kbr-unlocking current refinery constraints

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Authors:

Rashid Iqbal - KBR

Asif Khan - KBR

Odette Eng - KBR

Raymond Floyd - KBR

Publication / Presented:

PTQ Q2www.eptq.com

Date:

2008

UNLOCKING CURRENT

REFINERY CONSTRAINTS



Unlocking currentrefnery constraints

When processing heavy feeds, technology based on residuum supercritical solvent

extraction provides higher volumes of gas oil and DAO for conversion units. Potential

constraints through existing vacuum and coker units can also be resolved

The escalating demand or

petroleum-refned products andhigh dierentials between light

and heavy crude oils have increased the

usage o heavier crude oils.

Examples o heavy crude oils beingused by reiners today includeAthabasca bitumen, Lloydminster and

Cold Lake heavy oils rom Canada,Maya rom Mexico, Arab Heavy rom

the Middle East, and other Arican andVenezuelan crude oils. When added to

the conventional crude diet, theseheavier crude oils with higher resid

content will either increase uel oilmake or begin to burden existing

vacuum and coking units. At the sametime, the gas oil content in heavier

crudes is usually lower compared to

conventional crudes, resulting in lowereed to conversion units, such as the

FCC or hydrocracker unit.The increasing oil price is motivating

refners to look or solutions to extractmore rom the bottom o the barrel in a

more cost-eective way. Refners areincreasingly using solvent deasphalting

in the ollowing applications:— Debottlenecking existing vacuumand coking units: or refneries eedingvacuum residue to cokers, the addition

o KBR’s ROSE (residuum oil supercriticalextraction) unit reduces the coker eed

rate by up to 50%. The coke make is alsoreduced by 15–20%, thus debottle-

necking the existing cokers

— In place o vacuum distillation: the higher yields rom a ROSE unit

when compared to vacuum distillationunits help refners improve overall

refnery liquid yields by 2–5 vol%.Figures 2 and 3 show the processing

options or debottlenecking existingvacuum and coker units by using a ROSE

unit in a revamp situation, or investingin a ROSE unit instead o a vacuum unit

in a grassroots application.

SDA historyThe oil refning industry has used

solvent deasphalting (SDA) or over 50years. Conventional SDA units separate

solvent rom deasphalted oils (DAO) by

boiling. The SDA process was initiallyused or recovering lube base oils rom

vacuum residues. The units were small,so energy efciency was not a high

priority. The Kerr McGee Corporationstarted research in the 1950s to extend

the application o solvent extraction inthe production o uels and to improve

energy efciency by separating solvent

rom the DAO in supercritical phase.The frst supercritical solvent-extraction

ROSE units were licensed in 1979.Subsequently, the success o the process

has turned conventional SDA into anuneconomical practice in comparison.

KBR acquired the technology rom the

Kerr McGee Corporation in 1995. Todate, 48 ROSE licenses with a combined

capacity o over 900 000 bpsd have beenobtained by users all over the world.

Rashid Iqbal, Asi Khan, Odette Eng and Raymond Floyd

KBR

www.eptq.com PTQ Q2 2008 31

Figure 1 Increased yields rom bottom o barrel

Figure 2 ROSE unit to debottleneck vacuum and coker

Figure 3 ROSE unit where there is novacuum and coker



ComparisonsHow is this process dierent toconventional SDA? It is a highly energy-

efcient solvent deasphalting technology

in which most o the solvent is recoveredin supercritical mode. In Figure 4, point

“C” represents supercritical phaseseparation conditions and point “F”

represents conditions used byconventional SDA processes or

separating solvent. The energy requiredor supercritical separation (C–A) is less

than one-third o that required orconventional (F–A) SDA processes.

