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Lo, B., Tehnologija hvatanja i spremanja ugljikovog dioksida , Energija, god. 58(2009), br. 2., str. 110-135Lo, B., Carbon Dioxide Capture and Storage Technologies , Energija, vol. 58(2009), No. 2, pp. 110-135105

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UREIVAKA POLITIKA

asopis Energija znanstveni je i struni asopis sdugom tradicijom vie od 50 godina. Pokriva po-druje elektroprivredne djelatnosti i energetike.asopis Energija objavljuje izvorne znanstvenei strune lanke irokoga podruja interesa, od

specinih tehnikih problema do globalnih ana-liza procesa u podruju energetike.

U vrlo irokom spektru tema vezanih za funkci-oniranje elektroprivredne djelatnosti i openitoenergetike u trinim uvjetima i opoj globali-zaciji, asopis ima poseban interes za specineokolnosti ostvarivanja tih procesa u Hrvatskoj injezinu regionalnom okruenju. Funkcioniranjei razvoj elektroenergetskih sustava u sredinjoj i

jugoistonoj Europi, a posljedino i u Hrvatskoj,optereeno je mnogobrojnim tehniko-tehno-lokim, ekonomskim, pravnim i organizacijskim

problemima. Namjera je asopisa da postaneznanstvena i struna tribina na kojoj e se kritikii konstruktivno elaborirati navedena problemati-ka i ponuditi rjeenja.

asopis je posebno zainteresiran za sljedeu te-matiku: opa energetika, tehnologije za proizvod-nju elektrine energije, obnovljivi izvori i zatitaokolia; koritenje i razvoj energetske opreme isustava; funkcioniranje elektroenergetskoga su-stava u trinim uvjetima poslovanja; izgradnjaelektroenergetskih objekata i postrojenja; infor-macijski sustavi i telekomunikacije; restrukturi-

ranje i privatizacija, reinenjering poslovnih pro-cesa; trgovanje i opskrba elektrinom energijom,odnosi s kupcima; upravljanje znanjem i obrazo-vanje; europska i regionalna regulativa, inicijativei suradnja.

Stranice asopisa podjednako su otvorene isku-snim i mladim autorima, te autorima iz Hrvatskei inozemstva. Takva zastupljenost autora osigu-rava znanje i mudrost, inventivnost i hrabrost, tepluralizam ideja koje e itatelji asopisa, vje-rujemo, cijeniti i znati dobro iskoristiti u svojemprofesionalnom radu.

EDITORIAL POLICY

The journal Energy is a scientic and profession-al journal with more than a 50-year tradition.Covering the areas of the electricity industryand energy sector, the journal Energy publishesoriginal scientic and professional articles with

a wide area of interests, from specic technicalproblems to global analyses of processes in theenergy sector.

Among the very broad range of topics relatingto the functioning of the electricity industry andthe energy sector in general in a competitiveand globalizing environment, the Journal hasspecial interest in the specic circumstancesin which these processes unfold in Croatia andthe region. The functioning and development ofelectricity systems in Central and South EastEurope, consequently in Croatia too, is bur-

dened with numerous engineering, economic,legal and organizational problems. The inten-tion of the Journal is to become a scientic andprofessional forum where these problems willbe critically and constructively elaborated andwhere solutions will be offered.

The Journal is especially interested in the fol-lowing topics: energy sector in general, elec-tricity production technologies, renewablesources and environmental protection; use anddevelopment of energy equipment and systems;functioning of the electricity system in competi-

tive market conditions; construction of electricpower facilities and plants; information systemsand telecommunications; restructuring andprivatization, re-engineering of business pro-cesses; electricity trade and supply, customerrelations, knowledge management and train-ing; European and regional legislation, initia-tives and cooperation.

The pages of the Journal are equally open toexperienced and young authors, from Croatiaand abroad. Such representation of authorsprovides knowledge and wisdom, inventivenessand courage as well as pluralism of ideas whichwe believe the readers of the Journal will appre-ciate and know how to put to good use in theirprofessional work.

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UVODINTRODUCTION

108

Dear readers!

Before you is the second edition of Energija for the year 2009. After thethemes related to supply security as well as to customers supply withenergy, that is, different energy sources, the most interesting themesare related to reduced environment impact of energy objects as wellas the themes related to the energy sources market. Therefore, inthis issue of Energija, we present articles related to the developmentand application of the technologies which, to a certain extent, reducegreenhouse gas emission as well as certain events related to theelectricity market. It need not be especially stressed that this periodis marked by decreased investment into the energy sector so this isthe right occasion to address more seriously the analyses of differentaspects of the energy sector and for that purpose, we invite you to join

us with your works addressing these and similar issues.In this issue of Energija, we present very interesting articles from vari-ous elds, from the energy-related to specialist electrical engineeringelds:

Carbon dioxide capture and storage technologies in the electricpower sector overview of the relevant situations,

Price anomaly on the European Energy Exchange (Leipzig) electri-city market,

Analysis of a major failure of the transformer unit on the island ofCrete,

Load angle estimation of a synchronous generator using dynami-

cal neuron networks, Maintaining declared performance in gas turbines during increa-sed ambient temperatures.

The rst article presents an overview of the situation of developmentand the perspectives in a very interesting eld related to carbon diox-ide capture. Environment protection regarding the reduction of green-house gas emission achieves certain results and that being primar-ily in the area of increased energy efciency. However, it comes outnevertheless that this will not sufce so it is necessary to develop alsosome other technologies which reduce the carbon dioxide emissioninto the atmosphere to a certain extent. Carbon dioxide capture, iso-lation and storage technologies thus constitute the second, promis-

ing option which can drastically reduce these emissions. Signicantprogress accomplished in the last ten years enabled some complextechnological solutions to come close to commercial application. Thisarticle enables a short overview of the relevant situation in carbon di-oxide capture, isolation, transport and storage which could be widelyused in the electric power sector two decades from now.

The second article of this issue of Energija describes one extremelyinteresting occurrence which happened, or better said, is happeningon the electricity market. The EEX (European Energy Exchange) hasbecome, along with Nord Pool in Nordic countries, the most signi-cant energy exchange in continental Europe. The work also showsand deliberates on the occurrence of negative prices on the EEX elec-

tricity spot market at the end of December 2008. The negative price,when predicted and allowed at the energy exchange, mirrors the situ-

Potovani itatelji!

Pred Vama je drugi broj asopisa Energija u 2009. godini. Nakontema vezanih uz sigurnost dobave kao i opskrbe kupaca energi-

jom odnosno razliitim energentima, najzanimljivije su teme ve-zane uz smanjenje utjecaja na okoli energetskih objekata kao iteme vezane uz trite energenata. Tako u ovom broju asopisaEnergija donosimo lanke vezane uz razvoj i primjenu tehnologijakoje u odreenoj mjeri smanjuju emisiju staklenikih plinova kao ineke pojavne oblike vezane uz trite elektrine energije. Ne trebaposebno naglaavati kako je ovo razdoblje oznaeno smanjenjeminvesticija u energetski sektor pa je to upravo prigoda da se malovie bavimo analizama razliitih aspekata energetskog sektora i utom smislu vas pozivamo da nam se pridruite svojim radovima na

ovim i slinim temama.U ovom broju asopisa Energija objavljujemo vrlo zanimljive lankeiz razliitih podruja, od energetskih do specijalistikih podrujaelektrotehnike:

Tehnologije hvatanja i spremanja ugljikovog dioksida u elektro-energetskom sektoru pregled relevantnih stanja,

Anomalija cijene na spot tritu elektrine energije europskeburze energije EEX (Leipzig),

Analiza velikog kvara u transformatorskoj stanici na otoku Kre-ti,

Estimacija kuta optereenja sinkronog generatora dinamikim

neuronskim mreama, Odravanje nazivnih performansi plinske turbine pri povienimtemperaturama okolia.

U prvom lanku daje se prikaz stanja razvoja i perspektive u jed-nom vrlo zanimljivom podruju koje se odnosi na spremanje uglji-kovog dioksida. Zatita okolia koja se odnosi na smanjenja emisijestaklenikih plinova postie odreene rezultate i to prvenstveno napodruju poveanje energetske uinkovitosti. Pokazuje se ipak dato nee biti dovoljno pa je nuno razviti i neke druge tehnologijekoje na odreeni nain smanjuju emitiranje ugljikovog dioksida uatmosferu. Tehnologije hvatanja, izdvajanja i spremanja ugljikovogdioksida sainjavaju tako drugu obeavajui opciju koja moe dra-

stino reducirati ove emisije. Znaajan napredak, napravljen u za-dnjih desetak godina, omoguio je da se neka kompleksna tehno-loka rjeenja nalaze vrlo blizu komercijalne primjene. Ovaj lanakomoguava kratak pregled relevantnog stanja tehnologija hvatanja,izdvajanja, transport i skladitenja ugljikovog dioksida koje e mo-da za dva desetljea biti u irokoj primjeni u elektroenergetskomsektoru.

Drugi lanak u ovom broju asopisa Energija opisuje jednu krajnjezanimljivu pojavu koja se dogodila ili je bolje rei dogaa na tri-tu elektrine energije. Europska burza energije EEX postala je, uzNord Pool u nordijskim zemljama, najznaajnija burza energije ukontinentalnoj Europi. U radu je prikazana i razmatrana pojava ne-

gativne cijene na spot tritu elektrine energije na EEX-u krajemprosinca 2008. godine. Negativna cijena, kada je predviena i dopu-

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ation on the market in which the offer has signicantly exceeded thedemand. The article is especially interesting because it provides theanalysis of the causes which brought about such an unusual occur-rence. This occurrence is however unusual because a negative priceof some other goods on the market practically cannot occur and thisis another reason for the specicity of the electricity market in relationto the standard market of other goods.

The third, very interesting article written by our established associatesfrom Greece, professor Papazoglou and associates, gives a full over-view of the events related to the major failure of the electrical powersystem of Crete the consequence of which was major damage on theTS Iraklio 3. The problem began due to a failure on the middle voltageof the transformer station, and then, as the failure was not repairedon time, extensive short circuit currents occurred in the duration of 16minutes, re to the equipment and signicant damage to the high andmiddle voltages as well as to the DC power distribution in the trans-former station. The article provides a description of the line of eventsof that failure with a detailed analysis of the line of events. All of theabove yields conclusions of practical importance as well as recom-

mendations regarding the improvements in the hardware and protec-tive system and the available technical support which could be crucialfor the evasion and/or limitation of damage at future failures.

