Unit type pressure swing adsorption nitrogen making machine and nitrogen making method thereof

Abstract

The invention discloses a unit type pressure swing adsorption nitrogen making machine, and belongs to the technical field of nitrogen making machines, the main points of the technical scheme are that the unit type pressure swing adsorption nitrogen making machine comprises: a box body, the box body comprises a base, the base is arranged in the box body, and the base is provided with a support; the plurality of adsorption cylinders are arranged in the box body and are arranged on the bracket, and the adsorption cylinders are uniformly distributed; the mounting seats are mounted at the two ends of the adsorption cylinder, the mounting seats and the adsorption cylinder are mounted and connected, and each mounting seat comprises a first communication cavity and a second communication cavity; the first electromagnetic valve is mounted on the mounting seat and independently corresponds to the adsorption cylinder, and the first electromagnetic valve is connected among the adsorption cylinder, the first communication cavity and the second communication cavity; and the first electromagnetic valves can be switched back and forth between communication of the adsorption barrel and the first communication cavity or the second communication cavity, and only one pair of first electromagnetic valves is communicated with the second communication cavity at the same time. The concentration stability in the continuous nitrogen preparation process can be improved.

Description

Technical Field

[0001] This application belongs to the field of nitrogen generator technology, and particularly relates to a unit-type pressure swing adsorption nitrogen generator and its nitrogen generation method. Background Technology

[0002] Nitrogen generators typically use physical methods to separate oxygen and nitrogen from the air, thus obtaining high-purity nitrogen. Pressure swing adsorption (PSA) nitrogen generators, on the other hand, selectively adsorb oxygen from the air under varying pressure conditions using specialized adsorbents (such as carbon molecular sieves), achieving nitrogen-oxygen separation. Nitrogen generators have wide applications in many fields and play a vital role in modern industry and production, providing a reliable nitrogen source for various applications requiring nitrogen.

[0003] Existing unit-type pressure swing adsorption nitrogen generators rely on two large adsorption towers working alternately. The continuous operation of the adsorption towers can cause significant fluctuations in nitrogen purity, especially when the adsorption towers are about to be replaced. This issue needs to be addressed. Summary of the Invention

[0004] The purpose of this application is to address the aforementioned technical problems by providing a unit-type pressure swing adsorption nitrogen generator that can improve the concentration stability during the continuous nitrogen production process.

[0005] This application provides a unit-type pressure swing adsorption nitrogen generator, comprising: The housing includes a base, which is placed inside the housing and is provided with a support. The adsorption cylinders are provided in a box and placed on a support, and the adsorption cylinders are evenly distributed. Mounting bases are installed at both ends of the adsorption cylinder, and the mounting bases are installed and connected to the adsorption cylinders. The mounting bases include a first communicating cavity and a second communicating cavity. The first solenoid valve is installed on the mounting base and corresponds to the adsorption cylinder separately. The first solenoid valve is connected between the adsorption cylinder, the first connecting cavity, and the second connecting cavity. The first solenoid valve can switch back and forth between the adsorption cylinder and the first or second connecting cavity, and only one pair of first solenoid valves can connect to the second connecting cavity at any given time.

