Eurecat.in

MINIMIZING CATALYST COSTS BY SOUND
CATALYST MANAGEMENT
Francis Valeri, Frédéric Girardier
Eurecat SA - La Voulte-sur-Rhône - France Dr. Saleh Abotteen
Al-Bilad Catalyst Co. - Jubail - Saudi Arabia ABSTRACT
Specialized companies are now available to provide services to oil refineries andpetrochemical plants, in relation to their catalyst operations, such as off-siteregeneration, off-site presulfiding or other catalyst preconditioning, handling andrecycling services.
The growth of catalyst services relates to the fact that catalyst requirements formany industrial units are becoming more severe, due to more stringent productspecifications or unit severity requirements. In some cases, use of increasedcatalyst volumes and/or reduced cycle lengths are observed.
This paper presents the financial and technical advantages brought by theavailability of those catalyst services, together with the various options now offeredto the refiner to manage its catalytic units. Various scenarios are described,applicable either to a simple refinery scheme, or to a more complex multi-sitesand/or multi-units operation.
Each operator can now adapt the various catalyst management options to itsparticular needs, in order to minimize catalyst costs and maximize unitsprofitability.
An active partnership with a local specialized service company is a key element toensure maximum success of such programs.
INTRODUCTION
Until the seventies, catalysts used in the oil refining and petrochemical industrieshad a very simple life cycle: they were either used for one production cycle untilexhaustion of their catalytic properties, or otherwise they were used for a fewcycles, with some in-situ regeneration between cycles. Disposal, in a more or lessacceptable environmental way was the last step. Under those conditions, therewas a rather limited need for off-site services.
The situation has changed drastically, more recently as off-site regeneration ofmany catalysts, and particularly hydroprocessing catalysts, has become widelyaccepted and preferred by the industry. This is due to a number of reasons,including safety and time considerations and better catalyst activity recovery.
Together with off-site regeneration, other services such as off-site presulfiding,other preconditioning processes and catalyst handling have become available tohelp the refiners manage their unit shutdowns and start-ups. Furthermore, spentcatalyst disposal is evolving towards more environmentally acceptable recyclingschemes.
The growth of catalyst services is the result of more severe catalyst requirementsdue to more stringent product specifications or performance needs. In addition,the availability of catalyst services enables plant operators to look at their catalyticunits in a more global and optimized way, best suited for their needs. At present,catalyst management has become a reality.
Catalyst management possibilities exist for a single refinery unit operation or formore complex operation involving more units or more sites. Managing catalystoperations becomes increasingly complicated and partnership with a specializedservice and technology company (such as Eurecat) provides key benefits to therefiner.
1. CATALYST AGING PROCESS
During a catalytic operation, various factors can cause a temporary or permanentaging of the catalyst. As an example, let us illustrate the case of hydroprocessingcatalysts : 1.1. Deactivation
Depending on the type of service and unit severity, the cycle length of ahydroprocessing unit is typically between 6 months to 4 years. In fixed bed unitscatalyst deactivation during the run is compensated by a progressive increase inbed temperature, up to a certain value dictated by metallurgical constraints orproduct qualities.
Deactivation is due to three main causes: carbon (or coke) laydown, active phasesintering, and metal poisoning. During off-site regeneration, good success isachieved with carbon elimination as well as active phase redispersion.
The end-of-cycle is usually determined by a level of activity too low to meetproduct specifications, but it also can be due to a unit upset (high pressure drop,compressor failure, hydrogen shortage), or to a scheduled unit shutdown. This isconfirmed by the carbon content on spent HDS catalysts before regeneration.
The detrimental effects of coke are a reduction of support porosity, leading todiffusional limitations, and blocked access to active sites.
1.2. Metal contamination
Metal contamination by nickel or vanadium is observed in units running withfeedstocks such as VGO, atmospheric resids, or vacuum resids. The V :Ni weightratio depends on the type of crude, and is usually in the range of 2:1 to 4:1. Asnickel is not a poison for catalyst activity, being itself an active metal forhydroprocessing reactions, the criterion for reuse of a regenerated catalyst isgenerally based on the vanadium content.
