N QT&TB KHOA : C KH CNG NGHM U

Vit Nam l t nc nng nghip vi truyn thng trng la t rt lu i. Chng ta t ho c xem l mt trong nhng chic ni ca cy la. T nhng nm kh khn phi nhp lng thc, chng ta vn ln thnh nc xut khu go ng th hai trn th gii. Tuy nhin gi tr xut khu go ca Vit Nam cn cha cao do cng ngh sau thu hoch cn lc hu. Do , vic tm hiu v cc tnh `cht ca ht thc, cc bin php hn ch cc tn tht sau thu hoch, cc quy trnh ch bin nng cao gi tr s dng ca thc l mt vn cn quan tm v gii quyt nhanh chng. Trc nhng nguy c c th gy h hng nh iu kin thi tit tht thng, vi sinh vt, nm th phng php duy nht nhm gim ti a s h hng ca ht la l phng php sy. Khng nhng vy, sy cn gp phn lm gim nng lng tiu tn trong qu trnh vn chuyn v thun li cho qu trnh gia cng tip theo nh lm sch, tch v Sy l qu trnh dng nhit nng lm bay hi nc ra khi vt liu n gi tr m cn thit bo qun. Khi p dng bin php sy ng k thut s gim c m ht n mc an ton cho tn tr v gi c phm cht ca ht. iu ny cho thy tnh cn thit ca vic tnh ton v thit k h thng sy thc.

Chng 1. TNG QUAN1.1. Ngun gc, thnh phn v tm quan trng ca thcLa l ngun lng thc chnh ca gn mt na dn s trn tri t. La c trng nhiu khu vc ng Nam . Rice is the most important cereal on the globe, Go l ng cc quan trng nht trn th gii,being the main source of energy and income for the l ngun chnh ca nng lng v thu nhp cho ngi majority of the world's human populatphn ln dn s ca con ngi trn th gii. Aside Ngoi from being the staple food, or a carbohydrate l lng thc ch yu, hoc carbohydrate component of a meal, rice is also used in numerous thnh phn ca ba n, go cng c s dng trong rt nhiu industrial applications. cng nghip. Its use in the diet and inS dng ca n trong ch n ung v industry depends on its cooking properties. ngnh cng nghip ph thuc vo cc tnh cht nu n ca mnh. V din tch t canh tc la hng th hai sau la m nhng v nng xut ca la l loi cao nht.Cu to ca ht thc gm: V hat, lp alrn, ni nh, phi. Cc lp ngoi v v trong ca go lt chim khong 4-5% khi lng ca ht, lp t bo alron chim khong 2-3%, ni nh chim t l 65-67%.Thnh phn ha hc ca ht la gm ch yu l tinh bt, protein, xenlulose. Ngoi ra trong ht la cn cha mt s cht khc vi hm lng t hn so vi 3 thnh phn k trn nh: ng, tro, cht bo, sinh t. Thnh phn ha hc ca ht la ph thuc vo nhiu yu t nh ging, t ai trng trt, kh hu v ch chm sc. Cng chung iu kin trng trt v sinh trng.Thnh phn ha hc ca ht la:Thnh phnha hcHm lng cc cht ( % )

Nh nhtLn nhtTrung bnh

Protein6.6610.438.74

Tinh bt47.7068.0056.20

Xenluloze8.7412.229.41

Tro4.686.905.80

ng0.104.503.20

Cht bo1.602.501.90

ectrin0.803.201.30

Khi mi thu hoch v la thng c m cao nn mt s ging la c th ny mm, men mc v nm d pht trin, lm h km phm cht ca thc go. m trung bnh ca thc khi mi thu hoch 20- 27%. la khng b h hi hoc gim phm cht, th trong vng 48 ting sau khi thu hoch phi lm kh la t m 20%. Theo thng k, m an ton ca ht thc cho bo qun ph thuc vo tnh trng thc, kh hu cng nh iu kin bo qun. Khi thc c m 13- 14% c th bo qun c t 2-3 thng, nu mun bo qun hn 3 thng th m ca thc tt nht t 12- 12,5%. m thc, cng ngh sy cng nh hng ti hiu sut thu hi go v t l go trong qu trnh xay xt, m thch hp cho qu trnh xay xt t 13- 14%.Ngoi ra, thc l mt loi vt liu yu cu sy ch mm v tnh bn chu nhit ca thc rt km, khng cho php nng nhit t nng ht ln cao. Nguyn nhn l s hnh thnh cc vt nt ca ni nh do trong qu trnh sy m ca lp ngoi ht gim nhanh, to nn trng thi cng th tch ca phn trung tm, khi tng nhit lm cho sc cng vt qu bn chc ca ht th to nn cc vt nt. Cc vt nt xut hin theo cc vch protein ngn cch gia cc ht tinh bt. Do khi thit k h thng sy ta cn xc nh r thng s ca tc nhn sy ph hp cho thc, thc c bo qun lu, cht lng tt v lng ph phm khi xay xt thp.1.2 Tnh hnh sn xut la Vit Nam Vit Nam, la go l ngun lng thc chnh khng th thiu trong i sng con ngi. La cn l nguyn liu sn xut tinh bt, s dng nhiu trong cc ngnh cng nghip thc phm. La cng c lm thc n gia sc, gia cm.Hin nay, Vit Nam ang ng th hai th gii v lng go xut khu trn th gii, v tip tc y mnh vic xut khu go sang cc nc trn th gii. y l mt trong nhng ngun thu ngoi t chnh ca t nc. Din tch trng la chim mt t l rt ln tng din tch trng trt Vit Nam. V trong tng lai, Vit Nam s khng tng din tch trng la m tp trung tng nng sut bng cch ci to ging, phng cch trng trt, k thut canh tcnhm tng sn lng la go. Lng la go Vit Nam ch yu tp trung vng ng bng sng Cu Long v ng bng sng Hng. Vi nhng iu kin thun li cho cy la nc, Vit Nam tr thnh mt trong nhng nc sn xut v xut khu la go hng u th gii. Ngoi nhng ging la cao sn, nhng ging lai cho nng sut cao (c th t 7 tn/ha) p ng nhu cu la go v mt s lng, Vit Nam cn thc hin trng trt v sn xut nhng ging go c sn c gi tr dinh dng v cm quan. Cc ging la c sn ny tuy khng cho nng sut cao, nhng vi nhng c tnh nh mi thm, mu sccc ging la ny c mt th trng nht nh.Sn lng la trong c nc: Sn lng la ca cc a phng khng ngng tng qua cc nm. Trong , vng ng bng sng Hng chim hn 50% sn lng la min Bc, ng bng sng Cu Long chim hn 80% sn lng la min nam. ng bng sng Hng v sng Cu Long c th coi l hai ni sn xut la ch yu trong vng vi din tch trng, nng sut, v sn lng la t c cao hn cc a phng khc trong c nc.

