Question

Electrostatic precipitator question,

I'm designing an electrostatic precipitator (ESP) to capture the particulate matter(fly ash) from flue gas at 130C that exits from a coal-fired power plant.

My question is: how can i increase the efficiency of the electrostatic precepitator without conditioning the flue gas (ie. injecting so3 or ammonia or water)? what are the alternative ways to increase the efficiency of the ESP? please show references with solution. Thanks

Answer 1

1. Most recently it was recognized that a major reason for the loss of efficiency of the electrostatic precipitator is due to particle buildup on the charging wires in addition to the collection plates. This is easily remedied by making sure that the wires themselves are cleaned at the same time that the collecting plates are cleaned.

2. The original parallel plate–weighted wire design has evolved as more efficient and robust discharge electrode designs were developed, today focusing on rigid pipe-frame discharge electrodes to which many sharpened spikes are attached (barbed wire), maximizing corona production

3. The ESP can be put in series with an existing one, though it is subjected to CAPEX calculation and expected Return on Investment (Internal Rate of Return IRR)

4.Intermittent charging to suppress back corona discharges. The system simply energizes ESP unit for a specified number of cycles and suppresses the ESP energization for specified number of cycles not by gating thyristors. The system works because of time dependence of the formation of back corona in a resistive dust layer, which can be considered equivalent to an electrical circuit having capacitor and resistor in parallel. The capacitors must be charged a voltage across the dust layer just before back corona can form. With normal continuous operation with high resistivity fly ash this condition is met continuously. However, with intermittent charging the voltage is never allowed to reach like critical break-down level. The time it takes the voltage to break-down level depends on number of factors such as resistivity, dielectric constant, break down strength, current density etc. Intermittent charging is the periodic gating(on) and suppression of gating(off) of the thyristor. The duty cycle or the charge ratio is defined as the ratio of the number of on cycle to the sum of the on and off cycle. A high peak voltage increases the effective migration velocity and thus increases the collection efficiencies.