Emissions of non-methane hydrocarbons and typical volatile organic compounds from various grate-firing coal furnaces

Non-methane hydrocarbons (NMHCs) and volatile organic compounds (VOCs) emitted from grate-firing coal furnaces cause serious harmful impacts on the atmospheric environment and human health. To investigate the effects of coal type and grate-firing mode on the emissions of NMHCs and VOCs, four different coal fuels (i.e., bituminous coal (BC), bituminous briquette (BB), anthracite briquette (AB) and semi-coke (SC)) were burnt in three typical grate-firing modes (i.e., updraft mode (UDM), downdraft mode (DDM) and cross-draft mode (CDM)). Offline GC-MS (Gas Chromatography-Mass Spectrometry) analyses show that the mass of benzene and toluene accounts for more than 60% of the total amount of quantifiable benzenoid compounds under the smoldering condition, and up to almost 100% under the flaming condition. The BB burnt in the CDM produces lower NMHCs and VOCs than in the other two modes and the SC burnt in the three modes yields the lowest NMHCs and VOCs among the four coal fuels, as further clarified by online FTIR (Fourier-Transform Infrared spectroscopy) measurements. Combustion mode was found to have a prominent impact on the NMHCs and VOCs emissions in household coal stoves. The NMHCs emission factor determined by the GC-MS measurements under the flaming and smoldering stages is inversely proportional to combustion efficiency. The average VOCs emission factor calculated from the FTIR measuring data inversely varies with combustion efficiency too.

Automated summary

The study finds that coal type and combustion mode have significant impacts on NMHCs and VOCs emissions in household coal stoves. Benzene and toluene account for more than 60% of the total quantifiable benzenoid compounds in the smoldering condition and almost 100% in the flaming condition. The cross-draft mode results in lower VOC emissions compared to the other two modes, and the semi-coke fuel yields the lowest NMHCs and VOCs emissions among the four coals regardless of the combustion mode.