Economic Bottom of the Barrel Processing To Minimize Fuel Oil

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        Economic Bottom of the
        Barrel Processing
        To Minimize Fuel Oil
        Production                                                                            The best projects of the future
                                                                                           should not only allow processing of
                                                                                           less expensive, opportunistic crude
                                                                                           oils but should be able to reduce
        Vasant Patel*, Rashid Iqbal, Odette Eng, Anand                                     fuel oil make without compromising
                                                                                           refinery reliability. In order to meet
        Subramanian                                                                        the above objectives the new proj-
        Kellogg Brown & Root, Inc.                                                         ects may include some or all of the
                                                                                           following elements:
        Houston, Texas USA                                                                    ● Allow shift to less expensive

                                                                                           heavier, sour crude oils and other
        The recent years have been marked by global uncertainties                          opportunity crude oils.
                                                                                              ● Convert all or a high percent-
        ranging from economic to geopolitical. These uncertainties                         age of fuel oils, particularly high
        have resulted in a steep rise in crude prices affecting world-                     sulfur fuel oil, into more valuable
        wide refinery operations. Faced with the burden of skyrock-                        products.
                                                                                              ● Reduce processing cost by using
        eting feedstock prices and uncertainty of supplies, refiners                       more optimized processing scheme.
        are much more conscious of these issues than in years past.                           ● Reduce utility costs and keep

        As feedstock prices play a crucial part to the profitability of                    emissions low.
        refiners the natural thought is to find ways to process less                          TYPical residue
        expensive crude oils. As crude prices increase so does the                            ProcessiNG
64 64   cost for refiners to bring in feed to process at the refinery.                        coNFiGuraTioNs
        There are around 160 types of crude oils being produced
                                                                                              Simple Refinery
        worldwide and the price differentials between crude oils can
        be $15 /barrel or higher. Refiners find themselves faced
        with the difficult question of searching for crude blends to
        maximize the use of their existing assets or to choose crude
        blends, which will require additional capital investment but
        will offer opportunity to increase return on investment.

        I n parallel to this phenomenon,
          there is another challenge, which
        has developed through the years.
                                                    Two criTical issues:
                                                    crude oils & Fuel oil
                                                     As security of supply and rising
        As the world recognizes the benefits      crude prices are becoming greater
        of using natural gas as fuel, demand      concerns, refiners’ attention turn to       Representative of many Indian
        for fuel oil has seen a drop, adverse-    less traditional crude oils. As crude    refineries, these do not include any
        ly affecting fuel oil prices. This in     price differentials also continue to     conversion or upgrading facilities
        turn has weakened the economics           widen due to the direct link of sup-     for the bottom of barrel streams. The
        of those refiners with limited fuel       ply shortage & demand increase,          entire vacuum residue (VR) is typi-
        oil outlets, and has reached a level      refiners see in less traditional crude   cally disposed off by blending into
        where changes are needed.                 oils another venue to maximize mar-      high sulfur fuel oil product. When
           These are the major factors driv-      gins; but how to get there is the key    available, decant and cycle oils from
        ing refiners to look at ways to process   question. These crude oils could be      fluid cracking units, unconverted
        alternative lower costs crude oils,       high in Sulfur, low in API, contain-     oil from hydrocrackers, heavy gas
        and the primary cause of the wave of      ing high Total Acid Number (TAN).        oils, etc. can be used as cutter stocks
        interest in bottom of the barrel solu-    Production of less traditional crude     to produce a high sulfur fuel oil.
        tions. Most refineries will need to       oils is also on the rise.                Sometimes even higher value distil-
        install new units using either carbon        The net result of processing a        lates have to be blended into fuel oil
        rejection or / and hydrogen addition      higher volume of heavy or extra          to meet viscosity specifications.
        technologies to convert fuel oil into     heavy crudes in the refinery diet is        Fuel oil producers will also find it
        more valuable products. Many of           an increase in Vacuum Residue (VR)       difficult to sell large volumes of high
        the traditional solutions will result     volume and a decrease in feed sup-       sulfur fuel oil as new regulations
        in capital intensive projects. With       ply to the existing conversion units.    have already been introduced which
        coke disposal being a problem for            The disposition of this high sul-     limit sulfur in fuel oil. These refiner-
        certain refiners and the high cost        fur fuel oil will become difficult       ies typically look for the addition
        of hydrogen consumption becoming          due to new environmental require-        of cost effective residue upgrading
        an increasing burden, refiners often      ments. Moreover, with the decline        options.
        wonder what other alternatives they       in fuel oil demand and the natural          Some of the potential technolo-
        may have.                                 gas switch, fuel oil pricing could       gies that are available to the refiner
                                                  continue to drop in the long run.        for achieving the above goals are as

