Fuel Processing Technology最新文献

This study has analysed and optimised a 5-column sorption enhanced water gas shift (SEWGS) pilot unit, set to operate for the first time in a waste gasification facility for the production of transport-grade hydrogen and CO₂ streams. Full process simulation was undertaken by developing a one-dimensional model of each reactor, with boundary conditions directly informed by real plant operation. From the sensitivity analysis performed, syngas flowrate variations were seen to have a minor but temporary, impact on hydrogen product specifications, while changes to syngas composition were shown to have a longer-lasting effect on system performance. Based on full cycle operation results, the current 5-column SEWGS unit design was concluded to be inadequate for fuel-cell-grade H₂ production, despite obtaining a high H₂ purity of 99.5%, mainly due to its excessive steam consumption. However, the process achieved an exceptionally high CO₂ purity of 99.9%, and 88.6% hydrogen recovery rate, suggesting its potential use in carbon capture and heat-grade hydrogen production applications.

Alkali species present in biomass pose significant challenges in chemical looping combustion (CLC) processes and other thermal conversion applications. The interactions between different alkali species and three common oxygen carrier (OC) materials that are considered to be state of the art in CLC applications have been investigated. A dedicated fluidized bed laboratory reactor was used to study interactions of KCl, NaCl, KOH, NaOH, K₂SO₄ and Na₂SO₄ with manganese oxide, calcium manganite and ilmenite. Alkali vapor was generated by injecting alkali salts under reducing, oxidizing and inert conditions at 900 °C. Gaseous species were measured online downstream of the reactor, and the efficiency of alkali uptake was determined under different conditions. The result show significant alkali uptake by all OCs under the studied conditions. Ilmenite shows near complete alkali uptake in reducing conditions, while manganese oxide and calcium manganite exhibited less effective alkali uptake, but have advantages in terms of fuel conversion and oxidizing efficiency. Alkali chlorides, sulfates and hydroxides show distinctly different behavior, with alkali hydroxides being efficiently captured all three investigate OC materials. The findings contribute to a deeper understanding of alkali behavior and offer valuable guidance for the design and optimization of CLC with biomass.

In light of the increasing concern for sustainable growth and development, there is a rising demand for energy-efficient conversion processes. Chemical Looping (CL) technology has emerged as a promising solution that utilizes chemical intermediates, such as metal oxides or other metal derivatives, to decompose complex reactions into multiple sub-reaction steps. This innovative approach enables the separation of the overall reaction into distinct stages, which can be conducted in separate reactors. Consequently, the direct contact between inert substances present in reactant feedstocks and the desired product can be avoided, leading to reduced purification costs. This state-of-the-art literature review provides an updated overview of the potential of perovskite structures in chemical looping technology. Perovskite materials exhibit desirable properties, including excellent oxygen transport capabilities, high chemical stability, and adjustable redox properties, making them ideal candidates for CL applications. By examining recent advancements and research efforts, this review aims to shed light on the current state of perovskite based CL, its challenges, and future prospects. The findings presented here contribute to the understanding of the potential of perovskite structures in enabling energy-efficient and sustainable chemical conversion processes. This review includes two major parts, the first part is dedicated to the structure of the perovskites and the corresponding classifications based on the cell structure, ionic size cation phase, and dimension, while the second part of the work focuses on the applications of those structures in seven different chemical looping technologies, including chemical looping combustion (CLC), chemical looping reforming (CLR), chemical looping gasification (CLG), chemical looping oxygen uncoupling (CLOU), chemical looping air separation (CLAS), chemical looping dehydrogenation (CLDH), and chemical looping epoxidation (CLEPOX).