The ROSE process uses special internalsand design parameters that permit the

extraction o maximum quantities o high-quality DAO rom atmospheric or

vacuum residues and other heavypetroleum eedstocks. The high-efciency

internals reduce capital costs by allowing

the use o smaller separator vessels. Theasphaltene content o the DAO rom the

ROSE unit is normally less than 200ppmw, compared to around 800 ppmw

or other SDA processes. The DAOproduced also has substantially reduced

contaminants, such as nickel, vanadium,sulphur and Conradson carbon when

compared to residues.These benefts (ie, lower energy usage,

use o smaller separators and cleanerDAO) have been particularly useul in

the conversion o conventional andthird-party SDA units to ROSE. Some

licensees have doubled throughput,

reduced energy consumption by asmuch as 30%, improved DAO yield by

2–5% and at the same time have seen anorder o magnitude reduction in

asphaltene carryover in DAO.In summary, the process oers the

ollowing operational and economic

advantages over conventional SDA:— Higher yield and improved DAO

quality— Flexibility in varying DAO yield and

quality by adjusting operatingconditions and, i necessary, changing

solvent— Supercritical solvent recovery

signifcantly reduces operating costs byalmost eliminating evaporation and

condensation o solvent.

Unlocking current refneryconstraintsWith the higher utilisation o heavy

crude oils, refners oten encounterhigher resid loads with higher levels o

contaminants (such as sulphur,nitrogen, metals, CCR), increased

aromatics content and, more oten thannot, higher acid content in their eeds.

On the other hand, the gas oil contento the new eeds will be lower, creating

a potential loss o eed in downstreamVGO processing units, such as the FCC

or hydrocracking units. All these

elements present challenges that refnersneed to solve.

Refners with no coker or vacuum unitsVacuum distillation units (VDUs) areconsidered to be one o the conventional

building blocks in refnery operations.However, with time, the higher

utilisation o heavy and high-acid crude

oils has started to push the limit o thevacuum distillation process. Highoperating temperatures in vacuum units

have a tendency to crack some o theheavy crude oils. To avoid coking o

internals due to cracking, vacuum units

have to operate at lower temperatures,thereby limiting the lit o vacuum gas

oils. This is an ineective use o vacuumunits when it comes to the distillation o

heavy oils, which are prone to cracking,and this limitation will hold back more

heavy material in the residue stream.Another aspect also associated with

some heavy crudes is the high acidcontent. The acids in crude require the

use o 317L stainless steel or equivalentmaterial in all areas where temperatures

exceed 450°F. Thus, the vacuum towerup to the top neck has to be lined with

317L. This increases both the cost o the

vacuum unit and the overall projectschedule.

These two problems can be easilysolved using a ROSE unit in place o a

vacuum unit.3 The reasons or the

avourable economics in using a ROSEunit in place o a vacuum unit are as

ollows:— Higher yields: the lower operating

temperatures in ROSE units eliminatethe potential or cracking o the heavy

oil, providing the ability to extractmuch higher volumes o DAO than the

VGO removed by the vacuum unit.

Examples o higher yields rom somecrude oils are as ollows:

Vacuum VGO, ROSE DAO,vol% vol%

Arab Heavy 26.5 38.5Maya 26.5 34.0

Athabasca Bitumen 16.0 32.0

Marlim 36.0 52.5

— The high hydrogen content o DAOgives higher liquid yields: ROSEseparates DAO by dissolving primarily

parafns in solvent. Thus, the DAOproduced is more parafnic than the

VGO, which includes aromatics boilingbelow the VGO cut-o temperatures.

Thereore, the DAO has a higher

hydrogen content and gives a substantialyield advantage over VGO in downstream

catalytic cracking units. For example, theWatson “K” actor o VGO or 71 vol%

yield on ATB is 11.67. The Watson K orDAO at a yield o 90 vol% is 11.74. So not

only was more DAO was extracted, it alsohad higher hydrogen content

Figure 4 Supercritical solvent recovery mollier diagram

“The ROSE process uses

special internals and

design parameters that

permit the extraction o

maximum quantities o

high-quality DAO rom

atmospheric or vacuum

residues and other heavy

petroleum eedstocks”




— Reduced residue stream: in manycases, the amount o ROSE asphaltenes

produced is about hal o the vacuum

bottoms. This reduces the size o a newcoker when coking is used to crack

residue; i the residues are blended intouel oil, the uel oil make drops to less

than hal when compared to vacuumdistillation, saving substantial quantities

o valuable cutter stock.

