Processing difficult feedstocks
Coker naphtha places extraordinary demands on hydrotreating processes. These difficult-to-process streams often contain high levels of silica, which decrease HDN catalyst activity. Complications can also arise because they have high concentrations of conjugated di-olefins that tend to polymerize, as well as olefins that immediately saturate and release heat that challenges temperature control. The sulfur content of coker naphtha can be 20 times higher than in straight-run naphtha.
The coker naphtha hydrotreater needs to run under severe operating conditions to meet product specifications. Yet refiners will still expect these units to operate at high levels of utilization and availability. To do this, carefully managed HDS and HDN feeds are required over the entire planned unit run length. The values of reactor temperature, hydrogen partial pressure, and treat gas-to-oil ratio must be set and controlled with extreme accuracy.
The typical coker naphtha hydrotreating reactor loop has three stages. The first stage selectively saturates diolefins to olefins, which react quickly at high temperatures. The second removes silica and saturates monoolefins. If not removed, silica quickly deactivates HDS/HDN catalysts. The third stage addresses the HDS/HDN reactions and drives bulk conversion.
Topsoe licenses and designs revamps and grassroot coker naphtha hydrotreating units at multiple capacities.
Typical coker naphtha hydrotreater reactor layout
Silicon guard swing reactor layout
Optimal to your objectives
Topsoe’s silicon guard configuration designs offer several advantages over competing systems.
Our bypass configuration (Figure 1) can overcome pressure drop problems and keep your unit on stream while you change catalysts, boosting levels of unit availability and utilization.
Topsoe’s lead/lag configuration (Figure 2) maximizes the silicon pick-up capacity of catalysts in your two reactors. Plus, it gives you the flexibility to replace catalysts in one reactor while still running the unit at full capacity.
Silicon swing reactors
A bypass configuration to the left, and a lead/lag reactor system to the right