Lower D50 Research Articles

Ultra-fine slag activated by sodium carbonate at ambient temperature

Na2CO3 (NC)-activated slag was one of the main directions for low carbon cementitious materials. However, its application in the civil engineering field was restricted because of the slow compressive strength development at ambient temperature. To solve this problem, slag with high fineness was used in the present study. The compressive strength and hydration process of NC-activated slag with various fineness slag was systematically researched, and the related mechanisms was studied by hydration heat, X-ray diffractometer (XRD), Thermogravimetric (TG), Nuclear magnetic resonance (NMR), and Mercury intrusion porosimetry (MIP). Results showed that the compressive strength of slag with D50 = 3.1 μm activated by 4% sodium oxide equivalent (Na2O-E) of NC reached 46.3 MPa and 91.6 MPa at 28 d and 90 d age. Decreasing slag D50 (i.e. increasing fineness) augmented the compressive strength obviously, and more obvious enhancing effect was observed over time. On the one hand, the more reaction sites and the higher reactivity offered by slag with lower D50 could accelerate the activation process significantly, leading to a higher reaction degree of slag; on the other hand, the greater filling effect of slag with lower D50 was more beneficial to refine the microstructure. The optimization of slag fineness was an efficient method to augment the mechanical property of NC-activated slag system at ambient temperature.

Comparative Effects of Hydro-, Hormonal-, Osmotic-, and Redox-Priming on Seed Germination of Creeping Bentgrass under Optimal and Suboptimal Temperatures

Reseeding of creeping bentgrass (Agrostis stolonifera L.) under unfavorable temperature (≈10 °C) is a common practice on golf putting greens and fairways. Seed priming to enhance germination and early emergence increases seeding success. Seed priming comparing abscisic acid (ABA), gibberellic acid (GA), glycinebetaine (GB), hydrogen peroxide (H2O2), and polyethylene glycol (PEG) has not been investigated in turfgrass. Our objective was to compare these chemical primers at three concentrations with water- and unprimed-seed at two competing germinating temperatures (10 vs. 25 °C). Two seed lots of ‘T-1’ creeping bentgrass were compared. Curve fitting of daily germination was used to compute days to 50% germination (D50) and maximum germination percentage (Gmax). Cold (10 °C) significantly inhibited emergence (higher D50) more than Gmax. The effects of primers and their rates varied with the seed lot and temperature. Enhancement of seed germination measured as early emergence (lower D50) and/or higher Gmax were only detected at 10 °C. Osmotic primers (GB and PEG) were most effective in promoting germination relative to unprimed seed followed by hormone primers (ABA and GA) with redox primers (H2O2) least effective. Glycinebetaine primed seed was the only primer effective at all concentrations, with the 100 mм concentration the only concentration to enhance germination by increasing both Gmax and early emergence (lower D50) compared with unprimed seed.

Experimental research of particle size and size dispersity on the explosibility characteristics of coal dust

In the present research work, the effects of particle size (D50) and size dispersity (σD) on the explosion severity of coal dust were investigated using a 20L spherical explosion vessel. Coal dust samples with similar median diameter (D50) and different size dispersity (σD) and similar size dispersity (σD) and different size diameter (D50) were specially prepared by mixing original coal samples having a narrow size distribution. The explosion severity of each sample was evaluated by measuring the maximum pressure (Pmax) and the maximum rate of pressure rise ((dP/dt)max). Interestingly, results show that almost all of the selected coal dusts present the same optimum explosion concentration of 250g/m3. The parameters of Pmax and (dP/dt)max show an increasing trend in explosion severity as size dispersity (σD) and particle size (D50) decrease, which indicate a more notable effect due to the contribution of finer coal particles on the dust cloud deflagration dynamics. The higher the volatile matter content, the more severe is the explosion. The presence of the finer particles would greatly increase the total effective specific surface area and speed up the devolatilization rate, which would cause acceleration of the dust explosion process. Furthermore, the effects of dust concentration on the explosion process were analyzed by comparing the defined time span (τ1) from ignition point to reach (dP/dt)max point and time span (τ2) from (dP/dt)max point to reach Pmax point. For the coal dust with lower D50 and lower σD, τ1 and τ2 are always short. Under lower coal dust concentration condition (<250g/m3), τ1 and τ2 present a stronger dependence on σD and dust concentration. However, the effect of σD and dust concentration on τ1 and τ2 becomes weak for the higher coal dust clouds (>250g/m3). Results indicated that the evaluation of coal dust explosion hazard should be considered in terms of not only dust concentration, but also particle size (D50) and size dispersity (σD).

