Study of a sieved tray column for methanol water distillation

7/25/2019 Study of a sieved tray column for methanol water distillation

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STUDENT ID 4202858STUDENT NAME Tom CullinanL3 Ya!2 LA" CODE #$ UO32% D&L3 Ya!2 LA" CON'ENOR An(a )o!*aASSESSOR #i+ *i,!n- -o La.

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Moderately well presented tables and graphs with correct calculations.Results are analysed and interpreted to a reasonable level. Discussions

address some questions and issues relating to the practical. Conclusions

describe some of the ndings of the experiment and attempt to compare

these nding to theoretical predictions. Overall report is reasonable clear

and concise with some citations and references.

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ell presented tables and graphs with correct calculations. Results are

analysed and interpreted to a reasonable level. Discussions address most

questions and issues relating to the practical and relate to real world

applications! where appropiate. Conclusions describe most of the ndings ofthe experiment and compare these nding to theoretical predictions. Overall

report is clear and concise with most citations and references correctly

formatted.

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"xcellent presentations of tables and graphs with correct calculations.

Results are analysed and interpreted to a high level. Discussions address all

questions and issues relating to the practical and relate to real world

applications! where appropiate. Conclusions describe the ma#or nding of

the experiment and compare these nding to theoretical predictions. Overall

report is very clear and concise with citations and references correctly

formatted.

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D1: Study of a sieved tray column for methanol water distillation

L3-D1

Tom Cullinan 4202858

4th December 2014

Submission date - 11th December 2014

(Submission deadline - 11th December 2014)

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Contents

5

bstract

!ntroduction

6

"ealth and Sa#et$

Theor$

8

%ethod

&esults

13

Discussion

15

Conclusion

&e#erences

5


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bstract

!n this in'estiation the mole #raction o# methanol in a methanol*+ater mi,ture +as obser'ed +hile

the o+er to a total reboiler heatin said mi,ture +as 'aried. distillation column containin sie'e-tra$s +as used and at each di##erent tra$ a di##erent deree o# #oamin +as e,hibited (in#luenced b$

the reboiler o+er). The deree o# #oamin +as h$othesised to ha'e an imact on the ressure dro

that occurred across the distillation and results suorted this h$othesis. !t +as #ound that there +as

an otimal o+er #or the reboiler to oerate at out o# the choices that +ere ro'ided (0.5 / 0.5

/ 0.8 / 0.5 / and 1.1 /).

The otimal 'alue +as #ound to be 0.8 / as it roduced the hihest mol #raction o# methanol in the

distillate samle that +as collected #rom the column. This +as determined b$ use o# a re#ra

ctometer and the inection o# a small samle o# the distillate. t 0.8 / the lo+est ressure dro +as

e,hibited as +ell. !t +as also obser'ed that the 'aour 'elocit$ la$ed a role in the ressure dro that

+as e,erienced across the column. s the 'aour ressure o# the mi,ture increased (measured o'er

all reboiler o+ers) the ressure dro increased and lead to a decrease in o'erall column e##icienc$.ote ressure dro is not the same as the ressure e,erted b$ the reboiler.

#ter consultin /no+n literature on the toic it +as concluded that #or the desin o# a distillation

column li/e the one that +as used there are man$ desin arameters to ta/e into account. These

include the o+er to the reboiler t$e o# tra$ that is used +ithin the column diameter o# the internal

column tra$s and man$ other #actors. 6'erall the in'estiation ro'ed a success as clear correlations

+ere made bet+een the e##icienc$ o# the searation rocess and the o'erall column itsel# and the

o+er that +as ro'ided to the total reboiler. These results can be #ound in the results section.

!ntroduction

This in'estiation +as er#ormed in order to ain the necessar$ s/ills re7uired to al$ theoretical

/no+lede o# basic binar$ distillation to a real-+orld conte,t. Distillation usin either tra$s or ac/ed

columns are emlo$ed in re#ineries etrochemical lants as rocessin lants and oranic chemical

lants to uri#$ natural as all around the +orldC!TT!6 SDa13 l 2059 . :or these reasons it is there#ore

imortant to be able to understand the enineerin bac/round behind such rocesses. here 'aour-

li7uid e7uilibriums are in'ol'ed in the searation o# a desirable substance #rom its counterart

calculations can become comle, and detrimental to the desin o# the column due to the uncertain

nature o# the ossible #ormation o# an a;eotroic mi,ture.

