Compression system, method for starting the compression system, and method for stopping the compression system

Abstract

This compression system comprises: a supply line which supplies a raw material gas; a first compression part which compresses the raw material gas that flows through the supply line; an impurity removal part which removes an impurity from the raw material gas that has been compressed by the first compression part; a second compression part which further compresses the raw material gas that has passed through the impurity removal part; a discharge line which guides the raw material gas that has been compressed by the second compression part to the outside; an upstream side shutoff valve and downstream side shutoff valve which are respectively provided at a stage prior to and a stage after the impurity removal part so as to sandwich the impurity removal part, and the flow rate of at least one of which is adjustable; a gas addition line which can introduce compressed gas between the downstream side shutoff valve and the second compression part; and an open / close valve which is provided to the discharge line.

Description

Technical Field

[0001] The present disclosure relates to a compression system, a method for starting the compression system, and a method for stopping the compression system.

Background Art

[0002] For example, as shown in Patent Documents 1 and 2 below, systems for compressing and storing carbon dioxide have been put into practical use in recent years. In this type of system, measures are taken to remove impurities contained in carbon dioxide as a raw material gas. Specifically, an apparatus for removing oxygen as an impurity from the raw material gas by reacting oxygen and hydrogen to generate water, and an apparatus for removing this water are mainly used.

Prior Art Documents

Patent Documents

[0003]

Patent Document 2

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Apparatuses for removing oxygen mainly use, for example, catalytic reactions and are often not easily affected by pressure fluctuations. On the other hand, in order to remove water, substances such as gels having hydrophilicity are used. When this type of substance is exposed to rapid ambient pressure fluctuations, it may be physically or chemically damaged and may not be able to exhibit its original performance. For this reason, there has been an increasing demand for a compression system that can be smoothly operated while avoiding the influence of pressure fluctuations.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a compression system, a method for starting the compression system, and a method for stopping the compression system that can be smoothly operated while avoiding the influence of pressure fluctuations. [Means for solving the problem]

[0006] To solve the above problems, the compression system according to the present disclosure comprises: a supply line for supplying raw material gas; a first compression unit for compressing the raw material gas flowing through the supply line; an impurity removal unit for removing impurities from the raw material gas compressed by the first compression unit; a second compression unit for further compressing the raw material gas that has passed through the impurity removal unit; a discharge line for guiding the raw material gas compressed by the second compression unit to the outside; an upstream shut-off valve and a downstream shut-off valve provided before and after the impurity removal unit so as to sandwich the impurity removal unit, with at least one of them being capable of flow rate adjustment; a gas addition line for introducing compressed gas between the downstream shut-off valve and the second compression unit; and an on / off valve provided in the discharge line.

[0007] The method for starting a compression system according to the present disclosure is a method for starting a compression system as described above, and includes the steps of: closing the upstream shut-off valve and the downstream shut-off valve; circulating the raw material gas through the supply line; starting the first compression unit; starting the second compression unit; introducing the raw material gas into the impurity removal unit while maintaining a predetermined pressure fluctuation rate by opening the upstream shut-off valve and adjusting the opening of one of the flow-adjustable valves in a direction that increases; opening the downstream shut-off valve when the pressure in the impurity removal unit exceeds a predetermined reference value; and opening the on / off valve provided in the discharge line.

[0008] The method for stopping the compression system according to this disclosure is a method for stopping the compression system described above, and includes the steps of closing the upstream shut-off valve, the downstream shut-off valve, and the on / off valve, and stopping the first compression unit and the second compression unit. [Effects of the Invention]

[0009] This disclosure provides a compression system that can be operated smoothly while avoiding the effects of pressure fluctuations, a method for starting the compression system, and a method for stopping the compression system. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram illustrating the configuration of a compression system according to an embodiment of this disclosure. [Figure 2] This is a system diagram showing the status of each device in step S1 when the compression system is started up. [Figure 3] This is a system diagram showing the status of each device in step S2 when the compression system is started up. [Figure 4] This is a system diagram showing the status of each device in steps S3 and S4 when the compression system is started up. [Figure 5] This is a system diagram showing the status of each device in step S5 when the compression system is started up. [Figure 6] This is a system diagram showing the status of each device in step S6 when the compression system is started up. [Figure 7] This is a system diagram showing the status of each device in step S7 when the compression system is started up. [Figure 8] This is a system diagram showing the status of each device in step S11 when the compression system is stopped. [Figure 9] This is a system diagram showing the status of each device in step S12 when the compression system is stopped. [Figure 10] This is a system diagram showing the state of each device after step S12 when the compression system is stopped. [Figure 11] This flowchart shows the steps involved in starting the compression system. [Figure 12] This flowchart shows the steps involved in stopping the compression system. [Figure 13] This is an enlarged view of a key part showing a modified example of the compression system according to the present disclosure. [Figure 14]It is an enlarged view of the main part showing another modification of the compression system according to an embodiment of the present disclosure.

