Removing Catalyst Fines From Raney Nickel Catalyst Reactions

 

Raney nickel catalysts
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Whether you call it Raney nickel or Raney mud, this alloy of aluminum and nickel is a reagent common to many organic processes. Currently, most Raney nickel catalyst slurries are clarified with the use of manual plate or nutsche filters, bag filters, or cartridge filters. 

Yet any of these approaches require manual operations for cake discharge and cleaning between batches or campaigns. At the same time, they accrue high labor, maintenance and disposal costs  and  expose operators and the environment to toxic and hazardous solvents, solids and contaminated filter tools.  

BHS developed a more contained, cost-effective approach using batch-operated, pressure-filtration systems candle filters. 

A Candle Filter Primer

A candle filter is a pressure vessel filled with tubular filters called candles. The candle is comprised of a filtrate pipe, a perforated core with supporting tie rods, and a filter sock.

The filtrate pipe runs the length of the candle and ensures high liquid flow, as well as maximum distribution of the gas during cake discharge. The tie rods create an annular space between the filter sock and the perforated core, which helps maintain a low pressure drop during operation and promotes efficient expansion of the filter sock during cake discharge. The filter sock, made of various synthetic materials, is installed over the candle and can remove particles smaller than 1 micron (μm).

As the cake builds during operation, the candle filter’s removal efficiency increases, enabling removal of particles as small as approximately 0.5 μm. During operation, pressure from the reactor forces the slurry into the bottom of the pressure vessel. The solids build up on the outside of the filter sock, while the liquid filtrate flows into the candle through the registers and out of the vessel. This process continues until the maximum pressure drop, design cake thickness, minimum flow, or filtration time is reached. 

For concentrated cake discharge, low-pressure gas enters in the reverse direction through the registers and into the individual candles and expands the filter socks. This process breaks apart the cake, which detaches from the filter sock and falls into the vessel cone. The cake is then discharged as a concentrated slurry. 

Raney Nickel Catalyst with Candle Filters for Slurry Discharge

In this application, the current process after the reactor is gravity separation, hydrocyclones and then followed with cartridges and bag filters.  The specification for the process liquid (diamine and water) is less than 3 ppm catalyst.  This recovery process was inefficient and exposes the operators to the diamine and catalysts creating a safety hazard.  The average particle size is 2 um and amorphous crystals.   

Lab testing and pilot testing was conducted to determine a processing scheme that eliminates solvent exposure, reduces the maintenance and operation requirements of the current scheme and recovers the catalyst to less than 3 ppm.  The final design was a BHS slurry-discharge candle filter with 19 m2 of filtration area. 

Candle Filters for Raney nickel Slurry Discharge

BHS developed this approach working with a client whose process after the reactor included gravity separation, hydrocyclones, then followed with cartridges and bag filters. The specification for the process liquid (diamine and water) was less than 3 ppm catalyst. The average particle size was 2 um and amorphous crystals. Yet, this recovery process was inefficient and exposed operators to the diamine and catalysts, which created a safety hazard.  

BHS conducted lab  and pilot testing to determine a processing scheme that eliminated solvent exposure, reduced maintenance and operation requirements, and recovered the catalyst to less than 3 ppm. The final design was a BHS slurry-discharge candle filter with 19 m2 of filtration area. Learn more about this application in this article.

Chemical Engineers & Our Superstitions

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Superstitions surround us: Touching wood? Carrying a rabbit’s foot? Collecting lucky pennies? Not stepping on any cracks? The list goes on and on. 

On one of my many chemical filtration business trips (many people have superstitions making flights safer), I read an interesting article on superstitions in the Wall Street Journal’s (WSJ) Magazine. Six luminaries from different walks of life — photography, acting, cooking, writing, directing and music — weighed in. But, alas, there were no chemical engineers.  So, I thought I’d remedy that in a blog. 

