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Phosphate based fertilizers
- 2. Classification of Phosphate Based Fertilizers Phosphate Rock Single Super Phosphate Direct Application Phosphoric Acid Triple Super Phosphate Monoammonium Phosphate Diammonium Phosphate Nitric Acid Potassium NPK Compound Fertilizer Sulfuric Acid Sulfuric Acid Phosphate Rock Ammonia Ammonia
- 3. Other Fertilizers Made From Phosphoric Acid 1. Ammonium Phosphate Sulphate (APS): The best known grade is 16-20-0, which essentially consist of MAP and ammonium sulphate (AS). 2. Ammonium Phosphate Chloride (APC): Ammonium chloride is used in japan and some other countries, both as straight nitrogen fertilizer and as an ingredient of NP (18-22-0) and NPK (14- 14-14) fertilizers. 3. Ammonium Phosphate Nitrate (APN): Available in the grades of 25-25-0 and 30-10-0. 4. Urea-Ammonium Phosphate (UAP): Ammonium phosphate is supplied either as slurry or in the solid form as MAP or DAP. Urea is supplied as a solid, as a melt or as a concentrated solution. UAP grades are 28-28-0,22-22-11,18-18-18.
- 4. 1. Principal fertilizer for more than a century and supplied over 60% of the world’s phosphate as late as 1955. 2. It supplied only 20% of phosphate fertilizer in 1975. 3. In 1988, its supply was only 17%. The advantages of SSP are 1. The process is simple, requiring little technical skill and small capital investment. 2. SSP supplies two secondary elements, Sulphur and calcium, which are sometimes deficient to soil. Single Super Phosphate (SSP)
- 5. Overall Chemical Reaction: Ca10F2(PO4)6 + 7H2SO4 + 3H2O 3Ca(H2PO4)2. H2O + 7CaSO4 + 2HF Monocalcium phosphate monohydrate (MCP) Calcium Sulfate (gypsum) Single Super Phosphate (SSP) Chemical Properties: • P2O5 content: 18 to 20% • Calcium (Ca) content: 18 to 21% • S content: 11 to 12% Continued
- 6. Manufacturing Process Steps: 1. Mixing of ground phosphate rock (90% < 100-mesh) with sulfuric acid (68-76%). 2. Solidification of the mixture. 3. Curing of the final product. 4. Granulation (if desired) Batch Manufacturing of Single Super Phosphate Sulfuric Acid Ground Phosphate Rock Phosphate Hopper Pan Mixer Acid Scale Rock Scale Den/Accumulator Cutter To Scrubbing System (90% < 100-mesh) (68-76%) (0.5 – 4.0 hours) (100 C) (2 – 6 weeks) Screening (2 minutes) Slurry Storage Pile (6 – Mesh Size) 5
- 7. Continuous Manufacturing of Single Super Phosphate To Scrubbing System Storage Pile Phosphate Rock Rock Storage Silo Bucket Elevator Surge Hopper Metering Screw Weigh Feeder Water H2SO4 Cone Mixer Slat Conveyor Continuous Den Belt Conveyor
- 8. Phosphate Rock (Direct Application) Direct use of phosphate rock avoids the extra processing. The minimal processing may results in a lower cost nutrient source and make it acceptable for crop production systems. To optimize the effectiveness of phosphate rock, consider these factors: Soil PH: PRs require acidic soil conditions to effectively nourish crops. It is usually recommended for the with the pH 6 or less. Soil P-fixing capacity: The dissolution of phosphate rock increases with the greater P-fixing capacity of soil. Placement: Broadcasting phosphate rock and incorporating it with tillage speed and reaction of the soil. Timing: The time required for the dissolution of phosphate rock necessities its application in advance of the plant demand.
- 9. Continued Advantages: 1. The principal advantage of PR is its low cost. 2. A very low capital investment is required for processing. 3. Energy requirement is small. 4. No particular technical skill are required. 5. There is little or no loss in processing. Disadvantages: 1. Relatively low P2O5 content as compared to TSP or ammonium phosphates. 2. Less effective for short-season crops grown under cool soil temperature. 3. Effective only on the soils with pH 6 or less.
