Laboratory Furnace Research Articles

Mechanical properties of fiber-reinforced concrete containing waste porcelain aggregates under elevated temperatures

Concrete has recently found increasing applications in structures exposed to high temperatures. It is, therefore, necessary from an engineering viewpoint to improve the mechanical properties of the concrete used in such structures. Concrete structures exposed to high temperatures are prone to serious damages due to the heat-induced physical and chemical changes in concrete that reduce its compressive, tensile, and flexural strengths as well as its modulus of elasticity. A remedy is to use refractory materials to increase the heat resistance of concrete. In this study, waste porcelain ceramic was used as aggregate material to achieve enhancements in concrete mechanical properties under high temperatures with the simultaneously additional advantage of abating environmental pollution. Additionally, polypropylene and steel fibers, as well as ordinary Portland and refractory cement, were used to cast 120 cylindrical specimens 100 mm × 200 mm in size to be exposed to temperatures of 400 and 800 °C in a laboratory furnace. The compressive and tensile strengths of the specimens were measured upon cooling, their weight losses were determined, and finally, crack assessment was performed using fractal dimension. All the specimens exhibited reduced compressive and tensile strengths with increasing temperature albeit at different rates depending on their ingredient materials such that higher strengths were recorded at 400 °C for specimens containing Portland cement and at 800 °C for those containing refractory cement. Application of steel fibers increased heat resistance and decreased strength drop by up to 20% and 30% at 400 and 800 °C, respectively. This is while the application of polypropylene (PP) fiber had no significant effects on such mechanical properties as compressive or tensile strength but it prevented concrete spalling.

Study of the Hydration Behavior of Synthetic Ferropericlase with Low Iron Oxide Concentrations to Prevent Swelling in Steel Slags

Steel slags generally swell when subjected to water or humidity, which prevents proper recycling in the cement or asphalt industries. The MgO and CaO phases in steel slags are responsible for this phenomenon, as both minerals easily absorb water to form their respective hydroxides. MgO is often present in steel slags in a solid solution with several oxides, constituting the so-called RO phase. This study investigates the hydration rate of an RO phase consisting of FeO and MgO called ferropericlase. The material was synthesized in a laboratory furnace by sintering a FeO–MgO powder mixture with varying initial FeO contents (approximately 10, 15, and 20 wt%). Thereafter, electron probe micro-analyzer (EPMA) and X-ray diffraction (XRD) spectroscopies were used to characterize the structure of the samples, which were mainly composed of ferropericlase and an exsolution of magnesioferrite. Also, Mossbauer spectra showed that the total ferrous iron proportion (Fe2+/ΣFe) of the sintered samples was in the range of 0.55–0.72. To measure the hydration behavior, the samples in powder form were cured in an autoclave at an H2O partial pressure of 2 atm. Thereafter, thermal gravimetric analysis (TGA) was performed to measure the amount of water absorbed during the autoclave curing from the mass drop associated with the dehydration of the hydroxide. The study found a linear correlation between the initial FeO content and the weight loss after TGA, with a reduction down to 6% in the sample with an initial FeO content of 20 wt% content compared to pure MgO.

Experimental and numerical investigation on the heat transfer of an automotive engine’s turbocharger

Measuring the temperature distribution in a complex and important engine part, such as a turbocharger, is essential for improving engine performance and efficiency. Heat transfer from the turbine to the compressor can strongly influence the turbocharger performance. One of the main measurement methods involves the installation of multiple K-type sensors. However, the location as well as the maximum and minimum temperatures of the turbocharger and the subsequent critical points may not be obtained by using sensors. In the current study, thermocouples, as well as an infra-red camera, are used to study the temperature distribution of the turbocharger housing in a spark ignition engine. A new method is introduced to determine the thermal radiation coefficient of the turbocharger housing by using a laboratory furnace and an infra-red camera. Together with experiments, the finite element method is used to find the temperature distribution in the turbocharger for all thicknesses. Comparing the temperature distribution obtained from simulation with experimental data, an acceptable level of agreement is observed. The location and temperature of the hottest area in experimental and numerical investigations are close to the waste gate. Temperatures using the finite element method for bearings exhibit maximum and minimum errors of 4.9% and 2.3%, respectively, indicating reasonable accuracy for the simulation.

