Comprehensive treatment process combining ardealite resource modification and phosphoric acid production

Abstract

The invention discloses a comprehensive treatment process combining ardealite resource modification and phosphoric acid production. The comprehensive treatment process comprises the following steps: S1, mixing ardealite and fresh water according to a ratio, and repulping; s2, adding an acid treatment agent to remove harmful substances, and reacting for 25-40 minutes; s3, adding a calcium carbonate / calcium hydroxide finishing agent to oxidize and degrade organic matters and convert metal ions; s4, after filtering, adding quick lime into a filter cake, stockpiling and curing for more than or equal to 30 days to obtain modified ardealite; and S5, adjusting the pH value of the filtrate, treating and recycling part of the filtrate, and returning the rest to a phosphoric acid device to recover phosphorus resources. According to the process, removal and resource utilization of harmful components of phosphogypsum are realized through physical and chemical synergistic treatment, the problems of land occupation and environmental pollution caused by traditional stockpiling are solved, meanwhile, phosphorus resources are recycled, and water consumption is reduced. The method has the advantages of simple process, easily available chemicals and low cost, has both economic benefits and environmental benefits, and is suitable for comprehensive treatment and resource utilization of phosphogypsum in phosphoric acid production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial waste treatment, in particular to a phosphogypsum resource modification and production of phosphoric acid combined comprehensive treatment process. BACKGROUND

[0002] Phosphogypsum is an industrial solid waste generated during the production of wet-process phosphoric acid. The production of 1 ton of phosphoric acid will produce 4-6 tons of phosphogypsum. With the expansion of the scale of phosphoric acid production, the amount of phosphogypsum produced is also increasing. In 2023, China's phosphogypsum production was about 810 million tons, and in 2024, the production of phosphogypsum increased rapidly, with an annual output of about 150 million tons by the end of the year, accounting for more than 40% of the total global output, and the annual increase has a rapid growth trend.

[0003] The main component of phosphogypsum is CaSO4·2H2O (calcium sulfate dihydrate), in addition to a variety of impurities. These impurities include undecomposed phosphate rock, as well as phosphoric acid, fluorine, heavy metals (such as lead, cadmium, etc.), radionuclides, etc. that have not been removed. At the same time, phosphogypsum has strong acidity and fine particles. The physical properties of this complex composition make the treatment and utilization of phosphogypsum face many challenges.

[0004] Traditional stockpiling methods can cause harmful substances and heavy metals in phosphogypsum to seep into rivers, lakes, and groundwater, and the phosphoric acid and fluoride in it can cause water pollution, causing serious damage to aquatic ecosystems. Due to the fine particles of phosphogypsum, dust is released during the stockpiling process, and acid gas is also volatilized, causing air pollution. In recent years, the government and local authorities have further increased their efforts to promote the comprehensive utilization of phosphogypsum, and relevant policies have been introduced to provide strong policy support and direction for the comprehensive utilization of phosphogypsum. According to relevant statistics, in 2023, China's phosphogypsum production was 810 million tons, an increase of 5.2% over the previous year; the amount of comprehensive utilization reached more than 40 million tons, an increase of about 600 million tons over 2022, an increase of 15.0% over the same period. The comprehensive utilization rate was about 50.0%, an increase of 5.2 percentage points over the same period. However, from the perspective of environmental impact, the impact on the environment is still very large. From the perspective of environmental protection and technical safety, the treatment of phosphogypsum solid waste has become an important research topic in the near future.

[0005] The current methods for pretreatment of phosphogypsum mainly include physical pretreatment, chemical pretreatment, physical-chemical combined pretreatment, and new biological pretreatment technology. The pretreated phosphogypsum is mainly used in the production of building materials, cement, roadbeds, mine filling, soil improvement, etc.

[0006] However, the current phosphogypsum pretreatment method has large water resource consumption, high secondary pollution risk, high reagent cost, complex process, and needs to set up a large storage yard, and a large area of anti-seepage treatment is needed to avoid soil pollution.

[0007] Therefore, a physical and chemical combined method is proposed, and a phosphoric acid production device and a harmless and resource comprehensive modification treatment process of phosphogypsum are combined. SUMMARY

[0008] The purpose of the present application is to provide a comprehensive treatment process combining phosphogypsum resource modification and phosphoric acid production, to solve the problems in the above background art.

