Coal Ash Reuse Options: A Strategy for Moving Forward. Dr. Jack Groppo University of Kentucky Center for Applied Energy Research Lexington, Kentucky

Transcription

1 Coal Ash Reuse Options: A Strategy for Moving Forward Dr. Jack Groppo University of Kentucky Center for Applied Energy Research Lexington, Kentucky

2 Source: EIA Annual Energy Outlook, 212 Early Release

3 Electricity Generation by Fuel B kwhr Billion kwhr B kwhr 5 Coal Natural Gas Nuclear Renewable Petroleum & Other Source: EIA Annual Energy Outlook, 21

4 Non-Hydro Renewable Generation Offshore Wind Wind Solar Photovoltaic Solar Thermal Wood and Other Biomass Biogenic Municipal Waste Geothermal Generation, Bkwhr Source: EIA, Annual Energy Outlook 212

5 U.S. Capacity Additions: Source: Energy Velocity Add Campaign Funded by Chesapeake Energy (natural gas producer) Source: Gooden Group Public Relations

6 Projecting Ash Production 1,4 18 Coal Consumption or Ash Production, Mst 1,2 1, Coal Consumption Ash Production** Ash Content Ash Content, % Source: ACAA, National Mining Assoc.

7 1,4 12 1,2 1 Coal Consumption, Mst 1, Coal Consumption Ash Production** Ash Production, Mst

8 Fly Ash and Bottom Ash % Utilization % Utilized Tons Produced Tons Utilized Production and Utilization, Million tons

9 Fuel Delivered to US Utilities Electric Utility Receipts, K tons 6, 5, 4, 3, 2, 1, - Subbituminous Bituminous Lignite Ash Content, % Lignite Bituminous Subbituminous 2

10 US Ash Production Estimate 6, 5, Thousand Tons 4, 3, 2, Class F Class C 1, -

11 Fly Ash & Bottom Ash Major Uses MillionTons

12 Portland and Masonry Cement Consumption Metric Tons (s) % 25 Source: PCA

13 FGD Gypsum 25 2 Million tons 15 1 Unused Other Clinker Concrete Wallboard Source: ACAA

14 Wallboard Demand 2,, 4 Single Family Housing Starts,SAAR 1,8, 1,6, 1,4, 1,2, 1,, 8, 6, 4, HOUSING STARTS WALLBOARD DEMAND Wallboard Demand, BSF 2, 5 Source: American Homebuilders Assoc.

15 US Gypsum Production and Utilization Total Gypsum Consumption M Tons 35 3 Units Wallboard Production B ft2 Synthetic Gypsum % of Total Consumption 1 5 Synthetic Gypsum Consumption M Tons Source: USGS

16 FBC Ash 14, 1 K Tons 12, 1, 8, 6, 4, 2, Utilization Rate, % Unused Waste Stabilization Mining Applications Soil Modification Road Base/Subbase Structural Fill Concrete/Flowable Fill Utilzation Rate

17 Assumptions Unconfined CCB uses will be curtailed and eventually eliminated by regulation Renewable energy growth will be realized by co-firing biomass primarily in FBC units

18 CCB Production Projections Million Tons FBC FGD PC Ash 6 4 2

19 CCB Utilization Projections Million Tons Utilization Rate, % FBC FGD PC Ash Rate

20 Summary Projections % Change Coal Utilization M tons 1,35.2 1, % Production PC Ash M tons % FGD Products M tons % FBC Ash M tons % Total CCBs M tons % Utilization PC Ash M tons % FGD Products M tons % FBC Ash M tons % Total CCBs M tons % Utilization Rate % 38.% 28.6%

21 Current CCP Research Efforts Beneficiated Ash To improve concrete performance New cements based on CCPs CSAB Cements Clinkerless Cements Plaster Cements

22 Beneficiate Ash to Reduce Water Demand Water % D 5 Fineness (cm 2 /g) Underflow Product Ghent Lab Product (2%) Ghent Lab Product (2%) Ghent Field Product (2%) Ghent Field Product (2%) Ghent Econosizer Product (2%) Ghent Flotation Product (2%) Mill Creek Product (2%) Coleman Product (2%) Trimble (2%) Rockport (2%) Mill Creek (2%) Micron3 (2%)

23 Product Evaluations in Mortar Flowsheet Flowsheet Flowsheet Flowsheet Processed Fly Ash Product EP FP UFA FUFA d5 microns Water Reduction % Substitution % of Control 7 Day Day Day Mortar Air ul of AEA To Constant 6% air

24 Chloride Permeability with Processed Fly Ash Concrete Mix RCP ASTM Chloride (coulombs) Rating Control 2418 Moderate F Ash 2% 12 Low Ghent CP 2% 426 Very Low Ghent CP 4% 15 Very Low

