Limestone Particle Size Research Articles

Limestone particle sizes and sulfate impact on the early hydration of limestone calcined clay cement

This study explores the underlying mechanisms behind the varying grain size distribution of limestone and sulfate requirement in Limestone Calcined Clay Cements (LC3) on the effects of early hydration and rheological properties. In this paper, the experimental study involving a 45 % replacement of cement demonstrates that the filler effect increases with the fineness of limestone. This is evidenced by the observed acceleration and enhancement of silicate reaction, as monitored through isothermal calorimetry (ICC). The precipitation rate of calcium-silicate-hydrate (C-S-H) increases, and the sulfate adsorption by C-S-H is also augmented correspondingly, leading to accelerated depletion of gypsum during the hydration process. The effect of limestone on the particle size of rheology was also shown that the finer the limestone, the greater the yield stress, while the sulfate has the opposite effect. The results of the Krstulovic-Dabic kinetic model indicated that the exponent and rate constant values decreased with the finer limestone and increased with the addition of gypsum. These results aid in understanding the role of limestone and sulfate requirements on LC3 systems.

Effect of limestone particle size and microbial phytase on phosphorus and calcium digestion kinetics along the gastrointestinal tract in laying hens

ABSTRACT 1. This study assessed the effect of limestone particle size and microbial phytase incorporation on the fate of phosphorus (P) and calcium (Ca) along the gastrointestinal tract in 72 laying hens. 2. Four experimental diets were formulated according to a 2 × 2 factorial arrangement to evaluate the effect of two coarse limestone (CL) inclusion. This included a mix (MIX) of 75% CL (2 − 4 mm) and 25% fine particles (FL, <0.5 mm) or 100% FL, in two different basal diets formulated without (MIX0 and FL0) or with 300 FTU of microbial phytase/kg (MIX300 and FL300). 3. Contents of the crop, gizzard, duodenum, jejunum and ileum were collected to determine the mean retention time (MRT) of dry matter (DM), the recovery rate of Ca and P in each segment of the gastrointestinal tract and the apparent fractional digestibility coefficient (AD) of Ca and P in each intestinal segment. 4. In hens fed FL, microbial phytase decreased the MRT of DM along the intestine (p < 0.05). In the crop and the gizzard, Ca recovery increased with MIX incorporation to a greater extent in hens fed without microbial phytase (p < 0.05). The mixed particle size incorporation decreased absorption kinetics of Ca in hens fed microbial phytase. The AD of P and the absorption kinetics of P were significantly decreased in hens receiving FL300, probably due to complex formation between Ca and phytic acid. 5. This study showed that coarse limestone particles incorporation improved mineral utilisation along the digestive tract.

Attrition and morphological analysis of CaCO3 corresponding to oxy-fuel circulating fluidized bed conditions

The specific surface area of CaCO3 has always been an essential parameter for various oxy-fuel combustion processes and chemical looping processes. However, the circulating of bed material through the furnace, cyclone and loop-seal in an oxy-fuel circulating fluidized bed (CFB) reactor may trigger the particle size changes as a result of rapid collisions among particles and friction with the inner refractory wall. Rather than considering only the effect of initial particle size, it is significantly important to emphasize on the change in limestone particle size due to in-reactor attrition. In addition, the changes are further enhanced with calcination reaction that occurred under high-temperature conditions. Herein an investigative account of limestone in a lab-scale CFB process was presented by using two types of fluidizing media (Air, CO2) to determine its attrition and morphological changes under simulated operating conditions for riser and loop-seal. A significant difference in attrition index was observed as calcination of limestone occurred at high temperature under air atmosphere which was not observed under CO2 condition. With similar cross-sectional area observed for both the tested (CO2 condition) and re-carbonated limestone, it was concluded that re-carbonation of calcined lime at high CO2 concentration in the loop-seal resulted in a comparable abrasion resistance that further improved desulfurization performance by reducing the amount of ultra-fine particles generated from limestone.

