Higher Devolatilization Research Articles

322P/SOHO: The counterpart of a historical comet in 254 CE?

The historical observations of East Asia provide a systematic and accurate record of bright periodic comets and could help us understand their past states. However, except for these comets, few other comets have been successfully associated with historical observations. Here we report that the sunskirter 322P/SOHO is probably associated with a historical comet in 254 CE, although it appeared no visible cometary activity in recent observations. By analyzing astrometric data from the IAU Minor Planet Center, we determine the orbit of 322P and suggest that its motion is affected by non-gravitational forces based on sodium sublimation, indicating its high devolatilization. The orbital integration shows that the position and perihelion date of 322P are highly corresponding to a historical comet in 254 CE. This comet had an extremely long tail that stretched across the sky, indicating the intense activity outburst. The dynamical properties of 322P and its similarity to dark comets suggests that it possibly originated from a volatile object in the main belt, but has undergone the rotational splitting and devolatilization. Previous studies have also suggested the possible splitting. Given that splitting is a common cause of activity outburst, we suggest that 322P might have experienced a fragmentation in 254 CE and released a large amount of material, which led to the spectacular tail and devolatilization. Only faint sodium-driven activity remained afterwards, which could explain the lack of historical observations after 254 CE.

Design of novel bracket structure for falling film devolatilizer and numerical simulation of its film-forming property

The falling film devolatilizer is a new type of devolatilization equipment, which has the advantages of high film-forming efficiency and no mechanical transmission. In this study, a devolatilizer with an open falling film substrate was designed, and the film-forming performance and surface renewal performance of high viscosity fluids under the falling film structure were numerically simulated. The results indicate that the opening of the falling film substrate makes the liquid film thinner, which is beneficial for the stretching of the liquid film. The advantages of the falling film under low viscosity and high flow rate conditions are more significant. Simultaneously, four bracket structures were designed. Compared with the rectangular bracket, the renewal frequency of fan-shaped brackets can be increased by more than 20%, and the flow rate can be increased by about 10%. The improvement of the two can directly improve the falling film devolatilization performance, so as to improve the polymer polymerization degree and improve the product performance. Therefore, exploring the falling film support frame with high devolatilization performance provides a certain engineering practical significance for the design of devolatilization equipment.

Hydrothermal carbonization of mixture waste Gingko leaf and wheat straw for solid biofuel production

Co-hydrothermal carbonization (co-HTC) of ginkgo leaf residues (GLR) and wheat straw (WS) were conducted to investigate the possibility for mutually benefitting the two residues as feedstock to produce solid biofuel pellets. The mass yield, proximate, and elemental analysis of the hydrochar were characterized. The energy consumption during pelletization, pellet density, pellet durability, water resistance ability, and pyrolysis characteristics of hydrochar pellets were evaluated. The results show that when WS blended with 50%, the energy density of pellet increased from to the highest of 26.7 GJ/m3. The ash content decreased from 7.7% to 6.3% when the WS blended with 30%− 70%, while HHV showed a opposite trend. As the WS blended ratio increased from to 30–70%, the high lignin content in WS helped to enhance the mechanical properties of pellet including pellet density, durability, and hardness. The hydrochar pellets from high ratio WS had high devolatilization index indicating increased devolatilization ability. These findings imply adding WS in co-HTC would potentially promote the GLR to manufacture high quality solid biofuel. Overall, the co-HTC of WS and GLR is a promising alternative to transfer solid wastes to renewable fuels.

Recycling Pomelo Peel Waste in the Form of Hydrochar Obtained by Microwave-Assisted Hydrothermal Carbonization.

Pomelo peel (PP) is a kind of solid waste that is produced in the processing industry of honey pomelo. This study deeply explored the feasibility of recycling PP in the form of hydrochar (HC) by microwave-assisted hydrothermal carbonization (HTC) technology. Under the non-catalytic reaction conditions, the yield of hydrochar initially increased with the rise of reaction temperature (150-210 °C) until it remained relatively stable after 210 °C. Under the CaO-catalytical reaction condition, the yield of hydrochar did not change much at first (150-190 °C) but decreased significantly when the reaction temperature exceeded 190 °C. After the microwave-assisted HTC treatment, the PP-derived HC presented higher aromaticity, carbonization degree, porosity, and caloric value. Compared with raw PP, the nutrients in HC were more stable (conducive to being used as slow-release fertilizer). The application of CaO increased the pH value of HC and effectively promoted the accumulation of phosphorus in HC. The HC produced at 210 °C without any catalyst possessing a high devolatilization ability. Additionally, the HC obtained at 190 °C with CaO as the catalyst presented a high combustion property. In general, PP-derived HC showed great application potential in the field of soil remediation/improvement and solid fuels. This preliminary study would undoubtedly provide some important fundamental understanding of the microwave-assisted HTC of PP.

