ing a commercially available simulation model.a The crude assay data are a com-
bination of several crude data bases.b The
Eagle Ford assay is an estimate.a, 5 The re-
ported Eagle Ford crude properties vary significantly depending on the production well, and a typical assay is not published. The Eagle Ford assay estimate assumes qualities similar to crudes having similar API gravities and properties as report- ed.5–8 Although not shown in the tables,
the individual test methods are the typical ASTM type for each reported quality.
Refinery crude evaluation procedure.
Changing crude source may trigger a
management of change (MOC) process; thus, the hazards from new crude oils must be carefully considered.9 A step-
wise process is recommended that assists in meeting the standards of the MOC.
TABLE 1 summarizes the procedure.
The economic evaluation of the new crude requires accurate market pricing data that is often not available. The best initial estimate is determined by understanding the crude’s value to the refinery and back- calculating a breakeven cost for processing. A critical component of the business case is an accurate estimate of both the operat- ing and capital costs associated with the new crude. It is possible to develop a rank-
ing of crudes specific to a given refinery’s configuration and operation.
LTO CRUDE QUALITY
LTO crude indicates the formation from which the oil is derived but not nec- essarily the oil’s quality (TABLE 2). The
common link between different forma- tions is the production chemicals used in the fracturing process. LTO crudes tend to be low in S and high in N, and the bottoms concentration is low. The low-cost, favor- able quality aspects and quantity of the crude can make it a very attractive choice for the refineries.
LTO general observations. Common observations about LTO crudes are that they produce high-value, low-S products. But, these crude oils require changes to the operation due to the differences in quality. Some general observations are:
Salt composition. Salt composition
is higher in the concentration of calcium (Ca) and magnesium (Mg) salts (70 wt%–90 wt%) vs. typical crudes, which are sodium based (70 wt%–80 wt%).6, 10 The
impact of the shift to Ca and Mg salts is the potential for hydrolysis in the atmospheric tower fired heater. Hydrolysis is the conver- sion or decomposition of a salt to the ion and HCl. Sodium salts do not hydrolyze, while Mg and Ca will hydrolyze. Result: At constant total salt concentration, the expectation is higher chloride levels in the atmospheric tower overhead, thus leading to the potential for higher corrosion.
Phosphorus. The phosphorus (P)
content is another difference among typi- cal crudes. P tends to accumulate in the upper section of the atmospheric tower, causing tray fouling. The P source is an on- going investigation. However, data from several atmospheric towers indicated foul- ing caused by P when processing Eagle Ford, Bakken and/or WTI.10, 11
Common observations. TABLE 2 sum-
marizes some common observations for LTO and Pacific crude.5–7, 11–14 The fol-
lowing sections describe some of the yield and quality shifts between Pacific Rim and LTO crudes.
CRUDE YIELDS
Bakken crude production is located in the northern US and southern Canada, and Eagle Ford production is in southern Texas. The AP crudes range from Vietnam to Australia, and these crude oils have been
TABLE 2. Common observations for LTO and Pacifi c crudes5–7, 11–14 Refi nery gasoline + distillate increases compared to conventional crudes.
Wax formation in the cold crude and distillate hydrotreater preheat exchangers causes fouling, which reduces heat transfer and increases pressure drop, requiring cleaning at shortened intervals. Diffi culties in desalting due to the formation of emulsions and other factors:
• High fi lterable solids add to the desalter load and reduce effi ciency.
• High API gravity improves desalting by creating a greater density diff erence between crude and water, increasing the Stokes settling velocity.
H2S and odors are higher, and the use of H2S scavengers creates amine salts and corrosion
products in the crude unit.
Distillate cetane is excellent, while waxes tend to create cold-fl ow (CFPP and PP) issues, leading to modifi cations of the process, additives or jet fuel downgrading to meet specifi cations Crude quality is variable between cargoes, leading to unpredictable operational changes. High VGO paraffi n content allows high conversion, low coke yields and low naphtha octanes:
• Catalyst circulation becomes limiting due to the coke yield. • Gasoline selectivity increases.
• C3/C4 olefi n yields increase.
• Slurry rate decreases with a corresponding increase in API gravity: ° Distillate blendstock requirements are reduced.
