Electric Kiln Research Articles

Fast-drying of red ceramics: A new evaluating approach based on the combined use of optical dilatometry and thermogravimetric analysis

This study aimed to evaluate the effects of composition and heating rate on the fast-drying (∼60 min) of red ceramics obtained by extrusion using optical dilatometry and thermogravimetry to obtain the drying curve. Three different plastic clays were used in the four formulations investigated, as well as three heating rates with a total time of 60 min and a maximum drying temperature of 200 °C: 5.83, 3.89, and 2.92 °C/min. Based on the results obtained from the modified Bigot curves, a fast-drying curve (3 °C/min) was established in a static laboratory dryer with a total cycle of 60 min and a maximum temperature of 160 °C. The samples were characterised in terms of compressive resistance and visual aspects related to drying cracks. Formulation F5, containing 50 wt% AM clay and 50 wt% AV clay, exhibited the worst performance in fast-drying with drying cracks, whereas formulation F7, containing 33.3 wt% AC clay, 33.3 wt% AM clay and 33.3 wt% AV clay, exhibited the best performance. Formulations F7 and F8 (16.7 wt% of AC clay, 66.6 wt% of AM clay and 16.7 wt% of AV clay) were fired at 900 °C in an electric kiln, with a heating rate of 1.5 °C/min and a 2 h holding time, and then characterised in terms of firing shrinkage, water absorption and compressive strength. The results showed that Formulation F7 presented suitable behaviour in the fast-drying process at 160 °C for 60 min in a laboratory dryer at a heating rate of 3 °C/min, 0.9 wt% a residual moisture. It exhibited no drying cracks and a dry compressive strength of 0.94 ± 0.09 MPa. However, the combined analysis of optical dilatometry and thermogravimetry indicated that the drying conditions could be optimised for a residual moisture of 2 wt%, using a thermal cycle of 138 °C for 19 min (heating rate of 5.83 °C/min) if adequate control of the humidity of the chamber atmosphere in the first drying stage is employed to avoid drying cracks. The results also showed that the specimens of formulations F7 and F8 met the technological requirements defined by the Brazilian standard ABNT NBR 15270-1, demonstrating the feasibility of producing red ceramic bricks by extrusion with fast-drying. The combined optical dilatometry and thermogravimetry techniques used to obtain the Bigot curve applied to fast-drying showed very good agreement with those obtained in the laboratory dryer. These combined techniques represent promising approaches for studying the fast-drying of red ceramics.

Determining the Structural Properties and Vibrational Modes of Annealed Lead Composite Material Deposit

Techniques for effectively harnessing lead (Pb) deposits for optimum utilization have attracted a lot of research interest. Results obtained from investigating the elemental composition, vibrational modes, and structural properties of a fired Pb composite deposit, which is purified using an electric kiln furnace and further annealed in palladium‐diffused hydrogen ambient, are reported in the present study. Both atomic force microscopy and scanning electron microscopy analysis on the deposit indicate that the Pb composite is composed of crystal‐like morphology. The vibrational modes obtained from the material are identical to the Raman spectrum reported for PbSO4. Also, data acquired from the energy‐dispersive X‐ray analysis of the annealed Pb composite material confirm the presence of zinc, carbon, silicon, sulfur, and oxygen in the material. At the same time, Pb appears to be the primary constituent with reference to its weight percentage composition compared to other elements. The findings from the present study may be vital for providing an improved understanding of the electronic and structural properties of the annealed Pb composite deposit while promoting the development of a feasible approach for the recovery and recycling of Pb for future related applications.

Preliminary investigation of temperature and pressure profile of pudam in the preparation of Siddha medicine Padigara parpam

