United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-81 -123 August 1982
Project Summary
Combustion Modification
Controls for Residential and
Commercial Heating Systems
C. Castaldini, K. J. Lim, and L R. Waterland
This report provides an environ-
mental assessment of combustion
modification techniques for residential
and commercial heating systems. The
assessment evaluates NOX reduction
effectiveness, operational impact,
thermal efficiency impact, control
costs, and effects on pollutant emis-
sions other than NO*. Major equip-
ment types and design trends are
reviewed, although emissions and
control data for commercial systems
are very sparse. Natural gas and
distillate oil are the principal fuels.
IMOx, CO, and unburned hydrocarbons
(and particulates for oil-firing) are the
primary pollutants. High radiative heat
transfer burners have been developed
for gas-fired residential systems,
lowering NOX emissions by about 80
percent without increasing emissions
of combustibles. For oil-fired resi-
dential systems, several new burner
designs (including integrated burner/
furnace systems) have been devel-
oped, lowering NO, by 20 to 85
percent and generally decreasing CO,
HC, and particulate emissions. Com-
mercial application of these systems is
very limited. No operational or main-
tenance problems are expected. Since
the control techniques generally
increase thermal efficiency, the addi-
tional initial investment cost will be
offset by operational savings. Field
test data from a commercially available
oil-fired low-NO* residential system
suggest that the system poses less of a
potential environmental hazard than a
conventional unit.
This Project Summary was devel-
oped by EPA's Industrial Environ-
mental Research Laboratory. Research
Triangle Park. NC. to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
With the increasing extent of NOX
control application in the field, and
expanded NOX control development
anticipated for the future, there is
currently a need to ensure that: (1) the
current and emerging control tech-
niques are technically and environ-
mentally sound and compatible with
efficient and economical operation of
systems to which they are applied, and
(2) the scope and timing of new control
development programs are adequate to
allow stationary sources of NO* to
comply with potential air quality
standards. With these needs as back-
ground, EPA's Industrial Environmental
Research Laboratory, Research Triangle
Park (IERL-RTP) initiated the "Environ-
mental Assessment of Stationary Source
NOx Combustion Modification Tech-
nologies Program" (NOx EA) in 1976.
This program has two main objectives:
(1) to identify the multimedia environ-
mental impact of stationary combustion
sources and NO* combustion modifica-
tion controls applied to these sources,
and (2) to identify the most cost-
effective, environmentally sound NOx
combustion modification controls for
attaining and maintaining current and
-------
projected NC>2 air quality standards to
the year 2000.
The NOx EA's assessment activities
have placed primary emphasis on:
major stationary fuel combustion NOx
Sources (utility boilers, industrial boilers,
gas turbines, internal combustion
engines, and commercial and residential
heating systems); conventional gaseous,
liquid, and solid fuels burned in these
sources; and combustion modification
control applicable to these sources with
potential for implementation to the year
2000.
This report summarizes the environ-
mental assessment of combustion
modification controls for commercial
and residential heating systems. It
presents an outline of the environ-
mental, economic, and operational
impacts of applying combustion modi-
fication controls to this source category.
Results of a field test program aimed at
providing data to support the environ-
mental and operational impact evalua-
tion are also summarized.
Conclusions
Source Characterization
Figure 1 shows that commercial and
residential sources with a heat input
capacity <2.9 MW «107 Btu/hr)
constitute the fourth largest NOx
emission category, contributing nearly
7 percent of the total NOx from all
stationary sources. Major fuel combus-
tion sources in the residential and
commercial category are central warm
air furnaces, room or direct heaters,
residential hot water heaters, and
steam and hot water hydronic boilers
used for space or water heating. Minor
sources include stoves and fireplaces;
these consume a relatively insignificant
quantity of fuel compared to other space
heating equipment. A breakdown of
1977 NO, emissions from residential
and commercial sources indicates that
central warm air furnaces contributed
14 percent, steam and hot water
heaters 26.1 percent, and warm air
space heaters 4.3 percent of the total
NOx from the sources. A variety of
factors, including continuing demand
for new housing and fuel use trends,
will tend to increase NOx emissions
from residential heating systems. Thus,
given this trend and their potential for
NOx control, residential and commercial
heating systems represent a priority
source category for evaluation in the
NOx EA.
The primary fuels used for residential
heating are natural gas and distillate
Commercial and
residential 2.9 MW
(10 x 10s Btu/hr) 6.8%
Incineration 0.4%
Noncombustion 1.9%
Gas turbines 2.0%
Others (fugitive) 4.1%
Industrial process
heaters 4.1%
Industrial and commercial
boilers >2.9 MW
f>10x 10* Btu/hr) 9.7%
Reciprocating
1C engines
18.9%
Total from all sources: 10.5 Tg/yr (11.6 x 10* ton/'
Warm air space heaters 4.3%
Warm air
central
furnaces 14.0
Miscellaneous combustion" 11.4%
Firetube boilers 12.5%
Watertube boilers 1.4%
Steam and hot
water heaters
26.1%
Cast iron boilers
30.3%
Total from all sources with capacity less than 2.9 M\
(10 x 10s Btu/hr): 0.7O9 Tg/yr (0.781 x 10s tons/yr)
"Includes cooling and air conditioning
Figure 1. Distribution of stationary man-made sources of NO*
emissions for the year 1977 (controlled NO* levels.(Reference 1).
