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Файл:Chemical Engineering of Natural Fuels and Carbon Materials. Study Guide
.pdf
The Ministry of education and science of the Russian Federation
Federal state budget educational
institution of higher education
«Kazan National Research Technological University»
CHEMICAL ENGINEERING OF NATURAL
FUELS AND CARBON MATERIALS
Study Guide
Kazan
KNRTU Publishing house
2016
1
UDK 665.642.2
Reviewers:
E. S. Okhotnikova, A. E. Arbuzov Institute of Organic
and Physical Chemistry, Ph.D. in Chemical Science
A. F. Kemalov, Professor of Kazan Federal
University, D.Sc. in Technical Science
ISBN 978-5-7882-1927-1
©
Emelyanycheva Е. А., Abdullin A. I.,
Timirbaeva G. R., Khamidullin R. F., 2016
©
Kazan National Research Technological
University, 2016
BBK 35.51
Authors: E. A. Emelyanycheva, A. I. Abdullin, G. R. Timirbaeva,
R. F. Khamidullin
Chemical Engineering of Natural Fuels and Carbon Materials : Study
Guide / Е. А. Emelyanycheva [et al]; The Ministry of Education and Science
of the Russian Federation, Kazan National Research Technological
University. – Kazan : KNRTU Publishing House, 2016. – 96 p.
ISBN 978-5-7882-1927-1
The Study Guide presents the basic content of practical part of the
course "Fundamentals of natural fuels and carbon materials chemical
engineering" with examples and tasks for student self-directed learning.
The Study Guide is intended for students studying Bachelor program
18.03.01 "Chemical Engineering" and 21.03.01 "Petroleum Engineering." It
can be also useful for students studying Bachelor programs of Petroleum and
Petrochemistry Faculty.
The Study Guide is prepared by Chemical Technology of Petroleum
and Gas Processing Department of KNRTU.
It is published by the decision of Editing and Publishing Board of
Kazan National Research Technological University
2
TABLE OF CONTENTS
INTRODUCTION
5
1. THERMOCHEMISTRY. CALCULATION OF THERMAL
EFFECTS OF HYDROCARBON REACTIONS
9
2. THERMAL PROPERTIES OF PETROLEUM PRODUCTS.
TEMPERATURE DEPENDENCE OF THERMAL EFFECT OF
A REACTION
15
3. GIBBS FREE ENERGY AS A MEASURE OF THE
THERMODYNAMIC FEASIBILITY OF A CHEMICAL
REACTION
20
4. THE EQUILIBRIUM CONSTANT OF A CHEMICAL
REACTION
24
5. KINETICS OF CHEMICAL REACTIONS
28
6. BOND STRENGTH IN THE MOLECULES OF
HYDROCARBONS. REACTIONS OF THE RADICALS.
THERMAL CONVERSION OF HYDROCARBONS
32
3
7. OIL REFINING PROCESSES IN THE PRESENCE OF
ACIDIC CATALYSTS. CONVERSION OF CARBOCATIONS
IN CATALYTIC PROCESSES
41
8. THE CHEMISTRY OF HYDROCATALYTIC PROCESSES
52
9. HYDROCARBON PROCESSING MATERIALS AND HEAT
BALANCES CALCULATIONS
55
VOCABULARY BANK
68
APPENDIXES
78
BIBLIOGRAPHY
95
4
INTRODUCTION
An oil refinery is considered to be an essential part of the petroleum
industry.
An oil refinery or petroleum refinery includes industrial
processes, where crude oil is processed and refined into such products
as petroleum naphtha, gasoline, diesel fuel, asphalt base, heating oil,
kerosene and liquefied petroleum gas (LPG). Oil refineries are typically
large industrial complexes with extensive piping running throughout,
carrying streams between large chemical processing units. Oil refineries are
a type of chemical plants.
The crude oil feedstock is typically processed in an oil production
plant. Crude oil contains hydrocarbons of varying molecular masses, forms
and lengths such as paraffins (alkanes), aromatics
(arenes), naphthenes (or cycloalkanes). Refined fractions can also contain
alkenes, dienes and alkynes. Also there are heteroatoms such as sulfur,
nitrogen and oxigen containing compounds of varying complexity in crude oil.
