阅读说明：本技术 Nf3气体检测预处理炉 (NF3 gas detection pretreatment furnace ) 是由 郑锐 于 2020-10-13 设计创作，主要内容包括：本发明公开了一种NF3气体检测预处理炉,包括外壳,外壳一侧设置待测气体NF3的气嘴进气口,和转化气体NO2的气嘴出气口,另一侧安装PCBA、PCB材质环氧玻璃布层压板F4、单面布元器件；设置包含NF3气体进气口和NO2出气口的外壳,在进气口上游安装稳流阀,保证NF3进气流量稳定在200～250ml/min内；将反应质加热并恒定保持在设计温度的恒温内腔,内部安装有陶瓷加热元件和测温PT100热电阻,两者与恒温内腔间通过无机粘结剂气密封接。(The invention discloses a NF3 gas detection pretreatment furnace, which comprises a shell, wherein one side of the shell is provided with an air nozzle gas inlet of gas NF3 to be detected and an air nozzle gas outlet of converted gas NO2, and the other side of the shell is provided with PCBA, a PCB epoxy glass cloth laminated board F4 and a single-sided cloth component; arranging a shell comprising an NF3 gas inlet and an NO2 gas outlet, and installing a flow stabilizing valve at the upstream of the gas inlet to ensure that the flow of NF3 gas inlet is stabilized within 200-250 ml/min; the reaction mass is heated and constantly kept in a constant temperature inner cavity at the designed temperature, a ceramic heating element and a temperature measuring PT100 thermal resistor are arranged in the constant temperature inner cavity, and the ceramic heating element and the temperature measuring PT100 thermal resistor are hermetically sealed with the constant temperature inner cavity through an inorganic binder.)

1. A NF3 gas detection pretreatment furnace is characterized in that: the device comprises a shell, wherein one side of the shell is provided with an air nozzle air inlet of to-be-detected gas NF3 and an air nozzle air outlet of converted gas NO2, and the other side of the shell is provided with PCBA, a PCB epoxy glass cloth laminated board F4 and a single-sided cloth component;

be the inner chamber in the shell, between shell and inner chamber, the air cock air inlet is connected and is admitted air communicating pipe, and the communicating pipe of giving vent to anger is connected to the air cock gas outlet, admit air communicating pipe, give vent to anger and connect the inner chamber communicating pipe, set up heating element in the inner chamber, for the reaction mass installation area in the heating element, the business turn over inner chamber is equipped with the quartzy cotton barrier layer, separates fixed reaction mass, the intracavity sets up and preheats the coil pipe, and heating element is in preheating the coil pipe, the intracavity sets up temperature measuring element, temperature measuring element is.

2. The NF3 gas detection pretreatment furnace of claim 1, wherein: the reaction mass is selected from materials which can react with NF3 at 200-400 ℃ to generate corresponding metal fluorine compounds and nitrogen oxide gas, the reaction is sustainable, the utilization rate of the reaction mass is more than 80%, the conversion rate of NF3 is more than 90%, and the generated nitrogen oxide gas is stable in composition.

3. The NF3 gas detection pretreatment furnace of claim 2, wherein: the reactive material comprises three components: (1) a loose porous or thin-shelled gamma-phase or amorphous alumina support; (2) manganese/cobalt/iron and other metal elements playing a role in fixing fluorine; including without limitation oxides, hydroxides, carbonates, nitrates, phosphates, sulfates, acetates, silicates; (3) metals that promote the low temperature decomposition of NF3 include, but are not limited to, potassium, calcium, magnesium, and alkali metal, alkaline earth metal elements including, but not limited to, carbonates, phosphates, nitrates, sulfates, acetates, silicates.

4. The NF3 gas detection pretreatment furnace of claim 3, wherein: in practical application, the reactant material is the component (1) used alone or the components (1) + (2), (1) + (2) + (3) mixed together, but alumina is necessarily present, and the alumina carrier is an amorphous compound modified by doping or a single compound of a single crystal form gamma phase; transition metal elements including manganese, cobalt and iron are used independently or in a compound way, and the function is to react with NF3 to generate corresponding metal fluoride and fix fluorine elements; the alkali metal and alkaline earth metal elements are used independently or in a compound way, have higher reaction activity with NF3, can promote the decomposition of NF3 at low temperature, improve the decomposition rate of NF3 and promote the generation of a reaction byproduct NOx.

5. The NF3 gas detection pretreatment furnace of claim 4, wherein: the process by which the reactants react with NF3 is: the transition metal oxide firstly reacts with NF3 on the surface of the alumina carrier to generate metal fluoride, then the metal fluoride is transferred with the alumina on the surface of the alumina carrier by F-/O2-, the transition metal oxide is regenerated, flows to a new position and then reacts with NF3, and the process is repeated. The addition of alkali metal/alkaline earth metal elements has a modifying effect on the transition metal element compound.

6. The NF3 gas detection pretreatment furnace of claim 5, wherein: the morphology of the reactive material includes, but is not limited to, the following classes:

(1) powder, submicron and micron powder synthesized by a water-based solution wet method according to a proportion;

(2) granulated particles, which are irregular-shaped or spherical particles manufactured by a special granulator;

(3) the surface and the interior of the porous support;

(4) and loading metal compounds such as thin-shell carbon spheres, fibers, nanotubes and the like.

7. The NF3 gas detection pretreatment furnace of claim 6, wherein: the shell and the inner cavity are provided with a heat-insulating interlayer, and the heat-insulating interlayer is filled with fumed silica powder with low heat conductivity coefficient or vacuumized or not filled with any substance.

8. The NF3 gas detection pretreatment furnace of claim 7, wherein: the air inlet of the air tap adopts a breathable membrane current limiting mode, and is realized by superposing and connecting two membranes in series, wherein one membrane is an open-pore air-tight polytetrafluoroethylene film A, the other membrane is a micro-air-resistance ePTFE waterproof breathable membrane B, and the minimum breathable quantity is 38-45 Liter/Hour/cm²@70mbar, airtight polytetrafluoroethylene film A all takes the gum at the waterproof ventilated membrane B of ePTFE, and the cascade connection is installed at the gas circuit cross section, and wherein, airtight polytetrafluoroethylene film A is in the waterproof ventilated membrane B's of ePTFE upper reaches, and airtight polytetrafluoroethylene film A all is in the low reaches of air cock air inlet at the waterproof ventilated membrane B of ePTFE.

9. The NF3 gas detection pretreatment furnace of claim 8, wherein: the heating element is a ceramic heating pipe, the temperature measuring element is a PT100 thermal resistor, an inner cavity end cover is arranged on one side of an air inlet communicating pipe of the inner cavity, an outer shell end cover is arranged on one side of the outer shell, which is provided with an air inlet of an air faucet, and the outer shell end cover is installed on the outer shell through four supporting columns.

10. The NF3 gas detection pretreatment furnace of claim 9, wherein: the utility model discloses a shell, including shell, air tap, PCBA, PCB material epoxy glass cloth laminated board F4, single-sided cloth components and parts, shell size length wide is 85 36mm, and the shell material is the aluminum alloy, and the air tap air inlet is the L type, and the air tap gas outlet is a style of calligraphy, PCBA, PCB material epoxy glass cloth laminated board F4, single-sided cloth components and parts are installed on the shell through four support columns, 5 ~ 10mm interval between PCB board and shell.

11. The NF3 gas detection pretreatment furnace of claim 10, wherein: the air inlet communicating pipe and the air outlet communicating pipe are made of stainless steel, and have the outer diameter of 4mm and the inner diameter of 2 mm; the preheating coil is made of stainless steel, and has an outer diameter of 4mm and an inner diameter of 2 mm.

