The document discusses various types of machinery used in tea production, including withering troughs, rolling machines, CTC machines, CTC rollers, and dryers. It provides details on the principles and design of withering troughs, which are used to control the withering of fresh tea leaves by managing temperature, humidity, and air flow. Tea rolling machines and CTC machines apply different processes to further prepare the leaves for drying. The document also examines freeze dryers and spray dryers as two common types of industrial dryers used in tea processing.

1. Contents:
Withering trough: Principles of withering trough,
trough design and analysis
Rolling Machine: principles and mechanism
Totorvane: Principles of Totorvane
CTC Machine: Principles of CTC machine, Machine
specification
CTC Roller: Sizes, Shapes, Speed, Capacity, Power
Requitement
Dryer Machine: Types of dryer machine

2. Withering trough
It is a long, narrow open container for keeping fresh tea leaf for withering
towards made tea production.
Withering process/principles:
The moment a tea leaf is plucked from the tea plant, it begins to wilt
naturally, a process we call withering. But once the tea leaves reach the
processing facility, this process is controlled by the tea producer. The
purpose of a controlled wither is to prepare the leaves for further
processing by reducing their moisture content and to allow for the
development of aroma and flavor compounds in the leaves. Controlling the
withering process means closely monitoring humidity, temperature and
air-flow over time where withering trough is used as an important tool to
perform this. A controlled wither can occur indoors in troughs with forced
air. The air may be heated to speed up the process if necessary. Great care is
also given to the density of the withering leaves to ensure that they wither
evenly. The withering process is complete once the tea leaves have achieved
a desired percentage of water-loss.

3. Size of Withering Trough
WITHERING TROUGHS are generally installed in the first floor
of the factory. Green leaf is spread over a wire mesh which is
fitted on plenum chamber. Height of the plenum chamber is 0.6-
.76 m (2-2.5 feet) and leaf is loaded over the mesh to.20-.23 m (8-
9″) height or 8-9 kg/sq. m. (2.5-3 kg/sq. ft.) of the withering
trough. Size of the withering trough is 30.5 m (100′) long 1.8 m
(6′) wider or 22.9 m (75′) long and 1.8 m (6′) wide. Better
withering can be achieved with smaller trough 22.9 X 1.8 m (75′ x
6′). The trough should be fitted with a suitable fan to deliver the
required quantity of air as per the size of the trough. To achieve
proper withering the fan has to deliver 45 CFM air for every one
square foot of trough area. For artificial withering hot air from
the drier room is bulked with outside air and used. Fans are
arranged in such a way that they can draw hot air from the drier
and cool air from the atmosphere

4. Tea rolling machine
A Tea Roller Machine: is a roller for tea mashing/rolling consists
of three parts- the table, the hood and the pressure cap. Rotation
of the machine is achieved through three crankshafts attached to
the table. The level gear mechanism transmits power to one of
the crankshafts at a time, while the other two rotate freely on
their bearings and play an auxiliary role. The pressure cap applies
pressure to the leaf mass during rolling, imparting the proper
twisting and brushing action. It is the pressure applied during
orthodox rolling that causes the extraction of sap and imparts
twist to the leaf. In some kinds of rolling tables, both vertical and
lateral pressures may be applied. Vertical pressure is applied with
the help of pressure caps, whereas lateral pressure is applied by a
cone fitted in the middle of the table. This cone also causes
greater circulation of leaf than that provided by battens alone

5. CTC Machine
The CTC machine achieves the three actions of Crushing, Tearing and
Curling in the same machine at one go. Instead of working on large
volumes of leaf, the CTC takes a fast, thin, but steady stream of leaf to
pave the way to continuous processing in place of the batch mode of
orthodox rollers. Leaf appearance, make, grade percentage, fibre
content, liquor and infusion depend on the cut obtained in the CTC
machine.
Two stainless steel rollers with circumferential as well as helical grooves
machined to certain definite specification, meshed closely, rotated in
opposite directions at a speed differential of 1:10. The diameter of the
roller varies between 20.3 cm (8 inch) – 20.95 cm (8.25 inch). The
larger 33 cm (13 inch) diameter CTC machines are gaining popularity
now days.

6. CTC-ROLLERS
CTC-ROLLERS consist of a main shaft on which the
segments are fixed by heat treatment on a mandrel
form. The diameter of the roller is generally 200 cm
(8″) and the latest senova rollers are of 330 cm (13″)
diameter. Depending on the capacity of the rollers,
their length varies from 600 (24″) to 910 cm (36″).
Generally two rollers are fixed horizontally and parallel
to each other and both rotate in opposite directions.
The ratio of speed between the low speed and high
speed rollers is 1:10 depending on the requirement of
leaf or dust grade.

