This document discusses pneumatic drying technology for food products. It describes the working principle of pneumatic dryers, which use high-velocity hot air to quickly dry materials through indirect heating and co-current flow. Key factors that influence drying speed such as temperature, moisture dispersion, and particle size are examined. Common types of pneumatic dryers like flash dryers, rotary dryers, and two-stage dryers are outlined. Applications for drying foods like wheat, starches, and meat are provided. Advantages of short residence times and disadvantages like required efficient exhaust systems are also summarized.
spray drying is technology widely used in milk powder and coffee powder manufacturing industry because of its working principle and technology involved..
spray drying is technology widely used in milk powder and coffee powder manufacturing industry because of its working principle and technology involved..
size reduction,laws involved in size reduction ,application & millsM Swetha
size reduction basic principles,laws&machanism of size reduction with all mills .I gave a note on size separation .it is very useful for the teaching staff &students of B.pharmacy
Single and multiple effective evaporator (mee)Sumer Pankaj
A multiple-effect evaporator, as defined in chemical engineering, is an apparatus for efficiently using the heat from steam to evaporate water.[1] In a multiple-effect evaporator, water is boiled in a sequence of vessels, each held at a lower pressure than the last. Because the boiling temperature of water decreases as pressure decreases, the vapor boiled off in one vessel can be used to heat the next, and only the first vessel (at the highest pressure) requires an external source of heat. While in theory, evaporators may be built with an arbitrarily large number of stages, evaporators with more than four stages are rarely practical except in systems where the liquor is the desired product such as in chemical recovery systems where up to seven effects are used.
The multiple-effect evaporator was invented by an African-American inventor and engineer Norbert Rillieux. Although he may have designed the apparatus during the 1820s and constructed a prototype in 1834, he did not build the first industrially practical evaporator until 1845. Originally designed for concentrating sugar in sugar cane juice, it has since become widely used in all industrial applications where large volumes of water must be evaporated, such as salt production and water desalination.
Multiple effect evaporation commonly uses sensible heat in the condensate to preheat liquor to be flashed. In practice the design liquid flow paths can be somewhat complicated in order to extract the most recoverable heat and to obtain the highest evaporation rates from the equipment.
Multiple-effect evaporation plants in sugar beet factories have up to eight effects. Six effect evaporators are common in the recovery of black liquor in the kraft process for making wood pulp.
The objective of this experiment is to study spray dryers and spray drying operation. In industry, spray drying is used to separate liquid from solid. In a spray dryer, a liquid solution is dispersed into a stream of hot gas in the form of a mist of fine droplets. Moisture is rapidly vaporized from droplets and leaves residue particles of dry solid. These are then separated from the gas stream by the separator. In this experiment, dry milk was used for dry solid. The milk solution was used as liquid feed and the performance of spray dryer is observed.
Size reduction is a process of reducing large solid unit masses into small unit masses, coarse particles or fine particles.
Size reduction process is also termed as
Comminution/Diminution/Pulverizations.
Solid pieces of food is reduced by the
application of grinding, compression
or impact forces.
In many food processes it is frequently
necessary to reduce the size of solid
materials for different purposes
introduction, theory of drying, applications of drying, construction & working about fluidised bed dryer,use of tray dryer,construction about vacuum dryer, construction & working about drum dryer, construction about spray dryer
Pharmaceutical Dryers. Dryers are used in a variety of industries, such as the food processing, pharmaceutical, paper, pollution control and agricultural sectors. ... Direct dryers convectively heat a product through direct contact with heated air, gas or a combusted gas product.
What is a Rapid Dryer, And How Does It Work? What is Its Purpose?VJInstruments
A rapid dryer (also known as a fbd fluid bed dryer) is a piece of process equipment that is widely used to decrease the moisture content of a variety of products such as food, pharmaceuticals, and chemical powders and granules, among others.
size reduction,laws involved in size reduction ,application & millsM Swetha
size reduction basic principles,laws&machanism of size reduction with all mills .I gave a note on size separation .it is very useful for the teaching staff &students of B.pharmacy
Single and multiple effective evaporator (mee)Sumer Pankaj
A multiple-effect evaporator, as defined in chemical engineering, is an apparatus for efficiently using the heat from steam to evaporate water.[1] In a multiple-effect evaporator, water is boiled in a sequence of vessels, each held at a lower pressure than the last. Because the boiling temperature of water decreases as pressure decreases, the vapor boiled off in one vessel can be used to heat the next, and only the first vessel (at the highest pressure) requires an external source of heat. While in theory, evaporators may be built with an arbitrarily large number of stages, evaporators with more than four stages are rarely practical except in systems where the liquor is the desired product such as in chemical recovery systems where up to seven effects are used.
The multiple-effect evaporator was invented by an African-American inventor and engineer Norbert Rillieux. Although he may have designed the apparatus during the 1820s and constructed a prototype in 1834, he did not build the first industrially practical evaporator until 1845. Originally designed for concentrating sugar in sugar cane juice, it has since become widely used in all industrial applications where large volumes of water must be evaporated, such as salt production and water desalination.
Multiple effect evaporation commonly uses sensible heat in the condensate to preheat liquor to be flashed. In practice the design liquid flow paths can be somewhat complicated in order to extract the most recoverable heat and to obtain the highest evaporation rates from the equipment.
Multiple-effect evaporation plants in sugar beet factories have up to eight effects. Six effect evaporators are common in the recovery of black liquor in the kraft process for making wood pulp.
The objective of this experiment is to study spray dryers and spray drying operation. In industry, spray drying is used to separate liquid from solid. In a spray dryer, a liquid solution is dispersed into a stream of hot gas in the form of a mist of fine droplets. Moisture is rapidly vaporized from droplets and leaves residue particles of dry solid. These are then separated from the gas stream by the separator. In this experiment, dry milk was used for dry solid. The milk solution was used as liquid feed and the performance of spray dryer is observed.
