Oilseed and oil processing technology-Evaporation and stripping of miscella
1.Process flow
Miscella filtration → miscella tank → first evaporator → second evaporator → stripping tower → extraction crude oil.
The miscella (a solution composed of oil and solvent) pumped from the extractor must be treated to separate the oil from the solvent.The separation method is to use the difference in boiling point between oil and solvent. First, the miscella is heated and evaporated to vaporize most of the solvent and separate from the oil.Then, using the difference in volatility between oil and solvent, the concentrated mixed oil is steam distilled (that is, stripping) to distill out the residual solvent in the crude oil, so as to obtain the extracted crude oil with very low solvent content. Before evaporation and stripping, the miscella must be "pre-treated" to remove the solid meal and colloidal substances in it, creating conditions for the separation of the components of the miscella.
2. Filtering
Let the miscella pass through the filter medium (wire screen), the solid meal contained in it will be intercepted, and a cleaner miscella will be obtained. In the rotocel extractor with larger processing capacity, a rich miscella screen filter is installed on the second miscella collection chamber. The filter screen is 100 mesh. The concentrated mixed oil is filtered and then pumped.
3. Centrifugal sedimentation
Nowadays, liquid-cyclone are often used to separate the coarse powder in the miscella.It uses the different weights of the components of the miscella and uses centrifugal rotation to generate the difference in centrifugal force, so that the meal powder sinks and the liquid rises to achieve the purpose of cleaning the miscella.
4. Miscella evaporation
Evaporation is the process of vaporizing a part of the solvent in the solution by heating, thereby increasing the concentration of the solute in the solution, even if the volatile solvent is separated from the non-volatile solute. The miscella evaporation is a process in which the oil is almost non-volatile, but the solvent has a low boiling point and is easy to volatilize. Heating is used to vaporize most of the solvent, thereby greatly increasing the concentration of the oil in the miscella. In the selection of evaporation equipment, oil plants often use long tube evaporators (also called "rising film evaporators"). Its characteristic is that the heating pipe is long, the miscella enters the heating pipe from the lower part after being preheated, and boils quickly, producing a large amount of vapor bubbles and rising rapidly. The miscella is also driven by the rising vapor bubbles and drawn as a liquid film that rises along the pipe wall, and the solvent continues to evaporate in the process. Since heat is transferred in a thin film state, the evaporation efficiency is higher. The equipment is a rising film evaporators.
5. Miscella stripping
Through evaporation, the concentration of the miscella is greatly increased. However, the boiling point of the solvent also increases. Regardless of whether the normal pressure evaporation is continued or the reduced pressure evaporation is changed, it is quite difficult to basically remove the remaining solvent in the miscella. Only by stripping can the remaining solvent in the miscella be basically removed.
Stripping is steam distillation. The principle is: miscella and water are not compatible, direct steam with a certain pressure is passed into the concentrated miscella with a high boiling point, and indirect steam is passed into the jacket of the equipment for heating. Direct steam into the miscella will not condense.The sum of direct steam and solvent vapor pressure balances with the external pressure, and the solvent boils, thereby reducing the boiling point of the high boiling point solvent. The uncondensed direct steam entrains the distilled solvent into the condenser for condensation recovery. The equipment includes tubular stripping column, disk stripping column, and inclined plate stripping column.
Miscella filtration → miscella tank → first evaporator → second evaporator → stripping tower → extraction crude oil.
The miscella (a solution composed of oil and solvent) pumped from the extractor must be treated to separate the oil from the solvent.The separation method is to use the difference in boiling point between oil and solvent. First, the miscella is heated and evaporated to vaporize most of the solvent and separate from the oil.Then, using the difference in volatility between oil and solvent, the concentrated mixed oil is steam distilled (that is, stripping) to distill out the residual solvent in the crude oil, so as to obtain the extracted crude oil with very low solvent content. Before evaporation and stripping, the miscella must be "pre-treated" to remove the solid meal and colloidal substances in it, creating conditions for the separation of the components of the miscella.
2. Filtering
Let the miscella pass through the filter medium (wire screen), the solid meal contained in it will be intercepted, and a cleaner miscella will be obtained. In the rotocel extractor with larger processing capacity, a rich miscella screen filter is installed on the second miscella collection chamber. The filter screen is 100 mesh. The concentrated mixed oil is filtered and then pumped.
3. Centrifugal sedimentation
Nowadays, liquid-cyclone are often used to separate the coarse powder in the miscella.It uses the different weights of the components of the miscella and uses centrifugal rotation to generate the difference in centrifugal force, so that the meal powder sinks and the liquid rises to achieve the purpose of cleaning the miscella.
4. Miscella evaporation
Evaporation is the process of vaporizing a part of the solvent in the solution by heating, thereby increasing the concentration of the solute in the solution, even if the volatile solvent is separated from the non-volatile solute. The miscella evaporation is a process in which the oil is almost non-volatile, but the solvent has a low boiling point and is easy to volatilize. Heating is used to vaporize most of the solvent, thereby greatly increasing the concentration of the oil in the miscella. In the selection of evaporation equipment, oil plants often use long tube evaporators (also called "rising film evaporators"). Its characteristic is that the heating pipe is long, the miscella enters the heating pipe from the lower part after being preheated, and boils quickly, producing a large amount of vapor bubbles and rising rapidly. The miscella is also driven by the rising vapor bubbles and drawn as a liquid film that rises along the pipe wall, and the solvent continues to evaporate in the process. Since heat is transferred in a thin film state, the evaporation efficiency is higher. The equipment is a rising film evaporators.
5. Miscella stripping
Through evaporation, the concentration of the miscella is greatly increased. However, the boiling point of the solvent also increases. Regardless of whether the normal pressure evaporation is continued or the reduced pressure evaporation is changed, it is quite difficult to basically remove the remaining solvent in the miscella. Only by stripping can the remaining solvent in the miscella be basically removed.
Stripping is steam distillation. The principle is: miscella and water are not compatible, direct steam with a certain pressure is passed into the concentrated miscella with a high boiling point, and indirect steam is passed into the jacket of the equipment for heating. Direct steam into the miscella will not condense.The sum of direct steam and solvent vapor pressure balances with the external pressure, and the solvent boils, thereby reducing the boiling point of the high boiling point solvent. The uncondensed direct steam entrains the distilled solvent into the condenser for condensation recovery. The equipment includes tubular stripping column, disk stripping column, and inclined plate stripping column.