25 CSAB Cements Not a new idea Quillin, Mehta and others Purpose: To develop a calcium sulfoaluminate-belite cement (CSAB) with CFBC ash as a key ingredient High strength, low-energy, and low CO 2 emitting Calcium sulfoaluminate (C 4 A 3 S`) Increases early strength Hydration of this phase forms ettringite (C 6 AŚ 3 H 32 ) Contributes to early strength Belite (C 2 S) Hydrates slowly Low compressive strengths compared to Alite (C 3 S) Ettringite

26 Formulation of CSAB Cement Commercially produced CSAB cement acquired from China Shenzhen Chenggong Trade Co. CSA Major cementitious phases and oxide compositions X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) Klein s compound and belite need to be optimized Initial formulations Bogue equations modified for CSAB cement These normative equations could not be used Minor amounts of other phases formed (i.e. gehlenite; C 2 AS) Formulations adjusted to meet several objectives: Minimize limestone and thus the free lime formed (CaO) Maximize the byproduct used (CFBC and PCC ash) Produce a cement that approaches the performance of commercial CSAB cement CSAB#1 CSAB#2 CSAB#4

27 Laboratory Cement Formulations Component CSAB#1 CSAB#2 CSAB#4 HS CSAB#4 MS CSAB#4 LS Limestone Bauxite FBC Spent Bed Class C Fly Ash Class F Fly Ash Gypsum Ultra Fine Ash Total CCBs Byproduct of fluidized bed combustion (FBC) of coal 2 Gypsum and Ultra Fine Ash are milled with the clinker; percentage is calculated on a mass basis of the cement product 3 Ultra Fine Ash is a processed material from ponded, Class F fly ash Procedure: 1. Raw materials are milled to 16 microns 2. Fired in a furnace at 125 o C for 1 hr to produce clinker 3. Clinker is milled with FGD gypsum to produce cement

28 Laboratory Cement made from FBC Ash 8 Compressive Strength 7 PSI OPC CSAB#1 CSAB#2 CSAB#4 HS CSAB#4 MS CSAB#4 LS Time (days)

29 XRD Analysis of Cement Clinkers = Klein s Compound = Anhydrite = Belite

30 Future CSAB Work Large scale production of CSAB#4 for testing in concrete with new rotary kiln Sources of aluminum other than bauxite are being investigated (i.e. aluminum refinery byproduct)

31 Clinkerless Cement Mainly produced from Class C fly ash and/or Clean Coal Technology byproducts Cementitious reactions are mainly ettringite- and pozzolanbased Main problems: Slow strength gain Calcium Sulfate Hemihydrate Potential for destructive expansion Excessive Ca(OH) 2 High ph Colloidal ettringite crystals

32 Clinkerless Cement Formulation 1. Spent bed material is prehydrated with 1% water then dried 2. Material milled with fly ash to a median size of ~15 microns 3. Some formulations milled with FGD gypsum hemihydrate ( plaster ) for rapid strength gain Moistened with 7.5% water; pressed at 4, lbs (1815 kg) Steam autoclave and heated 13 o C and 3 bars for 4 hours Ingredient FBC:UFA 7:3 Formulation (% by weight) FBC:UFA 4:6 FBC:UFA 4:6 HH FBC:FA 5:5 FBC:FA 5:5 HH FBC Spent Bed Ultrafine Fly Ash Ordinary Fly Ash Hemihydrate 47 47

33 Compressive Strength (PSI) Mortar Strength Data for Spent Bed and Class F UFA CL 7/3 CL 4/6 CL 4/6 HH Curing Time (days)

34 Plaster Cements All are based on calcium sulfate Many varieties Alpha hemihydrate: produced by heating gypsum in autoclave Rapid hardening, but poor durability Cementitious reactions produce gypsum: Plaster: CaSO 4.5H 2 O + 1.5H 2 O CaSO 4 2H 2 O

35 ASTM C 19 Compressive Strength Data 7 for FBC:Fly Ash:Plaster Mortars Compressive Strength, p.s.i FBC:UFA 7:3HH FBC:UFA 4:6HH FBC:FA 5:5HH

36 2.5 ASTM C 157 Expansion of FBC:UFA Mortars Expansion (%) FBC:UFA 7:3 FBC:UFA 4:6 7:3 HH Dry 4:6 HH Dry Time (days)

37 Compressive Strength, p.s.i ASTM C192/C 39 Compressive Strength of FBC:UFA 4:6 HH Concrete Time (days)

38 ASTM C 666 Freeze Thaw Resistance Dynamic Modulus (% of initial) Cycles Control (OPC) #1 Control (OPC) #2 FBC:UFA 4:6HH#1 FBC:UFA 4:6HH #2