Catalytic Materials for High-Temperature Combustion

Catalytic combustion, as an alternative to conventional thermal combustion, has received considerable attention during the past decade. Research efforts have been promoted by the need to meet governmental demands concerning pollution and the wish to use energy sources more efficiently. The two main advantages offered by catalytic combustors over flame combustors apply to these goals:

1. Catalytic combustion can be carried out over a wide range of fuel concentrations in air and at low temperatures.
2. These low temperatures result in attaining NO, emission levels substantially lower than possible with conventional combustors.

     

Aerodynamic High-Temperature Particle Characterization

For the purpose of in situ sampling at high temperatures the INertial SPECtrometer (INSPEC) has been modified by the adoption of appropriate materials (stainless steel and mineral seals). Since membrane filters suitable for this environment are not easy to find, the INSPEC architecture has been changed in order to allow quartz fiber filters to be used: because of their surface roughness, they are used downstream of a grid that has the purpose of flow confinement; the filter mat captures the particles and controls the flow rate in each grid slot. The particles are separated with a resolution of 2%–6%, in the aerodynamic size range, 0.5–10 or 1–20 μm, according to the total flow rate. The sampling flow rate ranges from a few tens of milliliters per minute to 0.5 L/min, with some sacrifice in resolution at higher values. The relationship between deposition distance and size can be drawn with a confidence of above 3%. The filter can be subjected to scanning electron microscopic measurement of the geometric size: this can be compared to the aerodynamic size and the particle density can be assessed with precision and accuracy comparable to the size resolution. At present, the unit has been successfully tested up to 300° C; for higher temperatures a test apparatus is yet not available.     

A Physicochemical Study of Properties of Integrated High-Temperature Heat-Insulating Materials

Results of a study of properties of integrated high-temperature heat-insulating materials based on expanded vermiculite are reported. These materials combining low heat conductivity and high strength, have a potential for use as lining refractories in thermal power units with operating temperatures not exceeding 1100°C.     

丁醇柴油的燃油经济性和排放特性研究

按照体积分数配制出10%的丁醇柴油,在一台四缸柴油机上,对燃烧10%的丁醇柴油和国标0#柴油的燃油经济性和排放性进行了试验。研究结果表明:在柴油机参数不做改变的情况下,外特性工况下燃烧10%的丁醇柴油(B10)的动力性有所下降,输出转矩最大降幅达7.9%,油耗有所升高,在负荷特性工况下,发动机燃用B10时的油耗率与燃用国标0#柴油的油耗率相差不大。两种工况下的排放,相对于国标0#柴油:发动机燃用10%的丁醇柴油时,除HC排放上升外,CO、CO2、NOx和碳烟排放都有所降低,其中碳烟排放显著降低,体现出丁醇柴油这一含氧混合燃料的排放优势。     

Technology Status of Particulate Removal from High-Temperature High-Pressure Combustion Gases

The adoption of coal-fired pressurized fluidized-bed combined-cycle combustion systems by utilities for electric power generation depends to a large extent on the development of an efficient and economic cleanup system between the combustor and gas turbine. To accomplish particulate removal from a dust-laden gas stream, a number of separation devices have been developed. These include conventional and augmented cyclones; porous metal, fabric, and ceramic membrane filters; fixed-, continuously moving-, and fluidized-bed granular filters; electrostatic precipitators; as well as several other novel separation devices. The results of tests of these devices are discussed in relation to pressurized fluidized-bed combustion applications.     

