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STANDARD OPERATING PROCEDURE

Dryer, Spray Dryer, Mini, SolventModel: B-290

Manufacturer: Buchi Labortechnik AG

Location: Processing Lab, 1384 Food Sciences Building

Publication Date: 03/10/2014

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Description and Uses

Spray drying is the evaporation of moisture from an atomized feed by mixing the spray and drying medium (typically air or nitrogen). Drying proceeds until the desired moisture level is reached in the sprayed particles which are then separated from the air. The mixture being sprayed can be a solvent, emulsion, suspension or dispersion. The drying medium is heated electrically. When spray droplets come in contact with the medium, evaporation occurs from the saturated vapor film at the droplet surface. Evaporation results in cooling of the droplet. As a result, likelihood of heat damage to the product is minimized. When moisture removal is complete, the product is removed from the dryer. The Buchi Model B-290 Mini-Spray Drier is used for quick and gentle drying of liquid end products to powder. Features include efficient performance with very short set-up times, an effective integrated nozzle cleaning mechanism, and a high degree of application flexibility. The mini-spray drier can be used for gentle spray drying of solutions and suspensions, spray crystallization, agglomeration, structural modifications of substrates, isolating pharmaceutical active agents, or the micro-encapsulation of aromas and coatings.

Power Specifications

Motor: Buchi Model B-290

Voltage/Wattage: 230-V/AC, 2900 W

Speed/Frequency: Maximum Air-Flow: 35m3/hr@50-60 Hz

Potential Hazards and Safety Precautions

Electric Shock/High Voltage (230-V)

• Make certain to use the correct outlet that is specifically designed to fit the electrical cord plug.

• Make sure the area around the outlet, floor and your hands are completely dry when plugging or unplugging the electrical cord to/from the outlet.

Hot Surfaces/Possible Burns to Hands and/or Extremities

• The glass components of the dryer can become very hot during operation. Be careful in the placement of your hands and/or extremities.

Flying Debris/Potential Eye Damage

• The spray chamber, cyclone, collecting vessel and connections are made of glass. During operation of the dryer, be sure that the plastic “curtains” are closed to prevent injury in case of breakage and flying glass.

• Wear safety goggles while dryer is in operation.

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Required Personal Protective Equipment

Lab Coat

Hair Net

Safety Goggles

Heat-resistant Rubber Gloves

Ear Protection

No Open-toed or Open-heeled Shoes

Training

Required Training

*Denotes courses offered online

Machine & Site-Specific Training

Fire Safety & Extinguisher Training*

Laboratory Safety: Core Concepts*

Recommended Training for Frequent Users

Electrical Safety & Lockout/Tagout

Laboratory Safety: Spill Procedures

Operation

1. The Operation Manual provides a more complete description of the dryer components and their function. Be sure to read the manual before operating the dryer to become familiar with its correct operation and individual component parts. There is a copy of the Operation Manual near this machine and another copy in the pilot plant office, 1955 Food Sciences Building. For general questions, you may also refer to the Quick Operation Guide attached to this Standard Operating Procedure (SOP).

2. There are several different modes in which the dryer can be operated, such as the blowing or sucking mode, with organic or aqueous solvents, etc. These are described in the manual and in the accompanying photographs. Please note that the Buchi Inert Loop B-295 must be used in conjunction with the mini-spray dryer to safely spray organic solvents (see Figure 1).

Figure 1. Buchi Inert Loop B-295

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3. Assemble the spray dryer according to the diagrams in the Operation Manual. Please note that the spray chamber, cyclone, fittings, etc. are made of blown glass and are very expensive. Please handle with care!

4. Controls for the dryer (Model B-290) are on the front panel of the machine. Please refer to the Operation Manual before turning the apparatus on.

5. Turn the apparatus ON. The dryer performs a self check, after which it goes into the operating mode.

6. Air/Gas Flow: Air can be used as the drying medium. For samples that are sensitive to oxidation, nitrogen is the recommended medium. Nitrogen should be used with feed stocks containing organic solvents.

