Gas purification system and treatment method

Abstract

The invention discloses a gas purification system and a treatment method, the gas purification system is especially suitable for purifying nitrogen with high oxygen content, the gas purification system comprises a raw gas input unit, a gas distribution branch unit, a control system unit, a flow control unit, a gas mixing unit, a catalytic reaction unit, a heat exchange unit, a purity detection unit and an adsorption unit; the purity detection unit comprises an oxidizing and reducing impurity gas analyzer; the control system unit can be a single chip microcomputer, a PLC (Programmable Logic Controller), a computer and the like, receives a signal of the purity detection unit, and controls the flow control unit to compensate proper hydrogen after logical operation; the gas mixing unit is positioned behind the flow controller; by adopting the scheme, the oxygen content of the raw gas can be accurately calculated in real time, and hydrogen is supplemented according to the reaction molar ratio; the gas is completely removed in the catalytic reaction unit, so that the purification efficiency is improved to a certain extent.

Description

Technical Field

[0001] The invention relates to the field of high-purity gas purification, and in particular to a gas purification system and a treatment method with high oxygen content. Background Art

[0002] High-purity nitrogen is widely used. In the field of hydrogen production from ammonia decomposition and the evaluation of catalysts for hydrogen production from ammonia decomposition, nitrogen is used as purge gas, regeneration gas, carrier gas, etc.; in metallurgy, welding, casting, etc., it is used as protective gas, cooling gas, hydrogen ratio adjustment gas, etc.; in the electronics industry, it is used for processes such as lithography, deposition, welding, and annealing. At present, industrial nitrogen mainly includes cryogenic air separation nitrogen production and PSA pressure swing adsorption nitrogen production. Both use air as raw material, but the operating cost of cryogenic air separation nitrogen production is usually several times that of PSA pressure swing adsorption nitrogen production. Therefore, PSA pressure swing adsorption nitrogen production is the mainstream in small and medium-sized applications. According to the process characteristics, cryogenic nitrogen is stored in the form of liquid nitrogen with high purity, which meets the 99.99% pure nitrogen index in GB / T 8979-2008. PSA pressure swing adsorption nitrogen is continuously produced and used in the form of high-pressure nitrogen with a purity range of 98% to 99.99%. The main impurity gases include oxygen, carbon dioxide, water vapor and a small amount of other gases, among which oxygen is the majority. Its purity is affected by many factors, such as upstream and downstream pressure fluctuations, changes in water and oil content in the air source, adsorbent poisoning, ambient temperature effects, equipment load changes, etc. Therefore, although the operating cost of PSA pressure swing adsorption nitrogen is low, the long-term stability of purity is not as high as that of liquid nitrogen.

[0003] Common nitrogen purification processes are catalytic conversion and catalytic absorption. The catalytic conversion is to convert one or more impurity gases into one or more gases that are easier to handle, such as converting trace impurity gases such as H2, O2, CO, CH4, hydrocarbons, etc. into CO2 and H2O that are easily adsorbed by adsorbents. The catalytic absorption method is to directly chemically adsorb the impurity gases without generating new impurities. When the reducing and oxidizing impurities in nitrogen do not meet the full reaction molar ratio, the conversion method cannot theoretically remove them all. When a certain impurity component in nitrogen is seriously high, such as high-oxygen nitrogen, the absorption method will result in a large catalyst loading or an increased cost of replacing or regenerating the catalyst, which is not economical. Therefore, a more scientific and economical purification method is needed. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a gas purification system and treatment method, wherein the software core is a PID control algorithm, and the hardware core is composed of a compensation / gas distribution branch flow controller, a catalytic reaction / conversion unit and a purity detection / feedback unit. The purity detection unit can collect the impurity gas components in the pure gas in real time, and the PID control system controls the mass flow controller in real time to accurately compensate the raw gas, so that the oxidizing and reducing impurity gases can enter the catalytic reaction unit according to the molar ratio of the complete reaction and be completely reacted and removed.

