Process system for purifying phosphoric acid through ion exchange and working process of process system

Abstract

The invention relates to the technical field of wet-process phosphoric acid purification, and discloses a process system for purifying phosphoric acid through ion exchange and a working process thereof.The process system comprises a resin rotation purification and regeneration unit and a regeneration tail liquid concentration and purification unit, and the resin rotation purification and regeneration unit comprises a closed circulation system composed of a plurality of resin columns; and the resin columns can sequentially rotate and move in the closed circulating system. According to the process system provided by the invention, to-be-purified raw materials (phosphoric acid), washing water (pure water) and regenerated liquid (dilute sulfuric acid) are simultaneously conveyed into the resin rotation purification and regeneration unit from different areas to continuously produce purified phosphoric acid and regenerated tail liquid, and the regenerated tail liquid is purified by the regenerated tail liquid concentration and purification unit (acid-resistant RO membrane) and then returns to the system; the whole-process continuous operation of phosphoric acid purification and resin regeneration is realized, the defects of traditional intermittent production are avoided, and the production efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of wet-process phosphoric acid purification technology, specifically to a process system and workflow for ion exchange purification of phosphoric acid. Background Technology

[0002] Phosphoric acid is an important chemical intermediate product, and its production process can be divided into two types: thermal phosphoric acid and wet phosphoric acid. Thermal phosphoric acid uses high-grade phosphate rock as raw material, reducing phosphate rock powder in an electric furnace to produce yellow phosphorus, which is then further processed through oxidation and hydration to obtain phosphoric acid. Thermal phosphoric acid requires high-grade phosphate rock, resulting in high energy consumption, high cost, and significant pollution during production, but the product has relatively high purity. Wet phosphoric acid uses medium- to low-grade phosphate rock as raw material, decomposing the phosphate rock powder with strong acids such as sulfuric acid, hydrochloric acid, and nitric acid. After pretreatment and purification processes including filtration, decolorization, defluorination, desulfurization, arsenic removal, and removal of metal ions, the final phosphoric acid product is obtained. Due to China's unique situation where its phosphate rock is mainly of medium- to low-grade grade, domestic phosphoric acid production currently relies primarily on the wet process. Wet phosphoric acid has advantages such as a wide availability of raw materials, low energy consumption, low cost, low pollution, and the purified phosphoric acid product being comparable to that of thermal phosphoric acid.

[0003] Ion exchange is an important wet-process phosphoric acid purification technology. It utilizes resin to selectively adsorb impurity ions (such as metal cations) in phosphoric acid, thereby purifying the phosphoric acid. Ion exchange purification of wet-process phosphoric acid has advantages such as simple process, mild conditions, and environmental friendliness. However, the resin requires regeneration. Traditional fixed-bed processes are intermittent operations, requiring regeneration after phosphoric acid purification, resulting in poor process continuity and impacting production efficiency. Furthermore, resin regeneration consumes large amounts of acid, alkali, and water, generating regeneration wastewater and increasing system waste liquid discharge, which is detrimental to environmental protection.

[0004] Patent CN 116532164 A discloses a system and method for purifying phosphoric acid via ion exchange. The system includes an ion exchange tower, a buffer tank, a washing tank, a calcium and magnesium washing tank, and a pulse chamber. A wet phosphoric acid storage tank is connected to the upper inlet of the ion exchange tower via a wet phosphoric acid pump, and the lower outlet of the ion exchange tower is connected to the purified phosphoric acid pump via the purified phosphoric acid storage tank. Wet phosphoric acid enters the ion exchange tower through the upper inlet, where ion exchange resin is installed. The phosphoric acid flows down through the resin, and the calcium and magnesium ions in the phosphoric acid are bound by the resin. The purified phosphoric acid flows out from the lower outlet of the tower. This invention uses a single-column method for ion exchange, which has limited purification effect and phosphorus yield, and easily generates a large amount of acidic regeneration wastewater (calcium and magnesium washing solution). Furthermore, the resin described in this invention needs to be circulated between multiple devices, which increases the resin breakage rate and degree of damage during the transfer process due to mechanical wear and fluid erosion. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a process system and workflow for ion exchange purification of phosphoric acid, aiming to solve the problems of limited phosphoric acid purification effect, limited phosphorus yield, high resin breakage rate, inability to operate continuously, and environmental pollution caused by waste liquid discharge in existing ion exchange purification technologies for phosphoric acid.