12. The NF3 gas detection pretreatment furnace of claim 11, wherein: the inner cavity is erected in the center of the shell through a suspension, and the suspension is a stainless steel top wire with the length of 8-12 mm from M2 to M4; and sealing grooves are processed at the outer sides of the two ends of the air inlet communicating pipe and the air outlet communicating pipe, and high-temperature-resistant inorganic sealant, polytetrafluoroethylene sealing rings, high-temperature-resistant thread sealant and liquid raw material belts are filled in the sealing grooves.

13. The NF3 gas detection pretreatment furnace of claim 12, wherein: the preheating coil is a ceramic heating pipe, tungsten paste is printed on the inner wall of the ceramic heating pipe and sintered at high temperature, a lead leading-out part of the heating element is a nickel-chromium wire with the wire diameter of 1-2 mm, polytetrafluoroethylene PTFE electric wire wrappers are sleeved outside the lead leading-out part, lead fixing grooves are designed on the end faces of the left side and the right side of the shell, and after the nickel-chromium wire penetrates through the lead fixing grooves, an insulating heat-resistant inorganic binder is filled and sealed in the grooves.

14. The NF3 gas detection pretreatment furnace of claim 13, wherein: the material of inner chamber adopts high strength corrosion resistant stainless steel 316L, barreled structure, and internal diameter 20 ~ 28mm, length 18 ~ 30mm, wall thickness 0.8 ~ 1mm, and the inner chamber sets up airtight end cover, the end cover lateral wall of inner chamber is provided with the seal groove, installation polytetrafluoroethylene sealing ring.

15. The NF3 gas detection pretreatment furnace of any of claims 1 to 14, wherein: 4 heat insulation necks with the length of 3-10 mm are arranged in the inner cavity, and the outer diameter of each heat insulation neck is 2-5 mm, preferably 3 mm; printing and high-temperature sintering of tungsten paste in the heating element, wherein the heating element is an annular heating through pipe with the outer diameter of 12mm, the inner diameter of 8mm and the length of 12 mm; the airtight sealing of the heating element and the temperature measuring element with the inner cavity end cover adopts inorganic high-temperature adhesive; the reactant is selected from materials capable of reacting with NF3 at 200-400 ℃ to generate corresponding metal fluorine compounds and nitrogen oxide gas.

Technical Field

The invention relates to the technical field related to NF3 gas detection, in particular to a NF3 gas detection pretreatment furnace.

Background

The use of etching or cleaning nitrogen trifluoride (NF3) gas in a semiconductor manufacturing process flow has a very high greenhouse potential (GWP), a GWP of 17200, and a residence time in the atmosphere of about 740 years. With the rapid development of the semiconductor industry, the emission amount thereof is increasing year by year. The united nations environment in 2008 will largely list NF3 as a greenhouse gas that limits emissions. NF3 is toxic, allowing a maximum concentration (TLV) of 10ppm, and chronic exposure to high concentrations can cause liver and kidney damage, and acute high doses can trigger hypoxic death.

The NF3 gas leakage is monitored on line, and countermeasures are taken in time, so that the harm to personnel and the surrounding environment caused by continuous discharge can be avoided. Currently, NF3 gas cannot be directly detected through electrochemical reaction, and can be converted into Hydrogen Fluoride (HF) through high-temperature thermal cracking in advance, and then the Hydrogen Fluoride (HF) is catalytically converted into nitrogen dioxide (NO2) at medium temperature for detection.

According to the scheme of the invention, the medium-temperature solid-phase reaction (200-400 ℃) of NF3 gas and the reactant is utilized for the first time, the concentration of NF3 gas is detected by detecting nitrogen dioxide (NO2) gas generated by the reaction, the detection principle is simple, the manufacturing cost is low, and the performance is stable and reliable.

Disclosure of Invention

The technical scheme adopted by the invention for solving the technical problems is to provide the NF3 gas detection pretreatment furnace, and the NF3 gas is detected by detecting NO2 gas generated by pre-reaction.

The specific technical scheme is as follows:

the NF3 gas detection pretreatment furnace comprises a shell, wherein one side of the shell is provided with an air nozzle gas inlet of gas to be detected NF3 and an air nozzle gas outlet of converted gas NO2, and the other side of the shell is provided with PCBA, a PCB epoxy glass cloth laminated board F4 and a single-sided cloth component; be the inner chamber in the shell, between shell and inner chamber, the air cock air inlet is connected and is admitted air communicating pipe, and the communicating pipe of giving vent to anger is connected to the air cock gas outlet, admit air communicating pipe, give vent to anger and connect the inner chamber communicating pipe, set up heating element in the inner chamber, for the reaction mass installation area in the heating element, the business turn over inner chamber is equipped with the quartzy cotton barrier layer, separates fixed reaction mass, the intracavity sets up and preheats the coil pipe, and heating element is in preheating the coil pipe, the intracavity sets up temperature measuring element, temperature measuring element is.

The NF3 gas detection pretreatment furnace described above, wherein: the reaction mass is selected from materials which can react with NF3 at 200-400 ℃ to generate corresponding metal fluorine compounds and nitrogen oxide gas, the reaction is sustainable, the utilization rate of the reaction mass is more than 80%, the conversion rate of NF3 is more than 90%, and the generated nitrogen oxide gas is stable in composition.

The NF3 gas detection pretreatment furnace described above, wherein: the reactive material comprises three components: (1) a loose porous or thin-shelled gamma-phase or amorphous alumina support; (2) manganese/cobalt/iron and other metal elements playing a role in fixing fluorine; including without limitation oxides, hydroxides, carbonates, nitrates, phosphates, sulfates, acetates, silicates; (3) metals that promote the low temperature decomposition of NF3 include, but are not limited to, potassium, calcium, magnesium, and alkali metal, alkaline earth metal elements including, but not limited to, carbonates, phosphates, nitrates, sulfates, acetates, silicates.

The NF3 gas detection pretreatment furnace described above, wherein: in practical application, the reactant material is the component (1) used alone or the components (1) + (2), (1) + (2) + (3) mixed together, but alumina is necessarily present, and the alumina carrier is an amorphous compound modified by doping or a single compound of a single crystal form gamma phase; transition metal elements including manganese, cobalt and iron are used independently or in a compound way, and the function is to react with NF3 to generate corresponding metal fluoride and fix fluorine elements; the alkali metal and alkaline earth metal elements are used independently or in a compound way, have higher reaction activity with NF3, can promote the decomposition of NF3 at low temperature, improve the decomposition rate of NF3 and promote the generation of a reaction byproduct NOx.

The NF3 gas detection pretreatment furnace described above, wherein: the process by which the reactants react with NF3 is: the transition metal oxide firstly reacts with NF3 on the surface of the alumina carrier to generate metal fluoride, then the metal fluoride is transferred with the alumina on the surface of the alumina carrier by F-/O2-, the transition metal oxide is regenerated, flows to a new position and then reacts with NF3, and the process is repeated. The addition of alkali metal/alkaline earth metal elements has a modifying effect on the transition metal element compound.

The NF3 gas detection pretreatment furnace described above, wherein: the morphology of the reactive material includes, but is not limited to, the following classes:

(1) powder, submicron and micron powder synthesized by a water-based solution wet method according to a proportion;

(2) granulated particles, which are irregular-shaped or spherical particles manufactured by a special granulator;

(3) the surface and the interior of the porous support;

(4) and loading metal compounds such as thin-shell carbon spheres, fibers, nanotubes and the like.

The NF3 gas detection pretreatment furnace described above, wherein: the shell and the inner cavity are provided with a heat-insulating interlayer, and the heat-insulating interlayer is filled with fumed silica powder with low heat conductivity coefficient or vacuumized or not filled with any substance.

