Dynamic mixed gas distribution method and system

Abstract

The invention discloses a dynamic gas distribution method and system for mixed gas. The method comprises the following steps: standard mixed gas with different target concentrations is correspondingly connected with one MFC in a gas distribution instrument, and high-purity diluted gas is correspondingly connected with one MFC in the gas distribution instrument; the mass flow to be output of the MFC on the gas distribution channel where the corresponding standard mixed gas is located is calculated; acquiring a flow compensation coefficient corresponding to the standard mixed gas; the mass flow to be output of the corresponding compensated MFC is obtained; obtaining the sum of the to-be-output mass flows of all the compensated MFCs; and dynamic gas distribution is completed based on the compensated to-be-output mass flow of all the MFCs and the preset total mass flow. According to the invention, the to-be-output mass flow of the MFC is compensated, the accuracy of the mass flow of the mixed gas output by the MFC is improved, and the accuracy of the mixed gas distribution concentration is improved.

Description

Technical Field

[0001] This invention relates to the field of dynamic gas mixing technology, and in particular to a dynamic gas mixing method and system for mixed gases. Background Technology

[0002] Currently, the methods for preparing gaseous reference materials are relatively mature. In the production of gaseous reference materials, the most commonly used methods include static gas mixing and dynamic gas mixing. The basic principle of static gas mixing is to mix the required gas in parts according to different components, while dynamic gas mixing is to mix the gas during the flow process.

[0003] The principle of dynamic gas mixing is to continuously inject the source gas into a dilution gas stream with a known flow rate, and then into a gas mixer. The gas is then mixed thoroughly in the mixer and continuously flows out. By accurately measuring the flow ratio of the source gas and the dilution gas (e.g., mass flow ratio or volume flow ratio, i.e., dilution factor), the required concentration of the mixed gas standard can be precisely obtained. Compared to static gas mixing, dynamic gas mixing can generate a larger quantity of standard mixed gas over a wider concentration range. Its dynamic characteristics also largely eliminate the influence of adsorption on the container wall on the final concentration of the mixture, thereby reducing mixture loss. In this process, the stability and measurement accuracy of the flow rates of the source gas and the dilution gas directly affect the accuracy of the gas mixing.

[0004] Existing dynamic gas mixing methods include thermal mass flow controllers (MFCs), which utilize a mass flow controller (MFC) to accurately measure and control the mass flow rate of gases, thereby achieving the preparation of gas mixtures with target concentrations. However, the calibration process of conventional MFCs only calibrates the purity coefficient of any high-purity gas (e.g., air, nitrogen). Currently, in addition to using high-purity gases for standard substance preparation, the industry also uses high-purity mixed gases for gas mixture preparation. The mass flow coefficient of high-purity gases is significantly different from that of high-purity mixed gases, and its variation is related to the proportion of high-purity mixed gases. Therefore, when using MFCs to prepare gas mixtures, the mass flow rate generated based on the purity coefficient will deviate significantly from the actual flow rate. This deviation in mass flow rate will directly affect the concentration of the diluted gas mixture, leading to significant concentration deviations when measuring and analyzing the concentration of the diluted gas mixture using standard gas analyzers. Summary of the Invention

[0005] To address the aforementioned technical problems, one aspect of this invention provides a dynamic gas mixing method. When using a gas mixing instrument to control the mass flow rate output of standard mixed gases with different target concentrations, the method considers the influence of the mass flow rate coefficient of the high-purity mixed gas and compensates for the mass flow rate to be output by the MFC, thereby improving the accuracy of the mass flow rate of the mixed gas output by the MFC and improving the accuracy of the mixed gas concentration.

[0006] To achieve the above-mentioned objectives, the present invention employs the following technical solution: This application provides a method for dynamic gas mixing, including: S1: Standard mixed gases of different target concentrations are connected to one MFC in the gas mixing instrument, and high-purity dilution gas is connected to one MFC in the gas mixing instrument. S2: Calculate the mass flow rate to be output by the MFC in the gas distribution channel of the corresponding standard mixed gas based on the different target concentrations of the standard mixed gas, the target concentration of the mixed gas output by the MFC in the gas distribution channel of the corresponding standard mixed gas, and the preset total mass flow rate. S3: Call the preset compensation coefficient model corresponding to different standard mixed gases to obtain the flow compensation coefficient of the corresponding standard mixed gas; S4: Use the corresponding flow compensation coefficient to compensate the calculated mass flow rate of the MFC to be output, and obtain the corresponding compensated mass flow rate of the MFC to be output. S5: Obtain the sum of the mass flow rates of all MFC components to be output after compensation; S6: Determine whether the sum of the mass flow rates is equal to the preset total mass flow rate. If yes, proceed to S7. If no, determine whether the sum of the mass flow rates is greater than the preset total mass flow rate. If yes, proceed to S8. Otherwise, proceed to S9. S7: Controls the MFC output of the corresponding compensated MFC mass flow rate in the gas distribution channel where the corresponding standard mixed gas is located, to form a mixed gas distribution; S8: Normalize the mass flow rate to be output by each compensated MFC and multiply it by the preset total mass flow rate to obtain the mass flow rate to be output by the MFC in the gas distribution channel where the corresponding standard mixed gas is located, and control the output to form a mixed gas distribution. S9: Obtain the mass flow rate of the MFC to be output in the gas distribution channel where the high-purity dilution gas is located, and control all MFC outputs to form a mixed gas distribution; The preset compensation coefficient model represents the relationship between the concentration and flow rate compensation coefficients of the corresponding standard mixed gas.

