A process for producing high-purity ammonia by indirect heat pump distillation

Abstract

The present invention belongs to the field of ultra-pure ammonia purification and discloses a process for producing high-purity ammonia by indirect heat pump distillation. Industrial liquid ammonia feedstock enters a light component removal tower. After pressurized separation, liquid ammonia containing heavy components is extracted from the bottom of the tower and enters the product tower through a pressure difference. Qualified ultra-pure ammonia product is extracted from the side line of the product tower. The refrigerant channel of the compressor is a closed cycle. After being compressed by the compressor, the refrigerant enters an oil separator for separation. The gaseous refrigerant exchanges heat with the light component removal tower reboiler and the product tower reboiler, condensing the refrigerant into a liquid state. The liquid refrigerant enters a refrigerant storage tank. The liquid refrigerant exchanges heat with the light component removal tower condenser and the product tower condenser respectively. The gaseous refrigerant returns to the compressor for pressurization, completing the closed cycle. The present invention adopts distillation technology and refrigeration heat coupling technology to simplify the process flow and solve the problem of excessive impurities in the ultra-pure ammonia product and the high energy consumption during the ultra-pure ammonia separation process.

Description

Technical Field

[0001] The present invention belongs to the field of ultrapure ammonia purification, and in particular relates to a process for producing high-purity ammonia by indirect heat pump distillation. Background Art

[0002] Electronic-grade ultra-pure ammonia refers to ammonia with a purity of ≥99.99999% (7N). Ultra-pure ammonia has a wide range of applications. In the field of optoelectronic materials, ultra-pure ammonia is an important basic material for the preparation of GaN (gallium nitride) using new vapor phase epitaxial growth technology, and is widely used in scenarios such as LEDs, liquid crystal panels, radio frequency amplifiers, and power devices. In the chemical industry, ultra-pure ammonia is the basic material for the preparation of nitrogen trifluoride and silicon nitride, and is mainly used in scenarios such as metallurgy, machinery manufacturing, and industrial valves. In addition, ultra-pure ammonia has great application prospects in the fields of semiconductors, photovoltaic cells, integrated circuits, etc.

[0003] Electronic-grade ultra-pure ammonia has extremely high purity and is more difficult to produce. Currently, the production of electronic-grade ultra-pure ammonia is mainly completed using distillation equipment and adsorption equipment. The distillation process mostly uses hot water or steam as the reboiler heat source and cold water as the condenser cooling source. The adsorption process has low product yield, high production energy consumption, and unstable product purity.

[0004] In recent years, driven by the rapid development of industries such as semiconductors and LEDs, the market demand for ultra-pure ammonia, a type of specialty gas with good performance and high purity, has continued to increase, and its output has continued to rise. Finding a process method with low energy consumption and high product purity has become a top priority. Summary of the Invention

[0005] The object of the present invention is to overcome the shortcomings of the prior art and provide a process for producing high-purity ammonia by indirect heat pump distillation. The process adopts distillation technology and refrigeration heat coupling technology to simplify the process flow, reduce equipment investment, and solve the problems of excessive impurities in the ultra-pure ammonia product and high energy consumption during the ultra-pure ammonia separation process.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] On one hand, the present invention discloses a process for producing high-purity ammonia by indirect heat pump distillation. Industrial liquid ammonia raw material enters the upper part of a light component removal tower, the tower top pressure is controlled at 0.5 MPa to 2.2 MPa, and the tower top temperature is controlled at -35°C to 50°C. After pressurized separation, the light components gather at the tower top. The top gas phase is condensed in the light component removal tower condenser, and the liquid phase refluxes into the distillation tower. The condensed non-condensable gas is extracted from the tower top; liquid ammonia containing heavy components is extracted from the tower bottom and enters the product tower through the pressure difference.

[0008] The pressure at the top of the product tower is controlled at 0.5Mpa to 2.2Mpa, and the temperature at the top is controlled at -30°C to 50°C. After pressurized separation, the top of the tower is further treated to remove light components brought by the light component removal tower kettle, and heavy components including water, oil, and metal ions are removed from the kettle. The gas phase at the top of the product tower is condensed in the product tower condenser, and the liquid phase refluxes back into the tower. The condensed non-condensable gas is extracted from the top of the tower. Qualified ultra-pure ammonia product is extracted from the side line of the product tower. The liquid ammonia containing water, oil, and heavy metals in the kettle enters the industrial ammonia recovery system through the pressure difference.

