Device and method for producing electronic-grade carbon monoxide by a dual refrigeration method

Abstract

The present invention relates to a device and method for producing electronic-grade carbon monoxide by a dual refrigeration method; it includes a raw material gas storage tank. The raw material gas buffer tank is sequentially connected to a raw material separator through an ammonia cooler, the first inlet of the main condenser of the main condenser, the first outlet of the main condenser, the first inlet of the subcooler of the subcooler, and the first outlet of the subcooler. The gas-phase outlet and the liquid-phase outlet at the top of the raw material separator are both connected to the first rectification column. The inlet of the first reboiler is connected to the gas-phase outlet at the top of the second rectification column. The liquid-phase outlet at the bottom of the first reboiler is connected to a product tank, the third raw material gas inlet of the first rectification column, and the first raw material gas inlet of the second rectification column through a liquid storage tank respectively. It has the advantages of simple process flow, convenient operation, stable operation, low energy consumption, and the ability to prepare liquid-phase carbon monoxide with a purity not lower than 99.999%.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon monoxide production, and specifically to an apparatus and method for producing electronic-grade carbon monoxide by a dual refrigeration method. Background Art

[0002] In the current production process of carbon monoxide, the methods for producing carbon monoxide mainly include pressure swing adsorption, membrane separation, and cryogenic separation; the adsorption method and membrane separation method have problems such as large equipment floor area, low product purity, large equipment investment, and complex process flow; the cryogenic separation method mainly has the problem of large liquid nitrogen consumption. Summary of the Invention

[0003] In view of the deficiencies of the prior art, the present invention provides an apparatus and method for producing electronic-grade carbon monoxide by a dual refrigeration method, which adopts a low-temperature rectification method of heat pump rectification, double-column rectification, and expansion refrigeration, has a simple process flow, is easy to operate, runs stably, has low energy consumption, and can prepare liquid-phase carbon monoxide with a purity of not less than 99.999%.

[0004] To achieve the above object, the technical solution adopted by the present invention is: including a raw material gas storage tank, the raw material gas buffer tank is sequentially connected to a raw material separator through an ammonia cooler, the first inlet of the main condenser of the main condenser, the first outlet of the main condenser, the first inlet of the subcooler of the subcooler, and the first outlet of the subcooler. The gas-phase outlet at the top of the raw material separator enters the middle of the first rectification column through the second raw material gas inlet of the first rectification column, and the liquid-phase outlet at the bottom of the raw material separator is connected to the middle of the first rectification column through the first raw material gas inlet of the first rectification column;

[0005] The gas-phase outlet at the top of the first rectification column is connected to the inlet of the washing column. A first reboiler is provided in the lower part inside the washing column. The inlet of the first reboiler is connected to the gas-phase outlet at the top of the second rectification column. The liquid-phase outlet at the bottom of the first reboiler is connected to a product tank, the third raw material gas inlet of the first rectification column, and the first raw material gas inlet of the second rectification column through a liquid storage tank respectively;

[0006] It also includes a recycle compressor, a medium-pressure nitrogen buffer tank, an expander, and a liquid nitrogen storage tank. The outlet of the recycle compressor is sequentially connected to a recycle gas balance tank through the fourth inlet of the main condenser, a fourth three-way joint, the fourth outlet of the main condenser, and a second reboiler; the liquid-phase outlet at the bottom of the recycle gas balance tank is connected to the first liquid nitrogen washing port at the upper part of the washing column through the fourth inlet of the subcooler and the fourth outlet of the subcooler. The liquid nitrogen storage tank is connected to the first liquid nitrogen washing port of the washing column;

[0007] The medium-pressure nitrogen buffer tank is connected to a liquid nitrogen balance tank through the fifth inlet of the main condenser, the fifth outlet of the main condenser, the fifth inlet of the subcooler, and the fifth outlet of the subcooler. The liquid-phase outlet of the liquid nitrogen balance tank is connected to the second liquid nitrogen washing port at the upper part of the washing column;

[0008] The outlet at the bottom of the scrubbing tower is connected to the fourth inlet of the first rectification tower. The top of the scrubbing tower is provided with a gas outlet of the scrubbing tower. The gas outlet of the scrubbing tower is connected to the inlet of the recycle gas compressor through a first three-way, the second inlet of the subcooler, the second outlet of the subcooler, the second inlet of the main condenser, the second outlet of the main condenser, a second three-way, a recycle gas buffer tank, and a third three-way; the third end of the fourth three-way is connected to the inlet and outlet of the expansion end of the expander, the sixth inlet of the main condenser, and the sixth outlet of the main condenser is connected to the third end of the second three-way. The pressurized port of the recycle gas buffer tank in the recycle gas buffer tank is connected to the third end of the third three-way through the inlet and outlet of the compression end of the expander.

[0009] Preferably, the bottom of the first rectification tower and the second rectification tower are respectively connected to a common reboiler, and the second reboiler is arranged in the common reboiler.

[0010] Preferably, a baffle is provided at the inlet of the liquid storage tank. The baffle divides the interior of the liquid storage tank into a reflux cavity and a product cavity that are connected at the upper part. The outlet at the bottom of the product cavity is connected to the product tank; the outlet at the bottom of the reflux cavity is respectively connected to the third raw material gas inlet of the first rectification tower and the first raw material gas inlet of the second rectification tower through a fifth three-way;

[0011] The gas outlet at the top of the liquid storage tank is connected to the catalytic oxidation device.

[0012] Preferably, the gas outlet at the top of the recycle gas balance tank is connected to the catalytic oxidation device; the third end of the first three-way is connected to the catalytic oxidation device through the third inlet of the subcooler, the third outlet of the subcooler, the third inlet of the main condenser, and the third outlet of the main condenser.

[0013] Preferably, a first regulating valve is provided between the bottom liquid phase outlet of the raw material separator and the first raw material gas inlet of the first rectification tower, and a second regulating valve is provided between the gas phase outlet at the top of the raw material separator and the second raw material gas inlet of the first rectification tower.

[0014] Preferably, a third regulating valve is provided between the fifth three-way and the third raw material gas inlet of the first rectification tower, and a fourth regulating valve is provided between the fifth three-way and the first raw material gas inlet of the second rectification tower.

[0015] Preferably, a fifth regulating valve is provided between the liquid phase outlet of the liquid nitrogen balance tank and the second liquid nitrogen washing port of the scrubbing tower, and a sixth regulating valve is provided between the fourth outlet of the subcooler and the first liquid nitrogen washing port of the scrubbing tower.

[0016] Preferably, a sewage discharge pipe with a sewage discharge valve is provided at the bottom of the common reboiler.

[0017] Preferably, the main condenser, subcooler, first distillation column, second distillation column, scrubbing column, liquid storage tank, recycle gas balance tank, liquid nitrogen balance tank, and raw material separator are all arranged inside the cold box.

[0018] The present invention also provides a method for producing electronic-grade carbon monoxide by a dual refrigeration method. The method comprises the following steps:

[0019] Step 1: The raw material gas in the raw material gas buffer tank enters the raw material separator through the ammonia cooler, the first inlet of the main condenser, the first outlet of the main condenser, the first inlet of the subcooler, and the first outlet of the subcooler. The gas-phase outlet at the top of the raw material separator enters the first distillation column through the second raw material gas inlet of the first distillation column, and the liquid-phase outlet at the bottom of the raw material separator enters the first distillation column through the first raw material gas inlet of the first distillation column. The above gas phase and liquid phase are subjected to a primary rectification and purification. The composition of the raw material liquid entering the first distillation column is: H2: 0.5%, N2: 47%, CO: 43%, O2: 101 ppm, AR: 3%, CH4: 5%; the temperature of the raw material liquid is -183.4 °C, the pressure is 0.15 MpaG, the flow rate is 164 Nm 3 / h, and the gas-phase fraction is 0.1.

[0020] Step 2: The liquid phase that enters the first distillation column in Step 1 for primary rectification and purification enters the common bottom of the first distillation column and the second distillation column. After the second reboiler provides heat, the liquid phase in the common bottom is vaporized and enters the second distillation column for secondary rectification and purification; the gas-phase product after secondary rectification and purification successively passes through the gas-phase outlet at the top of the second distillation column and the first reboiler in the scrubbing column, and after liquefaction, enters the liquid storage tank; the gas-phase composition at the top of the second distillation column is: H2: 0%, N2: 3 ppm, CO: 99.999%, O2: 0.0549 ppb, AR: 2 ppm, CH4: 0, the temperature: -182.5 °C, the pressure: 0.15 MpaG, the flow rate: 488 Nm 3 / h;

[0021] Step 3: For the product liquid that enters the liquid storage tank in Step 2, a part of the liquid phase enters the product tank for storage and external sale, and the other part enters the first distillation column and the second distillation column respectively through the first raw material gas inlet of the first distillation column and the first raw material gas inlet of the second distillation column by the fifth three-way joint. The gas phase in the liquid storage tank enters the catalytic oxidation device through the gas-phase outlet at the top of the liquid storage tank; the temperature of the liquid phase entering the product tank is: -182.5 °C, the pressure is: 0.15 MpaG, the flow rate is: 95 Nm 3 / h; the temperature of the liquid phase entering the first distillation column and the second distillation column is: -182.5 °C, the pressure: 0.15 MpaG, the flow rate: 393 Nm 3 / h;

