A multi-emission analysis of organic and inorganic pollutants during the combustion of sludge with high and low calorific value coals.

To achieve allowable gas emission limits and eliminate the high cost and challenges associated with pre-treatment of sludge before incineration, a new technique was proposed to co-incinerate wet printing and dyeing sludge with different calorific values of coal while conducting a full evaluation of organic and inorganic emission of pollutants. Different proportions (0%, 10%, 20%, 30%, 40%) of the wet sludge-coal slurry (peat) were incinerated using a commercialized fluid bed (circulating) incinerator. The results showed the that flue gas emitted contained sulfur oxides (SOx), nitrogen oxides (NOx), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and heavy metals in bottom ash. The ΣPCBs content produced from the 7 congeners was 6.4014 μg/m3 with more than 65% below tetra-chlorinated biphenyls which are the most harmful and persistent. An increment in the sludge (peat) ratio caused the content of SOx to decrease drastically, while the content of NOx exhibited two maxima. The heavy metal concentrations of Cd, Zn, Mn, Pb, Fe, Ni, Cr, and Cu decreased with increasing sludge ratio. The leaching toxicity of heavy metals in the bottom ash proved to be lower than the limit values for hazardous waste. The PCDD/F 1-TEQ emissions of the flue gas increased from 0.06844 to 0.10779 ng/m3 as the proportion of sludge increased in peat. The I-TEQ values of the PCDD/Fs showed a slight increment with increasing sludge ratio. The sum of the PCDD/Fs (ideally at 20-30%) does not exceed the 0.1ng/Nm3 of the EU and the 0.5 ng TEQ/Nm3 of the new Chinese emissions standard. Statement of novelty Different calorific values of coal of different proportions were incinerated with wet printing and dyeing sludge in order to achieve the new allowable gas emission limits, tap heat energy and eliminate high cost.