Air separation device

Abstract

To provide an air separation device capable of adjusting the flow amount of nitrogen waste gas with no influences on a process balance during a pressure fluctuation in a regeneration gas pipe and no intervention by an operator even when using two types of gases having a small pressure difference as regeneration gas.SOLUTION: The air separation device includes a first waste gas control valve V7 for a first waste gas pipe L22, a first waste gas flow control part F7 for controlling the first waste gas control valve so that a gas flow amount measurement value for the first waste gas pipe becomes a set value, a second waste gas control valve V71 for a second waste gas pipe L23, a regeneration gas flow control part F8 for outputting a first output value based on the gas flow amount measurement value and the regeneration gas flow amount set value for the regeneration gas pipe L20, and a control part 80 for setting a value obtained by subtracting the first waste gas flow amount set value from the regeneration gas flow amount set value as a target value for the second waste gas flow amount, comparing a second output value based on a value obtained by subtracting a measurement value by the first flow control part from a measurement value by the regeneration gas flow control part with the first output value, and controlling the second waste gas control valve to adjust a second waste gas flow amount on the basis of a lower value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0004] , ,

[0001] The present invention relates to an air separation device.

Background Art

[0002] The raw air supplied to the air separation device is compressed and cooled in advance, and after preliminary purification (carbon removal and dehumidification), it passes through a heat exchanger and is supplied to a rectification column (see, for example, Patent Documents 1 and 2, etc.). In this preliminary purification device for compressed raw air, an adsorption process for purifying the raw air with an adsorbent when sending the raw air to the air separation device and a regeneration process for regenerating the adsorbent using the waste gas sent from the air separation device are performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When there are a nitrogen gas piping line and an oxygen gas piping line as waste gases sent from the air separation device, these pipes merge before being sent to the preliminary purification device. At the confluence point of these pipes, if the pressure of the nitrogen gas and the pressure of the oxygen gas are different, there is a concern that the flow on the low-pressure side will deteriorate. When a differential pressure type flow meter is provided in the above piping, the pressure on the piping side may decrease and the differential pressure between the two may become small. Furthermore, while the pre-purification unit is operating normally and in the pressurization phase, the waste gas for regeneration is vented. During this period, the pressure in the piping increases, the differential pressure of one waste gas decreases, and the valve opening increases to maintain the flow rate. At the same time, the valve opening is increased to maintain the flow rate of the other waste gas. However, even with the valves open, there are cases where one waste gas is not supplied due to insufficient pressure. In this case, operator intervention is required to adjust the openings of both valves to restore normal flow. Also, a larger flow of one waste gas can affect the process balance of the air separation unit.

[0005] This disclosure provides an air separation system that can adjust the flow rate of nitrogen waste gas without affecting the process balance of the air separation system and without operator intervention, even when using two types of gases with a small pressure difference as regenerated gases, during pressure fluctuations in the regenerated gas piping. [Means for solving the problem]

[0006] The air separation apparatus (100) of this disclosure is an air separation apparatus (100) that supplies regenerated gas for a regeneration process in a pre-purification section (50), A first exhaust gas control valve (V7) is provided in the first exhaust gas piping (L22) downstream of the main heat exchanger (1) to which the raw material air treated in the aforementioned pre-purification section (50) is supplied, and whose valve opening degree is adjustable. A first exhaust gas flow control unit (F7) measures the gas flow rate of the first exhaust gas piping (L22) downstream of the main heat exchanger (1), and adjusts the valve opening of the first exhaust gas control valve (V7) so that the measured value (F7_pv) becomes a preset first exhaust gas flow rate setting value (F7_sv), A second exhaust gas control valve (V71) is provided in the second exhaust gas piping (L23) downstream of the main heat exchanger (1), and its valve opening is adjustable. A regenerative gas flow control unit (F8) measures the gas flow rate in the regenerative gas pipeline (L20) through which regenerative gas flows, and outputs a first output value (mv1) based on the measured value (F8_pv) and a preset regenerative gas flow rate setting value (F8_sv). The system includes a control unit (80) that sets the target setting value (80_sv) for the flow rate of the second exhaust gas as the value obtained by subtracting the first exhaust gas flow rate setting value (F7_sv) of the first flow rate measuring unit F7 from the flow rate setting value (F8_sv) of the regenerated gas flow rate, and compares the second output value (mv2), which is obtained by subtracting the measured value (F7_pv) of the first flow rate control unit (F7) from the measured value (F8_pv) of the regenerated gas flow rate control unit (F8) (F8_pv - F7_pv), with the first output value (mv1), and adjusts the flow rate of the second exhaust gas by controlling the valve opening of the second exhaust gas control valve (V71) based on the lower value. This allows the valve opening of the second exhaust gas control valve (V71) to remain virtually unchanged both under normal conditions and during the pressurization phase.

