Phosphoric acid extraction tank and method for manufacturing tank top thereof

Abstract

The invention discloses a phosphoric acid extraction tank and a method for making a tank top thereof, and belongs to the field of phosphorus chemical technology. The phosphoric acid extraction tank includes a tank body and a tank top; the tank top includes a steel frame and a cast body cast thereon, the cast body only includes an anti-corrosion layer (1) or includes an anti-corrosion layer (1) and a tank top concrete layer (2) arranged sequentially from bottom to top, the anti-corrosion layer (1) is cast by an anti-corrosion composite material, and the tank top concrete layer (2) is cast by concrete; the anti-corrosion layer (1) is made of the following raw materials in parts by weight: 48-55 parts of barium sulfate particles, 28-35 parts of graphite powder, 12-15 parts of furan resin, 0.2-0.6 parts of a curing agent, and 1-3 parts of an anti-aging agent; the particle size of the barium sulfate particles is 5-30 mm. The phosphoric acid extraction tank of the present invention has the advantages of longer service life, easier construction, and low construction difficulty.

Description

Technical Field

[0001] The invention belongs to the technical field of phosphorus chemical industry, and in particular relates to a phosphoric acid extraction tank and a method for manufacturing the tank top thereof. Background Art

[0002] Phosphoric acid, or orthophosphoric acid, with the chemical formula H₃PO₄ and a molecular weight of 97.994, is a common inorganic acid and a medium-strong acid. It is primarily used in the pharmaceutical, food, and fertilizer industries, including as a rust inhibitor, food additive, dental and orthopedic applications, EDIC etchant, electrolyte, solder flux, dispersant, industrial etchant, fertilizer raw material, and component of household cleaning products. It is also used as a chemical reagent. Phosphates are nutrients for all life forms. In the ammonium phosphate and fertilizer industries, phosphoric acid is typically prepared using a wet process. This process involves extracting concentrated sulfuric acid with calcium phosphate and phosphate rock in an extraction tank. The slightly water-soluble calcium sulfate precipitate is filtered out, and the resulting filtrate is a phosphoric acid solution.

[0003] For example, Chinese patent application number CN201310111584.5 discloses a method for producing monoammonium phosphate (taking only the phosphoric acid production part), which includes the following steps: Step 1: The weight ratio of phosphate rock is: P2O5% 25.8-26.3%, MgO <3%, K+Na <1%.

[0004] Process 2: Slurry preparation: The phosphate rock obtained in process 1 is crushed into 15-25mm particle size by two-stage jaw crusher and one-stage cone crusher, and then enters the vibrating screen for screening. The coarse material on the top returns to the fine jaw crusher and cone crusher for crushing again. The fine material with a particle size of 15-20mm at the bottom of the vibrating screen enters the ball mill to obtain slurry, so that the slurry fineness reaches 85-90%-100 mesh.

[0005] Process 3: Extraction: The ore pulp obtained in process 2, as well as the sulfuric acid from the sulfuric acid reservoir, which accounts for 1 / 5 of the total amount of the reaction, and the return acid from the phosphoric acid sedimentation tank are pumped into the pre-reactor, and the three are pre-reacted. The reaction materials then enter the extraction tank, and sulfuric acid, which accounts for 4 / 5 of the total amount of the reaction, is added to further completely decompose the ore pulp and form a slurry. The extraction tank of this process is a six-grid square tank structure with four reaction zones and two digestion zones. The inlet and outlet positions of the circulation pump are interchanged, and the slurry overflow port from four reaction chambers to four reaction chambers is expanded. The phosphoric acid P2O5 concentration is controlled at 17%-19%, the extraction temperature is controlled at 83-87°C, and the vacuum degree of vacuum cooling is controlled at -0.050 to -0.055MPa. An automatic defoaming agent adding device is installed on the extraction tank, and a defoaming device is added at the flash chamber outlet.

