OIL AND FAT TECHNOLOGY LECTURES III Crude Oil Production

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OIL AND FAT TECHNOLOGY LECTURES III (Crude
Oil Production)

• Prof.Dr.Aytaç SAYGIN GÜMÜSKESEN
• Yrd.Doç.Dr.Fahri YEMISÇIOGLU

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Extraction of Vegetable Oils

• Basic approaches
• Mechanical Oil Extraction
• - cold pressing means no heat applied
• - hot pressing - external heat is applied
• Solvent Extraction
• - organic solvent (hexane, isopropyl alchool)
• - supercritical solvent (carbondioxide)

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Mechanical oil extraction

• Mechanical oil extraction (expression) is a
  solid-liquid phase seperation method which is
  applied to cooked seed flakes.
• It can be executed by batch, mainly
  hydraulically, and by continous, mainly
  mechanically, working presses.

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• Screw presses
• In oil industry, screw presses (expellers) are
  mostly utilized for expression. The main parts of
  continous-screw press are
• Seed feeder,
• Cone-shaped cage
• Adjustable cone for press-cake outlet
• Worm (pressure and feed)

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• Screw press

Cooked seed flakes
Adjustable cone for press-cake outlet
knife
Cone shaped pressure cage
Main worm shaft
cake
Crude oil
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• The seeds enter the barrel and falls on the
  helical pressure worm.During movement in the
  barell, between worm and cage is gradually
  reduced and the seed flakes are subjected to
  increasing pressure.The cage is made of a number
  of special stell bars which let liquids pass
  through. The oil passes between the bars an flows
  out of the cage. The cone moves along the shaft
  of the expeller and the space between the worm
  and cone can be regulated.This permits easy
  control of the thichnesses of cakes and of the
  degree of pressure to which the cooked flakes are
  subjected.

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Screw Press
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Shaft Arrangement-- Screw Press
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Cage ArrangementFrench Press
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• Advantages and disadvantages of the expeller
  process
• Expellers can be used with almost any kind of
  oilseeds and nuts. The process is relatively
  simple and not capital-intensive. While the
  smallest solvent extraction plant would have a
  processing capacity of 100-200 tons per day,
  expellers are available for much smaller
  capacities, from a few tons per day and up.
• The main disadvantage of the screw-press process
  is its relatively low yield of oil recovery. Even
  the most powerful presses cannot reduce the level
  of residual oil in the press-cake below 3 to 5.
  In the case of oil-rich seeds such as sesame or
  peanuts this may still be acceptable.
  Furthermore, most of the oil left in the cake can
  be recovered by a stage of solvent extraction.
  Such two stage processes (pre-press/solvent
  extraction) are now widely applied . In the case
  of soybeans, however, a 5 residual oil level in
  the cake represents an oil loss of about 25.
  Solvent extraction of the cake would not be
  economical, because of the bulk of material which
  must be processed.

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• The quality of the meal is therefore a factor of
  particular importance in the selection of a
  processing method for soybeans. In this respect,
  the expeller process has several disadvantages.
  The first is the poor storage stability of the
  press-cake, due to its high oil content.
  Furthermore,the extreme temperatures prevailing
  in the expeller may impair the nutritive value of
  the meal protein, mainly by reducing the
  biological availability of the amino acid lysine.
  At any rate, expeller press-cake is not suitable
  for applications requiring a meal with high
  protein solubility.

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Crude oil production (mechanical expression)

• Cooked flakes
• Screw press
• Crude oil seed particles
  Cake
• 
  (4-6oil)
• Crude oil seed particles

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Crude oil production (pre-pressing extraction
solvent extraction)

• Cooked flakes
• Screw press
• Crude oil
  Oily cake
• 
  (10-16 oil)
• 
  
  
  
• Cake (0.5 oil)
  Solvent extraction
• 
  Crude oil

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Solvent extraction(solid-liquid
extraction-leaching)

• The lowest levels of residual oil after pressing
  are 3-8 exhaustive removal of the oil present
  in the cake by mechanical means alone is
  imposible. The residual oil in cake , therefore,
  only be removed by a different approach, this
  being solvent aided extraction.

