When fertilizer are produced a drying process is required after the granulation, so the product can be packed and stored. A gentle drying process is necessary to keep the grain size distribution processed in the granulation nearly unchanged. To meet exactly the customers’ requirements JOEST supplies a drying system, consisting of two vibration ﬂuid bed dryers connected in series with multilevel air duct.
The product, which is still moist after granulation, is conveyed continuously to the ﬁrst vibrating ﬂuid bed dryer. It will be streamed with temperature-controlled hot air (re-heated exhaust air from the second dryer) in the drying area, meanwhile dried and fed to the subsequently arranged second ﬂuidized bed dryer. The second vibrating ﬂuid bed dryer is equipped with a drying and a cooling zone. In the drying zone the product is streamed with temperature-controlled hot air (ambient air heated with natural gas burner) and dried. In the cooling zone, situated directly after the drying zone in the same machine it will be ﬁnally dried and cooled with ambient air.
The drying zone of the second dryer is – according to the drying characteristics of the product - designed for operation with a reduced hot air ﬂow. Due to the multitude of different formulations the second vibrating ﬂuid bed dryer is equipped with an electronic adjustment of the angle of attack during operation. This tool enables the control of the product layer - and therefore directly the retention time of the product in the drying and cooling area by adjustment of the angle of attack.
The exhaust air of the second ﬂuid bed dryer with low water content is sucked off from the dryer and fed to a steam-heated air exchanger. Reheated to the required air temperature, the air is blown as drying air to the ﬁrst vibrating ﬂuid bed dryer. The exhaust air of the ﬁrst vibrating ﬂuid bed dryer is de-dusted in an exhaust air ﬁlter and ﬁnally blown to the environment.