Co-firing Torrefied Wood with Coal

The torrefaction process is the key element to Integro’s business model for delivering high quality, economical feedstock for electricity generation.  Co-firing involves substituting biomass fuels for a portion of coal in an existing power plant furnace.   This allows the energy in biomass to be converted to electricity with the high efficiency of a modern coal-fired power plant.  

Torrefaction is a thermo-chemical process conducted in an inert gas atmosphere at temperatures of 485°F to 535°F (250°C-270°C) during which the biomass undergoes an extraordinary transformation that overcomes many of the constraints associated with co-firing.  (See Diagram)

Specifically, torrefaction of biomass achieves the following properties:

  1. It is carbon neutral, as all renewable biomass sequesters an equal amount of CO during growth as is released upon its burning
  2. An increase of the heating value per weight unit (9,500 to 11,000 Btu/lb)
  3. Achievement of a hydrophobic property, with a moisture content of less than 3%
  4. Improved grinding, crushing, or pulverizing properties (40 on the Hardgrove Grindability Index, comparable to coal)
  5. Increased uniformity and durability
  6. Removal of volatiles, most acids and smoke-producing agents

The properties produce the following benefits for the coal-fired electrical utility:

  1. Each ton of torrefied wood burned in the facility reduces their carbon output by up to 2.4 tons, earning them an estimated $72 in carbon credits.
  2. Torrefied wood can be handled just like coal.  It can be placed on the coal pile and processed alongside the coal.  It has been tested to 10% and will likely go to 30% mix with coal.
  3. It does not take on water so it can be left uncovered like coal.
  4. It has lower levels of NOx and SOx than coal—primary pollutant emissions by EPA—lowering emissions and associated costs
  5. During the torrefying process, most volatiles are burned off, eliminating the concerns over slagging in the boiler.
  6. Because torrefied wood is handled identically to coal, little or no CapEx is required of the utility.                                  

Integro’s torrefied biomass solution overcomes the limitations previously attributed to biomass co-firing through its unique treatment process.    It produces a high-grade, smokeless fuel suitable for co-firing in coal powered electric plants.