Device for concentrating dilute phosphoric acid with by-product primary steam
By combining a flash chamber, a steam scrubbing tower, and a reboiler, low-pressure steam is produced using the heat from concentrated steam and condensate, solving the problems of secondary steam utilization and scaling, and achieving the effect of saving steam and water costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- HUBEI SANNING CHEM
- Filing Date
- 2025-06-12
- Publication Date
- 2026-06-09
AI Technical Summary
In existing phosphoric acid concentration processes, the utilization of secondary steam is difficult, and the presence of acidic gases can easily lead to scaling, affecting the stability of equipment operation. Furthermore, the costs of steam and circulating water are high.
A device for producing primary steam as a byproduct of dilute phosphoric acid concentration was designed. By combining a flash chamber, a steam scrubbing tower, a heat exchanger, and a reboiler, low-pressure steam is produced using the heat of the concentrated steam. Steam condensate is used as makeup water for the reboiler. Combined with a steam compressor, the steam is reused.
It effectively saves on steam and circulating water costs, prevents scaling, ensures continuous production, and reduces equipment maintenance frequency.
Smart Images
Figure CN224331519U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of wet phosphoric acid technology, specifically relating to a device for producing primary steam as a byproduct of dilute phosphoric acid concentration. Background Technology
[0002] Wet-process phosphoric acid is a fundamental intermediate product in the phosphate fertilizer and phosphate industry, holding a very important position and in high demand. Currently, phosphoric acid concentration widely adopts the forced circulation vacuum concentration single-effect evaporation process. The biggest drawback of single-effect evaporation is its poor heat utilization rate and high steam consumption. The heat of fresh steam is only utilized once, and the generated secondary steam is not utilized and is directly sent to condensation, requiring a large amount of circulating cooling water.
[0003] Some existing literature describes utilizing the secondary steam produced by phosphoric acid concentration to form a double-effect concentration, saving a significant amount of steam. However, the steam produced by double-effect phosphoric acid concentration contains large amounts of acidic gases such as F, Cl, and PO4, placing high demands on the equipment materials. Simultaneously, the secondary steam contains SiF4; after condensation, water reacts with SiF4 to produce large amounts of silica gel, easily forming scale and clogging the equipment. Therefore, utilizing this secondary steam in continuous production is challenging. Summary of the Invention
[0004] This invention provides a device for producing primary steam as a byproduct of dilute phosphoric acid concentration. By utilizing the heat of the concentrated steam and the steam condensate, low-pressure steam can be produced for subsequent production, greatly saving steam and circulating water costs.
[0005] The technical solution of this utility model is to provide a device for producing primary steam as a byproduct of dilute phosphoric acid concentration, including a flash chamber. The lower outlet of the flash chamber is connected back to the flash chamber via a pipeline, a flash circulation pump, and a flash heater. The gas phase pipeline at the top of the flash chamber is connected to a steam scrubbing tower via a demister. The gas phase pipeline at the top of the steam scrubbing tower is connected to a gas-liquid separator via a heat exchanger. The steam pipeline is connected to a steam condensate tank via the flash heater. The outlet of the steam condensate tank is connected to a reboiler via a pump, a pipeline, and a heat exchanger. The gas phase outlet of the reboiler is connected to a steam compressor. The outlet of the steam compressor is connected to a steam pipeline. The liquid phase outlet of the reboiler is connected to a heat exchanger.
[0006] Furthermore, a concentrated phosphoric acid production branch pipe and a dilute phosphoric acid feed branch pipe are sequentially installed on the pipeline between the lower outlet of the flash chamber and the circulating pump.
[0007] Furthermore, the top of the steam condensate tank is provided with a gas phase outlet, which is connected to the flash heater through a pipeline; the lower part of the demister is provided with a liquid phase outlet, which is connected to the flash chamber through a pipeline.
[0008] Furthermore, the phosphoric acid to be concentrated flows through the tube side of the flash heater, while the steam flows through the shell side; in the heat exchanger, the vapor phase from the top of the steam scrubbing tower flows through the tube side, while the steam condensate and the material from the reboiler flow through the shell side.
[0009] Furthermore, the lower part of the steam scrubbing tower is provided with a discharge port, which is connected to the upper part of the steam scrubbing tower through a pipeline and a washing circulation pump. The upper part of the steam scrubbing tower is provided with at least one layer of spray pipes.
[0010] Furthermore, a branch pipe for discharging washing liquid is installed on the pipeline between the washing circulation pump and the steam washing tower.
[0011] Furthermore, the gas phase from the gas-liquid separator is led out to the subsequent process, while the liquid phase outlet is connected to the wastewater pipeline.
