Desiccant and Hot Air Dryers
Foremost Machine Builders designs and manufactures hot air and dehumidifying or desiccant dryers for drying hygroscopic and non-hygroscopic plastic resins. To create a high quality product from a particulate material you have to make sure that the moisture content of the material is reduced to an acceptable level as quickly and as efficiently as possible. While our hot air dryers can handle both hygroscopic and non-hygroscopic materials, our patented twin tower desiccant dyers were specifically designed for drying hygroscopic materials such as plastic resins.
Many plastic pellets are hygroscopic in that they absorb moisture both on the surface and inside the granulate pellet. While there are many theories as to what is the most effective way to reduce the moisture content of a plastic pellet, the most successful drying technology has been the desiccant based drying system. For the last fifty years, desiccant dryers have been a stalwart in the plastics industry proving time and again that they are the most reliable, economical and effective plastic resin dryers on the market.
Choosing the correct dryer for your process can be difficult given that there are as many types of dryers as there are materials to dry. As always, your buying decision will have to balance initial price against operating cost, flexibility, reliability, and any extra features.
Download the Resin Dryers Brochure.
Models Available: TTD Series
Before you buy a desiccant dryer you should know what your options are and be clear about what you expect from the dryer you choose. When selecting a dehumidifying or desiccant dryer, you have four basic configurations to choose from: machine-mounted, beside-the-press, and the newer portable or off-the-press systems. Central drying systems - a larger version of beside-the-press designs - are the fourth option. Within each of the basic configurations, you also have a choice between the traditional twin-tower dual desiccant units, multiple-bed units and the more unconventional types, i.e., desiccant impregnated cartridges.
|Hot Air Dryers|
Models Available: DH-4 Series
Hot air dryers use warmed air as their drying medium and are typically chosen for particulate materials that are non-hygroscopic, i.e., have moisture only on the surface, or for surface drying hygroscopic regrind material such as polypropelene and polyurethane. Heat lowers the relative humidity of the surrounding air improving its drying ability. The moist air is expelled into the atmosphere while fresh ambient air is drawn in to continue the process. These dryers are not known for removing absorbed water from hygroscopic materials. But if your processing plant is located in a climate with relatively low humidity, with the right hopper size, a hot air dryer can be the solution you are looking for. Typically, hot air dryers, which only supply hot air and have no dehumidification system, may also be used on non-hygroscopic materials as a preheater. In drier areas of the world that have relatively low humidity, a processor can use these units on hygroscopic materials with decisive results. With only one blower and a heater, the initial cost will be much easier to handle and your maintenance and service costs will be minimal.
Traditional twin tower desiccant dryers work the following way: warm dry air is sent through a hopper containing plastic resin and removes the moisture from the resin. The moisture laden air is sent through a dessicant bed where the moisture is absorbed from the air stream by the desiccant. This air is then reheated and sent back to the hopper of resin to remove additional moisture in a closed loop. The quality of the dry air is monitored by a dew-point sensor set as required for the desired degree of drying. When the moisture-absorbing capacity of the desiccant reaches its limit, the airflow is automatically switched to a second desiccant chamber to maintain the drying process. Meanwhile the first desiccant chamber is regenerated by heating it to remove moisture and then cooling it so it can resume absorbing water. As an alternative to electric heaters, gas fired process heaters are frequently used for more efficient use of energy. As a trusted drying technology, twin tower desiccant dryers function well and typically last a very long time.