Dilute sulfuric acid separation and purification system
By optimizing the spray nozzle position in the stripping tower and using low-pressure steam condensate to heat the inert gas, the problems of high energy consumption and low concentration of dilute sulfuric acid in mixed acid stripping were solved, thereby increasing the concentration of dilute sulfuric acid and improving the fluorine recovery rate, and reducing production costs.
Patent Information
- Application Number
- CN202520335118.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-28
- Publication Date
- 2026-02-27
- Estimated Expiration
- 2035-02-28
AI Technical Summary
In existing technologies, the process of separating hydrogen fluoride and sulfuric acid by mixed acid stripping consumes a lot of energy, has a low concentration of dilute sulfuric acid, and contains a high fluorine content, which limits its effective utilization and causes the loss of fluorine.
The stripping tower is equipped with multiple mixed acid spray nozzles and cooler spray nozzles at different vertical heights. It combines low-pressure steam condensate as a heat exchange medium and inert gas for stripping, forming a temperature gradient to optimize the stripping process. The low-pressure steam condensate and inert gas are used for heating to improve the fluorine recovery rate and dilute sulfuric acid concentration.
It achieves an increase in dilute sulfuric acid concentration to 73%~77% and a reduction in fluorine content to 500~1000 ppm, thereby reducing energy consumption and improving fluorine recovery rate. It has good adaptability, low cost, and wide market application.
Smart Images
Figure CN223945021U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to a kind of separation purification field, especially a kind of separation purification dilute sulfuric acid system. BACKGROUND
[0002] Anhydrous Hydrofluoric Acid (AHF) is an important chemical raw material, which is the basic raw material of fluorine chemical industry chain. It can be used as raw material for the production of refrigerants, fluorine-containing polymer materials, fluorine-containing fine chemicals, inorganic fluorides, etc. At the same time, it can also be used for metal surface treatment and glass etching.
[0003] Currently, the production of anhydrous hydrofluoric acid mainly adopts fluorite method process, which is quite mature. However, with the increasing strictness of environmental protection policy, the efficient utilization of fluorosilicic acid, a byproduct of phosphoric acid production from phosphate rock, is important. The common fluorosilicic acid route is to react concentrated sulfuric acid with fluorosilicic acid to generate hydrogen fluoride and silicon tetrafluoride gas. Hydrogen fluoride can be absorbed by sulfuric acid to form mixed acid, which is then desorbed and distilled to obtain high-purity hydrogen fluoride. At the same time, this route produces dilute sulfuric acid with a mass fraction of ~72%. However, the process of stripping hydrogen fluoride and sulfuric acid from mixed acid has high energy consumption, and the concentration of dilute sulfuric acid obtained is relatively low. Moreover, the dilute sulfuric acid solution still contains a certain amount of fluorine (fluorine content is ~5000 ppm), which to some extent limits the effective utilization of dilute sulfuric acid by downstream production enterprises and causes the loss of effective fluorine elements. SUMMARY
[0004] The purpose of the utility model is to solve the above technical problems, and to provide a dilute sulfuric acid separation and purification system that is extremely simple, has good stripping effect, high dilute sulfuric acid concentration, high fluorine recovery rate, and good process adaptability.
[0005] The dilute sulfuric acid separation and purification system of the utility model comprises a heat exchanger and a stripping column connected thereto. The top of the stripping column is provided with a gas outlet, the upper section is provided with a mixed acid spraying port, the lower section is provided with an inert gas inlet, and the bottom is provided with a dilute sulfuric acid outlet. The inert gas inlet is connected to the heat exchanger, and the dilute sulfuric acid outlet is connected to a primary cooler. The outlet of the primary cooler is connected to a downstream pipeline and a dilute sulfuric acid spraying port in the lower part of the stripping column, respectively. The upper section of the stripping column is provided with at least two mixed acid spraying ports with different vertical heights.
[0006] The highest mixed acid spraying port is located at the upper end of the stripping column, which is 1 / 10 of the total height of the stripping column from the top of the stripping column. The lowest mixed acid spraying port is located at the upper middle part of the stripping column, which is 2 / 5 of the total height of the stripping column from the top of the stripping column.
