Carmeuse FGD experience in USACarmeuse FGD experience in USA

Bob RodenDirector FGT Markets

Customers

Currently supplying 20,000 MWs to FGD Ranging in size from 50 to 1,400 MWs

Providing 4 million tons of reagent per year Lime and Limestone

Carmeuse is in a unique position to observe both

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Carmeuse is in a unique position to observe bothstart-up and long term operation of FGD systems

What have we seen work successfully?

What Goes on in the FGD System

First SO2 Dissolved in Liquid Sulfur Dioxide Dissolves in Water SO2 (g) + H2O HSO3- + H+

Limestone Neutralizes Acid in the Liquid Liquid drop to Reaction Tanks

Sulfite goes to Sulfate (Oxidation)

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Sulfite goes to Sulfate (Oxidation)HSO3-1 (l) + 0.5 O2 SO4-2 (l) + H+

Oxidation - Air blown into absorber with oxidation aircompressors, dispersed by the agitators

Enhances Speed of Second Reaction SO4 reacts with limestone forming gypsumSO4-2+Ca+2+2H2O CaSO4 .2H2O

You are operating a CHEMICAL plant

Staffing requirements

Process owner Lab personnel Dedicated operators Dedicated maintenance

Mechanics

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Mechanics Instrumentation

Variables for System Control

Limestone Quality Absorber Operating Variables Dewatering Operating Variables

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Process Stream Testing Limestone Limestone Slurry Absorber Bleed Slurry

Monitoring and Testing

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Hydroclone Slurries Gypsum

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Process Testing Limestone

CaCO3, MgCO3 , Inerts, Silica Limestone Slurry

Particle Size and Limestone Purity Absorber Slurry

Monitoring and Testing

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Absorber Slurry pH Oxidation (Calcium Sulfate vs. Calcium Sulfite) Inerts Chloride Density Gypsum particle Size

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Process Testing Hydroclone Slurries

Particle Size Gypsum Purity Inerts Density

Monitoring and Testing

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Density Gypsum Final Product

Particle Size Purity Moisture Chloride Inerts

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Variables Effecting FGD Goals Limestone Quality

Limestone Quality Purity (Calcium Carbonate) 95%

Better the limestone, less usage, less waste, better SO2 reaction If it is not CO3 , it is a waste product Every % Inert material results in cost

Iron (Iron Oxide) less than 0.25% Adversely effects gypsum production above 0.8%

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As Iron gets higher, more fine gypsum particles are produced

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0%

10%

20%

30%

40%

50%

0%5%

10%15%20%25%30%35%40%

Particle Size Particle Size

TYPICAL GYPSUM PARTICLE SIZE CURVE GYPSUM SIZE CURVE EXCESS IRON

5 microns 40microns 80 microns 5 microns 40microns 80 microns

Limestone Quality (Continued) Hardness

Got to be able to grind material 14 on index Harder material more horse power to grind Hard material will reduce Ball Mill Capacity

Silica Silica Limit on Stone should be at 2%

Variables Effecting FGD Goals Limestone Quality

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Silica Limit on Stone should be at 2% Higher Silica, More wear and tear Ball Mills, pumps and valves

- Ball Mill Liners- Recycle and Process Pumps- Limestone Control Valves

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Limestone Quality (Continued) How to Control

Monitor Supplier Vendor Data, Quarry Info (know before it gets in their shipping pile) Do your own testing

Equipment Surveillance Equipment Inspection

Variables Effecting FGD Goals Limestone Quality

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Equipment Inspection- Mills, Mill Product Pumps, Hydroclones & Control valves best

indicators Ensure Proper Mill Operation

Maintaining Mill operation to grind material to sizing and density- Mill fineness test Want limestone less than 325 mesh (44m)- Looking for surface area, smaller particle, higher surface area

To avoid such problems consider outsourcing milling step to a strategicpartner

May be the key to get guaranteed reagent availability at best price with lowestoperating concerns

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Absorber Operating Parameters for Control Everything occurs in the Absorber, actions downstream are

difficult to make to impact corrective action pH/Reagent Control

Variables Effecting FGD

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pH/Reagent Control Density Oxidation Recycle Rate/Retention Time

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pH and Reagent Control Reagent Control is important for two reasons

Required to supply enough limestone to neutralize acids (HCl,SO2) Provide appropriate pH for optimum Oxidation

Reagent Control Philosophy Feed forward from SO2 Monitors provide main control

pH is the trim control

Variables Effecting FGD Absorber Operating Parameters

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pH is the trim control Each control Limestone Slurry Feed Control Valve

CaCO3 Required = SO2 flow * 100/64 * removal rate Control valve set by reading flow (flow * density = lbs/hr of CaCO3 )

Adverse Effects from non conformance Low pH

Not removing enough SO2 Increased Corrosion Potential

High pH poor oxidation and excess limestone in gypsum and scaling

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Density Control Density should be controlled at 20% solids

Surface area (Particles) is required for site to precipitate gypsum Low density will provide multiple issues

- Gypsum will form small particle as it precipitates instead ofprecipitating on other gypsum particle, making them grow to

Variables Effecting FGD Absorber Operating Parameters

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precipitating on other gypsum particle, making them grow tolarger size

- Gypsum will find surface area if one is not provided- Pumps, piping, tank walls, MEs

High density will cause slurry difficult to pump and potential pluggage of recycleheader nozzles and on the absorber tower tray

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Oxidation You want all Sulfate in Tank no Sulfite

Force the reaction speed to increase SO3 to SO4 does not occur quickly, must Force Oxidation

Force all gypsum to deposit in reaction tank onto other solids Inhibits/Eliminates Re-Emission of Mercury

Variables Effecting FGD Absorber Operating Parameters

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Inhibits/Eliminates Re-Emission of Mercury Oxidation Requirements

Correct pH Range Enough Air

O2/S ration of 2.5/1 (By Design) Higher Sulfur Coal More Air

Good distribution of air bubbles Tank Level to provide head required for bubble retention

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of

head

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Dewatering System Vacuum Belt Operation

Correct Solids Density Provides Better Dewatering Even Flow of Material Across the Vacuum Belt

Variables Effecting FGD Dewatering Operating Parameters

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Quality Wash Water Delivered evenly across filter Vacuum Pumps and System Operating per design

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Production of Specification Gypsum Bad Actors in Gypsum Production

Inerts (Ash and Silica) Ash from Boilers Silica from Limestone

Small Particle Size Will not dewater Too much energy into gypsum, breaking crystals

Poor overall Chemical control -Chlorides, pH

Variables Effecting FGD Dewatering Operating Parameters

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Poor overall Chemical control -Chlorides, pH

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Questions?

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