Resid Conversion Through the Aquaconversion™ Technology —An Economical and Environmental SolutionR. Marzin, P. Pereira, L. Zacarias, and L. Rivas, PDVSA-INTEVEP, Los Teques, Venezuela; Michael McGrath, Foster Wheeler, Clinton, New Jersey, USA; and Gregory J. Thompson, UOP, Des Plaines, Illinois, USAAbstractINTEVEP’s Aquaconversion™ technology features a mild residuehydrogenation/cracking process that is achieved by aunique catalyst activated transfer of hydrogen from waterpresent in the process to the residual oil being thermallycracked.The operating conditions are such that it will be an economicallyattractive process for many refiners. The application of this technology in refinery allows an increase in conversion level as well as in fuel gain above those normally achieved in similar processes such as thermal cracking or visbreaking units that are characterized by their low capital andinvestment costs. The absence of any solid by-product such ascoke will be another significant advantage of the technology for many refiners.This novel concept has been fully demonstrated in large scale pilot plants. The process itself, has also been confirmed at the commercial scale during short test runs in a full-size visbreaker. An immediate economically advantageous area ofapplication of the technology is the upgrading of H/XH crudes, to produce a synthetic crude meeting transport and stability specifications. A project for upgrading 100,000 BPD of an extra-heavy Venezuelan crude from 9–15°API utilizing this technology is now under planning by a PDVSA affiliate.The simplicity of the process and the absence of any solid byproduct will allow this grassroots upgrade to be located in or nearby to the production field, substantially reducing the requirements for diluent transport.Economics for the AquaconversionTM based integrated production-upgrading plant show a clear advantage of this technology over coking to produce transportable heavy syncrudes.This paper reviews the process features and demonstrationsteps as well as the ongoing applications of the technologyand its economic competitiveness.IntroductionThe rush for heavy and extraheavy (H/XH) oil has already started in Venezuela. Multinational oil companies are pledging nearly $17 billion along with Petroleos de Venezuela PDVSA) to develop Venezuela’s vast Orinoco reserves.

These companies are looking at these projects as a way to secure their crude supply. Another attraction is that Venezuela is right on the doorstep of the United States, which is a huge market for crude oil. The reasons for this recent interest in heavy oil are the improvements in production and upgradingtechnologies as well as attractive fiscal incentives that have been offered by the Venezuelan government. If oil companies can make these projects pay, the implications for world supply are significant because of the huge reserves in the Orinoco Belt.Within PDVSA, technology has been recognized from the early days as the only way to significantly reduce production and upgrading costs of these H/XH crudes and economically convert them into high-quality fuels for the growing energy market. PDVSA-Intevep, the technological arm of PDVSA,has devoted significant resources since the early 1970s toanswer this technology need. Today, a new thermal catalyticsteam conversion technology called Aquaconversion™ processis now available as a competitive alternative to traditionalupgrading routes. This process allows the H/XH crude oil of 9API to be upgraded to a syncrude of 15 API. This syncrudecan be transported without the need for diluent and processedto final fuels in conventional refineries. Although the conventionaldelayed coking technology has been selected in the fourprojects for the Orinoco Belt already approved by the VenezuelanCongress, this new technology is seriously being consideredfor the new projects that are in the conceptual stage. Thispaper describes the Aquaconversion technology and its economicscompared with alternative upgrading routes.Technologies for H/XH CrudesUpgradingThe countries with the largest resources in H/XH crudes are Canada, Russia, and Venezuela. Current world reserves of H/XH crudes and bitumen are estimated to be about 1,000 billion barrels (proven + potential recovery), and these three countries have more than 80% of these reserves. Venezuelaconcentrates most of its heavy oil and bitumen in the Orinoco 2Belt in the eastern part of the country. Stretching 800 km from east to west and 200 km from north to south, this area represents the largest accumulation of heavy crude in the world (Figure 1). Back in the late 1970s, PDVSA made a huge effort to quantify the in-place reserves, which were estimated at 1.2trillion barrels. 1

