Questions You Should Know about Industrial Dryer Supplier

Rotary dryers are a significant capital expenditure, necessitating a thorough discovery process to assess the unique requirements of the system. In preparing to purchase a rotary dryer, keep the following questions in mind to protect the investment and ensure the appropriate solution is acquired. 

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Replacement Rotary Dryer prepared for shipment

Is a rotary dryer appropriate for my capacity requirements? 

Rotary dryers are widely used throughout various industries, but as continuous equipment meant for large-scale production facilities, they are generally not the best choice for small-scale settings. Rotary dryers are typically chosen for facilities processing anywhere from 1TPH – 200TPH. Those processing small batches of material should consider alternative dryer options better suited to their capacity requirements. 

Is a rotary dryer the right drying system for my product/material? 

Rotary dryers are a diverse industrial drying system, but they are not a fit for all materials. They are generally not appropriate for high-moisture materials such as slurries and liquids, unless pretreatment or back mixing will precede drying. 

Will any pretreatment be required? 

While they can accept a wide range of materials, rotary dryers do require materials to fall within a given range of specifications in terms of moisture content and particle size.

When the moisture content falls outside of this range (specific to each material), the material may require pretreatment to bring it into a more manageable moisture range. 

Similarly, material should fall within a predetermined particle size distribution (PSD) for effective drying. A crushing or grinding step may be necessary to bring material into the optimal size range. 

What configuration will best suit my needs? 

Rotary dryers are best designed around the specific characteristics of the material to be dried for optimal efficiency and product quality. This means the best configuration is highly dependent on the material. 

Several key aspects of the dryer must be engineered around these parameters, including air flow (co-current or counter-current), flight design and pattern, whether the dryer is direct or indirect, whether or not a combustion chamber is employed, as well as the size and diameter of the dryer and any special modifications that may be necessary to achieving process or product goals. 

The 3D rendering above illustrates the co-current air flow configuration (top) versus the counter-current configuration (bottom) in a rotary dryer.

If the ideal dryer design is not clear, the rotary dryer manufacturer selected to engineer the unit will often be able to assist in defining the dryer parameters. This may come in the form of past experience, expertise, material testing, or a combination thereof. 

It’s important to note, however, that not all rotary dryer manufacturers are capable of assisting in this aspect of development. Beware of those selling one-size-fits-all dryers.

What happens when something goes wrong? 

Remember that the dryer will require routine maintenance and potential repairs. Consider what happens when something goes wrong; is the OEM available to assist, or will a third party service provider be required? 

Does the dryer come with any sort of warranty or support from the OEM? Many plant managers have learned the hard way that not all rotary dryer manufacturers will provide assistance after installation is complete. 

A FEECO Customer Service Engineer arrives on site to inspect a rotary dryer

Can my site support a rotary dryer?

The intended site must also be considered in the purchasing process. Will electricity at the site be reliable? Is the fuel source readily and economically available? What sort of regulatory requirements will govern the site’s emissions? Is there space to accommodate the dryer?

Is testing needed before engineering a full-scale unit? 

Material testing may be a necessary step in the buying process. Testing is often used as a means of gathering the process and material data necessary for scale up, particularly when the application is new, or when working with materials that exhibit a high level of variation. 

Pellets in a rotary dryer during testing in the FEECO Innovation Center

Will/Can an OEM assist with process/system integration?

The capabilities of individual OEMs vary significantly. Some OEMs will only provide the dryer, while others will fully assist with process engineering and integrating the unit into the existing system, along with streamlining its performance in the operation. 

What sort of quality control practices do we need to be aware of? 

The purchase of a rotary dryer is just like anything else, with quality ranging from poor to exceptional. When looking for a high-quality rotary dryer, ensure the chosen manufacturer adheres to a strict quality control program. Consider materials of construction, welding certifications, rolling techniques, allotted tolerances, and more. 

Rotary dryer in fabrication at FEECO

What other equipment is needed to support the dryer? 

Remember that several other pieces of equipment are needed to support the drying system. A complete dryer system requires an exhaust gas handling system, a burner, a combustion chamber (optional), and material handling equipment to carry material to and away from the dryer. 

What can I expect in terms of maintenance?

Apart from minor maintenance procedures such as changing the gearbox oil, maintaining adequate lubrication, and the like, rotary dryers are relatively low-maintenance, though the level of maintenance required by an individual dryer depends largely on the specific demands of the application. 

FEECO recommends annual inspections to catch and address any potential problems early in order to minimize maintenance and repair requirements. Rotary dryers should also be periodically realigned, as they fall out of alignment over time through normal wear and tear. 

Rotary drum tire and trunnion grinding may also be necessary from time to time to recondition worn load-bearing surfaces. 

Rotary dryer tire grinding in progress

Will this equipment be a fit if we want to automate our process in the future? 

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Automation capabilities are also highly specific to the manufacturer. That said, automation should be a consideration in the purchasing process if it is not already. 

Automation is becoming increasingly more relevant to industrial equipment, allowing producers to collect and monitor data in real time, and also use trends for predictive maintenance and expedient troubleshooting and issue resolution. 

How do I choose a supplier? 

Identify critical objectives and evaluate manufacturers based on how they align with these goals. 

Factor in other important considerations in choosing a rotary dryer manufacturer, such as material expertise and ability to customize a dryer, in order to reach the best possible outcome. 

Will this equipment allow us to comply with emissions and any regulatory requirements? 

Regulatory compliance cannot be overlooked. Ensure the chosen manufacturer is prepared to address emissions for compliance. 

What sort of installation costs can I expect with a new rotary dryer? 

