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More Than Just a Dryer

December 18, 2015
Rotary drum for cleaning stone
Rotary drum for cleaning stone

In many process industries there are applications that are specifically engineered for the job they perform. Using a machine that performs exactly the required job can allow for more efficient product treatment, lower process time, and longer machine life. With this in mind, it is important to consider the robust variety of industrial dryer types, as well as the options that dryers can have. In many process operations there is more than one process required. This is where dryers with other operations can excel. Performing both of these processes at once saves time and floor real estate, as there is only one machine required. There are multiple examples of combined process dryers including separation (screening), cleaning, cooling, granulation, and crushing.
    
Screening is often done as its own process step requiring multiple decks of separation, prior drying and sorting, as well as other requirements. For certain solutions however, there are dryers that can screen up to one separation. This reduces need for further screening down the line in some operations, or even just reduces the amount of separations needed by performing it while drying. These dryers are useful for aluminum scrap and shredded recyclable products. The need to screen after drying is a common problem and alleviating this step can save energy and time. The process works like any regular rotating drum, however the outside of the drum is perforated to let material through. Smaller particles fall through the drum and are separated as they would be in a screener. In certain plants where only one separation is needed, these dryers allow for the removal of a screener. In others where multiple separations are needed money can be saved due to one separation being performed during the drying step.  
      
Dryers are often used when recycling glass and processing stone such as limestone. The issues that arise in these processes are often unwanted particulates or material finding their way into the process flow and compromising the product or causing costly damage to machines further down the line. In the case of recycled glass this would be left over labels or in the case of stone, dirt and other particles. This is where a dryer with cleaning capabilities would be a great fit, saving time and money where separate process and machine would otherwise be needed. The processes for these machines are similar. First the product is dried in a rotating drum. Then the paddles inside of the drum pick up and move the product into the drying air flow. This causes the product to dry and rub against each other. These combined forces remove the unwanted particulates, which are then removed from the machine through the exhaust. Clean product then continues through the process flow.  As with all examples of combined dryers, the energy, time, and maintenance saved make this a great solution to your process.
      
Cooling dryers perform the exact job that one would expect. These normally come in rotating drum varieties (usually with two or more drums), and perform an additional cooling step after drying the product. This can be useful in products such as sand, mortar, and plaster. The operation is simple when compared to normal rotating drum dryers. The inner drum will dry the material as normal. When the material has reached the end of the drum and is dry, it transfers to the outer drum to allow the heat to dissipate through evaporative cooling. Once this step is done a dry product flows through the output at a reasonable temperature. These dryers take a two-step process and perform it within one machine without taking up much more room than a normal rotating drum dryer, a common theme among combined process dryers.
      
Granulation dryers are typically fluid bed dryers with the added capability of creating granules or powders out of liquids. It achieves this through the process of granulation or agglomeration, and subsequent drying of the product. The fluid containing solid particles is injected to the fluidized bed dryer. The heat will dry the liquid leaving the solid material to attach to granulates in the bed, growing as the material is dried. Once granulates have reached the desired size, they drop through he classification tube and are removed from the dryer. An additional capability of many granulation dryers is coating. Coating will introduce another step of spraying a coating onto the granules for processes where this is necessary (urea, potash granules). The rest of the process is performed as usual, and the coating step is performed after the ideal particle size has been reached. Like the other examples, this is an efficient way to shrink the process flow. This machine has the unique ability to define the final product size, removing the need for screening or sorting down the line.
      
Crushing dryers are simply explained by mentioning that they are a rolling bed dryer with a grinder on the inside. The grinder rotates, breaking up clumps and allowing product to be dried quickly and efficiently, as well as allowing the particle size to be more carefully regulated. Additionally it allows more air flow to reach the product as smaller particles have more gaps for air to flow through than clumped material. These are mostly used for lumpy materials such as filter cakes. These enable the drying of lumpy products to produce fine grained dry materials. As with the other combined processes, this saves time and space, while taking up less room on the process floor.
      
As a concept, process combination has broad implications for creating efficiency and establishing new best practices across an industry. By eliminating process steps, throughput is increased, while saving time and cost. In many of these cases, one fewer step actually takes the process one step ahead. In addition to requiring less space on the process floor and less power requirement than two machines would, these combined processes offer the same product quality and treatment. Innovation comes from the need for an optimized and efficient solution, and optimized and efficient solutions are not found with standard commodity type machines. With customized machines there is no need for compromises as they are specifically designed for the solution required.  The combination of processes into a single machine may result in highly specific solutions that are an ideal way to solve a highly specific problem.
       
    Jarrett Bowling is a marketing specialist with Almo Process Technology Inc., Cincinnati, OH, a member of the Allgaier-Group. For more information, visit www.almoprocess.com

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