Depending on the type of service, catalysts containing more than 2 to 4 wt%vanadium are usually considered unsuitable for regeneration and reuse.
Vanadium concentration has been found to vary with bed depth, but may also varyradially in case of flow maldistribution. Figure 1 shows one example of vanadiumcontamination observed on a catalyst coming from a VGO unit.
We observe a 0.41 slope relating sulfur content to vanadium, for spent catalyst,whereas 0.94 corresponds to stoichiometry for vanadium sulfide V2S3. Afterregeneration, a 0.21 slope is observed, significantly lower than the 0.63 ratio forvanadyl sulfate VOSO4. This shows that vanadium is probably present in theregenerated catalyst as vanadium oxide, and that the remaining sulfur is presentas aluminium sulfate.
Vanadium & Sulfur content on Catalyst
Vanadium % wt
Traces amounts of arsenic are found on some spent catalysts, and they remain onthe catalyst after regeneration. Arsenic is probably stabilized by forming an inter-metallic compound with the catalyst metals or as a mixed oxide with the support.
When arsenic is present, levels of 500 to 2000 wt ppm are often found on thespent catalyst. It is generally observed that there is a very steep arsenic gradientfrom the top to the bottom of the bed under hydroprocessing conditions. Vacuumunloading of the top catalyst layers is advised to permit catalyst segregation and analysis whenever arsenic contamination is suspected. In most cases, whenarsenic contents exceed 1000 wt ppm on the catalyst, catalytic activity starts to beseriously affected.
Iron, sodium and silica are other metal contaminants often found in the spentcatalysts. Iron has a rather low catalyst deactivating effect and comes essentiallyfrom corrosion of upstream equipment, and is generally found in low quantities.
Sodium is encountered in cases of unit upsets, such as desalter malfunctioning,contamination by caustic soda or sea water heat exchanger leakage. Siliconcontamination is also quite common for naphta HDS units running on cokernaphta, due to use of silicon-based anti-foaming agents.
2. CATALYST SERVICES
The availability of various catalyst services has gradually increased since the late1970s, initiated by the rapid spread of off-site regeneration, offering alternative ornew ways for refiners to more precisely evaluate catalyst aspects of theirhydroprocessing or other process unit operation.
2.1 Regeneration
Until the mid 1970s, all regenerations were conducted in-situ in the unit reactors,but off-site regeneration has gradually become the industry standard in thewestern world, as illustrated in Figure 2. The other parts of the world are rapidlyincreasing their use of off-site regeneration services. This technique is preferred tothe in-situ regeneration for many reasons including safety, time considerations,and better activity recovery.
Catalyst quality and performance tests are a critical part of all regeneration jobsperformed by Eurecat in order to assess the regenerability or interest for reuse ofa given lot of spent catalyst, and to ensure optimal quality control during theindustrial process.
First, physical properties of the catalyst, such as mechanical strength (BulkCrushing Strength or Side Crushing Strength), average length and lengthdistribution must be monitored. Comparing the surface area of the regeneratedcatalyst to that of the fresh catalyst provides an excellent indication of thecatalyst’s quality. Carbon and sulfur analyses are also key factors and elementalmetal analyses are necessary to identify metal contamination. The presence ofmetal contamination is not always linked with a loss in surface area.
Trends in Off-Site Regeneration in Europe
Dynamic Oxygen Chemisorption (DOC) is a good complementary tool to evaluateactive phase sintering for some special catalysts. Sensitivity to metal poisoningand the difficult analytical techniques involved in the DOC procedure requirecareful interpretation of the DOC test results.
The most reliable tool to evaluate the global performance of a hydroprocessingcatalyst is clearly an activity test.
