Process heating encompasses a variety of industrial technologies ranging
from blast furnaces for iron ore processing to steam heat exchangers for
batch chemical production. While natural gas furnaces are traditionally
used, electric resistance and induction furnaces are popular options.
In order to address issues within this wide-ranging technology sector,
the U.S. DOE has assembled an advisory committee that published a useful
guide for industrial process heat users, entitled “Roadmap for Process
Heating Technology: Priority Research and Development Goals and Near-Term
Non-Research Goals to Improve Industrial Process Heating.”
The presentation and workshop materials developed as part of the Illinois
IOF program are intended to summarize the US DOE efforts and motivate
process heating system operators and then to provide the equations and
tools necessary to quantify any energy and cost savings potential.
Steps to Improving System Efficiency
The workshop materials developed for the Illinois IOF program detail
best practices and potential savings for the following improvement strategies.
These focus on each component of any process heating system: heat generation,
heat transfer, containment, recovery and controls.
Heat Generation Improvements
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Furnace Combustion Efficiency: Combustion efficiency
is often discussed in reference to steam boilers. Optimizing air/fuel
ratios is even more important for process heating furnaces given the
size and temperature requirements of such applications. Testing combustion
efficiency is often difficult as the flame may not be contained inside
a chamber, but the Illinois IOF program developed a worksheet
to assist companies in assessing the potential savings from improving
combustion performance.
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Oxygen enriched combustion air: Combustion efficiency
can be improved further by using oxygen enriched air or pure oxygen
as the combustion air. While the infrastructure to receive and deliver
oxygen is expensive, the combustion efficiency gains often payback
investments for new or large installations.
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Preheat combustion air: Significant savings are
possible from preheating combustion air to the burner. Heat can be
recovered by recuperators in the exhaust stack or from the furnace
shell itself.
Heat Transfer Improvements
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Pipe or Duct Insulation: Hot oil or hot air systems
distribute the heat transfer fluid from the generating furnace to
the end user. Pipes and ducts must be properly insulated, including
valves and fittings. The Illinois IOF program recommends removable
blanket insulation for valves and other maintenance prone locations.
The following table predicts fuel savings from using preheated combustion
air.
Heat Containment and Recovery Improvements
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Proper Insulation and Containment: Since furnaces
and other process heat equipment operate at such high temperatures,
proper insulation and containment are extremely important. Operators
should eliminate or reduce furnace openings and provide heat shields
to reduce heat losses from stacks, furnace openings, and doors.
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Heat Recovery: In addition to preheating combustion
air, waste heat from the exhaust stack can be used to heat product,
preheat other furnaces or produce steam. Many facilities utilize this
waste heat to generate electricity through steam turbine technology.
Control Improvements
