Fuel Processing Technology最新文献

In liquid discharging furnace, crystallization can occur in slags during the cooling process. The presence of crystal changes the structure, flow, heat transfer, especially the viscosity with a sharp increase. A deep understanding of the crystal kinetics is significant to optimize the flow of liquid slag. Crystal kinetics varies significantly with different slags due to the complexity and variability of the multi components in slags. In this paper, a high-temperature microscopy with high-resolution is used to clearly observe the in situ precipitation of different crystals and the kinetic parameters of different crystals are analyzed. Microscopic structure analysis of both the melt and the precipitated crystal shows that the proportion of basic oxygen structure and the diffusion coefficient of the basic cation in the melt have a direct correlation with the growth of crystal. A structural parameter St of the melt is developed, which has a positive correlation with the crystal growth rate. This is a new discovery in bridging the gap between the melt and precipitated crystals and it provides a way to control the crystal growth during slag cooling.

Serious coking from the bio-oil polymerisation is a bottle-neck challenge for bio-oil thermal upgrading. Probing the mechanism of bio-oil coking is the first step to achieve high carbon conversion efficiency. In this study, in-situ electron paramagnetic resonance (EPR) spectroscopy was used to characterise the stable free radical generation during bio-oil pyrolysis at 250–350 °C with reaction time of 2–10 min, which identify the coking process of bio-oil. The liquid and solid products were characterised using gas chromatography-mass spectrometer (GC–MS), ultraviolet fluorescence (UV-F) and Raman spectroscopy. The results indicate that the coking of bio-oil in pyrolysis can be divided into three stages of varied characteristics. The coke formation precedes with an initial induction period that lasts for 2–8 min and shortens with increasing pyrolysis temperature. In the period, light components polymerise into heavy ones, including polycyclic aromatics as the essential coke precursors. After the induction period, significant amounts of stable free radicals are generated with coke formation, and the content increases from 0.2 to 1.6–7.8 μmol/g bio-oil in the early stage of coking. Meanwhile, the coke precursors, polycyclic aromatics, are rapidly depleted. Afterwards, in the late stage, the nascent coke gradually condenses and the stable free radical content increases slowly.

Liquefaction of lignocellulosic biomass through fast pyrolysis, to yield fast pyrolysis bio-oil (FPBO), is a technique that has been extensively researched in the quest for finding alternatives to fossil feedstocks to produce fuels, chemicals, etc. Properties such as high oxygen content, acidity, and poor storage stability greatly limit the direct use of this bio-oil. Furthermore, high coking tendencies make upgrading of the FPBO by hydrodeoxygenation in fixed-bed bed hydrotreaters challenging due to plugging and catalyst deactivation. This study investigates a novel two-step hydroprocessing concept; a continuous slurry-based process using a dispersed NiMo-catalyst, followed by a fixed bed process using a supported NiMo-catalyst. The oil product from the slurry-process, having a reduced oxygen content (15 wt%) compared to the FPBO and a comparatively low coking tendency (TGA residue of 1.4 wt%), was successfully processed in the downstream fixed bed process for 58 h without any noticeable decrease in catalyst activity, or increase in pressure drop. The overall process resulted in a 29 wt% yield of deoxygenated oil product (0.5 wt% oxygen) from FPBO with an overall carbon recovery of 68%.

