CA2291785C

CA2291785C - Process and apparatus for the treatment of carbon dioxide with carbonic anhydrase

Info

Publication number: CA2291785C
Application number: CA002291785A
Authority: CA
Inventors: Rejean Blais; Peter A. Rogers
Original assignee: Co2 Solutions Inc
Current assignee: Co2 Solutions Inc
Priority date: 1997-06-04
Filing date: 1998-06-02
Publication date: 2005-08-16
Anticipated expiration: 2018-06-02
Also published as: CA2291785A1; WO1998055210A1; JP2002508702A; EP0991462A1; DE69813811D1; US6524843B1; EP0991462B1; AU7753398A; ATE238094T1; GB9711439D0; DE69813811T2

Abstract

A process is disclosed for the extraction, production and purification of carbon dioxide gas. The process may also be employed for the production of aqueous and/or organic solutions of bicarbonate ions using a precursor feed stream of gas containing carbon dioxide. The process consists of the countercurrent flushing of a packed tower-type bioreactor with gas containin g carbon dioxide and a liquid solvent. The bioreactor contains carbonic anhydrase covalently bound to an inert inorganic support. The carbon dioxide of the gaseous phase diffuses into the liquid phase. The immobilized carbonic anhydrase catalyses the hydration of the carbon dioxide which forms hydrogen and bicarbonate ions. The solution of ions may be employed directly or, alternatively, subjected to an ion-exchange resin to immobilize the bicarbonate ions. The aqueous solution of hydrogen and bicarbonate ions may also be recirculated into a second identical bioreactor, wherein they are catalytically converted to water and carbon dioxide.

Description

KCV. vON : EPA-~tUENCHEN U5 ~ 10- 8-99 ,:T 21 : 52 : 514 8-~5 J6518y~ +49 89 23994465 : # 8 a iiv.riv ~~~./a u-r,.. v..~.r~ vm wr n.. v~ .licus~a n..w=~ uy.. ~rm.r ",y,.. .,....y" ~,~,..~~,...

CARBON DIOXIDE MANAGEMENT
WITH CARBONIC ANHYDRASE

The present invention relates generally to a process for the extraction, production and pur~cation of caution dioxide gas. More particxrlarly, it relates to the use of a biological molecule, namely carbonic anhydrase, to effect the reversible hydration of carbon dioxide. Carbonic anhydrase can be used for the production, purrfcation of carbon dioxide and the products of !he hydration reaction, hydrogen std bicarbonate ions. Spe~calty, the invention relates to a process whereby immobiEized carbonic anhydrase contained within a reactor device catalyses the reversible hydration cf c~bon dioxide. The invention also relates to an apparatus for perforrr~ing the process. The process may be employed for the production of hydrogen and bicartiortate ions.
BACKGROiJND OF THE INVENTION
zo Carbonic anhydrase t;EC 4.2.1.1.y is a globular zinc metatloertzyme of molecular mass 30,000. The enzyme was discovered in 1933 and has been the sut~ject of intense scientific investigation. Multiple isoforms have been discovered in piattt and animal rissues. The enzyme also eyos#.s in plat tissues where it is believed to facilitate the transport o~ carbon diobde_ Red blood cells oontairt isoenzymes I and tl, which are the most active. Carbonic anhydrase !! has the highest molecular turnover number of any known enzyn~. One molecule of carbonic anhydrase can hydrate 36,000,000 molecules of carbon dioxide in a period of 60 seconds.
Physiologically, carbonic arthydrase facilitates the removal of carbon dioxic~a from the mammalian body. The general enzyme reaction is shewn below in equation 1.
pN~ENDED ~E~

