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Z. Xiao et al.
2.1.2.1 Molecular Diffusion
Molecular diffusion refers to the transfer of substances in the form of a single
molecule, which is caused by the random thermal motion of molecules. When the
oil is in contact with the solvent, the oil molecule in the oil seeps out of the oil and
diffuses to the solvent by means of its thermal movement, thus forming a mixed oil.
At the same time, solvent molecules also permeate and diffuse into the oil. So the
two different concentrations of mixed oil are formed on both sides of the interface
between oil and solvent. Because of the heat movement of the molecules and the
difference of the oil concentration between the two sides, the oil molecules will continuously transfer from the higher concentration region to the lower concentration
region, until the two sides of the molecular concentration reach equilibrium.
2.1.2.2 Convection–Diffusion
Convection–diffusion refers to the transfer of a substance solution in the form of
a smaller volume. Like molecular diffusion, the quantity of diffusions is related to
diffusion area, concentration difference, diffusion time, and diffusion coefficient.
In the convection–diffusion process, the larger the volume of convection, the more
the volume per unit area per unit time; and the greater the convection–diffusion
coefficient, the greater the amount of mass transfer.
The essence of the oil leaching process is the mass transfer process. The mass
transfer process is completed by both molecular diffusion and convective diffusion. In
molecular diffusion, matter is transferred by the kinetic energy of molecular thermal
motion. Increasing the extracting temperature properly is helpful to improve the
molecular diffusion coefficient and accelerate molecular diffusion. In convection–
diffusion, matter is mainly dependent on the energy provided by the outside world
for transfer. Generally, the liquid level difference or the pressure produced by the
pump is used to make the solvent or mixed oil and oil stock in a state of relative
movement to promote convection and diffusion.
2.2 Storage and Preparation of Oilseeds
The process of producing oil from plant oil has certain requirements for the properties
of oilseeds. Therefore, the oilseeds should be treated before extracting the oil, so
that the oilseeds have the best adaptability to meet the requirements of the relevant
process. The function of the preparation process is to properly prepare the oilseeds
for extraction of the oil, either by solvent or mechanical methods and, if applicable,
remove the hulls and other materials from the seed kernel or meal. While a particular
seed may contain from 20 to 50% oil, the oil is tightly bound within the cell and
mechanical action must be taken to either forcefully remove the oil or to make the oil
more accessible to subsequent solvent extraction. So the common functions of storage
Z. Xiao et al.
2.1.2.1 Molecular Diffusion
Molecular diffusion refers to the transfer of substances in the form of a single
molecule, which is caused by the random thermal motion of molecules. When the
oil is in contact with the solvent, the oil molecule in the oil seeps out of the oil and
diffuses to the solvent by means of its thermal movement, thus forming a mixed oil.
At the same time, solvent molecules also permeate and diffuse into the oil. So the
two different concentrations of mixed oil are formed on both sides of the interface
between oil and solvent. Because of the heat movement of the molecules and the
difference of the oil concentration between the two sides, the oil molecules will continuously transfer from the higher concentration region to the lower concentration
region, until the two sides of the molecular concentration reach equilibrium.
2.1.2.2 Convection–Diffusion
Convection–diffusion refers to the transfer of a substance solution in the form of
a smaller volume. Like molecular diffusion, the quantity of diffusions is related to
diffusion area, concentration difference, diffusion time, and diffusion coefficient.
In the convection–diffusion process, the larger the volume of convection, the more
the volume per unit area per unit time; and the greater the convection–diffusion
coefficient, the greater the amount of mass transfer.
The essence of the oil leaching process is the mass transfer process. The mass
transfer process is completed by both molecular diffusion and convective diffusion. In
molecular diffusion, matter is transferred by the kinetic energy of molecular thermal
motion. Increasing the extracting temperature properly is helpful to improve the
molecular diffusion coefficient and accelerate molecular diffusion. In convection–
diffusion, matter is mainly dependent on the energy provided by the outside world
for transfer. Generally, the liquid level difference or the pressure produced by the
pump is used to make the solvent or mixed oil and oil stock in a state of relative
movement to promote convection and diffusion.
2.2 Storage and Preparation of Oilseeds
The process of producing oil from plant oil has certain requirements for the properties
of oilseeds. Therefore, the oilseeds should be treated before extracting the oil, so
that the oilseeds have the best adaptability to meet the requirements of the relevant
process. The function of the preparation process is to properly prepare the oilseeds
for extraction of the oil, either by solvent or mechanical methods and, if applicable,
remove the hulls and other materials from the seed kernel or meal. While a particular
seed may contain from 20 to 50% oil, the oil is tightly bound within the cell and
mechanical action must be taken to either forcefully remove the oil or to make the oil
more accessible to subsequent solvent extraction. So the common functions of storage