Hydroprocessing rate increase using shaped ch charges arges Catalyst size and shape are critical contributors to hydroprocessing reactor performance Technologies/Zeolyst International Adrienne Van Van Kooperen Criterion Catalysts & Technologies/Zeolyst Technologies chnologies James Esteban Esteban Criterion Catalysts & Te Brandon Murphy Marathon Petroleum Company
A
chieving increases in pressure on reners to maximise Trilobe (TL) shape hydrocracker capachydrocracking unit throughput up ity of 20-35% without to hydraulic limitations which in any capital investment sounds many cases is a limit set by reacimpossible; however, novel tor pressure drop. Limitations in changes in catalyst design reactor pressure drop can be mithave enabled just that for igated by many means, but ultitwo North American reners. mately catalyst selection is the most Conventional HC catalyst shape Hydrocracking units have rapcritical factor in hydrocracker optiUsed in all HC catalysts offered after 1994 idly become one of the highmisation. Criterion developed the est prole units in the modern Gradient Advanced Advanc ed Trilob Trilobee eXtra (ATX) cat cat-renery with increasing prespres alyst shape to allow hydrocracking Low High sure to maximise charge rates units to reduce pressure drop and Trilobe eXtra (ATX) (ATX) shape improve activity simultaneously. up to a multitude of con- Advanced Trilobe straints including reactor sysThere are several signicant advanadvan tem pressure drop. This article tages of the ATX shape (see Figure provides two examples of 1), but it is rst important to reect hydrocracking units processon how catalyst shape affects reacing signicantly higher rates tor performance to understand fully as a direct result of Criterion’s the benets of this revolutionary Proprietary technology offered new hydrocracking catalyst product. for majority of HC catalyst Lower CBD shape. Approx 10% lower fill cost Criterion and its customCatalyst shape and size Better liquid yield; ers have seen that a ne balbal All hydrop hydroprocessi rocessing ng reacto reactorr sysshorter diffusion path Reduced over-cracking ance of activity and pressure tems operate with a few standLarger void fraction drop has long since created ard objectives that apply from the Higher particulate uptake a challenge when considersmallest of naphtha hydrotreating Delayed onset of rapid ∆P build ing the maximisation of perapplications to the largest of hydroLower SOR ∆P 15 to 20% lower commercial formance for hydroprocessing cracking operations. While this performance demonstarted vs. and hydrocracking units. It is list may seem rudimentary, every conventional TL especially a critical balance for hydroprocessing unit must provide high prole units in hydrochydroc - Figure 1 ATX catalyst shape advantages the desired catalytic activity, proracking service that receive tection from feed poisons and the gen large margins for product upgrades and also have ltration of feed contaminants (though not genhigh incentives for incremental processing capac- erally a desired function for catalytic solutions). A ity. Recent margins have placed a great deal of properly designed catalyst system should employ a
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Medallion 16mm
MacroRing 8 mm
Ring 6.4, 4.8, 3.2mm
FilterLobe 5.6, 3.2, 2.5mm
Inert, high void, flow improvement Crush strength: >8 lb/ lb/mm mm Loaded density density:: 50 lb/ft3 Macro porous, high void, low activity Crush strength: >8 lb/ lb/mm mm Loaded density: density: 45 lb/ft3 High void, good activity Crush strength: >1.2lb/mm Loaded density: density: 35 lb/f lb/ftt3 Large diameter, extra long trilobe Crush strength: >3.0lb/mm Loaded density: 26lb/ft3
Figure 2 Common graded bed particle shapes
wide variety of shaped and sized particles to support this set of target objectives for each specic hydroprocessing unit large or small.
Grading catalyst catalystss For several decades, the industry has capitalised on the advantages offered from graded bed solutions to enable improved performance with respect to increasing system pressure drop throughout the catalyst cycle life. This has employed the use of a multitude of materials that have varying void fractions and structures with a common objective to provide the optimum available bed void space and transition layers to remove contaminants from the feed stream over an extended portion of the catalyst bed. The application of grading materials and layers is common to hydroprocessing units as pressure drop across the leading bed remains a challenge for many units in the industry. This deep bed ll tration phenomenon has led to the development of several extruded shapes with varying degrees of catalytic activity including, but not limited to, hollow cylinders, macroporous lobed particles, and specialty shaped extrudates (see Figure 2). In many cases, these materials developed as top bed grading are not suitable for a large volume of the reactor due to low inherent activity. In addi tion, many reners are beginning to capitalise on new technologies with regard to reactor internals to further improve the ltration of feed contamicontami 1 nants and extend catalyst life cycles.
