Method for producing superphosphate fertilizer by using medium and low grade phosphate ore to produce by-product dilute phosphoric acid

Abstract

The application provides a method for producing superphosphate fertilizer by using medium and low grade phosphate ore and by-product dilute phosphoric acid, and belongs to the technical field of superphosphate fertilizer production. The method comprises the following steps: S1, mixed acid preparation: mixing concentrated sulfuric acid, dilute sulfuric acid and by-product dilute phosphoric acid according to a certain mass ratio, and stirring to obtain mixed acid; S2, adding phosphate ore powder into the mixed acid according to a certain mass ratio, stirring uniformly, and then performing chemical treatment to obtain fresh fertilizer; and S3, performing curing treatment on the fresh fertilizer after the chemical treatment in step S2 to obtain superphosphate fertilizer. By using the method for producing superphosphate fertilizer by using medium and low grade phosphate ore and by-product dilute phosphoric acid, the raw material cost can be reduced by 15.42% when producing superphosphate fertilizer of the same grade, a new way for resource utilization of medium and low grade phosphate ore and by-product dilute phosphoric acid is opened up, and good economic benefit and social benefit are obtained.

Description

Technical Field

[0001] This invention belongs to the technical field of production methods for superphosphate fertilizer, specifically to a method for producing superphosphate fertilizer by means of low-grade phosphate rock and dilute phosphoric acid. Background Technology

[0002] Phosphate rock resources are a vital non-renewable strategic resource, an important raw material for the fertilizer industry, a crucial guarantee for national food security, and the material basis for fine phosphate chemicals. my country's phosphate resources are abundant but not plentiful; high-grade phosphate rock resources (P2O5 mass fraction >30%) are increasingly scarce, with approximately 90% of phosphate rock being medium- to low-grade and not directly usable. Therefore, intensifying research on the utilization of medium- to low-grade phosphate rock resources is urgently needed and is an important issue for improving the utilization rate of phosphate rock resources, protecting natural resources, and promoting the sustainable and healthy development of the phosphate fertilizer industry.

[0003] Patent application number 201410492932.2 discloses a system for producing superphosphate using medium- and low-grade phosphate rock. The system involves thoroughly mixing 98% sulfuric acid and dilute phosphoric acid containing 7-8% P2O5 in an acid mixer before adding them to a reaction tank. Simultaneously, a slurry containing 18% P2O5 is added to the reaction tank. After sufficient reaction, the slurry enters an intermediate tank for further processing. Qualified slurry undergoes liquid-solid separation via a filter, and the resulting phosphoric acid is stored in a phosphoric acid storage tank. Phosphogypsum is washed with washing water via a filter and then sent to a phosphogypsum storage yard. The resulting dilute phosphoric acid is transported to the reaction tank to reduce the slurry density and further recover phosphorus. The tail gas generated in the reaction tank is treated via a pipeline. The finished phosphoric acid is then pumped into a mixer along with the slurry containing 18% P2O5 and 98% sulfuric acid. The resulting superphosphate slurry is sent to a formation tank, and the matured superphosphate is packaged and stored. The reaction tank is heated to 79–89°C, the phosphoric acid storage tank to 40–50°C, and the mixer to 115±2°C. This method involves high reaction temperatures and requires sophisticated equipment.

[0004] Patent application No. 201610762330.3 discloses a method for preparing ordinary superphosphate using phosphate rock tailings, phosphate residue acid, and phosphate rock powder as raw materials. The method is characterized by thoroughly mixing 1 t of phosphate rock tailings with a P2O5 effective component content of 8%–8.5% and a solid content of 12%–15%, 0.3–0.8 t of phosphate residue acid with a P2O5 effective component content of 45.0%–46.0% and a solid content of 12%–15%, and 0.2 t of phosphate rock powder with a P2O5 effective component content of 25.0%–26.0%. Then, 0.4 t of concentrated H2SO4 is added, and the mixture is reacted for 1 hour under stirring. Finally, 0.03–0.08 t of quicklime is added to neutralize the free acid. The mixture is then transferred to a composting facility for 5–7 days to mature, resulting in a qualified ordinary superphosphate phosphate fertilizer product with a P2O5 effective component content of over 14%. The method of this invention provides a new channel for the comprehensive application of phosphate rock tailings and phosphate residue acid, and uses the addition of quicklime to neutralize excess free acid, thereby improving the utilization rate of phosphorus to a certain extent. Summary of the Invention

[0005] To achieve the resource utilization of by-product dilute phosphoric acid and increase the utilization of medium and low-grade phosphate rock resources, this invention provides a method for producing superphosphate fertilizer by co-producing dilute phosphoric acid from medium and low-grade phosphate rock at a lower cost and with lower requirements for production equipment.

