United States
Environmental Protection
Agency
Industrial Environmental
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-84-086 Sept. 1984
Project Summary
Status of Dry S02 Control
Systems: Fall 1983
M. A. Palazzolo and M. A. Baviello
This report, on the status of dry SO2
control for utility and industrial boilers
in the U.S., reviews current and re-
cently completed research, develop-
ment, and commercial activities. Dry
SO2 control systems covered include:
(1) spray dryers with a fabric filter or an
electrostatic precipitator (ESP), (2) dry
injection of alkaline material into flue
gas accompanied by collection of prod-
uct solids and fly ash in a fabric filter or
an ESP, and (3) electron-beam (E-beam)
irradiation. Spray drying and dry injec-
tion systems generally include a fabric
filter or an ESP and control SO2 and
particulate matter simultaneously; E-
beam technology is designed to also
control NOX.
Spray drying continues to be the only
technology commercially applied to
utility and industrial boilers. The two
new utility systems sold since the last
status report (Fall 1982) bring the total
utility spray drying flue gas desulfuriza-
tion (FGD) capacity to about 7150 MWe.
Also, 10 recently sold new industrial
units bring the total of commercial in-
dustrial boiler unit sales to 21. Perfor-
mance data for five utility systems and
three industrial systems were recently
published. Some full-scale systems
that have come on-line since the last
survey have experienced atomization
problems and solids buildup on the
dryer walls during initial operation.
The first planned commercial applica-
tion of trona dry injection technology
has been announced for a 500 MWe
unit.
This Project Summary was de-
veloped by £PA'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 or-
dering information at back).
Introduction
The report summarized here updates
the status of dry flue gas desulfurization
(FGD) processes in the U.S. for both
utility and industrial applications. As in
previous reports (EPA-600/7-83-041, -
81-097, -81-018, and -80-030), dry FGD
is defined as any process that involves
contacting a sulfur-containing flue gas
with an alkaline reagent and that results
in a dry waste product for disposal.
Such systems include: (1) those that
use spray dryers for a contactor with
subsequent baghouse or electrostatic
precipitator (ESP) collection of waste
products, (2) those that involve dry in-
jection of alkaline reagent into the flue
gas with subsequent baghouse or ESP
collection, and (3) those that involve
reagent injection into the flue gas fol-
lowed by electron-beam (E-beam) ir-
radiation. Such a definition of dry sys-
tems excludes several dry adsorption or
"acceptance" processes (e.g., the Shell/
UOP copper oxide process and the
Bergbau-Forschung adsorptive char
process) whose status has been
documented in previous EPA reports.
Fluidized-bed combustion, the regener-
able Rockwell Aqueous Carbonate Pro-
cess (ACP), and limestone injection into
multistage burners (LIMB) have also
been excluded.
The report is divided into five sec-
tions: (1) the first gives generalized
process descriptions of the three
technologies covered; (2) the second is
an overview of the current status of dry
FGD systems, including (a) a summary
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of recent commercial and developmen-
tal activities for each process, and (b)
highlights of recent technological de-
velopments, including design and
operating experience with commercial
systems; (3) the third provides detailed
discussions of commercial activities
and current and recently completed re-
search and demonstration programs;
(4) the fourth discusses results of recent
cost studies on dry FGD systems; and
(5) the fifth gives highlights of research
in the area of dry FGD waste characteri-
zation and disposal.
Summary of Project Findings
Interest in dry SO2 control has re-
mained strong since the Fall 1982 status
report. Two new utility systems and 10
new industrial spray drying units have
been sold. Seven utility systems and 10
industrial units are now operational,
and operating experience with several
of these systems has been reported.
New information has been published
on the use of spray drying for high sul-
fur coal applications, an area that is the
focus of several current or recently
completed pilot- and demonstration-
scale test programs. Also, the first plan-
ned commercial application of dry in-
jection technology has been an-
nounced, following the completion of a
demonstration-scale test program.
Plans for the construction and testing
of E-beam irradiation pilot plants have
been finalized, and testing of the E-
beam/lime spray drying version of the
process is now underway.
