KHOA HQC - C 6 N G N G H E
NGHIEN Cllu THUTC NGHIEM XAC DjNH MOT SO THONG SO KET CAU VA THONG SO LAM VIEC CUA M A Y EP BA SAN
Tran Quoc Hoan ', Chu VSn Thien '
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TOM TAT
. Trong bdi ndy gidi thieu ket qud nghien cuu vi cdc thdng sd kit cdu vd thdng so ldm viec cda mdy ep bd san theo ngi^en ly ep the tich vai cdc dia lgc bang phuang phdp thuc nghidm. Cdc thdng sd dirge dua vdo nghien ciru Id: luu lugng cdp ba; dp sudt ep cue dgi; bi rdng cua lap ep. Chi tieu ddu ra Id do dm trung binh cua ba dugc ep.
EXPERIMELTAL RESEARCH FOR STRUCTURAL
AND WORKING PARAMETERS OF THE CASSAVA PULP FILTER PRESS Tran Quoc Hoan ', Chu Van Thien ^ SUMMARY
This paper shows the results of the experimeltal research on structural and working parameters of the cassava pulp filter press by volumetric principle with the filter disks. Parameters included in the study are:
flow of cassava pulp, maximum pressing pressure, width ofthe pressed layers. Criteria is the detennination of average moisture content ofthe pressed pulp.
I. Di^T VAN DE
Hien nay, tai cac nha may san xuat tinh bdt san tap trung thai ra mdt lugng ba san rat lon, neu khdng xu Ii kip thdi se trd thanh ngudn d nhifim trim trgng. Trong khi dd ba san khd la mdt Ioai thiic an kha tdt cho gia siic. Vific tan chfi bifin ba san ddng thdi giai quyfit dugc van dfi vfi mdi trudng ciing nhu tao them lgi nhuan gdp phan nang cao hieu qua kinh te. Hifin cd nhifiu nguyen Iy dfi thuc hi?n vific ep ba san nhu ep bang tai lgc, ep tam ban, ep vit, ep theo budng...
II. THIET BI VA PmrOfNG PHAP NGHIEN CUU 2.1. Thi^t hi
Thifit hi tach nudc ba sSn theo nguyen Iy ep thfi tich dugc thifit kfi bao gdm 2 khoang Idn rifing bifit, ben trong cd cac dia lgc. Kfit cau ciia may dugc thfi hifin trfin hinh 1.
' ThS. Viln ca di?n nong nghiep vd Cong nghfi STH
^ TS. Vien co difin nong nghifip vd Cong nghe STH.
Hinh I. Kit cdu tdng thi thiit bi ep ba sdn 1- H? thfing khung b?; 2- Bom; 3- Van; 4- Ong n?p li^u;
5- Thiing lgc, 6- Cym 6ng trong, 7- Bp ph^ thdo li?u
May bao gom nhiing bd phan chinh sau:
- Bd phan budng ep;
- Bg phan nap lieu-;
- Bg phan lay li?u;
- He thdng khung be va bd phin phu trg.
TAP CHI CONG NGHIEP NONG THON - SO 11 - 2013
K H O A H Q C - C 6 N G N G H ] ^ May dugc thifit ke gom 2 buong ep thuc
hifin nhiem vu ep va thao li?u ludn phifin nhau.
Ba sdn udt dugc bd phan nap li$u bom lien tuc theo dudng dng dan lifiu qua van ddng md vao theo dng trong dng cua budng ep. Khi budng ep thii nhat lam nhiem vv ep ba san thi budng cdn Iai se thuc hifin nhifim vu thao lieu da dugc ep trudc dd va nguge Igi. Moi budng ep gdm nhifiu khoang ep. BS dugc bom lieu ba sin udt trong dng cdp Hfiu, nam d tSm khoang ep dugc dua qua cac dudng dng dan vao tung khoang. Dudi ap luc bom lifiu, b§ san dugc ep trong mdi khoang va nudc dugc tach khdi ba se chay dgc qua cac tam lgc vao cac Id thdng vdi ranh nhd dugc each ly vdi thiing lgc thoat ra ngoai. Sau khi vific ep ba tai budng ep thii nhat kfit thiic, cum thiing ep dugc chuyfin ngay tdi budng ep thii hai thuc hifin qua ttinh ep tiep theo. Trong khi budng ep thii hai thuc hifin qua trinh ep thi cdng tac thao Hfiu dugc thirc hifin cho budng ep thii nhat. Trong qua trinh lam vific cum dng trong quay va ba san da dugc ep dugc thao ra nhd bd phan thao lieu gdm cac dao cao tach ba ra. Ddng thdi, d budng ep ben canh, nhd vao ap cua cac vdi phun gan tren thiing ep phun vao budng ep trong ma cac tSm lgc trong budng ep dugc lam sach, nudc dugc dan ?(udng thifit bi thoat nudc phia dudi. Cac qua trinh cap ep va thao lieu ra dugc thuc hien tuan hoan.
