Phosphatic Ammonium Operation Procedures

Thread Content

Practice Report: Department, Major, Class, Name, Title, Instructor, Academic Year, Semester, Week, Grade. Zibo University of Technology – Production of Phosphoric Ammonium by Slurry Method. Abstract: The raw materials used in the industrial production of phosphoric ammonium, as well as the process and operational procedures involved in its production via the slurry method. Keywords: Slurry method, process, operation. In the early days, the main type of phosphoric ammonium fertilizer produced was monoammonium phosphate; the United States was the first country to produce it in 1917. It wasn’t until the late 1940s that Germany began producing diammonium phosphate using thermal phosphoric acid. In 1966, Nanjing Chemical Company utilized domestically developed equipment and technology to build a facility capable of producing 30,000 tons of monoammonium phosphate, thus marking the beginning of phosphoric ammonium production in China. The production methods of ammonium phosphate include the traditional solid method and the slurry method; our company’s slurry-based production process has an annual capacity of 150,000 tons of ammonium phosphate. I. Introduction to Raw Materials 1. Phosphorus ore: Phosphorus is a very common element in nature, accounting for about 21% of the Earth’s crust. Due to its tendency to oxidize, it exists in nature in the form of compounds; its main components are calcium salts such as Ca5F(PO4)3, along with various unnecessary impurities. 2. Sulfuric acid: a acid with the molecular formula H2SO4 and a concentration of 93%. 3. Ammonia: With the molecular formula NH3, it is highly soluble in water, alcohol, and other solutions. It is a colorless gas at normal pressure, and can be turned into a liquid by applying pressure at room temperature. (2) Job operating procedures: 1. Wear the appropriate personal protective equipment for this job. 2. Before driving, check that all equipment, valves, instruments, and pipelines are in good condition and complete. 3. Check the readiness of phosphoric acid, water, and electricity, and coordinate with the ammonia station to prepare for starting up and supplying ammonia gas. 4. Before starting rotating equipment, it should be rotated to check for any obstruction and to ensure proper lubrication. 5. The operating procedure requires that acid should be turned on first and then ammonia before driving, and ammonia should be turned off first and then acid before stopping the vehicle. 6. Prepare the instruments, reagents, and meters required for production analysis, with analyses to be conducted once per hour. 7. Maintain close contact with various positions to ensure proper control of all process parameters. 8. Regularly monitor temperature, pressure, flow rate, liquid level, etc. to ensure they remain within specified ranges. 9. The use of fire and smoke is prohibited in this position; no such activities are allowed without permission. II. Process Overview: The production of phosphate ammonium involves two methods: material concentration and phosphoric acid concentration. Our company uses the material concentration method to produce granular diammonium phosphate/ammonium phosphate. 1. The slurry-based method for producing phosphate ammonium is a process that combines wet-process phosphoric acid production; it involves reacting low-concentration phosphoric acid (P2O5 at 20%) with ammonia to produce phosphate ammonium (with a slurry moisture content of 60%). The moisture content is then reduced to around 25% through material concentration, followed by a second neutralization step to ensure the product’s nitrogen content meets the required level (13%). Finally, granular phosphate ammonium products are obtained through spray granulation. 2. Principle: Ca5F(PO4)3 + 5 H2SO4 + 10H2O = H3PO4 + 5H2SO4·2H2O + HF; H3PO4 + NH3 = NH4H2PO4; H3PO4 + 2 NH3 = (NH4)2HPO4.
III. Process Flow Diagram: Phosphorus ore →鄂式 crusher → Vertical crusher → Ball mill → Slurry tank → Liquid seal tank → Large vacuum pump → Sedimentation tank → Extraction tank → Filter → Gas-liquid separator → Washing liquid tank → Three-stage fluorine absorption chamber → Exhaust fan → Venting → Dilute acid return → Finished phosphoric acid tank. Phosphoric acid process flow diagram: Ammonia → Large phosphoric acid tank → Backwashing tank → Low-level phosphoric acid tank → Forced neutralization flash chamber → Secondary steam → Ammonia → Second-effect flash chamber → First-effect flash chamber → Secondary neutralization tank → Spraying tank → Semi-finished product bucket elevator → Roller screen → Vibrating screen → Bucket elevator → Granulator → Large particles → Small particles → Storage tank → Crusher → Coloring cylinder → Return conveyor belt → Cooling roller → Finished product conveyor belt → Finished product silo → Packaging. Ammonium phosphate process flow diagram.
IV. Operational Positions: Ammonium phosphate control room. The control room for ammonium phosphate production is one of the quality control points in the entire process; it controls the nitrogen content in the product. 1. Job responsibilities: Responsible for carrying out the reaction between phosphoric acid and ammonia gas, concentrating the slurry, testing the slurry on a hourly basis, as well as maintaining and servicing the associated equipment. 2. Production principle: H3PO4 + NH3 = NH4H2PO4; H3PO4 + 2NH3 = (NH4)2HPO4. Concentration principle: The concentration process makes use of a two-effect system, where the secondary steam generated in the first effect is used as a heat source for the heater in the second effect. Steam is supplied to the heater in the first effect itself, while the second effect operates under negative pressure; the lower boiling point of gases as pressure increases facilitates rapid evaporation of water, thereby achieving concentration. In the flash chamber of the first effect, water evaporates rapidly due to heat exchange with the heater, with the slurry in the first effect containing 20%-25% water. 3. Process flow diagram: Evacuation → Mixing condenser → Gas (vacuum level) → Tail gas fan → Secondary steam → Forced neutralization flash drum → Second-effect A flash drum → First-effect flash drum → Steam, NH3 → Heat exchangers → Forced circulation pump, circulation pumps → Neutralization tank (secondary neutralization), NH3
