Carbon Bricks Research Articles

Developing a low carbon brick for residential building construction

The construction industry is trying to become more eco-friendly and minimise environmental impact. One way to achieve this is by using innovative building materials. Traditional clay bricks are not eco-friendly due to the depletion of resources, emissions, and waste generated during production. In this study, a new alternative called the Novel Organic Brick (NOB) was produced and evaluated, which was made from recycled construction and demolition sand and red clay as partial replacements for traditional virgin clay. A Life Cycle Assessment (LCA) was conducted to compare the environmental impact of NOBs to that of Kiln Fired Bricks (KFBs). The inventory flows from material sourcing to brick shaping were modelled in SimaPro 8.1 and characterised into impact indicators using the ReCiPe 2016 method. The LCA showed that NOBs can reduce the impact of climate change by 39-56% compared to KFBs, depending on the type and source of recycled sand. This study encourages the construction industry to adopt alternative solutions for greater sustainability by demonstrating the viability of incorporating secondary materials and quantifying environmental performance improvements in India.

Effect of the void and crack quantity and location on ultrasound: resin experiments and carbon brick validation

ABSTRACT In industrial applications, there is a lack of methods applicable to large-scale, rapid and non-destructive detection of voids and cracks inside carbon bricks. This paper used the ultrasonic testing (UT) A-scan method to investigate the influence of quantity (void fraction:1.4%-4.6%; number of artificial cracks:1–7) and location (five layers) of voids and cracks inside the resin on ultrasonic waves. Both fast Fourier transform (FFT) and synchrosqueezed wavelet transform (SWT) are employed to analyse the amplitude, main frequency and normalised peak time of ultrasonic waves. The results indicate that increased void fraction and number of cracks lead to greater amplitude attenuation, promoting the transition from the fundamental wave to harmonics. Void and crack location symmetrically affect ultrasound amplitude, main frequency, and normalised peak time around the sample centre. Meanwhile, fitting equations are established for the main frequency of the fundamental wave (f 1) in relation to defect quantity. A high-precision quantitative defects detection standard is also developed based on normalised peak time. The validation based on carbon bricks indicates that the derived empirical relations between these parameters and defects can lay the foundation for large-scale and rapid non-destructive detection in carbon bricks.

Analysis of destructive effect of Zn on carbon brick and way of Zn into carbon brick

Analysis of destructive effect of Zn on carbon brick and way of Zn into carbon brick

Wettability Characteristics of Nanoporous Carbon Bricks Incorporated with Al2O3 Phase and Molten Iron in Sustainable and Low‐Carbon Blast Furnace

Analyzing the wetting behavior between carbon brick and molten iron in a blast furnace is crucial for understanding prolonging the furnace's lifespan. This study investigates the wetting behavior between microporous carbon brick and molten iron. The contact angle between the carbon brick and molten iron is measured at various temperatures and carbon saturation conditions, while the microscopic morphology of the reacted interface is examined. Furthermore, the wetting mechanism of molten iron on the carbon brick surface is elucidated. The findings reveal that both the microporous carbon brick and molten iron remain in a never‐wetting state within the furnace. As the temperature rises from 1150 to 1450 °C, the contact angle decreases from 138° to 128°, whereas the initial carbon content in the molten iron increases from 2.6 wt% to 4.1 wt%. Additionally, the initial contact angles gradually increase from 128.3° to 133.6°, with final equilibrium contact angles of 119.2° to 127.0°, indicating a nonwetting state. The carbon dissolution reaction occurs within the carbon matrix region of the microporous carbon brick prior to carbon saturation in the molten iron. Conversely, the presence of a ceramic phase in the ceramic area hampers both chemical erosion and physical penetration of the molten iron.

