Air Tray Dryers are the most commonly used, most basic and economical dryers used for drying wet powders.
WORKING PRINCIPLE
Air Tray Dryers (ATD) are insulated chambers having forced circulation of hot air in which trays loaded with product to be dried are suitably placed.

The heating is either by electric power with U type air heaters or by steam/hot water/thermic fluid with finned tube radiator.

The moisture/solvent is evaporated by convection process due to recirculating hot air.

The hot air is partially purged through exhaust damper to continuously remove evaporated moisture/solvent.

The make up air enters the chamber through air inlet.

MAJOR COMPONENTS

Chamber
The box type drying chamber consists of outer body, inside body and LRB insulating material in between. The access door is from the front side.

Door
Doors have insulated construction with outside wall, inside wall and LRB insulating material in between.
Door has sturdy hinges, opening handle, locking arrangement and suitable gasket for air tight operation.

Air Circulation System
In standard design, the air circulation is achieved by coaxial fans mounted on sides. The shaft passes through the side wall and is connected to motor through pedestal bearings, pulley and V belt all mounted outside the drying chamber.

Heating System
U type electrical heaters for electrical heating. Finned tube radiator for steam/hot air/
thermic fluid heating.
Heating elements are fitted on one side of chamber.

Loading System
Material to be dried is spread evenly on trays.
Standard tray size is 32" length x I6: width x 1%" depth.
For upto 24 trays capacity, fixed angle supports are provided inside the drying
chamber on which the trays are loaded.
For higher capacity models the trays are loaded on removable trolleys made from angles and square pipes. Standard trolley is suitable for 48 trays.

Air inlet
Make up suitable size cutout in chamber body for make up air. Air inlet is fitted with Air filter.

Exhaust damper
Suitable size cut out on chamber top for partially purging air concentrated with
moistures/solvent vapours.
Exhaust damper is provided with manually adjustable flap.

Control System
For switching ON/OFF the recirculation fan and heating system. Suitable temperature controller and process timer can be incorporated. Suitable temperature sensor is provided on the drying chamber.

Safety
a. Safety grids made from wire mesh are provided on both sides of drying chamber to prevent accidental access to rotating parts and heating elements.
b. Explosion flap made from thin aluminum sheet is provided on drying chamber to expel the pressure and prevent major damage to equipment and operator in case of accidental explosion.

USER REQUIREMENT SPECIFICATIONS (IIRS)
Material of Construction
a. For recirculating Air contact parts. : Inside body Recirculation fan, Shaft, Safety
grids, Heaters/Radiators, Exhaust damper, Trolley/Fixed angle supports.
b. For Powder contact parts : Trays
c. For External/Non contact parts : Outside body, Drive Supports, Drive cover,
Control Panel, Chamber supports, Hinges/Handles/Lock, Control Panel, enclosure. Under carriage/ Transfer cart.
d. For Gaskets : Neoprene rubber/Silicon rubber.
e. For Insulation medium. : Standard is LRB.
Capacity
Each tray can hold approximately 4 Kgs material (Assumed b.d=0.5gm/cc)
The standard capacities are.
6 tray with fixed angle supports.
12 trays with fixed angle supports.
24 trays with fixed angle supports.
48 trays (on one trolley )
96 trays ( on two trolleys )
192 travs ( on Fourtrollevs )

Vacuum Tray Dryers are the most commonly used equipment for low temperature drying for heat sensitive products.

WORKING PRINCIPLE
Vacuum Tray Dryers are insulated chambers with fully openable door suitable to withstand full
vacuum.
Hot plates/heating shelves are suitably mounted one above the other inside the
vacuum chamber.
Hot plates are heated either by hot water, thermic fluid or steam which is circulated
between top and bottom of the hot plate.
Product to be dried is loaded in the trays which are places on the hot plate.
The heat transfer takes place by conduction process through top surfaces of hot plate
to tray to product. Some radiant heat is also transferred to the product from the hot plate above
it.
The evaporation takes place at lower temperatures because of reduced boiling point of moisture/solvent under vacuum created by suitable evacuation system like water ring vacuum pump, oil sealed vacuum pump, water/ setam jet ejector or any other method.
Solvent is recovered with the help of suitable condenser and receiver placed between vacuum chamber and evacuation system.

ADVANTAGES OF VACUUM TRAY DRYER.
OVERCOME PROCESS CONSTRAINTS.
Drying takes place at lower temperature than at atmospheric conditions. This is necessary when the product is heat sensitive at higher temperature OR melting point of product is less than boiling point of solvent.
OVERCOME PRODUCT CONSTRAINTS.
Can work with liquids, slurries, crystalline, amorphous, irregular shapes and size products. There is no limitation due to There is no limitation due to physical characters of product dryers. There is not possible with other vacuum dryers.
REDUCED PRODUCTION COST
Major amount of solvent is recovered even with basic shell and tube condenser and receiver. This results in substantial savings in production costs, as compared to atmospheric dryers.