Work is also continuing on waste dis-
posal. Recent studies are focused on
characterizing solid waste properties as
a function of coal type and FGD process
conditions.
Highlights of New
Developments
Spray drying continued to be the only
dry SO2 control process commercially
applied to utility or industrial boilers.
Contracts for two new utility systems
were awarded since the Fall 1982 re-
port, bringing the total utility spray dry-
ing FGD capacity to about 7,200 MWe,
including the 110 MWe demonstration
system at the Northern States Power
Company's (NSP's) Riverside Station,
now being operated by the utility.
Contracts for 10 new industrial units
have been awarded since late 1982 for
three Federal government installations
(one Navy and two Air Force). The in-
dustrial systems now sold total 21 units.
Performance and compliance test re-
sults were recently reported for four
utility systems, including Basin Elec-
tric's Antelope Valley (Unit No. 1) and
Laramie River (Unit No. 3) Stations,
United Power Association's Stanton
Station, and Marquette Board of Light
and Power's Shiras Station. Test results
were also reported for the industrial
systems at Argonne National Labora-
tory, Austell Box Board, and Container
Corporation. Data from EPA/EPRI-
funded testing at NSP's Riverside Sta-
tion and the results from pilot-scale
testing funded by EPRI, EPA, and DOE
have also been published. In general,
the performance test results have
shown that the commercial systems
have met or exceeded SO2 and particu-
late matter removal guarantees, except
for the Laramie River system which is
still undergoing further process de-
velopment and optimization. Recently
published data have confirmed earlier
indications that 90 percent or greater
S02 removal is achievable for high sul-
fur coal applications (3 - 4 percent sulfur
coal with a corresponding .inlet SO2
concentration of 2,000 - 2,500 ppmv).
Several commercial spray drying sys-
tems have only recently become opera-
tional, and compliance and perfor-
mance testing is planned for early 1984.
At least one other system is in the initial
start-up stage and one additional sys-
tem should be in the start-up or perfor-
mance test stage by the end of 1984.
Vendors report having several utility
and industrial system bids under evalu-
ation with at least two industrial system
awards expected by mid-1984. The mar-
ket outlook for utility systems, particu-
larly for retrofits, is improving with the
growing concern over acid deposition,
and the market outlook for industrial
systems has improved with the recent
economic upturn.
A major development in spray drying
during the past 2 years has been the
successful application of the technol-
ogy to higher sulfur coal-fired boilers.
Data have recently been made available
from the industrial system at Argonne
National Laboratory, EPA/EPRI-funded
Riverside process tests, and DOE-
funded tests at Babcock and Wilcox's
Alliance Research Center. Most of these
tests were conducted at flue gas inlet
S02 concentrations of 1,900 ppmv or
greater. The data confirm earlier high
sulfur test results which showed that,
at a relatively close approach to satura-
tion of 18° to 20°F, reagent ratios of at
least 1.3 are required to achieve 90 per-
cent SO2 removal.*
A novel spray drying process for
simultaneous SOX/NOX removal has
been developed by Joy Industrial
Equipment Company and Niro
Atomizer, Inc. The process, which in-
volves lime-based spray drying with
NaOH addition, has been demonstrated
on pilot, industrial, and utility scales.
NOX removals of 50 - 60 percent with
concurrent S02 removals of 90 - 95 per-
cent have been reported. Also, the
capability of calcium chloride addition
to reduce lime consumption in spray
drying systems was demonstrated on a
utility scale during the EPA/EPRI testing
at NSP's Riverside Station.
Operating experience with full-scale
commercial systems has been reported
as relatively trouble-free. However,
some systems experienced problems
with atomizer pluggage, inadequate
gas/liquid mixing, and buildup of wet
solids on the dryer walls during initial
operation.
Spray drying demonstration- and
pilot-scale testing and research con-
tinue to focus on refinement of spray
dryer design and operation, compari-
son of rotary and nozzle atomizers, in-
vestigation of the benefits of solids re-
cycle, and characterization of ESPs
downstream of the spray dryer. Other
areas of spray dryer research and de-
velopment include the optimization of
lime slaking, application of cooling
tower blowdown as makeup water, and
investigation of alternate reagents and
additives such as thiosorbic lime and
lime or limestone with calcium chloride
addition.
