Efficient and energy-saving phosphoric acid gas stripping defluorination purification system and operation method thereof

Abstract

The invention relates to the technical field of phosphoric acid purification, and discloses an efficient and energy-saving phosphoric acid gas stripping defluorination purification system and an operation method thereof.The efficient and energy-saving phosphoric acid gas stripping defluorination purification system comprises a fluidized bed defluorination tower, a finned heat exchanger, a high-pressure centrifugal fan, an air filtering and purifying device, a tail gas washing tower, a steam-water separator and a circulating pump; by adopting the combined design of the fluidized bed defluorination tower and the finned heat exchanger, the heat energy utilization efficiency is remarkably improved, waste of sensible heat of phosphoric acid in the traditional process is avoided, and meanwhile, the cleanliness of air entering the system is ensured through matched use of the high-pressure centrifugal fan and the air filtering and purifying device; in addition, due to the design of multi-stage spraying and a top rotational flow plate demister of the tail gas washing tower, the tail gas treatment effect is effectively improved, the discharged tail gas reaches the environmental protection standard, and the recycled high-concentration fluosilicic acid has high economic value.

Description

Technical Field

[0001] This invention relates to the field of phosphoric acid purification technology, and in particular to a highly efficient and energy-saving phosphoric acid stripping defluorination purification system and its operation method. Background Technology

[0002] Traditional phosphoric acid defluorination processes often employ a bubble cap tower structure, utilizing low-pressure steam to directly contact phosphoric acid for defluorination. This process suffers from low thermal energy utilization; the phosphoric acid temperature drops during aging and clarification after the concentration process, resulting in wasted sensible heat; impurities in the steam can enter the phosphoric acid, affecting product quality; low defluorination efficiency, requiring multi-stage treatment to meet food-grade standards (fluorine content <8ppm); high system resistance, prone to clogging, frequent maintenance; high energy consumption and noise from Roots blowers; and fluctuations in steam consumption affecting the stability of the entire plant's steam network. Furthermore, the exhaust gas treatment is incomplete, resulting in low fluorosilicic acid concentration and low recovery value.

[0003] Therefore, we propose a highly efficient and energy-saving phosphoric acid stripping defluorination and purification system and its operation method. Summary of the Invention

[0004] The present invention mainly addresses the technical problems existing in the prior art and provides a highly efficient and energy-saving phosphoric acid stripping defluorination and purification system and its operation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system, comprising a fluidized bed defluorination tower, a finned heat exchanger, a high-pressure centrifugal fan, an air filtration and purification device, a tail gas scrubbing tower, a gas-water separator, and a circulating pump. The finned heat exchanger is connected to the fluidized bed defluorination tower, the high-pressure centrifugal fan is located at the front end of the finned heat exchanger, and the air filtration and purification device is located at the front end of the high-pressure centrifugal fan.

[0006] Preferably, the fluidized bed defluorination tower is equipped with a single-layer fluidized bed tray.

[0007] Preferably, the exhaust gas scrubbing tower is equipped with three sets of spray devices and a top cyclone demister.

[0008] Preferably, the circulating pump is connected to the outlet and inlet of the fluidized bed defluorination tower via a pipeline.

[0009] Preferably, the high-pressure centrifugal fan has a wind pressure ≥7000Pa.

[0010] An operating method for a high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system, comprising the aforementioned high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system, specifically including the following steps: Step 1: Spray treatment: Concentrated phosphoric acid at around 70℃ is directly fed into the upper part of the fluidized bed defluorination tower for spraying; Step 2: Air contact: Air is filtered, heated to 150°C, and then introduced from the bottom of the tower to contact phosphoric acid in a countercurrent manner. Step 3: Condensation and separation: Fluorine-containing gas is condensed and separated into vapor and water to obtain high-concentration fluorosilicic acid; Step 4: Spraying and defoaming: The exhaust gas is discharged in compliance with standards after undergoing multi-stage spraying and defoaming. Step 5: Recirculation treatment: If the fluoride content of phosphate exceeds the standard, it is sent back to the fluidized bed defluorination tower for reprocessing via a circulation pump.

[0011] Preferably, the concentration of high-concentration fluorosilicic acid in the third step is 12-18%.

