Amine circulation pumps are the heart of gas sweetening (amine treating) systems, circulating MDEA, DEA, or MEA solutions to absorb H2S and CO2 from natural gas and refinery gas. These pumps handle corrosive amine solutions at elevated temperatures, requiring reliable mechanical seals and proper material selection. This guide covers amine pump selection, gas sweetening process, corrosion management, and reliability.
Amine Gas Sweetening System Overview
| Component | Function | Typical Spec | Pump Type |
|---|---|---|---|
| Absorber (contactor) | Amine absorbs H2S/CO2 from gas | 20โ100 bar, 40โ60ยฐC | โ |
| Lean amine pump | Pump lean amine to absorber | 30โ50% MDEA/DEA, 40โ60ยฐC, 50โ1000 mยณ/h, 20โ100 bar | API 610 OH2 (316SS trim) |
| Rich amine (from absorber) | Amine + H2S/CO2 | 40โ60ยฐC, high pressure | โ |
| Rich amine letdown | Pressure reduction to regenerator | 5โ10 bar, hydraulic turbine (energy recovery) | โ |
| Rich amine pump | Pump rich amine to regenerator (if needed) | 40โ60ยฐC, 50โ1000 mยณ/h, 5โ20 bar | API 610 OH2 |
| Regenerator (stripper) | Strip H2S/CO2 from amine | 1โ2 bar, 100โ120ยฐC | โ |
| Reboiler pump | Circulate amine to reboiler | 100โ120ยฐC, high flow | API 610 OH2 (high temp) |
| Lean amine cooler | Cool lean amine (120โ40ยฐC) | Shell-and-tube, 316SS | โ |
| Amine storage/makeup | Store and makeup amine | 30โ50% solution, ambient | 316SS centrifugal |
| Amine filtration | Remove particulates/HC | Mechanical + carbon filters | API 610 OH2 (filter feed) |
Critical: Amine Solution Properties
| Amine Type | Concentration | Corrosivity | Use | Pump Material |
|---|---|---|---|---|
| MDEA (methyldiethanolamine) | 30โ50 wt% | Low-moderate (selective H2S) | Most common, low energy | Carbon steel (low vel) / 316SS (high vel) |
| DEA (diethanolamine) | 25โ30 wt% | Moderate | H2S + CO2 removal | 316SS trim recommended |
| MEA (monoethanolamine) | 15โ20 wt% | High (more corrosive) | Deep CO2 removal | 316SS (wetted parts) |
| DGA (diglycolamine) | 50โ60 wt% | Moderate | High pressure, low temp | 316SS trim |
| MDEA + piperazine | 30โ40% + 5โ10% | Moderate | High CO2 capacity | 316SS trim |
Critical: MDEA is the most common amine (30โ50 wt%, selective for H2S, lower corrosion, lower energy). Amine solutions are alkaline (pH 10โ12) and become corrosive when loaded with H2S/CO2 (rich amine) and at high temperature (reboiler 100โ120ยฐC). Pump material: carbon steel for lean amine (low velocity ๏ผ1.5 m/s), 316SS for rich amine and high-velocity areas. Our API 610 OH2 pumps with 316SS trim are standard for amine circulation.
Critical: Lean Amine Pump (Main Circulation)
- Service: Pump lean amine (regenerated, 40โ60ยฐC) from surge drum to absorber top. High pressure (20โ100 bar, to overcome absorber pressure + friction). High flow (50โ1000 mยณ/h, depends on gas flow and acid gas loading).
- Pump selection: API 610 OH2 (overhung, single-stage) for most services. For very high pressure (๏ผ80 bar), API 610 BB2 or multistage. 316SS trim (impeller, shaft sleeve, wear rings) for corrosion resistance. Carbon steel casing acceptable for lean amine (low temp, low velocity).
- Seal: API 682 single or dual mechanical seal. Amine is not highly toxic (but H2S in rich amine is toxic). Lean amine: single seal with Plan 11 (recirculation) or Plan 32 (external flush). Rich amine: dual seal with Plan 53/54 (barrier fluid) for H2S containment. Our pumps use API 682 seals.
- Efficiency: Amine circulation is energy-intensive (large flow, high pressure). High-efficiency pump + VFD saves significant energy. Proper sizing (avoid over-sizing) critical. Our high-efficiency pumps reduce operating cost.
Critical: Rich Amine and Reboiler Pumps
- Rich amine pump: Rich amine (loaded with H2S/CO2) from absorber to regenerator. Often pressure-let down (hydraulic turbine recovers energy). If pump needed, API 610 OH2 with 316SS trim (rich amine more corrosive). H2S in rich amine โ toxic โ dual seal.
