Cooling Tower Water Conservation: Simple Strategies & Advanced Treatment Eric Elam Water Savers LLC, RTS Water August 15 th, 2017

Transcription

1 Track 2 Core Energy Technologies Advanced Water Management Cooling Tower Water Conservation: Simple Strategies & Advanced Treatment Eric Elam Water Savers LLC, RTS Water August 15 th, 2017 Tampa Convention Center Tampa, Florida

2 Cooling towers come in all sizes 2

3 Cooling Tower Water Use Typical Cooling Tower Flow Diagram Fan and Motor Process Return Drift Eliminators Fill Material Make-up Overflow Float To Process Blow Down Pump Basin Conductivity Controller 3

4 Cooling Tower Water Use Six Ways of Water Loss Evaporation Blowdown Drift loss Wind loss Overflow Leaks 4

5 Cooling Tower Water Use Water Use Equations for Cooling Towers MU = E + BD + D + L Where MU = Makeup E = Evaporation BD = Blowdown D= Drift and wind loss - accounts for less than 0.001% of water use L = Leaks, overflows, and other losses - Should be controllable with proper fill valves and routine maintenance 5

6 Cooling Tower Water Use Water Use Equations for Cooling Towers E = 1% x CWFR x T/10 x 60min/hr x Annual Runtime Hours Where E = Evaporation CWFR = Condenser Water Flowrate T= Temp Change Across Tower - Generally towers are designed at 10 o F T - Higher T generally translates to higher evaporation, but towers experience shorter runtimes in order to meet load requirements Annual Runtime Hours = Actual operating hours - Can be estimated using ASHRAE Full Load Equivalent Hours 6

7 Cooling Tower Water Use Water Use Equations for Cooling Towers Full Load Equivalent Cooling Hours by Region Tampa Area = 3,068 FLE Cooling Hours Region Specific FLE Cooling Hours: Pacific Northwest = Northern CA = Northeast = Midwest = Mid-Atlantic = Southern CA = Southeast = Texas & Florida = Hawaii = 5000 Be Mindful of System Redundancy 7

8 Cooling Tower Water Use Water Use Equations for Cooling Towers Evaporation is a function of Cooling LOAD! So, Water Conservation opportunities result primarily from a reduction in blow-down losses by increasing cycles of concentration. 8

9 Cooling Tower Water Use Gallons per Ton-hr. CoolingTowerWaterUse GallonsperTon-Hour CyclesofConcentration 2.0kWh/ton-hr. 1.5kWh/ton-hr. 1.0kWh/ton-hr. 0.5kWh/ton-hr. Process 9

10 Cooling Tower Water Use Water Quality Dictates Cycles of Concentration Limits ph TDS (Total Dissolved Solids) TSS (Total Suspended Solids) Calcium Hardness Total Silica Organic Contamination 10

11 Cooling Tower Water Use What Determines the Amount of Blowdown? There are many factors that limit cooling water concentration The blowdown required is the least needed to satisfy ALL of the constraints. The only control the operator has to meet these limits is blowdown. Typical CWS Water Chemistry Limits Parameter Limit Constraint Conductivity < 4000 us Calcium > 75 ppm Tower warranty Corrosion Control LSI < 2.5 Calcium Scale Control Silica < 180 ppm Magnesium Silicate <25,000 Silica Scale Control MgSiO2 Scale Control ph 8 9 Corrosion Control Discharge Limits 11

12 Cooling Tower Water Use Cycles of Concentration (CoC) A Measurement of Cooling Tower Water Efficiency CoC = MU / BD BD = E / (CoC 1) CoC = κ condenser / κ make-up Where κ = (kappa) Conductivity in µs/cm, or µmhos - Condenser water conductivity is presumably at or near the blow-down setpoint - Make-up water conductivity will fluctuate seasonally and depends on water sourcing 12

13 Cost Savings & Water Conservation Strategies Sewer Exemption Sub-Metering Evaporation Credits are available from most Water/Sewer Providers, especially in metropolitan areas. Each Provider may have a different policy/procedure for obtaining the evaporation exemption, and may also impose significant fees/permitting requirements in effort to recover lost revenue. Evaporation Credits are NOT a water conservation measure! But they can result in significant cost savings opportunities. In Tampa area, the cost savings can equate to nearly $16 per Ton annually. (Lower Rate, Higher Cooling Load) In DC area, the cost savings can equate to nearly $18 per Ton annually. (Higher Rate, Lower Cooling Load) 13

