Formula and method for curing soluble phosphorus, eutectic phosphorus, soluble fluorine and ammonia nitrogen in fresh phosphogypsum of rotary table type vacuum filter

Abstract

The invention relates to the technical field of phosphogypsum harmlessness, in particular to a formula and method for curing soluble phosphorus, eutectic phosphorus, soluble fluorine and ammonia nitrogen in fresh phosphogypsum of a rotary table type vacuum filter. Comprising the following components: ardealite, calcium hydroxide, anionic polyacrylamide, magnesium chloride, aluminum chloride, deacetylated chitin, potassium dichromate and deionized water. Agents adopted by the invention are common industrial agents which are convenient to purchase on a large scale. The medicament is low in cost and has no special requirements for storage and transportation. The agent cost for harmlessly treating each ton of fresh phosphogypsum of the large rotary table type vacuum filter is lower than 30 yuan. According to the method, the concentration of fluoride in the phosphogypsum leachate can be effectively controlled to be 4 mg / L or below.

Description

TECHNICAL FIELD

[0001] The present application relates to the harmless technology field of phosphogypsum, in particular to a formula for solidifying fresh phosphogypsum of soluble phosphorus, eutectic phosphorus, soluble fluorine, ammonia nitrogen and a method thereof. BACKGROUND

[0002] Phosphogypsum is the residue of phosphorus ore after phosphoric acid is prepared, is acidic, and mainly contains dihydrate calcium sulfate (CaSO4·2H2O), attached water (H2O), water-soluble diphosphorus pentoxide (P2O5), water-soluble fluoride ion (F - ), ammonia nitrogen ion, eutectic phosphorus and water-soluble magnesium oxide (MgO).

[0003] At present, the domestic phosphogypsum stockpile has exceeded 700 million tons. In the process of long-term stockpiling, soluble phosphorus and fluorine can be released rapidly under the action of natural weather such as sunlight, wind and rain, and soluble phosphate and other acidic waste can be leached with rainfall.

[0004] In various scenes of comprehensive utilization of phosphogypsum, the migration of water-soluble phosphorus, water-soluble fluorine, ammonia nitrogen and low-pH pollutants will cause irreversible pollution to soil, surface water and groundwater, and seriously restrict the resource utilization of phosphogypsum.

[0005] At present, most of the phosphorus chemical enterprises using wet-process phosphoric acid process choose large-scale rotary vacuum filter as the process equipment for phosphogypsum dewatering. The large-scale rotary vacuum filter dehydrates the phosphogypsum to a water content of less than 25%. The dewatered phosphogypsum cake is crushed by the spiral discharging device attached to the rotary vacuum filter and discharged from the rotary vacuum filter. The phosphogypsum just discharged from the large-scale rotary vacuum filter is mainly in the form of dihydrate calcium sulfate, with good crystallization, and the crystal is in the form of needle, plate, compact crystal and polycrystalline nucleus. The molecular structure of magnesium, aluminum and silicon is stable. At this time, the phosphogypsum still has a temperature of 40-50°C, and the eutectic phosphorus crystal lattice is in a stable process. After the phosphogypsum is placed for a long time under natural conditions, part of the dihydrate calcium sulfate is converted into monohydrate and hemihydrate calcium sulfate with the slow rise of pH, the phosphogypsum crystal is in a mixed and agglomerated state, part of the eutectic phosphorus crystal lattice is replaced again, which promotes the escape of phosphate again, causing the rebound of the phosphate index of the phosphogypsum.

[0006] We found that the phosphogypsum discharged from the large-scale rotary vacuum filter is most conducive to the solidification of phosphate and fluorine within 48 hours, most conducive to the stable pH after harmless treatment, and most conducive to the efficient treatment of eutectic phosphorus.

[0007] At present, the industrial harmless treatment of phosphogypsum generally adopts lime neutralization method, which neutralizes the residual acid in phosphogypsum by adding lime, slaked lime and other alkaline substances, adjusts the pH value of phosphogypsum, and eliminates the environmental hazards of residual acid in phosphogypsum; at the same time, the alkaline substances react with part of the soluble P2O5, F - to generate inert insoluble substances, harmless the part of soluble substances into inert substances, and reduce the adverse effects of phosphogypsum on the environment. After lime neutralization, a large amount of water-soluble phosphorus, eutectic phosphorus and water-soluble fluorine will still remain in the phosphogypsum. Moreover, the lime neutralization method has no obvious effect on the removal of ammonia nitrogen and eutectic phosphorus.

