134 (A) Ancillary use, where VAM is added (auxiliary) to power equipment, where the high combustion temperature is provided by another base fuel. (B) Principal use, where VAM is the primary or even sole fuel. Category (A) includes those solutions in which the ventilation air would replace the atmospheric air introduced in known combustion methods (Deng et al., 2018). Thus, (Su et al., 2005) mentions gas turbines, internal combustion engines, as well as (basically primarily) coalburning power plants and heating devices. It seemed, that such solutions would be the simplest and cheapest in terms of investment and operation. However, it quickly turned out that these ideas were more theoretical than practical. The ventilation shaft emits several hundreds of thousands of m3 /h of ventilation air. In Poland, there are shafts operating at flows significantly exceeding one million m3 /h. In order to use such large streams large power plants of at least several hundred MW, would have to be located a short distance from the mine (maximum distance up 6 km (Chen et al., 2015). This condition is difficult to meet, although the supply of local heat plants with at least a part of the ventilation air should be taken into account. Category (B), in which VAM is the basic fuel, mainly includes the so-called flow reverse reactors, although (Su et al., 2005) also mentions recuperative gas turbines, catalytic combustion turbines, and monolithic recuperative reactors (CMR). A more recent publication (Warmuziński et al., 2004) shows that solutions using turbine combustion, to be effective, may require upgrading VAM to higher concentrations. Currently, in the literature on VAM utilization, the most attention is paid to reverse reactors, search for new catalysts, and enrichment of VAM. Figure 3. Illustrative diagram of CMM source and typical drainage gas and VAM flows in the mine.
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