ENE HELSINKI UNIVERSITY OF TECHNOLOGY SULPHUR #2

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1 SULPHUR #2 In situ SO 2 capture in fluidised bed combustors H 2 S control: - low temperature processes - the Claus process - high temperature processes: regenerable sorbents Sulphur emissions from transport vehicles see: rzevenho/gasbook

2 Combustion of solid fuels in fluidised beds

3 High temperature SO 2 capture during FBC Calcium-based sorbent Temp. 800 ~900 C Calcined and uncalcined limestone calcination, followed by sulphation CaCO 3 (s) CaO (s) + CO 2 CaO (s) + ½O 2 + SO 2 CaSO 4 (s) or direct sulphation CaCO 3 (s) + ½O 2 + SO 2 CaSO 4 (s) + CO 2 Dolomite fully-calcined dolomite sulphation CaCO 3 MgCO 3 (s) CaO (s)+ MgO (s) CaO + ½O 2 + SO 2 CaSO 4 or half-calcined dolomite sulphation CaCO 3 MgCO 3 (s) CaCO 3 (s)+ MgO (s) CaCO 3 (s) + ½O 2 + SO 2 CaSO 4 (s) + CO 2

4 Sulphur capture in fluidised beds: the CaCO 3 calcination reaction equilibrium p(co2), MPa MPa Pressurized Pressurized combustion combustion Pressurized Pressurized gasification gasification CaCO CaCO 3 3 Atmospheric Atmospheric processes processes CaO CaO TEMPERATURE, C C

5 SO 2 capture in FBC : Ca/S ratio Bubbling (BFBC) vs. circulating (CFBC) beds

6 SO 2 capture in FBC Different sorbent qualities SORBENTS CaCO 3 * (%wt) MgCO 3 * (%wt) Specific Surface ** (m²/g) Particle Porosity (-) Particle Density (kg/m³) Average Pore Diameter *** (µm) Limestone Limestone Limestone Limestone Limestone Dolomite Dolomite * Chemical composition taken from Yrjas et al. (1993) ** Found from N 2 BET surface measurement *** Found from mercury penetration porosimetry

7 SO 2 capture in FBC Different sorbents, 850 / 950 C, 15 bar Conversion Conversion of of CaCO3 CaCO3 to to CaSO4 CaSO4 (-) (-) Time Time (s) (s) Conversion Conversion of of CaCO3 CaCO3 to to CaSO4 CaSO4 (-) (-) Time Time (s) (s)

8 Sulphur capture in FBC : product layer on dolomite

9 Sulphur capture in FBC: single particle models

10 Sulphur capture in FBC : reducing zones

11 Sulphur capture in FBC : effect of pressure

12 Sulphur capture in FBC : 1 bar versus 15 bar Conversion Conversion to to CaSO4 CaSO4 (%) (%) CaO (1 bar) 10 CaO (1 bar) 10 CaCO3 (15 bar) CaCO3 (15 bar) Time Time (h) (h)

13 High temperature SO 2 capture (BFBC, CFBC in situ and pulverised fuel (furnace injection) Sulphur Sulphur capture, capture, % CFBC CFBC BFBC BFBC PC PC Lime Lime addition addition Ca/S, Ca/S, --

14 H 2 S control at low temperatures Principle Temperature range Process names Sorbent / catalyst Physical absorption product: H 2 S Chemical absorption product: H 2 S Oxidation product: sulphur Dry bed process product: sulphur K Selexol, Rectisol, Sulfinol, Purisol, CNG K Alkanol amines, Girbotol, SNPA- DEA, ADIP, Econamine K Stretford, Takahax, Townsend Methanol, dimethyl ether of polyethylene glycol, carbon dioxide Amines (MEA, DEA, MDEA, MGA, DIPA), potassium carbonate Solution of Na-salts of H2CO3, anthraquinone-2- sulphonic acid,... ~ 300 K Iron sponge Hydrated Fe2O3

15 Chemical and physical absorption

16 H 2 S chemisorption process chemistry with primary or secondary amines: H 2 S + R 2 NH R 2 NH HS - CO R 2 NH 2 R 2 NH R 2 NCOO - CO 2 + R 2 NH + H 2 O R 2 NH HCO3 - with tertiary amines: H 2 S + R 3 N R 3 NH + + HS - CO R 3 N no reaction CO 2 + R 3 N + H 2 O R 3 NH + + HCO3 -

17 H 2 S chemi-/physi-sorption process selection

18 H 2 S to sulphur : the Claus process Equilibrium conversion vs. vs. temperature Oxidise 1 / 3 of the gas flow: 2H 2 S + 3O 2 2SO 2 + 2H 2 O Recombine gas streams : 2H 2 S + SO 2 Overall : 2H 2 S + O 2 3/x S x + 2H 2 O 2/x S x + 2H 2 O

19 Claus reaction process chemistry 2H 2 S + O 2 2/x S x (s) + 2H 2 O Oxidation of 1/3 of the incoming H 2 S and mixing it with the rest: 2 H 2 S + O 2 SO H 2 O 2 H 2 S + SO 2 3/x S x (s) + 2 H 2 O Other reactions taking place, depending on the presence of CO 2 and NH 3 : H 2 S H 2 + 1/x S x (s) H 2 S + CO 2 H 2 O + COS COS + H 2 S H 2 O + CS 2 2 NH O 2 2 NO + 3 H 2 O

20 H 2 S control by the Claus process 1. H2S > 50% 2. H2S 15 50% 3. H2S < 15%

21 High temperature H 2 S removal: sorbents Sulphidation: Me x O y (s) +y H 2 S Me x S y (s) + y H 2 O Regeneration: Me x S y (s) + 1½y O 2 Me x O y (s) + y SO 2 Examples: MnO(s) + H 2 S MnS (s) + H 2 O MnS (s) + 1½O 2 MnO (s) + SO 2 ZnO(s) + H 2 S ZnS (s) + H 2 O ZnS (s) + 1½O 2 ZnO (s) + SO 2 with, for ZnO, the following side-reactions : Sulphidation : ZnO (s) + H 2 /CO Zn + H 2 O/CO 2 Regeneration : ZnS (s) + 2 O 2 ZnSO 4 (s)

22 H 2 S sorbents types and characteristics

23 Temperature ranges for H 2 S sorbents

24 H 2 S removal with regenerable sorbents

25 H 2 S removal with calcium-based sorbents /1:

26 H 2 S removal with calcium-based sorbents /2: H 2 S and COS equilibrium pressure High residual partial pressures for H 2 S and COS

27 HELSINKI UNIVERSITY OF TECHNOLOGY H2S removal with regenerable sorbents : the Piñon Pine (NV) coal gasification project

28 H 2 S removal with calcium-based sorbents : CaS stabilisation to CaSO 4

29 The CaO / CaSO 4 / CaS phase diagram

30 ENE-4J.153 Regenerative H 2 S capture (with zinc titanates)

31 The Zn-O-S equilibrium

32 Reactor types for H 2 S removal from gases with regenerable sorbents

33 Sulphur emissions from ships

34 H 2 S emissions from cars Ce + SO 2 + ½O 2 Ce(SO 4 ) 2 reducing conditions Ce(SO 4 ) H 2 CeO 2 + 2H 2 S + 6 H 2 O CeO H 2 Ce + 2 H 2 O