The first planned commercial applica-
tion of dry injection technology has
been announced by Public Service
Company of Colorado (PSCC) for a 500
MWe unit. The system will use trona
ore as the sorbent, and waste solids will
be disposed of in a clay- and plastic-
lined landfill.
EPRI has completed the 22 MWe dry
injection demonstration tests at PSCC's
Cameo Station. Test results showed 70
percent SO2 removal for trona and
nahcolite at reagent ratios of 1.3 and
0.8, respectively, and an inlet SO2 con-
centration of about 450 ppmv. A recent
cost study based on the Cameo results
*To conform with general engineering practice, En-
glish Engineering rather than metric units are
used in this Summary. Readers more familiar with
metric units are asked to use the following conver-
sion factors: cfm x 1.7 = m3/hr; Ib x 0.454 = kg;
and°C = 5/9(°F-32).
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indicates that dry injection of sodium
compounds may be less expensive than
lime spray drying, depending on rea-
gent cost, coal sulfur content, SO2 re-
moval requirements, and waste dis-
posal costs.
The E-beam process, aimed at achiev-
ing simultaneous SO2 and NOX control,
is still in an early developmental state.
A pilot unit to test the E-beam/lime
spray dryer version of the process has
been constructed, and testing began in
early 1984. Construction of an E-beam/
ammonia pilot plant was begun in late
1983.
Spray Drying — Commercial
Activities
Utility Systems
Table 1 shows the 19 utility systems
sold to date. The applications range in
size from 44 to 860 MWe (gross electri-
cal output) and total about 7,200 MWe
in FGD system capacity. The retrofit
system at NSP's Riverside Station was
operated as a demonstration unit by the
system vendor, Joy/Niro, for 9 months
in 1981 and about 6 months in 1982.
The Riverside system is now being op-
erated by NSP. A second retrofit system
at Pacific Power and Light's Jim Bridger
Station was operated by Flakt as a de-
monstration unit for 9 months in 1982.
This system was shut down in October
1982, and no additional operation of the
unit is planned.
Seven commercial utility spray dry-
ing systems are now operational. Of
these the sodium-based system at
Coyote Station was turned over to Mon-
tana-Dakota Utilities for operation fol-
lowing final acceptance and compliance
testing in August 1982.
Three of the operational utility sys-
tems (Stanton, Shiras, and Antelope
Valley 1) met performance guarantees
in mid- to late-1983. The Antelope Val-
ley system has been turned over to
Basin Electric for commercial operation.
Initial performance testing at Sunflower
Electric's Holcomb Station is scheduled
for January 1984.
One utility system (Rawhide Unit 1) is
in the initial start-up stage, and one
other system (Craig Unit 3) is scheduled
for start-up by the end of 1984.
Two new utility systems were sold
since January 1983. Both systems were
awarded to-Joy/Niro. One contract was
for a lime-based spray dryer/ESP sys-
tem to serve a new 720 MWe unit at
Central and Southwestern Services'
Coleto Creek Station. Six parallel spray
dryers, each with a rotary atomizer, will
treat 2,800,000 acfm of flue gas from a
boiler firing a 0.4 percent sulfur sub-
bituminous coal. The second system is
for an existing 330 MWe boiler at Pacific
Power and Light's Wyodak Station.
Three parallel lime-based spray dryers,
each with a rotary atomizer, will treat
flue gas from a boiler firing a 0.4 per-
cent sulfur subbituminous coal. An
existing ESP will be used for particulate
collection. Both of the new utility sys-
tems will use warm gas bypass and sol-
ids recycle.
Industrial Boilers
Table 2 shows the 21 industrial boiler
commercial spray drying units sold to
date. (A few vendors have also sold
spray drying systems for incinerators or
kilns, but these applications are not cov-
ered in detail in this report.) Table 2
shows that the industrial systems range
in size from one 85,000 Ib steam/hr
boiler at Strathmore Paper Company's
Woronoco, MA, plant to two 40 MWe
boilers that are part of a cogeneration
system at the University of Minnesota
in Minneapolis.
