SHASTA COUNTY AIR QUALITY MANAGEMENT DISTRICT
RULE 3:26 - INDUSTRIAL, INSTITUTIONAL, AND COMMERCIAL BOILERS, STEAM GENERATORS, AND PROCESS HEATERS OXIDES
OF NITROGEN CONTROL MEASURE
(Adopted 6/6/95) (Amended 12/5/95)
a. Definitions
For the purposes of this section, the following definitions shall apply.
Annual Capacity Factor: The ratio of the amount of fuel burned by a boiler in a calendar year
to the amount of fuel it could have burned if it had operated at the rated heat input capacity for 100 percent
of the time during the calendar year.
Boiler or Steam Generator: An individual piece of combustion equipment fired with liquid, gaseous,
or solid fuel with the primary purpose of producing steam. Boiler or steam generator does not include water heaters,
any waste heat recovery boiler that is used to recover sensible heat from the exhaust of a combustion turbine,
nor does it include equipment associated with a chemical recovery cycle.
Btu: British thermal unit.
Gas-Fired: Using natural gas, propane, or any other gaseous fuel for firing the boiler or steam
generator.
Heat input: The chemical heat released due to fuel combustion in a boiler, using the higher
heating value of the fuel. This does not include the sensible heat of incoming combustion air.
Higher Heating Value: The total heat liberated per mass of fuel burned (Btu per pound), when
fuel and dry air at standard conditions (68oF and one atmosphere pressure) undergo complete combustion
and all resultant products are brought to their standard states at standard conditions. Higher heating value shall
be determined by one of the following test methods: 1) ASTM D 2015-85 for solid fuels; 2) ASTM D 240-87 or ASTM
D 2382-88 for liquid hydrocarbon fuels; or 3) ASTM D 1826-88, or ASTM D 1945-81 in conjunction with ASTM D 3588-89
for gaseous fuels. (Amended 12-5-95)
Oxides of nitrogen emissions: The sum of nitric oxide (NO) and nitrogen dioxide (NO2)
in the flue gas, collectively expressed as nitrogen dioxide.
Process heater: Any combustion equipment fired with liquid, gaseous, or solid fuel and which
transfers heat from combustion gases to water or process streams. A process heater does not include any kiln, furnace,
recovery furnace, or oven used for drying, baking, heat treating, cooking, calcining, vitrifying or chemical reduction.
Rated heat input capacity: The heat input capacity specified on the nameplate of the combustion
unit. If the unit has been permanently altered or modified such that the maximum heat input is different than the
input capacity specified on the nameplate and this alteration or modification has been approved
in writing by the Air Pollution Control Officer (APCO), then the new maximum heat input shall be considered as
the rated heat input capacity.
Reasonably Available Control Technology (RACT): The lowest emission limitation that a particular
source is capable of meeting by the application of control technology that is reasonably available considering
technological and economic feasibility.
Unit: Any boiler, steam generator or process heater as defined in this definition section.
b. Applicability
This rule applies to all boilers, steam generators, and process heaters used in industrial, institutional, and
commercial operations that exist within the boundaries of the Shasta County Air Quality Management District on
the date of adoption of this Rule.
c. Requirements
- 1. No later than one year following District adoption of this Rule, all existing units with
a rated heat input capacity greater than or equal to 5 million Btu per hour shall demonstrate final compliance
with the following reasonably available control technology (RACT) emission limitations dependent upon the specific
fuel fired in the unit and based upon a three-hour averaging period. All new units shall comply with the requirements
of District Rule 2:1 - New Source Review.
EMISSION LIMITS FOR OXIDES OF NITROGEN (AS NO2)
Gaseous (only) fuel firing |
Gaseous & Non-gaseous fuel co-firing |
Liquid or Solid fuel firing |
0.084 lbs/MMBtu of heat input or 70 ppmv |
Heat input weighted average of gaseous and non-gaseous fuel limits as calculated per Section c.1(a)
below |
0.15 lbs/MMBtu of heat input or 115 ppmv |
- The weighted average shall be calculated as follows:
Emission Limit |
= |
(70 ppmv * x)+(115 ppvm * y) ppm |
|
|
|
x+y
|
|
or
|
|
Emission Limit |
= |
(0.084 * x)+(0.15 * y) #/MMBTu Heat Input x+y |
|
|
x+y
|
|
or Emission Limit = (0.084 * x)+(0.15 * y)#/MMBTu
Heat Input x+y
Where:
X = annual heat input from gaseous fuel and
Y = annual heat input from non-gaseous fuel
(Amended 12-5-95)
- No later than one year following District adoption of this Rule, the owner or operator of any existing unit(s)
with a rated heat input capacity less than 5 million Btu per hour shall submit for the approval of the Air Pollution
Control Officer a list of all units operating within the District boundaries and a selection of one of the following
four options to be added as a permit condition to the Permit to Operate for each such unit in order to achieve
compliance with this rule:
- Operate in a manner that maintains stack gas oxygen concentrations at less than or equal to 3% by volume on
a dry basis for any 15 consecutive minute averaging period; or
- Operate with a stack gas oxygen trim system set at 3% by volume oxygen. The operational tolerance of the setting
shall be within the range of 2.85% TO 3.15%; or
- Tune the unit at least once per year by a technician that is qualified to the satisfaction of the Air Pollution
Control Officer to perform a tune-up in accordance with the procedure described in either Attachment 1 or Attachment
2; Note: The owner/operator of any unit(s) who specifies the annual tune-up option in the plan
is required to submit an annual report verifying that the tune-up has been performed. The report shall contain
any other information or documentation that the Air Pollution Control Officer determines to be necessary.) or
- Operate in compliance with the emission limits specified in Section c.1. of this rule. (Amended 12-5-95)
- Emissions from units subject to this rule shall not exceed a carbon monoxide concentration of 400 parts per
million by volume when using only gaseous or a combination of gaseous and liquid fuels. Solid fuel-fired units
shall not exceed carbon monoxide limits expressed in permit to operate conditions.
