Biomass boilers need a silo for bio fuel storage located near the boiler. From it, an endless screw or suction feeder, takes it to the boiler, where the combustion takes place. The fuel must be stored at an inclination of about 45 ° for proper insertion into the boiler.
The combustion chamber is the whole area where combustion takes place in a boiler, and in which three parts can be clearly distinguished:
The first is the area where the fuel is mixed with the primary air and, by means of a partial combustion, the biomass is gasified, that is, it is transformed into a combustible gas. In the case of stoves or gasification boiler of efflorescence (load from below) would be equivalent to the crucible, in burners would be the fixed grid and in large boilers the mobile grid.
The second is the area where you can clearly see a flame and where the secondary air usually enters.
And finally, the third composed by the rest of the chamber where there is no visible flame. This part continues to produce combustion, but the oxidation concentration is low and invisible to the naked eye, although it is a key area for the reduction of CO and unburned. In some chambers, this space is separated and then called the post-combustion chamber.
As a general rule, the combustion chambers have an optimum working temperature range between 600 and 900°C. Below that temperature, the unburned and CO increase very clearly. On the contrary, above that temperature, NO levels are triggered by oxidation of the nitrogen in the air, and also cause the need to use more resistant and expensive materials in the construction of the chambers.
The temperature of the flame depends on the moisture, density and calorific value of the material to be burnt, which causes it to be much higher or much lower.
The heat generated during this combustion (in this case of natural fuel) is transmitted to the water circuit in the exchanger built into the boiler. The hot water generated is used for heating and sanitary hot water, air conditioning of swimming pools, etc. The heating can be by any of the conventional water systems, for example, under floor heating, radiators or fan coils.
Advanced models include switching on and cleaning the automatic heat exchangers as well as automatic extraction and compression of the ash so they have to be removed a few times a year. Some manufacturers even offer to monitor and control the operation of the boiler.
When burning biomass some ash is produced, which is usually collected automatically in an ashtray that must be emptied about four times a year. The amount generated depends mainly on the fuel used and the power of the gasification boiler.
To optimize the operation of the biomass boiler, we can install an accumulator (depending on the use of the boiler and the manufacturer), which will store the heat in a similar way to a solar energy system.
As you see, they require many more elements than a fossil fuel boiler, and here we have not named many of them. It is therefore logical that they are more expensive, but the price of solid biofuel, much cheaper than conventional fossil fuels will make you recover the initial investment very soon.