Maximum recovery of energy and materials
Indaver processes the non-recyclable fraction of non-hazardous household and similar industrial waste at temperatures exceeding 900 °C in its three grate incinerators.
The process is designed to achieve maximum recovery of materials and energy. The thermal processing plant is equipped with an extensive flue gas cleaning system. The energy present in the hot flue gasses is recovered during the energy recovery process which takes place in the steam boiler and steam condensate network. The steam boiler is made up of a vast number of pipes filled with water. The hot flue gasses pass through the steam boiler, heating the boiler water in the process which is then converted into steam.
The steam drives a steam turbine which produces electricity. This is then fed into the electricity grid. Some of the steam is not converted into electricity, but is instead supplied directly to neighbouring company Ineos Phenol which uses the steam in its production processes.
Recovery of materials
In addition to energy, Indaver also recovers as many materials as possible from the waste. The following materials are recovered from the ash treatment plant on the site:
- Metals: uses are found for ferrous and non-ferrous metals alike (iron, aluminium and so on) via the scrap metal industry.
- Aggregates: are used in the construction industry, including for road sub-bases and other structures.
- Sand fractions: are used for construction or stability applications at landfill sites.
Extensive flue gas cleaning system
Once the waste has been incinerated and the heat has been recovered from the flue gasses, the flue gasses need to be treated. The flue gas scrubbing consists of a semi-wet cleaning and wet scrubbing. During the semi-wet cleaning process, the flue gasses in the spray dryer are cooled down to 160 °C using water from the downstream wet scrubbing; salts and dust particles in the baghouse filter are removed from the flue gas stream. At the same time, activated carbon is injected. Dioxins and heavy metals are adsorbed into the pores of the activated carbon, which, like the salts and the dust particles, are trapped in the baghouse filter. During wet scrubbing, the flue gasses are cooled to approx. 60 °C and are washed intensively through spraying at various levels. By adding other substances (lime and limestone), any impurities present are converted into harmless residual products, such as gypsum. Given that the water from the wet scrubbing is reused during the semi-wet cleaning process, the plant has no wastewater. So no water is discharged!