Practical application cases of flue gas purification technology for waste incinerators

A large waste incinerator in Shanghai uses a combined flue gas cleaning process of acid removal with dust filtration, combined denitrification and deep dioxin removal, with emissions controlled to strict local standards.

Combined acid removal and dust filtration

The system combines semi-dry rotary spray drying acid removal with a bag filter. In the rotary spray dryer, lime slurry is sprayed into the flue gas and reacts with acid gases, and the treated gas passes to the bag filter. Acid removal efficiency reaches about 85% and dust removal efficiency 99.9% or more.

Combined SNCR-SCR denitrification

Selective non-catalytic reduction (SNCR) is applied at a suitable point in the incinerator, using urea solution as the reducing agent to lower nitrogen oxides initially; a selective catalytic reduction (SCR) unit further downstream removes more. The combined process achieves a nitrogen oxide removal rate above 80%.

Deep dioxin removal

An activated carbon injection unit is installed ahead of the bag filter, with injection rate and position optimised; a catalytic dioxin decomposition unit downstream breaks dioxins down into harmless substances with a catalyst. With these measures the dioxin emission concentration is held below 0.1ng TEQ/m³.

Results

As Shanghai grew quickly, waste disposal pressure rose, and the plant needed to process waste efficiently while meeting emission limits under national and local rules. After the cleaning technologies were commissioned, particulate emissions fell below 20mg/m³, sulphur dioxide below 100mg/m³ and nitrogen oxides below 300mg/m³.