The NF3 gas detection pretreatment furnace described above, wherein: the air inlet of the air tap adopts a breathable membrane current limiting mode, and is realized by superposing and connecting two membranes in series, wherein one membrane is an open-pore air-tight polytetrafluoroethylene film A, the other membrane is a micro-air-resistance ePTFE waterproof breathable membrane B, and the minimum breathable quantity is 38-45 Liter/Hour/cm²@70mbar, airtight polytetrafluoroethylene film A all takes the gum at the waterproof ventilated membrane B of ePTFE, and the cascade connection is installed at the gas circuit cross section, and wherein, airtight polytetrafluoroethylene film A is in the waterproof ventilated membrane B's of ePTFE upper reaches, and airtight polytetrafluoroethylene film A all is in the low reaches of air cock air inlet at the waterproof ventilated membrane B of ePTFE.

The NF3 gas detection pretreatment furnace described above, wherein: the heating element is a ceramic heating pipe, the temperature measuring element is a PT100 thermal resistor, an inner cavity end cover is arranged on one side of an air inlet communicating pipe of the inner cavity, an outer shell end cover is arranged on one side of the outer shell, which is provided with an air inlet of an air faucet, and the outer shell end cover is installed on the outer shell through four supporting columns.

The NF3 gas detection pretreatment furnace described above, wherein: the utility model discloses a shell, including shell, air tap, PCBA, PCB material epoxy glass cloth laminated board F4, single-sided cloth components and parts, shell size length wide is 85 36mm, and the shell material is the aluminum alloy, and the air tap air inlet is the L type, and the air tap gas outlet is a style of calligraphy, PCBA, PCB material epoxy glass cloth laminated board F4, single-sided cloth components and parts are installed on the shell through four support columns, 5 ~ 10mm interval between PCB board and shell.

The NF3 gas detection pretreatment furnace described above, wherein: the air inlet communicating pipe and the air outlet communicating pipe are made of stainless steel, and have the outer diameter of 4mm and the inner diameter of 2 mm; the preheating coil is made of stainless steel, and has an outer diameter of 4mm and an inner diameter of 2 mm.

The NF3 gas detection pretreatment furnace described above, wherein: the inner cavity is erected in the center of the shell through a suspension, and the suspension is a stainless steel top wire with the length of 8-12 mm from M2 to M4; and sealing grooves are processed at the outer sides of the two ends of the air inlet communicating pipe and the air outlet communicating pipe, and high-temperature-resistant inorganic sealant, polytetrafluoroethylene sealing rings, high-temperature-resistant thread sealant and liquid raw material belts are filled in the sealing grooves.

The NF3 gas detection pretreatment furnace described above, wherein: the preheating coil is a ceramic heating pipe, tungsten paste is printed on the inner wall of the ceramic heating pipe and sintered at high temperature, a lead leading-out part of the heating element is a nickel-chromium wire with the wire diameter of 1-2 mm, polytetrafluoroethylene PTFE electric wire wrappers are sleeved outside the lead leading-out part, lead fixing grooves are designed on the end faces of the left side and the right side of the shell, and after the nickel-chromium wire penetrates through the lead fixing grooves, an insulating heat-resistant inorganic binder is filled and sealed in the grooves.

The NF3 gas detection pretreatment furnace described above, wherein: the material of inner chamber adopts high strength corrosion resistant stainless steel 316L, barreled structure, and internal diameter 20 ~ 28mm, length 18 ~ 30mm, wall thickness 0.8 ~ 1mm, and the inner chamber sets up airtight end cover, the end cover lateral wall of inner chamber is provided with the seal groove, installation polytetrafluoroethylene sealing ring.

The NF3 gas detection pretreatment furnace described above, wherein: 4 heat insulation necks with the length of 3-10 mm are arranged in the inner cavity, and the outer diameter of each heat insulation neck is 2-5 mm, preferably 3 mm; printing and high-temperature sintering of tungsten paste in the heating element, wherein the heating element is an annular heating through pipe with the outer diameter of 12mm, the inner diameter of 8mm and the length of 12 mm; the airtight sealing of the heating element and the temperature measuring element with the inner cavity end cover adopts inorganic high-temperature adhesive; the reactant is selected from materials capable of reacting with NF3 at 200-400 ℃ to generate corresponding metal fluorine compounds and nitrogen oxide gas.

Compared with the prior art, the invention has the following beneficial effects:

(1) arranging a shell comprising an NF3 gas inlet and an NO2 gas outlet, and installing a flow stabilizing valve at the upstream of the gas inlet to ensure that the flow of NF3 gas inlet is stabilized within 200-250 ml/min;

(2) a constant temperature inner cavity for heating and constantly keeping the reactant at a designed temperature, wherein a ceramic heating element and a temperature measuring PT100 thermal resistor are arranged in the constant temperature inner cavity, and the ceramic heating element and the temperature measuring PT100 thermal resistor are hermetically sealed with the constant temperature inner cavity through an inorganic binder;

(3) the heat preservation interlayer is vacuumized or filled with fumed silica powder with low heat conductivity coefficient to realize heat preservation, NF3 gas to be detected and NO2 gas generated by reaction can pass through the stainless steel gas pipe and pass through the heat preservation interlayer without loss, the stainless steel gas pipe plays a role in gas circuit connection and is also a heat insulation neck of the heat preservation interlayer, the cross section is minimized, heat conduction is reduced to the maximum degree, and the heat preservation effect is improved;

(4) constant temperature control PCBA (Printed Circuit Board Assembly, Printed Circuit Board patch and connector welding Assembly), through the PT00 thermal resistance of arranging inside the reactant, PID algorithm closed loop feedback realizes the constant temperature control within 200 ~ 400 ℃.

Drawings

FIG. 1 is a schematic view of a NF3 gas detection pretreatment furnace;

FIG. 2 is a view showing the internal structure of a NF3 gas detection pretreatment furnace;

FIG. 3 is a fully enclosed submerged thermal insulation structure of a NF3 gas detection pretreatment furnace;

FIG. 4 is a schematic structural view of a heating element and a temperature measuring element in a constant temperature cavity;

FIG. 5 is a schematic of the reaction curve of a pretreatment furnace Kylin-A3 at 400 ℃ with 40ppm NF 3;

FIG. 6 is a graph showing the sensitivity of Kylin-A3 at different operating temperatures (reactant temperatures);

FIG. 7 is a graph showing the sensitivity of Kylin-A3 at 400 ℃ at different flow rates of 40ppm NF 3/Air;

FIG. 8 is a graph showing the reaction time (T90/rising edge) of Kylin-A3 with a flow rate of 200ml/min passing 40ppm NF 3/Air;

FIG. 9 is a graph showing the response of Kylin-A3 to Air at 400 ℃ with a flow rate of 200ml/min and a flow rate of 40ppm NF 3/Air;

FIG. 10 is a graph showing the reading of Kylin-A3 for NO2 at 400 ℃ with a flow rate of 200ml/min to 5/10/20/40ppm NF 3/Air.

In the figure:

1 inner cavity of housing 2, 3 air tap air inlet, 4 air tap air outlet, 5PCBA 6 air inlet communicating pipe, 7 air outlet communicating pipe, 8 quartz wool barrier layer, 9 temperature measuring element, 10 heating element, 11 reactant mounting area, 12 preheating coil pipe, 13 heat insulation neck, 14 heat insulation interlayer, 15 housing end cover, 16 inner cavity end cover, 17 reactant

Detailed Description

The invention is further described below with reference to the figures and examples.

NF3 gas detects the configuration of the pretreatment furnace.

