Effects of Operating and Structural Parameters on Removal of Nitric Oxide by Oxidation in a Ceramic Hollow Fiber Membrane Contactor

Wei Yu,Fangyang Yuan,Xiaoyin Li

doi:10.3390/membranes11090704

Abstract

A numerical study on the oxidation removal of nitric oxide in a ceramic hollow fiber membrane contactor was performed. To represent the transport and absorption process, the model was created by combining multiphase, species, reaction, and porous models. The numerical results were verified by comparing them with experimental data. The tube and lumen sides both have laminar parabolic velocity distributions. The nitric oxide concentration decreases gradually from the membrane wall to axis at the cross-section except on the inner and outer sides of the membrane tube. The equivalent diffusion length was proved useful for evaluating the entrance effect. At low concentrations, the reduction efficiency was proportional to the absorbent concentration, and at large concentrations, it neared a maximum value. The reduction efficiency was positively affected by elevated operating temperature and pressure. With a gas channel width of 13 mm, the reduction flow rate achieves its maximum. The efficiency of NO reduction per area decreases as the effective membrane length increases. Increasing the operating temperature and membrane length are recommended as design priorities due to high relative enhancements. It is not recommended to improve reduction efficiency by increasing membrane tube diameter and operating pressure in design. Changing the gas flow rate, absorbent concentration and gas channel width are moderate recommended as well.

Highlights

Accepted: 13 September 2021Nitrogen oxides (NOx) are considered as one of the principal pollutants in exhaust gases, as they are thought to be the source of environmental issues such as acid rain, the ozone hole, and photochemical smog [1]
Liu et al [11,12] investigated the ultraviolet (UV)/H2 O2 /NaOH process for advanced oxidation removal of nitric oxide (NO), and the results revealed that OH free radicals play an important role
To represent the transport and absorption process, the model was created by combining multiphase, species, reaction, and porous models

Summary

Introduction

Nitrogen oxides (NOx) are considered as one of the principal pollutants in exhaust gases, as they are thought to be the source of environmental issues such as acid rain, the ozone hole, and photochemical smog [1]. As nitric oxide (NO) is difficult to absorb directly with the aqueous solution, removing NOx from flue gas is more challenging than removing CO2 or SO2 .There is less literature on the topic of NOx removal than that of other acid gases. Ding et al [5] proposed an oxidation-removal process capable of removing NOx and SO2 simultaneously, and they discovered that the NOx removal efficiency reached 80%, and was primarily dependent on the flow rate of H2 O2 solution as well as the gas volume concentration. Wang et al [6] developed a dual oxidant system composed of H2 O2 /S2 O8 2−

Methods

Discussion

Conclusion