Flashing vacuum

Vacuum flashing of an effluent from thermal conyersion allows recovery of a distillate that is sent to the FCC and replaced as diluent by a product of lesser quality coming from the FCC, (HCO or LCO). 

Vacuum flash processes, which operate under the atmospheric boiling point of the solution, include the Uhde—LG. Farbenindustrie process and the closely related Kestner process (22). In these, ammonia, nitric acid, and recirculated ammonium nitrate solution are fed into the neutralizer. Hot solution overflows to an intermediate tank and then to a flash evaporator kept at 18—20 kPa (0.18—0.2 atm) absolute pressure. Partial evaporation of water at this point cools and concentrates the solution, part of which is routed to evaporation. The rest is circulated to the neutralizer. 

The fuel vacuum pipe still is also used to recover cracked gas oil from the tar formed in residuum cracking (visbreaking) processes. In this service, it it frequently referred to as a vacuum, flash unit. Pipe stills designed for the production of asphalt are usually the fuel type of unit. 

Inbreathing (Vacuum) Flash Point I00F(37,78C) Flash Point < lOOF (37.780... 

UV irradiation (A>300nm) of an argon matrix containing tetra-fluoromethane led to the formation of difluorocarbene CF2 (Milligan and Jacox, 1968a). It was shown that the IR spectrum of this species contains three bands at 1222 (i i), 1102 (v ), and 668 (i 2)cm . Some time later difluorocarbene was stabilized in a neon matrix at 4.2 K from the gas phase after vacuum flash pyrolysis (1300°C) of perfluoroethene (Snelson, 1970b). In this case the IR bands of CF2 differed from those in an argon matrix by less than 2 cm . ... 

In the HTFT oil refinery the light oil and <345°C fraction of the decanted oil (obtained by passing the decanted oil through a vacuum flash drum) were clay treated. Clay treatment is similar to Bauxite treatment and is used to increase the octane number of the naphtha by acidic isomerization and to reduce the oxygenate content of the oil. Processing the LTFT and HTFT in separate (and different)... 

With telluronium salt (d) (typical procedure) A solntxon of n-BuLi (1.5 mmol) in hexane is added to a solution of the telluronium salt (0.65 g, 1.5 mmol) in dry THF (10 mL) at -78°C under N2. After 30 min, a solution of p-chlorobenzaldehyde (0.168 g, 1.2 mmol) in THF (2 mL) is added dropwise at -78°C and the reaction mixture is allowed to warm at room temperature. After the reaction is complete (monitored by TLC), H2O (1 mL) is added and the solution is stirred for another 1 h. The mixture is then extracted with ether (3x5 mL). The combined extracts are washed with brine, dried (Na2S04), filtered and concentrated under vacuum. Flash chromatography on an SiOj column gives l-(p-chlorophenyl)-4-(trimethylsilyl)-3-butyn-l-ol (0.265 g (87%) (98% GC purity)). 

Fluid milk is commonly subjected to a combination steam injection/in-fusion and vacuum flash evaporation process to remove volatile off-flavor compounds. The process is designed to remove the same amount of water by the flash treatment as is added during steam injection/infu-sion, so that the composition of the milk remains unchanged. This treatment is most effective for removing volatile, water-soluble flavor compounds, such as those from weeds and feed consumed by the cow. The additional heat from this process usually provides further improvement in product shelf life. 

Drying. Liquid base soap is dried from a 30% water liquid form to a solid of about 15% water content. If desired, some minor ingredients may be blended into the soap stream prior to drying. Methods of drying used m common practice are (1) chip drying, (2) atmospheric flash drying, and (3) vacuum flash drying. 

Vacuum Flash Drying. In this most recent technique, drying takes place m a vacuum vessel similar to an atmospheric tower but smaller. The soap is similarly heated before flashing but under less pressure, so that boiling (actually drying of the soap) occurs in the heat exchangers. Since there is boiling in the heaters, the moisture of the dried soap depends primarily upon soap flow rate, soap pressure, and steam pressure to the heater and to a minor extent on the absolute pressure in the vacuum chamber The final temperature of the soap depends entirely upon the absolute pressure m the vacuum chamber. 

