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<br />Mr. Frank DeMaris
<br />October 18, 2010
<br />Page 2 of 7
<br />From all this, we are proposing a controlled CO emission level that assumes a minimum 50%
<br />} reduction efficiency of the catalyst is sustainable and accounts for the natural CO drift that will
<br />occur on the uncontrolled emissions up to the NTE level. Also for these reasons, we are proposing
<br />,, this same emission rate Ameresco believes to be sustainable at Ox Mountain. This emission level
<br />i r is more stringent than the BAAQMD CO BACT for LFG engines. Results of the testing at the
<br />!
<br />li . ' Ameresco Ox Mountain facility can be found in Appendix B.
<br />By including a CO Catalyst, which will operate ahead of the SCR in the engine exhaust path in
<br />Fiorder to protect the SCR, the CO emissions will be reduced from the original estimate of 145.42
<br />tpy to 104.70 tpy for the two engines.
<br />+ The volatile organic compound (VOC) emissions will remain the same as the original application.
<br />The emissions using 20 parts per million by volume (ppmv) @ 3% oxygen as hexane (outlet) and
<br />maximum exhaust flow at 10% oxygen (converted to 3% oxygen) will be used because that is
<br />E + considered the lowest emission level achievable based on discussions with GE Jenbacher, the
<br />engine manufacturer. It is based on the maximum exhaust flow rate provided by GE Jenbacher.
<br />The 20 ppmv outlet limit is also considered BACT/ Lowest Achievable Emission Rates (LAER) in
<br />other Districts including Ventura County Air Pollution Control District (VCAPCD), South Coast
<br />Air Quality Management District (SCAQMD), .BAAQMD, San :Diego County Air Pollution
<br />Control District (SDCAPCD), in addition to the limit under the landfill New Source Performance
<br />Standards (NSPS).
<br />F,
<br />• Ameresco proposes to revise the carbon monoxide (CO) emission factor based in part on Bay Area
<br />x
<br />Air Quality Management District's (BAAQMD) "Revisiting BACT for Lean Burn Landfill Gas
<br />Fired Internal Combustion Engines"(2009). This document states that improved lean -burn low-
<br />NOx combustion design can maintain low NOx emission rates during operation, but under these
<br />`
<br />conditions, the engine CO will increase ("creep") over time up to a Not to Exceed (NTE) limit.
<br />4
<br />The upper end of the range of the uncontrolled CO emission factor for an engine that can achieve a
<br />E
<br />0.6 g/bhp NOx emission rate is 3.6 g/bhp-hr. This NTE level was established by the BAAQMD in
<br />rFit
<br />an effort to allow flexibility for variable CO levels while achieving low NOx levels.
<br />From all this, we are proposing a controlled CO emission level that assumes a minimum 50%
<br />} reduction efficiency of the catalyst is sustainable and accounts for the natural CO drift that will
<br />occur on the uncontrolled emissions up to the NTE level. Also for these reasons, we are proposing
<br />,, this same emission rate Ameresco believes to be sustainable at Ox Mountain. This emission level
<br />i r is more stringent than the BAAQMD CO BACT for LFG engines. Results of the testing at the
<br />!
<br />li . ' Ameresco Ox Mountain facility can be found in Appendix B.
<br />By including a CO Catalyst, which will operate ahead of the SCR in the engine exhaust path in
<br />Fiorder to protect the SCR, the CO emissions will be reduced from the original estimate of 145.42
<br />tpy to 104.70 tpy for the two engines.
<br />+ The volatile organic compound (VOC) emissions will remain the same as the original application.
<br />The emissions using 20 parts per million by volume (ppmv) @ 3% oxygen as hexane (outlet) and
<br />maximum exhaust flow at 10% oxygen (converted to 3% oxygen) will be used because that is
<br />E + considered the lowest emission level achievable based on discussions with GE Jenbacher, the
<br />engine manufacturer. It is based on the maximum exhaust flow rate provided by GE Jenbacher.
<br />The 20 ppmv outlet limit is also considered BACT/ Lowest Achievable Emission Rates (LAER) in
<br />other Districts including Ventura County Air Pollution Control District (VCAPCD), South Coast
<br />Air Quality Management District (SCAQMD), .BAAQMD, San :Diego County Air Pollution
<br />Control District (SDCAPCD), in addition to the limit under the landfill New Source Performance
<br />Standards (NSPS).
<br />F,
<br />Ameresco's experience at Ox Mountain indicated that a CO Catalyst is required in order for the
<br />SCR to sustain its reduction efficiency for NOx emissions. The manufacturer, Miratech, has
<br />verified this (the CO Catalyst operates upstream of the SCR in the engine exhaust path). However,
<br />with approximately 12,000 hours of operating experience at the Ameresco Ox Mountain facility, it
<br />`
<br />has been shown that the oxidation catalysts were unable to sustain 75% design for CO reduction
<br />4
<br />efficiency, the level posed in the initial permit to construct. Their efficiency continues to be
<br />slightly better than 50% at this time (on a sustainable basis), and Ameresco is proposing that this
<br />'
<br />reduction level be applied to the BAAQMD NTE level, resulting in an emission rate of 1.8 g/bhp
<br />r
<br />of CO.
<br />_3
<br />Ameresco has been and continues to look for ways to improve the CO Catalyst reduction
<br />efficiency at Ox Mountain by looking at changes with the fuel pretreatment system, engine
<br />operation and catalyst design and operation. However, any changes toward that end must not
<br />negatively impact operation of the SCR.
<br />From all this, we are proposing a controlled CO emission level that assumes a minimum 50%
<br />} reduction efficiency of the catalyst is sustainable and accounts for the natural CO drift that will
<br />occur on the uncontrolled emissions up to the NTE level. Also for these reasons, we are proposing
<br />,, this same emission rate Ameresco believes to be sustainable at Ox Mountain. This emission level
<br />i r is more stringent than the BAAQMD CO BACT for LFG engines. Results of the testing at the
<br />!
<br />li . ' Ameresco Ox Mountain facility can be found in Appendix B.
<br />By including a CO Catalyst, which will operate ahead of the SCR in the engine exhaust path in
<br />Fiorder to protect the SCR, the CO emissions will be reduced from the original estimate of 145.42
<br />tpy to 104.70 tpy for the two engines.
<br />+ The volatile organic compound (VOC) emissions will remain the same as the original application.
<br />The emissions using 20 parts per million by volume (ppmv) @ 3% oxygen as hexane (outlet) and
<br />maximum exhaust flow at 10% oxygen (converted to 3% oxygen) will be used because that is
<br />E + considered the lowest emission level achievable based on discussions with GE Jenbacher, the
<br />engine manufacturer. It is based on the maximum exhaust flow rate provided by GE Jenbacher.
<br />The 20 ppmv outlet limit is also considered BACT/ Lowest Achievable Emission Rates (LAER) in
<br />other Districts including Ventura County Air Pollution Control District (VCAPCD), South Coast
<br />Air Quality Management District (SCAQMD), .BAAQMD, San :Diego County Air Pollution
<br />Control District (SDCAPCD), in addition to the limit under the landfill New Source Performance
<br />Standards (NSPS).
<br />F,
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