Refinery Structure- EvolutionRefinery Structure- Evolution
Topping Refinery
Hydroskimming Refinery
Conversion Refinery
Mainly fractionation by distillationFor production of industrial fuels
Hydro treating units added for fuelsquality improvement
Addition of several conversion processesto improve: fuels recovery efficiency, further quality improvement, process heavier fractions / crudes & energy efficiency
Processing of light crude Processing of light crude
Processing of light crude, even in a complex/modern refinery with FCC,
hydrocracking etc. does not yield a satisfactory product distribution.
The amounts of fuel oil are too high.
Processing of heavy oilProcessing of heavy oilFor heavy oil the situation is even worse with ~ 50% fuel oil being produced even in a complex /modern refinery.
Fuel oil is worth < original crude. The value of the products decreases in the order: gasoline> kerosene/gas oil > crude oil > fuel oil.
Bottom of the barrel treatment is vitalChallenge – Meeting Strict Quality standards & Increasing Demand
Gasoline Specs-IndiaGasoline Specs-India
Diesel Specs- IndiaDiesel Specs- India
Structure of refineryStructure of refinery
Flow Scheme of modern oil refineryFlow Scheme of modern oil refinery
Catalytic processes in refineryCatalytic processes in refinery
Petroleum refining processesPetroleum refining processes
Petroleum Refining- Types of OperationsPetroleum Refining- Types of OperationsFractionation (distillation)-
Separation of crude oil in atmospheric and vacuum distillation towers into groups of hydrocarbon compounds of differing boiling-point ranges called "fractions" or "cuts."
Conversion Processes Changing the size and/or structure of hydrocarbon molecules via different processes:
Decomposition (dividing) by thermal and catalytic cracking; Unification (combining) through alkylation and polymerization; andAlteration (rearranging) with isomerization and catalytic reforming.
Treatment Processes For additional processing and to prepare finished products. Removal or separation of aromatics / naphthenes/ impurities / undesirable contaminants. Chemical or physical separation e.g. dissolving, absorption, or precipitation Desalting, drying, hydro de-sulfurization, sweetening, solvent refining, solvent extraction, and solvent de-waxing.
Processes in Oil RefiningProcesses in Oil Refining
Physical Thermal CatalyticDistillation Visbreaking Fluid Catalytic
Cracking
Solvent extraction
Delayed coking
Hydrotreating
Solvent dewaxing Fluid cocking Catalytic Reforming
Propane deasphalting
Flexi coking Catalytic dewaxing
Blending Hydrocracking
Isomerization
Alkylation
Etherification
Polymerization
Petroleum - PropertiesPetroleum - PropertiesDensity Specific gravity - Ratio of mass of specific volume to mass of the same
volume of water, both at the same temperatureAPI GravityDegrees API = (141.5/Specific gravity at 60/60 °F) – 131.5
Viscosity- cP- Flow characteristicsKinematic viscosity/fluidity = Viscosity/ Specific gravity
Carbon residue (wt%) Carbonaceous residue left out after destructive distillation- non-volatile part of petroleum/petroleum products Ramsbottom method- ASTM D 189 IP3Conradson method - ASTM D 189 IP4Viscosity and Asphaltenes, Nitrogen & Sulfur contents increase with
increasing carbon residueIndicates the potential for coke formation
Signify Light/Heavy character of Crude oilSignify Light/Heavy character of Crude oil
Petroleum - PropertiesPetroleum - Properties
Aniline point
Temperature at which exactly equal parts of two components are
Miscible- Aniline & Any petroleum fraction/oil
Increases slightly with molecular weight
Increases rapidly with paraffinic character/
Higher the aniline point- lower is the aromatics content in the fraction
Reid vapor pressure (RVP)
A measure of the volatility of gasoline. It is defined as the absolute vapor pressure exerted by a liquid at 100 °F (37.8 °C) as determined by the test method ASTM-D-323.
RVP differs slightly from the True Vapor pressure (TVP) of a liquid due to some small sample vaporization and the presence of water vapor and air in the confined space of the test equipment, i.e. the RVP is the absolute vapor pressure and the TVP is the partial vapor pressure
Petroleum - PropertiesPetroleum - PropertiesCloud point
The temperature of the test specimen at which wax crystals have formed sufficiently to be observed as a cloud from a petroleum fractionApplicable for petroleum products and biodiesel fuelsAn index of the lowest temperature of their utility for certain applications. Petroleum blending operations require a precise measurement of the cloud point.
Smoke point Provides an indication of the relative smoke producing properties of kerosines and aviation turbine fuels in a diffusion flame. Related to the hydrocarbon type composition of such fuels, esp. aromaticsMore aromatic the fuel the smokier the flame. A high smoke point indicates a fuel of low smoke producing tendency.The smoke point is quantitatively related to the potential radiant heat transfer from the combustion products of the fuel.
Petroleum- PropertiesPetroleum- Properties
Pour pointThe lowest temperature at which it will pour or flow under prescribed conditions. It is a rough indication of the lowest temperature at which oil is readily pumpable. Can be defined as the minimum temperature of a liquid, particularly a lubricant, after which, on decreasing the temperature, the liquid ceases to flow.