Formation Process of Brittle Layer in Carbon Brick and Kinetic Analysis of Dendritic Penetration

Formation Process of Brittle Layer in Carbon Brick and Kinetic Analysis of Dendritic Penetration

Phase and formation mechanism of the brittle layer of ASC castable in blast furnace hearth

An Al2O3-SiC C castable BF was dissected and investigated in the present work. The phase composition and microstructure of the brittle layer of castable and the original castable after service were analyzed by XRD, chemical analysis, and SEM-EDS. The results show that a brittle layer of castable with a thickness of about 50–300 mm is found at the bonding surface between the carbon brick and castable on the sidewall of the hearth. Zn enrichment was found in the brittle layer of castable. In the high-temperature environment of the furnace sidewall, the evaporation of water and formation of mullite phase in the process of phase transformation at high-temperature lead to the formation of pores and microcracks in the castable. Stress concentration in the joint area of the castable and carbon brick was produced due to their different expansion coefficient, and the microcracks in the castable gradually develop and expand under the action of thermal stress. In addition, the diffusion of CO, alkali metal steam, and Zinc vapor in the blast furnace hearth and the expansion caused by the reaction product with the original phase of castable accelerated the propagation of microcracks in castable and finally formed the macro-brittle layer.

Erosion Mechanism of Carbon Brick in Hearth of 4000 m3 Industrial Blast Furnace

After dissection of a large blast furnace, the erosion mechanism of carbon bricks after service in a blast furnace (BF) hearth was studied. Obvious “elephant foot” erosion characteristics emerged in the height direction of the BF. The existing forms of carbon bricks after service were characterized by X-ray diffraction (XRD), scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS), and chemical analysis. The results showed that Zn and iron erosion above and below the taphole was observed in the BF, while iron and Zn erosion acted only as a key factor of carbon brick erosion. The convective heat transfer coefficient in the lower part of the hearth of the BF was large, which increased the temperature of the hearth sidewall, resulting in the increase in the carbon-unsaturation of the molten iron at the sidewall, and intensified erosion to the hearth sidewall. The average pore size (1.083 μm) of the carbon bricks on the hot-face of the hearth sidewall was smaller than the critical size (2.12 μm) of the molten iron that penetrated the pores of the carbon bricks, which was not conducive to the penetration of molten iron.

Formation Mechanism of the Brittle Layer in Carbon Brick of Blast Furnace Hearth

The brittle layer of carbon brick in a Chinese 4000 m3 blast furnace hearth is investigated in detail, and its formation mechanism is proposed correspondingly. The occurrence form of the brittle layer in carbon brick is characterized by chemical analysis, X‐ray diffraction, and scanning electron microscopy–energy dispersive spectroscopy. The results show that obvious harmful element (K, Na, and Zn) erosion on the sidewall of the blast furnace hearth is observed, in which Zn erosion is dominant. The K2O, Na2O, and KCl produced in the carbon brick by K and Na are the inducement of the brittle layer formation, and the ZnO formed by Zn is the main reason for the brittle layer formation. The thermal stress caused by temperature gradients in carbon brick is greater than its bending strength, which will increase the microcracks in carbon brick. The brittle layer has a lower thermal conductivity due to higher porosity, resulting in a large temperature difference. The resulting thermal stress will aggravate the embrittlement degree.

Bonding phase formation in eco-friendly periclase−spinel−Al bricks used in RH degassing process

Mere unburnt periclase–spinel–Al bricks have been accepted by steel mills in the chromium-free campaign of the lining materials for Ruhrstahl ̶ Heraeus (RH) degassers, in terms of comparable/optimistic performance to traditional material, low carbon emission due to unburnt manufacturing process and chromium-free material for eco-friendly steel-making process. Investigations are made on the used periclase–spinel–Al bricks for the thermal evolution of their components and the formation of novel phase and bonding structure. Under the working atmosphere of RH degasser, metallic Al particles got molten above its melting point, leaving Al rim at their surroundings, and AlN formed in the gaseous state dispersing into overall matrix of periclase–spinel–Al bricks with rising temperature. AlN formed and Mg reduced in their gaseous state germinated MgAlON whisker initially in the original space of metallic Al particles, and MgAlON whisker grew further everywhere in the matrix. A whisker interwoven network has been full of the matrix behind the hot face and toward the cold face of the used bricks, which is a completely novel type of bond and distinguished from traditional ceramic one. The whisker-interwoven network is somewhat like the stripe graphite containing microstructure of magnesia–carbon brick, which results in low wettability and high flexibility. The superior performance of periclase-spinel-Al brick is attributed to such a bonding structure of whisker-interwoven network, which could reduce slag penetration and facilitate thermomechanical stress resistance.

