菱镁矿浮选精矿流态化煅烧制备高活性MgO试验研究

轻烧MgO是重要的化工原料，随着资源高效利用要求的提高，粉状菱镁矿煅烧制备MgO工艺逐渐受到重视。高效传热传质流化床是粉体煅烧最为理想的反应器之一。以辽宁菱镁矿浮选精矿为研究对象，开展流态化煅烧基础试验研究，通过XRD物相分析、柠檬酸法活性测试及SEM分析，讨论了2种粒级样（120~200目和200~300目）在不同煅烧温度、煅烧时间下的物相变化、微观形貌及产品MgO活性。结果表明：①对于120~200目样，随着煅烧温度的升高和煅烧时间的延长，MgO含量增加，MgO的衍射峰逐渐变窄变强；200~300目样的物相转变规律与120~200目基本一致，粒度对分解过程影响较小。②120~200目和200~300目样适宜的煅烧条件分别为800 ℃下煅烧10 min和850 ℃下煅烧5 min，此时煅烧产物MgO活性最高，柠檬酸显色时间分别为38 s、21.5 s。2种粒级的适宜煅烧工艺差别较大，工业中需控制不同粒级物料的煅烧停留时间，避免过烧和欠烧。③粒度对分解过程影响较小，但对晶粒生长影响较大，进而影响MgO活性。相比120~200目试样，200~300目粒度细，传热传质效率更高，同时表面吸附CO2能力强、晶格缺陷少、晶粒生长速度相对快，因此活性转折点发生相对早。

Experimental Study on Preparation of High Activity MgO by Fluidized Calcination with Magnesite Flotation Concentrate

Light burned MgO is an important chemical raw material. With the increase of the requirements for high-efficient utilization of resources， the process of preparing MgO by calcination of powdered magnesite gradually received attention. Fluidized bed with high efficiency heat and mass transfer is one of the most ideal reactors for powder calcination. Magnesite flotation concentrate in Liaoning were regarded as the research object， and the basic experimental study of fluidized calcination was carried out. Through XRD phase analysis， citric acid activity test and SEM analysis， the phase change， microscopic morphology and MgO activity of two kinds of samples (120~200 mesh and 200~300 mesh) under different calcined temperature and time were discussed. The results showed that: ① With the increase of calcination temperature and the extension of calcined time， the contents of MgO increases and the diffraction peak of MgO becomes narrower and stronger. The phase transition law of samples with granularity between 200 and 300 mesh is basically the same as that of the samples with granularity between 120 and 200 mesh. The particle size has little effect on the decomposition process. ② The suitable calcination conditions of samples with granularity between 120 and 200 mesh， and 200 and 300 mesh are calcined at 800 ℃ for 10 min and 850 ℃ for 5 min， respectively. At this time， the calcined product MgO activity is the highest， and the citric acid color development time is 38 s and 21.5 s， respectively. There is a great difference between the two kinds for suitable calcination processes. In the industry， the residence time of calcined materials with different particle sizes should be controlled to avoid overburning and underburning. ③ Particle size has little effect on the decomposition process， but has a great effect on the grain growth， thus affects the MgO activity. Compared with the samples with granularity between 120 and 200 mesh， the samples with granularity between 200 and 300 mesh has finer particle size， higher heat and mass transfer efficiency， stronger CO2 adsorption capacity on the surface， less lattice defects， and relatively fast grain growth rate， so the turning point of activity appeared earlier.