The rice grain (rough rice or paddy) consists of an outer protective covering, the hull, and the rice caryopsis or fruit (brown, cargo, dehulled or dehusked rice), (Juliano and Bechtel, 1985), (Figure 2). 1.3. S lc v qu trnh sy 1.3.1 Tm quan trng ca vic sy la Trong ma ma m ht la ngoi ng lc thu hoch khong 28-30%, nu khng phi sy kp thi ( trong bao hoc ng) th sau 24 gi ht s ny mm. Vi iu kin thi tit bt thng v H Thu v Thu ng, khi phi la s gp nhiu kh khn nh: khng phi c trong nhng ngy ma dm, ph thuc nhiu vo sn bi, chi ph lao ng cao, kh tm nhn cng, ht d b ln tp cht, ht kh khng u nu phi qu dy v t co o, cht lng ht b gim do khng nng, phi khng ng k thut s cho t l go xay xt thp.V vy trong ma ma cn lm kh ht kp thi bng bin php sy.Khi p dng bin php sy la ng k thut s gim c m ht n mc an ton cho tn tr v xay xt, gi c phm cht ht v mu sc, mi v, gi tr dinh dng, tng t l thu hi go nguyn khi xay xt, gim hao ht ht trong ma ma; ngoi ra vic sy la s hn ch tnh trng phi la trn l ng lm nh hng n an ton giao thng, m ra dch v mi thu ht lao ng nng thn. Nu chng ta p dng sy la ng cch cng gp phn nng cao cht lng go, gia tng gi tr ht go Vit Nam trn th trng th gii.Tuy nhin t c hiu qu ti u trong khu sy la cn ch my vn sau: - Nu la b ln mng, mc, m vng th d c sy k cht lng la vn khng cao, do cn em la i sy ng lc, kp thi.- La em i sy khng c ln nhiu tp cht nh: rm vn, dy buc bao, bn t...- Chn my sy t yu cu k thut. - Chn ch l sy c uy tn, gi sy chp nhn c

1.3.2 S lc v qu trnh sySy l qu trnh tch m ra khi vt liu bng phng php nhit. Kt qu qu trnh sy l hm lng cht kh trong vt liu tng ln. Hay qu trnh sy l qu trnh khng kh c m tng i thp hoc khng kh nng tip xc vi ht. Trong qu trnh khng kh s ly m t ht. Kt qu l thy phn ca ht gim.Thy phn tn ti trong ht nng sn hai dng: m b mt v m bn trong. m b mt bay hi ngay sau khi tip xc vi khng kh nng. Qu trnh bay hi ca m bn trong chm hn do n phi tri qua hai giai on: giai on di chuyn t bn trong ni nh ra ngoi b mt v giai don chuyn m t b mt ra khng kh xung quanh. V vy, tc thot m ca m b mt v m bn trong l khc nhau. Kt qu l tc sy (tc gim thy phn ca ht) trong qu trnh sy thay i. thc hin qu trnh sy, ngi ta s dng mt h thng gm nhiu thit b nh: thit b sy ( bung sy, hm sy, thit b sy kiu bng ti, my sy thng quay, sy phun, sy tng si, my sy trc ), thit b t nng tc nhn, qut, bm v mt s thit b ph khc, Trong n ny em tnh ton v thit k thit b sy kiu bng ti. My sy bng ti l my sy a nng nht c s dng sy nhiu loi sn phm vi kch c, cu to v hnh dng khc nhau. Nhn chung loi my sy ny thch hp sy vt liu dng ht c ng knh t 1 50mm, khng thch hp sy vt liu mng v huyn ph c. Vi cc yu cu v cht lng sn phm s dng thit b sy kiu bng ti vi nhiu bng ti lm vic lin tc vi tc nhn sy l khng kh nng.Vt liu sy c cung cp nhit bng phng php i lu. u im ca phng thc sy ny l thit b n gin, r tin, sn phm c sy u, tc ca khng kh i qua phng sy ln, nng sut kh cao, hiu qu, c th thc hin sy cng chiu, cho chiu hay ngc chiu.