-------
>ils (No. 1 and 2 distillate). These fuels
lombined account for nearly 90 percent
»f all fuel burned for domestic heating.
.iquefied petroleum gas(LPG-butaneor
iropane), coal, and wood are also used,
ilthough in relatively small quantities.
n 1976, LPG-fired equipment accounted
or about 6 percent of domestic heating
iquipment, while coal- and wood-fired
mils accounted for only 2 percent.
uilt-in, residential, electric heating
ystems, including heat pumps, have
ecome increasingly popular as
omestic supply of clean fuels dwindles
nd fuel costs increase. Electric heaters
11976 accounted for nearly 14 percent
f residential heating equipment.
The primary fuels and equipment
/pes used for domestic heating show
ignificant regional variations. For
xample, the Northeast depends pri-
larily on oil-fired steam or hot water
nits, while in all other regions, natural-
as-fired central warm air furnaces are
sed primarily for domestic space
eating.
Combustion equipment designs for
lost residential heating systems are
uite similar. For natural-gas-fired
quipment, the single-port upshot or
ie tubular multiport burners are the
lost common. Natural-gas-fired warm
ir furnaces, room heaters, or hot water
eaters generally use a pilot flame to
Unite the burner automatically.
istillate-oil-fired residential heating
ystems generally use high-pressure
tomizing gun burners. Nearly all new
il-fired burners use the flame retention
urner head which promotes more
fficient combustion.
Commercial heating systems can be
ivided into three general categories:
i/arm air unit heaters or space heaters,
i/arm air furnaces or duct heaters, and
lot water or steam systems. The
ombustion systems for commercial
i/arm air units (or space heaters) and
uct heaters are generally similar to
esidential systems, although there are
few unique commercial gas-fired
esigns. Warm air units and duct
leaters are either direct or indirect
ired. Direct fired heaters use only clean
aseous fuels, exhausting the combus-
ion products directly into the heated
pace. Indirect fired heaters use either
as or oil and are vented to the outdoors.
"hese units, except for their larger
:apacity, are generally similar to
esidential central warm air furnaces.
Hot water and steam systems in the
lommercial size capacity, here defined
n the range of 0.12 - 2.9 MW[(0.4 -10)
x 106 Btu/hr] heat input capacity,
include cast iron hydronic boilers, and
small firetube and watertube boilers
used in both the commercial and
industrial sectors. Cast iron hydronic
boilers are also used in residential
applications. These units, common in
the Northeast and Northcentral regions
of the U.S., are primarily either gas- or
distillate-oil-fired. Firetube and small
watertube boilers used to heat large
commercial plants and buildings are
similar to the smaller industrial boilers
used to generate process steam. These
boilers are generally fired with gas, oil,
or (less frequently) stoker coal, and
account for about 25 percent of the
installed capacity of steam and hot
water boilers with heat input capacity
less than 2.9 MW (10 x 106 Btu/hr).
Source Emissions
Because natural gas and distillate oil
are the principal fuels used in residential
and commercial heating systems, air
pollutant emissions represent the
primary waste stream of environmental
concern. Coal- and wood-fired furnaces
and stoves, however, also produce ash
solid waste streams. Although increas-
ing m popularity due to the scarcity and
high cost of other fuels and electricity,
residential wood- and coal-fired systems
still account for only 2 percent of all
domestic heaters. Thus, nationally,
solid waste streams from residential
heating pose an insignificant environ-
mental concern. Commercial coal-fired
watertube and firetube stokers are also
the source of solid waste streams.
These units, which account for about 15
percent of the firetube and watertube
population, could increase in popularity
with economic and political incentives
for increased use of domestic coal.
Flue gas emissions from natural-gas-
fired residential and commercial com-
bustion sources include primarily NOx,
CO, and unburned hydrocarbons (HC).
When fuel oil or coal is burned, smoke,
paniculate, and SOa are also emitted.
The levels of NOX, CO, and HC from oil
and coal combustion are usually higher
than those from gas combustion. Figure
2 shows the general trends of steady-
state smoke and gaseous emissions
from oil-fired residential heaters as a
function of combustion air settings.
Commercial boilers show similar trends.
For both equipment types, the operating
setting corresponding to lowest emis-
sions of CO, HC, and smoke coincides
with high NOx levels. As the excess air is
reduced from the theoretical setting,
concentrations of CO, HC, and smoke
increase because of lack of oxygen in
the flame and reduced turbulent mixing
which leads to incomplete combustion.
At very high excess air levels, these
emissions can also increase due to the
excessive combustion air which cools
the flame, also resulting in incomplete
combustion.
A major factor contributing to high
combustible emissions, particularly in
residential burners, is the transient
operating mode. The on/off cycle is a
dominant characteristic of warm air
furnaces, and is quite important as a
cause of increased emissions. Figure 3
shows qualitative emission traces from
an oil burner during a typical cycle. CO
and HC emissions peak at ignition and
shutoff. HC concentration drops to
insignificant levels between the peaks,
while CO emissions tend to flatten out
at a measurable level. Particulate
emissions continuously taper off after
the ignition-induced peak, whereas NO
emissions first rise rapidly for a short
period and then continue to rise at a
more moderate rate as the combustion
chamber temperature increases. These
transient emissions are caused mainly
by variations in combustion chamber
temperature. At ignition, a cold re-
fractory will not assist complete com-
bustion; therefore, peaks of CO, HC, and
smoke can occur. In addition to the cold
refractory, wear and tear on the oil
pump causes poor shutoff performance
and (thus) high smoke and combustible
emissions.
