uu RAO DOI
Xac djnh ton ap cua tac nhan khi qua \6p hat mud1 tinh trong qua trinh
say b^ng may say tang soi lien tuc
(*) BUI TRUNG THANH (**)NGUY6NHAY
1. Gidi thieu
Hat vat lieu riin hda sdi trong ddng khi xay ra khi cd mdt ddng khi cd van tdc, cd ap suat du Idn, di chuyen theo hffdng tff dffdi len qua ldp hat vat lieu thdng qua mdt ghi phiin phdi khi (distributor) gdm vd so'cac Id phiin phd'i khi dffdc bd tri d day ldp vat lieu hat. Ddng khi dffdc thdi tff mat diiy ldp hat, di xuyen qua cac hat thdng qua nhffng khoang trdng giffa cac hat vat lieu lam mat dp cua khdng gian hat giam di, nhffng khdng liim iinh hffdng den nhffng tinh cha't can biin cua ldp hat. Khi van tdc ddng khi thap, ap lffc tac diing len ciic hat nhd, ldp hat v i n duy tri va giff nguyen trang thiii tinh ban diiu. Khi tang van tdc khi len, lffc keo ciia khi ddng xuiit hien ngffdc chieu vdi trpng lffc ciia hat va lam cho ldp hat bat dau gian nd ve the tich, cac hat biit diiu di chuyen tiich rdi xa nhau hinh thiinh ldp hat sdi tdi thieu.Tang van tdc ddng khi len hdn nffa den giii trj tdi han thi lffc ma sat giffa ciic hat va khdng khi ciin biing vdi trpng Iffdng hat. thiinh phiin thang dffng ciia ap lffc nen triet tieu, lffc keo hffdng len dung bang vdi trpng lffc hffdng xudng lam cho viit lieu Id Iffng trong ddng tac nhiin thdi qua. Tai giii tri niiy dffdc L.T Fan[2] dffdc gpi lii ldp hat biin sdi nghia lii \ a n tdc khi qua ldp hat cd gia tri Idn hdn \iin tdc hda sdi tdi thieu, tiep tuc tang van tdc khi len nffa thi Idp \ a t lieu miy dffdc sdi va hinh thiinh ciic bpt khi(bubbling) \ii dffdc gpi lii ldp hat sdi bpt khi, ldp hat giii long hoan toan. Tiep tuc tang van tdc khi hdn nffa thi miit dp khdi cua ldp hat tiep tuc giiim va sff hda sdi xay ra manh me cho den khi viit lieu khdng cdn d dang ket ldp nffa \ii bj cudn len va rdi trd lai trong chuyen ddng sdi ngiiu nhien. Khi hat sdi mdi hat vat lieu dffdc bao phii bdi ddng khi ndng \-ii thffc hien muc dich trao ddi nhiet. trao, ddi am neu ffng dung cho say hat hoac lam ngudi hat....
Khi ldp hat sdi, xiiy ra sff hda trcin manh liet giffa khi va viit lieu hat, ket quii lii tao ra mdi trffdng ddng deu ve nhiet dp vii dp am trong toiin bp ldp hat [4]
Nham md tii \ e mat lip suiit ciia ddng khi di qua cac loai ldp h a t , bai bao trinh biiy cac ket qua tinh toan tdn dp ciia ddng khi qua ldp hat tinh. qua ldp hat sdi tdi thieu, qua ldp hat biin sdi va qua ldp hat sdi cua ciic tac giii trong nffdc va ngoai nffdc da de cap trong cac cdng trinh khoa hpc nghien cffu vecdng nghe tang sdi, dac biet bai bao trinh bay cac linh toiin cu the ve tdn iip cua ddng khi hda sdi di qua ldp hat mudi tinh trong qua tnnh thffc hien sa'y hat trong ldp hat sdi lien tuc vii thffc hic-n dd'i chieu ciic ket qua tinh toiin
ly thuyet nay vdi cac ket qua thffc nghiem tren md hinh thi nghiem vdi cac loai hat mudi tinh cd cac dffdng kinh hat trung binh lay tff mau mudi tinh ciia cdng nghe nghien -rffa va phan ly thuy lffc trong cac nha may che bien mudi tinh cao Clip ciia Tong Cdng ty Mudi Viet Nam theo cac cap kich thffdc hat phan bd trong phamvid=0,225mm;d=,45m;
d=0.75mm: d=1.05mm;d= l,35mm:d=l,65mm, ma chung dffdc sff dung de lam ldp dem hd trd qua trinh tao sdi ban dau trong qua trinh say ldp sdi lien tuc [17]
2. Dir lieu va phifdng phap
2.1. Xac djnh trot li/c ciiia dong tac nhan khi qua ldp hat tinh
Dac tinh trd lffc qua ldp hat tTnh tinh theo cdng thffc thffc nghiem ciia N.M. Javorosky [1]:
(1) AP,=2(; ^„-P*
2.g.<,
Trong dd: H|,-chieu cao ldp hat tinh; m, p^-khdi Iffdng rieng ciia khi; kg/m'; V|^-van tdc khi be mat ldp hat; m/s;
g-gia tdc trpng trffdng, m/s2; dtd-dffdng kinh thiiy lffc tffdng dffdng, m; ,; la he sd trd lffc di qua ldp hat, la'y theo gidi ban cua tieu chuan Renol:
Neu Re < 4 thi ; = 34/ Re
Neu 4 < Re < 80 thi ; = 0,8 + (27,8/Re) + 0,8 He sd Re trang thai tinh nay dffdc tinh:
(2) R e , , . ^ ^ - ^ ' - ^ " - - ^
Trong dd: ^-tinh cau ciia hat vat lieu cd hinh dang bat ky; Hi^-dd nhdt ddng lffc hpc, kg/m.s;
Dffdng kinh thiiy lffc tffdng dffdng dffdc xac djnh theo cdng thffc:
2s..f.d„
(3) < ,
Trong dd:
3(1-^J
d^^ -dffdng kinh trung binh cua mdt hat e -la dp rdng ciia ldp hat d trang thdi hat tTnh.
