ANINDIRECT-FIREDROTARYSUGARCANEBAGASSETORREFYER:DESIGNANDPERFORMANCEbyAlexisBelonio,IsidoreAlcantaraandDanielBelonioSugarmillsbasicallyrequirealotofpowerforthermalaswellasforelectricaluses.Boilers,whichareusedintheproductionofsugarcrystals,consumealotofbiomassfueltoboilwaterinordertoproducesteamwhich,inturn,vaporizessugarcanejuice.Sugarbagassearealsousedtofuelsteamturbineorgasifiertogenerateelectricitytorunelectricmotorsthatdrivedifferentmachinerypartsofthesugarmill.Sugarbagasseandcanetrashesaretwopotentialsourcesofbiomassfuelthatcanbeusedtoaugmentenergysupplyinthemill,particularlyforheatingapplicationandforgeneratingelectricalpower.Basically,0.33tonofsugarbagasseisproducedpertonofrawsugarcanemilledintheplantandaround5tonsofcanetrashisavailableperhectareofsugarcaneplantation.Despitetheirabundantsupply,however,thesebiomassmaterialsarenotcommonlyutilizedinsugarmilloperationsduetotheirhighmoisturecontent(morethan55%)andtotheirhygroscopicnaturewhichmakesthemdifficulttodry.Toeradicatethem,especiallyduringpreparationofthefieldforthenextplanting,thecurrentpracticeisbyspreadingandburningthemopenlyinthefieldproducingheavysmokepollutionandemittingcarbondioxidetotheatmosphere.Tomitigatesuchproblems,anindirect-firedrotarysugarcanebagassetorrefyerwasdesignedandtested.Thetorrefiedmaterial,whichisagoodqualityfuel,canbeusedasfuelforsteamboilersmakingtheproductionofheatandthegenerationofelectricalpowerfortheplantmoreefficientandreliable.Intorrefaction,themoistureandpartsofvolatilemattersinthematerialsareremovedhenceleavinghigheramountofcombustiblesolidsandgasespresentinthematerial.Theindirect-firedrotarytorrefyer,showninFigures1,2,and3,wasdesignedtoproducetorrefiedfuelfromsugarcanebagasse.Itconsistsofthefollowingmajorcomponents

Figure1.TheSugar-CaneBagasseTorrefyer(SCBT).

TechnicalBulletinNo.40

Figure2.Left-SideViewofSCBT.

Figure3.Right-SideViewofSCBT.

namely:(1)RotaryTorrefyingCylinder,(2)BeltConveyorFeeder,(3)BiomassFurnace,(4)HammerMill,(5)PneumaticConveyorCooler,and(6)StorageBin.Itwasdesignedtotorrefydriedsugarcanebagassebyconductionheatinginarotatingcylinderusingchoppedsugarcanetrashasfuelforthefurnace.Therotarytorrefyingmachineiswheresugarcanebagasseissubjectedtoconductionheatingtoremovemoistureandalittleofvolatilematter.Table1givesthedesignspecificationofthemachine.Therotatingcylinder,whichismadeof5mm-thickMSplate,hasadiameterof1.2mandalengthof9.6mrotatingataspeedof6.5rpm.ARC160sprocket-and-chaindrivewith5-hpgearmotor(1:3)isusedtorotatethecylinder.Thecylinderisinclinedat2degreestoallow

Figure4.TheBiomassFurnace. Figure5.TheBeltConveyor.

