Calcite Powder Research Articles

Study on calcium precursors for CaO preparation to capture CO<sub>2</sub> at high temperature

As an abundant and cheap material,calcium oxide(CaO) is an efficient sorbent for CO2 capture at high temperature.The carbonation/calcination loop of CaO/CaCO3 is an effective process for CO2 capture and storage(CCS).However,both the gradual decline of the CO2 capture capacity and the poor stability,because of the pore filling and pore closure at the high calcination temperature,limit the industrial application of calcium-based sorbents.In this paper,study on calcium precursors was carried out in order to obtain CaO sorbents to capture CO2 with high efficiency.The candidate materials include seashell materials(oyster shells),natural minerals(calcite) and chemical reagents(calcium acetate hydrate).Oyster shell powder and calcite powder were analyzed by XRD,and CaO sorbents prepared from various precursors were characterized by nitrogen physisorption apparatus.The fresh CaO sorbents and CaO after multiple cycles to capture CO2 were characterized by scanning electron microscopy(SEM).The capture CO2 capability and the stability of CaO sorbents were investigated using a thermogravimetric analyzer(TGA),where multiple capture cycles were carried out alternatively in the simulation flue gas(10% CO2 in N2) and in decomposition purge gas(N2).Moreover,comparing the CO2 capture capability and the CaO stability with published works,and taking account of the market prices of precursors,calcium acetate hydrate is thought to be an economically appropriate calcium precursor,which has acceptable CO2 adsorption capacity and good stability at high temperature.

Effect of chemical additive on stirred bead milling of calcite powder

The effect of liquid additive on the dry ultrafine grinding of calcite powder (CaCO3) was investigated by using a stirred bead mill. The experiments were carried out by a batch operation, and the change in particle size distribution (PSD) and volumetric surface area (Sv) (m2/cm3) of calcite. The results show that the chemical additive promotes the fine grinding of calcite and that the maximum volumetric surface area of calcite obtained with additives 0.2%.

Fabrication of microporous calcite block from calcium hydroxide compact under carbon dioxide atmosphere at high temperature

Effects of carbonation temperature and compacting pressure on basic properties of calcite block were studied using Ca(OH)2 compact made with 0.2-2.0 MPa and their carbonation at 200-800ºC for 1 h. Microporous calcite was obtained only when carbonated at 600ºC using Ca(OH)2 compact made with 0.2 MPa even though thermogravimetry analysis showed that calcite powder was stable up to 920ºC under CO2 atmosphere. CaO formed by carbonation at 700ºC and 800ºC is thought to be caused by the limited CO2 diffusion interior to the Ca(OH)2 compact. Also, unreacted Ca(OH)2 was found for Ca(OH)2 compact prepared with 0.5 MPa or higher pressure even when carbonated at 600ºC. As a result of high temperature carbonation, crystallite size of the calcite, 58.0 nm, was significantly larger when compared to that of calcite prepared at room temperature, 35.5 nm. Porosity and diametral tensile strength of the microporous calcite were 39.5% and 6.4 MPa.

Calcium carbonate thermal decomposition in white-body wall tile during firing. II. Influence of body thickness and calcite content

The thermal decomposition process of the calcium carbonate (calcite powder) contained in porous ceramic pieces, with the same composition as that used industrially to manufacture white-firing wall tile bodies, was studied using test disks with different thicknesses and calcite concentrations.The experiments were conducted in a CO2-free air atmosphere, and the results confirmed the validity of the kinetic model and the equation proposed in a previous paper to reproduce the experimental results in the studied range of operating conditions.

Use of Wet Grinding and Aging to Produce Narrow Particle Size Distribution

An experimental study on the improvement of particle size distribution of calcite powder (d50 = 3.23 μm) was carried out. Ultrafine grinding of calcite powder was studied under batch wet conditions in a laboratory stirred mill. After grinding, the suspension was allowed to age at 30°C for 12 and 24 h. The results indicated that the fineness narrow particle size distribution is influenced to a small extent by altering some operating parameters, such as suspension temperature and aging time. Further increase in the fineness narrow particle size distribution is likely with additional optimization work on the operating parameters of aging process.

