Silicon tetrafluoride concentrator

Abstract

This invention relates to a chemical equipment, specifically a silicon tetrafluoride concentrator. The technical solution includes a main gas inlet pipe, characterized in that at least one set of spray cylinder sections are connected in series within the main gas inlet pipe. Each spray cylinder section includes vertical and horizontal sections. The vertical section has gas inlets and outlets at different heights. The gas inlet of the vertical section is connected to the main gas inlet pipe, and the gas outlet of the vertical section is connected to the inlet of the horizontal section. The top of the horizontal section has multiple spray mounting ports, into which spray pipes are inserted. The lower end of each spray pipe is connected to a nozzle, and the upper end is connected to a main liquid pipeline. This invention features simple structure, low equipment height, low investment and operating costs, sufficient gas-liquid contact, good concentration effect, corrosion and wear resistance, convenient maintenance, and stable and reliable operation.

Description

Technical Field

[0001] This invention relates to a chemical equipment, specifically a silicon tetrafluoride concentrator. Background Technology

[0002] Silicon tetrafluoride (SiF4) is a key intermediate gas in the process of producing hydrogen fluoride from fluorosilicic acid. The gaseous components from the reaction and stripping processes contain a large amount of SiF4, which needs to be absorbed, reacted, and concentrated in a silicon tetrafluoride concentrator. The reaction formula is as follows: 5SiF4 + 2H2O → 2H2SiF6·SiF4 + SiO2.

[0003] The equipment in this process operates under negative pressure, high temperature, strong corrosion, and SiO2 abrasion conditions for a long time. The medium contains fluorosilicic acid (mass concentration ≤45%), hydrofluoric acid, silicon tetrafluoride, and silica gel, which places extremely high demands on the equipment's structural design, material selection, gas-liquid mass transfer efficiency, and operational reliability.

[0004] The existing silicon tetrafluoride concentration and absorption devices mainly suffer from the following technical defects: 1. Traditional stirring or spray concentrators use rotating parts such as sprayers to achieve gas-liquid mixing, which has problems such as high power consumption, difficulty in sealing the shaft end, and poor reliability. In addition, the atomized droplet size is large, the gas-liquid contact area is limited, the SiF4 absorption reaction is insufficient, the fluorine content in the tail gas is high, and the fluorine recovery rate is low.

[0005] 2. Existing spray absorption towers mostly adopt a vertical high tower with a multi-layer spray structure, such as the structure disclosed in patent documents CN202110363427.8 and CN202120680309.5 for silicon tetrafluoride concentration devices. Although spray absorption can be achieved, there are obvious shortcomings: the total height of the tower is too large, and the investment and operation and maintenance costs of the supporting frame and maintenance platform are high; the multi-layer spray liquid collects at the bottom of the tower, which cannot achieve graded absorption and cascaded reuse. If graded absorption is required, multiple towers need to be connected in series, which further increases the investment in equipment and the land area; some solutions use a ring-shaped spray main pipe, which has complex fittings, is difficult to process with fluoroplastic lining, and is difficult to clean when blocked; the spray pipe needs to be connected to the downward-facing nozzle with an elbow, the cylinder opening is large and the spray pipe extends long, and the extended spray pipe is a cantilever structure, which is subject to large forces and vibrations during operation and is prone to damage.

[0006] 3. Conventional lining structures are prone to failure under high temperature and negative pressure conditions, such as softening, detachment, and bulging of the fluoroplastic lining. This results in a short equipment lifespan and makes it difficult to adapt to the conditions of strong HF penetration and strong acid corrosion. Simultaneously, the lack of airflow deflection and disturbance makes short circuits more likely, leading to short gas residence time and insufficient mass transfer, which affects concentration efficiency and fluorine yield. Spray pipes often have residual liquid, which can cause corrosion or scaling after shutdown due to stagnant media, resulting in high maintenance frequency and high replacement costs for spare sections.

