459
17
Distillation
17.1 INTRODUCTION
Petroleum in the unrefined state is of limited value and of limited use. Refining is required to produce the products that are attractive to the market place. Thus, petroleum refining is a series of steps
by which the crude oil is converted into salable products in the desired qualities and in the amounts
dictated by the market (Priestley, 1973). In fact, a refinery is essentially a group of manufacturing
plants that vary in number with the variety of products produced; the processes and products manufactured give a balanced operation.
Most petroleum products, including kerosene, fuel oil, lubricating oil, and wax, are fractions of
petroleum that have been treated to remove undesirable components. Other products, for example,
gasoline, aromatic solvents, and even asphalt, may be partly or totally synthetic in that they have
compositions that are impossible to achieve by direct separation of these materials from crude oil.
They result from chemical processes that change the molecular nature of selected portions of crude
oil; in other words, they are the products of refining or they are refined products.
The petroleum refinery of the twenty-first century is a much more complex operation (Chapter 15)
than those refineries of 100–120 years ago. Early refineries were predominantly distillation units,
perhaps with ancillary units to remove objectionable odors from the various product streams. The
refinery of the 1930s was somewhat more complex but was essentially a distillation unit, but at this
time, cracking and coking units were starting to appear in the scheme of refinery operations. These
units were not what we imagine today as a cracking and coking unit but were the forerunners of
today’s units. Also at this time, asphalt was becoming a recognized petroleum product. Finally, current refineries are a result of major evolutionary trends and are highly complex operations. Most of
the evolutionary adjustments to refineries have occurred during the decades since the commencement of World War II. In the petroleum industry, as in many other industries, supply and demand is
key factor in efficient and economic operation. Innovation is also a key.
A refinery is essentially a group of manufacturing plants (Chapter 15) that vary in number with
the variety of products produced. Refinery processes must be selected and products manufactured
to give a balanced operation; that is, crude oil must be converted into products according to the rate
of sale of 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, they accumulate until refinery storage facilities are full. To prevent
the occurrence of such a situation, the refinery must be flexible and able to change operations as
needed. This usually means more processes to accommodate the ever-changing demands of the
market (Hobson and Pohl, 1973). This could be reflected in the inclusion of a cracking process to
change an excess of heavy fuel oil into more gasoline with coke as the residual product or inclusion
of a vacuum distillation process to separate the heavy oil into lubricating oil stocks and asphalt.
In addition, a refinery must include the following (Kobe and McKetta, 1958): (1) all necessary
non-processing facilities, (2) adequate tank capacity for storing crude oil, intermediate, and finished
products, (3) a dependable source of electrical power, (4) material-handling equipment, (5) workshops and supplies for maintaining a continuous 24 × 7 operation, (6) waste-disposal and watertreating equipment, and (7) product-blending and product-monitoring facilities.
Distillation has remained a major refinery process and a process to which crude oil that enters
the refinery is subjected. A multitude of separations are accomplished by distillation, but its most
17
Distillation
17.1 INTRODUCTION
Petroleum in the unrefined state is of limited value and of limited use. Refining is required to produce the products that are attractive to the market place. Thus, petroleum refining is a series of steps
by which the crude oil is converted into salable products in the desired qualities and in the amounts
dictated by the market (Priestley, 1973). In fact, a refinery is essentially a group of manufacturing
plants that vary in number with the variety of products produced; the processes and products manufactured give a balanced operation.
Most petroleum products, including kerosene, fuel oil, lubricating oil, and wax, are fractions of
petroleum that have been treated to remove undesirable components. Other products, for example,
gasoline, aromatic solvents, and even asphalt, may be partly or totally synthetic in that they have
compositions that are impossible to achieve by direct separation of these materials from crude oil.
They result from chemical processes that change the molecular nature of selected portions of crude
oil; in other words, they are the products of refining or they are refined products.
The petroleum refinery of the twenty-first century is a much more complex operation (Chapter 15)
than those refineries of 100–120 years ago. Early refineries were predominantly distillation units,
perhaps with ancillary units to remove objectionable odors from the various product streams. The
refinery of the 1930s was somewhat more complex but was essentially a distillation unit, but at this
time, cracking and coking units were starting to appear in the scheme of refinery operations. These
units were not what we imagine today as a cracking and coking unit but were the forerunners of
today’s units. Also at this time, asphalt was becoming a recognized petroleum product. Finally, current refineries are a result of major evolutionary trends and are highly complex operations. Most of
the evolutionary adjustments to refineries have occurred during the decades since the commencement of World War II. In the petroleum industry, as in many other industries, supply and demand is
key factor in efficient and economic operation. Innovation is also a key.
A refinery is essentially a group of manufacturing plants (Chapter 15) that vary in number with
the variety of products produced. Refinery processes must be selected and products manufactured
to give a balanced operation; that is, crude oil must be converted into products according to the rate
of sale of 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, they accumulate until refinery storage facilities are full. To prevent
the occurrence of such a situation, the refinery must be flexible and able to change operations as
needed. This usually means more processes to accommodate the ever-changing demands of the
market (Hobson and Pohl, 1973). This could be reflected in the inclusion of a cracking process to
change an excess of heavy fuel oil into more gasoline with coke as the residual product or inclusion
of a vacuum distillation process to separate the heavy oil into lubricating oil stocks and asphalt.
In addition, a refinery must include the following (Kobe and McKetta, 1958): (1) all necessary
non-processing facilities, (2) adequate tank capacity for storing crude oil, intermediate, and finished
products, (3) a dependable source of electrical power, (4) material-handling equipment, (5) workshops and supplies for maintaining a continuous 24 × 7 operation, (6) waste-disposal and watertreating equipment, and (7) product-blending and product-monitoring facilities.
Distillation has remained a major refinery process and a process to which crude oil that enters
the refinery is subjected. A multitude of separations are accomplished by distillation, but its most