mixing and drying technology

Mixing Drying Technology Across Industries

mixing and drying technologyLast year, BHS announced its acquisition of AVA-GmbH company and its mixing, drying technology. Combining our engineering expertise and project management know-how helps us both better provide a full process solution including mixing-reacting-filtration-cake washing-dewatering and final bone-dry powder. It’s been a year, so let’s now take a look at the different industry application for AVA dryers.
The AVA dryer technology handles mixing, drying, reacting, granulating, sterilizing, evaporating, humidifying, and homogenizing. The tech is batch and continuous, vertical-conical and horizontal for atmospheric and vacuum mixing and drying operations.
mixing and drying technology
In the pharmaceutical  industry, the AVA mixers and dryers have uniform heat transfer and drying for temperature sensitive APIs without crystal breakage. The horizontal designs homogenize and dry with very short residence times taking advantage of the  AVA back-mixing techniques. For vertical designs, the agitator is heated and sealed with dry-running mechanical seals. These applications benefit also from:

  • Validated PLC control systems with CIP 
  • Complete discharge without residual product for batch-to-batch integrity
  • Easy handling of pasty and poor-flowing products 

The agricultural chemical industry can also benefit from consistent product quality with CIP and complete discharge without residual product. The AVA mixers and dryers have uniform heat transfer and drying for bulk material products. Integrated dust filters are included. In the vertical designs, the agitator is heated and sealed with dry-running mechanical seals. 
Similarly, end users in the fine and specialty chemical industry, can rely on AVA mixers and dryers for uniform heat transfer and drying for bulk material products. The horizontal ploughshare and paddle drying designs homogenize and mix/dry with very short residence times. Taking advantage of the  AVA back-mixing and turbulent-mixing techniques allows for pasty and poor-flowing products processing.  High-density blending and granulation are also typical operations.  

More Markets for Mixing and Drying Technology

In the environmental market, horizontal ploughshare and paddle drying designs homogenize and mix/dry with very short residence times. AVA’s back-mixing and turbulent-mixing techniques allow for the processing of hazardous and combustible waste as well as mixing of dewatered cake and dehydrated pellets at municipal wastewater sludge drying facilities.  
The metals market is another primary user of AVA mixing and drying technology. The horizontal ploughshare and paddle drying designs offer the benefits already outlined. Meanwhile, the vertical agitated cone mixer is intended for mixing of free flowing bulk goods within a wide range of particle sizes. The units are equipped with a spraying system used for spray coating of materials.   
In the metals industry, high-density blending and granulation are also typical operations with AVA tech.  Metals include phosphorus, lithium, anode and cathode pastes and pyrolysis reactions at high processing temperatures, up to 650 degrees C, and drying of single lithium components as well as their precursors, to obtain the required dryness or chemical reactions.
Whatever your industry. the choice of vertical or horizontal designs for batch or continuous operations requires careful analysis of the process and the bulk material. AVA mixing and drying technology is adapted exactly to your respective requirements and raw material properties. At the AVA technical center, each individual application can be tested on horizontal and vertical systems to decide upon the best possible configuration. 
You can rely on AVA mixers and dryers along with BHS-Sonthofen many years of process know-how and continuous product development to optimize your full process solution. The goal is to accomplish as many processes as possible in one unit in order to minimize investment and process costs. Learn more today!

Know Your Options for Particle Fine Removal

photo of hill under cloudy sky
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Process engineers struggle to clarify process liquids. Particle fine removal is part of the ongoing battle. But there are ways to automate the clarification processes to improve filtration and minimize operator exposure. The cake solid’s structure and the nature of the process will determine which types of pressure-filtration automated clarification technologies are best for you.
Before we discuss removal of particle fines, let’s discuss how they are generated.  Tom Blackwood, in his Chemical Processing article, Fend Off Fine Particle Frustrations, talks about two main areas for fines generation.  First, the problem can start in the particle formation step (crystallization, reaction or extraction). Excess supersaturation or the lack of nucleation control can allow fine particles to persist through the process.  
Next, upstream processing can lead to particle fines through attrition. Attrition can occur in centrifugation, drying, conveying and storage. Tom has even seen attrition in liquid/liquid separation processes where crystals have formed due to the immiscibility of the chemical in a solvent. Centrifuges are a common source of attrition due to their filtration and discharge mechanism via the solids hitting the cloth or solid surface due to a poorly designed inlet.

Particle Fine Removal Approaches

How can pesky particle fines be removed? Throughout my career in the solid-liquid separation market space, I have seen some interesting solutions. At one melamine resin facility, the slurry was in a formaldehyde process. The operators were wearing masks and 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!
There are better ways! Engineers have many choices to automate the particle fine removal process. This might involve candle filters, pressure plate filters, or sintered metal filters. Each type has its place. With testing and careful evaluation, engineers can make the correct choice. 
Candle filters, for instance, are best suited for filter cakes that are vertically stable. Pressure plate filters are used for filtration of cakes up to 75 mm thick. Sintered metal cartridges are used for high temperature applications greater than 200 degrees Celsius where the solids are well-defined hard crystalline shaped. But there’s so much more to know about these options, check out what I’ve written about these in the past.
In the meantime, I’ll tell you filter aids are generally the last resort. Filter aid improves filtration, but there’s more work involved. 
Finding the right approach to particle fine removal is going to take into consideration cake structure and thickness, filtration pressure, filter media and more. At least with automated clarification technologies the process can be a little easier once you find the best choice for your needs.

