Thermodynamic behaviors of Cu in interaction with chlorine, sulfur, phosphorus and minerals during sewage sludge co-incineration

Thermodynamic equilibrium calculations were performed to reveal effects of interactions among Cl, S, P and other minerals on Cu migration. Our results showed that HCl(g), SO2(g) and(P_2O_5)_2(g) were released from the sewage sludge co-incineration. Cl was found to weaken adsorption of Cu by Al_2O_3, CaO and Fe_2O_3, while S delayed reactions of Fe_2O_3 and Al_2O_3 with Cu, with P having no effect on reactions between the minerals and Cu.Among the coupled systems of Cl, S and P, the co-existences of Cl and S, and Cl, S and P were determined to inhibit Cu volatilization, and the co-existence of Cl and P had an enhancing effect. Cu migration was affected only by S in the S and P system. With the SiO_2, CaO and Al_2O_3 system, both Cl alone and Cl and P led to failed reactions between the minerals and Cu. In the systems of S, S and Cl, S and P, and S, Cl and P, the migration behavior of Cu was mainly affected by S at low temperatures and by Cl at high temperatures, whereas P had no effect on Cu migration during the entire process.

Energetic,bio-oil,biochar,and ash performances of co-pyrolysis-gasification of textile dyeing sludge and Chinese medicine residues in response to K_(2)CO_(3),atmosphere type,blend ratio,and temperature

Hazardous waste stream needs to be managed so as not to exceed stock-and rate-limited properties of its recipient ecosystems.The co-pyrolysis of Chinese medicine residue(CMR)and textile dyeing sludge(TDS)and its bio-oil,biochar,and ash quality and quantity were characterized as a function of the immersion of K_(2)CO_(3),atmosphere type,blend ratio,and temperature.Compared to the mono-pyrolysis of TDS,its co-pyrolysis performance with CMR(the comprehensive performance index(CPI))significantly improved by 33.9%in the N_(2)atmosphere and 33.2%in the CO_(2)atmosphere.The impregnation catalyzed the co-pyrolysis at 370℃,reduced its activation energy by 77.3 kJ/mol in the N_(2)atmosphere and 134.6 kJ/mol in the CO_(2)atmosphere,and enriched the degree of coke gasification by 44.25%in the CO_(2)atmosphere.The impregnation increased the decomposition rate of the co-pyrolysis by weakening the bond energy of fatty side chains and bridge bonds,its catalytic and secondary products,and its bio-oil yield by 66.19%.Its bio-oils mainly contained olefins,aromatic structural substances,and alcohols.The immersion of K_(2)CO_(3)improved the aromaticity of the copyrolytic biochars and reduced the contact between K and Si which made it convenient for Mg to react with SiO_(2)to form magnesium-silicate.The co-pyrolytic biochar surfaces mainly included-OH,-CH_(2),C=C,and Si-O-Si.The main phases in the co-pyrolytic ash included Ca_(5)(PO_(4))_(3)(OH),Al_(2)O_(3),and magnesium-silicate.

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 Fact Sage 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 Pb SiO4 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）2and Pb Cl2O4.

Thermal behaviors, combustion mechanisms,evolved gasses, and ash analysis of spent potlining for a hazardous waste management

An unavoidable but reusable waste so as to enhance a more circular waste utilization has been spent potlining(SPL) generated by the aluminum industry.The combustion mechanisms, evolved gasses, and ash properties of SPL were characterized dynamically in response to the elevated temperature and heating rates.Differential scanning calorimetric(DSC) results indicated an exothermic reaction behavior probably able to meet the energy needs of various industrial applications.The reaction mechanisms for the SPL combustion were best described using the 1.5-, 3-and 2.5-order reaction models.Fluoride volatilization rate of the flue gas was estimated at 2.24%.The SPL combustion emitted CO_(2), HNCO, NO, and NO_(2) but SO_(x).The joint optimization of remaining mass, derivative thermogravimetry, and derivative DSC was achieved with the optimal temperature and heating rate combination of 783.5 ℃, and 5 ℃/min, respectively.Interaction between temperature and heating rate exerted the strongest and weakest impact on DSC and remaining mass, respectively.The fluorine mainly as the formation of substantial NaF and CaF_(2) in the residual ash.Besides,the composition and effect of environment of residual solid were evaluated.The ash slagging tendency and its mineral deposition mechanisms were elucidated in terms of turning SPL waste into a benign input to a circular waste utilization.