Evaporator/Crystallizer Combined with Salt Exchange Pretreatment is the Answer for this Demonstration Plant.
A major European utility has several power block units fitted with wet limestone FGD scrubbers at their 600 MW power station in southern Germany. The blowdown from the scrubbers is treated to remove the heavy metals and suspended solids. The blowdown is discharged into the adjacent Rhine River.
Future new power block units and retrofit of some existing units in Germany will be subjected to stricter environmental permit regulations. The utility was looking for new technologies to make their power station more environmentally sound. One waste stream they wanted to eliminate from discharging into the river was the FGD scrubber blowdown. Although already treated, physically and chemically, the blowdown still contained high concentrations of chlorides and nitrates.
After thorough evaluation of the problem and possible alternative solutions, the utility selected the team of Philipp Müller and Aqua-Chem ICD to provide a zero discharge demonstration plant. Philipp Müller, Aqua- Chem ICD ’s joint venture partner for FGD wastewater treatment plants, has provided over 20 heavy metal reduction plants to power plants. Additionally, for this current treatment plant, they provided the pretreatment system which removes the magnesium and converts calcium to sodium ions. This allows the evaporator/ crystallizer to produce a final product salt purity > 97% for use in cation exchangers.
The evaporator and crystallizer system was designed with the flexibility to handle sodium chloride or calcium chloride based solutions, either unseeded or seeded with gypsum. With the high grades of materials used (i.e. titanium, Hastelloy, Alloy 20), it can handle a wide range of chemistries, concentrations and temperatures. It also has many built-in automation features to reduce operator attention.
The demonstration plant was fabricated in the USA and in Germany. It began operation in the spring of 1993. Several different trials were made to demonstrate the optimum performance and operating characteristics.