| Landfill leachate produced during the process of municipal solid waste (MSW) disposal is a kind of organic wastewater with high concentration, containing a large mass of hazardous and noxious substances. Landfill leachate causes secondary pollution to environment and has a serious impact on the development of the disposal of MSW.The existing technology can't achieve harmless treatment of landfill leachate. It has been an important research topic to explore a way to realize the treatment of landfill leachate with harmlessness and reduction. Burning can completely decompose harmful organics oxidatively at high temperature, with the removal rate of organics above99.99%. The integrated drying incineration technology is proposed in this paper, with which evaporation and burning can be proceed at the same time, realizing the treatment of landfill leachate with harmlessness.Taking the leachate from Beijing Asuwei MSW Landfill as research object, the leachate's characteristics of water quality are introduced. The characteristics and organic components of the research object are analyzed. The experiments are carried out in a rotating evaporation experiment system (REES) and a5kW lab-scale bubbling fluidized bed combustor (BFBC) in order to investigate the characteristics of evaporation and burning.The organic components of leachate from a landfill are analyzed by gas chromatograph-mass spectrometry (GC-MS). The results indicate that there are at least50kinds of organic pollutants in leachate, with Nicotine and3-methyl-phenol the highest relative content.The experiment system of REES is designed to investigate the the effects of vacuum degree, evaporation temperature and pH on the concentration of chemical oxygen demand (COD), total organic carbon (TOC) and ammonia-nitrogen in condensate during the leachate evaporation process. And the organic components in condensate are also analyzed. The results show that the rate of evaporation and COD concentration in condensate tend to increase with the increase in the evaporation temperature and vacuum degree, which have little effect on TOC concentration in condensate. Ammonia-nitrogen concentration in condensate decreases as the evaporation temperature increases. Within the temperature range of60-120the main organic components in condensate are alkanes and Nicotine. The precipitation of alkanes only relates to the evaporation temperature, while the precipitation of phenol relates both to the vacuum degree and evaporation temperature. COD and TOC concentration in condensate at the acid condition is far higher than that at the neutral and alkaline conditions, while ammonia-nitrogen concentration reverses. The organic components in condensate at the acid condition are mainly organic acid and alkanes. At two-stage evaporation condition, ammonia-nitrogen concentration in condensate meets the emission standards of wastewater, and TOC concentration decreases significantly. But the removal of COD at two-stage evaporation condition is not as effective as that at single-stage neutral condition.When the leachate is combusted in CFB combustor, the results present that the condensate of flue gas can't meet the emission standards of wastewater within the range of100-200℃and200℃is a turning point of condensate water quality. Below200℃water evaporation and the precipitation of small-molecule volatile organic substances occur in landfill leachate,while when the temperature is over300℃organic substances begin to decompose. Within the range of700-950℃NO concentration and SO2convert ratio in flue gas increase firstly and then decrease with the increase in the furnace temperature, while NOX convert ratio reverses. NO2and SO2concentration decreases continuously. NH3and HC1concentration and C1-HC1convert ratio are all low. |
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