Focus on Producing High Quality Refractory Materials !
Focus on Producing High Quality Refractory Materials !
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Kinds of Refractory Bricks and Monolithic Refractories for Sale
Rongsheng Refractory Supplier provides kinds of refractory bricks and monolithic refractories. Exclusive customer service and refractory lining material solutions.
Rongsheng's advanced fully automatic monolithic refractory production line has an annual output of 80,000 tons. Two high-temperature tunnel kilns and two shuttle kilns ensure the supply of refractory bricks.
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Properties of Fused-Cast Z80 Bricks. Linear Thermal Expansion Rate: The linear thermal expansion rate is one of the key parameters for evaluating the performance of refractory materials. It reflects the dimensional changes a material undergoes in response to temperature fluctuations. This parameter is crucial for the selection of furnace body materials in fused-cast furnaces, as it directly impacts the structural stability and crack resistance of the furnace.
A comparison of the linear thermal expansion rates of Fused-Cast Z80 bricks and Fused-Cast AZS41# bricks reveals that the rates for both materials are quite similar at 1400°C. However, the variation in the linear thermal expansion rate of Fused-Cast Z80 bricks across different temperature ranges is significantly smaller. Consequently, Fused-Cast Z80 bricks present a lower risk of cracking during heating cycles or rapid temperature changes (thermal shock). By selecting Fused-Cast Z80 bricks as the refractory material, it is possible to more effectively mitigate structural damage to glass furnaces caused by temperature fluctuations, thereby enhancing the safety and reliability of fused-cast furnaces throughout their operational cycles.
Bubble Generation Rate. The bubble generation rate of Fused-Cast Z80 bricks stands at 0% at 1300°C and 0.1% at 1500°C—levels considered extremely low. Fused-Cast Z80 bricks exhibit the lowest bubble generation rate among comparable materials, demonstrating excellent efficacy in suppressing bubble defects in glass products caused by the refractory lining. This superior performance is attributed to the uniform elemental composition and density distribution of Fused-Cast Z80 bricks; as they undergo no changes in their phase structure, they are able to consistently maintain an exceptionally low bubble generation rate.
Physicochemical Properties of Fused-Cast Z80 Bricks
As a refractory material utilized in glass melting furnaces, the physicochemical properties of fused-cast Z80 bricks are of paramount importance. A comparative analysis against fused-cast AZS33#, AZS41#, and fused-cast 95% high-zirconia bricks reveals that the Z80 variety is characterized by a low impurity content, as well as high uniformity in apparent porosity and density. During service, the material exhibits no formation of glass phases, bubbles, or needle-like defects; furthermore, it possesses a relatively low coefficient of thermal expansion. Consequently, it demonstrates excellent resistance to corrosion, erosion, and thermal shock. Its comprehensive performance significantly surpasses that of fused-cast AZS33# and AZS41# bricks, placing it on par with fused-cast 95% high-zirconia bricks. However, given that its cost is lower than that of fused-cast 95% high-zirconia bricks, it offers an optimal balance between extending the service life of glass furnaces and managing investment costs.
Microstructure of Fused-Cast Z80 Bricks
The grain size of fused-cast Z80 bricks is significantly smaller than that of fused-cast 95% high-zirconia bricks—a characteristic that exerts multifaceted influences on the material’s overall performance.
First, a smaller grain size results in a higher density of grain boundaries. As key pathways for diffusion, grain boundaries effectively impede ion migration within high-temperature environments, thereby enhancing the material’s corrosion resistance and chemical stability. During the vitrification process of fly ash, fused-cast Z80 bricks demonstrate superior corrosion resistance, thereby minimizing material loss.
Second, a fine and uniformly distributed grain structure contributes to improved overall strength and toughness. Compared to materials with coarse grains, fine-grained materials exhibit reduced internal stress concentration and possess more tortuous crack propagation paths. Consequently, fused-cast Z80 bricks offer superior thermal shock stability and mechanical strength, resulting in a lower risk of fracture. In summary, the fine-grained microstructure of fused-cast Z80 bricks makes them an ideal choice for the refractory lining configurations of fly ash vitrification furnaces.