The WSJ article featured various thoughts on superstitions. Some defined superstitions based upon religion and culture passed on from many generations. Another outlined a simple ritual such as “when hearing the title of a Scottish play, one would run outside, turn around three times, then knock on the door to come back inside the theatre.” Then, there were “routines” to keep your days identical (i.e. the same workout, the same coffee, etc.). Others talked about superstitions as an attempt at “having control of what you can control.”

However, the one overriding theme, as photographer Gregory Crewdson stated, is that a belief in superstition “comes down to order” and wanting “to clear your path of unknowns.”  

Clearing the Path for Chemical Engineers

So, how does all that relate to chemical engineering?

If you accept Crewdson’s view, all chemical engineers are superstitious. We are always trying to clear our paths of the unknown. In every chemical filtration process, it is the unknowns that give us the most headaches. Why does the pump keep plugging? Why does the filtration system not produce a clean filtrate? Why is the process not meeting the production rates?  The questions we face are endless! But our job remains the same, we must “clear our paths of the unknown.”

Regular readers will know where I’m going with this…Test! Test! Test! Testing is our way of answering questions in controlled environments. To develop a process or troubleshoot an existing one, we need to ask the correct questions, think critically, walk around the plant, etc.  

Contact me with your superstitions for solving critical filtration and drying applications.  Let’s have fun exploring what we all do in chemical filtration.  

Inventive Filtration Technologies for Palladium Recovery 

 

Palladium Recovery
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Many times we encounter an “if it ain’t broke don’t fix it,” mentality. Process engineers in particular run up against this constantly. Yet, when it comes to palladium recovery, we’ve seen some strong results from taking an inventive approach to the filtration technologies uses. Currently, in recovering palladium catalysts the slurries are clarified with the use of filter presses, manual plate or nutsche filters, bag filters, or cartridge filters.  

All of these require manual operations for cake discharge and cleaning between batches or campaigns. Other drawback include: 

  • high labor and maintenance costs
  • high disposal costs 
  • exposure of the operators to toxic and hazardous solvents and solids 
  • environmental impact of used and contaminated filter cloth, bag filters and filter cartridges.  

A new approach developed by BHS uses Pressure Plate Filters, which are batch-operated, pressure-filtration systems. Here’s what’s involved.

Pressure Plate Filtration SystemsScreen Shot 2019-01-14 at 3.13.55 PM.png

Pressure plate filters are comprised of filter plates, contained within a pressure vessel. The vessel contains the circular horizontal filter plates in a plate stack. The slightly sloped plates are conical-shaped metal that support a coarse-mesh backing screen covered with filter cloth. An opening in the center of the plate allows the filtrate to travel between plates and out of the vessel. 

The slurry enters the bottom of the vessel and is pumped upward. The solids build up between the plates, while the liquid flows through the core of the filter plates and exits from the top of the vessel. The cake is then washed and dried. Two unbalance motors vibrate the filter plates to dislodge the cake from the filter cloth so it can be discharged. 

Pressure plate filters are used for filtration of cakes greater than 20 mm thick. They are selected for cakes that are stable horizontally because of the orientation of the plates. 

Palladium Catalyst Filtration, Washing and Drying 

There are many choices of technologies, but we’ve found pressure plate filters provide higher quality filtration. In one application, manual filter presses were used to recover and reuse the palladium catalyst. The filter presses exposed the operators to the process and had inefficient washing and drying. The process had a very short cycle of 4 hours per batch.

However, when the BHS pressure plate filter technology was implemented, the filtration, two-step cake washing, nitrogen blow drying and cake discharge were all completed in less than 4 hours with full containment.  Read the full article to learn more.

Changing it Up with Mixer-Dryer-Reactor Acquisition

 

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Starting off 2019, I talked about push pushing ourselves personally and professionally to embrace change. Well, I’m a man of my word, and I’m proud to announce a big change in filtration technology at BHS-Sonthofen GmbH. We’re looking at 2019 as a year of growth, starting with the acquisition of the internationally active AVA-GmbH technology company.

