Petroleum physical properties

Experience has shown that certain carefully selected physical properties could be correlated with the dominant composition of a petroleum cut or crude oil. 

Knowledge of physical properties of fluids is essential to the process engineer because it enables him to specify, size or verify the operation of equipment in a production unit. The objective of this chapter is to present a collection of methods used in the calculation of physical properties of mixtures encountered in the petroleum industry, different kinds of hydrocarbon components, and some pure compounds. 

Amyx, Bass Whiting, (1960), Petroleum Reservoir Engineering - Physical Properties, McGraw-Hill... 

Physical Properties. Benzene, C H, toluene, C Hj-CH, and petrol (a mixture of aliphatic hydrocarbons, e.g., pentane, hexane, etc.) are colourless liquids, insoluble in and lighter than water. Benzene and toluene, which have similar odours, are not readily distinguishable chemically, and their physical constants should therefore be carefully noted benzene, m.p. 5 (solidifies when a few ml. in a dry test-tube are chilled in ice-water), b.p. 8i toluene, m.p. —93°, b.p. 110°. Petroleum has a characteristic odour. 

The feedstocks used ia the production of petroleum resias are obtaiaed mainly from the low pressure vapor-phase cracking (steam cracking) and subsequent fractionation of petroleum distillates ranging from light naphthas to gas oil fractions, which typically boil ia the 20—450°C range (16). Obtaiaed from this process are feedstreams composed of atiphatic, aromatic, and cycloatiphatic olefins and diolefins, which are subsequently polymerized to yield resias of various compositioas and physical properties. Typically, feedstocks are divided iato atiphatic, cycloatiphatic, and aromatic streams. Table 2 illustrates the predominant olefinic hydrocarbons obtained from steam cracking processes for petroleum resia synthesis (18). 

Fluid mixing is a unit operation carried out to homogenize fluids in terms of concentration of components, physical properties, and temperature, and create dispersions of mutually insoluble phases. It is frequently encountered in the process industry using various physical operations and mass-transfer/reaction systems (Table 1). These industries include petroleum (qv), chemical, food, pharmaceutical, paper (qv), and mining. The fundamental mechanism of this most common industrial operation involves physical movement of material between various parts of the whole mass (see Supplement). This is achieved by transmitting mechanical energy to force the fluid motion. 

In the fire codes, the atmospheric boiling point is an important physical property used to classify the degree of hazardousness of a Hquid. If a mixture of Hquids is heated, it starts to bod at some temperature but continues to rise ia temperature over a boiling temperature range. Because the mixture does not have a definite boiling poiat, the NFPA fire codes define a comparable value of boiling poiat for the purposes of classifying Hquids. For petroleum mixture, it is based on the 10% poiat of a distillation performed ia accordance with ASTM D86, Standard Method of Test for Distillation of Petroleum Products. 

Ozokerite and Geresin Waxes. 02okerite wax [8001-75-0] was a product of Poland, Austria, and in the former USSR where it was mined. Tme o2okerite no longer seems to be an article of commerce, and has been replaced with blends of petroleum-derived paraffin and microcrystalHne waxes. These blends are designed to meet the specific physical properties required by the appHcation involved. 

Distillation appHcations can be characterized by the type of materials separated, such as petroleum appHcations, gas separations, electrolyte separations, etc. These appHcations have specific characteristics in terms of the way or the correlations by which the physical properties are deterrnined or estimated the special configurations of the process equipment such as having side strippers, multiple product withdrawals, and internal pump arounds the presence of reactions or two Hquid phases etc. Various distillation programs can model these special characteristics of the appHcations to varying degrees and with more or less accuracy and efficiency. 

The general proportions may be varied from one end of the tower to the other to accommodate changing liquid volumes and physical properties. These towers have been used in diameters ranging from a few inches for laboratory work up to 2.4 m (8 ft) in diameter by 12.2 m (40 ft) tall for purposes of deasphalting petroleum. Other commercial services include furfural extraction of lubricating oils, desulfurization of gasoline, phenol recoveiy from wastewaters, and many others. Columns up to 4.5 m in diameter and up to 50 m in height have been constructed. 

Hydrocarbons are segmented into a variety of categories. Each category possesses a distinct molecular profile and, in turn, set of chemical and physical properties. Each class of hydrocarbons therefore has historically served different markets. Crude petroleum is composed of four major hydrocarbon groups paraffins, olefins, naphthenes, and aromatics. 

The material in this section is divided into three parts. The first subsection deals with the general characteristics of chemical substances. The second subsection is concerned with the chemistry of petroleum it contains a brief review of the nature, composition, and chemical constituents of crude oil and natural gases. The final subsection touches upon selected topics in physical chemistry, including ideal gas behavior, the phase rule and its applications, physical properties of pure substances, ideal solution behavior in binary and multicomponent systems, standard heats of reaction, and combustion of fuels. Examples are provided to illustrate fundamental ideas and principles. Nevertheless, the reader is urged to refer to the recommended bibliography [47-52] or other standard textbooks to obtain a clearer understanding of the subject material. Topics not covered here owing to limitations of space may be readily found in appropriate technical literature. 

Hydrogen sulphide occurs naturally, e.g. in natural gas and petroleum, volcanic gases, and from decaying organic matter. It may be present near oil wells and where petroleum is processed. Commercially it is obtained as a by-product from many chemical reactions including off-gas in the production of some synthetic polymers (e.g. rayon, nylon) from petroleum products, and by the action of dilute mineral acids on metal sulphides. Physical properties are summarized in Table 9.14 and effects of temperature on vapour pressure are shown in Figure 9.5. 

Liquefied gases. See also Liquefaction Cryogens and individual chemicals Liquefied Natural Gas (LNG), 263 physical properties, 295 precautions, 264, 292 vapour pressure, 294 Liquefied Petroleum Gas (LPG), 15, 287 hazards, 287 physical properties, 289 precautions, 292... 

Besides petroleum products, other hazardous substances (see Tables 18.7-18.9) are also stored in USTs. Among them, a common and important group is the dense nonaqueous phase liquids (DNAPLs). This group has some different physical properties from petroleum (especially gasoline) that make them behave differently in the way they move underground. This section presents the important factors associated with the cleanup of DNAPLs. 

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