Rethinking Engineering Standards: The Importance of Getting it Right

engineering standards

Normally, as my readers know, my blogs cover a wide variety of topics. I like to relate and link seemingly unrelated topics to each other in innovative ways. It keeps our critical thinking faculties sharp! However, this blog deviates from the pattern to share two fresh viewpoints on changes in engineering standards. It’s technical, but important. Science textbooks will need to be rewritten!

It doesn’t happen often, but after a November 2018 vote at the Congress Chamber in the Palace of Versailles, four fundamental units of measure have been redefined. An assembly of metrologists (those who study the science of weights and measures) voted to redefine the International System of Units (SI)’s ampere, kelvin, kilogram, and mole. 

These four units join the meter, candela, and second in being defined not in reference to physical artifacts, but in reference to fundamental physical constants. Scientists say redefining these units to be based on a physical constant will make measurements more accurate and stable. 

Science students may not be too happy about having to pay for new science textbook editions, but the unanimous vote was followed by a standing ovation by the assembly’s participants from over 60 countries.

Engineering Standards Must Be Correct

The news was followed up by a Wired blog by Rhett Allain, an Associate Professor of Physics at Southeastern Louisiana University. He agreed the “definition-based standard” was a better choice:

There is a new standard in town, and it’s sort of a big deal…It replaces the old definition of the kilogram that didn’t even have a definition. The old kilogram was an actual object. It was a cylinder made of a platinum alloy and it had a mass of 1 kilogram. It was THE kilogram. If you wanted to find the mass, you had to take it out and measure it. You could then use it to make other kilograms.  

He was behind the new standard of defining the kilogram using another constant—Planck’s constant (the details are in the Wired story). However, Allain also cautioned that there is a wrong way to define the kilogram. “Unfortunately, I have already seen some very poor explanations of this new definition of the kilogram,” he wrote. His fear, he wrote, was that “these super-simple (and technically wrong) explanations might become very popular.”

For example, he cites an example: “The new definition of the kilogram sets it equal to the mass of 1.4755214 x 1040 photons from a cesium atom.” Of this he notes, “That is so bad. I’ve even seen a diagram with a traditional balance. On one side there is a kilogram mass, on the other side a bunch of photons. Please help; please don’t share that kind of stuff. You might as well just say ‘Oh, hey—the kilogram is now defined by some magical spell.’”

For Allain, this change is another argument in favor of his number one rule about science communication:

You can rarely be 100 percent correct in your explanation, but you can be 100 percent wrong. The goal isn’t to be correct in your writing—it’s to not be wrong.

I have to agree with Allain. Scientific writing is hard, but propagating the “wrong information” can have serious consequences. 

I always encourage readers to test, test, test, and look at things with a fresh perspective. Add to my mantras an echo of Allain’s: write with care.

Clear thinking about automated clarification technologies

automated clarification technologies
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This is an edited version of an article I wrote for The Chemical Engineer. I hope you enjoy this take on automated clarification technologies.

Throughout my career in the solid-liquid separation market space, I have seen some interesting solid-liquid separation solutions. At one melamine resin facility, the slurry was in a formaldehyde process. The operators were wearing masks, opening up a manual plate filter in a room with residential floor fans, to dig out the cake from the paper filter media. 

In another case for zeolites, the client had multiple bag filters to clarify the filtrates following a vacuum belt filter. When the filtrates, the final product, remained cloudy, to my surprise, the client decided to add another set of bag filters!

A clarification system is employed after coarse-particle filtration or as a stand-alone system to remove fine particles at low concentrations. These particles are typically less than 5 µm and are in concentrations less than 5% solids down to ppm levels. 

Process engineers struggle to clarify process liquids. But there are ways to automate the clarification processes to improve filtration and minimize operator exposure. The cake solids structure and the nature of the process will determine which types of pressure-filtration, automated clarification technologies are best for you.

Candle Filters

A candle filter is a pressure vessel filled with tubular filters (called filter candles). A typical filter candle comprises a dip pipe to flow the filtrate and pressurized gas, a perforated core with supporting tie rods, and a filter sock. 

