Purification process and purification system for continuously producing high-purity 7N-grade ammonia by utilizing industrial-grade ammonia

Abstract

The invention belongs to the technical field of purification processes and devices of high-purity electronic chemicals, and particularly relates to a purification process and a purification system for continuously producing high-purity 7N-grade ammonia by using industrial-grade ammonia. The process comprises the following steps: cooling industrial ammonia, quantitatively feeding into a 1 # rectifying tower, heating and gasifying by a 1 # reboiler, condensing by utilizing a built-in condenser at the top of the tower, feeding ammonia condensate collected in the tower into an evaporator, heating, removing trace impurities by a fixed bed reactor, treating, performing heat exchange in the evaporator, and rectifying in a 2 # rectifying tower, obtaining high-purity ammonia from the tower; light components enriched at the tower top of the 1 # rectifying tower after passing through a built-in condenser are absorbed by an absorber. According to the purification process for continuously producing the high-purity 7N-grade ammonia from the industrial-grade ammonia, continuous, stable and efficient operation can be achieved, energy consumption is remarkably reduced, the purification process has great significance in meeting the increasing requirement of high-end industries for ultra-high-purity ammonia, and the invention further provides a purification system of the purification process for continuously producing the high-purity 7N-grade ammonia from the industrial-grade ammonia.

Description

Technical Field

[0001] This invention belongs to the technical field of purification processes and equipment for high-purity electronic chemicals, specifically relating to a purification process and system for the continuous production of high-purity 7N-grade ammonia using industrial-grade ammonia. Background Technology

[0002] Ammonia (NH3), as an important basic chemical raw material and specialty gas, has purity requirements that vary greatly depending on the application. Industrially used liquid ammonia (typically with a purity ≥99.9%, i.e., 3N grade) contains various impurities, mainly including light hydrocarbons such as water (H2O), oxygen (O2), nitrogen (N2), hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4), as well as trace amounts of metal ions (such as Fe, Na, K, Ca, Ni, etc.) and sulfur-containing compounds. This type of industrial-grade ammonia is mainly used in fertilizer production, refrigerants, and chemical synthesis (such as nitric acid and acrylonitrile), where the tolerance for trace impurities is relatively high.

[0003] However, in high-end semiconductor manufacturing, flat panel displays, LED epitaxial growth, photovoltaic cells, and cutting-edge scientific research, the purity requirements for ammonia are extremely stringent, namely 7N grade (99.99999%) or higher. 7N grade high-purity ammonia means that its total impurity content must be controlled below 0.1 ppm, and there are extremely strict individual limits (usually requiring ppb or even ppt levels) for specific key impurities (such as moisture, oxygen-containing compounds O2 / CO / CO2, hydrocarbons CH4, and total metal ions). The presence of these trace impurities, especially oxygen-containing compounds (leading to oxygen contamination in thin films such as silicon nitride / gallium nitride), moisture (causing increased interface state density in compound semiconductors), metal ions (causing device leakage and gate oxide breakdown), and hydrocarbons (affecting the crystal quality of epitaxial layers), significantly degrades the performance, reliability, and yield of semiconductor devices. Therefore, stable, efficient, and large-scale production of 7N grade high-purity ammonia is a crucial link supporting the development of these high-tech industries.

[0004] Currently, the mainstream process routes for purifying industrial-grade liquid ammonia (3N grade) to 7N grade high-purity ammonia mainly revolve around two core unit operations: adsorption and distillation, often combined. However, existing technologies generally suffer from several bottlenecks that restrict product quality stability and production efficiency: intermittent adsorption-distillation combined processes, adsorption-dominated processes (deep adsorption methods), and distillation-dominated processes (deep distillation methods). Therefore, purification using these methods results in unstable product quality. Periodic saturation of the adsorbent leads to fluctuations in the concentration of key impurities (moisture, oxygen-containing compounds, methane, etc.), making it difficult to guarantee consistently stable 7N grade purity. The process is discontinuous; intermittent operation limits production efficiency and scale, and switching processes introduce risks. Operating costs are high; frequent adsorbent regeneration / switching and the energy-intensive distillation process increase production costs. System complexity and reliability are also affected; intermittent operation requires complex valve switching and control systems, increasing failure rates and maintenance costs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a purification process for the continuous production of high-purity 7N grade ammonia using industrial-grade ammonia. This process can achieve continuous, stable and efficient operation, effectively solve the problem of impurity concentration fluctuation caused by adsorbent saturation, and significantly reduce energy consumption. It is of great significance for meeting the growing demand of high-end industries for ultra-high purity ammonia. The present invention also provides its purification system.

