Low temperature gas generator

Abstract

To provide a low temperature gas generator capable of improving temperature control accuracy and reducing a flow rate fluctuation width.SOLUTION: A low temperature gas generator for acquiring gaseous low temperature gas using liquefied gas and gaseous first gas having a temperature higher than a boiling point of the liquefied gas includes: a heat exchanger for generating second gas by vaporizing the liquefied gas and acquiring low temperature gas from mixed gas of the first gas and the second gas; first control means for controlling a supply flow rate of the liquefied gas based on a difference between a first temperature of the low temperature gas and a target temperature; a first stabilizing mechanism that can supply the liquefied gas in a liquid state; and a second stabilizing mechanism that is provided at a merging portion of the first gas and the second gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a low-temperature gas generator. [Background technology]

[0002] Chemical reaction processes such as organic synthesis require highly accurate temperature control in the low temperature range. For example, low-temperature reactors used for low-temperature reactions use a double-walled vessel with an independent tank (jacket) outside the reaction tank through which a heat transfer medium can flow. A heat transfer medium controlled at a low temperature is supplied to this jacket, and the reaction liquid in the reaction tank is cooled and adjusted to a constant temperature.

[0003] As a method for supplying a heat transfer medium to a reaction vessel, Patent Document 1 discloses a method for generating low-temperature gas by bubbling gas in an insulated container that stores low-temperature liquefied gas.

[0004] As another method for supplying a heat medium, Patent Document 2 discloses a method for generating low-temperature gas by exchanging heat among a low-temperature liquefied gas, the vaporized gas, and a gas having a higher temperature than the vaporized gas. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 4-285553 [Patent Document 2] International Publication No. 2013 / 054844 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the method of Patent Document 1, when the low-temperature liquefied gas is replenished into the insulated container, it is sent into the insulated container as a gas-liquid two-phase flow, which increases the gas flow rate when the low-temperature liquefied gas is replenished, making it difficult to control the overall gas flow rate. Also, in the method of Patent Document 2, the flow rate of the liquefied gas has a large effect on the overall gas flow rate, and the gas-liquid two-phase flow state and pulsation state of the liquefied gas affect the overall flow rate and the amount of heat exchanged, which tends to result in poor temperature control accuracy and poor flow rate range.

[0007] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a low-temperature gas generator capable of improving the accuracy of temperature control and reducing the range of fluctuation in flow rate. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention proposes the following means. <1> The low-temperature gas generator of the first aspect of the present invention comprises: Liquefied gas and a first gas in a gaseous state having a temperature higher than the boiling point of the liquefied gas; A low-temperature gas generator for obtaining gaseous low-temperature gas using a heat exchanger that generates a second gas by vaporizing the liquefied gas and obtains the low-temperature gas from a mixture of the first gas and the second gas; a first control means for controlling the supply flow rate of the liquefied gas based on a difference between a first temperature of the low-temperature gas and a target temperature; a first stabilization mechanism capable of supplying the liquefied gas in a liquid state; a second stabilization mechanism provided at a confluence of the first gas and the second gas; Equipped with. <2> A second aspect of the present invention is the low-temperature gas generator of the first aspect, The first stabilization mechanism may be a gas-liquid separator, a subcooler, or a counterflow heat exchanger. <3> A third aspect of the present invention is the low-temperature gas generator of the first or second aspect, The second stabilization mechanism may be an accumulator or a buffer tank. <4> A fourth aspect of the present invention is the low-temperature gas generator of the first or second aspect, The supply pressure of the liquefied gas before being introduced into the heat exchanger may be 200 kPa or less. [Effects of the Invention]

