Vertical Vessel VOC Adsorber Manufacturer: Radial-Flow Beds for 25,000 to 80,000 CMH

NextAir Systems, Faridabad, India. Last reviewed October 2026.

Above about 20,000 CMH, a rectangular housing of media cells becomes a very large box. For one large process stream, a vertical cylindrical vessel is the sensible shape: it has a small footprint, a strong structure, and it can be built in sections and assembled where the plant stands.

NextAir builds vertical vessel VOC adsorbers with a radial-flow annular bed for large single streams. This page explains the geometry, shows how height follows airflow, and lists what a civil and mechanical engineer needs to know before the vessel is ordered.

At a glance

• Above 20,000 CMH we build a large cylindrical vessel with a radial-flow annular bed, where the diameter is fixed and the height grows with airflow. The same 900 mm media bay depth and about 0.45 m/s design face velocity apply, giving roughly 2 seconds of contact time.
• Using the 4,400 mm vessel diameter of our odor control vessels as a worked case, the geometry reproduces the published heights, from about 3,425 mm at 25,000 CMH to about 6,559 mm at 80,000 CMH.
• At an assumed media bulk density of 500 kg/m³, the bed of an 80,000 CMH vessel holds roughly 23 tonnes of media, which matters for the foundation.
• For streams that cannot be interrupted, two vessels each sized for the full flow are the usual arrangement.

Why a vertical vessel

The three formats we build for VOC adsorbers follow scale. A compact box serves a single point source up to 2,000 CMH. A multi-cell rectangular housing, made of 1.25 m x 1.25 m cells in parallel, serves 3,500 to 20,000 CMH. Above 20,000 CMH, the cell count and the plan area of a rectangular housing become awkward, and the vessel takes over. It is one large process stream treated in one structure, and the format scales by making the vessel taller. We describe the smaller formats in our packaged adsorber page.

How a radial-flow annular bed works

In a radial-flow vessel the media sits in a ring between two perforated cylinders, an outer one and an inner one. The air enters the outside, flows radially inward through the bed and leaves up the central core, or in the opposite direction. The bed is as thick as the ring, here 900 mm, so the contact time is set by the ring thickness and the radial velocity. Because the area of the ring wall is large and grows with the height, a tall vessel presents a large face to the air, and the velocity through the media stays low at high airflow. That is why capacity grows with height while the diameter stays fixed.

The geometry, worked

The diameter of our VOC vessels is fixed. Our odor control vessels, built on the same principle, use a 4,400 mm outer diameter, and we use that value for a worked case. With a 900 mm bed the inner diameter is 2,600 mm, and the annulus plan area is π ÷ 4 × (4.4² − 2.6²) = 9.9 m². The bed volume is airflow in m³/s times the 2.03 seconds of design contact time, and the bed height is that volume divided by the annulus area. We then add 2 m for the inlet and outlet sections, as our odor vessel table does.

The calculated and published heights agree to within a few millimetres, which shows the geometry is the same logic. The media mass uses an assumed bulk density of 500 kg/m³, not our media’s actual figure, and the real weight is stated on the quotation. For the foundation, add the empty vessel, the ductwork and the fan. The sizing of the bed itself follows empty bed contact time.

Built in sections, assembled on site

Vessels in this range are fabricated in sections in our factory and assembled on site, because a 4.4 m diameter vessel of 6.5 m height is not a road load. That affects three things: the site needs a crane and a welding or bolting plan, the flange or joint design must be agreed, and the vessel must be inspected and leak-tested after assembly. Ask any supplier who does the site assembly and what is included. Our factory has 10-ton EOT cranes, rolling machines and MIG and TIG welding lines for the shell fabrication.

Protection and monitoring

Our packaged units carry a MERV 8 pre-filter, bed temperature monitoring, inlet LEL monitoring with a high-level interlock and a pressure gauge across the bed. Large vessels on solvent streams need the same protection, so ask for the vessel’s instrumentation list and the interlock scheme. Continuous outlet VOC monitoring by PID or FID, a multi-stage bed in series and BACnet or Modbus integration are options. How the bed is judged full is explained in breakthrough monitoring or scheduled change-out.

When to choose a vessel, and when not to

• One large stream, such as a major coating or printing facility’s central exhaust, where a single treatment point is simpler than several units.
• Limited floor area with vertical space available.
• Not for many small sources, where a bank of packaged units close to each source cuts duct length.
• Not for very concentrated streams, where an oxidizer such as our regenerative thermal oxidizer may suit better.

Our general checklist for suppliers is in how to choose a dry VOC adsorber manufacturer.

What to send us for a quotation

• The VOC compounds and concentrations, and the airflow
• Exhaust temperature and humidity
• Operating hours and the permit limit
• Whether the stream can be interrupted, and so whether two vessels are needed
• Site plan: available footprint, height limits, crane access and foundation constraints
• Electrical supply and control integration requirements

Send these to us through our contact page and we will give the vessel dimensions, media quantity and weights for your airflow. See the full dry VOC adsorber range and our guide to dry VOC adsorption. Large streams occur in chemical and pharmaceutical plants and automotive paint shops, and the exhaust fan is usually a centrifugal blower.

Types and variants we build

• Paint Booth VOC Control System Supplier: Sizing an Adsorber From Paint Usage
  Paint booth VOC control: how paint use becomes solvent concentration, when a dry adsorber lasts weeks or days, and what the booth needs upstream.
• Vertical Vessel VOC Adsorber Manufacturer: Radial-Flow Beds for 25,000 to 80,000 CMH
  Vertical vessel VOC adsorbers for large single streams, 25,000 to 80,000 CMH: how a radial-flow annular bed works, the geometry, media weight and site assembly.

Frequently Asked Questions