Inhibitory effect of premixed feedstock on particle agglomeration in fluidized pyrolysis reaction of waste resin

doi:10.11949/0438-1157.20240072

Abstract

Abstract:

During the fluidized pyrolysis of radioactive waste resin, a novel approach involving the pre-mixing of kaolin and ceramic particles in the feedstock to inhibit particle agglomeration was proposed, and via a fluidized pyrolysis experimental apparatus, effects of kaolin addition amounts on fluidization and particle agglomeration were investigated by measuring the bed pressure drop and analyzing the products with XRD, SEM, and elemental analysis. The results indicate that a uniform coating layer forms on surfaces of ceramic particles after pre-mixing with kaolin. Notably, when the kaolin addition is larger than 0.20%(mass), it significantly inhibits particle agglomeration in the fluidized pyrolysis of waste resin, though the effect has a specific duration. Consequently, it is necessary to periodically reload the ceramic particles pre-mixed with kaolin to maintain the kaolin coating layer on the surface of the ceramic balls. When the kaolin premix addition amount is 0.20%(mass), the kaolin premix feed inhibits agglomeration for about 70 min. Compared to the situation in which kaolin and waste resin were fed simultaneously, pre-mixing feeding can achieve the same inhibition effect on particle agglomeration with a lower addition amount of kaolin, which is beneficial for the volume reduction treatment of radioactive waste resin.

Key words: radioactive waste resin, pyrolysis, fluidization, agglomeration, kaolin

摘要：

针对放射性废树脂流化裂解反应过程中颗粒团聚问题，提出了高岭土和陶瓷颗粒预混进料抑制颗粒团聚的新思路，在流化裂解实验装置中通过测量床层压降和对产物的XRD、SEM以及元素分析，考察预混时高岭土添加量对流化特性和颗粒团聚的影响规律。研究结果表明，高岭土与陶瓷球预混后可在陶瓷球颗粒表面形成均匀的涂覆层，当高岭土添加量≥0.20%(质量分数)时具有显著的抑制废树脂流化裂解反应中颗粒团聚的作用，但存在一定的作用时长，应定期补加预混高岭土的陶瓷球颗粒以维持陶瓷球表面的高岭土覆层，当高岭土预混添加量为0.20%(质量分数)时高岭土预混进料抑制团聚的作用时长约为70 min。与高岭土和废树脂共混进料相比，预混进料可在更低的高岭土添加量条件下达到颗粒团聚抑制效果，有利于放射性废树脂的减量化处理。

关键词: 放射性废树脂, 热解, 流态化, 团聚, 高岭土

CLC Number:

TL 941⁺.39

Zhengliang HUANG, Mingrui FENG, Qi SONG, Congjing REN, Yao YANG, Jingyuan SUN, Jingdai WANG, Yongrong YANG. Inhibitory effect of premixed feedstock on particle agglomeration in fluidized pyrolysis reaction of waste resin[J]. CIESC Journal, 2024, 75(9): 3094-3102.

黄正梁, 冯铭瑞, 宋琦, 任聪静, 杨遥, 孙婧元, 王靖岱, 阳永荣. 预混进料对废树脂流化裂解反应中颗粒团聚的抑制作用[J]. 化工学报, 2024, 75(9): 3094-3102.

Figures/Tables 12

Table 1 Physical properties of fluidized particles

流化颗粒	Geldart分类^[26]	颗粒密度ρ_p/ (kg/m³)	平均粒径d_p/mm
阳离子交换树脂	B	1475	0.5
氧化铝陶瓷球	B/D	3925	0.5
高岭土	C	2481	0.01

Fig.1 Fluidized pyrolysis experimental device

Fig.2 Morphologies of original Al2O3 particle (a) and particles after premixed with 0.04% (b), 0.20% (c) and 0.40% (d) kaolin

Fig.3 Effect of kaolin premixed amount on pressure drop before and after resin feeding (T=700℃, ug=0.8 m/s, H=45 mm)

Fig.4 Morphologies of particles premixed with 0.04% (mass) (a), 0.2% (b) and 0.4% (c) kaolin after reaction

Fig.5 Elements distribution in ceramic sphere particles premixed with 0.04% (mass) kaolinite: (a) within solid bridges of agglomerates； (b) on surface of dispersed particles

Table 2 Ash composition element contents at different locations in ceramic sphere particles premixed with 0.04% （mass） kaolin

灰分组成元素	聚团中固桥的元素组成/%(质量分数)	分散颗粒表面元素分布/%(质量分数)
O	49.56	50.12
Na	31.64	27.17
S	18.80	22.19
Si	0	0.51
C	0	0

Fig.6 XRD patterns of reaction product of resin and kaolin blended at a 1∶2 mass ratio

Fig.7 Variation of pressure drop at H=45 mm from fluidization of particles premixed with kaolin before and after resin feeding at 0.8 m/s in 700℃

Fig.8 Variation of average pressure drop and standard deviation of fluidized bed premixed with kaolin during reaction

Fig. 9 Morphologies of kaolin premixed particles after reaction by 10 times resin feeding

Fig.10 Relationship between kaolin to waste resin mass ratio and reaction time in reactor under different kaolin feeding methods

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