Effect of the Sample Concentration on the Submicrometer Particles Produced During a Stirred Ball Milling of Calcite Powders

Wet ultra fine grinding of a calcite powder has been investigated in a stirred ball mill with respect to the effect of slurry concentration. The grinding rate on the submicrometer range was measured and the grinding constant on the grinding rate (K) in the grinding kinetics equation was examined. It is observed that the grinding rate for calcite in the submicrometer size range is different for different sample concentrations. It was found that the lower the sample concentration, the better the grinding rate. Furthermore, an empirical grinding rate (K)-sample concentration model provides a good fit to the grinding results under the experimental conditions investigated. The K improved by a maximum of 1.6 times at 700 rpm and 19.1 times 300 rpm for various sample concentrations, respectively. We confirmed that sample concentration affected the grinding rate of the submicrometer-size powder during the grinding process.

Speleothems in the dry Cave Parts of the Gamslöcher-Kolowrat Cave, Untersberg near Salzburg (Austria)

New, remarkably dry parts of the Gamslöcher-Kolowrat Cave at 728 to 853 m depth have been explored in the Untersberg near Salzburg in Austria. This region is called the Desert, its greatest cavity is called the White Hall. The new cave part is characterized by various white speleothems. The predominant ones are snow-like calcite powder with an extremely low density, and fine gypsum needles. Gypsum also occurs in the form of balls stuck to vertical walls. In addition, fluorescent hydromagnesite crusts, Mg5(CO3)4(OH)2·4H2O, as well as the sodium sulfate mineral mirabilite were identified in this part of the cave. Mirabilite and gypsum needles differ from the gypsum balls in their isotopic sulfur signature (δ34S of -16.9‰ and -18.4‰ vs. +2.9‰). The unusually low sulfur isotopic compositional values are tentatively explained by a source of bacteriogenetic sulfur from sulfides.

Effect of Various Operating Factors on Wet Stirred Mill Performance

In this study, the effects of various operating factors, such as initial particle size, feed quantity, filling volume of the ball, and ball size distribution on fine grinding of calcite powders (CaCO3) were studied using a laboratory stirred mill under wet conditions. A series of laboratory experiments using 24 full factorial designs was conducted to determine the optimum grinding parameters. The main and interaction effects on the specific surface area (m2/g) of the ground product were evaluated using Yates' analysis. The test results showed that the main factors that influence the mill grinding performance are the feed quantity and the ball size distribution.

Characterization of wettability alteration of calcite, quartz and kaolinite: Surface energy analysis

The paper addresses wettability alteration of calcite, quartz and kaolinite powders, with stearic acid (SA), N,N-dimethyldodecylamine (NN-DMDA) and asphaltene as oil soluble additives. It is a challenge to convert silicate based mineral surfaces from strongly water-wet to more oil-wet. Thermogravimetric analysis (TGA) of the modified powders is used to quantify the monolayer adsorption and is suggesting the possible molecular orientation on the mineral surfaces. Characterization of the mineral surface hydrophilicity/hydrophobicity due to modification is determined by the enthalpy of the water vapor adsorption isotherm. From the quantity and the affinity to water vapor adsorption, a new wettability index is suggested. The enthalpy of water adsorption relative to liquefaction enthalpy shows that stearic acid and asphaltene deeply modify the calcite toward more oil-wet for treated humidified surfaces. It is interesting to observe that although the presence of a water film on quartz and kaolinite surfaces, enhance the adsorption of N,N-dimethyldodecylamine (NN-DMDA), does not eliminate but reduces the asphaltene adsorption.