Könnyű adalékanyag felhasználásával készített téglaipari termékek vizsgálata

Ebben a tanulmányban duzzasztott perlit téglaipari alkalmazhatóságát és kész termék tulajdonságaira gyakorolt hatását vizsgáltuk. Ez az adalékanyag az építőipar más területén, mint például a könnyűbeton gyártás széles körben elterjedt kiváló hőszigetelő tulajdonsága miatt. A kísérletekhez agyagmasszákat készítettünk laboratóriumi kollerjárat alkalmazásával, a masszák nedvességtartalma 25m/m% volt minden esetben. A perlit bekeverésének arányát 2,5-6,5m/m% között változtattuk. A masszákból hengeres próbatesteket készítettünk vákuum extruderrel, majd 880°C-on 140°C felfűtési sebességgel kiégettük. A kiégetett próbatestek testsűrűsége 1855-1695kg/m3 között változott a perlit bekeverési arányának emelésével. Az adalékanyag nélkül készített minták átlag nyomószilárdsága 32MPa volt, a perlit bekeverésével ez az érték 27MPa körüli értékekre csökkent, amely a vizsgált tartományban a perlit mennyiségének emelésével jelentős változást nem mutatott, ezzel szemben a szerves pórusképző adalékanyagok mennyiségének emelése jelentősen rontja a nyomószilárdságot.

A comparative exploration of thermal, radiative and pollutant emission characteristics of oil burner flame using palm oil biodiesel-diesel blend fuel and diesel fuel

The lack of petroleum resources and environmental problems of petroleum fuels have led to growing interest in biodiesel fuels. This study compares diesel fuel and palm oil biodiesel-diesel blend fuel in terms of their effect on the thermal, radiative and pollutant emission characteristics of the flame of an oil burner. The blend fuel consisted of diesel fuel and palm oil biodiesel, which was synthesized by transesterification reaction. In the experiments, the same mass flow rates of B20 palm oil biodiesel-diesel blend fuel and diesel fuel were separately combusted in a laboratory furnace. Then, we measured the flame temperature, the total and luminous radiations of the flame and the concentrations of CO and NOx pollutant emissions. The results indicate that the blend fuel, compared with diesel fuel, produces a voluminous flame. Further, although the flame of blend fuel has a lower temperature than diesel fuel flame does, blend fuel produces a higher concentration of intermediate soot particles in the flame reaction zone. This phenomenon, in comparison with the case of diesel fuel, increases the IR wavelengths emitted from flame and enhances the average radiation heat transfer of flame from 2080 to 5094 W/m2. Also, the use of blend fuel instead of diesel fuel enhances the luminosity of flame and decreases the NOx emission significantly from 33 to 11 ppm.

The Cooling Media Influence on Selected Mechanical Properties of Steel

Abstract The aim of experiment was to analyse the structural transformations and changes in mechanical properties of K720 steel during heat treatment (quenching). Three types of cooling medium were selected. The heating parameters and subsequent delays at the recrystallisation temperature were the same for all samples and were observed in a laboratory furnace. Water with the highest cooling capacity was selected as the benchmark cooling medium. Subsequently, the hardening oil TK – 46 was used. Sunflower oil was selected as the last quenching medium, which can be considered an ecological replacement of quenching oil with possibility of biological disposal. The microstructure and microhardness of individual samples were subjected to a metallographic evaluation and evaluated according to ČSN EN ISO 6507, respectively. The impact toughness analysis was performed according to the ČSN EN ISO 148-1 and a three-point bending test was performed according to ČSN EN ISO 7438. This test specifies a method for determining the ability of metallic materials to undergo plastic deformation in bending. The bend test includes subjection of round, square, rectangular or polygonal cross-section to plastic deformation by bending, without changing the direction of loading, until the specified angle of bend is reached.

