Fractionator primary

The primary fractions from a distUlation unit are equUibrium mixtures and contain some proportion of the lighter constituents characteristic of a lower boiling fraction. The primary fractions are stripped of these constituents (stabUized) before storage or further processing. 

AOAC Method 985.29for TDF. This AO AC method (3), referred to as the method of Prosky and co-workers (4), was cited in the Nutritional Labeling and Education Act of 1990 as the general analytical approach for food labeling of dietary fiber content. The method has undergone several modifications for IDE and for the primary fractions, SDE and IDE. 

The cracked products pass out through two stages of cyclones which collect entrained catalyst and return it to the dense bed. Velocities at the outlet of the dense bed are normally 2.0-3.0 ft./sec. Upon leaving the cyclones, the vapors go to the primary fractionator which separates the heavy products from the gasoline and lighter components. The light products go on to the light ends recovery unit. The heavy material is separated and either recycled to the reactor or withdrawn from the system. 

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. 

Catalytic cracking units operate at low pressure, and the primary fractionator... 

Steam stripping is not adequate for the bottoms purity required. More positive stripping is obtained by charging the tower bottom liquid to a heating unit known as a reboiler. In a typical reboiler, 50% of the feed is vaporized and returned to the tower below the bottom plate. A fractionating tower equipped with a steam heated reboiler is shown in Figure 4. The reboiler may also be heated by a hot oil stream, such as a pumparound reflux stream from the primary fractionator of a cracking unit, or by a fired furnace. 

In a typical gas oil design, the lighter products overhead from the quench tower/primary fractionator are compressed to 210 psi, and cooled to about 100°F. Some Q plus material is recovered from the compressor knockout drums. The gases are ethanolamine and caustic washed to remove acid gases sulfur compounds and carbon dioxide, and then desiccant dried to remove last traces of water. This is to prevent ice and hydrate formation in the low temperamre section downstream. 

An olefin plant that uses liquid feeds requires an additional pyrolysis furnace, an effluent quench exchanger, and a primary fractionator for fuel oil separation. 

Condensate is normally considered the entrapped liquids in process or production gas streams due to temperature or pressure, in the typically in the range of C3, C4, C5 or heavier hydrocarbon liquids. It is also known as natural gasoline C5 plus and pentanes plus, and as a liquid at normal temperatures and pressures it generally consists of a mixture of the C5 (pentanes) and heavier hydrocarbons. It is normally condensed (i.e., by expansion and cooling of the gas) out of the process stream in primary separation processes, where it is then sent to other refinery processes to further separate the condensate into its primary fractions, i.e., propane, butane, and liquids constituents. 

The solution with the precipitant was gently warmed to 45°C to redissolve the precipitate and gradually cooled in the thermostat. Phase separation took place after a while, and the phases were Isolated from each other by filtration. The gel like phase thus Isolated was the first primary fraction. The subsequent fractions were Isolated in the same way by the further successive additions of precipitant to the solution. The last fraction was Isolated by the addition of a large volume of the precipitant and allowing the solution to stand for 72 hours before the phase separation is affected by filtration as stated above. 

Seven primary cellulose triacetate fractions were Isolated by this method. The first primary fraction rich in hemlcellulose was redissolved and reprecipitated into three subfractions in the same way as described above. The refractionation of the first fraction was necessary to isolate the hemlcellulose material for subsequent analysis and characterisation. 

Crude oil, intermediate, and finished products are stored in tanks of varying size to provide adequate supplies of crude oils for primary fractionation mns of economical duration to equalize process flows and provide feedstocks for intermediate processing units and to store final products prior to shipment in adjustment to market demands. Generally, operating schedules permit sufficient detention time for settling of water and suspended materials. 

Cycle Oil. Heavier, distillate range compounds formed during FCC processing can accumulate within the FCC fractionator. The primary fraction is called light cycle oil (LCO) and contains high percentages of monoaromatic and diaromatic compounds plus olefins and heavier branched paraffins. Unhydrotreated LCO is often quite unstable and has a very low cetane number. For this reason, it is blended into diesel fuel in controlled amounts. Heavy cycle oil and heavy naphtha are additional side cuts that can be produced. These streams can be pumped around to remove heat from the fractionator, used to supply heat to other refinery units, or used as low-quality blendstock component. 