The Effect of Limestone Particle Size on Hardness of Polylactic Acid/Hydroxyapatite Composite

Limestone is a mineral that mainly contained calcium oxide. Limestone has been used in manufacture industries for decades. Many researchers utilized limestone as a material for hydroxyapatite. Hydroxyapatite is a biocompatible material for human body and it is a potential material to restore the damaging bone. However, the hardness of hydroxyapatite is low. In this research, hydroxyapatite made from limestone and disodium hydrogen phosphate dihydrate were mixed with polylactic acid. The limestone was added as a source of calcium and increased the hardness of the composite. Polylactic acid was added to increase the compatibility between the components. The limestone particles sizes effect was studied using limestone powder size of 56 μm, 100 μm, and 150 μm. The composite was prepared by weighting, pre-heating, mixing, heating and pressing of the ingredients. The mechanical characterization was carried out through Micro Vickers Hardness Test. The composition of the composite was analyzed using X-ray Fluorescence. The surface morphology, interface adhesion, and element distribution were observed using scanning electron microscope and energy dispersive spectroscopy. The calcium-phosphor ratio of the composite similar with the one in the human bone. The composite that contained the finer size of limestone powder has the highest hardness. The ratio of the calcium to phosphor is 1.63.

The response of laying hen production, performance, bone health, and inositol levels to limestone particle size ratios and phytase levels supplemented during the post-peak period (40–60 wk of age)

The response of laying hen production, performance, bone health, and inositol levels to limestone particle size ratios and phytase levels supplemented during the post-peak period (40–60 wk of age)

A comparative study on the effect of limestone particle size on performance, ileal digestibility of calcium and phosphorus, and bone characteristics in broilers and pullets

ABSTRACT 1. The effects of limestone particle size on growth performance, gastrointestinal tract (GIT) traits, ileal morphology, duodenal gene expression of calbindin, apparent ileal digestibility coefficients (AIDC) of calcium (Ca) and phosphorus (P) and tibia characteristics in broilers and pullets were assessed in broilers and pullets. These birds have different growth rates and likely different responses to parameters, such as particle size. 2. A total of 240 chicks aged one day, 120 Ross 308 female broilers, and 120 Hy-Line pullets were allocated randomly into four treatments in a 2 × 2 factorial arrangement with two bird types (broilers vs. pullets) and two limestone particle sizes (<0.5 mm versus 1–2 mm) to give six replicates containing 10 chicks in each from 1 to 21 d of age. 3. Feed intake and weight gain were greater (P < 0.001) and feed per gain (FCR) was better (P < 0.001) in broilers compared to pullets from 1 to 21 d of age. Greater villus width (P < 0.01), villus height (P < 0.001) and crypt depth (P < 0.01) were seen for broilers compared to pullets. 4. Pullets fed coarse Ca particles had higher calbindin gene expression at 21 d of age (P = 0.05). Both AIDC of Ca and P were higher (P < 0.001) in broilers compared to pullets. The AIDC of Ca from 0.463 to 0.516 was increased (P < 0.05) by feeding coarse limestone particles. A significant interaction was found between bird type and limestone particle size (P < 0.01), where pullets fed coarse Ca particles had higher bone P concentration in tibia than broilers. 5. Broilers had better ileum absorptive capacity and growth performance compared to pullets. The AIDC of Ca and P was higher in broilers than in pullets. Increased limestone particle size elevated villus height, AIDC of Ca and concentration of P in the tibia.

Effect of the Textures and Particle Sizes of Limestone on the Quicklime Reaction Activity

Quicklime is not only an important raw material for the steel and nano-calcium carbonate industries but also a key carrier for capturing carbon dioxide in the fight against global warming, and its reaction activity plays a vital role in these processes. Recent studies have found that quicklime produced from limestones with similar chemical compositions under the same production process has significantly different reaction activities, which indicates that something other than the chemical composition of limestone affects quicklime reaction activity. To explore the factors affecting quicklime reaction activity, this study analyzed the textures and calcite particle size of limestone collected from different areas of Guangxi, China, and measures the quicklime reaction activity with different calcination times. It has been found that: (1) limestone with a clastic texture is preferred to that with a crystalline texture (including transition type) in yielding quicklime with higher reaction activity; and (2) for limestone with a clastic texture, fine-grained limestone tends to produce the same or higher quicklime reaction activity with lower energy consumption.