[0006] Process 4: Filtration: The slurry obtained in process 3 is sent to the filtration section, where phosphoric acid is separated from the slurry by a disc filter. The separated phosphoric acid is further purified in a phosphoric acid sedimentation tank. The upper clear liquid is sent to the neutralization and concentration section, and the lower thick slurry is returned to the extraction tank as return acid. The separated gypsum is washed and filtered, and finally sent to the phosphogypsum slag yard by a belt conveyor for storage.

[0007] The phosphoric acid extraction tank has the characteristics of high temperature (around 90°C), high acidity (high concentration of sulfuric acid), high oxidation (high concentration of sulfuric acid) and high corrosiveness (reaction produces hydrogen fluoride and fluosilicic acid, etc.).

[0008] The phosphoric acid extraction tank consists of a rectangular array of multiple (usually 6-9) square troughs. Each trough comprises a body and a roof, with an agitator mounting hole located in the center. The body is typically constructed of a carbon brick layer, a rubber sheet layer, and a concrete layer. However, the roof cannot be constructed with carbon bricks (which are heavier). The existing method involves bonding resin-impregnated fiberglass cloth to the roof (concrete) to form a multi-layer (specifically, 10 layers, with resin between layers) anti-corrosion coating. The applicant encountered the following problems when using the aforementioned process for the extraction tank roof:

[0009] (1) The service life of the tank top is short. The anti-corrosion layer needs to be removed and re-made in about one year, which takes at least half a month;

[0010] (2) The construction is difficult, requiring each layer of glass fiber cloth to be flat and free of bubbles, and to solidify before the next layer can be processed. Continuous construction is required, requiring professional personnel for construction, and the labor cost is high;

[0011] (3) Construction needs to be carried out in a square tank. The extraction tank is a semi-open tank. The resin has a strong odor, which affects the physical and mental health of people when inhaled. That is, the construction environment is harsh. Summary of the Invention

[0012] To solve the above problems, the present invention provides a method for manufacturing a phosphoric acid extraction tank and a tank top thereof, which has the advantages of longer service life, easier construction, and lower construction difficulty. The technical solution is as follows:

[0013] On the one hand, an embodiment of the present invention provides a phosphoric acid extraction tank, a phosphoric acid extraction tank, comprising a tank body and a tank top; the tank top comprises a steel frame and a cast body cast thereon, the cast body comprising only an anti-corrosion layer 1 or comprising an anti-corrosion layer 1 and a tank top concrete layer 2 arranged in sequence from bottom to top, the anti-corrosion layer 1 being cast from an anti-corrosion composite material, and the tank top concrete layer 2 being cast from concrete; the anti-corrosion layer 1 being made of the following raw materials in parts by weight: 48-55 parts of barium sulfate particles, 28-35 parts of graphite powder, 12-15 parts of furan resin, 0.2-0.6 parts of a curing agent, and 1-3 parts of an antioxidant; the particle size of the barium sulfate particles is 5-30 mm.

[0014] In one scheme, the cast body includes an anti-corrosion layer 1 and a trough top concrete layer 2. Accordingly, the steel skeleton is made of three layers of steel mesh arranged side by side up and down; the anti-corrosion layer 1 is cast at the lower two layers of steel mesh and its thickness is ≥100mm, and the trough top concrete layer 2 is cast at the upper two layers of steel mesh and its thickness is ≥150mm. The distance between the lower side of the anti-corrosion layer 1 and the steel skeleton is ≥20mm.

[0015] In the preferred embodiment of the above-mentioned solution, the thickness of the anti-corrosion layer 1 is 150 mm and the distance between its lower side and the steel skeleton is 30 mm, and the thickness of the trench top concrete layer 2 is 250 mm.

