25.11 cm for microwaves having a frequency of 915MHz, and the discharge vessel 14 has an outer diameter D1 of 1.2 to 9.2 cm.
The wall of the buffer chamber outer sleeve 21 may be made of insulating and heat-resistant material.
The discharge tube 14 is made of heat-resistant insulating materials such as quartz tube or ceramic tube, the epitaxial tube 26 is made of heat-resistant insulating materials such as ceramic material or quartz material, the epitaxial tube 26 and the discharge tube 14 can be made of the same material or different materials, and when the epitaxial tube 26 and the discharge tube 14 are made of the same material, only a complete through tube with proper length is needed; when the epitaxial tube 26 and the discharge tube 14 are made of different materials, the epitaxial tube 26 and the discharge tube 14 are butted at the interface between the buffer chamber 2 and the plasma torch waveguide, and if the discharge tube 14 is made of a quartz tube and the epitaxial tube 26 extending into the buffer chamber is made of a ceramic tube, the inner diameter of the ceramic tube is required to be slightly larger than the outer diameter of the quartz tube, so that the two are sleeved together to form a tight butt joint.
The specific value of the structural parameter of the gas buffer chamber 2 is determined by considering the condition of the total flow of the working gas, and ensuring that the working gas pressure in the buffer chamber 2 is kept in the range of 0.6-1.2 atmospheres, so that the plasma torch keeps a stable discharge form, and the disturbance of the discharge stability of the plasma torch due to the introduction of the gas buffer chamber is eliminated.
The gas buffer chamber flange (13) and the buffer chamber cover 23 are made of metal.
Further, since the plasma torch discharges a lot of heat, a cooling water jacket can be added to the gas buffer chamber cover 23, and cooling is performed before gas discharge and gas pressure measurement, so that the exhaust pump 4 or the gas pressure gauge 3 is effectively protected.
The invention has the beneficial effects that:
(1) an extension tube of a plasma torch discharge tube is introduced into the gas buffer chamber, and the distribution of an airflow field in the gas buffer chamber is optimized by setting and adjusting parameters of the gas buffer chamber, so that the interaction area of expanded plasma and gas formed at the end part of the extension tube is increased, and the chemical reaction rate of plasma gas-phase reaction is improved.
(2) When the outer sleeve of the gas buffer chamber is made of metal pipe wall, a cylindrical resonant cavity is formed, the microwave is coupled to the gas buffer chamber through the connecting part of the gas buffer chamber and the plasma torch wave guide pipe to establish an electromagnetic mode, and the axial field intensity of an electric field along the extension pipe of the discharge pipe is increased in the electromagnetic mode, so that the plasma density and the electron temperature in the interaction area of the plasma and the gas are increased, and the chemical reaction rate of the plasma gas phase reaction is further improved.
Drawings
FIG. 1 is a schematic view of the reaction buffer chamber for degrading CF according to the present invention4A graph of the Degradation Rate (DRE) obtained by experimental measurement along with the change of microwave power;
FIG. 2 shows the degradation of SF using the reaction buffer chamber of the present invention6A graph of the Degradation Rate (DRE) obtained by experimental measurement along with the change of microwave power;
FIG. 3 is a schematic view of a gas buffer chamber;
FIG. 4 is a schematic view of a cover structure of the buffer chamber;
FIG. 5 is a schematic view of a buffer chamber flange structure;
in the figure: 1 a gas injection part; 2 a buffer chamber; 3, a barometer; 4 an exhaust pump; 11 a rectangular waveguide; 12 a movable metal baffle; 13 a buffer chamber flange; 14 a discharge tube; 21 an outer sleeve; 22 a metal cylinder; 23, sealing a buffer chamber; 24 an exhaust port; 25 air pressure measuring port; 26 an extension tube; 41 an exhaust pump outlet; 131 outer sleeve mounting groove 1; 132 discharge tube mounting holes, 231 outer sleeve mounting slots.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. These examples are only for illustrating the present invention and are not to be construed as limiting the scope of the invention. In addition, after reading the contents of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalents also fall within the scope defined by the claims of the present application. The structure of the gas buffer chamber provided by the invention is not only used for removing and degrading perfluorinated compound gas, but also suitable for the application of treating other industrial exhaust tail gas by adopting an atmospheric pressure plasma technology.