BNSOOCID: <E2 98005410G>

~
2CU: 40V ~ t-:f'A-VIl!E~iCHEN U5 : LO- 8-99 :~, 21 : 53 , ~ 51~ ,845~65t8~ s j<i49 8~a,.2~3994-4-EMS: ry 9 v...y.n vi.. i.r.....". v a mvru.v ~w.f,u a r ~.u , v v r .r ~
~wtm..Ji . my Equation t COz+H2(aaH;+HCO~
It is n aw generally accepted that the reaction occurs as two half reactions shown below in equations 2 and 3.
Equation 2:
tp E-Zn-HzQaE-Zn-OH-+ii' Equation 3:
E-Zn-OH'+C02aE-Zn-HC03-+H*G(+HzO,-H~)~E-Zn-H20+HCOs Carbonic anhydrase has been used in rttany studies directed at improving or testing of various methods of protein immobilization. The high moiearlar turnorrer rate of the enzyme renders it an ideal protein for these types of experiments.
The presence of carbonic anhydrase in solution facilitates the transfer of 2,o carbon dioxide from the gas to the liquid ptZ$se. This effect is based on the well established laws governing the mass transfer of gases.
The management of carbon dioxide has begun to attract tt~e attention of the scientific community, due primarily to the problem of globai warming. Previous interest in carbon dioxide hss be~n centered around the use of the gas in a variety of industrial processes. None of the airrer~y employed carbon dioxide management systems involve enzymatic conversion of the gas and are therefore not relevant to the present application. Prior art processes for the management of carbon dioxide are described in the following US docurttents: 3.659,400; 3,853,722;
4,Q32,fi16;
4,047, B9~E; 4,162, 298; 4, 452,fi7G; 4, 52'J ,387; 4, 79 0, 362; 5, 061,455;
5,1 't 2, 740;
30 5,609,838; 5,618,506; 5,fi24,812; 5,665,31 S; 5,674,463; and 5,6"90,099.
CA 02291785 1999-11-25 ~~ND~9 ~-IE~T
-BNSDOCIDv <E2 9&7a5410G>

Kt:v. VU:v : EF'A-MUEVCHE': 05 ~, ~ ~ "~lU~ 8-99 ,:T u? 1 : 5:3 , : 514 840 6518-~ +4.9 89 23994466 : #10 .... v ,... , ~ y.. , . ~ ~ ~ ,.., , ~ t ,. .r.. .. ~ ,. ~ ~ ,. r ..... ~ .. .
.. . ~ ly~,~ad-T.....-. ~ w. y .. ~ ,. i ".~

Also know in prior act, there is the process disclosed in 1N0 96I4.Q~14 in the name of Trachtenberg. Tractttenberg discloses a process for gas separation wherein a selected gas in a mixed gas stneat~ is contacted by an enzyme having an active site directly contacted t;y the mixed gas stream, ~d the selected gas is at least partially removed from the mixed gas stream.
EP51 '1719 disdases a process where carbon dro~de is being removed from a g~ stream using a enzyme reactor in which carbonic anhydrase is immobilized on a porous substrate_ Moreover, the United States Air Force carried out two investigations in 1965 and 1966 on the possible use of carbonic anhydrase to remove carbon dioxide from vehicles. The first study explored the absorption of carbon dio~ade from an a~
Stream using a Dosed air loop apparatus. A variety of chemicals atone andlor in combination with CA were evaluated, with respell to their c~paciiy to remove carbon dicucide. The princ~al conclusion drawn was that the closed air loop system provided an adequate method to study the removal of carbon diowde from a stream of air.
The second study was directed at determining tt~e ~ciex~cy of r rbon dioxide retnovat from an air stream usirvg cart~onic anhydrase in the presence of various amines. The conclusion reached was tat enzymatic amine solutions could possibly be used for dioxide absorption and desorptlon in atmosphere control concepts.
2o Although many studies relating to the management of carbon dioxide have been conducted in prior art, there is stilt presently a need for a process and an apparatus ttsat will efihc~aousfy manage carbon diaoade rapidly and at a relatively Ivw cost either for producing carbon dioxide cr removing it from a COrcor~taining gas.
SUN~AAIQY OF THE INyENTIO~I
An object of the present invention is to propose a process and an apparatus that wilt satisfy these needs.
In accordance with the present invention, that object is achieved with a 3o process for removing COZ firom a COz-containing gas, the process being performed in a packed tower bioreactor comprising;
CA 02291785 1999-m-ZS a~..~f_~.1D~~ ~''~'=T
BNSDOCIO:<E2 98005410G> .

