Preliminary Study On The Characteristics Of Textile Dyeing Sludge And Chinese Medicine Residue Solid Waste Synergistic Heat Treatment

Textile dyeing sludge（TDS）contains a large number of toxic and harmful pollutants,and it is urgent to develop a safe and effective disposal method.TDS contains a large amount of dyes,surfactants and dyes,etc.,and has the characteristics of high water content,low volatile content and high ash content.The technical method of co-thermal disposal of biomass and printing and dyeing sludge is currently an important way to safely and effectively dispose of,and to effectively achieve sludge reduction,harmlessness and resource utilization.Chinese Medicine Residue（CMR）is a biomass solid waste with large output and wide sources.It is rich in hemicellulose,cellulose and lignin.At the same time,it has the characteristics of high calorific value and high volatile content,and has good thermochemical synergistic treatment potential.In this paper,TDS and CMR wastes are listed as the research objects,and the thermal decomposition reaction characteristics of the co-thermal process（co-pyrolysis/co-combustion）of TDS and CMR are deeply understood,the law of product release and transformation is explored,and the characteristics of thermal reaction bottom slag are analyzed.It provides a basic theoretical reference for the co-thermal treatment of TDS and CMR.The main research contents of this thesis are as follows:（1）The pyrolysis behavior of CMR under N₂ was analyzed by thermogravimetric（TG）,and the pyrolysis characteristics of CMR were understood by calculating the pyrolysis characteristic parameters combined with kinetic and thermodynamic parameter information.At the same time,the combined thermogravimetric-Fourier transform infrared spectroscopy（TG-FTIR）and pyrolysis-gas chromatography/mass spectrometry（PY-GC/MS）were used to monitor the release of CMR pyrolysis gas products online in real time.The research shows that CMR pyrolysis is mainly divided into three stages:water loss,hemicellulose and cellulose devolatilization,and lignin decomposition.The main pyrolysis temperature range is:150～600°C.During the period,the initial release temperature（T_i）,the maximum weight loss rate（R_m）and the peak temperature（T_p）of volatiles increased with the increase of the heating rate.The comprehensive pyrolysis index（CPI）also showed the good pyrolysis performance of CMR.The kinetics were estimated by model-free fitting methods（FWO,Friedman,Straink,and KAS）,and the main reaction process was differentiated into four stages in combination with the master graph method.The obtained reaction models were:D1:f（α）=1/（2α）,D3:f（α）=3/2（1-α）^2/3[1-（1-α）^1/3]^-1,D4:f（α）=（3/2）[（1-α）^-1/3-1]^-1 and F2:f（α）=（1-α）~2).The obtained activation energy Ea is 209.32～243.84 k J/mol.The varying thermodynamic parameters also indicate the complexity of the CMR pyrolysis process.The main gases and functional groups detected by TG-FTIR are:H₂O,CH₄,CO₂,CO,C-H,C=O,C=C and C-O.Through PY-GC/MS detection,it was found that CMR pyrolysis products include:alkanes,nitrides,aromatic hydrocarbons,acids,furans,esters,phenols,ketones,alcohols and others,of which the highest proportion of substances is Methyl trans-9-octadecenoate（53.75%）.（2）The differences in the co-pyrolysis behavior of CMR and TDS before and after impregnation were investigated by pre-processing CMR by K₂CO₃ impregnation,and the effects of different atmospheres,different mixing ratios and different impregnation conditions on the co-pyrolysis characteristics were explored.The results show that the co-pyrolysis of CMR and TDS can produce a synergistic effect.Under N₂ and CO₂,the comprehensive pyrolysis performance CPI of co-pyrolysis was 33.9%and 33.2%higher than that of TDS single pyrolysis,respectively.After impregnation pretreatment,the co-pyrolysis reaction was catalyzed in advance at 370°C,and the activation energy was reduced by 77.3 k J/mol and 134.6 k J/mol under N₂ and CO₂,respectively.At the same time,the impregnation treatment also deepened the coke gasification degree（44.25%）.In addition,after the metal potassium enters the sample through impregnation,it can increase the decomposition degree of CMR and TDS by weakening the bond energy of fatty side chains and bridge bonds,catalytic product cracking and secondary cracking,etc.,and improve the bio-oil yield（66.19%）,which mainly contains olefins,aromatic structural substances,alcohols,etc.The immersion of K₂CO₃ improved the aromaticity of the co-pyrolytic biochars and reduced the contact between K and Si which made it convenient for Mg to react with Si O₂ to form magnesium-silicate.The co-pyrolytic biochar surfaces mainly included-OH,-CH₂,C=C,and Si-O-Si.The main phases in the co-pyrolytic ash included Ca₅（PO₄）₃（OH）,Al₂O₃,and magnesium-silicate.