- Dehydrogenation - The STAR process®
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Why deciding for the The STAR process®?
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The STAR process® (Steam Active Reforming) is a commercially established techno logy for the production of propylene and isobutylene.
The technology is used to dehydrogenate lower paraffins (propane or butanes) into their corres ponding olefins (propylene or butylenes), which can be further processed to valuable downstream products (see possible applications below).
The reactor system is based on several independent parallel reaction trains. If one reaction train is stopped the remaining trains will be able to continue production.
Due to in-situ regeneration coke deposits are effectively removed from catalyst and reactor internals at the same time. An annual time-consuming cleaning step is not needed.
As the STAR process® additionally uses process steam the risk of coking is even further reduced and fewer safeguards to prevent coking are required. As a result trips are generally less likely with the STAR process® compared to other technologies.
Even in the unlikely event of a trip, production of a STAR process® plant will start within minutes after solving the potential problem thanks to the so-called hot stand-by mode, in which the plant is kept in safe but hot condition just by closing the hydrocarbon feed to the affected reactor(s). No cool-down sequence and long-lasting re-heat of the reactor system is required. Therefore, in the event of a reactor trip a PDH plant based on the STAR process® is usually back in operation one shift faster than with competing process technologies.
Low reactor/catalyst volume: The STAR process® reformer is the only PDH reactor system commercially available with direct heating of the reaction zone, thereby significantly increasing reaction velocity. This results in the lowest catalyst inventory / reactor volume on the market. The system is simple, reliable and robust in operation and offers in-situ regeneration, which means no expensive extra reactor is required for regeneration of the catalyst.
Low gas compression costs: The high absolute pressure in the reaction section leads to the desired high suction pressure of the downstream raw gas compressor. Therefore, compression ratio and inlet volume flow of this compressor are low compared to other technologies. As a result the STAR process® offers significant savings for raw gas compression.
STAR catalyst® – high yield and long lifetime: The STAR catalyst® consists of a platinum promoted basic calcium and zinc aluminate which is very stable in the presence of steam at high temperatures. It shows high selectivity at near equilibrium conversion. Regeneration is simple and sustainable by simply using air to burn off coke deposits and to re-oxidize the precious metal. No chemicals are required for catalyst activation or coke suppression. Before delivery to site tkIS will qualify the performance of the catalyst in its test facilities. In order to continuously improve the performance of the STAR process® plants tkIS has established a continuous catalyst development program together with its production partner.
Typically, the feedstock is first sent to a feed preparation unit to separate any heavier components or possible contaminants.
The remaining paraffin is fed to the reaction section where it is heated up and mixed with process steam before it is sent to the externally heated and catalyst-filled reformer tubes. After reacting inside the catalyst bed the hot reactor effluent is cooled down in several steps, recovering energy for feed preheating and steam generation.
Subsequently, all the steam contained in the process gas is condensed and the heat is recovered by heating the distillation columns in the fractionation unit.
The remaining dry process gas is compressed and partially condensed. The liquid phase is directly fed to the fractionation unit while gaseous components are fed to the gas separation unit. In a cryogenic process light uncondensables are removed. Optionally high-purity hydrogen can be generated by applying pressure swing adsorption (PSA).
The fractionation unit of a dehydrogenation plant consists of a stripper column to remove light uncondensables, which are fed to the gas separation unit, and a splitter column to separate olefin product and unconverted paraffin. For C4 applications such a splitter column may not be required depending on the downstream products. Finally, unconverted paraffin is recycled back to the feed preparation unit.