Qua hinh tach nudc ra khdi ba sdn la qua trinh lpc ep. Cac thdng sd anh hudng tdi qua trinh la: Be day ldp vat lieu ep (khoang each giiia 2 dia kfi nhau); luu lugng cap ba udt trfin mdt dan vi difin tich dia lgc; ap suat ep cudi cimg. Dfi cd ca sd cho viec tinh toan thifit kfi may cSn thifit phai xac dinh dugc cac thdng sd trfin.
2.2. Phirong p h a p nghien cuu De nghien ciiu cac thdng sd cua may ep ba sdn, tu CO sd ciia nguyfin 1^ va kfit cdu ciia may ep, sir dung phuang phap nghifin ciiu dua vao md
hinh thi nghi?m de cd dugc cac thdng so ca ban.
Trfin ca sd dd xdc dinh cdc thdng s6 khac cua may thyc.
m . KET QUA VA THAO LUAN
2.1 Xac dinh cac thong so lam v i ^ cua may a) Mo hlnh thi nghi&m
Dfi xac dinh cac thdng so hgp Iy ciia may ep, dfi tai da thifit ke, che tao md hlnh tiii nghifm budng ^p.
Ket cau budng ep dugc thfi hifin d hinh 2.
Hlnh 2. Kit cdu buong ep I- Tryc; 2- M?lt bfch; 3- DTa lpc; 4- V6 ngoii;
5- ThSnh tryc;
Budng ep dugc tao bdi vd ngoai (4) va true trong ngan each bdng cac dta lgc (3). Ap suat trong budng ep rat lan (cd the tdl 4 Mpa), dfi dam bao do b^n da thifit kfi kfit cau chiu tai trgng Ifin hoan toan la ndi luc.
Ba dugc cap vao budng ep tir ngoai dgc long tryc (1) qua cac Id cap Heu d trfin true.
Nudc sau khi ep di qua vai lgc nam trfin cac tdm lgc di cac ranh tren dia lgc (3) chay vfi cac ranh ndm trfin thanh true (5) va thoat ra ngoai.
Nhiing thdng sd dugc nghifin ciiu la:
- Khoang each giiia cac dta lgc (chifiu day lap vat lieu khd);
- Luu lugng ba dugc cap tren 1 don vi difin tich tdm lgc (van tdc lgc);
- Ap suat ep cudi cung;
28 TAP CHi CONG NGHI§P NONG THON - SO 11 - 2013
KHOA HQC - CONG NGHE
Luu lugng ba dugc thay ddi nhd vao v|ln tdc xi lanh bam thdng qua vific thay dfii luu lugng bam thuy lire.
Van tdc lgc dugc tinh theo cdng thiic:
<l = Q S*t Trong do:
Q la the tich ba dugc cap;
S - tdng difin tich lgc;
t - Thdi gian ep.
Chi tifiu danh gia:
- Do am tnmg binh cua vat Heu;
- Nang suat ep.
b) Kit qud Ihi nghiem
Ket qua thi nghiem dugc the hien tren hinh 3 , 4 v a 5 .
^, X
\ N^
V
p. MPa
Hinh 3. Anh hudng ciia dp sudt cudi tdi do dm trung binh
Hinh 4. Anh hirdng cua chiiu ddy lap bd tdi dg dm trung binh
/
0 1 0125 015 0 175 0 2 0225 q.dmfmin
Hlnh 5. Anh hirdng ciia van tdc Igc(ep) tdi do dm trung binh.
Qua ket qua thi nghifim trfin, chgn thdng sd P=4 MPa; q=0,175 dm/phiit; b= 60 mm lam co sd cho viec tinh toan thiet ke may.