The fourth article gives a very interesting analysis and modelling ofthe angle estimation of the generator loading. The loading of the syn-chronous generator in operation on the electric power system (EPS)is a drive-dimension which provides virtually direct information on theposition of the generators operative point in relation to the stabilitylimit. The EPSs operation is characterized by signicant changes inthe operative regime of the synchronous generator operation, so thatthe transition from one operative state to another is usually followedby signicant dynamic changes of the load angle. The article denes

the procedure of the operative synchronous generator load angle esti-mation on the electrical power system based on dynamic neuron net-works. The comparison of the results obtained by the application ofthe dened load angle estimation procedure with the results obtainedby measurements indicates the applicability of the suggested estima-tion procedure based on dynamic neuron networks.

The fth Article shows the analysis of how the cooling of air enter-ing the gas turbine impacts its performance. The classical gas tur-bine process is characterized by the compression of ambient air whichheats up in the combustion chambers by fuel combustion and the uegases generated in such way expand in the turbine and produce me-chanical operation. The performances of the gas turbine depend on

everything that changes the density and/or air mass ow rate at thecompressor suction point. The most signicant changes in the gas tur-bine performance are reduced power and increased fuel consumptionfollowing higher ambient temperatures, whereat signicant deviationsoccur from the values guaranteed (and achieved) at ISO conditions.The cooling of air at the compressor suction hole at increased ambienttemperatures provides for an increased mass ow rate and compres-sion ratio and prevention of reduced power and increase of specicfuel consumption. The work uses the example of the GE-PG6101FAturbine to depict the dependence on ambient climatic conditions andthe way in which such dependence can be reduced or removed.

The articles in this issue of Energija were written by the authors both

from the academic community and from practice which surely result-ed in articles of high quality as well.

Editor-in-chief.Goran Slipac, MSc

tena na burzi energije, odraava situaciju na tritu u kojoj je po-nuda znaajno nadmaila potranju. lanak je posebno zanimljiv

jer daje i analizu uzroka koji su doveli do ovako neobine pojave.Ova pojava je meutim neobina jer se negativna cijena neke drugerobe na tritu praktiki ne moe pojaviti pa se i po tomu triteelektrine energije izdvaja od uobiajenog trita ostalih roba.

U treem, vrlo zanimljivom lanku od naih sada ve starih surad-nika iz Grke, profesora Papazoglou-a i suradnika, daje se jedanpotpun prikaz dogaanja vezanih uz veliki kvar u elektroenerget-skom sustavu Krete koji je za posljedicu imao veliku tetu na TSIraklio 3. Problem je poeo zbog kvara na srednjem naponu utransformatorskoj stanici pa kako se kvar nije uklonio na vrijeme,dolo je do velikih struja kratkog spoja tijekom 16 minuta, poarana opremi i velike tete na visokom i srednjem naponu kao i razvo-dima istosmjerne struje u transformatorskoj stanici. U lanku sedaje opis slijeda dogaaja tog kvara s podrobnom analizom slijedadogaanja. Rezultat svega su zakljuci od praktine vanosti kaoi preporuke u odnosu na poboljanja u hardverskom i zatitnomsustavu i dostupnoj tehnikoj potpori, koje mogu biti presudne za

izbjegavanje i/ili ograniavanje tete kod buduih kvarova.U etvrtom lanku se daje vrlo zanimljiva analiza i modeliranjeestimacije kuta optereenja generatora. Kut optereenja sinkronoggeneratora u radu na elektroenergetski sustav (EES) pogonska jeveliina koja daje praktiki direktni podatak o poloaju radne tokegeneratora u odnosu na granicu stabilnosti. Rad EES-a karakteri-ziraju velike promjene pogonskog reima rada sinkronog genera-tora, tako da prijelaz iz jednog u drugo ustaljeno pogonsko stanjenajee prate znaajne dinamike promjene kuta optereenja. Ulanku je deniran postupak estimacije kuta optereenja sinkro-nog generatora u radu na elektroenergetski sustav zasnovanog nadinamikim neuronskim mreama. Usporedbom rezultata dobive-

nih primjenom deniranog postupka estimacije kuta optereenja,s rezultatima dobivenim mjerenjem, pokazana je primjenjivostpredloenog estimacijskog postupka zasnovanog na dinamikimneuronskim mreama.

U petom lanku je prikazana analiza utjecaja hlaenja ulaznog zra-ka u plinsku turbinu na njene performanse. Klasini proces plinsketurbine karakterizira kompresija zraka iz okoline, koji se u komora-ma izgaranja zagrijava izgaranjem goriva te tako stvoreni dimni pli-novi ekspandiraju u turbini i proizvode mehaniki rad. Performanseplinske turbine ovise o svemu to mijenja gustou i/ili maseni pro-tok zraka na usisu kompresora. Najoitije promjene u performan-sama plinske turbine su smanjenje snage i poveanje specine

potronje goriva s porastom temperature okolia, pri emu nastajuznaajna odstupanja od vrijednosti garantiranih (i postignutih) priISO uvjetima. Hlaenjem zraka na usisu kompresora pri povienimtemperaturama okolia postie se poveanje masenog protoka ikompresijskog omjera, te se sprjeava smanjenje snage i povea-nje specine potronje goriva. U radu je na primjeru turbine GE-PG6101FA prikazana ovisnost o okolinim klimatskim uvjetima, tenain na koji se ta ovisnost moe smanjiti ili otkloniti.

lanke u ovom broju asopisa Energija potpisuju autori iz sveui-line zajednice, ali i iz prakse, to je, sasvim sigurno, rezultiralo ikvalitetnim lancima.

Glavni urednik:Mr. sc. Goran Slipac

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110Lo, B., Tehnologija hvatanja i spremanja ugljikovog dioksida , Energija, god. 58(2009), br. 2., str. 110-135Lo, B., Carbon Dioxide Capture and Storage Technologies , Energija, vol. 58(2009), No. 2, pp. 110-135

TEHNOLOGIJE HVATANJA ISPREMANJA UGLJIKOVOG DIOKSIDA

U ELEKTROENERGETSKOMSEKTORU PREGLEDRELEVANTNOG STANJA

CARBON DIOXIDE CAPTURE ANDSTORAGE TECHNOLOGIES IN

THE ELECTRIC POWER SECTOR OVERVIEW OF THE RELEVANTSITUATION

Branimir Lo, Zagreb, HrvatskaU dolazeih pola stoljea fosilna goriva e biti ekstenzivno koritena, a emisija CO2 rasti, ukoliko ne bude

provedena u djelo nova energetska politika. Postoje brojne opcije kojima se moe reducirati emisija CO2 izenergetskih sustava. One ukljuuju poboljavanje energetske ekasnosti, prijelaz na obnovljivu i nuklearnu

energiju. Meutim, politika temeljena na ovim opcijama e, u najboljem sluaju, samo djelomino rijeitiproblem. Tehnologije hvatanja, izdvajanja i spremanja ugljikovog dioksida sainjavaju drugu obeavajui

opciju koja moe drastino reducirati ove emisije. Zbog tog razloga se hvatanje, izdvajanje, transport iskladitenje ugljikovog dioksida studiraju godinama. Brojni tehniki koncepti se predlau; esto spekulativnenaravi plod apstrakcije, daleko od iskustva i prakse. Mnogi od njih iziskuju vrlo velike istraivake i razvojne

napore prije komercijalizacije. Znaajan napredak, napravljen u zadnjih desetak godina, omoguio je dase neka kompleksna tehnoloka rjeenja nalaze vrlo blizu komercijalne primjene. Ovaj lanak omoguava

kratak pregled relevantnog stanja tehnologija hvatanja, izdvajanja, transport i skladitenja ugljikovog dioksidakoje e moda za dva desetljea biti u irokoj primjeni u elektroenergetskom sektoru.

In the next half century, fossil fuels will be used extensively and the CO2emission will increase unless new

energy policies are put through. There are numerous possibilities for the reduction of the CO2emission from

the energy systems. These include the improvement of energetic efciency and the switch to renewable andnuclear energy. However, the policy based on these options will, in the best case, solve the problem only

partially. Carbon dioxide capture, isolation and storage technologies constitute the second, promising optionwhich can drastically reduce these emissions. Because of that, carbon dioxide capture, isolation, transport

and storage have been studied for years. Numerous concepts have been proposed, often of speculativenature- products of abstraction, far from experience and practice. Many of these require great research and

developmental efforts before commercialization. Signicant progress accomplished in the last ten yearsenabled some complex technological solutions to come close to commercial application. This article enables

a short overview of the relevant situation in carbon dioxide capture, isolation, transport and storage, whichcould be widely used in the electric power sector two decades from now.

Kljune rijei: demonstracijska postrojenja; ekasnost; istraivanje; nadzor;neizvjesnost; planiranje; primjena; rizici; trokovi; znaajke

Key words: application; costs; demonstration plants; efciency; planning; properties;research; risks; supervision; uncertainty

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Lo, B., Tehnologija hvatanja i spremanja ugljikovog dioksida , Energija, god. 58(2009), br. 2., str. 110-135Lo, B., Carbon Dioxide Capture and Storage Technologies , Energija, vol. 58(2009), No. 2, pp. 110-135 112

Slika 1 Promjena koncentracija (ppm)ugljikovog dioksida u atmosferi u zadnjih tisuu godina

Figure 1 Change of carbon dioxide concentrations (ppm)in the atmosphere in the last thousand years.

1 UVOD

Intenzivni razvitak industrije datira od sredine 19.stoljea. Razvitak prati poveanje razine koncen-tracije ugljikovog dioksida u atmosferi sa 280 ppm(partes per milion mol)na skoro 370 ppm [1] .Nema tonog odgovora, kolika je granina kon-

centracija nakon koje e negativne i nepovratneklimatske promjene prouzroiti u konanici pro-padanje ljudske civilizacije. Struka smatra da jeona blie 450 ppmnego 750 ppm. Bez ikakvihmjera za smanjenje koncentracije ugljikovog di-oksida u atmosferi bit e ga oko 900 ppm2100.godine. Na slici 1 je prikazan porast koncentraci-

je CO2u atmosferi od 1000. do 2000. godine.

1 INTRODUCTION

Intense industry development dates back to themid-19th century.The development was accompa-nied by an increased concentration of carbon dioxi-de in the atmosphere from 280 ppmto almost 370ppm [1] (ppm partes per million mol). There is

no correct answer as to the amount of the cut-offconcentration beyond which negative and irreco-verable climatic changes will nally cause the de-struction of human civilization. The profession be-lieves that it is closer to 450 ppmthan to 750 ppm.Without any measures for the reduction of the car-bon dioxide concentration in the atmosphere, in theyear 2100, it will amount to about 900 ppm. Figure 1shows the increase of the CO

2concentration in the

atmosphere from 1000 to 2000.

