Cheial and Poess Engineeing, 33 (), 43-5 DOI:.478/v76--4-3 EFFECTIVE DIFFUSIVITY OF MOISTURE IN OW RANK COA DURING SUPERHEATED STEAM DRYING AT ATMOSPHERIC PRESSURE Zdisła Pakoski *, Robe Adaski, Słaoi Kapis Tehnial Univesiy of od, Fauly of Poess and Envionenal Engineeing, ul. Wólańska 3, 9-94 Łódź, Poland The effeive diffusiviy of ae in bon oal of Bełhaó ine as expeienally deeined. The expeiens ee pefoed in supeheaed sea a C and aosphei pessue using slighly opessed pelles of ylindial shape. The dying and epeaue uves of he saple ee used o idenify diffusiviy. An invese poble as foulaed and solved by he finie eleen ehod fo 3D axially syei ylindial geoey of he saple. A saisfaoy fi of he siulaed uves o expeienal esuls as obained. The obained dependene of effeive diffusiviy on oisue onen and epeaue ay be used in designing lignie dyes. Keyods: diffusion, oisue, lignie. INTRODUCTION Fossil fuels ae so fa doinaing boh heal and eleial enegy poduion all ove he old. Coal and lignie shae is in oal a. 3%. o ank oal shae ill inease in he fuue. A he oen Euope is he hid old lages onsue of lignie afe USA and China. In Poland lo ank oal s shae in enegy poduion is uenly 36%. Poland has one of he lages bon oal deposis in Euope and ou dependene on i is bound o inease in he fuue (Kaselei and Koioł, 7; Zapooski B., 8). Consideing ha oveall os (inluding ining) of he enegy podued fo lo ank oal is -3% loe han ha of blak oal, his endeny is undesandable. Hoeve, all enegy podues in Euope ae liied by CO eission quoas. In ode o edue he eission of CO he effiieny of he poe geneaion poess us be ipoved. Dying of oal befoe obusion is one of he ays. Alhough nueous dying ehods of oal ee elaboaed (Alladie e al., 4; Pikoń and Mujuda, 7; Ross e al., 5), supeheaed sea dying sees o be he os suiable fo he poe indusy (Kuda and Mujuda, 9; Pakoski, ). o gade sea geneaed in supeheaed sea dying an be easily inopoaed ino he syse of he plan. Dus explosion haad is eliinaed due o oxygen-fee aosphee. Finally, hee is no eission o he aosphee sine he dying yle is fully losed. Fo he supeheaed sea dye design he popeies of lignie neessay inlude sopion isohes and effeive diffusiviy. Suh daa ae eihe diffiul o obain in lieaue o nonexisen. We deal ih sopional equilibiu of lignie in ou ealie ok (Pakoski e al., ). In his ok e onenae on he effeive diffusiviy of ae in lignie. *Coesponding auho, e-ail: pakoski@heeng.p.lod.pl 43
Z. Pakoski, R. Adaski, S. Kapis, Che. Poess Eng.,, 33 (),43-5. EARIER WORK Nueous papes pesen expeienal esuls of dying of lignie eihe in ai o in supeheaed sea. Hoeve, he odel hih is used fo poess siulaion of he single gain dying is he eeding oe odel (Chen e al.,, Chen e al.,, ooi e al., ). In he eeding oe odel i is assued ha poes ae open and evapoaion fon eedes ino he paile duing dying. Thus he enie solid is spli ino dy and e ones. Thee is no oisue anspo in he e one bu only in he dy one. Sine he poes ae filled ih vapo hee is no oisue diffusion in he poes bu only he Day flo of vapo. The diving foe fo his flo is pessue diffeene beeen pessue on he evapoaion fon and he exenal pessue. Pessue on he evapoaion fon is podued by he vapo-e solid equilibiu (sopional equilibiu). The only fied paaee needed in he odel is peeabiliy of oal suue o vapo. In he odel i is assued ha he fon is shap and no oisue is eained in he solid i.e. he solid is non-hygosopi. Hoeve, i follos fo he shape of sopion isohe ha lignie is in fa hydophili. In suh a ase he evapoaion fon ay be ide and evenually fill he enie solid. This oesponds o puely diffusional odel hih is ofen used o desibe dying in solids of uh fine poe suue suh as polyes, fui and vegeable issue, pape, ood e. Indeed, he eal ehanis of oisue anspo duing dying ay be oposed of boh ehaniss i.e. Day flo and diffusion. Suh a odel as developed fo supeheaed sea dying of ood (Adaski, 9). 