A device for preparing and dispensing a standard gas of trace moisture in ultrapure inert gas

Abstract

The present application relates to the field of gas dilution, in particular to a kind of trace moisture standard gas preparation and dispensing device in ultrapure inert gas, comprising: moisture standard generator is used to provide liquid water by moisture generator and is vaporized by evaporator to generate water vapor, dilution gas input unit is used to provide the dry dilution gas after being purified, mixing pipeline is used to mix water vapor and dilution gas according to set proportion and dilute, background moisture determination unit is used to determine the background moisture concentration of system, desorption unit is used to carry out gas adsorption and desorption dynamic test, adsorption decoupling unit is used to determine fast adsorption state capacity coefficient and strong retention state capture capacity, pre-saturation unit determines whether strong retention state active site has reached saturation, and flow compensation unit is used to compensate the push rate of moisture generator.The present application improves the accuracy and long-term stability of trace moisture standard gas dilution concentration.

Description

Technical Field

[0001] This invention relates to the field of gas dilution, and more particularly to a device for preparing and distributing a standard gas containing trace moisture in an ultrapure inert gas. Background Technology

[0002] Gas reference materials serve as metrological standards for measuring gas composition, playing an indispensable role in environmental monitoring, semiconductor manufacturing, industrial safety testing, and metrological calibration. With the increasing demands for detection accuracy in these fields, particularly in scenarios such as online monitoring of trace moisture in the atmosphere, stringent control of trace moisture in ultrapure gases during semiconductor processes, and precise measurement of dew point temperature in lithium battery production workshops, low-concentration moisture standard gases (ppb level) are frequently required for calibrating analytical instruments or for quantitative analysis of samples. Since conventional static dilution methods are difficult to directly prepare low-concentration standard gases, dynamic dilution methods are widely used due to their advantage of continuously generating standard gases of varying concentrations.

[0003] Currently, the mainstream dynamic dilution system mainly adopts a dynamic dilution system based on mass flow controller, combined with a water generation device such as a permeation tube or injection pump. By controlling the mixing ratio of water vapor and dilution gas, the target concentration can be prepared. Its advantage is that the dilution ratio can be continuously adjusted, and it can flexibly generate water standard gases of different concentrations.

[0004] However, existing technologies still have significant drawbacks in practical applications. As polar molecules, water readily adsorbs onto the inner surfaces of metal or polymer walls of pipes, valves, and joints through hydrogen bonding, forming strongly retained bound states. Simultaneously, reversible physical adsorption occurs through van der Waals forces. This adsorption process results in some water being trapped on the pipe surface, with the actual amount of water participating in the dilution being less than the theoretical input, leading to an output concentration lower than the target value. Furthermore, the adsorbed water molecules, especially those in the strongly retained bound state, desorb at an extremely slow rate during subsequent dilution. This manifests as a prolonged tailing of the concentration signal after the water source is cut off, making it difficult to return to zero, exhibiting a moisture memory effect. This leads to instability in the concentration output and batch-to-batch non-repeatability. Particularly when diluting the moisture standard gas to the ppb level, the relative concentration loss due to adsorption can reach several percentage points, far exceeding the allowable error range for precision gas dilution.

[0005] Furthermore, the adsorption behavior of moisture in pipelines is influenced by a variety of factors, including pipeline material, inerting process, inner wall surface roughness, usage time, ambient temperature, and the moisture concentration and duration of the previous gas introduction, exhibiting significant time-varying and uncertainties. In particular, once moisture forms a strongly retained bound state in the pipeline, its desorption time constant can reach tens of minutes or even hours, an effect that cannot be accurately compensated for by simple offline calibration. However, existing systems lack methods for detecting and evaluating these adsorption effects, failing to perceive the current adsorption state of the system, and unable to distinguish between fast adsorption and strongly retained bound states. This makes it impossible to determine whether the inert coating has failed or whether the active sites have become saturated.

[0006] Chinese Patent Application Publication No. CN1382256A discloses an apparatus and method for generating a moisture standard in a gas. Specifically, it relates to an apparatus for adding a preselected amount of water vapor or other vaporized liquid to a flowing gas stream at a constant rate. The apparatus includes: a suitable syringe having a needle connected thereto; an evaporator connected to the needle, wherein the evaporator is located within the flowing gas stream; and a component for applying pressure to the syringe such that water or other liquid is delivered from the syringe through the needle to the evaporator at a constant rate. The invention also relates to a method for adding a preselected amount of water vapor or other vaporized liquid to a flowing gas stream at a constant rate, the method comprising using a syringe having a needle connected thereto, wherein a moisture generator is filled with water or other vaporized liquid to be vaporized.

