CN115575566A - Nitrogen oxide measuring system and mass flow controller - Google Patents
Nitrogen oxide measuring system and mass flow controller Download PDFInfo
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- CN115575566A CN115575566A CN202210934649.5A CN202210934649A CN115575566A CN 115575566 A CN115575566 A CN 115575566A CN 202210934649 A CN202210934649 A CN 202210934649A CN 115575566 A CN115575566 A CN 115575566A
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- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 title claims abstract description 163
- 239000012530 fluid Substances 0.000 claims abstract description 111
- 239000007789 gas Substances 0.000 claims description 165
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 76
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 68
- 238000010531 catalytic reduction reaction Methods 0.000 claims description 49
- 238000006243 chemical reaction Methods 0.000 claims description 42
- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 claims description 33
- 238000005259 measurement Methods 0.000 claims description 33
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 claims description 33
- 238000000197 pyrolysis Methods 0.000 claims description 28
- 238000010438 heat treatment Methods 0.000 claims description 23
- 238000004891 communication Methods 0.000 claims description 22
- 230000002093 peripheral effect Effects 0.000 claims description 4
- 230000004308 accommodation Effects 0.000 claims 1
- 230000006641 stabilisation Effects 0.000 abstract description 6
- 238000011105 stabilization Methods 0.000 abstract description 6
- 230000008859 change Effects 0.000 description 6
- 238000012545 processing Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 230000000087 stabilizing effect Effects 0.000 description 5
- 238000011144 upstream manufacturing Methods 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 3
- 238000012937 correction Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 229910052750 molybdenum Inorganic materials 0.000 description 3
- 239000011733 molybdenum Substances 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 239000007809 chemical reaction catalyst Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
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- Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Medicinal Chemistry (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Food Science & Technology (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Fluid Mechanics (AREA)
- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
Abstract
The embodiment of the invention relates to a nitrogen oxide measuring system and a mass flow controller. Wherein the mass flow controller comprises a capillary tube having a fluid channel for the passage of a fluid, the cross-sectional profile of the fluid channel is circular, the diameter of the fluid channel is less than or equal to 400 μm, optionally, the fluid channel is cylindrical, and the diameter of the fluid channel is greater than or equal to 160 μm and less than or equal to 300 μm. The mass flow controller provided by the embodiment of the invention has stable flow when the Knudsen coefficient of the capillary is less than 0.1 and the pressure ratio is higher than 2.5, is not changed along with downstream pressure fluctuation, and can realize the purposes of flow stabilization and flow limitation. In addition, the mass flow controller of the embodiment of the invention does not need a circuit control module to realize the purposes of current stabilization and current limitation, so the mass flow controller of the embodiment of the invention does not have the problem that the circuit is interfered by electromagnetism.
Description
Technical Field
The invention relates to the technical field of gas flow detection, in particular to a nitrogen oxide measuring system and a mass flow controller.
Background
Mass flow controllers are used to precisely measure and control the mass flow of a gas or liquid. The mass flow controller commonly adopted in the prior art has the problems of short service life and no high temperature resistance, the rubber gasket in the mass flow controller is easily corroded by corrosive gas, the control precision is further seriously influenced, and in addition, the general working temperature of the mass flow controller is less than 50 ℃, and the mass flow controller is difficult to apply in an extremely high temperature environment. In addition, the mass flow controller adopted in the prior art has poor anti-interference performance, the control circuit of the mass flow controller is easily affected by electromagnetic interference to influence the measurement precision, and the fluctuation of the downstream pressure of the mass flow controller can also cause interference and influence on the measurement precision.
Disclosure of Invention
The present invention is directed to solving, at least in part, one of the technical problems in the related art. To this end, embodiments of the present invention propose a measurement system of nitrogen oxides with high measurement accuracy.
The embodiment of the invention also provides a mass flow controller.
The system for measuring nitrogen oxides according to the embodiment of the invention comprises:
the reactor comprises a reaction chamber, an ozone inlet, a first nitrogen-containing gas inlet, a second nitrogen-containing gas inlet and a gas outlet, wherein the ozone inlet, the first nitrogen-containing gas inlet, the second nitrogen-containing gas inlet and the gas outlet are communicated with the reaction chamber;
a first mass flow controller having a first fluid passageway, an outlet of the first fluid passageway being in communication with the ozone inlet;
a nitric oxide flow path comprising a second mass flow controller having a second fluid passageway with an outlet in communication with the first nitrogen-containing gas inlet;
a nitrogen dioxide flow path comprising a third mass flow controller having a third fluid channel, wherein each of the first, second and third fluid channels is circular in cross-sectional profile, each of the first, second and third fluid channels has a diameter of 400 μm or less, and a catalytic reduction device having a third nitrogen-containing gas inlet and a first nitrogen-containing gas outlet, the outlet of the third fluid channel being in communication with the third nitrogen-containing gas inlet, the first nitrogen-containing gas outlet being in communication with the first nitrogen-containing gas inlet.
The nitrogen oxide measuring system provided by the embodiment of the invention adopts the first mass flow controller to control the flow of air input into the measuring system, adopts the second mass flow controller and the third flow controller to control the flow of nitrogen-containing oxidizing gas input into the measuring system, can provide stable-quality gas for a reactor, can effectively eliminate error signals generated by interference of the mass flow controllers, and has high measuring precision.
In some embodiments, the system for measuring nitrogen oxides further comprises an ozone generator having an air inlet and an ozone outlet, the first fluid passage being in communication with the air inlet, the ozone outlet being in communication with the ozone inlet.