Stanje je alarmantno jer nije izglednija masov-nija uporaba tehnologija za hvatanje, izdvajanje,transport i skladienje (u nastavku HITS CO

2)u

iduih 15 godina. Pretpostavlja se da e emisijaugljikovog dioksida porasti na 30 Gt CO

2te da e

se od 3 Gt CO2do optimistikih 76 Gt CO

2[2] moi

trajno zbrinuti u geoloke naslage ispod zemlje.Sustav HITS CO

2, proizvednog tijekom uporabe

fosilnih goriva, moe se izgraditi na postojeimtehnologijama. Sve aktivnosti su ve pojedina-

no implementirane u odreenim aplikacijamana komercijalnoj razmjeri. Danas, niti jedan HITSCO

2sustav u svijetu ne djeluje na komercijalnim

postrojenjima za proizvodnju elektrine energi-je.

Proizvodnja elektrine energije ostvarena loe-njem fosilnih goriva je odgovorna za vie od 30 %

ukupne dananje emisije CO2. Usporeujui

druge opcije ublaavanja emisije CO2 u elek-

troenergetskom sektoru, HITS CO2treba manja

restrukturiranja sustava energetske dobave, paak i u samo nekoliko izvedenih projekata se

moe postii znaajan utjecaj na emisije CO2nadravnoj ili regionalnoj razini.

The situation is alarming because a more extensi-ve use of capture, isolation, transport and storagetechnologies (hereinafter: CITS CO2)in the next 15years is not probable. The assumption is that car-bon dioxide emission will increase to 30 Gt CO

2and

that from 3 Gt CO2up to the optimistic amount of

76 Gt CO2[2] could be permanently put into geolo-

gical underground deposits. The CITS CO2system,

produced during the use of fossil fuels, can be bu-ilt on existing technologies. All the activities have

already been separately implemented in certainapplications at commercial levels. Today, none ofthe CITS CO

2systems in the world are applied on

commercial plants for the production of electricity.

Electricity production realized by the ring of fossilfuels is accountable for more than 30 %of todaystotal CO

2emission. By comparing other options for

CO2 emission amelioration in the electric power

sector, the CITS CO2requires less restructuring of

the energy supply system, and therefore in only afew executed projects a signicant impact on CO

2-

emission can be achieved at the national or regional

level.

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Vano je naglasiti da industrijski procesi generi-raju oko 23 % emisije CO

2u svijetu, a mogue je

realizirati HITS CO2tijekom proizvodnje eljeza,

cementa, kemikalija i papira. U nekim sluaje-vima trokovi HITS-a mogu biti i nii nego u pro-izvodnji elektrine energije. Problem je to su

jedinini izvori emisije manji od elektroenerget-

skih, tako da je njihovo povezivanje glede tran-sporta CO2sloenije i skuplje.

U lanku je dan pregled razvoja znaajnih teh-nolokih rjeenja na kojima je zasnovan kom-pleksan sustav za hvatanje, izdvajanje, transporti skladitenja CO

2. Kvanticirane su njegove

tehnike znaajke, za koje tek treba razviti odgo-varajui globalni sustav poslovanja. Meunarod-na agencija za energiju (IEA)je pokrenula 1991.godine provedbu Programa razvoja i istraivanjastaklenikih plinova (u nastavku IEA GHG). IEAGHG je kroz meunarodnu suradnju, 26 zema-

lja lanica i Europske (EU)komisije, inicirala ra-zvoj tehnologija sposobnih za postizanje velikogsmanjenja emisije staklenikih plinova. IEA zna-ajno organizacijski i nancijski pomae proved-bu Programa, utjee na dinamiku napredovanjaniza projekata i objektivno godinje izvjeuje onjihovom napredovanju.

2 SVOJSTVA UGLJIKOVOGDIOKSIDA

Pri normalnoj temperaturi i tlaku je ugljikov di-oksid u plinovitom stanju. Fiziko stanje variras temperaturom i tlakom, kako je prikazano naslici 2. Pri niskim temperaturama CO

2je u kru-

tom stanju, zagrijavanjem se, ako je tlak ispod5,1 bar, iz krutog stanja izravno sublimira u pli-novito stanje. Na meutemperaturama (izmeutemperature trojne toke 56,5 C,i temperaturekritine toke od 31,1 C), uz uklanjanje proizve-dene topline CO

2moe prelaziti od pare u tekue

stanje komprimiranjem na odgovarajuem tlakuukapljivanja. Pri temperaturama viim od 31,1C(ukoliko je tlak vii od tlaka u kritinoj toci,

73,9 C), za CO2 se kae da je u nadkritinomstanju u kojem se ponaa kao plin; pod doistavisokim tlakom gustoa plina moe veoma va-rirati pribliavajui se ili ak biti vea od gustoetekue vode. Ovo je znaajan aspekt ponaanjaCO

2i osobito je znaajan za njegovo odlaganje.

Toplina se oslobaa ili apsorbira pri svakoj pro-mjeni faza/stanja preko granice kruto-plinovitoi tekue-plinovito. Meutim, fazne promjene iznadkritinog stanja u tekue ili iz nadkritinogstanja u plinovito ne zahtijevaju ili oslobaajutoplinu. Ovo svojstvo je korisno za projektiranjeureaja za komprimiranje. Znaajnija zika

svojstva CO2su prikazana u tablici 1.

It is important to point out that industrial proce-sses generate about 23 %of CO

2emissions in the

world, and it is possible to realize CITS CO2in the

course of the production of iron, cement, chemicalsand paper. In certain cases, the CITS costs can beeven lower than those in electricity production. Theproblem is that unit emission sources are smaller

than the electrical energy sources, therefore, theirinterconnection as regards CO2 transport is more

complex and more expensive.

The article depicts the overview of the developmentof signicant technological solutions on which thecomplex system for the capture, isolation, transportand storage of CO

2is based. Its technical properti-

es are quantied and for these an adequate globalbusiness operation system still needs to be deve-loped. In 1991, the International Energy Agency(IEA) launched the implementation of the Green-house Gas Research and Development Program-

me (hereinafter: IEA GHG). By virtue of internatio-nal cooperation of 16 EU member states and theEuropean Commission, the IEA GHG initiated thedevelopment of technologies capable of achievingsignicant reduction of greenhouse gas emissions.The IEA signicantly supports the implementationof the Programme organizationally and nancially,it impacts the dynamics of the progress of a num-ber of projects and issues objective annual reportson their progress.

2 CARBON DIOXIDE FEATURES

At a normal temperature and pressure, carbon di-oxide is in gaseous state. Its physical state variesdepending on the temperature and the pressure,as shown in Figure 2. At low temperatures, CO

2is

in gaseous state, and, when heated, if the pressureis lower than 5,1 bar, from solid state it directly su-blimates into gaseous state. At inter-temperatures(between the triple point temperature of 56,5 Cand the critical point temperature of 31,1 C), withthe removal of the generated heat, CO

2can change

from gaseous to liquid state by compression at theadequate liquication pressure. At temperatureshigher than 31,1 C (if the pressure is higher thanthe pressure at the critical point, 73,9 C), CO

2 is

said to be in supercritical state in which it behavesas gas; at a very high pressure, gas density mayvary signicantly and come close to or even higherthan liquid water density. This is an important as-pect of CO

2behaviour and it is especially important

for its disposal. Heat is released or absorbed at anychange of phase/state over the solid-gaseous andliquid-gaseous boundary. However, phase changesfrom supercritical state to liquid or from supercriti-cal state to gaseous do not require or release heat.This feature is useful for the design of compressiondevices. Key physical features of CO

2are shown in

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Svojstvo / Property Vrijednost / Value

Molekularna teina / Molecular weight 44,01

Kritina temperatura / Critical temperature, C 31,1

Kritini tlak / Critical pressure,bar 73,9

Kritina gustoa / Critical density, kg/m3 467

Temperatura u trojnoj toci / Triple point temperature, C 56,5

Tlak u trojnoj toci / Triple point pressure,bar 5,18

Toka kljuanja (sublimacije)na / Boiling (sublimation)point at 1,013bar, C 78,5

Plinovita faza / Gaseous phase

Specina gustoa u toki kljuanja / Specic density at the boiling point(1,013bar), kg/m3 2,814

Specina gustoe STP / Specic density STP, kg/m3 1,976

Specini volumen STP / Specic volume STP, kg/m3 0,506

Viskozitet (STP)/Viscosity (STP), Pa s 13,72

Topivost u vodi (STP)/ Solubility in water (STP), vol/vol 1,716

Entalpija (STP)/ Enthalpy (STP), kJ/mol 21,34

Tekue stanje / Liquid state

Tlak pare / Vapour pressure(pri / at20C),bar 58,5

Gustoa tekue faze / Liquid phase density(20Ci / and19,9bar), kg/m3 1032

Viskozitet (STP)/ Viscosity (STP), Pa s 99

Kruto stanje / Solid state

Gustoa CO2u toki zaleivanja / CO2 density at freezing point, kg/m

3 1562

Latentna toplina isparavanja / Latent vaporization heat(1,013bar u toki sublimacije / atsublimation point), kJ/kg 571,1

Slika 2 Fazni dijagram za CO2

Figure 2 Phase diagram for CO2

Tablica 1 Fizika svojstva ugljikovog dioksidaTable 1 - Carbon dioxide physical properties

Napomena: STP standardna temperatura i tlak, jednaki 0 C i 1,013bar. Izvor: Air Liquid gas data table (Kirk-Otmer,Encyclopedia of Chemical Technology 1985)

Remark: STP standard temperature and pressure, equal to 0 C and 1,013barSource: Air Liquid gas data table (Kirk-Ot-hmer, Encyclopedia of Chemical Technology 1985)

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3 TEHNOLOGIJE HVATANJA IIZDVAJANJA CO

2

Tehnologije hvatanja i izdvajanja CO2(u nastavku

HICO2)se temelje na: apsorpciji (kemijska i zi-ka), adsorpciji, kriogenim postupcima i membra-

nama. Trenutano su u pogonu apsorpcioni reak-tori dnevnog kapaciteta manjeg od 1 000 t CO2.