De Iam c a sd cho viec thiet ke xi lanh nit dng ngao sau khi ep, da thu nghiem vdi thdng sd trfin va do lire keo nit dng ngoai. Ap suat tifip tuyen trfin thanh dng ngoai dugc xac dinh theo cdng thiic:
Trong dd:
Ff - Lyc ma sat cue dai trong qua trinh nit dng, N;
St - Difin tich mat trong ciia dng, m2.
Trong md hinh thi nghiem: St = 0,22 m2;
Ff= 1,76.104 N.
Thay vao cdng thiic tren ta cd:
Ff 1,76.10'
= 8.10" Pa 5, 0,22
2.2. Tinh toan cac thdng s^ ctf ban cua thiet bi
Tinh todn thong so chinh cua buong ep:
Vdi do am ban dau ciia ba 85%, sau khi ep cdn 54%. Ty lfi nen giiia the tich ban dau va the tich cudi dugc tinh theo cong thiic.
TQ _ 1 - W _ 1 - 0 , 5 4
~~V~\-W. ~ l - 0 - 8 5 = 2,7
TAP CHI CONG NGHIEP NONG THON • SO 11 - 2013 29
KHOA HOC - CONG N G H $
V6i cac th6ng so tren, thai gian ep cho 1 me dugfC tinh theo cong thuc;
k*B _ 2 , 7 * 0 ^
= A,6phut 2*0,175
Trong cong thilc trSn m6i khoang loc c6 2 vach lpc nen b6 day lop ep cho m6i mat tim lgc chi bang B/2;
Voi k8t cau 2 bu6ng ep lien hoan thai gian chuySn tiSp tir bu6ng ep nay sang bu5ng ep khac khoang 20s, thai gian can thiet cho qua trinh ep la 5 phut.
Vol thai gian lam viec 16h, so me co the dat dugc la 196 me.
Vai nang sudt qn=50 m3/ngay, moi me c6 till tich la 50/196 =0,26 m3. Vai ty le ep k=2,7, ThS tich thung cln thiSt la 0,26/2,7=0,096 m3.
Chgn ths tich thung la 0,12 m3.
T6ng di$n tich tim lgc la 2*0,12/0,06= 4ni2.
Ltm lugng ba cua bam cap dugc xac dinh thong qua nang suat ciia may:
Trong do:
Qp - Lim lugng cap tren 1 phiit, mS/phiit;
Qm - Thfi tich 1 me, m3;
tc - Thdi gian cap, phiit.
_ 0,12*2,7
^^ " 4,66 = 0,07mV;7/iut Cdc thong so ca bdn cua mdy ep TT
1 2 3 4 5 6
Thong so The tich thung ep, m3 Tong dign tich tdm loc, m2 Luu lugng bom cap lieu, dm3/phut Thcri gian ep 1 me, phut Khoang each giira 2 dTa ep, mm Ap suat ep cue dai, MPa
Gia tri 0,12
4,0 70 5 60 4,0
ULKfeXLUAN
1. Bang phuang phap th\rc nghifim da xac djnh dugc anh hudng cua cdc thfing s6 co ban tdi do am ciia ba sau khi ep theo nguyen Iy ep the tich cd dia lgc. Tren c a sd do, theo yeu cdu thuc tifin dd dm dudi 55% da chgn dugc bg thdng s6 ap sudt ep cue dai P=4 MPa; van tfic ep q=0,175 dm/phtit; khoang each giiia 2 dta b= 60mm Iam ca sd cho tinh toan, thifit kfi may.
2. Tren ca sd cac sd ligu thuc nghiem da xac dinh dugc cac thdng sd chinh cua may ep ba sdn theo nguyen Iy ep thfi tich cd dia lgc nang sudt 50 m3/ngay la: Thfi tich thung ep 0,12 m3 ; tdng dien tich tSm lgc 4,0 m2 ; luu lugng bam cdp lieu 70 dm3/phut; thdi gian ep 1 me 5 phiit; khoang each giila 2 dia ep 60 mm;
ap sudt ep cuu dai 4,0 Mpa.
TAI LIEU THAM KHAO 1. Hristo Beloev, Tran Quoc Hoan, Dau The Nhu.
Principle of work and structure of a machine for lowering the moisture in the solid wastes received as a result of processing of raanioka. Procedings VolumSl, book 1.1, Agricultural machinery aod technologies. Agricultural sciences and veterinary medicine. Repair and reliablity.