[0007] The pressure of the first waste gas is higher than that of the second waste gas, and the flow rate is adjusted so that the first waste gas is mainly used as regenerated gas. The first waste gas is, for example, oxygen-enriched gas (GOX), and the second waste gas is, for example, nitrogen waste gas. The mixing ratio of the first and second waste gases in the regenerated gas is controlled by the first and second waste gas control valves (V7, V71) so that it is, for example, 7-9:3-1. The control unit (80) controls the flow so that the second waste gas does not flow at an abnormally high rate compared to the first waste gas. An output value (mv) is calculated as the control amount for the valve opening based on the set value (sv) and measured value (pv) of the flow rate, and the valve opening is adjusted based on this output value (mv).

[0008] The air separation device (100) is A compressor (C1) that compresses the raw air, A refrigerator (R1) cools the raw material air (compressed air) compressed by the compressor (C1), A pre-purification unit (50) pre-purifies the raw material air (cooled compressed air) cooled by the refrigerator (R1) (for example, by removing carbon dioxide and / or moisture), The main heat exchanger (1) introduces the raw material air (pre-purified raw material air) that has been pre-purified in the aforementioned pre-purification section (50) and performs heat exchange, The raw material air discharged from the main heat exchanger (1) is supplied via piping (L20), and product nitrogen (high-purity nitrogen) is extracted from the raw material air to a rectification column (2), which may also be provided with the above.

[0009] Oxygen-enriched gas (GOX) is discharged from the medium-pressure rectification section of the rectification column 2, passes through the main heat exchanger (1) via the first exhaust gas piping (L22), and can be used as regenerated gas, or it may be extracted as product oxygen gas or released into the atmosphere. Nitrogen waste gas is discharged from the low-pressure rectification section of the rectification column (2), passes through the second waste gas piping (L23) to the main heat exchanger (1), and can be used as regenerated gas or released into the atmosphere. The first exhaust gas pipeline (L22) and the second exhaust gas pipeline (L23) may merge at confluence point M and be sent to the pre-purification section (50) as regenerated gas via the regenerated gas pipeline (L20). The air separation apparatus (100) may further include a crude argon column, a high-purity refined argon column, another heat exchanger, and so on.

[0010] (Effects and Benefits) (1) Even when using two types of gas with a small pressure difference as regenerated gas, pressure fluctuations in the regenerated gas piping do not affect the process balance of the air separation device. (2) The flow rate of nitrogen exhaust gas can be adjusted without operator intervention. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram showing the air separation device of Embodiment 1. [Modes for carrying out the invention]

[0012] Some embodiments of the present invention are described below. The embodiments described below illustrate just one example of the present invention. The present invention is not limited in any way to the embodiments described below and includes various modifications that are implemented without changing the gist of the present invention. Not all of the configurations described below are necessarily essential to the present invention. Upstream and downstream are set based on the gas flow direction.

[0013] (Embodiment 1) The air separation device 100 of Embodiment 1 will be described with reference to Figure 1. The feed air passes through the filtration means 301 and catalyst tower 302 in the path (piping) L10, removing foreign matter and solids from the air. The compressed feed air, compressed by the compressor C1 located in path L10, is cooled to a predetermined temperature by the refrigerator R1.

