Device and method for preparing nitrogen trifluoride raw material electrolyte

Abstract

The invention particularly relates to a nitrogen trifluoride raw material electrolyte preparation device and method.The device comprises an HF storage tank, an ammonia conveying unit, an electrolyte preparation unit and an electrolyte storage tank, the HF storage tank and the ammonia conveying unit communicate with the electrolyte preparation unit through pipelines, and the electrolyte preparation unit communicates with the electrolyte storage unit through a pipeline; the ammonia gas conveying unit comprises a liquid ammonia storage tank, a liquid ammonia conveying pump, an ammonia vaporizer and an adsorption tower which are sequentially communicated along the material flow direction; and the electrolyte preparation unit comprises a mixing reaction kettle and an electrolyte heat exchanger. According to the method, liquid hydrogen fluoride and liquid ammonia are pumped from a storage tank to a mixing reaction kettle, hydrogen fluoride reacts with ammonia gas to generate a molten electrolyte of NH4HF2 and HF, the electrolyte is conveyed through a circulating pump after the reaction, one part of the electrolyte is stored in an electrolyte storage tank, and the other part of the electrolyte is cooled by a heat exchanger and then returns to the reaction kettle to maintain the temperature stable. The method has the advantages of energy conservation, high product purity, high yield and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nitrogen trifluoride production, and particularly relates to a device and method for preparing an electrolyte of a nitrogen trifluoride raw material. BACKGROUND

[0002] As an electronic special gas, nitrogen trifluoride (NF3) plays an important role in modern electronic industry, especially in the fields of semiconductor manufacturing, flat panel display production and solar cell manufacturing, and is widely used as an efficient plasma etchant and cleaning agent for chemical vapor deposition (CVD) chambers.

[0003] Currently, the mainstream technical path for preparing NF3 in industry includes direct combination method and electrolysis method. The direct combination method is to synthesize NF3 by directly reacting ammonia or ammonium salt with fluorine gas, but this method has a violent reaction process and is difficult to control accurately, and the chemical reaction path is complex and has many by-products, so it does not dominate in large-scale production. In contrast, the electrolysis method has been widely adopted by the industry due to its unique advantages. This method uses molten ammonium bifluoride salt (NH4HF2-HF) as the electrolyte, and NF3 gas can be obtained in one step through the electrolysis process. The equipment used in the electrolysis method is relatively simple, the production cost is low, and high product yield and current efficiency can be achieved, so it has become the preferred technology for current industrial production of NF3.

[0004] The core of the electrolysis method is the stable preparation of high-quality electrolyte, i.e. the molten NH4HF2-HF system, which is usually prepared by reacting raw materials ammonia (NH3) and hydrogen fluoride (HF). There are still some problems to be solved in the prior art, which are directly related to the quality of the final NF3 product, the energy consumption of the production process, and the safety and efficiency of the equipment operation.

[0005] ① Insufficient control of raw material purity affects the quality of the final product

[0006] In the production chain of NF3, the purity of the raw material is a prerequisite for determining the grade of the final product. The Chinese utility model patent with publication number CN221480099U discloses a batching and feeding equipment for a nitrogen trifluoride electrolysis tank, and its process flow involves vaporizing liquid ammonia and liquid hydrogen fluoride respectively, and then sending them into a reactor to synthesize NH4HF2-HF electrolyte. In this scheme, the liquid ammonia is not subjected to any purification treatment after vaporization, especially not subjected to effective water removal and oil removal operations, and is directly used in the subsequent synthesis reaction. As an electronic-grade gas, NF3 has extremely strict requirements on impurity content in its application scenarios.

[0007] In the electronic special gas industry, there are clear and strict technical specifications for the purity of raw ammonia. For example, the national standard GB / T14601 series makes detailed provisions for the technical requirements of high-purity ammonia for electronic industry. In the standard of optoelectronic grade high-purity ammonia, the water content is strictly limited to below 0.2 ppm, and advanced production technology can even control it at the level of 10 ppb. At the same time, the content of hydrocarbon impurities such as oil is also strictly regulated, for example, it is required to be less than 5 mg / kg. In order to achieve such high purity, a series of mature purification technologies including rectification, deep adsorption drying and high-efficiency oil removal have been developed in industry, and the method described in CN221480099U ignores this key factor.

[0008] Directly using ammonia gas containing water and oil impurities to prepare electrolyte will bring a series of negative effects. First of all, the presence of water will directly affect the electrolysis process. Water in the electrolyte not only consumes electric energy and causes electrolysis side reactions, but also reacts with NF3 or affects the stability of the anode, thereby reducing the yield of NF3 and current efficiency. Secondly, hydrocarbon impurities such as oil are likely to react with fluorine in a high-temperature and strong fluorination environment to generate carbon-containing fluorine compounds such as carbon tetrafluoride (CF4). CF4 is one of the common impurities in NF3 production, which is difficult to separate due to its similar physical properties to NF3, and its presence will seriously affect the purity of NF3 products, increasing the difficulty and cost of subsequent separation and purification. Therefore, controlling the purity of raw ammonia from the source is a key link to ensure the quality of NF3 products and reduce production costs, and the existing technology has obvious deficiencies in this regard.

