Journal of The Energy Institute最新文献

In the present work, co-pyrolysis experiments of walnut shell (WS), polyethylene (PE) and their blends were performed in the thermogravimetric analyzer and lab-scale bubbling fluidized bed reactor, to clarify co-pyrolysis behaviors, synergy interactions and pyrolysis oil properties. Besides, the HZSM-5 zeolite was used as the catalyst and its catalytic characteristics were studied. Results indicated that as PE mass ratio rose from 0 to 100 %, the initial temperature monotonically increased from 265.4 to 417.3 °C, while its terminal temperature progressively decreased from 668.3 to 527.5 °C, suggesting that the addition of PE was able to accelerate the pyrolysis of samples. The co-pyrolysis of blends was distinguished into three stages, with a negative interaction observed in the first stage and positive interactions found in second and third stages. Besides, in the bubbling fluidized bed experiments, the liquid phase product yield first elevated and then reduced with rising temperature, and a high temperature promoted the degradation of oxygen-containing compounds and enhanced aromatics generation. The synergistic interaction in the co-pyrolysis of WS and PE declined the liquid phase product yield while elevating the gas phase product yield. On the other hand, blending with PE facilitated the generation of alkanes and olefins, while inhibiting the contents of oxygen-containing components and aromatics, and simultaneously, the heavy oil fraction was increased. Finally, the carbon deposited on the surface of catalysts was amorphous carbons, and could be removed by oxidation process, whereas its catalytic properties progressively declined with rising cycle number, leading to a downtrend of aromatics and olefins and an opposite trend for oxygen-containing components.

The impacts of climate change and the issue of greenhouse gas emissions have sparked research into renewable energy alternatives to fossil fuels. Hydrogen has gained attention as a clean, renewable and environmentally friendly energy source. Enhanced-ethanol steam reforming has been proposed as a promising method for blue hydrogen production, addressing greenhouse gas emission issues. The use of catalysts enhances the adsorption of ethanol and water molecules on the surface, promoting the reaction rate. This study systematically explored the effects of different Fe loading and CaO addition ratios on the ethanol steam reforming and CO₂ conversion processes to optimize catalyst performance. The experimental results showed that Fe/SiC catalysts effectively promoted the conversion of ethanol and generated high-purity hydrogen, exhibiting excellent catalytic activity. Specifically, a catalyst with 10 % Fe loading and mixed with 0.3g CaO significantly increased the hydrogen yield to 64.4 mmol/g, which was 2.88 times higher than that without the catalyst.

A process of producing hydrogen-rich syngas by chemical looping steam gasification is proposed, using pickling sludge (PS) as the oxygen carrier and paper-making sludge(PMS) along with municipal sludge(MS) as the fuel. The reaction characteristics of producing hydrogen-rich syngas through the gasification of PMS and MS were studied. The effects of temperature, steam flow rate and the blended ratio of PS on carbon conversion rate and gasification reaction efficiency were discussed, and the migration mechanisms of the main elements were explained. The results show that FeF₃ in PS exhibits stronger activity than conventional Fe₂O₃ in catalyzing the gasification of PMS and MS at high temperature. With the blended mass ratio of 1:1 of PS, the carbon conversion rate of PMS and MS was increased by 11.8 % and 42.5 %, and the gasification efficiency was increased by 11.1 % and 25.85 %. The Fe³⁺ in PS catalyzed the cleavage of C-H bonds in biomass sludge, and Fe³⁺ was reduced to form the intermediate product FeCr₂O₄ with tar cracking function. After the gasification reaction, the Fe in PS was completely converted to Fe₃O₄ under the action of MS, while the CaO in PMS promoted the valence cycle of Fe to some extent, resulting in partial Fe being fully cycled to Fe³⁺ to form γFe₂O₃. In addition, the CaO can fix the F element in PS to form CaF₂, thus reducing the environmental hazard.