[0009] According to the above aspects of the present invention, it is possible to provide a low-temperature gas generator capable of improving the accuracy of temperature control and reducing the range of fluctuation in flow rate. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a system diagram showing the configuration of a low-temperature gas generation device according to a first embodiment. [Figure 2] FIG. 10 is a system diagram showing the configuration of a low-temperature gas generation device according to a second embodiment. [Figure 3] FIG. 10 is a system diagram showing the configuration of a low-temperature gas generation device according to a third embodiment. [Figure 4] FIG. 10 is a system diagram showing the configuration of a low-temperature gas generator according to a third embodiment. [Figure 5] FIG. 2 is a system diagram showing the configuration of a low-temperature gas generator according to Comparative Example 1. [Figure 6] 1 shows the time changes in the flow rate and temperature of the low-temperature gas in Comparative Example 1. [Figure 7] 1 shows the time changes in the flow rate and temperature of the low-temperature gas in Example 1. [Figure 8] 1 shows the time changes in the flow rate and temperature of the low-temperature gas in Example 1. [Figure 9] 10 shows the time changes in the flow rate and temperature of the low-temperature gas in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0011] (First embodiment) Hereinafter, a low-temperature gas generator 100 according to a first embodiment of the present invention will be described with reference to the drawings. The low-temperature gas generator 100 is an apparatus that generates gaseous low-temperature gas using a liquefied gas and a gaseous first gas having a temperature higher than the boiling point of the liquefied gas. Examples of the liquefied gas include liquefied nitrogen, liquefied oxygen, liquefied argon, liquefied natural gas (LNG), liquefied methane, liquefied hydrogen, and liquefied helium. The first gas is preferably a gas having the same components as the gas obtained by vaporizing the liquefied gas. The temperature of the first gas is, for example, room temperature (20°C to 30°C).

[0012] As shown in FIG. 1 , the low-temperature gas generation apparatus 100 of the present disclosure includes a liquefied gas supply amount control valve 1, a gas supply amount control valve 2, a flow meter 3, a check valve 4, a temperature sensor 5, an indicating regulator (first control means) 6, a flow meter 8, an accumulator (second stabilization mechanism) 9, a pressure gauge 10, a gas-liquid separator (first stabilization mechanism) 11, a liquid level sensor 12, a solenoid valve 13, a needle valve 14, a liquid level sensor controller 15, a temperature sensor 16, and a heat exchanger 17.

[0013] (Liquefied gas supply control valve 1) The liquefied gas supply amount control valve 1 controls the supply flow rate of the liquefied gas based on an instruction from an indicating controller 6 (described later). The liquefied gas whose supply flow rate has been controlled is introduced into the low-temperature path L2 of the heat exchanger 17 via the liquefied gas path L6.

[0014] (Gas supply control valve 2) A first gas (e.g., nitrogen gas) is introduced from a first gas supply source S1 through a first gas supply path LS1 into a first gas path L1. A gas supply amount control valve 2 adjusts the flow rate of the first gas supplied to the first gas path L1. The opening of the gas supply amount control valve 2 is adjusted by the control of a controller (not shown) based on the reading of a flow meter 3.

[0015] (Flowmeter 3) The flow meter 3 measures the flow rate of the first gas. The flow meter 3 is, for example, a mass flow meter (MFM). The flow rate of the first gas measured by the flow meter 3 is sent to a control unit (not shown).

[0016] (Check valve 4) The check valve 4 is disposed between the first gas path L1 and the first gas supply path LS1, and prevents gas from flowing back toward the flow meter 3. This makes it possible to prevent damage to the flow meter 3.

[0017] (Temperature sensor 5) The temperature sensor 5 measures the temperature of the low-temperature gas (for example, low-temperature nitrogen gas) discharged to the low-temperature gas path L4 from the heat exchanger 17. The measured temperature of the low-temperature gas (first temperature) is sent to the indicating controller 6.

[0018] (indicating controller 6) The indicating controller 6 adjusts the aperture of the liquefied gas supply amount control valve 1 based on the difference between the temperature of the low-temperature gas measured by the temperature sensor 5 (first temperature) and the target temperature of the low-temperature gas. This adjusts the amount of liquefied gas supplied. The target temperature is, for example, -180°C. The indicating controller 6 is an example of a first control means.