3. EPERIMENTA 3.. Saple pepaaion Ra lignie as obained fo Bełhaó open pi ine. The saple of lignie as shipped in a double sealed bag and soed in efigeao unil needed. The a lignie oisue onen easued upon eeiving he saple, by dying o onsan eigh a 5 C, as. kg/kg. Ganula lignie as opessed ino pelles of ylindial shape, in a ubula old losed a one end. The pelles ee in diaee and 35 high jus befoe easueens. Alays he sae ass i.e. 4 g of a lignie as used. I as noied ha duing opession a eain aoun of ae dipped fo he old. I as hen neessay o e-hek he pelle oisue onen. By epeaing gaviei analysis i as found ha opessed pelles have oisue onen.9 kg/kg, hih as onsisen houghou all easueens. I eans ha a lignie onains a leas.3 kg/kg of fee ae, hih an be eoved by ehanial ehods. In his poedue he appaen densiy of dy opessed lignie as also easued and as found equal o 58 kg/ 3. Fig.. ignie pelle used fo saple epeaue easueens. ines sho posiions of heoouples 44
Effeive diffusiviy of oisue in lo ank oal duing supeheaed sea dying a aosphei pessue To pelles ee siulaneously used in eah dying expeien. One seved fo easuing dying kineis and as oninuously eighed duing dying. The seond seved fo solid epeaue easueens. The saple had o fine holes dilled: one along is axis and he ohe paallel o he axis 5 aay (appoxiaely in he iddle of saple adius) as shon in Fig.. Thin ( ) Fe- CuNi heoouples ee ighly pessed ino he holes. The hole assebly onsised of saple suppoing esh and Teflon soppe, hih seved fo insalling he saple in plae. 3.. The expeienal se-up and poedue The expeienal se-up is shon in Fig.. I povides seady flo of supeheaed sea of onsan epeaue and veloiy, in hih a ylindial saple of lignie undegoes dying. Sea is geneaed in a boile () by o iesed elei heaes 5W eah. I passes hough a buefly valve () and is hen supeheaed in an elei supeheae (3) o he equied epeaue. The flo of sea is hen equalied by a seion (4) filled ih sainless seel shavings. The fis saple (Fig. ) is fixed hoionally in habe (5). I seves aeial epeaue easueens. The seond idenial saple is plaed in habe (6). I is suspended in a ie esh baske unde a balane (7) and oninuously eighed. Sea veloiy in easuing habes is appoxiaely 5 /s and is individually easued in eah un. The sea leaving he habes is ondensed and ondensae is euned o he boile. The ove has a sall enal hole hih seves as a ven, so he inenal pessue is equal o he aosphei one. The esaping sea also enes he ie, on hih he saple baske is suspended so i neve ouhes he alls. The enie se-up is apped in elei heaing blanke and insulaed ih ineal ool o poe agains sea ondensaion on he alls. Addiionally, he op eovable ove has o hoional holes in hih aidge heaes ae insalled. This pevens sea ondensaion and evenual dipping of ondensae on he saples. Fig.. Expeienal se-up fo supeheaed sea dying a) vie b) sheai. boile ih o elei heaes, buefly valve, 3 supeheae, 4 flo equalie, 5 epeaue easuing seion, 6 eighing seion, 7 eleoni balane 3.3. Diffusiviy idenifiaion Mass ansfe in poous solids duing supeheaed sea dying is due o a leas hee ehaniss: Day flo of liquid oisue aused by geneaed pessue gadien, diffusion of oisue in vapo 45
Z. Pakoski, R. Adaski, S. Kapis, Che. Poess Eng.,, 33 (),43-5 46 phase and diffusion of bound oisue, boh aused by oisue onen gadien (Pakoski, ). In his peliinay ok, hoeve, he effeive diffusiviy enopassing all he hee ehaniss as used. The axially syei, ylindial, hee-diensional desipion of ass and hea balanes in he saple is as follos: ass balane: τ D eff () hea balane: τ ρ λ ρ τ D T S eff S ) ( () The iniial ondiions: a, [ C] and.9 [kg/kg] Bounday ondiions fo ass ansfe: a ylinde axis (3) a ylinde peiphey D eff D ρ (4) a ylinde bases D Z eff D ρ, (5) Bounday ondiions fo hea ansfe (likeise): (6) v D h Δ α λ ) ( (7) v D Z h Δ α λ ) (, (8) The solid as assued o be isoopi. The effeive diffusiviy dependene on oisue onen and epeaue as assued o have he folloing fo (Pakoski Z., ) RT d d D d eff 3 exp (9) Dying ae D as alulaed using he folloing elaionship: ( ) v D h Δ α * ()
