Technical
Paper
Slag Control Treatment Program at EKPC
Spurlock Station
Authors:
Mark Gabriel, Manager, Business Development, GE
Water & Process Technologies
Logan Pickrell, Process Engineer, East Kentucky
Power Cooperative
Abstract
Coal burning power plants today are challenged by
economic slowdowns and lower prices for the electric power they produce. With reduced power prices,
many power companies are looking to stay competitive by burning lower cost, lower quality fuels.
Switching fuels can often be more difficult for the
plants to burn. Moreover, the most efficient and low
cost producing plants are being kept at higher load
for longer periods of time than ever before. The
changes in fuel quality and boiler operation have
caused many plants to experience an increase in
slag deposits on the furnace walls and superheater
sections of their boilers.
Spurlock Station boilers 1 and 2 are sub-critical boilers with a capacity of 340 MW and 585 MW respectively. Both units currently burn 100% Illinois Basin
coal. Illinois Basin coal is high sulfur, low fusion
temperature coal. Burning some Illinois Basin coals
would create a buildup of hard slag formation inside
the boiler. Typical issues included the formation of
large clinkers on SH assemblies. Spurlock Station
has experienced large slag falls causing boiler damage and safety concerns.
In January of 2010, Spurlock started treating their
boilers with a unique GE Water & Process Technologies chemical additive to reduce the detrimental
effects of burning high slagging index, low fusion
temperature coal. This paper describes how the
evaluation was conducted and summarizes the
boiler performance results.
Discussion
In addition to carbon, hydrogen and oxygen found
in coal, there are numerous inorganic impurities
that are not combustible and contribute to slagging and convective pass fouling in the boiler.
These inorganic constituents impact the ash fusion temperatures. Fusion temperatures often
can correlate directly to the tendency for slag
formation in the boiler. Slag deposits form when
boiler fireside temperatures exceed the fusion
temperature of the ash.
Slag density increases with time and temperature,
creating a deposit that is hard and difficult to remove with normal sootblowing. If the sootblowers
cannot remove the ash build up from the upper
areas of the boiler in a timely manner, the slag
deposits can continue to grow, harden, and form
to an enormous size. These slag deposits typically
form on the leading edge of the platen superheat
tubes, secondary superheater tubes or pendant
reheat tubes located above the furnace or above
the bull nose of the boiler. When the slag eventually does fall, it can puncture slope tubes or damage entire sections of the lower furnace, forcing
unscheduled downtime and lost generation.
Fouling deposits may also form in the convective
back-pass sections of the boiler by condensation
of gaseous ash components. Fouling deposits are
typically associated with the Vertical Reheater,
Primary Superheater, and Horizontal Reheater
tubes. Fouling deposits can bridge across these
tubes and restrict gas flow to the point of furnace
plugging off. Fouling may result in a Unit derating
on load, or force the boiler to be shut down for a
cleaning.
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TP1190EN.doc Jul-11
2. Also, clinkers that did form were much more
difficult to grind in the bottom ash grinding operation. Operating experience also showed that under operating conditions of 100% of Coal-A,
conditions could deteriorate in a matter of a few
days. In order to minimize the impact of the high
sulfur ILB coal, Spurlock Station opted to blend
their high sulfur, high slagging index coal with
lower sulfur, higher cost coal. Table 1 shows the
plants typical fuel sources, tonnage and relative
cost.
The impact of slagging and fouling can be costly.
The lost economics can be the result of unit derates,
unscheduled outages, high cleaning cost, repair
costs from slag fall damage, and incremental costs
associated having to burn more expensive fuels.
Chemical additives in combination with mechanical
ash removing devices can improve control of slagging and fouling deposits on the fireside of the boiler
and reduce their overall negative impact.
Boiler Operating History
Chemical Additive for Slag Control
Spurlock Station boilers 1 and 2 are sub-critical boilers with a capacity of 340 MW and 585 MW respectively. Unit 1 is a B&W opposed wall-fired design
while Unit 2 is a CE T-fired design. The scrubber for
Spurlock Unit 2 became operational in October of
2008 while the scrubber for Unit 1 became operational in June of 2009. Installing the scrubbers allowed Spurlock to switch from low-sulfur
compliance coal to high sulfur Illinois Basin coal.
Cost advantages of high sulfur Illinois Basin coal
were significant, however there were concerns that
slagging tendencies would increase significantly.
Fuelsolv* FMG2960 is a highly concentrated oil
based liquid additive that contains a proprietary
blend of magnesium and copper based compounds. Its primary use is to inhibit slag build up
on the radiant sections of the boiler (furnace walls,
nose arch, radiant superheaters, and finishing superheaters). It works by altering the sintering
characteristics of slag. The FMG2960 is fed directly
to the coal, which greatly simplifies the feed.
Transition metals and other multivalent metals
such as copper have been used for many years as
combustion catalysts. Not as well known is that
copper, in combination with magnesium, can be
an effective slag control agent and acts to reduce
the cohesive strength of ash particles. If the cohesive strength is reduced, the ash becomes more
friable and easily removed by soot blowing and
operational load shedding.
Operating experience in 2009 showed that burning
100% of Illinois Basin (ILB) Coal-A caused a severe
slagging situation that resulted in the formation of
large clinkers on the bottom of Pendant Platen
Superheat assemblies on Unit 1. Severe slagging
caused bridging across RH assemblies, blockage of
gas lanes, costly de-rates and slag falls and resulted
in unscheduled outages for off-line cleaning on Unit
Coal Source
Relative Price,
$/MMBTU
Heat Value,
BTU
Sulfur Content
lb/MMBtu
Slagging Index
Tons/ Month
Coal-A
$0.0000
11,200
6.79
2.81
45,000
Coal-B
$0.1995
12,500
4.13
0.95
30,000
Coal-C
$0.2466
11,300
5.21
1.50
15,000
Coal-D
$0.3463
11,300
5.21
1.50
25,000
Coal-E
$0.5011
11,000
5.92
1.50
30,000
Coal-F
$0.6343
12,200
6.57
2.01
20,000
Coal-G
$0.8309
11,500
4.05
0.89
20,000
Coal-H
$1.8857
11,500
4.87
1.13
20,000
Table 1
Page 2
Technical Paper
Treatment Application
Fuelsolv FMG2960 was applied directly to the coal at
the Unit 1 and 2 Crusher House. The target dosage
was 75 ml of FMG2960 per ton of coal treated. See
Figure 3.
FMG2960 feed was automated to two belts, PC1A
and PC1B. Typically PC1A feeds Unit 1 while PC1B
feeds Unit 2, however either belt can feed either
unit. Chemical feed was automated using a 4-20 mA
signal from each belt scale, with coal-on-belt and
belt running permissive signals. An ACTech Variable
Frequency Drive (VFD) and Periflo peristaltic chemical metering pump were dedicated to each belt. The
Fuelsolv FMG2960 was delivered to the plant in 240gallon totes and transferred using a high volume
transfer pump.
A temporary feed system, for the purpose of conducting an evaluation of the FuelSolv FMG2960 slag
control technology was relatively simple to install
once all of the feed system components were on
site. The feed system for Spurlock station was installed and operational in about 3 weeks’ time. (See
Figure 1 and Figure 2)

