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Improving Air Quality in Your Community

Outdoor Air - Industry, Business, and Home: Industrial, Commercial, and Institutional (ICI) Boilers

You can help ICI boiler owners and operators reduce emissions of hazardous air pollutants (HAPs), particle pollution (dust), and volatile organic compounds (VOC) that may affect employees and the community by encouraging boiler owners and operators to conduct these activities:


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Conduct An Energy Efficiency Audit

      How?
  • Consult with facility managers and power plant operators to collect information on types and configuration of combustion devices, steam systems, and fuel use records.
  • Review previous audit or testing reports, stack testing, and permits.
  • Inspect the facility to assess the feasibility and effectiveness of implementing specific combustion and steam efficiency measures, including:
    • Combustion evaluation and optimization methods.
    • Combustion monitoring and systems controls.
    • General operations and training of staff.
    • Steam load and efficiency measures.
    • Combined heat and power potential.
  • Prepare a report on recommendations related to the feasibility of implementing specific combustion and steam efficiency measures, including:
    • Costs to implement.
    • Fuel and cost savings.
    • Specific emissions reductions.
      Benefits
  • A study in the Great Lakes region showed that a conservative 10% efficiency improvement would reduce over 900 pounds of mercury emissions as well as reduce criteria pollutants from industrial boilers in the Great Lakes Basin (The Delta Institute).
  • Average annual cost savings ranged from $1,500 to over $300,000 for the measures studied (The Delta Institute).
      Costs
  • Costs to conduct energy audit and/or hire a consultant.
  • Capital costs to make improvements ranged from $0 to $93,200, but most had a 2-year or less payback period (The Delta Institute).
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Reduce Heat Losses

      How?
  • Manage Excess Air
    • Measure excess air with a flue gas analyzer.
    • If the flue gas contains too much excess air, have a qualified burner technician adjust the burner and combustion air dampers to reduce excess air levels over the boiler operating range.
    • Inspect and maintain covers, observation ports, gaskets, and other openings to avoid the infiltration of unwanted air into the boiler cavity or flue system.
  • Use Heat Recovery Methods
    • Reduce heat loss in the flue gas by installing equipment such as deconomizers and combustion-air preheaters.
    • Install a direct-contact flue gas condensing unit.
    • Add a heat pump to convert low-temperature heat into high-temperature heat for other uses in the plant.
    • Install heat-reclaim burners to preheat the combustion air.
  • Clean Heat Exchangers
    • Whenever the boiler plant is shut down, inspect the fireside surface for a buildup of soot and the waterside surface for a buildup of scale, both of which can increase flue gas temperatures and heat loss and interfere with heat exchange.
    • Treat boiler feedwater as required to reduce deposits.
    • Use soot blowers, brushes, or manual lances as required.
  • Return Condensate to the Boiler
    • Return hot condensate from steam-using equipment to the boiler whenever possible to avoid an increase in the use of water, water-treatment chemicals, and thermal energy needed to heat the make-up water.
    • Partially recover heat that may be lost in the form of flush steam by submerging the condensate return inlet in the tank or by installing a spray condenser fitted to the top of the tank.
      Benefits
  • Energy-saving measures that reduce consumption of boiler fuel reduce emissions of air pollutants into the atmosphere in direct proportion to the amount of fuel reduction.
  • A Canadian firm employed a steam-condensate closed system that allows condensate to return in a closed pressurized loop to be reboiled. Energy consumption was reduced by 18% when compared with a conventional steam-condensate open system (Canadian Industry Program for Energy Conservation).
  • Direct-contact flue gas condensing removes particles and acid gases (such as sulfur dioxide [SO2]) from exhaust. Recovery of 80% to 90% of heat in the flue gas previously exhausted to the atmosphere is possible, and such a system can reduce fuel consumption by the facility by 50% (Canadian Industry Program for Energy Conservation).
      Costs
  • Costs of equipment to measure and monitor heat losses.
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Optimize Boiler Operation