- 10. 4. Process step are similar to those of SSP, except that phosphoric acid is used instead of sulfuric acid. Triple Super Phosphate 1. Triple superphosphate (TSP) was one of the first high analysis P fertilizers that became widely used in the 20th century. Technically, it is known as calcium dihydrogen phosphate and as monocalcium phosphate, [Ca(H2PO4)2 . H2O]. It is an excellent P source, but its use has declined as other P fertilizers have become more popular. 2. It has the highest P content of dry fertilizers that do not contain N 3. It contains about 2.5 times of P2O5 content of SSP.
- 11. Overall Chemical Reaction: Ca10F2(PO4)6 + 14H3PO4 + 10H2O 10Ca(H2PO4)2. H2O + 2HF Monocalcium phosphate monohydrate (MCP) Triple Super Phosphate (TSP)Chemical Properties: • P2O5 content: 42-50 % • Calcium (Ca) content: 13.6% • S content: 1.4 % Continued
- 12. Process Steps: 1. Mixing of ground phosphate rock (95%-98% < 100-mesh) with phosphoric acid (52%). 2. Solidification of the mixture. 3. Curing of the final product. 4. Granulation (if desired) TSP Production By Den Process Phosphoric Acid Phosphate Hopper Cone Mixer Rock Scale Den/Accumulator Chain Mill (95%- 98% < 100-mesh) (52%) (10 – 30 minutes) (3 – 6 weeks) Screening Storage Pile (6 – Mesh Size) Ground Phosphate Rock To Scrubbing System Run-of-pile TSP / ROP-TSP
- 13. Granulation Of Cured ROP-TSP Bucket Elevator Cured TSP Belt Feeder Screen Crusher Bucket Elevator Bucket Elevator To Scrubbing System Surge Hopper Weigh Feeder Water Steam Granulator Dryer Air Fuel Screen Crusher Belt Feeder Recycle Bucket Elevator TSP cooling and to Storage
- 14. Ex-Den Granulation of TSP Ground Phosphate Rock Phosphoric Acid Hopper Mixer Slat Conveyor Continuous Den Belt Conveyor Bucket Elevator Steam Water Gases to Scrubber Granulator Dryer Screen TSP cooling and to Storage Bucket Elevator Crusher Recycle
- 15. Slurry Process For The Manufacturing Of Granular TSP Steam Heated Reactor Ground Phosphate Rock Phosphoric Acid Blunger / Rotary Drum Bucket Elevator Dryer Bucket Elevator Cyclone Cyclone Gases to Scrubber Screen Crusher Cooler Product to Storage Recycle Belt Conveyor Retention Time (30 minutes) (90C) Recycle Ratio: For Blunger =10-12:1 For Granulator =8:1
- 16. Ammonium Phosphates Raw Materials: 1. Phosphoric Acid 2. Anhydrous Ammonia 3. Sulfuric Acid (Used for grade adjustment) Chemical Reactions MAIN REACTIONS 1. NH3 + H3PO4 (NH4)H2PO4 (MAP) + 32.18 Kcal/mole 2. NH3 + (NH4)H2PO4 (NH4)2HPO4 (DAP) + 18.10 Kcal/mole SIDE REACTION 1. 2NH3 + H2SO4 (NH4)2SO4 + 65.44 Kcal/mole
- 17. Ammonium Phosphates Standard Grades: 1. MAP - 11 % Nitrogen and 55 % Phosphate (P2O5) - 10 % Nitrogen and 50 % Phosphate (P2O5) - 11 % Nitrogen and 52 % Phosphate (P2O5) MAP Production Methods: Forward Titration: The Pre-neutralizer is operated at an NH3:H3PO4 mole ratio of 0.6 and the balance of ammonia is added in the granulator. Reverse Titration: The Pre-neutralizer is operated at an NH3:H3PO4 mole ratio of 1.4~1.5 and the phosphoric acid is added in the granulator to decrease the ratio to 1. 2. DAP - 18 % Nitrogen and 46 % Phosphate (P2O5)
