Research On Phase Transformation Law And Leaching Property Of Contained MgO Calcium Aluminate Slag

MgO is one of the impurities in calcium aluminate slag.20CaO·13Al2O3·3MgO·3SiO2(Q phase)will be formed by MgO with other phases.So the phase composition is changed,the alumina leaching and the self-disintergtating properties are deteriorated.In response to these problems,the phase formation law of 12CaO·7Al2O3(C12A7),Q phase and the phase composition in the slag,which contained MgO,was researched under high temperature in this paper.X-ray diffraction,Differential thermal analysis and other testing methods were used to reveal the effect mechanism of MgO on calcium aluminate slag equilibrium.Many methods were studied to improve the leaching propetities of slag and eliminate or reduce the negative effect of MgO on phase composition of the slag.Changing the material ratio,adding trace elements,and changing the sintering system were studied.The results show that:(1)The content of Q phase increased and the leaching ratio of alumina decreased with increasing of MgO,when C/A is 1.4,A/S is 1.3.MgO has impact on the self-disintegration property of the slag.which smelted at lower temperature.(2)The method of elevating the leaching temperature,increasing the concentration of sodium carbonate,reducing the particle size,extension the leaching time are beneficial to improve the alumina leaching ratio of Q phase.(3)The formation temperature of Q phase is about 1300? and the reaction equation is C2AS(C2S)+CA(CA2,C12A 7)+f-MgO?Q phase.(4)The leaching and formation kinetic parameters 'of Q phase is calculated by the liquid-solid,solid-solid reaction kinetics theory.(5)CaSO4 can improve the leachingc properties of calcium aluminate clinker containing MgO.The addition of CaSO4 plays a role in providing CaO and promoting the transformation of Q phase to C12A7 when the A/S is less than or equal to 2,the alumina leaching ratio can be reached to 91.34%.And when the A/S is 3,the addition of CaSO4 makes Q phase transform to C4A3S,the alumina leaching ratio of clinker is increased to 91.02%.Partial of Ca2+,which are exist in 2CaO·SiO2,are replaced by Na+to improve the ratio of calcium in the calcium aluminate slag,and the formation of C12A7 is promoted,the alumina leaching ratio can be reached to 100%.(6)Rapid sintering temperature system is conducive to improve the leacing ratio of calcium at the 1350?,when the C/A,A/S is lower and the slag containing MgO.