Recoverable reserves were estimated at 267 billions barrels. At an aggressive exploitation rate of 1 million barrels per day, these reserves would represent more than 700 years of production.Several international companies have shown an interest in investing in Venezuela for the production and upgrading of these H/XH crude reserves. Their main interest is to secure a reliable source of oil supply at a minimum cost per barrel. To date, four strategic associations among PDVSA and othercompanies have been approved by the Venezuelan Congress(Table 1), and others are at the conceptual stage. Several technologieshave been considered within these approved projects,but the final decision in all four cases was to use delayed cokingtechnology. With the existing delayed coking in nationaland international refineries and these new projects in theOrinoco Belt, PDVSA will become the leader in this technologyon an installed capacity basis (about 15% of the worldpetroleum coke market). These four upgrading plants will bebuilt at Jose in eastern Venezuela in what is called the “Condominium”because the different projects will share some offsitesand utilities. A typical block diagram is shown in Figure2. A more complete description of these projects can be foundelsewhere.2More advanced technologies are being considered for theother projects being conceptualized. BP is looking at the ebullatedbed technology from IFP and Lummus; the emphasis ison a lower-pressure level and optimized catalyst consumptionto improve the economics of such a route. Exxon is bringingin its own Flexcor-T technology, which can be described as alow-severity visbreaking that reduces H/XH crude acidity,slightly improves crude API and viscosity, and maintains syncrudestability. Coastal has been looking at visbreaking as anupgrading route. In these associations, the PDVSA share ofthe investment will be significant, and because of limitedresources, further projects will be considered only on the basisof originality while maintaining the same level of economicalattractiveness. This approach opens the door to what has beenreferred to as a “beauty contest.” In such a contest, delayedcoking could be at a disadvantage. However, the novel Aquaconversiontechnology, developed by PDVSA-Intevep, isentering this “beauty contest” as a favorite, and the following

sections describe its concept and advantages.

The Aquaconversion Process

The main strategy in the conceptualizing of the Aquaconversionprocess as an option for H/XH crude upgrading is to use aconversion process severity that is just sufficient to transformthese heavy crudes into transportable and marketable stablesyncrude and still maintain investment and operating costs atminimum levels. Thus, further conversion will have to be doneabroad in the client’s refinery using existing capacity. Additionalinvestment in this refinery may have to be considered. Acomparison of grassroots investment in Venezuela and additionalinvestment in existing refineries abroad clearly favorsthe latter, and as a result, the concept of doing just the necessaryamount of upgrading in Venezuela should be more economicallyattractive.Coke handling and shipping requirements have forced theexisting projects to move to Jose and as a result the transportationof diluent over more than 250 Km between the production site and the upgrader is required. An important aspect of the Aquaconversion technology is that it does not produce any solid by-product such as coke, nor does it require any hydrogen source or high-pressure equipment. Consequently, Aquaconversioncan be located in the production area, and thus the need for external diluent and its transport over large distances is eliminated. As can be seen on the process scheme shown of Figure 3, the natural light distillates from the raw crude can beused as diluent for both the production and desalting processes.The restrictions on the diluent API gravity and viscositycan therefore be relaxed because of the shorter distancesassociated with the upgrader field location.

The process:

The Aquaconversion technology is a catalytic visbreaking process which operates in the presence of steam. The visbreaking technology is limited in conversión level because of the stability of the resulting product. Becauseone process requirement is that the syncrude has to be stable, standard visbreaking allows only a 2 API upgrading of the heavy crude and only a limited

viscosity reduction, which does not ensure its transport without external diluent. The Aquaconversion process pushes this maximum conversionlevel within the stability specification by adding a homogeneouscatalyst in the presence of steam. This novel catalytic system allows hydrogen from the water to be transferred to the resid when operated at the conditionsnormally used for the visbreaking process. Similar operating conditions (pressure and temperature) are used. This hydrogen incorporation is much lower than that obtained when using a deep hydroconversion process under high hydrogen partial pressure. Nevertheless, it is high enough to saturatethe free radicals, formed within the thermal process, that would normally lead to polymerization reactions that form large asphaltenes and cause stability problems. With this hydrogen incorporation, a higher conversion level can be

reached, thus enabling higher API and viscosity improvements to be achieved while maintaining product stability.The Aquaconversion reaction mechanism is

shown in Figure 4.

