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Effective Boiler Utilization

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Effective Boiler Utilization Why go to all the trouble ? Steam is an easy method for transferring heat energy from a heat source to a heat load. – PowerPoint PPT presentation

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Title: Effective Boiler Utilization


1
Effective Boiler Utilization
2
Why go to all the trouble ?
  • Steam is an easy method for transferring heat
    energy from a heat source to a heat load.
  • Addition of heat and moisture into the material
    improves processing.
  • Goal is to produce a gelatinized material with
    improved feed value.

3
Benchmark your cost of steam production.
  • Determine your annual fuel cost based on utility
    bills.
  • Install a steam flow meter or water flow meter in
    your facility and calculate your steam generation
    costs.
  • Compare your actual costs with the benchmark.
  • (Use a water flow meter on water feed into the
    boiler will also cover boiler blow down effects.)

4
Performing Benchmark
  • You will need to know the following.
  • Operating boiler pressure.
  • Feedwater Temperature.
  • Type of fuel used.
  • Cost of fuel.

Energy Required to Produce One Pound of Saturated
Steam, Btu.
5
Benchmark Continued
  • Example
  • Producing 100 psig steam, 101 Deg F feed water,
    and 7.50/MMBtu Natural gas.
  • Steam Cost (7.50/MMBtu/106 Btu/MMBtu) 1,000
    lb 1,119.1 Btu/lb/0.857
  • Steam Cost 9.79/1,000 lb steam

6
Factors Effecting Steam Costs.
  • Feed Water Temperature.
  • Heat Transfer (Chemistry).
  • Burner Efficiency
  • Steam Application
  • Distribution System.
  • Steam Traps
  • Condensate Return
  • Insulation

7
Feed Water Temperature
  • Proper feed water temperature control can be a
    major factor when looking at improving steam
    system efficiencies.
  • Compare Benchmark calculation for 90 psig steam
    at 53 Deg vs 162 Deg F feed water.
  • 54 Deg F 10.21/1,000 lb of steam
  • 162 Deg F 9.26/1,000 lb of steam
  • A difference of 0.95/1,000 lb of steam
    production

8
Feed Water Temperature
  • There are a several ways to increase the feed
    water temperature in the system. Two of the most
    common methods would be
  • Direct Steam injection into the feed water
    make-up tank with thermostatically controlled
    valve.
  • Install Feedwater Economizer.
  • Proper condensate return and blowdown heat
    exchangers.

9
Feed Water Temperature
  • Direct Steam Injection.
  • Steam injected directly into the feed water tank
    can be used as a heat source, but it is important
    to remember that this is also a heat load on the
    boiler and will not provide a high energy savings.
  • Economizer
  • Generally, boiler efficiency can be increased by
    1 for every 40 Deg. F reduction in flue gas
    temperature.
  • Economizers have limits for both cold end
    corrosion and exhaust gas temperatures that must
    be observed.

10
Heat Transfer
  • Proper Boiler Chemistry control is critical in
    efficient boiler operation as well as boiler
    safety.
  • 1/50th of an inch of hard scale buildup on boiler
    tubes can result in an increase in fuel usage of
    up to 20,000/ year.
  • Find a reliable boiler chemistry company and
    perform tests as required.

11
Burner Efficiency
  • The purpose of the burner is to mix molecules of
    fuel with molecules of air. A boiler will run
    only as well as the burner performs. Burners are
    designed to maximize combustion while minimizing
    the release of emissions.
  • An efficient natural gas burner requires only 2
    to 3 excess oxygen, or 10 to 15 excess air.

12
Burner Efficiency
  • Flue Gas Analyzers
  • The percentage of oxygen in the flue gas can be
    measured by inexpensive gas absorbing test kits.
  • More expensive analyzers are available that
    display Oxygen, stack gas temp., and boiler
    efficiency. These are recommended for boilers
    with annual fuel costs over 50,000.
  • Oxygen Trim Systems
  • If fuel composition is highly variable or in
    cases where steam flows are highly variable, an
    online oxygen analyzer should be considered.
  • The oxygen Trim system provides feedback to the
    burner controls to automatically minimize excess
    combustion air and maximize the fuel-to-air ration

13
Steam Application
  • Boiler systems in the feed industry have few
    similarities with industrial boiler systems. One
    of the main differences is with the condensate
    return system. Commercial boiler systems can
    return over 90 of the condensate while boiler
    systems in the feed industry typically return
    less than 5 condensate into the feed water
    system.
  • In short, almost all of the steam delivered into
    the distribution system is used or lost.