BackgroundPudam is one of the manufacturing processes used extensively in preparing parpam and chenduram in the Siddha healthcare system. The scientific understanding of the process is not fully understood. ObjectiveIn this work, our objective was to investigate the temperature and pressure profile of the pudam process and also to understand the porous nature and low thermal conductivity of the sealed agal (Earthen vessel) used by replicating the traditional manufacturing process of Padigara parpam medicine in a pit. Materials and methodsThe temperature and pressure profiles were recorded. The size and mass of the cow dung cakes required to conduct the pudam process were discussed. The agal's porosity, thermal conductivity, and thermal diffusivity were experimentally determined. The pressure test of an empty agal was performed in an electric kiln and a pit to find the pressure development inside it and understand the sealed agal's role. ResultsThe maximum temperature of the pudam process was recorded as 807 °C, and the maximum heating and maximum cooling rate were calculated to be 30 °C/min and 8 °C/min, respectively. The holding time was found to be 66 min above 600 °C and 51 min above 700 °C. The maximum pressure built during the pudam process was 8.2 mbar. ConclusionThe test results indicate that the bottom location of the sealed agal is the optimum place to record the temperature of a pudam process. The sealed agal does not allow pressure to build inside, and the pudam process can be considered a heating process that occurs at atmospheric pressure. Increasing the quantity of cow dung cakes for the exact size of the sealed agal and pit increases the raw material's temperature and holding time and reduces the maximum heating rate.

Characterization of the radiation shielding properties of fired lead sample for X-ray shielding applications

The characterization of the radiation shielding properties of a fired lead ore deposit (LOD) found in Enyigba, Ebonyi state have been investigated experimentally and by XCOM calculation. The electric kiln furnace purification technique and the Atomic Absorption Spectroscopy (AAS) were used in establishing the lead content in the ore, while the X - ray transmission measurement at peak voltages of 100 kVp and 120 kVp with a 500 cc PTW ionization chamber was used in determining the mass attenuation coefficient (μm). The linear attenuation coefficient (μ), half value layer (HVL), tenth value layer (TVL) and mean free path (MFP) were calculated from the obtained μm values. Results of the parameters were compared with calculated XCOM μm values and with other studied shielding materials. It was found that the deposit reduced effectively, the X-ray photons with increase in lead slab thickness which supported its obtained radiation shielding properties which also agreed with the calculated XCOM μm values. The natural abundance and established lead ore concentration in the LOD gave credence to its efficacy to be used as x–ray shield with the 5 mm lead slab having the optimum shield irrespective of the firing process introduced.

Optimal Allocation of Comprehensive Resources for Large-Scale Access of Electric Kiln to the Distribution Network

With the significant progress of the “coal to electricity” project, the electric kiln equipment began to be connected to the distribution network on a large scale, which caused power quality problems such as low voltage, high harmonic distortion rate, and high reactive power loss. This paper proposes a two-stage power grid comprehensive resource optimization configuration model. A multi-objective optimization solution based on the joint simulation platform of Matlab and OpenDSS is developed. The solution aims to control harmonics and optimize reactive power. In the first stage, a multi-objective optimization model is established to minimize the active network loss, voltage deviation, and equipment cost under the constraint conditions of voltage margin, power factor, and reactive power compensation capacity. Furthermore, the first stage uses a particle swarm optimization (PSO) algorithm to optimize the location and capacity of both series and parallel compensation devices in the distribution network. In the second stage, the optimal configuration model of the active power filter assumes the cost of the APF as the objective function and takes the harmonic voltage content rate, the total voltage distortion rate, and the allowable harmonic current as the constraint conditions. The proposed solution eliminates the harmonics by uniformly configuring active filters in the distribution network and centrally control harmonics at the system level. Finally, taking the IEEE33 distribution network as the object and considering the change of electric furnace permeability in the range of 20%–50%, the simulation results show that the proposed algorithm effectively reduces the distribution network’s loss, its harmonic content and significantly improve its voltage.

Fine Particulate Deposition in an Effusion Plate Geometry

Abstract Fine particulate deposition testing was conducted with an effusion plate geometry representative of a gas turbine combustor liner. Preheated coolant air with airborne particulate was fed into an effusion plate test fixture with the flow parallel to the target plate. The test fixture was in an electric kiln that establishes elevated plate temperature, similar to a gas turbine combustor. Test variables include hole diameter, length/diameter ratio, inclination angle, and compound angle. In addition, coolant and plate temperature were varied independently to determine their influence. All tests were continued until the effusion holes had blocked to produce a 25% reduction in mass flowrate while maintaining constant pressure ratio. The blockage rate was found to be more sensitive to flow temperature than to plate temperature over the range studied. Blockage rate was insensitive to effusion hole diameter from 0.5 to 0.75 mm but increased dramatically for hole diameter below 0.5 mm. Blockage shows a moderate increase with hole length/diameter ratio. The strongest dependency was found with the inclination angle; roughly an order of magnitude increase in blockage rate was documented when increasing from a 30 deg to 150 deg. A compound angle of 45 deg caused a negligible change in blockage rate, while a compound angle of 90 deg increased blockage rate for low inclination angles while decreasing it for high inclination angles. For the flow angle dependency, interpretation is provided by means of computational fluid dynamics (CFD) simulations of the particulate delivery and initial deposition location prediction using the Ohio State University (OSU) deposition model.

