Ceramics composites from iron ore tailings and blast furnace slag

The search for materials and methods capable of reducing human impacts on the environment is of utmost importance nowadays. This study's primary purpose was to analyze the technical feasibility of ceramic composites production utilizing Fundão Dam's Iron Ore Tailings (IOT), Blast Furnace Slag (BFS) from charcoal, and Foundry Sand (FS) as partial substitutes for the traditional raw materials – sand and clay – for application in building industry materials. The composites were molded in rectangular specimens and fired at temperatures of 900, 950, 1000, 1050, and 1200 °C. The developed materials were analyzed and characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Thermogravimetry (TGA), and Differential Thermal Analysis (DTA). The obtained materials had flexural strength modulus of up to 12.19 MPa, water absorption ranging from 2 to 22%, linear shrinkage ranging from 0.02 to 6.50%, and apparent density ranging from 2.03 to 1.63 g/cm³. The study of the internal structure formation process revealed the formation of amorphous structures in the composites. The results demonstrated that these waste materials may be jointly used in construction materials, contributing to the reduction of natural resource extraction, besides enabling their correct disposal, minimizing environmental impacts, and improving the life quality of the surrounding communities.     

Gasification of charcoal using supercritical CO2 at high pressures

A novel one-shell high temperature and high pressure semi-continuous reactor has been developed for the study of the Boudouard reaction at temperatures up to 820 °C and pressures up to 32.5 MPa. Semicontinuous gasification of charcoal using supercritical CO₂ has been achieved at conversions up to 90.8% (w/w) at LSHV between 20 and 30 h⁻¹ after 5–9 h. A gasification model is proposed and validated. Effective rates of gasification (1.32 ± 0.12) × 10⁻⁶ to (6.10 ± 2.03) × 10⁻⁵ s⁻¹ were obtained. The results indicated that this method is technically feasible for the on-line production of high pressures streams of CO/CO₂ in the lab for carrying out further chemistries, avoiding the use of CO high pressure bottles.     

被动式活性炭氡采样器扩散控制管设计参数的选择

本文介绍被动式活性炭氡采样器扩散控制管设计参数的选择方法。通过对活性炭吸附氡量与暴露时间的关系式的线性化处理,选择了适当的扩散控制管的参数,可以大大减小温度对测量结果的影响,同时可保持探测器有较高的灵敏度。     

Depollution of atmospheric emissions of wood pyrolysis furnaces

The wood carbonization in Tunisia consists essentially of traditional activity using charcoaling stacks and pits characterized by high atmospheric pollution and poor energy conversion. Indeed, 70% of the initial mass of anhydrous wood are found in the vapor as aerosols, polluting and toxic gases and complex condensable organic compounds that can cause a substantial pollution of air, ground and water. Several processes of treatment and energy valorization of such effluents were proposed, but the incineration remains at present the most promising technique of depollution. The results show that the incineration, at about 1000°C, of wood carbonization smokes allows the destruction of 99% of the mass of pollutants except CO₂ and the reduction of polluting gas emission. The possible valorization of the smoke’s energy in the exit of the incinerator enhances the thermal efficiency of the process.     

Gasification reactivity of charcoal with CO2. Part I: Conversion and structural phenomena

The gasification reaction of fir charcoal with CO₂ was studied by isothermal thermogravimetric analysis under kinetic control. The derived reaction rate (r=dX/dt) as a function of the converted carbon mass (X) was compared with random pore model predictions and found to be much higher at elevated conversion levels than predicted by theory. Similar enhanced reaction rate behaviour was evidenced after removing the natural alkali catalyst from the charcoal by acid washing, suggesting that with untreated charcoal the late reaction rate contribution stems from both, catalytic and additional structure effects. Literature attributes the unpredicted late reaction rate behaviour to the disintegration of the porous char particle into small fragments, which, in line with percolation theory predictions, seems to occur only after a critical conversion level has been reached. However, our gasification data reveal a gradual rise in the charcoal reactivity thereafter, suggesting a breaking up (embrittlement) of the solid phase accompanied by the exposure of fresh surface area from fracturing. The original random pore model derivation given by Bhatia and Perlmutter is extended to account also for these peculiarities and the resulting kinetic relation described our reaction rate data well over the entire conversion range.     