The role of thermal improvements in indurating machines for pellet production from high-sulfur magnetite concentrate

Mostly, magnetite iron ore mine materials contain significant amounts of sulfur base components. This can cause disturbance in production process of steel. Although high-sulfur magnetite concentrate has not been inciting enough yet to be employed by steel industry, these compounds are potential alternatives for iron ore resources. In this work, oxidation and sulfur removal of magnetite iron ore pellets were studied during the thermal treatment in the pelletizing indurating machine. The oxidation phenomenon and sulfur removal, in the magnetite iron ore pellets, were assessed by determination of appropriate thermal conditions employing thermogravimetric as well as differential scanning calorimetric tests accompanied by heat treatment procedure in a laboratory furnace. The residual sulfur-based compounds were considered as an indicator for the reaction rate; the results showed the reaction progress had a lower rate in the temperature range of 500–750 °C. Furthermore, the high-rate pre-heating and firing processes of pellets caused a higher level of residual magnetite phase within the microstructure, whereas crack initiation and growth were probable within the oxide pellets. The findings did highlight the role of thermal profiling and eventually, led to redesigning the thermal profile for pelletizing indurating machines.

Solid Waste Incineration Modelling for Advanced Moving Grate Incinerators

Currently, the design of advanced moving grate (AMG) incinerators for solid waste is aided by computational simulations. The simulation approach couples a waste bed model to characterize the incineration processes of the waste material on top of the moving grate, with a computational fluid dynamics (CFD) model to reproduce the heated air movement and reactions in the incinerator space above. However, the simulation results of AMG incinerators are rarely compared with actual field measurements for validation in the literature so far. In this study, we first examine the sensitivity of pyrolysis kinetics in the waste bed model using three existing alternatives. The predictions of combustion characteristics, including the bed height, flow and temperature distributions, composition of stack gases and gas emissions are obtained for the three alternatives and compared with measurements from a simple laboratory furnace. The results show that the pyrolysis kinetics mechanism can significantly affect the outputs from the waste bed model for incineration modelling. Subsequently, we propose a new coupling approach based on a recent AMG waste bed model (which includes the complex pyrolysis kinetics inside the waste bed on top of the moving grate) and the freeboard CFD simulations. The new approach is then used to predict the field performance of a large scale waste-to-energy (WTE) plant and the predictions are compared directly with the real measurements in various operational scenarios. The comparison shows an overall satisfactory agreement in terms of temperature and exit gases composition given the complexity of the real life operations, although the CO emission is slightly underpredicted.

Combustion and emission behavior of different waste fuel blends in a laboratory furnace

The paper discusses the results of lab-scale combustion of complex waste-derived fuel mixtures in different forms. Composite fuels based on a combination of widespread industrial and municipal waste were considered. The scientific and practical novelty of this study comes from the fact that for the first time, a group of integral parameters was researched. They describe the ignition and combustion of mixtures in different forms: pressed dry fuel (pellets), a wet slurry, and granules of different moisture content. The most efficient method in terms of increasing the rate and reducing the temperature threshold of the oxidation reaction is firing a low-moisture mixture based on municipal solid waste (with a predominance of wood components). Pelleted coal sludge combustion was characterized by a rather long delay in heterogeneous ignition and underburning. It was shown that in order to reduce emissions and increase the degree of burnout, coal processing waste should be burned as wet granules or slurry droplets.