Klasini termoenergetski blok elektrine snageod250 MW

loen kamenim ugljenom dnevno emi-

tira oko 4 500 t CO2, a kombi blok loen prirodnim

plinom jednake snage oko 2 150 t CO2. To znai

da bi se za vee proizvodne jedinice, postrojenje zaHI moralo izgraditi od veeg broja manjih jedinica,to bi za posljedicu imalo poveana ulaganja, ve-liku vlastitu potronju i dvojbenu sigurnost pogo-na. Struni krugovi oekuju da e bar jedna od triglavne skupine tehnolokih postupaka, prikazanena slici 3, moi biti komercijalno primijenjena, u

sljedeih deset do petnaest godina kod velikihproizvodnih jedinica u elektroenergetskom i indu-strijskom sektoru za hvatanje i izdvajanje CO

2 iz

fosilnih goriva [3], [4] i [5]:

hvatanje i izdvajanje ugljikovog dioksida nakonizgaranja (HICO

2-NI),

hvatanje i izdvajanje ugljikovog dioksida prijeizgaranja (HICO

2-PI),

hvatanje i izdvajanje ugljikovog dioksida izga-ranjem u struji kisika (HICO

2-Ox).

Mogunost njihove primjene se temelji na kompo-

nentama provjerenima u komercijalnom pogonukao to su ranacija nafte, procesuiranje prirod-nog plina i proizvodnja sintetikih goriva. Trenu-tano ne postoji u pogonu termoenergetsko poka-zno postrojenje s potpunim HICO

2, u kojem bi se

mogli provjeriti tehniki i komercijalni pokazateljiposlovanja.

Svi ostali tehnoloki postupci za termo-elektroe-nergetska postrojenja su spekulativne naravi, e-sto utemeljeni samo na laboratorijskim opitima ilipilot postrojenjima ije specine rezultate rada jevrlo teko generalizirati.

Trenutano se moe izgraditi i staviti u funkciju HI-CO

2za dekarbonizaciju fosilnih goriva u proizvod-

nji vodika (izdvajanje prije izgaranja)ili za hvatanje iizdvajanje CO

2iz dimnih plinova nakon nekih indu-

strijskih procesa (izdvajanje nakon izgaranja). Po-boljanja, u praksi dokazanih tehnologija manjih

jedininih snaga, ukljuuju razvoj novih kemijskihi zikih otapala za CO

2s ciljem smanjenja ener-

getskih potreba procesa izdvajanja. Za novije pro-cese, istraivanja se usmjeravaju na bolje i jeftinijemembrane za postupke poveanja koncentracijeCO

2, ekasniju tehnologiju razdvajanja zraka (neke

opcije ukljuuju izgaranje u istom kisiku), jeftinijei ekasnije gorive elije (za pretvaranje kemijske

3 CO2CAPTURE AND ISOLA-

TION TECHNOLOGIES

CO2capture and isolation technologies (hereinaf-

ter CICO2)are based on: absorption (chemical andphysical), adsorption, cryogenic procedures and

membranes. At the moment, absorption reactorswhich are in operation are of daily capacity below1000 t CO

2.The classic thermal energy block of

250 MW red by hard coal emits about 4 500 t CO2

daily, and the combined block red by natural gasof equal power emits about 2 150 t CO

2. This me-

ans that for larger production units, the CI plantshould be built from a larger number of smallerunits which would result in signicant inves-tments, extensive own spending and uncertainsafety of the plant. Expert circles expect that atleast one of the three main groups of technolo-gical procedures, shown in Figure 3, could be co-

mmercially applied in the next ten to fteen yearsin large production units in the electric power andindustrial sector for the capturing and isolation ofCO

2from fossil fuels [3], [4] and [5]:

capture and isolation of carbon dioxide aftercombustion (CICO

2-AC),

capture and isolation of carbon dioxide beforecombustion (CICO

2-BC),

capture and isolation of carbon dioxide by oxy-fuel (CICO

2-Ox),

The possibility of their application is based on the

components tested in commercial plants such asoil renery, processing of natural gas and produc-tion of synthetic fuels. At the moment, no thermalenergy demonstration plant with complete CICO

2,

in which the technical and commercial businessindicators could be tested, is in operation.

All other technological procedures for thermal-electric power plants are of speculative nature,often based only on laboratory tests or pilot plantsthe specic results of the work of which are dif-cult to be generalized.

Now, a CICO2 for decarbonisation of fossil fuelsin hydrogen production (isolation before combu-stion)or for the capture and isolation of CO

2from

ue gases after certain industrial processes (iso-lation after combustion)can be constructed andput into operation. Improvements of technologiesof smaller unit powers proven in practice includethe development of new chemical and physicalsolvents for CO

2with the aim to reduce energy

requirements of the isolation process. For newerprocesses, research is focused on better and che-aper membranes for the CO

2concentration incre-

ase processes, more efcient air separation tech-

nology (some options include combustion in pureoxygen), cheaper and more efcient combustive

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energije spremljene u vodiku ili metanu u elek-trinu energiju), turbine na vodik, kemijske petljeitd. U tablici 2 prikazane su mogunosti smanjenjaemisije CO

2iz nekih fosilnih goriva.

cells (for the transformation of chemical energystored in hydrogen or methane into electricity),hydrogen-driven turbines, chemical loops, etc.Table 2 shows the possibilities of reduction of CO

2

emission from certain fossil fuels.

Procjena mogunost tehnologija za 2020. godinu / Evaluation oftechnologies possibilities for the year 2020

Ugljen /Coal

Loivo ulje /Heating oil

Prirodni plin /Natural gas

g CO2/kWh(bez HITS/ without CITS) 900 660 330

g CO2/kWh+ HITS/CITS 108 - 54

Udio, %, uhvaenog od emitiranog /Share, %, of captured out of the emitted

90 - 85

Dodatno gorivo za pogon HITS opreme, % od izvornog konceptabez HITS / Additional fuel for the CITS equipment drive, % oforiginal concept without CITS

20 - 10

Slika 3 Tri glavne opcije za hvatanje CO2iz termoelektrana

Figure 3 Three main options for the capture of CO2from thermal power plants

Tablica 2 Procjena tehnologija glede mogunosti smanjenja emisije CO2[2]

Table 2 - Evaluation of technologies as regards the possibilities of reduction of CO2emission [2]

Kod koritenja kamenog ugljena (tablica 3)pred-nost se daje tehnologiji HICO

2-PI, kod koje se iz-

dvajanje obavlja u struji dimnih plinova s povea-nom koncentracijom CO

2budui da se rasplinja-

vanje obavlja u struji istog kisika bez nazonostiduika. Nuno je naglasiti da jo nije, nakon dugo-godinjih istraivanja, postignuta konkurentnostpostrojenja za rasplinjavanje kamenog ugljena.Klasina tehnologija spaljivanja ugljene praine je

jo uvijek bez konkurencije glede uinka, raspolo-ivosti, pouzdanosti i trajnosti opreme. Niti jednopostrojenje u svijetu ne rasplinjava na komerci-

jalnoj osnovici kameni ugljen, ve samo ostatkeprerade nafte u ranerijama. Izgaranje kisikom,

When using hard coal (Table 3), preference is givento the CICO

2-BCtechnology in which the isolation

is performed in the ue gases current with an in-creasedCO

2concentration because the carbureti-

on is performed in the pure oxygen current witho-ut the presence of nitrogen. It is important to pointout that, in spite of years of research, competi-tiveness of the hard coal carburetion plants hasnot been achieved yet. Classic technology of coaldust combustion is still unparalleled as regardsthe effect, availability, reliability and durability ofequipment. None of the world plants perform the

carburetion on the hard coal commercial basis,but only on the basis of the waste from oil proce-

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Tablica 3 Usporedba ekasnosti i trokova hvatanja i izdvajanja CO

2iz elektrana loenih ugljenom [5], [6] i [7]

Table 3 - Comparison of efciency and isolation of CO2from the coal-red power plants [5], [6] and [7]

HICO2-Ox, pokazuje dobre rezultate na jednom

malom pokaznom postrojenju toplinske snage od30 MW, ali na pitanja o ivotnom vijeku opremekotlovskog postrojenja nema odgovora. Izgara-nje u struji kisika, HICO

2-Ox, je po ocjeni struke

u prednosti kod dogradnje na postojea postro-jenja budui da je potrebno izgraditi samo novo

kotlovsko postrojenje; postojee parno-turbinskopostrojenje ostaje u funkciji.

ssing in reneries. Oxyfuel, CICO2-Ox, shows good

results on one small demonstration plant with30 MW(thermal), but it does not have answers asregards the life span of the boiler plant equipment.According to professional judgement, oxyfuel,CICO

2-Ox is in an advantageous position when it

comes to upgrading of the existing plants because

the only thing that is required is the constructionof a new boiler plant; the existing steam-turbineplant remains in operation.

Tip HICO2tehnologije /

Type of CICO2technology

HICO2-AC HICO

2-BC HICO

2-Ox + DESOx

Izvor podataka /Information source 2003 IAE GHG 2003 IEA GHG

2002 CTH Lippendorfprojekt / project

Tip proizvodne jedinice /

Production unit type

klasini /

classic

+ HICO2

klasini /

classic

+ HICO2

klasini(zrak)/classic (air)

Kisikom /oxygen

+ HICO2

Termoelektrana na ugljen /Coal-red thermal power plant

Praina /Dust

Praina /Dust

Rasplinjavanje/ Carburetion

Rasplinjavanje/ Carburetion

Lignitpraina /Lignite dust

Lignitpraina /Lignite dust

Jedinina snaga /Unit power, MW

e

500 362 776 676 865 681

Neto ekasnost /Net efciency, %

46 33 43 34 43 34

Emisija /EmissionCO

2, kg/MWh

e

722 148 763 142 858 69

Uhvaeno /CapturedCO

2, kg/MWh

e

- 850 - 809 - 1085

Izbjegnuta emisija u zrak /Avoided emission into air,kg/MWh

e(*)

- 574 - 621 - 852

Specino ulaganje /Specic investment,EUR/kW

e(**)

1020 1855 1370 1860 1270 1790

Troak pogona i odravanja /Cost of operation andmaintenance, EUR/MWh

e

7 13 12 16 3,9 3,9

Troak izbjegnutog CO2/ Cost of

avoided CO2, EUR/t CO

2

0 39,3 0 23,1 0 14,7

Hvatanje i izdvajanje su energetski vrlo intenzivnitehnoloki procesi koji imaju za posljedicu znaa-

jan porast potronje ugljena i prirodnog plina zavlastitu potronju. Raspon prirasta vlastite po-tronje procesa se kree od oko 39 %za dananjeizvedbe do oekivanih 6 %za napredne izvedbe ubudunosti iza 2025. Energetska ekasnost proi-zvodnje elektrine energije je jedan od preduvjetaza koritenje HITS u energetskom sektoru. Na-

knadna dogradnja HITS-a na vrlo ekasne kombiblokove loene prirodnim plinom bi moda mogla

Napomena / Remark:(*)Izbjegnuta emisija u zrak = (CO

2emisija kg/MWh

eiz klasinog tipa elektrane) (CO

2emisija kg/MWhe klasini + HICO2)/Avo-

ided emission into air = (CO2emission kg/MWhe from the classic power plant type) (CO

2emission kg/MWh

eclassic + CICO

2)

(**)ulaganja bez troka kapitala i graevinskog zemljita na zelenoj livadi / investment without capital costs and constructionland on green meadows procjene specinih ulaganja su napravljene prije naglog skoka opreme koncem 2008. godine za 50 %do 70 %/

assessments of specic investments have been made before the abrupt leap, at the end of 2008, of 50 % to 70 %

komprimiranje ugljikovog dioksida / compression of carbon dioxide na /at100 bar.

