Jingyong Liu

Effects of sawdust-CPAM on textile dyeing sludge dewaterability and filter cake properties

Sawdust was used as a filter aid for the textile dyeing sludge dewatering in this study. Results showed that sawdust conditioning in conjunction with cationic polyacrylamide (CPAM) presented much better dewaterability than CPAM alone. The optimal sawdust and CPAM dosage for the best dewaterability was found to be 60 wt.% (mass percent) and 15 kg/t DS (dry solid), the time to filter (TTF) and the yield at 90% degree of the filtration completion (YN90) were 5s and 15.6 kg/m(2)h under the conditions, respectively. TTF and YN90 were more appropriate parameters than specific resistance to filtration (SRF) for assessing the sludge dewaterability as affected by physical conditioners. The moisture content of various filter cake layers gradually became the same with the increase of sawdust dosage. The flocculated sludge cake became relatively incompressible after sawdust conditioning. Sawdust acts to maintain the permeability during the compressed filtration by resisting cake compression.

Thermodynamics and kinetics parameters of co-combustion between sewage sludge and water hyacinth in CO2/O2 atmosphere as biomass to solid biofuel

Thermodynamics and kinetics of sewage sludge (SS) and water hyacinth (WH) co-combustion as a blend fuel (SW) for bioenergy production were studied through thermogravimetric analysis. In CO2/O2 atmosphere, the combustion performance of SS added with 10-40wt.% WH was improved 1-1.97 times as revealed by the comprehensive combustion characteristic index (CCI). The conversion of SW in different atmospheres was identified and their thermodynamic parameters (ΔH,ΔS,ΔG) were obtained. As the oxygen concentration increased from 20% to 70%, the ignition temperature of SW decreased from 243.1°C to 240.3°C, and the maximum weight loss rate and CCI increased from 5.70%·min(-1) to 7.26%·min(-1) and from 4.913%(2)·K(-3)·min(-2) to 6.327%(2)·K(-3)·min(-2), respectively, which corresponded to the variation in ΔS and ΔG. The lowest activation energy (Ea) of SW was obtained in CO2/O2=7/3 atmosphere.

Investigation of co-combustion characteristics of sewage sludge and coffee grounds mixtures using thermogravimetric analysis coupled to artificial neural networks modeling

Artificial neural network (ANN) modeling was applied to thermal data obtained by non-isothermal thermogravimetric analysis (TGA) from room temperature to 1000°C at three different heating rates in air to predict the TG curves of sewage sludge (SS) and coffee grounds (CG) mixtures. A good agreement between experimental and predicted data verified the accuracy of the ANN approach. The results of co-combustion showed that there were interactions between SS and CG, and the impacts were mostly positive. With the addition of CG, the mass loss rate and the reactivity of SS were increased while charring was reduced. Measured activation energies (Ea) determined by the Kissinger-Akahira-Sunose (KAS) and Ozawa-Flynn-Wall (OFW) methods deviated by <5%. The average value of Ea (166.8kJ/mol by KAS and 168.8kJ/mol by OFW, respectively) was the lowest when the fraction of CG in the mixture was 40%.

Degradation of polycyclic aromatic hydrocarbons (PAHs) in textile dyeing sludge with ultrasound and Fenton processes: Effect of system parameters and synergistic effect study

To establish an efficient oxidation process for the degradation of polycyclic aromatic hydrocarbons (PAHs) in textile dyeing sludge, the effects of various operating parameters were optimized during the ultrasound process, Fenton process and the combined ultrasound-Fenton process. The results showed that the ultrasonic density of 1.80w/cm(3), both H2O2 and Fe(2+) dosages of 140mmol/L and pH 3 were favorable conditions for the degradation of PAHs. The degradation efficiency of high molecular weight PAHs was close to or even higher than that of light molecular weight PAHs. The highest degradation efficiencies of Σ16 PAHs were obtained within 30min in the order of: Fenton (83.5%) >ultrasound-Fenton (75.5%) >ultrasound (45.5%), then the efficiencies were decreased in the other of: ultrasound-Fenton (73.0%) >Fenton (70.3%) >ultrasound (41.4%) in 60min. The extra PAHs were released from the intracellular substances and the cavities of sludge due to the disruption of sludge during the oxidation process. Also, the degradation of PAHs could be inhibited by the other organic matter in the sludge. The combined ultrasound-Fenton process showed more efficient than both ultrasound process and Fenton process not only in the surface of sludge but also in the sludge interior.

