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Source Testing Requirements for Rule 4306

Boilers, Steam Generators, and Process Heaters

Source Testing Requirements for Alternative Monitoring Schemes

I. Purpose

The purpose of this bulletin is to assist operators of boilers, steam generators, or process heaters, who have elected to perform Alternative Monitoring instead of installing Continuous Emission Monitors, in determining the number and duration of tests that may be required as part of any approvable Alternative Monitoring Scheme under District Rule 4306.

II. Background

District Rule 4306: Boilers, Steam Generators, and Process Heaters, section 5.4.2, requires the owner of any unit equipped with NOx reduction technology to either install and maintain a Continuous Emission Monitoring system (CEMS) for NOx, CO and O2 or to install and maintain an APCO-approved Alternative Monitoring Scheme (AMS). An AMS is an approved method of monitoring surrogate process parameters that provide a reasonable assurance of compliance with applicable emission limitations when the unit is operated within specified limits or parameters. This bulletin identifies a pre-approved abbreviated testing procedure for establishing the correlation between the observed surrogate process parameters and the resultant emission concentrations over the range of firing rates typical for that unit. The owner is not limited to the use of this testing procedure; however, any other testing procedure is subject to approval by the District prior to use.

III. Definitions

The following definitions are applicable to this bulletin:High Firing Rate: The highest load at which the unit operates for more than 10% of its annual operating time.

Low Firing Rate: The lowest load at which the unit operates for more than 10% of its annual operating time. However, the lowest load shall not be less than 25% of the maximum heat input capacity of the unit.Normal Firing Rate: The load at which the boiler operates for the largest percentage of its annual operating time.

Constant Load Unit: A unit for which the firing rate varies no more than ±10 percentage points except during periods of startup and shutdown.

Variable Load Unit: Any unit other than a Constant Load Unit.

Formal Compliance Test: Testing conducted pursuant to Rule 4306 section 5.5, to determine compliance with applicable NOx and CO emission limits at the normal firing rate.

AMS Validation Test: Testing conducted to establish the correlation between the observed surrogate process parameter(s) specified in the AMS and the emission concentration(s).

 

IV. Testing Duration

The Formal Compliance Test shall consist of triplicate 30-minute test runs unless otherwise specified in the source test plan and approved by the District. On the other hand, AMS Validation Tests will be abbreviated and can be as short as a single, continuous 5-minute period of stabilized operation at each firing rate tested. Surrogate process parameter(s) shall be observed and recorded in accordance with the following procedures:

  1. The process operation shall be adjusted such that the unit stabilizes at the firing rate at which the correlation between the observed surrogate process parameter(s) and the corresponding emission concentration is to be established.

  2.  

  3. AMS Validation Test shall be conducted for 5 continuous minutes of stabilized emissions readings or a total of 30 continuous minutes if emissions are not stabilized. Emissions shall be considered stabilized for a period of time if the highest reading during that period is no more than 20% greater than the lowest reading taken during that period (i.e., ±10 % fluctuation).

  4.  

  5. The average value of each surrogate process parameter over the 5 to 30 minute data recording period shall be deemed the value that correlates to the average emission concentration at that firing rate. The average emission concentration over the data recording period shall be deemed the emission concentration at that firing rate.

  6.  

  7. This procedure shall be repeated as necessary for each firing rate that the correlation between the observed surrogate process parameter(s) and the resultant emission concentration is to be established.

 

V. Number of Tests Required

The Formal Compliance Test shall be performed in accordance with the test methods specified in section 6.2, at a frequency identified in section 6.3, unless otherwise specified on the Authority to Construct (ATC) or the Permit to Operate (PTO).

During the Formal Compliance Test surrogate parameters may also be monitored and recorded. If this is done the test will suffice for both the Formal Compliance Test as well as any testing necessary for validating the AMS.

    1. Constant Load Units
    2. For a constant load unit the Formal Compliance Test and AMS Validation Test may be conducted simultaneously. If the surrogate parameters are monitored and recorded during the Formal Compliance Test then a separate AMS Validation Test will not be required.

       

    3. Variable Load Units

For a variable load unit the AMS Validation Tests shall be performed at high, normal, and low firing rates. If the normal firing rate is within 10 percent of the high or low firing rate, the AMS Validation Test at that rate (high or low) is not required if AMS Validation Test was conducted at the normal firing rate.

Note that the acceptable value for the surrogate process parameters may be more precisely determined with more AMS Validation Tests at additional operating loads. Operators may perform additional AMS Validation Tests to establish acceptable operating levels for each surrogate parameter at operating loads other than high, normal, and low firing. The District will recognize the acceptable range for each surrogate parameter as follows:

For each operating load tested the observed surrogate process parameter(s) average value(s) applies to all firing rates within 10 percentage points of the tested firing rate. For firing rates not within 10 percentage points of a tested firing rate, the observed surrogate process values that are applicable to the next higher firing rate tested shall apply (See attached examples).