[0008] The State Department of Ecological Environment of the People's Republic of China issued the national ecological and environmental standard "Phosphogypsum Utilization and Harmless Storage Pollution Control Technical Specification" (HJ1415-2025) on July 1, 2025. The "Phosphogypsum Utilization and Harmless Storage Pollution Control Technical Specification" requires that the pretreated phosphogypsum be used as raw material for activities such as desertification control, degraded forest and grassland restoration, land consolidation, abandoned land treatment, mine reclamation, slope treatment, and landscaping. The total fluorine content should not be higher than the regional soil environmental background value, and the fluorine concentration in the leaching liquid prepared according to HJ 557 should not exceed 5 mg / L. Compared with the requirement of 10 mg / L of fluorine concentration in the leaching liquid of the first general industrial solid waste defined in GB18599, this standard proposes a higher control standard for fluorine.

[0009] At present, the raw material for harmless treatment of phosphogypsum in various phosphorus chemical enterprises is the backfilling phosphogypsum aged in the slag bin for more than half a year. After aging in the slag bin, the water-soluble phosphorus and water-soluble fluorine content of the phosphogypsum is relatively significantly reduced compared with that of the fresh phosphogypsum from the large-scale rotary vacuum filter, usually less than half of that of the fresh phosphogypsum from the large-scale rotary vacuum filter. At present, the cost of reagent for harmless treatment of each ton of aged phosphogypsum in various enterprises is 30-45 yuan.

[0010] The new requirements of the state for phosphogypsum entering the slag bin are about to be implemented, which requires that the phosphogypsum entering the phosphogypsum slag bin meet the requirements of the first general industrial solid waste. The phosphogypsum of various phosphorus chemical enterprises needs to be harmless treated before entering the slag bin.

[0011] The present application is suitable for the harmless treatment of fresh phosphogypsum produced by large-scale rotary vacuum filter. SUMMARY

[0012] (I) Technical problems solved

[0013] The present application aims to provide a formula and method for solidifying soluble phosphorus, eutectic phosphorus, soluble fluorine and ammonia nitrogen in fresh phosphogypsum of a rotary vacuum filter, wherein the reagents used are common and easy to purchase in large quantities, and the reagent cost is low and there is no special requirement for storage and transportation. The reagent cost for harmless treatment of one ton of fresh phosphogypsum of a large rotary vacuum filter is less than 30 yuan, and the fluoride concentration in the phosphogypsum leaching solution can be effectively controlled below 4 mg / L.

[0014] (II) Technical scheme

[0015] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0016] A formula for solidifying soluble phosphorus, eutectic phosphorus, soluble fluorine and ammonia nitrogen in fresh phosphogypsum of a rotary vacuum filter, comprising the following components: phosphogypsum, calcium hydroxide, anionic polyacrylamide, magnesium chloride, aluminum chloride, deacetylated chitin, potassium dichromate and deionized water.

[0017] Preferably, the formula comprises the following components in the following proportions: 70-75 parts by weight of phosphogypsum, 8-15 parts by weight of calcium hydroxide, 4-8 parts by weight of anionic polyacrylamide, 6-10 parts by weight of magnesium chloride, 1-5 parts by weight of aluminum chloride, 1-3 parts by weight of deacetylated chitin, 0.1 part by weight of potassium dichromate and 5-10 parts by weight of deionized water.

[0018] Preferably, the calcium hydroxide is a 300-mesh powder, the anionic polyacrylamide is a 6 million molecular weight powder, the deacetylated chitin is a powder, the potassium dichromate is a powder, the aluminum chloride is an aqueous solution and the magnesium chloride is an aqueous solution.

[0019] A method for solidifying soluble phosphorus, eutectic phosphorus, soluble fluorine and ammonia nitrogen in fresh phosphogypsum of a rotary vacuum filter, comprising the following steps:

[0020] (1) crushing dry phosphogypsum, and making the phosphogypsum clumps with a diameter of less than 2 mm;

[0021] (2) dissolving analytical pure magnesium chloride in deionized water to prepare a magnesium chloride solution;

[0022] (3) dissolving analytical pure aluminum chloride in deionized water to prepare an aluminum chloride solution;

[0023] (4) mixing the phosphogypsum obtained in step (1) with calcium hydroxide, potassium dichromate and deacetylated chitin uniformly;