Characteristic of calcined diatomaceous earth from Aceh Besar District - Indonesia as cementitious binder

Diatomaceous earth is a naturally occurring, soft, siliceous sedimentary rock, which is easily crumbled into a fine powder. In this paper, the characteristic of calcined diatomaceous earth from Aceh Besar District – Indonesia as a cementitious binder is studied. The chunk of diatomaceous earth was burned in the brick burning furnace for 4 days, then ground so that it becomes a powder. The powder was sieved to form the binder having the particle sizes less than 250 μm. The binder then calcined at the temperature of 600°C for 5 hours in a laboratory furnace. The density, specific gravity, absorption, particle size analyzer, X-ray diffraction, X-ray fluorescence, and scanning electron microscopy tests were therefore performed. The test results show that the density, saturated surface dry specific gravity, and absorption of calcined diatomaceous earth binder are 767 kg/m3, 2.000, and 6.535 %, respectively. The particle sizes range from 0,107 μm to 231 μm. The main minerals of the particle are graphite, quartz, and lead-silver thallium antimony sulphide. The main chemical compositions of calcined diatomaceous earth are SiO2, 56.00 %; Fe2O3, 26.40 %; ZrO2, 7.20 %; and Al2O3, 6.50 %.

Development of Crystallinity of Triclinic Polymorph of Tricalcium Silicate.

Tricalcium silicate phase is one of the main components of modern Portland cements. One of the major industrial challenges in the field of cement production is mapping the influence of individual clinker minerals and their polymorphs on the properties of industrially produced clinkers. The primary goal of this work is to improve the fundamental knowledge of understanding the process of alite formation and development from a crystallographic point of view. This study focuses on the observation of the crystallization process of triclinic alite during the firing process, which to date has not been thoroughly described. The effects of a wide range of temperatures and sintering periods on crystallinity were assessed on samples fired in platinum crucibles in a laboratory furnace. X-ray analysis—together with calculation of crystallinity using Scherrer’s equation—was used for observing the crystallite size changes of T1 alite polymorph. According to the acquired results, among the most technologically and economically advantageous regimes of production of a high-quality triclinic alite is the temperature of 1450 °C and sintering time of two hours. The most significant changes in the crystallite size occurred within the first hour of sintering for the whole investigated temperature range.

Dynamic interactions of ingested molten silicate particles with air plasma sprayed thermal barrier coatings

Abstract

Sintering properties of olivine and its utilization potential as a refractory raw material: Mineralogical and microstructural investigations

In this study, an olivine sample obtained as final tailing from a chromite enrichment plant was examined for its sintering properties and utilization potential as a refractory raw material. For this purpose, cylindrical specimens were first prepared and then sintered at the temperatures of 1300, 1400, 1450 and 1500 °C for 2 h in a laboratory furnace. Quality of the products was evaluated in terms of some physical and mechanical refractory specifications such as bulk density, water absorption, porosity, shrinkage and cold crushing strength. Furthermore, phase developments and microstructural changes due to the sintering were determined in detail with X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, respectively. According to the experimental results, with increasing temperature, the bulk density and shrinkage values increased while the porosity and water absorption values decreased. Specifically, the bulk density and shrinkage values varied in the ranges of 2.33–2.60 g/cm3 and 1–5%, respectively. The porosity values of 24.10 and 15.68% were obtained after sintering at 1300 and 1500 °C, respectively. The cold crushing strengths slowly increased from 46.90 to 55.86 MPa after sintering between 1300 and 1450 °C. A sudden rise to 93.44 MPa was then observed at 1500 °C. Accordingly, the thermo-optical analysis indicates that the olivine exhibited a sintering point of 1478 °C and no softening up to 1500 °C. However, the formation of undesirable low-melting enstatite was detected by the XRD and SEM analysis which also specified the increasing amorphous phase and crystallizations of forsterite and spinels with rising temperature. Overall results have shown that the olivine sample used has a promising potential as a refractory raw material mainly due to its high MgO content, low loss on ignition (LOI) value and appropriate particle size.