In general, except for SOa emissions
which depend entirely on the sulfur
content of the fuel, all other criteria
pollutant emissions are primarily a
function of burner nozzle type, combus-
tion chamber shape and material, and
operating practice.
Table 1 summarizes 1977 emissions
for stationary combustion sources with
heat input less than 2.9 MW(10 x 106
Btu/hr). These sources include pri-
marily residential and commercial
heating systems, as well as small
industrial boilers. Residential and
commercial heating systems contribute
56 and 28 percent, respectively, of the
total NOx from these sources. These
emissions are seasonal; nearly all the
total annual output occurs in the winter
months, during which the impact of
residential and commercial heating on
ground level ambient N02 concentra-
tion in urban areas can be significant.
-------
2.00-
i Optimum setting for minimum \
\emissions and maximum efficiency
1.50
1.00-
i
0.50
0.00
-10
I
Q.
7
5
K ^
O 4)
I
<8
I
3
2
^^ 4
8
-20 0
I I I
20 40 60 80 H
Excess air, %
_L
I
I
720 140
I
16 14 12
10
8
COi,%
Figure 2. General trend of smoke, gaseous emissions, and efficiency
versus stoichiometric ratio for a residential oil burner.
Control Alternatives
\n general, very little emission control
technology for gas- and oil-fired resi-
dential and commercial systems has
been implemented in the field. Most
emission control work- for residential
heaters has centered on tuning and
maintenance of exisitng equipment or
installation of new more efficient
equipment for reduced fuel consump-
tion and minimum visible emissions.
Tuning usually reduces CO, HC, and
particulates (smoke), without much
effect on NOX emissions. New furnace
concepts utilize advanced burner
designs which aNow efficient operation
at low excess air. Some of these burners
are also capable of low NOX emissions.
NOX emission control techniques
under development for residential and
commercial equipment are typically
adapted to the specific fuel and burner
type. Because NOX emissions from
either gas or distillate oil combustion
are primarily thermal NOX, control
techniques are aimed at controlling
temperature or oxygen availability in the
high temperature flame region. Tables 2
and 3 summarize NOX control alterna:
lives for residential heaters firing
natural gas and distillate oil, respec-
tively. These controls have been devel-
oped primarily for warm air furnaces;
however, the advanced burners and
combustor redesign technology pre-
sented in these tables could possibly be
applied to other domestic heating
equipment and some larger commercial
installations.
For residential gas-fired heaters, the
American Gas Association Laboratories
(AGAL) has developed radiant screens
and secondary air baffles capable of
average NOX reductions of 58 and
percent, respectively. However, th
controls may find little applicat
because of installation and performa
problems subsequently identified by
Gas Appliance Manufacturers Assoi
tion (GAMA). Two advanced NOX con
alternatives are the Bratko Surf,
Combustor and the Amana Heat Tra
fer Module (HTM). In these conce
radiation from the combustion z<
maintains a lower temperature in
combustion products and thus lo\
NOX production while maintaining g<
efficiency and low CO levels. r<
emissions from both the Bratko <
Amana burners are about 80 perc
below levels of conventional warm
furnaces. Unlike the Bratko, the Am.
unit is commercially available, and
cost to the consumer is generally $1
to $300 above that of a conventic
furnace.
The modulating furnace syst<
produces a cooler flame by altering 1
burner firing rate to respond to 1
heating load instead of cycling on and
NOX reductions of about 40 pero
have been reported. AGAL is currer
investigating pulse combustion
residential heating using a condens
exhaust gas system, with prelimin
NOX emissions reported as 19 to
ng/J. Commercialization of the pu
combustor residential heating systen
expected to begin in 1981. Cataly
promoting combustion of fuel at I
temperature offer potential for very I
NO, emissions while maintaining gc
combustion efficiency. Research groi
and trade organizations are inves
gating the commercial feasibility
catalytic combustion for resident
warm air and hot water systei
burning natural gas. Performance a
emission data for these systems he
not yet been published; however, r>
emissions are expected to be very Ic
Residential oil-fired heaters c
forced draft fired and therefore mi
readily modified for reduced emissic
and increased efficiencies than natu
draft gas-fired heaters. Early w<
focused on the development of t
flame retention oil burner. The
burners produce lower CO, HC, a
smoke emissions and operate at lov
excess air levels than previous convt
tional oil burners. In some designs, 1
flame retention devices also lower N
emissions by 20 to 40 percent. Furth
more, they stay tuned longer and th
maintain low combustible emissi
-------
Filterable
Particulate
NO
Burner
On
Burner
Off
\ -\
Time
Time
HC
Burner
On
Burner
Off
|\
CO
Burner
Off
Time *-
igure 3. Characteristic emissions of oil burners during one
complete cycle.
Time
evels. These units are now the primary
esidential oil burners sold.
As part of its combustion research
irogram, EPA has supported low-NOx
ligh efficiency residential burner
evelopment since 1971. Under one
>rogram, Rocketdyne developed a
lontrolled-mixing burner head for
etrofit and new applications on
lomestic heaters. It was estimated that
widespread application of the relatively
nexpensive burner head would be
effective in reducing NOX by 20 percent
md increase efficiency by 5 percent on
he average for each retrofitted furnace.