AVA, based just outside of Munich, Germany, has 25+ years under its belt producing innovative machines and efficient processes for any industry. They tackle mixing, drying, reacting, granulating, sterilizing, evaporating, humidifying, and homogenizing to combine engineering expertise and project management know-how to provide “tailor-made solutions from a single source.”

AVA’s product portfolio is a perfect fit with BHS. Having already cooperated with them on joint projects in the past, we can be sure that our company is only strengthened by this move.

In addressing the sale, Dennis Kemmann, Managing Director of BHS-Sonthofen GmbH was enthusiastic about the opportunity to combine our products to have an “even more comprehensive offering in all of our chemical, pharmaceutical and other markets.” 

Expanding Process Filtration Technology Technologies

BHS’s latest newsletter looks at the pairing in more particular applications. You can read more about selecting AVA Vertical or Horizontal Mixer-Dryers for Batch of or Continuous Operations. The goal is a streamlined approach handling as many processes as possible in one unit to curtail investment and process costs. 

Three of AVA’s multipurpose process machines are presented as possibilities to cover the vast majority of the application spectrum of the powder and granule processing industry:

  • AVA Vertical mixer-dryers for batch operation
  • AVA Horizontal mixer-dryers for batch operation
  • AVA Horizontal mixer-dryers for continuous operation

The newsletter also mentions the AVA test center in Germany, which allows customers to scale up from 15 – 90 liter batch mixer-dryer to full scale batch and continuous operations with full scale-up reports and drying curves issued after testing. The US test center in Charlotte, North Carolina will be completed in 4Q, 2019.

Ultimately, the AVA acquisition is good news for current and prospective clients. This change means more innovative process engineering solutions as well as an expanded team to support our customers. The combination of BHS and AVA systems will provide important process benefits for turnkey projects for our clients worldwide. Let me know what we can do for you!

Novel Filtration Technologies for Pharmaceutical Hydrogenation

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When it comes to removing catalyst fines from pharmaceutical hydrogenation reactions, BHS Filtration has come up with a novel approach.

Currently, most hydrogenation slurries are clarified with the use of manual plate or nutsche filters, bag filters, or cartridge filters. All of these require manual operations for cake discharge and cleaning between batches or campaigns. At the same time, these units suffer from high labor, maintenance and disposal costs as well as the exposure of the operators and the environment to toxic and hazardous solvents and solids, used and contaminated filter cloth, bag filters, and filter cartridges.  

A new approach uses candle filters which are batch-operated, pressure-filtration systems.

Understanding Candle Filters

A candle filter is a pressure vessel filled with tubular filters called candles. The candle is comprised of:

  • filtrate pipe —  runs the length of the candle and ensures high liquid flow, as well as maximum distribution of the gas during cake discharge.
  • perforated core with supporting tie rods —  the tie rods create an annular space between the filter sock and the perforated core, which helps to maintain a low pressure drop during operation and promotes efficient expansion of the filter sock during cake discharge
  • filter sock — installed over the candle, and made of various synthetic materials, the filter sock is capable of removing particles smaller than 1 micron (μm). As the cake builds during operation, the candle filter’s removal efficiency increases, enabling removal of particles as small as approximately 0.5 μm.

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Candle Filter in Action

During operation, pressure from the reactor forces the slurry into the bottom of the pressure vessel. The solids build up on the outside of the filter sock, while the liquid filtrate flows into the candle, through the registers, and out of the vessel. This process continues until the maximum pressure drop, design cake thickness, minimum flow, or filtration time is reached. The cake is then washed to remove impurities and residual mother liquor. Finally, the cake is dried. 

For cake discharge, low-pressure gas enters in the reverse direction through the registers and into the individual candles and expands the filter socks. This process breaks apart the dry cake, which detaches from the filter sock and falls into the vessel cone. The cake can also be discharged as a concentrated slurry. 

