The Study Of Coal Slag On Corrosion Behavior Of Magnesia Alumina Spinel Refractories

The lining of the coal water slurry gasifier is a high chromium brick with a Cr₂O₃ content of more than 85%.However,the high chromium brick will affect the environment,so it is imperative to study the low chromization and non chromization of the lining material of the coal slurry gasifier.Magnesia alumina spinel refractories in cement kiln,refining furnace RH immersion tube multiple high temperature parts instead of chrome brick,it is a potential material to realize chrome free gasification furnace.So this paper chose magnesia aluminum spinel as a substitute for high chromium brick,and studied the erosion behavior of coal slag to magnesia aluminum spinel.In this paper,the static crucible method is used to study the erosion mechanism of coal slag to magnesia alumina spinel material,and the physical properties of different aluminum content spinel and the erosion and penetration resistance of coal slag are compared.Then,based on the best al rich spinel,adding different contents of ZrO₂,Cr₂O₃ and hercynite as additives,their corrosion resistance to coal slag is analyzed.The results are as follows:?1?The erosion mechanism of coal slag on magnesia alumina spinel material is studied.The results show that the coal slag is filled into the matrix of magnesia alumina spinel with complex silicate liquid phase,and the spinel particles of magnesium and aluminum retain their original morphology without dissolution.The erosion mode of coal slag to magnesia alumina spinel is mainly infiltration.After the erosion of coal slag,magnesia alumina spinel is loose,and cracks appear in the erosion layer,indicating that magnesium aluminum spinel is resistant to high temperature coal slag.In the osmosis layer,the elements of Si,Ca and Na are mainly distributed in the matrix,and the Fe elements will spread to the spinel particles,forming a magnesium iron aluminum composite spinel.?2?Study on the anti erosion properties,spinel materials with different aluminum content of coal slag.The results showed that the matrix of alumina rich spinel can be seen in the more obvious signs of chemical reaction,slag and matrix material after reaction to form a dense layer,to a certain extent,prevent the slag penetration to.Magnesia alumina spinel and magnesia rich spinel materials are corroded by molten slag,and their slag is all infiltrated into the material.The structure of the permeable layer is loose,and the chemical reaction with slag is not obvious.The erosion mechanism is mainly permeation.The physical properties of the aluminum rich spinel and the permeability of the coal slag are the best.?3?The influence of the amount of Zr O₂ on the magnesia alumina spinel was studied,the results show that:The addition of ZrO₂ can promote the sintering of samples at room temperature,the compressive strength of the material have been greatly improved,and anti permeability of spinel materials can be improved significantly,the reason is that ZrO₂ can absorb CaO in the slag,forming high melting point CaZrO₃ solid phase,the porosity and crack in the matrix will be blocked,thereby preventing the penetration of coal slag,the erosion of CaO to magnesia alumina spinel was also reduced.?4?The effect of Cr₂O₃ addition on magnesia alumina spinel was studied,the results show that the addition of Cr₂O₃ can form a?Al,Cr?₂O₃ solid solution with Al₂O₃,so that the physical properties of the material have been greatly improved.After the addition of Cr₂O₃,the magnesia alumina spinel material is changed by the coal slag erosion,which is mainly changed from the original osmosis erosion to chemical dissolution.The addition of Cr₂O₃ can enhance the absorption ability of FeO matrix material,composite spinel formation,delaying the coal slag inward penetration.The addition of Cr₂O₃ can improve the permeability of the material,and the higher the content of Cr₂O₃,the better the corrosion resistance of the material.?5?The effect of the addition of ferric aluminum spinel on the magnesia alumina spinel material was studied,the results show that the addition of iron and aluminum spinel,spinel and can form magnesium aluminum spinel solid solution,so as to improve the physical properties of materials,but adding too much will make the material micro cracks increased,the physical properties of materials decreased.After adding iron and aluminum spinel,the erosion mode of the coal slag to the material is infiltration erosion and reaction erosion.The CaO in the coal slag reacts with the iron-aluminum spinel,producing a high viscosity C₄AF,which prevents the further infiltration of the slag.At the same time,the precipitation of CaO increased the Si O₂content in the slag,and the slag became thicker and inhibited the penetration ability of the coal slag.When the content of Fe Al spinel was 3%,the comprehensive properties of the material were the best.?6?Comparison of magnesia alumina spinel refractories and high chrome brick corrosion penetration ability,the results show that the coal slag,the damage mechanism of magnesia alumina spinel refractories and high chrome brick is not the same,adding 3%ZrO₂ and spinel 6%Cr₂O₃ doped sample with high chrome brick is anti corrosion and penetration ability.