Mode for Carrying Out the Invention

[0011] (Configuration of Compression System) Hereinafter, a compression system 1 according to a first embodiment of the present disclosure, a method for starting the compression system 1, and a method for stopping the compression system 1 will be described with reference to FIGS. 1 to 12. This compression system 1 is used, for example, to compress carbon dioxide. In each of the drawings referred to in the following description, a valve device painted black indicates that it is in a closed state, and a valve device painted white indicates that it is in an open state.

[0012] As shown in FIG. 1, the compression system 1 includes a supply line L1, a pressurizing unit 10, a first on-off valve 20, a first check valve 30, a first compression unit 40, a first cooler 50, a first impurity removal unit 60, a second cooler 70, a first recycling unit 80, an upstream shut-off valve 90, an upstream bypass line 91, a sub-shut-off valve 92, a second impurity removal unit 100 (impurity removal unit), a fluctuation rate acquisition unit 110, a downstream shut-off valve 120, a downstream bypass line 121, a flow rate adjustment valve 122, a second check valve 130, a second compression unit 140, a discharge line L2, a third cooler 150, a second recycling unit 160, a fourth cooler 170, a second on-off valve 180 (on-off valve), and a gas addition unit 190.

[0013] Carbon dioxide as a raw material gas is supplied to the supply line L1 from an external tank or the like. In the following description, the side from which the raw material gas flows in the supply line L1 is referred to as the "upstream side", and the opposite side is referred to as the "downstream side". On the supply line L1, among the above-described elements, the first on-off valve 20, the pressurizing unit 10, the first check valve 30, the first compression unit 40, the first cooler 50, the first impurity removal unit 60, the second cooler 70, the first recycling unit 80, the upstream shut-off valve 90, the second impurity removal unit 100, the downstream shut-off valve 120, the second check valve 130, and the second compression unit 140 are arranged in this order from the upstream side to the downstream side.

[0014] The first on-off valve 20 is a valve for switching the flow state of the supply line L1. The pressurizing unit 10 is a device for increasing the pressure of the supply line L1 and each device on the supply line L1 to be equal to the pressure of the raw material gas. Specifically, the pressurizing unit 10 includes a pressurizing line 11 through which the compressed gas flows, a first shut-off valve 12 provided on the pressurizing line 11, and a fourth check valve 13. One end of the pressurizing line 11 is connected to a tank or a compression device in which the compressed gas is stored. The other end of the pressurizing line 11 is connected between the first on-off valve 20 and the first check valve 30 on the supply line L1. The first shut-off valve 12 is a valve device for switching the flow state of the pressurizing line 11. The fourth check valve 13 allows the compressed gas in the pressurizing line 11 to flow only in the direction toward the supply line L1 side. Similarly, the first check valve 30 provided on the supply line L1 also allows the raw material gas in the supply line L1 to flow only in the direction from the upstream side to the downstream side.

[0015] The first compression unit 40 includes a first low-pressure compressor 41 and a first high-pressure compressor 42. The outlet-side end of the first low-pressure compressor 41 is connected to the inlet side of the first high-pressure compressor 42. The first low-pressure compressor 41 and the first high-pressure compressor 42 are, for example, centrifugal compressors or axial-flow compressors. Thereby, the raw material gas can be compressed. Further, a first cooler 50 is provided between the first low-pressure compressor 41 and the first high-pressure compressor 42. The first cooler 50 is a heat exchanger that performs heat exchange between the refrigerant supplied from the outside and the raw material gas. As the refrigerant, low-temperature air or liquid refrigerant is used.

[0016] The first impurity removal unit 60 is a device for removing oxygen as an impurity contained in the raw material gas flowing out from the first compression unit 40. For example, it is conceivable to reduce the oxygen concentration in the raw material gas by combining oxygen and hydrogen through a catalytic reaction to make it in a state of water. The second cooler 70 is a heat exchanger for lowering the temperature of the raw material gas by heat exchange with the refrigerant, similar to the other coolers described above.

[0017] The first recycling unit 80 includes a first recycling line 81 and a first expansion valve 82. The first recycling line 81 connects the second cooler 70 and the upstream shut-off valve 90 on the supply line L1, and the first check valve 30 and the first compression unit 40. The first expansion valve 82 is provided on the first recycling line 81. As will be described in more detail later, the first recycling unit 80 is provided to circulate the raw material gas between the first compression unit 40 and the first impurity removal unit 60 when operating the compression system 1 in a circulating operation.

[0018] The upstream shut-off valve 90 is located on the supply line L1 between the first impurity removal section 60 and the second impurity removal section 100. The upstream shut-off valve 90 is a valve that can be switched between open and closed. In other words, the upstream shut-off valve 90 does not have a flow rate adjustment function. Furthermore, an upstream bypass line 91 is provided to bypass the upstream shut-off valve 90. One end of the upstream bypass line 91 is connected to the upstream side of the upstream shut-off valve 90, and the other end is connected to the downstream side of the upstream shut-off valve 90. A sub-shut-off valve 92 is provided on the upstream bypass line 91. The flow path cross-sectional area of ​​the upstream bypass line 91 and the sub-shut-off valve 92 is set to be smaller than that of the supply line L1 and the upstream shut-off valve 90.

