Aromatic steam stripping

The solubility of hydrocarbon liquids from the same chemical family diminishes as the molecular weight increases. This effect is particularly sensitive thus in the paraffin series, the solubility expressed in mole fraction is divided by a factor of about five when the number of carbon atoms is increased by one. The result is that heavy paraffin solubilities are extremely small. The polynuclear aromatics have high solubilities in water which makes it difficult to eliminate them by steam stripping. 

Solvents are recovered from the oil stream through distillation and steam stripping in a fractionator. The stream extracted from the solvent contains high concentrations of hydrogen sulfide, aromatics, naphthenes and other hydrocarbons, and is often fed to the hydrocracking unit. 

In the pesticide industry, steam-stripping has proven effective for removing groups of priority pollutants such as volatile aromatics, halomethanes, and chloroethanes as well as a variety of nonpriority pollutant compounds such as xylene, hexane, methanol, ethylamine, and ammonia [11]. Thus, this process is used to reduce or remove organic solvents from waste... 

SCT can be converted into highly aromatic pitches by physical, thermal and chemical processes such as vacuum or steam stripping, thermal or catalytic oxidative-polymerization at 229-260°C, or by a thermal process at 370-450°C at atmospheric nitrogen or hydrogen pressure. The physical or chemical characteristics of the pitches produced from SCT depend on the type of process and conditions used. Table II gives the characteristics of SCT pitches produced by distillation, catalytic air-oxidation and thermal process. 

Description Extractive distillation is used to separate close-boiling components using a solvent that alters the volatility between the components. An ED Sulfolane unit consists of two primary columns they are the ED column and the solvent recovery column. Aromatic feed is preheated with lean solvent and enters a central stage of the ED column (1). The lean solvent is introduced near the top of the ED column. Nonaromatics are separated from the top of this column and sent to storage. The ED column bottoms contain solvent and highly purified aromatics that are sent to the solvent recovery column (2). In this column, aromatics are separated from solvent under vacuum with steam stripping. The overhead aromatics product is sent to the BT fractionation section. Lean solvent is separated from the bottom of the column and recirculated back to the ED column. 

Rich solvent from the bottom of the EDC is routed to the solvent-recovery column (SRC), where the aromatics are stripped overhead. Stripping steam from a closed-loop water circuit facilitates hydrocarbon stripping. The SRC operates under vacuum to reduce the boiling point at the column base. 

Carom [Carbide aromatics extraction] A two-stage process for removing aromatic hydrocarbons from petroleum refining streams. In the first stage, the aromatics are removed by liquid-liquid extraction with a proprietary solvent (a mixture of polyalkylene glycols and a glycol ether) at ambient temperature. In the second stage, the aromatics are stripped from the solvent by steam distillation. Developed by Union Carbide Corporation first commercialized in 1986, and now licensed by UOP. Seven units had been licensed by 2002. 

In the acid-catalyzed process, crude DCPD is mixed with a Lewis acid such as BF3 in the presence of an alcohol or ether (52). An aromatic co-solvent may also be used. Temperature control is critical for producing the resin. After reaction, the Lewis acid is removed by a caustic solution and the resin is fiirther washed with water to remove any caustic and catalyst residues. Unreacted DCPD and the co-solvent are removed by steam stripping. 

Soluble nonbiodegradable HC such as aromatics make up a fourth category which rarely but nevertheless effectively undergoes treatment such as steam stripping for high concentrations and percolation on granular activated carbon (GAC) for low concentrations. 

Aromatic HC in alkaline water are steam stripped to residual values lower than 20 mg l k... 

Polymerizations are typically quenched with water, alcohol, or base. The resulting polymerizates are then distilled and steam and/or vacuum stripped to yield hard resin. Hydrocarbon resins may also be precipitated by the addition of the quenched reaction mixture to an excess of an appropriate poor solvent. As an example, aUphatic C-5 resins are readily precipitated in acetone, while a more polar solvent such as methanol is better suited for aromatic C-9 resins. 

Reactor effluent is cooled in a series of exchangers (3) to recover waste heat and to condense (4) the hydrocarbons and steam. Uncondensed offgas—primarily hydrogen—is compressed (5) and then directed to an absorber system (6) for recovery of trace aromatics. Following aromatics recovery, the hydrogen-rich offgas is consumed as fuel by process heaters. Condensed hydrocarbons and crude styrene are sent to the distillation section, while process condensate is stripped (7) to remove dissolved aromatics and gases. The clean process condensate is returned as boiler feedwater to offsite steam boilers. 

The operations described above require mass transfer of a substance from the gas stream to the liquid. When mass transfer occurs in the opposite direction (i.e., from the liquid to the gas) the operation is called desorption, or stripping. For example, the benzene and toluene are removed from the absorption oil mentioned above by contacting the liquid solution with steam, whereupon the aromatic vapors enter the gas stream and are carried away, and the absorption oil can be used again. Since the principles of both absorption and desorption are the same, we can study both operations simultaneously. 

An aromatic compound is to be stripped from oil by direct contact with counterflowing superheated steam in a plate column. The operation is isothermal at 130°C and the total pressure is 108.3 kPa. 

The vapor leaving the top of the column is condensed in a water- or air-cooled condenser. The liquid distillate is a heavy naphtha stream, which is used for the production of gasoline. It has ASTM 5% and 95% boiling points of 195 and 375 °F, respectively. In some refineries, it is sent to a reforming unit to produce aromatics (benzene, toluene, and xylenes) and hydrogen. The condensed water is decanted off the reflux drum. Note that this water stream is quite large (17,180 Ib/h) because of all the open stripping steam that is used in the column base and sidestream strippers. 

Spent caustic is washed by steam which removes the acetylenic fractions or partially eliminates heavy aromatic fractions. It is effective only as long as it is carried out before the general storage tank, which in Itself induces polymerization. This operation is a preliminary stripping process in an alkaline environment ... 

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