Reaction sections
The feedstock to the STAR process® is propane and/or butane-rich streams from gas fields, refinery operations, etc.
The fresh C3/C4 paraffin feed, recycled unconverted light paraffins and process steam are preheated and fed to the first part of the reaction section - the STAR process® reformer. Uhde's reformer is a tubular top-fired reactor furnace, the tubes of which are filled with Uhde's proprietary technically proven STAR catalyst® based on a zinc and calcium aluminate support impregnated with various noble metals. This catalyst is extremely stable at high temperatures in the presence of steam and oxygen and demonstrates excellent dehydrogenation properties with very high selectivities at near equilibrium conversion. The endothermic dehydrogenation reaction takes place at 500-600°C and pressures of 6-9 bar.
In the second step, part of the hydrogen from the intermediate reaction product leaving the reformer is reacted selectively with oxygen or oxygen-enriched air at a maximum 600°C and 5-6 bar in the adiabatic catalytic oxyreactor, thereby forming steam. This is followed by further dehydrogenation over the same STAR catalyst® bed.
Internally supplied heat from the exothermic hydrogen conversion reduces the external heat required for the endothermic dehydrogenation.
The reaction section operates on an eight-hour operational cycle, i.e. seven hours of operation followed by one hour regeneration. A typical design features two parallel reaction trains, each with a reformer and a downstream oxyreactor. Within an eight-hour cycle both trains are in operation for six hours and in the other two hours each of the two trains is regenerated for an hour while the other is in operation. Fluctuation of the product flow due to the process cycle is equalised in an intermediate storage vessel upstream of the fractionation section.
