Emission and Risk Assessment of Organic Pollutants in the Co-combustion Process of Oil-based Cuttings in a Circulating Fluidized Bed

To investigate the emission characteristics of organic pollutants during the co-combustion of oil-based cuttings and evaluate the environmental and health risks associated with this process, co-combustion experiments were carried out on a 600 MW circulating fluidized bed boiler. The emission concentrations of organic pollutants in the products were analyzed, and health risks were assessed using the incremental lifetime cancer risk model and the health standard model. Experimental results reveal that the emission concentrations of polycyclic aromatic hydrocarbons (PAHs) and dioxins (PCDD/Fs) are extremely low under all operating conditions. After co-combustion with oil-based cuttings, the increased chlorine content in the furnace lead to a 29% reduction in PAHs concentrations in the flue gas. Compared with low-load operating conditions, higher PAH concentrations are observed in the flue gas under high-load co-combustion conditions, as the elevated temperature promotes the formation of PAHs. Relative to the baseline condition, the toxic equivalent concentrations of dioxins in the flue gas decrease by 25% and 60% under low- and high-load co-combustion conditions, respectively, as the higher sulfur content in oil-based cuttings is found to be unfavorable for dioxin formation. The health risk assessment results indicate that, under high-load co-combustion conditions, PAHs in the fly ash could pose a potential carcinogenic risk to individuals of all age groups, while the carcinogenic and non-carcinogenic risks associated with dioxins in the fly ash remain below the relevant threshold values.