Dry Granulation:The Definitive Guide

In a study that was published on the National Center for Biotechnology Information , Srinivasan Shanmugam defines dry granulation as:

It is a process that uses either compaction or mechanical compression to agglomerate dry powder particles.

But, what is agglomeration?

The Collins Dictionary defines agglomeration as a process where particles stick together forming groups that are loosely attached.

This implies that the process involves applying a certain degree of force, causing powder particles to adhere to each other. You don’t need any binding solution.

Look at these:

Different types of powders

Final product after dry granulation

You must be wondering how this can be possible…you’ll learn about it shortly in chapter 3.

Generally, in pharmaceutical or food processing industries, you can use either wet granulation or dry granulation processed to form granules. That is, to enlarge and increase the density of powders.

Depending on the material processing needs, you can adopt wet granulation or dry granulation. Normally, the end product is almost the same however, the process is quite different.

In chapter 6, there is an ultimate comparison of dry granulation vs. wet granulation.

Up to this point, I am sure you can confidently give an accurate answer when you come across the question – what is dry granulation.

With that in mind, let me take you a step further:

In chapter 1, it is quite clear that dry granulation process does not require:

• Moisture or liquid to bind powder particles
• Heat to dry wet granules

Since the 1940s, dry granulation has not been common among many material processing industries.

However, with researchers focusing more on active pharmaceutical ingredients (APIs), dry granulation technique has become a perfect solution.

The truth is:

You cannot use wet granulation to process certain APIs without compromising their quality. Definitely, you will need a roller compactor for dry granulation.

A roller compactor is a machine you can use in dry granulation. Don’t worry I will discuss this equipment in chapter 9.

Now, at what point should you choose dry granulation:

Dry granulation is suitable for:

Moisture Sensitive APIs/Materials/Substances

Normally, these are substances that react on exposure to moisture. This moisture can be from water or any other granulation solution (for the case of wet granulation).

Under such circumstances, the API or excipient may lose vital chemical properties making it ineffective.

In such situations, you cannot use wet granulation to form granules. Dry granulation will be the best alternative.

Below in an example of how some excipients react with water or moisture:

A clear change in structure – Photo Credits: NCBI

You can follow this link to learn more about the effects of moisture/water on pharmaceutical excipients.

Remember, in dry granulation process, you don’t need water or any binding solution.

Temperature Sensitive APIs/Materials/Substances

Well, once you use water or any binding solution, the next step will be to dry the API or excipient.

What if they are temperature sensitive?

Wet granulation may not be the best solution.

So, this makes dry granulation the only viable solution for temperature sensitive APIs and excipients.

In case you want to learn more about this, you can read: Drug Degradation Pathway. For today, I will not go into that subject since it is beyond the scope of this guide.

The main takeaway here:

You should choose dry granulation technique when processing moisture and temperature sensitive products, API, excipients or materials.

Speaking of dry granulation; let me explain to you the steps in this material processing technique.

Knowing what dry granulation is and when to choose this process is not enough.

You need to understand the dry granulation method steps.

I mean how the process takes place.

Generally, there are only two ways of producing granules through dry granulation process. The two processes include:

• Slugging process in dry granulation
• Roller compaction dry granulation

So, what is the main difference between these two principles of dry granulation?

Let’s find out:

Slugging Process in Dry Granulation

Slugging method is one of the oldest techniques in dry granulation process. In fact, as early as the 1950s, it was a popular process in most pharmaceutical companies.

However, due to the many disadvantages, most companies now use the roller compaction dry granulation technique.

Basically, the slugging of granules involves the following key processes:

Step 1:

Feed the powder in a large compression machine.

Feeding powder in the compression chamber – Photo Credits: KHRISTELLE ENANO

Step 2:

Compress the powder into a large slug or tablets where the diameter can either be 0.25 or 1 inch. This is basically a slugging process in tablet compression.

Powder compression in progress – Photo Credits: KHRISTELLE ENANO

Slug/tablet ready for the next stage – Photo Credits: KHRISTELLE ENANO

Step 3:

Use a sizing machine to breakdown the large slug or tablet into suitable sizes. Here, you’ll be milling the tablet.

Milling machine – Photo Credits: KHRISTELLE ENANO

Granules from the milling machine – Photo Credits: KHRISTELLE ENANO

As you can see, this is a simple and straightforward process.

Although it is an old process, there are some pharmaceutical companies that still use slugging in dry granulation.

Later in chapter 8, you will learn how dry slugging machine works.

Under normal circumstances, the following are key factors that determine the efficiency of slugging in dry granulation:

• Material property such as particle size, flow characteristics, powder cohesiveness and density.
• Machine design features; slugging pressure, feed hopper, compression speed, feed frame, tool design and die diameter, among other factors.

In most cases, slugging of granules requires a 4 to 6 tons hydraulic pressure with a turret speed of 10 to 30revolutions/minute.

So, why are many companies abandoning slugging of granules?

Disadvantages of Slugging in Dry Granulation

Below are some of the main reasons why I cannot recommend slugging method in dry granulation:

• Poor process control; it is virtually impossible to control the size and density of the granules, hence resulting in many variations.
• Low production capacity; slugging of granules is a slow process that may not meet the high production needs in the modern food processing, chemical or pharmaceutical industries.
• Frequent part wear leads to high cost of maintenance and part changeover.
• Pool economy of scale; an increase in production results in more expenses in terms of machine maintenance, power consumption, production time, etc. Hence, it is not suitable in modern production setups.
• High pollution; most slugging machines for dry granulation may cause air pollution as a result of both noise and dust.
• Requires large space; slugging in dry granulation requires more space due to large machines.

Clearly, this is not a method that I can recommend for any dry granulation process. From experience, slugging dry granulation process is not economical at all.

So, which dry granulation process should you go for?

Roller Compaction Dry Granulation

Roller compaction is a popular dry granulation technology. So far, it has replaced the slugging granulation process in most material processing setups.

The principle of dry granulation here is quite different and guarantees high efficiency.

For the purpose of this process, you need a roller compaction machine. You will learn more about this machine later in chapter 9.

Here is exactly how roller compaction technology works:

Roller compaction process

Step 1:

Put all material in the feeding hopper. With the help of the machine feeding auger, material will move to the rolling system.

Step 2:

Once the material reaches the rolling system, it will compress the material into a ribbon. Remember, the machine will direct the material into the gap in between the two rollers.