slowmovementofthematerialfromtheinlettotheoutletendofthecylinder.Insidetherotatingcylinderare16pcsof10cm-widestraightbaffles,with1-cmstiffenerforeachbaffle,thatliftsandstirsthematerialwhilepassingfromoneendtotheotherendofthecylinder.Therotatingcylinderisheatedbyhotfluegasfromthebiomassfurnace(Fig.4)locatedradiallyattheinletsectionofthecylinder.Fluegasentersandtravelsthroughtheannularspacebetweentherotatingandthestationarycylindersandexitsthroughthechimneylocatedattheendsectionofthecylinder.Heatistransferredintothematerialbyconductionheatinginarotatingcylinderwheremoistureandsomevolatilemattersareremoved.Twobeltconveyors(Fig.5)feedthedryrawsugarcanebagasseintotherotatingcylinderofthetorrefyer.Onebeltconveyorhasa10-mlength,0.4-mwidthand10-mmthicknessmadeofrubber.Theotherhas8-mlengthandofthesamewidthwiththefirstconveyor.Botharedrivenby2-hpgearmotors,whicharepositionedinseriesperpendicularlywitheachothertofacilitatemovementoffreshlydriedsugarcanebagassefromtherotarydryertothetorrefyer.Ontheotherhand,thebiomassfurnacesuppliestheneededheatbythetorrefyer.Itisadoubleinclined-gratefurnacewithinduced-draftblowertosupplytherequiredamountofheat.Ithasa1.2m-diameterby2m-highcombustionchamberinsulatedwithlocally-producedrefractorycement.Sugarcanetrashesarechoppedintosuitablesizeandareusedasfuelforthefurnace.A20cm-diameterscrewconveyorrunningataspeedof24rpmisusedtofeedthefuelintothefurnace.Manualloadingofcanetrashissometimesdonetoobtainsufficientamountofheatforthetorrefyer.Thetorrefiedsugarcanebagasseisimmediatelyreducedinsizeinafastrotatinghammerlocatedattheoutletendofthetorrefyingmachine.Apneumaticconveyor,equippedwithabackward-curved-bladeblower,isusedtocoolandtodeliverfinetorrefiedsugarcanebagasseintoarectangularstoragebin.Thestoragebinisequippedwitha0.6m-diameterby0.9m-longcycloneseparatortominimizedustemissiontotheatmosphereduringoperation.Dischargingoftorrefiedmaterialsisaccomplishedwiththeuseofascrewdischargefeeder.SchematicdrawingofthetorrefyingmachineisshowninFigure6.

Type IndirectRotaryCylinderDiameterandLength 1.2mDx9.6mLInclination 2degBaffles 16pcsstraight10-cmwideSpeedofRotation 6.5rpmPowerSource 5-hpgearmotorHeatSource BiomassFurnaceFuel ChoppedSugarCaneTrashFeedingMethod ScrewFeederandManualAirSupply PrimaryAir ½-hpcentrifugalblowerSecondaryAir 3-in.electricblowerSize-ReductionEquipment HammerMillPowerSource 3-hpElectricMotorConveyor PneumaticAir-MovingDevice CentrifugalFanat3,600

rpm,3.7kWDuct 20cmDx50mLCycloneSeparator 0.6mDx0.9mLBin Size 1.8mx1.8mx3.2mDischargeMechanism 20-cmscrew

Table1.DesignSpecificationofSCBT.

PerformancetestingofSCBTtorrefyershowedthatsugarcanebagassecanbesuccessfullytorrefiedinthemachineusingsugarcanetrashasfuelforthefurnace.ThemachinecanbesimplyoperatedbyswitchingONthemotorsthatdrivethevariouspartsofthetorrefyer.Theuseofafrequencyinverterforthemotorsfacilitatesthechangingofspeedofthecylinderandoftheothermachineparts.Sugarcanetrashwithenergycontentofabout16,260kJ/kgandisusedasfuelforthefurnacetosupplytheneededheatbythetorrefyer,canbeeasilyignitedinstartingupthefurnace.Spontaneouscombustionofsugarcanetrashfuelinthefurnaceisachievedwithinaminute.OncethebloweratthefurnaceisswitchedON,tremendousburningoffuelisobservedandflamemovesdirectlytowardstherotatingcylinder.AsshowninTable2,sugarcanebagasseisfedintotheheatedrotatingcylinderatarateof60kgperhourusingaspringscalefortherecordedtimeof1.2hours,anditsmoistureimmediatelydropsfrom13%to0%afterpassingthetorrefyer.Moisturemeasurementwastakenusingaprobe-typemoisturemeter.Theburningrateofsugarcane DESCRIPTIONITEM QTY