        PeTroleuM #5 / October 2008

   ● Technologies that reject car-           In refineries with no FCC pre-                    Typically 40 -70% of the VR can be
bon:                                      treatment, a significant debit in FCC                economically extracted at a quality
   - Solvent deasphalting (ROSETM)        performance will occur. In general,                  suitable for processing in an FCC
and Pelletizer (AQUAFORMTM)               a negative impact on existing sec-                   unit. The pitch can be pelletized for
   - Thermal cracking processes           ondary processing units – hydro-                     sale as solid fuel in the cement, steel
(coking, thermal cracking, & vis-         processing, FCC, reformer, sulfur                    or power industry.
breaking)                                 plant and amine system will occur.                      The sulfur or metals content in
   ● Technologies that add hydro-                                                              the feed is attractive to the cement
gen:                                        Hydrogen Addition                                  industry, which currently thrives on
   - Fixed bed hydrotreating /                                                                 low BTU coal and petroleum coke
hydrocracking                                       Vacuum
                                                                    Liquid Product
                                                                                               fuel sources. Specifically for the
   - Ebullated bed hydrotreating /                                                             Indian market, where the fuel needs
hydrocracking                                                                                  for the cement industry are enor-
   - Fluidized bed hydrocracking                        Vac resid
                                                                                               mous, the partial switch to high BTU
   All of the above technologies                                                               asphaltenes represents an attractive
except the fluidized bed hydroc-                                                               synergistic opportunity for both
racking are well established and are                                                           industries.
in use today. This paper will focus                                     LSFO
                                                                                                  This paper will focus on the tech-
on the ROSE and AQUAFORM                                                                       nologies involved highlighting the
technology option, the effects of the        Vacuum residues can be                            performance, benefits and limita-
DAO on FCC and the options for the        hydrotreated or even hydrocracked                    tions for the specific applications
disposition of Asphaltenes.               using either fixed bed or more typi-                 under consideration.
                                          cally in an ebullated bed reactor.
                                          The high metal content of the VR                        Supercritical Solvent Deasphalt-
  Carbon Rejection                        require use of guard beds or one of                  ing Unit - ROSETM
                                          the online catalyst removal / addi-                     Solvent extraction was first intro-
                                          tion systems to achieve long runs.                   duced in the 1930’s as a means of
                                          Unfortunately both options signifi-                  extracting paraffinic lube oil blend-
                                          cantly increase capital and operat-                  ing stocks from mixed base and
                                          ing costs.                                           naphthenic crude oils. After wide-
                                             The ebullated bed reactor designs                 spread implementation of fluid cata-
                                          include provision for online catalyst                lytic cracking, refiners soon recog-
                                          addition and removal. Resid hydro-                   nized the negative impact on FCC
                                          processing units are generally very                  yield performance from processing
                                          expensive and require significant                    aromatic feed stocks. Recogniz-
                                          plot space. The products from the                    ing an opportunity soon thereafter,