[0006] The purification process for the continuous production of high-purity 7N-grade ammonia using industrial-grade ammonia as described in this invention includes the following steps: After industrial ammonia is cooled, it is quantitatively fed into the No. 1 distillation column. After being heated and vaporized at 20~60℃ in the No. 1 reboiler, it is condensed by the built-in condenser at the top of the column. The ammonia condensate collected in the column enters the evaporator and is then sent to the fixed bed gas-solid phase reaction for impurity removal. After heating, it passes through the fixed bed reactor to remove trace impurities. After treatment, it enters the evaporator for heat exchange and then enters the No. 2 distillation column for rectification to obtain high-purity ammonia. The fixed bed reactor includes fixed bed reactor A and / or fixed bed reactor B.

[0007] The light components enriched at the top of the No. 1 distillation column after passing through the built-in condenser are absorbed by the absorber, and the vapor phase at the top of the No. 1 distillation column is sent to the energy converter for heat recovery; the heavy component impurities in the bottom of the No. 1 distillation column are absorbed and converted by the absorber. The top components and bottom weights of the No. 2 distillation column are recycled to the No. 1 distillation column.

[0008] The purity of industrial ammonia is 99.9%. Industrial ammonia is fed quantitatively at a rate of 10-100 kg / h into the feed inlet of the No. 1 distillation column via a feed pump. Liquid ammonia at the bottom of the column is heated to 20-60°C in the No. 1 reboiler, causing partial vaporization. The vaporized ammonia rises along the column, while the gaseous ammonia containing light impurities (hydrogen, nitrogen, oxygen, argon, CO, etc.) passes through an internal condenser at the top of the column. The temperature is controlled by cooling water at 5-45°C, causing the gaseous ammonia to become liquid and reflux completely. This differs from conventional external condensers in distillation columns. The internal condenser is a finned condenser without an outer shell, allowing the liquid ammonia to be cooled on its outer surface. The non-condensable light impurities accumulate at the top of the column. By precisely controlling the top pressure (0.1-1.5 MPa) and adjusting the proportion of vapor phase collected from the top, the reflux ratio is controlled within the range of 5-500, thus controlling the concentration of impurities at the top. This differs from conventional distillation methods, where liquid phase is collected and the reflux ratio is controlled. The entire vaporous liquid ammonia condensate from the top of the column flows to the No. 1 distillation column. The light components and some uncondensed ammonia gas, controlled at a pressure of 0.1~1.5MPa, enter the absorber, where a weakly acidic gas absorbs and purifies the ammonia gas. The light components are discharged to the absorber using the light component discharge valve, which can remove most of the light components (including hydrogen, nitrogen, oxygen, carbon monoxide, carbon dioxide, and low-boiling-point hydrocarbon impurities).

[0009] After industrial ammonia is cooled, it is quantitatively fed into the No. 1 distillation column, with a flow rate of 10~100 kg / h.

[0010] The No. 1 distillation column is an existing device. A collection component is installed in the upper part of the No. 1 distillation column to collect the liquid reflux portion into a collection tank. Ammonia (99.999%) is continuously collected by controlling the flow rate and the liquid level in the column. This method differs from conventional distillation column top or bottom collection. The No. 1 distillation column of this invention purifies industrial ammonia feed from 99.5% to 99.995%, and then uses the No. 2 distillation column to further enhance it to 99.99999%, simultaneously removing light and heavy components and obtaining a high-purity product with a purity greater than 5N. The feed liquid ammonia is completely refluxed in the No. 1 distillation column and collected in the bottom. It is then circulated through the No. 1 reboiler. Heavy components (H2O, methylamine, methanol, ethylamine, oil, ash, etc.) are enriched in the bottom of the column. The No. 1 reboiler heats the ammonia partially by a heating medium, continuously enriching the bottom with more difficult-to-vaporize heavy component impurities. These heavy component impurities in the bottom are absorbed by the absorbent liquid and become by-products. The heat source for the No. 1 reboiler in the tower is taken from the heat source gas of the energy converter for heat exchange.

