氮-碱耦合改性生物炭的制备及CO2吸附性能

Preparation and CO2 adsorption of nitrogen-alkali coupling modified biochar

摘要:

以酸枣木屑为原料，通过尿素改性得到氮改性酸枣木基生物炭，在此基础上进行KOH活化得到氮-碱耦合改性生物炭。通过正交实验考察耦合改性生物炭制备条件，包括活化温度、活化时间和浸渍KOH质量分数对其综合吸附性能（CO2动态吸附容量、再生特性和耐水性）的影响，并在模拟电厂烟气环境下（CO2体积分数15%，吸附压力0.1 MPa，吸附温度25 ℃，进气流速2.1 m/min）筛选出综合吸附性能最优的氮-碱耦合改性生物炭，对其进行SEM、XRD、FTIR和BET表征和探究不同吸附工况条件下（烟气温度、进气流速、CO2体积分数）的CO2动态吸附特性的变化规律。结果表明，在活化温度1073 K，活化时间1.5 h，浸渍KOH质量分数30%条件下制备的氮-碱耦合改性生物炭（SAC-1073-1.5-K30）综合吸附性能最优，其在模拟电厂烟气环境下的CO2动态吸附容量（4.17 mmol/g）、再生特性（96.6%）和耐水性（95.4%）均表现良好；SAC-1073-1.5-K30的CO2动态吸附容量与吸附温度、进气流速呈负相关，与CO2体积分数呈正相关。SAC-1073-1.5-K30的最佳吸附工况为：吸附温度25 ℃、进气流速8.4 m/min、CO2体积分数15%，此时其CO2动态吸附容量为3.59 mmol/g，穿透时间33.8 s。

Abstract:

Using sour jujube wood chips as raw materials, nitrogen-modified jujube wood based biochars were obtained through urea modification. Based on this, nitrogen alkali coupling modified biochars were successfully obtained through KOH activation. The influence of activation temperature, activation time, and impregnation KOH mass fraction on the comprehensive adsorption performance of coupled modified biochars was investigated through orthogonal experiments. The best performing coupled modified biochar was selected under a simulated power plant flue gas environment (15 vol% CO2, 0.1 MPa, 25 ℃, 2.1 m/min), and its CO2 dynamic adsorption characteristic was studied under varying operating conditions (flue gas temperature, inlet flow rate, and CO2 concentration). Current work indicates that the selected coupled modified biochar exhibited the highest CO2 dynamic adsorption capacity (4.17 mmol/g) under the simulated flue gas environment, with good regeneration characteristic(96.6%) and water resistance(95.4%). Furthermore, the CO2 dynamic adsorption capacity of the selected coupled modified biochar was found to be negatively correlated with adsorption temperature and inlet flow rate, and positively correlated with CO2 concentration. The optimal adsorption conditions identified were adsorption temperature of 25 ℃, intake flow rate of 8.4 m/min, and intake CO2 concentration of 15 vol%. The CO2 dynamic adsorption capacity is 3.59 mmol/g, and the penetration time is 33.8 s.