Influence of electric arc furnace dust and lime kiln waste in Portland cement hydration

Abstract Studies have indicated that the use of electric arc furnace dust (EAFD) results in a delay in the hydration time of Portland cement. Calcium-rich waste such as lime kiln waste (LKW) is one of the techniques used to offset this delay as it accounts for the lack of this element in calcium silicate hydrate (C-S-H) production in the mixture. The objective of this study was to evaluate the influence of electric arc furnace dust (EAFD) and lime kiln waste (LKW) in the hydration process of Portland cement pastes and their influence in setting time and hydration heat. The methodology used required several steps: physiochemical and micro-structural characterization of waste samples; definition and production cement pastes with different levels of waste substitution and a reference paste and evaluation of the cement pastes with respect to setting time and hydration heat. Results showed that the substitution of 1% EAFD with or without LKW presented similar hydration heats as the reference paste. This indicated that EAFD+LKW substitution would not affect substantially the hydration reactions of cement and could allow waste recycling in construction materials.

Valorization of faecal and sewage sludge via pyrolysis for application as crop organic fertilizer

In developing countries, faecal sludge treatment facilities are non-existent in most cities and small towns resulting in untreated and improper disposal of sludge. In Ghana 85 % of faecal sludge produced each day is discharged into the earth with no effective treatment. Converting sewage and faecal sludge to biochar addresses the stigma of fertilizer obtained from human excreta, since the pyrolysis process guarantees a 100 % pathogen elimination, and enrich nutrients in faecal sludge biochar. The interest to convert sludge waste into biochar is that it ensures a pathogen free fertilizer. Sewage sludge and faecal sludge with sawdust were pyrolysed at different temperatures in this study. Sewage sludge (SSB1−300 °C, SSB2−450 °C and SSB3−600 °C) as well as faecal sludge with sawdust (CTB1−300 °C, CTB2−450 °C and CTB3−600 °C) were both converted to biochar at 300 °C, 450 °C and 600 °C, respectively using an electric kiln. Physicochemical parameters such as Total Nitrogen (TN), Total Potassium (TK), Total Phosphorous (TP), Calcium (Ca), Magnesium (Mg), Organic Carbon (OC), Organic Matter (OM), Cadmium (Cd), Arsenic (As), Ash content, pH, Electrical Conductivity (EC), Moisture content, Porosity and Bulk Density and germination test were performed. It was found that at 300 °C nitrogen content, organic matter, bulk density, biochar yield and moisture content were high, and longer root lengths were observed as well. Biochars produced at 450 °C produced the longest shoot lengths. Also, biochars produced at 600 °C had high phosphorous, potassium, calcium and magnesium levels, high porosity, pH and high heavy metal concentration as well. The outcomes demonstrate that biochars produced at higher temperatures are high in heavy metal concentration, but were within acceptable limits for application in agriculture. Biochar produced at moderately lower temperature is favourable for agriculture purposes. SSB1−300 °C, SSB2−450 °C, CTB1−300 °C and CTB2−450 °C had moderate pH and ash levels and so are less toxic to the growth of plants. Faecal sludge biochar produced at the three temperatures were suitable for use as fertilizer. The conversion of sludge waste into biochar will help improve faecal sludge management.

Examination of mullite ceramic specimens made by conventional casting method from kaolin and sawdust

Using relatively low-cost raw materials (conventional kaolin and sawdust powders) and simple technology, the authors have developed new ceramic composite materials which can successfully meet different industrial requirements. Casting masses (slurries) were made by mixing and milling different compositions of the powders with distilled water. The ceramic specimens were made by conventional gravitation slipcasting method, after drying of the green specimens, the samples were sintered in an electric kiln under oxidation and reduction atmosphere at 1250°C. The prepared and sintered specimens were tested based on geometrical sizes, microstructures and morphologies using scanning electron microscopy. In this work, the authors present some parts of the results of their research and investigation.

