Gas processing plants separate natural gas into methane (pipeline gas) and NGL (natural gas liquids: ethane, propane, butane, pentane+). Fractionation distills NGL into individual products. Pumps handle cryogenic liquids, high-pressure hydrocarbon liquids, and corrosive contaminants (H₂S, CO₂, mercury). This guide covers pump selection for gas processing, NGL fractionation, and LPG handling.
Gas Processing / NGL Fractionation Pump Services
| Service | Fluid | Temp | Pressure | Key Characteristic | Pump Type |
|---|---|---|---|---|---|
| Amine circulation (gas sweetening) | MEA/DEA/MDEA amine solution (30–50 wt%) | 40–120°C | 5–80 bar | Corrosive (amine + CO₂/H₂S), viscous (1–10 cP), large flow, continuous, foaming, carbon steel corrosion | 316SS centrifugal or API 610 OH2 (316SS, large flow, corrosion-resistant, mechanical seal) |
| Amine booster/lean/rich | Lean amine (regenerated) / rich amine (loaded) | 40–120°C | 5–80 bar | Corrosive, precise, continuous, high pressure (to absorber), temperature difference | API 610 OH2 or BB2 (316SS, high pressure, corrosion, API 610) |
| Dehydration (glycol circulation) | TEG (triethylene glycol, 95–99%) | 40–200°C (regenerator) | 5–70 bar | Viscous (5–50 cP), hygroscopic, hot (regenerator), corrosive (some), large flow, continuous | API 610 OH2 (316SS, high temp, viscous) or screw pump (viscous, jacketed, precise) |
| NGL feed (to fractionation) | Mixed NGL (ethane + propane + butane + C5+) | -40 to 40°C | 15–40 bar | Cryogenic/cold, volatile (high vapor pressure), multi-component, large flow, continuous, precise | API 610 OH2 or BB2 (low-temp materials, high vapor pressure, API 610, double mechanical seal) |
| Deethanizer bottoms (C3+) | Propane + butane + C5+ (ethane removed) | 50–100°C | 15–30 bar | Volatile, hot, multi-component, large flow, continuous, precise | API 610 OH2 or BB2 (carbon steel/316SS, high temp, API 610) |
| Depropanizer bottoms (C4+) | Butane + C5+ (propane removed) | 60–110°C | 5–15 bar | Volatile, hot, multi-component, large flow, continuous | API 610 OH2 (carbon steel, moderate pressure, API 610) |
| Debutanizer bottoms (C5+ / gasoline) | Pentane+ (natural gasoline) | 80–150°C | 2–10 bar | Hot, volatile, moderate flow, continuous, valuable | API 610 OH2 (carbon steel, moderate temp, API 610) |
| Propane product (LPG) | Propane (C3H8, product) | 40–60°C | 10–20 bar | Very volatile (vapor pressure ~10 bar), flammable, precise (product), moderate flow, continuous, refrigerated option | API 610 OH2 (carbon steel, double mechanical seal, high vapor pressure, API 610) or screw pump (positive displacement, metering) |
| Butane product (LPG) | Butane (C4H10, product) | 40–70°C | 3–8 bar | Volatile, flammable, precise, moderate flow, continuous | API 610 OH2 (carbon steel, mechanical seal, API 610) |
| Ethane product (petrochemical feed) | Ethane (C2H6, product) | -30 to 30°C | 20–40 bar | Very volatile (vapor pressure ~40 bar), cryogenic/cold, flammable, precise, high pressure | API 610 OH2 (low-temp 316SS/LN2 steel, high pressure, double seal, API 610) or BB3 multistage (high pressure) |
| Reflux pumps (columns) | Column overhead liquid (various) | Variable | Column pressure | Precise (reflux ratio), volatile, continuous, critical for separation, moderate flow | API 610 OH2 (carbon steel/316SS, precise, mechanical seal, API 610) |
| Reboiler feed | Column bottoms (hot) | 80–200°C | Column pressure | Hot, precise, continuous, critical for separation, moderate flow | API 610 OH2 (carbon steel/alloy, high temp, centerline mounting, API 610) |
| Sour water (from gas treating) | Sour water (H₂S + NH₃ + phenols) | 40–100°C | 2–10 bar | Corrosive (H₂S, NH₃), toxic, abrasive (some), moderate flow, environmental | 316SS centrifugal or fluoroplastic (corrosion-resistant, zero leakage) |
| Sulfur recovery (SRU) | Liquid sulfur (Claus process) | 130–150°C (molten) | 2–5 bar | Very hot, solidifies below 115°C, corrosive (H₂S), jacketed, small/moderate flow | Screw pump or gear pump (jacketed, molten sulfur, 316SS, self-priming) |
| Mercury removal (guard bed) | Hydrocarbon liquid (through mercury guard) | Ambient–60°C | 10–40 bar | Clean, precise, moderate flow, continuous, mercury contamination (hazardous) | API 610 OH2 (carbon steel/316SS, mechanical seal, API 610) |
| CIP/utility | Water, solvent, steam condensate | Variable | Variable | Intermittent, clean, precise, maintenance | 316SS centrifugal or OH2 |
Critical: High Vapor Pressure + NPSH + Double Mechanical Seal
NGL products (ethane, propane, butane) have very high vapor pressure — NPSH and sealing are critical:
- High vapor pressure: Ethane ~40 bar at 30°C, propane ~10 bar at 40°C, butane ~3 bar at 40°C. Pump must handle high suction pressure without vaporization. Use API 610 OH2 with high-pressure casing. Low-NPSH impeller (large eye, inducer). Flooded suction (mount pump below column/tank). NPSH margin ＞3m (volatile fluids). Chilled fluid (lower vapor pressure). Avoid throttling suction. Our low-NPSH API 610 range handles high vapor pressure NGL.
