Rhode Island Code of Regulations › Title 250 - Department of Environmental Management › Chapter 120 - Air Resources › Subchapter 05 - Air Pollution Control › Part 27 - Control of Nitrogen Oxide Emissions › Section 250-RICR-120-05-27.11 - Equipment Tuning Procedure

Current through June 14, 2024
A. This tuning
				  procedure, based on a tune-up procedure developed by KVB Inc. for the EPA, in
				  §§
										27.11(A)(1) through
				  (10) of this Part, shall be followed
1. 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.
2. At this firing rate,
				  record stack gas temperature, oxygen concentration and CO concentration (for
				  gaseous fuels) or smoke-spot number (for liquid fuels) and observe flame
				  conditions after the unit 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
				  values, and if the 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.
a.
				  The smoke-spot number can be determined with ASTM Test Method D- 2156-09,
				  incorporated in §
												27.4(B) of
				  this Part, or with the Bacharach method. ASTM Test Method D- 2156-09 is
				  included in a tune-up kit that can be purchased from the Bacharach
				  Company.
b. Typical minimum oxygen
				  levels for boilers at high firing rates are:
(1) For natural gas: 0.5% - 3.0%
(2) For liquid fuels: 2.0% - 4.0%
3. Increase combustion
				  air flow to the furnace until stack gas oxygen levels increase by one to two
				  percent over the value measured in §
											27.11(B)(2)
				  of this Part. As in §
											27.11(B)(2)
				  of this Part 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.
4. Decrease combustion air flow until the
				  stack gas oxygen concentration is at the level measured in §
											27.11(B)(2)
				  of this Part. 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.
5. Continue to reduce
				  combustion air flow stepwise until one of these limits is reached:
a. Unacceptable flame conditions - such as
				  flame impingement on furnace walls or burner parts, excessive flame carryover
				  or flame instability.
b. Stack gas
				  CO concentration greater than 400 ppm.
c. Smoking at the stack.
d. Equipment related limitations - such as
				  low windbox/furnace pressure differential, built in air flow limits,
				  etc.
6. Develop an
				  O2/CO curve (for gaseous fuels) or
				  O2/smoke curve (for liquid fuels) similar to those in
				  Figures 1 and 2 using the excess oxygen and CO or smoke-spot number data
				  obtained at each combustion air flow setting.
7. From the curves prepared in §
											27.11(B)(6)
				  of this Part, 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 & #2 oils
Smoke-spot number
Number 1
#4 oil
Smoke-spot number
Number 2
# 5 oil
Smoke-spot number
Number 3
# 6 oil
Smoke-spot number
Number 4
The above conditions are referred to as CO or smoke
					 threshold, or as the minimum excess oxygen level.
Compare this minimum value of excess oxygen to the expected
					 value provided by the combustion unit manufacturer. If the minimum value found
					 is substantially higher than the value provided by the combustion unit
					 manufacturer, burner adjustments shall be made to improve fuel and air mixing,
					 thereby allowing operation with less air.
8. Add 0.5 to 2.0 percent to the minimum
				  excess oxygen level found in §
											27.11(B)(7)
				  of this Part and reset burner controls to operate automatically at this higher
				  stack gas oxygen level. This margin above the level accounts for fuel
				  variations, variations in atmospheric conditions, load changes and
				  non-repeatability or play in automatic controls.
9. If the load of the combustion unit varies
				  significantly during normal operation, repeat §§
											27.11(B)(1) through
				  (8) of this Part 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 the
				  best performance over the range of firing rates. If one firing rate
				  predominates, settings should optimize conditions at that rate.
10. 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 §
											27.11(B)(5)
				   of this Part 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.