• There is very little competition on those products. No structured player on small plants is already established.
  • Biogas in landfill and in biodigestion. Biomass leftovers still have to be eliminated, bacterias have health problems, there are problems of leaking of landfills
  • Fixed and moving grate combustors: Much polluting technology, with scarce control of the temperature of combustion, lower combustion efficiency, higher O&M costs
  • Existing Pirolisers: for a lack of control in temperature, the quality of Diesel is poor
  • Gasifiers from India: poor quality, dangerous, polluting for water

Trade off evaluation between grate combustor and Fluid Bed Combustor

Combustion efficiency

  • The typical increment in efficiency of the FBC combustion compared to the grate combustor is between 10 to 12%. In the case of CHP application the typical fuel savings on yearly basis could be 5-6%.
  • Combustion efficiency is greater than 98%.

Emission reduction

  • The thermal and prompt NOx are reduced over 90% and fuel-NOx is lowered to below EU emissions. Furthermore, the total combustion gas mass flow is reduced so the emissions per Nm3 of combustion gas is reduced . By adding the fuel at two stages, conditions of NOx reduction by NH3 are created. The NOx levels with the control of operating conditions could be brought down to below 150 mg/Nm3 corrected to 6%O2. It is not possible to get to such low NOx levels with the grate system
  • CO and VOC emission levels are in the order of 30 and 3 mg/Nm3 corrected to 6%O2 in the flue gases, resulting from very high combustion efficiencies 99% or above.
  • SO2 levels below 5 mg/Nm3 for peat with the addition of sorbents directly to the bed which could partially remove HCl if present.

Other advantages

  • Less sensitive to variations in fuel moisture content as FBC could handle fuels with moisture content up to 40% which is difficult with grate system to be able to maintain high efficiency. The grate system cannot accept such high humidity levels.
  • Lower air excess which is in the order of 25to 30% less.
  • Ability to accept fuel with large particle size variations as grate system is more selective to fuel size. The fuel size range could be 0-50mm. The grate system cannot accept great variations in solid size and preferably the fuel size should be above 10 mm.
  • Very homogeneous and controlled combustion strongly reducing the level of unburned carbon in ashes. The level of unburned carbon will be less than 0.7% of total carbon input. The unburned carbon levels are usually above 4% with the grate system.
  • Much better controlled air staging that permits high efficiency combustion with low levels of CO and NOx. The CO levels will be lower than 30 mg/Nm3 corrected to 6%O2.
  • In-bed removal of SO2 during combustion with 95% capture. This is achieved with the grate system
  • Uniform fuel mixing across the combustor cross sectional area that can ensure that fuel particles will have enough air for combustion. The addition of secondary air to the freeboard to ensure very efficient mixing of air and volatiles for total combustion which could not be achieved so easily with grate systems.
  • Lower operating and maintenance costs having no moving part in the hot zone of the boiler and with very simplified air distributor design. Much simplified ash removal. The combustor zone maintenance could be 20% higher with grate system.
  • If required, possibility of recycling hot ash and sand particles removed to ensure very balanced thermal equilibrium and reduced fuel consumption. This is not possible with the grate system.
  • Controlled air supply to the combustion zone that enables to achieve high turn-down
  • Possibility to have a single unit boiler having a wide range of flexibility in the fed mass flow rate feeding and humidity.