含导流板喷雾流化床内颗粒包覆过程热质传递特性模拟研究

doi:10.11949/0438-1157.20251005

摘要/Abstract

摘要：

喷雾流化床湿法造粒技术通过动态流化与雾化喷涂的协同作用，已成为制药、食品及化工领域颗粒功能化制造的核心技术之一。然而，颗粒包覆过程涉及到复杂的气液固三相耦合过程，进而难以实现造粒过程的精确控制。因此，以离散单元模型为基础，耦合液滴运动和蒸发模型、液滴与颗粒碰撞模型以及液桥力模型，发展了适用于描述喷雾流化床内颗粒包覆过程的“气体-液滴-颗粒”拟三相数学模型。在该模型基础上研究了不同导流板结构对颗粒流动、传热传质特性以及颗粒包覆机制的影响。研究发现，在本文工况内，合适的导流板间距、提高导流板长度和降低导流板高度，能够加快颗粒进入喷泉区，延长喷泉区的停留时间，进而改善床层颗粒流化状态，优化颗粒循环路径，有效提高颗粒包覆比例和颗粒生长均匀性，减少喷动区的过度包覆现象。

关键词: 流化床, 多相流, 数值模拟, 导流板, 喷雾造粒, 热质传递

Abstract:

Spray fluidized bed wet granulation, combining dynamic fluidization with atomized spraying, is widely used for functional particle manufacturing in pharmaceuticals, food, and chemicals. However, the coating growth process involves complex gas–liquid–solid coupling, making precise control challenging. To address this, a quasi-three-phase "gas–droplet–particle" mathematical model was developed based on the discrete element method, incorporating a droplet motion and evaporation model, a droplet–particle collision model, and a liquid bridge force model, to describe the particle coating growth process in a spray fluidized bed. On this modeling basis, the effects of different draft plate configurations on particle flow, heat and mass transfer characteristics, and particle growth mechanisms were investigated. Under the investigated operating conditions, it was found that optimizing draft plate spacing, increasing plate length, and reducing plate height promote faster particle entry into the fountain zone and extend their residence time therein. These adjustments improve the overall fluidization state of the bed, enhance particle circulation trajectories, and effectively increase both the coating ratio and growth uniformity of particles, while mitigating excessive coating in the spouted zone.

Key words: fluidized bed, multiphase flow, numerical simulation, draft plate, spray granulation, heat and mass transfer

中图分类号:

TQ051.13

邓爱明, 何玉荣, 唐天琪. 含导流板喷雾流化床内颗粒包覆过程热质传递特性模拟研究[J]. 化工学报, DOI: 10.11949/0438-1157.20251005.

Aiming DENG, Yurong HE, Tianqi TANG. Numerical study on heat and mass transfer characteristics of particle coating in a spray fluidized bed with draft plates[J]. CIESC Journal, DOI: 10.11949/0438-1157.20251005.

图/表 12

图1 液滴碰撞结果示意图[33]

Fig. 1 Schematic diagram of droplet collision outcomes [33]

表1 二元液滴不同碰撞结果的判定准则［35-36］

Table 1 Criteria for different outcomes of binary droplet collisions ［35-36］

判别准则	公式	文献
聚合（I）	$I ≤ - 0.36 W e + 0.9$	[35]
反弹（Ⅱ）	$W e < Δ (1 + Δ 2) (4 Φ' - 12) χ 1 (c o s (a r c s i n I)) 2$ ， $χ 1 = 1 - (2 - τ) 2 (1 + τ) 4 τ > 1 χ 1 = τ 2 (3 - τ) 4 τ ≤ 1$ $Φ' = 3.351 (ρ g 1.16); τ = (1 - I) (1 + Δ); Δ = r s / r l$	[35]
聚合（Ⅲ）（We_s< 2.5）	$W e s = W e Δ 2 12 (1 + Δ 3) (1 + Δ 2)$ $W e s ≤ 0.45, I < 0.4 W e s W e s ≤ 0.45, 0.28 1 - 0.45 W e s < I < 0.4 W e s$	[36]
反溅分离（Ⅳ）	$W e s > 0.45, I ≤ 0.28 1 - 0.45 W e s W e s < 2.5 I ≤ 0.253 W e s ≥ 2.5$	[36]
拉伸分离（Ⅴ）	$I ≥ 0.4 W e s W e s < 2.5 I > 0.253 W e s ≥ 2.5$	[36]