[0019] The second impurity removal unit 100 is located between the upstream shut-off valve 90 and the downstream shut-off valve 120. The second impurity removal unit 100 is a device for removing water originally contained in the raw material gas and water generated in the first impurity removal unit 60 described above from the raw material gas. Specifically, it works by bringing a water-containing raw material gas into contact with a highly hydrophilic gel or pellet, causing the gel or pellet to absorb the water. It is known that gels and pellets used for this type of dehydration can be physically or chemically damaged if exposed to rapid pressure fluctuations. Therefore, as will be described in more detail later, it is necessary to control the pressure fluctuation rate (pressure fluctuation rate) when increasing the internal pressure of the second impurity removal unit 100. For this reason, a fluctuation rate acquisition unit 110 for acquiring the pressure fluctuation rate of the raw material gas is provided downstream of the second impurity removal unit 100. After acquiring the pressure fluctuation rate of the raw material gas, the fluctuation rate acquisition unit 110 compares it with a reference value and generates a drive signal to control the opening degree of the flow rate control valve 122, which will be described later.

[0020] The downstream shut-off valve 120, like the upstream shut-off valve 90, is a valve that can be switched between open and closed. In other words, the downstream shut-off valve 120 does not have a flow rate adjustment function. Furthermore, a downstream bypass line 121 is provided to bypass the downstream shut-off valve 120. One end of the downstream bypass line 121 is connected to the upstream side of the downstream shut-off valve 120, and the other end is connected to the downstream side of the downstream shut-off valve 120. A flow rate adjustment valve 122 is provided on the downstream bypass line 121. The flow path cross-sectional area of ​​the downstream bypass line 121 and the flow rate adjustment valve 122 is set to be smaller than that of the supply line L1 and the downstream shut-off valve 120. The flow rate adjustment valve 122 can continuously change the flow rate of the raw material gas flowing through the downstream bypass line 121. Furthermore, the opening degree of the flow rate adjustment valve 122 is feedback controlled or feedforward controlled based on the pressure fluctuation rate of the raw material gas by the fluctuation rate acquisition unit 110 described above. In other words, if the pressure fluctuation rate is higher than the standard value, the opening of the flow control valve 122 is adjusted to decrease. Conversely, if the pressure fluctuation rate is lower than the standard value, the opening of the flow control valve 122 is adjusted to increase.

[0021] A second check valve 130 is provided downstream of the downstream shut-off valve 120. Similar to the first check valve 30, the second check valve 130 restricts the flow direction of the raw material gas in the supply line L1 to only the direction from upstream to downstream. A gas supply unit 190 is provided between the second check valve 130 and the downstream shut-off valve 120. As will be described in detail later, the gas supply unit 190 supplies compressed gas onto the supply line L1 to ensure the smooth operation of the second compression unit 140 when the compression system 1 is started. Specifically, the gas supply unit 190 includes a gas supply line 191, a second shut-off valve 192, and a fifth check valve 193. One end of the gas supply line 191 is connected to the compressed gas supply source, and the other end is connected between the second check valve 130 and the downstream shut-off valve 120 on the supply line L1. The second shut-off valve 192, like the first shut-off valve 12 described above, is a valve that switches the flow state of the gas supply line 191. The fifth check valve 193 restricts the direction of compressed gas flow to only the direction toward the supply line L1.

[0022] A second compression section 140 is provided downstream of the second check valve 130. The second compression section 140 includes a second low-pressure compressor 141 and a second high-pressure compressor 142. The outlet end of the second low-pressure compressor 141 is connected to the inlet side of the second high-pressure compressor 142. The second low-pressure compressor 141 and the second high-pressure compressor 142 are, for example, centrifugal compressors or axial flow compressors. This makes it possible to compress the raw material gas. Furthermore, a third cooler 150 is provided between the second low-pressure compressor 141 and the second high-pressure compressor 142. The third cooler 150 is a heat exchanger that performs heat exchange between a refrigerant supplied from the outside and the raw material gas. Low-temperature air or liquid refrigerant is used as the refrigerant.

[0023] A discharge line L2 is connected to the downstream side of the second compression section 140. The discharge line L2 is a passage for guiding the raw material gas, which has become high-pressure after compression by the first compression section 40 and the second compression section 140, to the outside. A fourth cooler 170 is provided downstream of the second compression section 140 on the discharge line L2. The fourth cooler 170 is a heat exchanger that, like the third cooler 150, performs heat exchange between a refrigerant supplied from the outside and the raw material gas. Low-temperature air or liquid refrigerant is used as the refrigerant. A second recycling section 160 is provided between this fourth cooler 170 and the second compression section 140. The second recycling section 160 has a second recycling line 161, a second expansion valve 162, and a fifth cooler 163. The second recycling line 161 connects the space between the fourth cooler 170 and the second compression section 140 on the discharge line L2, and the space between the second check valve 130 and the second compression section 140. A second expansion valve 162 and a fifth cooler 163 are provided on the second recycling line 161. As will be described in more detail later, the second recycling section 160 is provided to circulate the raw material gas within the second compression section 140 when operating the compression system 1 in a circulating manner.