[0006] To achieve the above objectives, the present invention provides the following technical solution.

[0007] First, the present invention provides a process system for ion exchange purification of phosphoric acid, which includes a raw material tank, a purified finished product tank, a first washing water tank, a regenerated liquid tank, a regenerated tail liquid tank, a second washing water tank, a resin rotation purification and regeneration unit, and a regenerated tail liquid concentration and purification unit. The resin rotation purification and regeneration unit includes a closed circulation system composed of multiple resin columns, and the resin columns can move positions sequentially within the closed circulation system. The resin rotation purification and regeneration unit is divided into a phosphoric acid purification section, a phosphoric acid washing section, a waste acid utilization section, a resin regeneration section, a regenerated liquid washing section, and a phosphoric acid pre-washing section connected in sequence. The inlet of the phosphoric acid purification section is connected to the raw material tank, and the outlet is connected to the purified finished product tank. The inlet of the phosphoric acid washing section is connected to the first washing tank, and the outlet is connected to the raw material tank. The inlet and outlet of the waste acid utilization section are respectively connected to the regeneration tail liquid tank. The outlet of the regeneration tail liquid tank is also connected to the regeneration tail liquid concentration and purification unit. The clear phase outlet of the regeneration tail liquid concentration and purification unit is connected to the regeneration tank. The inlet of the resin regeneration section is connected to the regeneration liquid tank, and the outlet is connected to the regeneration tail liquid tank. The inlet of the regenerated liquid washing section is connected to the second washing tank, and the outlet is connected to the regenerated liquid tank; The inlet of the phosphoric acid prewashing section is connected to the purified finished product tank, and the outlet is connected to the second washing water tank.

[0008] This invention employs a "stationary pipeline, rotating resin column" design to construct the aforementioned process system. The process flow consists of four simultaneous steps: phosphoric acid purification, resin regeneration, pure water rinsing, and reverse resin washing. In the phosphoric acid purification step, the phosphoric acid to be purified in the raw material tank is pumped into the resin column of the phosphoric acid purification section for purification. The purified sulfuric acid then enters the purified finished product tank to obtain purified phosphoric acid. In the resin regeneration step, the regeneration liquid tank pumps the regeneration liquid (such as dilute sulfuric acid) into the resin column of the resin regeneration section. The regeneration tail liquid (waste acid) generated after resin regeneration enters the regeneration tail liquid tank. The pure water rinsing step includes rinsing before entering the resin regeneration step and rinsing before entering the phosphoric acid purification step. In the phosphoric acid purification step, the resin column, saturated with adsorbed phosphoric acid after purification, is first transferred to the phosphoric acid washing section before entering the resin regeneration section. The first washing tank pumps pure water to flush the phosphoric acid in the resin column back to the raw material tank. In the resin regeneration step, the regenerated resin... Before entering the phosphoric acid purification section, the resin column is first transferred to the regenerated liquid washing section. The second washing tank pumps in pure water to flush the regenerated liquid in the resin column back to the regenerated liquid tank. The reverse top resin process includes reverse top of the purified phosphoric acid before entering the phosphoric acid purification process and reverse top of the regenerated tail liquid before entering the resin regeneration process. The resin in the regenerated liquid washing section is first transferred to the phosphoric acid pre-washing section before entering the phosphoric acid purification section. The purified finished product tank is pumped in purified phosphoric acid to replace the residual water in the resin column and turn the resin into acidic. The resin in the phosphoric acid washing section is first transferred to the waste acid utilization section before entering the resin regeneration section. The regenerated tail liquid tank is pumped in waste acid to replace the residual water in the resin column and turn the resin into acidic. The replaced residual water is returned to the regenerated tail liquid tank. The regenerated tail liquid (waste acid) in the regenerated tail liquid tank enters the regenerated tail liquid concentration and purification unit (acid-resistant RO membrane) for purification and concentration. The clear phase enters the regenerated liquid tank for use as regenerated liquid, while the high-concentration sulfuric acid concentrated by the RO membrane enters the mineral processing workshop for use in phosphate ore beneficiation.

