Ammonia refining device and method

Abstract

The invention discloses an ammonia refining device and method, and belongs to the technical field of sewage steam stripping. The ammonia refining device comprises a refining tower, a crystallizing tank, an adsorption tank, a cyclone separator, a variable-frequency refrigerator, a low-pressure liquid ammonia tank, a low-pressure liquid ammonia pump, a high-pressure liquid ammonia tank, a first heat exchanger, a third heat exchanger and a fourth heat exchanger which are sequentially connected, and gas ammonia discharged from the adsorption tank enters the variable-frequency refrigerator after carbon powder and water are removed through the cyclone separator; the liquid ammonia is directly converted into liquid ammonia after exchanging heat with a refrigerant medium of the cold variable-frequency freezer, the liquid ammonia enters the low-pressure liquid ammonia tank to be temporarily stored, the liquid ammonia in the low-pressure liquid ammonia tank is sequentially pumped into the first heat exchanger, the second heat exchanger, the third heat exchanger and the fourth heat exchanger through the low-pressure liquid ammonia pump to be subjected to heat exchange, then the temperature and the pressure are increased, and the liquid ammonia enters the high-pressure liquid ammonia tank to be safely stored. The process flow is short, the energy consumption is low, the system operation is safe and reliable, and the purity of the recovered liquid ammonia is high.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonia refining, and in particular to an ammonia refining device and method. Background Art

[0002] With the improvement of crude oil processing depth, especially the increase in the processing ratio of high-sulfur crude oil, the amount of wastewater generated by refining equipment and the pollutant content in the wastewater continue to increase. In order to meet the requirements of environmental protection and motor vehicle pollutant emission standards, refineries are generally equipped with sour water stripping equipment and ammonia refining equipment to treat sour water. The crude ammonia gas extracted from the side line of the sour water stripping equipment is condensed for three times and the ammonia concentration reaches 97%. It enters the ammonia refining equipment, where it is desulfurized and compressed to obtain industrial ammonia.

[0003] The ammonia refining device mainly includes a refining tower, a crystallizer and an adsorption tank connected in sequence. The crude ammonia from the stripping device first enters the refining tower to reduce the content of hydrogen sulfide and water, and then enters the crystallizer and the adsorption tank in sequence to further remove the sulfide and purify; the refined ammonia from the adsorption tank is mainly liquefied by the following two processes. In the early stage, the ammonia compressor was used for liquefaction. The ammonia compressor was damaged frequently, the ammonia refining system operated poorly, and accidents often occurred; later, the ammonia distillation process was used to produce liquid ammonia. This process is safer than the ammonia compression process, and the system operates well, but the ammonia distillation process still has the following problems:

[0004] 1. The energy consumption is high, and the water content of the obtained liquid ammonia is also high;

[0005] 2. Both the refining tower and the crystallization tank need to use recycled liquid ammonia to spray and cool the gas ammonia at the inlet to reach the process temperature required for washing and crystallization, thereby reducing the ammonia recovery rate;

[0006] 3. The refining tower and crystallization tank use liquid ammonia gasification for cooling, the washing temperature control is unstable, and the desulfurization effect is poor. Summary of the invention

[0007] In order to solve the above problems, the present invention provides an ammonia refining device and method.

[0008] The technical solution adopted by the present invention is:

[0009] An ammonia refining device comprises a refining tower, a crystallization tank, an adsorption tank, a cyclone separator, a variable frequency refrigerator, a low-pressure liquid ammonia tank, a low-pressure liquid ammonia pump, a high-pressure liquid ammonia tank, a first heat exchanger, a third heat exchanger and a fourth heat exchanger connected in sequence.

[0010] The first heat exchanger is arranged at the bottom of the crystallizer, and comprises a heat exchange tube A, and the heat exchange tube A is used to cool the concentrated ammonia water at the bottom of the crystallizer;

[0011] The third heat exchanger is arranged at the bottom of the refining tower, and includes a heat exchange tube C, and the heat exchange tube C is used to cool the concentrated ammonia water at the bottom of the refining tower;

[0012] The inlet of the cyclone separator is connected to the top outlet of the adsorption tank, the top air outlet of the cyclone separator is connected to the inlet of the variable frequency refrigerator, and the outlet of the variable frequency refrigerator is connected to the inlet of the low-pressure liquid ammonia tank; the inlet of the low-pressure liquid ammonia pump is connected to the low-pressure liquid ammonia tank, the outlet of the low-pressure liquid ammonia pump is connected to the inlet of the heat exchange tube A, the outlet of the heat exchange tube A is connected to the inlet of the heat exchange tube C, the outlet of the heat exchange tube C is connected to the cold medium inlet of the fourth heat exchanger, and the cold medium outlet of the fourth heat exchanger is connected to the inlet of the high-pressure liquid ammonia tank.

