Rotary Dryer vs. Fluid Bed Dryer: A Comparative Study
Jun. 17, 2024
Rotary Dryer vs. Fluid Bed Dryer: A Comparative Study
Willing to invest in a dryer? Not sure which dryer will be the appropriate one for you? Well, the two most common varieties of dryers are available to us: rotary dryers and fluid bed dryers.
So, here we will provide a detailed comparison of rotary and fluid bed dryers so that you can invest in the right dryer for yourself that will perfectly serve your industrial needs and will also help you to generate maximum revenue from the same.
Brief description of Rotary Dryer and Fluid Bed Dryer
A rotary dryer is an industrial dryer that removes moisture content for items by rotating the content inside the dryer. It has a rotating drum inside which keeps the material to be dried. Hot air is continuously blown to the rotating cylinder to remove moisture evenly.
These dryers can handle large quantities of material. They are also available in different sizes and can efficiently dry materials. They can also be used for drying a wide range of materials uniformly.[1]
Fluid bed dryers mainly remove moisture from granular or powdered material. The machine works on the principle of fluidization. It passes hot air at high temperature and pressure over a perforated bed consisting of solid particles.
The hot air gradually passes through the granular material and removes moisture. You will find fluid bed dryers in the food, pharmaceuticals and chemical industries. These dryers require low maintenance and can offer you satisfactory results.
Key Features of Rotary Dryers
Functionality: The main functionality of a rotary dryer is to remove moisture content from the items fed to it. Because of their ability to remove moisture properly from materials of different sizes, these dryers are a crucial component of various industries.
These rotary dryers are designed in such a way that they can operate efficiently without requiring regular maintenance. The machine also allows you to adjust the drying temperature whenever required. This again adds to the enhanced functionalities of the rotary dryers.[2]
Pros and cons of rotary dryers:
Here are some of the major pros of using rotary dryers for industrial purposes:
Efficient drying: This is one of the biggest advantages of rotary dryers. It can transfer heat uniformly into the rotary cylinder where the materials to be dried are added. This makes the rotary dryers extremely efficient for use.
Uniform drying: With rotary dryers, you can remove moisture uniformly from the raw materials. This makes it suitable for a wide range of industries requiring uniform drying conditions.
Excellent solvent recovery: With rotary dryers, you can easily recover the solvent used for the drying process. This again adds to the device&#;s efficiency and makes it one of the most suitable forms of dryers for industrial use.
Speedy drying process: Now, you will no longer have to wait for hours for the rotary dryer to remove moisture content from the material. Instead, the drying process can occur within just a few minutes. This will increase the productivity of your workplace.
Low power consumption: The rotary dryers work with a reduced power supply. Because of the reduced energy efficiency, you will no longer have to pay a huge sum of money on electricity bills every month.
Reduced workplace hazards: Many dryers cause various workplace hazards because drying occurs in an open area. However, this is not the case for rotary dryers. The closed system drying operations contribute to low workplace hazards.[3]
Here are some of the major cons of rotary dryers:
Complex structure: The structure of the rotary dryer is quite complex. Because of the complex arrangement, getting the desired parts repaired sometimes takes a lot of money.
Specializations required: Necessary specializations are required for operation and design for the device to operate efficiently.
Leakage problems: Leakage of steam is a big problem in the case of rotary dryers because of the rotating parts.
So, if you are on the lookout for one such dryer that will allow you to eliminate the disadvantage and enjoy all the advantages that a rotating dryer has got to offer, then the TCPEL rotary dryer is the right choice for you.
It will help you to carry out your drying operations in a smooth and streamlined way. The lubricating system present in these dryers makes the dryer process more efficient.
The device is highly energy efficient and helps you to save a ton on electricity bills. The rotary dryer also operates tirelessly 24/7 without requiring regular maintenance.
The TCPEL rotary dryers are also affordably priced. So, you will no longer have to spend much money on your industrial drying machine.
How to Tutorial:
Key Features of Fluid Bed Dryers
Functionality: The main function of a fluid bed dryer is to remove the moisture content from granules or particles. These dryers are quite effective in all those industries where you must deal with granular particles. This mainly includes pharmaceutical, agricultural, and food processing industries.
