Source: www.osha.gov
ABSORPTION The disappearance of one substance
into another so that the absorbed substance loses its identifying
characteristics, while the absorbing substance retains most of its original
physical aspects. Used in refining to selectively remove specific components
from process streams.
ACID TREATMENT A process in which unfinished
petroleum products such as gasoline, kerosene, and lubricating oil stocks are
treated with sulfuric acid to improve color, odor, and other properties.
ADDITIVE Chemicals added to petroleum products
in small amounts to improve quality or add special characteristics.
ADSORPTION Adhesion of the molecules of gases
or liquids to the surface of solid materials.
AIR FIN COOLERS A radiator-like device used to
cool or condense hot hydrocarbons; also called fin fans.
ALICYCLIC HYDROCARBONS Cyclic (ringed)
hydrocarbons in which the rings are made up only of carbon atoms.
ALIPHATIC HYDROCARBONS Hydrocarbons characterized by open-chain
structures: ethane, butane, butene, acetylene, etc.
ALKYLATION A process using sulfuric or
hydrofluoric acid as a catalyst to combine olefins (usually butylene) and
isobutane to produce a high-octane product known as alkylate.
API GRAVITY An arbitrary scale expressing the
density of petroleum products.
AROMATIC Organic compounds with one or more
benzene rings.
ASPHALTENES The asphalt compounds soluble in
carbon disulfide but insoluble in paraffin naphthas.
ATMOSPHERIC TOWER A distillation unit operated
at atmospheric pressure.
BENZENE An unsaturated, six-carbon ring, basic
aromatic compound.
BLEEDER VALVE A small-flow valve connected to a
fluid process vessel or line for the purpose of bleeding off small quantities
of contained fluid. It is installed with a block valve to determine if the
block valve is closed tightly.
BLENDING The process of mixing two or more
petroleum products with different properties to produce a finished product with
desired characteristics.
BLOCK VALVE A valve used to isolate equipment.
BLOWDOWN The removal of hydrocarbons from a
process unit, vessel, or line on a scheduled or emergency basis by the use of
pressure through special piping and drums provided for this purpose.
BLOWER Equipment for moving large volumes
of gas against low-pressure heads.
BOILING RANGE The range of temperature (usually
at atmospheric pressure) at which the boiling (or distillation) of a
hydrocarbon liquid commences, proceeds, and finishes.
BOTTOMS Tower bottoms are residue remaining in
a distillation unit after the highest boiling-point material to be distilled
has been removed. Tank bottoms are the heavy materials that accumulate in the
bottom of storage tanks, usually comprised of oil, water, and foreign matter.
BUBBLE TOWER A fractionating (distillation)
tower in which the rising vapors pass through layers of condensate, bubbling
under caps on a series of plates.
CATALYST A material that aids or promotes a
chemical reaction between other substances but does not react itself. Catalysts
increase reaction speeds and can provide control by increasing desirable
reactions and decreasing undesirable reactions.
CATALYTIC CRACKING The process of breaking up
heavier hydrocarbon molecules into lighter hydrocarbon fractions by use of heat
and catalysts.
CAUSTIC WASH A process in which distillate is
treated with sodium hydroxide to remove acidic contaminants that contribute to
poor odor and stability.
CHD UNIT See Hydrodesulfurization.
COKE A high carbon-content residue remaining
from the destructive distillation of petroleum residue.
COKING A process for thermally converting and
upgrading heavy residual into lighter products and by-product petroleum coke.
Coking also is the removal of all lighter distillable hydrocarbons that leaves
a residue of carbon in the bottom of units or as buildup or deposits on
equipment and catalysts.
CONDENSATE The liquid hydrocarbon resulting
from cooling vapors.
CONDENSER A heat-transfer device that cools and
condenses vapor by removing heat via a cooler medium such as water or
lower-temperature hydrocarbon streams.
CONDENSER REFLUX Condensate that is returned to
the original unit to assist in giving increased conversion or recovery.