[0006] The base is installed inside the housing, and the base and housing are connected by bolts or other fasteners. The bracket is welded to the base or connected by bolts or other fasteners. The adsorption cylinder is installed on the bracket. The housing improves the overall structural stability and protection performance. Clean air flows through the adsorption cylinder to achieve nitrogen adsorption. The mounting base is installed and connected to all adsorption cylinders. The mounting assembly is threaded or connected to the adsorption cylinders by bolts or other fasteners. Air is evenly delivered to the adsorption cylinders through the first connecting cavity of the mounting base. The produced nitrogen can be centrally output through the mounting base. The first solenoid valve is connected between the adsorption cylinder, the first connecting cavity, and the second connecting cavity. When the first solenoid valve connects the adsorption cylinder to the first connecting cavity, air can be delivered into the adsorption cylinder. When the first solenoid valve connects the adsorption cylinder to the second connecting cavity, air can be delivered into the adsorption cylinder. When the two connecting cavities are connected, the pressure change within the adsorption cylinder allows the adsorbed oxygen, moisture, carbon dioxide, and other impurities to be released into the second connecting cavity for discharge. Each adsorption cylinder has a separate first solenoid valve at both ends. The first solenoid valves corresponding to the adsorption cylinders connected to the same mounting base connect the adsorption cylinder to the second connecting cavity at any given time. The other first solenoid valves connect the adsorption cylinder to the first connecting cavity. By setting the first solenoid valves on the mounting base to connect the adsorption cylinder and the second connecting cavity in turn, only one adsorption cylinder is in a low-pressure desorption state at any given time, while the other adsorption cylinders are in the adsorption and nitrogen generation state. The above nitrogen generation method can improve the uniformity and stability of the nitrogen concentration and achieve a continuous and stable output of nitrogen generation. It can also be used without a nitrogen buffer tank.

[0007] Furthermore, it also includes: The gas input pipe is connected to the first communicating cavity on the mounting base at one end of the adsorption cylinder; The gas discharge pipe is connected to the second communicating cavity on the mounting base at both ends of the adsorption cylinder; The nitrogen exhaust pipe is connected to the first communicating cavity on the mounting base at the other end of the adsorption cylinder.

[0008] Furthermore, it also includes: The air compressor is installed inside the housing and placed on the base; An air buffer canister is installed in a housing and placed on a base, and the output end of the air buffer canister is equipped with a filter; The air buffer tank is connected between the gas input pipe and the air compressor.

[0009] Furthermore, the mounting base also includes: A connecting pipe is installed in the mounting base, the connecting pipe is connected between the first communicating cavity and the first solenoid valve, and the connecting pipe passes through the second communicating cavity; A seal is placed between the connecting pipe and the mounting base.

[0010] Furthermore, it also includes: Negative pressure source, connected to the gas exhaust pipe; The first pressure detection device is installed on the gas discharge pipe.

[0011] Furthermore, it also includes: A nitrogen buffer tank is installed inside the box and placed on the base, and the nitrogen buffer tank is connected to the nitrogen discharge pipe; The second pressure detection device is installed on the nitrogen exhaust pipe; The second solenoid valve is connected to the nitrogen discharge pipe and the nitrogen buffer tank; The nitrogen exhaust end is connected to the second solenoid valve.

[0012] Furthermore, the mounting base also includes: A signal light is mounted on a mounting base and corresponds to the adsorption cylinder. The signal light is connected to the corresponding first solenoid valve via a signal connection.

[0013] This application also provides a nitrogen generation method using a unit-type pressure swing adsorption nitrogen generator, the specific steps of which include: S1, clean air enters the first connecting cavity on the mounting base at the bottom of the adsorption cylinder. The first solenoid valve controls the first connecting cavity to connect with the adsorption cylinder, and the air enters the adsorption cylinder to adsorb and produce nitrogen. The nitrogen gas is discharged from the first connecting cavity on the mounting base at the top of the adsorption cylinder. S2, the first solenoid valve on the control mounting base is connected to the second connecting chamber and the adsorption cylinder in sequence, so that the impurity air in the adsorption cylinder is discharged through the second connecting chamber, and the adsorption cylinder is controlled to circulate and release impurities.

[0014] By setting the first solenoid valve on the mounting base to alternately connect the adsorption cylinder and the second connecting chamber, only one adsorption cylinder is in a low-pressure desorption state at any given time, while the remaining adsorption cylinders are in an adsorption and nitrogen production state. The above nitrogen production method can improve the uniformity and stability of the nitrogen concentration and achieve a continuous and stable output of the nitrogen production process.

[0015] The beneficial effects of this application are: 1. Several adsorption cylinders are used to adsorb nitrogen simultaneously, while one adsorption tower desorbs. The first solenoid valve controls the adsorption towers to desorb in turn, which can ensure the concentration stability of nitrogen production by the adsorption cylinders as a whole.