[0009] The refrigerant channel of the compressor is a closed cycle. After the refrigerant is compressed by the compressor, the pressure rises to 1.0Mpa~2.2Mpa, and the exhaust temperature is 60℃~105℃. It enters the oil separator for separation. The gaseous refrigerant exchanges heat with the light component removal tower reboiler and the product tower reboiler. The refrigerant is condensed to 10~80℃ and becomes liquid. The liquid refrigerant enters the refrigerant storage tank. After the liquid refrigerant is throttled by the first throttle valve and the second throttle valve, it exchanges heat with the light component removal tower condenser and the product tower condenser respectively. The gaseous refrigerant returns to the compressor for pressurization to complete the closed cycle.

[0010] Furthermore, the light component removal tower and the product tower both adopt internal reflux for reflux.

[0011] Furthermore, the light component removal tower reboiler adopts gaseous refrigerant as a heat source, the temperature of the gaseous refrigerant entering the light component removal tower reboiler is 60°C ~ 105°C, preferably 70°C ~ 92°C, and the temperature of the gaseous refrigerant leaving the light component removal tower reboiler is 10°C ~ 80°C, preferably 15°C ~ 60°C; the product tower reboiler adopts gaseous refrigerant as a heat source, the temperature of the gaseous refrigerant entering the product tower reboiler is 60°C ~ 105°C, preferably 70°C ~ 92°C, and the temperature of the gaseous refrigerant leaving the product tower reboiler is 10°C ~ 80°C, preferably 15°C ~ 60°C.

[0012] Furthermore, the light component removal tower condenser uses liquid refrigerant as a cold source, and the temperature of the liquid refrigerant entering the light component removal tower condenser is between -40°C and 30°C; the product tower condenser uses liquid refrigerant as a cold source, and the temperature of the liquid refrigerant entering the product tower condenser is between -40°C and 30°C.

[0013] Furthermore, the compressor is a screw compressor, a piston compressor or a centrifugal compressor.

[0014] Furthermore, the refrigerant is R290, R717, R507, R134A, R22 or R404A, and the refrigeration temperature range is -40°C to 30°C.

[0015] On the other hand, the present invention discloses a production process system for realizing an indirect heat pump distillation method for producing high-purity ammonia, comprising a light component removal tower, a product tower, a compressor, an oil separator, and a refrigerant storage tank; the light component removal tower has a liquid ammonia raw material inlet, a light component extraction port at the top of the tower, a liquid ammonia extraction port at the bottom of the tower, a light component removal tower condenser at the top of the light component removal tower, a light component removal tower reboiler at the bottom of the tower, and the liquid ammonia extraction port at the bottom of the light component removal tower is connected to the inlet of the product tower through a pipeline; the product tower is provided with a product tower condenser at the top of the tower, a product tower reboiler at the bottom of the tower, a light component extraction port at the top of the product tower, an ultra-pure ammonia product extraction port at the side line, and a heavy component extraction port at the bottom of the tower. outlet; the outlet of the compressor is connected to the oil separator through a pipeline, the oil outlet of the oil separator is connected to the reflux port of the compressor through a pipeline, the gas phase outlet pipeline of the oil separator is divided into two paths, one path is connected to the shell side inlet of the light component removal tower reboiler, and the other path is connected to the shell side inlet of the product tower reboiler, the shell side outlet of the light component removal tower reboiler and the shell side outlet of the product tower reboiler are both connected to the inlet of the refrigerant storage tank through a pipeline, the outlet pipeline of the refrigerant storage tank is divided into two paths, one path is connected to the inlet of the light component removal tower condenser, and the other path is connected to the inlet of the product tower condenser, and the outlets of the light component removal tower condenser and the product tower condenser are both connected to the inlet of the compressor through a pipeline.

[0016] Furthermore, a first throttle valve and a second throttle valve are respectively provided on the inlet pipelines of the light component removal tower condenser and the product tower condenser.

