湿法烟气脱硫塔内传递与化学反应过程CFD模拟

doi:10.11949/j.issn.0438-1157.20181368

化工学报 ›› 2019, Vol. 70 ›› Issue (6): 2117-2128.DOI: 10.11949/j.issn.0438-1157.20181368

湿法烟气脱硫塔内传递与化学反应过程CFD模拟

曲江源¹(),齐娜娜¹(),关彦军¹,滕阳¹,徐文青²,朱廷钰²,张锴¹

1. 华北电力大学热电生产过程污染物监测与控制北京市重点实验室，北京 102206
2. 中国科学院过程工程研究所湿法冶金清洁生产技术国家工程实验室，北京 100190

收稿日期:2018-11-18 修回日期:2019-03-10 出版日期:2019-06-05 发布日期:2019-06-05
通讯作者: 齐娜娜
作者简介:<named-content content-type="corresp-name">曲江源</named-content>（1993－），男，博士研究生，<email>qujy_ncepu@163.com</email>
基金资助:
国家重点研发计划项目(2017YFC0210601);青年科学基金项目(51706070)

CFD simulation of transfer and chemical reaction process in wet flue gas desulfurization tower

Jiangyuan QU¹(),Nana QI¹(),Yanjun GUAN¹,Yang TENG¹,Wenqing XU²,Tingyu ZHU²,Kai ZHANG¹

1. Beijing Key Laboratory of Emission Surveillance and Control for Thermal Power Generation, North China Electric Power University, Beijing 102206, China
2. National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China

Received:2018-11-18 Revised:2019-03-10 Online:2019-06-05 Published:2019-06-05
Contact: Nana QI

摘要/Abstract

摘要：

以某330 MW燃煤发电机组湿法烟气脱硫塔为研究对象，采用欧拉-拉格朗日方法建立了塔内气-液两相流动、热质交换模型，以溶解平衡、质量守恒及电荷守恒描述浆液内13种溶质组分瞬时化学反应特性，通过用户自定义函数实现流动模型与传质模型、化学反应模型的耦合。基于上述模型预测了脱硫塔内气-液两相流动、液滴蒸发与SO₂化学吸收过程，获得了SO₂浓度与浆液pH的径向分布特性，详细分析了气-液流动对化学吸收特性的影响，结果表明局部液气比分布特性是影响SO₂径向分布的关键因素之一，可通过调控近壁区及主管道区的两相流动状态提高脱硫塔的吸收性能；随着气相侧SO₂浓度提高或液滴粒径减小，浆液pH下降速率增大且各化学组分浓度达到稳定状态用时缩短。

关键词: 湿法烟气脱硫, 气液两相流, 热质交换, 吸收, 数值模拟

Abstract:

The Eulerian-Lagrangian method is employed to describe the gas-liquid flow and the heat and mass transfer process in a full-scale wet flue gas desulfurization(WFGD) tower, which is in operation at a 330 MW coal-fired power unit. Instantaneous chemical reactions involving 13 dissolved species in aqueous phase are assumed to be at equilibrium obeying mass balance for the specific chemical compositions and electro neutrality. The gas-liquid flow model is coupled with mass transfer and chemical reactions procedures through user defined functions (UDFs). The gas-liquid hydrodynamics, droplets evaporation and SO₂ chemical absorption is predicted in the spray scrubber. Radial distribution characteristics of SO₂ concentration and pH of the droplets are obtained and the effect of gas-liquid flow behavior on chemical absorption process is analyzed. The results show that the local liquid-gas ratio distribution is one of the key factors affecting the radial distribution of SO₂. Furthermore, the absorption performance of the desulfurization tower can be improved by controlling the two-phase flow pattern in the area around the wall and that beneath the main pipe. The drop rates of pH increase with the raise of SO₂ concentration in flue gas or the decrease of droplet diameter. Besides, the higher concentration of SO₂ in gas phase or the smaller characteristic size of droplet can accelerate the process that the concentration of each chemical component reaches a stable state.

Key words: wet flue gas desulfurization, gas-liquid flow, heat and mass transfer, absorption, numerical simulation

中图分类号:

X 701.3

曲江源, 齐娜娜, 关彦军, 滕阳, 徐文青, 朱廷钰, 张锴. 湿法烟气脱硫塔内传递与化学反应过程CFD模拟[J]. 化工学报, 2019, 70(6): 2117-2128.

Jiangyuan QU, Nana QI, Yanjun GUAN, Yang TENG, Wenqing XU, Tingyu ZHU, Kai ZHANG. CFD simulation of transfer and chemical reaction process in wet flue gas desulfurization tower[J]. CIESC Journal, 2019, 70(6): 2117-2128.