The thermal degradation of lignocellulose biomass with an acid leaching pre-treatment using a H-ZSM-5/Al-MCM-41 catalyst mixture

Improvements on the pyrolysis process of biomass fuels are needed to obtain a high-quality of bio-oil. Pre-treatment by acid leaching prior to the pyrolysis process is considered to remove Alkali and Alkaline Earth Metal (AAEM) from the biomass, since AAEM adversely affect the catalytic pyrolysis process. Therefore, the main objective of the present work was to determine and compare the effect of mixed-catalysts consisting of H-ZSM-5 and Al-MCM-41, which are used at different ratios in lignocellulose biomass pyrolysis via Thermal Gravimetric Analysis (TGA) for both, un-leached and leached biomass. In addition, the activation energies have been determined based on the solid-state reaction mechanism. The results from the acid leaching treatment showed that the optimum leaching process was set to 30 min, 30 °C and 5 wt% acetic acid in the leaching liquid. This resulted in 59%, 95%, 99%, and 96% reduction degree of Calcium (Ca), Magnesium (Mg), Potassium or Kalium (K), and Natrium (Na), respectively. The Higher Heating Values (HHVs) for un-leached and leached biomass were 19.42 and 19.14 MJ/kg, respectively, calculated by using the Milne formula. The HHV value is not significantly influenced by the acid-leaching pre-treatment. Thermogravimetric analysis showed similar trends for the mass loss as a function of temperature and four stages could be determined from the thermal degradation of biomass. There was no significant shift in the temperature profiles between un-leached and leached biomass degradations. However, the removal of AAEM significantly affected the degradation of hemicellulose, cellulose, and lignin. A 12.4–18.2% increase of mass losses could be found in Phase 2 for leached biomass, compared to un-leached biomass. The mass losses in Phase 2 also increased with increased heating rates. From the un-leached biomass experiments using a catalyst mixture, the percentage of mass loss increased from 64.95 wt% at 10 K min−1 to 68.33 wt% at 50 K min−1. Moreover, for the leached biomass, it rose from 65.71 wt% at 10 K min−1 to 66.73 wt% at 30 K min−1, before decreasing to 62.44 wt% at 50 K min−1. A lower mass loss in Phase 4 for leached biomass compared to un-leached biomass showed the influence of an AAEM removal. The second order (F2) mechanism was able to illustrate the catalytic pyrolysis process, proven by the result that the coefficient of determination (R2) was higher than 0.99, which was high compared to other mechanisms. An acid leaching pre-treatment led to a reduction in the activation energies. The activation energies for the un-leached biomass were 26.94 and 25.56 kJ mol−1 at a heating rate of 10 K min−1 for a process without and with a catalyst mixture, respectively. The activation energies for leached biomass were 24.05 and 21.80 kJ mol−1. The results also showed that the use of the acid leaching process as a treatment prior to catalytic pyrolysis is positive, since it resulted in high devolatilization and reaction rate.

Causes of distal volcano-tectonic seismicity inferred from hydrothermal modeling

Distal volcano-tectonic (dVT) seismicity typically precedes eruption at long-dormant volcanoes by days to years. Precursory dVT seismicity may reflect magma-induced fluid-pressure pulses that intersect critically stressed faults. We explored this hypothesis using an open-source magmatic-hydrothermal code that simulates multiphase fluid and heat transport over the temperature range 0 to 1200°C. We calculated fluid-pressure changes caused by a small (0.04km3) intrusion and explored the effects of flow geometry (channelized vs. radial flow), magma devolatilization rates (0–15kg/s), and intrusion depths (5 and 7.5km, above and below the brittle-ductile transition). Magma and host-rock permeabilities were key controlling parameters and we tested a wide range of permeability (k) and permeability anisotropies (kh/kv), including k constant, k(z), k(T), and k(z, T, P) distributions, examining a total of ~1600 realizations to explore the relevant parameter space. Propagation of potentially causal pressure changes (ΔP≥0.1 bars) to the mean dVT location (6km lateral distance, 6km depth) was favored by channelized fluid flow, high devolatilization rates, and permeabilities similar to those found in geothermal reservoirs (k~10−16 to 10−13m2). For channelized flow, magma-induced thermal pressurization alone can generate cases of ∆P≥0.1 bars for all permeabilities in the range 10−16 to 10−13m2, whereas in radial flow regimes thermal pressurization causes ∆P<0.1 bars for all permeabilities. Changes in distal fluid pressure occurred before proximal pressure changes given modest anisotropies (kh/kv~10–100). Invoking k(z,T,P) and high, sustained devolatilization rates caused large dynamic fluctuations in k and P in the near-magma environment but had little effect on pressure changes at the distal dVT location. Intrusion below the brittle-ductile transition damps but does not prevent pressure transmission to the dVT site.