4.
a bottom chamber having a gay: inlet and a liquid outlet;
an upper chamber having a liquid inlet and a gas outlet;
a reaction c:hambE'r disposed het:ween and being in fluid communication with the bottom chamber and the upper chamber, the reaction chamber being packed with a plurality of solid supports having a nan-pox:ous surface on which surface carbonic anhydi.~ase or an analogue thereof is immobilized; the process comprising the steps of:
a) supplying the liquid inlet of the upper chamber with an aqueous liquid stream while supplying the gas inlet of tree bottom Cr~am:ber with a C02-containing gas stream, the gas stream 2:hean flowing upwards into the reaction chamber;
b) directing the aqueous liquid stream downwards into the packed reaction chamber to contact the C02-containing gas with the aqu.eo~,~s L.i.quid and promote diffusion of the C02 irl t: he aqueous a.i.quid, and thereby allowing the carbonic anl-rydra5e imrno.bil:~.zed :in the reaction chamber to catalyze the hydration of the diffused C02 into hydrogen ions and bicarbonate ions;
c) evacuating from the liquid outlet of the bottom chamber a liquid solution ~c~nt;:~ining the hydrogen ions and bicarbonate ions produced i..r~ he reaction chamber and evacuating from the gas outlet of t;he upper chamber a treated gas.
The present inveantion is aLSO directed to a process for removing CO2 from a x'01-containing gas, characterized in that it cornpr~ises trm step of 4a a) contacting the CO~ -containing gas with an aqueous liquid, preferably water, in a bioreactor containing immobilized carbonic anhydrase, or an analog thereof, the carbonic anhydrase catalys.i.ng the hydration of the C02 into hydrogen ions and bicarbonate ions.
Preferably, pr:~or to step a) , ther_e is a step of immobilizing carbonic anhydrase in the bioreactor. T'he step of immobilizing carbonic anhydrase in the bioreactor may comprise the step of covalently bindinct carbonic anhydrase to an inert solid support material mounted in the bioreact:or. The step a) of contacting the C02-containing gas ttt:v. vin ~ tt~A-u~ut~c-HW u5 : 1U- 8-99 :T p1 ~ 54 : 514 845 6518 +49 89 23994465: #12 1 1~:1L..~~n .. u-r , i a y. m a. v a.nrv.urv. .-...y.,n "vur,.. mvµ v ~.w mvuiu ,u.~r u-r.J u~riu~ vm ,u,.u.r n.n r wifh an aqueous liquid comprises the steps of directing a stream of the COz-cantaining gas upwards into the bioreactor and directing a stream of the aqueous liquid downwards such that the stream of COz-containing gas flows countercurrent the stream of the aqueous solution. _ According to a first preferred embodiment of the present invention, !he process c~mpcises, after step a), step b) of feeding the hydrogen ions and bir~bonate ions obtained in step a) into a second bioreactor containing immobilized carbonic anhydrase which catalyses the conversion of the hydrogen ions and the bicarbonate ions into concentrated COx and water.
A~rdfng to a second preferred embodiment of the invention, the process comprises, after step a), the step of feeding the hydrogen ions and bicarbonate ions obtained in step a) into an ion exchanger containing hydroxyl ions so that the bicarbonate ions are exd~anged for the hydroxyl ions which ~e then free to combine with hydrogen ions to form water.
The present invention also relates to an apparatus for the rnar~gement of C02 usir~ immobilized carbonic anhydrase or analog thereof. The apparatus comprises an upright bioreactor.
The bioreactar comprises a t5otiorn chamber having s gas inlet to receive a COz-containing gas and a liquid outlet to evacuate from the bioreaotor a liquid solutiars containing hydrogen ions and bicarbonate ions produced in the bforeactor.
The biareactor further comprises an upper chamber having a liquid inlet to receive an aqueous liquid and a gas outlet to evacuate any gas atom the bioreactor.
A reaction chamber is disposed been and is in fluid communication with ifie bottom chamber and the upper chamber. This reaction cxlamber is characterized in that it comprises a plurality of solid supports mount~d therein for covalently immobilizing carbonic anhyckase.
In use, the COTeontaining gas is fed through the gas infet and an aqueous liquid, preferably water, is fed through the liquid inlet. The C0z-containing gas and the aqueous liquid flows through the reaction chamber where carbonic anhydrase 3o therein catalyses the hydration of C02, thereby fotrning hydrogen ions and bicarbonate ions. Then, the solution containing the hydrogen ions and bicarbonate -aNSOOCio: <e2 saoosa~ac>