[0014] (Preparation Unit) The pre-purification section 50 includes a first adsorption tower A1 and a second adsorption tower A2 positioned alongside the first adsorption tower A1. Adsorption processing is performed in one adsorption tower, and regeneration processing is performed in the other adsorption tower, with adsorption processing and regeneration processing being performed alternately. First, let's explain the adsorption process. The path L10 for introducing raw air into the adsorption tower branches into a first branch introduction path L101 connected to the first adsorption tower A1 and a second branch introduction path L102 connected to the second adsorption tower A2. The first branch introduction path L101 is equipped with a first inlet valve V11, and the second branch introduction path L102 is equipped with a second inlet valve V12. When adsorption processing is performed in the first adsorption tower A1, the first inlet valve V11 is opened and the second inlet valve V12 is closed. When adsorption processing is performed in the second adsorption tower A2, the first inlet valve V11 is closed and the second inlet valve V12 is opened. A first outlet valve V21 is provided in a first branch lead-out path L101 on the outlet side of the first adsorption tower A1, and a second outlet valve V22 is provided in a second branch lead-out path L102 on the outlet side of the second adsorption tower A2. When performing an adsorption process in the first adsorption tower A1, the first outlet valve V21 is opened and the second outlet valve V22 is closed. When performing an adsorption process in the second adsorption tower A2, the first outlet valve V21 is closed and the second outlet valve V22 is opened. In FIG. 1, the first branch lead-out path L101 and the second branch lead-out path L102 merge into a path L10. The raw material air preliminarily purified in the first adsorption tower A1 or the second adsorption tower A2 is introduced into the downstream main heat exchanger 1 through the path L10.

[0015] Next, the regeneration process will be described. The oxygen-enriched gas passes through the main heat exchanger 1 via the first waste gas pipe L22, and the nitrogen waste gas passes through the main heat exchanger 1 via the second waste gas pipe L23. They merge at the merging point M to form a regeneration gas, which is introduced into the preliminary purification unit 50 via the regeneration gas pipe L20. The pressure of the oxygen-enriched gas, which is the first waste gas, is higher than the pressure of the nitrogen waste gas, which is the second waste gas, and the flow rate is adjusted so that the oxygen-enriched gas is mainly used as the regeneration gas.

[0016] The regeneration gas pipe L20 branches into a first branch introduction path connected to the first adsorption tower A1 and a second branch introduction path connected to the second adsorption tower A2. A first waste gas inlet valve V31 is provided in the first branch introduction path, and a second waste gas inlet valve V32 is provided in the second branch introduction path. When performing a regeneration process in the first adsorption tower A1, the first waste gas inlet valve V31 is opened and the second waste gas inlet valve V32 is closed. When performing an adsorption process in the second adsorption tower A2, the first waste gas inlet valve V31 is closed and the second waste gas inlet valve V32 is opened. A first exhaust gas outlet valve V41 is provided in the first branch outlet path on the exhaust gas outlet side of the first adsorption tower A1, and a second exhaust gas outlet valve V42 is provided in the second branch outlet path on the exhaust gas outlet side of the second adsorption tower A2. When regeneration treatment is performed in the first adsorption tower A1, the first exhaust gas outlet valve V41 is opened and the second exhaust gas outlet valve V42 is closed. When regeneration treatment is performed in the second adsorption tower A2, the first exhaust gas outlet valve V41 is closed and the second exhaust gas outlet valve V42 is opened. In Figure 1, the first branch outlet path and the second branch outlet path merge to form path L20, from which the gas is released, for example, into the atmosphere.

[0017] (Configuration of the refining tower) The air separation apparatus 100 comprises a main heat exchanger 1 and a rectification column 2 into which the raw material air that has passed through the main heat exchanger 1 is introduced via piping L10.

[0018] The rectification column 2 may be separated into two sections: a low-pressure rectification section and an intermediate-pressure rectification section. Nitrogen-enriched gas may be discharged from the top of the low-pressure rectification section or the top of the intermediate-pressure rectification section and removed via piping L24 after passing through the main heat exchanger 1. The intermediate-pressure rectification section may be equipped with one or more nitrogen condensers to condense the rectified product discharged from its top. Oxygen-enriched liquid discharged from the bottom of the intermediate-pressure rectification section may be introduced into the low-pressure rectification section. A vent 90 may be provided that branches off from the regenerated gas piping L23 and releases the regenerated gas into the atmosphere. A vent 90 may also be provided that branches off from the second exhaust gas piping L23 and releases the second exhaust gas into the atmosphere.

