Power conditioning for pulsed electrostatic precipitators

In many industrial applications like coal-fired power plants, cement kilns and sintering plants, electrostatic precipitators (ESP) are the best choice to reduce particulate emissions from the off-gas stream into the environment. Although it is well known that optimization of ESP efficiency in many cases can be achieved by enhancing the static electric field (which is used for both particle charging and precipitation) with short (≈10 μs) high voltage (≈50 kV) pulses, the technical challenges for the realization of a pulsed power generator suitable for industrial use are enormous. We report on laboratory and field experiments of a novel pulse generator using a fast recovery pseudospark switch and high-power semiconductor diodes. The prototype pulse generator is able to drive capacitive loads of over 150 nF, at peak voltages of up to 40 kV, pulse duration of 6 to 10 μs FWHM (full width at half maximum), and repetition rates of over 40 pps. The intentional mismatch between the pulse forming capacitor and the load capacitance reduces the voltage constraints on the switching element by a factor of ≈0.65 while not sacrificing the overall energy efficiency. An efficient energy recovery scheme leads to efficiencies of the order of 90% and above. The pulse generator is able to withstand frequent flashover events in the ESP, with the main limitation in lifetime caused by the high peak current load in the semiconductor diodes during flashover, which can reach up to 8 kA in some cases. Field experiments on sintering plants have shown the suitability of this pulse forming scheme to drive full-scale industrial ESPs.