MATS Compliance Initiative at Grant Town Power Plant

Report
MATS Compliance Initiative
at
Grant Town Power Plant
Background Information
• Grant Town looked at requirements of MATS and learned early on in that
process that Acid Gas emissions were likely our biggest hurdle to
overcome
• Stack testing confirmed HCl emissions were some 12x higher than the
proposed limit in MATS – 0.024 lb/mmBTU versus the limit of 0.002
lb/mmBTU
• Typical SO2 emissions average 0.5 – 0.55 lb/mmBTU thus requiring a 90%
SO2 removal efficiency per requirements of the WVDEP air permit. In
order to comply with the surrogate HCl limit, SO2 emissions would need to
be reduced to less than 0.20 lb/mmBTU – excess of 96% SO2 removal
• Staff was not initially sure that additional limestone injection alone would
meet the surrogate limit
Initial Testing
• Series of three test periods using additional limestone injection to meet
HCL surrogate have been run – latest during CEMS RATA testing of 2014
• Consistently have met surrogate limit with no observed detriments to
boiler operation in the short term
i.
Limestone Feed System able to keep pace with increased input –
appears input increases about 15- 20% to meet lower SO2 limit
ii. Ash systems able to handle additional loading without limitation
iii. Limestone processing system capable of additional production to
meet increased demand – increased run time from a average of 10
hours per day to approximately 12 hours per day
iv. With limited test intervals, boiler tube erosion rates have not been
quantified, though certainly would increase with additional
limestone feed
Initial Reactions
• Even though additional limestone feed had proven compliance to the HCl
surrogate was possible, several items needed to be considered moving
forward with this option:
a.
Reliability of the current limestone feed system and limestone
processing system to meet boiler production demands
b. Cost of supply of additional limestone and could the current
supplier meet those levels of supply
c. Erosion impacts on the boiler tubing – in particular the combustor
waterwalls
d. Other operational impacts
•
Baghouse bag life
•
Wear and tear on ash handling systems
•
Expense of additional limestone processing
Thoughts for Alternative Compliance Options
• In 2010, Grant Town had been approached by EnviroResolutions to test a
“hybrid” scrubber design that had been developed for control of
particulates from diesel powered ships in the marine industry
• EnviroResolutions had tested their concept scrubber on a biomass fired
facility and found that by varying the solution of the scrubber medium
significant reductions in SO2 could be achieved
• Looking to test on a coal fired facility for proof of concept and that SO2
emissions could be reduced enough to prove the technology as a viable
alternative to conventional post-combustion control technologies
• Grant Town agreed to test pilot scale system – thought at that time the
system might offer more economic approach to SO2 control
EnviroResolution Pilot Scale Unit
Pilot Scale Test
•
Slip stream of flue gas taken from Boiler B to the pilot scale unit –
approximately 1.5% of total boiler combustion gas flow – about 2,000 ACFM
•
SO2 measurements taken at inlet and outlet to the test unit to verify reduction
•
Three test runs using hydrated lime as the scrubbing fluid
•
Results indicated high levels of SO2 removal
a) Average SO2 in to test unit – 157 ppm
b) Average SO2 out from test unit – 1.32 ppm
c) Average Removal Efficiency – 99.2%
•
Results confirmed that the technology was likely a good fit for additional SO2
control – considered as an option for CAIR/CSAPR compliance at that time
but not implemented
EnviroResolutions and MATS Compliance
•
As more became know with the MTAS program, EnviroResolutions was
approached by Grant Town to consider their system as an alternative to
provide control for Acid Gas Emissions
•
Options considered included a modular approach to control emissions from
one boiler or a slip stream of both boilers to reduce SO2 to the HCl surrogate
•
Initial design concept was to reduce SO2 emissions just low enough to meet
MATS
•
Modelling lead us to believe the entire SO2 scheme could be realized using the
EnviroResolutions system
•
Entered into agreement with EnviroResolutions to complete additional
modeling, economic analysis and independent third party feasibility study to
determine if the technology was viable for a CFB application
EnviroResolutions and MATS Compliance
• Issues with combining cooled stack gas from the scrubber outlet back with
the uncooled gas from the other boiler/remaining from the slipstream led
to a change in the conceptual design
• Current concept has a total of 6 scrubber modules to provide 100% SO2
control
• Modeling and analysis of our current limestone supply would indicate that
it would be acceptable for the scrubbing fluid for the system – current
processing system could be used to grind the raw limestone to a size
consist suitable for mixing for the scrubber
• Significant reduction in the amount of limestone consumed to meet
compliance versus the amount required to meet the MATS HCl surrogate
Preliminary Design
Preliminary Design
Preliminary Design
Concerns with Current Design Concept
Beyond proof of concept – items to consider moving forward:
• Will the CFBs be able to maintain steaming rate if limestone is no longer
added to the combustor
•
Disposal of the scrubber residual sludge could present an issue with ash
disposal
i.
Storage of residuals during periods when ash is not being unloaded
ii. Impact of residual on ash stream quality – beneficial reuse status
impacts – modeled but not physically proven
iii. Stability concerns for ash disposal areas
•
Affordability of the project if economic justification proves beneficial
•
Impacts to other CFB/IPP operators
Current Status
• Grant Town obtained an extension of the MATS compliance deadline from
WVDEP moving our compliance date until April 16, 2016
• MPR Associates currently finalizing initial draft of the feasibility study
review for proof of concept
• Detailed economic analysis to be completed once feasibility study report
finalized and pricing proposals are firmed up
• Considering/pursuing other post combustion scrubber options as well
i.
MHPSA Post Combustion Controls
ii. CBPGA Post Combustion Controls
Potential GHG Impact
• Although not fully quantified at the time of this presentation, the scrubber
could offer potential reductions in the emissions of CO2 given the
reduction in the amount of limestone required for SO2 compliance. More
research and modeling will need to be completed to fully understand the
potential benefits of CO2 reduction
Questions???

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