Nghien Ray Tron

i hc Quc gia Tp. H Ch Minh

Trng i hc Bch Khoa

Khoa K Thut Ha hc

B MN QU TRNH & THIT B

Phc trnh th nghim

Qu trnh & Thit b

Bi:

NGHIN RY TRN

CBHD: Thy Ng Vn Tuyn

Sinh vin: L Nguyn Th Giang

MSSV: 61200870

Nhm: 2.2

Lp: HC12TP

Ngy TN: Sng th 3, 31/3/2015

Th nghim Qu Trnh & Thit b Bi Nghin Ry Trn

-Trang 2-

Nm hc: 2014-2015

I. Trch yu:

1. Mc ch:

- Nghin mt loi vt liu, da vo kt qu ry xc nh s phn phi kch thc vt liu

sau khi nghin, cng sut tiu th v hiu sut ca my nghin.

- Ry vt liu sau khi nghin, xc nh hiu sut ry, xy dng gin phn phi v tch

ly ca vt liu sau khi nghin, t xc nh kch thc vt liu sau khi nghin

- Trn hai loi vt liu xc nh ch s trn ti cc thi im, xy dng th ch s

trn theo thi gian xc nh thi gian trn thch hp.

2. Phng php th nghim

- Thc hin nghin 200g go bng my nghin ba mt trc, c b phn nhp liu bng

vt ti. Da vo cng thc ton hc v cc s liu v kch thc ht go trc, sau khi

nghin c c t th nghim ry, nng sut nhp liu, hiu in th,. Ta tnh c

cng sut nghin cng hiu sut my nghin.

- Ly mt na lng sn phm sau khi nghin em ry qua ry c kch thc l 0.2mm,

ry 5 ln mi ln trong 5 pht, sau mi ln ry ta em cn s lng vt liu lt qua ry

ri tho b. Th nghim tip tc c tin hnh vi lng cn nm trn ry. Da vo

khi lng vt liu lt qua ry sau mi ln, ta tnh c hiu sut ry theo thi gian.

- Thc hin trn 3kg u nnh v 1,5kg u xanh trong my trn thng quay, sau cc

mc thi gian 5 giy, 15 giy, 60 giy, 120 giy v 300 giy, ta tin hnh ly mu theo

th t, tnh ch s trn. T ta v c th ch s trn theo thi gian.


-Trang 3-

3. Kt qu th

Bng 1. Nghin 200g go

Khi lng (g) Thi gian nghin (s) Cng dng in (A)

Khng ti C ti

200 27 4 5.4

Bng 2. Ry vi khi lng 80g

Ln ry Thi gian (pht) Khi lng qua ry (g)

1 5 29.2

2 5 0.6

3 5 0.3

4 5 0.2

5 5 0.1

Bng 3. Ry vi 80g go 4 kch thc ry khc nhau

Kch thc ry (mm) Khi lng trn ry (g)

0.425 17.9

0.315 23.5

0.2 9.3

0.16 14.2


-Trang 4-

Bng 4. Trn

MU 5" 15" 30" 60" 120" 300"

N X N X N X N X N X N X

1 152

61 170 120 172 96 163 102 183 98 156 67

2 176 109 171 135 178 137 191 98 190 98 176 111

3 135 365 157 153 178 169 177 142 177 139 176 149

4 183 127 191 127 165 111 167 105 120 100 192 147

5 136 190 159 167 174 141 199 145 177 132 202 141

6 173 97 162 88 172 94 183 126 147 119 156 113

7 174 159 166 170 197 130 162 135 187 132 186 135

8 85 333 168 211 170 153 180 202 152 130 159 172


-Trang 5-

T

P

II. L thuyt th nghim

1. Nghin

- Nghin l qu trnh m trong vt liu rn c ct ra hoc lm v ra thnh nhng

ht c kch thc nh hn.

a. Cc thuyt v qu trnh nghin

nh lut Bond

- Cng cn thit to nn ht c ng knh D t vt liu ban u rt ln t l vi cn

bc hai t s din tch b mt th tch ca sn phm S/V = D

6. Nh vy:

D

KE

b

Nng lng chi ph cho qu trnh nghin nghin vt liu c kch thc ban u Dp1 thnh sn phm c kch thc Dp2 l:

12

i

1119W

pp DDE

- Nu nghin kh th E c nhn vi 3

4.