[0019] The first exhaust gas control valve V7 is installed in the first exhaust gas piping L22 downstream of the main heat exchanger 1. The first flow control unit F7 measures the gas flow rate of the first exhaust gas piping L22 downstream of the main heat exchanger 1, and adjusts the valve opening of the first exhaust gas control valve V7 so that the measured value (F7_pv) becomes the preset first exhaust gas flow rate setting value (F7_sv). The second exhaust gas control valve V71 is installed in the second exhaust gas piping L23 downstream of the main heat exchanger 1. The valve opening of the second exhaust gas control valve V71 is adjusted by two control units. The mixing ratio of the first exhaust gas flow rate setpoint (F7_sv) and the second exhaust gas flow rate setpoint (F71_sv) in the regenerated gas may be, for example, 7-9:3-1. The first and second exhaust gas control valves V7 and V71 control the flow rate to achieve this mixing ratio. During normal operation, the flow rate may be controlled at 9:1.

[0020] The regenerated gas flow control unit F8 is installed in the regenerated gas piping L20 downstream from the confluence point M. The regenerated gas flow control unit F8 measures the gas flow rate in the regenerated gas piping L20 through which the regenerated gas flows. The gas flow rate in the regenerated gas piping L20 is the sum of the first and second waste gases. For example, when the first waste gas is "9" and the second waste gas is "1", the regenerated gas will be "10". The first waste gas flow rate is controlled to maintain the first waste gas flow rate set value, and the second waste gas flow rate is controlled to maintain the second waste gas flow rate set value. The regenerated gas flow control unit F8 outputs a first output value (mv1) to the control unit 80 based on the measured value (F8_pv) and the preset regenerated gas flow rate set value (F8_sv).

[0021] Conventionally, during the pressurization phase, the first exhaust gas control valve V7 opens to maintain a set value of "9," while the second exhaust gas control valve V71 also opens to maintain a set value of "10" for the regenerated gas flow rate. As a result, the pressure on the secondary side (downstream side of the valves) of both control valves V7 and V71 increases, and the first exhaust gas, which has a lower pressure, stops flowing (the measurement value F7_pv from the first flow rate measuring unit F7 becomes smaller than the set value (F7_sv)). Consequently, the amount of regenerated gas also decreases, meaning the measurement (F8_pv) from the regenerated gas flow rate measuring unit F8 drops further, causing the second exhaust gas control valve V71 to open even further. In this embodiment, the control unit 80 sets the target setting value (80_sv) for the flow rate of the second exhaust gas to be the value obtained by subtracting the first exhaust gas flow rate setting value (F7_sv) of the first flow rate measuring unit F7 from the flow rate setting value (F8_sv) of the regenerated gas flow rate (F8_sv). Alternatively, a predetermined value (approximately 5 to 15% of the second exhaust gas flow rate setting value) may be further subtracted from the subtracted value (F8_sv - F7_sv) to set the target setting value (80_sv). The control unit 80 calculates a second output value (mv2) based on the value obtained by subtracting the measured value of the first flow control unit F7 (F7_pv) from the measured value of the regenerated gas flow control unit F8 (F8_pv) (F7_pv). The control unit 80 compares the first output value (mv1) and the second output value (mv2) sent from the regenerated gas flow control unit F8, and controls the valve opening degree of the second exhaust gas control valve V71 based on the lower value. This prevents the secondary waste gas (nitrogen waste gas) from flowing more rapidly than the primary waste gas (oxygen-enriched gas), and instead allows more oxygen-enriched gas to flow.