[0016] In another embodiment, the cast body only includes the anti-corrosion layer 1, and accordingly, the steel skeleton is made of two layers of steel mesh arranged side by side up and down; the thickness of the anti-corrosion layer 1 is ≥300mm, and the distance between the upper and lower sides of the anti-corrosion layer 1 and the corresponding sides of the steel skeleton therein is ≥20mm.

[0017] Preferably, the anti-corrosion layer 1 in the embodiment of the present invention is made of the following raw materials in parts by weight: 51 parts of barium sulfate particles, 34 parts of graphite powder, 13 parts of furan resin, 0.5 parts of curing agent and 1.5 parts of antioxidant.

[0018] Furthermore, the surface of the steel bars of the steel bar skeleton in the embodiment of the present invention is coated with epoxy resin.

[0019] Among them, the trough body in the embodiment of the present invention is composed of a carbon brick layer, a rubber plate layer and a trough body concrete layer from the inside to the outside. The carbon brick layer is made of carbon bricks, and the trough body concrete layer is made of cast concrete.

[0020] On the other hand, the present invention also provides a method for manufacturing a phosphoric acid extraction tank top, the method comprising:

[0021] S101: A steel frame is fabricated on the top of the tank body. The steel frame is fabricated from three layers of steel mesh arranged side by side, with the distance between the lower two layers of steel mesh being ≥80 mm, and the distance between the upper two layers of steel mesh being ≥130 mm.

[0022] S102: Derust the steel bar skeleton and apply epoxy resin on the steel bar surface;

[0023] S103: Setting up a casting template below the steel frame, with a distance between the casting template and the steel frame being 20-50 mm;

[0024] S104: pouring the anti-corrosion composite material at the lower two layers of steel mesh, vibrating and compacting without spreading and pressing, and curing for 4-7 days to obtain the anti-corrosion layer 1;

[0025] S105: pouring concrete at the upper two layers of steel mesh, and obtaining the trough top concrete layer 2 after vibration and solidification;

[0026] S106: Remove the casting formwork to obtain the trough top.

[0027] Preferably, in step S104, before pouring the anti-corrosion composite material, a plurality of large-grain barium sulfate particles are evenly placed on the upper side of the formwork, wherein the particle size of the large-grain barium sulfate particles is greater than 20 mm.

[0028] Among them, in step S104, the preparation process of the anti-corrosion composite material is: adding barium sulfate particles, graphite powder, furan resin, curing agent and antioxidant in order according to the proportion, stirring for at least 30 minutes and then pouring.

[0029] The present invention has the following advantages:

[0030] (1) It has better anti-corrosion performance. The service life of a conventional phosphoric acid extraction tank top is about 1 year, while the service life of the tank top of the present invention is at least 3 years. The cost of the tank top of the present invention is only 2.0-2.2 times that of a conventional tank top. Combined with the repair time of the tank top (the annual production capacity of the phosphoric acid production line is hundreds of thousands of tons), it can save a lot of costs;

[0031] (2) The production time of the trough top of the present invention is similar to that of the conventional trough top, which is about half a month;

[0032] (3) The manufacturing method of the trough top of the present invention is simple. It only requires pouring and waiting for solidification. There is no need for continuous construction. Multiple square troughs can be constructed at the same time (while one square trough is solidifying, another square trough is poured and constructed); no professional personnel are required for construction, and the safety hazard is low;

[0033] (4) No need to construct in the extraction tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic structural diagram of a cast unit provided by an embodiment of the present invention;

[0035] Figure 2 This is a flow chart of a method for manufacturing a phosphoric acid extraction tank top.

[0036] In the picture: 1 anti-corrosion layer, 2 trench top concrete layer. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be described in further detail below with reference to the accompanying drawings.

