Lime Layer Research Articles

Role of self-disintegrating effect produced by decomposition of limestone core on accelerating dissolution of lime in CaO–SiO2–FeOx slag

ABSTRACT The dissolution behaviours of lime, limestone and lime sample with limestone core-lime shell structure in CaO–SiO2–FeOx slag were investigated. The results show that dissolution of lime slows down once 2CaO·SiO2 layer is formed at slag/lime interface. Self-disintegrating effect produced by decomposition of limestone core can accelerate dissolution, but dissolution rate firstly increases, and then decreases with the CaCO3 content of samples increasing. Limestone must decompose to form lime before dissolution, and too much CO2 generated by decomposition of limestone bearing 98.9 wt% CaCO3 blocks the contact between molten slag and lime layer. Thus, limestone hardly dissolves after 60s contacted with molten slag. For lime sample with core–shell structure, the surface of sample is lime layer that can be directly dissolved in molten slag. Meanwhile, self-disintegrating effect produced by decomposition of limestone core enhances slag penetration, and accelerate dissolution. The optimum CaCO3 content in lime sample is 22.7 wt%.

Contribution to the Understanding of Mural Painting Techniques of Jinpari Tomb No. 4 of the Complex of Koguryo Tombs, World Heritage

In this study, we have analyzed the chemical components and crystal structures of minerals found in the Jinpari Tomb No. 4 mural paintings, which has allowed us to identify component materials comprising each layer. During the analysis of the painting layer, the green material was identified as malachite. The use of malachite is supported by the high Cu content, the flower-shaped crystals in the microstructures of the painting layer, and the XRD identification results. The ground layer consists of layers of panel-shaped particles. The main component materials were Ca, Al, Si, K, Mg, and Fe, which are usually found in earthen materials. The earthen layer showed high peaks of silicon oxide and calcium carbonate, along with potassium aluminum silicate. The findings indicate quartz, limestone, and mica. The lime layer showed the diffraction patterns corresponding to calcium carbonate, which indicates the use of limestone. The earthen layer consists of aggregated layers of thin panel-shaped structures, with small particles attached around the structures. The lime layer showed aggregations of multi-angle panel-shaped structures and pillar-shaped structures of various types. The analysis has allowed us to shed light on the techniques used in the Jinpari Tomb No. 4 mural paintings.

Magical practices? A non-normative Roman imperial cremation at Sagalassos

Many thousands of burials have been excavated from across the Roman world, documenting a variety of funerary practices and rites. Individual burials, however, sometimes stand out for their atypical characteristics. The authors report the discovery of a cremation burial from ancient Sagalassos that differs from contemporaneous funerary deposits. In this specific context, the cremated human remains were not retrieved but buried in situ, surrounded by a scattering of intentionally bent nails, and carefully sealed beneath a raft of tiles and a layer of lime. For each of these practices, textual and archaeological parallels can be found elsewhere in the ancient Mediterranean world, collectively suggesting that magical beliefs were at work.

Pigments and Techniques of Hellenistic Apulian Tomb Painting.

The wall paintings of five Hellenistic tombs in Apulia were analysed using a multi-technique approach to discern the painting techniques used and contextualise them within the phenomenon of Hellenistic tomb painting in Southern Italy. In particular, the question was asked whether technical knowledge played a role in the reception of Hellenistic artistic models and whether this knowledge was present locally. Raman and IR spectroscopies were used to identify pigments, colourants, and binders; light and electron microscopy were used to determine the structural characteristics of the paint layers and recognise the manufacturing technique. Analyses identified a fresco application for the Tomba dei Cavalieri (Arpi) and a dry application for the Canosian hypogea. The palette-typical for Hellenistic tomb painting in Southern Italy, Etruria and Macedonia-was composed of lime (white), charcoal (black), hematite (red), goethite (yellow), and Egyptian blue (blue). In the Tomba della Nike (Arpi), meanwhile, two particularly refined preparatory layers were observed. The palette was enriched with precious cinnabar and madder lake. The colouring components of the root were mixed with clay and K-alum applied on an additional layer of lime. The use of madder lake and a pink background link the painting to the polychrome Daunian pottery, and the contribution of a local workshop to the decoration of this tomb thus seems plausible.

