Maximizing Boiler Plant Efficiency. Presenter: Dan Watkins, LEED BD+C Sales Engineer Bornquist, Inc.

Transcription

1 Maximizing Boiler Plant Efficiency Presenter: Dan Watkins, LEED BD+C Sales Engineer Bornquist, Inc.

2 Efficient Boiler Design Boiler Types Efficiency Definition Non-Condensing Condensing Maximizing Efficiency Understanding Efficiency Outdoor Reset Short Cycle Prevention Hybrid Systems

3 Efficient Boiler Design Combustion Efficiency 100 percent of efficiency minus the percentage of heat lost up the vent. Thermal Efficiency The combustion efficiency minus the jacket losses of the boiler. Based on ANSI Z For boilers 300,000 to 12.5 million Btu. A.F.U.E. The measure of annual efficiency of a boiler that takes into account the cyclic on\off operation and associated losses as it responds to changes in load. For boilers under 300,000 Btu

4 Efficient Boiler Design Non-Condensing Cast Iron Steel Tube Copper Fin Modulating 75-88% Efficiencies

5 Efficient Boiler Design Condensing Cast Aluminum Stainless Steel Cast Iron Dual Heat Exchanger 85-99% Efficiencies depending on operating conditions

6 MARKETING AND REALITY Thermal efficiency.can reach efficiencies of 98% - and more.. 98% EFFICIENT 3/20/12 Condensing Boilers 6

7 ENERGY CONTENT OF NATURAL GAS LATENT HEAT 10.2% SENSIBLE HEAT 89.8% Latent Definition: Latin for hidden Heat that can be measured or felt by a change in temperature 3/20/12 Condensing Boilers 7

8 NON-CONDENSING BOILER HEAT FLOW 3/20/12 Condensing Boilers 8

9 CONDENSING BOILER HEAT FLOW 3/20/12 Condensing Boilers 9

10 What is a Condensing Boiler? A condensing boiler is a boiler which has a heat exchanger that is made of materials which will withstand acidic condensate. 3/20/12 Condensing Boilers 10

11 MATERIAL CHOICES FOR CONDENSING BOILERS Materials on the market: Aluminum Alloy SA Ti 316L Cast Iron? Copper Tube w/ secondary heat exchanger 3/20/12 Condensing Boilers 11

12 Flue gas condensate Typical household sewage Oil Gas Acidic ph-value Basic Battery acid Gastric acid CORROSIVE FLUE GAS CONDENSATE ph Values of various fluids Lemon juice Vinegar Rain water Clean rain water Distilled water (neutral) Tap water Lake water Ammonia 3/20/12 Condensing Boilers 12

13 What about Efficiency? Condensing boilers are NOT 99% efficient all of the time. 3/20/12 Condensing Boilers 13

14 120 o F return water 100% input 87% efficiency Where is the condensation? 3/20/12 Condensing Boilers 14

15 Condensing/Modulating Boiler With efficiencies like this our customers have reduced their fuel bills by up to 80%. Now you can, too! 140 F EWT 120 F EWT 100 F EWT 80 F EWT 3/20/12 Condensing Boilers 15

16 LATENT HEAT RECOVERY WATER VAPOUR LIQUID Water vapor turns to liquid when it is reduced in temperature. 3/20/12 Condensing Boilers 16

17 HEAT RECOVERY FROM FLUE GASES Water vapor (steam) containing latent heat Simplified Chemical Combustion Formula: CH O 2 CO 2 +2 H 2 O 3/20/12 Condensing Boilers 17

18 LATENT HEAT RECOVERY 1 pound of water Water vaporizing (Latent heat of condensation) 970 Btus Steam Ice melting (Latent heat of fusion) Ice 144 Btus 3/20/12 Condensing Boilers 18

19 WATER VAPOUR DEW POINT 3/20/12 Condensing Boilers 19

20 NATURAL GAS COMBUSTION +Excess air 1 part gas 10 parts air More excess air = Lower CO 2 % Lower C0 2 % = Lower dew point temperature Lower dew point temp. = Less condensation 3/20/12 Condensing Boilers 20

