1. Feed Filters: cartridge type 10-25 microns-not recommended due disposal issue or automatic backwash systems 20-30 microns, very flexible & low maintenance but CAPEX intensive, feed filtration is a must to avoid fouling and deposits
2. Feed pump: a beast with discharge pressure up to 200 barg, multistage high head centrifugal with steam turbine / electrical motor, should be never operating below min flow
3. Feed/Reactor Effluent HX: special design due to effluent characteristics & high operating p & T 400°C / 190 barg, traditional or modified “D” TEMA type not recommended due to maintenance / reliability issues, but special type from Lummus Breech-lock high pressure is mandatory due to safe, easy & reliable conferred by new breech lock pressure closure system
4. Fired Heater combined feed recommended due to high thermal efficiency, natural draft or forced/induced usually gas fired. The heat distribution is approximately 70-73% in radiation section and the rest in convection with flame T 1800°C, bridge wall T 780°C and Stack 205°C. Combined fired heater preferred option vs recycle gas furnace because operates in elastic region & if thermal excursion occurs shall remain in elastic region while the gas recycle furnace operates in creep region with negative well known consequences
5. Reactors: ID up to 6.5-6.8 m with 400 mm wall thickness need to be forged ring welded with mass flux impacting the ID, weight of reactor could arrive at 1100 MT just to have an idea of magnitude. Inlet diffuser, top distribution tray quench zone & mixing chamber, outlet collector are mandatory for a robust design
6. Hot HP Separator: vertical vessel operates up to 315°C minimize the downstream air cooler size due to liquid separation, could be filled with a catalyst bed
7. High pressure Air Cooler: cool down 230-250°C the reactor effluent, wash water at inlet is a must & the inlet/outlet manifolds shall assure proper distribution / velocity to avoid corrosion issues
8. Low pressure Separator horizontal type operate at 55-60°C & 25-35 barg provide adequate separation of hc vapor & gas & water-SS lined
9. Recycle Gas Compressor centrifugal not spare due to higher reliability but the CAPEX is high powered by steam turbine / electrical motor
10. Stripper 32 real trays with 70% efficiency, main goal to stripp H2S by steam to avoid downstream corrosion, must maintain a top T with 15-20°C higher than H2O dew point & provision for corrosion inhibitor injection is a must
11. Main Column: 52 real trays, separate gas, LPG, Kerosene, Diesel & UCO, with the main portion of UCO recycle back to 3rd hydrocracker reactor & the rest purged out from system. 1.4 barg / 155°C on top, 2.0 barg / 262°C in bottom. The main technical issue is the management of HPNA (heavy polynuclear aromatics) - at 350C are in solution, at 200-210C start to drop from solution and at lower T 50C shall agglomerate providing fouling.
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