(4) f „ = 1 - Pi,
(*) Dai hpc Cdng nghiep TP. Ho Chi Minh
(**) Dai hoc Nong Lam - TP. Ho Chi Minh d K t r l TAP CHi Cd KHi V I E T N A M ^ .So 149 - Thang 12 n:1m 20O9
NGHIEN CC^U - TRAO DOI
f-la he sdhinh dang dffdc xac dinh bang:
(5) . / = ^ « ^ ^ ^ ^
6 day As dien tich be mat.m-; V - the tich cua khd'i hat.
m'; (dpc gia xem each tinh As va Vs ddi vdi hat mud'i tinh trong [13|).
HuKill va Sheld 11 ] da dffa ra cdng thffc tinh trd lffc qua ldp hat ndng san trong say tinh:
(6) P, ^ "g'' Ln(\ + bQ,)
Trong dd :
Qi-lffu Iffdng khdng khi qua 1 m- Iffdi san (mVs.m-); a, b la cac he sd phu thudc vat lieu (xem trong bang 1):
Bang 1: He so a va b
Gao Hat ngo Dau nanh Luatni
a 2,57. 10""
2,07. 10""
1,02. 19""
2,70. 10""
b 13,2 30,4 16,0 8,77
Vk ( m / s )
0,15-0,75 0,1-0,5 0,1-0,65
0.1-0,5
Theo gian dd Shed [1] bieu dien quan he Ap^^^^ = f (V ).
Cong thffc dao:
(7) Q,= exp I A + B Ln Ap^^^,„ + C (Ln Ap^^^J^ ] Gia tri A,B,C dffdc lay tff bang 2:
Liia
Bap
Dau nanh
A
-7.68 -6.55 -6.53
B
1.10 1.01 1.07
c
-2,79.10"' -3.25.10"' 3,45.10"'
Khi ddng khi di xuyen qua ldp hat trang thai tTnh dffdi dang chay tang( laminar flow) thi trd lffc qua ldp hat tTnh cd hinh dang bat ky dffdc tinh thao cdng thffc cua blacke-Kozeny [8]:
k,.^,(\-£^)\^
(8) ^P,
ey'iV'd;)
Trong dd: APt- trd lffc qua ldp hat tTnh ;kg/m-; k^-la hang sd thffc nghiem khdng thff nguyen. vt- van tdc ddng khi qua ldp hat tTnh, H„- chieu cao ldp hat trang thai tTnh;
E„ - dp rdng ldp hat trang thai tTnh. Trong nhieu thffc nghiem blacke-Kozeny da xiic dinh k = 150. Pham vi sff dung (Ct 8) ciia Blake-Kozeny khi Re< 10 va dp rdng ldp hat trang thiii tinh t:„ = 0.5 khi dd he sd Reynol (Ret) tffdng ffng dffdc tinh:
(9) R e ,
( 1 - ^ 0 ) A
Khi ddng khi thdi xuyen qua ldp hat la chay rdiiturbullent flow),Re|> 1000 Burker va Plummer da xac dinh ddng chay rdi da lam sinh ra tdn thii't nang Iffdng ddng hpc. Luc nay trd lffc qua ldp hat hinh dang khdng cau dffdc tinh theo (PtlO)[8]:
(10) ^P,
s^'cpd,,
Trong dd:, k,-la hang sd thffc nghiem khdng thff nguyen va gia tri thffc nghiem xac dinh;k,= 1.75.
Trffdng hdp tac nhan khi qua ldp hat tinh cd hinh dang bat ky che dp chay qua dp (Intermediater flow) Ergun da dffa ra cdng thffc tinh trd lffc qua ldp hat tTnh bang tdng ciia trd lffc ddng chay ldp va ddng chiiy rdi.
\5Q^,(\-£,fv,.H, ^ \,15(\-E,)p,v,\H, e,;(p-dl SoV'd,
(11) A;^2.2. Xac djnh trci life qua Idp hat trang thai Icfp hat soi td'i thieu
Tiep tuc tang van tdc khi qua ldp hat len den trang thai ma ldp hat bat dau giiin nd. luc nay dp xdp (dp rdng) ciia ldp hat chuyen tff trang thiii tinhtrang thai biit dau gia long E^^= E|,.n va luc nay tdn ap qua ldp hat trang thai sdi tdi thieu (tai vi tri A, hinh 1) cd the bieu dien bang tffdng quan (Ptl8) | 3 | , tdn lip ciia ddng tiic nhan khi qua ldp hat bang vdi trpng Iffdng ciia ldp hat tren mdt ddn vi dien tich mat cat ngang thi ldp hat bat dau gian nd:
(12) ^ ^ " = ^ - ' ^ " " " ^ ' " * * ' ^ ' ' " ' ' ' * *
= gH,,(\-£,)(p,,-pi) = cons tan /
Trong dd: H^ - chieu cao ldp hat sdi tdi thieu. m: H^^- chieu cao Idphat sdi bpt khi, m; e^^-dp xdpcua ldp ha td trang thai sdi tdi thieu; e^^- phan the tich bpt khi chiem chd trong ldp h a t d trang thai sdi bpt. Ap suat khdng ddi sudt tff trang thai ldp hat sdi tdi thieu den trang thai sdi hdp ly (tff A-B Hinh 1). Trong each tinh tdn ap qua ldp hat (Ptl2)chu yeu phu thupc vao khdi lffdng rieng ciia loai hat va dp xdp ciia hat trang thai sdi tdi thieu.