[0007] The vertical distance between the adjacent two mixed acid spraying ports is 1 / 20 to 3 / 10 of the total height of the stripping column.
[0008] The outlet of the first cooling device is connected with the upper dilute sulfuric acid spraying port, and the outlet of the second cooling device is connected with the lower dilute sulfuric acid spraying port.
[0009] The outlet of the second cooling device is connected with the downstream pipeline and the lower dilute sulfuric acid spraying port in the stripping tower.
[0010] The upper and lower dilute sulfuric acid spraying ports in the stripping tower are arranged at different vertical heights.
[0011] The outlet of the first cooling device is connected with the upper dilute sulfuric acid spraying port, and the outlet of the second cooling device is connected with the lower dilute sulfuric acid spraying port.
[0012] The upper section of the stripping tower is provided with three mixed acid spraying ports at different vertical heights.
[0013] The heat exchanger is provided with an inlet and an outlet for connecting the low-pressure steam condensate pipeline.
[0014] In view of the problems in the background art, the inventor has made the following improvements:
[0015] 1) At least two mixed acid spraying ports at different vertical heights are arranged in the upper section of the stripping tower, the mixed acid solution is vertically injected at multiple positions, and part of the circulating dilute sulfuric acid from the first cooling device and the second cooling device is also sprayed into the upper and lower dilute sulfuric acid spraying ports at different vertical heights, so that a temperature gradient gradually increasing from bottom to top is formed in the stripping tower, the stripping effect is effectively improved, the fluorine recovery rate is increased, the by-product dilute sulfuric acid with high sulfuric acid concentration and low fluorine content is more friendly to the downstream device, and the application market is wider, and meanwhile, the formation of the temperature gradient is helpful to the selection of the material of the stripping tower and the subsequent cooling device, and the construction cost is reduced; 2) The low-pressure steam condensate generated in the upstream process is used as the heat exchange medium of the heat exchanger to heat the inert gas, so that the utilization efficiency of waste heat is effectively improved, the energy consumption of the device is reduced, and the production cost is reduced to a certain extent; 3) The hot inert atmosphere (nitrogen and / or argon) is used as the stripping gas, and after being heated by the heat exchanger, the inert gas is sent into the stripping tower through the inert gas inlet, compared with the traditional air and / or steam as the stripping gas, the amount of the stripping gas is small, the safety is high, and meanwhile, the water vapor in the stripping gas can be effectively reduced, and the concentration of the final dilute sulfuric acid is improved. 4) The system of the utility model has the advantages of simple system, good stripping effect, good process adaptability, low investment and operation cost, the fluorine content in the by-product dilute sulfuric acid can be reduced to 500 ppm-1000 ppm (mass concentration), and the product sulfuric acid concentration can be increased to 73%-77% (mass concentration). BRIEF DESCRIPTION OF DRAWINGS
[0016] Figure 1 FIG. 1 is a structural schematic view of the embodiment 1 of the utility model.
[0017] Figure 2Structure schematic view of the embodiment 2 of the present utility model.