1

2

3 1

REFERENCE/MATERIAL

4

45

6 1

1

1

7 1

DESCRIPTIONITEM QTYREFERENCE/MATERIAL

1 FRAMING 5

2 PERFORATED SHEET 1

SEE DWG NO. 04

S.S. PERFORATED SHEET 2MMØ STAGGERED

DESCRIPTIONITEM QTYREFERENCE/MATERIAL

1 DUCT 1

2 FLANGE 1

M.S. PLATE 3MM

M.S. PLATE 5MM

DESCRIPTIONITEM QTYREFERENCE/MATERIAL

1 MAIN SUPPORT 4

2 DIAGONALS 6

G.I. PIPE 2-1/2"Ø SCH40

ANGLE BAR 25 X 25 X 3MM

3 TOP PLATE 4

4 BOTTOM PLATE 4

M.S. PLATE 3MM

M.S. PLATE 6MM

DATEDESCRIPTIONREV APPROVEDDATEDESCRIPTIONREV APPROVEDDATEDESCRIPTIONREV APPROVEDDATEDESCRIPTIONREV APPROVED

DATEDESCRIPTIONREV APPROVED

DATEDESCRIPTIONREV APPROVED

1220

2440

1220

4" COMPACTED

GRAVEL

20MM CONCRETE

COVER

BAR EXPOSED TO GROUND

TO BE COATED W/ EPOXY PRIMER

1110

1220 1220 1220

1630

1220

2440

1210

600

620

1525

1125

150

100

150

10MM VERTICAL

BAR @ 500MM

SPACING ON CENTER.

10MM HORIZONTAL

BAR @ 500MM SPACING

ON CENTER.

3 AT 500MM SPACING,

REST AT 250MM SPACING.

50

400

325

4-8MMØ THROUGHHOLE FOR 8MM

THREADED ROD.

Ø905

Ø1005

700

200

150

150

150

WALL SECTION

SCALE: NTS

1

02

DETAIL A

SCALE: NTS

2

02

DETAIL OF

DOOR OPENING

SCALE: NTS

3

02

DETAIL OF

SUPPORT FRAME

SCALE: NTS

1

07

DETAIL OF

BOTTOM PLATE

SCALE: NTS

3

07

DETAIL OF

TOP PLATE

SCALE: NTS

2

07

DETAIL OF FIXED

FLOOR FRAMING

SCALE: NTS

1

06

DETAIL OF

PERF. FLOORING

SCALE:

1

05 NTS

500

350

420

95

200

120

400

325

375

200

175

115

135

22°

48°

150

DETAIL OF

HOPPER

SCALE: NTS

4

04

DETAIL OF

REAR BAR

SCALE: NTS

3

04EXPLODED

ASSEMBLY

SCALE: NTS

1

04

DETAIL OF DOOR

SCALE: NTS

2

04

DESIGNED BY:

DRAWN BY:

CHECKED BY:

TOLERANCES ARE:

LINEAR

ANGULAR

DIMENSIONS:UNLESS OTHERWISE

SPECIFIED

1234

C

B

A

M

± 1MM± 1°

D

SHEETREVSIZE DWG NO.

THIRD ANGLE PROJECTION

TITLE:

FRAME SUPPORT 1

1

0A

DESIGNED BY:

DRAWN BY:

CHECKED BY:

TOLERANCES ARE:

LINEAR

ANGULAR

DIMENSIONS:UNLESS OTHERWISE

SPECIFIED

1234

C

B

A

M

± 1MM± 1°

D

SHEETREVSIZE DWG NO.

THIRD ANGLE PROJECTION

TITLE:

FIXED FLOOR FRAMING 1

1

0A

DESIGNED BY:

DRAWN BY:

CHECKED BY:

TOLERANCES ARE:

LINEAR

ANGULAR

DIMENSIONS:UNLESS OTHERWISE

SPECIFIED

1234

C

B

A

M

± 1MM± 1°

D

SHEETREVSIZE DWG NO.