- No person shall allow the discharge into the atmosphere from any emission control device installed and operated
pursuant to the requirements of Section c. of this Rule, ammonia (NH3) emissions in excess of 20 ppm
by volume at dry stack conditions adjusted to 3% oxygen unless compliance with this requirement is deemed to be
technically or economically infeasible by the APCO due to fuel type, boiler configuration, or any other design
characteristic of the unit.
d. Exemptions
- The requirements of Section c. shall not apply to the units which are willing to accept a permit condition
that restricts operation to an annual capacity factor of 15% or less and requires compliance with one (1) of the
options specified in Sections c.2 a), b) or c) of this rule. (Amended 12-5-95)
- To continue to qualify for the exemption provided in Section d.1. the owner or operator of any applicable unit(s)
shall submit to the Air Pollution Control Officer annual fuel use data that demonstrates that the unit(s) operated
at or below the allowable 15% annual capacity factor(s). For the purposes of this section, the annual capacity
factor for multiple units may be calculated based on the total fuel input to multiple like units.
- Following adoption of this rule, an exemption granted for any unit will become null and void if that unit operates
for more than 1 calendar year at an annual capacity factor greater than 15%.
- The requirements of Section c. shall not apply to units that the APCO has determined that it is not technically
or economically feasible to comply with the RACT emission limitations.
- The requirements of Section c. shall not apply to units with a rated heat input capacity less than one (1)
million Btu per hour.
e. Compliance Determination
- An owner or operator of any unit(s) shall have the option of complying with either the pounds-per-million-Btu
emission rates or parts-per-million-by-volume emission limits specified in Section c.1. of this Rule. Periodic
demonstration of compliance with this Rule with respect to emission limitations shall be as specified in District
Rule 2:11a.3(f).
- All emission determinations shall be conducted at the maximum firing rate allowed by the district permit, and
no compliance determination shall be established within two hours after a continuous period in which fuel flow
to the unit is zero, or shut off, for 15 minutes or longer. (Amended 12-5-95)
-
- All ppmv emission limits for gaseous, liquid, or gaseous/liquid fuel firing specified in Section c. of this
rule are referenced at dry stack-gas conditions and corrected to 3% by volume stack gas oxygen.
Emission concentrations shall be corrected to 3% oxygen as follows:
[ppm]corrected |
= |
20.95% - 3.00% * [ppm]measured |
|
|
20.95% - [%O2]measured |
- All ppmv emission limits for solid fuel firing specified in Section c. of this rule are referenced at dry stack-gas
conditions and corrected to 12% by volume stack gas CO2.
Emission concentrations shall be corrected to 12% CO2 as follows:
[ppm]corrected |
= |
12% * [ppm]measured |
|
|
[CO2]measured |
(Amended 12-5-95)
- All emission concentrations and emission rates shall be calculated or obtained from continuous emission monitoring
data obtained by utilizing the test methods specified in Section f. of this Rule.
f. Test Methods
- Compliance with the emission requirements in Section c.1. shall be determined using the following test methods:
- Oxides of Nitrogen - EPA Method 7E or ARB Method 100
- Carbon Monoxide - EPA Method 10 or ARB Method 100
- Stack Gas Oxygen - EPA Method 3A or ARB Method 100
- NOx Emission Rate (Heat Input Basis) - EPA Method 19
- If certification of the higher heating value (HHV) of the fuel is not provided by a third party fuel supplier,
it shall be determined by the test methods specified in the definition of HHV found in section a. of this rule.
