Flash co-pyrolysis of biomass with polylactic acid. Part 1: Influence on bio-oil yield and heating value

High amounts of water present in bio-oil are one of the major drawbacks for its utilisation as a fuel. One technology that shows the potential to satisfy the demand for bio-oil with a reduced water content is the flash co-pyrolysis of biomass with polylactic acid, PLA. The influence of PLA on the pyrolysis of willow is investigated with a semi-continuous home-built pyrolysis reactor. Flash co-pyrolysis of willow/PLA blends (10:1, 3:1, 1:1 and 1:2) show synergetic interaction. A higher bio-oil yield and a lower water content as a function of the willow/PLA ratios are obtained. Among the tested blends, the 1:2 willow/PLA blend shows the most pronounced synergy: a reduction in the production of pyrolytic water of almost 28%, accompanied by an increase of more than 37% in the production of water-free bio-oil. Additionally, PLA shows to have a positive influence on the energetic value of the bio-oil produced and on the resulting energy recuperation.     

桑蚕茧丝的热裂解气相色谱研究

本文用裂解气相色谱法研究了桑蚕茧丝的热裂解行为。研究结果表明,桑蚕茧丝在管式炉中220℃左右时开始裂解,裂解的主要产物是氢、氧、氮、一氧化碳,二氧化碳和甲烷等六种气体。丝素有与此相同的裂解产物。裂解气体中各种气本的相对含量,随裂解温度和裂解时间的变化而变化。由此算出了在1000℃时的热裂解反应的动力学参数,推测了热裂解反应的历程。     

Textures of pyrolytic carbon formed in the chemical vapor infiltration of capillaries

Capillaries, 1.1 mm in diameter and 17.0 or 32.5 mm in length, were infiltrated at a temperature of 1100 °C and methane pressures from 5 to 30 kPa. Layer thickness and carbon texture were determined at cross-sections of 2, 16 and 32 mm from the open end of the capillaries using polarized light microscopy. Average deposition rates, determined from layer thickness and infiltration time, as a function of methane pressure indicate a rate increase up to a saturation adsorption at pressures between 10 and 15 kPa (range 1) and a strong rate increase above these pressures (range 2). This result implies carbon formations based on the growth mechanism in range 1 and the nucleation mechanism in range 2. The carbon texture shows a maximum in range 1 and a minimum in the transition from range 1 to range 2 followed by a clear increase in range 2. The maximum in range 1 corresponds to the particle-filler model describing formation of various textures of carbon by the ratio of aromatic species to C₂ species. Increasing texture degrees in range 2 suggest that the nucleation mechanism may lead to high textured carbon provided that the residence time for intramolecular rearrangments of polycyclic aromatic hydrocarbons is sufficient.     

Effects of needle-punched felt structure on the mechanical properties of carbon/carbon composites

The effects of needle-punched felt structure, including mass ratio of non-woven cloth to short-cut fiber web, PAN-based carbon fiber types of non-woven cloth and thickness of unit (one layer of non-woven cloth and short-cut web was named as a unit), on the flexural properties of C/C composites from pressure gradient CVI are discussed. Results show that flexural strength and modulus increase when mass ratio of non-woven cloth to short-cut fiber web changes from 7:3 to 6:4 and that PAN-based carbon fiber types of non-woven cloth strongly influence the flexural properties. The strength of C/C composites is not linear with the strength of non-woven cloth carbon fiber because of the important interface between carbon fiber and matrix carbon. It is suitable to choose T300 or T700 as reinforcing carbon fiber for C/C composites in the present study. An optimum unit number per cm of the needle-punched felts for higher flexural properties exists.     