Energy-wise, capture and isolation are very inten-sive technological processes the consequence ofwhich is signicant increase of consumption ofcoal and natural gas for own consumption. Thescope of increment of own process consumptionuctuates from about 39 %for todays performan-ce up to the expected 6 %for advanced performan-ces in the future after 2025. Electricity productionenergetic efciency is one of the preconditions for

the use of the CITS in the energy sector. Subsequ-ent upgrading of the CITS to very efcient combi-

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biti opravdana opcija, ukoliko cijena prirodnogplina bude dovoljno niska.

Noviji tehnoloki postupci, esto pekulativnenaravi, zasnovani na separatorima, izgaranju ki-sikom u kombinaciji s naprednim rjeenjima zanjegovu proizvodnju, kemijskoj petlji i elijama

goriva, smatraju se obeavajuim za smanjiva-nje vlastite potronje procesa HICO2. Kombini-ranje biomasom loenih postrojenja za raspli-njavanje goriva s HITS-om moe postati veomaprihvatljivo, ak i za mnogo manja postrojenjaod ugljenom loenih postrojenja za rasplinjava-nje i to zbog dvostruke koristi od CO

2u uspored-

bi prema ugljenu s HITS-om. Takva kombinacijaima negativnu emisiju, jer se ugljik iz biomasetemelji na CO

2 koji je uhvaen iz atmosfere (i

moe ponovno biti vraen ili izdvojen).

4 TEHNOLOGIJA TRANSPOR-TA IZDVOJENOG CO2

CO2moe biti transportiran cjevovodima, elje-

znikim cisternama i brodovima. U praksi, zbogvelikog volumena, jedino su transport cjevovodi-ma i brodovima trokovno prihvatljivi. Openitose smatra da transportni trokovi, bez obzira narastojanja i koliine, trebaju biti manji dio uku-pnih trokova HITS-a. Trokovi transporta CO

2po

jedinici teine su daleko nii, nego za prirodni plinili vodik, jer je CO

2u tekuem ili nadkritinom

stanju 10 do 100 puta vee gustoe. Zbog toga je,po jedinici teine, transport CO2trokovno mno-

go sliniji transportu nafte nego prirodnog plinaili vodika. Inenjerska studija za termoelektranuKarsto u Norvekoj, na prirodni plin, ukazuje datransport cjevovodom predstavlja 40 %ukupnihulaganja u HITS. Opisani sluaj je specian jere se cjevovod velikih dimenzija polagati povr-inski zbog specinih geolokih uvjeta.

Transport cjevovodom je nepobitno dokazanatehnologija u dugogodinjoj praksi i ne pred-stavlja poseban rizik, ukoliko se odabere od-

govarajua komercijalno provjerena opremasukladna zakonskoj regulativi. Trenutano jena globalnoj razini aktivno oko 3 100 km cje-vovoda, godinjeg kapaciteta oko 45 Mt CO

2

na tlaku 120 bardo 140 bar. Nije bilo incidena-ta velikog rizika po okoli. Prikladno smjeteniHITSprojekti mogu znaajno smanjiti potrebuza ekstenzivnim transportnim sustavima. Iznu-eni smjetaj HITSprojekata, poput postojeihlokacija termoelektrana, transportne sustavemoe poveavati stotinama kilometara, tada jenuno izgraditi magistralnu transportnu mreuna koju bi bio prikljuen vei broj termoelektra-

na i spremnika CO2radi smanjenja trokova iz-gradnje i pogona.

nation blocks red by natural gas could be a justiedoption if the natural gas price was low enough.

Recent technological procedure, often of speculativenature, based on separators, oxygen combustion incombination with advanced solutions for their pro-duction, the chemical loop and fuel cells, are consi-

dered promising for the reduction of own consump-tion of the CICO2 process. Combining the biomass-red carburetion plants with the CITS could becomevery acceptable, even for plants much smaller thanthe coal-red carburetion plants and that becauseof the double benet of CO

2in comparison with the

coal combined with the CITS. Such a combinationhas negative emission because the coal from thebiomass is based on CO

2captured from the atmosp-

here (which can be returned or isolated).

4 THE TECHNOLOGY FOR THE

TRANSPORT OF THE ISOLATEDCO

2

CO2can be transported by pipelines, railway tankers

and ships. In practice, because of the extensive volu-me, only transport by pipelines and ships is accepta-ble as regards their costs. It is generally consideredthat transport costs, regardless of the distance andthe quantities, have to be lower than the total CITScosts. The costs for the transport of CO

2per weight

unit are by far lower than for natural gas or hydro-gen because CO

2 in liquid or supercritical state is

of 10 or 100 times greater density. Thus, accordingto the weight unit, CO2transport is cost-wise much

more similar to oil transport than to natural gas orhydrogen transport. Engineering study for the Kar-sto thermal power plant in Norway, red by naturalgas, shows that transport by pipelines makes 40 %of total investments into the CITS. The above case isspecic because the large-size pipeline will be laidsupercially due to specic geological conditions.

Transport by pipelines is a technology irrefutablyproven through years of practice and does not re-present a special risk if adequate, commercially te-

sted, equipment, compliant with legal regulations, ischosen. At the moment, at the global level, about 3100 kmpipelines are active, and their annual capaci-ty amounts to about 45 Mt CO

2at the pressure of 120

barto 140 bar. There were no incidents of high riskfor the environment. Suitably positioned CITSpro-jects could signicantly reduce the need for extensi-ve transport systems. The extorted location of CITSprojects, such as the existing locations of thermalpower plants, can expand the transport systems byhundreds of kilometres; therefore, it is necessaryto build a main transport network onto which a si-gnicant number of thermal power plants and CO

2

reservoirs would be connected for the purpose ofreducing construction and operation costs.

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ski prijevoz CO2moe biti istog reda veliine kao

i transport svih speciciranih roba zajedno! Zbogtoga izazovi koji stoje pred razvojem sustava zatransport CO

2 nikako ne smiju biti podcijenjeni.

Neki struni krugovi smatraju organiziranje glo-balnog transporta upitnim u bliskoj budunostite polau nade u razvoj spekulativne tehnologije

uklanjanja ugljikovog dioksida iz zraka!

5 TEHNOLOGIJA SPREMANJACO

2Generalno, jedina realna opcija u iduem kratko-ronom i srednjoronom vremenskom perioduplaniranja je podzemno skladitenje CO

2u du-

bokim leitima nafte, plina, ugljena i naslagamapropusnih stijena koja sadre vodu visokog salini-teta (u nastavku slani vodonosnik).

U drugi plan se stavlja mogunost spremanje uoceane i nadzemno skladitenje i to zbog rizikapo okoli i problema koji mogu pratiti spremanje inadzor spremljenog CO

2.

Teoretski potencijal i kapacitet spremanja CO2

u duboke slane vodonosnike se procjenjuje na1 000 Gtdo 10 000 Gt, to omoguava spremanjedecenijima i stotinama godina. Naslage slanihvodonosnika, kao potencijalnih spremnika, sudaleko ravnomjernije rasporeene od leita naf-te i prirodnog plina. Trenutano vrlo uspjeno radiodlaganje CO

2u slani vodonosnik Sleipner (Nor-

veka)[9] kapaciteta 1 000 kt/god. Usporedbe radi,proizvodna postrojenja Hrvatske elektroprivreded.d. imaju godinju emisiju oko 6 000 kt CO

2.

Duboka nalazita plina i nafte mogu pohranjivatidecenijima emisiju CO

2uz prihvatljiv stupanj rizi-

ka. Injektiranje CO2radi unaprjeenja iskoritenja

leita fosilnih goriva moe postati, rana i kljuna,povoljna prilika za spremanje, i to posebno onda,kada se mogu ostvariti prihodi koji pokrivaju sveili dio trokova HITS. Realizirano je nekoliko proje-kata od kojih je najvei lociran u Weyburnu (USA/

Kanada)kapaciteta 2 000 kt/gods ciljem povea-nja iscrpka nafte i Snhvit (Norveka)700 kt/godu slani vodonosnik. Projekti su pokazali pogonskusposobnost spremanja CO

2u podzemna skladi-

ta. Svi navedeni projekti su namijenjeni za po-veanje iscrpka nafte injektiranjem CO

2ili kiselih

plinova u buotine. Potencijal ovakvih projekatanije do sada dovoljno distribuiran.

Trenutano se istraivanje i razvoj tehnolokogpostupka skladitenja fokusira na sljedee opci-

je:

poveanje iscrpka nafte utiskivanjem CO2 uleite, (u nastavku EOR)

that, the challenges which are set before the CO2

transport system should not be underestimatedno matter what. Some professional circles believethat the organization of the global transport in thenear future is questionable and they have expec-tations as regards the development of speculativetechnology for the removal of carbon dioxide from

the air!

5 CO2STORAGE TECHNOLOGY

Generally, the only real option in the followingshort-term and middle-term planning period isunderground storage of the CO

2 in deep oil, gas

and coal deposits and layers of porous rocks whi-ch contain high-salinity water (hereinafter: salineaquifer).

The position of second importance is given to the

possibility of storage in oceans and surface storageand that without risk for the environment and theproblems which could accompany the storage andsupervision of the stored CO

2.

Theoretically, the potential and capacity of CO2sto-

rage in deep saline aquifers is estimated at 1 000 Gtup to 10 000 Gtwhich enables storage for decadesand hundreds of years. Saline aquifers layers, aspotential reservoirs, are far more equally spreadthan oil and natural gas deposits. At the moment,the storage of CO

2 into the Sleipner saline aqui-

fer (Norway) [9] with the capacity of 1 000 kt/year

is operating very successfully. For the purpose ofcomparison, the plants of Hrvatska elektroprivredad.d. have annual emissions of about 6 000 kt CO

2.

