A production system and process for g5 grade nitric acid

Abstract

The present application relates to high-purity nitric acid preparation technical field, specifically to a kind of G5 grade nitric acid production system and process, its technical scheme is: including raw material section, evaporative rectification section, decoloring section, gas washing section, product storage section and filling section;All tower body, storage tank and pipeline in the raw material section, evaporative rectification section, decoloring section, gas washing section, product storage section and filling section are with fluorine lining material;The beneficial effects of the present application are: tower body, storage tank and pipeline in the system of the present application are with fluorine lining material instead of traditional high boron silica glass, perfluoro material has excellent chemical inertia to boiling concentrated nitric acid, avoids the metal ion impurities introduced by equipment body corrosion, compared with glass material, fluorine lining equipment has excellent impact resistance and drop performance, reduces equipment load, and geometric shape design is more flexible, and adaptability is strong.

Description

Technical Field

[0001] This invention relates to the field of high-purity nitric acid preparation technology, specifically to a production system and process for G5 grade nitric acid. Background Technology

[0002] G5 grade nitric acid, as a high-purity chemical, plays an irreplaceable role in high-end manufacturing fields such as electronics and pharmaceuticals. In the electronics industry, G5 grade nitric acid is widely used in the cleaning and etching processes of semiconductor materials, and its purity directly affects the yield and performance of chip manufacturing. However, the current nitric acid production industry generally adopts atmospheric pressure or pressurized process, and these traditional processes have certain limitations in meeting the G5 grade nitric acid standard. Traditional nitric acid production systems have several shortcomings in meeting G5-grade nitric acid standards, mainly in terms of purity and material properties. First, while distillation and extraction separation technologies commonly used in traditional processes can improve product purity to some extent, they are mostly single-stage distillations, which are insufficient to reduce impurities such as metal and non-metal ions to extremely low levels. They also cannot effectively remove fine solid particles that are harmful to integrated circuits or photovoltaic manufacturing, failing to meet the stringent standards for impurity content in high-purity nitric acid and the purity requirements of high-end applications. Second, existing purification equipment mostly uses high borosilicate glass, which has limited corrosion resistance and is easily damaged by long-term contact with strong corrosive media. It also has poor mechanical shock resistance and is prone to breakage under vibration or drop conditions. Furthermore, its high density increases the equipment load, and the processing geometry is limited by the glass material. Furthermore, the purification equipment (distillation columns, decolorization columns) in the existing production system also have certain defects in hardware design. These defects directly affect the purity of the produced nitric acid, for example: Traditional decolorization towers mostly use packed tower bubbling or Venturi jetting methods, which use compressed air to come into countercurrent contact with nitric acid in the tower to blow off NOx. However, the specific surface area of ​​the packing in traditional decolorization towers is limited, which easily leads to channeling and incomplete decolorization. In addition, in order to ensure sufficient contact time, traditional towers are usually tall, thus occupying a large area. In traditional decolorization towers, compressed air carries particulate matter from the environment or oil from the compressor (even after treatment) when it enters nitric acid. More importantly, when compressed air bubbles and bursts in nitric acid, it produces tiny aerosol droplets. These droplets easily carry away packing wear material or particles from the environment and remix them into the nitric acid, making it difficult to meet the stringent requirements of G5 grade for particle size. Traditional distillation columns lack efficient demisting structures, resulting in low collection efficiency for small droplets (such as <3-5um), leading to incomplete removal of impurities such as acid droplets, particles, and metal elements, and low impurity removal efficiency, which affects product purity. In summary, traditional nitric acid production processes have certain limitations, both in terms of hardware equipment and production technology, and are difficult to meet the G5 grade nitric acid standard. Therefore, it is necessary to invent a G5 grade nitric acid production system and process. Summary of the Invention

[0003] To achieve the above objectives, the present invention provides the following technical solution: a production system for G5 grade nitric acid, comprising a raw material processing section, an evaporation and distillation section, a decolorization section, a gas washing section, a finished product storage section, and a filling section; The raw material processing section includes a mixing tank, and the output end of the mixing tank is connected to a preheater; The evaporation and distillation section includes a distillation column, the input end of which is connected to a preheater, the bottom of which is connected to a heat exchanger, and the output end of which is connected to a top condenser. The decolorization section includes a decolorization tower, which is equipped with a membrane decolorization component. The input end of the decolorization tower is connected to the top condenser, and the output end of the decolorization tower is connected to the decolorization receiving tank. The gas scrubbing section includes an acid gas scrubbing tower, the input end of which is connected to a condenser at the top of the tower, the acid gas scrubbing tower is connected to an acid gas cooler, and the output end of the acid gas scrubbing tower is connected to a mixing tank. The finished product storage section includes a finished product intermediate tank, the input end of which is connected to a decolorization receiving tank, and the output end of which is provided with a circulation return pipeline. The circulation return pipeline is connected to a finished product condenser and is equipped with an online concentration meter. The filling section includes a finished product filter cabinet and a 200L filling line. The input end of the finished product filter cabinet is connected to the output end of the circulating return pipeline, and the output end of the finished product filter cabinet is connected to the 200L filling line. An online particle analyzer is installed on the pipeline between the finished product filter cabinet and the 200L filling line. All towers, storage tanks, and pipelines in the raw material section, evaporation and distillation section, decolorization section, gas washing section, finished product storage section, and filling section are lined with fluoropolymer materials. The distillation column includes a distillation column body, a distillation column outlet is provided at the top of the distillation column body, and a wire mesh demister is installed inside the upper end of the distillation column body near the distillation column outlet. The decolorization tower includes a decolorization tower body, with a condenser inlet at the upper end of one side and a receiving tank inlet at the lower end of the same side. The membrane decolorization assembly includes a top support plate and a bottom support plate. The top support plate is installed on the inner wall of the decolorization tower body above the condenser inlet, and the bottom support plate is installed on the inner wall of the decolorization tower body below the receiving tank inlet. A plurality of mass transfer membrane fibers are installed between the top support plate and the bottom support plate, and a filler wire is provided between each of the mass transfer membrane fibers. The surface of the filler wire is provided with a rough turbulence structure.