[0007] The existing technology also has the following problems: the system cannot sense the degree of water adsorption in the current pipeline, cannot distinguish between the fast desorption equilibrium state and the strong retention bound state, cannot determine whether the inert coating has failed or whether the active sites of the strong retention state have been saturated, and cannot accurately compensate the flow rate based on the adsorption state. As a result, the concentration deviation caused by adsorption during the dilution process cannot be identified and corrected, and the dilution ratio is not accurate enough. Summary of the Invention

[0008] To address this, the present invention provides a standard gas preparation and distribution device for trace moisture in ultrapure inert gas, which overcomes the problems in the prior art where the system cannot sense the degree of moisture adsorption in the current pipeline, cannot distinguish between fast desorption equilibrium state and strong retention bound state, cannot determine whether the inert coating has failed or whether the active sites of the strong retention state have been saturated, and cannot accurately compensate the flow rate based on the adsorption state. As a result, the concentration deviation caused by adsorption during the dilution process cannot be identified and corrected, and the dilution ratio is not accurate enough.

[0009] To achieve the above objectives, the present invention provides a device for preparing and distributing a trace moisture standard gas in an ultrapure inert gas, comprising: The dilution gas input pipeline is connected to the dilution gas source and is used to input the dilution gas; A first dilution line, connected to the dilution gas input line, includes a first mass flow controller for controlling the flow rate of the dilution gas; The second dilution line, which is connected to the dilution gas input line, includes a second mass flow controller for controlling the flow rate of the dilution gas; A moisture generating device, which is connected to the first dilution pipeline, is used to introduce vaporized water and dilution gas into the first dilution pipeline at different push rates to mix and obtain several primary mixed gases with calibrated moisture concentrations. A mixing pipeline, which is connected to the first dilution pipeline and the second dilution pipeline respectively, is used to mix the primary mixed gas with the dilution gas in the second dilution pipeline to form a secondary mixed gas; The background moisture determination unit is used to determine the background moisture concentration of the diluted gas based on the background moisture test. An adsorption testing unit is used to generate a concentration-time response curve based on the adsorption-desorption test of the primary mixed gas, and to determine the total number of moles of water adsorbed in the primary mixed gas by the background moisture concentration determination pipeline. The desorption analysis unit is used to determine the adsorption state of the adsorbed water based on the inflection point of the desorption segment of the concentration-time response curve. A curve decoupling unit is used to determine the fast adsorption capacity coefficient and strong retention capture capacity of the pipeline for the adsorbed water based on a two-dimensional adsorption scatter plot generated from several total adsorption moles. The presaturation unit is used to determine whether the highly retained active sites in the pipeline have reached saturation based on the moisture presaturation test. A flow compensation unit is used to compensate the push rate based on the fast adsorption state capacity coefficient.

[0010] Furthermore, the background moisture determination unit determines the moisture level based on the average reading of the moisture analyzer located at the end of the mixing pipeline during the continuous purging process of the dilution gas while the moisture generator is off.

[0011] Furthermore, the adsorption testing unit determines the total number of moles of water adsorbed by the pipeline in the primary mixed gas by subtracting the background moisture concentration from the measured concentration in the adsorption segment of the concentration-time response curve.

[0012] Furthermore, the desorption analysis unit determines that the adsorption state of the adsorbed water is a fast adsorption state based on the condition that there is no inflection point in the desorption segment of the concentration-time response curve.

[0013] Furthermore, the desorption analysis unit determines that the adsorption state of the adsorbed water is a coexistence of a fast adsorption state and a strong retention state based on the condition that there is an inflection point in the desorption segment of the concentration-time response curve.

[0014] Furthermore, the curve decoupling unit, under the condition that the adsorption state of the adsorbed water is a coexistence of fast adsorption state and strong retention state, generates a two-dimensional adsorption scatter plot with the calibrated water concentration as the abscissa and the corresponding total number of adsorbed moles as the ordinate.

[0015] Furthermore, the curve decoupling unit determines the fast adsorption capacity coefficient based on the slope of the fitted line obtained by first-order linear regression fitting of the two-dimensional adsorption scatter plot.

[0016] Furthermore, the curve decoupling unit determines the strong retention state capture capacity based on the intercept of the fitted line obtained by first-order linear regression fitting of the two-dimensional adsorption scatter plot.

[0017] Furthermore, the pre-saturation unit determines that the strongly retained active sites have reached saturation based on the difference between the first concentration and the second concentration determined in the pre-saturation test process being within the allowable error range; The pre-saturation unit determines that the strongly retained active sites have not reached saturation based on the fact that the difference between the first concentration and the second concentration is not within the allowable error range.

[0018] Furthermore, the flow compensation unit compensates for the push rate based on the fast adsorption capacity coefficient when the active sites in the pipeline are saturated with only fast adsorption or strong retention states.