[0007] In summary, existing silicon tetrafluoride concentrators cannot simultaneously meet the comprehensive requirements of corrosion resistance, wear resistance, negative pressure resistance, low height, low cost, easy maintenance, and high mass transfer efficiency, and cannot well adapt to the industrial stable operation requirements of fluorosilicic acid to hydrogen fluoride production units. Summary of the Invention

[0008] To overcome the technical defects of existing silicon tetrafluoride concentration equipment, such as high operating power consumption, poor sealing reliability, large tower height, complex spray structure, difficulty in fluoroplastic lining, difficulty in clearing blockages, airflow short circuit, low absorption efficiency, inconvenient maintenance, and high cost of spare replacement cylinder sections, the present invention aims to provide a silicon tetrafluoride concentrator for hydrogen fluoride plants. This concentrator adopts a combination of vertical and horizontal cylinder sections, multi-directional baffle mass flow, no annular spray main pipe, detachable pipeline, and integrated design of negative pressure anti-corrosion lining. It features simple structure, low equipment height, low investment and operating costs, sufficient gas-liquid contact, good concentration effect, corrosion resistance and wear resistance, convenient maintenance, stable and reliable operation, and fewer cylinder section specifications for easy spare replacement.

[0009] The technical solution includes a main gas inlet pipe connected in series with at least one set of spray cylinder sections. Each spray cylinder section comprises vertical and horizontal sections. The vertical section has gas inlets and outlets at different heights. The gas inlet of the vertical section connects to the main gas inlet pipe, and the gas outlet connects to the inlet of the horizontal section. The top of the horizontal section has multiple spray mounting ports, into which spray pipes are inserted. The lower end of each spray pipe is connected to a nozzle, and the upper end is connected to the main liquid pipeline. The spray cylinder section assembly uses a combination of vertical and horizontal sections, significantly reducing the overall height of the equipment and minimizing the investment in frames and maintenance platforms. The gas undergoes multi-directional flow within the cylinders, with both horizontal and vertical deflections, resulting in stronger turbulence, longer residence time, and more complete gas-liquid mass transfer and absorption reactions. The spray mounting ports on the top of the horizontal section, with nozzles arranged vertically downwards, ensure uniform spray coverage, a large gas-liquid contact area, and better silicon tetrafluoride absorption and concentration effects. The cylinder sections adopt a modular series connection, which can be flexibly increased or decreased according to the processing capacity and concentration requirements, making it more adaptable. The spray pipeline is uniformly connected to the main liquid pipeline, with simple piping layout, no complex ring main pipe, easy to clean and not easy to clog, and easy to process with fluoroplastic lining.

[0010] The top cover of the vertical cylindrical section has a spray installation port, into which a spray pipe is inserted. The lower end of the spray pipe is connected to a nozzle, and the upper end is connected to the main liquid pipeline. The spray structure on the top cover of the vertical cylindrical section enables dual spraying in both the vertical and horizontal sections, further improving the gas-liquid contact and absorption efficiency.

[0011] The main gas inlet pipe is a horizontal cylindrical section with multiple spray installation ports at the top. Spray pipes are inserted into these ports, with nozzles connected to the lower end of each pipe and the main liquid pipeline connected to the upper end. Pre-spraying absorption begins at the inlet section, capturing some of the silicon tetrafluoride and reducing the processing load on subsequent cylindrical sections.

[0012] The main liquid pipeline is composed of multiple detachable tee pipes connected in series, with the vertical port of each tee pipe connecting to the upper end of the spray pipe. The end port of the main liquid pipeline is detachably connected to the upper end of the spray pipe at the top of the vertical cylindrical section via a bend. The main liquid pipeline uses detachable series tee pipes, eliminating the need for complex ring-shaped main pipes, resulting in a simple structure and low manufacturing and installation difficulty; the vertical port of the tee pipe connects directly to the spray pipe, making fluoropolymer lining easier; the end of the main liquid pipeline connects to the spray pipe of the vertical cylindrical section via a bend, ensuring smooth pipeline routing without dead angles and good spraying effect. All spray pipes and nozzles are vertically downward, allowing for complete drainage of accumulated liquid during shutdown, eliminating residual liquid, reducing corrosion, and preventing scale formation.

