Petroleum refining plays an important role in people’s lives. Most transportation vehicles are powered by refined products such as gasoline, diesel, aviation turbine kerosene, and fuel oil. The recent price rise of crude oil over the last 2 years has affected the refining industry in several ways: there is an increased search for fuel products from non-fossil sources such as biodiesel and alcohols from vegetable sources; the development of better methods to process tar sand, coal gasification and synthesis of fuels by the Fischer–Tropsch technology; and the initiation of long-term plans to look for renewable energy sources. Although crude oil prices are still a cheap source for transportation fuels and petrochemicals, stricter environment regulations have raised the cost of producing clean fuels. This motivates the search for producing clean fuels by non-conventional methods, such as by ambient desulfurization by liquid oxidants. Olefin alkylation and Fischer–Tropsch are other possible methods for producing clean fuels. New technology and better design of refinery equipment are also being developed to produce clean and less expense fuels. In the modern refinery, the refining processes are classified as either physical separation or chemical conversion ones. This chapter provides an introduction to petroleum refining. It discusses different refining processes and refinery configuration, which can range from single topping for crude distillation to high conversion refinery for petro-refinery.
A petroleum refining study starts with describing its feedstock, the crude oil and the range of products that are produced by the various processes. Crude oil comes from different parts of the world and has different physical and chemical characteristics. On the other hand, the products that are produced have to meet market requirements and as such, should comply with certain specifications. Crude oil is a complex liquid mixture made up of a vast number of hydrocarbon compounds that consist mainly of carbon and hydrogen in differing proportions. In addition, small amounts of organic compounds containing sulfur, oxygen, nitrogen, and metals such as vanadium, nickel, iron, and copper are also present. Hydrogen to carbon ratios affects the physical properties of crude oil. As the hydrogen to carbon ratio decreases, the gravity and boiling point of the hydrocarbon compounds increases. Moreover, the higher the hydrogen to carbon ratio of the feedstock, the higher its value is to a refinery because less hydrogen is required. There are specifications for over 2000 individual refinery products. Intermediate feedstocks can be routed to various units to produce different blend products depending on market demand. This chapter also explores typical refinery products with their carbon atom contents and boiling ranges, and discusses the specifications of each product.
A petroleum refinery is a collection of unit operations, such as fractionation towers, pumps, and heat exchangers. Analysis and design of these units require knowledge of the thermodynamic and physical properties of the petroleum fluids. Designing a crude distillation tower requires knowledge on how hydrocarbons in crude oil are distributed on each tray of the tower, that is vapor–liquid distribution, and the densities of the mixture. Heat exchanger design depends on enthalpies, thermal conductivity and viscosity of certain streams. This chapter discusses thermophysical properties of petroleum fractions and crude oils. It presents thermophysical properties required for the design and operation of almost all processing equipment in a refinery. Due to the complexity of the composition of petroleum fractions and crude oils, it is not possible to measure or calculate accurately all of those properties. Furthermore, calculation methods developed for pure hydrocarbons are not always applicable. Therefore, over the years chemical and petroleum refining engineers have developed special methods or correlations to estimate the properties of petroleum fraction from easily measured properties like normal boiling point and specific gravity. Such methods and schemes characterize those petroleum fractions.
