laboratory preparation of bio diesel

8/13/2019 Laboratory Preparation of Bio Diesel

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PLANT DESIGN

6.1 Laboratory Preparation of Bio Diesel

6.1.1 Equipment needed:

Four 500 ml Erlenmeyer flasks containing 200 g of egetable oil

Four 125 ml Erlenmeyer flasks! " containing #" g of met$anol! one containing

21.5 g of met$anol

Four $ot plate%stirrers

Four separatory funnels &it$ ringstan's (luminum foil )for capping flasks* +mall

bottles containing pre&eig$e' so'ium $y'ro,i'e! t$ree &it$ 2 g! one &it$ 10 g.

6.1.2 Task

Group 1:-oo muc$ &ater +tarting &it$ 200 g of egetable oil in a 500 ml flask. ('' 10 g of &ater.

('' 2 g of so'ium $y'ro,i'e pellets to #" g of met$anol an' agitate until t$e

pellets are 'issole'.

('' t$e met$anol%so'ium $y'ro,i'e solution to t$e egetable oil. ('' a

magnetic stirring bar an' place on t$e $ot plate. /eat to 6065 an' agitate for 1$our. Pour into a separatory funnel an' allo& separating.

Group 2:-oo muc$ catalyst

+tart &it$ 200 g of egetable oil in a 500 ml flask.

('' 10 g of so'ium $y'ro,i'e pellets to #" g of met$anol an' agitate until t$epellets are 'issole'. /eating may be re3uire'.



Group 3:4ot enoug$ alco$ol

+tart &it$ 200 g of egetable oil in a 500 ml flask.

('' 2 g of so'ium $y'ro,i'e pellets to 21.5 g of met$anol an' agitate until t$e

pellets are 'issole'. /eating may be re3uire'.



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Group 4:/ig$ free fatty aci' fee'stock

+tart &it$ 200 g of animal fat in a 500 ml flask.

('' 2 g of so'ium $y'ro,i'e pellets to #" g of met$anol an' agitate until t$e

pellets are 'issole'.

('' t$e met$anol%so'ium $y'ro,i'e solution to t$e animal fat. ('' a magneticstirring bar an' place on t$e $ot plate. /eat to 6065 an' agitate for 1 $our.Pour into a separating funnel an' allo& separating.

Group 5: il E,traction from (lgae.

Let t$e (lgae 'ry in oen for 2 $ours.

7i, n$e,ane an' rigi'ly stir.

(long &it$ n$e,ane mi,es take t$e algae oil.

Let n$e,ane eaporate t$e rest &ill be algae oil.

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Fig 11: Laboratory wor at IESE !N"ST#

6.2 Propose' Bio Diesel Plant

Fig 12: Propo$%& 'io Di%$%( P(a)t

6.2.3 'a$i* P(a)t E+uip,%)t a)& -p%ratio)

-$e intent of t$e basic plant e3uipment an' operation section is to 'iscuss t$e

principles be$in' t$e primary plant e3uipment t$at &oul' be use' in a bio'ieselpro'uction facility. 8nclu'e' &ill be 'iscussion of reactors )bot$ batc$ an' continuous

types*! pumps! centrifuges! an' 'istillation columns. (lt$oug$ t$ere &ill be a''itional

e3uipment in t$e plant suc$ as settlers! storage tanks! etc.! t$e four classes of e3uipment'iscusse' $ere represent t$e $eart of t$e process.

6.2.3.1Reactors

-$e reactor is t$e only place in t$e process &$ere c$emical conersion occurs.

-$erefore! it 'ictates &$at c$emical species must be $an'le' 'o&nstream of t$e reactor.

9eactors can be place' into t&o broa' categories! batc$ reactors an' continuous reactors.

-&o of reactors &it$in t$e continuous reactor category are continuous stirre' tankreactors )+-9s* an' plug flo& reactors )PF9s*. 8n t$e batc$ reactor! t$e reactants are

c$arge' into t$e reactor at t$e 'etermine' amount. -$e reactor is t$en close' an' taken tot$e 'esire' reaction con'itions )temperature! pressure! an' stir rates*. -$e c$emical

composition &it$in t$e reactor c$anges &it$ time.

nce t$e prescribe' reaction time is complete! t$e c$emical contents of t$e

reactor are remoe' an' sent for subse3uent processing. 8n contrast! continuous reactors

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$ae a stea'y flo& of reactants into t$e reactor an' pro'ucts out of t$e reactor. nce a

continuous flo& reactor reac$es stea'ystate operation! t$e pro'uct composition leaing

t$e reactor becomes constant. For +-9s! t$e reactants are fe' into a &ellmi,e' reactor.

-$e composition of t$e pro'uct stream is i'entical to t$e composition &it$in t$e

reactor. /ol'up time in a +-9 is gien by a resi'ence time 'istribution. For PF9s! t$ereactants are fe' into one si'e of t$e reactor. -$e c$emical composition c$anges as t$e

material moes in plug flo& t$roug$ t$e reactor. -$e resi'ence time is 'efine' by t$e

lengt$ of time re3uire' for molecules to trael t$roug$ t$e reactor. -$e most importantconsi'erations &it$in a reactor are t$e e,tent of reaction of t$e reactants! &$ic$ is kno&n

as conersion! an' t$e selectiity of t$e reaction to t$e 'esire0' pro'ucts! &$ic$ is kno&n

as t$e selectiity. :ey reactor ariables t$at 'ictate conersion an' selectiity

aretemperature! pressure! reaction time )resi'ence time*! an' 'egree of mi,ing. 8ngeneral! increasing t$e reaction temperature increases t$e reaction rate an'! $ence! t$e

conersion for a gien reaction time. /o&eer! if more t$an one reaction is taking place!

t$e selectiity to t$e 'esire' pro'ucts can be impacte' by c$anging t$e reaction

temperature.