COOLER A heat exchanger in which hot liquid
hydrocarbon is passed through pipes immersed in cool water to lower its
temperature.
CRACKING The breaking up of heavy molecular
weight hydrocarbons into lighter hydrocarbon molecules by the application of
heat and pressure, with or without the use of catalysts.
CRUDE ASSAY A procedure for determining the general
distillation and quality characteristics of crude oil.
CRUDE OIL A naturally occurring mixture of
hydrocarbons that usually includes small quantities of sulfur, nitrogen, and
oxygen derivatives of hydrocarbons as well as trace metals.
CYCLE GAS OIL Cracked gas oil returned to a cracking
unit.
DEASPHALTING Process of removing asphaltic
materials from reduced crude using liquid propane to dissolve nonasphaltic
compounds.
DEBUTANIZER A fractionating column used to
remove butane and lighter components from liquid streams.
DE-ETHANIZER A fractionating column designed to
remove ethane and gases from heavier hydrocarbons.
DEHYDROGENATION A reaction in which hydrogen
atoms are eliminated from a molecule. Dehydrogenation is used to convert
ethane, propane, and butane into olefins (ethylene, propylene, and butenes).
DEPENTANIZER A fractionating column used to remove
pentane and lighter fractions from hydrocarbon streams.
DEPROPANIZER A fractionating column for
removing propane and lighter components from liquid streams.
DESALTING Removal of mineral salts (most
chlorides, e.g., magnesium chloride and sodium chloride) from crude oil.
DESULFURIZATION A chemical treatment to remove
sulfur or sulfur compounds from hydrocarbons.
DEWAXING The removal of wax from petroleum
products (usually lubricating oils and distillate fuels) by solvent absorption,
chilling, and filtering.
DIETHANOLAMINE A chemical (C4H11O2N)
used to remove H2S from gas streams.
DISTILLATE The products of distillation formed
by condensing vapors.
DOWNFLOW Process in which the hydrocarbon
stream flows from top to bottom.
DRY GAS Natural gas with so little natural gas
liquids that it is nearly all methane with some ethane.
FEEDSTOCK Stock from which material is taken to
be fed (charged) into a processing unit.
FLASHING The process in which a heated oil
under pressure is suddenly vaporized in a tower by reducing pressure.
FLASH POINT Lowest temperature at which a
petroleum product will give off sufficient vapor so that the vapor-air mixture
above the surface of the liquid will propagate a flame away from the source of
ignition.
FLUX Lighter petroleum used to fluidize heavier
residual so that it can be pumped.
FOULING Accumulation of deposits in condensers,
exchangers, etc.
FRACTION One of the portions of fractional
distillation having a restricted boiling range.
FRACTIONATING COLUMN Process unit that
separates various fractions of petroleum by simple distillation, with the
column tapped at various levels to separate and remove fractions according to
their boiling ranges.
FUEL GAS Refinery gas used for heating.
GAS OIL Middle-distillate petroleum fraction with a
boiling range of about 350°-750° F, usually includes diesel fuel, kerosene,
heating oil, and light fuel oil.
GASOLINE A blend of naphthas and other refinery
products with sufficiently high octane and other desirable characteristics to
be suitable for use as fuel in internal combustion engines.
HEADER A manifold that distributes fluid from a
series of smaller pipes or conduits.
HEAT As used in the Health Considerations
paragraphs of this document, heat refers to thermal burns for contact with hot
surfaces, hot liquids and vapors, steam, etc.
HEAT EXCHANGER Equipment to transfer heat
between two flowing streams of different temperatures. Heat is transferred
between liquids or liquids and gases through a tubular wall.
HIGH-LINE OR HIGH-PRESSURE GAS
High-pressure (100 psi) gas from cracking unit distillate drums that is
compressed and combined with low-line gas as gas absorption feedstock.