As shown in fig. 1, the length, width and height of the shell 1 are 85, 36 and H (L, W, H), the shell 1 is made of aluminum alloy, preferably aluminum alloy 6063-T5, the right end of the shell is provided with an L-shaped air nozzle air inlet 3 of the to-be-tested gas NF3 and a linear air nozzle air outlet 4 of the converted gas NO2, the left side of the shell is provided with a PCBA5 through four support columns, the PCB material epoxy glass cloth laminated board F4 is provided with a thickness of preferably 1.6mm, the components are arranged on a single surface, certain mechanical strength and heat insulation effect are ensured, the distance between the PCB board and the shell 1 is 5-10 mm, the temperature of the components on the PCB board is prevented from being overheated, preferably 5mm, the distance cannot be too large, and the size of the device is prevented from being.

The internal gas path structure of the pretreatment furnace is shown in figure 2, the whole pretreatment furnace is composed of a shell 1 and an inner cavity 2, the shell 1 is communicated with the inner cavity 2 through a stainless steel pipe, and the preferred outer diameter is 4mm, and the inner diameter is 2 mm. The gas of NF3 with a certain concentration enters from an NF3 gas inlet of the shell 1, enters the leftmost side of the inner cavity 2 of the pretreatment furnace through a gas inlet communicating pipe and a stainless steel preheating disc 12 (preferably with the outer diameter of 4mm and the inner diameter of 2mm), passes through a quartz wool barrier layer 8, enters a reactant 17 heated at a constant temperature by a ceramic heating pipe, is converted into NO2 after full reaction, then passes through the quartz wool barrier layer 8 and a gas outlet connecting pipe on the other side, is discharged from a NO2 gas outlet, and enters a subsequent NO2 electrochemical module for detection.

The working principle of the pretreatment furnace.

The method comprises the steps that NF3 gas continuously fed from an NF3 gas inlet is in full contact with a heated reactant 17 such as modified alumina in a constant-temperature inner cavity 1, NO2 gas is generated through gas-solid reaction at 200-400 ℃, the gas is discharged from a linear gas nozzle gas outlet 4, NO2 generated through reaction is detected through an electrochemical sensor of a gas detection instrument such as a NO2 module of Midas of Honeyville, and detection of NF3 gas is achieved.

The gas to be detected is NF3, the converted gas is NO2, and when the reactant 17 is alumina, the gas-solid reaction process is shown as the following formula:

Al₂O₃+2NF₃→2AlF₃+NO+NO₂

the modified gamma phase (gamma phase) alumina directly undergoes a gas-solid anhydrous decomposition reaction with NF3 at 200-400 ℃ under an anhydrous condition, nitrogen dioxide NO2 and aluminum fluoride AlF3 are main reaction products, and the alumina is not a catalyst but a consumable product. Compared with the catalytic hydrolysis method, the anhydrous decomposition of NF3 is simple, and hydrogen fluoride HF with strong corrosivity is not generated.

NF3 sample gas entering at a constant flow rate is converted into NO2 gas through medium-temperature gas-solid reaction in a heating closed space of the constant-temperature inner cavity 2, an electrochemical sensor of the gas detection instrument measures the concentration of the NO2 gas, the concentration of the NO2 gas corresponds to the concentration of the NF3 sample gas to be detected one by one, and the concentration of NF3 can be obtained through concentration correction.

The thermostatic chamber 2 is filled with excess reactant 17 to ensure that the incoming NF3 sample gas can be completely converted by reaction. The constant temperature cavity 2 is provided with a heating device and a built-in temperature sensor, and is controlled by a main control circuit board PCBA to keep constant temperature. The pretreatment furnace is connected with a sensor bin of a gas detection instrument in an airtight and serial mode, and the used gas detection instrument requires an exhaust device on the sensor bin to meet the requirement of the electrochemical sensor on detecting the required flow, and no pressure is generated in the sensor bin.

According to the above detection principle, typical specification parameters of the pretreatment furnace are as follows:

the technical details are detailed.

The shell 1:

the pretreatment furnace housing 1 of the present invention has the following functions and features:

the air path air inlet/outlet interface and the air path are provided, the shell is made of metal materials easy to machine, material and machining cost, heat conducting performance and corrosion resistance are comprehensively considered, aluminum alloy 6063-T5 is preferably selected, the air inlet/outlet is provided with an M5 threaded hole for air-tight installation of an air nozzle, a through hole with the diameter of 0.8-2.5 mm is machined in the side wall, and the air path is preferably selected to be 2.0 mm.

The aperture of the gas path is too large, the filling space of NF3 sample gas is large, more reactant 17 is needed for converting reaction into NO2, the reaction consumption of the reactant 17 is large, the frequency of replacing the reactant 17 is high, and the maintenance cost is increased; the aperture is too small, and the gas circuit easily produces the air lock, influences the detection precision of gas circuit downstream electrochemical sensor, increases reaction time simultaneously. In addition, the stainless steel preheating coil pipe with the moderate gas path aperture can preheat the entering NF3 sample gas, promote the gas-solid reaction with reactant 17, and at 2 downstream of the constant temperature inner cavity, the gas-solid reaction at 200-400 ℃ can generate NO2 gas for rapid cooling, without affecting the detection performance and service life of the downstream electrochemical NO2 sensor.

Providing an installation position of an air inlet flow limiting film:

the air inlet adopts a ventilation diaphragm flow limiting mode, and is realized by superposing and connecting two diaphragms in series, one is an open-pore airtight polytetrafluoroethylene film A, preferably Saint goban2045-5 PTFE film with gum; one is an ePTFE waterproof breathable film B with micro air resistance, preferably VE0001DAV of Goer, and the minimum air permeability is 38-45 Liter/Hour/cm²@70mbar, airtight polytetrafluoroethylene film A and the waterproof ventilated membrane B of ePTFE all take the gum, and the cascade connection is installed at the gas circuit cross section, and wherein air cock A is at the upper reaches of B. Both downstream of the inlet.

Typical installation examples: the end face of the thread relief groove is provided with a cylindrical pit with the diameter of 5-10 mm and the height of 2-5 mm, the flatness error of the end face is less than 0.02mm, and the cylindrical pit is used for installing a diffusion control film and is shown in an attached drawing 2 in detail.

Mounting bracket for providing a constant temperature inner chamber 2:

the constant temperature inner chamber 2 is installed inside the shell 1, and in order to reach the heat preservation effect, the distance of the inner chamber 2 from each direction of the shell 1 is the better. Considering that the gas path needs to enter/exit gas through the inner cavity 2, the gas inlet/outlet path is designed into a cantilever beam supporting structure, the constant-temperature inner cavity 2 is suspended in the center of the shell, and the mounting bracket is a stainless steel top wire with the length of 8-12 mm from M2 to M4, which is shown in the attached drawing 2 in detail.

The airtight gas circuit between constant temperature inner chamber 2 and shell 1 is connected, adopt seamless stainless steel pipe, preferred external diameter 4mm, internal diameter 2mm, in order to guarantee that airtight is effective for a long time, can process the seal groove outside stainless steel pipe both ends pipe, fill high temperature resistant inorganic sealant, polytetrafluoroethylene sealing ring, high temperature resistant thread sealant, liquid raw material area etc. preferably Japanese triple bond ThreeBond3732 insulating heat-resisting inorganic binder, metal alkoxide is the binder, one-component low-temperature hardening, the condensate is 100% inorganic matter, the leakproofness is good, water and acid and alkali resistance, long-term service temperature is up to 1400 ℃.

