Date:	May 10, 2006

To:	  SEQ CHAPTER \h \r 1 Docket ID No. A-2000-56 (Iron and Steel
Foundries)

From:	Phil Mulrine

Subject:	  SEQ CHAPTER \h \r 1 Determination of a MACT Floor Equivalent
Emission Limit for Cupola Melting Furnaces

	

I.	Purpose

  SEQ CHAPTER \h \r 1 	The purpose of this memorandum is to document the
procedures used to determine equivalent mass-based PM emission limits
for cupola melting furnaces that achieve the same emission reductions as
the current MACT floor PM concentration emission limits. 

II.	Background

	On April 22, 2004, EPA promulgated National Emission Standards for
Hazardous Air Pollutants (NESHAP) for Iron and Steel Foundries.  This
NESHAP included PM emission limitations for cupolas that were based on
an evaluation of the maximum achievable control technology (MACT) and
the average performance achieved by the top 12 percent of the cupola
emission sources (i.e., the “MACT floor”).  As baghouses (the
technology on which the MACT floor performance was based) are generally
designed to meet a specified outlet concentration limit and because EPA
Method 5 directly determines concentration, a concentration-based
emission limit was selected as the basis on which the MACT floor was
determined.  In the final rule, we also provided an alternative
concentration-based total metal HAP emission limit that provided
equivalent metal HAP emission reductions as the MACT floor PM emission
limit.  The determination of these emission limits are documented in a
memorandum from Kevin Cavender to the Iron and Steel Foundries docket
dated August 23, 2003 (see Docket Item No. IV-B-5).  

After promulgation, we received petitions from three industry trade
organizations.  As part of our discussions on technical issues raised
for reconsideration, we recognized the need for an equivalent mass based
emission limit for cupola melting furnaces.  The remainder of this
memorandum documents the approach used to establish mass-based emission
limits for cupola melting furnaces that provide equivalent emission
reductions as compared to the existing concentration-based emission
limits.

III.	Approach for Determining MACT-Equivalent, Mass-Based Emission
Limits

In the Cavender memorandum (Docket Item No. IV-B-5), the MACT floor PM
emission limit for cupolas at new sources was determined to be 0.002
gr/dscf and the MACT floor PM emission limit for cupolas at existing
sources was determined to be 0.006 gr/dscf.    SEQ CHAPTER \h \r 1 

	

The source test data used to determine these PM concentration
performance limits were used to calculate PM mass emission rate
performance limits as follows:

EPM,limit = (CPM,limit × Q) / (Mmelt) × (60 min/hr)/(7000 gr/lb)

Where:   	EPM,limit = mass-based emission limit, lb/ton

		CPM.limit = PM concentration performance limit, gr/dscf

Q = measured exhaust gas flow rate, dscfm

Mmelt = measured metal melting rate, ton/hr.

The concentration performance limits were used in this calculation
because these limits already account for variability.  The calculated
average PM mass emission rate for new sources achieving the 0.002
gr/dscf  concentration limit is 0.02 lb/ton; the calculated average PM
mass emission rate performance limit for existing sources achieving the
0.006 gr/dscf was 0.10 lb/ton.  These emission limits represent the
MACT-equivalent, mass-based performance limits for cupolas at new and
existing sources.   As described in the Cavender memo, a metal HAP
content of 8 percent can be used to convert these PM emission limits
into equivalent metal HAP emission limits.

IV.	Conclusion

The MACT-equivalent, mass-based emission limits for cupolas at existing
iron and steel foundries are:  0.10 lb/ton PM or 0.008 lb/ton total
metal HAP.

The MACT-equivalent, mass-based emission limits for cupolas at new iron
and steel foundries are:  0.02 lb/ton PM or 0.002 lb/ton total metal
HAP.

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