Com a crescente diminuição de recursos minerais e o alto custo envolvido na construção da estrutura de uma mina, a recuperação máxima possível de uma jazida vem se tornando fundamental. Para isso além da escolha do método de lavra ter a necessidade de ser feito cautelosamente, é possível lançar mão de métodos adicionais de recuperação, como por exemplo, a recuperação de pilares. Essa pesquisa foi baseada na determinação da caracterização do enchimento (backfill cimentado) utilizado nas câmaras vazias que possibilita a posterior recuperação dos pilares. A caracterização do enchimento é composta da determinação da resistência simples do backfill necessária para que o enchimento cumpra com seu objetivo, desenvolvimento da classificação granulométrica ótima para os agregados e dosagem de cimento e água para alcançar a resistência proposta. A metodologia desenvolvida para obter a nova caracterização é composta de várias etapas que incluem pesquisas em campo e trabalhos em laboratório. Primeiramente, foram obtidos através de análise em campo os parâmetros de dosagem de cimento e classificação granulométrica dos agregados já utilizados na planta de fabricação do enchimento, bem como sua resistência correspondente. Em seguida definições teóricas da dosagem de cimento ideal e classificação granulométrica ótima foram realizadas com base na resistência à compressão simples que foi identificada como necessária para cumprir com as solicitações geomecânicas do maciço rochoso, então posteriormente, a nova caracterização definida teoricamente foi posta à prova através da confecção de corpos de prova de backfill, seguido de execuções de ensaios de compressão. Durante a primeira etapa da metodologia, já se pôde identificar que os agregados possuíam um alto índice de partículas tamanho argila que estavam afetando os resultados de resistência obtidos com a caracterização empregada inicialmente. A partir disso se optou por construir a curva granulométrica ótima sem essa fração. A resistência à compressão simples calculada de 2,69 MPa, foi obtida com base no planejamento de longo prazo que prevê a total recuperação dos pilares existentes na mina. Dessa maneira toda a área que será minerada foi considerada como um único bloco. Finalmente, foi identificada a dosagem de cimento sendo de 4% em peso, que juntamente com a granulometria ótima é capaz de alcançar os valores esperados de resistência. Para que o planejamento da produção da mina durante os próximos anos de vida útil seja efetivamente cumprido, o enchimento deverá prover à mina estabilidade geomecânica local a nível de câmaras abertas com paredes verticais de backfill estáveis e também estabilidade global a nível de contato entre níveis e galerias de acesso. Isso somente será alcançado se a nova caracterização for corretamente aplicada. / As a consequence of the ongoing reduction of mineral resources and the high cost involved in the construction of a mine, the maximum recovery of a mineral deposit becomes a fundamental issue. Therefore, besides the need of caution on the choice of the mining method, it is possible to make use of additional recovery methods, such as the recovery of pillars. This research was based on the determination of the characterization of the fill (cemented backfill) used in avoid stopes that allows the subsequent recovery of adjacent pillars. The characterization of the fill consists of determining the uniaxial compressive strength of the backfill required for an efficient filling, developing an optimal particle-size distribution for the aggregates and finding the cement-water ratio necessary to reach the desired resistance. The methodology developed to obtain the new characterization is comprised of several steps which include field work and laboratory tests. First, cement dosing parameters and particle size of the aggregates (already used at the filling manufacturing plant), as well as their corresponding strength, were obtained through analyses in the field work. Then, theoretical definitions of the ideal cement dosing and optimal particle-size analysis were carried out based on the uniaxial compressive strength that has been identified as necessary to comply with the geomechanical requests from the rock mass, and then later, the new theoretical characterization was tested by making backfill samples, followed by execution of compression tests. During the first stage of this methodology, it has been identified a high proportion of clay particle size for the aggregates, that have affected the strength results obtained from the characterization used initially. From this point, we decided to build the optimal particle-size curve without this fraction. Uniaxial compressive strength, calculated as 2.69 MPa, was obtained from the long-term planning that determines the full recovery of the existing pillars in the mine. In this way, the entire area to be mined was considered as a single block. Finally, the cement dosing has been identified as 4% by weight, which together with the optimal particle size, is able to achieve the expected strength values. In order to effectively fulfill the mine production planning over the next years of lifespan, the filling should provide the mine local geomechanical stability at open stopes level, with vertical walls of stable backfill, and also global stability at the contacts between levels and access galleries. This will only be achieved if the new characterization is correctly applied.