[0013] The inlet end of the horizontal cylindrical section is equipped with a vertical baffle. The upper part of the vertical baffle is a closed zone, and the middle part is a ventilation zone. Forced gas passes through the middle of the cylindrical section. The gas must pass through the spray zone to prolong the effective contact time, avoid short-circuiting of the airflow, further increase turbulence, increase gas-liquid contact mass transfer, and improve the absorption rate of silicon tetrafluoride and the fluorine recovery rate.

[0014] The bottom of the vertical baffle is provided with a liquid isolation zone to restrict the flow of liquid at the bottom to the liquid outlet at the bottom of the vertical cylinder section, so as to collect and reuse the liquid phase of the corresponding spray cylinder section group, effectively achieving the purpose of graded recovery and recycling.

[0015] The main gas inlet pipe is connected in series with multiple spray cylinder sections. The outlet of the horizontal cylinder section in the previous spray cylinder section is connected to the gas inlet of the vertical cylinder section in the next spray cylinder section. Furthermore, the gas inlet and gas outlet on the vertical cylinder section are not in the same position, which allows for convenient and flexible series connection of multiple spray cylinder sections. The multiple spray cylinder sections are connected in a three-dimensional staggered arrangement. The staggered arrangement in three-dimensional space only increases the floor space, without increasing the installation height, and multiple connections can be achieved, making installation, inspection, and maintenance more convenient and reliable.

[0016] This invention effectively solves the defects of traditional equipment, such as high height, high cost, difficulty in cleaning and clogging, difficulty in fluoroplastic lining, easy short circuit, low absorption efficiency, and inconvenient maintenance, through structural design that combines vertical and horizontal cylindrical sections, modular series connection, detachable spray without annular pipe, baffle to prevent short circuit, and full drainage with no residue. It has the advantages of reliable operation, low energy consumption, corrosion resistance and wear resistance, high concentration efficiency, convenient maintenance, long service life, and fewer cylindrical section specifications for easy spare replacement. It is particularly suitable for silicon tetrafluoride concentration in the fluorosilicic acid to hydrogen fluoride production unit. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a single spray cylinder assembly of the present invention.

[0018] Figure 2 This is a schematic diagram of the structure of the multiple spray cylinder sections of the present invention.

[0019] Figure 3 This is a schematic diagram of the structure of baffle 3.

[0020] Among them, 1-main liquid pipeline, 1.1-te-pipe, 1.2-bend, 2-end cap, 3-baffle, 3.1-closed area, 3.2-ventilated area, 3.3-liquid isolation area, 4-vertical cylindrical section, 4.1-spray installation port, 4.2-liquid outlet, 5-horizontal cylindrical section, 5.1-spray installation port, 6-main gas inlet pipe, 6.1-spray installation port, 7-spray pipe, 8-spray head. Detailed Implementation

[0021] The present invention will be further explained below with reference to the accompanying drawings: The silicon tetrafluoride concentrator of this invention is made of steel lined with fluoroplastic material. The fluoroplastic lining is clamped and pressed by multiple flanges. It is suitable for working conditions with negative pressure, high temperature, strong corrosion and silica abrasion. The equipment mainly includes a main gas inlet pipe 6, at least one set of spray cylinder sections, a liquid main pipe 1, a tee pipe 1.1, a bend pipe 1.2, a spray pipe 7, a nozzle 8, an end cap 2, a baffle 3, and corresponding spray installation ports 4.1, 5.1, 6.1 and liquid outlet 4.2.

[0022] See Figure 1 The main gas inlet pipe 6 adopts a horizontal cylindrical structure with multiple spray installation ports 6.1 at its top. Spray pipes 7 and nozzles 8 are inserted into the spray installation ports 6.1 and connected to the main liquid pipeline 1. After the gas containing silicon tetrafluoride enters, it can be pre-sprayed and absorbed to capture some of the silicon tetrafluoride and reduce the processing load of the subsequent cylindrical sections.