Charge stock for the catalyst testing experiment was prepared by topping a sample of the in situ crude shale oil to 600°F in a batch still equipped with a column having 35 trays and then separating the 600°— 1000°F fraction in a vacuum flash distillation unit. Properties of the 600°-1,000°F fraction of in situ crude shale oil are shown in Table III. 

For the generation of the parent silene H2Si=CH2 25 the vacuum flash photolysis of 5,6-bis(trifluoromethyl)-2-silabicyclo[2.2.2]octa-5,7-diene 30 was shown to be the most... 

Disilene and its isomer silylsilylene were neither available by standard vacuum flash pyrolysis of precursors 59-63, nor by the more elaborate method of pulsed flash pyrolysis of 60-63, a pulsed discharge in mixtures of argon and mono- and disilane74 or by the matrix photolysis of educts 59-66 using various light sources (Hg lamps, excimer laser)69,70,72, the microwave discharge in disilane 66 or the cocondensation of silicon atoms with SiFLt. 

The process has three basic variations-the Type II unit, the Type III unit, and the Type IV unit with the degree of desulfurization, and process severity, increasing from Type I to Type IV. Thus, liquid products from Types III and IV units can be used directly as catalytic cracker feedstocks and perform similarly to virgin gas oil fractions, whereas liquid products from the Type II unit usually need to be vacuum-flashed to provide a feedstock suitable for a catalytic cracker. 

The flow from the liquid phase hydrogenation reactors is routed to a hot separator, where gases and vaporized products are separated from unconverted material. A vacuum flash recovers distillates in the hot separator bottom product. 

High temperature deep flashing and vacuum flashing of thermally cracked distillate also contributes to increasing the percentage of the crude, which can be routed to the FCC unit. 

VG0 Cracking - Vacuum Gasoil clear, no metals - Vacuum Flashed distillate from atmospheric resid... 

Because ethanol fermentation is inhibited by product, the selective extraction of ethanol during fermentation is also important to improve process performance. Silva et al. (3) have reported that the scheme that combines a fermentor with a vacuum flash vessel presents many positive features and good performance when compared to a conventional process (4). 

A general scheme of the extractive alcoholic fermentation proposed by Silva et al. (3) is shown in Fig. 1. The process consists of four interlinked units the fermentor (ethanol production unit), the centrifuge (cell separation unit), the cell treatment unit, and the vacuum flash vessel (ethanol-water separation unit). A detailed description of the process and mathematical model can be found in ref. 5. 

The chemical properties of 2,3-dihydro-1,4-diazepines are dominated by the presence of the diene portion of the molecules, either by electrophilic attack at the 1, 4 or 6 positions, or nucleophilic attack at positions 5 or 7. There have previously been no observations of the involvement of the saturated part of the molecule. It has now been demonstrated, however, that in vacuum flash pyrolysis there is a suprafacial 1,5 hydrogen shift of a proton from position 7 to position 3 . This has been confirmed by deutero-labelling studies when 7-deutero-2,3-dihydro-methyl-1,4-diazepine is converted into the 3-deutero-isomer. When the study is repeated with the bicyclic t/.s-2,3-cyclohexano derivative the /ram-isomer is isolated, confirminf a suprafacial shift mechanism... 

The aluminum alkoxide mixture or "oxidized growth product is fed to a series of vacuum flash evaporators to remove solvent introduced earlier in the triethylaluminum preparation. This vacuum stripping step also removes olefins formed during the growth reaction and the myriad of by-products formed during oxidation (14) Efficiency of this stripping process is a key factor in alcohol product quality. This is the opportunity to separate volatile impurities—olefins, esters, aldehydes, paraffins, etc.—from product alcohols while the alcohols are in a nonvolatile form (aluminum alkoxides). 

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