The differences in the structure of these molecules account for their
varying physical and chemical properties, and it is this variety that makes
crude oil useful in a broad range of applications.
Crude oil is divided into petroleum fractions which can be used
as fuels, lubricants, and as feedstocks in other processes.
Isobutane and propylene or butylenes can be recombined to meet
specific octane requirements by processes such as alkylation, or less
commonly, dimerization. The octane grade of gasoline can also be improved
by catalytic reforming, which involves removing hydrogen from
hydrocarbons producing compounds with higher octane ratings such
as aromatics. Intermediate products such as gasoils can be reprocessed to
break a heavy, long-chained molecules into a lighter short-chained ones by
various forms of cracking such as catalytic cracking, thermal cracking, and
hydrocracking. The final step in petroleum products production is the
compounding of products with different properties to meet final
specifications.
Petroleum products are usually grouped into three categories: light
distillates (LPG, gasoline, naphtha), middle distillates (kerosene and
related jet aircraft fuels, diesel), heavy distillates and residues (heavy fuel
oil, lubricating oils, wax, asphalt and tar), petroleum coke and sulfur. This
classification is based on the way crude oil is distilled and separated into
fractions, also called distillates.
5
Oil refineries also produce various intermediate products such
as hydrogen, light hydrocarbons and pyrolysis gasoline. These are not
usually transported but instead are blended or processed further on-site. For
example, light hydrocarbons are steam-cracked in an ethylene producing
unit, and the produced ethylene is polymerized to produce polyethene.
Thus every refining process and unit has its purpose.
The desalter unit washes out salt from the crude oil before it enters
the crude oil distillation unit (CDU), which is the first processing unit in
virtually all petroleum refineries. The CDU distills the incoming crude oil
into various fractions of different boiling ranges (each fraction has initial
boiling point and ending boiling point), each of which are then processed
further into other refinery processing units. The CDU is often referred to as
the Atmospheric Distillation Unit (ADU) because it operates at pressure
slightly above atmospheric one. The atmospheric distillation unit distills
crude oil into fractions. Vacuum distillation unit (VDU) distills residual
bottoms after atmospheric distillation. The naphtha hydrotreater unit
uses hydrogen to desulfurize naphtha from atmospheric distillation before
sending it to a catalytic reforming unit. The catalytic reforming unit is used
to convert the naphtha-boiling range molecules into higher
octane reformate. The reformate has the higher content of aromatics and
cyclic hydrocarbons. An important byproduct of a reformer is hydrogen
released during main reactions. The hydrogen is used either in the
hydrotreaters or the hydrocrackers. Distillate hydrotreater desulfurizes
distillates, such as diesel, after atmospheric distillation. The Fluid Catalytic
Cracker (FCC) unit and the Hydrocracker unit upgrade heavier fractions
into lighter, more valuable products. The Visbreaking unit upgrades heavy
residual oils by thermally cracking them into lighter reduced viscosity
products. The Merox unit treats LPG, kerosene or jet fuel by
oxidizing mercaptans to organic disulfides. Coking units, delayed coking
unit, fluid coker, and flexicoker, process very heavy residual oils into
gasoline and diesel fuel, leaving petroleum coke as a residual product. The
Alkylation unit uses sulfuric acid or hydrofluoric acid to produce highoctane components for gasoline. The Isomerization unit converts linear
molecules to higher-octane branched molecules for blending into gasoline
or feeding to alkylation units. The Steam reforming unit produces hydrogen
for the hydrotreaters or hydrocrackers. The Amine tail gas treater, Claus
unit converts hydrogen sulfide from hydrodesulfurization into elemental
sulfur.
6
gas
fractionation
plant
dry gas
liquefied
petroleum gas
SRU
sulfurH2S
SRU
natural gas H2
naphta HT
ADU / VDU
isomerization
reforming
i.b.p.-70
70-180
Isomerizate (compounding)
reformate (compounding)
kerosen HT
kerosen (realization)
diesel fuel HT
summer diesel fuel
gasoline-distilled
(realization)
240-350
CC gasoline HT
CC light gasoline
CC naphta
FCC
VG HT
CC gasoline
butane-butylene fraction
FCC light
gas oil
VG
visbreaking
bitumen blowing unit
FCC heavy
gas oil
fuel oil (realization)
bitumen (realization)
tar
oil
7
Fig. 1.1. Process flow diagram of the petrol profile of oil refinery
HT – Hydrotreating, CC gasoline – Catalytic Cracking gasoline,
FCC – Catalytic Cracking Fluid Unit, VG – vacuum gas oil, HPU –
Hydrogen Production Unit, SRU – Sulfur Recovery Unit, VBR –
visbreaking, ADU/VDU – Atmospheric/Vacuum Distillation Unit
Solvent refining units use solvent such as cresol or furfural to
remove unwanted components, mainly aromatics, from lubricating oil stock
or diesel stock.
