Do We Need a Dust Filter Upstream of a Mercury Removal Unit


Dust in Feed Gas toMercury Removal Units



Dust particles must be removed from the Feed Gas, Up-Stream of ANY kind of Adsorption Unit, and that includes Mercury Removal Units (MRU). Many types of industrial process gas streams contain particles: produced natural gas, incinerator off-gases, & carbon kiln off gases in gold ore processing, for example.

If there are particles in the feed gas, then these particles can and will accumulate in an adsorbent bed. Adsorbent beds are high-efficiency “molecular filters,” not particle filters, so adsorbent beds are not the most efficient traps for particles. However, a significant portion of the dust carried in a feed gas can and will be trapped in the adsorbent bed.

DUST TRAPPED IN AN ADSORBENT BED CAN CAUSE –

• GAS FLOW CHANNELLING, leading to
(a) Early Breakthrough of Contaminant into the bed Outlet Gas Stream
(b) Increased Pressure Drop
(c) Hot Spot Formation, if the gas contains a significant amount of O2
(See “TR-Hot Air, O2 + Activated Carbon”)

• EMISSION OF MERCURY-CARRYING PARTICLES INTO THE BED OUTLET
Most of the particles from the Feed Gas will pass through the adsorbent bed. If mercury is attached to the particles, the particles will release Hg, increasing the effluent Hg conc.

RECOMMENDATION
If the Feed Gas contains particles, a High-Efficiency Particle Filter (HEPA) should be installed upstream of the adsorption unit.

HYDROCARBON GASES
Produced Natural Gas typically flows from the well to a Slug-Catcher (also called a Three- Phase Separator or Test Separator). A Knock-Out Drum with a Mist-Reduction-Pad should be installed downstream of the Three-Phase Separator. A Filter-Separator typically provides high- efficiency removal of both particles & liquid mists and should be installed after the Knock-Out Drum & Upstream of the Adsorption Unit.

OFF-GASES FROM INCINERATORS & KILNS
Upstream of the adsorption unit, Install a Bag-House filter and a HEPA filter. We generally do not recommend using a water-spray scrubber to remove particles, because it creates a contaminated wastewater stream that must be processed for removal of particles and mercury.



Providing Solutions to remove mercury for emission control, corrosion prevention and catalyst protection.



Selective Adsorption Associates, Inc. (SAA) offers over 40 years of experience in Process Engineering of Adsorption Systems for Gas and Liquid Drying, Sulfur Compound Removal, Emission Control, and over 20 years of Process Design experience in Mercury Removal Systems.

CAUTION: Wet activated carbon removes oxygen from air. Thus, an asphyxiation hazard exists inside enclosed spaces containing activated carbon. Use appropriate safety precautions when entering vessels or other enclosed spaces containing activated carbon. Exposure to strong acids and oxidizers can cause formation of toxic H2S gas.

MERSORB® is a trademark of Nucon International, Inc. (NUCON®) for impregnated activated carbons used to remove mercury from gases and liquids. Information presented herein is believed to be accurate and reliable but does not provide any guarantee or warrantee by NUCON® or by Selective Adsorption Associates, Inc. Nothing herein shall be construed as an invitation to use processes covered by patents without proper arrangements with individuals or companies owning those patents.

AntiMercure® is a Registered Trademark of Selective Adsorption Associates, Inc. (SAA) for its Process for removing mercury from water; AntiMercure™ is a trademark of SAA for its pre-Engineered Systems for removing mercury from water. All Rights Reserved.