Fluid Catalytic Cracking Unit (FCCU) converts heavy gas oil into gasoline, LPG, and light olefins using fluidized catalyst. Pumps handle hot slurry (catalyst + oil), high-vapor-pressure products, and corrosive contaminants. This guide covers pump selection for FCCU main fractionator, slurry circulation, and product handling.
FCCU Pump Services
| Service | Fluid | Temp | Key Characteristic | Pump Type |
|---|---|---|---|---|
| Slurry circulation (bottom of main fractionator) | Heavy cycle oil + catalyst fines (slurry) | 300–380°C | Very abrasive (catalyst fines 0.1–2%), hot, viscous, large flow, continuous, critical (fouling) | API 610 OH2 (hardened chrome iron/duplex, large passage, high temp, flush) or slurry pump (high catalyst loading) |
| Slurry to riser (feed) | Slurry (recycle to riser) | 250–350°C | Abrasive, hot, large flow, continuous, critical | API 610 OH2 (hardened, high temp, large passage) |
| LCO (Light Cycle Oil, product) | LCO (diesel range, 200–350°C) | 150–250°C | Hot, moderate viscosity, corrosive (some), moderate flow, product | API 610 OH2 (carbon steel/Cr-Mo, high temp) |
| HCN (Heavy Catalytic Naphtha) | HCN (gasoline range, 100–200°C) | 80–180°C | Hot, volatile, olefinic (unstable), moderate flow, product, flammable | API 610 OH2 (carbon steel, mechanical seal, volatile) |
| LCN (Light Catalytic Naphtha) | LCN (C5–100°C) | 40–100°C | Very volatile, olefinic, flammable, moderate flow, product | API 610 OH2 (carbon steel, double mechanical seal, high vapor pressure) |
| Main fractionator reflux | Column overhead liquid (naphtha) | 40–150°C | Volatile, precise (reflux ratio), continuous, critical, moderate flow | API 610 OH2 (carbon steel, precise, mechanical seal) |
| Main fractionator pump-around | HCO/LCO (pump-around) | 150–350°C | Hot, large flow, continuous, heat removal, critical | API 610 OH2 or BB2 (carbon steel/Cr-Mo, high temp, large flow) |
| Wet gas compressor suction (not liquid pump) | Wet gas (C3/C4 + H₂S) | 40–100°C | Gas (compressor, not liquid pump) | Not liquid pump (centrifugal compressor) |
| Debutanizer feed/reflux | C3/C4 + naphtha | 40–150°C | Volatile, precise, moderate flow, continuous | API 610 OH2 (carbon steel, mechanical seal, volatile) |
| LPG product (C3/C4) | LPG (propane/butane) | 40–60°C | Very volatile (high vapor pressure), flammable, precise, product, moderate flow | API 610 OH2 (carbon steel, double mechanical seal, high vapor pressure) or screw pump (metering) |
| Sour water (fractionator boot) | Sour water (H₂S + NH₃ + phenols + cyanide) | 40–100°C | Very corrosive, toxic (cyanide), abrasive (catalyst fines), moderate flow, environmental | 316SS centrifugal or fluoroplastic (corrosion, zero leakage, NACE) |
| Spent caustic (from treater) | Spent caustic (NaOH + Na₂S + phenols + cyanide) | 40–80°C | Very corrosive, toxic, viscous, small/moderate flow, environmental | Fluoroplastic pump or 316SS (corrosion, zero leakage) |
| Amine (gas sweetening) | DEA/MDEA amine solution | 40–120°C | Corrosive (amine + H₂S), viscous, large flow, continuous, foaming | 316SS centrifugal or API 610 OH2 (316SS, corrosion) |
| Catalyst slurry (to catalyst cooler) | Catalyst + oil (very high solids) | 300–400°C | Very abrasive (high catalyst), very hot, critical, special | Special slurry pump (hardened, high temp) — not standard API 610 |
| Flushing (oil flush) | Light gas oil (flush slurry pumps) | 200–300°C | Hot, clean, intermittent, prevents catalyst deposition | API 610 OH2 (carbon steel/Cr-Mo, high temp) |
Critical: Abrasive Catalyst Fines + Slurry Service
FCCU slurry contains catalyst fines (zeolite, alumina-silica) — the most abrasive fluid in a refinery:
- Very abrasive: Catalyst fines (0.1–2% solids, 20–100 μm) are highly erosive. Use hardened materials: chrome iron (28% Cr) or duplex SS wetted parts, tungsten carbide or silicon carbide seal faces, hardened 17-4PH shaft. Large passage (reduce velocity ＜3 m/s). Flush with clean gas oil (seal plan 32 — dilutes catalyst at seal). Strainer upstream (self-cleaning, but catalyst passes). Monitor wear (vibration, flow, thickness). Replace wear parts on schedule (6–18 months depending on loading). Our abrasive-resistant API 610 range handles FCCU slurry.