In some embodiments, the ozone inlet, the first nitrogen-containing gas inlet, and the second nitrogen-containing gas inlet are the same opening; the measuring system further comprises a sleeve assembly, the sleeve assembly comprises an outer pipe and an inner pipe, the inner pipe is sleeved in the outer pipe, the outer peripheral surface of the inner pipe is spaced from the inner peripheral surface of the outer pipe, the inner pipe is communicated with the ozone outlet, or the inner pipe is communicated with the second fluid channel and the first nitrogen-containing gas outlet, the outer pipe is communicated with the second fluid channel and the first nitrogen-containing gas outlet, or the outer pipe is communicated with the ozone outlet, and each of the inner pipe and the outer pipe is communicated with the ozone inlet.
In some embodiments, further comprising a switching device comprising an inlet, a first outlet, and a second outlet, the inlet switchably communicating with one of the first outlet and the second outlet, each of the second fluid channel and the third fluid channel communicating with the inlet, the first outlet communicating with the first nitrogen-containing gas inlet, the second outlet communicating with the third nitrogen-containing gas inlet.
In some embodiments, the measurement system further comprises an ozone decomposing device having a tail gas inlet and a tail gas outlet, the tail gas inlet in communication with the gas outlet;
alternatively, the catalytic reduction device comprises:
a housing having a receiving cavity,
the catalytic reduction pipeline is positioned in the accommodating cavity, one end of the catalytic reduction pipeline forms the third nitrogen-containing gas inlet, and the other end of the catalytic reduction pipeline forms the first nitrogen-containing gas outlet;
the pyrolysis pipeline is positioned in the accommodating cavity, one end of the pyrolysis pipeline forms the tail gas inlet, and the other end of the pyrolysis pipeline forms the tail gas outlet; and
the heating element is arranged in the accommodating cavity so as to heat the catalytic reduction pipeline and the pyrolysis pipeline.
In some embodiments, at least a portion of the heating element is positioned between the catalytic reduction conduit and the pyrolysis conduit.
In some embodiments, the pyrolysis tube is U-shaped and comprises:
the catalytic reduction device comprises a first straight section and a second straight section, wherein the first straight section and the second straight section are arranged at intervals along a preset direction, the catalytic reduction pipeline and the heating element are positioned between the first straight section and the second straight section in the preset direction, and the heating element is wound on the catalytic reduction pipeline; and
and one end of the arc-shaped section is connected with the first straight section, and the other end of the arc-shaped section is connected with the second straight section.
In some embodiments, each of the first, second, and third fluid channels is cylindrical, and each of the first, second, and third fluid channels has a diameter equal to or greater than 160 μm and equal to or less than 300 μm.
The mass flow controller comprises a capillary tube, wherein the capillary tube is provided with a fluid channel for fluid to pass through, the cross section of the fluid channel is circular, the diameter of the fluid channel is less than or equal to 400 microns, optionally, the fluid channel is cylindrical, and the diameter of the fluid channel is greater than or equal to 160 microns and less than or equal to 300 microns.
The mass flow controller provided by the embodiment of the invention has stable flow when the Knudsen coefficient of the capillary is less than 0.1 and the pressure ratio is higher than 2.5, is not changed along with downstream pressure fluctuation, and can realize the purposes of flow stabilization and flow limitation. In addition, the mass flow controller provided by the embodiment of the invention does not need a circuit control module to realize the purposes of current stabilization and current limiting, so that the mass flow controller provided by the embodiment of the invention does not have the problem that a circuit is interfered by electromagnetism.
In some embodiments, the capillary tube is provided in plurality, the mass flow controller further comprises a vacuum joint, the plurality of capillary tubes are connected in series, and two adjacent capillary tubes are connected through the vacuum joint;
or, the capillary tube is in plurality, the mass flow controller further comprises a trunk line and a plurality of vacuum joints, the capillary tubes are connected in parallel, the capillary tubes are connected with the vacuum joints in a one-to-one correspondence manner, and each vacuum joint is connected with the trunk line.
In some embodiments, the diameters of the fluid channels of a plurality of the capillaries in series are equal to each other; the diameter of the fluid channel of at least one of the capillaries in parallel is not equal to another of the capillaries in plurality.
Drawings
FIG. 1 is a schematic view of an axial cross-sectional configuration of a mass flow controller in accordance with an embodiment of the present invention;
FIG. 2 is a schematic diagram of a radial cross-sectional configuration of a mass flow controller in accordance with an embodiment of the present invention;
FIG. 3 is a schematic diagram of a multiple capillary tube series configuration of a mass flow controller according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a multiple capillary parallel configuration of a mass flow controller in accordance with an embodiment of the present invention;
FIG. 5 is a pressure ratio versus flow graph of a mass flow controller having a single capillary tube in accordance with an embodiment of the present invention;
FIG. 6 is a graph of inside diameter versus flow for a mass flow controller having a single capillary tube in accordance with an embodiment of the present invention;
FIG. 7 is a schematic view of a nitrogen oxide measurement system according to an embodiment of the present invention;
FIG. 8 is a schematic cross-sectional view of a catalytic reduction unit according to an embodiment of the present invention;
FIG. 9 is a schematic cross-sectional view of a nitrogen oxide measurement system according to another embodiment of the present invention;
reference numerals:
a mass flow controller 100, a capillary tube 1, a fluid channel 11, a vacuum connector 2;
an ozone generator 4, an air inlet 41, an ozone outlet 42;
a nitric oxide flow path 5, a second mass flow controller 51, a second fluid passage 511;
a first mass flow controller 6, a first fluid passage 61;
the reactor 7, the reaction chamber 71, the gas inlet 72, the gas outlet 73, the amplifying circuit 74 and the data acquisition and processing system 75;
a nitrogen dioxide flow path 8, a third mass flow controller 81, a third fluid channel 811, a catalytic reduction device 82, a housing 820, a third nitrogen-containing gas inlet 821, a first nitrogen-containing gas outlet 822, a catalytic reduction pipeline 823, a pyrolysis pipeline 824, a first straight section 8241, a second straight section 8242, an arc-shaped section 8243, a heating element 825, an exhaust gas inlet 831, an exhaust gas outlet 832,
a sleeve assembly 9;
a switching device 10, a first outlet 101, a second outlet 102, an inlet 103;
a pump 11;
a measurement system 200.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are illustrative and intended to explain the present invention and should not be construed as limiting the present invention.