Basically, it is the two rollers that increase material density, forming a ribbon.

Step 3:

At this stage, the machine will mill the ribbon or briquettes to a required shape and size. This section of the machine has a sieve that allows only the right size of granules to pass through.

At the same time, the machine recirculates very tiny particles (powder) back into the system to steps 1 and 2 again.

As you can see, this is a simple and straightforward process.

The truth is:

Roller compactor technology is popular among many material processing companies. It is basically an advanced and modern dry granulation technique.

Advantages of Roller Compaction Technology

Below are some of the main advantages of roller compaction in dry granulation process:

• It simplifies the dry granulation process; unlike slugging, roller compaction is simple and eliminates the difficulty in material processing.
• Cost saving; roller compactors require less material and energy to operate
• Being a fully automated system, it requires less manpower and energy to operate.
• It is an accurate dry granulation process that helps to control weight and density of the granules. As a result, it is easier to produce consistent and accurate granule density.
• Granulates from roller compactors form capsules and tablet that disintegrate easily.
• There is no need for solvent or aqueous granulation process.
• It allows for continuous granulation of materials
• A perfect equipment for processing hygroscopic materials
• Improves process cycle time
• Guarantees a shorter material processing time
• Facilitates powder flow
• Roller compactor machines save on dry granulation processing space while maximizing the production

Powder for dry granulation

Clearly, you can see roller compaction technology offer quite a number of benefits. This is why I can confidently recommend it in any dry granulation process.

Later in chapter 9, I will take you through an in-depth analysis of roller compactor machine.

Please, note!

I am not saying that roller compactor for dry granulation is 100% perfect. No, that’s not the case.

It has some disadvantages and these include:

• Possible loss in tensile strength; at times, when you use granules from roller compactor machines to make tablets, they tend to have inferior tensile strength. So, you need to improve the tensile strength by choosing appropriate excipients.
• There is a possibility of less product yield; this is due to the non-compacted powder as high amount of fine powder remain. To eliminate this, the design of roller compactor machine should be such that it allows the fine powder back into the system for compression.

In short, you can easily modify the roller compactor machine to ensure efficiency. This is only possible if you know the design and working principle of roller compactor machine.

You will learn that later in this guide.

In the meantime, I want to let’s now review the advantages and disadvantages of dry granulation process.

Like other material processing technologies, dry granulation has both advantages and disadvantages. With this knowledge, you can easily know when to go for dry granulation or other material processing techniques.

Let’s have a quick overview of the advantages and disadvantages of dry granulation:

Advantages of Dry Granulation Process

Below are some of the main reasons why you can consider dry granulation:

Dry Granulation Requires Less Space

In any material processing setup, space is always a major issue. However, when it comes to dry granulation, the design of the machine is that it requires less space.

For example, when you look at the SaintyCo RC-100 Roll Compactor, it requires less space.

Roll Compactor machine

This makes roll compactor machine a perfect solution for material processing applications that require less space.

Remember, the size of the machine and floor space for the installation will depend on the production capacity. However, when you compare dry granulation and wet granulation machines with the same production capacity, the latter requires a large floor space.

Suitable for both Hard Continuous and Batch Granulation Process

Dry granulation technique is suitable for both continuous and batch granulation process. Thus, it is a perfect choice for small and large scale material processing.

This is basically the kind of flexibility in the manufacturing process you could wish for.

Remember, the roller compactor for dry granulators feature a fully automatic system. You can control and monitor all operations via the control panel.

Control panel for a dry granulation machine

Guarantees Quality Granules

If there is one thing that you’re certainly looking for is the ability to produce high quality granules by the end of the process. That being said, it is worth noting that dry granulation process ensures:

• High mechanical strength of granules
• Uniform size and shape of granules

• Predictable production

With these, you can easily optimize subsequent operations such capsule filling or tablet compression. This is because you know what to expect from your granules.

Preventing powder segregation through granulation – Photo Credits: CLINICALGATE

Offers Cost Saving Granulation Process

An effective way to maximize on your profits is to adopt a material processing technique that will reduce the cost of production.

Well, when it comes to processing certain materials, you can save a lot by adopting a dry granulation process. Here are a few practical examples you should note:

First, with dry granulation process, you don’t have to add moisture or binding solution.

Second, since you don’t need binding solution, there will be no need for drying granules (use of heat). Obviously, this will save you granulation cost and time.

An illustration of wet granulation process (you don’t need to add binder liquid in dry granulation)

In most cases, you will realize that dry granulation guarantees low cost of operation. Besides, it is also an efficient way to form granules.

Again, the fact that the dry granulation equipment requires less space is also a way to save costs.

Improving Tablet Disintegration

A roll compactor machine produces granules which when you use to make tablets, improves disintegration of the final product. Normally, such tablets have high water-uptake ability since the process of forming granules does not require water.

Photo Credits: RESEARCH GATE

A Perfect Alternative for Producing Effervescent Tablets

Effervescent tablets are known for their ability to dissolve in water and producing carbon dioxide.

Effervescent tablet dissolving in water – Photo Credits: PHARMA TIPS

When it comes to producing some dosages of this type, you can always count on dry granulation process.

In short, these are the main advantages of dry granulation technique.

On the other hand, there are situations where this process may not be a perfect alternative. This is due to certain disadvantages the machine comes with.

Disadvantages of Dry Granulation Process

Below are some of the key aspects you need to know before choosing this manufacturing process:

A Poorly Designed Machine Produces More Dust

There are two scenarios here:

• Possibility of air pollution is high since the machine produces granulation without adding binder solution or granulation solution.
• With dust, there is a high possibility of cross contamination.

To solve some of these problems, you must choose a machine that strictly adheres to CGMP design requirements.

SaintyCo RC-200 Roller Compactor Pharmaceutical

Dry Granulation may Require More Power

Companies that use slugging process require heavy duty machines that require more power. This can make the production process even more expensive.

High Chances of Static Charges Build Up

Dry granulation process may result in charge build in particles.

As you had seen earlier in chapter 3, there are some advantages and disadvantages that are unique to specific dry granulation process.

But more importantly, you need to choose a suitable machine for this process.

You’ll have all that in chapter 8 and 9…keep reading.

For now, let’s review yet another critical aspect you cannot ignore whenever you’re considering dry granulation for material processing.

In this section, you’re going to learn about the various factors that may affect the efficiency of dry granulation process.