The Kinetic Mechanism of the Thermal Decomposition Reaction of Small Particles of Limestone at Steelmaking Temperatures

Converter blowing limestone powder making slag steelmaking process has the advantages of low carbon and high efficiency, and can realize the resource utilization of CO2 in the metallurgical process, which is in line with the development direction of green metallurgy. Based on a thermogravimetric-differential thermal analyzer, the kinetic mechanism of decomposition of small limestone at steelmaking temperatures was investigated by a modified double extrapolation method. The results showed that with a higher rate of heating, limestone decomposition lagged, and decomposition temperature increased. Furthermore, the smaller the limestone particle size, the lower the activation energy of decomposition. Compared with N2, air, and O2, small limestone powder used for converter blowing could complete more rapid decomposition, and the time required for decomposition shortened by about 1/3, although the decomposition temperature increased in the CO2. The limestone decomposition rate increased and then decreased at low to high CO2 partial pressures. With a limiting link, the inhibition was more significant under high CO2 partial pressure, but the reaction can be fully completed by 1000 °C. The decomposition type modeled was stochastic nucleation and subsequent growth. As the partial pressure of CO2 increased from 25% to 100%, the number of reaction stages, n, increased.

Kecernaan Kalsium dan Fosfor, pH gizzard, Kadar Air Ekskreta dan Digesta pada Ayam Petelur yang Diberi Ukuran Partikel Batu Kapur Berbeda dan Enzim Fitase

This study aimed to determine the coefficient of total calcium and phosphorus digestibility effects from limestone as a source of calcium and the effect of phytase enzymes on laying hens. This study used 180 Hy-line Brown laying hens aged 75 weeks. The experimental design used was a 2x2 factorial complete randomized design (CRD) with 9 replications. The first factor was limestone particle size, i.e., P1 = limestone flour and P2 = limestone granules, and the second factor was phytase enzyme dose, i.e., Q1 = 0 FTU and Q2 = 1000 FTU. The observed variables were gizzard pH, excreta moisture content (MC), digesta MC, calcium and phosphorus digestibility using two samples and ileal digestibility. The results showed that the digestibility of calcium from limestone flour was significantly different compared to limestone granules at P&lt;0.05. The phytase addition and the interaction with limestone particle size did not affect gizzard pH, total and ileal digestibility of calcium and phosphorus. Excreta and digesta MC had a significant effect on the particle size of limestone, the highest MC was limestone granules compared to flour (P&lt;0.001). The addition of phytase had an effect on reducing excreta MC (P&lt; 0.001). There was interaction between limestone size and phytase in excreta and digesta MC. The conclusion of the research was that laying hens were more efficient in digesting calcium from limestone flour compared to limestone granules. Phytase could reduce excreta and digesta MC.&#x0D; Key words: calcium, digestibility, limestone, particle size, phytase

Particle evolution mechanism of wide size distribution limestone under fluidized bed combustion conditions

The dynamic evolution of particles in limestone with a wide size distribution is significant for in-furnace desulfurization in circulating fluidized beds (CFB). In this study, air/SO2 mixtures were selected to simulate the flue gas combustion atmosphere, and the evolution on particle size of limestone with a wide size distribution was investigated using a self-built fluidized bed, with a focus on the evolution mechanism. The results show that the change in the cumulative particle size distribution (PSD) of limestone with a wide size distribution exhibited three stages as a function of reaction time. The cumulative PSD decreased continuously and reached 79.3% after 20 min during the first stage. The cumulative PSD was unchanged from 30 to 120 min in the second stage. The cumulative PSD increased from 81.9% to 88.3% in the range of 120–240 min during the third stage. The effects of attrition, heat stress, calcination, and sulfation on the changes in particle size were quantified and correlated with time. A novel method is proposed to predict the evolution mechanism of limestone with a wide size distribution. Calcination dominated in the time range of 0–60 min, and the predominant effect transformed from calcination to attrition at 240 min. However, the contribution of calcination was not negligible. The evolution of limestone with a wide size distribution can be promoted by the interactions of different effects.

