Neqsim Teg Dehydration Modeling

TEG Dehydration Modeling

Use this skill to build a complete, converging triethylene-glycol (TEG) gas dehydration plant in NeqSim. It captures a validated flowsheet topology and the non-obvious settings (CPA fluid setup, regeneration-column tolerances, recycle priorities, condenser/preheat energy coupling, makeup calculator) needed for the process to solve as a closed loop. It returns a ProcessSystem plus the key streams an agent needs for water dew point, lean-TEG purity, and still-vent emission classification.

This is a real NeqSim build, not a public correlation placeholder. For a quick "is dehydration required?" triage without building a plant, use neqsim-water-dewpoint-dehydration-screening instead.

When to Use

• When a user asks to model a TEG dehydration unit and read water dew point, lean

TEG purity, or regeneration still-vent emissions.

• When an agent needs a runnable TEG flowsheet to study stripping gas, reboiler

temperature, TEG circulation rate, or once-through vs recirculated stripping gas.

• When emissions (NMVOC, methane, benzene, CO2, water) from the regeneration

still vent must be quantified and classified for an environmental screening.

Inputs

The build_teg_plant(...) function is fully parameterized. Key inputs:

• feed_fractions: list of mole fractions (or percentages) aligned with

GAS_COMPONENTS (nitrogen, CO2, methane, ... , benzene).

• feed_flow_MSm3_day: wet/dry feed gas flow rate in MSm3/day.
• feed_temp_C, feed_pressure_bara: feed gas conditions.
• absorber_pressure_bara, absorber_temp_C: contactor conditions.
• teg_flow_kg_hr, teg_feed_temp_C, lean_teg_purity: lean TEG circulation.
• flash_drum_pressure_bara, reboiler_temp_C, stripping_gas_Sm3_hr:

regeneration conditions.

• n_absorber_stages, stage_efficiency: absorber model resolution.
• water_mode: 'saturated' (water-saturate the feed) or 'specified'

(set an inlet water content in mol-ppm via water_content_ppm_mol).

• saturation_temp_C, saturation_pressure_bara: optional saturation TP setter.
• recirculate_stripping_gas: True builds a true closed-loop stripping-gas

recycle (split dried overhead, blower, heater) to cut still-vent emissions.

Outputs

build_teg_plant(...) returns (process, streams):

• process: a NeqSim ProcessSystem ready to run.
• streams: a dict of handles — dehydratedGas, flashGas, stillVent,

leanTEGtoAbs, waterDewAnalyser, strippingGas, recircBlower.

Helper functions produce the engineering results:

• comp_mass_flows_kg_hr(stream): per-component mass flow (kg/hr).
• teg_mass_fraction(stream): TEG weight percent of a stream.
• classify_emissions(stream): dict with NMVOC, methane, CO2, water,

TEG, benzene, and total mass flows (kg/hr).

Engineering Method

The flowsheet follows the standard TEG dehydration topology:

1. Fluid — SystemSrkCPAstatoil (CPA EOS) with setMixingRule(10) and

setMultiPhaseCheck(False). TEG is added last so the lean-TEG composition maps to leanComp[-1] = lean_teg_purity and leanComp[-2] = 1 - lean_teg_purity.

1. Feed conditioning — optional saturation TP setter + StreamSaturatorUtil

(saturated mode) or an inlet water component (specified mode), then a heater to absorber TP.

1. Absorber — SimpleTEGAbsorber with gas-in and lean-TEG solvent-in streams.
2. Rich TEG let-down and pre-heat — HP flash valve, rich preheater,

lean/rich exchangers (HeatExchanger with UA values), degassing separator, fine filter, LP flash valve.

1. Regeneration — DistillationColumn (reboiler + condenser) with **loosened

tolerances** (temperature 5e-2, mass 2e-1, enthalpy 2e-1) so the glycol/water split converges; stripping gas fed to the reboiler tray; WaterStripperColumn for deep lean-TEG purity.

1. Recycles — lean-TEG recycle (priority 200, setDownstreamProperty('flow rate'))

closes the solvent loop; the internal stripping-gas recycle returns stripper overhead to the reboiler. With recirculate_stripping_gas=True, a second makeup recycle (priority 150) recirculates dried overhead as stripping gas.

1. Makeup and energy coupling — a Calculator sizes TEG makeup from TEG lost

in the dry gas, flash gas, still vent, and water draws; the rich preheater is driven by the condenser energy stream: richPreheat.setEnergyStream(column.getCondenser().getEnergyStream()).

1. Run — process.runAsThread() then thr.join(...) (worker thread avoids

blocking and tolerates the recycle iterations).