Deep gas and oil sites can store CO2 emissions

for decades with an acceptable risk level. CO2

injections for the purpose of improvement of em-ployment of fossil fuel layers can become an earlyfavourable chance for storage with key importance,especially when income can be realized which co-vers all or a part of the CITS costs. Several projectshave been realized the greatest of these is loca-ted in Weyburn (USA/Canada)and has a capacity of2 000 kt/year its purpose is enhanced oil recovery;and Snhvit (Norway)has a capacity of 700 kt/year into the saline aquifer. The projects have shownthe plants capability of storing CO

2in underground

reservoirs. All the above projects are intended forenhanced oil recovery by injection of CO

2or acid

gases into the boreholes. The potential of theseprojects has not been distributed enough so far.

At the moment, research and development of thetechnological process of storage focuses on thefollowing options:

enhanced oil recovery by CO2injection into the

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poveanje iscrpka prirodnog plina utiskiva-njem CO

2u leite, (u nastavku EGR),

poveanje iscrpka metana utiskivanjem CO2

u leita ugljena, (u nastavku ECBM), spremanje u iscrpljena leita nafte ili pri-

rodnog plina, spremanje u duboke slane vodonosnike (u

nastavku SA), ostale opcije skladitenja.

U veem broju objavljenih studija se navodi dae trokovi skladitenja biti sekundarne va-nosti u usporedbi s trokovima hvatanja i tran-sporta. Tvrdnja je jedino tona ukoliko je troakkompresije ukljuen u trokove hvatanja i tran-sporta. Trokove je vrlo teko uprosjeiti buduida osciliraju ovisno od sluaja do sluaja 5 (aki 10)puta. Radi jednostavnije analize je pretpo-stavljena vrijednost tlaka skladita od 100 bar.Tlak utiskivanja i rastojanje na koje se tran-

sportira odreuju polazni tlak CO2. Tlak utiski-vanja je ovisan o dubini injektiranja i o tlanomprolu u podzemlju. Minimalna dubina skladi-tenja je oko 800 m (na toj dubini je CO

2u su-

perkritinom stanju). U superkritinom stanjune postoji vidljivi prijelaz iz plinovitog u tekuestanje pri porastu tlaka. Gustoa CO

2pri 100 C

i 200 bar je 0,5 t/m3 a pri 500 bar 0,8 t/m3.Lokalni tlak i temperatura odreuju gustouCO

2i ona se obino kree u rasponu od 0,61 t/m3

do 0,72 t/m3.

Veina potencijalnih spremnika je locirana na

dubinama 2 kmdo 4 kmispod povrine. Za spre-mnike na dubinama od800 km, moe biti dovoljantlak utiskivanja od 100 bar. Meutim spremanjau iscrpljena leita plinskih polja e zahtijevatipovrinski tlak pred utiskivanjem od 200 bar do300 bar, tablica 4. Sastavni dio tehnolokog po-stupka je i recirkuliranje CO

2, na ega se troi

veoma znaajna energija. Na primjer, u praksikod poveanja iscrpka nafte utiskivanjem CO

2u

leite, u stalnoj recirkulaciji se nalazi od 16 %do 40 %mase CO

2koja se utiskuje (20 %do 67 %

se obino u konanici trajno zadri u sloju!).

Kod poveanja iscrpka prirodnog plina utiskiva-njem CO

2u leite, koliina zadranog i uskla-

ditenog CO2 u sloju, kojom se postie eljeni

uinak, iznosi skromnih 14 %! Recirkuliranakoliina CO

2, kod opcije poveanja iscrpka meta-

na utiskivanjem u leita ugljena, moe biti vrlovelika ukoliko CO

2kroz pukotine stijena obilazi

leite ugljena/metana ili ako samo leite vesadri veu koliinu prirodnog CO

2. Prosjeno

se, u opciji utiskivanja u leite ugljen/metanobino zadrava oko 20 %.

deposit, (hereinafter EOR) enhanced natural gas recovery by CO

2injection

into the deposit, (hereinafter EGR) enhanced coal bed methane extraction by injec-

tion of CO2into coal beds, (hereinafter ECBM)

storage in depleted oil or natural gas deposits, storage in deep saline aquifers (hereinafter:

SA), other storage options.

A large number of published studies state thatstorage costs will be of secondary importance incomparison with capture and transportation costs.The claim is accurate only if the compression costis included in capture and transportation costs. It isvery difcult to determine the average of the costsbecause they oscillate, depending on the case, by 5(even up to 10)times. For the purpose of a simpleranalysis, the value of storage pressure is assumedto be 100 bar. The injection pressure and the dis-

tance of the transportation are the determinantsof the initial CO2pressure. The injection pressure

depends on the injection depth and the undergro-und pressure prole. The minimum storage depthis about 800 m(at that depth, CO

2is in supercritical

state). At increase of pressure in supercritical statethere is no evident transition from gaseous to liquidstate. CO

2density at 100 Cand 200 baris 0,5 t/m3

and at 500 barit is 500 bar 0,8 t/m3. Local pressureand temperature determine CO

2density and it usu-

ally uctuates in the scope between 0,61 t/m3up to0,72 t/m3.

Most potential reservoirs are located at the depths of2 kmto 4 kmbeneath the surface. For the reservoirsat the depths of 800 km, injection pressure of 100 barcould sufce. However, storage in depleted gas el-ds will require a surface pressure prior to injectionof 200 barup to 300 bar, Table 4. An integral partof the technological process is also the recyclingof CO

2 which consumes a signicant amount of

energy. For example, in practice, at enhanced oilrecovery by injection of CO

2into the deposit, there is

about 16 %up to 40 %of CO2mass which is in con-

stant recirculation and which is injected (20 %up to67 %usually ends up in the layer permanently!).

At enhanced natural gas recovery by injection ofCO

2 into the deposit, the amount of CO

2 retained

and stored in the layer which enables the achieve-ment of the desired effect, amount to a mere 14 %!The quantity of CO

2in recirculation, at the enhan-

ced coal bed methane extraction by injection intocoal beds, may be very high if the CO

2roams the

coal/methane bed through rock fractures or if thebed itself already contains a large quantity of natu-ral CO

2. At the bed injection option, coal/methane

usually lingers at about 20 %.

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5.1 Tehnoloki postupci EOR i EGR

Poveanje iscrpka nafte utiskivanjem CO2u le-

ita donosi najvee prihode u usporedbi s osta-lim opcijama. U nekim posebnim sluajevima sespremanjem moe jedno vrijeme ostvariti i istadobit (diktirano potranjom i cijenom barela naf-te). Presudne su geoloke formacije i lokacijaleita u odnosu na izvor CO

2.

U pogonu je 2004. godine bilo 105 skladita tipaEOR, od kojih se 85 nalazi u SAD i 8 u Kanadi.Vei broj projekata je u razliitom stupnju razvo-

ja. Primarni i sekundarni naini iskoritavanjanaftnih leita openito imaju za posljedicu iscr-pak izmeu 40 %i 50 %. To ovisi od: komplek-

snosti i uvjeta u leitu, strategije iskoritavanjaleita i ekonomskih kriterija. Dobivanje naftetercijarnim metodama ili metodama poveanjaiscrpka (EOR)kljuni je proces nadomjetanja ilipoveanja rezervi koje se mogu koristiti na eko-nomian nain, i to bez primjene konvencional-nih metoda. Utiskivanje raznih plinova se danassmatra drugom (prva je voda)po djelotvornostimetodom poveanja iscrpka nafte. Utiskivanjevode ili plinova u iscrpljena naftna polja povea-va tlak u leitu koji omoguava istiskivanje nafteiz upljina stijena i strujanje prema proizvodnimbuotinama.

U SAD se tijekom 2003. godine proizvodilo oko200 000 bbl nafte po danu utiskivanjem CO

2 u

naftna leita. Ovaj postupak je zastupljen s udje-lom od oko 31 %u ukupnoj proizvodnji nafte ter-cijarnim mjerama poveanja iscrpka. Preostalih69 %ini utiskivanje duika, dimnih plinova, uglji-kovodika, vodene pare i polimera. Koliine CO

2

utisnute radi poveanja iscrpka nafte iznose oko32 000 kt/godCO

2iz prirodnih izvora i oko 11 000 kt

iz industrijskih procesa. Izvan SAD postoji ne-koliko projekata u pogonu. EOR utiskivanje CO

2

radi poveanja iscrpka nafte se primjenjuje vie

od tri desetljea i smatra se provjerenom teh-nologijom. Meutim, ova tehnologija je razvijena

5.1 EOR and EGR technological procedures

Enhanced oil recovery by injection of CO2 into the

deposits yields the highest income in comparisonwith the other options. In certain special cases, thestorage may, for a certain time, yield pure prot(dictated by demand and oil barrel price)as well.Geological formations and deposit locations as re-gards the CO

2source are decisive.

In 2004, 105 storages of EOR type were in operation;85 of these were located in the USA and Canada. Asignicant number of projects is in different deve-lopmental stages. Primary and secondary methodsof oil deposit exploitation generally result in theextraction of between 40 %and 50 %. That depends

on: deposit complexity and state, deposit exploita-tion strategies and economic criteria. Obtainmentof oil by tertiary methods or enhanced oil recoverymethods (EOR)is the key process for the substituti-on or increase of reserves which may be used in aneconomical manner and that without the applicati-on of conventional methods. Today, the injection ofdifferent gases is considered to be the second mosteffective method of enhanced oil recovery (the rstbeing the injection of water). The injection of wateror gases into depleted oil elds increases the de-posit pressure which enables the oil to be extractedfrom the rocks cavities and the circulation towards

production boreholes.

