Quartz Slurry Research Articles

Comparison of ultra-flocculation reactors applied to fine quartz slurries

Ultraflocculation can be defined as: flocculation performed in a highly non-uniform hydrodynamic field (ε>1 [J/kg·s], G > 103 [s-1]) in a short period of time (t<10 [s]), which is used mainly to aggregate fine particles in dispersed, and diluted systems.In this study, four hydraulic ultra-flocculation reactors were tested, UF1, UF2, UF3 and UF4 with tangential inlets/outlets and a cylindrical body, the inside of which varies by reactor. Model flocculated fine quartz slurries were employed as material. Based on a comparison of the three flocculation process indicators – initial settling velocity, supernatant turbidity, and sludge volume – in general the reactors present better performance than that in the base case. There was an average improvement in settling velocity of 300[%], turbidity remains below 100 [NTU], and sludge volume values indicated a higher possibility of water recirculation. Additionally, it was observed that the ultra-flocculation process could be used in relatively concentrated suspensions (φ>10-2) with treatment times below to 5 [s].

Slurry and dry particle erosion wear properties of WC-10Co4Cr and Cr3C2-25NiCr hardmetal coatings deposited by HVOF and HVAF spray processes

Thermally sprayed hardmetal coatings were produced to provide improved erosion wear compared to conventional cast GX4CrNi13-4 martensitic steel (CA6NM) used in hydro turbine components. Sprayed coatings and reference materials were tested with high-speed slurry pot tester using either fine or coarse quartz as the erosive media. Additional erosion tests were carried out with centrifugal dry erosion tester. Tungsten carbide based coatings provided the highest wear resistance due to the high hardness and even distribution of the fine carbide particles. The cast 13-4 steel samples experienced up to 180 times higher wear rates in fine quartz slurry and up to 36 times higher wear rates in coarse slurry compared to the sprayed coatings.

Abrasive Slurry Erosion Behavior of Nitrile-Butadiene Rubber with Different Acrylonitrile Contents

Nitrile-butadiene rubber (NBR) with different acrylonitrile contents were eroded by quartz slurry using a self-made erosion testing apparatus to study the erosion wear behavior. Quartz slurry with a concentration of 33 wt.% was used to impact the specimen surface at 45° sample angle. The experimental data, such as erosion rate, hardness and swelling increment were compared and analyzed. The morphologies of worn surfaces were characterized using the field emission scanning electron microscopy to reveal the wear mechanism. The results showed that the acrylonitrile content in the molecular chains had a significant effect on the erosion performance of NBR. Furthermore, a static swelling test was conducted as a contrast experiment to investigate the effect of erosion on the swelling behavior of rubber surface. By comparing the results it could be found that the dynamic swelling increment during the erosion test was almost four or five times larger than that of static swelling. Mechanism of the interaction between swelling and erosion was also discussed.

Viscoelasticity of Quartz and Kaolin Slurries in Seawater: Importance of Magnesium Precipitates

In this study, the viscoelastic properties of quartz and kaolin suspensions in seawater were analysed considering two distinct conditions: pH 8 and 10.7. Creep and oscillatory sweep tests provided the rheological parameters. An Anton Paar MCR 102 rheometer (ANAMIN Group, Santiago, Chile) was used with a vane-in-cup configuration, and the data were processed with RheoCompassTM Light software (ANAMIN Group, Santiago, Chile). The outcomes were associated with the formation of solid species principally composed of magnesium precipitates. The magnesium in solution reduced in the presence of quartz (68 wt %), from 1380 to 1280 mg/L. Since the difference was not large regarding the solid-free seawater, the disposition of solid complexes at pH 10.7 was expected to be similar. The jump in pH caused both yield stress and viscoelastic moduli to drop, suggesting that the solid precipitates diminished the strength of the particle networks that made up the suspension. For the kaolin slurries (37 wt %), the yield stress raised when the pH increased, but unlike quartz, there was significant adsorption of magnesium cations. In fact, the concentration of magnesium in solution fell from 1380 to 658 mg/L. Dynamic oscillatory assays revealed structural changes in both pulps; in particular, the phase angle was greater at pH 8 than at pH 10.7, which indicates that at more alkaline conditions, the suspension exhibits a more solid-like character.