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• Single stage leaching

miscella V1
Solvents V0
Seed flakes solvents
Cake L1
flakes L0
L0 V0 L1
V1
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• Ideal equilibrium

A B C
A C
B C
B
A inert solid B solvent C oil
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• Basic principles of solvent extraction The
  extraction of oil from oilseeds by means of
  non-polar solvents is, basically, a process of
  solid-liquid extraction. The transfer of oil from
  the solid to the surrounding oil-solvent solution
  ( miscella ) may be divided into three steps
• diffusion of the solvent into the solid
  dissolution of the oil droplets in the
• solvent diffusion of the oil from the
  solid particle
• to the surrounding liquid

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• Due to the very high solubility of the oil in the
  commonly used solvents, the step of dissolution
  is not a rate limiting factor. The driving force
  in the diffusional processes is, obviously, the
  gradient of oil concentration in the direction of
  diffusion. Due to the relative inertness of the
  non-oil constituents of the oilseed, equilibrium
  is reached when the concentration of oil in the
  miscella within the pores of the solid is equal
  to the concentration of oil in the free miscella,
  outside the solid. These considerations lead to a
  number of practical conclusions

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• Since the rate-limiting process is diffusion,
  much can be gained by reducing the size of the
  solid particle. Yet, the raw material cannot be
  ground to a fine powder, because this would
  impair the flow of solvent around the particles
  and would make the separation of the miscella
  from the spent solid extremely difficult. The
  oilseeds are rolled into thin flakes, thus
  reducing one dimension to facilitate diffusion,
  without impairing too much the flow of solvent
  through the solid bed or contaminating the
  miscella with an excessive quantity of fine solid
  particles.

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• The effect of flake thickness on the efficiency
  of solvent extraction

Solution extraction
Diffussion extraction
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• The rate of extraction can be increased
  considerably by increasing the temperature in the
  extractor. Higher temperature means higher
  solubility of the oil, higher diffusion
  coefficients and lower miscella viscosity.
• An open, porous structure of the solid
  material is preferable, because such a structure
  facilitates diffusion as well as percolation. A
  number of processes have been proposed for
  increasing the porosity of oilseeds before
  solvent extraction.

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• Although most of the resistance to mass
  transfer lies within the solid, the rate of
  extraction can be increased somewhat by providing
  agitation and free flow in the liquid phase
  around the solid particles. Too much agitation is
  to be avoided, in order to prevent extensive
  disintegration of the flakes.

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• Choice of solvents
• An ideal solvent for the extraction of oil from
  oil seeds should possess the following
  properties
• Good solubility of the oil. Poor
  solubility of non-oil components. High
  volatility (i.e. low boiling point), so that
  complete removal of
• the solvent from the miscella and the
  meal by evaporation is
• feasible and easy. Yet, the boiling
  point should not be too low, so that extraction
  can
• be carried out at a somewhat high
  temperature to facilitate mass
• transfer. Low viscosity. Low latent
  heat of evaporation, so that less energy is
  needed for
• solvent recovery. Low specific heat, so
  that less energy is needed for keeping the
• solvent and the miscella warm. The
  solvent should be chemically inert to oil and
  other
• components of the seed flakes. Absolute
  absence of toxicity and carcinogenicity, for the
  solvent
• and its residues. Non-inflammable,
  non-explosive. Non-corrosive Commercial
  availability in large quantities and low cost. 

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• A typical commercial solvent for oil extraction
  would have a boiling point range (distillation
  range) of 65 to 70oC and would consist mainly of
  six-carbon alkanes, hence the name "hexane by
  which these solvents are commonly used in oil
  extraction.
• The quality parameters which make up the
  specifications usually include boiling
  (distillation) range, maximum non-volatile
  residue, flash point, maximum sulphur, maximum
  cyclic hydrocarbons, colour and specific gravity.