[0023] The main gas inlet pipe 6 is connected in series with at least one set of spray cylinder sections. The spray cylinder section consists of a vertical cylinder section 4 and a horizontal cylinder section 5. The vertical cylinder section 4 is provided with gas inlets and gas outlets at different heights. The gas outlet of the vertical cylinder section 4 is connected to the inlet of the horizontal cylinder section 5. The gas inlet of the vertical cylinder section 4 is connected to the main gas inlet pipe 6. The top end cap 2 of the vertical cylinder section 4 has a spray installation port 4.1. The spray pipe 7 and the nozzle 8 are inserted into the spray installation port 4.1 and connected to the main liquid pipeline 1. The bottom end cap 2 of the vertical cylinder section 4 has a liquid outlet 4.2 for discharging the concentrated fluorosilicic acid liquid, realizing graded drainage and recycling. The top of the horizontal cylindrical section 5 also has multiple spray installation ports 5.1. Spray pipes 7 and nozzles 8 are inserted into the spray installation ports 5.1 and connected to the main liquid pipeline 1. The inlet end of the horizontal cylindrical section 5 is equipped with a vertical baffle 3. The upper part of the baffle 3 is a closed area 3.1, and the middle part is a ventilation area 3.2, which can force gas to flow through the middle of the cylindrical section, avoid airflow short circuit, and improve the gas-liquid contact effect. The bottom of the baffle 3 is also equipped with a liquid-separating area 3.3, which allows the liquid at the bottom to flow to one side of the baffle 3. The inlet end of the main gas inlet pipe 6 can be equipped with a baffle 3 of the same structure.

[0024] The main liquid pipeline 1 is composed of multiple detachable tee pipes 1.1 connected in series. The vertical port of each tee pipe 1.1 is connected to the upper end of the spray pipe 7. The end port of the main liquid pipeline 1 is connected to the spray pipe 7 at the top end cap 2 of the vertical cylindrical section 4 via a detachable elbow 1.2. The spray pipes 7 are all without bends and are arranged vertically downwards. When the pipeline is stopped, the medium in the pipeline can be completely drained, leaving no residual liquid, reducing corrosion and preventing residual liquid from scaling.

[0025] See Figure 2 As another embodiment, multiple spray cylinder sections can be connected in series. Simply connect the outlet of the horizontal cylinder section 5 in the previous spray cylinder section to the gas inlet of the vertical cylinder section 4 in the next spray cylinder section. Since the gas inlet and gas outlet on the vertical cylinder section 4 are not at the same height or in the same position (the gas outlet in different spray cylinder sections can be arranged in the upper or lower section as needed, and the corresponding gas inlet is arranged in the lower or upper section), multiple spray cylinder sections connected in series can be arranged in staggered upper and lower layers in three-dimensional space, just like modular assembly. This only increases the floor space without increasing the arrangement height. The flow time, stroke, and fluorine absorption degree of the gas in the silicon tetrafluoride concentrator are flexible and controllable.

[0026] During operation, the gas containing silicon tetrafluoride passes sequentially through the main gas inlet pipe 6 for pre-spraying, the vertical cylindrical section 4 for spraying, the baffle absorption, and the horizontal cylindrical section 5 for deep spraying. Through multiple sets of spray cylindrical sections, multi-stage baffles and progressive concentration can be achieved. Finally, it is discharged from the outlet of the last horizontal cylindrical section 5. The liquid after absorption reaction is guided by the baffle 3 and collects at the bottom of the vertical cylindrical section 4 in each set of spray cylindrical sections. It is discharged from the liquid outlet 4.2 and can be circulated for spraying, forming a stepped spraying effect, which improves the concentration of fluorosilicic acid and the fluorine yield.

