Transcript Northeast States CLEAN AIR ACADEMY

Advanced Mobile Source Training Course
MS 201 - Diesel
Session I. Motor Vehicle Diesel Fuel
a. The Refining and Distribution Process
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Overview
• In the last several years, it has become clear that fuels
and vehicles must be regulated together to achieve the
highest level of pollution control
• In this portion of the course, we will discuss
– Characteristics of crude oils
– The refining process
– Technologies for achieving “clean fuels”
– How fuel is distributed
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Crude Oils
• On average, crude oils are made up of the following
elements or compounds:
– Carbon – 84%
– Hydrogen – 14%
– Sulfur – 1 to 3%
– Nitrogen - <1%
– Oxygen - <1%
– Metals - <1% (nickel, iron,vanadium, etc.)
– Salts - <1%
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Hydrocarbons in Crude Oil
• Paraffins – methane, ethane, propane, butane, etc.
• Aromatics – benzene, naphthalene
• Naphthenes or Cycloalkenes – cyclohexane, methyl
cyclopentane
• Alkenes – ethylene, butene, isobutene
• Dienes and Alkynes – acetylene, butadienes
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Products From Refining
• Petroleum Gas – used for heating, cooking, making
plastics
• Naphtha – an intermediate product used to make
gasoline
• Gasoline – motor fuel
• Kerosene – fuel for jet engines and tractors and a
starting material for making other products
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Products From Refining
• Gas Oil or Diesel – used for diesel fuel and heating oil
and a starting material for making other products
• Lubricating Oil – used for motor oil, grease, other
lubricants
• Heavy Gas or Fuel Oil – used for industrial fuel and a
starting material for making other products
• Residuals – coke, asphalt, tar, waxes, and a starting
material for making other products
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Flow Chart of the Distillation Process
Crude Oil Distillation: The First Step
(Source: Energy Information Administration)
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Sources and Quality of Crude Oil
• Physical characteristics of crude oil streams differ
• Streams with similar characteristics may come from a
single reservoir, a field, or sometimes even a region
• Crude oils are classified by density and sulfur content
– Light
– Heavy
– Sweet
– Sour
• Price differentials reflect the relative ease of refining
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Characteristics of Some Crude Oils
• West Texas Intermediate (light and sweet)
• Nigeria’s Bonny Light (middle distillates)
• Saudi Arabia’s Arabian Light (contains heavy residue)
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Other Characteristics of Crude Oils
• The type of hydrocarbon molecules may affect the
cost of processing or suitability for specific uses
• Presence of heavy metals is a contaminant for the
processing and the finished product
• It is not easy (at least not profitably) to substitute one
crude oil for another, so refineries tend to be designed
and operated around a specific crude oil or mix of
crude oils
• Today’s demand is for lighter products of higher
quality from a crude supply that is increasingly
heavier, with a higher sulfur content
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The Refining Process
• Bending, breaking, and boiling
• Distillation separates crude oil into various
components (fractions) using the difference in boiling
temperatures
• Chemical processing breaks longer chain hydrocarbons
into shorter ones – makes diesel into gasoline, for
example
• Fractions are treated to remove impurities
• Mixtures are blended to meet market specifications
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Chemical Processing
• Cracking
– Takes larger hydrocarbons and makes them into smaller ones
– Types of cracking
• Thermal – heats large hydrocarbons at high temperatures
(sometimes high pressures, as well) until they break apart
• Catalytic – uses a catalyst to speed up the breaking
process
– Fluid catalytic cracking (heavy gas oil to diesel and gasoline)
– Hydrocracking – adds hydrogen gas (heavy oil to gasoline
and kerosene)
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Chemical Processing
• Catalytic Reforming
– Uses a catalyst to rearrange molecules into more
valuable ones of generally the same size and to
produce aromatics
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Chemical Processing
• Alkylation
– Small hydrocarbons (isobutane and an olefin,
usually butylene) are combined to produce a larger
molecule
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Intermediate Products
• Refining processing generally produces blendstocks
suitable for making finished products rather than
producing finished products directly
• Blendstocks may be traded between companies
• Other blendstocks may come from outside the
petroleum refining industry. Examples include fuel
ethanol and biodiesel from agriculture and MTBE and
GTL (gas to liquids) diesel from natural gas
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Blending
• Blending is a sophisticated optimization process where
producers attempt to maximize profit by blending the
most valuable set of finished products possible given
the blendstocks available and the constraints imposed
by product specifications (including environmental
regulations)
• Not all blending is done at refineries or by refining
companies
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Saleable Products
• In addition to gasoline and diesel fuel, refineries sell
petroleum gas, kerosene, heating oil,lubricating oil,
industrial fuel, asphalt, tar, waxes, and other products.
