Transcript Big Sandy Plant

Big Sandy Plant
Update
Loesche Dynamic Classifier
2012
Executive Summary
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20% increase in fuel thru put was noticed on this pulverizer
Total overall project cost: ~ $1 million (labor and material)
Project time line - 8 weeks (one shift); 6000 man hours **
Initial testing shows installation on all 6 pulverizers would produce a
spare pulverizer (based on this one)
• System wide revenue potential ~ $9.5M based on lost MWH’s from
GADS data
• Other potential benefits include NOx reduction with improved
fineness, increased mill performance and increased boiler efficiency
thru improved combustion
• Project under review by AEP Program Management Office as an
Engage 2 Gain idea
** All craft hours – removal and install
Background
• Big Sandy Plant’s Unit 2 is an 800 MW
Foster Wheeler Boiler with six MB23
hybrid MPS 89 Pulverizers.
• Full load requires all six Pulverizers.
• One Pulverizer O/S is approximately 100
MW curtailment.
History
• MPS mills in 2010 accounted for 286,080 MWH’s of
curtailments on the 800 and 1300 series units.
• The 800mw series without spare mills lost 263,850
MWH’s while the 1300mw series with spare mills only
lost 22,230 MWH’s
• Inspections and rebuilds accounted for 150,000 MWH’s
of curtailments in 2010 on the 800mw series.
• Pulverizer Inspections (only) were the 4th Largest driver
of Plant EFOR in 800mw units in the last 7 years.
• Given these statistics AEP is looking for ways to reduce
these curtailments.
Project
• Loesche approached AEP and it was agreed to
install one of their Dynamic Classifiers at Big
Sandy Plant on the #21 Pulverizer.
• Loesche claimed 15% - 20% increase in thru put
at the current fineness or improved fineness at
same thru put.
• If successful and installed on all mills, this would
allow minimal unit load curtailment when one
mill is out of service.
Removal of existing classifier
• During the fall outage of 2012 the installation / removal began on
Pulverizer 21. All the coal piping, shutoff gates and walkways on top
of the mill had to be removed to clear the top area and the classifier
reject chute was cut loose from the inside. The existing seal air
piping for the roll wheels was removed to later be reinstalled going
thru the new classifier housing.
• Once these items were removed, the top flange of the classifier
housing was all that needed to be unbolted to remove the housing
and classifier assembly as a whole. Once removed the reject chute
was lifted up thru the top opening of the mill.
• No other internal parts had to be removed and the large
maintenance doors stayed closed on the mill. For safety reasons,
the spring tension was released for fear of not knowing what forces
could be on a 40 year old housing after removing the top section.
Removal Continued
• The removal of the existing classifier and housing had
some challenges. The existing trolley beams could not
make the lift due to the angle of the pull. Lifting beams
had to be fabricated to keep a straight pull on the
structure.
• The tight clearances were the biggest challenge to
overcome. We had to find dimensionally small chain
hoist and shackles that were load rated. Once found,
there was only 4 inches clearance between the upper
and the lower housing.
• The yoke seal air piping on the pulverizer next to this
one had to be removed to allow for room to lower the old
classifier and housing to the ground. There was only a
few inches on each side between the two pulverizers
when setting on the floor.
Background continued
Installation
• The new classifier was made in two sections. This
helped with the installation since the overall height of the
new classifier was taller. The lower housing section
included the classifier lower cone which hung below the
flange line. This required this section to be raised high
to clear the housing on the pulverizer. Loesche
accounted for these issues in the design and
engineering and installed lifting lugs such that the new
lifting beams worked on the two new sections.
Installation
• The classifier fit perfectly. No modifications were needed.
• The ancillary equipment however did need slight modifications. The
walkways, platforms and seal air pipe had to be modified in the field
to make them fit. Loesche performed a laser survey of the area
prior to the project and used it in the design all of the equipment.
However, there were still some modifications necessary. Loesche
provided quick assistance on correcting these and any other
problems or issues that would arise.
• Some of the new coal pipe spool pieces were already completely
fabricated while some required to be field fit and the flange welded
on.
Installation
• Due to limiting seal air available from our existing pulverizer seal air
system, Loesche provided two seal air fans to provide seal air for
the bearing cavity on the classifier; a duty and backup fan. These
were sized to provide enough air for any additional classifiers and
occupy approximately 6 ft x 10 ft section of floor.