[0012] Furthermore, the liquid phase pipeline of the steam condensate tank is also equipped with a pipeline for external return of steam condensate.
[0013] This utility model has the following beneficial effects:
[0014] This invention washes and absorbs the steam evaporated in the flash chamber, removing silica gel and other substances that are retained in the washing tower to prevent scaling in subsequent heat exchangers. The steam then exchanges heat with the water coming from the reboiler in the heat exchanger. Simultaneously, the condensate from the flash steam is used as makeup water for the reboiler. The water after heat exchange enters the reboiler to generate steam, which is further compressed and used in subsequent production, greatly saving steam and circulating water costs.
[0015] The heat exchanger of this invention can be redundantly configured, with one unit in standby mode. Scale buildup can be cleaned promptly without shutdown, ensuring uninterrupted production. By combining a reboiler and a steam compressor, acidic gases containing F, Cl, and PO4 are condensed separately to produce fresh primary steam for subsequent processes. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the structure of the present utility model;
[0017] In the diagram: 1. Flash chamber; 2. Circulating pump; 3. Flash heater; 4. Demister; 5. Steam scrubbing tower; 6. Heat exchanger; 7. Gas-liquid separator; 8. Steam condensate tank; 9. Reboiler; 10. Steam compressor; 11. Concentrated phosphoric acid output branch pipe; 12. Dilute phosphoric acid feed branch pipe; 13. Washing circulation pump; 14. Spray pipe; and 15. Washing liquid outlet branch pipe. Detailed Implementation
[0018] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.
[0019] like Figure 1 As shown, this utility model provides an apparatus for producing primary steam as a byproduct of dilute phosphoric acid concentration, including a flash chamber 1. The lower outlet of the flash chamber is connected back to the flash chamber via a pipeline, a flash circulation pump 2, and a flash heater 3. The gas phase pipeline at the top of the flash chamber is connected to a steam scrubbing tower 5 via a demister 4. The gas phase pipeline at the top of the steam scrubbing tower is connected to a gas-liquid separator 7 via a heat exchanger 6. The steam pipeline is connected to a steam condensate tank 8 via the flash heater 3. The outlet of the steam condensate tank is connected to a reboiler 9 via a pump, a pipeline, and a heat exchanger. The gas phase outlet of the reboiler is connected to a steam compressor 10. The outlet of the steam compressor is connected to a steam pipeline. The liquid phase outlet of the reboiler is connected to the heat exchanger.
[0020] The material at the bottom of the flash chamber is fed into the flash heater 3 via pipelines and a flash circulation pump to exchange heat with steam, and then returns to the flash chamber for evaporation and concentration, continuously increasing the concentration of phosphoric acid in the flash chamber. The evaporated gas phase removes acid droplets in a demister, preferably a cyclone demister. The intercepted acid droplets are collected and returned to the flash chamber for further concentration. The demisted gas phase enters a steam scrubbing tower for washing, and finally undergoes heat exchange and condensation, absorbing the heat for steam generation. The surfaces of the flash chamber, flash circulation pump, flash heater, demister, and other equipment in contact with the material are made of PTFE, and the internal pressure is controlled at a slightly positive pressure (gauge pressure approximately 0-90 kPa) during operation to avoid damage to the PTFE material due to negative pressure.
[0021] In some embodiments, a concentrated phosphoric acid production branch pipe 11 and a dilute phosphoric acid feed branch pipe 12 are sequentially installed on the pipeline directly connecting the lower outlet of the flash chamber and the circulating pump. The concentrated phosphoric acid production branch pipe 11 is located near the lower outlet end of the flash chamber, and the dilute phosphoric acid feed branch pipe 12 is located near the rear end of the concentrated phosphoric acid production branch pipe 11.
[0022] In some embodiments, the top of the steam condensate tank is provided with a gas phase outlet, which is connected to the flash heater via a pipeline; the lower part of the demister is provided with a liquid phase outlet, which is connected to the flash chamber via a pipeline. This allows for the full utilization of uncondensed steam.
[0023] In some embodiments, the phosphoric acid to be concentrated flows through the tube side of the flash heater, while the steam flows through the shell side; in the heat exchanger, the vapor phase from the top of the steam scrubber flows through the tube side, while the steam condensate and the material from the reboiler flow through the shell side. The acid liquid or acid-containing vapor phase flows through the tube side, which is preferably made of silicon carbide or graphite to reduce scaling. It is preferable to have two heat exchangers, one as a backup, which can be switched at any time, preventing production shutdown in case of blockage.
