Vacuum distillation columns

The distillation of crudes chosen for their yield in heavy fractions is the most common means. Bitumen is extracted from the residue from a vacuum distillation column (a few dozen mm of mercury), the latter being fed by atmospheric distillation residue. Unlike the practice of a decade ago, it is now possible to obtain all categories of bitumen, including the hard grades. 

Problem A 100-tray vacuum distillation column was run in blocked operation mode. After a run on a previous product the column would not run properly for a new product. 

The injection of superheated steam at the base of the vacuum fractionator column further reduces the partial pressure of the hydrocarbons in the tower, facilitating vaporization and separation. The heavier fractions from the vacuum distillation column are processed downstream into more valuable products through either cracking or coking operations. 

Figure 7-4. The Scientific Design Co. process for producing ethylene glycols from ethylene oxide (1) feed tank, (2) reactor, (3,4,5) multiple stage evaporators, 4 operates at lower pressure than 3, while 5 operates under vacuum, evaporated water is recycled to feed tank, (6) light ends stripper, (7,8) vacuum distillation columns.

In vacuum distillation columns, the plate-support rings will act as stiffening rings and strengthen the vessel see Example 13.2. 

A vacuum distillation column is to operate under a top pressure of 50 mmHg. The plates are supported on rings 75 mm wide, 10 mm deep. The column diameter is 1 m and the plate spacing 0.5 m. Check if the support rings will act as effective stiffening rings. The material of construction is carbon steel and the maximum operating temperature 50° C. If the vessel thickness is 10 mm, check if this is sufficient. 

Commercial production of ethanolamines (EOA) is by reaction of ethylene oxide with aqueous ammonia. The ethylene oxide reacts exothermically with 20% to 30% aqueous ammonia at 60 to 150°C and 30 to 150 bar in a tubular reactor to form the three possible ethanolamines (mono-ethanolamine - MEA, di-ethanolamine - DEA and tri-ethanolamine - TEA) with high selectivity. The product stream is then cooled before entering the first distillation column where any excess ammonia is removed overhead and recycled. In the second column, ammonia and water are removed and the EOA s are separated in a series of vacuum distillation columns. 

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... 

The catalytic cracking unit is often referred to as the gasoline workhorse of a refining unit. As shown in Fig. 18.9, feeds to the catalytic cracking unit are gas oils from the atmospheric and vacuum distillation columns and delayed coker. These heavier fractions also carry metals such as nickel, vanadium, and iron. More important, sulfur compounds concentrate in the heavier product fractions. Table 18.8 lists a typical mass balance for sulfur.25 FCC blend-stocks comprise 36 percent of the volume of the gasoline pool. However, this stream also contributes 98 percent of the sulfur concentration to blended procucts.25 As specifications on sulfur concentrations in diesel and gasoline tighten, more efforts are focused on how feeds and product streams from the FCC are pre- and posttreated for sulfur concentrations. 

Crude oil is distilled in a distillation column operating near to atmospheric pressure to produce naphtha (b.p. 30°C - 180°C) and gas oil (b.p. 25°C - 360°C). The bottoms of the column, known as atmospheric residua, are passed to a vacuum distillation column which produces vacuum gas oil (b.p. 350°C - 550 C). Any of these distilled liquid feeds can be used to produce petrochemicals. 

The remaining furoyl chloride (b.p. 173 °C) is transferred into a vacuum distillation column 15 energized by a steam coil, where the furoyl chloride is obtained as the head fraction liquefied in condenser 16. The vacuum pump 17 maintains this system at a pressure of 7 mm Hg., A part of the condensate is used as reflux, while the product is collected in tank 18. The yield of furoyl chloride is in excess of 89 percent, the losses being a small fore-run collected in tank 19, a small after-run collected in tank 20, and a small quantity of a carbonaceous residue. 

Two or three steam ejectors (similar to laboratory water aspirators) operating in series with interstage condensers provide the pressure reduction necessary and are connected to the top end of the vacuum distilling column (Fig. 18.5). Each take-off point on the main vacuum column is also passed... 

Purification. The dehydrated methacrylic add is purified in a series of three vacuum distillation columns, with the separations the top in succession of acetic add by-product and light ends (40 to 50 trays), 99.9 per cent weight methacrylic add (10 to 50 trays) and residual amounts entrained in the heavy compounds. 

The gaseous reactor effluent is first cooled with the production of low-pressure steam (1.106 Pa absolute), and the residual gases scrubbed with water and then discharged to the atmosphere. The condensed stream obtained is then sent to batch condensers, where it is melted at 130 0 and sent to a storage tank. The crude product is vacuum preheated in the presence of additives to decompose the nonvolatile impurities (polymers and colored products). It then goes to a first vacuum distillation column (15 kPa absolute which separates the maleic anhydride and benzoic and toluic adds at the top, and then to a second column where 99.5 percent weight phthalic anhydride is recovered at the top. 

Baffle columns and shower tray columns, shown in Fig. 2.27, are characterized by relatively low liquid dispersion and very low pressure drops. The major application of this type of flow regime is in cooling towers, where the water flows across wooden slats and very large volumes of gas are handled. Here economics dictate that fans rather than compressors be used. Some gas absorption and vacuum distillation columns employ baffle or shower trays. 

Refinery Crude residuum vacuum distillation column Tray effidemy was lower than expected. Cdunm contained valve trrys and operated at low liquid loads and with wide variations in veqxir loads. Beware of overpredicting effidenry at very low liquid loads. 

To the dried monomer is added 0.5% of recrystallized dibenzoyl peroxide. The solution is transferred to a boiling flask attached to high-vacuum distillation column and blanketed with oxygen-free nitrogen. The monomer is wanned at 45°C until the increase in viscosity is judged to represent a conversion to approximately 10% of polymer. The flask is then cooled, and the pressure in the apparatus is lowered to 0.1 mm Hg. At this pressure, the monomer is fractionally distilled and a center-cut is retained as purified monomer. 

Of greatest interest to chemical processing is the rough region, which covers most polymer reactors, vacuum distillation columns, vacuum stripping columns, pervaporation membrane separations, vacuum-swing adsorbers, and vacuum crystallizers, evaporators, filters, and dryers. 

A vacuum distillation column produces an overhead vapor of 1,365 kmol/hr of ethylbenzene and 63 kmol/hr of styrene at 30 kPa. The volume of the column, vapor line, condenser, and reflux drum is 50,000 ft. The overhead vapor is sent to a condenser where most of the vapor is condensed. The remaining vapor at 50°C and 25 kPa is sent to a vacuum system. Determine the air leakage rate in the distillation operation and the flow rate to the vacuum system. Select an appropriate vacuum system and determine its f.o.b. purchase cost at a CE cost index of 400. 

Microsyringe (0.5 cm ) and needle Equipment for vacuum distillation Column chromatography equipment... 

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