Casting, gilding and corrosion mechanisms in two gilded hollow bronze statues from ancient Egypt

This research aims to study two gilded hollow bronze statues from pharaonic Egypt excavated in a karnak temple. The two objects had an unusual casting core and one of them was gelded on the ground. Various parts and layers, including the casting core, gold layer, gilding ground, corrosion products, and metallic structures, were characterized via scanning electron microscopy (SEM), polarized light microscopy (PLM), and USB digital microscopy. X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and SEM coupled with energy-dispersive spectroscopy (EDS) were employed for the analysis. The features related to manufacturing and gilding technologies of the two statues are presented. Specifically, the casting core consisted of an external lime layer on the clay-based internal core, contrarily to the typical casting cores in ancient Egypt and other ancient civilizations consisting of a clay-based mixture. The study proposed a specific method of hollow casting to obtain the casting core, reasonably adopted by the ancient Egyptians to replicate analogous hollow objects from a master mold, whereas the mold of usual hollow casting methods was destroyed after casting. Moreover, the gilding of one of the statues is a unique example of gilded bronze with ground calcite as filler material and beeswax as blinding medium. Finally, the chemistry and structure of the corrosion layers were characterized to gain insights into the morphology and corrosion mechanisms in the presence of calcite ground and gold layers.

The Preparatory Layers in the Etruscan Paintings of the Tomba dei Demoni Alati in the Sovana Necropolis (Southern Tuscany, Italy)

The Tomba dei Demoni Alati is located in the Etruscan necropolis of Sovana (Grosseto, Southern Tuscany, Italy). At the end of the 1990s, excavation revealed remains of this aedicule tomb, carved into red tuff; in 2004, further excavation highlighted new important figurative elements. The Etruscans used different methods to decorate the rock surfaces of the tomb, which were particularly difficult to paint. For this reason, the porous and irregular surface of the tuff was modelled and coated with specific materials. The aim of this work was to study the materials and manufacturing techniques of the preparatory layers applied onto the rock surface in the Tomba dei Demoni Alati. Minero-petrographic, chemical, and micro-chemical characterization of the layers was carried out. The obtained results suggest that different methods were used to prepare the tomb surfaces to be painted. In particular, in the niche of the tomb, two preparatory layers were found: a Ca-based plaster covers the rock; above it, a thin white Ca lime layer was applied. In the sculptures inside the niche, the colors were applied onto two finishing white Ca lime layers of similar composition, whereas, in the decorations of the sculptured surfaces on the outside, paint layers were laid onto a thin white silica stratum. The data allow us to determine the use of plaster, for the first time, in Tuscany, as well as the discovery of a preparation layer never before found in any other local archaeological context.

Evaluation of Cleaning Processes Using Colorimetric and Spectral Data for the Removal of Layers of Limewash from Medieval Plasterwork.

In the cultural heritage preservation of medieval buildings, it is common to find plaster walls covered in lime, which previously were painted in polychromy. The conservation interventions usually try to remove the whitewash, whilst maintaining the original color of the painted wall as much as possible. However, there is no agreement on which cleaning technique best preserves the original appearance of the colored plaster. Different pigments found below the lime layer may behave differently depending on the cleaning technique used. Usually, colorimetric or photometric area-based measurements are carried out to study the color of the cleaned areas to compare with their original color, obtained from pre-made plaster probes. However, this methodology fails when the mean color difference is not enough to fully characterize the changes in texture and color appearance. This study presents a set of experiments carried out using two different pigments (cinnabar and malachite) covered with lime, and treated with nine different cleaning techniques on plaster probes prepared according to medieval techniques. We have studied the effect of the cleaning process on the color and the homogeneity of the samples using a hyperspectral imaging workflow. Four different analysis methods are presented and discussed. Our results show that the proposed analysis is able to provide a much more comprehensive and diversified characterization of the quality of the cleaning method compared to the commonly used colorimetric or photometric area-based measurements.

