Naphtha atmospheric distillation unit

Naphtha is a generic term normally used in the petroleum refining industry for the overhead liquid fraction obtained from atmospheric distillation units. The approximate boiling range of light straight-run naphtha (LSR) is 35-90°C, while it is about 80-200°C for heavy straight-run naphtha (HSR). ... 

Heavy naphtha from atmospheric distillation units or hydrocracking... 

The feed to a catalytic reformer is normally a heavy naphtha fraction produced from atmospheric distillation units. Naphtha from other sources such as those produced from cracking and delayed coking may also be used. Before using naphtha as feed for a catalytic reforming unit, it must be hydrotreated to saturate the olefins and to hydrodesulfurize... 

The Fe-HTFT syncrude is fractionated in an atmospheric distillation unit to produce mainly naphtha and distillate, with a small amount of residue that is used as fuel oil (not shown in Figure 18.7). No vacuum distillation unit has been included in the design, since it would be superfluous with the limited residue production. The natural gas liquids are fractionated separately. 

Jet fuels are typically prepared from either straight-run kerosene or from wide-cut kerosene/naphtha blends off of the atmospheric distillation unit. TABLE 3-10 briefly describes the composition of some typical jet fuel grades. 

Although gas oils obtained from the atmospheric distillate still remain the main source of diesel fuels, in order to cope with the increased consumption of naphtha and middle distillates almost all refineries in Romania use conversion processes such as fluid catalytic cracking on vacuum distillates and coking or visbreaking on residue. These processes generate middle distillates with higher olefins, diolefins, sulphur, nitrogen and aromatics content compared to gas oil obtained from an atmospheric distillation unit... 

The current oil sands bitumen upgrading processes for the production of synthetic crude oil (Table 4) begin with diluted bitumen being processed through the diluent recovery units. The diluent recovery units are atmospheric distillation units that serve three purposes 1) distill off diluent naphtha and return it to the froth treatment process 2) distill off light gas oil and send it directly to a light gas oil hydrotreater and 3) produce hot atmospheric topped bitumen as feedstock for vacuum distillation unit and downstream bitumen conversion processes. 

A combination unit is a special type of unit that was developed to reduce the investment for a small refinery. In effect, one main distillation unit serves as a crude fi-actionator as well as the cat unit primary fractionator. This same tower also serves the naphtha reformer and visbreaker. A schematic diagram of a combination unit is shown in Figure 2. Crude oil is topped (material boiling below 650°F is removed) in the atmospheric tower, and the topped crude is sent to the combination tower along with cat products and naphtha reformer products. These latter streams provide heat to distill the topped crude and also, being more volatile than topped crude, provide a lifting effect which assists in vaporizing more of the crude. 

Naphtha is also obtained from other refinery processing units such as catalytic cracking, hydrocracking, and coking units. The composition of naphtha, which varies appreciably, depends mainly on the cmde type and whether it is obtained from atmospheric distillation or other processing units. 

Kerosine, a distillate fraction heavier than naphtha, is normally a product from distilling crude oils under atmospheric pressures. It may also he obtained as a product from thermal and catalytic cracking or hydrocracking units. Kerosines from cracking units are usually less stable than those produced from atmospheric distillation and hydrocracking units due to presence of variable amounts of olefinic constituents. 

ARDS unit works as the springboard in the new scheme of Mina Abdulla Refinery operation Primarily a desulfurization unit, ARDS also reduces the metals, asphaltenes and nitrogen in the products, thereby, ensuring proper quality of feed for downstream conversion units. As an additional benefit, ARDS is also a mild hydrocracking process, partially upgrading high sulfur atmospheric residue to low boiling products like naphtha and distillate. 

Consideration of the nature of the petrochemical refinery itself gives some clues as to another source of its profit problem. In the simple, basic unit depicted in Figure 2 thermal cracking dominates the operation. Over 90% of the crude input is consumed without regard to relative values. Thus, it is an indiscriminate cracker of butanes, light naphtha, heavy naphtha, kerosene, distillate, atmospheric gas oil, and vacuum gas oil. Since acceptably similar product slates can be obtained from many of these fractions, it is obvious that the economics suffer when the high valued naphtha and kerosene fractions are thermally cracked. 

