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J. Korean Wood Sci. Technol. 2018, 46(5): 597~609 pISSN: 1017-0715 eISSN: 2233-7180https://doi.org/10.5658/WOOD.2018.46.5.597
Original Article
Analysis of Emission Characteristics and Emission Factors of Carbon Monoxide and Nitrogen Oxide Emitted from Wood Pellet Combustion in Industrial Wood Pellet Boilers Supplied According
to the Subsidy Program of Korea Forest Service1 KORAPP
Sea Byul Kang2โ Kyu Sung Choi2โ Hyun Hee Lee2โ Gyu-Seong Han 3,โ
ABSTRACT1)
Korea Forest Service has supplied 76 industrial wood pellet boilers from 2011 to 2015 through subsidy programs.
Since carbon monoxide (CO) and nitrogen oxides (NOx) generated during boiler combustion are substances that lead
to death in the case of acute poisoning, it is very important to reduce emissions. Therefore, the CO and NOx emission
values of 63 boilers excluding the hot air blower and some boilers initially supplied were analyzed. The emission
factor was also calculated from the measured exhaust gas concentration (based on exhaust gas O2 concentration of
12%). The average value of CO emitted from industrial wood pellet boilers was 49 ppm and it was confirmed that
the CO concentration was decreasing as the years passed. The emission factor of CO was 0.73 g/kg. The average
value of NOx emitted from industrial wood pellet boilers was 67 ppm and the emission factor of NOx was 1.63 g/kg.
Unlike CO, there was no tendency to decrease according to the installation year. Both CO and NOx measurements
met the limits of the Ministry of Environment. These NOx emission factors were compared with the NOx emission
factors produced by certified low NOx burners. The NOx emission factor of industrial wood pellet boilers was about
1.9 times that of certified low NOx LNG combustors and about 0.92 times that of coal combustion.
Keywords: emission, carbon monoxide, nitrogen oxide, industrial wood pellet boiler
1. INTRODUCTION
Korea Forest Service (KFS) have subsided the
distribution and installation of industrial wood pellet
boilers from 2011 to 2015 by expanding wood pellet
consumption. This has helped step up the domestic
industrial wood pellet boiler technology as it resulted
in installing 76 industrial wood pellet combustors during
the same period. For the effective distribution and
management of the industrial wood pellet boilers, KFS
established the Industrial Wood Pellet Boiler Subsidy
Standards (KFS, 2015) and the Construction Inspection
1 Date Received August 14, 2018, Date Accepted September 11, 20182 Energy Network Laboratory, Korea Institute of Energy Research, 152 Gajung-ro, Yuseong-Gu, Daejeon 34129, Republic of
Korea3 Department of Wood and Paper Science, College of Agriculture, Life & Environments Sciences, Chungbuk National University,
Cheongju 28644, Republic of Koreaโ Corresponding author: Gyu-Seong Han (e-mail: [email protected], ORCID: 0000-0003-3835-2063)
Sea Byul Kangโ Kyu Sung Choiโ Hyun Hee Leeโ Gyu-Seong Han
- 598 -
Standards for Industrial Wood Pellet Boilers (KFS,
2013). The target industrial wood pellet boilers were
steam boilers in 0-5 to 7.0 ton/h or hot water boilers
and heaters in 230kW or over. 63 of them were steam
boilers, 7 of them were hot water boilers, and 6 of
them were hot wind heaters. To receive subsidies for
wood pellet boilers, the following conditions need to
be met: 1) The boiler heat efficiency at over 85% based
on the lower heating value; 2) the preparation of safety
device like a backfire prevention device; and 3) the
CO emissions, one of the air pollution substances, being
below 200 ppm.
In Korea, air pollutants related to the combustion
of wood pellets are regulated by the Clean Air
Conservation Act (ME, 2017). The target missions
generated by combustion facilities at or over a certain
size according to the Clean Air Conservation Act are
1) among wood pellet manufacturing facilities
(screening, drying and heating facilities, crushing and
grinding facilities, compression and molding facilities),
facilities in which fuel consumption is over 30kg per
hour, the capacity is over 3m2 or more, or power capacity
is 2.25 kW (15 kW for crushing and grinding facilities)
or more and 2) among the facilities that use wood pellets,
those in which the usage of fuel products is over 200kg
per hour (excluding those that use other fuels together
with wood pellets) (ME, 2017).
The allowable criteria of the air pollutants applied
since 2015 shows that the CO concentration in a facility
that uses wood pellets should be at or below 200 ppm
(12% of the actually measured oxygen concentration).
Nitrogen oxide (NOx, NO2) should be at or below 100
ppm for drying and heating facilities of wood pellet
manufacturing facilities, or at or below 150 ppm for
facilities that use wood pellets (12% of the actually
measured oxygen concentration). Fine dust should be
at or below 50 ใ/Sใฅ for both wood pellet
manufacturing facilities or those which use wood pellets
(12% of the actually measured oxygen concentration)
(ME, 2017). With very low sulfur oxide and heavy
metal content in wood pellets due to the fuel
characteristics, there is no allowable criteria for those
substances.
At the Parliamentary Inspection of the Administration
in 2017, it was argued that the wood pellet combustion
test showed that it produced 20 times as much nitrogen
oxide, which generates ultrafine dust, as coal briquette,
and there was a social controversy as the contents were
quoted and reported without verification. (Kim, 2017).
This is because while there has been research on the
manufacturing characteristics of wood pellets in Korea
(Kim et al., 2015; Yang et al., 2017), there has been
little on air pollutants during wood pellet combustion.
The study aimed to measure air pollutants generated
during the combustion of wood pellet boilers subsided
by KFS, through which it verified whether industrial
wood pellet boilers conformed the allowable criteria
of air pollutants by the Ministry of Environment.
Furthermore, based on the emissions of air pollutants,
it determined the emission factors of industrial wood
pellets boilers, which was compared to the NOx emitted
from low-NOx certified burner.
2. MATERIALS and METHODS
2.1. Survey target
There were 9 KFS subsidized industrial wood pellet
boilers (steam boilers, hot water boilers, hot wind heaters)
in 2011, 27 in 2012, 21 in 2013, 10 in 2014, and 9
in 2015. 63 boilers excluding hot wind heaters and
some distributed earlier were the target for this study.
Shown in Fig. 1 is the current installation conditions
by region. Over 50% of the subsidized industrial wood
pellet boilers were installed in Gyeonggi-do and
Gyeongsangnam-do. It is believed that this is because
there are many companies in industrial regions where
there is high demand on industrial boilers. It also shows
Analysis of Emission Characteristics and Emission Factors of Carbon Monoxide and Nitrogen Oxide Emitted from Wood Pellet Combustion in Industrial Wood Pellet Boilers Supplied According to the Subsidy Program of Korea Forest Service
- 599 -
0
2
4
6
8
10
12
14
16
Gyeonggi Gyeongbuk Gyeongnam Chungbuk jeju Gangwon Jeonnam Gwangju Sejong Jeonbuk Chungnam Daegu
Inst
alla
tio
n nu
mbe
r o
f ind
ustr
ial w
oo
d pe
llet
boile
r
Province
Fig. 1. Number of industrial wood pellet boiler with subsidy with respect to installed province.
average : 3.0MW (2,600,000kcal/h)
0
1
2
3
4
5
6
7
8
9
10
2011 2012 2013 2014 2015 2016
Boile
r cap
acity
(MW
)
Year
Fig. 2. Industrial wood pellet boiler thermal capacity with subsidy by ForestService in Korea.
that Gwangju and Daegu among the metropolitan cities
have many such boilers.
Fig. 2 shows the capacity of the installed industrial
wood pellet boilers. The average capacity of these
boilers is 3.0 MW (2,600,000 kcal/h), which is about
4.2 ton/h (wood pellet consumption is about 740 kg/h
based on the low-level heat generation of wood pellets
at 4,100 kcal/h and the boiler efficiency at 85%) if
converted into the amount of steam generated. With
low capacity boilers, 1.5 to 2 MW wood pellet boilers
have been widely installed, as well as 5.0 MW boilers
have also been installed in many places. Converted into
steam generation, these capacities are about 2.5 ton/h
as well as 7.0 ton/h.
Sea Byul Kangโ Kyu Sung Choiโ Hyun Hee Leeโ Gyu-Seong Han
- 600 -
average : 56 ppm (@O2 12%)
0
50
100
150
200
250
2011 2012 2013 2014 2015 2016
CO c
once
ntra
tion
(ppm
)
Year
Fig. 3. CO emission of industrial wood pellet boiler according to the installation year.