[0024] (5) adding the uniformly mixed phosphogypsum obtained in step (4) to deionized water and stirring thoroughly; after sufficient precipitation, the supernatant is taken to measure the pH; when the pH reaches 8.5-9, the next step is entered;

[0025] (6) the phosphogypsum obtained in step (4) is mixed with anion polyacrylamide;

[0026] (7) the mixed phosphogypsum obtained in step (6) is added into deionized water and stirred thoroughly; after sufficient precipitation, the supernatant is taken to measure the pH; if the pH is less than 8.5, calcium hydroxide is added to adjust the pH to 8.5-9, and the next step is entered;

[0027] (8) the phosphogypsum obtained in step (6) is mixed with the magnesium chloride solution obtained in step (2) and the magnesium chloride solution obtained in step (3);

[0028] (9) the phosphogypsum obtained in step (8) is mixed with calcium hydroxide to ensure that the pH reaches 8.5-9;

[0029] (10) the phosphogypsum obtained in step (9) is aged for 4-6 hours.

[0030] Preferably, the following steps are included:

[0031] (1) 70-75 parts by weight of dry phosphogypsum (main component is calcium sulfate, content is more than 90%) is kneaded and crushed, and the phosphogypsum is gathered into a diameter of less than 2 mm;

[0032] (2) 6-10 parts by weight of analytical pure magnesium chloride (MgCl2·6H2O) is dissolved in 1-5 parts by weight of deionized water to prepare a magnesium chloride solution;

[0033] (3) 1-5 parts by weight of analytical pure aluminum chloride (ALCl3·6H2O) is dissolved in 1-5 parts by weight of deionized water to prepare an aluminum chloride solution;

[0034] (4) the phosphogypsum obtained in step (1) is mixed with 8-10 parts by weight of calcium hydroxide, 0.1 parts by weight of potassium dichromate and 1-3 parts by weight of deacetylated chitin;

[0035] (5) 10 grams of the mixed phosphogypsum obtained in step (4) is added into 100 grams of deionized water and stirred thoroughly; after sufficient precipitation, the supernatant is taken to measure the pH; if the pH is less than 8.5, 0.5-1 parts by weight of calcium hydroxide is added to adjust the pH to 8.5-9, and the next step is entered;

[0036] (6) the phosphogypsum obtained in step (4) is mixed with 4-8 parts by weight of anion polyacrylamide (6 million molecular weight);

[0037] (7) 10 grams of the mixed phosphogypsum obtained in step (6) is added into 100 grams of deionized water and stirred thoroughly; after sufficient precipitation, the supernatant is taken to measure the pH; if the pH is less than 8.5, 0.5-1 parts by weight of calcium hydroxide is added to adjust the pH to 8.5-9, and the next step is entered;

[0038] (8) mixing the phosphogypsum obtained in step (6) with the magnesium chloride solution obtained in step (2) and the magnesium chloride solution obtained in step (3) uniformly;

[0039] (9) mixing the phosphogypsum obtained in step (8) with 1-4 parts by weight of calcium hydroxide uniformly to ensure that the pH reaches 8.5-9;

[0040] (10) allowing the phosphogypsum obtained in step (9) to stand and age for 4-6 hours.

[0041] After the curing agent is applied, the phosphogypsum needs to be mixed with the agent uniformly. Under general industrial conditions, a double-shaft mixer is usually used to mix the phosphogypsum and the agent uniformly, and the water content of the phosphogypsum should be controlled to be below 35% when the double-shaft mixer is working. At the same time, after the harmless treatment, the phosphogypsum is used for the ways of storage in a slag yard, ecological restoration materials, land reclamation materials and the like, and the water content needs to be comprehensively considered to meet the requirements of suitable transportation and engineering mechanical construction.

[0042] Compared with the prior art, the present application has the following beneficial effects:

[0043] The deacetylated chitin has good antibacterial activity. The polycation of the deacetylated chitin is easy to interact with the groups with negative charges on the surface of fungus cells, thereby changing the fluidity and permeability of the cell membrane of pathogenic bacteria, interfering with the replication and transcription of DNA of the pathogenic bacteria and blocking the metabolism of the pathogenic bacteria. The addition of the deacetylated chitin can inhibit the propagation and growth of harmful insect eggs and pathogenic bacteria after the phosphogypsum is stored, and becomes an isolation barrier for the application of the phosphogypsum to planting soil.

[0044] The mixing of calcium hydroxide into the phosphogypsum can increase the causticity of the phosphogypsum and neutralize the acid residues. At the same time, the calcium hydroxide provides calcium ions to react with fluorine ions to generate calcium fluoride precipitate.