With this knowledge, I am quite sure you can optimize the dry granulation process.

Here are key factors you need to know:

Design of the Granulation Machine

Well, more of this you will learn in chapters 8 and 9.

Still, it is important to note that the design of a dry granulation machine will play a critical role here.

Take for example, slugging dry granulation machine and roller compactor granulation machine. The latter is highly efficient, a reason why most pharmaceutical companies go for the roller compactor machine.

SaintyCo RC-V200 Roller Compactor Machine

Well the design features that will affect the efficiency of the dry granulation process include:

• Design of the rotating rollers
• Orientation of the roller system; they can be vertically or horizontally positioned
• Feeding mechanism
• Milling system
• Feeding system
• Control mechanism

Basically, their unique designs will affect the dry granulation process.

Therefore, it is important to know the critical features and design specifications of the roller compactor machine. This way, you will easily choose a machine that best suits your unique material processing specifications.

The bottom line:

Choose a roll compactor machine after doing in-depth research and analysis of every component. But, knowing the machine alone is not enough…what exactly do you intend to granulate?

Physical & Chemical Properties of Material

Earlier in this guide, I did mention that dry granulation process is suitable for moisture and heat sensitive materials. Of course, this is because you don’t need granulation solution; hence, there is no need for drying the final product.

For a fact, different substances or excipients have varying physical and chemical properties. Thus, for the scope of this guide, it is quite impossible to discuss each material.

The bottom line:

Do a proper research to establish whether by adopting dry granulation process, you can produce granules with better flowability and compressibility.

Granules in capsules

Remember, during the dry granulation process, you will pay attention to a range of granules characteristics such as:

• Particle size
• Bulk density
• Surface area
• Flow properties
• Strength and friability

All these will vary depending on the physical and chemical properties of the material you intend to granulate. Also, the type of machine plays a critical role here.

But, wait a minute…

There is one more thing you must consider too – choice of material and type of machines are not enough.

Process Parameters in Dry Granulation

Dry granulation process parameters refer to the variables that may determine the quality of the final product.

For instance, the following play a significant role in determining the roller compactor granulation process:

• Speed of the feeding screw
• Force for compacting powder
• Hydraulic pressure on the rollers
• Rotational speed of the rolls

I will expound on these parameters in chapter 9…keep reading.

Other aspects will include various variable temperature and relative humidity of the surrounding.

The bottom line:

The fundamental aspects that determine the efficiency of dry granulation process are:

• Type of machine, which basically determines the granulation process
• Physical and chemical property of powder
• Process variable/parameters of dry granulation process

With these in mind, now let me take you a step further and do a brief comparison of wet and dry granulation techniques.

With all that you’ve learnt, let’s have a side by side comparison between dry granulation and wet granulation technologies.

By doing such a comparison, you’re likely to choose an appropriate process for your material processing needs.

Here’s everything you need to know about wet and dry granulation:

        i.            Process

In wet granulation technology, you need a solution (granulating or binding solution) to form granules. Thus, we use the name “wet” to refer to this process.

Basically, at some point material will be wet as a result of spraying it with a solution.

Wet granulation process

On the other hand, dry granulation is the process of forming granules without adding any form of liquid or solution. It is for this reason that we refer to this process as “dry” granulation.

Dry granulation process

      ii.            Types of Machines in the Granulation Technologies and Techniques

Clearly, the main difference between dry granulation and wet granulation depends on the process – how to make granules.

Obviously, from point (i) above, the two processes are completely different. As a result, you will expect machines in the two granulation processes to have different designs.

This is:

For wet granulation machine; it has a slightly complex design with many features and functionalities. For instance, it has a mechanism for mixing powder, spraying, drying and ultimately milling, among other components.

Below is a video of fluid bed granulator and coater

In dry granulation machine, there is the roller system, milling and sieving system, among other components.

Below is a video of a roller compactor machine.

Clearly, you can see the design of dry granulation machine is quite different from that of the wet granulation machine.

    iii.            Applications of Dry Granulation vs. Wet Granulation Process

As earlier stated, you will use wet and dry granulation to make granules. You can pack granules as the final product, or process them further using either tablet press or capsule filling machine.

But more importantly, I want you to note the following when doing a comparison of granulation technologies:

You can use dry granulation process material or substances that are moisture and heat sensitive. This is the main purpose of dry granulation machine.

I had explained this in chapter 2 of this guide.

On the other hand, you can use wet granulation on products that are not moisture and heat sensitive. Moreover, you can adopt this process in situations where you do not want to destroy the active ingredients in powders.

Whichever option you opt for, by the end of it all, you should have powder granules.

End product of wet or dry granulation process

In short, these are the main differences between wet and dry granulation processes. Always remember, it is purely based on the process, design of the machine and type of material.

With this, let me take you to another critical stage of this guide – practical applications of dry granulation machines.

From chapter 1, I know you’ve been asking yourself this simple question:

Where exactly can I use dry granulation technique?

Even before I discuss that, here are a few aspects that most material companies consider when adopting dry granulation process.

        i.            Helps to Improve Flowability of Material

This is an important aspect in tablet compression and capsule filling process in high speed machines.

For an optimal capsule filling process, you should be able to control the key aspects that influence the flowability of powder such as:

• Moisture content; an increase in moisture content from 1% to 1.5%, will have an impact on the flowability of a powder.
• Temperature; a slight change in temperature will affect the flowability of powder
• Particle size; handling very fine powder, especially in tablet compression and capsule filling process is quite cumbersome. A reason why you need to deal with granules.

Capsules and tablets

By adopting dry granulation technique, you will increase the bulk density of powder. At the same time, you will increase the particle size.

In the long run, you will improve the flowability of material, making it easier to compress (for tablet press) or fill in capsules.

      ii.            Reduces Segregation in Material Processing Industries

Homogeneity of various APIs or excipients is critical. This is because in the case of drugs, it will definitely improve the uniformity in every dose of tablet or capsule.

It is for this reason that you need a process that can bond the particles together, preventing possible segregation of particles. Even when you’re dealing with moisture or heat sensitive products, dry granulation process will guarantee an efficient compaction process.

As a result, your granules will remain intact with no possibility of segregation. Therefore, it is suitable for making tablets or any other pharmaceutical dosing products.

Tablets

Look, these are critical considerations in choosing specific applications of dry granulation techniques.

