391
15
Introduction to
Refining Processes
15.1 INTRODUCTION
In a very general sense, petroleum refining can be traced back over 5000 years to the times when
asphalt materials and oils were isolated from areas where natural seepage occurred (Abraham, 1945;
Forbes, 1958; Hoiberg, 1960). Any treatment of the asphalt (such as hardening in the air prior to use)
or of the oil (such as allowing for more volatile components to escape prior to use in lamps) may
be considered to be refining under the general definition of refining. However, petroleum refining
as we know it is a very recent science and many innovations evolved during the twentieth century.
Briefly, petroleum refining is the separation of petroleum into fractions and the subsequent treating of these fractions to yield marketable products (Kobe and McKetta, 1958; Nelson, 1958; Gruse
and Stevens, 1960; Bland and Davidson, 1967; Hobson and Pohl, 1973). In fact, a refinery is essentially a group of manufacturing plants that vary in number with the variety of products produced
(Figure 15.1). Refinery processes must be selected and products manufactured to give a balanced
operation in which petroleum is converted into a variety of products in amounts that are in accord
with the demand for each. For example, the manufacture of products from the lower-boiling portion
of petroleum automatically produces a certain amount of higher-boiling components. If the latter
cannot be sold as, say, heavy fuel oil, these products will accumulate until refinery storage facilities
are full. To prevent the occurrence of such a situation, the refinery must be flexible and be able to
change operations as needed. This usually means more processes: thermal processes to change an
excess of heavy fuel oil into more gasoline with coke as the residual product, or a vacuum distillation process to separate the heavy oil into lubricating oil stocks and asphalt.
As the basic elements of crude oil, hydrogen and carbon form the main input into a refinery,
combining into thousands of individual constituents and the economic recovery of these constituents varies with the individual petroleum according to its particular individual qualities, and the
processing facilities of a particular refinery. In general, crude oil, once refined, yields three basic
groupings of products that are produced when it is broken down into cuts or fractions (Table 15.1).
The gas and gasoline cuts form the lower-boiling products and are usually more valuable than the
higher-boiling fractions and provide gas (liquefied petroleum gas), naphtha, aviation fuel, motor
fuel, and feedstocks for the petrochemical industry. Naphtha, a precursor to gasoline and solvents,
is extracted from both the light and middle range of distillate cuts and is also used as a feedstock for
the petrochemical industry. The middle distillates refer to products from the middle boiling range of
petroleum and include kerosene, diesel fuel, distillate fuel oil, and light gas oil. Waxy distillate and
lower-boiling lubricating oils are sometimes included in the middle distillates. The remainder of the
crude oil includes the higher-boiling lubricating oils, gas oil, and residuum (the nonvolatile fraction of the crude oil). The residuum can also produce heavy lubricating oils and waxes but is more
often sued for asphalt production. The complexity of petroleum is emphasized insofar as the actual
proportions of light, medium, and heavy fractions vary significantly from one crude oil to another.
The refining industry has been the subject of the four major forces that affect most industries and
which have hastened the development of new petroleum refining processes: (1) the demand for products such as gasoline, diesel, fuel oil, and jet fuel; (2) feedstock supply, specifically the changing
quality of crude oil and geopolitics between different countries and the emergence of alternate feed
supplies such as bitumen from tar sand, natural gas, and coal; (3) environmental regulations that
15
Introduction to
Refining Processes
15.1 INTRODUCTION
In a very general sense, petroleum refining can be traced back over 5000 years to the times when
asphalt materials and oils were isolated from areas where natural seepage occurred (Abraham, 1945;
Forbes, 1958; Hoiberg, 1960). Any treatment of the asphalt (such as hardening in the air prior to use)
or of the oil (such as allowing for more volatile components to escape prior to use in lamps) may
be considered to be refining under the general definition of refining. However, petroleum refining
as we know it is a very recent science and many innovations evolved during the twentieth century.
Briefly, petroleum refining is the separation of petroleum into fractions and the subsequent treating of these fractions to yield marketable products (Kobe and McKetta, 1958; Nelson, 1958; Gruse
and Stevens, 1960; Bland and Davidson, 1967; Hobson and Pohl, 1973). In fact, a refinery is essentially a group of manufacturing plants that vary in number with the variety of products produced
(Figure 15.1). Refinery processes must be selected and products manufactured to give a balanced
operation in which petroleum is converted into a variety of products in amounts that are in accord
with the demand for each. For example, the manufacture of products from the lower-boiling portion
of petroleum automatically produces a certain amount of higher-boiling components. If the latter
cannot be sold as, say, heavy fuel oil, these products will accumulate until refinery storage facilities
are full. To prevent the occurrence of such a situation, the refinery must be flexible and be able to
change operations as needed. This usually means more processes: thermal processes to change an
excess of heavy fuel oil into more gasoline with coke as the residual product, or a vacuum distillation process to separate the heavy oil into lubricating oil stocks and asphalt.
As the basic elements of crude oil, hydrogen and carbon form the main input into a refinery,
combining into thousands of individual constituents and the economic recovery of these constituents varies with the individual petroleum according to its particular individual qualities, and the
processing facilities of a particular refinery. In general, crude oil, once refined, yields three basic
groupings of products that are produced when it is broken down into cuts or fractions (Table 15.1).
The gas and gasoline cuts form the lower-boiling products and are usually more valuable than the
higher-boiling fractions and provide gas (liquefied petroleum gas), naphtha, aviation fuel, motor
fuel, and feedstocks for the petrochemical industry. Naphtha, a precursor to gasoline and solvents,
is extracted from both the light and middle range of distillate cuts and is also used as a feedstock for
the petrochemical industry. The middle distillates refer to products from the middle boiling range of
petroleum and include kerosene, diesel fuel, distillate fuel oil, and light gas oil. Waxy distillate and
lower-boiling lubricating oils are sometimes included in the middle distillates. The remainder of the
crude oil includes the higher-boiling lubricating oils, gas oil, and residuum (the nonvolatile fraction of the crude oil). The residuum can also produce heavy lubricating oils and waxes but is more
often sued for asphalt production. The complexity of petroleum is emphasized insofar as the actual
proportions of light, medium, and heavy fractions vary significantly from one crude oil to another.
The refining industry has been the subject of the four major forces that affect most industries and
which have hastened the development of new petroleum refining processes: (1) the demand for products such as gasoline, diesel, fuel oil, and jet fuel; (2) feedstock supply, specifically the changing
quality of crude oil and geopolitics between different countries and the emergence of alternate feed
supplies such as bitumen from tar sand, natural gas, and coal; (3) environmental regulations that