图/表 12

图1 脱硫塔及计算域

Fig.1 Schematic diagram of desulfurization tower and computational domain

表1 液相内化学反应平衡常数

Table 1 Reaction equilibrium constants in droplets

Parameter	Formula	Eq.
$K_{H_{2} O}$ /(mol/L)²	[H⁺][OH^-]	(19)
$K_{S O_{2}, a q}$ /(mol/L)	[H⁺][HSO₃ ^-]/[SO_2,aq]	(20)
$K_{H S O_{3}^{-}}$ /(mol/L)	[H⁺][SO₃ ^2-]/[HSO₃ ^-]	(21)
$K_{H S O_{4}^{-}}$ /(mol/L)	[H⁺][SO₄ ^2-]/[HSO₄ ^-]	(22)
$K_{C O_{2}, a q}$ /(mol/L)	[H⁺][HCO₃ ^-]/[CO_2,aq]	(23)
$K_{H C O_{3}^{-}}$ /(mol/L)	[H⁺][CO₃ ^2-]/[HCO₃ ^-]	(24)

表1 液相内化学反应平衡常数

Table 1 Reaction equilibrium constants in droplets

Parameter	Formula	Eq.
$K_{H_{2} O}$ /(mol/L)²	[H⁺][OH^-]	(19)
$K_{S O_{2}, a q}$ /(mol/L)	[H⁺][HSO₃ ^-]/[SO_2,aq]	(20)
$K_{H S O_{3}^{-}}$ /(mol/L)	[H⁺][SO₃ ^2-]/[HSO₃ ^-]	(21)
$K_{H S O_{4}^{-}}$ /(mol/L)	[H⁺][SO₄ ^2-]/[HSO₄ ^-]	(22)
$K_{C O_{2}, a q}$ /(mol/L)	[H⁺][HCO₃ ^-]/[CO_2,aq]	(23)
$K_{H C O_{3}^{-}}$ /(mol/L)	[H⁺][CO₃ ^2-]/[HCO₃ ^-]	(24)

图2 网格划分与不同高度XY截面SO2平均浓度相对偏差分布

Fig.2 Schematic diagram of geometry discretization and relative errors profiles of average SO2 concentration at different XY planes

图3 烟气速度分布云图

Fig.3 Contour of gas velocity distribution

图4 无量纲轴向速度径向分布

Fig.4 Dimensionless axial velocity radial profiles

图5 浆液浓度分布云图

Fig.5 Contour of discrete phase concentration

图6 不同截面液滴粒径分布特性

Fig.6 Diameter distribution character of droplets in different cross sections

表2 温度、水蒸气体积分数实测值与计算值

Table 2 Measured values and simulation results of gas temperature and vapor volume fraction

项目	T _g,in /℃	T _g,out /℃	$V_{H_{2} O, i n}$ /%	$V_{H_{2} O, o u t} / %$
实测 Ⅰ	125.0	48.0	7.5	13.2
实测 Ⅱ	135.0	50.0	6.2	13.7
实测 Ⅲ	131.0	51.0	7.1	13.4
平均值	130.3	49.7	7.0	13.4
模拟值	130.0	50.0	7.0	13.8
相对误差	—	0.60%	—	2.99%

表2 温度、水蒸气体积分数实测值与计算值

Table 2 Measured values and simulation results of gas temperature and vapor volume fraction

项目	T _g,in /℃	T _g,out /℃	$V_{H_{2} O, i n}$ /%	$V_{H_{2} O, o u t} / %$
实测 Ⅰ	125.0	48.0	7.5	13.2
实测 Ⅱ	135.0	50.0	6.2	13.7
实测 Ⅲ	131.0	51.0	7.1	13.4
平均值	130.3	49.7	7.0	13.4
模拟值	130.0	50.0	7.0	13.8
相对误差	—	0.60%	—	2.99%

图7 入口烟气温度对塔内烟气温度与相对湿度的影响

Fig.7 Influence of initial gas temperature on temperature and relative humidity of flue gas in tower

图8 烟气中SO2浓度径向分布

Fig.8 Radial profiles of SO2 concentration in gas phase

图9 喷淋浆液空间分布与pH分布

Fig.9 Slurry distribution in spray scrubber colored by pH

图10 喷嘴位置与液滴粒径对pH的影响

Fig.10 Influences of injection location and droplet diameter on pH

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湿法烟气脱硫塔内传递与化学反应过程CFD模拟

CFD simulation of transfer and chemical reaction process in wet flue gas desulfurization tower

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