Fused-cast Z80 bricks possess exceptional resistance to thermal shock and exhibit favorable thermal penetration characteristics. During the furnace heat-up and commissioning process, fused-cast Z80 bricks remain free from cracking caused by thermal shock or linear thermal expansion variations; moreover, their efficient thermal penetration minimizes thermal shock-induced damage to the adjacent outer refractory layers.
Performance of Electrofused Z80/AZS Composite Bricks
Compared to electrofused AZS bricks, electrofused Z80 bricks exhibit superior resistance to corrosion and erosion, as well as excellent reheat performance; however, they come at a higher cost. Conversely, electrofused AZS bricks possess commendable mechanical strength and thermal stability. To extend furnace service life and reduce refractory material costs, a composite brick—comprising electrofused Z80 as the working face material and electrofused AZS as the backing support—has been developed. To ensure a robust bond between the two materials, a method combining physical structural design with the use of a high-temperature binder was adopted. During fabrication, mechanical interlocking was achieved through the precise control of interfacial roughness and geometry, while a high-temperature binder with a zirconia (ZrO₂) content of 90% by mass was selected to fill and reinforce the interface. Upon drying and curing at 200°C, this binder forms a strong bonding layer that enhances the structural integrity of the assembly and improves the composite material’s resistance to thermal shock and chemical attack.
In practical applications, the electrofused Z80/AZS composite brick has demonstrated excellent performance when compared against the electrofused AZS41# bricks and fused-cast 95# high-zirconia bricks produced by a renowned domestic manufacturer. The electrofused Z80/AZS composite brick offers several significant advantages in real-world usage:
(1) It resolves the inherent challenge faced by single-material refractories—namely, the difficulty of simultaneously balancing manufacturing costs with performance requirements.
(2) Through rational material pairing and optimized design, it enhances the cost-effectiveness of the refractory lining configuration, enabling users to achieve a longer furnace service life with a lower initial investment.
(3) It reduces the frequency of maintenance and material replacements, thereby minimizing furnace downtime and generating substantial economic benefits for enterprises.
Binders play a pivotal role in the production of Al₂O₃-SiC-C bricks (alumina-silicon carbide-carbon bricks), significantly influencing the mixing and forming properties of the green mix, as well as the microstructure of the final product. The primary requirements for binders used in Al₂O₃-SiC-C bricks are as follows:
(1) They must exhibit excellent wettability with the Al₂O₃-based refractory aggregates and matrix materials.
(2) They should contain no—or minimal—components that are harmful to human health.
(3) The properties of the mixed batch should remain relatively stable over time, and the extent of chemical reaction with the aggregates should be minimal.
(4) During the heating process of the product, the binder should maintain a high residual carbon yield; furthermore, the polymer structure formed after carbonization must possess excellent high-temperature strength.
Good wettability between the binder and the refractory aggregates and graphite—combined with appropriate viscosity—can significantly enhance the bulk density and mechanical strength of the final product. Moreover, excellent wettability with graphite facilitates the uniform dispersion of graphite particles throughout the product, ideally forming a continuous network structure. Upon carbonization, this network evolves into a continuous carbon-bonded skeleton, thereby substantially improving both the mechanical strength and high-temperature slag resistance of the product. Consequently, the selection of an appropriate binder is of paramount importance. In the manufacture of Al₂O₃-SiC-C bricks, phenolic resins and aluminum dihydrogen phosphate are frequently selected as the binders.
Phenolic resins are synthesized through a polycondensation reaction involving phenolic compounds (such as cresol, phenol, xylenol, and resorcinol) and aldehyde compounds (such as formaldehyde and furfural), catalyzed by acids or bases. In the refractory industry, phenolic resins are widely utilized in the production of carbon-containing refractories due to their high carbon yield, excellent bonding strength—which enhances product mechanical strength—low emission of harmful volatile organic compounds, and high thermal stability. Based on their thermal behavior and structural morphology, they are primarily classified into two categories: thermosetting phenolic resins and thermoplastic phenolic resins.