14 Cost Savings & Water Conservation Strategies Traditional Chemical Treatment Depends on Regional Make-up Traditional chemical treatments typically involve 3 main components: Anti-scalant to combat against scale forming compounds such as calcium, magnesium Water Quality Biocide to combat against algae, bacteria, and other biofouling contaminants Corrosion Inhibitor to prevent degradation of mechanical components and piping. 14

15 Cost Savings & Water Conservation Strategies Traditional Chemical Treatment Major treatment providers get very comfortable operating in the 3 cycle range. THIS MEANS 50% of Evaporative load is lost as Blow-down Waste Contact your Chemical Treatment Provider about opportunities for High Cycle water treatment programs, and real-time monitoring capabilities. 15

16 Cost Savings & Water Conservation Strategies What if there was ANOTHER OPTION? Treat water from the source! 16

17 Cost Savings & Water Conservation Strategies Advanced Water Treatment Solutions Partial Softening Softeners are designed to remove calcium hardness They do so by exchanging with sodium, which results in higher conductivity of make-up water, but lowered calcium hardness Allows for an increase of blow-down set-point Why not make up with fully softened water? Corrosivity is increased, which can shorten life of capital equipment. 17

18 Cost Savings & Water Conservation Strategies From Ground Water System Partial Demineralization City Water (2 inch copper or steel) Demineralization = Reverse Osmosis Softeners will not reduce conductivity or remove silica, so demineralization approach may be an effective solution Partial De-min utilizes pre-filtration and softening, and ultimately generates ideal condenser water make-up quality by blending RO permeate with filtered water Can achieve 15+ cycles of concentration, while effectively maintaining corrosion rates Sensors WM WM To Softeners MMF MMF SOFT SOFT Brine Tank Chem Tank WM UV UV Nanofilter Unit Break Tank From softener, filter backwash, and nanofilter discharge Sensors WM 18

19 Cost Savings & Water Conservation Strategies Advanced Water Treatment Solutions Side-stream Filtration Side-Stream Filtration DOES NOT Save Water Allows for better high cycle cooling tower operation by filtering out debris, organics, and some bacterial contaminants Reduces bio-film on heat transfer surfaces May result in heat transfer efficiency gains of 5-15% depending on current tower conditions But, will actually result in increased water consumption due to filter backwashing 19

20 Cost Savings & Water Conservation Strategies Advanced Water Treatment Solutions Real-time Monitoring & BAS Integration with Advanced Controllers BAS Integration Capable utilizing BACNet or MODBUS Allows for real-time monitoring of system conditions Creates alarm case conditions for targeted maintenance Provides for accurate measurement and verification of system performance, with over 30 critical data points 20

21 MCRD Parris Island (Parris Island, SC) Eleven locations with small packaged Partial Softening and Sidestream Filters ( ton chiller systems) One location with Centralized Partial Softeners and localized Side- Stream Filters (4x200 ton chiller system) 21

22 MCRD Parris Island 22

23 NMSHA (Beaver, WV) Centralized Partial Softening and SSF (750 ton chiller system) 23

24 NMSHA 24

25 Corpus Christi Army Depot (Corpus Christi, TX) Phase 1 (4 space cooling systems ~2,730 ton total cooling capacity) Central Demineralization Plant with Distributed Make-up Localized Side Stream Filtration, BAS Integration Phase 2 (10 process cooling towers ~500 ton equiv. each) Partial Softening Side-stream Filtration 25

26 CCAD Phase 1 26

27 CCAD Phase 1 27

28 CCAD Phase 1 28

29 CCAD Phase 1 29

30 CCAD Phase 2 30

31 Department of Interior HQ (Washington, DC) Groundwater Collection Partial Demineralization Side-stream Filtration BAS Integration 31

32 DOI HQ Its what you cant see that matters the most Several underground sumps pits to capture ground water 2-large sump pumps discharging water to storm sewer system 32

33 DOI HQ Measurement and Verification Water flow were measured at 30 gallons per minute 43,200 Gallons per day or 15,768,000 Gallons per year potential Cooling tower annual make-up is 6,500,000 gallons per year 33

34 DOI HQ Ground Water Collection and Re-Use 34

35 DOI HQ Water Reclamation System Overview 35

36 DOI HQ Ground Water Filtration System 36

37 DOI HQ 37

38 THANK YOU Eric Elam Vice President Design & Engineering Water Savers LLC, RTS Water 38