Annular groove isothermal graphite absorbers

Annular groove Isothermal graphite absorbers

Annular groove isothermal graphite absorbers are graphite heat exchangers adapted to the absorption of ultra-corrosive gases such as hydrochloric, bromhydric or hydrofluoric acids. The equipment works as a number of water cooled-wall tiny columns in parallel. Each tiny column is provided with a liquid distribution system on top to ensure the uniform distribution of both liquid and gas and also form a thin liquid film at the surface of the column.


3D Renderings

3D Animations


  • Impervious graphite: GAB GPX1, GPX1T or GPX2
  • Pressure plates and flanges: carbon steel or stainless steel
  • Tie rods, nuts, bolts, washers, springs: stainless steel


  • Totally modular design: number of discs and size of discs can be adjusted.
  • Maximum disc diameter: 900 mm
  • Impervious graphite discs with straight flow channels on process side and annular grooves on service side.
  • Different channel widths possible
  • Graphite nozzles on product and utility sides
  • Thermal expansion compensation ensured by tie rods and helical springs
  • Carbon-fiber reinforcement (optional)

Key Features:

  • Design pressure: -1 barg (full vacuum) to +10 barg (145 psig)
  • Design temperature: -60 to +200°C (-76 to 392°F)
  • Heat transfer area: up to 55 m2 (592 ft2)
  • Design:  according to European PED, ASME code, Chinese Pressure Vessel code and other national pressure vessel codes on request

Key Benefits:

  • Outstanding corrosion resistance
  • Superior heat transfer performance
  • Large liquid-vapor interfacial area and good wetting characteristics
  • Perfectly adapted liquid distribution design as well as unique design made of offset annular slots guarantees the most intimate contact between the gas and absorption liquid
  • Straight flow channels for low pressure drop
  • Liquid distribution plates with overflow candles to ensure homogenous liquid distribution
  • Cross section adapted to progressively decreasing gas volume
  • Annular groove channels on service side for optimum heat transfer
  • Impregnation before machining ensures resin free surfaces
  • High operational safety
  • Sturdy and modular design
  • Short lead time
  • Long lifetime

Optional features:

  • Carbon fiber reinforcement
  • Sight glass

Main applications:

  • Isothermal absorption of ultra-corrosive gases
  • Hydrochloric acid recovery

Technical documentation


PIRNS1-EN-US Graphite Annular Groove Absorber - A Series (SI and US units)

Annular groove Isothermal absorbers

The efficient absorption of a gas by a liquid depends mostly on the possibility to create an intimate contact between the gas to be absorbed and the absorption liquid as well as the possibility to remove the absorption enthalpy from the system thus meaning the ability to cool down efficiently. This can be achieved in a falling film absorber which is essentially a heat exchanger in which both gas to be absorbed and absorbing liquid flow co-currently downward with extraction of heat by circulation of coolant on the service side. If suitable a counter-current design is also possible. The absorbing liquid is usually circulated through a tank till desired concentration is achieved. The liquid flows at such a rate that the tubes do not flow full of the liquid but instead, descends by gravity along the walls of the absorber as a thin film. The equipment works as a number of water cooled-wall tiny columns in parallel. Each tiny column is provided with a liquid distribution system on top to ensure the uniform distribution of both liquid and gas and also form a thin liquid film at the surface of the column.

The thermal performance of isothermal absorbers can vary significantly. It is therefore essential to select the type and moreover size of isothermal absorber that is the most adapted to the specific application, industrial process and process conditions. There are a number of considerations including flow rate, pressure drop, turndown ratio, design pressure and temperature, materials compatibility, fouling, and many more that should be taken in account. 

GAB Neumann’s isothermal graphite absorbers - A series

GAB Neumann’s isothermal graphite absorbers are vertically mounted. They include a liquid distribution plate in their upper section as well as an abortion section with simultaneous cooling. Simultaneous cooling increases absorption efficiency and enables the production of stronger acid. GAB Neumann’s isothermal graphite absorbers are designed to distribute the absorption liquid into the absorption grooves, to ensure the proper absorption of the gas by the liquid and to efficiently cool down the progressively formed acidic liquid (removal of the absorption enthalpy). Alternating grooves arrangement increase the interface surface between gas and the liquid thus ensuring an optimal mass transfer. Safety, reliability, and performance on the long-term are our primary considerations when we size, design and manufacture annular groove isothermal absorbers.

Our extended and highly customizable isothermal annular groove absorbers portfolio enables us to provide particularly adapted solutions to ultra-corrosive gas absorption. All our isothermal annular groove absorbers’ designs are totally modular to best fit with individual process specification. The number and size of discs as well as the number of passes both on service side can be adapted to best meet the flowrates, velocities, pressure drops, and heat transfer requirements.

All our annular groove graphite absorbers are machined after phenolic resin impregnation thus guarantying a heat transfer 

Industrial processes:

  • Crop protection
  • Fumed silica
  • Silicones
  • Titanium dioxide
  • Fine chemicals
  • Active pharmaceutical ingredients
  • Epichlorohydrin
  • Vinyl chloride monomer
  • Fire retardants
  • Flavors and fragrances
  • Vitamins
  • Isocyanates
  • Polycarbonate
  • Coagulants
  • Treatment, purification and concentration of spent acids
  • and many more…

GAB Neumann GmbH

Alemannenstrasse 29

79689 Maulburg


Tel: +49 (7622) 6751 0

Fax: +49 (7622) 6751 20

GAB Neumann GmbH | Alemannenstrasse 29 | D-79689 Maulburg | Phone +49 (7622) 6751 0 | Fax +49 (7622) 6751 20 | E-Mail |