2.2. Measurement method
The study conducted the performance test of the KFS
subsidized industrial wood pellet boiler by installing
it based on the โConstruction Inspection Standards for
Industrial Wood Pellet Boilersโ (KFS, 2013). When
the boiler operation stabilized, the O2, CO, and NOx
concentration were measured for one hour using a
portable multifunctional combustible gas meter (Testo
350), the results of which were averaged. Testo 350
can analyze various combustible gases (O2, CO, NOx
and SO2, etc.) and allows for large amount of data
records linked to a PC. The null adjustment was
performed using the standard gas before the test to
acquire the data reliability. The measurement scope of
O2 is 0-25% at which the accuracy level is ยฑ0.01%,
and that of CO is 0-10000 ppm, and the accuracy level
between 200-2000 ppm is ยฑ5%. The measurement scope
of NO is 0-4000 ppm, and the accuracy level between
100-1999 ppm is ยฑ5%. Finally, the measurement scope
of NO2 is 0-500 ppm, and the accuracy level between
100-500 ppm is ยฑ5%. The measured carbon monoxide
and nitrogen oxide were converted into the value of
the state of 12% of emission gas O2.
3. RESULTS and DISCUSSION
3.1. Carbon monoxide (CO)
Fig. 3 shows the carbon monoxide (CO) emissions
from the installed industrial boilers by the year of
installation. As has been shown, the average CO
emission concentration from the installed industrial
wood pellet boiler is 56 ppm when the oxygen
concentration in the emissions was 12%. The maximum
CO emission among the measured boilers was 220 ppm.
High concentration of CO would lead to CO poisoning,
causing nausea and in serious cases, death. There may
be incomplete combustion or air is lacking in boilers.
As shown in the figure, the CO emissions change by
installation year. To clearly understand such a tendency,
Fig. 4 shows the average CO emissions by taking five
values based on the time of the CO emissions. Since
2012, the average CO emissions have decreased until
2015. While in 2012, it was within 50 - 100 ppm,
in 2015, it decreased to 20 - 30 ppm. This is considerably
below the allowable criteria of the air pollutants
stipulated by the Enforcement Regulations of the Clean
Air Conservation Act (at or below 200 ppm for facilities
Analysis of Emission Characteristics and Emission Factors of Carbon Monoxide and Nitrogen Oxide Emitted from Wood Pellet Combustion in Industrial Wood Pellet Boilers Supplied According to the Subsidy Program of Korea Forest Service
- 601 -
y = -13.3 x + 26,823.5
0
50
100
150
200
250
2011 2012 2013 2014 2015 2016
CO c
once
ntra
tion
(ppm
, 5 p
oint
s ave
rage
)
Year
Fig. 4. Average CO emission of industrial wood pellet boiler accordingto the installation year.
average : 0.73 g/kg
0.0
0.5
1.0
1.5
2.0
2.5
3.0
2011 2012 2013 2014 2015 2016
CO e
mis
sion
fact
or (g
/kg)
Year
Fig. 5. CO emission factor of industrial wood pellet boiler according to the installation year.
using wood pellets). Generally, CO emissions decrease
by reducing incomplete combustions through the
optimization of the combustion system. It is believed
that such CO emission reduction was due to the
improvement of boiler efficiency and CO emissions
reduction by boiler manufacturers since 2011 when
industrial wood pellet boilers were distributed by KFS.
The study calculated the emission factor using the
CO emission from the boiler. The emission factor for
CO or NOx (g/kg_fuel) is defined as the weight of
the pollutant (g) emitted by the combustion of 1kg
of fuel, which can be determined by the following
equation.
Emission factor (g/kg)
= pollutant concentration (g/m3) ร flue gas volume
flow rate (m3/h) / fuel consumption (kg/h)
Sea Byul Kangโ Kyu Sung Choiโ Hyun Hee Leeโ Gyu-Seong Han
- 602 -
0
100
200
300
400
500
600
700
800
0 1 2 3 4 5
NO
x E
mis
sion
(ppm
@ 1
3% O
2)
Nitrogen content in the pellets (wt %)
โ : This study (min and max value)โ : Sepnt coffee ground โฒ : Pine โ : Peach stones โ : Industrial wood wasteโก : Wood B โ : Wood C โณ : Citrus pectin waste
Fig. 6. Influence of the nitrogen content of the pellets on the NOx emissions.
In the equation above, the pollutant concentration
is calculated by the emission concentration of each
pollutant (ppm) measured at the time of the actual
combustion of wood pellets, and the fuel consumption
is the amount of fuel injected during the actual boiler
operation. Finally, the gas emissions are based on the
oxygen concentration in the emissions gas measured
during the actual combustion of the boiler. Fig. 5 shows
the CO emission factor for the industrial wood pellet
boiler. The average CO emission factor of the distributed
industrial wood pellet boiler is 0.73 g/kg. The average
CO emissions of the industrial wood pellet boiler
installed in 2015 was 25.7 ppm, which is considerably
lower than 62.5 ppm, that of the wood pellet boiler
installed in 2012. Such a trend can be verified in Fig.
5 which showed the CO emission factors by the time
of installation where the CO emission factors decrease
by the time of installation. The average CO emission
factor of five industrial wood pellet boilers installed
latest was very low at 0.36 g/kg.
3.2. Nitrogen oxide (NOx)
Fig. 6 shows the NOx emissions based on the nitrogen
content contained in various types of wood chip fuel
including the wood pellets used in this study (referring
to the data by Kang et al., 2017). The figure shows
the maximum and minimum values of NOx emissions
measured when the nitrogen content of wood pellets
used in the industrial boiler installed by the KSF's
subsidy project was 0.3%. It shows the tendency that
the NOx value increases linearly based on the nitrogen
content included in the fuel. Even the same wood fuels
will have different NOx emissions based on the
contained nitrogen content. However, wood pellets
usually have nitrogen content below 0.5%, and thus,
the NOx content will become 100 ppm or below. The
study results on the NOx emissions characteristics based
on the types of coal (bituminous coal and subbituminous
coal) from a 500 MW coal-fired boiler showed that
the nitrogen content in coal is 0.76 - 1.7 %. As such,
it was also confirmed that the emissions from a coal-fired
plant were mainly thermal NOx emissions at high
temperature, but when coal with high nitrogen content
was used, the NOx generation increased.
Shown in Fig. 7 and Fig. 8 are the average of the
five values of NOx emissions from industrial wood pellet
boilers. The average NOx emissions measured from the
boilers is 76 ppm at 12% of the oxygen concentration.
The NOx emissions were between 44 - 128 ppm, which
Analysis of Emission Characteristics and Emission Factors of Carbon Monoxide and Nitrogen Oxide Emitted from Wood Pellet Combustion in Industrial Wood Pellet Boilers Supplied According to the Subsidy Program of Korea Forest Service
- 603 -
average : 76 ppm (@O2 12%)
0
20
40
60
80
100
120
140
160
2011 2012 2013 2014 2015 2016
NO
x co
ncen
trat
ion
(ppm
)
Year
Fig. 7. NOx concentration of industrial wood pellet boiler according to theinstallation year.
average : 1.63 g/kg
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
2011 2012 2013 2014 2015 2016
NO
x em
issi
on fa
ctor
(g/k
g)
Year
Fig. 8. NOx emission factor of industrial wood pellet boiler according to the installation year.
is considerably lower than the allowable standards of
the air pollutants stipulated in the Enforcement
Regulations of the Clean Air Conservation Act (at or
below 150 ppm of NOx for facilities that use wood
pellets). At this point, the emission factor of NOx is
1.63 g/kg. The two figures do not show the tendency
of the decrease in the emissions by the time of
installation, as opposed to the CO distribution. This
is because the CO emissions can be reduced by
providing the optimal combustion conditions by
improving the burner. However, for NOx, wood pellets
contain nitrogen by about 0.1 to 0.5%, as opposed to
LNG which does not contain nitrogen (N). Such nitrogen
is oxidized via the combustion at high temperature and
turned into NO and NO2 among others. Such generated
NOx is called fuel NOx, which is fundamentally difficult
Sea Byul Kangโ Kyu Sung Choiโ Hyun Hee Leeโ Gyu-Seong Han
- 604 -
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50
NO
x [p
pm]
index
Industry averge : 35 ppm
Fig. 9. NOx concentration of low NOx burners in Korea (Ministry of
Environment of Korea).
Fuel type NOx (ppm) O2 (%) NOx emission factor (g/kg) Based on LNG
LNG 35 3 0.96 1.00
Wood pellet 67 13 1.82 1.90
Coal or bunker-C with de-NOx facility
70 3 1.98 2.06
Note: NOx emission of LNG is average of those of low NOx burners and NOx emission of Coal or bunker-C with de-NOx facility is referred to the exhaust gas regulation standard of Clean Air Conservation Act.
