Simulation Study on Centrifugal Spray Evaporation Characteristics and Process Optimization of Desulfurization Wastewater

Ning Zhao,Debo Li,Zongkun Li,Yongxin Feng

doi:10.3390/coatings11070837

Ning Zhao, Debo Li + Show 2 more

Open Access

https://doi.org/10.3390/coatings11070837

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Abstract

As an advanced treatment of desulfurization wastewater, centrifugal spray drying technology, which can achieve a zero liquid discharge target, has attracted wide attention and great interest in recent years. However, the results of previous studies were based on the laboratory-scale centrifugal spray dryer. In order to study the evaporation characteristics of desulfurization wastewater and the parameter optimization of the dryer, the evaporation model of wastewater droplets was established. The effects of parameters such as the angle of the deflectors, gas–liquid ratio and atomizer speed on droplet evaporation were studied by numerical simulation. The results show that with the increase in the angle of the deflectors, the swirl effect of flue gas flow field is more obvious and the time and axial distance required for the complete evaporation of the droplets are shorter. Reducing the gas–liquid ratio will make the average evaporation time longer. Moreover, a higher atomizer speed is helpful for the evaporation of the droplets. The optimum gas–liquid ratio and rotational speed are found to be 9300 m3/Nm3 and 16,000 rpm, respectively.

Highlights

With the development of industrialization and urbanization, people’s demand for electricity is increasing [1,2]
China has begun to increase the treatment of desulfurization wastewater and put forward zero liquid discharge (ZLD) processes for coal-fired power plants
The angles of the inner and outer deflectors are set as 0◦, 15◦, 30◦ and 45◦, respectively, to investigate the changes of the flow field and the evaporation condition of the droplets

Summary

Introduction

With the development of industrialization and urbanization, people’s demand for electricity is increasing [1,2]. It has a diameter of 7.2 m and a height of 11.7 m, including the gas distributor and tower body. (2) When the liquid temperature is greater than the evaporation temperature and less than the boiling temperature, the heat absorbed by the droplet from the flue gas is used for the temperature increase and the evaporation process at the same time Under these circumstances, the heat transfer equation is:. (3) When the liquid temperature reaches boiling temperature, the unevaporated droplets and the flue gas undergo a strong heat and mass transfer process and the boiling rate equation is as follows: d(dp) dt ρ p. Where Rep is the Reynolds number of the liquid droplet relative to the gas motion

Numerical Procedures

Boundary Conditions and Operating Parameters

Reliability Verification to CFD Model

Effect of Angle of Deflector