• Standards are set for these products by ASTM –
consensus standards aimed at improving product
quality, safety, and cost-effectiveness
• Fuel quality regulations have existed for many years –
for example, gasoline volatility was controlled
regionally to ensure driveability long before it was
regulated for environmental purposes
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Diesel Fuel Quality Regulation
• The introduction of catalyst-based diesel particulate
filters created a need to reduce the sulfur content of
diesel fuels
• Options to reduce sulfur include:
– Increasing the proportion of low-sulfur crude oil
– Hydro-treating straight run diesel and thermally
cracked diesel
– Reducing the proportion of FCC oil blended into
the final product
– Installing hydrocrackers
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Hydrotreating
• The primary means to achieve ULSD levels
• Passes a mixture of heated feedstock and hydrogen
through a catalyst-laden reactor to remove sulfur and
other impurities
• Hydrotreating can occur at many places in the refining
process – right after distillation or at various points of
chemical processing
• To achieve 15 ppm diesel, refineries must desulfurize
essentially all diesel blending components
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2 Stage Process
• Probably will be required at most refineries
• 1st stage – conventional hydrotreating unit
• 2nd stage – using higher pressures, increasing hydrogen
rate and purity, newer catalysts
• Higher pressures may require new reactors with
thicker walls
• Hydrogen consumption is the largest operating cost –
10 ppm sulfur may require 25 to 45% more hydrogen
than 500 ppm
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New Technologies for Sulfur Reduction
•
•
•
•
Sulfur adsorption
Biodesulfurization
Sulfur oxidation
These technologies are in experimental stages of
development
• They may affect the market by 2010
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Costs of Sulfur Reduction
• EPA estimates that average investment for diesel
desulfurization will cost $50 million per refinery
• EPA analysis also assumes that 121 new or modified
units will be added to make ULSD
• EPA estimates (xx) cents per gallon increase in diesel
fuel price once regulations are fully in effect
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U.S. Oil Flow 2002
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Fuel Distribution
• In 2001, the U.S. consumed 19.5 million barrels per
day of petroleum products
• Crude oil is transported to refineries
• Refined products are transported to consumers
• The primary transportation modes in the U.S. is
through pipelines
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Domestic Oil Shipment
• Domestic Shipments of Petroleum, 2003
• (Source: Association of Oil Pipe Lines, May 2005)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Pipelines
Water Carriers
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Trucks
Railroads
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Why Pipelines?
• During World War II, German submarines began
sinking tankers along the East Coast
• In 1942, nearly 500 U.S. merchant ships were sunk by
German U-boats
• A joint industry-government effort constructed longdistance pipelines
• Pipelines now transport roughly two-thirds of the
petroleum shipped in the U.S.
• Trucking is generally limited to short hauls, but is
essential to the completeness of the system
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The PADD System
• During World War II, the government divided
America into five economically and geographically
distinct regions for the purposes of oil allocation
• The original segments and names are still used:
Petroleum Administration for Defense Districts –
PADDs
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PADDs
• PADD I: East Coast and Atlantic Seaboard – virtually
no production of crude oil, but the highest demand
for refined products in the country
• PADD II: Midwest – lately a significant drop in local
crude oil production; two-thirds now comes from
Canada for local refineries
• PADD III: Gulf Coast – America’s major refining area
and former supplier of domestic crude; lately a
significant decrease in crude production
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PADDs
• PADD IV: Rocky Mountains – lower population
density limits demand with the consequence that the
pipeline infrastructure is not well developed; demand
is growing, however, with new pipelines bringing in
Canadian crude to local refineries
• PADD V: West Coast, Hawaii and Alaska – rapid
population increases and stringent environmental
regulations present special challenges; PADD V is not
connected by pipeline to and other PADD
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Logistics Hubs
• Interconnections of pipelines, tankers, rail and truck;
terminals with substantial storage capacity
• New York Harbor; Cushing, Oklahoma; Chicago; Los
Angeles; Texas-Louisiana Gulf Coast
• Large diameter “trunk” lines (fungible mode) bring
products in, and smaller diameter “delivering” lines
distribute the products
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Managing Oil Pipeline Flow
• Centrifugal pumps are located at the origin and at 20
to 100 mile increments
• Operation goes on 24/7/365
• 3-8 miles per hour – 14 to 22 days to move oil from
Houston to New York City
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Potential for Contamination
• Always a certain amount of intermixing at the
interface where batches meet
• If they are similar products, then the resulting mixture
is added to the lower value product
• If the products are dissimilar, the “transmix” must be
channeled to separate storage for reprocessing
• Products with tighter specifications require more
batching and reprocessing
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Motor Vehicle Fuels - Summary
• New emission control technology requires “cleaner
fuels”
• There are a large number of different crude oils with
different compositions requiring different processing
• Technology for producing fuels with the desired
characteristics is currently available, and new
technologies are under development
• Investment in new infrastructure is required
• Distribution must be carefully managed
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Go to: Projects/Academy
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