[0019] Compared with existing technologies, the advantages of this invention are as follows: This invention determines the adsorption state of water on the inner wall of the pipeline by detecting the inflection point of the desorption segment of the concentration-time response curve on a semi-logarithmic coordinate system using a desorption / desorption unit. When a clear inflection point appears on the semi-logarithmic curve of the desorption segment, it indicates that two adsorption sites with different desorption activation energies—a fast desorption equilibrium state and a strong retention bound state—coexist on the inner wall surface of the pipeline. This allows for real-time output of qualitative judgment results after testing, providing directional guidance for subsequent quantitative analysis and compensation operations. It avoids the problems of blindly performing pre-saturation treatment or neglecting chemisorption, leading to improper compensation, as seen in existing technologies, and significantly improves the efficiency and specificity of adsorption state determination.

[0020] Furthermore, this invention utilizes an adsorption decoupling unit to perform first-order linear regression fitting on the total adsorption moles measured at different target concentrations and the corresponding two-dimensional scatter plots generated at those concentrations. The slope of the fitting represents the adsorption capacity of the fast desorption state, and the intercept represents the capture capacity of the strong retention state. This achieves quantitative separation of fast desorption equilibrium adsorption and strong retention bound adsorption within the same system. This method leverages the fundamental physical difference between fast desorption equilibrium adsorption, which follows Henry's Law, and strong retention bound adsorption, which exhibits saturation capacity characteristics. By mathematically resolving the two adsorption mechanisms, it avoids the compensation bias caused by the inability to distinguish between adsorption types in traditional methods, thus significantly improving the accuracy of dilution concentrations.

[0021] Furthermore, this invention, through a pre-saturation unit, performs a pre-saturation test after determining that the strongly retained active sites have not reached saturation, accurately determining the saturation state of the active sites. The pre-saturation test eliminates the influence of the strongly retained bound state on the accuracy of subsequent dilution, allowing subsequent gas mixing processes to only require dynamic compensation for the fast desorption equilibrium adsorption, significantly reducing the compensation complexity during system operation, extending the effective service life of the pipeline coating, and lowering system maintenance costs.

[0022] Furthermore, the flow compensation unit of the present invention compensates the push rate of the moisture generator based on the adsorption capacity of the fast desorption equilibrium state determined by the adsorption decoupling unit. When the target concentration changes, the compensation amount is adjusted linearly, achieving dynamic matching. By eliminating the constant loss of the strong retention state through pre-saturation, and then performing precise compensation based on a physical model for the fast desorption equilibrium state, the accuracy and long-term stability of the trace moisture standard gas dilution concentration are significantly improved across the entire range. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the device for preparing and distributing trace moisture standard gas in ultrapure inert gas according to an embodiment of the present invention; Figure 2 This is a structural block diagram of the trace moisture standard gas dilution and distribution device according to an embodiment of the present invention; Figure 3 These are concentration-time response curves for different calibrated moisture concentrations in embodiments of the present invention. Figure 4 This is a flowchart illustrating the process of determining the adsorption state in an embodiment of the present invention; Figure 5 This is a comparison of the concentration-time response curves of the fast adsorption state and the strong retention state in an embodiment of the present invention; Figure 6 This is a first-order linear regression fitted line graph of the two-dimensional adsorption scatter plot in an embodiment of the present invention; Figure 7 This is a flowchart illustrating how to determine whether strongly retained active sites have reached saturation, as described in an embodiment of the present invention. Figure 8 This is a comparison chart of the output concentration before and after push rate compensation in an embodiment of the present invention.

[0024] In the diagram: 1-Two-stage pressure reducing valve, 2-Gas source purifier, 3-Dryer, 4-First back pressure valve, 5-First mass flow controller, 6-Second mass flow controller, 7-Moisture generator, 8-Second back pressure valve, 9-Moisture analyzer, 10-Connecting pipe, a-Dilution gas input pipeline, b-First dilution pipeline, c-Second dilution pipeline, d-Mixing pipeline. Detailed Implementation