Physicochemical and Rheological Characterization of Roll-in Shortenings

The composition and physical properties of roll‐in shortenings, commonly rich in trans and saturated fatty acids, were investigated and compared to other specialty fats, to provide insights into the physico‐chemical origins of their functionality. Triacylglycerols and fatty acid composition, polymorphic and melting behavior, solid fat content and large deformation rheological properties were determined. Roll‐in shortenings contained higher amounts of trisaturated and unsaturated triacylglycerols (12–27 %; 47–62 %) than other shortenings (9–11 %; 6–44 %). However, all exhibited high levels of saturates and trans fatty acids and similar crystal characteristics: β′ or mixed β′ and β, irrespective of their end use. Roll‐in shortenings had comparable melting peaks (42–52 °C) but sharper melting endotherms with higher enthalpies (38.6–43.3 J/g) than other bakery fats (18.7–25.4 J/g). This was in accordance with their well‐defined short spacings, indicative of smaller crystallites with more‐ordered packing. Solid fat profiles of roll‐in shortenings were akin to all purpose and cake interesterified shortenings, but not to all‐purpose and icing shortenings which displayed substantial melting as temperature rises. Differences in large deformation rheology (yield stress: σ^*, apparent Young modulus: E_app, yield value: C) were marginal and inconsistent with their solid fat content. Roll‐in shortenings exhibited E_app, σ and C in the order of 1–2 × 10⁶, 4–7 × 10⁴, and 7–29 × 10⁴ Pa, respectively. Particularly, the σ*and C, previously established as major parameters to specify the functionality of roll‐in shortenings, were not significantly different (p > 0.05). Overall, roll‐in shortening differed from other samples in regard to molecular makeup but not greatly in their physical parameters, suggesting that triacylglycerol composition has important implications on their functionality.     

Local Fluctuations of Physicochemical Parameters in Condensed System Combustion

Using the 3Zr + 2WO₃ system as an example, it is shown that fluctuations of physicochemical parameters in the combustion wave of a condensed system in both loose and pressed forms can be recorded by means of two parallel wires placed in the burning system. It is established that changes in the initial density of the system and its burning rate results in corresponding changes in the fluctuation frequency. The relationship between these three parameters can be expressed, as a first approximation, by a fairly simple analytical relation.     

Effects of High-Temperature Drying on Physicochemical Properties of Various Cultivars of Rice

Abstract

Three varieties of paddy rice, namely Langi and Amaroo from Australia and Chainart I from Thailand, were dried from high initial moisture content of about 27% down to 13–14% wet basis using a two-stage drying system. A fluidized bed dryer reduced the moisture content down to 18%. Drying experiments were carried out at 100, 125, and 150°C. Further moisture content reduction down to 14% was achieved by shade drying. As a result of these treatments, head rice yield increased proportionally with the drying temperature. In contrast to that, the yellowness, measured by colorimeter in terms of b value, showed an opposite trend. Starch characteristics were studied by Rapid Visco Analyser (RVA), x-ray diffraction, and differential scanning calorimetry (DSC). Pasting properties were affected by the drying temperature. The peak viscosity and break down were decreasing with the increase of drying temperature in all varieties while the setback values were increasing in Langi and Amaroo only. All starch samples displayed the typical A type x-ray diffraction pattern. The apparent crystallinity determined by x-ray diffraction was reduced with increasing drying temperature. The gelatinization peak shifted to higher temperature while the endothermic enthalpy of gelatinization decreased with increasing drying temperature.     

Physicochemical Characterization of Polymer-Stabilized Coacervate Protocells

The bottom-up construction of cell mimics has produced a range of membrane-bound protocells that have been endowed with functionality and biochemical processes reminiscent of living systems. The contents of these compartments, however, experience semidilute conditions, whereas macromolecules in the cytosol exist in protein-rich, crowded environments that affect their physicochemical properties, such as diffusion and catalytic activity. Recently, complex coacervates have emerged as attractive protocellular models because their condensed interiors would be expected to mimic this crowding better. Here we explore some relevant physicochemical properties of a recently developed polymer-stabilized coacervate system, such as the diffusion of macromolecules in the condensed coacervate phase, relative to in dilute solutions, the buffering capacity of the core, the molecular organization of the polymer membrane, the permeability characteristics of this membrane towards a wide range of compounds, and the behavior of a simple enzymatic reaction. In addition, either the coacervate charge or the cargo charge is engineered to allow the selective loading of protein cargo into the coacervate protocells. Our in-depth characterization has revealed that these polymer-stabilized coacervate protocells have many desirable properties, thus making them attractive candidates for the investigation of biochemical processes in stable, controlled, tunable, and increasingly cell-like environments.     