"Distillation can be carried out in a tray or a packed column. The major considerations involved in

the choice of the column type are operating pressure and design reliability. As pressure increases, tray

coulmns become more effcient for mass transfer and can often tolerate the pressure drop across thetrays. The design procedure for the large diameter tray column is also more reliable than that for the

packed column. Thus, trays are usually selected for large pressurized column applications."1

!t is there#ore aroriate that the 'ariation o# column ressure dro +ith 'aour 'elocit$ is studied

and thus the e##icienc$ o# the o'erall column as a #unction o# the 'aour 'elocit$ calculated. This +ill

be done b$ alterin the o+er ro'ided to a total reboiler and obser'in the di##erent temeratures

roduced at each late alon +ith the deree o# #oamin that is associated +ith it.

C$%&%$O' (Da)* +l ,-/ 0'anda1umar! ,---2


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%otal reboiler3alve 34

3alve 3/

"ealth and Sa#et$

There are man$ #actors to be ta/en into consideration +hen desinin*oeratin distillation columns

+ith reards to sa#et$.

:irstl$ the oeratin conditions +ithin the column itsel# ose a otential ha;ard. The column isoeratin at temeratures u to 100

o heat losses #rom column

o heat o# mi,in

There is no ressure dro across the column

Constant molar latent heats o# secies in'ol'ed

s can be seen #rom the results section the third assumtion o# a ;ero ressure dro +as in #act

unust and thus leads to uncertainties in the #inal results.

?:iure 1. D1 Tra$-distillation column +ith labels@

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%

%5

:iure 1 sho+s the setu that +as used in the in'estiation. :iure 2 belo+ sho+s a close u o# the

tra$s +ithin the distillation column and their arranement. t 100A e##icienc$ the #ollo+in

conclusions can be made> #irstl$ that the 'aour #lo+s onl$ u+ards bet+een the do+ncomers and

throuh onl$ the oen reions o# the tra$ secondl$ that li7uid #lo+s do+n+ards #rom tra$ to tra$ onl$

'ia the do+ncomers. Thirdl$ that there is no +eein o# the li7uid throuh the tra$ er#orations and

none is carried as entrainment b$ the 'aour. :inall$ that 'aour is ne'er carried throuh the

do+ncomer b$ the li7uid. Bn#ortunatel$ these assumtions do not hold entirel$ 'alid.

s the condenser is oeratin at total re#lu, the

to oeratin line (T6L) e7uation isy=x (as

can be seen in rah 1) this ma/es the

calculations o# the theoretical number o# staes needed to conduct the distillation eas$. "o+e'er i# as

is the case a lot o# the time in industr$ the condenser is not oeratin at total re#lu, e7uations 1 and 2

belo+ must be used to enerate a T6L and 6L #or the rocess.

yn+1= Lt

Vtxn+DVt

xD

?7uation 1@

here>

yn+1 > %ol #raction o# $ at stae (nE1)

Lt > To stream li7uid #lo+rate

Vt > To stream 'aour #lo+rate

xn > %ol #raction o# , at stae n

xD > %ol #raction o# , in distillate

D> Distillate #lo+rate

ym=Lb

Vbxm1

W

VbxW

?7uation 2@

here>ym > %ol #raction o# $ at stae m

8

?:iure 2. Close u o# the basic

lass sie'e-tra$ column@

?:iure 3. Detailed diaram

sho+in #lo+ o# 'aour and li7uid

in a ortion o# a column@


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Lb > ottom stream li7uid #lo+rate

Vb > ottom stream 'aour #lo+rate

xm1 > %ol #raction o# , at stae (m-1)

xW > %ol #raction o# , in bottom stream

W> ottom stream #lo+rate

%ethod

&e#er to #iure 1.

1. Durin the start-u that +as er#ormed b$ the demonstrator the reboiler +as set to 0.8 /.

The reboiler contains the methanol-+ater mi,ture.

2. !denti#$ each iece o# e7uiment in the ri and as/ an$ rele'ant 7uestions #or the

demonstrator to ans+er to ensure a comlete understandin o# ho+ the ri is to be used.

