Removing methane gas from underground coal mines is a necessary safety measure and the realisation that methane is a valuable commodity that can be burnt to create electricity, either for localised use or to be sold on to aggregators, has encouraged the uptake of methane recovery systems.
Methane can be a big revenue earner as demonstrated by UK Coal, which has pioneered the technology, and which in 2011 generated around 105 000 MW of power, enough electricity to power over 32 000 homes. That highly valued profit for the company was realised from just four operational sites.
With the practice of methane drainage for power generation increasing, accurate continuous monitoring is crucial as changes in gas composition inherently affect the satisfactory and efficient running of plant and equipment, reducing revenue and possibly endangering both plant and personnel.
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. In addition, the systems can be used for the very low concentration methane in mine ventilation air, known as VAM systems, 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.
Catalytic gas sensing cells have limitations when higher concentrations of gas need to be monitored, negating their use for utilisation and drainage applications. The introduction of infrared detectors allows for monitoring up to 100% v/v.
Mine gas is made up of a number of different hydrocarbons, the complex mixture of hydrocarbons in CMM gas results in significantly higher responses than that due to the methane content alone, and this value can often exceed what would be expected for even 100% v/v methane.
The combination of using infrared detectors and mass flow monitoring devices, in conjunction with complex algorithms containing gas sample constituent analysis detail, provide the most reliable detailed information for methane monitoring and utilisation.
Such systems for methane recovery monitoring are either approved or registered with the UNFCCC Clean Development Mechanism (CDM) for gas to energy generation.
Written by Dave Vernon, Trolex Ltd
Edited by Callum O'Reilly
Read the article online at: https://www.worldcoal.com/coal/21102013/trolex_methane_monitoring_and_recovery/
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