Ruse-2012
2. 4AH KVOK XOAH, X. BEJIOEB, ^V BAH TXMEH, MoflejiMpane Ha npouec oxflejiaHero na BOM Ha MaHonecKHTe oinaatUH no Merojia npecoeaHe Haan-hHteH ^iJirbp; Ruse-12013
3. Lam Trln Vu; Dau ThS Nhu; Nguyin Minh TuySn. T6i uu hoa qua trinh loc 6p ba tiiai san.Tap chi H6ahgc,T.42(l)-/2004.
Ngay nh$n bai; 9/11/2013 Ngay phan bi?n: 9/12/2013
NgurM phan bifn: TS. Bau Thl Nhu, Vien Ca di|n nong nghiep va Cong ngh^ STH.
Day la cac thdng sd can thiet cho viec thifit kfi, che tao mau may thirc cd the ap dung trong san xuat.
30 TAP CHI CONG NGHIEP NONG THON - SO 11 - 2013
THAM KHAO - TIIM HIEU
HlTOfNG DAN KY THUAT GIEO MA NEN stf DVNG CHO MAY CAY LLFA HAMCO
KS. Nguyen Dire Ban Gidm ddc Cdng ty TNHH Mdy ndng nghiep vd khuyin ndng Hd Ngi 1. Ngam ii hstt giong
Cach tuyfin, ngSm, u hat gidng trudc khi gieo nhu phuang phap gieo ma thdng thudng, khdng dfi mam va re dai. Mdng gieo tdt nhdt cd mam va re tir 1mm dfin 1,5mm.
Chgn hgt gidng:
Tuyen chgn hat gidng bang nudc mudi nham chgn dugc nhiing hat gidng khde manh.
Cach lam: Hda tan mudi trong nudc, vai ty trgng tifiu chuan la 1,08 (ty lfi 1,5 kg mudi va 10 lit nudc). Vdi ty trgng 1,08, ty Ifi nay mam giiia cac hat gidng se ludn dn dinh.
Cach nhan bifit ty trgng 1,08: Su dung trimg ga hoac sii dung ty trgng ke.
Cdch nhgn biet ty trgng Sau khi tuyfin chgn 1 hoac 2 Ian ty trgng se thay ddi, do do can difiu chinh cho nudc cd ty trgng 1,08.
Sau khi tuyfin chgn dugc nhirng hat gidng tdt, can nia lai bang nudc sach, de loai bd mudi ra khdi hat gidng. Vi nfiu cdn Ian mudi, mudi se lam cho hat gidng phat trien kem.
Ngdm gidng
Su dung nudc sach de ngam vdi ty lfi 1kg gidng diing 3,5 h't nudc.
Thdi gian ngam theo diing quy trinh ky thuat da dugc ghi trong bao bi thde gidng.
Thdng thudng thdi gian ngam hat gidng tir 36 dfin 48 gid thy theo nhifit do ngoai trdi.
Trong qua trinh ngam cii 6 gid thi thay nudc, rda chua 1 lan, ngam cho dfin khi thdy h£it thde hht no nudc (heit thde hong, nhin thdy phdi hat), rdi dai sach, dfi rao nudc sau dd tifin hanhu.
Xu ly hat gidng bang thudc xii ly gidng va tru sau bfinh (xii ly hat giong theo hudng din ciia nha san xuat thudc). Vdi phuang phap xii
\^ ngay tii giai doan hat gidng, se mang dfin cho ba con ndng dan nhifiu lgi ich:
- Giam cdng phun thudc, ma van dat dugc muc dich phdng trir dich hai; cdng vific trgn thudc chi don gian nhu la thao tac u gidng, ngdt giong binh thudng.
- Toan bd thudc dugc tap trung bao ve cay;
tranh lang phi, vi vific phun thudc trai dfiu trfin mat rudng khi cay liia cdn nhd la mdt lang phi bdi phan ldn thudc da khdng the tifip xiic vdi cay Ilia ma roi vao dat, khdng phat huy dugc vai trd phdng trir dich hai.
- Cay Ilia dugc bao vfi ngay tir dau.
- Vific xu ly giong an toan hon cho cac sitih vat cd ich hong rudng liia, so vdi giai phap phun.
- Vdi nhiing hoat chat tifin tien, cd tinh chgn lgc cao, chi can Hfiu diing thap ciing giai quyet dugc dich hai, han che tdi miic thap nhat vific rai hda chdt tren ddng rudng, phu hgp vdi chuang trinh IPM.
