Coromax® pulse system

Coromax is an advanced high voltage power supply for electrostatic precipitators, designed to capture high resistivity particles emitted by coal fired power plants and sinter strands in steel works. Coromax power supplies overcome back corona problems, decrease dust emission of fine particles and reduce power consumption.

Coromax
  • Overview
  • COROMAX 4
  • COROMAX 3

Pulse energization and lower emissions

The FLSmidth Airtech Coromax® pulse system is an advanced high-voltage power supply for electrostatic precipitators (ESPs). It is designed to capture even the finest high-resistivity particles commonly emitted by coal-fired boilers and steel sintering plants.

This is achieved by generating a special voltage waveform consisting of a smooth base voltage with superimposed narrow pulses. In the figure, the output voltage of a Coromax unit is compared with the output voltage typical for a standard T/R set. The first is generally referred to as ‘pulse energization’, while the second is generally referred to as ‘DC energization’.

The Coromax system dates from the late 1970s, when it was first developed by FLSmidth Airtech in cooperation with the Technical University of Denmark (DTU). After extensive testing in various plants around the world, it was commercially released in the early 1980s. Since then, it has been constantly improved, with the Coromax mk3 released in the early 1990s and Coromax mk4 released in 2007. These two versions are in wide use.

Performance and references

With more than 500 units installed around the world, the Coromax pulse system has become the preferred power supply for coal-fired power plants and sintering plants.

Coromax systems can be installed on new ESPs or retrofitted on existing ESPs to improve efficiency. A Coromax system can typically reduce dust emissions by 30 to 50%, while significantly decreasing power consumption, especially in high-resistivity applications.

Coromax voltage wave

Voltage waveform applied to the ESP (pulse energization)

Coromax® pulse system mk4

Coromax 4

The Coromax pulse system mk4 generates a special voltage waveform on the ESP characterised by a smooth base voltage superimposed by extremely narrow pulses. Like its predecessors, it is designed to capture high-resistivity dust, such as dust emitted by coal-fired power plants and steel sintering plants. High dust resistivity normally leads to high levels of dust emission from ESPs powered by transformer/rectifier (T/R) sets or switch mode power supplies (SMPS).

For Coromax mk4, the base voltage can be up to 60 kV, while the nominal pulse width is 75 µs and its amplitude can be up to 80 kV, for a total maximum peak voltage up to 140 kV. The rated pulse repetition frequency is equal to 100 pulses per second (PPS). In contrast to its predecessor, the pulse generation circuit comprises switching devices in the medium voltage range, which increases the system’s reliability.

Features and benefits

  • Varying the frequency of pulse repetition allows the current to be controlled independently from the voltage, which allows the ESP to operate at a high voltage level while maintaining a low current level, thus eliminating back corona
  • Narrow pulses allow the ESP to reach higher voltage levels, improving the charging and collection of small particles
  • Narrow pulses and the high voltage level cause a more intense corona discharge, which results in better current distribution inside the ESP

Coromax mk4 is controlled by the EPCU, a specially designed microprocessor-based control unit. Using a proprietary and patented control strategy, the EPCU can optimally control the amplitude of the base voltage, the amplitude of the pulses and the pulse repetition frequency. Furthermore, an EPCU can control rapping and heating systems.

Coromax® pulse system mk3

Coromax 3

The Coromax pulse system mk3 generates a special voltage waveform on the ESP characterized by a smooth base voltage superimposed by narrow pulses.
Like its predecessors, it is designed to capture high-resistivity dust, such as dust emitted by coal fired power plants and sintering plant in steel works. High dust resistivity normally leads to high levels of dust emission from ESPs powered by transformer/rectifier (T/R) sets or switch mode power supplies (SMPS).

For Coromax mk3, the base voltage can be up to 60 kV, while the nominal pulse width is 140 µs and its amplitude can be up to 70 kV, for a total maximum peak voltage up to 130 kV. The rated pulse repetition frequency is equal to 100 pulses per second (PPS), but it can operate up to 200 PPS with reduced voltage level.

In contrast to the Coromax mk4, the pulse generation circuit comprises a series connection of switching devices to create a high-voltage switching device.

Features and benefits

  • Varying the frequency of pulse repetition allows the current to be controlled independently from the voltage, which allows the ESP to operate at a high voltage level while maintaining a low current level, thus eliminating back corona
  • Narrow pulses allow the ESP to reach higher voltage levels, improving the charging and collection of small particles
  • Narrow pulses and the high voltage level cause a more intense corona discharge, which results in better current distribution inside the ESP

The Coromax mk3 is controlled by PIACS Coromax, a specially designed microprocessor-based control unit. Using a proprietary and patented control strategy, PIACS Coromax can optimally control the amplitude of the base voltage, the amplitude of the pulses and the pulse repetition frequency. Rapping and heating systems can be controlled by an external programmable logic controller (PLC).