Furnace Material Research Articles

Decomposition of paper wastes in presence of ceramics and cement raw material

Paper recycling is an environmental important activity that is carried out in all the countries, but during the recycling process a paper waste is produced. Generally these wastes are placed in landfill sites but it is possible to profit it as secondary fuel and raw material in manufacture furnaces. In this work the combustion of the waste papers with cement and ceramic raw material has been studied with the objective to analyse the interaction of these substances with the emitted pollutants like PAHs and PCDD/Fs. The results of the study show that the presence of inorganic material produces an increment in the lighter PAH emission but chlorinated compounds are not affected. The PCDD/F emission level found in the combustion of this waste is quite low compared with other wastes subjected to similar conditions.

Fiberization of Ceramics Using Melt-Blowing Method

Ceramic fibers that are used as heat-insulating material for high-temperature furnaces are produced by a process in which melted ceramic material is dropped into the path of a high-speed jet of air. The insulation performance of these fibers is improved when the length of the fibers is long, and when the material contains fewer spherical shots of ceramic that have solidified without fiberization. These fiber properties are strongly affected by the shape of the jet nozzle, but currently there is no logical scientific method for designing such nozzles. Empirical methods of design are limited to optimization, so more detailed information about the fiberization process needs to be obtained in order to design optimum nozzles. In this study, a high-speed camera and the schlieren method are used to obtain images of the molten ceramic material. In addition, the velocity distributions of the jet flow are measured. Images of the molten ceramic material show that the fiberization process is completed within a short streamwise region, where the flow immediately accelerates the molten ceramic material. Images taken using the schlieren method indicate the existence of strong turbulence in the jet flow, suggesting that this turbulence may be the dominant factor in the final process of fiberization.

A study of the phase composition of iron-ore briquets to assess their behavior in a blast furnace

We study a mechanism for maintaining the strength of cement-bonded iron-oxide-bearing briquets when heated under reducing conditions. These briquets retain their strength when heated in a reducing atmosphere: up to 700–750°C, strength retention is due to the cement stone; strength retention under further heating is due to the continuous metal shell formed on the surface of the briquet as the iron oxide in the surface layer of the briquet is reduced to iron. Fabrication and usage of briquets of iron-ore concentrate can be recommended as a wash material for blast furnaces. Disperse materials containing SiO2 and MgO should be added to the charge during fabrication of the briquets in order to improve the washing properties of briquet slag.

Characterization of iron phosphate glasses prepared by microwave heating

Phosphate glasses have been prepared by melting batch materials in electric furnaces, induction furnaces, and in microwave ovens. In the present work mixtures of (NH4)2HPO4 and Fe3O4 or Fe2O3 were exposed to microwave energy, heated to 1200°C, and cast to produce iron phosphate glasses. Glasses were also produced in electric furnaces for comparison. The material was analyzed by X-ray diffraction, Mössbauer spectroscopy, and differential thermal analysis. For magnetite-based glasses produced in an electric furnace, the Fe2+/(Fe2++Fe3+) ratio is compatible with the value in the batch material. The Fe2+/(Fe2++Fe3+) ratio is higher for glasses produced in a microwave oven. Glasses with nominal composition 55Fe3O4–45P2O5 (mol%) produced in an electric furnace present an arranged magnetic phase with hyperfine field that could be associated to hematite (estimated to be 21%). All the glasses submitted to heat treatments for crystallization present the following crystalline phases: FePO4, Fe3(PO4)2, Fe(PO3)3, Fe(PO3)2 and Fe7(PO4)6. The amount of these phases depends on the glass composition, and glass preparation procedure. Microwave heating allows to reach melting temperatures at high heating rates, making the procedure easy and economical, but care should be taken concerning the final Fe2+/(Fe2++Fe3+) ratio.

Topotactic growth of α-alumina platelets on 2/1 mullite single crystal surfaces upon thermal decomposition of mullite in dry and wet atmospheres