[0019] (Flowmeter 8) Flow meter 8 measures the flow rate of the low-temperature gas that has passed through low-temperature gas path L4. Flow meters for low-temperature gas include Coriolis flow meters, vortex flow meters, electromagnetic flow meters, turbine flow meters, and area flow meters. The liquefied nitrogen flow rate can be calculated from the difference between the reading of flow meter 8, which indicates the total flow rate, and the reading of flow meter 3, which indicates the nitrogen gas flow rate.

[0020] (Accumulator 9) The accumulator 9 is provided at the confluence of the first gas and the second gas produced by vaporizing the liquefied gas. The confluence to which the accumulator 9 is connected is not particularly limited as long as it is a location where the first gas and the second gas converge. The confluence may be, for example, between the connection point of the first gas path L1 and the low-temperature path L2 and the connection point of the first gas path L1 and the mixing path L3. In this embodiment, the accumulator 9 is connected to the connection point between the first gas path L1 through which the first gas passes and the low-temperature path L2 through which the second gas passes. This makes it possible to suppress fluctuations in the supply flow rate of the liquefied gas. The first gas and the second gas are mixed at a junction G, which is the connection point between the first gas path L1 and the mixing path L3, and the mixed gas is introduced into the mixing path L3 of the heat exchanger 17. The capacity of the accumulator 9 can be set appropriately depending on the flow rates of the first gas and the second gas.

[0021] (Pressure gauge 10) A pressure gauge 10 measures the pressure inside the accumulator 9. The capacity of the accumulator 9 may be set so that fluctuations in the pressure value fall within a predetermined range.

[0022] (Gas-liquid separator 11) Liquefied gas is supplied to the gas-liquid separator 11 from the liquefied gas source S2 via the liquefied gas supply path LS2. The gas-liquid separator 11 separates the liquefied gas from the vaporized gas. This allows the liquefied gas to be supplied in a liquid state. In other words, it is possible to prevent the liquefied gas from being supplied to the heat exchanger 17 in a gas-liquid two-phase flow state. This allows the supply flow rate of the low-temperature gas to be precisely controlled.

[0023] (Liquid level sensor 12) The liquid level sensor 12 measures the liquid level of the liquefied gas in the gas-liquid separator 11. The measured liquid level of the liquefied gas is sent to the liquid level sensor controller 15.

[0024] (Solenoid valve 13) The solenoid valve 13 adjusts the opening degree in accordance with an instruction from the liquid level sensor controller 15, and discharges the vaporized gas (exhaust gas) in the gas-liquid separator 11 via a discharge path L5.

[0025] (Needle valve 14) Needle valve 14 controls the flow rate (exhaust volume) of exhaust gas. If the exhaust volume is large, liquefied gas may be entrained, while if the exhaust volume is small, liquefied gas may not be stored in gas-liquid separator 11. It is preferable to determine the range of exhaust volume in advance by examining the relationship between the exhaust volume and liquefied gas, and then control the exhaust volume so that it falls within the determined range.

[0026] (Liquid level sensor controller 15) The liquid level sensor controller (liquid level control unit) 15 closes the solenoid valve 13 when the liquid level of the liquefied gas measured by the liquid level sensor 12 reaches a height equal to or higher than a threshold value. When the liquid level of the liquefied gas falls below a predetermined height, the solenoid valve 13 opens. This makes it possible to further suppress supply in a gas-liquid two-phase flow state.

[0027] (Temperature Sensor 16) The temperature sensor 16 measures the temperature of the liquefied gas supplied to the heat exchanger 17 .

[0028] (heat exchanger 17) In the heat exchanger 17, the low-temperature path L2 and the mixture path L3 run in parallel, and are configured so that the liquefied gas flowing through each path and the mixed gas of the first gas and the second gas exchange heat with each other. The low-temperature path L2 and the mixing path L3 are arranged so that the liquefied gas and the mixed gas flow in opposite directions. The liquefied gas is vaporized while passing through the low-temperature path L2, generating a second gas. The generated second gas is mixed with the first gas, for example, at the confluence G. The mixed gas obtained by mixing the first gas and the second gas passes through the mixing path L3 and is cooled. This results in low-temperature gas. The obtained low-temperature gas is discharged from the heat exchanger 17, passes through the low-temperature gas path L4, and is then discharged.

