JP2007190448A - Mixed gas manufacturing apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mixed gas manufacturing apparatus capable of accurately and stably maintaining a composition of a product, i.e., a mixed gas regardless of variation in the composition of the mixed gas becoming a material and a flow rate of the product mixed gas used, and a method. <P>SOLUTION: A pressure of the material gas comprising the mixed gas is adjusted to a set pressure, a pressure of an addition gas is adjusted to a set pressure and the flow rate is adjusted. The material gas adjusted to the set pressure and the addition gas adjusted to the set pressure and flow rate-adjusted are mixed to create the product mixed gas. A part of the product mixed gas is taken out, a concentration of at least one kind of gas in the product mixed gas is measured and a flow rate of the product mixed gas is measured. The flow rate of the addition gas is adjusted from the concentration of at least one kind of gas of the previously set product mixed gas, a concentration measurement value of at least one kind of gas in the product mixed gas and a variation ratio of the flow rate measurement value of the product mixed gas. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mixed gas production apparatus and method, and more specifically, a composition set in advance by adding at least one of the main gas components to a raw material mixed gas containing a plurality of main gas components. And a mixed gas production apparatus and method for producing a product mixed gas adjusted to a flow rate.

  In recent years, it is rare to use only a single component gas at a manufacturing site where gas is used, and many of them are used as a mixed gas adjusted to a target composition of a plurality of component gases. As for the supply form of the mixed gas, a case where the mixed gas is supplied from a cylinder filled with a mixed gas in which a plurality of component gases are mixed at a target concentration, a mixer or the like so that a plurality of gases are at a target concentration, etc. In some cases, the mixture is supplied after mixing, but generally the latter is often used from the viewpoint of cost, frequency of use, amount of use, and the like. In such a situation, a mixed gas production apparatus that produces a mixed gas having a target composition using a plurality of gases is widely used.

  In a conventional concentration control system used in a mixed gas production apparatus, a plurality of single component gases are used as a raw material gas and an additive gas, and the flow rates of the raw material gas and the additive gas are set according to the concentration and flow rate preset as the product mixed gas. It was the mainstream that controlled. Even when a mixed gas is used for the source gas and the additive gas, it is necessary to obtain concentration information of the mixed gas in advance.

On the other hand, in an apparatus that uses high-concentration oxygen and low-concentration oxygen whose concentrations are not specified for the raw material gas and the additive gas to produce a product mixed gas by mixing with a mixer or the like, the oxygen concentration signal of the product mixed gas has a predetermined value. A gas mixing device that feeds back to the supply flow rate control of the source gas and additive gas is disclosed (see Patent Document 1).
JP-A-1-321508

  In the gas mixing device described in Patent Document 1, the oxygen concentration value can be accurately and stably maintained at a constant product mixed gas flow rate regardless of the oxygen concentrations of the raw material gas and the additive gas before mixing. However, the product mixed gas obtained must have a constant flow rate, and it has not been possible to satisfy the demand for using a mixed gas whose concentration is accurately maintained at a free flow rate.

  Therefore, the present invention can arbitrarily set the composition of the product mixed gas, and the composition of the product mixed gas can be set regardless of the composition variation of the mixed gas as a raw material and the flow rate of the product mixed gas. An object of the present invention is to provide a mixed gas production apparatus and method that can be accurately and stably maintained.

  In order to achieve the above object, the mixed gas production apparatus of the present invention contains at least two kinds of main gas components, a mixed gas whose composition and flow rate change with time is used as a raw material gas, and at least one kind of the main gas components is used. A mixed gas production apparatus for producing a product mixed gas in which a gas containing the mixture is added to the raw material gas as an additive gas and the concentration of at least one of the main gas components in the mixed gas after the addition is adjusted to a preset concentration The source gas pressure adjusting means for adjusting the pressure of the source gas to flow out, the additive gas pressure adjusting means for adjusting the pressure of the additive gas to flow out to the set pressure, and the flow rate of the additive gas The additive gas flow rate adjusting means to be adjusted is mixed with the source gas adjusted to the set pressure and the additive gas adjusted to the set pressure and the flow rate adjusted. Mixing means, an analysis means for taking out a part of the product mixed gas mixed by the gas mixing means and measuring the concentration of at least one kind of gas in the product mixed gas, and measuring the flow rate of the product mixed gas Product mixed gas flow rate measuring means, set concentration input means for setting the concentration of at least one kind of gas in the product mixed gas, set concentration input to the set concentration input means, and concentration measurement value measured by the analyzing means And a calculating means for calculating an additive gas flow rate setting value of the additive gas flow rate adjusting means based on a change rate of the flow rate measurement value measured by the product mixed gas flow rate measuring means.