Decomposition Mechanism and Calcination Properties of Small-Sized Limestone at Steelmaking Temperature

Limestone with a particle size of less than 5 mm was rapidly calcined in a high-temperature resistance furnace at 1623 K to simulate the conditions of rapid calcination of limestone at ultra-high temperature in a converter. In this study, the decomposition mechanism and calcination characteristics of small-sized limestone at steelmaking temperature were investigated. The study shows that the shrinking sphere or cylinder models with phase boundary reaction were found to be the best representation of limestone kinetic data, and the mechanism function equation is G(α) = 1 − (1 − α)n, n = 1/2 or 1/3. Limestone particles with a size of 0.18–1.0 mm can be quickly calcined to obtain a typical active lime microstructure and a high activity of more than 350 mL, which is the preferred limestone particle size range in the steelmaking process in which limestone powder is injected into the converter.

Effect of phytase and limestone particle size on mineral digestibility, performance, eggshell quality, and bone mineralization in laying hens

The effect of microbial phytase and limestone particle size (LmPS) was assessed in Lohmann Tradition laying hens from 31 to 35 wk of age. Seventy-two hens were used in a completely randomized trial according to a 2×2 factorial arrangement with 2 levels of phytase/basal available P (aP); 0 FTU/kg with 0.30% aP or 300 FTU/kg with 0.15% aP, and 2 limestone particle sizes; fine particles (FL, <0.5 mm) or a mix (MIX) of 75% coarse limestone (CL, 2-4mm) and 25% FL. Diets contained equivalent levels of Ca (3.5%), phytic P (PP; 0.18%), and aP (0.30%) considering the P equivalency of phytase. Thus, dietary treatments were FL0 and MIX0 without phytase, and FL300 and MIX300 with 300 FTU/kg phytase. Performance were recorded daily and eggshell quality (eggshell weight proportion, weight, thickness, and breaking strength) was measured weekly. At the end of the trial, bone parameters (tibia breaking strength, elasticity, and ash) and the apparent precaecal digestibility (APCD) of P and Ca were determined. No differences were observed between treatments in feed intake, FCR and bone parameters. Addition of MIX increased the eggshell proportion, weight and thickness in groups receiving no phytase (+6.5, +6.9, and +4.5%, respectively) while no effect was observed in groups receiving phytase (Phytase×LmPS, P<0.05). In hens receiving FL, the APCD of P was lower in diets supplemented with phytase (-14 percentage points; Phytase×LmPS, P<0.001). A higher phytate disappearance was observed in hens fed diets with phytase in combination with MIX (Phytase×LmPS, P=0.005). Phytase and MIX together increased the APCD of Ca by 7.3 percentage points (Phytase×LmPS, P<0.001). In conclusion, addition of CL could limit the formation of Ca-phytate complex thus improving the response of the birds to phytase compared to FL.

Apparent calcium retention and digestibility coefficients of limestone with different particle sizes in laying hens

Apparent calcium (Ca) retention and digestibility coefficients are affected by limestone particle size in the diet of laying hens. This study aimed to determine the apparent retention and digestibility coefficients of Ca in limestone of different particle sizes in laying hens. The study comprised 288 Lohmann Brown laying hens (50 weeks of age; 1,964 ± 98 g) distributed in a completely randomized experimental design with a 3 × 2 factorial arrangement [three Ca concentrations (10, 20, and 30 g kg–1) × two limestone particle sizes (480 and 1,978 µm)] with eight repetitions per treatment and six birds per experimental unit. The experiment included five days for adaptation and five days for total excreta collection. All birds were slaughtered at the end of the ten days to collect the ileal contents. The total or ileal Ca content was plotted against the Ca of diets concentration using linear regression analysis. The regression line slope represented the apparent retention (CaR) and digestibility coefficients of Ca (CaD) in limestone. There was interaction between Ca concentration in the diet and limestone granulometry on CaD (p = 0.001) and CaR (p < 0.001). The CaD and CaR of fine- and coarse-grained limestone increased linearly with increasing Ca concentrations in the diet. The apparent digestibility coefficients estimated for laying hens fed with fine-grained and coarse-grained limestone were 0.72 and 0.35, respectively. The apparent retention coefficients estimated for laying hens fed fine-grained and coarse-grained limestone were 0.96 and 0.47, respectively.