[0029] The above has described the low-temperature gas generator 100 according to the first embodiment. The low-temperature gas generator 100 can improve the accuracy of temperature control and reduce the range of flow rate fluctuations.

[0030] In the low-temperature gas generator 100, a gas-liquid separator is used as the first stabilization mechanism, but a subcooler or a counterflow heat exchanger may be used instead of the gas-liquid separator. By using a subcooler, the proportion of liquefied gas in the mixture of liquefied gas and gas obtained by vaporizing the liquefied gas can be increased.

[0031] In the low-temperature gas generator 100, an accumulator is used as the second stabilization mechanism, but the second stabilization mechanism may also be a buffer tank.

[0032] (Second embodiment) Next, a low-temperature gas generator 100A according to a second embodiment will be described. As shown in Fig. 2, the low-temperature gas generator 100A of the present disclosure includes a liquefied gas supply amount control valve 1, a gas supply amount control valve 2, a flow meter 3, a check valve 4, a temperature sensor 5, an indicating regulator (first control means) 6, a flow meter 8, an accumulator (second stabilization mechanism) 9A, a pressure gauge 10, a gas-liquid separator (first stabilization mechanism) 11, a liquid level sensor 12, a solenoid valve 13A, a needle valve 14A, a liquid level sensor controller 15, a temperature sensor 16, and a heat exchanger 17A. The same components as those in the first embodiment are designated by the same reference numerals, and their description may be omitted.

[0033] (Accumulator 9A) The accumulator 9 is provided at a confluence of the first gas, the second gas generated by vaporizing the liquefied gas in the heat exchanger 17A, and the second gas generated by vaporizing the liquefied gas in the gas-liquid separator 11. The confluence to which the accumulator 9A is connected is not particularly limited as long as it is a location where the first gas and the second gas converge. In this embodiment, the accumulator 9A is connected near a confluence point G where the first gas, the second gas vaporized in the heat exchanger 17A and passed through the low-temperature path L2, and the second gas vaporized in the gas-liquid separator 11 and passed through the second gas path L5A converge. More specifically, the accumulator 9A is connected to a connection point between the first gas path L1 and the low-temperature path L2. The mixed gas obtained at the confluence point G is introduced into the mixing path L3 of the heat exchanger 17A. The capacity of the accumulator 9A can be set appropriately according to the flow rates of the first gas, the second gas vaporized in the heat exchanger 17A and passed through the low-temperature path L2, and the second gas vaporized in the gas-liquid separator 11 and passed through the second gas path L5A.

[0034] (Pressure gauge 10) The pressure gauge 10 measures the pressure inside the accumulator 9A. The capacity of the accumulator 9A may be set so that the fluctuation of the pressure value falls within a predetermined range.

[0035] (Solenoid valve 13A) The solenoid valve 13A adjusts its opening according to an instruction from the liquid level sensor controller 15, and introduces the vaporized gas in the gas-liquid separator 11 into the first gas path L1 via the second gas path L5A.

[0036] (Needle valve 14) The needle valve 14 is disposed between the first gas path L1 and the second gas path L5A, and controls the flow rate of the gas vaporized in the gas-liquid separator 11 (second gas).

[0037] (Heat exchanger 17A) Within the heat exchanger 17A, the low-temperature path L2 and the mixing path L3 run parallel to each other, and are configured so that the liquefied gas flowing through each path exchanges heat with the mixed gas of the first gas and the second gas. The low-temperature path L2 and the mixing path L3 are arranged so that the liquefied gas and the mixed gas flow in opposite directions. The liquefied gas is vaporized while passing through the low-temperature path L2, generating a second gas. The first gas, the second gas vaporized in the heat exchanger 17A and passing through the low-temperature path L2, and the second gas vaporized in the gas-liquid separator 11 and passing through the second gas path L5A are joined and mixed, for example, at a junction G. The mixed mixed gas passes through the mixing path L3 and is cooled. This produces low-temperature gas. The obtained low-temperature gas is discharged from the heat exchanger 17A, passes through the low-temperature gas path L4, and is then discharged.