(1) R-Rn´ R. + Rn´. THERMAL CRACKING(2) H2O 2 H. + O. O-H BONDS DISSOCIATION(3) R., R n´. + 2 H. R-H, R n´-H FREE RADICAL H-SATURATION(4) Rn´.+ 2 O. Rn-1´ + CO 2 +H2 CARBON OXIDATION(5) Rn´., R. Rn´-Rn´ , R-R CONDENSATIONcat.cat.cat.

The catalyst precursor is dispersed in the feedstock byreaction with its polar components. The polar nature of theresulting mixture allows the catalyst to migrate toward thefeedstock’s more-aromatic, multiring components. The catalyst,which is produced and activated by heat in the presenceof water, then catalyzes the dissociation of water into hydrogenand oxygen radicals. As thermal cleavage of the carboncarbonbonds progresses, hydrocarbon free-radicals would 3begin to be formed. Unlike the typical visbreaking reactionsequence, where these materials polymerize to eventuallyform asphaltenes, the Aquaconversion reaction mechanismreduces the tendency for polymerization by promoting theaddition of hydrogen radicals to the hydrocarbon free-radical.This catalyst also accomplishes dealkylation of the alkyl aromaticstructures to form smaller aromatics, hydrogen, and carbon

dioxide. In addition, oxygen radicals from water saturatesome hydrocarbon free radicals to form carbon oxides, mostlycarbon dioxide because the thermodynamic equilibriumfavors its formation at the Aquaconversion temperature. Thisentire reaction sequence can effectively terminate severalundesirable asphaltene polymerization reactions, and resultsin a catalytic steam visbroken product with lower asphaltenecontent than conventional visbreaking.

Process development:The main stages in the development of the process are shown in Figure 5.

Initial studies at bench scale initiated in early 1990s, focused on catalyst andchemistry evaluation. The process was then evaluated in acontinuous 1 BPD pilot plant at PDVSA-Intevep to assess itsperformance using different feedstocks and operating conditions.Feedstock from refineries as well as H/XH crudes fromthe Orinoco Belt were tested in this small unit. The next stagewas the testing at commercial scale, which was performed inan existing visbreaking unit of 18,000 BPD capacity in theIsla refinery at Curacao. To adapt this unit to the Aquaconversionscheme, a catalyst preparation skid was designed andbuilt by PDVSA-INTEVEP and connected to the visbreakingplant. Two tests were performed in this unit in 1996 and 1997.Although some constraints specific to the unit did not allowthe process to reach its full potential, most of the processadvantages obtained at the pilot plant level were reproduced atcommercial scale. Additional adaptation of the unit is requiredto maintain commercial operation for a long period.

An existing 10 BPD pilot plant available at PDVSAINTEVEPwas then adapted to the Aquaconversion schemeand is now being used to evaluate and optimize the processingof H/XH crudes and to support engineering designs that arebeing carried out by companies interested in the technology.Several conceptual engineering studies are now being conductedto determine both investment and operating costs ofthe Aquaconversion process compared with other technologies.

AQUACONVERSION PERFORMANCEWITH H/XH CRUDES

As an example of the capability of the Aquaconversion process,its performance with the Pilon crude is described in thefollowing section. Pilon is a 14 API blend consisting of a mixtureof heavy crudes, such as Morichal or Cerro Negro, and adiluent. Its atmospheric resid is therefore representative of theOrinoco Belt resids, and its characteristics are shown in Table 2.This resid was fed in the Aquaconversion 10 BPD pilotplant at PDVSA-INTEVEP and processed at different severitylevels. The severity level was controlled through the soakertemperature, and its effect on product quality was monitoredprincipally in terms of stability through the P-value and resultingsyncrude API and viscosity. The results can be seen in Figures6–8. As severity is increased, a slow decrease in the Pvaluecan be observed, but it allows for a significant increasein the syncrude API of 5 and similarly a drastic reduction inthe syncrude viscosity of 99% at 50°C, which allows economicaltransportation. The improvement relative to visbreakingcan be derived from these same graphs through the differencein syncrude API and viscosity between 20% (visbreaking) and40% (Aquaconversion process) 500°C + conversion levels.Figure 9