[0024] A second on-off valve 180 is provided downstream of the fourth cooler 170. The second on-off valve 180 is a valve for switching the flow state of the raw material gas flowing through the discharge line L2. It is also possible to use a valve with a flow rate adjustment function as the second on-off valve 180. Furthermore, a third check valve 194 is provided downstream of the second on-off valve 180. The third check valve 194 restricts the flow direction of the raw material gas to only the direction from upstream to downstream.

[0025] (How to start the compression system) Next, the method for starting the compression system 1 described above will be explained with reference to Figures 1 to 7 and Figure 11. In the figures referred to in the following explanation, the pressure state of a total of nine locations from the first measurement unit 201 to the ninth measurement unit 209 is shown by numbers enclosed in circles in order to visually explain the pressure state of each part of the compression system 1. The unit of the numbers is, for example, bar. Specifically, the first measurement unit 201 is the first unit provided on the supply line L1. The second measurement unit 202 is provided between the first on-off valve 20 and the pressurizing line 11. The third measurement unit 203 is provided between the first check valve 30 and the first compression unit 40. The fourth measurement unit 204 is provided between the second cooler 70 and the upstream shut-off valve 90. The fifth measurement unit 205 is provided between the upstream shut-off valve 90 and the second impurity removal unit 100. The sixth measurement unit 206 is provided between the downstream shut-off valve 120 and the second check valve 130. The seventh measurement unit 207 is located between the second check valve 130 and the second compression unit 140. The eighth measurement unit 208 is located between the second compression unit 140 and the fourth cooler 170. The ninth measurement unit 209 is located downstream of the third check valve. Furthermore, the numbers shown for each measurement unit are not absolute values, but rather indicate the relative pressure relationships between each unit. In other words, various absolute values ​​can be taken depending on the design and specifications.

[0026] First, as shown in Figure 11, this startup method includes the steps of: step S1 closing the upstream shut-off valve 90 and the downstream shut-off valve 120; step S2 supplying raw material gas to the supply line L1; step S3 starting the first compression unit 40; step S4 starting the second compression unit 140; step S5 introducing raw material gas into the second impurity removal unit 100; step S6 opening the downstream shut-off valve 120; and step S7 opening the second on / off valve 180.

[0027] In step S1, the compression system 1 is transitioned from the initial state shown in Figure 1 to the state shown in Figure 2. Specifically, in the initial state, all valve devices except the first expansion valve 82 and the second expansion valve 162 are closed. Also, at this time, the pressure state in all measurement units except the first measurement unit 201 is lower than the pressure of the raw material gas. In the state shown in Figure 2, the first shut-off valve 12 is open. As a result, compressed gas is supplied to the section from the first shut-off valve 20 to the upstream shut-off valve 90 on the supply line L1, and the pressure in the second to fourth measurement units 204 becomes 1.0, the same as the raw material gas. In addition, by opening the second shut-off valve 192 and the flow rate control valve 122, compressed gas is supplied onto the supply line L1 through the gas addition line 191. As a result, the pressure in the fifth to seventh measurement units 207 becomes 10. In other words, the pressure of the compressed gas supplied from the gas addition line 191 is higher than the pressure of the compressed gas supplied from the pressurization line 11. Furthermore, at this time, the flow rate of compressed gas supplied to the second impurity removal unit 100 is controlled by the flow control valve 122. Specifically, as described above, the opening degree of the flow control valve 122 is controlled so that the pressure fluctuation rate of the second impurity removal unit 100 does not exceed a standard value. Alternatively, at this time, instead of opening the flow control valve 122 in step S1 to raise the pressure of the second impurity removal unit 100 from 0 to 10, the pressure of the second impurity removal unit 100 may be raised from 0 to the target pressure in step S5, which will be described later.

[0028] From the above state, in step S2, the flow control valve 122 is closed and the first shut-off valve 20 is opened (Figure 3). At this time, the first shut-off valve 12 and the second shut-off valve 192 are closed to stop the supply of compressed gas. As a result, the raw material gas flows through the section upstream of the upstream shut-off valve 90 in the supply line L1. By closing the flow control valve 122, the pressure in the second impurity removal section 100 is maintained at the state of step S1 (pressure 10). The section between the downstream shut-off valve 120 and the second shut-off valve 180 is also maintained at the state of step S1 (pressure 10).

[0029] In the following step S3, the first compression unit 40 is activated in the state described above. Furthermore, in step S4, the second compression unit 140 is activated. As a result, as shown in Figure 4, the pressure at the fourth measuring unit 204 downstream of the first compression unit 40 rises to 20. Furthermore, due to the activation of the second compression unit 140, the pressure in the section from the downstream shut-off valve 120 to the second compression unit 140 (i.e., the section upstream of the second compression unit 140) drops to 5, and the pressure on the discharge line L2 (i.e., the pressure downstream of the second compression unit 140) rises to 25.