1.4. S quy trnh cng ngh:

54IIIIII231

Vt liu vo

Hi nc

IVKhng kh

Vt liu raHi nc bo ha

Ch thch: 1- qut y2- calorife3- phng sy4- cyclon5- qut htThuyt minh quy trnh cng ngh.Do thc l loi vt liu sy dng ht nn thit b sy thch hp l sy bng ti lm vic lin tc vi tc nhn sy l khng kh nng. Vt liu sy c cung cp nhit theo phng php i lu.Thit b sy kiu bng ti gm mt phng sy hnh ch nht trong c mt hay vi bng ti chuyn ng nh cc tang quay, cc bng ny ta trn cc con ln khi b vng xung. Bng ti lm bng li kim loi, khng kh c qut 1 a vo t nng trong Caloripher 2, y khng kh nhn nhit gin tip t hi nc bo ho qua thnh ng trao i nhit. Hi nc i trong ng, khng kh i ngoi ng, sau cho vo phng sy ti IV. Vt liu sy cha trong phu tip liu, a vo phng sy 3 ti I, gia hai trc ln i vo bng ti trn cng. Nu thit b c mt bng ti th sy khng u v lp vt liu khng c xo trn do loi thit b c nhiu bng ti c s dng rng ri. Vt liu t bng trn di chuyn n u thit b th ri xung bng di chuyn ng theo chiu ngc li cui cng vt liu kh vo ngn tho III. Khng kh nng i cho dng vi chiu chuyn ng ca bng. Do lng khng kh nng v thc tip xc vi nhau rt ln lm cho lng m c tch ra trit hn. Khng kh sau khi ra khi phng sy ti II c ln bi v cc tp cht khc c thu hi xyclon 5, khng kh sau khi lm sch c qut 6 y ra ngoi

Chng 2: CN BNG VT CHT2.1. Cc s liu ban u

-Nng sut tnh theo sn phm : G = 8.5 (tn/ngy)- m vt liu vo : W1 = 23%- m vt liu ra : W2 =13%-Nhit sy cho php : t1 = 70oC suy ra p1bh = 0.3177(at) ( bng I .250.STQTTB I / Trang 313)-Nhit ra ca tc nhn sy : t2 = 46oC suy ra p2bh =0,103 (at)-Cht ti nhit : hi nc bo ha-Trng thi khng kh ngoi tri ni t thit b sy Hu nn ta chn nhit l + t0 = 25oC suy ra Pbh0 = 0,03166(at )

+ = 81% suy ra pkq = p =1.033 at2.2. X l s liu- t mt s k hiu: G1,G2 : Lng vt liu trc khi vo v sau khi ra khi my sy (Kg/h)Gk : Lng vt liu kh tuyt i i qua my sy (Kg/h)W1, W2 : m ca vt liu trc v sau khi sy tnh theo % khi lng vt liu tW : m c tch ra khi vt liu khi i qua my sy (Kg/h)L : Lng khng kh kh tuyt i i qua my sy (Kg/h)xo : Hm m ca khng kh trc khi vo caloripher si (Kg/Kgkkk)x1, x2 : Hm m ca khng kh trc khi vo my sy (sau khi i qua caloripher si) v sau khi ra khi my sy,(Kg/Kgkkk)- Hm m ca khng kh c tnh theo cng thc sau:

( Cng thc 16-3/sch QTTBII-156) Thay s vo ta c

x0= =0,01588( kg/kkk )Nhit lng ring ca khng kh trc khi vo calorife I0=Ckkk*t0+x0*ih = Ckkk*to+(r0+Ch*t0)x0 (Cng thc 16-4/sch QTTBII trang 156) Ckkk: nhit dung ring ca khng kh J/kg Ckkk=103 J/kg

to: nhit ca khng kh to=25 0 C Ch: nhit lng ring ca hi nc r0 t0 J/kg - Nhit lng ring ca hi nc t0 c tnh theo cng thc: Ih=Ch*T0+r0=(2493+1,97 t0)*103 J/kg ( sch QTTB2-156)Trong ro:2493*103:Nhit lng ring ca hi nc 00c Ch=1.97*103: nhit dung ring ca hi nc J/kg I0=(1000+1,97*103 x0)T0+2493*103x0 J/kgKKK = 65,17*103 J/kgkkk =65,17 kJ/kgkkk Trng thi ca khng kh sau khi i khi calorife ( s tay QTTBT-312) T1=70 P1bh= 0.3177 at khi i qua calorife khng kh ch thay i nhit cn hm m khng thay i. Do x1 = x0 nn ta c :

1= (VII.11-s tay QTTB2) = = 0.081 = 8.1%Nhit lng ring ca khng kh sau khi i khi calorife I1 = (1000+1,97*103*x1)T1+2493*103*x1 = (1000+1,97*103*0,01588)*70+2493*103*0,0158 = 111,80*103 (J/kgkkk) = 111,80 (kJ/kgkkk) Trng thi ca khng kh sau khi phng sy T2=460C, P2bh=0,103(at) Nu sy l thuyt I1=I2 =111,80 (kJ/kgkkk ) I2=Ckkk *T2+x2*ih T hm m ca khng kh:

x2=== = 0,0259 (kg/kgkkk) 2.3. Cn bng vt liu:2.3.1 Cn bng vt liu cho vt liu sy:Trong qu trnh sy ta xem nh khng c hin tng mt mt vt liu, lng khng kh kh tuyt i coi nh khng b bin i trong sut qu trnh sy. G1: lng vt liu trc khi sy.G2: lng vt liu sau khi sy. Gi thit trong mt ngy nh my hot ng trong 16 gi nn G2 = = 531 (kg/gi) Gk: lng vt liu kh tuyt i.Lng vt liu kh tuyt i: Gk

Gk= G1= G2 (7.22 QTTB4 trang 289)Trong : W2 = 13%, G2 = 566 ( kg )=> Gk =531 = 461,97 (kg/h )Lng m tch ra khi vt liu trong qu trnh sy: W

W = G2 ( 7.27 QTTB4 trang 289) = = 68,96 ( kg/h).Lng vt liu trc khi vo phng sy:G1 = G2+ W = 531+68,96=599,96 ( kg/h).