Table 1. NOx emission factors of wood pellet, LNG, coal and bunker-C fuel
to decrease, and due to such characteristics, NOx
emissions tend not to decrease.
Shown in Fig. 9 are the NOx emissions on domestic
low- NOx certified products. As shown in the figure,
the average NOx is 35 ppm. The low-NOx burner criterial
for industrial boilers is below 40 ppm at 4% of oxygen
concentration. Generally, the LNG burner that satisfies
the low-NOx burner criteria is around 35 ppm at 3%
of oxygen concentration.
Shown in Table 1 are the average NOx emission
factors under the normal combustion of boilers with
LNG, wood pellets, and coal (or bunker-C). In case
of wood pellets, the average NOx value emitted from
the industrial wood pellet boiler, measured previously
used. Coal-fried or bunker-C-fired boilers run with NOx
at or below 70 ppm (facilities installed before December
2014, Clean Air Conservation Act). Assuming that such
a condition was the representative situation for each
fuel, the NOx emission factors could be calculated,
which are shown in Table 1. When the NOx emission
index of LNG is set to 1, that of wood pellets is 1.90,
and coal or bunker-C is 2.01. For coal or bunker-C,
it was assumed that there would be post-processing
facilities to reduce NOx such as SCR (selective catalytic
reduction) at the end of the boiler. Otherwise, the
emission index would have been higher.
Analysis of Emission Characteristics and Emission Factors of Carbon Monoxide and Nitrogen Oxide Emitted from Wood Pellet Combustion in Industrial Wood Pellet Boilers Supplied According to the Subsidy Program of Korea Forest Service
- 605 -
4. CONCLUSION
The CO and NOx measurement values of 63 KFS-
subsidized industrial wood pellet boilers between 2011
and 2015 all satisfied the allowable criteria by the
Ministry of Environment. Based on the CO and NOx
emissions values, the emission factors of industrial wood
pellet boilers were calculated and compared with NOx
emitted from the low-NOx certified burner. The analyzed
results are summarized as follows.
1. The average capacity of the KFS-subsidized
industrial wood pellet boilers was 3.0 MW, and
the wood pellet consumption was about 740 kg/h.
2. The average CO emission from the industrial wood
pellet boilers distributed for the five years was
56 ppm (@O2 12%), which can be converted into
the emission factor at 0.73 g/kg.
3. The average CO emission from the industrial wood
pellet boilers installed in 2012 during the early
period of the subsidy program was 70.3 ppm (@O2
12%), but that from the boilers installed at the
ending year of the subsidy program was 28.9 ppm.
Such a result is determined to be due to the
optimization of the burner and boiler system
through technical development.
4. The average NOx emission from the industrial wood
pellet boilers installed for the five years was 76
ppm (@O2 12%), which can be converted into
the emission factor at 1/63 g/kg.
5. NOx did not show the tendency of reduction by
time. It is determined that this is because fuel
NOx generation did not decrease along with the
nitrogen content included in the fuel.
6. The NOx emission factor from the industrial wood
pellet boilers was compared to that from low-NOx
certified LNG burner and coal (bunker- C)-fired
burners. The former was about 1.90 times higher
than that of the latter and was about 0.92 times
lower than the coal- or bunker-C-fired boilers with
denitrification facilities.
REFERENCES
Kang, K., Song, J., Yoon, M., Lee, B., Kim, S., Chang,
Y., Jeon, C. 2009. A Numerical Study on the Effects
of SOFA on NOx Emission Reduction in 500MW
Class Sub-bituminous Coal-Fired Boiler. of the
Korean Society of Mechanical Engineers โ B
33(11): 858-868.
Kang, S.B., Oh, H.Y., Kim, J.J., Choi, K.S. 2017.
Characteristics of spent coffee ground as a fuel and
combustion test in a small boiler (6.5kW).
Renewable Energy 113: 1208-1214.
Kim, K.H. 2017. Wood Pellet โ Renewable energy?
Ultra fine dust 20 times, http://news.kbs.co.kr/news/
view.do?ncd=3559653, Seoul, Korea.
Kim, S.H., Yang, I., Han, G.-S. 2015. Effect of sawdust
moisture content and particle size on the fuel
characteristics of wood pellet fabricated with
Quercus mongolica, Pinus densiflora and Larix
kaempferi Sawdust. Journal of the Korean Wood
Science and Technology 43(6): 757-767.
Korea Forest Service. 2013. Construction Inspection
Standards for Industrial Wood Pellet Boilers.
Daejeon, Korea.
Korea Forest Service. 2015. Industrial Wood Pellet
Boiler Subsidy Standards, Daejeon, Korea.
Korea Standards and Certifications, 2014, Land Boilers
- Heat Balancing (KS B 6205).
Ministry of Environment. 2017. Clean Air Conservation
Act, ME, Sejong, Korea.
Yang, I., Chae, H.-G., Han, G.-S. 2017. Effect of bark
and drying waste liquor of Larix kaempferi used
as an additive on the fuel characteristics of wood
pellet fabricated with Rigida pine and Quercus
mongolica sawdust, Journal of the Korean Wood
Science and Technology 45(3): 258-267.
Sea Byul Kangโ Kyu Sung Choiโ Hyun Hee Leeโ Gyu-Seong Han
- 606 -
APPENDIX(Korean Version)
์ฐ๋ฆผ์ฒญ ์ง์์ฌ์ ์ ๋ฐ๋ผ ๋ณด๊ธ๋ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์์ ๋ชฉ์ฌํ ๋ฆฟ ์ฐ์ ์
๋ฐฐ์ถ๋๋ ์ผ์ฐํํ์์ ์ง์์ฐํ๋ฌผ์ ๋ฐฐ์ถ ํน์ฑ ๋ฐ ๋ฐฐ์ถ๊ณ์ ๋ถ์
์์ฝ : ์ฐ๋ฆผ์ฒญ์ ๋ณด์กฐ๊ธ ์ง์์ฌ์ ์ ํตํด 2011๋ ๋ถํฐ 2015๋ ๊น์ง 76๋์ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ๋ฅผ ๋ณด๊ธํ์๋ค. ๋ณด์ผ๋ฌ์
์ฐ์ ์ ๋ฐ์ํ๋ ์ผ์ฐํํ์(CO) ๋ฐ ์ง์์ฐํ๋ฌผ(NOx)๋ ๊ฐ๊ฐ ๊ธ์ฑ ์ค๋ ์ ์ฌ๋ง์๊น์ง ์ด๋ฅด๊ฒ ํ๋ ๋ฌผ์ง์ด๊ธฐ ๋๋ฌธ์
๋ฐฐ์ถ๋์ ์ค์ด๋ ๊ฒ์ด ๋งค์ฐ ์ค์ํ๋ค. ๋ฐ๋ผ์ ์ด๋ค ๋ณด์ผ๋ฌ ์ค ์ดํ๊ธฐ์ ์ด๊ธฐ์ ๋ณด๊ธ๋ ์ผ๋ถ ๋ณด์ผ๋ฌ๋ฅผ ์ ์ธํ 63๋์ ๋ณด์ผ๋ฌ์
์ ๋ฐฐ์ถ๋ CO ๋ฐ NOx ๊ณ์ธก๊ฐ์ ๋ถ์ํ์๋ค. ๋ํ ์ธก์ ๋ ๋ฐฐ์ถ๊ฐ์ค ๋๋(๋ฐฐ๊ธฐ๊ฐ์ค O2 ๋๋ 12% ๊ธฐ์ค)๋ก๋ถํฐ ๋ฐฐ์ถ๊ณ์๋ฅผ
์ฐ์ถํ์๋ค. ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์์ ๋ฐฐ์ถ๋ CO์ ํ๊ท ๊ฐ์ 49 ppm์ด์์ผ๋ฉฐ, ํด๋ฅผ ๊ฑฐ๋ญํจ์ ๋ฐ๋ผ CO์ ๋๋๊ฐ ์ค์ด๋ค
๊ณ ์์์ด ํ์ธ๋์๋ค. ์ด๋ CO์ ๋ฐฐ์ถ๊ณ์๋ 0.73 g/kg์๋ค. ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์์ ๋ฐฐ์ถ๋ NOx์ ํ๊ท ๊ฐ์ 67 ppm์
์ผ๋ฉฐ, NOx์ ๋ฐฐ์ถ๊ณ์๋ 1.63 g/kg์ด์๋ค. CO์๋ ๋ฌ๋ฆฌ ์ค์น๋ ๋์ ๋ฐ๋ผ ๊ฐ์ํ๋ ๊ฒฝํฅ์ ๋ํ๋์ง ์์๋ค. CO ๋ฐ NOx
๊ณ์ธก๊ฐ์ ๋ชจ๋ ํ๊ฒฝ๋ถ์ ํ์ฉ๊ธฐ์ค์ ๋ง์กฑํ์๋ค. ์ด๋ฌํ NOx ๋ฐฐ์ถ๊ณ์๋ฅผ ์ NOx ์ธ์ฆ๋ ์ฐ์๊ธฐ์์ ์์ฑ๋๋ NOx ๋ฐฐ์ถ๊ณ์
์ ๋น๊ตํ์๋ค. ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ NOx ๋ฐฐ์ถ๊ณ์๋ ์ NOx ์ธ์ฆ๋ LNG ์ฐ์๊ธฐ์ NOx ๋ฐฐ์ถ๊ณ์์ ๋นํด ์ฝ 1.9๋ฐฐ,
์ํ ์ฐ์์ ๋นํด ์ฝ 0.92๋ฐฐ์๋ค.
