143 Figure 6. Gas compositions of exhaust streams from (a) the first and (b) second stages. The VAMCAP prototype unit was designed, constructed and installed in accordance with relevant Australian Standards to enrich VAM up to a level that is beyond the methane explosive range. The results of site trials at an Australian coal mine site are summarized as below: • With average actual VAM concentrations of 0.57-0.73 vol%, the CH4 concentrations in the final product were 27.65-35.89 vol%, which is 44-63 times enrichment. • The average oxygen concentration in the final product was less than 10 vol%, enhancing the safe operation of the VAMCAP unit • The methane explosive range was successfully avoided during the enrichment process. • There was no sign of the negative effect of high humidity on VAM enrichment. CATAVAM Catalytic oxidation of CH4 completely to CO2 is an effective route to mitigate VAM emissions at a relatively low temperature. The use of a catalyst reduces the VAM mitigator operating temperature below 650 oC, which is well below the stone dust decomposition temperature of above 800-850 oC, thus avoiding sintering and ceramic corrosion with CaO. The lower operation temperature of catalytic mitigation is also beneficial for safety management and the reduction of pressure drop across the regenerative bed, compared to TFRRs operating at much higher temperatures 850-1100 oC. The catalytic oxidation can process a much higher VA flow than thermal oxidation unit, resulting in smaller-size mitigation units and a smaller footprint. The catalytic-version VAM mitigator requires a lower minimum operating methane concentration, making it self-sustained at lower VAM concentrations. CSIRO-developed catalytic VAM mitigator (CataVAM™) is a catalytic oxidation process operating at lower temperatures (450-650 °C). It enables self-sustaining destruction of low levels of VAM below 0.2% methane without external fuel or energy input. At its core is a proprietary honeycomb-shaped catalytic regenerative bed, engineered for high performance and robust deployment in real-world mining conditions. The pilot unit of CataVAM was constructed
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