[0027] This device can arrange multiple spray cylinder sections in a staggered manner in three-dimensional space, increasing the floor space without increasing the overall height of the equipment, significantly reducing the investment in the frame and maintenance platform. The spray installation ports 4.1, 5.1, and 6.1 have small opening sizes (compared to the traditional structure of spray pipes with elbows, the cylinder opening size can be reduced by 50%) and short spray extensions. The pipelines and spray pipes 7 are all detachable, which is convenient for cleaning, maintenance and replacement. The equipment has no rotating parts, low power consumption and high reliability, and can be stably used for long-term application in the silicon tetrafluoride concentration process in the fluorosilicic acid to hydrogen fluoride production unit.

[0028] See Example 1 Figure 1 A set of spray cylinders has a total of 5 nozzles (8), and the total absorption rate of silicon tetrafluoride is 50% to 60%. See Example 2. Figure 2 There are 11 nozzles in three spray cylinder sections. The spray liquid is divided into three stages of spraying. The total absorption rate of silicon tetrafluoride is 85wt% ~ 90wt%. The effluent from the first spray cylinder section can obtain 42wt% ~ 45wt% concentrated fluorosilicic acid.

[0029] The following comparative test is conducted using silicon tetrafluoride concentration in a hydrogen fluoride unit as an example: silicon tetrafluoride gas 1000 Nm3 / h (containing 90wt%~95wt% silicon tetrafluoride), and the equipment material is carbon steel lined with PTFE.

Claims

1. A silicon tetrafluoride concentrator, comprising a main gas inlet pipe, characterized in that, The main gas inlet pipe is connected in series with at least one set of spray cylinder sections. The spray cylinder section includes a vertical cylinder section and a horizontal cylinder section. The vertical cylinder section is provided with gas inlets and gas outlets at different heights. The gas inlet of the vertical cylinder section is connected to the main gas inlet pipe, and the gas outlet of the vertical cylinder section is connected to the inlet of the horizontal cylinder section. The top of the horizontal cylinder section has multiple spray installation ports, and spray pipes are inserted into the spray installation ports. The lower end of the spray pipe is connected to a nozzle, and the upper end is connected to the main liquid pipeline.

2. The silicon tetrafluoride concentrator as described in claim 1, characterized in that, The top cover of the vertical cylindrical section has a spray installation port, into which a spray pipe is inserted. The lower end of the spray pipe is connected to a nozzle, and the upper end is connected to the main liquid pipeline.

3. The silicon tetrafluoride concentrator as described in claim 1, characterized in that, The main gas inlet pipe is a horizontal cylindrical section with multiple spray installation ports at the top. Spray pipes are inserted into the spray installation ports, with nozzles connected to the lower end of the spray pipes and the main liquid pipeline connected to the upper end.

4. The silicon tetrafluoride concentrator according to any one of claims 1-3, characterized in that, The main liquid pipeline is composed of multiple detachable tee pipes connected in series, with the vertical port of each tee pipe connected to the upper end of the spray pipe.

5. The silicon tetrafluoride concentrator as described in claim 4, characterized in that, The end port of the main liquid pipeline is detachably connected to the upper end of the spray pipe at the top of the vertical cylindrical section via a bend.

6. The silicon tetrafluoride concentrator according to any one of claims 1-3, characterized in that, The inlet end of the horizontal cylindrical section is provided with a vertical baffle. The upper part of the vertical baffle is a closed area, the middle part is a ventilated area, and the bottom part is a liquid-blocking area.

7. The silicon tetrafluoride concentrator as described in claim 1, characterized in that, The gas inlet and gas outlet on the vertical cylindrical section are not in the same position.

8. The silicon tetrafluoride concentrator according to any one of claims 1-3, characterized in that, The bottom of the vertical cylindrical section is provided with a liquid outlet.

9. The silicon tetrafluoride concentrator as described in claim 1 or 8, characterized in that, The main gas inlet pipe is connected in series with multiple spray cylinder sections. The outlet of the horizontal cylinder section in the previous spray cylinder section is connected to the gas inlet of the vertical cylinder section in the next spray cylinder section.

10. The silicon tetrafluoride concentrator as described in claim 9, characterized in that, The multiple spray cylinder sections are arranged in a three-dimensional staggered series.

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