Ramming Refractories

Aluminum sulfate solution as a binder, clay clinker, high aluminum clinker, or corundum as aggregate, with plastic refractory clay and admixture and made of plastic clay, known as aluminum sulfate combined plastic. Aluminum sulfate bonded plastics have similar high temperature properties to phosphoric acid but lower production costs. Therefore, it is a common refractory plastic. Aluminum sulfate [Al2(SiO4)3·18H2O] is a solid substance, which must be dissolved in water to make an aqueous solution for use. Solid aluminum sulfate dissolves slowly at room temperature, so hot water or hot steam can be used to accelerate the dissolution. Table 17-24 shows the relationship between the addition amount of aluminum sulfate and the density of the aluminum sulfate solution prepared. The density of aluminum sulfate solution prepared for plastics is generally 1.15~1.20g/cm3.

Aluminum sulfate can be composed of plastic ingredients: refractory aggregate (aggregate and powder) 80%~84%, plastic refractory clay powder 10%~12%, admixture (mainly volume stabilizer, such as bluestone) 5%~6%. Aluminum sulfate solution (density: 1.15~1.20g/cm3) added amount (plus) was 9%~13%. The particle size composition of plastics is as follows: the ratio of refractory aggregate (greater than 100 m) to refractory powder (less than 100 m) is (55:65) :(35~45).
The mixing and billet process of this kind of plastic is similar to that of phosphoric acid combined plastic. The preparation process is first mixing → strainer → second mixing → billet. In the first mixing, 60% to 70% of the aluminum sulfate solution is added to make the aggregate well wetted by the aluminum sulfate solution. The iron in the refractory aggregate can fully react with sulfate and release H2 gas to prevent the billet from expanding. During the second mixing, the remaining 30%~40% aluminum sulfate solution was added, and then the clay material was pressed or extruded into the blank, and sealed and packed with polyethylene film to prevent water evaporation and loss of plasticity. The physical and chemical properties of typical aluminum sulfate combined with aluminum silicate plastics are shown in table 17-25.

The application scope of aluminum sulfate combined plastic is the same as that of clay combined plastic, but the mechanical strength of aluminum sulfate combined plastic is higher than that of clay combined plastic, which is suitable for the lining of industrial furnace which requires higher structural strength, such as the lining of ring heating furnace bottom prefabricated block, forging furnace lining and vertical kiln.
Fire-resistant ramming compound
The refractory mixture in semi-wet state constructed by tamping method is called refractory ramming material. Different from refractory plastics, this kind of refractory mixture is a kind of low plastic or no plastic tamping material, which forms dense body by forced tamping, and then hardens by heating, baking or roasting to obtain certain structural strength. Now tamping construction materials, in addition to plastic (wet tamping materials) and tamping materials (semi-wet tamping materials), and dry tamping materials (do not contain liquid tamping materials), is a completely plastic tamping materials, see dry tamping materials section.
Refractory ramming materials in the past more materials and varieties, the use of a wide range, but because of ramming construction labor intensity, long construction time, it is difficult to obtain a uniform overall liner, has been gradually replaced by other construction methods of amorphous refractory. Now the use of this semi - wet state of ramming material place. At present, the main varieties of ramming materials are: aluminum - magnesium ramming materials, high aluminum (or corundum) - silicon carbide - carbon ramming materials, alkaline refractory ramming materials and pavilion mullite ramming materials.
Aluminum magnesium ramming material
This is a kind of semi-wet mixture mainly composed of alumina and magnesium oxide, which can be tamped and formed. It is made of high aluminum-hot material (first or special grade bauxite clinker) or corundum as aggregate and powder, and made of water glass solution as binder. The proportion of ramming materials is: high aluminum clinker (or corundum) aggregate and powder 88%~92%, sintered or fused magnesia powder 8%~ 12%, plus 7%~ 10% water glass solution. The particle size composition of ramming materials is as follows: the maximum particle size is 10~15 mm, the ratio of aggregate (> 100 m) to powder (less than 100 m) is (60~65):(35 ~40), while the ratio of coarse aggregate (> 8 mm) to fine aggregate (less than 1 mm) in aggregate is (60~ 70):(30~40).
The sintered or electrofused magnesite is added to the matrix in the form of fine powder in order to generate aluminum magnesium spinel (AL2O3 ·MgO) by in-situ reaction between MgO and AL2O3. The production of spinel can not only compensate for the sintering shrinkage of ramming material, but also improve the permeability and erosion resistance of high-temperature slag.
The binder should use high modulus water glass solution, because the smaller the modulus, the higher the Na2O content, will reduce the high temperature slag resistance ramming materials. Generally, water and glass solutions with a modulus greater than 2.6 and a density of 1.2~1.3g/cm3 are used as binders. The general physical and chemical properties of the aluminum-magnesite mash prepared with super high aluminum clinker and medium-grade sintered magnesia are as follows: chemical composition :AI2O370%~ 75%,MgO 6% ~ 10%, volume density after drying 2.60~ 2.75g /cm3, compressive strength 45~ 55mpa, 1400℃, porosity 22 ~ 23% after 3h firing, compressive strength 70~ 85mpa, line change rate - (2.0~0.8)%.
Aluminum-magnesite ramming material can be used for ladle ramming lining, induction furnace lining, electric furnace lining, and high temperature containers in contact with high temperature metal solutions and slag.