Research On Composition,Structure And Properties Of Lightweight Periclase-spinel Refractories

The main disadvantages of magnesia-spinel refractories for burning zone of cement rotary kiln are poor kiln coating adherence,high thermal conductivity coefficient and high density.Under the condition of ensuring high cement clinker resistance and good kiln coating adherence,the lightweight design on magnesia-spinel refractory by replacing dense magnesia aggaregate with porous aggaregates is an effective way tosolve the above problems.Three research works including“Investigation on the reaction simulation of cement clinker and magnesia-spinel refractories”,“Investigation on the pore forming mechanism of porous MgO-Al₂O₃ aggaregates”and“Investigation on the cement clinker resistance and adherence performance of lightweight magnesia-spinel refractories”,were investigated in the present project.The main results are as follows:?1?The investigation on the reaction simulation of cement clinker and magnesia-spinel refractories indicates that:comparing with magnesia,spinel are more likely to react with cement clinker to generate liquid phase;in the process of penetration,the penetrated liquid phase can continue to react with spinel,and the viscosity of the penetrated liquid phase incerases;when the cycle reaction time is more than 30 times,the concentrations of the compositions in the penetrated liquid phase become near saturated to spinel.?2?The investigation on the pore forming mechanism of porous MgO-Al₂O₃ceramics finds that:the porous MgO-Al₂O₃ ceramics with different phase composition,apparent porosity,median pore size and pore size distribution were prepared from magnesite and Al?OH?₃ through an in-situ decomposition pore-forming technique;and the effects of sintering temperature,raw material ratio,Al?OH?₃ particle size and TiO₂ addition on the phase composition and pore structure parameters of porous MgO-Al₂O₃ ceramics were investigated.Based on the analysis of the particle packing behavior and decomposition of the raw materials,the spinel formation and the reaction sintering process,the pore forming mechanism are proposed,and the technology controlling micro-sized pore structure of MgO-Al₂O₃ ceramics are formed.?3?The investigation on the cement clinker resistance and adherence performance of lightweight magnesia-spinel refractories finds that:the pore structure of aggaregate,the spinel content of aggaregate,the spinel particle size in aggaregate and the composition and microstructure of matrix strongly affect the cement clinker resistance and kiln coating adherence of lightweight refractories;when the lightweight magnesia-spinel refractories contact with cement clinker,spinel reacts with cemen clinker to form liquid phase,the formation of appropriate liquid phase can improve the cement clinker resistance and kiln coating adherence of lightwight magnesia-spinel refractory;when the content of spinel in aggregate is more than 50wt%,the lightwight magnesia-spinel refractory are seriously damaged;When the spinel contents of porous aggaregate and matrix both are 25wt%,the lightweight refractory has the best comprehensive performance.And smaller pore size and smaller spinel particle size are conducive to improve the cement clinker resistance and kiln coating adherence of lightwight magnesia-spinel refractories;the amount,viscosity and distribution of the liquid phases at interface of refractory and cement clinker are the key factors to infulence kiln coating adherence,the“glass bolt”formed by glass phase connects the cement clinker and refractory,making the cement clinker adhere to refractories.On the basis of the above investigation,the cement clinker corrosion and penetration mechnism are revealed,the correlations between the glass phase formation and kiln coating adherence are established,and the technologies optimizing the phase composition and microstructure of lightweight magnesia-spinel refractory are formed.