World’s First Large-Scale Testing Facility for Assessment of VAM Abatement Systems

A major source of greenhouse gas emissions is low concentration methane in mine ventilation air streams from coalmines (i.e. VAM). The capture and use of VAM is considered the most effective means of mitigating such fugitive methane emissions. However, VAM is a difficult feedstock due to its high flow rates (~600 m3/s), low and variable methane concentrations (<1%), coal dust content and the explosive nature of hybrid methane / coal dust mixtures. The principal vision in this project was to develop large-scale capabilities for assessing the effectiveness of VAM abatement systems / components in resolving the above technical and safety challenges.

The solution was to build a large-scale detonation tube facility (also referred to as the large-scale demonstration VAM capture duct) with a modular design where VAM abatement systems and components (e.g. capture ducts, explosion prevention / mitigation measures, thermal oxidisers) can be tested and subjected to a variety of operating scenarios including controlled methane / coal dust explosions. The corresponding responses of VAM abatement systems and components in mitigating fugitive methane emissions can then be accurately measured and analysed, allowing their effectiveness to be quantified at full-scales under realistic conditions.

The large-scale testing facility designed and built as part of this project would facilitate the development of more scalable and safer VAM abatement systems. This, in turn, should facilitate a greater uptake of such technologies by the coal mining sector leading to significant reductions in fugitive methane emissions. As an example, If 50% of NSW gassy coalmines are fitted with VAM abatement systems optimised using the above large-scale testing facility, approximately 33% reduction in annual fugitive emissions and 4% reduction in total annual emissions will be achieved in NSW (equivalent to the annual CO2 emissions from ~1 million passenger cars).

The large-scale detonation tube (or VAM demonstration capture duct) facility is an open ended continuous flow duct complex located at Testsafe site, Londonderry NSW. The facility is approximately 100 m long and consists of a 2 m diameter duct and two smaller 0.5 m diameter tubes of modular designs constructed as pressure vessels (36 modules). The duct airflow moves in one direction only through to the 0.5 m diameter tube and exits the stack at the far end. Methane is supplied by large LNG vessels and coal dust (if needed) is injected by a specialised hopper and auger with positive pressure supplied from compressed air. The tube is designed to withstand an explosion pressure rise of 60 bar. The facility is fitted with a range of explosion mitigation systems including vent panels, high speed isolation valves, passive isolation valves, a hot water suppression, a powder suppression and a detonation arrester. Several of these systems can be used in combination to provide a system with explosion protection across all possible scenarios. The system is fully automated and instrumented and has been fitted with an array of sensors / detectors including 200 pressure transducers and 180 photodiodes.