United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
v°xEPA
Research and Development
EPA-600/S2-80-186 Dec 1980
Project Summary
Evaluation and Application of
SO, Measurement Procedures
for Kraft Recovery Furnaces
A. K. Jam, R. 0. Blosser, D. B. Newport, and H. S. Oglesby
A research program was initiated to
determine sulfuric acid (SOa/hbSOi)
and sulfur dioxide (SOz) emissions
from kraft recovery furnaces using an
extractive sampling system. The
Goksoyr and Ross controlled conden-
sation technique, which uses a
modified Grahm condenser, was
chosen because of its reported
accuracy. Equipment was designed
and fabricated to evaluate the effect of
coil length, frit porosity, temperature,
flow rate, and concentration on the
efficiency of H 2864 capture.
Laboratory tests were conducted to
determine the optimum design and
operating conditions to minimize
SO3/H2SO4 losses in filter holders
used in the sampling train for
particulate separation. The effects of
recovery furnace particulate on
SO3/H2SO4 losses were investigated.
The alkaline particulate from the
recovery furnace reacted with a part of
SO3/H2SO4 in the sample. Although
the losses could not be correlated with
the alkalinity of the particulate, they
were not considered significant.
Field studies were conducted on five
representative kraft recovery furnaces
to determine SOa/hhSO and S02
concentrations in flue gases. The
SO3/H2SO4 concentrations varied
from 0 to 2.98 ppm, and the range of
SO2 concentrations varied from 1 4 to
416 ppm. A comparison of these
emissions with the SO3/H2SO4
and SO2 emissions from oil- and coal-
fired utility boilers shows the kraft
recovery furnace emissions to be
much lower.
Introduction
Because of their adverse effect on
respiratory functions, acid sulfate
aerosols in the ambient air are of special
concern in air quality management
programs One of the precursors of
ambient acid sulfate aerosols is sulfur
trioxide (SOa), which is formed during
the combustion of sulfur containing
fossil fuels
In the kraft pulping industry, the con-
centrated spent cooking liquor (black
liquor), which consists of wood compon-
ents, inorganic chemicals, and sulfur
compounds, is sprayed into a furnace
and combusted Although the kraft
recovery furnace burns black liquor m a
manner to minimize sulfur dioxide (SOa)
generation, the presence of high
concentrations of sulfur in the black
liquor has raised the question of the
possible presence of sulfur trioxide
(SO3)/sulfunc acid (H2S04) in kraft
recovery furnace flue gas
The objective of this investigation was
to determine representative SO2 and
SO3/H2SO
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investigation was divided into four
areas'
1. Development and laboratory
testing of a suitable method to
measure SOs/HaSCU concentra-
tion m a particulate-free gas
stream,
2. Determination of the effect of the
presence of kraft recovery furnace
paniculate on the measurement of
S03/H2S04,
3 Selection and testing of a suitable
paniculate separation device to
minimize paniculate interaction
with SO3/H2S04 in the sampling
tram if paniculate is found to inter-
fere in SO3/H2SO4 measurement,
and
4 Measurement of S02 and
SO3/H2SC>4 levels in kraft recovery
furnaces from five representative
sources in the southeast
Conclusions
The kraft recovery furnace SOX study
results can be divided into two parts
laboratory investigation and field mea-
surements of SOx emissions
Laboratory Investigation
A study of the Goksoyr and Ross
method for S03/H2SO4 measurement
showed that the efficiency of SO3/H2SO4
capture in the modified Grahm con-
denser was dependent upon the frit
porosity and coil length (Table 1) A con-
denser with Type C (Ace Glassjfrit and a
200-cm coil maintained at 75° to 85°C
(1 67-1 95°F) was the most suitable for
use in the sampling train because of its
ability to provide high H2SC>4 capture
efficiency and acceptable sampling rate
in the range of 6-8 L/m
Tests to find a suitablefilter holderfor
removing paniculate from the gas
stream prior to SOa/I^SCU measure-
ment showed that the conventional EPA
Method-5 type of filter holders could not
withstand the desired temperature of
260°C(500°F) A quartz filter assembly,
developed for another EPA project, was
fabricated and tested in the laboratory
The study showed no significant loss of
H2SC>4 in the filter support assembly
maintained above 260°C (500°F)
The effect of kraft recovery-furnace
paniculate upon the passage of
S03/H2S04 through the filter holder
Table 1. Effect of Frit Porosity Upon SOa Condenser Efficiency.
