What Are Tray Towers?
Tray towers are gas scrubbing vessels that remove both particulate and soluble gas pollutants from an air stream in a single piece of equipment, by forcing the gas to bubble upward through a series of liquid-covered trays stacked inside the vessel. Each tray acts as its own scrubbing stage, so a single tray tower can achieve the kind of combined particulate-and-gas removal that would otherwise need two separate technologies.
That dual capability — capturing particulate above roughly 2 microns and soluble gases together, in one compact footprint — is what sets tray towers apart from most other scrubber configurations, which are usually optimised for one contaminant type or the other.
How Does a Tray Tower Work?
1. Gas enters at the base and rises through the vessel. Contaminated gas flows upward, passing through a series of stacked horizontal trays.
2. Gas bubbles through liquid on each tray. At each stage, the gas pushes up through orifices in the tray plate and bubbles through a shallow layer of scrubbing liquid sitting on top of it.
3. Contaminants transfer into the liquid. As the gas bubbles through, particulate is captured and soluble gas contaminants are absorbed into the liquid layer.
4. Liquid cascades down, gas continues up. Scrubbing liquid flows across each tray, over a weir, and down to the tray stage below, while progressively cleaner gas continues rising through the stack.
5. Additional stages boost efficiency. More tray stages can be added to increase overall contact time and push removal efficiency higher for demanding applications.
What Does a Tray Tower Remove?
– Particulate larger than 2 microns — both soluble and insoluble solid particles
– Soluble gaseous contaminants — acid gases and other absorbable pollutants, captured simultaneously with particulate in the same vessel
This combined capability is the core reason tray towers get specified: where a stream carries both particulate and soluble gas contaminants together, a tray tower can often do the job of two separate scrubbing stages in one vessel.
Types of Tray Tower Configuration
– Perforated plate trays — simple, robust tray design suited to a wide range of general scrubbing duties
– Impaction valve trays — designed to improve gas-liquid contact and capture efficiency for more demanding applications
– Cylindrical vessels — the standard configuration for most flowrates
– Rectangular cross-section vessels — used at the top end of the flowrate range, or where footprint constraints favour a non-cylindrical shape
Where Are Tray Towers Used?
Tray towers are typically specified in industrial applications where gas streams carry a mix of particulate and soluble gas contaminants, including:
– Chemical and process manufacturing — combined particulate and acid gas scrubbing from reactor or process vents
– Metals and minerals processing — treating gas streams with both particulate fume and soluble gas components
– Large-volume industrial gas cleaning — where a compact, high-throughput single-vessel solution is preferred over multiple separate scrubbing stages
They’re frequently integrated alongside other mass and heat transfer equipment — such as quench systems, venturi scrubbers, packed towers or carbon filters — as part of a wider air pollution control system.
Tray Towers vs. Other Scrubber Configurations
– Packed towers generally offer higher mass-transfer efficiency for soluble-gas-only streams with low particulate loading, since packing provides more surface area than trays. Tray towers earn their place when particulate is present alongside the soluble gas load.
– Venturi scrubbers are the stronger choice when fine particulate capture (down to sub-micron levels) is the primary requirement, rather than combined particulate-and-gas removal.
– Spray towers trade some removal efficiency for very low pressure drop and strong resistance to fouling from sticky or high-solids streams.
Benefits and Limitations
Benefits:
– Removes particulate and soluble gas contaminants in a single vessel, avoiding the need for two separate scrubbing stages
– Comparatively low capital cost for the gas flow capacity delivered
– Low running costs due to low gas-side pressure drop and modest liquor rates
– Self-cleaning tray design supports robust, continuous industrial operation
– Handles very large gas flows — up to around 100,000 m³/hr per tower
Limitations:
– Removal efficiency (typically 90–95%, up to 99%) is generally lower than a dedicated packed tower stage for soluble-gas-only duties
– Taller vessels are needed to accommodate multiple tray stages for higher-efficiency requirements
– Solids-laden applications need careful sump and dewatering design to manage captured particulate
Frequently Asked Questions
What is a tray tower used for?
A tray tower is used to remove both particulate and soluble gas contaminants from an industrial gas stream in a single vessel, by passing the gas up through a stack of liquid-covered trays.
Can a tray tower remove both particulate and gas pollutants at the same time?
Yes — this dual capability is the main reason tray towers are specified. Each tray stage captures particulate above roughly 2 microns while simultaneously absorbing soluble gas contaminants into the scrubbing liquid, so a single vessel handles both contaminant types together.
How many tray stages does a tray tower typically need?
The number of stages depends on the required removal efficiency and contaminant load — more stages increase gas-liquid contact time and push overall performance higher, with additional stages typically added for more demanding scrubbing duties.
Are the trays in a tray tower self-cleaning?
Yes, tray towers are designed to be self-cleaning, reliable and robust in continuous industrial service, with features such as under-tray sprays and adjustable weirs helping to resist fouling during operation.
Explore ERG’s Tray Tower Technology
For the detailed engineering specification — flowrate ranges, tray types, materials of construction, and design codes — see ERG’s dedicated technical page, which remains the authoritative source on this technology:
– Tray Towers — full technical range, design parameters and system integration options – Packed Towers Guide — the complementary configuration for soluble-gas-only duties – Venturi Scrubbers Guide — the complementary technology for fine particulate-focused duties – Chemical Scrubbers Guide — the broader chemical scrubbing process this equipment is often used for
Talk to our team about a tray tower solution for combined particulate and gas scrubbing at your site.