° Diesel production increases.
• Existing units require evaluation of the main fractionators and vapor recovery unit to accommodate the changes in yields.
Compatibility is poor with asphaltic crudes, leading to sedimentation and asphaltene precipitation. Residue yield is low, decreasing the vacuum and coker charge rates.
LPG and naphtha yields on crude increases requiring more lift, either as a prefl ash or in the atmospheric tower:
• Produced LPGs may require modifi cations to the saturate gas plant. • Naphtha-splitter upgrades are also a consideration.
The NHT, reforming and isomerization unit rates increase, requiring evaluation for performance or expansion
Hydrogen requirements are reduced due to lower hydrotreating severity at the low feedstock S and N concentrations.
Distillate production is generally higher due to the FCC selectivity improvements, and has about the same distillate yield on crude.
Naphtha paraffi n content is higher:
• CCR units have higher coke, lower yields and poorer activity. • Semi-regen units have lower yields and octane.
FCC increased olefi n production tends to increase: • Alkylation iC4 requirements
• Isomerization of nC4 to meet alkylation requirements
• Higher utilization of polyunit to react the C3 =
• Potential for refi nery-grade C3= production
Refining Developments
in production for many years. Bach Ho crude was used as the reference crude and has had very successful refinery operation experience. The incremental yields were calculated using proprietary simulation models, and are shown with Bach Ho as the base crude.a, 5, 15 In general, the yields
are similar with the exception for light-end yields, which are higher than Bach Ho. The Cossack, Gippsland and Kubutu crudes have higher light naphtha yield, while Bak- ken crude has more light naphtha yield. The Eagle Ford crude has less light naph- tha yield as compared to Bach Ho.
Bakken crude yields less heavy naph- tha than Bach Ho (TABLE 3). In contrast,
Eagle Ford crude produces more heavy naphtha compared to Bach Ho. The Cos- sack, Gippsland and Kubutu crudes yield more heavy naphtha yield than the Bach Ho crude. The distillate yields are about the same. For all crudes, the light vacuum gasoil (LVGO), heavy VGO (HVGO) and vacuum resid (VR) yields are less than the Bach Ho crude, but are about the same when compared to the other yields within this group.
In general, the light yield structure is an advantage, and it provides high-value prod- ucts. The heavy naphtha plus yields offer the greatest value. However, the high light- ends yield (C1 to C6) from the LTO crudes
is creating a potential surplus in the US market.1 The market is reacting, and pres-
ent pricing on a Btu basis places ethane be- low natural gas (NG). This trend provides advantages to ethane crackers producing ethylene and to refiners by reducing fuel costs. Recovery of C3 as LPG offers ben-
efits, while the C4 to C5 boiling range is at a
disadvantage due to gasoline volatility.
CRUDE QUALITY
TABLE 4 summarizes the crude qualities
for several shale oil plays.13, 16, 17 The Bak-
ken and Eagle Ford crudes have higher pour points (PPs), while the other quali- ties are about the same. The crude qualities for API gravities, PP and N vary by loca- tion. While 1,000°F+ S, aromatics, paraf- fin and viscosity are comparable. High iron (Fe) content is typical for paraffinic crudes. The high-Fe concentration causes catalyst deactivation in downstream units and other operating problems.
PRODUCT QUALITY
Paraffinic crude cut qualities generally have high API gravity and wax content. The
low S and N levels are observed for all of the cuts. The PP is generally higher for all LTOs, with the exception of Bakken crude. The high PP leads to storage challenges re- quiring either heated systems or storage as blends for intermediate feeds. The quality
of the light ends and light naphtha is about the same for all of the LTOs, although the yields do vary by location. The light naph- tha is a particular challenge. The base gaso- line volatility is reduced due to ethanol added in the final blending.