Recently the burner was integrated with
an "optimum"* low emission, high
Terminology used by Rocketdyne to characterize
he final design capable of achieving program goals
efficiency warm air furnace. NOx
emissions have been reduced by 65 to
70 percent, and steady state efficiencies
have been increased by as much as 10
percent over those of conventional
designs. The EPA program emphasized
the necessity to match the firebox,
burner, and heat exchanger design to
achieve low NOx emissions while also
maintaining low levels of CO, HC, and
smoke.
Both the Blueray "blue flame" and
the M.A.N. burners use aerodynamic
flue gas recirculation to achieve a blue
flame with distillate fuel oil. These
burners thus achieve reduced flame
temperature, reduced oxygen concen-
trations in the near-burner zone, and
rapid vaporization of the fuel prior to
ignition. These conditions result in low
NOx emissions on the order of 15 to 40
ppm corrected at zero percent excess
air, representing NOx reductions of 50 to
80 percent. Theoretically, these burners
could be scaled up to larger commercial
sizes. The Blueray furnace system is
currently the only commercially avail-
able low NOx system in the U.S. for oil-
fired residential use. The M.A.N. burner,
developed in West Germany, is marketed
in parts of Europe and Canada.
Techniques aimed at reducing sea-
sonal pollutant emissions from resi-
dential heating systems are also ef-
fective in delivering improved fuel
economy and generally reduced equip-
ment use. Replacement of wornout
furnaces, tuning, and changes in
thermostat anticipator settings are the
most effective emission reduction tech-
niques, with overall combustible emis-
sion reductions ranging from 16 to 65
percent for CO, 3 to 87 percent for HC,
59 percent for smoke, and 17 to 33 per-
cent for particulates. Installation of de-
layed action solenoid valves and re-
duced firing capacity through minor
modification or installation of a new
flame retention burner are effective in
reducing excessive smoke emissions
during furnace start-up and shutdown.
Reported average smoke reductions
range from 24 to 82 percent. In general,
all these techniques result in fuel sav-
ings, sometimes as high as 39 percent,
in addition to lowering combustible
emissions.
Application of control technology to
commercial heating equipment is very
limited. Theoretically, the flame
quenching and surface combustion
concepts investigated for gas-fired
residential equipment could also apply
to commercial heaters burning natural
gas. Similarly, low-NOx burner designs
for distillate oil firing or optimum
air/fuel mixing concepts could possibly
be scaled up to the larger commercial
equipment.
NOX control technology from gas- and
oil-fired industrial boilers include low-
NOx burners, staged combustion, flue
gas recirculation, load reduction, and
low excess air operation. These tech-
niques could possibly apply to com-
mercial size boilers of similar design.
Low-NOx burners are the most attractive
control alternative for this boiler size.
Some U.S. companies are currently
working on new burner designs,
primarily for oil-fired boilers. Most of
these efforts, however, have been
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Table 1. Estimated 1977 Air Pollutant Emissions from Stationary Fuel Combustion Sources with Heat Capacity Less t
2.9 MW (10 x 106 Btu/hr)
Sector
Equipment
Fuel
Fuef
Total Capacity, Consumption
MW (JO6 Btu/hr} EJ (Quads)
Air Pollutant Emissions Gg (103 tons)
/VO* CO HC Particulates SO
Residential
Residential
and Commercial
Commercial
and Industrial
Total
Warm air central
furnaces
Warm air space
heaters
Miscellaneous
combustion
Steam and hot
water heaters
Cast iron
boilers
Watertube
boilers
Firetube
boilers
All equipment
Natural gas
Distillate
oil
Natural gas
Distillate
oil
Natural gas
Distillate
oil
Natural gas
Distillate
oil
Residual oil
Coal
Natural gas
Distil/ate
oil
Residual oil
Coal
Natural gas
Distillate
oil
Residual oil
Coal
Natural gas
Distillate
oil
Residual
oil
Coal
All fuels
743,520
(489.495)
33.730
(115,041)
53,790
(183,456)
31,590
(107.742)
5,770
(19.679)
4,490
(15,313)
5,240
(17.872)
1,900
(6,480)
79.090
(269,748)
31,530
(107,538)
48.200
(164,393)
14,420
(49,181)
1.876
(1.979)
1.354
(1.428)
0.57
(0.60)
0.42
(0.44)
1.524
(1.608)
0.926
(0.977)
2.1
(22)
1.4
(1.5)
0.11
(0.12)
0.043
(0.045)
1.8
(1.9)
0.35
(0.37)
0.47
(0.50)
0.097
(1.0)
0.053
(0.056)
0.021
(0.023)
0.015
(0.016)