Pharmaceutical Hydrogenation Application 

In the pharmaceutical catalytic hydrogenation application, the current process after the reactor is metal bag filters for slurry discharge into manual nutsche “clamshell” filters for vacuum filtration and drying.  The process was time-consuming and required handling of liquids and solids including final “manual dig out” of the filters.  The process solvent was tetrahydrofuran (THF) and ethanol.

Lab testing was conducted to develop a new, one-step process for filtration and drying.  The BHS candle filters with pharma designed candles and cGMP compliance allowed for a revamp of the operation with two filters, one-on/one-off for continuous operation.  Read the full article and let me know what you think!

Application of Separation Techniques & Full Containment

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Process engineers devote their time to finding the appropriate application of separation techniques. There’s need for effective solid-liquid separation, cake washing, and drying steps across industries. In many chemical and pharmaceutical processes, the production operations are further complicated by the nature of the process, especially if the process is air-sensitive or toxic.  

The solid-liquid separation step may be accomplished by pressure, vacuum, or centrifugation in a batch or continuous mode. In this step, further choices need to be made regarding the type of filter media and the thickness of the cake or the cake depth during which the separation occurs. To optimize the production process, I’ve found value in thin-cake (2-25 mm) pressure separation technology for full containment, no residual heel.

Importance of Thin-Cake Filtration

Thin-cake solid-liquid separation can be defined as the formation of a cake in the 2-20 mm thickness range.  In this range, cake compressibility becomes less important in the cake building stage of a separation process.  Compressible cakes can be better handled at thinner cake depths and higher pressures. 

For example, an amorphous crystal that does not centrifuge well or requires long filtration times on Nutsche Filter-Dryers can be filtered at 45 psig with a cake thickness of 2 – 3 mm.  Thin-cakes also lend themselves to more effective washing and drying as there is less of a chance of channeling and the mechanism of “plug-flow” of liquids or gases is enhanced.

Impacting Filtration Performance

There are several parameters that can impact filtration performance:

  • Filtration pressure
  • Temperature
  • Particle size/Particle size distribution
  • Particle shape
  • Cake washing
  • Drying of the filter cake.

BHS’s Autopress technology can conduct filtration, cake washing, pressure and vacuum drying all in a contained environment. Cake discharge is complete. There is no residual liquid or solid heel, which is an important benefit for air-sensitive and toxic products.

Application of filtration techniques
Filter plate

Understanding Autopress Technology

This fully enclosed filter press, with circular filter plates, allows flow in forward and reverse directions. The filter plates (which can use synthetic or metal media) are contained in pressurized filter housing with a gas-inflated membrane sealing the annular space. Thus, all operations are contained from full vacuum to 150 psig.  

The operation of the AP Filter begins with slurry filling to form thin filter cakes of typically 5 – 25 mm thickness.  Pressure filtration continues operating up to 8 barg.  The cake can then be mechanically compressed to eliminate cracking to ensure maximum washing efficiency in the forward or reverse direction.  Finally, the cake can be pre-dried or fully dried either by vacuum or blowing gas through the cake. Gentle drying without agitation or tumbling is especially important for fragile crystals and thixotropic cakes.  Elastomeric knives sequentially and automatically discharge the circular cakes after which the filter begins a new cycle. 

Read more about this topic in an article I wrote for PharmaChem. My take-away is that with close collaboration between the client and the vendor, we can do the kind of creative problem-solving that applies the separation technique needed to achieve production objectives.

Becoming Uncomfortable in 2019

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Welcome to 2019.  

This blog marks the beginning of Perlmutter Unfiltered’s 5th year; it’s been fun writing and hearing from friends, colleagues, customers, and others from all over the world. I hope my mix of topics — innovation, leadership, and technical insight — have inspired you professionally and personally. 

Thinking about 2019 and preparing for another great year put me in mind of an interesting Fast Company article about what we can do to improve our work space.

Everyone gets comfortable at work, from where we sit and who we prefer to work with on our projects and teams.  As leaders in filtration technology, we look for “no-drama” days in which the process is optimized, production is overcapacity, and customers have no machine issues.  However, these calm and steady-state environments can lead to complacency and learning plateaus. On the flip side, when we experience periodic disruptions, we develop new views and new ideas.  