Max. Pore Length of
Frit D/'a. Flange Condensing Coil
No. Type* (fjM) (cm)
1 B 70-100 100
2 D 10-20 200
3 C 25-50 200
Flow Rate % H2SO4
(Lpm) Capture
2 20-40
2 99
2-8 90-99
*Ace Glass
Table 2. H2S04 Losses in Tests With Recovery Paniculate
H2SOs Cone , H2S04 Loss,
ppm
200
230
288
323
8.8
11 1
222
194
177
ppm
3.4
60
4.3
0.3
1 4
4 1
24
2 7
25
Percent
17
26
15
1
16
37
1 1
14
14
H2SO4 Loss*
Possible
ppm
1 4
1 6
1 4
1 0
3 1
32
0 7
06
0.5
Percent
7
7
5
3
35
29
3
3
3
Difference
ppm
2.0
4.4
2.9
-07
1 7
09
1 7
2.1
2.0
Percent
10
19
10
- 2
-19
8
8
11
11
t all alkalinity present was neutralized
was determined by continuously load-
ing the quartz filter with recovery-
furnace paniculate while passing a gas
stream containing H2SO4 through the
filter The results (Table 2) show sub-
stantially higher losses of H2SC>4 than
were expected based upon the alkalinity
of the paniculate and may be due to the
adsorption of H2SC>4 on the paniculate
surface. The absolute values of H2SO4
losses were, however, low and, for pur-
poses of estimating emission levels
from kraft recovery furnaces, of little
significance
The alkaline paniculate present in the
kraft recovery furnace stack gas offered
a potential for SOs/H2SO4 loss from the
sample To minimize the contact
between the gas and the collected parti-
culate and to reduce the potential for
SO3/H2SC>4 loss, tests were conducted
with an electrostatic precipitator
obtained from the EPA Environmental
Sciences Research Laboratory Tests
showed that the precipitator removed
99 percent of the paniculate present in
a stack gas following a precipitator, and
there was no conversion of SO2 to SOs
in the precipitator
Field Measurement of SO«
Emissions
The SO, emissions from five kraft
recovery furnaces were measured
Included were two furnaces with direct
contact evaporators (DCE) and three
without any contact evaporators One of
the non-contact furnaces was a cross-
recovery furnace in which 30 percent of
the liquor was from the sodium-based.
semichemical cooking process U
The sampling tram is shown in Figure^
1 Table 3 summarizes test results by
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furnace type and sample conditioning
techniques The data for all the tests
show a SC>3/H2SC>4 concentration
range of 0 to 2 98 ppm, with an average
value of 0 81 ppm. When separated
according to the type of furnaces, the
data show that DCE furnaces have an
average SOa/HjSO* concentration of
0 24 ppm in stack gases; non-DCE
furnaces have a slightly higher average
concentration (1 07 ppm) Non-DCE
furnaces had an average concentration
of 356 ppm of flue gas SC>2, substanti-
ally higher than the average concentra-
tion in furnaces with DCE (80 ppm)
The data in Table 3 indicate that non-
DCE furnaces have an average
S03/H2SCu level of 0.90 ppm when a
quartz filter was used in the sampling
tram, a lower average than the
SC>3/H2S04 concentration of 1 62 ppm
obtained with a miniature electrostatic
precipitator (ESP) in the sampling tram
for paniculate separation These differ-
ences, too small to be of any
importance, may be due to source vari-
ability, oxidation of SO2 to S03 in the
ESP during sampling, or lower losses of
SO3/H2SO4 in the ESP.
The lower SOzconcentrations in DCE
furnaces were anticipated and are gen-
erally due to SO2 scrubbing in the DCE
To determine any linear correlation
between the SO3/H2S04 and the SO2
concentrations, the values of coefficient
Table 3.
Emission Data Summary
SOz/HzSOt Cone, ppm
Samples
AH Samples
No.
26
Max.
298
Mm
0
Avg
0.81
SO2 Cone.,
ppm
260
Types of Furnaces
-DCE Furnaces 9 1 10 0 0 24 80
-non-DCE Furnaces 17 298 017 107 356
Non-DCE Furnaces
-Quartz Filter Only 13 263 0.17 090 430
-ESP Only 4 298 0.91 162 305
Insulated
'Box
Heated
Probe
w/Quartz
Tube
High Temperature
r~ Heating Elements
Thermocouple
Greenburg
Smith
Impmgers
Silica Gel
Drying Tube
Thermometer
\-Water
3% Hydrogen
Peroxide
Needle Valve
Pump
Rate Meter
Figure 1. SO, sampling tram
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of correlation (r) between
and 862 were determined for each
recovery furnace and are tabulated in
Table 4 These results, except for
recovery furnace C, show a very poor
correlation between SO3/H2SC>4 and
862. If a high level of SOz is noted in a
particular furnace's stack gas, it should
not be assumed that the same furnace
also emits a high concentration of
S03/H2S04.
Table 4. Coefficient of Correlation
SO3/H2SO4 and S02.
Recovery
Furnace
A
B
C
D
E
Coefficient of
Correlation
-0.33
-0.50
099
-042
-046
To understand the relative signifi-
cance of the SOx levels in kraft recovery
furnace stack gases, these levels must
be compared to emissions from oil- or
coal-fired utility or industrial boilers.
Some of the recently published SOa and
h^SCU emission data from oil- and coal-
fired boilers show that both theSOaand
the H2S04 concentrations in flue gases
from oil- and coal-fired boilers are much
higher than the levels m kraft recovery
furnace stack gases
A. K. Jam, R. O. Blosser, D. B. Newport, and H. S. Oglesby are with the National
Council of the Paper Industry for Air and Stream Improvement, Inc., New York,
NY 10016.
Michael D. Strutz is the EPA Project Officer (see below).
The complete report, entitled "Evaluation and Application of SO* Measurement
Procedures for Kraft Recovery Furnaces," (Order No. PB 81-109092;
Cost: $7.00, subject to change} will be available 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
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency I U-SJ
EPA 335
Official Business
Penalty for Private Use $300
L
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