In the fabrication of Al2O3-SiC-C bricks, thermosetting phenolic resins are typically selected as the binder; they are generally added at a concentration of approximately 5%, resulting in refractory products with relatively low porosity after molding. When subjected to heat in a neutral or reducing atmosphere, phenolic resins undergo thermal decomposition, generating gaseous products such as CO2, CO, CH4, H2, and H2O.
Within the temperature range of 200°C to 1000°C, phenolic resins continuously decompose to generate gases. As these gases volatilize, they create open pores, thereby increasing the apparent porosity of the refractory material and negatively impacting the mechanical strength, oxidation resistance, and slag resistance of carbon-containing refractory products. Consequently, to ensure the optimal performance of refractory products, two key measures must be taken: firstly, selecting a resin binder characterized by low gas evolution and a high carbon yield; and secondly, determining and utilizing an appropriate addition level for the resin.
Aluminum Dihydrogen Phosphate
Aluminum phosphate is widely utilized in the preparation of refractory materials. One of its primary advantages as a binder for refractories is that the resulting bonded structure exhibits excellent properties at intermediate temperatures. Aluminum phosphate is typically synthesized through the reaction of aluminum hydroxide with phosphoric acid. Depending on the degree of neutralization during this reaction, three distinct products can be formed: aluminum dihydrogen phosphate [Al(H₂PO₄)₃], aluminum hydrogen phosphate [Al₂(HPO₄)₃], and aluminum orthophosphate [AlPO₄]. For refractory applications, aluminum dihydrogen phosphate is the preferred choice of binder; its primary mechanism involves the polymerization of reaction products upon heating to a specific temperature, thereby enhancing the intermediate-temperature performance of the refractory product. At room temperature, aluminum dihydrogen phosphate is water-soluble; however, when heated to a certain temperature, it decomposes into aluminum pyrophosphate and aluminum metaphosphate, simultaneously undergoing polymerization reactions.
The formation and polymerization of aluminum metaphosphate [Al(PO₃)₃]n generate strong adhesive forces, thereby imparting strength to the refractory material at intermediate temperatures. As the temperature continues to rise, the aluminum metaphosphate decomposes to yield AlPO₄ and P₂O₅. The P₂O₅ can further react with the Al₂O₃ present in the refractory material to form additional AlPO₄, thereby further enhancing the intermediate-temperature strength of the refractory product.
Below 500°C, the aluminum dihydrogen phosphate primarily undergoes a dehydration process as the temperature increases. As the free water within the refractory product is expelled, the product undergoes shrinkage. During this dehydration phase—prior to reaching 500°C—the overall volume of the product remains relatively stable; however, the porosity of the binder phase increases, while its bulk density decreases. At this stage—due to the gradual precipitation of AlPO₄ and the subsequent formation and polymerization of aluminum pyrophosphate and aluminum metaphosphate—the density of the bonded structure may decrease slightly, yet its mechanical strength increases significantly.
When the temperature exceeds 500°C, the dehydration process within the bonded structure diminishes, and the product’s weight loss becomes negligible. Prior to the onset of high-temperature ceramic bonding within the material, there are no significant changes observed in the product’s porosity or density.
For refractory specimens utilizing aluminum dihydrogen phosphate as a binder, the cold-state strength begins to decline once the temperature surpasses a turning point of approximately 500°C; the strength does not begin to rise again until high-temperature ceramic bonding is established within the interior of the specimen. In contrast to its cold strength, the hot strength of the specimen increased continuously, reaching a maximum value at a temperature of 900°C. This increase in hot strength with rising temperature is likely attributable to the formation of compounds such as AlPO4 and Al(PO3)3 during the heating process; furthermore, the thermal expansion of the material fills the pores, resulting in a denser structure.