[0022] Step 4: The waste gas after the first rectification and purification of the liquid phase entering the first rectification column in Step 1 enters the scrubber through the gas phase outlet at the top of the first rectification column for scrubbing. After scrubbing, the gas phase in the scrubber enters the first three-way through the scrubber gas phase outlet. A part of the gas phase enters the recycle gas compressor through the second inlet of the subcooler, the second outlet of the subcooler, the second inlet of the main condenser, the second outlet of the main condenser, the second three-way, the recycle gas buffer tank, and the third three-way; Another part of the gas phase enters the catalytic oxidation device through the third end of the first three-way, the third inlet of the subcooler, the third outlet of the subcooler, the third inlet of the main condenser, and the third outlet of the main condenser; The liquid phase in the scrubber flows back into the first rectification column through the outlet at its bottom and the fourth inlet of the first rectification column; The content of N2 in the waste gas after the first rectification and purification is: 93.7%, the flow rate is: 1171 Nm 3 / h, the pressure is: 0.15 MpaG; The content of N2 in the gas phase at the scrubber gas phase outlet is: 98.2%, the flow rate is: 1870 Nm 3 / h, the pressure is: 0.15 MpaG, and the temperature is: -187 °C;

[0023] When expansion refrigeration and medium-pressure nitrogen are required to provide liquid nitrogen scrubbing liquid for the scrubber:

[0024] Step 5: Pressurize the recycled nitrogen entering the recycle gas compressor in Step 4. A part of the pressurized recycle gas sequentially passes through the fourth inlet of the main condenser, the fourth three-way, the fourth outlet of the main condenser, and the second reboiler and enters the recycle gas balance tank. The gas phase in the recycle gas balance tank enters the catalytic oxidation device. The liquid phase at the bottom of the recycle gas balance tank enters the scrubber through the fourth inlet of the subcooler, the fourth outlet of the subcooler, and the first liquid nitrogen scrubbing port of the scrubber to provide liquid nitrogen for scrubbing the scrubber; The temperature of the recycled nitrogen leaving the recycle gas compressor after pressurization is: 40 °C, the pressure is: 0.9 MpaG, and the flow rate is: 2680 Nm 3 / h, the gas phase fraction is: 1; The flow rate of the above-mentioned part of the recycle gas is: 1680 Nm 3 / h;

[0025] Step 6: Another part of the pressurized recycle nitrogen in Step 5 enters the expander through the third end of the fourth three-way. After gas expansion, it provides cooling capacity for the main condenser through the sixth inlet and the sixth outlet of the main condenser. The recycle gas after recovering the cooling capacity re-enters the recycle gas compressor through the third end of the second three-way; A part of the gas phase in the recycle gas buffer tank in Step 4 is compressed by the compression end of the expander and enters the recycle gas compressor through the third end of the third three-way; The temperature of a part of the gas phase in the recycle gas buffer tank is: 40 °C, the pressure: 0.15 MpaG, the flow rate: 1000 Nm 3 / h;

[0026] Step Seven: The medium-pressure nitrogen in the medium-pressure nitrogen buffer tank enters the liquid nitrogen balance tank through the fifth inlet of the main condenser, the fifth outlet of the condenser, the fifth inlet of the subcooler, and the fifth outlet of the subcooler. The liquid nitrogen in the liquid nitrogen balance tank enters the scrubbing tower through the second liquid nitrogen scrubbing port of the scrubbing tower to provide liquid nitrogen for scrubbing the scrubbing tower. The temperature of the medium-pressure nitrogen in the medium-pressure nitrogen buffer tank is: 40°C, the pressure is: 3.0 MpaG, and the flow rate is: 80 Nm 3 / h; The medium-pressure nitrogen passing through the main condenser and the subcooler changes from gaseous nitrogen to liquid nitrogen. The parameters of the liquid nitrogen are temperature: -179°C, pressure: 3.0 MpaG, and flow rate: 80 Nm 3 / h;

[0027] When it is necessary to purchase liquid nitrogen and medium-pressure nitrogen externally to provide liquid nitrogen scrubbing liquid for the scrubbing tower:

[0028] Step Eight: Pressurize the recycle nitrogen entering the recycle gas compressor in Step Four. The pressurized recycle gas passes through the fourth inlet of the main condenser, the fourth three-way, the fourth outlet of the main condenser, and the second reboiler in sequence and enters the recycle gas balance tank. The gas phase in the recycle gas balance tank enters the catalytic oxidation device. The liquid phase at the bottom of the recycle gas balance tank enters the scrubbing tower through the fourth inlet of the subcooler, the fourth outlet of the subcooler, and the first liquid nitrogen scrubbing port of the scrubbing tower to provide liquid nitrogen for scrubbing the scrubbing tower. The temperature of the recycle nitrogen exiting the recycle gas compressor 12 after compression is: 40°C, the pressure is: 0.9 MpaG, and the flow rate is: 1680 Nm 3 / h, and the gas phase fraction is: 1;

[0029] Step Nine: The medium-pressure nitrogen in the medium-pressure nitrogen buffer tank enters the liquid nitrogen balance tank through the fifth inlet of the main condenser, the fifth outlet of the condenser, the fifth inlet of the subcooler, and the fifth outlet of the subcooler. The liquid nitrogen in the liquid nitrogen balance tank enters the scrubbing tower through the second liquid nitrogen scrubbing port of the scrubbing tower to provide liquid nitrogen for scrubbing the scrubbing tower. The temperature of the medium-pressure nitrogen in the medium-pressure nitrogen buffer tank is: 40°C, the pressure is: 3.0 MpaG, and the flow rate is: 80 Nm 3 / h; The medium-pressure nitrogen passing through the main condenser and the subcooler changes from gaseous nitrogen to liquid nitrogen. The parameters of the liquid nitrogen are temperature: -179°C, pressure: 3.0 MpaG, and flow rate: 80 Nm 3 / h;

[0030] Step Ten: The externally purchased liquid nitrogen enters the scrubbing tower through the liquid nitrogen storage tank and the first liquid nitrogen scrubbing port of the scrubbing tower to provide liquid nitrogen for scrubbing the scrubbing tower.

[0031] Step Eleven: After operating for a period of time, open the blowdown valve to discharge the waste liquid from the common tower kettle through the blowdown pipeline.

