Business: Industrial

Getting Ideas for Energy Management Opportunities
2.2.2 Managing fuels

While the marketplace for the natural gas industry has long been competitive
in the three of Canada’s western provinces, customers in Ontario and
Quebec are getting used to deregulated market conditions. Apart from New
Brunswick and Nova Scotia, where an alliance was formed for natural distribution
rights, there are few if any gas lines in the rest of Canada. Natural gas
prices rose sharply in 2000. Energy efficiency and demand side management
(DSM; described in Section 2.2.1, “Managing electricity,” page
36) will be increasingly important tools for foundries in managing costs.
Large users of natural gas are purchasing gas on the spot market and are
using software to manage the task for maximum financial benefit. Although
escalating gas costs are a major factor in energy budgets, some larger companies
have managed to offset them by installing combined heat and power (CHP) cogenerators
for generating their own electricity and selling a potential surplus to the
distribution net. This option is now being intensely scrutinized by many
companies.

Many foundries in parts of Quebec, the Maritimes and northeastern
Ontario, depend on oil for their energy needs. To change one source of energy
(oil,
gas, electricity) for another is always expensive and difficult to do in an
established foundry. Many aluminum foundries, however, made the switch from
gas to electricity, and the necessary investment (roughly $500,000 for the
purchase and installation of a medium-sized induction furnace). They justified
it on the grounds of quality, and about 7% savings from gas-melting losses.
In addition
to better metal yield, the melt cleanliness improved and hydrogen pickup was
reduced.

Burning of oil may present special problems. It requires storage systems
that must meet rigorous criteria to prevent environmental contamination from
overfills
and leakage. In the winter, the lines must be heat-traced to prevent gelling
of the oil or precipitation of waxes. Due to high combustion temperatures,
the burning of oil tends to produce oxides of nitrogen (NO_x). The potentially
high sulphur content (especially in heavy or “bunker” oil) may
preclude utilization of flue gas economizers due to corrosion problems arising
from condensation
and formation of acids from sulphur oxides (SO_x).

The priority in reducing natural
gas or fuel oil consumption is to concentrate on making the combustion process
as efficient as possible. These points should be examined:

• Gas/oil delivery
  system
  
  Is the delivery system tight, without obstructions and leaks? Gas lines, many
  of which may be decades old and buried underground, may have corroded and have
  leaks. To find out whether they are leaking, during a no-production period,
  record the gas meter reading and check it again after 12 to 24 hours.
  Providing that not even the gas water heater was on, there should be no difference.
  Account for legitimate gas consumption for space heating, etc., by estimating
  the consumption based on the plate information. Otherwise, leaks
  may be indicated, and work should start on uncovering their source and fixing
  them promptly (safety may be involved!).
  
  
  In oil supply systems, ensure that filters are regularly checked and that
  pumps are maintained.
  
   
• Combustion
  
  Oil and gas furnaces very frequently lack adequate controls. Poor control
  of air/gas ratio results in wasted energy, frequently excessive temperatures
  and
  metallurgical problems. Consider replacing burners without adequate means to
  correctly control air-to-fuel ratio. Ideally, air-to-fuel ratio controls should
  also account for temperature of combustion air, which affects its density (which
  depends on time of the day and seasons), to provide a correct burning regime.
  Fuel gas analysis will show the correct composition. For natural gas, under
  equilibrium conditions, the flue gas composition should show close to 12%
  CO₂, about 20–22%
  water vapour and the rest nitrogen. Lower percentages of CO₂, and the presence
  of carbon monoxide (CO) and hydrogen, indicate poor combustion (reducing fire)
  and chemical energy losses in the two escaping gases; a portion of the gas
  has been wasted. On the other hand, in excess air supply
  conditions, all the gas will be burnt, but the analysis will reveal the presence
  of oxygen. Again, energy was wasted, this time by heating the extra air passing
  through the furnace.
  
  
  The issue of burner adjustment is just as serious in heat-treating ovens, where
  multiple burners may be used. Maintenance and burner adjustments also tend
  to be neglected. The remedy lies in upgrading your burner to an energy-efficient
  type with good controls (also see Section 2.3.3, “Melting,” page
  51), regular maintenance of the burners and regular flue gas analyses.
  
   
• Airtightness
  of the furnace chamber
  
  Air ingress into the furnace (heat treatment furnace) causes significant
  loss of energy. All that extra air needs to be heated to maintain the proper
  furnace
  chamber temperature. Air ingress may produce “cold” spots and
  quality problems as well.
  
   
• Thermal losses – conductive, heat sinks and radiation
  
  For thermal losses and conductive heat sinks, it is a question of adequate
  insulation and furnace or ladle lining with the right type of refractory
  materials. If dense firebrick is used for lining the furnace, it needs
  to be installed
  in adequate thickness to limit the heat conductive losses. The large mass
  of the firebrick, however, acts as a heat sink. It is expensive to heat
  up and
  keep
  at the right temperature. New low-density ceramic fibre materials are used,
  often in combination with other refractory materials, to remove these heat
  sinks and
  provide superior thermal insulation. (For more information, see Section 2.3.3, “Melting” (page
  51) and Section 2.3.9, “Heat treating” (page 70).
  
  
  The radiation losses are serious in melting furnaces (e.g., electric arc
  or induction furnaces) where they occur through open lids, open dross removing
  or slagging
  doors, from ladles with no or inadequate covers during heating, and especially
  during molten metal transfer (see Section 2.3.3, “Melting,” page
  51).

In foundries, the use of steam is usually limited to heating or conditioning
purposes. Except for small-output boilers, which may be heated by electricity,
most boilers and heaters are usually gas- or oil-fired. The same principles
of proper combustion apply to boiler burners, as discussed above, and under
melting,
heating and heat-treating. Steam generation requires a separate water treatment
system and an effective collection and return system for the condensate. Attention
to air elimination from the steam, boiler and pipes insulation, and steam traps
maintenance are also important points in making the system efficient. Some
of the EMOs, specific to steam boilers, are listed below.

Other EMOs
Housekeeping

• Maintain the burner setting in proper adjustment under a regular
  maintenance program.
• Control the flue gas composition, checking for oxygen
  and CO levels regularly.
• Prevent air ingress: maintain the airtightness of the
  furnace/oven, caulk and seal cracks, and maintain seals on lids and opening
  covers.
• Clean and maintain heat-transfer surfaces in a steam boiler.
• Control the quality
  of boiler feedwater and minimize the blowdown.
• Inspect boiler insulation; stem
  pipes and condensate return pipes insulation.
• Maintain steam traps to minimize
  steam/condensate loss.
• The gas company can be approached with a request for
  a loan of extra gas
  meters for sub-metering major gas-burning equipment.

Low cost

• Consider installing gas flow meters to manage the consumption of the major
  gas-using equipment – such as furnaces and ovens.
• Monitor and control
  the inside furnace/oven pressure.
• Consider using the local gas company as a
  contractor for maintenance services to your gas burners.
• Your local oil supply
  company can help with oil burner maintenance, efficiency testing and off-gas
  analyses.

Retrofit; high cost

• Consider repositioning upgraded burners in the furnace.
  A foundry in Quebec did this. It improved furnace heat distribution and achieved
  natural gas savings
  at the same time.

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