[0009] To achieve the above purpose, the present application provides the following technical solution: a comprehensive treatment process combining phosphogypsum resource modification and phosphoric acid production, comprising the following steps: S1, re-slurry water washing: mixing the phosphogypsum produced by the phosphoric acid device with fresh water required for the production of the phosphoric acid device at a ratio of 1:1 to 1:1.3 cubic meters per ton, fully stirring to form a re-slurry slurry; S2, acid reagent treatment: adding a first acid treatment agent to the phosphogypsum slurry obtained in step S1, the acid treatment agent being a mixture of multiple acids, for removing harmful substances in the slurry; the reaction time is controlled at 25-40 minutes, and the reaction is carried out under any of the following conditions: a when the phosphogypsum needs to be transported, the reaction is completed during the transportation process, and a slurry storage tank meeting the reaction time is arranged at the receiving end of the material; b when the phosphogypsum does not need to be transported, the reaction is completed in a special slurry storage tank; S3, oxidation adjustment treatment: adding a second finishing reagent to the slurry treated in step S2, the finishing reagent including calcium carbonate, calcium hydroxide and a mixture thereof, stirring for 14-16 minutes, oxidizing and degrading organic impurities and converting divalent metal ions into insoluble high valence state; S4, filtration and curing: filtering the slurry treated in step S3, adding a third balancing reagent, i.e. lime reagent, to the obtained phosphogypsum filter cake, fully stirring and then stacking and curing for ≥30 days to obtain modified phosphogypsum; S5, recycling of filtrate: collecting the high-concentration filtrate generated in step S4 in a filtrate tank, adding a fourth water treatment reagent to the filtrate tank to adjust the pH, and after removing Cl⁻, PO4 3 ⁻ in part of the filtrate by sedimentation / filtration and ion exchange / membrane separation, forming filtrate circulating water, returning it to the phosphoric acid device as raw material processing fresh water for recycling; the remaining high-concentration filtrate is transported to the upstream phosphoric acid device for use as raw material processing water, and phosphorus is recovered therefrom.

[0010] Preferably, the amount of fresh water in step S1 is dynamically adjusted according to the composition detection data of phosphogypsum.

[0011] Preferably, the acid treatment agent reaction in step S2 needs to be synchronized and matched with the production rhythm of phosphoric acid and the post-treatment process of phosphogypsum.

[0012] Preferably, the modified phosphogypsum in step S4 is used for gypsum powder production or downstream building material raw materials.

[0013] Preferably, the proportion of filtrate circulating water reuse in step S5 is adjusted in real time according to the water balance demand of the phosphoric acid device.

[0014] Beneficial effects The present application provides a phosphogypsum resource modification and phosphoric acid production combined comprehensive treatment process, which has the following beneficial effects: The present application combines physical and chemical methods to treat phosphogypsum, which can be widely applied in phosphoric acid production and can be directly applied to subsequent product processing, thereby saving land, avoiding soil pollution, changing the problem of large-area storage of phosphogypsum produced by previous phosphoric acid production, which brings great harm to soil and environment, effectively reducing the risk of secondary pollution; at the same time, due to the influence of harmful components contained in phosphogypsum on the application of phosphogypsum, the present phosphogypsum resource modification and phosphoric acid production combined comprehensive treatment process fully combines phosphoric acid production and solid waste resource treatment, and recovers part of the effective resources in the phosphogypsum modification process, achieves the concept of comprehensive utilization, effectively reduces water resource consumption, and brings certain technical progress to phosphoric acid production and environmental impact. The process is simple and effective, the reagent raw material is easily obtained material on the market, the source is wide and the cost is low, the cost of phosphogypsum treatment is limited, and once put into engineering, it will play a good effect of economic and environmental governance. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Figure 1 is a process flow diagram of an embodiment of the phosphogypsum resource modification and phosphoric acid production combined comprehensive treatment process according to the present application; Figure 2 Figure 2 is a process flow diagram of another embodiment of the phosphogypsum resource modification and phosphoric acid production combined comprehensive treatment process according to the present application. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0017] FromFigure 1 and Figure 2 As can be seen in the process flow diagram of

[0018] Example 1 According to the process flow of Figure 1 This example includes the re-slurry water washing section of the pre-treatment device of the phosphogypsum, the filtration section, the modification section, the curing section, and finally the delivery to the gypsum processing device.

[0019] The upstream phosphogypsum is delivered at a rate of 20 t / h via a belt to the re-slurry tank (180 m 3 ), and 25 m 3 / h of water is continuously added via a flow meter for re-slurry water washing. At the same time as the feed, the stirring of the re-slurry tank is started for thorough water washing and stirring. After 3 h of feeding, the feeding is stopped, and the amount of material in the re-slurry tank is about 75%. Then, 3.6 m 3 of mixed acid is added, and stirring is continued for 40 min to ensure sufficient reaction. Then, 3.3 m 3of the slurry tank to a plate and frame filter. The filtrate produced by the filter is transferred to a filtrate tank and then to a filtrate clarification tank after the addition of a water treatment agent. The clarified filtrate is metered using a flow meter, 60% of which is returned to the slurry tank for use as wash water, and 40% of which is pumped to an upstream phosphoric acid plant for recovery of phosphorus therein. The phosphogypsum filter cake produced by the filter is transferred to a silo for storage and then to a mixer where a small amount of balancing agent, about 2.4 m 3 of the balancing agent, is added. After mixing is complete, the mixture is transferred to a gypsum stockpile for storage in a sun shed for about 30 days, which can be used to produce downstream gypsum product raw materials.