[0017] Furthermore, the bottom extraction pipeline of the light component removal tower (4) is connected to the tube side inlet of the light component removal tower reboiler (6), and the tube side outlet of the light component removal tower reboiler (6) is connected to the bottom reflux port of the light component removal tower (4) through a pipeline.

[0018] Furthermore, the bottom extraction pipeline of the product tower (8) is connected to the tube side inlet of the product tower reboiler (10), and the tube side outlet of the product tower reboiler (10) is connected to the bottom reflux port of the product tower (8) through a pipeline.

[0019] In existing solutions, the condensers of the light component removal tower and product tower are cooled with low-temperature water, while the reboilers are heated using thermal oil, electric heaters, hot water, steam, and other methods. This effectively inefficiently utilizes the low-temperature energy in the tower kettle, resulting in energy waste and high energy consumption. The low-temperature refrigerant is generated by a refrigeration unit that uses circulating water for direct cooling, resulting in waste of low-grade waste heat and increased consumption of circulating water. The adsorption process for producing ultra-pure ammonia suffers from low product yields, high energy consumption, and unstable product purity.

[0020] The present invention removes light components in two steps, namely, a light component removal tower and a product tower, thereby ensuring that the light component content in the product does not exceed the standard. The product is extracted from the side line of the distillation section of the product tower, thereby ensuring that the heavy components and metal ions in the ammonia product do not exceed the standard.

[0021] The light component removal tower and the product tower of the present invention both adopt an internal reflux mode, which saves a reflux pump and a reflux tank, simplifies the process, saves investment, and avoids external pollution caused by too many external devices.

[0022] This invention uses the high-temperature, high-pressure gaseous refrigerant at the compressor outlet as a heat source to provide heat for the light component removal tower reboiler and the product tower reboiler. Simultaneously, the gaseous refrigerant itself is condensed into a high-pressure liquid, which is then throttled to provide cooling for the light component removal tower condenser and the product tower condenser. This saves energy such as circulating water, gas, electricity, and steam.

[0023] The present invention optimizes the heat exchange network and combines the compressor with the distillation system to achieve combined cooling and heating, thereby achieving the purpose of energy saving and consumption reduction.

[0024] The advantages and positive effects of the present invention are:

[0025] 1. The present invention adopts a two-step light component removal tower and a product tower to remove light components, ensuring that the light component content in the product does not exceed the standard, and the ammonia product is produced by the side line to ensure that the heavy components and metal ions in the product do not exceed the standard.

[0026] 2. This process optimizes the heat exchange network and combines the compressor system with the distillation system to achieve co-generation of heat and cold. Low-grade heat is fully utilized, and the cooling capacity of the tower kettle is recovered. This not only saves the consumption of circulating water, but also saves the steam and electricity consumption of the entire device, achieving the purpose of energy saving and consumption reduction.

[0027] 3. The present invention has low energy consumption, reasonable design, high product purity and low investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of the process for producing high-purity ammonia by indirect heat pump distillation according to the present invention;

[0029] 1-compressor; 2-oil separator; 3-first throttle valve; 4-light component removal tower; 5-light component removal tower condenser; 6-light component removal tower reboiler; 7-second throttle valve; 8-product tower; 9-product tower condenser; 10-product tower reboiler; 11-refrigeration tank. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the scope of protection of the present invention cannot be limited thereto.

[0031] Example 1

[0032] A high-purity ammonia production process system for realizing an indirect heat pump distillation process for producing high-purity ammonia includes a light component removal tower 4, a product tower 8, a compressor 1, an oil separator 2, and a refrigerant storage tank 11.

[0033] The light component removal tower 4 has a liquid ammonia raw material inlet, a light component extraction port at the top of the tower, and a liquid ammonia extraction port at the bottom of the tower. A light component removal tower condenser 5 is provided at the top of the light component removal tower 4, and a light component removal tower reboiler 6 is provided at the bottom of the tower. The bottom extraction pipeline of the light component removal tower 4 is connected to the tube-side inlet of the light component removal tower reboiler 6, and the tube-side outlet of the light component removal tower reboiler 6 is connected to the bottom reflux port of the light component removal tower 4 through a pipeline. The heavy component extraction port at the bottom of the light component removal tower 4 is connected to the inlet of the product tower 8 through a pipeline.