Providing a wiring interface for the heating element and the PT100 thermal resistor:

the heating element of the constant-temperature inner cavity 2 adopts a high-temperature ceramic heating pipe, tungsten paste is printed on the inner wall of the ceramic pipe and is sintered at high temperature, a lead leading-out part of the heating element adopts a nickel-chromium wire with the wire diameter of 1-2 mm, a polytetrafluoroethylene PTFE electric wire wrapper is sleeved outside the nickel-chromium wire, the nickel-chromium wire and the ceramic heating pipe are both hard, a built-in welding spot between the nickel-chromium wire and the ceramic heating pipe is fragile (easy to crack and peel), lead fixing grooves are designed on the end faces of the left side and the right side of the shell 1, and after the nickel-chromium wire passes through the grooves, a Japan three-key ThreeBond3732 insulating heat-resistant inorganic binder is filled and sealed in the; and secondly, the shell 1 is sealed to prevent the heat insulation material in the heat insulation interlayer from leaking.

Providing a PCBA installation supporting seat:

through the screw thread blind hole of 4M 2 or M3 of terminal surface, double-end hexagonal screw copper post, it is built on stilts with the parallel terminal surface of PCB, PCB has via hole pad and independent binding post to heating element wire and PT100 thermal resistance design, guarantees the shortest most reliable electrical connection.

The reaction of the reactant 17 and the NF3 belongs to consumption reaction, and according to the concentration, the flow and the working time of a NF3 sample, the reactant 17 can be completely consumed in stages and needs to be replaced by new reactant 17 at regular time.

According to the design of the fully-enclosed immersed heat insulation structure, the shell 1 is mounted in the constant-temperature inner cavity 2 through the jackscrews on four surfaces, the heat insulation layer can be filled with fumed silica powder with low heat conductivity coefficient and can be vacuumized or not filled with any substance, the shell 1 and the inner cavity 2 are convenient to disassemble, and the heat insulation interlayer does not influence the replacement of the reactant 17, as shown in fig. 3.

Constant flow sampling:

be applied to the fixed detector of NF3 of semiconductor high-tech trade, at the preliminary treatment furnace upper reaches or lower reaches of gas circuit, generally all install the sampling pump, like Honeyville's Midas, the sampling pump adopts the suction type initiative sampling of pump, and gas circuit gas flow is generally at 200 ~ 800ml/min, along with the increase of detector live time, the performance decay of sampling pump can lead to the whole decline of NF3 appearance gas flow, and the flow reduction of NF3 appearance gas can influence the precision and the timeliness (reaction time) that detect.

The sampling pump is arranged at the upstream of the heat treatment furnace, the flow stabilizing valve is arranged between the sampling pump and the gas path of the pretreatment furnace, the flow control membrane is arranged at the gas inlet of the pretreatment furnace, and the flow stabilizing valve and the flow control membrane are matched to realize constant flow sampling.

The flow stabilizing valve is in a non-metal membrane type, the structure of the flow stabilizing valve is composed of a needle valve for adjusting output flow and a pressure difference self-operated flow stabilizer, the sampling pump is used for actively sampling large flow to ensure that the upstream pressure is unchanged, and the diffusion control membrane is used for limiting the change range of the downstream pressure to realize the output flow stabilization in a certain range. The diaphragm working area of the flow stabilizing valve is 24-30 cm2, the spring stiffness is 0.30-0.38 kg/mm, the aperture diameter of the valve seat is 0.6-1.2 mm, preferably WLF-1 model of Nanjing Ke Li Hua instrument and meter Limited, the diaphragm working area is 24.6cm2, the spring stiffness is 0.38kg/mm, the aperture diameter of the valve seat is 0.8mm, and the stable output flow is 5-400 ml/min.

The flow control membrane is realized by connecting two membranes in series, one membrane is a perforated air-tight film A, the other membrane is a PTFE porous air-permeable membrane B which is integrally air-permeable but has certain air resistance, the A membrane and the B membrane both have back glue, and the membranes are connected in series and are sequentially arranged on the cross section of an air path, wherein the A membrane is arranged at the upstream of the B membrane.

The membrane A is a wafer with the diameter of 4-12 mm, preferably 5mm, the thickness of 0.12-0.25 mm, preferably 0.18mm and annular gum. The base material is a temperature-resistant plastic film such as air-tight PTFE/PEEK, the thickness is 0.1-2 mm, the preferred thickness is 0.127mm, the gum is silica gel, the radial width of the glue layer is more than 1mm, the axial thickness is 0.04-0.1 mm, the preferred thickness is 0.05mm, the surface temperature is less than 60 ℃, the flatness error is less than 0.02mm, and the airtight sealing service life is more than 2 years on the flat surface of metal/plastic/ceramic. The opening can be a through hole in the center of a circle or 2-4 through holes uniformly distributed on a circle with the diameter of 1-4 mm, the aperture is 0.2-0.6 mm, and a through hole with the diameter of 0.3mm is preferably arranged in the center.

The membrane B is a wafer with the diameter of 3-10 mm, preferably 3mm, the thickness of 0.12-0.25 mm, preferably 0.18mm and annular gum. The base material is air-permeable ePTFE, the preferred minimum water seepage pressure is 23psi (differential pressure is 1.585mbar), the minimum air permeability is 38.5Liter/Hour/cm2 (differential pressure is 103mbar), the thickness is 0.1-2 mm, the preferred thickness is 0.127mm, the gum is silica gel, the radial width of the glue layer is more than 0.6mm, the axial thickness is 0.04-0.1 mm, the preferred thickness is 0.05mm, the surface temperature is less than 60 ℃, the flatness error is less than 0.02mm on flat surfaces of metal/plastic/ceramic and the like, and the airtight sealing service life is more than 2 years.

And the gas path structure matched with the diffusion control film: through holes with the inner diameter of 0.8-2.4 mm, preferably 2.0mm, are adopted. The membrane A + membrane B + air path structure can ensure that the air permeability resistance is within 100-900 mm & Pa & lt-1 & gt/s & lt-1 & gt, preferably within 400-450 mm & lt-1 & gt/s & lt-1 & gt, and even if the sampling flow rate of the sampling pump fluctuates within the range of 400-800 ml/min, the flow stabilizing valve + the flow control membrane can ensure that the flow rate of NF3 sample air entering the pretreatment furnace is always kept constant within the range of 200-250 ml/min. Because the flow control membrane has air resistance, NO2 gas cannot be diffused reversely and returns to an upstream gas path after the reaction of the reactant 17 in the constant-temperature inner cavity 2, and the NO2 gas can be detected completely.

The constant-current sampling gas circuit is characterized in that:

the collected amount does not depend on the flow rate of the gas to be detected, even if the performance of a sampling pump of an upstream gas circuit is attenuated, the flow rate of NF3 sample gas is integrally reduced, and the flow rate of the collected NF3 sample gas every time is constant within the range of 200-250 ml/min;

the collection amount is proper, the reactant 17 in the constant-temperature inner cavity 2 can be completely converted into NO2 gas within a set time (generally within 60 seconds), even if the reactant 17 is consumed and the reaction activity is attenuated, the requirement of more than 99% conversion of the collected NF3 sample gas within the service life of 6-12 months can be met. The gas to be detected which is collected at a time and the converted gas generated by the reaction of the analytical substances can meet the requirement that a gas sensor of a gas detection instrument completes a complete test at a time, namely the converted gas quantity meets the requirement that the output signal of the sensor reaches a stable value at full range;

the diffusion control film has non-return property, NO gas generated by reaction can not be diffused reversely and returns to an upstream gas path, and harmful pollution enrichment is avoided in the gas path;

the gas path arranged in the shell has no adsorption material and the dead volume is minimum, and the NF3 sample gas fed in the previous time remains in the tube, so that the concentration of the NF3 sample gas fed in the next time is not obviously influenced.

