Optimizing downstream final drying

Every year I look forward to attending AICHE, learning from peers, and sharing what knowledge I’ve gained in the past year. COVID-19 pushed us to meet virtually this year. Still, I was pleased to continue to share my talk on BHS-Sonthofen Inc.’s continuum approach to optimizing downstream final drying with upstream solid-liquid filtration. I thought I’d offer a recap here for those who missed the online event.

Most often when analyzing a new process development approach, engineers take a “silo” approach and look at each step independently. I suggest that by taking a holistic approach and looking at each step not individually but as a continuum, the process solution becomes much more efficient. I highlighted my perspective with data showing how to balance each of process steps for maximum efficiency.

My discussion of process filtration and optimizing downstream final drying centered on a specialty chemical process that has crystals in a methanol slurry which must be filtered, washed, dewatered and then dried. In looking to expand the existing process our objectives were to:

  • Migrate to continuous operation from batch operation
  • Maximize solid-liquid filtration performance
  • Achieve low wash ratios for minimum wash media consumption
  • Accomplish lowest possible residual moisture in discharged filter cake 
  • Reach final moisture of <1.0% 

Testing a Continuum Approach to Optimizing Final Drying

The standard approach is to optimize the solid-liquid filtration step with maximum washing and pre-drying efficiency, Then, with this information we’d optimize the downstream drying. However, the client wanted us to look at the process as a continuum from solid-liquid filtration through cake washing and dewatering to final drying. 

Our testing started at BHS-Sonthofen in Charlotte labs with our Pocket Leaf Filter. Starting with the slurry, we tested for cake thickness, pressure filtration, filter media, cake washing and drying and discharge. 

The flux rate of less than two minutes at @ 200 kg DS/m2/hour) indicated this process was suitable for continuous operation. The cake drying moisture content, varying between 11 – 30%, was another positive indicator for an integrated approach.

optimizing downstream final drying
Example results from the RPF testing

Our lab testing of the slurry led us to recommend a continuous approach using the BHS Rotary Pressure Filter, which conducts pressures, cake watering, dewatering, and cake discharge all, continuously, in a slowly-rotating sealed drum. In testing for this client we achieved:

  • Media = 14 micron and a cake thickness of 25 mm 
  • Desired filtration times and filtrate quality
  • Efficient wash ratios of 0.7 to 1.2 kg MeOH/kg DS
  • Moisture content varying between 11 – 30% based upon the nitrogen for blowing for drying 

Based on the moisture of 11%, we sized the Rotary Pressure Filter filtration area at 2.88 m2 with a nitrogen solvent recovery package to reduce the nitrogen usage. This led to the next step in the integrated process: looking at the dryers.

Optimization testing of AVA dryer

BHS Sonthofen last year acquired AVA dryer, so we turned to their vertical conical dryer for testing. This dryer’s cleanable, contained design conveys solids gently down and out, which was useful for this project’s specialty chemicals.

In pilot testing in Munich, Germany, we were able to determine what moisture level to use out of the pressure filter to get the best continuous approach to final drying. We initially designed a 2.88 m2 with 11% moisture, which led to a dryer of 1.93 m3 and a dryer cycle time of 35 minutes. That system would have cost the client $2 million. 

However, our testing optimized the design to increase moisture out of a smaller filter and use a larger dryer for longer. This saved $500,000 on the total system.

The Continuous Optimized Design

  • Filter Size: 1.44 m2 with 30% moisture using 200 m3/hr N2 + Vacuum
  • Dryer Size: 3.0 m3  
  • Dryer Cycle Time: 60 minutes 
  • Total System Budget Price: $1.5 million 
optimizing downstream final drying
The optimized design

The optimized system with a continuum approach resulted in operational energy and nitrogen savings as well as lower capital and installation costs for a more reliable process. 

I’d have liked to answer your questions about this approach in person. Still, I’d be happy to hear your thoughts. Contact me or check out my P&ID site.

Benefits of a Continuum Approach to Optimizing Final Drying 

Screen Shot 2019-07-17 at 11.41.29 AM

 

As we announced in March, BHS has acquired AVA-GmbH. The AVA technologies provide for turbulent mixing, reacting and drying of wet cakes as well as powders and process slurries. The vertical and horizontal technologies are vacuum or atmospheric, batch and continuous, for final drying to “bone-dry” powders. They are an essential part of our “Continuum Approach.” 