Hard slag formation across Pendant RH on
Unit 2

Clinker formation on bottom of Pendant SH on
Unit 2

Large clinker formation on Platen SH sections
on Unit 1

Damaging slag falls on both units

Unscheduled down time due to slag falls

Unscheduled down time for off-line cleaning
Boiler Performance

Derates due to uncontrolled slag formation
The objective of the FuelSolv FMG2960 slag control
program was to minimize the impact of slagging
while burning a high percentage of lowest cost, high
sulfur, high slagging index coal. The intent was to
burn 100% of Coal-A during an initial evaluation,
when possible. Success of the program would be
determined by the following criteria:
Tools
Technical Paper
A number of different tools were used to document the conditions in the boilers treated with the
FuelSolv FMG2960. These included:

FMG2960 Application Rate

Visual Inspections

Slag Ratings
Page 3

Digital Infrared Photography

Digital Videography

Off-line inspections with standard digital photography

Daily Coal Belt Samples
The FMG2960 Application Rate was monitored daily. Actual product usage was compared to coal tonnage since last reading to calculate milliliters of
FMG2960 per ton of coal and compared to the target rate of 75 ml/ton. Application rate monitoring
provides alerts to potential feed system problems
and helps ensure a consistent product application
rate over time. Figure 4 shows typical application
rate over time. The addition of a 4-20 mA signal
from each coal belt improved overall application
rate control.
Figure 4
Visual Inspections were conducted on a daily basis
and recorded in a Visio template with Digital IR
Photography. The inspections establish a point in
time record and form the basis for daily slag ratings.
Figures 5 and 6 represent examples of the inspection document format.
Slag Ratings were developed in order to convert
information from visual observations into empirical
data. The data can then be used to trend performance of the slag control program when compared
to coal quality or other boiler operating conditions.
The slag rating used is on a scale from 0 to 5 with
boiler specific criteria for each level. A slag rating of
0 represents very little slag formation while a rating
of 5 represents severe slag conditions.
Page 4
Figure 5
Digital Videography was used routinely to record
conditions and observe the impact of periodic
events such as soot blowing. A standard digital
video camera in an air-cooled enclosure was typically used to record slag buildup between RH assemblies from either sidewall observation port on
the Unit 2 CE boiler, in 15-30 second video clips.
Off-line inspections documented with digital photography were conducted following every planned
and unplanned outage. Inspections were conducted at the earliest possible time following boiler cool down. This is the best time to examine the
fireside of the boiler for clinkers. It is also a good
time to assess the ability for existing slag to shed
as the boiler cools down and the friability of any
remaining slag
Technical Paper
significantly with the addition of the FMG2960 slag
control program.
Unit 2 operated at very good levels of slag control
throughout the evaluation period. The feed of the
highest slagging index coal began following the
start of the FMG2960 slag control treatment program.
Daily Coal Samples were conducted to provide a
reference to coal and ash quality through the early
stages of the FMG2960 evaluation. The intention
was to compare coal quality to observed slagging
conditions in the treated boilers.
The evaluation period on Unit 2 began on
1/29/2010 and ended on 5/9/2010. Throughout
this period plant operations experienced no observed clinker formation on Planten SH and were
able to consistently control slag buildup at the hot
spot on the right side of the Front Pendant RH.
Results Summary
Unit 1 and 2 began evaluations of the FMG 2960 at
different points in 2010. Unit 2 began its slag control evaluation on January 29th, while Unit 1 began
its slag control evaluation on April 19th. The plan
with Unit 2 was to run 3 of 5 silos with 100% Coal-A
throughout the evaluation period. The plan with Unit
