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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
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Energy efficiency in industrial steam production and distribution
Workshop Energy-efficiency 13-15 March 2006, Ljubljana
Dries MaesFlemish Institute for Technological ResearchBelgium
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
2
Structure1) Working with steam ? 2) To Determine the cost of steam3) Different points and ideas to save
energy in a steam system
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
3
Structure1) Working with steam ? 2) To Determine the cost of steam3) Different points and ideas to save
energy in a steam system
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
4
Working with steam in the industry ?Different heat transport fluids are available - Water
- no transition to steam allowed- temperatures are not too high : ± 150°C
- Thermal oil- specific composition of the oil for long lifetime - higher boiling temperatures so higher operating temperatures.
- Steam- Specific use of latent energy in the fluid- High heat transfer gives smaller heat exchangers
• Water : 4.000 W/m²C• Oil : 1.500 W/m²C• Steam : > 10.000 W/m²C
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
5
Working with steam in the industry ?Boiling point of water at
different pressures
0
50
100
150
200
250
300
0 10 20 30 40
Absolute Pressure [Bar]
Boiling point [°C]
Distribution of the energy content in steam between the sensible and latent heat
0
500
1000
1500
2000
2500
3000
0 5 10 15 20 25 30 35 40
Absolute Pressure [Bar]
Enth
alpy
[kJ/
kg]
Sensible heat
Latent heat
Total energy content
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
6
The right pressure..• Benefits of higher pressure :
– The steam has a higher temperature– The volume is smaller, the distribution pipes are smaller. – It is possible to distribute at high pressure and to relax steam prior to
application. The steam thus becomes dryer and reliability is higher.– a more stable boiling process in the boiler.– ...
• Benefits of lower pressure : – There is less loss of energy at boiler level and in the distribution– The amount of remaining energy in the condensate is relatively small.– Leakage losses in the pipe system are lower. – ...
!! Working with steam also has implications for safety, reliability, costs, lifespan of the equipment... !!!
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
7
Structure1) Working with steam ? 2) To Determine the cost of steam3) Different points and ideas to save
energy in a steam system
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
8
The cost of steam ? Different factors :• CF Fuel • CW Water supply• CBFW Feed water treatment (includes softening, clarification..)• CP Feedwater pumping power• CA Combustion air fan• CR Sewer charges for boiler blowdown• CD Ash disposal costs• CE Environmental emissions management and control cost
(includes additives)• CM Maintenance materials and labour
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
9
The cost of steam• Fuel costs are normally by large the most important costs :
– CG = 1.1 x CF
• What does this cost mean ?– average cost– no effect of different pressure levels– no effect of marginal consumption– no effects of regulation or intermediate electricity production– ....
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
10
Average versus marginal costs of steamAverage cost = Total operating cost / Total Steam
= CO/SMarginal cost = Marginal production cost /
Marginal quantity of Steam Consumption = ∆CO/∆S
Very different approach, but more correct for the evaluation of energy saving measures
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
11
The cost of steam : via marginal costs, example
Boiler 2
Cap. 18 ton/h
Eff. 83%
Boiler 1
25 ton/h
84%
Cap.
Eff. 82%
Boiler 4
Cap. 19,5 ton/h
Eff. 83%
Boiler 3
Cap. 19,5 ton/h
Eff.
Boiler 5
Cap. 19,5 ton/h
Eff. 81%
50 Barg Users
Boiler 6
Cap. 19,5 ton/h
Eff. 73%
Boiler 7
Cap. 65 ton/h
Eff. 83%
Deaerator
Flash recuperator
116,2 ton/h
74,3 ton/h
1 Barg Users
0,4 ton/h
PRV Turbines 2 & 3 Turbine 1
Fresh water makeup
Blowdown
Condensate recuperation
PRV
PRV
10 Barg Users7,5 ton/h
25 Barg Users
8,3 ton/h
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
12
The cost of steam : via marginal costs, example• Marginal cost is highly
variable• Picture differs for every
steam pressure level• cost shows influences of
varying efficiencies, turbines, pressure-reducing valves,...
