Double combustion pellet stove: how a second flame cuts emissions

How a pellet stove normally burns

In a pellet stove, a feed screw carries pellets from the hopper to a burner pot, where they burn with air supplied by a fan. Combustion is never perfectly complete. Part of the fuel leaves the flame as unburned gases, carbon monoxide and fine particles, and goes straight up the flue.

Those losses matter twice. They are emissions released outside your home, and they are energy contained in the pellet that you paid for but did not turn into heat. They also show up indoors as soot on the glass and ash in the burner pot.

An innovative pellet stove: what double combustion changes

Ambelys produces a first flame that is tall and lively, closer in appearance to a log fire. The gases and fine particles that escape it do not go directly to the flue. They are led through a second flame, a post-combustion zone where the temperature reaches 380 to 800 °C depending on the power setting.

In that second flame, much of what remained unburned is burned inside the stove, before it reaches the flue. The result is that about 95% of each pellet is burned, with very little ash and unburned residue left behind.

This design is protected: Schulhof Energies has filed four European patents with the INPI, the French intellectual property office. You can read more about the company on our made in France page.

• First flame: tall and lively, like a log fire
• Second flame (post-combustion): 380 to 800 °C depending on power
• Unburned gases and fine particles burned inside the stove, before the flue

Measured emissions compared with Ecodesign limits

Ambelys was tested to EN 16510-1:2022 and EN 16510-2-6:2022, the current European standards for residential solid-fuel appliances. The figures below set its results against the Ecodesign limits for comparison.

• Fine particles: 10 mg/Nm³ (Ecodesign limit 20 mg/Nm³)
• Carbon monoxide (CO): 175 mg/Nm³ at 13% O2 (Ecodesign limit 300 mg/Nm³)
• Nitrogen oxides (NOx): 72 mg/Nm³ (Ecodesign limit 200 mg/Nm³)
• Efficiency: 92%

An eco-friendly pellet stove: why the second flame matters

Fine particles are one of the main concerns with wood heating, both for outdoor air quality and for neighbours. With 10 mg/Nm³, Ambelys emits half of the Ecodesign limit for particles. Its CO figure is a little over half the limit, and its NOx figure is around a third of it.

For you, that means an eco-friendly pellet stove: you heat with a renewable fuel while keeping the impact on the air around your home low. If you live in a town or in a valley where smoke tends to linger, a low emission pellet stove is a sensible choice.

Benefits you notice day to day

Post-combustion is not only about test figures. Because so much of the pellet is burned, there is less ash to empty and less residue in the burner pot. Combined with a three-sector airwash, the glass stays clean for days and can be wiped with a dry cloth.

The 92% efficiency means most of the energy in your pellets ends up as heat in the room. With a 30 kg hopper, Ambelys runs for about 17 hours at its full output of 8.8 kW, and longer at the 6 kW setting.

• Cleaner outdoor air: low particle, CO and NOx emissions
• Cleaner glass: three-sector airwash, dry-cloth cleaning
• Less ash: about 95% of each pellet burned
• More heat from each bag: 92% efficiency

A double combustion stove that is also room-sealed and quiet

Double combustion works alongside the other features of Ambelys. It is a room-sealed stove, drawing its combustion air through a concentric flue, and a quiet stove at 38 dB or less. You can see all the specifications, dimensions and prices on the Ambelys pellet stove page.