[0016] 2. The air compressor is used to compress air and then deliver it to the air buffer tank. The air supplied by the air buffer tank is supplied through the gas input pipe.

[0017] 3. The first solenoid valve is connected to the first connecting cavity via a connecting pipe, which passes through the second connecting cavity. A sealing element provides a sealing performance between the connecting pipe and the first and second connecting cavities.

[0018] 4. The negative pressure source generates negative pressure suction, which accelerates the airflow speed in the gas discharge pipe, rapidly reducing the gas pressure in the adsorption cylinder to be desorbed, and quickly expelling impurity gases. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the nitrogen generator of this application; Figure 2 This is a schematic diagram of the mounting base of this application; Figure 3 For the purposes of this application Figure 2 A magnified view of point A; In the attached diagram, the following labels are used: 100, housing; 110, base; 120, bracket; 200, adsorption cylinder; 210, gas inlet pipe; 220, gas outlet pipe; 230, nitrogen outlet pipe; 300, mounting base; 310, first connecting cavity; 320, second connecting cavity; 400, first solenoid valve; 410, connecting pipe; 420, seal; 500, air compressor; 510, air buffer tank; 520, filter; 600, negative pressure source; 610, first pressure detection device; 700, nitrogen buffer tank; 710, second pressure detection device; 720, second solenoid valve; 730, nitrogen outlet; 800, indicator light. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0021] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0022] The embodiments of this application are described in detail below with reference to the accompanying drawings, through specific examples and application scenarios.

[0023] Example 1: like Figures 1-3As shown in the figure, this application provides a unit-type pressure swing adsorption nitrogen generator, including: The housing 100 includes a base 110, which is placed inside the housing 100 and is provided with a support 120. Adsorption cylinders 200 are provided, which are installed inside the box 100 and placed on the bracket 120, and the adsorption cylinders 200 are evenly distributed. Mounting base 300 is installed at both ends of adsorption cylinder 200. The mounting base 300 and adsorption cylinder 200 are both installed and connected. The mounting base 300 includes a first communicating cavity 310 and a second communicating cavity 320. The first solenoid valve 400 is mounted on the mounting base 300 and corresponds to the adsorption cylinder 200. The first solenoid valve 400 is connected between the adsorption cylinder 200, the first connecting cavity 310, and the second connecting cavity 320. The first solenoid valve 400 can switch back and forth between the adsorption cylinder 200 and the first connecting cavity 310 or the second connecting cavity 320, and only one pair of first solenoid valves 400 can be connected to the second connecting cavity 320 at the same time.

[0024] The base 110 is installed inside the housing 100, and the base 110 is connected to the housing 100 by bolts or other fasteners. The bracket 120 is welded to the base 110 or connected by bolts or other fasteners. The adsorption cylinder 200 is installed on the bracket 120. The housing 100 improves the overall structural stability and protective performance. Clean air flows through the adsorption cylinder 200 to achieve nitrogen adsorption. The mounting base 300 is installed and connected to all the adsorption cylinders 200. The mounting assembly is threaded or connected to the adsorption cylinders 200 by bolts or other fasteners. The first connecting cavity 310 of the mounting base 300 ensures that air is evenly delivered to the adsorption cylinders 200. The produced nitrogen can be centrally output through the mounting base 300. The first solenoid valve 400 is connected between the adsorption cylinder 200, the first connecting cavity 310, and the second connecting cavity 320. When the first solenoid valve 400 connects the adsorption cylinder 200 to the first connecting cavity 310, air can be delivered into the adsorption cylinder 200. When the adsorption cylinder 200 is connected to the second connecting cavity 320, the pressure change within the adsorption cylinder 200 can release the adsorbed impurities such as oxygen, moisture, and carbon dioxide into the second connecting cavity 320 for discharge. Each adsorption cylinder 200 has a first solenoid valve 400 at each end. The first solenoid valves 400 corresponding to the adsorption cylinders 200 connected to the same mounting base 300 can only connect the adsorption cylinder 200 to the second connecting cavity 320 at any given time. The other first solenoid valves 400 connect the adsorption cylinder 200 to the first connecting cavity 310. By setting the first solenoid valves 400 on the mounting base 300 to connect the adsorption cylinders 200 and the second connecting cavity 320 in turn, only one adsorption cylinder 200 is in a low-pressure desorption state at any given time, while the other adsorption cylinders 200 are in an adsorption nitrogen production state. The above nitrogen production method can improve the uniformity and stability of the nitrogen concentration and achieve a continuous and stable output of the nitrogen production process. It can also be used without the need for a nitrogen buffer tank 700.