Effects of pore fluid flow and chemistry on compaction creep of calcite by pressure solution at 150°C

Uni-axial compaction creep experiments were performed on crushed limestone and analytical grade calcite powders at 150°C, a pore fluid pressure of 20 MPa, and effective axial stresses of 30 and 40 MPa. Previous experiments have shown that compaction under these conditions is dominated by intergranular pressure solution (IPS). The aim of the present tests was to determine the inter-relationship between pore fluid chemistry, compaction rate and the rate-controlling process of IPS. Intermittent flow-through runs conducted using CaCO3 solution showed no effect on creep rate at low strains (<4–5%) but a major acceleration at high strains (5–10%). Measurements of the Ca concentration present in fluid samples revealed the build-up of a high super-saturation of CaCO3 during compaction under zero flow conditions, especially at high strains. Active flow-through led to a drop in Ca concentration, which corresponded with creep acceleration. Addition of NaCl to the pore fluid, at a concentration of 0.5 m, increased the creep rate of the analytical grade calcite samples roughly in proportion to the enhancement of calcite solubility. Addition of Mg2+ and to the pore fluid, in concentrations of 0.05 and 0.001 m, respectively, caused major retardation of compaction creep. Integrating our mechanical, flow-through and chemical data points strongly to diffusion-controlled IPS being the dominant deformation mechanism in the calcite-water system under closed-system (zero flow) conditions at low strains (<4–5%), giving way to precipitation control at higher strains. Our fluid composition data suggest that this transition is because of accumulation of impurities in the pore fluid. As Mg2+ and phosphate ions are common in natural pore fluids, it is likely that retarded precipitation will be the rate-limiting step of IPS in carbonates in nature. To quantify diagenetic compaction and porosity-permeability reduction rates by IPS in carbonates needs to account for this.

Adsorption of Anionic, Cationic and Nonionic Surfactants on Carbonate Rock in Presence of ZrO2 Nanoparticles

The adsorption of surfactants at the solid–water interface is important for the control of wetting, lubrication, detergency and in mineral flotation.We have studied the adsorptions of different types of surfactants, cationic (Dodecyl trimethylammonium bromide, DTAB), anionic (sodium dodecyl sulfate, SDS) and non-anionic (lauryl alcohol-7 mole ethoxylate, LA7) on carbonate rock in presence of zirconium oxide spherical nanoparticles (17-19nm). ZrO2 nanoparticles with tetrahedral structure have significant effect on adsorption of surfactants on the carbonate rock. We have used the measured conductivities to determine the rate of adsorption of surfactants at rock-water interfaces. The conductivity of DTAB in aqueous solutions containing calcite powder decreases more than the other surfactants in contact with ZrO2 nanoparticles. We have also investigated the adsorption of surfactants at the air-water interface. The presence of nanoparticles, as demonstrated by our experiments, enhances the surface activity and surface adsorption of the surfactants through electrostatic forces or formation of nanostructures. Dynamic light structuring data shows similar aggregation number of nanoparticles in presence of nanoparticles.

Raman microspectrometric investigationof urea in calcite and gypsum powder matrices

AbstractRaman microspectrometry was used for the nondestructive detection of urea in artificially prepared mineral matrices. Various concentrations of urea, a possible biomarker, mixed with calcite and gypsum powders were analyzed using the 514.5‐nm line of an argon laser. Two types of measurements were carried out: direct measurements of powders and analysis of the same mixtures through natural, transparent crystals of calcite and gypsum. The detection limit for urea in artificial powder mixtures was 1 wt% for both calcite and gypsum. In the case of measurements through the monocrystals, the detection limit was between 1 and 5 wt% for calcite and slightly above 5 wt% in the case of gypsum. Copyright © 2010 John Wiley &amp; Sons, Ltd.

High-pressure compaction modelling of calcite (CaCO 3) powder compact

Numerical simulation of manufacturing processes with working conditions at high pressure (above 1 GPa) requires constitutive data of the powder for the whole range of pressure and density. Most of the test apparatuses commonly used to obtain such data are only working in the lower pressure regions. Because of the absence of high-pressure data, many parameters have to be guessed or extrapolated. A material used in high-pressure applications is Calcite (CaCO 3). The material can be used as an insulator in high-pressure capsules it is also a common material in the earth core. An apparatus often used to generate high pressure during compaction is the Bridgman anvil apparatus. In this work experimental tests with a Bridgman anvil set-up using Calcite powder discs with different thicknesses were done. A nonlinear elastic-plastic cap model was developed to model the behaviour of powder material from low pressure and loose state to high pressure and solid state. The constitutive model was implemented in a finite element code. The constitutive data were identified by optimization of experimental data. Validation was done by numerically reproduce the mechanical behaviour of uni-axially pressing Calcite to different pressure (up to 5 GPa) including unloading. The load–displacement curves, density distribution and the surface displacement were measured and compared to the finite element results. The results of the compaction simulations agree reasonably well with the experimental results.