TABLE 5. Heavy naphtha incremental quality
Bach Ho Bakken Eagle Ford Cossack Gippsland Kubutu
Vietnam
US/
Canada US Australia Australia
Papua New Guinea
API Base 1 4 –2 –2 0
S, wppm Base 19 53 10 294 114
N, wppm Base 0 0 0 0 0
Paraffi ns, vol% Base –24 8 –10 –2 –11
Naphthene, vol% Base –9 –6 6 –5 3
Aromatics, vol% Base 33 –2 4 7 7
TABLE 3. Crude incremental yields
Bach Ho Bakken Eagle Ford Cossack Gippsland Kubutu
Vietnam
US/
Canada US Australia Australia
Papua New Guinea
Light ends, vol% Base 2% 4% 5% 5% 6%
Light naphtha, vol% Base 5% –4% 18% 28% 13% Heavy naphtha, vol% Base 10% 14% 7% 3% 9%
Kerosine, vol% Base 0% –1% 1% –3% 0%
Diesel, vol% Base –2% 3% –2% –3% –1%
LVGO, vol% Base –4% –4% –8% –7% –6%
HVGO, vol% Base –5% –6% –13% –14% –12%
VR, vol% Base –5% –7% –9% –10% –8%
TABLE 4. Crude incremental quality comparison
Bach Ho Bakken Eagle Ford Cossack Gippsland Kubutu
Vietnam
US/
Canada US Australia Australia
Papua New Guinea API Base 0.4 3.6 7.8 13.4 14.6 S, wt% Base 0.1 0.1 0.0 0.0 0.0 N, wppm Base 265 –338 –27 –263 –275 PP, °F Base –52 –92 –72 –59 –47
Paraffi ns, vol% Base –17 NA –2 11 6
Aromatics, vol% Base 13 NA 0 –1 –2
Iron, wppm Base 3 –1 0 –1 –1
TABLE 6. Lubricity test methods
Test description Abbreviation Method Limit
High-frequency reciprocating rig HFRR ASTM D6079 < 460 micron Ball-on-cylinder BOCLE ASTM D5001 < 0.85 mm Scuffi ng load ball-on-cylinder SL-BOCLE ASTM D6078 3,000 gms Low-lubricity fl uid endurance LLFE SAE ARP 1797 Performance
64MARCH 2015 | HydrocarbonProcessing.com
Refining Developments
Heavy naphtha quality. As summa- rized in TABLE 5, the heavy naphtha frac-
tionation of LTOs have low S levels, but will still require hydrotreating before be- ing sent to the catalytic reforming unit. 5, 15 The heavy naphtha is similar in qual-
ity to Bach Ho crude for all of the LTOs except Bakken crude, which has a higher aromatic and lower naphthenic concen- trations, and it is an excellent reformer feed. The low aromatic and naphthen- ic concentrations for the other crude
sources make the heavy naphtha a mar- ginal reformer feed.
Distillate quality. Distillates have high cetane and poor cold-flow (CF) proper- ties. High straight-chain paraffinic con- centration and yields make these crudes great for diesel production. Straight- chain paraffin properties are prone to wax production, thus creating floccula- tion, which is seen as high cloud points. Also, they crystallize due to high PPs, as illustrated in FIG. 1.
CF-depressant (CFD) additive chem- istry consists of polymers that modify the initial wax formation from large to small wax crystals and then inhibit the agglomeration. Wax formation starts with a nucleation point for small crystals to collect (cloud point). As the crystal grows, the larger crystals combine or ag- glomerate into larger collected masses until the fuel begins to gel (PP or CFPP). The thermodynamics are such that the heat of fusion can be measured by the differential temperature of the mixture. As a result, CF properties must be im- proved, usually through chemical addi- tives (CFDs), isomerization or blending with other streams.
Another potential issue requiring monitoring is lubricity. Four tests are available to measure lubricity (TABLE 6).