As shown in fig. 1 to 6, a mass flow controller 100 according to an embodiment of the present invention includes a capillary tube 1, the capillary tube 1 having a fluid passage 11 for passing a fluid therethrough, the fluid passage 11 having a circular cross-sectional profile, the fluid passage 11 having a diameter of 400 μm or less.
The diameter of the fluid channel 11 of the capillary 1 of the mass flow controller 100 according to the embodiment of the present invention is 400 μm or less, and for the fluid channel 11 having the diameter size, the thin-surface collision effect of the gas moving inside thereof increases, and when the knudsen coefficient (knudsen number indicates the ratio of the mean free path λ of the gas molecules to the characteristic length L of the object in the flow field) is less than 0.1, the sensitivity of the gas flow rate through the fluid channel 11 to the pressure ratio at both ends thereof decreases, and when the ratio (i.e., the pressure ratio) of the inlet pressure (upstream pressure) to the outlet pressure (downstream pressure) of the capillary 1 is higher than 2.5, the flow rate of the gas remains stable at the time of the increase in the pressure ratio due to the influence of the tangential momentum of the wall surface.
That is, when the knudsen coefficient of the capillary 1 is less than 0.1 and the pressure ratio is higher than 2.5, the mass flow controller 100 according to the embodiment of the present invention has the flow rate of the gas flowing through the capillary 1 in a stable state and does not change with the change of the pressure ratio, so as to achieve the effects of stabilizing and limiting the flow rate of the gas by the capillary 1, thereby achieving the effects of stabilizing and limiting the flow rate of the mass flow controller 100 according to the embodiment of the present invention. In addition, the mass flow controller 100 according to the embodiment of the present invention does not need a circuit control module to achieve the purpose of current stabilization and current limiting, so the mass flow controller 100 according to the embodiment of the present invention does not have the problem that a circuit is interfered by electromagnetic interference.
The mass flow controller 100 of the embodiment of the invention has stable flow when the Knudsen coefficient of the capillary 1 is less than 0.1 and the pressure ratio is higher than 2.5, does not change along with the fluctuation of downstream pressure, and can realize the purposes of flow stabilization and flow limitation.
Alternatively, the fluid channel 11 is cylindrical, and the capillary tube 1 is a straight tube, which has the advantages of simple structure, small volume, easy manufacture and low cost.
The capillary 1 can be made of silicon dioxide, and the silicon dioxide has the characteristics of high temperature resistance and corrosion resistance, and can avoid the problems of high-temperature pyrolysis, acid corrosion and the like.
The diameter of the fluid passage 11 of the capillary 1 of the mass flow controller 100 of the embodiment of the present invention is 400 μm or less, and the flow rate calculation formula for the capillary in the submillimeter range is shown in formula (1)
In the formula: f is mass flow rate, mL/min;
d is the inner diameter of the capillary 1 (i.e. the diameter of the fluid channel 11), m;
P upstream of Is the inlet pressure, pa, of the capillary 1;
P downstream Is the outlet pressure, pa, of the capillary 1;
P average out The equivalent pressure in the capillary 1 is generally (P) Upstream of +P Downstream )/2，Pa；
μ is the kinetic viscosity coefficient of the gas, pa · s;
r is a gas constant;
t is temperature, K;
l is the length of the capillary 1, m;
A n the nth order flow correction coefficient when the diameter of the fluid passage 11 of the capillary tube 1 is D and the length of the fluid passage is L is related to a gas collision model and an upstream-downstream pressure ratio, and specific values are measured through experiments, and the first three items are generally reserved (namely A) 1 、A 2 And A 3 ) The precision requirement can be met;
K n the knudsen coefficient.
To further illustrate the mass flow controller 100 according to the embodiment of the present invention, referring to FIGS. 1 and 2, for capillaries 1 having a length of 50mm and a diameter of the flow channel 11 of 180 μm, 210 μm, 250 μm, 300 μm, 341 μm, 380 μm, 400 μm, 420 μm, respectively, the pressure P at the upstream inlet end of each capillary 1 is controlled Upstream At 101kPa, the downstream outlet end of each capillary 1 was pumped by a vacuum pump to change its pressure ratio. The pressure ratio was adjusted to a range of 1 to 27 by a vacuum pump, and the flow rate results of each capillary 1 are shown in FIG. 5. As can be seen from the comparison of the results shown in fig. 5, for the capillary tube 1 having a diameter of 400 μm or less in the fluid passage 11, the flow rate value of the capillary tube 1 tends to be stable when the pressure ratio is higher than 2.5, the flow rate value of the capillary tube 1 does not increase or decrease with the change of the pressure ratio, and the capillary tube 1 has a good flow stabilizing and limiting function, that is, when the pressure ratio is higher than 2.5, the flow rate value of the mass flow controller 100 according to the embodiment of the present invention does not change with the fluctuation of the pressure value at the downstream end.
