Papers by Keyword: Firing

Abstract: The main purpose of this work is to evaluate the influence of the thickness and thermophysical properties of insulating materials on the maximum external surface temperature and energy gain provided for an intermittent ceramic kiln operating with natural gas as fuel. To evaluate the influence of independent variables on response variables, a factorial experimental design was developed. From the analysis of variance (ANOVA), it was possible to determine significant and well-adjusted mathematical models for both response variables. It was verified that the thickness and thermal conductivity of thermal insulation are the independent variables that have the greatest influence on the process efficiency.

Abstract: The paper presents the results of the studies on the phase conversions taking place during the firing of the refuse piles processing sieve residue in the Eastern Donbass, which are the promising raw materials for the production of various types of structural ceramics – common, lining and clinker bricks, high-performance ceramic stones, ceramic tiles and siding. It is established that the sieve residue is the raw material of the low-temperature baking. Depending on the degree of grinding, the raw material may belong to the group of mid-baking or high-baking raw materials. The sieve residues have a rather narrow baking interval - no more than 50 °C, which is possible to expand by increasing the content of fine fractions during the preparation of sieve residue. The main mineral phases at the firing temperature of 1000-1100 ^оС are quartz, feldspar, ferrous silicates and aluminum silicates (fayalite, hypersten, etc.), hematite. The features of the phase and mineralogical conversions allow us to recommend to fire products on the basis of sieve residue at temperatures of 1000 °C and higher.

Abstract: Fluid fuel combustion technology in coal-fired power plants is very popular in the Czech Republic, resulting in a relatively high production of a specific by-product - fluidized fly ash (class C according to ASTM definition), which differs from the classical high-temperature fly ash in mineralogical composition with a high sulphur content of anhydrite CaSO₄. Fluidized ash is not yet used in the production of fired building materials, where it could be used as a source of calcium oxide (for example, the production of porous ceramic tiles). However, high volume of sulphur dioxide emissions during the re-firing of fluidized fly ash in ceramic raw materials mixtures has been solved. The aim of the paper is definition of temperature ranges of anhydrite decomposition (formation of SO₂ emission) from pure class C (fluidized) fly ashes from different sources (power plants) depending on granulometry of fly ash especially.

Abstract: The aim of the article is to determine the possibility of domestic inorganic nanofibers utilization (Pardam, Ltd.) for experimentally developed porcelain body based on calcium aluminate cement. Two types of nanofibers based on pure SiO₂ and Al₂O₃ were mixed with the casting slip prepared in the system calcium aluminate cement – quartz – feldspar. The properties of the raw materials mixture (mixing water content, drying shrinkage, strength of green body) and fired body at different temperatures (strength, porosity) were tested.

Abstract: Heat-resistant materials are commonly used in industry where technological processes require high temperatures. The research represents possibility to obtain Al₂O₃–SiO₂–ZrO₂ based composition from local raw like zirconium silicate of Tugansk deposit of Tomsk region and white clay of Kailinsk deposit of Kemerovo region in Russia. There is possible application in gunning-mass form for restoration industrial thermal units. X-ray Diffraction Analysis demonstrates that mullite and zirconium compounds are formed in samples content after firing. The infra-red spectrums of heat-resistant gunning masses samples have been described by Fourier Transform Infrared Spectroscopy method. The thermal analysis has been performed using Differential Scanning Calorimetry and Derivative Thermogravimetry.

Abstract: The texture in illite-based ceramics was introduced by spreading a large number of thin layers of a wet plastic mass one on top of the other. The basal planes of the plate-like illite crystals are predominantly oriented parallely with the direction of spreading. The samples were fired at different temperatures ranging from room temperature up to 1100 °C with a heating rate of 5 °C/min, then freely cooled and measured at room temperature. We determined Young modulus (E), thermal diffusivity (a) and relative dimension changes (Δl/l₀) in two directions: parallely to the basal planes (a subscript ||) of the illite crystals and perpendicularly to these planes (a subscript ⊥). It was found that the ratio E_|| / E_⊥ ≈ 2.9 and a_|| / a_⊥ ≈ 2.0 up to 900 °C. Above 900 °C, the values of E and a increase due to sintering, and the differences between the values measured in the two directions decrease. In the case of the thermal diffusivity these differences do not disappear even after firing at the temperature of 1200 °C.

