菱镁矿输送床轻烧过程反应与产物微观结构特性

doi:10.11949/0438-1157.20200530

化工学报 ›› 2020, Vol. 71 ›› Issue (12): 5735-5744.DOI: 10.11949/0438-1157.20200530

菱镁矿输送床轻烧过程反应与产物微观结构特性

孙聪¹(),闫博威¹,蔡长庸¹,韩振南¹(),许光文^1,²()

^1.沈阳化工大学能源与化工产业技术研究院，资源化工与材料教育部重点实验室，辽宁沈阳 110142
^2.中国科学院过程工程研究所多项复杂系统国家重点实验室，北京 100190

收稿日期:2020-05-08 修回日期:2020-06-30 出版日期:2020-12-05 发布日期:2020-12-05
通讯作者: 韩振南,许光文
作者简介:孙聪(1994—)，男，硕士研究生，1187875448@qq.com
基金资助:
辽宁省教育厅重点项目(LZ2017001);国家自然科学基金项目(U1903130)

Characteristics of reaction and product microstructure during light calcination of magnesite in transport bed

SUN Cong¹(),YAN Bowei¹,CAI Changyong¹,HAN Zhennan¹(),XU Guangwen^1,²()

^1.Institute of Industrial Chemistry and Energy Technology, Laboratory on Resources Chemicals and Materials of Ministry of Education, Shenyang University of Chemical Technology, Shenyang 110142, Liaoning, China
^2.State Key Laboratory of Multi-phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China

Received:2020-05-08 Revised:2020-06-30 Online:2020-12-05 Published:2020-12-05
Contact: HAN Zhennan,XU Guangwen

摘要/Abstract

摘要：

利用高温烟气加热实验室规模输送床模拟菱镁矿闪速轻烧工业输送床反应器，建立基于热重分析计算菱镁矿中MgCO₃分解率方法，研究了煅烧条件和原料粒径对菱镁矿细粉输送床分解的转化率和产品活性的影响，揭示了煅烧过程中产物微观结构变化特性。菱镁矿粉（<150 μm）轻烧为秒级快速反应，仅需1~2 s菱镁矿中MgCO₃分解率即可达98%以上，验证了输送床闪速轻烧技术的可行性。输送床煅烧产物的柠檬酸显色时间17~55 s，活性显著高于固定床煅烧产物（显色时间294 s），且产物活性由菱镁矿分解率和微观结构共同决定；煅烧过程中产物MgO晶粒尺寸逐渐增大，表面结构由疏松多孔变为致密光滑，该结构变化可在数秒内完成。

关键词: 菱镁矿, 轻烧, 流态化, 活性, 微观结构

Abstract:

A gas-heating laboratory transport bed was adopted to simulate the industrial transportbed reactor for flash calcination of magnesite, and a method based on TG analysis of a reacted sample was further developed to calculate the decomposition rate or conversion of its containing MgCO₃. The study investigated how the conversion and product reactivity as well as microstructure vary with reaction conditions including temperature, particle size and times of re-calcination for powder magnesite. Magnesite powder (<150 μm) calcination is a quick reaction that reaches 98% decomposition of its containing MgCO₃ in 1—2 s,corroborating the feasibility of magnesite flash-calcination in transport bed reactors. The coloration time given by the citric acid chromogenic method was 17—55 s and 294 s for the obtained products from transport and fixed beds, respectively. This proves the obviously higher activity and thus improved microstructure of the product from transport bed. During the calcination process, the MgO grain size of the product gradually increases, and the surface structure changes from loose and porous to dense and smooth. This structural change can be completed within a few seconds.

Key words: magnesite, light calcination, fluidization, reactivity, microstructure

中图分类号:

TQ 026.7

孙聪,闫博威,蔡长庸,韩振南,许光文. 菱镁矿输送床轻烧过程反应与产物微观结构特性[J]. 化工学报, 2020, 71(12): 5735-5744.

SUN Cong,YAN Bowei,CAI Changyong,HAN Zhennan,XU Guangwen. Characteristics of reaction and product microstructure during light calcination of magnesite in transport bed[J]. CIESC Journal, 2020, 71(12): 5735-5744.

图/表 14

图1 菱镁矿原料XRD谱图

Fig.1 XRD patterns of magnesite

表1 菱镁矿原料化学组成

Table 1 Chemical compositions of magnesite

Composition	Content/%(mass)
MgO	46.12
SiO₂	0.58
Al₂O₃	1.27
CaO	0.53
MnO	0.01
Fe₂O₃	0.24
LOI^①	51.24

表2 菱镁矿马弗炉煅烧条件及产物性质

Table 2 Calcination conditions in muffle furnace and product property

Particle size/μm	Temperature/℃	Residence time /h	LOI/%(mass)	Coloration time/s
106~150	900	2	0.1	294

图2 气体加热输送床煅烧装置

Fig.2 Diagram of gas-heating transport bed calcinatory

图3 气体加热输送床反应器内温度分布

Fig.3 Temperature distribution of gas-heating transport bed reactor

表3 不同煅烧条件下输送床操作参数

Table 3 Operation parameters of transport bed under different calcination conditions

Case	Feeding rate of magnesite/ (kg/h)	Bottom temperature of calcinator /℃	Flow rate of propane/ (m³/h)	Flow rate of air / (m³/h)	Content of CO₂ in flue gas/ % (vol.)	Flow rate of flue gas/ (m³/h)	Gas velocity in calcinatory/ (m/s)	Residence time /s
Case 1	1.2	850	1.05	64.18	4.18	75.36	9.7—12.3	0.91
Case 2	1.2	900	1.13	68.74	4.32	78.4	10.5—13.5	0.84
Case 3	1.2	950	1.25	71.25	4.71	79.67	10.9—14.2	0.79
Case 4	1.2	1000	1.33	74.83	4.98	80.96	11.4—15.2	0.75

图4 菱镁矿原料和煅烧产物热重分析

Fig.4 TG analysis of magnesite and calcined product

图5 煅烧条件和原料粒径对菱镁矿分解率的影响

Fig.5 Influence of calcination conditions and particle size on decomposition ratio of magnesite

图6 不同煅烧条件下菱镁矿煅烧产物热重分析

Fig.6 TG analysis of calcined magnesite products under different calcination conditions

图7 煅烧条件对产物显色时间(a)和活性指数(b)的影响

Fig.7 Influence of calcination conditions on coloration time (a) and activity index (b) of products

图8 原料粒径对产物显色时间(a)和活性指数(b)的影响

Fig.8 Influence of particle size on coloration time (a) and activity index (b) of products

图9 菱镁矿煅烧产物XRD谱图

Fig.9 XRD patterns of calcined magnesite products

表4 煅烧产物XRD谱图半峰宽和MgO晶粒尺寸

Table 4 Half-peak width of peak at 2θ=42.9° in XRD pattern and grain size of MgO crystal

Number of calcination cycles	B^①	D^②/nm
1	0.81	10.5
2	0.72	12.3
3	0.64	13.3
4	0.63	13.8

图10 菱镁矿煅烧产物SEM图

Fig.10 SEM images of calcined magnesite products

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菱镁矿输送床轻烧过程反应与产物微观结构特性

Characteristics of reaction and product microstructure during light calcination of magnesite in transport bed

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