[0007] In some embodiments of this application, the preset compensation coefficient models corresponding to different standard mixed gases are specifically obtained as follows: At multiple different concentrations of the standard mixed gas, the corresponding actual mass flow rate and target mass flow rate were obtained; Calculate the flow compensation coefficient by dividing the actual mass flow rate at the corresponding concentration by the target mass flow rate, and form at least one set of fitted data. Each set of fitted data includes the flow compensation coefficient and the corresponding concentration. For multiple flow compensation coefficients corresponding to multiple different concentrations, multiple sets of fitting data were obtained; By using multiple sets of fitted data, the relationship between the flow rate compensation coefficient and the concentration is fitted to form a preset compensation coefficient model corresponding to the standard mixed gas.

[0008] In some embodiments of this application, the gas mixing instrument has a human-machine interface and a computer control system. The human-machine interface can be used to configure the target concentration and preset total mass flow rate of the mixed gas output by the MFC on the gas mixing channel where each standard mixed gas is located. The computer control system is used to control the execution of processes S2 to S9.

[0009] In some embodiments of this application, the dynamic gas mixing method further includes: The mixed gas mixture is input into a standard gas analyzer for analysis.

[0010] In some embodiments of this application, the dynamic gas distribution method further includes: calculating the gas dilution concentration output by the MFC on the gas distribution channel corresponding to the standard mixed gas, specifically: First, normalize the mass flow rate output of the MFC in the gas distribution channel corresponding to the standard mixed gas, and then multiply it by the target concentration of the standard mixed gas in the corresponding gas distribution channel.

[0011] Compared with existing technologies, the dynamic gas mixing method provided in this application has the following advantages and beneficial effects: (1) When standard mixed gases with different target concentrations are mixed using MFC, the mass flow rate output by the control MFC deviates from the actual mass flow rate output and is related to the concentration. Therefore, a preset compensation coefficient model corresponding to different standard mixed gases is used to obtain the flow compensation coefficient, which is used to compensate the actual mass flow rate output by the MFC, improve the accuracy of the actual mass flow rate output by the MFC, and improve the accuracy of the gas mixing concentration. (2) The dynamic gas distribution process does not require any changes to the original hardware architecture of dynamic gas distribution, making it easy to implement.

[0012] Some embodiments of this application also relate to a dynamic gas mixing system, including: At least one mixed standard gas cylinder, each containing a standard mixed gas of different target concentrations; A dilution gas bottle containing a high-purity dilution gas; A gas mixing device has multiple gas mixing channels, each corresponding to at least one standard gas mixing bottle and one dilution gas bottle. Each gas mixing channel is equipped with an MFC (Medium-Fuel Mixer), and the input of the MFC is connected to either the standard gas mixing bottle or the dilution gas bottle. The gas mixing device is used to perform the following process: S11: Calculate the mass flow rate to be output by the MFC in the gas distribution channel of the corresponding standard mixed gas based on the different target concentrations of the standard mixed gas, the target concentration of the mixed gas output by the MFC in the gas distribution channel of the corresponding standard mixed gas, and the preset total mass flow rate. S12: Call the preset compensation coefficient model corresponding to different standard mixed gases to obtain the flow compensation coefficient of the corresponding standard mixed gas; S13: Use the corresponding flow compensation coefficient to compensate the calculated mass flow rate of the MFC to be output, and obtain the corresponding compensated mass flow rate of the MFC to be output. S14: Obtain the sum of the mass flow rates of all MFC components to be output after compensation; S15: Determine whether the sum of the mass flow rates is equal to the preset total mass flow rate. If yes, proceed to S16. If no, determine whether the sum of the mass flow rates is greater than the preset total mass flow rate. If yes, proceed to S17. Otherwise, proceed to S18. S16: Control the MFC output of the corresponding compensated MFC mass flow rate in the gas distribution channel where the corresponding standard mixed gas is located, to form a mixed gas distribution; S17: After normalizing the mass flow rate to be output by each compensated MFC, multiply it by the preset total mass flow rate to obtain the mass flow rate to be output by the MFC in the gas distribution channel where the corresponding standard mixed gas is located, and control the output to form a mixed gas distribution. S18: Obtain the mass flow rate to be output by the MFC in the gas distribution channel where the high-purity dilution gas is located, and control all MFCs to output to form a mixed gas distribution; The preset compensation coefficient model represents the relationship between the concentration and flow rate compensation coefficients of the corresponding standard mixed gas.