[0045] Ca 2+ +2F - →CaF2

[0046] In the above formula, the concentration product generated by the precipitation is K sp = 2.7 x 10 -11

[0047] The anionic polyacrylamide is a high-molecular polymer and is widely used in soil improvement and water environment treatment. The amide group functional group (-CONH2) contains an amide bond (-CONH), and the amide bond can be affinity and mutual adsorption with many substances. The amide group functional group bridges the adsorbed substances, accelerates the aggregation of several substances into flocculent substances, adsorbs water-soluble ions in the phosphogypsum, and achieves the purpose of removing part of the soluble phosphorus and soluble fluorine.

[0048] The anionic polyacrylamide hydrolyzes in an alkaline environment while adsorbing water-soluble ions, releases negative chain segments, repels the negative-charged soluble phosphorus and fluorine in the phosphogypsum, promotes the solidification reaction of the soluble phosphorus and fluorine with calcium hydroxide, and improves the solidification rate.

[0049] Magnesium chloride can be used as a food additive, and its aqueous solution has neutral pH. 2+ reacts with PO4 3+ in the phosphogypsum to generate a stable precipitate.

[0050] 3Mg 2+ +2PO4 3+ →Mg3(PO4)2

[0051] In the above formula, the concentration product of the precipitate is K sp =9.8x10 -25

[0052] Meanwhile, Mg 2+ can also react with PO4 3+ and NH4 + in the phosphogypsum to generate a stable magnesium ammonium phosphate precipitate.

[0053] Mg 2+ +NH4 + +PO4 3+ +6H2O→MgNH4PO 4˙ 6H2O

[0054] The optimal pH stable condition of the magnesium ammonium phosphate precipitate is 9-10.7, and the final pH of the harmless phosphogypsum is 8.5-9.

[0055] There are differences in process control in the wet-process phosphoric acid production, and hydrogen fluoride (HF) remains in part of the phosphogypsum.

[0056] Under certain conditions, Mg 2+ , OH - and HS jointly react to produce a stable magnesium fluoride precipitate.

[0057] Mg(OH)2+2HF→MgF2+2H2O

[0058] After the eutectic phosphorus enters the calcium sulfate dihydrate crystal lattice, the water washing, flotation, lime neutralization and other treatment methods cannot promote the effective precipitation of the eutectic phosphorus. The replacement adsorption reaction of the hydrochloric acid formed by the magnesium ions, a small amount of chloride ions and hydrogen ions and the amide ion group makes the calcium sulfate dihydrate containing the eutectic phosphorus dehydrate into anhydrous calcium sulfate. After the eutectic phosphorus is separated from the crystal lattice, it combines with calcium ions to generate Ca3(PO4)2 precipitate, so that the eutectic phosphorus in the gypsum crystal lattice is removed.

[0059] When using this curing agent to cure the water-soluble phosphorus, eutectic phosphorus, water-soluble fluorine, and ammonia nitrogen in fresh phosphogypsum of a rotary vacuum filter, a mixing and stirring reaction process between the curing agent and phosphogypsum is adopted to achieve a better curing and harmless effect.

[0060] The purpose of this invention is to provide a method for removing soluble phosphorus, eutectic phosphorus, soluble fluoride, and ammonia nitrogen from fresh phosphogypsum using a solidification rotary vacuum filter. This method significantly reduces the risk of pollutant spillage from phosphogypsum, enhances its application value, and expands its application scenarios. This method is suitable for large-scale industrial implementation, is simple, and easy to promote; it can effectively control the fluoride concentration in phosphogypsum leachate to below 4 mg / L. Attached Figure Description

[0061] Figure 1 SEM image of phosphogypsum raw material;

[0062] Depend on Figure 1 It is evident that harmful impurities in the phosphogypsum raw material are adhered to the phosphogypsum crystals.

[0063] Figure 2 This is a SEM image of phosphogypsum from Example 1 after it has undergone the harmless treatment of this invention.

[0064] Figure 3 This is a SEM image of phosphogypsum from Example 2 after it has undergone the harmless treatment of this invention.

[0065] Depend on Figure 2 , Figure 3 As can be seen, the phosphogypsum crystals are clear and intact. The geophysical properties of the phosphogypsum after harmless treatment are good. Detailed Implementation

[0066] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0067] The following examples and comparative examples all prepared leachates from harmless phosphogypsum samples according to the "Horizontal Oscillation Method for Leaching Toxicity of Solid Waste" (HJ557-2009), and the pH, soluble phosphorus (calculated as P), soluble fluoride, and ammonia nitrogen content of the leachates were determined.