14
Steam Application
  • Performing the Benchmark test we learned that
    even the best situation will result in a given
    steam production cost.
  • 60 psig - 198 deg F - 7.50/MMBtu 8.89/1000
    lb steam
  • 100 psig 198 deg F - 7.75/MMBtu 8.95/1000
    lb steam
  • By insuring that we are not over-steaming, we can
    achieve enough heat input to cook while
    minimizing the total steam contribution.

15
Steam Application
  • 60 psig 198 Deg F - 7.50/MMBtu
  • 8.89/1,000 lb of steam
  • Adding 6 moisture in the steam chest requires
    approx. 127 lbs of steam application. At 0.0089
    per pound of steam that means that adding 6
    moisture (127 lbs) will have a cost of 1.13 per
    ton.
  • Compare this to adding only 3 moisture, 62 lbs,
    and a cost of 0.55 per ton.
  • 100 psig 198 Deg F - 7.50/MMBtu
  • 8.95/1,000 lb of steam
  • Adding 6 moisture in the steam chest requires
    approx. 127 lb of steam application. At 0.0090
    per pound of steam, that means that adding 6
    moisture (127 lbs) will have a cost of 1.14 per
    ton.
  • Compared to 0.56 per ton for 3
  • The higher pressure also insures that enough
    heat will be added for cooking with the reduced
    stem addition

16
Steam Application
There are a few options when looking at
monitoring steam application. The object is to
provide enough heat input for cooking while
minimizing pounds added.
  • Steam Flow Meters There are a number of steam
    flow meters that can be installed in the
    distribution system to allow operators to monitor
    and adjust steam application within specified
    ranges to insure adequate cooking while
    minimizing the pounds applied.

17
Distribution System
  • The steam distribution system includes everything
    from the boiler discharge valve out to the
    processing units and any condensate return system
    that may be in place.
  • The boiler blow down system, while not actually
    part of the distribution system may also offer
    some efficiency options and should be looked at.

18
Distribution System
  • Steam Traps
  • Every distribution system should include steam
    traps.
  • Steam traps provide a means for removing water
    droplet and condensate from the header prior to
    utilizing the steam for heating.
  • While extremely important in turbine
    applications, they also are important in our
    process to insure the highest energy and best
    quality steam is being applied.

19
Steam Traps
  • Steam loss from traps.
  • Steam traps should be tested to insure they are
    not cold plugging or failing open allowing steam
    to escape directly into the CR line
  • Four ways to test Temp., Sound, Visual,
    Electronic
  • Traps should be tested monthly to Quarterly.

20
Condensate Return
  • Returning hot condensate to the boiler makes
    sense for several reasons.
  • The more condensate that is returned, the less
    make-up water is required.
  • Chemicals and Chemical treatment costs.
  • Fuel savings with higher temperature make-up
    water.
  • Reduced boiler blowdown with return of high
    purity water.

21
Insulation
  • Un-insulated steam piping is a constant source of
    wasted energy.
  • Proper insulation can typically reduce energy
    losses by 90 and help insure proper steam
    pressure at processing equipment.
  • Any surface over 120 Deg. F should be insulated
    including boiler surfaces, steam piping and
    fittings, and CR lines.

22
Insulation
  • Proper insulation can provide a great deal of
    energy savings when properly selects and
    maintained.
  • Use insulating jackets for valves, flanges and
    traps. A 6-inch gate valve may have more than 6
    sq. feet of surface area.

23
Conclusion
  • There are obviously a number of factors that
    effect boiler utilization and efficiency.
  • If you dont know what your cost of steam
    production is, how can you improve it.
  • If your not monitoring your steam usage, it is
    impossible to tell if you are being efficient.
  • Use the various resources available to you for
    better steam and boiler utilization

24
Resources
  • www.eere.energy.gov/industry/bestpractices
  • This site has a lot of information available and
    can be a great resource for improving
    efficiencies.
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