However, if the material&#;s size is large, you cannot use these dryers effectively. So, the functionality depends on how you are willing to use the dryer. These dryers are also capable of drying, cooling and heating materials. They do so by consuming a minimum amount of energy.[4]
Pros and cons of a fluid bed dryer:
Let us have a look at some of the advantages of a fluid bed dryer:
Versatility: The fluid bed dryers are quite versatile, and they can be used for performing a lot of operations like drying, cooling, heating, coating and much more. The exact function will depend on your industry.
Customization: The device can be customized as per your individual needs. This again contributes to the device&#;s versatility and makes it suitable for various industries.
Low maintenance: As only a few mechanical components are involved in these dryers, the maintenance required is considerably less. You will not have to go for regular maintenance for these dryers.
Here are the disadvantages of using fluid bed dryers:
High cost: The initial cost of setting up these dryers in your workplace is considerably high, leading to an overall increase in operational costs.
Suitable only for granular particles: You cannot use fluid bed dryers to dry materials of larger sizes. They can only be used for drying granular particles.
Comparative Analysis: Rotary Dryer vs. Fluid Bed Dryer
Now let us compare the rotary dryer and fluid bed dryer based on various parameters:[5]
Operating principle:
Rotary dryer: A rotary dryer works by rotating the raw materials inside a cylindrical drum that contains the material to be dried. The cylindrical drum is exposed to hot air, gradually removing the material&#;s moisture content. The materials are then moved into the cylinder, allowing even drying conditions.
Fluid bed dryer: The fluid bed dryer operates on the principle of fluidization. In a fluid bed dryer, moisture is removed by passing hot air over materials in a granular state. This causes the particles to behave like boiling liquids. It also allows for the transfer of heat from the material in an even manner. These fluid bed dryers are more effective in drying materials that are in a granular state.
Energy-efficiency:
Rotary dryer: In the case of a rotary dryer, as the drying takes place in a closed system, the devices are energy efficient. A lot of heat isn&#;t lost to the surroundings because of the closed structure of the dryer. The heat transfer is also quite good.
Fluid bed dryer: A lot of energy is involved in drying the materials in a fluid bed dryer. This causes you to spend more on your electricity bill. Also, the energy required to get the particles to a fluidized state is more, thereby requiring additional energy.
Material Handling Capabilities:
Rotary dryer: You can efficiently use a rotary dryer for drying materials of different shapes and sizes including free-flowing materials, which makes them a perfect choice for multiple industries. So, it doesn&#;t matter what the size of the materials are, the drying process can take place efficiently. In fact, particles of larger sizes can also be fed to the dryer for efficient moisture removal.
Fluid bed dryer: Fluid bed dryers can only remove moisture from smaller particles that can be fluidized. So, in case the materials are larger, then the drying will not be as effective as the rotary dryers. So, there is a restriction on the choice of material that can be used for drying purposes.
Maintenance Requirements:
Rotary dryer: In the case of rotary dryers, many components are involved in the drying operation. You require a rotating drum, wearing seals, etc. All these components require regular maintenance. You will also have to clean up the different components for efficient operations.
Fluid bed dryer: In the case of fluid bed dryers, the maintenance required is considerably less. This is mainly because fewer mechanical components are involved, and the dryer&#;s structure is simpler than rotary dryers.
Cost Effectiveness
Rotary dryer: The rotary dryers are quite cost-effective. The initial investment is considerably less. You no longer have to spend much on setting up a drying unit in your workplace. However, you may need to go for regular maintenance activities occasionally.
Fluid bed dryer: In the case of a fluid bed dryer, the initial investment cost is high, as rotary dryers are more expensive. However, as less maintenance is required, they may be more cost-effective in the long run.
Applications of Rotary Dryer & Fluid Bed Dryer
Both rotary dryers and fluid bed dryers have different applications and you will be able to choose your dryer on the basis of your exact needs and requirements.
Usage of Rotary Dryer
The application of rotary dryers is not fixed to any particular industry. Rotary dryers are used in many industries depending on the exact business requirements.
Goto Zoneding machine to know more.
These rotary dryers also have excellent drying capabilities and can handle materials of all sizes, which makes them suitable for all kinds of industrial conditions.