[0018] Wherein, 1-heat exchanger, 1.1-low pressure steam condensate import, 1.2-low pressure steam condensate export, 2-stripping tower, 2.1-gas export, 2.2-mixed acid spraying port, 2.3-inert gas import, 2.4-dilute sulfuric acid export, 2.5-upper dilute sulfuric acid spraying port, 2.6-lower dilute sulfuric acid spraying port, 3-primary cooler, 4-secondary cooler. DETAILED DESCRIPTION
[0019] The present utility model will be further explained and described below in combination with the drawings:
[0020] Embodiment 1
[0021] Heat exchanger 1, stripping tower 2 and primary cooler 3 are sequentially connected, the top of stripping tower 2 is provided with gas export 2.1, the upper section is provided with three mixed acid spraying ports 2.2 of different vertical heights, the highest mixed acid spraying port is located at a position with a height of 1 / 10 of the total height of stripping tower from the top of stripping tower, and the lowest mixed acid spraying port is located at a position with a height of 3 / 10 of the total height of stripping tower from the top of stripping tower. The vertical distance between adjacent two mixed acid spraying ports is 1 / 10 of the total height of stripping tower, by optimizing the position distribution, the temperature gradient formed is more uniform and smooth, the stripping effect is further effectively improved, and the recovery rate of fluorine is increased; the lower section is provided with inert gas import 2.3, and the bottom is provided with dilute sulfuric acid export 2.4, heat exchanger 1 is connected with inert gas import 2.3, dilute sulfuric acid export 2.4 is connected with primary cooler 3, and the outlet of primary cooler 3 is connected with downstream pipeline and upper dilute sulfuric acid spraying port 2.5 in the lower part of stripping tower 2 respectively. Heat exchanger 1 is provided with import and export 1.1 and 1.2 of low pressure steam condensate connected with heat exchange medium pipeline.
[0022] Process: pure nitrogen enters heat exchanger 1 for heating, heat exchanger 1 uses 180 DEG C low pressure steam condensate as heating medium, and the heated nitrogen enters stripping tower 2 for stripping operation through inert gas import 2.3 in the lower part through pipeline. The mixed acid composed of hydrogen fluoride and sulfuric acid is sampled through three mixed acid spraying ports 2.2 in the upper part of stripping tower through pipeline, is sprayed into sample at three vertical height points, and the ratio of the sampling flow rate of the upper point to the sampling flow rate of the middle point to the sampling flow rate of the lower point is 1:2:5. After stripping, hydrogen fluoride and inert gas are sent to the subsequent rectification process through pipeline from the gas export 2.1 in the upper part of stripping tower 2, and the dilute sulfuric acid separated from the mixed acid is discharged from the dilute sulfuric acid export 2.4 in the lower part of stripping tower, is cooled by primary cooler 3, part of which is directly supplied to downstream manufacturers, and the rest of the dilute sulfuric acid cooled by primary cooler 3 is pumped to upper dilute sulfuric acid spraying port 2.5 in the middle-lower part of stripping tower 2 for spraying, so that the cyclic stripping is realized.
[0023] In this embodiment, the heat exchanger 1 adopts graphite column tube type internal structure, and the temperature of the nitrogen gas after heat exchange into the stripping tower 2 is 177℃.
[0024] The stripping tower 2 is made of NEW-PTFE material, and the first cooler 3 is made of 904L stainless steel material.
[0025] After running for a period of time, a gradually increasing temperature gradient is formed in the stripping tower 2 from bottom to top, the temperature range is 110-160℃, and the temperature of the dilute sulfuric acid sent to the downstream device is 90℃.
[0026] The dilute sulfuric acid obtained by separation and purification in this embodiment has a concentration of 74.8% (mass concentration) and a fluorine content of 807ppm (mass concentration), the fluorine recovery rate of the whole system is increased by 8.9%, and the total energy consumption is reduced by 7.1%.
[0027] Example 2
[0028] Different from example 1, two different vertical height mixed acid spray nozzles 2.2 are arranged in the upper section of the stripping tower 2, the highest mixed acid spray nozzle is located at a position 1 / 10 of the total height of the stripping tower from the top of the stripping tower, and the lowest mixed acid spray nozzle is located at a position 1 / 5 of the total height of the stripping tower from the top of the stripping tower. The ratio of the sample flow rate at the upper position to the sample flow rate at the lower position is 1:1.5. Meanwhile, a first cooler 3 and a second cooler 4 are arranged, the dilute sulfuric acid obtained by separation of the mixed acid is discharged from the dilute sulfuric acid outlet 2.4 at the lower part of the stripping tower, is cooled by the first cooler 3, and then is partially sent to the second cooler 4 for further cooling, the rest of the dilute sulfuric acid is pumped to the upper dilute sulfuric acid spray nozzle 2.5 at the lower part of the stripping tower 2 for spraying; the dilute sulfuric acid cooled by the second cooler 4 is partially directly supplied to the downstream manufacturer, and the rest is pumped to the lower dilute sulfuric acid spray nozzle 2.6 at the lower part of the stripping tower 2 for spraying, so as to realize the circulation stripping. The ratio of the dilute sulfuric acid flow rate after the first cooling to the dilute sulfuric acid flow rate after the second cooling is 1:2.1, by sending the circulating dilute sulfuric acid from the two coolers to the dilute sulfuric acid spray nozzles at different heights of the stripping tower 2 according to the temperature, a more smooth temperature gradient is formed locally, which is also beneficial to further improve the stripping effect and increase the fluorine recovery rate. In addition, the circulating cooling water is used to cool the first cooler 3 and the second cooler 4 in series.