Now, with that in mind, let me take you through a quick overview of various practical applications of dry granulation techniques in industries.

For the scope of this section, I will focus on the main industries that benefit from dry granulation techniques. They include:

Dry Granulation in Pharmaceutical Industries

As you can recall, there are two critical aspects I have mentioned earlier in this chapter – preventing product segregation and increasing flowability.

The truth is:

Pharmaceutical companies leverage on these to make various products such as:

• Different shapes of tablets
• Fill different capsule sizes

Capsules with granules

These tablets and capsules may include riboflavin, antibiotics, lactose, etc. Basically, they can use dry granulation to process most of these excipients or APIs, ready for the next stage in the manufacturing process.

Dry Granulation in Chemical Industries

Like in the pharmaceutical industries, dry granulation also plays a pivotal role in chemical industries. These may include producing chemical tables or capsules.

Others may include producing various agricultural products or water purification tablets. For example, dry granulation of fertilizers is common in many industries.

Chlorine tablets by OPC

The point is:

Dry granulation provides a better way of producing chemical tablets or granules, alongside other products.

Dry Granulation in Food Processing Industries

Food processing industries have benefited from dry granulation process. Take for instance, the manufacturing of tablet or capsule supplements.

Vitamin supplements – Photo Credits: WIKIPEDIA

Normally, these supplements may come in the form of vitamins or mineral ions. Other products may include spice extracts, instant blends, etc.

So, what’s the bottom line here?

You can use dry granulation process for a range of material processing needs in industries. All you have to do is to choose an appropriate material whose properties will not be altered by the process.

As I said earlier, dry granulation technology is suitable for moisture and temperature sensitive materials.

But I know you’re probably wondering how exactly you can achieve this:

In chapters 8 and 9, the main focus will be on dry granulation machines. It covers all the fundamental aspects on dry granulation machines such as features, working principle, specifications, etc.

In case you want to be an expert in dry granulation machines, then those are a must read chapters.

So stay with me on this page to learn more.

Anyway, let’s dive right in:

For many years, slugging machine played a pivotal role in dry granulation process. However, it was until the invention of a roller compactor machine that these machines are now becoming obsolete.

I am not saying that these slugging of granules is no longer being used.

But, over 77% of companies have opted for the roller compactor machine…you’ll learn more about this machine shortly.

So, what is a slugging machine?

And, how does it work?

Here is what you should know:

Generally, the dry granulation process uses two main machines to form granules – slugging machine or roller compactor machine.

8.1. Slugging of Granules (What it is & Basic Facts)

Slugging for dry granulation is the process of forming granules by exerting high pressure on the powder particles. To achieve this, you need to take powder materials through a series of processes that you will learn shortly in this guide.

Normally, slugging in dry granulation occurs at high pressures that range from 30 to 70bar.

During the process, the machine exerts high bonding pressure that makes powder particles to develop boding forces between particles.

Granules

Forming granules involve a range of forces such as Van der Waals, recombination of bonds, interlocking between surfaces.

By the end of the slugging in dry granulation process, you will have granules that you can further process to your market needs. That is, you can compress them into tablets or fill in capsules.

With that in mind, so how exactly does slugging of granules take place?

8.2 Understanding Slugging Process in Dry Granulation

Even before I discuss the key stages in this section, I want you to watch this slugging in dry granulation video:

The video was uploaded by John Jairo Rojas Camargo.

Just like the video, I am going to take you through how slugging of granules takes place:

Step 1: Prepare Material You Want to Granulate

You should choose an appropriate powder that you intend to granulate. You can use a bin blender to mix it so that you have a homogeneous mixture.

SaintyCo bin blender

Once you have an appropriate mixture, it is now time to compress the powder into tablets.

Step 2: Compress Powder into Slug or Tablets

Here, you will need a compression or slugging machine. In fact, this machine resembles the normal tablet compression equipment.

However, the difference here with slugging in tablet manufacturing is the size of the tablets and the amount of pressure you’ll require for the process.

Remember, the normal hydraulic pressure tablet press operates at about 4 tons. This is quite low when you compare it with a hydraulic press in slugging for dry granulation.

At times, you may require as high as nearly 15 tons for materials that are difficult to compress.

What’s the aim here?

To compress the powder into a large tablet or slug-about an inch diameter and a gauge of about 0.25 inch

Slug or tablets after compression

Still, this is not what you need.

Step 3: Mill the Slug into Appropriate Granules Sizes

This is basically breaking down tablets into very small or tiny granules. It is yet another critical stage in slugging for dry granulation.

Now, you will use an appropriate milling machine to resized and separate the right particle of granules.

During this stage, the milling machine may also produce very tiny particles (nearly the size of powder). You can recycle them by putting them back into the slugging machine again.

Granules which you can use to make tablets or capsules

As you can see, the process is quite simple and straightforward.

Well, to make good granules when you adopt this principle of dry granulation, you must pay attention to some fundamental aspects.

Let’s go further to see how you can optimize the slugging in dry granulation:

8.3. Factors Affecting the Efficiency of Slugging in Dry Granulation

Broadly, there are two factors that determine the efficiency of slugging in dry granulation. These include:

• Material feeding properties
• Slugging machine design features

The truth is:

There are quite a number of raw material feeding properties that determine the final output of the process – granules. These include:

• Cohesiveness
• Density
• Flow characteristics
• Particle size distribution

Apart from the power properties, you must evaluate the design features of the machine. This way, you can easily make adjustments to optimize slugging of granules.

Some of the main design features of the slugging machine for dry granulation include:

• Slugging machine type
• Feed hopper
• Feed frame
• Die diameter
• Tooling feature
• Compression speed
• Slugging pressure

The bottom line:

Both the type of material and design feature will determine the quality of the final product.

Again, to ensure consistency (uniform powder slugs and densified granules) in the manufacturing process, you must take the following precautions:

• Always maintain consistent and uniform powder fill into the die cavities
• An appropriate design, setup will minimize the possibility of die powder flow and hopper feed frame problems.

But, that’s not all.

Here is yet another critical aspect you must know:

8.4. Production Capacity of Slugging Machine in Dry Granulation

Like other pharmaceutical equipment, slugging machines have different product capacities depending on their design and configuration.

For a fact, the production capacity will depend on the following key aspects:

• Type and design of the machine
• Turret speed may vary from 10 to 30revolutions/minute.

In most cases, the production output ranges from 30 to 50kg/hr. As you can see, the production capacity is quite low.