Trong : Wi l ch s cng (kW.h/tn vt liu nghin). Ch s cng c nh ngha l lng

nng lng cn thit nghin vt liu c kch thc ban u rt ln n sn phm c 80% lt

qua ry 100 micron.

- Ch s cng ph thuc vo loi my nghin (cc my khc nhau nhng cng loi c Wi

xp x nhau) v vt liu nghin (cc vt liu khc nhau c Wi khc nhau)

- nh lut ny dng cho nghin trung bnh v mn.

nh lut Rittinger

- Cng dng cho qu trnh nghin t l thun vi din tch b mt mi to thnh ca sn

phm nghin.

1p2p

r

D

1

D

1KE

Trong :

E : cng dng cho qu trnh nghin. E =

P : cng sut tiu th, kW

T: nng sut, tn/h

Kr : hng s Rittinger

Dp1 : kch thc ban u ca vt liu, mm

Dp2: kch thc ca sn phm, mm


-Trang 6-

nh lut Kick

- Cng cn thit nghin mt lng vt liu cho trc l khng i ng vi cng mt

mc nghin, bt chp kch thc ban u ca vt liu.

ilgKEk

- Trong I l mc nghin l Kk l hng s Kick.

- Nng lng chi ph cho qu trnh nghin t l nghch vi s gim th tch ca b mt

vt liu

2p

1p

k

D

D

lgKE

- Thuyt ny dng trong trng hp p nghin th v nghin mn bng va p.

b. Cng sut v hiu sut my nghin

Cng sut nghin

- Trong bi th nghim ny, ta s dng nh lut Bond cho trng hp nghin kh

tnh cng sut nghin.

T

D

1

D

1W19

3

4P

1p2p

i

Hiu sut my nghin

- Cng sut tiu th cho ng c ca my nghin: P = UIcos

Trong :

U: hiu in th, V. Trong bi th nghim, U c gi tr l 220V.

I: cng dng in, A.

cos: h s cng sut. Trong bi th nghim, cos mang gi tr l 0,8.

- Hiu sut ca my nghin c tnh bng cng thc: %100'P

PH

2. Ry

- Ry l qu trnh phn loi hn hp vt liu ri thnh nhng phn on ht c kch

thc khc nhau nh vo cc tm ry v tc dng ca lc c hc

a. Mc ch

- Mc ch ca ry l phn loi ht ri thnh nhng phn on ht c khong kch thc

theo yu cu.

- Nguyn tc ca phng php ry l cho vt liu i qua h ry c kch thc l xc

nh. Cc ht c kch thc nh hn l ry s lt qua ry, cc ht c kch thc ln

hn s b gi li trn b mt ry.


-Trang 7-

- xc nh phn b kch thc ht, ta s dng cc tm ry xp song song v chng

ln nhau. Mt ry c kch thc l ln t ln trn, kch thc l nh t di. Cho

hn hp vt liu chuyn ng t trn xung, cn khi lng vt liu trn mi ry, ta s

xc nh c phn b kch thc trong khi ht

b. Phng trnh biu din n s phn phi kch thc i vi ht nhuyn

- Phng trnh vi phn:

b

p

p

KD

dD

d

Trong :

: khi lng tch ly trn kch thc DP, g.

DP: kch thc ry, mm.

K,b: hai hng s biu th c tnh phn phi ca - Ly tch phn t = 1 n = 2, tng ng vi Dp = Dp1 v Dp = Dp2 ta c:

- 1 = )DD(1b

K1b

2p

1b

1p

- Tng qut ta xt gia ry th n v ry th (n 1) v gi s s dng ry tiu chun c

pn

1pn

D

D

r = hng s.

n = n n-1 = 1b

pn

1b

pn

1b

D'KD

1b

)1r.(K

Vi K = 1b

)1r.(K1b

- Hoc: log = (b + 1) logDpn + logK

- logK v (b + 1) c xc nh bng cch v log theo logDpn trn th log log.