Growth of metastable phases during brick firing: Mineralogical and microtextural changes induced by the composition of the raw material and the presence of additives

This paper studies the mineralogical and textural changes that take place during the firing in an electric kiln at 800, 950 and 1100 °C of brick samples made with or without additives. Samples were made with a clayey raw material which was mixed with either halite or calcined diatomite sludge and then fired. These samples were then compared with control samples made without additives. Different analytical techniques (X-ray fluorescence, thermogravimetric and differential scanning calorimetric analyses, X-ray diffraction, polarized optical microscopy and scanning electron microscopy) were used to reconstruct the changes that took place inside the bricks from a mineralogical and textural point of view, changes that are similar to those that take place in nature during pyrometamorphism. The carbonates decomposed and reacted with silicates to form gehlenite, diopside and wollastonite; the plagioclase was enriched in calcium and the quartz concentration fell; the clay minerals favoured the melting of the matrix and the appearance of mullite, and K-feldspar changed from microcline to sanidine. The extent of vitrification increased in line with the increase in the firing temperature. When halite was added, new silicates appeared earlier at lower firing temperatures and molysite was formed, while the most important mineralogical difference in the bricks made with added calcined diatomite sludge was the presence of cristobalite, a component of the sludge. It is interesting to observe that the newly-formed phases contain certain chemical elements that are not normally found in their standard chemical composition.

Sawdust recycling in the production of lightweight bricks: How the amount of additive and the firing temperature influence the physical properties of the bricks

This paper studies the influence of sawdust on the petrophysical properties of solid bricks. Brick samples without additives were handmade using a clayey earth that is rich in quartz and phyllosilicates and has some carbonate content. Similar bricks were made with added sawdust at 2.5%, 5% and 10% weight. The bricks were fired in an electric kiln at 800 °C, 950 °C and 1100 °C. The addition of sawdust did not change the mineralogy of the fired bricks. As the firing temperature increased, the quartz content fell and carbonates and phyllosilicates disappeared causing new silicates (gehlenite, wollastonite, anorthite and diopside) to develop. There was an increase in the vitrification of bricks, which also became more compact. At high firing temperature, the bricks had a higher water absorption capacity and worse interconnection between the pores. The high level of vitrification reached at 1100 °C enabled greater transmission of heat inside the bricks. The most refractory bricks were those fired at 800 °C with a 10% sawdust content. When subjected to the salt crystallization test, the most resistant bricks were those with the lowest sawdust content and the highest firing temperature.

Effect of biochar on mechanical and permeability properties of concrete exposed to elevated temperature

Although many inorganic fillers have been explored as supplementary cementitious admixtures, there is limited exploration into role of porous biochar, prepared from lignocellulosic biomass, in modifying mechanical and durability performance of structural grade concrete exposed to elevated temperature. This study investigates the effect of biochar particles, prepared by pyrolysis of woody biomass at 500 °C (BC 500), on mechanical strength (compressive, flexural and split-tensile strength) and permeability properties of concrete under normal condition (only wet-curing) and after exposure to high temperature (300 °C and 550 °C in this study) at 28-day age. Biochar was added at 0.50%, 1% and 2% by weight of cement in concrete. Thermal damage was inflicted to 28-day wet-cured concrete samples by placing in an electric kiln with residence time of 1 h (at steady state) and ramp rate of 5 °C/min. The strength and permeability performance of biochar-concrete composite were compared with plain concrete and concrete with 10 wt% silica fume (SF 10%) exposed to similar conditions. The findings show that addition of 0.50 wt% and 2 wt% of BC 500 increase 28-day compressive strength of concrete by 16% and 9% respectively compared to control mix, while 2 wt% addition led to reduction in permeability by 40%, measured by water sorptivity and water penetration test. After exposure to elevated temperature, addition of 1–2 wt% BC 500 to concrete is found to minimize thermal damage and retain 20% and 11% higher strength compared to control and concrete with silica fume respectively. Investigations show that biochar addition leads to lower damage to microstructure of concrete during thermal treatment, leading to 22–25% higher water tightness compared to control mix. The findings suggest that biochar from wood waste can be applied as a sustainable admixture and alternative to silica fume in order to improve compressive strength and durability of structure exposed to high temperature. Nevertheless, this can be also be an effective means to valorize lignocellulosic waste for high value construction applications.