With the classical fractionation technique, CF requires subdividing the sample into 5-10 primary fractions and each of them into 5-10 subfractions, with isolating and characterizing the polymer material of each final portion for molar mass, composition, and amount. This requires at least 15 g of starting material and several weeks of skillful work. 

Some investigators have found the enzyme primarily in the 100,000 X g supernatant fluid of extracts of rabbit brain (37), dog heart (42), rat liver (45), rat brain, and beef pineal gland (48). In contrast, other investigators have reported that the enzyme from beef heart (36) and rat brain (49, 50) is mostly particulate being present in all the primary fractions nuclear, mitochondrial, microsomal, and 100,000 X 9 supernatant. The reasons for these discrepancies are not entirely clear but most likely result from differences in fractionation technique. Evidence from density gradient procedures coupled with electron microscopic examination indicate that the enzyme is preferentially located at nerve... 

Fractionation on the basis of solubilities at different pH values has always been a major procedure for the fractionation of HS, and thus there arose the primary fractionations into HAs and FAs. Further fractionations on the basis of different solubilities in alcohol gave rise to additional components, as outlined in Section... 

The cracked gas stream is cooled and purified in the primary fractionator (3) and quench water tower (5). Waste heat is recovered by a circulating oil cycle, generating dilution steam (4) and by a water cycle (5) to provide heat to reboilers and process heaters. The cracked gas from the quench tower is compressed (6) in a 4- or 5-stage compressor and dried in gas and liquid adsorbers (8). C02 and H2S are removed in a caustic-wash system located before the final compressor stage. 

The hydrocarbon mixture at the furnace outlet is quenched rapidly in the transfer line exchangers (2) (TLE or SLE), generating high-pressure steam. In liquid crackers, cracked gas flows to a primary fractionator (3) after direct quench with oil, where fuel oil is separated from gasoline and lighter components, and then to a quench water tower (4) for water recovery (to be used as dilution steam) and heavy gasoline production (end-point control). 

Combined cracked-gas stream is cooled and purified in the primary fractionator (3) and quench-water tower (5). Waste heat is recovered... 

The effluents from the different quench boilers are first collected together. They undergo supplementary in-line cooling, and are then sent to a so-called primary fractionation columj whose bottom stream, itself previously cooled, serves for the direct quench operation. This column also separates the gases at the top that are sent to the compression section, and a gasoline sidestream. The diluent steam which is condensed at various levels, is purified and re-used in a closed circuit with make-up process water. 

The distillation of the effluents that leave primary fractionation in gaseous fonn first requires their condensation to the liquid phase. Given the high volatility of some com-... 

Feedstock (after pre-treatment if necessary) is passed along with steam to the pyrolysis furnace. This cracks the compounds in the naphtha, producing a full range of products which are extremely complex. As with gas feedstock, heavier products are produced, but in increased volumes. After quenching a primary fractionator (not present in gas crackers) separates the heavy pyrolysis fuel oil from the cracked gases. 

One of the issues that concern liquid feedstock cracking operations is a higher rate of fouling. This is not only a consequence of heavier coke forming precursors, but also as a consequence of long lived free radicals which act as agents for the formation of a polymer (often referred to as pop-corn polymer) in the primary fractionator and downstream units. For instance, free radicals based on styrene or indene have sufficiently long half-lives to pass from the pyrolysis section into the primary fractionator. These can concentrate in this unit and produce polymer (free radical polymerisation) when sufficient amounts of suitable olefins are present, in particular styrene itself and di-olefins such as cyclo-pentadiene or butadiene. 

Although refractionation may narrow the molecular weight distributions of primary fractions such operations are subject to a law of diminishing returns because of the complications of Eq. (12-30) which have just been mentioned. 

Gum arable, also known as gum acacia [64,65,66], is another gum that is ionic because of the presence of uronic acid units. The structure of the most important polysaccharide of gum arable is that of a highly branched, branch-on-branch (bushlike), anionic polymer that is attached to a polypeptide. The structure is not only complex, but variable. What is harvested as, and called, gum arable is a heterogeneous material, but generally consists of two primary fractions. One, which accounts for about 70% of the gum, is composed of polysaccharide molecules with... 

Cracking of crude oil in the presence of steam superheated to 2000°C. with the formation, in addition to acetylene and ethylene, of various co-products (fuel gas, propylene, benzene, naphthalene, tars, pitches, etc.). This operation is followed by quenching and primary fractionation. 

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