Between 900°C and 1000°C, the material’s hot strength declined significantly. This decline may be attributed to two factors: on one hand, the P2O5—generated from the decomposition of aluminum phosphate and aluminum pyrophosphate within the product—begins to volatilize; on the other hand, it may be related to the crystallographic phase transformation of AlPO4. As the temperature rises, AlPO4 undergoes a series of phase transformations: the low-temperature quartz form (low-temperature berlinite) transforms into the high-temperature quartz form (high-temperature berlinite) at 586°C. The high-temperature berlinite form can further transform into the tridymite form at 815°C, and the tridymite form transforms into the cristobalite form at 1025°C. During these phase transformations, the various crystalline forms of AlPO4 undergo volume expansion or contraction; this disrupts the product’s structural integrity, induces cracking, and consequently reduces the product’s bonding strength. When the temperature exceeds 1000°C, aluminum dihydrogen phosphate completely decomposes to yield AlPO4 and P2O5 (note that AlPO4 itself does not undergo decomposition to form M2O3 and P2O5 until reaching 1760°C); once the P2O5 has volatilized, only AlPO4 remains. Calculations based on solid-solution formulas indicate that, at high temperatures, AlPO4 can react vigorously with SiO2 to produce mullite and P2O5.
Overview of Refractory Linings in Gasifiers. Refractory bricks designed for GE coal-water slurry gasification systems constitute a critical component of the gasifier’s reaction chamber; they are required to meet stringent criteria regarding high-temperature resistance and resistance to erosion. These materials are characterized by their corrosion resistance, high mechanical strength, absence of toxic substance leaching, and long service life. The hot-face refractory materials must be capable of withstanding slag attack and corrosion by high-temperature syngas under the normal operating temperature conditions of the gasifier’s reaction chamber. Furthermore, they must endure the erosive forces of high-temperature syngas—as well as the abrasion caused by flowing molten coal slag—should the reaction chamber’s operating temperature rise to 1500°C.
Refractory materials for GE coal-water slurry gasifiers represent one of the key consumable items that significantly impact the long-term, economical operation of the gasifier. However, many gasifiers of this type encounter numerous issues regarding the application of refractory materials. This often results in shortened service lives for the furnace bricks and, in extreme cases during normal production, leads to unplanned system shutdowns caused by localized overheating of the furnace’s steel shell—a direct consequence of refractory lining failure—thereby posing substantial risks to both production continuity and equipment safety. With a specific focus on the application of refractory linings, this discussion examines various aspects—including material selection, masonry requirements, furnace drying and cooling procedures, normal operational protocols, and the root causes of material degradation—and proposes specific improvement measures aimed at extending the service life of the refractory lining.
Refractory Lining Structure of the Gasifier Combustion Chamber
The combustion chamber of the gasifier features a vertical structural arrangement; extending from the furnace throat down to the slag tap, the refractory lining covers various sections, including the dome, the cylindrical shell, and the conical section.
Dome Section
The refractory lining in the dome section consists of three layers, arranged from the interior outward: a hot-face refractory brick layer, a layer of chrome-corundum castable, and a layer of refractory fiber plastic materials. The installation ports for the process burners at the furnace throat are constructed from two layers of refractory material, arranged from the interior outward: an inner layer of high-chrome bricks and an outer layer of alumina hollow-sphere bricks. A thick layer of refractory fiber felt is placed as a cushion between the refractory materials at the furnace throat and the large flange at the furnace head.
Cylindrical Shell Section
The refractory lining in the cylindrical shell section consists of four layers, arranged from the interior outward: a hot-face refractory brick layer—specifically, high-chrome refractory material that interacts directly with the process gas and molten slag generated by the gasification reaction; a layer of chrome-corundum bricks, positioned immediately adjacent to the outer side of the hot-face refractory layer; a layer of alumina hollow-sphere bricks; and a layer of refractory fiber plastic refractory, which serves to fill the space between the alumina hollow-sphere bricks and the steel shell of the gasifier cylinder.