[0004] Preferably, the upper end of the decolorizing tower body is provided with a CDA exhaust port, the lower end of the decolorizing tower body is provided with a CDA inlet, the CDA inlet is connected to a CDA supply system, and a decolorizing tower reflux port is provided on the outer wall of the decolorizing tower body on the side opposite to the condenser inlet. Preferably, the surfaces of the top support plate and the bottom support plate are provided with pores arranged in a square array, the mass transfer membrane filaments are hollow tubular structures, and a plurality of the mass transfer membrane filaments are arranged in a square array between the top support plate and the bottom support plate, with the upper and lower ends of the mass transfer membrane filaments respectively connected to the pores on the surfaces of the top support plate and the bottom support plate.

[0005] Preferably, the lower end of the filler wire is fixedly installed on the bottom support plate, and a filler wire is arranged between the four mass transfer membrane wires. The surface of the filler wire is equidistant from the surface of the surrounding four mass transfer membrane wires. An outer guide plate is installed on the inner wall of the decolorization tower between the top support plate and the bottom support plate. The inner wall of the outer guide plate is equidistant from the surface of the adjacent mass transfer membrane wires. The inner wall of the outer guide plate is also provided with a rough turbulence structure.

[0006] Preferably, the input end of the decolorizing receiving tank is connected to the receiving tank inlet, the bottom output end of the decolorizing receiving tank is connected to the receiving tank output pump, the output end of the receiving tank output pump is connected to the decolorizing tower reflux port, and the top output end of the decolorizing receiving tank is connected to the input end of the finished product intermediate tank.

[0007] Preferably, a gas-liquid inlet is provided at the lower end of one side of the distillation column, a heat exchanger inlet is provided at the bottom of the distillation column, a distillation column liquid inlet is provided on one side of the middle part of the distillation column, and a distillation column reflux inlet is provided on the other side. The distillation column liquid inlet is connected to the output end of the preheater.

[0008] Preferably, the distillation column is filled with a plurality of packing materials stacked inside. The packing material below the liquid inlet of the distillation column is the stripping section packing material, and the packing material above the liquid inlet of the distillation column is the rectification section packing material. The wire mesh demister is located above the rectification section packing material, and a distributor is provided above the stripping section packing material. The top of the distributor is connected to the liquid inlet of the distillation column and the reflux port of the distillation column, respectively.

[0009] Preferably, the top condenser includes a condenser tank. A steam inlet is provided on one side of the top of the condenser tank, and a gas scrubbing tower inlet is provided on the other side. The steam inlet is connected to the gas outlet of the distillation column, and the gas scrubbing tower inlet is connected to the gas scrubbing tower input end. A condenser tube is installed inside the condenser tank. A condensate reflux pump is connected to one output end of the bottom of the condenser tank, and a condensate output pump is connected to the other output end. The output end of the condensate reflux pump is connected to the distillation column reflux port, and the output end of the condensate output pump is connected to the condenser inlet.

[0010] Preferably, the heat exchanger input end is connected to a heat exchanger input pump, the heat exchanger input pump input end is connected to the heat exchanger inlet, the heat exchanger output end is connected to a gas-liquid inlet, and a heat medium pipeline is provided inside the heat exchanger.

[0011] The production process of a G5-grade nitric acid production system described above includes S1-S5; S1. Nitric acid in the mixing tank is preheated and then introduced into the distillation column. The nitric acid in the distillation column flows down the packing of the stripping section to the bottom of the distillation column and is introduced into the heat exchanger. Then, low-pressure saturated steam is introduced into the heat medium pipeline to indirectly heat the nitric acid in the heat exchanger, causing it to vaporize. The nitric acid vapor is reintroduced into the bottom of the distillation column and passes upward through the packing of the stripping section and the packing of the rectification section for heat and mass transfer. Then, the entrained droplets are removed by the wire mesh demister to obtain high-purity gaseous nitric acid. The high-purity gaseous nitric acid escapes from the top of the distillation column and enters the condenser for condensation. After condensation, the nitric acid flows back into the distillation column through the reflux port and enters the decolorization column through the condenser inlet. Non-condensable gases are discharged from the inlet of the gas scrubbing tower and enter the acid gas scrubbing tower. S2. Start the CDA gas supply system and introduce ultrapure CDA gas into the bottom of the decolorization tower through the CDA inlet. Adjust the inlet flow rate through a proportional valve and a flow meter. The ultrapure CDA gas at the bottom of the decolorization tower enters the inner wall of the mass transfer membrane fiber through the pores on the surface of the bottom support plate and then exits to the top of the decolorization tower through the pores on the surface of the top support plate. At the same time, the high-purity nitric acid solution flowing into the decolorization tower flows downward along the outer wall of the mass transfer membrane fiber from top to bottom. During the downward flow of the high-purity nitric acid solution, it is affected by the rough turbulent structure on the surface of the filling wire, generating eddies and turbulence. The eddies and turbulence spread in all directions and directly impact the surface of the mass transfer membrane fiber. Nitrogen dioxide gas molecules dissolved in nitric acid diffuse through the mass transfer membrane fiber and enter the CDA gas flow, where they are carried away and discharged from the top of the decolorization tower. They then enter the acid gas scrubbing tower through the CDA exhaust port. The nitric acid solution after decolorization flows into the decolorization receiving tank through the receiving tank inlet and is then pumped to the finished product intermediate tank by the decolorization circulation pump.