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, a feed pump or pressure from the reactor or feed tank 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 maximum filtration time is reached. The cake is washed to remove impurities and residual mother liquor, and then dried by blowing gas through the cake. Next, low-pressure gas enters 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. Candle filters are used for thin-cake (5–20 mm) pressure filtration applications. They are best suited for filter cakes that are vertically stable.

Pressure Plate Filters

Like the candle filter, pressure plate filters comprise filter elements contained within a pressure vessel. However, instead of vertical filter candles, the vessel containshorizontal filter plates. These elements are slightly sloped, conical-shaped metal plates that support a coarse-mesh backing screen covered with filter cloth. 

An opening in the centre of the plate allows the filtrate to travel between plates and throughout the vessel. The filter cloth can be synthetic, as in the candle filter, or metallic as the cake discharge is by vibration or spinning. 

Operation is similar to that of a candle filter. For cake discharge, there are two main designs. In one, two unbalanced motors vibrate the filter plates to dislodge the cake from the filter cloth. In a second design, the plates spin so that the cake can be ‘thrown’ off the plates. Pressure plate filters are used for filtration of cakes up to 75 mm thick. 

Sintered Porous Metal Cartridges 

Another type of automated clarification technology is based upon sintered porous metal cartridges. These can be used in a variety of process flows such as inside-out filtration. After each cycle, solids are backwashed off the inside of the elements and discharged as a concentrated slurry or wet cake. They can also operate in a conventional outside-in filtration. Porous metal cartridges are used for high temperature applications greater than 200oC where the solids are well-defined hard crystalline shaped. 

Filter Aids 

Filter aids are generally the last resort. Often in clarification applications, the solids are very fine or amorphous, so can be difficult to filter. When filtered, the solids will create a thin, impermeable coating over the filter media and immediately reduce the filtration rate to an unacceptable level. In these difficult cases, filter aid pretreatment can be used to improve filtration properties and efficiently remove the fine solids from the process liquids. The types of filter aid include diatomite, perlite, and cellulose. 

In the precoat method, filter aid is used to generate a thin layer of solids on top of the filter media. Once formed, the filter aid cake functions as the primary filter media. Therefore, the filter cloth is no longer the real filter when precoat is used. For that reason, the filter cloth should be as open as possible while still retaining the filter aid material. 

The precoat process is achieved by mixing the filter aid into clear liquid or mother filtrate in a precoat tank. This slurry is then recirculated through the filter where the solids are captured by the filter media. The clean filtrate is recirculated back into the precoat tank. The precoat should be thick enough to ensure that the entire media surface is coated but thin enough so that it does not provide significant resistance to filtration. 

In body feed filtration applications, the filter aid is blended with the slurry feed either by dosing the concentrated filter aid suspension into the slurry feed with in-line mixing or by mixing the filter aid into the entire slurry batch and maintaining agitation. By adding filter aid into the slurry feed, the resulting filter cake is more porous, allowing higher and longer sustained flow rates. Body feed also helps to restrict solids movement which improves filtrate clarity. 

Needless to say, the use of filter aid improves filtration but requires more equipment, more process control, and results in more solids for disposal. 

Final Thoughts on Automated Clarification Technologies

How can the process engineer be successful? When confronted with a clarification process, don’t simple throw more bag filters at the problem. Conduct lab testing to analyze the cake structure, filter media, filtration pressure and cake thickness. With the data in hand, you can evaluate the different technologies and design a more reliable and cost-effective clarification process. Find a different approach!

 

 

P&IDs and Process Evolution

P&IDs and Process

P&IDs are par for the course in process engineering. Recently, I was poring over P&IDs and process planning for several projects. Each project was multinational, multicultural, and extremely complex. For one specialty chemical filtration application, part of a plant expansion in the southern United States, the engineering company is in the Southeast while the existing processes were from the Netherlands and Austria. In another project, with a similar scope, the plant expansion and the engineering company were both in the Northeast U.S., yet the current processes operate all throughout the UK.

As you can imagine, the piping and instrumentation diagrams (P&IDs) had many changes, each shown in a different color —the Christmas Trees of P&IDs.  There were extensive e-mail threads of comments and questions and, of course, questions/comments about the comments/questions. Plus, the projects required equally fun conference / video calls accounting for time zone differences, various languages and accents, and varied engineering cultures and operating philosophies. You’ve been in this situation too, I’ll bet.