[0013] By adopting the above technical scheme, the gaseous ammonia coming out of the adsorption tank passes through a cyclone separator to remove carbon powder and moisture, then enters the variable frequency refrigerator, exchanges heat with the refrigerant medium of the variable frequency refrigerator, and is converted into liquid ammonia, which is then stored in a low-pressure liquid ammonia tank; the liquid ammonia in the low-pressure liquid ammonia tank is pumped into the first heat exchanger, the third heat exchanger and the fourth heat exchanger in sequence by a low-pressure liquid ammonia pump, and the temperature and pressure are increased after heat exchange, and then the liquid ammonia is stored in a high-pressure liquid ammonia tank.

[0014] The ammonia refining process does not use a distillation tower, the process is simple, and energy consumption is greatly reduced; the refrigerant circulates in a closed loop in the refrigerator and does not come into direct contact with ammonia, avoiding compressor failure caused by liquid in the process medium (ammonia) and ensuring the safe operation of the system. Ammonia does not come into direct contact with the compressor, and the recovered liquid ammonia does not contain oil, and the purity is improved. The use of a cyclone separator can separate carbon powder and water from ammonia, improving the quality of recovered liquid ammonia.

[0015] Under the conditions of a pressure of 1.3MPa and a temperature of about 37°C, liquid ammonia can be stably stored in a liquid state and cooled to a low-temperature liquid ammonia of about -16°C by a variable frequency refrigerator. There is a temperature difference of 53°C from -16°C to 37°C. This part of the cold energy can be fully utilized to cool the crystallizer and the refining tower through three-stage heat exchange. The remaining part of the cold energy is exchanged with purified water to achieve cold energy recycling, further reduce the energy consumption of the ammonia production process, reduce the ammonia loss caused by the cooling of the liquid ammonia, and improve the ammonia recovery rate; and through indirect heat exchange cooling, the temperature of the outlet gas ammonia is easy to control, the temperature fluctuation range is small, and the desulfurization effect is improved.

[0016] Furthermore, it also includes a second heat exchanger, which is arranged at the bottom of the refining tower and above the third heat exchanger, and includes a heat exchanger shell. The bottom of the heat exchanger shell is provided with an ammonia inlet, the top is provided with an ammonia outlet, and the middle is provided with a heat exchange tube B. The heat exchange tube B is used to cool the ammonia entering the refining tower, and its inlet is connected to the outlet of the heat exchange tube C, and the outlet is connected to the cold medium inlet of the fourth heat exchanger.

[0017] The second heat exchanger is used to cool the gaseous ammonia entering the refining tower, and the third heat exchanger is used to cool the concentrated ammonia water at the bottom of the refining tower, which is conducive to better adjusting the outlet temperature of the refining tower and improving the desulfurization effect; and the temperature of the liquid ammonia entering the second heat exchanger can be appropriately increased to reduce crystallization on the surface of the heat exchanger.

[0018] Furthermore, the heat exchange tube B is a finned heat exchange tube, which improves the heat exchange efficiency of the heat exchanger.

[0019] Furthermore, a gas distributor is provided at the bottom of the heat exchanger shell, and the gas distributor is located between the ammonia inlet and the heat exchange tube B. The distribution uniformity of the inlet gas ammonia is improved, and the desulfurization effect of the refining tower is improved.

[0020] Furthermore, the inlet and outlet of heat exchange tube A are connected through connecting pipe A, and temperature regulating valve A is provided on connecting pipe A; the inlet of heat exchange tube C and the outlet of heat exchange tube B are connected through connecting pipe B, and temperature regulating valve B is provided on connecting pipe B.