- Slurry pump design: For high catalyst loading (＞1%), use horizontal slurry pump (rubber-lined or hardened metal, recessed impeller, large passage) instead of standard API 610. Slurry pumps handle 10–60% solids. For moderate loading (＜1%), API 610 OH2 with hardened materials is standard. Our slurry pump range handles high catalyst loading.
- Fouling prevention: Slurry tends to foul (catalyst deposition) in pump — reduces flow, increases vibration. Use large passage, continuous flow (avoid deadhead), oil flush (plan 32), steam jacketing (maintain temp), self-cleaning strainer. Periodic decoking/cleaning. Our fouling-resistant design minimizes catalyst deposition.
Critical: High Temperature (300–380°C) + Alloy
- High temperature: Slurry 300–380°C, pump-around 150–350°C. Use Cr-Mo alloy (1.25Cr-0.5Mo up to 480°C) or carbon steel (up to 400°C for non-corrosive). Centerline-mounted pump (thermal expansion). High-temp mechanical seal (plan 32 flush with cool gas oil, plan 53B barrier). Jacketed seal chamber. API 610 OH2 with centerline mounting. Our high-temp API 610 range handles FCCU temperatures.
- Naphthenic acid: Some FCCU feeds (VGO from high-TAN crudes) contain naphthenic acid — corrosive at 220–400°C (slurry range). Use 316SS/317SS or alloy for high TAN. Upgrade wetted parts. Monitor TAN. Our alloy range handles naphthenic acid.
Critical: High Vapor Pressure LPG/Naphtha + NPSH
- High vapor pressure: LPG (propane ~10 bar, butane ~3 bar), LCN (high vapor pressure). Use API 610 OH2 with low-NPSH impeller (large eye, inducer). Flooded suction (mount below column). NPSH margin ＞3m. Double mechanical seal (plan 53B barrier) — zero leakage for flammable LPG. Avoid suction throttling. Our low-NPSH API 610 range handles high vapor pressure products.
- Olefinic instability: FCCU naphtha/LPG is olefinic (reactive) — can polymerize and foul pumps. Use stainless steel (resists polymerization), minimize dead legs, continuous flow, flush with clean product. Temperature control (avoid hot spots). Our 316SS range resists olefin fouling.
Critical: Sour Water + Cyanide Corrosion
- Sour water + cyanide: FCCU sour water contains H₂S, NH₃, phenols, and cyanide (HCN) — highly corrosive and toxic. Use 316SS or duplex SS (resists wet H₂S + cyanide). NACE MR0175 compliance. Zero leakage (double seal or magnetic drive). Cyanide accelerates corrosion — monitor. Our 316SS/fluoroplastic range handles FCCU sour water.
