粉煤灰提铝硅钙渣矿化固定CO2

CO2 Sequestration by Mineralization of Silica Calcium Slag Generated in Process of Extracting Alumina from Fly Ash

矿化是CO2减排和资源化利用非常重要的途径,而粉煤灰提铝后的硅钙渣因碱性物质含量高可以用作矿化原料。本文采用pH值在线测试方法,分别对硅钙渣水解、矿化速率进行监测。采用XRF、XRD、FT-IR、SEM-EDS和TGA分析测试手段,分别对原料及水解、矿化产物的化学组成、矿物组成、特征官能团、微观形貌特性和热失重特性进行了表征。结果表明,在温度为55℃,固液比为1∶10,搅拌速率为300 r/min的条件下,硅钙渣水解后pH值达到10.91。待pH值稳定5 min后,以1.2 L/min的流量通入CO2,矿化反应于850 s内完成。矿化反应后的固相产物为CaCO3、C-S-H,液相产物为CaCO3、Na2CO3及C-S-H。所生成的CaCO3全部为方解石型,未见其它晶型生成。在常压、反应温度为55℃,未加任何化学试剂的低成本条件下实现了硅钙渣矿化固定CO2。硅钙渣的固碳率为9.25%,即92.5 kg CO2/t硅钙渣。

Mineralization is a very important way for CO2 emission reduction and resource utilization.The silica calcium slag generated in process of extracting alumina from fly ash can be used as mineralization raw material due to its high content of alkaline substances.In this paper,the rates of hydrolysis and mineralization reaction were investigated by testing the pH value during the reaction process.The characteristic of the raw material and mineralization products were characterized by XRD,XRF,FT-IR,SEM-EDS,TGA.The results indicate that under the conditions of temperature of 55℃,solid-liquid ratio of 1∶10 and stirring rate of 300 r/min,the pH value of silica calcium slag after hydrolysis reaches 10.91.After pH value stays stable for 5 min,CO2 is injected at a flow rate of 1.2 L/min,and the mineralization reaction is completed within 850 s.The solid phase products after mineralization are CaCO3 and C-S-H,the liquid phase products are CaCO3,Na2CO3 and C-S-H.The CaCO3 is calcite,and no other crystal types are observed.Mineralization of silica calcium slag for CO2 sequestration is realized under 55℃at atmosphere without any additives.The mineralization efficiency of silica calcium slag is 9.25%,that is,92.5 kg CO2/t silica calcium slag.