Approximately 1500 km (43%) of the strategic Scottish trunk road network drainage asset takes the form of Highway Filter Drains (HFDs). However, despite their popularity, they are prone to clogging, therefore they have an estimated operational life-cycle of ten-years. This research was undertaken to investigate the complex inter-relationship between catchment characteristics, road dynamics and the physical characteristics of the road to establish the key factors that govern the generation and spatial variability of Road-Deposited-Sediment (RDS). The aim being to establish the impact RDS Particle Size Distribution (PSD) has on clogging and the operational life-cycle of HFDs. The research adopted an integrated approach, incorporating: (i) a Field Study to investigate RDS PSD grading envelopes across the Scottish trunk road network, (ii) a HFD Field Survey (HFD-FS) to investigate the current condition of HFDs across a range of catchments, (iii) a HFD Field Study to establish whether, or not, graded stone PSD envelopes comply with specification requirements when first placed in the trench, (iv) 3 HFD Field Studies to assess the level of risk of system failure through evaluating the causes and quantifying the individual, cumulative and influencing factors which contribute to the evolution of clogging in HFDs, and (v) a Field Study utilising Ground Penetrating Radar data to explore why stratified (clogged) layers evolve within some HFDs. Based on the results of this research, design and maintenance procedures were then identified to improve the performance of HFDs. Results established that Scottish trunk roads operate under variable catchment characteristics and road dynamics, with the condition and specification of the road surface, volume of traffic, road geometry, number of running lanes and adjacent land use governing the generation and spatial variability of RDS. Five of the nine trunk road RDS PSD profiles shared a peak particle diameter of 425 μm, two had a peak of 600 μm, one had a peak of 1180 μm and one resulted in a peak of 2120 μm. Particles >1000 μm were mostly mineral or asphalt and it was shown that there is a direct link between the factors that govern the generation and spatial variability of RDS and those that govern the evolution of clogging and actual operational life-cycle of HFDs. The HFD-FS revealed that 69% were assigned Filter Drain Condition Index ratings of 3 or below, which identifies these as having exceeded the ten-year estimated operational life-cycle. 94% of those deemed to have reached the end of their operational life-cycle were over-the-edge (OTE) HFDs, which supports the assertion that pre-treatment would increase their operational life-cycle. Results also established that introducing a kerb-line and gully-pots or grass-strip between the road and the HFD significantly reduced the indices of particle size composition d50 and d90 and percentage of RDS retained at depths spanning 0 - 400 mm, compared to OTE HFDs with comparable catchment characteristics and road dynamics. Based on these results, the operational life-cycle of HFDs with a kerb-line and gully-pots and OTE HFDs with a grass-strip can be expected to exceed twenty-years, if catchment characteristics and road dynamics are representative of those in this study. This research also identified that compacting Type B graded stone with ‘heavy vibrating machinery’ during construction could potentially contribute to clogging. It was also established that HFD harrowing may exacerbate clogging because the process of disintegrating the cake-layer mobilises an otherwise rigid and compacted RDS mass and this is more likely to penetrate deeper into the HFD and inundate the HFD during a storm event. These findings indicate that current HFD construction and maintenance practice could have a detrimental impact on the effective operational life-cycle of HFDs. Overall, this research study has demonstrated that there are considerable uncertainties related to PSD grading envelopes and percentage of RDS migrating from roads to HFDs. It is clear therefore that one of the most notable findings of this research is that given the scale of strategic trunk road networks, assuming a single HFD operational life-cycle profile, for a trunk road or trunk road network, is highly unlikely to be representative of a HFD at the local level. It follows then that the widely accepted estimated ten-year operational life-cycle for HFDs, does not reflect the actual operational life-cycle of HFDs.