(Amended 12-5-95)
- For determination of the NH3 concentrations in stack gases, Bay Area Air Quality Management District
(BAAQMD) Source Test Procedure ST-1B, "Ammonia, Integrated Sampling" shall be utilized for stack sampling
and EPA Method 350.3, "Ion Specific Electrode," shall be utilized as the analysis method. (Reference
EPA 600/4-79-020.)
Alternate methods may not be used without prior approval of the Air Pollution Control Officer.
g. Recordkeeping Requirements
- Any persons subject to the provisions of Subsection c.1 of this rule shall install, no later than one year
following District adoption of this rule, a non-resettable totalizing volumetric or mass-flow fuel meter in each
fuel line for each applicable unit that fires gaseous and/or liquid fuel. The meter shall be used to demonstrate
that each unit operates at or below the applicable emission limitation. (Amended 12-5-95)
Meters shall be accurate to ± one (1) percent, as certified by the manufacturer in writing. Meter readings
shall be recorded at the end of each operating day in units of either cubic feet per day or gallons per day. At
the end of each month, daily records shall be compiled into a monthly report. Both monthly reports and daily records
shall be maintained for a period of four (4) years and shall be made available for inspection by the Air Pollution
Control Officer upon request.
- Any person subject to the provisions of Subsection c.1 of this rule who fires a solid fuel in an applicable
unit shall provide a means of calculating or verifying fuel input to the unit in lbs/hr that is acceptable to the
Air Pollution Control Officer for purposes of documenting compliance with the specified emission limit.
Attachment 1
Tuning Procedure1
Nothing in this Tuning Procedure shall be construed to require any act or omission that would result in unsafe
conditions that would be in violation of any regulation or requirement established by Factory Mutual, Industrial
Risk Insurors, National Fire Prevention Association, the California Department of Industrial Relations (Occupational
Safety and Health Division), the Federal Occupational Safety and Health Administration, or other relevant regulations
and requirements.
- Operate the unit at the firing rate most typical of normal operation. If the unit experiences significant load
variations during normal operation, operate it at its average firing rate.
- At this firing rate, record stack gas temperature, oxygen concentration, and CO concentration (for gaseous
fuels) or smoke-spot number2 (for liquid fuels), and observe flame conditions after unit operation stabilizes
at the firing rate selected. If the excess oxygen in the stack gas is at the lower end of the range of typical
minimum values3, and if CO emissions are low and there is no smoke, the unit is probably operating at
near optimum efficiency -- at this particular firing rate. However, complete the remaining portion of this procedure
to determine whether still lower oxygen levels are practical.
- Increase combustion air flow to the unit until stack gas oxygen levels increase by one to two percent over
the level measured in Step 2. As in Step 2, record the stack gas temperature, CO concentration (for gaseous fuels)
or smoke-spot number (for liquid fuels), and observe flame conditions for these higher oxygen levels after boiler
operation stabilizes.
- Decrease combustion air flow until the stack gas oxygen concentration is at the level measured in Step 2. From
this level gradually reduce the combustion air flow, in small increments. After each increment, record the stack
gas temperature, oxygen concentration, CO concentration (for gaseous fuels) and smoke-spot number (for liquid fuels).
Also, observe the flame and record any changes in its condition.
- Continue to reduce combustion air flow stepwise, until one of these limits is reached:
- Unacceptable flame conditions -- such as flame impingement on furnace walls or burner parts, excessive flame
carryover, or flame instability.
- Stack gas CO concentrations greater than 400 ppm.
- Smoke at the stack.
- Equipment-related limitations -- such as low windbox/unit pressure differential, built in air-flow limits,
etc.
- Develop an 02/CO curve (for gaseous fuels) or 02/smoke curve (for liquid fuels) similar
to those shown in Figures 1 and 2 using the excess oxygen and CO or smoke-spot number data obtained at each combustion
air flow setting.
- From the curves prepared in Step 6, find the stack gas oxygen levels where the CO emissions or smoke-spot number
equal the following values:
FUEL |
MEASUREMENT |
VALUE |
Gaseous |
CO emissions |
400 ppm |
#1 and #2 Oils |
Smoke-spot number |
number 1 |
#4 Oil |
Smoke-spot number |
number 2 |
#5 Oil |
Smoke-spot number |
number 3 |
Other Oils |
Smoke-spot number |
number 4 |
The above conditions are referred to as the CO or smoke thresholds, or as the minimum excess oxygen levels.
Compare this minimum value of excess oxygen to the expected value provided by the combustion unit manufacturer.
If the minimum level found is substantially higher than the value provided by the combustion unit manufacturer,
burner adjustments can probably be made to improve fuel and air mix, thereby allowing operations with less air.
- Add 0.5 to 2.0 percent to the minimum excess oxygen level found in Step 7 and reset burner controls to operate
automatically at this higher stack gas oxygen level. This margin above the minimum oxygen level accounts for fuel
variations, variations in atmospheric conditions, load changes, and nonrepeatability or play in automatic controls.
