Propane deasphalting unit

One obvious method of cleaning the feed is to remove asphaltic material (asphaltenes plus resins) using a solvent such as propane in a deasphalting unit. The resulting deasphalted oil has less metals than the original feedstock but coke formation and catalyst deactivation are not completely eliminated. The byproduct stream is usually only acceptable as a raw material for asphalt manufacture. Even then, the asphaltic by-product may be unsuitable for a specification grade asphalt and require disposal by other means. 

The Demex process is an extension of the propane deasphalting process and employs a less selective solvent to recover not only the high quality oils but also higher molecular weight aromatics and other processable constituents present in the feedstock. Furthermore, the Demex process requires a much less solvent circulation in achieving its objectives, thus, reducing the utility costs and unit size significantly. 

In the second step, the preprocessor builds and prints out tables showing the extracted crude assay data. The preprocessor also prints out in tabular form all information which the user has specified by card input for the following process units o Crude distillation unit o Propane deasphalter o FCC... 

Activities in the propane deasphalting (PDA) unit submatrix represent the operations on vacuum tower bottoms from the base crude mix and from the incremental crudes. The de-asphalter overhead streams from all activities enter one stream balance row with common properties. Each deasphalter bottoms enter a separate row for No. 6 fuel oil blending. 

Miscellaneous units-fluid catalytic cracking, monoethanolamine (MEA) extraction. HF alkylation, boiler, propylene polymerization, propane deasphalting. 

Cince the first commercial H-Oil unit came on-stream at Lake Charles in 1963, a variety of feedstocks have been processed, including heavy cycle oils, atmospheric bottoms, vacuum bottoms, and cutback propane deasphalter bottoms. The unit has operated successfully with both microspheroidal and extrudate catalysts and has been expanded to 6000 bbl/day. 

The presence of asphaltenes in the feed to the propane dewaxer or in the propane will significantly reduce the filtration rate and must be avoided. Asphaltenes may be present in the heavy neutral due to entrainment from the VPS section below the heavy sidestream drawoff Contamination may occur if the lube deasphalting unit (LDU) and propane dewaxer share propane. 

Deasphalted Oil The extract or residual oil from which asphalt and resins have been removed by an extractive precipitation process called deasphalting. DeAsphalting Unit A process for removing asphalt from reduced crude or vacuum residua (residual oil) which utilizes the different solubilities of asphaltic and nonasphaltic constituents in light hydrocarbon liquids, e.g., liquid propane. 

Solvent deasphalting takes advantage of the fact that aromatic compounds are insoluble in paraffins. Propane deasphalting is commonly used to precipitate asphaltenes from residual oils. Deasphalted oil (DAO) is sent to hydrotreaters, FCC units, hydrocrackers, or fuel-oil blending. In hydrocrackers and FCC units, DAO is easier to process than straight-run residual oils. This is because asphaltenes easily form coke and often contain catalyst poisons such as nickel and vanadium, and the asphaltene content of DAO is (by definition) almost zero. 

The liquid hydrocarbon causes separation of the asphaltenes and/or the resins from the feedstock leaving a deasphalted oil that contains substantially less sulfur and metals than the feedstock. On a commercial scale, propane is the most common solvent (Figure 7-21) and the units are designed to operate at 40 to 80°C (105 to 175°F) and at pressures of 400 to 550 psi with the solvent/ feedstock ratio usually falling in the range 5 1 to 13 1. 

The solvent contained in the asphalt and deasphalted oil is condensed in the fractionator overhead condensers, where it can be recovered and used as lean oil for a propane/butane recovery in the absorber, eliminating the need for lean oil recirculation from the naphtha stabilizer. The solvent introduced in the coker heater and coke drums results in a significant reduction in the partial pressure of asphalt feed, compared with a regular delayed coking unit. The low asphalt partial pressure results in low coke and high liquid yields in the coking reaction. 

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