7. Drying: Principles and Practice
Content:
o Fundamentals of drying
o Types of dryer
o Working principles, advantages, disadvantages and uses of
different types of dryer

8. Drying Fundamentals
 Removal of a liquid from a solid/semi-
solid/liquid to produce solid product by therm
al
energy input causing phase change (Sometim
es converts solid moisture into vapor by subli
mation eg. Freeze drying with application of h
eat.)
 To arrest enzymic reaction as well as oxidation
 To remove moisture from the leaf particles and to
produce a stable product with good keeping
quality.

9. Drying Fundamentals
It is essential for the preservation and
storage, reduction in cost of
transportation, etc.
 Most common and diverse operation
with over 100 types of dryers in
industrial use
 Competes with distillation as the most
energyintensive operation

10. How many types of dryer & why?
 Over 500 reported in literature studies; over 100 commercially
available
 Over 50,000 materials are dried commercially at rates of a few kg/hr
to 30 T/hr or more
 Drying times (residence times within drying chamber) can range
from 1/3 sec. to months
 Temperature and pressure range from below triple point to
super‐critical
 Numerous constraints on physical/chemical properties of feed as
well as dried product require a bewildering array of dryer designs
 Wide range of feeds (liquid, solid, semi‐solid, particulate, pasty;
sludge‐like; sticky etc); wide specs on dried product
 Environmental regulations demand

11. Different types of dryer
 Freeze dryer
 Belt conveyor/cabinet dryer
 Fluidized bed dryer
 Rotary dryer
 Spray dryer
 Tray dryer (batch)
 Tray dryer (continuous)
 Drum dryer
 Microwave

12. Freeze Drying
 What is freeze drying?
 What is the advantage of freeze drying?
 What is the disadvantage of freeze drying?

13. What is freeze drying?
 Freeze drying is a process used to dry extremely
heat – sensitive materials. It allows the drying ,
without excessive damage, of proteins, blood
products and even microorganisms, which retain a
small but significant viability.
 In this process the initial liquid solution or suspension
is frozen, the pressure above the frozen state is
reduced and the water removed by sublimation. Thus a
liquid –to-vapour transition takes place, but here three
states of matter involved: liquid to solid, then solid to
vapour

14. Limitations of the freeze drying
The depression of the freezing point caused by the presence of
dissolved solutes means that the solution must be cooled below the
normal freezing temperature for pure water (-10-30).
Sublimation can only occur at the frozen surface and is slow process
(1mm thickness of ice per hour). So, the surface area must therefore
be increased and he liquid thickness prior to freezing be reduced in
order to reduce the thickness of ice to be sublimated.
At low pressure large volumes of water vapour are produced which must
be removed to prevent the pressure rising above the triple point
pressure.
The dry material often needs to be sterile, and it must also be prevented
from regaining moisture prior to the final packaging.

15. Advantages of freeze drying
 Drying takes place at very low temperatures, so the
chemical decomposition, particularly hydrolysis is
minimized.
 The solution is frozen occupying the same volume as the
original solution, thus , the product is light and porous.
 The porous form of the product gives ready solubility.
 There is no concentration of solution prior to drying.
Hence, salts do not concentrate and denature proteins,
as occurs with other drying methods.
 As the process takes place under high vacuum there is
little contact with air, and oxidation is minimized.

16. Disadvantages of freeze drying
 There are two main disadvantages:
 The porosity, ready solubility and complete dryness
yield a very hygroscopic product. Unless products
are dried in their final container and sealed in situ,
packing require special conditions.
 The process is very slow and uses complicated plant,
which is very expensive. It is not a general method of
drying but limited to certain types of valuable
products.

17. Uses of freeze drying
The method is used for products that can not be dried
by any other heat method. These include biological
products, e.g. antibiotics, blood products, vaccines,
enzyme preparations and microbiological cultures.

18. Spray Dryer
What is Spray dryer?
What are the advantage, disadvantage and uses of Spray
dryer?

19. Spray dryer?
 In Spray dryer, the material to be dried is sprayed
as a fine mist into a hot-air chamber and falls to
the bottom as dry powder. The period of heating
is very brief and so nutritional and functional
damage are avoided. Dried powder consists of
hollow particles of low density; widely applied to
many foods and pharmaceuticals.
 Spray Dryers are relatively simple in operation
which accept feed in fluid state and convert it into
a dried particulate form by spraying the fluid into
a hot drying medium.

20. Characterization of spray dried
products
The products are uniform in appearance and have
characteristic shape, in the form of hollow spheres
with a small hole. This arises from the drying process,
since the droplet enters the hot air stream, and dries
on the outside to form an outer crust with liquid still
in the center. This liquid then vaporizes, the vapour
escaping by blowing a hole in the sphere.
This method of drying allows a dry product to retain
some properties of feed , e.g., a drop from an emulsion
dries with continuous phase on the outside. When
reconstituted, the emulsion is easily re- formed.