8n t$e transesterification reaction! t$e selectiity of t$e reaction is not negatielyimpacte' by increasing temperature. 8ncreasing temperature in t$e transesterification

reaction 'oes impact t$e operating pressure. -$e reaction is a li3ui' p$ase reaction! so t$e

pressure in t$e reactor must be maintaine' at a leel t$at keeps t$e met$anol in t$e li3ui'p$ase. -$erefore! as t$e reaction temperature is increase' t$e pressure must also be

increase'. (not$er means to increase t$e conersion in a reactor is to increase t$e

reaction time. For a gien temperature! conersion &ill increase as t$e reaction time

increases. 8ncreasing t$e reaction time $as t$e negatie effect of 'ecreasing t$e c$emicalt$roug$put in a gien plant or increasing t$e reactor si;e for a gien c$emical t$roug$put.

( final ery important parameter in t$e reactor is t$e 'egree of mi,ing or masstransfer. For batc$ reactors an' +-9s t$e 'egree of mi,ing is 'irectly relate' to t$e

amount of energy intro'uce' t$roug$ t$e impeller. 8ncreasing t$e spee' of t$e impeller!

&$ic$ increases t$e energy input to t$e reactor! increases t$e 'egree of mi,ing! &$ic$improes t$e performance of t$e reactor.

( t$res$ol' e,ists &$ere a''itional mi,ing &ill not proi'e any performance

en$ancement. For PF9s! t$e 'egree of mi,ing is 'ictate' by t$e 'esign of t$e reactoran'%or catalyst use' &it$in t$e reactor! since no mi,ing 'eice is present in t$e reactor

t$at can be in'epen'ently manipulate'. Batc$ reactors $ae seeral positie features

inclu'ing goo' mi,ing c$aracteristics an' relatie ease of $an'ling $omogeneouscatalysts as use' in t$e bio'iesel transesterification reaction.

(s mentione' aboe! t$e reactant concentrations c$ange &it$ time in t$e reactoras 'oes t$e pro'uct concentration. -$erefore! t$e effect of reaction in$ibition by reaction

pro'ucts suc$ as e,perience' &it$ glycerol can be minimi;e'. /o&eer! batc$ reactors

are generally not use' in t$e pro'uction of large olume c$emicals since it is most

efficient to operate t$e subse3uent separation an' purification steps in a continuous

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mo'e. -$is batc$ to continuous mo'e can be oercome by using multiple reaction essels

se3uence' to gie effectiely continuous operation or by employing a large $ile t$e role of pumps in a c$emical plant seems rat$er mun'ane! t$ey play t$e

key role in moing c$emicals t$roug$ t$e manufacturing plant. -$e most common type

of pump in t$e c$emical in'ustry is a centrifugal pump. 8n many applications! t$e flui'

s$ear intro'uce' by a centrifugal pump is not a point of concern. /o&eer! t$e s$earcreate' by a centrifugal pump can create emulsion problems for t$e pro'uct stream from

t$e bio'iesel reactor. -$e amount of flui' s$ear imparte' by t$e pump can besignificantly re'uce' by using a positie 'isplacement pump. -$ere are a number of

'ifferent types of positie 'isplacement pumps inclu'ing gear pumps )e,ternal an'

internal* an' lobe pumps. E,ternal gear pumps generally $ae t&o gears &it$ e3ualnumber of teet$ locate' on t$e outsi'e of t$e gears! &$ereas! internal gear pumps $ae

one larger gear &it$ internal teet$ an' a smaller gear &it$ e,ternal teet$. -$e li3ui' is


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conerts t$e kinetic energy imparte' by t$e impeller into feet of $ea'. -$e role of t$e

impeller is to increase t$e kinetic energy of t$e li3ui'. -$e li3ui' enters an' leaes t$e

impeller at t$e same pressure. (s t$e li3ui' flo&s t$roug$ t$e olute! t$e elocity is'ecrease' &it$ t$e energy transferre' to pressure.

Fig 13: %)tri/uga( Pu,p

>$ile leaking pump seals or impeller &ear can be operational issues &it$ pumps!

t$e most common issue &it$ pumps is t$e loss of suction pressure. +uction pressure is t$e

pressure supplie' to t$e suction si'e of t$e pump by t$e li3ui'. During loss of suctionpressure! &$ic$ is kno&n as caitation! t$e pump 'isc$arge pressure an' t$e 'isc$arge

flo& rates become erratic an' lo&. aitation is create' by apori;ation of li3ui' at t$e

pump suction. -$is situation can be create' be a plug in t$e suction piping or by starting

t$e pump up too rapi'ly. 8n general! positie 'isplacement pumps are more 'ifficult tocaitate t$an centrifugal pumps.

entrifuges are most typically use' to separate soli's an' li3ui's! but t$ey canalso be use' to separate immiscible li3ui's of 'ifferent 'ensities. -$is type of separation

can also be ac$iee' using a settling tank. >$ile a settling tank may be c$eaper! a

centrifuge can be use' to increase t$e rate of separation relatie to a settling tank. 8n acentrifuge t$e separation is accomplis$e' by e,posing t$e mi,ture to a centrifugal force.

-$e more 'ense p$ase &ill be preferentially separate' to t$e outer surface of t$e

centrifuge. ( centrifuge generally consists of

!1#( bo&l containing t$e mi,ture!

!2#( 'rie s$aft an' 'ries$aft bearings!

!3#( 'rie mec$anism! an'

!4#( casing to segregate t$e separate' pro'ucts.


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Fig 14: %)tri/ug%$

-$e performance of a centrifuge 'epen's on t$e specifications of t$e centrifuge as&ell as t$e c$aracteristics of t$e mi,ture to be separate'. >$ile centrifuges are generally

rate' in terms of mi,ture $an'ling capacity! t$e pro'uct 3uality specifications are t$e

most important consi'eration. -$e c$oice of appropriate centrifuge type an' si;e arepre'icate' on t$e 'egree of separation nee'e' in a specific system. -$e iscosity of t$e

li3ui' $as important implications on t$e c$oice of centrifuge si;e since $ig$er iscosity

flui's are more 'ifficult to $an'le. 8f a sufficient 'ensity 'ifference e,ists bet&een

immiscible flui's! centrifugation is a faster means of separation t$an settling.