Main bed catalysts Historically, main bed catalysts used in hydroprocessing reactors were manufactured in the
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Trilobe
d p L p Quadlobe
d p L p
Figure 3 Typical TL and QL catalyst shapes
form of cylindrical shapes of varying diameters, but in the early 1970s American Cyanamid Company pioneered the production of shaped catalysts with the introduction of trilobe (TL) catalysts for residual oil and gasoil hydrodesulphurisation.2 To this day, a large majority of the hydroprocessing market’s catalysts are still manufactured in this same shape, and the transition in the past to the use of shaped catalyst particles is one of extreme importance because of the impact it has had on overall reactor performance. Currently, the two most common main bed catalyst shapes offered by hydroprocessing catalyst manufacturers are TL and quadlobe (QL) extruextru dates of varying particle diameters (see Figure 3). The particle length of commercial catalysts offered is variable to some degree within tolerances set by each manufacturer, but ultimately is determined by properties of the substrate mixture, operating conditions, and particle diameter as the weight of the extruded mixture drives the length by breakage of the extrudate simply as a function of gravitational force. While both catacata lyst shapes are common in industry, each offers a distinct set of advantages and disadvantages. Multi-lobed catalyst shapes offer signicant advantages in general over historical conventional shapes and have higher particle surface area (S p) to particle volume (V p) ratios when compared to a standard cylinder of equal particle length (L p) and particle diameter (D p). This increase in sursur face area results in greater activity as a result of reactions that occur on the catalyst particle surface, and those that occur within the pore structure of the catalyst pellets. Since many of the reactions that occur in the hydroprocessing reac-
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tor are governed by mass transfer, the advent of shaped particles 0.9 ATX A TX has provided increased access for ) 0.8 QL η ( reactants to contact active sites r T o 0.7 in the pore structure closer to t Cylinder c the centre of the pellet by reduc a 0.6 f Sphere ing diffusion distance limitations. s s 0.5 e Inherently, this also provides n e 0.4 greater selectivity when consid v i t ering reactions that continue to c e 0.3 propagate, such as the formation f f E 0.2 of light ends from over-cracking. Furthermore, an increase in 0.1 the number of lobes is associated 1 2 3 4 5 with incre increasing asing the overal overalll catd pe ), mm Effective particle diameter ( d alyst effectiveness factor, which implies a catalyst with more lobes Figure 4 Catalyst effectiveness factor factor as a function of effective particle diameter is capable of providing higher activity per volume, assuming that the catalyst is manufactured in the same of the shape, which inuences diffusivity to the manner as its comparison. Figure 4 illustrates this inner surfaces of the catalyst pellet, plays a key concept as a function of catalyst pellet effective role in overall system activity. This implies that diameter (dpe) as dened in Equation 3 for a typtyp - shapes with a higher S p/V p ratio will inherently 3,4 ical hydrodesulphurisation operation. The effeceffec - provide a higher effectiveness factor which is syntiveness factor (η) and Thiele modulus (Φ) for the onymous with activity given the same catalyst catalyst pellets are determined from the relation- mass. This does not, however, imply that comcom5 ships in Equations 1 and 2: parative samples of the same total volume of two differing catalyst shapes will result in differing ℎ( ) (1) activity performance, because the overall loaded density also plays a key role in the available activity that can be loaded in a xed volume such as a ! +1 !" (2) reactor. 2 ! When considering TL versus QL catalyst shapes, both exhibit similar effectiveness factors (3) on the basis of common effective particle diameter, and commercial experience demonstrates that both load with similar bed void fractions k e = Activation energy (εB). QL catalysts do provide higher effectiveness C A = Concentration of species A factors than TL catalysts of the same actual physphys nro = Reaction order ical diameter which in many cases can permit Lpe = Effective diffusion length lower activity catalysts to provide similar perforDe = Effective diffusivity mance to higher activity TL catalysts at the cost of increased bed pressure drop. This disadvandisadvan Φ = Thiele modulus V p = Particle volume