Introducing low-carbon oxygenated fuels into the current transport sector provides an effective pathway for mitigating the emissions of greenhouse gases and harmful pollutants such as soot. Previous studies have revealed that oxygenated fuels can reduce soot formation, but the soot-reduction potential is closely related to the chemical interaction between the oxygenates and the baseline hydrocarbons. This work is devoted to study the effects of blending dimethoxymethane (DMM) and isopropanol (IPA) on soot formation in ethylene-based and propane-based counterflow diffusion flames. Soot formation in the target flames was experimentally characterized using a planar light extinction technique, accompanied by numerical analysis to provide complementary insights. The results confirmed that the effects of blending oxygenates on soot formation are sensitive to the fuel-specific molecular structure of the oxygenates and hydrocarbons. For the C₂H₄-based flames, blending DMM and IPA could lead to a synergistic effect on soot formation due to chemical fuel interaction, with stronger synergy observed with IPA blending. In contrast, no evident synergistic effects on soot formation were observed in the C₃H₈-based flames, for which a notable soot reduction was observed with DMM blending. Reaction pathway analysis suggested that the occurrence of soot synergy in the C₂H₄-based flames is mainly due to the chemical interaction between the methyl radicals generated from DMM/IPA and the C₂ species from C₂H₄. This study is expected to deepen our understanding of the soot formation behavior of DMM- and IPA-blended flames, thus contributing to their successful usage as clean alternative fuels.

DIB (Diisobutylene, JC₈H₁₆) strongly correlates with real gasoline and significantly impacts the combustion behavior of alternative fuels designed as gasoline substitutes. However, accuracy concerns persist in laminar burning velocity data reported in literature. In this paper, the laminar burning velocities of DIB + air, DIB + PRF + air, and DIB + TRF + air mixtures were measured by the heat flux method at 1 atm. (PRF, Primary Reference Fuel; TRF, Toluene Reference Fuel) The equivalence ratio was controlled within 0.6–1.3, and the initial temperatures were set at 298K, 318K, and 338K. Additionally, by employing the mechanism proposed by Ren et al., the simulated values align with the experimental data, thus prompting the conduction of a reaction kinetic analysis. The analysis of chemical reaction kinetics reveals the reaction pathways of DIB, with a notable observation that an increase in temperature or a decrease in equivalence ratio can both lead to an elevation in the degree of unsaturation in the bonds of intermediate species. During laminar flame combustion, PRF and TRF compete with DIB for oxygen, with PRF appearing to have a stronger ability to capture oxygen. In addition, the laminar burning velocity temperature dependence coefficient α decreases first and then increases with the increase of the equivalence ratio, where the minimum α is obtained at equivalence ratio = 1.1. Additionally, the laminar burning velocity at higher initial temperatures is estimated by the extrapolation method and compared with the experimental data reported in literature.

Co-pyrolysis technology offers a viable solution for utilizing biomass and waste plastics as a valuable energy resource, to support waste management, energy supply and environmental protection. In this paper, co-pyrolysis of poplar tree (PT) and polystyrene (PS) at mixture ratios of 0:1, 3:1, 2:1, 1:1, 1:2, 1:3 and 1:0 under different pyrolysis temperatures (450, 550, 650, and 700 °C), using different catalysts (HZSM-5, MCM-41, Fe/HZSM-5, and Cu/HZSM-5) were investigated using gas chromatography/mass spectrometry (Py-GC/MS) diagnostics for determining products distribution and synergistic effects. The results showed that PT performed best at a pyrolysis temperature of 650 °C, whereas PS performed best at 550 °C. The relative amount of aromatics in the co-pyrolysis products of PT and PS was highest at 550 °C that showed positive synergistic effects. The synergistic effects from the co-pyrolysis of PT and PS were significantly different at different mixture ratios of the PT and PS feedstocks. At mixture ratios of 1:1 and 1:2, the relative amounts of polycyclic aromatic hydrocarbons (PAHs) and monocyclic aromatic hydrocarbons (MAH) were higher and showed positive synergistic effects. The catalysts promoted the generation of MAH and inhibited the PAHs formation in the co-pyrolysis. The Fe/HZSM-5 catalyst provided the most significant effect on MAH showing the highest relative amounts. The results showed that highest yield of monocyclic aromatic hydrocarbons can be achieved from the pyrolysis of PT and PS materials at 1:1 mixture ratio using Fe/HZSM-5 catalyst, at a reaction temperature of 550 °C.