[0038] Example 1

[0039] Example 1 provides a phosphoric acid extraction tank. The phosphoric acid extraction tank of this embodiment can specifically be a square tank constituting the extraction tank. The phosphoric acid extraction tank includes a tank body and a tank top. The tank body adopts existing technology, and an agitator mounting hole is set in the middle of the tank top. The tank top includes a steel skeleton and a cast body cast thereon, and the steel skeleton is located in the cast body. The cast body includes only an anti-corrosion layer 1 or includes an anti-corrosion layer 1 and a tank top concrete layer 2 arranged in sequence from bottom to top. The anti-corrosion layer 1 is cast from an anti-corrosion composite material. The tank top concrete layer 2 is cast from concrete; specifically, it can be cast from C40 concrete. The anti-corrosion layer 1 is made of the following raw materials in parts by weight: 48-55 parts of barium sulfate particles, 28-35 parts of graphite powder, 12-15 parts of furan resin, 0.2-0.6 parts of a curing agent, and 1-3 parts of an anti-aging agent. The particle size of the barium sulfate particles is 5-30 mm. Barium sulfate and graphite powder are both resistant to concentrated sulfuric acid. Barium sulfate is equivalent to aggregate in concrete. Graphite powder has smaller particles and is incorporated into the barium sulfate framework, similar to the fine sand in concrete. Furan resin is used as a binder in very small quantities (conventional methods use larger amounts of resin). It is acid and alkali resistant and more heat resistant than epoxy resin. Although furan resin is not resistant to concentrated sulfuric acid, its small usage (not as a skeleton material), reduced exposure to concentrated sulfuric acid, and the use of anti-aging agents allow its use on the tank roof. Both the curing agent and antioxidant are commonly available commercially, using furan resin.

[0040] Preferably, the anti-corrosion layer 1 in the embodiment of the present invention is made of the following raw materials in parts by weight: 51 parts of barium sulfate particles, 34 parts of graphite powder, 13 parts of furan resin, 0.5 parts of curing agent and 1.5 parts of antioxidant.

[0041] Furthermore, the surface of the steel bars of the steel bar skeleton in the embodiment of the present invention is coated with epoxy resin.

[0042] Among them, the trough body in the embodiment of the present invention is composed of a carbon brick layer, a rubber plate layer and a trough body concrete layer from the inside to the outside. The carbon brick layer is made of carbon bricks, and the trough body concrete layer is made of cast concrete.

[0043] Example 2

[0044] Example 2 provides a phosphoric acid extraction tank, comprising a tank body and a tank roof. The tank roof comprises a steel frame and a cast structure cast thereon. The cast structure comprises only an anti-corrosion layer 1. Accordingly, the steel frame is formed from two layers of steel mesh arranged side by side. The anti-corrosion layer 1 has a thickness of 300 mm or greater, and the distance between the upper and lower sides of the anti-corrosion layer 1 and the corresponding sides of the steel frame therein is 20 mm or greater.

[0045] Specifically, the thickness of the anti-corrosion layer 1 is 400 mm and the distance between its upper and lower sides and the corresponding sides of the steel skeleton is 30 mm.

[0046] Through practice, it is found that the service life of the trough top in this embodiment is at least five years, and the strength reaches the use standard.

[0047] Example 3

[0048] See also Figure 1 Example 3 provides a phosphoric acid extraction tank, which includes a tank body and a tank top. The tank top includes a steel skeleton and a cast body cast thereon. The cast body includes an anti-corrosion layer 1 and a tank top concrete layer 2. Compared with Example 2, this solution can reduce the cost to about 4,000 yuan per square meter. Accordingly, the steel skeleton is made of three layers of steel mesh arranged side by side. The anti-corrosion layer 1 is cast on the lower two layers of steel mesh and its thickness is ≥100mm. The tank top concrete layer 2 is cast on the upper two layers of steel mesh and its thickness is ≥150mm. The distance between the lower side of the anti-corrosion layer 1 and the steel skeleton is ≥20mm.

[0049] Specifically, the thickness of the anti-corrosion layer 1 is 150 mm and the distance between its lower side and the steel skeleton is 30 mm, and the thickness of the trench top concrete layer 2 is 250 mm.

