Flue gas refers to the combustion exhaust gases produced when fossil fuels such as coal, diesel, natural gas, or heavy fuel oil are burned in furnaces, boilers, kilns, or other industrial combustion equipment used across mining operations. In bauxite mining and processing, flue gas is generated during the calcination of alumina hydrate in rotary kilns, where temperatures exceed 1,000°C. In gold mining, flue gases arise from roasting refractory ores to oxidize sulfide minerals before cyanide leaching. Iron ore sintering and pelletizing plants produce significant quantities of flue gas due to high-temperature agglomeration processes. Diamond mining operations generate flue gases primarily from diesel power generators, heavy earth-moving equipment, and processing plant boilers.
Flue gas typically contains nitrogen (N₂), carbon dioxide (CO₂), water vapor (H₂O), oxygen (O₂), sulfur dioxide (SO₂), nitrogen oxides (NOₓ), carbon monoxide (CO), particulate matter, and trace heavy metals. These constituents pose significant environmental and human health risks if released untreated into the atmosphere. Regulatory frameworks in most mining jurisdictions require flue gas monitoring and treatment through technologies such as electrostatic precipitators, fabric filters (baghouses), wet and dry scrubbers, selective catalytic reduction (SCR), and flue gas desulfurization (FGD) systems.
Flue gas management is critical to a mining operation's environmental compliance program and contributes directly to greenhouse gas accounting and carbon footprint calculations. Modern operations implement continuous emissions monitoring systems (CEMS) to track real-time flue gas composition, enabling prompt corrective action when emission thresholds are approached. Heat recovery from flue gases through waste heat boilers or heat exchangers is increasingly practiced to improve overall energy efficiency and reduce operational costs at processing facilities.