[0009] ②The energy consumption of the raw material pretreatment process is too high, which does not meet the energy saving principle

[0010] The second major defect in the CN221480099U patent technology solution is reflected in the energy utilization efficiency. The solution uses liquid hydrogen fluoride (HF) heated and vaporized before being sent to the reactor for dosing. The vaporization heat of hydrogen fluoride is high, and it requires a large amount of heat energy to completely convert a large amount of liquid HF into gas. The process described in CN221480099U simply inputs heat for vaporizing HF, but does not design any corresponding heat recovery mechanism, increasing the operating cost of production. In the context of large-scale production, this energy waste will be further amplified, becoming an important factor restricting the economic efficiency of the technology. Therefore, developing a feeding method that does not require large-scale heating and vaporization of liquid HF, or can effectively utilize the heat of the reaction itself, is an important direction to improve the economic efficiency and sustainability of NF3 production.

[0011] ③It is difficult to control the heat release of the synthesis reaction, which restricts the production efficiency and safety

[0012] The reaction between ammonia and hydrogen fluoride is a neutralization reaction that releases a large amount of heat, which is a strong exothermic reaction. Timely and effective removal of this part of the reaction heat is the core technical problem to ensure the stable and safe operation of the electrolyte synthesis process. If the heat is not removed in time, the temperature and pressure inside the reactor will rise sharply, which not only may cause equipment over-temperature and over-pressure, leading to safety accidents, but also will have an adverse effect on the composition and quality of the electrolyte. Local overheating may cause NH4HF2 decomposition or induce side reactions, making the final obtained electrolyte composition deviate from the optimal ratio, thereby affecting the stability of the electrolysis process and the yield of NF3.

[0013] Chinese invention patent application No. CN117364112A discloses a method for preparing NH4HF2-HF electrolyte using a mixing reaction kettle. The idea of this scheme is to mix and react in the reaction kettle, but its technical limitation is that it relies only on the heat exchange area of the jacket or coil of the mixing reaction kettle. For laboratory scale or small batch production, this design may still be able to cope. However, in industrial large-scale production, the amount of raw materials will increase significantly. According to the principle of chemical reaction engineering, the rate of heat generation is proportional to the amount of feed (i.e. the amount of reaction material), while the ratio of heat exchange area to volume of the traditional kettle reactor (the area is proportional to the square of the radius, and the volume is proportional to the cube of the radius) determines that as the size of the equipment increases, the heat exchange area per unit volume will decrease. When the amount of feed increases to a certain level, the heat exchange area of the reaction kettle itself will be far from enough to remove the huge heat generated by the vigorous reaction.

[0014] This bottleneck of heat exchange capacity directly limits the improvement of production efficiency. In order to ensure safety, the factory has to reduce the feeding rate of raw materials, thereby limiting the production of electrolyte per unit time, and making the production capacity of the entire NF3 production line constrained. In addition, the temperature fluctuation caused by insufficient heat exchange will also make the quality of the electrolyte unstable, bringing disturbance to the subsequent electrolysis process.

[0015] In summary, in the existing technology for preparing NF3 electrolyte by reacting ammonia and hydrogen fluoride, there are multiple defects such as not strict control of raw material purity, high energy consumption in pretreatment process, and insufficient heat exchange capacity of synthesis reaction to support efficient large-scale production. These problems restrict the technical obstacles of NF3 production cost, product quality and production efficiency, and an urgent need for a nitrogen trifluoride raw material electrolyte preparation system to systematically solve these problems. SUMMARY

[0016] In order to overcome the shortcomings of the prior art, the present application provides a nitrogen trifluoride raw material electrolyte preparation device and process method, which has the advantages of energy saving, high product purity and high yield.

[0017] The technical scheme adopted by the present application is:

[0018] On the one hand, this application provides a nitrogen trifluoride raw material electrolyte preparation device, including an HF storage tank, an ammonia gas conveying unit, an electrolyte preparation unit and an electrolyte storage tank. The HF storage tank and the ammonia gas conveying unit are both connected to the electrolyte preparation unit through pipelines, and the electrolyte preparation unit is also connected to the electrolyte storage tank through pipelines.

[0019] The ammonia conveying unit includes a liquid ammonia storage tank, a liquid ammonia conveying pump, an ammonia vaporizer, and an adsorption tower connected sequentially in the direction of material flow.

[0020] The electrolyte preparation unit includes a mixing reactor and an electrolyte heat exchanger for exchanging heat between the materials in the mixing reactor.

[0021] Preferably, the outlet of the HF storage tank is connected to the HF transfer pump via a pipeline with a valve, and the outlet of the HF transfer pump is connected to the mixing reactor via a pipeline with a valve.