A constant-temperature inner cavity 2:

considering that the gas-solid reaction of NF3 can generate fluorine-containing corrosive gas and oxidize at 200-400 ℃ in long-term air, the constant-temperature inner cavity is made of high-strength corrosion-resistant stainless steel 316L, and the constant-temperature inner cavity is of a barreled structure with the inner diameter of 20-28 mm, the length of 18-30 mm, the wall thickness of 0.8-1 mm, preferably the inner diameter of 24mm, the length of 20mm and the wall thickness of 0.9 mm. In order to ensure air tightness, an air-tight end cover is designed in the inner cavity, a sealing groove is designed in the side wall of the end cover, and a polytetrafluoroethylene sealing ring is installed. The heating element and the temperature measuring element are mounted inside the thermostatic chamber 2, as shown in fig. 4.

For reducing the heat conduction loss of inner chamber 2, design 4 thermal-insulated necks 13 (jackscrews) of length 3 ~ 10mm, preferred length 6mm guarantees under the prerequisite of inner chamber easy to assemble, and the thermal-insulated neck cross-sectional area is dwindled to the at utmost, and jackscrew external diameter 2 ~ 5mm, preferred external diameter 3 mm.

Heating element adopts high temperature ceramic heating pipe, and inside tungsten thick liquid printing high temperature sintering, the external diameter 12mm internal diameter 8mm, length 12 mm's annular heating siphunculus, it only needs 5 minutes to heat up to 250 ℃, acid and alkali corrosion resistance, no naked light, insulating nature is good, the stable performance. Supplying power by direct current of 12V, heating to 250 ℃, and consuming 15W maximally, introducing NF3 sample gas at a flow rate of 200-250 ml/min by adopting the heat preservation structure of the pretreatment furnace, and keeping the temperature at 250 ℃ and consuming less than 8W.

The heating element and the temperature measuring element are hermetically sealed with the end cover of the constant temperature cavity 2 by using an inorganic high-temperature adhesive, preferably an insulating heat-resistant inorganic adhesive of Japanese triple bond ThreeBond 3732. In order to ensure the air tightness stability, the working temperature of the pretreatment furnace is less than 400 ℃, the temperature rising and reducing speed is less than 10 ℃/min, the sealant adhesive can shrink after long-time high-temperature service, and the bonded surface is easy to crack due to frequent and rapid temperature rising and reducing speed.

The temperature sensing element used a PT100 platinum thermistor as shown in fig. 4: the diameter is 2mm, the length is 5-10 mm, the stainless steel 316 shell is used, the temperature measuring range is above 550 ℃, the precision is 0.1 ℃, the lead is a ceramic tube shell, and a plurality of silver-plated wires can resist the temperature of 220 ℃ after long-term service.

Constant temperature inner chamber 2 is connected with the airtight of shell 1, uses external diameter 4.0mm, and the seamless nonrust steel pipe of internal diameter 2.0mm, and in order to guarantee airtight effective for a long time, at the sealed recess of pipe both ends mounting hole processing, installation polytetrafluoroethylene sealing ring.

A quartz cotton barrier layer 8 is designed in the constant-temperature inlet and outlet inner cavity 2 to separate and fix the reaction mass, so that the gas flowing is prevented from carrying the reaction mass to enter the gas pipe to cause blockage. In addition, the quartz wool barrier layer 8 can also uniformly distribute NF3 sample gas to be reacted, adsorb impurities and promote the gas-solid reaction of the reactant 17 and the NF 3. The quartz wool is silanized quartz wool with the fiber diameter of 3-5 mu m, the purity of 99.99 percent, the density of 2.2g/cm3, the resistance to 1300 ℃ high temperature, high strength retention rate at the high temperature, softness and stable size, and the gasified filter wool for the Agilent/Shimadzu gas chromatography liner tube is preferably selected.

A heat insulation interlayer:

the constant-temperature inner cavity 2 is externally coated with fumed silica heat-insulating material with the thickness of 5-10 mm, nano-scale white powder, the absolute thermal conductivity coefficient of 200-250 ℃ is less than 0.02 W.m < -1 >. cndot.. cndot. -1, the density is 60g/L, the specific surface area is 175-225 m2/g, preferably the fumed silica heat-insulating material and the nano-scale white powder are prepared by the Cabot company

Due to the adoption of the four-side wrapping structure, the uniform temperature of the internal temperature is ensured, the heat loss in the temperature rising/constant temperature process is reduced, and the power consumption of the pretreatment furnace is reduced. For better heat insulation effect, the fumed silica of the heat insulation interlayer is preferably vacuumized, the surface of the powder is coated with aluminum foil, the vacuum air pressure is less than 1mbar, or a vacuum layer is added on the inner side/outer side of the fumed silica heat insulation layer.

Reactant 17:

the material composition is characterized in that the material selection principle of the reactant 17 is that the reactant can react with NF3 at 200-400 ℃ to generate corresponding metal fluorine compound and nitrogen oxide gas, the reaction is sustainable, the utilization rate of the reactant is more than 80%, the conversion rate of NF3 is more than 90%, the generated nitrogen oxide gas is stable in composition, and the main component is nitrogen dioxide NO 2.

The reactant 17 material includes three components: (1) a loose porous or thin-shelled gamma-phase or amorphous alumina support; (2) manganese/cobalt/iron and other metal elements playing a role in fixing fluorine, and specific materials such as oxides, hydroxides, carbonates, nitrates, phosphates, sulfates, acetates, silicates and the like; (3) potassium/calcium/magnesium and the like which promote the low-temperature decomposition of NF3, alkali metal/alkaline earth metal elements, and specific materials such as carbonate, phosphate, nitrate, sulfate, acetate, silicate and the like.

In practice, the component (1) may be used alone or in combination of (1) + (2), (1) + (2) + (3), one of the characteristics being the presence of alumina. The alumina carrier can be a doped modified amorphous compound or a single compound of a single crystal form gamma phase, the alumina carrier plays a role of a support and a reactant, the specific surface area of alumina is improved, NF3 reaction diffusion channels can be increased, the diffusion resistance of the reactant is reduced, the utilization rate of the alumina is improved, and after a compact aluminum fluoride layer is formed on the surface of the alumina, the specific surface area is reduced, the pore channel is narrowed, the NF3 diffusion rate is reduced, and deep-layer alumina is prevented from participating in the reaction.

The transition metal elements such as manganese, cobalt, iron and the like can be used independently or in a compound way, and mainly have the functions of reacting with NF3 to generate corresponding metal fluoride and fixing fluorine elements. Among them, oxides such as MnO2, Co2O3 and Fe2O3 are preferable because they are easily available, and fluorides produced by the reaction with NF3 are stable in properties and easy to handle. More specifically, 5 wt% of metallic Mn doped gamma phase alumina 0.3mm to 2mm porous granulated particles (50 mesh to 10 mesh) are preferred.

The alkali metal/alkaline earth metal elements can be used independently or in a compound way, and have the main effects of higher reaction activity with NF3, promoting the decomposition of NF3 at low temperature, improving the decomposition rate of NF3 and promoting the generation of reaction by-products NOx. The alkali metal elements include lithium, sodium, potassium, rubidium and cesium, the alkaline earth metal elements include magnesium, calcium, strontium and barium, and the compound forms include oxides, hydroxides, carbonates, phosphates, aluminates, nitrates, sulfates, acetates, silicates, and the like. The usage amount of the alkali metal/alkaline earth metal compound is moderate, the usage amount is too small, and the promotion effect is limited; if the dosage is too large, no obvious promotion phenomenon exists, but the dosage of solid fluorine metal elements such as aluminum, manganese and the like is relatively reduced, and the service life of the reaction mass is shortened.