It can be known through experimental measurement that, for different stable flow values of capillaries with different diameters of the flow channel 11, the corresponding stable flow value and the diameter of the flow channel 11 thereof exhibit an exponential distribution rule, as shown in fig. 6, which illustrates that the mass flow controller 100 according to the embodiment of the present invention can realize adjustment of different flow values by changing the diameter of the flow channel 11.
Alternatively, the diameter of the fluid channel 11 is 160 μm or more and 300 μm or less.
For a mass flow controller 100 having a single capillary 1, the diameter of the fluid channel 1 of the capillary 1 is the inner diameter of the mass flow controller 100, and the length of the fluid channel 1 of the capillary 1 is the length of the mass flow controller 100.
In some embodiments, referring to fig. 3, the capillary tube 1 is provided in plurality, and the mass flow controller 100 according to the embodiment of the present invention further includes a vacuum connector 2, wherein the plurality of capillary tubes 1 are connected in series, and two adjacent capillary tubes 1 are connected by the vacuum connector 2. The series connection of the plurality of capillaries 1 changes the length of the mass flow controller 100 of the embodiment of the present invention, and indirectly changes the equivalent inner diameter of the mass flow controller 100, so that the mass flow controller 100 of the embodiment of the present invention has better adaptability and wider application range.
In order to facilitate the assembly of the capillary tube 1 and the vacuum connector 2, the outer diameter of the capillary tube 1 is selected to be 6mm, and the vacuum connector 2 can be conveniently used for sealing.
In some embodiments, the diameters of the fluid channels 11 of multiple capillaries 1 in series are equal to each other. For such a series connection, when the pressure ratio of the single capillary 1 is constant, the calculation formula of the equivalent inner diameter of the mass flow controller 100 according to the embodiment of the present invention (in this case, the equivalent inner diameter is an inner diameter value corresponding to a case where the total length of the series connection is equivalent to the standard length L when the flow rates of the mass flow controller 100 formed by the plurality of equal-diameter capillaries 1 connected in series and the mass flow controller 100 formed by the single capillary 1 are the same) is shown in equation (2)
When L is i ＝L j (i ≠ j) when,
where D is the diameter of the fluid channel 11 of the capillary 1, m;
L i is the length of the ith capillary 1, m;
A n the nth order flow correction coefficient when the diameter of the fluid passage 11 of the capillary 1 is D and the length is L.
In another embodiment, referring to fig. 4, the capillary tube 1 is provided in plurality, the mass flow controller 100 further includes a trunk and a vacuum connector 2, the plurality of capillary tubes 1 are connected in parallel, the plurality of capillary tubes 1 are connected to the plurality of vacuum connectors 2 in a one-to-one correspondence, and each vacuum connector 2 is connected to the trunk. The parallel connection of the plurality of capillary tubes 1 changes the equivalent inner diameter of the mass flow controller 100 of the embodiment of the invention to enable the mass flow controller 100 of the embodiment of the invention to have a wider flow range, thereby improving the range of the mass flow controller 100 of the embodiment of the invention for measuring and controlling the flow and achieving the purpose of variable flow regulation.
Alternatively, the diameters of the fluid passages 11 of the plurality of capillaries 1 connected in parallel are equal to each other.
Optionally, the diameter of the fluid channel 11 of at least one of the capillaries 1 in parallel is not equal to another of the capillaries 1.
For the parallel connection of the capillary tubes 1 having different diameters of the fluid passage 11, the calculation formula of the equivalent inner diameter of the mass flow controller 100 of the embodiment of the present invention is shown in formula (3) when the pressure ratio of the single capillary tube 1 is constant
In the formula, D i Is the diameter of the fluid passage 11 of the capillary 1 of length L when D i ＝D j (i ≠ j) when the number of the first time interval,
A n the diameter of the fluid channel 11 being the capillary 1 is D Average And the nth-order flow correction coefficient when the length is L.
The measurement system of nitrogen oxide of the embodiment of the present invention is described below.
As shown in fig. 8 to 9, a measurement system 200 of nitrogen oxide according to an embodiment of the present invention includes a reactor 7, a first mass flow controller 6, a nitric oxide flow path 5, and a nitrogen dioxide flow path 8. The reactor 7 comprises a reaction chamber 71, an ozone inlet, a first nitrogen-containing gas inlet, a second nitrogen-containing gas inlet and a gas outlet 73, wherein the ozone inlet, the first nitrogen-containing gas inlet, the second nitrogen-containing gas inlet and the gas outlet 73 are communicated with the reaction chamber 71. The first mass flow controller 6 has a first fluid passage 61, and an outlet of the first fluid passage 61 communicates with the ozone inlet.
The nitric oxide flow path 5 includes a second mass flow controller 51, the second mass flow controller 51 has a second fluid passage 511, and an outlet of the second fluid passage 511 communicates with the first nitrogen-containing gas inlet. The nitrogen dioxide flow path 8 comprises a third mass flow controller 81 and a catalytic reduction device 82, the third mass flow controller 81 having a third fluid channel 811. Wherein each of the first fluid channel 61, the second fluid channel 511 and the third fluid channel 811 has a circular cross-sectional profile, and each of the first fluid channel 61, the second fluid channel 511 and the third fluid channel 811 has a diameter of 400 μm or less. The catalytic reduction device 82 has a third nitrogen-containing gas inlet 821 and a first nitrogen-containing gas outlet 822, the outlet of the third fluid passage 811 being in communication with the third nitrogen-containing gas inlet 821 and the first nitrogen-containing gas outlet 822 being in communication with the first nitrogen-containing gas inlet.
In the system 200 for measuring nitrogen oxides according to the embodiment of the present invention, the first mass flow controller 6 is used to control the flow rate of the air supplied to the system 200, and the second mass flow controller 51 and the third mass flow controller 81 are used to control the flow rate of the gas containing nitrogen oxides supplied to the system 200, so that the gas with stable quality can be supplied to the reactor 7, and the error signal caused by the interference of the mass flow controllers can be effectively eliminated, thereby achieving high measurement accuracy.
