Contribute to a Holistic Approach to Unit Operations!

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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.

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 Unit Operations 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.

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 

 

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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.


Slurries

Containment of Slurries in Continuous and Batch Operations

Slurries
Image source

In the 1970s, the chemical operations used acetone and benzene for the main slurries 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

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!


common myths about engineers

Common Myths About Engineers

common myths about engineers
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As a regular reader of Chemical Engineering Progress (CEP), I was impressed to see its Editor-in-Chief Cindy Mascone writing her monthly editorial as a poem. She mentioned that when she writes for the magazine "accuracy, clarity, and conciseness take precedence over all else." But that doesn't mean she can't be creative too! Her poem got me thinking about common myths about engineers.

  1. We aren't creative
  2. We lack social skills
  3. We want to fix everything (whether it needs it or not)
  4. We're quantitative wonks
  5. We are boring (just in case that wasn't clear from being a quantitative wonk)
  6. We're not open to new areas of inquiry or interest

Get to know an engineer!

Of course, I beg to differ. I like to think of this blog as one outlet for creativity. Plus, every time we come up with a new solution or problem-solve in a new way, we're showing not only critical, but also creative thinking.
I've written a lot about troubleshooting in filtration technology, but not because we do it for kicks. We do it to improve a process or solve a problem. Really, we'd rather be innovating — which, again, is just how non-boring and creative we can be.
We may know our numbers, and some of us can be a little socially awkward (but plenty of liberal arts enthusiasts are too). Still, I'd argue that we are generally creative, inquisitive, and downright interesting folks!
And now, because I know you're curious, I can also share the poem itself:

Ode to the March 2019 Issue of CEP
This month we feature process intensification
One aspect of which may be flow augmentation
Equipment that is smaller or does more than one function
To the old paradigm, PI causes disruption.
The first article tells of three RAPID teams
Whose projects are the stuff of dreams
Microwaves, solar hydrogen, and hydrofracking
Energy-saving ideas, they are not lacking.
A dividing-wall column replaces two towers with one
It changes the way distillation is done
With a smaller footprint and lower capital cost
And on top of that, no efficiency's lost.
So how do you optimize an intensified route?
That's what the next article is about
Use this building block approach to process design
And watch your energy use decline.
A digital twin software tools can create
To capture the process's every possible state
You can study alternatives and run what-if tests
To figure out which option is best.
This issue contains many other things, too
Whatever your interests, there's something for you
The same can be said of the Spring Meeting which will
Take place in New Orleans and be quite a thrill
Check out the preview after page seventy-four
For sessions and keynotes and events galore.
I've run out of space so now I must stop
But if you like this poem, to the website please hop
There's more rhyming about CEP and its staff
I hope I have made you smile and laugh.
Thank you for coming to read more of my poem
On the website or app that is our virtual home.
The authors who write for this fine magazine
Do it not for the money but to get their names seen
By thousands of people at sites far and wide
For this publication is a valuable guide.
The topics they cover in their technical articles
Range from safety and computers to fluids and particles
From water and energy, from bio to dust
From nano to columns that are resistant to rust
From instrumentation to exchangers of heat
Among chemical magazines, CEP can't be beat.
Our readers know not what we editors do
To make the articles understandable for you
Each page is read over many times with great care
To ensure that no typos can be found anywhere
That tables and figures are in the right places
That all the text fits with no empty spaces
That references include all the necessary data
That symbol font correctly displays mu, rho, and beta
That hyphens appear everywhere hyphens are needed
That the proofreader's comments have been fully heeded.
We take pride in our work and we love what we do
Bringing the latest technology and information to you
But now we must turn to next month's content
And make sure every moment on the job is well spent.

Reprinted with permission from Chemical Engineering Progress (CEP), March 2019. Copyright © 2019 American Institute of Chemical Engineers (AIChE)

Inspired to write your own technical poetry? Engineering verse? I'd love to see it and share it here! Who knows, maybe there is an anthology in the works!