Evaluation of Crude Oil, Petroleum Products and Petrochemicals
Indigenous and imported crude oils are being process in India for production of gasoline, diesel, kerosene and lube oil, wax and feed stock for petrochemical industry like naphtha, kerosene etc.
Various sources of indigenous crude are:
Various sources of imported crude are
Types of Evaluation
Depending on the objective of evaluation, following are the types of evaluation generally carried out.
Rude Oil Evaluation
Quality of crude being processed affect
Significant effect on processing scheme and product pattern
Effect of change in crude quality
Various parameters for prediction of crude oil storage and handling behavior are viscosity, pour point, H2S, base of the crude (characterization factors, BMCI index, viscosity index), mercaptans, acidity, salt and BS & W, distillation, RVP, characteristics of crude, light end analysis, rheology, corrosiveness, impurities, volatility, LPG potential, sulphur wax, CR, Trace metals, naphthenic acid, asphaltenes etc. Details description of parameters are given in Table MVI 2.1.
Table M-VI 2.1: Various Parameters used for Storage & Handling of Crude Oil
Density and API gravity.
Weight to volume and vice versa
calculation, checking consistency of crude oil, control of refinery operation and give a rough estimation of crude oil. API gravity of lighter crude oil may be of the order of 45 whereas in heavier asphaltenes API is 10-12.
Density = Mass/volume
API gravity =
Reid vapor pressure and light end analysis
Indicates the relative percentage of gaseous and lighter hydrocarbons.
Cloud point and Pour
For estimating the relative amount of
wax present in the crude oil. Cloud point gives a rough idea above which the oil can be safely handled.
Viscosity indicates the relative mobility of various crude oils. Temperature has a marked effect on viscosity.
Kinematic viscosity = absolute
Redwood Viscometer, Saybolt Viscometer are used
Aniline point indicates the lowest temperature at which the oil is completely mixed with an equal volume of aniline. High aniline point indicates that the fuel is Paraffinic and hence has a high diesel index and very good ignition quality.
Carbon residue and asphaltenes indicate the presence of heavier hydrocarbons in the crude. Carbon residue is the measure of thermal coke forming property.
It is determined by Conradson carbon residue and Ramsbottom
carbon residue method.
Flash point is the lowest temperature at
Penskys Martens open/closed cup
which application of the test flame causes the vapour and air mixture above the sample to ignite.
Fire point is the lowest temperature at which the oil ignites and continues to burn.
It is an indication of the smoking tendency of fuel. It is used for evaluating the ability of kerosene to burn without producing smoke. It is the maximum flame height in mm at which the fuel will burn without smoking.
Smoke volatility Index( SKI)
= Smoke point + 0.42 x recovery at 204 oC
It is an indication of the corrosive properties of products.
This test serves as a measure of
possible difficulties with copper, brass, bronze part of the fuel system.
These causes irregular behavior in the
distillation and cause blocking and fouling of heat exchanger and result in corrosion
Water content is determined by
Dean & Starck. Sediment and water is determined by centrifuging a mixture of crude oil and toluene. Salt content is determined by titrating the water extract with KCNS/AgNO3.
Base of the
For characterisation of the crude oil base- paraffinic / intermediate /Naphthenic and for measurement of the aromaticity. Various parameters used are characterisation factor, BMCI, VGC
K=VTB / Sp. Gr at 15.6/15.6.
Tb =Mean av. Boiling point in Rankin
paraffinic base k= >12.1; Intermediate base k= 11.5-12.1; naphthenic k = 11.5; aromatics k = 9.8-12.0
BMCI (Bureau of Mines Correlation Index)
BMCI= 48640/ oK + 473.7 g- 456.8
K= avg. boiling point in oK, g specific gravity 15.6/15.6 oC
Paraffinic = <15;
Intermediate =15-50; Naphthenic = >50
Viscosity Gravity correlation (VGC)
VGC= 10 G - 1 0752 log( V - 38 )
10 - log( V - 38 )
G is sp gravity and V is Saybolt universal viscosity
Paraffinic base: 0.80-0.83; Intermediate base: 0.83-0.88, Naphthenic base: 0.88-0.95
It is done for generating distillation data and for study of variations of some key properties throughout the distillation range.
