Duke Energy Seminar September 3 5, 2008 Concord, NC

Transcription

1 Duke Energy Seminar September 3 5, 2008 Concord, NC

2 Dry Scrubber Fundamentals September 3, 2008 Charlotte, NC 2008 The Babcock & Wilcox Company. All rights reserved. 1

3 Dry Scrubber Can Have Several Meanings Furnace Sorbent Injection (FSI) Dry Sorbent Injection (DSI) Spray Dry Absorption (SDA) Flash Dry Absorption (FDA) Circulating Dry Scrubbers (CDS) 2008 The Babcock & Wilcox Company. All rights reserved. 2

4 Spray Dry FGD Fundamentals Coal-Fired Dry FGD Installations SDA Process Fundamentals SDA Process Flowsheets Key Component Design Considerations Key Operating Considerations 2008 The Babcock & Wilcox Company. All rights reserved. 3

5 US / Canadian Coal-Fired Dry FGD Installations by Dry FGD Technology US / Canadian Dry FGD Technology Installations % of Total 37,680 M W SDA 94.9% DSI 0.4% CDS 2.4% FDA 2.3% B&W Estimate based on market data July, The Babcock & Wilcox Company. All rights reserved. 4

6 US / Canadian Coal-Fired SDA Installations by Coal Type US / Canadian Coal-Fired Spray Dry FGD Systems % of Total 36,120 MW Installed / Committed Sub-Bit 70% Other 5% East Bit 15% West Bit 4% Lignite 6% B&W Estimate based on market data July, The Babcock & Wilcox Company. All rights reserved. 5

7 US / Canadian Coal-Fired SDA Installations by Unit Generating Capacity US / Canadian Coal-Fired Spray Dry FGD Systems Total Installations / Committed Projects by Unit Size MW (24) MW (31) < 100 MW (20) > 750 MW (6) MW (14) B&W Estimate based on market data July, The Babcock & Wilcox Company. All rights reserved. 6

8 SDA Process Fundamentals AQCS Configuration / Selection Two stage emissions control Slurry Atomization Absorption and drying Terminology 2008 The Babcock & Wilcox Company. All rights reserved. 7

9 Typical FGD Configurations Wet FGD Dry FGD 2008 The Babcock & Wilcox Company. All rights reserved. 8

10 Dry vs. Wet FGD Considerations Lower sulfur fuel range Lower capital cost Lower aux. power consumption Lower water consumption Improved secondary emissions control in combination with fabric filter Limited value by-product 2008 The Babcock & Wilcox Company. All rights reserved. 9

11 Spray Dryer Absorption Process Hot flue gas Flue gas cooled and humidified by reagent slurry Particulate removed SDA BH / ESP SO 2 / H 2 SO 4 / HCl / HF Cleaned Gas Dryer performance is critical for long term operability 2008 The Babcock & Wilcox Company. All rights reserved. 10

12 Two Stage Emissions Control Process Add reagent Dry slurry Humidify gas Collect solids Continue reactions 2008 The Babcock & Wilcox Company. All rights reserved. 11

13 Slurry Atomization Dual Fluid Rotary Wheel 2008 The Babcock & Wilcox Company. All rights reserved. 12

14 Atomization Good mixing of reagent and flue gas for acid gas control Fine drops for evaporation and drying Controlled spray cloud for long term operability Stable temperature control 2008 The Babcock & Wilcox Company. All rights reserved. 13

15 SO 2 Absorption Absorption of acid gases most rapid when water is present Dissolution rate of SO 2, reagent solubility or absorption may be rate limiting High reagent solubility and drop ph promote absorption Inert solids provide more surface area and enhance gas/reagent contact Enhanced by good distribution of high surface area reagent SO 2 OH - CA ++ Flue Gas SO 2 + OH - HSO 3 - CA ++ + SO 3 -- CaSO 3 Solid Lime Particle Ca(OH) 2 Water Film 2008 The Babcock & Wilcox Company. All rights reserved. 14

16 Drying Initial, rapid first order drying period determined by: Outlet temperature Feed slurry solids loading Drop size Chloride content Second order drying period brings solids to final moisture content Particles / agglomerates leave SDA at 1 to 2% surface moisture 2008 The Babcock & Wilcox Company. All rights reserved. 15

17 Key SDA Terminology and Operating Concepts Lime Use Rate (lb/hr) Saturation 3500 Safe Drying Removal 95% 90% Design SDA Outlet Temperature (F) Approach Temperature (30 F) Flue gas and process water determine acceptable operating conditions Typical design requirement 30 to 35 degree approach 2008 The Babcock & Wilcox Company. All rights reserved. 16

18 SDA Process Flowsheets Single Pass Solids Recycle Fly Ash Pre-Collection 2008 The Babcock & Wilcox Company. All rights reserved. 17

19 Single Pass or Lime Only H 2 O F F SDA BH / ESP Low sulfur coal ---- Very low feed slurry solids Lime H 2 O Only about 10% of large coal-fired installations use this approach 2008 The Babcock & Wilcox Company. All rights reserved. 18

20 Solids Recycle F F SDA BH / ESP Lime Recycle Solids H 2 O H 2 O 2008 The Babcock & Wilcox Company. All rights reserved. 19

21 Spray Dry FGD Solids By-Product Recycle Lime Only Single Pass Lime carried on larger fly ash particle surfaces has more readily available surface area for reaction than an agglomerate of fine lime particles The Babcock & Wilcox Company. All rights reserved. 20