21 Dew point water vapor o F o C WATER VAPOR DEW POINT Natural Gas (95% CH 4 ) CO 2 % of flue gas influences dew point temperature Higher CO 2 =Higher Dew point =More Condensation Lower CO 2 =Lower Dew point =Less Condensation CO 2 in Vol % 3/20/12 Condensing Boilers 21

22 Heat Exchanger Design: PRIMARY HEAT EXCHANGER DESIGN SECONDARY HEAT EXCHANGER DESIGN 3/20/12 Condensing Boilers 22

23 PRIMARY HEAT EXCHANGER DESIGN 3/20/12 Condensing Boilers 23

24 SECONDARY HEAT EXCHANGER 3/20/12 Condensing Boilers 24

25 Efficient Boiler Design Condensing Boiler Design Guidelines Design system for lower water temperatures Use larger delta T s Radiant floor heat / snow melt Water Loop Heat Pumps Select boiler plant for small turndown capabilities Save initial cost by using both condensing and non-condensing boilers when possible

26 Outdoor Reset Efficient Boiler Design Designing a Reset Curve Cycle Efficiency How the cycle suffers Adjusting the differential Buffer Tanks Piping Systems Maximizing Efficiency

27 Efficient Boiler Design Outdoor Reset

28 Boiler Plant Cycle Efficiency 28

29 CHICAGO, IL 29

30 Cycle Efficiency Curve Analysis 30

31 Energy Use (Therms, DecaTherms, etc.) Energy Use Per Unit of Load (e.g., HDDs) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun 31

32 Old Energy Use Per Unit of Load (e.g., HDDs) New Energy Use Per Unit of Load (e.g., HDDs) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun 32

33 Old Energy Use Per Unit of Load (e.g., HDDs) New Energy Use Per Unit of Load (e.g., HDDs) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun 33

34 Old Energy Use Per Unit of Load (e.g., HDDs) New Energy Use Per Unit of Load (e.g., HDDs) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun 34

35 Energy Use (Therms, DecaTherms, etc.) Energy Use Per Unit of Load (e.g., HDDs) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun 35

36 Energy Use (Therms, DecaTherms, etc.) Energy Use Per Unit of Load (e.g., HDDs) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun 36

37 The E/L Curve Fast Billing Period Therms HDDs Therms/HDD December January February Best? March etc Total Therms Total HDD Total HDD x Best Therms/HDD = What s Possible Total Therms What s Possible = What Was Wasted 37

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39 To achieve HCE performance, you must 1 track small fracponal loads at high efficiency 2 make the efficiency rise as the load falls 3 size boilers so all loads fall within plant modulapon range 4 use low mass boilers for jockey service 5 use modulapng burners 6 oppmally match fuel input to real- Pme load 39

40 Piping Design Examples 40

41 Boiler Piping Examples

42 Boiler Piping Examples BOILER BOILER BOILER BOILER 42

43 Boiler Piping Examples

44 Boiler Piping Examples

45 Boiler Piping Examples

46 Boiler Piping Examples

47 Boiler Piping Examples

48 Boiler Piping Examples

49 Boiler Piping Examples

50 Boiler Piping Examples

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52 Hybrid Boiler System

53 Buffer Tank Example Using a buffer tank to add 200 gallons will increase firing to almost 3 minutes for a 20 F delta T. Using reset on the system loop could allow for a 50 or 60 F delta T. Using a 60 F delta T would mean a minimum run time of over 8 minutes!

54 Buffer Tank Example

55 Buffer Tank Example

56 Buffer Tank Example Condensing Boiler Non- condensing Boilers

57 Buffer Tank Example BufferTank Non- condensing Boilers Condensing Boiler

58 Design Guidelines Utilize Buffer tanks and water temperature reset Design for long on/off cycles Boilers do not need to be same size/style Use small, modulating boilers as a jockey boiler Design for efficiency during light loads

59 Final Thoughts System design is typically more important than individual equipment selections. Energy retro-fits should be based potential savings and initial cost. Every building and every system is different, so there is no one-size-fits-all approach to Energy Saving Design.

60 Thank You! 60