Method and device for dehydrating liquid ammonia

Abstract

The invention relates to the technical field of preparation of electronic chemicals, and discloses a liquid ammonia dehydration device and method.The device comprises an evaporation tank and an adsorption bed; wherein the upper part of the evaporation tank is provided with silk screen filler, and the lower part of the evaporation tank is provided with fin type heat exchange tubes; wherein the height of the silk screen filler ranges from 300 mm to 600 mm; wherein the distance between the lowest end of the horizontal plane of the heat exchange tube and the bottom of the evaporation tank is 300-600mm; the distance between the uppermost end of the horizontal plane of the heat exchange tube and the liquid level of liquid ammonia is 100-200mm; wherein the adsorption bed consists of at least three adsorption beds with three functions of adsorption, regeneration and cooling. According to the invention, a specific process method and device are adopted, industrial liquid ammonia is taken as a raw material, heating pretreatment and adsorption treatment are carried out, water in the liquid ammonia is further removed without introducing extra impurities, and the prepared high-purity ammonia gas with the water content lower than 2 * 10 <-7 > (volume fraction) meets the standard requirements of photoelectron-grade ammonia gas and has a good industrial application prospect. Meanwhile, the dehydration operation process is simple, low in energy consumption and high in efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic chemical preparation, and in particular relates to a method and a device for dehydrating liquid ammonia. Background Art

[0002] High-purity ammonia is one of the important electronic chemical gases required by the electronics industry. It is mainly used to produce high-quality silicon nitride films and nitrogen-doped gallium phosphide (nitride) green light-emitting materials in optoelectronics and microelectronics fields such as semiconductor lighting, integrated circuits, flat panel display panels, and solar cells. With the in-depth development of the electronics industry towards low-nanometer processes, the requirements for electronic substrates such as silicon nitride films have been raised, thereby increasing the requirements for the purity of high-purity ammonia required for source production.

[0003] Using industrial liquid ammonia as raw material to produce high-purity ammonia is a highly economical way. Industrial liquid ammonia usually contains water. According to the requirements of GB / T 14601-2009 "Gas Ammonia for Electronic Industry", the water content of optoelectronic grade ammonia should not be higher than 2×10 -7 (volume fraction).

[0004] In terms of removing impurities such as water from industrial liquid ammonia, distillation is commonly used in industry. CN115364505A discloses a production device for producing high-purity ammonia by integrated evaporation and distillation, including an evaporator, a de-heavy distillation tower, a de-light distillation tower and a high-purity liquid ammonia product tank. The top of the evaporator is directly connected to the bottom of the de-heavy distillation tower, the bottom of the de-light distillation tower is directly connected to the top of the high-purity liquid ammonia product tank, the top gas outlet of the de-heavy distillation tower is connected to the first condenser gas inlet through a first gas outlet pipeline, and the first condenser liquid outlet is respectively connected to one end of the first reflux pipeline and the first inlet The first condenser is connected to the first condenser at one end of the first reflux pipeline, the other end of the first reflux pipeline is connected to the reflux port of the de-heavy distillation tower, the other end of the first liquid inlet pipeline is connected to the liquid inlet of the de-light distillation tower, the top gas outlet of the de-light distillation tower is connected to the gas inlet of the second condenser through the second gas outlet pipeline, the liquid outlet of the second condenser is respectively connected to one end of the second reflux pipeline and the impurity component venting pipeline, and the ammonia is purified by the above device. Although the purity of the obtained liquid ammonia is as high as 99.99%, the water content is difficult to reach no more than 2×10 -7 The requirements cannot meet the stringent requirements of ammonia purity in the semiconductor field. In addition, the process of producing high-purity ammonia using this device is long, and a large number of intermediate tanks and pumps need to be added, resulting in high investment costs.