As industries develop, perfluorinated gases are widely used in semiconductor industry and power industry due to their low toxicity and stable chemical properties. CF (compact flash)4And SF6Are typical perfluorinated gases which have strong infrared absorption capacity and global warming potential index GWP100 of 6500 and 8000 respectively, and have long existence time caused by slow natural decomposition in the atmosphere. CF (compact flash)4The gas is an important raw material gas for completing the etching process and the chemical vapor deposition processing process in the semiconductor industry, and SF6Due to excellent insulating property and good arc extinguishing performance, the material is widely applied to gas insulated switchgear (GIS, SF) in the power industry6Load switch gear, SF6The insulating transmission pipeline GIL, the transformer and other medium-high voltage equipment have the largest proportion in the same industry in China due to the high-speed development of the power industry, and SF6The amount of emissions is also increasing. Thus, CF is formed4And SF6Gas grows faster and faster in the atmosphere, so CF4And SF6The impact on the greenhouse effect is already of non-negligible magnitude. The Beijing protocol, the compendium for climate change of United nations, has agreed on the prevention of adverse effects of greenhouse gases on climate and economic problems, and the control of the emission of perfluorinated gases is an important environmental problem to be solved urgently.
Currently, methods for reducing the emission of perfluorinated gases are: search for alternative compounds, optimize process, and recoverAnd recycling, and removing trim. In view of economics and process maturity, abatement is the preferred option for emission control in the industry. The use of plasma technology for exhaust gas removal is considered to be a promising approach compared to conventional combustion decomposition methods. Wherein, because the generation of the microwave plasma does not need an electrode and the discharge process is always kept in a controllable stable state, the discharge condition of the atmospheric pressure microwave plasma torch in the practical application of the treatment of industrial tail gas and the modification of gas can be optimized and the process can be regulated and controlled, thereby having great promotion space in the aspect of improving the removal rate and the energy efficiency, which is in the aspect of CF4And SF6And the outstanding effect on the degradation of typical greenhouse gases is verified. The following two examples are two applications that have been carried out using an atmospheric pressure microwave plasma torch in combination with the chemical vapor reaction buffer chamber we propose.
The patent CN207070436U discloses a double-cavity excited atmospheric pressure microwave plasma torch, the structure and working principle of which refer to a gas phase reaction buffer chamber based on an atmospheric pressure microwave plasma torch, the gas phase reaction buffer chamber comprises a gas injection component 1, a buffer chamber 2, a gas pressure meter 3 and an exhaust pump 4. The gas injection component 1 comprises a rectangular waveguide 11, a movable metal baffle plate 12, a buffer chamber flange 13 and a discharge tube 14, and the buffer chamber 2 comprises an outer sleeve 21, a metal cylinder 22, a buffer chamber cover 23, an exhaust port 24, a gas pressure measuring port 25 and an outer extension tube 26. The buffer chamber 2 is arranged above the gas injection component 1, and the top of the buffer chamber 2 is connected with the barometer 3 and the exhaust pump 4.
The movable metal baffle 12 is arranged at one end of the rectangular waveguide 11, the microwave generated by the microwave generator is introduced into the rectangular waveguide 11 by the transmission device, and the microwave generates TE in the rectangular waveguide 11 under the reflection of the waveguide end face formed by the movable metal baffle 201Standing wave mode, the electric field within the waveguide is perpendicular to the broad face of the rectangular waveguide 11. A discharge tube 14 is installed through the wide surface of the rectangular waveguide 11 perpendicularly by making a hole in the wide surface of the waveguide corresponding to the maximum position of the electric field intensity14 is positioned in the waveguide excitation area of the atmospheric pressure microwave plasma torch, working gas is introduced into the discharge tube 14 through the gas injection component 1 to form a vortex gas flow field distributed in the radial direction, and the working gas introduced into the discharge tube 14 is ionized under the induction of a microwave electric field to form microwave plasma discharge under the atmospheric pressure.