[0030] Next, in step S5, from the above state, the sub-shut-off valve 92 is opened and the opening of the flow control valve 122 is adjusted to increase (Figure 5). As a result, the raw material gas compressed by the first compression unit 40 is introduced into the second impurity removal unit 100 through the shut-off valve. At this time, the opening of the flow control valve 122 is controlled so that the pressure fluctuation rate (pressure fluctuation speed) of the second impurity removal unit 100 does not exceed a predetermined standard value. Subsequently, when the pressure of the second impurity removal unit 100 reaches a specified value, the sub-shut-off valve 92 is closed and the upstream shut-off valve 90 is opened. Also, the flow control valve 122 is closed and the downstream shut-off valve 120 is opened (Figure 6: step S6). Finally, in step S7, the second on-off valve 180 is opened to guide the compressed, high-pressure raw material gas to the outside (Figure 7). With this, all steps related to the method of starting the compression system 1 are completed. After the compressor has started up, the first expansion valve 82 and the second expansion valve 162 are closed, and the discharge rate of the compressed, high-pressure raw material gas is set to the rated value.

[0031] (How to stop the compression system) Next, the method for stopping the compression system 1 will be described with reference to Figures 8 to 10 and Figure 12. As shown in Figure 12, this stopping method includes step S11 of opening the first expansion valve 82 and the second expansion valve 162 and closing the first on-off valve 20, the upstream shut-off valve 90, the sub-shut-off valve 92, the downstream shut-off valve 120, the flow rate control valve 122, and the second on-off valve 180, and step S12 of stopping the first compression unit 40 and the second compression unit 140.

[0032] In step S11, the first expansion valve 82 and the second expansion valve 162 are opened, and the first shut-off valve 20, the upstream shut-off valve 90, the sub-shut-off valve 92, the downstream shut-off valve 120, the flow rate control valve 122, and the second shut-off valve 180 are closed, thereby isolating the second impurity removal unit 100 from the other sections, as shown in Figure 8. In other words, the fifth measurement unit 205 indicates that the operating pressure 20 is maintained. Also, closing the first shut-off valve 20 stops the supply of raw material gas. Similarly, closing the second shut-off valve 180 stops the discharge of high-pressure raw material gas to the outside.

[0033] If the first compression unit 40 is kept running in this state, the raw material gas will circulate through the first recycling unit 80. At this time, the raw material gas is released through the first expansion valve 82 of the first recycling unit 80, causing the pressure of the raw material gas to decrease. Similarly, if the second compression unit 140 is kept running, the raw material gas will circulate through the second recycling unit 160. At this time, the raw material gas is released through the second expansion valve 162 of the second recycling unit 160, causing the pressure of the raw material gas to decrease (Figure 8). Finally, in step S12, the operation of the first compression unit 40 and the second compression unit 140 is stopped (Figure 9). This completes all steps related to the method of stopping the compression system 1. If, after stopping, the pressure of the first compression unit 40 and the second compression unit 140 is higher than the pressure range in which restart is possible, the pressure may be naturally or artificially reduced until the pressure reaches the level necessary for restarting the first compression unit 40 and the second compression unit 140 (Figure 10).

[0034] (Effects and Benefits) Here, devices for removing oxygen, such as the first impurity removal unit 60, mainly use catalytic reactions and are less susceptible to pressure fluctuations. On the other hand, to remove water, hydrophilic substances such as gels are used, as in the second impurity removal unit 100 described above. These types of substances can be physically or chemically damaged when exposed to rapid pressure fluctuations in the surroundings, and may not be able to perform as intended. For this reason, there has been a growing demand for a compression system 1 that can operate smoothly while avoiding the effects of pressure fluctuations. Furthermore, there was an operational challenge that the compression system 1 required a long time to start up in order to avoid the rapid pressure fluctuations described above. Therefore, in this embodiment, the above-described configurations and methods are adopted.

[0035] According to the above configuration, an upstream shut-off valve 90 and a downstream shut-off valve 120 are provided before and after the second impurity removal unit 100, respectively, and a flow rate adjustment valve 122 capable of adjusting the flow rate is provided in conjunction with at least one of them. By controlling the opening degree of this flow rate adjustment valve 122, the raw material gas can be supplied to the second impurity removal unit 100 over a long period of time. Therefore, pressure fluctuations in the impurity removal unit become gradual, and deterioration of substances and components required for water removal, such as gels and pellets inside, can be avoided. Furthermore, since a gas addition line 191 is provided upstream of the second compression unit 140, even when the second compression unit 140 is shut off from the upstream supply line L1, the amount of compressed gas necessary to start the second compression unit 140 can be pre-filled. Conversely, if the downstream shut-off valve 120 is closed in a configuration without a gas addition line 191, raw material gas will not be supplied to the second compression unit 140 from the supply line L1, which may cause a surge in the second compression unit 140. According to the above configuration, such possibilities can be significantly reduced, and the compression system 1 can be started and operated stably.