- Reboiler pump: Circulate hot amine (100โ120ยฐC) through reboiler. High temperature โ seal/casing challenges. API 610 OH2 with high-temp design (centerline mounting, proper thermal expansion). 316SS trim (high temp + rich amine = most corrosive). API 682 high-temp seals with Plan 32 (cool external flush). Our high-temp pumps handle reboiler service.
Critical: Amine Corrosion Management
| Corrosion Area | Mechanism | Solution |
|---|---|---|
| Rich amine (H2S/CO2 loaded) | Acid gas corrosion, pitting | 316SS trim, velocity ๏ผ3 m/s, filtration |
| Reboiler (100โ120ยฐC) | High temp + acid gas โ severe corrosion | 316SS/duplex, proper velocity, amine reclaimer |
| High velocity areas | Erosion-corrosion | 316SS, limit velocity ๏ผ3 m/s, smooth passages |
| Amine degradation products | Heat-stable salts (HSS) โ corrosion | Amine reclaimer, filtration, anion exchange |
| Entrained hydrocarbons | Erosion, foaming | Carbon filtration, coalescer, antifoam |
Critical: Amine corrosion is managed by: (1) material selection (316SS for rich/high-temp), (2) velocity control (๏ผ3 m/s for carbon steel, ๏ผ5 m/s for 316SS), (3) amine purification (reclaimer removes heat-stable salts), (4) filtration (particulate + carbon), (5) proper operating temp (avoid ๏ผ120ยฐC). Our amine pumps use 316SS trim and proper velocity design.
Critical: Common Problems
- Problem 1: Amine pump seal failure. Amine crystallizes on seal faces โ seal wear โ leak. Solution: API 682 seal with proper flush (Plan 11/32), clean amine (filtration), proper seal material (silicon carbide),ๅฎๆ maintenance. Our pumps use reliable seals.
- Problem 2: Corrosion (rich amine/reboiler). H2S/CO2 + high temp โ corrosion โ pump failure. Solution: 316SS trim, velocity control, amine reclaimer, proper temp. Our pumps use corrosion-resistant materials.
- Problem 3: Amine foaming. Contaminants (HC, solids) โ foaming โ poor absorption, carryover. Solution: carbon filtration, coalescer, antifoam dosing (metering pump), proper amine level. Our systems include filtration.
- Problem 4: Heat-stable salts (HSS). Amine degradation โ HSS โ corrosion, foaming, reduced capacity. Solution: amine reclaimer (distillation or ion exchange),ๅฎๆ analysis, makeup fresh amine. Our systems include reclaimer.
- Problem 5: Lean/rich exchanger fouling. Solids/corrosion products โ fouling โ poor heat transfer โ energy waste. Solution: filtration (10โ25ฮผm),ๅฎๆ cleaning, amine reclaimer. Our systems include filtration.
- Problem 6: Energy waste (over-sized pump). Over-sized amine pump โ throttled โ energy waste. Solution: proper sizing, VFD, high-efficiency pump,ๅฎๆ efficiency testing. Our pumps are properly sized.
Selection Summary
- Lean amine circulation (main): API 610 OH2 (316SS trim, 40โ60ยฐC, 50โ1000 mยณ/h, 20โ100 bar, API 682 seal, high efficiency)
- Lean amine (very high pressure ๏ผ80 bar): API 610 BB2 or multistage
- Rich amine: API 610 OH2 (316SS trim, dual seal for H2S, 40โ60ยฐC)
- Reboiler circulation: API 610 OH2 (high-temp design, 316SS, 100โ120ยฐC, API 682 high-temp seal with Plan 32)
- Amine makeup/transfer: 316SS centrifugal (ambient, low pressure)
- Amine filtration feed: API 610 OH2 (316SS, moderate pressure)
- Antifoam/corrosion inhibitor: Diaphragm metering (PTFE, ยฑ1%, precise)
- Critical: amine sweetening = CIRCULATION PUMP DOMINANT (lean amine pump is largest energy user, API 610 OH2 316SS trim) + CORROSION (rich amine + reboiler = 316SS, velocity control, amine reclaimer) + HIGH TEMP (reboiler 100โ120ยฐC โ high-temp pump design) + H2S SAFETY (rich amine dual seals, gas detection) + ENERGY EFFICIENCY (high-efficiency pump, VFD, proper sizing), all = gas sweetening + safety + energy cost
- Our API 610 OH2, BB2, 316SS pumps, and metering pumps cover amine gas sweetening. For amine pump selection, talk to our oil & gas engineers with your amine type, concentration, flow rate, pressure, and temperature.