• We also had no expansion room in our existing DCS system and
limited available power in the local motor control center. Loesche
designed and provided a PLC control system, a variable speed drive
unit for the classifier motor, a transformer, a motor control section
and a HMI for the new classifier. All of these items required
approximately 6 ft x 15 ft section of floor.
• The new MCC section had to be powered from the 600 VAC
switchgear in the 4kv room. Overall there was a considerable
amount of cable pulls that had to be made.
Block diagram of cable
Installation / Removal
• Overall, the installation and removal went well. There were minor
issues that were always quickly resolved.
• The total contractor labor was approximately 6000 man hours for
both the removal and installation. This is for all crafts; electrical,
mechanical, insulators (lead abatement) and the scaffold contractor.
• The controls were a bit more difficult. The company that had built
and tested the PLC programming logic inadvertently had left
simulated points in the programming and did not get all the point
names changed to the correct program before shipping. This took
several hours to decipher before things worked as they should.
Installation / Removal continued
• Reasons for high man hours: 1) First time evolution. 2)
This pulverizer has limited access from one side. All
coal pipes, platforms and anything lifted had to be
coordinated and made from one side. (Any other
pulverizer 22 – 26 has access from both sides making
coordinating lifting easier.)
• Loesche had a service man on site to help oversee the
installation, startup and testing during the project. They
provided guidance, answered questions and found
solutions to any issue. They wanted to prove success as
much as we wanted it.
Future Installs
• For future installs on the remaining 5 pulverizers, the electrical
system would have to be copied 5 times over with the exception of
the PLC. The MCC’s could be reduced in foot print but would need
to be fed from more than one 600 VAC buss to obtain reliability.
This would require several square feet of real-estate. (This may not
be required for everyone)
• While the seal air fans provided by Loesche are larger than required
for the one classifier, consideration should be given to power feeds
to provide reliability in the event a 600 volt buss had to be removed
from service.
• Overall project cost would be reduced. Most engineering and
design should be completed. Advanced planning and coordination
would reduce labor time since this has now been performed.
Testing
• No other internal work or maintenance was performed on
this pulverizer to obtain a true test of what the classifier
could produce on it’s own.
• Once the unit returned to service, testing was performed
following the procedure from Loesche.
• Testing was conducted before and after the change out
to determine what if any improvement was made with the
new classifier.
• AEPSC, Loesche, REO and plant personnel assisted in
the test work using the EUCoalsizer laser probe to
perform the fineness testing.
Test continued
• The following are the test results:
PRE
POST
Classifier RPM
Coal Flow
50 - MESH
200 - MESH
HGI
------------------
87
99.35
50.8
70
90
99
53.7
48
75
105
99.7
60.025
48
80
110
99.725
61.75
48
95
90
99.525
62.35
48
70
105
98.775
55
51
70
110
99.1
58.375
51
70
115
99.325
58.475
51
65
115
98.2
56.15
51
100
87
99.75
66.95
51
Testing Conclusion
• While the goal was to increase thru put without effecting
fineness, it can be seen in the test results this was
achieved along with the potential for increased fineness.
• This mill was previously limited to approximately 87,000
– 90,000 lb/hr coal thru put due to excessive dribble and
primary air limited. There were multiple fires from coal
build up both internal in the mill and in the pyrites in the
past.
• With the Loesche Classifier, we were able to obtain
significantly more PA Differential and pass 115,000 lb/hr
coal flow with out any dribble while maintaining fineness
at pre change out levels.
Conclusion
• When the unit returned to service this mill had an original 600 hp
motor. While testing at 115,000 lb/hr coal flow, mill amps continued
to increase over time. Fearing an overload trip, the mill was reduced
to 110,000 lb/hr without mill amperage increasing. This is over a
20% increase in thru put on this mill.
• Mill amperage was a limiting factor in the higher RPM trials while
determining the improvement in fineness and this is why the faster
speeds could not be maintained and allow more thru put.
• During our most recent outage, this pulverizer motor has been
increased to 700 hp and new testing will be conducted to determine
maximum output on the mill and also an optimum speed for the
classifier to obtain the best fineness with maximum output.
Conclusion
• While the Loesche Classifier did what they promised,
other manufactures also make dynamic classifiers.
• Other technologies that predict saving time with reduced
maintenance, provide increased thru put and improve
mill performance need to be looked at and tested.
• We (AEP) need to continue to focus on improving
pulverizer performance both in output and reduced
outages. Remember 286,080 MWH’s is a lot of
curtailments and lost revenue.
QUESTIONS??