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• Types of Extractors
• Solvent extractors are of two types
• batch
• continuous
• In batch processes, a certain quantity of flakes
  is contacted with a certain volume of fresh
  solvent. The miscella is drained off, distilled
  and the solvent is recirculated through the
  extractor until the residual oil content in the
  batch of flakes is reduced to the desired level.

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• Batch extractor

Seed flakes
solvent
cake
miscella
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• In continuous extraction, both the oilseeds and
  the solvent are fed into the extractor
  continuously. The different available types are
  characterized by their geometrical configuration
  and the method by which solids and solvents are
  moved one in relation to the other, in
  counter-current fashion.

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• Two different methods can be used to bring the
  solvent to intimate contact with the oilseed
  material
• percolation
• immersion

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• In the percolation method, the solvent trickles
  through a thick bed of flakes without filling the
  void space completely. A film of solvent flows
  rather rapidly over the surface of the solid
  particles and efficiently removes the oil which
  has diffused from the inside to the surface. This
  mode of contact is preferable whenever the
  resistance to diffusion inside the flake is
  relatively low (thin flakes with large surface
  area, open tissue structure).

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• In the immersion mode, the solid particles are
  totally immersed in a slowly moving, continuous
  phase of solvent. Immersion works better with
  materials offering a greater internal resistance
  to oil transfer (thick particles, dense tissue
  structure).

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Percolation type extractor

• Belt extractors_(DE SMET extractor) The
  extractor consists of a horizontal, sealed vessel
  in which a slowly moving screen belt is
  installed. Flaked oil seeds are fed on the belt
  by means of a feeding hopper. A damper attached
  to the hopper outlet acts as a feed regulating
  valve and maintains the solids bed on the belt at
  constant height. This height can be adjusted
  according to the expected rate of percolation of
  the miscella through the bed. Difficult
  percolation is compensated for by lowering bed
  height. The throughput rate of the extractor is
  adjusted by changing the belt speed. There are no
  dividing baffles on the belt and the solid bed is
  one continuous mass. Yet the extractor is divided
  to distinct extraction stages by the way in which
  the miscella stream is advanced.

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• The solvent is introduced at the spent flake
  discharge end. It is sprayed on the flakes,
  percolates through the bed, giving the spent
  flakes a last wash and removing some oil. The
  resulting dilute micella is collected in a
  sectional hopper underneath the belt, from which
  it is pumped and sprayed again on the flakes at
  the next section in the direction opposite to
  belt movement. This process of miscella
  collection, pumping and spraying at the next
  section is repeated until the miscella leaves the
  hopper at the head-end of the extractor, carrying
  the highest concentration of oil (heavy
  miscella).

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• The screen is washed with heavy miscella at the
  head-end, just before the entrance of fresh
  flakes, and then again with fresh solvent, right
  after the discharge of spent flakes.Washing of
  the screen is essential to prevent clogging.
  Washing with full miscella at the feed-end
  provides surface lubrication and prevents
  adhesion of the flakes to the surface of the
  screen. The entire extractor vessel is maintained
  at a slight negative pressure so as to prevent
  leakage of solvent vapours to the atmosphere.

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Belt Extractor (DeSmet)
Seed flakes
high oil seed flakes
Pure solvent
Miscella
Cake (0.5 oil)
Full miscella 25 oil
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Continuous horizontal extractor
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Bollmann extractor
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Basket type- Sliding cell extractor (Lurgi)
In this class of extractors, the flakes do not
constitute a continuous mass but are filled into
separate, delimited elements (baskets) with
perforated bottoms for draining. The baskets can
be moved vertically (bucket elevator extractors),
horizontally ( frame belt and sliding cell
extractors), or can be rotated around a vertical
axis (roto-cell extractors). Vertical
bucket-chain extractors are among the first
industrial solvent extractors constructed for
continuous operation. Many are still in operation
but they are less frequently found in more recent
installations.
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Sliding cell extractor (Lurgi)
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Roto-cell extractor (Reflex extractor-DeSmet)
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Rotocell extractor
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Hildebrandt extractor(immersion type)

• The solid material is extracted according to the
  immersion method. Screw conveyors are installed
  in the extractor for transporting the solid
  material. Again the solvent flows countercurrent
  to the solid materials through the extractor.

