Atmospheric distillation tower

The feeds used in all experiments presented in this paper are North Sea atmospheric residues originating from the atmospheric distillation tower at the Statoil Mongstad refinery in Norway. After the start-up of the residue fluid catalytic cracker at this refinery in 1989, the same feed has been used both in the commercial FCCU and in the ARCO pilot unit at Chalmers. Typical data for some North Sea atmospheric residue feeds used in the ARCO pilot unit are shown in Table 3.1. 

Figure 1-10 General temperature distribution in a noncracking atmospheric distillation tower.

Crude oil enters the refinery and is stored and excess salt removed prior to distillation. Often several different crude oils are co-mingled before distillation in the atmospheric distillation tower. This has the duty to separate the crude oil into fractions according to distillation range. 

Figure P5.17 Phenosolvan plant—only one stream shown. Key 1, Tar-oil separation (gravity) 2. Saturation tower 3. Phenol extractor 4. Butyl-acetate recovery tower 5. Butyl-acetate stripping tower 6. Ammonia stripping tower 7. Atmospheric distillation tower 8. Vacuum distillation tower 9. Separator drum 10. Butyl-acetate circulating drum.

The residue from an atmospheric distillation tower can be sent to a vacuum distillation tower, which recovers additional liquid at 0.7 to 1.5 psia (4.8 to 10.3 kPa). The vacuum, which is created by a vacuum pump or steam ejector, is pulled from the top of the tower. Relative to atmospheric columns, vacuum columns have larger diameters and their internals are simpler. Often, instead of trays, random packing and demister pads are used. 

The crude will next go through a fired furnace to be heated to 650-700 F (343-37rC), and it will then go to the atmospheric distillation tower. Here it will be broken into four major fractions gas and naphtha, gas oil, kerosene, and bottoms (the heavier fraction that is removed from the bottom of the tower). 

We have followed the path of the bottom cuts from the crude processing unit. We are now left with the naphtha and gas cuts from the atmospheric distillation tower. As both these cuts leave the area, they will be "sweetened in a hydrotreater or amine unit before being further processed. 

To prevent condensation of water and hence corrosion, the operating temperature at the top section of the atmospheric distillation tower is raised. Therefore, more economical materials can be used here. 

Vacuum distillation. In this process, the residue from the atmospheric distillation tower is separated under vacuum into one or more heavy gas oil streams and heavy residual pitch. 

An existing refinery at which the primary crude oil atmospheric distillation tower was replaced afl r October 31, 1973. 

Propane Asphalt. As noted above, cmde oils contain different quantities of residuum (Fig. 2) and, hence, asphalt. Asphalt is also a product of the propane deasphalting and fractionation process (5,6,21,22) which involves the precipitation of asphalt from a residuum stock by treatment with propane under controlled conditions. The petroleum charge stock is usually atmospheric-reduced residue from a primary distillation tower. 

TABLE 13-27 Light-Component Analysis and TBP Distillation of Feed for the Atmospheric Crude Tower of Fig. 13-94... 

In the atmospheric distillation process (Figure 2.1), heated crude oil is separated in a distillation column (distillation tower, fractionating tower, atmospheric pipe still) into streams which are then purified, transformed, adapted, and treated... 

Prefractionation is an optional distillation process to separate economic quantities of very light distillates from the crude oil. Lower temperatures and higher pressures are used than in atmospheric distillation. Some process water can be carried over to the prefractionation tower from the desalting process. 

Some years later Statoil decided to start a project within catalytic cracking in order to learn more abont residue fluid catalytic cracking in general, and particnlarly abont catalysts suitable for this process. The project started as a prestudy for the residue fluid catalytic cracker unit (FCCU) that Statoil was planning to bnild at the Mongstad refinery in Norway. The intention was to crack North Sea atmospheric residue directly, without first using a vacuum gas distillation tower followed by cracking... 

Fig 9. View from base upward of atmospheric crude distillation tower... 

Heavy materials remaining at the bottom are called the bottoms, or residuum, and include such components as heavy fuel oil (see fuel oil) and asphaltic substances (see asphalt). Those fractions taken in liquid form from any level other than the very top or bottom are called sidestream products a product, such as propane, removed in vapor form from the top of the distillation tower is called overhead product. Distillation may take place in two stages first, die lighter fractions—gases, naphtha, and kerosene-are recovered at essentially atmospheric pressure next, the reamining crude is distilled at reduced pressure in a vacuum tower, causing the heavy lube fractions to distill at much lower temperatures than possible at... 

Samples. Table I lists the six residua studied and their sulfur, nickel, vanadium, and weight percent asphaltenes data. The Arabian Light is a vacuum (1000 + °F) residuum, while the other five are atmospheric (650 -f °F) residua. The samples were analyzed as received from the refinery distillation tower. 

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