THE ENERGY INDUSTRY TIMES - MARCH 2018
of 242°C.
For a CHP plant that is also being
used to handle municipal waste, ZFC
is fairly large; only a few sites in Poland
would be suited to a plant of this
type and size. Many of the municipalities
have smaller energy and/or
waste handling requirements and
would therefore be better suited to a
smaller installation. Future plants of
this type in Poland are therefore likely
to be the trend.
Many (55 per cent) of the country’s
district heating systems are small or
middle sized, with a steam capacity
between 10 and 200 MWth supplied
from grate hot water heaters fired by
hard coal. Existing plants average 25-
30 MWth heating load. If an average
size “small” district heating system is
considered to be 26 MWth, this size
CHP plant is applicable to hundreds
of municipalities in Poland.
Such a plant would be a scaled-down
version of ZFC, producing about 41
t/h of steam at 67.5 bara/490°C over
a load range of 40-100 per cent. An
extraction-condensing steam turbine
will produce 10.9 MWe with a maximum
district heating capacity of 26
MWth when supplied with 140°C
feedwater temperature. The boiler
can also utilise higher steam parameters
(90 bar, 520°C).
Based on these design parameters,
the small multi-fuel CHP plant would
have an annual production of 74 GWh
of electricity and 76 GWh of heat. A
yearly average fuel mix of 50 per cent
Special Project Supplement
amount of waste material. Since 2016,
landfill of any waste product with a
LHV of more than 6 MJ/kg has been
prohibited in the EU.
The plant’s SO2 and NOx emissions
will remain well below the IED requirements
of 150 mg/Nm3 when
burning design coal and biomass
mixes using only furnace limestone
injection and SNCR, respectively.
When firing RDF, it meets the current
WID (Waste Incineration Directive)
and LCP BAT (Large Combustion
Plant, Best Available Techniques)
rules ratified on April 28, 2017 that
require compliance by 2020 and define
the emission limits for many other
pollutants.
These pollutants are removed by an
external flue gas cleaning system
consisting of a CFB scrubber (for
SO3, HF, and HCl removal) and a
pulverised activated coal injection
system (for heavy metals, TOC, furan,
and dioxin removal). Particulate emissions
from the stack are controlled by
a four-compartment pulse jet fabric
filter. Provisions for more stringent
emissions limits were also considered
in the boiler design, such as space to
accommodate a future SCR catalyst
and excess capacity designed into the
external flue gas cleaning system.
ZFC will have an estimated annual
production of approximately 730
GWh of heat and 550 GWh of electricity.
Full thermal load represents
270 t/h of steam flow at 92 bar and
536°C with a feedwater temperature
coal, 40 per cent RDF, and 10 per cent
bio-sludge equates to an annual consumption
of 22 800 tonnes of coal, 32
200 tonnes of RDF and 16 300 tonnes
of bio-sludge. The plant would use the
same emission control technology as
ZFC, and so would similarly limit
pollutants produced from the burning
of these fuels. Notably, the example
26 MWth CHP plant produces CO2
emissions that are more than 50 per
cent less than the national average for
coal fired district heating plants.
In addition to having the ability to
burn a range of fuels cleanly, smallscale
CHP plants have a number of
other advantages.
Local power plants create local jobs,
and such a CHP installation requires
more operators to run the plant and
sort and prepare fuel than would be
needed for a package boiler or enginebased
facility.
There can also be a good economic
case for this type of plant. Because of
the recycled waste fuel they burn, some
of these CHP plants can compete in the
energy spot market against large centralised
coal plants. Further, since many
of the main components can be modularised
and built off-site, both the construction
costs and time to build can be
kept down. But much depends on the
specifics of the site and its operation.
Giglio explained: “The economics
get more complicated with these
types of plant. When you look at a
coal plant, the economics are strongly
based on the price of the coal, capital
cost of the plant and the selling price
of electricity. But these CHP plants
depend on multiple fuel sources. And
for trash, you are paid to take the
trash – it’s called a tipping fee – which
needs to be high enough to make the
economics work… but much depends
on how much you pay for the other
fuels – the coal and the biomass – and
the logistics of getting the trash to the
plant.”
He noted, however, that the value of
these small-scale CFB CHP plants is
not just about economics; it is about
value to a community. Giving an example,
he explained: “A paper mill
typically builds a cogeneration plant
on site to convert its waste wood into
steam and power needed to run the
mill. This is just that same type of
thinking, but extended beyond the
mill for the benefit of the nearby town,
which would be connected to the same
heating and power system. It’s like
extending an industrial captive power
application to a municipal or community
level.”
He noted that producing power and
steam from burning waste in smallscale
plants will always be more expensive
than burning natural gas or
coal in large power plants.
“For these small CHP plants, the
fuels are very variable and unique to
the region or community and the plant
is custom-designed for each application.
It’s not like a big coal plant,
where you take a cookie-cutter approach
– by building the same plant
repeatedly to squeeze all the cost out
of it. But when you look at it holistically
– in terms of environmental,
energy security and the community
needs – it offer high value.”
Giglio is therefore confident in the
market prospects for distributed
multi-fuel CHP plants, citing a number
of areas where they could be utilised.
“Developing countries are a
good example,” he said. “India, for
example has many villages – many of
which are not connected to the grid –
but yet they have these waste fuels
and local fuels available to them; so
it’s a solution there. It’s a solution for
Eastern Europe, where the concept
works well for small industrial towns.
Other countries like Bangladesh and
countries in Africa, which are prime
for this solution, don’t have policies
as progressive as in Poland but they
are coming.”
There will certainly be more opportunities
as environmental pressure
grows and countries move away from
large centralised coal plant. Sumitomo
FW is seeing a growing need for these
organic energy solutions in countries
like South Korea and Japan, where
power demand is strong and costs are
high due to import fuel.
In Korea, this approach is being
encouraged on a larger scale, where
similar plants are being built of up to
100 MWe. Sumitomo FW’s Dangjin
plant started as a coal/biomass plant
– capable of burning 100 per cent of
either fuel – but now no longer burns
coal due to new environmental laws.
The plant now only burns locally
sourced recycled wood as well as
wood pellets and PKS imported
mainly from Indonesia.
With waste becoming a growing
problem in many countries, the deployment
of plants able to convert
waste to energy is likely to grow over
time. Certainly small-scale plants that
can integrate heat, power production,
waste recycling with the ability to burn
carbon-neutral fuels is an elegant solution
to the challenges facing communities
now and in the coming years.
The multi-fuel CHP plant
shows a much better CO2
performance than a coal fired
CHP unit and rests well below
not only the national average,
but also below the upper
limit of eligibility for support
through the capacity market
mechanism
The Dangjin 1 Biomass Power
Plant now only burns locally
sourced recycled wood as
well as wood pellets and palm
kernel shells