[0034] Product tower 8 has a light component extraction outlet at the top, an ultrapure ammonia product extraction outlet at the side line, and a heavy component extraction outlet at the bottom. Product tower 8 is equipped with a product tower condenser 9 at the top and a product tower reboiler 10 at the bottom. The bottom extraction pipeline of product tower 8 is connected to the tube-side inlet of product tower reboiler 10, and the tube-side outlet of product tower reboiler 10 is connected to the bottom reflux port of product tower 8 via a pipeline.

[0035] The compressor 1 is a screw compressor, a piston compressor, or a centrifugal compressor. The outlet of the compressor 1 is connected to the oil separator 2 via a pipeline. The oil outlet of the oil separator 2 is connected to the reflux port of the compressor 1 via a pipeline. The gas phase outlet pipeline of the oil separator 2 is divided into two routes, one route is connected to the shell-side inlet of the light component removal tower reboiler 6, and the other route is connected to the shell-side inlet of the product tower reboiler 10. The shell-side outlet of the light component removal tower reboiler 6 and the shell-side outlet of the product tower reboiler 10 are both connected to the inlet of the refrigerant storage tank 11 via pipelines. The outlet pipeline of the refrigerant storage tank 11 is divided into two routes, one route is connected to the inlet of the light component removal tower condenser 5 after passing through the first throttle valve 3, and the other route is connected to the inlet of the product tower condenser 9 after passing through the second throttle valve 7. The outlets of the light component removal tower condenser 5 and the product tower condenser 9 are both connected to the inlet of the compressor 1 via pipelines.

[0036] Example 2

[0037] like Figure 1The flow chart of the process method for producing high-purity ammonia by indirect heat pump distillation is shown. A process method for producing high-purity ammonia by indirect heat pump distillation is shown. Industrial liquid ammonia raw material (containing impurities such as N2, H2, CH4, CO2, CO, H2O, etc.) enters the upper part of the light component removal tower 4, the tower top pressure is controlled at 0.5Mpa(G)~2.2Mpa(G), and the tower top temperature is controlled at -35℃~50℃. After pressurized separation, the light components gather at the top of the tower. After the top gas phase is condensed by the light component removal tower condenser 5, the liquid phase refluxes into the distillation tower, and the condensed non-condensable gas (containing N2, H2, CH4, CO2, CO, NH3, etc.) is extracted from the top of the tower; liquid ammonia containing heavy components is extracted from the bottom of the tower and enters the product tower 8 through the pressure difference.

[0038] Light component removal tower 4 is a packed distillation tower, divided into a rectifying section and a stripping section. It utilizes high-efficiency packing for separation, with a top temperature of -35°C to 50°C. The light component removal tower reboiler 6 uses the high-temperature, high-pressure vapor refrigerant discharged from compressor 1 as its heat source. The vapor refrigerant enters the reboiler 6 at a temperature between 70°C and 85°C, and exits the reboiler at a temperature between 30°C and 50°C. The light component removal tower condenser 5 uses liquid refrigerant as its cooling source, providing cooling for the tower top. The temperature of the liquid refrigerant entering the condenser is between -40°C and 30°C.

[0039] Liquid ammonia containing heavy components from the bottom of light component removal tower 4 enters product tower 8. The top pressure is controlled between 0.5 MPa(G) and 2.2 MPa(G), and the top temperature is controlled between -30°C and 50°C. After pressurized separation, the top of the tower undergoes further light component removal treatment to remove light components from the bottom of light component removal tower 4. Heavy components including water, oil, and metal ions are removed from the bottom of the tower. The gas phase at the top of product tower 8 is condensed in product tower condenser 9. The condensed liquid phase refluxes into the tower, and the condensed non-condensable gases (including N2, H2, etc.) are extracted from the top of the tower. Qualified ultra-pure ammonia product is extracted from the side line of product tower 8. The liquid ammonia containing water, oil, and heavy metals in the bottom of the tower enters the industrial ammonia recovery system through the pressure difference.