[0032] An apparatus and method for producing electronic-grade carbon monoxide by a dual-refrigeration method according to the above solution. By setting up expansion refrigeration, medium-pressure nitrogen refrigeration, and purchased liquid nitrogen refrigeration, and adopting corresponding combinations, it can be adjusted according to market conditions. That is, when the price of liquid nitrogen in the market is high, the expansion refrigeration and medium-pressure nitrogen refrigeration modes are used to meet the production needs; when the price of liquid nitrogen in the market is low, the medium-pressure nitrogen refrigeration and purchased liquid nitrogen refrigeration modes are used to meet the production needs, so as to achieve the purpose of reducing energy consumption. At the same time, the present invention uses a cold box, which not only saves the floor area of the equipment but also is conducive to further reducing energy consumption in combination with the above refrigeration modes. By adopting the form of a common reboiler for the first distillation column and the second distillation column, the present invention can overcome problems such as pipeline resistance, pressure difference between the two columns, and system fluctuations caused by the need to enter the bottom liquid of the first distillation column into the second distillation column to remove heavy components after the light components are removed from the first distillation column. At the same time, there are also defects such as unsmooth liquid inlet to the second distillation column, insufficient liquid inlet to the second distillation column in severe cases, and poor system stability affecting the distillation effect. The above setting can effectively avoid the problem of liquid inlet from the first distillation column to the second distillation column. At the same time, connecting the top gas phase outlet of the second distillation column to the first reboiler can facilitate stabilizing the loads of the two distillation columns. Further, by setting up a liquid storage tank connected to the first reboiler, the liquid storage tank is divided into a reflux cavity and a product cavity that are connected in the upper part by a baffle. The above design can ensure taking product liquid on the premise of sufficient reflux liquid. The above setting can not only effectively ensure the stable operation of the system but also effectively ensure the product quality and improve the stability of the product quality. A washing column is also provided in the present invention. The washing column is used to wash the light components removed from the raw material gas after distillation in the first distillation column. Liquid nitrogen is used for washing in the above washing process to recover carbon monoxide in the above light components. Specifically, 4.1% of CO in the light component gas phase can be mostly liquefied and enter the bottom of the washing column and then reflux to the first distillation column, so that the recovery rate of CO is increased to 93.7% under the combined action of the first distillation column and the washing column. It has the advantages of adopting heat pump distillation, double-column distillation, low-temperature distillation method of expansion refrigeration, simple process flow, easy operation, stable operation, low energy consumption, and being able to prepare liquid-phase carbon monoxide with a purity of not less than 99.999%. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic structural diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0035] See Figure 1: The present invention relates to a device and method for producing electronic-grade carbon monoxide by a dual refrigeration method. The device includes a raw material gas storage tank 1. The raw material gas buffer tank 1 is sequentially connected to a raw material separator 5 through an ammonia cooler 2, a first inlet 18 of a main condenser 3 of the main condenser, a first outlet 19 of the main condenser, a first inlet 20 of a subcooler 4, and a first outlet 21 of the subcooler. The gas-phase outlet at the top of the raw material separator 5 enters the middle part of a first rectification column 6 through a second raw material gas inlet 24 of the first rectification column. The liquid-phase outlet at the bottom of the raw material separator 5 is connected to the middle part of the first rectification column 6 through a first raw material gas inlet 26 of the first rectification column. The gas-phase outlet at the top of the first rectification column is connected to the inlet of a scrubbing tower 8. A first reboiler 11 is arranged at the lower inner part of the scrubbing tower 8. The inlet of the first reboiler 11 is connected to the gas-phase outlet at the top of a second rectification column 27. The liquid-phase outlet at the bottom of the first reboiler 11 is respectively connected to a product tank 10, a third raw material gas inlet 35 of the first rectification column, and a first raw material gas inlet 36 of the second rectification column through a liquid storage tank 9. It also includes a recycle compressor 12, a medium-pressure nitrogen buffer tank 18, an expander 14, and a liquid nitrogen storage tank 23. The outlet of the recycle compressor 12 is sequentially connected to a fourth inlet 53 of the main condenser, a fourth three-way valve 54, a fourth outlet 55 of the main condenser, and a second reboiler 15 and then connected to a recycle gas balance tank 16. The liquid-phase outlet at the bottom of the recycle gas balance tank 16 is connected to a first liquid nitrogen scrubbing port 60 at the upper part of the scrubbing tower 8 through a fourth inlet 58 of the subcooler and a fourth outlet 59 of the subcooler. The liquid nitrogen storage tank 23 is connected to the first liquid nitrogen scrubbing port 60 of the scrubbing tower 8. The medium-pressure nitrogen buffer tank 18 is connected to a liquid nitrogen balance tank 17 through a fifth inlet 62 of the main condenser, a fifth outlet 63 of the main condenser, a fifth inlet 64 of the subcooler, and a fifth outlet 65 of the subcooler. The liquid-phase outlet of the liquid nitrogen balance tank 17 is connected to a second liquid nitrogen scrubbing port 66 at the upper part of the scrubbing tower 8. The outlet at the bottom of the scrubbing tower 8 is connected to a fourth inlet 22 of the first rectification column. A gas-phase outlet 39 of the scrubbing tower is arranged at the top of the scrubbing tower 8. The gas-phase outlet 39 of the scrubbing tower is connected to the inlet of the recycle compressor 12 through a first three-way valve 40, a second inlet 41 of the subcooler, a second outlet 42 of the subcooler, a second inlet 43 of the main condenser, a second outlet 44 of the main condenser, a second three-way valve 45, a recycle gas buffer tank 13, and a third three-way valve 46. The third end of the fourth three-way valve 54 is connected to the inlet and outlet of the expansion end of the expander 14, a sixth inlet 61 of the main condenser, a sixth outlet 57 of the main condenser, and the third end of the second three-way valve 45. The pressurization port 56 of the recycle gas buffer tank in the recycle gas buffer tank 13 is connected to the inlet and outlet of the compression end of the expander 14 and the third end of the third three-way valve 46. The bottoms of the first rectification column 6 and the second rectification column 7 are respectively connected to a common tower kettle, and the second reboiler 15 is arranged in the common tower kettle.A baffle plate 25 is provided at the inlet of the liquid storage tank 9. The baffle plate 25 divides the interior of the liquid storage tank 9 into a reflux cavity and a product cavity that are connected to each other at the upper part. The outlet at the bottom of the product cavity is connected to the product tank 10; the outlet at the bottom of the reflux cavity is respectively connected to the third raw material gas inlet 35 of the first distillation column and the first raw material gas inlet 36 of the second distillation column through the fifth three-way pipe 34; the top gas phase outlet of the liquid storage tank 9 is connected to the catalytic oxidation device 28. The top gas phase outlet of the circulating gas balance tank 16 is connected to the catalytic oxidation device 28; the third end of the first three-way pipe 40 is connected to the catalytic oxidation device 28 through the third inlet 48 of the subcooler, the third outlet 49 of the subcooler, the third inlet 50 of the main condenser, and the third outlet 51 of the main condenser. A first regulating valve 29 is provided between the bottom liquid phase outlet of the raw material separator 5 and the first raw material gas inlet 26 of the first distillation column, and a second regulating valve 30 is provided between the top gas phase outlet of the raw material separator 5 and the second raw material gas inlet 24 of the first distillation column. A third regulating valve 31 is provided between the fifth three-way pipe 34 and the third raw material gas inlet 35 of the first distillation column, and a fourth regulating valve 32 is provided between the fifth three-way pipe 34 and the first raw material gas inlet 36 of the second distillation column. A fifth regulating valve 33 is provided between the liquid phase outlet of the liquid nitrogen balance tank 17 and the second liquid nitrogen washing port 66 of the washing tower, and a sixth regulating valve 38 is provided between the fourth outlet 59 of the subcooler and the first liquid nitrogen washing port 60 of the washing tower. A sewage discharge pipe 47 with a sewage discharge valve is provided at the bottom of the common reboiler. The main condenser 3, the subcooler 4, the first distillation column 6, the second distillation column 7, the washing tower 8, the liquid storage tank 9, the circulating gas balance tank 16, the liquid nitrogen balance tank 17, and the raw material separator 5 are all arranged in the cold box 52.

[0036] A method for producing electronic-grade carbon monoxide by a dual refrigeration method, the method comprising the following steps:

[0037] Step 1: The raw material gas in the raw material gas buffer tank 1 enters the raw material separator 5 through the ammonia cooler 2, the first inlet 18 of the main condenser, the first outlet 19 of the main condenser, the first inlet 20 of the subcooler, and the first outlet 21 of the subcooler. The top gas phase outlet of the raw material separator 5 enters the first distillation column 6 through the second raw material gas inlet 24 of the first distillation column, and the bottom liquid phase outlet of the raw material separator 5 enters the first distillation column 6 through the first raw material gas inlet 26 of the first distillation column. The above-mentioned gas phase and liquid phase are subjected to primary rectification and purification. The components of the raw material liquid entering the first distillation column 6 are: H2: 0.5%, N2: 47%, CO: 43%, O2: 101 ppm, AR: 3%, CH4: 5%; the temperature of the raw material liquid is -183.4 °C, the pressure is 0.15 MpaG, the flow rate is 164 Nm 3 / h, and the gas phase fraction is 0.1.

[0038] Step 2: The liquid phase after the primary rectification and purification in the first rectification column 6 in Step 1 enters the common reboiler of the first rectification column 6 and the second rectification column 7. After the second reboiler 15 provides heat, the liquid phase in the common reboiler is vaporized and then enters the second rectification column 7 for secondary rectification and purification. The gaseous product after the secondary rectification and purification successively passes through the top gas outlet 27 of the second rectification column 7 and the first reboiler 11 in the scrubber 8, and after liquefaction, enters the storage tank 9. The gaseous components at the top of the second rectification column 7 are: H2: 0%, N2: 3 ppm, CO: 99.999%, O2: 0.0549 ppb, AR: 2 ppm, CH4: 0, temperature: -182.5 °C, pressure: 0.15 MpaG, flow rate: 488 Nm 3 / h;

[0039] Step 3: For the product liquid entering the storage tank 9 in Step 2, a part of the liquid phase enters the product tank 10 for storage and external sales, and the other part enters the first rectification column 6 and the second rectification column 7 respectively through the third raw material gas inlet 35 of the first rectification column and the first raw material gas inlet 36 of the second rectification column via the fifth three-way valve 34. The gaseous phase in the storage tank 9 enters the catalytic oxidation device 28 through the top gas outlet of the storage tank 9. The temperature of the liquid phase entering the product tank 10 is: -182.5 °C, the pressure is: 0.15 MpaG, and the flow rate is: 95 Nm 3 / h; The temperature of the liquid phase entering the first rectification column 6 and the second rectification column 7 is: -182.5 °C, the pressure: 0.15 MpaG, and the flow rate: 393 Nm 3 / h;

[0040] Step 4: The waste gas after the primary rectification and purification of the liquid phase entering the first rectification column 6 in Step 1 enters the scrubber 8 through the top gas outlet 37 of the first rectification column for scrubbing. After scrubbing, the gaseous phase in the scrubber 8 enters the first three-way valve 40 through the scrubber gas outlet 39. A part of the gaseous phase enters the recycle gas compressor 12 through the second inlet 41 of the subcooler, the second outlet 42 of the subcooler, the second inlet 43 of the main condenser, the second outlet 44 of the main condenser, the second three-way valve 45, the recycle gas buffer tank 13 and the third three-way valve 46. Another part of the gaseous phase enters the catalytic oxidation device 28 through the third end of the first three-way valve 40, the third inlet 48 of the subcooler, the third outlet 49 of the subcooler, the third inlet 50 of the main condenser and the third outlet 51 of the main condenser. The liquid phase in the scrubber 8 returns to the first rectification column 6 through its bottom outlet and the fourth inlet 22 of the first rectification column. The content of N2 in the waste gas after the primary rectification and purification is: 93.7%, the flow rate is: 1171 Nm 3 / h, the pressure is: 0.15 MpaG; The content of N2 in the gaseous phase at the scrubber gas outlet 39 is: 98.2%, and the flow rate is: 1870 Nm 3 / h, the pressure is: 0.15 MpaG, and the temperature is: -187 °C;

[0041] When expansion refrigeration is required and medium-pressure nitrogen is used to provide liquid nitrogen washing liquid for the washing tower 8:

[0042] Step Five: Pressurize the recycled nitrogen entering the recycle gas compressor 12 in Step Four. A part of the pressurized recycle gas sequentially passes through the fourth inlet 53 of the main condenser, the fourth three-way valve 54, the fourth outlet 55 of the main condenser, and the second reboiler 15 and enters the recycle gas equilibrium tank 16. The gas phase in the recycle gas equilibrium tank 16 enters the catalytic oxidation device 28. The liquid phase at the bottom of the recycle gas equilibrium tank 16 enters the washing tower 8 through the fourth inlet 58 of the subcooler, the fourth outlet 59 of the subcooler, and the first liquid nitrogen washing port 60 of the washing tower to provide liquid nitrogen for washing for the washing tower 8. The temperature of the recycle nitrogen after leaving the recycle gas compressor 12 after pressurization is: 40 °C, the pressure is: 0.9 MpaG, and the flow rate is: 2680 Nm 3 / h, the gas phase fraction is: 1; the flow rate of the above part of the recycle gas is: 1680 Nm 3 / h;

