Coarse Sand Particles Research Articles

Impact of water recycle on water-based processing of Whiterocks tar sand

Water recycle is an essential part of the hot water process for bitumen recovery from tar sands. The current investigation was primarily designed to evaluate the direct recycle of process water after separation of coarse sand particles. Representative Whiterocks tar sand samples were used in all experiments. Tar sand tailings, after bitumen air flotation, were left 10 min for sedimentation, and the supernatant containing 4–5 wt% suspended matter was used in hot water batch experiments with 8 kg tar sand feed. For the processing conditions used (temperature 50–60 °C, pH at digestion < 9.5, recycled water) it was found that complete water recycle had no deleterious effect on the separation efficiency after six cycles.

Runoff sampler for small agricultural watersheds

Development and testing of a simple runoff sampler which can be used to monitor the quantity of sediment carried by runoff from small agricultural watersheds is presented. The sampler uses the rapidly fluctuating flow nature to account for the temporal variation in sediment concentration. Intensive laboratory testing was carried out for sampler efficiencies at various flow and sediment conditions. Overall efficiency obtained was in the range of 87 to 98%. The sediment catching efficiencies for clay, silt, fine sand and coarse sand particles were 96%, 87%, 75% and 60%, respectively. The sampler has been in use for the last 4 years in the field and its general performance has been satisfactory.

An Experimental Study of the Annulus Pressure Drop in a Simulated Air-Drilling Operation

Summary A comprehensive experimental wellbore model was built to simulate the multiphase flow of compressed air and sand that occurs in an air-drilling process. The model was designed to control the air volumetric flow rate and sand mass flow rate through a transparent annulus. The model also permitted observation of the sand and air in the annulus and allowed measurement of the pressure drop across the annulus. An empirical equation was developed for the minimum annulus pressure drop as a function of the sand mass flow rate through the system, the optimum annulus air velocity, the weight fraction of coarse sand particles entering the annulus, the weight fraction of coarse sand particles in the annulus, and solids loading in the annulus. The experimental results were compared with annulus pressures predicted by a semiempirical model of the air-drilling process developed by Angel. Angel's model failed to predict the observed minimum annulus pressure drops. In addition, the experimental results indicated that an annulus air velocity lower than the value assumed by Angel's model may be required.

The vegetation of ultrabasic soils on the Isle of Rhum I. Physical environment, plant associations and soil chemistry

Summary Rhum is a cool, windy island which has a high rainfall. Its ultrabasic soils are mildly acid, have exchangeable Mg/Ca quotients of 1.0–1.5, total nickel concentrations up to 2100 µg g− 1, and have a very high proportion of coarse sand particles. Mg/Ca quotients were higher in extracted soil solutions. A TWINSPAN classification of vegetation data from 283 quadrats on ultrabasic and non-ultrabasic soils produced seven interpreted vegetation Groups on the former soils and five on the latter. The Groups fit more or less into Associations or Communities described by Birse (1980, 1984). The vegetation of the more open ‘debris’ has some rare or uncommon species and is unusual amongst British ultrabasic areas in often having Calluna vulgaris and Molinia caerulea even when the total cover values are less than 5%.

Fluidization and slugging in large-particle systems

Square-nose slugging that occurs with large particles in relatively small-diameter fluidized beds shows certain similarities with the fluidization behaviour in a fluidized bed coal combustion system with closely packed heat-exchanger tubes. In the present investigation, square-nose slugging is studied in fluidized beds of 0.1 and 0.15 m I.D. with coarse sand and alumina particles, at ambient conditions. Recording of pressure fluctuations was used to analyse the fluidization behaviour. A remarkable change in the pressure fluctuation pattern occurs at the transition from normal fluidization to slugging: a more regular signal with a narrowed frequency spectrum is found. In the square-nose slugging regime, the pressure fluctuations seem to be caused by the disintegration of a rising solids slug, followed by the raining down of the particles. Experimental evidence for this mechanism was found in the behaviour of the magnitude of the pressure fluctuations as a function of operating variables. The frequency of square-nose slugging increases with approximately the square root of the bed diameter and appears to be independent of the type of particles used. The slug frequency decreases slightly with the gas velocity between about 0.8 and 1.8 m.s −1, and is inversely proportional to the stationary bed height between 0.15 and 0.4 m.

The heat-transfer performance of gas—solid trickle flow over a regularly stacked packing

The heat-transfer behaviour of a countercurrent gas—solid trickle flow contactor is studied, using coarse sand particles as the solids phase. Experimental data on the overall heat-transfer rate constant between the gas flow and the solid particle flow were obtained in a 0.15 m square cross-section column packed with regularly stacked packing elements specially developed for dilute countercurrent gas—solid contactors. Pressure drop over these packings is low, while countercurrent heat-transfer properties are remarkable; for 0.5 m of packing, the number of transfer units may amount to about 2 to 4, depending on the gas and solids mass flow rates and the packing construction used. Therefore, the present contactor might be attractive for application as a heat exchanger. The pressure drop caused by the solids flow and the heat-transfer rate constant show very similar behaviour and at low solids mass fluxes their values agree with the data obtained from the single-particle flow model described in a previous paper [1]. Heat-transfer behaviour is described reasonably well by a model based on single-particle flow and by incorporating the effect of particle agglomeration at higher solids fluxes.

Modelling the stress-strain relationship of structural concrete

Synopsis Recent research has led to an improvement in the properties of model reinforcement, but similitude of deformations, over the complete range of loading, andshear strength has not been achieved. It is well known that a number of size effects are due mainly to the properties of microconcrete because, in comparison with structural concrete, this material is stronger in tension and more ductile in compression. As a result of a detailed investigation into the compressive to tensile strength ratio and the stress-strain relationship of various model concrete mixes, a new type of microconcrete has been produced. The new mix is gap-graded, some of the coarsesand particles being replaced by glass beads, It has been tried in a number of model beams with an over-all depth of 30 mm and has given useful results.

Fucoidal Markings in the Swan Peak Formation, Southeastern Idaho

Physical features of the fucoidal markings in the Swan Peak formation suggest a mode of origin involving incorporation of coarse sand particles and organic fragments in a gelatinous organism plus the influence of the chemical by-products of the decomposition of the organism on the cementation process during diagenesis.

Removal of Coatings from Soil Particles for Petrographic Analysis

AbstractDetergents and builders have been used successfully to remove the organic and inorganic coatings from soil particles prior to petrographic analysis. Essentially, the procedure consists of triturating the soil sample in a liter beaker with a cationic detergent, dilution and decantation of the clay and fine silt, followed by several triturations with an anionic detergent and builders, dilution and decantation of the clay and fine silt.Soils representative of the Prairie, Chernozem, Chestnut, Reddish Chestnut, Gray‐Brown Podzolic, Podzol, Red‐Yellow Podzolic, Planosol, Grumusol, Humic Glei and Ground‐Water Podzol were investigated. All coarse silt and sand particles after treatment were free of organic matter, iron oxide and other coatings. No hydrogen peroxide was needed to remove the organic matter from the soil.The effect of the reagents of this and of Jeffries' nascent hydrogen procedure on apatite, hornblende and albite are shown on photomicrographs. Considerably less breakdown of the minerals is evident with the proposed method. In general, the suggested new procedure is more rapid, simple and less destructive than the currently used soil cleaning methods.