[0038] The above has described the low-temperature gas generator 100A according to the second embodiment. According to the low-temperature gas generator 100A, it is possible to improve the accuracy of temperature control and reduce the range of fluctuation in flow rate. Furthermore, the low-temperature gas generator 100A reuses all of the vaporized liquefied gas more efficiently than the low-temperature gas generator 100, and therefore can achieve a higher efficiency.

[0039] Next, a low-temperature gas generator 100B according to a third embodiment will be described. Fig. 3 is a system diagram showing the configuration of the low-temperature gas generator 100B. The low-temperature gas generator 100B includes a liquefied gas supply amount control valve 1B, a gas supply amount control valve 2, a flow meter 3, a check valve 4, a temperature sensor 5, an indicating regulator (first control means) 6, an accumulator (second stabilization mechanism) 9, a pressure gauge 10, a gas-liquid separator (first stabilization mechanism) 11, a liquid level sensor 12, a solenoid valve 13, a needle valve 14, a liquid level sensor controller 15, a temperature sensor 16, a heat exchanger 17, a temperature sensor 18, a pressure sensor 19, an indicating regulator 20, and an indicating regulator 21. Components identical to those in the first and second embodiments are designated by the same reference numerals, and their description may be omitted.

[0040] (Liquefied gas supply control valve 1B) The liquefied gas supply amount control valve 1 controls the supply flow rate of the liquefied gas based on instructions from the indicating controller 6, the indicating controller 20, and the indicating controller 21. The liquefied gas whose supply flow rate has been controlled is introduced into the low-temperature path L2 of the heat exchanger 17 via the liquefied gas path L6.

[0041] (Temperature sensor 5) The temperature sensor 5 measures the temperature of the low-temperature gas (for example, low-temperature nitrogen gas) discharged to the low-temperature gas path L4 from the heat exchanger 17. The measured temperature of the low-temperature gas (first temperature) is sent to the indicating controller 6.

[0042] (indicating controller 6) The indicating controller 6 adjusts the aperture of the liquefied gas supply amount control valve 1 based on the difference between the temperature of the liquefied gas measured by the temperature sensor 5 (first temperature) and the target temperature of the low-temperature gas. The indicating controller 6 also adjusts the aperture of the liquefied gas supply amount control valve 1 based on the difference between the temperature of the liquefied gas measured by the temperature sensor 16 (second temperature) and the target temperature of the low-temperature gas. These operations adjust the amount of liquefied gas supplied. The target temperature (first target temperature) of the low-temperature gas is, for example, -180°C. For example, by setting the target value of the indicating controller 6 to -180°C and the deviation alarm value to 2°C, the aperture of the liquefied gas supply amount control valve 1 is reduced when the indicated value of the temperature sensor 16 reaches or exceeds -182°C, thereby preventing the liquefied gas from being entrained in the low-temperature gas.

[0043] (Temperature Sensor 16) The temperature sensor 16 measures the temperature (second temperature) of the liquefied gas supplied to the heat exchanger 17 and sends the measured temperature to the indicating controller 6 .

[0044] (heat exchanger 17) In the heat exchanger 17, the low-temperature path L2 and the mixture path L3 run in parallel, and are configured so that the liquefied gas flowing through each path and the mixed gas of the first gas and the second gas exchange heat with each other. The low-temperature path L2 and the mixing path L3 are arranged so that the liquefied gas and the mixed gas flow in opposite directions. The liquefied gas is vaporized while passing through the low-temperature path L2, generating a second gas. The generated second gas is mixed with the first gas, for example, at the confluence G. The mixed gas obtained by mixing the first gas and the second gas passes through the mixing path L3 and is cooled. This results in low-temperature gas. The obtained low-temperature gas is discharged from the heat exchanger 17, passes through the low-temperature gas path L4, and is then discharged.