[0043] Step Six: Another part of the pressurized recycle nitrogen in Step Five enters the expander 14 through the third end of the fourth three-way valve 54. After gas expansion, it passes through the sixth inlet 61 of the main condenser and the sixth outlet 57 of the main condenser to provide cooling capacity for the main condenser 3. The recycle gas after recovering the cooling capacity re-enters the recycle gas compressor 12 through the third end of the second three-way valve 45 of the recycle gas; a part of the gas phase in the recycle gas buffer tank 13 in Step Four is compressed by the compression end of the expander 14 and enters the recycle gas compressor 12 through the third end of the third three-way valve 46; the temperature of a part of the gas phase in the recycle gas buffer tank 13 is: 40 °C, the pressure: 0.15 MpaG, the flow rate: 1000 Nm 3 / h;

[0044] Step Seven: The medium-pressure nitrogen in the medium-pressure nitrogen buffer tank 18 enters the liquid nitrogen equilibrium tank 17 through the fifth inlet 62 of the main condenser, the fifth outlet 63 of the condenser, the fifth inlet 64 of the subcooler, and the fifth outlet 65 of the subcooler. The liquid nitrogen in the liquid nitrogen equilibrium tank 17 enters the washing tower 8 through the second liquid nitrogen washing port 66 of the washing tower to provide liquid nitrogen for washing for the washing tower 8; the temperature of the medium-pressure nitrogen in the medium-pressure nitrogen buffer tank 18 is: 40 °C, the pressure is: 3.0 MpaG, and the flow rate is: 80 Nm 3 / h; the above medium-pressure nitrogen passing through the main condenser 3 and the subcooler 4 changes from gaseous nitrogen to liquid nitrogen, and the liquid nitrogen parameters are temperature: -179 °C, pressure: 3.0 MpaG, flow rate: 80 Nm 3 / h;

[0045] When it is necessary to purchase liquid nitrogen and medium-pressure nitrogen externally to provide liquid nitrogen washing liquid for the washing tower 8:

[0046] Step Eight: Pressurize the recycled nitrogen entering the recycle gas compressor 12 in Step Four. The pressurized recycle gas sequentially passes through the fourth inlet 53 of the main condenser, the fourth three-way pipe 54, the fourth outlet 55 of the main condenser, and the second reboiler 15 and enters the recycle gas equilibrium tank 16. The gas phase in the recycle gas equilibrium tank 16 enters the catalytic oxidation device 28. The liquid phase at the bottom of the recycle gas equilibrium tank 16 enters the scrubbing tower 8 through the fourth inlet 58 of the subcooler, the fourth outlet 59 of the subcooler, and the first liquid nitrogen scrubbing port 60 of the scrubbing tower, providing liquid nitrogen for scrubbing the scrubbing tower 8. The temperature of the recycled nitrogen after being compressed and exiting the recycle gas compressor 12 is: 40°C, the pressure is: 0.9 MpaG, and the flow rate is: 1680 Nm 3 / h, and the gas phase fraction is: 1;

[0047] Step Nine: The medium-pressure nitrogen in the medium-pressure nitrogen buffer tank 18 enters the liquid nitrogen equilibrium tank 17 through the fifth inlet 62 of the main condenser, the fifth outlet 63 of the condenser, the fifth inlet 64 of the subcooler, and the fifth outlet 65 of the subcooler. The liquid nitrogen in the liquid nitrogen equilibrium tank 17 enters the scrubbing tower 8 through the second liquid nitrogen scrubbing port 66 of the scrubbing tower, providing liquid nitrogen for scrubbing the scrubbing tower 8. The temperature of the medium-pressure nitrogen in the medium-pressure nitrogen buffer tank 18 is: 40°C, the pressure is: 3.0 MpaG, and the flow rate is: 80 Nm 3 / h;

[0048] The above-mentioned medium-pressure nitrogen passing through the main condenser 3 and the subcooler 4 changes from gaseous nitrogen to liquid nitrogen. The parameters of the liquid nitrogen are temperature: -179°C, pressure: 3.0 MpaG, and flow rate: 80 Nm 3 / h;

[0049] Step Ten: The purchased liquid nitrogen enters the scrubbing tower 8 through the liquid nitrogen storage tank 23 and the first liquid nitrogen scrubbing port 60 of the scrubbing tower, providing liquid nitrogen for scrubbing the scrubbing tower 8.

[0050] Step Eleven: After operating for a period of time, open the blowdown valve to discharge the waste liquid in the common tower kettle through the blowdown pipeline 47.

[0051] The present invention can adjust the relevant refrigeration mode according to the liquid nitrogen price in the market to achieve the purpose of reducing production costs. At the same time, by using the cold box 52, not only can the cold loss be effectively reduced, but also the purpose of effectively saving the occupied space of the equipment can be achieved. At the same time, the above refrigeration mode in the present invention can provide liquid nitrogen, the medium for washing, for the scrubbing tower 8. During normal production, the first rectification tower 6 is used to remove light components from the raw materials. The light components are the gas phase at the top of the first rectification tower 6. The general composition of the gas phase at the top is: N2: 95.5%, CO: 4.1%. By washing the above light components with liquid nitrogen, the present invention can liquefy carbon monoxide in the light components. Specifically, 4.1% of CO in the light component gas phase can be mostly liquefied in the scrubbing tower 8 and enter the bottom of the scrubbing tower, and then flow back to the first rectification tower 6, so that the recovery rate of CO is increased to 93.7% under the combined action of the first rectification tower 6 and the scrubbing tower 8, and the composition of the raw material gas discharged from the scrubbing tower 8 is N2: 98.3%, CO: 1.1%; to achieve the purpose of effectively recovering carbon monoxide in the raw material gas. By adopting the form of a common bottom for the first rectification tower 6 and the second rectification tower 7, the present invention can overcome problems such as pipeline resistance, pressure difference between the two towers, and system fluctuations caused by the need for the bottom liquid of the first rectification tower to enter the second rectification tower to remove heavy components after the first rectification tower removes light components. At the same time, there are also defects such as unsmooth liquid inlet of the second rectification tower, insufficient liquid inlet of the second rectification tower and poor system stability affecting the rectification effect in severe cases. The above setting can effectively avoid the problem of liquid inlet from the first rectification tower 6 to the second rectification tower 7. At the same time, by connecting the gas phase outlet at the top of the second rectification tower 7 to the first reboiler 11, it is convenient to stabilize the loads of the two rectification towers. Further, by setting a liquid storage tank 9 connected to the first reboiler 11, the liquid storage tank 9 is divided into a reflux cavity and a product cavity that are connected in the upper part by a baffle 25. The above design can ensure the extraction of product liquid on the premise of sufficient reflux liquid. The above setting can not only effectively ensure the stable operation of the system, but also effectively ensure the product quality and improve the stability of the product quality.

[0052] To explain the present invention in more detail, the present invention will be further described in conjunction with embodiments. The specific embodiments are as follows:

