Fahim M.A., Sahhaf T.A., Elkilani A.S. Fundamentals of Petroleum Refining
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Dehydrogenation A reaction in which hydrogen atoms are eliminated from a
molecule. Dehydrogenation is used to convert ethane, pro-
pane and butane into olefins (ethylene, propylene and
butenes).
Desalting Removal of mineral salts (most chlorides, e.g. magnesium
chloride and sodium chloride) from crude oil.
Desulphurization A chemical treatment to remove sulphur or sulphur com-
pounds from hydrocarbons.
Dewaxing The removal of wax from petroleum products (usually lubri-
cating oils and distillate fuels) by solvent absorption, chilling
and filtering.
Diethanolamine A chemical (C
4
H
11
O
2
N) used to remove H
2
S from gas
streams.
Distillate The products of distillation formed by condensing vapours.
Dry gas Natural gas with so little natural gas liquids, that it is nearly all
methane with some ethane.
Feed stock Stock from which material is taken to be fed into a processing
unit.
Flash point Lowest temperature at which a petroleum product will give
off sufficient vapour so that the vapour–air mixture above the
surface of the liquid will propagate a flame away from the
source of ignition.
Flashing The process in which a heated oil under pressure is suddenly
vaporized in a tower by reducing pressure.
Flexicoking Thermal process in which coke is gasified into fuel gas using
steam and air.
Fouling Accumulation of deposits in condensers, exchangers, and
so on.
Fractionating tower 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 suffi-
ciently high octane and other desirable characteristics to be
suitable for use as fuel in internal combustion engines.
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.
Appendix B 471
Hydrodesulphurization A catalytic process in which the principal purpose is to
remove sulphur from petroleum fractions in the presence of
hydrogen.
Hydrogenation The chemical addition of hydrogen to a material in the
presence of a catalyst.
Isomerization A reaction that catalytically converts straight-chain hydrocar-
bon molecules into branched-chain molecules of substan-
tially 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.
Kerosene A middle distillate product composed of material of 300–
550
F boiling range.
Knockout drum A vessel wherein suspended liquid is separated from gas or
vapour.
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.
LPG Liquefied petroleum gas. Liquefied light end gases used for
home heating and cooking. The gas contains 95% propane,
and the balance is a split between ethane and butane.
MON Motor octane number. A measure of resistance to self-
ignition (knocking) of gasoline. It is the percentage by volume
of isooctane in a mixture of isooctane and n-heptane that
knocks with the same intensity as the fuel being tested.
Napthenes Hydrocarbons (cycloalkanes) with the general formula
C
n
H
2n
, in which the carbon atoms are arranged to form
a ring.
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 C
3
to C
16
. Aromatic
naphthas have carbon numbers from C
6
to C
16
and contain
significant quantities of aromatic hydrocarbons such as ben-
zene (>0.1%), toluene and xylene.
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 C
n
H
2n
.
Paraffins A family of saturated aliphatic hydrocarbons (alkanes) with
the general formula C
n
H
2nþ2
.
472 Appendix B
Pour point The lowest temperature at which a petroleum oil will flow or
pour when it is chilled without disturbance at a controlled
rate.
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 some-
times done by burning off the coke deposits under carefully
controlled conditions of temperature and oxygen content of
the regeneration gas stream.
RON Research octane number: same definition of MON except
the engine operates here at 600 rpm.
RVP Reid vapour pressure. The vapour pressure at 100
Fofa
product determined in a volume of air four times the liquid
volume.
Salt content Salts in solution that are emulsified with the crude.
Scrubbing Purification of a gas or liquid by washing it in a tower.
Severity The degree of intensity of the operating conditions of a
process unit.
Smoke point A test measuring the burning quality of jet fuels, kerosene
and illuminating oils. It is defined as the height of the flame.
Solvent extraction The separation of materials of different chemical types and
solubility by selective solvent action.
Appendix B 473
Sour gas Natural gas that contains corrosive, sulphur-bearing com-
pounds such as hydrogen sulphide 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 evapo-
ration) of the more volatile components from a cut or
fraction.
Sulphuric acid treating A refining process in which unfinished petroleum products
such as gasoline, kerosene and lubricating oil stocks are
treated with sulphuric acid to improve their colour, odour
and other characteristics.
Sulphurization Combining sulphur compounds with petroleum lubricants.
Sweetening Processes that either remove obnoxious sulphur compounds
(primarily hydrogen sulphide, mercaptans and thiophens)
from petroleum fractions or streams, or convert them, as in
the case of mercaptans, to odourless disulphides to improve
odour, colour and oxidation stability.
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.
Turn around 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.
