Packed Towers

ERG packed tower scrubbers provide high‑efficiency mass and heat transfer for industrial gas cleaning, liquid stripping and direct‑contact gas cooling duty. They are applied to remove soluble gaseous contaminants from process and exhaust streams, to strip contaminants from liquid streams and to cool saturated gases as part of integrated air pollution control systems. All designs are bespoke, matched to the detailed application specification and supplied with defined performance guarantees.

Packed tower technology and applications

Packed tower scrubbers are a highly efficient way to remove soluble contaminants from air and other gas streams. Packed towers are also used for stripping contaminants from liquid streams and for direct‑contact cooling of gas streams. Key advantages of packed towers include their suitability for high‑efficiency mass transfer (scrubbing and stripping) and heat transfer (gas cooling), and their flexibility across a wide range of flowrates and contaminant loadings.

All ERG designs are bespoke and matched to the detailed requirements of the application specification. ERG uses industry‑standard random packing to optimise operating efficiency alongside system pressure drop and equipment size, and all packages carry a performance guarantee and are designed to provide robust operation at the lowest capital and operating costs. Our extensive design and operating experience enables us to optimise system performance in a wide range of industrial gas cleaning and thermal conditioning duties.

Design parameters and typical duties

Flowrate ranges from 100 to 100,000 m³/hr per tower, with multiple towers in parallel used for higher flowrates.
Contaminant loadings dependent on type, with typical inlet loadings ranging from 100 mg/m³ up to 100,000 mg/m³.
Typical removal efficiency of 99.5%, up to 99.95% as required.
Vessel diameters from 200 to 4,000 mm, with heights typically up to 10 m or higher if the process requires it.
Removal of any soluble gaseous contaminant, subject to appropriate solvent selection and design.
Cooling of saturated gas streams from typically around 60 °C to <30 °C, or as required.

These parameters allow packed towers to be applied to a wide range of industrial applications, including acid gas scrubbing, H₂S removal, ammonia scrubbing, VOC absorption and gas cooling prior to downstream treatment.

Diagram of a typical chemical scrubber

System design and key features

ERG supplies complete packed tower systems including:

Recirculation pump, pipework, fan, access platform, instrumentation and control system – which may be integrated further with other ERG mass/heat transfer equipment (for example quench systems, venturi scrubbers, carbon filters) into a single air pollution control solution.
Common packing types including Snowflake / AstraPAC and 1″, 1.5″ and 2″ Pall rings.
Recirculated liquor flowrate selected to minimise pump flow and energy consumption while maintaining optimal scrubbing performance.
Liquor distribution across the packing using sprays, trough or ladder distributors depending on the application.
Droplet elimination using chevron, impaction blade or woven mesh designs to suit the application, with clean‑in‑place sprays available to assist with on‑line maintenance.
Scrubber sump tank integrated into the packed column vessel.
Chemical dosing, water make‑up and blowdown control configured to match specific performance requirements.
Instrumentation selection to give robust operation, high reliability and tight performance control.
System control by stand‑alone MCC / C&I panel or integrated DCS, with HART or Profibus protocols available as standard.
Vessels designed as standard to PD 5500 (metal) and BS EN 13121 (GRP) with UKCA or CE marking to PE(S)R or PED as appropriate; other design codes are available as required.
Material selection to suit contaminants and reaction chemistry; common materials include uPVC, PP, cPVC, Derakane® GRP, Crystic® GRP, 304SS and 316SS.
Heat transfer using in‑line heat exchangers where required.

Typical scrubbing and stripping solutions

Examples of typical scrubbing and stripping solutions include:

HCl scrubbing using water / dilute HCl solution to recover HCl for reuse.
HCl scrubbing using NaOH solution to achieve extremely low discharge concentrations.
SO₂ scrubbing using NaOH solution – for scrubbing solutions with lime see here.
H₂S scrubbing using NaOH and NaOCl solution.
NH₃ scrubbing using dilute sulphuric acid solution.
VOC scrubbing using water or mineral oils.

Further information is available in the product brochure.

Frequently asked questions

When is a packed tower scrubber preferred over other scrubber designs?

Packed towers are typically preferred where high‑efficiency absorption of soluble gases is required, with relatively low particulate loadings and when a compact, vertically oriented column is suitable. For streams with high particulate loadings, sticky solids or strong fouling tendencies, venturi scrubbers or other configurations may be selected ahead of or instead of a packed tower stage.

How do you select packing type and tower size for a specific duty?

Packing type and tower size are selected based on the required mass or heat transfer performance, gas and liquid flowrates, contaminant characteristics, allowable pressure drop and fouling potential. From these parameters, ERG defines tower diameter, packing depth, packing type and recirculation rate to meet the specified removal efficiency and gas cooling duty with appropriate design margins.