Continuous Catalyst Regeneration
Continuous Catalyst RegenerationA continuous catalyst regeneration (CCR) scheme for reforming came on stream in 1971. Figure 8.5 shows a flow diagram for the CCR process. The reactors are stacked with a moving bed of catalyst trickling from the top reactor to the bottom reactor by gravity. Partially deactivated catalyst from the bottom of the reactor stack is continuously withdrawn and transferred to the CCR regenerator. The regenerated catalyst is re-injected to the top of the first reactor to complete the catalyst circulation cycle. Hydrotreated naphtha feed is combined with recycled hydrogen gas and heat exchanged with the reactor effluent. The combined feed is then raised to the reaction temperature in the charge heater and sent to the first reactor section. Because the predominant reforming reactions are endothermic, an inter-reactor heater is used to reheat the charge to the desired reaction temperature before it is introduced to the next reactor. The effluent from the last reactor is heat exchanged with the combined feed, cooled, and separated into vapor and liquid products in a separator.
Text description of Figure 8.4.
This diagram illustrates a semi-regenerative catalytic reforming process labeled “A semi-regenerative process: Platforming,” showing the flow of hydrocarbon feed through heaters, reactors, separation, and fractionation, along with hydrogen recycling.
At a high level, the process shows feed being heated and passed through two reactors in series, followed by cooling and separation. Hydrogen (H₂) is recycled, while liquid products are sent to a fractionator to produce reformate and light gases.
Process flow (left to right):
Feed, labeled “Feed,” enters from the left and flows to a unit labeled “Heater.” The heated stream then enters a first reactor labeled “Reactor-1 (925–975°F).” The effluent passes through another heater and then into “Reactor-2.” The output is cooled in a unit labeled “Heat Exchanger,” then sent to a “Separator.” From the separator, hydrogen labeled “H₂” is recycled back to the front of the process, while liquid products go to a “Fractionator,” which produces “Gas (C₃, C₄)” and “Reformate.”
Feed and heating section (left side):
- A line labeled “Feed” enters the system and flows into a unit labeled “Heater.”
- The heater raises the temperature of the feed before it enters the reactor system.
First reactor stage:
- The heated stream enters a vertical vessel labeled “Reactor-1,” with a temperature range indicated as “925–975°F.”
- Catalytic reforming reactions occur in this reactor.
Interstage heating and second reactor:
- The effluent from Reactor-1 flows through another heater (shown as a smaller heating unit).
- The reheated stream enters a second vertical vessel labeled “Reactor-2,” where additional reforming reactions occur.
Cooling and heat recovery:
- The effluent from Reactor-2 flows downward into a unit labeled “Heat Exchanger.”
- This unit cools the stream and recovers heat for process efficiency.
Separation section (center-right):
- The cooled stream enters a vessel labeled “Separator.”
- In this unit, hydrogen gas is separated from liquid hydrocarbons.
Hydrogen recycle:
- A line labeled “H₂” exits the separator and loops back across the top of the diagram to join the incoming feed stream.
- This indicates hydrogen recycle to maintain hydrogen partial pressure in the reactors.
Fractionation section (right side):
- Liquid from the separator flows to a vertical column labeled “Fractionator.”
- The fractionator separates the liquid into:
- A top stream labeled “Gas (C₃, C₄)”
- A bottom stream labeled “Reformate,” which is the high-octane product.
The vapor phase is rich in hydrogen gas, and a portion of the gas is compressed and recycled back to the reactors. Recycling hydrogen is necessary to suppress coking on the catalysts. The hydrogen-rich gas is compressed and charged together with the separator liquid phase to the product recovery section. The performance of the unit (i.e., steady reformate yield and quality) depends strongly on the ability of the CCR regenerator to completely regenerate the catalyst. In addition to UOP’s Platforming process, the major commercial catalytic reforming processes include PowerformingTM (ExxonMobil), UltraformingTM and MagnaformingTM (BP), Catalytic Reforming (Engelhard), Reforming (IFP), and RheniformingTM (Chevron).
Text description of Figure 8.5.
The continuous catalytic reforming process starts at the heater, which goes to the reactor. From the reactor, it can either go back to the heater or move on. The spent catalyst exits and goes to a regenerator to regenerate the catalyst and burn off coke with air. The reformate continues to a low p separator and then a high p separator. Both separators give off H2 gas. Reformate excits and recycled H2 heads back to the heater. The temperatures are 925-975*F, Hydrogen – 4000-8000 scf/bbl fee, Pressure – 50-300 psig, LHSV – 2-3/hr.