Trong khi dd Ergun lai dffa ra phffPng trinh tinh tdn ap ciia ddng khi di qua ldp hat cd hinh dang bat ky. trang thai sdi td'i thieu (vi tri A hinh 1) biing (PT12)|4|:
(13) ^
H.. 150
[\-E„)- j " ^ ^ , . 7 5 i l l ^ ) Av,/
[<pd,, <pd„
Trong dd: AP^^-trd lffc ddng khi di xuyen qua ldp hat trang thai sdi tdi thieu; d,^- dffdng kinh trung binh ciia hat viit lieu, m; Htt - chieu cao ldp hat.m; E„-dd xdp ciia ldp hat trang thiii sdi tdi thieu; v - van tdc khi be mat di qua ldp hat trang thai sdi tdi thieu, m/s; i^i^-dd nhdt ddng lffc hpc ciia ddng khi. kg/m.s,^, -cau tinh ciia hat.
Dtl' cd the sff dung (Ctl2). dp rdng ciia ldp hat if trang
TAP CHi C d KHi VIET NAM .So l i 9 • IIKHII; 12 nnni 2iliW
NGHIEN CCrU- TRAO DOI
thai sdi tdi thieu phai dffdc xac djnh. Wen va Yu dffa ra each tinh c khi biet cau tinh ciia hat [5]:
\-£ 1 (14) - ^ = ll.Ohoac = 14
<P' £„ (P£„
Hay cd the sff dung each tinh 8_tff mdt tffdng quan khac dffdc bien ddi tff Wen va Yu de tinh khi biet cau tinh cua hat [3]:
(15) 0,071
(P
6 trang thai ldp hat sdi tdi thieu, Kunii va Levenspiel dffa ra phffdng trinh tffdng quan ve mat can bang khdi Iffdng [4]:
(16) g . / / „ (1 - ^ 0 ) A - ^ = (1 - £„ )p,,g-H„
Nhff vay, ti le chieu cao ldp hat trang thai sdi tdi thieu va trang thai tinh ban dau dffdc thiet lap.
H„ ( l - £ - n )
Rut ra : (18) H„
l-s..
\-e..
Theo McCabe va Harriott (2001) [61, trffdng hdp tinh toan vdi cac hat giin gidng hinh ciiu ma khdng cd san gia tri ciiu tinh, cd the lay s = 0,4-0,45 va tang them £_^ =0,5 khi kich thffdc hat Idn. Tdn ap qua ldp hat trang thai sdi td'i thieu dffdc tinh theo (Ctl9) [3]:
(19) A / ^ , = / / . A v , / C ,
Trong dd: C^- la hang sd cho mdi loai hat,l/m; xac dinh Cd theo Rett:
Re„ < 0,4, thi cd Cd = 24/Re^, 0,4'<Re <500, C d = 10/Re ""
Theo J.R.Howard [5] de ldp hat chuyen tff trang thai tinh sang trang thai biit diiu gia long, ap suat ddng khi phai du Idn thang dffdc trpng Iffdng ciia ldp hat va ap suat ddng khi dffdc xac dmh theo (Pt20) [5]:
(20) ^P„=—{P,-P,)g
Trong dd: M la khdi Iffdng ciia hat tren ghi, kg; p,,-khd'i Iffdng rieng cua hat; p^ - khdi Iffdng rieng cua khi; A-dien tich mat cilt ngang chffa ldp sdi, m-; g-gia tdc trpng trffdng, m/s-.
Trong (Pt20) xem nhff khdng cd lffc tffdng tac giffa cac hat. lffc tffdng tac giffa hat va vach budng say. Do khdng cd sff suy giiim nang Iffdng nen khdng gay ra cac va cham, khdng giiy hieu ffng lam tang tdn ap cua ddng khi qua ldp hat. Ton ap se khdng ddi khi van tdc khi tang len tff van tdc hda sdi nhd nhat den viin tdc mil tai dd bat dau cd sff cudn hat xiiy ra (tff vi tri A den vi tri C hinh 1). Khi tdc dp ddng khi cang Idn thi dp xdp ldp hat cang Idn va dp cao ldp hat sdi Cling Idn. Tai thdi diem hat hda sdi thi e > £„ va H^^ >H„
va gia iri ciia chung trong tinh toiin gia tri la'y tang them 10% [121.
Ldp hai chdm sol
Lop tut s6< c6 bd khi p h ^ klp ngang
Ldp hat tinh
T
ip(mm HjO)
o
Lwyii
^ Ldp hat Ml bi cu6n
• ••theo dong khi -••• I c
T M M A / ~ ^ \
A[ suit thay doi
Vung hat sol Vai tockhibemat (ua ldp hat soi
(m/s)
Hinh 1: Ton ap qua ldp hat tinh va cac che dp soi ciia hat
Phedorop da tinh trd Iffc cua ddng khi qua Idp hat sdi tdi thieu bang (Pt21) [ I I ] :
(21) A ; ? „ = 0 , 1 7 M
Re„ (p.d,
Trong dd: M-khd'i Iffdng hat tren ghi phan phdi khi, kg; A-dien tich ghi phan phdi khi, m-; He sd Re^^ trong (Pt21 dffdc tinh theo cdng thffc ciia Groshko-Rozembaum - T o d e s . Dd'i vdi hat cd hinh dang la hat cau:
(22) Re„ = ^ ' ' 150 \-£.