竹炭的改性及对PP废塑料性能影响的研究

首先用硅烷偶联剂γ-氨丙基三乙氧基硅烷(KH550)处理竹炭(BC)得到K-BC,再通过熔融共混制备了一系列的K-BC/聚丙烯废洗衣机料(X-PP)复合材料,通过扫描电子显微镜(SEM)表征了BC的形貌,分析了K-BC含量对复合材料物理性能、尺寸稳定性、热变形温度(HDT)及维卡软化温度(VST)的影响。结果发现,BC内部拥有很多的孔隙,且这些孔隙都能被X-PP填充;KH550处理后的BC对X-PP的物理性能、尺寸稳定性、热变形及维卡软化温度的提升比未处理的BC好;随着K-BC的加入,复合材料的熔体质量流动速度、缺口冲击强度和断裂伸长率降低,K-BC添加量越大,降低的越多;复合材料的弯曲模量、HDT、VST和尺寸稳定性随着K-BC添加量的增大而上升,拉伸强度和弯曲强度随着K-BC添加量的增大,先增大后减少。     

The role of charcoal on DTA curves of organo-clay complexes: an overview

DTA of organo-clay complexes supplemented by other thermal analysis methods supplies information on the thermal reactions, properties and stability of the complex, the amount and properties of the adsorbed water in the organo-clay and on the bonding between the organic species and the clay. It is used to identify the mineral to differentiate between various complexes composed of the same clay and the same organic ligand and to establish their composition. During the gradual heating in oxidizing atmospheres the adsorbed organic material is oxidized, giving rise to significant exothermic peaks. DTA curves of organo-clays are divided into three regions: (1) the dehydration of the clay, (2) the thermal oxidation of the organic material and (3) the dehydroxylation of the clay. The exothermic oxidation reaction occurring during the gradual heating of the sample takes place in two steps, in the range 200–500 °C, oxidation of organic hydrogen and formation of water and charcoal, and 400–750 °C, oxidation of charcoal and formation of CO₂. The exothermic peak temperatures depend on the mineral and on the organic compound and on the types of bonding between these two components of the organo-clay complex. The present communication concentrates in the role of the combustion of charcoal in the study of the fine structure of the complex and of the type of associations between the organic compound and the clay.     

PAH emissions from an African cookstove

Combustion of wood and other biomass is a significant contributor to poor air quality in many developing countries. Emissions of particulates and Polycyclic Aromatic Hydrocarbons (PAH) are a major health hazard, particularly in Africa where the use of domestic cookstoves has increased alongside population expansion. Because of economic factors firewood is commonly used in place of the more expensive charcoal; particularly in rural areas. This work conducts a study of PAH emissions from an African cookstove comparing the combustion of both charcoal and firewood. It is demonstrated that PAH and particulate emissions are much higher from the firewood compared to the charcoal. The difference in levels can be interpreted due to the importance of the pyrolysis reactions of the volatile components of wood in PAH formation, whereas these volatiles emissions are much smaller from charcoal. Analysis of the combustion phases (flaming, smouldering) is undertaken and a computer model has been developed to link the composition of the fuels to the emissions of the PAH and particulates. The modelled PAH levels are shown to follow a similar trend to the experimental results.     

Research on the thermal decomposition and kinetics of byproducts from MgO wet flue gas desulfurization

This paper was aimed at the thermal decomposition and kinetics of the byproducts from MgO flue gas desulfurization. The effects of particle size and charcoal on thermal decomposition of the byproducts were investigated by the thermogravimetric analysis method, and the non-isothermal kinetic parameters of the byproducts were evaluated with the Coats–Redfern method. The results showed that the mass loss increased with the decrement of the particle size. However, the effect of the particle size on the mass loss of each thermal decomposition stage was different. Increasing the amount of charcoal powder in the byproducts had an obvious effect on the temperature characteristics of the thermal decomposition of magnesium sulfate, resulting in a reduced thermal decomposition temperature which could facilitate the thermal decomposition process. The equations G(α) = 1−(1−α)^1/2, G(α) = [−ln(1−α)]², and G(α) = 1−(1−α)^1/3 were the quite appropriate kinetic mechanisms describing the thermal decomposition process of MgCO₃, MgSO₃, and MgSO₄, respectively.     

QXX116-1.6/130/70-M型循环流化床热水锅炉木炭点火过程及分析

介绍唐山锅炉厂116MW循环流化床热水锅炉(相当于165t/h蒸汽锅炉)的木炭点火实践，并阐述原理。