（3）The combustion behavior of CMR in air and oxy-fuel atmosphere was analyzed by thermogravimetric（TG）,and the combustion reaction and characteristics of CMR were analyzed combining kinetics and thermodynamics.Thermogravimetric-Fourier transform infrared spectroscopy（TG-FTIR）was used to monitor the flue gas emissions of CMR combustion in different atmospheres,and 2D-TG-FTIR-COS was used to analyze the disturbance of temperature on gas emissions.XRF,Factsage and XRD were used to analyze the characteristics of ash produced by CMR combustion under different atmospheres.The results show that CMR starts to lose water at 150°C,and the main organic components start to combustion and decompose at 150-560°C.The combustion characteristic parameter CCI shows that the combustion characteristic of 8-2/CO₂-O₂ oxy-fuel atmosphere is inferior to that of air atmosphere,which is also proved by the joint optimization based on ANN.However,increasing the oxy-fuel oxygen content can improve the oxy-fuel combustion characteristics,and the CCI increases from 4.413×10^-7 to 7.798×10^-7%~2/min~2/°C~3.Compared with oxy-fuel,air has higher activation energy at the beginning and end of the main reaction:275.15 and 520.91 k J/mol,but whenα=0.7,oxy-fuel has higher activation energy of 400.22k J/mol.The combustion of CMR follows the reaction sequence type（Fn）.CMR combustion flue gas mainly includes:CO₂,H₂O,gas containing C=O and C-（O）H,etc.The results of2D-TG-FTIR-COS show that the oxy-fuel with high oxygen content are more conducive to the preferential release of CO₂.CMR ash mainly contains calcium,potassium,silicon and phosphorus,etc.The calculation parameters of ash slagging show that oxy-fuel is more prone to slagging than air.FTIR revealed that the oxygen-enriched ash retained more CO₃^2-and PO₄^3-,mainly calcium carbonate and calcium hydroxyphosphate.（4）Through tube furnace and TG-FTIR incineration experiments,the co-combustion behavior,flue gas emission and ash slagging characteristics of CMR and TDS with different mixing ratios in air and oxy-fuel atmospheres were studied.The results showed that:CMR mainly experienced water loss,volatile release and combustion,and combustion of residual substances;TDS mainly experienced the combustion of microbial degradation of small molecular substances,the combustion of macromolecular organic substances and the decomposition of residual refractory substances.Co-combustion of CMR and TDS not only improves the combustion efficiency of TDS,but also increases the degree of decomposition of TDS,reduces the residual combustion rate,and shows an obvious positive synergistic effect.However,since oxy-fuel is not conducive to the formation of voids,the strength of synergy produced under air and oxygen enrichment is different.In terms of co-combustion flue gas（HCN,NO,SO₂,CO,CO₂）,due to the characteristics of high volatile content and low ash content of CMR,the emission of NO,SO₂,CO,and CO₂ is higher than that of TDS.Afterwards,the emission of gas pollutants has been significantly improved.The difference in thermal atmospheres inhibited the oxidative conversion of HCN under oxy-fuel,and the release of HCN under oxy-fuel was higher than that of air,but the addition of CMR significantly reduced the HCN emission of TDS.According to Factsage simulation results,TDS ash mainly contains Si O₂ and Al₂O₃.With the addition of CMR,the alkali metal content in ash increases,the probability of forming metal silicates（KAl Si₃O₈,KAl Si₂O₆）increases,and the risk of ash slagging increases.But with increasing P content,alkali metals can react with phosphorus to form phosphates.Alkaline earth metals further react with these phosphates（Na₂Ca P₂O₇,Na₂Mg P₂O₇,Mg₃P₂O₈,Ca₃Mg₃（PO₄）₄）,reducing the chance of forming low melting metal silicates and thus reducing the risk of slagging.This result is consistent with the ash characteristic parameter results.