[0012] S3. Acid gas from the decolorization tower and condenser is collected in the acid gas scrubbing tower. The acid gas enters from the bottom of the acid gas scrubbing tower in a countercurrent manner and is absorbed by ultrapure water in the packing layer to form nitric acid, which is then deposited in the lower part of the acid gas scrubbing tower. The product from the lower part of the acid gas scrubbing tower is discharged in two ways: one way is cooled by the silicon carbide acid gas condenser and then returned to the acid gas scrubbing tower as the absorbent; the other way is discharged to the mixing tank through the proportional valve interlocking the tower bottom liquid level. S4. High-purity nitric acid from the decolorization receiving tank enters the finished product intermediate tank from the top output end. The finished product cooler is started to cool the circulation return pipeline of the finished product intermediate tank. The cooled nitric acid flows back to the finished product intermediate tank. The concentration can be adjusted according to customer needs through the online concentration meter on the circulation return pipeline. After the nitric acid in the finished product intermediate tank is fully mixed and homogeneous, it is sent to the central control room for testing. S5. High-purity nitric acid is drawn from the output end of the circulation reflux pipeline of the finished product intermediate tank to the finished product filter cabinet. The finished product filter cabinet performs three-stage circulation filtration of the high-purity nitric acid. After the filtered product passes the online particle size analyzer test, it is divided into two streams and enters the 200L filling line. Finally, the 200L filling line is started to complete the filling of G5 grade high-purity nitric acid.

[0013] The beneficial effects of this invention are: In this invention, the tower body, storage tank and pipelines are all lined with fluoropolymer material instead of traditional high borosilicate glass. Fluorine material has excellent chemical inertness to boiling concentrated nitric acid, avoiding metal ion impurities introduced by the corrosion of the equipment body. Compared with glass material, fluoropolymer-lined equipment has excellent impact resistance and drop resistance, reduces equipment load, and has more flexible geometric design and strong adaptability. In the decolorization section, hollow mass transfer membrane fibers are used to physically separate nitric acid (shell side) and CDA (tube side), preventing direct contact between the gas and liquid phases and fundamentally eliminating aerosol and droplet entrainment caused by bubble bursting. At the same time, the traditional structure of randomly packed packing in the decolorization tower is eliminated, removing the source of wear particles caused by fluid scouring of the packing, greatly reducing the particulate matter content in the finished nitric acid, and ensuring that the product meets the stringent requirements of G5 grade for ultra-low particle size. In the decolorization section, an innovative "anti-turbulence structure based on rectangular array fixed-point filling" was designed. By setting the filling wire at the center of the four mass transfer membrane wires, the nitric acid fluid is forced to flow around it, eliminating the mass transfer dead zone. The rough turbulence structure on the surface of the filling wires and the outer guide plate generates high-frequency micro-eddies in the shell side, which continuously destroys the concentration boundary layer on the surface of the membrane wires, significantly reducing the mass transfer resistance and greatly increasing the diffusion rate of nitrogen dioxide from the liquid phase to the gas phase. This makes the decolorization process more thorough and faster, and the equipment volume is much smaller than that of traditional towers. This invention incorporates a wire mesh demister at the top of the distillation column, which effectively captures minute acid mists, preventing them from being carried into subsequent processes and further removing metal elements and particulate impurities. By linking the acid gas scrubbing tower with the condenser, the nitric acid vapors in the non-condensable gas and decolorization tail gas are countercurrently absorbed and returned to the mixing tank, achieving zero emissions and resource recovery of acidic waste gas. This not only protects the environment and improves the utilization rate of raw materials but also avoids cross-contamination that may result from waste gas emissions. Attached Figure Description

[0014] Figure 1A flow chart of a G5 grade nitric acid production system provided by the present invention; Figure 2 Schematic diagram of the evaporation and distillation section and the decolorization section provided by the present invention; Figure 3 Cross-sectional views of the distillation column, decolorization column, and condenser provided by the present invention; Figure 4 This is a schematic diagram of the internal structure of the distillation column provided by the present invention; Figure 5 This is a schematic diagram of the internal structure of the decolorization tower provided by the present invention; Figure 6 This is a cross-sectional view of the internal structure of the decolorization tower provided by the present invention; Figure 7 This is a detailed view of the upper end of the membrane decolorization assembly provided by the present invention; Figure 8 This is a cross-sectional view of the upper end of the membrane decolorization assembly provided by the present invention; Figure 9 A cross-sectional view of the membrane decolorization component provided by the present invention; Figure 10 Provided by the present invention Figure 9 Detailed image A.