^-^/f
ArDd'i vdi ldp hat da phan tan (kich thffdc phan bd tff nhien khdng deu nhau) khi sff dung (PT22), he sd Rett sai sdtff 15- 20 % [12]. Trffdng hdp khi tinh toan nhanh ta xem dp rdng ldp hat d trang thai tTnh bang vdi trang thai sdi tdi thieu £ = £__ = 0,4 thi he sd Rett dffdc tinh theo (Pt23):
(23) Re„
1400 + 5 , 2 2 V ^ r
He sd Archimete (Ar) tinh vdi hat cd hinh dang bat ky:
(24) Ar
PkiP,,-Pk)S (Pdl PI
2.3. Ton ap cua dong khi qua ldp hat ban soi
Khai niem ldp hat ban sdi dffdc L.T Fan va cdng sff dffa ra va dffdc G.K.Roy, tiep tuc phat trien [2]. Trang thai ldp hat ban sdi (Semi-fluidized bed) cd the dffdc hieu la thdi ky dau cua ldp hat biit chuyen sang trang thai sdi hoan toan (hinh l,vung lan can sau diem A), ldp hat bdn sdi c6 tdc dp gi Idng nhieu hdn sdi tdi thieu, nhffng lai sdi yeu hdn sdi hoan toan. Gia tri dp suat qua ldp hat ban sdi dffdc xdc dinh bang tdng dai sd' cua trd lffc qua ldp hat tinh va trd lffc qua ldp hat sdi. LT Fan da do dffdc tffng loai dp suii't rieng re sau cdng hai thanh phan nay lai [2|:
(25) ^Pi,. = AP
H ( / ' - / ? , ) + AP H
TAP CHi Cd KHi VIET NAM • So 149 - Thiing 12 nSm 2009
N G H I E N CC^U - T R A O D d i Trong dd: H^s- chieu cao cpt hat ban sdi, m; HO- chieu
cao phan hat tTnh trong ldp hat ban sdi, m;
["^J - gradien ap suat qua Idp hat sdi ( ^ ] gradien dp sua't qua ldp hat tTnh
Ket hdp vdi cdng thffc Leva, trd lffc qua ldp hat sdi va trd lffc qua ldp hat tTnh ciia Ergun cdng thffc tinh trd lffc qua ldp hat bdn sdi dffdc viet:
' ^P.-i^]Mj^].iH^^-H,,-
H
150 \-s„
n-//*
<pdi -1,75
(Pd„
(26) (H..-H„) (!-«,)
('^, -i:«). Hh
(!-£-„)(//,.-//„) i'?,-^.) ( l - t - J ( f t - A )
Trong dd: H,|-chieu cao ldp hat trang thdi tTnh, m;
H^-chieu cao cua ldp hat sdi, m; E„-dd xdp ciia ldp hat trang thai tTnh; E-dp xdp cua ldp hat trang thdi sdi; p^- khdi Iffpng rieng ldp hat ; p^-khd'i Iffdng rieng ciia khi hda sdi;
G-lffu Iffdng khi, kg/m2.s;
Dp xdp cua ldp hat d trang thai hat sdi £^ dffdc tinh theo cong thffc Zabrodsky[3]
'2^'^'=i Jr
Trffdng h d p h a t d t r a n g thdi bi ldi c u d n thi £ =1 (vi tri C Hinh 1).
Roy va S e n G u p t a | 2 ] da dffa ra t h d n g s d d i e u chinh d e xac dinh dp chinh x d c tdn thiit d p s u a t qua l d p hat bdn sdi cd hinh d a n g b a t k y ;
C- ' ^ ' • > - = 1 . 9 5 . 1 0 ' 1 ^ 1 1 ^ (28) (A/"),,.*,,,,,. d,. A
(«)"
Trong dd: R-ti le gian nd trong ldp hat bdn sdi, ddn vi khdng thff nguyen (H/Hs); Dc-dffdng kinh budng sa'y (dang Iron), m. Nhffviiy sau khi tinh todn tdn dp qua ldp hat d che dp bdn sdi, ta sff dung thdng sd'dieu chinh C de tinh chinh xac lai tdn dp qua ldp hat bdn sdi.
2.4. X a c djnh t o n a p c u a d o n g k h i k h i di q u a ghi phdn p h o i khi
Tdn dp trong budng sii'y la tdng dp ciia thanh phan trd lffc qua ldp hat AP^ va trd lffc qua ghi phan phdi khi AP^
(29) AP = APb + A P
ppk-
•> '''' , .. . Trong dd ton dp qua ldp hat bao gdm tdn ap trang thai
ldp hat tinh, tdn dp ldp hat sdi td'i thieu, tdn dp qua ldp hat bdn sdi.
Thffc te la trffde khi ddng khi di vao dffdc ldp hat phai di qua ghi phan phdi khiva tdn dp khi ddng tdc nhan khi di qua ghi phan phdi khi kieu dang dot id (perforated late) 115] dffdc tinh theo (PT30);
(30) AP = A P , ( 1.8-0.035 X)
Vdi X la ti le Id Iffdi tren dien tich ghi phan phdi tdc nhan (tinh theo %):
dientich 16 / „, dientich sdng F
X
/ o ,Trong dd: f-dien tich Id phan phdi khi; m-, F-tdng dien tich sang; m2;
Thffdng chuan Iffdi sff dung phan phd'i tdc nhan say tinh nam trong khoang 20 % - 40 % [12].
Henderson, dffa ra cdng thffc tinh tdn dp qua ghi phan phd'i khi kieu ghi dot ld[l]:
(31) Ap,„=l,07 =
' V, ^-e.O,
Vdi: Ap|-tdn dp qua san id: Pa; V^-van tdc khi be mat ldp hat; m/s; £-dd rdng cua khdi hat (lay sdthap phan); O^^- ty le Id cua ghi phan phdi khi cung nam trong pham vi 25
% - 4 0 % ( l a y s d % ) .
Krishnaiah[6] da lam thffc nghiem xdc dinh trd lffc qua ghi phan phdi khi vdi may say tang sdi da xdc dinh gid tri tdn dp dffdc lay trong pham vi tff 15 den 40 9f- ap suat qua ldp hat.
