7 Technologies for Conversion Bio-Lubricant …
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result of the high viscosity of castor oil. The ricinoleic acid is gadoleic acid with a
hydroxy group, so it has a strong polarity and strong affinity to water, which means
ricinoleic acid is easy to emulsify and difficult to demulsify. Although castor oil is
stable at the room temperature, the acid value will decrease after a long time storage,
normally below 10 mg KOH/g. Castor oil is easy to dehydrate and be oxidized under
high temperature, deepening the color, reducing the transparency, increasing the
viscosity as well as reducing oil quality. According to these features of the castor
oil, semi-continuous refining technics, the combination of batch caustic refining and
continuous desiccation, decoloration and deodorization (desolvation), is the best
choice, as it can prevent the emulsification and simplify the separation steps. What’s
more, semi-continuous can also keep the system stable, preventing the production
line breaking off.
The proportion of phospholipids in castor oil is no more than 0.3%, so the castor
oil can undergo caustic refining process directly. The temperature for alkali refining
is normally 60 °C. To avoid the formation of loose nigre during this process, it is
necessary to use lye with high concentration. Meanwhile, adding hot water during
alkali refining process can prevent the emulsification. Oil refining caldron should
have enough space to add a large amount of water as well as demulsifier. After
washing, alkali process is completed.
The castor oil produced from alkali refined process is deep in color as a result of
the oxidation at high temperature. Therefore attapulgite, sometimes combined with
a small amount activated carbon, is always used to decolor castor oil. To meet the
demand of the national standard, castor oil is stirred with atlapulgite at 95 °C for 1 h.
After separating castor oil and atlapulgite, decolored castor oil is produced.
To increase the efficiency of the deodorization, the vacuum degree of equipment
should achieve 667 Pa. The temperature and time should also be controlled precisely
for the purpose of preventing the intermolecular dehydration of the castor oil. The
temperature should between 130 and 140 °C and the time should be no more than
30 min. After decreasing the temperature to 90 °C and removing vacuum, castor oil
can be obtained with high quality.
7.2.1.9 Mixed Oil Refining
Although the refining process introduced before has been used widely, there are
some drawbacks for this method as a result of the unique properties of castor oil.
Firstly, castor oil has a high polarity and strong affinity to water, which results in
the emulsification during the alkali refining process and difficulties in separation.
Adding sodium chloride solution is an efficient way to demulsify, but this will cause
the waste of the castor oil and the increase in cost. Additionally, the density of
castor oil and water is close, so they are difficult to separate from each other after
the washing process. During the desiccation, ricinoleic acid is easy to dehydrate
under high temperature, yielding unsaturated diolefinic acid, which will decrease the
transparency and quality of the oil. The temperature of desolvation and deodorization
should be controlled strictly as castor oil is liable to be oxidized [34].
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result of the high viscosity of castor oil. The ricinoleic acid is gadoleic acid with a
hydroxy group, so it has a strong polarity and strong affinity to water, which means
ricinoleic acid is easy to emulsify and difficult to demulsify. Although castor oil is
stable at the room temperature, the acid value will decrease after a long time storage,
normally below 10 mg KOH/g. Castor oil is easy to dehydrate and be oxidized under
high temperature, deepening the color, reducing the transparency, increasing the
viscosity as well as reducing oil quality. According to these features of the castor
oil, semi-continuous refining technics, the combination of batch caustic refining and
continuous desiccation, decoloration and deodorization (desolvation), is the best
choice, as it can prevent the emulsification and simplify the separation steps. What’s
more, semi-continuous can also keep the system stable, preventing the production
line breaking off.
The proportion of phospholipids in castor oil is no more than 0.3%, so the castor
oil can undergo caustic refining process directly. The temperature for alkali refining
is normally 60 °C. To avoid the formation of loose nigre during this process, it is
necessary to use lye with high concentration. Meanwhile, adding hot water during
alkali refining process can prevent the emulsification. Oil refining caldron should
have enough space to add a large amount of water as well as demulsifier. After
washing, alkali process is completed.
The castor oil produced from alkali refined process is deep in color as a result of
the oxidation at high temperature. Therefore attapulgite, sometimes combined with
a small amount activated carbon, is always used to decolor castor oil. To meet the
demand of the national standard, castor oil is stirred with atlapulgite at 95 °C for 1 h.
After separating castor oil and atlapulgite, decolored castor oil is produced.
To increase the efficiency of the deodorization, the vacuum degree of equipment
should achieve 667 Pa. The temperature and time should also be controlled precisely
for the purpose of preventing the intermolecular dehydration of the castor oil. The
temperature should between 130 and 140 °C and the time should be no more than
30 min. After decreasing the temperature to 90 °C and removing vacuum, castor oil
can be obtained with high quality.
7.2.1.9 Mixed Oil Refining
Although the refining process introduced before has been used widely, there are
some drawbacks for this method as a result of the unique properties of castor oil.
Firstly, castor oil has a high polarity and strong affinity to water, which results in
the emulsification during the alkali refining process and difficulties in separation.
Adding sodium chloride solution is an efficient way to demulsify, but this will cause
the waste of the castor oil and the increase in cost. Additionally, the density of
castor oil and water is close, so they are difficult to separate from each other after
the washing process. During the desiccation, ricinoleic acid is easy to dehydrate
under high temperature, yielding unsaturated diolefinic acid, which will decrease the
transparency and quality of the oil. The temperature of desolvation and deodorization
should be controlled strictly as castor oil is liable to be oxidized [34].