6.2.3.3Distillation

(not$er means of separating c$emicals in a flui' mi,ture is by e,ploiting t$e

'ifferences in boiling points bet&een t$e c$emicals. 8f t$e boiling points are sufficiently

'ifferent for t$e c$emicals to be separate'! suc$ as &it$ &ater an' bio'iesel! aneaporator or flas$ apori;er can be use' for t$e separation. 8n t$e eaporator! t$e li3ui'

is $eate' to a temperature in &$ic$ only t$e more olatile c$emical species &ill apori;e.

(s suc$ t$e apor stream leaing t$e aporator &ill be enric$e' in t$e more olatilespecies an' t$e li3ui' stream from t$e eaporator &ill be enric$e' in t$e less olatilespecies. 8n an eaporator! t$e separation is accomplis$e' by supplying $eat &$ile t$e

mi,ture is $el' at a fi,e' pressure. 8n contrast! a flas$ apori;er first $eats t$e li3ui'! at

an eleate' pressure. -$en! t$e $eate' li3ui' is sent t$roug$ a flas$ ale t$at 'ecreasest$e pressure. -$e 'ecrease in pressure causes t$e more olatile portion of t$e li3ui'

mi,ture to apori;e.

(n important separation 'eice for miscible flui's &it$ similar boiling points

)e.g.! met$anol an' &ater* is t$e 'istillation column. +eparation in a 'istillation column is

pre'icate' on t$e 'ifference in olatilities )boiling points* bet&een c$emicals in a li3ui'

mi,ture. 8n a 'istillation column t$e concentrations of t$e more olatile species areenric$e' aboe t$e fee' point an' t$e less olatile species are enric$e' belo& t$e fee'

point. -$e apori;ation in t$e column is 'rien by $eat supplie' in t$e reboiler! &$ic$ is

subse3uently remoe' in t$e oer$ea' con'enser. -$e temperature in t$e 'istillationcolumn is t$e $ig$est at t$e bottom an' 'ecreases moing up t$e column. Distillation

columns can use eit$er trays or packing.

-$e 'egree of separation t$at can be ac$iee' in a 'istillation column is 'ictate'

by t$e relatie olatilities of t$e c$emicals to be separate'! t$e number of trays or t$e

$eig$t of t$e packing! an' t$e reflu, ratio. $emicals &it$ ery 'ifferent boiling pointsare easier to separate t$an t$ose &it$ similar boiling points. 8ncreasing t$e number of

trays or t$e $eig$t of packing can increase t$e amount of separation. 9eflu, ratio is t$eamount of con'ense' oer$ea' apor t$at is fe' back into t$e top of t$e column.

8ncreasing t$e reflu, ratio increases t$e 'egree of separation. 8ncreasing t$e number oftrays or $eig$t of packing increases t$e column $eig$t an' increasing t$e reflu, ratio

increases t$e column 'iameter. Eit$er of t$ese increases in column 'imensions increases

t$e capital cost of t$e column.

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-raye' 'istillation columns are t$e most common. ( tray is &$ere contacting

occurs bet&een t$e apor stream an' t$e li3ui' stream. -$e li3ui' enters t$e fee' tray

t$roug$ t$e 'o&ncomer from t$e aboe tray! flo&s across t$e tray &$ere is interacts &it$t$e apor! spills oer a &eir! an'! finally! flo&s t$roug$ t$e 'o&ncomer to t$e ne,t tray.

-$e apor flo&s up t$roug$ $oles in t$e tray. 8t is important to $ae appropriate flo&

rates of t$e li3ui' an' apor to get optimal column operation. 8f t$e li3ui' flo& ratesbecome too $ig$! poor contacting occurs &it$ t$e apor an' in t$e e,treme floo'ing of

t$e column can occur. -$e onset of floo'ing in a column is easy to obsere since t$e

column pressure 'rop &ill increase marke'ly &$en floo'ing begins. 8f t$e apor flo& rateis too $ig$! li3ui' can be entraine' an' carrie' oer to t$e aboe tray lea'ing to poorer

separation. 8n contrast! too lo& of a apor rate can lea' to &eeping of t$e li3ui' t$roug$

t$e tray! &$ic$ 'iminis$es t$e separation. -$e li3ui' an' apor flo& rates are 'ictate' by

t$e operation of t$e reboiler an' t$e con'enser! &$ic$ means t$ey are controlle' by t$eenergy input an' remoal.

-$e materials of construction is an important consi'eration for t$e reactor an'

storage tanks. -$e 'eman's on t$e materials use' for t$e storage tanks 'o&nstream of t$ereactor are lo&er since t$ese tanks contain nearly p/ neutral c$emicals. -$e materials of

construction for t$e storage tanks are 'iscusse' in t$e -ransportation an' +torage section.8n contrast! t$e materials of construction re3uire' in t$e reactor must &it$stan' basic

con'itions for t$e transesterification reaction or aci'ic con'itions if an esterification

approac$ is use' to conert free fatty aci's. For t$e basecataly;e' transesterificationreaction! stainless steel is t$e preferre' material for t$e reactor. /o&eer! stainless steel

&ill not be goo' c$oice for use in t$e aci'cataly;e' esterification reaction because

stainless steel is sub@ect to attack by aci's. An'er t$ese con'itions! an aci' resistant

material suc$ as /astelloy s$oul' be use' for t$e reaction essel.