[0068] A phosphogypsum leaching experiment device disclosed in CN220231734U is used to carry out leaching experiment on the harmless phosphogypsum. 10 Kg of the harmless phosphogypsum sample is placed in the glass column of the device, and the device automatically leaches the phosphogypsum column according to the local rainfall data collected in advance. After the leaching solution flows out from the bottom of the device, the device automatically times and samples. The pH, soluble phosphorus (in terms of P), soluble fluorine and ammonia nitrogen contents of the leaching solution are determined.

[0069] The following examples adopt a mixed stirring reaction method.

[0070] The phosphogypsum sample is taken from the material drop port of a rotating vacuum filter of a certain phosphorus chemical enterprise in Guizhou, and is fresh phosphogypsum.

[0071] 1000±5 g of the phosphogypsum sample dried in a drying oven at a set temperature of 45℃ for 48 hours is weighed, and different proportions of reagents are added and fully mixed and stirred. The reagents are: 300 mesh 95% effective content calcium hydroxide powder, 6 million molecular weight anionic polyacrylamide powder, analytical pure magnesium chloride and deionized water. After stirring, the sample is left to stand for 36 hours to prepare the leaching solution, and the pH and the residual contents of soluble phosphorus (in terms of P), soluble fluorine and ammonia nitrogen are determined, and the solidification rates of soluble phosphorus (in terms of P), soluble fluorine and ammonia nitrogen are calculated.

[0072] The characteristic indexes of the phosphogypsum sample are determined as follows:

[0073] pH (dimensionless) Phosphate (mg / 1) Fluoride (mg / 1) Ammonia nitrogen (mg / 1) 2.35 215.7 422.2 1.44

[0074] Example 1

[0075] A method for solidifying soluble phosphorus (in terms of P), soluble fluorine and ammonia nitrogen in fresh phosphogypsum of a rotating vacuum filter by a mixed stirring reaction. The method comprises the following steps:

[0076] (1) 8 wt% calcium hydroxide and 0.1 wt% potassium dichromate are added to the phosphogypsum and mixed and stirred for 10 minutes;

[0077] (2) 6 wt% polyacrylamide is added to the phosphogypsum and mixed and stirred for 10 minutes;

[0078] (3) 10 wt% analytical pure magnesium chloride (MgCl 2˙ 6H2O) is dissolved in 8 wt% deionized water to prepare a magnesium chloride solution;

[0079] (4) 3 wt% analytical pure aluminum chloride (AlCl 3˙ 6H2O) is dissolved in 4 wt% deionized water to prepare an aluminum chloride solution;

[0080] (5) The magnesium chloride solution and the aluminum chloride solution are added to the phosphogypsum and mixed and stirred for 20 minutes;

[0081] (6) standing and aging for 8 hours to prepare the leaching solution;

[0082] detection

[0083] pH (dimensionless) Phosphate (mg / 1) Fluoride (mg / 1) Ammonia nitrogen (mg / 1) 8.76 0.35 6.2 0.45

[0084] The phosphogypsum of Example 1 is harmless after treatment

[0085] Comparative Example 1

[0086] A method for neutralizing and mixing fresh phosphogypsum to solidify soluble phosphorus (in terms of P), soluble fluorine, and ammonia nitrogen by using a rotary vacuum filter.

[0087] The method comprises the following steps:

[0088] (1) adding 8wt% calcium hydroxide to the phosphogypsum and mixing for 10 minutes;

[0089] (2) standing and aging for 48 hours to prepare the leaching solution;

[0090] detection

[0091] pH (dimensionless) Phosphate (mg / 1) Fluoride (mg / 1) Ammonia nitrogen (mg / 1) 12.4 4.4 16.7 1.04

[0092] Compared with Example 1, the treated phosphogypsum does not meet the harmless requirements.

