Treatment of Sydney Tar Pond Sludge in CFBC

Test burns of mixtures of Sydney tar pond sludge and coal were carried out using CETC’s mini-circulating fluidized bed combustor (mini-CFBC). The goal was to determine if CFBC technology could be used to treat the tar pond sludge. During the tests, CO₂, O₂, CO, SO₂, and NO_x in the flue gas were monitored continuously. Stack gas sampling was carried out for HCl, metals, particulate matter, VOCs, total hydrocarbons, semi-volatile organic compounds, dioxins and furans and PCBs. Results showed that HCl, Hg, particulate matter, PCDD/Fs and metal concentrations were all below both the current limits and the gas release limits to be implemented in 2008 in Canada. Sulphur capture efficiency was about 89–90%. The percentage of fuel nitrogen converted to NO_x was of the order of 4.7 to 6.1, which is significantly lower than that of conventional pulverized coal-fired boilers and well within normal range of FBC boilers. PCB and PAH emissions levels were comparable or lower than levels reported in the literature for industrial-scale FBCs. VOC concentrations were low except for benzene, for which the concentration was higher than that reported for utility-scale FBC and pulverized coal-fired boilers. In addition, CO concentration was high at 1200 to 2200 ppm. However, these CO concentrations are typical of CETC’s mini-CFBC firing coal. The trials showed that, for 10% by weight tar pond sludge mixed with 90% by weight coal, the combustion was both stable and efficient. The tests demonstrated that CFBC technology could be an environmentally sound option for eliminating wastes from the Sydney tar pond.