Journal of The Energy Institute最新文献

By reasonably controlling the lattice oxygen of oxygen carrier (OC), the biomass chemical looping gasification (CLG) technology can convert biomass into syngas dominated by H₂ and CO, which is a prevalent topic in the world. However, in practical applications, the mechanism underlying OC agglomeration induced by alkali and alkaline earth metals (AAEMs), along with effective countermeasures, remain ambiguous. In this paper, AAEM elements were added to the biomass after pickling to explore the effects of K, Na, Ca, and Mg on agglomeration. The results indicated that with the increase of K and Na additions from 0.5 % to 18 %, the deformation temperature (DT) of spent OC decreased, leading to a marked intensification of agglomeration, with degree of agglomeration increases from 2.88 % and 1.74 % to 17.44 % and 13.91 %, respectively. In contrast, with the increase of Ca and Mg additions from 0.5 % to 18 %, the DT of spent OC increased, and the degree of agglomeration remained lower than that of K and Na, with values ranging only from 1.03 % and 0.95 % to 11.17 % and 2.66 %, respectively. Besides, with augmented alkali metal chloride addition, the amount of low melting point aluminosilicates formed from SiO₂ and Al₂O₃ increased, further exacerbating the OC agglomeration.

We have reported the importance of biomass ratio in the co-pyrolysis of waste plastics to regulate the aromatic content and oxygenated compounds in hydrocarbon-rich fuels for enhancing engine performance. The study revealed that changing biomass to plastic ratio can control aromatic compositional change. The obtained product was characterized using different instrumentation techniques, such as NMR, FTIR, GCMS, etc., to identify the hydrocarbon types in the liquid product. Results revealed that it contains C₈-C₂₄ range carbon compounds with dominating aromatics compounds, as confirmed by ¹H NMR and FTIR analysis. The pyro-oils contain different hydrocarbons: olefins, paraffin, aromatics, esters, and alcohols. It was observed that the presence of biomass in co-pyrolysis produces oxygenated compounds up to ∼12.08 % and also enhances calorific value up to 55.4 MJ/kg from 48.3 MJ/kg due to the presence of longer hydrocarbon chains of esters in pyro-oil. Biomass co-pyrolysis also improved the fuel properties such as pour point (<-25°C) and 4°C increment in flash point. Engine performance showed that blending biomass pyro-oil obtained from B25PS75 reduced fuel consumption and increased BTE.

It is crucial to study the Fe-O coordination environment due to oxygen defects for elucidating the dynamic active center during CO chemical looping combustion with hematite. In this work, Fe-based oxygen carriers with varying oxygen vacancy concentrations were firstly synthesized by direct thermal decomposition of ferric nitrate and subsequently evaluated through fixed-bed experimentation. It was showed that the reactivity of oxygen carriers produced by calcination at 700 °C exhibited a higher CO conversion rate due to the moderate oxygen vacancy concentration. Then, density-functional theory (DFT) calculations were conducted to examine the impact of oxygen vacancies. The results indicated that the formation of oxygen vacancies exhibited a proximity effect, resulting in the emergence of various Fe-O coordination environments. The low coordination number of Fe-O enhances the reactivity of the lattice oxygen and significantly lowers the activation energy barrier for the oxidation of CO to CO₂. Furthermore, the effect of oxygen vacancies on the migration of bulk phase oxygen was also investigated. It was shown that the migration barriers of bulk oxygen increased with the concentration of oxygen vacancies, resulting in a reduction in the oxygen supply rate. Moderate concentration of oxygen vacancies facilitates CO oxidation by aligning surface catalysis with the oxygen migration rate. This evidence suggests that the Fe-O coordination environment and oxygen vacancy concentration serve as key factors in controlling in controlling CO oxidation over Fe-based oxygen carriers.

Converting hydrocarbons can make the fossil fuel industry more flexible in responding to market changes by producing various products to meet market demands. Efficient, clean, and flexible plasma processes are a highly promising technology for hydrocarbon processing and conversion. In this study, the conversion of n-hexadecane was investigated using ethanol solution-assisted pulsed liquid-phase discharge plasma. The effects of recycle and batch devices and discharge frequency on feedstocks conversions and product yields were examined. The use of a recycle device facilitated the conversion of n-hexadecane. Adjusting the frequency enabled the regulation of products concentration. High discharge frequency increased the cracking of n-hexadecane and promoted further cracking of reactants into smaller molecular products, boosting the proportion of H₂ and C₂ hydrocarbons, and enhancing the yield of gases and light hydrocarbons. Reducing the frequency favored polymerization reactions, resulting in the formation of heavy hydrocarbons. At a frequency of 10.2 kHz, the recycle device achieved a gas production rate of 112.1 mL/min and a gas production efficiency of 87.5 mL/kJ. With an SEI of 3202 kJ/L, the conversion of n-hexadecane was 15.5 %, the yield of light hydrocarbons was 717.0 mg, and the light product selectivity was 97.1 %. This study offers an efficient approach for the processing and conversion of hydrocarbons in the fossil fuel industry.

This study presents the synthesis of a series of FeO_x-NbO_x mixed oxide catalysts for the selective catalytic reduction (SCR) of NO by NH₃. By meticulously controlling the Fe/Nb molar ratio, we have rationally tailored the proceeding of the main reaction of NO reduction and the side reaction of NH₃ oxidation to NO_x. The incorporation of NbO_x introduced a significant number of acid sites, which enhanced the adsorption of NH₃ on the catalyst surface, particularly at elevated temperatures. Additionally, the oxidative capacity of the catalyst was moderated by the addition of NbO_x, hindering the over-oxidation of NH₃ to NO or NO₂, thus preserving more NH₃ to act as a reductant for NO reduction. Consequently, the NbO_x-enriched samples exhibited improved deNO_x performance. However, an excessive amount of NbO_x led to a notably weakened oxidative ability, which negatively impacted the activation of reactants and resulted in decreased NO conversion at lower temperatures. The optimized catalyst presented >80 % NO conversion and >95 % N₂ selectivity within a temperature range of 250–400 °C. These findings offer valuable insights for the development of new catalysts with an extended operational temperature window.

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.