Solvent dewaxing units remove the heavy waxy
constituents (petrolatum) from vacuum distillation products.
Petroleum refinery also includes any of the usual refinery facilities
providing utilities such as steam, cooling water, and electric power as well
as storage tanks for crude oil feedstock and for intermediate products and
end products.
8
1. THERMOCHEMISTRY.
CALCULATION OF THERMAL EFFECTS
OF HYDROCARBON REACTIONS
All chemical processes of substances transformation proceed with a
particular thermal effect.
In thermodynamics, the following designation has been adopted:
1) ∆Н < 0 is for an exothermic process, heat release (dissipation);
2) ∆Н > 0 is for an endothermic process, heat absorption.
Generally, almost all synthesis processes, various addition reactions
proceed with heat release, they are called exothermic processes (for
example, hydrogenation, hydration, condensation, polymerization,
alkylation).
Decomposition reactions proceed with heat absorption, they are
endothermic processes (for example, cracking, dehydrogenation,
dehydration, dealkylation, depolymerization, dehydrocyclization).
Thermal effect is usually referred to 1 mol of a substance (usually a
reaction product). Its unit of measure is J/mol (joule per mole) or kJ/mol
(kilojoule per mole). Sometimes off-system units are used, such as cal/mol
(calories per mole) or kcal/mol (kilocalories per mole).
The value in calories per mole, multiplied by 4.19, equals the value
in kilojoules per mole.
Often during the solving tasks and exercises the standard thermal
effect is used (it is determined at standard conditions, which correspond to
the temperature of T = 25 °C = 298 ° K and preassure P = 1 atm (1.013 ∙ 10
Pa = 0.1 MPa).
The thermal effect is calculated on the basis of Hess’s law.
In accordance with Hess's law, the thermal effect of the reaction
does not depend reaction behavior, but only on the nature and condition of
the initial substances and resulting products.
Hess's law has a number of consequences, the most important of
which are two:
1) The thermal effect of the reaction is equal to the difference
between the sums of the heat of formation values of the final products and
the heat of formation values of the initial substances (taking into account the
stoichiometric coefficients):
5
9
Heat of formation (heat of combination) is the thermal effect of
the reaction of the formation of 1 mole of the compound from simple
substances. Wherein, the heat of formation value of simple substances is
equal to zero.
Standard heat of formation is designated as
.
2) The thermal effect of the chemical reaction is equal to the
difference between the sums of the values of combustion heat of initial
substances and the values of combustion heat of products:
.
The heat of combustion (along with calorific value, combustion
heat in engineering literature) is the thermal effect of the reaction of
oxidation of 1 mole of the compound with oxygen to form higher oxides of
elements. For example, for hydrocarbons, it will be carbon dioxide (CO2)
and water (H2O).
The standard heat of combustion of oxides is equal to zero. The
standard heat of formation and heat of combustion of various compounds
are given in the reference tables (Appendix 1). We obtain more accurate
results using the values of the heat of formation in our calculations.
The thermal effect of the chemical reaction can also be calculated as
the difference between the sums of the bond energies (or binding energy,
cohesive energy) of initial substances and the bond energies of products:
This method is implemented for calculating the thermal effects of
chemical transformations of aliphatic (acyclic) organic compounds. In
aliphatic organic compounds, the carbon atoms are linked in open chains.
As for the sign of the value of thermal effect there, there is no single
approach. In thermodynamics, the heat released by the system is considered
as negative, and the heat absorbed by the system is considered as positive,
in chemistry and some other fields it is on the contrary. This fact should be
taken into the consideration during the calculations.
Example 1.1
Determine the thermal effect of the reaction of the dehydrogenation
of ethane into ethylene under standard conditions using different methods.
10
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