Biodiesel Processing
Biodiesel production begins with pressing the crop, which yields a liquid oil fraction to be converted and a first by-product, oil cake, used as cattle feed. Vegetable oils are extracted from oil seeds by mechanically pressing or extraction with a solvent, like hexane, the latter technology resulting in higher yields.
Vegetable oils can be used directly as diesel engine fuels, but this requires engine modification because some of their properties are less advantageous for this application. Two major problems are their very high viscosity and poor thermal and hydrolytic stability. They also have less favourable ignition qualities.
After filtering the vegetable oil, esterification transform the large branched molecule structure of the oils into smaller, straight chained molecules similar to the standard diesel hydrocarbons.
Three basic routes to producing biodiesel from oils can be distinguished:
- Base catalyzed trans-esterification of the oil,
2. Direct acid catalyzed trans-esterification of the oil,
3. Conversion of the oil to its fatty acids and then to biodiesel. (biodiesel.org)
Most of the biodiesel produced today is done with the base catalyzed reaction for several reasons:
- It is a low temperature and pressure process,
- It has a high yield (98%) with minimal side reactions and reaction time,
- It is a direct conversion to biodiesel with no intermediate compounds.
This process takes place in a simple reactor system at low temperature (range 50-66 ºC) and pressure (around 1.4 bars). The first step in conversion process is the mixing of methanol and the catalyst, which is usually sodium hydroxide (caustic soda) or potassium hydroxide (potash). Excess methanol is added to ensure the total conversion of the triglycerides into esters. The catalyst/methanol mixture is fed into a closed reactor vessel, which prevents the loss of alcohol, then the vegetable oil is added to the reactor. The reaction mixture is left to settle in the vessel for 1 to 8 hours.
After being separated from the glycerin, the methyl esters are purified. By means of a washing process, residual catalyst and soaps are removed. The purity of the esters produced in this way amounts to about 98%. This can be improved further by distillation. The end product is an amber-yellow colored liquid with a strongly reduced viscosity.
As an indication regarding the proportions in the reaction, 100 units of fat or oil (e.g. rapeseed oil) react with 10 units of a short chain alcohol in the presence of a catalyst (usually sodium or potassium hydroxide) to produce 10 units of glycerin and 100 units of biodiesel.
Quality Control
To ensure our Biodiesel quality could fulfill international standard like EN14214 for Europe and ASTM6751 for US
ZRS Biodiesel laboratory have strict quality monitor for the production process by collecting and testing the sample to control quality.
Apart from monitoring our product and production process, we evaluate all product and raw materials’ quality. Our laboratory provides commodity chemicals, petrochemical, bio-fuel, waste water, oil product and grease analysis testing services, helping you understand your supply chain and the potential operating risk.