Mercury removal from the flue gases of crematoria via pre-injection of lime and activated carbon into a fabric filter

The emissions from crematoria have been identified as a source of mercury not currently being remediated. However, the effects of changing the operational conditions by installing a fabric filter (FF) to remove mercury from the flue gas of a crematorium have not been examined in detail. In this study, the mercury concentrations of crematoria flue gases before and after passing through a pre-treated FF and a selective catalytic reactor (SCR) were recorded via continuous emission monitors to examine the effect of pre-injecting a mixture of lime and 10 % activated carbon into the flue. After the filter was installed and treated, mercury concentrations at the outlet of the SCR were very low, with a maximum of less than 5 μg/Nm3. The mercury removal efficiency ranged from 87.5–99.9%. The thick layer of lime and activated carbon on the surface of the FF effectively suppressed the peak mercury concentration at the outlet of the SCR. The relationship between the average mercury concentration at the inlet of the FF and the age of the person at death indicates that the age at death could be a key factor in controlling mercury emissions from a crematorium.

Decomposition behavior and kinetics of limestone in early converter slag

The decomposition of limestone in converter slag directly determines the speed of slag melting for lime that has a strong effect on the steelmaking process of the converter. In this paper, a high temperature furnace was used to study the decomposition behavior of cylindrical limestone samples in the converter early slag at the temperatures of 1250 °C, 1300 °C, and 1350 °C under laboratory conditions, and macro-dynamics equation was used to determine the rate-determining step for limestone decomposition in the converter early slag. The results show that when the limestone is decomposed in the early converter slag, the heat transfer from the slag through the lime layer to the unreacted core is the rate-determining step. The limestone decomposition rate in converter slag is slightly lower than that in hot metal. Finally, the suitable grain size of the limestone added into the converter was determined. Thus, this study provides theoretical guidelines for practical use of converter steelmaking in industrial production.

The nesting habits of Chalybion bengalense (Dahlbom) (Hymenoptera: Sphecidae)

ABSTRACT The nesting habits of Chalybion bengalense are described. Copulation takes place at the nesting site. For nesting, the female uses old nests of Sceliphron and various eumenids, preexisting holes, and trap nests. The wasp cleans the nest cell and provisions it with paralyzed spider prey, 8–32 per S. madraspatanum (Fabricius) cell or 30–60 per trap nest cell. The female lays an egg on one of her prey, frequently the second or the third brought to the nest. Chalybion bengalense closes the nest cells with mud and on the cell cap adds an extra layer of lime, mud, cow dung, resinous material, or rotting plant. The total time from egg to emergence of the adult wasp is 27–34 days. The longevity of adults is 15–47 days for males and 21–49 days for females. Chalybion bengalense overwinters as prepupa from mid November to early April of the following year.

Kinetics of limestone decomposition in hot metal

Compared with the traditional limestone calcination, this paper focuses on the conditions and temperature in hot metal where limestone calcines in converter steelmaking process. Considering heat transfer, mass transfer driven by concentration gradient and mass transfer (CO2 gas flow) driven by pressure gradient, macro kinetic models are established to describe limestone decomposition rate respectively. The method of rotating cylinder sample is used in the experiment of limestone decomposition in hot metal. The image processing software Image-Pro Plus is used to analyze the cross section of limestone calcined to get the unreacted core radius of cross section of cylindrical limestone. The results show that the decomposition mechanism of limestone follows the unreacted shrinking core model, the heat conduction of lime layer is the controlling step, the heat conduction and CO2 migration through the product layer determine the rate of limestone decomposition, and the corresponding kinetic equations are established.

