furnaces.txt

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Metal Furnaces
March 1995

TNRCC Rule 116.111(3) in Regulation VI requires that Best Available Control Technology
(BACT) be applied to all facilities that must obtain a permit.  BACT determinations are made on a
case-by-case basis.  Current BACT guidelines for metal furnaces operations:  

Aluminum Processing

BACT Controls:
Smelting and sweating furnaces and dross handling operations are usually equipped with hoods
and duct systems (90 - 95% efficiency) venting to scrubbers or fabric filters (99% efficiency).  If
necessary, the building is maintained under negative pressure and vented to a baghouse (99%
efficiency).  If a dryer is used for burning off contaminants from raw materials, hooding and vents
to a thermal oxidizer or afterburner (90 - 99% efficiency) is necessary.

Steel Production

BACT Controls:
Significant amounts of PM emissions (mainly iron oxide) can be captured by fixed and retractable
hoods and vent systems (90 - 99% capture efficiency) and sent to a variety of control devices.   If
not captured at the source, fugitive PM in the mill can be difficult to control.  If necessary, this
may necessitate keeping the building under negative pressure and vented to a large fabric filter
device, but is often uncontrolled.  BACT for control devices, if required, is often in the range of
99%.

Gray Iron Foundries

BACT Controls:
All of the furnaces listed above can be hooded and vented to either fabric filters or scrubbers. 
Reverberatory furnaces can sometimes be controlled by an electrostatic precipitator (ESP),
depending on design and space constraints.  If not captured at the source, fugitive PM in the
foundry can be difficult to control.  If necessary, this may necessitate keeping the building under
negative pressure and vented to a large fabric filter device.  BACT for capture efficiency is at least
90% and control efficiency is often in the range of 95 - 99%, depending on design and operation.