Ventilation
air methane (VAM) mitigation has been challenging to
the coal mining industry because (1) VAM represents the largest proportion
of coal mine methane emissions, (2) its air volume flow rate is large
and the methane concentration is dilute and variable, and (3) it is
almost 100% moisture saturated, and contains dust. This paper presents
a novel pilot-scale VAM mitigator (VAMMIT) with a newly structured
regenerative bed consisting of honeycomb monolith ceramic blocks for
VAM destruction. The bed is designed to process 0.5–1 N·m3/s ventilation air. For the first time, a series of site trials
of the VAMMIT prototype unit using actual ventilation air (VA) with
0.25–1.0 vol % methane was successfully carried out at an Australian
coal mine site. The site trial results showed that the VAMMIT unit
was able to operate as a thermal flow reversal reactor and was self-sustainable
at VAM concentrations between 0.3 and 1.0 vol %. The pressure drop
across the regenerative bed was 853–923 Pa, implying the potential
to significantly reduce the energy consumption and VAM abatement cost.
Regardless of the inlet VAM concentrations, less than 0.02% CH4 was measured in the flue gas. On average, over 96% of methane
oxidation efficiency was achieved through the novel regenerative bed.
The influence of dust on the mitigator’s performance was found
negligible through a 2-week site trial with actual VA only. The VAMMIT
unit is the first of its kind in the world, possessing significant
advantages over other packed-bed mitigators in terms of no dust deposition,
less footprint, and lower energy consumption.
Current
utilization practices have not fully appreciated the potential
of coal mine drainage gas and have resulted in significant greenhouse
gas emissions. This paper introduces a novel pathway of using coal
mine drainage gas, regardless of its methane concentration, as a chemical
feedstock for ammonia syngas production without CO2 emissions.
The new pathway employs an enrichment process for concentrating drainage
gas with low to medium CH4 concentrations and a sorption-enhanced
autothermal reforming (SE-ATR) process for ammonia syngas production
with in situ CO2 capture. Experimental
results for the enrichment process showed that the CSIRO-developed
single-stage adsorption process was able to concentrate drainage gas
with 4.5 and 20.3% methane to 31.7 and 79.3%, respectively. Autothermal
reforming (ATR) tests with a 30% CH4/air mixture using
two commercial Ni-based catalysts demonstrated that, as the operating
temperature decreased, the methane conversion rate decreased, while
the CO2/CO molar ratio increased, leading to an almost
constant H2 concentration (∼45–47% on a dry
basis) in the product. With CaO as CO2 sorbents, the SE-ATR
process further took the water–gas shift reaction to a complete
extent at 600 °C through in situ CO2 capture and, thus, led to a completed methane conversion and a syngas
product with a H2/N2 molar ratio of ∼3:2.
When the CO2 sorbent became saturated, the SE-ATR test
evolved to an ATR process. The experimental results for both ATR and
SE-ATR tests were close to the thermodynamic equilibrium values. The
H2/N2 ratio in the syngas can be further tuned
to produce ammonia, which is a valuable commercial commodity with
various favorable attributes and a H2 carrier for safer
transportation and storage.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.