Example Calculation
From the screening study, the new plants included in the selected case (which was
case 1) were as follows:
• Naphtha hydrotreater (13,500 BPSD) licensed
• Naphtha splitter (13,500 BPSD)
• Catalytic reformer (9,000 BPSD) licensed
• Depropanizer (3,830 BPSD) and deethanizer (2,176 BPSD)
• Diesel hydrotreater (9,000 BPSD) licensed
• Thermal cracker (34,320 BPSD)
The existing debutanizer is to be revamped and a new sized equipment list will
be prepared for this unit.
The units of normally licensed processes are indicated as such in the above list.
The thermal cracker may be licensed or can be designed by some major engineering
companies as a nonproprietary process. It is a major item of cost, and for this
example, the degree of process engineering required at this stage of the study is
demonstrated for this unit.
The Process Design of the Thermal Cracker
The process flow sheet for this unit is given in Fig. 6. This process flow sheet
contains the overall material balance for the unit together with the calculated reflux
and quench flows. Major process stream routes are shown with stream temperatures
where appropriate. The material balance table also gives the flow conditions
(temperature and pressure) for those major streams. The pump capacities are
shown on the flow sheet next to the respective pump. These quantities are flows
in gallons per minute at the pump temperature.
The major item in a thermal cracker is the furnace or heater. This has two duties,
the first being to heat the feed to its reaction temperature and the second to maintain
the feed at its reaction temperature for the prescribed period of time. Note therefore
that the duty of this heater is shown on the flow sheet as the duty to heating the oil
(which also includes the steam in this case) and the duty to supply the heat of reaction.
Data for the remainder of the equipment are given in Tables 9, 10, and 11.
Sufficient data for obtaining a cost and efficiency for the heater is provided in a
“process specification” shown in Table 12. A special specification sheet is required
for this item because, besides being an oil heater, it is also a cracking reactor. In this
function, the design of the unit must be such as to allow the oil to be retained for a
specific period of time at the reaction temperature.
Summary Data Sheets
Coil tubes should be standard 4
00 11/13 Cr with wide radius bends. The firebox
should be constructed to heat the incoming feed to a temperature of about 870
F in
the first 150 cu. ft. of coil. This should constitute the Heater Section. The Soaker
714
D.S.J. Jones and P.R. Pujado ´
From the screening study, the new plants included in the selected case (which was
case 1) were as follows:
• Naphtha hydrotreater (13,500 BPSD) licensed
• Naphtha splitter (13,500 BPSD)
• Catalytic reformer (9,000 BPSD) licensed
• Depropanizer (3,830 BPSD) and deethanizer (2,176 BPSD)
• Diesel hydrotreater (9,000 BPSD) licensed
• Thermal cracker (34,320 BPSD)
The existing debutanizer is to be revamped and a new sized equipment list will
be prepared for this unit.
The units of normally licensed processes are indicated as such in the above list.
The thermal cracker may be licensed or can be designed by some major engineering
companies as a nonproprietary process. It is a major item of cost, and for this
example, the degree of process engineering required at this stage of the study is
demonstrated for this unit.
The Process Design of the Thermal Cracker
The process flow sheet for this unit is given in Fig. 6. This process flow sheet
contains the overall material balance for the unit together with the calculated reflux
and quench flows. Major process stream routes are shown with stream temperatures
where appropriate. The material balance table also gives the flow conditions
(temperature and pressure) for those major streams. The pump capacities are
shown on the flow sheet next to the respective pump. These quantities are flows
in gallons per minute at the pump temperature.
The major item in a thermal cracker is the furnace or heater. This has two duties,
the first being to heat the feed to its reaction temperature and the second to maintain
the feed at its reaction temperature for the prescribed period of time. Note therefore
that the duty of this heater is shown on the flow sheet as the duty to heating the oil
(which also includes the steam in this case) and the duty to supply the heat of reaction.
Data for the remainder of the equipment are given in Tables 9, 10, and 11.
Sufficient data for obtaining a cost and efficiency for the heater is provided in a
“process specification” shown in Table 12. A special specification sheet is required
for this item because, besides being an oil heater, it is also a cracking reactor. In this
function, the design of the unit must be such as to allow the oil to be retained for a
specific period of time at the reaction temperature.
Summary Data Sheets
Coil tubes should be standard 4
00 11/13 Cr with wide radius bends. The firebox
should be constructed to heat the incoming feed to a temperature of about 870
F in
the first 150 cu. ft. of coil. This should constitute the Heater Section. The Soaker
714
D.S.J. Jones and P.R. Pujado ´