6.2.4 0%,i*a( P(a)t o)tro($

-o pro'uce 3uality pro'ucts from a bio'iesel pro'uction plant it is necessary to be

able to control t$e pro'uction process. >$ile a tremen'ously important control ariable

is t$e properties of t$e fee'stock to t$e process! t$is section &ill only 'iscuss t$e controlof c$emical plants &it$in t$e unit operation of t$e processes! suc$ as t$ose 'iscusse' in

t$e preious section. -&o general types of processes can be use' in t$e pro'uction of

bio'iesel! eit$er batc$ or continuous. For batc$ processes t$e process control ariables

&ill be temperature! pressure! an' leels. -emperature an' pressure control are critical&it$in t$e reaction an' separation sections of t$e plants. Leel control 'ictates c$arging

to t$e reactor! operation of separation 'eices! an' pro'uct storage. For continuous

processes t$e process control ariables inclu'e temperature! pressure! leel! an' flo&rate. 8t is important to note t$at process ariables! &$ic$ are monitore' an' controlle'!

are not t$e same as t$e pro'uct specifications. +pecifications are properties t$at are

re3uire' of t$e final pro'uct suc$ as t$ose gien in (+-7 D 651 for bio'iesel. ontrolariables are t$ose process ariables t$at are monitore' an' a'@uste' to meet t$e 'esire'

specifications. (s suc$! specifications are generally measure' offline in an analytical

laboratory! &$ile t$e process ariables are process con'itions t$at are measure' in real

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-$e process ariables are relate' to t$e specifications t$roug$ some type of

process mo'el. -$e process mo'el &ill typically be proi'e' by t$e process licensor &it$

subse3uent refinement from plant operation e,perience. +ome manufacturing plants &ill'eelop t$eir o&n statistical or empirical mo'els. 8t s$oul' be note' t$at t$e process

mo'els are typically fee'stock 'epen'ent.

8n 'iscussing process ariable measurement instruments! t$e performance of t$e

instruments can be c$aracteri;e' by t$eir accuracy an'%or precision. (ccuracy is t$e

ability of an instrument to measure t$e correct or $en consi'ering an instrumental control system for a c$emical plant t$ere are anumber of factors t$at s$oul' be consi'ere'C cost! precision! reliability! an' operator

interface. 8t is 'esirable to $ae t$e lo&est cost monitoring system t$at &ill allo&appropriate control of t$e process. Precision is important to assure t$at t$ere is

repro'ucibility of measurements. 9eliability insures t$at t$e system is not prone to

failures. Finally! it is 'esirable to $ae a monitoring an' control system t$at proi'es aneasy interface &it$ t$e plant operators.

6.2.4.1 Temperature Measurement-$e most common process ariable monitore' in a

c$emical plant is t$e temperature. -$e temperature at a specific point is generallymeasure' using t$ermocouples! &$ic$ are electrical 'eices. -$ermocouples are ma'e of

t&o 'ifferent metallic &ires. -$ese &ires are connecte' at a @unction. (n electrical

current is establis$e' &$en t$e @unction is $eate'. -$e electrical current is proportional tot$e temperature at t$e @unction. For t$is reason! t$e t$ermocouple must be calibrate' to

correlate temperature to current.

Fig 15:T0%r,o*oup(%

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-$ermocouples are categori;e' by t$e metals use' in t$eir @unctions! &it$

'ifferent metal @unction combinations being more appropriate for 'ifferent temperature

ranges. 8n'ii'ual t$ermocouples are typically not calibrate' by t$e supplier. 8nstea'!manufacturers &ill typically test a representatie portion of t$e t$ermocouples t$ey

pro'uce. Due to t$e manufacturing proce'ure! t$ermocouples are usually precise )or

completely 'ont &ork* but can be inaccurate. -$e t$ermocouple is typically enclose'&it$in a t$ermo &ell. -$e t$ermocouple must be fully inserte' into t$e t$ermo &ell &it$

t$e t$ermo &ell e,ten'e' appropriately into t$e process to obtain a correct rea'ing. 8f t$e

temperature of a process li3ui' is being measure' it is generally a'e3uate for t$e t$ermo&ell to e,ten' about 2" inc$es into t$e li3ui'. Due to inferior $eat transfer! t$e t$ermo

&ell s$oul' e,ten' about 6 inc$es into a process apor.

-$ermocouples are typically use' in processes for bot$ monitoring an'controlling t$e process. >$en a t$ermocouple is use' as part of a process control loop!

t$e electrical current output from t$e t$ermocouple is compare' &it$ t$e current e,pecte'

for t$e set point temperature. Deiation of t$e actual temperature from t$e set point

temperature &ill cause a c$ange in t$e output to a $eater or cooler t$at is inclu'e' in t$econtrol loop.

6.2.4.2Pressure Measurement: Pressure alues can be measure' using seeral 'ifferent

types of 'eices suc$ as li3ui' column! elastic element! an' electrical sensing. -$e most

common form of a li3ui' column 'eice is a manometer in &$ic$ t$e li3ui' $eig$t can beobsere' isually an' correlate' to t$e pressure t$roug$ t$e 'ensity of t$e li3ui'. Li3ui'

column 'eices are rarely use' in c$emical processes. Elastic element 'eices measure

pressure by 'etermining 'eformation of an elastic material. -$is elastic material is

usually metallic. ne type of elastic element 'eice uses bello&s elements. -$e'isplacement of t$e bello&s can be correlate' to t$e pressure alue. -$e most common

pressure measurement instruments use' in c$emical processes are electrical sensing

'eices! &$ic$ are kno&n as strain gauges. +train gauges are pre'icate' on t$e fact t$att$e electrical resistance of con'ucting soli's c$anges &it$ lengt$ an' 'iameter of t$e

soli'. -$e 'imensional c$anges of t$e soli' in'uce' by a pressure cause an increase in t$e

electrical resistance of t$e con'ucting soli'. (n elastic element or electrical sensing'eice use' to measure pressure is calle' a pressure trans'ucer.

Fig 16: Pr%$$ur% Tra)$&u*%r

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-$e pressure tap for a trans'ucer s$oul' be locate' in t$e apor p$ase of a

process. ( trans'ucer locate' in t$e li3ui' p$ase &ill 'etect a 'ifferent pressure at

'ifferent 'ept$s in t$e li3ui'.

-o use a pressure trans'ucer for process control or in continuous monitoring! t$e

trans'ucer must pro'uce an electrical signal. For t$e elastic element 'eice! t$e 'irectpressure rea'ing 'ue to 'isplacement must some$o& be conerte' to an electrical signal.

(n a'antage of t$e electrical sensing approac$ is t$at t$ese 'eices 'irectly proi'e an

electrical signal. (s &it$ t$ermocouples! pressure trans'ucers can be use' for processcontrol by comparing t$e measure' pressure to a 'esire' set point pressure.