In this study, the acid-base bifunctional magnetic ZrMg@Fe₃O₄ metallic oxide catalysts with remarkable structural properties were synthesized by the co-precipitation method for the catalytic transfer hydrogenation (CTH) of furfural (FF), ethyl levulinate (EL), and 5-methylfurfural (5-MF) to furfuryl alcohol (FFA), gamma-valerolactone (GVL), and 5-methyl-2-furanmethanol (5-MFA). Characterization results indicated that the ZrMg@Fe₃O₄ (7: 1:1) catalyst possesses a substantial pore volume, large specific surface area, and mesoporous properties, which play an important role in improving catalytic activity. The leaching experiment indicated that the catalyst was not prone to leaching, proving its structural stability. The yield of FFA, GVL, and 5-MFA could be as high as 92.50%, 95.00%, and 53.95% by optimization experiments. The Py-FTIR, CO₂-TPD, and poisoning experiments showed that Lewis acid-base sites significantly impact the catalytic activity. The catalyst can be readily isolated and retrieved from the liquid reaction mixture by applying the external magnetic field. The reaction mechanism and catalytic stability were also conducted by systematically studying the reaction experiments and physicochemical properties of the catalyst.

Reliable and stable ignition under lean conditions is essential for safe operation of the engine. Nanosecond pulsed discharge non-equilibrium plasma assisted ignition characteristics of premixed ethylene-air flow in an advective combustion chamber were investigated. The effects of the equivalence ratio, discharge gap distance, flow velocity, discharge frequency or inter-pulse time, and pulse number were quantified in terms of ignition probability. Shadow images of ignition kernel development were captured and used to extracted the averaged kernel projected area. The results indicated that increasing the equivalence ratio, a higher flow velocity, a wider discharge gap distance, and a larger number of pulses are all conducive to the increasing of ignition probability via inducing a larger initial kernel. Increasing inter-pulse time has a non-monotonic effect on ignition probability for multiple nanosecond pulsed discharges ignition. As the inter-pulse time decreases, when neighboring kernel boundaries happen to overlap each other, the partially-coupled regime shows a higher ignition probability. Longer or shorter inter-pulse time both cause the decrease in ignition probability. The shortest inter-pulse time shown as the fully-coupled regime is the most favorable for ignition with the highest ignition probability. A method is proposed to estimate the critical frequency at which partially-coupled regime transitions to fully-coupled regime by 95% of the asymptotic time of flame development time.

Sustainable production of jet fuel additives plays an essential role to decrease greenhouse gas emissions in the aviation industry. Acetone obtained from biomass fermentation is one of the platform molecules of the bio-refinery that can be used as raw material of newly developed sustainable processes. Mesitylene jet fuel additive can be obtained by acetone self-condensation reaction catalyzed by porous solids. In the present work, TiO₂ and Al-MCM-41 have been chosen, respectively, as basic and acid catalysts, because of having some tolerance to deactivation. The reaction was studied in a continuous fixed-bed reactor operated in the gas phase at space velocities of 7900 mol/kg h for TiO₂ and 5000 mol/kg h for Al-MCM-41. The influence of feed concentration (5–20% acetone and 0–5% mesityl oxide) and temperature (200–350 °C) was studied. First, the reaction scheme was assessed based on the product distribution. It was found that the acid catalyst Al-MCM-41 favors mesityl oxide decomposition to undesired isobutylene and acetic acid. Then, a mechanistic kinetic model of the different steps of the reaction scheme was developed and fitted the experimental results of each catalyst. This model constitutes a valuable tool for the scale-up of this process.

In this study, we demonstrate the continuous catalytic hydrotreating of sewage sludge-derived hydrothermal liquefaction oil on a versatile, pilot-scale testing unit, equipped with both a slurry and a fixed-bed reactor. Comparison of the two reactors shows that slurry hydrocracking is consistently more efficient in both heteroatom removal and cracking performance compared to the fixed-bed operation. The upgraded HTL oil from the slurry reactor contains 35% less nitrogen that the equivalent oil produced from the fixed-bed reactor at 350 °C and is lighter, consisting of 84 wt% molecules in the gasoline and diesel range, compared to 63 wt% in its counterpart. This is tentatively ascribed to the higher residence time and the lower mass-transfer limitations in the slurry reactor that enhance the hydrogenation and cracking reactions. Upgrading the HTL oil in a two-stage configuration improves only the nitrogen removal, which increases from 40‐55% in the one-stage process to 83%. Overall, slurry hydrocracking appears to be a promising strategy for the upgrading of bio-oils from renewable feedstocks, such as waste and biomass. Further research is required to study operability and stability issues for longer time-on-stream and investigate the process in the presence of dispersed liquid catalysts.