  Furthermore, in the mixed gas manufacturing apparatus of the present invention, the gas mixing means is formed in a T-shape having a branch pipe branched at a right angle from an intermediate portion of the straight pipe, and the source gas is formed on one opening side of the straight pipe. A gas mixer in which a raw material gas introduction part for introducing the additive gas is introduced to the other opening side of the straight pipe, a product mixed gas outlet part is provided in the branch pipe, respectively. It is characterized by use.

  Further, the mixed gas production method of the present invention uses at least two main gas components, a mixed gas whose composition and flow rate change over time as a raw material gas, and a gas containing at least one of the main gas components as an additive gas In the mixed gas production method for producing a product mixed gas, which is added to the raw material gas and the concentration of at least one kind of the main gas component in the mixed gas after the addition is adjusted to a preset concentration, The pressure of the additive gas is adjusted to the set pressure, the flow rate is adjusted, the source gas adjusted to the set pressure, and the additive gas adjusted to the set pressure and the flow rate adjusted Is mixed into a product mixed gas, a part of the product mixed gas is taken out and the concentration of at least one kind of gas in the product mixed gas is measured, The flow rate of the product mixed gas is measured, the concentration of at least one kind of gas in the preset product mixed gas, the measured concentration value of at least one kind of gas in the product mixed gas, and the measured flow rate value of the product mixed gas The flow rate of the additive gas is adjusted on the basis of the change rate.

  According to the present invention, when the composition of the raw material gas is changed or the set concentration of the product mixed gas is changed, the composition of the product mixed gas is changed by the feedback control calculation from the measured concentration value of the specific component analyzed. When the flow rate of the additive gas is changed following the change, the flow rate of the additive gas is changed according to the flow rate change rate of the product mixed gas derived from the gas mixing means. Even when the flow rate changes with time, the composition of the product mixed gas can be maintained with high accuracy. Further, by using a gas mixer formed in a T shape, the source gas and the additive gas can be mixed efficiently in a short time.

  FIG. 1 is a system diagram showing an embodiment of the mixed gas production apparatus of the present invention. This mixed gas manufacturing apparatus includes a source gas introduction path 11 through which a source gas is introduced, an additive gas introduction path 12 through which an additive gas is introduced, and a source gas and an additive gas introduced from both the introduction paths 11 and 12. A gas mixing means 13 for mixing, an analysis path 14 for taking out a part of the product mixed gas mixed by the gas mixing means 13, and a product gas supply path 15 for sending the remainder of the product mixed gas as a product are provided. .

  Further, a source gas pressure adjusting means 21 is provided in the source gas introduction path 11, an additive gas pressure adjusting means 22 and an additive gas flow rate adjusting means 23 are provided in the additive gas introduction path 12, and an analysis gas pressure is provided in the analysis path 14. The adjustment means 24, the analysis means 25, and the analysis gas flow rate adjustment means 26 are provided in the product gas supply path 15, and the product flow rate measurement means 27 and the product supply valve 28 are provided, respectively.

  The concentration measurement value 25a of the analysis unit 25, the flow rate setting value 26a of the analysis gas flow rate setting unit 26, and the flow rate measurement value 27a of the product flow rate measurement unit 27 are set concentrations that set the concentration of a specific component of the product mixed gas. The added gas flow rate setting value 32a calculated based on these input values by the calculation means 32 together with the set concentration 31a input to the input means 31 is input to the calculation means 32 as an electrical signal. The flow rate of the additive gas introduced from the additive gas introduction path 12 is adjusted by operating the additive gas flow rate adjusting means 23 based on the additive gas flow rate setting value 32a.

  The raw material gas introduced from the raw material gas introduction path 11 is a mixed gas containing at least two kinds of main gas components and changing in composition and flow rate with time. For example, the raw material gas is discharged from various facilities, apparatuses, and devices. Exhaust gas or the like can be used as a raw material gas. Moreover, the supply destination of the product mixed gas delivered from the product gas supply path 15 can also target various facilities, apparatuses, and devices that use various mixed gases, and these are not particularly limited.

  The analysis means 25 can use any analyzer or analyzer as long as it can continuously measure the concentration of at least one of the main gas components in the product mixed gas. It may be one that can be analyzed simultaneously. Further, the analysis gas pressure adjusting means 24 and the analysis gas flow rate adjusting means 26 may be provided separately from the analysis means 25 or may be provided in the analysis means 25.