2.3.2 Cn bng vt liu cho tc nhn sy:Cng nh vt liu kh, coi nh khng kh kh tuyt i i qua my sy khng b mt mt trong sut qu trnh sy. Khi qua qu trnh lm vic n nh lng khng kh i vo my sy mang theo lng m l: Lx1 Sau khi sy xong lng m bc ra khi vt liu l W do khng kh c thm lng m l WNu lng m trong khng kh ra khi my sy l L.x2 th c phng trnh cn bng: L.x1 + W = L.x2 (728-QTTB4-290)

L =

= = = 6882,24( kg/h ).

L: L lng khng kh ti thiu kh cn thit lm bc hi W kg m trong vt liu. ta li c t0=250C,ng vi =1,185 kg/m3 (phc lc 6 tnh ton v thit k h thng sy Trn Vn Ph)Lng khng kh cn thit lm bc hi 1kg m trong vt liu l; l

l = = (kg/kg m). Lng khng kh kh cn thit lm bc hi 1kg m vt liu: l ( kg/kg m).(VII.20 s tay QTTBII trang 102)Cc thng sTrc khi vo caloripherSau khi ra khi caloripherSau khi ra khi phng sy

T (0C)257046

Pbh ( at )0,031660,31770,103

( %)818,140,72

x (kg/kgkkk)0,015880,015880.0259

I( kJ/kgkkk)65,17111,80111.80

Chng 3. CN BNG NHIT LNG V TNHTON THIT B CHNH3.1. Cc thng s v thit b sy3.1.1. Th tch khng kh :a. Th tch ring ca khng kh vo thit b sy:

v1=(m3/kgkkk) (Cng thc 7.2 QTTB4 trang275)T1 = 70+273 = 343K => 0 = 1,029 R=287(J/kg0k)P=1,033(at)P1bh=0,3177(at) (1 at = 9,81104 N/m2 )

1=0,081(m3/kgkkk)b. Th tch khng kh vo phng sy: V1=Lv1=6882,240,9962 = 6856,087 (m3/h)c.Th tch ca khng kh ra khi phng sy l;

v2= T2=45+273=318K

= 0,4134 P2bh= 0,103 at (m3/kgkkk)d. Th tch ra khi phng sy V2 = Lv2 = 6882,24 0,938= 6455,54 (m3/h)e. Th tch trung bnh ca khng kh trong phng sy

Vtb = = = 6655,8135 (m3/h) 3.1.2. Chn kch thc ca bng tiChn kch thc bng ti; Gi :Br: Chiu rng lp bng ti (m) H : Chiu dy lp thc (m) ly h=0,05(m) w : Vn tc bng ti chn w=0,4 m/pht= 24 m/h

: Khi lng ring ca thc =500 kg/m3- Nng sut qu trnh sy:

Gr=Br*h*w* (kg/m3)

- Chiu rng thc t ca bng ti:

(:hiu s hiu chnh)

= 0,9 Btt = 1,19 (m) Gi Lb:chiu di bng ti (m) Ls:chiu di ph thm;Ls= 1 (m) T : Thi gian sy, chn T= 0,5h T+Ls (trang 121 s tay QTTBII)

= = 11,8 (m)- Ta chn s bng ti l i = 2 chiu di mi bng ti =5,9 (m)ng knh bng ti d=0,3 (m)3.1.3. Chn vt liu lm phng sy- Chiu di Lph= Lb+2Lbs = 5,9+2*0,5 = 6,9(m)(sch tnh ton v thit k h thng s trang 191 Trn Vn Ph)- Chiu cao khong cch gia 2 bng: Hph= i*dbng+(i-1)d+2dbs = 2*0,3+0,5+2*0,5= 1,7

- Chiu rng: Bph= B+2Bbs=1,19+2*0,3 =1,79 (m) Kch thc ph b:

- Tng xy bng gch, b dy gch = 0,2 m

+ Tng c ph lp cch nhit = 0,02 m

- Trn b tng dy= 0,17 m

+ Lp cch nhit= 0,07 m

+ Lp b tng dy = 0,1 mVy kch thc ca phng sy k c tng l: + Chiu di L= 6,9+ 2*( 0,04+0,2 ) = 7,38m + Chiu rng B = 1,79 + 2*( 0,04+0,2 ) = 2,27 m + Chiu cao H =1,7 + 0,17 + 0,02 = 1,89 m3.1.4.Vn tc chuyn ng ca khng kh v ch chuyn ng ca khng kh trong phng sy.a.Vn tc ca khng kh trong phng sy ( tnh ton v thit k h thng sy trang 198) b.Ch chuyn ng ca khng kh

Re = (Cng thc V.36 sch QTTBII trang 35)Re : l hng s Reynol c trng cho ch chy ca dnglt : ng knh tng ng Nhit trung bnh ca khng kh trong phng sy -T nhit trung bnh ny tra bng ph lc 6. Trang 350 sch '' tnh ton v thit k h thng sy '' Vi: = 18,7710-6 m2/s

Vy Re = 5,8104 ch chuyn ng ca khng kh trong phng sy l chuyn ng xoy3.1.5 Hiu s nhit trung bnh gia tc nhn sy v mi trng xung quanh

Vi: t1 : Hiu s nhit gia tc nhn sy vo phng sy vi khng kh bn ngoi t1 7025= 45

t2: Hiu s nhit gia tc nhn sy i ra khi phng sy vi tc nhn sy bn ngoi

t2 = 46-25 = 210C 3.2 Cn bng nhit lng3.2.1 Lng nhit tn tht do vt liu sy mang ra :

