Cold-rolling oily sludge contains high amounts of oil and iron resources that can be recycled by pyrolysis. We investigated the pyrolysis behavior and volatile products of oily sludge by thermogravimetric analysis (TG) coupled with Fourier transform infrared spectroscopy (FTIR) and a pyrolyzer (PY) coupled with gas chromatography/mass spectrometry (GC/MS). The pyrolysis process was divided into three stages: H₂O drying and CO₂ desorption at low temperatures (below 393 K); the volatilization of low-molecular-weight organics and the covalent bond cleavage of C=C, C-O, and C-H in the medium-molecular-weight organics at medium temperatures (393–844 K); and chain scission of the high-molecular-weight organics and reduction of iron oxides by CO at high temperatures (above 844 K). The weight losses of oily sludge in the three stages were 0.4 wt %, 47.9 wt %, and 14.7 wt %, respectively. According to the kinetic models, stage 2 and stage 3 could be described with the second-order and third-order reaction models, and their activation energies were 40.22 kJ/mol and 214.99 kJ/mol, respectively. The compounds in the volatile products were identified by FTIR and GC/MS. The organics in the volatile products from stage 2 pyrolysis mainly consisted of aliphatic hydrocarbons, fatty acids, esters, ketones, and nitrogen compounds, while the volatile products from stage 3 predominantly contained aliphatic hydrocarbons, mononuclear aromatic hydrocarbons, and small amounts of nitrogen compounds and CO, suggesting the occurrence of chain scission of heavy organics.

Biodiesel is a green, low-carbon, and renewable fuel with the potential to substitute fossil fuels. The effects of reaction temperature (175–290 °C), residence time (5–75 min), and molar ratio of methanol to palmitic acid (6:1–35:1) on the non-catalytic esterification of palmitic acid with methanol to produce biodiesel were investigated by using a batch reactor. Moreover, the reaction parameters were optimized by using the response surface methodology (RSM), and the reaction kinetics were analyzed. The results showed that the conversion rate of palmitic acid to methyl palmitate increased to 100% as the reaction temperature rose from 175 °C to 225 °C, slightly changed until 275 °C, and then decreased to 94.81% at 290 °C. The conversion rate increased with residence time and reached the maximum value of 94.93% at 60 min. With increasing the molar ratio, the conversion rate rose to a maximum value of 85.46% at 15:1 and subsequently decreased. RSM results indicated the relative influence of factors on the conversion rate as reaction temperature > residence time > molar ratio. The optimal reaction parameters were 224 °C, 26 min, and a molar ratio of 16:1, affording a palmitic acid conversion rate of 99.30%. The esterification reaction between methanol and palmitic acid follows the first-order kinetics model.

Sinter is the main raw material of blast furnaces, and its strength influences its running condition. Nevertheless, there is no comprehensive definition of the influencing mechanisms of the strength of the sinter. In this paper, the influences of the quantity and quality of the bonding phase on the strength of the sinter were investigated by changing the sintering parameters, such as the maximum sintering temperature, the binary basicity of adhering fines, holding time at high temperature, and types of core ores. As the maximum temperature increased from 1240 °C to 1320 °C and the binary basicity of the adhering fines increased from 5.0 to 9.0, and the strength of the sinter increased first and then decreased. The strength of the sinter was improved by increasing the holding time at high temperatures and reducing the melt absorbability of core ores. The strength of the sinter was comprehensively influenced by the strength of the bonding phase, the fluidity of the original melt, and the melt absorbability of core ores. There is a multivariate linear relationship between them. Moreover, the strength of the bonding phase had the greatest effect on the strength of the sinter, followed by the fluidity of the original melt, and the melt absorbability of core ores was the smallest.

Biodiesel is a promising green and renewable fuel that can replace fossil fuels and reduce greenhouse gas emissions. The effects of reaction temperature (200–290 °C), residence time (0–75 min), and methanol-to-oleic acid molar ratio (6:1–35:1) on the esterification of oleic acid with supercritical methanol were investigated in a batch reactor. Furthermore, orthogonal experiments were designed to explore the optimal reaction conditions. and the influences of H₂O (0–33.3 wt%) and Fe (0–20.0 wt%) contents were examined. Results showed that the conversion of oleic acid to methyl oleate exhibited a volcano-type dependence on both temperature and molar ratio, peaking at 250 °C and a ratio of 15:1, respectively. Conversion initially increased with residence time, then plateaued around 30 min. Under the optimal conditions of 250 °C, 30 min, and a 15:1 molar ratio, the conversion reached 76.8%. Both additives enhanced conversion at low loadings (≤5.0 wt%). However, higher water content inhibited conversion, whereas the promotional effect of Fe saturated beyond 5.0 wt%. The co-addition of 5.0 wt% water and 5.0 wt% Fe yielded a positive but sub-additive effects: conversion exceeded that with water alone but remained lower than with Fe alone. These findings contribute to advancing the high-efficiency and low-cost production of biodiesel.

The apparent viscosity of the oil–solid interface in steel rolling oily sludge (SROS) is governed by the amount, identity, and size of solid particles. To decouple these factors, oleic acid was used as a model oil phase, and Fe, Fe₃O₄, and Fe₂O₃ were selected as representative iron-bearing minerals. The effects of mineral type, Fe₃O₄ volume fraction, and particle size on the rheological behavior of oleic acid–mineral suspensions were systematically investigated using a rotational rheometer. Pure oleic acid behaved as a Newtonian fluid (24.96 mPa·s), and all suspensions exhibited near-Newtonian behavior with flow indices close to unity (0.959–1.048) and small yield stresses; no shear thickening was observed. At a matched loading of 4 vol%, the apparent viscosity followed the order Fe₃O₄ > Fe > Fe₂O₃. Notably, the Fe₂O₃ system exhibited a viscosity almost identical to that of neat oleic acid, which indicates that the reactivity of the mineral surface towards the carboxyl group of oleic acid, and the resulting aggregation state, dictate the particle–oil coupling, rather than the degree of oxidation. Furthermore, the apparent viscosity increased monotonically with Fe₃O₄ volume fraction (2–6 vol%) and decreased with increasing particle size (Dv(50) = 13.3–29.2 μm). Interestingly, the yield stress was highest for the coarsest powder, revealing that the static network strength and steady-flow viscosity are controlled by different microstructural features. These findings provide a quantitative basis for interpreting the oil–solid contribution to the viscosity of iron-bearing sludges and for developing targeted viscosity-reduction strategies.