Therefore, for 2019,  I suggest “becoming uncomfortable.” Shake up projects, teams and tasks/responsibilities. Sit somewhere new. Push yourself personally and professionally to embrace change.

Becoming Uncomfortable

First, step-up to new roles and look for new responsibilities. This could be as simple as becoming an expert in distillation or solid-liquid separation (contact me and I can help you!) or developing expertise on a specific process at your company.  

Next, constantly challenge yourself to get better… call a vendor for a “lunch & learn” seminar, call a new customer and more importantly, make a call rather than sending an e-mail or text. The act of picking up the phone often makes us more uncomfortable in this digital age.

Going further, make small changes every day. A small change is easy to make and before long, the team, the process, the office will see improvements.  Working for BHS Filtration, we say, in German, eins bei eins (one by one) or as I like to say “millimeter by millimeter.”

So, let’s all become more uncomfortable in 2019. Make proactive changes rather than reactive.  Let me know your ideas on this, share your successes, and we can all learn to become uncomfortable together.  

Thinking Critically in Process Troubleshooting

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In past blogs, I’ve talked about reactive and proactive process troubleshooting. Reactive troubleshooting requires quick action to look at mechanical issues, upstream and downstream equipment, and operational procedures.  In proactive troubleshooting, we ask probing questions and walk around the plant to uncover potential problems and offer solutions.  

Dirk Willard, Contributing Editor of Chemical Processing, in his recent article “Read and Think Critically” offered more to think about on this subject. 

Dirk used an example of trying to write a debottling report and discovering several missteps:

  • The product manual was poorly written
  • The plant engineer had not identified what was missing from the manual and what he didn’t understand
  • No logic was applied to decide who would know best how to run the equipment — “the engineer who built it or the process expert who operates it”
  • The engineer could have paid more attention to the section that was more detailed on the topic at hand.

Ultimately, what was missing? Critical thinking! He called for “questioning the value of information, its relevance and validity, the agenda of the source and, most importantly, the logic on which the data are based.”  

process troubleshooting
Photo by Bernal Saborio G. (berkuspic) on Foter.com / CC BY-SA

He offered real world examples of critical review, “identifying what’s being done, how it’s done, why it’s done, and who’s doing it” with a paper mill selecting a close-coupled water pump without considering all angles of the decision.

Take a Critical Approach to Process Troubleshooting

I bet you can easily add your own examples. For instance, there always seems to be a question about instrument and compressed air for the process. The process design for valve actuation has one pressure, but the operators know that in normal operation there is high demand. So the instrument air pressure drops and the valve actuates more slowly. Slow actuation results in lower production. Thus, we need to keep in mind the actual conditions versus the design conditions.  

As for compressed air, it used to be “free” at the plant. Not any more. Every plant now considers this a cost of operation. Once again, operators know that during high demand, the air pressure drops. But the process designers may not have considered this. Next time, design in a compressed air tank so that your process can meet the requirements.  

To do your best work, keep thinking, keep reading, and keep asking questions. If you have an area of expertise, let me know; I am always learning and maybe I can use your skills. I’m always interested in learning more about process troubleshooting.

Busyness versus Business and Chemical Engineering Action

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My first blog of 2018 talked about the “speed” of the world and recommended slowing down and reflecting. Well, here’s some free chemical engineering advice as the year draws to a close: It’s important to take the time to review facts and data, analyze decisions, gather inspiration from many sources, and finally proceed with definite actions. Still, you’ll need to be ready to change, as things will come at you at “breakneck speed.”  

In my out-of-the-box way of thinking, I’m going to relate these ideas to the World Cup — Congratulations to France! During the big tournament of the big game in summer 2018, there was a lot of discussion about penalty kicks. 

