The reaction section comprises an externally heated reactor (STAR process® reformer) including a highly efficient heat recovery system for feed preheating and steam generation.
Based on our advanced, proven Uhde dehydrogenation technologies, the STAR process® and the STAR catalyst®, we can supply, from a single source, complete, optimized process routes to propylene and butylene derivatives, e.g. Polypropylene, Propylene Oxide, ETBE and other high-value products
The STAR process®, STAR being the acronym for Steam Active Reforming, is a commercially established dehydrogenation technology.
Propylene is a base petrochemical used for the production of, among other things, polypropylene (PP), oxo alcohols, acrylonitrile, acrylic acid (AA), propylene oxide (PO) and cumene.
About 60 % of the propylene produced today is used as feedstock for the production of PP.
With the STAR process®, thyssenkrupp Industrial Solutions can offer customers single-point responsibility for complete process routes to propylene derivatives, e.g. PP or PO, based on on-purpose propylene production from the dehydrogenation of propane and subsequent polymerization. The process economics of such production complexes are very favourable.
The hydrogen produced by dehydrogenation can be purified and used as feedstock for downstream plants (e.g. for H2O2 production by means of the Evonik-Uhde HPPO process), thus minimizing raw material costs.
Dehydrogenation of isobutane to isobutene for the production of MTBE is a commercially well-established process route. Although MTBE is no longer used in significant quantities in the USA, it is not clear if this will happen in other regions, too.
Other octane-boosting options are alkylates and dimers, which are used as blending stock to enhance the quality of unleaded gasoline to premium grade. Dehydrogenation of butanes to butenes can also be used for the production of these kinds of compounds.
High reaction operating pressure / low operating temperature
- Fewer byproducts
- Low compression costs
Highly efficient reaction section
- Low catalyst inventory
- In-situ regeneration
Fixed-bed reactor type
- Simple, robust operation – less maintenance
No chemicals for catalyst activation or coke suppression
- No environmental issues
High availability and reliability
- Independent parallel reactor trains
Short start-up and overall shut-down time
- Simple to switch from regeneration to production mode
- Shorter re-start from “hot stand-by”
The STAR catalyst® is based on a zinc and calcium aluminate support that, impregnated with various metals, demonstrates excellent dehydrogenation properties with very high selectivities at near equilibrium conversion rates. Due to its basic nature it is also extremely stable in the presence of steam and oxygen at high temperatures. This commercially proven noble metal promoted catalyst in solid particulate form is used in the STAR process®.
The reaction takes place in the presence of steam, which reduces the partial pressure of the reactants. This is favourable, as the endothermic conversion of paraffin to olefin increases with decreasing partial pressures of hydrocarbons. Competing dehydrogenation technologies operate at reactor pressures slightly above atmospheric pressure or even under vacuum. In the STAR process®, however, the reactor outlet pressure is significantly above atmospheric pressure. This results in a sufficient pressure drop allowing to efficiently utilise the heat available in the reactor effluent and to design the raw gas compressor with a higher suction pressure thancompeting technologies, thus saving investment and operating costs.
During normal operation a minor amount of coke is deposited on the catalyst which requires frequent regeneration. Steam present in the system converts most of the deposited coke to carbon dioxide. This leaves very little coke to be burnt off during the oxidative regeneration, extending operating cycles and ensuring quick and simple regeneration. Also no additional treatment is required for coke suppression or catalyst reactivation (e.g. sulfiding or chlorinating). The cycle length is seven hours of normal operation followed by a regeneration period of one hour. Therefore only 14.7% additional reactor capacity is needed to account for regeneration requirements, which is the lowest of all commercial technologies.
The STAR process® offers a higher space-time yield than competing technologies because of significantly higher reaction velocities in the reactors. This results in a very compact reactor design.
• The higher yield reduces the dry gas flow to the raw gas compressor and to the down-stream units for product treatment.
• These advantages result in lower investment and utility consumption.
Heat from the process gas is efficiently recovered and utilised for:
• Feed vaporisation and superheating
• Direct heating of fractionation column reboilers
• Generation of refrigerant
Product quality is ensured by a steady continuous feed of constant composition to the fractionation unit. The gas separation unit is designed to meet these requirements.
The main features of this design are as follows:
• The cold box removes all light ends, including hydrogen from the reactor product.
• Only approx. 10% of the propane/propylene mixture enter the cold box so that in case of a cold box failure a production rate of approx. 90% can still be achieved, which is a unique feature of the STAR process®.
• In case of PDH, very low olefin losses as > 99% of the olefin produced in the reactor are recovered.
The main features of the fractionation are:
• No gas phase is admitted to the fractionation. The entire fractionation feed is liquid, which is collected in an intermediate storage vessel, from where it is continuously fed to the distillation columns. Hence the operation of this section is not influenced by the load variations (between the normal and regeneration mode) at the front end.
• Light ends are removed as tail gas.