[0024] In some embodiments, the lower part of the steam scrubbing tower is provided with an outlet, which is connected to the upper part of the steam scrubbing tower via a pipeline and a scrubbing circulation pump. The upper part of the steam scrubbing tower is provided with at least one layer of spray pipes. The acidic gases such as F, Cl, and PO4 are removed by spray scrubbing, reducing their entry into the heat exchanger and causing scaling on the heat exchanger.
[0025] In some embodiments, a washing liquid outlet branch pipe is provided on the pipeline between the washing circulation pump and the steam washing tower. The washing liquid is continuously circulated and discharged after reaching a certain concentration.
[0026] In some embodiments, the gas phase of the gas-liquid separator is led out to the subsequent process, and the liquid phase outlet is connected to the wastewater pipeline.
[0027] In some embodiments, the liquid phase pipeline of the steam condensate tank is also provided with a steam condensate return pipeline, and excess condensate is directly returned for reuse.
[0028] When using the apparatus provided by this invention for production, the phosphoric acid solution with a P2O5 concentration of 15%-26% is fed into the flash chamber. Fresh steam provides a heat source for the flash heater 3, and continuous heat exchange promotes the evaporation and concentration of the phosphoric acid solution, resulting in a P2O5 concentration of 26-32%. The steam generated during the flash evaporation process enters a washing tower for washing. The washing liquid temperature is 100-115℃, the pressure is 0-90KPa (gauge pressure), and the fluorine content is ≤0.4%. The washed vapor phase is introduced into a heat exchanger to exchange heat with the water from the reboiler. The water, after heat exchange, is heated and enters the reboiler, generating steam which is then compressed by a compressor. The saturated steam temperature entering the steam compressor is 65-95℃, and the primary saturated steam temperature is 105-135℃.
[0029] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including combining the various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed by the present invention and all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be determined by the appended claims.
Claims
1. An apparatus for concentrating dilute phosphoric acid to produce primary steam as a byproduct, characterized in that: The system includes a flash chamber. The lower outlet of the flash chamber is connected back to the flash chamber via a pipeline, a flash circulation pump, and a flash heater. The vapor phase pipeline at the top of the flash chamber is connected to a steam scrubbing tower via a demister. The vapor phase pipeline at the top of the steam scrubbing tower is connected to a gas-liquid separator via a heat exchanger. The steam pipeline is connected to a steam condensate tank via the flash heater. The outlet of the steam condensate tank is connected to a reboiler via a pump, pipeline, and heat exchanger. The vapor phase outlet of the reboiler is connected to a steam compressor. The outlet of the steam compressor is connected to a steam pipeline. The liquid phase outlet of the reboiler is connected to a heat exchanger.
2. The apparatus for producing primary steam as a byproduct of dilute phosphoric acid concentration according to claim 1, characterized in that: A concentrated phosphoric acid production branch pipe and a dilute phosphoric acid feed branch pipe are sequentially installed on the pipeline between the lower outlet of the flash chamber and the circulating pump.
3. The apparatus for producing primary steam as a byproduct of dilute phosphoric acid concentration according to claim 1, characterized in that: The top of the steam condensate tank is equipped with a gas phase outlet, which is connected to the flash heater via a pipeline; the bottom of the demister is equipped with a liquid phase outlet, which is connected to the flash chamber via a pipeline.
4. The apparatus for producing primary steam as a byproduct of dilute phosphoric acid concentration according to claim 1, characterized in that: The phosphoric acid to be concentrated flows through the tube side of the flash heater, while the steam flows through the shell side; in the heat exchanger, the vapor from the top of the steam scrubber flows through the tube side, while the steam condensate and the material from the reboiler flow through the shell side.
5. The apparatus for producing primary steam as a byproduct of dilute phosphoric acid concentration according to any one of claims 1 to 4, characterized in that: The lower part of the steam scrubbing tower has a discharge port, which is connected to the upper part of the steam scrubbing tower through a pipeline and a washing circulation pump. The upper part of the steam scrubbing tower has at least one layer of spray pipes.
6. The apparatus for producing primary steam as a byproduct of dilute phosphoric acid concentration according to claim 5, characterized in that: A branch pipe for discharging washing liquid is also installed on the pipeline between the washing circulation pump and the steam washing tower.
7. The apparatus for producing primary steam as a byproduct of dilute phosphoric acid concentration according to claim 1, characterized in that: The gas phase from the gas-liquid separator is led out to the subsequent process, while the liquid phase outlet is connected to the wastewater pipeline.
8. The apparatus for producing primary steam as a byproduct of dilute phosphoric acid concentration according to claim 1, characterized in that: The liquid phase pipeline of the steam condensate tank is also equipped with a pipeline for external return of steam condensate.