(32) AP = APb ( 0,2 - 0.4 )
p p i ' ^
Theo [12] tdn dp cua ddng khi di qua ghi phan phdi khi cd the xdc dinh gid tri theo (PT33)
Trong dd: C - he so trd lffc Id phan phdi khi phu thudc vao ty sd giffa dffdng kinh Id do va chieu day ghi dd hat 6 (do/6 ). He sd nay dffdc xac dinh qua dd thi quan he chuan sdLiasenco (Ly) va chuan sd Archi meter (Ar) 112|.
3. Ket qua vii thao luan
De md ta, minh hpa cung nhff ffng dung tinh tdn dp qua ldp hat ciia cdc tdc gia, ta thffc hien tinh todn cu the cho trffdng hdp thiet ke md hinh may say mudi tinh bang phffdng phdp siiy tang sdi theo cdc yeu ciiu ky thuiit ciia [ l()|. Ddng thdi thffc hien khiio nghiem say mudi tinh tren md hinh thiet ke'de ddi chieu vdi cdc ket qua da tinh toan.
3.1. C a c t h o n g so'difa v a o t i n h t o a n
Vat lieu tinh todn la hat mudi tinh cd kich thffdc hat lay theo ket qua thffc nghiem [ 13.14| bao gdm cdc loai hat d=0.225mm; 0,45mm; 0,75mm; l,05mn-i; 1,35mm; 1,65mm va loai hat da phiin tdn cd dffdng kinh trung binh d = 956mm[ 14] Cdc thdng so' vat ly cua hat va cua khdng khi d trang thai sdi tdi thieu va chieu cao ldp hat cho trong bang 3:
C ^
TAP CHi Cd KHi VliT NAM • So 1-19 - Thang 12 ni-lin 2U09
NGHIEN CUfU- TRAO DO!
Bang 3: Thdng so vat ly hat mudi va khdng khi
CAc thong so vat ly ( gia trj trung binh) C i c l a i d irong kinh hat sOr d u n g khao sat ton a p qua lop hat dh
DiroTig kinh hat t r u n g binh d „
D p x o p l a p hat trang thai tinh Eo
D p x o p lop hat trang thai lop hat soi toi thieu £„
D p x o p hat soi ES
Khoi lirgmg rieng hat ph Khoi lirgng khoi hat p b C a u tinh ciia hat (p Khoi lugmg rieng khi pk D p n h a t dpng lire hpc n Chieu cao l a p hat Hi, Chieu cao lap hat hoa soi toi thieu Ht,
L u a n g vat lieu muoi tucmg img theo chieu cao l a p hat tren ghi H(,
Di?n tich ghi d a hat va phan phoi khi m o hinh m a y say tang soi lien tuc thi nghiem
D a n vi
m m
m m
kg/m^
kg/m
kg/m-' kg/m.s m m m
kg
m"
Gia tri
0,225;0,45;
0.75:1.05;
1.35:1.65 0,956
0.51
0,56
Tinh theo P t 2 7 2 1 3 8 982 0.71 0,815 2 , 4 5 * 1 0 * 30 33
11
0,36
Ghi chicDuifng kinh hat 0.956 la lay gid tri trung binh lit kiwi hill da phan tun tif nhien theo cong nghe nghien riia thii cong duac .xdc dinh theo [13]
2
1
6
1
1
3 -"
7
-
. - - ;
4
8
I
5
Hinh 2: Sd do xac dinh tdn ap va van tdc khi tren may say tang soi
l-quat ly tam; 2-bp dien trd nung khdng khi; 3-cffa cap tac nhiin viio budng; 4-ghi phiin phdi khi; 5-budng chffa hat hda sdi; 6-nhiet ke do nhiet dp be mat ldp hat; 7-d'ng pito do dp suii't ddng be mat. dp sua't tons ciia khi; 8-dp ke chffU.
Bang 4-k^t qua khao nghifm vital tAc khi qua ldp h*t iM toi thi^u va dp suat qua 16p h^t sdi toi thieu v<h C h i ^
cao Urp h ^ H= 30min
stt 1 2 3 4 5 6 7
(mm) 0.225 0.45 0.75 0,953
1.05 1.35 1.65
\„
thuc nghiem)
(m/s)
0.15 0 . 2 0.42 0.55 ().58 0 . 6 0 . 8
APj AP, inmHjO inmHiC
12 23.3 30.8 3 6 43.3 53.3 65.8
14 2 8 4 2 S 3 6 0 66.3
7 2
Ap thyc nghiem (mrnHjO)
2 6 51.3 72.8 8 9 103.3 119.6 137.8
3.2. Khao sat tinh toan trd Irfc qua ldp hat of cac che' do cung cap khi khac nhau
3.2.L Tinh todn trd lUc dong khi qua ldp hat dnh tren mo hinh thiet ke
Trd lffc qua ldp hat trang thai tinh dffpc xac dinh bang 4 cdng thffc d tren. trong dd cdng thffc cua HuKill va Sheld, thich hpp cho loai hat cd kich thffdc Idn, dac biet la cho ldp hat ndng s a n [ I ] , kich thffdc cac loai hat nay Idn hdn rat nhieu so vdi hat mudi, ta khdng dp dung chung cho trffdng hpp tinh toan nay.