[0022] Preferably, the outlet of the liquid ammonia storage tank is connected to the liquid ammonia transfer pump via a pipeline with a valve, the outlet of the liquid ammonia transfer pump is connected to the ammonia vaporizer via a pipeline with a valve, the outlet of the ammonia vaporizer is connected to the adsorption tower via a pipeline with a valve, and the outlet of the adsorption tower is connected to the mixing reactor via a pipeline with a pressure reducing valve and a manual valve.

[0023] Preferably, the pressure before the pressure reducing valve is ≤1.6MPa and the pressure after the valve is ≤0.3MPa.

[0024] Preferably, the outlet of the mixing reactor is connected to the electrolyte circulation pump via a pipeline with a valve, and the outlet of the electrolyte circulation pump is connected to the mixing reactor and the electrolyte storage tank via a pipeline with a valve; an electrolyte heat exchanger is provided on the pipeline between the outlet of the electrolyte circulation pump and the mixing reactor; the electrolyte outlet of the electrolyte storage tank enters the electrolytic cell via a pipeline with a valve.

[0025] Preferably, the mixing reactor and the electrolyte heat exchanger are made of Monel, nickel, or Hastelloy.

[0026] On the other hand, this application provides a method for preparing a nitrogen trifluoride feedstock electrolyte, comprising the following steps:

[0027] Step S1. Raw material preparation and transportation

[0028] Liquid hydrogen fluoride in the HF storage tank is pumped at a rate of 0-1 m³ / h under conditions of 0-19°C and 0-0.1 MPa. 3 A flow rate of [value] m / h and a head of 40 m are delivered to the mixing reactor; simultaneously, liquid ammonia is drawn from a liquid ammonia storage tank with a temperature ≤40℃ and a pressure ≤1.6 MPa, and the flow rate of liquid ammonia is 0–1 m³ / h.3 The liquid ammonia is transported using a liquid ammonia transfer pump with a flow rate of / h and a head of 100m.

[0029] Step S2. Ammonia vaporization and purification

[0030] Liquid ammonia enters the ammonia vaporizer, and the vaporized ammonia gas enters the adsorption tower filled with 3A aluminosilicate molecular sieve for purification. The working temperature of the adsorption tower is ≤50℃ and the working pressure is ≤1.6MPa. The purified ammonia gas enters the mixing reactor.

[0031] Step S3. Mixing reaction and electrolyte generation

[0032] In a mixing reactor, liquid hydrogen fluoride and ammonia react at a mass ratio of (2.6–4):1, wherein the feed flow rate of ammonia is 0–400 kg / h, the feed flow rate of hydrogen fluoride is 0–1600 kg / h, the working temperature of the mixing reactor is 20–120℃, the working pressure is 0–0.2 MPa, and the reaction produces a molten electrolyte with a mass ratio of NH4HF2 to HF of (2–12):1.

[0033] Step S4. Electrolyte circulation and storage

[0034] The electrolyte flowing from the bottom of the mixing reactor is transported by an electrolyte circulation pump, with a flow rate of 0–60 m³ / h. 3 The pump has a flow rate of 1000 m / h and a head of 40 m. The pumped electrolyte has two flow directions: one is to the electrolyte storage tank, which has an operating temperature of 0-80℃ and an operating pressure of 0-0.2 MPa; the other is to flow into the electrolyte heat exchanger for cooling. The cooled electrolyte is then returned to the mixing reactor, thus maintaining the stability of the reactor temperature through this cycle.

[0035] Preferably, in step S2, the medium in the tube side of the ammonia vaporizer is ammonia gas with a temperature of -5 to 40°C and a pressure of ≤1.6MPa; the medium in the shell side of the ammonia vaporizer is hot water with a temperature of 40 to 60°C and a pressure of 0 to 0.3MPa.

[0036] Preferably, in step S4, the tube side of the heat exchanger contains an electrolyte with an operating temperature of 20–120°C and a pressure ≤0.7 MPa; the shell side medium of the heat exchanger is cooling water with a temperature of 20–50°C and a pressure of 0–0.3 MPa.

[0037] The beneficial effects of this application are:

[0038] (1) The present invention removes the moisture and oil from the liquid ammonia raw material by adsorption, resulting in a higher purity NH4HF2-HF electrolyte product and a more stable quality of nitrogen trifluoride product produced by the electrolytic cell.

[0039] (2) The mixing reactor uses liquid hydrogen fluoride as feed, which avoids the energy waste caused by the vaporization of hydrogen fluoride;

[0040] (3) The electrolyte heat exchanger is used to cool the electrolyte in the mixing reactor, which can effectively remove the heat of reaction of ammonia and hydrogen fluoride, stabilize the temperature of the mixing reactor, solve the problem of overheating and overpressure of the equipment under large flow rate, and effectively improve the production of NH4HF2-HF electrolyte. Attached Figure Description

[0041] Figure 1 This is a diagram of the apparatus for preparing the nitrogen trifluoride feed electrolyte according to this application.

