Application of chromium oxide green in ceramic industry
Abstract: This paper briefly introduces the chromium oxide green productionpreparation process, the physical and chemical properties of chromium oxide green is discussed, and an introduction and analysis of chromium oxide green in theapplication of ceramic related industries in the.
Keywords: chromium oxide green; ceramic; black; blue; metallurgy
1 Introduction
Chrome oxide green, also known as chromium oxide, chromium oxide, as the six party system, green powder. Its molecular weight was 151.99, the density is 5.21g/cm3; the Mohs hardness is 8.5 ~ 9, close to the corundum (Al2O3), while more than quartz(SiO2) and Topaz (Al2 (SiO4) (OH) 2); refractive index of 2.5 (coverage), specific heat capacity (20 DEG C) to 0.17J/ (G - K); insoluble in water, acid and organic solvent,slightly soluble in concentrated sodium hydroxide solution, dissolved in concentratedperchloric acid solution with sodium bromate solution, hot hot or boiling phosphoricacid. Light, air and corrosive gases (H2S, SO2) is extremely stable, excellent weatherability; chromium oxide green heat stability, the melting point of 2265 DEG C,the boiling point of 3000 DEG C, is a high-quality refractory materials. In the market the chromium oxide green common appears bright green to dark green, with metallic luster; with magnetic, high covering power, high temperature resistant, resistant to sunlight, not soluble in water, insoluble in acids and other characteristics, is relatively stable in the atmosphere, the general concentration of acid and alkali and sulfur dioxide gas has no effect on it, with excellent quality and outstanding fastness ofpigment.
The amount of use of chrome green oxidation ceramic industry is very alarming,according to incomplete statistics, the annual applied to ceramic and related enterprises of the chromium oxide green consumption in the 20 to 300000 tons,basically as long as the ceramic enterprises are directly or indirectly use chrome oxide green. Especially the pigment manufacturers of ceramic enterprises are matched to the desired chemical material, chrome oxide green occupies a large proportion, andchrome oxide green market prices in the past two years also gradually on the rise,from 2008 20000 yuan / tons has been up to the current 40000 yuan / tons. But due to the increase in raw material and other labor costs, in addition, a very important reason is that the state began to chromium oxide green enterprises began to environmental rectification from last year, particularly serious chromium slag pollution incident last year in Henan area, and further cause the social attention on chromium salt production enterprises of environmental protection.
2 chrome oxide green production process
At present, the production process of chromium oxide green has many kinds, but themethod commonly used in industry are: chromium hydroxide, ammonium sulfate -sodium dichromate thermal decomposition method and direct thermal decomposition process of chromic anhydride. At present, the basic method of producing chromium oxide USA, UK and Germany is ammonium sulfate - sodium dichromate thermal decomposition method, by adopting the technology of chromate manufacturers in foreign production of chromic oxide yield the largest and best quality, most varieties.The utility model has the advantages of a production process than the liquid phase reduction method is simple and the cost is lower than that of chromic aciddecomposition method, wide adaptability (can be prepared pigments, abrasives,refractories and metallurgical grade chrome oxide), suitable for rotary kiln for mass production, in the production process and the basic does not produce harmful gases,which replaced the earlier chromate and sodium chloride. Thermal decomposition of ammonium method (ammonium chloride volatile loss). Most commodity chromium oxide by sodium dichromate directly or indirectly obtained, its output accounts for about 20% of the consumption of sodium dichromate.