EFFECT OF PARTICLE SIZE ON SIMULTANEOUS CALCINATION AND SULFATION OF LIMESTONE

The simultaneous calcination and sulfation characteristics of limestone in simulative CFB flue gas atmosphere is examined using a slidable tube furnace system combined with X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) with a focus on the effect of particle size. The effect mechanism of particle size on simultaneous calcination and sulfation of limestone is further analyzed based on the effect of temperature and CO&lt;sub&gt;2&lt;/sub&gt; concentration. The qualitative and quantitative results show that calcination reaction dominates in the early simultaneous calcination and sulfation reaction of limestone and the predominant effect transforms from calcination to sulfation reaction in the late simultaneous reaction of limestone. Compared with small particle size limestone, the big particle size limestone slows the weight loss rate and weight gain rate and needs more time to achieve the lowest weight point. This is related to lower mole fraction loss rate of CaCO&lt;sub&gt;3&lt;/sub&gt; and mole fraction gain rate of CaSO&lt;sub&gt;4&lt;/sub&gt; during simultaneous calcination and sulfation of limestone with big particle size. The effect mechanism of particle size on simultaneous calcination and sulfation of limestone is mainly due to the change of reaction specific surface area, heat transfer, and mass transfer from the surface to the inside of limestone with different particle sizes.

Effect of limestone particle size on performance, eggshell quality, bone mineralization, and in vitro/in vivo solubility in laying hens: a meta-analysis approach

Effect of limestone particle size on performance, eggshell quality, bone mineralization, and in vitro/in vivo solubility in laying hens: a meta-analysis approach

Mucosal expression of Ca and P transporters and claudins in the small intestine of broilers is altered by dietary Ca:P in a limestone particle size dependent manner.

High calcium (Ca) intake and fine limestone reduces precaecal phosphorus (P) absorption independently of P solubility in broilers. This study aimed to determine whether dietary total Ca: total P ratio (Ca:P) and limestone particle size (LPS) affect gene expression of P transporters in the small intestine. A total of 384 one-day-old Ross 308 male broiler chickens received diets low (0.50), medium (1.00) or high (1.75) in Ca:P containing either fine (160 μm) or coarse (1062 μm) limestone, in a 3×2 factorial arrangement. Expression of Ca- and P-related genes were determined using real-time quantitative PCR (RT-qPCR) in duodenum and jejunum. Increasing dietary Ca:P decreased duodenal calcium-sensing receptor (CaSR), calbindin-D28k (CaBP-D28k), plasma membrane Ca-ATPase 1 (PMCA1) and sodium-coupled P cotransporter type IIb (NaPi-IIb), but not transient receptor potential canonical 1 (TRPC1) mRNA. This effect was greater with fine limestone when Ca:P increased from low to medium, but greater with coarse limestone when increased from medium to high. A similar inhibitory effect was observed for jejunal CaBP-D28k expression where increasing dietary Ca:P and fine limestone decreased CaSR mRNA, while dietary Ca:P decreased TRPC1 mRNA only for coarse limestone. It also decreased jejunal NaPi-IIb mRNA irrespective of LPS. Dietary treatments did not affect jejunal PMCA1 mRNA expression or that of inorganic phosphate transporter 1 and 2 and xenotropic and polytropic retrovirus receptor 1 in both intestinal segments. Dietary Ca increase reduced mucosal claudin-2 mRNA in both segments, and jejunal zonula occludens-1 (ZO-1) mRNA only for coarse limestone. In conclusion, increasing dietary Ca:P reduced expression of duodenal P transporters (NaPi-IIb) in a LPS dependent manner, hence Ca induced reduction in intestinal P absorption is mediated by decreasing P transporters expression. Dietary Ca reduces Ca digestibility by downregulating mRNA expression of both Ca permeable claudin-2 and Ca transporters (CaBP-D28k, PMCA1).