tage generally limits the layer size of QL materimateri als in reactor loading design, especially for units Since the catalyst effectiveness factor is a funcfunc- limited by pressure drop. However, when com tion of the Thiele modulus, there are only a few pared to traditional shapes, lobe-shaped particles key variables which differ between the various load with a higher bed void fraction. catalyst particle shapes. This includes the effeceffec When considering the value of shaped par par-tive diffusion length and the effective diffusiv- ticles in reactor applications, it is important to ity, since individual reaction rates are constant observe the relative crush strength of the catafor similar catalyst activities. Thus, the geometry lyst particles as it relates to operating pressure =
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drop across the catalyst bed. This can be perper- extruded shape load at similar void fractions ceived as an area of exposure for particles with and densities for commercial sized vessels since shapes that inherently have weaknesses, and packing efciency is determined by the parti lobed particles certainly have a central weakness cle shape rather than particle diameter when when compared to cylinders and spheres since considering a bed of particles of equal diamediame the lobes can be broken away from the centre ter. 7 In addition, there is very little inuence on of the pellet under high stresses. In general, the bed void from wall effects in commercia commerciall scale crush strength and any other typical bulk prop- reactors because of the large ratio between the erty of the catalyst is also a function of the S p/ diameter of the vessel and the diameter of the V p ratio.4 The resulting changes in bulk properproper - particles.8 ties have led the industry to target TL and QL However, larger particle diameter extrudates shapes, as these shapes result in acceptable bulk of a similar shape do result in lower catalyst bed properties for optimum performance performance.. pressure drop at the same operating conditions Another key factor in the value of shaped par- (i.e. equal mass ow rate of vapour and liquid). ticles is a reduction in reactor pressure drop at This is due to the effect of liquid hold-up and constant operating conditions and particle diam- relative velocity in the bed voids. 9 Larger parpareters from benecial changes in reactor bed void ticles, while having similar bed voids, create a (εB). This is when comparing lobe-shaped partiparti - less tortuous path for materials owing across cles to conventional particles. More specically, the catalyst bed and ultimately it is the frictional individual lobe- shaped particles also exhibit dif- losses due to the impact of particle contact which fering performance with regard to pressure drop results in a pressure gradient across the packed across the catalyst bed. Pressure drop in packed bed. Thus, less particle contact results in lower beds is commonly modelled by the Ergun equa equa-- pressure drop given the same overall packed bed tion which is applicable for single phase ow, but void space. In addition to particle size, particle to model two phase ow through packed beds shape also has a signicant impact on pressure there are modied versions of the Ergun equa - drop. Note that pressure drop is inversely pro tion. Using the modied Reynolds number, the portional to the effective hydraulic diameter of Ergun equation can be simplied as shown in the particle which is a direct function of the physEquation 4:6 ical characteristics of the particle shape. In order to model the comparative pressure drop performance of differing particles in a packed bed, it 150 + 1.75 (4) is common practice to relate the actual diameter 1− of the particles to an effective particle diameter. Work from Brunner et al asserts that the effective dph = Particle hydraulic diameter diameter of a catalyst particle can be modelled εB = Catalyst bed void fraction by a sphere s phere which exhibits the same physical volLB = Catalyst bed length ume as the catalyst particle,3 while work from Ancheyta et al asserts that the effective diameter This equation illustrates that pressure drop of a catalyst particle can be modelled by a sphere across the reactor bed is inversely proportional to which exhibits the same physical surface as the both catalyst catalys t bed void fraction (εB) and the effeceffec - catalyst particle.5 Since lobed particles provide tive particle hydraulic diameter (d ph). higher Sp/V p ratios than spheres, these particles Void fraction itself is a function of loading result in effective diameters that are a fraction method (dense versus sock) and particle shape. of their actual diameter regardless of the calcuSince the maximum system activity is achieved lation method mentioned above. It is common when a bed is dense loaded, it is common to practice in industry to model the effective diamapply one of many commercial techniques to eter of particles in a packed bed by either aforeimprove the arrangement of catalyst particles mentioned method for use in modelling pressure during the loading process. In general, the dense drop with the Ergun equation to achieve a relarela loading process can result in a load that achieves tionship for normalised particle characteristics. 