During 2003, in the USA, about 200 000 bbl of oilwere produced daily by injection of CO

2into oil de-

posits. This procedure participates with about 31 %in the total oil production by virtue of tertiary enhan-ced recovery methods. The remaining 69 % inclu-des the injection of nitrogen, ue gases, hydrocar-bon, water vapour and polymers. Quantities of CO

2

injected for the purpose of enhanced oil recoveryamount to about 32 000 kt/year CO

2 from natural

sources and to about 11 000 ktfrom industrial pro-cesses. There are several operating projects outsi-

de the USA. EOR CO2 injection for the purpose ofenhanced oil recovery has been implemented for

Tlak od 100 bar na 800 mdubine / Pressure of 100

bar at the depth of 800 m,GJ

e/t CO

2

Tlak od 200 bar na1 600 m dubine / Pressureof 200 bar at the depth of 1

600 m,GJe/t CO

2

Poveanje iscrpka nafte utiskivanjem CO2 /Enhanced oil recovery by CO

2injection 0,34 0,50

Poveanje iscrpka prirodnog plina utiskivanjem CO2/

Enhanced natural gas recovery by CO2injection

0,25 0,40

Poveanje iscrpka metana utiskivanjem CO2/

Enhanced coal bed methane extraction by injection of CO2

0,25 0,40

Spremanje CO2u duboke vodonosnike /

Storage of CO2into deep aquifers 0,22 0,38

Tablica 4 Potrebna energija tlaenja CO2 za injektiranje ovisno o vrsti spremnika i dubini [9]Table 4 - CO2pressing energy necessary for the injection depending on the type of reservoir and depth [9]

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s ciljem poveanja iscrpka nafte, a ne za trajnospremanje CO

2. Poveanje iscrpka nafte tercijar-

nim mjerama u prosjeku obino poveava uku-pno iskoritenje naftnih polja do 50 %. EOR se nemoe obino primijeniti na sva naftna polja. Du-bina leita nafte obino mora biti vea od 600 m.Sirova nafta treba biti gustoe najvie 910 kg/m3,

to ini ovu metodu nepodobnom za teke nafte,uljni pijesak ili leita s plinskom kapom. Utiski-vanje CO

2je ogranieno na naftna polja kod ko-

jih je zavrena proizvodnja primarnim mjerama(tlak leita)i sekundarnim mjerama (pumpanjei utiskivanje vode). U sluaju velikih plinskih kapaekasnost utiskivanja CO

2je ograniena. Znaa-

jan dio utisnutog CO2se vraa s naftom i vodom

na povrinu; tada se CO2mora izdvojiti i ponovno

utiskivati. Po zatvaranju naftnih polja angairaniCO

2je trajno spremljen. Do temperatura leita

od 120 C, CO2se mijea s naftom, dok na viim

temperaturama CO2nadomjeta naftu. Povoljni-

je je mijeanje CO2s naftom jer rezultira relativ-no veim iscrpkom. Mijeanje CO2i nafte omo-

guava da se na tonu nafte utisne 2,4 t CO2do

3 t CO2. Procjene potencijala spremanja u buo-

tine naftnih polja osciliraju i ovise o kriterijimaselekcije (trokovi, geoloka struktura, koncen-tracija polja). Nove utisne buotine za EOR pred-stavljaju glavni dio ulaganja.

Za EOR treba postojati potencijal od mini-malno 5 milijuna barela nafte i vie od 10 bu-otina. Tada bi ukupni pr fte oko 110 USD/t(15 USD/bbl), uz pretpostavljenu koliinu utiski-

vanja od 2,5 t CO2po toni sirove nafte, dobit je oko25 USD/t CO2za gratis koliinu CO

2. Pretpostav-

ljena dobit je proraunata za izvrsnu specinuutisnutu koliinu; to kod veine leita nafte nijemogue postii, tako da je i dobit znatno manja.

U veini polja je nuno buiti nove utisne buo-tine, budui da su stare eksploatacijski nepouz-dane; zapaena su izbijanja CO

2kroz zabrtvljene

buotine. Tehno-ekonomske analize opravdano-sti mogu, zbog velikog broja nepoznanica podci-

jeniti potencijal tehnologije EOR; to je sluaj sutiskivanjem u polja Sjevernog mora kod kojih je

iscrpak udvostruen.

EGR je teoretska metoda podizanja tlaka u iscr-pljenim (oko 85 %)plinskim leitima. Podobnaiscrpljena leita metana imaju tlak od 20 bardo50 bar. Bez obzira na stanje u kojem se nalazi,CO

2(plinovito, tekue ili superkritino)je znaaj-

no gui od CH4pri svim relevantnim tlakovima

i temperaturama i ima tendenciju strujanja nanie pri utiskivanju u buotinu, to ima za poslje-dicu istiskivanje prirodnog metana i podizanjetlaka u leitu. Utiskivanje CO

2 do 2007. godi-

ne nije koriteno u komercijalne svrhe. Postoje

dvojbe oko opravdanosti primjene ove teoretskemetode. Sve ovisi o vremenu potrebom da CO

2

more than three decades and is considered testedtechnology. However, this technology has been de-veloped with the aim to increase oil recovery andnot for permanent storage of CO

2. Enhanced oil re-

covery by tertiary measures usually increases thetotal exploitation of oil elds by up to 50 % in theaverage. The EOR usually cannot be applied to all

oil elds. Oil deposit depth usually has to be over600 m. Crude oil density has to be at the most, andthis makes this method ineligible for heavy oils, oilsands or gas-cap deposits. CO

2injection is limited

to oil elds in which the production by primary met-hods (deposit pressure) and secondary methods(pumping and water injection)is completed. In caseof large gas caps, the efciency of CO

2injection is li-

mited. A signicant share of the injected CO2comes

back with oil and water onto the surface; CO2must

then be separated and re-injected. After the sealingof the oil elds, the employed CO

2is stored perma-

nently. Up to the deposit temperatures of 120 C,

CO2is mixed with oil, while at higher temperatures,CO2substitutes oil. Mixing with CO

2is more favou-

rable because it yields relatively higher extractionratios. Mixing CO

2and oil provides for the injection

of 2,4 t CO2up to 3 t CO

2per ton of oil. Estimates

of the potential of the storage in oil eld boreholesvary and depend on the selection criteria (costs, ge-ological structure, eld concentration). New injecti-on boreholes for the EOR constitute the major partof the investment.

The EOR requires the potential of at least 5 millionoil barrels and more than 10 boreholes. Total pro-

duction costs would then amount to (without the CO2cost)about 50 USD/t(7 USD/bbl). If at the top of theborehole the oil price is about110 USD/t (15 USD/bbl)with the presumed amount of injection of 2,5 t C O

2

per ton of crude oil, the prot is about 25 USD/t CO2

for a gratis amount of CO2. The predicted prot is

calculated for an excellent specic injected quantityand this cannot be achieved in most oil deposits andtherefore the prot is lower as well.

In most of the elds, new injection boreholes needto be drilled because the old ones are unreliable forexploitation; CO

2bursts through sealed boreholes

have been recorded. Technological-economicaljustiability analyses could, because of the largenumber of unknown terms, underestimate the po-tential of the EOR technology which is the case withthe injections into the Northern Sea elds which yi-eld double extraction ratios.

EGR is the theoretical method of pressure increasein depleted (about 85 %)gas deposits. Eligible de-pleted methane beds have pressures of 20 barupto 50 bar. Regardless of its state (gaseous, liquid orsupercritical), CO

2is signicantly denser than CH

4

at all relevant pressures and temperatures and has

the tendency of downward ow at injection into theborehole, the consequence of which is the extrac-

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dopre do plinskog leita. Procjenjuje se da ka-pacitet spremanja CO

2u plinska leita ima vei

potencijal od mogunosti spremanja u leitanafte. Tehno-ekonomskim analizama opravda-nosti veeg broja projekata su utvreni znaajnomanji prihodi (npr. oko 1,8 GJprirodnog plina sedobije utiskivanjem jedne tone CO

2) nego kod

utiskivanje u leita nafte.5.2 Spremanje u iscrpljena leita nafte iliprirodnog plina

Operacija spremanja je vrlo jednostavna bu-dui da jedino treba izgraditi utisne buotine(ovisno o geologiji polja i brzini utiskivanja). Veidio postojee infrastrukture se moe iskoristi-ti, to znatno smanjuje ulaganja. U budunostie potencijal spremanja rasti jer e biti sve veibroj iscrpljenih leita nafte i plina i to naroitona Bliskom istoku i u zemljama biveg SSSR-a.

Koritenje njihovog potencijala e podrazumi-jevati brodski transport CO2do tih regija; to u

sutini smanjuje njihov ekonomski potencijal.Ukupni iskoristivi kapacitet spremanja u iscr-pljena leita prirodnog plina se procjenjuju na1 000 Gt CO

2i odgovara svjetskoj emisiji od 50-

ak godina.

Ovo je vrlo gruba teoretska procjena kapacitetaiscrpljenih leita, stvarni potencijal moe bitibitno reduciran prirodnim zavodnjavanjem (po-tapanjem)i nemogunou postizanja izvornogtlaka leita.

Vano je napomenuti da je odlaganje u iscrplje-na i naputena leita nafte i prirodnog plina(ukljuujui i opcije poveanja iscrpka aktivnihleita) osjetno manji rizik nego spremanje uduboke slane vodonosnike, budui da je geolo-gija vodonosnika esto velika nepoznanica.

5.3 Odplinjavanje leita ugljena od metana

Poveanje iscrpka metana (ugljeni plin)iz lei-ta ugljena je spekulativna metoda. Kod kon-vencionalnog iskoritenja metana iz leita

ugljena se moe postii 40 %do 50 % iscrpkau neposrednoj blizini buotine, dok se u sluajuutiskivanja CO

2iscrpak teoretski moe poveati

na 90 %do 100 %. ECBM je ogranien na le-ita ugljena koja nije mogue eksploatirati ilinisu tehno-ekonomski isplativa, to je glavniizvor neizvjesnosti koji ovisi o razvoju rudarsketehnologije i energetskih potreba. ECBM semoe primijeniti u leitima ugljena dovoljnepropusnosti. Porastom tlaka, adsorpcija CO

2

raste od 2 mola/molu metana na 700 mna 5mola/molu na 1 500

m. Rezerve ugljena ne smi-

ju biti na dubinama veim od 2 000 m jer po-

rast temperature ograniava sadraj metanau ugljenu, a porast tlaka na veim dubinama

tion of natural methane and increase of pressurein the deposit. Until 2007, injection of CO

2has not

been used for commercial purposes. It is not certainwhether the application of this method is justied. Itall depends on the time necessary for CO

2to reach

the gas deposit. The capacity of CO2storage in gas

deposits is estimated to be of larger potential than

the possibility of storage into oil deposits. Technolo-gical-economical justiability analyses of many pro-jects determined much lesser income (e.g. about 1,8GJof natural gas is obtained by injection of one tonof CO

2)than at injection into oil deposits.

5.2 Storage in depleted oil or natural gas

deposits

The storage activity is quite simple because onlyinjection boreholes need to be constructed (depen-ding on the eld geology and the injection speed).Most of the existing infrastructure can be used and

this signicantly reduces the investments. The sto-rage capacity will grow in the future because thenumber of depleted oil and gas deposits will grow,particularly in the Middle East and the former USSRcountries. The use of the potential thereof will requ-ire ship transport of CO

2to those regions; this basi-

cally reduces their economic potential. Total usefulcapacity of storage into depleted natural gas de-posits is estimated at 1 000 Gt CO

2and this equals

some 50 years of world emission.

This is a very rough theoretical estimate of the de-pleted deposits capacity; actual capacity may be si-

gnicantly reduced by natural inundation (ooding)and by the inability to achieve the original depositpressure.

