Coal

1
Coal Power-Part 2 What Can Be Done
Differently?
2
Coal Power-Part 2 What Can Be Done
Differently?
1. Technology to Control Smokestack Emissions
Pre-combustion sulfur control technology
(removing sulfur before burning)

• Change the design of the boiler to install
  pressurized fluidized bed combustors (FBC) which
  remove sulfur from coal during the burning
  process.

At right Fluidized bed combustion systems use a
heated bed of sand-like material suspended
(fluidized) within a rising column of air to burn
many types and classes of fuel.
3

• Pre-combustion sulfur control technology
  (removing sulfur before burning)
• coal scrubbing.

At left External view of a coal scrubber is at
the Indianapolis Power Light Co. generating
station in Petersburg, Indiana.
4

• Post-combustion sulfur controls (removing sulfur
  after burning)
• Flue Gas Desulfurization (FGD). In FGD
  processes, waste gases are scrubbed with a
  chemical absorbent such as limestone to remove
  sulfur dioxide. There are many different FGD
  processes, the main ones being the
  limestone-gypsum process and the Wellman-Lord
  regenerative process. The limestone-gypsum FGD
  involves mixing limestone and water with the flue
  gases to produce a slurry which absorbs the
  sulfur dioxide. The slurry is then oxidized to
  calcium sulfate (gypsum) which can then be used
  in the building trade.

FGD at a plant in Cheshire, England.
5
Unlike sulphur, it is not possible to reduce the
nitrogen content of the fuel before combustion by
physical cleaning since it is combined within the
organic matter of the fuel. At present there are
no commercially available methods to reduce
organic nitrogen. Instead, nitrogen oxides can
be removed during combustion. Low nitrogen oxides
burners ensure that the fuel is burnt in low
oxygen concentrations, such that any nitrogen
oxides produced are reduced to nitrogen gas. Once
initial combustion has taken place, further air
is added to the combustion chamber to ensure that
the fuel is completely burnt. Advanced low
nitrogen oxides burners can reduce emissions by
up to 30. Such burners can be installed on
either new or existing power plants.
Nitrogen oxide burner in Fullerton, CA.
6
Unlike sulphur, it is not possible to reduce the
nitrogen content of the fuel before combustion by
physical cleaning since it is combined within the
organic matter of the fuel. At present there are
no commercially available methods to reduce
organic nitrogen. Instead, nitrogen oxides can
be removed during combustion. Low nitrogen oxides
burners ensure that the fuel is burnt in low
oxygen concentrations, such that any nitrogen
oxides produced are reduced to nitrogen gas. Once
initial combustion has taken place, further air
is added to the combustion chamber to ensure that
the fuel is completely burnt. Advanced low
nitrogen oxides burners can reduce emissions by
up to 30. Such burners can be installed on
either new or existing power plants.
Emissions of nitrogen oxides, like for sulphur
dioxide, can also be reduced by treating the
smokestack gases. One method involves mixing the
flue gases with ammonia, converting the nitrogen
oxides to nitrogen and water. This process can
be fitted to existing and new power plants, and
can achieve an emissions reduction of up to 80 to
90.
Nitrogen oxide burner in Fullerton, CA.
7
Current technology can reduce pollution from
coal-fired power plants by over 90, if it is
installed. Most states now require that such
equipment be installed.
8
Current technology can reduce pollution from
coal-fired power plants by over 90, if it is
installed. Most states now require that such
equipment be installed.
Idealized picture, by a power companyno
pollution.
9
2. Technology to change how coal is used in
power plants.
An Integrated Coal-gasification Combined-Cycle
(IGCC) power plant turn the coal into natural
gas (syngas) and burn the gaswhich is easier
to control for emissions.
10
An IGCC power plant in Puertollano, Spain.
11
The coal gasification unit provides clean,
coal-fueled power, with a minimum removal of 95
percent of the sulfur from the coal gas. This
exceeds the performance of today's most advanced
coal-fired generating units. Furthermore,
nitrogen oxides emissions are also lower than
many of todays most advanced coal-fired
generating units. The sulfuric acid and solid
byproducts are then sold for industry use.
Polk IGCC Power Station, along with Tampa
Electric's other power plants, serve customers
across the West Central Florida service area.
12
The plant is considered "zero process water
discharge. A brine concentration unit, which
produces an effluent that is reused in the
process, handles all of the liquid waste. The
combined-cycle technology requires much less
cooling water than conventional technology, and
Tampa Electric was able to modify existing
conventional mine cuts on the phosphate land
(where the plant was built) to become the plants
cooling reservoirTampa Electric
http//www.tampaelectric.com/TEEVPowerPlantsPolk.c
fm
13
What about other IGCC power plants in the US?
From Coal gasification for advanced power
generation by Andrew J. Minchener, Fuel 84
(2005) 2222-2235.
There is one test facility (started by Texaco in
1996). The technology and the economic viability
are what are being tested. What is economically
viable depends on local energy costs and
local/national regulations.
14
The way forward for IGCC power plants At
present coal fired IGCC is not the technology of
choice for power generators since it is deemed to
be a more expensive fossil fuel technology
compared to alternative. Thus in the near term,
when coal fired systems are introduced, it is
likely there will be an emphasis on pulverised
fuel systems with best practice NOx and SO2
control and advance steam conditionsA.J.
Michener (Fuel 2005, just quoted).
15
The way forward for IGCC power plants At
present coal fired IGCC is not the technology of
choice for power generators since it is deemed to
be a more expensive fossil fuel technology
compared to alternative. Thus in the near term,
when coal fired systems are introduced, it is
likely there will be an emphasis on pulverised
fuel systems with best practice NOx and SO2
control and advance steam conditionsA.J.
Michener (Fuel 2005, just quoted). Energy
generation companieslike LS Powerconstantly
review the market and spend a good deal of time
considering likely future regulation. Power
plants have lives of 40 years and the plants
must meet current and future pollutions
requirements.