Micronized natural talc with a low particle size and a high carbonate rate is more effective at breaking down oil‐in‐water emulsion

Micronized natural talc (MNT) has demonstrated to be very useful to break down emulsions formed during the virgin olive oil extraction process, improving the oil yield. This study was aimed to obtain more insights into the mechanisms of MNT to break down oil‐in‐water emulsions. For this purpose, laboratory scale experiments were performed in order to evaluate the effect of different pectin concentrations (0.5, 1, 1.5, and 2%), used as an emulsifier agent, on the behavior of an oil‐in‐water interface. Afterward, to evaluate the effect of MNT dosage as well as its physicochemical characteristics on breaking o‐reducing emulsions, four MNTs differing in their particle size (D50) and carbonate rate were assayed at doses ranging from 0 to 1%. Increasing pectin concentration gave a rise in the emulsifying activity (EA). The emulsifier effect of pectins was weakened by the addition of increasing MNT dose. MNT physicochemical characteristics markedly affected the breaking of oil‐in‐water emulsions. Nonetheless, its effect depends on the dose of MNT applied to the emulsion. The highest decrease in EA was observed for MNT with the lowest D50 (2.4 μm) and the highest carbonate rate (4%) at 0.5%. In general, MNT containing lower D50 and high rate of carbonate showed better capacity for breaking oil‐in‐water emulsion.Practical applications: So far as can be ascertained, no quantitative study has been made, in vitro, on the relative merits of MNT addition as a technological aid in breaking down oil‐in‐water emulsions. This study provides deeper insights into the clarification of the effect of pectins as emulsifier agents, on aqueous emulsions of Hojiblanca virgin olive oil and how the addition of different doses of MNT, with different physicochemical characteristics, carried out the breaking of the oil‐in‐water emulsions.Effect of micronized natural talc physicochemical characteristics and dosage on the break‐down of oil‐in‐water emulsion.

Lactose Caking: Influence of the Particle Size Distribution and the Water Content

Industrially, after the crystallisation of lactose from mother liquor, the crystals are separated by centrifugation and then dried in a flash drier followed by a fluid bed drier. It is known that if the moisture content and/or particle size is not correct then lumping and caking of the lactose can occur in the flash drier causing operational problems.The aim of this study was to characterize the influence of water content and particle size distribution on the caking of lactose powders.Powders with different d50's and different water contents had their caking/clumping characteristics analyzed with a texture analyzer, a sticky plate and a blow tester to determine their cohesion. A theoretical approach looking at the capillary interactions of the liquid bridges between lactose crystals was taken from the literature to explain the results obtained.The results showed that lactose powder with a low d50 can cake easily as soon as the water content is higher than 3%. This cohesion between lactose crystals is due to liquid bridges linking them together. The number of bridges formed affects the level of cohesion: the more numerous they are, the more cohesive the lactose crystals are. Therefore, small particles cake more easily because the number of bridges in a given volume is higher than for bigger particles.It was predicted that the capillary force cannot hold together particles with d50 bigger than 400μm and that was confirmed by experiment.Finally, in order to prevent the caking of lactose powders obtained by processes such as a decanter centrifuge, the lactose crystallization step should be controlled to obtain large crystal (with d50>300μm) and/or the final water content should not be higher than 3%.

Effect of solids concentration on particle size distribution of deagglomerated barium titanate in stirred media mills

The effect of solids concentration on particle size distribution of a suspension of barium titanate in toluene/ethanol solvent, deagglomerated in a re-circulating stirred media mill, has been examined by experimentation. The effect on the particle size distribution curves was recorded for solids concentrations ranging from 10% to 85% by weight and for impeller tip velocities of 4m/s, 6m/s and 8m/s. Lower D50 (median) particle sizes were found at both low and high concentrations. Additionally the span of the distribution curves was found to be widest at both the lower and higher concentrations. At low concentrations high specific energies per pass of product through the grinding chamber were measured and this was as a result of high calculated stress numbers indicating high numbers of successful contact between particles and media. At high concentrations, high specific energies per pass were also measured and this was due to the increased density and viscosity of the suspension which had the effect of increasing residence time, reducing the number of passes. Thus an optimum range for solids concentration was determined which gave the narrowest spans of the particle size distribution curve, an important characteristic for deagglomeration of barium titanate for MLCC manufacture.