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Hildebrandt extractor
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• Extraction unit (DeSmet)

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• Post-extraction operations
• Two streams leave the solvent extraction stage
• an oil-rich fluid extract (full miscella)
• cake meal (spent flakes)
• The next operations have the objective of
  removing and recovering the solvent from each one
  the two streams.

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• a.Miscella distillation Full miscella contains
  typically 30 oil. Thus, for every ton of crude
  oil some 2.5 tons of solvent must be removed by
  distillation. Most manufacturers of solvent
  extractors also offer miscella distillation
  systems.
• The characteristics of a good miscella
  distillation system are
• good energy economy,
• minimal heat damage to the crude oil and its
  components,
• minimal solvent losses ,
• efficient removal of the last traces of solvent
  from the oil
• good operation safety.
• The modes of solvent vaporization include flash
  evaporation, vacuum distillation and steam
  stripping.

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• Miscella filtration Because of the quality
  criteria for crude oils, but also to ensure the
  least possible fluid transport defects (clogging
  in pumps, pipes etc.) and heat transfer
  resistances, the miscella must be freed of solide
  meal particles with special closed filter presses
  before proceeding to distillation.
• Miscella distillation Distillation is the most
  energy consuming part of the total extraction
  process.In general the evaporation is carried out
  in two or three stages, mostly in longtube type
  evaporators with a vapor head.

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• b. Meal desolventizing The spent flakes carry
  with them about 35 solvent. The removal and
  recovery of this portion of the solvent is also
  one of the most critical operations in oil mill
  practice, since it determines, to a large extent,
  the quality of the meal and its derivatives.

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• The most common type of desolventizer-toaster
  consists of a vertical cylindrical stack of
  compartments or "pans". Each compartment is
  fitted with stirrers or racks attached to a
  central vertical shaft. Spent flakes are fed at
  the top of the desolventizer-toaster. The pan
  floors are equipped with adjustable-speed
  rotating valve, to permit downward movement of
  the material , through the pans, at the desirable
  rate.

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• Two methods of heating are used
• direct steam heating
• indirect steam heating
• For heating with indirect steam, the pans are
  equipped with double bottoms acting as steam
  jackets. For direct steam heating, hot live steam
  is injected into the mass through spargers. The
  rotating stirrers spread the material and provide
  the necessary mixing action.

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• Direct steam is used for three reasons
• The transfer of heat from the heated surface of
  the pan floor to the oilseed material is slow and
  difficult, especially after a considerable
  proportion of the solvent has been removed and no
  fluid medium is available for heat transfer. In
  this case, direct contact between the solid
  material and condensing steam is a more efficient
  method of heating. Condensation of the steam adds
  moisture to the flakes.
• The added moisture facilitates the protein
  denaturation reactions leading to the
  inactivation of trypsin inhibitor (for soybean
  cake). It is also believed that the toasting
  effect accomplished by the combined action of
  heat and moisture enhances the palatability of
  the meal to animals.
• The steam distillation effect is necessary in
  order to remove last traces of solvent from the
  meal.

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• Desolventizer

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Soybean oil production
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Sunflower oil production

• Sunflower seed
• Cleaning
  foreign matter
• Dehulling hulls
• Flaking
• Cooking
• Pressing
  crude oil

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Cottonseed oil production

• Cottoseed
• Cleaning
  foreign matter
• Delinting lints
• Dehulling hulls
• Flaking
• Cooking
• Pressing
  crude oil

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Rapeseed oil production

• Rape seed
• Cleaning
  foreign matter
• Flaking
• Cooking
• Pressing
  crude oil
• Oily cake