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Z. Xiao et al.
extensive adaptability for raw material, and oil yield efficiency is high; the meal is
of good quality and low processing cost. But the extracting process has the poor
quality of raw oil, solvent is generally flammable and explosive, and there is certain
toxicity. In order to make sure of the quality of the oil, refining the oil is a necessary
process. So this chapter will refer to the production technology of industrial plant oil
mainly such as the principle of oil extraction mechanical crushing method, solvent
extracting method, and oil refining.
2.1 Principle of Oil Extraction
2.1.1 Principle of Mechanical Extraction
Mechanical extraction of the oilseeds is the process of extruding the oil from the
blank with mechanical force. In the process of pressing, the extraction of oil can be
regarded as the movement of incompressible liquid in the deformed porous medium,
following the movement of mucilage fluid. The average velocity of the oil movement
is mainly determined by the friction and driving force in the liquid layer. At the same
time, the thickness of the liquid layer and the length of the oil pipeline are also
important factors affecting the oil discharge rate. Generally speaking, the smaller the
oil viscosity, the greater the pressure, the faster the oil flows from the pores. At the
same time, the longer the flow path, the smaller the pore which will reduce the flow
rate and make the press more slowly.
Under strong pressure, the pressed particles will leave a single molecular oil layer
or a multi-molecular oil layer similar to a single molecule on the surface of the
pressed particles. Because of the huge molecular force field on the surface, this oil
layer is completely combined between the surfaces, and no longer follows the general
law of fluid dynamics to flow, nor can it be squeezed out from the gaps between the
surfaces. At this point, the oil molecules are in a very thin adsorption film state.
In fact, the amount of oil that remains in the cake is much higher than the amount
of monomolecular oil that remains on the surface of the particles. This is mainly
because the inner and outer surfaces of the particles are not all tightly packed. At
the same time, the surface of individual particles contacts directly, so that a part of
residual oil remains in the sealed oil circuit.
In addition, under the action of pressure, the particles will squeeze more tighter
with the oil discharged. The plastic deformation will be made between the particles
contacting each other. Especially the press particles will be integrated when the oil
film breaks. In this way, at the end of the press, the press particles are no longer loose
and began to form a complete plastic body, called cake. The cake is not bound to
all the particles, but is an incompletely bound gel porous body with a large number
of pores. That is to say, apart from the continuous gel skeleton of the cake formed
by the partial binding action of the particles, there are still many pores between the
particles or between the groups of combined particles. Some of these pores are likely
Z. Xiao et al.
extensive adaptability for raw material, and oil yield efficiency is high; the meal is
of good quality and low processing cost. But the extracting process has the poor
quality of raw oil, solvent is generally flammable and explosive, and there is certain
toxicity. In order to make sure of the quality of the oil, refining the oil is a necessary
process. So this chapter will refer to the production technology of industrial plant oil
mainly such as the principle of oil extraction mechanical crushing method, solvent
extracting method, and oil refining.
2.1 Principle of Oil Extraction
2.1.1 Principle of Mechanical Extraction
Mechanical extraction of the oilseeds is the process of extruding the oil from the
blank with mechanical force. In the process of pressing, the extraction of oil can be
regarded as the movement of incompressible liquid in the deformed porous medium,
following the movement of mucilage fluid. The average velocity of the oil movement
is mainly determined by the friction and driving force in the liquid layer. At the same
time, the thickness of the liquid layer and the length of the oil pipeline are also
important factors affecting the oil discharge rate. Generally speaking, the smaller the
oil viscosity, the greater the pressure, the faster the oil flows from the pores. At the
same time, the longer the flow path, the smaller the pore which will reduce the flow
rate and make the press more slowly.
Under strong pressure, the pressed particles will leave a single molecular oil layer
or a multi-molecular oil layer similar to a single molecule on the surface of the
pressed particles. Because of the huge molecular force field on the surface, this oil
layer is completely combined between the surfaces, and no longer follows the general
law of fluid dynamics to flow, nor can it be squeezed out from the gaps between the
surfaces. At this point, the oil molecules are in a very thin adsorption film state.
In fact, the amount of oil that remains in the cake is much higher than the amount
of monomolecular oil that remains on the surface of the particles. This is mainly
because the inner and outer surfaces of the particles are not all tightly packed. At
the same time, the surface of individual particles contacts directly, so that a part of
residual oil remains in the sealed oil circuit.
In addition, under the action of pressure, the particles will squeeze more tighter
with the oil discharged. The plastic deformation will be made between the particles
contacting each other. Especially the press particles will be integrated when the oil
film breaks. In this way, at the end of the press, the press particles are no longer loose
and began to form a complete plastic body, called cake. The cake is not bound to
all the particles, but is an incompletely bound gel porous body with a large number
of pores. That is to say, apart from the continuous gel skeleton of the cake formed
by the partial binding action of the particles, there are still many pores between the
particles or between the groups of combined particles. Some of these pores are likely