[0021] By adopting the above technical solution, the flow rate of gas ammonia entering the refining tower and the crystallization tank can be adjusted by the temperature regulating valve, thereby controlling the temperature of gas ammonia at the outlet of the refining tower and the crystallization tank to ensure the desulfurization effect.

[0022] Furthermore, a branch is provided on the refining tower circulation pipeline, a circulating ammonia water spray pipe is provided above the second heat exchanger, the circulating ammonia water spray pipe is connected to the branch of the refining tower circulation pipeline, a flow regulating valve is provided on the branch, a drain pipe is provided at the bottom of the refining tower, and the drain pipe is connected to the raw wastewater tank.

[0023] By adopting the above technical solution, the concentrated ammonia water with a flow rate of no more than 10% of the circulation volume of the refining tower is controlled by the liquid level regulating valve to enter the second heat exchanger and spray the finned heat exchange tubes, thereby dissolving the ammonium hydrogen sulfide crystallized on the finned heat exchange tubes due to low temperature, ensuring that the heat exchanger has a high heat exchange efficiency. After the water in the gaseous ammonia is condensed, the liquid level at the bottom of the tower will gradually rise, and the washed hydrogen sulfide reactant will be sent to the raw material wastewater tank together with the concentrated ammonia water at the bottom of the tower through the drain pipe.

[0024] Furthermore, the high-pressure liquid ammonia tank is provided with a first liquid ammonia outlet and a second liquid ammonia outlet, the first liquid ammonia outlet is connected to the liquid ammonia delivery pump, the second liquid ammonia outlet is connected to the refining tower ammonia feed port and the crystallizer ammonia feed port through the first ammonia feed pipeline and the second ammonia feed pipeline respectively, the refining tower ammonia feed port is located above the second heat exchanger, and the crystallizer ammonia feed port is connected to the crystallizer gas ammonia inlet pipeline.

[0025] By adopting the above technical scheme, if the temperature of the top outlet ammonia gas still cannot be reduced to the process requirements after the heat exchange of the refining tower and the crystallization tank is completed, liquid ammonia can be added through the ammonia replenishment pipeline, and the liquid ammonia can be gasified and cooled, thereby further ensuring the desulfurization effect of the refining tower and the crystallization tank.

[0026] Furthermore, an ammonia replenishment regulating valve A and an ammonia replenishment regulating valve B are respectively provided on the first ammonia replenishment pipeline and the second ammonia replenishment pipeline.

[0027] By adopting the above technical solution, the flow rate of added liquid ammonia can be controlled by the ammonia feed regulating valve, so as to better control the process temperature of the refining tower and the crystallization tank.

[0028] Furthermore, non-condensable steam discharge ports are provided on the tops of the low-pressure liquid ammonia tank and the high-pressure liquid ammonia tank. The non-condensable steam discharge ports are connected to the slag discharge pipeline at the bottom of the cyclone separator through a pipeline. The slag discharge pipeline is connected to a sewage tank, and the sewage tank is connected to the raw wastewater tank through a sewage pump.

[0029] The above technical solution is adopted to ensure the safe storage of liquid ammonia, reduce waste gas emissions and protect the environment.

[0030] A method for refining ammonia using any one of the above-mentioned ammonia refining devices comprises the following steps:

[0031] (1) The gaseous ammonia with a temperature of 0±3℃ coming out of the adsorption tank passes through a cyclone separator to remove carbon powder and water, and then enters a variable frequency refrigerator to cool down to -19℃~-13℃, and is converted into liquid ammonia and temporarily stored in a low-pressure liquid ammonia tank;

[0032] (2) Liquid ammonia at a temperature of -19°C to -13°C is first pumped from a low-pressure liquid ammonia tank into the first heat exchanger in the crystallizer to exchange heat with concentrated ammonia water at the bottom of the crystallizer. After the heat exchange is completed, the ammonia gas at the outlet of the crystallizer drops to -5±3°C, and the liquid ammonia is heated to -14±3°C;

[0033] (3) Liquid ammonia at a temperature of -14±3°C enters the third heat exchanger of the refining tower and exchanges heat with the concentrated ammonia water at the bottom of the refining tower. After the heat exchange is completed, it enters the second heat exchanger and exchanges heat with the 40±5°C gaseous ammonia entering the refining tower. After the heat exchange is completed, the gaseous ammonia at the outlet of the refining tower drops to 0±3°C, and the liquid ammonia is heated to 30±5°C.

