I. Nanofiltration Membrane Ammonium Nitrate Solution Concentration Process and Parameters

1. Process Overview

2. Process Parameters

2.1 Nanofiltration Membrane Selection

• Membrane Type: Select ultrafiltration or nanofiltration membranes suitable for ammonium nitrate solution, typically with a membrane pore size of 0.5-1 microns.
• Membrane Flux: The flux of nanofiltration membranes is usually 1-10 L/(m²·h), chosen based on the solution's viscosity and concentration requirements.
• Membrane Material: Use high-performance polyamide-based membranes or super molecular weight polyethylene (SPE) membranes to ensure long-term stability.

2.2 Pressurized Concentration Parameters

• Pressurized Pressure: The pressure for pressurized concentration is typically between 50-100 bar. Excessive pressure can increase solution viscosity, affecting concentration efficiency, while too low pressure will not effectively concentrate the solution.
• Pressurized Flow Rate: The feed flow rate is usually 1-10 L/min, adjusted according to equipment capacity and solution viscosity.
• Concentration Ratio: The concentration ratio is 1:10 to 1:50, chosen based on the solution's characteristics.
• Concentration Temperature: The concentration temperature is controlled at 50-70℃ to prevent decomposition of the ammonium nitrate solution.

2.3 Post-Treatment Parameters

• Reverse Osmosis Equipment: Use reverse osmosis membranes for further concentration. The flux of reverse osmosis membranes is typically 0.1-0.5 L/(m²·h).
• Ion Exchange: Use ion exchange resins (such as C18-M Gundlach) to remove excess ions and impurities from the solution.
• pH Control: After reverse osmosis and ion exchange, the pH value should be controlled between 6.0 and 8.0.

2.4 Evaporation Crystallization Parameters

• Evaporation Temperature: The evaporation temperature is typically controlled at 100-120℃ to promote the crystallization of ammonium nitrate.
• Evaporation Rate: The evaporation rate is usually 1-10 kg/(m²·h), adjusted based on the viscosity of the concentrated solution and the crystallization ability.
• Crystallization Time: The crystallization time is typically 1-3 hours, adjusted according to the capacity of the evaporation equipment and the nature of the concentrated solution.

2.5 Pressure and Temperature Control

• Pressure Fluctuation: During pressurized concentration, pressure fluctuations should be within ±10%-15% to avoid damaging the membrane.
• Temperature Fluctuation: Temperature fluctuations during the concentration process should be within ±2-3℃ to ensure solution stability.

2.6 Flow Rate Parameters

• Feed Flow Rate: Choose an appropriate feed flow rate (usually 1-10 L/min) based on the flux of the nanofiltration membrane and concentration requirements.
• Concentrated Flow Rate: The flow rate after concentration is typically 0.1-1 L/min, adjusted according to specific needs.

3. Quality Control Parameters

• Sampling Frequency: Analyze pH value, ion concentration, and impurity content by sampling before and after concentration, before reverse osmosis, and before crystallization.
• Impurity Content: The impurity content in the final concentrated solution should be ≤0.1%, with a pH value between 6.0 and 8.0.
• Ammonium Nitrate Purity: The purity of the crystallized product should reach 99.9%-99.99%, adjusted according to specific application requirements.

4. Process Optimization Suggestions

• Pressure Adjustment: Adjust the pressurized pressure according to the solution's viscosity and concentration requirements to improve concentration efficiency.
• Temperature Optimization: Optimize the concentration temperature based on the thermal stability of the ammonium nitrate solution to avoid decomposition caused by excessive temperature.
• Membrane Life Management: Regularly check the flux changes of the nanofiltration membrane. Replace the membrane in time when the flux decreases by more than 10% to extend its service life.

II. Brief Plan

1. Equipment Selection

• Nanofiltration Membrane: Select ultrafiltration or nanofiltration membranes with a pore size of 0.5-1 microns based on solution concentration and concentration requirements.
• Pressurized Equipment: Pressurized concentration equipment, typically using reverse osmosis or nanofiltration membrane pressurized concentration systems.
• Reverse Osmosis Equipment: Reverse osmosis equipment for further impurity removal.
• Ion Exchange Equipment: Ion exchange resins for ion impurity removal.
• Evaporation Equipment: Evaporation equipment for concentration and crystallization.

2. Operating Parameters

• Nanofiltration Membrane Flux: Typically 1-10 L/(m²·h).
• Pressure: During pressurized concentration, the pressure is usually between 50-100 bar.
• Temperature Control: The concentration process is controlled at 50-70℃ to prevent solution decomposition.

3. Quality Control

• Sampling Analysis: Regularly sample and analyze the pH value, ion concentration, and impurity content of the solution during the concentration, post-treatment, and purification processes.
• Product Purity: Ensure that the concentrated ammonium nitrate product meets the specified purity requirements (e.g., impurity content ≤0.1%, pH value between 6.0 and 8.0).

4. Process Optimization

• Pressure Adjustment: Adjust the pressurized pressure according to the solution's viscosity and nanofiltration membrane flux to improve concentration efficiency.
• Temperature Optimization: Optimize the concentration temperature based on the solution's thermal stability to prevent decomposition caused by excessive temperature.
• Membrane Life Management: Regularly check the flux changes of the nanofiltration membrane and replace it in time to extend its service life.