Ten of the industrial boiler units are
Table 1. Summary of Utility Spray Drying Systems Sold (March 1984)
System Purchaser
Station/
Location
Size
Gross MWe acfm
Status
Vendor"
Northern States Power Co.
Pacific Power and Light
Otter Tail Power Co.
(Montana-Dakota Utilities)
United Power Association
Marquette Board of Light
and Power
Basin Electric Power Coop.
Colorado Ute Electric Assoc.
Basin Electric Power Coop.
Basin Electric Power Coop.
Riverside, Units 6 and 7
(Minneapolis, MN)
Jim Bridger, Unit 2,
(Rock Springs, WY)
Coyote, Unit 1
(Beulah, ND)
Stanton, Unit 1A
(Stanton, ND)
Shiras, Unit 3
(Marquette, Ml)
Laramie River, Unit 3
(Wheat/and, WY)
Craig, Unit 3
(Craig, CO)
Antelope Valley, Unit 1
(Beulah, ND)
Ante/ope Valley, Unit 2
(Beulah, ND)
110
640,000 @ 150°F
100 389,000 @230-240°F
440 1,890,000 @ 28S"F
60 324,500 @ 232°F
44 226,000 @ 227-265°F
575 2,300,000 @ 286" F
447 1,770,000 @245°F
440 2,055,000 @31SfF
440 2,055,000 @31SfF
Operated for 15 months by
vendor in 1981 and 1982.
System now being operated
by utility.
Operated for 9 months by
vendor. Testing completed;
no plans for additional system
operation.
Operational. Turned over to
utility. Has achieved performance
guarantees.
Operational. Passed initial
performance tests. Final stages
of acceptance testing.
Operational. Passed initial
performance tests. Final stages of
acceptance testing.
Operational. Has not yet met
performance guarantees. Additional
testing planned for early 1984.
Initial operation in late 1984.
Operational. Turned over to utility.
Has achieved performance
guarantees.
April 1985 start-up.
Joy/Niro
Flakt
Kockwelll
Wheelabrator-Frye
Cottrell Environmental/
Komline-Sanderson
G.E. Environmental
Services
Babcock and Wilcox
Babcock and Wilcox
Joy/Niro
Joy/Niro
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Table 1. (Continued)
System Purchaser
Tucson Electric Power
Tucson Electric Power
Platte River Power Authority
Sunflower Electric
Sierra Pacific Power
Grand River Dam A uthority —
State of Oklahoma
Northern States Power
Company
Cajun Electric
Central and South-
western Services
Pacific Power and Light
Station/
Location
Springerville, Unit 1
(Springerville, AZ)
Springerville, Unit 2
(Springerville, AZ)
Rawhide, Unit 1
(Fort Collins, CO)
Ho/comb, Unit 1
(Holcomb, KS)
North Va/my
(Valmy, NV)
Pry or, Unit 2
(Pryor, OK)
Sherburne County, Unit 3
(Becker, MN)
Oxbow, Unit 1
(Conshoutta, LA)
Coleto Creek, Unit 2
(Corpus Christ!, TX)
Wyodak, Unit 1
(Gillette, WY)
Gross MWe
350
350
280
319
270
520
860
563
720
330
Size
acfm
1,660,000 @256°F
1,660,000® 256" F
1,206,000® 270° F
1,340,000 @ 26CFF
1,200,000 @266°F
1,850,000 @
250-300°F
3,930,000 @ 308?F
2,600,000 @348°F
2,800.000 @27
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Table 2. (Continued)
Size
System Purchaser/Location
Ma/mstrom Air Force Base;
Units 1,2, and 3
Great Falls, MT
Griff iss Air Force Base;
Units 1,2, 3, and 4
Rome, NY
acfm
50,000 each
@350FF
50,000 each
@350°F
Ib steam/hr
90,000 each
hot water
90,000 each
Status
Start-up scheduled for Spring 1985.
Start-up scheduled for Fall 1984.
