活性氧化镁的制备及其对煤的黏结作用

Preparation of active magnesium oxide and its bonding effect on coal

通过煅烧菱镁矿制备活性氧化镁,并与粉煤混合成型。利用水合法测定氧化镁的活性,采用N_2吸附仪、X射线衍射仪（XRD）和扫描电镜（SEM）等设备表征氧化镁的结构与形貌;通过机械强度值表征氧化镁对粉煤的黏结效果,采用XRD和SEM等手段研究其黏结机理。结果表明：随着煅烧温度的升高（500~900℃）、煅烧时间的延长（0.5~2.5 h）,所制氧化镁的活性均呈现出先升高后降低的趋势。菱镁矿在700℃下煅烧1.5 h后,氧化镁大量生成且结晶度不高,比表面积最大,活性最高。氧化镁的活性决定其对煤粒的黏结效果,活性越高,形成的稳定水化物越多,对煤粒的黏结作用越强,相应型块的机械强度越高（最大值超过500 N/块,约30 MPa）。

Active magnesium oxide was prepared by the calcination of magnesite,and then used as binder for coal bri-quetting. The activity,specific surface area,crystal structure and morphology of as-prepared magnesium oxide wereevaluated by N_2 adsorption,scanning electron microscope（SEM） and X-ray diffraction（XRD）. The bonding effect ofmagnesium oxide hydrates on coal and corresponding mechanism were studied by briquette compressive strength test,XRD and SEM. The results show that the activity of magnesium oxide increases and then decreases with the increase ofthe calcination temperature（from 500 to 900 ℃） and calcination time（from 0. 5 to 2. 5 h）. The optimal calcinationconditions are as follows：temperature of 700 ℃,time of 1. 5 h,therefore,the resultant magnesium oxide possesses alower crystallinity,largest surface area and highest activity among all the samples prepared. The activity of magnesiumoxide is the key factor to determine its bonding effect on coal particles. The magnesium oxide with higher activity mayconvert to more stable hydrate,and the corresponding briquette exhibit a higher compressive strength（ higher than30 MPa）.