Bradley Staats discussed them in the Wall Street Journal article “Don’t Simply Dive into Action:  Think.” He looked at various research sources and concluded that “the goalie’s best strategy may be not to move at all.”  At the same time, surveyed goalies have said that they would regret allowing a goal more if they stayed in the center (rather than diving left or right).  This impulse reflects an “action bias.” The idea that doing nothing could be the best strategy for goalies or businesses is seldom discussed.  

Action Bias in Chemical Engineering

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In the world of chemical engineering, when looking at a problem, we are all taught to gather more data, do more testing, investigate more research, get more sources, etc.  And yes, sometimes this is the best strategy when coming across a problem that is new to the plant or to the specific process.  However, there are many different thoughts on this topic from Sherlock Holmes who employs occasional silence and distancing for problem solving to Thomas Watson, longtime CEO of IBM who would tell his salespeople “the trouble with everyone is that we do not think enough…knowledge is the result of thought.”

So, what is the answer?  As we sit at our computers and study the data, we all debate with ourselves whether to take a short walk or brainstorm for 5 minutes.  As the title of the blog states, busyness does not lead to business or to learning.  So, as an engineer, I suggest the brainstorm approach and thinking.  For vendors and sales people too, the tendency is for action.  But, even for sales people, thinking and slowing down to develop the correct approach is critical to success.

My chemical engineering advice is to avoid acting just to show “action.” Instead, take some time to think.  We may have to change Notre Dame Football coach Frank Leahy’s quote to read instead: “when the going gets tough, the tough get thinking.”  Let me know your ideas.

Real World Examples of Particle and Cake Formation Influences

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Process engineers might love it if all of the filtration technology solutions they developed ran flawlessly, at all times, under all conditions. But, this isn’t realistic. Something might go wrong with the filtration mechanism itself. A change in the environment — upstream or downstream — could cause problems with particle or cake formation. Even the smallest shift in the operation process or procedure can prompt the dreaded phone call to the engineer: “the filtration system isn’t working.”

In my work at BHS-Sonthofen Inc., I’ve seen filtration technology impacted by particles and cake formation that weren’t predicted in designing the solid-liquid separation solutions. 

Particle Sizes Changes from Lab to Production

The existing process was a batch crystallizer operating at 0 – 5 degrees C with 13- 20% solids  to a batch vacuum filtration operation. The filter was designed for a five inch cake height. The objective of the process optimization was to move to a continuous process of continuous reaction to continuous filtration, cake washing and drying.

The BHS rotary pressure filter was installed for continuous pressure filtration.  What did the client find out?  Only the particle size has changed from lab to production!  As you can imagine, this was not a small change.

cake formation

Going back to the drawing board and testing processes again, we made the following changes to the filtration system:  new filter media, increased cloth wash pressure with a new solvent and finally a reduced cake thickness.  Yes, this trouble shooting required about 6 months of work, but problem solved!

Troubleshooting Filtration Technology

In another instance with grey water treatment units, a clarification application for the purge water treatment unit (PWTU) was installed and started up for a year of successful running. Then, inexplicably, the performance changed and the filter began plugging quickly during cycles.

cake formation

 

Troubleshooting the system we had to re-examine the filtration system under different conditions:

  • Clarifier overflow with no coagulant / no flocculants 
  • Clarifier overflow with only coagulant / no flocculants
  • Clarifier overflow with both coagulant and flocculants
  • Clarifier overflow with only flocculants / no coagulant

Taking a holistic approach to the system, we were able to determine chemical changes caused the larger particles to settle out. Only the smaller particles were reaching the filtration system, which was blinding the filter media.  By eliminating the flocculants  and reducing coagulant usage (even though this was better for the client, and not necessarily BHS as the chemical supplier, we were able to improve filtration rates and once again offer a consistent PSD.

Ultimately, with the right approach to troubleshooting, and by embracing the idea that we do on a daily basis is an art coupled with science, we can enjoy a strong sense of satisfaction when we get that filtration technology up and running again.

This blog is based on a presentation I made to the  8th World Congress on Particle Technology. View the presentation slides in full!