Vendor'
Niro/Joy
Ecolaire
* Niro/Joy: Niro takes the lead in industrial sales, while Joy takes the lead in utility sales.
Mikropul/Koch: Mikropul originally sold the Strathmore system, but now operates with Koch Engineering in a joint venture for future spray dryer sales.
Rockwell/Wheelabrator-Frye: No longer a joint venture, but both are offering spray drying systems.
"Part ofcogeneration system.
'Originally sold by Kennecott Development Co., which was purchased byFlakt in early 1982.
operational. Four units have achieved
performance guarantees and are being
operated by their respective purchas-
ers, including the Celanese, Strath-
more, Argonne, and Container systems.
A fifth unit (Austell Box Board) has
passed compliance tests but has not yet
been turned over to the system purch-
aser. The remaining five units have only
recently become operational, and per-
formance and compliance testing is
planned for early 1984.
Ten new industrial units were sold
since late 1982 for three Federal govern-
ment installations (one Navy and two
Air Force). Each unit will consist of a
lime-based spray dryer equipped with
a single rotary atomizer and followed
by a fabric filter for paniculate collec-
tion. Six of the units will use reverse-air
fabric filters, and the other four will use
pulse-jet fabric filters. Seven units will
use solids recycle. The new industrial
units were sold by General Electric for
the Puget Sound Naval Shipyard (three
boilers, 1.6 percent maximum sulfur
coal), Niro/Joy for the Malmstrom Air
Force Base (three boilers, 1 percent sul-
fur coal), and Ecolaire for the Griffiss Air
Force Base (four boiler, 3 percent sulfur
coal).
Municipal waste incinerators are a re-
latively new application for spray dry-
ing technology. At least two vendors
are conducting research and develop-
ment on the use of spray drying to con-
trol SO2, HCI, and HF emissions from
these incinerators, and Combustion En-
gineering has sold a 40 to 50 MWe equi-
valent spray drying/fabric filter system
for this application.
Spray Drying—Research
and Development Activities
As part of EPA/EPRI-funded process
testing at the Riverside Station, high
sulfur coal (3.4 percent S) was tested
with and without calcium chloride addi-
tion for lime utilization enhancement.
Results of the tests without calcium
chloride showed 90 percent SO2 re-
moval at a reagent ratio of 1.3 to 1.4
and an approach to saturation of 20°F.
With calcium chloride, lime require-
ments were reduced by 20-25 percent.
Other tests conducted at the Riverside
Station involved operation at 75 and 90
percent S02 removal with low sulfur
coal.
High sulfur coal has also been tested
under DOE funding at B&W's Alliance
Research Center and on the spray dry-
ing system at Argonne National Labora-
tory. In addition, preliminary results
have been reported from pilot spray
drying studies by Cottrell Environmen-
tal and Rockwell under joint funding
agreements with TVA. Results from
these four programs showed that, at a
relatively close approach to saturation
of 20°F, reagent ratios of at least 1.3 are
required to achieve 90 percent SO2 re-
moval on high sulfur coals (2.5-4 per-
cent S).
The EPRI-funded pilot tests to date
has focused on low to moderate sulfur
operation. EPRI found that spray dryer
operability and S02 removal are im-
proved with solids recycle. Also, two
simulated cooling tower blowdown
streams were found to be suitable for
spray dryer system makeup water.
In general, these and earlier R&D
programs have indicated that the major
process variables influencing SO2 re-
moval in the spray dryer system are:
(1) fresh reagent ratio, (2) approach to
saturation at the dryer outlet, and (3) re-
cycle ratio. However, optimization of
gas/liquid contact, atomization quality,
and gas residence time in the dryer has
been shown to be important not only
for S02 removal, but also in ensuring
trouble-free spray dryer operation.
Spray dryer operability has also been
shown to improve with increased
weight percent solids (up to 35-40 per-
cent) in the atomizer feed slurry.
Other variables that have been shown
to impact SO2 removal in the spray dry-
ing system are: (1) inlet S02 concentra-
tion, (2) temperature drop across the
spray dryer, (3) slaking water composi-
tion, and (4) lime reactivity.