[0034] (4) Liquid ammonia at a temperature of 30±5°C enters the fourth heat exchanger and exchanges heat with purified water at a temperature of 45±5°C in the fourth heat exchanger. After the heat exchange is completed, the temperature of the liquid ammonia rises to 37±2°C and the pressure rises to 1.3±0.1MPa, and then enters the high-pressure liquid ammonia tank for storage.

[0035] By adopting the above technical solution, the cooling capacity of liquid ammonia can be fully utilized, the energy consumption of the ammonia production process can be reduced, and the desulfurization effect can be improved.

[0036] The beneficial effects of the present invention include short process flow, low energy consumption, safe and reliable system operation, and high purity of recovered liquid ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a structural diagram of the ammonia refining device of the present invention.

[0038] Figure 2 This is a structural diagram of the second heat exchanger of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clear, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and a preferred implementation manner.

[0040] See also Figure 1 and Figure 2 The present invention provides an ammonia refining device, including a refining tower 1, a crystallization tank 2, an adsorption tank 3, a cyclone separator 4, a variable frequency refrigerator 5, a low-pressure liquid ammonia tank 6, a low-pressure liquid ammonia pump 7, a high-pressure liquid ammonia tank 8, a liquid ammonia delivery pump 9, a refining tower circulation pump 10, a first heat exchanger 11, a second heat exchanger 12, a third heat exchanger 13, a fourth heat exchanger 14, a sewage tank 15 and a sewage pump 16.

[0041] A refining tower 1, a crystallizer 2, and an adsorption tank 3 are connected in sequence, and three-stage desulfurization is performed on the ammonia gas from the sewage stripping device after three-stage condensation and cooling. The desulfurization process is a prior art; that is, the three-stage gas ammonia first enters the lower part of the refining tower 1, and the refining tower circulating pump 10 pumps the concentrated ammonia water at the bottom of the refining tower to the top of the refining tower as a washing agent, and the gas ammonia contacts with it in countercurrent to wash and remove most of the hydrogen sulfide and water in the gas ammonia; the washed sulfur-containing gas ammonia enters the bottom of the crystallizer 2, is evenly dispersed into the liquid ammonia in the crystallizer through a distributor, and is fully contacted with the liquid ammonia to exchange substances, and ammonia reacts with hydrogen sulfide at low temperature to generate ammonium hydrogen sulfide, and most of the hydrogen sulfide is fixed in the liquid phase and removed; the gas ammonia containing a small amount of hydrogen sulfide from the crystallizer 2 enters the adsorption tank 3, and the hydrogen sulfide, water, phenol, oil and other impurities in the ammonia gas are adsorbed by an activated carbon adsorbent.

[0042] The existing process is that the ammonia gas coming out of the adsorption tank enters the compressor, is compressed and condensed into liquid ammonia for storage; or enters the distillation tower, is pressurized and distilled by the distillation tower, and high-pressure gas ammonia is obtained at the top of the tower. The gas ammonia is cooled by a cooler to obtain high-purity liquid ammonia.

[0043] The inventors found that in actual operation, the purity of ammonia gas coming out of the adsorption tank can reach more than 99.7%, and the hydrogen sulfide content is less than 10ppm, which meets the industrial liquid ammonia use standard. Therefore, a method is proposed in this embodiment, which eliminates the distillation process, adds a cyclone separator 4, a variable frequency refrigerator 5, a low-pressure liquid ammonia tank 6, a low-pressure liquid ammonia pump 7 and a high-pressure liquid ammonia tank 8 behind the adsorption tank, and adds a second heat exchanger 12 and a third heat exchanger 13 in the refining tower 1, adds a first heat exchanger 11 in the crystallization tank 2, and adds a fourth heat exchanger 14 on the inlet pipeline of the high-pressure liquid ammonia tank 8;

[0044] The inlet of the cyclone separator 4 is connected to the top outlet of the adsorption tank 3 through a pipeline, the top air outlet of the cyclone separator 4 is connected to the inlet of the variable frequency refrigerator 5 through a pipeline, and the outlet of the variable frequency refrigerator 5 is connected to the inlet of the low-pressure liquid ammonia tank 6 through a pipeline; the inlet of the low-pressure liquid ammonia pump 7 is connected to the low-pressure liquid ammonia tank 6, and the outlet of the low-pressure liquid ammonia pump 7 is connected to the inlet and outlet of the first heat exchanger 11, the second heat exchanger 12, the third heat exchanger 13 and the fourth heat exchanger 14 in sequence through a pipeline, and the outlet of the fourth heat exchanger 14 is connected to the inlet of the high-pressure liquid ammonia tank 8 through a pipeline.