Marginal cost for steam production
€ 0
€ 5
€ 10
€ 15
€ 20
€ 25
€ 30
€ 35
0 20 40 60 80 100[ton/h]
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
13
Structure1) Working with steam ? 2) To Determine the cost of steam3) Different points and ideas to save
energy in a steam system
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
14
Different ways to save energy in a steam system• Use economisers to pre-heat feedwater• Install an air pre-heater• Prevent scale deposits on heat transfer surfaces. Ensure deposits are regularly removed on
the waterside of boilers• Minimize boiler blowdown• Recoverable heat from boiler blowdown• Minimise boiler short cycling losses• Consider installing high-pressure boilers with backpressure turbine generators for the
production of electricity or for rotating installations• Implement a control and repair programme for steam traps• Install insulation on steam pipe and condensate return pipes• Installation of removable insulating pads on valves and fittings• Collect condensate and return it to the boiler for re-use• Re-use of flash steam• Use of flash steam on the premises or through recovery of condensate at low pressure• .....
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
15
1) Implement a control and repair programme for steam traps
• Steam systems without regular inspection often have defect steam traps
• Without inspection, after 3 to 5 years, 30% of all steamtraps needs repair or replacement
• Normally, a distribution system should have less then 5% of defective steam traps.
• Critical traps :– High pressure steam traps– Traps connected to expensive or critical equipment.
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
16
Function of steam traps• prevent the
steam to pass.• evacuate the
condensate(once all the energy hasbeen used)
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
17
Different operation modes for steam traps
The steam trap cannot be reached and was therefore not tested. Not testedNT
This line of out of order. Out of orderOO
This steam trap can no longer deal with the flow of condensate. To be replaced with a trap of the right size.
SubmergedSB
The steam trap is closed. No condensate can flow through it. To be replaced
FixedFX
The cycle of this thermo-dynamic steam trap is too fast. Must be repaired or replaced.
Fast cycleFC
Steam leaks from this steam trap. It needs to be repaired or replaced.LeaksLK
Steam is escaping from this steam trap, with maximum steam losses. Needs to be replaced.
Steam escapingESWorks as it shouldAll rightOK
DefinitionDescription
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
18
Related costs of escaping steam• Amount of escaping steam can be
huge.• Defective trap represents large losses• Example :
– leakage– standard application– operating pressure difference : 15 bar– losses : 16.650 € per year
• If not simply leaking, but full Blow-through : 66.570 € per year
• These costs easily justify a control programme for steam traps.
Yearly steam losses in function of operating pressure
0
20000
40000
60000
80000
100000
120000
0 5 10 15 20[bar]
[Ton/year]
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
19
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
20
2) High pressure boilers and turbines to producelow-pressure steam
• The intervention is large. Economic yield can be equallylarge.
• This is applicable if :– continuous steam supply is necessary– or continuously steam is being reduced in pressure by PRV’s
• Alliance with electricity providers is often possible.
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
21
Pressure-Enthalpy Diagram for Water and SteamBased on the IAPWS-95 Formulation for General and Scientific Use
1
10
100
1000
10000
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5Enthalpy, kJ/kg
Pres
sure
, bar
Copyright © 1998 ChemicaLogic Corporation.Drawn with SteamTab V3.0.
1
2 3 Steam is used at this point.
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
22
Pressure-Enthalpy Diagram for Water and SteamBased on the IAPWS-95 Formulation for General and Scientific Use
1
10
100
1000
10000
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5Enthalpy, kJ/kg
Pres
sure
, bar
Copyright © 1998 ChemicaLogic Corporation.Drawn with SteamTab V3.0.