- Hifiu ling xanh cay dugc mang tdi tir cac hoat chdt thudc trir benh tao difiu kien cho cay khoe ngay tir dau.
U hgt giong
Sau khi hat gidng dugc ngam no nudc, dai riia sach, cho hat gidng vao tiii vai hoac bao tai cd kha nang giii am, giii am va thoat nudc tot dfi ll hat gidng. Tuyet ddi khdng diing tiii nilon
TAP CHI CONG NGHIEP NONG THON - SO 11 - 2013 31
J5
THAM KHAO - TIM HlfeU hoac bao bi khd thoat nudc va bi hai sfi gay thdi
hat gidng.
Thdi gian u theo diing quy trinh ky thuat da dugc ghi trong bao bi thde gidng.
Trong qua trinh u hat giong, can thudng xuyfin kifim tra nhifit do va do am, ludn de hat gidng du dm va du dm, cii 6 gid tudi nudc 1 lan va dao hat gidng dfi hat nay mam deu.
Khi hat da nhii mam, can chii y can ddi phat trifin mdm va rfi deu nhau, khi hat nut nanh, nhii mam nhu gai diia, chieu dai ciia mam tir 1mm dfin 1,5mm dem hat giong di gieo. Nfiu mam va re qua dai khi gieo se khdng ddng nhat, neu mam khdng phat trien dii, qua trinh tang trudng ciia tham ma se khdng dfiu dhi dfin thifiu khdm trfin rugng cay.
Can chii y: Trudc khi gieo hat gidng can dugc lam rao nudc. Nfiu hi udt se lam cho viec gieo gidng khdng chinh xac. Dfi mgng ma noi cd bdng ram cho rao nudc trudc khi gieo.
2. Chuan bj dat gieo ma
Dai 1 lap nilong mdng xudng mat nfin dat Cling hoac san gach, be rdng tam nilong 1,4m, chifiu dai tam nildng L = Chieu dai ludng ma + 10 cm (tdm nildng thua ra so vdi ludng ddt moi canh 10cm).
Sli dung khung sat hoac khung go cd chifiu day 16-20mm, cliieu dai va chifiu rgng trong long ciia khung la 2,24m x 0,6m dfi lam cir cho ludng ma.
Chudn bi ddl gieo mg Lay biin d rugng liia hoac rugng mau, bun ao, kenh mucmg (bun sach, xdp, thoang khi, it tap chat, khdng cd sdi da) can dfiu va phing thanh ludng hen tdm nildng da dat trfin nfin ddt
Cling ho$c san gsich theo khung cii ciia d ma.
Tiiy theo tap quan canh tac ciia timg dia phuang, cd th^ six dung ddt mau, hoac ddt mau bai sdng nghifin nhd dfi gieo m?.
Nhat sach cd rac va cac v^t ciing nhu: da, sdi, vat Cling trong biin cd kich thudc theo chieu ldn nhdt Idn ban 5mm (vi nfiu cd, sg Iam kgt tay cdy ciia may).
3. Gieo m^
Dfi cay gidng khde manh cdn gieo chinh xac va ddng nhdt. Dfi cdy 1 ha Ilia (loai lua cd trgng lugng 1.000 h£it = 20 gram) cdn chudn hi hi 28 - 30kg thde gidng, 83 - 90m2 ddt gieo.
Tuong duang 0,33 kg hat gidng / lm2 ddt gieo ma, 3m2 ma cdy cho 1 sao Bde Bg.
Vdi cac loai gidng cd trgng Iugng 1000 hat Idn ban hoac nhd ban, thi trgng lugng hat gidng gieo dugc nhan vdi ty trgng chenh lech (Vi dy: gidng cd trgng Iugng 1.000 hat = 24 gram, ty trgng =24/20=1,2; gidng cd trgng lugng 1.000 hat s 18 gram, ty ttgng = 18/20 = 0,9).
Mat do gieo hat vdi Ioai h^t cd trgng Iugng 1.000 hat = 20 gram la 0,33 kg hgt thoc gidng/
m2 dat gieo, khi dd khdm se cd sd ranh ma trung binh la 3. Tuy theo tap quan canh tac ciia timg dia phucmg, neu can cay nhifiu ranh/khdm ta se difiu chinh ttfin may.
