10
6.3 - FIREWOOD
Woodisformedmainlybycelluloseandlignite.
It also contains other substances, such as
resin(r-pine),tannin(oak-chestnut)and,
obviously,alargequantityofwater.
Good quality woods are oak, ash, beech,
mapleandfruittrees,exceptcherry;medium
qualitywoodis:chestnutandbirch;sufcient
quality wood: lime tree, poplar and willow.
Resinoustreesare,normally,second-ratequalityfuels.
Wood is therefore an extremely heterogeneous fuel,
due to different essences (beech, oak, fruit, resinous),
different moisture content, and due to different shapes
anddimensions.
Boiler operation will inevitably be effected by all these
factors. Especially by the log dimensions, the moisture
contentandthewaywoodisloadedintheboiler.
6.4 - WOOD MOISTURE
The caloric value of the different types of
wooddependsontheirmoisturecontent,as
illustratedinthetable.Boileroutputandauton-
omywilldiminishasthemoistureincreases.
Thetableprovidesthepowerreductionfactor
basedonthemoistureofthewoodbeingused.
TheheatoutputoftheFIREXboileriscalcu-
latedforwoodwitha15%moisturecontent.
Asanexample,woodwhichhasbeendried
for 2 years in a sheltered area has a 25%
moisturecontent.
Example:
moistureofthewoodbeingused=25%
output=nominaloutputx0.86
6.5 - FIREWOOD DIMENSIONS
The dimensions, together with the moisture
content, contribute to determine the boiler’s
output.Smallpieces(withalength,however,
conforming to indications indicated hereby)
aremoreeasilyammableandthereforehave
the tendency to increase the boiler’s output
andthereforetoreduceitsautonomy.Moreo-
ver,theyfallwithgreaterfacility,inthelower
chamber,reducingtheriskoftheformationof
“bridges”.Theso-called“bridge”isanempty
spaceintherewoodstoragecompartment,whereun-
burntwoodlogsremain.Inthiscasethebedofembersis
notfedwithcontinuityandtherefractoryburner’sslotis
uncovered.Intheseconditions,preferentialairductsare
createdwithaverysmallameduetoanexcessofair.
TheFIREXboilermustbefedwithnaturalwoodlogsof
thelengthsetoutinparagraph6.6.Thelogsectionmust
normallyberound(Øapproximately10cm).
6.6 - START-UP
Ensurethechecksreferredtoinpoint6.2
havebeenperformed.
Closethebottomdoorandpowerthecontrol
board(fortheoperationmode,seepoint6.1).
Openthetoploadingdoorandplacesome
dry wood kindling crosswise on the main
stone,abovethecentralslot.
Usehighlyammablematerialonthewood,avoidinglarge
andsquarelogs.
Lightthewoodusingthinsheetsofpaper(newspaperor
thelike).
Therstignitionofthenewboilercouldbedifcultdueto
moistrefractorycementcasting.
Accordingly,weadvisefullyopeningtheprimaryairand
loweringthesecondaryair.
Closetheupperdoorandwaitafewminutesforthere
tostartandproducesomeembers(about5minutes).
Afterafewminutes,iflookingthroughtheamesightglass
ofthelowerdooryouseethatameinversionisbeginning,
addotherlargerlogs.
Closethetopdoor.
Presskey for1second,andthecombustionphase
willstart.
Correctionfactorsforwoodmoisture
%OF
HUMIDITY
CALORIFIC
VALUE
kWh/kg
CORRECTION
FACTOR
15
20
25
4.50
4.18
3.87
1
0.93
0.86
CALORIFIC
VALUE
MJ/kg
16.20
15.05
13.93