[0006] The method for producing superphosphate fertilizer by co-producing dilute phosphoric acid from medium- and low-grade phosphate rock includes the following steps:

[0007] S1. Preparation of mixed acid: Mix concentrated sulfuric acid, dilute sulfuric acid and by-product dilute phosphoric acid in a certain mass ratio and stir evenly to obtain mixed acid;

[0008] S2. Add phosphate rock powder to the mixed acid according to a certain mass ratio, stir evenly, and then carry out chemical treatment to obtain fresh fertilizer;

[0009] S3. The fresh fertilizer after the transformation treatment in step S2 is subjected to a maturation treatment to obtain superphosphate fertilizer.

[0010] In step S1, the concentrated sulfuric acid, dilute sulfuric acid, and by-product dilute phosphoric acid are stored in storage tanks respectively. After being metered according to a set ratio by a magnetic pump, a pneumatic regulating valve, and a flow meter, they are mixed and stirred in a reaction vessel and then overflow into a mixed acid storage tank to obtain a mixed acid.

[0011] Preferably, in step S1, the concentrated sulfuric acid has a mass concentration of 98% to 99%, the dilute sulfuric acid has a mass concentration of 45% to 55%, and the by-product dilute phosphoric acid has a mass concentration of 30% to 40%.

[0012] Preferably, in step S1, the mass ratio of concentrated sulfuric acid: dilute sulfuric acid: by-product dilute phosphoric acid is 22.63-27.91: 63.01-65.37: 9-12.

[0013] The addition of by-product dilute phosphoric acid can provide a phosphorus source for superphosphate fertilizer. Therefore, for the production of superphosphate fertilizer of the same grade, this invention can use lower-grade phosphate rock. Through the synergistic effect of phosphate rock and by-product dilute phosphoric acid, superphosphate fertilizer that meets national standards can be prepared. However, further increasing the amount of phosphoric acid and reducing the grade of phosphate rock poses a risk of damaging equipment.

[0014] Further optimization is needed to produce 12% grade superphosphate fertilizer. In step S1, the mass ratio of concentrated sulfuric acid: dilute sulfuric acid: by-product dilute phosphoric acid is 22.63:65.37:12.

[0015] Further optimization is needed to produce 16% grade superphosphate fertilizer. In step S1, the mass ratio of concentrated sulfuric acid: dilute sulfuric acid: by-product dilute phosphoric acid is 27.91:63.09:9.

[0016] Preferably, in step S1, the content of P2O5 in the by-product dilute phosphoric acid is 20% to 30%.

[0017] Preferably, in step S1, the mass concentration of the mixed acid is 59.0% to 62.0%, and the P2O5 content in the mixed acid is 2.25% to 3%.

[0018] Preferably, in step S2, the fineness of the phosphate rock powder is 100 mesh to 120 mesh.

[0019] Preferably, in step S2, the P2O5 content in the phosphate rock powder is 18% to 28%.

[0020] Preferably, in step S2, the phosphate rock powder is dried before use.

[0021] Preferably, in step S2, the moisture content of the phosphate rock powder after drying is not higher than 0.8%.

[0022] Preferably, in step S2, the mass ratio of phosphate rock powder to mixed acid is 0.96 to 1.17:1.

[0023] Further optimization, in the production of 12% grade superphosphate fertilizer, the mass ratio of phosphate rock powder to mixed acid in step S2 is 1.17:1.

[0024] Further optimization, in the production of 16% grade superphosphate fertilizer, the mass ratio of phosphate rock powder to mixed acid in step S2 is 0.96:1.

[0025] Preferably, in step S2, the temperature and duration of the formation treatment are 30 to 60 minutes.

[0026] Preferably, in step S3, the aging process lasts for 3 to 5 days.

[0027] The advantages of this invention compared to the prior art are as follows:

[0028] 1. The method for producing superphosphate fertilizer by synergistic dilute phosphoric acid from medium and low grade phosphate rock provided by this invention has a mixed acid temperature not exceeding 80°C, which reduces the temperature resistance requirements of production equipment such as magnetic pumps, flow meters, and reaction vessels, thereby reducing the cost of production equipment.