[0042] Attached diagram labels: 1. HF storage tank; 2. Mixing reactor; 3. Electrolyte heat exchanger; 4. HF transfer pump; 5. Liquid ammonia storage tank; 6. Liquid ammonia transfer pump; 7. Ammonia vaporizer; 8. Adsorption tower; 9. Electrolyte circulation pump; 10. Electrolyte storage tank. Detailed Implementation

[0043] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0044] Device Examples

[0045] This embodiment provides a nitrogen trifluoride raw material electrolyte preparation apparatus, including:

[0046] HF storage tank 1, ammonia gas delivery unit, electrolyte preparation unit and electrolyte storage tank 10. The HF storage tank and ammonia gas delivery unit are connected to the electrolyte preparation unit through pipelines. The electrolyte preparation unit is also connected to the electrolyte storage tank through pipelines.

[0047] The ammonia conveying unit includes a liquid ammonia storage tank 5, a liquid ammonia conveying pump 6, an ammonia vaporizer 7, and an adsorption tower 8, which are connected in sequence along the material flow direction.

[0048] The electrolyte preparation unit includes a mixing reactor 2 and an electrolyte heat exchanger 3 for exchanging heat between the materials in the mixing reactor 2. Both the mixing reactor 2 and the electrolyte heat exchanger 3 are made of Monel, nickel, or Hastelloy.

[0049] The outlet of HF storage tank 1 is connected to HF transfer pump 4 via a pipeline with a valve. The outlet of HF transfer pump 4 is connected to mixing reactor 2 via a pipeline with a valve. The outlet of liquid ammonia storage tank 5 is connected to liquid ammonia transfer pump 6 via a pipeline with a valve. The outlet of liquid ammonia transfer pump 6 is connected to ammonia vaporizer 7 via a pipeline with a valve. The outlet of ammonia vaporizer 7 is connected to adsorption tower 8 via a pipeline with a valve. The outlet of adsorption tower 8 is connected to mixing reactor 2 via a pipeline with a pressure reducing valve (pressure before the pressure reducing valve ≤ 1.6 MPa, pressure after the valve ≤ 0.3 MPa) and a manual valve. The outlet of mixing reactor 2 is connected to electrolyte circulation pump 9 via a pipeline with a valve. The outlet of electrolyte circulation pump 9 is connected to mixing reactor 2 and electrolyte storage tank 10 via a pipeline with a valve. The liquid from electrolyte storage tank 10 enters the electrolytic cell via a pipeline with a valve.

[0050] Working principle of the device:

[0051] (1) Raw material preparation and transportation

[0052] First, liquid hydrogen fluoride from HF storage tank 1 is stored at a temperature of 0–19°C and a pressure of 0–0.1 MPa, and then pumped by an HF transfer pump at a rate of 0–1 m³ / min. 3 A flow rate of [value] m / h and a head of 40 m are conveyed to the mixing reactor 2. Simultaneously, liquid ammonia is drawn from the liquid ammonia storage tank 5, which has an operating temperature ≤40℃ and an operating pressure ≤1.6 MPa, with a flow rate of 0–1 m³ / h. 3 The liquid ammonia is transported by a liquid ammonia transfer pump 6 with a flow rate of 100 m / h and a head of 100 m.

[0053] (2) Ammonia vaporization and purification

[0054] Liquid ammonia first enters the ammonia vaporizer 7, where the medium in the tube side is ammonia gas with a temperature range of -5 to 40℃ and a pressure ≤1.6MPa. Hot water at a temperature of 40 to 60℃ and a pressure of 0 to 0.3MPa is introduced into the shell side to heat and vaporize the liquid ammonia. The vaporized ammonia then enters the adsorption tower 8 for purification. The adsorption tower 8 operates at a temperature ≤50℃ and a pressure ≤1.6MPa, removing moisture, oil, and other impurities from the ammonia. The purified ammonia then passes through a pressure reducing valve, reducing its pressure to approximately 0.2MPa, before being sent to the mixing reactor 2.

[0055] (3) Mixed reaction and electrolyte generation

[0056] In mixing reactor 2, liquid hydrogen fluoride and ammonia react at a mass ratio of (2.6-4):1, with the ammonia feed flow rate ranging from 0 to 400 kg / h and the hydrogen fluoride feed flow rate from 0 to 1600 kg / h. The reactor operating temperature is maintained at 20-120℃ and the operating pressure at 0-0.2 MPa. Under these conditions, the two react to generate an NH4HF2-HF molten electrolyte, with the final product having a NH4HF2 to HF mass ratio of (2-12):1.