HYDROCRACKING A process used to convert heavier
feedstock into lower-boiling, higher-value products. The process employs high
pressure, high temperature, a catalyst, and hydrogen.
HYDRODESULFURIZATION A catalytic process in
which the principal purpose is to remove sulfur from petroleum fractions in the
presence of hydrogen.
HYDROFINISHING A catalytic treating process
carried out in the presence of hydrogen to improve the properties of low viscosity-index
naphthenic and medium viscosity-index naphthenic oils. It is also applied to
paraffin waxes and microcrystalline waxes for the removal of undesirable
components. This process consumes hydrogen and is used in lieu of acid
treating.
HYDROFORMING Catalytic reforming of naphtha at
elevated temperatures and moderate pressures in the presence of hydrogen to
form high-octane BTX aromatics for motor fuel or chemical manufacture. This
process results in a net production of hydrogen and has rendered thermal
reforming somewhat obsolete. It represents the total effect of numerous
simultaneous reactions such as cracking, polymerization, dehydrogenation, and
isomerization.
HYDROGENATION The chemical addition of hydrogen
to a material in the presence of a catalyst.
INHIBITOR Additive used to prevent or retard
undesirable changes in the quality of the product, or in the condition of the
equipment in which the product is used.
ISOMERIZATION A reaction that catalytically
converts straight-chain hydrocarbon molecules into branched-chain molecules of
substantially higher octane number. The reaction rearranges the carbon skeleton
of a molecule without adding or removing anything from the original material.
ISO-OCTANE A hydrocarbon molecule (2,2,4-trimethylpentane)
with excellent antiknock characteristics on which the octane number of 100 is
based.
KNOCKOUT DRUM A vessel wherein suspended liquid
is separated from gas or vapor.
LEAN OIL Absorbent oil fed to absorption towers
in which gas is to be stripped. After absorbing the heavy ends from the gas, it
becomes fat oil. When the heavy ends are subsequently stripped, the solvent
again becomes lean oil.
LOW-LINE or LOW-PRESSURE GAS
Low-pressure (5 psi) gas from atmospheric and vacuum distillation
recovery systems that is collected in the gas plant for compression to higher
pressures.
NAPHTHA A general term used for low boiling
hydrocarbon fractions that are a major component of gasoline. Aliphatic naphtha
refers to those naphthas containing less than 0.1% benzene and with carbon
numbers from C3 through C16. Aromatic naphthas have
carbon numbers from C6 through C16 and contain
significant quantities of aromatic hydrocarbons such as benzene (>0.1%),
toluene, and xylene.
NAPHTHENES Hydrocarbons (cycloalkanes) with the
general formula CnH2n, in which the carbon atoms are
arranged to form a ring.
OCTANE NUMBER A number indicating the relative
antiknock characteristics of gasoline.
OLEFINS A family of unsaturated hydrocarbons
with one carbon-carbon double bond and the general formula CnH2n.
PARAFFINS A family of saturated aliphatic
hydrocarbons (alkanes) with the general formula CnH2n+2.
POLYFORMING The thermal conversion of naphtha
and gas oils into high-quality gasoline at high temperatures and pressure in
the presence of recirculated hydrocarbon gases.
POLYMERIZATION The process of combining two or
more unsaturated organic molecules to form a single (heavier) molecule with the
same elements in the same proportions as in the original molecule.
PREHEATER Exchanger used to heat hydrocarbons
before they are fed to a unit.
PRESSURE-REGULATING VALVE A valve that releases
or holds process-system pressure (that is, opens or closes) either by preset
spring tension or by actuation by a valve controller to assume any desired
position between fully open and fully closed.
PYROLYSIS GASOLINE A by-product from the
manufacture of ethylene by steam cracking of hydrocarbon fractions such as
naphtha or gas oil.
PYROPHORIC IRON SULFIDE A substance
typically formed inside tanks and processing units by the corrosive interaction
of sulfur compounds in the hydrocarbons and the iron and steel in the
equipment. On exposure to air (oxygen) it ignites spontaneously.
