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**PART 75 SPAN & RANGE Manuel J Oliva Clean Air Markets Division**

Sam, Sarah suggested this would be a good presentation for the Division. Manuel J Oliva Clean Air Markets Division U.S. Environmental Protection Agency

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**Instrument Span & Range**

Question: Aren’t Span and Range the Same? Answer: Under Part 75 Span and Range can be equal in value, but are not the same. However, the range value must always be the span value. PART 75

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**Span & Range Defined Range: Instrument Full-Scale**

“What the instrument is set up to measure” Span: Highest concentration or flow rate that a monitor component is required to be capable of measuring. (§72.2) “What the rules require to be measured, Quality assured portion of the range” “Rules of the Game” - Appendix A, §2 Affected Parameters: SO2, NOX, CO2, O2 and Flow Rate 1. Kenon was gracious enough to provide initial allocation data.

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**Example of Span & Range Case 1: Span = Range Case 2: Span < Range**

0 ppm 500 ppm Span Case 2: Span < Range 400 ppm 0 ppm 500 ppm

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Range Settings Select a range so majority of readings obtained during typical unit operation are kept within 20 to 80 percent of instrument full scale range (to extent practicable) Importance: Avoid signal to noise problems at low end of range, and inaccuracies or exceedance at high end of range. Accuracy of measured values is objective Exceptions: (SO2) low sulfur fuel, (SO2/NOX) emission controls and two span values, (SO2/NOX) dual span unit Range Signal Noise Level Not Necessarily Linear at Extremes 1. Cement kilns in NY provided with 8,085 tons.

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**Span Settings Span Settings: Dependant on pollutant**

Importance: Concentrations of calibration gases used for daily QA and linearity checks, as well as daily control limits for gas and flow monitors are expressed as % span “Simple” rule of thumb, range and span values can be equal

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**Setting the Span - SO2 Monitors**

Define MPC Maximum Potential Concentration (MPC) is based on analysis of highest sulfur fuel burned (max % sulfur and min GCV, or max % sulfur/GCV ratio) or historical CEMS data Define MEC if Appropriate Maximum Expected Concentration (MEC) is based on expected % SO2 removal, fuel analysis or historical CEMS data MEC is appropriate for units with SO2 controls or both high-sulfur and low-sulfur fuels, including blends

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**Setting the Span - SO2 Monitors (Continued)**

High Span* = MPC × 1.00 to MPC × 1.25 Rounded to nearest 100 ppm (or 10 ppm if SO2 500 ppm) Full Scale Range Span Value Low Span = 1.00 × MEC to 1.25 × MEC (If Required) Rounded to nearest 10 ppm (or 100 ppm as appropriate) Low Span Required if MEC < 20% of High Range (Controls or low sulfur fuels) Use the Low Span when SO2 readings are expected to be below 20% of High Full-Scale Range * If unit has SO2 control it can forgo high span and report a “default high range value” of 200% of MPC during hours when low range is exceeded. Full scale of low range cannot exceed five times MEC.

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**Setting the Span - NOX Monitors**

Define MPC Maximum Potential Concentration (MPC) is based on the fuel (or blend) that gives highest uncontrolled NOX emissions. Options include: fuel based defaults, boiler type defaults, NOX emission test results, historical CEMS data or manufacturer data Define MEC if Appropriate Maximum Expected Concentration (MEC) is based on expected NOX removal efficiency, NOX concentration testing, historical CEMS data, or permit limit Determine a separate MEC for each fuel (or blend)

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**Setting the Span - NOX Monitors (Continued)**

High Span* = MPC × 1.00 to MPC × 1.25 Rounded to nearest 100 ppm (or 10 ppm if NOX 500 ppm) Full Scale Range Span Value Low Span = 1.00 × MEC to 1.25 × MEC (If Required) Rounded to nearest 10 ppm (or 100 ppm as appropriate) Low Span Required if MEC < 20% of High Range (If more than one MEC, use MEC closest to 20% of High Range) Use the Low Span when NOX readings are expected to be below 20% of High Full-Scale Range * If unit has Add-On NOX control it can forgo high span and report a “default high range value” of 200% of MPC during hours when low range is exceeded. Full scale of low range cannot exceed five times MEC.

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**Setting the Span - CO2 & O2 Monitors**

Define MPC for CO2 CO2 Maximum Potential Concentration (MPC) is 14% CO2 (boilers) or 6% CO2 (turbines) default values, or determine based on historical CEMS data MPC is used only for substitute data purposes Define Minimum Potential Concentration for O2 O2 Minimum Potential Concentration is determine based on historical CEMS data Minimum Potential Concentration is used only for substitute data purposes for units using flow monitors and O2 diluent monitors to determine Heat Input Bullet 1 - Allocations are initially set to “cap” emissions to a certain level (I.e. 20% reduction in emissions). Sources will generally reduce emissions under cap by controls or operational changes. It is expected therefore that sources would be sellers in a mature program. Bullet 2 - 3% reduction required not counting sources with zero emissions. 27% reduction assuming sources with zero emissions emitted at their allowance levels. 5% surplus with cement kilns and not subtracting out zero emissions sources.

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**Setting the Span - CO2 & O2 Monitors (Continued)**

O2 Span Between 15% and 25% O2 Below 15% O2 allowed with technical justification CO2 Span Between 14% and 20% CO2 (for boilers) Between 6% and 14% CO2 (for turbines)

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**Setting the Span - Flow Monitors**

Define MPV Maximum Potential Velocity (MPV) is based on equations in Appendix A (F-factors, heat input, diluent concentration and moisture concentration), or Highest values from traverse testing (Ref. Method 2) Define MPF Maximum Potential Flow Rate (MPF) is equal to MPV × stack area Used only for substitute data purposes

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**Setting the Span - Flow Monitors (Continued)**

Calibration Span = MPV* × 1.00 to MPV* × 1.25 Rounded up to at least two significant figures Flow Rate Span = 1.00 × MPF to 1.25 × MPF Expressed in the units used for Part 75 reporting (scfh) Rounded to nearest 1000 scfh * MPV must be converted to the units of daily calibration (e.g. kscfm, inches of H20, etc.)

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**Adjustments to Span and Range**

Perform at least annual evaluation of the span and range settings (Appendix A, § ) DAHS

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**Summary Process Diagram**

RANGE ?? SPAN VALUE Single Span (or High Span) Based on maximum potential concentration or flow rate 20% to 80% of Full Scale Range (Majority of Data) Low Span (if Required) Based on maximum expected concentration

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Optimal Range

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