[0057] (4) Electrolyte circulation and temperature control

[0058] The electrolyte flowing from the bottom of mixing reactor 2 is transported by an electrolyte circulation pump with a flow rate of 0–60 m³ / h. 3 The pumping speed is 40m. Most of the pumped electrolyte flows into the electrolyte heat exchanger 3 for cooling. The tube side of the heat exchanger contains the electrolyte, with an operating temperature of 20-120℃ and a pressure ≤0.7MPa. Cooling water is circulated in the shell side, with a water temperature of 20-50℃ and a pressure of 0-0.3MPa, cooling the electrolyte through heat exchange. The cooled electrolyte returns to the mixing reactor 2, thus maintaining a stable temperature inside the reactor. A small portion of the pumped electrolyte is sent to the electrolyte storage tank 10 for storage. The prepared molten NH4HF2-HF electrolyte is stored in the electrolyte storage tank 10, which has an operating temperature of 0-80℃ and an operating pressure of 0-0.2MPa. When the downstream electrolyzer needs to replenish electrolyte, the outlet valve at the bottom of the electrolyte storage tank 10 is opened, and the electrolyte can be transported to the electrolyzer through pipelines to meet the needs of the electrolyzer for continuous production of nitrogen trifluoride gas.

[0059] Examples 1-3 are based on the device examples, and are detailed below:

[0060] Example 1

[0061] Step S1. The HF storage tank operates at a temperature of 10℃ and a pressure of 0.05MPa. Liquid hydrogen fluoride enters the mixing reactor via an HF transfer pump with a flow rate of 0.53m³ / h and a head of 40m. The liquid ammonia storage tank operates at a temperature of 20℃ and a pressure of 0.85MPa. Liquid ammonia enters the ammonia vaporizer via a liquid ammonia transfer pump with a flow rate of 0.3m³ / h and a head of 100m. The ammonia vaporizer's tube-side medium is ammonia gas at a temperature of 20-25℃ and a working pressure of 1MPa. The ammonia vaporizer's shell-side medium is hot water at a temperature of 40-60℃ and a working pressure of 0.2MPa.

[0062] Step S2. The ammonia gas from the outlet of the ammonia vaporizer enters the adsorption tower for purification to remove moisture and oil. The adsorption tower operates at a temperature of 40°C and a pressure of 1 MPa. The ammonia gas exiting the adsorption tower passes through a pressure reducing valve, and after the pressure drops to 0.2 MPa, it enters the mixing reactor.

[0063] Step S3. The ammonia feed flow rate of the mixing reactor is 200 kg / h, the hydrogen fluoride feed flow rate is 520 kg / h, and the liquid hydrogen fluoride and ammonia react at a mass ratio of 2.6:1 to produce a molten electrolyte with a mass ratio of NH4HF2:HF of 12:1. The working temperature of the mixing reactor is 110℃ and the working pressure is 0.05 MPa.

[0064] Step S4. The electrolyte flowing out from the bottom of the mixing reactor passes through the electrolyte circulation pump. Most of it enters the electrolyte heat exchanger for cooling and then returns to the mixing reactor to maintain a stable temperature inside the reactor. A small portion flows into the electrolyte storage tank. The electrolyte circulation pump has a flow rate of 10 m³ / h. 3 The head is 40m, the tube-side medium of the electrolyte heat exchanger is electrolyte, the working temperature is 80~110℃, the working pressure is 0.53MPa, the shell-side medium of the electrolyte heat exchanger is cooling water, the working temperature is 20~50℃, the working pressure is 0.2MPa; the electrolyte storage tank stores molten NH4HF2-HF electrolyte, the working temperature of the electrolyte storage tank is 75℃, and the working pressure is 0.03MPa.

[0065] After 24 hours of continuous mixing, 17.28 tons of molten electrolyte with a mass ratio of NH4HF2:HF of 12:1 can be prepared, with a moisture content of 2 ppm and an oil content of 0.03 ppm.

[0066] Example 2

[0067] Step S1. The HF storage tank operates at a temperature of 10℃ and a pressure of 0.05MPa; liquid hydrogen fluoride enters the mixing reactor via an HF transfer pump with a flow rate of 0.92m³ / h. 3 / h, head 36m; liquid ammonia storage tank operating temperature 20℃, operating pressure 0.85MPa; liquid ammonia enters the ammonia vaporizer for vaporization via a liquid ammonia transfer pump, the liquid ammonia transfer pump flow rate is 0.48m³ / h. 3 / h, head 95m; the tube side medium of the ammonia vaporizer is ammonia gas, temperature 20~25℃, working pressure 1MPa; the shell side medium of the ammonia vaporizer is hot water, temperature 40~60℃, working pressure 0.2MPa.

[0068] Step S2. The ammonia gas from the outlet of the ammonia vaporizer enters the adsorption tower for purification to remove moisture and oil. The adsorption tower operates at a temperature of 40°C and a pressure of 1 MPa. The ammonia gas exiting the adsorption tower passes through a pressure reducing valve, and after the pressure drops to 0.2 MPa, it enters the mixing reactor.

