Knowledge Base
III.   Petroleum Refining Operations

A.  INTRODUCTION. Petroleum refining begins with the distillation, or fractionation, of crude oils into separate hydrocarbon groups. The resultant products are directly related to the characteristics of the crude processed. Most distillation products are further converted into more usable products by changing the size and structure of the hydrocarbon molecules through cracking, reforming, and other conversion processes as discussed in this chapter. These converted products are then subjected to various treatment and separation processes such as extraction, hydrotreating, and sweetening to remove undesirable constituents and improve product quality. Integrated refineries incorporate fractionation, conversion, treatment, and blending operations and may also include petrochemical processing.

B.   REFINING OPERATIONS. Petroleum refining processes and operations can be separated into five basic areas:

1.   Fractionation (distillation) is the separation of crude oil in atmospheric and vacuum distillation towers into groups of hydrocarbon compounds of differing boiling-point ranges called "fractions" or "cuts."

2.   Conversion processes change the size and/or structure of hydrocarbon molecules. These processes include:

Decomposition (dividing) by thermal and catalytic cracking;
Unification (combining) through alkylation and polymerization; and
Alteration (rearranging) with isomerization and catalytic reforming.

3.   Treatment processes are intended to prepare hydrocarbon streams for additional processing and to prepare finished products. Treatment may include the removal or separation of aromatics and naphthenes as well as impurities and undesirable contaminants. Treatment may involve chemical or physical separation such as dissolving, absorption, or precipitation using a variety and combination of processes including desalting, drying, hydrodesulfurizing, solvent refining, sweetening, solvent extraction, and solvent dewaxing.

4.   Formulating and Blending is the process of mixing and combining hydrocarbon fractions, additives, and other components to produce finished products with specific performance properties.

5.   Other Refining Operations include: light-ends recovery; sour-water stripping; solid waste and wastewater treatment; process-water treatment and cooling; storage and handling; product movement; hydrogen production; acid and tail-gas treatment; and sulfur recovery.

        Auxiliary operations and facilities include: steam and power generation; process and fire water systems; flares and relief systems; furnaces and heaters; pumps and valves; supply of steam, air, nitrogen, and other plant gases; alarms and sensors; noise and pollution controls; sampling, testing, and inspecting; and laboratory, control room, maintenance, and administrative facilities.

FIGURE IV:2-6. REFINERY PROCESS CHART.
Refinery process chart

TABLE IV: 2-3. OVERVIEW OF PETROLEUM REFINING PROCESSES.
Process name

Action

Method

Purpose

Feedstock(s)

Product(s)

FRACTIONATION PROCESSES
Atmospheric distillation
Separation
Thermal
Separate fractions
Desalted crude oil
Gas, gas oil, distillate, residual
Vacuum distillation
Separation
Thermal
Separate w/o cracking
Atmospheric tower residual
Gas oil, lube stock, residual
CONVERSION PROCESSED--DECOMPOSITION
Catalytic cracking
Alteration
Catalytic
Upgrade gasoline
Gas oil, coke distillate
Gasoline, petrochemical feedstock
Coking
Polymerize
Thermal
Convert vacuum residuals
Gas oil, coke distillate
Gasoline, petrochemical feedstock
Hydro-cracking
Hydrogenate
Catalytic
Convert to lighter HC's
Gas oil, cracked oil, residual
Lighter, higher-quality products
*Hydrogen steam reforming
Decompose
Thermal/ catalytic
Produce hydrogen
Desulfurized gas, O2, steam
Hydrogen, CO, CO2
*Steam cracking
Decompose
Thermal
Crack large molecules
Atm tower hvy fuel/ distillate
Cracked naphtha, coke, residual
Visbreaking
Decompose
Thermal
reduce viscosity
Atmospheric tower residual
Distillate, tar
CONVERSION PROCESSES--UNIFICATION
Alkylation
Combining
Catalytic
Unite olefins & isoparaffins
Tower isobutane/ cracker olefin
Iso-octane (alkylate)
Grease compounding
Combining
Thermal
Combine soaps & oils
Lube oil, fatty acid, alky metal
Lubricating grease
Polymerizing
Polymerize
Catalytic
Unite 2 or more olefins
Cracker olefins
High-octane naphtha, petrochemical stocks
CONVERSION PROCESSES--ALTERATION OR REARRANGEMENT
Catalytic reforming
Alteration/
dehydration
Catalytic
Upgrade low-octane naphtha
Coker/ hydro-cracker naphtha
High oct. Reformate/ aromatic
Isomerization
Rearrange
Catalytic
Convert straight chain to branch
Butane, pentane, hexane
Isobutane/ pentane/ hexane
TREATMENT PROCESSES
*Amine treating
Treatment
Absorption
Remove acidic contaminants
Sour gas, HCs w/CO2 & H2S
Acid free gases & liquid HCs
Desalting
Dehydration
Absorption
Remove contaminants
Crude oil
Desalted crude oil
Drying & sweetening
Treatment
Abspt/ therm
Remove H2O & sulfur cmpds
Liq Hcs, LPG, alky feedstk
Sweet & dry hydrocarbons
*Furfural extraction
Solvent extr.
Absorption
Upgrade mid distillate & lubes
Cycle oils & lube feed-stocks
High quality diesel & lube oil
Hydrodesulfurization
Treatment
Catalytic
Remove sulfur, contaminants
High-sulfur residual/ gas oil
Desulfurized olefins
Hydrotreating
Hydrogenation
Catalytic
Remove impurities, saturate HC's
Residuals, cracked HC's
Cracker feed, distillate, lube
*Phenol extraction
Solvent extr.
Abspt/ therm
Improve visc. index, color
Lube oil base stocks
High quality lube oils
Solvent deasphalting
Treatment
Absorption
Remove asphalt
Vac. tower residual, propane
Heavy lube oil, asphalt
Solvent dewaxing
Treatment
Cool/ filter
Remove wax from lube stocks
Vac. tower lube oils
Dewaxed lube basestock
Solvent extraction
Solvent extr.
Abspt/ precip.
Separate unsat. oils
Gas oil, reformate, distillate
High-octane gasoline
Sweetening
Treatment
Catalytic
Remv H2S, convert mercaptan
Untreated distillate/gasoline
High-quality distillate/gasoline

* Note: These processes are not depicted in the refinery process flow chart.

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