[0050] Through practice, it is found that the service life of the trough top in this embodiment is at least five years, and the strength reaches the use standard.

[0051] Verification Example

[0052] The phosphoric acid extraction tank includes six square tanks, each measuring 6.0m*6.0m*6.8m, and with an agitator mounting hole measuring 2.4m*2.2m. One of the square tanks was constructed using the process of Example 2 (Test Example 1), two of the square tanks were constructed using the process of Example 3 (Test Example 2), and the remaining three square tanks were constructed using conventional processes (Comparative Example). After completion in May 2019, the roofs of the three comparative tanks required annual replacement at a cost of 1,400-1,800 yuan per square meter (consistent concrete use), with a production time of approximately 15 days and a replacement time of at least 10 days (referring to the usable period). The cost of Test Example 2 was 4,000 yuan per square meter, and the production time was approximately 15 days. After three years of use, the roofs of both Test Examples 1 and 2 were intact, with no obvious signs of corrosion. A conservative estimate suggests at least two years of service life, and a non-conservative estimate suggests seven years of service life.

[0053] Example 4

[0054] See also Figure 2 Example 4 provides a method for manufacturing a phosphoric acid extraction tank top, the method comprising:

[0055] S101: A steel frame is fabricated at the top of the trough. The steel frame is made of three layers of steel mesh arranged side by side, with the distance between the lower two layers of steel mesh being ≥80 mm, and the distance between the upper two layers of steel mesh being ≥130 mm. Specifically, the mesh size of the steel mesh can be 250 mm * 250 mm, but this is not a limitation of this patent.

[0056] S102: Derust the steel bar skeleton and apply epoxy resin on the steel bar surface. Epoxy resin should preferably be applied at least twice to prevent rust and facilitate bonding with the cast body.

[0057] S103: Set up a casting template below the steel skeleton. The distance between the casting template and the steel skeleton is 20-50 mm (specifically 30 mm) to ensure that the distance between the lower layer of the anti-corrosion layer 1 and the steel skeleton is greater than 20 mm.

[0058] S104: Pour the anti-corrosion composite material over the lower two layers of steel mesh and vibrate (specifically, a vibrating rod can be used) without smearing or pressing to ensure a better bond between the anti-corrosion layer 1 and the trench top concrete layer 2. Curing for 4-7 days to obtain the anti-corrosion layer 1. The thickness of the anti-corrosion layer 1 is ≥100mm, and specifically 150mm.

[0059] S105: pouring concrete at the upper two layers of steel mesh, vibrating and solidifying to obtain the trough top concrete layer 2. The thickness of the trough top concrete layer 2 is ≥150 mm, and the thickness of the trough top concrete layer 2 is specifically 250 mm.

[0060] S106: Enter through the mixer installation hole, remove the casting template to obtain the trough top.

[0061] Preferably, in step S104, before pouring the anti-corrosion composite material, multiple large barium sulfate particles are evenly placed (or spaced apart) on the upper side of the formwork. The large barium sulfate particles have a particle size greater than 20 mm, preferably less than 30 mm. The use of large barium sulfate particles can further reduce the possibility of furan resin contact with sulfuric acid, further improving strength and corrosion resistance.

[0062] Among them, in step S104, the preparation process of the anti-corrosion composite material is: barium sulfate particles, graphite powder, furan resin, curing agent and antioxidant are added in sequence according to the ratio (48-55 parts of barium sulfate particles, 28-35 parts of graphite powder, 12-15 parts of furan resin, 0.2-0.6 parts of curing agent and 1-3 parts of antioxidant), stirred for at least 30 minutes and then poured.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A phosphoric acid extraction tank comprising a tank body and a tank top; characterized in that: The trough top comprises a steel frame and a cast body cast thereon, the cast body comprises only an anti-corrosion layer (1) or comprises an anti-corrosion layer (1) and a trough top concrete layer (2) arranged in sequence from bottom to top, the anti-corrosion layer (1) is cast from an anti-corrosion composite material, and the trough top concrete layer (2) is cast from concrete; the anti-corrosion layer (1) is made of the following raw materials in parts by weight: 48-55 parts of barium sulfate particles, 28-35 parts of graphite powder, 12-15 parts of furan resin, 0.2-0.6 parts of a curing agent, and 1-3 parts of an anti-aging agent; the particle size of the barium sulfate particles is 5-30 mm.

