transfer of hygroscopic material safely

Transfer of hygroscopic material safely

Transfer of hygroscopic material safely – To transfer hygroscopic materials (which absorb moisture from air) using a pneumatic conveying system, you must prevent moisture exposure and ensure smooth flow. Here’s a detailed guide:

✅ Preferred System: Vacuum or Dense Phase Pneumatic Conveying

• Vacuum Conveying is ideal for short to medium distances.

• Dense Phase Conveying is better for fragile, sticky, or cohesive hygroscopic powders.

Transfer of hygroscopic material safely

🔧 System Design Essentials

1. Use Dehumidified or Inert Gas

• Never use ambient air — it contains moisture.

• Use dry air (via a desiccant or refrigerated air dryer) or nitrogen for critical applications (pharma, food, chemicals).

2. Closed Loop System

• Prevents outside air (and moisture) from entering.

• Ensures controlled low-humidity conditions inside the system.

3. Material of Construction

• Use SS304/316 or other non-corrosive materials.

• Interior surfaces should be smooth to avoid sticking or bridging.

4. Maintain Low Velocity (Dense Phase)

• Prevents attrition or heat buildup that can cause moisture absorption or lumping.

5. Insulated & Heated Lines (Optional)

• Keeps powder above dew point to prevent condensation inside pipes.

6. Efficient Filter Receiver

• Use sealed filter receivers with automatic pulsing for powder collection.

• Include vacuum relief valves and dust-tight discharge valves.

7. Purge System with Dry Air or Nitrogen

• Continuous or pre-transfer purging helps maintain dryness.

Transfer of hygroscopic material safely

📊 Typical Setup Flow:

1. Feeding Hopper → sealed and purged

2. Vacuum Pump or Compressor → fitted with air dryer

3. Transfer Line → insulated, minimal bends

4. Filter Receiver → HEPA filters + dry discharge

5. Discharge to downstream process

🧪 Examples of Hygroscopic Powders:

• Sorbitol

• Citric Acid

• Calcium Chloride

• Pharmaceutical APIs

• Detergents

• Salt (NaCl)

🔁 Maintenance Tips:

• Regularly check filters for clogging.

• Monitor dew point of conveying air.

• Clean lines frequently to prevent build-up.

Here’s a sample P&ID layout description and basic equipment specification for transferring hygroscopic materials using a vacuum pneumatic conveying system:

📌 P&ID Layout Description (Vacuum Transfer System)

🛠️ Equipment Specifications

1. Feeding Hopper

• Material: SS316 (pharma/food grade), SS304 (industrial)

• Design: Conical bottom with air purge ports

• Options: Vibration pads / agitator

2. Rotary Airlock Valve

• Type: Drop-through rotary valve with tight clearance

• Material: SS316

• Special: Dry air purge on shaft to prevent moisture ingress

3. Transfer Line

• Material: SS316 with electro-polished finish

• Diameter: 50–100 mm (based on flow)

• Features: Minimal elbows, insulated if necessary

4. Filter Receiver

• Type: Pulse jet filter with cartridges or bags

• Material: SS316

• Sealing: Dust-tight with gasketed lid

• Sensors: DP transmitter, level switch, vacuum sensor

5. Vacuum Pump

• Type: Oil-less rotary vane / side channel blower

• Capacity: Based on conveying distance and flow rate (e.g., 100–500 m³/hr)

• Add-ons: Inlet HEPA filter, silencer, pressure gauge

6. Air Preparation Unit

• Includes: Refrigerated / desiccant air dryer

• Dew Point: –40°C or better

• Additional: Particulate filter, coalescing filter, regulator

7. Nitrogen Blanketing System (Optional)

• For pharma/highly sensitive powders

• Includes: N₂ generator or cylinder bank, flow meter, pressure regulator

📏 Typical Design Parameters