[0011] The reflux ratio of the No. 1 distillation column is controlled at 5~500, and the pressure at the top of the column is controlled at 0.1~1.5MPa.

[0012] The built-in condenser is set to a temperature of 5~45℃.

[0013] The temperature of the No. 2 distillation column is controlled at 10~60℃, the pressure at 0.5~1.5MPa, and the reflux ratio at 10~1000.

[0014] The purification system used in the purification process includes a No. 1 distillation column, a No. 2 distillation column, an energy converter, a fixed-bed reactor A, and a fixed-bed reactor B. An internal condenser is installed at the top of the No. 1 distillation column. The top pipe of the No. 1 distillation column is connected to the energy converter. After heat exchange, the condenser pipe circulates back to the top of the No. 1 distillation column. The vapor phase outlet pipe of the energy converter is connected to the No. 1 reboiler. The liquid phase outlet pipe of the No. 1 distillation column is connected to an evaporator. The evaporator is connected to the inlet pipes of fixed-bed reactor A and fixed-bed reactor B. The outlet pipe then passes through the evaporator and connects to the middle of the No. 2 distillation column.

[0015] The top pipeline of distillation column #2 is connected to the middle pipeline of distillation column #1. A reboiler is installed at the bottom of distillation column #2, and its bottom pipeline is connected to the middle pipeline of distillation column #1. The outlet pipeline of distillation column #2 is connected to the product tank. A condenser is installed at the top of distillation column #2. Both distillation columns #1 and #2 are packed columns, filled with high-efficiency PP spiral packing. The packing dimensions are 7mm × 10mm × 10mm (inner × outer × height), and the packing height is 5-30m. High-purity 7N grade liquid ammonia is obtained in the middle of the column after removing trace amounts of hydrogen and other impurities.

[0016] The built-in condenser is a series finned condenser.

[0017] The outer layer of the energy converter body is configured as a shell and an insulating shell in sequence. The body is provided with an annular cavity, and the inlet is located in the annular cavity of the body. The inlet is connected to the inner cavity of the energy converter body. The inlet divides the inner cavity of the energy converter body into two parts. One part is a cold air expansion port, and the other part of the inner cavity is provided with an adjustment structure. The inner wall of the body is set in a spiral shape, and the cold air expansion port is a conical structure that is connected to the cold air extraction port on the body.

[0018] A hot air outlet is provided at the regulating structure end on the main body of the energy converter; a cold air outlet is provided on the main body of the energy converter.

[0019] The energy converter achieves the coupled utilization of cold and heat. Utilizing a conical structure with a spiral inner cavity, it leverages the expansion of compressible gas as it passes through. One end has a 1-5mm cold gas expansion port, while the other end features a cone shape with adjustable space. Gas is injected tangentially from the inlet nozzle, creating a spiral flow that generates a pressure difference and subsequently a temperature difference due to the difference in gas velocity between the inner and outer rings. This allows for gas energy exchange, creating a temperature gradient and converting the gas's compression potential energy into low-temperature and high-temperature gas energy. In the low-temperature section, ammonia gas at -25℃ to -45℃ is delivered from the cold gas expansion port to the cold gas outlet. This low-temperature ammonia is used for low-temperature drying of high-purity liquid ammonia to remove trace amounts of H2O, reducing H2O impurities in high-purity ammonia from 50ppm to 1ppm. The high-temperature section generates 40-100℃ high-temperature gas, which is output from the hot gas outlet and fed into the shell side of the reboiler in the No. 1 distillation column to heat the liquid ammonia inside the column, controlling the temperature of the liquid ammonia in the column bottom at 20-100℃, thus achieving the coupled utilization of energy. It can use ammonia as a medium, and is also applicable to air, nitrogen, oxygen, water vapor, etc. Theoretically, it can be used for all gases, such as NF3, SF6, N2O, CO2, O2, CO, etc. The gas energy converter is different from the usual refrigerant refrigeration and adopts the throttling expansion refrigeration method, which is also different from conventional electric heating, steam, hot water and other heat transfer medium heating.

