17 Jan
17Jan

Triethylene Glycol (TEG) dehydration remains one of the most widely used and reliable methods for removing water from natural gas. However, the design of the gas–liquid contactor and regeneration internals has evolved significantly over the last two decades. Where traditional designs relied heavily on trays or low-efficiency random packing, modern TEG units increasingly use structured packing in both absorbers and stripping columns. This shift is not just driven by vendor preference — it is supported by plant data, improved mass-transfer performance, and better hydraulic behaviour. Recent research based on operating industrial units provides strong technical evidence for why structured packing enables more compact, higher-capacity, and more energy-efficient TEG dehydration systems.


What Is Structured Packing in TEG Contactors?

Structured packing consists of corrugated metal sheets arranged in a highly ordered geometry, creating:

  • High effective interfacial area between gas and liquid
  • Uniform liquid distribution paths
  • Lower pressure drop compared with trays or random packing

In TEG dehydration contactors, structured packing promotes efficient counter-current contact between wet gas and lean glycol, allowing water to transfer from the gas phase into the glycol phase more effectively over a shorter column height. Common structured packings used in glycol service include geometries similar to Mellapak 250Y or equivalent products from other internals suppliers like us.


Limitations of Traditional Design Methods

Historically, TEG contactor sizing has relied on:

  • Tray efficiency assumptions, or
  • HETP values derived from generic packed column correlations

However, these methods often fail to accurately predict performance in glycol systems because:

  • Glycol–water systems do not behave like typical absorption solvents
  • Heat and mass transfer occur simultaneously and interact strongly
  • Many correlations were developed using air–water or solvent systems, not TEG

As a result, many operating units show significant deviation between predicted and actual performance, especially when units are pushed to higher throughput or when revamping older towers.


What Industrial Data Shows About Structured Packing Performance

A detailed 2022 study by Filep, Todinca, and Dumitrel evaluated mass and heat transfer in industrial TEG units using structured packing, with plant data reconciled through Aspen HYSYS simulations.Key findings include:

1. Gas-Side Mass Transfer Is Strongly Linked to F-Factor

For absorption in TEG contactors:

  • The overall gas-side mass transfer coefficient (Ky) increases strongly with gas F-factor
  • Liquid load has a much weaker influence than traditionally assumed

This supports the feasibility of higher gas throughput per unit diameter, enabling:

  • Smaller contactor vessels
  • Higher turndown capability
  • Easier debottlenecking of existing units

2. Heat Transfer Is Much Higher Than Predicted by Classical Analogies

The study found that:

  • Actual heat flux in structured packing contactors is approximately 2.5 times higher than predicted by Chilton–Colburn analogy

This matters because temperature profiles strongly affect:

  • Water equilibrium
  • Driving force for mass transfer
  • Lean glycol effectiveness

Ignoring this effect can lead to under-prediction of dehydration performance or poor regeneration targeting.


3. Absorbers and Strippers Behave Very Differently

The research highlights that:

  • Absorber columns should be modelled using overall gas-side mass transfer coefficients
  • Stripping columns are better represented using volumetric mass transfer coefficients (Ky·a)

Stripping performance was found to depend strongly on:

  • Stripping gas rate
  • Liquid load
  • Operating pressure near atmospheric conditions

This reinforces the need for separate design approaches rather than assuming absorber and regenerator internals behave similarly.


Why This Matters for Modern TEG System Design

More Compact New Builds

With higher mass-transfer efficiency per meter of packing height, structured packing enables:

  • Shorter contactor beds
  • Smaller vessel diameters
  • Reduced steel tonnage and fabrication cost
  • Lower transport and installation costs

This is particularly important for:

  • Offshore platforms
  • Modular gas processing skids
  • Remote or space-constrained facilities

Cost-Effective Revamps and Debottlenecking

For existing dehydration units, replacing trays or older packing with modern structured packing can:

  • Increase gas capacity without changing vessel shell
  • Improve outlet water dew point
  • Reduce glycol circulation requirements
  • Lower pressure drop across the contactor

These upgrades can often be achieved with internal modifications only, avoiding major shutdowns or vessel replacement.


Better Alignment with Rate-Based Modelling

Modern process simulators (such as Aspen HYSYS with Glycol or CPA property packages) increasingly support rate-based modelling of mass and heat transfer. Structured packing correlations derived from real plant data improve:

  • Predictive accuracy
  • Confidence in performance guarantees
  • Design margin optimisation

This enables engineers to move beyond simple stage-based or HETP-only approaches and design closer to actual operating behaviour.


Key Takeaway: Internals Matter as Much as Vessel Size

While vessel diameter and height still define overall capacity limits, internals design is now the primary driver of performance in modern TEG dehydration systems. Structured packing provides:

  • Higher efficiency
  • Lower pressure drop
  • Better temperature control
  • Greater flexibility for revamps and future capacity increases

As gas dehydration specifications tighten and facilities push for higher throughput and lower CAPEX, packing selection and internals configuration have become strategic design decisions, not just mechanical details.


Looking Ahead: Smarter, More Compact Dehydration Systems

As industry moves toward:

  • Modular gas processing plants
  • Brownfield capacity upgrades
  • Stricter pipeline water specifications

the role of high-performance internals such as structured packing will continue to grow.Future TEG systems are increasingly being designed with:

  • Integrated inlet devices
  • Optimised liquid distributors
  • High-capacity structured packing
  • Improved regeneration and stripping efficiency

All aimed at delivering more performance from smaller equipment.

Want to Improve Your TEG Dehydration Performance?

Whether you are:

  • Designing a new dehydration unit
  • Evaluating a revamp of an existing contactor
  • Investigating capacity bottlenecks or high glycol losses

a detailed review of internals, hydraulics, and mass-transfer performance can often unlock significant improvements without major plant modifications.

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