Some of the popular industries where these dryers are used on a regular basis are:
&#; Chemical &#; Agriculture &#; Pharmaceutical &#; Mining &#; Food
Both medium and large-scale companies can make use of these dryers.
Usage of Fluid Bed Dryer
As the fluid bed dryers are used for drying granular particles only, they are particularly popular in all those industries where drying of powders or granules are required. These dryers are also capable of removing moisture from substances carefully.
They are also known for their heat-sensitive properties. Here are some of the industries where you will find the use of fluid bed dryers:
&#; Pharmaceutical &#; Chemical &#; Mining &#; Dues &#; Food
The choice of material will determine where these dryers are used. If it involves drying materials of larger particles, then fluid bed dryers are not the appropriate choice.
Conclusion: Which is better &#; Rotary or Fluid Bed Dryer?
Now the question that might be occupying your head is: Which dryer is better: the rotary or the fluid bed dryer? Well, there is no definite answer to the question as the dryer choice will depend on your exact requirements.
Each of these dryers comes with a set of pros and cons. So, you should consider all these points and choose the right dryer.
If you are looking for a dryer that can handle materials of all sizes in an energy-efficient way, then rotary dryers are the perfect choice. These dryers are cost-friendly and help you save up on the initial setup.
However, if you are willing to dry granular particles only, then the fluid bed dryers are your choice. These dryers do not require regular maintenance and can offer you enhanced performance.
Also, if you are looking for the finest rotary dryer that will solve all your industrial needs, the TCPEL dryer is the appropriate choice. It will help you carry out your industrial operations easily and conveniently.
The business productivity will increase, and you will also be able to generate a lot of revenue. Contact us to know more about the TCPEL rotary dryer and we will share the details with you.
Original article from: https://www.tcpel.com/rotary-dryer-vs-fluid-bed-dryer/
Co-Current Vs. Counter Current Drying
Many factors are taken into consideration when designing a rotary drum dryer that can both efficiently and effectively dry a material. Factors such as the material&#;s bulk density, heat sensitivity, particle size, and flowability, among others, all interact to influence how the material will behave in the dryer, and subsequently, how the dryer should be designed to optimally work with those characteristics. One critical factor in designing a rotary dryer that produces the desired end product characteristics is the air flow configuration, or the direction in which the process gas flows through the dryer in relation to the material.
Rotary dryers are available in two types of air-flow configurations: co-current and counter current. Both options have been developed through extensive research and development in order to maximize the thermal efficiency of the rotary drying process. The selection of which configuration will best suit the process is based on the material&#;s properties, as well as overall process requirements, making it important to understand how each air-flow configuration works in order to fully grasp which type will best suit the drying process at hand.
Below is an overview on the advantages and disadvantages of these two types of rotary drum dryer designs.
The Co-Current Rotary Dryer
Best for: Materials that are heat-sensitive, maintaining product quality (NOTE: 90% of all rotary dryers are co-current for these reasons)
Key Advantages: Greater control over solids temperature and avoidance of overheating
Disadvantages: Slightly less thermally efficient than counter-current air flow
Co-current or parallel flow drying occurs when the drying air flows in the same direction as the material, or rather, when the material and process gas enter the dryer at the same end of the drum, as shown in the illustration below.
Co-current dryer (drier)
Advantages of the Co-Current Rotary Dryer
As mentioned, the majority of rotary drum dryers utilize the co-current air flow design. This configuration is chosen for several reasons:
Rapid Removal of Free Moisture
By introducing the solids and process gas in the same location, the process gas contacts the material in its wettest state, resulting in a quick initial reduction of surface moisture. Because of this fast initial drying, co-current dryers work best with materials that have high surface/free moisture such as glass. The lower surface moisture at the inlet of the drum also promotes improved flowability of the material through the drum, as the solids are less likely to stick as they tumble and cascade.
Ideal for Heat-Sensitive Materials
The co-current dryer is ideal for drying heat-sensitive materials. When a material is heat-sensitive, overheating can result in unwanted reactions, undesirable color changes in product, product degradation, or even a risk of fire. By utilizing a co-current configuration with heat-sensitive materials, it is much easier to prevent overheating, because the hottest gases are in contact with the wettest material and the temperature of the solids instead decreases as it moves through the dryer, preventing the potential for overheating.