Results from R&D programs such as
those discussed above, combined with
operating data from full-scale commer-
cial systems and demonstration pro-
grams, have provided better definition
of the important spray dryer FGD de-
sign and operating parameters. How-
ever, consistent well-characterized data
have not been published in several
areas. The six major areas of current
technical interest are: atomization, the
roles of fly ash and recycle solids, high
sulfur coal applications, less expensive
reagents than lime, paniculate collec-
tion and S02 removal in ESPs, and utili-
zation schemes for solid waste.
Recent data from high sulfur coal
(such as Riverside, Argonne, and
B&W's Alliance Research Center) have
provided information on the reagent
ratios, approach to saturation, and recy-
cle ratios required to achieve 90 percent
or greater S02 removals at 2,000-3,000
ppm inlet SOa.^R&D activities for high
sulfur coal continue to focus on optimi-
zation of atomization, spray dryer oper-
ation, solids recycle, and additives to re-
duce fresh reagent requirements. Re-
ducing reagent requirements will be
particularly important to the economics
of high sulfur spray drying because re-
agent-related costs are a major compo-
nent of annual operating costs for these
systems.
Alternate reagents that have been or
are being tested in spray drying R&D
programs include limestone, MgO,
adipic-acid-enhanced lime and lime-
stone, thiosorbic lime, and lime or lime-
stone with CaCI2 addition. As discussed
earlier, recent EPA/EPRI-funded tests at
the Riverside Station showed a 20-25
percent reduction in lime requirements
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for a 3.4 percent sulfur coal with addi-
tion of calcium chloride. Joy/Niro has
also recently demonstrated a lime-
based spray dryer process that removes
both NOX and SOX when NaOH is added
to the feed slurry.
Renewed interest in the particulate
removal performance of ESPs down-
stream of spray dryers has resulted
from the potential applicability of spray
drying as a retrofit technology for acid
rain control. Information needs in this
area include data on the resistivity of
spray drying product for the various
coals and documentation of how FGD
process conditions, such as approach to
saturation and recycle ratio, may affect
this resistivity.
In the waste disposal area, efforts are
being directed primarily toward com-
plete characterization of waste proper-
ties as a function of coal type and FGD
process conditions.
Dry Injection
Dry alkali injection technology has
not yet been commercially applied to
either industrial or utility boilers. How-
ever, the first planned commercial ap-
plication of dry injection technology has
been announced by Public Service
Company of Colorado for a 500 MWe
unit scheduled for start-up in 1990. The
system, which will use trona ore as the
sorbent, will be designed for 70 percent
SO2 removal on a 0.4 percent sulfur
western coal. The sorbent will be in-
jected just upstream of the fabric filter
into flue gas at about 270° to 280°F. A
clay- and plastic-lined landfill will be
used for solids disposal.
A recent study has shown that dry in-
jection economics are extremely sensi-
tive to reagents costs. A key considera-
tion for future dry injection applications
will, therefore, be location of the plant
relative to trona or nahcolite sources.
Another important consideration for
dry injection is the high solubility and
leachability of the sodium-based
wastes. Application of dry injection may
be limited in some locations by the
costs of disposing of the wastes in an
environmentally safe manner.
Electron-Beam Irradiation
Systems
The E-beam process for SOX/NOX con-
trol is in an early developmental state.
Pilot studies on both lime- and am-
monia-based E-beam process config-
urations are currently underway or
planned. These programs are being
partially funded by the DOE and TVA.
Research-Cottrell is developing the E-
beam/lime spray dryer process, while
EBARA International is developing the
E-beam/ammonia injection process.
The pilot systems will treat flue gas
from high sulfur coal-fired boilers.
M. Palazzolo andM. Baviello are with Radian Corporation. Research Triangle Park.
NC 27709.
Theodore G. Brna is the EPA Project Officer (see below).
The complete report, entitled "Status of Dry SOz Control Systems: Fall 1983,"
(Order No. PB 84-232 503; Cost: $14.50, subject to change) 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, NC27711
. S. GOVERNMENT PRINTING OFFICE: 1984/759-102/10676
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
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