[0036] Furthermore, with the above configuration, since there is a flow control valve 122 provided in the upstream bypass line 91 or the downstream bypass line 121, it is possible to adjust the flow rate of the raw material gas more precisely than, for example, when the flow control function is provided in the upstream shut-off valve 90 or the downstream shut-off valve 120 itself. In particular, the upstream bypass line 91 and the downstream bypass line 121 have a smaller flow path cross-sectional area than the supply line L1. In other words, only raw material gas at a flow rate smaller than that of the supply line L1 flows through these upstream bypass lines 91 and the downstream bypass lines 121. As a result, the pressure fluctuation rate of the impurity removal section can be controlled more accurately.

[0037] In addition, with the above configuration, by supplying compressed gas to the supply line L1 through the pressurization line 11, it is possible to raise the pressure in the supply line L1 to the same level as that of the raw material gas. This makes it possible to avoid damage to components caused by the rapid supply of high-pressure gas to the first compression section 40. In particular, the impeller of the compressor, which serves as the first compression section 40, is generally formed in the shape of a thin plate, and there is a risk of damage if it is suddenly exposed to high-pressure fluid. With the above configuration, such risks can be reduced, and the compression system 1 can be operated stably and smoothly.

[0038] Furthermore, with the above configuration, when operating the compression system 1 in a circulating manner, the first compression unit 40 can be isolated from other systems and the circulating operation can be performed through the first recycling line 81. At this time, the gas pressure decreases through the first expansion valve 82. Similarly, the second compression unit 140 can be isolated from other systems and the circulating operation can be performed through the second recycling line 161. At this time, the gas pressure decreases through the second expansion valve 162. This allows the compression system 1 to be operated in a circulating manner.

[0039] Furthermore, with the above configuration, the pressure fluctuation rate of the second impurity removal unit 100 can be acquired by the fluctuation rate acquisition unit 110, and based on this fluctuation rate, the opening degree of the flow control valve 122, which is attached to at least one of the upstream shut-off valve 90 and the downstream shut-off valve 120, can be autonomously adjusted. This makes it possible to maintain the pressure fluctuation rate of the second impurity removal unit 100 stably and accurately, compared to, for example, manual management.

[0040] Furthermore, according to the above method, by first closing the upstream shut-off valve 90 and the downstream shut-off valve 120, the pressure in the impurity removal section can be maintained at the operating state. By stopping the first compression section 40 and the second compression section 140 in this state, the compression system 1 stops while maintaining the pressure in the second impurity removal section 100. On the other hand, when restarting, since the pressure in the impurity removal section is maintained at the operating state, it becomes unnecessary to pressurize the second impurity removal section 100 again, and the time required for startup can be greatly reduced. In particular, as mentioned above, since the second impurity removal section 100 has a limited pressure fluctuation rate, it is necessary to pressurize it again for a long time. However, with the above method, this drawback is eliminated, and the compression system 1 can be restarted stably in a short time.

[0041] The embodiments of this disclosure have been described above. It is possible to make various changes and modifications to the above configuration and method without departing from the gist of this disclosure. For example, as shown in Figure 13 as a modified example, it is possible to provide a flow control valve 122 on the upstream bypass line 91 and a sub-shut-off valve 92 on the downstream bypass line 121. Furthermore, as shown in Figure 14 as another modified example, it is possible to replace the downstream shut-off valve 120 itself, or the upstream shut-off valve 90 itself, with the flow control valve 122. In any configuration, the same effects and advantages as those described above can be obtained. Also, the arrangement and number of coolers and check valves described above are examples and can be changed as appropriate according to the design and specifications. Furthermore, if the raw material gas is supplied at atmospheric pressure, the pressurization line 11 described above can be omitted. Moreover, the number of stages of the compressors included in the first compression section 40 and the second compression section 140 are also examples and may be single-stage or three or more stages. Furthermore, the installation of the first impurity removal section 60 is also an example and can be changed as appropriate according to the specifications of the gas to be produced. Furthermore, the first recycling line 81 is normally installed between the first high-pressure compressor 42 and the second check valve 130 on the supply line L1, and in the example of Figure 1, it connects the second cooler 70 and the upstream shut-off valve 90 on the supply line L1, and the first check valve 30 and the first compression unit 40. Also, the second recycling line 161 is normally installed between the second high-pressure compressor 142 and the second on-off valve 180 on the discharge line L2, and in the example of Figure 1, it connects the fourth cooler 170 and the second compression unit 140 on the discharge line L2, and the second check valve 130 and the second compression unit 140. The gas addition line 191 is installed between the upstream shut-off valve 90 and the second on-off valve 180, and in the example of Figure 1, it is installed between the downstream shut-off valve 120 and the second compression unit 140.

[0042] <Note> The compression system 1, the method for starting the compression system 1, and the method for stopping the compression system 1 described in each embodiment can be understood, for example, as follows.