炭黑的物化性质及表征

炭黑是一种微观结构，粒子形态和表面性能都极为特殊的炭素材料，炭黑原生粒子是由同心石墨层排列组成，炭黑含有氢，氧及硫等元素，它们基本上位于炭黑表面，形成具有化学活性的表面官能团，决定了炭黑的化学性质，仪器分析技术的发展，为人们研究炭黑表面性质提供了有效的手段，进一步认识了炭黑粒子的表面形态。     

Physicochemical Processes in Pyrolysis and Combustion of Fireproof Polyacrylonitrile and Viscose Fibres

The characteristics of thermooxidative degradation of fibres in the presence of flame retardants, manifested by predominance of cross-linking processes which favors formation of CR over degradation processes, are established. Modification with flame retardants decreases the yield and toxicity of combustible volatile products, the rate of thermolysis, the activation energy of dehydration (for VF) and cyclization (for PAN fibres), and the exothermic effects and reverse heat flow to the polymer. The fibres obtained have OI of 32 vol. % and are resistant to wet treatments with a fireproofing effect.     

Creation of Shock-Abrasion Resistance Build-up Metal Using a Physicochemical Model of High-Temperature Processes

Build-up metal for shock-abrasion resistance was the focus of this work, where the mathematical model of physicochemical high-temperature processes developed by the authors in their previous works was used. A computer program based on the model permitted forecasting of the required chemical composition and structure of the build-up metal. Flux-cored wires were fabricated from a cold-rolled ribbon (1008 steel) and filled with a powder mixture. Low carbon steel (A 516) was used as the base metal. The specimens were prepared by 3-layered build-up. The prepared specimens were tested using light microscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), hardness measurements, and shock-abrasion resistance measurements. The results of the above-mentioned tests confirmed the correct calculation of the model and the good shock-abrasion resistance of the suggested build-up metal.     

Preparation and Characterization of High-Temperature Thermally Stable Alumina Composite Membrane

A crack- and pinhole-free composite membrane consisting of an α-alumina support and a modified γ-alumina top layer which is thermally stable up to 1100°C was prepared by the sol–gel method. The supported thermally stable top layer was made by dipcoating the support with a boehmite sol doped with lanthanum nitrate. The temperature effects on the microstructure of the (supported and unsupported) La-doped top layers were compared with those of a common γ-alumina membrane (without doping with lanthanum), using the gas permeability and nitrogen adsorption porosimetry data. After sintering at 1100°C for 30 h, the average pore diameter of the La-doped alumina top layer was 17 nm, compared to 109 nm for the common alumina top layer. Addition of poly(vinyl alcohol) to the colloid boehmite precursor solution prevented formation of defects in the γ-alumina top layer. After sintering at temperatures higher than 900°C, the common alumina top layer with addition of poly(vinyl alcohol) exhibits a bimodal pore distribution. The La-doped alumina top layer (also with addition of poly(vinyl alcohol)) retains a monopore distribution after sintering at 1200°C.     

Toxic Species Emissions from Controlled Combustion of Selected Rubber and Plastic Consumer Products

The main objective of this research is to identify the principal toxic species, either airborne or ash phase, expected to be released to the environment when selected plastics or rubberized materials undergo controlled combustion. The results are indicative of what can occur in municipal incinerators, in residential or industrial fires, or in open-air burning of waste materials in areas that are not serviced by trash pickup. The current emphasis is on materials used by the shoe manufacturing industry, especially rubber and plastic-type materials. The results are compared to those obtained during the combustion of a vehicle rubber tire, which was adopted as an arbitrary standard for comparison because of its current importance in recycling efforts. In addition, a comparison is made with the published results on a related topic dealing mainly with polyvinylchloride plastics. Highly toxic gases such as hydrocyanic acid, sulfur dioxide, and hydrogen chloride were among the main substances found during gas colorimetric testing. More than 92% of the particulate mass was found to be in the respirable range (i.e., less than 10 μm in size as based on cascade impactor analysis). In addition, toxic heavy metals, such as lead, chromium, and antimony, were detected in the smoke and ash phases of some of the materials. One of the materials analyzed (USA rubberized sole) was found to generate more hazardous gaseous contaminants (hydrogen chloride in both the smoke and ash phases, in addition to hydrocyanic acid and sulfur dioxide) than the rubber arbitrary standard. This result is suggestive of the need for additional studies with a larger sampling base. Should future studies show a similar trend, then recycling efforts to collect the huge amount of rubber and plastic that is discarded every year as harmless waste in the form of footwear would seem to be in order.