[0015] In the diagram: 111. Distillation column body; 112. Distillation column inlet; 113. Distillation column reflux inlet; 114. Distillation column outlet; 115. Heat exchanger inlet; 116. Gas-liquid inlet; 117. Liquid distributor; 118. Packing; 119. Wire mesh demister; 121. Condenser; 122. Steam inlet; 123. Gas scrubber inlet; 124. Condensate reflux pump; 125. Condensate outlet pump; 126. Condenser tube. 131. Decolorization tower body; 132. Condenser inlet; 133. Receiving tank inlet; 134. Decolorization tower reflux port; 135. CDA inlet; 136. CDA exhaust port; 141. Heat exchanger; 142. Heat exchanger input pump; 151. Decolorization receiving tank; 152. Receiving tank output pump; 161. Top support plate; 162. Bottom support plate; 163. Mass transfer membrane fiber; 164. Packing fiber; 165. Peripheral guide plate. Detailed Implementation

[0016] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0017] like Figure 1 - Figure 10 As shown, a G5 grade nitric acid production system includes a raw material section, an evaporation and distillation section, a decolorization section, a gas washing section, a finished product storage section, and a filling section. The raw material section includes a mixing tank, and the output end of the mixing tank is connected to a preheater; The evaporation and distillation section includes a distillation column, with a preheater connected to the inlet end of the distillation column, a heat exchanger 141 connected to the bottom of the distillation column, and a condenser connected to the top of the column at the outlet end. The decolorization section includes a decolorization tower, which is equipped with a membrane decolorization component. The input end of the decolorization tower is connected to the top condenser, and the output end of the decolorization tower is connected to the decolorization receiving tank 151. The gas scrubbing section includes an acid gas scrubbing tower, the input end of which is connected to the top condenser, the acid gas scrubbing tower is connected to an acid gas cooler, and the output end of the acid gas scrubbing tower is connected to a mixing tank. The finished product storage section includes a finished product intermediate tank. The input end of the finished product intermediate tank is connected to a decolorization receiving tank. The output end of the finished product intermediate tank is equipped with a circulation return pipeline, which is connected to the finished product condenser. An online concentration meter is installed on the circulation return pipeline. The filling section includes a finished product filter cabinet and a 200L filling line. The input end of the finished product filter cabinet is connected to the output end of the circulating return pipeline, and the output end of the finished product filter cabinet is connected to the 200L filling line. An online particle analyzer is installed on the pipeline between the finished product filter cabinet and the 200L filling line. All towers, storage tanks, and pipelines in the raw material section, evaporation and distillation section, decolorization section, gas washing section, finished product storage section, and filling section are lined with fluoropolymer materials. The distillation column includes a distillation column body 111, a distillation column outlet 114 is provided at the top of the distillation column body 111, and a wire mesh demister 119 is installed inside the upper end of the distillation column body 111 near the distillation column outlet 114. The decolorization tower includes a decolorization tower body 131. A condenser inlet 132 is provided at the upper end of one side of the decolorization tower body 131, and a receiving tank inlet 133 is provided at the lower end of the same side. The membrane decolorization assembly includes a top support plate 161 and a bottom support plate 162. The top support plate 161 is installed on the inner wall of the decolorization tower body 131 above the condenser inlet 132, and the bottom support plate 162 is installed on the inner wall of the decolorization tower body 131 below the receiving tank inlet 133. A plurality of mass transfer membrane fibers 163 are installed between the top support plate 161 and the bottom support plate 162, and a packing wire 164 is provided between each mass transfer membrane fiber 163. The surface of the packing wire 164 is provided with a rough turbulence structure.

[0018] In the above embodiments, it should be noted that the tower body, storage tank, and pipelines in the system of the present invention all use fluoropolymer lining material instead of traditional high borosilicate glass. Its core advantages are: fluoropolymer lining material is inert to almost all chemical reagents, resistant to long-term corrosion by strong corrosive media, significantly exceeding the corrosion resistance limit of high borosilicate glass, while avoiding metal ion impurities introduced by the corrosion of the equipment body; the properties of fluoropolymer lining material give it excellent resistance to mechanical impact, making it less prone to breakage under vibration or drop scenarios, completely avoiding the risk of brittle fracture of high borosilicate glass; the density of fluoropolymer lining material is only 1 / 4 to 1 / 3 of that of high borosilicate glass, significantly reducing the equipment load, and supporting injection molding of complex irregular parts, breaking through the processing geometry limitations of glass; The distillation process employed here involves condensing and removing light component impurities after distillation to improve product purity and reduce impurity content to extremely low levels, meeting the requirements of high-purity nitric acid for metal ions and other impurities. The distillation column is the core equipment in the process; the column body 111 is lined with 10mm thick 304 stainless steel lined with ultra-pure PFA, ensuring high purity while maximizing the equipment's high-temperature resistance, corrosion resistance, and resistance to negative pressure and permeation. A wire mesh demister 119 is installed at the top of the distillation column; the wire mesh demister 119 is effective for mist particles with a diameter ≥3-5µm. The collection efficiency reaches 99%-99.8%, while the pressure drop of the gas passing through the demister is very small, only 250-500 Pa, which is conducive to improving the purification efficiency of the equipment and improving the removal of impurities (particles, metal elements and acid mist). It can effectively capture tiny acid mist and prevent acid mist from being carried into subsequent processes. In addition, the bottom of the distillation column 111 is also connected to a residual liquid tank. Through quantitative drainage, various impurities in the liquid nitric acid enriched at the bottom of the distillation column 111 are cooled and discharged to the residual liquid tank. The temperature at the top of the distillation column is controlled at about 120℃, and the operating pressure of the distillation column is atmospheric pressure. The mass transfer membrane filament 163 uses PFA hollow fiber filaments with an outer diameter of 1.5 mm as the main mass transfer membrane filament. Inside the module, these filaments are arranged in a rectangular array with a spacing controlled at 2.0 mm. The surface of the packing filament 164 is formed by extrusion through a die to create spiral raised ribs (5 mm pitch, 0.2 mm height), forming a rough turbulent flow structure. This process uses the mass transfer membrane filament 163 to physically separate nitric acid from ultrapure CDA gas, preventing direct contact between the gas and liquid phases and fundamentally eliminating aerosol and droplet entrainment phenomena caused by bubble bursting. At the same time, it abandons the structure of randomly packed packing in traditional decolorization towers, eliminating the abrasive particle source caused by fluid scouring of the packing, greatly reducing the particulate matter content in the finished nitric acid, and ensuring that the product meets the stringent requirements of G5 grade for ultra-low particle size. An innovative "anti-turbulence structure based on fixed-point filling of rectangular array" was designed. By setting the filling wire at the center of the four mass transfer membrane wires, the nitric acid fluid is forced to flow around it, eliminating the mass transfer dead zone. The rough turbulence structure on the surface of the filling wires and the outer guide plate generates high-frequency micro-eddies in the shell side, which continuously destroys the concentration boundary layer on the surface of the membrane wires, significantly reducing the mass transfer resistance and greatly increasing the diffusion rate of nitrogen dioxide from the liquid phase to the gas phase. This makes the decolorization process more thorough and faster, and the equipment volume is much smaller than that of traditional towers. By setting up a linkage between the acid gas scrubbing tower and the condenser, the nitric acid vapor in the non-condensable gas and decolorization tail gas is absorbed countercurrently and returned to the mixing tank, achieving zero emission and resource recovery of acidic waste gas. This not only protects the environment and improves the utilization rate of raw materials, but also avoids cross-contamination that may be caused by waste gas emissions.