Chemical looping steam methane reforming (CL-SMR) via iron-based oxygen carriers is a promising method for efficient hydrogen production. To overcome challenges such as high reaction temperatures (>850 °C) and scarcity of low-cost, durable oxygen carriers (OCs), we have developed iron-based particles mixed with various ratios of nickel-based particles to achieve remarkable performance in CL-SMR at 600 °C. The mixed particles showed 85.23% methane conversion and 3.47 and 1.01 mL/min/g_OC hydrogen production rates in the reduction and steam oxidation steps, respectively, in the two-step CL-SMR reaction. In the three-step CL-SMR reaction, air oxidation led to full recovery of oxygen carriers, enhancing methane conversion to 93.30% and elevating hydrogen production rate to 1.41 mL/min/g_OC during steam oxidation. Precise control over methane conversion and hydrogen production in the three-step CL-SMR system is achievable by manipulating the mixing ratios of iron-based to nickel-based OC particles. Comprehensive experimental tests were conducted, covering practical aspects like support materials, gas velocity, and steam-to-carbon ratios. The outstanding cyclic stability of OC particles was confirmed over 200 consecutive redox cycles at 600 °C. The mid-temperature iron-based oxygen carrier particles, integrated with chemical looping demonstration project, might provide a powerful approach toward more efficient and scalable hydrogen production.

Steam reforming of biomass-derived pyrolysis liquids (bio-oil) to produce hydrogen with carbon-based Ni catalysts is gaining attention due to their advantages in terms of cost, sustainability and activity. However, the catalytic activity at long times on stream is compromised by either coke deposition or gasification of the support. To face these drawbacks, two activated carbons have been studied as Ni catalyst support: a microporous carbon of high purity and a mesoporous carbon with phosphorus surface groups. The activity and long-term stability of these catalysts have been studied for the steam reforming of model compounds of bio-oil. The microporous support provided a slightly higher H₂ production and lower contribution of methanation reaction. However, gasification of this support after 20 h led to a decline in the activity, and massive formation of carbon nanotubes and coke. Nevertheless, the resulting material maintained an outstanding stability with high and stable H₂/CO ratio for 50 h. The P-containing catalyst showed a remarkable long-term stability, but lower H₂/CO ratio. Carbon gasification was less significant in this catalyst due to the presence of surface phosphorus groups, and the generation of nickel phosphides, which hampers the growth of pyrolytic carbon and carbon nanotubes, leading to a superior stability.

The microwave pyrolysis (MWP) of sewage sludge (SS) was conducted to investigate the impact of the organic composition of SS on the yield and composition of the derived bio-oil. The experiments were conducted in a microwave oven at 900 °C with a heating rate of 50 °C/min and achieved the product yield of 43.10 ± 2.23% bio-oil, 48.07 ± 1.26% bio-char, 8.83 ± 1.65% bio-gas. The chemical composition of bio-oil was investigated using gas chromatography–mass spectrometry and 145 species were identified. Protein and lipid contents in SS are the primary source of bio-oil yield, while bio-gas are predominantly derived from lignocellulosic materials. The unique non-thermal effects of microwaves can facilitate the ring-opening of small cycloalkanes to form straight olefins through hydrogen transfer reactions. Additionally, they can promote aldol condensation reactions, Pinacol rearrangements, and methoxy cleavage to form phenolic and aromatic structures with methyl groups. Furthermore, microwaves can aid in the dehydration, condensation, and cyclization reactions of amino acids to produce N-heterocycles while also facilitating lipid depolymerization into fragments for Diels–Alder cyclization. The results of this study will be beneficial for deeply understanding reactant characteristics and the reaction process during the MWP of SS.

This paper assesses the potential of plastics valorization by pyrolysis and in line catalytic dry reforming for syngas production. Previous studies showed the suitability of a continuous process made up of a conical spouted bed reactor for fast pyrolysis and a fluidized bed reactor for catalytic steam reforming. In order to step further in the application of this technology under dry reforming conditions, equilibrium simulation was approached to analyze process performance, as the development and optimization of this technology for the production of high-quality syngas requires understanding in detail the complex influence of process parameters. Thus, this study deals with the influence of main process parameters, namely, temperature, CO₂/C ratio and the type of plastic, on the process performance. Furthermore, the role played by steam co-feeding in the dry reforming in order to adjust syngas H₂/CO ratio was evaluated by varying the steam/carbon ratio. The obtained results clearly show that a strict control of process conditions is required to ensure high conversion to syngas and avoid undesired reactions, such as reverse WGS. Among the plastics studied, polyolefins are those of highest potential for syngas production, but polystyrene allows producing a high quality syngas through a combined reforming strategy.