T suy ra K v b.

c. Hiu sut ry

100

Fa

JE

Trong :

F: khi lng vt liu ban u cho vo ry, g

J: khi lng vt liu di ry, g

a: t s ht c th lt qua ry, %


-Trang 8-

- Tch s F.a trong th nghim c xc nh nh sau:

em ry mt khi lng F ca vt liu, kho st xc nh c J1. Ly vt liu cn li trn ry (F J1) v ry li xc nh c J2, tip tc ly vt liu trn ry F (J1 + J2) v ry li ln na.

Tng s J1 + J2 + J3 + s tim cn n F.a

Hiu sut ry l 100% nu J1 = F.a d. Cc yu t nh hng

- m ca vt liu ry: m ca vt liu ry nh hng ln n qu trnh ry. Khi

cc vt liu chuyn ng trn b mt ry, cc ht vt liu s va chm vo nhau, do

nu chng c m cao chng s d dnh vo nhau lm tng kch thc ht v s

khng lt c qua ry. Mt khc, vt liu m d kt dnh vo l li, gy bt l li

ry. m l tng ca vt liu hiu sut ry t cao nht l 5%.

- B dy lp vt liu trn b mt ry: Chiu dy lp vt liu trn b mt ry cng nh

hng n hiu sut ry. Nu lp vt liu qu dy th lp vt liu nm trn b mt s

kh i xung pha di tip xc vi b mt li ry v lt qua ry. C th chn

chiu dy lp vt liu trn ry ph thuc vo kch thc vt liu.

Khi d < 5mm th b dy lp vt liu h = (10 15)d

Khi d = (5 50)mm th h = (5 10)d.

Khi d > 50mm th h = (3 5)d - Kch thc ca vt liu trn ry

- Khi vt liu chuyn ng trn b mt li ry, s c mt s ht vt liu nm lt trong

l li ry. chng khng bt l ry v chuyn ng ra ngoi th cn phi tc dng

vo ht vt liu mt lc no c gi tr thch hp.

- Gi thit ht vt liu hnh cu, c ng knh l 2r nm trn l li c kch thc l

2R v gc bt kn l . cho ht vt liu bt ra khi l ta c iu kin:

a g. tg

Trong :

a: gia tc ca ry, m/s2

g: gia tc trng trng, m/s2

ph thuc vo t s hai bn knh:

- Mt ry: Mt ry phi phng th hiu sut ry mi cao.

- Hnh dng l ry: Hnh trn hoc hnh oval th hiu sut cao nht cn cc hnh dng

khc th hiu sut thp.

3. Trn

- Trn l qu trnh to mt hn hp ng nht t cc thnh phn khc nhau di tc

dng ca lc c hc.

sin

1

R

r


-Trang 9-

a. Cc tnh cht ca vt liu nh hng n qu trnh trn

- S phn phi c ht

- Khi lng ring xp

- Khi lng ring ca vt liu

- Hnh dng ht

- c trng b mt

- c trng lu chuyn

- Tnh d v

- Tnh kt dnh

- m ca vt liu

- Khi lng ring

- Nhit gii hn ca vt liu

Trc khi chn la mt my trn cn xem xt k cc tnh cht trn ca vt liu em trn.

b. Cc qu trnh xy ra trong my trn

- Khi trn vt liu ht, cc ht chu tc dng ca nhng lc c hc c hng khc nhau

v dn ti chuyn ng ca cc ht trong th tch khi ht. Qu trnh chuyn ng ca

cc ht ph thuc vo cu to my trn, phng php tin hnh qu trnh trn. Trong

my trn c nm qu trnh c bn xy ra:

To ra cc lp trt vi nhau theo cc mt phng trn ct.

Chuyn dch mt nhm ht t v tr ny n v tr khc - trn i lu.

Thay i v tr tng ht ring r trn khuch tn.

Phn tn tng phn t do va p vo thnh thit b trn va p

Bin dng v nghin nh tng b phn - trn nghin.

- Nhng c ch trn trn xy ra ring r hay ng thi vi nhng mc khc nhau ty

thuc vo loi my trn v vt liu trn.

c. nh gi mc ng u ca hn hp trn

- Khi trn mt khi lng a cht A vi khi lng b cht B to thnh hn hp ng

nht AB th thnh phn ca cht A v B trong hn hp l:

ba

aCA

v

ba

bCB

- Trong hn hp l tng, CA v CB s nh nhau mi phn th tch. Hn hp l tng

ny ch t c khi thi gian trn tin ti v cng v khng c cc yu t chng li

qu trnh trn.