[0040] Product tower 8 is a packed distillation tower, divided into a rectifying section and a stripping section, and also uses high-efficiency packing for separation. Product tower reboiler 10 uses a vapor-phase refrigerant as a heat source to provide heat to the bottom of product tower 8. The temperature of the vapor-phase refrigerant entering the product tower reboiler 10 is between 70°C and 85°C, and the temperature of the vapor-phase refrigerant exiting the product tower reboiler 10 is between 30°C and 50°C. Product tower condenser 9 uses a liquid refrigerant as a cooling source, providing cooling to the tower top. The temperature of the liquid refrigerant entering the product tower condenser 9 is between -40°C and 25°C.

[0041] The refrigerant path of compressor 1 is a closed-loop system. After being compressed by compressor 1, the low-pressure refrigerant is raised to a pressure of 1.0 MPa(G) to 2.2 MPa(G), with an exhaust temperature of 75°C to 92°C. It then enters oil separator 2 for separation, and the lubricating oil returns to compressor 1. The gaseous refrigerant exchanges heat with the de-light component tower reboiler 6 and the product tower reboiler 10, condensing to a liquid temperature of 10-40°C before entering refrigerant storage tank 11. This reduces the circulating water required to condense the high-temperature gaseous refrigerant into a high-pressure liquid. After being throttled by the first throttle valve 3 and the second throttle valve 7, the liquid refrigerant exchanges heat with the de-light component tower condenser 5 and the product tower condenser 9, respectively, providing cooling capacity for these two towers. The gaseous refrigerant then returns to compressor 1 for pressurization, completing the closed-loop system.

[0042] The refrigerant is R290, R717, R507, R134A, R22 or R404A, and the refrigeration temperature range is -40℃~30℃.

[0043] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention.

Claims

1. A process for producing high-purity ammonia by indirect heat pump distillation, characterized in that: The industrial liquid ammonia raw material enters the upper part of the light component removal tower (4), the tower top pressure is controlled at 0.5MPa~2.2MPa, and the tower top temperature is controlled at -35℃~50℃. After pressurized separation, the light components gather at the tower top. The gas phase at the tower top is condensed by the light component removal tower condenser (5), and the liquid phase refluxes into the light component removal tower (4). The condensed non-condensable gas is extracted from the tower top; the liquid ammonia containing heavy components is extracted from the tower bottom and enters the product tower (8) through the pressure difference. The pressure at the top of the product tower (8) is controlled at 0.5MPa~2.2MPa, and the temperature at the top of the tower is controlled at -30℃~50℃. After pressurized separation, the top of the tower is further subjected to light component removal treatment to remove the light components brought by the bottom of the light component removal tower (4). The bottom of the tower removes heavy components including water, oil, and metal ions. The gas phase at the top of the product tower (8) is condensed by the product tower condenser (9), and the liquid phase flows back into the tower. The condensed non-condensable gas is extracted from the top of the tower. The qualified ultra-pure ammonia product is extracted from the side line of the product tower (8). The liquid ammonia containing water, oil, and heavy metals in the bottom of the tower enters the industrial ammonia recovery system through the pressure difference. The refrigerant channel of the compressor (1) is a closed cycle. After the refrigerant is compressed by the compressor (1), the pressure rises to 1.0MPa~2.2MPa, and the exhaust temperature is 60℃~105℃. It enters the oil separator (2) for separation. The gaseous refrigerant exchanges heat with the light component removal tower reboiler (6) and the product tower reboiler (10). The refrigerant is condensed to 10~80℃ and becomes liquid. The liquid refrigerant enters the refrigerant storage tank (11). After the liquid refrigerant is throttled by the first throttle valve (3) and the second throttle valve (7), it exchanges heat with the light component removal tower condenser (5) and the product tower condenser (9) respectively. The gaseous refrigerant returns to the compressor (1) for pressurization, completing the closed cycle.

2. The process for producing high-purity ammonia by indirect heat pump distillation according to claim 1, characterized in that: The light component removal tower (4) and the product tower (8) both adopt an internal reflux method for reflux.