Annealing experiments of Czochralski-grown 2/1 mullite single crystal coupons, oriented parallel to (1 0 0), (0 1 0), and (0 0 1) were performed in the temperature range 1200–1650 °C for 4–16 h in different atmospheres (dry versus wet air) at normal pressure. Upon thermal decomposition of the Al 2O 3-supersaturated 2/1 mullite, metastable in the two-phase region “mullite plus Al 2O 3”, the simultaneous release of alumina and silica gave rise to nucleation and growth of thin, perfect (0 0 · 1) α-alumina platelets which were completely wetted by a glassy phase. The chemical composition of the initially siliceous glassy phase at the mullite surfaces was shifted to a Na–Mg–Ca bearing alumosilicate composition via uptake of network modifying cations from external impurity sources (kiln furnace material, alumina reaction tube), independent of the nature of the atmosphere. It is this modified glassy phase which filled the mullite dissolution paths driven forward by the growing platelets and provided a build-in flux. Growth faces of α-alumina included only special forms of the trigonal point group 3 ¯ 2 / m . The habit was very similar to that of sapphire crystals grown from molten fluxes, in agreement with the Wulff shape of undoped α-alumina. Three different types of α-alumina platelets could be distinguished including (i) type I platelets parallel, (ii) type II platelets perpendicular, and (iii) type III platelets inclined to the mullite surfaces. While type I showed on all mullite substrates investigated, type II platelets did predominantly occur on (0 0 1) and were rarely observed on (1 0 0) and (0 1 0) mullite surfaces. Type III platelets were restricted to (1 0 0) and (0 1 0) mullite surfaces. Platelet types II and III were not independent from each other. Furthermore, for each type of platelets the azimuthal rotation around [0 0 · 1] was restricted to well defined snap-in conditions. A total of 14 symmetrical non-equivalent, topotactic α-alumina/mullite orientation relationships was derived unambiguously by the combined approach of optical microscopy, X-ray diffraction, and focused-ion-beam assisted transmission electron microscopy confirming previous solutions as a sub-assembly group. Possible composition planes characteristic of platelet nucleation on mullite were identified and discussed in terms of coherency of cation sublattices. Short-term wet annealing of 2/1 mullite at 1650 °C characterized by a low gas flow rate and a water partial pressure of P H 2 O = 0.2 P total had no effect on the general platelet formation processes and the prevalent orientation relationships as the mullite decomposition rate was distinctly higher than the silica volatilization rate. Topotactic growth of α-alumina (0 0 · 1) platelets influenced by vapor phase impurity doping has been recognized as a widespread phenomenon in numerous other high-temperature investigations of 2/1 mullite single crystals.

Washing the hearth of blast furnaces with briquets made from scale

A comparative analysis made of the use of washing sinter and scale briquets to wash the hearth of blast furnaces showed that similar results are obtained in both cases. Scale briquets with a cement binder can be effectively used as a washing material for blast furnaces, which will make it possible to end the production of washing sinter, increase the productivity of sinter plants, and improve the quality of the sinter they produce.

Testing of cement bonded briquettes under laboratory and blast furnace conditions Part 1 – Effect of processing parameters

Cement bonded agglomerates made of iron rich byproducts from the iron and steel industry have been used as burden material for blast furnaces for over a decade. In spite of that, their use is restricted to less than 5% of the total burden material, because at higher percentages the blast furnace starts behaving erratically. It is suspected that this is due to the disintegration of the agglomerates under high temperature and reducing conditions. In order to improve the quality of the cement bonded briquettes, the effects of various parameters on their behaviour have been studied. The briquettes have been tested in the laboratory under isothermal test conditions and under simulated blast furnace conditions. The briquettes have also been tested in a pilot blast furnace. This paper describes the effect of different parameters on the performance of briquettes tested under the three conditions.

Unusual defects in silicon carbide thin films grown by multiple or interrupted growth technique

This paper discusses the growth and characterization of 3C-SiC films on Si (1 0 0) and (1 1 1) substrates using hexamethyldisilane (HMDS) as the source material in a resistance-heated furnace as well as the formation and microstructure of various types of unusual defects. Apart from common triangular and square voids, some unusual shaped voids like hexagonal, truncated octahedron, etc. and some irregular features (like hockey stick or pipes) were observed regularly, which are related to voids. SiC whiskers and wires with a wide range of diameters (nm to μm) were formed inside cracked regions as well as within voids. Optical microscopy, scanning electron microscopy (SEM) and Raman spectroscopy were used to study these features.

Evaluation of Corrosion Resistance of Refractory Materials in Furnaces for Melting Frit Glazes

The corrosion resistance of refractories to frit melts applied at the Velor Nompany (city of Orel) are investigated. Based on the results of the study, it is proposed to replace the refractory MKS, which is currently used in furnaces for melting frit glazes, by the refractory material KMTs that is more resistant to frit melts.

A numerical investigation on the thermal impact of foam on an oxy-fuel-fired glass furnace

Gas evolution during the melting and refining of raw materials in glass melting furnaces may result in the formation of a layer of foam on the molten glass surface. The foam layer presents an additional thermal resistance to melting and refining between the furnace crown and combustion products and the raw materials/molten glass. A simple foam thermal model has been incorporated into an advanced comprehensive model for the prediction of the primary thermal phenomena in a prototypical oxy-fuel-fired industrial glass furnace. Heat fluxes and temperatures at the interfaces between the combustion space, the batch, the glass melt tank and the foam layer are calculated in an iterative procedure in order to simulate the entire furnace in an integrated fashion. The thermal impact of the foam on furnace behaviour is studied by comparing model simulations using different values of foam thickness and effective thermal conductivity in a 150-tonne-per-day, oxy-fuel-fired glass furnace to predictions in the same furnace without the presence of foam. The numerical results obtained quantify the effect of foam on important furnace operating parameters such as glass surface temperature, crown temperature and exhaust gas temperature.