Control Over Solids Temperature
Because the solids temperature correlates directly with the process gas temperature, the co-current design makes controlling the temperature of the dried material much easier. This is ideal for heat-sensitive materials that must be kept below a certain temperature threshold during the drying process.
Improved Dryer Longevity
The introduction of the material and process gas at the same location of the dryer causes a rapid initial cooling of the process gas, causing the dryer shell to run at a cooler surface temperature. This lower temperature reduces stress on the drum shell, promoting a longer life.
Disadvantages of the Co-Current Rotary Dryer
Higher Exhaust Gas Temperatures
The primary disadvantage of the co-current design is that it is slightly less thermally efficient, because the exhaust gas can never be cooler than the temperature of the solids, requiring more energy to be spent on keeping the exhaust temperature up. The need to ensure that the exhaust gas exceeds the temperature of the solids therefore results in wasted energy and slightly greater fuel consumption.
The Counter Current Rotary Dryer
Best for: Materials with bound moisture, or that require heating to a higher temperature
Key Advantage: More efficient
Disadvantages: Less control over solids temperature, greater potential for overheating
Counter-current drying occurs when the gas and material flow in opposing directions (i.e., the material is fed into one end of the drum, while the process gas is fed into the other end of the drum, as shown in the illustration below).
Counter current dryer (drier)
Advantages of the Counter-Current Rotary Dryer
The counter-current air flow design offers several advantages:
Gradual Removal of Moisture
Because the material comes in contact with the hottest process gas at its most dehydrated state, the counter-current configuration is ideal for materials with bound moisture. Bound moisture is typically not affected by the initial &#;flash-off&#; of free moisture, instead requiring more gradual heating to draw out moisture from within the material.
High Heat Capabilities
Similarly, materials that require high temperatures to release their moisture are also best served in a counter-current rotary dryer, since the solids are coming into contact with the hottest gases toward the end of the drying process.
Greater Thermal Efficiency (Lower Exhaust Gas Temperatures)
Counter-current dryers are often chosen for their efficiency, because more heat is spent on drying the solids than ensuring the exhaust gas temperature remains high. In other words, because counter-current dryers can tolerate gas temperatures lower than the solids, less fuel is required and excess energy is not wasted in the exhaust gas.
It&#;s important to note that the exhaust gas temperature must always be above the dew point. The potential for the exhaust gas temperature to reach the dew point is greater with a counter-current configuration and must be carefully managed; if the temperature were allowed to reach the dew point, condensation could occur in the ductwork and baghouse, clogging up the system. This is especially likely if the ductwork is not insulated.
Disadvantages of the Counter-Current Rotary Dryer
Less Control Over Solids Temperature
While a direct relationship exists between the material and process gas in the co-current design, the opposing flow of the solids and gas employed in the counter-current configuration makes it more difficult to control the temperature of the solids.
Risk of Overheating
Because the solids come into contact with the hottest gas in their driest state, the counter-current air flow also makes it easier to overheat the material.
If the inlet gas temperatures need to be lower to avoid overheating the material, additional fuel will be required, because more air which needs to be heated will be required, which can cut into the initial energy savings.
Other Considerations with Air Flow
While not directly related to the chosen configuration, there are a few other air flow considerations that should be kept in mind during the design process:
Whether or Not to Use a Combustion Chamber
Combustion chambers are often employed with direct rotary dryers in order to prevent contact between the burner flame and the material being processed. This is advantageous when working with heat-sensitive materials, or materials that might form undesirable compounds if exposed to the additional radiation of a flame. For more information on employing a combustion chamber, see: Rotary Dryers: When is a Combustion Chamber Necessary?.
Exhaust Gas Recycling
When using a combustion chamber, the secondary air can sometimes be provided via recycled exhaust gas from the dryer. Since this air is already preheated, a savings in fuel can be achieved if designed properly.
Conclusion
Understanding how each dryer configuration works is an important factor in designing the most efficient rotary dryer for the job, with each configuration offering unique advantages and disadvantages. FEECO encourages that each material go through a research and development process at our on-site concept testing facility, The FEECO Innovation Center. The information gained through our proven testing procedures allows us to design the most efficient and beneficial drying system for our customer&#;s material requirements. For more information on co-current or counter-current drying, contact us today!