Python Usage Pattern

from teg_dehydration_modeling import (
    DEFAULT_FEED,
    build_teg_plant,
    classify_emissions,
    teg_mass_fraction,
)

process, streams = build_teg_plant(
    feed_fractions=DEFAULT_FEED,
    feed_flow_MSm3_day=4.65,
    feed_temp_C=25.0,
    feed_pressure_bara=70.0,
    absorber_pressure_bara=85.0,
    absorber_temp_C=35.0,
    teg_flow_kg_hr=5500.0,
    teg_feed_temp_C=48.5,
    lean_teg_purity=0.97,
    flash_drum_pressure_bara=4.8,
    reboiler_temp_C=197.5,
    stripping_gas_Sm3_hr=180.0,
    n_absorber_stages=4,
    stage_efficiency=0.7,
)

thr = process.runAsThread()
thr.join(300000)  # ~15 s once-through, ~40 s with stripping-gas recirculation

water_dew_C = float(streams["waterDewAnalyser"].getMeasuredValue("C"))
lean_teg_wt = teg_mass_fraction(streams["leanTEGtoAbs"])
still_vent = classify_emissions(streams["stillVent"])

print(water_dew_C, lean_teg_wt, still_vent["NMVOC"])

Validation Checklist

• [ ] Water dew point of the dry gas is well below 0 C at the reference pressure.
• [ ] Lean TEG purity is above 90 wt% (typically 97-99 wt% with stripping gas).
• [ ] Still-vent NMVOC and methane mass flows are finite and non-negative.
• [ ] With recirculate_stripping_gas=True, still-vent NMVOC and methane do not

increase versus the once-through case.

• [ ] The process is run on a worker thread and the join timeout is large enough

for the recycles to converge.

• [ ] Example inputs are public and synthetic.

Common Mistakes

| Symptom | Cause | Fix | | --- | --- | --- | | Regeneration column will not converge | Default tolerances too tight for glycol/water split | Loosen setTemperatureTolerance(5e-2), setMassBalanceTolerance(2e-1), setEnthalpyBalanceTolerance(2e-1) | | Lean TEG purity wrong / NaN | TEG not added last, or composition indices off | Add water then TEG last; set leanComp[-1]=purity, leanComp[-2]=1-purity | | Lean-TEG loop never closes | Recycle priority/property not set | Lean TEG recycle priority 200 with setDownstreamProperty('flow rate') | | Class not found | Wrong CPA class name | Use SystemSrkCPAstatoil (lowercase statoil) | | Run blocks or stalls | Running inline instead of on a thread | Use process.runAsThread() + thr.join(timeout_ms) | | TEG inventory drifts | No makeup | Add the Calculator makeup sized from TEG in dry gas, flash gas, still vent, water draws | | Water balance looks ~1-2% open | Only counting still vent + regen water draw | Water removed from the gas leaves via still vent + regen water/HC draw + degassing flash gas; include the flash-gas water term and closure tightens to <0.1% |

Limitations

• Inputs and examples are public and synthetic; no proprietary plant data,

vendor glycol packages, or company emission factors are included.

• Emission classification is a component-bucketing of stream mass flows

(NMVOC/methane/benzene/CO2/water); it is not a regulatory emission inventory.

• The absorber uses SimpleTEGAbsorber with stage efficiency, not a rate-based

contactor model; deep dew-point design needs validated review.

• Convergence depends on reasonable inputs; extreme TEG rates, stripping gas, or

reboiler temperatures may require tolerance or guess-temperature tuning.

Related NeqSim Functionality

• neqsim.thermo.system.SystemSrkCPAstatoil — CPA equation of state for

glycol/water/hydrocarbon systems (reached via from neqsim import jneqsim).

• neqsim.process.equipment.absorber.SimpleTEGAbsorber,

neqsim.process.equipment.absorber.WaterStripperColumn — TEG contactor and stripper.

• neqsim.process.equipment.distillation.DistillationColumn — TEG regeneration column.
• neqsim.process.equipment.util.Recycle, Calculator — solvent/stripping-gas

recycles and TEG makeup sizing.

• neqsim.process.measurementdevice.WaterDewPointAnalyser — dry-gas water dew point.
• For a screening-only water-content triage before building a plant, use the

neqsim-water-dewpoint-dehydration-screening community skill.

References

• NeqSim repository: https://github.com/equinor/neqsim
• NeqSim TEG dehydration emissions notebook:

https://github.com/equinor/neqsim/blob/master/examples/notebooks/tegdehydrationemissions.ipynb

• NeqSim Skills Guide:

https://github.com/equinor/neqsim/blob/master/docs/integration/skills_guide.md

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: equinor
• Source: equinor/neqsim-community-skills
• License: Apache-2.0
• Homepage: https://equinor.github.io/neqsimhome/

Install and usage instructions live in the source repository linked above.