1. ์ ๋ก
์ฐ๋ฆผ์ฒญ์ 2011๋ ๋ถํฐ 2015๋ ๊น์ง ์ ์ฌ์์๋์ง์ธ ๋ชฉ์ฌํ ๋ฆฟ ์๋น๋์ ํ๋ํ์ฌ ์ ํ์ ๋ น์ ์ฑ์ฅ์ ๊ธฐ์ฌํ๊ณ ์ ์ฐ์ ์ฉ
๋ชฉ์ฌํ ๋ฆฟ ๋ณด์ผ๋ฌ ๋ณด๊ธ ๋ฐ ์ค์น๋ฅผ ์ง์ํด์๋ค. ์ด๋ฅผ ํตํด ๊ตญ๋ด์ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ ๊ธฐ์ ์์ค์ ํ ๋จ๊ณ ๋์ด๋๋ฐ ๊ธฐ์ฌํ์ผ
๋ฉฐ, ๋ ๊ธฐ๊ฐ ์ค 76๋์ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ ์ฐ์๊ธฐ๊ฐ ์ค์น๋์๋ค. ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ ํจ์จ์ ์ธ ๋ณด๊ธ ๊ด๋ฆฌ๋ฅผ ์ํ์ฌ, ์ฐ๋ฆผ์ฒญ์
์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ ์ง์ ๊ธฐ์ค(KFS, 2015), ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ ์ค๊ณต๊ฒ์ฌ๋ฅผ ์ํ ์ํ๊ธฐ์ค(KFS, 2013)์ ์ฑ ์ ํ์๋ค.
์ด์ ๋ฐ๋ฅธ ์ง์ ๋์์ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ ์ฐ์๊ธฐ๋ 0.5 โ 7.0 ton/h๊ธ ์คํ ๋ณด์ผ๋ฌ ๋๋ 230 kW ์ด์ ์จ์ ๋ณด์ผ๋ฌ ๋ฐ ์ดํ๊ธฐ์ด๋ค.
์ด์ค์์ 63๋๋ ์คํ ๋ณด์ผ๋ฌ์์ผ๋ฉฐ, 7๋๋ ์จ์๋ณด์ผ๋ฌ, 6๋๋ ์ดํ๊ธฐ์๋ค. ๋ชฉ์ฌ ํ ๋ฆฟ ๋ณด์ผ๋ฌ์ ๋ํ ๋ณด์กฐ๊ธ์ ์ง์๋ฐ๊ธฐ ์ํด์
๋ ๋ค์๊ณผ ๊ฐ์ ์กฐ๊ฑด์ ๋ง์กฑํ์ฌ์ผ ํ๋ค. 1) ๋ณด์ผ๋ฌ ์ดํจ์จ์ ์ ์๋ฐ์ด๋ ๊ธฐ์ค 85% ์ด์, 2) ์ญํ๋ฐฉ์ง์ฅ์น ๋ฑ ์์ ์ฅ์น์
๋ํ ๊ตฌ๋น 3) ๋๊ธฐ ์ค์ผ๋ฌผ์ง ์ค ํ๋์ธ ์ผ์ฐํํ์(CO) ๋ฐฐ์ถ๋์ด 200 ppm ๋ฏธ๋ง ๋ฑ์ด ์๋ค.
๋ชฉ์ฌํ ๋ฆฟ์ ์ฐ์์ ๋ฐ๋ฅธ ๋๊ธฐ์ค์ผ๋ฌผ์ง๊ณผ ๊ด๋ จ๋ ๊ตญ๋ด ๊ท์ ์ผ๋ก๋ ๋๊ธฐํ๊ฒฝ๋ณด์ ๋ฒ์ด ์๋ค(ME, 2017). ์ผ์ ๊ท๋ชจ ์ด์์
ํฐ ์ฐ์์ค๋น์์ ๋ฐ์๋๋ ๋ฐฐ์ถ๋ฌผ์ ๋ํ์ฌ ํ์ฌ ๋๊ธฐํ๊ฒฝ๋ณด์ ๋ฒ์ ๋ช ์๋์ด ์๋ ์ ์ฉ ๋์์ 1) ๋ชฉ์ฌํ ๋ฆฟ ์ ์กฐ์์ค(์ ๋ณ์์ค,
๊ฑด์กฐใ๊ฐ์ด์์ค, ํ์ใ๋ถ์์์ค, ์์ถใ์ฑํ์์ค) ์ค ์ฐ๋ฃ์ฌ์ฉ๋์ด ์๊ฐ๋น 30 kg ์ด์์ด๊ฑฐ๋, ์ฉ์ ์ด 3 ใฅ ์ด์์ด๊ฑฐ๋, ๋๋ ฅ์ด
2.25kW(ํ์ใ๋ถ์์์ค์ 15 kW) ์ด์์ธ ์์ค๊ณผ, 2) ๋ชฉ์ฌํ ๋ฆฟ ์ฌ์ฉ์์ค ์ค ์ฐ๋ฃ์ ํ ์ฌ์ฉ๋์ด ์๊ฐ๋น 200 kg ์ด์์ธ ์์ค(๋ค๋ฅธ
์ฐ๋ฃ์ ๋ชฉ์ฌํ ๋ฆฟ์ ํจ๊ป ์ฐ์ํ๋ ์์ค์ ์ ์ธ)์ด๋ค(ME, 2017).
2015๋ ๋ถํฐ ์ ์ฉ๋ ๋๊ธฐ์ค์ผ๋ฌผ์ง์ ํ์ฉ๊ธฐ์ค์ ์ดํด๋ณด๋ฉด, ๋ชฉ์ฌํ ๋ฆฟ ์ฌ์ฉ์์ค์์์ CO ๋๋๋ 200 ppm ์ดํ(์ค์ธก์ฐ์๋๋
12%) ์ด์ด์ผ ํ๋ค. ์ง์์ฐํ๋ฌผ(NOx, NO2๋ก์)์ ๋ชฉ์ฌํ ๋ฆฟ ์ ์กฐ์์ค ์ค ๊ฑด์กฐยท๊ฐ์ด์์ค์ ๊ฒฝ์ฐ 100 ppm ์ดํ, ๋ชฉ์ฌํ ๋ฆฟ ์ฌ์ฉ์
์ค์์ 150 ppm ์ดํ(์ค์ธก์ฐ์๋๋ 12%) ์ด์ด์ผ ํ๋ค. ๋ฏธ์ธ๋จผ์ง๋ ๋ชฉ์ฌํ ๋ฆฟ ์ ์กฐ์์ค ์ค ๊ฑด์กฐยท๊ฐ์ด์์ค์ ๊ฒฝ์ฐ 50 ใ/Sใฅ ์ดํ, ๋ชฉ์ฌํ ๋ฆฟ ์ฌ์ฉ์์ค์์ 50 ใ/Sใฅ ์ดํ(์ค์ธก์ฐ์๋๋ 12%) ์ด์ด์ผ ํ๋ค(ME, 2017). ๋ชฉ์ฌํ ๋ฆฟ์ ๊ฒฝ์ฐ ์ฐ๋ฃ ํน์ฑ ์
ํฉ์ฐํ๋ฌผ ๋ฐ ์ค๊ธ์ ๋ฑ์ ํจ์ ์จ์ด ๋งค์ฐ ๋ฎ๊ธฐ ๋๋ฌธ์ ์ด์ ๋ํ ํ์ฉ๊ธฐ์ค์ด ์ค์ ๋์ด ์์ง ์๋ค.
