Study On Co-pyrolysis And Co-combustion Characteristic Of The Textile Dyeing Sludge And Durian Shell And The Migration Behavior Of Heavy Metals

Textile dyeing sludge(TDS)is a kind of solid waste containing a variety of heavy metals,organic pollutants and high toxicity.At present,the mainstream treatment technology is sanitary landfill and incineration.However,due to the inherent defects of high moisture content and low calorific value of printing and dyeing sludge,it is difficult to combustion alone.Therefore,it is necessary to find suitable auxiliary fuel to make up for its own shortcomings.Pyrolysis technology can achieve the dual goals of waste reduction and recovery of value-added products at the same time,and the treatment of printing and dyeing sludge also has great potential.Based on the background of the carbon reduction and optimization of energy structure,the purpose of this article selects the regional agricultural waste durian shell(DS)as auxiliary fuel with textile dyeing sludge treatment,key research durian shell with textile dyeing sludge incineration/heat transfer behavior and characteristics of pyrolysis,interaction,thermal dynamic characteristic and transformation of heavy metal migration behavior,etc.,The results can provide reference for the co-thermal treatment of similar biomass and textile dyeing sludge.The specific research contents are as follows:(1)The thermochemical transformation and kinetic characteristics of durian shell and the emission rules of typical gas pollutants were studied by thermogravimetric analysis,spectroscopy and mass spectrometry.The main stage of DS combustion is 130.2-481.9?,and the activation energy of DS combustion is 192.82-213.24 k J/mol.The third-order(F3)model best describes the most likely reaction mechanism of DS combustion.The main escaping gas is CO₂,and the emission of SO₂ is very small.DS combustion produces k-type ash.618°C and 8 K/min are the best operating conditions for DS combustion.The activation energy of DS pyrolysis reaction is 221.58-245.71 k J/mol.The main gases produced by pyrolysis include CO₂,CO,CH₄,H₂O,carbonyl compounds,acids and NH₃.The main pyrolysis products are aromatic hydrocarbons,aliphatic cyclic hydrocarbons,phenols and nitrogenous compounds.999?and 5 K/min are the best operating conditions for pyrolysis.(2)Combined with kinetics,principal component analysis,2D-COS,Thermogravimetric infrared spectroscopy,thermodynamic simulation software and gas chromatography-mass spectrometry technology,the thermal conversion behavior,pyrolysis products,interaction and gas emissions of textile dyeing sludge and durian shell under different conditions were studied.The results show that pyrolysis at high temperature in CO₂atmosphere(>720°C)is the best choice for waste volume reduction.(Co)-pyrolysis in CO₂atmosphere enhances S pollutants,CO and CH₄,but reduces NOx emissions.The interaction between TDS and DS promoted the production of furans and acidic compounds,and inhibited the production of aromatic,phenolic and nitrogenous compounds.The simulation results confirm that co-pyrolysis in CO₂ atmosphere can increase H₂ production and reduce NOx production.The stability of TDS biochar prepared in N₂ atmosphere was the highest,and the stability of TDS biochar prepared in N₂ atmosphere was better than that in CO₂atmosphere.(3)The effects of reaction atmosphere,mixing ratio and temperature on thermal degradation behavior,interaction law and gas solid products during the co-incineration of durian shell and textile dyeing sludge were studied by thermogravimetric analysis,thermogravimetric infrared spectroscopy,tubular furnace experiment and thermodynamic simulation software.The results show that higher oxygen concentration can improve the combustion performance of the sample,but has no significant effect on the residual mass of the sample after the reaction.Under the same conditions,the performance of(co-)incineration in N₂/O₂ atmosphere is better than that in CO₂/O₂ atmosphere.The addition of DS improves the co-combustion performance of TDS.The interaction of other samples in the co-incineration process promotes the mass loss.Under the same oxygen concentration,the maximum absorption intensity of CO in N₂/O₂ atmosphere is higher than that in CO₂/O₂atmosphere,and the maximum absorption intensity of C-O(H)and C=O in CO₂/O₂atmosphere is higher than that in N₂/O₂ atmosphere.Co-incineration does not aggravate the slagging and scaling problems of samples,and the multi-objective optimization results also confirm that the addition of DS can improve the combustion efficiency of TDS.(4)The bottom slag and biochar were obtained through tube furnace experiment,and the distribution and content of heavy metals in durian shell and textile dyeing sludge bottom slag/biochar obtained under different conditions during heat treatment were tracked by ICP-OES and continuous extraction method,and ecological impact assessment was conducted.At the same time,the influence of mineral-heavy metal coupling interaction on heavy metal migration and transformation was studied in depth with thermodynamic simulation software(Fact Sage 7.1).The results show that the pyrolysis of TDS and DT11 in N₂ atmosphere has more environmental benefits.The contents of Cd,Cr,Mn and Ni in TDS and DT55 in80N₂20O₂ atmosphere increase with the increase of temperature(800-1000?).The enrichment ratio of Cd,Mn,Ni and Cr in the combustion slag of TDS and DS in 80N₂20O₂atmosphere increases with the increase of temperature.The interaction between DS and TDS during the combustion process increases the heavy metal residues in the bottom slag.After pyrolysis,the risk levels of all heavy metals in the solid products were reduced.Most of the heavy metals in the biochar had a low migration trend in the environment,and the potential environmental risk of heavy metals in the biochar prepared in CO₂ atmosphere was lower.The concentration enrichment ratio of Leaching toxicity of Cr,Zn and Cu is the highest in TDS combustion at 900?in 80N₂20O₂ atmosphere.The concentration enrichment ratio of leaching toxicity first increases and then decreases with the increase of temperature.At800?,the enrichment multiple of TDS and DT55 in different atmosphere for different heavy metal leaching toxicity is Cr>Cu>Zn>Mn;Cr>Zn>Cu.Thermodynamic simulation calculation show that oxygen concentration and reaction atmosphere have less effect on the form and transformation of heavy metals,K elements impact on form and migration regularity of heavy metal,the existence of the K improve the Ni(s)into the Ni O(slaga₁)temperature in DS and mainly affect the transformation temperature and strength of melting states of Ni,Zn and Pb metals in TDS and DT55 at high temperature.