[0045] Through the above improvements, the gaseous ammonia coming out of the adsorption tank passes through the cyclone separator 4 to remove carbon powder and moisture, and then enters the variable frequency refrigerator 6. After exchanging heat with the refrigerant medium of the cold variable frequency refrigerator 6, it is directly converted into liquid ammonia and enters the low-pressure liquid ammonia tank 6 for temporary storage. The liquid ammonia in the low-pressure liquid ammonia tank 6 is pumped into the first heat exchanger 11, the second heat exchanger 12, the third heat exchanger 13 and the fourth heat exchanger 14 in sequence through the low-pressure liquid ammonia pump 7. After heat exchange, the temperature and pressure increase, and then enter the high-pressure liquid ammonia tank 8 for safe storage.

[0046] The improved ammonia refining process does not use a distillation tower, the process is simple, and the energy consumption is greatly reduced; a variable frequency refrigerator is used to cool the gaseous ammonia, and the refrigerant circulates in a closed loop in the refrigerator without direct contact with the ammonia gas, avoiding compressor failure caused by liquid in the process medium (ammonia gas) and ensuring the safe operation of the system. Through the three-stage heat exchange, the coldness of the liquid ammonia in the low-pressure liquid ammonia tank 6 can be fully utilized to cool the crystallizer and the refining tower, and the remaining coldness is exchanged with purified water. On the one hand, the coldness is reused and the energy consumption of the ammonia production process is reduced. On the other hand, it also reduces the ammonia loss caused by the cooling of the liquid ammonia in the existing process, and improves the ammonia recovery rate.

[0047] In specific implementation, the first heat exchanger 11 is arranged at the bottom of the crystallizer 2, including a heat exchange tube A, preferably a coil, and both ends of the coil extend from the side wall of the crystallizer 2 to form an inlet and outlet of the heat exchange medium, and the inlet is located above the outlet. The inlet and the outlet are connected by a connecting pipe A, and a thermostatic valve A is provided on the connecting pipe A; the thermostatic valve A adjusts the flow rate of gas ammonia entering the crystallizer, thereby controlling the temperature of gas ammonia at the outlet of the crystallizer to ensure the desulfurization effect. The low-pressure liquid ammonia pump 8 is arranged on the front side of the low-pressure liquid ammonia tank 6, and the inlet of the low-pressure liquid ammonia pump is connected to the low-pressure liquid ammonia tank 6 through a pipeline, and the outlet of the low-pressure liquid ammonia pump is connected to the inlet of the heat exchange tube A through a pipeline and a valve.

[0048] The second heat exchanger 12 and the third heat exchanger 13 are arranged at the bottom of the refining tower 1 and are located below the tower packing layer.

[0049] The third heat exchanger 13 includes a heat exchange tube C, and preferably the heat exchange tube A is a coil, both ends of the coil extend from the side wall of the crystallization tank 2 to form an inlet and outlet of the heat exchange medium, and the inlet is located below the outlet.

[0050] The second heat exchanger 12 includes a square shell 121, an ammonia inlet 122 is provided at the bottom of the shell 121, a lower cap is provided above the ammonia inlet 122, and a gas distributor 125 is provided above the lower cap; a finned heat exchange tube B124 is provided in the middle of the shell, a spray pipe 126 is provided above the finned heat exchange tube B124, and an atomizing nozzle is installed on the spray pipe 126; an ammonia outlet 123 is provided at the top of the shell, and an upper cap is provided above the ammonia outlet 123. The lower cap and the upper cap are used to allow ammonia to pass through the shell 121, while ammonia water cannot enter the shell 121, which is conducive to improving the heat exchange effect of the second heat exchanger 12 and accurately controlling the temperature of the ammonia gas at the outlet of the refining tower.

