A perfectly tight turbine condenser and long-term operation of the unit, turbine condensate of high quality is also consistently obtained. Even after injection of make-up water (which is usually no more than 2% of the feedwater) into the condenser and with the condenser connected to the pump, feedwater with an oxygen content below 200 µg O2/l can be obtained with other impurity contents that ideally already meet the feedwater standard. It is then only necessary to degas this feedwater in a pressurized thermal degasser at 0.5-0.8 MPa.
A dramatic increase in all pollutants of the turbine condensate occurs when the unit is started up, even after a short boiler shutdown. The values of impurities in the condensate increase by a factor of 20 compared to continuous operation. The materials used are very important here. If they are not corrosion-resistant, the iron and copper content in particular rises significantly. These form the aforementioned very undesirable porous deposits on the boiler's boiler tubes. The aim is then to clean the block of corrosion products as soon as possible by increased scrubbing and scaling and to connect the turbine and generator to the grid.
With time, condenser leaks will periodically start to appear. It is therefore advisable to ensure that the turbine condensate is fully treated. This full-flow cleaning of the turbine condensate is economically worthwhile in terms of reduced boiler surface blow down as well as reducing maintenance costs for the entire unit and extending its overall life.
High-flow float filters are used to treat the turbine condensate (cellulose is most often used as the float medium, less often perlite...). Ionex filters or filters with dust ionexes are classified as float filters. The purpose is to remove corrosion products, impurities due to leaks and impurities during commissioning to prevent the formation of deposits on the turbine blades and corrosion in the steam circuit.
Benefits
- Excellent quality of treated condensate
- Minimisation of deposits and corrosion in the steam circuit
- Improved operating economy
