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desulfurization
Application: GT-BTX PluS accomplishes desulfurization of FCC gasoline with no octane loss and decreased hydrogen consumption by using a proprietary solvent in an extractive-distillation system. This process also recovers valuable aromatics compounds, which can be used as petro-chemical feedstock.
Description: The optimum feed is the mid fraction of FCC gasoline from 70°C to 150°C. This material is fed to the GT-BTX PluS unit, which extracts the sulfur and aromatics from the hydrocarbon stream. The sulfur-containing aromatic components are processed in a conventional hydrotreater to convert the sulfur into hydrogen sulfide (H2S). Because the portion of gasoline being hydrotreated is reduced in volume and free of olefins, hydrogen consumption and operating costs are greatly reduced. In contrast, conventional desulfurization schemes must pro-cess the majority of the gasoline through hydrotreating units to remove sulfur, which inevitably results in olefin saturation, octane downgrade and yield loss.
FCC gasoline is fed to the extractive distillation column (EDC). In a vapor-liquid operation, the solvent extracts the sulfur compounds into the bottoms of the column along with the aromatic components, while rejecting the olefins and non-aromatics into the overhead as raffinate.
Nearly all of the non-aromatics, including olefins, are effectively separat-ed into the raffinate stream. The raffinate stream can be optionally caus-tic washed before routing to the gasoline pool or to an aromatization unit to further increase benzene, toluene and xylene (BTX) production.
Rich solvent, containing aromatics and sulfur compounds, is routed to the solvent recovery column (SRC), where the hydrocarbons and sul-fur species are separated and lean solvent is recovered in columns bot-toms. The SRC overhead is hydrotreated by conventional means and either used as desulfurized gasoline or directed to an aromatics plant.
Lean solvent from the SRC bottoms is recycled back to the EDC.
Process advantages:
• Eliminates FCC gasoline sulfur species to meet a pool gasoline target of 10 ppm sulfur.
• Rejects olefins from being hydrotreated in the HDS unit to prevent loss of octane rating and to reduce hydrogen consumption.
• Fewer components (only the heavy-most fraction and the aro-matic concentrate from the ED unit) are sent to hydrodesulfurization, resulting in a smaller HDS unit and less yield loss.
• Purified benzene and other aromatics can be produced from the aromatic-rich extract stream after hydrotreating.
• Olefin-rich raffinate stream (from the ED unit) can be directed to an aromatization unit to produce additional BTX or recycled to the FCC unit to increase the light olefin production.
Economics: Feedrate 1,000 thousand tpy (22,000 bpsd); erected cost (including Fractionation and Hydrotreating) $30 MM (ISBL, 2007 US Gulf Coast Basis).
Installation: Technology available for license.
Licensor: GTC Technology US, LLC contact
Feed fractionation
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dewaxing
Application: Bechtel’s Dewaxing process is used to remove waxy com-ponents from lubrication base-oil streams to simultaneously meet de-sired low-temperature properties for dewaxed oils and produce slack wax as a byproduct.
Description: Waxy feedstock (raffinate, distillate or deasphalted oil) is mixed with a binary-solvent system and chilled in a very closely con-trolled manner in scraped-surface double-pipe exchangers (1) and re-frigerated chillers (2) to form a wax/oil/solvent slurry.
The slurry is filtered through the primary filter stage (3) and dewaxed oil mixture is routed to the dewaxed oil recovery section (5) to separate solvent from oil. Prior to solvent recovery, the primary filtrate is used to cool the feed/solvent mixture (1). Wax from the primary stage is slurried with cold solvent and filtered again in the repulp filter (4) to reduce the oil content to approximately 10%.
The repulp filtrate is reused as dilution solvent in the feed chilling train. The wax mixture is routed to a solvent-recovery section (6) to re-move solvent from the product streams (hard wax and soft wax). The recovered solvent is collected, dried (7) and recycled back to the chilling and filtration sections.
Economics:
Investment (Basis: 7,000-bpsd feedrate
capacity, 2011 US Gulf Coast), $/bpsd 17,500 Utilities, typical per bbl feed:
Fuel, 103 Btu (absorbed) 160
Electricity, kWh 15
Steam, lb 35
Water, cooling (25°F rise), gal 1,100
Installation: Over 100 have been licensed and built.
Licensor: Bechtel Hydrocarbon Technology Solutions, Inc. contact
Refrigerant
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dewaxing
Application: Selectively convert feedstock’s waxy molecules by isomeriza- tion in the presence of ISODEWAXING Catalysts. The high-quality prod-ucts can meet stringent cold flow properties and viscosity index (VI) re-quirements for Group II or Group III baseoils.
Description: ISODEWAXING Catalysts are very special catalysts that con-vert feedstocks with waxy molecules (containing long, paraffinic chains) into two or three main branch isomers that have low-pour points. The product also has low aromatics content. Typical feeds are: raffinates, slack wax, foots oil, hydrotreated VGO, hydrotreated DAO and uncon-verted oil from hydrocracking.
As shown in the simplified flow diagram, waxy feedstocks are mixed with recycle hydrogen and fresh makeup hydrogen, heated and charged to a reactor containing ISODEWAXING Catalyst (1). The effluent will have a much lower pour point and, depending on the operating severity, the aromatics content is reduced by 50– 80% in the dewaxing reactor.
In a typical configuration, the effluent from a dewaxing reactor is cooled down and sent to a finishing reactor (2) where the remaining single ring and multiple ring aromatics are further saturated by the ISO-FINISHING Catalysts. The effluent is flashed in high-pressure and low-pressure separators (3, 4). Small amounts of light products are recovered in a fractionation system (5).
Yields: The base oil yields strongly depend on the feedstocks. For a typical low wax content feedstock, the base oil yield can be 90–95%.
Higher wax feed will have a little lower base oil yield.
Economics:
Investment: This is a moderate investment process; for a typical size ISODEWAXING/ISOFINISHING Unit, the capital for ISBL is about $9,000/bpsd.
Utilities: Typical per bbl feed:
Power, kWh 3.3
Fuel , kcal 13.4 x 103
Steam, superheated, required, kg 5.3
Steam, saturated, produced, kg 2.4
Water, cooling, kg 192
Chemical-hydrogen consumption, Nm3/m3 oil 30~50
Installation: More than 15 units are in operation and five units are in various stages of design or construction.
Reference: NPRA Annual Meeting, March 2005, San Francisco, Paper AM-05-39.
Licensor: Chevron Lummus Global LLC contact
Medium
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