[0051] The finned heat exchange tube B124 can be one group or multiple groups connected in series. Both ends of the finned heat exchange tube B124 extend from the side wall of the refining tower 1 to form an inlet and outlet for the heat exchange medium, and the inlet is located above the outlet.

[0052] The outlet of heat exchange tube A is connected with the inlet of heat exchange tube C through a pipeline, the outlet of heat exchange tube C is connected with the inlet of finned heat exchange tube B124 through a pipeline, the outlet of finned heat exchange tube B124 is connected with the inlet of heat exchange tube C through a connecting pipe B, and a thermostatic valve B is provided on the connecting pipe B; the thermostatic valve B adjusts the flow of low-temperature liquid ammonia entering the refining tower, thereby controlling the temperature of the gaseous ammonia at the outlet of the refining tower to ensure the desulfurization effect.

[0053] The outlet of the heat exchange tube B124 is connected to the cold medium inlet of the fourth heat exchanger 14 through a pipeline, and the cold medium outlet of the fourth heat exchanger 14 is connected to the inlet of the high-pressure liquid ammonia tank 8 through a pipeline; purified water is introduced into the hot medium inlet of the fourth heat exchanger 14, and the purified water is used to absorb the remaining cold of the liquid ammonia to ensure that the liquid ammonia is in a stable temperature state before entering the high-pressure liquid ammonia tank, thereby controlling the pressure of the high-pressure liquid ammonia tank. A temperature regulating valve is set on the purified water inlet pipeline, and the temperature regulating valve is adjusted according to the pressure of the high-pressure liquid ammonia tank. The control pressure can be slightly lower in winter and slightly higher in summer to ensure that the high-pressure liquid ammonia delivery pump will not be emptied.

[0054] In this embodiment, the high-pressure liquid ammonia tank 8 is provided with a first liquid ammonia outlet and a second liquid ammonia outlet, the first liquid ammonia outlet is connected to the liquid ammonia delivery pump 14, and the second liquid ammonia outlet is connected to the ammonia feed port of the refining tower 1 and the ammonia feed port of the crystallizer 2 respectively through the first ammonia feed pipeline and the second ammonia feed pipeline, the ammonia feed port of the refining tower is located above the second heat exchanger 12, and the ammonia feed port of the crystallizer is connected to the gas ammonia inlet pipeline of the crystallizer through a pipeline, and the first ammonia feed pipeline and the second ammonia feed pipeline are respectively provided with an ammonia feed regulating valve A and an ammonia feed regulating valve B.

[0055] If the temperature of the top outlet ammonia of the refining tower 1 and the crystallizer 2 cannot be reduced to the process requirements after the heat exchange is completed, liquid ammonia can be added through the ammonia supply pipeline, and the liquid ammonia can be gasified to reduce the temperature, thereby further ensuring the desulfurization effect of the refining tower 1 and the crystallizer 2. In addition, when the heat exchange tube leaks and needs to be shut down, or when there are specific processes such as the start-up and shutdown stages, liquid ammonia can be added to the refining tower and the crystallizer through the ammonia supply pipeline, and the liquid ammonia can be gasified to reduce the temperature.

[0056] In order to further improve the control effect, temperature controllers can also be installed on the outlet pipelines of the refining tower and the crystallization tank, so that the refining tower temperature controller is connected to the ammonia feed regulating valve A and the temperature regulating valve A respectively, and the crystallization tank temperature controller is connected to the ammonia feed regulating valve B and the ammonia feed regulating valve B respectively.

[0057] In this embodiment, the circulation pipeline of the refining tower 1 is provided with a branch, which is connected to the ammonia spray pipe of the second heat exchanger 12. The branch is provided with a flow regulating valve. A drain pipe is provided at the bottom of the refining tower 1, and the drain pipe is connected to the raw wastewater tank.

[0058] In this embodiment, non-condensable steam discharge ports are provided at the tops of the low-pressure liquid ammonia tank 6 and the high-pressure liquid ammonia tank 8. The non-condensable steam discharge ports are connected to the slag discharge pipeline at the bottom of the cyclone separator 4 through a pipeline. The slag discharge pipeline is connected to a sewage tank 15, and the sewage tank 15 is connected to the raw wastewater tank through a sewage pump 16.