[0045] (Temperature Sensor 18) The temperature sensor 18 measures the temperature (third temperature) of the gas flowing through the first gas path L1 and sends it to the indicating controller 20.

[0046] (Pressure Sensor 19) The pressure sensor 19 measures the supply pressure of the liquefied gas passing through the liquefied gas path L6 before being introduced into the heat exchanger 17. The supply pressure of the liquefied gas measured by the pressure sensor 19 is sent to an indicating controller 21.

[0047] (Indicating controller 20) The indicating controller 20 controls the liquefied gas supply amount control valve 1 based on the difference between the temperature (third temperature) measured by the temperature sensor 18 and the target temperature (second target temperature), thereby adjusting the supply flow rate of the liquefied gas. For example, by setting the target value (first target temperature) of the indicating controller 6 to -180°C and the target value (second target temperature) of the indicating controller 20 to -175°C, the opening of the liquefied gas supply amount control valve 1 is controlled to be smaller when the indicated value of the temperature sensor 18 falls below -175°C. This makes it possible to suppress entrainment of the liquefied gas into the second gas.

[0048] (Indicating controller 21) The indicating controller 21 controls the liquefied gas supply amount control valve 1 based on the difference between the pressure sensor 19 and the target pressure, thereby adjusting the supply flow rate of the liquefied gas. It is preferable to set the supply pressure (target pressure) of the low-temperature liquefied gas before introducing it into the heat exchanger to 200 kPa or less. By setting the target pressure to 200 kPa or less, it becomes easier to lower the temperature of the liquefied nitrogen at the inlet of the heat exchanger 17 to a temperature below -180°C. By setting the supply pressure of the low-temperature liquefied gas to 200 kPa or less, it is possible to prevent the liquefied gas from being entrained in the second gas, and to prevent damage to equipment and devices caused by contact with the cooled object or the like and rapid cooling.

[0049] The above has described the low-temperature gas generator 100B according to the third embodiment. The low-temperature gas generator 100 can improve the temperature control accuracy and reduce the range of flow rate fluctuations. Furthermore, by controlling the supply amount of liquefied gas based on the pressure sensor 19, it is possible to prevent the liquefied gas from being entrained in the second gas.

[0050] It is also possible to perform program control to gradually lower the target value of the indicating controller 6. For example, by setting the target value of the indicating controller 6 to -180°C and the temperature drop rate to 5°C / min, the aperture of the liquefied gas supply amount control valve 1 gradually increases toward the provisional target value, thereby making it possible to prevent excessive supply of liquefied gas.

[0051] A program control method may be performed in which the first gas flow rate of the gas supply amount control valve 2 is gradually increased. Liquefied gas is supplied from the liquefied gas supply amount control valve 1 in an amount corresponding to the amount of cold energy required for the first gas flow rate of the gas supply amount control valve 2. For example, by setting the initial flow rate of the gas supply amount control valve 2 to 50 L / min, the target flow rate to 500 L / min, and the flow rate increase rate to 10 L / min, and gradually increasing the amount of liquefied gas supplied from the liquefied gas supply amount control valve 1, it is possible to prevent excessive supply of liquefied gas.

[0052] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. In addition, within the scope of the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Example]

[0053] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0054] Example 1 Using the low-temperature gas generator of Example 1 (low-temperature gas generator 100 of Figure 1), the target temperature setting value of the indicating controller 6 was set to -180°C and low-temperature nitrogen gas was generated. As a comparative example, a low-temperature gas generator 200 of Comparative Example 1 (low-temperature gas generator of Figure 5) was used, in which the accumulator 9 and gas-liquid separator 11 were removed from the low-temperature gas generator 100 of Figure 1, and the target temperature of the indicating controller 6 was similarly set to -180°C and low-temperature gas was generated. The results obtained are shown in Table 1. Note that the flow rates measured in the examples were measured using a flow meter for room temperature after heating once.