[0029] 2. Compared with the method of producing superphosphate from relatively high-grade phosphate rock, the method of producing superphosphate from medium- and low-grade phosphate rock with the by-product dilute phosphoric acid provided by this invention can reduce raw material costs by 15.42% when producing the same grade of superphosphate fertilizer.

[0030] 3. The method for producing superphosphate fertilizer by synergistic co-production of dilute phosphoric acid from medium- and low-grade phosphate rock provided by this invention opens up a new avenue for the resource utilization of medium- and low-grade phosphate rock, while also enabling the resource reuse of dilute phosphoric acid by-product, achieving good economic and social benefits. Attached Figure Description

[0031] Figure 1 This is a block diagram of the production process of Embodiment 1 of the present invention. Specific implementation methods

[0032] The technical solution of the present invention will be further described and illustrated below through examples. All raw materials used in the examples are commercially available or prepared using conventional methods.

[0033] Example 1

[0034] A method for producing superphosphate fertilizer from low- to medium-grade phosphate rock in conjunction with dilute phosphoric acid as a byproduct includes the following steps:

[0035] S1. Concentrated sulfuric acid with a concentration of 98.12%, dilute sulfuric acid with a concentration of 50.14%, and by-product dilute phosphoric acid with a P2O5 content of 25.01% and a concentration of 34.48% are stored in separate storage tanks. A DCS integrated automatic control system is used. After setting the mass ratio of concentrated sulfuric acid: dilute sulfuric acid: by-product dilute phosphoric acid to 22.63:65.37:12, the concentrated sulfuric acid, dilute sulfuric acid, and by-product dilute phosphoric acid are metered into the reaction vessel through a magnetic pump, a pneumatic regulating valve, and a flow meter according to the set mass ratio. After mixing and stirring, the overflow flows into the mixed acid storage tank.

[0036] S2. Phosphate rock powder with a mesh size ≥ 100 mesh, a P2O5 content of 18%, and a moisture content of 0.8% is loaded into the mineral powder silo. After setting the mass ratio of phosphate rock powder to mixed acid to 54:46, the phosphate rock powder is conveyed by a conveying screw (frequency conversion speed regulation) to a metering screw for metering and then enters the four-slurry mixer. At the same time, the mixed acid (concentration of about 59%) in the mixed acid tank is metered by a magnetic pump, a pneumatic regulating valve, and a flow meter and then enters the four-slurry mixer. The mixed acid and phosphate rock powder are stirred and mixed together and then enter the formation chamber for formation treatment for 30 minutes to obtain fresh fertilizer. The fluorine-containing gas generated during the mixed formation process is treated by a six-stage scrubbing tower to meet the standards before being discharged into the atmosphere. The entire system is automatically controlled by DCS and implements negative pressure clean automated production.

[0037] S3. The fresh fertilizer after the chemical treatment in step S2 is removed from the warehouse by an excavator. The fresh fertilizer after removal from the warehouse is transferred to the maturation warehouse by a bridge grab crane for maturation treatment for 4 days to obtain superphosphate fertilizer.

[0038] Example 2

[0039] A method for producing superphosphate fertilizer from low- to medium-grade phosphate rock in conjunction with dilute phosphoric acid as a byproduct includes the following steps:

[0040] S1. Concentrated sulfuric acid with a concentration of 98.12%, dilute sulfuric acid with a concentration of 50.14%, and by-product dilute phosphoric acid with a P2O5 content of 25.01% and a concentration of 34.48% are stored in separate storage tanks. A DCS integrated automatic control system is used. After setting the mass ratio of concentrated sulfuric acid: dilute sulfuric acid: by-product dilute phosphoric acid to 27.91:63.09:9, the concentrated sulfuric acid, dilute sulfuric acid, and by-product dilute phosphoric acid are metered into the reaction vessel through a magnetic pump, pneumatic regulating valve, and flow meter according to the set mass ratio. After mixing and stirring, the overflow flows into the mixed acid storage tank.