22 Example Mass Balance Sub-Bituminous Coal 1.29 gr/acf gr/acf Fly ash 16,540 lb/hr SDA BH CaO 1,680 lb/hr Recycle Solids 107,025 lb/hr Disposal / Utilization 20,650 lb/hr 92% SO 2 Removal By-product / Recycle Solids Composition (wt. %) Fly Ash Inerts 0.62 Free Water 1.00 Crystal Water 1.77 CaSO CaSO CaF Ca(OH) CaCl CaCO The Babcock & Wilcox Company. All rights reserved. 21

23 Fly Ash Pre-Collection ESP SDA BH / ESP Fly ash Pre-Collection Lime Recycle Solids H 2 O H 2 O Typical European semi-dry FGD practice 2008 The Babcock & Wilcox Company. All rights reserved. 22

24 Key Component Design Considerations Reagent Preparation SDA Components Typical design criteria 2008 The Babcock & Wilcox Company. All rights reserved. 23

25 Typical Lime Specification Quicklime (CaO) Material Sizing ¾ inch with no more than 50% passing less than 10 mesh Availability 90% CaO or greater per ASTM C25 Reactivity 40 C temperature rise or greater in 3 minutes Total temperature rise in 10 minutes max 2008 The Babcock & Wilcox Company. All rights reserved

26 Lime Slaking Horizontal Ball Mill Detention Slaker Vertical Ball Mill 2008 The Babcock & Wilcox Company. All rights reserved. 25

27 Recycle Slurry Make Up Minimize wet/dry interface zone Minimize dusting Two x 100% capacity trains for a 600 MW installation 2008 The Babcock & Wilcox Company. All rights reserved. 26

28 Rotary Atomizer Assembly Lube oil cooler Motor Gear box Oil Pump Wheel Skirt 2008 The Babcock & Wilcox Company. All rights reserved. 27

29 Rotary Atomizer Wheel Slurry Solids 2008 The Babcock & Wilcox Company. All rights reserved. 28

30 Flue Gas Distribution Roof Gas Disperser 60 / 40 Split Central Gas Disperser 2008 The Babcock & Wilcox Company. All rights reserved. 29

31 Key Design Considerations Number of SDA Modules per Unit Determined by gas flow and/or atomizer capacity Drying chamber residence time 10 to 15 seconds Gas flow determines module size Performance limiting factors SDA inlet temperature Inlet SO 2 concentration Process water quality Must consider in selection of operating conditions Slaking water quality impacts reagent slurry 2008 The Babcock & Wilcox Company. All rights reserved. 30

32 Key Operating Considerations Process control Consumables By-product generation Typical emission requirements 2008 The Babcock & Wilcox Company. All rights reserved. 31

33 Basic Process Control Absorber Outlet Temperature Setpoint SO 2 Emission Setpoint TCs SO 2 Monitor SDA BH / ESP Slaker Temperature Setpoint Lime Density Monitor Recycle Slurry Solids Setpoint Recycle Solids H 2 O H 2 O 2008 The Babcock & Wilcox Company. All rights reserved. 32

34 Lime slurry by stack SO 2 Total atomizer feed by flue gas temperature 2008 The Babcock & Wilcox Company. All rights reserved. 33

35 SDA Temperatures Well Mixed Reactor Temp (F) Distance From Roof (FT) Flue gas temperature fairly even through out the chamber 2008 The Babcock & Wilcox Company. All rights reserved. 34

36 Minimize Radiant Heat Loss 2008 The Babcock & Wilcox Company. All rights reserved. 35

37 What Determines SDA Consumables? Lime Use Inlet conditions, lime and water quality and required performance Pressure Drop Flue gas flow and conditions, arrangement, SDA selection, FF design and operation Power Consumption Water Use Gas flow and temperature, slurry solids loading and flow Gas flow and temperature, spraydown 2008 The Babcock & Wilcox Company. All rights reserved. 36

38 Estimating By-Product Generation Rate 2.5 to 3.0 lb by-product solids / lb SO 2 removed Excluding fly ash 2.5 is good first estimate for Western coals 0.2 to 1.0 % S in coal 3.0 is better estimate for Eastern coals 1.0 to 1.5 % S in coal 90 to 94% SO 2 reduction 2008 The Babcock & Wilcox Company. All rights reserved. 37

39 SDA By-Product Utilization 159,198 tons put to beneficial use out of 1,427,263 tons generated (11.2%) SDA By-Product Solids Use (2005) Agriculture 12.10% Concrete Products 8.77% Flowable Fill 6.08% Structural Fill 1.67% Soil Mod. / Stabilization, 0.96% Mining Applications 70.42% Source American Coal Ash Association 2005 Coal Combustion Product (CCP) Production and Use Survey,

40 SDA By-Product Utilization - Europe 371,542 tons put to beneficial use out of 464,152 tons generated (80.0%) SDA By-Product Solids Use (2004) General Eng. Fill 16.62% Infill 12.17% Reclamation / Restoration 48.96% Other Use 12.46% Plant Nutrition 9.79% Source European Coal Combustion Products Association,

41 Typical SDA Emission Requirements SO to 0.10 lb/mbtu SO 3 (as H 2 SO 4 ) to HCl HF PM 10 (filterable) to PM 10 (total) to Selected Trace Metals 2008 The Babcock & Wilcox Company. All rights reserved. 40

42 Thank You Kevin Redinger Technical Consultant