105% of the compacted bulk density (CBD) of a However, both methods do not supply completely catalyst. Differing diameter particles of the same reliable estimates for bed pressure drop predic
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Catalyst particle properties3,5,9 Shape SPH, 2.5 mm CYL, 2.5 mm TL, 2.5 mm QL, 2.5 mm ATX, 2.5 mm
dp, mm 2.5 2.5 2.5 2.5 2.5
Lp, mm 5.0 5.0 5.0 5.0
Sp, mm2 19.63 49.09 56.93 55.17 -
V p, mm3 8.18 24.54 17.20 17.20 17.76 -
Sp/V p, mm 2.40 2.00 3.31 3.11 -
dpe, Brunner, mm 2.50 3.61 3.20 3.24 -
dpe, Ancheyta, mm 2.50 3.95 4.26 4.19 -
, B Dense 0.36 0.34 0.41 0.42 0.50
dhp, mm 2.50 3.00 2.41 1.93 2.02
B 0.27 0.23 0.49 0.55 0.55
Relative P/LB ( Pi/ PTL) 1.25 1.15 1.00 1.20 0.80
Table 1
tions in two phase trickle bed systems without overall catalyst system load since the increase in correlated modifying constants. These modiers pressure drop can result in hydraulic limitations, are functionally dependent on the physical char- reducing hydroprocessing unit capacity. QLs can acteristics of the particle shape and can be deter- be loaded at higher void fractions via sock loadmined by experimental methods. Ultimately, the ing methods or applied in larger particle diameresulting modied diameter value is applied as ters to overcome the increases in system pressure the effective particle hydraulic diameter (dph) drop, but these methods reduce the effectiveness for the comparisons in this work and the devel- advantages offered from the shape difference by opment of novel catalyst shapes of the future by reducing the overall catalyst mass loaded in the Criterion. Table 1 illustrates a variety of catalyst xed volume. The QL shape is also often used to particle shapes, their physical characteristics and boost the activity of lower performance catalyst calculated properties. Figure 5 provides insight formulations to achieve close to similar activinto the effect of particle shape on system pres- ity of high activity TL catalysts. Thus, when tartar sure drop for each of the particles listed in Table geting development of an all new revolutionary 1 with the common TL particle set as the stand - catalyst shape, Criterion chose to modify the conard for comparison. ventional TL shape and release to the market the It is clear from this comparison of the various ATX shape. particle shapes in Table 1 and Figure 5 that the modern catalyst particle shapes deliver higher AT ATX-sh X-shaped aped cat catalyst alystss effectiveness at lower packing densities, leading Criterion has been producing catalysts for hydroto overall greater system performance with less cracking applications in the ATX shape for catalyst mass in a xed volume such as a comcom- several years and the commercial results are mercial reactor. However, when comparing TL and QL partiparti 130 cles, there is a distinct advan120 tage to the use of TL-shaped main bed catalyst particles due 110 to the reduction in system pres % , sure drop relative to alterna L 100 T P tive options. Coupled with more ∆ 90 / I attractive bulk physical prop P ∆ erties for TL-shaped particles 80 which lead to less breakage, TLs remain the primary preferred 70 shape for hydroprocessing cata60 lysts since their introduction to ) ) ) ) ) m m m m m the market in the 1970s. While 5 m 5 m 5 m 5 m 5 m 2 . 2 . 2 . 2 . 2 . ( ( ( ( ( QL particles are used in comcom L L L X H T Y T Q P A C S mercial hydroprocessing applications, their use is generally limited to small layers of an Figure 5 Pressure drop relative to TL particle shape