Steam cracking in fluidized beds offers an alternative to conventional steam cracking for sustainable hydrocarbon production. This approach has gained interest, particularly in the context of recycling plastics to generate valuable hydrocarbons. Integrating this process into existing petrochemical clusters necessitates a thorough characterization of the products derived from this new feedstock. This work focuses on addressing the challenges associated with species quantification and characterization time for assessing the product mixture resulting from a steam cracking process. The experiments were conducted in a semi-industrial scale dual fluidized bed steam cracker, utilizing polyethylene as the feedstock. To sample species spanning from C1 to C18, cooling, scrubbing, and adsorption were introduced. These steps were integrated with GC-VUV (Gas Chromatography with Vacuum Ultraviolet Spectroscopy) and other widely recognized analytical methods to quantify the sampled species. The primary focus was on GC-VUV analysis as a suitable characterization method for identifying and quantifying C4 to C18 species, which can constitute up to 35% of the product mixture obtained from polyethylene steam cracking (750 °C to 850 °C). Quantifying C6 to C18 hydrocarbons becomes the time-critical step, with GC-VUV potentially achieving this in 1/6th of the analysis time and with relatively optimal quantification compared to the traditional characterization methods.

The electric-field assisted deposition is successfully proposed as a method for the manufacturing of carbon nanostructured films with tunable properties, benefiting from the superimposition of electric fields on the thermophoretic deposition. Morphology, optical, and thermo-resistive properties of the carbon nanoparticle (CNP) films have been studied by UV–vis Absorption Spectroscopy, Scanning Electron Microscopy, Atomic Force Microscopy, and Current-Voltage analysis. In comparison to thermophoresis alone, the introduction of an electric field results in a six-fold increase in the deposition rate characterized by a non-linear film growth influenced by a three-fold augmentation in surface roughness and polarization effects. Notably, the surface morphology of the CNP films undergoes modification, exhibiting larger grains and a reduced optical band gap energy. Moreover, while maintaining a non-ohmic behaviour, the electric field plays a crucial role in increasing by about two orders of magnitude the electrical conductance of CNP films at ambient temperature. This effect is accompanied by a decrease in temperature sensitivity, attributed to the low and nearly temperature-independent activation energy for the tunneling of electrons in the percolative network. In summary, electric-field assisted deposition is a promising approach to tailor the thermal response of CNP films, which could be beneficial for the development of next-generation sensors.

Catalytic combustion of volatile organic compounds from industrial flue gases at low temperatures remains a challenge. Herein, we developed a mesoporous Mn-Co-Ti catalyst for o-xylene degradation by a solvothermal strategy. The optimized Mn_0.1Co-TiO₂ catalyst possessed a nanoflower structures with a surface area of 83.1 m²/g and mesoporous volume of 0.1191 cm³/g. Mn-doping modulated the electronic interactions between Mn and Co, which promoted the formation of MnCo₂O_4.5 phase and increased Co³⁺ and Mn⁴⁺ content of the catalyst. The Mn_0.1Co-TiO₂ catalyst had an improved reduction capacity from 170 to 644 °C, with a maximum H₂ consumption of 4.56 mmol/g. The Mn_0.1Co-TiO₂ catalyst achieved 50% o-xylene conversion at 193 °C at a GHSV of 60,000 h⁻¹, whereas the equivalent catalyst prepared by impregnation required 315 °C for 50% o-xylene conversion. In the presence of NO, the generated NO₂ accelerated o-xylene conversion because it promoted the generation of more Mn⁴⁺-O-Co³⁺ active sites and accumulation of intermediates such as maleate and acetate species. NH₃ and H₂O had slight inhibitory effects on o-xylene conversion, which were attenuated by abundant mesopores and redox ability of catalyst. SO₂ gas caused inactive sulfates and chemical deactivation on catalyst surface, thus leading to excessive formation of benzoquinone products.