Distillation of crude oil

The stocks used for jet fuel production come almost essentially from direct distillation of crude oil. They correspond to the fraction distilled between 145 and 240°C, more or less expanded or contracted according to the circumstances. The yield of such a cut depends largely on the nature of the crude but is always larger than the demand for jet fuel which reaches about 6% of the petroleum market in Europe. For the refiner, the tightest specifications are ... 

FIGURE 2 11 Distillation of crude oil yields a series of volatile fractions having the names indicated along wih a nonvolatile residue The number of carbon atoms that characterize the hydrocarbons in each frac tion IS approximate... 

In addition to the distillation of crude oil coming into the refinery, stills of various designs are used in other types of service throughout the refinery. Cracked products are separated in distillation equipment which is very similar to an atmospheric crude pipe still. The principal difference is that these products are hot from the cracking operation, so that a fired heater is not required. 

Figure 1 shows a simplified flow plan for a typical hydroskimming refinery. The atmospheric pipestill performs the initial distillation of crude oil into gas, naphtha, distillates, and residuum. The naphtha may be separated into gasoline blending stock, solvents, and Powerformer feed. The distillates include kerosene, jet fuel, heating oil and diesel oil. The residuum is blended for use as bunker fuel oil. 

In addition to the distillation of crude oil coming into the refinery, stills of various designs are used in other types of service throughout the refinery. 

From the late 1850s to the turn of the ccntui-y, the major interest in petroleum was as a source of kerosene, as both a fuel and illuniinant. As early as the 1820s, it was generally known from chemical experiments that illuminants, heating fuels, and lubricants could be obtained relatively cheaply from the distillation of crude oil. 

Gas oil is a heavier petroleum fraction than kerosine. It can be obtained from the atmospheric distillation of crude oils (atmospheric gas oil, AGO), from vacuum distillation of topped crudes (vacuum gas oil, VGO), or from cracking and hydrocracking units. 

Petroleum refining begins by fractional distillation of crude oil into three principal cuts according to boiling point (bp) straight-run gasoline (bp 30-200 °C), kerosene (bp 175-300 °C), and heating oil, or diesel fuel (bp 275-400 °C). Further distillation under reduced pressure then yields... 

High-Temperature Defoamers. Polyisobutylene compounds are particularly effective in high-temperature (300° to 1 XX)° F) treatments of hydrocarbon fluids [786,788], such as during the distillation of crude oil and coking of crude oil residues. Polyisobutylene compounds are less expensive than silicone-based compounds. 

Single-stage flash distillation processes are used to make a coarse separation of the light components in a feed often as a preliminary step before a multicomponent distillation column, as in the distillation of crude oil. 

The distillation of crude oil under conditions slightly above atmospheric pressure is limited by the maximum temperature that can be tolerated by the materials being distilled, otherwise there would be decomposition. Further separation of the bottoms of the column (the atmospheric residue) would require higher temperature, and therefore... 

The first step in the treatment of crude oil at a refinery is fractional distillation. The mixture is separated into various groupings of compounds, called fractions, by making use of the different boiling points of the components of the mixture. The main fractions obtained from the initial distillation of crude oil are shown below. 

A gas oil fraction from the distillation of crude oil contains hydrocarbons in the C16 to C20 range. These hydrocarbons can be cracked by heating in the presence of a catalyst. 

Liquefied petroleum gas (LPG) was used as fuel for the first time in the USA in 1912. Under the general term natural gas liquids (NGL), 60% of global LPG originates as a fraction separated from methane during the production of oil and gas the remaining 40% are generated as a by-product from the fractionated distillation of crude oil in refineries. Liquefied petroleum gas is a mixture of propane and butane, with the mixing ratio dependent on the country and season. 

Refinery gas process gas) is the noncondensable gas that is obtained during distillation of crude oil or treatment (cracking, thermal decomposition) of petroleum (Gary and Handwerk 1975 Austin, 1984 Speight, 1999 Robinson and Faulkner, 2000 Speight and Ozum, 2002). There are also components of the gaseous products that must be removed prior to release of the gases to the atmosphere or prior to use of the gas in another part of the refinery (i.e., as a fuel gas or as a process feedstock). 

Several thousand compounds are present in petroleum. Few are separated as pure substances. Many of the uses of petroleum can be served by certain fractions from the distillation of crude oil. Typical distillation fractions and their uses are given in Table 7.3 and a distillation unit is shown in Fig. 7.5. The complexity of the molecules, molecular weight, and carbon number increase with the boiling point. The higher boiling fractions are usually distilled in vacuo at lower temperature than their atmospheric boiling points to avoid excessive decomposition to tars. 

Typical products obtained from the atmospheric and vacuum distillation of crude oil are briefly described in TABLE 2-1. 

TABLE 2-1. Typical Products Obtained from Atmospheric and Vacuum Distillation of Crude Oil... 

Asphalt Hydrocarbon material ranging in consistency from heavy liquid to a solid. Most common source is residue left after fractional distillation of crude oils used primarily for surfacing roads. Asphyxia Suffocation from lack of oxygen. Chemical asphyxia is produced by a substance, such as carbon monoxide, that combines with hemoglobin to reduce die blood s capacity to transport oxygen. Simple asphyxia is the result of exposure to a substance, such as carbon dioxide, that displaces oxygen. 

Very few alkenes are found in nature. Most of the alkenes used by the petrochemical industry are obtained by breaking up larger, less useful alkane molecules obtained from the fractional distillation of crude oil. This is usually done by a process called catalytic cracking. In this process the alkane molecules to be cracked (split up) are passed over a mixture of aluminium and chromium oxides heated to about 500 °C. 

Inspection of some of the fractions of the primary distillation of crude oil - colour, viscosity, boiling point and flammability. 

The crude oils that are being refined for the production of transportation fuels have become heavier. Because of this many topping refineries have shut down because of their inability to process these heavier crude oils. In comparison, the total capacity of those processes that are intended for upgrading the heavier distillates of crude oils has increased (Rhodes, 1991). 

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