The objective of this work is to optimize high-power low-frequency sonication (US) pretreatment of sludge, and especially to investigate for the first time possible improvements by higher pressure and audible frequency. After a preliminary examination of regular process conditions (sludge conditioning, sludge type, prior alkalization, temperature control, etc), effects of US parameters (power -PUS, intensity -IUS, specific energy input -ES, frequency -FS, etc.) and of hydrostatic pressure (Ph) were specifically looked into, separately and in combination, first under cooling at constant temperature (28°C), then under the progressive temperature rise provoked by sonication. First, it was confirmed that specific energy input (ES) plays a key role in sludge US disintegration (i.e. solubilisation of organic matter) and that temperature rise during adiabatic-like sonication is beneficial through additional effects of thermal hydrolysis and cavitation. At a given ES value, low FS (12 kHz vs. 20 kHz) and high PUS enhance soluble chemical oxygen demand (SCOD) due to more violent cavitation, while hydrostatic pressure gives rise to an optimum value due to its opposite effects on cavitation threshold and intensity. One major result is that optimal pressure depends on IUS (P¬US) as well as temperature profile, but not on ES, FS, nor sludge type. Setting the other parameters at the most favorable conditions expected, i.e. 12 kHz, 360 W , 28 gTS/L, and adiabatic conditions, final optimization was achieved by searching for this pressure optimum and examining sequential procedure to avoid too high temperature dampening cavitation intensity and damaging the transducer. Such conditions with sequential mode and Ph of 3.25 bar being selected succeeded in achieving very high SCOD, but only marginally improved subsequent methanization yield.

In this study, we developed and standardized a sanding method to evaluate the emission of airborne particles from products that contain carbon nanotubes (CNTs) under different conditions, including three types of sandpaper and three sanding disc speed. We also characterized the emission of the airborne particles from one neat epoxy test sample, four CNTs-incorporating test samples with different CNTs loading, and two commercial products. The total number concentration, respirable mass concentration, and particle size number/mass distribution of the emitted particles were calculated and compared, followed by an electron microscopy (EM) analysis. These data suggest that the sanding process can produce substantial quantities of airborne particles. Also, the emission of airborne particles was associated with different test conditions. EM analysis of the airborne particle samples showed embedded CNTs protruding from the outer surface, which was different from CNTs-incorporating bulk material. Our study suggests a potential generation of particles during the life cycle event of sanding. Further studies should be carried out to investigate the potential human health hazard in other life cycle events.

Summary: A process is under investigation for the manufacture of dicalcium phosphate by the hydrolosis of concentrated superphosphate containing recycled monocalcium phosphate. The hydrolysis also results in the formation of an aqueous solution of monocalcium phosphate and free phosphoric acid. The phases are separated, followed by washing and drying of the solid dicalcium phosphate. The wash water is used in the hydrolyzer. The solution is returned to the superphosphate production step, where phosphate rock and additional phosphoric acid are added, and where water is evaporated to form the solid superphosphate. Pilot plant results have indicated that filtration rates vary widely under almost identical mixing conditions, presumably due to variations in particle size ranges. It was thought worthwhile, therefore, to study the effects of different mixing variables on the relative particle sizes as indicated by the settling rates of the mixture.

Grinding of clinker is the last and most energy-consuming stage of the cement manufacturing process, drawing on average 40% of the total energy required to produce one ton of cement. During this stage, the clinker particles are substantially reduced in size to generate a certain level of fineness as it has a direct influence on such performance characteristics of the final product as rate of hydration, water demand, strength development, and other. The grinding objectives tying together the energy and fineness requirements were formulated based on a review of the state of the art of clinker grinding and numerical simulation employing the Markov chain theory. The literature survey revealed that not only the specific surface of the final product, but also the shape of its particle size distribution (PSD) is responsible for the cement performance characteristics. While it is feasible to engineer the desired PSD in the laboratory, the process-specific recommendations on how to generate the desired PSD in the industrial mill are not available. Based on a population balance principle and stochastic representation of the particle movement within the grinding system, the Markov chain model for the circuit consisting of a tube ball mill and a high efficiency separator was introduced through the matrices of grinding and classification. The grinding matrix was calculated using the selection and breakage functions, whereas the classification matrix was defined from the Tromp curve of the separator. The results of field experiments carried out at a pilot cement plant were used to identify the model's parameters. The retrospective process data pertaining to the operation of the pilot grinding circuit was employed to validate the model and define the process constraints. Through numerical simulation, the relationships between the controlled (fresh feed rate; separator cut size) and observed (fineness characteristics of cement; production rate; specific energy consumption) parameters of the circuit were defined. The analysis of the simulation results allowed formulation of the process control procedures with the objectives of decreasing the specific energy consumption of the mill, maintaining the targeted specific surface area of the final product, and governing the shape of its PSD.