6.2.4.3Level measurement: Leel measurement can be use' to yiel' mass balance

information across t$e process or loa'ing in a batc$ reactor. /istorically! leelmeasurement 'eices $ae typically been 'isplacerbase' meters or 'ifferential pressure

meters. -$e 'isplacerbase' meter is base' on buoyancy. -$e 'isplacer is immerse' in a

'isplacer c$amber t$at is locate' as a si'e c$amber. -$e 'isplacer is restraine' by an

elastic element &$ose motion is proportional to t$e buoyant force! so t$e leel can be'etermine' by t$e ertical location of t$e 'isplacer. Differential pressure meters! &$ic$

are t$e most common leel in'icating 'eices! measure t$e 'ifference in pressurebet&een t&o pressure taps in a essel. 8t is important to note t$at bot$ of t$ese leel

measurement in'icators are li3ui' 'ensity 'epen'ent! so t$at c$anges in li3ui' 'ensities

can affect t$eir rea'ings. -$is effect can be particularly important if seeral li3ui' p$asesare present in t$e 'eice. For e,ample! t$e $eig$t of li3ui' in a gauge glass connecte' to

a essel is not a 'irect measurement of t$e li3ui' leel 9ecently! leel measurement

'eices $ae been 'eelope' t$at use signal reflectance from an ultrasonic trans'ucer or

ra'io fre3uency! &$ic$ measures t$e c$ange in impe'ance bet&een t&o capacitorelectro'es.

Fig 1: L%%( ,%a$ur%,%)t

8n a''ition to 'ensity! t$ere are a number of factors t$at can influence t$ereliability of a leel measurement. Plugge' taps can occur &it$out causing apparent

'iscrepancies in t$e leel measurement 'eice. E,cursions to $ig$ li3ui' leels can

impact t$e reliability of t$e leel measurement as can t$e presence of foam in t$e essel.-$e measurement an' control of leel in a essel generally re3uires t&o taps into t$e

essel. 8t is important t$at t$ese taps are properly ale'. +ince t$e leel in'icator can be

?2


12/27

use' to monitor t$e amount of material in a essel! it can be use' to track c$emical

inentory &it$in t$e process as &ell as to control t$e c$arging of c$emicals into a batc$

process. Leel measurements can be conerte' to electrical signals t$at can be use' forcontrol. -$e most common control loop t$at inclu'es leel measurement is &it$

operation of pumps.

6.2.4.4: Flow Measurement-$e final process ariable t$at &ill be 'iscusse' is flo&

rate. Flo& rate measurement &ill generally only be nee'e' if a continuous flo& process is

use'. -$ere are a number of met$o's for measuring flo& rates! but t$e most commonlyuse' approac$ in c$emical processes are 'ifferential pressure flo& meters an' positie

'isplacement flo& meters. Flo& meters can be use' in monitoring an' control. -$e most

common control loop t$at inclu'es flo& rate is &it$ operation of pumps.

Differential flo& meters measure t$e 'ifference in pressure bet&een t$e t&o si'es

of a restriction in a confine' stream. -$ese flo& meters are base' on restrictions impose'

by a enturi tube! an orifice plate or a flo& no;;le &it$ t$e orifice plate meter being t$e

most common. -$e orifice plate $ole s$oul' be appropriately si;e' for t$e flo& rate rangeof interest. 8f t$e $ole is too large t$e resulting pressure c$ange an'! t$erefore! accuracy

of t$e flo& measurement &ill be inaccurate. 8n contrast! if t$e $ole is too small! t$e flo&rate measurement is at t$e cost of too $ig$ of a pressure 'rop. >$ile orifice plate meters

are typically use' for flo& rate measurement an' subse3uent control! it s$oul' be note'

t$at t$e meters 'o $ae some potential problems. First! t$is type of flo& meter is $ig$ly'epen'ent on t$e 'ensity an' iscosity of t$e li3ui'. rifice plates can ero'e or $ae

blockage! &$ic$ &ill lea' to inaccurate measurement. -$e pressure taps can become

plugge' lea'ing to erroneous flo& alues.

Positie 'isplacement flo& meters measure flo& rates using t$e flui' to 'isplace a

measuring 'eice. 7ost common are rotary 'isplacement flo&meters. 8n t$ese meters!

flo& rate is measure' by t$e amount of rotation create' by flo& of t$e flui' past a rotary'eice. (n e,ample of a rotary flo& meter is a aneli3ui' flo& meter in &$ic$ a set of

anes mounte' on a rotor &it$ opposing pairs rotate' in a cylin'rical c$amber. -$e

oerall monitor an' control system for a process can be ac$iee' by in'ii'ual monitorsan' controllers locate' 'irectly at t$e process. /o&eer! it is most common in t$e

c$emical processes to $ae a centrali;e' system for monitoring an' controlling. -$is can

be rea'ily accommo'ate' for most processes by a P base' system. ( number of

'ifferent soft&are options are rea'ily aailable for t$ese types of systems.

Fig 1 Turbi)% F(ow ,%t%r

?"


13/27

6.2.4.1Pretreatment of Hig Free Fatt! "cid Feedstocks

7any lo& cost fee'stocks are aailable for bio'iesel pro'uction. Anfortunately!

many of t$ese fee'stocks contain large amounts of free fatty aci's )FF(s*. (s 'iscusse'

else&$ere! t$ese free fatty aci's &ill react &it$ alkali catalysts to pro'uce soaps t$atin$ibit t$e reaction.

-$e follo&ing ranges of FF( are commonly foun' in bio'iesel fee'stocks

9efine' egetable oils G 0.05 H

ru'e egetable oil 0." I 0.H

9estaurant &aste grease 2 I H

(nimal fat 5 I "0H

-rap grease #0 I 100H

Jenerally! &$en t$e FF( leel is less t$an 1H! an' certainly if it is less t$an 0.5H!

t$e FF(s can be ignore'. ommon catalyst amounts are

+o'ium $y'ro,i'e 1H of triglyceri'e &eig$t

Potassium $y'ro,i'e 1H of triglyceri'e &eig$t

+o'ium met$o,i'e 0.25H of triglyceri'es &eig$t

+oaps may allo& emulsification t$at causes t$e separation of t$e glycerol an' ester

p$ases to be less s$arp. +oap formation also pro'uces &ater t$at can $y'roly;e t$etriglyceri'es an' contribute to t$e formation of more soap. Furt$er! catalyst t$at $as been

conerte' to soap is no longer aailable to accelerate t$e reaction.

