Replacing Coal with Over 20 MWe of Clean, Renewable Energy

Outotec’s Fluidized Bed Technology Replaces Coal-FiredBoilers at the U.S. Department of Energy’s Savannah River Nuclear Site in the DOE’s largest energy savings performance contract (ESPC) to date.

The US Department of Energy needed to replace aging and inefficient coal-fired boilers at its Savannah River Nuclear site (SRS). Energy services provider, Ameresco proposed a solution utilizing two, parallel Outotec boiler islands generating 20 MWe of clean, renewable power as well as steam for building heating.

The boilers are fueled using up to 385,000 tons of locally-sourced forestry residues and tire-derived fuel (TDF) per year. Outotec provided the boiler island equipment solution, complete from metering bins to stacks.

Outotec´s bubbling fluidized bed boilers equipped with a patented bed material cleaning, handling, and storage system are able to handle challenging fuels, such as tire derived fuel, as part of the plant´s fuel mixture.

Summary

Download
Download PDF
Customer
Ameresco
Location
United States
Delivery year
2015
Technology
BFB
Commodity
Biomass
Scope
EPS

Challenge

  • High fuel moisture content
  • Mixed fuel types
  • Strict emissions limits

Solution

  • Outotec Bubbling Fluidized Bed Thermal Oxidizer with patented online bed recycling system.
  • Supplied to the client as a “metering bin-to-stack” solution

Benefits

  • Stable operation with varying fuel quality
  • No additional fuel drying needed before combustion
  • No tire-dewiring requirement. Produces ready-to-recycle tire wires

Clean wood chips, sized four inches minus, are sourced from the local area and delivered to the SRS biomass plant via truck. Tire-derived fuel is delivered to the facility and stored in separate fuel bunkers for blending with the primary fuel.

A reclaimer system conveys mixed fuel to the metering bins. The metering bins deliver controlled quantities of the fuels via an air-swept stoker into the thermal oxidizer vessel, which is based on Outotec’s fluidized bed technology.

Initial heat for starting the renewable energy system is provided by overbed and underbed burners fired by biodiesel. The preheated air from the forced-draft system then fluidizes the bed media such that it bubbles like a boiling pot of water. Fuel entering this hot, bubbling bed area, first releases its moisture, and subsequently oxidizes, releasing its thermal energy.

In-bed and vapor space steam tubes improve the thermal efficiency of the system. To increase the efficiency, a flue gas preheater heats the feedwater and an air preheater heats the combustion air while lowering the stack temperature. Hot flue gas rises into the vapor space of the main vessel. NOx abatement occurs inside the main vessel’s upper vapor space via nozzles that spray ammonia into the flue gas, which then reacts with nitrous oxides to form nitrogen, carbon-dioxide and water.

Any remaining heavy, inert fuel contaminants, such as TDF wires, metal or rock are removed from the fluidized bed continuously during normal operation via Outotec’s proprietary bed material cleaning, handling, and storage system. Wires from the tire-derived fuel are recovered via the bed material cleaning and handling system by a magnetic separator. The wires are then placed into a container for recycling as a high- value material.

Flue gas cleanup is accomplished via dry sorbent injection into the flue gas which then enters a pulse-jet fabric filter baghouse. More than 99% of the particulate matter is removed from the flue gas in the baghouse, after which, an induced draft fan disperses it via the stack.

Emissions are monitored via a continuous emissions monitoring system (CEMS)

Scope of Supply

Outotec´s scope included the design, manufacturing and supply of the Bubbling fluidized bed boiler system from the metering bin to the stack.

BFB Plant facts:

Fuel Flow: 510 tpd [464 mtpd] of wood and TDF
Steam Generation: 120,000 lbs/hr x 2 [54.43 tonnes/hr]
Pressure: 865 psia [59.7 bara]
Temperature: 825°F [441°C]
Air Quality Control System:  
Selective non-catalytic reduction (SNCR) NOx abatement system  
Dry sorbent injection Pulse-jet fabric filter  
Continuous emissions monitoring system (CEMS)  
NOx, SOx, PM, HCl, CO, Opacity complies with all standards for the state of South Carolina.  

Share this page