549
Solvent Processes
the DAO mix flows from the pressure vapor heat exchanger to the low-pressure flash tower where
low-pressure solvent vapor is taken overhead, condensed and collected in the low-pressure solvent
receiver. The DAO mix flows down the low-pressure flash tower to the reboiler, where it is heated,
and then to the DAO stripper, where the remaining solvent is stripped overhead with superheated
steam. The DAO product is pumped from the stripper bottom and is cooled, if required, before
flowing to battery limits.
The raffinate phase containing asphalt and small amount of solvent flows from the bottom of the
RDC to the asphalt mix heater. The hot, two-phase asphalt mix from the heater is flashed in the asphalt
mix flash tower where solvent vapor is taken overhead, condensed, and collected in the low-pressure
solvent receiver. The remaining asphalt mix flows to the asphalt stripper where the remaining solvent
is stripped overhead with superheated steam. The asphalt stripper overhead vapors are combined with
the overhead from the DAO stripper, condensed, and collected in the stripper drum. The asphalt product is pumped from the stripper and is cooled by generating low-pressure steam.
20.2.2.2 Demex Process
The Demex process is a solvent extraction demetallization process that separates high metal vacuum residuum into demetallized oil of relatively low metal content and asphaltene of high metal
content (Table 20.4; Salazar, 1986; RAROP, 1991, p. 93; Houde, 1997). The asphaltene constituents
and condensed aromatic contents of the demetallized oil are very low. The demetallized oil is a
desirable feedstock for fixed-bed hydrodesulfurization and, in cases where the metals content and
TABLE 20.3
Feedstock and Product Data for the ASCOT
Process, Delayed Coking, and LEDA Process
Feedstock
ASCOT
Delayed Coking
LEDA
API
2.8
2.8
2.8
Sulfur, % w/w
4.2
4.2
4.2
Nitrogen, % w/w
1.0
1.0
1.0
Carbon residue, % w/w
22.3
22.3
22.3
Products
Naphtha, % v/v
7.7
19.4
API
54.7
Sulfur, % w/w
1.1
Nitrogen, % w/w
0.1
Gas oil, % v/v
69.9
51.8
API
13.4
Sulfur, % w/w
3.4
Nitrogen, % w/w
0.5
Coke, % w/w
25.0
32.5
Sulfur, % w/w
5.8
5.7
Nitrogen, % w/w
2.7
2.6
Nickel, ppm
774.0
609.0
Vanadium, ppm
2656.0
2083.0
Deasphalted oil, % v/v
50.0
Asphalt, % v/v
50.0
Sulfur, % w/w
5.0
Nitrogen, % w/w
1.4
Nickel, ppm
365.0
Vanadium, ppm
1250.0
Solvent Processes
the DAO mix flows from the pressure vapor heat exchanger to the low-pressure flash tower where
low-pressure solvent vapor is taken overhead, condensed and collected in the low-pressure solvent
receiver. The DAO mix flows down the low-pressure flash tower to the reboiler, where it is heated,
and then to the DAO stripper, where the remaining solvent is stripped overhead with superheated
steam. The DAO product is pumped from the stripper bottom and is cooled, if required, before
flowing to battery limits.
The raffinate phase containing asphalt and small amount of solvent flows from the bottom of the
RDC to the asphalt mix heater. The hot, two-phase asphalt mix from the heater is flashed in the asphalt
mix flash tower where solvent vapor is taken overhead, condensed, and collected in the low-pressure
solvent receiver. The remaining asphalt mix flows to the asphalt stripper where the remaining solvent
is stripped overhead with superheated steam. The asphalt stripper overhead vapors are combined with
the overhead from the DAO stripper, condensed, and collected in the stripper drum. The asphalt product is pumped from the stripper and is cooled by generating low-pressure steam.
20.2.2.2 Demex Process
The Demex process is a solvent extraction demetallization process that separates high metal vacuum residuum into demetallized oil of relatively low metal content and asphaltene of high metal
content (Table 20.4; Salazar, 1986; RAROP, 1991, p. 93; Houde, 1997). The asphaltene constituents
and condensed aromatic contents of the demetallized oil are very low. The demetallized oil is a
desirable feedstock for fixed-bed hydrodesulfurization and, in cases where the metals content and
TABLE 20.3
Feedstock and Product Data for the ASCOT
Process, Delayed Coking, and LEDA Process
Feedstock
ASCOT
Delayed Coking
LEDA
API
2.8
2.8
2.8
Sulfur, % w/w
4.2
4.2
4.2
Nitrogen, % w/w
1.0
1.0
1.0
Carbon residue, % w/w
22.3
22.3
22.3
Products
Naphtha, % v/v
7.7
19.4
API
54.7
Sulfur, % w/w
1.1
Nitrogen, % w/w
0.1
Gas oil, % v/v
69.9
51.8
API
13.4
Sulfur, % w/w
3.4
Nitrogen, % w/w
0.5
Coke, % w/w
25.0
32.5
Sulfur, % w/w
5.8
5.7
Nitrogen, % w/w
2.7
2.6
Nickel, ppm
774.0
609.0
Vanadium, ppm
2656.0
2083.0
Deasphalted oil, % v/v
50.0
Asphalt, % v/v
50.0
Sulfur, % w/w
5.0
Nitrogen, % w/w
1.4
Nickel, ppm
365.0
Vanadium, ppm
1250.0