Fabrication and abrasive wear behavior of ZrO2-SiC-Al2O3 ceramic

Abstract In this paper, ZrO 2 -SiC-Al 2 O 3 ceramic was fabricated by as-prepared ZrO 2 -SiC powders and commercial α-Al 2 O 3 powders, sintered at 1450 °C for 1 h. ZrO 2 -SiC composite powders were synthesized through carbothermal reduction with zircon as raw material and carbon black as the reductant. Through ZrO 2 -SiC-Al 2 O 3 ceramic mechanical properties measurements it was indicated that this ceramic had excellent properties in both bending strength and hardness. In addition, ZrO 2 -SiC-Al 2 O 3 ceramic abrasive wear property was measured. ZrO 2 -SiC-Al 2 O 3 ceramic mass loss increased along with the increase in both wheel rate and applied load. The type of wear particles had an important effect on abrasive wear resistance. ZrO 2 -SiC-Al 2 O 3 ceramic displayed excellent abrasive wear resistance in bentonite and quartz slurries in comparison with SiC slurry.

Effect of galena on thiosulfate leaching of gold

Galena and reference quartz were artificially added into the ammoniacal thiosulfate solution to clarify the role of galena on thiosulfate leaching of gold. The effects of galena on thiosulfate decomposition and gold leaching and the possible effect mechanisms were studied by the thermodynamic calculation, leaching tests, SEM-EDS and XPS analyses. Results showed that from the onset of gold leaching, the leaching kinetics was restricted severely in the presence of galena. This is caused by the fact that galena is easily oxidized by copper(II) and the dissolved oxygen, thus the mixed slurry potentials initially experienced a significant decline to relatively stable lower levels of 230–240mV which are nearly 50mV lower than that of the quartz slurry. This is disadvantageous to gold leaching and results in undesirable gold dissolutions during the process. The results suggest that the decrease of slurry potentials from the presence of galena is the principal cause of a reduction in the gold leaching rate.

Microstructure and erosion wear of LM-13 alloy composites with dual reinforcement by silicon carbide and zircon sand in fine silica quartz slurry

Microstructure and erosion wear of LM-13 alloy composites with dual reinforcement by silicon carbide and zircon sand in fine silica quartz slurry

Study on the Classification Performance of Vibration Lamella Thickener

This paper mainly describes the relation between the overflow quantity, separation size, classification efficiency and Reynolds number under the stable stage of vibration lamella thickener. Using a device with one tilting-narrow flow classification element, experiments on classification of pure quartz slurry have been carried out.we can conclude that the overflow quantity is proportional to the separation and classification is best under the condition of turbulent flow.

Corrosion–erosion wear of N80 carbon steel and 316L stainless steel in saline–quartz slurry

AbstractThe corrosion–erosion behavior of carbon steel N80 and austenitic stainless 316L are investigated both in water–quartz slurry and saline–quartz slurry. The sample mass losses after each test and the roughness of sample surfaces are measured and a potentiostat is used to gain the polarization curves. The worn surfaces and the corrosion–erosion wear mechanism are analyzed using scanning electron microscopy (SEM) and 3D ultra‐deep microscopy. Results show that the Ra for N80 is much larger than 316L under the same experimental condition, and the weight losses of the two materials show a similar trend except for tests with higher impact angles. The lowest Rsm for 316L matches along with the highest Rsm for N80 at the 45 min testing time. According to the obtained results of the corrosion–erosion mechanism of the N80 and 316L based on the SEM and 3D ultra‐deep microscopy, the conclusion is drawn that the ploughing and crashing are the major mechanisms for the forming of surface morphologies and the mass removal. Different impact angles and materials affect the corrosion–erosion process to some extent.