Different technologies are available in the industry to carry out off-siteregeneration : rotating kiln, belt oven or fluidized bed oven.The industrial regeneration process employed by Eurecat is based on the use of a Roto-Louvreoven technology, which enables an excellent contact between gas and solids(Figure 3). A high degree of homogeneity and excellent temperature control areachieved from the contact between hot air, passing through the spaces betweenthe louvres, and the thin layer of catalyst rotating slowly inside this conical innershell.
Side & Cross view of a roto-louvre oven
Cross view
Side view
Spent
Catalyst
Regenerated
catalyst
2.2. Catalyst Physical Separation
Various grading or physical separation equipment are required to address allkinds of individual needs or situations : length grading, separation of componentsfrom catalyst mixtures, separation of ceramic balls of various sizes, etc. Quiteoften, grading requirements are connected with an off-site regeneration.
2.3. Presulfiding and other Preconditioning
In order to be “active”, all hydroprocessing catalysts containing molybdenum,nickel or cobalt must be sulfided. Thus, the metal oxides must be converted tothe sulfided form.
Ten years ago, all sulfiding operations were carried out in-situ, i.e. after the freshor regenerated catalyst had been loaded into the unit reactors. Various methodswere used, the most efficient one being the use of a sulfur containing agent, suchas dimethyl disulfide. Drawbacks to the in-situ method include: the handling of atoxic, environmentally unfriendly sulfur compound ; risk of non-homogeneoussulfiding; and the lost production time required for sulfiding.
Since 1986, our company has pioneered the use of a new technology for off-sitepresulfiding (or presulfurization) of hydroprocessing and other catalysts followedmore recently by other companies. It provides the refiner with a stable non-toxiccatalyst, homogeneously presulfided with each catalyst grain containing thecorrect amount of sulfur. This technique simplifies of the unit start-up procedureand reduces start-up time considerably.
Innovation continues to take place with the introduction of technologies designedto provide complete catalyst activation off-site and to skin-passivate the catalyst toallow its safe handling. As a result, the catalyst will be ready for use, and the start-up procedure will be reduced to a bare minimum, i.e., the heating of the unit to oil-in temperature.
Other preconditioning processes have been developed, that provide oil refinersand petrochemical plants some new options for the utilization of their catalysts, asshown on Table 1. Preconditioning Processes
2.4. Catalyst Resale
Each individual refinery or unit determines its catalyst requirements and the mosteconomical way to achieve them. As a consequence, refiners have from time totime surplus amounts of regenerable catalyst. Eurecat, through a catalyst resaleprogram, assists refiners in finding an outlet for their material, and acts as asource point for those seeking to employ available regenerated catalyst.
2.5. Catalyst Handling
Spent catalysts due for unloading from a reactor are most of the time highlyreactive materials, owing to their sulfided form. As such, they can reactspontaneously when exposed to oxygen or air and require special handling,storage and transportation procedures. The presence of pyrophoric iron sulfide inspent catalyst, compounds the problem even more.
Various precautions, including unloading under inert atmosphere, either by gravityor by vacuum, are recommended by specialized handling service companies forsafety reasons. Catalyst passivation methods also exist to render the spentcatalyst less hazardous, but they exhibit various degrees of success.
Depending on the shutdown procedure used, the quantity of hydrocarbonsadsorbed in the spent catalyst porosity may vary considerably. A film ofhydrocarbons makes the catalyst less sensitive to oxidation, but this requires anadditional stripping step prior to regeneration.
Catalyst loading is a critical factor for maximizing catalyst performance. Drums,bins or bags are-used, depending on the refiner’s choice and safetyconsiderations. Minimization of catalyst breakage and uniform catalyst distributionin the reactor are critical to the success of this operation. Dense-loadingtechniques are very popular to achieve an improved catalyst orientation anduniform void spacing and maximize bed density.
Supervision of the catalyst unloading and loading by a competent expert companyprovides additional help or insurance for the plant operator : it mainly aims athaving a permanent “process” look, in addition to the conventional shutdownmaintenance activities.