0.012
(0.013)
1.358
(1.433)
0.37
(0.39)
0.354
(0.374)
0.11
(0.116)
15.22
(16.97)
65.7
(72.5)
33.8
(37.3)
19.9
(21.9)
10.5
(11.6)
53.3
(58.8)
27.4
(30.2)
82.8
(91.3)
77.9
(85.9)
17.5
(19.3)
7.1
(7.8)
91.7
(101.1)
23.7
(26.1)
84.6
(93.3)
14.6
(16.1)
3.16
(3.5)
1.18
(1.3)
2.38
(2.6)
3.0
(3.3)
31.0
(34.2)
12.8
(14.1)
30.7
(33.9)
14.1
(15.6)
708.8
(781.6)
19.0
(20.9)
33.8
(37.3)
5.7
(6.3)
10.5
(11.6)
15.2
(16.8)
27.4
(30.2)
17.8
(19.6)
41.7
(46.0)
1.64
(1.81)
7.53
(8.3O)
35.3
(38.9)
0.56
(0.61)
0.66
(0.73)
21.3
(23.5)
1.06
(1.17)
0.06
(0.07)
0.02
(0.02)
0.91
(1.00)
15.2
(16.8)
0.34
(0.38)
0.29
(0.32)
5.40
(5.95)
261.4
(288.3)
6.40
(7. 10)
6.40
(7.06)
1.94
(2.14)
1.97
(2.17)
5.20
(5.73)
5.15
(5.68)
4.76
(5.25)
13.4
(14.8)
2.74
(3.02)
2.12
(2.34)
4.06
(4.48)
3.34
(3.68)
11.8
(13.8)
5.53
(6.10)
0.18
(0.20)
0.01
(0.01)
0.07
(0.08)
0.19
(0.21)
1.75
(1.93)
2.05
(2.26)
5.12
(5.65)
3.40
(3.75)
87.6
(96.6)
7.50
(8.27)
10.3
(11.4)
2.30
(2.54)
3.20
(3.53)
6.10
(6.73)
8.33
(9. 19)
16.6
(18.3)
10.6
(11.7)
9.09
(10.0)
150.2
(165.6)
6.88
(7.59)
4.18
(4.61)
13.2
(14.6)
314.3
(346.6)
0.05
(0.05)
0.18
(0.20)
0.42
(0.46)
23.5
(25.9)
3.02
(3.33)
2.57
(2.83)
5.73
(6.32)
130.0
(143.4)
728.3
(803. 1)
0.4
(0.5
(16
0.1
(0.1
45.
(SO.
0.4
(0.4
118
(130
0.6
0.6
150
(165
52.
(58.
30.
(33.
0.5
(0.5
37.
(41
225
(248
110
(122
0.0
(0.0
3.2
(3.6
6.7
(7.3
16.
(17.
0.2
(0.2
18.
(20.
92
(101
91
(101
1.14,
*EJ = 10'* Joules = 0.948 Quads = 0.948 x JO'5 Bw
oriented toward industrial (2.9 to 73.3
MW heat input) size boilers.
Cost of Control
Table 4 summarizes estimated costs
for the most effective NOX control
alternatives for residential heating
systems. As indicated, retrofit of the
controlled mixing burner head for
residential oil-fired warm air furnaces is
the most cost-effective alternative to
achieve a NO, emissions level of about
45 ng/J of useful heat. Cost-effect
ness of other alternatives for oil-f
warm air furnaces is generally o
parable, falling in the $1 to $4 n
range. Similarly, for gas-fired warn
furnaces, both the Amana HTM furn
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Table 2. Performance Summary of Low-NO* Control Equipment for Natural
Control
Baseline
Radiant screens
Secondary air
baffles
Bratko Surface
combustion burner
Amana (HTM)
Modulating
furnace
Pulse
Combust or
Catalytic
Combustor
Average
Operating
Excess Air,
percent
40-120
40-120
60-80
10
NA
NA
NA
NA
Cyclic Pollutant Emissions,
ng/J heat input i.
NO**
28-45
15-18
22
7.5
7.7
25
10-20
<5
CO
8.6-25
6.4
14
5.5-9.6
26
NA
NA
NA
UHC"
3.3-33
NA
NA
NA
NA
NA
NA
NA
Steady State
Efficieney,
percent
70
75
NA
NA
85
75
95
90
Cycle
Efficiency.
percent
60-65
70
NA
NA
80
70
95
85
Gas-Fired Residential Heaters
1978
Installed
Control
Cost
($500-$800f
NA
NA
$100-$200
$100 -$300
over
conventional
furnace
$50-$250
over con-
ventional
furnace
$300-$600
$100-$250
Comments
Costs include installation
Emissions of CO and HC can increase
significantly if screen is not placed
properly or deforms
Requires careful installation. Best
suited for single-port upshot burners
Not commercially available. Still
under development
Commercially available design. Spark
ignited, thus requires no pilot
Furnace is essentially derated. Thus
it requires longer operation to deliver
a given heat load
Currently being investigated by AGAL.
Efficiencies correspond to condensing
systems.
Still at the R&D stage. Efficiencies
correspond to condensing systems.
"Sum of NO + NOz reported as NOz
hUnburned hydrocarbons calculated as methane (CHt)
^Typical costs of uncontrolled unit
NA = not available
Table 3. Performance Summary of Low-NO* Control Equipment for Distillate-Oil-Fired Residential Heaters
Cyclic Pollutant Emissions.
Control
Baseline
Flame Reten-
tion Burner
Head
Controlled
Mixing Burner
Head by EPA/
Rocketdyne
Integrated
A verage
Excess Air.
percent NO"
SO-85 37-85
20-40 26-88
10-50 34
2O-3O 19
rig/ j neai input
Smoke
CO UHC" Number Paniculate
15-30 3.0-9.O 3.2 76-30
11-22 0.2-18 2.0 NA
13 0.7-1.0 0.5-09 NA
2O 1.2 032 NA
Steady State
Efficiency,
percent
75
80-83
also depends
on heat
exchanger
80
also depends
on heat
exchanger
34
Cycle
Efficiency.
percent
65-70
NA
NA
74
1978
Installed
Control
Cost
l$650-
$1000f
$52
$43
$25O over
Comments
Range in /V0« emissions is
for residential systems not
equipped with flame retention
burners. Emissions for other
pollutants are averages
If a new burner is needed as well
as a burner head, the total cost
would be $385.