      How?
  • Stage Boilers to Meet the Load
    • Avoid operating several boilers at part load or on standby, as this increases energy use and emissions.
  • Practice good start-up and shutdown procedures .
    • Use a relatively low-emission fuel, such as natural gas, to alleviate incomplete combustion and increased emissions until the boilers reach operating temperature.
    • Manage start-up procedures and fuel choices to minimize both emissions of air toxics and regulatory compliance issues.
    • If boiler units are relatively small, shut down the units in the evening to save energy.
  • Manage Fuel
    • Manage fuel storage areas to reduce excess water and debris, which will decrease fuel contamination and increase fuel efficiency.
    • Enhance fuel input mechanisms.
  • Develop and Implement Control Strategies
    • Develop and implement control strategies that take advantage of improved measurement techniques such as computer-based control systems for
      • Air flow.
      • Pressure.
      • Temperature.
      Benefits
  • Results in energy and operating cost savings.
      Costs
  • Costs to install controls and monitors.
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Maintain equipment

      How?
  • Establish a routine maintenance inspection program for burners in the boiler.
  • Keep burner tips in top condition. Fouled or burned-out tips do not promote the proper mixing of the fuel and primary air needed to ensure good combustion at the burner.
      Benefits
  • Results in energy and operating cost savings.
      Costs
  • Costs to install controls and monitors.
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Manage Boiler Blowdown

      How?
  • Conduct frequent chemical analyses to determine the frequency and length of blowdown.
  • Consider the addition of heat-recovery and surface blowdown systems for better boiler chemistry control.
  • Use ultrasonic imaging, thermocouples, removable test strips, and fiberscopic inspections to determine the location and/or type of deposits in boiler tubes.
  • Inspect the boiler tubes annually to track scale buildup.
  • Return as much condensate as possible. Water lost through steam or condensate leaks must be made up, introducing contaminants with the makeup.
  • Use a de-aerator or hot-condensate well to minimize oxygen loading in the feedwater. This will reduce the amount of sodium sulfite needed to control residual oxygen at acceptable levels.
  • Inspect and replace seals on steam-cycle system components to reduce the amount of oxygen that enters the system, which leads to faster corrosion and scale buildup and, in turn, the frequency of boiler cleanings.
      Benefits
  • Reduces both the volume and hazardous makeup of blowdown water.
  • One textile facility with an industrial boiler expended only $500 in capital costs and managed the temperature of the effluent via heat recovery from the boiler blowdown. It reduced fuel costs by $2,700 per year (Kansas Small Business Environmental Assistance Program).
      Costs
  • Costs to install controls and monitors.
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Use Alternative or Lower-Pollution Fuels

      How?
  • Use low-sulfur high-grade fuels to reduce SOx and particulate emissions.
  • Alternatively, biofuels may be an option. Fats and other byproduct oils from food processing operations are at times less expensive than some fossil fuels and have similar heat values.
  • Under certain conditions, used motor oil may be burned as fuel in on-site boilers and furnaces that are designed to burn natural gas, propane, or virgin heating oil.
    • Burning can be used to heat buildings or to heat water for other applications.
    • Some pretreatment will be required to remove impurities that could foul the furnaces and increase maintenance costs.
    • Pre-treatment can vary depending on the oil and furnace conditions. Options range from simple water and sediment removal through settling or filtration to removing contaminants and neutralizing acidic compounds using advanced treatment such as flash distillation and chemical additives.
    • After treatment, the used oil is blended with virgin oil at a concentration of 10% or less used oil. Regular analysis of the used oil will be required to show that the used oil is on-specification for used oil as defined in 40 CFR 279. The regulations set limits on heavy metals, flash point, and halogen content. If any regulatory limits are exceeded, the oil is classified off-specification or hazardous and is regulated more stringently.
      Benefits
  • Biofuels are known to have low sulfur and particulate air emissions when combusted.
  • Biofuel combustion results in no net increase in carbon dioxide, a greenhouse gas, in the atmosphere.
  • Biofuels are safe to handle.
  • No odors have been experienced away from the steam plant.
  • The annual savings of burning used oil will be the avoid disposal costs of the used oil and avoided purchase cost of virgin fuel.
      Costs
  • Lower boiler retrofit cost (less than $30,000 for one university plant).
  • Burning used oil depends on the degree of contamination of the used oil. If the oil is significantly above specified contaminant levels, treatment costs could be prohibitive. Regular testing of the oil will be required so an on-site laboratory or a contract with an off-site lab will be needed.
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