wood fuel drying- some of the issues - oct 2017 fuel drying: some of the issues -november 2017 since...
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1stFloor,1LinnetCourt,CawledgeBusinessPark,Alnwick,Northumberland,NE662GD.Telephone:07970522160 Website:www.reheat.uk.com:[email protected]
PaperonbehalfoftheWoodFuelSupportService,whichisfundedbyForestryCommissionScotlandandtheScottishGovernment,anddeliveredbyre:heatLimited.
Woodfueldrying:someoftheissues-November2017
Since around 2013, the use of mechanical chip drying
systems,supportedbytheRHI,hasbecomewidespread.It
isnowthenormforwoodchipsuppliers toemploysuch
systemstosomedegreeorotherwithintheirbusinesses.
This has undoubtedly benefited the industry. Customers
enjoy consistently dry wood fuel, avoiding the age-old
problem of high moisture content fuel, particularly
towardstheendof thewinterseason.For fuelsuppliers,
instead of relying on natural seasoning, with the
associated the cash flow problems which arise from
keeping stock in hand for 12 months or more, they are
able to turn fresh timber into dry chips in a matter of
days,andemploytheircapitalresourcesforotherpurposes.
Withoutmechanical chip drying, it is unlikely
that the market would have been able to
meet the demand for dry chip that resulted
fromthe‘RHIboom’of2014-15.
Anumberof solutionshaveappeared.At the
mostbasiclevel,dryingfloorsofferalowcost,
simplesolution,albeitwithgreaterspaceand
mechanicalhandlingrequirementsthanthemoremechanisedsystems.
‘Hook-bin’baseddryingsystemsareagainrelativelylowcost,andcanareplacedoutside,freeingup
expensive barn storage for bulk chips. These are quite labour intensive though, as the containers
needtobepickedupandemptiedintothebulkstores,unlesstheyaretobedelivereddirecttothe
1stFloor,1LinnetCourt,CawledgeBusinessPark,Alnwick,Northumberland,NE662GD.Telephone:07970522160 Website:www.reheat.uk.com:[email protected]
customer. Belt dryers offer perhaps the ultimate in operational efficiency, and control, but come
withahighpricetag.
The effectiveness of the different systems varies. By effectiveness, wemean to what extent the
resultantmoisturecontentcanbecontrolled,andachievereasonablyconsistency.Operators learn
theirsystems,andcompensateaccordinglythough.
What is not clear however is how their
efficiencycompares–theamountoffuelused
in relation to the amount of water removed.
Various factors will impact efficiency – the
effectiveremovalofthemoistureladenair,the
temperatureoftheresultingchips,thecontrol
ofairflowthroughthechips,thetemperature
differential across theheat exchanger, and so
on. None of these questions have ever been
properlyexaminedandreportedinsuchaway
as to allow anyone considering drying can
makeaninformeddecision.
Efficiency is important. Publicmoney is being
usedtosupportthisprocess,andRHIfundsare
finite. Drying has become a difficult issue for
BEISandOfgem tounderstandanddealwith,
hencetherecentconsultation.Dependingontheoutcomeofthisconsultation,thesequestionsmay
becomemuchlessrelevant.
@usewoodfuelscot