Vegetable Oil Refineries

VEGETABLE OIL REFINING PLANT

The vegetable oil refining process is essential to ensure that oils extracted from various oil-bearing seeds, grains, and nuts are safe, palatable, and suitable for consumption. Common sources include rice bran, cottonseed, palm, peanut, soybean, sunflower, rapeseed, and specialty oils from almonds, cashews, and shea. The refining process removes impurities that affect the quality and usability of the oils.

Impurities in Vegetable Oils

Vegetable oils often contain several types of impurities, including:

• Moisture: Excess water that can promote spoilage.
• Solids: Undesirable particles that can cause cloudiness and affect flavor.
• Gums (Lecithins): Phospholipids that can make oils viscous and affect stability.
• Free Fatty Acids (FFAs): Result from oil breakdown, affecting flavor and shelf life.
• Waxes: Can cause cloudiness and stability issues.
• Metal Compounds: From the oil extraction process, such as sodium, potassium, magnesium, and calcium.

To enhance the oil's quality, the refining process consists of several key steps: degumming, neutralizing, bleaching, deodorizing, and dewaxing.

1. Degumming

Degumming removes hydratable and non-hydratable gums to improve oil quality.

• Water Degumming: Hydratable gums are removed by adding water to the oil, which causes the gums to hydrate and separate. The gums can then be dried and used to produce lecithin.
• Acid Degumming: Non-hydratable gums are treated with an acid to promote separation from the oil.

2. Neutralizing

Neutralization removes free fatty acids, which can lead to off-flavors and reduced shelf life.

• The oil is treated with caustic soda (NaOH), which reacts with the FFAs to form soap. This soap is then separated from the oil.

Some facilities may opt for Physical Refining, where FFAs are evaporated under high temperature and vacuum, eliminating the need for caustic treatment and soap production

3. Bleaching

Bleaching aims to remove color pigments and improve oil appearance.

• The oil is treated with bleaching clays that adsorb pigments.
• After contact, the clays are filtered out, resulting in a clean, bleached oil ready for further processing.

4. Deodorizing

Deodorization eliminates odor-causing substances, enhancing the oil's flavor profile.

• The oil undergoes steam distillation at high temperatures and under vacuum.
• This process effectively removes volatile compounds responsible for undesirable odors, resulting in a bland, tasteless oil.

5. Dewaxing

Dewaxing is performed to remove waxes, particularly from oils prone to crystallization at low temperatures.

• Oils are chilled to solidify waxes, which are then filtered out.
• Winterization may also be used to separate saturated fats from unsaturated fats, enhancing oil clarity.

Fatty Acid Recovery

During deodorization or FFA stripping, evaporated fatty acids are condensed and recovered.

• This process uses high vacuum conditions to lower boiling points, preventing oxidation.
• Recovered fatty acids can be reused or sold as a by-product, enhancing the refinery’s economic viability.

Palm Kernel Section

The press cake from the screw press is a compact mass with high moisture content. It is fed into a paddle screw conveyor, which helps break up the compact mass. The loosened mixture of fruits and nuts is then sent to a vertical separating column, where fibers are separated from the upward airflow through a cyclone separator and collected at the bottom. The fibers obtained are reused as boiler fuel.

The heavier nuts drop to the bottom of the separating column and are directed to a rotating nut polishing drum. The polishing drum removes fiber residues attached to the nuts. The polished nuts exiting the polishing drum are taken for kernel recovery.

Polished nuts from the nut recovery section are cracked using a nut cracker/ripper mill. Winnowing technology is employed to separate dust, small shell particles, and dirt from the cracked mixture.

The remaining mixture of kernel and shell is fed into a water mixture tank and pumped using a hydrocyclone pump, where kernel and shell separation occurs. The separated kernels are sent to drying silos, and the dried kernels are bagged or taken for further extraction processing.

The palm kernel and other by-products like empty fruit bunches and palm press fibers can be utilized for various applications such as animal feed, energy production, and as organic fertilizers.