Hot rolling sludge incineration: Suppression of PCDD/Fs by spent anion exchange resins

Ingenious use of autocatalytic hydrodeoxygenation for the separation and recovery of oil and iron from rolling oil sludge

This paper introduces a transformative hydrodeoxygenation process for the simultaneous recovery of oil and iron from hazardous rolling oil sludge (ROS). Leveraging the inherent catalytic capabilities of iron/iron oxide nanoparticles in the sludge, our process enables the conversion of fatty acids and esters into hydrocarbons under conditions of 4.5 MPa, 330 °C, and 500 rpm. This reaction triggers nanoparticle aggregation and subsequent separation from the oil phase, allowing for effective resource recovery. In contrast to conventional techniques, this method achieves a high recovery rate of 98.3% while dramatically reducing chemical reagent consumption. The reclaimed petroleum and iron-ready for high-value applications-are worth 3910 RMB/ton. Moreover, the process facilitates the retrieval of nanoscale magnetic Fe and Fe0 particles, and the oil, with an impressive hydrocarbon content of 87.8%, can be further refined. This energy-efficient approach offers a greener, more sustainable pathway for ROS valorization.

Suppression on PCDD/Fs formation by a novel inhibition system consisting of phosphorous-based compounds coupled with a chlorine-deactivation material

The SN-containing inhibitors are effective for suppressing the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the post-combustion zone of municipal solid waste incineration systems, but the industrial application of the SN-containing inhibitors is restricted by the high cost and the generation of corrosive by-products (e.g., SOx). To develop cost-effective and environmentally friendly inhibitors, a new inhibition system consisting of P-based compounds (i.e., NH₄H₂PO₄ (ADP) and KH₂PO₄ (PDP)) and a chlorine-deactivation material (CaO) was proposed in this study. Also, the performance of this inhibition system in terms of suppressing PCDD/Fs formation was evaluated in an experimental system which simulated PCDD/Fs generation in the post-combustion zone. Generally, the formation of PCDD/Fs was effectively suppressed by over 95 % by the mixed inhibitors (ADP/CaO and PDP/CaO) and the individual inhibitor of ADP. Based on the observation on PCDD/F-fingerprints and the chemical speciation of Cl and Cu, the mechanisms of inhibitors were identified as: (i) passivating metal catalyst by converting the speciation of Cu from chlorides and Cu²⁺ with high reactivities to phosphates, oxides, and Cu⁺ with low reactivities, and (ii) deactivating Cl by CaO to prevent the formation of organic Cl which was critical for PCDD/Fs formation. In addition, both mechanisms were supported by (i) the better performance of inhibitors on suppressing the PCDD/F-congeners formed via de novo pathway than congeners synthesized from chlorophenols and (ii) lower degrees of chlorination of PCDD/Fs for reaction systems with CaO involved than other systems.

The Influence of Copper on Halogenation/Dehalogenation Reactions of Aromatic Compounds and Its Role in the Destruction of Polyhalogenated Aromatic Contaminants

The effect of copper and its compounds on halogenation and dehalogenation of aromatic compounds will be discussed in the proposed article. Cu oxidized to appropriate halides is an effective halogenation catalyst not only for the synthesis of halogenated benzenes or their derivatives as desired organic fine chemicals, but is also an effective catalyst for the undesirable formation of thermodynamically stable and very toxic polychlorinated and polybrominated aromatic compounds such as polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans accompanied incineration of waste contaminated with halogenated compounds or even inorganic halides. With appropriate change in reaction conditions, copper and its alloys or oxides are also able to effectively catalyze dehalogenation reactions, as will be presented in this review.

Decomposition and reformation pathways of PCDD/Fs during thermal treatment of municipal solid waste incineration fly ash

Thermal treatment of municipal solid waste incineration (MSWI) fly ash (FA) allows heavy metals solidification, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) decomposition, and environmentally stable materials production, but lacking advanced insights into PCDD/Fs dramatically limits its development. In this study, the decomposition and reformation of PCDD/Fs during thermal treatment of two typical fly ashes (loading 0.294 and 0.594 ng I-TEQ/g PCDD/Fs, respectively) are systematically investigated, under conditions of three heating temperature (500, 800, and 1100 °C) and two atmospheres (oxidative and inert). Over 95 % of PCDD/Fs in FA are effectively decomposed for all tests mainly via cyclic skeleton destruction accompanied by dechlorination, but reformation predominantly through de novo synthesis in off-gases significantly reduces the overall elimination efficiency. Moreover, both de novo synthesis and chlorination are enhanced as temperature increase promoting migrations of catalytic metals and chlorine, yet are weakened at the absence of oxygen, both of which are revealed by PCDD/F-signatures evolution. Catalytic metal is identified as the most critical factor accounting for PCDD/Fs reformation, which is also evidenced by kinetic models of de novo synthesis. Finally, the decomposition and reformation pathways during thermal treatment of fly ashes are proposed. The results pave the way for controlling PCDD/Fs reformation and improving the thermal treatment of fly ashes.

Parameters affecting the formation mechanisms of dioxins in the steel manufacture process

With the implementation of the new national standards in the steel industry, dioxins (polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs)) emission and control have attracted more and more attention in China. The PCDD/Fs levels and signatures of nine steelmaking materials and by-products were experimentally analysed and compared, including five kinds of steelmaking fly ash (sintering fly ash, basic oxygen furnace fly ash, electric arc furnace fly ash and two kinds of blast furnace fly), three kind of steel sludge (continuous casting sludge, hot rolling sludge and cold rolling sludge) and sintering raw material. Dioxin formation from the sintering fly ash was highest of all 9 materials. Furthermore, highly chlorinated PCDD/Fs homologues were abundant in that sample, while the profiles were contrary to those of other materials. More importantly, the entire isomer signatures of all 61 samples were analysed, involving various materials, temperatures, oxygen levels, particle size and inhibitors, with special emphasis on those congeners associated with chlorophenol precursor routes, as well as seventeen 2,3,7,8-substituted PCDD/Fs. Strong correlation was found among seven PCDD-congeners of CP-route. The analysis of the molecular structure of these congeners revealed that 2,4,6/2,3,5-trichlorophenol may act as a precursor to form all those PCDD-congeners by condensation. In addition, the influence of various factors (temperature, oxygen level, particle size, inhibitors addition etc.) on the relative importance of CP-route congeners and 2,3,7,8-substituted congeners was discussed, with the goal of shedding more light on the mechanism of PCDD/Fs-formation.