Optimization Method of Flow Field for Alleviating Clogging of Mist Eliminator in Desulfurization Tower

doi:10.12096/j.2096-4528.pgt.23176

Abstract

Abstract:

Objectives Desulfurization tower mist eliminator is widely used in coal-fired power plants due to its simple structure and good fog removal effect. However, due to the limitation of its own gas-water separation principle, it is prone to scaling up and blocking on the plate surface, which seriously affects the output power of the unit. Therefore, it is necessary to solve the problem of frequent scaling and clogging of the wet desulfurization tower mist eliminator and the resulting excessive resistance loss. Methods The method of optimizing the flow field of desulfurization tower and its inlet flue using deflector plates was proposed, and the simulation calculations and engineering application verifications of the Z-shaped desulfurization tower and its L-shaped inlet flue before and after optimization were carried out. Results The simulation results indicate that under rated boiler load conditions, the relative standard deviation of the velocity at the outlet section of the L-shaped inlet flue decreases from 27.57% to 19.99% after optimization. The relative standard deviation of the velocity at the inlet section of the mist eliminator in the Z-shaped desulfurization tower decreases from 45.66% to 40.24%. Meanwhile, the mass flow rate of the slurry droplets at the mist eliminator inlet section drops from 441.136 kg/s to 368.498 kg/s, indicating that the optimization scheme effectively reduces the workload of the mist eliminator. Experimental results show that prior to the modification, there were regions with a velocity of 0 m/s at the mist eliminator inlet section, which are improved to a velocity of 1-5 m/s after the modification, consistent with the trends observed in the simulation. Data from 180 days of operation after the modification indicate that the pressure drop before and after the mist eliminator does not exceed 200 Pa. On-site measurement results during maintenance show that the scaling thickness on the mist eliminator plate is reduced from over 1 cm before the modification to about 0.1 cm, eliminating severe scaling and blockage phenomena. Conclusions The proposed flow field optimization method significantly improves the uniformity of the flue gas flow field in the desulfurization tower, reduces the workload of the mist eliminator, and effectively slows down the fouling problem of the mist eliminator, which has great engineering application value.

Key words: coal-fired unit, desulfurization tower, boiler, mist eliminator, clogging, flow field uniformity, flue gas desulphurization, numerical simulation

CLC Number:

TK 09

Zhuo LIU, Donglin CHEN, Shuqi WANG, Yijiang YANG, Youyang YAN, Zhan YANG. Optimization Method of Flow Field for Alleviating Clogging of Mist Eliminator in Desulfurization Tower[J]. Power Generation Technology, 2024, 45(6): 1087-1094.

Figures/Tables 14

Fig. 1 Profile flow field distribution of Z-shaped desulfurization tower

Fig. 2 Cross section flow field distribution of L-shaped inlet flue

Fig. 3 Optimization scheme of L-shaped inlet flue guide plate

Fig. 4 Optimization scheme of guide plate in Z-shaped desulfurization tower

Tab. 1 Shaping and positioning dimensions of guide plate

$∆ X L 1 = 1.8$

$∆ X L 2 = 4.6$

$∆ Y L 1 = 1.8$

$∆ Y L 2 = 4.6$

—

$l L 1' = 1.5$

$l L 2' = 1.0$

$r L 1 = 1.8$

$r L 2 = 4.6$

$θ 1 = 80 °$

$θ 2 = 92 °$

Z形脱硫塔

$∆ X Z 1 = 3.0$

$∆ X Z 2 = 1.9$

$∆ X Z 3 = 1.7$

$∆ X Z 4 = 3.3$

$∆ Y Z 1 = 1.0$

$∆ Y Z 2 = 2.0$

$∆ Y Z 3 = 3.0$

$∆ Y Z 4 = 3.8$

$l 1 = 0.5$

$l 2 = 0.5$

$l 3 = 0.5$

$l Z 1' = 1.5$

$l Z 2' = 1.5$

$l Z 3' = 1.5$

$l Z 4' = 1.5$

$r Z 1 = 1.0$

$r Z 2 = 1.0$

$r Z 3 = 1.0$

$r Z 4 = 2.0$

—

Tab. 1 Shaping and positioning dimensions of guide plate

三维模型

横向定位尺寸/m

纵向定位尺寸/m

横向定形尺寸/m

纵向定形尺寸/m

半径/m

角度定位尺寸/(°)

L形进口烟道

$∆ X L 1 = 1.8$

$∆ X L 2 = 4.6$

$∆ Y L 1 = 1.8$

$∆ Y L 2 = 4.6$

—

$l L 1' = 1.5$

$l L 2' = 1.0$

$r L 1 = 1.8$

$r L 2 = 4.6$

$θ 1 = 80 °$

$θ 2 = 92 °$

Z形脱硫塔

$∆ X Z 1 = 3.0$

$∆ X Z 2 = 1.9$

$∆ X Z 3 = 1.7$

$∆ X Z 4 = 3.3$

$∆ Y Z 1 = 1.0$

$∆ Y Z 2 = 2.0$

$∆ Y Z 3 = 3.0$

$∆ Y Z 4 = 3.8$

$l 1 = 0.5$

$l 2 = 0.5$

$l 3 = 0.5$

$l Z 1' = 1.5$

$l Z 2' = 1.5$

$l Z 3' = 1.5$

$l Z 4' = 1.5$

$r Z 1 = 1.0$

$r Z 2 = 1.0$

$r Z 3 = 1.0$

$r Z 4 = 2.0$

—

Fig. 5 Change of total pressure difference between inlet and outlet with the number of grids

Fig. 6 Velocity map on cross section of L-shaped inlet flue at Y=16 m

Fig. 7 Velocity map on exit cross section of L-shaped inlet flue

Fig. 8 Velocity map on cross section of Z-shaped desulfurization tower at Z=0 m

Fig. 9 Velocity map on cross section of Z-shaped desulfurization tower at Y=23 m

Fig. 10 Relative standard deviation of velocity of exit section of L-shaped inlet flue and entrance section of mist eliminator in Z-shaped desulphurization tower

Fig. 11 Mass flow rate of slurry droplets at inlet section of mist eliminator before and after optimization

Fig. 12 Flue gas velocity distribution at inlet cross section of mist eliminator of Z-shaped desulfurization tower before and after modification

Fig. 13 Scale accumulation on mist eliminator plate before and after modification

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