3. The process for producing high-purity ammonia by indirect heat pump distillation according to claim 1, characterized in that: The light component removal tower reboiler (6) uses a gaseous refrigerant as a heat source, the temperature of the gaseous refrigerant entering the light component removal tower reboiler (6) is 60°C~105°C, and the temperature of the gaseous refrigerant leaving the light component removal tower reboiler (6) is 10°C~80°C; the product tower reboiler (10) uses a gaseous refrigerant as a heat source, the temperature of the gaseous refrigerant entering the product tower reboiler (10) is 60°C~105°C, and the temperature of the gaseous refrigerant leaving the product tower reboiler (10) is 10°C~80°C.

4. The process for producing high-purity ammonia by indirect heat pump distillation according to claim 1, characterized in that: The light component removal tower condenser (5) uses a liquid refrigerant as a cold source, and the temperature of the liquid refrigerant entering the light component removal tower condenser (5) is between -40°C and 30°C; the product tower condenser (9) uses a liquid refrigerant as a cold source, and the temperature of the liquid refrigerant entering the product tower condenser (9) is between -40°C and 30°C.

5. The process for producing high-purity ammonia by indirect heat pump distillation according to claim 1, characterized in that: The compressor (1) is a screw compressor, a piston compressor or a centrifugal compressor.

6. The process for producing high-purity ammonia by indirect heat pump distillation according to claim 1, characterized in that: The refrigerant is R290, R717, R507, R134A, R22 or R404A, and the refrigeration temperature range is -40°C to 30°C.

7. The production process system of the process for producing high-purity ammonia by indirect heat pump distillation according to any one of claims 1 to 6, characterized in that: The invention comprises a light component removal tower (4), a product tower (8), a compressor (1), an oil separator (2), and a refrigerant storage tank (11); the light component removal tower (4) has a liquid ammonia raw material inlet, a light component extraction outlet at the tower top, and a liquid ammonia extraction outlet at the tower bottom; a light component removal tower condenser (5) is provided at the tower top of the light component removal tower, a light component removal tower reboiler (6) is provided at the tower bottom, and a heavy component extraction outlet at the bottom of the light component removal tower (4) is connected to the inlet of the product tower (8) through a pipeline; the product tower (8) has a product tower condenser (9) at the tower top, a product tower reboiler (10) at the tower bottom, a light component extraction outlet at the tower top of the product tower (8), an ultra-pure ammonia product extraction outlet at the side line, and a heavy component extraction outlet at the tower bottom; the outlet of the compressor (1) is connected to the inlet of the product tower (8) through a pipeline An oil separator (2) is provided. The oil outlet of the oil separator (2) is connected to the reflux port of the compressor (1) through a pipeline. The gas phase outlet pipeline of the oil separator (2) is divided into two routes, one route is connected to the shell side inlet of the light component removal tower reboiler (6), and the other route is connected to the shell side inlet of the product tower reboiler (10). The shell side outlet of the light component removal tower reboiler (6) and the shell side outlet of the product tower reboiler (10) are both connected to the inlet of the refrigerant storage tank (11) through a pipeline. The outlet pipeline of the refrigerant storage tank (11) is divided into two routes, one route is connected to the inlet of the light component removal tower condenser (5), and the other route is connected to the inlet of the product tower condenser (9). The outlets of the light component removal tower condenser (5) and the product tower condenser (9) are both connected to the inlet of the compressor (1) through a pipeline.

8. The production process system according to claim 7, characterized in that: A first throttle valve (3) and a second throttle valve (7) are respectively provided on the inlet pipelines of the light component removal tower condenser (5) and the product tower condenser (9).

9. The production process system according to claim 8, characterized in that: The bottom extraction pipeline of the light component removal tower (4) is connected to the tube side inlet of the light component removal tower reboiler (6), and the tube side outlet of the light component removal tower reboiler (6) is connected to the bottom reflux port of the light component removal tower (4) through a pipeline.

10. The production process system according to claim 9, characterized in that: The bottom extraction pipeline of the product tower (8) is connected to the tube side inlet of the product tower reboiler (10), and the tube side outlet of the product tower reboiler (10) is connected to the bottom reflux port of the product tower (8) through a pipeline.

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