Bio-diesel (methyl ester) is a renewable source of energy.
The initial products are vegetable oils, old salad oils, animal fats, and
fatty acids. Apart from bio-diesel, other recoverable products are produced,
such as glycerine. Bio-diesel is produced above all from rape (brassica napus
oleifera). The seeds are cleaned, pressed, and then the oil is extracted.
Subsequently, the oil that mainly consists of triglycerides, is de-slimed,
deacidified, and dehydrated. The subsequent transesterification process is
based on the chemical reaction of the triglycerides with methanol into methyl
ester and glycerine in the presence of alkaline catalysts which are added to
the methanol. Then, methyl ester and glycerine are separated (decanter).
The phase rich in methyl ester also contains methanol, glycerine, and small
quantities of catalyst and low-volatility components. The methyl ester is
dehydrated in the stripping column, i. e. the water-soluble components are
"scrubbed off" or "stripped".
The phase rich in glycerine is collected in a
tank together with the scrubbing water, and is concentrated in an evaporator.
Depending on the intended use, the raw glycerine is then cleaned and bleached.
Methanol and water are separated in a rectification column. The
water-free methanol recycled to the process.
GEA Wiegand plants are used in the following process steps:
- Methyl ester dehydration (falling film evaporator, stripping column)
- Methanol separation (rectification column)
- Concentration of glycerine water (falling film, natural circulation, forced
circulation evaporator)
- Glycerine distillation (falling film evaporator)
Methyl ester (bio-diesel) can be deodorized and decolorized in a fine vacuum
distillation system, especially if old oils or animal fats are used as initial
substance.