水煤浆技术应用现状及对策分析

文章对水煤浆技术在工业化应用过程中出现的技术问题进行了分析并提出了相应的对策。     

Z型管道中气体火焰传播规律的实验研究

本文实验研究了丙烷／氧气／空气的当量比气体燃烧火焰通过两个90°弯管形成的“z”型管道的传播规律,通过改变第一个弯管前加速段的长度和改变气体浓度,实验研究了稳定爆轰波,非稳定爆轰波以及爆燃火焰通过“z”型管道的传播规律。利用光电传感器记录弯管前后的火焰传播速度,运用燃烧理论和爆轰波的理论对实验结果做了分析。结果表明:稳定爆轰波通过“z”型管道时传播速度有明显的下降;但“z”型管道对非稳定爆轰波的传播作用受到非稳定爆轰波自身速度的影响;爆燃火焰通过“z”型管道时火焰传播速度的变化呈现不确定性。     

风障减少尘埃飞起的风洞模拟研究

在环境风洞中对具有相同孔率但孔径不同的11种风障模型(金属网)的流场特性及网后煤堆模型的起尘特性进行模拟实验?结果表明,风障(网)的屏蔽作用取决于网的孔率;孔径雷诺数Re*存在着临界值(该实验为1200),当Re*小于临界值时,网后附近气流的湍流运动受到抑制,此时煤堆模型的起尘率随Re*的减小而减小,且对来流的湍流结构很敏感,当Re*大于临界值时,起尘率基本上不再随Re*变化而变化?      

Airborne particulate matter from livestock production systems: A review of an air pollution problem

Livestock housing is an important source of emissions of particulate matter (PM). High concentrations of PM can threaten the environment, as well as the health and welfare of humans and animals. Particulate matter in livestock houses is mainly coarse, primary in origin, and organic; it can adsorb and contain gases, odorous compounds, and micro-organisms, which can enhance its biological effect. Levels of PM in livestock houses are high, influenced by kind of housing and feeding, animal type, and environmental factors. Improved knowledge on particle morphology, primarily size, composition, levels, and the factors influencing these can be useful to identify and quantify sources of PM more accurately, to evaluate their effects, and to propose adequate abatement strategies in livestock houses. This paper reviews the state-of-the-art of PM in and from livestock production systems. Future research to characterize and control PM in livestock houses is discussed.     

Towards zero industrial waste: Utilisation of brick dust waste in sustainable construction

Laboratory investigations were carried out to establish the potential utilisation of brick dust (BD) in construction. The dust is a waste material from the cutting of fired clay bricks. Currently, the disposal of the dust is a problem to the brick fabrication company, and hence an environmental pollution concern. The dust was stabilised either used on its own or in combination with Pulverised Fuel Ash (PFA), a by-product material from coal combustion. The traditional stabilisers of lime and/or Portland Cement (PC) were used as controls. The main aim was to use a sustainable stabiliser material, where these stabilisers were partially replaced with Ground Granulated Blastfurnace Slag (GGBS), a by-product material from steel manufacture. Compacted cylinder test specimens were made at typical stabiliser contents and moist cured for up to 56 days prior to testing for compressive and California Bearing Ratio (CBR) strength tests, and to linear expansion during moist curing and subsequent soaking in water. The results obtained showed that partial substitution of the dust with PFA resulted in stronger material compared to using it on its own. The blended stabilisers achieved better performance. These results suggest technological, economic as well as environmental advantages of using the brick dust and similar industrial by-products to achieve sustainable infrastructure development with near zero industrial waste.     

First assessment of population exposure to perfluorinated compounds in Flanders, Belgium

With the objective to evaluate exposure of the population in Flanders (Belgium) to perfluorinated compounds (PFCs), we measured perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in settled dust in homes and offices, in a selection of food items from local origin, in drinking-water and in human serum. We complemented the data with results from a literature survey. Based on this dataset we calculated intake by children and adults from food, drinking-water, settled dust and soil, and air. Dietary exposure dominated overall intake. For adults, average dietary intake equalled 24.2 (P95 40.9) ng PFOS kg⁻¹ d⁻¹ and 6.1 (P95 9.6) ng PFOA kg⁻¹ d⁻¹, whereas for children the dietary intake was about 3 times higher. Predicted intake is high when compared to assessments in other countries, and to serum levels from Flanders, but comparable to the intakes published by The European Food Safety Authority (EFSA) in 2008. Intake of PFOS and PFOA remained below the Tolerable Daily Intake.     

Experimental study on vented deflagration of hydrocarbon fuel-air mixtures in a 20-L semi-confined cylindrical vessel with a slight static activation pressure

The overpressure peaks and flame propagation characteristics of hydrocarbon fuel-air mixtures vented deflagration in a 20-L cylindrical vessel with a slight static activation overpressure (P_ST = 2.5 kPa) and five vent opening ratio were studied by a series of experiments. The experiments focused on the effect of vent opening ratio on the overpressure peaks and flame propagation characteristics of hydrocarbon fuel-air mixture vented deflagration. The internal overpressure-time profiles and high-speed photographs of flame propagation processes were obtained. The results showed that three overpressure peaks were distinguished in the internal overpressure-time profiles, caused by the burst vent cover (p_burst), the acceleration of burnt gas (p_fv), and the fierce external deflagration of vented unburned fuel (p_ext), respectively. The changing of the vent opening ratio had almost no effect on the value of p_burst and (dp_burst/dt). With increasing vent opening ratio, the values of p_fv, p_ext, (dp_fv/dt) and (dp_ext/dt) showed a decreasing trend while the values of p_burst and (dp_burst/dt) were nearly constant. The flame presented a hemispherical shape before the vent cover ruptured then developed as a mushroom shape after accelerated to external field. There were three flame speed peaks during flame propagation process, resulted from venting flow acceleration, external deflagration, and axial heat flux formed by internal combustion. With the increase of vent opening ratio, all of the maximum flame speed, external average flame speed, maximum flame distance and external flame duration showed a downward trend, excepting for the internal average flame speed almost remained constant.     

