Light 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). ... 

The separate stepwise condensation of the products from Fe-LTFT and Fe-HTFT synthesis produces streams of different carbon number distributions that serve as feeds to the oil refinery (Figure 18.4).30 It is consequently not necessary to employ an atmospheric distillation unit as the first step in the refinery. The stepwise condensation products from Fe-LTFT are reactor wax (liquid at LTFT conditions), hot condensate (>100°C), cold condensate (produced by condensation with the aqueous product and then phase separated), and tail gas (typically C4 and lighter). The stepwise condensation products from Fe-HTFT are decanted oil (liquid at 145°C 1.6 MPa), light oil (produced by condensation with the aqueous product and then phase separated), and tail gas. 

Atmospheric and vacuum distillation units (Figures 4.3 and 4.4) are closed processes, and exposures are expected to be minimal. Both atmospheric distillation units and vacuum distillation units produce refinery fuel gas streams containing a mixture of light hydrocarbons, hydrogen sulfide, and ammonia. These streams are processed through gas treatment and sulfur recovery units to recover fuel gas and sulfur. Sulfur recovery creates emissions of ammonia, hydrogen sulfide, sulfur oxides, and nitrogen oxides. 

The fractions obtained by vacuum distillation of the reduced crude (atmospheric residuum) from an atmospheric distillation unit depend on whether or not the unit is designed to produce lubricating or vacuum gas oils. In the former case, the fractions include (1) heavy gas oil, which is an overhead product and is used as catalytic cracking stock or, after suitable treatment, a light lubricating oil (2) lubricating oil (usually three fractions—light, intermediate, and heavy), which is obtained as a side-stream product and (3) asphalt (or residuum), which is the nonvolatile product and may be used directly as, or to produce, asphalt, and which may also be blended with gas oils to produce a heavy fuel oil. 

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. 

The atmospheric residuum is then fed to the vacuum distillation unit at the pressure of 10 mmHg where light vacuum gas oil, heavy vacuum gas oil, and vacuum residue are the products (Fig. 13.4). 

Atmospheric residue oil (Residue), containing compounds that boil above about 340°C (650°F). This is normally sent to a vacuum distillation unit to recover more light products, but parts of it may be blended into high sulfur fuels such as heating oil or bunker fuel (marine fuel). 

The vacuum distillation unit cuts deeper into the atmospheric topped bitumen. It distills off the remaining light gas oil and heavy gas oil that are sent directly to hydrotreaters. The remaining vacuum topped bitumen can be blended with atmospheric topped bitumen and then sent to bitumen conversion units. 

Liquid feeds can be atmospheric or vacuum gas oils from crude distillation units gas oils (light and heavy) from delayed cokers, fluid cokers, or visbreakers and cycle oils (light and heavy) from FCC units. 

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... 

In present-day refineries, the fluid catalytic cracking (FCC) unit has become the major gasoline-producing unit. The FCC s major purpose is to upgrade heavy fractions, that is, gas oil from the atmospheric and vacuum distillation columns and delayed coker, into light products. Atmospheric gas oil has a boiling range of between 650-725°F.9... 

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