What do I mean by that? This blog briefly reviews our first ground-breaking study showing the benefits of a “Continuum Approach” to final drying and upstream solid-liquid filtration, cake washing and dewatering.  

Most often when analyzing a new process development approach, engineers take a “silo” approach and look at each step independently.  Our article illustrates that by taking a holistic approach and looking at each step not individually but as a continuum, the process solution becomes much more efficient.  

In the manufacturing of the specialty chemical involved, the crystals coming from the reactor in a methanol slurry had to be filtered, washed and dewatered and then dried to a final moisture of less than 1.0 (<1.0 %).  The standard approach would be to first look at the solid-liquid filtration step and optimize this step for the maximum washing and drying efficiency. Then, with this information, we’d optimize the downstream drying.  The operating company, however, took a different approach and looked at the process as a continuum from solid-liquid filtration through cake washing and dewatering to final drying. The Continuum Approach” resulted in operational energy and nitrogen savings as well as lower capital and installation costs for a more efficient and reliable process.  

You can read the full technical article, but the overall result was a 50% decrease in the filtration area, elimination of a nitrogen recovery system with a 30 minute increase in batch drying time at a lower temperature for better product quality.

Contact me to optimize your current drying and filtration process. Let’s get more efficient together!

Quarantine-Inspired Culinary Innovation

culinary innovation

This is a difficult moment in the world. Maybe you know someone that has been impacted by or struggled with COVID-19. We have all seen businesses coming to a halt and our daily lives upended. My heart goes out to everyone who has been impacted. For some, cooking is a way to show love. So, I thought I’d share some of my quarantine-inspired culinary innovations.

If you’re working from home, you have begun cooking more. I know that I have! Let me share some stories about my cooking as well as companies that innovated to be nimble in the face of the current situation.

My readers know that I exercise, run, and practice yoga. What you may not know is that I am also a good cook. As I am home more and not traveling, I have returned to cooking seafood, tandoori, Spanish, French and other dishes. You can see some of my culinary innovations in this slide show. These are the best ones. Some, I must admit, did not warrant a photo. But we’re always learning.    

culinary innovation
Cooking salmon and veg with a 45-year-old wok!

Culinary Innovation and Agility

While I’ve been innovating in my home kitchen, companies have been innovative in finding ways to meet consumer needs. Let me give you some examples.

King Arthur, a 230-year-old flour company, ramped up production to meet the demands of a baking renaissance. Their flour sales more than tripled as the public seemed to reach a collective understanding that baking and self-reliance was just the thing to help while staying at home. Grocery stores saw increased demand, so King Arthur needed to change their packaging lines to produce more. What did they do? The company innovated and swiftly designed a new plastic pouch that could handle two, five or ten pounds of flour. Within weeks King Arthur was able to increase its packaging processes to add over 1 million bags of flour to inventory.

For another example of culinary innovation during COVID-19, let’s look to Milkrun. The company works with farmers to deliver their products direct to consumers.  This local food delivery service in Portland, Oregon, would normally distribute to restaurants, school districts, coffee shops, etc. However, in a few short weeks, this business disappeared. Milkrun needed to combat two challenges to local food systems to change the business situation: inefficient distribution and low farmer pay. They made changes and developed innovative packaging for items such as sheep’s milk and fruits, so that now they can distribute directly to consumers. Now they’re expanding to Seattle as well as Austin, Denver, Detroit, New York.

Gotham Greens is a fresh food company that builds and operates sustainable greenhouses in cities across America. They grow year-round to supply local produce. Their greenhouses are advanced data-driven, climate-controlled facilities with the highest-yielding farms around. They use less energy, less land, and less water than other farming techniques. Plus, innovative advancements in machine learning and data analysis allow for monitoring of crop health and progress. Yet when restaurants shut down inside dining, the company’s business changed overnight. All the major restaurant clients called to suspend orders. On the other hand, the CEO’s phone “was buzzing off the hook from the largest supermarkets saying can you run extra trucks.” The company upped its planting and production to meet the need. 

Adaptive Processes & Teamwork

These stories of food company agility remind us of the importance of flexibility in business. Innovating new approaches can help with business differentiation. But business also needs to have a solid foundation to be able to pivot quickly in times of crisis. Strong leadership and teamwork can make all the difference.