表1 二元液滴不同碰撞结果的判定准则［35-36］

Table 1 Criteria for different outcomes of binary droplet collisions ［35-36］

判别准则	公式	文献
聚合（I）	$I ≤ - 0.36 W e + 0.9$	[35]
反弹（Ⅱ）	$W e < Δ (1 + Δ 2) (4 Φ' - 12) χ 1 (c o s (a r c s i n I)) 2$ ， $χ 1 = 1 - (2 - τ) 2 (1 + τ) 4 τ > 1 χ 1 = τ 2 (3 - τ) 4 τ ≤ 1$ $Φ' = 3.351 (ρ g 1.16); τ = (1 - I) (1 + Δ); Δ = r s / r l$	[35]
聚合（Ⅲ）（We_s< 2.5）	$W e s = W e Δ 2 12 (1 + Δ 3) (1 + Δ 2)$ $W e s ≤ 0.45, I < 0.4 W e s W e s ≤ 0.45, 0.28 1 - 0.45 W e s < I < 0.4 W e s$	[36]
反溅分离（Ⅳ）	$W e s > 0.45, I ≤ 0.28 1 - 0.45 W e s W e s < 2.5 I ≤ 0.253 W e s ≥ 2.5$	[36]
拉伸分离（Ⅴ）	$I ≥ 0.4 W e s W e s < 2.5 I > 0.253 W e s ≥ 2.5$	[36]

表2 模型参数设置

Table 2 Parameters used in the simulation

模拟参数	物理量	数值	单位
喷动床	x、y、z方向尺寸	0.145×0.02×1	m
	x、y、z方向网格数	29×3×100
	导流板位置H_B	0.060/0.065/0.070/0.075/0.080/0.085/0.090	m
	导流板长度L_B	0.060/0.065/0.070/0.075/0.080/0.085/0.090	m
	导流板间距W_B	0.022/0.024/0.026/0.028	m
颗粒	颗粒直径，d_p	0.003	m
	颗粒密度，ρ_p	2505	kg/m³
	颗粒数，N_p	12000
	法向弹性恢复系数，e_n	0.97
	切向弹性恢复系数，e_t	0.33
	摩擦系数（颗粒-颗粒），μ_p-p	0.10
	摩擦系数（颗粒-壁面），μ_p-w	0.30
	滚动摩擦系数，μ_r	0.125
	初始颗粒温度，T_p	288.15	K
液滴	液滴直径，d_d	0.0003	m
	液滴密度，ρ_d	1000	kg/m³
	液体黏度，μ_d	0.001	Pa·s
	喷入液滴数目，N_d	120000	个/s
	液体内溶质质量分数，w	0.3
	表面张力系数，σ	0.0721	N/m
气体	喷口气速，u_sp	43.5	m/s
	背景气速，u_bg	2.4	m/s
	喷口气体温度，T_sp	323.15/363.15	K
	背景气体温度，T_bg	363.15	K
	气体剪切粘度，μ_g	1.8×10^-5	Pa∙s

图2 喷动床的结构示意图（a）和模拟结果与实验结果[23]对比图（b）

Fig. 2 Structure diagram of spouted bed (a) and comparison of simulation results and experimental results [23] (b)

图3 无导流板与含导流板工况下颗粒直径标准差随时间的变化、颗粒生长和干燥区域分布（a）及颗粒循环轨迹图（b）

Fig. 3 Variation of particle diameter standard deviation over time, distribution of particle growth and drying regions (a), and particle circulation trajectories (b) under conditions without and with draft plates

图4 无导流板与添加导流板下的涂层颗粒分布及喷雾结束和干燥结束后的颗粒直径增长量分布

Fig. 4 Particle coating ratio and particle diameter growth distribution at the end of spraying and drying under conditions without and with draft plates

图5 喷雾阶段无导流板与添加导流板颗粒在喷动区和喷泉区的停留时间及其平均包覆速率和干燥速率

Fig. 5 Particle residence time in the spouting and fountain regions and their average coating and drying rates during the spraying stage under conditions without and with draft plates

图6 干燥阶段无导流板与添加导流板颗粒在喷动区和喷泉区的停留时间及其平均干燥速率

Fig. 6 Particle residence time in the spouting and fountain regions and their average drying rates during the drying stage under conditions without and with draft plates

图7 不同导流板间距对涂层颗粒分布、粒径分布及喷雾阶段流化及热质传递特性的影响

Fig. 7 Effect of different draft plate spacings on particle coating distribution, particle size distribution, and fluidization and heat–mass transfer characteristics during the spraying stage

图8 不同导流板长度对涂层颗粒分布、粒径分布及喷雾阶段流化及热质传递特性的影响

Fig. 8 Effect of different draft plate lengths on particle coating distribution, particle size distribution, and fluidization and heat–mass transfer characteristics during the spraying stage

图9 不同导流板高度位置对涂层颗粒分布、粒径分布及喷雾阶段流化及热质传递特性的影响

Fig. 9 Effect of different draft plate heights on particle coating distribution, particle size distribution, and fluidization and heat–mass transfer characteristics during the spraying stage

图10 不同导流板间距、长度和高度位置对颗粒相对涂层比例和相对直径标准差的影响

Fig. 10 Effect of different draft plate spacing, length, and height on particle relative coating ratio and relative diameter standard deviation

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