Acknowledgement

We would like to express our special thanks of gratitude to FIL

industry limited especially to Mr Yaqoob Bhat (Assistant general
manager FIL industries Limited) who gave us the golden opportunity
to do this
wonderful project on Controlled Atmospheric Storage that helped us
to know about many new and informative things.

I cannot express enough thanks to Mr Naseer Lone for his continued

support and encouragement in completing this project.

Also we would like to thank our parents and friends who helped us lot
in finalizing this project within the limited frame.
TABLE OF CONTENT:
 FIL Industries Limited.
 Introduction to Controlled Atmosphere Storage.
 Construction of Chamber.
 Requirements of CA Storage.
 Working of CA Storage.
 Vapour Compression Cycle.
 Effects of variation in Carbon dioxide and Oxygen.
 Importance of CA Storage.
 Additional terms.
 Bibliography.
FIL Industries:
FIL, we work on the believe that the relationships are the core of success we
drive a culture of maintaining and sustaining relationships which are based on
providing the best customer experience. We go beyond customer satisfaction,
targeting every opportunity for creating customer delight. Our long term
association with our clients is testimony of our efforts and success in creating
lasting relationships.

The company today is known for maximizing customer satisfaction through

value addition/quality improvement in our entire product and service portfolio.
Our company is ISO and HACCP certified, further strengthening our resolve
and commitment to complete quality adherence.

As much as we value customer relationships, we also value our employee

relationship, and work towards creating a conductive environment for our
employees, which promotes excellence in the outputs pre-performance and
commitment levels. We, at FIL, create a work environment which fosters ethics
and integrity, while supporting the individual moral values. FIL behaves in
conducting business in a socially responsible manner that sustains and protects
the environment, and at the same time upload the principles of product standard
ships and values that take care of health and safety of employees, customers,
suppliers and overall community where ever we operate.
Introduction:
Controlled atmosphere storage is a system for holding produce in an atmosphere
that differs from normal air in respect of carbon dioxide and oxygen levels. It
works on the principle of constant monitoring and adjustment of the carbon
dioxide and oxygen levels within gas tight chambers. The mixture of gases
undergoes change due to metabolic activity of respiring commodities in the
chamber. The level of gases are therefore measured periodically and adjusted to
the predetermined levels by introduction of fresh nitrogen and/or removal of
carbon dioxide.

CAS is broadly divided into two types:

1. Static controlled atmosphere storage[SCAS]

2. Flushed controlled atmosphere storage[FCAS]
FCAS: is where the atmosphere is supplied from a flowing gas stream,
which purges the store continuously.
Construction of CA Chamber:
Storage chamber should be gas tight but in practice it is not possible to construct
or make a chamber absolutely gas tight.

General Specification for Construction:

Walls: generally bricks are not preferred for construction of walls instead
insulated puff panels with low thermal conductivity are used. Commonly
polyurethane foam is used as insulation.

Doors: of the chamber are mounted on sliding rails or may be mounted to open
vertically on overhead rails. Rubber gaskets are fitted around the door frames to
seal them properly.

Floor: made up of concrete along with insulation in order to prevent the entry
of moisture from the ground.
Checking of gas tightness of chamber (Pressure
test):
The checking of gas tightness is done when the chambers are first put into
service and then every year before the start of storage.

The most common method used to check air tightness of chamber, is based on
the study of pressure variation. All the openings, cavities, wires and joints
within the chamber are covered by silicon paint or plastic paints. After this, air
is blown into the chamber from outside. The drop in pressure level within the
chamber is measured with the help of manometer mounted on the wall of
chamber externally
.If there is slight decrease in pressure level then the chamber is considered gas
tight and fit for storage. In case there is abrupt decrease in pressure level, then a
soap solution is sprayed over the cavities, joints etc. to mark the points from
where leakage occurred .Then these points are sealed using silicon to make the
chamber gas tight.

Breather Bag:
Is present on the ceiling or outside the chamber and is used to prevent vacuum
build up in the sealed chamber. When the chamber goes into vacuum or low
pressure conditions, then air is sucked into the chamber through breather bags to
prevent contraction of chamber. The inlet of the bag should be situated before
the cooling coils of refrigeration unit in order to ensure the air from breather bag
is cooled before it enters the chamber.
Requirements of CA Storage:
Temperature: - The temperature to be maintained within the chamber depend
upon the commodity to be stored. For example temperature required for storing
cherry is 00C.

4 or more types of sensors/probes are used:-

1. Controller temperature
2. Product temperature
3. Supply temperature
4. Return temperature
5. Average temperature
Humidity: - The humidity is maintained at high levels, for example it is 90 to
95% for apples. This minimizes moisture loss from the produce thereby
preventing shrinkage of commodity. Humidifiers are used to maintain required
levels of humidity within the chamber.

Level of gases: - The level of O2 and CO2 are altered. Normal level of oxygen
within the atmosphere is 21% and that of CO2 is 0.03%. These normal ranges of
gases are altered within chambers. The level of O2 is maintained below or near
to 1% and that of CO2 are maintained between 3-5%.For example level of
oxygen and carbon dioxide maintained for cherry is 3-10% and 10-12%
respectively.
Working of CA Storage:
The working of CA storage is based on two aspects

1. Gaseous control

2. Temperature control

Gaseous Control:
Reduction of Oxygen Level (nitrogen generation):

The fastest reduction of oxygen level within the CA chamber is obtained by

flushing in nitrogen. Nitrogen generators are used to generate pure nitrogen.
Nitrogen generator consists of air compressor oil filters, activated carbon filters
and pressure sieving adsorption towers.

