1. Environmental Technology ChimH409 (2-0-1) Michel Verbanck mikeverb@ulb.ac.be 2012 Universite Libre de Bruxelles Welcome @ Bruface Dept Water Pollution Control

2. Course structure Part 1. Introduction (incl. generic methods) Part 2. Air pollution control engineering Part 3. Water & wastewater treatment Part 4. Solid and hazardous wastes

3. Part 2. Air pollution control engineering Gaseous Particulates

5. 5

6. Control of Sulfur Oxides (SO x ) Emission of SO x one of the major causes of acid precipitation

7. London fog event of December 1952

8. yearly moving-average month average

9. Evolution of SO 2 emissions in Belgium since 1990 Trend differs according to the industry / activity sector Target fixed by the Federal Government

10. .

11. Abatement of SO 2 Selection of fuel type Pre-treatment of the fuel (before use) Flue gas desulfurization (FGD)

12. Ethyl-mercaptanEthane C 2 H 5 -SHC2H6C2H6 Boiling point35°C-88.6°C this implies that sulfur compounds have a tendency to accumulate in heavy fractions when fuel is refined Sulphur compounds found in fossil fuels Hydrogen sulphide H 2 S

13. Heavy fuels used in maritime transport are now targetted (especially in SO x emission control areas) MARPOL Annex VI Change to Low-sulfur fuel Several options for control:

14. Coal-fired power plants - Desulphurization of a solid Sulfur in coal is either organic (usually about 60%) or inorganic (about 40%). The inorganic form is iron pyrite (FeS 2 ) which has a higher density than coal. From grinded coal it is removed by floatation. The removal of organic sulfur requires a chemical reaction that is accomplished best if the coal is gasified first. Gasified coal is like natural gas.

15. Desulphurization through catalytic hydrogenation – Step 1 ~ 400°C, ~ 50 bars Coal-fired power plants – Desulphurization of a solid Sulfur in coal is either organic (usually about 60%) or inorganic (about 40%). The inorganic form is iron pyrite (FeS 2 ) which has a higher density than coal. From grinded coal it is removed by floatation. The removal of organic sulfur requires a chemical reaction that is accomplished best if the coal is gasified first. Gasified coal is like natural gas.

16. Desulphurization through catalytic hydrogenation – Step 2 Then a Claus converter is used to recover S vapor by staged combustion oven ~ 1000°C 300°C, catalytic reduction of SO 2

17. Henry's Law states that the amount of a gas that dissolves into a liquid is proportional to the partial pressure that gas exerts on the surface of the liquid. where, C A = concentration of A, [mol/L] K H =equilibrium constant (Henry's Law constant), [mol/L-atm] p A =partial pressure of A, [atm]

19. Packed Bed Scrubber

20. reused in construction Lime treatment

21. Wellman-Lord (regenerative) process Na 2 SO 3 regeneration

22. A well-developed soda scrubber is the Wellman-Lord SO 2 recovery process, which has found use in powerplants, refineries, sulfuric acid plants, and other industrial installations. The process utilizes a water solution of sodium sulfite (Na 2 SO 3 ) for scrubbing and generates a concentrated SO 2 (about 90%), in effect removing the SO 2 gas from other flue gases. The flue gas from fossil powerplants (or nonferrous smelters) is first pretreated by cooling and removal of particulate matter, such as by electrostatic precipitators, prior to being sent to the absorber. In the absorber the water solution of sodium sulfite absorbs the SO 2 in the pretreated flue gas to produce sodium bisulfite NaHSO 3 according to SO 2 + Na 2 SO 3 + H 2 O --  2NaHSO 3 Actually the sodium bisulfite is sent to a forced-circulation evaporator- crystallizer (see sketch) via a surge tank. The evaporator-crystallizer is the herth of the system. The surge tank allows steady flow rates into it despite gas flow and concentration fluctuations. Through the application of low- pressure steam (such as from a turbine exhaust), the sulfite is regenerated. The desulfurized gas is reheated before going to the stack in order to improve atmospheric dispersion.