Olefins from conventional and heavy feedstocks: Energy use in steam cracking and alternative processes

Steam cracking for the production of light olefins, such as ethylene and propylene, is the single most energy-consuming process in the chemical industry. This paper reviews conventional steam cracking and innovative olefin technologies in terms of energy efficiency. It is found that the pyrolysis section of a naphtha steam cracker alone consumes approximately 65% of the total process energy and approximately 75% of the total exergy loss. A family portrait of olefin technologies by feedstocks is drawn to search for alternatives. An overview of state-of-the-art naphtha cracking technologies shows that approximately 20% savings on the current average process energy use are possible. Advanced naphtha cracking technologies in the pyrolysis section, such as advanced coil and furnace materials, could together lead to up to approximately 20% savings on the process energy use by state-of-the-art technologies. Improvements in the compression and separation sections could together lead to up to approximately 15% savings. Alternative processes, i.e. catalytic olefin technologies, can save up to approximately 20%.

Improvement of Sinter Softening Property and Reducibility by Controlling Chemical Compositions

Increasing permeability of packed materials in a blast furnace and decreasing reducing agent rate at a blast furnace process take an important role to improve productivity. In order to increase permeability and decrease reducing agent rate, sinter softening property during reduction and sinter reducibility are important.Effects of sinter compositions (CaO, SiO2, Al2O3, MgO, FeO) on the sinter softening property during reduction and sinter reducibility were examined by samples produced from pot scale sintering. These compositions were controlled by lime stone, serpentine, and coke breeze content and varying iron ore source in raw sinter materials. And sinter softening property was estimated by vertical pressure drop of sinter packed bed (70 mmφ×100 mm) during sinter reduction with raising temperature to 1 600°C under vertical loading force (9.8×104 N/m2). This pressure drop is caused by melt formation from slag compositions in sinter above 1 000°C. And sinter reducibility was estimated as reduction degree by CO(30%)-N2 gas under constant temperature conditions (900°C, 1 100°C).Results were obtained as follows.(1) Low SiO2 and low CaO sinter had superiority of sinter softening property. That is small pressure drop caused by decreasing SiO2-CaO-FeO melt.(2) And low SiO2 and low CaO sinter had high reducibility at both 900°C and 1 100°C. It is considered that decrease of these compositions affects restriction of calcium silicate containing ferrous oxides.(3) High MgO and high FeO sinter using dolomite instead of serpentine and blended with high coke breeze also had superiority of sinter softening property. Adding MgO to phase of CaO-FeO-SiO2 raises melting temperature. The raising melting temperature is considered to make high pressure drop region to be narrow.(4) And high MgO and high FeO sinter had low reduction degree at 900°C but kept high reduction degree at 1 100°C. X-ray diffraction pattern for the sinter indicated that it contained much magnetite structure (magnetite and magnesioferrite) instead of hematite. This mineral composition is consistent with low reduction degree at 900°C. On the other hand, keeping high reduction degree at 1 100°C is considered to correspond not to promote silicate (FeO-2SiO2, FeO-SiO2-CaO) formation. By X-ray micro analyzer, it was found that calcium ferrite contained more Si and more Mg ion with increasing MgO in sinter. Increasing Si ion in calcium ferrite is considered to be the cause of restricting silicate formation.(5) Al2O3 content has little effect to sinter softening property.Summarized these results, low SiO2, low CaO, high MgO and high FeO sinter has a good softening property and high reducibility. These characteristics indicate good performance as raw material in a blast furnace.

Claus recycle with double combustion process

A new modification is developed on conventional Claus process to increase the overall sulfur recovery as well as to decrease the costs. The modification combines both oxygen enrichment and recycling. The process is simulated and studied for various N 2/O 2 ratios with and without using SURE double combustion technique. The predictions show that using pure oxygen in combustion, condensing water vapor in a condenser following the first sulfur condenser and recycling the effluent gas to combine it with fresh acid gas feed leads to large savings in the production cost and to a clean environment. However, it leads to a high adiabatic flame temperature which exceeds the maximum allowable temperature of the furnace material of construction as well as its refractory. To avoid these effects, it is necessary to use SURE double combustion technique. The oxygen flow rate to the first combustion stage should not exceed 78% O 2.