[0005] CN111960436A discloses a method for producing ultrapure ammonia, wherein the raw ammonia is vaporized in a series of evaporators and then enters a dipping tower for rectification. The process only involves simple evaporation and primary distillation, and separate heat source systems and cold source systems are required during the evaporation and distillation processes, resulting in high energy consumption. Moreover, water and metal impurities cannot be removed to a lower standard only through evaporation and primary distillation.

[0006] Therefore, in view of the problems that the water content in the ammonia obtained by preparing high-purity ammonia from industrial liquid ammonia in the existing technology does not meet the standard requirements of optoelectronic grade ammonia, the energy consumption is high, and the impurities are difficult to remove, it is necessary to improve the liquid ammonia purification process and provide a method for dehydrating liquid ammonia. Summary of the invention

[0007] The purpose of the present invention is to overcome the problem in the prior art that the moisture content in ammonia does not meet the standard requirements of photoelectronic grade ammonia, and to provide a method and device for dehydrating liquid ammonia.

[0008] In order to achieve the above-mentioned object, the first aspect of the present invention provides a liquid ammonia dehydration device, wherein the device mainly comprises: an evaporation tank and an adsorption bed;

[0009] Wherein, the upper part of the evaporation tank is wire mesh filler, and the lower part is finned heat exchange tube;

[0010] Wherein, the height of the wire mesh filler is 300-600mm;

[0011] The distance between the bottom end of the horizontal plane of the heat exchange tube and the bottom of the evaporation tank is 300-600 mm; the distance between the top end of the horizontal plane of the heat exchange tube and the liquid ammonia surface is 100-200 mm;

[0012] The adsorption bed is composed of at least three adsorption beds that undertake the three functions of adsorption, regeneration and cooling.

[0013] The second aspect of the present invention provides a method for dehydrating liquid ammonia, wherein the method comprises subjecting industrial liquid ammonia to a conversion treatment and an adsorption treatment in the device described in the first aspect of the present invention to obtain purified ammonia gas.

[0014] Through the above technical solution, the present invention achieves the following beneficial technical effects:

[0015] (1) The method for preparing high-purity ammonia by dehydrating industrial liquid ammonia of the present invention can achieve a high dehydration accuracy, and the water content in the high-purity ammonia after dehydration is less than 1×10 -7 (volume fraction) without introducing other impurities, meeting the standard requirements of optoelectronic grade ammonia.

[0016] (2) By adopting the dehydration method of the present invention, only part of the raw gas is taken from the adsorption section when ammonia undergoes regeneration adsorption, and then deep dehydration is performed by heating, dehydration, and drying. The dehydration operation process is simple and energy consumption is low, which improves the dehydration efficiency. At the same time, it also avoids the disadvantage of using the traditional process of first dehydrating, heating, and then regenerating adsorption, which causes ammonia loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1This is a process flow chart for dehydrating industrial liquid ammonia to produce high-purity ammonia.

[0018] Description of Reference Numerals

[0019] 1. Evaporation tank 2. Adsorption bed in adsorption state 3. Adsorption bed in regeneration state

[0020] 4. Adsorption bed in cooling state 5. High precision filter 6. Ammonia buffer tank after dehydration

[0021] 7. Drying tank 8. Induced draft fan 9. Heater

[0022] 10. Compressor DETAILED DESCRIPTION

[0023] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] In order to achieve the above-mentioned object, the first aspect of the present invention provides a liquid ammonia dehydration device, wherein the device mainly comprises: an evaporation tank and an adsorption bed;

[0025] Wherein, the upper part of the evaporation tank is wire mesh filler, and the lower part is finned heat exchange tube;

[0026] Wherein, the height of the wire mesh filler is 300-600mm;

[0027] The distance between the bottom end of the horizontal plane of the heat exchange tube and the bottom of the evaporation tank is 300-600 mm; the distance between the top end of the horizontal plane of the heat exchange tube and the liquid ammonia surface is 100-200 mm;

[0028] The adsorption bed is composed of at least three adsorption beds that undertake the three functions of adsorption, regeneration and cooling.

