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Design - Justsen Biomass Boilers

Justsen have over 50 years of experience in the development of large scale biomass boilers with a design focus on efficiency, reliability, longevity and flexibility. See details below:

  • Unique water cooled moving grate principal (click here to read more), with scraping action to clean the air holes that deliver air to the gasification process. The grate bars remain stationary, while hydraulically actuated retractable plates slide out from underneath. This allows the fuel pile to be moved down the boiler at a controlled speed to ensure full burnout. The ash and char is kept moving and rolling over, ensuring full combustion and not allowing it to sit still which would allow clinker formation. Each section of the grate is individually controlled to allow a wide range of fuel types to be optimally burnt.
  • Water cooling of every single grate bar via 5 cross pipes with forced circulation, ensures there are no hot spots on the grate that would allow clinker formation. This is possible because the grate bars remain stationary, with hydraulically actuated retractable plates that slide out from underneath. Many competitors move the actual grate bars, as such only every other grate bar can be water cooled.
  • Large grate area per kW output allows the use of low calorific value or very wet fuels, whilst still allowing the rated power output (many competitions boilers are rated at nominal power output with dry, good quality fuel only)
  • Large heat exchangers with ideal gas flow velocity to ensure minimal fouling in the tubes and to allow for continued efficient operation with a high degree of fouling
  • Water cooling throughout the entire boiler, including the sides of the grate (combustion area). This allows control of combustion temperatures in key areas, preventing the build-up of slag or clinker on the combustion grate. This allows continued operation at high heat loads even with poor quality / high ash fuels prone to clinkering.
  • Ceramic tiles mounted high up in secondary combustion areas allow the correct combustion temperatures to be maintained, ensuring maximum efficiency and lowest possible emissions. These tiles are only installed in places that will not refract heat to the fuel pile and cause clinker (e.g. as in a fully brick lined boiler). Versions with or without tiles are available suitable for <60% / >35% moisture content fuels
  • Large diameter augers with a large pitch (spacing) allow use of larger granular sizes, and allow for successful transport of ‘oversize’ or rogue non-wood elements commonly found in clean waste fuels for example.
  • Trough shaped augers reduce torque and power consumption.
  • Properly dimensioned auger transfer drops minimise the chance of blockages, even with oversize in the fuel
  • Automated compressed air cleaning of fuel level sensors to prevent stoppages due to dirty sensors – critical particularly if using dusty and or wet fuels

    Pause or kindle mode removes the need for automatic ignition. The boiler maintains a fire bed at all times, even when heat demand is low. This allows for very quick response to heat demand, and maximise reliability by removing ignition problems. This mode of operation is particularly important for burning wet fuels and is highly suited to high heat load applications. Heat output in pause mode is ~2% of nominal output.
  • Bespoke fuel feeding systems / controls packages allow the boiler to be tailored to any specific requirements. Boilers for water and steam at a large range of temperatures and pressures are also available.
  • Specially constructed boilers to burn specific fuels are also available
Design Process
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