  The main gas component in the mixed gas that is the raw material gas is usually a component that exists at a concentration of 1 to several percent or more, and the specific component concentration in the product mixed gas also depends on the use conditions of the product mixed gas. Usually, it is assumed that the concentration is adjusted to 1 to several percent or more. For example, in the atmosphere, nitrogen, oxygen, and argon can be referred to as main gas components.

  The additive gas introduced from the additive gas introduction path 12 can be selected according to the composition of the raw material gas and its fluctuation state, the composition desired for the product mixed gas, the use conditions of the product mixed gas supply destination, etc. At least one kind of main gas component (single component), a mixed gas in which a plurality of main gas components are mixed in advance at a predetermined concentration, or at least one kind of main gas component and main gas component A mixed gas with other gases can be used. When a mixed gas with a gas other than the main gas component is used, a gas that does not cause inconvenience even when mixed in the product mixed gas is selected as the gas other than the main gas component.

  Further, the gas component analyzed by the analyzing means 25 and the gas component added as the additive gas may be the same or different, and the gas component whose concentration control is strict or the gas which is easy to analyze The components are preferably analyzed by the analyzing means 25.

  In order to manufacture a product mixed gas using the mixed gas manufacturing apparatus formed in this way, first, the set concentration of a specific component in the product mixed gas is input to the set concentration input means 31, and then the product supply valve 28 is closed. In this state, the set pressure of the raw material gas pressure adjusting means 21 is set to a pressure equal to or higher than the supply pressure of the product mixed gas, and the set pressure of the additive gas pressure adjusting means 22 is set to a pressure loss at the additive gas flow rate adjusting means 23. Is set to a pressure slightly higher than the set pressure of the raw material gas. The analysis gas pressure adjusting unit 24 and the analysis gas flow rate adjusting unit 26 are set in consideration of the analysis pressure and the analysis flow rate in the analysis unit 25.

  In this state, when a mixed gas as a raw material is introduced from the mixed gas generation source 41 to the raw material gas introduction path 11, the pressure of the raw material gas is adjusted to the set pressure of the raw material gas pressure adjusting means 21 and introduced into the gas mixing means 13. The At the same time, when the additive gas is introduced from the additive gas supply source into the additive gas introduction path 12, the pressure of the additive gas is adjusted to the set pressure of the additive gas pressure adjusting means 22, and the flow rate is set to the additive gas flow adjusting means 23. While being adjusted to the flow rate, the pressure loss when passing through the additive gas flow rate adjusting means 23 becomes substantially the same as the pressure of the raw material gas and is introduced into the gas mixing means 13.

  The mixed gas in which the raw material gas and the additive gas are mixed by the gas mixing means 13 is led out to the product gas supply path 15 as a product mixed gas. However, since the product supply valve 28 is closed, the total amount of the mixed gas is analyzed. Then, the analysis gas pressure adjusting means 24 adjusts the pressure, and the analysis gas flow rate adjusting means 26 adjusts the flow rate to a predetermined value.

  In the analyzing means 25, the concentration of the specific component in the product mixed gas is analyzed, and the measured concentration value 25a is sent from the analyzing means 25 to the calculating means 32, and the flow rate set value 26a is sent from the analyzing gas flow rate adjusting means 26 to the product. The flow rate measurement means 27 sends the flow rate measurement value 27a (zero at this time) to the calculation means 32, respectively.

  In the calculation means 32, the set concentration 31 a from the set concentration input means 31, the concentration measurement value 25 a from the analysis means 25, the flow rate set value 26 a from the analysis gas flow rate adjustment means 26, and the flow rate measurement from the product flow rate measurement means 27. The feedback control calculation is performed based on the total flow value of the value 27a, and the additive gas flow rate setting value 32a of the additive gas flow rate adjusting means 23 is calculated. The calculated additive gas flow rate setting value 32a is transmitted from the calculation means 32 to the additive gas flow rate adjusting means 23 as a flow rate setting instruction signal. Based on this signal, the additive gas flow rate adjusting means 23 is operated, and the additive gas flow rate is set. By adjusting, the concentration of the specific component in the product mixed gas mixed by the gas mixing unit 13 is adjusted to a concentration according to the specific component concentration input to the set concentration input unit 31, and the specific component having a predetermined concentration is adjusted. A mixed product gas containing is obtained.