Chrome Corundum Bricks for Refractory Linings in Gasifiers
The refractory lining in the conical section consists of two layers, arranged from the interior outward: a hot-face layer composed of high-chrome bricks; and a layer of chrome-corundum castable positioned between the high-chrome bricks and the conical furnace shell. This castable material is primarily utilized to fill the irregular void spaces situated behind the hot-face refractory bricks.
Material Selection and Masonry Requirements for Refractory Linings
When selecting raw materials for the hot-face bricks (facing the heat source), high-quality materials with a high Cr₂O₃ content must be utilized. The resulting hot-face refractory bricks must meet specific densification standards, exhibiting low porosity, a fine-grained microstructure, and a high bulk density. Furthermore, they must demonstrate exceptional resistance to slag corrosion and superior chemical stability at high temperatures to ensure the overall quality of the refractory lining.
For the back-side lining of the hot-face bricks in the dome and conical sections, chrome-alumina castables should be employed; these materials must possess superior strength, density, and effective insulating properties. During the furnace heat-up phase, this configuration facilitates the formation of a monolithic furnace roof structure, thereby preventing localized overheating and mitigating the risk of “narrow-gas” phenomena (localized flow constriction).
During the masonry construction of the gasifier, refractory expansion joints must be provided in accordance with specified requirements, and all technical parameters—particularly those pertaining to the dome and cylindrical sections—must be strictly adhered to.
The primary technical specifications for refractory brick masonry are as follows: horizontal joints must be <1.0 mm, vertical joints <1.8 mm, vertical alignment (plumbness) within ±5 mm, horizontal alignment (levelness) within ±4 mm, and concentricity within ±5 mm.
Given the unique nature of the reaction media and process conditions within the gasifier, the refractory lining—including expansion joints, nozzle ports, temperature measurement ports, pressure measurement ports, and brick-support areas—requires meticulous design and specialized treatment to ensure the safe, reliable, and long-term operation of the gasifier.
During the masonry process, a specific clearance must be maintained between adjacent refractory lining sections. This intermediate gap should be filled with compressible refractory fiber or plastic refractory material to ensure that adjacent lining sections remain free from compressive stress—and are able to undergo relatively free differential movement—during high-temperature thermal expansion. Additionally, the gaps between adjacent refractory lining sections should be lined with an organic film separator. The joints between hot-face bricks (or those in the insulating/thermal-retention layers) and their immediate lateral neighbors must not form continuous straight lines in the longitudinal direction. Furthermore, the corresponding vertical and horizontal joints across the various layers of the refractory lining—from the innermost hot-face layer outward—must not align to form continuous straight lines that traverse the entire lining structure. The precision of the refractory brickwork at the process burner location must be strictly controlled in accordance with technical specifications. The centerline and concentricity of the process burner must be aligned with the centerline of the furnace body, with a permissible deviation of no more than ±2 mm. The diameter deviation at any given cross-section shall not exceed ±6 mm; the straightness deviation of the furnace lining centerline shall be within ±3 mm; and the total height deviation shall not exceed ±6 mm.
Waterproofing measures must be applied to the interface between the refractory bricks and the castable material to prevent the bricks from absorbing moisture.
Upon completion of refractory brick masonry, the structure must undergo natural ventilation and drying for 2 to 3 days. For newly laid refractory bricks, the initial temperature rise—the “bake-out” process—must strictly adhere to the original prescribed heating curve. This process serves to eliminate free water, crystalline water, and residual chemically bound water present within the refractory bricks and mortar. During the bake-out, improper operation or failure to follow the heating curve can lead to cracking of the refractory lining, a reduction in its structural strength, or even spalling (flaking) of the lining material.