[0009] The process system provided by this invention simultaneously transports the raw material to be purified (phosphoric acid), wash water (pure water), and regenerated liquid (dilute sulfuric acid) from different areas to the resin rotary purification and regeneration unit to continuously produce purified phosphoric acid and regenerated tail liquid. The regenerated tail liquid is purified by the regenerated tail liquid concentration and purification unit (acid-resistant RO membrane) and then returned to the system, realizing the continuous operation of the entire process of phosphoric acid purification and resin regeneration, avoiding the drawbacks of traditional intermittent production and improving production efficiency.

[0010] In the process system provided by this invention, the pipeline remains stationary while the resin column rotates. The resin is relatively stationary inside the resin column, and the liquid (raw material, regenerated liquid, and wash water) flows through the resin from top to bottom. This can greatly reduce the resin breakage rate and lower the resin replacement cost.

[0011] The process system provided by this invention features a bottom-up resin back-topping process before the critical phosphoric acid purification and resin regeneration sections. This not only prevents the resin from being compacted due to prolonged stagnation, which would negatively impact purification and regeneration, but also provides purified phosphoric acid as top water before the resin column formally enters the phosphoric acid purification section. This top water replaces the residual water in the resin column and converts the resin to acidic conditions, further enhancing the resin's purification efficiency for phosphoric acid. Similarly, when the resin column formally enters the resin regeneration section, waste sulfuric acid is provided as top water from the regeneration tail liquid tank. This top water replaces the residual water in the resin column and converts the resin to acidic conditions, further improving the subsequent resin regeneration effect.

[0012] Furthermore, in some embodiments of the present invention, the aforementioned plurality of resin columns are installed in a disc-type multi-channel liquid distributor to form the closed-loop circulation system. The disc-type multi-channel liquid distributor is a rotatable multi-channel processing device that enables the "stationary pipes, rotating resin columns" function of the present invention. In this invention, resin columns are installed in the disc-type multi-channel liquid distributor. When the resin columns rotate, the connection between the distributor and the resin columns rotates with the resin columns, while the connection with the external pipes remains stationary. After rotation, different resin columns correspond to different pipes, achieving the function of stationary pipes and rotating resin columns.

[0013] Furthermore, the resin columns in the phosphoric acid purification section are connected in a multi-stage series configuration, with multiple resin columns connected in parallel at each stage. More preferably, in some embodiments of the present invention, the resin columns in the phosphoric acid purification section are connected in a three-parallel, two-series configuration. In this multi-stage series phosphoric acid purification mode, the raw phosphoric acid first flows through a partially saturated resin column with nearly exhausted adsorption capacity for primary purification, and then enters a freshly regenerated resin column for deep purification. This countercurrent contact method ensures that the acid with the lowest impurity concentration is matched with the resin with the strongest adsorption capacity, maximizing the utilization of the resin's adsorption capacity and significantly improving purification depth and efficiency.

[0014] Furthermore, the resin columns in the resin regeneration section are connected in a multi-stage series configuration, with multiple resin columns connected in parallel at each stage. More preferably, in some embodiments of the present invention, the resin columns in the resin regeneration section are connected in a three-parallel, two-series configuration. This multi-stage series resin regeneration mode allows the saturated resin to be regenerated first with a previously used regeneration solution, followed by a secondary regeneration with fresh regeneration solution, effectively improving the resin regeneration effect while reducing the amount of regeneration solution used.