-Trang 10-

- Trong thc t thi gian trn b gii hn, do trong hn hp thc cc thnh phn CA

v CB cc phn th tch khc nhau ca hn hp s khc nhau. Nu s khc nhau ny

cng t th hn hp cng gn vi hn hp l tng.

- nh gi mc ng u ca hn hp thc ta c th s dng 2 i lng sau:

sai lch bnh phng trung bnh

- Nu trong phn th tch Vi ca hn hp thc c thnh phn cht A l CiA v ca cht B

l CiB, lc sai lch bnh phng trung bnh ca hn hp thc s l:

1N

)CC(

s

N

1i

2

iAA

A

v

1N

)CC(

s

N

1i

2

iBB

B

Vi N s th tch mu Vi

- Nh vy sA v sB cng nh th mc ng u ca hn hp cng cao (cng gn vi

hn hp l tng). Ga tr ca sA v sB ph thuc c bn vo thi gian .

Ch s trn

Is =s

e

Vi e

: lch chun l thuyt

n

CCBA

e

N

1i

2

iAA

BA

s

)CC(.n

)1N(CCI

Vi n : s ht trong mt th tch mu hn hp.

Nh vy IS cng ln th mc ng u ca hn hp trn cng cao


-Trang 11-

III. Dng c, thit b v phng php th nghim

1. Thit b - Dng c

- My nghin ba mt trc, ba lp lng, c li tho sn phm, c b phn nhp liu

bng vt ti. Nguyn tc hot ng: vt liu trong my nghin ba c nghin nh do

s va p ca ba vo vt liu v ch xt vt liu gia ba vi thnh my. Cac ht vt

liu sau khi nghin c kch thc nh hn l li phn loi s i ra ngoi, cc ht c

kch thc ln hn tip tc c nghin. My nghin c gn vi mt ampere k

o cng dng in

- My trn thng quay gm thng ch vt liu c truyn ng quay qua cc gi

hay cc trc c gn vi thng, ca nhp liu, tho liu trn thn my. Nguyn tc

hot ng: khi thng quay, di tc ng ca lc ly tm, vt liu trong thng s c

nng ln v ri xung to ra s o trn trong vt liu. My c th khin vt liu dp

nt khi trn

- Thit b ry gm cc loi ry vi cc kch thc (mm): 0.425, 0.315, 0.2, 0.16 v mt

ry kn hng vt liu. Nguyn tc hot ng: s rung ng c to thnh nh i

trng quay. Cc a c i trng c gn ln trc dn ng ca my, khi trc quay

cc a ny gy lc qun tnh lm cho thng sng chuyn ng theo cc hng khc

nhau, cc ht ln c tch li ry trn, li ry di l cc ht nh hn

- Cn

- Cc thau ng mu trn

2. Nguyn liu:

- Go

- u nnh

- u xanh

3. Phng php th nghim

a. Nghin

- Cn mu vt liu go em nghin M = 200g, ly bao vi buc vo my nghin cha

sn phm nghin.

- Bt cng tc my nghin cho chy khng ti, o cng dng in lc khng ti.

- Cho vt liu vo my, bt cng tc vt ti nhp liu, bm th k. o cng dng

in c ti cc i.

- Khi cng dng in tr li gi tr khng ti, dng th k, xc nh thi gian

nghin.

- Tho sn phm ra khi my nghin.

b. Ry

- Th nghim xc nh hiu sut ry: Ly mt na sn phm nghin em ry ti ry c

kch thc 0.2 mm, di ry c lt giy cha lng vt liu lt qua ry. Ta thc


-Trang 12-

hin ry 5 ln, mi ln c thi gian 5 pht. Sau mi ln ry, em lng vt liu lt qua

ry i cn khi lng ri loi b. Tip tc ry vi lng vt liu cn trn ry.