[0053] Embodiment 1

[0054] An apparatus for producing electronic-grade carbon monoxide by a dual refrigeration method, comprising a raw material gas storage tank 1. The raw material gas buffer tank 1 is sequentially connected to a raw material separator 5 through an ammonia cooler 2, a first inlet 18 of a main condenser 3 of the main condenser, a first outlet 19 of the main condenser, a first inlet 20 of a subcooler 4, and a first outlet 21 of the subcooler. The gas-phase outlet at the top of the raw material separator 5 enters the middle of a first rectification column 6 through a second raw material gas inlet 24 of the first rectification column. The liquid-phase outlet at the bottom of the raw material separator 5 is connected to the middle of the first rectification column 6 through a first raw material gas inlet 26 of the first rectification column. The gas-phase outlet at the top of the first rectification column is connected to the inlet of a scrubbing tower 8. A first reboiler 11 is provided in the lower part inside the scrubbing tower 8. The inlet of the first reboiler 11 is connected to the gas-phase outlet 27 at the top of a second rectification column. The liquid-phase outlet at the bottom of the first reboiler 11 is connected to a product tank 10, a third raw material gas inlet 35 of the first rectification column, and a first raw material gas inlet 36 of the second rectification column through a liquid storage tank 9 respectively. It further comprises a recycle compressor 12, a medium-pressure nitrogen buffer tank 18, an expander 14, and a liquid nitrogen storage tank 23. The outlet of the recycle compressor 12 is sequentially connected to a fourth inlet 53 of the main condenser, a fourth three-way valve 54, a fourth outlet 55 of the main condenser, and a second reboiler 15 and then connected to a recycle gas balance tank 16. The liquid-phase outlet at the bottom of the recycle gas balance tank 16 is connected to a first liquid nitrogen scrubbing port 60 at the upper part of the scrubbing tower 8 through a fourth inlet 58 of the subcooler and a fourth outlet 59 of the subcooler. The liquid nitrogen storage tank 23 is connected to the first liquid nitrogen scrubbing port 60 of the scrubbing tower 8. The medium-pressure nitrogen buffer tank 18 is connected to a liquid nitrogen balance tank 17 through a fifth inlet 62 of the main condenser, a fifth outlet 63 of the main condenser, a fifth inlet 64 of the subcooler, and a fifth outlet 65 of the subcooler. The liquid-phase outlet of the liquid nitrogen balance tank 17 is connected to a second liquid nitrogen scrubbing port 66 at the upper part of the scrubbing tower 8. The outlet at the bottom of the scrubbing tower 8 is connected to a fourth inlet 22 of the first rectification column. A gas-phase outlet 39 of the scrubbing tower is provided at the top of the scrubbing tower 8. The gas-phase outlet 39 of the scrubbing tower is connected to the inlet of the recycle compressor 12 through a first three-way valve 40, a second inlet 41 of the subcooler, a second outlet 42 of the subcooler, a second inlet 43 of the main condenser, a second outlet 44 of the main condenser, a second three-way valve 45, a recycle gas buffer tank 13, and a third three-way valve 46. The third end of the fourth three-way valve 54 is connected to the inlet and outlet of the expansion end of the expander 14, a sixth inlet 61 of the main condenser, a sixth outlet 57 of the main condenser, and the third end of the second three-way valve 45. The pressurization port 56 of the recycle gas buffer tank in the recycle gas buffer tank 13 is connected to the inlet and outlet of the compression end of the expander 14 and the third end of the third three-way valve 46. The bottoms of the first rectification column 6 and the second rectification column 7 are respectively connected to a common still. The second reboiler 15 is arranged in the common still.A baffle plate 25 is provided at the inlet of the liquid storage tank 9. The baffle plate 25 divides the interior of the liquid storage tank 9 into a reflux cavity and a product cavity that are connected to each other in the upper part. The outlet at the bottom of the product cavity is connected to the product tank 10; the outlet at the bottom of the reflux cavity is respectively connected to the third raw material gas inlet 35 of the first rectification column and the first raw material gas inlet 36 of the second rectification column through the fifth three-way pipe 34; the top gas phase outlet of the liquid storage tank 9 is connected to the catalytic oxidation device 28. The top gas phase outlet of the circulating gas balance tank 16 is connected to the catalytic oxidation device 28; the third end of the first three-way pipe 40 is connected to the catalytic oxidation device 28 through the third inlet 48 of the subcooler, the third outlet 49 of the subcooler, the third inlet 50 of the main condenser and the third outlet 51 of the main condenser. A first regulating valve 29 is provided between the bottom liquid phase outlet of the raw material separator 5 and the first raw material gas inlet 26 of the first rectification column, and a second regulating valve 30 is provided between the top gas phase outlet of the raw material separator 5 and the second raw material gas inlet 24 of the first rectification column. A third regulating valve 31 is provided between the fifth three-way pipe 34 and the third raw material gas inlet 35 of the first rectification column, and a fourth regulating valve 32 is provided between the fifth three-way pipe 34 and the first raw material gas inlet 36 of the second rectification column. A fifth regulating valve 33 is provided between the liquid phase outlet of the liquid nitrogen balance tank 17 and the second liquid nitrogen washing port 66 of the washing tower, and a sixth regulating valve 38 is provided between the fourth outlet 59 of the subcooler and the first liquid nitrogen washing port 60 of the washing tower. A sewage discharge pipe 47 with a sewage discharge valve is provided at the bottom of the common still. The main condenser 3, the subcooler 4, the first rectification column 6, the second rectification column 7, the washing tower 8, the liquid storage tank 9, the circulating gas balance tank 16, the liquid nitrogen balance tank 17 and the raw material separator 5 are all arranged in the cold box 52.

[0055] A method for producing electronic-grade carbon monoxide by a dual refrigeration method, the method comprising the following steps:

[0056] Step 1: The raw material gas in the raw material gas buffer tank 1 enters the raw material separator 5 through the ammonia cooler 2, the first inlet 18 of the main condenser, the first outlet 19 of the main condenser, the first inlet 20 of the subcooler and the first outlet 21 of the subcooler. The top gas phase outlet of the raw material separator 5 enters the first rectification column 6 through the second raw material gas inlet 24 of the first rectification column, and the bottom liquid phase outlet of the raw material separator 5 enters the first rectification column 6 through the first raw material gas inlet 26 of the first rectification column. The above-mentioned gas phase and liquid phase are subjected to a primary rectification and purification. The composition of the raw material liquid entering the first rectification column 6 is: H2: 0.5%, N2: 47%, CO: 43%, O2: 101 ppm, AR: 3%, CH4: 5%; the temperature of the raw material liquid is: -183.4 °C, the pressure is 0.15 MpaG, the flow rate is 164 Nm 3 / h, and the gas phase fraction is 0.1.

[0057] Step 2: The liquid phase after the first rectification and purification in the first rectification column 6 in Step 1 enters the common reboiler of the first rectification column 6 and the second rectification column 7. After the second reboiler 15 provides heat, the liquid phase in the common reboiler is vaporized and then enters the second rectification column 7 for secondary rectification and purification; the gaseous product after the secondary rectification and purification passes through the top gas outlet 27 of the second rectification column 7 and the first reboiler 11 in the scrubber 8 in sequence, and after liquefaction, it enters the liquid storage tank 9; the gaseous components at the top of the second rectification column 7 are: H2: 0%, N2: 3 ppm, CO: 99.999%, O2: 0.0549 ppb, AR: 2 ppm, CH4: 0, temperature: -182.5 °C, pressure: 0.15 MpaG, flow rate: 488 Nm 3 / h;

[0058] Step 3: For the product liquid entering the liquid storage tank 9 in Step 2, a part of the liquid phase enters the product tank 10 for storage and external sales, and the other part enters the first rectification column 6 and the second rectification column 7 respectively through the third raw material gas inlet 35 of the first rectification column and the first raw material gas inlet 36 of the second rectification column via the fifth three-way pipe 34. The gaseous phase in the liquid storage tank 9 enters the catalytic oxidation device 28 through the top gas outlet of the liquid storage tank 9; the temperature of the liquid phase entering the product tank 10 is: -182.5 °C, the pressure is: 0.15 MpaG, and the flow rate is: 95 Nm 3 / h; the temperature of the liquid phase entering the first rectification column 6 and the second rectification column 7 is: -182.5 °C, the pressure: 0.15 MpaG, and the flow rate: 393 Nm 3 / h;

[0059] Step 4: The waste gas after the first rectification and purification of the liquid phase entering the first rectification column 6 in Step 1 enters the scrubber 8 through the top gas outlet 37 of the first rectification column for scrubbing. After scrubbing, the gaseous phase in the scrubber 8 enters the first three-way pipe 40 through the scrubber gas outlet 39. A part of the gaseous phase enters the recycle gas compressor 12 through the second inlet 41 of the subcooler, the second outlet 42 of the subcooler, the second inlet 43 of the main condenser, the second outlet 44 of the main condenser, the second three-way pipe 45, the recycle gas buffer tank 13 and the third three-way pipe 46; another part of the gaseous phase enters the catalytic oxidation device 28 through the third end of the first three-way pipe 40, the third inlet 48 of the subcooler, the third outlet 49 of the subcooler, the third inlet 50 of the main condenser and the third outlet 51 of the main condenser; the liquid phase in the scrubber 8 returns to the first rectification column 6 through its bottom outlet and the fourth inlet 22 of the first rectification column; the content of N2 in the waste gas after the first rectification and purification is: 93.7%, and the flow rate is: 1171 Nm 3 / h, the pressure is: 0.15 MpaG; the content of N2 in the gaseous phase at the scrubber gas outlet 39 is: 98.2%, and the flow rate is: 1870 Nm 3 / h, the pressure is: 0.15 MpaG, and the temperature is: -187 °C;

[0060] When expansion refrigeration is required and medium-pressure nitrogen is used to provide liquid nitrogen washing liquid for the washing tower 8:

[0061] Step Five: Pressurize the recycled nitrogen entering the recycle gas compressor 12 in Step Four. A part of the pressurized recycle gas sequentially passes through the fourth inlet 53 of the main condenser, the fourth three-way valve 54, the fourth outlet 55 of the main condenser, and the second reboiler 15 and enters the recycle gas equilibrium tank 16. The gas phase in the recycle gas equilibrium tank 16 enters the catalytic oxidation device 28. The liquid phase at the bottom of the recycle gas equilibrium tank 16 enters the washing tower 8 through the fourth inlet 58 of the subcooler, the fourth outlet 59 of the subcooler, and the first liquid nitrogen washing port 60 of the washing tower to provide liquid nitrogen for washing for the washing tower 8; the temperature of the recycle nitrogen exiting the recycle gas compressor 12 after pressurization is: 40 °C, the pressure is: 0.9 MpaG, and the flow rate is: 2680 Nm 3 / h, the gas phase fraction is: 1; the flow rate of the above part of the recycle gas is: 1680 Nm 3 / h;

[0062] Step Six: Another part of the pressurized recycle nitrogen in Step Five enters the expander 14 through the third end of the fourth three-way valve 54. After gas expansion, it provides cooling capacity for the main condenser 3 through the sixth inlet 61 and the sixth outlet 57 of the main condenser. The recycle gas after recovering the cooling capacity re-enters the recycle gas compressor 12 through the third end of the second three-way valve 45 of the recycle gas; a part of the gas phase in the recycle gas buffer tank 13 in Step Four is compressed by the compression end of the expander 14 and enters the recycle gas compressor 12 through the third end of the third three-way valve 46; the temperature of a part of the gas phase in the recycle gas buffer tank 13 is: 40 °C, the pressure: 0.15 MpaG, and the flow rate: 1000 Nm 3 / h;

[0063] Step Seven: The medium-pressure nitrogen in the medium-pressure nitrogen buffer tank 18 enters the liquid nitrogen equilibrium tank 17 through the fifth inlet 62 of the main condenser, the fifth outlet 63 of the condenser, the fifth inlet 64 of the subcooler, and the fifth outlet 65 of the subcooler. The liquid nitrogen in the liquid nitrogen equilibrium tank 17 enters the washing tower 8 through the second liquid nitrogen washing port 66 of the washing tower to provide liquid nitrogen for washing for the washing tower 8; the temperature of the medium-pressure nitrogen in the medium-pressure nitrogen buffer tank 18 is: 40 °C, the pressure is: 3.0 MpaG, and the flow rate is: 80 Nm 3 / h; the above medium-pressure nitrogen passing through the main condenser 3 and the subcooler 4 changes from gaseous nitrogen to liquid nitrogen. The parameters of the liquid nitrogen are temperature: -179 °C, pressure: 3.0 MpaG, and flow rate: 80 Nm 3 / h;

[0064] Step Eight: After operating for a period of time, open the blowdown valve to discharge the waste liquid in the common tower kettle through the blowdown pipeline 47.

