Process Dryers

8/3/2019 Process Dryers

1/12

Dryer Type

Air Bars / Floatation Dryer Air bars produce dispersed drying air. Flotation

dryers use a series of air bars or louvers to support

and gently dry webs of fragile materials.

Air Knife / Impingement Dryer Air knives use a high-pressure air blast to wipe-off

water. They are used also to dry discrete parts or

continuous sheets / webs or larger bulk materials.

Hot air impingement dryers use blasts of hot air to

convectively dry moving webs, boards, or other

large bulk materials.

Belt Conveyor Dryer Conveyor drying uses a perforated belt to transfer

feed materials through the dryer. Heated air is either

passed under and through, or over and through the

belt and product bed before being reheated and re-

circulated. Units usually have multiple zones, and

may have differing airflow in successive zones.

Additionally, each zone may use a different

temperature profile and control. Saturated or almost

saturated air is exhausted from the dryer via a

central exhaust duct.

Calciner / Rotary Tube Calciners remove bound water from a material. A

calciner consists of an angled drum tube that passes

through a furnace. The tube, which is in direct

contact with the tube feed, is heated either by

electrical elements or by gas burners. Special lifters

within the drum promote the exposure of the feed to

the heated surfaces by a rolling motion of the

material. The product is discharged through a

suitable airlock device.

Centrifugal Dryer Centrifugal dryers use a spinning action tomechanically enhance the removal of water, and to

increase drying line speed. Typically, centrifugal

dryers are used for discrete parts or products, or

after washing of these components.

Chamber Dryer Chamber-type dryers consist of a heated chamber

that is usually heated to a higher temperature than


2/12

other dryers.

Column / Cascade Dryer Column dryers consist of tall, vertical vessels often

with baffles to cascade the material. Powders or

bulk materials are fed down through the column and

heated by contact with baffles or drying air.

Conical / Tumbler Dryer Conical dryers are available in rotating and non-

rotating styles. The rotating styles have a rotating or

tumbling housing that keeps the media in motion to

prevent media buildup. The non-rotating styles have

internal moving components that also keep the

media in motion to prevent buildup.

Continuous Tray / Turbo Tray Dryer Continuous tray dryers have a series of horizontal

plates or trays with a single slot. Material is fed onto

the top tray. A series of plows wipes thematerial from the trays and drops it onto the next

tray. Hot air is circulated up through the unit to dry

the material.

Disc Dryer Disc dryers are drum-shaped units that are filled

with a series heated discs. Disc motion or airflow is

used to move powders or bulk material through the

dryer. Often, steam is used to heat the discs.

Cylinder / Roll Dryer (External) Cylinder or roll dryers usually consist of a steam-

heated drum with a smooth outer surface around

which a moving web or sheet is passed for drying.

Evaporator Evaporators use a mechanically-created vortex to

force a liquid sample outward against the tube walls.

This increases surface area for faster evaporation

and maximum sample recovery. Liquid can also be

removed by gentle heating at atmospheric pressure

with flowing air, an inert gas, or under vacuum

conditions.

Festoon / Loop Dryer Festoon or loop dryers are used to heat webs or

continuous sheets with minimal contact. The web is

held on bars or threaded onto movable idler

rolls that are driven by a conveyor. Festoon dryers

are used to dry or cure coated abrasive webs,

flocked wall paper or coated fabrics.

Roller / Flaker - Dryer Rollers or flakers are dryers where a film of a slurry,


3/12

paste, or melt is fed onto a drum or belt. The

material is dried or solidified and then flaked off

with a doctor blade. The drum or belt can be heated

or cooled.

Flash / Pneumatic Dryer Flash dryers offer an effective method of removingsurface or unbound moisture from a feed product.

The technology behind flash drying employs a low

residence time within the actual dryer; thus, the

unbound moisture is "flashed" off the feed. Flash

dryers, pneumatic dryers, ring dryers, and flash tube

or cyclone dryers use a heated carrier gas (usually,

air) to pneumatically convey the feed through the

flash dryer (flash tube) and into a primary gas-

separation device (most commonly, a cyclone or

series of cyclones in series or parallel). The carrier

is induced or forced into the feed throat from a hotgas generator that heats the gas to the desired

operating inlet temperature. In the feed throat, the

gas entrains the feed, and the moisture is evaporated

quickly as the product is conveyed through the

system to the primary gas / product separation

device. Because the entire product is entrained in

the gas stream, both primary product collection

(typically, cyclones) and secondary and tertiary dust

collection (such as multicyclones, bag houses,

scrubbers and electrostatic precipitators) usually are

installed to meet emission limits. Flash dryers are an

efficient method of drying products such as slurries,

pastes and sludge (most with back mixing), friable

filter cakes, powders and granules.