[0093] Comparative Example 2

[0094] A method for neutralizing and mixing fresh phosphogypsum to solidify soluble phosphorus (in terms of P), soluble fluorine, and ammonia nitrogen by using a rotary vacuum filter. The method comprises the following steps:

[0095] (1) adding 8wt% calcium hydroxide, 0.1wt% potassium dichromate, and 3wt% deacetylated chitin to the phosphogypsum and mixing for 10 minutes;

[0096] (2) adding 6wt% polyacrylamide to the phosphogypsum and mixing for 10 minutes;

[0097] (3) dissolving 10wt% analytical pure magnesium chloride (MgCl 2˙ 6H2O) in 8wt% deionized water to prepare a magnesium chloride solution;

[0098] (4) dissolving 3wt% analytical pure aluminum chloride (AlCl 3˙ 6H2O) in 4wt% deionized water to prepare an aluminum chloride solution;

[0099] (5) adding the magnesium chloride solution and the aluminum chloride solution to the phosphogypsum and mixing for 20 minutes;

[0100] (6) standing and aging for 36 hours to prepare the leaching solution;

[0101] detection

[0102] pH (dimensionless) Phosphate (mg / 1) Fluoride (mg / 1) Ammonia nitrogen (mg / 1) 8.77 0.36 6.2 0.44

[0103] Compared with Example 1, there is no obvious difference in soluble phosphorus (in terms of P), soluble fluorine and ammonia nitrogen after adding deacetylated chitin, and the deacetylated chitin can not be added if the phosphogypsum after harmless treatment is not used with soil.

[0104] Comparative Example 3

[0105] A method for solidifying soluble phosphorus (in terms of P), soluble fluorine and ammonia nitrogen in fresh phosphogypsum by using a mixed stirring reaction solidification turntable type vacuum filter. The method comprises the following steps:

[0106] (1) 8wt% calcium hydroxide and 0.1wt% potassium dichromate are added to the phosphogypsum, and mixed and stirred for 10 minutes;

[0107] (2) 6wt% polyacrylamide is added to the phosphogypsum, and mixed and stirred for 10 minutes;

[0108] (3) 10wt% analytical pure magnesium chloride (MgCl 2˙ 6H2O) is dissolved in 8wt% deionized water to prepare a magnesium chloride solution;

[0109] (4) 3wt% analytical pure aluminum chloride (AlCl 3˙ 6H2O) is dissolved in 4wt% deionized water to prepare an aluminum chloride solution;

[0110] (5) The magnesium chloride solution and the aluminum chloride solution are added to the phosphogypsum, and mixed and stirred for 20 minutes;

[0111] (6) The leaching liquid is prepared by standing and aging for 36 hours;

[0112] detection

[0113] pH (dimensionless) Phosphate (mg / 1) Fluoride (mg / 1) Ammonia nitrogen (mg / 1) 8.66 0.32 6.1 0.45

[0114] Compared with Example 1, under the condition of adding the same reagent, the standing and aging time is increased from 8 hours to 36 hours, the pH of the phosphogypsum slightly falls, and the solidification rate of soluble phosphorus (in terms of P) and soluble fluorine slightly increases. It can be seen that the present application has no specific requirement for the standing and aging time of the phosphogypsum after harmless treatment.

[0115] Example 2

[0116] A method for solidifying soluble phosphorus (in terms of P), soluble fluorine and ammonia nitrogen in fresh phosphogypsum by using a mixed stirring reaction solidification turntable type vacuum filter. The method comprises the following steps:

[0117] (1) phosphogypsum is added with 11wt% calcium hydroxide, 0.1wt% potassium dichromate and 3wt% deacetylated chitin, mixed and stirred for 10 minutes;

[0118] (2) phosphogypsum is added with 9wt% polyacrylamide, mixed and stirred for 10 minutes;

[0119] (3) 10wt% analytical pure magnesium chloride (MgCl 2˙ 6H2O) is dissolved in 8wt% deionized water to prepare a magnesium chloride solution;

[0120] (4) 5wt% analytical pure aluminum chloride (AlCl 3˙ 6H2O) is dissolved in 4wt% deionized water to prepare an aluminum chloride solution;

[0121] (5) the phosphogypsum is added with the magnesium chloride solution and the aluminum chloride solution, mixed and stirred for 20 minutes;

[0122] (6) standing and aging for 8 hours to prepare a leaching solution;

[0123] pH (dimensionless) Phosphate (mg / 1) Fluoride (mg / 1) Ammonia nitrogen (mg / 1) 8.96 0.11 3.4 0.31

[0124] Compared with Example 1, the weight parts of calcium hydroxide, polyacrylamide and magnesium chloride are increased, and the harmless effect of phosphogypsum is obviously improved.

