How Does a Steam Tube Dryer Work?
Concentric rows of tubes (one-six rows depending on the dryer size and duty) run the length of the dryer. Material is fed into the steam tube dryer generally through a screw conveyor. A product dam at the discharge end of the dryer creates a bed level which covers all of the rows of tubes with product, and maximizes the heat transfer area contact between the product and steam tubes.
A steam and condensate manifold chamber, Steam Chest, is mounted on the product discharge end of the dryer. This Steam Chest distributes steam to each of the steam tubes and also collects the condensate formed as the steam transfers its latent heat to the material being processed. Steam is delivered to, and condensate is removed from, the Steam Manifold by means of a rotary steam joint.
The residual non-condensable gases, left inside of the steam tubes once the steam has condensed, are vented through a flexible connection attached to a common “Vent Header” mounted at the feed end of the LOUISVILLE Steam Tube Dryer. This Vent Header has thermostatically controlled vent valves which allow the cooler non-condensable gases to be efficiently vented as they accumulate while containing valuable steam energy inside the steam tubes.
Since the Steam Tube Dryer utilizes the latent heat of steam to drive the drying process, only a small amount of sweep air is required to remove the water vapor driven off of the product generated in the drying process. This is usually less than about 30% of the exhaust gas required for a direct heat dryer for the same process parameters.
The gap between the stationary Feed and Discharge housings at either end of the Steam Tube Dryer are sealed to keep ambient air from leaking into the dryer. Various sealing technologies are used depending on the process parameters. These seals may be as simple as tensioned woven fabric belts, and as sophisticated as machined packed and inert gas purged seals.
LOUISVILLE Steam Tube Dryers are custom engineered for their specific application. The steam side component of the Steam Tube Dryer is a pressure vessel, designed and manufactured in conformance with the latest edition of ASME Section VIII, Division I. They are stamped and registered with the National Board. Materials of construction range from carbon steel, to various nickel alloys and duplex stainless steels.