[0013] In some embodiments of this application, the preset compensation coefficient models corresponding to different standard mixed gases are specifically obtained as follows: At multiple different concentrations of the standard mixed gas, the corresponding actual mass flow rate and target mass flow rate were obtained; Calculate the flow compensation coefficient by dividing the actual mass flow rate at the corresponding concentration by the target mass flow rate, and form at least one set of fitted data. Each set of fitted data includes the flow compensation coefficient and the corresponding concentration. For multiple flow compensation coefficients corresponding to multiple different concentrations, multiple sets of fitting data were obtained; By using multiple sets of fitted data, the relationship between the flow rate compensation coefficient and the concentration is fitted to form a preset compensation coefficient model corresponding to the standard mixed gas.

[0014] In some embodiments of this application, the gas mixing instrument has a human-machine interface and a computer control system. The human-machine interface can be used to configure the target concentration and preset total mass flow rate of the mixed gas output by the MFC on the gas mixing channel where each standard mixed gas is located. The computer control system is used to control the execution of processes S11 to S18.

[0015] In some embodiments of this application, the dynamic gas distribution system further includes: A standard gas analyzer is used to input the mixed gas mixture into the standard gas analyzer for analysis.

[0016] In some embodiments of this application, the gas mixing instrument is further used to calculate the post-mixing dilution concentration of the MFC output on the corresponding gas mixing channel, specifically: First, normalize the mass flow rate output of the MFC in the corresponding gas distribution channel, and then multiply it by the target concentration of the standard mixed gas in the corresponding gas distribution channel.

[0017] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of an embodiment of the dynamic gas mixing method proposed in this invention; Figure 2 The principle of one embodiment of the dynamic gas distribution system for mixed gas proposed in this invention. Figure 1 ; Figure 3 The principle of one embodiment of the dynamic gas distribution system for mixed gas proposed in this invention. Figure 2 .

[0020] Figure label: 100. Gas mixing device; 110. First MFC; 120. Second MFC; 130. Third MFC; 140. Fourth MFC; 200. First mixed standard gas cylinder; 300. Second mixed standard gas cylinder; 400. Third mixed standard gas cylinder; 500. Diluent gas cylinder. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. In the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0024] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0025] To address the issue of mass flow deviation when using MFC to prepare low-concentration mixed gas from high-purity mixed gas, where the mass flow coefficient of the mixed gas deviates from the mass flow coefficient of the high-purity gas calibrated by the MFC, this application provides a dynamic gas mixing method and system for compensating and controlling the mass flow rate output by the MFC, thereby improving the accuracy of the output mass flow rate.

[0026] The dynamic gas distribution method for mixed gas involved in this application is based on a dynamic gas distribution system for mixed gas. In the following description, the dynamic gas distribution method is described in conjunction with the dynamic gas distribution system.

[0027] The dynamic gas mixing process is achieved using a gas mixing instrument, which is an instrument that mixes multiple gases in a set ratio and outputs a gas with a precise concentration based on the principle of mass flow control. It is equipped with a human-machine interface (e.g., a touch screen, not shown) and a computer control system (as the core processing unit, not shown), and supports preset gas mixing parameters and AC / DC power supply.

[0028] See Figure 1 It shows a flowchart of a dynamic gas mixing method.

[0029] S1: Standard mixed gases of different target concentrations are respectively connected to one MFC in the gas mixing instrument 100, and high-purity dilution gas is connected to one MFC in the gas mixing instrument 100.

[0030] The gas mixer 100 is configured with different numbers of MFCs depending on the number of gas mixing channels. According to the preset gas mixing parameters, the computer control system in the gas mixer 100 will send instructions to the MFCs to realize the output of gas at a specified mass flow rate by the MFCs.

[0031] See Figure 2 A mixing standard gas cylinder (denoted as the first mixing standard gas cylinder 200) and a dilution gas cylinder 500 can be set up. The first mixing standard gas cylinder 200 contains, for example, 50% CO2 (for example, the dilution gas is nitrogen or argon) and is connected to the input inlet of an MFC (denoted as the first MFC 110). The dilution gas cylinder 500 contains, for example, pure N2 dilution gas and is connected to the input inlet of another MFC (denoted as the fourth MFC 140).

[0032] To achieve the production of CO2 at a low target concentration of 4%, the mass flow rates to be output from the first MFC 110 and the fourth MFC 140 need to be controlled separately.

