In the simplest terms, a precipitator is a large box. The dust laden gases are drawn into one side of the box. Inside, high voltage electrodes impart a negative charge to the particles entrained in the gas. These negatively charged particles are then attracted to a grounded collecting surface which is positively charged. The gas then leaves the box up to 99.9% cleaner than when it entered.

Inside the box, the particles from the continuing flow of dust build up on the collecting plates. At periodic intervals, the plates are rapped, causing the particles to fall into hoppers. The particles are then removed from the hoppers, usually by a rotary screw arrangement.

HOPPER

As oppose to conventional hoppers, the PPC precipitator hoppers have integral support members which simplifies supoort steel fabrication and structural steel erection. Additionally, this allows shop installation of insulation and heaters at substantial savings. PPC hopper openings are a minimum of 18" wider to allow free flow of ash and eliminate bridging. Hopper depth is kept to a minimum to reduce cooling of the ash and subsequent caking.

DISHARGE ELECTRODES

The negatively charged rigid type discharge electrodes are accurately centered between the collecting surfaces and supported from high-voltage insulators located in insulator compartments.

COLLECTING ELECTRODES

Individual plates are factory assembled on headers in units of five, seven, or nine with special builtin hoisting provisions to reduce erection time to a minimum.

RAPPER SYSTEM

One of the most important considerations in design and operation of precipitators is the removal of collected material from the collecting surfaces without re-entraining it in the gas stream. On PPC units, material removal from the plates is accomplished by electromagnetic rappers installed on the roof section. These rappers deliver hammer blows of pre-set intensity at pre-set intervals to the plate headers. A vertical shock wave is created in each plate causing the collected material to shear off and fall into the hopper. The rapping intensity and interval is dictated by the characteristics of the deposited material. These adjustments are made to the rapper system to suit the requirements of each installation and are part of the start up service provided by PPC.

ELECTRICAL SYSTEM

Maximum effectiveness of the electrostatic preciptitator system occurs when the voltage supply output reaches the sparking threshold. Variation in gas volume, dust loading and other factors, however, affect the sparking threshold level. Employing an advanced electrical control system, an automatic control circuit regulates each high voltage power supply output for maximum precipitator efficiency regardless of process variation. Sparking causes the power supply to " notch down" slightly with the automatic controls bringing it right back up to sparking potential. Modern digital electronic controls automate this process and assure the electrostatic precipitator operates at peak performance levels all the time.