Bang 5: Tdn that ap suat qua ldp hat trang thdi tinh theo
S T T
1 2 3 4 5 6 7
dh (mm)
1,65 1,35 1,05 0,956 0,75 0,45 0,225
Ap ttnh ( m m H2O) K o z e n y
7 2 . 7 0 1 8 8 1 1 6 108,6040447 143,6233081 174,3483022 175,9385524 2 9 3 , 2 3 0 9 2 0 7 7 8 1 , 9 4 9 1 2 1 8
Ergun 83,12919616 111,2779839 1 18,1521541 138,0703005 1 12,3377916 159,3598917 397,0899502
Kozeny va Ergun
(Ghi chu ldp hat kich thudc d= 0.953mm la kich thitdc hat trung binh cua khoi mudi hat lay tU nhien tu cdng nghe nghien riia)
Tinh todn cho trffdng hpp cu the ddi vdi mudi tinh nay,ta dp dung cdch tinh ciia Blacke-Kozeny (Pt8) ciia Burker va Plummer (PtlO va cua Ergun (PtI 1) theo gia trj tdng dan ciia van tdc thffc nghiem va theo dffdng kinh hat.
Van tdc dffdc dffa vao sff diing tinh cho ldp hat tinh dp dung vao 3 cdng thffc tren phai nam trong mien gid trj tff O den lan can A ( hinh 1) va gidi han sff dung tffng cdng thffc tren theo gid tri gidi han ciia Ret. Cac ket qua tinh todn khi dp dung 3 cong thffc tren dffdc dd'i chieu vdi ket qua do b^ng thffc nghiem tren md hinh va dffpt trinh bay trong bang 5.
3.2.2. Tinh todn trd lUc ddng khi qua ldp hat trang thdi ldp hat soi toi thieu) tren mo hinh thiet ke
Ta lan Iffdt ap dung tinh todn trd lffc cua ddng khi quarj
wn
TAP CHi Cd KHi VIET NAM • So 149 - Thiing 12 nam 2009NGHIEN ciiu - TRAO D 6 | ldp hat sdi td'i thieu tai vi tri A {hinh I) bhng cdc (Ptl2);
(Ptl3); (Ptl9); (Pt2()); (Pt21). Trong s d c a c cdng thffc tinh tren, rieng (Ptl3) ciia Ergun, trd lffc qua ldp hat cd lien quan den dffdng kinh hat. (Ptl2);(Ptl3) cd lien quan den dp rdng cua ldp hat trang thdi sdi tdi thieu, ta lay e^^ tff ket qua thffc nghiem e„ ( ldp hat tinh) e,, =0,51 va 8_ = 0,56. Van tdc sdi td'i thieu qua ldp hat lay theo thffc nghiem tren cP sd quan sdt ldp hat bat dau dan nd va hda long van tdc sdi bpt dffpc lay tren mffc van tdc hda sdi tdi hieu nhffng nhd hPn van tdc sdi nut khi [9] trinh bay trong Bang 4.
Sff dung cdng thffc ciia McCabe va Harriott fPT 19,van tdc khi ldp sdi td'i thieu vtt lay theo bang 4, trd lffc Cd tinh theo Rett vdi Rett la'y theo Groshko va Todes (Ct22) (Ct23) (CT24)
Tinh trd lffc qua ldp hat bang (CT20)va (CT12)[1] tren cd sd md hinh vat ly,vdi Iffdng hat tren ghi phan phdi khi M= 11kg va dien tich ghi A= 0,36m2, chieu cao ldp hat sdi tdi thieu Htt= 33mm cho ket qua tinh toan trinh bay trong bang 6. Tdn dp tinh theo Ct 20 va tdn dp Ct 12 khdng phu thupc theo dffdng kinh ciia hat nen cdc gid tri la bang nhau
Bdng 6; Gia tri ^ ^ theo cac phuong trinh tinh toan ty thuylt va th^rc nghiem
stt 1 2 3 4 5 6 7
dh
0,225 0,45 0.75 0,956
1,05 1.35 1.65
APlt ( mm H;())
Ergun 722.33 249.1 213.5 158,3 143.9 I I 8.6 128.3
Eqt (12) 303.7 303.7 303.7 303,7 303.7 303.7 303,7
Eqt (20) 299.6 299.6 299,6 299,6 299,6 299,6 299,6
Federop 607,3 809.7 1 700,4 1902,8 2024,3 2429,2 3238,9
Todes 217,3 754.3 1695.6 2372,4 2693.5 3652.6 4543,6
r h ^ c
nghiem 2 6 51,3 72,8 8 9 103,3 119,6 137,8
D A t h i s o s ^ n h cac phu-o-ng p h a p t i n h t o a n ly t h u y e t vA thi^c n g h i e m t 6 n dp qua Ib-o
h^t trying t h d i Id-p hat s o i t — • — ^ Q E'Q"'^
4000 3000 2000 S. 1000
• < *"
0 W 1 DLj>6-ng k i n h
2
y^^
3 4 5 Id'p h^t d ( m )
-m— EQ 12
^ r ^ e o 20
^ EQ Federop
— * « — E q Q Todes
— • — T h y c
J . nghiem 6 7
cho cdc loai ldp hat.
3.2.3. Tinh todn trd lijCc ldp hat bdn soi tren mo hinh thiet ke
Ap dung (Ct26) de tinh toan gid tri dp suii't va sff diing (Ct28) de hieu chinh lai gid tri tinh toan cho sat vdi thffc te.
Trong qua trinh tinh todn sff dung (Ct27) tinh loan dp xdp ldp hat trang thdi sdi| 13), ngoai ra cdn phai bd sung them gid tri G- lffu Iffdng tdc nhan khi kg/m2.s. Gid tri kru Iffdng khi dffdc tinh: G= F (ni- )*Vs (m/s) = mVs.
Vdi dien tich ghi may sa'y F= 0.36 m2. va van tdc V,
dffdc lay tff ket qua do thffc te' tff quan sdt ldp hat sdi tffdng ddi ddng deu (bang 4). Nhiet dp tdc nhan say lay trung binh d 1600c [ 17], ta tinh Q (kg/m-s). Vdi chieu cao ldp hat khi hda bdn sdi Hs lay them khoang 10 % so vdi Htt, vay Hs= 0,036m.