An Investigation on Erosion Wear Characteristics of SiC Particle Reinforced Steel Matrix Surface Composite

The erosion wear characteristics of SiC particles reinforced steel matrix surface composite were studied by self-made slurry erosion wear test apparatus with quartz slurries, and contrasted with that of plain carbon steel, high chromium cast iron and low chromium cast iron. The results indicated that the erosion wear rate of the four tested materials has the different changes not only with the quartz particles sizes in slurry, but also with the erosion angle of slurry. The erosion wear rate of SiC particle reinforced steel matrix surface composite is the lowest in four kinds of tested materials under the test conditions. And that of high chromium cast iron is less than that of low chromium cast iron under the same test conditions. The SiC particles embedded the steel matrix could prevent the steel surface from wear brought by quartz particles in slurry erosion wear, and protect the steel matrix, so that the erosion wear resistance of steel matrix could be increased.

An investigation of the erosion–corrosion characteristics of ductile cast iron

The erosion–corrosion wear characteristics and mechanism of martensitic ductile cast irons with different alloying compositions in quartz slurries with different pH values were determined and analysed. The results indicated that the erosion–corrosion wear resistance of martensitic ductile cast iron would be increased not only with the pH values of the slurry and the erosion angle, but also with the addition of copper, nickel and chromium elements, respectively. A few of eutectic carbides would appear in the microstructures of ductile cast iron when the chromium element is added into this cast iron. However, these carbides would harm the erosion–corrosion wear resistance of this cast iron in acidic slurry. The addition of Ni, Cu, Cr elements and increase of Si element content would be helpful to improve the erosion–corrosion wear resistance of this cast iron in neutral and alkaline slurry, especially for chromium. Because the hardness of ductile cast iron could be remarkably increased by the occurrence of carbides when the chromium element was added. The erosion–corrosion mechanisms of the martensitic ductile cast irons were dominated by particles erosion wear in alkaline and neutral slurries, and by the interaction of particle erosion wear and medium corrosion in acidic slurry.

Oxygen mass transfer into flotation slurries—Part 1: effect of mild steel corrosion during grinding of quartz

Under ordinary conditions of milling the consumption of oxygen by the grinding media relative to its consumption by a massive sulphide ore is not known. To help to distinguish between the two oxygen mass transfer into flotation slurries has been investigated under various conditions. Aeration studies were conducted on a quartz slurry following its grinding in a mild-steel mill in the absence and presence of sodium chromate as a corrosion inhibitor. During these studies such variables as the oxygen concentration, pH and pulp potential were monitored as a function of time by means of a customized data-acquisition system. A systematic increase in the amount of iron-bearing deposition on quartz particles was observed with increasing grinding time, which was accompanied by a decrease in pulp potential. The oxygen mass-transfer coefficient showed an exponential decrease from a value of 7.5 s-1 (in tap water) to about 0.11 s-1 (in slurry) with increasing fineness of quartz ground in the absence of sodium chromate. This trend appears to be completely reversible through the use of sodium chromate in grinding, the coefficient attaining a value that can be even greater than its original value prior to any grinding. The variations of pH and pulp potentials are discussed in relation to certain electrochemical and hydrolysis reactions relevant to the current system. An Eh-pH diagram constructed using specific experimental conditions indicates formation of an iron chromate as the main product of corrosion inhibition.

Corrosion–erosion of nitrogen bearing martensitic stainless steels in seawater–quartz slurry

AISI 410S stainless steel was nitrided at 1473 K in N 2 atmosphere, direct quenched and tempered at temperatures between 473 and 873 K. Martensitic cases with circa 0.52 wt.% N at the surface were obtained. Corrosion–erosion tests were carried out in slurries composed by quartz particles and tap or substitute ocean water. The concentration of solids, the impact angle and the pH of solution were fixed, while the temperature, surface changes and mass losses were monitored during the tests. Quenched and tempered AISI 410 and 420 stainless steels were used as comparison materials. The results showed that the erosion resistance and the corrosion–erosion resistance of the nitrided steel tempered at 473 K were higher than those of the AISI 410 and 420 steels tempered at the same temperature. This behavior was due to the higher hardness and better intergranular, pitting and generalized corrosion resistance of the nitrided alloy. The synergism between corrosion and wear was more important in the AISI 410 and 420 samples.

