The advance of methane recovery monitoring equipment technology is helping companies improve safety and generate new revenue. Phil McLean, Senior Engineer at gas sensing specialist Trolex explains the opportunities ahead. Underground mines are the single largest source of coal mine methane (CMM) emissions in most countries, although CMM is also produced from surface mines and as a result of post mining activities such as coal processing, storage and transportation. It is a greenhouse gas that has a global warming potential (GWP) 21 times as great as CO2 thus its escape into the atmosphere is clearly to be avoided. To put the scale of methane emissions into perspective, it is estimated that by 2020 CMM emissions from the world’s coal mines will be some 40 billion m3/y, about a 30% increase from current levels and about 8% of the total methane emissions from human activity.
Removing methane gas from underground coal mines is a necessary safety measure and it is only recently that there has been a realisation that methane is a valuable commodity which can be burnt to create electricity, either for localised use or to be sold on to aggregators. In fact methane can be a big revenue earner as demonstrated by (mining company) UK Coal, which has pioneered the technology, and which in 2007 realised some £4.3 million profit from gas extracted from its mines, and generated enough electricity to power over 40,000 homes.
With the practice of methane drainage for power generation now on the increase, it has become vital to ensure that effective methane recovery monitoring is in place. Accurate continuous monitoring is crucial as changes in gas composition in a system can lead to engine down time and possibly even damage, reducing revenue and endangering both plant and personnel.
McLean on the shortcomings of current methane monitoring methods
Current methane monitoring systems have a number of limitations. They use either thermal conductivity or infrared detectors. Thermal conductivity detectors measure the thermal conductivity of the whole gas sample, giving a collective reading for all the constituents of the gas, not just methane, and are therefore unreliable. Infrared detection specifically looks for carbon-hydrogen bonds in hydrocarbon which provides an ideal means of measuring the methane content. Unfortunately any other hydrocarbon components within the sample will also contribute to the response in an infra-red detector. The heavier the hydrocarbon, the disproportionately greater the effect on the detector response. The complex mixture of hydrocarbons in CMM gas results in significantly higher responses than that due to the methane content alone, and the response can often exceed what would be expected for even 100% methane.
At many mines Gas chromatography is used to analyse the CMM sample gas stream, periodically measuring individual amounts of each component gas. Because samples have to be collected from the gas stream and sent to a laboratory for analysis, and the results then have to be sent back to site, this clearly takes too much time and is far from a continuous measurement process.
New developments in methane monitoring
After much research and development at Trolex a new methane monitoring system has now been introduced which uses infrared detection coupled with a unique method to measure the methane content from the sample on a continuous basis. The way this works is that an initial gas analysis is used to ‘train’ the system and subsequent analysis can be used to fine-tune the system. The contributions to the overall signal from the detector caused by methane and other hydrocarbon gases are evaluated and the methane content is derived from the overall signal and the individual contributions from the different gases. This technique provides a continuous online, high accuracy monitoring capability for methane drainage.
Known as Sentinel, Trolex’s highly accurate new system for methane recovery monitoring is a huge step forward in addressing methane recovery, either as a stand-alone gas-to-energy project, or as part of the Clean Development Mechanism (CDM) and the Joint Initiative (JI) flexible mechanisms agreed under the Kyoto Protocol. It is a fully integrated system with the advantages of maximising safety, meeting legal and regulatory requirements as well as generating new revenue streams, all in parallel.
The scope for new methane monitoring
So what are the wider opportunities which this advanced method of methane monitoring is now helping to facilitate? To give some examples captured methane can be used for purposes such as natural gas pipeline injection, electric power generation, co-firing in boilers, district heating, mine heating, coal drying, vehicle fuel, and manufacturing uses such as feedstock for carbon black, methanol, and dimethyl ether production. For the very low concentration methane in mine ventilation air, technological development has progressed to the point that this CMM source can be oxidised and the resulting thermal energy used to produce heat, electricity, and refrigeration.
The new methane monitoring technology is the result of decades of expertise in gas monitoring, and most systems are bespoke precision-engineered to meet the needs of each individual project in order to maximise performance. Long-term system integrity is also ensured by dedicated support for initial installation and ongoing service.
Even though the Sentinel system is new, the technology has already been installed in two coal mines in the UK and one in China and is being effectively used in a gold mine in South Africa. Most schemes are either approved or registered with the UNFCCC CDM for gas to energy generation, and the system has been proven in dynamic testing conditions by independent authorities.
Now that there are significant advances in methane monitoring technology available, we will undoubtedly see many more projects around the world not only benefiting from increased site safety, but also protecting the environment and generating substantial additional revenue for their organisations at the same time.
Industrea sells more to China
As an example of current interest in methane drainage, Industrea, extending its Chinese growth, has signed A$13.6 million in new contracts with leading Chinese mining companies, Jincheng Blue Flame Coal and Shanxi Changping Coal Mining. The new contracts secured by Industrea’s Chinese subsidiary Wadam are for five AMT directional drilling and methane gas drainage systems, with a total value of A$11.7 million, together with associated spare equipment of A$1.9 million.
The contracts follow orders worth A$7.5 million announced in June and July this year for similar AMT systems, supplied to Jincheng Group’s Sihe mine in the northern Shanxi Province, along with a similar A$2 million contract announced in April for Shanxi Asian American Daning Energy’s (SAADEC) Daning mine in Jincheng.
Industrea Managing Director and CEO, Robin Levison, said the additional orders were secured due to excellent results from the AMT systems installed at the Sihe and other mines, and further boosted the company’s established and longstanding relationships with the Jincheng and Shanxi Mining Groups.
“Jincheng Group has achieved unparalleled levels of gas flow available for energy usage from its current installations of AMT methane gas drainage technology, with the potentially explosive gas extracted from the Sihe mine being used to power a gas-fired electricity plant in Jincheng city,” Levison said.
“In addition to the safety benefits of the system, the technology is providing a safe, reliable and productive energy source to power electrical generation equipment, while delivering substantial reductions in greenhouse gas emissions.
“Jincheng Group is already operating 11 of AMT’s directional drilling and methane gas drainage systems throughout China, with total group coal production of 40 Mt/y.
“SAADEC was the first Chinese user of the AMT technology, and its mine has become a role model for other Chinese mines in successfully removing very high methane gas content from the coal seam.
“AMT’s directional drilling and methane gas drainage system has become the industry standard in China, allowing the typically gassy Chinese coal mines to improve productivity and safety standards significantly,” Levison said. “Leading Chinese mining groups including Jincheng Group, China Shenhua and Shanxi have chosen Industrea’s advanced equipment in recognition of the fact that higher productivity and safety go hand in hand.
“Our commitment to supporting our Chinese customers is reflected in the recent establishment of a product support centre capable of providing a range of product spares along with training and maintenance, and this is delivering recurring revenue streams on top of new equipment orders.
“We anticipate continued growth in our Chinese business in line with the ongoing expansion of the underground coal mining industry.”