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astounding. The shape was developed in part Commercial performance of ATX catalysts to provide hydrocracking units with an option Hydrocracking units have recently gained high to reduce pressure drop and allow signicant visibility in the North American rening sec sec-increases in feed rates for units facing hydraulic tor due to their capability to produce high value limitations. However, there are several advanadvan - product streams from low cost, readily availatages offered by the ATX shape for cracking ser - ble hydrogen streams. These units have gained vice. All of Criterion’s new generation modern signicant favour in the global rening sector hydrocracking catalysts can be manufactured in to satisfy a multitude of challenges, including the ATX shape, allowing all hydrocracking appliappli - increasingly stringent environmental regulations, cations the exibility to benet from signicant higher conversion of low value heavy petroleum performance and capacity increases. fractions, and to satisfy the growing demand for The ATX shape is a modied TL shape with higher quality middle distillate fractions. The higher particle surface area and slightly lower demand from existing rening assets and the particle volume. Catalysts manufactured in the growing market of new assets in the hydrocrack ATX shape demonstrate lower bulk density when ing application space has led many reners to loaded by creating increased catalyst bed void. target the highest performance catalyst products This signicant increase in bed void is essential that offer advantages in operability and exibility to improving system pressure drop as the parti- for their reactor systems. cle does have a slightly lower effective particle The following two commercial examples hydraulic diameter than the conventional TL. The demonstrate the inuence of Criterion’s expert net effects from changes in bed void and effective technical services and the power of ATX-shaped particle hydraulic diameter provide a reduction products applied in two of several independent in catalyst bed pressure drop of 15-20% in com- hydrocracking units to unlock additional capacmercial applications relative to conventional TL ity, creating signicant increases in protability. catalysts of the same particle diameter depending on loading methods. Commercial performance: Lower bulk density also provides a signicant Case 1 (Marathon Garyville) reduction in the catalyst weight required to ll One of the highest capacity hydrocracking units reactor vessels, aiding in reducing the total ll in the world, operated by Marathon Petroleum cost for a catalyst system design. The ATX shape Company (MPC) at the Garyville renery in also provides a large boost in individual particle Louisiana, leverages the advantage of ATXperformance due to reduced effective diffusion shaped catalysts to maximise unit capacity lengths which leads to a higher catalyst effec- and performance. Over two operating cycles, tiveness factor. The resulting impact of higher the Garyville hydrocracker transitioned to effectiveness leads to an advantage in system Criterion’s ATX catalysts to reduce unit prespres activity performance despite the reduction in sure drop. While only ~30% of the overall curcur catalyst mass. For hydrocracking applications, rent catalyst load is now ATX-shaped cracking this performance advantage also translates to catalysts, the unit has been capable of increasimproved selectivity when considering reactions ing throughput by 35%. The unit processes a like over-cracking which continue to propagate combined feed stream of heavy vacuum gasas reactants exit the catalyst particles, causing the oil (HVGO), coker gasoil (CGO) and, intermitintermit formation of light ends. tently, deasphalted oil (DAO). Consistently, The additional void space created in the reacreac- feed rate is pushed to higher limits as the ren tor from the ATX shape also permits increased ery has a very high margin on the ULSD prod gas circulation rates to stabilise reactor temper- uct as well as high value unconverted oil which ature proles and minimise peak temperatures. is processed in the FCC. Overall, conversion and The minimisation of peak temperatures is key in yields have remained extremely stable throughhydrocracking service since this leads to stable out both operating cycles with extremely stable product yields for extended periods of the cycle cracking reactor operating temperatures. Figure and the minimisation of light ends production 6 illustrates the effect of ATX shape on normal at higher reactor weighted average bed tempera- ised pressure drop across the guard reactor sectures (WABT). tion as well as the overall reactor normalised
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pressure drop. It is clear that the material in the guard reactor which remains loaded as the typical standard TL-shaped particles has retained the same normalised pressure drop, while the hydrocra hydrocracking cking reactor has seen a reduction in normalised pressure drop by ~20% sourced from the change in catalyst shape loaded.