It is important to mention that disposal into depletedand abandoned oil and natural gas deposits (inclu-ding the options of increase of active deposit extrac-tion ratios)bears signicantly less risk than storageinto deep saline aquifers, as the geology of the aqui-fers is often a great unknown.

5.3 Coal seams methane degassing

Enhanced methane (coal gas)extraction from coalseams is a speculative method. At conventionalexploitation of methane from coal seams, in the di-rect vicinity of the borehole, 40 %up to 50 %can beobtained, while in the case of injection of CO

2, the

extraction ratio can theoretically rise to 90 %up to100 %. ECBM is limited to coal seams which cannotbe exploited or which are not technologically-econo-mically cost-effective. This is the main source of un-certainty and it depends on the development of minetechnology and energy requirements. ECBM can beapplied in coal seams of sufcient permeability. Byincrease of pressure, the CO

2adsorption increases

from 2 mol/ 1 mol of methane at 700 mto 5 mol/1mol methane at 1 500

m. Coal reserves must not be

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smanjuje propusnost leita. Sadraj meta-na u dubokim leitima moe varirati od 5 m3/tdo 25 m3/t ugljena ovisno od debljine sloja (iostalim znaajkama), tako da ECBM potencijalpo buotini i trokovima spremanja CO

2varira s

faktorom pet i vie. To znai da su najatraktivnijeopcije s gledita iscrpka metana - plitke rezerve

ugljena debelog sloja, ali one esto ne ispunjava-ju temeljne kriterije eksploatacije.

Selekcija leita ugljena za ECBM se mora te-meljiti na kriterijima kao to su:

homogena rezerva, poprena i vertikalna izoliranost od okolnih

slojeva, minimalna ispresijecanost rasjedima i nabo-

rima, propusnost minimalno od, 1x1015 m2 do

5x1015m2, veina ugljenih leita su mnogo

manje propusnosti.

Kriterije prema iskustvenim procjenama zadovo-ljava manji broj potencijalnih leita. Visoki sadr-aj metana, stratigraki koncentriranog leita

je u prednosti nad vieslojnim leitem. Mogu-nost iskoritenja ili eksport metana cjevovodomkao i raspoloivost CO

2(lokalne termoelektrane,

industrija ili magistralni cjevovodi za CO2)pozi-

tivno utjeu na selekciju leita. Svjetski potenci-jal spremanja u duboka neeksploatabilna leitaugljena se procjenjuje na 150 Gt CO

2. Analize po-

kazuju da samo 5 Gt CO2do15 Gt CO

2ECBM pro-

jekata pokazuje moguu protabilnost, dok oko50 Gt kapaciteta moe biti koriteno s umjere-nim trokovima spremanja, ispod 50 USD/t CO

2,

u koje nisu ukljueni trokovi hvatanja i transport(IEA GHG Programme, 1998). Uz pretpostavku da2 mola CO

2zamjenjuje jedan mol metana, uti-

snutih 10 Gt CO2odgovara energiji od 90 EJ

(E

= eksa = 1018=trilijun) sadranoj u prirodnomplinu potroenom tijekom jedne godine u svije-tu! Masovnije iskoritenje ECBM tehnologije sezbog toga trenutano smatra kcijom u realnomelektroenergetskom sektoru.

Ugljen je sklon bubrenju u kontaktu s CO2toima za posljedicu redukciju propusnosti. Niskapropusnost, u nekim sluajevima, moe bitinadjaana pucanjem formacije sloja ugljena.Troak izgradnje buotina za utiskivanje ekspo-nencijalno raste s dubinom leita ugljena; kosobuenje je 70 %

skuplje od vertikalnog buenja.

Velika gustoa utisnih buotina je presudnopotrebna za ECBR. Trokovi utisnih buotinapredstavljaju ukupnih trokova. Vrlo teko jegeneralno odrediti ukupne trokove za velikerazmjere primjene, budui da osjetno variraju odsluaja do sluaja. Veliki broj buotina dodatno

smanjuje upotrebljivost zemljita. Kod plitkih na-lazita ugljena pojava i problem dreniranja vode

at depths exceeding 2 000 m because the increaseof temperature limits the content of methane in thecoal, and the increase of pressure at greater dept-hs reduces deposit permeability. Methane contentin deep deposits may vary from 5 m3/tup to 25 m3/tof coal, depending on layer thickness (and otherproperties) and therefore the ECBM potential per

borehole and CO2storage costs vary with a factorof 5 or more. This means that the most attractiveoptions, from the aspect of the methane extract, areshallow thick-layer coal reserves but these often donot meet the basic exploitation criteria.

Selection of coal seams for the ECBM must be ba-sed on criteria such as:

homogenous reserve, transverse and vertical isolation from the sur-

rounding layers, minimal intersection by faults and folds,

permeability of at least1x1015

m2

up to5x1015

m2

,most coal deposits are of signicantly lesserpermeability.

According to experiential estimates, only a smallnumber of potential deposits meets the criteria.High methane content of a stratigraphically con-centrated deposit is preferable to the multi-layerdeposit. The possibility of exploitation or export ofmethane by pipelines as well as the availability ofCO

2(local thermal power plants, industry or main

CO2pipelines)positively impact the deposit selec-

tion. The global potential of storage into deep non-

exploitable coal seams is estimated at 150 Gt CO2.Analyses show that only 5 Gt CO2up to 15 Gt CO

2

of ECBM projects show potential protability, whileabout 50 Gtof the capacity can be used with mo-derate storage costs lower than 50 USD/t CO

2and

exclusive of capture and transportation costs (IEAGHG Programme, 1998). Under the presumptionthat 2 mol of CO

2substitute one mol of methane,

injected 10 Gt CO2equal the energy of 90 EJ con-

tained in natural gas used in a year throughout theworld! Mass exploitation of the ECBM technology istherefore currently not viewed as ctive in the realelectric power sector.

Coal tends to expand in contact with CO2which re-

sults in reduced permeability. Low permeability, insome cases, can be overcome by a burst of the coallayer formation. The cost of construction of injecti-on boreholes increases exponentially with the dep-th of the coal deposit; diagonal drilling is by 70 %more expensive than vertical drilling. High densityof injection boreholes is decisively necessary for theECBR. Costs of injection borehole represent 3/4 oftotal costs. It is very hard to determine generallythe total costs for wide application scopes becau-se they vary signicantly from case to case. A large

number of boreholes further reduces land exploi-tability. With shallow coal deposits, the occurrence

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iz slojeva ugljena moe prouzroiti tonjenje tla,a kod dubokih leita problem zbrinjavanja sla-ne vode moe biti naglaen. Dananji pilot pro-

jekti ECBM se nalaze u SAD i Kanadi, a trei je urazradi, u Poljskoj. Dosadanji rezultati nisu do-voljno uvjerljivi i smatraju se nedovoljnim za ge-neralne zakljuke vezane za dalji razvoj komer-

cijalizacije ECBM. Studija za projekt ECBM u Ni-zozemskoj pretpostavlja specinu cijenu tran-sporta i spremanja u rasponu od 50 USD/t CO

2

do 75 USD/t CO2bez trokova hvatanja i izdvaja-

nja i to pri cijeni plina od 3,5 USD/GJ.

Zakljuiti se moe da je tehnologija ECBM u ra-nom stupnju razvoja, tako da je njena perspek-tiva jo uvijek neizvjesna. Po realizaciji nekolikoveih razvojnih projekata moi e se nakon nji-hove viegodinje eksploatacije dati meritornaocjena o njihovoj sigurnosti i okolinoj prihvat-ljivosti. U veini sluajeva e dobit biti limitirana

gubitcima zbog nepredvidivih dodatnih troko-va.

5.4 Spremanje u duboki slani vodonosnik

Slani vodonosnik je sloj sedimentnih stijena,zasienih vodom, u koje se moe ukoliko su za-dovoljavajue poroznosti utiskivati uid. Poroznivodonosnici vrste spuvaste strukture su pri-kazani na slici 4. Karbonatne stijene su obinovodonosnici zadovoljavajue poroznosti.

and the problem of draining water from coal layerscan cause soil sinking, and in deeper layers, the pro-blem of disposal of saline water could be pronoun-ced. Todays ECBM pilot projects are located in theUSA and Canada and the third is being elaboratedin Poland. Results so far are not convincing enou-gh and are considered insufcient to make general

conclusions for the further development of ECBMcommercialization. The study for the ECBM projectin the Netherlands presumes the specic transportand storage price in the range between 50 USD/t CO

2

up to 50 USD/t CO2 exclusive of capture and iso-

lation costs and that being at the price of gas of3,5 USD/GJ.

The conclusion can be drawn that the ECBM tech-nology is at an early phase of development, so thatits perspective is still uncertain. After the implemen-tation of a few larger projects and several years ofexploitation, a merit-based assessment of their sa-

fety and environmental acceptability will be made. Inmost cases, the prot will be limited by losses due tounpredicted additional costs.

5.4 Storage in deep saline aquifers

A saline aquifer is a layer of water-protected sedi-mentary rocks into which uid can be injected if theyare of adequate porosity. Porous aquifers of solidspongy structure are shown in Figure 4. Carbonaterocks are usually aquifers of adequate porosity.

Slika 4 Pjeenjak duljine 2 cm (lijevo)i karbonatna stijena (desno)[10]Figure 4 2-cm long sandstone (left)and carbonate rock (right)[10]

Voda zadrana milijunima godine u porama ipukotinama stijena sadri visoku koncentracijuotopina, obino je to slana voda neprikladna zapie. Kristalno i metamorfno kamenje, poputgranita, nema potrebnu poroznost za skladite-nje CO

2, ali ukoliko se nalazi iznad sloja pjee-

njaka, funkcionira kao prirodno brtvilo. Otvorenii uski vodonosnici nemaju prirodnih barijera zastrujanje vode, tako da se odvija spora prirodnacirkulacija i naalost nisu podobni za skladite-nje CO

2.

U Norvekoj se na plinskom leitu Sleipner, se-parirani CO

2 skladiti u slani vodonosnik ispod

Water which has been kept for millions of years inpores and crevices contains a high concentration ofsolvents and this is usually saline water unsuitablefor drinking. Crystal and metamorphic stones, suchas granite, do not have the necessary porosity forthe storage of CO

2, but if located above the sandsto-

ne layer, they operate as natural sealants. Openand narrow aquifers do not contain natural barriersfor water ow, so that slow and natural circulationtakes place and thus these are unfortunately notadequate for storage of CO

2.

In Norway, in the Sleipner gas deposit, the separa-ted CO

2is stored in the saline aquifer under the gas

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