Fluidized Bed Dryer In fluidized bed dryers, a bed of material is fluidized

through vibration or air flow. The powders are then

dried by direct heating from hot air or combusted

gas flow (direct) or through contact with heated

surfaces (indirect).

In general, fluid bed dryers operate on a through-

the-bed flow pattern with the gas passing through

the product perpendicular to the direction of travel.

In batch operation, a dose of feed is metered into the

dryer bowl and processed until the desired final

moisture has been attained. For continuous systems,

wet feed is introduced by being metered into the

drying section (zone) by means of a suitable feeder.


4/12

The dry product is discharged from the same

section.

In direct systems, hot gas is introduced into the

dryer's wind box or plenum. The plenum is a

"pressurized box" that distributes the gas evenlyacross the distributor or fluidizing plate that

separates the product from the wind box. The

fluidizing plate is a proprietarily-designed

perforated plate that has either non-directional or

directional holes (nozzles), with or without caps,

through which the gas passes. The process gas

passes from the wind box into the drying chamber

and interacts with the feed, lifting and maintaining

the feed in a fluidized state termed a bed. The bed

attains fluid-like properties, flowing and mixing in a

similar fashion to a liquid. The fluidization providesintimate contact between each material particle and

the gas stream, creating an efficient transfer device.

Freeze Dryer Freeze drying, or lyophilization, is used for the

reliable preservation of a wide variety of heat

sensitive products and demands the highest

standards of reliability and control.

Pan Dryer Pan dryers are specialized units designed to dry

sensitive pharmaceutical and chemicals. Pan dryers

consist of a heated lower pan in an enclosed vessel

under air, vacuum or a pressurized cover gas. The

pan may rotate or a rotating agitator bar may be

used to prevent sticking and improve drying

uniformity.

Paddle / Agitator Dryer Blades, paddles, breaker bars or other internal

agitation devices are used to break up and disperse

the material to improve drying uniformity and

prevent agglomeration. Paddle dryers typically

consist of a long trough or drum along which runs a

shaft holding the paddles.

Predryer Predryers or preheaters provide initial heating or

drying of a material before the unit is passed into a

larger dryer. Often, radiant heating dryers are used

to pre-dry webs before the material is fed into a hot-

air dryer.


5/12

Rotary Dryer (Internal Drum) Rotary dryers feed the material into a tumbling or

rotating drum called a tumbler. The drum is heated

or heated air is fed into the unit. The internal surface

of the drum may have baffles or louvers to channel

the hot air or cascade the material.

Rotary cascade dryers pass feed materials through a

rotating cylinder together with a stream of hot gas.

Internal lifters or flights elevate the feed and drop it

in a curtain from the top to the bottom cascading

along the length of the dryer. Flights need to be

carefully designed to prevent asymmetry of the

curtain. Material moves from one end of the dryer to

the other by the motion of the material falling due to

the angle of inclination of the drum. Some rotary

dryers are double and triple pass units where each

drum is nested inside the previous drum.

Rotary louver dryers have the feed materials

supported and moving over a set of louvers mounted

to an external rotating drum. The hot gas is

introduced into a tapered bustle below the feed ring.

The air passes through the louvers and then the

product before being exhausted from the dryer. The

rotation of the drum causes the material to roll and

mix providing intimate contact with the drying gas.

Material moves from one end of the dryer to the

other by the motion of rolling, some fluidization and

due to the angle of inclination of the drum.

Screw / Auger Conveyor Dryer Screw or auger conveyor dryers use a screw

conveyor to agitate and feed a powder or bulk

material through the dryer.

Spray Dryer Spray drying is the most widely used industrial

process involving particle formation and drying. A

spray dryer consists of a feed pump, atomizer, air

heater, air disperser, drying chamber, and systems

for exhaust air cleaning and powder recovery.

Steam Tube Dryer Steam tube dryers are drum-shaped dryers with a

series of internally mounted and

spaced tubes. Steam passes through the tubes

and bulk material or powders are indirectly

heated through contact with the heated tubes

(tubular rotary).


6/12

Straight Pass Dryer Straight pass or flatbed dryers are used to dry

continuous webs or sheets that cannot be wrapped

around a cylinder or festoon rack.

Suction Drum Dryer Suction drum dryers consist of a series of perforatedcylinders or drums with an internal vacuum. Web or

sheet materials are held against the drum by the

vacuum or suction generated as a fan draws air from

the interior of the drum. This suction holds the

material to the surface of the drum, permitting air to

pass through the material being dried. A portion of

the drum at the transfer has no suction and permits

the material to transfer to the next drum without

interference.