1 was to run 100% Coal-A during its evaluation period. In the past, Spurlock Station was unable to run
either boiler with this fuel diet. In both cases, baseline information from visual observations was established.
Slag Ratings-Unit 1 operated at high slag ratings for
the period of approximately 3 months leading to the
start of the FMG2960 evaluation. Slag buildup in
trouble spots on Unit 1 decreased significantly as
indicated by the visual observations and the resultant slag ratings.
Figure 7 shows Unit 1 slag rating over time versus
coal burned. Coal-A and Coal-F are the highest
slagging index coals. Overall slag control improved
Technical Paper
Unit 2 slag control was most effective when sootblowers IK#5 through IK#10 were deployed every
3 to 4 hours. However compressed air capacity
was a limiting factor at times, restricting sootblower availability.
Infrared Digital Photo- The ability to control slag
was evident when comparing observed conditions
prior to and during treatment with the FuelSolv
FMG2960 additive.
Page 5
Unit 1-100% Illinois Basin Coal-No Treatment
Unt 1- Bottom of Rear SH Platen from Front wall at
Center Right 6-18-10
Unt 1- Pendant SH from Front wall Right
3-26-10
Unt 1- Pendant SH from Front wall Left
3-26-10
Heavy slag buildup on SH Pendants and bottom
edge of SH Platens. Slag falls from Platens caused
damage to lower furnace tubes.
No Slag buildup on SH Pendants. No Clinkers on bottom edge of SH Platens. No slag falls from Platens.
Unit 2 experienced similar results. The FuelSolv
FMG2960 treatment program did not eliminate slag
buildup; however, slag that did develop was more
friable and easier to remove with sootblowing.
Outages
Unit 2 experienced three outages in March, May
and October 2010, following the start of the FuelSolv FMG2960 treatment program.
In the March outage, clean gas paths between RH
assemblies were observed. Little slag was seen on
the bottom of the SH Pendants. The slag that was
present was a very brittle and friable deposit that
shed easily as the unit came down and cooled.
Some wall clinkers that did not shed as the unit
cooled were present. The largest wall clinker at
the Left Front Wall trouble spot was removed with
a shotgun in about an hour. Compared to the prePage 6
Technical Paper
vious clinker in the same location, the clinker was
more brittle and easier to remove. The previous
clinker had to be high-pressure water blasted.
possible to soot blow the areas where slag buildup
occurred at the frequency that was required.
Unit 2-October 12th Outage
Likewise in the May outage, most existing clinkers
shed as the unit came down and cooled. The largest
wall clinker at the Left Front Wall trouble spot was
removed with a shotgun in about 10 minutes. Compared to the previous clinker in the same location,
the clinker was more brittle and easier to remove.
The previous clinker took about an hour to remove.
No off-line, high-pressure water blasting was required.
Unit 2-March 5th Outage
SH Pendant,
Bullnose and RH
from IK #10
In the Unit 2 October outage, some slag was observed at the bottom of the RH at the bullnose near
the right corner. Mostly clear gas paths were observed between RH assemblies. The large clinker at
the Left Front Wall trouble spot would not break up
with a shotgun but shed as the boiler temperature
dropped overnight. Small clinkers present at the
bottom of SH Platens were easily removed with a
shotgun. Aside from some small clinkers, furnace
walls appeared very clean.
Lower Bullnose and SH
Assemblies from IK#1
RH Gas Lane Right Wall
from IK #10
Lower Bullnose and SH
Assemblies from IK#2
Impact of Load Drop
Unit 2 experienced 18 days at the highest slag rating due to bridging on right RH & inability to remove
with sootblowing. Under these circumstances Unit 2
was dispatched to a reduced load causing slag to
shed. No noise or damage was caused by the thermal de-slag.
Burning the same coal blend in 2009,
Through some periods during the FuelSolv FMG2960
treatment program, the ability to soot-blow was limited. This was primarily due to limitations of the
plants compressed air system. It was not always
Furnace pressure went positive and everything
behind the RH went very negative.
Technical Paper