Cost of mass produced burner head
only about $ 1 .50. Combustible
emissions are relatively low because
hot firebox was used.
Uses optimized burner head.
Furnace Sys-
tem by EPA/
Rocketdyne
Bluer ay
"blue flame"
Burner/Furnace
System
MA.N
Burner
20
10
4.5-7.5 1.5-25
10-15 1O-25
30
NA
1.0
NA
NA
84
85
conven- For new furnace installation
tional only. Combustible emissions are
furnace higher than with burner head
because of quenching in an air
cooled firebox. Recent cost estimate.
74 $100 over New installation only.
conven- Furnace is commercially
tional available. Recent cost estimate.
furnace
NA NA Both for retrofit or new
installations. Not yet
commercially available in U.S
Commercialization expected
in 1982.
'Sum of NO and /V02 reported as NOi
"Unburned hydrocarbons calculated as methane (CH,I
^Typical costs of uncontrolled unit
-------
Table 4. Cost Impact of NOt Control Alternatives
Control
Amana (HTM) Furnace
Modulating Furnace
Surface Combustion
Burner (Infrared Bratko)
Pulse Combustion
Burner0
Catalytic Combustion
Burner*
Flame Retention
Burner Head
Flame Retention
Burner
EPA/Rocketdyne
Burner Head
EPA/Rocketdyne
Furnace
Blue ray Furnace
Fuel
Natural Gas
Natural Gas
Natural Gas
Natural Gas
Natural Gas
Distillate Oil
Distillate Oil
Distil/ate Oil
Distillate Oil
Distillate Oil
Achievable /VO« Level,
ng/J useful heat
12
(390 ng/m3 fuel)
35
(920 ng/m3 fuel)
12
(390 ng/m3 fuel)
21
(683 ng/m3 fuel)
Estimated 5
(163 ng/m3 fuel)
50
(1. 8 g/ kg fuel)
50
(1. 8 g/ kg fuel)
45
(1. 6 g/ 'kg fuel)
29
(0.7 g/ kg fuel)
20
(0 7 g/kg fuel)
1978
Incremental
Investment Cost
$100 -$300 over cost of
conventional furnace
$50-$250 over cost of
conventional furnace
$ W0-$200 over cost of
conventional furnace/
heater
$300-$600 over cost of
conventional furnace/
heater
$150-$250 over cost of
conventional furnace/
heater
$52 retrofit
including installation
$385 retrofit of
reduced capacity burner
$43 retrofit
including installation
$250 over cost of
conventional furnace
$ 100 over cost of
conventional furnace
Cost Effectiveness.
$/ng/J"
1.7-52
1 4-7.0
1. 7-3.4
6.1-12.2
2.3-3.9
26
12.8
1.3
4.2
1.7
Payback Period Base
on Annual Fuel Bill
of $500. years
1-3
1-3.8
3.5-8.0
1.7-3.5
1 4-2.3
Less than 1
3.5
Less than 1
2.5
1
"Based on uncontrolled /VOx emissions of 70 ng/J heat output for natural-gas-fired heaters and80 ng/J heat output for distillate-oil-fired heaters
Cost effectiveness is based on the differentia/ investment cost of the control.
"Based on installation of a condensing system where seasonal efficiencies can be as high as 95 percent.
and the modulating furnace are com-
parably cost-effective, in the $1 to $7
ng/J range. Surface combustor, pulse
combustor, and catalytic burner for gas-
fired units and the Rocketdyne devel-
oped techniques for oil-fired units are
not commercially available. The pay-
back periods listed in the table, are
estimates based on the time required to
recover the money spent for the initial
investment of installing NOX control
equipment. Since all these control
alternatives increase thermal efficiency,
and thus fuel savings, the initial
investment cost is often recouped in 1
year or less.
Incremental Emissions Due
to Controls
To assess the effects of a low-NO*
burner/furnace design on the incre-
mental emissions of pollutant species
other than NO* from a residential heat-
ing unit, an oil-fired Blueray low-NOx,
high-efficiency home furnace was field
tested. The unit was in a Medford, LI,
NY, residence and had been in service
about 1 year. The model tested fired
distillate fuel oil at 0.63 mg/s (0.6
gal./hr) and had a rated heat input of
24.6k J/s (84,000 Btu/hr). The program
involved testing in two modes of oper-
ation: continuous and cyclic (10 mi-
nutes on and 10 minutes off). The cyclic
mode is more representative of typical
operation. Sampling and analysis of the
flue gas stream, using slightly modified
Environmental Assessment Level 1
procedures, were performed (Reference
2). Detailed test results are reported in
Volume II of the full report summarized
here.
Table 5 shows average flue gas
composition data for the two tests. In
the cycling test, there were peaks in the
CO and HC emissions at the start and
end of each period of operation. This
initial peak is included in the average
concentration noted. Start-up peak
emissions averaged 2000 ppm for CO
and 400 ppm for HC. The NOX levels
started at zero and, toward the end of
the firing cycle, reached 16 ppm which
was the average value for the continuous
firing test. Average N0« emissions were
also very low in both cyclic and con-
tinuous operation. Particulate emis-
sions were very low and did not vary
from continuous to cyclic operation.
