Simulation investigation on marine exhaust gas SO₂ absorption by seawater scrubbing

Figures & data

Table 1. Composition of exhaust gas

Item	quantity	Unit
N2	75.32	%
O2	13.73	%
CO2	4.49	%
H2O	6.64	%
SO2	600	ppm
NO2	1500	ppm

Table 2. Summary of involved chemical reactions in seawater droplets

Chemical reactions	Equilibrium Constant
$S{O}_{2\left(aq\right)}+H_{2}O\rightleftharpoons HS{O}_3^{-}+H^{+}$	$K_1=\frac{[HS{O}_3^{-}]\left[H^{+}\right]}{\left[S{O}_{2\left(aq\right)}\right]}$
$HS{O}_3^{-}\rightleftharpoons S{O}_3^{2-}+H^{+}$	$K_2=\frac{[S{O}_3^{2-}]\left[H^{+}\right]}{HS{O}_3^{-}}$
$C{O}_3^{2-}+H^{+}\rightleftharpoons HC{O}_3^{-}$	$K_3=\frac{\left[C{O}_3^{2-}\right]\left[H^{+}\right]}{[HC{O}_3^{-}]}$
$HC{O}_3^{-}+H^{+}\rightleftharpoons H_{2}O+C{O}_{2\left(aq\right)}$	$K_4=\frac{[HC{O}_3^{-}]\left[H^{+}\right]}{C{O}_{2\left(aq\right)}}$
$H_{2}O\rightleftharpoons H^{+}+O{H}^{-}$	$K_w=[O{H}^{-}\left][H^{+}\right]$

Figure 1. Seawater aqueous reaction system.

Figure 2. The strategy of calculation.

Figure 3. Geometry structure of spray scrubber and computational domain.

Figure 4. The main operation conditions of simulated scrubber.

Table 3. Comparation between simulation calculation and test results

Operation conditions	L/G (L/m^3)	Tested outlet SO2 (ppm)	Tested efficiency (%)	Calculated efficiency (%)	Relative error (%)
1	11.17	2.68	99.6	98.8	0.8
2	12.3	8.1	98.7	99.2	0.5
3	13.4	3.42	99.4	98.3	1.1

Figure 5. Comparison of continuous flow field in different scrubbers (flow rate of gas = 128,290 m³/h, flow rate of liquid = 0).

Figure 6. Droplet concentration distribution in Z section (flow rate of gas = 128,290 m³/h, flow rate of liquid = 1580 m³/h).

Figure 7. Concentration of droplets hitting wall under different conditions (flow rate of gas = 128,290 m³/h, flow rate of liquid = 1580 m³/h).

Figure 8. Droplet concentration variation in different heights (flow rate of gas = 128,290 m³/h, flow rate of liquid = 1580 m³/h).

Figure 9. Effect of distribution ring on gas flow field (flow rate of gas = 128,290 m³/h, flow rate of liquid = 1580 m³/h).

Figure 10. Pressure variation as height variation (flow rate of gas = 128,290 m³/h, flow rate of liquid = 1580 m³/h).

Figure 11. SO₂ absorption rate variation (flow rate of gas = 128,290 m³/h, flow rate of liquid = 1580 m³/h, inlet SO₂ concentration = 600 ppm, with DR).

Figure 12. pH variation as droplet falling (flow rate of gas = 128,290 m³/h, flow rate of liquid = 1580 m³/h, inlet SO₂ concentration = 600 ppm, with DR).

Figure 13. SO₂ concentration distribution (flow rate of gas = 128,290 m³/h, flow rate of liquid = 1580 m³/h, inlet SO₂ concentration = 600 ppm).

Figure 14. SO₂ concentration variation as height (vertical condition) (flow rate of gas = 128,290 m³/h, flow rate of liquid = 1580 m³/h, inlet SO₂ concentration = 600 ppm).

Table 4. The total desulfurization efficiency of scrubber under different conditions

Item	Vertical condition		Inclined condition
	Open	Distribution ring	Open	Distribution ring
Desulfurization efficiency (%)	93.3	99.2	84.6	92.8

Figure 15. Effect of liquid–gas rate on desulfurization efficiency (flow rate of gas = 128,290 m³/h, inlet SO₂ concentration = 600 ppm).

Figure 16. Effect of droplet diameter on desulfurization efficiency (flow rate of gas = 128,290 m³/h, inlet SO₂ concentration = 600 ppm, L/G = 12.3).

Figure 17. Application of spray scrubber with distribution rings in a container ship. 

Figure 18. SO₂/CO₂ of exhaust gas after scrubbing (sulfur content of fuel oil = 3.1%).