THIRD ANGLE PROJECTION

TITLE:

PERFORATED FLOORING 1

1

0A

DESIGNED BY:

DRAWN BY:

CHECKED BY:

TOLERANCES ARE:

LINEAR

ANGULAR

DIMENSIONS:UNLESS OTHERWISE

SPECIFIED

1234

C

B

A

M

± 1MM± 1°

D

SHEETREVSIZE DWG NO.

THIRD ANGLE PROJECTION

TITLE:

DISCHARGE DOOR ASSEMBLY 1

2

0A

DESIGNED BY:

DRAWN BY:

CHECKED BY:

TOLERANCES ARE:

LINEAR

ANGULAR

DIMENSIONS:UNLESS OTHERWISE

SPECIFIED

1234

C

B

A

M

± 1MM± 1°

D

SHEETREVSIZE DWG NO.

THIRD ANGLE PROJECTION

TITLE:

DESIGNED BY:

DRAWN BY:

CHECKED BY:

TOLERANCES ARE:

LINEAR

ANGULAR

DIMENSIONS:UNLESS OTHERWISE

SPECIFIED

1234

C

B

A

M

± 1MM± 1°

D

SHEETREVSIZE DWG NO.

THIRD ANGLE PROJECTION

TITLE:

CONCRETE WALL 1

2

0A

DESIGNED BY:

DRAWN BY:

CHECKED BY:

TOLERANCES ARE:

LINEAR

ANGULAR

DIMENSIONS:UNLESS OTHERWISE

SPECIFIED

1234

C

B

A

M

± 1MM± 1°

D

SHEETREVSIZE DWG NO.

THIRD ANGLE PROJECTION

TITLE:

AIR INLET DUCT 1

1

0A 2

2

0A

DESIGNED BY:

DRAWN BY:

CHECKED BY:

TOLERANCES ARE:

LINEAR

ANGULAR

DIMENSIONS:UNLESS OTHERWISE

SPECIFIED

1234

C

B

A

M

± 1MM± 1°

D

SHEETREVSIZE DWG NO.

THIRD ANGLE PROJECTION

TITLE:

CONCRETE WALL 2

2

0A

DISCHARGE DOOR ASSEMBLY

400

150

DETAIL OF AIR

INLET DUCT

SCALE: NTS

2

04

150

250

TITLE: MATERIALS ESTIMATE FOR BIN OF 6T FLATBED DRYER

SHEETREV

1

1

0

PREPARED BY:

CHECKED BY:

DATE:

MATERIALSITEM QTY/PCS

1 ANGLE BAR 25 X 25 X 3MM 31

2 ANGLE BAR 50 X 50 X 5MM 17

6 METERS

3 FLAT BAR 50 X 3MM

4 FLAT BAR 25 X 3MM

STD. SIZE

6 METERS

5 G.I. PIPE 2-1/2"Ø SCH40 4

6 G.I. PIPE 3/4"Ø SCH20 1

6 METERS

7 S.S. PERFORATED SHEET 2MMØ X 1.2MM THICK

8 G.I. SHEET GA.16

6 METERS

9 M.S. PLATE 3MM 1

10 M.S. PLATE 5MM 17

11 THREADED ROD M10 X 150MM LONG W/ 2PCS

12 EXPANSION BOLT 12MMØ

13 CEMENT 55

14 SAND 4

40 KG BAG

15 GRAVEL

CUBIC METER

6 METERS

6 METERS

2

1

OR ORDINARY SHEET 2MMØ X 1.5MM THICK1220 X 2440 12

1220 X 2440 1

1220 X 2440

HALF OF 1220 X 2440

HEX NUT AND 2 PCS FLAT WASHER

24PCS

PCS

CUBIC METER 8

15 TIE WIRE KG

15 10MM REINFORCEMENT BAR 6M 88

DOOR

HANDLE SUPPORT

HANDLE

2

2REAR BAR

G.I. SHEET GA.16

THREADED ROD W/ 2 PCS HEX

HOPPER FLANGE

FLAT BAR 25 X 3MM

G.I. PIPE 20MMØ SCH. 20

FLAT BAR 50 X 3MM & FLAT BAR 25 X 3MM

8MMØ X 150MM LONG

FLAT BAR 50 X 3MM

NUT & 2 PCS PLAIN WASHER

HOPPER G.I. SHEET GA. 16

12MMØHOLE

FB 50 X 3MM

50

50

X 1.2MM THICK

CLASS A

(1:2:4)

CONCRETE

WALL

Ø15

30

50

NOTE"/S

1. DIMENSIONS SHOULD FIT IN THE FIXED FLOOR FRAMING

ASSEMBLY. ADJUST DIMENSIONS WHEN NECESSARY.

