Pellets and Boilers

Boilers for emergency operation with pellets and firewood

Boilers can burn wood with or without low conversion work (rust). Wood pellets are not standard fuel, only a sort of bridge.

Normally, the combustion takes place following the upper fire principle (upper combustion) with intermediate grids. The relatively small pellet fire zone is used as feed chamber.


Disadvantages

Frequent refills

The burn is not clean

Unsatisfactory exhaust efficiency and wood quality
Pellet boilers can only be used with an authorization.

Combi boilers

- Top or bottom flanged fire boilers

Pellet burners can be modified in log boilers with little effort for low conversion times. Usually, the laterally flanged pellet burner is removed and the area is covered.


- Under-fire wood boilers with almost no modifications


Both logs and pellets can be used. In this case, the combustion chamber is adjusted with two fuels and has a special design. However, there is a small insertion/removal discomfort.

- Under-fire piece of wood boilers without modifications

Both logs and pellets can be used. Two separate firing systems are used and there is a common heat exchanger. The conversion is completed automatically.


Special solutions

A more expensive but also more variable solution is the combination of a special wood boiler with a pellet boiler.

Power control

It can be operated automatically in several pre-set levels or directly. The fuel and combustion air supplies vary. The best energy savings can be achieved with this type of boiler.
The control range is usually between 100% (full load) and 50% (partial load).

Below the lowest heat output, the plants operate in conjunction with an automatic ignition device or switch off.

Combustion control (firing control)

This is an additional function for power control. It guarantees a high burn-out and a high efficiency level.
The controlled variable is the setting of an optimum fuel/air ratio.

Lambda control

The lambda probe measures the excess air (O2) content in the exhaust stream. This is a defined value for the best CO values. In case of divergence, the fuel and air supplies are adjusted automatically. The probe is relatively expensive and has a limited life.

Good combustion and exhaust emissions can be achieved in a well-balanced pellet plant but also with a much cheaper temperature sensor.