Material Compatibility
| Material | Slurry (350°C, catalyst fines, abrasive) | LCN naphtha (80°C, volatile, olefinic) | LPG (50°C, high vapor pressure) | Sour water (80°C, H₂S/NH₃/CN) |
|---|---|---|---|---|
| Carbon steel (WCB) | NOT (catalyst erosion) | Good (standard) | Good (standard) | NOT (wet H₂S + CN) |
| 1.25Cr-0.5Mo | Fair (erosion, but temp OK) | Good | Good | Fair |
| 316SS | Good (erosion, check) | Excellent (olefin resistance) | Good | Good (wet H₂S, CN risk) |
| Chrome iron (28% Cr) | Excellent (catalyst erosion) | — | — | — |
| Duplex SS | Excellent (erosion + corrosion) | Excellent | Good | Excellent (H₂S + CN) |
| Tungsten carbide (seal) | Excellent (abrasion) | Good | Good | Good |
| Silicon carbide (seal) | Good (abrasion, brittle) | Excellent | Excellent | Excellent |
| FKM (Viton) seals | NOT (＞200°C) | Good | Good | Fair |
| FFKM (Kalrez) | Excellent (high temp) | Excellent | Excellent | Excellent |
| EPDM seals | NOT (oil) | NOT (hydrocarbon) | NOT | Good (water) |
Critical: Slurry (catalyst fines) = chrome iron/duplex + tungsten carbide + large passage + plan 32 flush + API 610 OH2 or slurry pump. High temp = Cr-Mo + centerline + FFKM. LPG/naphtha = carbon steel/316SS + double seal + low-NPSH. Sour water = 316SS/duplex/fluoroplastic + zero leakage. All = API 610 + NACE (H₂S) + standby (critical service).
Common Problems and Solutions
Problem 1: Slurry pump wears out (catalyst). Catalyst fines erode impeller/casing in 6 months. Solution: use chrome iron/duplex API 610 OH2 (hardened). Tungsten carbide seal. Plan 32 flush. For ＞1% solids: horizontal slurry pump. Monitor wear. Our abrasive-resistant range extends slurry pump life.
Problem 2: LPG pump leaks (single seal). Single seal fails — propane leaks (fire hazard). Solution: use double mechanical seal (plan 53B) API 610 OH2. Low-NPSH. Gas detection. Our zero-leakage range prevents LPG leakage.
Problem 3: Slurry pump fouls (catalyst deposition). Catalyst deposits in pump — reduces flow. Solution: large passage, continuous flow, plan 32 oil flush, steam jacketing. Self-cleaning strainer. Periodic cleaning. Our fouling-resistant design minimizes deposition.
Problem 4: Sour water pump corrodes (cyanide). HCN in sour water accelerates corrosion. Solution: use 316SS/duplex centrifugal or fluoroplastic. NACE. Double seal. Monitor. Our corrosion-resistant range handles cyanide.
Problem 5: Hot slurry pump cavitates (low NPSH). 350°C slurry high vapor pressure. Solution: low-NPSH API 610 OH2 (large eye, inducer). Flooded suction (mount below fractionator). NPSH margin ＞3m. Our low-NPSH range prevents cavitation.
Selection Summary
- Slurry circulation: API 610 OH2 (chrome iron/duplex, 300–380°C, large passage, plan 32 flush) or slurry pump (＞1% catalyst)
- Slurry to riser: API 610 OH2 (hardened, 250–350°C, large passage)
- LCO: API 610 OH2 (carbon steel/Cr-Mo, 150–250°C)
- HCN/LCN: API 610 OH2 (carbon steel/316SS, volatile, olefinic, mechanical seal)
- Reflux/pump-around: OH2 or BB2 (carbon steel/Cr-Mo, precise, large flow, 40–350°C)
- LPG: API 610 OH2 (carbon steel, double seal, high vapor pressure, low-NPSH) or screw (metering)
- Sour water: 316SS centrifugal or fluoroplastic (H₂S/NH₃/CN, zero leakage, NACE)
- Spent caustic: Fluoroplastic or 316SS (very corrosive, zero leakage)
- Amine: 316SS centrifugal or OH2 (316SS, corrosion, foaming)
- Critical: slurry = catalyst fines + chrome iron/duplex + tungsten carbide + plan 32 flush + large passage (most abrasive refinery service), high temp = Cr-Mo + centerline + FFKM, LPG = double seal + low-NPSH + NPSH margin ＞3m, sour water = 316SS/duplex + cyanide resistance + zero leakage, all = API 610 + NACE + standby (critical) + fouling prevention
- Our API 610 OH2, BB2 cover FCCU process; slurry pump covers high catalyst; 316SS and fluoroplastic cover sour water. For FCCU pump selection, talk to our refinery engineers with your catalyst loading, slurry temperature, and product slate.