2017๋ ๊ตญ์ ๊ฐ์ฌ์ฅ์์๋ ๋ชฉ์ฌํ ๋ฆฟ์ ์ฐ์ ์คํ ๊ฒฐ๊ณผ ์ด๋ฏธ์ธ๋จผ์ง๋ฅผ ์ ๋ฐํ๋ ์ง์์ฐํ๋ฌผ์ด ์ฐํ์ 20๋ฐฐ๋ ๋ฐ์ํ๋ค๋
๋ด์ฉ์ ์ฃผ์ฅ์ด ์ ๊ธฐ๋์๊ณ , ๊ฒ์ฆ์ด ๋์ง ์์ ์ฑ ์ด ๋ด์ฉ์ด ์ธ์ฉ๋์ด ๋ณด๋๋จ์ผ๋ก์จ ์ฌํ์ ์ธ ๋ ผ๋์ด ์ผ์๋ค(kim, 2017). ์ด๋
๊ตญ๋ด์์ ๋ชฉ์ฌํ ๋ฆฟ ์ ์กฐ ํน์ฑ์ ๊ดํ ์ฐ๊ตฌ๋ ์ด๋ฃจ์ด์ ธ ์์ผ๋(Kim et al., 2015, Yang et. al., 2017), ๋ชฉ์ฌํ ๋ฆฟ ์ฐ์ ์ ๋ฐ์ํ๋
๋๊ธฐ์ค์ผ๋ฌผ์ง์ ๊ดํ ์ฐ๊ตฌ๊ฐ ๊ทธ๋์ ๊ฑฐ์ ์์๊ธฐ ๋๋ฌธ์ด๋ค.
Analysis of Emission Characteristics and Emission Factors of Carbon Monoxide and Nitrogen Oxide Emitted from Wood Pellet Combustion in Industrial Wood Pellet Boilers Supplied According to the Subsidy Program of Korea Forest Service
- 607 -
๋ณธ ์ฐ๊ตฌ์์๋ ์ฐ๋ฆผ์ฒญ์์ ์ง์ํ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ ๋ํ์ฌ ์ฐ์ ์ ๋ฐฐ์ถ๋๋ ๋๊ธฐ์ค์ผ๋ฌผ์ง์ ์ธก์ ํ๊ณ ์ ํ์๋ค. ์ด๋ฅผ
ํตํด ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ๊ฐ ํ๊ฒฝ๋ถ์ ๋๊ธฐ์ค์ผ๋ฌผ์ง ํ์ฉ๊ธฐ์ค์ ๋ถํฉํ๋์ง๋ฅผ ํ์ธํ์๋ค. ๋ํ ๋๊ธฐ์ค์ผ๋ฌผ์ง์ ๋ฐฐ์ถ๊ฐ์
๊ธฐ๋ฐ์ผ๋ก ํ์ฌ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ ๋ฐฐ์ถ๊ณ์๋ฅผ ์ฐ์ถํ์์ผ๋ฉฐ, ์ด๋ฅผ ์ NOx ์ธ์ฆ๋ฒ๋์์ ๋ฐฐ์ถ๋๋ NOx์ ๋น๊ตํ์๋ค.
2. ์ฌ๋ฃ ๋ฐ ๋ฐฉ๋ฒ
2.1 ์กฐ์ฌ ๋์
์ฐ๋ฆผ์ฒญ์์ ์ง์ํ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ(์คํ๋ณด์ผ๋ฌ, ์จ์๋ณด์ผ๋ฌ, ์ดํ๊ธฐ)๋ 2011๋ ์ 9๋, 2012๋ ์ 27๋, 2013๋ ์
21๋, 2014๋ ์ 10๋, 2015๋ ์ 9๋์๋ค. ์ด๋ค ๋ณด์ผ๋ฌ ์ค ์ดํ๊ธฐ์ ์ด๊ธฐ์ ๋ณด๊ธ๋ ์ผ๋ถ ๋ณด์ผ๋ฌ๋ฅผ ์ ์ธํ 63๋์ ๋ณด์ผ๋ฌ๋ฅผ
์ธก์ ๋์์ผ๋ก ํ์๋ค. Fig. 1์ ์ด๋ค ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ ๋ณด์ผ๋ฌ์ ์ง์ญ๋ณ ์ค์นํํฉ์ ๋ณด์ฌ์ค๋ค. ์ง์๋ฐ์ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ
์ 50% ์ด์์ด ๊ฒฝ๊ธฐ๋์ ๊ฒฝ์๋จ๋ถ๋์ ์ค์น๋์๋ค. ์ด๋ ์ฐ์ ์ฉ ๋ณด์ผ๋ฌ์ ์์๊ฐ ๋ง์ ๊ณต์ฅ ๋ฑ ์ฐ์ ๋จ์ง๊ฐ ๋ง์ด ์๋ ์ง์ญ์
์ง์๋ฐ๊ณ ์ ํ๋ ์ ์ฒด๊ฐ ๋ง๊ธฐ ๋๋ฌธ์ผ๋ก ํ๋จ๋๋ค. ๊ด์ญ์ ์ค์์๋ ๊ด์ฃผ์ ๋๊ตฌ์ ์ค์น๊ฐ ๋ง์ด ๋ ๊ฒ์ ์ ์ ์๋ค.
์ค์น๋ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ ์ฉ๋์ Fig. 2์ ๋ํ๋ด์๋ค. ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ ํ๊ท ์ฉ๋์ 3.0 MW(2,600,000
kcal/h)์ด๋ฉฐ ์ด๋ ์ฆ๊ธฐ ๋ฐ์๋์ผ๋ก ํ์ฐํ๋ฉด ์ฝ 4.2 ton/h(๋ชฉ์ฌ ํ ๋ฆฟ ์๋น๋์ ์ฝ 740 kg/h์. ๋ชฉ์ฌํ ๋ฆฟ ์ ์๋ฐ์ด๋ 4,100
kcal/h ๋ฐ ๋ณด์ผ๋ฌ ํจ์จ 85% ๊ฐ์ )์ด๋ค. ์ฉ๋์ด ์์ ๊ฒฝ์ฐ๋ ๋๋ถ๋ถ 1.5 โ 2 MW ์ฉ๋์ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ๊ฐ ๋ง์ด ์ค์น๋์์ผ๋ฉฐ,
5.0 MW๊ธ๋ ๋ง์ด ์ค์น๋ ๊ฒ์ ์ ์ ์๋ค. ์ฆ๊ธฐ ์์ฐ๋์ผ๋ก ํ์ฐํ๋ฉด ์ฝ 2.5 ton/h๊ธ์ด ๋ง์ด ์ค์น๋์๊ณ ๋ํ์ผ๋ก๋ 7.0
ton/h๊ธ์ด ๋ง์ด ์ค์น๋ ๊ฒ์ ์ ์ ์๋ค.
2.2 ์ธก์ ๋ฐฉ๋ฒ
์ฐ๋ฆผ์ฒญ์์ ์ง์ํ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ ๋ํด โ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ ๋ณด์ผ๋ฌ ์ค๊ณต๊ฒ์ฌ๋ฅผ ์ํ ์ํ๊ธฐ์ค(KFS, 2013)โ์ ์๊ฑฐ
ํ์ฌ ์ค์น ์๋ฃ ํ ๋ณด์ผ๋ฌ ์ฑ๋ฅ ์ํ์ ์ํํ์๋ค. ๋ณด์ผ๋ฌ์ ์ด์ ์ํ๊ฐ ์์ ํ ๋์์ ๋ ํด๋ํ ๋ค๊ธฐ๋ฅ ์ฐ์๊ฐ์ค์ธก์ ๊ธฐ(Testo
350)๋ฅผ ์ฌ์ฉํ์ฌ ์ฐ์(O2), CO, NOx์ ๋๋๋ฅผ 1์๊ฐ ์ด์ ์ธก์ ํ์ฌ ์ธก์ ๊ฐ์ ํ๊ท ํ์๋ค. Testo 350์ ๋ค์์ ์ฐ์๊ฐ์ค(O2,
CO, NOx, SO2 ๋ฑ)๋ฅผ ๋ถ์ํ ์ ์๋ ๊ธฐ๊ธฐ๋ก์, PC์ฐ๊ฒฐ์ ํตํ ๋๋์ ๋ฐ์ดํฐ ๊ธฐ๋ก์ด ๊ฐ๋ฅํ๋ค. ์ธก์ ์ ํ์ค๊ฐ์ค๋ฅผ ํตํด
์์ ์กฐ์ ์ ์งํํ์ฌ ๋ฐ์ดํฐ์ ์ ๋ขฐ์ฑ์ ํ๋ณดํ์๋ค. O2์ ์ธก์ ๋ฒ์๋ 0-25%์ด๋ฉฐ, 0-25% ๋ฒ์์์์ ์ ํ๋๋ ยฑ0.01%์ด๋ค.