While cooking is fun, we all miss restaurants and their chefs, bartenders, owners, wait staff, and other employees. I’m sure, like me, you long for and hope to dine in again with them soon. In the meantime, send me your food pictures, recipes, and cooking adventures. I’d love to learn about your culinary inventions during quarantine and beyond.

Changing from Batch to Continuous Processing

batch to continuous processing

Our approaches to process engineering must always be evolving. Otherwise, we’ll never grow and innovate. Recently, I contributed a feature to The Chemical Engineer on making the change from batch to continuous processing. Here’s an edited version of that article for my loyal blog readers. 

As there is a push to become more efficient, many process industries have begun thinking about continuous processing. Many specialty and fine chemical operations are batch operated. It is easy and typically uses filter presses, vacuum nutsche filters, filter-dryers, plate and leaf filters, and batch centrifuges. 

Yet batch processing significantly lacks flexibility in scaling capacity, and typically requires larger manufacturing footprints and less efficient use of space. So, I’ve been seeing more of a shift from batch to continuous processing. 

In my career, I’ve helped engineers move to continuous operations for such applications in pharma and biochemical, specialty polymers, starch and cellulose, aromatic acids and fly ash wetting.

Why? In continuous processes: 

  • a filter is typically one-third the size of a batch filter
  • the process can increase yield and optimize quality
  • there are fewer reslurry/holding/buffer tanks
  • transfer pumps can be eliminated
  • complications from solids handling can be minimized
  • less agitation is used (which can impact crystal size and fines generation)
  • it can be easier to maintain constant flows, pressures and temperatures

Applications of Continuous Processing

In the article, I shared several examples of continuous processing applications in my career. I’ll recap a couple of them here too.

In a specialty chemical polymer application, a client wanted to transition to continuous processing to eliminate solids handling and reslurry tanks. Eliminating the liquid ring vacuum pump required for vacuum filtration would also cut energy costs. At BHS Filtration, we did lab and pilot testing to determine the rotary pressure filter was the best option.The continuous pressure filter saw a 16% increase in filtration rate; maintaining the temperature at -5oC resulted in a higher capacity. Secondly, we saw a more efficient washing due to less cake cracking in the thin cake (5 mm) as compared with 150 mm (6-inch) cake. 

For a pharmaceutical client, BHS was involved with a transition to fully-automated continuous processing in extracting phospholipids from egg yolk for preparation as a pet food additive. After consulting with the client and testing, the choice was a continuous-indexing vacuum belt filter for vacuum filtration, cake washing, and dewatering of the cake. The technology is based upon fixed vacuum trays, a continuously feeding slurry system, and indexing or stepwise movement of the filter media. In practical terms, the operational features of the belt filter can be viewed as a series of Buchner funnels. Making that change to the filter validated, as a GMP installation, for pharmaceutical production has increased the yield of the phospholipids by 3–5%. 

 In doing this kind of work, we’ve run into different challenges. We’ve been reminded that process scale matters and what works in the lab may not work in the plant. We’ve seen the need to silo both batch and continuous processes in the same line as a continuum. We’ve been reminded of the need to understand how one upstream decision will impact downstream processes.

We must also remember making the transition from batch to continuous processing requires more than just new equipment. The entire manufacturing operation and the mindset of staff need transformed. 

Process engineers have many choices to transition to a continuous operation. Continuous can be more challenging, but the benefits are there. Just be ready for some unexpected consequences along the way, and always test, test, test!

Of course, if you want to read the entire article, and I hope you will, it’s available! I’d be happy to discuss any of the ideas or possible applications of these insights with you. Reach out to me today!

 

Road Warrior’s First Business Travel after 96 Days    

business travel
Photo by Sheila on Pexels.com

First, let me say that in these challenging times, we all must be diligent in our approaches to our business and personal lives.  My heart goes out to everyone who has been impacted by COVID-19.  To help in my own way, I wanted to offer my recent experience with business travel.

Precautions during the pandemic saw me staying put for the longest stretch of time without travel in over 35 years. Of course, it was good to be home. But the time came to get out and see customers again. My first trip was to Appleton, Wisconsin to visit a customer that I have known for several years for a project that may be funded in the 3rd Q. I thought I would share my experience.