The general agreement is that the HFRR test is the most reproducible and is rec- ommended as the standard. However, the specifications are typically BOCLE (TABLE 6). Recent changes to jet fuel
specifications allow additives to address lubricity.14 The Defense Standard gives a
list of approved lubricity additive pack- ages, suppliers and acceptable blending limits in the relevant section of Annex A.18
Kerosine quality. The kerosine incre- mental quality compared to Bach Ho as simulated is summarized in TABLE 7.15
Kerosine appears to need undercutting, blending, hydrocracking or dewaxing to meet freeze-point specifications. Virgin kerosine-jet blends potentially would re- quire clay treating or mild hydrotreating. Recent changes in specifications allow ad- ditives to improve lubricity.18
Diesel quality. Diesel quality is accept- able for cetane numbers with higher CF and S reductions than ULSD specifica- tions. TABLE 8 shows the incremental
TABLE 8. Diesel incremental quality
Bach Ho Bakken Eagle Ford Cossack Gippsland Kubutu
Vietnam
US/
Canada US Australia Australia
Papua New Guinea
API Base –6 –6 –5 –4 –9
S, wppm Base 247 247 1,015 660 294
N, wppm Base 12 12 –25 –28 50
Paraffi ns, vol% Base –13 –13 –2 –11 –21
Naphthene, vol% Base 3 3 –8 2 5
Aromatics, vol% Base 10 10 11 10 16
Cloud, °F Base –21 –21 –1 –3 –11
PP, °F Base –22 –22 –5 –4 –14
Cetane index Base –11 –11 –8 –7 –14
TABLE 7. Kerosine incremental quality
Bach Ho Bakken Eagle Ford Cossack Gippsland Kubutu
Vietnam
US/
Canada US Australia Australia
Papua New Guinea
API Base –5 –4 –4 –5 –5
S, wppm Base 109 32 32 610 506
N, wppm Base 4 0 0 0 –1
Paraffi ns, vol% Base –19 –10 –10 –9 –14
Naphthene, vol% Base 12 3 3 0 5
Aromatics, vol% Base 7 7 7 10 10
Freeze, °F Base –27 –23 –23 –7 –6
Cetane index Base –9 –9 –9 –11 –9
Smoke point, mm Base –4.7 –1.0 –4.7 –5.8 –5.7
Name mechanism Growth agglomeration Nucleation wax appearance temp. (WAT) Extension molecular alignment Liquid state random motion Molecular type n-Paraffin Iso-paraffin Heat of fusion Cyclo-paraffin (Naphthene)
Cloud point depressant
Cloud flow depressant
Reduces the rate of wax nucleation
Reduces the rate of agglomeration
Temperature
Heat of fusion
Refining Developments
diesel quality as fractionated by the model.a, 15 High paraffin levels have the
potential for water containment result- ing in hazy final products. Hydrotreating, dewaxing or jet downgrading are options to be considered in producing ULSD.19, 20
VGO quality. The VGO has low aromat- ic content and cracks well. TABLE 9 lists
the incremental VGO qualities as frac- tionated by the model and compared to Bach-Ho.15 The low Conradson carbon
residue (CCR) and high paraffin levels al- low high conversion and low coke make. Fluid catalytic cracking unit (FCCU) catalyst circulation will reach limitations due to low coke. Resid is potentially the best feed for the FCCU.
ATB quality. TABLE 10 summarizes the
atmospheric tower bottoms (ATB). The ATB has moderate CCR and low metals content. It is a good choice as feed to the FCCU. Processing the full-range ATB produces a higher-S gasoline than is al- lowed by US Tier III and would require additional post-treating. Hydrotreating full-range ATB is possible with an exist- ing GO hydrotreater, and it would pro- vide an alternative to produce ULSG.
Options. Crudes from the AP rim are similar to the Bakken and Eagle Ford pro- duction. The similarities allow more flex- ibility to process LTOs, using knowledge gained in modeling.
NOTES
a The data tables presented in the article were developed
using the KBC Petro-SIM simulation model. Petro- SIM is a trademark of KBC Advanced Technologies plc, and it is registered in various territories.
b The crude assay data are a combination of either the
H/CAMS Haverly Systems Inc. crude data base15 or
as modified by KBC.
LITERATURE CITED
1 Kuhl, et al., “Capitalizing on shale gas in the down-
stream energy sector,” AFPM Annual Meeting, March 2013.
2 Sayles, S., “Upgrading technology selection,” 2007
Oil Sands and Heavy Oil Technology Conference, Calgary, Alberta, Canada, July 2007.
3 Sayles, S., “Shale or tight oil processing,” AFPM
Q&A, October 2012.
4 Sayles, S., et al., “Unconventional crude oil selec-
tion and compatibility,” NPRA Annual Meeting, March 2011.