Slag developed over 80% of RH

ID Fan Inlet pressure equaled –33 inches

Furnace pressure at +9.6 inches (Unit trips at
+10 inches)
Page 7
Fuel Cost Savings
Unit 2 RH from Right Wall at IK #10 7-2-10
As many as eight different Illinois Basin coal
sources were used to fuel Units 1 and 2 in 2010.
Coal-A was the lowest cost, but the coal with the
highest slagging tendencies. In the past Spurlock
Station was unable to continuously burn Coal-A.
Burning alternate fuels came at an incremental
cost per ton. Coal-A comprised 22% of all coal
burned in 2010. Relative costs of all fuels are
shown in Table 10. Minimum savings associated
with the ability to burn Coal-A are shown in Table
11 while maximum savings are shown in Table 12.
Replacing Coal-A with 100% Coal-B is not practical and so the total Fuel Cost savings are realistically between $2,413,000 and $7,600,000.
Total operating cost for the FuelSolv FMG2960
program is estimated at $2,172,000.
Conclusions
Unit 2 RH from Right Wall at IK #10 after De-rate 7-4-10
Impact of Slagging and Fouling Index
The fouling index of coal burned in Unit 2 increased
significantly. EKPC Spurlock found a different type of
buildup during the May 2010 Air Heater repair outage. A lighter weight fouling deposit was seen as
opposed to the heavy slag typically seen. Slagging
or fouling that did form came off tubes easier with
sootblowing. Figure 9 shows coal slagging and fouling index plotted against slag rating.
We saw Unit 2 slag rating increase due to deterioration of burner tips over time.
Page 8
The FuelSolv FMG2960 program was successful
when applied directly to a coal belt and combined
with targeted sootblowing practices. Application
of FMG2960 slag control chemistry with consistent
boiler operating practices produced the following
results:

Eliminated clinkers on Unit 1 SH Platens and
eliminated damaging slag falls

Reduced pluggage on Unit 2 RH. Slag that
formed was brittle and easily removed with air
sootblowers

The majority of slag that developed shed at
shutdown, eliminating much of the cost of offline high pressure water blasting

Slag that did form broke up very easily, significantly reducing problems with grinding hard
bottom ash

FMG2960 enabled EKPC Spurlock to regularly
burn high slagging coals without pluggage or
large slag falls

Enabled EKPC Spurlock to burn high slagging
coals that they were not able to burn in the
past

Reduced overall fuel costs by as much as
$7,000,000 per year
Technical Paper
Table 10
Supplier
Incremental Delivered
Price, $/ MMBtu
BTU/lb
Tons/Month
Coal A
$0.0000
11,200
45,000
Coal B
$0.1995
12,500
30,000
Coal C
$0.2466
11,300
15,000
Coal D
$0.3463
11,300
25,000
Coal E
$0.5011
11,000
30,000
Coal F
$0.6343
12,200
20,000
Coal G
$0.8309
11,500
20,000
Coal H
$1.8857
11,500
20,000
Total Tons
205,000
Total Tons Non “Coal A”
160,000
Table 11
Alternative to
“Coal A” Source
% of Total Coal
Burned (less
Coal A)
Equivalent Tons
MMBtu
Monthly
Savings
Annual Savings
Coal B
100
40,320
1,008,000
$201,096
$2,413,052
Total Savings Assuming Replacement with 100% of Lowest Cost Alternative
$2,413,052
Table 12
Alternate to
“Coal A” Source
% of Total Coal
Burned (less
Coal A)
Equivalent Tons
MMBtu
Monthly
Savings
Annual Savings
Coal B
18.8
7,560
189,000
$37,706
$452,466
Coal C
9.4
4,181
94,500
$23,304
$279,644
Coal D
15.6
6,969
157,500
$54,542
$654,507
Coal E
18.8
8,591
189,000
$94,708
$1,136,495
Coal F
12.5
5,164
126,000
$79,922
$959,062
Coal G
12.5
5,478
126,000
$104,693
$1,256,321
Coal H
12.5
5,478
126,000
$237598
$2,851,178
$632,473
$7,589,673
Total Savings Assuming Replacement with Historical Proportion of Alternatives
Technical Paper
Page 9