The different travel experience started with packing. I began with all my protective gear. Two N95 masks, two disposable masks, two bandanas (Carolina Panther and The Dead & Company) and one infrared thermometer. Next, what cleaning supplies did I need?  Disinfectant wipes as well as a 12 ounce hand sanitizer; TSA will allow this exception. Finally, sealed googles to fit over my glasses to be used in the airport and airplane. The sealed googles are recommended to help you avoid touching your eyes or face.

Business travel

For the hotel it’s recommended to bring along your own pillowcases. So I packed two. In case the hotel gym is closed I bring along my yoga mat, yoga workout clothes, running shoes and my running clothes. I also throw in my running wind-breaker just in case the weather is a little cooler or rainy.

On the customer visit, I need steel-toed safety shoes and safely glasses. Add those to the pack! Finally, I get to my regular clothes. In the end, a pack that normally takes less than 30 minutes, required 2+ hours and a lot of discussions.

At the airport, with no shuttle buses for long-distance parking, all cars are in the parking deck. Finding a space was another challenge. Once this was accomplished, the TSA checkout point required more time and more space. Finally, the airport and airplane were relatively easy.  The American Airlines “concierge” team was very happy to see me.

Upon landing, the car rental facility also was easy and there were large stickers on each car indicating “cleaned and sealed.” The hotel was also following CDC guidelines with masks, social distancing, cleanliness, etc. So, drinks and dinners in the hotel bar for two nights were fun again. These interactions with the staff and other business travelers are always an entertaining part of business travel.  

As for the business, the visit and meetings were successful. We all wore masks; my temperature was checked. Our lunch was in a large conference room and followed all of the social distancing protocols.  

Oh, one more point. No elevators. I walked every staircase. It’s another thing to keep in mind when you’re packing.

So, now I am back “on the road again” (I think that this is a song?) and hopefully to a healthy and successful remainder of 2020. Let me know how you all are doing! What changes have you made to your business travel practices? I can’t wait to see you at the next hotel bar for drinks and dinner.

Stay safe and take care. By having concerns and respect for your friends, families, colleagues, and strangers, we will all make the world a better place.

The Wisdom of Silence this Summer

dawn sunset beach woman
Photo by Jill Wellington on Pexels.com

       

2020 has gotten off to a really weird start. Many of us have been working remotely, trying to continue to design projects and meet with clients. But, even in the best of situations, we can lose track of ourselves in the process. Consider the wisdom of silence.

This feeling of being pulled in too many directions at once need not be inevitable. We can find ways to ground ourselves amidst all the chaos. Create moments of stillness where you can.

When silence is intentional, it is valuable and restorative. Check out my blog about Sherlock Holmes and the value he found in taking a moment to just think. The great detective would employ occasional silence and distancing for problem solving. In the BBC’s version they show this when Benedict Cumberbatch retreats to his “mind palace.”

We may not have mind palaces, or even mind sheds, but finding silence can bring us back to our senses. Like intentional breathing, which I’ve written about before, silence is essential to our holistic well-being. Silence is a powerful tool that allows us to take a step back from the atmosphere around us and realign with our intentions and ourselves.

Realigning Intentions — Professionally and Personally

I started the year offering a roadmap for 2020. Now, as a midway check-in, here are my suggestions for what we can do to benefit our personal and work lives.

  1. Listen to the customers.  First, broaden your definition of customer. Customers can be your clients, coworkers, vendors, your family. Listen and learn from their feedback and suggestions.
  1. Be useful.  If you listen, you can be useful. And there’s nothing more rewarding than being of use to others.
  1. Make things faster and simpler. Of course, this can’t be at the expense of accuracy, but try not to overly complicate decisions, tasks, actions, etc. We must strive to reduce complications.
  1. Innovate, don’t imitate. To succeed, we need to continually look for new approaches. We love experiments. They help us think differently.
  1. Give back. At some point in all of our lives, we’ve received other people’s help. Try to give back this summer. This may seem like one more thing to cram into the schedule, but the benefits will outweigh that aspect.
  1. Be honest. Speak in an open and ethical manner. As I’ve discussed before, this may even mean being authentic and expressing anger. It’s better to communicate fully than to let resentments fester or leave frustrations unattended.
  1. Keep learning and improving. Loyal readers know that this is a key point for me.  There’s (always) plenty of room for improvements and innovation. That’s how we create better experiences for all.  