Now, why is slugging method not popular in modern dry granulation processes?

• Automating slugging for dry granulation is a problem. Hence, controlling process qualities is quite difficult.
• It is quite difficult to integrate slugging and milling machine.
• In case of very fine powder as part of the final output, you have to take them back into the machine manually

In short, very few companies use slugging in dry granulation. It is basically an old way of making granules.

Remember:

I had highlighted the disadvantages of slugging for dry granulation earlier in this guide.

With all these, let’s again move a step further and discuss modern dry granulation machine – roller compactor for dry granulation.

This is a must have machine in dry granulation process.

Just stay with me….there’s a lot more you need to learn to improve on your dry granulation process.

If you’re struggling to optimize your dry granulation process, then this is a MUST read chapter.

Reason:

Roller compactor machine is a reliable and efficient machine when it comes to dry granulation. In fact, nearly all pharmaceutical, food processing or chemical industries use this machine.

Of course, this is due to its high processing speed, cGMP compliance, ease to automate and ability to produce quality granules.

In this chapter, I will take you through all the critical aspects of roller compactor for dry granulation.

SaintyCo Roller Compactor Machine

But first, let’s have a quick overview of the history of roller compactor machine.

9.1. History of Roller Compactor Machine for Dry Granulation

Since the invention of roller compactor for dry granulation by Francis Xavier Chilson, there has been a lot of technological advancements and improvement. In fact, it is from this this that at times, you can refer to roller compactor machine as a chilsonator.

Since then, there has been a series of innovations and improvements, aiming to enhance performance and reliability. These also include a number of in-depth studies and analyses – I have links to those studies at the end of this guide.

For instance, James Alan Clark patented the screw feeder for a roller compactor machine. A patent was granted on 10^th June 2008.

A number of roller compactor manufacturers have come up with unique designs, aiming to improve performance and reliability. For instance, they have an improved auger-feed system, pressure roller mechanism and low shear mill.

Horizontal feed screw for roller compactor – Photo Credits: Alexanderwek Inc., USA.

Indeed, it requires analysis of various aspects of final granules such as density, size, shape, flowability, etc.

As a matter of fact, I can confidently confirm to you that the future of dry granulation will depend on technological advancements on roller compactor machine.

Here is all you have to do:

Choose a high quality and reliable roller compactor machine for dry granulation.

But, how can you achieve this?

Let me take you through that by discussing this:

9.2. What is Roller Compaction Technology for Dry Granulation?

Even as you plan to venture in the dry granulation process, it is important to acquaint yourself with the machine you will use.

That way, you will choose suitable equipment that can optimize all your material processing needs.

The question is:

What is roller compaction technology?

From a layman point of view, a roller compaction technology is a process that transforms powder into granules.

That is, your input into the machine will be powder and the output granules.

How this process takes place is a subject for section 9.4 (the roll compaction technology). I want you to know the different parts of this machine first before discussing the working principle.

Making granules from Calcium Nitrite powder

Now, to expound on my earlier definition:

Roller compaction technology for dry granulation is a process of transforming the powder into suitable granules with predictable density, size and shape. The roller compaction granulation involves the action of rotating rollers, milling and material grading equipment.

All these processes take place within a single machine. So you don’t have to transfer material from one machine to another in roller compaction technology for dry granulation.

I know you’re probably wondering how complex and big a roller compactor machine looks like.

It is a small machine – look at this:

SaintyCo RC – V200 Roller Compactor Machine

Its dimensions are as follows:

• Length: 1400mm
• Width: 1150mm
• Height: 1950mm
• Weight: 1800kg

In short, this is what I am trying to say:

All the mechanisms that help in roller compactor for dry granulation are assembled in this single equipment.

Of course, it also depends on a range of engineering principles. These include electrical, hydraulic, pneumatic and mechanical systems integrated together to convert powder into granules.

I hope we are together up to this point.

As I said, roller compactor granulation is the core of dry granulation process. That’s why I want you to understand every concept as we move along.

With that in mind, let’s explore another critical aspect you need to know IF you want to be an expert in roller compaction technology.

9.3. Parts of Roller Compactor Machine (Learn Part Name & Function)

Do you remember this quote by Steve Jobs?

“Design is not just what it looks like and how it feels. Design is how it works.”

Well, in this section, I am going to take you through various critical parts of roller compactor machines.

But, more importantly:

You need to pay attention to how that particular part or feature works. That way, you can easily optimize processes in dry granulation.

For instance:

• Why should you design rollers to rotate in a particular direction?
• What is the best design for feeder system?
• What should be the appropriate gap between the rollers?

Basically, the issue here is not just a matter of designing various parts of a roller compactor machine for dry granulation. You need to establish why the components and parts are assembled in a particular manner.

I am sure now you know why this is a MUST read chapter.

First, I want you to review this video:

As you can see, from this simple assembly process, roller compactor machine has many parts and components. However, for the scope of this section, the main focus will only be on critical parts.

Main parts of roller compactor

The following are the key parts of roll compactor machine for dry granulation:

Raw Material Feeding Unit

This is the point where you’ll pour/put all the powder material you intend to granulate. In most machine designs, it is found on the upper most section of the dry granulation machine.

Here is a good example:

See the position of the material feeding unit in roll compactor machine

Normally, the design of this section is such that it allows material to flow into the feeding system. This is the reason why most machines feature slanting sides.

Feeding System of Roller Compaction Machine

It is the feeding system that conveys powder from the raw material feeding unit to the rollers (you will learn about the rollers shortly).

So far, quite a number of machines in the industry use the screw feeding system.

Remember, it is this feeding system that determines the production capacity of the roller compaction machine for dry granulation.

As a matter of fact, different roller compaction machine manufacturers have adopted different feeding roller designs. Notably, you will find the machine with different orientation of the feeding screw.

Here are good examples:

See the orientation of the feeding system (part 2) and feeding auger (part 3) – Photo Credits: AYASHA RANA ET AL

At the material feeding system, the machine pre-compact the powder, while removing any entrapped air at the same time.

Again, as the screw feeding system removes air, it allows faster and more powder feeding. Also, depending on the design of the roller compactor machine, you may go for either:

• Twin pre-compression feed system or,
• Single pre-compression feed screw system

With these unique designs, you can count on a roller compactor machine for dry granulation when dealing with even low bulk density powders.

In short, choose a machine with an appropriate feeding system.