Ket qua tinh todn tdn dp qua ldp hat ban sdi trinh bay trong bang 7. trong dd dp ,\d'p ciia Idp hat ban sdi ta tinh e theo Zabrodsky (PT27) trong dd he sd Renol va he sd Archimeter (Ar) tinh theo (PT 34) [12]:
(34) R e = ( 0 . 2 2 ^ 0 . 3 3 ) . A r ' ' "
Vi du tinh cho ldp hat cd dffdng kinh trung binh theo Ar
0.0009538818.430.4065
Re
Es0.616348
Bang 7 gia tri ton that ap suat qua ldp hat ban soi
stt
1 2 3 4 5 6 7
dh
0.225 0.45 0.75 0.956
1,05 1,35 1,65
Vn
0.15 0.2 0.42 0.57 0.5 0.6 0.8
APb, tinh toan ly thuyet 350.043 97.094 41.4719 29.1875 25.6031 18.8532 15.3262
C, he so hieu chinh
18.61577 15.76281 13.94409 13.16505 12.86232 12.10946 11.54007
APbs thiJC
nghiem cua ly thuyet 6516.324
1530.474 578.2873 384.2547 329.3150 228.3019 176.865
Gid tri AP thffc nghiem ly thuyet cung chi la gia tri tham khao dffpc hieu chuan tff ket qua tinh ly thuyet nhan vdi he sd hieu chinh | 2 | .
3.2.4. Xdc dinh ton dp cua dong khi di qua ghi phan phoi khi.
Theo cdch tinh sff diing tffdng quan ty le dien tich Id tren dien tich ghi A. Md hinh dffdc tinh todn va thiet ke theo [16] A= 0,36m-, Id phan phd'i khi tp = 12mm, sd Id 318 id, he s d d i e n tich X= 10% dffa gid tri nay vao (Ct30) (Ct31) \ a (Ct32) tren cd sd cd gid tri tdn dp qua ldp hat trang thdi tinh de tinh dffdc cdc gid tri cti the cua tdn dp qua ghi phan phd'i khi. trinh bay trong bang 8. Tdng trd lffc ciia tac nhan khi trong budng say se la tdng trd lffc qua ghi phiin ph(')i khi vdi trd lffc qua ldp hat sdi ttii thieu hoac ldp bdn sdi.
Md hinh thi nghiem (Hinh 2) dffdc thiC't ke c(') luing suii't 48kg/gid. chiC-u da\ hip iinidi liim Idp dem sdi ban diiu I I7|lrang thai tinh difdc thffc nghiC-m vii xac dmh HCEO ttC^
T A P C H i C d K H i VlfeT N A M J So 119 - lining 12 n i m 2009
NGHIEN ciiu • TRAO DOI
B t o g 8-XAc dinh ton thElt qua ghi phan phoi khi
su 1 2 3 4 5 6 7
Jh (mm) 0.225
0 . 4 5 0.75 0 . 9 5 6
1.05 1.35 1.65
vtl (m/s)
0.1 0.15 0.25 0.4 0.4 0.5 0.5
API Ergun) 397.09 159,36 11 2..34 138.07 118.15 111.28 8.1.129
\ P (ppk) 158.84 63.75 44.94 55.23 47.26 44.51 33.25
[ Henderson H Krishnaiah) 0.659
1.481 4.1139 10.534 10.53 16.456 16.456
99.28 39.84 28.085
34.52 29.54 27.g2 20.79
30mm. Tien hanh thffc nghiem xdc djnh van td'c hod sdi tdi thieu vtt cho cdc cap hat cd kich thffdc khac nhau:
Ghichu: Cdc kich thudc ciia ldp hat
dh=l,65mm; 1.35mm: 1,05mm:0, 75mm;0.45mm;
0,225mm dU0c lay tit khd'i hat nguyen lieu cdng nghe nghien rda va phan ly thiiy luc. Ldp hat co kich thudc dm =0,956mm la dudng kinh trung binh khdi hat xdc dinh bang phuong phdp ray tit phuong phdp nghien rvla bdng mdy nghien bua thu cdng thdng thudng [13]
Thdng qua thffc nghiem va ket qua tinh todn tff cac bang ta rut ra mdt sd nhan xet nhff sau:
3.3. Nhan xet
3.5.7. Trd lite qua ldp hat dnh
Theo each tinh cua Blacke-Koze, do pham vi dp dung Re<10 nen cho cd cac hat mudi tinh kich thffdc d^={ 0,75; 0,45;0,225)mm la thda man, trong khi each tinh ciia Plummer chi dp dung khi R> 1000 nen khdng dp dung dffdc trpng trffdng hdp sii'y mudi tinh tiing sdi nay.
Sff dung Cdng thffc Ergun de tinh tdn dp qua ldp hat cd dffdng kinh hat cang nhd thi tdn dp qua ldp hat cang Idn, dieu nay ngffpc vdi ket quii thffc nghiem la kich thffdc hat Cling Idn thi tdn dp cang Idn.
3.3.2. Trd lUc qua ldp hat soi td'i thieu
Cung gidng nhff Idp hat tinh, tinh tdn dp qua ldp hat sdi tdi thieu theo Ergun, vdi ldp hat cd kich thffdc be trd lffc thi tang dan, dieu nay thi phu hdp vdi dp rdng ldp hat.
Gid tri tdn dp tinh theo Federop khac biet va Idn hPn rat nhieu so phffdng phdp tinh khde va gid tri thffc te.
Khac vdi cdch tinh ciia Ergun, tdn dp tang dan khi tinh cho ldp hat tang Idn dan.
Gid tri Rett tinh theo cdng thffc Todes gan vdi bang vdi gia tri tinh Rett thdng thffdng.
