New CSIRO technology that destroys methane at mine sites is showing great promise – and attracting great interest from industry and governments worldwide, the organisation says.
Released from coal during the mining process, methane is a highly explosive gas and therefore a serious safety concern in coal mining.
Underground coal mines use large-scale ventilation systems to move fresh air into the mine to flush out methane and other gases. This dilutes methane in the mine to make working conditions safer. However, ventilation air methane (VAM) is then released into the atmosphere, significantly adding to fugitive greenhouse gas emissions.
Dr Yonggang Jin, Team Leader for Environment and Sustainability within CSIRO’s Mining Research and Development Program, explained: “Over 60% of emissions from coal mining is from VAM. VAM emissions account for about 15% of total Australia methane emissions and about 4% total greenhouse gas emissions.”
Atmospheric methane levels have more than doubled since pre-industrial times, largely due to human activity. As methane is much more potent than carbon dioxide per molecule in trapping heat in the atmosphere, this is an important environmental issue.
With this in mind, CSIRO researchers have been developing a suite of three patented technologies that mitigate methane emissions at mines:
- VAMMIT the destroyer is a methane mitigation unit with a compact flow reversal reactor and regenerative bed that destroys methane;
- VAMCAP the concentrator is a capture and enrichment unit that collects and separates methane from ventilated air using carbon composites; and
- VAMCAT the generator uses a catalytic combustion gas turbine to create electricity from captured methane, creating energy from a mining waste product.
In particular, a novel catalytic VAMMIT unit has recently shown great potential for addressing safety and environmental concerns, with, in December 2023, Yonggang and his research team completing a world-first pilot scale trial of a catalytic VAMMIT unit at an Australian mine, funded by Coal Innovation New South Wales. This mine site is understood to be the Appin coal mine.
While successful, this trial highlighted technical and economic limitations that would prevent the unit’s large-scale adoption, so this year, Yonggang’s team fast-tracked changes to address these limitations.
With funding from the Department of Industry, Science and Resources, they developed a prototype catalytic VAMMIT unit with a unique honeycomb-shaped catalytic regenerative bed. This optimised design was recently tested in a small-scale pilot trial at CSIRO’s Queensland Centre for Advanced Technologies (QCAT), with outstanding results, CSIRO claims.
Catalytic VAMMIT keeps its cool
The enhanced catalytic VAMMIT unit shows several distinct advantages over its predecessor, regenerative thermal oxidiser (RTO) VAMMIT.
Significantly, catalytic VAMMIT achieved self-sustaining destruction of VAM with 0.15–0.4% methane, compared with RTO VAMMIT that can only destroy methane above 0.3% VAM.
This makes catalytic VAMMIT more suitable for Australia’s low level VAM conditions. It also achieved this at significantly lower temperatures than RTO, making it safer and more economical to run, according to the company.
Dr Marc Elmouttie, Acting Research Director for the Sustainable Mining Technologies Program, said: “A big benefit of catalytic VAMMIT is the ability to deal with the lower concentration methane. When it’s at higher concentrations, you can utilise it or you can flare it. When it’s at low concentrations, that’s a technically challenging thing.”
The catalytic VAMMIT unit has around five times the throughput capacity of the RTO VAMMIT unit, despite being smaller and requiring less power consumption. It also has a much lower pressure drop, at around one-third the pressure of RTO VAMMIT. This means it is more efficient and economical to operate, and produces less GHG emissions itself, CSIRO says.
However, arguably its most important advantage is its lower operational temperature of between 450 and 600°C, compared with RTO VAMMIT’s operational temperature of around 1,000°C. This not only enhances workplace safety, but also significantly reduces operational costs.
Yonggang says: “The first benefit is a lower safety risk with the lower temperature. There is a reduced risk of ignition of methane in the mine. With high temperature, air expands and a larger volume goes through the reaction bed. With a lower temperature there is lower pressure and reduced operating costs for electricity to drive the fan to push air through the reactor.”
A lower operational temperature also helps to maintain the unit, reducing risk of sintering (forming solid mass through heat or pressure, without melting it) and ceramic corrosion.
Catalytic VAMMIT has potential to not only improve industry conditions and efficiencies but could also play a key role in helping the Australian Government achieve its Net Zero Plan. This plan aims to reduce domestic emissions by 43% of 2005 levels by 2030, and reach net zero greenhouse gas emissions by 2050.
Catalytic VAMMIT could also play a key role in achieving the Global Methane Pledge. Under this pledge, more than 120 countries, including Australia, committed to collectively reducing global methane emissions across all sectors by at least 30% below 2020 levels by 2030.
The urgent need for this sort of technology has led CSIRO to explore a rapid commercialisation pathway for catalytic VAMMIT.
Yonggang says: “We are already starting to explore opportunities and working with potential commercial partners for full-scale development. If everything’s successful, we can come to some arrangement to commercialise and bring our technology to the market fully.”
Yonggang and his team are currently refining catalytic VAMMIT to improve heat and mass flows to optimise performance, and further lower the pressure drop at high ventilation air flow rates. They plan to start a full-scale catalytic VAMMIT trial at a New South Wales coal mine this month.
“We really want to fast track the commercialisation of this, because if this technology has been fully demonstrated on-site, and has been taken up by industry, we can simultaneously reduce net carbon emissions and safety risks,” Yonggang said.