[0020] For the removal of trace water, trace carbon oxides, and trace impurity hydrocarbons from liquid ammonia, conventional distillation methods can only reduce water content from 1000 ppm to 10-100 ppm, and further reduction is difficult to achieve even lower removal efficiency. This invention, however, utilizes a low-temperature dehydration process, reducing water content in high-purity ammonia from 10-50 ppm to <5 ppm and carbon oxides and hydrocarbons to <1 ppm at -20 to -60°C, meeting the requirements for high-purity nitrogen trifluoride feedstock. However, optoelectronic-grade ultrapure ammonia requires these impurities to be less than 0.1 ppm. This invention processes industrial ammonia through a No. 1 distillation column. Subsequently, gaseous ammonia is heated to 100-400℃ via electric heating and then fed into fixed-bed reactor A and / or fixed-bed reactor B. The ammonia is then adsorbed by a getter (using one or more synthetic composite metal getters such as nickel, titanium, zirconium, cobalt, manganese, aluminum, sodium, potassium, gallium, zinc, etc.). Stability is maintained through cyclic heating, controlling the temperature of the two fixed-bed reactors within the 100-400℃ range. This process achieves the absorption of water, carbon oxides, and impurity hydrocarbons (methane, methylamine, ethylamine, etc.), reducing impurities such as carbon oxides, moisture, and hydrocarbons to <0.1ppm, with a maximum reduction to 0.03ppm. These two fixed-bed getter reactors can be periodically switched via a logic programmable controller and can be regenerated using hydrogen.

[0021] This invention is used for optoelectronic grade ultrapure ammonia. In addition to requirements on the composition of impurity gases, in order to control metal ion impurities in ultrapure ammonia, the metal ion impurities in the product are reduced to less than 0.5 ppb during the product purification process.

[0022] Compared with the prior art, the beneficial effects of the present invention are: (1) The process of the present invention completely solves the problem of product purity fluctuation caused by the periodic saturation of adsorbent in the traditional batch process through a continuous closed-loop process of "distillation-evaporation-reaction-re-distillation", realizing the stable and continuous production of 7N grade ultrapure ammonia. The single unit has high capacity and high production efficiency, meeting the urgent needs of industries such as optoelectronics and semiconductors for batch and stable supply.

[0023] (2) The present invention couples the energy converter with the dual-tower distillation system and uses the composite energy management technology of throttling expansion refrigeration + waste heat recovery to convert the potential energy of the compressed gas discharged from the top of the tower into low-temperature cold energy of -25℃~-45℃ (for deep removal of trace water to <1ppm) and high-temperature heat of 40℃~100℃ (for reboiler heating). The overall energy consumption of the system is reduced, and no additional refrigeration unit or steam boiler is required, which significantly reduces the operating cost.

[0024] (3) By setting up a fixed-bed reactor A and a fixed-bed reactor B after the evaporator, the present invention uses composite metal getters such as nickel-titanium-zirconium-aluminum to selectively adsorb water, carbon oxides and hydrocarbons at 100~400℃, so that bond impurities are reduced to <0.1ppm and metal ions are controlled at <0.5ppb; the fixed-bed logic switching and hydrogen regeneration design ensure long-term uninterrupted operation, high system reliability, low maintenance, and impurity removal depth and stability far exceeding traditional single distillation or adsorption processes. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a purification system for the continuous production of high-purity 7N grade ammonia using industrial-grade ammonia.

[0026] Figure 2 This is a schematic diagram of the energy converter.

[0027] Figure 1 The components are as follows: 1. Industrial ammonia tank; 2. Precooler; 3. Distillation column #1; 4. Reboiler #1; 5. Condenser #1; 6. Energy converter; 7. Compressor; 8. Built-in condenser; 9. Evaporator; 10. Automatic switching valve; 11. Fixed bed reactor A; 12. Fixed bed reactor B; 13. Heat exchanger; 14. Distillation column #2; 15. Condenser #2; 16. Reboiler #2; 17. Product tank; 18. Light exhaust valve.