RCV. ~'U~\ ~ EFA-ML~E'.vCHEV 05 : 1.0- 8-99 , : 21 : 54 : X14 845 6518-. +49 89 2399446 : # 13 ~..npm.u.w. ,w.yv. muuw, .mn.ui a .a muiu ~w.p T V1... WJW ~ VVl IVi JJ nJ JVr J~f~,I~A .7JVl~y uyv mr~u ions flows out from the bioreactor via the liquid outlet and the gas free tram flows out via the gas outlet.
According to a first preferred embodiment of the present invention, the apparatus comprises a second bioreacior in series with the upright bioreactor which is t~reinafter tatted a first bioreactor. The second bioreactor is substantially similar to tile first bioreactor. It comprises a liquid inlet connected with the liquid outset of the fcrst bioreactar for receiving the liquid solution from the first bioreactor.
A reaction chamber is provided in order to contain carbonic anhydrase. This reaction chamber is in fluid communication with fhe liquid inlet and oomprise9 a l0 plurality of inert organic supports mounted therein for covaler~tiy immobili~ng carbonic an#tydcase. The reaction dumber is in fluid communication with a gas outlet to evacuate a gas containing carbon dioxide obtained in the chamber.
A liquid outlet is in fluid unication with the reaction ctrimtatlo evacuate water obtained in the reaction chamber.
The second bioreaa~ar preferably comprises means fnr controtlir~g a pressure in the reaction chamber of the second bioreactor.
Acxording to a second preferred embodiment of the present invention, the apparatus further comprises an ion exchanger having an inlet for receiving the liquid solution from the bioreactor.
20 The present invention is also directed to the use of carbonic anhydrase or analog tt~reof covaierrtly immobilized in a bioreactor to remove carbon dio~ode from a Car~cos~ining gas, ~ to produce hydrogen and bicarbonate ions, or to the use of carbonic arthydrase or analog thereof covelently immebitized in a bioreactor to produce COz from enriched solutions of hydrogen and bicarbonate ions.
A non restrictive description of preferred embodiments will now be given with reference to the appended drawings.
BRIEF DESCRIPTION OF THE QRAWINGS
30 Figure 7 is a cxOSS-sectional el8vati4n view Of a tower~type bioreactor according to a preferred embodiment of the present invention;