3. Bsin the electronic console in #ront o# the ri tole throuh the temerature readins #oreach late (T5-T) and record in results table 1.

4. %a/e note o# the aearance o# the li7uid-'aour mi,ture #ormed at tra$ T5 (to) usin one

o# the adecti'es rele'ant to this in'estiation (=Li7uid +eein=*=o #oamin=* =Fentle

localised=*=Giolent localised=*=Fentle o'er the +hole tra$=*=Giolent o'er the +hole tra$=*=Li7uid

#loodin=).

5. "old a lass bea/er underneath 'al'e G3 and oen to allo+ #or a discardin samle to be

collected and emt$ samle into the desinated +aste container. Then collect a samle o# the

distillate in a measurin c$linder usin the same 'al'e and measure the amount collected in

15 seconds. ith this data the li7uid boil-u rate can be calculated.

. nsurin the de'ice is clean b$ rinsin +ith distilled +ater iette a small amount o# the

distillate collected onto the re#ractometer and record the readin i'en in results table 3. To

ensure 'alidit$ in this result the samle should be collected at &TH.9. Ta/e ressure dro readins across the e7uiment b$ oenin 'al'es G and G9 on the

manometer. Gal'e G must al+a$s be oened be#ore G9 to re'ent 'aour #rom enterin the

manometer. Closin o# the 'al'es must ta/e lace in the same order. ait 2-3 minutes and

er#orm the readin aain recordin results in results table 2.

8. dust the reboiler o+er to 0.5 / usin the electronic console and +ait 20 minutes #or

e7uilibrium to be reached. This is imortant as it ta/es time #or the mi,ture comosition to

chane and this is one o# the /e$ asects o# the in'estiation bein measured.

. &eeat staes 3-9 and record all rele'ant in the aroriate results tables. Then adust reboiler

o+er to the ne,t settin (out o# 0.5 / 0.5 / 0.5 / and 1.10 /).

&esults

Power (kW !" (#$ !8 (#$ !% (#$ !6 (#$ !5 (#$&oil u' rate

()h

0.50 2.1 94.3 .4 .8 5.4 12.

0.5 2.1 94.9 90.3 9.3 5.9 1530.3

0.80 2.5 95.0 90. 8.1 .5 899.

0.5 3.1 95.9 91.3 8.3 . 2842.0

1.10 4.0 98.0 92.9 91.3 91.1 3512.5

*esults !a+le 1

&esults table 1 sho+s the di##erent temeratures o# each tra$ +ithin the distillation column at eachdi##erent reboiler o+er settin. !t can there#ore be seen that the temerature decreases u the column.

This is rele'ant to the in'estiation as the di##erent temeratures at each tra$ indicate a di##erent


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comosition o# mi,ture as deicted b$ the T-,-$ chart (rah (ii)) and the di##erent comositions at

each stae can be comared to the #inal comosition to hel calculate the e##icienc$ o# the o'erall

column and the 'aour 'elocities. The boil u rate o# the column has been calculated usin results

table 4 and is rele'ant as it can be seen that at 0.8 / the reboiler is e'identl$ +or/in at its

otimum o+er.

Power (kW,P1(cm

,P-(cm

,P3(cm

,P./0(cm

De2ree of foamin2

0.50 30 28 2 2 eein

0.5 30 2 31 30 Sliht +eein

0.80 30 33 33 32 Fentle localised

0.5 33 38 33 35 Giolent localised

1.10 49 50 53 50 Li7uid #loodin

*esults !a+le -

&esults table 2 reresents the di##erent ressure dros (in mm"26) associated +ith each reboiler

o+er. These results are lotted in rah 2. s can be seen #rom the table the a'erae ressure dro

increases as the reboiler o+er increases.

Power (kW * 4 to' 4 +ottom / (ml t (s iuid flow ()h

0.50 1.32 0.2 0.09 8.0 15.0 1.2

0.5 1.329 0.1 0.09 9.0 15.0 1.8

0.80 1.3283 0.5 0.0 5.0 15.0 1.20

0.5 1.329 0.1 0.0 13.0 15.0 3.12

1.10 1.3311 0.88 0.05 14.0 15.0 3.3*esults !a+le 3

&esults table 3 sho+s ho+ alterin the reboiler o+er in#luences the mole #raction o# methanol in the

to and bottom streams o# the distillation column. I to is obtained #rom usin rah (i) in the

re#erences section o# this reort b$ usin the re#racti'e inde, readins (&!) obtained #rom the

re#ractometer. I bottom can be obtained throuh t+o methods that +ill be comared in the discussion.

