The HWI process
Waste handling and inputs:
Hazardous waste incinerators are designed to handle and destroy the most difficult hazardous (explosive and/or toxic) substances.
Hazardous waste incinerators have specialized systems for the input of waste material, depending on the type of waste being handled. This is particularly important for some of the most hazardous and toxic wastes.
Options include a solid waste bunker, a tank farm for liquid and pasty wastes, drum storage and transportation facilities. For certain (highly reactive) wastes, a dedicated direct injection system is necessary.
Hazardous waste incinerators are generally of a rotary kiln design. This type of kiln ensures a more comprehensive combustion of waste than is possible with static kilns.
After the rotary kiln itself, there is a secondary combustion chamber. The design of a secondary combustion chamber ensures that waste is incinerated at a minimum of 1100°C for at least 2 seconds, leading to the complete destruction of organic substances. It is also possible to inject waste directly into this post-combustion chamber.
Energy is recovered in several ways in a hazardous waste incinerator. It is destined for direct use of heat in other parts of the process (e.g. flue gas cleaning, re-heating of gases passing through the bag filter), for generation of electricity or in some cases for direct use of heat/steam for other industrial processes or for district heating (NB: viability depends on local climatic conditions).
Flue gas cleaning:
There are many options for flue gas cleaning systems in hazardous waste incinerators, but they typically consist of a combination of:
- DeNOx systems for the reduction of Nox emissions
- Dust removal systems (e.g. electrostatic precipitator or bag filter)
- Gas scrubbing systems, using water or reagents for the removal of dioxins, heavy metals and acid gases (e.g. HCL and SO2)
- Carbon filters for the capture of remaining dioxins, heavy metals and acid gases
After the clean-up phase, the emissions are checked by sophisticated monitoring and analysis instruments to ensure that the emissions are below the plant’s permitted discharge consent levels. Finally, the cleaned gas is discharged via a chimney stack.