In order to make the measurement system 200 of nitrogen oxide according to the embodiment of the present invention more easily understood, an example will be described with reference to fig. 9. The system 200 for measuring nitrogen oxides comprises a reactor 7, a first mass flow controller 6, an ozone generator 4, a nitric oxide flow path 5, a nitrogen dioxide flow path 8, a switching device 10 and a pump 11.
The reactor 7 comprises a reaction chamber 71, an ozone inlet, a first nitrogen-containing gas inlet, a second nitrogen-containing gas inlet and a gas outlet 73, wherein the ozone inlet, the first nitrogen-containing gas inlet, the second nitrogen-containing gas inlet and the gas outlet 73 are communicated with the reaction chamber 71.
The ozone inlet, the first nitrogen-containing gas inlet and the second nitrogen-containing gas inlet may be three independent ports; the following steps are also possible: the ozone inlet is an independent port, and the first nitrogen-containing gas inlet and the second nitrogen-containing gas inlet are the same port; the following steps are also possible: the ozone inlet, the first nitrogen-containing gas inlet and the second nitrogen-containing gas inlet are the same.
The reaction chamber 71 generates a chemiluminescent reaction between the nitric oxide gas and the ozone to generate a light intensity, the reactor 7 calculates and converts the light intensity into the mass of the nitric oxide participating in the reaction, and the mass of the nitrogen-containing gas input into the nitric oxide flow path 5 or the nitrogen dioxide flow path 8 are used for calculating the concentration of the nitric oxide or the concentration of the nitrogen dioxide, and the calculation process of the concentration will be described in detail below.
The first mass flow controller 6 has a first fluid passage 61, the ozone generator 4 has an air inlet 41 and an ozone outlet 42, the outlet of the first fluid passage 61 communicates with the air inlet 41, and the ozone outlet 42 communicates with the ozone inlet. The first mass flow controller 6 controls the flow rate of air input to the ozone generator 4, and the ozone generator 4 converts the input oxygen into ozone, which is then delivered into the reaction chamber 71. The ozone generator 4 converts oxygen in the air into ozone to provide sufficient ozone for the chemiluminescent reaction to increase the reaction efficiency.
The nitric oxide flow path 5 includes a second mass flow controller 51, the second mass flow controller 51 has a second fluid passage 511, and an outlet of the second fluid passage 511 communicates with the first nitrogen-containing gas inlet. The second mass flow controller 51 controls the flow of the nitric oxide comprising gas delivered to the reaction chamber 71.
The nitrogen dioxide flow path 8 comprises a third mass flow controller 81 and a catalytic reduction device 82, the third mass flow controller 81 having a third fluid passageway 811, the catalytic reduction device 82 having a third nitrogen-containing gas inlet 821 and a first nitrogen-containing gas outlet 822, the outlet of the third fluid passageway 811 communicating with the third nitrogen-containing gas inlet 821 and the first nitrogen-containing gas outlet 822 communicating with the first nitrogen-containing gas inlet. The third mass flow controller 81 controls the flow of the nitrogen dioxide containing gas or the flow of the gas having both nitric oxide and nitrogen dioxide, and the catalytic reduction device 82 converts the nitrogen dioxide into nitric oxide, which is then delivered into the reaction chamber 71.
The switching device 10 includes an inlet 103, a first outlet 101 and a second outlet 102, the inlet 103 switchably communicating with one of the first outlet 101 and the second outlet 102, each of the outlet of the second fluid passage 511 and the outlet of the third fluid passage 811 communicating with the inlet 103, the first outlet 101 communicating with the first nitrogen-containing gas inlet, the second outlet 102 communicating with the third nitrogen-containing gas inlet 821. As shown in fig. 9, when the inlet 103 of the switching device 10 communicates with the first outlet 101, the nitric oxide flow path 5 is in a communicating state and the nitrogen dioxide flow path 8 is in a closed state; when the inlet 103 of the switching device 10 is in communication with the second outlet 102, the nitrogen dioxide flow path 8 is in a communicating state and the nitric oxide flow path 5 is in a closed state. The nitrogen oxide measurement system 200 according to the embodiment of the present invention simplifies the piping arrangement by providing the switching device 10, and the nitrogen oxide flow path 5 and the nitrogen dioxide flow path 8 can be switched by the switching device 10.
In some embodiments, as shown in FIG. 9, the ozone inlet, the first nitrogen-containing gas inlet, and the second nitrogen-containing gas inlet are the same opening to form the gas inlet 72. The measurement system further includes a sleeve assembly 9, the sleeve assembly 9 including an outer tube and an inner tube, the outer tube being sleeved outside the inner tube, an outer circumferential surface of the inner tube being spaced apart from an inner circumferential surface of the outer tube, the inner tube being in communication with the ozone outlet 42, the outer tube being in communication with the second fluid passage 511 and the first nitrogen-containing gas outlet 822, each of the inner tube and the outer tube being in communication with the gas inlet 72. The outer tube delivers nitrogen-containing gas into the reaction chamber 71 and the inner tube delivers ozone into the reaction chamber 71. The arrangement of the gas inlet 72 and the sleeve assembly 9 such that the initial positions of the ozone and nitrogen-containing gas as they enter the reaction chamber 71 are relatively close facilitates mixing of the gases delivered into the reaction chamber 71 to enable the reactant gases to fully participate in the reaction.
