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Reduction of mercury emissions

 This research group is focused on improvements towards conventional mercury reduction and especially the mercury emission reduction from burning processes (like waste incineration, sewage sludge incineration, coal burning processes in power plants), other thermal treatment processes (cement production, production of wallboards from FGD gypsum), gases from pyrolysation and natural gas.

A special point of interesst from actual projects is the oxidation of mercury in the vessel- or fluegas on both dry and wet flue gas cleaning. Non oxidized, elemental mercury (Hg⁰) is not soluable in water. However the ionic mercury (Hg²⁺) e.g. HgCl₂ (as most important representative form) is good soluable in water. The wet mercury separation e.g. in a multi-stage fluegas scrubber requires a high amount of Hg²⁺.

In our laboratories we have several test stands for research:

• Experimental rig for low- and middle      temperature oxidation of elemental mercury in gases of defined composition      (150 to 800°C)
• Experimental rig to investigate the      absorption and retention of elemental mercury and oxidized mercury in      several scrubber stages (e.g. heavyly acid scrubbers in waste      incineration, low acid FGD scrubber in coal buning power plants)
• Experimental rig fort he dry mercury pecipation      of fly-ash and dry-sobents
• Experimental rig to test the sorption and desorption      of mercury from SCR-DeNOx-Catalysts

For mercury emission analysis we have some portable devices:

• 4 devices for continuous mercury measurement      with wet chemical reduction and CV-AAS of company DURAG / VEREWA      (Type HM 1400, proved after 17. BImSchV      /GMBI 1996, Nr. 28, page 592)

These devices can used for both detection of elemental mercury or oxidized mercury, depending on the wet chemical treatment. So with 2 devices (one Hg⁰ and one Hg²⁺) it’s possible to have an online analysis of the mercury speciation. The devices are used in coal burning power plants (5 to 50 µg/m³) as well as in waste incineration plants ( 5 to 1500 µg/m³).

• 2 Hg- CEMs of Seefelder Messtechnik for      parallel continuous measurement of both mercury species (devices with      thermal catalytic reduction and mercury up concentration with a gold      trap/amalgamation)
• 1 MERCEM of SICK/MAIHAK       for continuous measurement of total      mercury (device with wet chemical reduction and mercury up concentration      with a gold trap/amalgamation)
• 2 Hg- Analysers RA-915+ of Lumex Analytics       with zeeman-effect to detect very low concentrations      online, as well as solid and liquid mercury analysis

Done and ongoing projects:

• Reduction of Hg emissions of the hazardous      waste incineration plant of Bayer Entsorgungszentrums Leverkusen- Bürrig (in cooperation with Vosteen      Consulting GmbH)
• Reduction of mercury emissions in coal      burning power plants (I cooperation with the BAYER-AG and Vosteen      Consulting GmbH)
• Reduction of the mercury emissions while      simultaneous combustion of waste in cement plant (in cooperation with      Vosteen Consulting GmbH)
• Researching the influence of „Non-mercury“      gaseous substances (e.g. SO2, HCl, Br2) to the continuous mercury analysis      to prevent errors in measurement and to improve the gaseous reduction
• Researching the influence of Na2S4 to the dry mercury precipation (in cooperation with FISIA BABCOCK ENVIRONMENT GmbH, Gummersbach)

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