The dry quenching furnace masonry is a vertical kiln structure, which is a barrel-shaped upright masonry in a positive pressure state. From top to bottom, the furnace body is divided into pre-storage section, chute area and cooling section. The entire dry quenching furnace is surrounded by an iron shell on the outside, and the inner layer is made of different refractory bricks, and refractory casting materials are also used in some parts.
(1) Refractory materials for pre-storage sections
The upper part of the pre-storage section is the cone top area. Because the temperature changes greatly before and after coke loading, the entrance is also greatly abraded by coke. This part is made of mullite that is resistant to erosion, abrasion, rapid cooling and heating, and has high flexural strength. Silicon carbide masonry. The middle part of the pre-storage section is a straight section of solid refractory brick masonry, which has to withstand the thermal expansion caused by loading red coke as well as the impact and wear of the loaded coke. This part is made of A-type mullite with high strength and wear resistance, and good resistance to rapid cooling and heat. Brick masonry. The lower part of the pre-storage section is an annular flue, which is divided into two layers of annular masonry, the inner wall and the outer wall; the inner wall must withstand the impact and wear of the coke, and also prevent leakage due to the pressure difference between the pre-storage section and the annular flue. , so A-type mullite bricks with grooved tongues are also used for construction.
(2) Refractory materials for ramp areas
The bricks in the ramp area are cantilevered layer by layer to support the load of the upper masonry. The temperature fluctuates frequently, and the coke dust entrained by the circulating gas causes violent erosion of this area. Therefore, the ramp area selects materials with thermal shock resistance, wear resistance and bending resistance. Mullite and silicon carbide bricks with good properties are used for masonry construction.
(3) Refractory materials for cooling section
Although the refractory brick masonry in the straight section of the cooling section has a simple structure, the refractory brick masonry on the inner wall is one of the most vulnerable parts because it has to withstand the intense wear and tear when the coke flows downward. Therefore, high-strength wear-resistant and quench-resistant bricks are selected. B-type mullite bricks with good thermal performance.
1. Types and usage parts of CDQ refractory materials
(1) Furnace mouth B-type mullite silicon carbide bricks and mullite silicon carbide fire clay.
(2) Pre-storage room A-type mullite bricks, mullite fire clay, dense clay bricks, clay fire clay.
(3) Chute A-type mullite silicon carbide bricks, mullite silicon carbide fire clay, dense clay bricks, lightweight insulation bricks, ceramic fiber felt.
(4) Annular air duct B-type mullite bricks, dense clay bricks, mullite fire clay, lightweight insulation bricks and others.
(5) Cooling room B-type mullite bricks, dense clay bricks, mullite fire clay, and wear-resistant castables.
(6) Other high-temperature sections: heavy high-aluminum castables and light-weight high-aluminum castables.
Performance of CDQ refractory materials
(1)mullite bricks
Mullite is the only stable binary mineral phase in the Al2O3-SiO2 binary system. Its chemical molecular formula is 3Al2O3·2SiO2. Mullite refractory materials are refractory products with mullite as the main crystal phase made of synthetic mullite (or natural purified mullite) as raw materials, and are a series of products. When the content of the product is lower than the theoretical composition of mullite, it also contains a small amount of cristobalite; when the content is higher than the theoretical composition of mullite, it contains a small amount of corundum. The resistance to high-temperature helical deformation of mullite products is much higher than that of other ordinary high-alumina bricks, including special high-alumina bricks. Its high-temperature performance is comparable to some properties of siliceous, magnesia, and corundum products. It has the characteristics of good chemical stability, small thermal expansion rate, thermal shock resistance, and strong resistance to acid and alkali residue erosion. The erosion resistance of acidic and low-alkalinity slag is higher than that of magnesia products, but not as good as that of corundum products.
(2) Silicon carbide bricks
Silicon carbide material is an advanced refractory material produced from silicon carbide. It has the advantages of good wear resistance and corrosion resistance, high high temperature strength, high thermal conductivity, small linear expansion coefficient, and good thermal shock resistance. Silicon carbide materials can be divided into many varieties according to the SiC content and the type and amount of binder. However, the quality of the material depends to a large extent on the binder. Mullite-silicon carbide brick is one of them. , its thermal expansion coefficient is very low, thermal conductivity is high, thermal shock resistance is good, and high temperature strength is high. It does not soften after long-term use at high temperatures, is not corroded by any acid or alkali, has good salt resistance, is not wetted by metal and slag, is lightweight, and is a high-quality high-temperature resistant material. The disadvantage is that it is easily oxidized at high temperatures and should not be used in an oxidizing atmosphere.
