CCTEG Coal Mining Research Institute
Coal Mining and Design Branch, China Coal Research Institute
College of Engineering, Huazhong Agricultural University

高钙粉煤灰浆pH较高，直接用于煤矿井下防灭火易污染地下水。为研究CO2矿化利用粉煤灰制井下防灭火材料固碳降碱反应特性，选取陕北某煤电一体化企业粉煤灰为样品，通过XRF、XRD分析了粉煤灰组分及物相结构，利用N2和CO2的混合气模拟电厂烟气，开展了CO2矿化利用粉煤灰实验室小试及扩试试验，研究了粉煤灰固碳降碱反应过程中浆液pH变化规律及模拟烟气CO2体积分数、烟气流量、固液比、温度、搅拌方式等关键参数对矿化反应过程的影响，并从粉煤灰固碳降碱浆液特性、矿化反应装置研制等方面提出了井下规模化应用有待攻克的关键技术，研究结果表明：① 粉煤灰原样中富含Ca2+、Mg2+、K+、Al3+等碱金属元素，其中CaO质量分数高达17.8%；② CO2与粉煤灰中含Ca2+、Mg2+等碱性矿物产生矿化反应，反应后CO2以方解石型碳酸钙附着在粉煤灰球形颗粒表面，表明了高钙粉煤灰固碳降碱具有可行性；③ 矿化反应过程中，浆液pH下降呈“慢—快—慢”3个阶段，当粉煤灰浆液pH降至7.0～7.5后，浆液返碱pH不会超过9，满足煤矿井下粉煤灰防灭火材料要求；④ 确定了最优矿化反应参数为CO2体积分数10%～15%、固液比300 g/L、每升浆液的烟气流量1.0 L/min、温度不高于55 ℃；⑤ 综合考虑固碳量、降碱返碱速度以及反应规模等因素，提出了涡流式反应器与旋桨式反应器串并联两级耦合反应系统。

High calcium fly ash slurry has a high pH value, which is prone to contaminating groundwater when it is directly used for fire prevention and extinguishing in gob. To study the reaction characteristics of carbon fixation and alkali reduction in the production of underground fire extinguishing materials using fly ash by CO2 mineralization, the fly ash from a coal and electricity integrated enterprise in northern Shaanxi is used to analyze its composition and phase structure through XRF and XRD. At the same time, using a mixture of N2 and CO2, laboratory experiments on CO2 mineralization is conducted to analyze the variation law of pH value during the carbon fixation and alkali reduction reaction process of fly ash, and the influence of key parameters such as CO2 concentration, gas flow rate, solid-liquid ratio, temperature and stirring method on the mineralization reaction process. Also, the key technologies that need to be addressed for a large-scale underground application are proposed from the characteristics of fly ash carbon fixation and alkali reduction, development of mineralization reaction equipment, diffusion law of slurry in gob, and the entire preparation process. The research results indicate that fly ash is rich in alkali metal elements such as Ca2+, Mg2+, K+, Al3+, with CaO content of up to 17.8%, belonging to high calcium ash. CO2 can be reacted with Ca2+, Mg2+ in the fly ash and CO2 is attached to the surface of spherical particles of fly ash with calcium carbonate type after the reaction, indicating the feasibility of carbon sequestration and alkali reduction of high calcium fly ash. During the mineralization reaction process, the pH value of the slurry decreases in three stages: slow−fast−slow. When the pH value of the fly ash slurry drops to 7.0−7.5, the pH value return will not exceed 9, meeting the requirements for fire prevention and extinguishing materials for coal mine gob. The optimal mineralization reaction parameters are that CO2 concentration being of 10%−15%, solid-liquid ratio being of 300 g/L, gas flow rate being of 1.0 L/min per liter of slurry, and temperature being not higher than 55 ℃. Taking into account factors such as carbon sequestration, alkali reduction and return rate, and reaction scale, a two-stage coupled reaction system consisting of a vortex reactor and a propeller reactor is proposed.

国家重点研发计划资助项目(2022YFB4102100)；陕西省厅市联动重点资助项目(2022GD-TSLD-40)；天地科技开采设计事业部科技创新基金资助项目(KJ-2021-KCQN-03)

尹希文，于秋鸽，甘志超，等. 高钙粉煤灰固碳降碱反应特性及煤矿井下规模化利用新途径[J]. 煤炭学报，2023，48(7)：2717−2727.

YIN Xiwen，YU Qiuge，GAN Zhichao，et al. Reaction characteristics of carbon fixation and alkali reduction in high calcium fly ash and new way of large-scale utilization in coal mine[J]. Journal of China Coal Society，2023，48(7)：2717−2727.