[0015] Furthermore, the regenerated tail liquid concentration and purification unit includes an acid-resistant reverse osmosis membrane. The acid-resistant reverse osmosis membrane is a positively charged acid-resistant RO membrane that is resistant to anionic SO4. 2- and small molecule H +It has high permeability and high rejection rate for other cations. During the concentration and purification of waste sulfuric acid, most of the sulfuric acid permeates through the membrane and continues to be used as the regeneration acid for the resin. The more concentrated sulfuric acid, rich in impurity ions, is used as the flotation acid for phosphate rock, converting crude phosphate rock into refined phosphate rock.

[0016] Furthermore, the resin column is filled with a strongly acidic cation exchange resin.

[0017] Secondly, the present invention also provides a workflow for the above-mentioned process system, which includes the following steps: Step 1, Resin Pretreatment: Rinse the resin with pure water until the effluent is clear. Then soak the resin in a mixed solution of sodium chloride and phosphoric acid for 24-36 hours at 20-25℃. Next, rinse the resin with pure water until the pH is neutral. Finally, use dilute sulfuric acid at 2m... 3 The resin is rinsed at a flow rate of / h for 2-3 hours, and then rinsed with pure water until the pH is neutral to obtain pretreated resin. After pretreatment and modification of the resin by this method, the resin can be more adaptable to the phosphoric acid environment and the resin adsorption rate of impurity ions can be improved.

[0018] Step 2: Load the resin column filled with the pretreated resin into the resin rotary purification and regeneration unit, and at the same time open the outlets of the raw material tank, purified finished product tank, first wash water tank, regeneration liquid tank, regeneration tail liquid tank and second wash water tank to supply liquid to the resin rotary purification and regeneration unit. Step 3: The resin columns in the resin rotation purification and regeneration unit rotate in the following order: "phosphoric acid purification section → phosphoric acid washing section → waste acid utilization section → resin regeneration section → regenerated liquid washing section → phosphoric acid pre-washing section". The rotation step is 1 column at a time, and the residence time after rotation is 15-25 minutes.

[0019] Furthermore, in step 2, the flow rates of the liquid supplied to the resin rotary purification and regeneration unit are as follows: raw material tank 10m³ / h. 3 / h, liquid temperature 20-25℃; the purified finished product tank and the first washing water tank are 1m each. 3 / h; Regeneration liquid tank 10m 3 / h, feed liquid temperature 30-35℃; regeneration tail liquid tank 3m 3 / h; Second washing tank 0.8m 3 / h.

[0020] Furthermore, the acid-resistant reverse osmosis membrane in the regenerated tail liquid concentration and purification unit operates at a pressure of 4-6 MPa, a temperature of 30-35℃, and a clear phase flow rate of 5 m³ / s. 3 / h, Dense phase flow rate 2m³ 3 / h.

[0021] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a continuous, efficient, low-consumption, and environmentally friendly process system and workflow for ion exchange purification of phosphoric acid. It achieves continuous operation of the entire process of phosphoric acid purification and resin regeneration, avoiding the drawbacks of intermittent production; it significantly reduces the breakage rate of ion exchange resin and lowers replacement costs; through countercurrent adsorption and regeneration processes, it significantly improves purification effect and regeneration efficiency, reducing the amount of regeneration liquid and washing water used; it achieves near-zero discharge of waste liquid within the system, especially by efficiently recovering and recycling acid and water in the regeneration tail liquid, thereby improving resource utilization.

[0022] The process of this invention is simple, does not require high temperature and high pressure, has low operating cost, is green and environmentally friendly, does not produce waste acid, wastewater or waste residue, has high added value and high economic benefits. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of the process system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the process system provided in an embodiment of the present invention.

[0025] In the picture: 1-First washing tank; 2-Raw material tank; 3-Purified finished product tank; 4-Second washing tank; 5-Regenerated liquid tank; 6-Regenerated tail liquid tank; 7-Regenerated tail liquid concentration and purification unit; 71-Clear phase outlet; 72-Dense phase outlet; 8-Resin rotation purification and regeneration unit; 81-Phosphoric acid purification section; 82-Phosphoric acid washing section; 83-Waste acid utilization section; 84-Resin regeneration section; 85-Regenerated liquid washing section; 86-Phosphoric acid pre-washing section; The letters A through T are used to indicate the location of the resin columns. Specific implementation methods

[0026] 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.