Trong nng sn, nhit vt liu sy ra khi thit b sy ly thp hn nhit tc nhn sy tng ng t (510 0C ) trong h thng sy ny, vt liu sy v tc nhn sy cho dng nn tvl =t1 - ( 5 v vy ta ly tvl = 70-7 =63 0C

qvl = (Trang 103 s tay QTTBII)tvl =250Ctvlc =630CNhit dung ring ca thc ra khi hm sy.Cvl = Cvlk*( 1 - W2 ) +Cn*W2Cvlk nhit dung ring ca thc kh bng 1,55 kJ/kg Cn = 4,19 kJ/kg W2 =13%

kJ/kg m Qvl =38201,0816 (kJ/kg m)3.2.2. Lng nhit tn tht ra mi trng :qm1 = qt1 + qc1 + qnTrong :qt1: tn tht nhit qua tng .qc1: tn tht nhit qua ca.qn: tn tht nhit qua nn.3.2.2.1. Lng nhit tn tht qua tng:

( CT 1.97 sch Cc qu trnh, thit b trong cng ngh ho cht v thc phm - tp 3 Phm Xun Ton) Trong :t2 = 700C: nhit tc nhn sy trong thit b.t1 = 460C: nhit khng kh ngoi mi trng.W = 68,96 (kg): lng m bay hi. kt1: h s truyn nhit qua tng.

kt1 = ( Cng thc T V.5 s tay QTTBII) Vi:= 0,01 (m): chiu dy lp va

= 0,2 (m): chiu dy lp gch.

= 1 (W/m2.0C): h s dn nhit ca va.

= 0,75 (W/m2.0C): h s dn nhit ca gch.

: h s cp nhit t tc nhn sy n tng.

: h s cp nhit t tng n mi trng.Lu th nng ( khng kh) chuyn ng trong phng do i lu t nhin ( v c s chnh lch nhit ) v cng bc ( qut) khng kh chuyn ng xoy do Re>104

Tnh :

= A( + ) Trong :A: h s ph thuc ch chuyn ng ca khng kh. Khi chuyn ng xoy v tng nhm th A = 1,2 1,3.Chn A = 1,3.

: h s cp nhit ca khng kh nng n thnh my sy do i lu cng bc. (W/m2.).

: h s cp nhit ca khng kh nng n thnh my sy do i lu t nhin t nhin.(W/m2.).

- Tnh .

( trang 23 s tay QTTBII) Vi: ttb: nhit trung bnh ca tc nhn sy trong thit b.

: h s dn nhit ca tc nhn sy nhit trung bnh.

= 0,02886 (W/m.) ( Bng I.255, s tay QTTB I)

: chun s Nuselt.i vi khng kh ta c cng thc sau:

= 0,008Re0,9*Pr0,4 ( Cng thc 1.34 sch Cc qu trnh, thit b trong cng ngh ho cht v thc phm - tp 3 Phm Xun Ton) Trong : Pr: chun s Prandtl theo ttb = 580C ca tc nhn sy.Pr = 0,6976 ( Bng I.255, s tay QTTBI )Re: chun s Renon.Re = 5,8104

=> = 0,008Re0,9*Pr0,4 = 0,008*(5,8.104)0,90,69760,4 = 134,16

=> = = 2,05 (W/m2.).

- Tnh :

( Trang 23 s tay QTTBII) Trong : H: chiu dai thit bi. H = 1.89 m.

: h s dn nhit ca tc nhn sy nhit trung bnh.

= 0,02886 (W/m2.0C). ( Bng I.255, s tay QTTBI )

: chun s Nuselt.i vi khng kh ta c cng thc sau:

= 0,47Gr0,25 ( CT 1.29 sch Cc qu trnh, thit b trong cng ngh ho cht v thc phm - tp 3 Phm Xun Ton) Gr: chun s Grashof

( Cng thc V.39 s tay QTTBI) Trong : tT1: nhit tng tip xuc vi tac nhn sy, chon tT1 = 480C.tm: nhit mang cua tng.Tm = = = 53

: hiu s nhit gia nhit trung binh cua tac nhn sy va nhit cua tng tip xuc vi tac nhn sy.

1= = 58 48= 100Cg = 9,81(N/m2).H = 1,89m: Chiu cao thit bi.

: H s gian n = = = 0,0031

: nht cua tac nhn sy tai tm, = 19,6175.10-6 (Ns/m2 ).

: Khi lng ring cua tac nhn sy tai tm,

= 1,08145(kg/m3) ( Bng I.255, s tay QTTBI )=>Gr = = 6,24.109

=> = 0,47(6,24109)0,25= 132,1

=> = = 2,02 Vy h s cp nhit t tc nhn sy n tng.

= A( + ) = 1,2( 2,05 + 2,02) = 4,884 (W/m2.).q1= 1 t1 = 4,88410= 48,84 (kJ/kg m)

Tnh :

=

: h s cp nhit do khng khi i lu t nhin (W/m2.).

: h s cp nhit do bc xa nhit t mt ngoai cua tng hm sy ra mi trng ngoai (W/m2.).

Trong qu trnh truyn nhit n nh th:q1 = vi i = 131 = 2 = 0,02 (lp va)3 = 0,2 (gch)1 = 2 = 1,23 = 0,7Vy tT1tT2 = 48,840,319 = 16 tT2 = 48 16= 32

- Tinh :

= 1,98 ( s tay QTTBII trang 24)

: hiu s nhit gia b mt ngoai cua tng va khng khi.

= = 3225 = 7

=> = 1,98 = 3,1(W/m2.).

- Tinh :

= ( CT 1.95 sch Cc qu trnh, thit b trong cng ngh ho cht v thc phm - tp 3 Phm Xun Ton) Trong :

= 0,81

= 4,5 - 4,25: h s bc xa chung

Chon = 4,2.TT: nhit tng ngoai tip xuc vi khng khi.TT = tt2 + 273 = 32+ 273 = 305KTK: nhit khng khi.TK = t0 + 273 = 25 + 273 = 2980K=> 2 = Vy h s cp nhit t tng n mi trng.