   Delayed coking is the most com-        ebullated bed units normally require                 refiners turned to solvent extraction
monly used carbon rejection pro-          further treating in fixed bed reac-                  as a means of producing viable high
cess. Roughly half of the US refiner-     tors. In most of the cases upgrading                 Watson K FCC feedstock from resi-
ies have cokers. Visbreaking and          the heaviest portion of the residue                  due that was otherwise too contami-
thermal cracking are less severe          through hydrogen addition will con-                  nated for economic FCC processing
thermal processes than delayed            sume large amounts of hydrogen                       (see Table 1).
coking and more popular in Europe.        and catalysts, and the incremental                      It was discovered that residual
Thermal cracking is normally used         benefits derived will not justify the                oils could be «decarbonized» with
for cracking distillates. Visbreak-       incremental investment require-                      paraffin solvents to produce FCC
ing is used for reducing viscosity of     ments.                                               feeds with sufficiently low concen-
residue by thermal cracking. These                                                             trations of carbon residue and met-
refineries include visbreaking/ther-                                                           als to allow economic processing in
mal cracking operations to reduce           solVeNT deasPHalTiNG                               the FCC units. In the 1970’s, Kerr
requirements for cutter stock for           wiTH PelleTiZaTioN                                 McKee developed a solvent deas-
blending into fuel oil.                                                                        phalting process, the ROSE Process,
   In delayed coking, VR feed can be                                                           that separates most of the solvent
typically cracked up to 65-80% with                                                            from the deasphalted oil (DAO) in
20-35% of the feed being rejected as                                                           the supercritical phase regime rath-
low value petroleum coke. The liq-                                                             er than utilizing energy intensive
uid products are further converted                                                             boil-off and condensation for sol-
into transportation fuels while gas                                                            vent recovery. The supercritical sol-
products are used as fuel.                                                                     vent recovery breakthrough greatly
   The cokers are capital intensive,                                                           reduced the utilities expense asso-
require large real estate, and will                                                            ciated with operation of the units,
produce hydrogen deficient product                                                             and the ROSE process quickly
streams that would require hydro-            The option to use Solvent Deas-                   became the dominant residue deas-
gen addition prior to being blended       phalting in combination with the                     phalting process. ROSE technology
in to the product streams or pro-         generation of solid fuels is a very                  was acquired by The M.W. Kellogg
cessed in the existing reformers and      cost effective means of dealing with                 Company in 1995 and now it is part
FCC units.                                atmospheric or vacuum residues and                   of the refining technology portfolio
                                          reducing the fuel oil production.                    offered by Kellogg Brown & Root
                                                                                               LLC (KBR).
  Table 1 – Watson K for typical FCC feedstocks                                                   The solvent deasphalting (SDA)
                                                                                               process removes asphaltenes from
Feedstock         Atm Resid     Vacuum      Propane          Butane                  Coker     atmospheric and vacuum residues
Source                          Gas Oil       DAO             DAO                    Gas Oil   using solvent extraction. Most of
Arabian Light       11.60        11.68       11.81            11.74                   11.4     metal, sulfur and carbon (Conrad-
Arabian Heavy       11.44        11.62       11.86            11.78                   11.4     son carbon -CCR) is concentrated in