[0059] The method for refining ammonia using the above-mentioned ammonia refining device comprises the following steps:

[0060] (1) The gaseous ammonia at a temperature of about 0°C coming out of the adsorption tank 3 passes through the cyclone separator 4 to remove carbon powder and water, and then enters the variable frequency refrigerator 5, where it is cooled to about -16°C and converted into liquid ammonia and temporarily stored in the low-pressure liquid ammonia tank 6;

[0061] (2) Liquid ammonia at a temperature of about -16°C is first pumped from the low-pressure liquid ammonia tank 6 into the crystallizer 2 to exchange heat with the concentrated ammonia water at the bottom of the crystallizer. After the heat exchange is completed, the ammonia gas at the outlet of the crystallizer 2 drops to about -5°C, and the liquid ammonia rises to about -14°C;

[0062] (3) Liquid ammonia at a temperature of about -14°C enters the refining tower 1 and exchanges heat with gaseous ammonia at a temperature of about 40°C at the inlet of the refining tower 1 entering the second heat exchanger 12. After the heat exchange is completed, the gaseous ammonia at the outlet of the refining tower 1 drops to about 0°C, and the temperature of the liquid ammonia rises to about 30°C;

[0063] (4) Liquid ammonia at a temperature of about 30°C enters the fourth heat exchanger 14 and exchanges heat with purified water at a temperature of about 45°C in the fourth heat exchanger 14. After the heat exchange is completed, the temperature of the liquid ammonia rises to about 37°C and the pressure rises to about 1.3 MPa, and then enters the high-pressure liquid ammonia tank 8 for storage.

[0064] Through the above process, the operating energy consumption of the ammonia refining device can be reduced by about 70%, and the purity of the liquid ammonia in the high-pressure liquid ammonia tank 8 can reach 99.7-99.8%, and the hydrogen sulfide content is 5-8ppm.

[0065] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications are also within the protection scope of the present invention.

Claims

1. An ammonia refining device, comprising a refining tower (1), a crystallization tank (2) and an adsorption tank (3) connected in sequence, characterized in that: It also includes a cyclone separator (4), a variable frequency refrigerator (5), a low-pressure liquid ammonia tank (6), a low-pressure liquid ammonia pump (7), a high-pressure liquid ammonia tank (8), a first heat exchanger (11), a third heat exchanger (13) and a fourth heat exchanger (14), The first heat exchanger (11) is arranged at the bottom of the crystallization tank (2), and comprises a heat exchange tube A, wherein the heat exchange tube A is used to cool the concentrated ammonia water at the bottom of the crystallization tank (2); The third heat exchanger (13) is arranged at the bottom of the refining tower (1), and comprises a heat exchange tube C, and the heat exchange tube C is used to cool the concentrated ammonia water at the bottom of the refining tower (1); The inlet of the cyclone separator (4) is connected to the top outlet of the adsorption tank (3), the top air outlet of the cyclone separator (4) is connected to the inlet of the variable frequency refrigerator (5), and the outlet of the variable frequency refrigerator (5) is connected to the inlet of the low-pressure liquid ammonia tank (6); the inlet of the low-pressure liquid ammonia pump (7) is connected to the low-pressure liquid ammonia tank (6), the outlet of the low-pressure liquid ammonia pump (7) is connected to the inlet of the heat exchange tube A, the outlet of the heat exchange tube A is connected to the inlet of the heat exchange tube C, the outlet of the heat exchange tube C is connected to the cold medium inlet of the fourth heat exchanger (14), and the cold medium outlet of the fourth heat exchanger (14) is connected to the inlet of the high-pressure liquid ammonia tank (8).

2. An ammonia refining device according to claim 1, characterized in that: The second heat exchanger (12) is arranged at the bottom of the refining tower (1) and above the third heat exchanger (13), and includes a heat exchanger shell (121). The bottom of the heat exchanger shell (121) is provided with an ammonia inlet (122), the top is provided with an ammonia outlet (123), and the middle is provided with a heat exchange pipe B (124). The heat exchange pipe B is used to cool the ammonia entering the refining tower, and its inlet is connected to the outlet of the cooling heat exchange pipe C, and the outlet is connected to the cold medium inlet of the fourth heat exchanger (14).