Tiiy theo tiing Ioai gidng lua cd thdi gian sinh trudng ngan ngay hay dai ngay, de nhanh khde hay kem, thd nhuong va t^p quan canh tac ciia vimg mifin ma cd thfi quyfit dinh so Iugng thde gidng (hoac mdng ma) dugc gieo trfin mgt don vi difin tich.
32
Gieo mdng
TAP CHl CONG NGHIEP NONG THON - SO 11 - 2013
THAM KHAO - TIM HljfeU Sau khi gieo mgng xong, tung 1 ldp tto hfip
hoai (tto bdn rugng) len tten ldp mgng ma, ttgng lugng ciia Idp tto la 0,1kg/ m2.
Sau khi gieo diing vat nhe cd mat phang nhu : Ban xoa, mat chau nhdm, thimg x6p... vo nhe Ifin ttfin mat mgng vCra gieo sao cho mgng ngap vao ttong bun thi diing lai.
-Sau dd tiep tuc tung 1 ldp tto bfip hoai (tto bdn rugng) Ien ttfin, ttgng lugng cua ldp tro la 0,1kg/m2.
O khu vyc mien Nam, ba con cd thfi su dyng so dira dfi thay tto bfip vol ttgng Iugng tuong duong va each lam tuong tir.
4. Cat ma
Khi Idp bun gieo ma se lai, tifin hanh cdt ma bang dudng cat dfi nhanh va chinh xac, thuan lgi cho cham sdc, chdng mit dat, dam bao giii am. Kich thudc mieng ma dugc cat la 22 x 60 cm.
5. Ket thuc gieo
Trong thdi gian 3 ngay ddu kfi tii khi gieo xong, can che phii phia trfin ludng ma dfi chdng mua. Chan xung quanh khu vuc gieo ma de han che chugt, gia cam pha hoai.
Che phil nildng
Che phu kin nildng giiip cung cap dii nhifit do cho hat gidng nay mam ddi vdi vu xuan cd nhifit dd qua thap (dudi 15°C).
6. Cham sdc sau khi gieo
Can dam bao nhifit do cho ma non phat trifin ddi vdi vu Xuan d mien Bde. Khi nhiet do qua thdp (dudi 15°C) se lam cho cay ma sinh trudng khdng tdt.
Dam bao cung cap du nudc cho cay ma, ludn gitt dm cho dat.
Tudi nudc cho m?i tu ngay thii 3 ttd di, dam bao dat dugc no nudc.
Cay mg tdt dfi cdy cd khoang 3 dfin 3,5 la va phai dat chifiu cao ttfin 10cm.
Ma can cd do day re tir 2,5 dfin 3cm, rfi ma dan xem vao nhau, dam bao cdt ma thanh tham khi nhac len khdi mat ddt.
Vdi thdi tifit vy miia (hoac khu vyc mifin nam) thdi gian phat trifin ciia cay ma la 8 dfin 12 ngay.
Vu xuan d phia Bac cd thdi tifit ret, thdi gian phat trien cua cay ma la 16 dfin 20 ngay.
7. V^n chuyen ma khi cay
Khi cay ma dat yfiu cau, su dung cac gid cd tang, hoac cudn lai de van chuyfin, ma cugn lai phai cho chifiu rfi phia ngoai.
Phai gift am cho dat de ma tir khi cat dfin khi cay khdng hi heo.
•\tsP CHi CONG NGHlfP NONG THON - SO 11 - 2013
Cugn mg de van chuyen 8. Lam dat ruong cay
Lam dat cay binh thudng nhu rugng cay bang tay, mat rudng bang phang, chifiu sau trung binh tii 12 dfin 15 cm. Yeu cau dat trudc khi cay phai sach gdc ra, cd dai...
Rudng dfi ldng bim tdi thieu 2 dfin 3 ngay, khdng can Iam ludng.
Dfi may chay dat nang suat cao, chat lugng cdy Ilia dfing dfiu, can thao can het nudc tten rudng trudc khi cdy, khi mat rugng se bun la cdy dugc. Thdng thudng, vdi rudng dat thit la tten 24 gid, vdi rudng ddt cat pha la tten 12 gid.
Bdn Idt sau khi thao nudc va trudc khi cay dfi phan bdn dugc ndm sau ttong dat, chdng bde hai va nia ttoi. •
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