If material charging is to commence immediately after the bake-out, the temperature may be raised from 800°C to the designated charging temperature at a heating rate of less than 50 K/h. If, however, the gasifier requires cooling to ambient temperature after the bake-out, the cooling process must not be abrupt; the rate of temperature decrease should be controlled at no more than 20 K/h. When initiating the bake-out by ignition, one must strictly avoid raising the furnace temperature too rapidly, as this risks cracking the furnace lining. The bake-out procedure must be conducted in strict accordance with operational protocols; specifically, the temperature differential between the upper and lower sections of the gasifier’s combustion chamber must be maintained below 80 K. Should an excessive temperature differential arise, it can be corrected by increasing the induced draft volume to adjust the furnace’s negative pressure, thereby elongating the flame and effectively controlling the temperature distribution. In the event of a flameout, the fuel supply must be immediately cut off, and negative pressure (draft) maintained for 5 minutes. Once analysis confirms that the concentration of combustible gases within the combustion chamber is within safe limits, re-ignition may proceed according to operational protocols. The furnace temperature should be raised at a rate of no more than 30 K/h until it reaches the temperature recorded just prior to the flameout, after which heating should continue in accordance with the prescribed heating curve. Upon completion of the gasifier bake-out, the internal furnace temperature should be measured using a temperature gun; the water supply to the quench ring may be shut off—allowing the furnace to cool naturally—only when the internal temperature has dropped below 140°C.
During a standard bake-out procedure, a heating rate of 40 to 50 K/h is required. The temperature is to be raised to the specified target of 1250°C, followed by a period of constant-temperature holding. Throughout the heating phase, raising the temperature too rapidly is strictly prohibited; furthermore, precautions must be taken to prevent excessive temperatures that could lead to slag accumulation and blockage of the slag tap. In the event of a flameout, immediately close the fuel control valve and the shut-off valve. After fully opening the preheating burner damper and maintaining a negative pressure draft for 5 minutes, reignite the burner. Then, increase the temperature at a rate of less than 50 K/h until the temperature prior to the flameout is reached; only then may the temperature be raised to the charging temperature in accordance with the prescribed heating rate.
The Impact of Process Operations on Furnace Bricks and Measures to Extend Their Service Life
Refractory bricks—particularly those on the hot face—experience wear during operation primarily due to mechanical erosion by coal ash and slag, spalling caused by thermal and chemical stresses, chemical corrosion, high-temperature ablation, and gradual thinning resulting from normal use. This section analyzes the actual operational conditions of refractory bricks.
An analysis of the multifaceted forms of wear experienced by refractory bricks—specifically those on the hot face—during operation reveals the following:
(1) Mechanical Erosion: Molten ash and slag flow across and erode the furnace bricks, leading to severe scouring, deformation, and even detachment of the bricks, often exacerbated by thermal stresses.
(2) Thermal Stress Spalling: Thermal expansion generates circumferential stresses within the hot-face bricks; this causes creep deformation in the refractory material on the hot-face side, subsequently leading to crack formation and spalling.
(3) Joint Erosion: When the gaps between refractory bricks are excessively wide, the refractory mortar within the joints shrinks. Consequently, these gaps become vulnerable to erosion by flowing ash and slag, as well as corrosion and ablation by high-temperature gases. The refractory bricks are gradually eroded—starting from these weak joint areas—resulting in “groove-like” or “pitted” forms of damage.
(4) Impact of Oxygen-to-Coal Ratio: An excessively high oxygen-to-coal ratio prevents the formation of a protective slag layer on the surface of the furnace bricks, thereby negating the “slag-against-slag” protective effect.
(5) Chemical Corrosion by Ash and Slag: Various elements present in the ash and slag react with different parts of the refractory bricks, thereby corroding them. For instance, K and Na tend to accumulate and react on the surface; Al and Fe react at the interface; while Ca and Si react within the interior of the brick structure.