[0069] Step S3. The ammonia feed flow rate of the mixing reactor is 300 kg / h, the hydrogen fluoride feed flow rate is 900 kg / h, and the liquid hydrogen fluoride and ammonia react at a mass ratio of 3:1 to produce a molten electrolyte with a mass ratio of 5:1 for NH4HF2:HF. The working temperature of the mixing reactor is 90℃ and the working pressure is 0.1 MPa.

[0070] Step S4. The electrolyte flowing out from the bottom of the mixing reactor passes through the electrolyte circulation pump. Most of it enters the electrolyte heat exchanger to cool down and then returns to the mixing reactor to maintain a stable temperature inside the reactor. A small portion flows into the electrolyte storage tank. The electrolyte circulation pump has a flow rate of 23 m³ / h. 3 The head is 35m, the tube-side medium of the electrolyte heat exchanger is electrolyte, the working temperature is 70~90℃, the working pressure is 0.52MPa, the shell-side medium of the electrolyte heat exchanger is cooling water, the working temperature is 20~50℃, the working pressure is 0.2MPa; the electrolyte storage tank stores molten NH4HF2-HF electrolyte, the working temperature of the electrolyte storage tank is 75℃, and the working pressure is 0.08MPa.

[0071] After 24 hours of continuous mixing, 28.8 tons of molten electrolyte with a mass ratio of 5:1 (NH4HF2:HF) can be prepared, with a moisture content of 4 ppm and an oil content of 0.02 ppm.

[0072] Example 3

[0073] Step S1. The HF storage tank operates at a temperature of 10℃ and a pressure of 0.05MPa; liquid hydrogen fluoride enters the mixing reactor via an HF transfer pump with a flow rate of 1.63m³ / h. 3 / h, head 30m; liquid ammonia storage tank operating temperature 20℃, operating pressure 0.85MPa; liquid ammonia enters the ammonia vaporizer for vaporization via a liquid ammonia transfer pump, the liquid ammonia transfer pump flow rate is 0.65m³ / h. 3 / h, head 90m; the tube side medium of the ammonia vaporizer is ammonia gas, temperature 20~25℃, working pressure 1MPa; the shell side medium of the ammonia vaporizer is hot water, temperature 40~60℃, working pressure 0.2MPa.

[0074] Step S2. The ammonia gas from the outlet of the ammonia vaporizer enters the adsorption tower for purification to remove moisture and oil. The adsorption tower operates at a temperature of 40°C and a pressure of 1 MPa. The ammonia gas exiting the adsorption tower passes through a pressure reducing valve, and after the pressure drops to 0.2 MPa, it enters the mixing reactor.

[0075] Step S3. The ammonia feed flow rate of the mixing reactor is 400 kg / h, the hydrogen fluoride feed flow rate is 1600 kg / h, and the liquid hydrogen fluoride and ammonia react at a mass ratio of 4:1 to produce a molten electrolyte with a mass ratio of NH4HF2:HF of 2:1. The working temperature of the mixing reactor is 40℃ and the working pressure is 0.12 MPa.

[0076] Step S4. The electrolyte flowing out from the bottom of the mixing reactor passes through the electrolyte circulation pump. Most of it enters the electrolyte heat exchanger to cool down and then returns to the mixing reactor to maintain a stable temperature inside the reactor. A small portion flows into the electrolyte storage tank. The electrolyte circulation pump has a flow rate of 30 m³ / h. 3 / h, head 30m; the tube-side medium of the electrolyte heat exchanger is electrolyte, operating temperature 20~40℃, operating pressure 0.48MPa; the shell-side medium of the electrolyte heat exchanger is cooling water, operating temperature 20~50℃, operating pressure 0.2MPa; the electrolyte storage tank stores molten NH4HF2-HF electrolyte, the operating temperature of the electrolyte storage tank is 75℃, and the operating pressure is 0.1MPa;

[0077] After 24 hours of continuous mixing, 48 tons of molten electrolyte with a mass ratio of NH4HF2:HF of 2:1 can be prepared, with a moisture content of 4 ppm and an oil content of 0.05 ppm.

[0078] As can be seen from the above Examples 1 to 3, using the apparatus of this application, continuous mixing for 24 hours can produce (17.28 to 48) tons of electrolyte, with the water content of the electrolyte being stable at 0.2 to 0.3 ppm and the oil content being stable at 0.02 to 0.05 ppm.

[0079] Comparative Example 1

[0080] The equipment used in the comparative example includes: HF storage tank, HF transfer pump, HF vaporizer, liquid ammonia storage tank, liquid ammonia transfer pump, ammonia vaporizer, mixing reactor, and electrolyte storage tank.