[0025] Furthermore, it also includes: The gas input pipe 210 is connected to the first communicating cavity 310 on the mounting base 300 at one end of the adsorption cylinder 200; The gas discharge pipe 220 is connected to the second communicating cavity 320 on the mounting base 300 at both ends of the adsorption cylinder 200; The nitrogen exhaust pipe 230 is connected to the first communicating cavity 310 on the mounting base 300 at the other end of the adsorption cylinder 200.

[0026] The gas input pipe 210 is installed and connected to the mounting base 300 at the top of the adsorption cylinder 200. The gas input pipe 210 is connected to the corresponding first connecting cavity 310 and is used to transport air. The nitrogen discharge pipe 230 is connected to the mounting base 300 at the bottom of the adsorption tower and is connected to the corresponding first connecting cavity 310 and is used to transport nitrogen. The gas discharge pipe 220 is connected to the second connecting cavity 320 on the mounting base 300 at both ends of the adsorption cylinder 200 and is used to discharge oxygen, moisture, carbon dioxide and other impurities released in the adsorption tower.

[0027] Example 2: like Figure 1 As shown, this application embodiment provides a unit-type pressure swing adsorption nitrogen generator, which, in addition to the above-mentioned technical features, further includes: Air compressor 500 is installed inside housing 100 and placed on base 110; An air buffer tank 510 is installed in the housing 100 and placed on the base 110. The output end of the air buffer tank 510 is equipped with a filter 520. The air buffer tank 510 is connected between the gas input pipe 210 and the air compressor 500.

[0028] Air compressor 500 is used to compress air and then deliver it to air buffer tank 510. Air buffer tank 510 is connected to gas input pipe 210. Air through gas input pipe 210 is supplied by air buffer tank 510. When air passes through filter 520, dust and impurities in the air are filtered out, so that the air delivered to adsorption cylinder 200 is clean air.

[0029] Furthermore, it also includes: The negative pressure source 600 is connected to the gas discharge pipe 220; The first pressure detection device 610 is installed on the gas discharge pipe 220.

[0030] The negative pressure source 600 generates negative pressure suction, which accelerates the airflow speed in the gas discharge pipe 220, rapidly reducing the gas pressure in the adsorption cylinder 200 to be desorbed, and quickly expelling impurity gas. This increases the speed of nitrogen production through recirculation adsorption in the adsorption cylinder 200, further improving the overall nitrogen production stability of the adsorption cylinder 200. The first pressure detection device 610 detects the air pressure on the gas discharge pipe 220 to determine the gas pressure in the connected adsorption cylinder 200. When the gas pressure in the corresponding adsorption cylinder 200 drops to a preset value, the adsorption tower is reconnected to the first connecting cavity 310.

[0031] Furthermore, it also includes: A nitrogen buffer tank 700 is installed inside the housing 100 and placed on the base 110. The nitrogen buffer tank 700 is connected to the nitrogen discharge pipe 230. The second pressure detection device 710 is installed on the nitrogen exhaust pipe 230; The second solenoid valve 720 is connected to the nitrogen exhaust pipe 230 and the nitrogen buffer tank 700. The nitrogen exhaust end 730 is connected to the second solenoid valve 720.

