煤矸石提铝提硅废液制备免烧砖试验研究

Experimental research on free fired bricks preparation using waste liquid after extracting aluminum and silicon from coal gangue

为解决煤矸石提铝提硅高值化利用工艺过程潜在的废液问题,重点考察了将其作为原料用于制备免烧砖可能的消纳途径。研究分析了掺加提铝提硅废液对免烧砖主要性能指标——抗压强度、抗冻性和吸水性的影响,并采用SEM和XRD分析了提铝提硅废液对免烧砖上述性能指标产生影响的内在机制。研究结果表明,当煤矸石提铝提硅废液用于制备免烧砖时,掺加废液可导致免烧砖的抗压强度降低,当掺量为50%时,抗压强度为23.75 MPa,降低4.93 MPa;当掺量为100%时,抗压强度为21.34 MPa,降低7.34 MPa。原因为废液中盐离子向砖体表面渗出且在渗出过程中形成孔隙以及掺加废液后生成了硬度较小的无水石膏和方解石导致免烧砖密实度降低,从而导致抗压强度降低。抗冻性试验中,掺量为50%时,15次冻融循环后免烧砖的强度损失率为2.82%,质量损失率为0.35%;掺量为100%时,15次冻融循环后免烧砖的强度损失率为-28.12%,质量损失率为0.76%。基于废液的双重作用,在冻融过程中,100%废液掺量时其正面作用得以充分发挥,导致抗压强度不降反增。吸水性试验中,掺量为50%时,免烧砖浸泡24 h吸水率为28.29%;掺量为100%时,免烧砖浸泡24 h吸水率29.99%,掺加煤矸石提铝提硅废液会导致免烧砖吸水率升高。

In order to solve the potential problem of waste liquid produced in the process of extracting aluminum and silicon from coal gangue,the waste liquid is used as a raw material to prepare free fired bricks which is a promising way of treatment.The effects of adding the aluminum and silicon extraction waste liquid on the main performance indexes of free fired brick,such as compressive strength,frost resistance and water absorption were studied and analyzed;the interal mechanism of the influence of aluminum and silicon extraction waste liquid on the above parameters were explained by SEM and XRD analysis.The result shows that when the waste liquid of aluminum and silicon extraction from coal gangue is used to prepare unfired brick,the compressive strength of the brick can be reduced by adding waste liquid.The compressive strength of unfired brick is 23.75 MPa,reduced by 4.93 MPa when adding 50%waste liquid as a substitute of water,and the compressive strength is 21.34 MPa,reduced by 7.34 MPa when the content is 100%.The salt ions in the waste liquid seep to the brick surface and the pores are formed during this process.Moreover,softer anhydrite and calcite appear with the addition of waste liquid,which can lead to the decrease of compactness and compressive strength of free fired brick.In the frost resistance tests,when the content is 50%,the strength loss rate of the free fired brick after 15 freeze-thaw cycles is 2.82%,and the mass loss rate is 0.35%;when the content is 100%,the strength loss rate after 15 freeze-thaw cycles is-28.12%,and the mass loss rate is 0.76%.Based on the dual effects of waste liquid,the positive effect of 100%waste liquid is exerted completely in tests,resulting in the increase of compressive strength instead of decreasing.In the water absorption tests,when the content is 50%,the water absorption rate is 28.29%after soaking for 24 h;when the content is 100%,the water absorption rate of free fired brick is 29.99%after soaking for 24 h.The water absorption rate of free fired brick increases with the addition of waste liquid of aluminum and silicon extraction from coal gangue.