The process by which the reactants react with NF3 is: oxides of transition metal elements such as manganese, cobalt, iron and the like firstly react with NF3 on the surface of the alumina carrier to generate metal fluorides, such as M2O3 and NF3 to generate MnF3 and NOx, then the metal fluorides react with alumina on the surface of the alumina carrier to perform F-/O2-transfer, the transition metal oxides are regenerated, such as MnF3 and Al2O3 to generate Mn2O3 and AlF3, and the transition metal oxides flow to new positions and then react with NF3, and the steps are repeated. The addition of alkali metal/alkaline earth metal elements can modify transition metal element compounds such as manganese, cobalt, iron and the like, for example, the addition of potassium element can enable the Mg-Mn-Co compound to be in a spinel crystal form, large in crystal grain, flaky, higher in reaction activity with NF3 and better in stability.

Material form and synthesis process:

the morphology of the reactant 17 material includes, but is not limited to, the following classes:

(1) powder, submicron and micron powder synthesized by water-based solution wet method according to proportion.

For example, Al (NO3) 3.9H 2O solution is prepared, stirred, NH 3. H2O solution is added dropwise, centrifugal separation is carried out after complete precipitation, and the precipitate is dried at 100 ℃ and roasted at 800 ℃ for 3 hours to prepare the gamma-phase alumina powder. The method comprises the steps of dipping nitrate solutions of alkali metals/alkaline earth metals (K, Mg, Ca, Sr and Ba) and transition metals (Fe, Co and Mn) on the surface of alumina powder, wherein the loading amount of metal additives is 5-10%, namely M/Al2O3 is 5-10% (mass percentage of M), drying at 100 ℃, and roasting at 600 ℃ for 3 hours.

(2) The granulated particles are generally irregular-shaped spherical particles which can also be prepared by a special granulator.

For example, manganese oxide supported by alumina, 99.99% gamma phase alumina with the specific surface area of more than 200m2/g is added with Mn (NO3)2+ K2CO3+ PVA aqueous solution, the mixture is pressed into cakes/sheets by a press, helium (with the purity of 99.999%) flows at 400 ℃ for 2 hours to remove PVA, and then the cakes/sheets are mechanically crushed into irregular powder with the particle size range of 0.3-2 mm (50 meshes-10 meshes), and fine powder is removed.

For example, the raw material of the alumina-supported cobalt oxide is prepared by using 50% Co (NO3)3 solution, 99.99% gamma phase alumina with the specific surface area of more than 200m2/g, potassium carbonate aqueous solution, PVA aqueous solution, wet ball milling and mixing, granulation and molding, drying at 110 ℃, carrying out heat treatment on flowing helium (with the purity of 99.999%) at 400 ℃ for 2 hours, promoting dehydration reaction, and preferably having 5 wt% weight loss because excessive moisture is not expected in the decomposition of NF3, and the inert atmosphere is adopted because the potassium carbonate is in the raw material, so that the consumption caused by high-temperature oxidation is avoided. The particle size range of the particles after heat treatment is 0.3-2 mm (50 meshes-10 meshes), and fine powder is removed.

(3) The surface and interior of the porous support, such as the beads or molecular sieves of the spherical catalytic combustion element, are impregnated or coated with the reactant.

For example, a gamma-phase alumina spherical molecular sieve is impregnated with a nitrate solution of alkali metals/alkaline earth metals (K, Mg, Ca, Sr, Ba) and transition metals (Fe, Co, Mn) on the surface, the metal additive loading is 5-10%, that is, M/Al2O3 is 5-10% (mass percentage content of M), dried at 100 ℃, and calcined at 600 ℃ for 3 hours. The dipping and sintering process can be repeated for a plurality of times, and in order to prolong the service life of the reactant, 1-5% (mass percentage content) of 99.99% gamma-phase alumina nano powder with the specific surface area of more than 200m2/g can be added into the nitrate solution.

(4) Metal-loaded compounds such as thin-shell carbon spheres, fibers, nanotubes, etc., e.g., 8 g of glucose, were dissolved in 45ml of deionized water to prepare a solution. Transferring to a reaction kettle with a 100ml polytetrafluoroethylene inner container, heating to 180 ℃, standing for 6 hours, washing the precipitate with ethanol and water, and drying at 80 ℃ for 2 hours to obtain the shell carbon spheres. Adding aluminum nitrate and urea aqueous solution into carbon spheres, rotating for 4 hours at 110 ℃ in a reaction kettle to obtain a carbon-hydrogen loaded alumina precursor, adding Mn (NO3)2+ K2CO3 aqueous solution, and roasting for 4 hours at 600 ℃ in a muffle furnace to obtain the thin-shell alumina loaded manganese oxide reactant.

The purpose of selecting different material forms is to improve the activity of the reaction of the reactant and the NF3, reduce the reaction temperature, for example, increase the specific surface area of the reactant and provide more channels for the contact of the NF3 and the reactant; and secondly, the stability and sustainability of the reaction of the reactant and the NF3 are improved, for example, the compact metal fluoride 'shell' is prevented from being formed after the reaction of the reactant surface layer and the NF3, and the subsequent continuous reaction of the NF3 and the internal reactant is prevented.

PCBA：

The master control circuit board is controlled by an STM32 or MSP430 series single chip microcomputer, and the STM32L051C8T6 is preferred from the aspects of function, price and easy acquisition. A temperature control system of the PCBA, an analog signal output by a PT100 platinum thermal resistance temperature sensor is converted into a voltage signal through an operational amplifier MCP6V31T and amplified, the voltage signal enters an ADC of a single chip microcomputer STM32L051C8T6, data controls a heating element through a PID control algorithm in the single chip microcomputer, and the constant temperature of a constant temperature inner cavity is guaranteed to fluctuate +/-5 ℃ at a certain temperature point within a range of 200-400 ℃.

The heating system adopts an analog control mode of PWM pulse width modulation, uses a DMT6012LSS 'n' channel enhancement mode field effect MOS tube, modulates the bias of the grid electrode of the MOS tube according to the change of a thermal resistance of a heating element, and realizes the change of the conduction time of the MOS tube, thereby realizing the change of heating power.

The PCBA has a hardware overload protection design, the MCP6541T electric comparator is used for comparing with a set maximum temperature, if the temperature is too high and exceeds the temperature which can damage the catalyst, the electric comparator automatically shuts down a heating system, and the hardware system realizes automatic overheat protection.

The main control circuit board is provided with a power indicator lamp, two PID algorithm optimization buttons, an independent power supply and a heating element wiring terminal, overload/surge protection and reverse connection protection are provided, power is supplied by 12-24 VDC, and the power consumption stable running state of the whole board is less than 8W; size 36 x 1.6 mm.

Best examples of the implementation.

Reactant 17 is a granulated solid spherical particle composed of manganese oxide, aluminum oxide and potassium carbonate in a mass ratio of Mn to Al2O3 to K to 10 to 100 to 2.5. The raw materials are prepared by using 50% of Mn (NO3)3 solution, 99.99% of gamma-phase alumina powder with the specific surface area of more than 200m2/g, 50% of potassium carbonate aqueous solution, 16000-20000 PVA aqueous solution with the average molecular weight of 85%, ball milling and mixing by a wet method, granulating and molding, drying at 110 ℃, carrying out heat treatment on helium gas flowing in a tube furnace at 400 ℃ for 2 hours (with the purity of 99.999%), carrying out heat treatment on particles with the particle size range of 0.83-1.7 mm (20 meshes-10 meshes) after the heat treatment, and removing fine powder.

The core reaction is that manganese oxide reacts with NF3 at the constant temperature of 400 ℃ to generate manganese fluoride MnF3 and nitrogen oxide, then the manganese fluoride MnF3 and the nitrogen oxide are transferred with aluminum oxide in an F-/O2-mode, Mn2O3 is regenerated while AlF3 is generated, the manganese oxide flows to a new position and then reacts with NF3, and the steps are repeated. The potassium carbonate is used for modifying the high specific surface area of Mn2O3, promoting mass transfer of NF3, slowing down the reduction of the specific surface area of Mn2O3 and the narrowing speed of an Al2O3 pore channel, having strong impurity adsorption capacity, controlling the generation proportion of nitrogen oxide serving as a reaction by-product, and enabling the generation amount of the NO2 gas to be measured to be maximum and stable. The amount of manganese determines the relative proportion of potassium, and to ensure complete decomposition of NF3, the sum of the weight of manganese atoms and the weight of potassium atoms requires more than 10% by mass, in this case up to 12.5% by mass, in the analyte.

