Alstom power plant - Wastewater treatment plant for wastewater from flue gas desulfurisation - Case Study
In Portugal's largest coal-fired power plant, flue gas desulphurisation creates wastewater which still contains heavy metals, fluoride and ammonia after the separation of the FGD gypsum.
The wastewater is treated with the EnviroChemie physico-chemical Envochem® COL process to maintain compliance with local limit values.
The amount of wastewater that must be discharged from the flue gas cleaning system mainly depends on the chloride content of the coal. The wastewater plant was designed as a two-line system so that the customer's choice of coal is not restricted. If the coal has a low chloride content, it is possible to operate on one line only.
A two-step heavy metal precipitation with separate sludge separation and sludge dewatering was built for each treatment line. This two-step operation allows for the selective separation of the individual heavy metals at an optimal pH value.
An alkaline treatment with subsequent air stripping was implemented for the separation of ammonium, which is carried over from the DENOX stage to the flue gas washing water. The loaded stripping air is fed to incineration.
EnviroChemie planned and constructed the plant on behalf of ALSTOM POWER ITALY.
- Hydraulic performance:: 2 x 25 m³/h
- Discharge values::
- pH: 8.5
- Hg: < 0.02 mg/l
- As: < 0.5 mg/l
- Cd: < 0.1 mg/l
- Pb: < 0.2 mg/l
- Cu: < 0.2 mg/l
- Cr: < 0.4 mg/l
- F: < 10 mg/l
- NH4: < 10 mg/l
- TS in the filter cake: > 45%