[0012] This invention provides a highly efficient and energy-saving phosphoric acid stripping defluorination purification system and its operating method. It has the following beneficial effects: 1. This highly efficient and energy-saving phosphoric acid stripping defluorination and purification system and its operation method significantly improve thermal energy utilization efficiency by adopting a combination design of fluidized bed defluorination tower and finned heat exchanger, avoiding the waste of sensible heat of phosphoric acid in traditional processes. At the same time, the combined use of high-pressure centrifugal fan and air filtration and purification device ensures the cleanliness of the air entering the system and reduces the potential impact of impurities on the quality of phosphoric acid products. In addition, the multi-stage spraying of the tail gas scrubbing tower and the top cyclone demister design effectively improve the tail gas treatment effect, enabling the exhaust gas to meet environmental protection standards. Moreover, the recovered high-concentration fluorosilicic acid has high economic value. This system not only solves the problems of low thermal energy utilization, product quality impact, and low defluorination efficiency in traditional phosphoric acid defluorination processes, but also achieves the dual goals of energy conservation, emission reduction, and resource recovery.

[0013] 2. This efficient and energy-saving phosphoric acid stripping defluorination and purification system and its operation method realize the circulation treatment of phosphoric acid through a circulating pump, further improving the defluorination efficiency and ensuring the stability of phosphoric acid product quality. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the system of the present invention; Figure 2 This is a flowchart of the method of the present invention. Detailed Implementation

[0015] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0016] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0017] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0018] In the description of the embodiments of the present invention, it should be noted that the terms "center," "upper," "lower," "inner," "outer," and "side," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0019] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: A highly efficient and energy-saving phosphoric acid stripping defluorination and purification system, such as Figures 1-2As shown, the system includes a fluidized bed defluorination tower, a finned heat exchanger, a high-pressure centrifugal fan, an air filtration and purification device, a tail gas scrubbing tower, a steam-water separator, and a circulating pump. The fluidized bed defluorination tower has a single-layer fluidized bed tray. The finned heat exchanger is connected to the fluidized bed defluorination tower. The high-pressure centrifugal fan is located at the front end of the finned heat exchanger. The air filtration and purification device is located at the front end of the high-pressure centrifugal fan. The tail gas scrubbing tower has three sets of spray devices and a top cyclone demister. The circulating pump is connected to the outlet and inlet of the fluidized bed defluorination tower through a pipeline. The air pressure of the high-pressure centrifugal fan is ≥7000Pa. An operating method for a high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system, comprising the aforementioned high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system, specifically including the following steps: Step 1: Spray treatment: Concentrated phosphoric acid at approximately 70°C is directly fed into the upper part of the fluidized bed defluorination tower for spraying; Step 2: Air contact: Air, after being filtered and heated to 150°C, is introduced from the bottom of the tower and comes into countercurrent contact with the phosphoric acid; Step 3: Condensation and separation: Fluorine-containing gas is condensed and separated into steam and water to obtain high-concentration fluorosilicic acid; Step 4: Spray defoaming: The tail gas is discharged after multi-stage spraying and defoaming to meet emission standards; Step 5: Circulation treatment: If the fluorine content of the phosphoric acid exceeds the standard, it is returned to the fluidized bed defluorination tower for further treatment via a circulation pump. The concentration of high-concentration fluorosilicic acid in Step 3 is 12-18%. By adopting a combined design of a fluidized bed defluorination tower and a finned heat exchanger, the thermal energy utilization efficiency is significantly improved, avoiding the waste of sensible heat from phosphoric acid in traditional processes. At the same time, the combined use of a high-pressure centrifugal fan and an air filtration and purification device ensures the cleanliness of the air entering the system, reducing the potential impact of impurities on the quality of phosphoric acid products. In addition, the multi-stage spraying and top cyclone demister design of the tail gas scrubbing tower effectively improves the tail gas treatment effect, enabling the exhaust gas to meet environmental protection standards. Moreover, the recovered high-concentration fluorosilicic acid has high economic value. This not only solves the problems of low thermal energy utilization, product quality impact, and low defluorination efficiency in traditional phosphoric acid defluorination processes, but also achieves the dual goals of energy conservation, emission reduction, and resource recovery.