Thin Film Dryer With thin film dryers, a wiper deposits a thin layeronto the inner surface of a drum. The thinness of the

layer promotes rapid drying.

Tray / Cabinet / Tunnel Dryer Tunnel dryers consist of an oven-like enclosure. The

material is loaded onto trucks or trays that are

stacked on a movable truck. The trucks are rolled

into the tunnel where the material is dried.

Air is drawn in through an inlet duct and heated

to the required temperature for drying. The heated

air is then distributed from side-to-side, or bottom-

to-top, in a circular motion. The system can be

automated with the trucks on a trolley, being moved

in and out continuously.

Vacuum Dryer Vacuum dryers use an applied vacuum to accelerate

drying. Vacuums can alter vapor pressure to

enhance evaporation rates. They can also increase

the drawing out of liquids in pastes by capillary

pressure.

Vibratory Dryer Vibratory dryers use a vibratory action to

agitate, feed or fluidize powders or other bulk

materials.

Other Other unlisted or proprietary dryer types.

Search Logic: All products with ANY of the selected attributes

will be returned as matches. Leaving all boxes


7/12

unchecked will not limit the search criteria for this

question; products with all attribute options will be

returned as matches.

Heat Source / Transfer:Your choices are...

Waste Heat Waste heat is heat generated or left over from

another process.

Direct / Convection Hot air or combusted (or heated) gas) is directly

circulated though the material being dried, to

convectively heat and evaporate moisture.

Combustion Dryers use heat generated by the combustion of gas,

oil, biomass, waste products, or other fuels. The

combusted gas may heat the material either directly

or indirectly.

Electric Electrical resistance heating

Indirect / Contact / Conduction Walls, tubes, jackets or discs are heated by steam,

gas, thermal oil, or hot air. These heated elements

transfer their heat to materials that come in contact

with them via conduction. Indirect dryers may be

useful when contact with combustible gas or hot air

is not desirable due to product or process

requirements.

Radiant / Infrared Dryers use radiant heat generated by electric or gas-

fired infrared heaters. Radiant heat dryers are useful

for drying surfaces, flat products or web materials

where a clear line of sight can be provided. Straight

pass infrared dryers are used to pre-dry web

materials before these materials are fed into a

conventional, direct, hot dryer.

Steam Steam dryers are indirect dryers that use equilibrium

or superheated steam. Typically, the steam is passed

through tubes (as in a steam tube dryer) or through

a jacket or wall passage (as in pan or rotary

drum dryers).

Thermal Oil / Fluid Thermal oil or fluid is heated and used to indirectly

transfer heat to a material through a process wall,

ackets, discs or other surfaces.


8/12

RF / Microwave / Dielectric Radio frequency (RF) generators create an

alternating electric field between two electrodes.

The material to be heated and dried is conveyed or

placed between the electrodes where the alternating

energy causes polar molecules in the material to

continuously reorient themselves to face oppositepoles, much like the way bar magnets behave in an

alternating magnetic field. The friction resulting

from molecular movement causes the material to

rapidly heat throughout its entire mass. Areas in the

material with greater moisture content heat up and

dry faster.

Other Other unlisted or specialized heat sources.


will be returned as matches. Leaving all boxesunchecked will not limit the search criteria for this



Secondary Process Capabilities:

Your choices are...

Agglomeration / Granulation Granules or agglomerates can be formed from

powder or fibrous feeds.

Classification / Screening Dryers have integral classification or screening

capability

Coating Dryers allow coating of the material before, during,

or after drying.

Cooling / Freezing Materials can be cooled or frozen during or after

drying.

Crystallization Materials such as PET plastic can be crystallized.

Filtration Dryers having integral filtration capabilities. Water

may be filtered off to reduce the drying time.

Moisturizing / Humidifying Dryers can restore a level of moisture to an over-

dried and possibly brittle product.

Preheating Dryers have an integral preheater or preheating

capability. For instance, a slurry could be preheated

in a tank before introduction to a drum dryer.


9/12

This technique reduces the heating demands on the

drying unit and increasing line speed.

Washing / Rinsing Dryers have an integral washing or rinsing

capability. For example, in some pharmaceutical

applications, the product may be passed throughseveral rinse and dry cycles to remove liquor.

Search Logic: Products with the selected attribute will be returned

as matches. Leaving or selecting "No Preference"

will not limit the search criteria for this question;

products with all attribute options will be returned

as matches.

Application / Media Selections

Material Form:Your choices are...