[0029] In the present invention, industrial liquid ammonia after light hydrocarbon impurities are removed continuously enters an evaporator, and the liquid ammonia absorbs heat in the evaporator and evaporates to become ammonia gas. Heat is provided by finned heat exchange tubes at the bottom of the evaporator, and a wire mesh filler is installed at the top. The entire evaporator and its internal heat exchange tubes, wire mesh fillers and other internal parts are made of 316 stainless steel. The liquid ammonia must cover the entire heat exchange tube, the uppermost surface of the heat exchange tube is 100-200mm away from the liquid surface, and the lowermost surface of the heat exchange tube is 300-600mm away from the bottom of the evaporator. At the same time, tongues are opened on the finned heat exchange tubes, and heat is provided by hot water at 20-30°C. In order to keep the industrial liquid ammonia from boiling during the evaporation process, the height of the wire mesh filler is 300mm-600mm.

[0030] In the present invention, when the evaporation tank meets the above range, the industrial liquid ammonia will not boil during the evaporation process, which is more conducive to the dehydration treatment of the liquid ammonia, reduces energy consumption, and improves the dehydration efficiency.

[0031] According to some embodiments of the present invention, the finned heat exchange tube is provided with tongues.

[0032] According to some embodiments of the present invention, the device further comprises a heater, a high-precision filter, a drying tank and a compressor.

[0033] Preferably, the heater is connected to the top of the evaporation tank and the inlet of the compressor respectively; the outlet of the compressor is connected to the bottom of the adsorption bed; and the high-precision filter is connected to the top of the cooling adsorption bed and the drying tank respectively.

[0034] In the present invention, there is no particular limitation on the material of the heat exchange tubes and wire mesh fillers in the evaporator, for example, both can be made of 316 stainless steel.

[0035] In the present invention, the adsorption bed is composed of adsorption beds that bear three functions: adsorption, regeneration, and cooling. The adsorption bed that bears the adsorption function is an adsorption bed in an adsorption state, the adsorption bed that bears the regeneration function is an adsorption bed in a regeneration state, and the adsorption bed that bears the cooling function is an adsorption bed in a cooling state. The functions of the three adsorption beds can be switched with each other. For example, (a) the ammonia coming out of the evaporation tank enters the adsorption bed in an adsorption state, and contacts the adsorbent in the adsorption bed from top to bottom in the adsorption bed. The water therein is adsorbed by the adsorbent. The dehydrated high-purity ammonia first enters a particle filter with a filtration accuracy of <0.1μm, and then enters a dehydrated ammonia buffer tank. The dehydrated high-purity ammonia is sent from the buffer tank to the downstream process. (b) Then, the adsorption bed that is close to saturation is switched to a regeneration state. (c) After the regeneration is completed, the ammonia coming out of the ammonia buffer tank enters the adsorption bed that has completed the regeneration, so that the regenerated adsorption bed is cooled and lowered in temperature, ready to be put into adsorption operation again.

[0036] In the present invention, the gas used for regenerating the adsorption bed is taken from the ammonia gas coming out of the adsorption section, and the adsorbent is regenerated through heating, dehydration, cooling, separation, drying, and pressurization cycles; after the regeneration gas is heated to 260-320°C by the heater, it enters from the lower part of the adsorption bed in the regeneration state, so that the moisture in the adsorbent is released, and is taken out from the top by the hot ammonia gas and enters the cooler, separator, and drying tank in turn. After coming out from the top of the drying tank, it is filtered by a high-precision filter and then enters the induced draft fan for pressurization, and then sent to the heater, and after heating to 260-320°C, it enters the regeneration tower for dehydration again, and the hot ammonia gas is recycled. During the regeneration process, the temperature of the circulating ammonia gas entering and leaving the regeneration state adsorption bed is monitored. When the temperature difference is lower than 5°C, that is, the adsorbent is regenerated, the heater is stopped, and the circulating ammonia gas is gradually cooled down. When the temperature of the circulating ammonia gas is lower than 100°C, the circulating ammonia gas is stopped, and the regeneration operation is completed.