[0025] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0026] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0027] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0028] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0029] Please see Figures 1-2 As shown, Figure 1 This is a schematic diagram of the structure of the device for preparing and distributing trace moisture standard gas in ultrapure inert gas according to an embodiment of the present invention; Figure 2 This is a structural block diagram of a trace moisture standard gas dilution and distribution device according to an embodiment of the present invention. This embodiment of the trace moisture standard gas preparation and distribution device in ultrapure inert gas includes: The dilution gas input pipeline a is connected to the dilution gas source and includes a two-stage pressure reducing valve 1 arranged sequentially along the gas flow direction to regulate the flow rate of the dilution gas, a gas source purifier 2 to remove impurities from the dilution gas, and a dryer 3 to remove moisture from the dilution gas. The first dilution pipeline b, which is connected to the dryer 3, includes a first back pressure valve 4 for controlling the pressure of the first dilution pipeline b, a first mass flow controller 5 for controlling the flow rate of the dilution gas, and a connecting pipe 10 arranged sequentially along the gas flow direction. The second dilution pipeline c, which is connected to the dryer 3, includes a second back pressure valve 8 arranged sequentially along the gas flow direction to control the pressure of the second dilution pipeline c and a second mass flow controller 6 to control the flow rate of the dilution gas. A moisture generating device, which is connected to the connecting pipe 10, includes a moisture generator 7 and an evaporator (not shown in the figure) disposed at the end of the moisture generator 7 for vaporizing liquid water, for introducing vaporized water into the first dilution pipeline b through the connecting pipe 10 at different pushing rates to mix with the dilution gas, thereby obtaining several primary mixed gases with calibrated moisture concentrations. A mixing pipeline d is connected to the first dilution pipeline b and the second dilution pipeline c respectively, so as to mix the primary mixed gas with the dilution gas in the second dilution pipeline c to form a secondary mixed gas with a moisture concentration reaching the target gas mixing concentration. A moisture analyzer 9 is provided at the end of the mixing pipeline d to detect the moisture content in the secondary mixed gas. The background moisture determination unit is used to determine the background moisture concentration of the diluted gas based on the background moisture test. An adsorption testing unit is used to generate a concentration-time response curve based on the adsorption-desorption test of the primary mixed gas, and to determine the total number of moles of water adsorbed in the primary mixed gas by the background moisture concentration determination pipeline. The desorption analysis unit, which is connected to the adsorption test unit, is used to determine the adsorption state of the adsorbed water based on the inflection point of the desorption segment of the concentration-time response curve, wherein the adsorption state includes a fast adsorption state and a strong retention state. A curve decoupling unit, which is connected to the desorption analysis unit, is used to determine the fast adsorption state capacity coefficient and strong retention state capture capacity of the pipeline for the adsorbed water based on a two-dimensional adsorption scatter plot generated by several total adsorption moles. The two-dimensional adsorption scatter plot uses the calibrated water concentration as the abscissa and the total adsorption moles as the ordinate. A pre-saturation unit, which is connected to the curve decoupling unit, is used to perform a water pre-saturation test based on the strong retention state to determine whether the strong retention state active sites in the pipeline have reached saturation. A flow compensation unit, which is connected to the curve decoupling unit and the presaturation unit respectively, is used to compensate the push rate based on the fast adsorption state capacity coefficient.

[0030] In this embodiment, the gas source purifier 2 is a composite purification system integrating adsorption, catalysis and distillation, used to deeply remove impurities from the dilution gas; the dryer 3 can be an adsorption dryer or a membrane dryer, used to reduce the background moisture in the dilution gas; the mass flow controller can be a laminar flow differential pressure mass flow controller.

[0031] In this embodiment, to minimize moisture adsorption in the pipelines, all pipelines undergo a special inertization treatment. This can be achieved by forming an inert hydrophobic coating on the inner wall of the pipeline using a chemical vapor deposition process, or by directly using pipelines made of a chemically inert and low-absorption polymer material. The chemically inert polymer material can be a perfluoroalkoxy resin, polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF). As an optional implementation, the inner wall of the pipeline can be electrolytically polished or mechanically ground to reduce surface roughness and the number of active adsorption sites.

[0032] Optionally, this embodiment also includes an electric heat tracing device disposed on the outer wall of the pipeline to maintain the temperature of the pipeline and reduce the adsorption rate of moisture on the inner wall of the pipeline. The temperature range of the electric heat tracing device is 40℃-70℃.

[0033] In this embodiment, the preparation process of the secondary mixed gas is as follows: the dilution gas enters the first dilution pipeline b and the second dilution pipeline c through the dilution gas input pipeline a respectively; the moisture generator 7 introduces vaporized water into the first dilution pipeline b through the connecting pipe 10 at different push rates to mix with the dilution gas to form a primary mixed gas; then the primary mixed gas enters the mixing pipeline d and mixes with the gas in the second dilution pipeline c to form a secondary mixed gas.

[0034] In this embodiment, the flow rate of water entering the first dilution pipeline b is controlled by controlling the push rate of the moisture generator 7, the flow rate of dilution gas in the first dilution pipeline b is controlled by the first mass flow controller 5, and the flow rate of dilution gas in the second dilution pipeline c is controlled by the second mass flow controller 6, thereby adjusting the mixing ratio of water and dilution gas to meet the requirements of different target gas concentrations.

[0035] In this embodiment, the target gas concentration for trace moisture is calculated using the following formula: In the formula: C - Moisture concentration of the secondary mixed gas output, in ppb; k - coefficient of vaporization volume expansion; v - Push rate, in mm / min; A-Moisture generator 7 internal cavity cross-sectional area, unit: mm 2 ; - The flow rate passing through the first mass flow controller 5, in ml / min; - The flow rate passing through the second mass flow controller 6, in ml / min.

[0036] The vaporization volume expansion coefficient is the volume expansion ratio after liquid water is converted into water vapor, which can be determined by referring to the table of thermodynamic properties of water vapor based on the temperature of the production environment and the pressure in the pipeline.