  Here, when the product supply valve 28 is opened and the supply of the product mixed gas to the mixed gas usage destination 42 is started, as a large amount of the product mixed gas flows out from the product gas supply path 15, the raw material gas introduction path 11 In the calculation means 32, the flow rate of the product mixed gas when the product supply valve 28 is closed, that is, the flow rate corresponding to the flow rate setting value of the analysis gas flow rate adjustment means 26 is increased. And the total flow rate obtained by adding the flow rate measured by the product flow rate measuring unit 27 to the flow rate corresponding to the flow rate set value of the analysis gas flow rate adjusting unit 26 when the product supply valve 28 is opened. A flow rate ratio is calculated, and the additive gas flow rate set value 32a is corrected based on the flow rate ratio.

  As a result, the additive gas flow rate adjusting means 23 is operated based on the corrected additive gas flow rate setting value 32a, and the flow rate of the additive gas introduced from the additive gas introduction path 12 is a flow rate corresponding to the increase in the inflow amount of the source gas. The concentration of the specific component in the product mixed gas is controlled to the set concentration. Therefore, even if the flow rate of the raw material gas changes, the concentration of the specific component in the product mixed gas can be controlled to the set concentration with high accuracy, and the product mixed gas having a predetermined composition can be stably supplied. .

  In this embodiment, the analysis gas flow rate adjusting means 26 and the product flow rate measuring means 27 are used as the product mixed gas flow rate measuring means for measuring the flow rate of the product mixed gas, and these total flow rates are measured as the product mixed gas flow rate. However, if a flow meter is installed between the gas mixing means 13 and the branch part of the analysis path 14, the measured value of the flow meter becomes the flow measurement value of the product mixed gas. .

  Next, an example in which the present invention is applied to an exhaust gas purifying apparatus that purifies xenon in exhaust gas discharged from a semiconductor manufacturing apparatus and supplies it again to the semiconductor manufacturing apparatus will be described with reference to a system diagram shown in FIG. To do. In the following description, the same components as those in the mixed gas production apparatus shown in the above-described embodiment are assigned the same reference numerals, and detailed description thereof is omitted.

  The semiconductor manufacturing apparatus exemplified here uses a mixed gas containing krypton or xenon and argon as main gas components as an atmospheric gas for plasma excitation, and this atmospheric gas is consumed by the semiconductor manufacturing apparatus. Since everything is exhausted as exhaust gas, expensive xenon and krypton are reused by purifying xenon and krypton by removing trace impurities with an exhaust gas purification device. However, since the composition and flow rate of the exhaust gas discharged from the semiconductor manufacturing apparatus largely fluctuate depending on the operation state of the semiconductor manufacturing apparatus, the composition and flow rate of the purified mixed gas obtained from the exhaust gas purifying apparatus also fluctuate. It was difficult to reuse.

  In this way, the purified mixed gas after purifying the exhaust gas from the semiconductor manufacturing apparatus whose composition and flow rate fluctuate is used as a raw material gas, and a product mixed gas having a predetermined composition and a predetermined flow rate is stably manufactured, so that expensive krypton And xenon can be easily reused.

  In FIG. 2, exhaust gas mainly containing xenon and argon discharged from the semiconductor manufacturing apparatus is introduced into an exhaust gas purification device 52 through an exhaust path 51, and nitrogen and oxygen are exhausted by the exhaust gas purification device 52. After the impurity components such as moisture are removed to form a mixed gas of xenon and argon, the raw material gas is introduced into the mixed gas production apparatus through the raw material gas introduction path 11 as a raw material gas.

  Since the product supply valve 28 is closed at the start of operation, the pressure of the source gas is adjusted by the source gas pressure adjusting means 21, and the source gas that has passed through the gas mixing means 13 passes through the analysis path 14 and is analyzed by the analysis gas pressure adjusting means 24. The pressure is adjusted to a predetermined value by the analysis gas flow rate adjusting means 26 and introduced into the analysis means 25, and the concentration of xenon in the raw material gas is measured. The gas discharged from the analysis means 25 is recovered by the exhaust gas purification device 52 through the recovery path 53 in order to effectively use xenon in the gas.

  A xenon concentration signal (concentration measurement value 25a) from the analysis means 25, a flow signal (flow rate set value 26a) from the analysis gas flow rate adjustment means 26, and a xenon concentration setting signal (set concentration) input to the set concentration input means 31 31a) is transmitted to the calculation means 32, feedback control calculation is performed with the xenon concentration signal and the xenon concentration setting signal, and an added argon flow rate signal (added gas flow rate set value 32a) is output as a control output signal.