p o r d e r u s s e r p d e s i l a m r o N
20% reduction
Previous cycle with conventional trilobe shape
Current cycle wih ATX shape
Guard RX HC RX
Guard RX nDP HC RX nDP Figure 7 shows the massive Time on stream, days increase in feed rate to the unit over the transition from the rst Figure 6 MPC Garyville normalised reactor pressure drops cycle with conventional TL to the current cycle loaded with ATX catalysts. The feed rate between the two trains in the 35% increase unit now supports one of the e t highest capacity hydrocracking a r units in the world. This increase d Previous cycle e Current cycle in feed rate is largely supported with conventional e f wih ATX shape trilobe shape l by the advantages offered from a t the ATX shape which permits o T sufcient activity and yields retention to achieve the desired performance from the MPC Garyville operating team. Time on stream, days MPC operates the unit in a manner that stabilises reac- Figure 7 MPC Garyville total unit feed rate tor temperatures and maximises gas rates to maximise product quality and yields. The resulting hydrocrack Train 1 ing reactor WABTs obviously Train 2 increased as a function of the significant increase in feed Previous cycle with conventional rate shown in Figure 8, but F trilobe shape º reactor operation has shown , T extremely stable performance. B A This stable performance from W Current cycle the cracking reactors is attribwih ATX shape uted to excellent operations and the highest activity pretreat catalyst system available which provi provides des the clea cleanest nest Time on stream, days possible feed to the cracking reactor. Figure 9 highlights the expert control of the hydrocracking Figure 8 MPC Garyville hydrocracking reactor WABT
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HC bed 1 HC bed 2 F º , T
HC bed 3 HC bed 4
∆
d e b g n i k c a r C
Previous cycle with conventional trilobe shape
Current cycle wih ATX shape
Time on stream, days
Figure 9 MPC Garyville cracking reactor bed ∆Ts
B F C S , o i t a r l i o / s a G
Previous cycle with conventional trilobe shape
Current cycle wih ATX shape Train 1 Train 2
Time on stream, days
Figure 10 MPC Garyville cracking reactor gas to oil ratios
F F l o v % , d l e i y d i u q i l l a t o T
Previous cycle with conventional trilobe shape
Current cycle wih ATX shape
Time on stream, days
reactor beds with stable control of equal bed temperature rise from cycle to cycle. The excess gas circulation provides a signicant advantage to stabilise bed temperature temp erature control c ontrol as well as hydrogen availability in the cracking reactors which pro vides the most stable cracking system available. Excess hydrohydrogen reduces the coking potential and minimises deactivation in the cracking beds. Figure 10 shows the retention of excess gas rates from cycle to cycle despite the signicant increase in feed rate. Ultimately, this advantage is made possible with the improvement improvementss in i n reacreac tor pressure prole via the ATX shape. Regardless of operating stasta bility and reactor pressure drop, the key performance from hydrocracking units is ultimately measured in the product yields. Figure 11 illustrates the stability of yields that MPC has enjoyed from cycle to cycle from a total liquid volume perspective. Note that the total liquid volume yield is retained despite the increase in feed rate which implies that while the percentage volume yields have remained similar, the total volume yield has increased in an equivalent manner to the total feed rate. This demonstrates the activity advantage from ATX-shaped catalys catalysts, ts, provid provid-ing excellent selectivity and performance. Figure 12 also highlights the advantages with regard to light ends production. While the cracking reactor temperatures have increased on an absolute basis, the light ends production has remained very stable, demonstra demonstrating ting the reduced over-cracking potential and yields selectivity.
Figure 11 MPC Garyville total liquid volume yield 8 April 2018
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Commercial performance: Commercial Case 2 (Shell Scotford)
Previous cycle with conventional trilobe shape
Current cycle wih ATX shape
C1
C2 The Shell Scotford renery C3 operates a large Shell licensed iC4 hydrocracking unit that pronC4 cesses a combined feed stream d of oil sands derived straight run l e i vacuum gas oil (SRVGO) and Y synthetic gasoil (GO). Figure 13 depicts a plot of the normalised pressure drop from the hydrocracker at Shell Scotford where the previous cycle applied Criterion’s previous generaTime on stream, days tion TL hydrocracking catalysts and a recent cycle operated Figure 12 MPC Garyville light ends yields with ATX cataly catalysts. sts. The reduc reduc-tion in pressure drop enabled a project to debottleneck the p Standard trilobe cycle o r unit. In addition to increasing ATX A TX cycle d unit protability and potential e r u capacity, the catalyst load also s s offered a reduced ll cost as e r p a result of lower loading den d sity. While the unit has only 10−15% e s i reduction l recently leveraged the advan a tages of the specialised ATX m 10−15% r o reduction shaped catalyst in the current N operating cycle to increase feed 0 100 200 300 400 500 600 700 800 rates, Scotford has been able Time on stream, days to increase operating severity to produce a set of improved product streams. The Scotford Figure 13 Shell Scotford normalised reactor pressure drop hydrocracker operation has been referenced in a previous publication by Sharpe et al where the product streams from the unit beneted sigsig p o r nicantly in terms of hethet d e eroatom concentration from r u catalytic advances. Namely, s s e Scotford targets production of r p blend quality product streams d e for their distillate pool which s i l requires both highest activ a m ity pretreatment catalysts r o and exceptional selectivity in N conversion. 0 100 200 300 400 500 600 700 800 Figure 14 highlights the perTime on stream, days centage reduction in normalised pressure drop for the Scotford hydrocracking reactor, which Figure 14 Shell Scotford normalised reactor pressure drop reduction
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T B A W r o t c a e r g n i k c a r C 0
decrease in temperature due to the improved performance of the catalyst despite the reduction in catalyst mass loaded.