Elemental development of beryllide electrode for pebble production by rotating electrode method

Beryllide (Be 12Ti) is being considered one of the promising candidates for advanced neutron multipliers. In order to realize the pebble production, a vacuum casting process has to be applied. In the present study, an elemental technology to fabricate beryllide rods by a vacuum casting was developed. There were two major technical subjects to realize this process. The first was to identify a furnace material that shows minimum chemical reaction with beryllide. Another was to develop a procedure to cast durable ingot without any shrinkages and cracks. Reactivity between Be 12Ti melt and refractory materials such as CaO, MgO and BeO was tested. It was clarified that the BeO crucible had less reactivity with melt and no contamination. Casting tests with a MgO cylindrical mold in a vacuum chamber revealed that the mold dimension was critical to minimize shrinkages and cracks. From this study, elemental technologies to be developed were made clear.

Effect of Reduction Conditions on the Swelling Behaviour of Cement-bonded Briquettes

Cement-bonded agglomerates of by-products generated in iron and steel plants are commonly used as burden material for blast furnaces. It has been observed that under certain conditions the briquett ...

Effect of Processing Parameters on the Swelling Behaviour of Cement-bonded Briquettes

The use of cement-bonded agglomerates of iron-rich by-products generated in iron and steel plants as burden material for blast furnaces is becoming quite common. It has been observed that under cer ...

Theoretical consideration of problems relating to high coal rate injection into blast furnaces

Some key problems relating to high rate pulverised coal injection into the blast furnace are discussed, including furnace permeability in the lower furnace and raw materials quality, heat compensation and theoretical flame temperature, oxygen enrichment, material and gas distribution control and so on. A new method of calculation of theoretical flame temperatures is proposed, taking into account coal combustion efficiency in the raceway. Measures that should be taken for increasing coal injection rates are discussed.

Corrosion of carbon steel with NaCl coating in an atmosphere produced by burning emulsified diesel oil

The high-temperature corrosion of boiler material (SB450) in a combustion furnace at 750 and 850 °C was studied using carbon steel with 2 mg cm −2 NaCl coating. The atmosphere in this furnace was produced by burning ASTM 2D diesel oil or an emulsion thereof with 10% water. The experimental results indicate that both the higher temperature and the water vapor in the atmosphere promoted metal loss. The metal loss of SB450 in the atmosphere that contained water vapor, resulting from the burning of emulsified oil, was larger than that obtained by burning just the diesel oil. Moreover, water vapor contributed to higher SO 2 concentrations in the gas produced. Therefore, SB450 suffers sulfidation more seriously in an atmosphere that contains water vapor than in one obtained by burning diesel oil; it thus deteriorates more rapidly.

The viscosity of CaMgSi 2O 6 liquid at pressures up to 13 GPa

The viscosity of CaMgSi 2O 6 (diopside) liquid has been determined up to 13 GPa and 2200 °C using in situ falling sphere viscometry with X-ray radiography. The experiments were carried out in a 1500 t multianvil apparatus at the SPring-8 synchrotron (Japan). A new, high-pressure sample assembly was developed with LaCrO 3 replacing the traditionally used graphite furnace material, allowing experiments within the diamond stability field to be carried out. The viscosity of CaMgSi 2O 6 liquid increases slightly from 3.5 to 10 GPa and then decreases slightly at higher pressures. However, over the entire ranges of temperature (2030–2473 K) and pressure (3.5–13 GPa) investigated, variation in viscosity does not exceed ±0.5 log units. The viscosity results from this study are consistent with those calculated from the pressure dependence of oxygen self-diffusion in CaMgSi 2O 6 liquid using the Eyring equation with a translation distance ( λ) of 0.45 nm providing the best correlation. Both sets of results indicate a change in pressure dependence at approximately 10 GPa, where viscosity results show a maximum with pressure and silicon and oxygen self-diffusivity results show a minimum.

Radiation Effects in Zircon

The widespread distribution of zircon in the continental crust, its tendency to concentrate trace elements, particularly lanthanides and actinides, its use in age-dating, and its resistance to chemical and physical degradation have made zircon the most important accessory mineral in geologic studies. Because zircon is highly refractory, it also has important industrial applications, including its use as a lining material in high-temperature furnaces. However, during the past decade, zircon has also been proposed for advanced technology applications, such as a durable material for the immobilization of plutonium or, when modified by ion-beam irradiation, as an optic waveguide material. In all of these applications, the change in properties as a function of increasing radiation dose is of critical importance. In this chapter, we summarize the state-of-knowledge on the radiation damage accumulation process in zircon.