[0019] like Figure 2 , Figure 3 and Figure 5 - Figure 10 As shown, a G5 grade nitric acid production system further includes: a CDA exhaust port 136 at the upper end of a decolorization tower body 131, a CDA inlet 135 at the lower end of the decolorization tower body 131 connected to a CDA supply system, a decolorization tower reflux port 134 on the outer wall of the decolorization tower body 131 opposite to the condenser inlet 132, vents arranged in a square array on the surfaces of the top support plate 161 and the bottom support plate 162, a hollow tubular mass transfer membrane filament 163 arranged in a square array between the top support plate 161 and the bottom support plate 162, with the upper and lower ends of the mass transfer membrane filament 163 connected to the vents on the surfaces of the top support plate 161 and the bottom support plate 162 respectively, and a packing wire 164. The lower end is fixedly installed on the bottom support plate 162. A filler wire 164 is arranged between the four mass transfer membrane wires 163. The surface of the filler wire 164 is equidistant from the surface of the surrounding four mass transfer membrane wires 163. An outer guide plate 165 is installed on the inner wall of the decolorization tower body 131 between the top support plate 161 and the bottom support plate 162. The inner wall of the outer guide plate 165 is equidistant from the surface of the adjacent mass transfer membrane wires 163. The inner wall of the outer guide plate 165 is also provided with a rough turbulence structure. The input end of the decolorization receiving tank 151 is connected to the receiving tank inlet 133. The bottom output end of the decolorization receiving tank 151 is connected to the receiving tank output pump 152. The output end of the receiving tank output pump 152 is connected to the decolorization tower return port 134. The top output end of the decolorization receiving tank 151 is connected to the input end of the finished product intermediate tank.

[0020] In the above embodiments, it should be noted that the decolorization tower body 131 adopts a DN200 stainless steel shell and is lined with PFA. Membrane decolorization component (core hardware) in decolorization tower body 131: (1) Membrane bundle structure: PFA hollow fiber membrane fibers with an outer diameter of 1.5 mm are selected as mass transfer membrane fibers 163. Inside the module, these mass transfer membrane fibers 163 are arranged in a rectangular array with a spacing of 2.0 mm. (2) Fixed-point filling: A solid PFA rod with a diameter of 1.0 mm is implanted in the center of the square formed by every 4 mass transfer membrane wires 163 as a turbulence generation filling wire 164; (3) Surface modification: The surfaces of the filler wire 164 and the outer guide plate 165 are formed by die extrusion to form spiral raised ribs (pitch 5mm, height 0.2mm), which constitute a rough turbulent structure; (4) Flow channel design: Nitric acid flows through the shell side (outer wall of mass transfer membrane filament 163), and ultrapure CDA gas flows through the tube side (inner wall of mass transfer membrane filament 163). An online heater is installed on the outer wall of the condenser inlet 132. The CDA air supply system performs oil and water removal treatment on the air. Membrane decolorization process flow: (1) The extracted nitric acid (temperature about 45°C) is heated to 60°C by an online heater and then enters the shell side of the membrane decolorization module through the condenser inlet 132; (2) The CDA (pressure 0.25MPa) after oil and water removal treatment enters the tube side of the membrane fiber through CDA inlet 135; (3) During the shell-side flow, nitric acid is blocked and disturbed by the filling wire 164. The spiral ribs on the surface of the filling wire 164 continuously cut the fluid and generate micro-scale eddies. These eddies force the nitric acid liquid to continuously scour the surface of the mass transfer membrane wire 163, which greatly reduces the liquid film boundary layer. (4) Nitrogen dioxide gas molecules dissolved in nitric acid are rapidly passed through the micropores of the membrane wall of the mass transfer membrane filament 163 under the drive of the partial pressure difference, and enter the ultrapure CDA gas flow in the tube side, and are discharged with the tail gas. (5) The nitric acid color after decolorization drops below 5 Hazen; Compared to traditional packed tower decolorization, the novel membrane module in this embodiment has a 60% smaller volume, and the lifespan of the terminal filter is extended by 3 times due to the elimination of aerosol entrainment, significantly reducing operating costs.

