What are the pollution emission control standards for waste incinerators?
Pollution emissions from municipal solid waste incinerators follow the Standard for Pollution Control on the Municipal Solid Waste Incineration (GB18485-2014). The content covers flue gas limits, combustion conditions, odour and wastewater control, and the handling of slag and fly ash.
Flue gas emission limits
For particulate matter in flue gas the 1-hour mean limit is 30mg/m³ and the 24-hour mean is 20mg/m³; for sulphur dioxide the 1-hour mean is 100mg/m³ and the 24-hour mean is 80mg/m³. For nitrogen oxides the 1-hour mean is 300mg/m³ and the 24-hour mean is 250mg/m³; for hydrogen chloride the 1-hour mean is 60mg/m³ and the 24-hour mean is 50mg/m³. For carbon monoxide the 1-hour mean is 100mg/m³ and the 24-hour mean is 80mg/m³.
The limit for dioxins is 0.1ng TEQ/m³. Among heavy metals, mercury and its compounds (as Hg) are limited to 0.05mg/m³, and cadmium, thallium and their compounds (as Cd+Tl) to 0.1mg/m³. Antimony, arsenic, lead, chromium, cobalt, copper, manganese and nickel and their compounds (as Sb+As+Pb+Cr+Co+Cu+Mn+Ni) are limited to 1.0mg/m³.
| Pollutant | 1-hour mean | 24-hour mean |
|---|---|---|
| Particulate matter | 30mg/m³ | 20mg/m³ |
| Sulphur dioxide | 100mg/m³ | 80mg/m³ |
| Nitrogen oxides | 300mg/m³ | 250mg/m³ |
| Hydrogen chloride | 60mg/m³ | 50mg/m³ |
| Carbon monoxide | 100mg/m³ | 80mg/m³ |
Dioxins and heavy metals follow the limits in the table below. These limits make no distinction between 1-hour and 24-hour means.
| Pollutant | Emission limit |
|---|---|
| Dioxins | 0.1ng TEQ/m³ |
| Mercury and its compounds (as Hg) | 0.05mg/m³ |
| Cadmium, thallium and their compounds (as Cd+Tl) | 0.1mg/m³ |
| Antimony, arsenic, lead, chromium, cobalt, copper, manganese, nickel and their compounds | 1.0mg/m³ |
Combustion conditions
The incineration temperature in the furnace must not be below 850℃, and flue gas in the secondary combustion chamber must stay at no less than 850℃ for at least 2 seconds, so that harmful substances decompose fully. Flue gas must also stay turbulent with moderate excess oxygen so the incineration system runs at rated duty, raw pollutant concentrations stay at a low level, and dioxins and other organic substances decompose completely. Temperature and residence time depend mainly on furnace geometry and secondary air arrangement, and operation generally uses furnace temperature measuring points and flue gas oxygen content as the basis for adjustment.
Odour and wastewater control
Waste transport should use compactor trucks with good sealing and an automatic loading and unloading structure, to keep odour from escaping. Air curtains are fitted at the inlet and outlet of the tipping hall, and the electric tipping doors are closed before and after the truck discharges so that odour does not escape. The waste pit is of sealed design with extract hoods above, drawing odorous gas as combustion air into the incinerator for high-temperature destruction and keeping the pit and the tipping hall under negative pressure. During plant-wide shutdown for maintenance, pit odour must pass through the standby activated carbon gas cleaning unit and be discharged only after meeting the standard.
Wastewater comes mainly from waste leachate and from washing of the tipping hall and vehicles, and must be treated to meet discharge limits, generally those of the Integrated Wastewater Discharge Standard (GB 8978-1996). Chemical oxygen demand, biochemical oxygen demand, ammonia nitrogen and suspended solids all have corresponding limits.
Slag, fly ash and monitoring
Slag can be comprehensively utilised after high-temperature harmless treatment and magnetic separation, and the part that cannot be used goes to a sanitary landfill. Fly ash collection, storage and treatment units should stay sealed; when flue gas cleaning uses dry or semi-dry deacidification, the fly ash treatment system needs measures such as mechanical deacidification, and fly ash is managed and disposed of as hazardous waste. The incinerator should have on-line monitoring of operating conditions, covering at least combustion temperature, furnace pressure, outlet oxygen content and carbon monoxide content, with a board in a prominent position showing the main parameters and the on-line monitoring data. Automatic continuous flue gas monitoring should cover at least hydrogen chloride, carbon monoxide, dust, sulphur dioxide and nitrogen oxides, and transmit data in real time to the local sanitation and environmental protection authorities.
During operation, management rules should be kept in order, waste storage should be monitored regularly and leachate drained off. The authorities concerned carry out regular inspections and random checks, and emissions above the limits are penalised by law with a deadline for correction.