- Th nghim xc nh s phn b kch thc vt liu sau khi nghin: Ly lng sn

phm cn li em i ry trong 20 pht, cc ry c xp chng ln nhau theo th t

gim dn kch thc l ry. Sau , em cn lng vt liu cn tch ly ti mi ry v

v sinh h thng.

c. Trn

- em cn 3kg u nnh v 1.5kg u xanh v cho vo thng quay.

- Khi ng my trn v bm ng h tnh gi.

- Sau cc thi im c lp ln lt l 5 giy, 15 giy, 30 giy, 60 giy, 120 giy v 300

giy, dng my trn li v tin hnh ly mu theo s sau. Lu khng tho g hay

tc ng dch chuyn ln thng quay trong sut qu trnh trn.

- Tin hnh m lng ht u nnh v u xanh trong tng mu, sau khi m xong

em lng mu cho tr li vo thng quay.

- Tho b nguyn liu v v sinh my trn sau khi hon thnh th nghim.


-Trang 13-

IV. Kt qu th nghim

1. S liu th

a. Nghin

Bng 5. Tnh ton s liu nghin

Khi lng (g) Thi gian nghin (s) Cng dng in (A)

Khng ti C ti

200 27 4 5.4

b. Ry

Bng 6. S liu th xc nh hiu sut ry

Ln ry Thi gian (pht) Khi lng qua ry (g)

1 5 29.2

2 5 0.6

3 5 0.3

4 5 0.2

5 5 0.1

Bng 7. S liu th xc nh nng sut nghin

Kch thc ry (mm) Khi lng trn ry (g)

0.425 17.9

0.315 23.5

0.2 9.3

0.16 14.2


-Trang 14-

c. Trn

Bng 8. Trn

MU 5" 15" 30" 60" 120" 300"

N X N X N X N X N X N X

1 152

61 170 120 172 96 163 102 183 98 156 67

2 176 109 171 135 178 137 191 98 190 98 176 111

3 135 365 157 153 178 169 177 142 177 139 176 149

4 183 127 191 127 165 111 167 105 120 100 192 147

5 136 190 159 167 174 141 199 145 177 132 202 141

6 173 97 162 88 172 94 183 126 147 119 156 113

7 174 159 166 170 197 130 162 135 187 132 186 135

8 85 333 168 211 170 153 180 202 152 130 159 172

2. Kt qu tnh ton

Bng 9. Tnh ton nng sut nghin

Kch thc ry Dp (mm)

Khi lng

trn ry (g)

log(Dp) log()

Khi lng

tch ly (g)

Phn khi

lng tch ly

Phn khi

lng

0.425 17.9 -0.372 1.253 17.9 0.224 0.224

0.315 23.5 -0.502 1.371 41.4 0.518 0.294

0.200 9.3 -0.699 0.968 50.7 0.634 0.116

0.160 14.2 -0.796 1.152 64.9 0.811 0.178


-Trang 15-


-Trang 16-

a. Tnh ton nng sut nghin

Xc nh ng knh tng ng ca ht go :

- Xem ht go l hnh tr, ta c :

2

2

( / 4)

( / 2) 4 2

V D L DL

S DL D L D

- ng knh tng ng ca ht go l ng knh tng ng ca ht hnh cu :

3

2

( / 6)

6td td

td

V D D

S D

- T (1) v (2), ta c :

3 3 1.5 62( )

6 4 2 2 2 6 1.5td

td

D DL DLD mm

L D L D

Vy Dp1 = Dtd = 2(mm)

Xc nh DP2

Bng 10: Tnh ton DP2

Kch thc ry Dp (mm)

Khi lng trn ry

D (g) Phn khi lng

xi

0,425 17.9 0.224

0,315 23.5 0.294

0,200 9.3 0.116

0,160 14.2 0.178

Cng sut tiu th cho ng c : P = 220(5.4 4)0.8 = 0.2464 kW

(1)

(2)


-Trang 17-

Cng sut nghin T tn vt liu trn mt pht t Dp1 n Dp2 (Wi=13kW.h/tn)

Cch 1: Tnh DP2 theo khi lng

= 0.239

= 0.19573

= 79.44%

Cch 2: Tnh DP2 theo s ht

= 0.200

= 0.22376

= 90.81%

Cch 3: Tnh DP2 theo b mt ring

= 0.317

b. = 0.15627

= 63.42%


-Trang 18-

Tnh ton ry

Bng 11: Tnh ton hiu sut ry

Ln ry Thi gian

(pht) Khi lng qua ry (g)