Installation costs vary per site, but generally add 1 to 2 percent to the cost of the unit. The installation contractor will lay out the associated installation costs.

What are the physical base requirements for a rotary dryer? 

Rotary dryers require a solid base capable of bearing both live and dead loads without distortion or vibration. This is typically handled by concrete piers and/or structural steel supports, with the specific requirements for the site laid out in general arrangement (GA) drawings. 

Rotary dryer on concrete piers

Conclusion

As a large capital expenditure, rotary dryers require careful attention to detail during the buying process. Be prepared for the many questions and issues that may arise by considering the factors listed above. 

>An industrial dryer is an essential part of most material processing procedures, but they are typically a large capital expense and can last for decades. This makes picking the best dryer for your processing needs especially important since picking the wrong dryer can have long term negative consequences for both material quality and company finances. With numerous types of industrial dryers available, all with their own unique pros and cons, this can feel like a daunting task.  

The most important part of choosing the right dryer for your needs is to test material on test drying equipment, ensuring that the tested process takes the wet beginning product and produces a dry final product at the quality and requirements you need. 

Before it even gets to testing though there are six things to take into consideration with narrowing down what type of drying system you should be considering.  

1. Size & Density

The starting point should be to take a look at the size of the individual particles within the material being dried, and the density that the material has when in the amount needing to be dried. A fine powder will require a different drying method than the same size material as a sludge, and large materials will have their own requirements.  

Additionally, if there are different sizes within the material, or there are significant fines that will be removed during the drying process, this needs to be taken into consideration. The density of the material will determine how it moves through the dryer and whether anything needs to be done to help it convey.  

2. Moisture Content to Be Dried

This may seem obvious, but it is commonly overlooked as something to consider when looking at drying methods. You will need to know the starting moisture percentage as well as the goal ending moisture percentage that the dryer should be reaching. Testing can help to determine the weight differences between the wet and dry percentages, and this water weight to be dried is then used to size the dryer. If the percentage is off by even a little bit it can cause the goal water weight to change dramatically, resulting in an inefficient and incorrectly sized dryer. 

It’s also helpful to know how the material is holding on to the water that is needing to be dried. If the moisture is surface water but not absorbed into the material at all, then it will need a different method of vaporizing external moisture than a particle that has internal moisture that needs to be diffused from the inside out to dry thoroughly. This will also help to determine whether any pre-drying needs to be added to the processing line. 

3. Reaction to Heat

Heat is used in most drying methods, but some materials react to heat once it reaches a certain temperature. In some products it can cause a chemical reaction, especially if the liquid being dried is a chemical solution. Other materials may melt or burn if they reach a certain temperature or are exposed to high heat for too long. It’s also possible that it will only react negatively when exposed to a certain type of heat source but will be fine with other heat sources.  

These reactions are important to know because they will determine if the dryer needs to be larger and slower to effectively use a lower temperature to dry the determined moisture, or if a short residence time at a high heat is the most effective method with the least product reaction. It will also let you know whether direct or indirect heating methods will produce the best final product, narrowing down the list of potential dryers.  

4. Material Handling    

How the material handles both while wet and while dry is important to think about when deciding on a dryer. Some materials are sludgy or sticky while wet and need to be forced through the dryer to keep material from plugging and backing up the line. Nonstick surfaces can also be used, and weirs or paddles can be built in to keep materials flowing as needed. Clean in place fittings can also be incorporated to keep the system clean and remove any potential build up.

The fragility and abrasiveness of the material also needs to be considered when planning a dryer. Some drying methods move the material roughly and can cause the material to degrade or break so a gentler method of drying should be pursued. Some materials are very coarse and will quickly wear through surfaces, reducing the lifespan of the dryer or causing maintenance issues as well as quality control issues with the material if it not reinforced or made with abrasive resistance in mind.  

5. Production Requirements

It’s important to make sure the dryer is sized correctly for the production amounts that will be expected and to know whether you plan on running continuously or doing batches. If the dryer is undersized it will clog and suffer from upset conditions when more material is forced through it, causing the product to not be properly dried and suffer other quality control issues. This will also cause the dryer to burn out sooner than if it was properly sized. If the dryer is too large for the actual production size it will be a waste of energy and fuel to run it and depending on the product it could cause it to dry too much or too quickly and potentially burn. 

Where in the facility the dryer will be installed is also important but often overlooked until far too late. Is the area long but has short ceilings, or is it tall with a small footprint? Can it withstand the weight of heavy equipment and vibratory equipment? Is there space for proper venting and area for the ductwork and baghouse filtration if it’s needed? Does the material need to be conveyed while being dried?  

This is also the time to look at the processing line before and after the dryer to determine if there are any potential issues. Will it be entering the dryer in clumps or dump loads? Is it coming out of the dryer onto a conveyor that is designed for the dry material?

6. Efficiency & Cost

An important part of purchasing an industrial dryer is of course the cost, both the upfront capital expense of the purchase as well as the cost of operation throughout its lifespan. Some options may be less expensive up front but operate less efficiently and cost more to operate than a more expensive but efficient dryer. Types of fuel being used for drying need to be considered, but pricing for that needs to look at long term trends and predictions and should not be based on current fuel prices.  

The return on investment goal for the equipment should be figured out early in the planning and research stages, which will help with knowing what to look for in an industrial dryer and what efficiencies you should be requesting.  

Once you have the answers to these questions you will be able to narrow down your search for the perfect industrial dryer and be positive that your decision will be the correct one.
  

Michael Entwistle is marketing director, Carrier Vibrating Equipment, Louisville, KY. For more information, call 502-969- or visit www.carriervibrating.com.

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