[0055] [Table 1]

[0056] FIG. 6 shows the changes over time in the flow rate and temperature of the low-temperature gas in Comparative Example 1. The horizontal axis of FIG. 6 represents time (min), the first vertical axis of FIG. 6 represents the temperature (°C) of the low-temperature gas, and the second vertical axis of FIG. 6 represents the flow rate (kg / h). FIG. 7 shows the changes over time in the flow rate and temperature of the low-temperature gas in Example 1. The horizontal axis of FIG. 7 represents time (min), the first vertical axis of FIG. 7 represents the temperature (°C) of the low-temperature gas, and the second vertical axis of FIG. 7 represents the flow rate (kg / h).

[0057] The total flow rate of the low-temperature gas generator 100 of Comparative Example 1 was 29.0 kg / h with a flow rate range of 9.12 to 35.6 kg / h. On the other hand, the total flow rate of the low-temperature gas generator of Example 1 was 21.2 to 28.0 kg / h with an average flow rate of 25.3 kg / h. The low-temperature gas temperature of Comparative Example 1 fluctuated between -146.1 and -185.2°C with an average temperature of -175.2°C, whereas the low-temperature gas temperature of Example 1 fluctuated between -176.8 and -181.4°C with an average temperature of -179.5°C.

[0058] Furthermore, in the low-temperature gas generator of Comparative Example 1, when the liquefied nitrogen temperature rose, the low-temperature gas temperature also rose, suggesting that it was affected by the pulsation of the liquefied nitrogen. From the above, it was confirmed that the degree of temperature control and the range of flow rate control were improved by the gas-liquid separator and accumulator.

[0059] Example 2 Using the low-temperature gas generator 100A of Example 2 (the low-temperature gas generator of FIG. 2), liquefied nitrogen was used as the liquefied gas and nitrogen gas (room temperature nitrogen gas) was used as the first gas to investigate the effect of recovering exhaust gas from the gas-liquid separator 11. The setting value of the indicating controller 6 was set to -180°C, and low-temperature nitrogen gas was generated. Table 2 shows the results with and without merging of exhaust gas from the gas-liquid separator.

[0060] FIG. 8 shows the changes over time in the flow rate and temperature of the low-temperature gas in Comparative Example 1. The horizontal axis of FIG. 8 represents time (min), the first vertical axis of FIG. 8 represents the temperature (°C) of the low-temperature gas, and the second vertical axis of FIG. 8 represents the flow rate (kg / h). FIG. 9 shows the changes over time in the flow rate and temperature of the low-temperature gas in Example 1. The horizontal axis of FIG. 9 represents time (min), the first vertical axis of FIG. 9 represents the temperature (°C) of the low-temperature gas, and the second vertical axis of FIG. 9 represents the flow rate (kg / h).

[0061] The total flow rate of the low-temperature gas generator 100 of Example 1 was 24.6 to 26.7 kg / h with an average flow rate of 25.6 kg / h, whereas the total flow rate of the low-temperature gas generator 100A of Example 2 was 22.4 to 23.1 kg / h with an average flow rate of 22.8 kg / h. The low-temperature gas temperature of the low-temperature gas generator 100 of Example 1 fluctuated between -179.2 and -179.8 °C with an average temperature of -179.5 °C. On the other hand, the low-temperature gas temperature of the low-temperature gas generator 100A of Example 2 fluctuated between -178.7 and -179.3 °C with an average temperature of -179.1 °C. From this, it was confirmed that there was no significant difference in the fluctuation range of the total flow rate and the temperature control accuracy regardless of whether or not exhaust gas was merged, and that the exhaust gas from the gas-liquid separator could be effectively utilized. The flash loss of liquefied gas at 0.6 MPaG is approximately 20%, and by effectively utilizing the exhaust gas in the gas-liquid separator 11, it is possible to effectively utilize up to 1.2 times more nitrogen gas, leading to reduced running costs. Here, flash loss refers to the phenomenon in which a saturated liquid of liquefied gas partially gasifies during adiabatic expansion. For example, if the saturated liquid at 0.6 MPaG is approximately -175°C and the saturated liquid at atmospheric pressure is -196°C, when the pressure is reduced from 0.6 MPaG to atmospheric pressure, the saturated liquid temperature drops. At this time, the liquefied gas evaporates itself in an attempt to maintain its liquid state, and the heat of evaporation causes it to self-cool, dropping from -175°C to -196°C. This phenomenon is called flash loss.