>$en FF( leels are aboe 1H! it is possible to a'' e,tra alkali catalyst. -$is allo&sa portion of t$e catalyst to be 'eote' to neutrali;ing t$e FF(s by forming soap! &$ile

still leaing enoug$ to act as t$e reaction catalyst.

+ince it takes one mole of catalyst to neutrali;e one mole of FF(! t$e amounts of

a''itional catalyst can be calculate' by t$e follo&ing formulas

+o'ium $y'ro,i'e KHFF()0.1##* M 1 H

Potassium $y'ro,i'e KHFF()0.1*%0.?6 M 1 H

+o'ium met$o,i'e KHFF()0.10* M 0.25 H

For example, when adding sodium methoxide to a feedstock with 1.5 % FFA, the

amount of catalyst would be:

)1.5*)0.10* M 0.25 H N 0.5# H of t$e triglyceri'es &eig$t

?#


14/27

4ote t$at a factor of 0.?6 $as been inclu'e' &it$ t$e potassium $y'ro,i'e

calculation to reflect t$at reagent gra'e :/ is only ?6H pure. 8f ot$er gra'es of catalyst

are use'! t$is factor s$oul' be a'@uste' to t$eir actual purity.

-$is approac$ to neutrali;ing t$e FF(s &ill sometimes &ork &it$ FF( leels as

$ig$ as 5 I 6H. -$e actual limit can 'epen' on &$et$er ot$er types of emulsifiers arepresent. 8t is especially important to make sure t$at t$e fee'stock contains no &ater. 2"H

FF( may be t$e limit if traces of &ater are present.

For fee'stocks &it$ $ig$er amounts of FF(! t$e a''ition of e,tra catalyst may

create more problems t$an it soles. -$e large amount of soap create' can gel. 8t can also

preent t$e separation of t$e glycerol from t$e ester. 7oreoer! t$is tec$ni3ue conerts

t$e FF(s to a &aste pro'uct &$en t$ey coul' be conerte' to bio'iesel.

>$en &orking &it$ fee'stocks t$at contain 5"0H FF( or een $ig$er! it is

important to conert t$e FF(s to bio'iesel or t$e process yiel' &ill be lo&. -$ere are at

least four tec$ni3ues for conerting t$e FF(s to bio'iesel

1.En#!matic metods -$ese met$o's re3uire e,pensie en;ymes but seem to be lessaffecte' by &ater. (t t$e present time! no one is using t$ese

met$o's on a commercial scale.

2. $l!cerol!sis -$is tec$ni3ue inoles a''ing glycerol to t$e fee'stock an' $eating it

to $ig$ temperature )200*! usually &it$ a catalyst suc$ as ;inc

c$lori'e.-$e glycerol reacts &it$ t$e FF(s to form mono an'

'iglyceri'es. -$e 'ra&back of glycerolysis is t$e $ig$ temperature an't$at t$e reaction is relatiely slo&. (n a'antage is t$at no met$anol is

a''e' 'uring t$e pretreatment so t$at as &ater is forme' by t$e reaction

FF( M glycerol O monoglyceri'e M &ater -$e &ater imme'iately apori;es an' can be ente' from t$e mi,ture.

3."cid %atal!sis : -$is tec$ni3ue uses a strong aci' suc$ as sulfuric aci' to cataly;e t$eesterification of t$e FF(s an' t$e transesterification of t$e

triglyceri'es. -$e reaction 'oes not pro'uce soaps because no alkali

metals are present. -$e esterification reaction of t$e FF(s to alco$ol

esters is relatiely fast! procee'ing substantially to completion in one$our at 60. /o&eer! t$e transesterification of t$e triglyceri'es is

ery slo&! taking seeral 'ays to complete. /eating to 1"0 can

greatly accelerate t$e reaction but reaction times &ill still be "0#5minutes. (not$er problem &it$ aci' catalysis is t$at t$e &ater

pro'uction from t$e follo&ing reaction

FF( M met$anol O met$yl ester M &ater stays in t$e reaction mi,ture an' ultimately stops t$e reaction! usually

&ell before reac$ing completion.

?5


15/27

4."cid catal!sis followed &! alkali catal!sis :

-$is approac$ soles t$e reaction rate problem by using eac$ tec$ni3ue to

accomplis$ t$e process for &$ic$ it is best suite'. +ince aci' catalysis is

relatiely fast for conerting t$e FF(s to met$yl esters! it is use' as apretreatment for t$e $ig$ FF( fee'stocks. -$en! &$en t$e FF( leel $as

been re'uce' to 0.5H! or lo&er! an alkali catalyst is a''e' to conert t$e

triglyceri'es to met$yl esters. -$is process can conert $ig$ free fatty aci'

fee'stocks 3uickly an' effectiely. >ater formation is still a problem'uring t$e pretreatment p$ase. ne approac$ is to simply a'' so muc$

e,cess met$anol 'uring t$e pretreatment t$at t$e &ater pro'uce' is 'ilute'

to t$e leel &$ere it 'oes not limit t$e reaction. 7olar ratios of alco$ol to

FF( as $ig$ as #01 may be nee'e'. -$e 'isa'antage of t$is approac$ ist$at more energy is re3uire' to recoer t$e e,cess met$anol. (not$er

approac$ &oul' be to let t$e aci'cataly;e' esterification procee' as far asit &ill go until it is stoppe' by &ater formation. -$en! boil off t$e alco$ol

an' &ater. 8f t$e FF( leel is still too $ig$! t$en a''itional met$anol an'!

if necessary! aci' catalyst can be a''e' to continue t$e reaction. -$isprocess can be continue' for multiple steps an' &ill potentially use less

met$anol t$an t$e preious approac$. (gain! t$e 'isa'antage is t$e large

amount of energy re3uire' by t$e 'istillation process.

