The Conversion of Methane from Coal Mines to Chemicals

This report was commissioned to assess the potential for targeted R&D programs to lead to opportunities for commercial use of coal mine methane as a feed gas for chemicals production.  It broadly concludes that such opportunities are limited at best.

Synthesis routes from natural gas are reviewed and considered in the light of probable yields of methane from coal seam locations.  Aside from combustion, methane processing in general is limited to synthesis gas (syngas) or pyrolysis routes.  Potential products from these include synthetic fuels (synfuels), methanol/dimethyl ether, acetylene/unsaturates and ammonia/ammonium nitrate.

Coal seam methane presents additional limitations in terms of supply volumes, location and continuity of supply.  The average mine production of coal seam methane is of the order of 70,000 m3/day.  The value of any chemical products synthesized must exceed on site use of the methane (possibly as electricity) or sale to the grid (as gas or electricity) for mines located in such positions, as well as justify the capital cost of the plant.  For remote mines, the end use of the product on site will also need consideration.

Methanol and dimethyl ether can be manufactured from syngas, but require large plants for economy of scale.  Research is continuing into the synthesis of these chemicals, however it is unlikely to affect the economics to any large extent.

Ammonium nitrate appears more favourable economically, however the demand for this explosive needs to be considered.  Ammonium nitrate manufacture is a mature process and unlikely to benefit from further research.

Methane pyrolysis to synfuels and chemicals offers the advantage of a smaller plant size and research opportunities exist for improving the catalytic processes involved.  Capital costs for the plant, although more favourable compared to other routes, remain high due to the low volumes of methane available as feed gas.