4. Specifications: First-stage neutralization degree: 1.0–1.15; Second-stage neutralization degree: 1.45–1.55; Slurry specific gravity: 1.45–1.50; Vacuum level: –0.03 to –0.04. The liquid levels in all flash drums must be kept stable: Forced neutralization flash drum: 0.40–0.50 m; First-effect flash drum: 0.30–0.40 m; Second-effect flash drum: 0.5–0.60 m.
5. Abnormal conditions and corrective measures:
Phenomenon | Cause | Corrective measure
Excessive neutralization degree | 1. Excessive ammonia addition; 2. Reduced phosphoric acid addition; 3. Low phosphoric acid concentration | 1. Reduce ammonia addition; 2. Increase phosphoric acid amount; 3. Raise phosphoric acid concentration
Insufficient neutralization degree | 1. Inadequate ammonia addition; 2. Excessive phosphoric acid addition; 3. High phosphoric acid concentration | 1. Increase ammonia amount; 2. Decrease phosphoric acid amount; 3. Lower phosphoric acid concentration
Reduced phosphoric acid supply | 1. Low level in phosphoric acid storage tank; 2. Partially closed valve at phosphoric acid pump outlet; 3. Pipe blockage; 4. Phosphoric acid pump malfunction | 1. Raise liquid level; 2. Increase valve opening; 3. Shut down for cleaning; 4. Replace pump
Reduced gaseous ammonia flow | 1. Low gaseous ammonia pressure; 2. Clogged ammonia nozzles | 1. Raise gaseous ammonia pressure; 2. Shut down for cleaning
Excess moisture content in first-effect slurry | 1. Excessively high steam temperature in first-effect heater; 2. Low liquid level in first-effect heater | 1. Lower steam pressure in first-effect heater; 2. Raise liquid level in first-effect heater
Insufficient moisture content in first-effect slurry | 1. Low heating steam pressure; 2. Scaling on heater walls; 3. Poor drainage from first-effect condenser; 4. Low vacuum level; 5. Excessively high liquid level in first-effect flash drum; 6. Cooling water entering slurry via packing seal | 1. Request boiler to raise steam pressure; 2. Shut down for caustic/acid cleaning or mechanical cleaning; 3. Open bypass valve of first-effect condensate; 4. Raise vacuum level in mixing condenser; 5. Maintain first-effect liquid level within limits; 6. Adjust cooling water flow
Slurry leakage from first-effect flash drum | 1. Excessively high liquid level; 2. Rapid steam injection | 1. Lower flash drum liquid level; 2. Inject steam gradually
Elevated current consumption by circulation pumps | 1. Low slurry moisture content; 2. Equipment malfunction; 3. Heater scaling | 1. Increase slurry moisture content; 2. Diagnose and repair faults; 3. Shut down for cleaning
Slurry leakage from forced neutralization flash drum | 1. Excessively high liquid level; 2. Excessive ammonia addition; 3. Excessively low liquid level | 1. Maintain liquid level within specified range; 2. Add ammonia gradually; 3. Ensure proper level control
Inability to feed slurry into IIA section | 1. Steam accumulation in discharge piping | 1. Raise vacuum level in IIA flash drum
Low vacuum level in double second-effect system | 1. Low circulation pump current; 2. Poor drainage from mixing condenser; 3. Blocked pump inlet; 4. Air leakage at pump packing; 5. System pipe leaks; 6. Clogged spray holes in mixing condenser; 7. Elevated circulating water temperature; 8. Low circulating water tank level | 1. Increase pump outlet valve opening; 2. Clear debris from seal tank; 3. Unclog pipes; 4. Tighten packing; 5. Locate and weld leak points; 6. Shut down for cleaning; 7. Add fresh water; 8. Raise water tank level
Low heating steam pressure in first-effect stage | 1. Low boiler steam pressure | 1. Request boiler to raise low-pressure steam output
Heater scaling | 1. Low heater liquid level during normal operation; 2. Improper handling during startup/shutdown leading to excessively low slurry moisture; 3. Overheated heating steam; Excessively high slurry specific gravity | 1. Maintain normal liquid level; 2. Regularly monitor moisture content during startup/shutdown; 3. Reduce steam pressure
Excess nitrogen content in final product | 1. High SO42− concentration in phosphoric acid solution; 2. Excessive neutralization degree | 1. Lower SO42− concentration; 2. Reduce neutralization degree
Insufficient nitrogen content in final product | 1. Low SO42− concentration; 2. Excessive impurities in phosphoric acid; 3. Insufficient neutralization degree | 1. Raise SO42− concentration; 2. Add flocculant to reduce impurities; 3. Increase neutralization degree
6. Main equipment:
Concentration equipment:
1) First-effect flash drum: Ø2000×5000, 1 unit
2) First-effect circulation pump: SPP30–35, Q=1150 m³/h, H=9 m, Motor: Y280M–6, N=55 kW
3) First-effect heater: Ø550×6966, heat exchange area: 75 m², 1 unit
4) Second-effect B and A flash drums: Ø3200×7000, one each
5) Second-effect B and A circulation pumps: SPP35–40, Q=1700–1800 m³/h, H=10 m, N=132 kW, Motor: Y315L2–6, one each
6) Second-effect B and A heaters: Ø820×6500, heat exchange area: 110 m², one each
7) Seal tank: Ø800×1000, 1 unit
8) Hot water pump: IS100–65–200, Y22 kW–2, 1 unit
9) Slurry collection tank pump: 40YU–1A–20–20, Y5.5 kW, 1 unit
10) Condensate circulation pump: IS100–65–200, Y22 kW–2, 1 unit