CO์ ์ธก์ ๋ฒ์๋ 0-10000 ppm ์ด๋ฉฐ, 200-2000 ppm ๋ฒ์์์์ ์ ํ๋๋ ยฑ5%์ด๋ค. NO์ ์ธก์ ๋ฒ์๋ 0-4000 ppm ์ด๋ฉฐ,
100-1999 ppm ๋ฒ์์์์ ์ ํ๋๋ ยฑ5%์ด๋ค. ๋ํ NO2์ ์ธก์ ๋ฒ์๋ 0-500 ppm ์ด๋ฉฐ, 100-500 ppm ๋ฒ์์์์ ์ ํ๋๋
ยฑ5%์ด๋ค. ๊ณ์ธก๋ ์ผ์ฐํํ์์ ์ง์์ฐํ๋ฌผ์ ๋ฐฐ๊ธฐ๊ฐ์ค O2 12%๋ก ํ์ฐํ์ฌ ๋ํ๋ด์๋ค.
3. ๊ฒฐ๊ณผ ๋ฐ ๊ณ ์ฐฐ
3.1 ์ผ์ฐํํ์(CO)
์ค์น๋ ์ฐ์ ์ฉ ๋ณด์ผ๋ฌ์ ๋ํด ์ผ์ฐํํ์ ๋ฐฐ์ถ๋์ ์ธก์ ๊ฒฐ๊ณผ๋ฅผ ์ค์น๋ ์ฐ๋์์ผ๋ก Fig. 3์ ๋ํ๋๋ค. ๊ทธ๋ฆผ์์ ํ์ธํ
์ ์๋ฏ์ด ์ค์น๋ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ CO ํ๊ท ๋ฐฐ์ถ ๋๋๋ ๋ฐฐ๊ธฐ๊ฐ์ค ์ค ์ฐ์์ ๋๋๋ฅผ 12%๋ก ํ์ฐํ์์ ๋ 56 ppm์ด๋ค.
์ธก์ ๋ ๋ณด์ผ๋ฌ๋ค ์ค ์ต๋ CO ๋ฐฐ์ถ๋์ 220 ppm์ด๋ค. CO์ ๊ฒฝ์ฐ ๋๋๊ฐ ๋๊ฒ ๋๋ฉด CO ์ค๋ ์ ์ ๋ฐ์์ผ ์ด์ง๋ผ์ฆ ๋ฐ ์ฌ๊ฐํ
๊ฒฝ์ฐ์๋ ์ฌ๋ง๊น์ง ์ ๋ฐํ๋ ๋ฌผ์ง๋ก ์๋ ค์ ธ ์๋ค. ๋ณด์ผ๋ฌ์์ CO๋ ์ฐ์๊ฐ ์ํ์ด ์ผ์ด๋์ง ์๋ ๊ฒฝ์ฐ๋ ์ฐ์์ฉ ๊ณต๊ธฐ๊ฐ ๋ถ์กฑํ
๊ฒฝ์ฐ ๋ค๋ ๋ฐ์ํ๋ค. ๊ทธ๋ฆผ์์ ํ์ธํ ์ ์๋ฏ์ด CO ๋ฐฐ์ถ๋์ ์ค์น๋ ๋์ ๋ฐ๋ผ ๋ณํํ๊ณ ์๋ ๊ฒ์ ์ ์ ์๋ค. ์ด๋ฌํ ๊ฒฝํฅ์
๋ณด๋ค ๋ช ํํ ๋ณด๊ธฐ์ํด ์ผ์ฐํํ์ ๋ฐฐ์ถ ์๊ฐ์ ๋ฐ๋ผ 5๊ฐ์ฉ ํ๊ท ์ ๊ตฌํ์ฌ CO ํ๊ท ๋ฐฐ์ถ๋์ ๊ตฌํ์ฌ Fig. 4์ ๋ํ๋๋ค. 2012๋
์ดํ CO ํ๊ท ๋ฐฐ์ถ๋์ด 2015๋ ๊น์ง ๊ณ์ ์ค์ด๋ค๊ณ ์๋ ๊ฒ์ ์ ์ ์๋ค. 2012๋ ์๋ 50 โ 100 ppm์ ๋ฒ์๋ก ๋ฐฐ์ถ๋๊ณ
์์ผ๋, 2015๋ ์๋ ๋ฐฐ์ถ๋์ด 20 โ 30 ppm์ผ๋ก ๋ฎ์์ง๊ณ ์๋ค. ์ด๋ ๋๊ธฐํ๊ฒฝ๋ณด์ ๋ฒ ์ํ๊ท์น์ ๊ท์ ๋ ๋๊ธฐ์ค์ผ๋ฌผ์ง์ ํ์ฉ๊ธฐ
์ค(๋ชฉ์ฌํ ๋ฆฟ ์ฌ์ฉ์์ค CO 200 ppm ์ดํ)์ ํจ์ฌ ๋ฐ๋๋ ๊ฐ์ด๋ค. ์ผ๋ฐ์ ์ผ๋ก CO ๋ฐฐ์ถ์ ์ฐ์์์คํ ์ ๋ํ ์ต์ ํ๋ฅผ ํตํด
๋ถ์์ ์ฐ์๋ฅผ ์ค์ด๊ฒ ๋๋ฉด ์ ๊ฐ๋๋ค. ์ด์ ๊ฐ์ CO ๋ฐฐ์ถ๋ ๊ฐ์๋ ์ฐ๋ฆผ์ฒญ์์ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ๊ฐ ๋ณด๊ธ๋๊ธฐ ์์ํ
2011๋ ์ดํ ๋ณด์ผ๋ฌ ์ ์์ ์ฒด๋ง๋ค ๋ณด์ผ๋ฌ ํจ์จ ํฅ์, CO ์ ๊ฐ ๋ฑ ๊ธฐ์ ๊ฐ๋ฐ์ ์ง์คํ์๊ธฐ ๋๋ฌธ์ผ๋ก ํ๋จ๋๋ค.
๋ณด์ผ๋ฌ์์ ๋ฐฐ์ถ๋ CO ๊ฐ์ ์ฌ์ฉํ์ฌ ๋ฐฐ์ถ๊ณ์๋ฅผ ๊ณ์ฐํด ๋ณด์๋ค. CO๋ NOx ๋ฑ์ ๋ํ ๋ฐฐ์ถ๊ณ์(g/kg_fuel)๋ ์ฐ๋ฃ 1kg์
์ฐ์์์ผฐ์ ๋ ๋ฐฐ์ถ๋๋ ์ค์ผ๋ฌผ์ง์ ๋ฌด๊ฒ(g)๋ก ์ ์๋๋ฉฐ, ์๋์ ๊ฐ์ ์์ผ๋ก ๊ณ์ฐํ ์ ์๋ค.
Sea Byul Kangโ Kyu Sung Choiโ Hyun Hee Leeโ Gyu-Seong Han
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Emission factor (g/kg) = pollutant concentration (g/m3) * flue gas volume flow rate (m3/h) / fuel consumption (kg/h)
์ ์์์ ์ค์ผ๋ฌผ์ง ๋ฐฐ์ถ๋(pollutant concentration)์ ์ค์ ๋ชฉ์ฌํ ๋ฆฟ ์ฐ์ ์ ๊ณ์ธก๋ ๊ฐ ์ค์ผ๋ฌผ์ง์ ๋ฐฐ์ถ ๋๋(ppm)๋ก๋ถํฐ
๊ณ์ฐ๋๋ฉฐ, ์ฐ๋ฃ ์๋น๋์ ์ค์ ๋ณด์ผ๋ฌ ๊ฐ๋ ์ ํฌ์ ๋๋ ์ฐ๋ฃ๋์ ์ฌ์ฉํ์๋ค. ๋ง์ง๋ง์ผ๋ก ๋ฐฐ๊ธฐ๊ฐ์ค ๋ฐฐ์ถ๋์ ์ค์ ๋ณด์ผ๋ฌ
์ฐ์ ์ ๊ณ์ธก๋ ๋ฐฐ๊ธฐ๊ฐ์ค ์ฐ์๋๋๋ฅผ ๊ธฐ๋ฐ์ผ๋ก ํ์ฌ ๊ณ์ฐํ์๋ค. Fig. 5์๋ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ ๋ํ CO ๋ฐฐ์ถ๊ณ์๋ฅผ
๋ํ๋๋ค. ๋ณด๊ธ๋ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ ํ๊ท CO ๋ฐฐ์ถ๊ณ์๋ 0.73 g/kg์ด๋ค. 2015๋ ์ ์ค์น๋ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์
CO ํ๊ท ๋ฐฐ์ถ๋์ 25.7 ppm์ผ๋ก ์ด๊ธฐ(2012)์ ์ค์น๋ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ CO ํ๊ท ๋ฐฐ์ถ๋์ธ 62.5 ppm์ ๋นํด ๋งค์ฐ ๋ฎ๋ค.
