Main fractionator

Material balance and properties of the main fractions resulting from primary and secondary fractionation of a 50/50 volume % mixture of Arabian Ligb and heavy crude oil (specific gravity d f = 0.875). 

HCl and 50 ml of water. The upper layer was separated off and the aqueous phase was extracted five times with small portions of THF. After drying the combined solutions over magnesium sulfate the solvent was removed in a water-pump vacuum. The residue was distilled through a 30-cm Vigreux column, connected to an air condenser. After a preliminary aqueous fraction of the carboxylic acid the main fraction passed over at 100°C/15 mmHg. The compound solidified in the receiver and (partly) in the condenser. The yield was almost quantitative. 

The price of Gedarwood oil from Texas in 1995 was 7.70/kg and the price of the oil from Virginia was 15.18/kg (69). Distillation of the oil gives two main fractions, the cedrene or hydrocarbon fraction, and the alcohol fraction consisting of impure cedrol, which when purified by crystallization can be used direcdy in perfumery. Gedrenol is a product comprising a mixture of cedrol and its isomers widdrol and some ketone components. 

Fig. 3. Schematic representation showing the anatomical basis for differences in the quantitative supply of absorbed material to the Hver. By swallowing (oral route), the main fraction of the absorbed dose is transported direcdy to the Hver. FoUowing inhalation or dermal exposure, the material passes to the pulmonary circulation and thence to the systemic circulation, from which only a portion passes to the Hver. This discrepancy in the amount of absorbed material passing to the Hver may account for differences in toxicity of a material by inhalation and skin contact, compared with its toxicity by swallowing, if metaboHsm of the material in the Hver is significant in its detoxification or metaboHc activation.

Tray requirements depend on internal-reflux ratios and ASTM 5-95 gaps or overlaps, and may be estimated by the correlation of Paclde (op. cit.) for crude units and the correlation of Houghland, Lemieux, and Schreiner (op. cit.) for main fractionators. 

Cycloocta l,5-dlona-2 -(or 3 )earboxyllc acid mattiyl aster (3) (4), A solution d eyclohe)(a-1,3-dlone 1 (1.00 g, 8.9 mmol) in methyl acrylate 2 (100 g. 1.16 mmol) was Irradiated with a X 450 W medkjm pressure lamp under Na through a pyrex (Iter (or 5 h. The semicrystalliM residue obtained after removal oi the solvent, was crystallized from MeOH, the n ther liquor, separated by preparative TLC (PhH Et20) and the main fraction oonMned vrilh the crystals to gM 1.06 g of 3 (60%), mp 104-105°C (MeOH), The second minor fraction (from TLC) gave 4, mp 91 C (MeOH). 

Phospholipids. For the removal of ionic contaminants from raw zwitterionic phospholipids, most lipids were purified twice by mixed-bed ionic exchange (Amberlite AB-2) of methanolic solutions. (About Ig of lipid in lOmL of MeOH). With both runs the first ImL of the eluate was discarded. The main fraction of the solution was evaporated at 40°C under dry N2 and recryst three times from n-pentane. The resulting white powder was dried for about 4h at 50° under reduced pressure and stored at 3°. Some samples were purified by mixed-bed ion exchange of aqueous suspensions of the crystal/liquid crystal phase. [Kaatze et al. J Phys Chem 89 2565 7955.]... 

After removal of a small amount of low-boiling material the main fraction distils in the range 8o-go°/i4 mm. or mm. 

It has been reported that tetramethylene chlorohydrin undergoes loss of hydrogen chloride when distilled at pressures appreciably above 15 mm. If an oil pump is used for the distillation of the main fraction, it should be protected from hydrogen chloride by means of soda-lime towers. 

This chapter has only provided a brief overview of the technology of distillation. In part, to highlight some important engineering concepts and equipment, the following summary is given. As described, refinery main fractionators are distillation towers that separate very wide boiling fractions into a series of rough... 

Refinery product separation falls into a number of common classes namely Main fractionators gas plants classical distillation, extraction (liquid-liquid), precipitation (solvent deasphalting), solid facilitated (Parex(TM), PSA), and Membrane (PRSIM(TM)). This list has been ordered from most common to least common. Main fractionators are required in every refinery. Nearly every refinery has some type of gas plant. Most refineries have classical distillation columns. Liquid-liquid extraction is in a few places. Precipitation, solid facilitated and membrane separations are used in specific applications. 

Product separation for main fractionators is also often called black oil separation. Main fractionators are typically used for such operations as preflash separation, atmospheric crude, gas oil crude, vacuum preflash crude, vacuum crude, visbreaking, coking, and fluid catalytic cracking. In all these services the object is to recover clean, boiling range components from a black multicomponent mixture. But main fractionators are also used in hydrocracker downstream processing. This operation has a clean feed. Nevertheless, whenever you hear the term black oil, understand that what is really meant is main fractionator processing. 

Crystals was deposited wheu the oil was cooled in a freezing miiiore. The oil coulains no oxypeu, and therefore uo allyl oxide. Wheu fractionated under a pressure of Jfi mm., lour main fractions were ohlaiond. Frn-olion 1 ffi per cent.) consisted of alJyl-)>ropyl diflulphide, a... 