One end face of the buffer chamber 2 is vertically butted with the wide wall face of the rectangular waveguide 11 through a buffer chamber flange 13, so that the discharge tube 14 vertical to the rectangular waveguide 11 extends into the buffer chamber 2 for a certain depth distance through a discharge tube mounting hole 132, and a microwave plasma torch generated in the discharge tube 14 is introduced into the gas buffer chamber 2; the extension tube 26, which is circumscribed by the length, can also be extended into the buffer chamber 2 by inserting an extension tube 26, which has an inner diameter slightly larger than the outer diameter of the discharge tube, into the end of the discharge vessel 14. The other end of the outer sleeve 21 of the gas buffer chamber is connected with the inlet of the exhaust pump 4 through an exhaust port 24 on a buffer chamber cover 23, and a gas pressure meter 3 is externally connected to a gas pressure measuring port 25 on the buffer chamber cover 23 and used for monitoring the gas pressure in the buffer chamber, so that the proper working gas pressure in the buffer chamber 2 is maintained by controlling the total gas flow on line, and the gas pressure in the buffer chamber 2 can be controlled by adjusting and setting the flow of input gas and the flow of exhaust gas.
The metal cylinder 22 forms the outermost layer of the buffer chamber 2 and is fixed between the buffer chamber flange 13 and the buffer chamber cover 23.
The total length of the outer sleeve 21 outside the gas buffer chamber is more than the extended length of the outer extension tube 26 or the discharge tube 14 in the gas buffer chamber by 3 times of the diameter D1 of the discharge tube, and the inner diameter D2 of the outer sleeve 21 is more than 2 times of the outer diameter D1 of the discharge tube 14; the length of the discharge tube 14 extending into the gas buffer chamber is set to be 1-5 discharge tubes 14 with the diameter D1; the diameter D3 of the metal cylinder 22 is larger than the outer diameter of the outer sleeve 21 of the gas buffer chamber and smaller than 22.98 x 109Interval of calculated values of/f cm, where f is the microwave frequency. 22.98 x 10 for microwaves of 2.45GHz frequency9Calculated/f is 9.38 cm, the outer diameter D1 of the discharge vessel 14 is 0.5 to 3.4 cm, and for a frequency of 915MHz, a few micrometers22.98 × 10 waves9Calculated as/f is 25.11 cm, the discharge vessel 14 has an outer diameter D1 of 1.2 to 9.2 cm.
The wall of the buffer chamber outer sleeve 21 is made of an insulating and heat-resistant material, specifically quartz glass or a ceramic material.
The discharge tube 14 is made of a heat-resistant insulating material such as a quartz tube or a ceramic tube, and the epitaxial tube 26 is made of a heat-resistant insulating material such as a ceramic material or a quartz material.
The volume of the gas buffer chamber 2 is in the range of 0.6-1.2 atm under the condition of the total flow of the working gas, so that the working gas pressure in the buffer chamber 2 is kept in the range of 0.6-1.2 atm, the plasma torch keeps a stable discharge form, and the disturbance of the discharge stability of the plasma torch due to the introduction of the gas buffer chamber is eliminated.
The gas buffer chamber flange 13 and the buffer chamber cover 23 are made of metal such as aluminum, aluminum alloy, copper or stainless steel.
Example 1
The application of a double-cavity-excited atmospheric pressure microwave plasma torch proposed by patent CN207070436U and the gas phase reaction buffer chamber for CF4Experimental results for degradation. Starting a microwave plasma torch under the condition that nitrogen is taken as background gas, setting the gas flow rate to be 15 liters/minute and the microwave power to be 1000W, keeping the plasma discharge stable, and mixing CF (carbon fluoride) into the plasma carrier gas4The gas concentration is gradually increased from the minimum value to the set value, and the discharge is kept stable. Measured to obtain at CF4The rates of mixing nitrogen carrier gas are 3000ppm and 4000ppm respectively, and the degradation rate DRE value is along the trend of the change of microwave power under the condition that the total gas flow is 15 liters/minute, wherein the DRE is defined by the following method:
wherein C isbeforeAndCafterrespectively representing CF before and after plasma removal from FTIR spectra4The concentration of (c). FIG. 1 shows CF4When the concentration is 3000ppm and 4000ppm respectively, the double-cavity excited atmospheric pressure microwave plasma torch provided by patent CN207070436U and the gas phase reaction buffer chamber provided by the invention are used for degrading CF4The trend of the measured DRE value with the increase of the microwave power from 1200W to 2000W.