์ด๋ฌํ ๊ฒฝํฅ์ CO ๋ฐฐ์ถ๊ณ์๋ฅผ ์ค์น๋ ์๊ฐ ์์ผ๋ก ๋ํ๋ธ Fig. 5์์๋ ์ค์น๋ ๋์ ๋ฐ๋ผ CO ๋ฐฐ์ถ๊ณ์๊ฐ ์ค์ด๋ค๊ณ ์๋ ๊ฒ์
ํ์ธํ ์ ์๋ค. ๊ฐ์ฅ ๋ง์ง๋ง์ ์ค์น๋ 5๊ฐ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ CO ๋ฐฐ์ถ๊ณ์์ ํ๊ท ์ 0.36 g/kg๋ก ๋งค์ฐ ๋ฎ๋ค.
3.2 ์ง์์ฐํ๋ฌผ(NOx)
๋ณธ ์ฐ๊ตฌ์์ ์ฌ์ฉํ ๋ชฉ์ฌํ ๋ฆฟ์ ํฌํจํ ์ฌ๋ฌ ์ข ๋ฅ์ ๋ชฉ์ง๊ณ ๊ณ ํ ์ฐ๋ฃ์ ํฌํจ๋ ์ง์ ํจ๋์ ๋ฐ๋ฅธ NOx ๋ฐฐ์ถ๋์ Fig. 6์
๋ํ๋๋ค(Kang et al., 2017์ ์๋ฃ ์ธ์ฉ). ๊ทธ๋ฆผ์์ ์ฐ๋ฆผ์ฒญ ๋ณด๊ธ์ฌ์ ์ ์ํด ์ค์น๋ ์ฐ์ ์ฉ ๋ณด์ผ๋ฌ์์ ์ฌ์ฉ๋ ๋ชฉ์ฌํ ๋ฆฟ์
์ง์ํจ๋์ด 0.3%์ผ ๋ ์ธก์ ๋ NOx ๋ฐฐ์ถ๋์ ์ต๋๊ฐ๊ณผ ์ต์๊ฐ์ ๋ํ๋๋ค. ์ฐ๋ฃ์ ํฌํจ๋ ์ง์ ํจ๋์ ๋ฐ๋ผ NOx๊ฐ์ด ์ ํ์ ์ผ
๋ก ์ฆ๊ฐํ๋ ๊ฒฝํฅ์ ํ์ธํ ์ ์๋ค. ๊ฐ์ ๋ชฉ์ฌ ์ฐ๋ฃ๋ผ๊ณ ํ๋๋ผ๋ ๊ทธ ์ฐ๋ฃ์ ํฌํจ๋ ์ง์ ํจ๋์ ๋ฐ๋ผ NOx ์์ฑ๋์ด ๋ฌ๋ผ์ง
๊ฒ์ด๋ค. ๊ทธ๋ฐ๋ฐ ๋ชฉ์ฌ ํ ๋ฆฟ์ ๊ฒฝ์ฐ ๋๋ถ๋ถ ์ง์ ํจ๋์ด 0.5 % ๋ฏธ๋ง์ด๊ธฐ ๋๋ฌธ์ NOx ์์ฑ์ 100 ppm ์ดํ๊ฐ ๋ ๊ฒ์ด๋ค. 500MW๊ธ
์ํํ๋ ฅ๋ณด์ผ๋ฌ์์ ์ํ ์ข ๋ฅ(์ญ์ฒญํ, ์์ญ์ฒญํ)์ ๋ฐ๋ฅธ NOx ๋ฐฐ์ถํน์ฑ ์ฐ๊ตฌ ๊ฒฐ๊ณผ๋ฅผ ์ดํด๋ณด๋ฉด(Kang et al., 2009), ์ํ์
ํฌํจ๋ ์ง์ ํจ๋์ 0.76 โ 1.7 % ์์ค์ด๋ค. ์ด๋ก ์ธํด ์ํํ๋ ฅ ๋ฐ์ ์์์๋ ๊ณ ์จ์์ ๋ฐ์ํ๋ thermal NOx ์์ฑ์ด ํฐ
๋ถ๋ถ์ ์ฐจ์งํ์ง๋ง, ์ง์์ฑ๋ถ์ด ๋์ ์ํ์ ์ฐ์์์ผฐ์ ๋ NOx ์์ฑ์ด ๋์์ง๋ค๋ ์ฌ์ค๋ ํ์ธ๋์๋ค.
์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ ๋ํ NOx ๋ฐฐ์ถ๋ ๋ฐ 5๊ฐ ํ๊ท ํ ๊ฐ์ Fig. 7๊ณผ 8์ ๋ํ๋๋ค. ๊ณ์ธก๋ ๋ณด์ผ๋ฌ์ ํ๊ท NOx ๋ฐฐ์ถ๋์
๋ฐฐ๊ธฐ๊ฐ์ค ์ฐ์๋๋ 12%์์ 76 ppm์ด๋ค. NOx์ ๊ฒฝ์ฐ 44 โ 128 ppm๊น์ง ๋ถํฌ๋์ด ์๋ ๊ฒ์ ์ ์ ์๋ค. ์ด๋ ๋๊ธฐํ๊ฒฝ๋ณด์ ๋ฒ
์ํ๊ท์น์ ๊ท์ ๋ ๋๊ธฐ์ค์ผ๋ฌผ์ง์ ํ์ฉ๊ธฐ์ค(๋ชฉ์ฌํ ๋ฆฟ ์ฌ์ฉ์์ค NOx 150 ppm ์ดํ)์ ํจ์ฌ ๋ฐ๋๋ ๊ฐ์ด๋ค. ์ด ๋ NOx์
๋ํ ๋ฐฐ์ถ๊ณ์๋ฅผ ๊ณ์ฐํด๋ณด๋ฉด 1.63 g/kg์ด๋ค. ๋ ๊ทธ๋ฆผ์ ๋ณด๋ฉด ์ค์น ๊ธฐ๊ฐ์ ๋ฐ๋ฅธ CO ๋ถํฌ์๋ ๋ฌ๋ฆฌ ์๊ฐ์ด ์ง๋จ์ ๋ฐ๋ผ ๋ฐฐ์ถ๋์ด
์ค์ด๋๋ ๊ฒฝํฅ์ ์๋ค. ์ด๋ฌํ ์ด์ ๋ฅผ ์ดํด๋ณด๋ฉด CO ๋ฐฐ์ถ์ ์ฐ์๊ธฐ๋ฅผ ๊ฐ์ ํ์ฌ ์ต์ ์ฐ์ ์กฐ๊ฑด์ ๋ง๋ค์ด์ฃผ์ด ์ ๊ฐํ ์ ์๋ค.
ํ์ง๋ง NOx์ ๊ฒฝ์ฐ ์ฐ๋ฃ์ ์ง์(N)์ฑ๋ถ์ด ์๋ ์ฒ์ฐ๊ฐ์ค(LNG)์๋ ๋ฌ๋ฆฌ ๋ชฉ์ฌํ ๋ฆฟ์ 0.1 โ 0.5%์ ๋ ์ง์๊ฐ ํฌํจ๋์ด ์๋ค.
์ด๋ฌํ ์ง์๊ฐ ๊ณ ์จ์ ์ฐ์๋ถ์๊ธฐ์์ ์ฐํ๋์ด NO์ NO2๋ฑ์ผ๋ก ๋ณํ๊ฒ ๋๋ค. ์ด๋ ๊ฒ ์์ฑ๋ NOx๋ฅผ Fuel NOx๋ผ ํ๋ค. ์ด๋ฌํ
NOx๋ ๊ทผ๋ณธ์ ์ผ๋ก ์ค์ด๊ธฐ ํ๋ค๊ฒ ๋๋ฉฐ ์ด๋ฌํ ํน์ฑ์ผ๋ก ์ธํด NOx ๋ฐฐ์ถ๋์ ์ค์ด๋ค์ง ์๋ ๊ฒฝํฅ์ ๋ํ๋ด๊ฒ ๋๋ค.