Bulk Materials / Briquettes Dryers are used with briquettes, pellets, or other

larger bulk solids

Discrete Parts / Products Dryers are used with discrete parts, packages,

bottles, boards or finished products. Air knives or

fans are often applied for these applications.

Free Flowing Powders / Granules Dryers are used with powders and granular

materials.

Fibers / Flakes Dryers are designed for fibers, flakes, or other

powders with poor flow characteristics. Agitators,

fluidizers, or other specialized devices may be used

to facilitate drying of these materials.

Pastes Pastes are thick, sludge-like mixtures of liquids and

solids. Specialized feeding, extruding or mixing

devices are sometimes used in dryers designed for

processing pastes.

Slurries Slurries are dispersions of solids or powders in

liquids. Spray, fluidized bed, or rotary drum type

dryers are used to process slurries.

Solutions / Liquids Dryers are designed for solutions (liquids that

contain dissolved salts or other chemicals), colloidal

suspensions, emulsions of two liquids, or two or


10/12

more mutually soluble liquids. Spray dryers,

fluidized bed dryers, or evaporator dryers are used

to process liquids or solutions.

Webs / Continuous Sheets Webs are continuous-sheet materials such as paper,

cardboard, textiles, plastic films, metal sheet,strip, non-woven mats or printed newspaper. Webs

are processed with festoon, cylinder, straight pass or

flat bed, and suction drum dryers.


will be returned as matches. Leaving all boxes

unchecked will not limit the search criteria for this



Applications / Materials Processed:

Your choices are...

Abrasives / Ceramics Equipment is suitable for drying abrasives, green

ceramics, refractories, or clay bodies before firing.

Adhesives / Curing Equipment is used for drying adhesives or

binders. Radiant heat dryers are useful for drying

adhesive layers on surfaces, as well as flat products

or web materials where a clear line of sight can be

provided. Rotary drum and fluidized bed dryers are

useful in drying the binders that form and hold

together agglomerates.

Chemicals / Fertilizers Equipment is suitable for the drying of fertilizers,

waxes, salts, or other inorganic or organic

chemicals.

Construction Materials / Cement Cement, limestone, gravel, sand, brick, grog, clay,

shale, or asphalt.

Electronics / Semiconductors Equipment is used in semiconductor or electronic

manufacturing (e.g., the drying of wafers after

etching and rinsing steps).

Foods / Grains Equipment is used to dry liquid, solid, and liquid-

solid mixtures of food products such as grain, milk,

dried potatoes, apples, sugar, spices, vegetables, or

other foods.

Metallurgical Equipment is used for drying metal sheet, metal


11/12

powders, carbide powders, metal casting or finished

products, slags or other components used in winning

metals (smelting), or scrap metal prior to recycling.

Mining / Ores / Minerals Dryers are used with ores and minerals for

subsequent extraction processing.

Paint / Coatings Equipment is used for drying paints or

coatings. Radiant heat dryers are useful for drying

paint layers or coatings on surfaces, as well as flat

products or web materials where a clear line of sight

can be provided. Straight pass infrared or forced hot

air dryers are also useful in drying thin, painted

layers or printed patterns.

Pharmaceutical Equipment is designed specifically for use in

processing pharmaceuticals.

Polymers / Molding Equipment is suitable for drying plastics,

elastomers, rubbers or other polymeric materials in

pellet, finish product, or sheet forms.

Power / Coal and Coke Equipment is used for drying coal or coke, as well

as ash in power generation applications.

Pulp and Paper Equipment is used for drying cellulose feeds, cotton

fiber, or pulp for the production of paper,

paperboard, fibre and other paper products.

Sanitary Equipment is designed for sanitary

applications. Dryers are constructed of an easily

sterilized material and are designed specifically for

hygienic purposes such as medical, pharmaceutical,

or food processing applications. Usually, the

equipment is certified by a national or international

organization (USDA, FDA, etc.), but this is not

required.

Textiles / Nonwovens Equipment is used to dry woven cloth webs or non-

woven mats of nylon, cotton, fiberglass, or other

fibrous materials.

Waste / Sludge Equipment is used for drying solid wastes, soil

reclamation materials, or waste water sludge.

Wood / Wood Products Equipment is used for drying lumber, forest


12/12

products (logs), wood boards, particle board,

plywood or wood chips

Other Other unlisted or proprietary applications.

Search Logic: Products with the selected attribute will be returnedas matches. Leaving or selecting "No Preference"

will not limit the search criteria for this question;

products with all attribute options will be returned

as matches.

Process Dryers

Documents

Transcript of Process Dryers