BNSOOCID: <E2 98005410G>

FtCV. VO\ : EF'A-Wl'G~Ci-~E~l 05 ~ a ~ 1~- W99 , T 21 r 54 v 514 845 6518-.
+49 89 23999~4~65: ti l4 uav ,w.~ w ul.. ~.r ~ v, vul WI -../ n.r .rv, l~c,~~~I1~~T)Wt.,7W ~ T/ c.u ~..M...,w. .~..y... m,m~.. ~.~....m Figure 2 is a schematic tfow chart of a first preferred embodi~xtent of the pracsss according to the present invention; arid Figure 3 is a schematic flow chart of a second preferred embodiment of the process according to the pr went invention.
QESCRIPT10N OF PI~EFERREO EMBODIMENTS
During the course of investigatiing possible uses of carbonic anhydrase for I4 managing carbon dioxin accumulation in submarines, it was noted that covalent immobilization of monotneric enzymes could result in a functional enzyme system of increased stability. Moreover, there has been a dramatic intxease in the use of immobilized enzymes in a wide variety of b~technologica! appiirafions. Tiws, it was reasoned that a bioreactor employing covalently immobilized carbonic anhydrase would provide an efficient biologically based system to manage carbon dioxide.
Referring to Figure 1, an apparatus (2) for the managerrrent of C02 according to a first prefen~ed embodiment of the present invention is illustrated. This apparatus (2) is devised primarily to extract or remove carbon dioxide from a COz~ontaining gas ark specifically transform this gas to hydrogen and bicarbonate ions. The 2o apparatus (2) ca>rprises an upright bioreactar (4y to contain carbonic anhydrase thereirL The bioreador (4) comprises a lower chamber (6) having a gas inlet (8) to receive a COrcontaining gas (10) and a liquid outlet (?2) to evacuate from the bioreador (4) a Liquid solution (14) containing hydrogen torte and bicarbonate ions produced in the bioreactor (4). The biereactor (4~ further comprises an upper chamber (163 having a liquid inlet (18) to receive an aqueous liquid (20) arid a gas outlet (22) to evacuate any gas (24) from the bioreactor (4).
A reaction chamber (26} is disposed between the lower chamber ~6) end the upper chamber(16). As can be appreciated, the reaction chamber (26) of the bior~eactor (4) illustrated is preferably divided in three sub-chambers. The reaction 3o chamber (26) is in ffuid communication with the tower chamber (6) and the upper dumber (16). Preferably, the liquid inlet (18) of the upper chamber (16) is connected CA 02291785 1999-11-25 ,ua:~. .
-ANSDOC~O:<E2 980054106>-~v. v~:~=rrA-atue.;verfr_v usr~. ~ J , ~ 1u- r3-:~:~ ,; ~~1 ~55, : 514 t~S~~iSl~f->~ +4:~ ~3J Z39J4-465:#t1S
-n,r...uw: y..y..,. mv.u.w ~.u...n ..:uav yr..~.n t,.. v.r v, ..vr .vr.u n..
,.m,, yewsw tr...a.-.~. uy... ..n,~u to a pipe syst~n (28) enclosed therein and having. at least one liquid outlet (30) into the reaction chamber (2fi) such that the aqueous liquid (20) entering the bioreactor (4) flows directly into the reaction chamber (2S). The reaction chamt~er~(26) has a lower surface perrne~ble to gas and liquid such that the stream of COrcontaining gas entering the bioreactor (4) from the lower chamber (6) flows upwards into the rsactian chamber (26) and the liquid in the reaction chamber (2E) flows dovrtrNards towards and into the tower chamber (6).
The reaction umber (26) is characterized in that it comprises a plurality of inert supports, schematically represented in Figure 1 as r=urt~eral reference (32), IO mounted therein far covalentty immobilizing carbonic anhydrase (33). These supports (32) are preferably made of ceramic such as silica, namely silica burl saddles or they may be made of polymer such as nylon, polystyrene a polyethylene.
The immobilization technique preferably uses one of tl~e following bonding ages:
imidocartsonate (siticort), carbortdiimide (silica and nylon) and imine (silica and nylon). The poiystyr~ene, nylon and polyethylene may be chemicaNy modifed with nitric aced to incxease covalent bounding with tfie amine groups of the enzyme.
The COr~ontaining feed gas ('l Q) may consist of ambient air or any gaseous mixture containing carbon dioxide. The gas (10) may be filtered through a conventional fcltering means (34) known in the art to ~ntrabe the carbon dlaxide Zo andlor remove physical impuri~es. Contrd means for controlling the C0z-containing gas flow (10) through the gas inlet (8) is provided. Thus, the gas (10) is then fed into the tower portion (6) of the bioreador body (4) using preferably an appropriate valve system (36) for volume and input velocity control. The bioreactor (4) is constructed as a packed tower, a dassical design used in nurtrerrous applications.
packed towers are used to contact a gas phase and a liquid phase in order that a gas in the gas phase is absorbed by the liquid phase. Packed towers are used to achieve appropriate mass transfer operations with a minimum expenditure of enefgy and cost. PaolCings are used in paced towers to have optimum mass transfer between the gas arid liq~sid phases_ Padcings are solid supports having different 30 forms, geometry and sizes and made of different materials. They are used to incxease contact area between gas and liquid phases and thus to increase mass CA 02291785 1999-11-25 a BNSDOCID: <E2 9B005410G> ~.-Ri.~ . VON:EYA-dl:Et~:CHEN 05 : 10- 8-99 : 21 :J5 : 514 845 &S18-~ +49 89 2:3994465: ~t16 UJn V.! W ! J.J I CI CA 7aW ,. v,LJ.. W I LV
~..N,.~y,., L..y,.~ ,"..,y,. ~,~,.I~~... ~ ~".~.,. ~,.,.,,.I r ,.-~,. ,,, ~
J..,J, ~r transfer between gas and liquid phases. common packings ate Faschig rings.
Berl saddles, Intalox metal, lntalox saddles, Patl rings, ... They can be made of polymer, ceramic, metal, ...
The preferably filtered aqueous or organic solvent (20) enters the bioteactor (4) from the upper chamber (16) and flows downwards either by gravity or pressure controlled pumping. In the reac~Ion chamber (26), as the carbonic anhydrase transforms the gas into hydrogen and bir~rbonate ions. The tesutting liquid sofiution (i~) of ions leaves the bioreactor (4) far subsequent use, The unique aspect of the invention is the use of carbonic anhydrase as a means to produce enriched solutions l0 of bicarbonate ions. There are several important variations possible with respect to the cor~guratiart of tt~te bioreactor (4). The co~ositian of the input gas (10) may be varied along with the volume and speed of delivery. The bioreactor (4) may be deployed as a closed system so that the feed gas (10) can be compressed andtor enriched to enhance the kinetics of the mass transfer of the carbon dio~ade from tt~e gas to the liquid phase. There is a large txxnber of methods whid~t may be employed to optimize the gas-liquid interaction in tf~e reaction chamber (26), and hence the diffusion of carbon dioxide. The oornposi~on ~e.g., pH) ofi the resulting ion solution may be modified aocorriing to need. This configuration can serve to extract carbon dioxide from a gas stream to produce a gas or gas mixture free of carbon dio>dde.
2o Refen'ing to Figure 2, this fret bioreactor (4) design may prefiarably be coupled to an anion e~ange system (39) with the resin in the hydroxide farm.
The i~ exchanger (39) has art inlet (37) for receiving the liquid solution ( f 4) from the bioreacta~ (4). Since the carbon doxide hydration reaction produces hydrogen and bicartaan~e ions in equ~notar quantities, this solut;on may be fed dlrerxly into the ion exchange system (37~. The bicarbonate ions will be e~od~ar~ged fnr the hydroxyl ions which will be free to combine with the hydrogen ions to farm water. This system could be deployed as a carbon dio~ade management system in any closed sQace such as a dine. As iilustrated in f=igure 2, the sdution (35 ) ~npoverished in hydrogen and btc~bortate ions may be recycled in the bioraactor (4).
30 Refetting to Figure 3, the apparatus (2) for the management of carbon diode may further comprise a end bioneactOr (38) simi lar to the first one and connected BNSOOCIO: <E2 98005410G>