[0062] [Table 2]

[0063] Example 3 The influence of the liquefied gas supply pressure was investigated using the low-temperature gas generator of Example 3 (low-temperature gas generator 100C in FIG. 4), which was equipped with a pressure sensor at the inlet of the heat exchanger 17 of the low-temperature gas generator 100 of Example 1 (low-temperature gas generator of FIG. 3). Liquefied nitrogen was used as the liquefied gas, and nitrogen gas was used as the first gas, which is gaseous at a temperature higher than the boiling point of the liquefied gas. The setting value of the indicating controller 6 was set to −180°C, and low-temperature nitrogen gas was generated. The results are shown in Table 3. As the total flow rate of the low-temperature gas generator 100C of Example 3 was increased, the readings of the temperature sensor 16 and the pressure sensor 19 increased. Under test condition 6 in Table 3, when the reading of the temperature sensor 16 was −181.4°C and the reading of the pressure sensor 19 was 226 kPaG, it was determined that some of the liquid nitrogen was entrained in the second gas. Here, when the temperature of the temperature sensor 5 became approximately the same as that of the temperature sensor 16, it was determined that the liquefied gas was entrained. The heat exchange of liquefied gas involves cooling using latent heat of vaporization and sensible heat (temperature change), and once the latent heat of vaporization is used up, the heat exchange switches to sensible heat. Therefore, if the temperature of temperature sensor 5 is almost the same as that of temperature sensor 16 (no temperature change), it can be assumed that liquefied gas remains. As the total flow rate increases, the back pressure of the entire system increases, raising the boiling point of the liquefied nitrogen, making it impossible to utilize the latent heat, and it is presumed that some of the liquid nitrogen became entrained in the low-temperature gas.

[0064] [Table 3] [Industrial Applicability]

[0065] The low-temperature gas generator according to this embodiment can improve the temperature control accuracy and reduce the range of flow rate fluctuations, and therefore has high industrial applicability. [Explanation of symbols]

[0066] 1 Liquefied gas supply amount control valve, 2 Gas supply amount control valve, 3 Flow meter, 4 Check valve, 5 Temperature sensor, 6 Indicating controller, 8 Flow meter, 9 Accumulator, 10 Pressure gauge, 11 Gas-liquid separator, 12 Liquid level sensor, 13 Solenoid valve, 14 Needle valve, 15 Liquid level sensor controller, 16 Temperature sensor, 17 Heat exchanger

Claims

1. Liquefied gas and a gaseous first gas having a temperature higher than the boiling point of the liquefied gas; A low-temperature gas generator for obtaining gaseous low-temperature gas using a heat exchanger that vaporizes the liquefied gas to generate a second gas and obtains the low-temperature gas from a mixture of the first gas and the second gas; a first control means for controlling a supply flow rate of the liquefied gas based on a difference between a first temperature of the low-temperature gas and a target temperature; a first stabilization mechanism capable of supplying the liquefied gas in a liquid state; a second stabilization mechanism provided at a confluence of the first gas and the second gas; A low-temperature gas generator comprising:

2. 2. The low-temperature gas generator according to claim 1, wherein the first stabilization mechanism is a gas-liquid separator, a subcooler, or a counterflow heat exchanger.

3. 3. The low-temperature gas generator according to claim 1, wherein the second stabilizing mechanism is an accumulator or a buffer tank.

4. 3. The low-temperature gas generator according to claim 1, wherein the supply pressure of the liquefied gas before being introduced into the heat exchanger is set to 200 kPa or less.

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