[0022] Example 2: Based on Example 1, as follows Figures 1-2As shown, the fluidized bed defluorination tower is equipped with a single-layer fluidized bed tray. A finned heat exchanger is connected to the fluidized bed defluorination tower. A high-pressure centrifugal fan is located at the front end of the finned heat exchanger. An air filtration and purification device is located at the front end of the high-pressure centrifugal fan. The tail gas scrubbing tower is equipped with three sets of spray devices and a top cyclone demister. The circulating pump is connected to the outlet and inlet of the fluidized bed defluorination tower through a pipeline. The air pressure of the high-pressure centrifugal fan is ≥7000Pa. An operating method for a high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system includes the aforementioned high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system, specifically comprising the following steps: Step 1: Spray treatment: Concentrated phosphoric acid at approximately 70°C is directly fed into the upper part of the fluidized bed defluorination tower for spraying; Step 2: Air contact: Air is filtered, heated to 150°C, and then introduced from the bottom of the tower, coming into countercurrent contact with the phosphoric acid; Step 3: Condensation and separation: Fluorine-containing gas is condensed and separated into gas and water to obtain high-concentration fluorosilicic acid; Step 4: Spray defoaming: The tail gas is discharged after multi-stage spraying and defoaming to meet emission standards; Step 5: Circulation treatment: If the fluorine content of the phosphoric acid exceeds the standard, it is returned to the fluidized bed defluorination tower for further treatment via a circulation pump. The concentration of high-concentration fluorosilicic acid in Step 3 is 12-18%. The circulation pump enables the circulation treatment of phosphoric acid, further improving the defluorination efficiency and ensuring the stability of the phosphoric acid product quality.

[0023] Example 3: Based on Examples 1 and 2, as follows... Figures 1-2 As shown, the finned heat exchanger is connected to the fluidized bed defluorination tower, the high-pressure centrifugal fan is located at the front end of the finned heat exchanger, the air filtration and purification device is located at the front end of the high-pressure centrifugal fan, the tail gas scrubbing tower is equipped with three sets of spray devices and a top cyclone demister, the circulating pump is connected to the outlet and inlet of the fluidized bed defluorination tower through a pipeline, and the air pressure of the high-pressure centrifugal fan is ≥7000Pa. An operating method for a high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system, comprising the aforementioned high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system, specifically including the following steps: Step 1: Spray treatment: Concentrated phosphoric acid at approximately 70°C is directly fed into the upper part of the fluidized bed defluorination tower for spraying; Step 2: Air contact: Air, after being filtered and heated to 150°C, is introduced from the bottom of the tower and comes into countercurrent contact with the phosphoric acid; Step 3: Condensation and separation: Fluorine-containing gas is condensed and separated into steam and water to obtain high-concentration fluorosilicic acid; Step 4: Spray defoaming: The tail gas is discharged after multi-stage spraying and defoaming to meet emission standards; Step 5: Circulation treatment: If the fluorine content of the phosphoric acid exceeds the standard, it is returned to the fluidized bed defluorination tower for further treatment via a circulation pump. The concentration of high-concentration fluorosilicic acid in Step 3 is 12-18%.

[0024] Example 4: Based on Examples 1, 2, and 3, as follows... Figures 1-2As shown, the air filtration and purification device is installed at the front end of the high-pressure centrifugal fan. The tail gas scrubbing tower is equipped with three sets of spray devices and a top cyclone demister. The circulating pump is connected to the outlet and inlet of the fluidized bed defluorination tower through a pipeline. The air pressure of the high-pressure centrifugal fan is ≥7000Pa. An operation method for a high-efficiency and energy-saving phosphoric acid stripping defluorination purification system includes the above-mentioned high-efficiency and energy-saving phosphoric acid stripping defluorination purification system, specifically including the following steps: Step 1: Spray treatment: Concentrated phosphoric acid at approximately 70°C is directly fed into the upper part of the fluidized bed defluorination tower for spraying; Step 2: Air contact: Air is filtered, heated to 150°C, and then introduced from the bottom of the tower, contacting the phosphoric acid countercurrently; Step 3: Condensation and separation: Fluorine-containing gas is condensed and separated into gas and water to obtain high-concentration fluorosilicic acid; Step 4: Spray demisting: The tail gas is discharged after multi-stage spraying and demisting to meet standards; Step 5: Circulation treatment: If the fluorine content of the phosphoric acid exceeds the standard, it is sent back to the fluidized bed defluorination tower for further treatment via a circulating pump. The concentration of high-concentration fluorosilicic acid in Step 3 is 12~18%.