Compaction creep of wet granular calcite by pressure solution at 28°C to 150°C

Uniaxial compaction experiments have been carried out on wet calcite powders prepared from milled limestone, analytical grade calcite, and superpure calcite. The tests were performed at 28°C–150°C, effective stresses of 20–47 MPa, and a pore pressure of 20 MPa, using presaturated CaCO3 solution as the pore fluid. Sample grain sizes ranged from 12 to 86 μm. The aim was to determine if creep occurs by intergranular pressure solution (IPS) under these conditions and to identify the rate‐controlling process. The wet samples showed significant creep, while dry and oil‐flooded samples did not. Wet samples were also characterized by microstructures such as sutured grain contacts, grain indentations, and overgrowths, suggesting the operation of IPS. The behavior of the wet samples at low strains (&lt;4–5%) agreed well with the predictions of standard models for diffusion‐controlled pressure solution. However, at higher strains (5–10%), creep slowed down compared with the model predictions. Transient flow‐through tests performed in this regime led to an acceleration of creep, consistent with models for precipitation‐controlled IPS, and demonstrated an increase in the impurity content of the pore fluid toward higher strains. Since some of these impurities (notably Mg2+) retard precipitation in calcite, we suggest that creep occurred by diffusion‐controlled IPS at low strain, giving way to precipitation control at larger strains as impurities accumulated. Fitting of the diffusion‐controlled IPS model to the low strain data yielded values of the grain boundary diffusion product DS in calcite of ∼10−19 m3 s−1 at 150°C.

Impact of Particle Generation Method on the Apparent Hygroscopicity of Insoluble Mineral Particles

Calcite (CaCO 3 ) mineral particles are commonly generated by atomization techniques to study their heterogeneous chemistry, hygroscopicity, and cloud nucleation properties. Here we investigate the significant artifact introduced in generating calcium mineral particles through the atomization of a saturated suspension of the powder in water, by measuring particle hygroscopicity via CCN activation curves. Particles produced from atomization displayed hygroscopicities as large as κapp > 0.1, 100 times more hygroscopic than that obtained for dry-generated calcite, κapp = 0.0011. The hygroscopicity of the wet-generated particles increased as a function of time the calcite powder spent in water, and with decreasing particle size. Wet-generated calcium oxalate was more hygroscopic through wet- (κapp = 0.34) versus dry-generation (κapp = 0.048). Atomized calcium sulfate particles, however, were only slightly more hygroscopic (κapp = 0.0045) than those generated dry (κapp = 0.0016). Single-particle analysis by AT...

A study on the effect of process parameters in stirred ball mill

An experimental study on the fine grinding of calcite powder ( d 50 = 62.16 μm) using a 0.75 l laboratory stirred ball mill has been carried out. The effects of various operating factors, such as grinding time (min), stirrer speed (rpm), slurry density (wt.%) and ball filling ratio on fine grinding was studied under batch wet conditions using alumina balls, 95% purity with diameters 3.5–4.0 mm. A series of laboratory experiments using 2 4 full factorial designs was conducted to determine the optimum grinding parameters. The test results showed that the stirrer speed and grinding time have strong effects on the grinding efficiency, based on the value of specific surface area (m 2/g).

Simulation of nucleation and growing of CaCO3 nanoparticles obtained in the rotating disk reactor

Abstract The new model for description of calcium carbonate precipitation in the rotating disk precipitation reactor has been elaborated. The model has taken into account not only kinetics of the multiphase reaction but also crystal growth rate. The obtained, during the precipitation process, crystal morphology data have been compared with the model simulation results. The obtained simulation results fully agree with the experimental data and explain why independent of the Ca(OH) 2 concentrations and speeds of disk rotation the obtained, in the reactor, ultrafine calcite powder has the same nanometric size (about 30 nm). The proposed model very well describes the CaCO 3 crystals formation in the rotating disk reactor and can be used and recommended for accurate calculation of the particle size and distribution obtained by gas–liquid precipitation in the reactor.

