Influence of iron-containing petrochemical sludge ash on the pyrolysis of pine wood: Thermal behaviors, thermodynamic analysis, and kinetic parameters

Kinetic analysis of slow pyrolysis of oily sludge at medium temperature (350 ℃-650 ℃) and the effects of heating rate on pyrolysis

ABSTRACTPyrolysis is an effective way for the harmless treatment of oily sludge. The composition, physicochemical properties, and pyrolysis of oily sludge were experimentally studied in the present study. The Starink and Coats-Redfern methods were used to analyze the pyrolysis kinetics of oily sludge. Pyrolysis of oily sludge is divided into four stages: water evaporation stage, light component evaporation stage, heavy component pyrolysis stage, and final pyrolysis stage. The light component evaporation and heavy component pyrolysis stages are the main stages of medium-temperature pyrolysis. The pyrolysis characteristic parameters under heating rates of 10, 20, 30, and 40 K/min were obtained, and the effects of heating rates on the pyrolysis characteristics of oily sludge were discussed. The results show that with the increase in heating rate, the temperature range of each stage expands, and the temperature of the pyrolysis peaks also increases, with an average increase of 14.88%. The activation energies of the main pyrolysis stages obtained by the Starink method and Coats-Redfern method are consistent. In the light component evaporation stage, the activation energies obtained by the two methods are 61.93kJ/mol and 68.6kJ/mol, while the activation energies are 294.88kJ/mol and 367kJ/mol in the heavy component pyrolysis stage. The pyrolysis mechanism functions are obtained, and the pyrolysis kinetic equations under 10, 20, 30, and 40 K/min were constructed and validated by comparison with the results of the calculated properties and experimental measurement. This study can provide a better insight into the heat and mass transfer processes of oily sludge in pyrolysis reactors for further development and optimization.

Optimizing performance of iron-rich sludge ash as cost-effective oxygen carrier by calcium-based additive for syngas production from biomass chemical-looping gasification

Chemical-looping gasification tests were conducted on pine sawdust using thermogravimetric analyzer and horizontal sliding resistance furnace to investigate the regulation effects of calcium-based additive on iron-rich sludge ash oxygen carrier. The impacts of temperature, CaO/C in mole, multiple redox cycles, CaO addition modes on gasification performances were analyzed. The TGA results indicated that the CaO addition could effectively capture CO2 from syngas to from CaCO3, which subsequently decomposed at high temperatures. From in-situ CaO addition experiments, the temperature rise resulted in higher syngas yields, while a decrease in syngas LHV. With the CaO/C growing, the H2 yield grew from 0.103 to 0.256Nm3/kg at 800.0℃, and the CO yield boosted from 0.158 to 0.317Nm3/kg. Multiple redox manifested that the SA oxygen carrier and calcium-based additive kept higher reaction stability. The possible reaction mechanisms showed that the syngas variations from BCLG were influenced by the calcium roles and valence change of iron.

Bidirectional Catalysis Disintegration and Mineral Polymerization via Endogenous Iron(III) from Iron-Rich Sludge in Synergy with Waste Incineration Fly Ash

To enhance the utilization of solid waste in cement kiln co-processing, this study analyzed the multifaceted synergy of pyrolysis and mineralization processes of iron-rich sludge (SS) and waste incineration fly ash (FA) at optimal blending ratios. Based on the physicochemical properties of SS and co-pyrolysis experiments, it was found that Fe acted as a positive catalyst in pyrolysis between 700 and 1000 °C, while the endogenous polymerization effect of Fe(III) mineral groups dominated above 800 °C. Additionally, the study investigated the solidification and migration of heavy metals and the transformation of harmful elements (S, Cl, and P). Results indicated that the best mixture ratios for SS and FA were 6:4 and 9:1, respectively, and synergistic pyrolysis and mineral co-curing effects were observed in the pyrolysis temperature range of 50-1000 °C. The synergy between SS and FA allowed for the decomposition and solidification of harmful organic components and heavy metals, reducing environmental risks. Furthermore, in actual production, by mixing 100 tons of SS and FA with Portland cement with a daily output of 2500 tons, the compressive strength during early hydration stages can reach 34.52 MPa on the third day, exceeding the highest performance of Portland cement (62.5R) strength index specified in the standard.

Catalytic hydrothermal carbonization of wet organic solid waste: A review

Hydrothermal carbonization has gained attention in converting wet organic solid waste into hydrochar with many applications such as solid fuel, energy storage material precursor, fertilizer or soil conditioner. Recently, various catalysts such as organic and inorganic catalysts are employed to guide the properties of the hydrochar. This review presents a summarize and a critical discussion on types of catalysts, process parameters and catalytic mechanisms. The catalytic impact of carboxylic acids is related to their acidity level and the number of carboxylic groups. The catalysis level with strong mineral acids is likely related to the number of hydronium ions liberated from their hydrolysis. The impact of inorganic salts is determined by the Lewis acidity of the cation. The metallic ions in metallic salts may incorporate into the hydrochar and increase the ash of the hydrochar. The selection of catalysts for various applications of hydrochars and the environmental and the techno-economic aspects of the process are also presented. Although some catalysts might enhance the characteristics of hydrochar for various applications, these catalysts may also result in considerable carbon loss, particularly in the case of organic acid catalysts, which may potentially ruin the overall advantage of the process. Overall, depending on the expected application of the hydrochar, the type of catalyst and the amount of catalyst loading requires careful consideration. Some recommendations are made for future investigations to improve laboratory-scale process comprehension and understanding of pathways as well as to encourage widespread industrial adoption.

In-depth insight into the effects of intrinsic calcium compounds on the pyrolysis of hazardous petrochemical sludge

To understand the potential effects of intrinsic calcium compounds on sludge pyrolysis, the pyrolysis behavior of petrochemical sludge (PS), calcium carbonate blend PS (CaPS), and decalcified PS (DePS) were investigated using thermogravimetric analysis (TGA) and in-situ Fourier-transform infrared spectroscopy coupled with pyrolysis-gas chromatography and mass spectrometry (Py-GC/MS). The TGA results indicated that decalcification increased and decreased the energy barriers of PS decomposition in ranges 200-350 °C and 350-600 °C, respectively. In contrast, copyrolysis with CaCO₃ decreased the activation energy (E) of the pseudoreaction phase 2 (PH2) and altered the mechanism model. Meanwhile, during copyrolysis, char deposition and interaction hindered CaCO₃ decomposition. The two-dimensional correlation spectroscopy results, on the other hand, showed that the reaction priority of O-containing groups and CH- vibration of methyl groups were affected by both decalcification and CaCO₃ copyrolysis. The Py-GC/MS results indicated that the three sludges mainly released hydrocarbons, N-containing organics, alcohols, aldehydes, and acids. During pyrolysis, CaCO₃ also played a neutralization role, which reduced the release of pyrolytic acidic products. In addition, the increase of the pyrolysis temperature increased the hydrocarbon content. This research will guide the industrial application of sludge pyrolysis.