= = 3,1+3,71= 6,81 (W/m2.).

q2 = 6,817= 47,67 : chp nhn H s truyn nhit kt1

( CT V.5 s tay QTTBII)

Lng nhit tn tht qua tng:

QT =3,6KFF = F1 + F2 F1 =2BphHph = 21,71,7 = 5,78 (m2) F2 =2LphHph = 26,951,7 = 23,63 (m2)

F = 5,78+23,63 =29,41 (m2)

QT = 3,61,6729,4131,49 = 5567,84 (kJ) 3.2.2.2. Lng nhit tn tht qua nn. Nhit trung bnh ca tc nhn sy bng 58 v gi s tng phng sy cch tng bao che ca phn xng 2m.Theo bng 7.1 ca sch tnh ton v TKHT sy-trang142 ta cq1 = 47,15 w/m2. Do tn tht qua nn bngQn= 3,6Fn q = 3,6(71,7)47,15 = 2019,906 (kJ/h) qn = = = 29,291(KJ/Kg m)

3.2.2.3. Tn tht qua trn Trn c lp btng

Trn c lp b tng =0,1 m =0,922(w/m )

Lp cch nhit dy =0,07 m =0,057(m) tnh tn tht qua trn ta xc nh:

=13*=137,19=93,47 (w/m2k) Do h s truyn nhit qua trn

Ktr = Vy tn tht qua trn

Qtr= 3,6KtrFtrt = 3,60,653(6,951,7)(58-25) = 916,57(KJ/Kg m)

Vy nhit ti ring:

qtr = = 13,29 (KJ/Kg m)3.2.2.4 Tn tht qua ca

Hai u phng sy c ca lm bng thp dy= 0.005m v lp cch nhit dy =0.02m c h s dn nhit ca nhm = 0.5 w/mk,= 0.057w/m Do h s dn nhit ca Kc bng:

kc= ( w/ Ca pha tc nhn sy vo c chnh lch nhit (t1-t2) cn u kia c chnh lch bng(t1-t0) Qc= 3,6KcFc(t1-t2)+(t2-t0) =3,61,776 (1,71,7)(70-25)+(46-25) = 852,49(KJ/h) qc = = 12,36 (KJ/Kg m)Nh vy tng tn tht nhit truyn qua kt cu bao che ra mi trng xung quanh l Qmt = Qt + Qc + Qtr + Qn = 5567,84+852,49+916,57+2929 = 7366,19 = 106,82(kJ/kg m) Xy dng ng sy thc tTa xc nh cc thng s ca qu trnh sy thc bng phng php gii tch v n da trn cc cng thc tnh ton nn chnh xc hn.- Nhit lng b sung thc t

= qbs + Cn tvl-q qbs= 0 ( do khng s dng caloripher b sung)tvl :nhit ca vt liu trc khi vo my sy tng tn tht trong qu trnh sy Nhit lng vo Nhit calorige ca cung cp

=qvl+qmt =553,96+106,82 =660,78 (KJ/kg m)

=4,1925-660,78 = -556,03 (KJ/Kg m)Hm m ca khng kh ra khi phng sy trong qu trnh sy thc l:

x2' ( Cng thc VII.26 s tay QTTBII/ trang 105) Nhit dung ring ca khng kh sau khi sy:I2'=(1+1,97x2')t2+2493x2' = (1+1,970,022)46+24930,022 = 108,01 (KJ)Hm m ca khng kh ra khi my sy l:

So vi sy l thuyt c= 0,4072 nn nhit t2 = 46 l thch hp.Lng khng kh cn thit bc hi 1kg m trong qu trnh sy thc l: l' = = 123,152(kgkkk/kg m) L'= l'w = 123,15268,96 = 8492,56(kg/h)

3.2.3. Cn bng nhit lng: - Nhit lng tiu hao(q)trong qu trnh sy

q = l'(I'2-Io)- (16-26 QTTBI trang168) = 123,152(108,01 - 65,17) + 556,03 = 5831,86 (KJ/kg m)- Tng nhit lng c ch v tn tht

q' = q1+q2+ Nhit lng c ch bc hi 1 kg m q1=i2-catkk i2: Nhit dung ring ca 1 kg hi nc i2= r+cpat r : nhit ha hi KJ/kg Cpa: nhit dung ring ca hi nc 1,842 KJ/kg T : nhit ra ca tc nhn sy i2= 2500+461,842 = 2584,732 (KJ/kg) q1 = 2584,732 - 4,1925 = 2479,982 (kJ/kg) Vi Ca : nhit dung ring ca nc 4,19 KJ/kg nhit lng do tc nhn thi mang i Nhit lng do tc nhn thi mang i: q2 = l'Ck(t2-t0) (k thut sy nng sn trang53) vi Ck= ckkk+0,47x0 = 1,005+0,470,01588 = 1,0125 KJ/kg q2 = 123,1521,0125(46-25) = 2618,5194 (KJ/kg) Vy tng lng nhit c ch v cc tn tht

q' = q1+q2+ = 2479,982 + 2618,5194 + 660,78 = 5759,2814 (KJ/kg) Theo cn bng nhit lng, qu trnh tnh ton trn c q v q' sai khc nhau rt t s sai khc ny l do sai

i lngK hiukJ/ kg m

Nhit c chq12479,982

Tn tht nhit do tc nhn syq22618,5194

Tn tht nhit do vt liu syqvl553,96

Tn tht ra mi trngqmt106,82

Tng lng nhit tnh tonq5759,2814

Tng lng nhit tiu haoq5831,86

Chng 4. TNH TON CC THIT B PH4.1. CalorifeDo yu cu v cht lng ca sn phm thc sau khi sy nn phi dng tc nhn sy l khng kh nng. Khng kh i qua caloripher si v nhn nhit gin tip t hi nc bo ha qua thnh ng.Khng kh dng sy phi c nhit theo yu cu l 70 oC cht truyn nhit l hi nc bo ho.Thit b chn l loi ng chm. Khng kh nng i ngoi ng, hi nc bo ha i trong ng. Hai lu th chuyn ng cho dng.4.1.1. Chn kch thc truyn nhit.