[0021] like Figure 2 - Figure 4As shown, a G5-grade nitric acid production system further includes: a gas-liquid inlet 116 located at the lower end of one side of a distillation column 111; a heat exchanger inlet 115 located at the bottom of the distillation column 111; a distillation column inlet 112 located on one side of the middle section of the distillation column 111; and a distillation column reflux inlet 113 located on the other side. The distillation column inlet 112 is connected to the output of a preheater. The distillation column 111 is filled with several packing materials 118. The packing materials 118 below the distillation column inlet 112 are stripping section packing, and the packing materials 118 above the distillation column inlet 112 are rectifying section packing. A wire mesh demister 119 is located above the rectifying section packing. A distributor 117 is located above the stripping section packing, with its top connected to both the distillation column inlet 112 and the distillation column reflux inlet 113. A top condenser includes a condenser... Tank 121 has a steam inlet 122 on one side of its top and a scrubbing tower inlet 123 on the other side. The steam inlet 122 is connected to the outlet 114 of the distillation column, and the scrubbing tower inlet 123 is connected to the inlet of the scrubbing tower. A condenser tube 126 is installed inside the condenser 121. A condensate reflux pump 124 is connected to one output end of the bottom of the condenser 121, and a condensate output pump 125 is connected to the other output end. The output end of the condensate reflux pump 124 is connected to the reflux port 113 of the distillation column, and the output end of the condensate output pump 125 is connected to the condenser inlet 132. The input end of the heat exchanger 141 is connected to the heat exchanger input pump 142, and the input end of the heat exchanger input pump 142 is connected to the heat exchanger inlet 115. The output end of the heat exchanger 141 is connected to the gas-liquid inlet 116. A heat medium pipeline is installed inside the heat exchanger 141.

[0022] In the above embodiments, it should be noted that the distillation column body 111 is a distillation column lined with high-purity PFA, and the packing 118 packed inside the distillation column body 111 is θ-type high-efficiency wire mesh corrugated packing. The condensation temperature in condenser 121 is controlled at 45℃±2℃. The nitric acid condensed in condenser 121 is controlled by a diversion valve, and the reflux ratio is set to 4:1. Distillation purification and condensation separation process flow: (1) Industrial-grade nitric acid feedstock is preheated to 80°C by a preheater and then enters the middle of distillation column 111. The temperature of the bottom heat exchanger 141 is controlled at 125°C, and the temperature of the top of the column is controlled at 120.5°C. Through distillation, metal ions and heavy component impurities in the feedstock are removed; (2) The high-purity nitric acid vapor at the top of the tower enters the condenser 121 and is condensed into liquid by the circulating water at 30°C. The liquid is refluxed back into the tower at 4 times the amount produced by the condensate return pump 124 and the condensate output pump 125 to establish a stable gas-liquid balance.

[0023] The production process of a G5 grade nitric acid production system according to the present invention is as follows: Nitric acid from the mixing tank is preheated and then introduced into the distillation column 111. The nitric acid in the distillation column 111 flows down the stripping section packing to the bottom of the column and is introduced into the heat exchanger 141. Low-pressure saturated steam is then introduced into the heat medium pipeline to indirectly heat the nitric acid in the heat exchanger 141, causing it to vaporize. The nitric acid vapor is then reintroduced into the bottom of the distillation column 111 and passes upwards through the stripping and rectification section packing for heat and mass transfer. It then passes through a wire mesh demister 119 to remove entrained droplets, yielding high-purity gaseous nitric acid. The high-purity gaseous nitric acid escapes from the top of the distillation column 111 and enters the condenser 121 for condensation. After condensation, one path of the nitric acid flows back into the distillation column 111 through the reflux port 113, and another path enters the decolorization column 131 through the condenser inlet 132. Non-condensable gases are discharged from the gas scrubbing tower inlet 123 and enter the acid gas scrubbing tower. The CDA gas supply system is activated, and ultrapure CDA gas is introduced into the bottom of the decolorization tower 131 through the CDA inlet 135. The inlet flow rate is adjusted by a proportional valve and a flow meter. The ultrapure CDA gas at the bottom of the decolorization tower 131 enters the inner wall of the mass transfer membrane filament 163 through the pores on the surface of the bottom support plate 162, and then exits to the top of the decolorization tower 131 through the pores on the surface of the top support plate 161. At the same time, the high-purity nitric acid solution flowing into the decolorization tower 131 flows downward along the outer wall of the mass transfer membrane filament 163 from top to bottom. The high-purity nitric acid solution flows downward during the downward flow process. The rough turbulent structure on the surface of the filling wire 164 generates eddies and turbulence, which spread outwards and directly impact the surface of the mass transfer membrane wire 163. Nitrogen dioxide gas molecules dissolved in nitric acid diffuse through the mass transfer membrane wire 163 into the CDA gas flow and are carried away. They are discharged from the top of the decolorization tower body 131 and enter the acid gas scrubbing tower through the CDA exhaust port 136. The nitric acid solution after decolorization flows into the decolorization receiving tank 151 through the receiving tank inlet 133 and is pumped to the finished product intermediate tank by the decolorization circulation pump.

