Removing Catalyst Fines From Raney Nickel Catalyst Reactions

 

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

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

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

A Candle Filter Primer

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

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

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

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

Raney Nickel Catalyst with Candle Filters for Slurry Discharge

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

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

Candle Filters for Raney nickel Slurry Discharge

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

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

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.

Changing it Up with Mixer-Dryer-Reactor Acquisition

 

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

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

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

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

Expanding Process Filtration Technology Technologies

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

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

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

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

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

Novel Filtration Technologies for Pharmaceutical Hydrogenation

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

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

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

Understanding Candle Filters

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

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

Screen Shot 2019-01-08 at 6.07.32 PM.png

Candle Filter in Action

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

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

Pharmaceutical Hydrogenation Application 

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

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

Application of Separation Techniques & Full Containment

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

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

Importance of Thin-Cake Filtration

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

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

Impacting Filtration Performance

There are several parameters that can impact filtration performance:

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

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

Application of filtration techniques
Filter plate

Understanding Autopress Technology

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

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

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

Real World Examples of Particle and Cake Formation Influences

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

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

Particle Sizes Changes from Lab to Production

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

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

cake formation

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

Troubleshooting Filtration Technology

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

cake formation

 

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

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

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

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

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

Troubleshooting When the Filtration System is Not Working

 

filtration system
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These are five dreaded words that no engineer wants to hear on a Saturday night or Sunday morning: “The filtration system is not working.” Of course, we never seem to get this call at 10 in the morning on a work day!

No matter the time of day, let’s not panic, take a deep breath and begin the analysis.  

There are normally three main areas that must be examined when you learn the filtration system is not working:

  1. The filter itself for mechanical reasons
  2. The equipment around the filter is not working
  3. The filter operational procedures are not correct.  

To fully understand the problem, it’s necessary to separate the symptoms from the causes. So, let’s examine each of these groups in more detail.

Troubleshooting Filter Problems

The first thing that should be checked is the filter itself. There could be a failure of the equipment mechanics such an internal components, seals, etc. Many of these issues will be described normally in the preventative maintenance section of the filter’s O & M manual. 

Second, keeping in mind, the filtration system is part of the entire process it’s important to examine the upstream and downstream equipment. For example, you might check:

  • Are the reactors performing correctly in terms of agitation, temperature control, etc. in order to produce the specified crystals?  
  • Are the precoat and body feed systems in tune for mixing, feeding, flow rates, solids loading, etc.?  
  • Are the valves and instruments operating correctly and reading the correct variables (calibrations), etc.?  

Next, take a look at the pumps that feed the slurry and washing liquids as well as the compressors the feed the gas streams for drying and cake discharge.  The pumps must produce the required pressure, flow rates, etc.  The compressors must also produce a certain gas flow at a specific pressure for a certain amount of time.  Are their interlocks in the control system or a control communication problem that are not being recognized that are causing the filter problem.  Finally, if flocculants and chemicals are being used, have these changed?  

Process Engineering Problems? 

The last place to look is the process or operational procedures. These could be responsible for the filtration problems.  For example, the particle size distribution may have changed, the amount of solids in the slurry may have changed, the cake compressibility may have changed, etc.  In terms of the operation, has the filtration pressure changed, timers changes, speed changed, etc.?  Finally, determine whether or not a process parameter has changed.  

Trouble shooting is not easy, but solving the problem brings a great sense of satisfaction. 

Let me know some of your troubleshooting horror stories! I’d love to share some in a future blog. Together, we can make it easier to handle the situation next time we hear those five dreaded words.  

filtration system
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Filtration of Liquefied Gases & Caesar’s Last Breath

liquified gases
foter.com

On the heels of my blog about “The Business of Breathing,” it’s time to talk about gas. I recently finished reading the Sam Kean book “Caesar’s Last Breath.”  For those of you who have not read Kean, his specialty is writing science books in an exciting and entertaining fashion.  His three other books focus on the elements in the periodic table, genetics, and the brain.  Meanwhile, Caesar’s Last Breath looks at gases and both how the atmosphere has shaped human beings and how human beings have shaped the atmosphere.

