Distillation D86 True Boiling Point

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Distillation (D-86) True Boiling Point
Asst. Prof. Dr. Pakamas Chetpattananondh In House
Practical Training (IHPT)
Department of Chemical Engineering, Faculty of
Engineering, PSU
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Vaporization of pure component
212 F
70 F
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Does "Boiling" Mean "Hot"?

• Boiling occurs when the vapor pressure inside the
  bubble equals atmospheric pressure.
• What would happen if the atmospheric pressure
  would drop?
• The simple example of this is the case of a
  camper who is on the top of a 10,000 ft mountain.
  While water boils at 100 degrees C at sea level
  (where the atmospheric pressure is 760mm Hg) the
  atmospheric pressure at 10,000 ft altitude is
  about 530 mm Hg.
• Because the boiling point of water is about 90
  degrees C at this altitude, not only will our
  camper find that his food will cook a little
  slower than normal, any attempt to boil water to
  kill germs and pathogens may be unsuccessful
  since the water isn't getting hot enough.

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Vaporization of mixtures
Pure ethanol BP 173 F
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Batch distiallation
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Continuous distillation
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Volatility

• A fuels ability to vaporize or change from
  liquid to vapor is referred to as its volatility.
• The volatility characteristics of a spark
  ignition (SI) engine fuel are of prime
  importance.
• Fuels that do not vaporize readily may cause hard
  starting of cold engines and poor vehicle
  driveability during warm-up and acceleration.
• Conversely, fuels that vaporize too readily at
  higher operating temperatures will cause too much
  vapor to form causing a decrease in fuel flow to
  the engine (known as vapor lock).

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Volatility
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Volatility

• The main parameters to establish volatility
  limits are Vapor/Liquid Ratio (V/L), Vapor
  Pressure (RVP), and Distillation Curve.
• The vapor/liquid ratio uses a test to determine
  the temperature required to create a V/L ratio of
  20.
• More volatile fuels require lower temperatures to
  achieve this ratio while less volatile fuels
  require higher temperatures to create the same
  ratio.
• The V/L ratio assists in defining a fuel's
  tendency to contribute to vapor lock.
• The V/L ratio and RVP are measurements of a
  fuel's "front end volatility", or more volatile
  components which vaporize first.
• The distillation test is used to determine fuel
  volatility over the entire boiling range of
  gasoline.

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Classification methods of petroleum fractions by
boiling point

• ASTM-D86
• Distillation method for light petroleum products
• ASTM D-1160
• Distillation method for heavier fractions
  (gt500F) carried out in vacuum

• ASTM-D2892
• True Boiling Point (TBP)

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How is D-86 important ?

• D 86 is used to determine fuel volatility across
  the entire boiling range of fuel.

• A Front End (020 evaporated)
• B Mid-range (20-90 evaporated)
• C Tail End (90-100 evaporated)

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How is D-86 important ?

• The 10 evaporated temperature must be low enough
  to provide easy cold starting but high enough to
  minimize vapor lock as well as hot driveability
  problems.
• The 50 evaporated temperature must be low enough
  to provide good warm up and cold weather
  driveabiity without being so low as to contribute
  to hot driveability and vapor locking problems.
• The 90 and end point evaporation temperatures
  must be low enough to minimize crankcase and
  combustion chamber deposits as well as spark plug
  fouling and dilution of engine oil.

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Flexible Volatility Index (FVI) This is a
parameter calculated from the RVP and the
measured value of E70, and is an indicator of the
hot running performance (the tendency for vapour
lock). FVI RVP (0.7 x E70)
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Using distillation curve
In New Zealand E 70?C at 25-45 E 100?C at 45-67
DI for UL 91 is about 495 DI 550 cause
driveability problem in cold
DI 1.5 x T10 3 x T50 T90
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True boiling point

• ASTM D-2892 is used for samples with a wide
  boiling range such as crude petroleum up to a
  final cut temperature of 400C (752F)
  atmospheric equivalent temperature (AET).
• Theoretical plate 14-18 (15)
• Distillation pot, volume 15 L
• Volumetric of feed 5 10 L
• Reflux ratio 51
• Temperature of distillation 350?C (AET)
• Weight loss 4

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True boiling point

• It is often useful to extend the boiling point
  data to higher temperatures than are possible in
  the fractionating distillation method and for
  this purpose a vacuum distillation in a simple
  still with no fractionating column (ASTM D-1160)
  can be carried out.
• This distillation, which is done under
  fractionating conditions equivalent to one
  theoretical plate, allows the boiling point data
  to be extended to about 600C (1112F) with many
  crude oils.
• This method gives useful comparative and
  reproducible results that are often accurate
  enough for refinery purposes, provided
  significant cracking does not occur.
• Usually seven fractions provide the basis for a
  reasonably thorough evaluation of the
  distillation properties of the feedstock

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True boiling point

• 1. Gas, boiling range lt15.5C (60F)
• 2. Gasoline (light naphtha), boiling range
  l5.5149C (60300F)
• 3. Kerosene (medium naphtha), boiling range
  149232C (300450F)
• 4. Gas oil, boiling range 232343C (450650F)
• 5. Light vacuum gas oil, boiling range 343371C
  (650700F)
• 6. Heavy vacuum gas oil, boiling range 371566C
  (7001050F)
• 7. Residuum, boiling range gt566C (1050F)

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Typical Refinery Products
From Schmidt, G.K. and Forster, E.J., Modern
Refining for Todays Fuels and Lubricants, SAE
Paper 861176, 1986.
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Crude Assay
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For vacuum residues a typical true boiling point
(TBP) cut point is 538?C, but it may be lower or
higher depending on the crude. The TBP cut point
will define the concentration of Conradson carbon
residue (CCR), sulfur, and metals in the feed and
thereby affect yields and product quality.
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Thanks for your attention