[0037] In the present invention, the gas used for cooling the adsorption bed is taken from the ammonia gas coming out of the adsorption section and the buffer tank.

[0038] In the present invention, the ammonia gas used for dehydration only needs to be obtained from the purified gas of the adsorption bed at the beginning, and only a small amount of supplement is needed after the whole device is in circulation.

[0039] The second aspect of the present invention provides a method for dehydrating liquid ammonia, wherein the method comprises subjecting industrial liquid ammonia to a conversion treatment and an adsorption treatment in the device described in the first aspect of the present invention to obtain purified ammonia gas.

[0040] According to some embodiments of the present invention, the method comprises the following steps: (1) converting industrial liquid ammonia in an evaporation tank included in the device to obtain ammonia gas;

[0041] (2) The ammonia gas is adsorbed in an adsorption bed included in the device to obtain purified ammonia gas.

[0042] According to some embodiments of the present invention, the conversion treatment method is a heating treatment. Preferably, the temperature of the heating treatment is 20-30°C.

[0043] According to some embodiments of the present invention, the adsorption bed is filled with an adsorbent, and the adsorbent includes: silica gel, 5A molecular sieve and 3A molecular sieve.

[0044] According to some embodiments of the present invention, the volume ratio of the silica gel, 5A molecular sieve and 3A molecular sieve is (1-2): (1-3): (3-7).

[0045] According to some embodiments of the present invention, the adsorption conditions include: a temperature of 30-50° C. and a pressure of 1.0 MPa-2.5 MPa.

[0046] According to some embodiments of the present invention, the method further comprises filtering and drying processes.

[0047] Preferably, the desiccant used in the drying treatment is selected from at least one of calcium oxide, magnesium oxide and lithium oxide.

[0048] Preferably, the desiccant is calcium oxide particles, and the average particle size of the desiccant is 3-5 mm.

[0049] Preferably, the drying temperature is 40-60°C.

[0050] According to some embodiments of the present invention, the filtering accuracy of the filtering is 0.01-0.1 μm.

[0051] Combination Figure 1 The method for dehydrating liquid ammonia provided by the present invention is described as follows:

[0052] (1) After the removal of light hydrocarbon impurities, industrial liquid ammonia continuously enters the liquid ammonia pretreatment system for liquid ammonia conversion treatment. Liquid ammonia absorbs heat in the evaporator 1 and evaporates into ammonia gas. The lower part of the evaporator 1 is provided with heat by a finned heat exchange tube, and a section of wire mesh filler is installed on the upper part. The entire evaporator and its internal heat exchange tubes, wire mesh fillers and other internal parts are made of 316 stainless steel. The liquid ammonia submerges the heat exchange tubes, the uppermost surface of the heat exchange tube is 100-200mm from the liquid surface, and the lowermost surface of the heat exchange tube is 300-600mm from the bottom of the evaporator. At the same time, tongues are opened on the finned heat exchange tubes to provide heat through hot water at 20-30℃. In order to prevent the industrial liquid ammonia from boiling during the evaporation process, the height of the wire mesh filler is 300mm-600mm.

