12. Drying.docx

Drying Processes

Mr. Pankaj Kusum Ramdas Khuspe Pharmaceutics-I

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Drying Processes Definition: Drying: Drying is defined as the process of removing liquid from solids by using heat. Applications of drying:  Used for drying of granules in tablet manufacturing  Reduce cost of transportation & storage  Used for preservation of crude drugs  Helps in size reduction of crude drugs  Used in preparation of dried aluminium hydroxide, solid extracts

Equipments used in drying process Dryer: Equipment used for drying is called dryer a) Tray dryer b) Tunnel dryer c) Rotary dryer d) Fluidized bed dryer e) Vacuum dryer f)

Freeze dryer

? Define Drying. *** ? Name the equipments used for drying. ** ? Write applications of drying in pharmaceutical industry. **

Pharmaceutics-I

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Tray dryer Construction: - It has cabinet with heater at the bottom. - Fan is fitted to the oven to circulate hot air. - Trays have wire mesh bottoms. - Shelves are arranged alternatively. - Uniform temp. & air flow maintained by fitting fan & heater. Working: - Material to be dried is spread on trays. - Air is introduced through air inlet. - Air gets heated by heater. - Fan is started for uniform circulation of heated air over each tray. - Heat & humidity can be controlled in dryer. - Material gets dried. Applications: Used for drying of: - Crude drugs - Chemicals - Powders - Granules used in tablet manufacturing ? Explain Tray dryer with advantages, disadvantages & figure. ? Explain briefly Tray dryer.*

Rotary dryer Construction: - Consists of cylindrical shell. - Cylindrical shell rotated at about 10 revolutions per minute. Working: - Material is introduced in cylindrical shell. - Cylindrical shell is heated by passing hot air current. - On rotation of cylinder, material gets dried. Application: - Used for drying of powder & granules Pharmaceutics-I

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? Explain drying of materials in a rotary dryer.

Fluidized Bed Dryer (FBD) Principle: - Gas passes through bed of solid particles. - Solid particles get suspended in gas. - Mixture of solids & gas behave like liquid & solid hence called fluidized. - Each solid particle surrounded by drying gas - Drying takes place in short time. Construction: - Fan is fitted at upper part of dryer. - Air flow rate controlled by recirculation control. - Heater is fitted in dryer. - Wet material placed in drying chamber having wire mesh bottom. - Filter bags are fitted in dryer to prevent passage of fines. Working: - Wet material placed in drying chamber. - Air introduced through air inlet & circulated by fan. - Air heated by heater & passed through material. - Material gets dried. - Batch type dryer hence drying chamber removed from dryer for feeding. - Takes 20 to 40 minutes for drying. Advantages: - Provide high drying rate. - Used for drying of thermo labile materials. - Less chances of overheating. - Temperature can be controlled in dryer. - Give high output. - Require small floor space. - Used for drying of granules. Disadvantages: - Production of fines. - Precautions should be taken because there is generation of electric charges. ? Explain construction & working of Fluidized bed dryer.*** Write its advantages & disadvantages. ? Explain construction, working & applications of Fluidized bed dryer. ? Give principle & working of FBD. ? Draw a labeled diagram of vertical Fluidized bed dryer. Give its advantages. Pharmaceutics-I

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Draw a well labeled diagram of Fluidized bed dryer.

Pharmaceutics-I

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Vacuum dryer / Vacuum Oven Construction: - Consists of jacketed vessel. - Dryer made up of material which can withstand vacuum in oven & steam pressure in jacket. - Door is closed for air tight seal. - Oven connected to vacuum pump through condenser & receiver. - Operated at pressure of 0.03 to 0.06 bars. Working: - Material placed in oven. - Vacuum pump started. - Water start to boil at 25 to 350 C at pressure of 0.03 to 0.06 bar. - Oven gets heated & so that material gets dried. Advantages: - Used for drying of thermo labile material. - Used for preparation of porous & soft dry extract. - Solvent can be recovered. Disadvantages: - Labor cost is high. - It has limited capacity. - Heat transfer coefficients are low. ? Explain construction & working of vacuum dryer.* ? Write short note on vacuum dryer with neat diagram.

Pharmaceutics-I

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Freeze Dryer OR Lyophilisation In this drying process, water vapours are removed from frozen solution by sublimation. So, it is also called as a ‘sublimation drying process’ OR ‘lyophilisation’. Construction: Freeze dryer has following parts:  Chamber (for vacuum drying)  Vacuum source  Heat source  Vacuum pump (to remove vapours) Chamber is designed for batch operation. It consists of shelves for keeping the material. Heat is provided by conduction or radiation or both. Vacuum is achieved by vacuum pump.

Working: Pre-treatment: It is done to reduce volume of solution. The solution is pre-concentrated under normal vacuum tray drying. This reduces drying time by 8-10 times. Pre-freezing: This is done to solidify water. Sample is frozen at a temp. below -50 °C. Primary drying: Material is spread on the surface to increase surface area. Temp. & pressure is kept below the triple point of water. Heat is supplied & ice sublimes directly into vapour form. Secondary drying: Moisture remained after primary drying is removed by an ordinary vacuum drying. Vacuum drying is done at a temp. 50-60 °C. Packing: Packaging of product is performed carefully to protect it from moisture. The containers should be closed under aseptic conditions. Containers are labeled and packed in card-board boxes. Pharmaceutics-I

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Advantages:  The product obtained is light, porous & have high solubility.  Drug is protected from hydrolysis.  Drying takes place in vacuum. So, drug is protected from oxidation.  Drying of heat sensitive material can be carried out.  Loss of volatile material during drying is very low.  The sterility of product can be maintained. Disadvantages:  It is very expensive.  The product obtained is very hygroscopic.  The period required for drying is long. Applications OR uses: Freeze drying is mainly used for drying of: Biological products Antibiotics Blood products Vaccines Enzymes Microbiological culture Heat sensitive materials ? What is lyophilisation? Give its pharmaceutical applications. ? Define lyophilisation. ? Explain briefly lyophilisation. ? Explain advantages & disadvantages of freeze dryer.

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Spray Dryer Construction: Drying chamber is like cyclone separator. Liquid is converted in droplets with the help of jet atomizer. Liquid inlet is present in upper part. Tangential inlet is present to introduce hot air. Working: Liquid is sprayed in the form of mist by jet atomizer. Liquid droplets are evaporated & get converted into solid particles. Vapours are transferred into separator & fine particles are separated & collected. Applications: It is used for drying of heat sensitive substances. Milk, soap & detergents can also be dried. Solutions & suspensions can be dried.

? Write construction, working & uses of spray dryer.

Pharmaceutics-I

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