[0065] Example 2

[0066] An apparatus for producing electronic-grade carbon monoxide by a dual refrigeration method, comprising a raw material gas storage tank 1. The raw material gas buffer tank 1 is successively connected to a raw material separator 5 through an ammonia cooler 2, a first inlet 18 of a main condenser 3 of the main condenser, a first outlet 19 of the main condenser, a first inlet 20 of a subcooler 4 and a first outlet 21 of the subcooler. The gas-phase outlet at the top of the raw material separator 5 enters the middle part of a first rectification column 6 through a second raw material gas inlet 24 of the first rectification column. The liquid-phase outlet at the bottom of the raw material separator 5 is connected to the middle part of the first rectification column 6 through a first raw material gas inlet 26 of the first rectification column. The gas-phase outlet at the top of the first rectification column is connected to the inlet of a scrubbing tower 8. A first reboiler 11 is provided in the lower part inside the scrubbing tower 8. The inlet of the first reboiler 11 is connected to the gas-phase outlet 27 at the top of a second rectification column. The liquid-phase outlet at the bottom of the first reboiler 11 is respectively connected to a product tank 10, a third raw material gas inlet 35 of the first rectification column and a first raw material gas inlet 36 of the second rectification column through a liquid storage tank 9. It further comprises a recycle compressor 12, a medium-pressure nitrogen buffer tank 18, an expander 14 and a liquid nitrogen storage tank 23. The outlet of the recycle compressor 12 is successively connected to a fourth inlet 53 of the main condenser, a fourth three-way valve 54, a fourth outlet 55 of the main condenser and a second reboiler 15 and then connected to a recycle gas balance tank 16. The liquid-phase outlet at the bottom of the recycle gas balance tank 16 is connected to a first liquid nitrogen scrubbing port 60 at the upper part of the scrubbing tower 8 through a fourth inlet 58 of the subcooler and a fourth outlet 59 of the subcooler. The liquid nitrogen storage tank 23 is connected to the first liquid nitrogen scrubbing port 60 of the scrubbing tower 8. The medium-pressure nitrogen buffer tank 18 is connected to a liquid nitrogen balance tank 17 through a fifth inlet 62 of the main condenser, a fifth outlet 63 of the main condenser, a fifth inlet 64 of the subcooler and a fifth outlet 65 of the subcooler. The liquid-phase outlet of the liquid nitrogen balance tank 17 is connected to a second liquid nitrogen scrubbing port 66 at the upper part of the scrubbing tower 8. The outlet at the bottom of the scrubbing tower 8 is connected to a fourth inlet 22 of the first rectification column. A gas-phase outlet 39 of the scrubbing tower is provided at the top of the scrubbing tower 8. The gas-phase outlet 39 of the scrubbing tower is connected to the inlet of the recycle compressor 12 through a first three-way valve 40, a second inlet 41 of the subcooler, a second outlet 42 of the subcooler, a second inlet 43 of the main condenser, a second outlet 44 of the main condenser, a second three-way valve 45, a recycle gas buffer tank 13 and a third three-way valve 46. The third end of the fourth three-way valve 54 is connected to the inlet and outlet of the expansion end of the expander 14, a sixth inlet 61 of the main condenser, a sixth outlet 57 of the main condenser and the third end of the second three-way valve 45. The pressurization port 56 of the recycle gas buffer tank in the recycle gas buffer tank 13 is connected to the inlet and outlet of the compression end of the expander 14 and the third end of the third three-way valve 46. The bottoms of the first rectification column 6 and the second rectification column 7 are respectively connected to a common tower kettle, and the second reboiler 15 is arranged in the common tower kettle.A baffle 25 is provided at the inlet of the liquid storage tank 9. The baffle 25 divides the interior of the liquid storage tank 9 into a reflux cavity and a product cavity that are connected to each other at the upper part. The outlet at the bottom of the product cavity is connected to the product tank 10; the outlet at the bottom of the reflux cavity is respectively connected to the third raw material gas inlet 35 of the first distillation column and the first raw material gas inlet 36 of the second distillation column through the fifth three-way joint 34; the top gas phase outlet of the liquid storage tank 9 is connected to the catalytic oxidation device 28. The top gas phase outlet of the circulating gas balance tank 16 is connected to the catalytic oxidation device 28; the third end of the first three-way joint 40 is connected to the catalytic oxidation device 28 through the third inlet 48 of the subcooler, the third outlet 49 of the subcooler, the third inlet 50 of the main condenser, and the third outlet 51 of the main condenser. A first regulating valve 29 is provided between the bottom liquid phase outlet of the raw material separator 5 and the first raw material gas inlet 26 of the first distillation column, and a second regulating valve 30 is provided between the top gas phase outlet of the raw material separator 5 and the second raw material gas inlet 24 of the first distillation column. A third regulating valve 31 is provided between the fifth three-way joint 34 and the third raw material gas inlet 35 of the first distillation column, and a fourth regulating valve 32 is provided between the fifth three-way joint 34 and the first raw material gas inlet 36 of the second distillation column. A fifth regulating valve 33 is provided between the liquid phase outlet of the liquid nitrogen balance tank 17 and the second liquid nitrogen washing port 66 of the washing tower, and a sixth regulating valve 38 is provided between the fourth outlet 59 of the subcooler and the first liquid nitrogen washing port 60 of the washing tower. A sewage discharge pipe 47 with a sewage discharge valve is provided at the bottom of the common still. The main condenser 3, the subcooler 4, the first distillation column 6, the second distillation column 7, the washing tower 8, the liquid storage tank 9, the circulating gas balance tank 16, the liquid nitrogen balance tank 17, and the raw material separator 5 are all arranged in the cold box 52.

[0067] A method for producing electronic-grade carbon monoxide by a double refrigeration method. This method includes the following steps:

[0068] Step 1: The raw material gas in the raw material gas buffer tank 1 enters the raw material separator 5 through the ammonia cooler 2, the first inlet 18 of the main condenser, the first outlet 19 of the main condenser, the first inlet 20 of the subcooler, and the first outlet 21 of the subcooler. The top gas phase outlet of the raw material separator 5 enters the first distillation column 6 through the second raw material gas inlet 24 of the first distillation column, and the bottom liquid phase outlet of the raw material separator 5 enters the first distillation column 6 through the first raw material gas inlet 26 of the first distillation column. The above-mentioned gas phase and liquid phase are subjected to primary rectification and purification. The components of the raw material liquid entering the first distillation column 6 are: H2: 0.5%, N2: 47%, CO: 43%, O2: 101 ppm, AR: 3%, CH4: 5%; the temperature of the raw material liquid is -183.4 °C, the pressure is 0.15 MpaG, the flow rate is 164 Nm 3 / h, and the gas phase fraction is 0.1.

[0069] Step 2: The liquid phase after the first rectification and purification in the first rectification column 6 in Step 1 enters the common bottom of the first rectification column 6 and the second rectification column 7. After the second reboiler 15 provides heat, the liquid phase in the common bottom is vaporized and then enters the second rectification column 7 for secondary rectification and purification; the gaseous product after the secondary rectification and purification successively passes through the top gas outlet 27 of the second rectification column 7 and the first reboiler 11 in the scrubbing tower 8, and after liquefaction, enters the liquid storage tank 9; the gaseous components at the top of the second rectification column 7 are: H2: 0%, N2: 3 ppm, CO: 99.999%, O2: 0.0549 ppb, AR: 2 ppm, CH4: 0, temperature: -182.5 °C, pressure: 0.15 MpaG, flow rate: 488 Nm 3 / h;

[0070] Step 3: For the product liquid entering the liquid storage tank 9 in Step 2, a part of the liquid phase enters the product tank 10 for storage and external sale, and the other part enters the first rectification column 6 and the second rectification column 7 through the third raw material gas inlet 35 of the first rectification column and the first raw material gas inlet 36 of the second rectification column respectively by the fifth three-way valve 34. The gaseous phase in the liquid storage tank 9 enters the catalytic oxidation device 28 through the top gas outlet of the liquid storage tank 9; the temperature of the liquid phase entering the product tank 10 is: -182.5 °C, the pressure is: 0.15 MpaG, and the flow rate is: 95 Nm 3 / h; the temperature of the liquid phase entering the first rectification column 6 and the second rectification column 7 is: -182.5 °C, the pressure: 0.15 MpaG, and the flow rate: 393 Nm 3 / h;