[0037] In this embodiment, the target gas concentration is calculated using the theoretical gas concentration without considering concentration loss. However, in actual operating conditions, there are adsorption losses and oxidation losses of water molecules on the inner wall of the pipeline, resulting in an actual secondary gas concentration lower than the target concentration. Therefore, in this embodiment, the required push rate for the target gas concentration is used as a reference value, and the actual push rate is corrected for adsorption losses based on the theoretical push rate.

[0038] In this embodiment, the detection principle of the moisture analyzer 9 can be cavity ring-down spectroscopy or tunable diode laser absorption spectroscopy. The specific model is not limited, and it is used to detect the moisture concentration of the gas in the output pipeline.

[0039] In this embodiment, the background moisture determination unit determines the background moisture concentration of the dilution gas by performing a background moisture test. Since the inert gas used as the dilution gas still retains trace levels of moisture after being processed by the gas source purifier 2 and dryer 3, when the target gas concentration is at a trace level, the background moisture will cause the actual value of the moisture concentration in the secondary mixed gas to be too high. Therefore, it is necessary to measure the background moisture of the dilution gas and subtract it from the concentration calculation to improve the accuracy of the moisture concentration in the secondary mixed gas.

[0040] In this embodiment, the background moisture test process is as follows: the moisture generator is turned off, dilution gas is continuously introduced through dilution gas input pipeline a to purge the pipeline, and the moisture concentration in the mixing pipeline d is continuously monitored by moisture analyzer 9 until the fluctuation of the moisture analyzer 9 reading within a preset time period does not exceed the allowable tolerance. The average reading of the moisture analyzer 9 within the preset time period is recorded as the background moisture concentration. The allowable tolerance is set as a preset multiple of the detection limit of the moisture analyzer 9. The specific value of the preset multiple is determined by those skilled in the art based on the magnitude of the target gas concentration.

[0041] In this embodiment, the adsorption testing unit determines the adsorption state of water in the pipeline by performing dynamic gas adsorption-desorption tests. Water molecules have strong polarity. When flowing through the inner surfaces of metal or polymer walls such as pipelines, valves, and joints, water molecules can form a fast adsorption state through van der Waals forces, or a strong retention state through hydrogen bonding with active sites on the pipe wall surface. This results in some water being trapped on the pipe wall surface, and the actual amount of water participating in the mixing and dilution is less than the theoretical input, causing the output concentration to be lower than the target value. Furthermore, the adsorbed water molecules will desorb at an extremely slow rate during subsequent dilution, leading to instability in the concentration output and batch-to-batch non-repeatability. In addition, the adsorption behavior of water in the pipeline is affected by a variety of factors, including pipeline material, inner wall surface roughness, ambient temperature, pipeline pressure, and the water concentration and duration of the previous gas flow, exhibiting significant time-varying and uncertainties that cannot be accurately compensated for by simple offline calibration. Therefore, before the actual dilution operation, it is necessary to determine the type of water adsorption in the pipeline and the total number of moles adsorbed by gas adsorption-desorption dynamic test, and then perform flow compensation or pre-saturation treatment on the device to eliminate the influence of adsorption on the dilution process and improve the accuracy of water concentration in the secondary mixed gas.

[0042] In this embodiment, the dynamic gas adsorption-desorption test process is as follows: After completing the background moisture test, the moisture generator is turned on and timing begins. The moisture generator 7 introduces vaporized water into the first dilution pipeline b at different push rates through the connecting pipe 10, and mixes it sequentially with the dilution gas in the first dilution pipeline b and the second dilution pipeline c to form a secondary mixed gas, which is output through the mixing pipeline d. The reading of the moisture analyzer 9 is recorded at a sampling frequency of not less than 1Hz until the reading of the moisture analyzer 9 fluctuates within a preset time window without exceeding the allowable tolerance. The average reading within the preset time window is recorded as the plateau concentration. The moisture generator is then turned off, and the reading of the moisture analyzer 9 is recorded again until the reading of the moisture analyzer 9 is lower than 10% of the plateau concentration. A concentration-time response curve is generated based on the reading of the moisture analyzer 9. The curve from the time the moisture generator is turned on to the time before it is turned off is recorded as the adsorption segment, and the curve from the time the moisture generator is turned off to the time the test is stopped is recorded as the desorption segment. Then, the dynamic gas adsorption-desorption test process is repeated using the i-th push rate and the (i+1)-th push rate, respectively, to generate corresponding concentration-time response curves, where i is an integer greater than 1.

[0043] Please see Figure 3As shown, this is the concentration-time response curve for different calibrated moisture concentrations in an embodiment of the present invention. In this embodiment, calibrated moisture concentrations of 50 ppb, 100 ppb, 200 ppb, 500 ppb and 1000 ppb were used to perform gas adsorption-desorption dynamic tests sequentially under the same experimental conditions. The changes in the moisture analyzer 9 readings corresponding to each concentration over time were recorded, and the curves obtained from each test were plotted on the same coordinate system.

