membrane cell technology

8/19/2019 Membrane Cell technology

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Membrane Celltechnology

Prepared by: Deep Shah Guided by: Dr. Ranjan Sengupta


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Introduction Procedure of Membrane Cell Development of Membrane

Content


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!he chlor"al#ali indutry i the indutry that produce chlorine $Cl%& andal#ali' odium hydro(ide $)a*+& or potaium hydro(ide $,*+&' byelectrolyi of a alt olution. !he main technologie applied for chlor"al#ali production are mercury' diaphragm and membrane cellelectrolyi' mainly uing odium chloride $)aCl& a feed or to a leere(tent uing potaium chloride $,Cl& for the production of potaium

hydro(ide. !he diaphragm cell proce $Grieheim cell' -/& and the mercury cell

proce $Catner",ellner cell' -0%& 1ere both introduced in the late-22.

!he membrane cell proce 1a developed much more recently $-032&.4ach of thee procee repreent a di5erent method of #eeping the

chlorine produced at the anode eparate from the cautic oda andhydrogen produced' directly or indirectly' at the cathode. Currently'0/6 of 1orld chlorine production i obtained by the chlor"al#ali proce.

D.4.Goldman

Introduction


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!he membrane cell proce ha inherent ecological advantage over

the t1o older procee' a it doe not ue mercury or abeto' and

it i the mot energy e7cient proce.

Depite thee advantage' the change of technology to membrane

cell ha been lo1 in 1etern 4urope becaue mot e(iting chlorine

plant 1ere intalled in the -032 1ith a plant life of 82"92 year and

there ha been no need for ne1 production capacity. )or ha there

been a legilativedrive to change technology.

ith the input;output of the chlor"al#ali ector' it i alo relevant to

point out the pecial importance of afety apect related to

production' handling and torage of chlorine.

D.4.Goldman


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!hree production method are in ue. hile the mercury cellmethod produce chlorine"free odium hydro(ide' the ue ofeveral tonne of mercury lead to eriou environmentalproblem.

In a normal production cycle a fe1 hundred pound of mercury

per year are emitted' 1hich accumulate in the environment.=dditionally' the chlorine and odium hydro(ide produced via themercury"cell chloral#ali proce are themelve contaminated 1ithtrace amount of mercury.

!he membrane and diaphragm method ue no mercury' but theodium hydro(ide contain chlorine' 1hich mut be removed.

D.4.Goldman


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Procedure


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>aic membrane cell ued in the electrolyi of brine. =t theanode $=&' chloride $Cl?& i o(idi@ed to chlorine. !he ion"electivemembrane $>& allo1 the counterion )aA to freely Bo1 acro' butprevent anion uch a hydro(ide $*+?& and chloride fromdi5uing acro. =t the cathode $C&' 1ater i reduced to hydro(ideand hydrogen ga. !he net proce i the electrolyi of anaueou olution of )aCl into indutrially ueful product odiumhydro(ide $)a*+& and chlorine ga.

!he mot common chloral#ali proce involve the electrolyi

of aueou odium chloride$a brine& in a membrane cell. Saturated brine i paed into the rt chamber of the cell 1here

the chloride ion are o(idied at the anode' loing electron tobecome chlorine ga $= in gure&:

%Cl? E Cl% A %e

=t the cathode' poitive hydrogen ion pulled from 1atermolecule are reduced by the electron provided by theelectrolytic current' to hydrogen ga' releaing hydro(ide ion intothe olution $C in gure&:%+%* A %e? E +% A %*+?


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!he ion"permeable ion e(change membrane at the center of thecell allo1 the odium ion $)aA& to pa to the econd chamber1here they react 1ith the hydro(ide ion to produce cauticoda $)a*+& $> in gure&. !he overall reaction for the electrolyiof brine i thu:

%)aCl A %+%* E Cl% A +% A %)a*+

= membrane cell i ued to prevent the reaction bet1een thechlorine and hydro(ide ion. If thi reaction 1ere to occur thechlorine 1ould be diproportionated to form chlorideand hypochlorite ion:

Cl% A %*+? E Cl? A Cl*? A +%* =bove about 92 FC' chlorate can be formed:

Cl% A 9*+? E /Cl? A Cl*? A +%*

>ecaue of the corroive nature of chlorine production' the anode$1here the chlorine i formed& mut be made from a non"reactive

metal uch a titanium' 1herea the cathode $1here hydro(ideform& can be made from a more eaily o(idi@ed metal ucha nic#el.


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In the membrane cell' the anode and cathode are eparated by anion"permeable membrane. Saturated brine i fed to thecompartment 1ith the catode $the anolyte&.

= DC current i paed through the cell and the )aCl plit into itcontituent component. !he membrane pae )aA ion to the

anode compartment $catholyte&' 1here it form odium hydro(idein olution.

!he membrane allo1 only poitive ion to pa through toprevent the chlorine from mi(ing 1ith the odium hydro(ide. !hechloride ion are o(idied to chlorine ga at the anode' 1hich icollected' puried and tored. +ydrogen ga and hydro(ide ion

are formed at the cathode


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Several rm participated in the development of the membranecell. Conceptual tudie of permelective membrane began in themid -082. .Huda of ionic corporation' and S.G. *borne ofhoo#er chemical hold early patent on the membrane cell proce.

Diamond and Ionic mounted a joint e5ort to develop the

membrane cell from the early -092. !hi 1or# demontrated thefeaibility of the concept' but eriou problem developed'including eroion of anode' high cell voltage' and very hortmembrane life. !he project 1a dormant for about -2 year.

M.Seayian and H.+.=utin'Membrane techology for e(iting chlor al#ali plant'%3th chlorine plant operationeminar'ahington$-08&

Development of membranes


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In the late -092' concern over environmental problemaociated 1ith mercury cell plant initiated a revival of interet inthe membrane cell technology. Initial problem aociated 1ithmembrane cell 1ere teadily being alleviated in the early -032.

!he development of metal anode negated problem aociated1ith graphite anode eroion. = a pin"o5 of the pace program'Dupont developed a perBuorinated ion"e(change membrane 1hileperforming fuel cell reearch. !hi membrane 1a initially calledJRK and 1a later trademar#ed a )aonK. )aon membrane1ere found to have good ion"e(change propertie a 1ell a highreitance to the harh environment of the chlor"al#ali cell.

M.Seayian and H.+.=utin'Membrane techology for e(iting chlor al#ali plant'%3th chlorine plant operationeminar'ahington$-08&


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!he rt membrane ' made from the perBuoroulfonate polymer)aon ' 1ere practical only at lo1 cautic concentration ' a thecautic e7ciency decreaed ignicantly at high cautic trength.

!o overcome thi problem ' aymmetric membrane having ulfonicacid group on the anode ide and converted group on the cathodeide 1ere developed. Later' a perBuorocarbo(ylate membrane '

lemion ' 1hich e(hibited better reitance to cautic bac#"migration1a produced .

!he lo1 electrical reitivity of perulfonate"baed membrane andthe lo1 cautic bac#"migration characteritic of perBuorocarbo(ylatemembrane 1ere coupled by converting the ulfonic acid group of)aon to carbo(ylate group on the cathode ide to reali@e the

benecial propertie of both the membrane type.

M.Seayian and H.+.=utin'Membrane techology for e(iting chlor al#ali plant'%3 th chlorine plant operation

eminar'ahington$-08&

!han# you

membrane cell technology

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