Effect of composition and heat treatment on porosity and microstructures of technical ceramics made from kaolin and IG-017 additive

Based on conventional kaolinite and IG-017 bio-original additives of IGREX Ltd. the authors have developed new ceramic composite materials for different industrial purposes. In this work, different powder mixtures of kaolinite and IG-017 bio-original additive were milled and uniaxially pressed at different compaction pressures into cylindrical discs, after compaction, the discs were sintered in electric kiln under oxidation atmosphere and in oxygen-free atmosphere. Using the oxygen-free sintering process, new high porosity ceramic materials were created. Through the examination of the microstructure of the produced specimens the authors have found that the ceramic structure is reinforced with carbon nanofibers.

Production of Thermal Insulating Material Using Scoria

Insulation of the combustion chambers has continued to gain prominence over time because of the desire to improve the thermal efficiency of the systems. The present study investigated the suitability of scoria as an insulating material. Three different batches of scoria, clay and naphthalene were mixed. Scoria served as the matrix, clay served as the binder and naphthalene as the pore creator. The first batch contained 17.6% clay, the second contained 30%, while the third batch contained 39.1%. From each batch, test samples were prepared at varying percentage naphthalene content. Test samples were moulded into different shapes, depending on the test to be carried out on them. They were then allowed to dry under ambient air. This process was followed by oven-drying for 2 hours at 110 o C to further reduce the moisture content of the test samples. The test samples from batch 1 disintegrated during the drying stage leaving only batches 2 and 3. The test samples were thereafter fired in an electric kiln to a temperature of 1000 ºC. Following the firing process, test samples from batches 2 and 3 were subjected to apparent porosity, bulk density, thermal shock resistance and thermal conductivity tests. At 40% naphthalene addition, the percentage apparent porosity values obtained for batch 2 and 3 test samples were 73.13% and 63.23%. Bulk density values at the same naphthalene addition were 1.27 and 1.36 gcm -3 respectively. Between 0% and 40% naphthalene addition, the thermal conductivity values for batches 2 and 3 test samples steadily reduced from 0.14 - 0.04 W/m.K and 0.27 – 0.09W/m.K. The thermal shock resistance of the test samples from batches 2 and 3 also decreased from 12 to 7 and 13 to 6.5 cycles respectively. Test samples produced from batch 2 produced better results overall, which proved scoria to be suitable for use as a thermal insulating material.

ENERGETIC VALORIZATION OF SAWMILL RESIDUES THROUGH SLOW PYROLISIS PROCESS

Brazil is a large producer of sawmill wastes, commonly used to supply boilers and produce energy. In order to reduce unwanted characteristics of the material, thermochemical conversions through carbonization is an alternative. The aim of this study is to characterize the energetic proprieties of raw biomass and pyrolyzed biomass of sawmill residues. In order to analyze the environmental impact in the emission of pyrolysis gases, the behavior of gases during the thermic treatment was determined. Eucalyptus sp. and Pinus sp. residues slow pyrolysis was performed in an electric kiln, whose gases were conducted through a condensable gas recovery system and an online gas analyzer. The charcoal, bio-oil and non-condensable gases yields were estimated. The wood’s and charcoal’s proximate analysis (extractives, lignin, holocellulosis, ash content), higher heating value, equilibrium moisture and density were appraised. The wood’s chemical components were esteemed. Hardwood and softwood’s charcoal presented several differences, especially in yields due to types of lignin. Hardwoods produce a higher amount of acetic acid in slow pyrolysis. This acid was converted, mainly, in carbon dioxide and e a minor extent in methane and carbon monoxide. The gas release was affected by the temperature and wood’s composition. The main gases resulting from the slow pyrolysis of wood are CO2, CO, CH4, H2. The emission of this gases to the atmosphere in addition to increasing the environmental impact caused by the industry is still a waste of energy that could be harnessed more efficiently. Pyrolysis increased the energetic characteristics of sawmill waste. However, in spite of the advantages of carbonization, ways to mitigate the emission of gases emitted in an operational scale should be evaluated.

