Modified on-line monitoring of total gaseous mercury in flue gases using Semtech (R) Hg 2000 analyzer

The Semtech Hg 2000 analyzer continuously monitors the Hg-o content in flue gas. An on-line measurement method of total gaseous mercury in flue gas de veloped in our laboratory is described, which uses the absorption cell of t he Semtech Hg Analyzer connected to a converter that is located in a furnac e heated up to 650 degreesC. The converter can be heated up to 800 degreesC by both the furnace and an extra heating of a Ni-Cr alloy heating wire. Bo th the absorption cell and the converter are made of quartz. All gaseous Hg 2+ species in flue gas are thermally reduced to Hg-o by the converter and d etected by the Semtech Hg 2000 analyzer. The thermal reduction efficiencies of different conversion materials, which were filled in the converter, suc h as quartz chips, granular MgO, Ni and CoO powder, were tested using diffe rent flue gas conditions. Studies have shown that HCl is the major factor t o inhibit the thermal reduction of Hg2+ to Hg-o, and in the converter and t he absorption cell Hg-o will react readily with HCl to form HgCl2. Both MgO and Ni could be used in the converter to absorb HCl in the flue gas, but N i has better absorption efficiency. By using an original Semtech and a modi fied one, both Hg-o and total gaseous Hg contents in flue gas could be moni tored simultaneously and continuously.