[0033] Multiple mixed standard gas cylinders can be set up, see [link / reference] Figure 3 For example, three standard gas mixing cylinders (denoted as first standard gas mixing cylinder 200, second standard gas mixing cylinder 300, and third standard gas mixing cylinder 400) and one dilution gas cylinder 500 are set up. The first standard gas mixing cylinder 200 contains, for example, 50% CO2 (for example, the dilution gas is N2) and is connected to the input inlet of an MFC (denoted as first MFC 110). The second standard gas mixing cylinder 300 contains, for example, 60% CO and is connected to the input inlet of an MFC (denoted as second MFC 120). The third standard gas mixing cylinder 400 contains, for example, 30% H2 and is connected to the input inlet of an MFC (denoted as third MFC 130). The dilution gas cylinder 500 contains, for example, pure N2 dilution gas and is connected to the input inlet of another MFC (denoted as fourth MFC 140).

[0034] S2: Calculate the mass flow rate to be output by different MFCs based on the different target concentrations of the standard mixed gas, the target concentration of the mixed gas output by the MFC on the gas distribution channel where the standard mixed gas is located, and the preset total mass flow rate.

[0035] To achieve the preparation of CO2 at a low target concentration, it is necessary to pre-set the target concentration and total mass flow rate of the mixed gas output by the MFCs in different gas distribution channels of different mixed standard gas cylinders (that is, the sum of the mass flow rates of all MFC outputs set by the gas distributor 100). In this way, the mass flow rate of the mixed gas to be output by each MFC can be controlled.

[0036] For ease of explanation, the gas distribution channel where the first MFC 110 is located is referred to as the first gas distribution channel, the gas distribution channel where the second MFC 120 is located is referred to as the second gas distribution channel, the gas distribution channel where the third MFC 130 is located is referred to as the third gas distribution channel, and the gas distribution channel where the fourth MFC 140 is located is referred to as the fourth gas distribution channel.

[0037] In some embodiments of this application, the mass flow rate output by the MFC needs to be determined based on the target concentration in the mixed standard gas cylinder on the corresponding gas distribution channel, the total mass flow rate, and the target concentration of the mixed gas output by the MFC on the corresponding gas distribution channel.

[0038] Definition: The target concentration of the standard mixed gas in different mixed standard gas cylinders is denoted as C. i_in (i is a natural number, representing the i-th gas distribution channel of the corresponding standard gas mixture), the target concentration of the gas mixture output by the MFC in different gas distribution channels is denoted as C. i_out The total mass flow rate is F total The mass flow rate of the mixed gas to be output by the MFC is F0. i .

[0039] As follows, Figure 3 The dynamic gas distribution is explained using the hardware structure as an example.

[0040] C 1_in This indicates the target concentration of the mixed standard gas in the first mixed standard gas cylinder 200, C. 2_in This indicates the target concentration of the mixed standard gas in the second mixed standard gas cylinder 300, C. 3_in This indicates the target concentration of the mixed standard gas in the third mixed standard gas cylinder 400. C 1_out This represents the target concentration of the mixed gas output from the first MFC 110, C. 2_out This indicates the target concentration of the mixed gas output from the second MFC 120, C. 3_outF01 represents the target concentration of the mixed gas output by the third MFC 130, F02 represents the mass flow rate of the mixed gas to be output by the first MFC 110, F03 represents the mass flow rate of the mixed gas to be output by the second MFC 120, and F04 represents the mass flow rate of the mixed gas to be output by the third MFC 130.

[0041] Therefore, the gas mixing unit 100 can be based on C i_in C i_out and F total F0 is calculated using the following formula (1). i .

[0042] F0 i = F total *C i_out / C i_in (1).

[0043] For example, the first standard gas mixing cylinder 200 contains 50% CO2, the second standard gas mixing cylinder 300 contains, for example, 60% CO, and the third standard gas mixing cylinder 400 contains, for example, 30% H2. If further preparation is required, then C... 1_in 50%, C 2_in 60%, C 3_in The target concentration C is 50%. 1_out C 2_out and C 3_out These are different preset concentrations set according to the requirements of the gas mixture components.

[0044] S3: Call the preset compensation coefficient model corresponding to different standard mixed gases to obtain the flow compensation coefficient of the corresponding standard mixed gas.

[0045] As is known in the background art, the calibration of each MFC is performed for high-purity gases. Therefore, when a high-purity mixed gas is input into the MFC's inlet, the F0 calculated above will be used... i When controlling each MFC output, the actual output mass flow rate and the required control output F0 are considered. i There is a deviation; therefore, in order to improve the accuracy of the mass flow rate output by the MFC in the i-th gas distribution channel corresponding to the standard gas mixture, F0 will be adjusted. i Perform coefficient compensation.

