Water Energy Nexus 10 18 11

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Water/Energy Nexus: Boiler water contains large amounts of energy. Practical ways of conserving this energy to save money and fuel are discussed.

Water/Energy Nexus: Boiler water contains large amounts of energy. Practical ways of conserving this energy to save money and fuel are discussed.

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  • 1. WelcomeAssociation ofEnergy EngineersPresented byJames McDonald, PE, CWT
  • 2. 2
  • 3. Squeezing $$ out ofBoiler WaterThe Water/Energy Nexus
  • 4. 1Water Energy NexusWater Value & Uses 4
  • 5. Value $$ of Water? Water Energy Sewer Pretreatment Chemical 5
  • 6. Water Uses = Energy Heat Cool Clean Cut Drive turbine Product component 6
  • 7. 2Water Energy NexusBoilers 7
  • 8. Heat: Boilers Heat water • Steam • Hot water Types • Watertube • Firetube 8
  • 9. Boilers Heat Water Makeup Temperature: 60°F • 28 BTU/lb Boiling Point: 212°F at 0 psig • 180 BTU/lb 9 Steam: 212°F at 0 psig • 1,150.2 BTU/lb 9
  • 10. Boilers Heat Water @ 150 psig Makeup Temperature: 60°F • 28 BTU/lb Boiling Point: 366°F at 150 psig • 338.47BTU/lb 1 0 Steam: 212°F at 0 psig • 1,196 BTU/lb 10
  • 11. Boiler System Operating Costs 11
  • 12. Eureka! We have Steam!!!! Mass Balance Makeup Water In = Steam Out Energy Balance Fuel Energy In = Steam Energy Out 12
  • 13. Water Mass Balance Makeup Water In = Steam Out?????? What’s left behind? • Contaminants Dissolved Solids: Calcium, magnesium, sodium, chloride, phosphate, bicarbonate, carbonate, iron, manganese, etc. –Retrograde solubility Suspended Solids: Silts, corrosion by-products, precipitated salts, etc. 13
  • 14. Boilers CyclesCycles begin when water evaporates. As water evaporates, solids stay behind.When the solids = twice the MU solids, So forth, and so on.you have 2 cycles of concentration.
  • 15. 3Water Energy NexusScale & Deposits 15
  • 16. Scale & Deposits 16 1
  • 17. Scale = More Fuel Monthly Savings (If your Fuel Costs average $1,000 per Thickness of Scale Extra Fuel Cost month, a clean Boiler would give you (inches) (Percent) these corresponding savings) 1/32" 8.50% $85.00 1/25" 9.30% $93.00 1/20" 11.10% $110.00 1/16" 12.40% $124.00 1/8" 25.00% $250.00 1/4" 40.00% $400.00 3/8" 55.00% $550.00 1/2" 70.00% $700.00 17
  • 18. Scale = More Energy 18
  • 19. How to Control Scale? Blowdown • Continuous/surface blowdown Control dissolved solids/conductivity • Bottom blowdown Control sludge New Mass Balance • Makeup Water In = Steam + Blowdown New Energy Balance • Fuel Energy In = Steam Energy Out + Blowdown Energy Out + radiant losses + stack losses + combustion inefficiencies 19
  • 20. 4Water Energy NexusBoiler Blowdown 20
  • 21. Blowdown vs. Cycles of Concentration 10 Cycles of Concentration = 10% Blowdown • 10% of the boiler makeup water is going down the drain 20 Cycles of Concentration = 5 % Blowdown • 5% of the boiler makeup water is going down the drain 50 Cycles of Concentration = 2% Blowdown • 2% of the boiler makeup water is going down the drain 100 Cycles of Concentration = 1% Blowdown • 1% of the boiler makeup water is going down the drain How high can you go? • American Society of Mechanical Engineers (ASME) Guidelines • Steam quality • Scale forming salts solubility • Current boiler conditions • ASME recommends 100 maximum 21
  • 22. Wait!!! There’s More! Maximizing Cycles of Concentration • Saves water • Saves FUEL! Boiler @ 50 psig • Blowdown heat content = 267 BTU/lb Boiler @ 150 psig • Blowdown heat content = 338 BTU/lb Boiler @ 250 psig • Blowdown heat content = 381 BTU/lb Maximizing Cycles of Concentration Minimizes the Heat Going Down the Drain! 22
  • 23. Maximizing Cycles of Concentration Improve Makeup Water Quality • ASME: “Where a choice is available, the reduction or removal of objectionable constituents by pretreatment external to the boiler is always preferable to, and more reliable than, management of these constituents within the boiler by internal chemical treatment.” • Water Softener • Dealkalizer • Demineralization • Reverse Osmosis 23
  • 24. Maximizing Cycles of Concentration Maximize Control of Cycles • Automatic blowdown controller 24
  • 25. Maximizing Cycles of Concentration Chemicals • Prevent scale formation Chelants Polymers Phosphates Phosphonates 25
  • 26. Maximizing Cycles of Concentration Maximizing Condensate Return • High purity water source • Condensate Value = Water + Sewer + Fuel + Pretreatment + Chemistry + Effects on Boiler Cycles • $10-$20+ per 1,000 gallons New Mass Balance • Makeup + Condensate = Steam + Blowdown 26
  • 27. Condensate Value Higher Fuel Costs = Higher Value Higher % Return = Greater Potential Effect on Boiler Blowdown Figure 1: Total Condensate Value 2% 16% 9% Water 18% Sewer 1% Fuel Chemical Pretreatment 54% Blowdown 27
  • 28. Whew! So far… • Kept boiler surfaces scale/deposit free • Minimized blowdown • What next? 28
  • 29. 5Water Energy NexusMore Energy Savings 29
  • 30. Economizers Extract more heat from fuel Not all energy absorbed by boiler Economizer transfers waste boiler stack heat to boiler feedwater For every 40-50°F drop in stack temperature • 1% gain in boiler efficiency Dew point of acids and water the limiting factor • Unless use corrosion resistant materials 30
  • 31. Blowdown Flash Tank & Heat Exchanger Recover heat from the blowdown! • Example: 150 psig Blowdown heat content = 338 BTU/lb 366°F Blowdown Flash Tank • Lower Pressure = Flashing of portion of blowdown to low pressure steam. Can use in Deaerator –E.g., 10 psig at 240°F Blowdown Heat Exchanger • Exchange remaining heat with incoming makeup water • 20°F approach temperature Typically, 80% of waste heat in blowdown can be recovered 31
  • 32. Maintain Boilers (Water Side) Corrosion control • Oxygen pitting • Acid corrosion • Under-deposit corrosion • Caustic corrosion 32
  • 33. 6Water Energy NexusEnergy Saving Summary 33
  • 34. Energy Saving Summary Maximize Cycles of Concentration • Pretreatment • Automatic blowdown control • Chemicals • Maximize condensate return Economizers • Extract remaining amount of heat out of fuel Blowdown Flash Tank & Heat Exchanger • Keep heat from going down the drain 34
  • 35. 7Water Energy NexusResources 35
  • 36. Resources DOE Steam Systems Tool Suit • Steam System Assessment Tool (SSAT) • http://www1.eere.energy.gov/industry/bestpractices/software_ss at.html#ssat • DOE offers classes Crown Solutions Website • www.crownsolutions.com • RESOUCES  TECHNICAL PAPERS Drop by Drop: Articles on Industrial Water Treatment Excel Workbooks • BP Save Proprietary: Call Crown • AWT Reverse Osmosis Calculation Workbook Members Only, but… 36
  • 37. Thank YouQuestions?