[0005] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0006] The first aspect of the present invention provides a gas purification system, including: a raw gas input unit, a gas distribution branch unit, a control system unit, a flow control unit, a gas mixing unit, a catalytic reaction unit, a purity detection unit, a first heat exchanger, a second heat exchanger and an adsorption unit, wherein the raw gas input unit is arranged on a process gas input main pipe, and the outlet of the process gas input main pipe is connected to the inlet of the gas mixing unit, the gas distribution branch unit is arranged on a compensation gas input branch pipe, and the outlet of the compensation gas input branch pipe is connected to the outlet of the process gas input main pipe, the flow control unit is installed at the outlet end of the compensation gas input branch pipe, the catalytic reaction unit is installed on the outlet side of the gas mixing unit, the first heat exchanger is installed on the catalytic reaction unit side by a waste heat recovery connection method, the inlet of the second heat exchanger is connected to the outlet of the first heat exchanger, and the outlet of the second heat exchanger is connected to the inlet of the adsorption unit, the outlet of the adsorption unit outputs pure gas through a process pure gas output main pipe after passing through a filter, and the purity detection unit is located on the main pipe after the second heat exchanger and before the adsorption unit or on the process pure gas output main pipe after the adsorption unit.

[0007] Furthermore, a filter, a valve and a flow meter are installed on the process gas input main pipe.

[0008] Furthermore, a filter, a valve and a flow control unit are installed on the compensation gas input branch pipe, and the flow control unit is installed after the filter and the valve along the process gas flow direction of the compensation gas input branch pipe.

[0009] Preferably, the flow control unit is preferably a mass flow controller, and the flow measuring instrument is preferably a mass flow meter or a thermal flow meter.

[0010] Furthermore, the outlet of the flow controller unit is installed on the process gas input main pipe at a downstream position of the flow meter, and the compensation gas is injected from the outlet of the compensation gas input branch pipe along the tangent direction of the main pipe. Preferably, the compensation gas is high-purity hydrogen or ultra-pure hydrogen in accordance with the national standard GB / T 3634.2-2011, thereby reducing the impurity gas brought in by the hydrogen itself.

[0011] Furthermore, the purity detection unit includes a trace oxidizing gas detector and a trace reducing gas detector. Specifically: when the process gas belongs to an atmosphere with more oxidizing impurity gases, the compensation gas should be a reducing gas, and the reducing gas detector is a necessary instrument; when the process gas belongs to an atmosphere with more reducing impurity gases, the compensation gas should be an oxidizing gas, and the oxidizing gas detector is a necessary instrument. Furthermore, both the necessary instruments and non-necessary instruments can be controlled, but necessary instruments are preferred.

[0012] Furthermore, the control system unit is a single chip microcomputer, a PLC or a computer, which receives the signal from the purity detection unit, sends a control signal after a logical operation, and controls the flow control unit to compensate the main process gas for appropriate gas distribution.

[0013] Preferably, the mixing unit is located between the flow controller and the catalytic reaction unit.

[0014] Furthermore, the catalytic reaction unit is installed after the gas mixing unit. The catalytic reaction unit needs electric heating when working, and catalyzes the reducing and oxidizing impurity gases in the process gas into water and carbon dioxide.

[0015] Furthermore, the low-temperature end inlet of the first heat exchanger is connected to the outlet of the gas mixing unit, the low-temperature end outlet is connected to the inlet of the catalytic reaction unit, the high-temperature end inlet is connected to the outlet of the catalytic reaction unit, and the high-temperature end outlet is connected to the inlet of the second heat exchanger, forming the waste heat recovery connection method. Further, the outlet of the second heat exchanger is connected to the inlet of the adsorption unit.

[0016] Furthermore, the outlet of the adsorption unit outputs pure gas after passing through a filter, and the adsorption unit adopts a double-tower parallel structure to form a one-in-use and one-in-standby mode.

[0017] Furthermore, the catalytic reaction unit uses a non-normal temperature catalyst and requires electric heating when working to catalyze the reducing and oxidizing impurity gases in the process gas into water and carbon dioxide.

[0018] Furthermore, the adsorption unit adopts a room temperature adsorbent, which can physically adsorb impurity gases such as water and carbon dioxide in the process gas. When one tower is saturated with adsorption, it needs to be regenerated, and then it switches to another tower to work. Furthermore, when the adsorption tower is regenerated, it is necessary to start electric heating to increase the temperature.