Influence mechanism of sulfur on dissolutive wetting between molten iron and carbon brick

Influence mechanism of sulfur on dissolutive wetting between molten iron and carbon brick

Effect of water vapour on the interface reaction between carbon brick and molten iron in blast furnace hearth

ABSTRACT In the production process of blast furnace, the damage of cooler and tuyere sleeve and some operation problems often lead to ponding in the hearth. Steam will not only oxidize carbon bricks, but also lead to the falling off of solidification layer, which poses a great threat to the longevity of the hearth. By studying the influence of water vapour content change, the influence mechanism of water vapour on the interface between carbon brick and molten iron in blast furnace hearth is revealed. The results show that the entry of water vapour will isolate the molten iron and carbon brick, and oxidize in contact with the carbon brick, increase the ceramic phase, dissolve into the molten iron, destroy the carbon brick structure at the iron carbon interface, produce spalling, accelerate the destruction and falling off of the solidification layer, so as to reduce the service life of the blast furnace.

Iron-Carbon Interface Phenomenon and Reaction Behavior Analysis in Blast Furnace Hearth

The iron-carbon interface plays an important role in hearth, the dissection investigation of BFs was carried out to clarify the iron-carbon interface phenomenon and reaction behavior. The results show that the iron-coke interface can be divided into two types: partial coverage and overall coverage. The molten iron penetration from the interface to the center of coke is found. The hot face of residual carbon brick has obvious embrittlement layers, the pulverization phenomenon of carbon brick is observed, cracks appear in the carbon brick near the iron-carbon brick interface. Many holes in coke are filled with iron and slag, the filling rate increases as the coke moves towards the lower part of hearth. The graphitization degree of coke increases through dissolution precipitation and carbide transformation mechanism, the high graphitization of coke caused by carburization at iron-coke interface is the essential cause of coke deterioration. The flexural strength of carbon brick decreases under the alternate process of penetration and dissolution, effect of Zn. The critical temperature difference for crack generation decreases from 286°C to 208°C after the reaction, which makes it easier for the carbon brick to produce cracks. These cracks produce brittle embrittlement layers, which accelerates the erosion of carbon brick. The carburization of coke and the dissolution carburization of carbon brick are carried out simultaneously in hearth, there is a competitive carburization between iron-coke interface and iron-carbon brick interface. The methods of controlling competitive carburization are put forward to delay the erosion of carbon brick.

Thermal Stress Analysis of Blast Furnace Hearth with Typical Erosion Based on Thermal Fluid-Solid Coupling

The life of the hearth is the main limiting link of the campaign of a blast furnace. As the equipment for holding molten iron in the furnace, the high-temperature molten iron is in direct contact with the refractory, which makes the refractory have a larger temperature increase. If the temperature gradient inside the refractory is large, it generates large thermal stress and causes the refractory to crack. Blast furnace gas and molten iron intrude into the gap, which directly causes melting erosion and other chemical erosion with carbon bricks. It aggravates the erosion degree of the furnace and seriously affects the production life of the furnace. Therefore, the furnace often occurs with different types of severe depression erosion in the late service of the blast furnace. In this study, the calculation model of the thermal fluid-solid coupling considering the molten iron flow and the solidification of molten iron was established. This calculation model was applied to study thermal stresses in the furnace with severe erosion. Based on the calculation model, the effect of blast furnace production parameters and deadman condition on thermal stresses in the furnace with severe depression erosion were analyzed, including tapping productivity, tapping temperature, cooling intensity, and deadman geometry. The research results are of great significance for prolonging the safe production life of blast furnaces.