7. For either gas, set the gas flow at ~30 mm with the rotary adjustment knob (refer to Operation Manual).

8. Select the desired inlet temperature with the adjustment button (refer to Operation Manual). For aqueous solutions, inlet temperatures are between 100–220°C. Use a lower setting for heat-sensitive products. A typical set point is 150°C.

9. Turn ON the aspirator. As a standard, the aspirator rate should be 100% to maximize the separation rate of the cyclone. If a small powder humidity is needed, decrease the aspiration rate.

10. Turn ON the heating element (refer to Operation Manual). Wait until the system reaches steady conditions. If needed, turn on the nozzle cooling system.

11. Thread a length of (feed) tubing through the rollers of the dryer’s peristaltic pump located above the control panel. Connect one end of the tubing to the inlet of the atomizer; insert the other end into a flask containing the solvent in which the sample is dissolved, e.g., water, ethanol, etc.

12. Switch ON the peristaltic pump. If the atomizer is working correctly, solvent will be sprayed into the spray cylinder in a symmetrical spray cone oriented in the axis of the cylinder. If this is not the case, the nozzle may be dirty or defective. If the nozzle is dirty, turn on the automatic nozzle cleaning feature. This will “pulse” a jet of solvent through the nozzle under pressure at user-determined intervals to remove substances that may clog the nozzle, and should be left on during the spray-drying process. Please note if clogging occurs and the nozzle cleaning feature fails, it may be necessary to remove, disassemble and clean the nozzle.

13. The spray quantity of solvent can be changed by using the push buttons on the peristaltic pump. Spray flow strongly influences the outlet temperature as water draws energy from the air by evaporation. The outlet temperature can be set to the desired value by varying the quantity of sprayed solution using the peristaltic pump speed. The outlet temperature should be no higher than that tolerated by the product to prevent degradation.

14. When the desired operating conditions are reached and have stabilized, transfer the feed tube from the solvent to the feed solution. Since the feed has a lower % solvent, less heat is required as less solvent has to be vaporized. Since evaporation is a cooling process, less solvent vaporization causes the outlet temperature to rise. If the product is heat-sensitive, it may be necessary to offset this by reducing the inlet temperature. Lowering the aspiration rate can be used to reduce the outlet temperature; however, this results in shorter sample residence times in the spray chamber and higher residual moisture in the final product. If the product moisture content is too high, you can

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increase the aspiration rate and decrease the pump speed. If the spray chamber is too wet and the product sticks to the glass, you may increase the inlet temperature as you decrease the pump speed. These variables need to be adjusted according to the physical requirements of the specific feedstock and product.

15. When the entire sample has been spray dried, spray pure solvent through the apparatus for a short time to remove product deposits from all hoses and the nozzle. Alternate air (or nitrogen) and solvent for an efficient cleaning.

16. Pump the feed tube empty, and then turn OFF the peristaltic pump. Lower the pump bed and remove the tubing.

17. Turn OFF the heating element and the nozzle cleaner.

18. Allow the temperature to fall below 70°C, and then turn OFF the aspirator.

19. Remove the product vessel. Note: Be certain that the aspirator is OFF during this step. Otherwise, the air stream could blow the product out of the vessel.

20. Recover the product from the vessel. Prepare for clean up.

Clean-up Procedures

1. The glass assembly should be carefully taken apart and thoroughly cleaned with soap and water.

2. Rinse the glass assembly with tap water, followed by a distilled water rinse.

3. Reassemble and remount the glass assembly when dry.

Machine Care and Maintenance

• The Buchi Model B-290 Mini-Spray Dryer must be properly cleaned and inspected after each use. Be sure to convey any operational problems directly to the pilot plant manager. All inspections are performed by the pilot plant manager.

• Motors and moving parts should be properly maintained on a regular basis by the pilot plant manager or a trained service technician.

Accessories

Buchi Inert Loop (Model B-295)

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