POLLUTION CONTROL
Pollution is reduced by equivalent amount of solvent recovered as compared to atmospheric dryer
IMPROVED PRODUCT QUALITY
Product quality is improved due to absence of air and foreign particle contact with Product.
BETTER CLEANING
Cleaning of Vacuum Tray Dryers is easier than any other dryer due to absence of moving rotary components. - Easy accessibility of inside parts due to fully openable construction.
Absence of inaccessible components like radiators, fans, etc.
Absence of inadequate or constrained access as in other vacuum dryers or fluid bed dryer.
CONTROL ON CROSS CONTAMINATION
It is difficult to beat VTD on this aspect.
The product under drying is static. There are no air currents which can carry powder particles.
Except for spillage the powder is totally contained in trays.
There are crevices or gaps. Where the powder can be deposited.
The chamber is virtually non contaminated during full drying cycle, hence cleaning is easy.
This virtually eliminates chances of cross contamination.
LOW MAINTENANCE
Simple construction without any moving or rotary parts or drive/transmission components. Hence negligible maintenance and service. There is virtually no down time for this equipment.
SAFE OPERATION
Very less chances of accidents as there is no scope of static electricity .
There is also no scope of sparking as there are no moving or rotary parts
SUITABLE FOR MULTT PRODUCT USAGE
Due to control on cross contamination and & also in cleaning the changeover to different
products is reasonably fast.
This helps in Multi product usage.
STERILE/CLEAN ROOM AREA PRODUCTION.
All above factors taken together VTD'S are best suited for drying under sterile/clean room conditions.

WE ARE CONFIDENT THAT NO TECHNICAL DIS-ADVANTAGES CAN BE POINTED OUT IN OUR DESIGN, AS COMPARED TO ANY OTHER EQUIPMENT CURRENTLY AVAILABLE IN MARKET.

MERITS
1. We provide 12 removable hot plates and 2 fixed hot plates as top and bottom of vacuum chamber.This is very useful for high boiling solvents and there is no accumulation of solvent at bottom of vacuum chamber at the end of drying cycle.
2. Utility connections to individual hot plates are 28 mm O.D. with 16 mm clear bore. Other designs provide a bore of 8 mm. Hence cross sectional area available for utility inlet and outlet to individual hot plates is four times more in our design.
3. Hot plate internal baffles are 20 x 20 instead of 12 x 12 standard in Industry. Because of the voidage between hot plate top and bottom is clear 20 mm which facilitates better flow of utility through hot plate. This results in better heat transfer and drying efficiency.
4. Hot plates to header connection is by triclover quick fit unions. Due to this no tooling is required for removing and fitting of headers. The operation is also very fast.
5. Hot plate individual nozzle sealing is plain washers and specially Machined threaded coupling.

6. Our hot plate supports are pin type. This has minimum surface contact with hot plates. Because of this , hidden places and gaps are completely eliminated. Hence cleaning of dying chamber is easy and efficient.
7. Our hot plate internal baffles are S.S. 304 quality. This prevents scaling and anodic corrosion over a period and results in long life for hot plates, with M.S. baffles either hot plates have to be changed after 2 to 3 years due to complete deformation or atleast heating efficiency is lost to due slight deformation of hot plates resulting in improper contact between
trays and hot plate top.
8. The gap between hot plate is sufficient even to insert complete
hand in the gap for cleaning or other operations.
9. The chamber door is insulated . This prevents the heat loss, reduces condensate formulation inside the vacuum chamber and reduces the load on air conditioning. If there is no air conditioning the working atmosphere in operating area is better as no heat from dryer is dissipated there.
10. The door clamping is by lC clamps instead of eyebolts. Thus there are no
cut grooves on body and door. This is aesthetically better as well as reduces cleaning troubles.
11. Clamp lock is specially machined, solid,locking knobs instead of hand wheels. This reduces damage and hence requirement of spares. Threading of clamping stud is square. This reduces wear and tear and hence requirement of spares.
12. Condensor if sourced from us is directly mounted on receiver in vertical position. This reduces space requirement.
13. Receiver if sourced from us is having a centre partition with interconnection between two compartment with isolation valve.
Hence condensate from receiver can be removed without stopping drying cycle or breaking vacuum.
14. Depth of Vacuum Chamber is moderate hence cleaning operation is easy.
15. Total height is such that even the loading on top hot plate can be done by average person from ground level.