139 approximately 8-21 kWe of electricity (Figure 2). Figure 1. VAMCAT unit installed at Appin Coal mine in Australia: (a) site infrastructure - safe ducting system and (b) VAMCAT unit. VAMMIT Thermal flow reversal reactor (TFRR) is the most mature technology for VAM abatement through thermal oxidation of methane at high temperatures above 850 oC. The TFRR technology employs the flow-reversal principle to transfer combustion heat to a solid medium, and then back to incoming ventilation air to raise its temperature to the ignition temperature of methane oxidation. CSIRO’s VAM mitigator (VAMMIT) uses a similar operational principle and configurations to the existing TFRRs but it includes a novel bed structure. As shown in Figure 3(a), the VAMMIT unit is mainly composed of (1(1) a novel regenerative bed made of honeycomb ceramic blocks and an innovatively designed flow diverting section that is connected with a start-up burner for easy start-up and a bursting disc for safety management, (2) two VA flow direction switch cylinders that periodically switch the flow direction of VA, and (3) a start-up burner, where liquified petroleum gas (LPG) is burnt to produce hot flue gas to preheat the regenerative bed. The novel honeycomb monolith bed has a square cross section and is made of ceramic honeycomb monolith blocks. The heat exchange, flow reversal and methane oxidation of VAMMIT take place in the individual passages of honeycomb monolith blocks as illustrated in Figure 3 (a). This can significantly reduce the operational and maintenance costs such as power consumption, regenerative bed cleaning and shutdown time due to the elimination of dust deposition inside the bed. The specific heat transfer surface area for the VAMMIT is 880 m2/m3, which is significantly higher than 400-600 m2/m3 of a packed bed and much higher than 30-85 m2/m3 of a chequer brick bed. Hence, it is more compact and has a smaller footprint compared to other reactors. (a) (b)
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