[0032] The nitrogen buffer tank is connected to the nitrogen discharge pipe 230. The nitrogen buffer tank is used to store nitrogen. The nitrogen can be directly discharged through the nitrogen discharge end 730 by the control of the second solenoid valve 720. Alternatively, the nitrogen can be stored in the nitrogen buffer tank first and discharged from the nitrogen discharge end 730 by the control of the second solenoid valve 720 when needed. It can be adapted to different working conditions. The second pressure detection device 710 can be used to detect the nitrogen pressure discharged from the nitrogen discharge pipe 230.

[0033] Example 3: like Figure 2 , Figure 3 As shown, this application embodiment provides a unit-type pressure swing adsorption nitrogen generator. In addition to the above-mentioned technical features, the mounting base 300 further includes: A connecting pipe 410 is installed in the mounting base 300. The connecting pipe 410 connects the first communicating cavity 310 and the first solenoid valve 400. The connecting pipe 410 passes through the second communicating cavity 320. The seal 420 is placed between the connecting pipe 410 and the mounting base 300.

[0034] The first connecting cavity 310 and the second connecting cavity 320 on the mounting base 300 are isolated from each other and are distributed along the axial direction of the mounting base 300. After the mounting base 300 and the adsorption cylinder 200 are installed, the second connecting cavity 320 is closer to the adsorption cylinder 200 than the first connecting cavity 310. The first solenoid valve 400 is connected to the first connecting cavity 310 through a connecting pipe 410. The connecting pipe 410 passes through the second connecting cavity 320. The sealing performance between the connecting pipe 410 and the first connecting cavity 310 and the second connecting cavity 320 is provided by the sealing element 420.

[0035] Example 4: like Figure 1 , Figure 2 As shown, this application embodiment provides a unit-type pressure swing adsorption nitrogen generator. In addition to the above-mentioned technical features, the mounting base 300 further includes: The signal light 800 is mounted on the mounting base 300 and corresponds to the adsorption cylinder 200. The signal light 800 is connected to the corresponding first solenoid valve 400.

[0036] The indicator light 800 is installed on the mounting base 300. The indicator light 800 has two states: on and off. When the indicator light 800 is on, the first solenoid valve 400 of the corresponding adsorption cylinder 200 is connected between the adsorption cylinder 200 and the second connecting cavity 320, indicating that the corresponding adsorption cylinder 200 is in the desorption state. When the indicator light 800 is off, it indicates that the adsorption cylinder 200 is in the adsorption and nitrogen generation state.

[0037] Example 5: This application also provides a nitrogen generation method using a unit-type pressure swing adsorption nitrogen generator, the specific steps of which include: S1, clean air enters the first connecting cavity 310 on the mounting base 300 at the bottom of the adsorption cylinder 200. Controlled by the first solenoid valve 400, the first connecting cavity 310 is connected to the adsorption cylinder 200. Air enters the adsorption cylinder 200 to adsorb and produce nitrogen. Nitrogen gas is discharged from the first connecting cavity 310 on the mounting base 300 at the top of the adsorption cylinder 200. S2, the first solenoid valve 400 on the control mounting base 300 is connected to the second connecting chamber 320 and the adsorption cylinder 200 in sequence, so that the impurity air in the adsorption cylinder 200 is discharged through the second connecting chamber 320, and the adsorption cylinder 200 is controlled to circulate and release impurities.

[0038] By setting the first solenoid valve 400 on the mounting base 300 to alternately connect the adsorption cylinder 200 and the second connecting cavity 320, only one adsorption cylinder 200 is in a low-pressure desorption state at any time, while the other adsorption cylinders 200 are in an adsorption nitrogen production state. The above nitrogen production method can improve the uniformity and stability of nitrogen concentration and achieve continuous and stable output of nitrogen production process.