๊ตญ๋ด ์ NOx ์ธ์ฆ์ ํ์ ๋ํ NOx ๋ฐฐ์ถ๊ฐ์ Fig. 9์ ๋ํ๋๋ค. ๊ทธ๋ฆผ์์ ๋ณด๋ ๊ฒ๊ณผ ๊ฐ์ด NOx ํ๊ท ๊ฐ์ 35 ppm์ธ ๊ฒ์
์ ์ ์๋ค. ์ฐ์ ์ฉ ๋ณด์ผ๋ฌ์ ๋ํ ์ NOx ๋ฒ๋ ๊ธฐ์ค์ ๋ฐฐ๊ธฐ๊ฐ์ค ์ฐ์๋๋ 4 %์์ 40 ppm ๋ฏธ๋ง์ด๋ค. ์ผ๋ฐ์ ์ผ๋ก ์ NOx
๋ฒ๋๊ธฐ์ค์ ๋ง์กฑํ๋ LNG ๋ฒ๋๋ ์ฐ์๋๋ 3 %์์ 35 ppm ์ ๋ ๋ฐฐ์ถ๋๊ณ ์๋ค.
LNG, ๋ชฉ์ฌํ ๋ฆฟ ๋ฐ ์ํ(๋๋ ์ค์ )์ ๋ํ ๋ณด์ผ๋ฌ ์ ์ ์ฐ์ ์์ ํ๊ท ์ ์ธ NOx ๋ฐฐ์ถ๊ณ์๋ฅผ Table 1์ ๋ํ๋๋ค. ๋ชฉ์ฌํ ๋ฆฟ์
๊ฒฝ์ฐ ์์์ ์ธก์ ํ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ ๋ณด์ผ๋ฌ์์ ๋ฐฐ์ถ๋๋ NOx ํ๊ท ๊ฐ์ ์ฌ์ฉํ์๋ค. ์ํ ๋๋ ์ค์ (bunker-C)๋ฅผ ์ฌ์ฉํ๋
๋ฐ์ ์ฉ ๋ณด์ผ๋ฌ์ ๊ฒฝ์ฐ ์ผ๋ฐ์ ์ผ๋ก NOx๋ฅผ 70 ppm ์ดํ๋ก ์ด์ ๋๊ณ ์๋ค(๋๊ธฐํ๊ฒฝ๋ณด์กด๋ฒ 2014.12 ์ด์ ์ค์น์ค๋น). ์ด๋ฌํ
์ํฉ์ ๊ฐ ์ฐ๋ฃ์ ๋ํ์ ์ธ ์ํฉ์ผ๋ก ๊ฐ์ ํ์์ ๋ NOx ๋ฐฐ์ถ ๊ณ์๋ฅผ ๊ณ์ฐํ์ฌ Table 1์ ๋ํ๋๋ค. LNG์ NOx ๋ฐฐ์ถ์ง์๋ฅผ
1๋ก ํ์์ ๋ ๋ชฉ์ฌํ ๋ฆฟ์ 1.90๋ฐฐ, ์ํ ๋๋ bunker-C์ ๊ฒฝ์ฐ 2.01๋ฐฐ ๋ฐฐ์ถ๋๋ ๊ฒ์ผ๋ก ๊ณ์ฐ๋์๋ค. ์ํ ๋๋ bunker-C์
๊ฒฝ์ฐ ๋ณด์ผ๋ฌ ํ๋จ์ SCR(selective catalytic reduction) ๋ฑ NOx๋ฅผ ์ ๊ฐ์ํค๊ธฐ ์ํ ํ์ฒ๋ฆฌ ์ค๋น๊ฐ ์๋ ๊ฒฝ์ฐ๋ก ๊ฐ์ ํ์๋ค.
๋ง์ผ SCR ๋ฑ ํ์ฒ๋ฆฌ ์ค๋น๊ฐ ์์ ๊ฒฝ์ฐ์๋ ๋ฐฐ์ถ๊ณ์๊ฐ ๋ ๋์ ๊ฒ์ด๋ค.
4. ๊ฒฐ ๋ก
2011๋ ๋ถํฐ 2015๋ ๊น์ง ์ฐ๋ฆผ์ฒญ์์ ์ง์ํ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ 63๋์ CO ๋ฐ NOx ๊ณ์ธก๊ฐ์ ๋ชจ๋ ํ๊ฒฝ๋ถ์ ํ์ฉ๊ธฐ์ค์
๋ง์กฑํ์๋ค. CO ๋ฐ NOx ๋ฐฐ์ถ๊ฐ์ ๊ธฐ๋ฐ์ผ๋ก ํ์ฌ ๋ฐฐ์ถ๊ณ์๋ฅผ ๊ณ์ฐํด๋ณด์๋ค. ์ด๋ ๊ฒ ๊ณ์ฐ๋ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ ๋ฐฐ์ถ๊ณ์๋ฅผ
์ NOx ์ธ์ฆ๋ฒ๋์์ ๋ฐฐ์ถ๋๋ NOx์ ๋น๊ตํด๋ณด์๋ค. ๋ถ์ํ ๊ฒฐ๊ณผ๋ฅผ ์์ฝํ๋ฉด ๋ค์๊ณผ ๊ฐ๋ค.
Analysis of Emission Characteristics and Emission Factors of Carbon Monoxide and Nitrogen Oxide Emitted from Wood Pellet Combustion in Industrial Wood Pellet Boilers Supplied According to the Subsidy Program of Korea Forest Service
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1. ์ฐ๋ฆผ์ฒญ์์ ์ง์ํ ์ฐ์ ์ฉ ๋ชฉ์ฌ ํ ๋ฆฟ ๋ณด์ผ๋ฌ์ ํ๊ท ์ฉ๋์ 3.0MW๋ก ๋ชฉ์ฌ ํ ๋ฆฟ ์๋น๋์ ์ฝ 740 kg/h์ด๋ค.
2. 5๋ ๊ฐ ๋ณด๊ธ๋ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ ํ๊ท CO ๋ฐฐ์ถ๋์ 56 ppm(@O2 12%)์ด๋ฉฐ, ์ด๋ฅผ ๋ฐฐ์ถ๊ณ์๋ก ํ์ฐํ๋ฉด 0.73
g/kg์ด๋ค.
3. ๋ณด๊ธ์ด๊ธฐ์ธ 2012๋ ๋ณด๊ธ๋ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ ๋ํ ํ๊ท CO ๋ฐฐ์ถ๋์ 70.3 ppm(@O2 12%)์ด์์ผ๋, ๋ณด๊ธ์ฌ์
๋ง์ง๋ง ์ฐ๋์ ์ค์น๋ ๋ณด์ผ๋ฌ์ ํ๊ท CO ๋ฐฐ์ถ๋์ 28.9 ppm์ด๋ค. ์ด๋ ๊ธฐ์ ๊ฐ๋ฐ์ ํตํด ์ฐ์๊ธฐ ๋ฐ ๋ณด์ผ๋ฌ ์์คํ ์ ์ต์ ํํ
๊ฒฐ๊ณผ๋ก ํ๋จ๋๋ค.
4. 5๋ ๊ฐ ๋ณด๊ธ๋ ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์ ํ๊ท NOx ๋ฐฐ์ถ๋์ 76 ppm(@O2 12%)์ด๋ฉฐ, ์ด๋ฅผ ๋ฐฐ์ถ๊ณ์๋ก ํ์ฐํ๋ฉด 1.63
g/kg์ด๋ค.
5. NOx๋ ์๊ฐ์ ๋ฐ๋ผ ๊ฐ์ํ๋ ๊ฒฝํฅ์ ๋ํ๋ด์ง ์์๋ค. ์ด๋ NOx ์์ฑ์ด ์ฐ๋ฃ์ ํฌํจ๋ ์ง์ํจ๋์ ๋ฐ๋ผ ์์ฑ๋๋ fuel
NOx๊ฐ ์ค์ด๋ค์ง ์์๊ธฐ ๋๋ฌธ์ผ๋ก ํ๋จ๋๋ค.
6. ์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ๋ณด์ผ๋ฌ์์ ์์ฑ๋๋ NOx์ ๋ฐฐ์ถ๊ณ์๋ฅผ ์ NOx ์ธ์ฆ LNG ๋ฒ๋ ๋ฐ ์ํ(์ค์ )์ ๋น๊ตํด ๋ณด์๋ค. ๋ณด๊ธ๋
์ฐ์ ์ฉ ๋ชฉ์ฌํ ๋ฆฟ ๋ณด์ผ๋ฌ์ ๋ฐฐ์ถ๊ณ์๋ ์ NOx ์ธ์ฆ LNG ์ฐ์๋ณด๋ค ์ฝ 1.90๋ฐฐ์ด์์ผ๋ฉฐ, ํ์ง์ค๋น๊ฐ ๋ถ์ฐฉ๋ ์ํ ๋ฐ ์ค์ ๋ณด์ผ๋ฌ
์ ๋นํด ์ฝ 0.92๋ฐฐ์ด๋ค.