Pollutant emissions during the pyrolysis and combustion of starch/poly(vinyl alcohol) biodegradable films

The massive use of petroleum-based polymers and their improper waste treatment has brought on significant global environmental problems due to their non-biodegradable nature. Starch/poly(vinyl alcohol) (PVA) bioplastics are suitable substitutes for conventional polymers, such as polyethylene, due to their full biodegradability and excellent mechanical properties. Knowledge of the pollutant emissions during pyrolysis and combustion of starch/PVA films is important because they can arrive at landfills mixed with conventional polymers and be thermally degraded in uncontrolled fires. On the other hand, controlled thermal treatments could result in thermal valorization of the waste. Pyrolysis and combustion experiments were carried out at 650, 750, 850 and 950 °C in a laboratory furnace. The analysis of carbon oxides, light hydrocarbons, and semivolatile compounds, including polycyclic aromatic hydrocarbons (PAHs), is shown. Experiments showed lower pollutant emissions than those found with conventional polymers, such as polyethylene and polyester, in the same equipment. Nevertheless, the pyrolysis run at 950 °C showed the highest light hydrocarbon yield (123013 mg kg−1), but this is considerably lower than the values found for polyethylene. The main semivolatile compounds (not PAHs) emitted, with maximum yields ranging from 1351 to 4694 mg kg−1, were benzaldehyde, phenol, indene, and acetophenone. Specifically, the total semivolatile compounds emitted after pyrolysis and combustion of starch/PVA samples represent only 38 and 50%, respectively, of those emitted with polyethylene. Further, the main PAHs were naphthalene, acenaphthylene, and phenanthrene with maximum values of 4694, 2704 and 1496 mg kg−1, respectively. The PAH yield was considerably higher in experiments with low oxygen content.

Quantification of the Phase Transformation Kinetics in High Chromium Cast Irons Using Dilatometry and Metallographic Techniques

Further development of high chromium cast irons (HCCI) is based on tailoring the microstructure, necessitating an accurate control over the phase transformation and carbide precipitation temperatures and can be achieved by thermal treatments (TT). To understand the underlying mechanisms controlling the transformation kinetics during the different stages of the TT, it is imperative to adjust the TT parameters to have information of the transformations occurring during non-thermal and isothermal heating cycles, since proper selection of the TT parameters ensures the optimum use of the alloying elements. In this work, the boundaries of the phase transformations for a HCCI containing 26 wt pct Cr for different cooling rates (continuous cooling transformation, CCT, diagram) were established by applying dilatometric measurements. Based on the CCT diagram, a temperature-time-transformation (TTT) diagram was constructed by isothermally holding the samples until complete phase transformation. For determining the initiation and finishing of the transformation, the lever rule assisted by derivatives was applied. The phases present after transformation were determined by combining X-ray diffraction (XRD) and metallographic characterization using optical microscopy (OM) and scanning electron microscopy (SEM). Finally, the data obtained from the dilatometer was experimentally verified by isothermally heat treating some samples using laboratory furnaces. The transformed phase fraction from OM and SEM images was then correlated to the fraction obtained from the TTT diagram.

Experiments for combustion temperature measurements in a sugarcane bagasse large-scale boiler furnace

This work presents a numerical and experimental study to measure local combustion temperature from the combustion reactive zone in an industrial sugarcane. A bagasse boiler furnace is utilized preliminary step towards obtaining online three-dimensional temperature measurements. Two different methods were used for in situ measurement of local temperatures in a sugarcane bagasse flame: Spectral Analysis and Image Processing in the Visible Spectrum. The maximum instantaneous temperatures found in the focused reactive zone area of the bagasse flame were 1623 K and 1520 K by the spectrometric and imaging system respectively and the time average maximum flame temperatures measured were 1443 K and 1496 K. Additionally, a set of flame temperature measurement tests was carried out in a laboratory furnace by the spectrometric method and a time average flame temperature of 1569 K was noted. The flame temperatures found in this work show reasonable agreement with results of CFD simulations and results obtained in laboratory tests which were also reported in the literature. Intensity of emission lines of alkali metal (K) were measured in the flame spectra during the bagasse combustion. Spectral flame emissivity was estimated for an industrial level operating condition.