Currently, a lack of accurate emission data exits for particulate matter (PM) in agricultural air quality studies (USDA-AAQTF, 2000). PM samplers, however, tend to over estimate the concentration of most agricultural dusts because of the interaction of the particle size distribution (PSD) and performance characteristics of the sampler (Buser, 2004). This research attempts to find a practical method to characterize and correct this error for the Federal Reference Method (FRM) PM10 sampler. First, a new dust wind tunnel testing facility that satisfies the USEPA’s requirement of testing PM10 samplers was designed, built, and evaluated. Second, the wind tunnel testing protocol using poly-dispersed aerosol as the test dust was proved to be able to provide results consistent with mono-dispersed dusts. Third, this study quantified the variation of over sampling ratios for the various cut point and slopes of FRM PM10 samplers and proposed an averaged over sampling ratio as a correction factor for various ranges of PSD. Finally, a method of using total suspended particle (TSP) samplers as a field reference for determining PM10 concentrations and aerosol PSD was explored computationally. Overall, this dissertation developed successfully the methodology to correct the sampling error associated with the FRM PM10 sampler: (1) wind tunnel testing facilities and protocol for experimental evaluation of samplers; (2) the variation of the oversampling ratios of FRM PM10 samplers for computational evaluation of samplers; (3) the evaluation of TSP sampler effectiveness as a potential field reference for field evaluation of samplers.

No description available.

Abstract In order to understand the source, transport pathway and sink of settling particulates off northeast Taiwan, time-series sediment traps (PPS-3/3) were deployed on the north slope of Ilan ridge (T18) and in the Okinawa trough (T15 and T16) to collect settling particulates. The trapped particulate samples were determined for apparent mass flux (T18), particle size distribution, and contents of lithogenic portion, metals (Al, Mg, Ca, Fe, Mn, Cu), opal, OC (organic carbon) and IC (inorganic carbon). The results show that mass flux in winter is higher than in summer except for typhoon or rainstorm in summer which may cause high particulate flux. At mooring T11 and T17, only 2 cups had collected particulates but with rapid decrease, and the remaining cups were empty. It is not clear whether Kuroshio plays a role and further investigation is needed. The trapped particulates were mainly clay and silt in the north slope of Ilan ridge and south Okinawa trough, and were sand and silt in the Mien-Hwa canyon. The portion of coarse silt and larger particles (>31 mm) decreases with an increase of distance from the land (from T11 to T18). The grain size distribution of particulate at T18 is similar to that at T15 and T16, but the mass flux in the north slope of Ilan ridge is an order of magnitude higher than in the south Okinawa trough. The size distribution pattern below 600m water depth is very similar at both T15 and T16, but the coarse fraction (> 31 mm) is more at the upper than lower traps, presumably due to lateral transport. The Mn content of the trapped particulates in the south Okinawa trough is twice as hign as that in the north slope of Ilan ridge. High Mn/Al ratio in the trough suggests that Mn is supplied by hydrothermal activities. Lithogenic portions occupy about 84~88.5% at T18, T16 and T15. Relative to other marginal seas biogenic contributions are clearly lower.

Summary: A process is under investigation for the manufacture of dicalcium phosphate by the hydrolosis of concentrated superphosphate containing recycled monocalcium phosphate. The hydrolysis also results in the formation of an aqueous solution of monocalcium phosphate and free phosphoric acid. The phases are separated, followed by washing and drying of the solid dicalcium phosphate. The wash water is used in the hydrolyzer. The solution is returned to the superphosphate production step, where phosphate rock and additional phosphoric acid are added, and where water is evaporated to form the solid superphosphate.Pilot plant results have indicated that filtration rates vary widely under almost identical mixing conditions, presumably due to variations in particle size ranges. It was thought worthwhile, therefore, to study the effects of different mixing variables on the relative particle sizes as indicated by the settling rates of the mixture.