deodorization

DEODORIZATION TECHNIQUES

BY

GURUPRASAD VENKATKRISHNA RAO

Refining of Edible oil

Deodourization

• Deodourization is a vaccum stripping process in which neutral oil is treated to remove malodorous compound ( volatile compound in general) to obtain fully refined oil.

• This process is similar to steam refining of neutral oil where along with malodorous compound even fatty acids are also removed.The above process is then known as steam deodourization.

Deodorization Process

• Deodorization is actually a combination of Two different effects on oil

1) Stripping 2) Temperature effect

Deodorization Technology

• Deodorization is a multi-step process comprising de-aeration, heating, deodorization- deacidification, and cooling of the oil.

• General overview of Deodorization plant can be shown as

Deaeration

• Carried out in order to avoid oxidation and hence avoid risk of polymerization.

• Oil is heated to 800c and sprayed in a tank, which is kept at a pressure below 50 mbar.

• Lower the pressure lower is residual air left in the oil.

Heating and Cooling

• The subsequent heating of the oil is usually accomplished in two stages.

• In the first stage, the incoming oil is heated counter currently in an oil-oil heat exchanger (economizer), with the finished oil leaving the deodorizer.

• Finally, the oil is heated under reduced pressure to the final deodorization temperature with a high-temperature source.

Heating and Cooling

• Source of Heating in the final stages are1) High-pressure steam boilers2) Thermal Oil Heaters3) Downtherm A (diphenyl/diphenyloxide)

• The net heating energy required for a deodorization system can be calculated as:

H= [ O.c.(T2-T1).fL.fR ]

Heating and Cooling

Heating and Cooling

• In industrial practice, heat recovery has become an important factor because it minimizes the cost of additional heating of the oil to the deodorization temperature.

• For above purpose Heat exchangers have been evolved and they are classified as follows

1) External Heat Exchanger 2) Internal Heat Exchanger

Heating and Cooling

• Heat recovery can be done directly by exchange of heat between the two oil stream at different stream ( e.g.. Bleached oil Vs Deodorized oil)flowing in counter current direction through the exchangers or indirectly by steam production.

Heating and Cooling

• Final cooling of the oil is usually conducted under reduced pressure to prevent the possible production of degradation by products.

• As a result of the technological complexity and for cost reasons, cooling under vacuum is usually applied only in a large capacity deodorizer. Small capacity plants often make use of external oil–oil heat-exchanging devices.

Steam Stripping

• Amount of stripping agent is proportional to its molecular weight.

• Hence steam is being used for stripping.• But N2 is being experimented to be used as stripping

agent.• studies have indicated that color, residual FFA,

oxidative stability, as well as the formation of trans-fatty acids and the stripping of tocopherols are not affected by the nature of the stripping agent.

• Stripping agent must be dry and free from oxygen.

Steam Stripping

• Deodorization only occurs at the vapor-liquid contact zone where the lowest operating pressure exists.

• Hence there are different Deodorizer design which attempt to provide the best contact between the gas phase and the oil phase by creating a large contact surface, together with an optimal sparge steam distribution.

Steam Stripping

Vapor scrubbing system

• Composition of vapor phase- Volatile components (FFA, odor components)- Stripping steam- Non condensable gases (air,…).• The volatile substances are condensed by

creating an intimate contact between the vapor and the fatty acid distillate circulating in the scrubber.

Vapor scrubbing system

• Condensation of vapour phase is achieved by series of sprayers or packed bed in vacuum

duct. Installation of demister at the top. improved scrubbers operating at two

different temperatures (so-called dual condensation principle) have been introduced.

Vapor scrubbing system

Vacuum systems

• Combination of steam jet ejectors (boosters), vapor condensers and mechanical (liquid-ring) vacuum pump

• High motive steam consumption (60-85% of total steam).

COMMERCIAL DEODORIZER SYSTEMS

• Batch Deodorization• Semicontinuous Deodorization• Continuous Deodorization• dual-temperature Deodourization

Batch Deodorization

• Batch deodorization is especially suitable for small capacities (<50 ton/day), irregular production, or in processing small batches of different oils that demand minimum cross-contamination.

• Batch deodorizers mainly consist of a single-shell welded vertical cylindrical vessel

Batch Deodorization

• Advantages : very simple construction and low capital cost

• Disadvantage: Low capacities high operating costs (high steam consumption, very low

heat recovery), relatively long processing times (sometimes up to 8 h)

Semi Continous Deoderisation

• Suitable for Large capacity.• Used when frequent feedstock changes of oil

sensitive to cross contamination.• Allows efficient Heat Recovery • Steam produced in the bottom deodorized oil-

cooling section is sent in a closed thermosiphon loop to the top bleached oil-heating section to heat the incoming oil.

• Main advantage is shorter hold up time.

Continuous Deodorization

• Several configuration of continous Deoderisation are

horizontal vesselsvertical tray-type deodorizers packed columns

Horizontal Vessels

Continuous Deodorization

• Advantages :Low utilities cost (high heat recovery)Short residence timeExcellent control of all parameters

• Disadvantage: Contamination during feedstock change

Improved Deodorization Technology

• Dual temperature deodorization- Deodorization at two different temperatures• Integration of packed columns- for specific application only- efficient stripping - lower steam consumption• Dual condensation- Condensation at two different temperatures- Higher added value of deodorizer distillate (physical refining)• Dry-Ice condensing- Lower deodorizing pressure (1 mbar)- Allows milder refining (lower temp)

REFERENCE

• Various Search results on www.google.com• Lipid Library• Oils and Fats by Alton Bailey• Chemistry and Technology of Oils and Fats by

M.M Chakrabarthy.• Dr A V JOSHI (ICT) & Dr AMIT PRATAP (ICT) for

giving advise.

THANK YOU