Silicate digestion with fructose under mild conditions

Treatment of silica gel or silicate mineral with an aqueous solution of the weak base triethylenetetraamine and the sugar fructose results in partial dispersion into particles smaller than 450 nm under conditions of ambient pressure and mild heating (60–100 °C) in times less than 1 h. Redeposition occurs at longer times. The final material has 13–31% higher surface area and 17–18% lower D50 (50% of the accumulated weight percentage is smaller than this particle size). Dissolution or decrystallization of some of the aluminosilicate phase is indicated by X-ray diffraction for the Berea sandstone. The proposed mechanism involves deprotonation at the anomeric hydroxyl, followed by attack on the solid silicate centers by fructose to form a pentacoordinate silicon complex. The stereochemistry of fructose then allows a planar diolato ring to form containing C2 and C3 of fructose and a second position on pentacoordinate silicon. The reaction results in displacement of a portion of the silicate matrix. Reformation of Si–O–Si bonds gives rise to redeposition. An equilibrium between dissolution and redeposition results in the final reworked material with reduced particle size.

Measurements of cloud droplet activation of aerosol particles at a clean subarctic background site

Two years of continuous aerosol particle size distribution measurements provided the basis for this cloud droplet activation study. The cloud droplet activation of aerosol particles was studied in Pallas, a clean background site in northern Finland. A slightly different approach compared with traditional methods is presented by measuring simultaneously the cloud interstitial particle size spectrum and a nearby out‐of‐cloud particle size spectrum. The main advantage of this approach is that one can determine the activated fraction of different‐size particles over the whole submicron‐size range and that a large number of cloud activation events can be analyzed. The number of cloud droplet activation days peaked in late autumn and was lowest in summer. The annual variation of “cloud droplet activation” events followed the annual pattern of low clouds (those below 1000 m). A relation was found between the total particle number concentration outside the cloud and the number of activated particles. A larger particle concentration led to a higher number of activated particles, a lower activation percent, and a larger activation diameter (D50). D50 was on average 80 nm and varied from 50 to 128 nm. The average fraction of activated particles during the cloud events was 47% and varied from 9 to 86%. The cleaner and colder air masses from the northern Atlantic or the Arctic Ocean had, on average, 15 nm lower D50 than the more polluted air masses from south and east containing more particles. The annual variation of the number of the activated particles and other variables were also closely related to the annual variation of particle concentration (high in summer and low in winter). On average 87 and 30% of accumulation and Aitken mode particles, respectively, were activated. Aitken mode particles were observed to cover up to 55% of the total number of activated particles (i.e., number of formed droplets), which demonstrates that they have a significant effect on cloud droplet activation and must be taken into account when estimating the aerosol indirect climate effects.

Clay Removal And Cut-point Curve Analysis of a One-step Solids Control Equipment: Theory And Field Application