- 18. Ammonium Phosphates DAP Production Processes: 1. TVA Basic Process (Pre-neutralizer Process) 2. AZF dual pipe-reactor Process (Pipe Reactor Process) 3. Jacobs Slurry Process (Combination of Pre-neutralizer and Pipe Reactor) Reactor Granulator Dryer Screen Cooler Product to Conditioning and StorageRecycle Ammonia & Dust Collecting System Air to Atmosphere H3PO4 H2SO4 NH3
- 19. Ammonium Phosphates Early Technology for the Manufacturing of MAP/DAP: 1. TVA Basic Process. H3PO4 NH3 Pre-neutralizer N/P = 1.4 NH3 16%-20% Moist. Solid Recycle Granulator Dryer Scrubbing System Scrubbing System Cyclone Cyclone Screen Crusher Cooler Belt Conveyor To Storage Bucket Elevator Bucket Elevator N/P = 2.0 N/P = 0.6 N/P = 1.0 H3PO4NH3 Reverse TitrationForward Titration Recycle Ratio: For DAP = 5:1 Solid Recycle
- 20. Ammonium Phosphates 2. AZF dual pipe-reactor Process. NH3 Solid Recycle Scrubbing System Cyclone Primary Screen Crusher Belt Conveyor To Storage After Cooling Bucket Elevator Granulator Dryer H3PO4 NH3 H3PO4 Solid Recycle Granulator Pipe Reactor Dryer Pipe Reactor Scrubbing Liquor Polishing Screen N/P 1.0 N/P 1.4-1.6 NH3 N/P 1.90 Air Fuel Recycle Ratio = 3:1
- 21. Ammonium Phosphates 3. Jacobs Slurry Process. Scrubbing Liquor Crusher Cooler H3PO4 NH3 H2SO4 Granulator Dryer NH3 Belt Conveyor Solid Recycle Air Fuel Pre-neutralizer Polishing Screen Primary Screen Cyclone Solid Recycle To Storage To Scrubbing To Scrubbing System To Scrubbing System Recycle Ratio = 4:1 N/P 1.4-1.5 N/P 1.45-1.6 N/P 1.80
- 22. NPK Compound Fertilizers NPK fertilizers are three-component fertilizers providing nitrogen, phosphorus and potassium. Compound fertilizers are usually manufactured to meet local or regional requirement. Compound fertilizer contains multiple nutrients in each individual granule. This differs from a blend of fertilizers mixed together to achieve a desired average nutrient composition. Common compound fertilizers include: 10-10-10, 12-12-12, 17-17-17, 21-7- 14, and many others formulations.
- 23. Continued NPK fertilizers can be produced by several processes depending upon the raw materials and equipment used. i. Urea ii. Ammonium Sulphate iii. Diammonium Phosphate iv. Monoammonium Phosphate v. Potassium Chloride vi. Potassium Shulphate vii. Sulfuric Acid viii. Phosphoric Acid i. Pan Granulator ii. Drum Granulator iii. Pugmill or Blunger iv. Compactor Raw Materials: Granulation Equipment:
- 24. Pan Granulator Pan granulator, granulates by giving adequate moisture and binder to a powdered material in a tilted rotating pan. Applications: i. Chemical Powders ii. Fertilizers iii. Coal Fines
- 25. Drum Granulator Granulation drums work by tumbling material in a rotating drum, typically in the presence of a binder. The binder causes the fines to become tacky and allows them to pick up additional fines, forming agglomerates. Applications: i. DAP & MAP ii. NPK grades iii. Ammonium Sulphates iv. SSP v. TSP
- 26. Pug mill or blunger Pug mills utilize dual rotating shafts with paddles assembly to create a kneading and folding over motion inside the trough. The action of the paddles moves material from the bottom of the trough, up the middle, and back down the sides to create an intimate mixture of materials.