[0024] Acid gas from decolorization tower 131 and condenser 121 is collected in acid gas scrubbing tower. Acid gas enters from the bottom of acid gas scrubbing tower and is absorbed by ultrapure water in the packing layer to form nitric acid, which is then deposited in the lower part of acid gas scrubbing tower. The product from the lower part of acid gas scrubbing tower is discharged in two ways: one way is cooled by silicon carbide acid gas condenser and then returned to acid gas scrubbing tower as absorbent; the other way is discharged to mixing tank through proportional valve interlocking the tower bottom liquid level. High-purity nitric acid from decolorization receiving tank 151 enters the finished product intermediate tank from the top output end. The finished product cooler is started to cool the circulation return pipeline of the finished product intermediate tank. The cooled nitric acid flows back to the finished product intermediate tank. The concentration can be adjusted according to customer needs through the online concentration meter on the circulation return pipeline. After the nitric acid in the finished product intermediate tank is fully mixed and homogeneous, it is sent to the central control room for testing. High-purity nitric acid is drawn from the output end of the circulation reflux pipeline of the finished product intermediate tank to the finished product filter cabinet. The finished product filter cabinet performs three-stage circulation filtration of the high-purity nitric acid. After the filtered product passes the online particle size analyzer test, it is divided into two streams and enters the 200L filling line. Finally, the 200L filling line is started to complete the filling of G5 grade high-purity nitric acid.

[0025] The above description is merely a preferred embodiment of the present invention. Any person skilled in the art can modify the present invention or modify it into an equivalent technical solution using the technical solutions described above. Therefore, any simple modifications or equivalent substitutions made based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A production system for G5 grade nitric acid, comprising a raw material processing section, an evaporation and distillation section, a decolorization section, a gas washing section, a finished product storage section, and a filling section, characterized in that: The raw material processing section includes a mixing tank, and the output end of the mixing tank is connected to a preheater; The evaporation and distillation section includes a distillation column, the input end of which is connected to a preheater, the bottom of which is connected to a heat exchanger, and the output end of which is connected to a top condenser. The decolorization section includes a decolorization tower, which is equipped with a membrane decolorization component. The input end of the decolorization tower is connected to the top condenser, and the output end of the decolorization tower is connected to the decolorization receiving tank. The gas scrubbing section includes an acid gas scrubbing tower, the input end of which is connected to a condenser at the top of the tower, the acid gas scrubbing tower is connected to an acid gas cooler, and the output end of the acid gas scrubbing tower is connected to a mixing tank. The finished product storage section includes a finished product intermediate tank, the input end of which is connected to a decolorization receiving tank, and the output end of which is provided with a circulation return pipeline. The circulation return pipeline is connected to a finished product condenser and is equipped with an online concentration meter. The filling section includes a finished product filter cabinet and a 200L filling line. The input end of the finished product filter cabinet is connected to the output end of the circulating return pipeline, and the output end of the finished product filter cabinet is connected to the 200L filling line. An online particle analyzer is installed on the pipeline between the finished product filter cabinet and the 200L filling line. All towers, storage tanks, and pipelines in the raw material section, evaporation and distillation section, decolorization section, gas washing section, finished product storage section, and filling section are lined with fluoropolymer materials. The distillation column includes a distillation column body, a distillation column outlet is provided at the top of the distillation column body, and a wire mesh demister is installed inside the upper end of the distillation column body near the distillation column outlet. The decolorization tower includes a decolorization tower body, with a condenser inlet at the upper end of one side and a receiving tank inlet at the lower end of the same side. The membrane decolorization assembly includes a top support plate and a bottom support plate. The top support plate is installed on the inner wall of the decolorization tower body above the condenser inlet, and the bottom support plate is installed on the inner wall of the decolorization tower body below the receiving tank inlet. A plurality of mass transfer membrane fibers are installed between the top support plate and the bottom support plate, and a filler wire is provided between each of the mass transfer membrane fibers. The surface of the filler wire is provided with a rough turbulence structure.

2. The production system for G5 grade nitric acid according to claim 1, characterized in that: The upper end of the decolorizing tower body is provided with a CDA exhaust port, the lower end of the decolorizing tower body is provided with a CDA inlet, the CDA inlet is connected to the CDA gas supply system, and the outer wall of the decolorizing tower body on the side opposite to the condenser inlet is provided with a decolorizing tower reflux port.

3. The production system for G5 grade nitric acid according to claim 2, characterized in that: The surfaces of the top support plate and the bottom support plate are provided with pores arranged in a square array. The mass transfer membrane filament is a hollow tubular structure. Several of the mass transfer membrane filaments are arranged in a square array between the top support plate and the bottom support plate. The upper and lower ends of the mass transfer membrane filaments are respectively connected to the pores on the surfaces of the top support plate and the bottom support plate.

4. The production system for G5 grade nitric acid according to claim 3, characterized in that: The lower end of the filler wire is fixedly installed on the bottom support plate. A filler wire is arranged between the four mass transfer membrane wires. The surface of the filler wire is equidistant from the surface of the four surrounding mass transfer membrane wires. An outer guide plate is installed on the inner wall of the decolorization tower between the top support plate and the bottom support plate. The inner wall of the outer guide plate is equidistant from the surface of the adjacent mass transfer membrane wires. The inner wall of the outer guide plate is also provided with a rough turbulence structure.

5. A G5-grade nitric acid production system according to claim 2, characterized in that: The input end of the decolorizing receiving tank is connected to the receiving tank inlet, the bottom output end of the decolorizing receiving tank is connected to the receiving tank output pump, the output end of the receiving tank output pump is connected to the decolorizing tower reflux port, and the top output end of the decolorizing receiving tank is connected to the input end of the finished product intermediate tank.

