18 MWe Renewable Energy Power Plant Eucalyptus Woodchips in Italy

Outotec’s bubbling fluidized bed technology is ideally-suited to meet stringent, European Union emissions regulations.

Outotec was the technology provider of choice for a renewable, biomass-to-energy system in the province of Enna, Italy. The system converts eucalyptus tree chips into steam to generate clean, renewable power.

The equipment was provided as a metering bin-to-stack solution that is based on Outotec’s fluidized bed boiler system.

Outotec energy system is a key component in meeting the stringent air emissions requirements established by the plant’s operating permit.

Outotec's patented fluidized bed technology was selected because of the excellent operating characteristics and superior emissions performance when burning solid fuels.

Outotec´s unique solution for thermal oxidation of solid fuels combines our in-vessel heat transfer tubes with a proprietary bed material cleaning and recirculation system thus ensuring reliable operation with biomass and other solid fuels which may have accompanying inert materials.

The energy system converts approximately 40,000 lbs/hr (136,000 tonnes/year) of eucalyptus wood into 164,400 lbs/hr (74.6 tonnes/hr) of superheated steam, which is used to produce up to a gross output of 18.7 MWe in a steam turbine-generator set.

Summary

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Location
Italy
Delivery year
2013
Technology
BFB
Commodity
Biomass
Scope
EPS

Challenge

  • Variable fuel quality
  • High operating efficiency requirements
  • High amount of inert materials accompanying fuel
  • Strict emissions limits

Solution

  • Outotec Bubbling Fluidized Bed with in-vessel tubes for highly-efficient heat transfer
  • Outotec Proprietary bed cleaning and recycling system

Benefits

  • Stable, efficient operation with varying fuel quality
  • Bed cleaning and recycling system ensure removal of the high volume of inert material
  • Optimum environment for inherently low NOx production and emissions abatement

Initial heat for starting up the renewable energy system is provided by startup burners fired with natural gas. Air from the forced-draft fan fluidizes the bed media such that it bubbles like a boiling pot of water. Processed fuel is then delivered to a dualscrew metering bin located adjacent to and elevated above the fluidized-bed thermal oxidizer. Upon discharge from the bin, the metered fuel gravity-flows to the inlet of an air-swept spreader. Pulsating sweep air disperses the fuel across the 20-foot span of the fluidized bed.

Fuel entering this hot, bubbling bed area, first releases its moisture, then thermally oxidizes at a low, controlled temperature, helping prevent ash from the fuel from melting and coating the boiler tubes. Limestone is also added into the bed in order to improve ash eutectics and capture oxides of sulfur (SOx).

Nitrous Oxides (NOx) abatement occurs inside the main vessel’s upper vapor space via nozzles that spray ammonia into the 1700°F (927°C) flue gas, which then reacts with nitrous oxides to form nitrogen, carbon-dioxide and water.

Any remaining inert fuel contaminants, such as metal or rock are removed from the bed automatically during normal operation via Outotec’s proprietary bed material cleaning, handling, and storage system.

Flue gas cleanup is completed by directing the gas through a pulse-jet fabric filter baghouse. Remaining particulate matter in the flue gas is removed in the baghouse with over 99% efficiency. Lastly, an induced-draft (ID) fan pulls the clean flue gas from the baghouse and disperses it via the stack.

Emissions are monitored via a continuous, emissions-monitoring system (CEMS) which measures carbon monoxide, oxygen, nitrogen oxides, and acid gases.

Scope of Supply:

Outotec supplied a complete boiler island equipment solution from metering bin to stack. Outotec expert advisors were also provided during construction and commissioning.

BFB Plant facts:

Fuel: Eucalyptus wood chips
Fuel consumption: =40,000 lb/hr [435 tonnes/day]
Steam parameters  
Flow: 164,400 lb/hr [74.6 tonnes/hr]
Temperature: 900 °F [482 °C]
Pressure: 900 psia [62 bara]
Air quality control system  
Limestone injection for SOx removal and ash eutectics  
Selective non-catalytic reduction (SNCR) NOx abatement system  
Pulse-jet fabric filter  

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