陶瓷膜接触器化学吸收氮氧化物的传质过程与阻力分析

doi:10.11949/0438-1157.20200242

摘要/Abstract

摘要：

针对选择性催化还原技术(SCR)存在装置大、运行费用高、催化剂中毒失活等问题，将平均孔径为100 nm的Al₂O₃陶瓷膜进行疏水改性并组装成膜接触器，以NaClO₂水溶液为吸收液，开展陶瓷膜接触器在烟气脱硝领域的应用研究。考察了陶瓷膜接触器在化学吸收脱硝中的稳定性，以及气体流量、吸收液浓度、吸收液流量、吸收液pH等因素对NO脱除率和传质通量的影响，基于阻力串联模型，建立总传质系数方程。研究表明，陶瓷膜接触器在连续600 min运行过程中，NO的脱除效率及传质通量分别稳定在99%和0.038 mol·m^-2·h^-1左右。进气流量的增加会促进NO的吸收，吸收液pH=3时具有最高的氧化吸收性能，同时提高吸收液的浓度会增强NO的脱除效果。NO的传质过程同时受气、液、膜三相阻力控制，传质阻力分析结果表明，可以通过增加气体流速减小气相阻力，增加吸收液浓度同时降低pH减小液相阻力。本研究在烟气脱硝领域具有良好的应用前景。

关键词: 陶瓷膜, 膜接触器, 脱硝, 膜吸收, 传质过程

Abstract:

To overcome the problems of large device, high operating cost and catalyst poisoning and deactivation in the selective catalytic reduction technology (SCR), Al₂O₃ ceramic membrane with an average pore diameter of 100 nm was hydrophobic modified and assembled into a membrane contactor, NaClO₂ was used as absorbent to carry out the application research of ceramic membrane contactor in the field of denitration of flue gas. The stability of ceramic membrane contactor in chemical absorption denitrification and the effect of the process parameters (i.e. gas flow rate, concentration of absorbent, liquid of absorbent, pH of absorbent) on NO removal efficiency and mass transfer flux were investigated in detail. Based on the resistance series model, the total mass transfer coefficient equation was established. The experiments showed that the NO removal efficiency and mass transfer flux of NO were stable at about 99% and 0.038 mol·m^-2·h^-1 during 600 min operation of the ceramic membrane contactor. The increase of the intake air flow will promote the absorption of NO, and the absorption liquid has the highest oxidation absorption performance at pH=3, while increasing the concentration of the absorption liquid will enhance the removal effect of NO. The mass transfer performance of NO is controlled by the resistance of the gas phase, liquid phase and the membrane phase at the same time. The mass transfer resistance analysis results show that the increase of gas flow rate can decrease the gas phase resistance, increasing the concentration of the absorbent and the lower pH can reduce liquid phase resistance. The study has a good application prospect in denitration of flue gas.

Key words: ceramic membrane, membrane contactor, denitration, membrane absorption, mass transfer performance

中图分类号:

TQ 174

周鑫, 邱鸣慧, 罗平. 陶瓷膜接触器化学吸收氮氧化物的传质过程与阻力分析[J]. 化工学报, 2020, 71(8): 3652-3660.

Xin ZHUO, Minghui QIU, Ping LUO. Mass transfer performance and resistance analysis of chemical absorption of NO_x based on ceramic membrane contactor[J]. CIESC Journal, 2020, 71(8): 3652-3660.

图/表 12

表1 陶瓷膜接触器的规格参数

Table 1 Structure of Al2O3 ceramic membrane contactor

规格参数	参数值
膜组件尺寸(外径/内径)/mm	25/22
膜尺寸(外径/内径)/mm	12/8
膜有效长度/mm	320
膜平均孔径/nm	100
膜孔隙率/%	40
膜管根数	1

图1 膜吸收流程示意图

Fig.1 Flow chart of membrane absorption process

图2 膜吸收NO传质过程的机理

Fig.2 Mechanism of gas-liquid-membrane mass transfer performance

图3 改性前后陶瓷膜的表面[(a)、(c)]和断面[(b)、(d)]SEM图

Fig.3 SEM images of surface [(a),(c)] and section [(b),(d)] of ceramic membrane before and after modification

图4 改性前后陶瓷膜水滴动态接触角随时间变化关系

Fig.4 Time dependence of water contact angle for unmodified and modified ceramic membrane

图5 疏水性陶瓷膜接触器的稳定性测试CNaClO2=0.02 mol·L-1, CNO=500 ml·m-3, Ql=30 ml·min-1, Qg=300 ml·min-1, T=293 K, pH=3

Fig.5 Stability performance of hydrophobic ceramic membrane contacor

图6 进气流量对NO脱除率、传质通量的影响CNaClO2=0.01 mol·L-1, CNO=500ml·m-3, Ql=30 ml·min-1, T=293 K, pH=3

Fig.6 Effect of gas flow rate on NO removal efficiency and mass transfer flux

图7 吸收液流量对脱硝的影响CNaClO2=0.01 mol·L-1, CNO=500 ml·m-3, T=293 K, pH=3

Fig.7 Effect of absorption liquid flow on denitration

图8 吸收液pH对NO脱除率和传质通量的影响CNaClO2=0.01 mol·L-1, CNO=500 ml·m-3, Ql=30 ml·min-1, T=293 K

Fig.8 Effect of absorbent pH on NO removal efficiency and mass transfer flux

图9 吸收液浓度对NO脱除率和传质通量的影响CNO=500 ml·m-3, Ql=30 ml·min-1, pH=3, T=293 K

Fig.9 Effect of absorbent concentration on NO removal efficiency and mass transfer flux

图10 气体流速与膜接触器总传质阻力的关系CNaClO2=0.01 mol·L-1, CNO=500 ml·m-3, Ql=30 ml·min-1,T=293 K, pH=3

Fig.10 Relationship between gas flow rate and membrane contactor mass transfer resistance

图11 吸收液浓度与膜接触器总传质阻力关系CNO=500 ml·m-3, Ql=30 ml·min-1, Qg=500 ml·min-1, T=293 K, pH=3

Fig.11 Relationship between absorption concentration and membrane contactor mass transfer resistance

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