[0071] Step 4: The waste gas after the first rectification and purification of the liquid phase entering the first rectification column 6 in Step 1 enters the scrubbing tower 8 through the top gas outlet 37 of the first rectification column for scrubbing. After scrubbing, the gaseous phase in the scrubbing tower 8 enters the first three-way valve 40 through the gas outlet 39 of the scrubbing tower. A part of the gaseous phase enters the circulating gas compressor 12 through the second inlet 41 of the subcooler, the second outlet 42 of the subcooler, the second inlet 43 of the main condenser, the second outlet 44 of the main condenser, the second three-way valve 45, the circulating gas buffer tank 13, and the third three-way valve 46; another part of the gaseous phase enters the catalytic oxidation device 28 through the third end of the first three-way valve 40, the third inlet 48 of the subcooler, the third outlet 49 of the subcooler, the third inlet 50 of the main condenser, and the third outlet 51 of the main condenser; the liquid phase in the scrubbing tower 8 returns to the first rectification column 6 through the outlet at its bottom and the fourth inlet 22 of the first rectification column; the content of N2 in the waste gas after the first rectification and purification is: 93.7%, and the flow rate is: 1171 Nm 3 / h, the pressure is: 0.15 MpaG; the content of N2 in the gaseous phase at the gas outlet 39 of the scrubbing tower is: 98.2%, and the flow rate is: 1870 Nm 3 / h, the pressure is: 0.15 MpaG, and the temperature is: -187 °C;

[0072] When it is necessary to purchase liquid nitrogen and medium-pressure nitrogen externally to provide liquid nitrogen washing liquid for the washing tower 8:

[0073] Step Five: Pressurize the recycled nitrogen entering the recycle gas compressor 12 in Step Four. The pressurized recycle gas sequentially passes through the fourth inlet 53 of the main condenser, the fourth three-way pipe 54, the fourth outlet 55 of the main condenser, and the second reboiler 15 and enters the recycle gas balance tank 16. The gas phase in the recycle gas balance tank 16 enters the catalytic oxidation device 28. The liquid phase at the bottom of the recycle gas balance tank 16 enters the washing tower 8 through the fourth inlet 58 of the subcooler, the fourth outlet 59 of the subcooler, and the first liquid nitrogen washing port 60 of the washing tower to provide liquid nitrogen for washing the washing tower 8; the temperature of the recycled nitrogen after being compressed and exiting the recycle gas compressor 12 is: 40 °C, the pressure is: 0.9 MpaG, and the flow rate is: 1680 Nm 3 / h, and the gas phase fraction is: 1;

[0074] Step Six: The medium-pressure nitrogen in the medium-pressure nitrogen buffer tank 18 enters the liquid nitrogen balance tank 17 through the fifth inlet 62 of the main condenser, the fifth outlet 63 of the condenser, the fifth inlet 64 of the subcooler, and the fifth outlet 65 of the subcooler. The liquid nitrogen in the liquid nitrogen balance tank 17 enters the washing tower 8 through the second liquid nitrogen washing port 66 of the washing tower to provide liquid nitrogen for washing the washing tower 8; the temperature of the medium-pressure nitrogen in the medium-pressure nitrogen buffer tank 18 is: 40 °C, the pressure is: 3.0 MpaG, and the flow rate is: 80 Nm 3 / h;

[0075] The above-mentioned medium-pressure nitrogen passing through the main condenser 3 and the subcooler 4 changes from gaseous nitrogen to liquid nitrogen. The parameters of the liquid nitrogen are temperature: -179 °C, pressure: 3.0 MpaG, and flow rate: 80 Nm 3 / h;

[0076] Step Seven: The externally purchased liquid nitrogen enters the washing tower 8 through the liquid nitrogen storage tank 23 and the first liquid nitrogen washing port 60 of the washing tower to provide liquid nitrogen for washing the washing tower 8;

[0077] Step Eight: After operating for a period of time, open the blowdown valve to discharge the waste liquid in the common tower kettle through the blowdown pipeline 47.

[0078] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An apparatus for producing electronic-grade carbon monoxide by a dual refrigeration method, comprising a raw material gas storage tank (1), characterized in that: The raw material gas storage tank (1) is connected to the raw material separator (5) successively through the ammonia cooler (2), the first inlet of the main condenser (3) of the main condenser, the first outlet (19) of the main condenser, the first inlet (20) of the sub-cooler (4) of the sub-cooler, and the first outlet (21) of the sub-cooler. The gas-phase outlet at the top of the raw material separator (5) enters the middle part of the first rectification column (6) through the second raw material gas inlet (24) of the first rectification column. The liquid-phase outlet at the bottom of the raw material separator (5) is connected to the middle part of the first rectification column (6) through the first raw material gas inlet (26) of the first rectification column. The gas-phase outlet (37) at the top of the first rectification column is connected to the inlet of the scrubbing column (8). The first reboiler (11) is arranged at the lower inner part of the scrubbing column (8). The inlet of the first reboiler (11) is connected to the gas-phase outlet (27) at the top of the second rectification column. The liquid-phase outlet at the bottom of the first reboiler (11) is connected to the product tank (10), the third raw material gas inlet (35) of the first rectification column, and the first raw material gas inlet (36) of the second rectification column respectively through the liquid storage tank (9). It further includes a recycle gas compressor (12), a medium-pressure nitrogen buffer tank, an expander (14), and a liquid nitrogen storage tank (23). The outlet of the recycle gas compressor (12) is connected to the recycle gas balance tank (16) successively through the fourth inlet (53) of the main condenser, the fourth three-way pipe (54), the fourth outlet (55) of the main condenser, and the second reboiler (15). The liquid-phase outlet at the bottom of the recycle gas balance tank (16) is connected to the first liquid nitrogen scrubbing port (60) at the upper part of the scrubbing column (8) through the fourth inlet (58) of the sub-cooler and the fourth outlet (59) of the sub-cooler. The liquid nitrogen storage tank (23) is connected to the first liquid nitrogen scrubbing port (60). The medium-pressure nitrogen buffer tank is connected to the liquid nitrogen balance tank (17) through the fifth inlet (62) of the main condenser, the fifth outlet (63) of the main condenser, the fifth inlet (64) of the sub-cooler, and the fifth outlet (65) of the sub-cooler. The liquid-phase outlet of the liquid nitrogen balance tank (17) is connected to the second liquid nitrogen scrubbing port (66) at the upper part of the scrubbing column (8). The outlet at the bottom of the scrubbing column (8) is connected to the fourth inlet (22) of the first rectification column. The scrubbing column gas-phase outlet (39) is arranged at the top of the scrubbing column. The scrubbing column gas-phase outlet (39) is connected to the inlet of the recycle gas compressor (12) through the first three-way pipe (40), the second inlet (41) of the sub-cooler, the second outlet (42) of the sub-cooler, the second inlet (43) of the main condenser, the second outlet (44) of the main condenser, the second three-way pipe (45), the recycle gas buffer tank (13), and the third three-way pipe (46). The third end of the fourth three-way pipe (54) is connected to the expansion end inlet and outlet of the expander (14), the sixth inlet (61) of the main condenser, and the sixth outlet (57) of the main condenser. The third end of the second three-way pipe (45) is connected to them. The pressurization port (56) of the recycle gas buffer tank in the recycle gas buffer tank (13) is connected to the third end of the third three-way pipe (46) through the compression end inlet and outlet of the expander (14). The bottom of the first rectification column (6) and the second rectification column (7) are respectively connected to a common reboiler, and a second reboiler (15) is arranged in the common reboiler; A baffle (25) is arranged at the inlet of the liquid storage tank (9). The baffle (25) divides the interior of the liquid storage tank (9) into a reflux cavity and a product cavity that are connected at the upper part. The outlet at the bottom of the product cavity is connected to a product tank (10); the outlet at the bottom of the reflux cavity is connected to the third raw material gas inlet (35) of the first rectification column and the first raw material gas inlet (36) of the second rectification column through a fifth three-way valve (34) respectively; The top gas phase outlet of the liquid storage tank (9) is connected to a catalytic oxidation device (28).

2. The device for producing electronic-grade carbon monoxide by the dual refrigeration method according to claim 1, characterized in that: The top gas phase outlet of the circulating gas balance tank (16) is connected to a catalytic oxidation device (28); The third end of the first three-way valve (40) is connected to a catalytic oxidation device (28) through a third inlet (48) of a subcooler, a third outlet (49) of the subcooler, a third inlet (50) of a main condenser, and a third outlet (51) of the main condenser.

3. The device for producing electronic-grade carbon monoxide by a dual refrigeration method according to claim 1, characterized in that: A first regulating valve (29) is arranged between the bottom liquid phase outlet of the raw material separator (5) and the first raw material gas inlet (26) of the first rectification column, and a second regulating valve (30) is arranged between the top gas phase outlet of the raw material separator (5) and the second raw material gas inlet (24) of the first rectification column.

4. The device for producing electronic-grade carbon monoxide by a dual refrigeration method according to claim 1, characterized in that: A third regulating valve (31) is arranged between the fifth three-way valve (34) and the third raw material gas inlet (35) of the first rectification column, and a fourth regulating valve (32) is arranged between the fifth three-way valve (34) and the first raw material gas inlet (36) of the second rectification column.

5. The device for producing electronic-grade carbon monoxide by a dual refrigeration method according to claim 1, characterized in that: A fifth regulating valve (33) is arranged between the liquid phase outlet of the liquid nitrogen balance tank (17) and the second liquid nitrogen washing port (66) of the washing tower, and a sixth regulating valve (38) is arranged between the fourth outlet (59) of the subcooler and the first liquid nitrogen washing port (60) of the washing tower.

6. The device for producing electronic-grade carbon monoxide by a dual refrigeration method according to claim 1, wherein: A sewage discharge pipe (47) with a sewage discharge valve is arranged at the bottom of the common reboiler.

7. The device for producing electronic-grade carbon monoxide by a dual refrigeration method according to claim 1, characterized in that: The main condenser (3), the subcooler (4), the first rectification column (6), the second rectification column (7), the washing tower (8), the liquid storage tank (9), the circulating gas balance tank (16), the liquid nitrogen balance tank (17), and the raw material separator (5) are all arranged in a cold box (52).

