The Biodiesel Manufacturing Process

There are three basic process components in the production of biodiesel:

  1. Oil seed crushing
  2. Crude oil degumming / neutralizing, also called partial refining
  3. Oil transesterification, which is the actual biodiesel process

OILSEED CRUSHING [BASIC PROCESS]

An oil mill is designed to efficiently, mechanically extract by full pressing the oil from canola. The efficiency and performance of oil extraction with screw presses is highly dependent on the condition of the raw material.

The whole canola seed is first cleaned and then pre-heated in a conditioner to allow the seeds to be flaked in preparation for further cooking. The flaking helps in the rupturing of the oil cells. It improves the efficiencies in the next steps of the crushing process, and if available, the solvent extraction. The flaked seed is then fed to a cooker where moisture levels of the seed are reduced and temperature increased in preparation for pressing.

Inside the press a specially designed worm configuration compresses the seeds allowing the controlled release of oil. Oil is allowed to drain from the bottom of the press while the cake is conveyed from the discharge end of the press. The crude oil contains solids that are removed using a vibrating screen or a horizontal centrifuge (decanter). Cake from the discharge end of the press goes through a cake breaker and cake cooler before being conveyed to storage.

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CRUDE OIL DEGUMMING / NEUTRALIZING [BASIC PROCESS]

Crude oil obtained from the canola seed pressing operation contains a number of impurities that have to be removed before the transesterification (biodiesel) process. The impurities are moisture, gums, free fatty-acids and soaps.

Typically the continuous steps include acid conditioning, neutralizing, washing and drying. For human food consumption the oil would further be bleached and deodorized.

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ACID CONDITIONING

The crude oil feedstock enters the plant at a controlled rate and is heated by processed oil in an economizer (heat exchanger) or by steam. Phosphoric acid is injected at a controlled rate and intensively contacted with the oil in an acid conditioning mixer, thereby precipitating gums, metal compounds and other impurities. These materials are later removed together with the soapstock formed during neutralization. In some cases an additional reaction time in an acid retention mixer is required.

The acid conditioned and / or heated oil is reacted with lye / water solution injected at a controlled rate in a caustic soda mixer, followed by a short retention in a caustic soda retention mixer. The lye neutralizes the free fatty acids and the excess of mineral acid in the oil forming soapstock, which isremoved together with excess caustic solution and other impurities in a soapstock separator (i.e. vertical axis centrifuge).

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WATER WASHING

The neutralized oil contains small amounts of residual soap, which must be minimized before further processing. The oil is therefore contacted with soft hot water in a high-speed wash mixer. This way, almost all soap is dissolved in the water phase and removed from the oil in the wash separator (i.e. vertical axis centrifuge).

In some cases it is desirable to eliminate also the last traces of soap, which can be done by dosing a small quantity of citric acid solution into the oil after the washing centrifuge.

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DRYING

The oil from the washing stage is sprayed into a dryer where residual moisture is reduced to a minimum. The dried oil is then finally cooled to a temperature adequate for storage.

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BIODIESEL [BASIC PROCESS]

The principles of the transesterification process are relatively simple and have been known and applied for many decades. The basic process for any catalyst induced transesterification process involves migrating ester chains from a triglyceride (fat) molecule and reconnecting the ester chains with a methanol or ethanol molecule, thus creating a methyl ester molecule. It is this methyl ester molecule that is Biodiesel. Various chemical and mechanical actions work together to make the transesterification process occur. The catalyst used is a strong base, either sodium or potassium. Once the ester chains are broken off, the left over glycerin molecule is a byproduct of the reaction.

Ester is a chemical substance of two or more different chemically bonded chemical elements (e.g. water H2O) with a group of atoms within a molecule (e.g. carbon, C)

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