Decomposition behavior of limestone in early converter slag

Better understanding the decomposition and dissolution behaviors of limestone under steelmaking condition is essential to evaluate the possibility of directly using limestone instead of lime in converter. In this paper, the decomposition behavior of limestone in early converter slag including the decomposition kinetics and microstructure of the produced lime layer were studied, and the effects of slag temperature and stirring speed introduced to the slag bath were examined. Kinetic analysis based both on shrinking core model and dimensionless chemical-heat transfer number (NCH) showed that the limestone decomposition at 1300–1400°C was a mixed control of chemical reaction and heat conduction through the lime layer. Slag temperature has a significant influence on the decomposition process while the stirring speed plays a minor role when a critical stirring intensity is reached. The obtained effective thermal conductivity varied from 0.21 to 2.51Wm−1K−1 and the chemical reaction rate constant ranged between 7.9×10−4 and 6.3×10−3ms−1. The produced lime layer has less grain size and apparent porosity than the calcined one. Besides, smaller limestone particle and more heat supply to the converter bath are recommended to accelerate the limestone decomposition in early converter slag.

Sand Dune Stabilization by Hydrated Lime

Formation and movement of sand dunes could be considered the most important problems thatsafer and destroy agricultural lands, domestic and industrial buildings. These dunes finally forma desertification state. The hard climate as high temperature and reduction in rainfall are themain factors affecting on this formation. This practical study is a trial to solve this problemthrough addition and covering the dunes by local material. Hydrated lime was used in this work,the lime was mixed with water in different ratios and covered a hills of sand. Three ratios of limewere selected to cover three sand hills with diameter 100 cm and height 50cm. The thickness ofthe lime layer is 6cm and covered all the hill. The hills were lifted for a year under the naturalcircumstances of sun shine, winds, rainfall and temperature. Results indicated that the hills werefixed and no sand were blown from dunes. Furthermore, some natural plants have been grownover them.

Sand Dune Stabilization by Hydrated Lime

Formation and movement of sand dunes could be considered the most important problems that safer and destroy agricultural lands, domestic and industrial buildings. These dunes finally form a desertification state. The hard climate as high temperature and reduction in rainfall are the main factors affecting on this formation. This practical study is a trial to solve this problem through addition and covering the dunes by local material. Hydrated lime was used in this work, the lime was mixed with water in different ratios and covered a hills of sand. Three ratios of lime were selected to cover three sand hills with diameter 100 cm and height 50cm. The thickness of the lime layer is 6 cm and covered all the hill. The hills were lifted for a year under the natural circumstances of sun shine, winds, rainfall and temperature. Results indicated that the hills were fixed and no sand were blown from dunes. Furthermore, some natural plants have been grown over them. DOI: http://dx.doi.org/10.25130/tjes.24.2017.16

Tanti cocci, quanti vasi?

The study of a massive waste dump of the Arretine potter Ateius, by means of the database FileMaker Pro 11, provided some evidence concerning the deposit’s formation. For part of the fragments there were at least two depositions at different times, as some potsherds were re-used as building material within the kiln itself, then discarded again, with a layer of lime and sand that still covered them. Some fragments were first used as slats for shaping vases, then thrown into the dump, and eventually re-used as building material. All these operations inevitably caused the alteration of the stratigraphy, making it quite difficult to piece together all the fragments pertaining to a single vase. Moreover, in a period that cannot be identified, part of the dump was moved from the original place to the location where it was found in the excavation carried out in the 1950s . All these events are reflected by the archaeological records. The Conspectus 9 cup is a good example: the fragments of rims largely outnumber those of foots. Assessing the minimum number of vessels present in the dump is not easy under these circumstances.

Physical and chemical changes in coal fly ash during acidic or neutral wastes treatment, and its’ effect on the fixation process