[0022] (Examples) (1) Setting the flow rate of each exhaust gas Oxygen-enriched gas flow rate setting value (F7_sv): 9 Nitrogen exhaust gas flow rate setting value (F71_sv): 1 Regenerated gas flow rate setting (F8_sv): 10 (2) Flow rate measurement values ​​for each exhaust gas Oxygen-enriched gas flow rate measurement (F7_pv): fluctuates up or down based on a baseline of 9. Nitrogen exhaust gas flow rate measurement (F71_pv): fluctuates up or down based on a baseline of 1. Regenerated gas flow rate measurement (F8_pv): fluctuates up or down based on a baseline of 10. (3) Pressure of each exhaust gas The nitrogen waste gas pressure should be operated at approximately 1.05 to 1.2 times the oxygen enriched gas pressure (1). Each pressure is determined by the operating pressure of the air separation unit and the number of differential pressure flow meters installed in the piping. (4) Initiate normal operation and pressurization phase in the pre-purification unit and control the flow rate while the regenerated gas is vented out. The value obtained by subtracting the first exhaust gas flow rate setting value of the first flow control unit F7 (F7_sv=9) from the regenerated gas flow rate setting value (F8_sv=10) (F8_sv-F7_sv=10-9=1) is set as the target setting value for the second exhaust gas flow rate (80_sv). The first exhaust gas becomes less fluid, so its value becomes less than "9". Therefore, the value obtained by subtracting the value obtained by the first flow control unit F7 (F7_pv<9) from the value obtained by the regenerative gas flow control unit F8 (F8_pv=10) (F8_pv-F7_pv) will be greater than "1". For example, "2". Compared to the second exhaust gas flow rate setting value (F71_sv=1) set above, the value obtained by subtracting (F8_pv-F7_pv) is larger, so a value (-1) that reduces the valve opening is set as the second output value (mv2). The first output value (mv1) sent from the regenerative gas flow control unit F8 is calculated by comparing the set value (F8_pv) with the measured value (F8_pv). When the set value (F8_sv) > measured value (F8_pv), the first output value (mv1) is set to a value (+1 or greater) that increases the valve opening corresponding to the difference. When the set value (F8_sv) < measured value (F8_pv), the first output value (mv1) is set to a value (-1 or less) that decreases the valve opening corresponding to the difference. When the set value (F8_sv) = measured value (F8_pv), the output value (0) is set to maintain the valve opening. The first output value (mv1) and the second output value (mv2) are compared, and the valve opening of the second exhaust gas control valve V71 is controlled based on the lower value.

[0023] (Example 1) First output value (mv1): 0 Second output value (mv2): -1 The lower value: -1 Valve opening of the second exhaust gas control valve V71: Reduce the opening from the current opening. As a result, the valve opening of the second exhaust gas control valve V71 remains almost unchanged both under normal conditions and during the pressurization phase, preventing a sudden flow of the second exhaust gas and maintaining the flow rate of the first exhaust gas. [Explanation of symbols]

[0024] 1 Main heat exchanger 2 Rectification tower 50 Pre-purification section 80 Control Unit F7 First flow measurement section F8 Regenerated gas flow rate measurement section V7 First Exhaust Gas Control Valve V71 Second Exhaust Gas Control Valve

Claims

1. An air separation device (100) that supplies regenerated gas for the regeneration process in the pre-purification section (50), A first exhaust gas control valve (V7) is provided in the first exhaust gas piping (L22) downstream of the main heat exchanger (1) to which the raw material air treated in the aforementioned pre-purification section (50) is sent, and whose valve opening degree is adjustable. A first exhaust gas flow control unit (F7) measures the gas flow rate of the first exhaust gas piping (L22) downstream of the main heat exchanger (1), and adjusts the valve opening of the first exhaust gas control valve (V7) so that the measured value (F7_pv) becomes a preset first exhaust gas flow rate setting value (F7_sv). A second exhaust gas control valve (V71) is provided in the second exhaust gas piping (L23) downstream of the main heat exchanger (1), and its valve opening is adjustable. A regenerative gas flow control unit (F8) measures the gas flow rate in the regenerative gas pipeline (L20) through which regenerative gas flows, and outputs a first output value (mv1) based on the difference between the measured value (F8_pv) and a preset regenerative gas flow rate setting value (F8_sv). An air separation device comprising: a control unit (80) that sets the target setting value (80_sv) for the flow rate of the second exhaust gas as the value obtained by subtracting the first exhaust gas flow rate setting value (F7_sv) of the first flow rate measuring unit F7 from the flow rate setting value (F8_sv) of the regenerated gas flow rate; a control unit (80) that compares the second output value (mv2), which is obtained by subtracting the measured value (F7_pv) of the first flow rate control unit (F7) from the measured value (F8_pv) of the regenerated gas flow rate control unit (F8) (F8_pv - F7_pv), with the first output value (mv1), and adjusts the flow rate of the second exhaust gas by controlling the valve opening of the second exhaust gas control valve (V71) based on the lower value.

2. The air separation apparatus according to claim 1, wherein the pressure of the first exhaust gas is higher than the pressure of the second exhaust gas, and the flow rate is adjusted so that the first exhaust gas is mainly used as recycled gas.

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