Combustion characteristics of pure aluminum and aluminum alloys powders

In this work, the explosion and combustion characteristics of aluminum and some aluminum alloys AlSi7Mg0.6, AlSi10Mg, AlMg5 under powders conditioning were studied. The idea was to compare the combustion of pure aluminum and aluminum alloys. The Minimum Ignition Energy (MIE) and explosion severity ΔP_max and (dP/dt)_max which represents the dust explosion parameters were measured for all powders using Hartman tube and 20 L spherical bomb. The particles temperature and flame temperature were determined by using IR pyrometer and spectroscopy respectively. The results showed that pure aluminum was more sensitive and severe than its alloys. MIE were: 4 mJ for pure aluminum, 13–23 mJ for aluminum alloys. For severity parameters, the overpressure ΔP_max were around 7–8 bars with maximum rate of pressure rise at 1170 bar/s for aluminum and 5–7 bars with 250–360 bar/s for alloys. However, it has been observed that flame temperatures were similar for aluminum and alloys and vary around 2800–3300 K as a function of concentration.     

Human exposure to polybrominated diphenyl ethers (PBDE), as evidenced by data from a duplicate diet study, indoor air, house dust, and biomonitoring in Germany

Polybrominated diphenyl ethers (PBDE) are used as flame retardants in a wide variety of products. As part of the Integrated Exposure Assessment Survey (INES), this study aimed to characterize the exposure of an adult German population using duplicate diet samples, which were collected daily over seven consecutive days, and indoor air and house dust measurements. Our study population consisted of 27 female and 23 male healthy subjects, aged 14–60 years, all of whom resided in 34 homes in southern Bavaria. In these 34 residences the air was sampled using glass fiber filters and polyurethane foams and the dust was collected from used vacuum cleaner bags.The median (95th percentile) daily dietary intake of six Tetra- to HeptaBDE congeners was 1.2 ng/kg b.w. (3.3 ng/kg b.w.) or 67.8 ng/day (208 ng/day) (calculated from the 7-day median values of each study subject). Concentrations in indoor air and dust (cumulative Tri- to DecaBDE congener readings) ranged from 8.2 to 477 pg/m³ (median: 37.8 pg/m³) and 36.6 to 1580 ng/g (median: 386 ng/g), respectively. For some congeners, we identified a significant correlation between air and dust levels.The median (95th percentile) blood concentration of total Tetra- to HexaBDE congener readings was 5.6 (13.2) ng/g lipid. No significant sex differences were observed, but higher blood concentrations were found in younger participants. Using a simplified toxicokinetic model to predict the body burden from exposure doses led to results that were of the same order of magnitude as the measured blood concentrations.Based on these measurements and given our exposure assumptions, we estimated for the total tetra- to heptabrominated congener count an average (high) comprehensive total daily intake of 1.2 ng/kg b.w. (2.5 ng/kg b.w.). Overall, our results suggest that dietary exposure is the dominant intake pathway at least in our study population, responsible for 97% (average intake) and 95% (high intake) of the total intake of an adult population.     

Dust dynamics in off-road vehicle trails: Measurements on 16 arid soil types, Nevada, USA

Soil analyses and measurements with the Portable In Situ Wind Erosion Laboratory (PI-SWERL) were conducted on 16 soil types in an area heavily affected by off-road vehicle (ORV) driving. Measurements were performed in ORV trails as well as on undisturbed terrain to investigate how ORV driving affects the vulnerability of a soil to emit PM10 (particles < 10 μm), during the driving as well as during episodes of wind erosion. Particular attention is paid to how the creation of a new trail affects those properties of the topsoil that determine its capability to emit PM10. Also, recommendations are given for adequate management of ORV-designed areas. The type of surface (sand, silt, gravel, drainage) is a key factor with respect to dust emission in an ORV trail. Trails in sand, defined in this study as the grain size fraction 63–2000 μm, show higher deflation thresholds (the critical wind condition at which wind erosion starts) than the surrounding undisturbed soil. Trails in silt (2–63 μm) and in drainages, on the other hand, have lower deflation thresholds than undisturbed soil. The increase in PM10 emission resulting from the creation of a new ORV trail is much higher for surfaces with silt than for surfaces with sand. Also, the creation of a new trail in silt decreases the supply limitation in the top layer: the capacity of the reservoir of emission-available PM10 increases. For sand the situation is reversed: the supply limitation increases, and the capacity of the PM10 reservoir decreases. Finally, ORV trails are characterized by a progressive coarsening of the top layer with time, but the speed of coarsening is much lower in trails in silt than in trails in sand or in drainages. The results of this study suggest that, to minimize emissions of PM10, new ORV fields should preferably be designed on sandy terrain rather than in silt areas or in drainages.