(6) Impact of Coal Type: Different types of coal exhibit distinct viscosity-temperature characteristics. Consequently, the corrosive and penetrative effects of the various constituents within the ash and slag on the refractory bricks also vary. Notably, SiO₂ and CaO possess stronger corrosive potential toward refractory bricks than do FeO and Al₂O₃; therefore, changes in the type of coal utilized have a profound impact on the service life of the bricks.
The interior of the gasifier is dominated by reducing gases—specifically H₂ and CO—meaning that the entire hot-face lining of the refractory structure is in constant contact with these reducing gases. Gases permeate into the interior of the refractory bricks through pores or cracks, reacting with the silicon (Si) and iron (Fe) present within the bricks; this reaction causes the cracks to widen, thereby damaging the structural integrity of the bricks.
During the frequent start-up and shutdown cycles of a gasifier, the furnace chamber’s temperature and pressure undergo drastic fluctuations. During the feeding process, the sudden ignition of the coal slurry leads to a rapid surge in gas volume, subjecting the furnace bricks to significant thermal and mechanical shock. Furthermore, frequent adjustments to the operational load—whether increasing or decreasing it—impose similar stresses on the furnace bricks. When the quality of the coal feedstock is unstable, frequent adjustments to the oxygen-to-coal ratio become necessary. An excessively high oxygen-to-coal ratio can result in an abnormal elevation of chromium levels within the furnace slag. In the event of system anomalies—such as a sudden and drastic rise or fall in pressure—the service life and performance of the refractory bricks are significantly compromised.
Following a gasifier shutdown, when the process burner is being extracted, the rate of temperature decline must be strictly controlled. This control can be achieved by covering the furnace opening with a lid to facilitate a slow, “smothered” cooling process, while simultaneously utilizing an induced draft fan to regulate the negative pressure within the chamber.
The refractory bricks situated in different sections of the gasifier exhibit distinct wear characteristics during operation. Generally, the bricks in the furnace dome (arch) demonstrate a lower rate of erosion and enjoy a longer service life. However, during prolonged periods of low-load operation—or when the volatile matter content of the coal is excessively high—the operational conditions for the dome bricks deteriorate, making them highly susceptible to issues such as spalling (detachment) and cracking. If the process burner is poorly designed, or if the gasifier is operated beyond its rated capacity—resulting in an excessively high velocity of oxygen flow into the furnace—the erosive scouring of the bricks on the hot face (the surface exposed to the flame) is significantly exacerbated. The combustion reaction between the excess oxygen and the coal slurry releases a massive amount of heat, causing the dome to remain under extreme thermal stress for extended periods, thereby accelerating the thermal erosion of the dome bricks. Following the installation of the gasifier’s process burner, a significant annular gap often remains between the burner’s outer diameter and the furnace opening. During the initial stages of feeding, this gap facilitates the formation of intense gas vortices within the dome area; these vortices channel high-temperature gases toward the furnace head, causing the large flange at the furnace head to overheat. This overheating compromises equipment safety and adversely affects the service life of both the furnace-opening bricks and the dome bricks. As operational time accumulates, fly ash or coal slag gradually fills this gap; the resulting reduction in the gap size attenuates the vortex phenomenon, allowing the temperature of the large flange at the furnace head to return to normal levels. To mitigate this issue, measures can be implemented—such as encasing the outer diameter of the burner with castable refractory material or wrapping it with refractory fiber insulation—to effectively reduce the gap between the process burner’s outer surface and the furnace opening. The barrel bricks are significantly influenced by the central oxygen flow, coal ash content, and gasifier load; their erosion rate falls between that of the dome bricks and the cone-bottom bricks. If burner misalignment occurs during operation, or if the gasifier’s concentricity deviates from the controlled range, high operating temperatures can lead to severe localized or generalized erosion, thereby compromising the overall service life of the barrel bricks. The cone-bottom bricks exhibit the highest erosion rate—particularly the slag-tap bricks. In the cone-bottom channel, where the cross-sectional area narrows abruptly and flow velocity increases, the volume of molten ash slag contacting the refractory bricks per unit of time is significantly higher; consequently, erosive wear is most severe in this region, necessitating the highest frequency of replacement. The actual service duration of refractory bricks in various sections of the gasifier is heavily dependent on the specific production conditions and operational practices of each facility, resulting in considerable variations in service life. The extent of refractory damage can be assessed and diagnosed by analyzing the chromium content in the coarse slag; a higher chromium content indicates more severe erosive wear.
