| Bioenergy is renewable and has large amount which has been widely studied and utilized with the depletion of fossil energy.Solid waste is one of the main factors causing environmental problem.Sewage sludge is a typical solid waste,it is rich in heavy metals、virus、bacteria and has high water content,large land occupation,unstable state,it is easy to seep into the soil and water if piled up at will,causing serious pollution.Using solid waste as resource and energy is crucial facing energy crisis and pollution control tough battle.Based on chemical looping gasification,three typical sludges were used:nicke-containing electroplating sludge(NiES),copper-containing electroplating sludge(cues),and textile dyeing sludge(DS)to prepare oxygen carriers and applied to the chemical looping gasification of DS.First,NiES,CuES and DS were burned in a tubular furnace.XRD and BET tests were applied to investigate the crystal and pore structure of the three sludge ashes at different incineration times(3,5,8 hours)and temperature(700℃,850℃,900℃).850℃ for 8 h was determined as the optimal preparation condition under which ashes shows stable phase and satisfactory pore structure.Three oxygen carriers 850NiES8、850CuES8、850DS8 were obtained.Second,the chemical components of the three oxygen carriers were studied by XRF and microwave digestion-ICP.The reaction activities,redox cycles and the effects on sludge pyrolysis were studied by H2-TPR and TGA.The active components of 850NiES8 are Fe2O3,NiO,NiFe2O4 and CaSO4 with a mass proportion of 74.83%,850CuES8 are Fe2O3 and CuFe2O4 with a mass proportion of 87.16%,850DS8 is Fe2O3 with a mass proportion of 56.44%;The H2-TPR curve of 850NiES8 shows remarkable synergistic effect between the active components.850CuES8 and H2 reaction temperature is the lowest,and it is not completely reduced after the test.And the activity of 850DS8 is inferior to 850NiES8 and 850CuES8.After certain activation process,all three oxygen carriers can provide sufficient lattice oxygen and this process of 850CuES8 is the longest.The mass of fully oxidized oxygen before a reduction cycle(moxi)decreases after the redox cycle,this phenomenon of 850DS8 is most obvious.The results also showes that the three oxygen carriers could promote the DS pyrolysis,especially at high temperature,and the effect of 850DS8 is a little inferior to the others.In general,all three sludge ash oxygen carriers have potential as promising oxygen carriers.Finally,the influence of oxygen caeeier and DS mass ratio,reaction temperature on the chemical looping gasification of DS with these three oxygen carrers were investigated.The addition of the three oxygen carriers all can improve the carbon conversion(ηC)、gas production(Gv)of DS,and improve the reaction rate,shorten full gasification time,achieve the purpose of saving the gasification cost.Excess oxygen carrier will has negative influence on its performance.While oxygen carrier also consumes combustible gas which will decrease the energy recovery efficiency,the downtrend is not obvious when the addition is small.And there even a certain degree of rise at 850NiES8/DS of 0.5,The increase of reaction temperature will also promote the gasification of DS,the performance 850DS8 on DS gasification below 850℃ is inferior to the other two oxygen carriers,but it has some advantages at high temperature.In summary,the three sludge(NIES,CuES and DS)ashes all have good performance as oxygen carrier,and can be used in chemical looping gasification of DS.This reserch provides a new method for sludge disposal,resource and energy utilization. |
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