Abstract:

Dolomite (CaCO₃·MgCO₃) is a widely-used raw material in metallurgy, building materials and chemical industry. Aiming at the problem of serious CO₂ emission during dolomite calcination, a new process of low-carbon calcined shaft kiln based on CO₂ cycle heat carrying and resource recovery was constructed. According to thermochemistry, Gibbs free energy change of CaCO₃·MgCO₃ decomposition in pure CO₂ environment is analyzed which shows that increase of temperature (50—100 K) is an efficient way to overcome the reaction depression by high CO₂ concentration. Thermogravimetric analysis of CaCO₃ decomposition in pure CO₂ atmosphere is conducted, which confirms the feasibility of dolomite calcining in high CO₂ concentration. The effect of CO₂ pressure (P_{\mathrm{C}{\mathrm{O}}_{\mathrm{2}}}) on CaCO₃·MgCO₃ decomposition is investigated. The heat transfer between gas and solid can be enhanced attributed to the high P_{\mathrm{C}{\mathrm{O}}_{\mathrm{2}}}, which therefore improve the dolomite calcination efficiency. Afterwards, thermal analysis of the dolomite calcination system with CO₂ loop is conducted, which turns out that the theoretical energy consumption is 140 kg/(t MgO), and more than 70% CO₂ emission would be reduced from the calcination process.

Key words: carbon dioxide, looping, dolomite, calcination, pyrolysis, reaction kinetics

摘要：

白云石是一种广泛应用的冶金、建材和化工原料。针对白云石煅烧过程中CO₂排放严重等问题，构建了基于CO₂循环载热与资源化回收的白云石低碳煅烧竖窑新工艺。通过白云石（CaCO₃·MgCO₃）煅烧过程的Gibbs自由能变计算，发现提高煅烧温度（50~100 K）可有效克服CO₂对反应的抑制作用；通过纯CO₂环境中CaCO₃分解过程的热重实验分析，验证了CO₂循环煅烧白云石煅烧的可行性；通过化学反应动力学计算，解析了全CO₂组分环境下CO₂压力对CaCO₃·MgCO₃高温分解过程的影响，并发现提高CO₂压力可促进气固传热，从而提升分解速率和改善矿料分解均匀性；对CO₂循环煅烧工艺系统能-质平衡计算表明：该工艺理论能耗仅为140 kg/(t 煅白)，且煅烧过程的CO₂排放降低70%以上，环境效益显著。

关键词: 二氧化碳, 循环, 白云石, 煅烧, 热解, 反应动力学