Development of an advanced evaporation system with fouling-free technology using a circulating fluidized bed heat exchanger

Abstract

The heat transfer rate and fouling characteristics of a circulating fluidized bed heat exchanger (CFBHE), and the treatability of landfill and municipal incinerator disposal pit leachate by advanced evaporation were investigated experimentally. The heat exchanger used glass beads (3.0-mm diameter with a specific gravity of 2.54) to control fouling. Glass beads enhanced heat transfer coefficients independently of water velocity within a superficial velocity range from 0.4-0.8 m/s. Fouling control tests using a 3,000-mg/L ferric oxide slurry revealed that the glass beads effectively removed deposits formed prior to introduction of the beads and enhanced the heat transfer coefficient. The beads also prevented the formation of deposits. Leachate from an industrial landfill in Yeochun, Korea, containing petroleum and chemical waste was treated using the CFBHE system. Treatment efficiency for CODCr, BOD5, and NH4+-N were 91, 91, and 50%, respectively at an influent pH of 7.0. Treatment of leachate from a second industrial landfill containing metal and petroleum processing industries in the city of Pohwang, Korea, was also studied and the CODCr, BOD5, and NH4+-N treatment efficiencies were 99, 99, and 41%, respectively, at an initial pH of 7.1. Finally, treatment efficiency of leachate from an incinerator storage pit for municipal solid waste disposal in Dongbu, Korea, was studied and the CODCr and NH4+-N removal efficiencies were 92 and 69% at an initial pH of 11.0. The circulating fluidized bed heat exchange process prevented fouling in the heat exchanger and maintained stable effluent from the evaporation process.