Example 2
SF is carried out by applying a double-cavity excited atmospheric pressure microwave plasma torch provided by patent CN207070436U and the gas phase reaction buffer chamber provided by the invention6Experimental data for degradation. And starting the microwave plasma torch under the condition that nitrogen is taken as background gas, gradually switching from nitrogen to oxygen under the condition that the total gas flow is kept unchanged by 15 liters/minute, and finally discharging under the condition of pure oxygen carrier gas. The gas flow rate was set to 15 l/min and the microwave power was set to 1000W so that the plasma discharge was stabilized, and SF was mixed into the plasma carrier gas6The gas, the concentration of the gas is gradually increased from a small value to a set value, and the discharge is kept stable. Measured at SF6The degradation rate DRE value was changed with the microwave power under the conditions that the ratio of the oxygen carrier gas mixed was 10000ppm, 20000ppm, 30000ppm, and 4000ppm, respectively, and the total gas flow rate was 15 liters/minute, wherein DRE was defined by the formula in example 1. FIG. 2 shows SF6When the concentration is 1000,2000,3000,4000ppm respectively, a double-cavity excited atmospheric pressure microwave plasma torch provided by patent CN207070436U and the gas phase reaction buffer chamber of the invention are used for degrading CF6The measured DRE value shows a trend with increasing microwave power from 1200W to 2400W.
The above-mentioned embodiments only express the embodiments of the present invention, but not should be understood as the limitation of the scope of the invention patent, it should be noted that, for those skilled in the art, many variations and modifications can be made without departing from the concept of the present invention, and these all fall into the protection scope of the present invention.
Claims (6)
1. A gas phase reaction buffer chamber based on an atmospheric pressure microwave plasma torch is characterized by comprising a gas injection component (1), a buffer chamber (2), a barometer (3) and an exhaust pump (4), wherein the buffer chamber (2) is arranged above the gas injection component (1), and the top of the buffer chamber (2) is connected with the barometer (3) and the exhaust pump (4); the gas injection component (1) comprises a rectangular waveguide (11), a movable metal baffle (12), a buffer chamber flange (13) and a discharge tube (14); the buffer chamber (2) comprises an outer sleeve (21), a metal cylinder (22), a buffer chamber sealing cover (23), an exhaust port (24), an air pressure measuring port (25) and an extension tube (26);
the movable metal baffle (12) is arranged at one end of the rectangular waveguide (11), the microwave generated by the microwave generator is introduced into the rectangular waveguide (11) by the transmission device, and the microwave generates TE in the rectangular waveguide (11) under the reflection of the waveguide end face formed by the movable metal baffle (2)01A standing wave mode, wherein an electric field in the waveguide is vertical to the wide surface of the rectangular waveguide (11); the method comprises the steps that holes are formed in a pair of waveguide wide wall surfaces corresponding to the position of the maximum electric field intensity, a discharge tube (14) vertically penetrating through the rectangular waveguide (11) wide surfaces is installed, the discharge tube (14) is located in an atmospheric pressure microwave plasma torch waveguide excitation area, working gas is introduced into the discharge tube (14) through a gas injection component (1) to form a vortex gas flow field distributed in the radial direction, and the working gas introduced into the discharge tube (14) is ionized under the induction of a microwave electric field to form microwave plasma discharge under atmospheric pressure;
one end face of the buffer chamber (2) is vertically butted with the wide wall face of the rectangular waveguide (11) through a buffer chamber flange (13), the discharge tube (14) extends into the buffer chamber (2) through a discharge tube mounting hole (132), a microwave plasma torch generated in the discharge tube (14) is introduced into the gas buffer chamber (2), or an extension tube (26) with the inner diameter larger than the outer diameter of the discharge tube is nested at the end part of the discharge tube (14), so that the extension tube (26) externally connected with the section extends into the buffer chamber (2); the other end of the gas buffer chamber outer sleeve (21) is connected with the inlet of the exhaust pump (4) through an exhaust port (24) on a buffer chamber sealing cover (23); the gas pressure measuring port (25) on the buffer chamber sealing cover (23) is externally connected with a gas pressure gauge (3) for monitoring the gas pressure in the buffer chamber, and the plasma torch is kept in a stable discharge state by adjusting and setting the flow of input gas and the flow of discharged gas to control the gas pressure in the buffer chamber (2);