Synergistic effects of surfactant-assisted ionic liquid pretreatment rice straw.

The aim of this work was to study an environmentally friendly method for pretreating rice straw by using 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) as an ionic liquid (IL) assisted by surfactants. Different temperatures, reaction times, and surfactant concentrations were studied. Compared with [BMIM]Cl only pretreatment, the addition of 1% sodium dodecyl sulfate (SDS) and 1% cetyl trimethyl ammonium bromide (CTAB) increased lignin removal to 49.48% and 34.76%, respectively. Untreated and pretreated rice straw was thoroughly characterized through FTIR, XRD, and FE-SEM. Cellulose crystallinity and surface morphology of the rice straw were substantially altered after surfactant-assisted IL pretreatment. In conclusion, surfactant-assisted IL pretreatment is an effective method for producing fermentable sugars from lignocellulosic substrates.

An experimental and thermodynamic equilibrium investigation of the Pb, Zn, Cr, Cu, Mn and Ni partitioning during sewage sludge incineration

The effects of different chlorides and operational conditions on the distribution and speciation of six heavy metals (Pb, Zn, Cr, Cu, Mn and Ni) during sludge incineration were investigated using a simulated laboratory tubular-furnace reactor. A thermodynamic equilibrium investigation using the FactSage software was performed to compare the experimental results. The results indicate that the volatility of the target metals was enhanced as the chlorine concentration increased. Inorganic-Cl influenced the volatilization of heavy metals in the order of Pb>Zn>Cr>Cu>Mn>Ni. However, the effects of organic-Cl on the volatility of Mn, Pb and Cu were greater than the effects on Zn, Cr and Ni. With increasing combustion temperature, the presence of organic-Cl (PVC) and inorganic-Cl (NaCl) improved the transfer of Pb and Zn from bottom ash to fly ash or fuse gas. However, the presence of chloride had no obvious influence on Mn, Cu and Ni. Increased retention time could increase the volatilization rate of heavy metals; however, this effect was insignificant. During the incineration process, Pb readily formed PbSiO4 and remained in the bottom ash. Different Pb compounds, primarily the volatile PbCl2, were found in the gas phase after the addition of NaCl; the dominant Pb compounds in the gas phase after the addition of PVC were PbCl2, Pb(ClO4)2 and PbCl2O4.

Effects of sulfur on lead partitioning during sludge incineration based on experiments and thermodynamic calculations.

Experiments in a tubular furnace reactor and thermodynamic equilibrium calculations were conducted to investigate the impact of sulfur compounds on the migration of lead (Pb) during sludge incineration. Representative samples of typical sludge with and without the addition of sulfur compounds were combusted at 850 °C, and the partitioning of Pb in the solid phase (bottom ash) and gas phase (fly ash and flue gas) was quantified. The results indicate that three types of sulfur compounds (S, Na2S and Na2SO4) added to the sludge could facilitate the volatilization of Pb in the gas phase (fly ash and flue gas) into metal sulfates displacing its sulfides and some of its oxides. The effect of promoting Pb volatilization by adding Na2SO4 and Na2S was superior to that of the addition of S. In bottom ash, different metallic sulfides were found in the forms of lead sulfide, aluminosilicate minerals, and polymetallic-sulfides, which were minimally volatilized. The chemical equilibrium calculations indicated that sulfur stabilizes Pb in the form of PbSO4(s) at low temperatures (<1000 K). The equilibrium calculation prediction also suggested that SiO2, CaO, TiO2, and Al2O3 containing materials function as condensed phase solids in the temperature range of 800-1100 K as sorbents to stabilize Pb. However, in the presence of sulfur or chlorine or the co-existence of sulfur and chlorine, these sorbents were inactive. The effect of sulfur on Pb partitioning in the sludge incineration process mainly depended on the gas phase reaction, the surface reaction, the volatilization of products, and the concentration of Si, Ca and Al-containing compounds in the sludge. These findings provide useful information for understanding the partitioning behavior of Pb, facilitating the development of strategies to control the volatilization of Pb during sludge incineration.