Relating LC3 microstructure, surface resistivity and compressive strength development

Concrete surface resistivity can be measured non-destructively, providing an indirect measurement of microstructural development which can be related to strength development. However, relating surface resistivity and strength can be challenging for limestone calcined clay cements (LC3) since they contain mineral components of varying composition and reactivity. In this study of LC3 formulations, concrete surface resistivity until 56 days of hydration and mortar compressive strength at 3, 7, and 28 days were investigated to explore the relationship between these properties while examining the influence of mixture proportioning, limestone particle size and gypsum dosage on LC3 surface resistivity and strength development. Microstructural development of these blends was also assessed by thermogravimetric analysis and formation factor. The results suggest a strong logarithmic relationship between the resistivity and strength development, which can both be predicted by the portlandite consumption. These correlations can allow prediction of later-age strength based on early-age resistivity and portlandite consumption.

Predicting the rheology of limestone calcined clay cements (LC3): Linking composition and hydration kinetics to yield stress through Machine Learning

The physicochemical characteristics of calcined clay influence yield stress of limestone calcined clay cements (LC3), but the independent influences the clay's physical and chemical characteristics as well as the effect of other variables on LC3 rheology are less well-understood. Further, a relationship between LC3 hydration kinetics and yield stress – important for informing mixture design – has not yet been established. Here, rheological properties were determined in pastes with varying water-to-solid ratio (w/s), constituent mass ratios (PC:metakaolin:limestone), limestone particle size and gypsum content. From these data, an ML model developed allowed the independent examination of the different mechanisms by which metakaolin fraction influences yield stress of LC3, identifying four predictors – packing index, Al2O3/SO3, total particle density and metakaolin fraction relative to limestone (MK/LS) – most significant for predicting LC3 yield stress. A methodology based on kernel smoothing also identified hydration kinetics parameters best correlated with yield stress.

Numerical Simulation Study of Mixed Particle Size Calcination Processes in the Calcination Zone of a Parallel Flow Regenerative Lime Kiln.

Limestone of different particle sizes is often calcined together to improve production efficiency, but the calcination effect of mixed particle size limestone is difficult to guarantee. To investigate the effect of different particle size combinations on calcination, this study uses a porous media model and a shrinking core model to simulate the calcination process for a single particle size and two mixed particle sizes in a Parallel Flow Regenerative lime kiln (PFR lime kiln). The results of the study show that an increase in void fraction has a small effect on the gas temperature. The temperature also does not change with particle sizes. At the same time, the decomposition is poor near the wall and better the closer to the center of the calcination zone. In addition, when the particle sizes differ by 2 times, the decomposition of small limestone particles had less influence, and the decomposition of large particles was also better. When the particle sizes differ by 3 times, the decomposition of both limestone sizes is more affected, especially for the larger limestone size, where only the outer surface is involved in the decomposition.

Global survey of limestone used in poultry diets: calcium content, particle size and solubility

Limestone is used in poultry diets as a calcium (Ca) source. Feed formulation is often based on an estimate of limestone Ca content or, less frequently, wet chemistry analysis. However, limestone composition may vary, which has not previously been studied on a large scale. In this study, 641 limestone samples supplied to poultry feed mills in 40 countries across eight global regions were collected and analysed for macro- and micromineral content, particle size (geometric mean diameter, GMD), and in vitro solubility. Mean Ca content of fine limestone (GMD&lt;1000 μm, n=566) was 37.8% (range 33.3-39.7%) and for coarse limestone (GMD&gt;1000 μm, n=75) was 38.0% (range 34.7-40.0%). There was marked variation among and within regions in the concentration of other macro minerals and microminerals. Particle size (GMD) of fine limestone was 288 μm (range 37.7-991.9 μm) and 1,689 mm for coarse limestone (range 301.6-3,067.9 μm). In vitro solubility of fine limestone (5 min incubation, pH=3.0) was 68.4% (range 18.8 to 99.4%). Particle size only explained 52% of the variation in 5 min incubation solubility (R2=0.52). For coarse limestone, mean solubility (30 min incubation) was 65.5% (range 23.2-96%) which was not correlated (R2=0.09) with particle size. Particle size and solubility rate of limestone have been shown to alter Ca and phosphorus utilisation in broilers and laying hens. Hence, better understanding of variation in mineral analysis, particle size and solubility rate would enable more accurate feed inclusion and subsequently digestibility to support health and performance.