Effective Boiler Utilization

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Effective Boiler Utilization
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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.

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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.)

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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.
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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

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Factors Effecting Steam Costs.

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

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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

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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.

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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.

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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.

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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.

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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

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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.

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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.

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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

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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

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Resources

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