Tng Ji Hiu sut ry

E

1 5 29.2 29.2

96.0526

2 5 0.6 29.8

3 5 0.3 30.1

4 5 0.2 30.3

5 5 0.1 30.4

- Hiu sut ry

E1 = 96.0526%

Tng t ta c

E2 = 98.03%

E3 = 99.01%

E4 = 99.67%

E6 = 100%


-Trang 19-

c. Tnh ton trn

Bng 12: Tnh ton trn thi gian 5

Mu N X CiA (CiA-CA)2 s n Is

1 152 61 0.7136 0.0022

0.4661 0.2581 2655 0.0091 0.0355

2 176 109 0.6175 0.0024

3 135 365 0.2700 0.1573

4 183 127 0.5903 0.0058

5 136 190 0.4172 0.0622

6 173 97 0.6407 0.0007

7 174 159 0.5225 0.0208

8 85 333 0.2033 0.2147



1 170 120 0.5862 0.0065

0.1602 0.1513 2515 0.0094 0.0621

2 171 135 0.5588 0.0116

3 157 153 0.5065 0.0257

4 191 127 0.6006 0.0044

5 159 167 0.4877 0.0320

6 162 88 0.6480 0.0003

7 166 170 0.4940 0.0298

8 168 211 0.4433 0.0499



1 172 96 0.6418 0.0006

0.0766 0.1046 2437 0.0095 0.0913

2 178 137 0.5651 0.0103

3 178 169 0.5130 0.0236

4 165 111 0.5978 0.0047

5 174 141 0.5524 0.0131

6 172 94 0.6466 0.0004

7 197 130 0.6024 0.0041

8 170 153 0.5263 0.0197


-Trang 20-



1 163 102 0.6151 0.0027

0.0842 0.1097 2477 0.0095 0.0864

2 191 98 0.6609 0.0000

3 177 142 0.5549 0.0125

4 167 105 0.6140 0.0028

5 199 145 0.5785 0.0078

6 183 126 0.5922 0.0055

7 162 135 0.5455 0.0147

8 180 202 0.4712 0.0382



1 183 98 0.6512 0.0002

0.0709 0.1006 2281 0.0099 0.0981

2 190 98 0.6597 0.0000

3 177 139 0.5601 0.0114

4 120 100 0.5455 0.0147

5 177 132 0.5728 0.0088

6 147 119 0.5526 0.0130

7 187 132 0.5862 0.0065

8 152 130 0.5390 0.0163



1 156 67 0.6996 0.0011

0.0855 0.1105 2438 0.0095 0.0864

2 176 111 0.6132 0.0029

3 176 149 0.5415 0.0157

4 192 147 0.5664 0.0101

5 202 141 0.5889 0.0060

6 156 113 0.5799 0.0075

7 186 135 0.5794 0.0076

8 159 172 0.4804 0.0347


-Trang 21-

Ta xy dng c gin ch s trn theo thi gian :


-Trang 22-

V. Bn lun

1. Bn lun s thch nghi ca nh lut Bond tin on cng sut nghin, c bit ch

trng v cc gi thit :

Ta c ni dung cc l thuyt v nghin nh sau:

Thuyt b mt ca P. R. Rittinger: ch c th p dng ng n trong iu kin nng

lng cung cp cho mt n v khi lng cht rn l khng qu ln v c th c dng

c tnh cho qu trnh nghin thc vi Kr c xc nh bng thc nghim trn my

nghin cng loi vi my nghin thc. V c iu kin rng buc v nng lng v vic

xc nh h s Kr rt phc tp do phi xc nh h s ny ng vi mt loi vt liu v mt

loi my nghin xc nh, cho nn thuyt ny khng c tnh thc t cao trong vic tin

on cng sut nghin.