UOP K factor ( Watson Characterization factor)
K = 3√ TB/ S TB- Average molal BP in Deg.Rankine ; S- Sp.gravity at 60°F
Crude Assay- Properties that determine the processibility, product pattern & hence the cost of the crude
These fractions need go through regular
refining processes to yield fuels of acceptable grade
Thermal Processes:Thermal Processes:
Cracking & CokingCracking & Coking
DesaltingDesaltingObjectivesRemoval of water, inorganic salts, water soluble metals & suspended
solids from crude oil –Prevention of corrosion, fouling & plugging of equipments
ProcessTwo stage desalting is carried out, with removal of most of the water at first
stage, followed by addition of dilution water in the second stage to extract
soluble salts & metals. Process conditions are 90-150°C and 50-250 psi.
Surfactants are added to demulsify & achieve proper separation and remove
water by settling. Application of electrostatic coalescing is also adopted
Thermal crackingThermal crackingDubbs process
Thermal cracking of reduced crude at 455-540°C & 100-1000 psi
Major products- Gasoline & middle distillates Soaking of light & heavier fractions & further cracking
Thermal cracking of Reduced crude oilFeedstock; API gravity 25 °C ; IBP- 227°C
Cracking parameters- 500 °C ; Soaker pressure; 225 psi Product yields (Vol%)
Gasoline Heating oil
Gas - 1.0
Naphtha 57.5 42.0
Heating oil 0.0 23.0
Residuum 37.5 34.0
VisbreakingVisbreaking
Viscosity-breaking- Cracking to reduce the viscosity A mild form of thermal cracking of the residue (10% conversion), at 50-300 psig
pressure at 455-520°C to reduce viscosity/ pour point. Liquid phase cracking. Process optimized to minimize coke formation Water injected with the feed to provide turbulance & control temperature Residue from Atmos. / Vac. distillation units can be used Coil/Furnace type- high temp. & short residence time Soaker type- Lower temp. & longer residence time Product stability is the issue- Olefinics
Feedstock From ProcessTypical products To
Residual Atmospheric tower & Vacuum tower
Decompose Gasoline or distillate
Hydrotreating
Vapor Hydrotreater
Residue Stripper or recycle
Gases Gas plant
Visbreaking- Yield patternVisbreaking- Yield pattern
Luisiana Vacuum Residue
Arabian Light Atmos.residue
Feed stock
Gravity API
Carbon residue
Sulfur wt %
11.9
10.6
0.6
16.9
3.0
Product yields
Naphtha 6.2 7.8
Light gas oil 6.3
Heavy gas oil 70.8
Residuum
Gravity API
Carbon residue
Sulfur wt %
88.4
11.4
15.0
0.6
20.9
1.3
5.0
Delayed cokingDelayed cokingThe feed is subjected to thermal cracking, in a coke drum, under high pressure & temperature-15-90 psig & 415-450 °C Held (delayed) ~24 hours for the process to get completedTwo coke drums used, one for processing and the other for coke
removal & cleaningVirtually eliminates residue fraction-forms solid carbon/fuelHighly aromatic coke, retains S,N & metalsNaphtha, LGO & HGO – used for gasoline/diesel/FCCU after hydrotreating
Luisiana Resid
Kuwait Resid
Feed stock
Gravity API
Carbon residue
Sulfur wt %
12.3
13.0
0.7
6.7
19.8
5.2
Product yields
Naphtha 22.8 26.7
Light gas oil 18.4 28.0
Heavy gas oil 37.6 18.4
Coke
Sulfur wt %
23.7
1.3
30.2
7.5
Both FLUID COKING (1954) and FLEXICOKING (1976) use fluid bed technology Thermally convert heavy oils such as vacuum residue, atmospheric residue,
tar sands bitumen, heavy crudes, deasphalter bottoms & other heaviers Heat for the process is supplied by partial combustion of coke. Remaining coke is
withdrawn as product Feed is injected into a fluidised bed with hot coke particles. Steam is injected at the
bottom for fluidization New coke formed is deposited as a thin layer on the surface of circulating coke
particles; Coking vessel temp-480-565°C;residence time 15-30 sec.
• FLEXICOKING goes one step beyond FLUID COKING: in addition to generating clean liquids, FLEXICOKING also produces a low-BTU gas in one integrated processing step that can virtually eliminate petroleum coke production.
Fluid Coking & Flexi CokingFluid Coking & Flexi Coking
Thermal Processes-ComparisonThermal Processes-Comparison
Visbreaking Delayed coking Fluid coking
Mild heating at 50-200psi;420-490°C
Reduction in viscosity
Low conversion `10%
Heated coil or drum
Moderate heating at 450-500°C & 90 psig
Soak drums at 450-480°C .Processes continues till complete coking occurs
Coke removed hydraulically
Coke- 20-40 % Yield 30%
Severe heating at 10 psi
450-565°C
Fluid bed with steam
Cracking on fluidized coke
Higher yield of < C5
Less/no coke yield
Fuel grade gas
• Coke-forming tendencies of heavier distillation products are reduced by removal of asphaltenic materials by solvent extraction.
• Liquid propane is a good solvent (butane and pentane are also commonly used).
• Deasphalting is based on solubility of hydrocarbons in propane, i.e. the type of molecule
• Vacuum residue is fed to a countercurrent deasphalting tower. Alkanes dissolve in propane whereas asphaltenic materials (aromatic compounds), ‘coke-precursors’ do not.
• Asphalt is sent for thermal processing.
Propane deasphaltingPropane deasphalting
Propane deasphalting