Compacting Roller System

Maybe you’ve been wondering why we refer to this dry granulation process as a roller compactor technique.

Here is the answer.

Just like the name suggests, this machine is made of two roller systems. It is in the roller system that the compaction process takes place.

That is, the rollers compress loose powder into flakes, which later form granules (you’ll learn about this shortly).

So basically, the design of this system will determine the efficiency of roll compactor dry granulation process.

Photo Credits: Vladimir Duz & V.S. Moxson

Now, what are the main design features of a compacting roller system for dry granulation process?

Direction in which the rollers rotate

Normally, these are two rollers with equal diameters that rotate towards the direction in which the powder from the hopper flows.

Direction of rotation of the two rollers

To get a high quality flakes at the end of this stage, the rollers must exert a constant pressure. Moreover, the gap between the two rotating rollers should be constant.

It is the pressure from the two counter rotating rollers that produce a compacted ribbon or flakes.

Gap Between the two Rollers

The gap between the two rollers will determine the efficiency of the dry granulation process. This is another design feature that you need to consider.

Generally, the design of the space between the two rollers is divided into three sections:

A view of the roller system

It is this section that will determine the quality of the final product. So this is what happens in the two regions:

• Feeding zone;

This is also the slip region. As you can see in the above image, it is just close to the feeding system.

Here are a few things you need to know about this section:

• Particle de-aeration and rearrangement take place at his stage
• Rollers exert less pressure on the powder

• Compaction zone or nip region

This is the region where maximum compression takes place. To achieve this, material must move at the same speed as that of the two roller surface.

In addition to these, the nip angle should be sufficiently large for maximum compression. Remember, the gap between the two rollers decreases in the nip region.

• Release region

Also called the extrusion region, the gap between the rollers begins to form, thereby reducing the total pressure on the powder. As a result, the ribbon may elastically increase in size.

This is basically the ejection stage – where the material leaves the roller compactor system to the next stage in the dry granulation process.

Normally, choosing the right roller and design is a challenging process when designing roller compactor machines for dry granulation.

But, this is not all when it comes to roller compactor granulation. Another aspect that you must pay attention to is:

• Fixed vs. Variable Roller Gap

When you have a fixed roller gap, then you should be able to use the screw feeding system to control the flow of material. On the other hand, with variable systems, you can use the screw feeder and the width between the rolls to control the powder feed.

Another aspect that is also evident in most roller designs is the orientation.

Again here, there are three options to choose from:

Different orientations of roller compactor machine for dry granulation

These include:

• Horizontal roller orientation;

This is one of the most common designs of roller compactor machine for dry granulation. Here, the rollers are arranged horizontally.

In these designs, the powder loss due to bypass is high. The bypass is a condition where material remains in the nip region for some period of time.

To reduce the possibility of powder bypass, you need have a side sealing mechanism. Here, the machine will have inclined or vertical feeding system.

• Vertical Roller Orientation

Roller compactor machine with vertical roller orientations are suitable for low dose materials. This is because it has less bypass material.

Besides, the powder movement does not depend on gravity feeding system.

• Inclined Roller Orientation

With these machine designs, the orientation of the roller systems lies between the horizontal and vertical plane. The good thing with these machines is that they reduce bypass by 10 to 15%

So, what’s the bottom line here?

The roller orientation determines the degree of material loss due to bypass and dosing capacity of the machine.

In addition to these aspects, another vital factor to consider on the roller design is the surface area.

Well, the surface area will depend on the design of the roller compactor machine for dry granulation. Besides, you may also have a smooth and corrugated roller surface.

Depending on the nature of the application, you can use:

• Smooth roll surface; this is a perfect choice for roller compactor machines in the pharmaceutical industry
• Corrugated roller surface; it is suitable when dry granulating aerated and fluffy materials, with an aim of increasing their bulk density.

Furthermore, you should be able to control the pressure responsible for the compaction process.

Now, once you make the flakes or ribbons, it is now time to reduce them to suitable granules.

And that takes us to yet another critical part of dry granulation machine:

Flake Crusher

Located just below the two rollers, the flake crusher reduces the ribbons or flakes into small sizes.

See the position of the flake crusher

It is important that the flake crusher features a dust free design as per the cGMP requirements. You can also refer to this as a pre-crushing mechanism.

This component mills the flakes or ribbons into suitable granule sizes.

To ensure only uniform size of granules leave the roller compaction machine for dry granulation, the machine is fitted with an appropriate size screen.

Normally, the milling process does the following:

• Improve flowability of granules
• Ensure content uniformity
• Reduce segregation
• Ensure particle size distribution

Granules from the roller compactor for dry granulation

Again, the choice of mill will determine the kind of force you intend to use when breaking flakes or ribbons from the roller system.

For instance:

• Shear force requires a cut mill
• Compression force you need a jaw crusher and conical screen mill
• Attrition force you need a ball mill
• Impact force you need hammer, screen and cut mill

In short, it will depend on the final product you intend to achieve by the end of the process.

Control Panel

A roller compactor machine for dry granulation is a fully automatic machine. Therefore, quite a number of machines feature a PLC control system with touchscreen human machine interface (HMI).

From the HMI, you can monitor, control and configure various roller compaction process parameters.

Control panel

Apart from these critical parts and components, a roller compactor machine for dry granulation has:

• Discharge chute/outlet of the final product
• Drive mechanism consisting of electric motors, shafts, gears and belts
• Entire structure that holds the machine and all its components
• Alarm systems

Remember, I had earlier indicated that a roller compactor machine for dry granulation has hundreds of parts and components. Some of which I have not discussed here.

So please, get the technical manual of the machine to know what new the roller compactor manufacturer has incorporated in their machine.

Even with those variations, the design aspects here form the main framework and working principle of roller compactor machine.

With these in mind, let now understand how a roller compactor for dry granulation works.

9.4 Principle of Dry Granulation with Roller Compaction Technology

In this section, you are going to learn how roller compactor for dry granulation works. It will take you through a step process, giving illustrations alongside images where possible.

If you were keen, in section 9.3 of this chapter, I have highlighted critical aspects of roller compaction technology.

In fact, from that section alone, you can easily figure out the basic principle of dry granulation and roller compaction technology.

But, even before I start discussing these processes, you need to watch this video. It illustrates how roller compactor works in a straightforward and simple.