[0046] The mass flow rate output by MFC is related to the concentration of its mixture. Therefore, for a certain standard gas mixture, the relationship between the ratio of the actual mass flow rate and the mass flow rate output by the control (i.e., the flow compensation coefficient) (the control output command sent to MFC by the computer control system) and the concentration is obtained in advance. In other words, a preset compensation coefficient module is set for each standard gas mixture.

[0047] In practical use, the preset compensation coefficient module corresponding to the standard mixed gas is directly called. Using the current concentration, the flow compensation coefficient is obtained and used to compensate the mass flow rate F0 of the control output. i Update the control output commands sent from the computer control system to MFC to change the corresponding mass flow rate F0 output by MFC. i '.

[0048] In some embodiments of this application, taking a mixed gas containing high-purity CO2 as an example, the following description is given of the module for obtaining its corresponding preset compensation coefficient.

[0049] For mixed gases with CO2 concentrations ranging from 0 to 100%, multiple different concentrations can be selected, such as 20%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc.

[0050] At a given concentration, the flow rate is calibrated using a certified standard volumetric flow meter, and the standard volumetric flow rate at different concentration gradients is recorded, where the standard volumetric flow rate can be easily converted to the standard mass flow rate.

[0051] Furthermore, at a certain concentration, the actual mass flow rate can be obtained using MFC.

[0052] Thus, by using the actual mass flow rate and the standard mass flow rate, the ratio between the two is calculated to obtain the flow compensation coefficient at the current concentration, which is denoted as a set of data DATA1 (concentration X1, flow compensation coefficient K1).

[0053] Similarly, at other different concentrations, the same set of data DATA2 (concentration X2, flow compensation coefficient K2) will be obtained.

[0054] Therefore, multiple sets of data (DATA1, DATA2, DATA3, ..., DATA) were obtained at various concentrations. j , where j is a natural number, DATA j This represents a set of data obtained at the j-th concentration.

[0055] Using the above sets of data, the relationship between concentration X and flow compensation coefficient K is fitted to obtain a preset compensation coefficient module for the mixed gas containing high-purity CO2, which is denoted as the first preset compensation coefficient module.

[0056] Similarly, a preset compensation coefficient module for a gas mixture containing CO can be obtained, denoted as the second preset compensation coefficient module; and a preset compensation coefficient module for a gas mixture containing H2 can be obtained, denoted as the third preset compensation coefficient module.

[0057] In the actual dynamic gas mixing process, if 50% CO2 from the first mixed standard gas cylinder 200 is used for gas mixing as described above, the current concentration of 50% is substituted into the first preset compensation coefficient module to calculate the flow compensation coefficient corresponding to the first gas mixing channel, denoted as K1; if 60% CO from the second mixed standard gas cylinder 300 is used for gas mixing as described above, the current concentration of 60% is substituted into the second preset compensation coefficient module to calculate the corresponding flow compensation coefficient, denoted as K2; if 30% H2 from the third mixed standard gas cylinder 400 is used for gas mixing as described above, the current concentration of 30% is substituted into the third preset compensation coefficient module to calculate the corresponding flow compensation coefficient, denoted as K3.

[0058] S4: Use the corresponding flow compensation coefficient to compensate the calculated mass flow rate to be output by MFC, and obtain the corresponding compensated mass flow rate to be output by MFC.

[0059] As described above, the mass flow rate F0 to be output by the MFC has been calculated in S2. i .

[0060] Therefore, the flow compensation coefficient calculated in S3 can be used to compensate F0 using formula (2). i Obtain the compensated mass flow rate F0 of the MFC output. i ',Right now: F0 i '= F0 i *Ki (2).

[0061] Where i is a natural number, representing the i-th gas distribution channel of the corresponding standard gas mixture.

[0062] See Figure 3 Given the hardware example, F01' = F01*K1, F02' = F02*K2, and F03' = F03*K3.

[0063] S5: Obtain the sum of the mass flow rates of all MFC components to be output after compensation.

[0064] When there are multiple gas distribution channels containing corresponding standard mixed gases, since the various standard mixed gases can be used as diluents for each other, whether additional high-purity diluent gas is needed depends on whether the sum of the mass flow rates to be output by all MFCs in the gas distribution channels containing the corresponding standard mixed gases is less than the preset mass flow rate.

[0065] That is, ∑F0 i =F01'+F02'+F03'.

[0066] S6: Determine if the sum of mass flow rates equals F. totalIf yes, proceed to S7; otherwise, determine if the sum of mass flow rates is greater than F. total If yes, proceed to S8; otherwise, proceed to S9.

[0067] In ∑F0 i '=F total When this occurs, it means that the sum of the mass flow rates to be output by the first MFC 110, the second MFC 120, and the third MFC 130 is exactly equal to F. total Without the need to add dilution gas, the mass flow rates to be output from the first MFC 110, the second MFC 120, and the third MFC 130 can be directly controlled.