[0020] The phosphogypsum obtained by the method has a eutectic phosphorus content of about 0.1%, a soluble phosphorus content of about 0.15%, a fluorine content of about 0.05%, a total phosphorus content of about 0.25%, a pH value of about 5-6, a phosphogypsum purity of about (CaSO4·2H2O)≥80%, and a whiteness of≥75%.

[0021] Example 2 According to the process flow of Figure 2 , this example includes a pre-treatment device of phosphogypsum, a re-slurry washing section, a filtration section, a modification section, a curing section, and finally a gypsum processing device. The filtrate obtained by the filtration section is reused to an upstream phosphoric acid plant after solid-liquid separation, which effectively recycles resources.

[0022] The upstream phosphogypsum is transported at a rate of 35 t / h by a belt to a re-slurry tank (200 m 3 long), 45 m 3 of water is continuously added to the re-slurry tank by a flow meter, and the re-slurry tank is stirred to wash the phosphogypsum. After 2 h of feeding, the feeding is stopped, and the amount of material in the re-slurry tank is about 80%. Then, 4.2 m 3 of mixed acid is added, and the re-slurry tank is stirred for 40 min to ensure sufficient reaction. Then, 3.85 m 3 of finishing agent is added, and the re-slurry tank is stirred for 15 min. The material in the re-slurry tank is then pumped to a plate and frame filter. The filtrate produced by the filter is transferred to a filtrate tank and then to a filtrate clarification tank after the addition of a water treatment agent. The clarified filtrate is metered using a flow meter, 50% of which is returned to the slurry tank for use as wash water, and 50% of which is pumped to an upstream phosphogypsum plant as raw material for use in a first water processing. The phosphogypsum filter cake produced by the filter is transferred to a silo and then to a mixer where a small amount of balancing agent, about 2.8 m 3 of the balancing agent, is added. After mixing is complete, the mixture is transferred to a gypsum stockpile for storage in a sun shed for about 30 days, which can be used to produce downstream gypsum product raw materials.

[0023] The phosphogypsum obtained by this method has a eutectic phosphorus content of about 0.1%, a soluble phosphorus content of about 0.14%, a fluorine content of about 0.06%, a total phosphorus content of about 0.24%, a pH value of about 5 to 6, a purity of about (CaSO4·2H2O) ≥80%, and a whiteness ≥75%.

[0024] Comparative Example 1 according to Figure 1 The process flow in this embodiment includes a pretreatment unit for phosphogypsum, a re-washing section, a filtration section, a modification section, a curing section, and finally, the phosphogypsum is transported to the gypsum processing unit.

[0025] The upstream phosphogypsum is transported at a rate of 20 t / h, and is conveyed by belt to the re-slurry tank (180m). 3 In the process, 25m³ of fluid was continuously added via a flow meter. 3 The feed is fed at a rate of [amount] / h for washing. Simultaneously, the agitator in the re-slurry tank is activated for thorough washing and agitation. After 3 hours of feeding, feeding is stopped, and the material level in the re-slurry tank is approximately 75%. The material in the re-slurry tank is then pumped to a plate and frame filter press. The filtrate produced by the filter press is transported to a filtrate tank, where a water treatment agent is added before transferring it to a filtrate clarification tank. The clarified filtrate is metered using a flow meter. 60% of the filtrate is returned to the re-slurry tank for washing, and 40% is pumped to the upstream phosphoric acid unit for phosphorus recovery. The phosphogypsum filter cake produced by the filter press is conveyed by a belt conveyor to a buffer silo, and then transported to a mixer via a metering screw propeller. A small amount of balancing agent (approximately 2.4 m³) is added to the mixer. 3 After mixing, the mixture is transported to the gypsum stockpile and dried in a sunroom for about 30 days before being used as raw material for the production of downstream gypsum products.

[0026] The phosphogypsum obtained by this method has a eutectic phosphorus content of about 0.1%, a soluble phosphorus content of about 0.20%, a fluorine content of about 0.2%, a total phosphorus content of about 0.3%, a pH value of about 4 to 5, a purity of about 80% (CaSO4·2H2O), and a whiteness of about 70%.