Analysis of the coke distribution characteristics in hearth based on blast furnace dissection

The occurrence state and consumption way of coke in blast furnace hearth are of great significance for efficient utilization of blast furnace fuel and low-carbon smelting. In this study, a 2200m3 blast furnace was dissected and core drilling was used to analyze the distribution characteristics of coke in the hearth systematically. It was found that the phases from the hot side of carbon brick to the hearth center were the hot metal channel, CaS agglomerate, slag‑iron-coke bonding phase, scattered coke along the radial direction. A large number of CaS were first found in the hearth with a radial width of 0.8 m. S and K elements were enriched at the interface between slag-coke and iron-coke, which hindered the carburization reaction and renewal mechanism of coke and was not conducive to its efficient utilization. In addition, the ore phase of the coke interface and interior alkali metal salt jointly led to its cracking. The distribution date and utilization ratio of coke in the hearth were clarified. The average coke size was 31.17 mm and the average voidage of the deadman was 40.99%. The mass loss of coke as reducing agent, heat source and carburizing agent during the decline in the furnace were 28.31%, 59.40% and 12.29% respectively.

Oxidation resistance of magnesia carbon bricks and the influence on their performance

ABSTRACT In this paper, the oxidation resistance of magnesia carbon bricks with different compositions was evaluated and the influencing factors were obtained, the influence of oxidation resistance on the performance of magnesia carbon bricks was investigated. The test results showed that for low-carbon MgO-C refractories, the influence of holding time was greater than that of oxidation temperature; for medium and high carbon MgO-C refractories, the influence of oxidation temperature was greater than that of holding times. The oxidation resistance of refractories, especially that of low-carbon MgO-C refractories, improved with the increase of the content of metallic additives. The oxidation resistance improved with the increase of graphite purity, especially in the low-temperature region. It is expected that this study can contribute to the optimal selection of magnesia carbon bricks in the trunnion area of furnace lining and provide a reference for the design of refractories with long overall service life.

Consideration of long campaign based on analysis of 4038 m3 blast-furnace hearth core investigation

In order to explore the erosion reason of the hearth sidewall built with high thermal conductivity and small hot-pressed graphite carbon bricks, the carbon brick samples were obtained by boring in different parts of the hearth sidewall. By the research on microcosmic structure, thermal conductivity, chemical composition of the carbon bricks, it was concluded that the high portion of large size pore leaded to poor properties of resistance to Zn permeation. And due to the formation of the weakened layer, the transfer system of lining was destroyed, which result in poor effect of titanium protecting and resistance to hot metal erosion. For the purpose of prolonging the campaign of BF hearth, the properties of resistance to hot metal erosion and the thermal conductivity of carbon brick should be matched well.

Thermal conductivity of alumina-carbon composite brick and its related phase analysis in a dissected blast furnace

Excellent performance of refractories in blast furnace hearth is one of the important factors to ensure longevity of blast furnaces. As an emerging refractory for application in blast furnace, alumina-carbon composite brick combines the superior properties of carbon and alumina. Firstly, the thermal conductivity of alumina-carbon composite brick was measured by the laser flash method and the new device method to verify the feasibility of the new device method for thermal conductivity measurement. Secondly, the influence of heating temperature of the heating furnace and cooling water flow on the thermal conductivity of the alumina-carbon composite brick, and the comparison of the thermal conductivity of carbon brick, alumina-carbon composite brick and corundum brick were investigated to confirm the heat transfer mechanism of alumina-carbon composite brick. High thermal conductivity and erosion resistance to slag and hot metal of the alumina-carbon composite brick are consequent from: (a) reasonable composition combination of Al2O3, C, SiO2, SiC, etc., (b) dense structure, small pore diameter, and uniform distribution of the pores, (c) the generated SiC whiskers and Al6Si2O13, which can fill in the pores and reduce the porosity. Finally, the analysis on the phase distribution of the alumina-carbon composite brick in a dissected blast furnace was performed to illustrate the relationship between the erosion resistance and the thermal conductivity of alumina-carbon composite brick.