2.6. Recycling
Various possibilities are offered to refineries and petrochemical plants to disposeof their spent catalysts, depending on factors such as catalyst type andcontaminant metals.
The non-availability of a “universal” recycling company, capable of handling alltypes of spent catalysts found in refineries and petrochemical plants, makes itsometimes difficult for the user to find the appropriate outlet for the spent catalystsor other spent materials. In addition, legislation and transportation regulationsoften vary between geographical regions and countries. The presence of manybrokers or other intermediators does not always guarantee a safe andenvironmentally acceptable recycling process. Many plants prefer to deal with wellestablished companies who can provide a unique expertise, and a network ofpartner companies to assist the user in finding the optimal recycling solutionsappropriate to his need.
Noble metal catalysts containing platinium (Pt) or paladium (Pd) are sent tospecialized metal reclamation companies. For spent hydroprocessing catalysts,pyrometallurgy or a combination of hydrometallurgy and pyrometallurgy areavailable options. Although landfilling is still widely practiced, increasinglyrestrictive environmental regulations regarding hazardous wastes and risks offuture liabilities are inducing most refiners turn to more environmentally soundoptions.
2.7. Transportation and storage
Regenerated catalyst can be transported or stored by means identical to thoseused for fresh catalyst, typically in drums, bins or bags.
As presulfided catalysts, spent catalysts are normally classified as self-heatingsubstances ; therefore, drums or bins are required. Other national or regionalrestrictions for shipping may apply in various parts of the world.
Specialized bins from rental companies are now available, which provide a safeand efficient means to transport spent, regenerated, and presulfided catalyst. Thismode of transportation is particularly attractive for turnaround operation, since thenumber of rental days is limited. In other cases, the cost of rental for a long periodmay be uneconomical.
3. ECONOMICS OF CATALYST SERVICES
The desire of many operators to subcontract more and more of their tasks, whichare not strictly part of their day-to-day activities, and the availability of variousinnovative catalyst services has resulted in a change of thinking regarding themanagement of all catalyst related operations. One of the clear changes has beenthe growing interest towards multi-cycle operations using the same catalyst batch,with off-site regenerations in between production cycles. For example, Eurecat’sexperience shows that many refiners now routinely run 2 or 3 cycles with any ofthe state-of-the-art HDS catalysts, either in the same unit, or through cascadingthe regenerated catalyst to a less severe unit.
Typical costs associated with some off-site services, relative to the cost of freshcatalyst, for a GO-HDS unit are given in Figure 4. Of particular significance is thelow cost of off-site regeneration relative to fresh catalyst, whereas the catalyticperformance of regenerated catalyst remains close to that of the fresh catalyst.
COST OF OFF-SITE SERVICES VS FRESH CATALYST
COST OF SERVICES, REL % OF FRESH CATALYST
It is also interesting to note that as the use of regenerated catalysts increasesrelative to fresh catalyst, the total expense (fresh catalyst + services) is reducedsignificantly, as shown in Figure5. Fresh Catalyst and Services Costs
Cost (Relative basis)
4. CATALYST MANAGEMENT
Total Catalyst Management can be defined as the actions taken to control allevents involving the catalyst during its service life, from purchase of the freshcatalyst to its disposal in an environmentally sound way.
As indicated previously, the use of various catalyst services are now an integralpart of catalyst management. We would like to describe here different particularcases : 4.1. Single refinery operation
Although having ensured the best activity recovery through ex-situ regeneration,the refiners requirements may be such that even after only one cycle, it is notpossible to reuse the catalyst in the same service. This is typically the case forvery high severity units, or units of strategic importance. The refiner then facesvarious options depending on the refinery lay out: 4.1.1. Multi-application cascading
If not reusable in the original unit, catalyst might still be suitable in less severeapplications. Typically cascading could be gasoil hydrotreater ⇒ naphtahydrotreater ⇒ kerosene hydrotreater. This type of cascading, although useful,does however have some limitations : • type of catalyst may differ for different units (CoMo for gasoil HDS/NiMo • larger inventories for severe applications (e.g. gasoil HDS), and longer cycle length on other units (e.g. naphta), may quickly lead an unbalancebetween supply and demand for regenerated catalyst.