Rotary DryerRotary Dryer vs. Fluid Bed Dryer: A Comparative Study
Willing to invest in a dryer? Not sure which dryer will be the appropriate one for you? Well, the two most common varieties of dryers are available to us: rotary dryers and fluid bed dryers.
So, here we will provide a detailed comparison of rotary and fluid bed dryers so that you can invest in the right dryer for yourself that will perfectly serve your industrial needs and will also help you to generate maximum revenue from the same.
Brief description of Rotary Dryer and Fluid Bed Dryer
A rotary dryer is an industrial dryer that removes moisture content for items by rotating the content inside the dryer. It has a rotating drum inside which keeps the material to be dried. Hot air is continuously blown to the rotating cylinder to remove moisture evenly.
These dryers can handle large quantities of material. They are also available in different sizes and can efficiently dry materials. They can also be used for drying a wide range of materials uniformly.[1]
Fluid bed dryers mainly remove moisture from granular or powdered material. The machine works on the principle of fluidization. It passes hot air at high temperature and pressure over a perforated bed consisting of solid particles.
The hot air gradually passes through the granular material and removes moisture. You will find fluid bed dryers in the food, pharmaceuticals and chemical industries. These dryers require low maintenance and can offer you satisfactory results.
Key Features of Rotary Dryers
Functionality: The main functionality of a rotary dryer is to remove moisture content from the items fed to it. Because of their ability to remove moisture properly from materials of different sizes, these dryers are a crucial component of various industries.
These rotary dryers are designed in such a way that they can operate efficiently without requiring regular maintenance. The machine also allows you to adjust the drying temperature whenever required. This again adds to the enhanced functionalities of the rotary dryers.[2]
Pros and cons of rotary dryers:
Here are some of the major pros of using rotary dryers for industrial purposes:
Efficient drying: This is one of the biggest advantages of rotary dryers. It can transfer heat uniformly into the rotary cylinder where the materials to be dried are added. This makes the rotary dryers extremely efficient for use.
Uniform drying: With rotary dryers, you can remove moisture uniformly from the raw materials. This makes it suitable for a wide range of industries requiring uniform drying conditions.
Excellent solvent recovery: With rotary dryers, you can easily recover the solvent used for the drying process. This again adds to the device&#;s efficiency and makes it one of the most suitable forms of dryers for industrial use.
Speedy drying process: Now, you will no longer have to wait for hours for the rotary dryer to remove moisture content from the material. Instead, the drying process can occur within just a few minutes. This will increase the productivity of your workplace.
Low power consumption: The rotary dryers work with a reduced power supply. Because of the reduced energy efficiency, you will no longer have to pay a huge sum of money on electricity bills every month.
Reduced workplace hazards: Many dryers cause various workplace hazards because drying occurs in an open area. However, this is not the case for rotary dryers. The closed system drying operations contribute to low workplace hazards.[3]
Here are some of the major cons of rotary dryers:
Complex structure: The structure of the rotary dryer is quite complex. Because of the complex arrangement, getting the desired parts repaired sometimes takes a lot of money.
Specializations required: Necessary specializations are required for operation and design for the device to operate efficiently.
Leakage problems: Leakage of steam is a big problem in the case of rotary dryers because of the rotating parts.
So, if you are on the lookout for one such dryer that will allow you to eliminate the disadvantage and enjoy all the advantages that a rotating dryer has got to offer, then the TCPEL rotary dryer is the right choice for you.
It will help you to carry out your drying operations in a smooth and streamlined way. The lubricating system present in these dryers makes the dryer process more efficient.
The device is highly energy efficient and helps you to save a ton on electricity bills. The rotary dryer also operates tirelessly 24/7 without requiring regular maintenance.
The TCPEL rotary dryers are also affordably priced. So, you will no longer have to spend much money on your industrial drying machine.
How to Tutorial:
Key Features of Fluid Bed Dryers
Functionality: The main function of a fluid bed dryer is to remove the moisture content from granules or particles. These dryers are quite effective in all those industries where you must deal with granular particles. This mainly includes pharmaceutical, agricultural, and food processing industries.