[0019] Furthermore, when the gas purification system is connected to the ammonia decomposition hydrogen production equipment, a compensating hydrogen output branch is led out from the hydrogen output main pipe of the ammonia decomposition hydrogen production equipment and connected to the compensating gas input branch, an auxiliary gas input branch is led out from the process pure gas output main pipe and enters the ammonia decomposition hydrogen production equipment, a hydrogen ratio adjustment input branch is led out from the process pure gas output main pipe and connected to the hydrogen output main pipe, and along the gas flow direction, the hydrogen ratio adjustment input branch is downstream of the compensating hydrogen output branch.

[0020] Furthermore, a first flow controller is installed on the compensation gas input branch, a second flow controller is installed on the hydrogen ratio adjustment input branch, and a third flow controller is installed on the hydrogen output main pipe. The gases output by the second and third flow controllers are respectively merged to form the adjusted nitrogen-hydrogen mixture.

[0021] The second aspect of the present invention is to provide a gas purification method for the above-mentioned gas purification system, wherein the control system unit comprises: an input acquisition unit, a logic control and operation unit, and an output control unit, wherein the input acquisition unit receives the data signal of the purity detection unit, the logic control and operation unit calculates the standard flow rate according to the temperature and pressure, and calculates the reducing and oxidizing component contents according to the impurity gas analysis data. When hydrogen is used as the controlled parameter, according to the reaction molar ratio of hydrogen to oxygen of 2:1, the trace hydrogen index in the pure gas should be X H (ppm), with X H (ppm) as the given value of the PID algorithm, the input acquisition unit receives the trace hydrogen analyzer data C of the purity detection unit H (ppm), as the PID algorithm feedback value, so as to calculate the deviation value Δe = X H (ppm)-C H (ppm), after the PID operation, the operation output value is used as the flow controller control signal to control the hydrogen compensation flow, thereby realizing PID negative feedback closed-loop control.

[0022] Furthermore, the signal may be a combination of one or more standard signals such as RS485 communication, 4-20 mA current, 0-5 V or 1-5 V or 0-10 V voltage.

[0023] Furthermore, in the treatment method applied to the ammonia decomposition equipment, the first flow controller is used to control the compensation hydrogen flow Q1, and its value is automatically controlled by the PID control system. The second flow controller is used to control the nitrogen flow Q2 and adjust the nitrogen-hydrogen mixing ratio. The third flow controller is used to adjust the ammonia decomposition hydrogen production mixed gas flow Q3. The ammonia decomposition hydrogen production mixed gas contains 75% hydrogen and 25% nitrogen. The proportion of hydrogen in the mixed gas can be controlled by adding high-purity nitrogen Q2. Specifically, the total flow rate Q 总 =Q2+Q3, where the hydrogen gas volume fraction is

[0024] The gas purification system of the present invention adopts a PID control algorithm. The user sets the purity index as a given value of the PID control system, and then detects the oxidizing and reducing impurity gas contents in the pure gas in real time as feedback values ​​in the PID algorithm, thereby calculating the purity deviation Δe. After completing the PID operation, the system outputs a control signal to the actuator, i.e., the flow controller, to control the gas distribution compensation flow, thereby realizing PID control.

[0025] In order to achieve negative feedback control, the controlled object in this system should be based on the properties of the compensation gas. For example, if the compensation gas is hydrogen, the controlled variable should be the hydrogen content, that is, when the hydrogen content in the pure gas purity is high, the hydrogen compensation amount should be reduced, and when the hydrogen content is low, the hydrogen compensation amount should be increased. In the same principle, if the compensation gas is oxygen, the controlled object should also be the oxygen content indicator.

[0026] By adopting the above technical solution, the beneficial effects of the present invention are:

[0027] 1. The advantage of the present invention is that the purity detection unit can collect the impurity gas components in the pure gas in real time, and the PID control system controls the mass flow controller in real time to accurately compensate the raw gas, so that the oxidizing and reducing impurity gases can enter the catalytic reaction unit according to the molar ratio of complete reaction and be completely removed by reaction.

[0028] 2. The advantage of the present invention is that the purity detection unit is installed after the catalytic reaction unit to directly detect the impurity content in the pure gas, which can most truly reflect the purity index of the pure gas.

[0029] 3. The advantage of the present invention is that the purity detection unit is preferably installed on the main pipe after the second heat exchanger and before the adsorption unit. It is closer to the flow controller than the process pure gas output main pipe after the adsorption unit, which can shorten the signal lag time and make the control response faster. However, when it is installed on the process pure gas output main pipe after the adsorption unit, the gas purity is higher. When the process gas comes from liquefied gas and the purity is very stable, the purity detector can be preferably installed after the adsorption unit.