[0053] (2) The ammonia gas coming out of the evaporation tank 1 is pressurized, deoiled and temperature adjusted by the compressor 10, and then enters the adsorption treatment system for fine dehydration. The adsorption bed is composed of at least three towers, including an adsorption bed 2 in an adsorption state, an adsorption bed 3 in a regeneration state and an adsorption bed 4 in a cooling state, which respectively bear the functions of adsorption, regeneration and cooling. At the same time, in order not to introduce other impurities, the adsorption dehydration also includes an induced draft fan 8, a heater 9 and a drying tank 7. First, the ammonia gas coming out of the evaporation tank 1 enters the adsorption bed 2 in an adsorption state, and contacts the adsorbent in the adsorption bed from top to bottom in the adsorption bed. The water in the adsorption bed is basically completely adsorbed by the adsorbent. The dehydrated ammonia gas enters the dehydrated ammonia buffer tank 6 after filtering through a particle filter with a filtration accuracy of <0.1μm. The dehydrated high-purity ammonia gas is sent from the buffer tank 6 to the downstream process. Then, the adsorption bed that is close to saturation is switched to the regeneration state. The gas used for regeneration is taken from the ammonia gas entering the evaporator 1. After being heated to 260-320°C, the gas enters the adsorption bed 2 in the adsorption state from the lower part of the adsorption tower 3 in the regeneration state, so that the moisture in the adsorbent is released, and the hot ammonia gas is brought to the top of the adsorption bed 2. After flowing out from the top, it enters the cooler, separator, and drying tank 7 in sequence. After coming out from the top of the drying tank 7, it passes through the high-precision filter 5 and is pressurized by the induced draft fan 8 and then sent to the heater 9. After being heated to 260-320°C, it enters the adsorption bed 3 in the regeneration state again for cyclic dehydration. After the regeneration is completed, the ammonia gas coming out of the evaporator 1 is cooled and lowered in temperature, and then put into the adsorption operation again.

[0054] According to a particularly preferred embodiment of the present invention, a method for dehydrating industrial liquid ammonia is provided, the method comprising the following steps:

[0055] Hot water at 20-30℃ is added to the evaporator to heat the liquid ammonia. The height of the wire mesh packing on the top of the evaporator is 300-600mm, the distance between the bottom end of the horizontal plane of the heat exchange tube and the bottom of the evaporator is 300-600mm, and the distance between the top end of the horizontal plane of the heat exchange tube and the liquid ammonia surface is 100-200mm; the evaporated ammonia is introduced into the three-tower adsorption bed for further dehydration, and then filtered and dried to obtain high-purity ammonia;

[0056] The adsorbent loading amounts in the adsorption bed are silica gel, 5A molecular sieve and 3A molecular sieve from top to bottom, and the volume ratio of silica gel, 5A molecular sieve and 3A molecular sieve is (1-2): (1-3): (3-7); the temperature of the adsorption treatment is 30-50°C, and the pressure is 1.0-2.5MPa; the circulating ammonia temperature at the outlet of the regeneration heater is 260-320°C; the filtration accuracy is 0.01-0.1μm; the drying tank uses calcium oxide particles with a particle size of 3-5mm, and the drying temperature is 40-60°C.

[0057] The present invention will be described in detail below through examples.

[0058] In the following examples, the water content was measured according to the method of "GB / T 14601-2009 Ammonia Gas for Electronic Industry".

[0059] Unless otherwise specified in the following examples, all raw materials are commercially available.

[0060] Example 1

[0061] This embodiment provides a method for dehydrating liquid ammonia, using Figure 1 The structure (or process) shown in the figure is carried out, and the specific operation method includes:

[0062] Hot water at 27°C was added to the evaporator to heat the liquid ammonia. The height of the wire mesh packing on the evaporator was 450 mm. The distance between the bottom of the horizontal surface of the heat exchange tube and the bottom of the evaporator was 300 mm, and the distance between the top of the horizontal surface of the heat exchange tube and the liquid ammonia surface was 100 mm. The evaporated ammonia gas was introduced into the three-tower adsorption bed for further dehydration, and then filtered and dried to obtain a water content of 3×10 -8 (volume fraction) of high-purity ammonia, the regeneration time is 6h;

[0063] Among them, the adsorbent loading in the adsorption bed is 16% silica gel, 27% 5A molecular sieve and 57% 3A molecular sieve from top to bottom; the adsorption treatment temperature is 35°C and the pressure is 1.5MPa; the circulating ammonia temperature at the outlet of the regeneration heater is 280°C; the filtration accuracy is 0.05μm; the drying tank uses calcium oxide particles with a particle size of 3.2mm, and the drying temperature is 40°C.

