Numerical Investigation on the Evaporation Performance of Desulfurization Wastewater in a Spray Drying Tower without Deflectors

Debo Li,Ning Zhao,Zhiwen Xie,Yongxin Feng

doi:10.3390/coatings11091022

Abstract

The desulfurization wastewater evaporation technology with flue gas has been widely applied to dispose of desulfurization wastewater. This paper investigates the effect of flue gas flow rate and temperature, wastewater flow rate and initial temperature, and droplet size on the evaporation performance of the desulfurization wastewater in a spray drying tower without deflectors. The results show that the flue gas flow rate and temperature affect the evaporation performance of desulfurization wastewater. The larger flow rate and higher temperature of flue gas correspond to the faster evaporation speed and the shorter complete evaporation distance of the wastewater droplet. Decreasing the flow rate and increasing the initial temperature of the desulfurization wastewater is advantageous to enhance the evaporation speed and shorten the complete evaporation distance of the wastewater droplet. Reducing the droplet size is beneficial to improve the evaporation performance of the desulfurization wastewater. The orthogonal test results show that the factors affecting droplet evaporation performance are ranked as follows: flue gas flow rate > wastewater flow rate > flue gas temperature > wastewater initial temperature > droplet size. Considering the evaporation ratio and the complete evaporation distance, the optimal setting is 14.470 kg/s for flue gas flow rate, 385 °C for flue gas temperature, 0.582 kg/s for wastewater flow rate, 25 °C for wastewater initial temperature, and 60 μm for droplet size. These studied results can provide valuable information to improve the operational performance of the desulfurization wastewater evaporation technology with flue gas.

Highlights

Some technologies have been proposed to dispose of the desulfurization wastewater, such as chemical precipitation, membrane separation, evaporative crystallization, electrodialysis technology, etc. [11–14]
By increasing the flue gas temperature, the turbulence kinetic energy in the mixing zone of the flue gas and the droplets changes slightly, which indicates the slight difference in the mixing intensity between flue gas and droplets
By increasing the droplet size from 5 to 60 μm, the turbulence kinetic energy in the mixing zone of the flue gas and the droplets changes slightly, which indicates the slight difference in the mixing intensity between flue gas and droplet

Summary

Introduction

In China, wet flue gas desulfurization technology is widely applied to coal-fired thermal power plants to remove SO2 in the flue gas because it has the advantages of high efficiency, low operating cost, and high reliability [1–4]. TThhee ccoonnttiinnuuoouuss pphhaassee ooff ddrryyiinngg ggaass iiss ttrreeaatteedd bbyy aann EEuulleerriiaann aapppprrooaacchh,, aanndd aa ssttaannddaarrdd kk--εεmmooddeelliissuuttiilliizzeeddffoorrtthheettuurrbbuulleenncceeddeessccrriippttiioonn. Cases 1, 2, and 3 are used to study the influence of flue gas flow rate on evaporation performance. Cases 1, 4, and 5 are used to discuss the effect of flue gas temperature on evaporation performance. Cases 1, 6, and 7 are used to discuss the effect of wastewater flow rate on evaporation performance. Cases 1, 8, Coatings 2021, 11, x FOR PEER REVIEW and 9 are used to discuss the effect of the initial temperature of wastewater on evaporation performance.

ValidatIinolnetowf tahsteeSwiamteurlatetemdpReerasutultrse (K)

Effect of Wastewater Initial Temperature on the Evaporation Performance

Effect of Droplet Size on the Evaporation Performance

Orthogonal Test of Evaporation Performance

Findings

Conclusions