Vacuum tower, refinery

Figure 2 shows a simplified flow plan for a typical conversion type refinery. The atmospheric P/S residuum can be fed to a vacuum pipestill. The vacuum tower enables the refiner to cut deeper into the crude, at the same time avoiding high temperatures (above about 750 °F) which cause thermal cracking with resultant deposition of coke and tarry residues in the equipment. 

Fractions from the atmospheric and vacuum towers are often used as feedstocks to these second-stage refinery processes that break down the fractions or bring about a basic chemical change in the nature of a particular hydrocarbon compound to produce specific products. 

Petroleum refinery crude-residue vacuum towers i Flash evaporators used to produce concentrated orange juice... 

Big Springs is located in the scrub desert of western Texas. Cold autumn mornings are followed by warm afternoons. The local refinery s cooling-water temperature follows this ambient-temperature trend. The vacuum tower in this refinery also seems to keep track of the time of the day. 

Fig. 3. Erection of 9.5-meter (31-foot) diameter, 263-ton vacuum tower at a petroleum refinery in Kuwait. (The Fluor Corp)...

Delayed coking is a thermal cracking process used in refineries to upgrade and convert crude oil residue known as vacuum tower bottom product (i.e. the bottoms fraction from a vacuum rectification tower) into liquid and gas product streams leaving behind a solid concentrated carbon material, coke. The vacuum towers referred to are generally used to further fractionate virgin atmospheric-... 

I-beam interference can be just as troublesome in the space above a chimney tray. In one case history contributed by D. W. Reay (334), this interference is believed to have led to severe vapor maldistribution in a refinery vacuum tower (Fig. 8.66). The maldistributed vapor profile was displayed as a carbon deposit on the siuTace of the bottom packing. The deposit formed an annular ring about 5 ft wide that extended about 1 in into the bed. In that case, liquid was known to overflow the chimneys for several months because of an incorrect location of level tappings. This overflow caused liquid entrainment. Some entrained droplets ultimately carbonized on the base of the bed. Had the vapor profile been uniform, entrainment (and therefore deposit laydown) would have been more uniform. It is believed that vapor from the side chimneys was blocked by the beams and preferentially ascended around the periphery. If liquid overflow (down the risers) had been uneven, the maldistribution could have been further aggravated. 

In a complex column (e.g., a refinery vacuum tower), it may be beneficial to conduct the test by sections (5, 345). For instance, the tower is tested first, then the connecting lines are tested one at a time by opening block valves. 

When the column feed passes through a heater (e.g., a refinery fractionator or vacuum tower), any water lying at low points in the coils must be blown out prior to startup. In multipass coils, water must be separately blown out of each pass block valves are sometimes installed on each pass to permit this (7). If blowing into the tower, it must be performed when the tower can still tolerate water. The coils must be kept hot and/or purged from then on to prevent condensation. One pressure surge incident (7) occurred when water accumulated in one heater pass entered a refinery vacuum tower which was under full vacuum and circulating 280°F oil. 

Refinery Crude and vacuum tower Caustic backflowed into colunm steam lines. This resulted in caustic being qprayed over a wide area via an atmo-qdieric steam vmit. PrQT special attention to blinding before performing a chemical wash. 

Residual fuel oil is a complex blend of hydrocarbons derived from various refinery streams, usually residue, and can contain hydrogen sulfide and polycyclic aromatic hydrocarbons. Typical streams include atmospheric tower bottoms and vacuum tower bottoms. Fuel oil is used in many countries... 

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