[0030] 4. The advantage of the present invention is that the compensating gas is injected from the outlet of the branch pipe along the tangential direction of the main pipe, with an angle of entry within a range of ±90°, and is mixed with the process gas flow in a spiral manner on the inner wall of the main pipe, making it easier to form turbulence, thereby enhancing the mixing effect.

[0031] 5. The advantage of the present invention is that the control system unit can be a single-chip microcomputer, a PLC (programmable controller), an industrial computer, etc. The control system unit includes: an input acquisition unit, a logic control and operation unit, and an output control unit. The control system adopts a PID control scheme, that is, a proportional, integral, and differential automatic control algorithm. The algorithm has good real-time performance and can achieve continuous adjustment of the controlled object. After adopting the PID control algorithm, there is no need to collect compensation algorithms such as the temperature and pressure of the process gas, which saves investment. After adopting the PID control algorithm, only a pure gas purity detection unit needs to be installed, and there is no need to install instruments such as temperature, pressure, and impurity component analysis in the original gas input unit and the compensation input unit, which saves investment.

[0032] 6. The advantage of the present invention is that the flow measurement and control adopts thermal flowmeter and mass flow controller. The principle of thermal flowmeter is to heat the measured gas, and the heat energy flows with the gas. The mass flow rate of the gas is calculated by measuring the heat change generated by the gas flow in the pipeline. Therefore, the secondary contamination of the process gas by the instrument is avoided.

[0033] 7. The advantage of the present invention is that the mixing unit is located between the flow controller and the catalytic reaction unit to further mix the mixed gas. Under normal circumstances, the flow rate of the gas distribution branch pipe is much smaller than the flow rate of the main process gas. The function of the gas mixing unit is to fully mix the compensation hydrogen gas with the process gas. The gas mixer is preferably a static mixer without moving parts.

[0034] 8. The advantage of the present invention is that the catalytic reaction unit is installed after the gas mixing unit. The catalytic reaction unit uses a very low temperature catalyst and needs to be electrically heated when working to catalyze the reducing and oxidizing impurity gases in the process gas into water and carbon dioxide. Research data shows that high temperature catalysts are more effective in converting CH4, CO, H2 and hydrocarbon impurity gases into CO2 and H2O.

[0035] 9. The advantage of the present invention is that the low-temperature end inlet of the first heat exchanger is connected to the outlet of the gas mixing unit, the low-temperature end outlet is connected to the inlet of the catalytic reaction unit, the high-temperature end inlet is connected to the outlet of the catalytic reaction unit, and the high-temperature end outlet is connected to the inlet of the second heat exchanger, forming the waste heat recovery connection method. Further, the outlet of the second heat exchanger is connected to the inlet of the adsorption unit. The high-temperature catalyst needs to be heated when working. After the process gas enters the catalyst bed, it will take away a large amount of heat. The first heat exchanger exchanges the heat in the outlet gas of the catalytic reaction unit to the inlet process gas, thereby reducing the energy consumption of the system. Usually, due to the manufacturing cost of the heat exchanger, the outlet temperature of the first heat exchanger is difficult to reduce to below 50°C, which is not conducive to the subsequent adsorption treatment. The function of the second heat exchanger is to further reduce the outlet gas temperature to below 50°C. The second heat exchanger can be an air-cooled heat exchanger or a water-cooled heat exchanger.

[0036] 10. The advantage of the present invention also lies in that the outlet of the adsorption unit outputs pure gas after passing through the filter, and the adsorption unit adopts a double-tower or multi-tower parallel structure to form a one-in-one-standby or one-in-multiple-standby mode, thereby achieving uninterrupted gas supply.

[0037] 11. The advantage of the present invention is that the adsorption unit uses a room temperature adsorbent, which does not require heating during operation and can physically adsorb impurity gases such as water and carbon dioxide in the process gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a purification process flow chart of the present invention.

[0039] Figure 2 This is a principle block diagram of the control system of the present invention.

[0040] Figure 3 This is a block diagram of the PID control principle of the present invention.