Preliminary study on HTR-10 operating at higher outlet temperature

High Temperature Gas-cooled Reactor (HTGR), which has well-known safety features and high temperature heat supply capability, is expected to be widely used for heat supply and technology heat utilization including the hydrogen production, and so contributing to the reduction of carbon dioxide emissions in various sectors. The 10 MW High Temperature gas-cooled test Reactor (HTR-10) had been constructed and operated in China as a pilot plant to demonstrate the inherent safety features of the modular HTGR. The first criticality of HTR-10 at air condition was realized on December 1, 2000, and the full power operation for 72 h on January 29, 2003.Supported by Chinese National S&T Major Project, HTGR for hydrogen production are now being studied. The physical and thermal hydraulic design to raise the outlet helium temperature of the HTR-10 reactor core from 700 °C to 850–1000 °C is carried out.In this paper, the preliminary thermal hydraulic design of the HTR-10 with the outlet helium temperature of 950 °C (HTR-10H) is introduced. The power density distribution, the fuel temperature distribution and the reactor pressure vessel (RPV) temperature are studied to identify what need to be focused on next. Besides, the DLOFC accident has been studied to evaluate the safety feature of the HTR-10 operating under higher core temperature and outlet temperature.Due to the lower power and power density, as well as the large heat capacity of the graphite reflector and the carbon brick, the maximal fuel temperature during the DLOFC would not exceed the limitation of 1620 °C (250th meeting of the reactor safety commission, 1990). Nevertheless, the higher fuel temperature during the normal operation should be of concern.

Thermal conductivity of porous refractory material after aging in service with carbon pick-up

Medium Density Insulating Boards, based on vermiculite, are used for the insulating lining of ladles in steel production. In service, carbon monoxide is generated from oxidation of neighbouring Magnesia – Carbon bricks and diffuses through the refractory brick lining to deposit carbon in the colder insulating lining via the Boudouard reaction. Characterization by laser flash and hot disk measurements of original and post-mortem samples reveals an approximate increase by 26% in the overall thermal conductivity of the board to 0.34 W m−1 K−1 at room temperature following 15 months service. This is attributed to carbon and chloride phases detected by X-ray fluorescence and energy dispersive X-ray spectroscopy in the outermost zone of the board, cut into three zones for analysis along the heat flow direction. The increase in thermal conductivity is reduced to 17% when the thermal gradient in service conditions is considered.

Comparative Analysis on the Corrosion Resistance to Molten Iron of Four Kinds of Carbon Bricks Used in Blast Furnace Hearth

The corrosion resistance to molten iron of four kinds of carbon bricks used in blast furnace hearth were investigated to elaborate the corrosion mechanism through the macroscopic and microscopic analysis of carbon bricks before and after reaction and thermodynamic analysis. The macroscopic analysis showed that brick A had the lowest degree of corrosion and highest uniformity at different heights, attributing to its moderate carbon content of 76.15%, main phases of C, Al2O3, SiC, and Al6Si2O13 (mullite), and lower resistance to molten iron infiltration, etc. The microscopic analysis showed that all the carbon bricks had more and larger pores than the original carbon bricks. The phenomena of the iron beads adhering to carbon brick and iron infiltration were observed between the interface of carbon brick and molten iron. In addition, the obvious corrosion process was presented that the carbon matrix was broken and peeled off during the iron infiltration process. For the carbon brick being corroded, the dissolution of carbon was the predominant reaction. The higher the carbon solubility of the molten iron, the easier the corrosion on the carbon brick. Al2O3 and SiC enhanced the corrosion resistance to molten iron of carbon bricks, and SiO2 could react with carbon to form pores as channels for the penetration of molten iron and increase the corrosion on carbon bricks. A higher graphitization degree of carbon bricks was beneficial to lessen their corrosion degree. The corrosion on carbon bricks by molten iron could be attributed to three aspects: carburization, infiltration, and scouring of molten iron. The carburization process of molten iron was the main reaction process. The molten iron infiltration into the carbon bricks facilitated the dissolution of carbon and destroyed the structure and accelerated the corrosion of the carbon bricks. The scouring of molten iron subjected the iron–carbon interface to interaction forces, promoting the separation of the exfoliated fragmented carbon brick from the iron–carbon interface to facilitate a new round of corrosion process.