3. An ammonia refining device according to claim 2, characterized in that: The heat exchange tube B (124) is a finned heat exchange tube.

4. An ammonia refining device according to claim 2, characterized in that: A gas distributor (125) is provided at the bottom of the heat exchanger shell (121), and the gas distributor (125) is located between the ammonia inlet (122) and the heat exchange tube B (124).

5. An ammonia refining device according to claim 2, characterized in that: The inlet and outlet of the heat exchange tube A are connected through a connecting tube A, on which a temperature regulating valve A is provided; the inlet of the heat exchange tube C and the outlet of the heat exchange tube B (124) are connected through a connecting tube B, on which a temperature regulating valve B is provided.

6. An ammonia refining device according to claim 2, characterized in that: A branch is provided on the circulation pipeline of the refining tower (1), a circulating ammonia water spray pipe is provided above the second heat exchanger (12), the circulating ammonia water spray pipe is connected to the branch of the circulation pipeline of the refining tower (1), a flow regulating valve is provided on the branch, and a drain pipe is provided at the bottom of the refining tower (1), the drain pipe is connected to the raw material sewage tank.

7. An ammonia refining device according to claim 1, characterized in that: The high-pressure liquid ammonia tank (8) is provided with a first liquid ammonia outlet and a second liquid ammonia outlet, the first liquid ammonia outlet is connected to a liquid ammonia delivery pump (9), the second liquid ammonia outlet is connected to an ammonia feed port of a refining tower (1) and an ammonia feed port of a crystallizer (2) through a first ammonia feed pipeline and a second ammonia feed pipeline, respectively, the ammonia feed port of the refining tower (1) is located above the second heat exchanger (12), and the ammonia feed port of the crystallizer (2) is connected to a gaseous ammonia inlet pipeline of the crystallizer.

8. An ammonia refining device according to claim 7, characterized in that: The first ammonia replenishment pipeline and the second ammonia replenishment pipeline are respectively provided with an ammonia replenishment regulating valve A and an ammonia replenishment regulating valve B.

9. An ammonia refining device according to claim 1, characterized in that: The tops of the low-pressure liquid ammonia tank (6) and the high-pressure liquid ammonia tank (8) are both provided with non-condensable steam discharge ports, which are connected to the slag discharge pipeline at the bottom of the cyclone separator (4) through a pipeline, and the slag discharge pipeline is connected to a sewage tank (15), and the sewage tank (15) is connected to the raw material sewage tank through a sewage pump (16).

10. A method for refining ammonia using the ammonia refining device according to any one of claims 2 to 9, characterized in that: The following steps are involved: (1) The gaseous ammonia at a temperature of 0±3°C coming out of the adsorption tank (3) passes through a cyclone separator (4) to remove carbon powder and water, and then enters a variable frequency refrigerator (6) to cool down to -19°C to -13°C, and is converted into liquid ammonia and temporarily stored in a low-pressure liquid ammonia tank (6); (2) Liquid ammonia at a temperature of -19°C to -13°C is first pumped from a low-pressure liquid ammonia tank (6) into a first heat exchanger (11) in a crystallizer (2) to exchange heat with concentrated aqueous ammonia at the bottom of the crystallizer. After the heat exchange is completed, the outlet gas ammonia of the crystallizer (2) drops to -5±3°C, and the liquid ammonia is heated to -14±3°C; (3) Liquid ammonia at a temperature of -14±3°C enters the third heat exchanger (13) of the refining tower (1) to exchange heat with concentrated aqueous ammonia at the bottom of the refining tower. After the heat exchange is completed, it enters the second heat exchanger (12) to exchange heat with gaseous ammonia at 40±5°C entering the refining tower. After the heat exchange is completed, the gaseous ammonia at the outlet of the refining tower (1) drops to 0±3°C, and the temperature of the liquid ammonia rises to 30±5°C. (4) Liquid ammonia at a temperature of 30±5°C enters the fourth heat exchanger (14) and exchanges heat with purified water at a temperature of 45±5°C in the fourth heat exchanger (13). After the heat exchange is completed, the temperature of the liquid ammonia rises to 37±2°C and the pressure rises to 1.3±0.1MPa, and enters the high-pressure liquid ammonia tank (8) for storage.

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