The influence of firing parameters on the crystallinity of ternesite

This work describes the crystallization and subsequent decomposition processes of ternesite when fired in an open air system. The effects of temperature and sintering period on phase composition and crystallinity were assessed post-mortem in samples fired in platinum crucibles in a laboratory furnace. High temperature XRD was used for observing phase and crystallinity changes in situ. The results indicate that the temperature of 1150 °C is neither high enough for a full synthesis of ternesite of sufficient quality nor high enough for its decomposition. It appears that the temperature of ternesite decomposition in an open system is around 1250 °C. The crystallites grow very fast at the beginning, until the size of 160 nm above which the grow rate is decreasing.

Влияние операционных аспектов процесса восстановления оксида кремния на соотношение материального и теплового потоков в рудно-термической печи

A study was carried out into the effect of the loading method and surface distribution of charges at the furnace top on the parameters of carbon reduction of silica in submerged arc furnaces. In the study, the direct physical modelling method was applied. The experiments were carried out under large-scale laboratory conditions using a 200 kVA single-electrode furnace of the Zh. Abishev Chemical and Metallurgical Institute (Kazakhstan). An additional dynamic industrial experiment was conducted in the 30 MVA furnace of Tau-Ken Temir LLP. In a large laboratory furnace, two smelting campaigns were performed, each using different approaches to the treatment of the furnace top. In the first campaign, no balancing in the energy and material flows of the system took place, resulting in forced slipping and an uncontrolled feed rate of the charge. The second campaign, conversely, included the specified balancing measures. A similar study took place over 3 days under industrial conditions. The following technological parameters were empirically determined: specific electricity consumption, furnace average active power and performance, as well as power per unit area of the furnace hearth. The Fe, Al, Ca, Si material balance of the smelting was compiled. In order to assess the load balance, the concept of charge excess in relation to charge demand at the current furnace power was used for the first time. This concept value was determined as the ratio of number of batches actually loaded relative to the theoretically-calculated number ensuring the harmonisation of material and energy flows in the furnace. As a result of the research, an increase in the interval between the furnace top treatments up to 30 min and maintenance of harmonisation between material and thermal flows in the ore smelting furnace was established for increasing silicon extraction efficiency by 10-15%. In addition, oscillations in the phase current were stabilised. The proposed balancing concept was established to support the rapid elimination of crisis conditions in an industrial furnace.

Particle history from massively parallel large eddy simulations of pulverised coal combustion in a large-scale laboratory furnace

A study on the coal particle history during combustion in a large-scale furnace using large eddy simulation is presented. The massively parallel execution produces a high-resolution representation of the fluid mixing and particle dispersion throughout the whole computational domain. The coal combustion is modelled using well-established, cost-effective combustion models. A specific feature of the devolatilization model is the optimisation of the kinetic constants for the furnace operating condition, which were obtained through an iterative procedure between particle heating rates from full large eddy simulation runs and the advanced model Chemical Percolation Devolatilization. In a previous work, we showed that the classical coal combustion models, when used in a high-resolution massively parallel large eddy simulation, lead to satisfactory predictions of the in-flame gas properties, namely gas temperature and gas species concentrations. In this work, we went beyond the comparisons between gas phase measurements and predictions. Single particles were tracked over time and instantaneous ensambles were collected to obtain a better understanding of the conditions that coal particles are subjected to in the investigated test case. The particles trajectory, combustion history and instantaneous state distribution were analysed. The volatile flame features were related with the characteristic trajectory of different sized particles. The combustion history revealed that particles are subjected to large variations of heating rates, including very short sequential periods alternating between heating and cooling during the early stages of combustion, due to the high turbulence intensity in the near burner region. Finally, the state distribution of the ensamble provided a global picture of the instantaneous coal combustion process.

New foaming agents for aluminum foams

This article provides alternatives to titanium hydride foaming compositions for the production of aluminum foam. Using methods of hot plastic deformation, preforms containing various blowing agents were obtained. In the laboratory furnace, the obtained samples were foamed. After that, samples were made and an analysis of the structure of the samples was carried out.