                                                                                                         PeTroleuM #5 / October 2008

     the asphaltenes. The deasphalted                 FCC Feedstock Considerations              charged to FCC units with little or
     oil (DAO), which contains very low               Feed properties that are most             no changes to the FCC hardware.
     quantities of metals, low sulfur, and         important to consider when process-          However, the availability of these
     CCR, is an excellent feedstock for            ing residue in an FCC unit are (1)           high quality crude oils is diminish-
     processing in conventional refin-             asphaltenes (C7 insolubles) which            ing and more contaminated, heavier
     ery units, such as, fixed bed VGO             cause deactivation of downstream             crude oils are making up an increas-
     hydrotreatreaters and the FCC.                catalyst systems (2) vanadium,               ing proportion of the worlds crude
     They can also be processed in high            which is the controlling parameter           oil supply.
     pressure hydrocrackers and ther-              setting FCC catalyst make-up rates,             Even if blended in small concen-
     mal cracker units. Typical yield and          (3) carbon residue which is the major        trations into FCC feedstocks, atmo-
     quality are shown in Table 2.                 factor affecting coke burning and            spheric or vacuum residues from
         Several SDA units (mostly ROSE            catalyst cooling requirements, and           lower quality crude oils often con-
     units offered by KBR of Houston,              (4) hydrogen content which impacts           tain higher concentrations of met-
     Texas) are operating successfully             FCC conversion and yield selectiv-           als and carbon residue than would
     in combination with hydrocrackers,            ity.                                         be economic for FCC processing
     hydrotreaters, and FCC units. This               Atmospheric or Vacuum Residues            because of the contaminant’s impact
     is an important aspect of ROSE units          with lower concentrations of carbon          on required catalyst make-up rate
     as refiners move towards heavier              residue and metals, particularly par-        and FCC yields; therefore before
     crude oils. The contaminants, if left         affinic, low vanadium crude oils, are        processing in the FCC unit, the resi-
     in the processing chain, will become          naturally better suited to upgrading         dues from such crude oils must first
     the limiting factors of downstream            in FCC units, and often significant          be upgraded with such processes as
     units.                                        volumes of such residues or even 100         vacuum distillation, coking, residue
                                                   percent atmospheric residue can be           hydrotreating or solvent deasphalt-
                                                                                                ing to reduce carbon residue and
       Table 2 – ROSE Yields and Qualities                                                      metals content.
                                                                                                   ● While directly processing resi-
       Feed: Middle East Vacuum Residue
                                                                                                due from some high quality crude
                                                                                                oils in the FCC unit can be eco-
                                       VR Feed          Asphaltene             DAO              nomic, this option is not very flex-
     Yield, wt%                          100                 51                 49              ible with respect to refinery crude
     SG, at 15.5oC                      1.043              1.118              0.974             oil supply.
                                                                                                   ● Vacuum distillation can sepa-
     Sulfur, wt%                         5.7                7.3                 4.0
                                                                                                rate vacuum gas oil from atmospher-
66   Conradson carbon, wt%              23.8               40.0                 6.6
                                                                                                ic residue, but vacuum distillation
     Nickel+Vanadium, ppmw               222                425                 11
                                                                                                leaves potential FCC feed behind in
     C7 Insolubles                                                          <100 ppmw
                                                                                                the vacuum residue.
     Watson K                                                                  11.71               ● Coking eliminates vanadium

                                                                                                and carbon residue from its gas oil
       Table 3 – FCC Yields from VGO, DAO and CGO                                               products but the coker gas oils are
                                                                                                hydrogen deficient, resulting in poor
                                  100% DAO            100% VGO              100% CGO            yield selectivity when processed in
     API                             19.2                24.7                  19.0             an FCC unit.
     Sulfur, WT%                     0.79                0.75                                      ●   Residue hydrotreating can
     CCR, wt%                         3.9                0.39         Less than 1               reduce contaminants to economic
     NI + V, PPM                      16                  1           Less than 1               levels while increasing FCC feed
                                                                                                hydrogen content but the capi-
     FCC Yields, WT%
                                                                                                tal and operating costs of residue
           Conversion              80.3                  81.05                 63.2             hydrotreating are high.
           C2-                     4.86                   3.65                 1.49                ROSE solvent deasphalting sepa-
           Total C3’s               6.37                 6.80                  4.60             rates a less contaminated, hydro-
           Total C4’s              10.30                 11.76                 8.87             gen rich material (DAO) from atmo-
           Total Gasoline          48.98                 52.12                 40.16            spheric or vacuum residue that
           Total Cycle Oil         19.70                 18.95                 35.78            can be economically cracked in an
                                                                                                FCC unit, mitigating issues associ-
           Coke                     9.79                  6.72                  6.0
                                                                                                ated with the processing schemes
       % COMPONENT IN DAO                                                                       described above. The increased
                                                                                                hydrogen content and lower con-
     100                                                                                        taminants of the DAO relative to the
                                                                                                residue together with low invest-
                                                                                                ment and operating costs often
      80                                                                                        makes ROSE an economical option
                                                                                                for producing good quality FCC
                                                                                                feed from residue.
      60                                                                                           It is interesting to note that the
                                                                                                contaminants that are most detri-
                                                                                                mental to the FCC unit operation are
      40                                                              METALS                    also the ones that show the sharpest
                                  NITROGEN                                                      partitioning in the ROSE unit. e.g.
                                                         CCR                                    metals > carbon residue > nitrogen
      20                                                                                        > sulfur, resulting in a natural syn-
                                                                            ASPHALTENES         ergy between these processes.
                                                                                                   The contribution of DAO and
       0                                                                                        CGO added to VGOs is shown in
           0     10          20   30    40        50      60     70    80        90       100   Table 3. For the same operating
                                             DAO YIELD, VOL %