[0028] Figure 2 In the middle: 61. Inlet; 62. Annular cavity; 63. Cold air extraction outlet; 64. Cold air expansion outlet; 65. Shell; 66. Adjustment structure; 67. Hot air outlet; 68. Cold air outlet; 69. Insulating shell. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments.

[0030] like Figure 1 As shown, the purification system used in the purification process includes a #1 distillation column 3, a #2 distillation column 14, an energy converter 6, a fixed-bed reactor A11, and a fixed-bed reactor B12. An internal condenser 8 is installed at the top of the #1 distillation column 3. The top pipe of the #1 distillation column 3 is connected to the energy converter 6. After heat exchange, the condenser pipe circulates back to the top of the #1 distillation column 3. The vapor phase outlet pipe of the energy converter 6 is connected to the #1 reboiler 4. The liquid phase outlet pipe of the #1 distillation column 3 is connected to the evaporator 9. The evaporator 9 is connected to the inlet pipes of the fixed-bed reactors A11 and B12. The outlet pipe passes through the evaporator 9 and connects to the heat exchanger 13. The heat exchanger 13 is connected to the interior of the #2 distillation column 14.

[0031] The top pipeline of distillation column 14 (No. 2) is connected to the middle pipeline of distillation column 3 (No. 1). A reboiler (No. 2) (No. 16) is installed at the bottom of distillation column 14, and its bottom pipeline is connected to the middle pipeline of distillation column 3 (No. 1). The outlet pipeline of distillation column 14 is connected to product tank 17. A condenser (No. 2) (No. 15) is installed at the top of distillation column 14. Distillation columns 3 (No. 1) and 14 (No. 2) are designed as packed columns, filled with high-efficiency PP spiral packing. The packing's inner × outer × height is 7mm × 10mm × 10mm. Trace amounts of hydrogen and other impurities are removed, resulting in high-purity 7N-grade liquid ammonia in the middle of the column.

[0032] The built-in condenser 8 is a series finned condenser.

[0033] like Figure 2 As shown, the outer layer of the energy converter 6 is sequentially configured as a shell 65 and an insulating shell 69. The body is provided with an annular cavity 62, and the inlet 61 is located in the annular cavity 62 on the body. The inlet 61 communicates with the inner cavity of the energy converter 6. The inlet 61 divides the inner cavity of the energy converter 6 into two parts. One part is a cold air expansion port 64, and the other part of the inner cavity is provided with an adjustment structure 66. The inner wall of the body is spiral-shaped, and the cold air expansion port 64 is a conical structure that communicates with the cold air extraction port 63 on the body.

[0034] A hot air outlet 67 is provided at the adjustment structure 66 end on the main body of the energy converter 6; a cold air outlet 68 is provided on the main body of the energy converter 6.

[0035] The industrial ammonia from industrial ammonia tank 1 is cooled by precooler 2 and then quantitatively fed into distillation column 3 (No. 1). After being heated and vaporized by reboiler 4 (No. 1), the ammonia condensate collected in the column is condensed by the built-in condenser 8 at the top of the column and then enters evaporator 9. After being heated, it passes through a fixed-bed reactor to remove trace impurities. The treated vapor phase is then heat-exchanged by evaporator 9 and enters distillation column 14 (No. 2) to obtain high-purity ammonia. Automatic switching valves 10 are installed on the inlet pipes of fixed-bed reactors A11 and B12 to achieve automatic switching.

[0036] The light components enriched at the top of distillation column 3 after passing through the built-in condenser 8 are condensed by condenser 5 and absorbed by the absorber. The vapor phase at the top of distillation column 3 is sent to the energy converter 6 for heat recovery. The liquid after being compressed by compressor 7 continues to enter distillation column 3 for recycling. The heavy components and impurities in the bottom of distillation column 3 are absorbed and converted by the absorber. The components at the top of distillation column 14 and the heavy components in the bottom of distillation column 14 are recycled to distillation column 3.

[0037] The above-described apparatus is used in all the following embodiments.