( less energy intensie approac$ is to let t$e aci'cataly;e' reactionmi,ture settle. (fter a fe& $ours! a met$anol&ater mi,ture &ill rise to t$e

top an' can be remoe'. -$en! a''itional met$anol an' aci' can be a''e'

to continue t$e reaction. 8t is also possible to use flui's suc$ as glycerolan' et$ylene glycol to &as$ t$e &ater from t$e mi,ture.

6.2.4.2Procedure for Hig FF" Feedstocks

1. 7easure FF( leel

2.('' 2.25 g met$anol an' 0.05 g sulfuric aci' for eac$ gram of free fatty aci' in t$e oil

or fat. +ulfuric aci' an' met$anol s$oul' be mi,e' first an' t$en a''e' slo&ly to t$e oil.

3.(gitate for one $our at 6065.

4. Let mi,ture settle. 7et$anol&ater mi,ture &ill rise to t$e top. Decant t$e met$anol!

&ater! an' sulfuric aci' layer.

5.-ake bottom fraction an' measure ne& FF( leel.

6.8f FF( is 0.5H! return to step 2 &it$ ne& FF( leel. 8f FF( is G 0.5H! procee' to

step .

.('' an amount of met$anol e3ual to 0.21 , Kgrams of unreacte' triglyceri'es an' an

amount of so'ium met$o,i'e e3ual to K0.25 M )HFF(*0.10%100 , Kgrams of unreacte'

triglyceri'es. 7i, t$e so'ium met$o,i'e &it$ t$e met$anol an' t$en a'' to t$e oil. -$is

?6


16/27

correspon's to a 61 molar ratio of met$anol to oil for t$e unreacte' triglyceri'es. 8t

ignores any met$anol t$at may $ae carrie' oer from t$e pretreatment.

.(gitate for 1 $our at 60.

6." perating BioDiesel Plant

-o make bio'iesel fuel efficiently from use' egetable oils an' animal fats &e $ae to

aoi' one ma@or problem soap formation. +oap is forme' 'uring basecataly;e'transesterification )using lye* &$en so'ium ions combine &it$ free fatty aci's present in

use' )an' some irgin* egetable oils an' animal fats. -$e soaps 'iminis$ t$e yiel'

because t$ey bon' t$e met$yl esters to &ater. -$e bon'e' esters get &as$e' out at t$e&as$ing stage but make &ater separation more 'ifficult an' increase &ater consumption.

-$is process takes care of t$e free fatty aci's

-$is is a simple proce'ure. -$e firststage process is not transesterification! but

pure an' simple E+-E98F8(-84. Esterification is follo&e' by transesterification! butun'er aci' con'itions itQs muc$ slo&er t$an un'er caustic con'itions an' it &onQt 'o a

complete oiltomet$yl ester conersion as t$e reaction is muc$ more e3uilibrium

sensitie. >it$out met$anol recoery! t$e alco$ol oer'ose re3uire' &oul' make t$eprice of your fuel @ump! an' een &it$ recoery it &oul' still be muc$ more e,pensie.

For t$e first stage youQll form a compoun' out of an aci' an' an alco$ol. -$e alco$ol is

still met$anol! but instea' of using lye )so'ium $y'ro,i'e*! t$e (-(LR+- in t$is

reaction is sulfuric aci' )Sbattery aci'S*. 8t nee's 5H sulfuric aci' )battery aci' is aroun'50H*. +ulfuric aci' is one of t$e commonest c$emicals on Eart$! @ust like lye. 7ore

concentrate' sulfuric aci' ?H an' aboe costs more! but 5H &orks @ust fine if you

follo& t$ese 'irections. t$er aci's &onQt &ork it must be sulfuric aci'. -$e secon'

stage uses lye! as usual but it only uses about $alf as muc$ as ot$er met$o's.-$e sulfate ion in t$e sulfuric aci' combines &it$ t$e so'ium ion in t$e lye 'uring t$e

secon'stage reaction to form so'ium sulfate! &$ic$ is a &atersoluble salt an' isremoe' in t$e &as$. 4o sulfur remains in t$e bio'iesel fuel pro'uct.

?


17/27


18/27

Fig 21: P(a)t !Top i%w#

6.3.1 E+uip,%)t

For t$e process you re3uire t$e follo&ing e3uipment

( bottom'raine' reactor essel of .5 liters is best! close' on top.

irculating pump 0.5 /P for mi,ing.

-&o 1.2 :> &as$ingmac$ine immersion $eaters to $eat t$e mi,ture.

( storage 'rum of 5.5 liters.

( mi,er c$amber of 1.5 liters.

Eig$t ball ales an' one gate ales for circulation process.

-$ree funnels for pouring reactors.

ne fifteen liter &as$ing 'rum.

(ir pump to pro'uce bubbles.

ne fume c$amber )( can &ill suffice* 1.5 liters.

ne con'ensing container of " liters.

+i, feet stainless steel pipe for fitting of 'ifferent c$ambers.

?


19/27


20/27

". 7easure t$e olume of oil%fats to be processe' )preferably in liters*.

#. /eat t$e oil to "5 'eg )5 'eg F* make sure t$at all soli' fats are melte'.

5. 7et$anol use only HM pure met$anol. 7easure out t$e met$anol 0.0? liters

of met$anol for eac$ liter of oil%fats )?H by olume*. ('' t$e .4Lmet$anol to t$e$eate' oil.

6. 7i, for fie minutes t$e mi,ture &ill become murky because of solentc$ange )met$anol is a polar compoun'C oil is strongly nonpolarC a suspension &ill

form*.

. For eac$ liter of oil%fats a'' 1 milliliter of 5H sulp$uric aci' )/2+#*. Ase agra'uate' eye'ropper! a gra'uate' syringe or a pipette. ('' 57L in aboe mi,.

?. 7i, gently at L> rpm )'onQt splas$* &$ile keeping t$e temperature at "5 'eg

. -$e rotation of your stirrer s$oul' not e,cee' 500 to 600 rpm spee' is notcrucial an' splas$e' oil is a mess to clean.