Neutralization of acid mine drainage using the final product from CO 2 emissions capture with alkaline paper mill waste

In this study, experiments were conducted to investigate the applicability of low-cost alkaline paper mill wastes as acidity neutralizing agents for treatment of acid mine drainage (AMD). Paper wastes include a calcium mud by-product from kraft pulping, and a calcite powder from a previous study focused on sequestering CO 2 by carbonation of calcium mud. The neutralization process consisted of increase of pH by alkaline additive dissolution, decrease of metals solubility and precipitation of gypsum and poorly crystallized Fe–Al oxy-hydroxides/oxy-hydroxysulphates, which acted as a sink for trace elements to that extent that solutions reached the pre-potability requirements of water for human consumption. This improvement was supported by geochemical modelling of solutions using PHREEQC software, and observations by scanning electron microscope and X-ray diffraction of reaction products. According to PHREEQC simulations, the annual amount of alkaline additive is able to treat AMD (pH 3.63, sulphate 3800 mg L −1, iron 348 mg L −1) with an average discharge of about 114 and 40 L s −1 for calcium mud and calcite powder, respectively. Likewise, given the high potential of calcium mud to sequester CO 2 and of resulting calcite powder to neutralize AMD, paper wastes could be a promising solution for facing this double environmental problem.

Texture and structural refinement using neutron diffraction data from molybdite (MoO3) and calcite (CaCO3) powders and a Ni-rich Ni50.7Ti49.30alloy

Preferred orientation or texture is a common feature of experimental powder patterns. The mathematics of two commonly used models for preferred orientation—the March-Dollase and the generalized spherical-harmonic models—is reviewed. Both models were applied individually to neutron powder data from uniaxially pressed molybdite (MoO3) and calcite (CaCO3) powders in Rietveld analyses, as well as the as-received powders. The structural refinement results are compared to single-crystal structures. The results indicate that reasonable refinement of crystal structures can be obtained using either the March model or generalized spherical-harmonic description. However, the generalized spherical-harmonic description provided better Rietveld fits than the March model for the molybdite and calcite. Therefore, the generalized spherical-harmonic description is recommended for correction of preferred orientation in neutron diffraction analysis for both crystal structure refinement and phase composition analysis. Subsequently, the generalized spherical-harmonic description is extended to crystal structure refinement of annealed and the aged polycrystalline Ni-rich Ni50.7Ti49.30shape memory alloys.

Brushite (CaHPO4·2H2O) to octacalcium phosphate (Ca8(HPO4)2(PO4)4·5H2O) transformation in DMEM solutions at 36.5 °C

The purpose of this study was to investigate the transformation of brushite (dicalcium phosphate dihydrate, DCPD, CaHPO4·2H2O) powders at 36.5°C in DMEM (Dulbecco's Modified Eagle Medium) solutions. Two sets of brushite powders with different particle shapes were synthesized to use in the above DMEM study. The first of these brushite powders was prepared by using a method which consisted of stirring calcite (CaCO3) powders in a solution of ammonium dihydrogen phosphate (NH4H2PO4) from 6 to 60min at room temperature. These powders were found to consist of dumbbells of water lily-shaped crystals. The second one of the brushite powders had the common flat-plate morphology. Both powders were separately tested in DMEM-immersion experiments. Monetite (DCPA, CaHPO4) powders were synthesized with a unique water lily morphology by heating the water lily-shaped brushite crystals at 200°C for 2h. Brushite powders were found to transform into octacalcium phosphate (OCP, Ca8(HPO4)2(PO4)4·5H2O) upon soaking in DMEM (Dulbecco's Modified Eagle Medium) solutions at 36.5°C over a period of 24h to 1week. Brushite powders were known to transform into apatite when immersed in synthetic (simulated) body fluid (SBF) solutions. This study found that DMEM solutions are able to convert brushite into OCP, instead of apatite.