[0027] See Figure 1This invention provides a process system for ion exchange purification of phosphoric acid, which includes a raw material tank 2, a purified finished product tank 3, a first washing water tank 1, a regenerated liquid tank 5, a regenerated tail liquid tank 6, a second washing water tank 4, a resin rotation purification and regeneration unit 8, and a regenerated tail liquid concentration and purification unit 7. The regenerated tail liquid concentration and purification unit 7 is equipped with an acid-resistant RO membrane.

[0028] The resin rotation purification and regeneration unit 8 is a closed-loop system consisting of 20 resin columns (position numbers A to T). The resin columns can be moved sequentially within this closed-loop system. Specifically, the resin columns are installed in a disc-type multi-channel liquid distributor to form the closed-loop system. When the resin columns rotate, the connection between the distributor and the resin columns rotates with the resin columns, while the connection with the external pipes remains stationary. After rotation, different resin columns correspond to different pipes, achieving the function of rotating resin columns while maintaining a stationary pipe. In this embodiment of the invention, the resin filled in the resin columns is a strongly acidic cation exchange resin.

[0029] The resin rotation purification and regeneration unit 8 is divided into a phosphoric acid purification section 81, a phosphoric acid washing section 82, a waste acid utilization section 83, a resin regeneration section 84, a regenerated liquid washing section 85, and a phosphoric acid pre-washing section 86, which are connected in sequence. The resin columns in the phosphoric acid purification section 81 are numbered C to H and connected in a three-parallel, two-series configuration. The resin columns in the phosphoric acid washing section 82 are numbered A and B and connected in series. The resin columns in the waste acid utilization section 83 are numbered T. The resin columns in the resin regeneration section 84 are numbered N to S and connected in a three-parallel, two-series configuration. The resin columns in the regenerated liquid washing section 85 are numbered K, L, and M and connected in series. The resin columns in the phosphoric acid pre-washing section 86 are numbered I and J and connected in series.

[0030] The inlet of the phosphoric acid purification section 81 is connected to the raw material tank 2, and the outlet is connected to the purified finished product tank 3; the inlet of the phosphoric acid washing section 82 is connected to the first washing water tank 1, and the outlet is connected to the raw material tank 2; the inlet and outlet of the waste acid utilization section 83 are respectively connected to the regeneration tail liquid tank 6, the outlet of the regeneration tail liquid tank 6 is also connected to the regeneration tail liquid concentration and purification unit 7, and the clear phase outlet 71 of the regeneration tail liquid concentration and purification unit 7 is connected to the regeneration liquid tank 5; the inlet of the resin regeneration section 84 is connected to the regeneration liquid tank 5, and the outlet is connected to the regeneration tail liquid tank 6; the inlet of the regeneration liquid washing section 85 is connected to the second washing water tank 4, and the outlet is connected to the regeneration liquid tank 5; the inlet of the phosphoric acid pre-washing section 86 is connected to the purified finished product tank 3, and the outlet is connected to the second washing water tank 4.