High entropy oxides (HEOs) show great prospects in catalysis owing to their widely tunable component structures and ease of combination with active metals. However, the development of HEO catalysts is limited by the lack of efficient synthesis methods due to the difficulty of homogeneously mixing at least five elements. In this work, flame spray pyrolysis (FSP) is successfully employed to synthesize (CrMnFeCoNi)₃O₄ HEO with a single phase spinel structure in one step, which is verified by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and energy-dispersive X-ray spectroscopy (EDS). Taking CO catalytic oxidation as a probe reaction, the Pt@(CrMnFeCoNi)₃O₄ HEO catalyst synthesized by FSP in one step is compared with the catalyst whose Pt is impregnated on (CrMnFeCoNi)₃O₄ HEO support. The FSP-made catalysts have a higher catalytic reaction rate and better redox ability, which lowers the temperature of complete CO conversion by nearly 100 °C. Furthermore, it can be observed that the flame parameters can be optimized to modify the particle size and oxygen vacancies of the HEO nanoparticles, thus enhancing the catalytic performances. This work demonstrates that FSP is an effective method for the one-step synthesis of HEO catalysts with excellent catalytic performance, providing a new perspective for the synthesis of HEO-based materials.

Disposable masks, predominantly made of polypropylene melt-blown fabric, present a significant environmental challenge due to their large volume and resistance to natural degradation. This study explores the co-gasification of forestry waste, specifically pine wood, and waste masks to enhance biomass gasification efficiency while enabling the high-value utilization of waste materials. The Fe/Dol catalyst, prepared by loading transition metal Fe onto calcined dolomite using the impregnation method, was tested in a two-stage fixed-bed gasification system. Steam was employed as the gasifying agent. The study systematically examines the effects of steam flow rate, gasification reforming temperature, the mixing ratio of pine wood to masks, and Fe loading on the catalyst's performance in gas-phase and liquid-phase product formation.Characterization analyses revealed that Fe oxides facilitate the cleavage of aromatic rings in aromatic compounds, leading to the formation of two-carbon chain segments and promoting the production of ethylene and propylene from aliphatic hydrocarbons. Additionally, the catalyst enhanced tar cracking, generating free radicals and ring bonds. Experimental results indicate that at a steam flow rate of 3 mg/min, a gasification temperature of 850 °C, a pine wood to mask mixing ratio of 1:2, and an Fe loading of 8 %, the hydrogen (H₂) volume fraction reached 52.48 %, with a gas yield of 1.67 m³/kg and a hydrogen production rate of 78.25 g/kg.

This study investigated the effects of initial temperature, equivalence ratio, and diesel injection timing on engine combustion and emission characteristics at high ammonia substitution ratios. Increased compression temperature and pressure significantly reduce ignition delay, enhance combustion speed and efficiency, and decrease N₂O and unburned NH₃ emissions. A strong correlation exists between the amount of N₂O produced and the mass of unburned NH₃ when ammonia combustion efficiency is high. The N₂O distribution is concentrated near the cylinder walls and the piston top surface, in areas with high concentrations of unburned NH₃. As the equivalence ratio increases from 0.6 to 0.75, flame propagation speed and indicated thermal efficiency (ITE) increase, while NOx, N₂O, and unburned NH₃ emissions decrease. The combustion performance and emissions were optimized by advancing the diesel injection timing and increasing the equivalence ratio to accelerate the combustion speed. This adjustment increases ITE to 47.6 % at an 80 % ammonia energy ratio. Post-optimization results show a reduction in unburned NH₃ emissions from 51.7 g/kW·h to 5.9 g/kW·h and a decrease in N₂O emissions from 0.930 g/kW·h to 0.370 g/kW·h, culminating in a 60.4 % reduction in greenhouse gas (GHG) emissions.

The micropore structure can serve as the diffusion channels for intermediates and light tar products during coal pyrolysis, which is very important for modulating the desired tar or char products. In this work, the micropore effects on product distribution and the reaction mechanisms during Hailaer coal pyrolysis was explored for the first time from the atomistic simulation point of view by using large-scale ReaxFF MD simulation and the reasonable model with the artificially adding micropore strategy. The results suggest that the micropore structure indeed has a significant impact on the major tar product distribution and competitive reactions during coal pyrolysis process at high temperature. The micropore can promote decomposition reactions through accelerating C–C bond breaking significantly and inhibit the recombination reactions accompanied with the char formation with more carbon in sp2 structure. Based on the oxygen-containing bond behaviors in char products obtained from coal pyrolysis process, it is unraveled that the more micropore exits in coal structure, the more C_sp3-O bonds and less C_sp2-O bonds in char precursors. Particularly, the light tar products with ring groups are more influenced by micorpore structures than those chain products. Considering that the limitation of current experimental techniques in micropore detection, the strategy sheds new light on the depth investigation of micropore effects on reactions, which can provide complement for experimental observations and tar product modulation.