2. The phosphoric acid extraction tank according to claim 1, characterized in that The cast body comprises an anti-corrosion layer (1) and a trough top concrete layer (2); accordingly, the steel frame is made of three layers of steel mesh arranged side by side; the anti-corrosion layer (1) is cast on the lower two layers of steel mesh and its thickness is ≥100 mm, the trough top concrete layer (2) is cast on the upper two layers of steel mesh and its thickness is ≥150 mm, and the distance between the lower side of the anti-corrosion layer (1) and the steel frame is ≥20 mm.

3. The phosphoric acid extraction tank according to claim 2, characterized in that: The thickness of the anti-corrosion layer (1) is 150 mm and the distance between its lower side and the steel skeleton is 30 mm. The thickness of the trough top concrete layer (2) is 250 mm.

4. The phosphoric acid extraction tank according to claim 1, characterized in that The cast body only includes an anti-corrosion layer (1), and accordingly, the steel skeleton is made of two layers of steel mesh arranged side by side; the thickness of the anti-corrosion layer (1) is ≥300 mm, and the distance between the upper and lower sides of the anti-corrosion layer (1) and the corresponding sides of the steel skeleton therein is ≥20 mm.

5. The phosphoric acid extraction tank according to claim 1, characterized in that: The anti-corrosion layer (1) is made of the following raw materials in parts by weight: 51 parts of barium sulfate particles, 34 parts of graphite powder, 13 parts of furan resin, 0.5 parts of curing agent and 1.5 parts of antioxidant.

6. The phosphoric acid extraction tank according to claim 1, characterized in that The steel bar surfaces of the steel bar skeleton are coated with epoxy resin.

7. The phosphoric acid extraction tank according to claim 1, characterized in that The trough body comprises a carbon brick layer, a rubber plate layer and a trough body concrete layer from the inside to the outside. The carbon brick layer is made of carbon bricks, and the trough body concrete layer is made of poured concrete.

8. The method for manufacturing a tank top in a phosphoric acid extraction tank according to claim 2, wherein: The method comprises: S101: A steel frame is fabricated on the top of the tank body. The steel frame is fabricated from three layers of steel mesh arranged side by side, with the distance between the lower two layers of steel mesh being ≥80 mm, and the distance between the upper two layers of steel mesh being ≥130 mm. S102: Derust the steel bar skeleton and apply epoxy resin on the steel bar surface; S103: Setting up a casting template below the steel frame, with a distance between the casting template and the steel frame being 20-50 mm; S104: pouring the anti-corrosion composite material at the lower two layers of steel mesh, vibrating and compacting without spreading and pressing, and curing for 4-7 days to obtain the anti-corrosion layer (1); S105: pouring concrete at the upper two layers of steel mesh, and obtaining a trough top concrete layer (2) after vibration and solidification; S106: Remove the casting formwork to obtain the trough top.

9. The production method according to claim 8, characterized in that: In step S104, before pouring the anti-corrosion composite material, a plurality of large-grain barium sulfate particles are evenly placed on the upper side of the formwork, wherein the particle size of the large-grain barium sulfate particles is greater than 20 mm.

10. The manufacturing method according to claim 8, characterized in that: In step S104, the preparation process of the anti-corrosion composite material is as follows: barium sulfate particles, graphite powder, furan resin, curing agent and antioxidant are added in order according to the proportion, stirred for at least 30 minutes and then poured.

Images