Thuyt th tch ca Kick: c da trn c s ca thuyt phn tch ng sut ca bin

dng do trong gii hn n hi. Thuyt ny cng khng c gi tr thc t cao do vic xc

nh hng s Kk kh phc tp.

nh lut Bond l nh lut c tnh thc t hn so vi nh lut Kick v nh lut

Rittinger trong vic c tnh cng sut nghin. V:

- Ch s cng Wi bao gm c ma st trong my nghin v cng sut tnh theo phng

trnh u bi l cng sut trn trc my nghin.

- ng thi n c gi tr sai khc khng nhiu khi tnh cng sut cho cc my nghin

khc nhau nhng cng loi v dng cho c qu trnh nghin kh ln nghin t. Cho

nn, nh lut ny rt thun tin cho vic tnh ton.

- nh lut Bond s dng kch thc ht sau khi nghin l kch thc l ry c 80% vt

liu sau khi nghin lt qua, tc Bond xem cc ht vt liu sau khi nghin lun c

mt t l sao cho kch thc trung bnh ca chng bng kch thc ni trn. Gi thuyt

nay xem ra vn cha hp l lm v sau khi nghin cc ht c kch thc khng ng

nht nhau v t l gia cc ht khng chc s ng nh nh lut Bond gi s.

- tm c kch thc ny, ta cn bit s phn phi c ht trong vt liu tc phi

thng qua th nghim phn tch ry mi c th tnh c cng sut nghin.


-Trang 23-

2. Nhn xt v hiu sut ry v nghin o c. So snh vi kt qu trong sch. Gii

thch cc sai bit

Hiu sut ry 0.2mm: E = 96.0526%

- Hiu sut ny tng i cao.

- Hu ht cc ht u lt qua ry.

- Nguyn nhn :

+ Vt liu c m thp, cc ht khng dnh vi nhau.

+ Khi lng vt liu nh nn lp vt liu va d dng i xung di tip xc

vi b mt li ry v lt qua ry.

+ Thi gian ry vt liu di chuyn xung di.

Hiu sut my nghin:

- Qu trnh nghin thng c hiu sut khng cao.

- Nguyn nhn khch quan :

+ Nng lng ca my nghin ch yu dng chy ng c.

+ Tht thot sn phm trong my nghin, sn phm nghin khng c thi ra ton

b.

- Nguyn nhn ch quan :

+ Thao tc trong qu trnh th nghim.

+ Phn tch kt qu ry cha chnh xc, tnh ton da trn nh lut Bond ch mang

tnh tng i.

+ Bt dnh li trn vt cha l ti vi.

+ Bt mn, nh, d b cun bi gi qut v gi t nhin.

3. Bn v tin cy ca kt qu v cc yu t nh hng nhiu nht.

Ry:

a. Ta nhn thy kt qu ry cng vi cc gin l hp l v kh st vi l

thuyt, hiu sut ry cng rt cao l do cc nguyn nhn trnh by trn.

Tuy nhin, kt qu ny vn cn sai s d l rt t, cc sai s ny l do sai s

trong thit b cn o v vic lm trn s, ly gn ng trong qu trnh tnh ton.

Ta c th kt lun th nghim c tin cy cao.

b. Mt s yu t gy nh hng ln th nghim ry:


-Trang 24-

m vt liu ry: khi thit b ry hot ng, cc ht vt liu s chuyn ng trn b mt ry. Nu vt liu c m ln th chng s dnh vo nhau lm tng kch thc ht v ht s khng lt qua c ry. Ngoi ra, nu c m cao th vt liu s d dng dnh vo l ry lm bt kn l ry gy ra sai s khi o v tnh ton. Do , m vt liu c nh hng rt ln n kt qu th nghim.

Kch thc vt liu trn ry: ht c kch thc cng chnh lch nhiu vi kch thc l ry th kt qu ry cng chnh xc.

B dy lp vt liu: lp vt liu cng dy th kt qu ry cng km chnh xc do lp vt liu bn trn kh i c xung di qua ry.

Thi gian ry: thi gian cng di th hiu sut cng cao.

Trng thi ca ry: ry sch, t ln tp cht s c hiu sut cao hn so vi ry khng c v sinh k, tp cht hoc nguyn liu t cc ln ry trc s ng, lm nghn cc l ry khin gim hiu sut.

Nghin: Nghin l mt qu trnh m trong c s tn tht ln v mt nng lng nn

dn n vic hiu sut nghin khng cao.