The discussion, though, is invigorating. The idea exchange goes well beyond solid-liquid separation to encompass types of valves, types of pumps, where to put the pumps, how to handle the solids, operator safety, disposal, and on and on and on.  I even had a question about desalination and how to operate the DAF (Dissolved Air Flotation) units (that’s a topic for another blog).

Developing A New Process Path with P & IDs

After one of these calls, I had an “A-Ha” moment about the true value of our plentiful rounds with P&IDs and process. This is where the innovation happens. The P&IDs are idea development in action. This is where we, as I wrote in one of my earlier blogs, clear our path of unknowns.  

Anyone who’s read my blog consistently will recognize this is what is excites me about process engineering and all we do in this role. I’ve decided to take my own early 2019 advice and stretch myself in new directions with the birth of “P&ID-Perlmutter Idea Development” which you can find at perlmutter-ideadevelopment.com.

To me, these two sites work together like a candle filter functions better with the right filter sock. I’m excited to see how this idea develops, and eager to see what my readers, colleagues, and fellow bloggers will want to add and change and discuss (after all, it’s a P&IDs and process we’re talking about here).

What We Learn from Baseball Data

action athletes audience ball
Photo by Pixabay on Pexels.com

Readers of my blog, know that I am a big baseball fan and now-retired player due to a bad-hop broken nose years ago. Golf is generally much safer. If you look back, you can see my blogs about juiced baseballs, Moneyball and baseball in Japan. I also write a lot about safety at chemical plants.  So, here we go again…let’s talk about baseball data and safety.  

This season there has been a lot of talk about foul balls striking and injuring fans and installing netting to protect fans. But, as process engineers, we know that we need to first consider the data before making any decisions. So, let’s get the data and discuss the best way for Major League Baseball to proceed.

Annette Choi and her team recently published, “We Watched 906 Foul Balls To Find Out Where The Most Dangerous Ones Land.”  Their research gathered the following data points:

Column Description
matchup The two teams that played
game_date Date of the most foul-heavy day at each stadium
type_of_hit Fly, grounder, line drive, pop up or batter hits self
exit_velocity Recorded exit velocity of each hit — blank if not provided
predicted_zone The zone we predicted the foul ball would land in by gauging angles
camera_zone The zone that the foul ball landed in, confirmed by footage
used_zone The zone used for analysis

This data collection was no easy feat. The MLB does not keep this type of statistics, even though baseball is really a numbers game. The team watched the 10 most foul-ball-heavy games this season to gather their findings.

Armed with the baseball data, Choi and her team determined the ball parks with the most foul balls:

MOST FOUL-HEAVY DAY
STADIUM AVERAGE NO. OF FOULS PER GAME DATE MATCHUP NO. OF FOULS
Camden Yards* 57 4/20/19 Baltimore Orioles vs. Minnesota Twins 113
PNC Park 57 6/1/19 Pittsburgh Pirates vs. Milwaukee Brewers 111
Oakland Coliseum 53 6/2/19 Oakland A’s vs. Houston Astros 109
T-Mobile Park 53 5/18/19 Seattle Mariners vs. Minnesota Twins 100
Globe Life Park 55 5/3/19 Texas Rangers vs. Toronto Blue Jays 87
Dodger Stadium 51 3/29/19 Los Angeles Dodgers vs. Arizona Diamondbacks 86
Miller Park 55 5/4/19 Milwaukee Brewers vs. New York Mets 85
Citizens Bank Park 53 4/27/19 Philadelphia Phillies vs. Miami Marlins 75
SunTrust Park 53 4/14/19 Atlanta Braves vs. New York Mets 73
Yankee Stadium 51 3/31/19 New York Yankees vs. Baltimore Orioles 67

The team then looked at netted versus non-netted areas as well as the ball velocities.  Interestingly enough, they found that almost an equal number of balls went to each area but the balls with the highest velocities went into the unprotected areas. 

Choi concludes, “Even with extensive netting, no one will ever be completely safe at a baseball game. But there are ways for MLB to protect its fans from foul balls — particularly in the most dangerous areas of the park.”

What I appreciate most is her observations are based in testing and learning about baseball data!

So, enjoy the World Series and root on your team and as Ernie Banks once said “It’s a beautiful day for a ballgame… Let’s play two!”

