| Abstract Title: | Mercury speciation in cement plant flue gases |
| Presenter Name: | Dr Jože Kotnik |
| Co-authors: | Mr Sreekanth Vijayakumaran Nair Dr Igor Živković Dr Jan Gačnik Dr Tanja Ljubič Mlakar Prof Milena Horvat |
| Company/Organisation: | Jožef Stefan Institute |
| Country: | Slovenia |
Abstract Information :
Samples from the stack gas were collected from the cement clinker production facility (Anhovo, Slovenia) using different types of commercial Ohio Lumex sorbent traps. The measurements were carried out with sorbent traps for the determination of total mercury (TM) in accordance with the new CEN TS 17286 method and the US EPA 30B method and with traps for speciation. Sorbent traps were used to collect flue gas for the determination of total Hg, mercury speciation, and stable isotope ratio analysis. The results of analyses using sorbent traps were in good agreement with the results measured by CEMS in the period from July 2020 to March 2021, where the total Hg content in the flue gas was measured continuously with a MERCEM300Z Hg gas analyser that was installed by the provider SICK in July 2020. At the cement plant, three modes of operation were employed during the sampling, depending on the number of mills operating. The number of raw mills in operation clearly influenced the amounts of TGM emitted from the plant because Hg was cycled between the kiln and raw mill system based on raw mill operating status (CM – combined mode, mills are in operation. or DM – direct mode mills are not in operation), resulting in Hg enrichment in the inner gas stream. Hg was emitted mainly in gaseous form, of which about two-thirds were GOM (gaseous oxidized Hg) and one-third were GEM (gaseous elemental Hg). In the present study, almost 73% of the cement clinker production was carried out with two raw mill regimes, 24% under one mill regime and less than 3% with no mills under operation. The average TGM concentration in the emitted stack gas was lower in CM (23.4 μg/m3) when both raw mills were operational, and moderate (39.5 μg/m3) when only one mill was online. However, the average Hg levels in the flue gas were highest (49.4 μg/m3) when no raw mills were online (DM). TGM concentrations in each individual month were lower under the two-mill regime than in the one-mill regime and highest under the no-mill regime, except in January 2021. Lower Hg levels in January could be due to low cement production rates resulting from the plant maintenance works.
