Petroleum refinery distillation hydrocarbons

The butane-containing streams in petroleum refineries come from a variety of different process units consequently, varying amounts of butanes in mixtures containing other light alkanes and alkenes are obtained. The most common recovery techniques for these streams are lean oil absorption and fractionation. A typical scheme involves feeding the light hydrocarbon stream to an absorber-stripper where methane is separated from the other hydrocarbons. The heavier fraction is then debutanized, depropanized, and de-ethanized by distillation to produce C, C, and C2 streams, respectively. Most often the stream contains butylenes and other unsaturates which must be removed by additional separation techniques if pure butanes are desired. 

Eluorides Hydrocarbons, general G S P A Hydrogen fluoride Calcium fluoride Cement Aluminium Coal distillation Petrochemicals Petroleum refineries... 

BTX (benzene-toluene-xylene) mixtures are an important petroleum refinery stream that is separated by extractive distillation (Fig. 1) from a hydrocarbon stream, usually a reformate, and followed by downstream fractionation for isolation of the pure materials for further treatment and use (Fig. 2). 

Asphalt is a product of many petroleum refineries (Barth, 1962) and may be residual asphalt, which is made up of the nonvolatile hydrocarbons in the feedstock, along with similar materials produced by thermal alteration during the distillation sequences, or asphalt may be produced by air-blowing an asphaltic residuum. 

A mixture of hydrocarbons such as petroleum does not boil at a single, sharply defined temperature. Instead, as such a mixture is heated, the compounds with lower boiling points (the most volatile) boil off first, and as the temperature increases, more and more of the material vaporizes. The existence of a boiling-point range permits components of a mixture to be separated by distillation (see discussion in Section 11.6). The earliest petroleum distillation was a simple batch process The crude oil was heated in a still, the volatile fractions were removed at the top and condensed to gasoline, and the still was cleaned for another batch. Modern petroleum refineries use much more sophisticated and efficient distillation methods, in which crude oil is added continuously and fractions of different volatility are tapped off at various points up and down the distillation column (Fig. 7.5). To save on energy costs, heat exchangers capture the heat liberated from condensation of the liquid products. 

Mineral oils are the by-products of the distillation of petroleum and are also called hydrocarbon oils and are obtained directly from petroleum refineries. The composition of these kinds of oil is predominately alkanes with trace amounts of aromatics and heterocyclics. They exhibit good lubricating properties and allow the attainment of low ultimate pressures. However, their chemical resistance is relatively poor, particularly to vigorous oxidants. As a result, mineral oils are very suitable for general-purpose use in vacuum pumps. 

Purification of Individual Molecular Species. The chemical process industries use large amounts of hydrocarbons, which can be individually recovered and purified from petroleum refinery fractions. Examples would include ethane, propene, butadiene, isoprene, benzene, toluene, and xylenes. Sometimes distillation must be supplemented with liquid-liquid extraction, as well as extractive and azeotropic distillation, to purify these materials. The technology of recovering individual chemical species will be dealt with in other parts of this encyclopedia. 

Crude oil contains a wide range of hydrocarbons and other compounds containing sulfur, nitrogen, etc. In the refinery, petroleum is distilled into various fractions. Depending on the desired final products, these fractions are further processed and then blended to yield a wide variety of products. 

Up to this point in this book, we have looked at distillation columns that separate specific chemical components. In the refining of crude oil, mixmres of many thousands of components must be handled. These components vary from quite fight hydrocarbons (methane, ethane, propane, etc.) to very high-molecular-weight components that boil at extremely high temperatures. Petroleum refineries have units that separate (by distillation) and transform (by a variety of reactions) these mixtures. 

Fluid Catalytic Cracking (FCC) is one of the most important processes in an oil refinery. Its function is to convert heavy hydrocarbon petroleum streams into more valuable, lighter hydrocarbon fractions such as middle distillate, gasoline and liquefied petroleum gas etc. Optimal operation of the process is decisive for overall economic and environmental health. Often several objectives and constraints are involved in the process, and optimisation studies incorporating these conflicting objectives would be invaluable to the process engineer. 

Petroleum is by far the largest source of the vast number of products broadly known as petrochemicals. Raw petroleum is a mixture of hydrocarbons containing up to 40 carbon atoms per molecule. These large molecules are not useful in their natural form, but they are broken into smaller molecules in petroleum refineries (Fig. 21.13 also see Fig. 18.7). Catalytic cracking essentially cracks the long carbon chains into shorter molecules of 5 to 10 carbon atoms. Fractional distillation separates hydrocarbons into fractions that boil at different temperatures. Alkanes of up to 4 or 5 carbon atoms per molecule may be obtained in pure form by this method. The boiling points of larger alkanes are too close for their complete separation, so chemical methods must be used to obtain pure products. 

Natural gas and crude oils are the main sources for hydrocarbon intermediates or secondary raw materials for the production of petrochemicals. From natural gas, ethane and LPG are recovered for use as intermediates in the production of olefins and diolefms. Important chemicals such as methanol and ammonia are also based on methane via synthesis gas. On the other hand, refinery gases from different crude oil processing schemes are important sources for olefins and LPG. Crude oil distillates and residues are precursors for olefins and aromatics via cracking and reforming processes. This chapter reviews the properties of the different hydrocarbon intermediates—paraffins, olefins, diolefms, and aromatics. Petroleum fractions and residues as mixtures of different hydrocarbon classes and hydrocarbon derivatives are discussed separately at the end of the chapter. 

The products derived from petroleum are produced in refineries using a fundamental separation process called distillation. The principal method for separating crude oil into useful products is through distillation. Distillation is the heating process whereby hydrocarbons, which make up the crude oil, are converted to vapor form and are... 

Distillation is a common method for the fractionation of petroleum that is used in the laboratory as well as in refineries. The technique of distillation has been practiced for many centuries, and the stills that have been employed have taken many forms (Speight, 1999). Distillation is the first and the most fundamental step in the refining process (after the crude oil has been cleaned and any remnants of brine removed) (Bland and Davidson, 1967 Speight, 1999, and references cited therein Speight and Ozum, 2002, and references cited therein), which is often referred to as the primary refining process. Distillation involves the separation of the various hydrocarbon compounds that occur naturally in a crude oil into a number of different fractions (a fraction is often referred to as a cut). 

---