. 7aintain t$e temperature at "5 'eg for one $our t$en stop $eating. ontinue

stirring.

10. +tir t$e un$eate' mi,ture for anot$er $our! a total of t&o $ours! t$en stop

mi,ing. Let t$e mi,ture sit for at least eig$t $ours! oernig$t is better.

11. 8n t$e meantime prepare t$e so'ium met$o,i'e measure 0.12 litre of met$anol for

eac$ litre of oil%fat )12H by olume* an' &eig$ ".1 grams )up to ".5 grams if purity

is in 'oubt* of so'ium lye )so'ium $y'ro,i'e! 4a/* per litre of oil%fat. 7i, t$elye into t$e met$anol until t$e lye is completely 'issole'. 7i, 0.6L of met$anol T

1.5gof 4a/.

Not% -$is process uses only about $alf t$e usual amount of lye as t$ere is less fat

left to transesterify. Ase HM pure so'ium $y'ro,i'e lye. (fter opening t$e

container! close it again as 3uickly as possible to preent moisture getting in.>eig$ t$e lye carefully using too muc$ &ill complicate t$e &as$ing process

later.

12. (fter settling for eig$t $ours! or t$e ne,t morning! pour $alf of t$e prepare'

met$o,i'e into t$e un$eate' mi,ture an' mi, for fie minutes. -$is &ill neutrali;e

t$e sulp$uric aci' an' boost t$e base catalysis. 8f youQe use' soli' fat! it probablysoli'ifie' 'uring settling gently melt t$e mi,ture first..

'econd stage

-$is is t$e basecataly;e' stage.

1


21/27

1". /eat t$e mi,ture to 55 'eg )1"1 'eg F* an' maintain for t$e &$ole reaction.

1#. ('' t$e secon' $alf of t$e prepare' so'ium met$o,i'e to t$e $eate' mi,ture an' start

mi,ing at t$e same lo& spee' of not more t$an 500 to 600 rpm.

15. -ptio)a( 8f your reactor allo&s for it! start 'raining glycerine bypro'uct from t$e

bottom 2025 minutes after t$e start of t$e base stage. )Pumpmi,ing &orks best for t$is

&it$ pump or mi,er! turn t$e motor off for a fe& minutes if necessary to allo& t$eglycerine to settle.* 9epeat eery 10 minutes take care! t$e glycerine is 3uite $ot an'

caustic +et asi'e see step 1?.

16. (ll users -ake regular samples in a 1S to 1.5S 'iam. glass container. >atc$ for astra& yello& colour of t$e ester portion. Jlycerine )bro&n an' sticky* &ill settle at t$e

bottom of t$e @ar. >$en t$is colour is reac$e' )usually in 1.52.5 $ours* turn t$e $eat an'

mi,er off. 8nstea' of taking out samples to c$eck t$e colour you coul' use translucent

brai'e' tubing for t$e pump.

1. (llo& to settle for one $our.

1?. -ptio)a(:For easier &as$ing Drain off t$e glycerine. 7easure off 25H of t$e total

glycerine )inclu'ing preiously 'raine' glycerine if you follo&e' step 15* an' mi, &it$10 millilitres of 10H p$osp$oric aci' )/"P#* for eac$ litre of oil%fat processe'. -$e

mi,ing can be 'one &it$ a &oo'en spoon in a plastic container. Pour t$e aci'ifie'

glycerin back into t$e reactor an' stir for 20 minutes! un$eate'. (llo& to settle for at least

si, $ours an' t$en 'rain t$e glycerin fraction completely.

(u&&le wasing

8t uses a small airpump! usually an a3uarium aerator pump &it$ a bubblestone.

>ater is a''e' to t$e bio'iesel in t$e &as$ tank )usually a 3uarter to a $alf as muc$ &ater

as bio'iesel*C t$e &ater sinks to t$e bottomC t$ro& in t$e bubblestone! &$ic$ also sinksto t$e bottom! an' s&itc$ on t$e pump. (irbubbles )lots of little bubbles is best* rise

t$roug$ t$e &ater an' into t$e bio'iesel! carrying a film of &ater aroun' t$em! &$ic$

&as$es t$e bio'iesel aroun' t$e bubble. >$en it reac$es t$e surface t$e bubble bursts!leaing t$e &ater to sink back 'o&n again! &as$ing t$e fuel again.

Asually t$ree or four &as$es are use'! eac$ of si, to eig$t $ours! often less for t$e first

&as$C &it$ a settling perio' of at least 1 $our bet&een &as$es )some people settle it formuc$ longer*. (fter itQs settle' t$e &ater is remoe' ia a bottom'rain an' replace' &it$

&ater. >as$ing is complete' &$en t$e &ater is clear after settling! &it$ a p/ of *.

Fig 22: P(a)t op%ratio)

2


22/27


23/27

4o& 'rain Jlycerin form ale 11T t$en close it.

lose ale 3T open ale 4! turn on t$e pump to get Bio Diesel in >as$ing

$amber.

-urn off Pump an' a'' mi,ture of &ater T /"P#for &as$ing.

Ase (3uarian pump to pro'uce bubbles in &as$ing $amber.

4o& 'rain t$e &ater from ale ! rest &ill be clean Bio Diesel in t$e &as$ing

$amber.

6.3.5 Pu,p S%(%*tio) Pro*%&ur%

'torage %am&er to Reaction %am&er

#


24/27

sing !ernoulli"s #$uation

P1; < 122g


25/27

elocity comes out to be

>34.5/t$%*

-$is yiel's $ea'

0p>32. ,%t%r

Reaction to Reaction

=2@=1>.

Pip% L%)gt0>22.1

P1; < 122g


26/27

Reactor to (io Diesel

Pip% L%)gt0>21.2

=2@=1>.3333

P1; < 122g


27/27

0pa>2.63 2. */,

omparing t$e pump $ea's &it$ pump po&er an' flo& rates>e get a pump po&er of 0.5 /P an' 0H

P>.5 CP

Fig 23: Pu,p S%(%*tio)

0.5 /P pump at#0 m flo& rate

T 2.cfm

laboratory preparation of bio diesel

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