GEA DeMerc: Removal of mercury

Separation of mercury — especially elemental mercury (Hg⁰) — from process and exhaust gas streams in the non-ferrous metal industry is critical due to mercury's toxicity, volatility, and persistence in the environment.

Process description mercury removal is a three-stage process.

The first stage abate HG at the dry ESP for bulk removal of liquid followed by fine removal of liquid in the subsequent wet ESP section. Here remaining small liquid droplets are removed to ensure dry gas flows into the final mercury removal bed. This is vital for the long life of the bed media. 

In the new third stage, the GEA DeMerc, this liquid-free gas flows into the mercury removal unit, where the elemental mercury is adsorbed by proprietary media adsorbent (GEA MercurySorb). In this filter bed the adsorption of Hg(0), Hg(I) and Hg(II) can be achieved and a Hg clean gas concentration ≤ 25 µg/m³ can be achieved. The usual abatement rate is ≥ 90 % over the runtime and the mercury is finally bound as mercuric sulfide.

Advantages of adsorption-based mercury removal

1. High efficiency:

• Capable of removing >90% of elemental mercury, even under challenging conditions (e.g., high SO₂ concentrations).

2. Operational simplicity:

• Adsorption systems are relatively easy to operate and integrate into existing flue gas treatment setups.

3. Cost-effectiveness:

• Materials like GEA MercurySorb are more affordable than activated carbon or noble metals.
• Regenerable adsorbents  reduce long-term costs 

4. Scalability and flexibility:

• Modular designs allow for easy scaling and retrofitting in existing plants.

Adsorption capacity and life time

The adsorption capacity on GEA MercurySorb depends on the process conditions and the type and concentration of mercury which has to be removed. 

Other harmful compounds such as common hydrocarbons, styrene, vinyl chloride monomer, pesticides, chlorinated hydrocarbons etc. can be adsorbed very well.
If the process conditions are known, a prediction of the life time can be made. Alternatively the life time can be controlled by an emission control device which detects the breakthrough after the adsorber bed.
Continuous monitoring of Hg is essential in order to monitor all possible plant conditions and Mercury CEM systems are available and fulfill the required accuracy

GEA MercurySorb increase the available surface for mercury adsorption with the following advantages:

• Long retention time
• Low temperatures, best < 140 °C