[0043] (1) The compression system 1 according to the first embodiment comprises: a supply line L1 to which raw material gas is supplied; a first compression unit 40 for compressing the raw material gas flowing through the supply line L1; an impurity removal unit for removing impurities from the raw material gas compressed by the first compression unit 40; a second compression unit 140 for further compressing the raw material gas that has passed through the impurity removal unit; a discharge line L2 for guiding the raw material gas compressed by the second compression unit 140 to the outside; an upstream shut-off valve 90 and a downstream shut-off valve 120 provided before and after the impurity removal unit so as to sandwich the impurity removal unit, with at least one of them being flow rate adjustable; a gas addition line 191 for introducing compressed gas between the downstream shut-off valve 120 and the second compression unit 140; and an on / off valve provided in the discharge line L2.

[0044] According to the above configuration, an upstream shut-off valve 90 and a downstream shut-off valve 120 are provided before and after the impurity removal section, respectively, and at least one of them is flow-rate adjustable. This allows the raw material gas to be supplied to the impurity removal section over a long period of time. Therefore, pressure fluctuations in the impurity removal section become gradual, and deterioration of internal materials can be avoided. Furthermore, since a gas addition line 191 is provided, even when the second compression section 140 is shut off from the upstream supply line L1, the amount of compressed gas necessary to start the second compression section 140 can be filled.

[0045] (2) The compression system 1 according to the second embodiment is the compression system 1 of (1), further comprising an upstream bypass line 91 and a downstream bypass line 121 that bypass the upstream shut-off valve 90 and the downstream shut-off valve 120, respectively, and a flow control valve 122 provided on at least one of the upstream bypass line 91 and the downstream bypass line 121.

[0046] With the above configuration, since there is a flow control valve 122 provided in the upstream bypass line 91 or the downstream bypass line 121, it is possible to adjust the flow rate of the raw material gas more precisely than, for example, if the upstream shut-off valve 90 or the downstream shut-off valve 120 itself has a flow control function. As a result, the pressure fluctuation rate of the impurity removal section can be controlled more accurately.

[0047] (3) The compression system 1 according to the third embodiment is the compression system 1 of (1) or (2), further comprising a pressurizing line 11 that can introduce compressed gas upstream of the first compression section 40 in the supply line L1.

[0048] With the above configuration, by supplying compressed gas to the supply line L1 through the pressurization line 11, it is possible to raise the pressure in the supply line L1 to the same level as that of the raw material gas. This makes it possible to avoid damage to components caused by the rapid supply of high-pressure gas to the first compression section 40.

[0049] (4) The compression system 1 according to the fourth embodiment is a compression system 1 according to any one embodiment of (1) to (3), further comprising: a first recycle line 81 connecting the downstream and upstream sides of the first compression unit 40; a first expansion valve 82 provided on the first recycle line 81; a second recycle line 161 connecting the downstream and upstream sides of the second compression unit 140; and a second expansion valve 162 provided on the second recycle line 161.

[0050] With the above configuration, when operating the compression system 1 in a circulating manner, the first compression unit 40 can be isolated from other systems and the system can be operated in a circulating manner through the first recycling line 81. At this time, the gas pressure decreases through the first expansion valve 82. Similarly, the second compression unit 140 can be isolated from other systems and the system can be operated in a circulating manner through the second recycling line 161. At this time, the gas pressure decreases through the second expansion valve 162. This allows the compression system 1 to be operated in a circulating manner.

[0051] (5) The compression system 1 according to the fifth embodiment is a compression system 1 according to any one embodiment of (1) to (4), further comprising a fluctuation rate acquisition unit 110 provided between the impurity removal unit and the downstream shut-off valve 120, which acquires the pressure fluctuation rate of the raw material gas and adjusts the opening degree of at least one of the upstream shut-off valve 90 and the downstream shut-off valve 120 based on the pressure fluctuation rate.

[0052] With the above configuration, the pressure fluctuation rate of the impurity removal section can be acquired by the fluctuation rate acquisition unit 110, and the opening degree of at least one of the upstream shut-off valve 90 and the downstream shut-off valve 120 can be autonomously adjusted based on this fluctuation rate. This makes it possible to stably maintain the pressure fluctuation rate of the impurity removal section.

[0053] (6) A method for starting the compression system 1 according to the sixth embodiment is a method for starting the compression system 1 according to any one embodiment of (1) to (5), comprising the steps of: closing the upstream shut-off valve 90 and the downstream shut-off valve 120; circulating the raw material gas through the supply line L1; starting the first compression unit 40; starting the second compression unit 140; introducing the raw material gas into the impurity removal unit while maintaining a predetermined pressure fluctuation rate by opening the upstream shut-off valve 90 and adjusting it in a direction that increases the opening of one of the flow-adjustable valves; opening the downstream shut-off valve 120 when the pressure in the impurity removal unit exceeds a predetermined reference value; and opening the on / off valve provided in the discharge line L2.

[0054] According to the above method, an upstream shut-off valve 90 and a downstream shut-off valve 120 are provided before and after the impurity removal section, respectively, and at least one of them is flow-rate adjustable. This allows the raw material gas to be supplied to the impurity removal section over a long period of time. Therefore, pressure fluctuations in the impurity removal section become gradual, and deterioration of internal materials can be avoided. Furthermore, since a gas addition line 191 is provided, even when the second compression section 140 is shut off from the upstream supply line L1, the amount of compressed gas necessary to start the second compression section 140 can be filled.