4.1.2. Catalyst shifting
Units built to meet the low sulfhur requirements are very often large multi-bedreactors, or even multi-reactor systems (typically a small guard reactor and alarger vessel downstream). VGO hydrotreaters are also often multi-reactorunits. In these cases, it is often possible to shift a regenerated catalystupstream (from the main vessel to the guard reactor for example).
This solution is to be considered especially when metals poisoning, even at lowlevels, is the reason for catalyst deactivation. Using a regenerated catalystupstream will provide sufficient HDS/HDN activity whilst not sacrificing the freshcatalyst to metals poisoning. Shorter cycle length of the guard reactorcompared to the downstream reactor will often allow use of most of theregenerated catalyst, as shown on Figure 6. Figure 6. Catalyst shifting
Protection of the HDS/HDN catalyst will be improved by using a demetallisationcatalyst as top layer. These top layer demetallisation catalysts are usually notregenerable.
Figure 7 illustrates, as an example, the economical benefits of the abovedescribed operation, resulting in a 30% savings over a 5-year period.
Figure 7.
S I N G L E R E F I N E R Y O P E R A T I O N
C A T A L Y S T S H I F T I N G
Since metals poisoning is a concern, special attention needs to be given to theanalyses performed before and after regeneration. If metal breakthrough issuspected, segregation of the potentially contaminated area may be possibleduring unloading (e.g. by vacuum unloading). Regeneration companies, throughtheir analytical capabilities and experience will be able to advise whenreusability of any given batch is questioned.
4.1.3. Catalyst resale
If not reusable internally, or not needed in the short/medium term by the refiner,catalyst might be of a sufficient quality for another refiner’s requirements, andresale is an option. This requires close collaboration between the refiner andthe service company. The catalyst needs to be to fully characterised, thoseparts which are not reusable need to be segregated, and the quality catalystproposed to the market (world-wide).
4.2. Multi-refinery operation
To reduce downtime to a minimum, allow stricter control of both fresh andregenerated catalyst quality, and also protect against emergency catalystrequirements, spare batch operation is becoming the norm. As a result larger andlarger catalyst inventories are observed.
To reduce total cost, companies which operate several refineries in a specificgeographical zone, are looking increasingly at setting-up pools of catalyst,dedicated to a specific application. This is being done in close collaboration withcatalyst manufacturers and service companies such as Eurecat.
The key element for a pool of catalyst is to have, at any time, a batch of qualitycatalyst ready for use. The size of this batch is typically equivalent to the capacityof the largest unit in the pool.
4.2.1. Pool operation
A catalyst pool, consisting of regenerated and fresh catalysts, which can beused by any of the hydroprocessing units which are part of this program. Anycatalyst lot which is part of the pool can be subject to various services,contracted by the client company.
Catalyst Life Cycle
S p e n t C a ta ly s t
P r o c e s s U n it
R e g e n e r a tio n
Q u a lity c ertif ic ation& T ran s p o rtation S p e n t C a ta ly s t
R e c y c lin g
P re s u lfid in g
R e s a le to le s s
c r itic a l u s e r s
C a ta ly s t p o o l
Q u a lity C e rtif ic a tio n& T ran s p o rtation C a ta ly s t
M a n u fa c tu rin g
Obviously, operation of such a pool requires a full partnership between therefiner and the service company, initially to set up the quality requirements forthe catalyst, and then at each step of the decision-making cycle. Collaborationis also necessary to decide how catalyst rejected from the pool can best beused: cascading, shifting, resale, or disposal.
4.2.2. Pool quality requirements
For the pool to function effectively the refiners must be sure that the catalyst willhave the required activity. It is therefore vital to have only top quality catalyst,and to quantify this.
A means of quantifying and/or testing activity is necessary, both to determinewhether catalyst is regenerable or not prior to regeneration, and also todetermine whether catalyst is acceptable for the pool.