1
23
4 Steam is used at this point.
Steam is prepared at
higher pressure(100 bar)
Expansion of the steam over a turbine to
produce electricity
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
23
Example• Situation : Boiler needs to be replaced : - 25 tonnes/h of steam - at 15 barg- efficiency 74 %- 6,500 hours per year operating timeOptions :1) Replace by equivalent boiler of better quality2) Replace by high-pressure boiler and back-pressure
turbine
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
24
Examplea) Yearly operating cost of the old boiler:
= 2.051.836 €/year
b) Operating cost of the new boiler (new boiler equivalent with the old one, option 1)
= 1.898.041 €/year
1000 x 0.74€/GJ 3,8 t/h x 25 x kJ/kg 2459h/year x 6500
1000 x 0.80€/GJ 3,8 t/h x 25 x kJ/kg 2459h/year x 6500
13
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
25
Examplec) High pressure boiler, yearly operating cost (option 2)
= 2.070.555 €/year
Steam is overheated to 330°C to make energy available for the turbine
d) Amount of electricity generated by the turbine
= 7.022 MWh/year
Annual gain is equivalent to 351.106 €/year
This compensates largely for the higher operating cost
1000 x 0.80€/GJ 3,8 t/h x 25 x kJ/kg 335) - (3017.5h/year x 6500
0.97 t/h 25 x kJ/kg 150.9h/year x 6500
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
26
Practically• Turbines can be interesting when :
– high operation load during the year– large use of lower pressure steam– energy prices have an important role
(collaboration with electricityproviders can be interesting)
– not the first measure to be taken, butcan be considered when high energyefficiency has been achieved byother measures.
50 Barg Users
Boiler 7
Cap. 65 ton/h
Eff. 83%
116,2 ton/h
1 Barg Users
0,4 ton/h
Turbine 1
10 Barg Users
7,5 ton/h
25 Barg Users
8,3 ton/h
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
27
3) Minimising Blowdown and recuperation of Blowdown energy
• Blowdown :– necessary discharge of boiler water to
• reduce concentration of salts in the boiler water• remove suspended particles in the boiler water
– Blowdown percentages depend largely on the quality of fresh water preparation.
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
28
Bottom blowdown
15
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
29
Deconcentration blowdown
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
30
Minimising Blowdown ? • TDS (Total dissolved salts) concentration needs to be
controlled. • Example : initial blowdown rate is 8%• Boiler :
– 25 bar – 5,500 hours a year. – 25 tonnes of steam per hour – boiler efficiency 82%– Gas : 5 €/GJ– Freshwater 1,3 €/ton– Discharging 0,1 €/ton
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
31
Minimising Blowdown ? • Automatic blowdown control reduces blowdown
rate from 8% to 6%. • 8% -> 2,08 t/h• 6% -> 1,5 t/h• Gains :
• Water savings : 4,451 €/year
• Total : 15,172 €.
€/year107211000.000x 0.82
€/GJ 5 x kJ/kg 553.1h x 5500l/h x 578=
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
32
Recuperation of energy from Blowdown
94873661451642110%
7585894914133378%
5694423683102526%
3792942462071684%
190147123103842%
95746152421%
50 barg20 barg10 barg5 barg2 barg% of boiler supply
Operating pressure of the boilerBlowdown rate
Recovered energy from blowdown losses, in MJ/h [1]
[1] These quantities have been determined based on a boiler supply of 10 tonnes/h, an average temperatureof the boiler water = 20°C, and a recovery efficiency of 88%.
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EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
33
Solubility of oxygen in water in function of the temperature
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60 70 80 90 100
Water temperature (oC)
Solu
bilit
y of
oxy
gen
(ppm
)
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
34
0,2 bar105°C
18
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
35
Conclusions• Much more interventions are possible• Raising energy prices make several interventions
economically interesting• Good set-up of priorities necessary among
different interventions (economic yield of interventions may interact)
• Definitively a good idea to look into any existingsteam system.
EU-Twinning Project SL04/EN/01Integrated Pollution Prevention and Control (IPPC)
Dries Maes, STEVITO, Mol
Ljubljana, 13 -15 March 2006
Mission 6.2: Energy Efficiency
36
Thank you Dries Maes
VITO, Flemish Institute for Technological ResearchBoeretang 2002400 MolBelgium+32/14/33.58.27Dries.maes@vito.be