Now, let me explain the working principle of a pharmaceutical roller compactor (well, it’s the same process for the industrial roller compactors too):

Step 1: Fill Powder into the Hopper or Material Feeding Equipment

Once you have an appropriate blend of powder, you will put it in the hopper or material feeding system. It is from this point that the powder will flow to the roller system.

I hope you remember the specifications of material hopper or the material feeding equipment. In case you’ve forgotten, please refer to section 9.3 of this chapter.

Step 2: Material Flows to the Roller System

The orientation of the roller system will solely depend on the design of the machine. Again, the feeding mechanism will also depend on the design of the machine.

Now, quite a number of machines use a screw material feeding system. This may include vertical and horizontal screw feeding systems.

At the screw feeding systems rotate, the powder flows towards the roller compaction systems. At the same time, it removes the air that could be present in the powder.

Moreover, it also recompresses powder.

Step 3: Roller Compress Powder into Flakes or Ribbon

The two rollers rotate in a counter clockwise direction (in the direction of flow of material), compressing the powder into appropriate flakes or ribbons.

As I had indicated in section 9.3, the material you’re dry granulating will pass through all the three regions.

By the time it reaches the lower edge of the rollers, it will be fully compacted flake or ribbon.

Step 4: Mill Ribbon or Flakes

In roller compaction technology, the machine is fitted with appropriate milling equipment. It is this milling machine that reduces the flakes into appropriate granule sizes.

I know you’re probably wondering how this machine can be accurate to produce the exact size of granules you need.

Let me explain:

As the milling equipment rotates breaking ribbon or flakes into smaller particles, there are three possibilities:

• Size of particles that are bigger than what you need
• Average size of granules you need
• Very fine particles, that are of equal size of the powder

This is how the roller compactor machine manufacturers ensure there is a high efficiency at all times.

• For very large particles they will remain in the milling chamber. This way, as the milling machine rotates, it will break them further into small sizes – probably the ones you need.
• The appropriate granule sizes will move to the next section of the sieve system where they will them move to the product collection unit.
• Very fine particles will move to the lower section of the sieve system. They will then be recycled back to the feeding system of the machine to be compressed again.

Well, all these processes have been automated. Therefore, all you need to do is to key in appropriate roller compaction process parameters.

As you can see, the working principle of roller compactor for dry granulation is quite simple and straightforward.

Here is a summary of the entire process:

A summary of a process of dry granulation using a roller compactor machine

Before I proceed to the next section of this chapter, I want you to note the following.

Both machine design and powder properties are key dry granulation parameters you need to evaluate to optimize the entire process.

Remember, adjusting any of these parameters can improve or prevent dry granulation of suitable granules.

Still, there is one more thing you need to know – how to get as a suitable roll compactor machine for dry granulation.

9.5. How to Buy Roller Compactor for Dry Granulation

I am not going to take you through obvious things like identifying or searching for reputable manufacturer.

Well, it is a common knowledge that you MUST buy a roller compactor for dry granulation from a reputable manufacturer.

So, what exactly should you know when buying a roller compactor machine?

1.      Consider Technical Specifications of the Roller Compactor Machine

This is information that clearly describes the capability of the roller compactor machine. From this information, you will know whether a machine meets your unique process requirements or not.

Remember, a technical specification is unique to a machine model. It is not like the operation manual where a roller compactor manufacturer may decide to have one for a particular series of machines.

This information has every detail and working parameters of the roller compactor machine model. Here is a good example:

Technical specifications of SaintyCo RC-5B Roller Compactor

From this information, you can configure the machine to meet your unique roller compactor for dry granulation needs.

In short, before you buy a roller compactor machine, please remember to evaluate the technical specifications of the machine.

2.      Features of Roller Compactor for Dry Granulation

These are the basic factors that help the machine to achieve the granulation process. I know you may confuse this with the technical specifications of the machine.

Anyway, let make it easier for you to understand:

Take for instance, SaintyCo RC-150C Roll Compactor machine has a granulation capacity of <100kg/hr. That is the technical specification.

Well, you need to look beyond this data to find out what exactly makes the machine to achieve such kind of performance.

Compaction system of roller compaction machine

That is exactly what you will learn here.

Here are some of the key features of roller compactor for dry granulation:

Automatic System

Quite a number of roller compactor machines for dry granulation feature fully automatic system. That is, from the material feeding system, removing air, pre-compression, compression, milling, etc.

All these processes require robust and reliable control system.

It is for this reason that roller compactor manufacturer includes a touchscreen human machine interface (HMI). This allows roller compactor machine operators to monitor different processes, configure and if possible troubleshoot the machine.

Depending on the capability of the control system of the machine, from the HMI, you can precisely control the sieving system, feeding pressure, force moment, speed, formula sheet thickness, etc.

With some machine, you can even print the process data.

cGMP Compliance is a MUST Feature

Look:

Here, you will be dealing with dry powder, so there is a high chance of air pollution or cross contamination. Therefore, whenever you are shopping for roller compactor machine, settle for nothing less than cGMP compliant roller compactor for dry granulation.

First, from the machine hopper, material feeding screw system, roller compaction to milling, among other parts must guarantee dust free operation.

Second, the roller compaction machine for dry granulation should have an FDA approved material. It is for this reason that these machines are made from stainless steel.

Parts of roller compaction machine for dry granulations

Three, all moving parts such as motors, gears or any other transmission mechanism must be completely isolated. This will ensure that dust never accumulates on these moving parts.

Four, you must go for a machine that is easy to clean and maintain. For example, modern machine features an automated cleaning system.

A good example is the self-configured negative air pressure air pump system like for the case of SaintyCo RC-150C Roll Compactor. It pre-cleans the entire working chamber.

By doing so, the machine will prevent any possible cross contamination by sucking any particles within the machine system.

Unique Feeding System

Let’s face it, the efficiency and reliability of a roller compaction dry granulation process depend on the efficiency of the feeding system.

What if you have a machine that can optimize flow of material for granulation?

Well, I know there are designs out there, however I find helical feeding mode a perfect choice for efficient dry granulation process.

Showing screw feeding system of roller compactor machines

The good thing about the helical feeding system is that, it combines the advantages of flat feeding and vertical feeding systems.

Precise Control of Rollers

The truth is, you can go for the “best” machine out there, however, without a proper choice of roller mechanism; all your efforts will be futile.

So, why don’t you consider a machine with a precisely controlled pneumatic controlled eccentric roller adjusts?