A mixture of 26.1 g of o-benzylphenoxy- J-chloropropane and 17 g of pipiridine Is refluxed over a period of 32 hours until the temperature is about 124t and a nearly solid mixture is formed due to the precipitation of a salt. The mixture is then refluxed over a period of 48 hours at about 160 3 and the reaction product obtained is cooled and dissolved in methanol. The solution is concentrated under reduced pressure to yield an oil which is added to 200 ml 3N hydrochloric acid whereupon the mixture is shaken with ether, 3 x 100 ml, until the aqueous phase Is clear. The ether solution is washed with water, 3 x 50 ml, and the water present in the combined aqueous phase and water used for washing Is evaporated under reduced pressure methanol being added three times when the residue appears to be dry. The impure hydrochloride of o-benzylphenoxy- J-N-piperidinopropane, 41 g, obtained is dissolved in 100 ml water and 100 ml 30% aqueous sodium hydroxide solution are added, whereupon precipitated oil is extracted with ether, 1 x 100 and 2 x 50 ml. The ether solution is washed with water, 4 x 50 ml, dried with magnesium sulfate and the ether is removed under reduced pressure. The residue, 252 g, is distilled under reduced pressure and the main fraction,... 

This Crude product (15.8 g) In water (360 ml) was added to a prehydrogenated suspension of 10% palladium on charcoal (4 g) in water (400 ml), and hydrogenation was continued for 30 minutes. The catalyst was removed and the filtrate was adjusted to pH 7.5 with sodium bicarbonate, then evaporated at low temperature and pressure. The residue was purified by chromatography on a column of cellulose powder, eluting first with butanol/ ethanol/water mixture and then with acetone/isopropanol/water. The main fraction was evaporated at low temperature and pressure to give a 32% yield of the sodium salt of a-carboxybenzylpenicillin as a white powder. The product was estimated by manometric assay with penicillinase to be 58% pure. 

A mixture of o-methoxyphenol (57 g), glycidol (32 g) and pyridine (1 g) is warmed to 95°C at which temperature a vigorous reaction takes place. The reaction mixture is cooled to prevent the temperature rising above 110°C. When the exothermic reaction has subsided the reactants are heated at 95°C for one hour longer and then distilled under low pressure. The main fraction boils in the range 176°C to 180°C/0.5 mm. It crystallizes on cooling. Recrystallization from benzene gives the pure product, MP 78.5°C to 79.0°C. 

The toluene was then stripped off by distillation and the residue was distilled under reduced pressure. The main fraction was redistilled. Yield of N-(2-pyridyl)-N-(2-thenyl)-N, -N -dimethyl-ethylenediamine was 69% BP 130° to 140°C/0.4 mm. A portion of the product was dissolved in ether and an ether solution of hydrogen chloride was added. The monohydrochloride of N-(2-pyridyl)-N-(2-thenyl)-N, N -dimethyl-ethylenediamine which separated was washed with ether and dried. 

All the extracts are combined and concentrated in vacuo (100°C/20 mm) to remove the n-butyl alcohol. The residue is submitted to fractionation under reduced pressure. The forerun (up to 1l2°C/2 to 3 mm) consists of a small amount of n-butyl alcohol and some 3-pyridylcarbinol. The main fraction, boiling at 1l2° to 114°C/2 to 3 mm, consists of 3-pyridylcarbinol. 

The purpose of the main fractionator, or main column (Figure 1 -1 o i, is to desuperheat and recover liquid products from the reactor vapors. The hot product vapors from the reactor flow into the main fractionator near the base. Fractionation is accomplished by condensing and revaporizing hydrocarbon components as the vapor flows upward through trays in the tower. 

Two sources of absorption oil are normally utilized in this tower. The first is the hydrocarbon liquid from the main fractionator overhead receiver. This stream, often called wild, or unstabilized, naphtha, enters the absorber a few trays below the top tray. The second absorbent is cooled debutanized gasoline, which generally enters on the top tray. It has a lower vapor pressure and can be considered a trim absorbent. The expression lean oil generally refers to the debutanized gasoline plus the unstabilized naphtha from the overhead receiver. 

The lean sponge oil enters the absorber on the top tray. The gas from the presaturator or from the primary absorber enters below the bottom tray. The rich sponge oil from the bottom is then returned to the main fractionator. The lean gas leaves the top of the absorber to an amine unit for H,S removal prior to entering the refinery fuel... 

The debutanizer separates the feed into two products. The overhead product contains a mixture of C3 s and C4 s. The bottoms product is the stabilized gasoline. Heat for separating these products comes from an external reboiler. The heating source is usually the main fractionator heavy cycle oil or slurry. Steam can also be used. 

A wet environment exists in the FCC gas plant. Water comes from the condensation of process steam in the main fractionator overhead condensers. In the presence of H S, NH3, and HCN, this environment is conducive to corrosion attacks. The corrosion attack can be any or all of the following types [2] ... 

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