The heating element of the constant-temperature inner cavity 2 is a high-temperature ceramic heating pipe, the interior of the heating element is printed with tungsten paste and sintered at high temperature, the outer diameter of the annular heating through pipe is 12mm, the inner diameter of the annular heating through pipe is 8mm, the length of the annular heating through pipe is 12mm, direct current is supplied by 12V, the temperature is increased to 400 ℃, the maximum power consumption is 16W, NF3 sample gas is introduced at the flow rate of 200-250 ml/min, the constant temperature is 400.

The main gas circuit is filled with 40ppm NF3 (back bottom gas is air, research institute of Zhongbo group 718) at a flow rate of 300ml/min, a PTFE air-impermeable film A with a central through hole diameter of 0.3mm and an ePTFE porous air-permeable film B with a thickness of 0.127mm are filled in the main gas circuit through a diffusion control film, the diffusion resistance is 400-450 mm Pa < -1 >. s < -1 >, the gas flow rate of NF3 sample entering a constant-temperature inner cavity is 200-250 ml/min in a free diffusion mode, and the oxygen content in the reaction is 20 vol%.

The space for installing the reactant in the constant-temperature inner cavity 2 is a cylindrical barrel body with the diameter of 8mm and the length of 12mm, the volume is 0.6cm3, the powder filling rate is 90%, the airspeed of the NF3 sample gas to be treated is 276h < -1 >, and the linear velocity of the NF3 sample gas to be treated is 0.64 m/min.

The decomposition rate of NF3 can reach 98.2% by constant temperature reaction at 400 ℃, and the gas phase product of the reaction is mainly NO2, including small amounts of O2, NO, N2O and N2.

Response performance:

FIG. 5 shows the reaction profile of a pretreatment furnace Kylin-A3 at 400 ℃ with 40ppm NF 3.

A power supply: MW bright weft LRS-350 switching power supply direct current 24V, maximum output current 15A;

standard gas: zhonghai group 718 research institute, 40ppm NF3/Air

A flow control device: horikoshi HORIBA S48300/HMT range 1L/min, precision 0.3% F.S.;

NO2 detection equipment, Germany Ennix GS10-NO2-100ppm portable single gas detector, and the resolution is 0.1 ppm.

Sensitivity:

continuously introducing 200ml/min of air into a pretreatment furnace Kylin-A3, electrifying to raise the temperature, stabilizing the furnace temperature at 400 +/-2 ℃ within 30 minutes, introducing GS10 into an air outlet, recording the reading value of GS10 in the air for 30 seconds, switching the gas to NF3 standard gas within 1 second, recording the reading value of NO2 within 1 second and continuing for 90 seconds.

FIG. 6 shows the sensitivity of Kylin-A3 at different operating temperatures (reactant temperatures). FIG. 6 shows the steady NO2 readings of the pretreatment furnace Kylin-A3 at a constant flow rate of 200ml/min and at operating temperatures of 200 deg.C, 250 deg.C, 300 deg.C, 350 deg.C, 400 deg.C and 450 deg.C, and it can be seen from the graph that as the temperature of the reactant increases, the conversion efficiency of NF3 increases and the sensitivity increases, and after 400 deg.C, the trend becomes slower, and the operating temperature is set at 400 deg.C by comprehensively considering the power consumption, the difficulty and cost of heat preservation and sealing, the time to zero, and other factors.

FIG. 7 shows the sensitivity of Kylin-A3 at 400 ℃ at different flow rates of 40ppm NF 3/Air; FIG. 7 is a graph of the steady NO2 reading of the pretreatment furnace Kylin-A3 at 400 ℃ operating temperature at various flow rates of 40ppm NF3, it being seen that the minimum NO2 reading occurs at 400ml/min, and that the NO2 reading increases with increasing flow rate or decreasing flow rate.

When the flow rate is more than 400ml/min, the solid-phase reactant is selectively adsorbed, and fresh NF3 gas molecules are continuously supplemented, so that the gas-solid diffusion process is promoted to be carried out, the gas-solid reaction is easier to occur, and the reading value of NO2 is increased.

When the flow is 200-250 ml/min, the air speed of the whole catalyst (the parameters of the bulk density, the particle size and the porosity of a reactant on the residence time of NF3 on the surface of the catalyst) and the linear speed influenced by the structure of a reaction cavity are optimized, the conversion rate of NF3 is the highest, and the reading value of NO2 is also increased.

The sensitivity obviously changes along with the flow change of the sampling gas, and is not acceptable in practical use. Particularly, after the sampling pump runs for a period of time, performance attenuation occurs, so that the air inlet flow rate is reduced, and in order to ensure stable performance of equipment testing sensitivity/reaction time and the like, a WLF-1 flow stabilizing valve with low air resistance is arranged at the air inlet end of the Kylin-A3 pretreatment furnace, so that the flow of NF3 sample air is kept constant within the range of 200-250 ml/min all the time.

Reaction time:

the measuring process of the reaction time is the same as the sensitivity, and the rising edge T90 of the reaction time is the corresponding time of starting to introduce 40ppm of NF3 standard gas to 90 percent of the stable value of the reading value of NO 2. The recovery time is the time for introducing 40ppm of NF3 standard gas, switching to clean air with the flow rate of 200ml/min within 1 second after the reading value of NO2 is stabilized, and returning the reading value of NO2 to zero.

FIG. 8 shows the reaction time (T90/rising edge) of Kylin-A3 with a different temperature flow of 200ml/min passing 40ppm NF 3/Air. As can be seen in fig. 8, the reaction time decreased gradually with increasing operating temperature at a constant flow rate of 200ml/min, which matches the increasing sensitivity, indicating that increasing operating temperature of the reactant favors the conversion of NF3 to NO 2. The reaction time T90 is 31 seconds under the condition of 400 ℃ flow rate of 200ml/min, if the NO2 module of Midas is used for detection, the sampling gas path is shortened, the gas resistance is reduced, the self T90 of the detection sensor is shortened, and the reaction time is further shortened.

Repeatability:

the test was repeated 3 times with a constant flow of 200ml/min at 400 ℃ with a reading of GS10 in air recorded for 30 seconds, the gas switched to NF3 standard gas within 1 second, the NO2 reading recorded 1 time in 1 second for 90 seconds, the air switched back in 1 second for 30 seconds.

FIG. 9 shows Kylin-A3 response curves to Air at 400 deg.C, flow rate 200ml/min, and aeration of 40ppm NF 3/Air. As can be seen from FIG. 9, under the condition of constant temperature and flow rate, the repeatability of the reaction curve is good, and the sensitivity and the reaction time can be reproduced.

Linearity:

the test was carried out at 400 ℃ under a constant flow of 200ml/min, the readings of GS10 in air were recorded for 30 seconds, the gas was switched to NF3 standard gas within 1 second, the concentrations of the standard gas were 5ppm, 10ppm, 20ppm and 40ppm, respectively, and the readings of NO2 were recorded 1 time per second for 90 seconds.

FIG. 10 shows the reading for Kylin-A3 for NO2 at 400 ℃ with a flow rate of 200ml/min passing 5/10/20/40ppm NF 3/Air. As can be seen from fig. 10, the reaction mass conversion is constant and the reading linearity of NO2 is good at constant temperature and flow rate.