[0068] In ∑F0 i >F total When this occurs, it indicates that the sum of the mass flow rates to be output by the first MFC 110, the second MFC 120, and the third MFC 130 has exceeded F. total No dilution gas is needed. At this time, in order to ensure normal gas distribution, the mass flow rates to be output by the first MFC 110, the second MFC 120 and the third MFC 130 are reallocated and controlled.

[0069] In ∑F0 i '<F total When the sum of the mass flow rates to be output by the first MFC 110, the second MFC 120, and the third MFC 130 does not exceed F, it indicates that the total mass flow rate is less than or equal to F. total At this point, dilution gas needs to be added.

[0070] S7: Controls the MFC output of the corresponding standard mixed gas in the gas distribution channel to form a mixed gas distribution.

[0071] In ∑F0 i '=F total When this occurs, it means that the sum of the mass flow rates to be output by the first MFC 110, the second MFC 120, and the third MFC 130 is exactly equal to F. total There is no need to reallocate the mass flow rates to be output from the first MFC 110, the second MFC 120, and the third MFC 130, nor is there a need to add additional dilution gas.

[0072] Thus, the gas mixing unit 100 sends a command to control the mass flow rate output of the first MFC 110 to be F01' to the first MFC 110, a command to control the mass flow rate output of the second MFC 120 to be F02' to the second MFC 120, and a command to control the mass flow rate to be output of the third MFC 130 to be F03' to the third MFC 130.

[0073] S8: After normalizing the mass flow rate to be output by each compensated MFC, multiply it by the preset total mass flow rate to obtain the mass flow rate to be output by the MFC in the gas distribution channel of the corresponding standard mixed gas, and control the output to form a mixed gas distribution.

[0074] The mass flow rate to be output by the first MFC 110, the second MFC 120 and the third MFC 130 is obtained by the following formula (3).

[0075] F0 i ''=F total *F0 i ' / ∑F0 i '(3)。

[0076] That is, the mass flow rate to be output by the first MFC 110 in the first gas distribution channel is F01'', the mass flow rate to be output by the second MFC 120 in the second gas distribution channel is F02'', and the mass flow rate to be output by the third MFC 130 in the third gas distribution channel is F03''.

[0077] Thus, the gas mixing unit 100 sends a command to control the mass flow rate output of the first MFC 110 to be F01'' to the first MFC 110, a command to control the mass flow rate output of the second MFC 120 to be F02'' to the second MFC 120, and a command to control the mass flow rate to be output of the third MFC 130 to be F03'' to the third MFC 130.

[0078] At this point, the gas mixing is complete, and the mixed gas mixture can then be output.

[0079] In some embodiments of this application, the mass flow rates F01'', F02'', and F03'' of the control output can be output and displayed on the gas mixing instrument 100.

[0080] S9: Obtain the mass flow rate of the MFC to be output on the gas distribution channel where the high-purity dilution gas is located, and control all MFC outputs to form a mixed gas distribution.

[0081] In ∑F0 i '<F total The mass flow rate F of the dilution gas is calculated using the following formula (4). dilute That is, the mass flow rate to be output by the fourth MFC 140.

[0082] F dilute =F total -∑F0 i '(4)。

[0083] Thus, the gas mixing unit 100 sends a command to control the mass flow rate output of the first MFC 110 to be F01', a command to control the mass flow rate output of the second MFC 120 to be F02', a command to control the mass flow rate output of the third MFC 130 to be F03', and a command to control the mass flow rate output of the fourth MFC 140 to be F01'. dilute The instruction is sent to the fourth MFC 140.

[0084] At this point, the gas mixing is complete, and the mixed gas mixture can then be output.

[0085] In some embodiments of this application, the mass flow rate F of the control output can be output, displayed, and controlled on the gas mixing device 100. dilute F01', F02' and F03'.

[0086] The prepared gas mixture can be bottled or fed into a standard gas analyzer for analysis of its composition.

[0087] The standard gas analyzer is certified by a professional metrology unit and can accurately analyze the composition of the mixed gas. The concentration of each gas component analyzed can be used to verify the accuracy of the dynamic gas mixing process.

[0088] In some embodiments of this application, the gas dilution concentration output by the MFC on the gas distribution channel of the corresponding standard mixed gas can be calculated and obtained. These calculated gas dilution concentrations can be compared with the target concentration of the mixed gas output by the MFC on the gas distribution channel of the corresponding standard mixed gas (e.g., C). 1_out C 2_out and C 3_out The gas mixing effect of the dynamic gas mixing method was verified by comparison.

[0089] Still referencing Figure 3 The given hardware architecture is described below.

[0090] For the different cases S8 and S9 (two days in the case of S7 and S8), since the mass flow rates output by the first MFC 110, the second MFC 120 and the third MFC 130 are different, it is also necessary to calculate the gas dilution concentration output by the first MFC 110, the second MFC 120 and the third MFC 130 separately.

