Common Chromium-free alkaline refractories

March 04, 2019

Refractories are the basic material for high temperature work. In high temperature process, due to the raw material, some raw materials will produce toxic substances at high temperature. For example, trivalent chromium in products will be converted into hexavalent chromium at high temperature, while the hexavalent chromium is toxic and soluble in water, which will cause harm and pollution to body health, environment and water resources. In the environment-friendly production, chromium-free products are launched one after another. What are the common chromium-free alkaline refractories?

1.       Magnesia alumina spinel brick

This product is to improve the thermal shock stability of magnesia products, and this magnesium alkaline product uses magnesite and magnesia-alumina spinel as main minerals adding magnesia-alumina spinel into the ingredients which is with characters of good thermal shock resistance, strong corrosion resistance and high temperature strength. It is more and more used in cement kilns and steel making furnace.

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2.       Magnesia iron spinel brick

   This kind of refractory bricks are based on the principle of high duty magnesia and iron-alumina spinel, by adjusting the dosage of iron oxide and magnesia-iron spinel, strictly controlling the firing temperature and atmosphere, the product 3.       Iron alumina spinel brick

Iron alumina spinel brick is made of magnesia and pre-synthesized ferrite-alumina spinel. After firing, iron diffuses from the iron alumina spinel into the matrix, forming a solid solution of periclase-magnesia-iron spinel. At the same time, magnesium diffuses into the iron-alumina spinel particles, forming a hemline of magnesia-alumina spinel around the ferrite-alumina spinel, which reduces the gas sensitivity of the bricks. Therefore, this product with good kiln skin adhesive performance and structural flexibility.

4.       Magnesium-zirconium brick

In the production, magnesium-alumina spinel is replaced by zirconia or calcium zirconate in large quantities. High-purity fused magnesia and synthetic magnesia-zirconia are used as raw materials to comprehensively improve the properties of magnesia-based materials. The product with good corrosion resistance to alkali metals, oxides and sulfides. They also have good high-temperature mechanical properties, and are mostly used in regenerators and cement kilns of glass kilns.

5.       Dolomite brick

Dolomite brick, made of sintered dolomite, which is a single raw material with good bonding property, but is easy to hydrate. It requires high storage and transportation conditions. It is widely used in alkaline converter. The oil-immersed magnesia dolomite brick is also used as the lining of some refining furnaces.

The production of chromium-free and environmentally friendly refractories has become an urgent measure for the refractory industry.  We need strengthen technological innovation, research and development, promote environmentally friendly refractories and make the new green production enterprises under the consideration of reducing the cost of materials production.

 

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