Definitions handbook of petroleum product analysis

Assignment Definitions of Important Terms Covered till now Thursday, May 02, 2013 in class – Handbook of Petroleum Product Analysis Chapter # 1: Petroleum Analysis Sampling The sampl

Assignment

Definitions of Important Terms Covered till now (Thursday, May 02, 2013) in class

– Handbook of Petroleum Product Analysis

Chapter # 1: Petroleum Analysis

Sampling

The sample used for test(s) must be representative of the bulk material otherwise the result will

be incorrect no matter how accurate or precise the method is

Accuracy

It is a measure of closeness of test result to the true value Absolute accuracy can be measured only if true value is known

Precision

The precision of a test method is the variability between test results obtained on the same material using the specific test method The precision of a test is usually unrelated to its accuracy The results may be precise but not necessarily accurate In fact, the precision of an analytical method is the amount of scatter in the results obtained from multiple analyses of a homogeneous sample To be meaningful, the precision study must be performed using the exact sample and standard preparation procedures that will be used in the final method Precision is expressed as repeatability and reproducibility

Method Validation

Method validation is the process of proving that an analytical method is acceptable for its intended purpose

Chapter # 2: Petroleum and Petroleum Products

Composition

Elemental analysis of petroleum shows that the major constituents are carbon and hydrogen with smaller amounts of sulfur (0.1–8% w/w), nitrogen (0.1–1.0% w/w), and oxygen (0.1–3% w/w), and trace elements such as vanadium, nickel, iron, and copper present at the part per million (ppm) level

Petroleum Assay

The testing of petroleum sample to determine its composition and quality is called petroleum assay

Carbon Residue

The carbon residues of petroleum and petroleum products serve as an indication of the propensity of the sample to form carbonaceous deposits (thermal coke) under the influence of heat – generally applicable to relatively nonvolatile samples that decompose on distillation at atmospheric pressure

Asphaltene Content

The asphaltene fraction is the highest molecular weight, most complex fraction in petroleum The asphaltene content gives an indication of the amount of coke that can

be expected during processing

Metallic Constituents

Petroleum, as recovered from the reservoir, contains metallic constituents but also picks

up metallic constituents during recovery, transportation, and storage Even trace amounts of these metals can be deleterious to refining processes, especially processes

in which catalysts are used Trace components, such as metallic constituents, can also produce adverse effects in refining either (1) by causing corrosion or (2) by affecting the quality of refined products

Salt Content

The salt content of crude oil is highly variable and results principally from production practices used in the field and, to a lesser extent, from its handling aboard the tankers bringing it to terminals The bulk of the salt present will be dissolved in coexisting water and can be removed in desalters, but small amounts of salt may be dissolved in the crude oil itself Salt may be derived from reservoir or formation waters or from other waters used in secondary recovery operations Aboard tankers, ballast water of varying salinity may also be a source of salt contamination

Salt in crude oil may be deleterious in several ways Even in small concentrations, salts will accumulate in stills, heaters, and exchangers, leading to fouling that requires expensive cleanup More importantly, during flash vaporization of crude oil certain metallic salts can be hydrolyzed to hydrochloric acid according to the following reactions:

The hydrochloric acid evolved is extremely corrosive, necessitating the injection of a basic compound, such as ammonia, into the overhead lines to minimize corrosion damage Salts and evolved acids can also contaminate both overhead and residual products, and certain metallic salts can deactivate catalysts

Thus knowledge of the content of salt in crude oil is important in deciding whether and

to what extent the crude oil needs desalting

Sulfur Content

Sulfur is present in petroleum as sulfides, thiophenes, benzothiophenes, and dibenzothiophenes In most cases, the presence of sulfur is detrimental to the processing because sulfur can act as catalytic poisons during processing

Water and Sediment

Considerable importance is attached to the presence of water or sediment in petroleum because they lead to difficulties in the refinery, for example, corrosion of equipment, uneven running on the distillation unit, blockages in heat exchangers, and adverse effects on product quality Water and Sediment result from production and transportation practices