the metal cylinder (22) forms the outermost layer of the buffer chamber (2) and is fixed between the buffer chamber flange (13) and the buffer chamber sealing cover (23);
the total length of the outer sleeve (21) of the gas buffer chamber is more than the extension length of the extension tube (26) or the discharge tube (14) in the gas buffer chamber by 3 times of the diameter D1 of the discharge tube, and the inner diameter D2 of the outer sleeve (21) is more than 2 times of the outer diameter D1 of the discharge tube (14); the length of the discharge tube (14) extending into the gas buffer chamber is set to be 1-5 distances of the diameter D1 of the discharge tube (14); the value of the outer diameter D1 of the discharge tube (14) is in the range of 0.05-0.38 times of the width of the rectangular waveguide (11); the diameter D3 of the metal cylinder (22) is larger than the outer diameter of the outer sleeve (21) of the gas buffer chamber and smaller than 22.98 multiplied by 109Interval of calculated values of/f cm, where f is the microwave frequency.
2. A gas phase reaction buffer chamber based on an atmospheric pressure microwave plasma torch, characterized in that the working gas pressure in the gas buffer chamber (2) is maintained in the range of 0.6-1.2 atmospheres.
3. A gas phase reaction buffer chamber based on an atmospheric pressure microwave plasma torch is characterized in that a discharge tube (14) is made of a quartz tube or a ceramic tube heat-resistant insulating material, an extension tube (26) is made of a ceramic material or a quartz heat-resistant insulating material, and the extension tube (26) and the discharge tube (14) can be made of the same or different materials: when the extension tube (26) and the discharge tube (14) are made of the same material, only a complete through tube with proper length is needed; when the extension tube (26) and the discharge tube (14) are made of different materials, the extension tube (26) and the discharge tube (14) are butted at the waveguide interface of the buffer chamber (2) and the plasma torch, if the discharge tube (14) is made of a quartz tube and the extension tube (26) extending into the buffer chamber is made of a ceramic tube, the inner diameter of the ceramic tube is required to be larger than the outer diameter of the quartz tube, and the extension tube and the discharge tube are sleeved together to form tight butt joint; the port of the discharge tube (14) or the extension tube (26) extending into the buffer chamber (2) can be an opening formed by cutting the tube vertically and orderly, and can also be an opening with a flaring or closing shape.
4. The gas phase reaction buffer chamber based on the atmospheric pressure microwave plasma torch is characterized in that the wall of an outer sleeve (21) of the buffer chamber is made of insulating and heat-resistant materials.
5. A gas phase reaction buffer chamber based on an atmospheric pressure microwave plasma torch is characterized in that a gas buffer chamber flange (13) and a buffer chamber sealing cover (23) are both made of metal.
6. A gas phase reaction buffer chamber based on an atmospheric pressure microwave plasma torch is characterized in that a gas buffer chamber cover (23) can be provided with a cooling water jacket due to a large amount of heat generated by plasma torch discharge, and the gas buffer chamber cover is cooled before gas discharge and gas pressure measurement so as to protect an exhaust pump (4) and a gas pressure gauge (3).
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| CN113401868A (en) * | 2021-08-04 | 2021-09-17 | 大连理工大学 | Device for preparing hydrogen and sulfur by decomposing hydrogen sulfide by using atmospheric pressure microwave plasma torch |
| CN113587084A (en) * | 2021-08-04 | 2021-11-02 | 大连理工大学 | Device for enhancing combustion by utilizing microwave plasma torch |
| CN114852962A (en) * | 2022-01-28 | 2022-08-05 | 大连理工大学 | Hydrogen production system and method for decomposing alcohols by microwave plasma under normal pressure |
| CN115584492A (en) * | 2022-10-19 | 2023-01-10 | 国网安徽省电力有限公司马鞍山供电公司 | Method for generating high-density atmospheric pressure fluorocarbon plasma jet |
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