Debottlenecking existing vacuum and coker unitsVacuum units generally become the frst

bottleneck when refners increase theintake o more heavy and/or high acid

crudes. The use o heavy oils increasesthe eed to the vacuum unit, overloading

its hydraulic capacity. Refners canchoose to revamp the constrained

vacuum units and associated cokers.However, when aced with high acid

crudes, revamping could becomeexpensive i existing vacuum columns

and associated transer lines do not havethe high metallurgy capable o handling

the high-acid crudes. The capacity and

the metallurgy constraints can beremoved by adding a ROSE unit in

parallel with the vacuum unit, aspreviously shown in Figure 2. The

unit can process all atmosphericbottoms above the capacity o the

vacuum units. It can also process allatmospheric bottoms rom the high-

acid crude train.Table 1 compares yields and qualities

o DAO separated rom atmospheric

(ATB) and vacuum bottoms (VTB) romArab Heavy and Maya crude oils. Column1 shows that 49.7 Mbpsd o vacuum resid

is produced as coker eed when processing

200 Mbpsd o Arab Heavy crude oil. TheROSE unit can separate 23.3 Mbpsd o

DAO as eed or hydroprocessing andFCC units, thus reducing total coker eed

to 26.5 Mbpsd, almost a 47% reduction.The DAO, when mixed with VGO, has

sufciently low metals to allow processingin fxed-bed hydroprocessing units.

While calculating yields, the CCR inasphalt has been limited to 38 wt% to

allow cracking in most modern delayedcokers.

The cokers are the next bottlenecks.As described, the coker can be

debottlenecked by installing a ROSE

unit upstream rom the coker. Aspreviously described, in addition to the

hydraulic debottlenecking, the cokemake drops by about 20%, thus

debottlenecking the coke drums.3

An overall mass balance will indicate

that the total liquid yields per barrel o eed will be increased by approximately

3–5 vol%. In essence, this solution willhave the net result o converting low-

value coke product into high-valuerefnery liquid yield. Moreover, the

addition o a ROSE unit may reducedowntime, as opposed to revamping

both the vacuum unit and the coker.The technology thus oers the ollowing

economic and operational benefts toreiners over other upgrading

technologies:— Easy integration with downstream

units through yield and quality control

o DAO— Signifcantly lower capital and

operating costs— Ease in processing o high-acid crude

oils— Faster project execution through

modular construction— High reliability (>95% onstream

actor) and long cycles (up to nine years)between major turnarounds.

Figure 5 shows the simplicity o theprocess and the reason or the associated

low installation cost.

ROSE is a mark o KBR.

Reerences1 Nelson R S, Roodman G R, ROSE The

energy-efcient bottom o the barrelalternative, presented at the 1985 SpringAICHE Meeting, Houston, Texas, USA.

2 Abdel-Halim T, Upalla R, Bansal B, Floyd R,Eastwood D, ROSE and bottom-o-the barrel:a synergistic approach, presented at the 2ndBottom o the Barrel Technology Conerence,October 2002, Istanbul, Turkey.

3 Patel V, Iqbal R, Eng O, To vacuum or notto vacuum, Hydrocarbon Engineering , June2007.

Rashid Iqbal is director, resid upgrading,or KBR in Houston, Texas, USA.Email: [email protected] Khan is principal tech proessional,process, or KBR in Houston, Texas, USA.Odette Eng is vice president, rening, or KBR in Houston, Texas, USA.Email: [email protected] Floyd is technology manager,resid upgrading, or KBR in Houston,Texas, USA.


Figure 5 ROSE process fow diagram

Arab Heavy VTB Arab Heavy ATB Maya VTB Maya ATBFeedRate, kbpsd 49.7 103.3 63.6 116.9

API 3.2 11.5 -0.2 7.6CCR, % 23.8 12.4 31.2 18.3Metals, ppmw 251 129 816 477

DAO Prod.Rate, kbpsd 23.3 76.8 14.5 67.7

API 13.4 18.1 17.9 18.0CCR, % 6.0 2.2 4.4 1.5

Metals, ppmw 9 3 8 6

Pitch Prod.Rate, kbpsd 26.5 26.5 49.1 49.1

API -4.7 -4.7 -4.7 -4.7CCR, % 38 38 38 38

Basis: refnery eed rate: 200 000 bpsd

ROSE generates more feed for downstream units

Table 1

kbr-unlocking current refinery constraints

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