What Type of Engineer Are You?

types of engineers
Image source

There are may different types of engineer. Recently, I read some interesting articles about defining engineers by their skills and depth of knowledge. This blog asks you to consider, what’s your skill shape: I…T…or Key?  

In the 1970’s, companies wanted staff with an I-shaped skill level. What does this mean? I-Shaped Skills reflected a person with a deep (vertical) expertise in one area and practically no experience or knowledge in other areas. This person would typically be known as a specialist. It could be one process, one type of distillation, one type of pump, etc. I remember the days when my customer, Eastman Chemical, had flange specialists, o-ring specialists, vacuum pump specialists. The other large chemical companies, such as Dow Chemical, had similarly focused engineers.

In the 1980s, McKinsey & Company developed the idea of the T-shaped professional. The vertical bar on the T represents strong knowledge in a specific discipline. The horizontal bar represents a wide yet shallow knowledge in other areas. This allows the person to collaborate across other disciplines and acquire new skills or knowledge. Chemical companies have T-shaped engineers such as filtration experts, drying experts, solids handling experts, etc. These engineers can support all types of applications across all of the operations at various sites.  

One classic T was Thomas Edison, who wanted the people around him to know a lot of different things. All his prospective employees had to take a test of 150 questions geared toward different jobs and classifications of workers.

Today, the visualization of skills concept has expanded to include the elusive key-shaped professional—a person who has several areas of expertise with varying degrees of depth. The introduction of the key-shaped professional is largely due to the rapid proliferation of technological advances and the cross-disciplinary nature of work. Across industries and professions, the ability to use technology to assimilate and apply information has created a new, broader expectation of the standard skills professionals should have.

As a result, we’re seeing new parallels between skills sought in business and process engineering.  The top skills include embracing new technology, understanding data, and thinking critically about that data. 

Becoming a Key-Shaped Engineer

types of engineers
Image source

So, how do you become a Key-shaped professional? I have made several suggestions in other blogs:

So, now you may ask, how do I describe myself? Early in my career, I was T-shaped with knowledge about solid-liquid separation. As I progressed, I became more of a Key shape with knowledge about varied topics such as centrifugation, drying, solids handling, mixing and other process operations as well as technical business marketing and startups. 

I encourage you to think about your own skills shape. It might prompt a learning opportunity, and I’d be happy to help where I can with your transformations.

Troubleshooting Filter Aids and Filtration Systems

 

filter aids
Cellulose filter: Imerys Filtration Minerals Inc.

Filter aid pretreatment can improve filtration properties and efficient removal of fine solids. Whether the filter aids are used in Plate-and-frame filter presses, horizontal and vertical pressure leaf filters, candle or tubular filters, Nutsche filters, or rotary vacuum drum filters, these practical tips can help this part of the process run smoothly.

We typically see diatomite, perlite and cellulose filter aids today. They meet the requirements of a filter aid in that they:

  • Consist of rigid, complex shaped, discrete particles;
  • Form a permeable, stable, incompressible filter cake;
  • Remove fine solids at high flow rates; and
  • Remain chemically inert and insoluble in the process liquid.

You’ll want to test different approaches to determine the best aid for your process and which of the methods — precoat or body feed — offers the greatest benefits. Once you’ve done so, though, it’s important to keep these troubleshooting tips in mind.

Practical Pointers for Using Filter Aids

Whether the process is precoating or body feeding, the filter aid slurry tank and pump are critical to the operation. 

In precoating, the mix tank should be a round, vertical tank with a height twice its diameter. Set the usable volume of the precoat tank at ≈1.25–1.5 times the volume of the filter plus the connecting lines. Use a mixer or agitator with large slow-speed impellers to avoid filter aid degradation and the creation of fines — otherwise you’ll dramatically change the filter aid process filtration.

The precoating pumps almost always are centrifugal pumps because they produce no pulsations to disturb precoat formation and their internal parts usually have hardened surfaces and open impellers to reduce wear. For body feeding, you’ll use positive displacement pumps.

Yet even when the feed tank and pump are correct, several typical issues with filtration/filter-aid systems can arise.