Ki:V. 4'UN : ~_'y~~lL'fJNCHEV 05 ~ ~ a ~ lU~ 8-99 T ~'T1 ' S5 : 514. 845v6518--~ +49 89 '?3994.4Ei5 : #17 ,,. ., ,... ~ ,., ",. ~ ~ ,. ~ , .. .....~, i.~u-as _r..,~T, , "~.. , . r ~..r,.,.y, . , , in series therewith. This particular corrF~guration operates as a Gosed system. This system serves to produce carbon dioxide and operates in a manner similar to the individual bioreactor design of Figure t.. The liquid solution (1~) coiztaining a relatively high concentration of hydrogen and bicarbonate ions produced in the first bioreacxor (4) is fed to the second bioreacior (38) in which carbon dioxide is formed in the reaction catatysed by the carbonic anhydrase. This removal of the gas from the aqueous phase may be enhanced by the application of a slight (i.e., 7-9 mm Hg) negative pressure. T'he concentrated carbon dioxide can then be recovered for subsequent use.
I o Since this second bioreactor (381 is simitar to the i'~st one, it is sd~amaticalty iiiustrated as a box in Figure 3. This second bioreactor (38) comprises a liquid inlet (40) connected with the squid outlet (12) of the first bioreactor (~4) for receiving the liquid solution (14) from the first bioreactor (4). The second bioreador (38) comprises a reaction chamber similar !o the reaction chamber (26) of the fcrst biorea~or (4) to contain carbonic anhydrase. 1'he reaction charr>ber is in fluid communication with the liquid inlet (40) and comprises a phrraiity of supports mounted therein for covalentty ir~rtobilizing carbonic anhydrase. A gas outlet (42) is in ftsriid communication with ttte reaction chamber to evacuate carbon dioxide obtained in the charr~ber. A liquid outlet (44) is in fluid communication with the ~o reaction chamber fio evacuate water (46) containing a smatl amount of hydrogen and bicarbonate ions obtained in the reaction chamber. The second bioreactor (38) may preferably comprise weans for controlling a pressure in the reaction c~a~nb~er.
As can be appreciated, the process and apparatus according to the present invention may be used for the extraction, produt~ion and purification of carbon dioxide gas. The process may also be employed for the production of aqueous andlor organic solutions of bicarbonate ions and hydrogen ions using a precursor feed stream of gas containing carbon dioxide. It could be very advantageous to use such process and apparatus in any closed dace such as a submarine.
prAEN~~ ~~~~