[0039] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0040] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A unitary pressure swing adsorption nitrogen generator, characterized by, include: The housing (100) includes a base (110) placed inside the housing (100), and the base (110) is provided with a bracket (120). The adsorption cylinder (200) is provided with several units installed inside the box (100) and placed on the support (120), and the adsorption cylinder (200) is evenly distributed; Mounting base (300) is installed at both ends of adsorption cylinder (200). The mounting base (300) and adsorption cylinder (200) are both installed and connected. The mounting base (300) includes a first communicating cavity (310) and a second communicating cavity (320). The first solenoid valve (400) is mounted on the mounting base (300) and corresponds to the adsorption cylinder (200) separately. The first solenoid valve (400) is connected between the adsorption cylinder (200), the first connecting cavity (310), and the second connecting cavity (320). The first solenoid valve (400) can switch back and forth between the adsorption cylinder (200) and the first connecting cavity (310) or the second connecting cavity (320), and only one pair of first solenoid valves (400) can connect to the second connecting cavity (320) at the same time.

2. The unit PSA nitrogen generator of claim 1, wherein, Also includes: The gas input pipe (210) is connected to the first communicating cavity (310) on the mounting base (300) at one end of the adsorption cylinder (200); The gas discharge pipe (220) is connected to the second communicating cavity (320) on the mounting base (300) at both ends of the adsorption cylinder (200); The nitrogen exhaust pipe (230) is connected to the first connecting cavity (310) on the mounting base (300) at the other end of the adsorption cylinder (200).

3. The unit-type pressure swing adsorption nitrogen generator according to claim 2, characterized in that, Also includes: An air compressor (500) is installed inside a housing (100) and placed on a base (110); An air buffer tank (510) is installed in a housing (100) and placed on a base (110), and a filter (520) is provided at the output end of the air buffer tank (510). The air buffer tank (510) is connected between the gas input pipe (210) and the air compressor (500).

4. The unit-type pressure swing adsorption nitrogen generator according to claim 2, characterized in that, The mounting base (300) also includes: A connecting pipe (410) is installed in the mounting base (300). The connecting pipe (410) is connected between the first communicating cavity (310) and the first solenoid valve (400). The connecting pipe (410) passes through the second communicating cavity (320). A seal (420) is placed between the connecting pipe (410) and the mounting base (300).

5. The unit-type pressure swing adsorption nitrogen generator according to claim 2, characterized in that, Also includes: A negative pressure source (600) is connected to a gas discharge pipe (220); The first pressure detection device (610) is installed on the gas discharge pipe (220).

6. The unit-type pressure swing adsorption nitrogen generator according to claim 1, characterized in that, Also includes: A nitrogen buffer tank (700) is installed inside the housing (100) and placed on the base (110), and the nitrogen buffer tank (700) is connected to the nitrogen discharge pipe (230); The second pressure detection device (710) is installed on the nitrogen exhaust pipe (230); The second solenoid valve (720) is connected to the nitrogen exhaust pipe (230) and the nitrogen buffer tank (700). The nitrogen exhaust end (730) is connected to the second solenoid valve (720).

7. The unit-type pressure swing adsorption nitrogen generator according to claim 1, characterized in that, The mounting base (300) also includes: A signal light (800) is mounted on a mounting base (300) and corresponds to the adsorption cylinder (200). The signal light (800) is connected to the corresponding first solenoid valve (400).

8. A nitrogen generation method applicable to the unit-type pressure swing adsorption nitrogen generator according to claim 1, characterized in that, The specific steps include: S1, clean air enters the first connecting cavity (310) on the mounting base (300) at the bottom of the adsorption cylinder (200). Controlled by the first solenoid valve (400), the first connecting cavity (310) is connected to the adsorption cylinder (200). Air enters the adsorption cylinder (200) to adsorb and generate nitrogen. Nitrogen gas is discharged from the first connecting cavity (310) on the mounting base (300) at the top of the adsorption cylinder (200). S2, the first solenoid valve (400) on the control mounting base (300) is connected to the second connecting chamber (320) and the adsorption cylinder (200) in sequence, so that the impurity air in the adsorption cylinder (200) is discharged through the second connecting chamber (320), and the adsorption cylinder (200) is controlled to circulate and release impurities.

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