Bleed-through is common where the filter aid is bypassing the filter media. It may stem from mechanical, operational or process causes. Check a couple of mechanical points: 

  • Is the filter medium secured to the filter correctly? 
  • Does the filter medium have a tear or pinholes? 
  • Is the type of filter aid correct for the filter medium mesh size and the particle size distribution of the process solids? 
  • Is the pump working correctly (flow, pressure, etc.)? 
  • Is the proper amount of filter aid being added?

Another issue may be reduced filtration cycles — i.e., the time to reach the maximum pressure drop becomes shorter and shorter. This may occur:

  • if the cake isn’t being discharged completely, then each new batch has residual solids in the filter, resulting in lower capacities. Increasing precoat height or lengthening cake drying time may help improve cake discharge. 
  • if the precoat doesn’t completely cover the filter medium, then the process solids may begin to blind the medium. 
  • if you’re using body feed, inadequate mixing with the process solids may result in filter medium blinding. This also can happen if the velocity in the filter vessel is too low, which will allow the filter aid to settle out before reaching the filter elements. A bypass at the top of the filter vessel can help keep the solids suspended within the vessel.

On filters with vertical elements, precoat pump flowrate or pressure may cause loss of the precoat from the filter medium, Improper valve sequencing creating a sudden change in the pressure or flowrate may also be to blame. Finally, a mechanical issue with the filter may prompt a pulsation or pressure change that impacts the cake structure.

Apply Filter Aids Wisely

Employing filter aids to help filtration is tricky; most process operations try to eliminate or minimize their use. However, sometimes they are unavoidable.

To succeed with filter aids, a process engineer should take three essential steps:

  1. Conduct lab testing to examine the filtration operation (vacuum or pressure), cake thickness, filter aid quantities, filter medium and other parameters that are crucial to the process design;
  2. Ensure correct mechanical design to provide optimum precoat or body feed handling and distribution; and
  3. Arrange for operator training on the filtration technology as well as on filter aid operation.

This blog is an edited version of an article I co-authored with Garrett Bergquist, BHS-Sonthofen Inc. for Chemical Processing.

Summer Workplace Safety & Testing Assumptions

workplace safety
Image source

Summer is here! That means swimming, barbecues, and watermelon. I’ve got to admit, though, I’ll be looking at watermelons a lot differently this season. 

Recently, I came across a Black & Veatch video illustrating the importance of wearing your hardhat. They did it by demonstrating structural bolt falling from 20 and 30 feet onto a watermelon. 

While physics is not my primary background, I thought it would be interesting to share Rhett Allain’s discussion of the video’s science.

Allain notes he’s skeptical of the video’s claim that the one-pound piece will have an impact force of about 2,000 pounds when it collides after falling 20 feet. He notes “it’s really difficult to calculate the impact force for a couple of reasons”: impact force is typically not constant plus impact force depends on the stopping distance. 

He suggests instead that the falling bolt problem is a “perfect situation in which to use the work-energy principle.” He goes on to discuss the many considerations such as the one pound bolt falling its distance, making contact with the watermelon and still moving some distance, and the backward-pushing force on the bolt. He puts it all together in a work-energy equation:

pastedGraphic.png

Then he considers impact force, and tries to determine why the bolt dropped from 30 feet instead of 20 feet smashes through the watermelon. He notes, “Honestly, I have no idea where they are getting their values for this video. (They probably need a good science consultant.)”

Clearly, in the video, the melon breaks. Its structural integrity is disrupted and it falls apart. It’s a gooey mess, and no one wants to think of the same thing happening to their head.

Allain points out also that a hard hat will increase impact force so that “if the bolt hits the hard hat and stops over a shorter distance, this would produce a higher average force.” Yet he also notes, “the hard hat does do one thing that’s very nice. Since the hat has a rigid surface, it distributes the impact force over a larger area, which reduces the impact pressure. Lower pressure means there is less chance that the bolt will penetrate your head.”

Ah, what a relief! Even if you don’t get the physics.

Key Takeaway

Ultimately, this video and Allain’s discussion had me thinking again about the importance of workplace safety. At the same time, Allain’s questioning the science demonstrated reminds me of my consistent warning against assumptions. We need to always be testing our thinking, whether it’s about filtration technology or busting watermelons. Be safe this summer!

Removing Catalyst Fines From Raney Nickel Catalyst Reactions

 

Raney nickel catalysts
Image source

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
Palladium image source

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.