Neutralization equipment:
1) Neutralization flash drum: Ø2000×5000, 1 unit
2) Forced neutralization circulation pump: SPP30–35, Q=1150 m³/h, H=9 m, Motor: Y280M–6, N=55 kW, 1 unit
3) Phosphoric acid storage tanks: Ø6500×6000, two units
4) Phosphoric acid storage tank agitators: Two units; Reducer: BLY33–59–7.5; Motor: Y132M–4, N=7.5 kW
5) Pump from tail wash sump to neutralization flash drum: YLG65–315, Y15 kW–4, 1 unit
6) Secondary neutralization tank: Ø2200×2800, 1 unit; Agitator reducer: XLD-8-17-15; Motor: Y160L–4, N=15 kW
7) Phosphoric acid pump: 80UHB–ZK–40–35, 1 unit
Q=40 m³/h, H=35 m, N=15 kW

Advantages of using slurry concentration for ammonium phosphate production:
(1) Lower corrosiveness of slurry; (2) Reduced steam consumption; (3) Easy cleaning of heater structures; (4) High production capacity.
Disadvantages: (1) Risk of slurry leakage due to improper operation; (2) Significant fluctuations in first-stage neutralization degree; (3) Greater environmental pollution.
Recommendations: Install a second-effect B flash drum to boost production capacity via triple-effect evaporation while reducing tail gas emissions. Process method: The process flow diagram shows that since the temperature of the gas coming out of the forced neutralization flash chamber can be raised to over 100 degrees, this temperature can be used as a heat source for the heater in the second-stage B flash chamber. The exhaust gases are connected to an atmospheric condenser, allowing the second-stage B flash chamber to operate under negative pressure; this increases the amount of moisture that evaporates, thereby increasing production while reducing pollution. Process Overview: Phosphoric acid is pumped from the washing unit to the forced-circulation flash chamber via a phosphoric acid pump, where it reacts with ammonia to produce monoammonium phosphate. This mixture is then transferred to the IIA flash chamber. The IIA flash chamber is heated using a heat exchanger to facilitate rapid evaporation of water; moreover, it operates under negative pressure, which lowers its boiling point. The mixture is subsequently sent to the first-stage flash chamber, which is also heated by a heat exchanger to achieve rapid water evaporation. The heat source for this heat exchanger is steam. Finally, the product is discharged into the secondary neutralization tank.

Summary: Raw materials used in the industrial production of ammonium phosphate, as well as the process and operational procedures involved in its production via the slurry method.
I. Introduction to raw materials and operating procedures
II. Process overview
III. Process flow diagram
IV. Actual operation sites
V. Advantages, disadvantages, and recommendations regarding the use of slurry methods for ammonium phosphate production
VI. Company profile
VII. Personal insights
VIII. References: Operations and management of ammonium phosphate
Keywords: Slurry method, process, operations

In the early days, the main type of ammonium phosphate fertilizer produced was monoammonium phosphate. The United States was the first country to produce monoammonium phosphate in 1917, while Germany did not begin producing diammonium phosphate using thermal phosphoric acid methods until the late 1940s. In 1966, Nanjing Chemical Company utilized domestically developed equipment and technology to build a facility capable of producing 30,000 tons of monoammonium phosphate, marking the beginning of ammonium phosphate production in China. The production methods of ammonium phosphate include the traditional solid method and the slurry method; our company’s slurry-based production process has an annual capacity of 150,000 tons of ammonium phosphate.