Carbothermal reduction reaction enhanced wettability and brazing strength of AgCuTi-SiO2f/SiO2 system

A carbothermal reduction reaction (CRR) approach was developed in this research to tailor the surface phase structure of the SiO_2f/SiO₂ composites with high chemical reactivity to replace the original inert surface. Results show that SiC can form after CRR treatments. For AgCuTi-SiO_2f/SiO₂ wetting interfaces, TiC and residual pyrolytic carbon layer can be found inside the reaction layer, which was the key, promoting the wettability of the AgCuTi-SiO_2f/SiO₂ system. The contact angle of the AgCuTi-SiO_2f/SiO₂ system dropped from 127° to 43° after the CRR treatments. The reliability of the bonded AgCuTi-SiO_2f/SiO₂ interface was also characterized by putting 3 different systems into comparison, i.e., the original AgCuTi-SiO_2f/SiO₂ system, the AgCuTi-SiO_2f/SiO₂ system with CRR treatments (SiC formation) and the AgCuTi-SiO_2f/SiO₂ system coated with powdered carbon (no SiC formation). The shear strength of the SiO_2f/SiO₂-AgCuTi-SiO_2f/SiO₂ system with CRR treatments was the highest, which was 3 times that of the other 2 brazing systems.     

中国含油气盆地与石油地质理论进展

中国沉积盆地受３个古陆块的离散、聚合和周边古板块作用演化的控制。整体上可划分灶蜃于纪－古生代海相盆地体系和中、新生代陆相盆地体系，前者具有天然气资源优势，后者具有石油资源优势。陆相石油地质理论已成为石油地质理论的重要组成部分，陆相成因油藏是中国石油开采的主体，理论和勘探和发展都在深入。     

Electrical resistance and magnetoresistance of pyrocarbon at low temperatures in fields up to 14 Tesla

Electrical resistivity measurements in an applied magnetic field B up to 14 T were performed at low temperatures T on several samples of pyrolytic carbon deposited on a substrate of pyrolytic boron nitride. The films were produced in a CVD reactor at 1100°C from a methane/argon gas flow. For B, a maximum is observed in the electrical resistance at low temperatures T≈10 K which has been previously found for carbon fibers. The magnetoresistance in this T region can be separated into an isotropic positive part and an anisotropic negative contribution.     

Nanocrystalline graphite-like pyrolytic carbon film electrode for electrochemical sensing of hydrazine

Pyrolytic carbon film (PCF) electrode fabricated by a non-catalytic chemical vapor deposition (CVD) process was used as an electrochemical sensor for the detection of hydrazine. The electrode response was found to be electrocatalytic producing a reduction in the overpotential compared to other unmodified carbon-based electrodes such as glassy carbon (GC), basal-plane pyrolytic graphite (BPPG), and edge-plane pyrolytic graphite (EPPG) electrodes. The overall number of electrons involved in the electro-oxidation of hydrazine, the number of electrons involved in the rate-determining step, and diffusion coefficient of hydrazine at PCF electrode were estimated using cyclic voltammetry and chronoamperometry. The performance of PCF electrode was comparable to and in some cases even better than many chemically modified electrodes in terms of detection limit, linear dynamic range, and sensitivity. Moreover, the sensor exhibited fast response time (within 2 s), high response stability, and reproducibility. All the results indicated this sensor is suitable for hydrazine analysis.     

Corrosion resistance of pyrolytic graphite in LiCl-KCl-UCl3 molten salt for pyrochemical reprocessing application

Pyrolytic graphite (PyG) is a highly oriented, dense and crystalline form of graphite, which exhibits superior air oxidation resistance, corrosion resistance, and favourable mechanical, thermal, and electrical properties compared to conventional graphite materials. It is proposed as the material of construction for high-temperature molten LiCl-KCl for pyrochemical reprocessing of metallic fuel. In the present study, long-term corrosion behaviour of PyG in LiCl-KCl molten salt with 5?wt-% UCl₃ was evaluated by immersion studies at 873?K for 2000?h, under inert argon atmosphere. Characterisation of PyG before and after molten salt exposure was carried out using X-ray diffraction technique, scanning electron microscope with energy dispersive spectroscopy, laser Raman spectroscopy and X-ray photo-electron spectroscopy. The results revealed the superior corrosion resistance and excellent phase stability of PyG with negligible weight change and no appreciable change in the surface chemistry and morphology up to the exposure time of 2000 h.