process called linear programming, which is discussed in more detail in the chapter
entitled “▶ Petroleum Refinery Planning and Economics” in this handbook.
Petroleum Products
Fractions from the Atmospheric and Vacuum Distillation
of Crude Oil
The most common fractions distilled from crude oil distillation processes are shown
in Fig. 1.
These cut lengths will vary slightly depending on the crude oil source and the
finished product slate requirements. These are the basic components which, after
further processing and blending, will make the finished products in the composition
and quantity required by the refinery. The cuts shown in Fig. 1 are called “straight
run” products , and these are described in the following paragraphs. The crude
source, in this case, is a medium Middle Eastern crude with a gravity of 33.9
API
and a sulfur content of 1.9 % wt.
Atmospheric overhead distillate. This is not strictly a cut but consists of all the
light material in the crude absorbed into the total overhead distillate from the crude
tower. This distillate, and in most cases, together with similar distillates from other
processes, forms the feed to the refinery’s light ends unit (see the chapter entitled
“▶ Distillation of the “Light Ends” from Crude Oil in Petroleum Processing”). It is
in the light ends unit that the straight run LPG, light naphtha, and the heavy naphtha
are separated. However, the end point of the heavy naphtha is determined by the cut
point of the overhead distillate and the fractionation between it and the first side
stream product from the atmospheric unit.
Refinery gas and LPGs. In many refineries, most of the C 4 s and lighter are
removed from the atmospheric column overhead distillate in the first column of the
light ends unit. This is the unit’s debutanizer column. Some refineries however
choose to separate the light naphtha and lighter from the heavy naphtha first. There
is no specific reason; it’s really a question of the specific refinery’s economic criteria.
Having separated the C 4 s and lighter as a distillate from the naphtha, the distillate
enters a depropanizer where C 3 and lighter are separated as a distillate from the
C 4 s. This distillate is further fractionated in a deethanizer column where the C 3 is
removed as the bottom product. There is no distillate product from this unit, but all
the gas lighter than C 3 leaves the tower as a vapor usually routed to the refinery fuel
gas system (see the chapter titled “▶ Refinery Gas Treating Processes”).
The C 4 portion of the overhead distillate is fractionated in the debutanizer so that it
meets finished product specifications with respect to its C 5 content. The fractionation
in the depropanizer will be such that the C 3 content of the bottom product – C 4 LPG –
will meet the butane LPG specification with respect to RVP (Reid Vapor Pressure).
The fractionation in this tower will also be such that the C 4 content in the overhead
Petroleum Products and a Refinery Configuration
55
entitled “▶ Petroleum Refinery Planning and Economics” in this handbook.
Petroleum Products
Fractions from the Atmospheric and Vacuum Distillation
of Crude Oil
The most common fractions distilled from crude oil distillation processes are shown
in Fig. 1.
These cut lengths will vary slightly depending on the crude oil source and the
finished product slate requirements. These are the basic components which, after
further processing and blending, will make the finished products in the composition
and quantity required by the refinery. The cuts shown in Fig. 1 are called “straight
run” products , and these are described in the following paragraphs. The crude
source, in this case, is a medium Middle Eastern crude with a gravity of 33.9
API
and a sulfur content of 1.9 % wt.
Atmospheric overhead distillate. This is not strictly a cut but consists of all the
light material in the crude absorbed into the total overhead distillate from the crude
tower. This distillate, and in most cases, together with similar distillates from other
processes, forms the feed to the refinery’s light ends unit (see the chapter entitled
“▶ Distillation of the “Light Ends” from Crude Oil in Petroleum Processing”). It is
in the light ends unit that the straight run LPG, light naphtha, and the heavy naphtha
are separated. However, the end point of the heavy naphtha is determined by the cut
point of the overhead distillate and the fractionation between it and the first side
stream product from the atmospheric unit.
Refinery gas and LPGs. In many refineries, most of the C 4 s and lighter are
removed from the atmospheric column overhead distillate in the first column of the
light ends unit. This is the unit’s debutanizer column. Some refineries however
choose to separate the light naphtha and lighter from the heavy naphtha first. There
is no specific reason; it’s really a question of the specific refinery’s economic criteria.
Having separated the C 4 s and lighter as a distillate from the naphtha, the distillate
enters a depropanizer where C 3 and lighter are separated as a distillate from the
C 4 s. This distillate is further fractionated in a deethanizer column where the C 3 is
removed as the bottom product. There is no distillate product from this unit, but all
the gas lighter than C 3 leaves the tower as a vapor usually routed to the refinery fuel
gas system (see the chapter titled “▶ Refinery Gas Treating Processes”).
The C 4 portion of the overhead distillate is fractionated in the debutanizer so that it
meets finished product specifications with respect to its C 5 content. The fractionation
in the depropanizer will be such that the C 3 content of the bottom product – C 4 LPG –
will meet the butane LPG specification with respect to RVP (Reid Vapor Pressure).
The fractionation in this tower will also be such that the C 4 content in the overhead
Petroleum Products and a Refinery Configuration
55