[0029] The heat exchanger 1 adopts a coiled tube type internal structure, and the temperature of the argon gas after heat exchange into the stripping tower 2 is 183℃.
[0030] The stripping tower 2 is made of steel lining PTFE, and the cooler 3 and the cooler 4 are made of 316L stainless steel material.
[0031] After running for a period of time, a gradually increasing temperature gradient is formed in the stripping tower from bottom to top, the temperature range is 100-170℃, and the temperature of the dilute sulfuric acid sent to the storage tank is 40℃.
[0032] The embodiment separates and purifies the obtained dilute sulfuric acid to have a concentration of 76.3% (mass concentration), a fluorine content of 538 ppm (mass concentration), an increased fluorine yield of 15.3% for the whole system, and a reduced total energy consumption of 5.5%.
Claims
1. A system for separating and purifying dilute sulfuric acid comprising a heat exchanger and a stripping column connected, characterized in that, The top of the stripping tower is provided with a gas outlet, the upper section is provided with mixed acid spraying ports, the lower section is provided with an inert gas inlet, the bottom is provided with a dilute sulfuric acid outlet, the inert gas inlet is connected with a heat exchanger, the dilute sulfuric acid outlet is connected with a primary cooler, the outlet of the primary cooler is respectively connected with a downstream pipeline and a dilute sulfuric acid spraying port in the middle and lower part of the stripping tower, and the upper section of the stripping tower is provided with at least two mixed acid spraying ports with different vertical heights.
2. The system for separating and purifying dilute sulfuric acid according to claim 1, wherein The highest mixed acid spraying port is located at the upper end of the stripping tower and is 1 / 10 of the total height of the stripping tower from the top of the stripping tower, and the lowest mixed acid spraying port is located at the middle upper part of the stripping tower and is 2 / 5 of the total height of the stripping tower from the top of the stripping tower.
3. The system for separating and purifying dilute sulfuric acid according to claim 2, wherein The vertical distance between the adjacent two mixed acid spraying ports is 1 / 20-3 / 10 of the total height of the stripping tower.
4. The system for separating and purifying dilute sulfuric acid according to any one of claims 1 to 3, wherein The primary cooler is further connected with a secondary cooler and a dilute sulfuric acid spraying port in the middle and lower part of the stripping tower.
5. The system for separating and purifying dilute sulfuric acid according to claim 4, wherein The outlet of the secondary cooler is respectively connected with a downstream pipeline and a dilute sulfuric acid spraying port in the middle and lower part of the stripping tower.
6. The system for separating and purifying dilute sulfuric acid according to claim 5, wherein The middle and lower part of the stripping tower is provided with two dilute sulfuric acid spraying ports with different vertical heights.
7. The system for separating and purifying dilute sulfuric acid according to claim 6, wherein The outlet of the primary cooler is connected with an upper dilute sulfuric acid spraying port, and the outlet of the secondary cooler is connected with a lower dilute sulfuric acid spraying port.
8. The system for separating and purifying dilute sulfuric acid according to claim 4, wherein The upper section of the stripping tower is provided with three mixed acid spraying ports with different vertical heights.
9. The dilute sulfuric acid separation and purification system as claimed in claim 1, wherein, The heat exchanger is provided with an inlet and an outlet of low-pressure steam condensate connected with a heat exchange medium pipeline.