Abstract The objective of this paper is to evaluate the performance of a One-step Solids Control Equipment (OSSCE) based on the actual field data. The material balance technique was used to achieve this objective. The data obtained consisted of density, volume flow rate, solids content, and size distribution of the mud in each flow stream of OSSCE. The cost-effectiveness of using OSSCE as compared to mud cleaners was investigated using the actual field data obtained upon running the same mud from the shale shaker underflow through the two equipment. In addition, the cut-point curve for each equipment was obtained. The results indicated that the cost of using mud cleaner on the mud sample analyzed is about 4.5 times higher than that of OSSCE if a 3% reduction in volume per cent of low gravity solids is desired and assuming a higher efficiency for both equipment due to less solids loading after each run of the entire mud system through each equipment. In our opinion, this is a reasonable assumption that will ensure that the 0.9% and 0.27% net reduction in volume per cent of low gravity solids calculated for OSSCE and mud cleaner, respectively, during the first run of the entire mud system is achieved at subsequent runs. The cost difference is due to the fact that the mud cleaner discarded only 1.7 times more low gravity- solids than weight material while OSSCE discarded 4 times more low gravity solids than weight Material. Results indicated that very high recovery efficiencies for commercial additives such as barite, lignite, and iron oxide were obtained using OSSCE. Based on mineral analysis, approximately 31 % of very small amounts of Chlorite that entered OSSCE (only 2% by volume of total clay minerals that entered OSSCE belongs to Chlorite) was discarded-by concentric discharge and screen overflow discharge. This high per cent by volume of Chlorite discarded may be attributed to its high density, small size, shape, and flocculation of Chlorite particles. The lowest per cent by volume of clay type discarded belongs to Kaolinite (3%), which may be due to the lesser amount of flocculation by this clay type and/or its size, shape, and low density. Finally, the results indicated that the cut-point curve will shift to the left as the volume flow rate of screen overflow discharge increases, resulting in sharper particle separation or lower d50. Therefore, the volume flow rate of the screen overflow discharge can be adjusted to obtain the desired cut-point. Introduction Drilling fluid is a major factor in the success of any drilling operation, and the key to any effective mud system is good solids control. Solids control is one of the most important phases of mud control on every well. Mud solids consist of particles which come from the formation being drilled and other particles which are added to the mud to control chemical and physical properties. The material added to the mud include:clay additives such as bentonite,weight material such as barite, andvarious chemicals to control rheological and filtration properties.

Multiple duodenal ulcer: natural history and pathophysiology.

It has not been established whether multiple duodenal ulcer is associated with a different natural history, pathophysiology, and therapeutic response than a single duodenal ulcer. A consecutive series of 96 patients with two or more duodenal ulcers at endoscopy, representing 9.6% of the total number of new patients with duodenal ulcer seen during the period 1980-1985, were compared with a random series of 200 patients with single duodenal ulcer seen in the middle years of this period. Multiple duodenal ulcer was associated with higher (p less than 0.02) male to female ratio, more (p less than 0.05) late onset patients (those with ulcer symptoms starting after age 30 years, more (p less than 0.05) chronic cigarette smokers, and more frequent (p less than 0.05) moderate to severe deformity of the duodenal bulb. More (p less than 0.05) patients with multiple duodenal ulcer had abnormally low D50 derived from pentagastrin dose response tests, indicating that they were more sensitive to gastrin stimulation. Furthermore, their mean fasting and meal stimulated serum gastrin concentrations were significantly higher than those of patients with single ulcer (p less than 0.005), or of controls (p less than 0.05). Compared with single duodenal ulcer, multiple ulcer had significantly lower placebo healing rate, and required a higher dose of misoprostol (1200 v 800 micrograms/day) to achieve a similar healing efficacy at four weeks. We conclude that multiple duodenal ulcer is associated with different clinical features, pathophysiology, and possibly therapeutic response from single duodenal ulcer, and appears to represent the more aggressive side of the ulcer spectrum.

Effects of very low doses of atropine on basal acid and pepsin secretion, gastrin, and heart rate in normals and DU.

Muscarinic mechanisms in basal acid and pepsin secretion in man were quantitated by graded intravenous doses of atropine (1-16 micrograms/kg). Secretion was dose-responsively inhibited in six healthy controls. For the mean dose response, maximum inhibition (Imax) was 100%, and D50 (dose inhibiting 50%) was 0.31 +/- 0.06 and 0.93 +/- 0.13 micrograms/kg, respectively, for acid and pepsin. In 24 patients with duodenal ulcer (DU), calculated Imax was also 100%, and D50S were 1.2 +/- 0.27 and 1.7 +/- 0.3 micrograms/kg, respectively. The low D50 values and the 100% calculated maximum inhibition indicated that in both groups basal secretion was largely or completely cholinergic dependent. We also found that atropine raised heart rate in controls by 44 +/- 1 beats per min (bpm) (D50 = 6 +/- 1.1 micrograms/kg), while the mean maximum increase in DU was only 23 +/- 2 bpm (P less than 0.01) with (D50 = 5.3 +/- 1.0 micrograms/kg (NS)). In DU atropine increased fasting serum gastrin from 62 to 82 pg/ml (P less than 0.05); the increase in normals from 32 to 38 pg/ml was not significant. Thus, while both normals and DU exhibited the same qualitative responses to muscarinic receptor antagonism by atropine with respect to gastric secretion, gastrin levels, and heart rate, there were quantitative differences in all three parameters.