In other embodiments, the inner tube is in communication with the second fluid passage 511 and the first nitrogen-containing gas outlet 822, the outer tube is in communication with the ozone outlet 42, and each of the inner and outer tubes is in communication with the ozone inlet. The pump 11 is in communication with the gas outlet 73 of the reactor 7, the pump 11 serving as a motive part for powering the flow of gas of the nitrogen oxide measurement system. Furthermore, the outlet pressure of the first mass flow controller 6, the second mass flow controller 51, and the third mass flow controller 81 can be changed by adjusting the power of the pump 11, and the pressure ratio of the first mass flow controller 6, the second mass flow controller 51, and the third mass flow controller 81 can be adjusted. When the pressure ratio of the first mass flow controller 6, the second mass flow controller 51, and the third mass flow controller 81 is ensured to be higher than 2.5, the control accuracy of the first mass flow controller 6, the second mass flow controller 51, and the third mass flow controller 81 on the flow rate of the gas is not affected by the fluctuation of the power of the pump 11.
In some embodiments, the system 200 for measuring nitrogen oxides further includes an ozone decomposition device having a tail gas inlet 831 and a tail gas outlet 832, wherein the tail gas inlet 831 is communicated with the gas outlet 73. The system 200 for measuring nitrogen oxides according to the embodiment of the present invention reduces the adverse effect of ozone on the environment by disposing an ozone decomposition device to decompose the unreacted ozone discharged from the reaction chamber 72.
In other embodiments, the catalytic reduction device 82 includes a housing 820, a catalytic reduction conduit 823, a pyrolysis conduit 824, and a heating element 825. The housing 820 has a receiving cavity. A catalytic reduction tube 823 is located within the containment chamber, one end of the catalytic reduction tube 823 forming a third nitrogen-containing gas inlet 821 and the other end of the catalytic reduction tube 823 forming a first nitrogen-containing gas outlet 822. The pyrolysis pipe 824 is located in the accommodating cavity, one end of the pyrolysis pipe 824 forms an exhaust gas inlet 831, and the other end of the pyrolysis pipe 824 forms an exhaust gas outlet 832. A heating member 825 is provided in the accommodating chamber to heat the catalytic reduction tube 823 and the pyrolysis tube 824. Under the high temperature environment formed by the heating element 825, nitrogen dioxide is converted into nitrogen monoxide in the catalytic reduction pipeline 823, a molybdenum net is arranged in the catalytic reduction pipeline 823 to serve as a reaction catalyst of the nitrogen dioxide, and the molybdenum net can be a molybdenum net with a large specific surface area and high porosity so as to improve the reduction efficiency of the nitrogen dioxide. At the same time, the high temperature created by the heating element 825 also facilitates the pyrolysis of the ozone within the pyrolysis conduit 824. This measurement system integrates catalytic reduction pipeline 823 and pyrolysis pipeline 824 in casing 820, has promoted this measurement system's integrated level, has reduced the complexity of this measurement system's equipment layout.
In some embodiments, at least a portion of the heating element 825 is positioned between the catalytic reduction conduit 823 and the pyrolysis conduit 824 to promote uniform heating of the catalytic reduction conduit 823 and the pyrolysis conduit 824 by the heating element 825 to ensure desired temperatures of the catalytic reduction conduit 823 and the pyrolysis conduit 824.
In some embodiments, referring to fig. 8, the pyrolysis duct 824 is U-shaped and includes a first straight section 8241, a second straight section 8242, and an arcuate section 8243. The first straight section 8241 and the second straight section 8242 are arranged at intervals along the preset direction, the catalytic reduction pipeline 823 and the heating member 824 are positioned between the first straight section 8241 and the second straight section 8242 in the preset direction, and the heating member 825 is wound on the catalytic reduction pipeline 823. That is, the heating member 825 is also located between the first straight section 8241 and the second straight section 8242 in the predetermined direction. One end of the curved section 8243 is connected to the first straight section 8241, and the other end of the curved section 8243 is connected to the second straight section 8242. The pyrolysis pipeline 824 is in a U shape, so that the layout of the catalytic reduction pipeline 823 and the heating element 824 is simpler and more reasonable, and the heating effect on the catalytic reduction pipeline 823 and the heating element 824 is ensured.
Preferably, the reaction chamber 71 is plated with a highly reflective gold film to reflect the light intensity generated by the chemiluminescence reaction, thereby preventing the wall surface of the reaction chamber 71 from reducing the light intensity. The reactor 7 is provided with a temperature control system outside the reaction chamber 71 to raise and control the temperature of the space inside the reaction chamber 71. The reactor 7 is further provided with a photoelectric detector, an amplifying circuit 74 and a data acquisition and processing system 75, the photoelectric detector is connected with the amplifying circuit 74, the amplifying circuit 74 is connected with the data acquisition and processing system 75, the photoelectric detector detects a light intensity signal generated by the reaction in the reaction chamber 71 and converts the light intensity signal into a current signal, the amplifying circuit 74 amplifies the current signal, and the data acquisition and processing system 75 records and calculates data to obtain the amount of the nitric oxide participating in the chemiluminescence reaction. In addition, before the experimental measurement is performed by using the measurement system 200, the mass flow information of the second mass flow controller 51 and the third mass flow controller 81 may be input into the data acquisition and processing system 75, and calculated by the data acquisition and processing system 75 to directly obtain the data of the nitric oxide concentration and/or the nitrogen dioxide concentration.