Organic emissions increased substan
tially for cyclic operation. Liquid colum
chromatographic, infrared, and lov
resolution mass spectrometric analyse
of the samples showed that, for botl
cyclic and continuous operation, thi
samples contained primarily aliphati
hydrocarbons, with some aromaticsani
carboxylic acids.
Table 6 summarizes flue gas emissioi
data, including those for trace elemen
Table 5. Flue Gas Composition:
Blueray Unit
Component Cyclic Continuous
NO t ng/J as NO2
ppm. dry
SOz, ng/J
SOa. ng/J
UHC, ng/J as CHt
ppm, dry
CO. ppm dry
COz, % dry
Oz, % dry
Particulate, ng/J
Total !>Cj)
Organics, /jg/m3
6.6
11
35.5
1.0
5.0
23
160
12.9
4.0
1.30
2 63x1 O4
10
16
26.9
0.2
0
0
25
13.1
3.8
1.32
1.300
-------
Table 6. Flue Gas Composition f/jg/dscmj: Residential Warm air Furnaces
A verage
Element
/vox
SOz
S03
CO
Antimony
Arsenic
Barium
Beryllium
Bismuth
Boron
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Manganese
Mercury
Molybdenum
Nickel
Selenium
Tellurium
Thallium
Tin
Titanium
Vanadium
Zinc
Organics f>Cj)
Blueray
Cyclic
5.4 x W3
2.7 x 104
770
4.5 x W4
<0.46
<0.54
<1 1
<0.014
<0.62
<10
<1 .1
<5.5
<5.7
11
46
<21
<2.5
<3.0
<3.5
<1 1
<1 .8
<0.77
<41
<0.92
<1 .0
<1 1
<2.8
6.0 x W3
Blueray
Continuous
7.7 x 103
2.1 x W4
150
6.9 x 103
<0.38
<0.46
<8.5
<0.012
<0.62
<3.0
<1 .7
<85
<6.8
15
420
<21
<12
<4.2
<1 1
<68
<2.3
<0.69
<37
<0.69
<2.5
<0.62
<3.2
290
Conventional
Cyclic
4.2 x 104&
8.2 x 104a
4.5 x 103
1.2 x 104a
4.4
1.2
12
8.5
22
120
11
32
0.92
220
2.2
85
2.4 x W3
"Calculated from emission factors in
Factors," EPA report AP-42
species. For comparison, average Level
1 emission data from several conven-
tional oil-fired furnaces recently tested
are also shown (Reference 3). To
facilitate direct comparisons, all con-
centration data in the table are shown
as//g/m3, adjusted to an end of flue pipe
C-2 content of 17 percent, the average
value found in the Reference 3 tests.
Environmental Impact
Evaluation
The data summarized in Table 6 were
evaluated by a Source Analysis Model
(SAM), specifically SAM/IA (Reference
4), to give a quantified measure of the
potential hazard posed by emissions
from a residential warm air furnace, and
to assess how a Iow-N0x design affects
the potential hazard.
SAM/IA was developed for use in
Environmental Assessment projects to
provide estimates of the potential
hazard associated with some discharge
streams. The basic index of potential
hazard defined by SAM/IA is Discharge
"Compilation of Air Pollutant Emission
Severity (DS). The DS for a given species
is defined as the ratio of that species'
discharge stream concentration to the
species' Discharge Multimedia Environ-
mental Goal (DMEG). DMEGs, defined
in the Environmental Assessment
program for a large number of species,
represent the maximum pollutant
concentration desirable in a discharge
stream to preclude adverse effects on
human health or ecological systems.
Table 7 presents human-health-
based DS values, calculated from the
data in Table 6, for species where DS
exceeded unity for any data set eval-
uated. The DS values for NOX, SOa, and
CO for the conventional furnace were
calculated using AP-42 emission
factors: these species were not directly
measured in the conventional furnace
test program.
The table indicates that, for both types
of units, Cr and Ni emissions appear to
present the greatest potential environ-
mental hazard; in all cases, their DS is a
sizable fraction of total stream DS.
However, measured levels of these
metals may be an artifact of the stream
sampling methodology. The flue gas
sampling trains in both the conventional
furnace test program and the NOX EA
contained many stainless steel com-
ponents. Thus, some of the reported Cr
and Ni could have come ft&frt the
sampling train itself, rather than being a
significant component of the flue gas.
For both units, SOa emissions were
flagged and emissions of certain organic
categories had DS values greater than
1. For the conventional units, amines
were flagged as being of potential
concern; for the Blueray unit, carboxylic
acids would be of potential concern
under cyclic operation. The DS for NOX
exceeds 1 for conventional units, but is
less than 1 for the Iow-N0x Blueray unit
under both continuous and cyclic
operations.
In summary, flue gas stream Total
Discharge Severity (TDS) for typical
conventional units appears to fall
between the TDS for the Iow-N0x unit
under cyclic (normal) operation and that
for the Iow-N0x unit under continuous
operation. If Grand Ni are removed from
the TDS calculations, adjusted TDS's of
22, 6.2, and 9.3 result for the conven-
tional, Blueray continuous, and Blueray
cyclic data, respectively. Thus, if mea-
sured Cr and Ni indeed come from the
sampling train, then the Iow-N0x unit's
TDS under both cyclic and continuous
operation is lower than that of the
conventional units. This suggests that
using the Blueray design to control NOX
from oil-fired heating units is environ-
mentally sound.