The word “gas” actually comes from the Greek word “Khaos” for chaos or empty space between the Greek gods and the earth. To the Greeks, gases were the least understood component and the most “wildest” of spirits that no one could tame.

liquified gases

Today we know gases can become liquids, solids or stay as gases.  The book is a survey of the history of the earth explored through the air that we breathe and the scientists that made major discoveries of gaseous properties.

Believe it or not, there are good guys and bad guys and conflicts in the book.  Kean covers the earth’s early days, atomic tests at Bikini Atoll, details of UFO sightings in Roswell, New Mexico, and the truth behind the US Air Force tests.  There is a whole chapter on nitrous oxide (laughing gas) as well as the Manhattan Project and the development of ammonia gas and fertilizers.  Of course, there is a discussion of ice seeding for rain, which I am am keenly interested in as well (remember my blog on the Cat’s Cradle and the Vonnegut family?).  Finally, Caesar’s Last Breath concludes with alien life, new planets, greenhouse gases and other crazy ideas for other civilizations. All of these chapters are a lot of fun to read.

Relating my Reading to Filtration Tech

Yet, while all of this is very interesting, especially Kean’s scientific data, the question remains for my blog readers: how does BHS handle liquified gases?  Knowing that gases, under pressure, act as a liquid The BHS Rotary Pressure Filter can conduct filtration, washing, and drying of slurries continuously under pressure to keep the gas as a liquid. We also have installed units for Dimethyl Ether (DME) with specialty containment; contact me  for further information or discuss your critical filtration applications.

In the meantime, what have you been reading lately that you might suggest I pick up? I’m always on the lookout for new must-reads with a scientific bent. Or anything you can share that offers a new perspective on liquified gases.

4 Key Differences between Filtration and Centrifugation

I’m always looking to collaborate and explore ideas with others in our filtration technology business. Happily, director of Oriental Manufacturers Jigar Patel, has offered this guest blog discussing differences between filtration and liquid solid centrifugation. I hope you enjoy Patel’s perspective:

liquid solid centrifugation
Photo by gemmerich on Foter.com / CC BY-SA

Filtration and centrifugation are two distinct separation techniques used for isolating the required components from the mixture. The major difference between the techniques is the nature of the force employed and the separation method used. While filtration uses a sieve or filter media to strain undesired constituents, centrifugation leverages the power of the centrifugal force for the separation.

What is Filtration?

Filtration is a physical separation technique, by pressure, vacuum or gravity, used for segregating one or more components from a mixture for different applications. Depending on the application, the process may employ one or multiple metal perforated layers or filter mesh for solid-liquid separation. 

What is Centrifugation? 

Centrifugation is a process that employs a centrifugal force to separate the elements of the liquid slurry.  The remaining liquid (supernatant) is then transferred from the centrifuge tube or removed without disturbing the precipitate. The precipitating particles left behind depend on the speed of the machine, the shape and size of the particles and their volume, viscosity, and density.

4 Major Differences between Filtration and Centrifugation

#1 Nature of Operation 

  • Filtration 

Large particles in a mixture are unable to pass through the perforated layers of the filter. Yet fluids and small particles easily pass through the filter mesh under the pressure, vacuum, or gravitational force. 

  • Liquid Solid Centrifugation 

The centrifugal machine forces the heavier solids to the bottom creating a firm cake. The lighter mixture that stays above the cake is then decanted. 

#2 Separation Techniques

  • Filtration 

Filtration uses different techniques depending on the expected outcome which can be classified as pressure, vacuum, or gravitational.

  • Centrifugation 

Centrifugation techniques can be classified as micro-centrifuges, high-speed centrifuges and ultra-centrifugations. Microcentrifuge is typically used for research studies that require the processing of biological molecules in very small volumes. High-speed centrifugal machines are designed to handle bigger batches and are mainly used for processing industrial mixtures on a large scale. The ultra-centrifugation technique is used to study the properties of biological particles.

#3 Function 

  • Filtration 

The main function of filtration is getting the desired output by eliminating impurities from any given liquid or isolating solids from a mixture. 