[0041] Figure 4 This is a schematic diagram of the present invention used in the field of hydrogen production by decomposing ammonia.

[0042] Markings in the figure:

[0043] 1. Process gas input main pipe; 2. Compensation gas input branch pipe; 3. Process pure gas output main pipe; 4. Auxiliary gas input branch pipe; 5. Hydrogen ratio adjustment input branch pipe; 6. Hydrogen output main pipe; 7. Compensation hydrogen output branch pipe; 8. Adjustment hydrogen output main pipe. DETAILED DESCRIPTION

[0044] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings and related known technical knowledge, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the protection scope of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0045] Example

[0046] like Figure 1 A gas purification system shown in the figure includes a raw gas input unit, a gas distribution branch unit, a control system unit, a flow control unit, a gas mixing unit, a catalytic reaction unit, a purity detection unit, a first heat exchanger, a second heat exchanger and an adsorption unit. The raw gas input unit is arranged on a process gas input main pipe 1, and the outlet of the process gas input main pipe 1 is connected to the inlet of the gas mixing unit. The gas distribution branch unit is arranged on a compensation gas input branch pipe 2, and the outlet of the compensation gas input branch pipe 2 is connected to the outlet of the process gas input main pipe 1. The flow control unit is installed at the outlet end of the compensation gas input branch pipe 2, and the catalytic reaction unit is installed on the outlet side of the gas mixing unit. The first heat exchanger is installed on the catalytic reaction unit side by a waste heat recovery connection method. The inlet of the second heat exchanger is connected to the outlet of the first heat exchanger, and the outlet of the second heat exchanger is connected to the inlet of the adsorption unit. The outlet of the adsorption unit outputs pure gas through the process pure gas output main pipe 3 after passing through a filter. The purity detection unit is located on the main pipe before the adsorption unit after the second heat exchanger or on the process pure gas output main pipe 3 after the adsorption unit.

[0047] Figure 2 The control system of the present invention is a principle block diagram, including a gas distribution process and a main control process. Specifically, after the system is powered on, if there is no fault and everything is normal, it is in a ready-to-wait state. When the start signal is detected, the catalytic reaction unit program is first started to heat up. After the temperature is constant, the gas distribution process and the main control process program are executed. The main control process program is responsible for controlling all programmable valves, electric heaters, low-voltage electrical components, touch screen communications, etc. The gas distribution process program is responsible for instrument communications and collecting analog signals, executing the PID control algorithm, and controlling the flow controller.

[0048] Figure 3This is a block diagram of the PID control principle of the present invention, including a given value, a feedback value, a PID operator, and an output actuator, forming a complete negative feedback closed-loop control. The figure also includes a mixer, a catalytic reaction unit, and an adsorption unit. The mixer fully mixes the compensation hydrogen and the process gas to improve the conversion rate. The catalytic reaction unit converts impurity components into carbon dioxide and water, and the adsorption unit adsorbs carbon dioxide and water. The feedback unit is located after the catalytic reaction unit.

[0049] Application Examples

[0050] like Figure 4 As shown, the gas purification system is connected to an ammonia decomposition hydrogen production device, which is widely used in metal heat treatment annealing protective atmosphere, metal reduction atmosphere, reduction protective atmosphere, and high-purity nitrogen is used to output the concentration adjustment gas of hydrogen, and is also used for equipment purge gas, catalyst regeneration gas, ammonia carrier gas, etc.

[0051] A compensating hydrogen output branch pipe 7 is led out from the hydrogen output main pipe 6 of the ammonia decomposition hydrogen production equipment and connected to the compensating gas input branch pipe 2, an auxiliary gas input branch pipe 4 is led out from the process pure gas output main pipe 3 and enters the ammonia decomposition hydrogen production equipment, a hydrogen ratio adjustment input branch pipe 5 is led out from the process pure gas output main pipe 3 to the hydrogen output main pipe 6, and along the gas flow direction, the hydrogen ratio adjustment input branch pipe 5 is downstream of the compensating hydrogen output branch pipe 7, and is connected to the adjustment hydrogen output main pipe 8 at the end of the hydrogen output main pipe 6.

[0052] A first flow controller is installed on the compensation gas input branch pipe, a second flow controller is installed on the hydrogen ratio adjustment input branch pipe 5 , and a third flow controller is installed on the adjusted hydrogen output main pipe 8 .

