9
Technical features and dimensions
fig. 3
AIREX BOILER STRUCTURE
The hydraulic system inside the boiler is designed in such a
way that a thermostatic system keeps always the water tem-
perature high that surrounds the wood storage room so as to
eliminate the dangerous phenomenon of condensation.
The boiler is composed of two oval elements placed inside
each other, so that between the two a cavity of water (Fig. 3)
is formed.
We can distinguish the following parts (fig.3):
1. Fire wood storage and drying area
2. Gasification zone
3. Embers zone
4. Refractory burner
5. Combustion chamber
6. Heat exchange surface
7. Refractory steel cradle
8. Boiler water
9. Thermostatic system
10. Safety heat exchanger
M C.H. system flow
R C.H. system return
fig. 4
A
A
M
R
8
7
9
10
1
2
3
4
5
6
GASIFICATION ZONE (2)
The gasification takes place in the lower part of the firewood
storage.
It is very important that the gasification is as regular as possible,
so as not to overload the burner with gas. The gasification speed
depends on the quantity of the wood and the dimensions of the
drying area. Generally, it is better to use large logs if they are
dry and small logs if the wood is wet . The quantity of primary
air, proportional to the delivered output, is regulated via the
adjustment system.
EXCHANGE SURFACE (6)
As the boiler operates on wood, and because the sulphur con-
centrations are not very high , it is important to obtain very low
smoke temperatures in order to increase the water efficiency.
To obtain this Unical has opted for an exchange surface with
dry smoke passes (fig. 4), which have already been extensively
tested in oil fired boilers working at low water temperature, thus
permitting low smoke temperatures without danger of conden-
sate forming.
The surfaces of the dry passages “A” (fig. 4) have had incisions
made on them in order to avoid dilatation problems.
The solid residues of combustion (ashes), which lie on the high
temperature refractory-lined cradle (fig. 3, pos. 7,) will become,
with the time, always lighter until they will be dragged by the
gas speed and will be deposited in the lowest area of the rear
smoke chamber, from which they will be removed during the
cleaning operation.
REFRACTORY BURNER (4)
The burner is made up of refractory stone (fig. 3, pos. 4).
This stone has an oval central opening through which the flame
passes.
The embers lie directly on the main stone which divides the fire
wood storage from the lower combustion chamber.
Furthermore the main refractory stone has a rectangular seat in
which the opportunely grooved cast iron fire bars are placed (fig.
5, pos. 2), which receive the secondary air from a front distributor.