[0027] The results above show that the phosphogypsum produced using the process of this invention can basically meet the requirements of gypsum board raw material standards (such as GB / T 9776-2022). It is significantly superior to phosphogypsum pretreated by simple water washing or conventional phosphogypsum pretreatment methods. Furthermore, compared to long-term stockpiling of phosphogypsum, it reduces environmental pollution and hazards, and also helps improve the quality of downstream gypsum products.

[0028] The application combines physical and chemical methods to treat phosphogypsum, can be widely applied in phosphoric acid production, can be directly applied to the processing of subsequent products, thereby saving land, avoiding soil pollution, changing the problem that the phosphogypsum produced by the previous phosphoric acid production needs a large area of site storage and brings great harm to the soil and the environment, effectively reducing the secondary pollution risk; at the same time, due to the influence of the harmful components contained in the phosphogypsum on the application of the phosphogypsum, the phosphogypsum resource modification and comprehensive treatment process combined with the phosphoric acid production fully combines the phosphoric acid production and solid waste resource treatment, and recycles part of the effective resources in the phosphogypsum modification process, achieves the concept of comprehensive utilization, effectively reduces the water resource consumption, brings certain technical progress to the phosphoric acid production and the environment, the process is simple and effective, the reagent raw material is easily obtained material on the market, the source is wide and the cost is low, the cost increase of the phosphogypsum treatment is limited, once put into engineering, the economic and environmental governance double effects will be achieved.

[0029] In the drawings of the embodiments disclosed in the application, only the structures related to the embodiments of the present application are involved, other structures can be referred to the general design, and the same embodiments and different embodiments of the present application can be combined with each other under the condition of no conflict. Finally: the above only describes the preferred embodiments of the present application and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A comprehensive treatment process combining phosphogypsum resource modification and phosphoric acid production, characterized in that: The method comprises the following steps: S1, re-slurry water washing: phosphogypsum produced by the phosphoric acid device is mixed with fresh water required by the phosphoric acid device production in a re-slurry tank at a ratio of 1:1-1:1.3 cubic meters / ton, and fully stirred to form a re-slurry slurry; S2, acid agent treatment: a first acid treatment agent is added to the phosphogypsum slurry obtained in step S1, the acid treatment agent is a mixture of multiple acids, and is used to remove harmful substances in the slurry; the reaction time is controlled at 25-40 minutes, and the reaction is carried out under any of the following conditions: a. when the phosphogypsum needs to be transported, the reaction is completed during the transportation process, and a slurry storage tank meeting the reaction time is arranged at the receiving end of the material; b. when the phosphogypsum does not need to be transported, the reaction is completed in a special slurry storage tank; S3, oxidation adjustment treatment: a second finishing agent is added to the slurry treated in step S2, the finishing agent comprises calcium carbonate, calcium hydroxide and a mixture thereof, and is stirred for 14-16 minutes, so as to oxidize and degrade organic impurities and convert divalent metal ions into insoluble high valence state; S4, filtration and curing: the slurry treated in step S3 is filtered, the obtained phosphogypsum filter cake is added with a third balancing agent, i.e. a lime agent, and is fully stirred and then stacked and cured for ≥30 days to obtain modified phosphogypsum; S5, filtrate recycling: the high concentration filtrate produced in step S4 is collected in a filtrate tank, a fourth water treatment agent is added to the filtrate tank to adjust the pH, and part of the filtrate is removed of Cl⁻, PO4 3 ⁻ by sedimentation / filtration and ion exchange / membrane separation to form filtrate circulating water, which is returned to the phosphoric acid device as raw material to process fresh water for recycling; the remaining high concentration filtrate is transported to the upstream phosphoric acid device as raw material for water use, and phosphorus is recovered therefrom.

2. The comprehensive treatment process of modifying phosphogypsum resources and combining with phosphoric acid production according to claim 1, characterized in that: The amount of fresh water used in step S1 is dynamically adjusted according to the composition detection data of the phosphogypsum.

3. The comprehensive treatment process of phosphogypsum resource modification combined with phosphoric acid production according to claim 1, characterized in that: The acid treatment agent reaction in step S2 needs to be matched with the production rhythm of the phosphoric acid and the post-treatment process of the phosphogypsum.

4. The phosphogypsum resource modification and combined comprehensive management process of phosphoric acid production according to claim 1, characterized in that: The modified phosphogypsum in step S4 is used for gypsum powder production or downstream building material raw materials.

5. The comprehensive treatment process of phosphogypsum resource modification combined with phosphoric acid production according to claim 1, characterized in that: The recycling water proportion of the filtrate in step S5 is adjusted in real time according to the water balance demand of the phosphoric acid device.

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