Effeive diffusiviy of oisue in lo ank oal duing supeheaed sea dying a aosphei pessue Whee * is he equilibiu epeaue of solid a a given oisue onen and vapo paial pessue (hee aosphei). This onep is a hypohesis ha as pesened in an ealie ok (Pakoski and Adaski, ). Hea ansfe oeffiien a ylinde peiphey as esiaed using available oelaions fo flo pas a ylinde and equaled o 4.8 W/( K). Hea ansfe oeffiien a ylinde bases as assued equal o he above one. The vapo-solid equilibiu fo lignie as aken fo (Pakoski e al., ). I has he fo of he Hendeson equaion (): ih a.763; a.5879; a 3.839 p P 3 ( a ) a a The folloing aeial popeies ee used: Dy lignie speifi hea apaiy (Heideneih e al., 999): exp () 3 S 5.3( T 3).55 ( T 3) [J/(kg K)] () Dy lignie hea onduiviy (Heideneih e al., 999) 4 λ.9.5 ( T 3) [W/( K)] (3) Dy lignie appaen densiy (easued in his ok) ρ 58 [kg/ 3 ] (4) Sea popeies ee alulaed fo elaionships available a (Pakoski e al., 99). Diffusiviy as idenified using he esuls of expeiens pefoed a sea epeaue of C. The kinei uves of he solid oisue onen and epeaue ee geneaed by he above odel solved by FEM using COMSO Muliphysis sofae. Opiiaion of leas squaes objeive funion as used o find paaees of he diffusiviy equaion (9) using he daa of boh dying uve and epeaue uve. In his ay he dependene of D eff on boh oisue onen and epeaue as aken ino onsideaion. Sea ondensaion peiod as no aken ino aoun as being vey sho. 4. RESUTS AND DISCUSSION The expeienal and opued esuls ae pesened in Figs. 3 and 4. The iniial peiod of sea ondensaion is visible as a apid inease of solid epeaue and oisue onen in he expeienal esuls. I is folloed by a peiod of onsan dying ae, hee epeaue eains equal o sauaion epeaue of sea (hee C). The expeienal dying ae is, in fa, no eally onsan sine a sall uvaue of he dying uve is obseved. The dying ae begins o fall hen appoxiaely equals.7. Hoeve, he epeaue uves sho he end of he onsan ae peiod a.5 kg/kg. A his poin he epeaue begins o aise apidly saing a he sufae and peneaing he solid. Finally, he dy saple eahes he sea epeaue. These esuls ee used o idenify he paaees of he diffusiviy equaion (9). The finie eleen ehod, pogaed in COMSO Muliphysis as used. The obained paaees ae: d.8-7 /s, d.773 i d 3 3549 kj/kol (ae). Gaphial epesenaion of his elaionship is shon in Fig. 5. 47
Z. Pakoski, R. Adaski, S. Kapis, Che. Poess Eng.,, 33 (),43-5.9.8.7 Exp. daa Model [kg/kg].6.5.4.3.. 3 4 5 6 7 8 9 [in] Fig. 3. Expeienal and siulaed dying uves. Muliple egession oeffiien R.98 8 6 Exp. daa R Exp. daa R5 Model R 4 [ C] 8 6 3 4 5 6 7 8 9 [in] Fig. 4. Expeienal epeaues and siulaed epeaue in he ene of saple. Muliple egession oeffiien R.93 A opaison of he obained dying uve ih he siulaed one shos ha he siulaed uve has an iniial saigh line segen indiaing he onsan ae peiod ending appoxiaely a. kg/kg. This is he esul of he sopion isohe indiaing unbound oisue pesen in his ange and he assupion ha he solid sufae insanly assues equilibiu epeaue. This is an ovesiplifiaion ha needs being eliinaed by a oe oplex odel of he dying ae. Also he falling dying ae, in ealiy, begins ealie han pedied by he odel. Fuhe ok o ipove he odel is equied. 48