[0044] In this embodiment, the adsorption testing unit determines the total number of adsorbed moles based on the difference between the total number of input water moles and the total number of detected water moles in the adsorption section. The total number of input water moles is the total number of vaporized water moles introduced into the adsorption section by the water generator 7. The volumetric flow rate of the liquid water is calculated based on the inner diameter and pushing rate of the water generator 7, and then converted to the molar flow rate by combining the liquid water density and the molar mass of water, multiplied by the total duration of the adsorption section. The total number of detected water moles is determined by integrating the product of the measured concentration of the water analyzer 9 at each moment in the adsorption section (after deducting the background water concentration) and the total molar flow rate over time. The total molar flow rate is determined by the sum of the flow rates of the first mass flow controller 5 and the second mass flow controller 6.

[0045] Please see Figure 4 As shown, it is a flowchart for determining the adsorption state in an embodiment of the present invention. In this embodiment, the desorption analysis unit determines the adsorption state of the adsorbed calibrated water based on the inflection point of the desorption segment of the concentration-time response curve. The adsorption state includes a fast adsorption state and a strong retention state. In this embodiment, the fast adsorption state is determined based on the condition that there is no inflection point in the desorption segment of the concentration-time response curve; The coexistence of fast adsorption and strong retention states is determined based on the condition that there is an inflection point in the desorption segment of the concentration-time response curve.

[0046] In this embodiment, the inflection point is determined based on the second derivative of the desorption segment of the concentration-time response curve. The point corresponding to the change from negative to positive of the second derivative is determined as the inflection point.

[0047] Please see Figure 5 As shown, this is a comparison of the concentration-time response curves of the fast adsorption state and the strong retention state in an embodiment of the present invention. Curve (a) is the curve when only the fast adsorption state exists, and curve (b) is the curve when the fast adsorption state and the strong retention state coexist. As can be seen from the figure, curve (a) shows a single exponential decay trend, and its desorption rate decreases continuously with time without a clear inflection point; curve (b) conforms to a double exponential decay trend. In the early stage of desorption, the desorption rate is relatively fast, mainly corresponding to the water desorption of the fast desorption state. In the later stage, the fast adsorption state is gradually exhausted, and the strong retention state becomes dominant, and the curve shows an inflection point.

[0048] In this embodiment, the desorption process corresponding to the fast adsorption state has a single activation energy distribution, and its kinetic behavior conforms to a single exponential decay model. The desorption rate decreases monotonically with increasing time. Therefore, its second derivative is always negative throughout the entire desorption time axis, and the concentration-time response curve shows a smooth downward trend without any abrupt changes. However, when a strong retention state exists on the inner wall of the pipeline, the desorption process is composed of the superposition of the fast adsorption state and the strong retention state. The overall behavior conforms to a double exponential or multi-exponential decay model. In the early stage of desorption, the fast adsorption state dominates, and the curve decreases rapidly. As the fast adsorption state is gradually depleted, the strong retention state becomes dominant in the middle and late stages of desorption. At this time, the degree of deceleration of the desorption rate changes abruptly, that is, the second derivative of concentration with respect to time flips from negative to positive. The flip point is the inflection point on the curve.

[0049] In this embodiment, the curve decoupling unit, under the condition that the adsorption state of the adsorbed water is a coexistence of fast adsorption state and strong retention state, establishes a two-dimensional adsorption scatter plot with the calibrated water concentration as the abscissa and the corresponding total number of adsorbed moles as the ordinate. The two-dimensional adsorption scatter plot is fitted with a first-order linear regression to obtain a linear regression equation. The fitting slope of the linear regression equation is determined as the fast adsorption state capacity coefficient of the calibrated water, and the fitting intercept of the linear regression equation is determined as the strong retention state capture capacity.

[0050] Please see Figure 6 As shown, this is a first-order linear regression fitted line graph of the two-dimensional adsorption scatter plot in an embodiment of the present invention. The two-dimensional adsorption scatter plot is generated by using the calibrated moisture concentrations of 50 ppb, 100 ppb, 200 ppb, 500 ppb, and 1000 ppb as the abscissa and the total number of adsorbed moles corresponding to each calibrated moisture concentration as the ordinate. The discrete data points in the scatter plot are fitted with a first-order linear regression using the least squares method to obtain the fitted line.

[0051] In this embodiment, the fast adsorption capacity coefficient is the rate of change in the fast desorption equilibrium adsorption amount caused by a unit change in moisture concentration, characterizing the sensitivity of the reversible adsorption sites on the pipeline inner wall to fluctuations in gas phase moisture concentration. Since fast adsorption is dominated by van der Waals forces, within the trace concentration range, the adsorption amount follows Henry's law and exhibits a good linear relationship with the change in moisture concentration. A larger fast adsorption capacity coefficient indicates a more significant tendency for reversible adsorption on the pipeline inner wall to intensify with increasing concentration.