[0064] Example 2

[0065] This embodiment provides a method for dehydrating liquid ammonia, using Figure 1 The structure (or process) shown in the figure is carried out, and the specific operation method includes:

[0066] Hot water at 22°C was added to the evaporator to heat the liquid ammonia. The height of the wire mesh packing on the evaporator was 450 mm. The distance between the bottom of the horizontal surface of the heat exchange tube and the bottom of the evaporator was 600 mm. The distance between the top of the horizontal surface of the heat exchange tube and the liquid ammonia surface was 100 mm. The evaporated ammonia was introduced into the three-tower adsorption bed for further dehydration. After filtration and drying, the water content was 3×10 -8 (volume fraction) of high-purity ammonia, the regeneration time is 6h;

[0067] Among them, the adsorbent loading in the adsorption bed is 16% silica gel, 27% 5A molecular sieve and 57% 3A molecular sieve from top to bottom; the adsorption treatment temperature is 40°C and the pressure is 2.0MPa; the circulating ammonia temperature at the outlet of the regeneration heater is 282°C; the filtration accuracy is 0.05μm; the drying tank uses calcium oxide particles with a particle size of 4.0mm, and the drying temperature is 50°C.

[0068] Example 3

[0069] This embodiment provides a method for dehydrating liquid ammonia, using Figure 1 The structure (or process) shown in the figure is carried out, and the specific operation method includes:

[0070] Hot water at 27°C was added to the evaporator to heat the liquid ammonia. The height of the wire mesh packing on the evaporator was 300 mm. The distance between the bottom of the horizontal surface of the heat exchange tube and the bottom of the evaporator was 600 mm. The distance between the top of the horizontal surface of the heat exchange tube and the liquid ammonia surface was 200 mm. The evaporated ammonia gas was introduced into the three-tower adsorption bed for further dehydration, and then filtered and dried to obtain a water content of 2×10 -8 (volume fraction) of high-purity ammonia, the regeneration time is 6h;

[0071] Among them, the adsorbent loading in the adsorption bed is 16% silica gel, 27% 5A molecular sieve and 57% 3A molecular sieve from top to bottom; the adsorption treatment temperature is 48°C and the pressure is 2.5MPa; the circulating ammonia temperature at the outlet of the regeneration heater is 312°C; the filtration accuracy is 0.02μm; the drying tank uses calcium oxide particles with a particle size of 4.8mm, and the drying temperature is 60°C.

[0072] Example 4

[0073] This embodiment provides a method for dehydrating liquid ammonia, using Figure 1 The structure (or process) shown in the figure is carried out, and the specific operation method includes:

[0074] Hot water at 28°C was added to the evaporator to heat the liquid ammonia. The height of the wire mesh packing on the evaporator was 300 mm. The distance between the bottom of the horizontal surface of the heat exchange tube and the bottom of the evaporator was 500 mm. The distance between the top of the horizontal surface of the heat exchange tube and the liquid ammonia surface was 150 mm. The evaporated ammonia gas was introduced into the three-tower adsorption bed for further dehydration. After filtration and drying, the water content was 3×10 -8 (volume fraction) of high-purity ammonia, the regeneration time is 6h;

[0075] Among them, the adsorbent loading in the adsorption bed is 13% silica gel, 25% 5A molecular sieve and 62% 3A molecular sieve from top to bottom; the adsorption treatment temperature is 40°C and the pressure is 2.0MPa; the circulating ammonia temperature at the outlet of the regeneration heater is 280°C; the filtration accuracy is 0.05μm; the drying tank uses calcium oxide particles with a particle size of 4.0mm, and the drying temperature is 40°C.