The air from the atmosphere is compressed within the compressor and is passed
onto carbon filter through oil filters where removal of oil (if present) occurs. In
activated carbon filter certain impurities are removed from the compressed air
by adsorption process. Then the air is passed onto PSA towers.PSA tower I and
II do not work simultaneously. The PSA technology allows nitrogen molecules
to be isolated from other molecules in the compressed air .The carbon molecular
sieves (CMS) which act as adsorbent in PSA towers retain all the molecules and
only allow nitrogen to pass through the outlet the nitrogen so generated is stored
in the storage tank where from it is flushed into chambers as per requirement.
The purity of nitrogen generated is 92-99% depending upon the generator.
Carbon dioxide Scrubbers:
When carbon dioxide level within the chamber exceeds a pre set level then
carbon dioxide scrubbers are used to reduce the level. Generally, activated
carbon is used for this purpose.
Gas Control System (ICA61)
These setups are present outside the chambers. Pneumatic pipes present within
the chambers are connected to these systems. These pipes collect samples of air
from the chamber after every one hour which are then analysed to check carbon
dioxide and oxygen levels. If the oxygen concentration exceeds the pre-set
value, Nitrogen is flushed in through solenoid valves.

Temperature Control:
Refrigerant:- is a substance or a mixture, usually a fluid, used in a heat pump
and refrigeration cycle. In most cycles it undergoes phase transition from a
liquid to a gas and back again. Many working fluids have been used for such
purposes.

Most common commercial used refrigerants are ammonia and Freon's.

Ammonia is a chemical consisting of one atom of nitrogen and three atoms of
hydrogen with a boiling point of -33.34o C.
Vapour Compression Cycle:
To maintain low levels of temperature within the CA chamber refrigerant is
used. A vapour compression cycle is employed to cool the storage chamber in
which working fluid (refrigerant) is pushed through the system which undergoes
phase change at different stages. The vapour compression cycle comprises of
four stages:

Compression: to compress the refrigerant, a reciprocating type compressor is

used which consists of piston cylinder arrangement. The refrigerant enters the
compressor as gas under low pressure and temperature. The refrigerant
undergoes compression which results in increase of pressure and temperature.

If the pressure inside the compressor exceeds a certain limit, water is supplied to
the condenser through the discharge tanks which are connected to the pumps. In
order to ensure compressor safety the following measures are taken into
consideration:-
1. Low suction safety.

2. Oil pressure safety.

3. High discharge safety.

Condensation: the high pressure, high temperature gas released from

compressor undergoes condensation inside the condenser. Here phase change
occurs and high pressure liquid is released.

The liquid ammonia then enters the high pressure tank.

Expansion:-the high pressure liquid refrigerant is pushed through expansion/

throttle valve which causes it to expand. Here abrupt reduction in pressure
occurs. This pressure reduction results in adiabatic evaporation of part of the
liquid refrigerant. The evaporation lowers the temperature of the liquid and
vapour refrigerant mixture to where it is colder than the temperature of the
chamber.

Evaporation:- the low temperature and pressure refrigerant enters the

evaporator, the refrigerant cools the atmosphere. The evaporator is attached to
fans that enhance heat transfer.
The refrigerant leaves the evaporator as low temperature and low pressure gas
and is taken into the low pressure tank, which is then further routed to the
compressor.

In CA stores defrosting pumps are provided, which are employed to defrost. For
defrosting following measures are used:

1. Takes water from the tanks and sprinkles it on the coils as a result ammonia
gets heated up.

2. Heating coils.

3. Hot gas.
Effects of variation in Carbon dioxide and Oxygen:
CA storage have also adverse effects, at oxygen levels below 1% , in the
absence of CO2, anaerobic conditions can prevail with the consequent
formation of alcohol and physiological changes. Also high CO2 and low oxygen
may cause abnormality in metabolism. The level of CO2 can cause damage to
fruit and vegetables, varies between cultivars of the same commodity.

The increased concentration of CO2 causes the browning of apples and hence
the rate of respiration decreases.
Importance of CA Storage:
1. A considerable decrease in respiration rate with a reduction in climacteric
maximum, accompanied by an expansion of pre-climacteric and post-
climacteric periods.
2. A reduction in the effect of ethylene on metabolism due to the interaction
of oxygen with ethylene, with a consequent delay of appearance of
senescence symptoms.
3. An extension in storage life, which can even be doubled, in as much as
the over ripening is delayed.
4. The preservation on an excellent firmness of flesh, due to effect of carbon
dioxide concentration on the enzymes acting on cellular membranes.
5. A high turgidity is achieved, such that fruits are more juicy and crisp.
6. A smaller loss of acidity, sugars and vitamin C, so that the nutritional and
sensory quality is higher.
7. A limited degradation of chlorophyll, with a consequent higher stability
of color.
8. Some physiological alterations such as chill injuries, spot, decay,
browning, water; core and scald are prevented or greatly limited.
9. Molds can be reduced in particular under low oxygen high carbon dioxide
atmospheres.
Additional Terms:
Super Heat: It refers to the number of degrees a vapour is above its saturation
temperature (boiling point) at a particular pressure.

Sub cooling: it is the condition where the liquid refrigerant is colder than the
minimum temperature (saturation temperature) required to keep it from boiling
and, hence, change the liquid to a gas phase.

Saturated Vapour: A vapour whose temperature and pressure are such that any
compression of its volume at constant temperature causes it to condense to
liquid at a rate sufficient to maintain a constant pressure.

Super Saturated Vapour: It refers to a vapour of a compound that has a higher

pressure than the vapour pressure of the compound.

Latent Heat: It is an energy released or absorbed by a body or a

thermodynamic system during a constant temperature process that is specified
in some way.
Bibliography:
 Wikipedia.com.
 Google.com.
 Post-harvest handling of fruits and vegetables Janet Bachmann.
 Islamic University of Science and Technology Awantipora.
 Fil industries limited.