基于烧结机制的钙基吸收剂团聚体结构演变模拟

doi:10.19894/j.issn.1000-0518.230151

摘要/Abstract

摘要：

钙循环工艺是一种具有很大应用潜力的脱碳技术，但其吸收剂晶粒间的烧结现象会随循环而加剧，导致高活性介孔及相应碳捕集能力衰减。根据煅烧进程中钙基吸收剂表界面结构的形成与演变特性，构建了再生CaO孔隙通道的拓扑结构和分级团聚体烧结模型，引入了二面角的影响，探讨了不同烧结机制下钙基吸收剂的孔隙迁移规律，并进行实验验证。结果表明，再生CaO的烧结由表面-晶界-体积扩散联合控制；所建数学模型可揭示钙基吸收剂孔结构动态演变规律，900 ℃不同烧结时间下（300~600 s），粒径75~150 μm的吸收剂（孔径25~75 nm）的模拟计算结果与实验结果的孔体积变化率最大平均相对误差为16.50%，最可几孔径所对应的相对误差在6%内。相同烧结条件下，各粒级吸收剂（38~75、75~150、150~180 μm）的烧结颈生长出现明显的三段式生长，颈部生长率均呈前期快速增长、后期平缓趋势，且颗粒间的烧结会随吸收剂粒极的减小而加剧。

关键词: 氧化钙烧结, 孔径分布, 烧结机制, 数值模拟

Abstract:

Calcium cycling is a kind of decarbonization technology with great potential application， but the sintering phenomenon between the grains of the absorbers will be intensified with the cycling， resulting in the decay of mesopores and the carbon capture capacity. According to the formation and evolution characteristics of the surface and interface structures of calcium-based absorbent during calcination， the topological structure of regenerated CaO pore channels and the sintering model of hierarchical agglomerates are constructed. The influence of dihedral angle is introduced， and the pore migration rule of calcium-based absorbent under different sintering mechanisms is discussed and verified by experiments. The results show that the sintering of regenerated CaO is controlled by surface-boundary-volume diffusion. The mathematical model reveals the dynamic evolution of pore structures of calcium-based absorbers. The maximum average relative error of absorbers with diameters of 75~150 μm （pore diameters of 25~75 nm） between simulation and experimental results at 900 ℃ and different sintering time （300~600 s） is 16.50%. The relative error corresponding to the maximum aperture is within 6%. Under the same sintering conditions， the neck growth of each particle grade （38~75， 75~150， 150~180 μm） shows obvious three-stage growth， and the neck growth rate shows a rapid growth in the early stage and a gradual trend in the late stage， and the sintering between particles would intensify with the decrease of the particle pole of the absorber.

Key words: Calcium oxide sintering, Pore size distribution, Sintering mechanism, Numerical simulation

中图分类号:

O649.1

纪杰, 李明春, 沈存粮, 杨鑫. 基于烧结机制的钙基吸收剂团聚体结构演变模拟[J]. 应用化学, 2023, 40(12): 1726-1736.

Jie JI, Ming-Chun LI, Cun-Liang SHEN, Xin YANG. Simulation of Aggregate Structure Evolution of Calcium-Based Absorbent Based on Sintering Mechanism[J]. Chinese Journal of Applied Chemistry, 2023, 40(12): 1726-1736.

图/表 11

图1 烧结物理模型A.Primary aggregates； B.Secondary aggregates； C.Tertiary aggregates

Fig.1 Sintering physical model

图2 双球几何模型A.Two-sphere model with constant center distance； B.Two-sphere model with shortened center distance； C.Diagram of dihedral angle

Fig.2 Double sphere geometric model

图3 初始堆积阶段孔隙及孔隙剖面图A.Face diagonal hole； B.Face angular section； C.Body diagonal face； D.Body diagonal face section

Fig.3 Pores and pore sections in the initial accumulation stage

表1 烧结模型中的计算参数

Table 1 Calculation parameters in sintering model

Parameter	D_s/（cm²·s^-1）^［35］	D_v/（cm²·s^-1）^［35］	$γ s$ /（cm²·s^-1）^［27］	Ω/cm^{3 ［36］}	ψ/（°）	k/（J·K^-1）
Value	8.5×10^-11	1.667×10^-15	1.5×10^-4	1.72×10^-23	5π/6~π	1.38×10^-23

表1 烧结模型中的计算参数

Table 1 Calculation parameters in sintering model

Parameter	D_s/（cm²·s^-1）^［35］	D_v/（cm²·s^-1）^［35］	$γ s$ /（cm²·s^-1）^［27］	Ω/cm^{3 ［36］}	ψ/（°）	k/（J·K^-1）
Value	8.5×10^-11	1.667×10^-15	1.5×10^-4	1.72×10^-23	5π/6~π	1.38×10^-23

图4 钙基吸收剂扫描电子显微镜图及孔结构演变的模型计算结果与实验测量结果分布图A.SEM image of calcium-based absorber sintered for 180 s； B. SEM image of calcium-based absorber sintered for 300 s； C.SEM image of calcium-based absorber sintered for 600 s； D.Comparison of pore size distribution at 180 s of sintering； E.Comparison of pore size distribution at 300 s of sintering； F.Comparison of pore size distribution at 600 s of sintering

Fig.4 Scanning electron microscope and model calculation and experimental measurement of pore structure evolution of calcium-based absorber

图5 不同粒级钙基吸收剂颈部生长变化曲线

Fig.5 ?Neck growth curve of different size calcium-based absorbents

表2 不同粒级吸收剂不同时间段烧结颈生长率

Table 2 Sintering neck growth rate of different particle size sorbents at different time periods

Time/s

r_j·r^-1 （38~75 μm）/%

r_j·r^-1 （75~150 μm）/%

r_j·r^-1 （150~180 μm）/%

300

600

33.81

45.24

50.30

25.66

34.98

39.09

20.55

28.55

31.93

图6 （A） 38~75 μm和（B） 75~150 μm粒级钙基吸收剂不同烧结机制控制下烧结300 s孔结构演变的模型计算结果与实验测量结果

Fig.6 Model calculation results and experimental measurement results of structural evolution of sintered for 300 s pore under the control of different sintering mechanisms of calcium absorbers with different particle sizes of （A） 38~75 μm and （B） 75~150 μm

图7 （A） 38~75 μm和（B）75~150 μm粒级钙基吸收剂不同烧结机制控制下烧结600 s孔结构演变的模型计算结果与实验测量结果

Fig.7 Model calculation results and experimental measurement results of structural evolution of sintered 600 s pore under the control of different sintering mechanisms of calcium absorbers with different particle sizes of （A） 38~75 μm and （B） 75~150 μm

图8 不同粒级钙基吸收剂体孔（A）和面孔（B）收缩率变化曲线

Fig.8 Variation curve of pore （A） and face （B） shrinkage rate of calcium based absorbers with different particle sizes

图9 不同粒级钙基吸收剂通道体孔通道（A）和面孔增长率（B）变化曲线

Fig.9 Variation curve of channel body pore channel （A） and face growth rate （B） of calcium absorbent with different particle sizes

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