旋流式冷却造粒塔的优势与风险分析

doi:10.11949/0438-1157.20251267

摘要/Abstract

摘要：

改善两相的流动和传热特性是提升造粒塔性能的关键。本文采用计算颗粒流体力学方法研究了硬脂酸在旋流式并流冷却造粒塔和常规逆流组合塔中的传热和造粒特性。结果表明：旋流塔中全部液滴降温至凝固点所需要的高度大约是常规塔的一半。颗粒在旋流塔内平均停留时间为5.3 s，常规塔的对应值为8.5 s，这意味着前者的生产效率更高。相较于常规塔，旋流式造粒塔在大部分区域内显示出更优的颗粒温度分布均匀性，这表明旋转并流工艺有助于实现更均匀的液滴凝固过程。旋流塔具有以上优势的原因在于入塔气体因旋转形成更高的流速，进而使气固湍动程度增强和对流传热系数提高。此外，气流旋转形成的离心力场促使液滴向塔壁迁移，存在黏壁风险，但迁移过程也是对流传热最强的阶段，合理调控流场可消除风险。

关键词: 造粒, 传热强化, 两相流动, 场流协同, 计算颗粒流体力学

Abstract:

Improving the flow and heat transfer characteristics of the two phases is key to enhancing the performance of granulation towers. This paper uses computational particle hydrodynamics to study the heat transfer and granulation characteristics of stearic acid in a swirling co-current cooling granulation tower and a conventional counter-current combined tower. The results show that the height required for all droplets to cool to their freezing point in the cyclone tower is approximately half that of the conventional tower. The average residence time of particles in the swirling tower is 5.3 s, compared to 8.5 s in the conventional tower, indicating higher production efficiency. Compared to the conventional tower, the swirling granulation tower exhibits better uniformity of particle temperature distribution in most areas, suggesting that the rotating co-current process helps achieve a more uniform droplet solidification process. The advantages of the swirling tower are due to the higher flow velocity of the inlet gas caused by rotation, which enhances gas-solid turbulence and increases the convective heat transfer coefficient. Furthermore, the centrifugal force field generated by the rotating airflow promotes droplet migration towards the tower wall, posing a risk of wall adhesion; however, this migration process is also the stage with the strongest convective heat transfer, and this risk can be eliminated by properly controlling the flow field.

Key words: granulation, heat transfer enhancement, two-phase flow, field-flow synergy, computational particle fluid dynamics

中图分类号:

TQ053.5

郑文杰, 杨景轩, 孙刚, 鲍鹏飞, 丛有祥, 郝晓刚. 旋流式冷却造粒塔的优势与风险分析[J]. 化工学报, DOI: 10.11949/0438-1157.20251267.

Wenjie ZHENG, Jingxuan YANG, Gang SUN, Pengfei BAO, Youxiang CONG, Xiaogang HAO. Advantages and risks of swirling cooling granulation towers[J]. CIESC Journal, DOI: 10.11949/0438-1157.20251267.

图/表 11

图1 造粒塔的几何模型、边界条件及切向速度径向分布：(a)组合塔，(b)旋流塔，(c)切向速度随径向位置的变化

Fig.1 Geometric model, boundary conditions, and variation of tangential velocity with radial position in the granulation tower: (a)combined tower, (b)swirling tower, (c)variation of tangential velocity with radial position

表1 颗粒计算所用参数

Table 1 Parameters used in Particle calculation

粒径

/mm

表2 空气计算所用参数

Table 2 Parameters used in air calculation

温度

密度

/(kg·m^-3)

黏度

/(Pa·s)

热导率

/(W·(m·K)^-1)

比热容

/(kJ·(kg·K)^-1)

进气量

/(m³·s^-1)

图2 模拟结果与前人研究进行验证

Fig.2 Validation of simulation results with previous research.

图3 颗粒凝固随轴向高度的变化

Fig.3 Variation of particle solidification with axial height

图4 温度均匀性随轴向高度的变化

Fig.4 Variation of temperature uniformity with axial height

图5 对流传热系数

Fig.5 Convective heat transfer coefficient

图6 不同区域的Reynolds数分布

Fig.6 Distributions of Reynolds Number in different zones

图7 造粒塔内总速度分布和颗粒分布

Fig.7 Distribution of total velocity and particle distribution in a granulation tower

图8 颗粒停留时间分布：(a)颗粒占比，(b)累计颗粒占比

Fig.8 Distribution of particle residence time: (a)particle proportion, (b)cumulative particle proportion

图9 旋流式造粒塔各区域内距壁面0.1 m处颗粒的最高温度Tmax

Fig.9 Maximum particle temperature Tmax at 0.1 m from the wall in each zone of the swirling granulation tower

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