MSW pyrolysis and gasification technologies have been recognized as effective means to enhance the resource utilization of MSW and promote a circular economy. However, the presence of HCl gas can significantly impact the quality and application of syngas. To maximize syngas resource utilization, develop highly efficient HCl adsorbent, this study investigates the performance and mechanism of HCl removal from syngas using a conventional hydrotalcite (Mg-Al-CO₃) and modified Ca-based hydrotalcite (Ca-Mg-Al-CO₃). The impact of CO₂, a component naturally presents in syngas, on the performance of both materials, were also investigated. Characterization techniques, including XRD, TGA, SEM, and analysis of pore properties and specific surface area, were employed to understand the underlying reaction mechanism. The results demonstrated that the performance of Ca-Mg-Al-CO₃ was significantly superior to that of conventional Mg-Al-CO₃ sorbents, particularly in the presence of CO₂ However, the presence of CO₂ had a detrimental impact on the performance of Ca-Mg-Al-CO₃ in HCl removal, and this effect became increasingly pronounced with higher concentrations of CO₂. TGA results revealed a competitive relationship between HCl and CO₂ during the adsorption process. Additionally, the fitting results of adsorption kinetics suggested that the adsorption reaction of HCl and CO₂ by Ca-Mg-Al-CO₃ followed multiple rate-controlling mechanisms.

To overcome the defects of the traditional selective non-catalytic reduction (SNCR) process (e.g., low efficiency, narrow temperature range), a new modified SNCR technology based on the solid complex polymer reducing agents, also called polymer non-catalytic reduction (PNCR), was investigated both in the laboratory and pilot scale to reveal its reaction characteristics and mechanism. The PNCR process demonstrates excellent removal efficiency (about 90%) of NO in furnace in the wide temperature range (850–1150 °C), and possesses promising application feasibility with an average NO_x emission concentration of 68.72 mg·m⁻³ even on unstable industrial operating conditions. The NO removal behaviors influenced by O₂, temperature, or water steam illuminate the unique O₂-independent and H₂O-promoted reaction characteristics of PNCR in the wide temperature range. The thermogravimetric infrared spectra/mass spectrometry (TG-IR/MS) results further reveal a pyrolysis-assisted formation mechanism of active NH₂/NH free radicals without the requirement of O₂ and high temperature, which avoids the overoxidation of active radicals and accounts for the wide denitrification temperature window, low oxygen compliance and high denitrification efficiency of PNCR process. The excellent NO removal performance as well as the unique reaction characteristics/mechanism of PNCR forebode its broad industrial application prospect in the field of flue gas cleaning.

Methanol steam reforming (MSR) for hydrogen production is a significant and promising clean energy technology. So, a comprehensive review focused on the analysis of high-temperature reforming, low-temperature reforming, autothermal reforming, and CO removal in MSR is conducted. The selection and design of catalysts play a crucial role in enhancing the efficiency and stability of MSR, which can improve the selectivity of methanol decomposition and hydrogen generation, and reduce the occurrence of side reactions. The optimized reactor design and better thermal management technology effectively reduce heat loss and achieve high energy efficiency in methanol autothermal reforming. Furthermore, gaining profound insights into the reaction mechanisms plays a pivotal role in guiding catalyst development and reactor enhancements, which is instrumental in addressing catalyst deactivation, catalyst longevity, and undesired side reactions. CO removal technology plays a pivotal role in the hydrogen production process of MSR. It is employed to eliminate CO impurities, thus enhancing the purity of the hydrogen production. This review contributes valuable insights into high-purity hydrogen production, catalyst stability improvement, and key challenges linked to CO removal in MSR, facilitating advancements in hydrogen technology.