[0053] The present invention is applied to the treatment method after the ammonia decomposition equipment, the first flow controller is used to control the compensation hydrogen flow Q1, and its value is automatically controlled by the PID control system, the second flow controller is used to control the nitrogen flow Q2, and adjust the nitrogen-hydrogen mixing ratio, and the third flow controller is used to adjust the ammonia decomposition hydrogen production mixed gas flow Q3. The ammonia decomposition hydrogen production mixed gas contains 75% hydrogen and 25% nitrogen. The proportion of hydrogen in the mixed gas can be controlled by adding high-purity nitrogen Q2. Specifically, the total flow rate Q 总 =Q2+Q3, where the hydrogen gas volume fraction is

[0054] This application example is matched with the ammonia decomposition hydrogen production equipment. The product gas contains 75% hydrogen and 25% nitrogen. Therefore, the hydrogen decomposed from ammonia can be directly used as the compensation gas, and no high-purity hydrogen cylinder is required to be configured separately. In this application example, the compensation hydrogen output branch pipe 7 is connected to the compensation gas input branch pipe 2 for this purpose.

[0055] This application example is matched with ammonia decomposition hydrogen production equipment. The product gas is hydrogen, that is, hydrogen is not an impurity gas. Therefore, when hydrogen is used as a compensation gas, it is advantageous for its molar ratio to be greater than the calculation requirement, which can further ensure that the oxidizing impurity gas can be completely removed and reduce the difficulty of the system.

[0056] This application example is matched with ammonia decomposition hydrogen production equipment. The nitrogen flow rate is adjusted by the second flow controller, and the nitrogen-hydrogen mixed gas flow rate is adjusted by the third flow controller, so that continuous adjustment of hydrogen in the range of 0% to 75% can be achieved.

[0057] In this application example, the original gas input unit, the gas distribution branch unit, and the first flow controller should be installed as close as possible to minimize the effects of signal acquisition delay, gas flow rate delay, etc. When the installation position is limited, the hydrogen compensation position delay should be considered. Preferably, increasing the volume of the gas mixing unit is conducive to eliminating the aforementioned delay effect.

[0058] This application example is matched with the ammonia decomposition hydrogen production equipment. The catalytic reaction unit is located after the gas mixing unit. Thanks to the high proportion of hydrogen in the process mixed gas, it can further ensure that the oxidizing impurity gas can be completely removed. The excess hydrogen is the product gas.

[0059] Further optimized, the first heat exchanger adopts waste heat recovery connection to recycle most of the heat generated by the catalytic reaction unit, thereby reducing system energy consumption. Preferably, the second heat exchanger adopts air cooling or water cooling to further cool the process gas to below 50°C.

[0060] Preferably, the adsorption unit requires the input process gas temperature to be no greater than 50°C, and adopts a one-in-one-standby method. When one tower is not saturated with adsorption, it switches to another standby tower to work, and starts the regeneration process for the saturated working tower. After the regeneration is completed, it is cooled and put into standby. Thus, the system can work continuously and uninterruptedly.

[0061] Preferably, the raw gas input and pure gas output interfaces can be provided in a variety of ways, such as ferrule interfaces, flange interfaces, threaded interfaces, welding interfaces, etc. Different interface forms can be selected according to different application scenarios to meet the pressure resistance requirements and ensure the air tightness and replaceability requirements.

[0062] Although the present invention has been described according to the above specific implementation methods, any modification using the concept of the present invention will be included in the scope of protection of this patent.

Claims

1. A gas purification system, characterized in that: include: A raw gas input unit, a gas distribution branch unit, a control system unit, a flow control unit, a gas mixing unit, a catalytic reaction unit, a purity detection unit, a first heat exchanger, a second heat exchanger and an adsorption unit. The raw gas input unit is arranged on a process gas input main pipe (1), the outlet of the process gas input main pipe (1) is connected to the inlet of the gas mixing unit. The gas distribution branch unit is arranged on a compensation gas input branch pipe (2), the outlet of the compensation gas input branch pipe (2) is connected to the outlet of the process gas input main pipe (1). The flow control unit is installed at the outlet end of the compensation gas input branch pipe (2). The catalytic reaction unit is installed at the outlet side of the gas mixing unit. The first heat exchanger is installed on the catalytic reaction unit side by a waste heat recovery connection method. The inlet of the second heat exchanger is connected to the outlet of the first heat exchanger, and the outlet of the second heat exchanger is connected to the inlet of the adsorption unit. The outlet of the adsorption unit outputs pure gas through a process pure gas output main pipe (3) after passing through a filter. The purity detection unit is located on the main pipe before the adsorption unit after the second heat exchanger or on the process pure gas output main pipe (3) after the adsorption unit.

