Reducing Energy & Water In Your Boiler House Charles Astbury Commercial Operations GE Water & Process Technologies Presented by
What areas can you impact? Reduce Blowdown Saves water and energy Recover heat from Blowdown Saves energy Recover Condensate Saves water and energy
Cycles of Concentration
Cycles of Concentration
Cycles of Concentration 8 2 = 4
Impact of blowdown on water At 10 cycles have 10% blowdown At 20 cycles have 5% blowdown At 50 cycles have 2% blowdown At 100 cycles have 1% blowdown 98 MT/Hr Fuel BFW 100 MT/Hr C=50 CBD At 10 Cycles BD = 10.9T/Hr 2% 2 MT/Hr IBD
Impact of blowdown on efficiency BTU Value of Blowdown Heat BD Heat Lost, $/yr With No Heat Recovery With Flash Tank Bottoms With Flash Tank and Heat Exch Cycles % BD FW BD klb/hr klb/hr 10 10% 111,111 11,111 $367,531 $147,947 $11,836 20 5% 105,263 5,263 $174,093 $70,080 $5,606 50 2% 102,041 2,041 $67,506 $27,174 $2,174 Basis Steam 100,000 lb/hr Pressure 600 psi 50 cycles versus 10 cycles saves $300,000/yr 50 cycles versus 10 cycles saves $120,000/yr 50 cycles versus 10 cycles saves $10,000/yr
How do you reduce blowdown? Turn it down... Increase deposition risk High performance chemicals Decline in steam purity Steam purity is a direct function of boiler water dissolved solids content Improve makeup water quality
Discussion Topics BFW & steam purity requirements Pretreatment Methods Membrane solutions for boiler RO in front of demineralizers RO replacement of softeners
Begin the feedwater system design process by defining your end state water quality needs What level of water purity do the boiler and steam processes require?
ASME GUIDELINES Table 1 - Watertube Boiler with Superheater/Turbine All Pressures: FW dissolved oxygen < 7 ppb (with DA) Feedwater ph: 8.3-10.0 (0-900 psig) / ph 8.8-9.6 (> 901 psig) Boiler Feedwater Boiler Water Drum Pressure (psig) Iron (ppm Fe) Copper (ppm Cu) Total Hardness ppm CaCO Silica ppm SiO Total alkalinity ppm CaCO ( ) ( )( ) 3 2 3 Specific Conductance ( µmhos/cm) (Unneutralized) 0 to 300 300 to 450 451 to 600 601 to 750 751 to 900 901 to 1,000 1,001 to 1,500 1,501 to 2,000 0.100 0.050 0.030 0.025 0.020 0.020 0.010 0.010 0.050 0.025 0.020 0.020 0.015 0.015 0.010 0.010 0.300 0.300 0.200 0.200 0.100 0.050 0.000 0.000 150 90 40 30 20 8 2 1 350 300 250 200 150 100 - - 3500 3000 2500 2000 1500 1000 150 100 Note: All limits are expressed less than the value specified (e.g., < 0.100 ppm)
GE Steam Purity Recommendations for Utility Steam Turbines with Reheat Steam Parameter All Volatile Treatment Phosphate Treatment Equilibrium Phosphate Treatment Sodium, ppb <3 <5 <3 Cation <0.15 <0.3 <0.15 Conductivity, us/cm Silica, ppb <10 <10 <10 Chloride, ppb <3 <3 <3 Sulfate, ppb <3 <3 <3 Total organic carbon, ppb * Steam Purity Recommendations for Utility Steam Turbines, GEK 72281A, July, 1996 <100 <100 <100
BFW quality considerations Boiler pressure and superheater/turbine steam purity requirements generally define pretreatment and feedwater quality requirements. In general: Softened or single pass RO < 600 psig Demineralized or RO/EDI > 900 psi RO Reverse Osmosis EDI - Electrodeionization
Technologies to Improve Makeup Water Purity Softeners Dealkalizers Demineralizers Reverse Osmosis Systems
Resin Based Pretreatment Performance System Softener Dealkalizer Standard two-bed demineralizer Two-bed demineralizer with counterflow regeneration Two-bed demineralizer with mixed bed polisher Typical Effluent Quality 0.2-1.0 ppm hardness (no TDS reduction) 50 to 90% alkalinity reduction (no TDS reduction) <10 µmho <200 ppb silica <5 µmho <50 ppb silica <0.1 µmho <10 ppb silica Typical Boiler Operating Pressure (psig) 0 to 600 0 to 600 400 to 900 900 to 1,200 1,200+
Zeolite Softening & Dealkalization Advantages Inexpensive Cap & Op costs Simple-to-operate Durable Safe & inexpensive sodium chloride regenerant Limitations No reduction in TDS FW quality can limit boiler cycles Not suitable for high-pressure boiler operation (> 900 psig) No silica reduction No alkalinity reduction without dealkalizer
Resin-based demineralization Advantages Limitations Reduction in all dissolved solids Enables high cycles operation Suitable for high-pressure boilers Can tailor to specific purity needs Excellent silica rejection Excellent alkalinity/co2 rejection Strong acid/caustic required for regeneration Caustic costs high & variable Limited anion resin life Silica and sodium leakage Manpower intensive Operating costs directly proportional to TDS
Reverse Osmosis Advantages Rejection of all dissolved solids Operating costs not directly dependant on TDS Enables high cycle boiler operation Requires no chemical regenerants (acid/caustic) Not labor intensive Versatile pairings with resin-based systems Ideal for mobile applications Limitations RO alone not suitable for HP boiler feedwater > 1000 psig with turbine Higher electrical costs than resinbased systems (high-pressure pumps) Generates significant reject stream (typically 20 30% of input stream) Does not reject CO2 (g)
What are the tools available? CCR Bankbook Feedwater Economic Models BoilerCalc Condensate Modeling System
What are the tools available? CCR Bankbook Feedwater Economic Models BoilerCalc Condensate Modeling System Touch on this Focus on this
CCR Bankbook
Potential Membrane Solutions for Boiler Systems 1. RO in front of existing demineralizers 2. RO in front of, or to replace existing softeners 3. New plant RO/MB or Demin/MB? 4. 2 pass RO/EDI to replace resin-based demineralizer - Mixed-bed quality train 5. Ultrafiltration in front of demin. or RO to replace traditional filtration/clarification
RO ahead of Existing Demin Reduced acid & caustic regenerant costs 90 95% reduction in regenerant usage is typical 10 to 15% more feedwater production each month 90% less (high TDS) regenerant waste Extended ion exchange resin life 40 50% extension in resin life typical Much longer regen. cycles & reduced iron/organic fouling Improved feedwater & steam quality Sodium & silica slippage & breaks reduced Detailed economic & environmental benefit analysis and modeling is required
Key input variables for modeling & analysis TDS of influent water Capital equipment costs Caustic and acid costs Electrical power rates Influent water costs Sewer costs o o o Economic Volume or Vol/TDS-basis? Can plant reuse RO reject? Credits or incentives for reuse Regenerant neutralization costs Differential labor costs Environmental Reduction of acid/caustic inventory Safety - chemical exposure Water scarcity issues Discharge/permitting issues
RO preceding Demineralizer Approximate TDS Breakeven Raw Water, $/kgal $.50 Waste Water, $/kgal $.50 Flow, 50 gpm 380 Flow, 450 gpm 230 $.50 $1.00 405 275 $.50 $2.00 470 310 $1.50 $2.00 500 360
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Saving Water & Energy is a Big Win in Every Way, and the creative use of Membrane solutions for Boilers can help you to make it happen at your facility! These are just two of the many possibilities Thank you for your time & attention