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 coalmines will be some 40 billion cubic metres per annum, 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 very 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 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.

The Need for Accurate Monitoring

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.

Trolex has been developing the new Sentrum system for two years and has now launched the only methane recovery monitoring system that functions across all industries, for all applications, putting the company at the forefront of the Clean Development Mechanism, gas-to-energy and safety monitoring movements. The new systems are able to assist with methane capture for use in 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. In addition, the systems can be used for the very low concentration methane in mine ventilation air, where technological development has progressed to the point that this methane source can be oxidised and the resulting thermal energy used to produce heat, electricity, and refrigeration.  Sentrum utilises proven technology to overcome the traditional problems encountered in monitoring methane and to deliver bespoke, high-accuracy solutions to clients’ specific requirements – allowing them to maximise safety, increase profits, and to comfortably meet legal and regulatory requirements.

How New Systems Overcome Previous Limitations

Current methane monitoring systems have a number of limitations. They use either thermal conductivity or infrared methane gas 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. Infra-red 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. With Sentrum, complex algorithms are used to correct the effects of non-methane hydrocarbons cross-sensitivity, together with mass flow calculations.   It uses infra-red 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.

These new systems for methane recovery monitoring are 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. They are fully integrated systems with the advantages of maximising safety, meeting legal and regulatory requirements as well as generating new revenue streams, all in parallel.

Each Sentrum Methane Recovery Monitoring system is bespoke precision-engineered to meet the needs of an individual project in order to maximise performance. Long-term system integrity is also ensured by dedicated support for initial installation and ongoing service.

Trolex’s Sentrum system has been installed at various locations worldwide including two coal mines in the UK, two coal mines in China and it is also being used effectively in a gold mine in South Africa.  Most schemes are either approved or registered with the UNFCCC Clean Development Mechanism (CDM) for gas to energy generation, and the system has been proven in dynamic testing conditions by independent authorities.

Further information on the new Sentrum methane monitoring technology is available from Trolex Ltd, Newby Road, Hazel Grove, Stockport, Cheshire SK7 5DY, telephone 0161 483 1435, email: or by visiting the company’s website

Trolex Ltd
Newby Road
Hazel Grove
telephone 0161 483 1435