!n results table 2 I bottom +as calculated usin the =temerature= 'ersus =, or $= rah ro'ided

(rah (ii) in the re#erences section). G reresents the 'olume o# li7uid obtained in the time #rame t

(set at 15 seconds).

:inall$ results table 4 disla$s the calculated #lo+rate o# both +ater and methanol li7uids and

'aours resecti'el$.

Water (l mass flowrate (k2)h ethanol (l mass flowrate (k2)h

0.153 1.318

0.151 1.140

0.00 0.850

0.280 2.118

0.402 2.20

Water (2 mass flowrate (m7)h ethanol (2 mass flowrate (m7)h

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0.9 0.8

0.954 0.99

0.2 0.59

1.401 1.441

2.012 1.501

Water (2 va'our velocity (m)s ethanol (2 va'our velocity (m)s

0.108 0.129

0.109 0.110

0.042 0.082

0.18 0.204

0.285 0.212

*esults !a+le

The resultin 'aour 'elocities o# +ater and methanol are calculated b$ #irstl$ di'idin the 'aour

'olumetric #lo+rates b$ 300 to chane the time unit #rom hours to seconds. Then these 'alues are

di'ided b$ the cross-sectional area o# the distillation column reresented b$ ? (( 502)103)

2

to roduce the #inal 'aour 'elocities. Frahs 2 3 and 4 can no+ be lotted.

Frah 1 belo+ sho+s ho+ the number o# theoretical lates +ere calculated #or a distillation column

oeratin at total re#lu, and at a reboiler o+er o# 0.5 /. The same calculations +ere conducted #or

the distillation column at each di##erent reboiler o+er.

ole fraction of methanol()water in liuid a2ainst that in va'our9 5 kW9 1 atm

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The number o# theoretical staes re7uired #or the searation +as calculated b$ lottin oints (IDID)

and (I) and dra+in hori;ontal and 'ertical lines that intersect +ith the e7uilibrium and T6L

resecti'el$. :or instance in the rah abo'e it can be seen that bet+een 3 and 4 staes are re7uired.

Number of t h eoretical stages 3.4

Efficiency of overall column=3.41

4

100

Efficiency(0 .5kW)=60

There#ore alon +ith the other necessar$ results the e##iciencies ha'e been tabulated and can be

#ound belo+ in results table 5.

Power(kW

0fficiency(;

,P (cm 4t / (m)s

12

G!a9; &= M-;anol mol +!a(-ion in liui* a$ain- -;a- in /a9ou!> 0=5 7


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0.50 0.0 2.0 0.2 0.129

0.5 59.5 30.0 0.1 0.110

0.80 99.5 32.0 0.5 0.082

0.5 0.0 34.9 0.1 0.204

1.10 59.5 50.0 0.88 0.212

*esults !a+le 5

:rom here the rele'ant rahs can be lotted that +ill allo+ #or the anal$sis o# ho+ methanol 'aour

'elocit$ as a #unction o# reboiler o+er a##ects the remainin 'ariables in the table.

0.050 0.090 0.00 0.110 0.130 0.150 0.190 0.10 0.210 0.230

40.0

50.0

0.0

90.0

80.0

0.0

100.0

A $!a9; -o 8;o: 'a9ou! /lo(i-< /!8u8 O/!all H(in( htt>**cornellarchi'es.com*sdaniels*2..8

anda/umar J. T. (2000). Tra$ Columns> Desin. niversity of Alberta hemical -ngineering 1.

Tham %. (2014 Kanuar$). olumn !nternals. &etrie'ed December 2014 #rom Lorien.ncl>

htt>**lorien.ncl.ac.u/*min*distil*distilint.htm

Frahs

?Frah (i). &e#racti'e !nde, 'ersus %ethanol mole #raction@

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?Frah (ii). T-,-$ rah #or %ethanol*ater at 1 atm.@

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Study of a sieved tray column for methanol water distillation

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