generation of CFB plants can do it
cleanly and efficiently by capturing
the pollution during the process.”
The CFB’s fuel flexibility is rooted
in its unique flameless, low-temperature
combustion process. Unlike
conventional pulverised coal (PC),
stoker or oil/gas boilers, instead of an
open flame, circulating solids are
used to achieve high combustion and
heat transfer efficiency to burn a wide
range of fuels. The fuel’s ash does not
melt or soften which allows the CFB
to avoid the fouling and corrosion
problems encountered in conventional
boilers.
From an environmental aspect, the
low temperature CFB combustion
process minimises NOx formation
and allows limestone to be fed directly
into the furnace to capture SOx
as the fuel burns. In most cases, selective
catalytic reduction (SCR) and
flue gas desulphurisation (FGD) are
not needed for NOx and SOx control.
This dramatically reduces plant construction,
operating cost and water
consumption while improving plant
reliability and efficiency.
ZFC is initially configured to burn
0-100 per cent domestic hard coal
with 0-40 per cent RDF, thus satisfying
the WFD and IED requirements.
This is equivalent to firing about 200
000 tons of RDF per year in the plant’s
CFB boiler. The fuel supply system is
designed with separate day silos and
chain conveyors that supply each fuel
to the CFB boiler’s front and rear
walls.
There are also provisions in the
plant design to add the capability to
burn 0-100 per cent biomass (including
agro biomass) and 0-60 per cent
coal slurry. Agro biomass includes
energy willow, agro pellets (agricultural
byproducts from straw: wheat,
barley, rye, oat), palm kernel shells
(PKS), sunflower pellets, corn chips,
shea nut cake, and olive cake. By
combusting these locally sourced
residential and industrial wastes, the
facility cuts the region’s CO2 emissions
and at the same time reduces the
Special Project Supplement
member states to increase the amount
of energy consumed for power generation
from renewable sources to 20
per cent by 2020. At the same time
directives on waste management and
use such as the Waste Framework
Directive (WFD) 2008/98, set rules
for waste separation and recycling,
reuse, and limits disposal of waste
materials. New EU rules state that
refuse derived fuels (RDF) with a
heating value greater than 6 MJ/kg
cannot be landfilled in the future.
Indeed waste could become an important
energy resource. In Poland,
waste materials are already collected
and sorted, including metals separation,
by recycling programmes.
Burning this fuel cleanly is being
encouraged through the Industrial
Emissions Directive (IED) 2010/75,
which requires CO2 emissions from
industrial activities, such as CHP
plants burning RDF and biomass fuels,
to remain under 550g/kWh to be
eligible for support through EU capacity
market mechanisms. This
means the CO2 limit in future CHP
systems can only be met by burning a
mixture of coal and biomass or RDF.
The new ZCP plant will demonstrate
how replacing aging coal fired district
heating plants with an integrated fuel
flexible circulating fluidised bed
(CFB) CHP plant burning coal, RDF,
bio-sludge and biomass mixtures
can be a good solution. It increases
overall scale and energy efficiency
of the district heating network, produces
dispatchable electricity, ensures
CO2 emissions remain below winter
package limits, and meets WFD RDF/
biofuels reuse requirements.
Waste recycled fuels when burned
locally also reduce transportation
costs and emissions while extending
the life of the landfill. There are also a
variety of CHP production and other
renewable energy financial incentives
for early adopters that can add to a
plant’s bottom line economics.
It is a solution that Giglio says is
being seen in other markets around
the world. “They are going to what I
call organic energy solutions that are
locally sourced and locally delivered.
Communities – towns, villages, rural,
suburban areas – have an energy
need. They need heating and electricity;
they might have a factory in a
town that needs steam, and they develop
their own ‘closed loop’ energy
solution.
“They build a plant that can burn
locally sourced waste materials, e.g.
from a local factory or paper mill, to
meet their energy, heat and steam
needs. In hot climates, it could also
meet their cooling needs.”
Sourcing local biomass, waste, or
even local coals, can increase energy
security in countries and communities.
For example, the CHP plant
would be more reliable than sourcing
power from an unstable grid, or if a
country was dependent on importing
a particular fuel. “If a market for this
fuel becomes tight, you might have to
pay a premium or you might not be
able to get the fuel at all,” noted
Giglio. “These closed loop solutions
protect communities from import fuel
market risks.”
ZFC will be able burn a wide range
of locally sourced fuels, and equally
importantly, it will do it cleanly.
“The old grate-type or stoker boilers
could do this combination burning
but with high emissions and low
efficiency,” said Giglio. “The new
THE ENERGY INDUSTRY TIMES - MARCH 2018
Multi-fuel capability: ZFC
will efficiently combust a
wide range of coal and RDF
mixtures, while remaining
under SO2 and NOx
emissions limits. The plant
will also have provisions to
burn biomass and coal slurry
A conceptual drawing of a
small-scale CHP CFB plant
designed to burn mixtures of
locally available fuels