However, if the material&#;s size is large, you cannot use these dryers effectively. So, the functionality depends on how you are willing to use the dryer. These dryers are also capable of drying, cooling and heating materials. They do so by consuming a minimum amount of energy.[4]
Pros and cons of a fluid bed dryer:
Let us have a look at some of the advantages of a fluid bed dryer:
Versatility: The fluid bed dryers are quite versatile, and they can be used for performing a lot of operations like drying, cooling, heating, coating and much more. The exact function will depend on your industry.
Customization: The device can be customized as per your individual needs. This again contributes to the device&#;s versatility and makes it suitable for various industries.
Low maintenance: As only a few mechanical components are involved in these dryers, the maintenance required is considerably less. You will not have to go for regular maintenance for these dryers.
Here are the disadvantages of using fluid bed dryers:
High cost: The initial cost of setting up these dryers in your workplace is considerably high, leading to an overall increase in operational costs.
Suitable only for granular particles: You cannot use fluid bed dryers to dry materials of larger sizes. They can only be used for drying granular particles.
Comparative Analysis: Rotary Dryer vs. Fluid Bed Dryer
Now let us compare the rotary dryer and fluid bed dryer based on various parameters:[5]
Operating principle:
Rotary dryer: A rotary dryer works by rotating the raw materials inside a cylindrical drum that contains the material to be dried. The cylindrical drum is exposed to hot air, gradually removing the material&#;s moisture content. The materials are then moved into the cylinder, allowing even drying conditions.
Fluid bed dryer: The fluid bed dryer operates on the principle of fluidization. In a fluid bed dryer, moisture is removed by passing hot air over materials in a granular state. This causes the particles to behave like boiling liquids. It also allows for the transfer of heat from the material in an even manner. These fluid bed dryers are more effective in drying materials that are in a granular state.
Energy-efficiency:
Rotary dryer: In the case of a rotary dryer, as the drying takes place in a closed system, the devices are energy efficient. A lot of heat isn&#;t lost to the surroundings because of the closed structure of the dryer. The heat transfer is also quite good.
Fluid bed dryer: A lot of energy is involved in drying the materials in a fluid bed dryer. This causes you to spend more on your electricity bill. Also, the energy required to get the particles to a fluidized state is more, thereby requiring additional energy.
Material Handling Capabilities:
Rotary dryer: You can efficiently use a rotary dryer for drying materials of different shapes and sizes including free-flowing materials, which makes them a perfect choice for multiple industries. So, it doesn&#;t matter what the size of the materials are, the drying process can take place efficiently. In fact, particles of larger sizes can also be fed to the dryer for efficient moisture removal.
Fluid bed dryer: Fluid bed dryers can only remove moisture from smaller particles that can be fluidized. So, in case the materials are larger, then the drying will not be as effective as the rotary dryers. So, there is a restriction on the choice of material that can be used for drying purposes.
Maintenance Requirements:
Rotary dryer: In the case of rotary dryers, many components are involved in the drying operation. You require a rotating drum, wearing seals, etc. All these components require regular maintenance. You will also have to clean up the different components for efficient operations.
Fluid bed dryer: In the case of fluid bed dryers, the maintenance required is considerably less. This is mainly because fewer mechanical components are involved, and the dryer&#;s structure is simpler than rotary dryers.
Cost Effectiveness
Rotary dryer: The rotary dryers are quite cost-effective. The initial investment is considerably less. You no longer have to spend much on setting up a drying unit in your workplace. However, you may need to go for regular maintenance activities occasionally.
Fluid bed dryer: In the case of a fluid bed dryer, the initial investment cost is high, as rotary dryers are more expensive. However, as less maintenance is required, they may be more cost-effective in the long run.
Applications of Rotary Dryer & Fluid Bed Dryer
Both rotary dryers and fluid bed dryers have different applications and you will be able to choose your dryer on the basis of your exact needs and requirements.
Usage of Rotary Dryer
The application of rotary dryers is not fixed to any particular industry. Rotary dryers are used in many industries depending on the exact business requirements.
These rotary dryers also have excellent drying capabilities and can handle materials of all sizes, which makes them suitable for all kinds of industrial conditions.
Some of the popular industries where these dryers are used on a regular basis are:
&#; Chemical &#; Agriculture &#; Pharmaceutical &#; Mining &#; Food
Both medium and large-scale companies can make use of these dryers.
