Waste incineration plants are highly complex facilities. They not only incinerate material but also use many different chemical processes, the majority of which are for cleaning the flue gases. These ensure that the waste incineration operations are kept clean. GMVA, therefore, needs a number of different raw materials for its various incineration and cleaning processes.
We use heating oil to heat up a boiler again after it has been cleaned or inspected – something that normally happens once a year. German law (‘17. BImSchV’ /17th Ordinance of the Federal Emissions Control Act) stipulates that a boiler must be heated up to the right operating temperature before waste may be added. All in all, the amount of energy provided by this heating oil represents just 0.2% - 0.4% of the total heat of combustion. Waste, therefore, is the main source of energy, lying at around 99.7%.
The so-called selective non-catalytic reduction process (SNCR) is the first part of our five-stage flue gas cleaning system. This is where an ammonia solution is injected into the boiler. This urea or ammonia solution causes a chemical reaction that converts the nitrogen oxides (NOx) into nitrogen and water. This procedure reduces the amount of nitrogen oxides by up to 80%.
Once the particulates have been extracted from the flue gases in the electrostatic precipitator, the gases are fed through the HCI scrubber. The flue gases contain hydrogen chloride – produced for example as a result of incinerating PVC material – and this is removed by the HCI scrubber. The milk of lime keeps pH levels at <1. Moreover, these conditions are just right for extracting heavy metals, in particular mercury, from the gases. We also use milk of lime in our wastewater treatment system to precipitate and neutralise our wastewater.
Any sulphur dioxide is absorbed by the sodium hydroxide solution in the SO2 scrubber, the fourth stage of our flue gas cleaning system. Sodium hydroxide solution is also used in our ion exchanger to regenerate the anion exchanger.
Additional adsorbents are injected into the flue gases during the final stage of the flue gas cleaning system (fabric filter) to remove any remaining heavy metals, dioxins and furans as well as other organic and inorganic pollutants. These pollutants are attracted to the adsorbent enabling them to be filtered out and separated as residue.
Our ion exchanger produces demineralised water for our water/steam circuit. The hydrochloric acid is used to regenerate the cation exchanger in our ion exchanger facility.