Effect of firing temperature on sintering of cordierite-mullite refractories from raw materials and Narathiwat clay in Thailand

Cordierite-Mullite is a refractory material produced by a fast firing process of kaolinitic clay (33%), quartz (62%) and talc (5%). This research aimed to study the effect of firing temperature on sintering of cordierite-mullite refractories from raw materials and Narathiwat clay in Thailand. An electric kiln was used to sintering took place temperature was 1300°C. Soaking temperature took for 1 hour. Then, they were characterized by physical properties, chemical analysis by X-ray fluorescence (XRF), phase change by X-ray diffraction (XRD), thermal changing of clay cordierite-mullite body by scanning electron microscopy (SEM). The results showed that raw refractories material can be used for the experiment. It was sintered at temperature of 1300°C and showed the phase of mullite and quartz. NRT specimens showed water absorption of 4.16% with bulk density of 2.27 g/cm3, apparent porosity of 9.2% after firing at 1300°C. This firing temperature, the flexural strength in NRT clay reached the highest value of 330.82 kg/cm3. The evidence indicated that the vitrification is completed.

Utilization of cullets for the production of glass tiles through likn casting

The study explored the technique of kiln casting of glass as a means of recycling glass for aesthetic and functional purposes. Some disposed glass bottles were collected and processed through crushing, milling and sieving to particle sizes of 60, 80 and 120 mesh size. These particle sizes were batched and fired in an electric kiln to temperatures of 1050oc and 1180oc. The study revealed that the 60 mesh and 80 mesh specimens fired at 1180oc gave very good translucent effect with rich clear colour. It was observed that the sample that had addition of colouring oxides gave the best result when it was double fired. The results of the study revealed that the two major parameters that were investigated in this research, (temperature and particle sizes), had an effect on each other and that they were very important for the study. The study concludes that glass recycling through kiln casting presents an avenue for producing glass tiles for functional and aesthetic applications.Keywords: Cullets; kiln casting; glass tiles; recycling; melting temperature

VOCs monitoring of new materials for ceramic tiles decoration: GC–MS analysis of emissions from common vehicles and inkjet inks during firing in laboratory

The decoration of ceramic tiles “ink-jet revolution” has brought significant advantages to tiles manufacturing, but the explosive diffusion, until 4–5 years ago, of this technique has not been accomplished by an adequate scientific research. Among all the features that have to be studied yet, one of the most important is the influence of the new generation inks on the total emission at ceramic chimneys. In this paper, we present a first characterization of emissions from a set of commercial inks and vehicles: they were collected by propter firing of samples in an electric kiln and analyzed by GC–MS. This study is part of a larger research project, which includes the chemical characterization and the evaluation of thermal behavior of inks and vehicles by TG-DTA and other techniques. The obtained results permit to divide common vehicles into 3 classes, depending on their thermal behavior and emissions pattern. Inks, most of which present an ester based formulation, sometimes mixed with glycols or paraffins, follow the behavior of their single components. The most common formulation leads to the presence in the emission pattern of evaporation products (2-ethylhexyl esters of lauric, myristic, decanoic and octanoic acids) and decomposition products (mainly aldehydes and 2-ethyl-1-hexanol).

Development ceramic composites based on Al2O3, SiO2 and IG-017 additive

Based on high purity alumina and quartz powders and IG-017 bio-original additives the authors have developed new ceramic composite materials for different industrial purposes. The main goal was to fine a material and morphological structures of high performance ceramic composites as frames for development complex materials for extreme consumptions in the future. For this the mixed powders of Al2O3, SiO2 and IG-017 bio-original additive were uniaxially pressed at different compaction pressures into disc shapes and were sintered in electric kiln under air (1) and nitrogrn (2) atmosphere. The grain size distributions of the raw materials were determined by laser granulometry. There thermo-physical properties were also determined by derivatography.The prepared and sintered specimens were tested on geometrical sizes, microstructure and morphology by scanning electron microscopy, porosity and water absorption. In this work the authors present the results of their research and investigation.

Energy efficient electric kiln with a mobile bottom platform for vermiculite firing

Energy efficient electric kiln with a mobile bottom platform for vermiculite firing