Furnace temperature can be inferred by analyzing parameters such as the particle size of discharged coarse slag, the extent of slag stringing, the residual carbon content in fine slag, and the composition of process gas (specifically, the content of effective gas components and methane). Where conditions permit, the furnace chamber temperature can be monitored directly; however, thermometers installed in a molten environment are prone to damage due to erosion by slag and gas flows. Additionally, after a scheduled shutdown, the wear on the furnace lining can be measured and evaluated to facilitate adjustments to process operating conditions, thereby ensuring the stable performance of the refractory bricks.
The precision of equipment installation also significantly impacts the furnace lining. Factors such as the vertical alignment of the gasifier vessel, the levelness of the large flange at the gasifier mouth, the concentricity between the process burner and the gasifier, and the concentricity between the burner’s large flange and the furnace mouth all directly determine whether the burner nozzle experiences off-center spraying during operation.
During normal operation, inspections conducted after each shutdown require the replacement of the furnace lining whenever the overall hot-face brick thickness is found to have diminished to one-third of its original design thickness; this measure prevents the furnace wall from overheating during subsequent operation. The hot-face bricks within the cylindrical section typically suffer from severe localized erosion and corrosion—particularly in the vicinity of the furnace chamber thermometer—rendering them unfit for continued use. However, if the surface condition and thickness of the bricks across a large area remain suitable for continued operation, localized patching and repair techniques can be employed to extend the overall service life of the hot-face lining. The bricks within the conical section are categorized numerically from #1 to #9, starting from the slag tap and extending toward the furnace wall; typically, the bricks most severely affected by erosion and corrosion are those located near the slag tap (bricks #1 through #4). By selectively replacing specific rings of bricks based on their individual condition, the overall service life of the entire conical lining can be effectively extended.
Most existing domestic production facilities prioritize economic efficiency, leading to a continuous drive to increase production output and operational load. Furthermore, newly constructed facilities are trending toward larger scales, resulting in ever-increasing coal feed rates. Under the combined influence of complex coal quality, high ash content, variable slag compositions, and high ash fusion temperatures, the refractory lining is subjected to intensified erosion, corrosion, and slag penetration, consequently shortening the service life of the refractory bricks. Consequently, overcoming the technical challenges associated with refractory materials—and thereby enabling long-duration, continuous operation—has emerged as a central focus of attention within the industry.
Extending the Service Life of Refractory Bricks in Gasifier Linings
Within a coal-water slurry gasifier, coal undergoes combustion reactions at operating temperatures exceeding the ash melting point. The resulting slag assumes a molten, liquid state, flowing downward along the inner walls of the furnace chamber and exiting through the slag tap. Should the furnace bricks or other refractory materials suffer any failure—such as gas channeling, brick dislodgment, or structural damage—localized overheating of the furnace’s steel shell may ensue. This, in turn, can trigger unplanned shutdowns and even pose safety risks involving potential equipment damage. Consequently, the service life of refractory bricks is primarily governed by factors such as material selection, furnace construction, kiln drying, startup and shutdown procedures, load adjustments, post-shutdown cooling protocols, and operator handling practices.
Currently, numerous domestic manufacturers are engaged in the development of refractory materials. Through continuous optimization of both refractory brick compositions and manufacturing processes, product quality has been significantly enhanced and reliably assured. Against the backdrop of fierce competition among peer enterprises—all striving to achieve “energy conservation and consumption reduction” as well as “safe, stable, high-capacity, and optimized operations”—extending the service life of refractory bricks has emerged as a central focus of shared interest among users and a critical direction for ongoing research.