Gid tri tdn dp qua ldp hat tinh theo Kozeny-Carman tang diin theo kich thffdc hat tang, cd gid tri tffdng dffdng vdi cdch tinh cua Ergun va tffdng dd'i hdp ly vdi gid tri thiTc nghiem.
Khdng cd sff chenh lech ve tdn dp cho ddng khi thdi qua cdc cdc ldp hat cd dffdng kinh, kich thffdc hat khde nhau khi sff dung (PT12 va PT 20) do tdn dp khdng phu thudc vao dffdng kinh.
3.3.3. Ldp bdn soi
Tdn dp qua Idp hat bdn sdi thi Idn hdn trd lffc qua ldp hat tinh. Vdi cdc hat cd kich thffdc be dh =0,45; 0,225 tdn dp tang hdn rat nhieu
3.3.4. Tdn dp qiui ghi phan phdi khi
Tdn dp qua ghi phan phdi khi tinh theo cdng thffc ciia
Henderson (Pt21) cho gid tri tffdng dd'i be (do thanh phan van tdc khi qua ldp hat trang thai tinh phu thudc theo kich thffdc hat).
Khoang bien thien dp suat tff 0,66 - 55 mmH20 cho dai phan bd kich thffdc hat. Ton dp qua ghi phan phd'i khi tinh theo Henderson thich hdp cho trffdng hdp say hat ndng san.
Ton dp qua ghi phan phd'i khi tinh theo Krishnaiah[6] cho gid tri hdp ly. Ton dp se tang khi dffdng kinh hat giam (Bang 8).
4. Ket luan Tdn dp qua ldp hat tuy thudc: 4
- Kich thffdc hat, cac phan tff min lan trong khdi hat, neu hat cd nhieu tap chat min, Ap tang.
- Dp rdng cua khdi hat, each dffa hat vao budng say dffdi dang bi nen chat cung deu lam tang trd lffc Ap.
- Dd'i chieu vdi dieu kien van hanh trong thffc te , khi tinh todn phai tinh bu them bang each nhan AP tff ket qua tinh theo cdc cdng thffc ndi tren vdi he sd ma cd tinh den ( yeu to nay.
- Ton dp cua ddngTchi qua Idp hat sdi phu thupc vao 1 thffdc hat (d^), dp rdng ciia ldp hat (E^^) va dp nhdt dpng Iffc hoc cua tac nhan khi hda sdi td'i thieu. •
9 9 ! ^
Tai lieu tham khao:
[1] Brooker.Donal B and Arkema Fred W.and Hall Carl W,l Drying and storage of grain and oilseeds.Hardcover.
[2] L.T Fan.S C Wang and CY Wen G.K.Roy Prediction of pressure drop across a gas-solid semi-tluidized bed A,I Ch E journal vol 57 pi CH3June 1977, India.
I-S] H.S.Fogle and LF.Brown,Fluidized bed Reactors, Vol 168,P31,1981.
14] D.Kunii and O.Levenspiel.Huidization Engineering,2nd,ed,Elsevier Science and Tectinology,1992
|5| Howard.J.R. Fluidized bed Technology, principles and application.
Publisher Taylor & Francis Group Date. 1989.
[6] W.McCabe.J.Smith and P.Harriot, Unit operation of cliemical Engineering. 7th ed, Mcgraw-Hill, 2(X)5.
17] Krishnaiah. K,Janaun, J.AnPrabhakar, A.Fluidized bed reactor as solid statefermenter. chemical Engineeringprogram, University Malaixia.
|8] Jenifer Sandidge, David Shin, Rui flow throuh packed beds, experi- ence data Ergun equation. The University of Texas of Austin,31.3.2(X)5.
[9] Bui Trung Thanh, Xac dinh mot so thong so thiiy dpng lire hoc trong say hat muoi tinh bang 16p soi, Tap chi khoa hoc Cong nghe Nhiet so thang 11/2(X)9.
1101 NguyenHay-Biii Trung Thhnh, thuyet minh de tai cap nhi nUtSc '"Nghien cufu thiei ke va che tao may ly tam vk m4y say muoi tinh lien tuc frang bi cho day chuyen san xuai muoi tinh nang suat 3 tan/giO",
1/2006. J 111] Tran van Phii.Ky thujt sSy, nhi xuai b4n giao due, 2006. ^
112] Nguyin Van Lua, Qua trinh va thiei bi cong nghe hoa hoc vi thitt pham. tap 1, Cac qua trinh va thiei bi cO hpc, quyen 1, khuay-liing Ipc.
nha xuai ban Dai hpc Quoc gia TP H& Chi Minh. 2005.
[13] Bui Trung Thanh, Nghien cifu xac djnh kich thi/6c hinh h(K hai muoi tinh ufng dung say bang Iflp soi. Tap chi Khoa hpc Cong nghe nhi?l so 3/2009.
[14] Biii Trung Thanh, Xac djnh mpt so thong so vat ly cd bdn ciia hat muoi tinh de ufng dung trong tinh loan thiei ke say bing miy say tang sfli lien tuc. Tap chi Ca khi Viet Nam so thang 9/2009
[ 16] Bui Trung Thanh-Nguyin Hay-Thiei ke ghi phan phoi t^c nhan khi cho may say muoi tinh tang soi lien tuc. Tap chi Khoa hpc Cpng nghe Nhiet nhan dang so thang 1/2010.
[ 17 ] Bui Trung Thiinh. say mufii tinh bhng miy say tang s6i lien tuc. Tap chi Khoa hpc Cong nghe Nhiet so thang 7.2009.
118] Bui Trung Thanh-Nguyen Hay. Xac djnh van toe khi h6a soi tffi thieu tren mo hinh may say mudi tinh lang soi lien tuc. Tap chi CtJ khi Viet Nam so thang 11.2009.
TAP CHI C d KHi VIET NAM O So 149 - Thang 12 nilm 2009