Size reduction is a process of reducing large solid unit masses into small unit masses, coarse particles or fine particles.
Size reduction process is also termed as
Comminution/Diminution/Pulverizations.
Solid pieces of food is reduced by the
application of grinding, compression
or impact forces.
In many food processes it is frequently
necessary to reduce the size of solid
materials for different purposes
introduction, theory of drying, applications of drying, construction & working about fluidised bed dryer,use of tray dryer,construction about vacuum dryer, construction & working about drum dryer, construction about spray dryer
Pharmaceutical Dryers. Dryers are used in a variety of industries, such as the food processing, pharmaceutical, paper, pollution control and agricultural sectors. ... Direct dryers convectively heat a product through direct contact with heated air, gas or a combusted gas product.
What is a Rapid Dryer, And How Does It Work? What is Its Purpose?VJInstruments
A rapid dryer (also known as a fbd fluid bed dryer) is a piece of process equipment that is widely used to decrease the moisture content of a variety of products such as food, pharmaceuticals, and chemical powders and granules, among others.
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2. CONTENTS
INTRODUCTION
WORKING PRINCIPLE
FACTORS GOVERNING DRYING SPEED
MECHANICAL FORCES
MECHANISM OF WATER EVAPORATION
FACTORS AFFECTING RESIDENCE TIME
BLOCK DIAGRAM
CONSTRUCTION
TYPES
ADVANTAGES & DISADVANTAGES
APPLICATIONS
LIMITATIONS
EXPECTED NEW DEVELOPMENTS
REFERENCES
3. Introduction
• Also known as “flash drying”
• Continuous convective process
• Indirect heating or direct firing
• Co-current flow
• High convective heat & mass transfer coeffient
• High drying rates & product quality
• Air velocity> free fall velocity of largest product
• Granular, crystalline, paste, powder, cake, flakes, gels,
slurry
• Extension of fluidized bed drying
• Feeder- screw feeder, rotary valve, vibrating feeder,
mixer
• Processes- pre-drying, drying & dehydration
4. SPECIFICATIONS
Dried product size range= (10- 500)µm
Short residence time = (0.5-10)sec
Dried product(m.c) = <=12%
Throughput= few kg/hr to several 100s tons/hr
Inlet air temp= (180-300˚c)
Incoming feed moisture= <40%(wb)
Bag filter pressure=(0.4- 0.6)Mpa
5. COMPONENTS
• Heater
• Wet material feeder
• Venturi
• Drying chamber
• Air Seperator(cyclone)
• Exhaust fan
• Dried product collector
• Dust seperator
ex-( bag filters, electrostatic precipitators, wet scrubbers & fabric filters)
9. MECHANISM OF WATER EVAPORATION
1. Convection heat transfer
2. Heat conduction
3. Mass transfer (granuels/ particles to surface)
4. Mass transfer(surface to drying air)
10. FACTORS GOVERNING THE SPEED OF DRYING
1. Moisture Dispersion
2. Temperature Differential
3. Agitation
4. Particle Structure
5. Particle Size
11. RESIDENCE TIME CAN BE ALTERED BY-
Increasing the flash tube length
Increasing holdup times in the product collection cyclone(s)
Adding cyclones in series.
20. ADVANTAGES OF PNEUMATIC DRYING
• Short contact time and parallel flow make possible to dry thermolabile
materials
• The dryer is easy to control.
• The low material content in the dryer enables equilibrium conditions to
be reached very quickly.
• Due to small no. of moving parts ,the maintenance cost is low.
• Handle high flow rates.
21. DISADVANTAGES
• High efficiency gas cleaning system is required
• For lumped materials difficult to disperse
• There is a risk of fire and explosion
• Dryer cannot be used for toxic materials
• Less suitable for removal of internal moisture .
22. APPLICATIONS
• Wheat sugar , gelatinized starch
• Powders like potato starch and corn starch
• Salt
• Flours
• Bread crumps
23. (a) Corn gluten (b) caesin ( c) soup powder (d) vegetable protein ( e) spent tea (f) meat residues (g) bone meal
25. LIMITATIONS
loss of power to the dryer will cause the product to fall out of suspension
and build up in the dryer base & feed throat.
If product hardens under heat ,it will cause blockage and require
significant time to remove.
Due to relatively high velocities, the particle size may be reduced
(undesired) to attrition & impact.
High velocities also may contribute to pre- mature component wear if
system is not designated to inhibit it.
26. EXPECTED NEW DEVELOPMENTS IN
FLASH DRYERS
These developments are expected in the fields of: .
Increased efficiency by heat recovery
Applications of heat pumps in drying systems
Efficient combined processes (hurdle technology)
Development of models for overall systems (mechanical dewatering,
drying, heat recovery, powder collection, cooling stages)
27. REFERENCES
• Earle RL, unit operations in food processing, second edition, pergamon press, 1983, pg-85-89
• Ramaswamy H, Marcotte M, Food Processing Principles and Applications,
Taylor and francis, 2009, Pg- 233- 302
• Kemp, I.C. and Oakley, D.E., Simulation and scale-up of pneumatic conveying and cascading
rotary dryers, Drying Technology, 15(6–8),1699–1710, 1997
• Mindziul, Z. and Kmiec, A., Modelling gas–solid flow in a pneumatic-flash dryer, Drying
Technology, 15(6–8), 1711–1720, 1997
• Thorpe, G.R., Pneumatic Conveying Driers, Chemical Industry Development, Incorporating
CP&E, 1975, pp. 13–19
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