Wax Content

Petroleum with high wax content presents difficulties in handling and pumping as well

as producing distillate and residual fuels of high pour point and lubricating oils that are costly to dewax

The temperature at which the wax first appears is the wax appearance point

Reid Vapor Pressure Test

Measures the vapor pressure of volatile petroleum

Acid Number

The acid number is the quantity of base, expressed in milligrams of potassium hydroxide per gram of sample that is required to titrate a sample in this solvent to a green/green-brown end point using p-naphtholbenzein indicator solution

Aniline Point

Used to estimate the aromatic content of petroleum

Chapter # 3: Gases

Liquefied Petroleum Gas

Liquefied petroleum gas (LPG) is a mixture of the gaseous hydrocarbons propane (CH3CH2CH3, boiling point: –42°C, –44°F) and butane (CH3CH2CH2CH3, boiling point: 0°C, 32°F) that are produced during natural gas refining, petroleum stabilization, and petroleum refining

Refinery Gas

Refinery gas is the non-condensable gas that is obtained during distillation or treatment (cracking, thermal decomposition) of petroleum It consists mainly of hydrogen (H2), methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10), and olefins (RCH=CHR1, where R and R1 can be hydrogen or a methyl group) and may also include off-gases from petrochemical processes

Chapter # 4: Naphtha

Lightest liquid petroleum product that boils from 30oC to 200oC

Naphtha Production: Naphtha is produced by any one of several methods, which include (1) fractionation of straight-run, cracked, and reforming distillates or even fractionation of crude petroleum; (2) solvent extraction; (3) hydrogenation of cracked distillates; (4) polymerization of unsaturated compounds (olefins) and (5) alkylation processes In fact, naphtha may be a combination of product streams from more than one of these processes

The more common method of naphtha preparation is distillation Depending on the design of the distillation unit, either one or two naphtha steams may be produced: (1) a single naphtha with an end point of about 205∞C (400∞F) and similar to straight-run gasoline or (2) this same fraction divided into light naphtha and heavy naphtha The end point of the light naphtha is varied to suit the subsequent subdivision of the naphtha into narrower boiling fractions and may

be of the order of 120∞C (250∞F)

Aromatic content is a key property of low-boiling distillates such as naphtha and gasoline because the aromatic constituents influence a variety of properties including boiling range, viscosity, stability, and compatibility with a variety of solutes

Evaporation Rate: The evaporation rate is an important property of naphtha, and although there

is a significant relation between distillation range and evaporation rate, the relationship is not straightforward

Flash point data are used in shipping and safety regulations to define flammable and

Kauri-Butanol Value: The kauri-butanol value is the number of milliliters of the solvent, at 15°C

(77°F), required to produce a defined degree of turbidity when added to 20 g of a standard

solution of gum kauri resin in n-butyl alcohol The kauri-butanol value of naphtha is used to

determine relative solvent power

For kauri-butanol values of 60 and higher, the standard is toluene, which has an assigned value

of 105, whereas for kauri-butanol values less than 60, the standard is a blend of 75% n-heptane

and 25% toluene, which has an assigned value of 40.The kauri-butanol value of products that are

classified as regular mineral spirits normally varies between 34 and 44; xylene is 93, and

aromatic naphtha falls in the range 55–108

However, the data obtained by the kauri-butanol test depend on factors other than solvent

power and are specific to the solute used For this reason, the aniline point is often preferred to

the kauri-butanol number

Chapter # 5: Aviation Fuel

Acidity

Acidic compounds can also be present in aviation turbine fuels either because of the acid

treatment during the refining process or because of naturally occurring organic acids Acidity is

an undesirable property because of the possibility of metal corrosion and impairment of water

separation characteristics of the fuel

Freezing Point

The freezing point of aviation fuel is an index of the lowest temperature of its utility for the

specified applications Aviation fuels must have acceptable freezing point and low-temperature

pumpability characteristics so that adequate fuel flow to the engine is maintained at high

altitude

Muhammad

Muhammad Bin Abbas CIIT/SP10-BEC-025/LHR Department of Chemical Engineering CIIT Lahore