[0052] The strong retention trapping capacity refers to the amount of adsorption retained on the inner wall of the pipeline due to the strong retention bound state when the moisture concentration in the pipeline approaches zero. When the moisture concentration approaches zero, the adsorption capacity in the fast desorption equilibrium state also approaches zero; at this point, the adsorption capacity corresponding to the area under the curve originates entirely from the strong retention bound state. Since the strong retention bound state originates from the hydrogen bonding between water molecules and the active sites on the inner wall of the pipeline, the adsorption capacity is only related to the total number of active sites and does not increase linearly with the increase of the gas phase concentration, exhibiting typical saturation capacity characteristics. Therefore, the fitting intercept can quantitatively characterize the absolute trapping capacity of the strong retention active sites on the inner wall of the pipeline.

[0053] Please see Figure 7 As shown, it is a flowchart of an embodiment of the present invention for determining whether the strongly retained active sites have reached saturation. In this embodiment, the pre-saturation unit determines that the strongly retained active sites in the pipeline have reached saturation based on the difference between the first concentration and the second concentration being within the allowable error range. In this embodiment, the pre-saturation unit determines that the strongly retained active sites in the pipeline have not reached saturation based on the fact that the difference between the first concentration and the second concentration is not within the allowable error range.

[0054] The first and second concentrations are determined based on a pre-saturation test. The pre-saturation test process is as follows: a gas adsorption-desorption test is performed according to the target gas concentration required for production, and the average reading of the moisture analyzer 9 is recorded as the first concentration. Then, the second dilution pipeline c is closed, and the push rate of the moisture generator 7 is increased to a preset multiple higher than the push rate required for the target concentration. This allows high-concentration water vapor with a concentration higher than the target gas concentration to be continuously introduced into the pipeline and maintained for a preset period of time. Then, the second dilution pipeline c is opened, and the push rate of the moisture generator 7 is restored to the push rate required for the target gas concentration. The gas adsorption-desorption test is performed again according to the target gas concentration, and the average reading of the moisture analyzer 9 is recorded as the second concentration.

[0055] In this embodiment, the method for determining the allowable error range is as follows: based on the pre-saturation unit performing no less than three sets of dynamic gas adsorption-desorption tests to determine the deviation between each measured concentration when the pipeline is in the initial state after inerting treatment or in the state confirmed by re-inerting treatment and restored to a qualified reference state, the allowable error range is calibrated with the maximum deviation value among them. The reference state is the state that meets the requirements of GB 50646 Special Gas System Engineering Technical Standard.

[0056] In this embodiment, when the strongly retained active sites are not saturated, some water molecules in the target concentration of water introduced during the first gas adsorption-desorption test are captured by the unoccupied active sites on the inner wall of the pipeline, resulting in a first concentration significantly lower than the theoretical concentration. Furthermore, after these captured water molecules occupy the active sites, they no longer consume the target concentration of water in the subsequent second test, thus the second concentration will be significantly higher than the first concentration. The difference between the two concentrations represents the amount of water lost due to irreversible capture by the active sites before reversible compensation. If the active sites are saturated, the number of available active sites before and after pre-saturation remains unchanged, and the amount of target concentration water captured in the two tests is essentially the same, within the allowable error range. Therefore, by comparing whether the difference between the two measured concentrations before and after pre-saturation is within the allowable error range, it can be determined whether the strongly retained active sites on the inner wall of the pipeline have reached saturation.

[0057] In this embodiment, the pre-saturation unit repeatedly performs the pre-saturation test until the strongly retained active sites are determined to be saturated, provided that the strongly retained active sites have not yet reached saturation. If the strongly retained active sites still have not reached saturation after at least two pre-saturation tests, the pipeline is inspected and cleaned. If the pipeline uses silanized inert coating technology, the pipeline is re-inertized and aged pipe fittings that have failed the special inertization treatment are replaced.

[0058] The flow compensation unit compensates for the push rate of the moisture generator 7 when only fast adsorption or strong retention active sites in the pipeline reach saturation.

[0059] In this embodiment, the compensation for the push rate of the compensating moisture generator 7 is determined based on the following formula: In the formula: v1 - The push rate of the moisture generator 7 after compensation, in mm / min; α-Fast adsorption capacity coefficient, dimensionless; C - Target gas concentration, in ppb; B - Background moisture concentration, in ppb; k - coefficient of vaporization volume expansion; v - Push rate, in mm / min; A-Moisture generator 7 internal cavity cross-sectional area, unit: mm 2 ; - The flow rate passing through the first mass flow controller 5, in ml / min; - The flow rate passing through the second mass flow controller 6, in ml / min.

[0060] Please refer to Figure 8 As shown, this is a comparison chart of the output concentration before and after push rate compensation in an embodiment of the present invention. In this embodiment, the flow compensation unit calculates the compensated push rate based on the fast adsorption state capacity coefficient generated by the curve decoupling unit, and collects the moisture concentration of the secondary mixed gas before and after compensation to generate a comparison curve. As shown in the figure, after the flow compensation unit compensates the flow rate, the deviation between the moisture concentration and the target gas concentration is significantly reduced, and the concentration fluctuation amplitude between each sampling time is reduced, and the concentration curve tends to be stable. This indicates that the flow compensation unit can significantly improve the accuracy and stability of the target gas concentration by compensating the push rate.