QUENCH OIL Oil injected into a product leaving
a cracking or reforming heater to lower the temperature and stop the cracking
process.
RAFFINATE The product resulting from a solvent
extraction process and consisting mainly of those components that are least
soluble in the solvents. The product recovered from an extraction process is
relatively free of aromatics, naphthenes, and other constituents that adversely
affect physical parameters.
REACTOR The vessel in which chemical reactions
take place during a chemical conversion type of process.
REBOILER An auxiliary unit of a fractionating
tower designed to supply additional heat to the lower portion of the tower.
RECYCLE GAS High hydrogen-content gas returned
to a unit for reprocessing.
REDUCED CRUDE A residual product remaining
after the removal by distillation of an appreciable quantity of the more
volatile components of crude oil.
REFLUX The portion of the distillate returned
to the fractionating column to assist in attaining better separation into
desired fractions.
REFORMATE An upgraded naphtha resulting from
catalytic or thermal reforming.
REFORMING The thermal or catalytic conversion
of petroleum naphtha into more volatile products of higher octane number. It
represents the total effect of numerous simultaneous reactions such as
cracking, polymerization, dehydrogenation, and isomerization.
REGENERATION In a catalytic process the
reactivation of the catalyst, sometimes done by burning off the coke deposits
under carefully controlled conditions of temperature and oxygen content of the
regeneration gas stream.
SCRUBBING Purification of a gas or liquid by
washing it in a tower.
SOLVENT EXTRACTION The separation of materials
of different chemical types and solubilities by selective solvent action.
SOUR GAS Natural gas that contains corrosive,
sulfur-bearing compounds such as hydrogen sulfide and mercaptans.
STABILIZATION A process for separating the
gaseous and more volatile liquid hydrocarbons from crude petroleum or gasoline
and leaving a stable (less-volatile) liquid so that it can be handled or stored
with less change in composition.
STRAIGHT-RUN GASOLINE Gasoline produced by the
primary distillation of crude oil. It contains no cracked, polymerized, alkylated,
reformed, or visbroken stock.
STRIPPING The removal (by steam-induced
vaporization or flash evaporation) of the more volatile components from a cut
or fraction.
SULFURIC ACID TREATING A refining process in
which unfinished petroleum products such as gasoline, kerosene, and lubricating
oil stocks are treated with sulfuric acid to improve their color, odor, and
other characteristics.
SULFURIZATION Combining sulfur compounds with
petroleum lubricants.
SWEETENING Processes that either remove
obnoxious sulfur compounds (primarily hydrogen sulfide, mercaptans, and
thiophens) from petroleum fractions or streams, or convert them, as in the case
of mercaptans, to odorless disulfides to improve odor, color, and oxidation
stability.
SWITCH LOADING The loading of a high
static-charge retaining hydrocarbon (i.e., diesel fuel) into a tank truck, tank
car, or other vessel that has previously contained a low-flash hydrocarbon
(gasoline) and may contain a flammable mixture of vapor and air.
TAIL GAS The lightest hydrocarbon gas released
from a refining process.
THERMAL CRACKING The breaking up of heavy oil
molecules into lighter fractions by the use of high temperature without the aid
of catalysts.
TURNAROUND A planned complete shutdown of an
entire process or section of a refinery, or of an entire refinery to perform
major maintenance, overhaul, and repair operations and to inspect, test, and
replace process materials and equipment.
VACUUM DISTILLATION The distillation of
petroleum under vacuum which reduces the boiling temperature sufficiently to
prevent cracking or decomposition of the feedstock.
VAPOR The gaseous phase of a substance that is
a liquid at normal temperature and pressure.
VISBREAKING Viscosity breaking is a low-temperature
cracking process used to reduce the viscosity or pour point of straight-run
residuum.
WET GAS A gas containing a relatively high
proportion of hydrocarbons that are recoverable as liquids.