It is indication of gum at the time of test and amount of deposition during service time.
Indication of the thoroughness of the refining process.
Octane number is the percentage of iso-octane in the reference fuel which match the knocking tendency of the fuel under test
Research octane number (RON)
and Motor octane number (MON) are two methods used.
Anti knock index (AKI)=
(RON + MON)/2
Cetane number is the percentage of
cetane which must be mixed with hepta methylnonane to give the same ignition performance as the fuel in question.
It is used for the evaluation of storage stability and resistance to oxidation.
CH ratio=(7 4+15 d)/(26-15 d), where d is sp. Gr. at 15 oC/15oC
It is an indication of ignition quality of a diesel.
Diesel index =
(Aniline point in oF x API)
Diesel Index = cetane number-
Weathering test for LPG
This test shows the volatility of the LPG
|Frass breaking point||This is the temperature below which the bitumen tends to break rather than flow.|
Major Parameters of Gasoline Specifications
Major parameters for gasoline included in Bharat or Euro norms are
Other parameters of importance are RON, MON, Lead, gum, oxidation stability, density, VLI index, FBP. In case of reformulated gasoline aromatics, olefins oxygen, Antiknock index, vapor lock index
Major Parameters of Diesel Specifications
Major parameters for diesel included in Bharat or Euro norms are
Evaluation of Feed Stocks for Petrochemicals (Olefin, Aromatics, and Linear Alkyl Benzen (Lab) Plants)
Olefin , aromatic and LAB production are three major Petrochemical building blocks. Various feed stocks olefins, aromatics and surfactants are given in Table M-VI 2.2.
Input cost of feed constituents is a major portion of the variable cost of production in petrochemical plants. Major feed input olefin, aromatics and surfactants are Ethane propane from natural gas, naphtha, kerosene from the refinery and LPG from refinery, pyrolysis gasoline from steam crackers, Benzene from aromatic plant. Feed quality monitoring and improvement efforts are therefore very important aspects having significant impact on the economics of the operation cost. The precursors and undesirable constituents in feed including catalyst and adsorbents poisons should be known, analyzed and monitored continuously.
Table M-VI 2.2: Feed stocks for Olefin, Aromatics ans LAB
Ethane, Propane, Naphtha, Gas oil
Naphtha, Pyrolysis gasoline, LPG
Kerosene for paraffins, benzene
Linear alkyl benzene is one of important feed stock for production of surfactant whose demands is increasing with increasing population all over the world. LAB requires paraffins for production of olefins of carbon range C10-12 to have more biodegradable detergent. Benzene is required for alkylation of olefin to produce LAB. Feed stock for praffins are Kerosene feed 150-265 oC cut from refinery containing mainly nC7 to NC18 components which is fractionated to remove lighter and heavier fractions. The fractionated cut is hydrotreated for removal of sulphur and nitrogen catalyst which are poisonous to molex adsorbent molecular sieve.
LAB requires olefin and benzene. At present trend is for manufacture of biodegradable low molecular weight LAB, Paraffins containing nC10 to nC13 carbon atoms are required in LAB manufacture which is obtained by fractionation of kerosene. Nc12 improve the flammability of LAB product.
Some of the undesirable components in the feed which are sensitive to molex molecular sieves are contaminants like water, sulphur, nitrogen, oxygen, chlorides, metallic poisons.Kkey properties of LAB feed stocks are density, ASTM distillation, IBP,FBP, sulphur, bromine index ,aromatics, saybolt colour, smoke point, flash point, nitrogen component analysis for n-C10 to nC13, total normal paraffins.