 

VI. Source Test Plan

The permit holder shall submit a source test plan to the District at least 15 days prior to each scheduled compliance determination date. This plan shall include:

  • The source test methods to be used.
  • The normal firing rate at which the Formal Compliance Test will be performed.
  • The high, low, and any other firing rates for which the AMS Validations tests will be performed.
  • A list of the surrogate process parameters that will be observed and recorded during each test.

 

The surrogate process parameters to be observed and recorded for each approved AMS shall be as follows:

 

Periodic Monitoring of NOx, CO and O2 Emission Concentrations

Not applicable

 

Periodic Determination of Flue Gas Recirculation Rate

The stack, wind box, and ambient temperatures shall be measured and recorded; or the stack and wind box O2 concentrations shall be measured and recorded.

 

Monitoring of Burner Mechanical Adjustments and O2 Concentration

The stack O2 concentration shall be measured and recorded. A diagram of the positioning of all pertinent burner mechanical linkage shall be made during each testing event. Any fluctuations in linkage positioning shall be measured and recorded.

 

Monitoring of the FGR Valve(s) Setting

A diagram of the valve and linkage positions shall be made during each testing event. Any fluctuations in valve positioning shall be measured and recorded.

 

Case-By-Case Approval of Other AMS

Process parameters as specified in the approved AMS shall be measured and recorded.

A copy of all data and abbreviated testing results shall be included with and are considered an integral part of the compliance determination to be submitted to the District.

 

Examples of Testing Scenarios

Example 1:

Boiler #1 at Company A is a variable load unit with a high firing rate of 100%, a normal firing rate of 70%, and a low firing rate of 35%. Company A performs a combined Formal Compliance and a AMS Validations Test at the normal firing rate of 70%, and AMS Validation Tests at the high firing rate of 100% and at the low firing rate of 35%.

The FGR rate during the source-testing event is determined to be as follows:

  • 15% at the low firing rate of 35%.
  • 20% at the normal firing rate of 70%.
  • 26% at the high firing rate of 100%.

Boiler #1 shall be operated as follows:

  • At any firing rate less than 45%, the minimum FGR rate shall be 15%.
  • At any firing rate between 45% and 80%, the minimum FGR rate shall be 20%.
  • At any firing rate greater than 80%, the minimum FGR rate shall be 26%.

Justification:

  • At any firing rate less than 35%, the minimum FGR rate shall be 15% because no lower firing rate was tested.
  • At any firing rate between 35% and 45%, the minimum FGR rate shall be 15% because this range is within 10 percentage points of the tested firing rate of 35%.
  • At any firing rate between 45% and 60%, the minimum FGR rate shall be 20% because this range is between the two tested firing rates of 35% and 70% and the surrogate operating parameter value at the higher operating point applies.
  • At any firing rate between 60% and 80%, the minimum FGR rate shall be 20% because this range is within ±10 percentage points of the tested firing rate of 70%.
  • At any firing rate between 80% and 90%, the minimum FGR rate shall be 26% because this range is between the two tested firing rates of 70% and 100% and the surrogate operating parameter value at the higher operating point applies.
  • At any firing rate greater than 90%, the minimum FGR rate shall be 26% because this range is within 10 percentage points of the tested firing rate of 100%.

Example 2:

Boiler #2 at Company A is a variable load unit with a high firing rate of 94%, a normal firing rate of 85%, and a low firing rate of 55%. Company A performs a Formal Compliance and AMS Validation Test at the normal firing rate of 85% and AMS Validation Test at the low firing rate of 55%. Company A elects not to do AMS Validation Test at the high firing rate since it is within 10 percentage points of the normal firing rate.

The FGR rate during the source-testing event is determined to be as follows:

  • 17% during the abbreviated testing at the low firing rate of 55%.
  • 23% during the Compliance Determination Source Testing at normal firing rate 85%.

Boiler #2 shall be operated as follows:

  • At any firing rate less than 65%, the minimum FGR rate shall be 17%.
  • At any firing rate greater than 65%, the minimum FGR rate shall be 23%.

Justification:

  • At any firing rate less than 55%, the minimum FGR rate shall be 17% because no lower firing rate was tested.
  • At any firing rate between 55% and 65%, the minimum FGR rate shall be 17% because this range is within 10 percentage points of the tested firing rate of 55%.
  • At any firing rate between 65% and 75%, the minimum FGR rate shall be 23% because this range is between the two tested firing rates of 55% and 85%.
  • At any firing rate between 75% and 95%, the minimum FGR rate shall be 23% because this range is within ±10 percentage points of the tested firing rate of 85%.
  • At any firing rate greater than 95%, the minimum FGR rate shall be 23% because testing at higher firing rates was not required.

Example 3:

Boiler #3 at Company A is a constant load unit with a normal firing rate of 93%. Company A performs a combineds Formal Compliance and AMS Validation Test at the normal firing rate of 93%.

The FGR rate during the source testing event is determined to be as follows:

  • 25% during the compliance determination at the normal firing rate of 93%.

Boiler #3 shall be operated as follows:

  • The minimum FGR rate shall be 25%.

Justification:

  • The minimum FGR rate shall be 25% because this constant load unit only operates within a range that is within 10 percentage points of the tested firing rate of 93%.