Jet fuel is kerosene-based aviation fuel. It is medium distillate used for aviation turbine power units and usually has the same distillation characteristics and flash point as kerosene. Jet fuels are manufactured predominately from straight-run kerosene or kerosene-naphtha blends in the case of wide cut fuels that are produced from the atmospheric distillation of crude oil. Jet fuels are similar in gross composition, with many of the differences in them attributable to additives designed to control some fuel parameters such as freeze and pour point characteristics. For example, the chromatogram (Figure 27.4) of a commercial jet fuel (Jet A) is dominated by GC-resolved n-alkanes in a narrow range of n-C-j to n-Cig with maximum being around n-Ci. The UCM is well dehned. 

Atmospheric distillation of the best crudes yields about 60% naphtha plus middle distillates (kerosene and gas oil), but the average is closer to 40%. In contrast. Table 9 shows that during 1991-2003, the United States consumed, on average, 70% of its petroleum as gasoline and middle distillates. This... 

As shown in Figure 1, hydrocracking often is an in-between process. The required hydrogen comes from catalytic reformers, steam/methane reformers or both. Liquid feeds can come from atmospheric and/or vacuum distillation units delayed cokers fluid cokers visbreakers or FCC units. Middle distillates from a hydrocracker usually meet or exceed finished product specifications, but the heavy naphtha from a hydrocracker usually is sent to a catalytic reformer for octane improvement. The fractionator bottoms can be recycled or sent to an FCC unit, an olefins plant, or a lube plant. 

Conversion units may employ a full-fledged fractionation train, with a preflash tower to remove light ends an atmospheric fractionator to separate light naphtha, heavy naphtha, middle distillates, and unconverted oil and a vacuum tower to maximize the recovery of diesel. Some hydrocrackers use the atmospheric tower to produce full-range naphtha, which is then separated into light and heavy fractions in a naphtha splitter. 

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. 

In view of these considerations, a large amount of effort is reported in the scientific press on the development of a process to produce benzene from n-hexane by combined cyclization and dehydrogenation. w-Hexane has a low Research octane number of only 24.8 and can be separated in fair purities from virgin naphthas by simple distillation. Recently, an announcement was made of a process in the laboratory stage for aromatiza-tion of n-hexane (16). The process utilizes a chromia-alumina catalyst at 900° F., atmospheric pressure, and a liquid space velocity of about one volume of liquid per volume of catalyst per hour. The liquid product contains about 36% benzene with 64% of hexane plus olefin. The catalyst was shown to be regenerable with a mixture of air and nitrogen. The tests were made on a unit of the fixed-bed type, but it was indicated that the fluid technique probably could be used. If commercial application of this or similar processes can be achieved economically, it could be of immense help in relieving the benzene short-age. 

Butane from natural gas is cheap and abundant in the United States, where it is used as an important feedstock for the synthesis of acetic acid. Since acetic acid is the most stable oxidation product from butane, the transformation is carried out at high butane conversions. In the industrial processes (Celanese, Hills), butane is oxidized by air in an acetic acid solution containing a cobalt catalyst (stearate, naphthenate) at 180-190 °C and 50-70 atm.361,557 The AcOH yield is about 40-45% for ca. 30% butane conversion. By-products include C02 and formic, propionic and succinic acids, which are vaporized. The other by-products are recycled for acetic acid synthesis. Light naphthas can be used instead of butane as acetic adic feedstock, and are oxidized under similar conditions in Europe where natural gas is less abundant (Distillers and BP processes). Acetic acid can also be obtained with much higher selectivity (95-97%) from the oxidation of acetaldehyde by air at 60 °C and atmospheric pressure in an acetic acid solution and in the presence of cobalt acetate.361,558... 

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