Development and application of refractory bricks that do not contain chromium

In operation of chrome-magnesia refractories, a problem of carcinogenic hexavalent chromium arises. In many countries, in accordance with the modern environmental standards production of refractories for cement kilns not containing chromium is developing. For an in-depth study of the harm caused by periclase-chromite materials to the environment, this paper describes the mechanism of hexavalent chromium formation in periclasechromite refractory bricks in the course of firing and operation. Regarding the operation conditions of different parts of the refractory lining of the cement kiln, the paper describes the trends in the development of basic chromium-free refractory materials by such parameters as resistance to heat and corrosion by alkali salts, cement clinker and products of fuel combustion. The use of periclase-spinel, periclasespinel-zirconia, magnesia-zirconia, periclase-dolomite, periclase-dolomite-zirconia and other basic refractory bricks that do not contain chromium, in China and abroad, and measures for their further improvement is described in detail. Due to good resistance to thermal shock periclase-spinel bricks have been successfully used in the cooling zone and the transition zone. These basic refractory materials containing zirconia exhibit improved thermal shock resistance and good corrosion resistance due to the chemical reaction of zirconia with CaO, contained in clinker, resulting in CaZrO3 compound with a high melting point. The bricks made from these materials have been successfully used in the burning zone.
This is demonstrated by examples of successful use of periclase-spinel and periclase-dolomite refractory bricks that do not contain chromium, manufactured by Qinghua Refractories Co., Ltd.

Author: Cao Junqing, Liu Puxiao

Section: Refractories

Keywords: refractory without chromium content, hexavalent chromium, thermal shock resistance, corrosion resistance, periclase-spinel and periclasedolomite refractories