  • Centrifugation 

The main purpose of centrifugation is fast, efficient separation of solids from a liquid solution or slurry.

#4 Efficiency 

  • Filtration 

Simple filtration techniques take time separating the desired materials, which makes the separation method less efficient. 

  • Centrifugation 

Centrifugation techniques employ machines that run with the aid of power, so the separation method is faster and more efficient. 

Both filtration and centrifugation are solid-liquid separation techniques that use different equipment and have different applications.

My two cents: Deciding which one is best suited to your process will take work. No matter the process in question, engineers are well served by taking the time to gather the information, make their own comparisons, and then develop a process solution.

Thanks to Jigar Patel. The director of Oriental Manufacturers believes in the power of good functional designs and their ability to boost productivity and drive growth. Fueled by his passion for innovation and all things EPC, Jigar writes on topics related to process plant equipments, process machinery production, turnkey solutions, best industry practices, liquid solid centrifugation, and his personal insights!‌

Keep the sharing going — let me know what you want to write about in this spot next!

Selecting the Right Types of Filtration for Solid-Liquid Separation

types of filtration
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Filtration selection, if we think back to Sherlock Holmes, means “not jumping to conclusions.”  There is no “one size fits all” process solution.  Selecting a filtration technology requires a systems approach incorporated with other solids processing such as reactors, dryers, solids handling, etc.  You could gain an objective overview by filling out an application data sheet (like the ones I use for new or existing applications) that can help identify what’s involved in the specific solid-liquid separation.

Ultimately, the process has three components:

  • Material properties, which I’ll describe in more detail below
  • Separation performance objectives including, for example, filtrate quality (conductivity or residual solids) cake dryness, flowability of the cake, crystal breakage /fines generation and conditioning of the cake for further processing
  • Mechanical properties — The specification must be clear in terms of material of construction, temperatures/pressures, FDA validation, cleaning procedures, manufacturing codes, etc.  Each equipment type will have its own mechanical specifications that must be satisfied.

These three considerations are combined and ranked choices are then evaluated for operational, economic, and plant (internal and external) objectives.

Finding the Best Filtration Procedure

Your examination of material properties considers the solids and the liquids.  For solids, the engineer needs to know the total suspended solids (TSS) and solids concentration, particle size distribution (PSD), and particle shape.  The PSD should be based upon particle counts at different sizes rather than by weight or volume.

The particle shapes can vary:  spheres, rounded, angular, flaky, or thinly-flaked are among the examples.  Shape will influence the filtration rates for the process and also impact the PSD due to the nature of particle size measuring equipment.

Knowing this, the solid-liquid filtration system further requires a systems approach to incorporate other solids processing such as reactors, dryers, and solids handling, etc.  The full scope should include the actual upstream and downstream.

Consider this typical example of a chemical process including all of the associated processing steps:

  • Chemical synthesis and Crystallization:
    • Types of catalysts
    • Solvents
    • Continuous or batch
    • Temperature
    • Flashing
    • Inerting
  • Filtration
  • Drying
  • Dissolution
  • Hydrogenation
  • Secondary crystallization
  • Filtration
  • Final drying
  • Solids and slurry handling in all steps

General Guidelines to Selection

So, the question is where to begin to make the preliminary filtration technology choices for solid-liquid separation?  Here are some general guidelines for selecting among types of filtration:

Filter Press Continuous Vacuum and Pressure Nutsche  Filter & Filter-Dryer Clarification
Solid content of the suspension (%) 5 to 30 10 to 40 10 – 40 < 5
Maximum Pressure Difference 100 bar -1 to 6 bar 6 bar 10 bar
Cake Thickness (mm) 5 to 50 5 to 150 5 to 300 20
Average Particle Size 1 to 100 micron 1 to 100 micron 5 to 200 micron 1 to 50 micron
Type of Operation Batch Continuous Batch Batch
Comments Good for slow filtration and can produce dry filter cakes; Excellent cake washing and pre-drying Good when reactor batch times equal to total cycle times Disposable for low flows; candle and plate filters for large flows

Let me know if this is helpful to you.  My idea is to do a series of types of filtration systems for solid-liquid separation for various applications.  What is troubling you?