[0091] For F01'', F02'' and F03'' calculated in S8, the gas dilution concentration of each MFC output is calculated using the following formula (5).

[0092] C i_out '= Ci_out *F0 i '' / ∑F0 i '' (5).

[0093] That is, the gas dilution concentration C output by the first MFC 110 1_out =C 1_out *F01'' / ∑F0 i The gas dilution concentration C of the second MFC120 output. 2_out =C 2_out *F02'' / ∑F0 i The gas dilution concentration C of the third MFC 130 output. 3_out '= C 3_out *F03'' / ∑F0 i ''.

[0094] For F01', F02' and F03' calculated in S9 (S7), the gas dilution concentration of each MFC output is calculated using the following formula (6).

[0095] C i_out '= C i_out *F0 i ' / ∑F0 i '(6)。

[0096] That is, the gas dilution concentration C output by the first MFC 110 1_out =C 1_out *F01' / ∑F0 i The gas dilution concentration C of the second MFC 120 output. 2_out =C 2_out *F02' / ∑F0 i ', The gas dilution concentration C of the third MFC 130 output 3_out =C 3_out *F03' / ∑F0 i '.

[0097] According to C 1_out 'With C 1_out In comparison, C 2_out 'With C 2_out C 3_out 'With C 3_out In comparison, calculate the gas distribution accuracy.

[0098] For example, taking the first mixed standard gas cylinder 200 containing 50% CO2 (with N2 as the background gas) as an example, it is diluted with pure N2, and the target concentration of CO2 after gas mixing is required to be 4%.

[0099] When the flow coefficient compensation involved in the dynamic gas mixing method of this application is not adopted, the concentration after dilution is measured by a standard gas analyzer certified by a professional metrology unit. The output concentration is 9.6%, which is 240% different from the target concentration of 4%.

[0100] When using the process coefficient compensation involved in the dynamic gas mixing method of this application, the concentration after dilution is measured using a standard gas analyzer. The output concentration is 4.2%, which deviates from the target concentration of 4% by 1.05%, and the gas mixing concentration accuracy is improved by 238.95%.

[0101] The dynamic gas mixing method disclosed in this application can improve the accuracy of the mass flow rate output by the MFC, thereby increasing the gas mixing concentration.

[0102] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A method for dynamic gas mixing, characterized in that, include: S1: Standard mixed gases of different target concentrations are connected to one MFC in the gas mixing instrument, and high-purity dilution gas is connected to one MFC in the gas mixing instrument. S2: Calculate the mass flow rate to be output by the MFC in the gas distribution channel of the corresponding standard mixed gas based on the different target concentrations of the standard mixed gas, the target concentration of the mixed gas output by the MFC in the gas distribution channel of the corresponding standard mixed gas, and the preset total mass flow rate. S3: Call the preset compensation coefficient model corresponding to different standard mixed gases to obtain the flow compensation coefficient of the corresponding standard mixed gas; S4: Use the corresponding flow compensation coefficient to compensate the calculated mass flow rate of the MFC to be output, and obtain the corresponding compensated mass flow rate of the MFC to be output. S5: Obtain the sum of the mass flow rates of all MFC components to be output after compensation; S6: Determine whether the sum of the mass flow rates is equal to the preset total mass flow rate. If yes, proceed to S7. If no, determine whether the sum of the mass flow rates is greater than the preset total mass flow rate. If yes, proceed to S8. Otherwise, proceed to S9. S7: Controls the MFC output of the corresponding compensated MFC mass flow rate in the gas distribution channel where the corresponding standard mixed gas is located, to form a mixed gas distribution; S8: Normalize the mass flow rate to be output by each compensated MFC and multiply it by the preset total mass flow rate to obtain the mass flow rate to be output by the MFC in the gas distribution channel where the corresponding standard mixed gas is located, and control the output to form a mixed gas distribution. S9: Obtain the mass flow rate of the MFC to be output in the gas distribution channel where the high-purity dilution gas is located, and control all MFC outputs to form a mixed gas distribution; The preset compensation coefficient model represents the relationship between the concentration and flow rate compensation coefficients of the corresponding standard mixed gas.

2. The dynamic gas mixing method according to claim 1, characterized in that, The preset compensation coefficient models for different standard gas mixtures are obtained as follows: At multiple different concentrations of the standard mixed gas, the corresponding actual mass flow rate and target mass flow rate were obtained; Calculate the flow compensation coefficient by dividing the actual mass flow rate at the corresponding concentration by the target mass flow rate, and form at least one set of fitted data. Each set of fitted data includes the flow compensation coefficient and the corresponding concentration. For multiple flow compensation coefficients corresponding to multiple different concentrations, multiple sets of fitting data were obtained; By using multiple sets of fitted data, the relationship between the flow compensation coefficient and the concentration is fitted to form a preset compensation coefficient model for the standard mixed gas.