[0031] See Figure 2The process flow for purifying phosphoric acid and regenerating resin provided in this embodiment of the invention is as follows: the resin column rotates from right to left, with a rotation step of one column at a time, and a residence time of 15-25 minutes after rotation. The resin columns in the phosphoric acid purification section and the resin regeneration section are connected in a three-parallel, two-series configuration. Raw phosphoric acid enters raw material tank 2, and the phosphoric acid in raw material tank 2 is simultaneously pumped to resin columns at positions C, D, and E. The phosphoric acid from resin columns at positions C, D, and E continues to enter resin columns at positions F, G, and H. The phosphoric acid produced from resin columns at positions F, G, and H enters the purified finished product tank 3 to obtain purified phosphoric acid product. The resin column saturated by adsorption in the phosphoric acid purification section is transferred to the phosphoric acid washing section (positions B and A), where pure water flushes the phosphoric acid from the resin column into raw material tank 2. The resin column after being replaced by pure water is transferred to the waste acid utilization section (position T). Waste acid is pumped into the regeneration tail liquid tank 6 to replace the water in the resin column, converting the resin to acidic conditions. The resin column is then transferred to the resin regeneration section. In the resin regeneration section, dilute sulfuric acid is pumped from regeneration tank 5 into the resin columns at the N, O, and P positions. The dilute sulfuric acid from these columns then flows into the resin columns at the Q, R, and S positions. The sulfuric acid produced from the Q, R, and S columns enters the regeneration tailings tank 6. On one hand, the waste acid in the tailings tank 6 can be used to flush the T-position resin column before returning to the tailings tank 6 (carrying back the water displaced from the resin column). On the other hand, the waste acid in the tailings tank 6 enters the tailings concentration and purification unit 7, where it is concentrated and purified by an acid-resistant RO membrane. The high-concentration sulfuric acid (concentrated phase) after RO membrane concentration enters the mineral processing workshop for use in phosphate ore beneficiation, while the clear phase enters regeneration tank 5 as regeneration liquid. High-concentration sulfuric acid (98% sulfuric acid) can be added to regeneration tank 5 as needed to adjust the pH of the regeneration liquid. After regeneration, the resin column is transferred to the regeneration solution washing section (positions K, L, and M). Pure water is pumped into the second washing tank 4 to flush the dilute sulfuric acid in the resin column back to the regeneration solution tank 5. The cleaned resin column is then transferred to the phosphoric acid pre-washing section (positions I and J). The purified finished product tank 3 pumps purified phosphoric acid into the resin column to flush the water in the resin column back to the second washing tank 4. The regenerated and cleaned resin column then re-enters the phosphoric acid purification section for phosphoric acid purification. This completes one cycle of phosphoric acid purification and resin regeneration.

[0032] Specifically, the workflow of the above-mentioned process system provided in this embodiment of the invention includes the following steps: Step 1: Resin Pretreatment: By pretreating and modifying the resin, it can be made more adaptable to the phosphoric acid environment, thereby improving the resin's adsorption rate for impurity ions. The resin pretreatment method is as follows: (1) Rinse the resin with pure water until the effluent is clear; (2) Soak the resin in a mixed solution of sodium chloride and phosphoric acid (sodium chloride mass concentration of 26-27% and phosphoric acid purified phosphoric acid mass concentration of 3%) for 24-36 hours at a temperature of 20-25℃; (3) Rinse the resin with pure water until the pH is neutral; (4) Then, use a 6-10% dilute sulfuric acid solution at a concentration of 2m 3 (5) Rinse the resin column with pure water until the pH is neutral to complete the pretreatment of the resin.

[0033] Step 2: Load the resin column filled with pretreated resin into the resin rotary purification and regeneration unit. Simultaneously, open the outlets of the raw material tank 2, purified finished product tank 3, first wash water tank 1, regenerated liquid tank 5, regenerated tail liquid tank 6, and second wash water tank 4 to supply liquid to the resin rotary purification and regeneration unit 8. Specifically, the flow rates of liquid supplied to the resin rotary purification and regeneration unit by each structure are as follows: raw material tank 10m³ / h... 3 / h, liquid temperature 20-25℃; the purified finished product tank and the first washing water tank are 1m each. 3 / h; Regeneration liquid tank 10m 3 / h, feed liquid temperature 30-35℃; regeneration tail liquid tank 3m 3 / h; Second washing tank 0.8m 3 / h. The acid-resistant RO membrane in the regenerated tail liquid concentration and purification unit 7 operates at a pressure of 4-6 MPa, a temperature of 30-35℃, and a clear phase flow rate of 5 m³ / h. 3 / h, Dense phase flow rate 2m³ 3 / h.