- 27. Compactor Compaction granulation is a dry particle size enlargement process in which powdery material is pressed into sheets through the use of counter rotating rolls. Applications: i. Fertilizers ii. Pharmaceuticals iii. Detergents iv. Clay v. Polymers vi. Coal
- 28. NPK Compound Fertilizers 1. Ammonium phosphates are produced by mixing phosphoric acid and anhydrous ammonia in a reactor to produce a slurry. (potassium and other salts are added during the process.) 2. Compound fertilizer can be made by blending basic fertilizers such as ammonium nitrate, MAP, DAP, and granular potash.
Editor's Notes
- Introduction: Production of fertilizer derived from phosphoric acid has increased significantly in the last 50 years because, these are high-analysis (A fertilizer that contains 30 percent or more of active ingredients) products.
- Single Super Phosphate (SSP), also called normal or ordinary super phosphate, has been the principal phosphate fertilizer for more than a century and supplied over 60 % o the world’s phosphate as late as 1955. Since than its relative importance has declined steadily. In 1975 it supplied only 20% of the phosphate fertilizer, and this figure fell to 17% in 1988. For the world as a whole, TVA estimated 1972 SSP production at 7.87 million tonnes of P2O5, and IFDC mentions a figure of 7.083 million tonnes in 1988, which means a decrease of 10% over 16 years. Economies of scale is the cost advantage that arises with increased output of a product. Economies of scale arise because of the inverse relationship between the quantity produced and per-unit fixed costs; i.e. the greater the quantity of a good produced, the lower the per-unit fixed cost
- This material was once the most commonly used fertilizer, but other phosphorus (P) fertilizers have largely replaced SSP because of its relatively low P content. The reaction proceeds in two stages: (1) the sulfuric acid reacts with the part of the phosphate rock, forming phosphoric acid and calcium sulfates and (2) phosphoric acid formed in the first step reacts with more phosphate roc, forming monocalcium phosphate. The two reactions take place concurrently, but first stage is completed rapidly while the second stage continues for several days or week.
- The production of SSP involves the following three (or four) operations The finely ground phosphate rock is mixed with the sulfuric acid having concentration about 68-76%. Pan mixer may have the capacity of 1 – 2 tones per batch. The fluid material from the mixer goes to a den where it solidifies. A accumulator can hold 10 – 40 tonnes. The SSP is excavated from the den after 0.5-4.0 hours. At this time it is still somewhat plastic and its temperature is about 100C. The product is removed from the accumulator and conveyed to the storage piles for final curing, which requires 2 – 6 weeks, depending on the nature and proportions of raw material and condition of manufacture. During curing reaction approaches completion. The free acid, moisture and unreacted rock contents decrease and the available and water soluble P2O5 increase. After curing the product is fed to a disintegrator, usually mill or cage mill. The product from the mill is discharge onto a screen of about 6-mesh size. If granular SSP is desired, the product is granulated either before curing or after curing. Granulation before curing has the advantage that less water or steam is required. After granulation the product is dried and screened. Product Properties: At least 16% P2O5 93% water soluble Granular 2 – 4 mm
- FAO reports consumption of ground phosphate rock separately, in 1976 reported consumption was equivalent to about 5% of phosphate fertilizer consumption.
- FAO reports consumption of ground phosphate rock separately, in 1976 reported consumption was equivalent to about 5% of phosphate fertilizer consumption. In the era of 1953 the PRs consumption was more than 1 million tpy. In 1976 consumption amounted to only 37000 tpy. The decreased use was because of two factors. First, large scale production of high analysis phosphates (TSP and DAP). Secondly the granular phosphates are much easier to handle and apply to the soil than the finely ground PR.
- This material was once the most commonly used fertilizer, but other phosphorus (P) fertilizers have largely replaced SSP because of its relatively low P content. The reaction proceeds in two stages: (1) the sulfuric acid reacts with the part of the phosphate rock, forming phosphoric acid and calcium sulfates and (2) phosphoric acid formed in the first step reacts with more phosphate roc, forming monocalcium phosphate. The two reactions take place concurrently, but first stage is completed rapidly while the second stage continues for several days or week.
- DAP (18-46-0) Water Solubility: 588 g/L MAP (P2O5=48-61%, N= 10-12%) Solubility = 370 g/L 2.1 (11-55-0) 2.2 (10-50-0) 2.3 (11-52-0)