Economics:
Typical utilities, per metric ton hexene-1 (80% butenes in feed)
Steam + fuel, MMKcal 5.3 Water, cooling (10°C rise), m3 1400
Electricity, MWh 0.2 Refrigeration (–25°C) MMKcal 0.2
Commercial plants: The hexene-1 process has been demonstrated in a
semi-commercial unit in Tianjin, China. The unit produced commercially accepted hexene-1 comonomer suitable for high-grade LLDPE used in film production. A CPT facility for butene-1 production is expected to start up in 2011.
Petrochemical Processes 20102010
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High-olefins FCC and ethylene plant
integration
Application: To convert a wide range of hydrocarbon feedstocks, from
ethane to vacuum gasoils (VGOs), into high-value light olefins. High ole- fins fluid catalytic cracking (HO FCC) processes, such as catalytic pyrolysis process (CPP) and deep catalytic cracking (DCC) are technologies that produce higher yields of ethylene and propylene than fluidized catalytic cracking (FCC). Both steam cracking and HO FCC reactor systems can be operated separately but are designed with a shared recovery system to reduce capital cost.
Description: HO FCC technologies are fluidized cracking processes that
convert heavy feedstocks, including vacuum and atmospheric gasoils, to gasoline, diesel and light olefins. The HO FCC reactor systems pro- duce 15 wt%–25 wt% propylene or 10 wt%–20 wt% ethylene. Steam cracking is commonly used on feedstocks from ethane to light GOs. The higher cracking temperatures of pyrolysis will result in higher ethylene yield than the HO FCC processes. Heavy GO feedstocks would foul the cracking furnace too quickly to be economical. To process both heavy GOs and light feeds, both fluidized catalytic cracking and steam crack- ing reactor systems are applied.
The HO FCC unit effluent must first be processed in an FCC style main fractionator. The main fractionator must remove catalyst fines from the heavy-oil product. The main fractionator also produces a light cycle oil and an overhead gas that is primarily light hydrocarbons and gaso- line. The overhead of the main fractionator can be further processed via a wet-gas compressor. The gas is then stripped with the gasoline ab- sorbed via a lean-oil absorber, followed by amine treatment and finally a caustic wash. The combined effluents are sent to compression and into a series of contaminant removal beds and hydrogenation steps.
The heavy GO feedstocks always include contaminants that foul subsequent purification processes like the driers and hydrogenation re-
actors. Therefore, the HO FCC effluent needs to be processed through contaminant removal beds prior to entering the ethylene recovery unit. If both steam cracking and the HO FCC reactor are processing con- taminated feeds, the caustic system, oxygen and NOx hydrogenation, mercaptan, mercury, COS and arsine removal beds can also be shared, as shown in the figure.
This integrated technology is suitable for revamps of ethylene plants, as well as grassroots applications. The figure shows a maximum integra- tion scenario for an HO FCC and steam cracking. The level of integration is a function of contaminant levels, HO FCC effluent gas composition and other capital reduction considerations.
Commercial plants: Currently, one integrated DCC and ethane cracker
is in operation in Rabigh, Saudi Arabia. A CPP unit has recently started up this year in Shenyang, China. There are three DCC units currently in design, with planned startup dates in 2011.
Licensor: The Shaw Group - CONTACT
Naphtha ethane Heavy feedstock
HP steam
Cracking furnace Quench-oil tower
Quench-water tower Main fractionator HO FCC Contaminats removal Cracked-gas compression To recovery 1
Petrochemical Processes 20102010
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Isobutylene
Application: Technology for dehydrogenation of isobutane to make high-purity isobutylene. The CATOFIN process uses specially formulated proprietary catalyst from Süd-Chemie.
Description: The CATOFIN reaction system consists of parallel fixed-bed reactors and a regeneration air system. The reactors are cycled through a sequence consisting of reaction, regeneration and evacuation/purge steps. Multiple reactors are used so that the reactor feed/product sys- tem and regeneration air system operate in a continuous manner.
Fresh isobutane feed is combined with recycle feed from the downstream unit, vaporized, raised to reaction temperature in a charge heater (1) and fed to the reactors (2). Reaction takes place at vacuum conditions to maximize feed conversion and olefin selectivity.
After cooling, the reactor effluent gas is compressed (3) and sent to the recovery section (4), where inert gases, hydrogen, and light hydrocarbons are separated from the compressed reactor effluent. Condensed liquid from the recovery section is sent to a depropanizer (5), where the remaining propane and lighter components are separated from the C4s.The bottoms stream containing isobutane, isobutylene, and other C4s is sent to the downstream unit (usually an MTBE unit). The unconverted isobutane is recycled back from the downstream MTBE unit to the CATOFIN reactors.
After a suitable period of onstream operation, feed to an individual reactor is discontinued and the reactor is reheated/regenerated. Reheat/regeneration air heated in the regeneration air heater (7) is passed through the reactors. The regeneration air serves to restore the temperature profile of the bed to its initial onstream condition in addition to burning coke off the catalyst. When reheat/regeneration is completed, the reactor is re-evacuated for the next onstream period.
The low operating pressure and temperature of CATOFIN reactors, along with the robust Süd-Chemie catalyst, allows the CATOFIN technology to process isobutane feedstock without fouling of process
equipment. The simple reactor construction, with its simple internals, results in a very high on-stream factor.
Yields and product quality: Isobutylene produced by the CATOFIN pro-
cess is typically used for the production of MTBE. The consumption of isobutane (100%) is 1.14 metric ton (mt) per mt of isobutylene prod- uct.
Economics: Where a large amount of low value LPG is available, the
CATOFIN process is the most economical way to convert it to high value product. The large single-train capacity possible with CATOFIN units (the largest designed to date are for 650,000 mtpy propylene and 452,000 mtpy isobutylene) minimizes the investment cost/mt of product.
i-Butane i-Butane recycle 1 2 On purge Isobutylene/ i-butane to MTBE Onstream On reheat 2 3 4 5 2 7 Air Exhaust air Light ends Steam Continued
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