[0034] Step 3: The resin columns in the resin rotation purification and regeneration unit rotate in the following order: "phosphoric acid purification section → phosphoric acid washing section → waste acid utilization section → resin regeneration section → regenerated liquid washing section → phosphoric acid pre-washing section" (i.e., Figure 1 and Figure 2 Rotate in a sequence from right to left, with each rotation consisting of one column, and the dwell time after each rotation is 15-25 minutes.

[0035] The following uses wet-process phosphoric acid with the composition shown in Table 1 as the phosphoric acid raw material to be purified. The above process system and workflow are used for purification. The composition of the liquid in the purified finished product tank 3, the liquid in the regeneration tail liquid tank 6, and the liquid at the clear phase outlet 71 and the dense phase outlet 72 of the regeneration tail liquid concentration and purification unit 7 are detected by inductively coupled plasma mass spectrometry (ICP-MS). The results are shown in Tables 2 to 5 below.

[0036] Table 1. Composition of Phosphoric Acid to be Purified

[0037] Table 2. Phosphoric acid composition in the purified finished product tank

[0038] Table 3. Composition of waste acid in the regeneration tailings tank

[0039] Table 4. Composition of the clear phase outlet liquid of the acid-resistant RO membrane.

[0040] Table 5. Composition of concentrated phase outlet liquid from acid-resistant RO membrane

[0041] As can be seen from the results in Tables 1 and 2, the process system provided by the present invention can effectively remove ions such as iron, calcium, magnesium, aluminum, sodium, and potassium from wet-process phosphoric acid, and can ensure that the phosphoric acid concentration is basically not reduced. The total amount of polyvalent impurity ions in the purified phosphoric acid is less than 1 ppm, and the content of monovalent impurity ions is less than 10 ppm.

[0042] As can be seen from the results in Tables 3, 4 and 5, after the regenerated tailings (waste acid) are purified by concentrated acid through an acid-resistant RO membrane, the clear phase (purified sulfuric acid) can be directly reused in the system to prepare regenerated liquid, while the concentrated phase (high-concentration impurity sulfuric acid) can be used as a by-product for phosphate rock beneficiation, thus realizing the recycling of regenerated liquid and improving resource utilization.

[0043] In summary, this invention provides a continuous, efficient, low-consumption, and environmentally friendly process system and workflow for ion exchange purification of phosphoric acid. It achieves continuous operation of the entire process of phosphoric acid purification and resin regeneration, avoiding the drawbacks of intermittent production; it significantly reduces the breakage rate of ion exchange resin and lowers replacement costs; through countercurrent adsorption and regeneration processes, it significantly improves purification effect and regeneration efficiency, reducing the amount of regeneration liquid and washing water used; and it achieves near-zero discharge of waste liquid within the system, especially by efficiently recovering and recycling acid and water in the regeneration tail liquid, thereby improving resource utilization.

[0044] The process of this invention is simple, does not require high temperature and high pressure, has low operating cost, is green and environmentally friendly, does not produce waste acid, wastewater or waste residue, has high added value and high economic benefits.

[0045] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, any improvements and modifications made based on the core ideas of the present invention—"the synergistic effect of resin column rotation and acid-resistant RO membrane to achieve continuous phosphoric acid purification and resin regeneration," "countercurrent adsorption of multi-stage series resin columns to improve purification effect and regeneration efficiency," and "reverse top resin to improve purification and regeneration effect"—such as adjusting the number of series / parallel resin columns, fine-tuning the position of each section, or specific process parameters, should be considered within the scope of protection of the present invention without departing from the spirit and scope of the present invention.