[0081] The connection methods of each piece of equipment in the comparative example are as follows: the outlet of the HF storage tank is connected to the HF transfer pump via a pipeline with a valve, and the outlet of the HF transfer pump is connected to the HF vaporizer via a pipeline with a valve; the outlet of the HF vaporizer is connected to the mixing reactor via a pipeline with a valve; the outlet of the liquid ammonia storage tank is connected to the liquid ammonia transfer pump via a pipeline with a valve, and the outlet of the liquid ammonia transfer pump is connected to the ammonia vaporizer via a pipeline with a valve; the outlet of the ammonia vaporizer is connected to the mixing reactor via a pipeline with a valve; a pressure reducing valve is installed between the outlet of the ammonia vaporizer and the mixing reactor; the outlet of the mixing reactor is connected to the electrolyte storage tank via a pipeline with a valve.

[0082] The comparative process method is as follows:

[0083] The HF storage tank operates at a temperature of 10℃ and a pressure of 0.05MPa; liquid hydrogen fluoride enters the HF vaporizer via an HF transfer pump with a flow rate of 0.2m³ / h. 3 The flow rate is 30m / h, and the head is 30m. The tube-side medium of the HF vaporizer is hydrogen fluoride, with a temperature of 10-25℃ and an operating pressure of 0.12MPa. The shell-side medium is hot water, with a temperature of 35-50℃ and an operating pressure of 0.2MPa. The hot water is supplied by an electric boiler. The liquid ammonia storage tank operates at a temperature of 20℃ and an operating pressure of 0.85MPa. Liquid ammonia enters the ammonia vaporizer for vaporization via a liquid ammonia transfer pump with a flow rate of 0.077m³ / h. 3 / h, head 100m; the medium in the tube side of the ammonia vaporizer is ammonia gas, temperature 20~25℃, working pressure 1MPa, the medium in the shell side of the ammonia vaporizer is hot water, temperature 40~60℃, working pressure 0.2MPa; the gas outlet of the ammonia vaporizer passes through the pressure reducing valve, and the pressure drops to 0.2MPa before entering the mixing reactor.

[0084] The mixing reactor is fed with ammonia at a flow rate of 50 kg / h and hydrogen fluoride at a flow rate of 130 kg / h. Liquid hydrogen fluoride and ammonia react at a mass ratio of 2.6:1 to produce a molten electrolyte with a mass ratio of NH4HF2:HF of 12:1. The mixing reactor contains the electrolyte and is equipped with a jacket for cooling via circulating water. The working temperature inside the mixing reactor is 130℃, and the working pressure is 0.06 MPa. The working temperature of the jacket is 10–45℃, and the working pressure is 0.2 MPa. The electrolyte in the mixing reactor overflows into an electrolyte storage tank, which operates at a temperature of 75℃ and a pressure of 0.03 MPa. Finally, the molten electrolyte in the storage tank flows through a pipeline into the electrolytic cell.

[0085] After 24 hours of continuous mixing, 4.3 tons of molten electrolyte with a mass ratio of NH4HF2:HF of 12:1 can be prepared, with a moisture content of 900 ppm and an oil content of 4 ppm.

[0086] The above comparative examples show that the heat exchange effect of the jacket of the mixing reactor is poor and the reactor temperature is high; after 24 hours of continuous mixing, only 4.3t of electrolyte was prepared, with a water content of 900ppm and an oil content of 4ppm. The daily power consumption of the electric boiler to supply hot water to the HF vaporizer is 300kw.h.

[0087] Table 1. Analysis of Examples and Comparative Examples

[0088]

[0089] By comparing the examples and comparative examples, we can conclude that:

[0090] (1) The present invention removes the moisture and oil from the liquid ammonia raw material by adsorption, and the resulting NH4HF2-HF electrolyte product has less moisture and oil content and higher electrolyte purity.

[0091] (2) The mixing reactor uses liquid hydrogen fluoride as feed, which can save 300 kWh of boiler electricity per day;

[0092] (3) The electrolyte heat exchanger is used to cool the electrolyte in the mixing reactor, which can effectively remove the heat of reaction of ammonia and hydrogen fluoride. The temperature of the mixing reactor can be stabilized at 40-110℃, which solves the problem of equipment overheating under large flow rate feeding. The daily output of NH4HF2-HF electrolyte can reach up to 48t.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A nitrogen trifluoride feedstock electrolyte preparation apparatus, characterized in that, It includes an HF storage tank (1), an ammonia delivery unit, an electrolyte preparation unit, and an electrolyte storage tank (10). The HF storage tank (1) and the ammonia delivery unit are connected to the electrolyte preparation unit through pipelines. The electrolyte preparation unit is also connected to the electrolyte storage tank (10) through pipelines. The ammonia conveying unit includes a liquid ammonia storage tank (5), a liquid ammonia conveying pump (6), an ammonia vaporizer (7), and an adsorption tower (8) connected sequentially along the material flow direction; The electrolyte preparation unit includes a mixing reactor (2) and an electrolyte heat exchanger (3) for exchanging heat with the materials in the mixing reactor (2).

