What is Phosphate Bonded High Alumina Brick?
Phosphate-bonded high-aluminum kiln-lined refractory bricks include two products, one is phosphate-bonded high-alumina refractory brick (referred to as phosphate refractory brick); the other is aluminum phosphate combined with high-aluminum wear-resistant refractory brick (referred to as resistance Grinding refractory bricks).
Phosphate refractory bricks are used as a binder in a concentration of 42.5% to 50% of a dish acid solution. The aggregate is a bauxite clinker calcined at a temperature above 1600 °C in a rotary kiln. During the use of the refractory bricks, the phosphoric acid reacts with the refractory brick-fired bauxite fine powder and the refractory clay to form a binder mainly composed of cristobalite-type orthophosphate.

The wear-resistant refractory brick is made up of industrial phosphoric acid and industrial aluminum hydroxide as an aluminum phosphate solution, and the molar ratio thereof is Al2O3:P2O5=1:3:2. The aggregate used was the same as the phosphate refractory brick. In the use of refractory bricks, a combination of cristobalite-type aluminum orthophosphate is formed as the phosphate refractory brick.

Although the two kinds of refractory bricks are all made of the same aggregate, machine-molded, and chemically bonded refractory bricks obtained by heat treatment at about 500 ° C, the final bond formed in use is the same. However, due to the different manufacturing processes of refractory bricks, they show different characteristics. For example, in the particle composition of aggregates, phosphate refractory bricks use a large amount of 5~10mm burnt bauxite, and the refractory bricks have a large porosity. After the same temperature treatment, the elastic modulus of the refractory bricks is more wear-resistant and fire resistant. The bricks are much lower and the thermal shock stability is good. The wear-resistant refractory brick adopts the alumina aggregate less than 5mm particles, and directly adopts the aluminum phosphate solution as the molding binder, and the pressing is also dense, so it shows higher strength and wear resistance, but the thermal shock stability is Poor. Therefore, phosphate refractory bricks are suitable for use in transition zones, kiln openings and other areas where refractory bricks are easily removed. At present, large and medium-sized precalciners are not used except for a few small kiln.

Performance of phosphate combined with high alumina brick
Phosphate-bonded high-alumina bricks are made of phosphoric acid solution or aluminum phosphate solution (aluminum dihydrogen phosphate, PA-80 rubber, etc.) as a binder, and aluminum bauxite clinker is used as an aggregate, machine-molded, and subjected to a temperature of 500 to 600 ° C. The resulting chemically bonded refractory product is treated.

Phosphate Bonded High Alumina Brick, referred to as phosphate bricks; and aluminum phosphate combined with high alumina bricks, referred to as wear resistant bricks. The latter has a higher compressive strength.

The traditional phosphate combined with high alumina bricks has two obvious shortcomings. One is that the load softening temperature is lower, about 1300 ° C; the second is that the reburning line shrinks more, affecting its use effect and field of use. In order to solve this problem, adding three stones to the material is an important measure. As mentioned above, the three stones are irreversibly converted to mullite and SiO2 at high temperatures, and accompanying volume expansion, using this property, the load softening temperature of the product is increased and the shrinkage at high temperatures is reduced, and the thermal shock resistance is improved.

The following examples illustrate the effect of the addition of sillimanite on the properties such as the load softening temperature of the product.
As the amount of sillimanite added increases from 5% to 8% to 12%, the load softening temperature increases. When the sillimanite is added to 12%, the load softening temperature (0.6%) is greater than 1500 °C. There are two reasons for this:

(1) The total amount of mullite has increased. The sillimanite is decomposed to obtain mullite, which is a primary mullite; the SiO2 decomposed by sillimanite and the Al2O3 in the high alumina bauxite form mullite (called secondary mullite), thereby increasing Mo Stone content,
(2) The amount of liquid phase is reduced. The above reaction and the formed mullite can dissolve a part of TiO2 and Fe2O3 in the high aluminum fine powder to reduce the amount of the liquid phase.

Research experiments show that the addition of 8% sillimanite has the best thermal shock stability of the product, but decreases when it exceeds 8%.

In recent years, many domestic refractory materials factories have developed high-soft soft non-burning high-alumina bricks with a load-softening temperature of not less than 1550 °C, becoming a new generation of phosphate-bonded high-alumina bricks. The main point of production is the more rational use of three stone minerals, such as the use of composite materials or to adjust the particle size and dosage.

The application fields of phosphate combined with high alumina bricks include electric furnace top, cement rotary kiln transition zone, cooling zone and high temperature zone of cement shaft kiln.

Technical requirements for phosphate combined with high alumina bricks
Phosphate-bonded high-aluminum brick is made of high-alumina bauxite clinker as aggregate and fine powder, phosphoric acid or aluminum phosphate as binder, semi-dry pressed and heat-treated from 400 ° C to 600 ° C. .

Phosphate combined with high alumina bricks can be divided into two codes according to the bonding agent:

1. Phosphate combined with high alumina brick (referred to as phosphate brick), the binder is a concentration of 42.5%~50% phosphoric acid solution. Codenamed P;

2, aluminum phosphate combined with high-aluminum wear-resistant brick (referred to as wear-resistant brick), the binder is a solution of industrial phosphoric acid, industrial aluminum hydroxide, the molar ratio is Al2O3: P2O5 = 1:3.2. Codenamed PA.

According to physical and chemical indicators, size and appearance can be divided into first-level and second-level.

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Henan hongtai kiln refractory co., LTD. Main products are high alumina brick, clay brick, fused zirconium corundum brick, fireproof ball lightweight insulation brick, wear-resistant pouring material, corundum pouring material, low cement high strength pouring material, impermeable material, self-flowing material, plastic material, and various types of refractory materials.For different industries, the cement industry with anti-flaking high-alumina bricks, alkali resistant bricks, phosphate bricks;Boiler industry USES all kinds of brand wear-resisting brick, corundum brick, mullite brick and other finalizing materials.The company insists on "product quality is the life, enterprise integrity is the foundation", in the fierce market competition, won many users' trust and praise.The products are sold all over the country, as far as Vietnam, India, Korea, Pakistan, kazakhstan, Iran and other southeast Asian countries and regions.

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