[0038] Example 1 Continuous operation verification of energy recovery coupled with dual-tower distillation: Raw material: 99.9% industrial ammonia, flow rate 50 kg / h; 1# Distillation Column 3: Top pressure 0.5MPa, built-in condenser temperature 10℃, reflux ratio 100; Built-in condenser 8: Set temperature is 5~45℃ (industrial verification, the temperature can be implemented during the process); Energy converter 6: Inlet pressure 1.0MPa, output low temperature end -35℃ cold air (for subsequent trace water removal), high temperature end 85℃ hot air to supply No. 1 reboiler; 2# Distillation Column 14: Temperature 40℃, Pressure 1.0MPa, Reflux ratio 10-500, product collected from the column.

[0039] Process execution: Industrial ammonia, after cooling, enters distillation column 3 (No. 1). Light components (H2, N2, etc.) at the top of the column pass through the light component discharge valve 18 and enter the absorber for absorption. Liquid ammonia (99.999%) in the column is collected and sent to evaporator 9, where it is converted to gas and then enters fixed-bed reactor A11 (set to 300℃). The gas, after removing trace impurities, is condensed back into liquid phase by heat exchange in evaporator 9 and then enters distillation column 2 for purification. Light components at the top of distillation column 14 and heavy components at the bottom of distillation column 2 are returned to distillation column 3 for recycling.

[0040] Results of this embodiment: Product purity: Ammonia extracted from tower #2 reached 7N grade (99.99999%), with total impurities <0.1ppm; Energy consumption comparison: Energy converter 6 provides 50% of the heat source for reboiler 4, and the overall energy consumption of the system is reduced by 30% compared with the traditional electric heating + external cooling process.

[0041] Continuous operation: Stable operation for 1200 hours, with product impurity concentration fluctuation < ±5% (proving that the adsorbent saturation problem has been eliminated).

[0042] Example 2 Verification of deep removal of trace impurities using a fixed-bed reactor (other parameters not shown are consistent with Example 1): Raw materials: Liquid ammonia with a purity of 99.999% after distillation in distillation column 1, water content of 30ppm, and CO2 content of 15ppm.

[0043] Fixed-bed reactor A11 and fixed-bed reactor B12: nickel-titanium-zirconium-aluminum composite getter, temperature 270℃ (fixed-bed reactor A11 and fixed-bed reactor B12 are regenerated every 500h). Regeneration conditions: During switching, introduce H2 (with 10% N2 by volume) and regenerate at 400℃ for 2 hours; The deep purification results are shown in Table 1.

[0044] Table 1 Purification results

[0045] The high-temperature getter reduces carbon oxides, hydrocarbons, and water to <0.1 ppm and metal ions to <0.5 ppb; It meets the standards for optoelectronic grade ultrapure ammonia (SEMI specification: H2O < 0.1 ppm, metal < 1 ppb).

[0046] Example 3 Long-term stability verification of the entire system (all other parameters not shown are consistent with those in Example 1): Raw material impurity fluctuations: simulated industrial ammonia impurity peak values ​​(CO2: 500ppm, O2: 200ppm). Energy converter operating condition 6: Pressure changes stepwise in the range of 0.3~1.5MPa (simulating load adjustment); Light component control: The light component concentration is stabilized at <10ppm by controlling the pressure matrix at the top of column 3 of distillation column 1 (0.5MPa→1.2MPa) and automatically adjusting the reflux ratio (50→300). Switching between fixed-bed reactor A11 and fixed-bed reactor B12: The logic controller switches between fixed-bed reactor A11 and fixed-bed reactor B12 every 500 hours. After regeneration, the adsorption capacity is restored to more than 98%. Product consistency: 7N ammonia purity is consistently maintained at 99.99999% ± 0.00001, and trace water content is < 0.05 ppm; The recombinant components are recycled to the absorber for conversion, with no waste accumulation. Energy converter 6 adapts to pressure changes, with cold / hot output temperature fluctuations < ±2℃; This breaks through the bottleneck of traditional processes that require shutdown and regular replacement of the adsorbent.