[0041] S2. Phosphate rock powder with a mesh size ≥100, a P2O5 content of 28%, and a moisture content of 0.8% is loaded into the mineral powder silo. After setting the mass ratio of phosphate rock powder to mixed acid to 49:51, the phosphate rock powder is conveyed by a conveying screw (frequency conversion speed regulation) to a metering screw for metering and then enters the four-slurry mixer. At the same time, the mixed acid (concentration of about 62%) in the mixed acid tank is metered by a magnetic pump, a pneumatic regulating valve, and a flow meter and then enters the four-slurry mixer. The mixed acid and phosphate rock powder are stirred and mixed together and then enter the formation chamber for formation treatment for 60 minutes to obtain fresh fertilizer. The fluorine-containing gas generated during the mixed formation process is treated by a six-stage scrubbing tower to meet the standards before being discharged into the atmosphere. The entire system is automatically controlled by DCS and implements negative pressure clean automated production.

[0042] S3. The fresh fertilizer after the chemical treatment in step S2 is removed from the warehouse by an excavator. The fresh fertilizer after removal from the warehouse is transferred to the maturation warehouse by a bridge grab crane for maturation treatment for 5 days to obtain superphosphate fertilizer.

[0043] Comparative Example 1

[0044] A method for producing superphosphate fertilizer from phosphate rock includes the following steps:

[0045] S1. 98.12% concentrated sulfuric acid and 50.14% dilute sulfuric acid are stored in separate storage tanks. Using a DCS integrated automatic control system, after setting the mass ratio of concentrated sulfuric acid to dilute sulfuric acid to 22.60:77.40, the concentrated sulfuric acid and dilute sulfuric acid are metered according to the set mass ratio by a magnetic pump, a pneumatic regulating valve and a flow meter and then enter the reaction vessel for mixing and stirring. After overflow, they enter the mixed acid storage tank.

[0046] S2. Phosphate rock powder with a mesh size ≥100, a P2O5 content of 21.5%, and a moisture content of 0.8% is loaded into the mineral powder silo. After setting the mass ratio of phosphate rock powder to mixed acid to 52:48, the phosphate rock powder is conveyed by a conveying screw (frequency conversion speed regulation) to a metering screw for metering and then enters the four-slurry mixer. At the same time, the mixed acid (concentration of about 63%) in the mixed acid tank is metered by a magnetic pump, a pneumatic regulating valve, and a flow meter and then enters the four-slurry mixer. The mixed acid and phosphate rock powder are stirred and mixed together and then enter the formation chamber for formation treatment for 30 minutes to obtain fresh fertilizer. The fluorine-containing gas generated during the mixed formation process is treated by a six-stage scrubbing tower to meet the standards before being discharged into the atmosphere. The entire system is automatically controlled by DCS and implements negative pressure clean automated production.

[0047] S3. The fresh fertilizer after the chemical treatment in step S2 is removed from the warehouse by an excavator. The fresh fertilizer after removal from the warehouse is transferred to the maturation warehouse by a bridge grab crane for maturation treatment for 4 days to obtain superphosphate fertilizer.

[0048] Comparative Example 2

[0049] A method for producing superphosphate fertilizer from phosphate rock includes the following steps:

[0050] S1. Concentrated sulfuric acid with a concentration of 98.12% and dilute sulfuric acid with a concentration of 50.14% are stored in separate storage tanks. Using a DCS integrated automatic control system, after setting the mass ratio of concentrated sulfuric acid to dilute sulfuric acid to 31.51:68.49, the concentrated sulfuric acid and dilute sulfuric acid are metered according to the set mass ratio by a magnetic pump, a pneumatic regulating valve, and a flow meter, and then enter the reaction vessel for mixing and stirring. After overflow, they enter the mixed acid storage tank.

[0051] S2. Phosphate rock powder with a mesh size ≥100, a P2O5 content of 30%, and a moisture content of 0.8% is loaded into the mineral powder silo. After setting the mass ratio of phosphate rock powder to mixed acid to 61:39, the phosphate rock powder is conveyed by a conveying screw (frequency conversion speed regulation) to a metering screw for metering and then enters the four-slurry mixer. At the same time, the mixed acid (concentration of about 65%) in the mixed acid tank is metered by a magnetic pump, a pneumatic regulating valve, and a flow meter and then enters the four-slurry mixer. The mixed acid and phosphate rock powder are stirred and mixed together and then enter the formation chamber for formation treatment for 60 minutes to obtain fresh fertilizer. The fluorine-containing gas generated during the mixed formation process is treated by a six-stage scrubbing tower to meet the standards before being discharged into the atmosphere. The entire system is automatically controlled by DCS and implements negative pressure clean automated production.