5 Huovie, et al., “Solutions for FCC refiners in the
shale oil era,” AFPM Annual Meeting, March 2013.
6 Lordo, S., et al., “Shale and tight oil new frontier,” 3rd
Opportunity Crude Conference, March 2012.
7 Lordo, S., et al., Opportunity Crude Conference 2008. 8 Sandu, C., et al., “Innovative solutions for processing
shale oils,” Hydrocarbon Processing, July 2013.
9 OSHA regulations, 29CFR 1910.119 Process Safety
Management of Highly Hazardous Chemicals, state
that any time a critical component in an oil or chemi- cal plant changes, a formal MOC program is required to ensure that the proposed change is made safely.
10 Ohmes, R., et al., “Characterizing and tracking trace
contaminants in opportunity crudes,” AFPM Annual Meeting, San Antonio, Texas, March 2013.
11 Sayles, S., “Unconventional crude processing
Part 1: Metals,” Crude Oil Quality Association, October 2008.
12 Sayles, S., “Unconventional crude processing—Part
2: Heteroatoms,” Crude Oil Quality Association, October 2010.
13 Sayles, S., “LTO heat transfer loss,” Unpublished. 14 Kramer, “Using proven technology to optimize
profits when processing opportunity crudes,” 3rd Opportunity Crude Conference, March 2012.
15 H/CAMS Haverly Systems Inc.
16 Saleh, et al., “Blending effects of fouling on four
crudes,” ECI Symposium Series, Vol. RP2: Proceedings 5th International Conference on Heat Exchanger Fouling and Cleaning, June 5–10, 2005.
17 http://crudemarketing.chevron.com/crude/far_
eastern/duri.aspx.
18 Defense Standard 91-91 Issue 7, Amendment 2,
March 2013.
19 Sayles, S., et al., “Solutions to common problems
in scoping, designing, implementing and operat- ing ULSD units,” NPRA Annual Meeting, March 2006.
20 Ohmes, R., et al., “Analyzing and addressing the
clean fuels and expansion challenge,” NPRA Annual Meeting, March 2007.
SCOTT SAYLES is a principal consultant for KBC Advanced Technologies Inc., Houston, with more than 35 years of refinery and petrochemical experience, ranging from refinery plant manager to research engineer. His technical areas of expertise include operation and design, ebullated-bed residual hydrocracking, hydrotreating, FCCU, and practical understanding of most processes. Mr. Sayles is a member of the American Fuel and Petrochemical Manufacturers. He holds a BS degree in chemical engineering from Michigan Technological University, and an MS degree in chemical engineering from Lamar University.
TABLE 9. VGO incremental quality comparison
LVGO Bach Ho Bakken Eagle Ford Cossack Gippsland Kubutu
API Base –9 –6 –6 –2 –1 S, wppm Base 1,984 590 590 1,361 742 N, wppm Base 0 0 0 0 0 Aromatics, wppm Base 466 240 240 1 –52 PP, °F Base 18 12 12 10 7 CCR, wt% Base –45 –31 –31 –17 –11 HVGO Base API Base 0 0 0 0 0 S, wppm Base –9 –7 –7 –3 0 N, wppm Base 2,515 1,094 1,094 2,244 1,229 Aromatics, wppm Base 0 0 0 0 0 PP, °F Base 946 1,110 1,110 29 –229 CCR, wt% Base 19 13 13 10 4 Metals Base –35 –24 –24 –7 –6 Fe, wppm Base 1 0 0 1 0
TABLE 10. Atmospheric tower bottoms incremental quality
ATB Bach Ho Bakken Eagle Ford Cossack Gippsland Kubutu
API Base –5 –5 –1 0 –8 S, wppm Base 931 931 2,150 1,790 765 N, wppm Base 803 803 –272 –362 744 Aromatics, wppm Base 13 13 10 7 20 PP, °F Base –33 –33 –22 –17 –28 CCR, wt% Base 0 0 0 0 1 Metals Base 0 0 0 0 0 Fe, wppm Base 7 7 –2 –1 –2 Ni, wppm Base 2 2 –1 –1 0 V, wppm Base –1 –1 –1 –1 –1