Claims

1. A purification process for the continuous production of high-purity 7N-grade ammonia using industrial-grade ammonia, characterized in that: Includes the following steps: After industrial ammonia is cooled, it is quantitatively fed into the No. 1 distillation column. After being heated and vaporized at 20~60℃ in the No. 1 reboiler, it is condensed by the built-in condenser at the top of the column. The ammonia condensate collected in the column enters the evaporator, is heated and then passes through a fixed-bed reactor to remove trace impurities. After treatment, it enters the evaporator for heat exchange and then enters the No. 2 distillation column for distillation to obtain high-purity ammonia. The light components enriched at the top of the No. 1 distillation column after passing through the built-in condenser are absorbed by the absorber, and the vapor phase at the top of the No. 1 distillation column is sent to the energy converter for heat recovery; the heavy component impurities in the bottom of the No. 1 distillation column are absorbed and converted by the absorber; the components at the top of the No. 2 distillation column and the heavy components in the bottom of the column are recycled back to the No. 1 distillation column.

2. The purification process for continuous production of high-purity 7N-grade ammonia using industrial-grade ammonia according to claim 1, characterized in that: After industrial ammonia is cooled, it is quantitatively fed into the No. 1 distillation column, with a flow rate of 10~100 kg / h.

3. The purification process for continuous production of high-purity 7N-grade ammonia using industrial-grade ammonia according to claim 2, characterized in that: The reflux ratio of the No. 1 distillation column is controlled at 5~500, and the pressure at the top of the column is controlled at 0.1~1.5MPa.

4. The purification process for continuous production of high-purity 7N-grade ammonia using industrial-grade ammonia according to claim 3, characterized in that: The built-in condenser is set to a temperature of 5~45℃.

5. The purification process for continuous production of high-purity 7N-grade ammonia using industrial-grade ammonia according to claim 1, characterized in that: The temperature of the No. 2 distillation column is controlled at 10~60℃, the pressure at 0.5~1.5MPa, and the reflux ratio at 10~1000.

6. A purification system used in the purification process according to any one of claims 1-5, characterized in that: The system includes a No. 1 distillation column (3), a No. 2 distillation column (14), an energy converter (6), a fixed-bed reactor A (11), and a fixed-bed reactor B (12). The No. 1 distillation column (3) has an internal condenser (8) at its top. The top pipe of the No. 1 distillation column (3) is connected to the energy converter (6). After heat exchange, the condenser pipe circulates to the top of the No. 1 distillation column (3). The gas phase outlet pipe of the energy converter (6) is connected to the No. 1 reboiler (4). The liquid phase outlet pipe of the No. 1 distillation column (3) is connected to the evaporator (9). The evaporator (9) is connected to the inlet pipes of the fixed-bed reactor A (11) and the fixed-bed reactor B (12). The outlet pipe then passes through the evaporator (9) and connects to the middle of the No. 2 distillation column (14).

7. The purification system used in the purification process according to claim 6, characterized in that: The top pipeline of the 2# distillation column (14) is connected to the middle pipeline of the 1# distillation column (3). The bottom of the 2# distillation column (14) is equipped with a 2# reboiler (16). The bottom pipeline of the 2# distillation column (14) is connected to the middle pipeline of the 1# distillation column (3). The outlet pipeline of the 2# distillation column (14) is connected to the product tank (17). The top of the 2# distillation column (14) is equipped with a 2# condenser (15).

8. The purification system used in the purification process according to claim 6, characterized in that: The built-in condenser (8) is a series finned condenser.

9. The purification system used in the purification process according to claim 6, characterized in that: The outer layer of the main body of the energy converter (6) is arranged as a shell (65) and an insulating shell (69) in sequence. The main body is provided with an annular cavity (62), and the inlet (61) is located in the annular cavity (62) on the main body. The inlet (61) is connected to the inner cavity of the energy converter (6). The inlet (61) divides the inner cavity of the main body of the energy converter (6) into two parts. One part is a cold air expansion port (64), and the other part of the inner cavity is provided with an adjustment structure (66). The inner wall of the main body is set as a spiral shape. The cold air expansion port (64) is a conical structure and is connected to the cold air extraction port (63) on the main body.

10. The purification system used in the purification process according to claim 9, characterized in that: A hot air outlet (67) is provided at the adjustment structure (66) end on the main body of the energy converter (6); a cold air outlet (68) is provided on the main body of the energy converter (6).

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