Usage of Fluid Bed Dryer
As the fluid bed dryers are used for drying granular particles only, they are particularly popular in all those industries where drying of powders or granules are required. These dryers are also capable of removing moisture from substances carefully.
They are also known for their heat-sensitive properties. Here are some of the industries where you will find the use of fluid bed dryers:
&#; Pharmaceutical &#; Chemical &#; Mining &#; Dues &#; Food
The choice of material will determine where these dryers are used. If it involves drying materials of larger particles, then fluid bed dryers are not the appropriate choice.
Conclusion: Which is better &#; Rotary or Fluid Bed Dryer?
Now the question that might be occupying your head is: Which dryer is better: the rotary or the fluid bed dryer? Well, there is no definite answer to the question as the dryer choice will depend on your exact requirements.
Each of these dryers comes with a set of pros and cons. So, you should consider all these points and choose the right dryer.
If you are looking for a dryer that can handle materials of all sizes in an energy-efficient way, then rotary dryers are the perfect choice. These dryers are cost-friendly and help you save up on the initial setup.
However, if you are willing to dry granular particles only, then the fluid bed dryers are your choice. These dryers do not require regular maintenance and can offer you enhanced performance.
Also, if you are looking for the finest rotary dryer that will solve all your industrial needs, the TCPEL dryer is the appropriate choice. It will help you carry out your industrial operations easily and conveniently.
The business productivity will increase, and you will also be able to generate a lot of revenue. Contact us to know more about the TCPEL rotary dryer and we will share the details with you.
Original article from: https://www.tcpel.com/rotary-dryer-vs-fluid-bed-dryer/
Co-Current Vs. Counter Current Drying
Many factors are taken into consideration when designing a rotary drum dryer that can both efficiently and effectively dry a material. Factors such as the material&#;s bulk density, heat sensitivity, particle size, and flowability, among others, all interact to influence how the material will behave in the dryer, and subsequently, how the dryer should be designed to optimally work with those characteristics. One critical factor in designing a rotary dryer that produces the desired end product characteristics is the air flow configuration, or the direction in which the process gas flows through the dryer in relation to the material.
Rotary dryers are available in two types of air-flow configurations: co-current and counter current. Both options have been developed through extensive research and development in order to maximize the thermal efficiency of the rotary drying process. The selection of which configuration will best suit the process is based on the material&#;s properties, as well as overall process requirements, making it important to understand how each air-flow configuration works in order to fully grasp which type will best suit the drying process at hand.
Below is an overview on the advantages and disadvantages of these two types of rotary drum dryer designs.
The Co-Current Rotary Dryer
Best for: Materials that are heat-sensitive, maintaining product quality (NOTE: 90% of all rotary dryers are co-current for these reasons)
Key Advantages: Greater control over solids temperature and avoidance of overheating
Disadvantages: Slightly less thermally efficient than counter-current air flow
Co-current or parallel flow drying occurs when the drying air flows in the same direction as the material, or rather, when the material and process gas enter the dryer at the same end of the drum, as shown in the illustration below.
Co-current dryer (drier)
Advantages of the Co-Current Rotary Dryer
As mentioned, the majority of rotary drum dryers utilize the co-current air flow design. This configuration is chosen for several reasons:
Rapid Removal of Free Moisture
By introducing the solids and process gas in the same location, the process gas contacts the material in its wettest state, resulting in a quick initial reduction of surface moisture. Because of this fast initial drying, co-current dryers work best with materials that have high surface/free moisture such as glass. The lower surface moisture at the inlet of the drum also promotes improved flowability of the material through the drum, as the solids are less likely to stick as they tumble and cascade.
Ideal for Heat-Sensitive Materials
The co-current dryer is ideal for drying heat-sensitive materials. When a material is heat-sensitive, overheating can result in unwanted reactions, undesirable color changes in product, product degradation, or even a risk of fire. By utilizing a co-current configuration with heat-sensitive materials, it is much easier to prevent overheating, because the hottest gases are in contact with the wettest material and the temperature of the solids instead decreases as it moves through the dryer, preventing the potential for overheating.