3. The dynamic gas mixing method according to claim 1, characterized in that, The gas mixing instrument has a human-machine interface and a computer control system. Through the human-machine interface, the target concentration and preset total mass flow rate of the mixed gas output by the MFC on the gas mixing channel of each standard mixed gas can be configured. The computer control system is used to control the execution of processes S2 to S9.

4. The dynamic gas mixing method according to claim 1, characterized in that, The dynamic gas mixing method further includes: The mixed gas mixture is input into a standard gas analyzer for measurement.

5. The dynamic gas mixing method according to claim 1, characterized in that, The dynamic gas distribution method further includes: calculating the gas dilution concentration output by the MFC on the gas distribution channel corresponding to the standard mixed gas, specifically: First, normalize the mass flow rate output of the MFC in the gas distribution channel corresponding to the standard mixed gas, and then multiply it by the target concentration of the standard mixed gas in the corresponding gas distribution channel.

6. A dynamic gas mixing system, characterized in that, include: At least one mixed standard gas cylinder, each containing a standard mixed gas of different target concentrations; A dilution gas bottle containing a high-purity dilution gas; A gas mixing device has multiple gas mixing channels, each corresponding to at least one standard gas mixing bottle and one dilution gas bottle. Each gas mixing channel is equipped with an MFC (Medium-Fuel Mixer), and the input of the MFC is connected to either the standard gas mixing bottle or the dilution gas bottle. The gas mixing device is used to perform the following process: S11: Calculate the mass flow rate to be output by the MFC in the gas distribution channel of the corresponding standard mixed gas based on the different target concentrations of the standard mixed gas, the target concentration of the mixed gas output by the MFC in the gas distribution channel of the corresponding standard mixed gas, and the preset total mass flow rate. S12: Call the preset compensation coefficient model corresponding to different standard mixed gases to obtain the flow compensation coefficient of the corresponding standard mixed gas; S13: Use the corresponding flow compensation coefficient to compensate the calculated mass flow rate of the MFC to be output, and obtain the corresponding compensated mass flow rate of the MFC to be output. S14: Obtain the sum of the mass flow rates of all MFC components to be output after compensation; S15: Determine whether the sum of the mass flow rates is equal to the preset total mass flow rate. If yes, proceed to S16. If no, determine whether the sum of the mass flow rates is greater than the preset total mass flow rate. If yes, proceed to S17. Otherwise, proceed to S18. S16: Control the MFC output of the corresponding compensated MFC mass flow rate in the gas distribution channel where the corresponding standard mixed gas is located, to form a mixed gas distribution; S17: After normalizing the mass flow rate to be output by each compensated MFC, multiply it by the preset total mass flow rate to obtain the mass flow rate to be output by the MFC in the gas distribution channel where the corresponding standard mixed gas is located, and control the output to form a mixed gas distribution. S18: Obtain the mass flow rate to be output by the MFC in the gas distribution channel where the high-purity dilution gas is located, and control all MFCs to output to form a mixed gas distribution; The preset compensation coefficient model represents the relationship between the concentration and flow rate compensation coefficients of the corresponding standard mixed gas.

7. The dynamic gas distribution system according to claim 6, characterized in that, The preset compensation coefficient models for different standard gas mixtures are obtained as follows: At multiple different concentrations of the standard mixed gas, the corresponding actual mass flow rate and target mass flow rate were obtained; Calculate the flow compensation coefficient by dividing the actual mass flow rate at the corresponding concentration by the target mass flow rate, and form at least one set of fitted data. Each set of fitted data includes the flow compensation coefficient and the corresponding concentration. For multiple flow compensation coefficients corresponding to multiple different concentrations, multiple sets of fitting data were obtained; By using multiple sets of fitted data, the relationship between the flow rate compensation coefficient and the concentration is fitted to form a preset compensation coefficient model corresponding to the standard mixed gas.

8. The dynamic gas distribution system according to claim 6, characterized in that, The gas mixing instrument has a human-machine interface and a computer control system. Through the human-machine interface, the target concentration and preset total mass flow rate of the mixed gas output by the MFC on the gas mixing channel of each standard mixed gas can be configured. The computer control system is used to control the execution of processes S11 to S18.

9. The dynamic gas distribution system according to claim 6, characterized in that, The dynamic gas mixing system also includes: A standard gas analyzer is used to input the mixed gas mixture into the standard gas analyzer for analysis.

10. The dynamic gas distribution system according to claim 6, characterized in that, The gas mixing instrument is also used to calculate the gas dilution concentration output by the MFC on the gas mixing channel corresponding to the standard mixed gas, specifically: First, normalize the mass flow rate output of the MFC in the gas distribution channel corresponding to the standard mixed gas, and then multiply it by the target concentration of the standard mixed gas in the corresponding gas distribution channel.

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