Abstract: Planarity is one of indispensable attribute of a ceramic tile quality. During the firing changes on curvature may be permanent causing damage on quality and productivity. The objective was to evaluate curvature evolution on porcelain tile during heating stage of firing. Effects of engobe and glaze coating were evaluated. The performance of two compositions of porcelain tile was studied on industrial (1000 mm x 500 mm x 10 mm) and laboratorial (100 mm x 50 mm x 6 mm) scale. Industrial test pieces were fired at 950 and 1200 °C. Final curvature was measured by conventional dial indicator. Curvature evolution of laboratorial test pieces was evaluated by thermal fleximetry from 25 to 1200 °C. This characterization was capable to identify very significant positive curvature deflection on temperature range from 930 to 1200 °C, directly associated to permanent planarity defects. Differences on composition affect significantly the curvature evolution.

Abstract: One of the most critical steps in brick making is firing, performed to harden the bricks. In a typical non-industrial setting, many pieces of extruded clays are stacked into a box-shaped kiln with equally-spaced rectangular vertical holes and another set of equally-spaced horizontal holes at the bottom across two sides. Roman roof tiles are used to cover the vertical sides, while leaving the horizontal holes opened, to complete the kiln assembly. Rice husk is filled in the holes of the kiln and is used as the fuel for firing. However, approximately 10% of the bricks, stacked conventionally, are always not appropriately fired. Therefore, this research aimed at simplifying model and redesigning the clay brick kiln using three-dimensional computational fluid dynamics (CFD). The studied parameters for 2³ factorial designs were as follows: kiln height (200 – 225 cm), horizontal holes width (7.5 – 15 cm) and height (45 – 60 cm). The total volume of brick stack, averaged steady-state temperature and time to reach a steady-state temperature were selected as the response parameters. The analysis of variance (ANOVA) of 2³ factorial design showed that the width and height of holes affected the time to reach steady-state but the averaged steady-state temperature and the total volume of brick stack were dependent on all 3 parameters. Then, a kiln was constructed according to the model with the maximum number of bricks and only 4% of the bricks were not appropriately fired.

Abstract: Micro-electro-mechanical system (MEMS) have recently seen their field of application extended to military. This is mainly due to the fact that MEMS technologies present a great to reduce the mass, cost, power consumption, while improving the reliability, performance and smartness. Application of MEMS technology, the micropyrotechnic igniter are produced.The principle is based on the integration of the potassium salt of 7-hydroxy-4,6-dinitro-5,7-dihydrobenzofuroxanide (KDNBF) material within a micropyrotechnic igniter, which is produced by MEMS with 3 by 3 micro-igniter. Each igniter contains three parts (the igniter chip, silicon chamber, KDNBF). One import point is the optimization of the igniter process obtaining Ni-Cr bridges with about 13Ω and Al bridges with about 350Ω, which are triggered by electrical power delivered to KDNBF. The resistance of Ni-Cr and Al bridges is used to sense the temperature on the KDNBF which are in contact. The other one point is firing testing of micropyrotechnic igniter. The ignition performance of micropyrotechnic igniter array are tested that including Ni-Cr bridges of the 50% sensitivity on voltage, current ignition is 10.83V,0.26A; including Al bridges of the 50% sensitivity on current ignition is 0.176A; the ignition of voltage is unstable. The experimental results will deeply contribute to the micropyrotechnic system. This paper will discuss all these point.

Abstract: Investigations were undertaken to assess the chemical and technological characteristics in clay products from the Cretaceous deposit (Moroccan Meseta), in order to use them in refractory products. We have focused mainly on this clay because of its high content of alumina, silica and magnesium oxide, which are very favorable for the synthesis of refractory and ceramic materials. That is why the study has used several techniques of analysis (FX, XRD, SEM and technological tests. The samples were dry pressed on clay bodies and sintered at temperatures ranging from 900 to 1200°C. The relationship between water absorption, shrinkage and flexural strength as a function of the firing temperature was examined in order to enhance the quality of the final products and to optimize the production process. The results revealed that these clays have qualities necessary for the manufacture of ceramic and refractory products.