Effect of dissolved metal sulphates on gas-liquid oxygen transfer in agitated quartz and pyrite slurries

A previous study on mass transfer in agitated three phase systems showed that for quartz slurries the volumetric oxygen transfer coefficient k La [s −1] decreases with increasing solids fraction, whereas pyrite particles increase the k La value. The present study was conducted in continuation of these results and attempts to explain why the addition of pyrite particles resulted in an increase in k La. For this purpose, the effect of ionic strength, mineral density and oxygen consumption due to homogeneous reactions was examined. Neither the high density of pyrite nor the oxygen consumption could offer an explanation for the increased k La values obtained for pyrite slurries. The variable mineral density did not affect k La at all, while the consumption of oxygen was not large enough to cause an enhancement of k La. However, by reducing bubble coalescence frequency and thus bubble size, the ionic strengths found for pyrite slurries could partially explain the increase in k La. For 15 vol.% pyrite slurries, the ionic strengths proved to account for at least 60% of the enhancement. The variable(s) and/or mechanism(s) causing the remaining 40% of the enhancement could not be identified (yet). To demonstrate the effect of ionic strength as such, various electrolytes (viz. CuSO 4, FeSO 4, ZnSO 4 and Al 2(SO 4) 3) were added to a 15 vol.% quartz slurry. For all metal sulphates, increasing the ionic strength up to about 0.25 mol/l resulted in an increase of k La by up to a factor 2.5.

DTA–TGA of unstirred autoclaved metakaolin–lime–quartz slurries. The formation of hydrogarnet

DTA–TGA was used to monitor the evolution of hydration products in unstirred autoclaved metakaolin–lime–quartz slurries with reaction time. Hydrogarnet was always one of the first phases formed at all metakaolin additions and invariably appeared before 11 Å tobermorite. These findings explain apparent inconsistencies in the literature because the continued existence of hydrogarnet depends on such factors as reaction time and bulk composition. DTA–TGA indicated that the lime–quartz reaction was retarded and inferred differences in the precursor silicate anion structure of calcium silicate hydrates with increasing metakaolin addition.

Simultaneous Corrosion and Abrasion Measurements under Grinding Conditions

Abstract The contribution of corrosion to the abrasive-corrosive wear of high-carbon, low-alloy steel (HCLA), commonly used for grinding balls, was evaluated in 15% quartz slurries. Results were co...

Mechanisms of grinding modification by chemical additives: organic reagents

The effects of dodecylammonium chloride on properties of quartz slurries that are relevant to grinding, such as pulp fluidity, flocculation and dispersion, and primary breakage, have been investigated in this study. These tests were conducted under chemical conditions (pH, ionic strength, additive concentration, etc.) similar to those used in wet ball milling tests. The data obtained were correlated with the grinding results. Amine was found to improve grinding, pulp fluidity, and primary breakage of quartz suspensions, especially in the alkaline pH range. These beneficial effects are attributed to the formation of highly surface-active amineaminium complexes in this pH range. In contrast to the above, amine decreased the grinding rate in the acidic pH range owing to increased flocculation of quartz fines in the presence of amine in this pH range. These results show that grinding of quartz can be improved by amine if other conditions such as pH are controlled. Also, the results indicate that the effect of chemical additives on grinding cannot be attributed to a single mechanism, but that the cumulative effect on different pulp properties has to be taken into consideration. Examination of the effect of all properties has led to a better understanding of the mechanisms responsible for the observed grinding aid effects in the present study.