- Double mechanical seal: Volatile, flammable hydrocarbons = zero leakage required. Use double mechanical seal (plan 53A/B/C barrier fluid) or magnetic drive pump (zero leakage, no seal). Single seal = not acceptable for ethane/propane (safety + environmental). Barrier fluid (glycol/water or clean oil). Seal flush plan 32 (clean flush). API 682 seal. Our double-seal/magnetic drive range prevents NGL leakage.
- Cryogenic/cold service: Ethane at -30°C, NGL feed at -40°C. Use low-temperature materials: 316SS (down to -196°C), 3.5% Ni steel, or 9% Ni steel. Carbon steel = NOT below -29°C (brittle fracture). Low-temp mechanical seal. Jacketed (prevent ice formation). Pre-cool pump before startup. Thermal contraction compensation. Our low-temp API 610 range handles cryogenic NGL.
Critical: Amine Corrosion + Gas Sweetening
- Amine corrosion: MEA/DEA/MDEA + CO₂/H₂S = corrosive (especially rich amine, hot lean amine ＞100°C). Use 316SS (standard for amine service) — carbon steel corrodes in rich amine and hot lean amine. 316SS impeller, casing, shaft. Mechanical seal (amine attacks some elastomers — use EPDM or PTFE). Velocity control (＜2 m/s in carbon steel, ＜3 m/s in 316SS). Heat stable salt monitoring. Our 316SS API 610 range handles amine service.
- Amine foaming: Amine solutions foam (contaminants, hydrocarbons) — causes pump cavitation and carryover. Use large suction, low NPSHr pump. Anti-foam injection. Strainer (remove particulates). Velocity control. Degassing drum. Our low-NPSH range resists foaming issues.
Critical: TEG Glycol + High Temp Regeneration
- TEG viscosity + temp: TEG is 5–50 cP (viscous at ambient, less at 200°C regeneration). Use API 610 OH2 (316SS, handles moderate viscosity) or screw pump (for high viscosity, jacketed). Regenerator pump = high temp (200°C) — use high-temp mechanical seal, centerline mounting. TEG hygroscopic = keep sealed (absorbs water). Our high-temp range handles TEG regeneration.
- TEG losses: TEG is expensive — minimize losses. Zero leakage seal. Efficient contactor. Flash tank (recover TEG from gas). Still column. Our zero-leakage range reduces TEG loss.
Critical: Molten Sulfur + Jacketed
- Molten sulfur: Sulfur melts at 115°C, handled at 130–150°C (minimum viscosity at 135°C — above 160°C viscosity increases dramatically due to polymerization). Use jacketed screw pump or gear pump (steam/hot oil jacket, maintain 130–150°C). 316SS wetted (sulfur + H₂S corrosion). Jacketed piping. Heat tracing. Temperature control critical (130–150°C window). Flush with hot sulfur before shutdown. Our jacketed range handles molten sulfur.