Referring to fig. 9, the measurement system of nox according to the embodiment of the present invention is used and the nox concentration is calculated as follows:
NO measurement mode: first, the inlet 103 of the switching device 10 is communicated with the first outlet 101 to close the nitrogen dioxide flow path 8, the inlet end of the first mass flow controller 6 is connected with the dry air, and the inlet end of the second mass flow controller 51 of the nitric oxide flow path 5 is inputted with the gas to be measured. Then, starting the pump 11 and the reactor 7, enabling the dry air to enter the ozone generator 4 through the first mass flow controller 6, controlling and stabilizing the air inflow of the air through the first mass flow controller 6, converting oxygen in the air into ozone in the ozone generator 4, and enabling the ozone to enter the reactor 7; the gas to be measured enters the reactor 7 through the second mass flow controller 51, and the second mass flow controller 51 controls and stabilizes the air inflow of the gas to be measured. The ozone and the nitric oxide in the gas to be detected generate a chemiluminescence reaction in the reaction chamber 71 of the reactor 7, the reactor 7 detects light intensity and converts and calculates the light intensity signal to obtain the amount of the nitric oxide participating in the reaction, and then the concentration of the nitric oxide in the gas to be detected can be obtained.
NO 2 Measurement mode: first, the inlet 103 of the switching device 10 is communicated with the second outlet 102 to close the nitric oxide flow path 5, the inlet end of the first mass flow controller 6 is connected with dry air, and the inlet end of the third mass flow controller 81 of the nitrogen dioxide flow path 8 is input with the gas to be measured. Then, starting the pump 11 and the reactor 7, enabling the dry air to enter the ozone generator 4 through the first mass flow controller 6, controlling and stabilizing the air inflow of the air through the first mass flow controller 6, converting oxygen in the air into ozone in the ozone generator 4, and enabling the ozone to enter the reactor 7; the gas to be measured enters the catalytic reduction device 82 through the third mass flow controller 81, nitrogen dioxide in the gas to be measured is converted into nitric oxide in the catalytic reduction device 82, the nitric oxide enters the reactor 7, and the third mass flow controller 81 controls and stabilizes the air inflow of the gas to be measured. In a reactor for measuring nitric oxide and ozone in gasThe reaction chamber 71 of the reactor 7 is subjected to a chemiluminescence reaction, the reactor 7 detects light intensity and converts and calculates a light intensity signal to obtain the amount of the nitrogen oxide participating in the reaction, and then the concentration of the nitrogen dioxide in the gas to be detected can be obtained.
If the gas to be measured contains both nitric oxide and nitrogen dioxide, the concentration of nitric oxide obtained by firstly carrying out NO measurement mode on the gas to be measured is marked as C1. Then NO is carried out 2 And obtaining the concentration of the sum of the nitric oxide and the nitrogen dioxide in a measurement mode, and marking the concentration as C2, wherein C2-C1 is the content of the nitrogen dioxide.
Depending on the measurement purpose, the second mass flow controller 51 can be used as a part of the nitric oxide flow path 5 to connect with the gas to be measured containing nitric oxide and also can be used to connect with a zero gas source, and the third mass flow controller 81 can be used as a part of the nitrogen dioxide flow path 8 to connect with the gas to be measured containing nitric oxide and also can be used to connect with a standard gas source (e.g., a gas containing known nitric oxide concentration and a gas containing known nitrogen dioxide concentration).
In the measurement process that this measurement system 200 connects zero gas source and standard gas source, zero gas source dilutes the standard gas source, measures the concentration of the nitric oxide of standard gas source through this measurement system, thereby compares known concentration and measured concentration and marks this measurement system, further reduces the error that this measurement system produced when measuring.
Preferably, the second mass flow controller 51 and the third mass flow controller 81 are the same mass flow controller, as shown in fig. 7. When the gas to be measured contains both nitric oxide and nitrogen dioxide, or when the composition of nitric oxide and nitrogen dioxide in the gas to be measured is unknown, the gas to be measured is connected to the second mass flow controller 51 or the third mass flow controller 81. When the inlet 103 of the switching device 10 is communicated with the first outlet 101, the gas to be measured is directly conveyed into the reaction chamber 71, and the nitric oxide in the gas to be measured participates in the reaction, so that the concentration C1 of the nitric oxide in the gas to be measured is obtained. When the inlet 103 of the switching device 10 is communicated with the second outlet 102, the gas to be detected enters the catalytic reduction device 82, nitrogen dioxide is converted into nitric oxide in the catalytic reduction device 82, then in the reaction chamber 71, the original nitric oxide and the converted nitric oxide in the gas to be detected simultaneously participate in the chemiluminescence reaction, so that the concentration C2 of the nitric oxide participating in the reaction is obtained, and the concentration of the nitrogen dioxide in the gas to be detected can be obtained through C2-C1.
In some embodiments, each of the first fluid channel 61, the second fluid channel 511, and the third fluid channel 811 is cylindrical, and each of the first fluid channel 61, the second fluid channel 511, and the third fluid channel 811 has a diameter of 160 μm or more and 300 μm or less.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise explicitly stated or limited, the terms "mounted," "connected," "fixed," and the like are to be construed broadly, e.g., as being permanently connected, detachably connected, or integral; may be mechanically coupled, may be electrically coupled or may be in communication with each other; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
In the present disclosure, the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" and the like mean that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. A system for measuring nitrogen oxides, comprising:
a reactor (7), the reactor (7) comprising a reaction chamber (71), an ozone inlet, a first nitrogen-containing gas inlet, a second nitrogen-containing gas inlet, and a gas outlet (73), the ozone inlet, the first nitrogen-containing gas inlet, the second nitrogen-containing gas inlet, and the gas outlet (73) all being in communication with the reaction chamber (71);
a first mass flow controller (6), the first mass flow controller (6) having a first fluid passage (61), an outlet of the first fluid passage (61) being in communication with the ozone inlet;
a nitric oxide flow path (5), the nitric oxide flow path (5) comprising a second mass flow controller (51), the second mass flow controller (51) having a second fluid passage (511), an outlet of the second fluid passage (511) being in communication with the first nitrogen-containing gas inlet;
a nitrogen dioxide flow path (8), the nitrogen dioxide flow path (8) comprising a third mass flow controller (81) and a catalytic reduction device (82), the third mass flow controller (81) having a third fluid channel (811), wherein each of the first, second and third fluid channels (61, 511, 811) has a circular cross-sectional profile, each of the first, second and third fluid channels (61, 511, 811) has a diameter of 400 μm or less, the catalytic reduction device (82) having a third nitrogen-containing gas inlet (821) and a first nitrogen-containing gas outlet (822), the outlet of the third fluid channel (811) communicating with the third nitrogen-containing gas inlet (821), the first nitrogen-containing gas outlet (822) communicating with the first nitrogen-containing gas inlet.