Recommendations
The Environmental Assessment of
combustion modification controls for
residential and commercial heating
units was often frustrated by the lack of
good quality data m several areas. Thus,
recommendations from the study focus
on extending the data base necessary
for evaluating the effects of these
controls on heating system operation,
costs of operation, and emissions.
With respect to emission data from
residential space heating equipment, a
substantial amount of information has
been gathered. Numerous control
alternatives for NOX and combustible
pollutants have been investigated.
Some Iow-N0x and high efficiency
furnace designs are commercially
available, while other equally effective
designs are either at final demonstra-
tion stages or await commercialization.
-------
Table 7. Flue Gas Discharge Severity: Oil-Fired Residential Warm Air Furnaces
Discharge Severity
Component
Cr
Ni
Alky lhal ides
S02
NO,
SOs
Amines
Carboxylic acids
CO
MEG
Category
68
76
2
53
47
53
10
8
42
Conventional
Cyclic
22
15
13
6.3a
4.7*
4.5
1.6
0.30a
Blueray
Continuous
85
4.5
1.6
0.86
0.15
0.20
0.17
Blueray
Cyclic
5.5
0.73
2.1
0.60
0.77
2.3
1.1
Total stream
59.0
95.7
15.5
*Not measured; DS based on AP-42 emission factor s.
Performance test data on these im-
proved designs are being gathered in
EPA sponsored field and laboratory
programs. These and other test pro-
grams will aid in further documenting
the performance and reliability of these
advanced controls and quantifying their
impact on other pollutant emissions.
Cost data on NOX control alternatives
for residential heating systems are
generally sparse and imprecise. This
lack of definitive cost data prevented a
detailed economic impact assessment
of widespread implementation of control
alternatives. As advanced controls
become available, future studies should
quantify the cost impact of NOxControl
implementation to achieve specific
levels of control.
Information on NO* control alter-
natives for commercial size steam and
hot water boilers burning gas or oil is
also scarce While it can be speculated
that some boiler designs lend them-
selves to NOx control techniques devel-
oped for industrial size boilers, little
experimental data exist to confirm this.
Low-NOx burner technology for heat
input capacities in the size range of 0.1
to 2.9 MW (0.4 to 10 x 106 Btu/hr)
shows promise based on advanced
burner technology developed for both
residential units on the small side and
industrial units on the larger side, but
definitive demonstration is needed.
NOx control alternatives for solid-
fuel-fired residential and commercial
equipment have also seen very limited
study. Past and on-going test programs
have mainly dealt with quantifying the
pollutant levels and identifying equip-
ment operating parameters and fuel
characteristics which have some impact
on these levels. Primary pollutants of
interest for this category of equipment
have been particulate and smoke
emissions as well as levels of unburned
HC, toxic elements, and polycyclic
organic matter (POM). The simplicity of
the solid-fuel-fired equipment, whether
coal- or wood-fired, often does not
permit extensive modification of existing
equipment or operating procedures
reduce NOX levels. Investigative effor
in this area should continue to determir
potential NOX control technology app
cable to new unit design, while st
concentrating on reducing the impact
other criteria and noncriteria pollutai
emissions.
References
1. Waterland, L.R., et a/., "Enviroi
mental Assessment of Stationa
Source NOX Control Technologic
Final Report," Acurex Draft Fin
Report FR-80-57/EE (IERL-RTI
1279), EPA Contract 68-02-2161
Acurex Corp., Mountain View, C/
April 1980.
2. Lentzen, D.E., et a/., "IERL-RT
Procedures Manual: Level 1 Env
ronmental Assessment (Secon
Edition)," EPA-600/7-78-201 (NTI
PB293795), Industrial Enviror
mental Research Laboratory, Re
search Triangle Park, NC, Octobt
1978.
3. Surpenant, N.F., et at., "Emission
Assessment of Conventional Stc
tionary Combustion Systems; Volum
I: Gas- and Oil-fired Resident!;
Heating Sources," EPA-600/7-7S
029b (NTIS PB298494), Industri;
Environmental Research Laboraton
Research Triangle Park, NC, Ma
1979
4. Schalit, L.M., and K.J. Wolfe
"SAM/IA: A Rapid Screening Meth
od for Environmental Assessmen
of Fossil Energy Process Effluents,
EPA-600/7-78-015 (NTIS PB277088
Industrial Environmental Researcl
Laboratory, Research Triangle Park
NC, February 1978.
10
-------
C. Castaldini, K. J. Urn, and L. R. Water/and are with Acurex Corporation.
Mountain View, CA 94042.
J. S. Bowen is the EPA Project Officer (see below).
The complete report consists of two volumes, entitled "Combustion Modification
Controls for Residential and Commercial Heating Systems,"
"Volume I. Environmental Assessment," (Order No. PB 82-231 168; Cost:
$16.50, subject to change)
"Volume II. Oil-Fired Residential Furnace Field Test, "(Order No. PB 82-231
176; Cost: $10.50, subject to change)
The above reports will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
11
U. S. GOVERNMENT PRINTING OFFICE: 1982/559-092/0481
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