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Part 2. Air pollution control engineering

Part 2. Air pollution control engineering. Gaseous Particulates. Control of Sulfur Oxides ( SO x ). Emission of SO x one of the major causes of acid precipitation. London fog event of December 1952. Sulfur dioxide in Brussels-Capital Region. yearly moving-average month average.

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Part 2. Air pollution control engineering

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  1. Part 2. Air pollution control engineering • Gaseous • Particulates

  2. Control of Sulfur Oxides (SOx) Emission of SOx one of the major causes of acid precipitation

  3. London fog event of December 1952

  4. Sulfur dioxide in Brussels-Capital Region yearly moving-average month average

  5. Evolution of SO2 emissions in Belgium since 1990 Target fixed by the Federal Government Trend differs according to the industry / activity sector

  6. .

  7. Sulphur compounds found in fossil fuels Hydrogen sulphide H2S

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

  9. 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 (FeS2) which has a higher density than coal. From grinded coal it is removed by elutriation or flotation. 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. Separation according to decreasing fall velocity Principle of an elutriator

  10. 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 (FeS2) which has a higher density than coal. From grinded coal it is removed by elutriation or flotation. 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. Desulphurization through catalytic hydrogenation – Step 1 ~ 400°C, ~ 50 bars

  11. 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 SO2

  12. Packed Bed Scrubber

  13. 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, • CA = concentration of A, [mol/L] • KH = equilibrium constant (Henry's Law constant), [mol/L-atm] • pA = partial pressure of A, [atm]

  14. Lime treatment reused in construction

  15. A well-developed soda scrubber is the Wellman-Lord SO2 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 (Na2SO3) for scrubbing and generates a concentrated SO2 (about 90%), in effect removing the SO2 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 SO2 in the pretreated flue gas to produce sodium bisulfite NaHSO3 according to SO2 + Na2SO3 + H2O --2NaHSO3 • 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.

  16. Wellman-Lord (regenerative) process Na2SO3 regeneration

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