2. The gas purification system according to claim 1, characterized in that: The process gas input main pipe (1) is equipped with a filter, a valve and a flow meter.

3. The gas purification system according to claim 1, characterized in that: The compensation gas input branch pipe (2) is equipped with a filter, a valve and a flow control unit. Along the process gas flow direction of the compensation gas input branch pipe (2), the flow control unit is installed after the filter and the valve.

4. The gas purification system according to claim 3, characterized in that: The outlet of the flow controller unit is installed on the process gas input main pipe (1) at a position downstream of the flow meter, and the compensation gas is injected from the outlet of the compensation gas input branch pipe (2) along the tangent direction of the main pipe.

5. The gas purification system according to claim 1, characterized in that: The purity detection unit includes a trace oxidizing gas detector and / or a trace reducing gas detector.

6. The gas purification system according to claim 3, characterized in that: The control system unit is a single chip microcomputer, a PLC or a computer, which receives the signal from the purity detection unit, sends a control signal after a logical operation, and controls the flow control unit to compensate the main process gas for appropriate gas distribution.

7. The gas purification system according to claim 1, characterized in that: The gas purification system is connected to the ammonia decomposition hydrogen production equipment. A compensation hydrogen output branch pipe (7) is led out from the hydrogen output main pipe (6) of the ammonia decomposition hydrogen production equipment and connected to the compensation gas input branch pipe (2). An auxiliary gas input branch pipe (4) is led out from the process pure gas output main pipe (3) and enters the ammonia decomposition hydrogen production equipment. A hydrogen ratio adjustment input branch pipe (5) is led out from the process pure gas output main pipe (3) and connected to the hydrogen output main pipe (6). Along the gas flow direction, the hydrogen ratio adjustment input branch pipe (5) is downstream of the compensation hydrogen output branch pipe (7) and is connected to the adjustment hydrogen output main pipe (8) at the end of the hydrogen output main pipe (6).

8. The gas purification system according to claim 7, characterized in that: A first flow controller is installed on the compensation gas input branch pipe (2), a second flow controller is installed on the hydrogen ratio adjustment input branch pipe (5), and a third flow controller is installed on the adjusted hydrogen output main pipe (8).

9. The gas purification method of a gas purification system according to any one of claims 1 to 8, characterized in that: The PID control algorithm is used to remove oxygen from high-oxygen nitrogen. The control system unit is the core component of the PID control algorithm, including: input acquisition unit, logic control and operation unit and output control unit. First, the trace oxygen index in the pure gas is set to X O (ppm), according to the reaction molar ratio of hydrogen and oxygen 2:1, the trace hydrogen index in pure gas should be X H (ppm), with X H (ppm) as the given value of the PID algorithm, the input acquisition unit receives the trace hydrogen analyzer data C of the purity detection unit H (ppm), as the PID algorithm feedback value, so as to calculate the deviation value Δe = X H (ppm)-C H (ppm), after the PID operation, the operation output value is used as the flow controller control signal to control the hydrogen compensation flow, thereby realizing PID negative feedback closed-loop control.

10. The gas purification method of the gas purification system according to claim 9, characterized in that: After being applied to the ammonia decomposition equipment, the first flow controller is used to control the compensation hydrogen flow Q1, and its value is automatically controlled by the PID control system. The second flow controller is used to control the nitrogen flow Q2 and adjust the nitrogen-hydrogen mixing ratio. The third flow controller is used to adjust the ammonia decomposition hydrogen production mixed gas flow Q3. The ammonia decomposition hydrogen production mixed gas contains 75% hydrogen and 25% nitrogen. The proportion of hydrogen in the mixed gas is controlled by adding high-purity nitrogen Q2, specifically the total flow rate Q of the nitrogen-hydrogen mixed gas. 总 =Q2+Q3, where the hydrogen gas volume fraction is

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