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Jun-2016

Look beyond the catalyst

Purification and dispersion strategies applied to hydroprocessing catalyst can improve reactor performance

AUSTIN SCHNEIDER
Crystaphase
Viewed : 1955
Article Summary
Refiners are feeling the pressure, and not just the kind of pressure found inside hydroprocessing reactors. Lacklustre catalyst performance and frequent shutdowns are eroding profits. Less product is refined, and what is refined is of a lesser quality, further cutting into margins. Additional changeouts and higher temperatures resulting from distribution and pressure drop issues mean greater risk exposure for equipment, personnel, and the environment. Certainly, companies are feeling the pressure to turn things around.

It is natural for refiners to look to the catalyst – the reactor’s heart and purpose – to solve the problem. Unfortunately, ‘new and improved’ catalyst based solutions can be expensive and may not really be solutions at all. Ultimately, this leaves refiners scratching their heads, wondering what sort of black magic is required to solve the performance problem.

Optimising catalysis has very little to do with the catalyst. And no magic is required.

Purification and dispersion strategies
Those seeking to improve catalyst performance should set their sights further upstream to the purification and dispersion of the feedstock.

Purification and dispersion represent two distinct phases of catalysis optimisation. Purification is the process of removing foulants (particles and poisons) from the feedstock that can interfere with catalyst performance. Dispersion is the process of maximising contact between the feed and the catalyst, resulting in stronger reactions sustained for longer periods.

In traditional systems, the process of purifying progressively impedes dispersion, creating a Catch-22 dilemma. Crusting occurs in the bed, blocking flow, creating hot spots, and dramatically diminishing catalyst contact, productivity, and profitability. However, there is 
an alternative to traditional systems.

Since 1989, Crystaphase has provided purification and dispersion strategies to hundreds of refining, petrochemical and chemical plants worldwide. Through a disciplined understanding of the quantifiable variables that impede performance, we have developed a systematic and replicable approach for removing those obstacles.

Crystaphase reticulation technology uses a proprietary internal filtration design that eliminates crusting in the purification phase, thus maintaining uniform distribution in the dispersion phase, allowing for longer production cycles while mitigating pressure drop problems.

Do you know your foulant?
Soluble and insoluble particles in refinery feedstocks are increasingly becoming a problem, due to the processing of high acid and high sulphur opportunity crude. Tight oil and high TAN stocks are also more commonplace, creating a challenge for, and wreaking havoc with, equipment. Cracked stocks come with diolefins that can polymerise in the reactor, forming carbonaceous foulants. Other particles, like silica fines, iron compounds and corrosion, can plug catalyst and equipment.

Effective solutions require not only knowing what is in your feed, but how and where it accumulates, and the chemistry behind it. This insight can mean the difference between developing a filtration solution and creating a bigger problem.

When examining elements in refinery feedstock, it pays to be thorough. Insoluble compounds found in deposits are often incorrectly identified as catalyst poisons. It is highly recommended that numerous procedures are conducted, so that the engineer or scientist can correctly diagnose the source and the chemistry behind the problematic compounds. At Crystaphase, a laboratory is dedicated to foulant analysis and can run a wide range of tests in order to provide this crucial insight:
• Particle size analysis  Using laser diffraction, this can determine particle size distribution in a range of 0.1 to 3500 microns (µm), making it possible to match a custom filtration solution specifically to the particles plaguing a reactor.
• Loss on ignition (LOI) Samples are heated to approximately 500°C, burning off any residual sulphur or carbon, so that we can measure how corrosion and carbon/polymer deposition accelerate deposit formation.
• Inductively coupled plasma (ICP)  We can test for a large array of elements, reporting values as low as a few ppm, identifying particles contributing to pressure drop and poisons shortening catalyst life.
• Scanning electron microscopy (SEM) At up to 1200x magnification, we can visually examine the shape of accumulated foulant particles for a clear picture of their role in diminished reactor performance. This allows for the resolution of particles and particle features as small as 1 µm. Understanding particle morphology helps identify filtration efficiencies and particle generation sources.
• Energy dispersive X-ray spectroscopy (EDS) EDS identifies the chemical elements that make up foulant particles. Together with SEM imaging, it helps determine their origin, trace their morphology under process conditions, and determine how they interfere with reactor performance.
•Digital microscopy This cutting edge tool can resolve samples down to 1 µm with full depth of field, for a lifelike, high acuity perspective on the formation of foulant deposits.
• X-ray microtomography This technology lets us see inside a sample and create a digital model of its structure, allowing us to evaluate the real world performance of its filtration ability.
• Pressure drop analysis Combining engineering and scientific programming, this technology lets us accurately predict the performance of Crystaphase solutions at different sizes and volumes.
• Reactor filtration and pressure drop simulation  A suite of software allows us to anticipate pressure drop issues and model proposed or current solutions before the next cycle, instead of after it.

The difference between particles and poisons
Purification constitutes a science in itself. While feed filters installed upstream of hydroprocessing reactors can remove particles larger than 10-50 µm (depending on the screening specifications), poisons or soluble foulants such as iron naphthenate and asphaltenes can bypass the filter system and precipitate out in the catalyst bed. Additionally, any particles below the micron rating of the filter remain in the feed post filtration, then agglomerate to create larger problems downstream.

Crystaphase has developed an understanding of these foulants, along with the means to eliminate them. Specifically, we can effectively capture and store particles in their reactor beds, using a system that is integrated directly into fixed bed process applications.

Marketed as Crystaphase CatTrap Technology, this solution features a bypass design that eliminates cake-layer formation. Here, particle filtration actually occurs within inert silica-alumina discs. With a high porosity matrix, the product lets you maintain flow much longer than conventional solutions. Better yet, it accomplishes this occupying far less volume in the reactor, allowing you to maximise catalyst load utilisation. With high crush strength, increased resistance to attrition and higher density, CatTrap discs vary in size and chemical composition, allowing the solution to be customised to specific applications.

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