     PeTroleuM #5 / October 2008

severity, the conversion, yields, and        Specialty products, such as pav-      ratio of feed CCR to coke yield is
product quality from processing           ing asphalt or roofing asphalt, can      about 1.2 for this feedstock. Lower
VGO and DAO are about the same.           be made by blending the ROSE             CCR feedstocks can be expected to
A very interesting observation is the     asphaltenes with suitable aromatic       have a feed CCR to coke yield ratio
CCR content of the DAO; an equiva-        oils.                                    of 1.5 to 1.6 under similar condi-
lent CCR in the VGO would have                                                     tions.
made this an unacceptable FCC                Asphaltene Coking
feed; but not so for DAO. This obvi-         Asphaltenes may be successfully          Asphaltene
ously confirms that coke precursors       coked in refineries with existing           to Partial Oxidation Unit
in the FCC feed are obviously bet-        cokers. Many refiners are now suc-          The asphaltene can be fed to a
ter correlated by asphaltene con-         cessfully cracking asphaltenes in        partial oxidation unit to produce
centration as opposed to the coarser      their cokers. Normally asphaltene        synthesis gas. Hydrogen in the syn-
determination of carbon residue by        is blended with vacuum residuum          thesis gas can be used for hydropro-
Conradson Carbon measurement              to achieve good flow properties.         cessing units. The remaining syn-
method.                                   The blend is then cracked in cok-        thesis gas is fired to produce steam
                                          ers. Asphaltene cracking is being        and power. There are presently two
                                          carried out by both delayed and          ROSE units in operation feeding
  asPHalTeNe uTiliZaTioN                  fluid coker operators. Cracking          partial oxidation units and three
   Economic utilization of the            ROSE asphaltene instead of vacuum        more planned as the prime outlet for
asphaltene product from a ROSE            residuum reduces total coke make         their asphaltene product.
unit is the key to ROSE process           by 10-20%. The liquid yield also
economics. Listed below are some          improves. At the 2003 NPRA, some            Solid fuel
of the options refineries are utiliz-     refiners have reported the use of           This represents the most sim-
ing to maximize the value of ROSE         more than 50 percent asphaltenes in      ple and cost effective option for
asphaltene product followed by a          their coker feedstocks.KBR has pro-      asphaltene disposition for the Indian
discussion of each option, with spe-      cessed asphaltene in the coker pilot     market, where a large demand for
cial emphasis on solid fuels which        plant. Typical pilot plant yields from   high BTU solid fuel exists.
we believe will be very attractive for    coking the asphaltenes are provided         The heating value, organic car-
the Indian market.                        in Table 4.                              bon and chemical properties such
   ● Fuel oil blend component                Note that the coke yield is much      as sulfur, nickel and vanadium are
   ●     Specialty       commercial       less than would be expected from a       governed by the feed properties.
asphaltenes                               traditional feed with high CCR. The      The asphaltene pellets can be used
   ● Conversion (coker) feedstock
   ● Partial oxidation feedstock
   ● Solid fuel

    Asphaltene Product to Fuel Oil
    It is sometimes possible to burn
the asphaltene product directly
as fuel oil, but in most cases, it is
first blended with other low-value
streams to produce a lower viscosity
product that meets fuel oil speci-
fications. The fuel oil production
can often be cut to less than half by
installing a ROSE unit and blend-
ing asphaltenes instead of vacuum
residuum into fuel oil.
    Some     refiners    blend      the
asphaltenes with distillate materi-
als to produce No. 6 fuel oil. Light
cycle oil and slurry oil from the
FCCU makes excellent blending
stocks because of their high aro-
matic content. A visbreaker can
be used to reduce the viscosity of
the asphaltene and thus reduce the
required amount of blending stock.
However, the high sulfur content of
the asphaltene may limit its use in
No. 6 fuel oil production.
                                            Table 4 - Data from KBR Delayed Coker Pilot Plant
    Asphaltene quality depends on
crude slate, and as the crude slate
becomes heavier and more sour, the        Feed
asphaltene produced from these            Source                                          Pentane asphaltene
crude oils will also contain a higher     Conradson carbon, wt%                                   38
quantity of sulfur. Environmental         Yields, wt%
regulations will therefore dictate how          Gas                                               6.9
much flue gas cleanup is required
                                                C3-C3                                             3.8
and, hence, the viability of direct
firing burning of asphaltenes.                  C5-205°C                                         12.1
                                                205-343°C                                        16.4
  Commercial Asphaltenes                        343°C+                                           15.0
                                                Coke                                             45.8