Chn ng truyn nhit bng ng,c gn nng h s truyn nhit,h s dn nhit ca ng l W/m (sch QTTB tp I trang 125)Chn ng:- ng knh ngoi ca ng:dng = 0,025 (m)- ng knh trong ca ng:dtr = 0,020(m)

- Chiu dy ca ng: = = 0,0025 (m)- ng knh ca gn:Dg = 1,4 dng = 0,035(m)- Bc gn:bg = 0,02 m

- Chiu cao ca gn:h = = 0,005 (m)- Chiu di ca ng:l = 1,4 (m)

- S gn trong trn mt ng:m == 70- B dy bc gn :b = 0,003(m)- Tng chiu di ca gn :Lg=b*m=0,003*70=0,21(m)- Tng chiu di khng gn:Lkg=l-Lg = 1,4-0.21=1,19(m)- Lng khng kh cn thit cho qu trnh sy (theo tnh ton thc t):l = 123,152 ( Kg/Kgm)L =8492,56 ( Kg/h)- Nhit ca khng kh ban u l: t = 25oC- khng kh sau khi ra khi caloripher l: t1=70oC- Th tch ring ca khng kh V70oC = 1/70o = 1/1,029 =0,97 (m3/kg) ( cng thc I.5 s tay QTTB tp 1) V46oC =1/46o = 1/1,107 = 0,903 (m3/kg) v25oC =1/25o = 1/1,18 = 0,844 (m3/kg)vtb =(v25o+v70o)/2 = 0,907 (m3/kg)- Lng khng kh kh i vo caloripher l:V=L*vtb = 8492,56 0,907=7702,75 (m3/h)

- H s cp nhit + Nhit trung bnh ca khng kh trong caloripher ttb

ttb = thn-

M: + Chn nhit hi nc bo ha khi vo l thnd = 105oC+ Chn nhit nc ngng t khi ra l thnc = 79oCNn ta c:

tc = thnc tc = 9Thay s vo ta c:ttb = 32,5Suy ra :ttb = 105 32,5 = 72,5oCng vi gi tr ttb ta c: = 1,022 (kg/m3) = 0,02983 (w/m) = 20,72510-6 (Ns/m2)4.1.2. Tnh ton.Din tch b mt ca mt ng : (pha trong ca ng)

Ftr = *dtr*l = 3,14*0,02*1.4 = 0,0879( m2)Din tch mt ngoi ca ng:

Fng = dng*l = 3,14*0,025*1,4= 0,1099 (m2)Din tch phn b mt ngoi ca mt ngFbm = Fgn+Fkgn-Din tch phn c gn

Fgn = = 0,02355(m2)-Din tch phn khng gn

Fkgn = Lkg*= 0,0934 (m2)Vy :Fbm = 0,02355+0,0934 = 0,117(m2)Chn s ng xp trn mt hng l: i = 20 Khong cch gia cc ng ny ng kia l d= 0,008(m) Khong cch gia ng ngoi cng n caloripher l 0,01 (m)Din tch t do ca caloripher l Ftd- Chiu di ca c caloripher lLx = Dng*i+i*Dg+(i-1)d = 0,01*2+(20-1)*0,008+20*0,035 = 0,872(m)- Din tch tit din ca c caloripher lFx= Lx*hcao = 1,4*0,872 = 1,2208 (m2)- Din tch cn ca gn l:Fcg = Dg*Lg*i = 0,035*0,21*20 = 0,15 (m2)- Din tch cn ca ng l: Fcng = dng*Lkg*i = 0,025*1,19*20 = 0,6( m2)Vy din tch phn t do: Ftd = Fx-Fcng-Fcg = 1,2208- 0,75=0,47(m2)Vn tc ca khng kh = (m/s) H s cp nhit t hi nc bo ho n b mt ngang ca ng:

(W/m2) ( cng thc 7-64 QTTB I ) ViH = 1,4 : chiu cao ng r : n nhit ho hi J/kg(Tra bng I250-s tay QTTB tp 1 ) T thn = 1050C tra bng I.250 STQTTB I ta c r = 2248103(J/Kg) - H s A c tr s ph thuc vo tmChn tT = 104,35oC : Nhit thnh ng trong ca ng

Vy tm = = 104,6750C ( trang 29 s tay QTTBII )S dng phng php ngoi suy, tra bng QTTBII trang 27 ta cA = 181,1

- : Hiu s nhit gia nhit hi ngng t v nhit thnh caloripher:

= thn - tT = 105-104,35 = 0,65oCVy thay s vo ta tnh c: 1= 14646,62 (W/m2)

q1 = = 9520,303 (W/m2)

Tnh h s cp nhit t mt ngoi ng n khng kh chuyn ng trong caloripher- Lu th chy qua bn ngoi ng chm ng c gn:

Nu = C (sch QTTB I trang 226)Trong :Dng : ng knh ngoi ca ng; dng = 0,025 (m)bg : bc ca gn ; bg = 0,02 (m)H :chiu cao gn ; hg = 0,005 (m)C,n : cc i lng ph thuc cch xp ng i vi ng xp hng : C = 0,116 ; n =0,72- Chun s Reynol :

Re > 3000 : Khng kh chy theo ch qu Pr = 0,6929

Vy Nu = 0.116=45,22- H s cp nhit i lu:- H s cp nhit lu thc t: dng phng php ngoi suy t hnh 7-10 QTTBI /trang 227

