Petroleum Refining Technology and Economics Chapter-3 Agenda

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Refinery Feedstocks

• Petroleum Refining
• Technology and Economics

Chapter-3
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Agenda
1. Composition Molecular Types
2. Characterization of Petroleum Products
3. Crude Oil Properties
4. Distillation Analysis
5. Exercise Problems
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Refinery Feedstocks

• Crude Oil
• Complex mixture of hydrocarbons
• Dissolved gases to non-volatiles (1000F boiling
  material)
• C1 to C90

Composition
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Crude Oil Molecular Types

• Crude Oil Molecular Types
• Paraffins
• Carbon atoms connected by single bond.
• Other bonds saturated with hydrogen.
• Naphthenes
• Ringed paraffins (cycloparaffins).
• All bonds saturated with hydrogen.

N-Butane
Cyclopentane
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Crude Oil Molecular Types

• Aromatics
• Six carbon ring (multiple bonding).
• All bonds are unsaturated.
• Olefins
• Usually not in crude oil.
• Formed during processing.
• At least two carbon atoms connected by double
  bond.

Benzene
Naphthalene
1-butene
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Characteristics of Petroleum Products
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Characteristics of Petroleum Products
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Crude Oil Assay

• Distillation Analysis
• Indicates the quality of the crude oil feedstock.
• Based on the amount of material that boils in a
  particular temperature range.
• Represents expected products from crude vacuum
  distillation.
• Amount of data depends on laboratory analysis.
• Quality Measures
• Gravity, API
• Characterization factor
• Sulfur content, wt
• Pour point, F (C)
• Carbon residue, wt
• Salt content, lb/1000 bbl
• Nitrogen content, wt
• Metal content, ppm

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Crude Oil Properties

• Distillation Analysis
• Amount collected from batch distillation at the
  indicated temperature.
• Most useful is TBP (True Boiling Point).
• Standardized tests ASTM D86, D1160, etc.
• API Gravity
• A measure of gravity or density.

• Arabian crudes are classified as follows
• Arabian Heavy (29 API and less)
• Arabian Medium (29-32 API)
• Arabian light (32-34 API)
• Arabian Extra Light (36-41 API)
• Arabian Super Light (49-52 API)

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Oil Classification Using Assay Data
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Crude Oil Characterizations

• Paraffinic (West Texas)
• Little heavy aromatic material (asphaltic).
• Good for paraffin wax manufacture.
• Quality Lube stocks.
• High grade kerosene.
• Naphthenic (Louisiana)
• Little heavy aromatic material (asphaltic).
• High quality gasoline (octane).
• Poor lubes kerosene.

• Aromatic (Maya)
• High quality gasoline asphalt.
• High levels of poisons sulfur nitrogen.
• Residue is asphaltic.

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Crude Oil Properties
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Crude Oil Properties

• Characterization Factor
• Watson factor (UOP)
• Indication of crude oil aromaticity and
  paraffinicity.
• Less than 10 is highly aromatic.
• Up to 15 is highly paraffinic.

• Correlation Index (U. S. Bureau of Mines)
• Individual fractions from crude oils.
• Straight-run paraffins have a CI of 0 and
  benzene have a CI value of 100.

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Crude Oil Properties
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Crude Oil Properties

• Sulfur Content
• Takes the form of hydrogen sulfide (H2S),
  mercaptans, sulfides, disulfides.
• Odorous and toxic.
• Sour vs. sweet 0.5 wt cutoff.
• Restrictions on sulfur in final products.
• Nitrogen Content
• Takes many forms (e.g. Cyanides)
• Odorous and corrosive.
• In heavy gas oil, acts as an inhibitor to FCCU
  and HCU catalyst.
• Usually tolerate up to 0.25 wt.

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Crude Oil Properties

• Metals Content
• Arsenic, nickel, vanadium, copper, etc.
• Poison catalysts.
• Nickle and vanadium affect FCCUs and HCU.

• Carbon Residue
• Carbon residues from specific ASTM tests.
• D524 Ramsbottom.
• D189 Conradson (CCR).
• Related to asphalt and lubricating oil content.
• Pour Point
• Rough indicator of paraffin vs. aromatic content.
• Specific flow test.
• The lower the pour point the lower the paraffin
  content.
• Salt Content
• Generally associated with emulsified water.

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Sample Crude Oil Assay
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Distillation Analysis
ASTM D86

• Gasoline, turbine fuels, naphtha, kerosene, gas
  oil and distillate fuel oils.
• Atmospheric pressure.
• No hotter than 650F to minimize cracking.
• Correlations to correct to TBP basis.

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Distillation Analysis
ASTM D1160

• Heavy petroleum products (650F).
• Vacuum conditions 10 to 40 mmHg.
• Correlations to correct to atmospheric.

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Simulated Distillation Analysis
ASTM D2892 D5236

• This method uses a 15 plate column operating
  under a reflux ration of 51.
• Starts at atmospheric pressure.
• Maximum temperature of 650 F.
• Switch to ASTM D5236 at o.1 mmHg pressure.
• Maximum temperature of 1000 F.
• TBP temperatures wt basis

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Distillation Curve Fractions
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Distillation Curve Fractions
Temperature, F
Volume percent vaporized
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Assay Data Manipulation

• Boiling Point Manipulation
• Correct temperatures to atmospheric pressure.
• Correct temperatures to TBP basis.
• Put onto cumulative basis for the whole crude.
• Cumulative Yield Curve
• S shaped curve yield vs. boiling point.
• Linearized using Gaussian normal probability
  functions.
• Standardized Cut Points
• Volume increments.
• Cut points corresponding to crude tower products.
• Temperatures associated with the lightest pure
  components.

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Assay Data Manipulation

• Properties for Fractions
• Properties inferred from measured trends.
• Relative density / specific gravity / API
  gravity
• Sulfur content
• Carbon residue
• Properties from correlations
• Molecular weight / molar mass

Critical properties acentric factor Heat
of combustion
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Assay Data Manipulation

• Adjusting Temperature for Pressure

• Equation form of Maxwell-Bonnell charts (1955)

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Interconvert D86 TBP Temperature
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Interconvert D1160 TBP Temp.

• D1160 temperatures at 10 mm Hg are converted to
  TBP temperatures at 10 mm Hg graphical method.
• D1160 temperatures at 50 higher equal to the
  TBP temperatures.
• 0 to 10, 10 to 30, 30 to 50 D1160
  temperature differences converted to TBP
  temperature differences.

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Interconvert D1160 TBP Temp.
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Average Boiling Point for a Fraction
Five types are defined in the API Technical Data
Book
Volume average boiling point Mass average boiling
point Molar average boiling point Cubic average
boiling point Mean average boiling point
Use either mid-boiling point or boiling point at
mid-cumulative amount
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Exercise Problems
http//www.jechura.com/ChEN409/Solution_03.pdf
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