2. The system of claim 1, further comprising an ozone generator (4), the ozone generator (4) having an air inlet (41) and an ozone outlet (42), the first fluid passage (61) communicating with the air inlet (41), the ozone outlet (42) communicating with the ozone inlet.
3. The system of claim 2, wherein the ozone inlet, the first nitrogen-containing gas inlet, and the second nitrogen-containing gas inlet are one and the same opening; the measuring system further comprises a sleeve assembly (9), the sleeve assembly (9) comprises an outer pipe and an inner pipe, the inner pipe is sleeved in the outer pipe, the outer peripheral surface of the inner pipe is spaced from the inner peripheral surface of the outer pipe, the inner pipe is communicated with the ozone outlet (42), or the inner pipe is communicated with the second fluid channel (511) and the first nitrogen-containing gas outlet (822), the outer pipe is communicated with the second fluid channel (511) and the first nitrogen-containing gas outlet (822), or the outer pipe is communicated with the ozone outlet (42), and each of the inner pipe and the outer pipe is communicated with the ozone inlet.
4. The system of claim 2, further comprising a switching device (10), the switching device (10) comprising an inlet (103), a first outlet (101), and a second outlet (102), the inlet (103) switchably communicating with one of the first outlet (101) and the second outlet (102), each of the second fluid passage (511) and the third fluid passage (811) communicating with the inlet (103), the first outlet (101) communicating with the first nitrogen-containing gas inlet, the second outlet (102) communicating with the third nitrogen-containing gas inlet (821).
5. The system for measuring nitrogen oxides according to claim 1,
the measuring system further comprises an ozone decomposing device having a tail gas inlet (831) and a tail gas outlet (832), the tail gas inlet (831) being in communication with the gas outlet (73);
alternatively, the catalytic reduction device (82) comprises:
a housing (820), the housing (820) having a receiving cavity,
a catalytic reduction conduit (823), the catalytic reduction conduit (823) being located within the containment cavity, one end of the catalytic reduction conduit (823) constituting the third nitrogen-containing gas inlet (821) and the other end of the catalytic reduction conduit (823) constituting the first nitrogen-containing gas outlet (822);
a pyrolysis pipe (824), wherein the pyrolysis pipe (824) is located in the accommodating cavity, one end of the pyrolysis pipe (824) forms the tail gas inlet (831), and the other end of the pyrolysis pipe (824) forms the tail gas outlet (832); and
a heating member (825), the heating member (825) being provided within the accommodation chamber so as to heat the catalytic reduction duct (823) and the pyrolysis duct (824).
6. A nitrogen oxide measurement system according to claim 5, characterized in that at least a part of the heating element (825) is located between the catalytic reduction conduit (823) and the pyrolysis conduit (824).
7. The system of claim 6, wherein the pyrolysis tube (824) is U-shaped and comprises:
a first straight section (8241) and a second straight section (8242), wherein the first straight section (8241) and the second straight section (8242) are arranged at intervals along a preset direction, the catalytic reduction pipeline (823) and the heating element (824) are positioned between the first straight section (8241) and the second straight section (8242) in the preset direction, and the heating element (825) is wound on the catalytic reduction pipeline (823); and
an arc-shaped section (8243), one end of the arc-shaped section (8243) is connected with the first straight section (8241), and the other end of the arc-shaped section (8243) is connected with the second straight section (8242).
8. The system according to any one of claims 1 to 7, wherein each of the first fluid passage (61), the second fluid passage (511) and the third fluid passage (811) is cylindrical, and each of the first fluid passage (61), the second fluid passage (511) and the third fluid passage (811) has a diameter of 160 μm or more and 300 μm or less.
9. A mass flow controller comprising a capillary tube (1), the capillary tube (1) having a fluid channel (11) for passage of a fluid, the cross-sectional profile of the fluid channel (11) being circular, the fluid channel (11) having a diameter of 400 μm or less, optionally the fluid channel being cylindrical, the fluid channel (11) having a diameter of 160 μm or more and 300 μm or less.
10. A mass flow controller according to claim 9,
the mass flow controller comprises a plurality of capillaries (1), and further comprises vacuum joints (2), wherein the capillaries (1) are connected in series, and two adjacent capillaries (1) are connected through the vacuum joints (2);
or, the number of the capillary tubes (1) is multiple, the mass flow controller further comprises a trunk line and vacuum joints (2), the capillary tubes (1) are connected in parallel, the capillary tubes (1) are connected with the vacuum joints (2) in a one-to-one correspondence manner, and each vacuum joint (2) is connected with the trunk line;
alternatively,
the diameters of the fluid channels (11) of a plurality of the capillaries (1) connected in series are equal to each other;
the diameter of the fluid channel (11) of at least one of the capillaries (1) in parallel is not equal to another of the capillaries (1).
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