As the start of summer approaches, let’s set aside time to tune out the noise. Turn off your device. Go for a walk or simply close your eyes. The magic in the wisdom of silence is that we can access it wherever we are — though I’ll be hoping you get to try this somewhere you love in the coming months (without the social distancing considerations!).

Contribute to a Holistic Approach to Unit Operations!

pexels-photo-3808904
Photo by Andrea Piacquadio on Pexels.com

As the chemical industry changes and becomes more integrated worldwide, there is a need for information exchange. This must include not only principles of operation but practical knowledge transfer. That’s why I have agreed to edit a new book for Elsevier, “Integration and Optimization of Unit Operations.”

As my readers know, in 2015, I published the “Handbook of Solid-Liquid Filtration” with Elsevier, UK. This new project offers up-to-date and practical information on chemical unit operations from the R & D stage to scale-up and demonstration to commercialization and optimization.  

For this exciting and unique book to work, I need your help. I’m currently seeking contributing authors who have skills at each stage of the process from lab-scale/R&D, through pilot plants to full-scale production and finally optimization or as I call it, Putting-It-All-Together, for actual case histories / war stories.  We will also cover decommissioning of plants. Check out the preliminary Table of Contents.

Currently, most books look unit operations, each in a silo.  In this book, at each stage, the information presented differs as the technology and issues faced at the lab scale differ through commercialization and optimization. So, we will move from a silo approach to an integrated – holistic approach.

Why this Book is Needed

This book addresses a need for engineers with a broader training background. In the early 70’s, companies wanted staff with an I-shaped skill level. Someone with I-Shaped Skills is a person with a deep (vertical) expertise in one area and practically no experience or knowledge in other areas. This person is typically known as a specialist.  

Then, in the 1980s, the industry wanted T-shaped professionals. The vertical bar on the T represents strong knowledge in a specific discipline. The horizontal bar represents a wide (horizontal) yet shallow knowledge in other areas. This allows the person to be able to collaborate across other disciplines and acquire new skills or knowledge. 

Yet what we need today, with the rapid proliferation of technological advances and the cross- disciplinary nature of our work, is key-shaped engineers who can address several areas of expertise with varying degrees of depth.  

This book aims to address the needs of engineers who want to increase their skill levels in various disciplines so that they are able to develop, commercialize and optimize processes. The engineers must be able to ask questions of experts to develop creative solutions.

What Can You Contribute?

Contributing authors should be able to discuss unit operations at each stage and then relate how these technology/process decisions impacts the next stage. I am targeting the first draft by the end of the year. I will provide technical guidance and assistance as well as from my associate who is skilled in technical writing along with the Elsevier requirements.

The book will be listed on ScienceDirect, Elsevier and others and chapters will receive individual indexing so they can be searched. Review the preliminary Table of Contents and let me know what interests you to write about!

I hope you’re as excited about this opportunity to share knowledge about unit operations as I am! I look forward to hearing from you.

Dryer Selection and Bulk Solids Handling 

 

blindspot-analysis-toolshero-1.jpg
Image source: https://www.toolshero.com/decision-making/blindspot-analysis/

Solids handling is not a unit operation. Therefore, it’s not covered in engineering courses. This leaves process engineers struggling to understand the “flowability” of bulk solids. This blind spot is huge. So, let’s talk about dryer selection and bulk solids handling.

Recently in The Chemical Engineer, Grant Wellwood described bulk solids handling as the biggest industrial activity on the planet. The article estimated “that >70% of everything we use or consume involves bulk solids handling somewhere in its lifecycle.”

Mishandled, this process can quickly and efficiently destroy product value, careers, projects and even organizations. Yet, bulk solids flow is often an afterthought once the separation and drying equipment is selected. This article aims to bring bulk solids handling to the forefront.

Bulk Solids Handling Parameters

Bulk solids are defined as materials (solids) handled in various volumes and counts. Their flowability is impacted or controlled by friction (particle-particle or particle-surface). During the drying process, solids go through different phases such as free moisture, bound moisture, thixotropic and finally (and hopefully) free flowing.  