-BNSOOCIO: <E2 980054100>

Claims

WHAT IS CLAIMED IS:

1. A process for removing CO2 from a CO2-containing gas, the process being performed in a packed tower bioreactor comprising:
a bottom chamber having a gas inlet and a liquid outlet;
an upper chamber having a liquid inlet and a gas outlet;
a reaction chamber disposed between and being in fluid communication with the bottom chamber and the upper chamber, the reaction chamber being packed with a plurality of solid supports having a non-porous surface on which surface carbonic anhydrase or an analogue thereof is immobilized; the process comprising the steps of:
a) supplying the liquid inlet of the upper chamber with an aqueous liquid stream while supplying the gas inlet of the bottom chamber with a CO2-containing gas stream, the gas stream then flowing upwards into the reaction chamber;
b) directing the aqueous liquid stream downwards into the packed reaction chamber to contact the CO2-containing gas with the aqueous liquid and promote diffusion of the CO2 in the aqueous liquid, and thereby allowing the carbonic anhydrase immobilized in the reaction chamber to catalyze the hydration of the diffused CO2 into hydrogen ions and bicarbonate ions;
c) evacuating from the liquid outlet of the bottom chamber a liquid solution containing the hydrogen ions and bicarbonate ions produced in the reaction chamber and evacuating from the gas outlet of the upper chamber a treated gas.

2. The process according to claim 1, comprising, after step c, the step of:
feeding the hydrogen ions axed bicarbonate ions obtained in step c) into a second bioreactor containing immobilized carbonic anhydrase which catalyses the conversion of the hydrogen ions and the bicarbonate ions into concentrated CO2 and water.

3. The process according to claim 1, comprising, after step c), the step of:
feeding the hydrogen ions and bicarbonate ions obtained in step c) into an ion exchanger.

4. The process according to claim 3, wherein the ion exchanger contains hydroxyl ions so that the bicarbonate ions are exchanged for the hydroxyl ions which are then free to combine with hydrogen ions to form water.

5. The process according to anyone of claims 1 to 4, comprising, prior to step a), a step of:
filtering the CO2-containing gas.

6. The process according to anyone of claims 1 to 5, wherein the aqueous liquid consists of water.

7. The process according to anyone of claims 1 to 6, wherein the CO2-containing gas flow through the gas inlet is controlled with a valve.

8. Use of a process as defined in claims 1 to 7, for the management of CO2 in a closed space.

9. Use according to claim 8, wherein the closed space is a submarine.