Mt s yu t nh hng ln th nghim nghin:

Tnh cht ca vt liu: kch thc vt liu trc v sau nghin, trng thi vt liu nh m, dn, do,, ng u ca vt liu cng c tc ng ln th nghim nghin.

Loi my nghin: ty loi my nghin m ta s c nhng thng s v ch lm vic khc nhau, nu loi my ph hp vi vt liu v ch nghin s cho hiu sut cao v ngc li.

Ch nghin: ch nghin cng cn ph hp vi vt liu v loi my s dng.

Sai s ca dng c o v thao tc th nghim: cc sai s tuy nh nhng lun tn ti cng c nh hng nht nh.

Kt qu th nghim ry: cc sai s trong th nghim ry cng gy nh hng v kt qu tnh c s c s dng tip tnh ton ra hiu sut nghin.

4. Nhn xt v cch ly mu trong th nghim trn.

Mu trong th nghim trn c ly ti 6 thi im khc nhau: 5" , 15", 30", 60", 120"

v 300". Ti mi thi im ta ly 8 mu theo s :


-Trang 25-

Do sau khi trn, cc vng khc nhau ca khi ht s c t l phn b ht khc bit

nhau. Cc a im ly mu phn tn u trong khi ht s cho ta kt qu mang tnh tng th,

c trng cho c khi ht. iu ny lm tng chnh xc ca kt qu th nghim trn.

5. Bn v tin cy ca kt qu trn v cc yu t no trong th nghim c nh hng

nhiu nht n th nghim trn.

Xt v tin cy ca kt qu trn, ta nhn thy tin cy l khng cao. Kt qu th

nghim trn thu c b sai lch so vi kt qu c d on t l thuyt. iu ny c

th c gii thch l do s nh hng ca cc yu t trong qu trnh thc hin th

nghim.

Do nguyn vt liu: hai loi ht u xanh v u nnh c kch thc cng nh khi

lng khc nhau, cc cng thc thit lp tnh thnh phn hn hp theo s ht c

dng cho hai vt liu c cng kch thc v khi lng, cho nn cch tnh thnh phn

theo khi lng v theo s ht cho u xanh v u nnh s khc nhau. iu ny dn

n sai s khi tnh thnh phn theo s ht.

Hot ng ca my trn thng quay khng cn n nh v chnh xc.

Cc ht u c ti s dng nhiu ln trong cc t th nghim dn n tnh trng ht

b nt, v to nn sai s trong qu trnh m ht.

Cc ln ly mu khng ng u nhau cng nh lng mu khng mang tnh thng k

cao dn n sai s.

- Cc yu t nh hng nhiu nht n th nghim trn:

Kch thc ht: cc ht cng ng u th trn cng tt.

Khi lng ring ca ht: cng chnh lch nhiu cng kh trn u, d dn n s phn tch theo khi lng ring.

m vt liu: m cng cao th s cng kh trn hn.

Tnh d v

Hnh dng ht

S tch in ca ht: nh hng xu n qu trnh trn v xut hin lc tnh in gia cc ht tch in tri du, kh khn cho vic phn phi u.


-Trang 26-

VI. Ph lc

- Cng thc tnh cng sut nghin:

- Cng sut ca ng c: P = Uicos

- Hiu sut ca my nghin:

- Phng trnh biu din n s phn phi kch thc i vi ht nhuyn:

b

p

p

KD

dD

d

hay log = (b + 1) logDpn + logK

- Hiu sut ry: 100

Fa

JE

-

- Thnh phn ca A v B trong hn hp AB:

ba

aCA

v

ba

bCB

- Cng thc tnh ch s trn:

N

1i

2

iAA

BA

s

)CC(.n

)1N(CCI

%100

'P

PH

T

D

1

D

1W19

3

4P

1p2p

i


-Trang 27-

VII. Ti liu tham kho:

[1]. V Vn Bang, V B Minh Qu trnh v Thit b cng ngh ha hc v thc phm -

Tp 2 Cc qu trnh c hc, HQG TP HCM, 2004.

[2]. Nguyn Hu Hiu Bi ging Cc qu trnh c hc A, 2014

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