Quantitative Analysis Of The Iron Valence State In Magnesia-Iron-Alumina System

Because of the excellent performance,magnesium chromes brick has been widely used in the burning zone of cement rotary kilns. While there is some Cr6+ produced in the material which causes serious pollution to the environment and leading to be replaced gradually. Magnesia-hercynite brick becomes the most promising substitutes of the magnesia chrome brick due to its excellent performance of forming a coating, thermal shock resistance, structure flexibility and physical properties. However there is some transformation existed between Fe3+ and Fe2+ in the magnesia-hercynite brick when it is being used in the kilns, which leads to the volume expansion or contraction of the brick structure and influences the elevate temperature properties, such as the shelling-out of bricks. Currently, the main raw materials of preparing magnesia-hercynite are hercynite and magnesia-iron clinker, which have different iron valence state and correspond distribution in the brick, leading markedly difference of the elevate temperature performance between the products. So it is essential to take quantitative analysis for the iron valence state such as iron, Fe2+ and Fe3+, and the analysis method also is an important measure to evaluate the properties of magnesia –hercynite material and the raw material of iron supporter. In this work, we found a suitable experiment method on quantitative analysis for the iron valence state in magnesia-iron–alumina system, referring to the theory of quantitative analysis for iron valence state in the iron ore. Through the study of testing iron valence state in hercynite and magnesia-iron clinker respectively, analyzing the data and verification testing we conclude the following conclusions:1. Through the decomposition of potassium dichromate by ferric chloride, the optimum experiment conditions of quantitative analysis for the iron in magnesia-iron–alumina system are : mass of the hercynite and magnesia-iron clinker is 0.1g and 0.2g respectively, the sample size is 270 mesh, and the concentration of the ferric chloride is 50g/L, using 15 ml parathion mixture to acidize, shocking 30 minutes,then using rapid qualitative filter pape to filt.2. Through the potassium dichromate volumetric method, the optimum experiment conditions of quantitative analysis for the ferrous oxide in magnesia-iron–alumina system are:the mass of hercynite sample is 0.1g, the sample size is 150 mesh, the mass of sodium bicarbonate is 0.5g, the amount of concentrated hydrochloric acid and concentrated sulfuric acid used is 30 ml and 5ml respectively. The mass of magnesia-iron clinker sample is 0.1g, the sample size is 150 mesh, the mass of sodium bicarbonate is 0.5g, the amount of concentrated hydrochloric acid and concentrated sulfuric acid used is 25 ml and 5ml respectively.3. The results show that there are 8.00 percent of iron, 30.79 percent of ferrous oxide and 1.23 percent of ferric oxide in the hercynite sample. And there are 0.50 percent of iron, 3.17 percent of ferrous oxide and 0.54 percent of ferric oxide in the magnesia-iron clinker sample.