| A large number of textile dyeing sludge?DS?is produced in the printing and dyeing industry every year in china,which has very complex chemical compositions,and usually contains more toxic organic matter.Improper treatment and disposal of DS has caused serious environmental problems.Furfural residue?FR?is generated from the furfural production by acidic hydrolysis from agricultural products,such as corncob and corn stalk,which hasn't been utilized effectively.However,DS and FR are industrial solid waste,which can be used to prepare sludge char/biochar.In this study,sludge char/biochar were prepared from DS and FR by microwave pyrolysis?MWP?in a continuously operated auger reactor.Elemental analysis,X-ray fluorescence spectroscopy?XRF?,Scanning electron microscopy?SEM?,BET surface area analysis,Fourier transform infrared spectroscopy?FTIR?,Gas chromatography?GC?,Inductively coupled plasma mass spectrometry?ICP-MS?and X-ray diffraction?XRD?have been conducted and analyzed.?1?The experiment of microwave pyrolysis of DS.It showed that the sludge char?SC?yield decreased and non-condensable gas yield increased as temperature increased.At 750 ?,the lowest SC yield and the highest non-condensable gas yield were 63.87%and 26.37%,respectively.At 650 ?,the SC yields increased with addition of CaO and Fe while the SC yields decreased with addition of bentonite and kaolin.CO2,CO,H2 and CH4 were the main non-condensable gas products observed from GC during MWP of DS.The elemental analysis showed that the content of carbon,hydrogen and nitrogen decreased gradually with the increase of pyrolysis temperature,but the content of sulfur increased gradually.CaO were beneficial for sulfur retention and some heavy metal immobilization for microwave pyrolysis of DS and promoted the decomposition of carbon and nitrogen containing organic matter.The maximum BET surface area of 123 m2 · g?-1? was observed for SC with addition of 20%kaolin at 650 ?,consistent with SEM observations.The heavy metals based on the decreasing order of contents in DS digestion solution were Zn>Pb>Cr>Cu>Ni>As.All the heavy metals contents?except Zn in SC850?in DS and SC were lower than those from the national standards?GB/T 23485-2009?and showed slight potential ecological risk to the environment after microwave pyrolysis of DS.The electricity consumption for pyrolysing DS of 60 wt%water content were 0.76-2.59 kWh·kg?-1? wet DS in the temperature range of 450-750? and auger speed range of 1-9 r·min?-1??rpm?.Higher pyrolysis temperature and lower auger speeds increased electricity consumptions.?2?The experiment of microwave pyrolysis of FR.Biochar?BC?yield decreased to 43.62%while non-condensable gas increased to 40.37%with temperature increasing from 450 ? to 750 ?.CO2,CO,H2 and CH4 were the main non-condensable gas products observed from GC during MWP of FR.On the whole,the yields of CO2,CO,H2 and CH4 increased with temperature increasing and obtained the highest yields at 750 ?,which were 20.31%?0.99%?15.22%and 4.21%,respectively.Addition of CaO increased the FRBC yield,and decreased CO2 and CO yields in the non-condensable gas at 650 ?.Whereas adding kaolin and K2CO3 increased the yields of CO2,CO and H2 and obtained the lower FRBC yields at 650 ?.Ultimate analysis showed that with the increase of pyrolysis temperature,the contents of carbon,nitrogen and sulfur increased,while the contents of hydrogen and oxygen decreased.Addition of CaO,kaolin and K2CO3 facilitated the conversion of carbon,hydrogen and sulfur into condensates and non-condensable gas phases.XRD analysis showed that SiO2,CaSO4,K2Ca?SO4?2·H2O and KCl are the main inorganic substances in FR and FRBC.The electricity consumption for pyrolysing FR of 15%water content were 0.755-2.846 kWh·kg?-1? wet FR in the temperature range of 450-750?. |
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