Rauchgasreinigung Flue Gas Cleaning - Hitachi Power Europe ...

Flue Gas CleaningESP filters and their electrical componentsThe high voltage required to generate the high field intensities is created by one 2- or 3-phasevoltage converter system per filter zone. Every one of these high voltage systems consistsof a high-voltage transformer with power rectifier as well as a phase control for the powersupply of the individual fields of the electrostatic filter.To attain the highest possible filtering effect, the operating voltage must be adjusted to justbarely below the breakdown voltage, which constantly varies depending on the process.For this purpose the control system continually samples the breakdown limit and sensitivelyadjusts the power supply.When dedusting high-impedance dusts, for instance, sometimes a respray behaviour sets inunder certain operating conditions, which considerably lowers the efficiency of the filtrationsystem. Using pulse control operation considerably improves the separation in case of dustparticles that tend to respraying. The efficiency of the electrostatic filter is thus not only improved,but in many cases it is possible to attain significant energy savings as well.A higher-level process control computer monitors the flue gas density throughout the entirededusting process and adjusts the voltage of the individual filter zones to the required separationcapacity. This way, saturation voltages that do not provide any increased performanceare avoided, achieving a maximum separation at the lowest possible energy consumption.The visualization system allows the operating personnel to centrally monitor and operate thecomplete filtration system and individual filter levels, right down to the individual fields of force. Atthe same time, every measured value recorded can be archived by every voltage converter unit.Additionally, by coordinating the rapping intervals of the collecting electrode rapping, aneffective cleaning of the internal components is achieved in combination with an optimumdegree of dust separation. To prevent increased dust emission due to accumulation, onefilter zone at a time undergoes the rapping process at certain times.Flue Gas Cleaning 15