The selected dryer must be able to handle each phase without creating fines, balls that can trap liquids, and without adding additional heat due to friction.  

Here are some of the process and design parameters engineers need to consider for dryer selection:

  • Dryer Process: Batch, Continuous, Atmospheric/ Vacuum, Turbulent, Gentle, Ring-Layer, Feeding  (Volumetric or Gravimetric), Upstream and Downstream Equipment
  • Recipes: Number of ingredients, Frequency of campaigns, Cleaning operations, Product integrity (fines generation) after drying and  Residence time
  • Dryer Performance: Batch size, Filling levels, and  Production volume
  • Product Characteristics: Quality, Bulk density, Tendency of segregation & agglomeration, Thixotropic phase, Shape, Size, Homogeneity, Risk of separation, Flow properties, Abrasiveness, and Moisture & Temperature
  • Mixer design: Material of construction,  Surface quality, Heating/cooling, Liquid feeding, Type of mixing tools, Speed of mixing tools and degree of back mixing
  • Dryer Integration: Material flow, Physical space, Process sampling, safety requirements, etc.

It’s a lot to think about. Westwood observed in his thorough article, “When handling bulk solids, it’s always important to take a holistic or systems view because of the complex dependencies.”

BHS & Bulk Solids Handling

As my readers know, BHS provides for thin-cake filtration, cake washing and dewatering based upon pressure or vacuum, for batch or continuous operations from high solids slurries to clarification applications with solids to 1% and trace amounts.  

In 2018, BHS acquired AVA mixers and dryers based in Herrsching (Munich) Germany.  VA is in the unique position to provide both vertical and horizontal technologies providing for turbulent as well as gentle mixing, reacting and drying of wet cakes, powders and process slurries. The technologies are vacuum or atmospheric, batch and continuous, for final drying to “bone-dry” powders. The BHS technical article, Dryer Selection, explains the designs as well as selection parameters.  

We know that solids change when processed from a wet-cake to bone-dry powder. Process engineers need to do the tests and trial and error to better understand these changes. As I often say, we can’t jump to conclusions.

Our process engineers would be happy to help at the BHS test center. With an understanding of how the flow properties change, depending on “complex interactions between particle size and distribution, moisture content and distribution, process history (time and manner), mineral composition, surface texture and condition as well as ambient conditions, just to name a few…” the dryer selection can begin in an educated manner. 

Good luck and feel free to contact me for help with your bulk solids handling questions.

Containment of Slurries in Continuous and Batch Operations

Slurries
Image source

In the 1970s, the chemical operations used acetone and benzene for the main slurry solid-liquid separation process. Next, there was a push to minimize solvent use. We looked to use water as the process liquid, but still had open filter presses and rotary drum filters; the entire plant was white from titanium dioxide or pharma stearates.

Today, we all know that processes remain open with filter presses, vacuum filters, and centrifuges. Our job is finding solid-liquid separation process solutions that can be contained for high solids slurries (greater than 10% solids) during filtration, cake washing, and dewatering/drying. This discussion considers your options for both batch and continuous operations.

Batch operations

When it comes to batch operations there are many possible ways to go.

Nutsche filter-dryers. Sized to take the complete batch from the reactor and process it to completion (final dryness). The nutsche filter contains an agitator, normally three blades, sealed to the vessel and moving up and down, clockwise and counter-clockwise. The agitated nutsche filter can conduct pressure filtration, cake smoothing, cake washing (displacement and reslurry washing), vacuum and pressure drying, and then automatic cake discharge.

The agitated nutsche filter-dryer is based upon thick cakes from 5–7 cm up to 30 cm and higher. For this type of filter to be successful, the cake permeability must be able to accept a deep cake without compression. Circular or rectangular filter media with a drainage layer is installed on a perforated filter plate.

Contained filter-presses. A contained unit does not require a process change and can operate at a cake thickness down to 2.5 cm, which is not possible in a nutsche filter-dryer. In a typical contained filter-press design a housing seals the plates. Improved designs include pressure filtration up to 1m Pa, cake washing in the forward and reverse direction, cake drying in the forward and reverse direction using pressure blowing and vacuum, as well as automatic cake discharge.

Contained centrifuges. These vary in design depending upon the operation and the type of centrifuge (such as horizontal peeler, inverting basket, and disk centrifuges). Centrifuges can be blanked or inerted for operation as well as sealed designs.