NOTE"/S

1. DIMENSIONS MAY DIFFER IN THE ACTUAL SET-UP OF THE

BIN. ADJUST DIMENSIONS WHEN NECESSARY.

DESIGNED BY:

DRAWN BY:

CHECKED BY:

TOLERANCES ARE:

LINEAR

ANGULAR

DIMENSIONS:UNLESS OTHERWISE

SPECIFIED

1234

C

B

A

M

± 1MM± 1°

D

SHEETREVSIZE DWG NO.

THIRD ANGLE PROJECTION

TITLE:

4

4

0A

PROPOSED BAGASSETORREFACTION PLANT

9

3.5

ELEVATION VIEW

SCALE: NTS

1

00

Biomass SugarCaneBagasseMoistureContentInitial 13%MoistureContentFinal 0%ThroughputCapacity 60kgperhourFuelUsed SugarCaneTrashConsumptionRate 45kgperhourFuel-to-MaterialRatio 0.75kgfuel/kgmaterialTemperature Furnace 640°to805°CDuct 468°to674°CChimney 95°to150°CSurfaceTemperature CylinderInlet 299°to440°CCylinderOutlet 53°to70°CColorofTorrefiedBiomass LighttoPaleBrown

Figure6.SchematicDrawingoftheTorrefyingMachine.

Table2.PerformanceofSCBT.

trashinthefurnaceis45.3kgperhourwithmaterial-to-fuelratioof0.75.Measurementoftemperatureshowedthatatthefurnacecombustionchamberthereadingobtainedrangesfrom640°to805°C,thatattheductbetweenthefurnaceandtherotatingcylinderrangesfrom468°to674°Candthatatthechimneyoutletrangesfrom95°to150°C.Surfacetemperaturetakenattheinletsectionofthestationarycylinderusinginfraredthermometerrangesfrom299°to440°Candthatattheoutletendofthecylinderrangesfrom53°to70°C.Itwasobservedthattorrefiedsugarcanebagasse,showninFigure5,havelight-to-pale=browncolorwhichislighterascomparedwiththatofrawsugarcanebagasse.Exposingtorrefiedsugarcanebagasseintheatmospherefor6hoursslightlyincreaseditsmoistureadsorptionfrom0to6.8%fornon-hammer-milledsampleswhile0to8.4%forhammer-milledsamples.Basedontheperformancetests,itcanbeconcludedthatthesugarcanebagassecanbetorrefiedsimplyinaindirect-firedrotarytorrefyerusingsugarcanetrashasfuelforthefurnace.Torrefiedmaterialsleavingtheheatedrotatingcylinderofthetorrefyercanbeeffectivelyreducedinsizeusingahammermillandconveyedintothestoragebinwhile,atthesametime,cooledtothelevelrequiredforstorage.Tofurtherimprovetheperformanceofthemachineparticularlyintermsofthroughputcapacity,thefollowingcoursesofactionarerecommended:(1)Enlargetheopeningofthetorrefyingmachineandofthebiomassfurnacetoincreaseitsthroughputcapacity;(2)Sealthegapsinvariousconnectionsinthetorrefyingmachineandprovideitwithrock-woolinsulationtominimizeheatlosses;(3)Conductactualandlong-termoperationofthemachinetofurtherseethepartsthatneedtobeadjustedandreplaced.Formoredetailcontact,CarbonNeutralCommonswww.carbonneutralcommons.orgReleased:November30,2017

Figure7.Samplesof(a)Rawand(b)TorrefiedSugarCaneBagasse.

(a)

(b)