Claims

1. A process system for purifying phosphoric acid by ion exchange, characterized in that: It includes a raw material tank, a purified finished product tank, a first wash water tank, a regenerated liquid tank, a regenerated tail liquid tank, a second wash water tank, a resin rotation purification and regeneration unit, and a regenerated tail liquid concentration and purification unit. The resin rotation purification and regeneration unit includes a closed circulation system composed of multiple resin columns, and the resin columns can move positions sequentially within the closed circulation system. The resin rotation purification and regeneration unit is divided into a phosphoric acid purification section, a phosphoric acid washing section, a waste acid utilization section, a resin regeneration section, a regenerated liquid washing section, and a phosphoric acid pre-washing section connected in sequence. The inlet of the phosphoric acid purification section is connected to the raw material tank, and the outlet is connected to the purified finished product tank. The inlet of the phosphoric acid washing section is connected to the first washing tank, and the outlet is connected to the raw material tank. The inlet and outlet of the waste acid utilization section are respectively connected to the regeneration tail liquid tank. The outlet of the regeneration tail liquid tank is also connected to the regeneration tail liquid concentration and purification unit. The clear phase outlet of the regeneration tail liquid concentration and purification unit is connected to the regeneration tank. The inlet of the resin regeneration section is connected to the regeneration liquid tank, and the outlet is connected to the regeneration tail liquid tank. The inlet of the regenerated liquid washing section is connected to the second washing tank, and the outlet is connected to the regenerated liquid tank; The inlet of the phosphoric acid prewashing section is connected to the purified finished product tank, and the outlet is connected to the second washing water tank.

2. The process system according to claim 1, characterized in that: Multiple resin columns are installed in a disc-type multi-channel liquid distributor to form the closed-loop circulation system.

3. The process system according to claim 1, characterized in that: The resin columns in the phosphoric acid purification section are connected in a multi-stage series configuration, with multiple resin columns connected in parallel at each stage.

4. The process system according to claim 1, characterized in that: The resin columns in the resin regeneration section are connected in a multi-stage series configuration, with multiple resin columns connected in parallel at each stage.

5. The process system according to claim 1, characterized in that: The regenerated tail liquid concentration and purification unit includes an acid-resistant reverse osmosis membrane.

6. The process system according to claim 1, characterized in that: The resin column is filled with a strong acid cation exchange resin.

7. The workflow of the process system according to any one of claims 1 to 6, characterized in that: Includes the following steps: Step 1, Resin Pretreatment: Rinse the resin with pure water until the effluent is clear. Then soak the resin in a mixed solution of sodium chloride and phosphoric acid for 24-36 hours at 20-25℃. Next, rinse the resin with pure water until the pH is neutral. Finally, use dilute sulfuric acid at 2m... 3 Rinse the resin at a flow rate of / h for 2-3 hours, and finally rinse the resin with pure water until the pH is neutral to obtain the pretreated resin. Step 2: Load the resin column filled with the pretreated resin into the resin rotary purification and regeneration unit, and at the same time open the outlets of the raw material tank, purified finished product tank, first wash water tank, regeneration liquid tank, regeneration tail liquid tank and second wash water tank to supply liquid to the resin rotary purification and regeneration unit. Step 3: The resin columns in the resin rotation purification and regeneration unit rotate in the following sequence: "phosphoric acid purification section → phosphoric acid washing section → waste acid utilization section → resin regeneration section → regenerated liquid washing section → phosphoric acid pre-washing section". The rotation step is 1 column at a time, and the residence time after rotation is 15-25 minutes.

8. The workflow according to claim 7, characterized in that: In step 2, the flow rates of the liquid supplied to the resin rotary purification and regeneration unit are as follows: raw material tank 10m³ / h. 3 / h, liquid temperature 20-25℃; the purified finished product tank and the first washing water tank are 1m each. 3 / h; Regeneration liquid tank 10m 3 / h, feed liquid temperature 30-35℃; regeneration tail liquid tank 3m 3 / h; Second washing tank 0.8m 3 / h.

9. The workflow according to claim 7, characterized in that: The acid-resistant reverse osmosis membrane in the regenerated tail liquid concentration and purification unit operates at a pressure of 4-6 MPa, a temperature of 30-35℃, and a clear phase flow rate of 5 m³ / s. 3 / h, Dense phase flow rate 2m³ 3 / h.

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