2. The apparatus for preparing nitrogen trifluoride raw material electrolyte according to claim 1, characterized in that, The outlet of the HF storage tank (1) is connected to the HF transfer pump (4) through a pipeline with a valve, and the outlet of the HF transfer pump (4) is connected to the mixing reactor (2) through a pipeline with a valve.

3. The apparatus for preparing nitrogen trifluoride raw material electrolyte according to claim 1, characterized in that, The outlet of the liquid ammonia storage tank (5) is connected to the liquid ammonia transfer pump (6) through a pipeline with a valve. The outlet of the liquid ammonia transfer pump (6) is connected to the ammonia vaporizer (7) through a pipeline with a valve. The outlet of the ammonia vaporizer (7) is connected to the adsorption tower (8) through a pipeline with a valve. The outlet of the adsorption tower (8) is connected to the mixing reactor (2) through a pipeline with a pressure reducing valve and a manual valve.

4. The apparatus for preparing nitrogen trifluoride raw material electrolyte according to claim 3, characterized in that, The pressure reducing valve has an inlet pressure of ≤1.6MPa and an outlet pressure of ≤0.3MPa.

5. The apparatus for preparing nitrogen trifluoride raw material electrolyte according to claim 1, characterized in that, The outlet of the mixing reactor (2) is connected to the electrolyte circulation pump (9) through a pipeline with a valve. The outlet of the electrolyte circulation pump (9) is connected to the mixing reactor (2) and the electrolyte storage tank (10) through a pipeline with a valve. An electrolyte heat exchanger (3) is provided on the pipeline between the outlet of the electrolyte circulation pump (9) and the mixing reactor (2). The electrolyte from the storage tank (10) enters the electrolytic cell through a pipeline with a valve.

6. The apparatus for preparing nitrogen trifluoride raw material electrolyte according to claim 1, characterized in that, The mixing reactor (2) and the electrolyte heat exchanger (3) are made of Monel, nickel, and Hastelloy.

7. A method for preparing a nitrogen trifluoride feedstock electrolyte, based on the nitrogen trifluoride feedstock electrolyte preparation apparatus according to claims 1-6, comprising the following steps: Step S1. Raw material preparation and transportation Liquid hydrogen fluoride in HF storage tank (1) is pumped by HF transfer pump (4) at a rate of 0-1 m³ / min under conditions of temperature 0-19℃ and pressure 0-0.1 MPa. 3 A flow rate of / h and a head of 40m are conveyed to the mixing reactor (2); simultaneously, liquid ammonia is drawn from the liquid ammonia storage tank (5), the temperature of which is ≤40℃ and the pressure is ≤1.6MPa, and the flow rate of liquid ammonia is 0~1m. 3 A liquid ammonia transfer pump (6) with a head of 100m and a flow rate of / h is used for transfer; Step S2. Ammonia vaporization and purification Liquid ammonia enters the ammonia vaporizer (7), and the vaporized ammonia enters the adsorption tower (8) filled with 3A aluminosilicate molecular sieve for purification. The working temperature of the adsorption tower (8) is ≤50℃ and the working pressure is ≤1.6MPa. The purified ammonia enters the mixing reactor (2). Step S3. Mixing reaction and electrolyte generation In the mixing reactor (2), liquid hydrogen fluoride and ammonia react at a mass ratio of (2.6-4):1, wherein the feed flow rate of ammonia is 0-400 kg / h, the feed flow rate of hydrogen fluoride is 0-1600 kg / h, the working temperature of the mixing reactor (2) is 20-120℃, the working pressure is 0-0.2 MPa, and a molten electrolyte with a mass ratio of NH4HF2 to HF of (2-12):1 is generated. Step S4. Electrolyte circulation and storage The electrolyte flowing out from the bottom of the mixing reactor (2) is transported by the electrolyte circulation pump (9), the flow rate of which is 0-60 m³ / h. 3 / h, with a head of 40m, the pumped electrolyte has two flow directions. One is to flow into the electrolyte storage tank (10), which has a working temperature of 0~80℃ and a working pressure of 0~0.2MPa. The other is to flow into the electrolyte heat exchanger (3) for cooling. The cooled electrolyte is returned to the mixing reactor (2) to maintain the stability of the reactor temperature.

8. The method for preparing a nitrogen trifluoride feedstock electrolyte according to claim 7, characterized in that, In step S2, the medium in the tube side of the ammonia vaporizer (7) is ammonia gas with a temperature of -5 to 40°C and a pressure of ≤1.6MPa; the medium in the shell side of the ammonia vaporizer (7) is hot water with a temperature of 40 to 60°C and a pressure of 0 to 0.3MPa.

9. The method for preparing a nitrogen trifluoride raw material electrolyte according to claim 7, characterized in that, In step S4, the tube side of the heat exchanger contains an electrolyte with an operating temperature of 20–120°C and a pressure ≤0.7 MPa; the shell side medium of the heat exchanger is cooling water with a temperature of 20–50°C and a pressure of 0–0.3 MPa.

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