[0125] Example 3

[0126] A method for removing soluble phosphorus (calculated as P), soluble fluorine and ammonia nitrogen from fresh phosphogypsum by using a mixed stirring reaction solidification rotary vacuum filter. The method comprises the following steps:

[0127] (1) phosphogypsum is added with 11wt% calcium hydroxide, 0.1wt% potassium dichromate and 3wt% deacetylated chitin, mixed and stirred for 10 minutes;

[0128] (2) phosphogypsum is added with 10wt% polyacrylamide, mixed and stirred for 10 minutes;

[0129] (3) 12wt% analytical pure magnesium chloride (MgCl 2˙ 6H2O) is dissolved in 8wt% deionized water to prepare a magnesium chloride solution;

[0130] (4) 7wt% analytical pure aluminum chloride (AlCl 3˙ 6H2O) is dissolved in 4wt% deionized water to prepare an aluminum chloride solution;

[0131] (5) the phosphogypsum is added with the magnesium chloride solution and the aluminum chloride solution, mixed and stirred for 20 minutes;

[0132] (6) standing and aging for 8 hours to prepare a leaching solution;

[0133] pH (dimensionless) Phosphate (mg / 1) Fluoride (mg / 1) Ammonia nitrogen (mg / 1) 8.23 0.04 2.1 0.25

[0134] Compared with Example 2, the weight parts of polyacrylamide, magnesium chloride and aluminum chloride are increased, and the effect of harmless treatment of phosphogypsum is obviously improved.

[0135] Comparative Example 4

[0136] A method for removing soluble phosphorus (calculated as P), soluble fluorine and ammonia nitrogen from fresh phosphogypsum by using a mixed stirring reaction solidification rotary vacuum filter. The method comprises the following steps:

[0137] (1) 11wt% calcium hydroxide, 0.1wt% potassium dichromate and 3wt% deacetylated chitin are added to the phosphogypsum, and mixed and stirred for 10 minutes;

[0138] (2) 10wt% polyacrylamide is added to the phosphogypsum, and mixed and stirred for 10 minutes;

[0139] (3) 10wt% of analytical pure magnesium chloride (MgCl 2˙ 6H2O) is dissolved in 8wt% deionized water to prepare a magnesium chloride solution;

[0140] (4) 7wt% of analytical pure aluminum chloride (AlCl 3˙ 6H2O) is dissolved in 4wt% deionized water to prepare an aluminum chloride solution;

[0141] (5) The magnesium chloride solution and the aluminum chloride solution are added to the phosphogypsum, and mixed and stirred for 20 minutes;

[0142] (6) The leaching solution is prepared by standing and aging for 8 hours;

[0143] pH (dimensionless) Phosphate (mg / 1) Fluoride (mg / 1) Ammonia nitrogen (mg / 1) 8.63 0.04 2.2 0.26

[0144] Compared with Example 3, the weight parts of the other reagents remain unchanged, and the amount of analytical pure magnesium chloride is reduced by 2 weight parts, and the pH is increased from 8.23 to 8.63. It can be seen that the reagents of the present application have a sensitive pH adjusting function, and the pH value of the harmless phosphogypsum can be adjusted according to different utilization occasions.

[0145] And it can be clearly seen from pH (dimensionless) and Phosphate (mg / 1) Fluoride (mg / 1) Ammonia nitrogen (mg / 1) Figure 2 Figure 3 that the phosphogypsum crystal grains are clear and complete. The geotechnical physical properties of the phosphogypsum after harmless treatment are good.

[0146] Finally, it should be noted that the above content is only used to illustrate the technical solutions of the present application, and is not a limitation on the protection scope of the present application. Simple modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A formulation for soluble phosphorus, eutectic phosphorus, soluble fluorine, and ammonia nitrogen in fresh phosphogypsum using a curing rotary vacuum filter, characterized in that: It includes the following components: phosphogypsum, calcium hydroxide, anionic polyacrylamide, magnesium chloride, aluminum chloride, deacetylated chitosan, potassium dichromate, and deionized water.

2. The formulation of soluble phosphorus, eutectic phosphorus, soluble fluorine, and ammonia nitrogen in fresh phosphogypsum for a curing rotary vacuum filter according to claim 1, characterized in that: The product comprises the following components: 70-75 parts by weight of phosphogypsum, 8-15 parts by weight of calcium hydroxide, 4-8 parts by weight of anionic polyacrylamide, 6-10 parts by weight of magnesium chloride, 1-5 parts by weight of aluminum chloride, 1-3 parts by weight of deacetylated chitin, 0.1 parts by weight of potassium dichromate, and 5-10 parts by weight of deionized water.