Standard trilobe cycle ATX cycle ATX
Conclusion
100
200
300
400
500
600
700
800
Time on stream, days
Figure 15 Shell Scotford hydrocracking reactor WABT
% t w , n o i s r e v n o c l l a r e v O 0
Standard trilobe cycle ATX A TX cycle 100
200
300
400
500
600
Time on stream, days
Figure 16 Shell Scotford overall HCU conversion
is maintained throughout the cycle, permitting increases in feed rate for the unit. Figures 15 and 16 in combination, demonstrate the stability of the catalyst system with a transition from standard TL particles to ATX-shaped particles. The hydrocracking reactor WABT remained very close to the same as the previous cycle, with a slight advantage offered from the ATX catalyst system. This is the result of a higher catalyst effectiveness factor which inherently improves the reactor performance in a similar operating regime with regard to space velocity. This advantage occurs along with the reduction in catalyst bulk density, which means greater performance is achieved with less overall catalyst mass. Together, both gures illustrate concon stant conversion from cycle to cycle with a slight ,
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700
800
Two of the most critical facfac tors affecting hydroprocessing/ hydrocracking reactor catalyst performance are simply shape and size. For generations, Criterion has led with innovation in the use of specialised shaped particles for maximum catalytic performance. The application and operation of hydroprocessing units with these products has resulted in both protability and sustainability gains for reners. Criterion’s ATX-shaped line of catalyst products has revolutionised the performance potential of hydrocracking units, enabling capacity increases and expanding the world’s largest cracking units. MPC makes no endorsement of the products described in this article. MPC’s opinions and conclusions are limited to its own experiential data included here.
References 1 Visser T, Maas E, How state-of-the-art reactor internals helped debottleneck a Total hydrocracker, Impact , issue 3, 2013. 2 Carruthers J D, D, DiCamillo D J, Pilot plant testing of hydrotreating catalysts influence of catalyst condition, bed loading and dilution, Applie dilution, Applied d Catalysis 43, Catalysis 43, Elsevier Science Publishers B.V., B.V., Amsterdam, 1988, 253-276. 3 Brunner K M, Perez H D, Peguin R P S, Duncan J C, Harrison L D, Bartholomew C H, Hecker W C, Effects of particle size and shape on the performance of a trickle fixed-bed recycle reactor for Fischer-Tropsch synthesis, Industrial synthesis, Industrial and Engineering Chemistry Research,, Feb 2015. Research 4 Worstell J H, Improve Fixed-Bed Reactor Performance without Capital Expenditure, CEP Magazine, Magazine, Jan 2004. 5 Ancheyta J, Muñoz J A D, Macias M J, Experimental and theoretical determination of the particle size of hydrotreating catalysts of different shapes, Catalysis Today 109, 2005, 120127. 6 Worstell J, Adiaba Adiabatic tic Fixed Fixed-Bed -Bed Reacto Reactors; rs; Prac Practical tical Guide Guidess in Chemical Engineering. Waltham, Engineering. Waltham, MA: Elsevier, 2014. 7 Trivizadaki Trivizadakiss M E, Giakoumakis D, Karabelas A J, A study of
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particle shape and size effects on hydrodynamic parameters of trickle beds, Chemical Engineering Science 61, 2006, 55345543. 8 Nemec D, Levec J, Flowthrough packed packed bed reactors: 1. 1. Singlephase flow, Chemical Engineering Science 60, Science 60, 2005, 6947-6957. 9 Afandizadeh S, Foumeny E A, Design Design of packed bed reactors: guides to catalyst shape, size, and loading selection, Applie Applied d Thermal Engineering 21, Engineering 21, 2001, 669-682.
Adrienne Van Koope Adrienne Kooperen ren is a Senior Hydrocracking Technical Service Engineer with Criterion Catalysts and Technologies in Houston, Texas. Her primary responsibility is providing technical support to Criterion’s customers: unit performance evaluation and optimisation; troubleshooting; start-up support; and evaluation
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of margin improvement opportunities. She also coordinates Criterion’s Hydrocracking Technical Service Pilot Plant Testing in Houston and instructs the Hydrocracking Catalyst Fundamentals portion of the Criterion University Hydrocracking Seminar.
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