The type of dryer best suited for a particular application depends upon both the feed characteristics and desired product characteristics. Wet and pasty materials can be dried when the feed is backmixed with dry product. Air flow can be parallel or counter current to the solids flow. Air flow is typically counter current to solids flow. Wet and pasty materials can be dried when the feed is backmixed with dry product.
Air flow is parallel to the solids flow.
Because of the short retention time in the dryer, higher outlet air temperatures may be required to achieve low product moistures. Air flow is perpendicular to solids flow. Fluid bed dryer can be provided with multiple zones to match the drying operating conditions with the material drying characteristics. Internal heating coils can be provided for additional heat input. Air flow is perpendicular to solids flow.