Effects of Humidity Pretreatment Devices on the Loss of HCl Gas Emitted from Industrial Stacks

Han-Nui Gil,In-Young Kim,Byeong-Gyu Park,In-Young Choi,Trieu-Vuong Dinh,Sang-Woo Lee,Jo-Chun Kim,Jee-Hyun Lee

doi:10.3390/atmos13010033

Abstract

A high humidity at a high temperature presents a common challenge in monitoring the air pollutants emitted from stationary sources. Thus, humidity removal is a pivotal issue. In this study, the effect of humidity pretreatment devices (HPDs) on hydrogen chloride (HCl) gas emitted from an incinerator stack was investigated. A conventional cooler (HPD_CL), and poly-tube (HPD_NP) and single-tube (HPD_NS) Nafion™ dryers were used as HPDs in this study. HCl concentrations varied at five and 10 parts per million in volume (ppmv). Low (i.e., ~4%) and high (i.e., ~17%) humidities were generated at 180 °C. The removal efficiencies of humidity and the loss rates of HCl by the devices were determined. The removal efficiencies of humidity by HPD_CL and the two dryers were found to be similar, at approximately 85% at a low humidity and 95% at a high humidity. In terms of HCl loss rates, HPD_CL revealed the highest loss rates in all conditions (i.e., >95%), followed by HPD_NP and HPD_NS. At normal room temperature (i.e., 25 °C), the HCl loss rates of HPD_NP were >40% at a low humidity and >70% at a high humidity, while those of HPD_NS were >10% at a low humidity and >60% at a high humidity. The performance of the two dryers improved when they were heated to 80 °C. However, this temperature caused damage to the dryers, which reduced their lifetime.

Highlights

Hydrogen chloride (HCl) is a colorless acid gas at room temperature and pressure because its boiling point is −85.05 ◦C [1]
The humidity removal efficiencies of the NafionTM dryers were similar to those of the cooler, the investment and operating costs associated with NafionTM dryers were much higher than those removal efficiency among the humidity pretreatment devices (HPDs) using MATLAB (Version 9.10.0.1684407, MathWorks, Inc.)
The experimental conditions were selected based on the stack conditions of a solid waste incinerator; the flue gas temperature was approximately 180 ◦C, the HCl concentration varied at 5 and 10 ppmv, and the humidity varied at 4 and 17% (v/v)

Summary

Introduction

Hydrogen chloride (HCl) is a colorless acid gas at room temperature and pressure because its boiling point is −85.05 ◦C [1]. Besides secondary formation from a reaction between HNO3 and sea-salt (i.e., NaCl), HCl is primarily emitted from industrial sources such as chemical production or semiconductor production and via combustion processes such as from medical waste or municipal solid waste incinerators [2,3,4].

Methods

Results

Conclusion