  On the other hand, argon is introduced as an additive gas from the additive gas introduction path 12, the pressure is adjusted by the additive gas pressure adjusting means 22, the flow rate is adjusted by the additive gas flow rate adjusting means 23, and introduced into the mixing means 13. The additive gas flow rate adjusting means 23 is in a fully closed state at the start of operation, and receives the additive argon flow rate signal from the computing means 32 to adjust the additive gas flow rate, that is, the argon additive amount.

  Thereby, the additive gas corresponding to the flow rate and composition (xenon concentration) of the raw material gas at that time is introduced, and the raw material gas and the additive gas are mixed by the gas mixing unit 13, whereby the xenon concentration from the gas mixing unit 13. The mixed gas adjusted to flow out into the product gas supply path 15. The total amount of the mixed gas is introduced into the analyzing means 25 through the analysis path 14, and the concentration of xenon in the mixed gas is measured.

  When the xenon concentration signal and the xenon concentration setting signal coincide, that is, when the xenon concentration of the mixed gas derived from the gas mixing unit 13 coincides with the set concentration, the product supply valve 28 opens and the xenon having a predetermined xenon concentration is obtained. After the flow rate of the argon mixed gas is measured by the product flow rate measuring means 27, it is supplied as a product mixed gas to the semiconductor manufacturing apparatus.

  At this time, in the calculation means 32, based on the flow rate set value 26a from the analysis gas flow rate adjusting means 26 and the flow rate measured value 27a from the product flow rate measuring means 27, the additive gas flow rate set value 32a is obtained by the following equation (1). Is calculated.

32a = Mv × (26a + 27a) / 26a (1)
“Mv” in Equation (1) is a concentration correction term obtained by feedback control calculation performed by the calculation means 32, and “(26a + 27a) / 26a” is the flow rate change rate of the mixed gas derived from the mixing means 13. Is a flow rate correction term. The flow rate correction term is based on when the product supply valve 28 is closed. The additive gas flow rate setting value 32a calculated in this way is transmitted to the additive gas flow rate adjusting means 23, and the additive gas (argon) having the flow rate set by the additive gas flow rate setting value 32a is introduced into the mixing means 13. .

  The composition of the raw material gas and the flow rate of the product mixed gas vary greatly depending on the operating state of the semiconductor manufacturing apparatus that is the supply destination, but the concentration correction term changes the raw material gas composition, and the flow rate correction term changes the product mixed gas flow rate. In addition, a product mixed gas having a constant xenon concentration can be supplied.

  Further, in this example, the gas mixing means 13 is formed in a T-shape having a branch pipe 13b branched at a right angle from an intermediate portion of the straight pipe 13a, and the source gas is introduced into one opening side of the straight pipe 13a. A gas in which a raw material gas introduction part 13c is provided, an additive gas introduction part 13d for introducing the additive gas into the other opening side of the straight pipe 13a, and a product mixed gas outlet part 13e in the branch pipe 13b, respectively. A mixer is used.

  By using the gas mixer having such a structure, the source gas and the additive gas can be mixed efficiently in a short time. Therefore, the flow rate is adjusted by the additive gas flow rate adjusting means 23 and xenon is added by argon. Since the delay time until the concentration change is measured by the analyzing means 25 can be shortened, the composition of the product mixed gas can be controlled with higher accuracy.

  The present invention can also be applied to a xenon recycling system for anesthesia. The xenon recycling system for anesthesia supplies xenon / oxygen mixed gas with an oxygen concentration of about 21% as an anesthetic gas to the patient, collects the patient's exhalation, and uses it again as an anesthetic gas. In addition to removing carbon dioxide and other impurities, the consumed oxygen is added to bring the oxygen concentration to about 21%.

  In this case, the xenon / oxygen mixed gas from which impurities such as carbon dioxide released by respiration are removed by the refining device is introduced as a raw material gas into the mixed gas production device, and oxygen is used as an additive gas. By using an oxygen concentration meter, a product mixed gas having an oxygen concentration of about 21% can be produced as described above, and can be reused as a xenon / oxygen mixed gas for anesthesia.

  Since the flow rate and oxygen consumption of the anesthetic gas to be supplied vary depending on the age, sex, etc. of the patient, the flow rate and oxygen concentration of the recovered gas are not constant, but the anesthetic gas having a stable oxygen concentration by applying the present invention. Can supply.