[0055] (7) A method for stopping the compression system 1 according to the seventh embodiment is a method for stopping the compression system 1 according to any one embodiment of (1) to (5), comprising the steps of closing the upstream shut-off valve 90, the downstream shut-off valve 120, and the on / off valve, and stopping the first compression unit 40 and the second compression unit 140.

[0056] According to the above method, by first closing the upstream shut-off valve 90 and the downstream shut-off valve 120, the pressure in the impurity removal section can be maintained at the operating state. In this state, the compression system 1 is stopped by stopping the first compression section 40 and the second compression section 140. On the other hand, when restarting, since the pressure in the impurity removal section is maintained at the operating state, re-pressurization is unnecessary, and the time required for startup can be significantly reduced. [Industrial applicability]

[0057] The above-described compression system 1, method for starting compression system 1, and method for stopping compression system 1 make it possible to operate the compression system 1 more smoothly while avoiding the effects of pressure fluctuations. [Explanation of Symbols]

[0058] 1…Compression system 10…Pressurization section 11…Pressurization line 12…First shut-off valve 13…Fourth check valve 20…First on / off valve 30…First check valve 40…First compression section 41…First low-pressure compressor 42…First high-pressure compressor 50…First cooler 60…First impurity removal section 70…Second cooler 80…First recycling section 81…First recycling line 82…First expansion valve 90…Upstream shut-off valve 91…Upstream bypass line 92…Sub-shut-off valve 100…Second impurity removal section 110…Variation rate acquisition section 120…Downstream shut-off valve 121…Downstream bypass line 122…Flow rate adjustment valve 130…Second check valve 140…Second compression section 141…Second low-pressure compressor 142…Second high-pressure compressor 150…Third cooler 160…Second recycling section 161…Second recycling line 162...Second expansion valve 163...Fifth cooler 170...Fourth cooler 180...Second on / off valve 190...Gas addition section 191...Gas addition line 192...Second shut-off valve 193...Fifth check valve 194...Third check valve 201...First measurement section 202...Second measurement section 203...Third measurement section 204...Fourth measurement section 205...Fifth measurement section 206...Sixth measurement section 207...Seventh measurement section 208...Eighth measurement section 209...Ninth measurement section L1...Supply line L2...Discharge line

Claims

1. The supply line from which the raw material gas is supplied, A first compression unit for compressing the raw material gas flowing through the supply line, The first compression unit includes an impurity removal unit that removes impurities from the raw material gas compressed by the first compression unit, A second compression unit further compresses the raw material gas that has passed through the impurity removal unit, The second compression section has an outlet line that guides the compressed raw material gas to the outside, An upstream shut-off valve and a downstream shut-off valve are provided in front of and behind the impurity removal section, with at least one of them being capable of flow rate adjustment, A gas addition line is provided between the downstream shutoff valve and the second compression section, allowing compressed gas to be introduced between them. A shut-off valve provided in the aforementioned discharge line, A compression system equipped with the following features.

2. The upstream bypass line and the downstream bypass line bypass the upstream shut-off valve and the downstream shut-off valve, respectively. A flow control valve provided in at least one of the upstream bypass line and the downstream bypass line, The compression system according to claim 1, further comprising:

3. The compression system according to claim 1 or 2, further comprising a pressurizing line capable of introducing compressed gas upstream of the first compression section in the supply line.

4. A first recycling line connecting the downstream and upstream sides of the first compression section, A first expansion valve is provided on the first recycling line, A second recycling line connecting the downstream and upstream sides of the second compression section, A second expansion valve is provided on the second recycling line, The compression system according to claim 1 or 2, further comprising:

5. The compression system according to claim 1 or 2, further comprising a pressure fluctuation rate acquisition unit provided between the impurity removal unit and the downstream shut-off valve, which acquires the pressure fluctuation rate of the raw material gas and can adjust the opening degree of at least one of the upstream shut-off valve and the downstream shut-off valve based on the pressure fluctuation rate.

6. A method for starting a compression system according to claim 1 or 2, The steps include closing the upstream shut-off valve and the downstream shut-off valve, The steps include: circulating the raw material gas through the supply line; The steps include starting the first compression unit, The steps include starting the second compression unit, The steps include: opening the upstream shut-off valve and adjusting the opening of one of the flow-adjustable valves in a direction that increases the flow rate, thereby introducing the raw material gas into the impurity removal section while maintaining a predetermined pressure fluctuation rate; The steps include opening the downstream shut-off valve when the pressure in the impurity removal section exceeds a predetermined reference value, The steps include opening the on / off valve provided in the discharge line, How to start a compression system, including the compression system.

7. A method for stopping a compression system according to claim 1 or 2, The steps include closing the upstream shut-off valve, the downstream shut-off valve, and the on / off valve, The steps include stopping the first compression unit and the second compression unit, A method for stopping a compression system, including the one described.

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