Visbreaking 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 hydrocar-
bons that are recoverable as liquids.
474 Appendix B
Appendix C
C. Process Simulator (UNISIM) Manual
Process simulation is the use of a computer program to quantitatively
model the characteristic equations of a process flowsheet by utilizing:
Mass and energy balance
Equilibrium relationships
Rate correlations (reaction and mass/heat transfer)
To obtain quickly an estimate of:
Stream flow rates, compositions and properties
Operating conditions
Equipment sizes
Steady state process simulation
Rigorous petroleum simulation
Petroleum/crude oil handling
Data regression, data fit and optimization
Some time models are used in:
Improving current processes
Answering ‘‘What If’’ scenarios
Determining optimal process conditions within given constraints
Assisting in locating constraining parts of a process (de-bottlenecking)
UNISIM, licensed by Honeywell Process Solutions, provides the user
with an intuitive and interactive approach towards process modelling,
simulation and optimization. This software lets you create detailed high
fidelity plant simulations for analyzing and optimizing your plant’s opera-
tion. Through the completely interactive UNISIM interface, you have
access to a fine level of equipment geometry, performance detail as well as
the ability to completely customize your simulation using its OLE extensi-
bility capability.
At any time, you can access help information by pressing F1. You can
also look at the entire help structure by clicking the UNISIM Help Topics
command in the Help menu.
Fundamentals of Petroleum Refining
#
2010 Elsevier B.V.
DOI: 10.1016/ B978-0-444-52785-1.00029-2 All rights reserved.
475
In the following sections, we will introduce flowsheeting concepts and
some UNISIM simulator program features.
The simulation basis manager is the main view of the simulation envi-
ronment. One of the important concepts is that UNISIM is based upon
environments. The simulation basis environment allows you to input or
access information within the simulation basis manager, while the other
areas of UNISIM are put on hold, avoiding unnecessary flowsheet calcula-
tions. Once the simulation environment is entered, all changes that were
made in the simulation basis environment will take effect at the same time.
Conversely, all thermodynamic data are fixed and will not be changed as
manipulations to the flowsheet take place in the simulation environment.
The minimum required inputs to run a simulation are:
Set-up
Components
Properties
Streams
Blocks
Simulator operation procedure:
Step 1: Opening a new case is shown in Fig. C.1
Step 2: Entering components (Fig. C.2)
New Case
Components
Crude Assay
Figure C.1 Opening a new case
476 Appendix C
The component ID is used to identify the component in simulation
inputs and results
Each component ID can be associated with a databank component as
either:
Formula: Chemical formula of component
Name: Full name of component
View component property in the databank as shown in Fig. C.3.
Select by name
or formula
Add components
View property
Figure C.2 Adding component list
Critical properties
Figure C.3 Viewing component properties
Appendix C 477
Step 3: Entering fluid package for thermo-physical property model
(Fig. C.4)
The choice of the thermodynamic property model depends on:
Degree of non-ideal behaviour of components
Range of operating conditions in the process
Samples of the fluid package are:
Equation of State Methods: Peng–Robinson (PR) and Soave–
Redlich–Kwong (SRK)
Activity Coefficient Methods: Non-random two liquid (NRTL),
unified functional activity coefficient (UNIFAC), universal quasi-
unified activity coefficient (UNIQUAC)
Step 4: Petroleum handling assay characterization
Entering oil environment (Fig. C.5)
Edit crude assay data such as TBP/vol%, ASTM or others (Fig. C.6)
Calculate the assay properties
Plot the distribution of cuts (Fig. C.7 )
The more ‘‘pseudo’’ or hypothetical components cut properties are
calculated
Fluid Package
(PR)
Figure C.4 Selection of fluid package for all property types
478 Appendix C
Step 5: Simulation environment
Figure C.8 shows the simulation environment containments
Figure C.9 shows the required data for each input stream in
the flowsheet such as name, temperature, pressure, composition
(mole, mass or volume fractions) of components, quality and others,
if any.
Oil Environment
Figure C.5 Oil environment from oil ma nage r
TBP-Vol% Data
Figure C.6 Entering crude assay data
Appendix C 479
Some unit operation models require additional specification forms (e.g.
reactors)
Reactions stoichiometry entered as equilibrium or conversion reac-
tion (Fig. C.10)
Entering the design connection stream data (Fig. C.11)
Recycle stream:
Flow (total and component), pressure and enthalpy are manipulated
by iteration
Assay
Distribution
A
Figure C.7 (A) Calculation of crude assay data and TBP distillation f it; (B) Calculation
of crude assay data andTBP distillation fit
480 Appendix C