                                                                                             PeTroleuM #5 / October 2008

     as solid fuel in the cement kilns,       dled, stored, and transported. The       helps to minimize dust formation
     the steel industry, and in the utility   asphaltene pellets have a higher         during transport.
     industries. The pellets can be added     heating value and better fuel prop-
     to fuel grade coke or coal as additive   erties compared to petroleum coke          coNclusioN
     to enhance combustion character-         and thus represent improved fuel            The combination of solvent deas-
     istics. The asphaltene pellets have      value.                                   phalting and asphaltene pelletizer
     20%-50% higher heating value than           A simplified flow diagram for the     technologies represents an econom-
     petroleum coke.                          AQUAFORM process is presented            ic solution to upgrade vacuum resi-
        The high HGI value of the pellets     below. Hot liquid asphaltenes are        dues and reduce or eliminate fuel oil
     indicates easy grindability. Unlike      pumped to a pelletizer vessel at         production that can be implemented
     coal, the asphaltene pellets have        the optimal temperature required         at a fraction of the cost of all other
     low ash content and high organic         for successful pelletization. Liquid     resid processing options.
     carbon content (high boiling hydro-      asphaltenes are converted to drop-          The deasphalted oil is an excel-
     carbons, typically >1000 F) that         lets in the vapor space of the pellet-   lent feedstock and can be easily
     provide improved combustion char-        izer vessel using a proprietary high     processed in the existing refinery
     acteristics.                             capacity feed distributor.               FCC or other conversion units, and
        In view of the superior heating          The surface hardened pellets          the solid asphaltene pellets can be
     value, combustion characteristics,       fall in to a water bath and on to a      sold to the cement, steel and power
     ease of grinding, the asphaltene pel-    vibrating screen where the pellets       industries.
     lets should demand a higher value        are dewatered. The pellets may be           Since the contaminants (metals,
     per ton when compared to fuel grade      transported to a silo or pit or other    sulfur etc.) are rejected in the solid
     coke and coal.                           loading facilities by a conveyor.        fuel to the cement industry, there is
                                                 KBR’s proprietary feed distribu-      very minimal impact to the auxiliary
       aQuaForMTM                             tor is the heart of the system, giv-     units (sulfur plant, amine regenera-
        There are existing older commer-      ing substantial capacity, flexibility,   tion etc.) within the refinery.
     cial technologies to produce solid       and reliability improvements versus         The Indian refiner and cement
     fuel from the solvent asphaltene.        other solidification process technol-    producer can benefit enormous-
     However, these processes are gener-      ogies. The feed distributor can be       ly from the synergies that exist
     ally high in maintenance, low in reli-   adjusted to vary the size of the pel-    between the two industries.          ■
     ability and are manpower intensive.      lets as well as unit capacity.
        KBR’s AQUAFORM technol-                  The pellets are near spherical
     ogy is an ideal solution to solidify     with an expected size distribution
     asphaltenes and other heavy hydro-       between 1 and 3 mm and have good
68   carbons. AQUAFORM is a low cost          grindability, storage and transpor-
     process, easy to operate, and has        tation characteristics as indicated
     a high expected on-stream factor.        by the high Hargrove Grindability
     This unit can process a variety of       Index (HGI), storage test tempera-
     feedstocks and is self cleaning dur-     ture and low friability. The high
     ing shutdown.                            angle of repose provides high capac-
        The pellets produced by the           ity on conveyors. The small amount
     AQUAFORM process are resistant           of residual moisture on the pellets
     to dusting and can be easily han-

     PeTroleuM #5 / October 2008

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