06 Carmeuse Broden
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Transcript of 06 Carmeuse Broden
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Carmeuse FGD experience in USACarmeuse FGD experience in USA
Bob RodenDirector FGT Markets
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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?
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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
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Staffing requirements
Process owner Lab personnel Dedicated operators Dedicated maintenance
Mechanics
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Mechanics Instrumentation
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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
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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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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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