=187Vy ( trang 34 QTTBII)-Vy nhit lng ring:q2 = k*ttb = 138,8872,5 = 10068,88 (kJ/kgm)So snh Vy tt c cc gi thit trn c th chp nhn c 4.1.3. Xc nh b mt truyn nhit- Lng nhit do caloripher cung cp:

(cng thc 3.4QT&TBTN ca Phm Ngc Trung)Trong : = 556,03 (kJ/Kgm)

Qs = qs*W = 5831,8968,96 = 402167,1344 (kJ/h)

- Hiu sut caloripher ly - Lng nhit thc t do caloripher cp: - Gi D l lng hi nc tiu tn trong 1h

Qt = D*r suy ra D = = = 198,78 (kJ/Kg)- Lng nhit thc t truyn t hi nc trong ng n thnh ng:

Qt = 3.6*k*F* Suy ra (m2)- B mt truyn nhit thc: Ft = k*F ; k = 1,2 n 1,5 Chn k = 1,2Suy ra Ft = 251,2 =30 (m2)- B mt truyn nhit trung bnh:

Ftb= (m2)- S ng truyn nhit trong caloripher: n = =293 ng- S ng xp theo chiu ngang: m = = = 15 ngVy kch thc caloripher:+ Chiu di ca caloripher Lx = 0,872 (m)+ Chiu rng caloripher: Bx = (15-1)0,008+0,012+150,035 = 0,657 (m)+ Chiu cao caloripher l: Hx = H+0,052 =1,5( m)4.2.Cyclon4.2.1. Gii thiu v cyclonDo yu cu v chnh xc ca thc,cng nh kh thi ngi ta dng tc nhn l khng kh nng.Trong qu trnh sy, khng kh nng chuyn ng vi vn tc ln nn mt phn thc s theo khng kh ra ngoi . lm sch kh thi v thc ngi ta t ng ng ra ca khng kh nng mt cyclon tch nhiu hn.4.2.2. Tnh ton- nhit 47oC th tch ring ca khng kh l:V46oC = 0,903(m3/Kg)- Lu lng khng kh ra khi phng syV2 = Lv46o = 8492,560,903= 7668,78 (m3/h)

-Gi l tr lc ca cyclon th:

(S tay QTTB I / trang 522) M KLR ca kh 460C l = 1,107 kg/m3

Ta c P = 597,78 (N/m)- Tc quy c l Wq

Wq= ( cng thc III.48 STQTTBI / Trang 522) Wq = 2,2 -2,5 Chn Wq= 2,5

Vi = 60- ng knh ca cyclon l:

D == = 1,04 m(cng thc III.47 s tay QTTB I) Da vo ng knh D = 1,04(m) ta chn cyclon n loi LIH III.4 (s tay QTTB I trang 524)- Kch thc c bn ca cyclon LIH III.4+ Chiu cao ca vo (kt bn trong) : a = 1,11*D = 1,1544 (m)+ Chiu cao ng tm c mt bch : h1 = 2,11*D = 2,1944 (m)+ Chiu cao phn hnh tr : h2 = 2,11*D = 2,1944 (m)+ Chiu cao phn hnh nn : h3 = 1,75*D = 1,82 (m)+ Chiu cao phn bn ngoi ng tm : h4 = 0,4*D = 0,416 (m)+ Chiu cao chung : H = 4,26*D = 4,4304 (m)+ ng knh ngoi ca ng ra : d1 = 0,6*D = 0,624 (m)+ ng knh trong ca ca tho bi : d2 = 0,3*D = 0,312 (m)+ Chiu rng ca vo: = = + Chiu di ng ca vo : l = 0,6*D = 0,624 (m)+ Khong cch t tn cng cyclon n mt bch: h5 = 0,24*D = 0,2496 (m)

+ Gc nghing gia np v ng vo : + ng knh ca cyclon : D = 1,04 (m)

+ H s tr lc ca cyclon : 4.3. Qut4.3.1. Gii thiu v qut- Qut l b phn vn chuyn khng kh v to p sut cho dng kh i qua cc thit b: Caloripher, my sy, ng ng, cyclon. Nng lng do qut to ra cung cp cho dng kh mt p sut ng hc di chuyn v mt phn khc phc tr lc trn ng ng vn chuyn.- Nng sut ca qut c c trng bi th tch kh i vo hay i ra thit b sy- S dng hai qut:+ Mt l dng ht kh thi cyclon i ra ngoi+ Mt l va ht kh vo calorife4.3.2. Tnh tr lc ca ton qu trnh1-Tr lc t ming qut n caloripher.Chn ng ni t qut n caloripher c ng knh l 0,25 (m) v chiu di l 1 (m)-Vn tc kh i trong ng l:

Ta c= 1.18 (Kg/m3) tM = 25 oC

F = ( m2)L = 8492,56 (Kg/h)

Vy = 39,984(m/s)Chun s Reynol l :

Re >10 Vy khng kh i trong ng theo ch chy xoy- Chuyn ng chy xoy da lm 3 vng + Vng 1: Nhn thu lc hc: Khu vc ny nhm khng nh hng n h s ma st

Regh = 6 (Cng thc II.60 STQTTB I / Trang 378)

= 6

=10: nhm tuyt i ca tn ( Bng II-15-s tay QTTB-trang 381)+ Vng 2: Khu vc nhm:Khu vc ny h s ma st ph thuc vo nhm m khng ph thuc vo Re

Ren = 220*=220*Vy Regh10:Vy khng kh chuyn ng theo ch xoy

T s

Tra bng QTTB I trang 387 Vy tr lc do t thu caloripher l:P4 = = 524,575-Tr lc ng ng dn khng kh t caloripher n phng sy + Chn ng ng di 1.5(m)+ ng knh ng d =0.25 (m)- Tnh ton ging ng t ming qut n caloripher ta c:Regh