Control Over Solids Temperature
Because the solids temperature correlates directly with the process gas temperature, the co-current design makes controlling the temperature of the dried material much easier. This is ideal for heat-sensitive materials that must be kept below a certain temperature threshold during the drying process.
Improved Dryer Longevity
The introduction of the material and process gas at the same location of the dryer causes a rapid initial cooling of the process gas, causing the dryer shell to run at a cooler surface temperature. This lower temperature reduces stress on the drum shell, promoting a longer life.
Disadvantages of the Co-Current Rotary Dryer
Higher Exhaust Gas Temperatures
The primary disadvantage of the co-current design is that it is slightly less thermally efficient, because the exhaust gas can never be cooler than the temperature of the solids, requiring more energy to be spent on keeping the exhaust temperature up. The need to ensure that the exhaust gas exceeds the temperature of the solids therefore results in wasted energy and slightly greater fuel consumption.
The Counter Current Rotary Dryer
Best for: Materials with bound moisture, or that require heating to a higher temperature
Key Advantage: More efficient
Disadvantages: Less control over solids temperature, greater potential for overheating
Counter-current drying occurs when the gas and material flow in opposing directions (i.e., the material is fed into one end of the drum, while the process gas is fed into the other end of the drum, as shown in the illustration below).
Counter current dryer (drier)
Advantages of the Counter-Current Rotary Dryer
The counter-current air flow design offers several advantages:
Gradual Removal of Moisture
Because the material comes in contact with the hottest process gas at its most dehydrated state, the counter-current configuration is ideal for materials with bound moisture. Bound moisture is typically not affected by the initial &#;flash-off&#; of free moisture, instead requiring more gradual heating to draw out moisture from within the material.
High Heat Capabilities
Similarly, materials that require high temperatures to release their moisture are also best served in a counter-current rotary dryer, since the solids are coming into contact with the hottest gases toward the end of the drying process.
Greater Thermal Efficiency (Lower Exhaust Gas Temperatures)
Counter-current dryers are often chosen for their efficiency, because more heat is spent on drying the solids than ensuring the exhaust gas temperature remains high. In other words, because counter-current dryers can tolerate gas temperatures lower than the solids, less fuel is required and excess energy is not wasted in the exhaust gas.
It&#;s important to note that the exhaust gas temperature must always be above the dew point. The potential for the exhaust gas temperature to reach the dew point is greater with a counter-current configuration and must be carefully managed; if the temperature were allowed to reach the dew point, condensation could occur in the ductwork and baghouse, clogging up the system. This is especially likely if the ductwork is not insulated.
Disadvantages of the Counter-Current Rotary Dryer
Less Control Over Solids Temperature
While a direct relationship exists between the material and process gas in the co-current design, the opposing flow of the solids and gas employed in the counter-current configuration makes it more difficult to control the temperature of the solids.
Risk of Overheating
Because the solids come into contact with the hottest gas in their driest state, the counter-current air flow also makes it easier to overheat the material.
If the inlet gas temperatures need to be lower to avoid overheating the material, additional fuel will be required, because more air which needs to be heated will be required, which can cut into the initial energy savings.
Other Considerations with Air Flow
While not directly related to the chosen configuration, there are a few other air flow considerations that should be kept in mind during the design process:
Whether or Not to Use a Combustion Chamber
Combustion chambers are often employed with direct rotary dryers in order to prevent contact between the burner flame and the material being processed. This is advantageous when working with heat-sensitive materials, or materials that might form undesirable compounds if exposed to the additional radiation of a flame. For more information on employing a combustion chamber, see: Rotary Dryers: When is a Combustion Chamber Necessary?.
Exhaust Gas Recycling
When using a combustion chamber, the secondary air can sometimes be provided via recycled exhaust gas from the dryer. Since this air is already preheated, a savings in fuel can be achieved if designed properly.
Conclusion
Understanding how each dryer configuration works is an important factor in designing the most efficient rotary dryer for the job, with each configuration offering unique advantages and disadvantages. FEECO encourages that each material go through a research and development process at our on-site concept testing facility, The FEECO Innovation Center. The information gained through our proven testing procedures allows us to design the most efficient and beneficial drying system for our customer&#;s material requirements. For more information on co-current or counter-current drying, contact us today!
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