Impact of surfactant type for ionic liquid pretreatment on enhancing delignification of rice straw.

This work describes an environmentally friendly method for pretreating rice straw by using 1-Allyl-3-methylimidazolium chloride ([AMIM]Cl) as an ionic liquid (IL) assisted by surfactants. The impacts of surfactant type (including nonionic-, anionic-, cationic- and bio-surfactant) on the ionic liquid pretreatment were investigated. The bio-surfactant+IL-pretreated rice straw showed significant lignin removal (26.14%) and exhibited higher cellulose conversion (36.21%) than the untreated (16.16%) rice straw. The cellulose conversion of the rice straw pretreated with bio-surfactant+IL was the highest and the lowest was observed for pretreated with cationic-surfactant+IL. Untreated and pretreated rice straw was thoroughly characterized through SEM and AFM. In conclusion, the results provided an effective and environmental method for pretreating lignocellulosic substrates by using green solvent (ionic liquid) and biodegradable bio-surfactant.

Influence of catalysts on co-combustion of sewage sludge and water hyacinth blends as determined by TG-MS analysis

Effects of the three metal carbonates (K2CO3, Na2CO3, and MgCO3) were quantified on catalytic co-combustion of the sewage sludge and water hyacinth (SW) blend using a thermogravimetric-mass spectrometric (TG-MS) analysis and kinetics modeling. The main dominating steps of the catalysts were the organic volatile matter release and combustion stage. Weighted mean values of activation energy (Em) were estimated at 181.18KJ·mol-1, 199.76KJ·mol-1, 138.76KJ·mol-1, and 177.88KJ·mol-1 for SW, SW+5% K2CO3, SW+5% Na2CO3, and SW+5% MgCO3, respectively. The lowest Em occurred with SW+5% Na2CO3. Overall, catalyst effect on co-combustion appeared to be negligible as indicated by Gibbs free energy (ΔG). The normalized intensities of SW+MgCO3 were strongest. The addition of Na2CO3 and MgCO3 to SW increased flue gases emissions (CO2, NO2, SO2, HCN, and NH3) of SW, whereas the addition of K2CO3 to SW reduced flue gases emissions from the entire combustion process.

Kinetics of coffee industrial residue pyrolysis using distributed activation energy model and components separation of bio-oil by sequencing temperature-raising pyrolysis

This study was carried out to investigate the kinetics of coffee industrial residue (CIR) pyrolysis, the effect of pyrolysis factors on yield of bio-oil component and components separation of bio-oil. The kinetics of CIR pyrolysis was analyzed using distributed activation energy model (DAEM), based on the experiments in thermogravimetric analyzer (TGA), and it indicated that the average of activation energy (E) is 187.86kJ·mol-1. The bio-oils were prepared from CIR pyrolysis in vacuum tube furnace, and its components were determined by gas chromatography/mass spectrometry (GC-MS). Among pyrolysis factors, pyrolysis temperature is the most influential factor on components yield of bio-oil, directly concerned with the volatilization and yield of components (palmitic acid, linoleic acid, oleic acid, octadecanoic acid and caffeine). Furthermore, a new method (sequencing temperature-raising pyrolysis) was put forward and applied to the components separation of bio-oil. Based on experiments, a solution of components separation of bio-oil was come out.