[0076] Example 5

[0077] Liquid ammonia dehydration was carried out according to the method of Example 1, except that the temperature of circulating ammonia gas at the outlet of the regeneration heater was 240°C, and the water content was 1.7×10-7 (volume fraction) of high-purity ammonia; the regeneration time is 1.4 times that of Example 1.

[0078] Example 6

[0079] The liquid ammonia dehydration was carried out according to the method of Example 1, except that the temperature of the circulating ammonia gas at the outlet of the regeneration heater was 350°C, and the water content was 3×10 -8 (volume fraction) of high-purity ammonia; the regeneration time is 1 times that of Example 1.

[0080] Example 7

[0081] The liquid ammonia was dehydrated according to the method of Example 1, except that 35°C hot water was used to heat the liquid ammonia in the evaporation tank to obtain a water content of 7.5×10 -7 (volume fraction) of high-purity ammonia; the regeneration time is 1.4 times that of Example 1.

[0082] Example 8

[0083] Liquid ammonia dehydration was carried out according to the method of Example 1, except that the adsorbent loading of the adsorption bed was 30% silica gel, 20% 5A molecular sieve and 50% 3A molecular sieve from top to bottom, and the circulating ammonia temperature at the outlet of the regeneration heater was 240°C. The water content was 4.2×10 -7 (volume fraction) of high-purity ammonia; the regeneration time of the adsorbent is 1.5 times that of Example 1.

[0084] Example 9

[0085] The liquid ammonia was dehydrated according to the method of Example 1, except that the adsorbent was alumina, and the water content was 2.58×10 -6 (volume fraction) of high-purity ammonia; the regeneration time is 8h.

[0086] Example 10

[0087] The liquid ammonia was dehydrated according to the method of Example 1, except that the temperature of the adsorption treatment was 60°C and the pressure was 2.3 MPa, and the water content was 2.35×10 -6 (volume fraction) of high-purity ammonia; the regeneration time is 8h.

[0088] Comparative Example 1

[0089] Liquid ammonia was dehydrated according to the method of Example 1, except that the height of the wire mesh filler was 200 mm, and the water content was 3.39×10 -6 (volume fraction) of high-purity ammonia; the regeneration time is 8h.

[0090] Comparative Example 2

[0091] Liquid ammonia dehydration was carried out according to the method of Example 1, except that the distance between the bottom of the horizontal surface of the heat exchange tube and the bottom of the evaporator was 250 mm, and the distance between the top of the horizontal surface of the heat exchange tube and the liquid ammonia surface was 200 mm. The water content was 2.7×10 -6 (volume fraction) of high-purity ammonia; the regeneration time is 6h.

[0092] It can be seen from the data of Examples 1-10 and Comparative Examples 1-2 that, compared with Examples 5-6, the circulating ammonia temperature at the outlet of the regeneration heater in Example 1-4 is too low or too high, which will prolong the regeneration time of the regenerated adsorbent; compared with Example 7, the temperature of the hot water in the evaporator is too high in Example 1, the water content in the prepared high-purity ammonia increases, and the regeneration time of the regenerated adsorbent is prolonged; compared with Example 8, the ratio of each component in the adsorbent is changed in Example 1, the water content in the prepared high-purity ammonia is still high, and the regeneration time of the adsorbent is prolonged; compared with Example 9, the type of adsorbent is changed in Example 1, the water content in the prepared high-purity ammonia increases, which does not meet the requirements, and the regeneration time of the regenerated adsorbent is prolonged; compared with Example 10, the conditions of the adsorption treatment are changed in Example 1, the water content in the prepared high-purity ammonia increases, and the regeneration time of the regenerated adsorbent is prolonged; compared with Comparative Examples 1-2, the structure of the evaporator in the liquid ammonia dehydration device is changed in Example 1, the water content in the prepared high-purity ammonia increases, and the regeneration time of the regenerated adsorbent is prolonged.