8. A method for an apparatus for producing electronic-grade carbon monoxide by a dual refrigeration method according to any one of claims 1-7, characterized in that: The method includes the following steps: Step 1: The raw material gas in the raw material gas storage tank (1) enters the raw material separator (5) through the ammonia cooler (2), the first inlet of the main condenser, the first outlet of the main condenser (19), the first inlet of the subcooler (20), and the first outlet of the subcooler (21). The gas-phase outlet at the top of the raw material separator (5) enters the first distillation column (6) through the second raw material gas inlet (24) of the first distillation column. The liquid-phase outlet at the bottom of the raw material separator (5) enters the first distillation column (6) through the first raw material gas inlet (26) of the first distillation column. The above-mentioned gas phase and liquid phase are subjected to primary distillation purification. The composition of the raw material liquid entering the first distillation column (6) is: H2: 0.5%, N2: 47%, CO: 43%, 02: 101 ppm, AR: 3%, CH4: 5%; the temperature of the raw material liquid is -183.4 °C, the pressure is 0.15 MpaG, and the flow rate is 164 Nm 3 / h, and the gas-phase fraction is 0.1; Step 2: The liquid phase after the primary rectification and purification in the first rectification column (6) in Step 1 enters the common reboiler of the first rectification column (6) and the second rectification column (7). After the second reboiler (15) provides heat, the liquid phase in the common reboiler is vaporized and enters the second rectification column (7) for secondary rectification and purification. The gaseous product after the secondary rectification and purification successively passes through the top gas outlet (27) of the second rectification column (7) and the first reboiler (11) in the scrubbing column (8), and after liquefaction, enters the liquid storage tank (9). The gas-phase components at the top of the second rectification column (7) are: H2: 0%, N2: 3 ppm, CO: 99.999%, O2: 0.0549 ppb, AR: 2 ppm, CH4: 0, temperature: -182.5 °C, pressure: 0.15 MpaG, flow rate: 488 Nm 3 / h; Step 3: For the product liquid entering the liquid storage tank (9) in Step 2, a part of the liquid phase enters the product tank (10) for storage and external sale, and the other part enters the first distillation column (6) and the second distillation column (7) respectively through the third raw material gas inlet (35) of the first distillation column and the first raw material gas inlet (36) of the second distillation column via the fifth three-way pipe (34). The gas phase in the liquid storage tank (9) enters the catalytic oxidation device (28) through the gas phase outlet at the top of the liquid storage tank (9); the temperature of the liquid phase entering the product tank (10) is: -182.5 °C, the pressure is: 0.15 MpaG, and the flow rate is: 95 Nm 3 / h; the temperature of the liquid phase entering the first distillation column (6) and the second distillation column (7) is: -182.5 °C, the pressure is: 0.15 MpaG, and the flow rate is: 393 Nm 3 / h; Step 4: The waste gas after the first rectification and purification of the liquid phase entering the first rectification column (6) in Step 1 enters the scrubber (8) through the top gas outlet (37) of the first rectification column for scrubbing. After scrubbing, the gas phase in the scrubber (8) enters the first three-way (40) through the scrubber gas outlet (39). A part of the gas phase enters the recycle gas compressor (12) through the second inlet (41) of the subcooler, the second outlet (42) of the subcooler, the second inlet (43) of the main condenser, the second outlet (44) of the main condenser, the second three-way (45), the recycle gas buffer tank (13) and the third three-way (46); Another part of the gas phase enters the catalytic oxidation device (28) through the third end of the first three-way (40), the third inlet (48) of the subcooler, the third outlet (49) of the subcooler, the third inlet (50) of the main condenser and the third outlet (51) of the main condenser; The liquid phase in the scrubber (8) returns to the first rectification column (6) through the outlet at its bottom and the fourth inlet (22) of the first rectification column; The content of N2 in the waste gas after the first rectification and purification is: 93.7%, the flow rate is: 1171 Nm 3 / h, the pressure is: 0.15 MpaG; The content of N2 in the gas phase at the outlet of the scrubber gas outlet (39) is: 98.2%, the flow rate is: 1870 Nm 3 / h, the pressure is: 0.15 MpaG, and the temperature is: -187 °C; When it is necessary to provide liquid nitrogen washing liquid for the washing tower (8) by expansion refrigeration and medium-pressure nitrogen: Step Five: Pressurize the recycle nitrogen entering the recycle gas compressor (12) in Step Four. A part of the pressurized recycle gas sequentially passes through the fourth inlet (53) of the main condenser, the fourth three-way pipe (54), the fourth outlet (55) of the main condenser, and the second reboiler (15) and enters the recycle gas equilibrium tank (16). The gas phase in the recycle gas equilibrium tank (16) enters the catalytic oxidation unit (28). The liquid phase at the bottom of the recycle gas equilibrium tank (16) enters the scrubbing tower (8) through the fourth inlet (58) of the subcooler, the fourth outlet (59) of the subcooler, and the first liquid nitrogen scrubbing port (60) of the scrubbing tower to provide liquid nitrogen for scrubbing the scrubbing tower (8). The temperature of the recycle nitrogen exiting the recycle gas compressor (12) after pressurization is: 40°C, the pressure is: 0.9 MpaG, and the flow rate is: 2680 Nm 3 / h, and the gas phase fraction is: 1; the flow rate of the above-mentioned part of the recycle gas is: 1680 Nm 3 / h; Step six: Another part of the pressurized circulating nitrogen in step five enters an expander (14) through the third end of a fourth three-way valve (54), and after gas expansion, it provides cooling capacity for the main condenser (3) through the sixth inlet (61) and the sixth outlet (57) of the main condenser. The circulating gas after recovering the cooling capacity re-enters the circulating gas compressor (12) through the third end of a second three-way valve (45) of the circulating gas; a part of the gas phase in the circulating gas buffer tank (13) in step four is compressed by the compression end of the expander (14) and enters the circulating gas compressor (12) through the third end of a third three-way valve (46). The temperature of a part of the gas phase in the circulating gas buffer tank (13) is: 40 °C, pressure: 0.15 MpaG, flow rate: 1000 Nm 3 / h; Step Seven: The medium-pressure nitrogen in the medium-pressure nitrogen buffer tank (18) enters the liquid nitrogen balance tank (17) through the fifth inlet (62) of the main condenser, the fifth outlet (63) of the condenser, the fifth inlet (64) of the subcooler, and the fifth outlet (65) of the subcooler. The liquid nitrogen in the liquid nitrogen balance tank (17) enters the scrubbing tower (8) through the second liquid nitrogen scrubbing port (66) of the scrubbing tower, providing liquid nitrogen for scrubbing the scrubbing tower (8); the temperature of the medium-pressure nitrogen in the pressure nitrogen buffer tank (18) is: 40°C, the pressure is: 3.0 MpaG, and the flow rate is: 80 Nm 3 / h; The medium-pressure nitrogen passing through the main condenser (3) and the subcooler (4) changes from gaseous nitrogen to liquid nitrogen. The parameters of the liquid nitrogen are temperature: -179°C, pressure: 3.0 MpaG, and flow rate: 80 Nm 3 / h; When it is necessary to purchase liquid nitrogen and medium-pressure nitrogen externally to provide liquid nitrogen washing liquid for the washing tower (8): Step Eight: Pressurize the recycled nitrogen entering the recycle gas compressor (12) in Step Four. The pressurized recycle gas sequentially passes through the fourth inlet (53) of the main condenser, the fourth three-way pipe (54), the fourth outlet (55) of the main condenser, and the second reboiler (15) and enters the recycle gas equilibrium tank (16). The gas phase in the recycle gas equilibrium tank (16) enters the catalytic oxidation unit (28). The liquid phase at the bottom of the recycle gas equilibrium tank (16) enters the scrubbing column (8) through the fourth inlet (58) of the subcooler, the fourth outlet (59) of the subcooler, and the first liquid nitrogen scrubbing port (60) of the scrubbing column to provide liquid nitrogen for scrubbing for the scrubbing column (8). The temperature of the recycled nitrogen exiting the recycle gas compressor (12) after compression is: 40°C, the pressure is: 0.9 MpaG, the flow rate is: 1680 Nm 3 / h, and the gas phase fraction is: 1; Step Nine: The medium-pressure nitrogen gas in the medium-pressure nitrogen buffer tank enters the liquid nitrogen balance tank (17) through the fifth inlet (62) of the main condenser, the fifth outlet (63) of the condenser, the fifth inlet (64) of the subcooler, and the fifth outlet (65) of the subcooler. The liquid nitrogen in the liquid nitrogen balance tank (17) enters the scrubbing tower (8) through the second liquid nitrogen scrubbing port (66) of the scrubbing tower, providing liquid nitrogen for scrubbing the scrubbing tower (8); the temperature of the medium-pressure nitrogen gas in the pressure nitrogen buffer tank is: 40°C, the pressure is: 3.0 MpaG, and the flow rate is: 80 Nm 3 / h; The medium-pressure nitrogen gas passing through the main condenser (3) and the subcooler (4) changes from gaseous nitrogen to liquid nitrogen. The parameters of the liquid nitrogen are temperature: -179°C, pressure: 3.0 MpaG, and flow rate: 80 Nm 3 / h; Step Ten: The purchased liquid nitrogen enters the scrubbing tower (8) through the liquid nitrogen storage tank (23) and the first liquid nitrogen scrubbing port (60) of the scrubbing tower to provide liquid nitrogen for scrubbing the scrubbing tower (8). Step Eleven: After operating for a period of time, open the blowdown valve to discharge the waste liquid in the common tower kettle through the blowdown pipeline (47).

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