高循环性能钙基吸收剂用于烟气CO2捕集与联合水泥生产的基础研究

As the largest carbon emitter in the world, China is facing not only the stringent emission reduction goal (peaking by 2030) but also the challenge of safe treatment for hundred million tons of Ca-and-Si-rich industrial wastes. Carbon Capture & Storage (CCS) is thus becoming a hot research area. CaO-based sorbents capture CO2 from flue gas via carbonation reactions, and release pure CO2 that is to be utilized or geologically stored; meanwhile, the sorbents are regenerated and to be reused. Ca-based CCS technology is efficient, cheap and friendly to the environment; furthermore, all the wastes generated from CCS could be reutilized for cement manufacture. A recycling industrial chain with central CCS could thus be expected. The technology, however, suffers from the rapid deactivation of sorbents due to sintering of CaO. This will greatly increase the consumption of materials and energy and accordingly the total costs. Conventionally, refractory particles are dispersed among CaO to mitigate sintering through steric hindrance. Unfortunately, this “static” effect appears very weak especially under severe industrial operating conditions. The applicant, for the first time, develops “dynamic” stabilizer, dicalcium silicate (Ca2SiO4), one of the major components of cement, which will present polymorphic transmission owing to temperature changes resulting in obvious volume expansion. The consequent strong shear force is expected to break down the densified particles and regenerate the porous structure of sorbents. This is called “self-reactivation”. Based on this new mechanism, this project will abstract polymorphic materials to produce highly stable Ca-based CO2 sorbents, and further investigate into the feasibility of reusing the sorbent wastes to make high-quality eco-cement.

我国作为世界碳排放第一的大国，面临着2030年达到峰值的减排要求，以及年产上亿吨高硅钙工业废渣的处置压力。二氧化碳捕集与封存近年来成为研究热点。氧化钙基吸收剂通过碳酸化反应捕集烟气中的CO2，高温下释放加以利用或封存，而氧化钙可循环使用。该技术高效、廉价、环境友好，且吸收剂废物可回收制造水泥，实现循环产业链和集中碳减排。然而，高温下氧化钙容易烧结失活，极大地抬高了材料和运营成本。传统的做法是添加高熔点耐火材料颗粒，通过空间效应减缓烧结。但这种“静态”的阻挡作用在工业的苛刻条件下效果微弱。本课题首次提出以多晶态硅酸二钙（水泥组分之一）作为稳定剂，利用其变温过程中的晶型转变引发体积膨胀，强大的应力使氧化钙趋向闭合的孔结构得以恢复，实现“动态”的“自激活”效应。本项目要在这一新理论基础上寻求从高硅钙工业废渣中获得多晶态材料，制备高循环性能钙基吸收剂，并探索其废弃后生产高品质生态水泥的可行性。

我国作为世界碳排放第一的大国，面临着2030年达到峰值的减排要求，以及年产上亿吨高硅钙工业废渣的处置压力。二氧化碳捕集与封存近年来成为研究热点。氧化钙基吸收剂通过碳酸化反应捕集烟气中的CO2，高温下释放加以利用或封存，而氧化钙可循环使用。该技术高效、廉价、环境友好，且吸收剂废物可回收制造水泥，实现循环产业链和集中碳减排。然而，高温下氧化钙容易烧结失活，极大地抬高了材料和运营成本。传统的做法是添加高熔点耐火材料颗粒，通过空间效应减缓烧结。但这种“静态”的阻挡作用在工业的苛刻条件下效果微弱。本课题首次提出以多晶态硅酸二钙（水泥组分之一）作为稳定剂，利用其变温过程中的晶型转变引发体积膨胀，强大的应力使氧化钙趋向闭合的孔结构得以恢复，实现“动态”的“自激活”效应。本项目在这一新理论基础上从工业废渣粉煤灰中提取多晶态稳定剂硅酸二钙，制备高循环性能钙基吸收剂，研究了在工业CO2捕集条件下硅酸二钙的相变体积效应抵抗烧结失活的机制。钙基吸收剂应用于生物质热解原位吸附提升H2产量是实现减排的另一有效途径，本项目首次制备了硅酸二钙稳定的复合功能材料，研究了它的催化吸附作用与机理。研究发现，多晶态稳定剂在苛刻条件下稳定化作用未达预期，因此本项目开发了替代稳定剂稳定的钙基吸收剂，包括Ca9Al6O18、CaZrO3，另外研究了部分碱性吸收剂的CO2吸收能力和作用机理，包括MgO、Na2ZrO3。为了提升钙基吸收剂的循环稳定性，需要向吸收剂引入稳定剂，而如果利用工业废渣制备吸收剂，也将引入其他组分，因此有必要研究引入的稳定剂或其他组分对水泥熟料性能的影响。本项目利用CaZrO3稳定的钙基吸收剂生产水泥熟料，发现引入少量的CaZrO3不会对水泥熟料的主要物相硅酸三钙的生成和含量产生明显影响，证明了废弃后钙基吸收剂生产高品质生态水泥的可行性。