The currently used mullite-silicon carbide bricks have unstable flexural resistance and thermal shock stability. Bricks with better index performance and higher stability can be considered, such as silicon nitride combined with silicon carbide, oxygen and nitrogen. The high-temperature flexural strengths of silicon-bonded silicon carbide and sialon-bonded silicon carbide reach 40MPa, 30MPa, and 60MPa respectively. Regarding the current performance improvement of mullite-silicon carbide bricks (including annular air channels), consider improving the load softening temperature >1550℃, increasing the high temperature flexural strength >25MPa, and improving the thermal shock stability (1100℃ water cooling) >60 times, and evaluate the main indicators such as wear resistance <5.0Crn3.
Simple Al2O3, Fe2O3 and calcium oxide decompose with silicon carbide at 1100~1150℃, resulting in slagging and expansion, so impurities must be controlled.
(3)Other silicon carbide products
①Oxide combined with SiC
Al2O3-SiO2 silicate is used as the binding phase, including clay-bound SiC, mullite-bound SiC and SiO2-bound SiC.
②Nitride combined with SiC
The binding phase is covalently bonded compounds such as Si3N4, Si2N2O, and Sialon. Silicon nitride combined with silicon carbide products are hard in texture, with a Mohs hardness of about 9, which is the hardest material among non-metallic materials, second only to diamond.
Silicon nitride combined with silicon carbide products have high strength at room temperature. At high temperatures of 1200~1400°C, they maintain their strength and hardness for almost the same time as at room temperature. Depending on the use atmosphere, the maximum safe use temperature can reach 1650~1750℃.
The thermal expansion coefficient is small, and compared with products such as silicon carbide, it has a higher thermal conductivity, is less prone to thermal stress, has good thermal shock stability, and has a long service life. It has strong high-temperature creep resistance, corrosion resistance, extreme cold and heat resistance, and oxidation resistance. It is easy to make products with high dimensional accuracy and meet the requirements.
Products are widely used in steel, non-ferrous metals, chemical building materials and other industries to save energy, protect the environment and reduce costs.
③The index binding phase of Sialon bonded silicon carbide bricks is mainly covalently bonded compounds such as Sialon, and some people also name it as non-oxide composite phase ceramic bonded silicon carbide bricks.
Self-bonding SiC includes (3-SiC bonded SiC and recrystallized SiC.
Siliconing reaction sintering SiC is a SiC engineering ceramic material composed of SiC and free silicon.
In addition, refractory products with SiC content below 50% are usually called semi-SiC products. Semi-SiC products include clinker SiC products, high-aluminum SiC products, zircon SiC products, mullite SiC products and corundum SiC products. .
(4)Dense clay bricks
Including low-pore clay bricks and ultra-low-pore clay bricks, which have low porosity, low Fe2O3 content, high compressive strength, and strong erosion resistance; they have small volume shrinkage under long-term operation at high temperatures, reducing the precipitation of carbon in the pores and avoiding Bricks expand, become loose and are damaged during use, and low melting point substances are less formed.
(5)Casting material
The parts where the castables are used in the dry quenching furnace: light and heavy high-aluminum castables are used from the outlet of the dry-quenching furnace to the boiler entrance; the ash discharge device of the primary dust collector uses high-aluminum castables; after the cooling chamber is worn, high-strength wear-resistant castables are used.
(6) Refractory mud
Different refractory muds are used in different parts of dry quenching coke ovens. The high and low temperature performance of refractory mud is an important factor in ensuring the tightness and strength of masonry. The damage to the annular air duct and the corbels mostly starts from the peeling off of the brick joints. It is necessary to study the improvement of the post-fired strength of the refractory mud, the thermal expansion and reburning line changes during the heating process of the refractory mud oven, and the requirements for matching the shaped bricks. To ensure the overall structural integrity of refractory mud and bricks.
