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Refining the Pure Oil
Filtered Jatropha Oil à De-gumming à Neutralization à Dewaxing à Bleaching & Deodorizing
The main aim of refining is to remove impurities such as colloidal matter, free fatty acid, colouring and other undesirable constituents, thus making the oil more resistant to deterioration during storage. The general method of refining used for edible oils is applicable to Jatropha oil.
The main processes involved in Jatropha oil refining are:
- Degumming
- Neutralization
- Dewaxing
- Bleaching & Deodorizing
The bleaching and deodorizing steps are optional when the oil is used to produce biodiesel.
Degumming
Gums in edible vegetable oil must be removed to avoid color and taste reversion during subsequent refining steps. The removal of phospholipids (referred to as ‘degumming’) is the first step in the process of refining Jatropha oil.
The process usually involves a single-stage phosphoric acid treatment and a single-stage hot water treatment, followed by continuous removal of the hydrated gums in a de-gumming centrifuge.
Neutralization
Neutralization is a reaction between acids and bases to produce salts.
All crude vegetable oils prepared for human consumption are neutralized to remove free fatty acids and latex-like matter and then washed to reduce the soap content of neutral oil. Neutralization produces a more stable product.
Effective neutralization results in enhanced effectiveness of subsequent steps, such as bleaching, deodorizing and furthermore, results in high yields of a quality product. Neutralization also aids in the removal of phosphatides, removal of free fatty acids, mineral and color bodies.
Neutralization can be done in one of two ways:
(a) Alkali (Chemical)
(b) Steam Stripping (Physical).
In the Alkali/Chemical method, caustic soda (alkali) is mixed in the proper amounts with Jatropha oil at 66-77oC and the aqueous solution is removed, leaving the neutral oil behind. Some plants use sodium carbonate or potassium hydroxide for alkali. The alkali reacts with the free fatty acids to form soap, which is an important byproduct. Processors remove the traces of soap and moisture through water washing and vacuum drying. In some cases, centrifuges separate neutral oil from soap-stock and wash water.
Steam stripping is done under vacuum, to remove moisture, free fatty acids, odour elements, and other impurities from the oil. As it is performed under vacuum conditions, the oil can be kept at a low temperature, preserving its chemical structure by not subjecting it to temperatures in which undesirable dehydration reactions can occur.
De-waxing
De-waxing refers to the removal of high melting point waxes extracted from Jatropha oil. While the wax does not negatively affect the functionality of products the presence of wax does affect the appearance of product. The de-waxing process that has proved most effective & efficient is to reduce the temperature down to 23-24oCelsius within cooling tanks known as crystallizers, and then filtering out the wax crystals either in a rotary drum vacuum filter or in filter presses made out of polypropylene plate & frame filters.
Bleaching & Deodorizing
Bleaching
The appearance of dark colour oil can be lightened by bleaching. Bleaching, the process for removing these pigments from fats and oils occurs when 1% bleaching clay is added to oil under vacuum at approximately 107-110oCelsius. The oil is later agitated and filtered to remove the clay. The high temperature drives moisture from the clay to absorb the pigments. Some systems also use activated carbon in the place of clay.
A high-tech bleaching plant may be equipped with hermetic leaf filters and operates under vacuum to prevent oil oxidation. The oil is cold-mixed with metered quantities of bleaching earth and/or other bleaching agents, heated to the correct temperature and pumped to a bleaching chamber operating under vacuum where an adequate retention time is provided to ensure effective bleaching. The oil/earth slurry is further pumped through hermetic leaf filters operating in sequence to enable continuous bleached oil (filtrate) discharge.
Deodorization
Volatile compounds present in the oil that produce bad odours can be eliminated through the process of deodorization.
Deodorization represents the last major processing step in refining of Jatropha oil. It separates the impurities and creates three groups of compounds:
1. Saponifiable compounds: free fatty acids, partial glycerides, esters, and gummy constituents,
2. Unsaponifiable compounds: parafinic hydrocarbons, olefinic and polyolefinic materials, sterols, triterpenic alcohols, and
3. Oxidative reaction products: aldehydes, ketones & peroxides.
This highly specialized process uses a type of steam distillation under high vacuum to remove objectionable volatile components. The bleached oil pumps through a de-aerator where the pretreated oil is de-gassed. This de-aerated oil passes through a heat exchanger where the oil is heated by exchanging the heat of the deodorized oil. Deodorization further heats the oil to the stripping temperature in a pre-heater. The oil then flows to a flash chamber and thereafter to an oil distributor inside falling film deodorizer. The oil descends counter-current to the stripping steam in the form of a very thin film and becomes completely deodorized. The process condenses cools and stores the distilled fatty acids.
The deodorized oil is pumped through a heat exchanger to the polishing filter and thereafter passes through a cooler.
Related Links
- Introduction to the Biofuel Industry
- Properties of Jatropha
- Characteristics of Jatropha
- Extracting Jatropha Oil
- Pre-extraction of Jatropha Oil
- Extraction of Oil from Jatropha Seed
- Filtration & Purification of Jatropha Oil
- Clarification of the Oil
- Getting Clean Jatropha Oil
- Refining the pure Oil
- Typical Processes & Equipments for Jatropha Oil Refinery Plants
- Removing the toxins from the Meal
- Uses of Jatropha Meal
- Properties of Jatropha Oil
- Global Biodiesel Production and Capacity
- Global Market View on Jatropha
- Strategies for Financing
- Status of Jatropha in Asia
- Status of Jatropha in Europe
- Status of Jatropha in Africa
- Status of Jatropha in South America
- Status of Jatropha in North America
- Status of Jatropha Oil Production in India
- Genetic Engineering in Jatropha
- Status of Genetic Engineering of Jatropha in India
- Present Market Scenario for Jatropha
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