Dry filter

A dry filter is an air treatment technique in which waste gases pass through a bed of solid sorbents, reactants or catalysts to remove volatile compounds. It is a compact and effective solution for achieving high removal efficiencies in small gas flows, provided the right sorbent materials are selected for the specific gas composition.

Dry scrubber with solid sorbents for removing sulphur compounds, acids, halogens and VOCs with controlled contact time and high efficiency.

Why choose a Dry filter?

Removal of various volatile compounds

volatile nitrogen compounds (NH₃, amines, …)
volatile sulphur compounds (H₂S, mercaptans, ...)
acid gases (NO, NO₂, SO₂, …)
halogen compounds (Cl₂, HCl, HBr, F₂, HF, SiCl₄, …)
solvents
odour

Pollutants treated with Dry filtration

Air treatment for ammonia and amine emissions

Ammonia and amines

Air treatment system for halogenated compound emissions

Halogenated compounds

Air treatment system for H₂S, DMS, DMDS and other volatile sulphur compounds from bio‑industry emissions to reduce odour impact.

Hydrogen sulphide and volatile organic sulphur compounds

Odour

Air treatment system for organic and inorganic acid emissions

Organic and inorganic acids

EtO abatement system for ethylene oxide waste gas treatment

Ethylene oxide and other epoxides

How does Trevi's Dry filter scrubber work?

Adsorption and reaction in a solid bed

In a dry filter, the gases to be treated are blown through a bed of solid adsorbents/reactants/catalysts. The volatile compounds to be removed will show a physical adhesion on or a chemical reaction with the solid sorbent in the dry scrubber.

When a dry filter is a suitable choice

Very high (> 99%) removal efficiencies can be obtained upon selection of the correct sorbent material for the specified waste gas and maintaining the correct gas contact time. Due to the cost of the sorbent material, this technique is mainly suited for rather small gas flows with low to moderate concentrations of volatile compounds.

Sorbent selection and performance

While activated carbon can be used for the adsorption of numerous volatile organic compounds, other sorbents such as Chemisorb S and Chemisorb P are suited for the removal of for example acid, alkaline and halogen gases. Advantage of these inorganic sorbents is that they are non-flammable and that their saturation can be checked visually since they change colour upon saturation. As a result of this, a sight glass on top of the bed is usually provided.

Layered sorbents for mixed gas streams

For gas mixtures, different layers of sorbents can be provided in a dry filter such as a lower layer of impregnated carbon, a middle layer of Chemisorb S and a top layer of Chemisorb P.

Waste gas characterisation is essential

A good characterisation of the waste gas is crucial for selection of the most appropriate sorbents since some of them require O2 to function properly, others get saturated by CO2, some require water vapour for optimal performance while others get inactivated by water vapour,…

Operational attention points

Attention should be paid to prevent overheating of the reactor upon input of high mass loads of volatile compounds towards the dry filter in small gas flows. Next to that, the pressure drop over some sorbents can gradually increase upon saturation, resulting in the need to provide a pressure transmitter and/or a pressure relief device such as a bursting disc.