Effeive diffusiviy of oisue in lo ank oal duing supeheaed sea dying a aosphei pessue Fig. 5. Dependene of oisue effeive diffusiviy on oisue onen and epeaue As obseved in Fig. 5 he effeive diffusiviy hee is - odes of agniude lage han diffusiviy obained ypially fo solids. Thee ae o ain easons fo his: ) a high epeaue (equal and above he boiling poin) oisue flo is diven by he inenal pessue in he fo of Day flo, ) he solid is highly poous and has lage poes han ypial onolihi poous solids suh as ood, lay, fui and vegeable issue e. A sall dependene of he diffusiviy on oisue onen indiaes ha he odel is a good desipion of he eal poess. 5. CONCUSIONS We Bełhaó bon oal as ined onains appoxiaely. kg/kg of oisue. This oisue onen an be edued o.9 kg/kg by ehanial pessing. The es us be eoved by dying. To desibe he dying poess by a siple odel an effeive diffusiviy of oisue is equied. A pesen no suh daa ae available in lieaue. The esuls obained in his ok on he basis of he pefoed expeiens indiae songe dependene of he effeive diffusiviy on epeaue han on oisue onen in he expeienal ange of hese paaees. Alhough he siulaed esuls saisfaoily fi he expeienal esuls, fuhe efineen of he odel ould ipove he fi auay. The ok on his is in pogess. This ok as finaned fo funds alloaed fo eseah unde Poje No. N N9 3537 in he yeas 9- by he Minisy of Siene and Highe Eduaion of he Republi of Poland. SYMBOS hea apaiy, J/(kgK) Δh v laen hea of vapoiaion of oisue, kj/(kg K) 49
Z. Pakoski, R. Adaski, S. Kapis, Che. Poess Eng.,, 33 (),43-5 p paial pessue, Pa P oal pessue, Pa R univesal gas onsan J/(ol K) R saple adius, uen adius, T epeaue, K epeaue, C D dying ae, kg/( s) oisue onen, kg/kg d.. uen lengh, Z saple lengh, Geek sybols λ hea onduiviy, W/( K) ρ appaen densiy, kg/ 3 τ elapsed ie, s Subsips S liquid oisue dy solid e solid a ylinde peiphey a ylinde base sea REFERENCES Adaski R., 8. The ehanis of oisue anspo in he aeial died ih supeheaed sea. PhD hesis, Tehnial Univesiy of od, od (in Polish). Alladie D.J., Chaffee A.., Jakson W.R., Mashall M., 4. Wae in bon oal and is eoval. In: i C.Z. (Ed.), Advanes in he Siene of Vioian Bon Coal, Elsevie, 85 33. Chen Z., Wu W., Agaal P.K.,. Sea dying of oal. Pa. Modeling he behavio of a single paile. Fuel, 79, 96-973. DOI:.6/S6-36(99)7-3. Chen Z., Agaal P.K., Agne J.B.,. Sea dying of oal. Pa. Modeling he opeaion of a fluidied bed dying uni. Fuel, 8, 9-3. DOI:.6/S6-36()8-8. Heideneih C.A., Yan H.M., Zhang D.K., 999. Maheaial odeling of epeaue esponse of lo-ank oal pailes duing pyolysis, Dev. Che. Eng. Mineal Poess., 7(5/6), 593-6. Kaselei Z., Koioł K., 7. Exavaion poenial of bon oal seo in Poland afe yea 5. Poliyka Enegeyna,,, 4-58 (in Polish). Kuda T., Mujuda A.S., 9. Advaned dying ehnologies. nd ediion, CRC Pess, Boa Raon (F). ooi A. Y., Golonka K., Rhodes M.,. Dying kineis of single poous pailes in supeheaed sea unde pessue. Che. Eng. J., 87, 39-338. DOI:.6/S385-8947()44-3. Pakoski Z., Baak Z., Suillo C., Sensoe S., 99. Evaluaion of equaions appoxiaing heodynai and anspo popeies of ae, sea and ai fo use in CAD of dying poesses, Dy. Tehnol., 9, 753 773. DOI:.8/737393989678. Pakoski Z.,. dypak 3.6 Poga fo psyhoei and dying opuaions. Onikon d., Łódź, 76. Pakoski Z.,. Design of supeheaed sea dyes. Wydanio Poliehniki Łódkiej, Łodź (in Polish). Pakoski Z., Adaski R., Kokoińska M., Kapis S.,. Genealied desopion equilibiu equaion of lignie in a ide epeaue and oisue onen ange. Fuel, 9, 333-3335. DOI:.6/j.fuel..6.44. Pakoski Z., Adaski R.,. On pediion of he dying ae in supeheaed sea dying poess, Dy. Tehnol., 9, 3, 49-498. DOI:.8/7373937..5763. 5
Effeive diffusiviy of oisue in lo ank oal duing supeheaed sea dying a aosphei pessue Pikoń J., Mujuda A.S., 7. Dying of oal. In: Mujuda A.S. (Ed.), Handbook of indusial dying, 3d ediion, CRC Pess, Boa Raon (F). Ross D., Dogupahy S., Huynh D., MInosh M., 5. Pessuied flash dying of Yalloun lignie. Fuel, 84, 47 5. DOI:.6/j.fuel.4.8.6. Zapooski B., 8. Analysis of geneaion oss of eleiiy. Poliyka Enegeyna,, 53-54 (in Polish). Reeived 3 Sepebe Reeived in evised fo 3 Novebe Aeped Deebe 5