3. The formulation of soluble phosphorus, eutectic phosphorus, soluble fluorine, and ammonia nitrogen in fresh phosphogypsum for a curing rotary vacuum filter according to claim 1 or 2, characterized in that: Calcium hydroxide is a 300-mesh powder, anionic polyacrylamide is a 6 million molecular weight powder, deacetylated chitosan is a powder, potassium dichromate is a powder, aluminum chloride is an aqueous solution, and magnesium chloride is an aqueous solution.

4. A method for removing soluble phosphorus, eutectic phosphorus, soluble fluorine, and ammonia nitrogen from fresh phosphogypsum using a solidification rotary vacuum filter, characterized in that: Includes the following steps: (1) Crush the dried phosphogypsum into small agglomerates with a diameter of less than 2 mm. (2) Dissolve analytical grade magnesium chloride in deionized water to prepare a magnesium chloride solution; (3) Dissolve analytical grade aluminum chloride in deionized water to prepare an aluminum chloride solution; (4) Mix the phosphogypsum obtained in step (1) with calcium hydroxide, potassium dichromate and deacetylated chitin evenly; (5) Take the mixed phosphogypsum obtained in step (4) and add it to deionized water. Stir thoroughly. After sufficient precipitation, take the supernatant and measure the pH. When the pH reaches 8.5-9, proceed to the next step. (6) Mix the phosphogypsum obtained in step (4) with anionic polyacrylamide until homogeneous; (7) Take the mixed phosphogypsum obtained in step (6) and add it to deionized water and stir thoroughly. After sufficient precipitation, take the supernatant and measure the pH. If the pH reaches 8.5-9, proceed to the next step. If the pH is less than 8.5, add calcium hydroxide and adjust the pH to 8.5-9 before proceeding to the next step. (8) Mix the phosphogypsum obtained in step (6) with the magnesium chloride solution obtained in step (2) and the magnesium chloride solution obtained in step (3) until homogeneous; (9) Mix the phosphogypsum obtained in step (8) with calcium hydroxide until the pH reaches 8.5-9; (10) Let the phosphogypsum obtained in step (9) stand for 4 to 6 hours to age.

5. The method for removing soluble phosphorus, eutectic phosphorus, soluble fluorine, and ammonia nitrogen from fresh phosphogypsum using a solidification rotary vacuum filter according to claim 4, characterized in that: Includes the following steps: (1) Crush 70-75 parts by weight of dried phosphogypsum (the main component is calcium sulfate, with a content of more than 90%), and the diameter of the phosphogypsum agglomerates is less than 2 mm; (2) Dissolve 6 to 10 parts by weight of analytical grade magnesium chloride (MgCl2˙6H2O) in 1 to 5 parts by weight of deionized water to prepare a magnesium chloride solution; (3) Dissolve 1-5 parts by weight of analytical grade aluminum chloride (ALCl3˙6H2O) in 1-5 parts by weight of deionized water to prepare an aluminum chloride solution; (4) Mix the phosphogypsum obtained in step (1) with 8-10 parts by weight of calcium hydroxide, 0.1 parts by weight of potassium dichromate and 1-3 parts by weight of deacetylated chitin until homogeneous; (5) Take 10 g of the mixed phosphogypsum obtained in step (4), add it to 100 g of deionized water, and stir thoroughly; after sufficient precipitation, take the supernatant to measure the pH; when the pH reaches 8.5-9, proceed to the next step; (6) Mix the phosphogypsum obtained in step (4) with 4 to 8 parts by weight of anionic polyacrylamide (6 million molecular weight) until homogeneous. (7) Take 10g of the mixed phosphogypsum obtained in step (6), add it to 100g of deionized water, and stir thoroughly. After sufficient precipitation, take the supernatant to determine the pH. If the pH reaches 8.5-9, proceed to the next step. If the pH is less than 8.5, add 0.5-1 parts by weight of calcium hydroxide to adjust the pH to 8.5-9, and proceed to the next step. (8) Mix the phosphogypsum obtained in step (6) with the magnesium chloride solution obtained in step (2) and the magnesium chloride solution obtained in step (3) until homogeneous; (9) Mix the phosphogypsum obtained in step (8) with 1 to 4 parts by weight of calcium hydroxide until the pH reaches 8.5 to 9. (10) Let the phosphogypsum obtained in step (9) stand for 4 to 6 hours to age.

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