6. The production system for G5 grade nitric acid according to claim 1, characterized in that: A gas-liquid inlet is provided at the lower end of one side of the distillation column body, a heat exchanger inlet is provided at the bottom of the distillation column body, a distillation column liquid inlet is provided on one side of the middle part of the distillation column body, and a distillation column reflux inlet is provided on the other side. The distillation column liquid inlet is connected to the output end of the preheater.

7. The production system and process for G5 grade nitric acid according to claim 6, characterized in that: The distillation column is filled with several packing materials. The packing material below the liquid inlet of the distillation column is the stripping section packing material, and the packing material above the liquid inlet of the distillation column is the rectification section packing material. The wire mesh demister is located above the rectification section packing material, and a distributor is provided above the stripping section packing material. The top of the distributor is connected to the liquid inlet of the distillation column and the reflux port of the distillation column, respectively.

8. A G5-grade nitric acid production system according to claim 7, characterized in that: The top condenser includes a condenser tank. A steam inlet is provided on one side of the top of the condenser tank, and a gas scrubbing tower inlet is provided on the other side. The steam inlet is connected to the gas outlet of the distillation column, and the gas scrubbing tower inlet is connected to the gas scrubbing tower input end. A condenser tube is installed inside the condenser tank. A condensate reflux pump is connected to one output end of the bottom of the condenser tank, and a condensate output pump is connected to the other output end. The output end of the condensate reflux pump is connected to the distillation column reflux port, and the output end of the condensate output pump is connected to the condenser inlet.

9. A G5-grade nitric acid production system according to claim 6, characterized in that: The heat exchanger input end is connected to the heat exchanger input pump, the heat exchanger input pump input end is connected to the heat exchanger inlet, the heat exchanger output end is connected to the gas-liquid inlet, and a heat medium pipeline is installed inside the heat exchanger.

10. A production process based on a G5-grade nitric acid production system according to any one of claims 1-9, characterized in that: Including S1-S5; S1. Nitric acid in the mixing tank is preheated and then introduced into the distillation column. The nitric acid in the distillation column flows down the packing of the stripping section to the bottom of the distillation column and is introduced into the heat exchanger. Then, low-pressure saturated steam is introduced into the heat medium pipeline to indirectly heat the nitric acid in the heat exchanger, causing it to vaporize. The nitric acid vapor is reintroduced into the bottom of the distillation column and passes upward through the packing of the stripping section and the packing of the rectification section for heat and mass transfer. Then, the entrained droplets are removed by the wire mesh demister to obtain high-purity gaseous nitric acid. The high-purity gaseous nitric acid escapes from the top of the distillation column and enters the condenser for condensation. After condensation, the nitric acid flows back into the distillation column through the reflux port and enters the decolorization column through the condenser inlet. Non-condensable gases are discharged from the inlet of the gas scrubbing tower and enter the acid gas scrubbing tower. S2. Start the CDA gas supply system and introduce ultrapure CDA gas into the bottom of the decolorization tower through the CDA inlet. Adjust the gas flow rate through the proportional valve and flow meter. The ultrapure CDA gas at the bottom of the decolorization tower enters the inner wall of the mass transfer membrane filament through the pores on the surface of the bottom support plate and is then discharged to the top of the decolorization tower through the pores on the surface of the top support plate. At the same time, the high-purity nitric acid solution flowing into the decolorization tower flows downward along the outer wall of the mass transfer membrane filament from top to bottom. During the downward flow of the high-purity nitric acid solution, it is affected by the rough turbulent structure on the surface of the filling filament, generating eddies and turbulence. The eddies and turbulence spread in all directions and directly impact the surface of the mass transfer membrane filament. Nitrogen dioxide gas molecules dissolved in nitric acid diffuse through the mass transfer membrane filament into the CDA gas flow and are carried away. They are discharged from the top of the decolorization tower and enter the acid gas scrubbing tower through the CDA exhaust port. The nitric acid solution after decolorization flows into the decolorization receiving tank through the receiving tank inlet and is pumped to the finished product intermediate tank by the decolorization circulation pump. S3. Acid gas from the decolorization tower and condenser is collected in the acid gas scrubbing tower. The acid gas enters from the bottom of the acid gas scrubbing tower in a countercurrent manner and is absorbed by ultrapure water in the packing layer to form nitric acid, which is then deposited in the lower part of the acid gas scrubbing tower. The product from the lower part of the acid gas scrubbing tower is discharged in two ways: one way is cooled by the silicon carbide acid gas condenser and then returned to the acid gas scrubbing tower as the absorbent; the other way is discharged to the mixing tank through the proportional valve interlocking the tower bottom liquid level. S4. High-purity nitric acid from the decolorization receiving tank enters the finished product intermediate tank from the top output end. The finished product cooler is started to cool the circulation return pipeline of the finished product intermediate tank. The cooled nitric acid flows back to the finished product intermediate tank. The concentration can be adjusted according to customer needs through the online concentration meter on the circulation return pipeline. After the nitric acid in the finished product intermediate tank is fully mixed and homogeneous, it is sent to the central control room for testing. S5. High-purity nitric acid is drawn from the output end of the circulation reflux pipeline of the finished product intermediate tank to the finished product filter cabinet. The finished product filter cabinet performs three-stage circulation filtration of the high-purity nitric acid. After the filtered product passes the online particle size analyzer test, it is divided into two streams and enters the 200L filling line. Finally, the 200L filling line is started to complete the filling of G5 grade high-purity nitric acid.

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