  The present invention is not limited to the above-described exhaust gas purifying apparatus and xenon recycling system for anesthesia, but can be similarly applied to a general gas mixing process. It is also possible to provide a plurality of additive gas introduction paths 12 including the additive gas pressure adjusting means 22 and the additive gas flow rate adjusting means 23 as described above, and the analysis means 25 analyzes and calculates a plurality of gas components. It can also be used for processing.

It is a systematic diagram which shows one example of a mixed gas manufacturing apparatus of this invention. It is a systematic diagram which shows an example which applied this invention to the exhaust-gas purification apparatus of a semiconductor manufacturing apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Raw material gas introduction path, 12 ... Addition gas introduction path, 13 ... Gas mixing means, 13a ... Straight pipe, 13b ... Branch pipe, 13c ... Raw material gas introduction part, 13d ... Addition gas introduction part, 13e ... Derivation of product mixed gas , 14 ... analysis path, 15 ... product gas supply path, 21 ... raw material gas pressure adjustment means, 22 ... additive gas pressure adjustment means, 23 ... additive gas flow rate adjustment means, 24 ... analysis gas pressure adjustment means, 25 ... analysis means 25a ... measured concentration value, 26 ... analysis gas flow rate adjusting means, 26a ... flow rate set value, 27 ... product flow rate measuring means, 27a ... flow rate measured value, 28 ... product supply valve, 31 ... set concentration input means, 31a ... set Concentration, 32 ... calculation means, 41 ... mixed gas generation source, 42 ... mixed gas use destination, 51 ... exhaust path, 52 ... exhaust gas purifier, 53 ... recovery path

Claims (3)

  A mixed gas containing at least two types of main gas components, the composition and flow rate of which changes over time is used as a source gas, and a gas containing at least one type of the main gas components is added to the source gas as an additive gas. In a mixed gas production apparatus for producing a product mixed gas in which the concentration of at least one kind of gas of the main gas component in the mixed gas is adjusted to a preset concentration, the pressure of the raw material gas is adjusted to a set pressure and is discharged. Raw material gas pressure adjusting means, additional gas pressure adjusting means for adjusting and flowing out the pressure of the additive gas, added gas flow rate adjusting means for adjusting the flow rate of the additive gas, and the pressure adjusted to the set pressure Gas mixing means for mixing the source gas and the additive gas whose flow rate is adjusted to a preset pressure, and a product mixed gas mixed by the gas mixing means Analyzing means for taking out a part and measuring the concentration of at least one kind of gas in the product mixed gas, product mixed gas flow rate measuring means for measuring the flow rate of the product mixed gas, and at least one kind of the product mixed gas Set concentration input means for setting the concentration of the gas, set concentration input to the set concentration input means, concentration measurement value measured by the analysis means, and change in flow rate measurement value measured by the product mixed gas flow rate measurement means And a calculating means for calculating an additive gas flow rate setting value of the additive gas flow rate adjusting means based on the rate.   The gas mixing means is formed in a T shape having a branch pipe branched at a right angle from an intermediate portion of the straight pipe, and a raw material gas introduction section for introducing the raw material gas into one opening side of the straight pipe is provided with the straight pipe. 2. The mixed gas production apparatus according to claim 1, wherein an additive gas introduction section for introducing the additive gas to the other opening side of the pipe is provided, and a product mixed gas outlet section is provided in the branch pipe.   A mixed gas containing at least two types of main gas components, the composition and flow rate of which changes over time is used as a source gas, and a gas containing at least one type of the main gas components is added to the source gas as an additive gas. In the mixed gas production method for producing a product mixed gas in which the concentration of at least one kind of gas of the main gas component in the mixed gas is adjusted to a preset concentration, the pressure of the raw material gas is adjusted to a set pressure, and the addition The gas pressure is adjusted to a set pressure and the flow rate is adjusted, and the raw material gas adjusted to the set pressure and the additive gas adjusted to the set pressure and the flow rate adjusted are mixed to obtain a product mixed gas, and the product A part of the mixed gas is taken out, the concentration of at least one kind of gas in the product mixed gas is measured, and the flow rate of the product mixed gas is measured. The addition based on the concentration of at least one kind of gas mixed in the product mixture gas, the measured concentration of at least one kind of gas in the product mixed gas, and the rate of change in the measured flow rate of the product mixed gas A method for producing a mixed gas, comprising adjusting a flow rate of a gas.

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