Coal fly ash (FA) is an abundant commodity in many countries using steam coal for power production. In some countries (e.g. Israel) all the FA is utilized whereas in some countries only low percentage is used (e.g. USA). The main mode of utilization is in the civil engineering industries as cement or clinker additive or for concrete production. In Israel (2014) 1.3Mt of highly basic type F FA has been produced, mostly from South African and Colombian coals, in the utilities. A potential application for type F FA could be as an efficient scrubber for hazardous acidic wastes (e.g. the phosphate industry). The scrubbing efficiency of FA stems from interactions of the aluminosilicate surface of the particles with trace elements or with fine precipitates of ionic solids (e.g. SrCO3). The process changes the chemical and physical nature of the FA surface. These changes have been studied using SEM, TEM, XRD and particle size measurements of non-treated, compared to treated FA with acidic or neutral aqueous solutions.The results indicate that an appreciable part of the outer lime layer and part of the glassy aluminosilicate material is dissolved, revealing the mullite skeleton as well as Ti, and Fe species. Moreover, formation of mixed ettringite/thaumasite and halite particles is observed. Thus, this study can lead to a better understanding of the fixation mechanisms of the trace elements by coal FA.

Consolidación y restauración de la fachada norte del Senado de España mediante reanclados, armados, sellados y coberturas

The consolidation and restoration of existing elements in the northern facade of the old Senate building in Spain is based on the anchorage of the windows massive artificial stone frame and the crown hollow moulding with polyester rods reinforced with fiberglass; on the elimination of the existing plaster and making a new one in two layers, arming with fiberglass mesh the base hydraulic lime layer prior to application of the finish coat of air lime; on the opening of expansion joints sealed with neutral silicone, both the mouldings and the render, and on the cover of the horizontal surfaces of the projecting elements (mouldings, overalls and flashing) with zinc sheeting. Previous studies are discussed with the results of historical documentation, with the materials analysis and the diagnosis of damages that support the intervention.

Decomposition of Limestone in Hot Metal at 1300 °C

Decomposition and dissolution of cylindrical limestone samples (ø16 mm × 50 mm approximately) in hot metal at 1300 °C are experimentally studied. The cross section of burned limestone is determined by using image processing and then the lime layer thickness is determined. The three layers of the cross section of burned sample are analyzed by using SEM, and the change of the Fe content along the radial direction is also analyzed. A kinetic model is established to characterize the calcination of limestone in hot metal. The results show that there are three distinct layers on cross section of burned limestone: a reacted layer in the outside, a burned lime layer in the middle, and an unburned limestone core in the inside. Heat transfer is the control step for limestone calcination in hot metal. Fe can be oxidized by carbon dioxide from limestone calcination, and ferrous oxide can permeate into burned lime layer along the radial direction of sample. The kinetic model for limestone calcination can be used to predict limestone conversion rate in hot metal.

Study and restoration of the Seville City Hall façade

Before restoring the Seville City Hall façade, a study of the original materials and the compounds added or formed was performed. The stone is fine-grained carbonate rock. Gypsum and mortars were used to restore stone fragments. A black crust was also found the wall was covered with an acrylic resin. A layer of lime on the surface was also detected. The restoration was intended to preserve the artistic quality and uniqueness of this building. The cleaning, reinforcing and innovatively consolidating and protecting the stone using suitable materials similar to those used in the original construction are described in this study.

Investigation of some factors that affect jakura limestone burning

Limestone calcination reaction seems to be a very simple and straight-forward reaction. However, there are numerous critical variables that exert profound effect on lime burning operations. The factors and variables that affect the burning of limestones must be considered in the selection, design and optimization of the calcininig equipment. Limestone burning in a vertical kiln often presents complex problems which can be solved from the conception by consideration of the prevailing factors that determine the progress of calcinations reactions. The evaluation of the influence of these factors on the progress of the burning of Jakura limestone in a vertical shaft lime kiln is the thrust of this work. Basic kinetic parameters such as: diffusivity, mass transfer coefficient, conductivity, heat transfer coefficient, convective parameter, and diffusive parameter of the lime layer of the calcining limestone particle were obtained from the calcinations tests. Computer programs were developed to evaluate the effects of these factors for typical burning conditions. The shrinking core kinetic model of the reaction limited by heat and mass transfer was employed in the evaluation. The effects of chemical kinetics, stone size and gradation, calcination tempera ture, calcination time, effect of pressure and flow conditions in the kiln were evaluated. Key words: Limestone, calcination, vertical shaft lime kiln, shrinking core kinetics, calcining equipment.