[0052] S3. The fresh fertilizer after the chemical treatment in step S2 is removed from the warehouse by an excavator. The fresh fertilizer after removal from the warehouse is transferred to the maturation warehouse by a bridge grab crane for maturation treatment for 5 days to obtain superphosphate fertilizer.

[0053] Test Analysis

[0054] The test was conducted according to the standard for superphosphate (GB20413-2017).

[0055] Table 1 Comparison of Fresh Manure Detection Data

[0056]

[0057] As shown in Table 1, for the production of the same grade of superphosphate fertilizer, the test data of the fresh fertilizer produced by low-grade phosphate rock and dilute phosphoric acid as a byproduct in Example 1 and the fresh fertilizer produced by relatively high-grade phosphate rock without adding phosphoric acid in Comparative Example 1 are quite similar; the test data of the fresh fertilizer produced by low-grade phosphate rock and dilute phosphoric acid as a byproduct in Example 2 and the fresh fertilizer produced by relatively high-grade phosphate rock without adding phosphoric acid in Comparative Example 2 are also quite similar, and both are within the normal range.

[0058] Table 2 Comparison of test data for superphosphate fertilizer

[0059]

[0060] As shown in Table 2, for the production of the same grade of superphosphate fertilizer, the test data of the superphosphate fertilizer produced by low-grade phosphate rock and dilute phosphoric acid as a byproduct in Example 1 and the superphosphate fertilizer produced by relatively high-grade phosphate rock without adding phosphoric acid in Comparative Example 1 are similar; the test data of the superphosphate fertilizer produced by low-grade phosphate rock and dilute phosphoric acid as a byproduct in Example 2 and the superphosphate fertilizer produced by relatively high-grade phosphate rock without adding phosphoric acid in Comparative Example 2 are also similar, and all fully comply with the national standard (GB / T20413-2017).

[0061] Table 3 Comparison of Raw Material Costs

[0062]

[0063] As shown in Table 3, compared with the method of producing superphosphate from relatively high-grade phosphate rock, the method of producing superphosphate from medium- and low-grade phosphate rock provided by this invention can reduce the raw material cost of producing 12% superphosphate fertilizer by 10.73% and the raw material cost of producing 16% superphosphate fertilizer by 15.42% when producing the same grade of superphosphate fertilizer.

[0064] It should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for producing superphosphate fertilizer from medium- and low-grade phosphate rock in conjunction with dilute phosphoric acid as a byproduct, characterized in that, Includes the following steps: S1. Preparation of mixed acid: Concentrated sulfuric acid, dilute sulfuric acid, and by-product dilute phosphoric acid are mixed in a mass ratio of 22.63~27.91:63.01~65.37:9~12, and stirred evenly to obtain a mixed acid. The temperature of the prepared mixed acid should not exceed 80 ℃. The concentration of the concentrated sulfuric acid is 98%~99%, the concentration of the dilute sulfuric acid is 45%~55%, and the concentration of the by-product dilute phosphoric acid is 30%~40%. S2. Add phosphate rock powder to mixed acid at a mass ratio of 0.96~1.17:1, stir evenly, and then perform a chemical reaction treatment for 30~60 minutes to obtain fresh fertilizer. S3. The fresh fertilizer after the chemical treatment in step S2 is matured for 3-5 days to obtain superphosphate fertilizer.

2. The method for producing superphosphate fertilizer from low-grade phosphate rock in synergy with dilute phosphoric acid as a byproduct, as described in claim 1, is characterized in that... In step S1, the fineness of the phosphate rock powder is 100-120 mesh.

3. The method for producing superphosphate fertilizer from low-grade phosphate rock in synergy with dilute phosphoric acid as a byproduct, as described in claim 2, is characterized in that... In step S1, the P2O5 content in the phosphate rock powder is 18%~28%.

4. The method for producing superphosphate fertilizer from low-grade phosphate rock in synergy with dilute phosphoric acid as a byproduct, as described in claim 3, is characterized in that... In step S1, the phosphate rock powder is dried before use.

5. The method for producing superphosphate fertilizer by co-producing dilute phosphoric acid from medium- and low-grade phosphate rock according to claim 4, characterized in that, In step S1, the moisture content of the phosphate rock powder after drying is not higher than 0.8%.

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