[0093] In summary, the specific process method and device of the present invention are used to take industrial liquid ammonia as raw material, and after heating and triple adsorption treatment, impurities and moisture in liquid ammonia are further removed without introducing additional impurities, and the water content of the prepared ammonia is less than 2×10 -7 (volume fraction) of high-purity ammonia meets the standard requirements of optoelectronic-grade ammonia and can meet the needs of subsequent further purification. Among them, the dehydration method includes an evaporator and a group of adsorption beds. There are finned heat exchange tubes at the bottom of the evaporator, which use hot water to provide heat for the evaporation of liquid ammonia. There are wire mesh fillers at the top to intercept droplets entrained by the evaporated ammonia. The adsorption bed is composed of an adsorption tower that has three functions: adsorption, regeneration, and cooling. The adsorbent uses silica gel, 5A molecular sieve and 3A molecular sieve grading to achieve deep and large-capacity dehydration. In addition, the raw gas taken from the adsorption bed section is heated, dehydrated, cooled, separated, dried, and pressurized, and the adsorbent is regenerated through a cyclic operation to improve the dehydration efficiency and reduce ammonia loss.

[0094] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A liquid ammonia dehydration device, characterized in that: The device comprises: an evaporation tank and an adsorption bed; Wherein, the upper part of the evaporation tank is wire mesh filler, and the lower part is finned heat exchange tube; Wherein, the height of the wire mesh filler is 300-600mm; The distance between the bottom end of the horizontal plane of the heat exchange tube and the bottom of the evaporation tank is 300-600 mm; the distance between the top end of the horizontal plane of the heat exchange tube and the liquid ammonia surface is 100-200 mm; The adsorption bed is composed of at least three adsorption beds that undertake the three functions of adsorption, regeneration and cooling.

2. The device according to claim 1, wherein: The finned heat exchange tube is provided with tongues.

3. The device according to claim 1 or 2, wherein: The device also includes a heater, a high-precision filter, a drying tank and a compressor; Preferably, the heater is connected to the top of the evaporation tank and the inlet of the compressor respectively; the outlet of the compressor is connected to the bottom of the adsorption bed; and the high-precision filter is connected to the top of the cooling adsorption bed and the drying tank respectively.

4. A method for dehydrating liquid ammonia, characterized in that: The method comprises subjecting industrial liquid ammonia to conversion and adsorption treatment in the device described in any one of claims 1 to 3 to obtain purified ammonia gas.

5. The method according to claim 4, wherein: The method comprises the following steps: (1) converting industrial liquid ammonia in an evaporation tank included in the device to obtain ammonia gas; (2) The ammonia gas is adsorbed in an adsorption bed included in the device to obtain purified ammonia gas.

6. The method according to claim 4 or 5, wherein: The conversion treatment method is a heating treatment; preferably, the temperature of the heating treatment is 20-30°C.

7. The method according to any one of claims 4 to 6, wherein: The adsorption bed is filled with an adsorbent, which includes silica gel, 5A molecular sieve and 3A molecular sieve.

8. The method according to claim 7, wherein: The volume ratio of the silica gel, 5A molecular sieve and 3A molecular sieve is (1-2): (1-3): (3-7).

9. The method according to any one of claims 4 to 8, wherein: The adsorption conditions include: temperature of 30-50° C. and pressure of 1.0 MPa-2.5 MPa.

10. The method according to any one of claims 4 to 9, wherein: The method further comprises filtering and drying processes; Preferably, the desiccant used in the drying process is selected from at least one of calcium oxide, magnesium oxide and lithium oxide; Preferably, the desiccant is calcium oxide particles, and the average particle size of the desiccant is 3-5 mm; Preferably, the drying temperature is 40-60°C.

11. The method according to claim 10, wherein: The filtering accuracy of the filtering is 0.01-0.1 μm.

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