[0025] Example 5: Based on Examples 1, 2, 3, and 4, as follows... Figure 2 As shown, an operation method for a high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system includes the aforementioned high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system, specifically comprising the following steps: Step 1: Spray treatment: Concentrated phosphoric acid at approximately 70°C is directly fed into the upper part of the fluidized bed defluorination tower for spraying; Step 2: Air contact: Air is filtered, heated to 150°C, and then introduced from the bottom of the tower, coming into countercurrent contact with the phosphoric acid; Step 3: Condensation and separation: Fluorine-containing gas is condensed and separated into gas and water to obtain high-concentration fluorosilicic acid; Step 4: Spray defoaming: The tail gas is discharged after multi-stage spraying and defoaming to meet emission standards; Step 5: Circulation treatment: If the fluorine content of the phosphoric acid exceeds the standard, it is sent back to the fluidized bed defluorination tower for further treatment via a circulation pump. The concentration of high-concentration fluorosilicic acid in Step 3 is 12-18%.

[0026] The working principle of this invention is as follows: A fluidized bed defluorination tower achieves countercurrent contact between phosphoric acid and heated air, utilizing air stripping to separate fluorides from the phosphoric acid. The fluorinated gas enters a finned heat exchanger for condensation, converting fluorosilicic acid vapor into a liquid state. After further purification by a steam-water separator, a high-purity fluorosilicic acid product with a concentration of 12-18% is obtained. Unreacted phosphoric acid is re-injected into the fluidized bed defluorination tower via a circulating pump, forming a closed-loop treatment system to ensure thorough defluorination. The tail gas scrubbing tower employs a three-stage spray device combined with a top cyclone demister, using circulating scrubbing liquid to deeply purify the exhaust gas, ensuring that the fluoride content in the final exhaust gas is below national environmental standards. This system optimizes heat utilization and gas-liquid contact efficiency, achieving energy savings of over 30% compared to traditional processes, while increasing single-tower processing capacity by 50%, significantly reducing operating costs.

[0027] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A highly efficient and energy-saving phosphoric acid stripping defluorination and purification system, characterized in that, It includes a fluidized bed defluorination tower, a finned heat exchanger, a high-pressure centrifugal fan, an air filtration and purification device, a tail gas scrubbing tower, a steam-water separator, and a circulating pump. The finned heat exchanger is connected to the fluidized bed defluorination tower, the high-pressure centrifugal fan is located at the front end of the finned heat exchanger, and the air filtration and purification device is located at the front end of the high-pressure centrifugal fan.

2. The high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system according to claim 1, characterized in that: The fluidized bed defluorination tower is equipped with a single-layer fluidized bed tray.

3. The high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system according to claim 1, characterized in that: The exhaust gas scrubbing tower is equipped with three sets of spray devices and a top cyclone demister.

4. The high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system according to claim 1, characterized in that: The circulating pump is connected to the outlet and inlet of the fluidized bed defluorination tower via a pipeline.

5. The high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system according to claim 1, characterized in that: The high-pressure centrifugal fan has a wind pressure ≥7000Pa.

6. An operating method for a high-efficiency and energy-saving phosphoric acid stripping defluorination and purification system, characterized in that, The high-efficiency and energy-saving phosphoric acid stripping defluorination purification system according to any one of claims 1-5 specifically includes the following steps: Step 1: Spray treatment: Concentrated phosphoric acid at around 70℃ is directly fed into the upper part of the fluidized bed defluorination tower for spraying; Step 2: Air contact: Air is filtered, heated to 150°C, and then introduced from the bottom of the tower to contact phosphoric acid in a countercurrent manner. Step 3: Condensation and separation: Fluorine-containing gas is condensed and separated into vapor and water to obtain high-concentration fluorosilicic acid; Step 4: Spraying and defoaming: The exhaust gas is discharged in compliance with standards after undergoing multi-stage spraying and defoaming. Step 5: Recirculation treatment: If the fluoride content of phosphate exceeds the standard, it is sent back to the fluidized bed defluorination tower for reprocessing via a circulation pump.

7. The operating method of the high-efficiency and energy-saving phosphoric acid stripping defluorination purification system according to claim 6, characterized in that: The concentration of high-concentration fluorosilicic acid in the third step is 12-18%.

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