Continuous Operations

In continuous operations with slurries new options surface.

Rotary pressure filters. A continuous pressure filter designed for thin cake to deep cake filtration with cake depths from 6–150 mm. A slowly rotating drum (6–60 rph) is divided into segments (called cells) each with their own filter media (synthetic cloth or single or multilayer metal) and outlet for filtrate or gas.

The outlets are manifolded internally to a service/control head where each stream can be directed to a specific plant piping scheme or collection tank. In this way, the mother liquor can be kept separate from the subsequent washing filtrates and drying gases. This allows for better process control as well as reuse and recovery of solvents and the gases. 

Pressurized vacuum drum filters. A rotating drum inside a pressure vessel. The unit consists of a filter drum, slurry trough, agitator, wash bars, and a pressure let-down rotary valve. The process begins by closing the pressure vessel, pressurizing the vessel with compressed gas. The rotary valve is also pressurized for sealing, and the filter trough is filled via the suspension feed pipe. The agitator is started to keep the solids in suspension. Filtration, cake washing, and drying are by vacuum operation.

Indexing vacuum belt filters. Provides for vacuum filtration, cake washing, pressing, and drying of high solids slurries. The technology is based upon fixed vacuum trays, a continuously-feeding slurry system and indexing or step-wise movement of the filter media. In practical terms, the operational features of the belt filter can be viewed as a series of Buchner funnels.

For the process operation, due to the stepwise operation of the belt, washing and drying efficiencies are maximized with the stopped belt and a plug-flow mechanism for gases and liquids. Cake pressing and squeezing further enhances drying. Finally, the fixed trays allow for the mother liquor and the wash filtrates to be recovered individually and recirculated, recovered, or reused for a more efficient operation. 

Final Thoughts

Process engineers have many choices to contain an operation. The decision is not easy:

  • Is the process batch or continuous?
  • Is it a thin-cake or thick-cake operation?
  • What is the filter media (synthetic or metal)?
  • What are the critical process steps?
  • What about maintenance and other parameters?

The design questions go on and on. In the end, whatever you choose, involve process, production, operations, and maintenance in your decisions.

This blog is an adapted version of my article for The Chemical Engineer. Read the full article here!

Engineer Checklists and Learning from Apollo

engineer checklists

Recently, I discussed the five management lessons that we can learn from the Apollo lunar landing in 1969. Continuing on this theme, an article in The Chemical Engineer, “Houston-We have a checklist” a UK magazine that I write for, had an interesting take on the lunar landing and engineer checklists.  I was intrigued, of course, as I periodically invoke Sherlock Holmes and the benefits of checklists for testing, analysis, etc.   

The magazine article, written by Mark Yates, looks at the checklists used both at Mission Control and in space. He takes us through the Apollo missions where there could be two spacecraft both operating remotely 240,000 miles from Earth and out of communications contact with Earth for significant periods of time.

Checklists and cue cards covered everything from mission rules, abort criteria, emergency procedures and activation of backup systems in the event of a total failure of a primary control system for example. These checklists and procedures went everywhere. In fact, each Moon-walking astronaut would have a book of procedures strapped to his left wrist that he could follow out on the lunar surface.

In fact, all of the Apollo crews would each log over 100 hours familiarizing themselves with the numerous procedures and checklists. Apollo 11’s Command Module Pilot Michael Collins called them the “fourth crew member.” These checklists were also one of the first examples of digital computers and man being able to operate together seamlessly.  One of the actual checklists used by the Apollo 11 crew is shown below:

Chemical Engineering Checklists

How do we use checklists in chemical engineering?  We have many uses for them. For example, if you visit an earlier blog, you’ll find checklists and application details for filtration testing.  

For AVA mixer and dryer testing, we use the following checklists:

  1. Measure bulk density
  2. Measure moisture content
  3. Measure wet cake 
  4. Make sure to ground the dryer for electrostatic charges
  5. Measure RPM
  6. Record jacket temperature and product temperature
  7. Measure vapor stream 
  8. Measure vacuum level
  9. Measure dry cake and drying time to develop drying curves 

The Apollo missions were 50 years ago, but checklists are still critical for safe and efficient operations. Whether you’re an astronaut or an engineer!