Material Compatibility
| Material | Propane (40°C, 10 bar, volatile) | Rich amine (80°C, CO₂/H₂S, corrosive) | TEG (200°C, viscous, hot) | Molten sulfur (140°C, H₂S) | Sour water (60°C, H₂S/NH₃) |
|---|---|---|---|---|---|
| Carbon steel (WCB) | Good (standard, ＞-29°C) | NOT (rich amine corrosion) | Fair (up to 200°C, but check) | Fair (H₂S corrosion) | NOT (H₂S/NH₃ corrosion) |
| 316SS | Good (low temp option) | Excellent (amine standard) | Excellent (high temp) | Good (sulfur + H₂S) | Good (H₂S/NH₃) |
| Duplex SS | Good | Excellent (high corrosion) | Good | Good | Excellent |
| 3.5% Ni steel | Excellent (cryogenic -100°C) | — | — | — | — |
| PTFE-lined | NOT (hydrocarbons) | Good (if very corrosive) | NOT (high temp) | NOT | Good (corrosion) |
| EPDM seals | NOT (hydrocarbon swells EPDM) | Excellent (amine + caustic) | Good (hot water) | NOT (sulfur/oil) | Good |
| FKM (Viton) seals | Good (hydrocarbon) | Fair (amine may affect) | Good (up to 200°C) | Good (sulfur) | Fair |
| FFKM (Kalrez) | Excellent | Excellent | Excellent (high temp) | Excellent | Excellent |
| NBR seals | Good (hydrocarbon) | NOT (amine) | NOT (high temp) | Good | NOT |
| PTFE/FFKM seals | Excellent | Excellent | Excellent | Excellent | Excellent |
Critical: NGL (propane/butane) = carbon steel + FKM/FFKM + double seal + API 610 OH2. Ethane (cryogenic) = 316SS/Ni steel + FFKM + double seal + low-NPSH. Amine = 316SS + EPDM/PTFE + API 610. TEG = 316SS + FKM/FFKM + high-temp OH2/screw. Molten sulfur = 316SS + jacketed screw/gear + 130–150°C. Sour water = 316SS/PTFE-lined + EPDM/PTFE. All = API 610 for critical + explosion-proof + zero leakage (double seal/magnetic drive).
Common Problems and Solutions
Problem 1: Propane pump cavitates (high vapor pressure). Propane vaporizes in pump — cavitation. Solution: use low-NPSH API 610 OH2 (large eye, inducer). Flooded suction (mount below tank). NPSH margin ＞3m. Chill propane. Double seal. Our low-NPSH range prevents propane cavitation.
Problem 2: Amine pump corrodes (carbon steel). Rich amine corrodes carbon steel pump. Solution: use 316SS API 610 OH2. EPDM/PTFE seals. Velocity control. Heat stable salt monitoring. Our 316SS range handles amine corrosion.
Problem 3: NGL pump leaks (single seal). Single seal fails — propane leaks (fire hazard). Solution: use double mechanical seal (plan 53B) or magnetic drive pump. API 682 seal. Barrier fluid. Gas detection. Our zero-leakage range prevents NGL leakage.
Problem 4: Molten sulfur solidifies in pump. Sulfur cools below 115°C — solidifies. Solution: jacketed screw pump (maintain 130–150°C). Jacketed piping. Heat tracing. Temperature control (130–150°C window). Flush before shutdown. Our jacketed range prevents sulfur solidification.
Problem 5: Cryogenic ethane pump brittle fracture. Carbon steel pump at -30°C — brittle fracture. Solution: use 316SS or 3.5% Ni steel API 610 OH2. Low-temp seal. Pre-cool. Thermal contraction. Our low-temp range handles cryogenic ethane.
Selection Summary
- Amine circulation: 316SS centrifugal or API 610 OH2 (316SS, large flow, corrosion, EPDM/PTFE, 40–120°C)
- Amine booster: API 610 OH2 or BB2 (316SS, high pressure 5–80 bar, corrosion)
- TEG glycol: API 610 OH2 (316SS, 200°C regeneration) or screw (viscous, jacketed)
- NGL feed: API 610 OH2 or BB2 (low-temp, high vapor pressure, double seal, -40 to 40°C)
- Fractionation bottoms: API 610 OH2 (carbon steel/316SS, 50–150°C, column pressure)
- Propane product: API 610 OH2 (carbon steel, double seal, high vapor pressure ~10 bar, 40–60°C) or screw (metering)
- Ethane product: API 610 OH2 (316SS/Ni steel, cryogenic -30°C, high pressure 20–40 bar, double seal) or BB3 (high pressure)
- Reflux/reboiler: API 610 OH2 (precise, volatile, column pressure, critical separation)
- Sour water: 316SS centrifugal or fluoroplastic (H₂S/NH₃ corrosion, zero leakage)
- Molten sulfur: Jacketed screw pump or gear (316SS, 130–150°C, jacketed, self-priming)
- Critical: NGL = API 610 OH2/BB2 + double mechanical seal (plan 53B) + low-NPSH + NPSH margin ＞3m, ethane cryogenic = 316SS/Ni steel + pre-cool, amine = 316SS + EPDM/PTFE (NOT carbon steel for rich), TEG = 316SS + high-temp + viscous, molten sulfur = jacketed screw/gear + 130–150°C window, all = API 610 + explosion-proof + zero leakage + NACE for H₂S
- Our API 610 OH2, BB2, BB3 cover NGL/fractionation; screw covers TEG/sulfur; 316SS centrifugal covers amine/sour water; magnetic drive covers zero-leakage. For gas processing pump selection, talk to our oil & gas engineers with your gas composition, NGL products, and operating pressures.