But other parameters are also critical in order to establish the quality of thecatalyst, such as the average length. Large units are particularly sensitive topressure drop, and catalyst particle length distribution must be studied closelybefore reloading any given batch. In many cases length grading will benecessary in order to obtain an acceptable product.
4.2.3. Pool management requirements
Pool management requires a designated catalyst co-ordinator within the group,responsible for: • incorporation (or rejection) of a regenerated catalyst into the pool, • catalyst mixing from various batches of regenerated and fresh catalyst to • dispatching of given batch to the end users.
End users requirements need to be clearly stated as far as batch size, activityand cycle length are concerned.
The service company will support the pool manager with analysis of each batchand keeping an up-to-date inventory available, but cannot replace him for keydecisions concerning reuse of catalyst.
In total, many services are provided by the service company, such as : • presulfiding or other preconditioning processes, • spent catalyst recycling (possibly through an external partnership), • handling/reactor loading expertise (possibly through an external • metallic containers/bins rental.
4.2.4. Economical incentives of pool management
Implementation of a pool of catalyst presents various economical incentives,besides improving the overall catalyst quality, which alone would justify itsexistence: • The existence of a spare charge guarantees that unit shutdown will be limited to the strict minimum (catalyst handling and unit inspection ifrequired).
• Accurate planning of expected cycle length is possible through catalyst quality controls : in fact, catalyst quality and performance is known andcertified at key steps of its life cycle.
• One spare charge is necessary for the whole group, instead of one per unit/refinery, substantially reducing the catalyst inventory, and thereforeoverall catalyst expenditures.
As an example, Figure 9 describes the economical benefits of a catalyst pooloperation. In this case a 35% savings is achieved over a 5-year.
Figure 9.
C A T A L Y S T P O O L M A N A G E M E N T
F O R A G R O U P O F R E F IN E R I E S
N o c a t a ly s t m a n a g e m e n t1 s p a re b a t c h f o r e a c h u n i t 1 s p a re b a t c h f o r t h e g ro u po f u n i t s CONCLUSION
The increased severity and economical constraints of all hydroprocessing unitoperations put added demand on the catalyst performance. Such performancemust therefore be monitored and optimized at all stages of the catalyst life cycle.
Various off-site services are available to achieve these objectives, includingregeneration and presulfiding.
In addition to providing such services, companies like Eurecat are now involved inpartnerships with refiners who are implementing a catalyst management programto satisfy their particular needs, with emphasis on product tracing andperformance control. This offers operating companies access to minimized overalloperating expenses and maximized profitability from their units.
Vanadium & Sulfur content on Catalyst
Vanadium % wt
Trends in Off-Site Regeneration in Europe
Side & Cross view of a roto-louvre oven
ROTO-LOUVRE OVEN
Cross view
Side view
Spent
Catalyst
Regenerated
catalyst
COST OF OFF-SITE SERVICES VS FRESH
CATALYST
COST OF SERVICES, REL % OF FRESH CATALYST
Fresh Catalyst and Services Costs
Fresh Catalyst and Services Costs
CATALYST LIFE CYCLES
COST (Relative basis)
S I N G L E R E F I N E R Y O P E R A T I O N
C A T A L Y S T S H I F T I N G
Catalyst Life Cycle
Spent Catalyst
Process Unit
Regeneration
Quality certification& Transportation Spent Catalyst
Recycling
Presulfiding
Resale to less
critical users
Catalyst pool
Quality Certification& Transportation Catalyst
Manufacturing
C A T A L Y S T P O O L M A N A G E M E N T
F O R A G R O U P O F R E F IN E R I E S
N o c a t a ly s t m a n a g e m e n t1 s p a re b a t c h f o r e a c h u n i t 1 s p a re b a t c h f o r t h e g ro u po f u n i t s

Source: http://www.eurecat.in/Technical_Doc/Minimiz_Catalyst_Petrotech.pdf