Application of pulsed spark discharge for mitigation of mineral fouling in a heat exchanger

One of the challenges in the production of electricity is the cooling water management because the calcium content in circulating cooling water continues to increase with time as pure water evaporates. Thus, the excessive mineral contents in water circulation systems could cause severe fouling in heat transfer equipment. To avoid the catastrophic failure in condensers, the cooling water is discharged after 3 cycles at a rate of 10 million gallons a day in a 1,000-MW thermoelectric power plant. The present study investigated the effect of pulsed spark discharges on the mitigation of mineral fouling in a concentric counterflow heat exchanger. Artificial hard water with calcium carbonate hardness ranging from 250 to 500 ppm was used with velocity varying over a range of 0.1 - 0.5 m/s and zero blowdown. Fouling resistances decreased by 50-88% for the plasma treated cases compared with the values for no-treatment cases. SEM photographs showed particle with larger sizes for the plasma treated cases comparing to smaller but more organized particles for the no-treatment cases. The different structures of particles were associated with pulsed spark discharge assisted precipitation of calcium carbonate in oversaturated hard water. X-ray diffraction data showed calcite crystal structures for all cases.