neqsim-teg-dehydration-modeling

name	neqsim-teg-dehydration-modeling
version	0.1.0
description	Build a validated, closed-loop TEG (triethylene glycol) gas dehydration plant in NeqSim, including absorber, flash drum, regeneration column, stripper, lean-TEG recycle, and still-vent emission classification. USE WHEN: a task needs a runnable NeqSim TEG dehydration flowsheet (water dew point, lean-TEG purity, NMVOC/methane/benzene still-vent emissions) rather than a screening-level water-content estimate.
last_verified	2026-06-26
requires	{"python_packages":["neqsim"],"java_packages":["neqsim"],"env":[],"network":[]}

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.
2. Feed conditioning — optional saturation TP setter + StreamSaturatorUtil (saturated mode) or an inlet water component (specified mode), then a heater to absorber TP.
3. Absorber — SimpleTEGAbsorber with gas-in and lean-TEG solvent-in streams.
4. 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.
5. 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.
6. 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.
7. 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()).
8. 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/teg_dehydration_emissions.ipynb
• NeqSim Skills Guide: https://github.com/equinor/neqsim/blob/master/docs/integration/skills_guide.md