- If the load of the combustion unit varies significantly during normal operation, repeat Steps 1-8 for firing
rates that represent the upper and lower limits of the range of the load. Because control adjustments at one firing
rate may affect conditions at other firing rates, it may not be possible to establish the optimum excess oxygen
level at all firing rates. If this is the case, choose the burner control settings that give best performance over
the range of firing rates. If one firing rate predominates, settings should optimize conditions at that rate.
- Verify that the new settings can accommodate the sudden changes that may occur in daily operation without adverse
effects. Do this by increasing and decreasing load rapidly while observing the flame and stack. If any of the conditions
in Step 5 result, reset the combustion controls to provide a slightly higher level of excess oxygen at the affect
firing rates. Next, verify these new settings in a similar fashion. Then make sure that the final control settings
are recorded at steady-state operating conditions for future reference.
1. This tuning procedure is based on a tune-up procedure developed by KVB, Inc.
for EPA.
2. The smoke-spot number can be determined with the ASTM test method D-2156 or with
the Bacharach methods. The Bacharach method is included in a tune-up kit that can be purchased from the Bacharach
Company.
3. Typical minimum oxygen levels for boilers at high firing rates are:
- For natural gas: 0.5 - 3%
- For liquid fuels: 2 - 4%
(REFER FIGURE 1 AND FIGURE 2)
Attachment 2
Equipment Tuning Procedure
for Natural Draft-Fired Equipment
Nothing in this Equipment Tuning Procedure shall be construed to require any act or omission that would result
in unsafe conditions or would be in violation of any regulation or requirement established by Factory Mutual, Industrial
Risk Insurors, National Fire Prevention Association, the California Department of Industrial Relations (Occupational
Safety and Health Division), the Federal Occupational Safety and Health Administration, or other relevant regulations
and requirements.
1. Preliminary Analysis
- Verify that the boiler, steam generator, or process heater (unit) is operating at the lowest pressure or temperature
that will satisfy load demand. This pressure or temperature will be used as a basis for comparative combustion
analysis before and after tuneup.
- Verify that the unit operates for the minimum number of hours and days necessary to perform the work required.
- Verify that the size of air supply openings is in compliance with applicable codes and regulations. Air supply
openings must be fully open when the burner is firing and air flow must be unrestricted.
- Verify that the vent is in good condition, properly sized, and free from obstruction.
- Perform a combustion analysis (CO, O2, etc.) at both high and low fire, if possible. Record all data, as well
as the following:
- Inlet fuel pressure at burner at high and low firing rates.
- Pressure above draft hood or barometric damper at high, medium, and low firing rates.
- Steam pressure, water temperature, or process fluid pressure or temperature entering and leaving the unit.
- Inlet fuel use rate if meter is available.
2. Checks and Corrections
- Clean all dirty burners or burner orifices. Verify that fuel filters and moisture traps are in place, clean,
and operating properly. Confirm proper location and orientation of burner diffuser spuds, gas canes, etc. Replace
or repair damaged or missing burner parts.
- Remove external and internal sediment and scale from heating surfaces.
- Verify that the necessary water or process fluid treatment is being used. Confirm flushing and/or blow-down
schedule.
- Repair all leaks. In addition to the high-pressure lines, check the blow-off drain, safety valve, bypass lines
and, if used, the feed pump.
3. Safety Checks
- Test primary and secondary low water level controls.
- Check operating and limit pressure and temperature controls.
- Check pilot safety shut-off operation.
- Check safety valve pressure setting and verify that the setting is consistent with unit load requirements.
- Check limit safety control and spill switch.
4. Adjustments
Perform the following checks and adjustments on a warm unit at high fire:
- Adjust unit to fire at the maximum inlet fuel use rate; record fuel manifold pressure
- Adjust draft and/or fuel pressure to obtain acceptable, clean combustion at both high, medium, and low firing
rates. The carbon monoxide (CO) value should not exceed 400 parts per million (PPM) at 3 percent O2.
Verify that unit light-offs are smooth and safe. Perform a reduced fuel pressure test at both high and low firing
rates in accordance with the manufacturers instructions.
- Check and adjust the modulation controller. Verify proper, efficient, and clean combustion through the range
of firing rates.
When optimum performance has been achieved, record all data.
5. Final Test
Perform a final combustion analysis on the warm unit at high, medium, and low firing rates, if possible. Record
data obtained from combustion analysis, as well as the following:
- Inlet fuel pressure at burner at high and low firing rates.
- Pressure above draft hood or barometric damper at high, medium, and low firing rates.
- Steam pressure, water temperature, or process fluid pressure or temperature entering and leaving the unit.
- Inlet fuel use rate if meter is available.