Effect of atmosphere on active performance of light-burned magnesium oxides from calcined magnesite in fluidized bed

doi:10.11949/0438-1157.20220428

Abstract

Abstract:

The light-burned products with different grades of magnesite are obtained by changing the concentrations of CO₂ and H₂O in a small fluidized bed. The physicochemical properties of the light-burned products are characterized by decomposition rate, iodine absorption value, XRD, BET and SEM. The effects of CO₂ and H₂O contents in the light-burned atmosphere on the activity of the products are studied. The results show that the activity of the product is determined by the microstructure when the raw material is completely decomposed. With the increase of CO₂ concentration, the iodine absorption value of light-burned products gradually decrease, the grain size gradually increase, and the surface structure changed from multiporous to less porous, indicating that the presence of CO₂ reduced the product activity. With the increase of H₂O concentration, the iodine absorption value of the light-burned products will gradually decrease, the specific surface area will decrease from large to small, and the surface structure will become dense and smooth from loose and porous. Under the same working conditions, the activity of light burning products of high grade magnesite is higher than that of low grade magnesite.

Key words: fluidized bed, magnesite, atmosphere, activity, light-burned

摘要：

利用实验室小型流化床装置，通过改变CO₂、H₂O浓度得到不同品位菱镁矿的轻烧产物，通过分解率、吸碘值、XRD、BET、SEM对轻烧产物的理化性质进行表征，研究了轻烧气氛中CO₂、H₂O含量对产物活性的影响。结果表明，在原料分解完全时，产物的活性由微观结构决定；增大CO₂浓度，轻烧产物的吸碘值逐渐降低，晶粒尺寸由小逐渐变大，表面结构由多孔变为少孔，说明CO₂的存在降低了产物活性；增大H₂O浓度，轻烧产物的吸碘值会逐渐降低，比表面积由大变小，表面结构由疏松多孔变得致密光滑，H₂O通过促进氧化镁的烧结来抑制产物的活性；相同工况下，高品位的菱镁矿轻烧产物活性高于低品位。

关键词: 流化床, 菱镁矿, 气氛, 活性, 轻烧

CLC Number:

TQ 026.7

Gang WANG, Zhihao XIA, Xiyan LI, Hong ZHANG, Zhennan HAN, Xingfei SONG, Guangwen XU. Effect of atmosphere on active performance of light-burned magnesium oxides from calcined magnesite in fluidized bed[J]. CIESC Journal, 2022, 73(8): 3699-3707.

王刚, 夏志豪, 李希艳, 张虹, 韩振南, 宋兴飞, 许光文. 不同气氛下流化床菱镁矿轻烧产物特性研究[J]. 化工学报, 2022, 73(8): 3699-3707.

Figures/Tables 13

Table 1 Chemical composition of two grade magnesite raw materials

Compositions	Mass fraction/%
Compositions	High grade	Low grade
MgO	43.65	38.31
SiO₂	2.92	7.89
CaO	1.50	1.62
Al₂O₃	0.29	0.94
Fe₂O₃	0.28	0.51
others	0.22	0.35
LOI	51.14	50.38

Fig.1 Schematic diagram of the fluidized bed

Fig.2 Thermogravimetric analysis of raw materials (a) and light-burned products (b) of magnesite

Fig.3 Iodine absorption value of light-burned products of magnesite in different CO2 atmosphere

Fig.4 Decomposition rate of light-burned products of magnesite in different CO2 atmosphere

Fig.5 XRD analysis of light-burned products of high grade (a) and low grade (b) magnesite in different CO2 atmosphere

Fig.6 Grain size and specific surface area of light-burned products of magnesite in different CO2 atmosphere

Fig.7 SEM images of magnesite light-burned products in different CO2 atmosphere (80000 times)

Fig.8 Iodine absorption value of light-burned products of magnesite in different H2O atmosphere

Fig.9 Decomposition rate of light-burned products of magnesite in different H2O atmosphere

Fig.10 XRD analysis of light-burned products of high grade (a) and low grade (b) magnesite in different H2O atmosphere

Fig.11 Specific surface area of light-burned products of different grades magnesite in different H2O atmosphere

Fig.12 SEM images of magnesite light-burned products in different H2Oatmosphere (80000 times)

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