If the Shoe Fits: Running and Innovation  

Two of my favorite things in one blog — running and innovation. Normally, I run 5K during the week. On the weekends, I find 8K and 10K races. While I would say I run at racing speed, I enjoy the atmosphere and the cold beer at the finish.  
My shoe of choice forever has been New Balance, 9 ½, EE. These fit like a glove and in all of my years, I’ve never had any problems. But then I read an article in Business Week that had me thinking.
How Nike Started a Sneaker Arms Race” talked about running and innovation. Nike’s innovation has led to a new shoe with a carbon fiber plate, lightweight foam, and a stiff forefoot that rocks you forward. According to the brand, out of the box, you are 4% better.  
The article offers technical discussion of the shoe and competitors complaining about unfair advantage. But innovation is innovation. And, as a runner, I was curious. 
Of course, Nike’s latest shoe comes at a price. Much more than I wanted to spend. But the article indicated that Hoka, as a competitor, came a close second, and at a lower price. So, yes, I purchased a pair of Hoka One carbon-fiber-plated shoes, More on how that turned out later. Let’s first look at the research into this new innovation in running shoes.

Innovation in Running Shoes

The New York Times published scientific details on Nike, Hoka and other shoes in its article “That Spring in Their Step? Even a Bigger Edge.”  Apparently, the carbon-fiber plate stores and releases energy with each stride and acts as a kind of slingshot or catapult to propel runners.  The lightweight foam also increases running economy.  
The Times analysis suggested, “that the advantage these shoes bestow is real — and larger than previously estimated.” Their findings:
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As for my training? I saw results too. Every year a 15 K “Hot Chocolate” Race is run in 18 cities in the US as well as Mexico City and Guadalajara for the “Make-A-Wish” foundation. I participated in 2018 and 2020. My time in 2018 was 2:09:29 running in New Balance 990. With the Hoka One One, my time improved to 2:03:14. That’s an improvement of 4.75%.10596_6542665_enm1767435957ram-1.jpg
I would like to say I trained better for 2020. But, maybe it was the running shoes. Or maybe I was just more motivated by the power of innovation on my feet!
Let me know your running style. We can get a couple kilometers in next time we see each other.  

Theory of Filtration and Theory of Creativity     

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Having been in the solid-liquid filtration, centrifugation, and drying marketplace since 1982, I have long said filtration is both a science and an art. I’ve witnessed the overlap of theory of filtration with theory of creativity. The practical and creative together make what we do so exciting. 
I entered the filtration business with Pall Corporation after five years with  the USEPA and receiving my MS in Environmental Science from Washington University in St. Louis. With Pall Corporation, I learned a lot about the science and art of filtration, marketing and sales, R & D, communication, and processes. It was during this time that I realized the creativity in the filtration market; every process, telephone call, e-mail was another challenge to solve a problem. 

Theory of Filtration

The theory of cake building filtration is based on Darcy’s law, describing the flow of fluids through porous materials. A practical equation was developed with a few assumptions:  

  • the build cake is (almost) incompressible
  • the pressure during the cake building is (almost) constant
  • the filtrate is clear (= (almost)) and all solids from the suspension do end up in the cake
  • the resistance created by the filter media is negligible compared with the cake resistance

 Experiences have shown that the following equation can be used:
theory of filtration
This equation describes most cases of everyday filtration testing. The most interesting parameter is alpha, the sum of all “unknowns” such as particle size distribution (PSD), porosity, solids shape and size, etc. Hence, the creativity.

Theory of Creativity

Robert J. Sternberg, Professor of Human Development at Cornell University, has developed two theories of creativity: The Investment Theory and the Propulsion Theory. What follows is a summary of Robert’s theories.

The investment theory of creativity holds that creativity is in large part a decision. Creative people generate ideas that are viewed as novel and perhaps slightly ridiculous. Creative individuals, by their nature, tend to defy the crowd. They resist merely thinking or doing what others are thinking or doing. The greatest obstacle to creativity, therefore, often is not exactly strictures from others, but rather the limitations one places on one’s own thinking.

People are not born creative or uncreative. Rather, they develop a set of attitudes toward life that characterize those who are willing to go their own way. Examples of such attitudes toward life are willingness to (a) redefine problems in novel ways, (b) take sensible risks,  (c) “sell” ideas that others might not initially accept, (d) persevere in the face of obstacles, and (e) examine whether their own preconceptions are interfering with their creative process. Such attitudes are teachable and can be ingrained in students through instruction that encourages students to think for themselves. Creativity comprises several different aspects: (a) abilities, (b) knowledge, (c) styles of thinking, (d) personality attributes, (e) motivation, and especially intrinsic motivation, and (f) environment.  

Robert continues with his propulsion theory, as follows:

Some kinds of creative contributions move forward in an already existing direction. The most basic kind of creativity is (1) conceptual replication, which is a product that basically repeats what has been done before with slight variation. (2) redefinition is a reconceptualization of a creative idea, so that an idea that was originally proposed for one purpose subsequently is used for another purpose. (3) forward incrementation is the next step in a usually long chain of ideas.  (4) advance forward incrementation is a next step that is a large leap beyond the last idea.  

Other kinds of creative contributions take a new direction from previous work. (5) redirection is a contribution that moves a field in a direction different from that in which it has been moving.  (6) regressive redirection is a contribution that takes a field in a new direction, but a direction that has been proposed earlier and perhaps discarded. (7) re-initiation is a contribution that not only moves a field in a new direction but also essentially starts a field over. Finally, (8) synthesis brings together previously divergent lines of thought, such as the invention of the seaplane.

Filtration & Creativity

Let me reiterate one of Sternberg’s observations: “The greatest obstacle to creativity, therefore, often is not exactly strictures from others, but rather the limitations one places on one’s own thinking.” I’ve written in the past about limitations that hinder our approaches to filtration. We can’t travel the same paths over and over again. We need to be willing to take a fresh look at each situation, think critically, test and test again, and innovate — with creativity.

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 today!