[0061] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A device for preparing and distributing a standard gas containing trace moisture in an ultrapure inert gas, characterized in that, include: The dilution gas input pipeline is connected to the dilution gas source and is used to input the dilution gas; A first dilution line, connected to the dilution gas input line, includes a first mass flow controller for controlling the flow rate of the dilution gas; The second dilution line, which is connected to the dilution gas input line, includes a second mass flow controller for controlling the flow rate of the dilution gas; A moisture generating device, which is connected to the first dilution pipeline, is used to introduce vaporized water and dilution gas into the first dilution pipeline at different push rates to mix and obtain several primary mixed gases with calibrated moisture concentrations. A mixing pipeline, which is connected to the first dilution pipeline and the second dilution pipeline respectively, is used to mix the primary mixed gas with the dilution gas in the second dilution pipeline to form a secondary mixed gas; The background moisture determination unit is used to determine the background moisture concentration of the diluted gas based on the background moisture test. An adsorption testing unit is used to generate a concentration-time response curve based on the adsorption-desorption test of the primary mixed gas, and to determine the total number of moles of water adsorbed in the primary mixed gas by the background moisture concentration determination pipeline. The desorption analysis unit is used to determine the adsorption state of the adsorbed water based on the inflection point of the desorption segment of the concentration-time response curve. A curve decoupling unit is used to determine the fast adsorption capacity coefficient and strong retention capture capacity of the pipeline for the adsorbed water based on a two-dimensional adsorption scatter plot generated from several total adsorption moles. The presaturation unit is used to determine whether the highly retained active sites in the pipeline have reached saturation based on the moisture presaturation test. A flow compensation unit is used to compensate the push rate based on the fast adsorption state capacity coefficient.

2. The apparatus for preparing and distributing trace moisture standard gas in ultrapure inert gas according to claim 1, characterized in that, The background moisture determination unit determines the moisture level based on the average reading of the moisture analyzer located at the end of the mixing pipeline during the continuous purging process of the dilution gas while the moisture generator is off.

3. The apparatus for preparing and distributing trace moisture standard gas in ultrapure inert gas according to claim 2, characterized in that, The adsorption testing unit determines the total number of moles of water adsorbed by the pipeline in the primary mixed gas by subtracting the background moisture concentration from the measured concentration in the adsorption segment of the concentration-time response curve.

4. The apparatus for preparing and distributing trace moisture standard gas in ultrapure inert gas according to claim 3, characterized in that, The desorption analysis unit determines that the adsorption state of the adsorbed water is the fast adsorption state based on the condition that there is no inflection point in the desorption segment of the concentration-time response curve.

5. The apparatus for preparing and distributing trace moisture standard gas in ultrapure inert gas according to claim 4, characterized in that, The desorption analysis unit determines that the adsorption state of the adsorbed water is a coexistence of a fast adsorption state and a strong retention state based on the condition that there is an inflection point in the desorption segment of the concentration-time response curve.

6. The apparatus for preparing and distributing trace moisture standard gas in ultrapure inert gas according to claim 5, characterized in that, The curve decoupling unit generates a two-dimensional adsorption scatter plot with the calibrated water concentration as the abscissa and the corresponding total number of adsorbed moles as the ordinate, under the condition that the adsorption state of the adsorbed water is a coexistence of fast adsorption state and strong retention state.

7. The apparatus for preparing and distributing trace moisture standard gas in ultrapure inert gas according to claim 6, characterized in that, The curve decoupling unit determines the fast adsorption capacity coefficient based on the slope of the fitted line obtained by first-order linear regression fitting of the two-dimensional adsorption scatter plot.

8. The apparatus for preparing and distributing trace moisture standard gas in ultrapure inert gas according to claim 7, characterized in that, The curve decoupling unit determines the strong retention state capture capacity based on the intercept of the fitted line obtained by first-order linear regression fitting of the two-dimensional adsorption scatter plot.

9. The apparatus for preparing and distributing trace moisture standard gas in ultrapure inert gas according to claim 8, characterized in that, The pre-saturation unit determines that the strong retention state active sites have reached saturation based on the difference between the first concentration and the second concentration determined by the pre-saturation test process being within the allowable error range. The pre-saturation unit determines that the strongly retained active sites have not reached saturation based on the fact that the difference between the first concentration and the second concentration is not within the allowable error range.

10. The apparatus for preparing and distributing trace moisture standard gas in ultrapure inert gas according to claim 9, characterized in that, The flow compensation unit compensates for the push rate based on the fast adsorption capacity coefficient when the active sites in the pipeline are saturated, only the fast adsorption state or the strong retention state exists.

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