21. Advantages of the spray drying
process
 The droplets are small, giving a large surface area for heat
transfer, so that evaporation is very rapid. The actual
drying time of a droplet is only a fraction of a second,
and the overall time in the dryer is only a few seconds.
 Because evaporation is very rapid, the droplets do not
attain a high temperature, most of the heat being used as
latent heat of vaporization.
 The characteristic particle form gives the product a high
bulk density and, in turn, ready solubility.
 The powder will have a uniform and controllable
particle size.

22. Disadvantages
 The equipment is very bulky, connected to
accessories, fans, heaters is difficult.
Uses:
o Drying of any substance in solution or in suspension
form.
o It is most useful for drying of thermolabile
materials e.g. antibiotics.
o Suitable for large quantities solution.
o Suitable for both soluble and insoluble substances
e.g. citric acid, gelatin, starch.
o It can produce spherical particles in the respiratory
range e.g. dry powder inhalers.
o Drying of milk, soap and detergents which is
pharmaceutically related compounds.

23. Drum Dryer (Film Drying)
What is drum dryer?
What is the principle of drum dryer?
What are the advantage, disadvantage and uses of drum
dryer?

24. Drum dryer?
 Drum dryers are film dryers in which the product only comes
into direct contact with the necessary drying temperature for a
few seconds therefore ensuring particularly quick drying.
It consists of a drum of about 0, 75-1.5 m in diameter and
2-4 m in length, heated internally, usually by steam, and
rotated on its longitudinal axis.
Operation: The liquid is applied to the surface and spread
to a film, this may be done in various ways, but the simplest
method is that shown in the diagram, where the drum
dips into a feed pan. Drying rate is controlled by using a
suitable speed of rotation and the drum temperature.
The product is scraped from the surface of the drum by
means of a doctor knife.

25. Advantages of the drum dryer
The method gives rapid drying, the thin film
spread over a large area resulting in rapid heat
and mass transfer.
The equipment is compact, occupying much
less space than other dryers.
Heating time is short, being only a few seconds.
The drum can be enclosed in a vacuum jacket,
enabling the temperature of drying to be
reduced.
The product is obtained in flake form, which is
convenient for many purposes.

26.  The only disadvantage : is that operating
conditions are critical and it is necessary to
introduce careful control on feed rate, film
thickness, speed of drum rotation and drum
temperature.
 Uses:It can handle a variety of materials, either as
solutions or as suspensions e.g. starch products,
ferrous salts and suspensions of kaolin.

27. Tray Dryers
The tray dryer is the device used the drying of the wet
products of the crude drugs, chemicals, powders or the
granules etc. The simplest form of the dryer in this
category is a cabinet with a heater at the bottom that is
laboratory oven.
 The basic configuration of a tray dryer consists of a
feeder, heater, and collector.

28. Microwave Drying
In microwave drying, heat is generated by directly
transforming the electromagnetic energy into kinetic
molecular energy, thus the heat is generated deep
within the material to be dried.
Uses
Microwaves are used in the food industry for drying
potato chips, blanching vegetables, quick thawing
frozen fish, precooking chicken and bacon, and
elimination of molds in dry fruits and milk products. It
is also use in ceramics industries & pharmaceuticals to
drive off final traces of moisture.

29. Advantages of Microwave Drying
• It provides rapid drying at low temperature.
 The thermal efficiency is high, as the drier casing and the air
remain cool. Most of the microwave energy is absorbed by the
liquid in the wet material.
 The bed is stationary, avoiding the problems of dust and
attrition.
 Solute migration is reduced as there is uniform heating of the
wet mass.
 Equipment is highly efficient; all the requirements of product
and operator safety follow the GMP considerations.
 Granulation end-point can be detected by measuring the
residual microwave energy, ( it is rises sharply when there is little
solvent left to evaporate).

30. Difference between drying and
evaporation
 In drying processes, the main operation usually carried out on
solid materials, e.g. powders, or products while evaporation
mainly occur on liquid materials.
 Drying in most of the cases means the removal of relatively
small amounts of water from solids .Evaporation include the
removal of large amounts of water from solutions.
 In most cases, drying involves the removal of water at
temperatures below its boiling point, whereas evaporation
means the removal of water by boiling a solution.
 In drying , water is usually removed by circulating air over the
material in order to carry away the water vapour , while in
evaporation , water is removed from the material as pure water
vapour mixed with other gases.

31. Important content-
Working principles, uses, advantages and
disadvantages of freeze dryer, microwave
machine, tray dryer
Definition/ working principles, advantages
and uses of withering trough, and CTC
machine
Fundamental concept of drying, differences
between drying and evaporation

32. Thank You