Roller compaction system for dry granulation

With such a machine, you can maintain the consistency in granules. That is, you will have a ribbon with uniform thickness.

Recycling Very Fine Powder

From the working principle of roller compaction machine for dry granulation, there are a few things that are quite clear. You can have:

• Very large granules, which the mill can still break into small pieces
• Suitable granules that will automatically move to the product collection chamber
• Very fine powder, that may require further processing

Now, you should have a machine with an appropriate sieving mechanism to separate fine powder from the end product.

Furthermore, it should have a mechanism to recycle this fine powder back into the system for compression again.

It is this simple:

Always go for a machine with features that can increase productivity on the roller compactor for dry granulation.

And please, don’t get me wrong:

I don’t imply that these are the only features to look for.

Roller compactor manufacturer may opt for a range of features depending on their research and what they believe can improve efficiency of dry granulation process.

3.      Design & Structure of the Roll Compaction Machine for Dry Granulation

You must consider the design and structure of a roller compaction machine for dry granulation. It is from this that you will know whether the machine is suitable for your specific manufacturing needs.

When I talk about the structure of a roller compaction machine, this is the overall design you can see. Look at these:

Two models of roller compactor machine

What you can see in the image above is exactly what I mean by roller compactor machine for dry granulation design.

Well, this design alone will determine whether the machine is suitable for dry granulation or not.

For instance, the RC-5B is portable hence, suitable for R&D or batch production. On the other hand, the RC-150 is suitable for medium scale production.

Other aspects of roller compactor machine for dry granulation design are:

• Easy part changeover
• Flexibility and adaptability of the machine to any dry granulation manufacturing process
• Modular design

Let’s face it:

I know you’d not wish to invest in a completely new machine when it comes to slight improvements in machine performance. Besides, no one wishes to experience the annoying downtimes in machine.

Obviously, you need a roller compactor for dry granulation that can guarantee:

• Optimum powder dosing
• Conveniently remove air without the need for vacuuming
• Ensure consistency in the dry granulation process

Well, you can achieve all these with a high quality roller compactor for dry granulation.

In short, the design and structure of the machine should meet your unique dry granulation needs.

Now, what’s the bottom line here?

Whenever you’re considering buying a new roller compactor for dry granulation, you must consider technical specifications, machine features and design/structure.

With these three aspects, you will never go wrong. In fact, they will lead you to finding a reputable roller compactor for dry granulation manufacturer.

Now, even as I am about to conclude this dry granulation guide, it will be unfair not to recommend a few roller compaction machines.

Let me take you through a quick overview of SaintyCo roller compactor machines:

9.6. SaintyCo Roller Compactor Machines

SaintyCo is a premier roller compactor machine manufacturer that invests in modern technologies a range of machines. Combining their own patented technologies, the European and American technologies, the company provides unlimited possibilities in pharmaceutical dry granulation processes.

Let’s have a quick overview of some of SaintyCo’s roller compactor machines for dry granulation:

SaintyCo RC-5B Automatic Dry Granulator

This is a portable dry granulation machine for R&D and clinical trial production.  As you can see, it has wheels making it easier to move from one point to another.

For technical manual and other specification, click here: SaintyCo Roller Automatic Dry Granulator.

RC-5B automatic dry granulator

SaintyCo RC-100 Roll Compactor

With a robust and cGMP compliant design, SaintyCo RC-100 Roll Compactor meets the production needs for both small and medium scale granulation processes. It has four wheels, making it easier to move from one point to another.

For more information on this machine, you can follow this link: RC-100 Roller Compactor Machine.

Figure 1: SaintyCo RC-100 Roll Compactor Machine

SaintyCo RC-V100 Roller Compactor

It features a unique structure with slightly high stainless steel frame. This roller compactor machine is suitable for small and medium dry granulation processes.

For more information about this equipment, click here: SaintyCo RC-V100 Roller Compactor.

RC-V100 Roller Compactor

RC-150 Roll Compactor Machine

For small and medium dry granulation process, you can consider this machine. It’s robust, versatile and precise design guarantees uniform granules.

To learn more about this machine, you can follow this link – SaintyCo RC-150 Roll Compactor Machine.

SaintyCo RC-150 Roll Compactor Machine

SaintyCo RC-V200 Roller Compactor

This is yet another handy and functional roller compactor machine for dry granulation you can count on for small, medium to large scale production process. To access technical information, designs and other related information, follow this link: SaintyCo RC-V200 Roller Compactor.

RC-V200 Roller Compactor

SaintyCo RC-200 Roller Compactor Pharmaceutical

For pharmaceutical dry granulation processes, SaintyCo RC-200 is a perfect choice. It features unique, adjustable and flexible roller design that meet the dynamic production needs.

To access the technical data of this machine click here: RC-200 Roller Compactor Pharmaceutical.

RC-200 Roller Compactor Pharmaceutical

All SaintyCo roll compactor machines for dry granulation are cGMP compliant with robust structure. They guarantee accurate and consistent dry granulation process.

Besides, they are also cost competitive.

I believe with this information, you can choose one that meets your unique specific needs.

As I promised you earlier, I have some useful links on the granulation process at the end of this guide. You can read them during your free time.

Now at this point, you should be able to:

• Define dry granulation
• Differentiate between wet granulation and dry granulation
• List benefits and applications of dry granulation technique
• Choose appropriate dry granulation machine (evaluate both slugging and roller compactor machines)

Still:

For questions or inquiries about dry granulation process and techniques, you can leave a quick comment below.

Alternatively, you can send me an e-mail since the reason I am here is to help you get the best dry granulation machine.

Further Reading:

Dry Granulation – Geraldo Garcia

Wet Granulation: Ultimate Guide for Beginners & Professionals – SaintyCo

Granulation I – Rahul Singour

Presentation on Dry Granulation – Girgis Attia

Granulation – Syed Waqas Haider

Advances in Roller Compaction/Dry Granulation – Saikh Mahammed Athar Alli

Granulation Techniques &Technologies (Recent Progress) – Srinivasan Shanmugam

Roller Compaction for Dry Granulation (Benefits that Guarantee Material Processing Success) – Tony

Understanding Critical Parameters in Roller Compaction Process – AIChE Academy

Overview on Roller Compaction/Dry Granulation – Ayasha Rana & Others

Handbook of Pharmaceutical Granulation Technology – Dilip M. Parikh