shows the general mass balance of the Aquaconversionflow scheme derived from the same pilot plant test runwith Pilon. Important parameters of the Aquaconversion performanceare shown in Table 3. The most relevant are the positiveasphaltene and carbon conversions that are far superior tothe negative conversions typical of visbreaking even at lowerseverity. These parameters influence the product yield to beobtained when the syncrude is processed in the client refinery,where the resid will most probably be processed in a coker.The overall coke yield obtained when the resid is first processedin the Aquaconversion process before being fed in acoker is lower than the yield from a single one stage full conversioncoker.Aquaconversion EconomicsTo assess the economics of the Aquaconversion route, a comparative

economical evaluation was performed for a typicalOrinoco Belt project. Three cases were selected: Aquaconversion process,Delayed coking, and Dilution. For the delayed coking case, the upgrader was located at Jose because existing projects based on this technology to date have chosen thatlocation. For the Aquaconversion case, the upgrader waslocated in the field because of the advantages specific to thetechnology. The three cases are shown in Figure 10. For theeconomical evaluation, the integrated production-upgradingscope was selected to fully present the attractiveness of theproject. The results shown in Figure 10 indicate that the Aquaconversionscheme is competitive with the traditional cokingroute.Based on the attractiveness of the Aquaconversion route,PDVSA-FAJA, which is the new organization of PDVSAlooking at all the Orinoco projects, is including Aquaconversionas an alternative for the new projects in the conceptualstage. Several international potential partners for theseprojects have signed secrecy agreement with the technologylicensors (UOP, Foster Wheeler, and Intevep) to fully evaluatethis new route.4

ConclusionPDVSA-INTEVEP has developed a new upgrading technologythat is competitive with the traditional delayed cokingroute. This technology has been tested extensively at pilotplant level and at commercial scale in an existing 18,000 BPDvisbreaker unit. The economics are attractive because the processuses a plant configuration similar to visbreaking with itslow pressure and temperature design parameters. The processallows the 9 API H/XH crude to be upgraded to a stable 15API syncrude with reduced bottoms that can be transportedwithout the need for diluent. Immediate plans are to adapt anexisting commercial visbreaking plant to the Aquaconversionmode to fully demonstrate the technology in long term operation.A syncrude shipment will be prepared from Orinoco H/XH crudes in this unit and tested in U.S. refineries to get an

early assessment of its performance in a client refinery. Severalinternational partners interested in joint ventures withPDVSA to secure their crude supply are now looking seriouslyat this new upgrading route. This new technological elementwithin the H/XH business could boost the exploitation ofthe huge existing reserves.References1. Tedeshi, M., Reserves and Production of Heavy CrudeOil and Natural Bitumen, 13thWPC, Topic 13, BuenosAires, Oct. 1991.2. Solari, R.B., Marzin, R., and Soler, L., Integration ofUpgrading in the Production of Extraheavy Crudes fromthe Orinoco Belt. 5thWorld Congress of Chemical Engineers,Paper 84c, San Diego, July 1996.3. Marzin, R., et al, The Aquaconversion Process, A newApproach to Residue Processing, 1998 NPRA AnnualMeeting, San Francisco, March 1998.

Diluted PilonCrude

350C+Resid

API gravitySulfur, wt%C7 Asphaltene, wt%Conradson carbon,

13.02.989.0911.3

7.13.6513.415.2

wt% Viscosity, cSt@ 60C

1498

@ 100C - 782

@ 135C - 152TAN, mg KOH/g 3.5 2.5Vanadium, wt ppm

271 449

Nickel, wt ppm 37 112

Diluted Pilon Crude and Resid Characteristics