Hydrocarbon processing water removal

Dehydration can be performed by a number of methods cooling, absorption and adsorption. Water removal by cooling is simply a condensation process at lower temperatures the gas can hold less water vapour. This method of dehydration is often used when gas has to be cooled to recover heavy hydrocarbons. Inhibitors such as glycol may have to be injected upstream of the chillers to prevent hydrate formation. 

The most common solvent employed is carbon dioxide gas, which can be injected between water spacers, a process known as WaterAlternating Gas (WAG). In most commercial schemes the gas is recovered and reinjected, sometimes with produced reservoir gas, after heavy hydrocarbons have been removed. Other solvents include nitrogen and methane. 

Refiners use sweetening processes to remove mcr-captans that give a vei y unpleasant odor to gasolines and middle distillates (the skunk uses mercaptans to protect itself). This is done by washing the hydrocarbon stream with a caustic solution followed by a wash with water to remove die caustic. 

Many process mixtures, notably fermentations, require sample preconcentration, microdialysis, microfiltration, or ultrafiltration prior to analysis. A capillary mixer has been used as a sample preparation and enrichment technique in microchromatography of polycyclic aromatic hydrocarbons in water.8 Microdialysis to remove protein has been coupled to reversed phase chromatography to follow the pharmacokinetics of the metabolism of acetaminophen into acetaminophen-4-O-sulfate and acetaminophen-4-O-glucu-ronide.9 On-line ultrafiltration was used in a process monitor for Aspergillus niger fermentation.10... 

Arosolvan A solvent extrachon process for removing aromatic hydrocarbons from petroleum mixtures, using N-methyl pynolidone (NMP) containing 12 to 14 percent water at 20 to 40°C. Developed by Luigi, and first used commercially in Japan in 1961. 

Drizo A variation of the glycol process for removing water vapor from natural gas, in which the water is removed from the glycol by stripping with a hydrocarbon solvent, typically a mixture of pentanes and heavier aliphatic hydrocarbons. The process also removes aromatic hydrocarbons. Last traces of water are removed from the triethylene glycol by stripping with toluene in a separate, closed loop. Invented in 1966 by J. C. Arnold, R. L. Pearce, and H. G. Scholten at the Dow Chemical Company. Twenty units were operating in 1990. U.S. Patent 3,349,544. 

Ifpexol A process for removing water and acid gases from hydrocarbon gas streams by washing with a proprietary solvent at a very low temperature. Developed by the Institut Frangais du Petrole. 

Mofex A liquid-liquid extraction process for removing aromatic hydrocarbons from hydrocarbon mixtures. The solvent is a monomethylformamide/water mixture, operated at 20 to 30°C, 0.1 to 0.4 bar. Developed by Leuna-Werke. 

PuraSiv HR A process for removing solvent vapors from air by adsorption on beaded activated carbon contained in a combined fluidized moving bed. For water-soluble solvents, the gas used for desorption is nitrogen and the process is known as PuraSiv HR, Type N (not to be confused with PuraSiv N) for chlorinated hydrocarbons, steam stripping is used and the process is known as PuraSiv HR, Type S. Developed by Kureha Chemical Company and now marketed by the Union Carbide Corporation. The process was originally known as GASTAK because it was developed by the Taiyo Kaken Company, subsequently acquired by Kureha Chemical Company. It is also marketed by Daikin Industries under the name Soldacs. 

The Macro porous polymer (MPP) system is an ex situ technology designed to remove hydrocarbon pollutants from process water, groundwater, and wastewater. This technology uses a patented, porous polymer containing an immobilized extraction fluid that assimilates the hydrocarbons into the polymer structure. The particles are regenerated with an in situ heating cycle, and the contaminants are recovered for reuse, recycle, or disposal. 

Molecular sieves are used in a variety of fuel processing applications. Uses include drying and water removal from fuel, product purification, hydrocarbon separation and catalysis. Molecular sieves are composed of sodium and calcium aluminosilicate crystals which have been produced from natural or synthetic zeolite compounds. The crystals are dehydrated through heating and are processed to ensure that pore sizes are tightly controlled. 

Commercial Examples. The small but often undesirable contents of water dissolved in hydrocarbons may be removed by distillation. In drying benzene, for instance, the water is removed overhead in the azeotrope, and the residual benzene becomes dry enough for processing such as chlorination for which the presence of water is harmful. The benzene phase from the condenser is refluxed to the tower. Water can be removed from heavy liquids by addition of some light hydrocarbon which then is cooked out of the liquid as an azeotrope containing the water content of the original heavy liquid. Such a scheme also is applicable to the breaking of aqueous emulsions in crude oils from tar sands. After the water is removed... 

Fig. 18.26. Ethers—Axens. Includes alcohol purification (1), hydrocarbon purification (2), main reactor (3), reactive distillation system (4), wastewater system to remove water from the raffinate (5), and product fractionation column (6). (Source Hydrocarbon Processing, 2004 Refining Process Handbook. CD-ROM. September 2004 copyright 2004 by Gulf Publishing Co., all rights reserved.)...

Gas Purification. The best-known purification process using 4A is that of natural gas this involves two benefits, namely, peak-shaving whereby the calorific value of fhe gas is adjusted by CO2 (and water) removal, and sweetening by H2S removal. The latter purification also is used in LPG treatment. Another example is the trapping of hydrocarbons in gas and vacuum circuits. 

---